HK1090201A - Code division multiplexing commands on a code division multiplexed channel - Google Patents

Description

Code division multiplexing commands on code division multiplexed channels

Cross-referencing

This application claims U.S. provisional application serial No. 60/448,269 entitled "reverse link data communication" filed on month 2 and 18 of 2003; U.S. provisional application serial No. 60/452,790, entitled "method and apparatus for reverse link communication in a communication system", filed on 6/3/2003; U.S. provisional application serial No. 60/470,225 entitled "method and apparatus for quality of service on IS-2000 reverse link" filed on 12/5/2003; and U.S. provisional application serial No. 60/470,770 entitled "outer loop power control for rel.d", filed on 14/5/2003.

Technical Field

The present invention relates generally to wireless communications, and more particularly to a novel and improved method and apparatus for code division multiplexed commands or signals on code division multiplexed channels.

Background

Wireless communications are widely used to provide different types of communications such as voice and data. These systems may be based on Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), or some other multiple access technique. CDMA systems provide certain advantages over other types of systems, including increased system capacity.

CDMA systems may be designed to support one or more CDMA standards, such as (1) "TIA/EIA-95-B mobile station-base station compatibility standard for dual-mode wideband spread spectrum cellular systems" (IS-95 standard), (2) a standard named "third generation partnership project" (3GPP) proposed by the protocol organization, which IS specified in a set of documents including: nos.3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214(W-CDMA standard), (3) a standard entitled "third generation partnership project 2" (3GPP2) provided by the protocol organization and specified in the TR-45.5 physical layer standard for CDMA2000 spread spectrum systems "(IS-2000 standard), and (4) some other standards.

In the above standards, the available spectrum is shared simultaneously among many users, and techniques such as power control and soft handoff are utilized to maintain good enough quality to support delay sensitive services such as voice. Data services may also be utilized. Recently, systems have been proposed that: capacity for data traffic is increased by using higher order modulation, very fast feedback of carrier-to-interference ratio (C/I) from the mobile station, very fast scheduling, and scheduling for traffic with more relaxed delay requirements. An example of such a data-only communication system using these techniques IS a High Data Rate (HDR) system that conforms to the TIA/EIA/IS-856 standard (the IS-856 standard).

In contrast to other above-specified criteria, the IS-856 system uses the entire available spectrum of each cell to transmit data to a single user at a time selected based on link quality. Because this is done, the system spends a greater portion of the time transmitting data at higher rates when the channel is good, thus avoiding the use of resources to support transmission at inefficient rates. The net result is higher data capacity, higher peak data rates, and higher average throughput.

The system can combine support for delay sensitive data, such as voice channels or data channels as specified by the IS-2000 standard, with support for packet data services, such as those described in the IS-856 standard. Such a system is described in the proposals filed by LG electronics, LSI logic, lucent technologies, the north electric network, the university and samsung to the third generation partnership project 2(3GPP 2). This proposal is described in detail in the following documents, which include: entitled "update connection physical layer recommendation for 1 xEV-DB", submitted to 3GPP2 on 6/11/2001 as file No. C50-20010611-; entitled "results of L3NQS simulation study", submitted to 3GPP2 at 8/20/2001 as file No. C50-20010820-; and entitled "System simulation results proposed for the L3NQS architecture of cdma20001 xEV-DV", filed 8/20/2001 with 3GPP2 as file Nos. C50-20010820-012. These and related files that are generated later, such as version C of the IS-2000 standard, include c.s0001.C through c.s0006.C, hereinafter referred to as 1xEV-DV recommendations.

In order to coordinate the use of the forward and reverse links in an efficient manner, systems such as the 1xEV-DV proposal may need to direct the feedback of the base station to a number of supported mobile stations. Feedback for this is typically sent on one or more control channels. In a CDMA system, such control channels may be multiplexed with other control and/or data channels using Code Division Multiplexing (CDM). Conventionally, to reach multiple mobile stations, a control channel is time-shared to be transmitted to each mobile station. In this way, Time Division Multiplexing (TDM) may be used to multiplex control channels to combine signals or commands for multiple mobile stations. The resulting TDM control channel may then be transmitted with other channels (whether control channels, voice channels, or data channels) using CDM. An example of TDM on such CDM channels is the power control channel of cdma 2000.

As is known in the design of wireless systems, the capacity of the system can be increased when the same reliability can be achieved by using less power to transmit the channel. Thus, there is a need in the art for a more efficient control channel. In addition, TDM on CDM channels may have peak power requirements for certain system design parameters that are inefficient or even difficult to achieve. There is therefore a need in the art for a control channel that can reach multiple mobile stations, thereby facilitating efficient use of shared communication resources while meeting peak power design constraints and reducing the amount of system capacity allocated to such control.

Disclosure of Invention

Embodiments disclosed herein address the need for efficient signaling to multiple mobile stations. In one embodiment, each of a plurality of symbol streams is encoded with one of a plurality of masking sequences, the masked symbol streams are combined to form a Code Division Multiplexed (CDM) signal, and the CDM signal is further masked by another masking sequence for code division multiplexing with one or more additional signals for transmission to a remote station. In another embodiment, multiple CDM signals are formed from the masked symbol streams and the multiple CDM signals are Time Division Multiplexed (TDM) prior to further masking. In other embodiments, demasking and demultiplexing is performed to recover one or more of the symbol streams. Various other aspects may also be presented. These aspects have the following advantages: the reverse link capacity is efficiently utilized to accommodate variable requirements such as low latency, high throughput, or varying quality of service, and the forward link overhead and reverse link overhead that provide these advantages are reduced, thus avoiding excessive interference and capacity increases.

The present invention provides methods and system elements that implement various aspects, embodiments, and features of the present invention, as described in further detail below.

Drawings

The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

FIG. 1 is a general block diagram of a wireless communication system capable of supporting multiple users;

fig. 2 illustrates an exemplary mobile station and base station configured for data communication in a system;

FIG. 3 is a block diagram of a wireless communication device, such as a mobile station or base station;

fig. 4 illustrates an exemplary embodiment of data and control signals for reverse link data communication;

FIG. 5 illustrates a prior art embodiment of a portion of a command stream transmitter;

fig. 6 shows an embodiment of a CDM-based CDM encoder for receiving multiple input sequences, combining those input sequences using code division multiplexing, and transmitting the combined signal with other CDM signals to one or more mobile stations;

fig. 7A and 7B illustrate an embodiment of a CDM signal-based combined CDM and TDM technique; and is

Fig. 8 shows an embodiment using pattern repetition.

Detailed Description

Fig. 1 IS a diagram of a wireless communication system 100 that may be designed to support one or more CDMA standards and/or designs (e.g., the W-CDMA standard, the IS-95 standard, the CDMA2000 standard, the HDR specification, the 1xEV-DV recommendation). In alternative embodiments, system 100 may additionally support the wireless standard or design of any non-CDMA system. In an exemplary embodiment, the system 100 is a 1xEV-DV system.

