HK1097678B - Methods and apparatus of providing transmit and/or receive diversity with multiple antennas in wireless communication systems - Google Patents

Description

Method and apparatus for providing transmit and/or receive diversity with multiple antennas in a wireless communication system

Technical Field

The present invention relates to communication systems, and more particularly, to a method and apparatus for providing transmit and/or receive diversity with multiple antennas in a wireless communication system.

Background

Channel fading (channel fading) is a ubiquitous basic characteristic of wireless communication systems. Fading deteriorates the connection reliability of the wireless channel, thereby reducing system capacity and/or reducing the service experience for the user. Diversity is a known principle that can effectively prevent fading of a wireless channel. Methods of achieving diversity include the use of space, angle, polarization, frequency, time, and multipath. Diversity may be implemented at the transmitter and/or receiver.

A form of diversity may be considered to be achieved by using multiple antennas at the transmitter and/or receiver of a wireless communication system. These forms can be classified according to the kinds of transmit and receive diversity, respectively.

Fig. 1 shows a simplified diagram of a receiver 100 in a prior art wireless system equipped with multiple antennas (receive antenna 1102, receive antenna N102') and using receive diversity. In the receiver 100, multiple antennas (102, 102') receive multiple versions of the same information-bearing signal. The wireless channel associated with each receive antenna is assumed to be substantially statistically independent of the channels experienced by the other antennas. Then the probability of each receive antenna fading simultaneously is significantly less than the probability of any one antenna fading. Therefore, the probability of fading of the synthesized signal is greatly reduced, thereby improving the reliability of the link. In practice, the implementation of the receive diversity gain is as follows. Signals received by multiple receive antennas (102, 102 ') are individually processed by different receive chains, each of which typically includes an analog signal processing module (104, 104'), an analog-to-digital conversion module (106, 106 '), and a digital signal processing module (108, 108'), respectively. The processed signals (109, 109') are then combined together in a combiner module 110. For example, the combiner module 110 may use a selective synthesis method or a maximum ratio synthesis method. The combiner 110 outputs a signal 112 for further signal processing.

Similarly, fig. 2 shows a simplified diagram of a transmitter 200 in a prior art wireless system equipped with multiple antennas (transmit antenna 1202, transmit antenna N202') and using transmit diversity. Here in the transmitter 200 shown in fig. 2, the same information-bearing signal, the source signal 204, is first split and pre-processed by a splitter pre-processor 206 to produce a plurality of transmit signals (208, 208') that are correlated with one another. The multiple transmit signals (208, 208 ') are then separately transmitted across different transmit chains, which include digital signal processing modules (210, 210 '), digital-to-analog conversion modules (212, 212 '), analog signal processing modules (214, 214 '), and then transmitted with multiple antennas (202, 202 '), respectively.

Transmit diversity refers to the diversity gain achieved by a transmitter transmitting multiple correlated signals over a channel. Typically, transmit diversity techniques transmit these correlated signals using multiple transmit antennas. First, transmit diversity is generally not simple to implement. Transmitting the same signal through multiple transmit antennas typically does not yield diversity gain anyway.

One of the earliest proposed transmit diversity techniques is delay diversity, in which a transmitter sends multiple copies of the same information over different antennas at different delays. A more sophisticated version of this scheme using two antennas is proposed by Alamouti, as described in "a simple transmitter diversity scheme for wireless Communication" by IEEE Journal on selected Areas in Communication, volume 16, pages 1451 and 1458, s.m. Alamouti, 1998, 10.

The signal to be transmitted is denoted by s (t), where t is assumed to be a discrete time instant. In the Alamouti scheme, two consecutive symbols are spaced and transmitted at two times using two antennas. By X₁(t) and X₂(t) represents signals respectively output from two antennas, which can be expressed as:

it is assumed that the time-varying channel responses from two transmit antennas, e.g. two base station transmit antennas, to a receiver, e.g. a mobile receiver, are h, respectively₁(t) and h₂(t) is shown. Is composed ofFor simplicity of illustration, we can assume a flat channel, but more generally can also handle frequency dependent channels. If it is assumed that the channel coefficients remain constant for two symbols, which is a mild assumption, then the composite signal received by the mobile receiver can be expressed as:

Y(t)＝h₁X₁(t)+h₂X₂(t)+W(t)

Y(t+1)＝h₁X₁(t+1)+h₂X₂(t+1)+W(t+1)

this expression can be rewritten from the initial signal s (t) as:

or alternatively:

if the channel responses from the two transmit antennas to the receiver are known, then the transmitter coding structure can be directly converted and the transmit signal deduced by the following transformation:

this will create a second order diversity over a fading channel. The Alamouti scheme is simpler but requires the receiver to track the gain of each of the two transmit antennas separately, which typically requires the use of two sets of pilot signals. This would be particularly complex in a cellular uplink, where, for example, the mobile device transmits to the base station receiver. Furthermore, each requirement of known transmit diversity techniques using multiple transmitter chains typically includes digital and analog processing modules, which can be very costly in many applications.

In light of the foregoing discussion, there is a need for improved methods and apparatus for implementing transmit and/or receive diversity in a wireless communication system. Methods and apparatus for achieving diversity while reducing the amount of signaling dedicated to pilot signals in known methods are useful. Methods and apparatus that achieve diversity without requiring multiple transmit chains are also useful.

Disclosure of Invention

Methods and apparatus for implementing transmitter and/or receiver diversity in a wide variety of communication applications are described. In various embodiments, transmit and/or receive diversity is achieved using multiple antennas. In some embodiments, a single transmitter chain within a wireless terminal is coupled in time to multiple transmit antennas. At any given time, a controllable switching component couples a single transmitter chain to one of a plurality of transmit antennas. Over time, the switching components couple output signals from a single transmitter chain to different transmit antennas. The handover decision is based on predetermined information, dwell information (dwell information) and/or channel state feedback information. The switching is performed on some dwell and/or channel estimation boundaries. In some OFDM embodiments, each of the plurality of transmitter chains is coupled to a different transmit antenna. The information to be transmitted is mapped onto a variety of tones. Different subsets of tones are formed simultaneously from and transmitted simultaneously through different transmit chain/antenna groups. The balance of tones allocated to the subsets for each antenna may be varied as a function of predetermined information, dwell information, and/or channel state feedback information.

Although described in terms of many possible OFDM implementations, the method and apparatus may be used with a wide variety of communication technologies, including CDMA.

Numerous additional features, advantages and embodiments of the invention will be discussed in the detailed description which follows.

Drawings

Fig. 1 is a simplified diagram of a receiver in a prior art wireless system equipped with multiple antennas using receive diversity.

Fig. 2 is a simplified diagram of a transmitter in a prior art wireless system equipped with multiple antennas using transmit diversity.

Fig. 3 illustrates an exemplary transmit chain and multiple transmit antennas implemented in accordance with the invention.

Fig. 4 illustrates exemplary downlink frequency hopping in an exemplary OFDM system.

Fig. 5 illustrates exemplary uplink frequency hopping based on dwell in an exemplary OFDM system.

Fig. 6 illustrates exemplary uplink frequency hopping and antenna switching for an exemplary OFDM uplink system in which a wireless terminal uses two different transmit antennas to achieve transmit diversity in accordance with the present invention.

Fig. 7 illustrates exemplary downlink frequency hopping and antenna switching for an exemplary OFDM downlink system having two transmit antennas in accordance with the present invention.

Fig. 8 shows an exemplary receive chain and multiple receive antennas in accordance with the present invention.

Fig. 9 shows an exemplary OFDM symbol including multiple tones that are split between two transmit antennas and are to be transmitted simultaneously in accordance with the present invention.

FIG. 10 illustrates an exemplary variation of the tone-splitting shown in FIG. 9, including: a change in tone splitting over time, a full distribution of tones to the first antenna and a zero distribution of tones to the second antenna, and a repeated distribution of tone splitting.

Fig. 11 illustrates another exemplary variation of the tone-splitting shown in fig. 9, in accordance with the present invention, wherein the tone-splitting varies as a function of channel quality feedback information.

Fig. 12 illustrates another exemplary variation of the tone splitting illustrated in fig. 9, in accordance with the present invention, wherein the tone subsets associated with each antenna may overlap at any given time interval, and the number of tones associated with each subset varies as a function of channel quality feedback information.

Fig. 13 illustrates an exemplary communication system implemented in accordance with the present invention and using methods of the present invention.

Fig. 14 illustrates an exemplary base station that can employ dwell boundary antenna switching, implemented in accordance with the present invention.

Fig. 15 illustrates another exemplary base station that can employ channel estimation boundary antenna switching, implemented in accordance with the present invention.

Fig. 16 illustrates another OFDM base station implemented in accordance with the invention that can assign different tone subsets to different transmit antennas for simultaneous transmission.

Fig. 17 illustrates an exemplary wireless terminal implemented in accordance with the present invention and using the methods of the present invention, which includes dwell boundary switching between multiple transmit antennas or antenna elements.

Fig. 18 illustrates another exemplary wireless terminal implemented in accordance with the present invention and using the methods of the present invention, which includes channel estimation boundary switching between multiple transmit antennas or antenna elements.

Fig. 19 illustrates another exemplary wireless terminal implemented in accordance with the present invention and using the methods of the present invention, which includes assigning different subsets of tones to different transmit antennas or antenna elements, and then transmitting the different assigned subsets of tones simultaneously using the different antennas or antenna elements.

Fig. 20 shows time being divided into a series of time intervals by an exemplary base station receiver, with individual channel estimates maintained from one time interval to another, in accordance with the present invention.

Fig. 21 is a flow chart of an exemplary method of operating a wireless terminal to communicate with a base station that includes performing dwell boundary switching of transmitter antenna elements in accordance with the present invention.

Fig. 22 is a flow chart of an exemplary method of operating a wireless terminal to communicate with a base station including performing dwell boundary switching of transmitter antenna elements based on quality indicator feedback information in accordance with the present invention.

Fig. 23 is a flow chart of an exemplary method of operating a wireless terminal to communicate with a base station that includes performing channel estimation boundary switching of transmitter antenna elements in accordance with the present invention.

Fig. 24 is a flow chart of an exemplary method of operating a wireless terminal to communicate with a base station that includes performing channel estimation boundary switching of transmitter antenna elements based on quality indicator feedback information in accordance with the present invention.

Fig. 25 is a flow diagram of an exemplary method of operating an OFDM communication device in accordance with the present invention that includes assigning different tone subsets to different antenna elements and transmitting on multiple parallel antenna elements.

Fig. 26 is a flow diagram of an exemplary method of operating an OFDM communication device in accordance with the present invention that includes receiving and processing channel quality indicator information, assigning different tone subsets to different antenna elements and transmitting on multiple antenna elements in parallel.

Fig. 27 shows an exemplary transmitter structure that may be used in the tone-splitting embodiment of the present invention.

Fig. 28 shows an exemplary variation of the transmitter structure of fig. 27, including the generality of the digital portion, in accordance with the present invention.

Fig. 29 shows another variation of the transmitter architecture of fig. 27, including only two transmit antenna chains, an antenna switching module, and more than two transmitter antennas, in accordance with the present invention.

Detailed Description

While the diversity principle helps to improve the reliability of the wireless connection, the use of multiple transmit and/or receive chains increases the cost and complexity of the transmitter and/or receiver. Typically, there are many wireless terminals for each base station deployed in a wireless communication system. For example, the wireless terminal may be a portable, battery-powered mobile device, such as a cell phone or cellular data communication device, that is owned and operated by the consumer. The increased cost and complexity is a particularly important consideration on the part of a wireless terminal, such as a mobile node. Various aspects and features of the present invention are directed to a wireless system equipped with multiple antennas that can achieve diversity with minimal increase in cost and/or complexity.

Various aspects of providing transmit diversity in accordance with the present invention will now be described. Transmit diversity may be achieved in a wireless communication system by employing a single transmit chain and by switching between multiple transmit antennas, in accordance with various embodiments of the present invention.

The diagram 300 in fig. 3 includes an exemplary transmit chain 302 in accordance with the present invention. The exemplary transmit chain 302 includes a digital signal processing module 304, a digital-to-analog conversion module 306, an analog signal processing module 308, and a switching module 310. The input signal 303 is input to a digital signal processing module 304. The digital signal processing block 304 contains and performs signal processing functions in the digital domain such as encoding, modulation, and digital filtering. The digital signal processing block 304 typically includes a baseband digital link. The signal 305 output from the digital signal processing block 304 is input to a digital-to-analog conversion block 306. The digital-to-analog conversion module 306 converts the digital signal 305 into an analog signal 307 and serves as an input to an analog signal processing module 308. The analog signal processing module 308 contains and performs signal processing functions in the analog domain, such as up-conversion to a carrier frequency, analog filtering, and power amplification. The analog signal processing block 308 typically includes a baseband analog link and an RF analog link. The output of the analog signal processing module 308 is then sent as an output signal (311 or 311 ') via the switching component module 310 and then transmitted through one of a plurality of transmit antennas (transmit antenna 1312 or transmit antenna N312'), respectively. The switching module 310 determines the transmit antennas (312, 312') to be used at any given time. Sometimes, the switching module 310 selects a different transmit antenna (312, 312 ') to use and then directs the output 309 of the analog signal processing module 308 to the selected transmit antenna (312 or 312').

The switching component 310 is controlled by signals received from the switching control component 318. Channel feedback signal 314 from the base station is input to uplink channel feedback component 316. The uplink channel feedback component 316 determines which transmit antenna (312, 312') produces better channel quality and forwards this information to the control component 318. In addition, dwell information 320, such as dwell boundary information, is input to the switching control module 318. The handover control component can use the received information to decide on the selection of the antenna. For example, the switching control module 318 can control switching on dwell boundaries. In some embodiments, the switching control module 318 alternates between antennas as a function of the number of dwells and the number of antennas. In some embodiments, the switching control component can select to use only the antenna associated with the better channel quality or to use that antenna more frequently than other antennas based on the channel quality estimation information. In some embodiments, uplink channel feedback component 314 is not used, and switching is controlled based on dwell information 320 without using channel feedback information 314.

Note that although there are multiple physical transmit antennas (312, 312'), the transmitter 300 uses only a single transmit chain 302. This is in contrast to the prior art system shown in fig. 2 which employs multiple transmit chains, one for each transmit antenna (202, 202').

Let N denote the number of transmit antennas. Let { H_kAnd k 1.. N } represents the wireless channel response from each transmit antenna to the receiver. In some embodiments, the transmit antennas are spatially arranged in such a way that the ensemble of channel responses { H }_kIs substantially independent. By switching from one transmit antenna to another, the effective channel response from the transmitter to the receiver is at { H }_kAnd the power is changed, thereby realizing the transmission diversity. For example, assume N ═ 2. Assume that the switching module selects transmit antenna 1 for use during time t 1-t 2, and then uses transmit antenna 1 during time t 2-t 3. It is assumed that code groups are transmitted in time intervals t1 to t 3. Then the partial code group will experience a channel response H₁While the rest will experience a channel response H₂. Thus, suppose H₁And H₂Are independent, then the code groups can gain the benefit of second-order diversity. This is particularly true at low coding rates (in this case below 1/2).

In various embodiments of the present invention, it is useful for the receiver to know the moment at which the transmitter switches antennas. This can be important, for example, when the receiver maintains different channel estimates for different antennas, and evolves a suitable channel estimate during any particular antenna transmission.

For purposes of illustration, the present invention is considered herein in the context of a spread spectrum Orthogonal Frequency Division Multiplexing (OFDM) system. Note that the present transmit diversity technique is also applicable to other systems, such as Code Division Multiple Access (CDMA) systems.

In this exemplary OFDM system, the tones hop to achieve the spread spectrum advantage. In the downlink, tones hop every OFDM symbol from base station to wireless terminal. Each logical tone is mapped to a different physical tone and the mapping varies at each OFDM symbol boundary as shown in figure 4. A diagram 400 of frequency on the vertical axis 402 versus time on the horizontal axis 404 of fig. 4 illustrates frequency hopping for an exemplary OFDM downlink. The basic unit on the frequency axis is the physical tones 406 and the basic unit on the horizontal axis 404 is the OFDM symbol duration 408. Exemplary logical tone hopping to different physical tones and variation at each OFDM symbol boundary is illustrated by the sequence of squares (410, 412, 414, 416, 418, 420, and 422), which illustrates the change in physical tone position at each OFDM symbol boundary. This hopping facilitates the spreading of code groups that include some subset of logical tones across the available frequency band.

In the uplink, from the wireless terminal to the base station, each logical tone is mapped onto a physical tone, which mapping is kept fixed for some OFDM symbol periods. This duration is referred to as the dwell period. The steps of uplink hopping over the dwell period are shown in fig. 5. The diagram of fig. 5 shows frequency on the vertical axis 502 versus time on the horizontal axis 504 and is used to illustrate exemplary uplink frequency hopping. The basic unit of the vertical axis 502 is physical audio; region 506 shows several, e.g., two exemplary, adjacent physical tones. The basic unit on the horizontal axis 504 is an OFDM symbol period 508. Each OFDM dwell period 510 includes four consecutive OFDM periods. In other embodiments, the dwell period may include a different number of OFDM symbol periods, such as seven OFDM symbol periods. Fig. 5 shows four consecutive OFDM dwell intervals: latch 1512, latch 2514, latch 3516, and latch 4518. As shown in fig. 5, the logical tones are mapped onto the physical tones and the mapping is kept fixed for four consecutive OFDM symbol periods; as represented by audio burst 520 during dwell 1512, audio burst 522 during dwell 2514, audio burst 524 during dwell 3516, and audio burst 526 during dwell 4518.

