HK1090234A

HK1090234A - Methods and apparatus of enhanced coding in multi-user communications systems

Info

Publication number: HK1090234A
Application number: HK06110681.7A
Authority: HK
Inventors: 拉吉弗．拉罗拉; 穆拉里．萨利尼瓦森; 厉隽怿
Original assignee: 高通股份有限公司
Priority date: 2003-02-19
Filing date: 2004-02-19
Publication date: 2006-12-15

Description

Method and apparatus for enhanced coding in a multi-user communication system

Technical Field

The present invention is directed to an improved method of encoding and transmitting information in a wireless communication system.

Background

Superposition coding in a multi-user communication system will now be discussed. A multi-user communication system includes several transmitters and receivers in communication with each other and may use one or more communication methods. Generally, multi-user communication methods can be classified into one of two cases:

(a) a single transmitter communicating with several receivers, commonly referred to as a broadcast communication method, an

(b) Several transmitters communicate with a common receiver, which is commonly referred to as a multiple access communication method.

The broadcast communication method is commonly referred to as a "broadcast channel" in the communications and information literature, and will be referred to as such in the remainder of this document. The "broadcast channel" refers to a physical communication channel between a transmitter and a plurality of receivers and a communication resource used by the transmitter for communication. Similarly, the multiple access communication method is commonly referred to as a "multiple access channel," and this term will be used for the remainder of this document. Also, the "multiple access channel" refers to a physical communication channel between a plurality of transmitters and a common receiver, and a communication resource used by the transmitters. Broadcast communication methods are often used to implement downlink communication channels in typical cellular wireless systems, where a base station broadcasts to a plurality of wireless terminals, while uplink channels in such systems are often implemented using multiple access communication methods, where a plurality of wireless terminals may transmit signaling to a base station.

The transmission resources in a multi-user communication system can typically be represented in time, frequency or code space. The information theory shows that in particular the capacity of the system can be increased in the same transmission resources, for example simultaneously in the same frequency, by transmitting simultaneously to a plurality of receivers in the case of a broadcast communication method, or by allowing a plurality of transmitters to transmit simultaneously in the case of a multiple access communication method. In the case of the broadcast communication method, a technique for simultaneously transmitting to a plurality of users in the same transmission resource is also referred to as "superposition coding". In the context of the present invention, controlled superposition coding represents a valuable practical technique in both broadcast and multiple access communication methods.

The advantages of superposition coding will be apparent in view of the following discussion of transmission techniques for use in broadcast communication methods. Consider a single transmitter communicating with two receivers whose channels may be defined by an ambient Gaussian noise level N₁And N₂Is described wherein N is₁＜N₂I.e. the first receiver has a stronger channel than the second receiver. Assume that the communication resources available to the transmitter are a total bandwidth W, and a total power P. The transmitter may employ several strategies toThe receiver communicates. Fig. 1 includes a graph 100 depicting the achievable rates in a broadcast channel for a first user with a stronger receiver and a second user with a weaker receiver under three different transmission strategies. The vertical axis 102 of fig. 1 represents the velocity of the stronger receiver, while the horizontal axis 104 represents the velocity of the weaker receiver.

First, consider a strategy in which a transmitter multiplexes between two receivers in time, allocating all of its resources to one receiver at a time. If the fraction of time it takes to communicate with the first (stronger) receiver is represented by a, it is not difficult to prove that the achievable speeds of both users are satisfactory

The speed achieved by the above formula is represented by the line 106 in fig. 1 representing the Time Division Multiplexing (TDM) strategy as the fraction of time spent serving the first user, alpha, varies. Now consider another transmission strategy in which the transmitter allocates a certain portion of the bandwidth, β, and a portion of the available power, γ, to the first user. The second user gets the remainder of the bandwidth and power. After the portions are allocated, the transmitter communicates with both receivers simultaneously. Under this transmission strategy, the velocity region can be characterized by the following formula.

The velocity achieved by the above formula is visualized by the convex piecewise curve 108 in fig. 1 representing the Frequency Division Multiplexing (FDM) strategy. It is clear that the strategy of allocating the available power and bandwidth in an appropriate manner between two users outweighs the time separation of resources. However, the second strategy is still not optimal.

The supremum of the achievable speed area under all transmission strategies is the broadcast capacity area. For the case of Gaussian noise level, the region is characterized by the formula

And is depicted by the dashed curve 110 in fig. 1 representing capacity. Consists of IT-18 (1): 214, 1972, broadcast channel, thomas cover in t.m. cover, indicates that a communication technique known as superposition coding can reach this capacity region. In this technique, signals to different users are transmitted using different powers in the same transmission resource and superimposed on each other. The gain achievable by superposition coding exceeds any other communication technique that requires sharing of transmission resources between different users.

The basic concept of superposition coding is illustrated in graph 200 of fig. 2. Graph 200 includes a vertical axis 202 representing quadrature and a horizontal axis 204 representing in-phase. Although this example employs QPSK modulation, in general, the choice of modulation settings is not limited. Furthermore, this example outlines the case of two users, but this concept can be generalized to multiple users in a simple manner. Assume that the total transmit power budget of the transmitter is P. It is assumed that the first receiver, referred to as the "weaker receiver", has greater channel noise and the second receiver, referred to as the "stronger receiver", has less channel noise. Four circles filled with a pattern 205 represent QPSK constellation points that will be transmitted at high power (better protected), (1- α) P, to a weaker receiver, with arrow 206 providing a measure of the strength of the high power QPSK transmission. At the same time, the QPSK constellation is also used to convey additional information to the stronger receiver at low power (less protected), ap, where arrow 207 provides a measure of the strength of the lower power QPSK transmission. The actual transmitted symbols that combine the two high and low power signals are represented in fig. 2 as a blank circle 208. The key concept expressed by this figure is that the transmitter communicates with both users simultaneously using the same transmission resources. In this document, high power signals are also referred to as protected signals, and low power signals are also referred to as conventional signals.

The receiver strategy is rather simple. The weaker receiver observes a high power QPSK constellation with a low power signal superimposed on it. When a weaker receiver decodes a high power signal, the signal-to-noise ratio (SNR) experienced by the weaker receiver may not be sufficient to analyze the low power signal, and thus the low power signal appears as noise and slightly degrades the SNR. On the other hand, the SNR experienced by the stronger receiver is sufficient to analyze both the high and low power QPSK constellation points. The strategy of the stronger receiver is to first decode the high power points (which are intended for the weaker receiver), remove their effect from the composite signal, and then decode the low power signal.

In practice, however, this strategy does not generally work well. Any imperfections in the removal of the high power signal appear as noise to the decoder recovering the low power signal.

In view of the foregoing discussion, it is apparent that there is a need for novel methods and apparatus that allow communication systems to operate using broadcast and/or multiple access communication methods with controlled superposition coding, thereby taking advantage of the higher speeds achievable in the channel, while overcoming the difficulties that are not perfectly eliminated from the high power signals and the complexity and cost associated with joint decoder methods.

Disclosure of Invention

The present invention is directed to transmitter and receiver techniques for encoding that enable decoding of conventional signals without being compromised by imperfect cancellation of protected signals.

Exemplary embodiments of the present invention are described below in the context of a cellular wireless data communication system using Orthogonal Frequency Division Multiplexing (OFDM). Although an exemplary wireless system is used for purposes of explaining the present invention, the present invention is not limited to the exemplary embodiment and may be applied to many other communication systems, such as systems using Code Division Multiple Access (CDMA).

In accordance with various embodiments of the present invention, the first and second sets of information are transmitted using a transport block comprising a plurality of minimum transmission units, each minimum transmission unit corresponding to a unique combination of resources including at least two of time, frequency, phase, and spreading code. The minimum transmission unit is also called a degree of freedom. In this document, the terms minimum transmission unit and degree of freedom are used interchangeably. The transport block may be relatively large when compared to the smallest size transport block that may be required to encode one of the sets of information to be transmitted.

An exemplary embodiment of the present invention includes defining a first group of the minimum transmission units for communicating the first group of information, the first group of minimum transmission units including at least a majority of the minimum transmission units in the transport block, defining a second group of the minimum transmission units for communicating the second group of information, the second group of minimum transmission units including fewer minimum transmission units than the first group; at least some of the minimum transmission units in the first and second sets of minimum transmission units are identical; and communicating the first and second sets of information using a minimum transmission unit contained in the first and second sets of minimum transmission units. A first set of the minimum transmission units contained in a transport block is used to convey the first set of information, the first set of minimum transmission units including at least a majority of the minimum transmission units in a transport block. Defining, e.g., selecting, a second group of the minimum transmission units for communicating the second set of information, the second group of minimum transmission units including fewer minimum transmission units than the first group; at least some of the minimum transmission units in the first and second sets of minimum transmission units are identical. The first and second sets of information are communicated by transmitting at least some of the minimum transmission units included in the first and second sets of minimum transmission units with corresponding information modulated thereon. The information may be communicated by superimposing the first and second information on a common minimum transmission unit or by puncturing the first set of information to transmit the second set of information on the first and second sets of common minimum information units. Error correction codes may be used to recover information lost by superimposing the second set of information on the common transmission unit. The information transmitted in the first and second sets of information may be, for example, user data and control information including acknowledgements and assignments.

The first and second sets of information may, and in various embodiments are, transmitted using the first and second portions of the minimum transmission unit by transmitting the minimum transmission unit including modulation information corresponding to the different sets of information from different transmitters. The transmitters may be located in different devices, such as wireless terminals. In other embodiments, the first and second sets of information are communicated by transmitting a minimum transmission unit for communicating the first and second sets of information from a single transmitter, such as a base station transmitter.

The first set of minimum transmission units comprises a majority of the minimum transmission units in the transport block, but typically a higher proportion of the minimum transmission units, for example in some embodiments the first set comprises at least 75% of the total number of minimum transmission units, and sometimes 100% of the minimum transmission units in the block. The second set of minimum transmission units typically comprises less than 50% of the minimum transmission units in a block, and sometimes comprises relatively few minimum transmission units, e.g. less than 5 or 10% of the minimum number of transmission units in a transport block. In this case, even if a receiver attempting to decode the smallest transmission unit used to convey the first set of information does not recover any smallest transmission unit in the second set of transmission units, the information of the first set intended to be transmitted on some smallest transmission units included in the second set may be recovered in some embodiments by using an error correction code.