For simplicity, system 100 is shown to include three base stations 104 in communication with two mobile stations 106. A base station and its coverage area are often collectively referred to as a "cell". A cell may include one or more sectors, for example, in IS-95, cdma2000, or 1xEV-DV systems. In the W-CDMA specification, each sector of a base station and the sector's coverage area are referred to as a cell. As used herein, the term base station can be used interchangeably with the terms access point or node B. The term mobile station can be used interchangeably with the terms User Equipment (UE), subscriber unit, subscriber station, access terminal, remote terminal, or corresponding other term known in the art. The term mobile station includes fixed wireless applications.

Depending on the CDMA system being implemented, each mobile station 106 may communicate with one (or possibly more) base stations 104 over a forward link at any given moment, and may communicate with one or more base stations over a reverse link depending on whether the mobile station is in soft handoff. The forward link (i.e., downlink) refers to transmission from the base station to the mobile station, and the reverse link (i.e., uplink) refers to transmission from the mobile station to the base station.

Although the various embodiments described herein are directed to providing reverse link or forward link signals for supporting reverse link transmissions, and some may be well suited to the nature of reverse link transmissions, those skilled in the art will appreciate that mobile stations as well as base stations can be equipped to transmit the data described herein and that aspects of the present invention are applicable in those situations as well. The term "exemplary" is used exclusively herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

1xEV-DV forward link data transmission and reverse link power control

A system 100, such as described in the 1xEV-DV proposal, typically includes four types of forward link channels: overhead channels, dynamically varying IS-95 and IS-2000 channels, forward packet data channel (F-PDCH), and some backup channels. The overhead channel assignments vary slowly, and they do not change for a few months. Typically they are changed when the primary network configuration changes. The dynamically changing IS-95 and IS-2000 channels are allocated or used for IS-95 or IS-2000 release 0 to B packet traffic on a per call basis. Typically, the remaining available base station power after the overhead channels and dynamically varying channels have been allocated is allocated to the F-PDCH for the remaining data traffic. The F-PDCH may be used for data traffic that IS less sensitive to delay, while the IS-2000 channel may be used for traffic that IS more sensitive to delay.

The F-PDCH, similar to the traffic channel of the IS-856 standard, may transmit data to one user in each cell at a time and at the highest supported data rate. In an IS-856 system, the entire power of the base station and the entire space of walsh functions are available when transmitting data to the mobile station. However, in the proposed 1xEV-DV system, some of the power and some of the walsh functions of the base station are allocated to overhead channels and existing IS-95 and cdma2000 services. The data rate that can be supported depends primarily on the available power and walsh codes after the power and walsh codes for the overhead, IS-95, and IS-2000 channels have been assigned. Data transmitted on the F-PDCH is spread using one or more walsh codes.

In the 1xEV-DV proposal, the base station typically transmits to one mobile station over the F-PDCH at a time, although many users may use packet services in the cell. (it is also possible to transmit to two or more users by scheduling transmissions to the two or more users and appropriately allocating power and/or walsh channels to each user.) the mobile station is selected for forward link transmission according to some scheduling algorithm.

In a system similar to IS-856 or 1xEV-DV, the scheduling portion IS based on channel quality feedback for the mobile station being served. For example, in IS-856, the mobile station estimates the quality of the forward link and calculates the transmission rate that the current conditions are expected to support. The desired rate for each mobile station is transmitted to the base station. To more efficiently use the shared communication channel, the scheduling algorithm may, for example, select a mobile station for transmission that supports a relatively higher transmission rate. As another example, in a 1xEV-DV system, each mobile station transmits a carrier/interference (C/I) estimate as a channel quality estimate over a reverse channel quality indicator channel or R-CQICH. The scheduling algorithm may be used to determine the mobile station selected for transmission, and the appropriate rate and transmission format for the corresponding channel quality.

As described above, the wireless communication system 100 may support multiple users sharing communication resources simultaneously, such as an IS-95 system, may allocate an entire communication resource to one user at a time, such as an IS-856 system, or may allocate communication resources to allow both types of access. The 1xEV-DV system is an example of a system that divides system resources between two types of access and dynamically allocates the apportionment (allocation) according to user requirements. The following is a brief background of how communication resources are allocated to accommodate different users of two types of access systems. Power control IS illustrated for multiple users simultaneously accessing a channel, such as an IS-95 type channel. Rate determination and scheduling IS discussed for multiple users time-shared access, such as the data-only portion (i.e., F-PDCH) of an IS-856 system or a 1xEV-DV type system.

System capacity, such as IS-95CDMA systems, IS determined in part by the interference generated when signals are transmitted to or from different users within the system. A feature of a typical CDMA system is that a signal is coded and modulated for transmission to or from a mobile station so that the signal is seen as interference by other mobile stations. For example, on the forward link, the channel quality between a base station and a mobile station is determined in part by the interference of other users. In order to maintain a desired level of performance in communication with a mobile station, the transmit power dedicated to that mobile station must be sufficient to exceed the power transmitted to other mobile stations served by the base station, as well as other interference and attenuation experienced in that channel. Thus, to increase capacity, it is desirable to be able to transmit the minimum power required by each served mobile station.

In a typical CDMA system, when multiple mobile stations transmit to a base station, it is desirable to receive multiple mobile station signals at the base station at a standardized power level. Thus, for example, the reverse link power control system can adjust the transmit power from each mobile station so that signals from nearby mobile stations do not overwhelm signals from more distant mobile stations. Maintaining the transmit power of each mobile station at the minimum power level required to maintain a desired level of performance for the forward link allows capacity to be optimized, and also has other power saving advantages, such as increased talk and standby time, reduced battery requirements, and the like.

Capacity in a typical CDMA system, such as IS-95, IS limited by some other occurrence, other user interference. Other user interference may be mitigated through the use of power control. The overall performance of the system, including capacity, voice quality, data transmission rate, and throughput, depends on the mobile station transmitting at the lowest power level possible to maintain the desired level of performance. To accomplish this, different power control techniques are known in the art.

One type of technique is closed loop power control. For example, closed loop power control may be applied on the forward link. Such a system may employ an inner power control loop and an outer power control loop in the mobile station. The outer loop determines a target received power level in accordance with the desired received error rate. For example, a target frame error rate of 1% may be predetermined as the desired error rate. The outer loop may update the target received power level at a relatively low rate, such as once per frame or per block of data (block). In response, the inner loop then sends an increase or decrease power control message to the base station until the received power reaches the target. These inner loop power control commands are generated relatively frequently in order to quickly bring the transmit power to the level necessary for the desired received signal to noise interference ratio required for effective communication. As described above, keeping the forward link transmit power for each mobile station at a minimum reduces other user interference seen at each mobile station and allows the remaining available transmit power to be reserved for other purposes. In systems such as IS-95, the remaining available transmit power can be used to support communication with other users. In a system such as 1xEV-DV, the remaining available transmit power can be used to support other users, or to increase the throughput of the system for the data only portion.