Various embodiments of the present invention may be used at a transmitter of a wireless terminal to achieve transmit diversity on a cellular uplink. In an exemplary embodiment according to the present invention, the transmitting antenna is switched on a dwell boundary of the uplink signal. That is, assume that dwell 1512 and dwell 2514 are two consecutive dwells. The transmitter may switch the antenna once per dwell or once every few dwells. For example, fig. 6 shows a diagram 600 illustrating exemplary uplink frequency hopping and antenna switching for an exemplary OFDM uplink system with two transmit antennas. Diagram 600 includes a graph of frequency on vertical axis 602 versus time on horizontal axis 604. The basic unit of frequency is audio 606. The basic unit of time is an OFDM symbol period 608 and an OFDM dwell period 610 includes four consecutive OFDM symbol periods 608. A logical tone is a frequency that hops to a physical tone and the hopping changes on the dwell boundary. For example, physical audio (620, 622, 624, 626) is used during (latch 1612, latch 2614, latch 3616, latch 4618). In fig. 6, the signals in the odd dwell (612, 616) are transmitted through antenna 1628 and the signals in the even dwell (614, 618) are transmitted through antenna 2 (630). It is assumed that the base station receiver does not employ channel coherence from one dwell to another. For example, the receiver may not perform channel estimation between dwells. Then switching the transmit antennas at the dwell boundaries does not affect the operations performed at the receiver. Of course, in this state, the receiver may not even be aware of the use of the present transmit diversity invention. If the code blocks are transmitted over several dwell intervals, then the code blocks, particularly for low code rate code blocks, may benefit from secondary diversity.

Similarly, various embodiments of the invention may be used at a base station to achieve transmit diversity on a cellular downlink. In some embodiments of the invention, the base station switches the transmit antennas once every few OFDM symbols, and the wireless terminal knows when the switching of antennas occurs. Fig. 7 shows a diagram 700 illustrating exemplary downlink frequency hopping and antenna switching for an exemplary OFDM downlink system with two transmit antennas. The diagram 700 includes a graph of frequency 702 on the horizontal axis versus time 704 on the vertical axis. The basic unit of frequency is audio 706. The basic unit of time is an OFDM symbol period 708. Logical tones are frequency hopped to physical tones and hopped for consecutive OFDM symbol periods. Fig. 7 shows an exemplary logical tone for one OFDM symbol period hopped to a different logical tone, as shown by the sequence of blocks (718, 720, 722, 724, 726, 728, 730, 732, 734, 736, 738, 740, 742, 744, 746, 748). Fig. 7 may correspond to an exemplary OFDM downlink system with two transmit antennas (antenna 1750 and antenna 2750), where antenna switching occurs only once every 4 OFDM symbols. For example, signals in time intervals denoted a (710, 714) are transmitted via antenna 1750, and signals in time intervals denoted B (712, 716) are transmitted via antenna 2750. The wireless terminal receiver maintains two independent channel estimates. The first channel estimate is followed and used in time interval a (710, 714) and the second channel estimate is followed and used in time interval B (712, 716).

In the above exemplary description, the switching module at the transmitter selects each transmit antenna fairly equally. It is now assumed that in some embodiments of the invention, the receiver feeds back some indication of the channel quality to the transmitter. Thus in a slow time varying environment, the transmitter can find out which transmit antenna can produce better channel quality and use that antenna only or more frequently than other antennas.

Practically speaking, in Radio Frequency (RF) transmit circuits, there is often a transient response associated with switching the antenna. The use of cyclic prefix in the exemplary OFDM system can effectively absorb the antenna transient response and maintain the basic characteristics of the OFDM system, such as orthogonality.

The present invention achieves transmit diversity gain without requiring multiple transmit chains. There is no explicit pre-processing of the included signals, such as space-time codes, which require different information signals to be transmitted on different antennas. Various embodiments of the present invention also confer additional advantages. Most transmit diversity schemes require the use of different pilot signals in the signals transmitted by different antennas so that the receiver can track the channel response individually. Various embodiments of the present invention avoid the need for multiple pilot signals since the same information signal is transmitted at different times through different antennas.

Various aspects of providing receive diversity in accordance with the present invention will now be described. According to the present invention, receive diversity can be achieved in a wireless communication system by using a single receive chain and by switching between multiple receive antennas.

Fig. 8 shows a schematic diagram 800 of an exemplary receive chain 802 and multiple receive antennas (receive antenna 1812, receive antenna N) in accordance with the present invention. The exemplary receive antenna 802 includes a switching component 810, an analog signal processing module 808, an analog-to-digital conversion module 806, and a digital signal processing module 804. The switching module 810 determines which receive antenna (812, 812') to use at a given time. At different times, the switching component module 810 selects different receive antennas to use and directs signals (811, 811 ') from the selected receive antennas (812, 812') to the inputs 809 of the analog signal processing module 808, respectively. The input 809 to the analog signal processing module 808 may come from one of the receive antennas (812, 812'). The analog signal processing block 808 contains and performs signal processing functions in the analog domain, analog filtering, low noise amplification, and down conversion to baseband. The analog signal processing block 808 typically includes a baseband analog link and an RF analog link. The analog signal processing block 808 outputs a signal 807. The analog-to-digital conversion module 806 converts the output 807 of the analog signal processing module 808 into a digital signal 805 and provides it as an input to the digital signal processing module 804. The digital signal processing module 804 contains and performs signal processing functions in the digital domain, such as digital filtering, decoding, and demodulation. The digital signal processing block 804 typically includes a baseband digital link. The digital signal processing module 804 outputs a digital signal 803.

Note that although there are multiple receive antennas (812, 812'), the wireless system has a single receive chain 802. This is in contrast to the prior art system shown in fig. 1 which employs multiple receive chains, one for each receive antenna.

Various features of the present invention may be used in a wireless terminal to achieve downlink receive diversity. In one exemplary embodiment, an exemplary wireless terminal with two receive antennas switches receive antennas every few OFDM symbols. This embodiment is very similar to the embodiment of the present invention shown in fig. 7 where the transmit antennas are switched at the base station. In particular, signals in time interval a (710, 714) are received through receive antenna 1812 and signals in time interval B (712, 716) are received through antenna 2812'. The wireless terminal receiver maintains two independent channel estimates, which are tracked and used in time intervals a and B, respectively.

Similarly, features of the invention can be used at a base station to achieve uplink receive diversity. An exemplary embodiment switches the receiving antenna on the dwell boundary of the uplink signal. This is very similar to the embodiment shown in fig. 6 that employs switching of transmit antennas at the wireless terminal transmitter. In particular, consider an exemplary base station with two receive antennas; signals in the odd dwell (612, 616) are received by receive antenna 1812 and signals in the even dwell (614, 618) are received by receive antenna 2812'. Switching the receive antennas at the dwell boundaries does not affect the operations performed at the receiver, assuming that the receiver does not assume channel coherence from one dwell to another.

In the above description, the switching module 810 selects each receive antenna substantially equally. The switching may be controlled by the processor or preset to occur in a particular manner or sequence. Now assume that the receiver estimates the channel quality. The receiver can then find out which receive antenna produces better channel quality and use that antenna only or more frequently than other antennas.

Note that the present invention can be used in conjunction with other methods for achieving diversity. For example, consider a wireless system that uses two switched antennas at the receiver of a wireless terminal, as described herein. The base station receiver uses a conventional maximum ratio in conjunction with two antennas. Collectively, this achieves four levels of diversity in the cellular uplink.

The audio splitting will now be described in the context of the present invention. The orthogonal nature of tones in an exemplary spread spectrum OFDM (orthogonal frequency division multiplexing) multiple access system enables a unique method of achieving transmit diversity gain. Consider diagram 900 of fig. 9, which shows an exemplary OFDM symbol 904 that includes a plurality of tones (tone 0906, tone 1908, tone 2910, tone 3912, tone 4914, tone 5916, tone 6918, tone 7920) transmitted as signals (924, 928) over two antennas (antenna 1922, antenna 2926), respectively. The tones (908, 912, 916, 920) of the symbols that are shaded are transmitted through a transmit antenna 1922, while the tones (906, 910, 914, 918) of the symbols identified as blank boxes are transmitted using a transmit antenna 2926. This may allow for secondary transmit diversity, especially for low code rates, since the code blocks are distributed over several OFDM symbols. Half of the modulation symbols in the block are transmitted over each of the antennas (922, 926). The extension of the transmit diversity method to multiple transmit antennas is apparent.

The diagram 1000 of fig. 10 illustrates a variation of the tone-splitting of fig. 9 according to the present invention. Fig. 10 includes a graph of frequency on the vertical axis 902 versus time on the horizontal axis 1003 represented by audio index numbers from 0 to 7. The basic unit of the time axis is the OFDM symbol time. Each of the exemplary OFDM symbols (1004, 1006, 1008, 1010, 1012, 1014, 1016, 1017) includes a plurality of tones (tone 01018, tone 11020, tone 21022, tone 31024, tone 41026, tone 51028, tone 61030, tone 71030) that are transmitted as signals (1038, 1040) by two antennas (antenna 11034, antenna 21036), respectively. The tones for each of the shaded OFDM symbols are transmitted via transmit antenna 11034, while the tones for those symbols marked with blank boxes are transmitted using transmit antenna 21036. Each tone in each OFDM symbol transmits a modulation symbol that carries coded information. Initially, for group 14 OFDM symbol time intervals (1004, 1006, 1008, 1010), half of the modulated symbols are transmitted via antenna 11034 and the other half are transmitted via antenna 21036. The communication device then decides to emphasize antenna 11034. For example, feedback information to the communication device may have shown that the channel from antenna 1 to the receiver is better than the channel from antenna 2 to the receiver, e.g., based on the received power level and/or based on positive/negative information. The communication device changes the number of tones allocated to each antenna. In interval 1012, antenna 11034 receives the entire set of audio, while antenna 2 does not receive audio for transmission. During the next interval 1014, each antenna receives half of the tones for transmission. This pattern of alternating between tone allocation duty cycles is repeated until the decision to change the balance between antennas 1034, 1036 occurs. In some embodiments, the basic unit of time is an interval containing several consecutive OFDM symbol times. In some embodiments, for example, where the communications device is a wireless terminal and the communications device transmits an uplink signal to the base station, the basic unit of time is a dwell comprising several consecutive OFDM symbol times.

Fig. 11 is a diagram 1100 illustrating another variation of the tone-splitting depicted in fig. 9 in accordance with the present invention. Fig. 11 includes a graph of frequency on the vertical axis 1102 versus time on the horizontal axis 1103, represented by audio index numbers from 0 to 7. The basic unit of the time axis is OFDM dwell. Each of the exemplary OFDM dwells (1104, 1106, 1108, 1110, 1112, 1114, 1116) includes a plurality of tones (tone 01118, tone 11120, tone 21122, tone 31124, tone 41126, tone 51128, tone 61130, tone 71130) that are transmitted as signals (1138, 1140) respectively through two antennas (antenna 11134, antenna 21136). The tones of each of the OFDM dwells that are graduated are transmitted through transmit antenna 11134, while those tones marked with blank boxes are transmitted using transmit antenna 21136. Each tone in each OFDM dwell transmits a set of modulation symbols that carry encoded information, e.g., one modulation symbol for each OFDM symbol time interval in the dwell. Initially, for group 13 OFDM dwell (1104, 1106, 1108, 1110), half of the modulated symbols are transmitted via antenna 11134 and the other half are transmitted via antenna 21136. The communication device then decides to reinforce antenna 11134 and to change the audio balance to slightly favor antenna 1 over latch 1110. For example, feedback information to the communication device may have shown that the channel from antenna 11134 to the base station receiver is better than the channel from antenna 21136 to the base station receiver, e.g., based on the received power level and/or based on ack/nack information. The communication device continues to monitor the feedback information and adjust the balance between the antennas as observed by the changes from exemplary dwells 1110 to 1112, 1112 to 1114, and 1114 to 1116. In some embodiments, no change occurs on dwell boundaries, but rather over a given number of OFDM symbol times or over channel condition measurement boundaries.

In the examples shown in fig. 9 and 10, the tones assigned to the antennas are mutually exclusive at any given time. However, in various embodiments of the present invention, the subset of tones assigned to each antenna may comprise overlapping subsets of tones. Fig. 12 is a diagram 1200 illustrating another variation of the tone-splitting described in fig. 9 in accordance with the present invention. Fig. 12 includes a graph of frequency on the vertical axis 1202 versus time on the horizontal axis 1203 represented by audio index numbers from 0 to 7. The basic unit of the time axis is OFDM dwell. Each of the exemplary OFDM dwells (1204, 1206, 1208, 1210, 1212, 1214, 1216) includes a plurality of tones (tone 01218, tone 11220, tone 21222, tone 31224, tone 41226, tone 51228, tone 61230, tone 71232) that are transmitted as signals (1238, 1240) by two antennas (antenna 11234, antenna 21236), respectively. The tones of each of the tapered OFDM dwells, which increase diagonally from left to right, are transmitted through transmit antenna 11234, while those tones, which decrease diagonally from left to right, are transmitted using transmit antenna 21236. Note that in the exemplary OFDM dwell 1204, 1216, a balanced state between the two antennas (1234, 1238) is represented, three tones (tone 01218, tone 11220, and tone 21222) are transmitted exclusively using antenna 11234, three tones (tone 51228, tone 61230, and tone 71232) are transmitted exclusively using antenna 21236, and two tones (1224 and 1226) are transmitted by the two antennas (1234 and 1236). Each tone in each OFDM dwell is used to transmit a set of modulation symbols that carry encoded information, e.g., one modulation symbol for each OFDM symbol time interval in the dwell. When the communications device decides to strengthen antenna 21236, the audio balance is changed to favor antenna 2, such as that observed in dwells 1206, 1208, 1210, 1212, and 1214. The amount of audio imbalance is adjusted, e.g., from dwell to dwell. For example, feedback information to the communication device may have shown that the channel from antenna 2 to the receiver is better than the channel from antenna 1 to the receiver, e.g., based on the received power level and/or based on positive/negative information, and this difference in the degree of channel quality is then used to determine the level of audio imbalance. In some embodiments, no change occurs on dwell boundaries, but rather over a given number of OFDM symbol times or over channel condition measurement boundaries.

Although frequency hopping is not shown in the examples of fig. 10-12 for simplicity of illustration, it should be understood that in many embodiments the tones hop from one OFDM symbol period to the next OFDM symbol period on the downlink or from one dwell to the next dwell on the uplink. In addition, the tones associated with one transmit antenna at any given time may form a tone subset, which is a disjoint set of tones. This method of achieving transmit diversity by employing tone splitting techniques uses multiple transmit chains.

Fig. 13 illustrates an exemplary communication system 10 implemented in accordance with the invention, e.g., to implement transmit and/or receive diversity using multiple antennas or antenna elements. The exemplary system 10 includes a plurality of units (unit 1(2), unit M (2')). Each cell (cell 1(2), cell M (2 ')) represents a radio coverage area of a base station (BS 1(12), BS 2 (12')), respectively. The system 10 further comprises a network node 3 connected to the base stations (BS 1(12), BS 2(12 ')) via network links (4, 4'), respectively. The network node 3, which may be a router for example, is also connected to the internet and other network nodes via a network link 5. The network links (4, 4', 5) may be fiber optic links, for example. Each cell includes a plurality of wireless terminals that are connected to the base station of the cell via wireless links and, if the wireless terminals are mobile devices, they may move throughout the system 10. In unit 1(2), a plurality of wireless terminals (WT 1(14), WT N (16), shown as mobile nodes (MN 1(14) through MN N (16), respectively, communicate with base station 1(12) by using communication signals (13, 15). in unit M (2 '), a plurality of wireless terminals (WT 1' (14 '), shown as mobile nodes (MN 1' (14 ') through MN N' (16 '), respectively, WT N' (16 ') communicate with base station M (12') by using communication signals (13 ', 15'), respectively, each mobile terminal may correspond to a different mobile user and may therefore sometimes be referred to as user terminals.e., signals (13, 15, 13 ', 15') may be Orthogonal Frequency Division Multiplexed (OFDM) signals 12 ') and wireless terminals (MN 1, MN N, MN 1 ', MN N ') (14, 16, 14 ', 16 ') each implement the method of the present invention. Thus, the signals (13, 15, 13 ', 15') comprise signals of the type discussed in the present application and transmitted in accordance with the present invention.