By using a minimum transmission unit common to both the first and second sets of minimum transmission units, a correct superposition can be used to convey information corresponding to both the first and second sets of information. Alternatively, information corresponding to the first set of information that is intended to be transmitted on the common smallest information unit may be punctured (e.g., not transmitted), while the punctured information may be recovered by using an error correction code.

In one particular exemplary embodiment, the first and second sets of information using at least some minimum transmission units included in the first set of minimum transmission units may be transmitted at a first power level as part of a transmission process, while the minimum transmission units of the second set of minimum transmission units are transmitted at a higher power level on a per minimum transmission unit basis than the first signal. The power level at which the smallest information unit in the second set is transmitted is, in some embodiments, at least 3dB greater than the power level at which the smallest transmission unit corresponding to the first signal is transmitted. It is sometimes possible, and indeed, to vary the power level of the smallest information unit in the first and second groups, for example to reflect changes in channel conditions.

Various embodiments of the receiver are possible in accordance with the invention. Two receivers, e.g., a first and a second receiver, may operate independently and in parallel. From the smallest information units in the transport block that are actually transmitted, one receiver is used to recover the first set of information and the other receiver is used to recover the second set of information. In one such embodiment, the first receiver treats the smallest information blocks comprising signals corresponding to the second set of information as comprising impulse noise and, for example, discards, ignores or minimizes their impact on the output of the receiver. In such an embodiment, the second receiver treats the effect of the received signal corresponding to the first set of information for the smallest transmission unit as background noise. Since the signals corresponding to the second set of information are typically transmitted using a relatively high power level, e.g., a power level sufficient for the first receiver to consider the signals as impulse noise, it is typically relatively easy to recover the second signal even if the signals corresponding to the first set of information appear as background noise. Since the effect of transmitting the second set of information is typically limited to relatively few symbols in the transport block, the effect of the high power signal on the signal used to transmit the first set of information tends to be very localized to allow for recovery of any lost information in most cases through the use of conventional error correction codes included in the transmitter information.

In another embodiment of the present invention, an apparatus also includes two receivers. However, rather than operating independently in parallel, the first receiver identifies a minimum transmission unit, e.g., a high power minimum transmission unit, corresponding to the second set of information. It then conveys to the second receiver information indicating which received minimum transmission unit corresponds to the second set of information. The second receiver discards the minimum transmission unit corresponding to the second set of information and then decodes the remaining received minimum transmission units. Since the number of discarded minimum information units tends to be small, e.g. in most cases below 5% of the received minimum information unit, the second receiver is still normally able to recover the complete first set of information by using an error correction code for protecting the transmitted information from errors due to loss or corruption of the minimum transmission unit during transmission.

In various embodiments, the present invention achieves the benefits of superposition coding in a multi-user communication system while using a receiver that is simple in design but still performs well in terms of performance. The present invention discloses novel and efficient superposition coding techniques for both broadcast channels and multiple access channels.

In the case of a broadcast channel, for example, a single transmitter transmits data to multiple receivers. In the context of a typical system, a transmitter is a base station that communicates in a cellular downlink with a wireless receiver (e.g., a mobile receiver). Mobile users in a cellular system may experience a wide variety of SNR states due to variations in path loss depending on location within the cell. It is assumed without loss of generality that a base station has two signals that want to communicate simultaneously with two different mobile receivers that experience different path losses. The conventional signal is intended for receivers experiencing a higher signal-to-noise ratio (SNR), which will be referred to as "stronger" receivers hereinafter. The second signal, termed the "protected" signal, is intended for use by a "weaker" receiver operating at a lower SNR on a lower quality channel. The classification of a mobile receiver as "stronger" or "weaker" is not static, but rather relatively bounded.

If superposition coding is not used, air link resources should be allocated between the regular and protected signals, which is not optimal. In order to distinguish the new superposition coding method disclosed in the present invention, the existing superposition coding method described in the background section is hereinafter referred to as "conventional superposition coding" in the rest of this document. In a conventional superposition coding environment, the same air link resources are used, while the protected and regular signals are transmitted. For example, assume that the air link resource for simultaneous transmission of normal and protected codewords comprises K symbols, A₁、...、A_K. Also, assuming that a regular codeword would carry M information bits, a protected codeword would carry N information bits. It is assumed that both the conventional and protected codewords use BPSK (binary phase shift keying) modulation. In conventional superposition coding, M conventional information bits are converted into K code bits by a coding scheme, such as convolutional coding, and the K code bits are then mapped to K BPSK symbols B₁、...、B_K. At the same time, the N protected information bits are converted into different K code bits by another coding scheme, e.g., convolutional coding, and the K code bits are then mapped to K BPSK symbols C₁、...、C_K. Finally, the K BPSK symbols from the protected information bits and the K BPSK symbols from the regular information bits are combined and the K air link resource symbols A are used₁、...、A_K：A₁＝B₁+C₁、...、A_K＝B_K+C_KIt is transmitted. In the composite signal, the protected symbols are typically transmitted at a higher power per bit so that the weaker receiver can reliably receive them. The regular symbols are transmitted at a relatively low power per bit. In this example, and in general in nature, the energy of the conventional signal will transmit over all degrees of freedom of the protected signalAnd (4) distributing.

The power of the transmitter is selected in such a way that the weaker receiver is typically only able to decode the protected codeword. For this receiver, the conventional signal appears as noise only. On the other hand, a stronger receiver should be able to decode both codewords. A strong good decoding strategy that a receiver can employ is to attempt to decode the two codewords together. However, this is often too complex for practical receivers. Therefore, the strategy typically employed by stronger receivers is sequential decoding. The stronger receiver first decodes the protected codeword, then removes it from the received composite signal, and finally decodes the regular codeword, which is a codeword that is meaningful to the stronger receiver. In practice, however, the successive cancellation and decoding schemes described above do not always perform well. If the SNRs of the stronger and weaker receivers and the speed of the desired communication are such that the normal and superimposed signals are transmitted at approximately the same power, then it may be difficult or inaccurate to eliminate the protected codeword.

In fact, even when the power transmitted on the two codewords is different, there is an obstacle to successive decoding. For example, most communication systems experience some degree of inherent noise at the receiver. Unlike additive noise, this intrinsic noise is typically associated with the transmitted signal and has an energy proportional to the transmitted power. Channel estimation noise in a wireless communication system is an example of inherent noise. In a conventional superposition coding environment, channel estimation noise causes imperfect cancellation of the protected signal at the stronger receiver. The residual cancellation error may have considerable energy, especially when compared to low power superimposed signals. Thus, a stronger receiver may not be able to correctly decode the conventional codeword, taking into account the residual erasure.

From the discussion it is clear that although conventional superposition coding allocates the energy of the protected codeword in each degree of freedom, it is desirable to concentrate the energy between one or a few degrees of freedom. According to the invention, the energy is concentrated in a limited number of degrees of freedom, facilitating easy detection and cancellation of the protected signal at the receiver, even when all the transmitted energy included in the two signals is similar. According to the invention, the energy in the codeword is concentrated between one or several degrees of freedom.

Using the encoding and transmission methods described above, multiple sets of information may be transmitted using a common set of overlapping communication resources, e.g., time, frequency, and/or code. Many additional features and advantages of the invention will be apparent in view of the detailed description that follows.

Drawings

Fig. 1 depicts a graph showing the achievable rates in a broadcast channel for a first user with a stronger receiver and a second user with a weaker receiver under three different transmission strategies.

Fig. 2 shows an example of superposition coding using QPSK modulation.

Fig. 3 shows an example of pulse position modulation.

Fig. 4 shows an example of high-speed superposition coding according to the invention.

Fig. 5 shows another example of high-speed superposition coding according to the invention, in which the glitch signal concentrates its energy over 4 symbol positions.

Fig. 6 illustrates exemplary high speed superposition coding in a multiple access channel, which is shown as a composite signal at a base station receiver, in accordance with the present invention.

Figure 7 shows a typical traffic segment and the assignment of the traffic segment to users by the base station.

Figure 8 shows an exemplary assignment segment corresponding to a traffic segment.

Figure 9 shows a typical downlink traffic segment and an acknowledgement segment.

Fig. 10 shows an exemplary assignment segment, downlink traffic segment, and acknowledgement segment, both using high speed superposition coding in accordance with the present invention.

Fig. 11 shows 2 exemplary sets of information, a transmission block of one Minimum Transmission Unit (MTU), and partially overlapping sets of minimum transmission units, which may be used to define sets of information and which may be used in part or in whole to transmit signals to convey information in accordance with the present invention.

Fig. 12 illustrates a transport block of another exemplary MTU in accordance with the present invention, which indicates that the transport block may be subdivided into sub-blocks.

Fig. 13 illustrates a method of transmitting two signals corresponding to two sets of information using different devices having different transmitters, each transmitter generating a signal corresponding to one set of information, in accordance with the present invention.

Figure 14 illustrates two other methods of transmitting two sets of information according to the present invention, either using a single transmitter outputting two signals, each signal corresponding to information in a set of information, or using a single transmitter that internally combines signaling to output a single composite signal.

FIG. 15 shows two devices including filtering and an error correction module in accordance with the present invention; each device includes two receivers and each device is operable to receive the composite signal and retrieve the two sets of information that have been transmitted.

FIG. 16 illustrates another apparatus including an MTU signal identification module in accordance with the present invention; the device comprises two receivers and the device is operable to receive the composite signal and retrieve the two sets of information that have been transmitted.

Figure 17 illustrates an exemplary communication system in which the apparatus and methods of the present invention may be implemented.

Figure 18 illustrates an exemplary base station implemented in accordance with the present invention.

Figure 19 illustrates an exemplary end node (wireless terminal) implemented in accordance with the present invention.