In a "data only" system such as IS-856, or in the "data only" portion of a system such as 1xEV-DV, a control loop may be utilized to manage transmissions from the base station to the mobile station in a time-shared manner. For clarity, in the following discussion, a transmission to a mobile station at a time may be described. This IS to be distinguished from simultaneous access systems, an example of which IS-95, or different channels in cdma200 or 1xEV-DV systems. Two points are noted at this time.

First, the term "data only" or "data channel" may be used to distinguish the channel from an IS-95 type voice or data channel (i.e., a simultaneous access channel using power control, as described above), merely for clarity of discussion. It will be apparent to those skilled in the art that only data or data channels described herein may be used to transmit any type of data, including voice (e.g., voice over internet protocol, or VOIP). The use of any particular embodiment for a particular type of data may be determined in part by throughput requirements, latency requirements, and the like. Those skilled in the art will readily adapt the various embodiments to combine any one of the access types with the selected parameters to provide the desired level of latency, throughput, quality of service, etc.

Second, only the data portion of the system, such as that described for 1xEV-DV, which is described as a time-shared communication resource, can be modified to provide access to more than one user simultaneously over the forward link. In the examples herein, where communication resources are described as being time-shared to provide communication with one mobile station or user for a period of time, those skilled in the art will readily adapt those examples to allow time-sharing of transmissions to or from more than one mobile station during that period of time.

A typical data communication system may include one or more different types of channels. More specifically, one or more data channels are typically utilized. It is also common for one or more control channels to be utilized, although in-band control signaling may be included on the data channel. For example, in a 1xEV-DV system, the forward packet data control channel (F-PDCCH) and the forward packet data channel (F-PDCH) are defined as the transmission of control and data, respectively, on the forward link.

Fig. 2 illustrates an exemplary mobile station 106 and base station 104 configured for data communication in system 100. Base stations 104 and mobile stations 106 are shown communicating over forward and reverse links. The mobile station 106 receives the forward link signal in the receive subsystem 220. As described in detail below, the base station 104 that communicates forward data and control channels may be referred to herein as a serving station for the mobile station 106. An exemplary receiving subsystem is described in further detail below in connection with fig. 3. A carrier/interference (C/I) estimate is made in the mobile station 106 for the received forward link signal from the serving base station. C/I measurements are examples of channel quality measures used as channel estimates, and alternative channel quality measures may be utilized in alternative embodiments. The C/I measurements are communicated to a transmit subsystem 210 in the base station 104, an example of which is described in further detail below in connection with fig. 3.

The transmit subsystem 210 communicates the C/I estimate over the reverse link, which is communicated to the serving base station. It is noted that in the case of soft handoff, the reverse link signal transmitted from the mobile station may be received by one or more base stations that are not serving base stations (referred to herein as non-serving base stations), as is known in the art. In the base station 104, the receive subsystem 230 receives C/I information from the mobile station 106.

In the base station 104, a scheduler 240 is used to determine whether and how data should be transmitted to one or more mobile stations within the coverage area of the serving cell. Any type of scheduling algorithm may be utilized within the scope of the present invention. An example is disclosed in U.S. patent application No. 08/798,951 entitled "method and apparatus for forward link rate scheduling", filed on 11/2/1997, which is assigned to the assignee of the present invention and is incorporated herein by reference.

In an exemplary 1xEV-DV embodiment, when a C/I measurement received from a mobile station indicates that data can be transmitted at a certain rate, that mobile station is selected for forward link transmission. In terms of system capacity, it is beneficial to select a target mobile station because it allows the shared communication resources to always be utilized at their maximum supported rate. Thus, a typical selected target mobile station may be the mobile station with the largest reported C/I. Other factors may also be introduced into the schedule determination. For example, minimum quality of service guarantees may have been made for different users. It is likely that mobile stations with relatively low reported C/I are selected to transmit to maintain a minimum data transmission rate to that user.

In the exemplary 1xEV-DV system, scheduler 240 determines which mobile station to transmit to, and also determines the data rate, modulation format, and power level for that transmission. In an alternative embodiment, such as an IS-856 system, for example, the supportable rate/modulation format may be determined at the mobile station based on the channel quality measured at the mobile station, and the transmission format may be transmitted to the serving mobile station as a substitute for the C/I measurement. Those skilled in the art will recognize that many known combinations of rate, modulation format, power level, and the like can be utilized within the scope of the present invention. Furthermore, although the scheduling tasks are performed at the base station in the different embodiments described herein, in alternative embodiments some or all of the scheduling process may be performed at the mobile station.

Scheduler 240 directs transmit subsystem 250 to transmit to the selected mobile station over the forward link using the selected rate, modulation format, power level, etc.

In an exemplary embodiment, messages on the control channel or F-PDCCH are sent along with data on the data channel or F-PDCH. The control channel can be used to identify the mobile station receiving data on the F-PDCH and to identify other useful communication parameters during the communication session. When the F-PDCCH indicates that the mobile station is a transmission target, the mobile station should receive and demodulate data from the F-PDCH. After receiving such data, the mobile station responds over the reverse link with a message indicating the success and failure of the transmission. As is well known in the art, retransmission techniques are commonly used in data communication systems.

In one state known as soft handoff, a mobile station may communicate with more than one base station. Soft handoff may include multiple sectors from one base station (or one Base Transceiver Subsystem (BTS)), known as softer handoff, and sectors from multiple BTSs. The base station sectors in soft handoff are typically stored in the mobile station's Active Set. In a simultaneously shared communication resource system, such as IS-95, IS-2000, or a corresponding portion of a 1xEV-DV system, a mobile station may combine forward link signals transmitted from all sectors in an active set. In a data-only system, such as IS-856, or a corresponding portion of a 1xEV-DV system, a mobile station receives a forward link signal from one of the base stations in the active set, the serving base station (as determined according to a mobile station selection algorithm such as those described in the c.s0002.c standard). Other forward link signals, examples of which are described in more detail below, may also be received from non-serving base stations.

Reverse link signals from the mobile station may be received at multiple base stations and the quality of the reverse link is typically maintained for the base stations in the active set. It is possible for reverse link signals received at multiple base stations to be combined. In general, soft combining (soft combining) of reverse link signals received from non-collocated base stations will require a very small delay and a very large amount of network communication bandwidth, so the above-mentioned example does not support it. In softer handoff, the reverse link signals received at multiple sectors in a single BTS can be combined without network signaling. Although any type of reverse link signal combination can be utilized within the scope of the present invention, in the exemplary system described above, reverse link power control maintains communication quality, which allows reverse link frames to be successfully decoded in one BTS (switch diversity).