Fig. 14 illustrates an exemplary base station-access node 1400 implemented in accordance with the invention. The base station 1400 may be any of the exemplary base stations 12, 12' of fig. 13. The base station 1400 includes a receiver chain/antenna module 1402 and a transmitter chain/antenna module 1404. The receiver chain/antenna module 1402 may be implemented similarly or identically to that shown in fig. 8. The transmitter chain/antenna module 1404 may be implemented similarly to that shown in fig. 3, but with the functionality of OFDM timing structure information, predetermined information, and/or downlink channel feedback information from WTs for handover control. The receiver chain/antenna module 1402 includes a receive antenna or antenna element 1406 and a receive chain 1410. Module 1402 in some embodiments includes multiple antennas or antenna elements (receive antenna 11406, receive antenna N1408), and its receiver chain 1410 includes a dwell boundary controllable switching module 1412, e.g., switching circuitry. The transmitter chain/antenna module 1404 includes a transmit antenna or antenna module 1414 and a transmitter chain 1418. In some embodiments, module 1404 includes multiple antennas or antenna elements (transmit antenna 11414, transmit antenna N1416), and its transmitter chain 1418 includes a controllable switching module 1420. The uplink signals received by receiver module 1402 from WTs include uplink signals transmitted from different WT transmit antennas or antenna elements of the same WT during different dwell periods. The transmitter module 1404 transmits downlink signals to WTs including channel quality indication feedback signals indicative of received WT uplink signals. The components 1402, 1404 are connected by a bus 1422 to an I/O interface 1424, a processor 1426, e.g., a CPU, and a memory 1428. The I/O interface 1426 connects the base station 1400 to the internet and other network nodes, e.g., routers, other base stations, AAA nodes, etc. Memory 1428 includes routines 1430 and data/information 1432. The processor 1426 executes the routines 1430 and uses the data/information 1432 in memory 1428 to cause the base station 1400 to operate in accordance with the invention.

Routines 1430 includes communications routines 1434 for controlling the base station 1400 to perform various communications operations and implement various communications protocols. The routines 1430 also includes base station control routines 1436 used to control the base station 1400 to implement the steps of the method of the present invention. The base station control routines 1436 include a scheduling component 1438 used to control transmission scheduling and/or communication resource allocation, e.g., assignment of uplink and downlink segments to WTs. In some embodiments, base station control routines 1436 also include components such as dwell boundary switching component 1412 and multiple receive antennas (1406, 1408), a receiver antenna switching control component 1440. In some embodiments, base station control routines 1436 also include components such as switching component 1420 and multiple transmit antennas (1414, 1416), a transmitter antenna switching control component 1442. Switching means 1412 in the receiver chain 1410 and 1420 in the transmitter chain 1418, when implemented, are responsive to control signals generated by the processor 1426 when operating under the direction of these components (1440, 1442), respectively. The control signal effects switching between the antennas or antenna elements in accordance with the present invention. The data/information 1432 that the receiver antenna switching control module 1440 may use in determining antenna switching includes uplink quality indication feedback information 1458, dwell information 1478, and receiver antenna switching information 1472. The data/information 1432 that the transmitter antenna switching control module 1442 may use in deciding antenna switching includes OFDM symbol timing information 1476, received downlink channel feedback report information 1459, and transmitter antenna switching information 1474.

Base station control routines 1436 also include an uplink channel feedback module 1444 that controls the evaluation of received uplink signals, the generation and transmission of channel quality indication feedback signals, such as feedback messages 1464, including WT power control feedback information 1460 and transmission acknowledgement/negative acknowledgement (ack/nack) feedback information 1462 indicating the success or failure of the uplink signal or signals.

Memory 1428 also includes data/information 1432 used by communications routines 1434 and control routines 1436. Data/information 1432 includes WT data/information 1446 and system information 1448. WT data/information 1446 includes multiple sets of WT information (WT1 data/information 1450, WT N data/information 1452). WT1 data/information 1450 includes user/device/session/resource information 1454, timing synchronization information 1456, uplink quality indication feedback message information 1458, and received downlink channel feedback report information 1459. User/device/session/resource information 1454 includes user/device identification information, session information such as peer node information and routing information, and resource information such as uplink and downlink traffic channel segments assigned to WT1 by scheduling component 1438. Timing synchronization information 1456 includes information to synchronize WT1 timing with respect to BS timing, e.g., adjustment information to compensate for propagation delay. Uplink quality indication feedback message information 1458 includes WT power control information 1460, ack/nack information 1462, and feedback messages 1464. Received downlink channel feedback report information 1459 includes information obtained from received downlink channel feedback reports transmitted by WT1 in response to downlink pilot broadcast signals transmitted by BS 1400. System information 1448 includes timing information 1466, tone information 1468, frequency hopping sequence information 1470, optional receiver antenna switching information 1472, and optional transmitter antenna switching information 1474. Timing information 1466 includes OFDM symbol timing information, e.g., time intervals at which OFDM symbols are transmitted, synchronization information relative to OFDM symbol intervals, timing information corresponding to OFDM symbol interval groupings such as redundant time slots, beacon time slots, and ultra-high time slots, and/or timing information corresponding to a fixed number of OFDM symbol intervals communicated prior to switching between transmit antennas or antenna elements. Timing information 1466 also includes dwell information 1478, e.g., a grouping of a number of consecutive OFDM symbol intervals in which the logical-to-physical frequency hopping remains constant during the uplink signal interval. Tones used for uplink signaling hop differently from one dwell to the next depending on the order of uplink hopping. Dwell information 1478 includes dwell boundary information 1480. Dwell boundary information 1478 determines the time at which the WT is able to perform transmitter antenna switching in accordance with the present invention. In some embodiments, the BS receiver component 1402 also performs dwell boundary switching operations between antennas and uses dwell boundary information 1480. Tone information 1468 includes sets of tones for the uplink and downlink signals, as well as subsets of tones that are assigned to particular portions of particular times. The hopping sequence information 1470 includes, for example, downlink hopping sequence information where tones are frequencies that hop for consecutive OFDM symbol times, and also includes, for example, uplink hopping sequence information where tones are frequencies that hop for consecutive dwells. Receiver antenna switching information 1472 includes information such as criteria, predetermined switching sequences, antenna element usage information, and antenna element control information used by the receiver antenna switching control component 1440. Transmitter antenna switching information 1474 includes information such as the standard, predetermined switching order, antenna element usage information, and antenna element control information used by transmitter antenna control components 1442.

In some systems, a base station receiver estimates the uplink channel of a wireless terminal in order to demodulate the signal received from the wireless terminal. The operation of channel estimation often depends on the structure of the received signal. Take an OFDM system as an example, where the tones of the uplink signal hop every few OFDM symbols. From one hop to another, the frequency location of the tones may be assumed to be random. In this case, the base station receiver may assume that the channel estimate has changed significantly from one hop to another, and thus may discard the memory of the channel estimate in the previous hop and then perform the channel estimation operation starting from the beginning of the new hop. In the case of an exemplary CDMA system, the base station receiver may divide time into a series of time intervals as shown in fig. 20, and then maintain independent channel estimates between the time intervals. The diagram 200 of FIG. 20 shows that the horizontal axis 2002 representing time has been divided into an exemplary sequence of time intervals: a 22004, B12006, a 12008, B2010, a 2012. For example, the channel estimate in time interval a2012 is not based on the signal received in time interval B2010. In this case, the time instant between time intervals a and B is referred to as the channel estimation boundary 2014. In one embodiment, the channel estimate for time interval a2012 may be independent of the signal received in any previous time interval, in which case the channel estimate is based only on the signal received in time interval a 2012. In another embodiment, the channel estimate in time interval a2012 may be based on signals received in previous time intervals a 12008, a 22004, and so on.

FIG. 15 illustrates another exemplary base station, access node 1800, implemented in accordance with the present invention. The base station 1800 may be any of the exemplary base stations (12, 12') of fig. 13. Base station 1800 includes a receiver chain/antenna module 1802 and a transmitter chain/antenna module 1804. The receiver chain/antenna module 1802 may be implemented similarly or identically to that shown in fig. 8. The transmitter chain/antenna module 1804 may be implemented similarly to that shown in fig. 3, but with the switching control being accompanied by channel estimation boundary information and/or downlink channel feedback information from WTs. Receiver chain/antenna assembly 1802 includes a receive antenna or antenna element 1806 and a receive chain 1810. Module 1802, in some embodiments, includes multiple antennas or antenna elements (receive antenna 11806, receive antenna N1808), and its receiver chain 1810 includes a channel estimation boundary controllable switching module 1812, e.g., switching circuitry. The transmitter chain/antenna assembly 1804 includes a transmit antenna or antenna element 1814 and a transmitter chain 1818. In some embodiments, module 1804 includes multiple antennas or antenna elements (transmit antenna 11814, transmit antenna N1816), and its transmitter chain 1818 includes a controllable switching module 1820. The uplink signals received by receiver module 1802 from WTs include uplink signals transmitted by different WT transmit antennas or antenna elements of the same WT, which are transmitted during different intervals corresponding to different base station channel estimates. Transmitter module 1804 transmits downlink signals to WTs including channel estimation indication feedback signals indicating received WT uplink signals. The components 1802, 1804 are connected by a bus 1822 to an I/O interface 1824, a processor 1826, such as a CPU, and a memory 1828. I/O interface 1824 connects the base station 1800 to the internet and to other network nodes, e.g., routers, other base stations, AAA nodes, etc. Memory 1828 includes routines 1830 and data/information 1832. The processor 1826 executes the routines 1830 and uses the data/information 1832 in memory 1828 to cause the base station 1800 to operate in accordance with the invention.

Routines 1830 includes communications routines 1834 used to control the base station 1800 to perform various communications operations and implement various communications protocols. Routines 1830 also includes base station control routines 1836 that are used to control the base station 1800 to implement the steps of the method of the present invention. Base station control routines 1836 include a scheduling component 1838 that is used to control transmission scheduling and/or communication resource allocation, e.g., assignment of uplink and downlink segments to WTs. In some embodiments, base station control routines 1836 also includes components such as a channel estimation boundary switching component 1812 and multiple receive antennas (1806, 1808), a receiver antenna switching control component 1840. In some embodiments, base station control routines 1836 also includes components such as switching component 1820 and multiple transmit antennas (1814, 1816), a transmitter antenna switching control component 1842. The switching device 1812 in the receiver chain 1810 and 1820 in the transmitter chain 1818, when implemented, are responsive to signals generated by the processor 1826 when operating under the direction of these components (1840, 1842), respectively. The control signal effects switching between the antennas or antenna elements in accordance with the present invention. The receiver antenna switching control module 1840 may use the data/information 1832 including uplink quality indication feedback information 1858, received uplink signaling channel estimation information 1868, and receiver antenna switching information 1874 in deciding antenna switching. The data/information 1832 that may be used by the transmitter antenna switching control module 1842 in determining antenna switching includes received downlink channel feedback report information 1859, and transmitter antenna switching information 1876.

Base station control routines 1836 also includes an uplink channel feedback module 1844 that controls the evaluation of received uplink signals, the generation and transmission of channel quality indication feedback signals, such as feedback messages 1864, including WT power control feedback information 1860 and transmission acknowledgement/negative acknowledgement (ack/nack) feedback information 1862 indicating the success or failure of the uplink signal or signals.

Memory 1828 also includes data/information 1832 used by communications routines 1834 and control routines 1836. Data/information 1832 includes WT data/information 1846 and system information 1848. WT data/information 1846 includes multiple sets of WT information (WT1 data/information 1850, WT N data/information 1852). WT1 data/information 1850 includes user/device/session/resource information 1854, timing synchronization information 1856, uplink quality indication feedback message information 1858, and received downlink channel feedback report information 1859. User/device/session/resource information 1854 includes user/device identification information, session information such as peer node information and routing information, and resource information such as uplink and downlink traffic channel segments assigned to WT1 by scheduling component 1838. Timing synchronization information 1856 includes information to synchronize WT1 timing with respect to BS timing, e.g., adjustment information to compensate for propagation delay. Uplink quality indication feedback message information 1858 includes WT power control information 1860, ack/nack information 1862, and feedback messages 1864. Received downlink channel feedback report information 1859 comprises information derived from received downlink channel feedback reports transmitted by WT1 in response to downlink pilot broadcast signals transmitted by BS 1800. System information 1848 includes received uplink signaling channel estimate information 1868, CDMA information 1870, OFDM information 1872, optional receiver antenna switching information 1874, and optional transmitter antenna switching information 1876. Received uplink signaling channel estimate information 1868 includes sets of channel estimate information (channel estimate 1 information 1878, channel estimate N information 1880), each channel estimate corresponding to a channel estimate of uplink signaling received from a WT using one antenna or antenna element. Information from channel estimates 1878, 1880 is associated with a particular WT and then processed, stored, e.g., in WT power control information 1860 and ack/nack information 1862. Information 1868 also includes channel boundary information 1882 and estimate reset information 1884. The time identified by channel boundary information 1882 defines the time at which the BS switches between intervals associated with multiple different channel estimates for the same WT, e.g., different channel estimates associated with different WT transmitter antenna elements. Estimate reset information 1884 includes information identifying times at which channel estimates are reinitialized, e.g., channel boundaries at which channel estimation filters are cleared and restarted.

CDMA information 1870 includes carrier frequency information, bandwidth information, CDMA timing synchronization information, and codeword information, and OFDM information 1872 includes OFDM timing information, dwell information including dwell boundary information, audio information, and frequency hopping information. In some embodiments, BS 1800 supports either CDMA communications or OFDM communications 1872, but is unable to support both communications, in which case BS 1800 includes CDMA information 1870 or OFDM information 1872.

Receiver antenna switching information 1874 includes information such as switching criteria, predetermined switching sequences, antenna element usage information, and antenna element control information used by receiver antenna switching control component 1440. Transmitter antenna switching information 1876 includes information such as switching criteria, predetermined switching sequences, antenna element usage information, and antenna element control information used by transmitter antenna switching control module 1842.

FIG. 16 illustrates another exemplary base station, access node 1900, implemented in accordance with the invention. The BS1900 may be any one of the exemplary BSs (12, 12') of fig. 13. The BS1900 includes a receiver chain/antenna module 1902 and a transmitter chain/antenna module 1904. Receiver chain/antenna assembly 1906 includes a receive antenna 11906 and a receive chain 1908. Receiver chain antenna assembly 1906 receives uplink signals from different transmit antennas or antenna elements of the same WT, the signals including different tone subsets, and the signals being transmitted simultaneously from the same WT. In some embodiments, e.g., with a controllable baseband transmitter unit 1914, the BS1900 includes multiple transmitter chains/antennas (1904, 1904'); component 1904 includes a transmit chain 11912 connected to a transmit antenna or antenna element 11910, while component 1904 ' includes a transmit chain N1912 ' connected to a transmit antenna or antenna element N1910 '. In accordance with the present invention, the use of multiple transmitter chains/antenna assemblies 1904, 1904' with subsets of tones or tones being transmitted by different antennas or antenna elements at the same time is used to obtain diversity. Transmitter chain/antenna assembly 11904 includes a transmit antenna 1910 coupled to a transmit chain 1912. Similarly, transmitter chain/antenna module N1904 ' includes a transmit antenna 1910 ' connected to a transmitter chain 1912 '. The transmitter chains 1912, 1912' are connected to a controllable baseband transmitter unit 1914. The receiver assembly 1902, the optional controllable baseband transmitter unit 1914, the processor 1916, e.g., CPU, the I/O interface 1918, and the memory 1920 are coupled together via a bus 1922 over which the various elements may exchange data and information. In some embodiments without controllable baseband transmitter unit 1914, transmitter chain/antenna module 1904 is connected to bus 1922. The I/O interface 1918 connects the BS1900 to the Internet and other network nodes, e.g., other BSs 1900, AAA nodes, home agent nodes, routers, etc. Memory 1920 includes programs 1924 and data/information 1926.

The processor 1916, which is controlled by one or more programs 1924 stored in memory 1920, uses the data/information 1926 and causes the base station 1900 to operate in accordance with the methods of the present invention. Routines 1924 include communications routines 1928 and base station control routines 1930. Communications routine 1928 performs various communications protocols and functions used by BS 1900. Base station control routines 1930 are responsible for ensuring that base station 1900 operates in accordance with the methods of the present invention.

Base station control routines 1930 include a scheduling component 1932 and an uplink channel feedback component 1936. In some embodiments, such as those incorporating a controllable baseband transmitter unit 1914 and transmitter chain/antenna module 1904', the base station control routines 1930 also include a frequency transmission division control module 1934. A scheduling component 1932, e.g., scheduler, schedules air link resources, e.g., uplink and downlink segments, to WTs.

The frequency transmission division control module 1934, when implemented, controls the operation of the controllable baseband transmitter unit 1914 to divide the frequency, e.g., into groups of tones for transmission, such that a first subset of tones is used to transmit some information to the transmitter link antenna module 11904, and a second subset of tones is used to transmit some information to the transmitter link/antenna module N1904', the first and second subsets of tones differing from each other by at least one tone. In some embodiments, more than two antennas or antenna elements are used to transmit simultaneously, with more than two tone subsets being transmitted simultaneously, e.g., one tone subset corresponding to each antenna or antenna element being used simultaneously. In some embodiments, different subsets of tones associated with different transmitter chains/antennas are mutually exclusive. In some embodiments, there is a partial overlap between the audio subsets. In accordance with the present invention, BS1900 may simultaneously transmit first and second sets of tones, the first set of tones being carried by a first communication channel from antenna 11910 to a WT, and the second set of tones being carried by a second communication channel from antenna N1910' to the same WT. The crossover control component 1934 includes a distribution subcomponent 1938 that distributes audio from a group of tones to a plurality of different tone subsets, including at least first and second tone subsets, each of which differ from one another by at least one tone. The crossover control component 1934 also includes a transmit subcomponent used to control the transmission of the selected subset of audio.