Detailed Description

Fig. 17 illustrates an exemplary communication system 1700 in which apparatus and methods consistent with the invention may be employed. Exemplary communication system 1700 includes a plurality of base stations, including base station 1(BS 1)1702 and base station N (BS N) 1702'. BS 11702 is connected to a plurality of End Nodes (ENs), EN11708, EN N1710, respectively, via wireless links 1712, 1714. Similarly, BS N1702 'is connected to a plurality of End Nodes (ENs), EN 11708', EN N1710 ', respectively, via wireless links 1712, 1714'. Element 11704 represents a wireless coverage area where BS 11702 may communicate with an EN, such as EN 11708. Element N1706 represents a wireless coverage area in which BS N1702 'may communicate with an EN, e.g., EN 11708'. ENs 1708, 1710, 1708 'and 1710' may move around in communication system 1700. The base stations BS 11702, BS N1702' are connected to a network node 1716 via network links 1718, 1720, respectively. Network node 1716 is connected to other network nodes, e.g., other base stations, routers, home agent nodes, Authentication Authorization Accounting (AAA) server nodes, etc., and the internet via network link 1722. The network links 1718, 1720, 1722 can be, for example, fiber optic cables. Network link 1722 provides an interface outside of communication system 1700 to allow users, such as ENs, to communicate with nodes outside of system 1700.

Fig. 18 illustrates an exemplary base station 1800 in accordance with the present invention. Exemplary base station 1800 may be a more detailed illustration of base stations 1702, 1702' of fig. 17. Exemplary base station 1800 includes a plurality of receivers, receiver 11802, receiver N1804, a plurality of transmitters, transmitter 11810, transmitter N1814, a processor 1822 such as a CPU, an I/O interface 1824, and memory 1828 coupled together via a bus 1826. The various units 1802, 1804, 1810, 1814, 1824, and 1828 may exchange data and information via a bus 1826.

Receivers 1802, 1804 and transmitters 1810, 1814 are coupled to antennas 1806, 1808 and 1818, 1820, respectively, to provide a path for base station 1800 to communicate, e.g., exchange data and information, with end nodes, e.g., wireless terminals, within its cellular coverage area. Each receiver 1802, 1804 may include a decoder 1803, 1805, respectively, to receive and decode signaling encoded and transmitted by the end nodes operating within its cell. The receivers 1802, 1804 may be any one of, or variations of, the exemplary receivers shown in device 51502 of fig. 15, device 61532 of fig. 15, or device 71562 of fig. 16, such as receivers (1506, 1508), (1536, 1538), (1563, 1564). In accordance with the present invention, the receivers 1802, 1804 should be capable of receiving a composite signal including a regular or fundamental signal and a strobe signal and retrieving sets of information corresponding to the original sets of previously transmitted information. Each transmitter 1810, 1814 may include an encoder 1812, 1816 that encodes signaling prior to transmission. The transmitters 1810, 1814 may be any one of, or variations of, the exemplary transmitters shown in apparatus 11302 and apparatus 21308 of fig. 13, apparatus 3 of fig. 14, or apparatus 41410 of fig. 14, such as transmitters (1304 and 1310), (1404), (1412). In accordance with the present invention, the transmitters 1802, 1805 should be capable of transmitting one or more of the following: a regular or base signal, a flicker signal and/or a synthetic signal.

Memory 1828 includes routines 1830 and data/information 1832. The processor 1822 performs processing to control basic base station functions and control and implement the new features and improvements of the present invention, including generating and transmitting a composite signal, receiving a composite signal, classifying the composite signal into regular or basic signal information and flicker signal information, classifying and recovering information, by executing the routines 1830 in the memory 1828 and using the data/information 1832 in the memory 1828 to control the operation of the base station 1800, to operate the receivers 1802, 1804, the transmitter 1810 and the I/O interface 1824. The I/O interface 1824 provides an interface to the internet and other network nodes, e.g., intermediate network nodes, routers, AAA server nodes, home agent nodes, etc., for the base station 1800 to allow end nodes that communicate with the base station 1800 over wireless links to connect, communicate, and exchange data and information with other peer nodes, e.g., another end node, throughout the communication system and outside of the communication system, e.g., via the internet.

Routines 1830 include communications routines 1834 and base station control routines 1836. Base station control routines 1836 include a scheduler 1838, an error detection and correction module 1840, a transmitter control routine 1844, and a receiver control routine 1846. Data/information 1832 includes received information 11850, received information N1852, transmitted information 11854, transmitted information N1856, identified MTU information 1858, and user data/information 1848. User data/information 1848 includes a plurality of user information, user 1 information 1860, and user N information 1862. Each user information, e.g., user 1 information 1860, includes terminal Identifier (ID) information 1864, data 1866, channel quality report information 1868, section information 1870, and classification information 1872.

Transmission information 11854 may include a set of information that may correspond to a first signal, e.g., a regular or fundamental signal, information defining the transport blocks of MTUs that may be used to transmit the first signal, information defining a first set of MTUs that will be used to define the signal, information that will be modulated on the first set of MTUs to define the first signal, information defining which MTUs corresponding to the first signal information should be transmitted, e.g., to a wireless terminal. In some embodiments, each MTU conveying the first set of information data will be transmitted. In other embodiments, most MTUs conveying the first set of information should be transmitted. In such an embodiment, the MTU corresponding to the first set of information and, at the same time, the second set of information, e.g., a strobe signal, may be discarded prior to transmission.

Transmission information N1856 may comprise a set of information which may correspond to a second signal, e.g. a blinking signal, information defining a transport block which may be used, e.g., to transmit said second signal to a wireless terminal, information defining a second set of MTUs to be used to define said second signal, information to be modulated on said second set of MTUs to define said second signal. The first and second transport blocks may be identical. In this case, transport block information from the transmission information 1854, 1856 specifying the size and/or shape of the common transport block may be, and often is, stored in memory 1828, respectively. The received information 11850 includes a first set of information recovered from the receiver 11802, such as information corresponding to previously transmitted information for a first set of wireless terminals. The first set of recovered information may be recovered, for example, from a regular or base signal. The received information N1852 includes a second set of information recovered from the receiver N1804, e.g., information corresponding to pre-transmitted information for a second set of wireless terminals. The second set of recovered information may be recovered, for example, from the flash signal.

The conventional and flash signals defining each original set of pre-transmitted information share some common MTU. The identified MTU information 1858 may include a set of MTUs identified in the second or flash signal, which may be obtained by the decoder 1805 of the receiver N. Identified MTU information 1858 may be forwarded to receiver 11802, which may exclude those MTUs prior to passing the received signal on to perform an error correction module, or alternatively, identified MTU information 1858 may be forwarded to an error detection and correction module 1840 in memory and/or an error detection and correction module in decoder 1803.

Data 1866 may include data received from and data to be transmitted to the end node. In some embodiments, one terminal identifier ID 1864 is used for each of the N wireless terminals that may interact with the base station at the same point in time. When entering a cell, a wireless terminal, e.g., a terminal node, is assigned a terminal ID 1864. Thus, as the wireless terminal enters and leaves the cell, the terminal ID will be used again. Each base station has a set of terminal identifiers (terminal IDs) 1864 assigned to users (e.g., wireless terminals) to be served. Channel quality report information 1868 may include information regarding the channel quality of the user as determined by base station 1800, as well as feedback information from the user including downlink channel quality reports, interference information, power information from wireless terminals. Section information 1870 may include information according to the type of use, e.g., traffic channel, assignment channel, request channel; characteristics such as MTU, frequency/phase and time, OFDM tone-symbol; the type of signal used for the portion, e.g. regular or basic versus blinking signal, defines the information of the portion assigned to the user. Classification information 1872 includes information that classifies a user, e.g., wireless terminal, as either a "stronger" or "weaker" transmitter.

Communications routines 1834 includes various communications applications that may be used to provide particular services, such as IP telephony services, text services, and/or interactive gaming, to one or more user terminal nodes in the system.

Base station control routines 1836 perform functions including basic base station control and controls related to the apparatus and methods of the present invention. Base station control routines 1836 exercises control over signal generation and reception, error detection and correction, data and pilot hopping sequences, I/O interface 1824, assigning sections to users, and scheduling users to terminal ID 1864. More specifically, scheduler 1838 schedules users to terminal IDs 1864 and assigns portions to users using user classification information 1872 and portion information 1870. According to the invention the scheduler decides as to which user and which part should be allocated to the regular or basic signal and which user and which part should be allocated to the flashing signal. Some users, such as those with high power available and who will transmit small amounts of information, may be better suited for strobe signaling than other users who may wish to transmit large amounts of information and have limited available power. Certain types of channels may be more suitable for transmission using a flash signal. For example, in many cellular communication systems, control channels are transmitted at broadcast power because they are constrained by the mobile user having the weakest channel. Flicker signaling is well suited for this application, and its use can often result in power reduction with little loss of robustness. Using classification information 1872 and section information 1870, scheduler 1838 may match users with low downlink signal-to-noise ratios (SNRs) to regular sections within the channel, while users with high SNRs may match flickering (e.g., "protected") sections within the channel.

Transmitter control module 1844 uses data/information 1832 including transmission information 11854, transmission information N1856, terminal ID 1864, data 1866, and section information 1870 to generate transmission signals and control the operation of transmitters 1810, 1814 in accordance with the present invention. For example, transmitter control module 1844 may control transmitter 1810 to encode, via its encoder 1812, the set of information included in transmit information 11854 into a signal, such as a conventional or fundamental signal, that transmitter 11810 may transmit. Transmitter control module 1844 may encode the set of information included in transmission information N1856 into a flashed or protected signal using the set of MTUs corresponding to that information 1856. The transmit control module 1844 may control transmitter N1814 to encode, via its encoder 1816, the set of information included in transmit information N1856 into a signal that transmitter N1814 may transmit. For example, the transmission control module 1844 may encode the set of information included in the transmission information 1856 into a flashed or protected signal using the set of MTUs corresponding to the information N1856. Alternatively, in various embodiments of transmitters 1810, 1814, a single transmitter may be used which internally combines or mixes the signals under the direction of transmitter control module 1844 according to transmission information 11854 and transmission information N1856. Such a mixing operation may include superimposing the regular and flashing signals prior to transmission, and/or selectively forming an MTU transmission group including each flashing signal element and elements of the regular signal not included in the flashing signal.

Receiver control module 1846 controls the operation of receivers 1802, 1804 to receive the combined signal and extract two sets of information, such as receiver information 11850 and receiver information N1852, in accordance with the present invention. The receive processing under control of receiver control module 1846 may include controlling decoders 1803, 1805, as well as controlling other units within the receiver. In some embodiments, the receiver control module 1846 controls the impulse noise filtering, background noise filtering, and error correction modules along with the receivers 1802, 1804. In some embodiments, the receiver control module controls the second signal MTU identifier module in one receiver, e.g., receiver N1804, and the discard module in another receiver, e.g., receiver 11802, and communicates the identified MTU information 1858 from the receiver N1804 to the receiver 11802; this allows the receiver 11802 to remove MTUs including glitch information from the stream of information entering the error detection module that attempts to recover the conventional signal information burst.