In a corresponding portion of a simultaneously shared communication resource system, such as an IS-95, IS-2000, or 1xEV-DV system, a base station in soft handoff (i.e., in the mobile's active set) for each mobile station measures the reverse link pilot quality for that mobile station and sends out a stream of power control commands. In IS-95 or IS-2000rev.b, each stream IS sent on either a forward fundamental channel (F-FCH) or a forward dedicated control channel (F-DCCH), if both channels are allocated. The command stream for a mobile station is referred to as the forward power control subchannel (F-PCSCH) for that mobile station. For each base station, the mobile station receives parallel command streams from all its active set members (sectors from one BTS, the same command being sent to that mobile station if all in the mobile station's active set) and determines whether to issue an "up" or "down" command. The mobile station modifies the reverse link transmit power level accordingly using the "Or-of-downs" principle (i.e., decreasing the transmit power level if any "down" command is received, and increasing the transmit power level otherwise).

Typically, the transmit power level of the F-PCSCH is tied to the primary F-FCH or F-DCCH carrying the sub-channels. The primary F-FCH or F-DCCH transmit power level at that base station is determined by feedback transmitted by the mobile station over the reverse power control subchannel (R-PCSCH), which occupies the last quarter of the reverse pilot channel (R-PICH). Since the F-FCH or F-DCCH from each base station forms the traffic channel frame of a single stream, the R-PCSCH reports the combined decoding results of the legs (legs). Erasure (erasures) of the F-FCH or F-DCCH determines the Eb/Nt set point for the outer-loop requirement, which in turn drives the inner-loop commands on the R-PCSCH and thus determines the base station transmission levels of the F-FCH, F-DCCH, and the F-PCSCH on them.

Some base stations in the active set cannot reliably receive the R-PCSCH and properly control the forward link power of the F-FCH, F-DCCH, and F-PCSCH due to potential differences in reverse path loss from a single mobile station in soft handoff to each base station. The base stations may need to redistribute the transmission levels among them so that the mobile station can maintain the spatial diversity gain of soft handoff. Otherwise, a portion of the forward link leg may carry little or no traffic signal energy due to errors in the feedback from the mobile station.

Since different base stations may require different mobile station transmit powers for the same reverse link set point or reception quality, the power control commands from different base stations may be different and cannot be soft combined at the MS. When a new member is added to the active set (i.e., soft handoff from non-soft handoff to one-way (1-way) or from one-way to two-way (2-way), etc.), the FPCSCH transmit power is increased relative to its primary F-FCH or F-DCCH. This may be because the latter has more spatial diversity (requires less total Eb/Nt) and load sharing (less energy per branch), while the former does not.

In contrast, in a 1xEV-DV system, the forward command power control channel (F-CPCCH) transmits reverse link power control commands for mobile stations without the need for a forward fundamental channel (F-FCH) or a forward dedicated control channel (F-DCCH). In earlier versions of the 1xEV-DV proposal, it has been assumed that the base station transmit power level of the F-CPCCH is determined by the reverse channel quality indication channel (R-CQICH) received from the mobile station. The R-CQICH may be used for scheduling to determine the appropriate forward link transmission format and rate in response to forward link channel quality measurements.

However, when the mobile station is in soft handoff, the R-CQICH only reports the forward link pilot quality of the serving base station sector and thus cannot be used directly for power control of the F-CPCCH from the non-serving base station. Such a technique is disclosed in U.S. patent application No. 60/356,929, entitled method and apparatus for forward link power control during soft handoff in a communication system, filed on 12/2/2002, which is assigned to the assignee of the present patent and is incorporated herein by reference.

Exemplary base station and Mobile station embodiments

Fig. 3 is a block diagram of a wireless communication device, such as a mobile station 106 or a base station 104. The functional blocks shown in this exemplary embodiment are typically a subset of the components that are included in either the base station 104 or the mobile station 106. Those skilled in the art will readily adapt the embodiment shown in fig. 3 for use with any number of base station or mobile station configurations.

The signal is received at antenna 310 and transmitted to receiver 320. Receiver 320 performs processing in accordance with one or more wireless system standards, such as those listed above. Receiver 320 performs various processing such as Radio Frequency (RF) to baseband conversion, amplification, analog to digital conversion, filtering, and so forth. Different reception techniques are known in the art. When the device is a mobile station or a base station, respectively, although a separate channel quality estimator 335 is shown for simplicity of illustration, the receiver 320 may be used to measure the channel quality of the forward or reverse link, as will be described in more detail below.

The signal from receiver 320 is demodulated in demodulator 325 in accordance with one or more communication standards. In an exemplary embodiment, a demodulator capable of demodulating 1xEV-DV signals is utilized. In alternative embodiments, alternative standards may be supported, and embodiments may support multiple communication formats. Demodulator 330 may perform RAKE reception, quantization, combining, deinterleaving, decoding, and other various functions required by the format of the received signal. Different demodulation techniques are known in the art. In base station 104, demodulator 325 will demodulate according to the reverse link. In mobile station 106, demodulator 325 will demodulate according to the forward link. The data and control channels described herein are examples of channels that can be received and demodulated in receiver 320 and demodulator 325. As described above, demodulation of the forward data channel will be in accordance with signaling on the control channel. In various exemplary embodiments described below, demodulator 325 may include one or more despreaders for decoding a CDM signal, where the CDM signal has been masked by a masking sequence. Demodulator 325 may also include a demultiplexer for demultiplexing the TDM signal.

Message decoder 330 receives the demodulated data and extracts the signals or messages on the forward link or reverse link that are intended for mobile station 106 or base station 104, respectively. Message decoder 330 decodes various messages used in setting up, maintaining and tearing down a call (including voice or data sessions) of the system. The messages may include channel quality indications such as C/I measurements, power control messages, or control channel messages used to demodulate the forward data channel. Other different message types are known in the art and may be specified in the different communication standards being supported. The message is passed to processor 350 for subsequent processing. Although a separate functional block is shown for clarity of discussion, some or all of the functions of message decoder 330 may be performed in processor 350. Alternatively, demodulator 325 may decode and send certain information directly to processor 350 (a single bit message such as an ACK/NAK or a power control increase/decrease command is an example). An exemplary command signal, forward common acknowledgement channel (F-CACKCH), is used to describe the various embodiments below.