Assignment subcomponent 1938 uses data/information 1926 to determine and assign tones into tone subsets (tone subset 1 information-interval 11974, tone subset N information-interval 11976, tone subset 1 information-interval M1978, tone subset N information-interval M1980), where data/information 1926 includes predetermined switching sequence information 1988, switching criteria information 1986, received downlink channel report feedback information 1958, tone group information 1970, and/or hopping information 1972. Distribution subassembly 1938 also generates and stores antenna element control information (antenna element 1 switching control information 1992, antenna element N switching control information 1994). The transmit subassembly 1940 uses data/information 1926 to implement the decision of the distribution module and control the operation of the controllable baseband transmitter unit 1914, where the data/information 1926 includes the tone subset (1974, 1976, 1978, 1980), OFDM timing information 1948, and antenna element switching control information (1992, 1993).

Uplink channel feedback module 1936 estimates and processes received uplink signaling to obtain WT power control information 1960 and ack/nack information 1962. From information 1960, 1962, uplink channel feedback module 1936 generates a feedback message 1964 and then sends to WTs for making decisions regarding tone splitting between WT transmit antennas or antenna elements.

Data/information 1926 includes WT data/information 1942, uplink audio information 1944, downlink OFDM audio information 1946, and OFDM timing information 1948. In some embodiments, such as embodiments that include a frequency transmission division control component 1934, the data/information 1926 also includes frequency division information 1950.

WT data/information 1942 includes multiple sets of data/information (WT1 data/information 1951, WTN data/information 1952). WT1 data/information 1951 includes user/device/session/resource information 1953, timing synchronization information 1954, uplink quality indication feedback message information 1956, and received downlink channel feedback report information 1958. User/device/session/resource information 1953 includes user/device identification information, session information including peer node identification and routing information, and resource information including uplink and downlink portions assigned by BS1900 to WT 1.

Timing synchronization information 1954 includes information used to synchronize WT1 and BS1900, e.g., to account for delay propagation.

Uplink quality indication feedback message information 1956 includes WT power control information 1960, e.g., power level of received WT1 uplink signals, SNR values, WT1 transmit power adjust signals, etc., information indicating uplink channel quality; also included are, e.g., acknowledgement/negative acknowledgement (ack/nak) signal information 1962 indicating success or failure of reception of one or more uplink signals transmitted by WT1, and feedback messages, e.g., messages containing information from 1960 and/or 1962 and communicated to WT 1.

Received downlink channel feedback report information 1958 includes information from WT feedback reports, e.g., return reports of downlink channel quality in terms of power level, SNR, etc., based on received pilot signals. The received downlink channel feedback report information also includes ack/nack signal information, e.g., downlink traffic channel signals, transmitted by WTs 1 in response to downlink signals. In some embodiments, the information 1958 is used by a distribution subcomponent 1938 in the crossover control component 1934 when making decisions regarding tone splitting.

Uplink tone information 1944 includes tone group information 1944, e.g., for uplink signaling from WTs to BS1900, and hopping sequence information, e.g., the uplink hopping sequence used by WTs, which hopping changes between dwells.

The downlink OFDM tone information 1946 includes tone group information 1970 such as a group of tones used by the BS for downlink signaling, and tone hopping information 1972 such as a tone hopping sequence of tone mapping on an OFDM symbol time basis. In some embodiments, e.g., with frequency transmission division control component 1934, OFDM information 1946 also includes a variety of audio subsets (audio subset 1 information-interval 11974, audio subset N information-interval 11976, audio subset 1 information-interval M1978, audio subset N information-interval M1980). According to the invention, each audio subset of the information (1974, 1976) is associated with a different transmitter chain/antenna (1904, 1904'), and the audio subsets (1974, 1976) are to be transmitted simultaneously. Similarly, according to the invention, each audio subset of the information (1978, 1980) is associated with a different transmitter chain/antenna (1904, 1904'), and the audio subsets (1978, 1980) are to be transmitted simultaneously. The weighting of the audio, e.g., the number of audios associated with each subset, can change over time. For example, during interval 1, tone subset 1 associated with transmitter chain/antenna 1 may use 6 tones, and tone subset 2 associated with transmitter chain/antenna 2 may also use 6 tones; but during the immediately following interval tone subset 1 associated with transmitter chain/antenna 1 may use 7 tones and tone subset 2 associated with transmitter chain 2/antenna 2 may use 5 tones. In addition, the tone groups may hop according to a downlink hopping sequence from OFDM symbol transmission time interval to OFDM symbol transmission time interval.

OFDM timing information 1948 includes symbol timing information 1982 and dwell information 1984. Symbol timing information 1982 includes information defining the timing of transmission of a single OFDM symbol that includes multiple tones that are transmitted simultaneously. Dwell information 1984 includes information identifying a number, e.g., 7, consecutive OFDM symbols, where the mapping of uplink tones from logical to physical tones does not change during dwell; the audio makes different transitions from dwell to dwell. Dwell information 1984 also includes information identifying dwell boundaries.

In some embodiments, the frequency division is based on a predetermined reference, e.g., the tones are divided among multiple transmitter chains/antenna assemblies (1904, 1904'), e.g., in alternating order with respect to physical index. In other embodiments, the weighting between different transmitter chain/antenna elements (1904, 1904') is varied as a function of the switching criteria information 1986 in the received downlink channel feedback report information 1958 and the frequency division information 1950. For example, if the BS1900 includes first and second transmitter chains/antenna elements 1904 and 1904 'and the feedback information shows that the channel quality is substantially the same, e.g., the difference between the channel qualities is less than a first criterion level, then the audio may be divided evenly between the two elements 1904, 1904'. However, if the same exemplary BS1900 determines that the channel quality for the transmitter link/antenna element 1904 is significantly better than the channel quality for the transmitter link/antenna element 1904 ', but that the channel quality for both channels is still acceptable based on the feedback information and comparison to the second and third standard levels, the crossover control component 1934 can control the baseband transmitter unit 1914 to occupy more audio, e.g., twice as much audio dedicated to the component 1904 as the component 1904'.

The frequency division information 1950 includes switching standard information 1986, predetermined switching sequence information 1988, antenna element usage information 1990, and multi-group antenna element switching control information (antenna element 1 switching control information 1992, antenna element N switching control information 1994). The switching criteria information 1986 includes threshold limits that are used by the assignment subcomponent 1938 to evaluate antenna element feedback information derived from or contained in the received downlink channel feedback information 1958 in order to decide whether, when, and to what extent to change the balance of tone splitting among the various transmitter chains/antennas (1904, 1904'). Predetermined switching sequence information 1988 includes a variety of predetermined sequences from which assignment subassembly 1938 may select. For example, the first predetermined order may alternate between two divisions, e.g., every or some fixed number of OFDM symbol transmission time intervals: (i) the uplink audio is split between the first transmitter link/antenna and the second transmitter link/antenna by 50-50, and (ii) the uplink audio is split between the first transmitter link/antenna and the second transmitter link/antenna by 60-40; for example, the second predetermined order may alternate between two division modes: (i) the uplink audio is split between the first transmitter chain/antenna and the second transmitter chain/antenna by 50-50, and (ii) the uplink audio is split between the first transmitter chain/antenna and the second transmitter chain/antenna by 40-60. In some embodiments, BS1900 will follow a predetermined switching sequence without changing as a function of feedback information, e.g., a fixed predetermined sequence that may result in equal or nearly equal frequency division in time between transmitter chains/antennas (1904, 1904'). The antenna element usage information 1990 includes information identifying the usage of each antenna element (1910, 1910'), e.g., in terms of the number of tones of the assigned tone subset relative to the tone group or relative to other tone subsets to be simultaneously transmitted on different transmit antenna elements. The antenna element switching control information (antenna element 1 switching control information 1992, antenna element N switching control information 1994) includes information such as the number of tones, the index or frequency of the assigned tones respectively associated with the antenna elements (1, N). Information 1992, 1994 is used by the controllable baseband transmitter unit 1914.

Figure 17 illustrates an exemplary Wireless Terminal (WT)1500, e.g., Mobile Node (MN), implemented in accordance with the invention. In accordance with the present invention, exemplary WT 1500 may switch between multiple transmit antennas or antenna elements on dwell boundaries, but may not switch between antennas or antenna elements. MN 1500 may be any of the exemplary MNs (14, 16, 14 ', 16') of fig. 13. Exemplary WT 1500 may be used in conjunction with exemplary BS 1400 of fig. 14. The mobile node 1500 may act as a Mobile Terminal (MT). The mobile node 1500 includes a receiver chain/antenna assembly 1502 and a transmitter chain/antenna assembly 1504 that can be implemented as shown in fig. 8 and 3, respectively. According to the invention, a single transmitter chain 1518 and transmit antenna switching is used to obtain diversity. The receiver chain/antenna assembly 1502 includes a receive antenna 11502 and a receive chain 1510. In some embodiments, receiver chain/antenna assembly 1502 includes multiple antennas or multiple antenna elements (receive antenna 11506, receive antenna N1508), and receiver chain 1510 includes controllable switching assembly 1512, e.g., switching circuitry. The transmitter chain/antenna assembly 1504 includes multiple antennas or multiple antenna elements (transmit antenna 11514, transmit antenna N1516) and a single transmitter chain 1518 that includes a controllable dwell boundary switching assembly 1520. In some embodiments, the multiple transmit antennas or antenna elements (1514, 1516) are positioned in different directions. In some embodiments, the plurality of different antennas or antenna elements (1514, 1516) are spaced apart such that different communication paths exist between the antennas or antenna elements and the base station. In some embodiments, the spacing between the antennas or antenna elements is at least 1/4 of the lowest frequency audio wavelength transmitted from the antennas or antenna elements. The receiver component 1502, transmitter component 1504, processor 1522, e.g., CPU, user I/O devices 1524, and memory 1526 are connected together via a bus 1528 over which the various elements can exchange data and information. Memory 1526 includes programs 1530 and data/information 1532.

The downlink signals received by the receiver chain/antenna assembly 1502 through the base stations include feedback signals such as quality indicator signals that identify the quality of the uplink signals. The uplink signals transmitted by the transmitter chain/antenna assembly 1504 comprise uplink communication channel signals to a base station and are transmitted using a plurality of transmit antennas or antenna assemblies (1514, 1516), wherein, in accordance with the present invention, one of the plurality of antennas is coupled to a single transmitter chain 1518 for any given dwell.

Processor 1522 executes programming 1530 and uses data/information 1532 in memory 1526 to control the operation of WT 1500 and implement the methods of the present invention. User I/O devices 1524, e.g., display, speaker, microphone, keyboard, keypad, mouse, etc., allow a user of WT 1500 to input user data and information intended for a peer node and to output user data and information from a peer node.

Routines 1530 include communications routines 1534 and mobile node control routines 1536. Mobile node control routines 1536 include a transmitter antenna switching control component 1538 and an uplink channel feedback component 1540. In some embodiments, e.g., including multiple receiver antennas 1506, 1508, and switching module 1512, mobile node control routines 1536 also includes a receiver antenna switching control module 1542.

Data/information 1532 includes user/device/resource information 1544, uplink channel condition feedback information 1546 acquired from the base station, and dwell information 1548. User/device/session/resource information 1544 includes information regarding communication sessions between WT 1500 and peer nodes, e.g., routing information, identification information, assigned communication channel segment information, etc.

The uplink channel condition feedback information from base station 1546 includes received quality indication signal information 1550 and sets of antenna feedback information (antenna element 1 feedback information 1556, antenna element N feedback information 1558). The base station receiving the uplink signal from WT 1500 determines the quality of the received uplink signal and then transmits a feedback signal indicating the reception quality to WT 1500. Reception quality indication signal information 1550 is the information carried by those feedback signals and includes transmit power control signal information 1552 and transmit acknowledgement signal information 1554. Transmit power control signal information 1552 may include information indicating changes in power level, relative power level, signal-to-noise ratio, and associated power level. The transmission acknowledgement signal information 1554 may include information indicating the success or failure of the reception of the transmitted one or more uplink signals, such as represented by positive/negative or statistical information on positive/negative.

The base station need not know, and in many embodiments does not know, when WT 1500 switches between multiple transmit antennas and/or WT 1500 switches. WT 1500 may use its knowledge of which WT transmit antenna (1514, 1516) WT 1500 uses for particular dwells to correlate received feedback information, e.g., ack/nack received with a particular antenna, to form and maintain multiple sets of feedback information for the antennas (antenna element 1 feedback information 1556, antenna element N feedback information 1558). In some embodiments, the base station knows that WT 1500 uses different transmit antennas (1514, 1516) and that the BS can maintain different sets of feedback information and send these sets of information to WT 1500 and store as antenna element feedback sets (antenna element 1 feedback information 1556, antenna element N feedback information 1558) without WT 1500 having to do the correlation.

The latching information 1548 includes latching characteristic information 1560 and latching switch information 1562. Dwell signature information includes a specific number, e.g., 7, OFDM symbol transmission time periods within each dwell 1564, dwell boundary information 1566, audio information 1568, and audio hopping sequence information 1574. Dwell boundary information 1566, which includes timing information used by WT 1500 to distinguish when a dwell ends and the next dwell begins, is used to control switching between transmit antennas (1514, 1516) so that antenna switching is performed over at least several dwell boundaries, but not between boundaries. Audio information 1568 includes dwell index N information 1570 and dwell indication N +1 information 1572. Dwell index N info 1570 includes a set of tones used by WT 1500 to transmit uplink signals to the base station during a first dwell, and dwell N +1 info 1572 includes a set of tones used by WT 1500 to transmit uplink signals to the base station during a second dwell, which is a dwell consecutively following the first dwell. Tone hopping sequence information 1574 includes information defining the hopping sequence from logical to physical tone used by WT 1500 in uplink signaling and is therefore used to determine dwell index N information 1570 and dwell index N +1 information 1572.

The locking switching information 1562 includes switching standard information 1576, predetermined switching order information 1578, antenna element usage information 1580, and multiple antenna element switching control information (antenna element 1 switching control information 1582, antenna element N switching control information 1584). The switching criteria information 1576 includes information identifying the switching methods and constraints used to determine the dwell boundary between the transmit antennas (1514, 1516). For example, the handover criteria information 1576 may include threshold limits for the received feedback quality level to determine handover. For example, one criterion may be a ratio of the positive/negative number corresponding to one antenna, triggering a switch to a different antenna element if exceeded, or for triggering a different proportion of the number of dwells assigned to a first antenna with respect to the number of dwells assigned to a second transmit antenna within a given time or a given number of dwells. Predetermined switching order information 1578 includes information identifying a predetermined dwell boundary switching order that may be used. For example, one exemplary sequence may connect a single transmit chain 1518 to one of multiple antennas, e.g., antenna 1514, through a fixed number of successive dwells, then switch to the other transmit antenna, e.g., antenna 1516, then dwell there for the same number of successive dwells, then repeat the process, alternating between each transmit antenna (1514, 1516), resulting in equal transmit antenna usage. The method can be extended to more than two antennas where the use of transmit antennas is equal between each antenna. In some embodiments, received quality indication signal information 1550 is not necessary or used by WT 1500 to perform a dwell switch when operating on a fixed predetermined switching sequence, e.g., WT 1500 follows a predetermined dwell boundary switching sequence regardless of variations in channel quality between different antennas (1514, 1516). In other embodiments, the predetermined switching order is used in conjunction with uplink channel condition feedback information from the BS 1546. For example, a different predetermined switching order from information 1578 may be selected based on quality feedback information, such as a particular predetermined order of favoring or dropping a transmit antenna. Alternatively, in some embodiments, a predetermined switching sequence is initially and/or intermittently used to estimate the different channel qualities, such that the dwell boundary switching is based on uplink channel quality feedback information. In some embodiments, a predetermined switching sequence is not used and dwell boundary switching is performed as a function of uplink channel quality. The antenna utilization information 1580 includes information identifying the current usage of each transmit antenna (1514, 1516), e.g., information in terms of time and/or number of dwells relative to other transmit antennas, and changes in antenna usage to be performed.

WT 1500 stores different sets of switching control information (antenna element 1 switching control information 1582, antenna element N switching control information 1584) corresponding to different sets of antenna feedback information (antenna element 1 feedback information 1556, antenna element N feedback information 1558).

In some embodiments, the previously described data/information 1532 may be used to select one or more channels from among the channels established in accordance with the present invention, the selected one or more channels being used more than other channels having lower channel quality.

Communications routines 1534 implement the various communications protocols used by WT 1500. The functionality of the WTs controlled by mobile node control program 1536 includes the operation of receiver assembly 1502, transmitter assembly 1504, and user I/O devices 1524, and the implementation of the methods of the present invention, including the processing of feedback information indicative of uplink signaling in accordance with the present invention, and the implementation and control of dwell boundary switching for a single transmitter link 1518 between different antennas or antenna elements (1514, 1516).