The error correction module 1840 operates in conjunction with or in lieu of an error detection and correction module that may be included in the receivers 1802, 1804. The error detection and correction capabilities included in the receivers 1802, 1804 and/or modules 1840 allow the base station 1800 to reproduce the set of information corresponding to the previously transmitted set of information even if the (regular or base) signal representing the previously transmitted set of information has been subject to superposition of or puncture phenomena caused by the second (flickering) signal, e.g., replacing some of the MTUs. In some embodiments, the MTU corresponding to the second set of information completely overlaps the MTU corresponding to the first set of information. Further, in some embodiments, the MTU corresponding to the first set of information fully occupies one transport block.

Fig. 19 illustrates an exemplary end node (wireless terminal) 1900 in accordance with the present invention. Exemplary terminal node 1900 may be used for any of terminal nodes 1708, 1710, 1708 ', 1710' of FIG. 17. Exemplary end node 1900, such as a wireless terminal, can be a mobile terminal, handset, mobile node, fixed wireless device, or the like. In this application, references to terminal node 1900 may be interpreted to correspond to any one of a wireless terminal, a mobile node, and the like. A wireless terminal may be a mobile node or a fixed device supporting a wireless communication link. Exemplary terminal node 1900 includes a plurality of receivers, receiver 11902, receiver N1904, a plurality of transmitters, transmitter 11910, transmitter N1912, a processor 1926, e.g., a CPU, and memory 1930 coupled together via bus 1928. Via bus 1928, the various units 1902, 1904, 1910, 1912, 1926, 1930 can exchange data and information.

The receivers 1902, 1904 and transmitters 1910, 1912 are coupled to antennas 1906, 1908 and 1914, 1916, respectively, to provide a path for a terminal node, e.g., a wireless terminal 1900, to communicate, e.g., exchange data and information, with a base station 1800 to which the cellular coverage area in which the wireless terminal 1900 operates belongs. Each receiver 1902, 1904 can comprise a decoder 1918, 1920, respectively, to receive and decode signaling encoded and transmitted by the base station 1800. Receivers 1902, 1904 may be any one of, or variations of, typical receivers shown in device 51502 of fig. 15, device 61532 of fig. 15, or device 71562 of fig. 16, e.g., receivers (1506, 1508), (1536, 1538), (1563, 1564). In accordance with the present invention, the receivers 1902, 1904 should be capable of receiving a composite signal comprising a regular or fundamental signal and a flicker signal and retrieving sets of information corresponding to the original sets of previously transmitted information. Each transmitter 1910, 1912 may include an encoder 1922, 1924 that encodes signaling prior to transmission. The transmitters 1910, 1912 may be any one of the exemplary transmitters shown in apparatus 11302 and apparatus 21308 of fig. 13, apparatus 3 of fig. 14, or apparatus 41410 of fig. 14, or variations thereof, such as transmitters (1304 and 1310), (1404), (1412). In accordance with the invention, the transmitter 1910, 1912 should be capable of transmitting one or more of the following: a regular or base signal, a flicker signal and/or a synthetic signal.

Memory 1930 includes routines 1932 and data/information 1934. Processor 1926 performs processing to control basic wireless terminal functions, and controls and implements the new features and improvements of the present invention, including generating and transmitting a composite signal, receiving a composite signal, classifying a composite signal into regular or basic signal information and blink signal information, classifying and recovering information, by executing routines 1932 in memory 1930 and using data/information 1934 in memory 1930 to control the operation of terminal node 1900, to operate receivers 1902, 1904 and transmitters 1910, 1912.

Routines 1932 include communications routines 1936 and wireless terminal control routines 1938. Wireless terminal control routines 1938 include a transmitter control module 1940, a receiver control module 1942, and an error correction module 1946. Data/information 1934 includes user data 1947, terminal Identifier (ID) information 1948, received information 11950, received information N1952, transmission information 11954, transmission information N1956, identified MTU information 1958, part information 1960, quality information 1962, and base station ID information 1964.

User data 1947 includes data to be transmitted to base station 1800 and data received from base station 1800, as well as intermediate data, such as data involved in the decoding process to recover the detected information. The transmission information 11954 may include a set of information that may correspond to a first signal, e.g., a regular or base signal, information defining the transport blocks of MTUs that may be used to transmit the first signal, information defining a first set of MTUs that will be used to define the signal, information that will be modulated on the first set of MTUs to define the first signal, information defining which MTUs corresponding to the first signal information should be transmitted, e.g., to a base station 1800. In some embodiments, each MTU conveying the first set of information data will be transmitted to the base station 1800. In other embodiments, most of the MTUs conveying the first set of information should be transmitted to the base station 1800. Transmission information N1956 may include a set of information that may correspond to a second signal, e.g., a flashing signal, information defining a transport block that may be used, for example, to transmit the second signal to a base station, information defining a second set of MTUs to be used to define the second signal, information that should be modulated on the second set of MTUs to define the second signal. Received information 11950 includes a first set of information recovered from receiver 11902, e.g., information corresponding to previously transmitted information for a first set of base stations. The first set of recovered information may be recovered, for example, from a regular or base signal. The received information N1952 includes a second set of information recovered from receiver N1904, e.g., information corresponding to the pre-transmitted information for the second set of base stations. The second set of recovered information may be recovered, for example, from the flash signal.

The conventional and flash signals defining each original set of pre-transmitted information share some common MTU. The identified MTU information 1958 may include a set of MTUs identified in the second or flash signal, which may be obtained by the decoder 1920 of the receiver N. The identified MTU information 1958 may be forwarded to the receiver 11902, where the receiver 1902 may exclude those MTUs before passing the received signal to the error correction module in the decoder 1918, or alternatively, the identified MTU information 1958 may be forwarded to the error correction module 1946 in memory and/or the error correction module in the decoder 1918.

Terminal ID information 1948 is an ID assigned by one base station. Base station ID information 1964 includes information, such as a tilt value, that can be used to identify the particular base station to which wireless terminal 1900 is connected. Using base station ID information 1964 and terminal ID 1948, the wireless terminal can determine the data and control the hopping sequence. Quality information 1962 may include information from detected pilots, downlink channel quality measurements and reports, interference levels, power information such as current transmission level and battery level, SNR, etc. In accordance with the invention, quality information 1962 can be fed back to the base station 1800 for classifying receivers as "stronger" or "weaker" receivers to facilitate scheduling and allocation by the base station 1800, including allocation of the normal or base portion and the high-speed portion. Part information 1960 may include information according to usage type, e.g., traffic channel, assignment channel, request channel; characteristics such as MTU, frequency/phase and time, OFDM tone-symbol; the type of signal used for the portion, e.g. regular or basic versus blinking signal, defines the information of the portion assigned to the user.

Communications routines 1936 include various communications applications that may be used to provide particular services, such as IP telephony services, text services, and/or interactive gaming, to one or more end node users.

Wireless terminal control routines 1938 control the basic functions of the wireless terminal 1900, including the operation of the transmitters 1910, 1912 and receivers 1902, 1904, signal generation and reception, including data/control hopping sequences, state control, and power control. The wireless terminal control routines 1938 also control and implement the new features and improvements of the present invention, including generating and transmitting a composite signal, receiving a composite signal, classifying the composite signal into regular or basic signal information and blink signal information, classifying and recovering information.

Transmitter control module 1940 may use data/information 1934 including transmit information 11954, transmit information N1956, terminal ID 1948, user data 1947, and portion information 1960 to generate transmit signals and control the operation of transmitters 1910, 1912 in accordance with the present invention. For example, transmitter control module 1940 may control transmitter 1910 to encode, via its encoder 1922, the set of information included in transmit information 11954 into a conventional or fundamental signal that transmitter 11910 can transmit. Transmitter control module 1940 may control transmitter N1912 to encode, via its encoder 1924, the set of information included in information 1956 into a flashed or protected signal using the set of MTUs corresponding to the information in transmitted information N1956. Alternatively, in various embodiments of the transmitters 1910, 1912, a single transmitter may be used that internally combines or mixes the signals under the direction of transmitter control module 1844 according to transmission information 11954 and transmission information N1956. Such a mixing operation may include superimposing the regular and flashing signals prior to transmission, and/or selectively forming an MTU transmission group including each flashing signal element and elements of the regular signal not included in the flashing signal.

Receiver control module 1942 controls the operation of receivers 1902, 1904 in accordance with the present invention to receive the composite signal and extract two sets of information, e.g., receiver information 11950 and receiver information N1952. The receive processing under control of the receiver control module 1942 may include controlling the decoders 1918, 1920, as well as controlling other elements within the receiver. In some embodiments, receiver control module 1942 controls the impulse noise filtering, background noise filtering, and error detection modules along with receivers 1902, 1904. In some embodiments, receiver control module 1942 controls the second signal MTU identifier module in one receiver, e.g., receiver N1904, and the discard module in another receiver, e.g., receiver 11902, and passes the identified MTU information 1958 from receiver N1904 to receiver 11902; this allows receiver 11902 to remove the MTU including the glitch information from the stream of information entering the error correction module that attempts to recover the set of regular signal information.

The error correction module 1946 operates in conjunction with or instead of one error correction module that may be included in the receivers 1902, 1904. The error detection and correction capabilities included in receivers 1902, 1904 and/or module 1946 allow wireless terminal 1900 to reproduce an information set corresponding to a previously transmitted information set even if the (regular or base) signal representing the previously transmitted information set has been subjected to superposition of a second glitch signal (glitch signal) or to a puncturing phenomenon caused by the second signal (glitch signal), e.g., to replace some MTU's.