Channel quality estimator 335 is coupled to receiver 320 and is used to make the different power level estimates used in the steps described herein and also used in different other processes used in the communication, such as demodulation. In the mobile station 106, C/I measurements may be made. Also, measurements of any signal or channel used in the present system may be made in channel quality estimator 335 of the present embodiment. As will be described more fully below, a power control channel is another example. In either the base station 104 or the mobile station 106, signal strength estimates, such as received pilot power, may be made. Channel quality estimator 335 is shown as a separate functional block for clarity of discussion only. Typically for such functional blocks to be combined within a functional block such as receiver 320 or demodulator 325. Different types of signal strength estimates may be made depending on which signal or which system type is being estimated. In general, any type of channel quality measure estimation function may be utilized in place of channel quality estimator 335 within the scope of the present invention. In base station 104, the channel quality estimates are passed to a processor 350 for scheduling, or determining, the reverse link quality, as described further below. The channel quality estimate may be used to determine whether an increase or decrease power control command is needed to drive the forward or reverse link power toward a desired set point. The desired set point may be determined using an outer-loop power control mechanism, as described above.

The signal is transmitted via antenna 310. The transmitted signals are formatted in transmitter 370 in accordance with one or more wireless system standards, such as those listed above. Examples of components that may be included in transmitter 370 are amplifiers, filters, digital-to-analog (D/a) converters, Radio Frequency (RF) converters, and so forth. Data for transmission is provided to transmitter 370 by modulator 365. The data and control channels can be formatted for transmission in different formats. Data for transmission on the forward link data channel may be formatted in modulator 365 according to a rate and format indicated by a scheduling algorithm according to a C/I or other channel quality measurement. A scheduler, such as scheduler 240 described above, may reside in processor 350. Similarly, transmitter 370 may be directed to transmit at a power level in accordance with a scheduling algorithm. Examples of components that may be combined into modulator 365 include encoders, interleavers, spreaders, and different types of modulators. In the following, CDM and TDM encoders are described in different embodiments. Reverse link designs suitable for use in 1xEV-DV systems, including exemplary modulation formats and access controls, are also described below.

The message generator 360 may be used to prepare different types of messages as described above. For example, the C/I message may be generated in the mobile station for transmission on the reverse link. Different types of control messages may be generated in the base station 104 or the mobile station 106, respectively, to be transmitted on the forward or reverse link. For example, described below are request messages and grant messages that are used to schedule reverse link data transmissions generated in a mobile station or base station, respectively.

Data received and demodulated in demodulator 325 may be passed to a processor 350 for use in voice or data communications, as well as to various other components. Data similarly intended to be transmitted may be sent from processor 350 to modulator 365 and transmitter 370. For example, different data applications may be present in the processor 350, or in another processor (not shown) included in the wireless communication device 104 or 106. The base station 104 may be connected to one or more external networks, such as the internet (not shown), via other means not shown. The mobile station 106 may include a link to an external device such as a laptop computer.

Processor 350 may be a general purpose microprocessor, a Digital Signal Processor (DSP), or a special purpose processor. Processor 350 may perform some or all of the functions of receiver 320, demodulator 325, message decoder 330, channel quality estimator 335, message generator 360, modulator 365, or transmitter 370, as well as any other processing required by the wireless communication device. Processor 350 may be connected with dedicated hardware to assist in these tasks (details not shown). The data or voice applications may be external, such as an externally connected laptop or connection to a network, may run on an additional processor (not shown) within the wireless communication device 104 or 106, or may run on the processor 350 itself. Processor 350 is coupled to memory 355, which is used to store data and instructions for performing the various steps and methods described herein. Those skilled in the art will recognize that memory 355 may include one or more memory components of various types, which may be embedded in whole or in part within processor 350.

1xEV-DV reverse link design considerations

In this section, various factors are described to be considered in designing an exemplary embodiment of a reverse link for a wireless communication system. In many of these embodiments, as described in further detail in the following sections, the signals, parameters, and steps associated with the 1xEV-DV standard are used. These standards are described for illustrative purposes only and may be applied to any number of communication systems within the scope of the present invention. Although this section is not exhaustive, it serves to partly summarize the different aspects of the invention. Example embodiments are described in further detail in subsequent sections below, in which additional aspects are described.

In many cases, the reverse link capacity is interference limited. To be efficiently utilized to maximize throughput in accordance with the quality of service (QoS) requirements of the various mobile stations, the base station allocates available reverse link communication resources to the mobile stations.

Maximizing the use of reverse link communication resources includes several factors. One factor to consider is the mix of reverse link transmissions from different mobile stations that are scheduled, each of which may experience varying channel quality at any given moment. To increase the overall throughput (the aggregate data sent by all mobile stations in a cell), it is desirable that the entire reverse link be fully utilized whenever there is reverse link data to send. To fill the available capacity, mobile stations may be granted access at the highest rate they can support, and other mobile stations may be granted access until capacity is reached. One factor that the base station may consider in determining which mobile stations to schedule is the maximum rate that each mobile station can support and the amount of data that each mobile station has transmitted. A mobile station capable of supporting higher throughput may be selected instead of another mobile station whose channel does not support higher throughput.

Another factor to consider is the quality of service required by each mobile station. Although access to one mobile station may be allowed to be delayed in hopes that the channel will improve, instead of selecting a more suitable mobile station, a mobile station that may be less than optimal may need to be granted access to meet minimum quality of service guarantees. Thus, the scheduled data throughput may not be the absolute maximum, but certainly maximizes the considered channel conditions, available mobile transmit power, and traffic demand. Any configuration is desirable to reduce the signal to noise ratio of the selected mix.

Various scheduling mechanisms are described below that enable a mobile station to transmit data over the reverse link. One type of reverse link transmission includes a mobile station requesting transmission over the reverse link. The base station determines whether the resources can accommodate the request. Permission may be made to allow the transmission. This handshaking between the mobile station and the base station introduces a delay before reverse link data can be transmitted. This delay may be acceptable for certain classes of reverse link data. Other types of data may be more sensitive to latency, and alternative techniques for reverse link transmission are described in detail below to eliminate latency.

In addition, reverse link resources are consumed at request transmissions, while forward link resources are consumed at responses to the requests, i.e., transmit grants. When the channel quality of the mobile station is low, i.e., low geometry or deep fading, the power required on the forward link to reach the mobile station may be relatively high. Various techniques are described in detail below to reduce the number of requests and grants required for reverse link data transmission or the required transmit power.

Autonomous reverse link transmission modes are supported in order to avoid the delay introduced by the request/grant handshake and to conserve the forward and reverse link resources needed to support them. The mobile station can transmit data on the reverse link at a defined rate without making a request or waiting for permission.

The base station allocates a portion of the reverse link capacity to one or more mobile stations. The mobile stations granted access are given the maximum power level. In the exemplary embodiment described herein, the reverse link resources are allocated by using a traffic/pilot (T/P) ratio. Since the pilot signal of each mobile station is adaptively controlled through power control, the specified T/P ratio indicates the power available when transmitting data on the reverse link. The base station may make a dedicated grant to one or more mobile stations indicating a dedicated T/P value for each mobile station. The base station may also make a common grant to the remaining mobile stations that have requested access indicating the maximum T/P values that those remaining mobile stations are allowed to transmit. Autonomous and scheduled transmissions, as well as dedicated and common grants, are described in further detail below.