Transmitter antenna switching control component 1538 uses data/information 1532 to implement a dwell boundary switching method that includes a decision of: the use of antennas, the order, changes in the order, and changes caused by quality feedback information. For example, if the channel quality corresponding to antenna 11514 is determined by WT 1500 to be higher than the channel quality corresponding to antenna N1516, transmitter antenna switching control component 1538 can in some embodiments select to use antenna N1516 for three dwells using antenna 11514 and one dwell for every four consecutive dwells. Transmitter antenna switching control element 1538 also controls the operation of dwell boundary switching element 1520, e.g., by controlling the selected signal to effect the switching decision.

The uplink channel feedback component 1540 controls the processing of the received feedback signal and extracts the transmit power control signal information 1552 and/or the transmit acknowledgement signal information 1554 therefrom. Uplink channel feedback module 1540 can also use its knowledge of which dwell is associated with which WT transmit antenna to split received feedback information 1550 into sets of information associated with different antennas (antenna element 1 feedback information 1556, antenna element N feedback information 1558). The output information obtained from the uplink feedback component 1540 may be used as an input to a transmitter antenna switching control component 1538, where this component 1538 is used to implement the dwell switching decision.

Optional receiver antenna switching control module 1542 is implemented to control switching of receive link switching control module 1512, connecting one of multiple receive antennas or antenna elements (1506, 1508) to a single receive link 1510 at any one time. Receive antenna switch control module 1542 sends control selection signals to switch module 1512 to control the selection of the antenna. Receiver antenna switching control component 1542 may provide receive diversity by selecting between antennas 1506, 1508. With regard to the handoff decision methodology, a variety of implementations are possible, such as periodic switching between antennas (1506, 1508) and/or switching based on the quality of the received downlink signal, such as testing each channel and locking the antenna that produces the best quality downlink channel.

Figure 18 illustrates another exemplary Wireless Terminal (WT)1600, e.g., mobile node, implemented in accordance with the invention. In accordance with the present invention, exemplary WT 1600 may switch between multiple transmit antennas or antenna elements on signal boundaries corresponding to base station channel estimation signal boundaries, but may not switch between antennas and antenna elements. MN 1600 may be any of the exemplary MNs (14, 16, 14 ', 16') of fig. 13. The exemplary WT 1600 may be used in conjunction with the exemplary BS 1800 of fig. 15. The mobile node 1600 may act as a Mobile Terminal (MT). Mobile node 1600 includes a receiver chain/antenna assembly 1602 and a transmitter chain/antenna assembly 1604. The receiver chain/antenna module 1802 may be implemented similarly or identically to that shown in fig. 8. The transmitter chain/antenna module 1804 may be implemented similarly to that shown in fig. 3, but with the switching control being accompanied by the functionality of channel estimation boundary information and/or uplink channel estimation feedback information. A single transmitter chain 1618 and transmit antenna switching is used to acquire diversity in accordance with the present invention. Receiver chain/antenna assembly 1602 includes a receive antenna 11602 and a receive chain 1610. In some embodiments, receiver chain/antenna assembly 1602 includes multiple antennas or multiple antenna elements (receive antennas 11606.., receive antenna N1608), and receiver chain 1610 includes a controllable switching assembly 1612, e.g., switching circuitry. Transmitter chain/antenna assembly 1604 includes multiple antennas or multiple antenna elements (transmit antenna 11614, transmit antenna N1616) and a single transmitter chain 1618 that includes a controllable channel estimation boundary switching assembly 1520. In some embodiments, the multiple transmit antennas or antenna elements (1514, 1516) are positioned in different directions. In some embodiments, the plurality of different antennas or antenna elements (1614, 1616) are spaced apart such that different communication paths exist between the antennas or antenna elements and the base station. In some embodiments, the spacing between the antennas or antenna elements is at least 1/4 of the lowest frequency audio wavelength transmitted from the antennas or antenna elements. The receiver component 1602, transmitter component 1604, processor 1622, e.g., CPU, user I/O device 1624, and memory 1626 are connected together via a bus 1628 over which the various elements may exchange data and information. Memory 1626 includes programs 1630 and data/information 1632.

The downlink signals received by receiver chain/antenna assembly 1602 through the base station include feedback signals such as quality indicator signals that identify the quality of the uplink signals. The uplink signals transmitted by transmitter chain/antenna assembly 1604, comprise the uplink communication channel signals to the base station, and are transmitted using a plurality of transmit antennas or antenna assemblies (1614, 1616), wherein, in accordance with the present invention, one of the plurality of antennas is connected to a single transmitter chain 1618 for any given dwell.

Processor 1622 executes the programs 1630 and uses the data/information 1632 in memory 1626 to control the operation of the WT 1600 and implement methods of the present invention. User I/O devices 1624, e.g., display, speaker, microphone, keyboard, keypad, mouse, etc., allow the user of WT 1600 to enter user data and information intended for a peer node and to output user data and information from a peer node.

Programs 1630 include communications programs 1634 and mobile node control programs 1636. The mobile node control program 1636 includes a transmitter antenna switching control component 1638 and an uplink channel feedback component 1640. In some embodiments, e.g., including multiple receiver antennas 1606, 1608 and switching component 1612, mobile node control routines 1636 also include a receiver antenna switching control component 1642.

Data/information 1632 includes user/device/session/resource information 1644, uplink channel condition feedback information 1646 obtained from the base station, and dwell information 1648. User/device/session/resource information 1644 includes information regarding communication sessions between WT 1600 and peer nodes, e.g., routing information, identification information, assigned communication channel segment information, etc.

The uplink channel condition feedback information from base station 1646 includes received quality indication signal information 1652 and sets of antenna feedback information (antenna element 1 feedback information 1658, antenna element N feedback information 1660). The base station receiving the uplink signal from WT 1600 determines the quality of the received uplink signal and then transmits a feedback signal indicating the reception quality to WT 1600. Received quality indication signal information 1652 is the information carried by those feedback signals and includes transmit power control signal information 1654 and transmit acknowledgement signal information 1656. Transmit power control signal information 1654 may include information indicating changes in power levels, relative power levels, signal-to-noise ratios, and associated power levels. Transmission acknowledgement signal information 1656 may include information indicating the success or failure of the reception of one or more transmitted uplink signals, such as indicated by positive/negative or statistical information on positive/negative.

The base station need not know, and in many embodiments does not know, when WT 1500 switches between multiple transmit antennas and/or WT 1600 switches. However, the WT 1600 tracks the channel estimation interval used by the base station and it appears on the channel estimation boundary when a switch between transmit antennas occurs. For example, the base station may perform 1 channel estimation for a fixed amount of time, then re-initialize the channel estimation and start over; WT 1600 may select a time corresponding to a re-initialization point to switch antennas. WT 1600 may use its knowledge of which WT transmit antennas (1614, 1616) WT 1600 is using for spacing corresponding to channel estimation, to correlate received feedback information, e.g., ack/nack received with a particular antenna, to form and maintain multiple sets of feedback information for the antennas (antenna element 1 feedback information 1658, antenna element N feedback information 1660). In some embodiments, the base station maintains different ongoing channel quality estimates, e.g., one for each transmit antenna (1614, 1616), and then the base station cooperates with the WT transmit antenna switching to alternate between these ongoing channel estimates. This implementation is useful for WTs 1600 having a fixed number of transmit antennas (1614, 1616) operating on a predetermined periodic sequence, e.g., the predetermined sequence being used for equalization between each antenna. In some embodiments, the base station knows that WT 1600 is using different transmit antennas (1614, 1616), and the BS may maintain different sets of feedback information and send these sets of information to WT 1600 and store as antenna element feedback sets (antenna element 1 feedback information 1658, antenna element N feedback information 1660) without WT 1600 having to perform correlation operations.

Channel estimate interval information 1648 includes timing information and signal type information 1664 corresponding to base station channel estimate boundary 1662. Timing information 1662 correlates base station uplink signal channel estimation cycles and intervals to WT timing, which can control antenna switching during times corresponding to channel estimation boundaries to help avoid degradation of the base station channel estimation by mixing of uplink signals from two different transmit antennas (1614, 1616). The signal type information includes type selection 1666, Code Division Multiple Access (CDMA) information 1668, and Orthogonal Frequency Division Multiplexing (OFDM) information 1670. Type selection 1666 includes user or service provider selection of the type of communications signaling to be used between WT 1600 and base station, e.g., CDMA signaling or OFDM signaling. As a function of this selection, different circuits are activated within WT 1600. CDMA information 1668 includes the carrier frequency used, the bandwidth, the codeword, and the channel estimation interval. OFDM information 1670 may include information identifying a dwell interval with a number of consecutive OFDM symbol transmission time periods, information identifying dwell boundaries, tone information including tones used in a given dwell, and tone hopping sequence information. In some embodiments, WTs 1600 support one type of signaling and not the other, in which case WTs 1600 would include one set of information 1668 or 1670.

Channel estimation boundary switching information 1650 includes switching criteria information 1672, predetermined switching order information 1674, antenna element usage information 1676, and multiple sets of antenna element switching control information (antenna element 1 switching control information 1678, antenna element N switching control information 1680). The switching criteria information 1672 includes information identifying methods and restrictions for determining channel boundary switching between transmit antennas (1614, 1616). For example, the handover criteria 1672 may include a quality level of feedback for reception to determine a threshold limit for handover. For example, one criterion may be a minimum value of the filtered SNR, which if exceeded triggers a switch to a different antenna element. Predetermined switching order information 1674 includes information identifying a predetermined channel estimation boundary switching order that may be used. For example, one exemplary sequence may connect a single transmit chain 1618 to one antenna, e.g., antenna 1614, through a fixed number of consecutive channel estimates, then switch to another transmit antenna, e.g., antenna 1616, then dwell there for the same number of consecutive channel estimates, then repeat the process, alternating between each transmit antenna (1614, 1616), resulting in equal transmit antenna usage. The method can be extended to more than two antennas where the use of transmit antennas is equal between each antenna. In some embodiments, received quality indication signal information 1652 is unnecessary or unused for WT 1600 to perform channel estimation boundary switching when operating on a fixed predetermined switching sequence, e.g., WT 1600 follows a predetermined dwell boundary switching sequence independent of variations in channel quality between different antennas (1614, 1616); however, WT 1600 needs to maintain synchronization between the channel estimation performed by the base station on the uplink signaling and the switch points. In other embodiments, the predetermined switching sequence is used in conjunction with uplink channel condition feedback information from BS 1646. For example, a different predetermined switching order from information 1674 may be selected based on the quality feedback information, such as a particular predetermined order of favoring or dropping one transmit antenna. Alternatively, in some embodiments, a predetermined switching sequence is initially or intermittently used to estimate the different channel qualities, such that the dwell boundary switching is based on uplink channel quality feedback information. In some embodiments, a predetermined switching sequence is not used and dwell boundary switching is performed as a function of uplink channel quality. Antenna utilization information 1676 includes information identifying the current usage of each transmit antenna (1614, 1616), such as information in terms of time or duty cycle relative to other transmit antennas, and changes in antenna usage to be performed.

WT 1600 maintains different sets of switching control information (antenna element 1 switching control information 1678, antenna element N switching control information 1680) corresponding to different sets of antenna feedback information (antenna element 1 feedback information 1658, antenna element N feedback information 1660).

Communications routines 1634 implement the various communications protocols used by WT 1600. The functionality of the WTs controlled by mobile node control program 1636 includes the operation of receiver components 1602, transmitter components 1604, user I/O devices 1624, and the implementation of the methods of the present invention, including the processing of feedback information indicative of uplink signaling in accordance with the present invention, and the implementation and control of channel estimation boundary switching for a single transmitter link 1618 between different antennas or antenna elements (1614, 1616).

Transmitter antenna switching control component 1638 uses data/information 1632 to implement a channel estimation boundary switching method that includes a decision to: the use of antennas, the order, changes in the order, and changes caused by quality feedback information. Transmitter antenna switching control component 1638 controls the operation of channel estimation boundary switching component 1618, e.g., via a control select signal, to implement the switching decision. Uplink channel feedback component 1640 controls processing of received feedback signals from which transmit power control signal information 1654 and/or transmit acknowledgement signal information 1656 are extracted. Uplink channel feedback module 1640 can also use its knowledge of which channel estimates are associated with which WT transmit antenna to split received feedback information 1652 into sets of information associated with different antennas (antenna element 1 feedback information 1658, antenna element N feedback information 1660). In some embodiments, the base station sends different channel estimate reports for each antenna (1614, 1616) to WT 1600, and the uplink channel feedback component may then store this information in the appropriate set of feedback information (1658, 1660). The output information obtained from the uplink feedback component 1640 is available as an input to a transmitter antenna switching control component 1638, where this component 1638 is used to implement channel estimation boundary switching decisions.

Optional receiver antenna switching control component 1642 is employed, when implemented, to control the switching of receive link switching control component 1612 to connect one of multiple receive antennas or antenna elements (1606, 1608) to a single receive link 1610 at any time. Receive antenna switch control component 1642 sends control select signals to switch component 1612 to control selection of antennas. Receiver antenna switching control component 1642 may provide receive diversity by selecting between antennas (1606, 1608). With regard to the handoff decision methodology, a variety of implementations are possible, such as periodic switching between antennas (1606, 1608) and/or switching based on the quality of the received downlink signal, such as testing each channel and locking the antenna that produces the best quality downlink channel.

Figure 19 illustrates another exemplary Wireless Terminal (WT)1700, e.g., Mobile Node (MN), implemented in accordance with the present invention. MN 1700 may be any of the exemplary MNs (14, 16, 14 ', 16') of fig. 13. Exemplary WT1700 may be used in conjunction with exemplary BS1900 of fig. 16. Mobile node 1700 may act as a Mobile Terminal (MT). Mobile node 1700 includes a receiver chain/antenna assembly 1702 and a plurality of transmitter chain/antenna assemblies (1704, 1704') with controllable baseband transmitter units 1718. The plurality of transmitter chains/antenna elements (1704, 1704') with controllable baseband transmitter unit 1718 may be implemented similarly or identically to any of the embodiments of fig. 27, 28 or 29. Receiver chain/antenna assembly 1702 includes a receive antenna 11706 and a receiver chain 1710. In some embodiments, receiver component 1702 includes multiple receive antennas or antenna elements (receive antenna 11706, receive antenna N1708) and a controllable switching component 1712, e.g., switching circuitry. Diversity is achieved in accordance with the present invention using multiple transmitter chains/antenna assemblies 1704, 1704' having different sets of frequencies or tones transmitted simultaneously on different antennas or antenna elements. The transmitter chain/antenna assembly 11704 includes a transmit antenna 1714 connected to a transmit chain 1716. Similarly, the transmitter chain/antenna assembly N1704 ' includes a transmit antenna 1714 ' connected to a transmitter chain 1716 '. The transmitter chains 1716, 1716' are connected to a controllable baseband transmitter unit 1718. The receiver component 1702, the controllable baseband transmitter unit 1718, the processor 1720, e.g., CPU, the user I/O device 1722, and the memory 1724 are connected together via a bus 1726 over which the various elements may exchange data and information. User I/O devices 1722, e.g., keypad, keyboard, mouse, video camera, microphone, display, speaker, etc., allow a user of WT1700 to enter user data/information into and output user data/information from a peer node. Memory 1824 includes programs 1728 and data/information 1730.

Processor 1720, controlled by one or more programs 11728 stored in memory 1724, causes mobile node 1700 to operate in accordance with the methods of the present invention. Routines 1728 include communications routines 1732 and mobile node control routines 1734. Communications routines 1732 perform the various communications protocols and functions used by WT 1700. Mobile node control program 1734 is responsible for ensuring that mobile node 1700 is operating in accordance with the methods of the present invention.

The mobile node control routines 1734 include a transmit frequency division control component 1736 and an uplink channel feedback component 1738. In some embodiments, e.g., embodiments that include receiver controllable switching component 1712 and multiple receiver antennas (1706, 1708), control routines 1734 include receiver antenna switching control component 1740. In such embodiments, receiver antenna switching control may be performed under the direction of a receiver antenna switching control component 1740, which component 1740 is responsible for the generation of antenna switching control signals that are used to control the switching performed by switching circuitry within component 1712 in receiver chain 1710 as the control component is executed by processor 1720.

The frequency transmission division control component 1736 controls the operation of the controllable baseband transmitter unit 1718 to divide the frequency, e.g., into groups of tones for transmission, such that a first subset of tones is used to transmit some information to the transmitter link antenna assembly 11704, and a second subset of tones is used to transmit some information to the transmitter link/antenna assembly N1704', the first and second subsets of tones differing from each other by at least one tone. In some embodiments, more than two antennas or antenna elements are used to transmit simultaneously, with more than two tone subsets being transmitted simultaneously, e.g., one tone subset corresponding to each antenna or antenna element being used simultaneously. In some embodiments, different subsets of tones associated with different transmitter chains/antennas are mutually exclusive. In some embodiments, there is a partial overlap between the audio subsets. In accordance with the present invention, WT1700 may transmit first and second sets of tones simultaneously, the first set of tones being conveyed by a first communication channel from antenna 11714 to the BS, and the second set of tones being conveyed by a second communication channel from antenna N1714' to the same BS. Crossover control assembly 1736 includes a distribution subassembly 1742 for distributing audio from a set of audio to a plurality of different audio subsets, including at least first and second audio subsets, each of the different audio subsets differing from one another by at least one audio. The crossover control component 1736 also includes a transmit subcomponent for controlling the transmission of the selected subset of audio.