On-off keying is a modulation technique in which a transmitter concentrates its energy along a subset of the degrees of freedom occupied by a codeword. For example, pulse position modulation is an example of on-off keying, where the transmitter uses energy only at those locations that pass a "1" and is turned off when a "0" is passed. Pulse position modulation can deliver log2(M) bits by concentrating the energy at one of M positions. By using positive and negative pulses, additional bits can be transferred. An example of pulse position modulation is shown in fig. 3. Fig. 3 shows a diagram 300 of 32 slots, e.g., typical individual slots 302. Energy is concentrated in the 17 th slot 306 and is represented by pulse 304. In fig. 3, if the pulse 304 can only be in one direction, e.g., the positive direction, then 5 bits of information can be conveyed using 32 positions or slots. In fig. 3, if the pulse 304 can be positive or negative, 6 bits of information can be conveyed using 32 positions or slots. In general, in the general case of on-off keying, information can be conveyed in two ways — first, the location of energy within the degree of freedom occupied by a code word, and second, the information contained within the signal occupying that location. For example, if the handset can estimate the channel by means of a reference signal, information can be encoded in phase and/or amplitude in addition to information encoded at the location of the energy of the prevalent switching signal. In the remainder of this document, this form of universal on-off keying will be referred to as flash signaling. Typically, in the example of flash signaling, the concentration of energy is limited to a small subset of the available degrees of freedom.

According to the invention, flash signaling may be used. A simple example of flicker coding according to the present invention will be described. Consider an embodiment of the present invention as applied to a digital communication system using BPSK signaling. In the example considered here, the air link resource is assumed to comprise 16 symbols. For example, in a typical spread-spectrum OFDM multiple-access system, the 16 air link resource symbols may be 16 orthogonal tones in one OFDM symbol period, or one tone in 16 OFDM symbol periods, or any suitable combination of tones and symbol periods (e.g., 4 tones in 4 OFDM symbol periods).

In fig. 4, the superimposed signal 400 comprises a conventional signal 420 conveyed using code words with energy spanning all 16 BPSK symbols, as shown in fig. 4 by the small unshaded rectangle. Conventional codewords may be constructed using, for example, convolutional codes. Assume that the protected signal is required to convey 5 information bits. In this embodiment, the location of the high energy symbol 430, as shown by the single shaded larger rectangle in fig. 4, may be used to convey the 5 protected bits. The protected signal comprises one BPSK symbol 430 transmitted at high power while a conventional signal 420 with energy distributed over 16 symbols is superimposed thereon. Note that the BPSK symbols of the protected signal may be located in any one of 16 different symbol positions. For reference, the first symbol 401 and the 16 th symbol 416 are identified in fig. 4. For example, in fig. 4, BPSK symbols are transmitted on the 9 th symbol. Thus, the symbol position conveys 4 of the 5 protected information bits. Further, the phase (e.g., sign) of the BPSK symbol conveys the 5 th protected bit.

To see the advantage of the coding scheme of the present invention over the conventional superposition coding scheme, the design of the stronger receiver is reconsidered. Stronger receivers may use the concept of sequential decoding. The stronger receiver first decodes the protected signal, then removes it from the received composite signal, and finally decodes the regular signal, or alternatively signals the weaker receiver to discard the tones on which the larger signal was detected. Note that with the new coding scheme of the present invention, even if the cancellation is not ideal, the corruption of the conventional codeword is limited to one or a few symbols, so the receiver can minimize the adverse effects of this corruption. For example, during decoding, the receiver may ignore symbols occupied by regular signals. In this case, the erasure operation is simplified to cause erasure at a specific symbol position, and it is possible to correct the loss using an error correction code.

In the example of fig. 4 above, each BPSK symbol of the 16 air link resource symbols represents one degree of freedom. The conventional signal distributes its energy in all 16 degrees of freedom. At the same time, each codeword of the protected signal concentrates its energy in one of 16 degrees of freedom. Note that as defined in the above embodiments, the glitch signal is an orthogonal code. However, the present invention is not dependent on any orthogonal nature of the codeword.

A transmitter design for use in coding implemented in accordance with the present invention will be described. The above-described examples illustrate the features and methods of the present invention, which may be implemented and utilized in a variety of communication systems. This method of superimposing a signal by concentrating the energy of the protected signal between a small subset of the available degrees of freedom, while distributing the energy of the regular signal between substantially all of the available degrees of freedom, is referred to in this document as flicker superposition coding. In the present discussion, protected codewords are denoted as "flash signals" and regular codewords are denoted as "regular signals" or "base signals". Although in general the method uses a blinking signal to transmit the protected information and a regular signal to transmit the regular information, in some embodiments of the invention this may be the opposite.

In accordance with the present invention, the glitch signaling provides a method of superimposed signals that allows the gain of the superimposed coding to be well obtained in a practical receiver. Generally, the same set of transmit resources is used to deliver the flash signal and the regular signal. However, each codeword of the flash signal concentrates its energy over a small subset of the available degrees of freedom. Each codeword of a conventional signal may spread its energy in each available degree of freedom. For easy detection and decoding of the flickering signal, it is desirable that its energy is high, which in some embodiments is significantly higher than the energy of the regular signal in the selected subset of degrees of freedom corresponding to the flickering signal. This relatively high energy concentration in the selected high-speed subset is feasible even when the total energy of the regular signal is higher than the total energy of the flicker signal. Finally, in order to easily detect and decode the regular signal, the impact of the glitch signal on the regular codeword should be minimal. In other words, the energy loss in the selected subset of degrees of freedom occupied by the flickering signal should have a small impact on decoding the conventional codeword.

The transmit power of the flash signal and the regular signal is selected based on several factors, including (a) the SNR of the intended receiver for both the high speed and regular signals; (b) information rates for high speed and conventional signaling; and (c) a method of constructing a code of a high-speed and regular signal. In general, the power can be independently selected to meet their own robustness and coding performance requirements. Furthermore, the flash signaling may be performed in an opportunistic manner to obtain maximum flexibility. In particular, the transmitter may opportunistically choose not to transmit the flickering signal and use a large portion of its available power to transmit the regular signal. Alternatively, the transmitter may choose to opportunistically transmit a flickering signal using a large portion of its available power, and choose not to transmit a regular signal.

A receiver design for use in coding implemented in accordance with the present invention will now be discussed. In one embodiment of the invention, the receiver first decodes the glitch signal. The glitch signal is detectable at the receiver because it is received at much higher power than the conventional codeword in the small subset of degrees of freedom. The receiver then removes the effect of the glitch before attempting to decode the conventional codeword. In the case of conventional superposition coding, the cancellation involves decoding the protected codeword and removing it from the received composite signal. In flicker superposition coding, in one embodiment, when the receiver is to decode a regular signal, the receiver completely discards the signals received in the subset of degrees of freedom of the decoded flicker signal codeword. Since a conventional signal distributes its signal energy in all degrees of freedom, in view of the error detection and correction capabilities of the decoder, eliminating the signal energy in a small subset of degrees of freedom will have little or negligible impact on the performance of decoding the conventional codeword.

In another embodiment of the invention, the receiver does not explicitly eliminate the glitch signal prior to decoding the regular signal. Alternatively, the receiver decodes the regular signal directly from the received composite signal, which may include a flickering signal. The receiver uses soft metrics plus saturation and inversion constraints. Thus, the glitch signal serves to saturate or substantially eliminate signal components in the subset of degrees of freedom it occupies, but has a negligible impact on the performance of decoding a conventional codeword. Furthermore, if the receiver is not interested in the glitch signal, the receiver may decode only the regular signal without decoding the glitch signal, in which case the receiver may not even be aware of the presence of the glitch signal, but may interpret and/or consider it as an impulse or background noise.

An embodiment of the control channel of the present invention will be discussed below. In this section, embodiments of the present invention will be described as applied to a control channel of a typical system. In this example, in a cellular radio system 1700 as shown in fig. 17, a control channel conveys information from a base station 1702 to a plurality of mobile users 1708, 1710 over a downlink broadcast channel. In most cellular radio systems, control channels are transmitted at broadcast power because they are constrained by the mobile user having the weakest channel. In this case, the blinking signaling is well suited for the application and causes a significant power reduction with no or little loss of robustness.

It is assumed that the information carried on the control channel can be divided into a plurality of subsets, each subset referring to one or more subsets of mobile users in the system. In this example, we assume that the control channel information can be divided into two subsets. The first subset is denoted "regular information" and is intended for mobile users experiencing moderate to high downlink SNR. The second subset, denoted "protected information", is intended for a subset of users experiencing a very low downlink SNR.

In the example considered here, it is assumed that the air link resource contains 32 symbols. For example, in a typical spread-spectrum OFDM multiple-access system, the air link resource may be 32 orthogonal tones in one OFDM symbol period, or one tone in 32 OFDM symbol periods, or any suitable combination of tones and symbol periods (e.g., 4 tones in 8 OFDM symbol periods).

As shown in the superimposed signal 500 of fig. 5, a 32-symbol codeword is used to transmit regular information 540, which in this example is represented by a small rectangle without shading. For reference, a first symbol position 501 and a 32 th symbol position 532 are shown. The codeword is transmitted at a power sufficient to be decoded by a subset of users experiencing medium or high SNR. Users with lower SNR may not be able to decode the codeword and thus the power requirement is much lower than if the codeword had to be decoded by each mobile user. This difference in the ability to decode codewords is particularly true in a wireless environment where the mobile user may experience SNRs that vary by orders of magnitude. The protected information intended for a subset of low SNR mobile users is transmitted using a flash signal 550, represented by 4 large shaded rectangles, as shown in fig. 5. In the present embodiment, it is assumed that each protected codeword concentrates its energy over 4 symbol positions 502, 512, 520, 530. Assuming in this example that the set of 4 symbol positions are non-overlapping, this results in 8 orthogonal sets, each set comprising 4 symbol positions. In general, however, in other configurations, the groups of codewords may partially or completely overlap. From the point of view of providing diversity in a cellular radio system, it is important to concentrate the energy of the protected codeword over more than one symbol position and to provide a higher degree of protection against channel fading and interference.

In the example of fig. 5, each protected subset of codewords passes 3 bits only by its position. Let k be the index of 8 different air link resource symbol groups. Assume that 32 air link resource symbols are indexed from 0 to 31. For k 0.. 7, the airlink resource symbols for the kth symbol set position are symbols k, k +8, k +16, and k + 24.

When the flash signal codeword comprises a plurality of symbols, those symbols may be used to convey additional information bits. Let { q0, q1, q2, q3} denote four symbols to be transmitted using four air link resource symbols of any one of eight air link resource symbol groups. In one embodiment { q0, q1, q2, q3} may be constructed using 4 length-4 Walsh codes as listed in Table 1. The selection of q0, q1, q2 or q3 yields an additional 2 bits passed through the selection of 4 codewords.