Different scheduling algorithms are known in the art and still in development for more algorithms that can be used to determine different private and public T/P values for grants based on the number of registered mobile stations, the probability of mobile stations transmitting autonomously, the number and size of unacknowledged requests, the expected average response to grants, and any number of other factors. In one example, the selection is made based on QoS priority, efficiency, and achievable throughput from the set of requesting mobile stations. An exemplary scheduling technique is disclosed in co-pending provisional U.S. patent application No. 60/439,989, filed on 13/1/2003, entitled "system and method for time-scalable priority-based scheduler," assigned to the assignee of the present invention and having the document number PA030159 (Attorney Docket), which is incorporated herein by reference. Additional references include U.S. patent 5,914,950 entitled "method and apparatus for reverse link rate scheduling" and U.S. patent 5,923,650 entitled "method and apparatus for reverse link rate scheduling," both of which are assigned to the assignee of the present invention and are incorporated herein by reference.

The mobile station may transmit the data of a packet using one or more subpackets, each of which contains the entire packet information (each subpacket need not be coded exactly the same, as different subpackets may utilize different coding or redundancy). Retransmission techniques may be utilized to ensure reliable transmissions, such as ARQ. Thus, if the first subpacket is received error-free (e.g., by using a CRC), a positive Acknowledgement (ACK) is sent to the mobile station and no further subpackets will be sent (recall that each subpacket includes the entire packet message, in one form or another). If the first subpacket is not received correctly, a negative acknowledgement signal (NAK) is transmitted to the mobile station, and a second subpacket is transmitted. The base station can combine the energy of the two subpackets and try to decode. Although a maximum number of subpackets is typically specified, the process may be repeated indefinitely. In the exemplary embodiment described herein, a maximum of four subpackets may be transmitted. Thus, the probability of correct reception increases when other subpackets are received. (Note that the third response from the base station, ACK-and-Continue, is useful for reducing request/grant overhead

As described, the mobile station may trade off throughput for latency to decide whether to send data with low latency using autonomous transmissions or to request higher rate data transmissions and wait for a common or dedicated grant. In addition, for a given T/P, the mobile station may select a data rate to accommodate latency or throughput. For example, a mobile station with a relatively few bits for transmission may decide that a low latency is desired. For the available T/P (which in this example may be the maximum value for autonomous transmission, but could also be a dedicated or common grant T/P), the mobile station may select the rate and modulation format so that the base station has a higher probability of correctly receiving the first subpacket. It is likely that this mobile station will send its data bits in one packet, although retransmission may be utilized if necessary. In the exemplary embodiment described herein, each subpacket is transmitted within 5 ms. Thus, in this example, the mobile station may make an immediate autonomous transmission that is likely to be received at the base station within the immediately following 5ms interval. Note that the mobile station may optionally use the availability of other subpackets to increase the amount of data transmitted for a given T/P. Thus, the mobile station may choose to autonomously transmit to reduce the latency associated with the request and grant, and may additionally balance the throughput for a particular T/P to minimize the number of subpackets required (and hence the latency). Even if the full number of subpackets is selected, autonomous transmission will be less delayed than request and grant for relatively small data transmissions. Those skilled in the art will recognize that as the amount of data to be transmitted increases, requiring multiple packets to be transmitted, by switching to the request and grant format, the overall latency can be reduced because the disadvantages of the request and grant are offset by the increased throughput at higher data rates across multiple packets. This process is described in further detail below, with an exemplary set of transmission rates and formats that may be associated with different T/P allocations.

A mobile station that is in a changing location within a cell and moving at a changing rate will experience changing channel conditions. Power control is used to maintain the reverse link signal. The pilot energy received at the base station may be power controlled to be approximately equal to that received from different mobile stations. Thus, as described above, the T/P ratio is an indicator of the amount of communication resources used during reverse link transmission. It is desirable to maintain an appropriate balance between pilot and traffic for a given mobile station transmit power, transmission rate, and modulation format.

Reverse link data transmission

The reverse link is typically not the same as the forward link. The following are several reasons: on the forward link, additional power is required to transmit from multiple cells — on the reverse link, receiving from multiple cells reduces the amount of transmit power required. On the reverse link, there are always multiple antennas to receive the mobile station. This may mitigate a portion of the significant fading that often occurs on the forward link.

When the mobile station is in the boundary area between cells, the forward link Ec/Io will change significantly due to fading of other cells. On the reverse link, the change in interference is not as significant as it would be, since any change is due to a combined change in the received power of all the mobile stations transmitting on the reverse link, which is power controlled.

The mobile station is power limited on the reverse link. Thus, depending on the channel conditions, the mobile station sometimes cannot transmit at very high rates.

A mobile station may not be able to receive a forward link from a base station receiving a reverse link transmission for the mobile station. As a result, if the mobile station were to rely on signaling from a single base station, such as the transmission of an acknowledgement, then the reliability of that signaling may be low.

One goal of reverse link design is to maintain a relatively stable rise-over-thermal (RoT) at the base station when there is reverse link data to transmit. Transmissions on the reverse link data channel are handled in two different modes:

and (3) autonomous transmission: this situation is for services that require low latency. The mobile station is allowed to immediately transmit at a transmission rate determined by the serving base station, i.e., the base station to which the mobile station transmits its Channel Quality Indicator (CQI). The serving base station may also be referred to as a scheduling base station or a licensed base station. The maximum allowed transmission rate for autonomous transmission may be dynamically signaled by the serving base station based on system load, congestion, etc.

Scheduling and sending: the mobile station sends an estimate of its buffer size, available power, and other parameters. The base station determines when the mobile station is allowed to transmit. The purpose of the scheduler is to limit the number of simultaneous transmissions, thereby reducing interference between mobile stations. The scheduler may try to have the mobile stations in the inter-cell region transmit at a lower rate to reduce interference in neighboring cells and tightly control RoT to protect voice quality on R-FCH, DV feedback and acknowledgement (R-ACKCH) on R-CQICH, and stability of the system.

Various embodiments described in detail herein include one or more features designed to improve the throughput, capacity, and overall system performance of the reverse link of a wireless communication system. For illustrative purposes only, the following are described: the data portion of a 1xEV-DV system, in particular, optimizes transmission by different mobile stations over an enhanced reverse supplemental channel (R-ESCH). The different forward and reverse link channels used in one or more exemplary embodiments are detailed in this section. These channels are typically a subset of the channels used in the communication system.