The allocation subcomponent 1742 uses data/information 1730 to decide and allocate audio into the audio subsets (audio subset 1 information-interval 11766, audio subset N information-interval 11770, audio subset 1 information-interval M1768, audio subset N information-interval M1772), where the data/information 1730 includes predetermined switching sequence information 1780, switching criteria information 1778, antenna element 1 feedback information 1758, antenna element N feedback information 1760, and/or hop information 1764. The distribution subassembly 1742 also generates and stores antenna element control information (antenna element 1 switching control information 1784, antenna element N switching control information 1786). The transmit subassembly 1744 uses the data/information 1730 to implement the operations of decision and control controllable baseband transmitter unit 1718 of the allocation component 1742, where the data/information 1730 includes tone subsets (1766, 1770, 1768, 1772), OFDM timing information 1752, and antenna element switching control information (1784, 1786).

Uplink channel feedback module 1738 processes uplink channel quality feedback signals from the BS and obtains uplink channel condition feedback information from BS 1748, including transmit power control signal information 1762 and transmit acknowledgement signal information 1764. In many embodiments, the BS need not know the tone subset information corresponding to the particular WT transmit antenna link/antenna (1704, 1704') used; however, WT1700 knows tone subset information (1766, 1770, 1768, 1772), e.g., weighting in terms of the number of tones assigned to each antenna or antenna element during a particular dwell, and associates feedback information 1756 with a particular antenna element, which is then stored as antenna element 1 feedback information 1758, antenna element N feedback information 1760.

Data/information 1730 includes user/device/session/resource information 1746, uplink channel condition feedback information 1748 obtained from the BS, OFDM audio information 1750, OFDM timing information 1752, and frequency division information 1754. User/device/session/resource information 1746 includes user/device identification information, session information including peer node identification and routing information, and resource information including uplink and downlink portions assigned by the BS to WT 1700.

The uplink channel condition feedback information from BS 1748 includes received quality indicator signal information 1762 and sets of antenna feedback information (antenna element 1 feedback information 1758, antenna element N feedback information 1760). Received quality indication signal information 1756 includes transmission power control signal information 1762, e.g., the power level of the received WT uplink signal, SNR value, WT1 transmit power adjustment signal, etc., information indicating the channel quality, and transmission acknowledgment signal information 1764, e.g., a received transmission acknowledgment signal indicating the success or failure of reception of one or more uplink signals transmitted by WT 1. Antenna element 1 feedback information 1758 and antenna element N feedback information 1760 comprise information extracted and/or processed from WT received quality indication signal information 1762, 1764, associated with each transmit antenna link/antenna (1704, 1704') used by WT 1700.

OFDM tone information 1750 includes tone group information 1762, e.g., a group of tones used by the WT for uplink signaling, tone hopping information 1764, e.g., uplink tone hopping sequence information, where the uplink tone hopping sequence information includes information based on the hopping sequence from logical tone hopping to dwell of physical tones. OFDM audio information 1750 also includes a variety of audio subsets (audio subset 1 information-interval 11766, audio subset N information-interval 11770, audio subset 1 information-interval M1768, audio subset N information-interval M1772). According to the invention, each tone subset of information (1766, 1770) is associated with a different transmitter chain/antenna (1704, 1704'), and the tone subsets (1766, 1770) are transmitted simultaneously. Similarly, according to the present invention, each tone subset of information (1768, 1772) is associated with a different transmitter chain/antenna (1704, 1704'), and the tone subsets (1766, 1770) are transmitted simultaneously. The weighting of the audio, e.g., the number of audios associated with each subset, may change over time. For example, during interval 1, tone subset 1 associated with transmitter chain/antenna 1 may use 6 tones, and tone subset 2 associated with transmitter chain/antenna 2 may also use 6 tones; but during the immediately following interval tone subset 1 associated with transmitter chain/antenna 1 may use 7 tones and tone subset 2 associated with transmitter chain 2/antenna 2 may use 5 tones. In addition, from dwell to dwell, the tone group may hop according to an uplink hopping sequence.

OFDM timing information 1752 includes symbol timing information 1774 and dwell information 1776. The symbol timing information includes timing defining the transmission of a single OFDM symbol carrying modulation symbols transmitted on each transmitted tone. Dwell information 1776 includes information identifying a number, e.g., 7, consecutive OFDM symbols, during which uplink tones mapped from logical to physical tones do not change; the tone makes different jumps from dwell to dwell. Dwell information 1752 also includes information identifying dwell boundaries. According to some embodiments of the invention, the change in subset weighting is made on dwell boundaries, rather than between dwell boundaries.

In some embodiments, the frequency division is based on a predetermined reference, e.g., the tones are divided among the plurality of transmitter chains/antenna elements (1704, 1704'), e.g., in an alternating sequence with respect to the physical index. In other embodiments, the weights between the different transmitter chains/antenna elements (1704, 1704') are varied as a function of the switching criteria information 1778 in the received uplink channel condition feedback information 1748 and crossover criteria information 1754. For example, if the WT1700 includes first and second transmitter chains/antenna elements 1704 and 1704 'and the feedback information indicates that the channel qualities are substantially the same, e.g., the difference between the channel qualities is less than a first criterion level, the tones may be evenly divided between the two elements 1704, 1704'. However, if the same exemplary WT1700 determines that the channel quality for transmitter link/antenna element 1704 is significantly better than the channel quality for transmitter link/antenna element 1704 ', and yet the channel quality for both channels is still acceptable based on the feedback information and comparison to the second and third criteria levels, then the crossover control module 1736 can control the baseband transmitter unit 1718 to dedicate more tones, e.g., twice as much tones as the module 1704' for the module 1704.

The frequency division information 1754 includes switching standard information 1778, predetermined switching order information 1780, antenna element usage information 1782, and multiple sets of antenna element switching control information (antenna element 1 switching control information 1784, antenna element N switching control information 1786). The switching criteria information 1778 includes threshold limits that the assignment subcomponent 1742 uses to evaluate the antenna element feedback information (1758, 1760) to decide whether, when, and to what extent to change the balance of tone-splitting among the various transmitter chains/antennas (1704, 1704'). The predetermined switching sequence information 1780 includes a variety of predetermined sequences from which the dispensing subcomponents may be selected. For example, the first predetermined sequence may alternate between two divisions, for example on latching: (i) the uplink audio is split between the first transmitter link/antenna and the second transmitter link/antenna by 50-50, and (ii) the uplink audio is split between the first transmitter link/antenna and the second transmitter link/antenna by 60-40; for example, the second predetermined order may alternate between two division modes: (i) the uplink audio is split between the first transmitter chain/antenna and the second transmitter chain/antenna by 50-50, and (ii) the uplink audio is split between the first transmitter chain/antenna and the second transmitter chain/antenna by 40-60. In some embodiments, WT1700 will follow a predetermined switching sequence without changing as a function of feedback information, e.g., a fixed predetermined sequence that may result in equal or nearly equal frequency division in time between transmitter chains/antennas (1704, 1704').

Figure 21 is a flow chart 2100 of an exemplary method of operating a WT to communicate with a base station including performing dwell boundary switching of transmitter antenna elements in accordance with the present invention. The WT may be, e.g., an exemplary WT similar or identical to WT 1500 of fig. 17, and the BS may be, e.g., an exemplary BS similar or identical to BS 1400 of fig. 14. Operation begins at step 2102 and proceeds to step 2104. In step 2104, a dwell boundary switching module in the WT transmitter signal processing chain is operated to connect a first antenna element of a group of multiple antenna elements, e.g., a group of two antenna elements, to a single transmitter chain. Operation proceeds from step 2104 to step 2106. In step 2106, the WT is operated to transmit an uplink signal to the base station through the first antenna element during the first dwell using a set of tones for transmission that matches the first set of tones. The first dwell is a set of consecutive OFDM symbol transmission time intervals, e.g., 7 consecutive OFDM symbol transmission time intervals, during which the assignment of logical audio markers to physical audio markers does not change.

Next, at step 2108, the dwell boundary switching module is operated to switch the antenna elements from the first antenna element to the second antenna. Operation proceeds from step 2108 to step 2110. In step 2110, the WT is operated to change the set of tones used for transmission from a first set of tones to a second set of tones, the second set of tones being different from the first set of tones, according to an uplink tone hopping sequence. Next, in step 2112, the WT is operated to transmit uplink signals to the base station through the second antenna element using the second set of tones during the second dwell. Operation proceeds from step 2112 to step 2114, where the WT is operated to replace tones in the first and second sets of tones in accordance with an uplink hopping sequence 2114. Operation proceeds from step 2114 to step 2104.

The operations of flowchart 2100 result in a predetermined and periodic switching sequence between the first and second antenna elements. Assuming that an exemplary WT has only two transmitter antenna elements, the operations of flowchart 2100 result in equal utilization of the antenna elements. In some embodiments, each antenna element is positioned in a different direction. In some embodiments, the first and second antenna elements are spaced apart such that a different communication path exists between each of the first and second antenna elements and the base station. In some embodiments, the spacing of the antenna elements is at least 1/4 of the lowest frequency audio wavelength transmitted from the antenna elements.

The method of flowchart 2100 is extendable to embodiments that include multiple two antenna elements. Further, in some embodiments, the antenna may remain connected to a selected antenna element for more than one consecutive dwell, e.g., a fixed number of dwells greater than 1, before switching to a different antenna element.

Figure 22 is a flow chart of an exemplary method of operating a WT to communicate with a base station including performing dwell boundary switching of transmitter antenna elements in accordance with the present invention. The WT may be, e.g., an exemplary WT similar or identical to WT 1500 of fig. 17, and the BS may be, e.g., an exemplary BS similar or identical to BS 1400 of fig. 14. Operation begins at step 2202 and proceeds to step 2204 where a dwell boundary switching module in the WT transmitter signal processing chain is operated to connect a single transmitter chain of the WT to a designated antenna element from a set of multiple antenna elements, e.g., two antenna elements. Then, in step 2206, the WT is operated to transmit uplink signals to the base station during the first dwell using a set of tones for transmission through the designated antenna elements, the set of tones for transmission matching the first set of tones. For example, the first dwell is a set of 7 consecutive OFDM symbol transmission time intervals. Operation proceeds from step 2206 to step 2208. In step 2208, the WT is operated to receive one or more feedback signals from the base station indicating the channel quality of the uplink signal received from the previous lock-up. The one or more feedback signals indicative of channel quality include a transmit power control signal indicative of WT uplink power control information and at least one of a transmit acknowledgement signal indicative of successful or failed reception of a transmitted uplink signal. Operation proceeds from step 2208 to step 2210. In step 2210, the WT is operated to correlate the received feedback signal or signals with the antenna element used during the previous dwell and then update a set of feedback information corresponding to the antenna element. The base station sending the feedback information need not know, and in many embodiments does not know, which antenna element to use for the transmission of the dwell, and the WT performs tracking and matching of the antenna elements for the received feedback information. In step 2212, the WT is operated to make antenna element switching decisions as a function of the received feedback signal. For example, if the power control feedback signal indicates that the WT transmit power level should remain constant or decrease, and the ack/nack signal indicates a high ratio of ack to nack, indicating a reliable uplink signal, the WT may be allowed to remain connected to the currently selected transmitter antenna element. However, if the power control feedback signal indicates a large rise in WT transmit power requirements, and/or the ack/nack signal indicates a very high ratio of negative to positive, then the WT may decide to switch to another antenna element, e.g., select the antenna element that is expected to produce greater channel variation, e.g., the antenna element with the greatest spacing and/or greatest positioning difference from the currently selected antenna element. The stored information about the channel quality of previous WT transmit antenna element connections may also be used in the selection process. In certain cases, where the quality indication information exhibits a marginal condition, the WT may be operated to select antenna elements having a slight spacing or positioning difference relative to the currently selected antenna element.

Operation proceeds from step 2212 to step 2214. In step 2214, operation continues based on whether the WT has decided to switch antenna elements. If the WT has decided not to switch antenna elements in step 2212, then operation proceeds from step 2214 to step 2220; otherwise the step proceeds to step 2216. In step 2216, the WT is operated to update and maintain sets of switching control information corresponding to different antenna elements, e.g., including setting a bit to correspond to an antenna element being connected to a single transmitter link and clearing a bit to correspond to a disconnection of the antenna element from the single transmitter link. Operation proceeds from step 2216 to step 2218 where the dwell boundary switching module is operated to switch the designated antenna element to a different transmitter antenna element from the set of multiple antenna elements, the different antenna element being the antenna element selected at step 2212, and the control activation information is configured at step 2216. According to the invention, switching is controlled to be performed on latching boundaries, rather than between boundaries. Operation proceeds from step 2218 to step 2220.

In step 2220, the WT is operated to change the tone group for transmission to a different set of tones according to the uplink hopping sequence. Then in step 2222, the WT is operated to transmit uplink signals to the base station via the designated antenna element during the next successive dwell period, e.g., 7 successive OFDM symbol transmission intervals, using the tone group designated for transmission by step 2220. Operation proceeds from step 2222 back to step 2208.

The operations of flowchart 2200 result in a dwell switch between multiple antenna elements based on uplink channel quality feedback information. In some embodiments, each antenna element is oriented in a different direction. In some embodiments, the antenna elements are spaced apart such that a different communication path exists between each antenna element and the base station. In some embodiments, the spacing between the antenna elements is at least 1/4 of the lowest frequency wavelength transmitted from the antenna elements.

The method of flowchart 2200 includes embodiments with only two antenna elements and embodiments with more than two antenna elements. Further in some embodiments, the antenna may remain connected to the selected antenna element for more than two consecutive dwells, e.g., a fixed number of dwells greater than 1, before performing a switching decision as to whether to switch to another antenna element. In some embodiments, the frequency of transmission of feedback information is higher or lower than once per dwell.

Figure 23 is a flow chart 2300 of an exemplary method of operating a WT to communicate with a base station that includes performing channel estimation boundary switching of transmitter antenna elements in accordance with the present invention. The WT may be, e.g., an exemplary WT similar or identical to WT 1600 of fig. 18, and the base station may be, e.g., an exemplary BS similar or identical to BS 1800 of fig. 15. Operation begins at step 2302 and proceeds to step 2304. In step 2304, the WT is operated to associate different base station uplink signaling channel estimates with different WT transmitter antenna elements. For example, based on some downlink broadcast signals received from the base station, the WT obtains information that is used to determine the timing of the channel estimation by the base station with respect to the uplink signaling it receives, e.g., information defining the boundaries between the multiple channel estimates that are performed, and/or information defining the boundaries used to define the initialization or resetting of the channel estimates. For example, if the base station periodically alternates between two channel estimates for uplink signaling and the WT has two transmit antenna elements, the wireless terminal can associate the first channel estimate with the first antenna element and the second channel statistic with the second antenna element and then synchronize its uplink signaling timing, which corresponds to a unique BS channel estimate. Thus, in step 2306, the channel estimation boundary switching module within the WT transmitter signal processing chain is operated to connect a first antenna element from a group of multiple antenna elements, e.g., a group of two antenna elements, to a single transmitter chain. Operation proceeds from step 2306 to step 2308. In step 2308, the WT is operated to transmit uplink signals to the base station using the first antenna element, and then in step 2310 the WT is operated to track the timing of BS channel estimates corresponding to uplink signaling.

Operation proceeds from step 2310 to step 2312 where a check is performed to see if a channel estimation boundary has been reached. If the channel estimation boundary has not been reached, operation proceeds to step 2308 where the WT is operated to transmit additional uplink signals using the same antenna element, i.e., the first antenna element. However, if it is determined at step 2312 that the channel estimation boundary has not been reached, then operation proceeds from step 2312 to step 2314. At step 2314, the channel estimation boundary switching component is operated to switch from the first antenna element to the second antenna element. Operation proceeds from step 2314 to step 2316. In step 2316, the WT is operated to track the timing of BS channel estimates corresponding to uplink signaling.

Operation proceeds from step 2318 to step 2320 where a check is performed as to whether a channel estimation boundary has been reached. If the channel estimation boundary has not been reached, operation proceeds to step 2316 where the WT is operated to transmit additional uplink signals using the same antenna element, i.e., a second antenna element. However, if it is determined in step 2320 that the channel estimation boundary has not been reached, then operation proceeds from step 2320 to step 2322. At step 2322, the channel estimation boundary switching component is operated to switch from the second antenna element to the first antenna element. Operation proceeds from step 2322 to step 2308, where the WT is operated to transmit uplink signals to the BS using the first antenna element.

The operations of the flowchart 2300 result in a predetermined and periodic switching sequence between the first and second antenna elements. Assuming that the exemplary WT has only two transmitter antenna elements, the operations of flow diagram 2300 may result in equal use of the antenna elements. In some embodiments, each antenna element is oriented in a different direction. In some embodiments, the first and second antenna elements are spaced apart such that a different communication path exists between each of the first and second antenna elements and the base station. In some embodiments, the spacing between the antenna elements is at least 1/4 of the lowest frequency wavelength transmitted from the antenna elements.