The information can be decoded in a simple manner at the mobile receiver. The mobile receiver can identify the location of the glitch due to the higher energy of the glitch signal that can be used to identify the 3-bit symbol set location. It then extracts the symbols containing the flicker signal and decodes the remaining 2 bits. Examples of the codeword structure yield codeword processing with non-uniform error protection properties. The bits resolved by the position of the glitch signal are received with high reliability. This is particularly true when communicating a glitch signal over a wireless channel, since only one of the four symbol positions needs to be received to specify a subset of the code words. The detection of q0, q1, q2 or q3 is more susceptible to errors from channel fading or interference. Alternatively, the receiver may employ a more complex decoder, such as a maximum likelihood decoder, to decode the entire content of the glitch signal. Also, the present invention is not dependent on the use of orthogonal codes on the glitch signal as shown in this example.

This concept can also be generalized to a diverse group of modulations in a simple way. For example, if BPSK modulation is to be used, one more bit may be transmitted using the phase (i.e., sign) of the glitch code word. Also, if QPSK modulation is to be used, an extra bit can be transmitted using the choice of in-phase or quadrature signaling.

TABLE 1 Structure of orthogonal codes on a flickering signal

Code word index	Bit value of { q0, q1, q2, q3}
Code word index	Bit value of { q0, q1, q2, q3}	0	{+，+，+，+}
1	{+，+，-，-}	0	{+，+，+，+}
1	{+，+，-，-}	2	{+，-，+，-}
3	{+，-，-，+}	2	{+，-，+，-}

The flashing signaling in the multiple access channel according to the invention will now be described. Although the invention has been described so far in the broadcast channel paradigm, it is equally applicable in the construction of multiple access channels. The described features of the invention will now be described in the context of a cellular uplink as a typical system of multiple access channels. Consider a base station receiver that receives signals from two mobile transmitters on the uplink. Since the base station 1702 is also the coordinating entity, it can distinguish between the two transmitters with relative sensitivity. It is assumed that a mobile transmitter operating on a channel with a lower path loss is designated as the "stronger" transmitter, while another transmitter experiencing a higher path loss is considered the "weaker" transmitter. The base station instructs the weaker transmitter to transmit its signal by allocating signal energy across each degree of freedom, while the stronger transmitter is instructed to concentrate its transmit energy in a few degrees of freedom. The received composite signal 600 at base station receiver 1802 is shown in fig. 6. The base station receiver 1802 can easily decode and eliminate the glitch signal 610, represented by the large shaded rectangle, transmitted from the "stronger" transmitter before decoding the weak signal 620, represented by the small non-shaded rectangle, transmitted from the "weaker" transmitter.

Mobile transmitters are classified as "stronger" or "weaker", not static, but rather relatively defined to allow flexibility within the system. Instead of or in addition to the path loss experienced on the uplink channel, the "stronger" or "weaker" concept of the mobile transmitter may be related to other standards. The marking or classification of "stronger" or "weaker" mobile transmitters in some embodiments may be applied in the context of interference costs in the cellular uplink. For example, a mobile transmitter that generates high uplink interference in other cells may be considered a "weaker" transmitter and may therefore be instructed by the base station to transmit its signal by allocating energy across each degree of freedom. On the other hand, a mobile transmitter with low interference cost due to location can be considered a "stronger" transmitter and can use a flickering superposition coding to superimpose its signal on the signal of the "weaker" transmitter. Alternatively, in some embodiments, a mobile transmitter may be classified as "stronger" or "weaker" depending on device constraints such as battery power or status.

Flash signaling in a typical system in accordance with the method and apparatus of the present invention will be described. In a typical wireless data communication system, the air link resources typically include bandwidth, time, and power. The air link resources that carry data and/or voice traffic are referred to as traffic channels. In a typical system, data is communicated over a traffic channel in a traffic channel segment (referred to simply as the traffic segment). The traffic segment may be a basic or minimal unit of available traffic channel resources. The downlink traffic segment conveys data traffic from the base station to the wireless terminal, and the uplink traffic segment conveys data traffic from the wireless terminal to the base station. In a typical system, the traffic segment includes a number of frequency tones over a finite time interval.

In a typical system for explaining the present invention, traffic segments are dynamically shared between wireless terminals 1708, 1710 in communication with a base station 1702. Scheduling functions, such as a module 1838 in the base station 1800, are arranged to assign each uplink and downlink portion to one of the mobile terminals 1708, 1710 according to a number of criteria. Different users may be assigned traffic segments from one segment to another. For example, in fig. 7, in a graph 700 of frequency on the vertical axis 702 versus time on the horizontal axis 704, the base station scheduler assigns a portion a 706, indicated by vertical line shading, to user #1 and a portion B708, indicated by horizontal line shading, to user # 2. The base station scheduler may quickly assign traffic channel segments to different users according to their traffic needs and channel conditions, which may typically vary over time. In this way, traffic channels are effectively shared and dynamically allocated between different users on a portion-by-portion basis. In a typical system, assignment information for traffic channel segments is transmitted in an assignment channel that includes a series of assignment segments. In cellular radio systems, such as the system 1700 shown in fig. 17, the allocation portion is typically transmitted in the downlink. There is an assignment segment for the downlink traffic segment and a separate assignment segment for the uplink traffic segment. Each traffic segment is associated with a unique assignment segment. The associated assignment segment conveys assignment information for the traffic segment. The allocation information may include an identifier of the user terminal allocated to use the traffic segment, and the coding and modulation scheme used in the traffic segment. Fig. 8 includes a graph 800 having a vertical axis 802 representing frequency and a horizontal axis 804 representing time. Fig. 8 shows two allocation sections, allocation section a '(AS a') 806 and allocation section B '(AS B') 808, which convey allocation information for traffic sections a (ts a)810 and B (ts B) 812. The allocation channel is a shared channel resource. A user, such as a wireless terminal, receives the assignment information conveyed in the assignment channel and then uses the traffic channel segment in accordance with the assignment information.

Data transmitted by the base station 1702 on the downlink traffic segment is decoded by a receiver in the intended wireless terminal 1708, 1710, while data transmitted by the assigned wireless terminal 1708, 1710 on the uplink segment is decoded by a receiver in the base station 1702. Typically, the transmitted portion includes redundant bits to assist the receiver in determining whether the data was decoded correctly. This is done because the wireless channel may be unreliable and useful data traffic typically has a high integrity requirement.

The transmission of the traffic segment may succeed or fail due to interference, noise and/or channel fading in the wireless system. In a typical system, the receiver of a traffic segment sends an acknowledgement to indicate whether the segment was received correctly. Acknowledgement information corresponding to a traffic channel segment is transmitted in an acknowledgement channel comprising a series of acknowledgement segments. Each traffic segment is associated with a unique acknowledgement segment. For the downlink traffic segment, the acknowledgement segment is in the uplink. For the uplink traffic segment, the acknowledgement segment is located in the downlink. The acknowledgement segment conveys at least one bit of information, e.g., a bit, to indicate whether the associated traffic segment was received correctly. Due to the predetermined association between the uplink traffic segment and the acknowledgement segment, there may be no need to communicate other information in the acknowledgement segment, such as a user identifier or a segment index. The acknowledgement segment is typically used by the user terminals, e.g., wireless terminals 1708, 1710, using the associated traffic segment, but not other user terminals. Thus, in both links (uplink and downlink), the acknowledgment channel is a shared resource since it can be used by multiple users. However, there is typically no contention resulting from the use of a common acknowledgement channel, since there is typically no ambiguity in which user terminal will use a particular acknowledgement segment. Fig. 9 shows a graph 900 of a downlink traffic segment, which includes a vertical axis 902 representing frequency, a horizontal axis 904 representing time, a first traffic segment, Traffic Segment (TS) a906, and a second traffic segment TS B908. Fig. 9 also shows a second graph 950 of an uplink Acknowledgement (ACK) portion, which includes a vertical axis 952 representing frequency and a horizontal axis 954 representing time. Fig. 9 further shows two uplink acknowledgement segments, a "956 and B" 958, which convey acknowledgement information for downlink traffic segments a906 and B908 from wireless terminal 1708 to base station 1702.

As described above, the exemplary system 1700 may be a packet-switched cellular wireless data system in which traffic segments are dynamically allocated by the base station 1702 on the downlink and uplink. The application of the present invention to exemplary system 1700 will now be described in the context of a cellular downlink. Assume that base station 1702 can allocate up to two traffic segments at a time in a time-slotted manner. The selection of which user these parts are intended for is broadcast on the allocation channel. Further assume without loss of generality that one of the two users is operating at a lower SNR than the other user. In this regard, two users are considered "stronger" and "weaker" with respect to each other.

The graph of fig. 10 shows frequency on the vertical axis 1002 versus time on the horizontal axis 1004. Fig. 10 also includes an a (normal) assignment segment (ASGr)1006, an a traffic channel segment (TCHa)1008, an a (high speed) acknowledgment segment (ACKf)1010, a B high speed assignment segment (ASGf)1005, a B traffic channel segment (TCHb)1007, and a B acknowledgment segment (ACKr) 1009. ASGf 1005 is within the spectral range of ASGr 1006. ACKf 1010 is within the spectral range of ACKr 1009.

As shown in fig. 10, the assignment information for the stronger users (ASGr)1006 is transmitted using a regular signal on the assignment channel, while the information for the weaker users (ASGf)1005 is conveyed using a flashing signal. The stronger receiver knows from its (regular) assignment that it will receive a traffic segment denoted TCHa 1008, and similarly, by means of a flash signal assignment (ASGf)1005, the weaker receiver is informed of its corresponding traffic segment denoted TCHb 1007. In a typical system, the mobile receivers 1708, 1710 provide a feedback acknowledgment on the uplink to the base station 1702 to indicate the status of the received traffic segment.

As shown in fig. 10, the two mobile users 1708, 1710 may superimpose their acknowledgement signals using a flash signal. For this purpose, the "stronger" receiver on the downlink is assumed to be the stronger transmitter on the uplink, thus using the flashing signal (ACKf)1010 to convey its acknowledgement. The weaker receiver allocates the energy of its acknowledgment signal in each degree of freedom and passes it as a regular signal (ACKr)1009 to the base station 1702.