Fig. 4 illustrates an exemplary embodiment of data and control signals for reverse link data communication. The mobile station 106 is shown communicating over different channels, each of which is connected to one or more base stations 104A-104C. Base station 104A is labeled as a scheduling base station. The other base stations 104B and 104C are part of the active set of the mobile station 106. Four types of reverse link signals and two types of forward link signals are shown. Which will be described below.

R-REQCH

A reverse request channel (R-REQCH) is used by the mobile station to request reverse link transmission of data from the scheduling base station. In an exemplary embodiment, the request is for transmission on the R-ESCH (as will be described in further detail below). In an exemplary embodiment, the request on the R-REQCH includes a T/P ratio that varies according to changing channel conditions, and a buffer size (i.e., the amount of data waiting to be transmitted) that the mobile station can support. The request may also specify a quality of service (QoS) for data waiting to be transmitted. It is noted that a mobile station may have a single QoS level assigned to the mobile station or, alternatively, different QoS levels for different types of data. Higher layer protocols may indicate the QoS, or other desired parameters for different data services (such as latency or throughput requirements). In an alternative embodiment, a reverse dedicated control channel (R-DCCH) used with other reverse link signals, such as a reverse fundamental channel (R-FCH) (e.g., for voice traffic), may be used to carry the access request. In general, an access request may be described as comprising a logical channel, i.e., a reverse scheduling request channel (R-SRCH), which may be mapped onto any existing physical channel, such as an R-DCCH. The exemplary embodiment is backward compatible with existing cdma2000 systems, such as cdma2000, and the R-REQCH is a physical channel that can be utilized without the R-FCH or R-DCCH. For clarity, the term R-REQCH is used to describe the access request channel in the description of embodiments herein, although those skilled in the art will readily extend this principle to any type of access request system, regardless of whether the access request channel is logical or physical. The R-REQCH may be disabled (gate off) until a request is needed, thus reducing interference and conserving system capacity.

In an exemplary embodiment, the R-REQCH has 12 input bits, which include the following: 4 bits specifying the maximum R-ESCH T/P ratio that the mobile station can support, 4 bits specifying the amount of data in the mobile station buffer, and 4 bits specifying QoS. Those skilled in the art will recognize that any number of bits and various other fields may be included in alternative embodiments.

F-GCH

A forward grant channel (F-GCH) is transmitted from the scheduling base station to the mobile station. The F-GCH may include multiple channels. In an exemplary embodiment, a common F-GCH channel is used to make common grants and one or more dedicated F-GCH channels are used to make dedicated grants. The grants are made by a scheduling base station that responds to one or more requests from one or more mobile stations sent through their respective R-REQCHs. The grant channel may be labeled GCH_xWhere the subscript x identifies the channel number. The channel number 0 may be used to indicate a common grant channel. The index x may vary from 1 to N if N dedicated channels are utilized.

The dedicated grant may be made to one or more mobile stations, each of which allows the identified mobile station to transmit at a specified T/P ratio or lower on the R-ESCH. Making a grant on the forward link would naturally introduce overhead that consumes some forward link capacity. Various options for eliminating the overhead associated with licensing are detailed below, and other options will be apparent to those skilled in the art in light of the principles described herein.

One consideration is that the mobile stations will be located such that each mobile station experiences varying channel quality. Thus, for example, a high geometry mobile station with good forward and reverse link channels may require relatively low power for the grant signal and is likely to be able to take advantage of the high data rates, and thus is expected to take advantage of the dedicated grant. A low geometry mobile station, or a mobile station experiencing more fading, may require significantly more power to reliably receive the dedicated grant. Such mobile stations may not be the best candidates for dedicated permission. Less forward link overhead may be consumed for common grants for such mobile stations, as described in detail below.

In an exemplary embodiment, multiple dedicated F-GCH channels are utilized to provide a corresponding number of dedicated grants at a particular time. The F-GCH channels are code division multiplexed. This facilitates the ability to send each grant at the power level just needed to reach a particular target mobile station. In an alternative embodiment, a single dedicated grant channel may be utilized, with the number of dedicated grants being time multiplexed. To change the power per grant on a time multiplexed dedicated F-GCH, additional complexity may be introduced. Any signaling technique for communicating a common or dedicated grant may be utilized within the scope of the present invention.

In some embodiments, a relatively large number of dedicated grant channels (i.e., F-GCH) are utilized, which may be utilized to simultaneously allow a relatively large number of dedicated grants. In this case, it may be desirable to limit the number of dedicated licensed channels that each mobile station must monitor. In one exemplary embodiment, different subsets of the total number of dedicated licensed channels are defined. Each mobile station is assigned a subset of dedicated grant channels to monitor. This allows the mobile station to reduce the complexity of the processing and correspondingly reduce power consumption. Scheduling complexity is traded off because the scheduling base station may not be able to arbitrarily assign a subset of the dedicated grants (e.g., all dedicated grants cannot be made to members of a single group because those members are not designed to monitor one or more of these dedicated grant channels). It is noted that the loss of complexity does not necessarily result in a loss of capacity. For purposes of illustration, consider an example that includes four dedicated grant channels. Even mobile stations may be assigned to monitor the first two licensed channels and odd mobile stations may be assigned to monitor the last two licensed channels. In another example, the subsets may overlap, such as even mobile stations monitoring the first three licensed channels and odd mobile stations monitoring the last three licensed channels. It is clear that the scheduling base station cannot arbitrarily allocate four mobile stations from any one group (even or odd). These examples are for illustration only. Any number of channels having any subset configuration may be utilized within the scope of the present invention.

The remaining mobile stations that have made requests but have not received the dedicated grant may be permitted to transmit on the R-ESCH with a common grant that specifies the maximum T/P ratio that each of the remaining mobile stations must adhere to. The common F-GCH may also be referred to as a forward common grant channel (F-CGCH). The mobile station monitors one or more dedicated grant channels (or a subset thereof) as well as the common F-GCH. Unless given a private license, the mobile station may transmit if a public license is issued. The common grant indicates the maximum T/P ratio that the remaining mobile stations (common grant mobile stations) may utilize to send certain types of QoS data.

In an exemplary embodiment, each common grant is valid for a plurality of subpacket transmission intervals. Upon receiving the common grant, a mobile station that has sent a request but not received a dedicated grant may begin transmitting one or more code packets in a subsequent transmission interval. The license information may be repeated multiple times. This allows the common grant to be transmitted at a reduced power level relative to the dedicated grant. Each mobile station can combine energy from multiple transmissions to reliably decode the common grant. Thus, a common grant may be selected for a mobile station with low geometry, for example, when a dedicated grant is considered too wasteful in terms of forward link capacity. However, common channels still require overhead, and different techniques for reducing this overhead are detailed below.