The method of flowchart 2300 may be extended to include embodiments having more than two antenna elements. The method of flowchart 2300 is well suited for both OFDM and CDMA applications. In some OFDM embodiments, the channel estimation boundary may correspond to a dwell boundary or a plurality of dwell boundaries. In some CDMA embodiments, each different channel estimate may correspond to a different codeword.

Figure 24 is a flow chart 2400 of an exemplary method of operating a WT for communicating with a base station, including performing channel estimation boundary switching of transmitter antenna elements in accordance with the present invention. The WT may be, e.g., an exemplary WT similar or identical to WT 1600 of fig. 18, and the base station may be, e.g., an exemplary BS similar or identical to BS 1800 of fig. 15. Operation begins at step 2402 and proceeds in parallel to step 2404 and step 2416. In step 2404, the channel estimation boundary switching module in the WT transmitter signal processing chain is operated to connect the single transmitter chain of the WT to a designated antenna element from a set of multiple antenna elements. Then, in step 2408, the WT is operated to track the timing of BS channel estimates corresponding to uplink signaling. For example, based on some downlink broadcast signals received from the base station, the WT obtains information that is used to determine the timing of the channel estimation by the base station with respect to the uplink signaling it receives, e.g., information defining the boundaries between the multiple channel estimates that are performed, and/or information defining the boundaries used to define the initialization or resetting of the channel estimates. For example, consider an exemplary embodiment in which the BS performs channel estimation of received uplink signaling for use in a fixed interval, initializes the estimation filter, then begins another channel estimation for use in a subsequent interval of the same period, and then periodically repeats the channel estimation method. The broadcast timing information from the BS may allow the WT to synchronize its uplink signaling with these channel estimation boundaries. Operation proceeds from step 2408 to step 2410 where a check is performed whether the channel estimation boundary is reached. If the channel estimation boundary has not been reached, operation proceeds from step 2410 to step 2412. In step 2412, the WT is operated to transmit an uplink signal to the BS, and then the operation returns to step 2408. However, if the channel estimation boundary is reached at step 2410, then operation proceeds to step 2414 where the WT makes antenna element switching decisions as a function of the received feedback signal.

Returning to step 2416, in step 2416, the WT operates to receive one or more feedback signals from the base station. The one or more feedback signals are indicative of channel quality of the received uplink signal and include at least one of a transmission power control signal for indicating WT uplink power control information and a transmission acknowledgement signal for indicating successful or failed reception of one or more transmitted uplink signals. Operation proceeds from step 2416 to step 2418. In step 2418, the WT is operated to correlate the received feedback signal or signals with the antenna element used, and then update a set of feedback information corresponding to that antenna element. The base station sending the feedback information need not know, and in many embodiments does not know, which antenna element is used to transmit the uplink signal corresponding to the channel estimate. The information of step 2418 may be used by the WT to make antenna element switching decisions in step 2414.

At step 2414, the quality indication information corresponding to the currently selected antenna element may be compared to a threshold for maintaining the connection. Quality indication information corresponding to a set of alternate replacement antenna elements may be used to determine which antenna element to select when a decision has been made to switch. Additionally, in some embodiments, switching between antenna elements may be performed periodically, for example, without or with little regard to stored channel quality information, in order to acquire new channel quality information and estimate the alternate channels corresponding to alternate antenna elements. Operation proceeds from step 2414 to step 2420.

If, at step 2414, it has been determined to be camped on the currently selected antenna element, then operation proceeds from step 2420 to step 2412, where the WT is operated to transmit uplink signals to the BS. However, if the WT has decided to switch transmitter antenna elements, then operation proceeds from step 2420 to step 2422. In step 2422, the WT is operated to update and maintain the set of switching control information corresponding to the different antenna elements, e.g., set the active control bits corresponding to the newly selected antenna element and clear the control bits corresponding to the previously used antenna elements. Thus, at step 1424, the channel boundary switching component is operated to switch the designated antenna element for transmission to a different antenna element from a set of multiple antenna elements, e.g., the antenna element selected at step 2414, and configured for step 2422. According to the present invention, handover is controlled so as to be performed on signal boundaries corresponding to base station channel estimation signal boundaries, rather than between the boundaries. Operation proceeds from step 2224 to step 2426.

In step 2426, the WT is operated to transmit the uplink signal to the base station through the designated antenna element. Operation proceeds from step 2426 to step 2408.

The method of flowchart 2400 is well suited for both OFDM and CDMA applications. In some OFDM embodiments, the channel estimation boundary may correspond to a dwell boundary or a plurality of dwell boundaries. In some OFDM embodiments, each channel estimation signal interval comprises a plurality of OFDM symbol transmission time periods, and the tones used by the WT in each channel estimation signal interval are determined according to a frequency hopping sequence. In some CDMA embodiments, each different channel estimate may correspond to a different codeword.

In some embodiments, each antenna element is oriented in a different direction. In some embodiments, the first and second antenna elements are spaced apart such that a different communication path exists between each of the first and second antenna elements and the base station. In some embodiments, the spacing between the antenna elements is at least 1/4 of the lowest frequency wavelength transmitted from the antenna elements.

Fig. 25 is a flow diagram 2500 of an exemplary method of operating an OFDM communications apparatus that includes assigning different tone subsets to different antenna elements and transmitting on multiple parallel antenna elements, e.g., the communications device may be an exemplary WT similar or identical to WT1700 of fig. 18, in accordance with the present invention. Operation begins at step 2502 and proceeds to step 2504. At step 2404, the communications device is operated to assign the audio in the first set of audio to a plurality of different subsets of audio, the subsets including at least first and second subsets of audio, each of said different subsets of audio differing from each other by at least one audio. In some embodiments, the audio assigned to the first and second subsets of audio are exclusive of each other. Operation proceeds from step 2504 to step 2506. At step 2506, the communications apparatus is operated to transmit each said different subset of tones in parallel using a different antenna element for each said different subset of tones during the same time interval. Operation proceeds from step 2506 to step 2508 where the communications device changes the number of tones assigned to at least one of the first and second subsets of tones. Operation proceeds from step 2508 back to step 2504. In some embodiments, the change in audio allocation is based on a periodic basis.

In some embodiments, the communications apparatus in flowchart 2500 is a wireless terminal that transmits an uplink signal to a base station, e.g., an uplink signal that uses tones that hop according to an uplink hopping sequence on a dwell-by-dwell basis, and the base station receives the uplink signal. In other embodiments, the communications apparatus of flowchart 2500 is, for example, a BS1900 base station similar or identical to the exemplary BS of fig. 16 that transmits a downlink signal, for example, a downlink signal using tones hopped according to an uplink hopping sequence for each OFDM symbol transmission time interval, and then receives the downlink signal by a wireless terminal.

Fig. 26 is a flow diagram 2600 of an exemplary method of operating an OFDM communications device, such as an exemplary WT similar or identical to WT1700 of fig. 19, in accordance with the present invention, including receiving and processing channel quality indication information, assigning different tone subsets to different antenna elements, and transmitting on multiple parallel antenna elements. Operation begins at step 2602 and proceeds to step 2604. At step 2604, the communications device is operated to assign the tones in the first set of tones to a plurality of different tone subsets, the subsets including at least first and second tone subsets, each of said different tone subsets differing from each other by at least one tone. In some embodiments, the change in audio allocation is based on a periodic basis. Operation proceeds from step 2604 to step 2606 where the communications device is operated to transmit each of said different subsets of tones in parallel during the same time interval using a different antenna element for each of said different subsets of tones. Operation proceeds from step 2606 to step 2608. At step 2608, the communications apparatus is operated to receive one or more signals indicative of channel quality including at least one of a transmission power control signal indicative of a transmission power of the communications apparatus and a transmission acknowledgement signal indicative of a successful or failed reception of one or more signals transmitted by the communications apparatus.

Thus, at step 2610, based on the received quality indication information, the communications device decides whether to change the allocation of audio to the subset of audio. For example, if not enough quality indication information is stored to reasonably determine which antenna element has better channel quality and should be favored, the communications device may decide to change the allocation of tones to favor one antenna, so that quality indication feedback information may be collected with high weighting to a single antenna, and the communications device may cycle periodically between each antenna element. If there is sufficient information to make the decision on the assignment of tones, the communications device can decide to change the assignment of tones to tone subsets in an attempt to achieve more favorable channel conditions, e.g., the same ack/nack ratio can be achieved but can result in a lower WT transmit power level change, can result in an improved ack/nack ratio change, and/or can result in a lower communications device transmit power level change. If it is determined in step 2610 that the assignment of audio to audio subsets is not to be changed. Then operation returns to step 2604. However, if it is determined in step 2610 that the audio-to-audio allocation itself should be changed, then operation proceeds to step 2612 where the communications device is operated to change the number of tones in at least one of the first and second subsets of audio. In some embodiments, the first subset of audio is allocated a plurality of audio and the second subset of audio is unallocated audio. Operation proceeds from step 2612 to step 2604.

In some embodiments, the audio allocation is performed as a function of a plurality of signals received from devices in communication with the communication device, the method comprising maintaining different audio group allocation control information for signals received from said devices in communication with the communication device, corresponding to signals transmitted from said communication device using different antenna elements.

In some embodiments, the communications apparatus in flowchart 2600 is a wireless terminal that transmits an uplink signal to a base station, e.g., an uplink signal that uses tones that hop according to an uplink frequency hopping sequence based on a dwell-by-dwell reference, and the base station then receives the uplink signal and transmits a feedback channel quality signal. In other embodiments, the communications apparatus of flowchart 2600 is, for example, an exemplary BS1900 base station similar or identical to fig. 16 that transmits a downlink signal, for example, a downlink signal using tones hopped according to an uplink hopping sequence for each OFDM symbol transmission time interval, and then the wireless terminal receives the downlink signal and transmits a feedback channel quality signal.

The invention will now be described further. While the following partial discussion may repeat some of the above discussion, features of some embodiments are discussed in more detail. As discussed above, the novel techniques employed by the present invention can enable a mobile transmitter to achieve uplink transmit diversity using a single RF link and multiple physical antennas without any significant cost or complexity.

For ease of illustration, the present invention is considered in the context of a spread-spectrum OFDM (orthogonal frequency division multiplexing) multiple access system. Note that the present transmit diversity technique is also applicable to other systems.

In an exemplary OFDM system, the tones are frequency hopped to achieve the spread spectrum advantage. In the downlink (from the base station to the wireless terminal), tones hop for each OFDM symbol. Each logical tone is mapped onto a different physical tone and the mapping varies at each OFDM symbol boundary. This hopping ensures that code groups containing certain logical audio subsets are spread across the entire available frequency band. In the uplink (from the wireless terminal to the base station), each logical tone is mapped onto a physical tone, and the tone remains constant for several OFDM symbol periods. This duration is referred to as the dwell period. The process of uplink hopping during the dwell period is shown in fig. 5.

The invention can be used at the transmitter of a wireless terminal to achieve transmit diversity on the cellular uplink. The invention requires that the mobile transmitter has multiple physical transmit antennas, but it is not required that it include multiple RF chains. A preferred embodiment of the present invention is to switch the transmit antennas at the dwell boundaries of the uplink signal.

To illustrate this, consider fig. 6, which shows codewords transmitted on the uplink over four consecutive dwell periods. Assume that the mobile transmitter has two physical transmit antennas and a single RF chain as shown in fig. 3. Although the transmitter shown in fig. 3 represents any system that uses selective diversity, the present invention achieves transmit diversity on fast time scales within codewords. A switching component operating under the direction of a switching control component within the transmitter may direct the transmit signal through one of the transmit antennas. The switching control module, in one embodiment, is aware of the latching information. The handover control component may receive the information and/or handover direction from a baseband unit within the mobile transmitter. The switching control component directs the switching unit to transmit the codeword through antenna 1 in dwells 1 and 3 and through antenna 2 in dwells 2 and 4. At the receiver, the partial code group experiences the channel response H from antenna 1₁The partial code group experiences a response H from antenna 2₂. In an exemplary OFDM system, a base stationThe receiver does not assume that the channel from dwell to dwell is coherent and estimates the channel independently in each dwell. Then the handoff on the dwell boundary does not interfere with the base station channel estimation or necessitate additional estimation. Thus, the transmit antenna does not affect the operations performed at the receiver. In this state, the receiver may not even be aware of the use of the present transmit diversity invention. Assume channel response H₁And H₂Is independent, then the receiver can achieve diversity over the code group.

In general, let N denote the number of transmit antennas on the mobile transmitter, let { H }_kAnd k 1.. N } represents the wireless channel response from each transmit antenna to the receiver. Preferably, the transmit antennas are spatially arranged in such a way that the ensemble of channel responses { H }_kIs substantially independent. In some embodiments, the antennas are spaced above 1/2 wavelengths of the carrier frequency used to transmit the signal. In many cases, the antennas are separated by more than one carrier wavelength. By switching from one transmit antenna to another transmit antenna over the codeword length, the effective channel response from transmitter to receiver is at { H }_kAnd the power is changed, thereby realizing the transmission diversity. As another implementation of the invention, the transmitter may switch the antenna once per dwell or once every few dwells.

In the above description, the switching module at the transmitter selects each transmit antenna fairly equally. However, non-equal use of antennas is possible. In some embodiments, the base station provides channel response information to the mobile node indicating the quality of the uplink channel corresponding to the different antennas used. The mobile node responds to the information used by controlling the switching component to cause one or more antennas corresponding to better channels to be used more than antennas corresponding to lower quality channels. It is assumed that the base station receiver feeds back some indication of the channel quality to the transmitter. The transmitter can find out which transmit antenna produces better channel quality and choose whether to use that antenna for a significant portion of the time. The transmitter typically continues to use the known less desirable antenna for at least several time periods so that the base station receiver can monitor changes in channel conditions. So that the base station can direct the mobile transmitter to switch antennas according to time-varying channel conditions. This feedback and antenna channel selection technique is particularly useful when channel conditions are slowly changing, e.g., remaining constant over multiple dwells. Such a condition may be encountered, for example, where the wireless terminal remains stationary for a period of time, such as when a person is working from the same location during a communication session.

The form of the invention to achieve transmit diversity at the mobile transmitter can be combined with the usual form of achieving receive diversity at the base station receiver, again resulting in additional diversity gain.

This embodiment of the invention is particularly valuable on the cellular uplink because it requires a single RF link at the transmitter. This significantly reduces the cost and complexity of achieving transmit diversity gain on the mobile device.

Various aspects of uplink transmit diversity using tone splitting will now be further described. Various embodiments of the proposed invention also introduce other techniques to achieve uplink transmit diversity in the context of OFDM multiple access systems. This embodiment of the invention requires that the mobile transmitter transmit information simultaneously using more than two transmit antennas.

For ease of illustration, consider a mobile transmitter having two transmit antennas. One subset of tones in each OFDM symbol is transmitted through the first antenna and the remaining set of tones is transmitted through the second antenna as shown in fig. 9. In an exemplary OFDM system, the uplink hopping sequence that maps logical tones to physical tones varies across dwell boundaries. Thus, the subset of tones transmitted through each antenna remains fixed over the entire dwell, thus maintaining channel coherence at the receiver. Again, the base station receiver does not need to know clearly the division of the tones between the different antennas on the transmitter.

When the codeword is transmitted over several dwell periods in this manner, diversity gain is achieved at the receiver because portions of the codeword are received on different channels corresponding to signals from multiple transmit antennas.

There are several different motivations for determining the tone-splitting. The division of the tones may be such as to maximize the diversity gain of a particular uplink channel. Another motivation may be to minimize the ratio of peak power to average power of any power amplifier driving each antenna.

One of the benefits of using tone splitting is to transmit higher power without an uneven increase in cost. In embodiments of the present invention using two transmit antennas, each power amplifier driving an antenna may be estimated to be 1 watt (watt), which would result in a total power of 2 watts (watts). This cost is typically much lower when compared to the cost of estimating a single power amplifier as 2 watts (watts).

This technique can be easily generalized to multiple antennas. Each physical transmit antenna is connected to an RF chain as shown in fig. 27. Diagram 2700 of fig. 27 illustrates an exemplary transmitter structure that can be used in the tone-splitting embodiments of the present invention. The exemplary transmitter of fig. 27 includes a single baseband unit 2706 and a single frequency transmission splitting component 2704. The baseband unit 2706 receives information 2702, e.g., encrypted user data, to be transmitted and also receives control signals from the frequency transmission division control component 2704. Information 2702 is mapped onto a set of audio for transmission. Different subsets of tones are formed from the set of tones, the different subsets of tones differing from each other by at least one tone. In some embodiments, different subsets of audio are mutually exclusive. In some embodiments, the number of tones in one tone subset is controlled to be different from the number of tones in another tone subset. In some embodiments, some of the subsets of audio are empty sets. The control signals from the frequency transmission splitting control component 2704 determine the characteristics of the audio subsets, such as the number and selection of tones in a given audio subset, and the number of tones in each subset over a particular time interval using a particular transmit chain/transmit antenna. The baseband module 2706 outputs signals to a plurality of transmit chains (transmit chain 12707, transmit chain N2707'). The information 2702 input to the baseband unit 2706 is sent to one or more transmit chains 2707, 2707' as a function of control signals from the frequency transmission division control component 2704. For a given OFDM symbol transmission time interval, the baseband unit 2706 maps the information bits to be transmitted onto a set of tones for transmission, and then identifies these tone subsets with associated transmitter chain/transmitter antenna (2707/2114, 2707 '/2714') pairs; this information is sent to the digital signal processing components (2708, 2708') in a digital format. Each transmit chain (2707, 2707 ') comprises a digital signal processing module (2707, 2708'), a digital-to-analog conversion module (2710, 2710 '), an analog signal processing module (2712, 2712'), respectively. Digital signal processing modules (2708, 2708') convert received information into digital signals to be transmitted. The digital-to-analog conversion components (2710, 2710 ') convert the digital signals into analog signals, e.g., analog modulation symbols at a selected audio or subcarrier frequency using a selected carrier frequency, and the analog signal processing links (2712, 2712') perform other analog signal processing, e.g., amplifying and filtering the signals to be transmitted. Each analog signal processing module (2712, 2712 ') is connected to a transmit antenna (transmit antenna 12714, transmit antenna N2714'), respectively. The different analog signals are transmitted simultaneously through multiple antennas (transmit antenna 12714, transmit antenna N2714'), and information 2702 containing the original set of encrypted information bits is included in the resultant analog signal.