The capacity impact of a cellular radio system is now discussed with respect to flash signalling. Cellular radio systems are typically interference constrained and their capacity depends on the amount of environmental interference and its characteristics. The use of flash signaling has a very important impact on the interference level. Gaussian noise produces the lowest capacity among all noise signals of the same energy, which is a well-known information theory result. The flicker signals, due to their structure, are peaky and highly non-gaussian in nature. Thus, given the same amount of interference, when one unit in a wireless system uses flickering signals, the effect of these signals on other units (e.g., interference) is less than if gaussian-like signals were used. This applies to the uplink as well as the downlink path of a cellular radio system.

Fig. 11 shows two exemplary sets of information, a first set of information 1150 and a second set of information 1160, that may be transmitted using one transport block in accordance with the present invention. The first information group 1150 includes information A₁1151. Information A₂1152. Information A_N1153; the second information group 1160 includes information B₁1161. Information B₂1162. Information B_M1163. The first set of information may be, for example, user data, assignments, or acknowledgements. The second set of information may be, for example, user data, acknowledgements or assignments. Fig. 11 also shows a graph 1100 of Minimum Transmission Units (MTUs), where the vertical axis represents frequency tones and the horizontal axis 1104 represents time. In fig. 11, each small box refers to a particular MTU unit, such as region 1112, and represents 1 degree of freedom that may be used to transmit information. Each slot on the horizontal axis, e.g., slot 1110, represents a time at which the MTU is transmitted, e.g., an OFDM symbol time. Each square in fig. 11, such as exemplary square 1114, represents an MTU cell. Each MTU corresponds to a unique combination of resources for transmitting information, the combination of resources including at least two of time, frequency, phase, and spreading code. In an OFDM system, the MTU may be a frequency or phase over time, such as an in-phase or quadrature component in an OFDM tone-symbol. In a CDMA system, the MTU unit may be, for example, a spreading code assigned to a time unit. The exemplary transport block 1106 shown in fig. 11 is a group of 24 MTUs. Information for the first information group 1150 is defined over the first set of minimum transmission units. The first set of minimum transmission units is identified by those squares having a diagonal 1116 that rises from left to right. The exemplary first set of MTUs includes 15 MTUs, e.g., exemplary MTU 1120 is in the first set of MTUs. In accordance with the present invention, the first set of MTUs includes at least a majority of the MTUs in the transport block 1106. In some embodiments, the first set of MTUs includes at least 75% of the MTUs in the transmission block 1106. The example of fig. 11 is an embodiment that includes a total of 75% MTUs for the 15 first-group MTUs/20 blocks 1106. Information for the second set of information 1160 is defined on the second set of minimum transmission units. The second group of minimum transmission units is identified by those squares having a diagonal 1118 that falls from left to right. A typical second set of minimum transmission units comprises 3 MTUs. In accordance with the present invention, the second set of MTUs includes fewer MTUs than the first set of MTUs, and some of the MTUs in the first and second sets of MTUs are the same. For example, in FIG. 11, 2 MTUs, MTU 1122 and MTU 1123, are included in twoIn a group. In some embodiments, the second set of MTUs is less than half the number of MTUs of the first set of MTUs; fig. 11 is an example of such an embodiment. The information in the first and second information sets 1150, 1160 may be communicated, for example, from the base station 1702 to the wireless terminals 1708, 1710 using the smallest transmission unit included in the first and second sets of smallest transmission units.

Fig. 12 shows a graph 1200 of Minimum Transmission Units (MTUs) on vertical axis 1202 versus time on horizontal axis 1204. Figure 12 shows an exemplary transmission block 1205 comprising 1600 MTUs. The first set of information may be represented by a first set of MTUs that includes a large portion of the 1600 MTUs in the transmission block 1205. In accordance with the present invention, transport block 1205 may be subdivided into sub-blocks. In fig. 12, a transmission block 1205 of MTUs is divided into sub-blocks of 16 MTUs, each subset including 100 MTUs. Each small square, such as typical square 1206, includes a sub-block of MTUs. In some embodiments, the first set of MTUs may be subdivided into small groups of information, each group being represented by the first set of MTUs within a separate sub-block. In combination, the small set of information represents the first set of information encoded over the majority of the large transport block 1205. Typical sub-blocks 1207 represent 100 typical MTUs of a typical sub-block. The exemplary sub-block 1208 represents 100 exemplary MTUs of another sub-block. The various MTUs for the other sub-blocks of the transmission block 1205 are not drawn, but it may be assumed that each other sub-block is similar to the typical sub-block 1207. Each circle in the sub-block represents an MTU. Each diagonal line rising from left to right through a circle represents an individual MTU for representing information in the first set of information. Each diagonal line descending from left to right through a circle represents an individual MTU for representing information in the second set of information. In fig. 12, the representative MTU 1208 is one of MTUs for representing the first information group; the representative MTU 1211 is another MTU for representing the first information group. In certain cases, the representative MTU 1209 is not used to represent information in the first or second set of information, although it is within the scope of the representative transport block 1205. That is, at the particular point in time shown, MTU 1209 is not used to communicate signals corresponding to the first or second set of information. An exemplary MTU 1210 is used to represent information in both the first information set and the second information set.

In the example of fig. 12, each sub-block, e.g., sub-block 1207, may be used to represent information that uniquely represents a portion of the first set of information that is uniquely defined on a small sub-block of MTUs. However, the second information group may represent a different information group, for example, 10 bits of information. To uniquely convey 10 bits of information, 2 may be required¹⁰1024 smallest transmission units possible. A transport block 1205 with 1600 possible minimum transmission units available may be used and assigned to a single MTU to represent a particular value of 10 bits of information. In this example, MTU 1210 is the only MTU used to communicate information for the second set of information when transmitting the information. Fig. 12 shows a case where each MTU included in the second set of MTUs is also included in the first set of MTUs.

FIG. 131301 illustrates a method for transmitting two sets of information, e.g., sets 1150 and 1160 of FIG. 11, in accordance with the present invention. Fig. 13 includes a first device, such as device 11302 including a transmitter, transmitter 11304, and a second device, such as device 21308 including a transmitter, transmitter 21310. Each device may be, for example, a base station or a wireless terminal of the type shown in fig. 17. The first set of information 1150 is conveyed by a signal, such as signal 11306, transmitted from transmitter 11304. Signal 11306 is sometimes referred to as a base or regular signal. The second information group 1160 is conveyed by a signal, such as signal 21312, transmitted from transmitter 21310. Signal 2 is sometimes referred to as a glitch. In the exemplary case of fig. 13, signal 11306 will use a first set of minimum transmission units, while signal 21312 will use a second set of minimum transmission units. Some of the first set of MTUs transmitted by transmitter 11304 will be the same as some of the second set of MTUs, which causes some superposition of signal 11306 and signal 21312.

Fig. 14 illustrates two methods for transmitting two sets of information, e.g., sets 1150 and 1160 of fig. 11, in accordance with the present invention. In a first approach, depicted in fig. 14, an exemplary device 31402, such as a base station or wireless terminal, includes a transmitter 31404 capable of transmitting signals corresponding to first and second sets of information 1150, 1160, respectively, simultaneously. In fig. 14, signal 31406 corresponds to a first information set 1150 and uses a first set of MTUs, and signal 41408 corresponds to a second information set 1160 and uses a second set of MTUs. The signal 31406 is sometimes referred to as the base signal or regular signal, while the signal 41408 is sometimes referred to as the flash signal. Signal 41408 is transmitted on a per minimum transmission unit basis at a higher power level than signal 31406. In some embodiments, the power level of the transmitted signal 41408 is at least 3db greater than the power level of the smallest transmission unit transmitting the signal corresponding to 31406. In some embodiments, the transmit power level of the minimum transmission unit used to transmit signal 31406 may be varied. The transmit power level of the MTU used to transmit signal 41408 may also be varied.

In a second method, depicted in fig. 14, an exemplary apparatus, i.e., device 41410, e.g., a base station or wireless terminal, includes a transmitter, i.e., transmitter 41412. The transmitter 41412 includes a first signal module 1411 and a second signal module 1413. The first signal module 1411 generates a signal 51414 corresponding to the first set of information 1150. The second signal module 1413 generates a signal 61416 corresponding to the second information group 1160. Signal 51414 and signal 61416 are combined by combiner module 1418 prior to transmitting the MTU in signal 1420. Signal 51414 is sometimes referred to as a base or regular signal, while signal 61416 is sometimes referred to as a flash signal. The combiner module 1418 may perform a superposition of the two signals, signal 51414 and signal 61416. Alternatively, combiner module 1418 may compare the set of MTUs to be used for transmit signal 51414 with the set of MTUs to be used for transmit signal 61416. Combiner module 1418 may direct the information in signal 61416 into each requested MTU; however, module 1418 may exclude those MTUs that have been assigned to convey signal 61416 from the set of MTUs assigned to signal 51414. For example, in the example of fig. 11, MTU 1122 and MTU 1123 may be caused to reject the information conveying signal 51414. Thus, the second set of information 1160 in signal 61416 punctures or replaces the first set of information 1150 in signal 51414 (which would occupy the same MTU). This embodiment assumes that the receiver has sufficient error detection and correction capability to recover the original first set of information 1150 from which some information was not transmitted. Thus, instead of using actual superposition, the signals corresponding to the second group may be transmitted to discard the overlapping first group of signals prior to actual transmission without having to superimpose them on the signals of the first group. In this case, the MTU puncture used to convey the second set of information is selected in a common transport block to transmit the MTU set of the first set of information.

Fig. 15 shows an exemplary device, device 51502, such as a base station or wireless terminal, which may be used to receive a composite signal and obtain two sets of received information, information a '1516 and information B' 1518, in accordance with the present invention. Information a' 1516 is a recovered set of information corresponding to the first set of original pre-transmitted information (i.e., information a 1150 of fig. 11). Information B' 1518 is a recovered set of information corresponding to the first set of original pre-transmitted information (i.e., information B1160 of fig. 11). The device 51502 includes a first receiver, receiver 11506, that includes an impulse noise filter 1510 and an error correction module 1512. The composite signal, signal 81520, containing the signals transmitted together over time, e.g., signal 31406 of fig. 13 (the normal or base signal) and signal 41408 of fig. 13 (the flicker signal), is processed by receiver 11506, where impulse noise filter 1510 filters or rejects the signals corresponding to the MTU cells originating from second information group 1160. The remaining signals (regular signals) corresponding to most of the MTUs in the MTU group corresponding to the first information group 1150 are processed by the error correction module 1512, which recovers the "lost information" so that the received information group a' 1516 is a good reproduction of the previously transmitted information group a 1150. Device 51502 also includes a second receiver, receiver 21508, that includes a background noise filter 1514. The resultant signal 81520 also enters a receiver 21508 where background noise filtering 1514 treats the signal corresponding to the first information set 1150, e.g., signal 31406, as noise and removes or rejects the low level signal, leaving a signal (e.g., a glitch signal) whereby a good reproduction of the previously transmitted second information set B1160 may be reproduced as the received information set B' 1518.

Similar to device 51502, the second device shown in fig. 15, device 6, performs composite signal reception and information recovery. Device 61532 includes a first receiver, receiver 11536 and a second receiver, receiver 21538. Receiver 11536 includes a decoder, decoder 11540, that includes a pulse filter 1544 and error correction module 1546. Receiver 21538 includes a decoder that includes a background noise filter 1548, i.e., decoder 21542. The operation of device 61532 is similar to that described with respect to device 51502 except for the additional decoding performed in device 61532. During operation, receivers 1536 and 1538 operate independently and in parallel. The first receiver 1536 treats the glitch signal as impulse noise and rejects the high-speed symbols as impulse noise, or performs other operations such as saturation operations that may treat the high-speed components as any other impulse noise signal. Receiver 21538 decodes the glitch signal when the lower power signal is considered background noise. The composite signal 91554 is similar to composite signal 81520, which includes both regular and flicker signals. The received set of information a "1550 corresponds to a good reproduction of the original first pre-transmitted set of information a 1150 of fig. 11. The received information set B "1552 corresponds to a good reproduction of the original second pre-transmitted information set B1160 of fig. 11.

Fig. 16 illustrates another exemplary device 71562, such as a base station or wireless terminal, that includes a first receiver, receiver 11563, and a second receiver, receiver 21564. Receiver 11563 includes a decoder 1565 that includes a discard module 1570 and an error correction module 1566. Receiver 21564 includes a decoder 1566 including a background noise filter 1567 and a second signal MTU identifier module 1568. Composite signal 101573 is received and enters receiver 21564. In the decoder 1566 of the receiver 21564, the signal may be filtered by a background filter 1567 and the information decoded and output as a reproduction of the set of information B' "1572, i.e., the original pre-transmitted set of information B1160 of fig. 11. In addition, the second signal MTU identifier module 1568 identifies a set of MTUs 1569 corresponding to the second (flash) signal and sends the information 1573 to the decoder 1565 of the receiver 11563. In some embodiments, the identified MTU group 1573 is one of the in-phase and quadrature components of the tone at different symbol times.

A discard module 1570 of the decoder 1565 in the receiver 11563 receives the identified MTU groups 1573 and rejects or removes information originating from those MTU units before the information enters the error correction module 1566. Alternatively, information identifying the MTUs of the second or "flash" signal may be passed directly to the error correction module 1566, and the error correction module 1566 may remove the effects from those MTUs. Set A' "1571 corresponds to the reproduction of the first previously transmitted set of information 1150 of FIG. 11. Discarding the identified MTUs and their impact on the lower power signal is in sharp contrast to prior art superposition decoding techniques that require accurate cancellation of the high power signal component from the received signal unit before the underlying signal can be recovered.

Although described 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 many non-OFDM and/or non-cellular systems.

In various embodiments nodes described herein are implemented using one or more modules to perform the steps corresponding to one or more methods of the present invention, such as signal processing, message generation and/or transmission steps. Thus, in some embodiments various features of the present invention are implemented using modules. Such modules may be implemented using software, hardware, or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, e.g., software, included in a machine readable medium such as a storage 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 a portion of the above described methods, e.g., in one or more nodes. Accordingly, among other things, the present invention is directed to a machine-readable medium including 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 additional 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. Such variations are to be considered within the scope 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 be used to provide wireless communications links between access nodes and wireless terminals. In some embodiments the base stations establish communications links with the mobile nodes using OFDM and/or CDMA. In various embodiments, the wireless terminal is implemented as a notebook computer, Personal Digital Assistant (PDA), or other portable device including receiver/transmitter circuits and logic and/or routines, to implement the methods of the present invention.

The techniques of the present invention may be implemented using software, hardware and/or a combination of software and hardware. The present invention is directed to an apparatus, such as a wireless terminal, a base station, and a communication system, that implement the present invention. It is also directed to methods, e.g., methods of controlling and/or operating a wireless terminal, a base station, and/or a communication system, e.g., a host, in accordance with the present invention. The present invention is also directed to a machine-readable medium, such as ROM, RAM, CDs, hard discs, etc., including machine-readable instructions for controlling a machine to perform one or more steps in accordance with the present invention.

Claims

1. A method of transmitting at least first and second sets of information using a transport block, the transport block comprising a plurality of minimum transmission units, each minimum transmission unit corresponding to a unique combination of resources for transmitting information, the resources comprising at least two of time, frequency, phase and spreading code, the method comprising:

defining a first set of said minimum transmission units for conveying said first set of information, said first set comprising at least a majority of said transport blocks;

defining a second set of the minimum transmission units for conveying the second set of information, the second set of minimum transmission units including fewer minimum transmission units than the first set; at least some of the minimum transmission units in the first and second sets of minimum transmission units are identical; and

the first and second sets of information are transmitted using a minimum transmission unit included in the first and second sets of minimum transmission units.

2. The method of claim 1, wherein said information is at least one of user data and control information including acknowledgement and allocation information.

3. The method of claim 1, wherein communicating the first and second sets of information comprises transmitting signals corresponding to the first and second sets of information, respectively, from different transmitters.

4. The method of claim 3, wherein the different transmitters are located on different devices.

5. The method of claim 1, wherein signals corresponding to said first and second sets of information are transmitted from the same transmitter.

6. The method of claim 1, wherein said first set of minimum transmission units comprises at least 75% of a total number of minimum transmission units in said transport block.

7. The method of claim 6, wherein said second set of minimum transmission units is less than half of a minimum number of transmission units of said first set of minimum transmission units.

8. The method of claim 6, wherein each minimum transmission unit included in the second set of minimum transmission units is also included in said first set of minimum transmission units.

9. The process of claim 1, wherein the first step is carried out,

wherein communicating the first and second sets of information comprises transmitting the second set of information using each minimum transmission unit in the second set of minimum transmission units, an

Wherein communicating the first set of information comprises transmitting the first set of information, including transmitting at least some of the first set of minimum transmission units.

10. The method of claim 9, wherein said at least some first set of minimum transmission units includes only minimum transmission units not included in said second set of minimum transmission units.

11. The method of claim 9, wherein said at least some of said first set of minimum transmission units includes a minimum transmission unit in said second set.

12. The method of claim 11, wherein at least first and second sets of information are communicated using at least first and second signals, respectively, and wherein the method further comprises combining the first and second signals to form a composite signal prior to transmitting the composite signal using a minimum transmission unit included in the first and second sets of minimum transmission units.

13. The process of claim 1, wherein the first step is carried out,

wherein a second signal is transmitted at a higher power level than the first signal on a per minimum transmission unit basis; and

wherein communicating the first and second sets of information comprises:

using minimum transmission units includes transmitting a first signal corresponding to a first set of information using at least some minimum transmission units included in the first set of minimum transmission units; and

a second signal corresponding to a second set of information is transmitted using a minimum transmission unit of the second set of minimum transmission units.

14. The method of claim 13, wherein the power level at which the smallest transmission unit corresponding to the second signal is transmitted is at least 3dB greater than the power level at which the smallest transmission unit corresponding to the first signal is transmitted.

15. The method of claim 13, further comprising varying a transmit power level of a minimum transmission unit used to transmit said second signal.

16. The method of claim 13, further comprising varying a transmit power level of a minimum transmission unit used to transmit said first signal.

17. An apparatus for receiving a composite signal comprising first and second signals transmitted together over time, the first and second signals sharing an overlapping set of communication resources, wherein the overlapping resources include at least two of time, frequency, phase, and spreading code, the apparatus comprising:

a first receiver for receiving said composite signal from a communication channel, said first receiver comprising a filter for treating a portion of said composite signal corresponding to said second signal as impulse noise; and

a second receiver arranged in parallel with said first receiver for receiving said composite signal from said communication channel, said second receiver comprising a filter for treating a portion of said composite signal corresponding to said first signal as background noise.

18. The apparatus of claim 17, wherein said apparatus includes error correction means for recovering information lost by treating a portion of said composite signal corresponding to said second signal as impulse noise.

19. The method of claim 17, wherein said first and second signals share the same frequency band.

20. An apparatus for receiving a composite signal comprising first and second signals transmitted together over time, the apparatus comprising:

a first receiver for receiving a composite signal, said first receiver comprising:

i) a first filter module for filtering impulse noise from said received composite signal, a portion of said signal corresponding to a second signal being treated by said filter module as impulse noise; and

ii) a first decoder coupled to said first filter module for decoding information corresponding to the first signal, said first decoder determining the composite signal values received over the first set of minimum transmission units; and

a second receiver, comprising:

i) a second filter module for filtering background noise from said received composite signal; and

ii) a second decoder coupled to the second filter module for decoding information corresponding to a second signal, the second decoder determining composite signal values received over a second set of minimum transmission units, a majority of the second set of minimum transmission units being included in the first set of transmission units.

21. An apparatus for receiving a composite signal comprising first and second signals transmitted together over time, the apparatus comprising:

a second receiver for receiving the composite signal and identifying a minimum transmission unit in said composite signal corresponding to said second signal, said second receiver outputting information to identify said identified minimum transmission unit corresponding to said second signal; and

a first receiver for receiving said composite signal, said first receiver comprising a decoder for decoding a portion of said composite signal corresponding to said first signal, said decoder receiving said information to identify said identified minimum transmission unit corresponding to said second signal and to discard said identified minimum transmission unit corresponding to said second signal.

22. The apparatus of claim 21, wherein said identified element corresponding to the second signal is one of an in-phase and a quadrature component of the tone at different symbol transmission times.

23. The apparatus of claim 21, wherein said first receiver comprises:

an error correction circuit for recovering first signal information lost due to discarding said identified transmission units corresponding to the second signal.