Diagram 2800 of fig. 28 shows another exemplary transmitter configuration that may be used in the tone-splitting embodiment of the present invention.

The various elements (2802, 2804, 2806, 2810, 2812, 2814, 2810 ', 2812', 2814 ') of fig. 28 are each similar or identical to the previously described elements (2702, 2704, 2706, 2710, 2712, 2714, 2710', 2712 ', 2714') of fig. 27. Transmitter link 12807 and transmitter link N2807 'of fig. 28 are similar to links (2707, 2707') of fig. 27; however, links 2807 and 2807' share a common digital signal processing module 2808. The common digital signal processing module 2808 performs the functions of both digital signal processing modules 2708 and 2708', such as providing efficiencies in terms of hardware cost, reduced weight, reduced size, and/or lower power consumption, based on a time-shared reference.

Fig. 29 is a diagram 2900 illustrating another exemplary transmitter configuration that may be used in the tone-splitting embodiment of the present invention. The various elements (2902, 2906, 2908, 2910, 2912, 2808 ', 2810', 2812 ') of fig. 29 are similar or identical to the previously described elements (2702, 2706, 2708, 2710, 2712, 2708', 2710 ', 2712') of fig. 27, respectively. The transmitter 2900 of fig. 29 includes two transmit chains (transmit chain 12907, transmit chain N2907 "), while the transmitter 2700 of fig. 27 includes N transmitter chains. Both transmitter chain 2700 and transmitter chain 2900 include N antennas or antenna elements. The transmitter 2900 of fig. 29 connects two of the antennas (antenna 12914, antenna 22914 ", antenna N2914') to the transmitter chain at any time using an additional antenna switching component 2813. As shown in fig. 29, transmit chain 12907 is currently connected to transmit antenna 22914 ", while transmit antenna N2914' is connected to transmit chain 22907". The frequency transmission division control component 2904 performs, in addition to the functions of the component 2904 of fig. 27, selection and control of an antenna matched to a transmission link, and the component 2904 transmits a control signal to the switching component 2913.

In some embodiments, multiple antennas or antenna elements used to obtain diversity may be mounted or located remotely from the mobile communication device, such as in different locations or on a car, in accordance with the present invention.

Although described herein in the context of an OFDM system, the methods and apparatus of the present invention are applicable to a wide range of communication systems, including non-OFDM systems and/or non-cellular systems.

Various embodiment nodes described herein are implemented using one or more components to perform the steps corresponding to one or more methods of the present invention, such as signal processing, antenna switching, message generation and/or transmission steps. In some embodiments, various features of the invention are implemented using components. The components may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods, or implementations of steps of methods, can be implemented using machine executable instructions, such as software contained in a machine readable medium such as a memory device, e.g., RAM, floppy disk, etc., to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, the present invention is directed to, among other things, a machine-readable medium having machine-executable instructions for causing a machine, e.g., processor and associated hardware, to perform one or more of the steps of the above-described method(s).

Many other variations of the methods and apparatus of the present invention described above will be apparent to those skilled in the art in view of the above description of the invention. The methods and apparatus of the present invention may be, and in various embodiments are, used with CDMA, Orthogonal Frequency Division Multiplexing (OFDM), and/or various other types of communications techniques which may provide wireless communications links between access nodes and mobile nodes. In some embodiments the access nodes are implemented as base stations which establish communications links with mobile nodes using OFDM and/or CDMA. In various embodiments the mobile nodes are implemented as notebook computers, Personal Digital Assistants (PDAs), or other portable devices including receiver/transmitter circuits and logic and/or routines, for implementing the methods of the present invention.

Claims (40)

1. A method of operating a wireless terminal to communicate with a base station, the wireless terminal comprising a plurality of antenna elements including at least a first antenna element and a second antenna element, the method comprising:

transmitting symbols during a time period, the time period comprising a plurality of dwell intervals, each dwell interval comprising a plurality of OFDM symbol transmission time periods, the transmitting during a dwell interval comprising using a set of tones during the dwell interval, using a different set of tones for successive dwell intervals occurring during the time period, wherein the different sets of tones used during successive dwell intervals differ in at least one tone; and

switching a transmitted signal between said first and second antenna elements during said time period, one of said first and second antenna elements being unused during any point within said time period, said switching being performed on at least some dwell boundaries during which no switching occurs between antenna elements, said dwell boundaries occurring between successive dwell transmission time intervals, a symbol transmission time period preceding a dwell boundary being immediately preceded by a subsequent symbol transmission time period within a subsequent dwell interval, and successive symbol transmission time periods not being separated from a preceding transmission time period by a non-transmission interval.

2. The method of claim 1, wherein switching between the first and second antenna elements occurs according to a predetermined switching sequence.

3. The method of claim 2, wherein the switching sequence is periodic.

4. The method of claim 3, wherein said transmitting is performed by a switching component using a single transmitter signal processing chain connected to said antenna element; and

wherein the periodic switching sequence switches between the antenna elements at uniform intervals, resulting in uniform use of the antenna elements.

5. The method of claim 1, wherein the switching between the first and second antenna elements is performed as a function of a signal from the base station indicative of channel quality.

6. The method of claim 5, wherein the signal indicative of channel quality is a transmit power control signal.

7. The method of claim 1, wherein each of the plurality of antenna elements is oriented in a different direction.

8. The method of claim 1, wherein the plurality of antenna elements are spaced apart such that different communication paths exist between the first and second antenna elements and the base station.

9. The method of claim 8, wherein the spacing between the antenna elements is at least 1/4 wavelengths of the lowest frequency of audio transmitted from the antenna elements.

10. A method of operating a wireless terminal to communicate with a base station, said wireless terminal including a single transmitter signal processing link including a dwell boundary switching module for connecting said single transmitter signal processing link to a plurality of antenna elements, said dwell boundary switching module for switching over dwell boundaries but not between boundaries, said plurality of antenna elements including at least a first antenna element and a second antenna element, wherein each antenna element is independently operable, the method comprising:

operating dwell boundary switching module during a first time period to switch between said first and second antenna elements, the switching occurring at least some dwell boundaries occurring between said first time periods to thereby change the antenna elements used to transmit signals from said single transmitter signal processing link, one dwell being a second time period within the first time period, such that said wireless terminal transmits signals to said base station using a single set of tones during a dwell, a different set of tones being used in immediately successive dwells during the first time period, wherein said dwell boundary switching module switches between the first and second antenna elements as a function of signals from the base station indicative of channel quality, and

where the transmission acknowledgement signal indicating the channel quality is the success or failure of the reception of the transmitted signal.

11. A method of operating a wireless terminal to communicate with a base station, said wireless terminal including a single transmitter signal processing link including a dwell boundary switching module for connecting said single transmitter signal processing link to a plurality of antenna elements, said dwell boundary switching module for switching over dwell boundaries but not between boundaries, said plurality of antenna elements including at least a first antenna element and a second antenna element, wherein each antenna element is independently operable, the method comprising:

operating dwell boundary switching module during a first time period to switch between said first and second antenna elements, the switching occurring at least some dwell boundaries occurring between said first time period to thereby change antenna elements used to transmit signals from said single transmitter signal processing link, a dwell being a second time period within the first time period such that said wireless terminal transmits signals to said base station using a single set of tones during the dwell, a different set of tones being used in immediately successive dwells during the first time period, wherein said dwell boundary switching module switches between the first and second antenna elements as a function of signals from the base station indicative of channel quality, said switching being performed as a function of a plurality of signals received from the base station; and

different sets of switching control information for signals received from the base station corresponding to signals transmitted from the wireless terminal using different antenna elements are stored.

12. The method of claim 11, wherein each dwell comprises a plurality of OFDM symbol transmission time periods, and wherein the tones used by the wireless terminal in each dwell are determined based on a frequency hopping sequence.

13. A wireless terminal for use in a communication system including a base station, the wireless terminal comprising:

a single transmitter signal processing chain including a switching module for connecting said single transmitter signal processing chain to a plurality of antenna elements, said switching module for switching on signal boundaries corresponding to base station channel estimation memory reset points, but not between boundaries, said plurality of antenna elements including at least a first antenna element and a second antenna element, each of which is independently operable,

means for controlling the switching module to switch between said first and second antenna elements during a first time period, the switching occurring on at least several signal boundaries corresponding to base station channel estimation memory reset points occurring during said first time period, thereby changing the antenna elements used to transmit signals from said single transmitter signal processing link, each switching being processed and followed by at least one dwell, one dwell being a time period within the first time period during which said wireless terminal transmits signals to said base station using a single set of tones, a different set of tones being used in immediately successive dwells during the first time period.

14. The wireless terminal of claim 13, wherein said switching component switches between the first and second antenna elements according to a predetermined switching sequence.

15. A method of operating a wireless terminal to communicate with a base station, the wireless terminal including a single transmitter signal processing link including a switching component for connecting the single transmitter signal processing link to a plurality of antenna elements, the switching component for switching on signal boundaries corresponding to points at which the base station performs a reset of a channel estimate stored in a memory of the base station, but not between the boundaries, the channel estimation performed by the base station in a channel estimation interval immediately preceding the channel estimate reset being independent of the channel estimation performed in an immediately succeeding channel estimate reset, the plurality of antenna elements including at least a first antenna element and a second antenna element, wherein each antenna element is independently usable, the method comprising:

operating the switching module for a first time period to switch between the first and second antenna elements at least some of the signal boundaries occurring between the first time period corresponding to points at which the base station performs a reset of the channel estimates stored in the base station memory, thereby changing the antenna elements used to transmit signals from said single transmitter signal processing link.

16. The method of claim 15, wherein the switching component switches between the first and second antenna elements according to a predetermined switching sequence.

17. The method of claim 16, wherein the switching sequence is periodic.

18. The method of claim 17, wherein said periodic switching sequence switches between antenna elements at equal intervals, thereby resulting in equal use of antenna elements.

19. The method of claim 15, wherein the switching component switches between the first and second antenna elements as a function of a signal from the base station indicative of channel quality.

20. The method of claim 19, wherein the signal indicative of channel quality is a transmit power control signal.

21. The method of claim 19, wherein the transmitted signal is a CDMA signal.

22. The method of claim 15, wherein each of the plurality of antenna elements is oriented in a different direction.

23. The method of claim 15, wherein the plurality of antenna elements are spaced apart such that different communication paths exist between the first and second antenna elements and the base station.

24. The method of claim 23, wherein the spacing between the antenna elements is at least 1/4 wavelengths of the lowest frequency transmitted from the antenna elements.

25. A method of operating a wireless terminal to communicate with a base station, the wireless terminal including a single transmitter signal processing link including a channel estimation boundary switching module for connecting the single transmitter signal processing link to a plurality of antenna elements, the channel estimation boundary switching module for switching on signal boundaries corresponding to channel estimation signal boundaries of the base station, but not between the boundaries, the base station channel estimation switching boundary being a signal point at which the base station transitions between channel estimation intervals, channel estimation performed by the base station within a channel estimation interval being independent of channel estimation performed within an immediately preceding channel estimation interval, the plurality of antenna elements including at least a first antenna element and a second antenna element, wherein each antenna element is independently operable, the method comprising:

operating the channel estimation boundary switching module for a first period of time to switch between the first and second antenna elements, the switching occurring at least some of the channel estimation boundaries occurring during the first period of time, thereby changing the antenna elements used to transmit signals from said single transmitter signal processing chain;

wherein the channel estimation boundary switching module switches between the first and second antenna elements as a function of a signal from the base station indicative of channel quality; and

where the transmission acknowledgement signal indicating the channel quality is the success or failure of the reception of the transmitted signal.

26. A method of operating a wireless terminal to communicate with a base station, the wireless terminal comprising a single transmitter signal processing chain, the link includes a channel estimation boundary switching module for connecting said single transmitter signal processing link to a plurality of antenna elements, said channel estimation boundary switching module for switching over signal boundaries corresponding to channel estimation signal boundaries of a base station, but not between boundaries, a base station channel estimation switching boundary being a signal point at which said base station transitions between channel estimation intervals, channel estimation performed by a base station in one channel estimation interval being independent of channel estimation performed in an immediately preceding channel estimation interval, the plurality of antenna elements including at least a first antenna element and a second antenna element, wherein each antenna element is independently operable, the method comprising:

operating the channel estimation boundary switching module for a first period of time to switch between the first and second antenna elements, the switching occurring at least some of the channel estimation boundaries occurring during the first period of time, thereby changing the antenna elements used to transmit signals from said single transmitter signal processing chain;

wherein the channel estimation boundary switching module switches between the first and second antenna elements as a function of a signal from the base station indicative of channel quality; and

wherein the handover is performed as a function of a plurality of signals received from a base station, the method comprising:

different sets of switching control information for signals received from the base station corresponding to signals transmitted from the wireless terminal using different antenna elements are stored.

27. The method of claim 26, wherein each channel estimation interval includes a plurality of OFDM symbol transmission time periods, and wherein the tones used by the wireless terminal in each signal estimation interval are determined according to a frequency hopping sequence.

28. A wireless terminal for use in a communication system including a base station, the wireless terminal comprising:

a single transmitter signal processing chain including a switching module for connecting said single transmitter signal processing chain to a plurality of antenna elements, said switching module for switching over, but not between, signal boundaries corresponding to base station channel estimate reset points, which are signal points at which said base station switches between channel estimation intervals and resets channel estimates included in the base station, channel estimation performed by the base station in a channel estimation interval immediately preceding the channel reset being independent of channel estimation performed in a subsequent channel estimation interval immediately following the channel estimate reset, said plurality of antenna elements including at least a first antenna element and a second antenna element, wherein each antenna element is independently usable, and:

means for controlling the switching module to switch between said first and second antenna elements during a first time period, the switching occurring on at least some of the signal boundaries occurring between said first time period corresponding to a base station channel estimate reset point, thereby changing the antenna elements used to transmit signals from said single transmitter signal processing link.

29. The wireless terminal of claim 28, wherein said switching component switches between the first and second antenna elements according to a predetermined switching sequence.

30. A method of operating an OFDM communications device, the method comprising:

i) assigning audio from the first group of audio to a plurality of different subsets of audio, the subsets including at least first and second subsets of audio, each of said different subsets of audio differing from each other by at least one audio;

ii) transmitting each of said different subsets of tones in parallel using different antenna elements during the same time interval; and

iii) repeating steps i) and ii).

31. The method of claim 30, wherein the audios assigned to the first and second audio subsets are mutually exclusive.

32. The method of claim 30 further comprising:

changing the number of audios assigned to at least one of the first and second subsets of audios while repeating steps i) and ii).

33. The method of claim 32, wherein the repeating of steps i) and ii) is performed periodically, and wherein the allocation of audio is changed periodically.

34. The method of claim 32, further comprising receiving a signal indicative of channel quality from a device, wherein the device receives signals transmitted from the first and second antenna elements; and

wherein said allocation of audio to audio subsets is performed as a function of a signal indicative of channel quality.

35. The method of claim 34, wherein the signal indicative of channel quality is a transmit power control signal.

36. The method of claim 34, wherein the signal indicative of the channel quality is a transmission acknowledgement signal indicative of success or failure of reception of the transmitted signal.

37. The method of claim 34, wherein the distribution of audio is performed as a function of a plurality of signals received from the device, the method comprising:

different sets of audio allocation control information for signals received from the base station corresponding to signals transmitted from the apparatus using different antenna elements are stored.

38. The method of claim 30, wherein the first subset of audio is allocated a plurality of audio and the second subset of audio is unallocated audio.

39. An OFDM communication apparatus, comprising:

distributing means for distributing audio from a first group of audio to a plurality of different audio subsets, the subsets comprising at least first and second subsets of audio, each of said different audio subsets differing in at least one audio from each other;

transmitting means for transmitting each of said different subsets of tones in parallel using different antenna elements during the same time interval; and

control means for controlling said dispensing means and said sending means to repeat the dispensing and sending operations.

40. The method of claim 39, wherein the audio assigned to the first and second subsets of audio are mutually exclusive.