R-PICH

A reverse pilot channel (R-PICH) is transmitted from the mobile station to the base stations in the active set. Power in the R-PICH may be measured at one or more base stations for reverse link power control. As is known in the art, for use in coherent demodulation, pilot signals may be used to provide amplitude and phase measurements. As described above, the amount of transmit power available to the mobile station (whether limited by the scheduling base station or inherent limitations of the mobile station's power amplifier) is divided among the pilot channel, the traffic channel or channels, and the control channel.

As described above, additional pilot energy may be required for higher data rates and demodulation formats. To simplify the use of the R-PICH for power control and to avoid some problems associated with instantaneous changes in required pilot power, additional channels may be allocated for supplemental or secondary pilots. Although the pilot signal is typically transmitted using a known data sequence as disclosed herein, the information-bearing signal may also be utilized for use in generating the reference information for demodulation. In an exemplary embodiment, an R-RICH (described in more detail below) is used to carry the required additional pilot power.

R-RICH

The reverse rate indicator channel (R-RICH) is used by the mobile station to indicate the transmission format on the reverse traffic channel, R-ESCH. The R-RICH 5 bit message is a set of 5 bits with a value of 1 or 0. The orthogonal encoder block maps each 5-bit input sequence to an orthogonal sequence of 32 symbols. For example, every 5-bit input sequence can be mapped to a different walsh code of length 32. The sequence repeat function repeats a sequence of 32-bit input symbols three times. The bit repetition block provides at its output the input bits which are repeated 96 times. The sequence selector module selects between these two inputs and passes that input to the output. For zero rate, the output of the bit repetition block passes. For all other rates, the output of the sequence repetition module passes. The signaling point mapping module maps input bit 0 to +1 and input 1 to-1. The next signaling point mapping module is a walsh spreading module. The walsh spreading module spreads each input symbol into 64 chips. Each input symbol is multiplied by a walsh code W (48, 64). The walsh code W (48, 64) is a walsh code of length 64 chips with an index of 48. TIA/EIAIS-2000 provides a table describing walsh codes of different lengths.

Those skilled in the art will recognize that this channel structure is for example only. In alternative embodiments, various other coding, repetition, interleaving, point mapping, or walsh coding parameters can be utilized. Additional encoding or formatting techniques well known in the art may also be utilized. Such modifications are intended to fall within the scope of the present invention.

R-ESCH

In the exemplary embodiment described herein, an enhanced reverse supplemental channel (R-ESCH) is used as the reverse link traffic data channel. Any number of transmission rates and modulation formats may be utilized for the R-ESCH. In an exemplary embodiment, the R-ESCH has the following characteristics: physical layer retransmissions are supported. For retransmission, when the first code is a Rate 1/4 code (Rate 1/4 code), the retransmission uses a Rate 1/4 code and Chase combining is used. For retransmissions when the first code is a rate greater than 1/4 code, incremental redundancy (incremental redundancy) is used. The base code is a rate 1/5 code. Alternatively, incremental redundancy may be used for all cases as well.

Both autonomous and scheduled users support hybrid automatic repeat request (HARQ), both of which may access the R-ESCH.

For the case where the first code is a rate 1/2 code, the frame is encoded as a rate 1/4 code and the encoded symbols are equally divided into two parts. The first part of the symbol is sent in a first transmission and the second part in a second transmission, then the first part in a third transmission, and so on.

Due to the fixed timing between retransmissions, the synchronous operation of multiple ARQ channels may be supported: a fixed number of subpackets may be allowed between consecutive subpackets of the same packet. Interleaved transmission is also allowed. As an example, for a 5ms frame, a 4-channel ARQ can be supported with a 3 subpacket delay between subpackets.

Table 1 lists exemplary data rates for the enhanced reverse supplemental channel. A sub-packet size of 5ms is described and the supplemental channel has been designed to be suitable for this option. Other subpacket sizes may also be selected, as will be apparent to those skilled in the art. The pilot reference level is not adjusted for these channels, i.e., the base station has the flexibility to select T/P to reach a given operating point. The maximum T/P value may be signaled on the forward grant channel. The mobile station may use a lower T/P if it runs out of transmitted power to let HARQ meet the required QoS. Layer 3 signaling messages may also be sent over the R-ESCH, allowing the system to operate without the FCH/DCCH.

Table 1 enhanced reverse supplemental channel parameters

Number of bits per encoder packet	Number of 5ms slots	Data Rate (kbps)	Data Rate/9.6 kbps	Encoding rate	Symbol repetition factor before interleaving	Modulation	Walsh channel	Number of binary coded symbols in all sub-packets	The effective code rate includes repetition
										192	4	9.6	1.000	1/4	2	BPSK on I	++--	6,144	1/32
192	3	12.8	1.333	1/4	2	BPSK on I	++--	4,608	1/24
										192	2	19.2	2.000	1/4	2	BPSK on I	++--	3,072	1/16
192	1	38.4	4.000	1/4	2	BPSK on I	++--	1,536	1/8
										384	4	19.2	2.000	1/4	1	BPSK on I	++--	6,144	1/16
384	3	25.6	2.667	1/4	1	BPSK on I	++--	4,608	1/12
										384	2	38.4	4.000	1/4	1	BPSK on I	++--	3,072	1/8
384	1	76.8	8.000	1/4	1	QPSK	++--	1,536	1/4
										768	4	76.8	4.000	1/4	1	QPSK	++--	12,288	1/16
768	3	102.4	5.333	1/4	1	QPSK	++--	9,216	1/12
										768	2	153.6	8.000	1/4	1	QPSK	++--	6,144	1/8
768	1	307.2	16.000	1/4	1	QPSK	++--	3,072	1/4
										1,536	4	76.8	8.000	1/4	1	QPSK	+-	24,576	1/16
1,536	3	102.4	10.667	1/4	1	QPSK	+-	18,432	1/12
										1,536	2	153.6	16.000	1/4	1	QPSK	+-	12,288	1/8
1,536	1	307.2	32.000	1/4	1	QPSK	+-	6,144	1/4
										2,304	4	115.2	12.000	1/4	1	QPSK	++--/+-	36,864	1/16
2,304	3	153.6	16.000	1/4	1	QPSK	++--/+-	27,648	1/12
										2,304	2	230.4	24.000	1/4	1	QPSK	++--/+-	18,432	1/8
2,304	1	460.8	48.000	1/4	1	QPSK	++--/+-	9,216	1/4
										3,072	4	153.6	16.000	1/5	1	QPSK	++--/+-	36,864	1/12
3,072	3	304.8	21.333	1/5	1	QPSK	++--/+-	27,648	1/9
										3,072	2	307.2	32.000	1/5	1	QPSK	++--/+-	18,432	1/6
3,072	1	614.4	64.000	1/5	1	QPSK	++--/+-	9,216	1/3
										4,608	4	230.4	24.000	1/5	1	QPSK	++--/+-	36,864	1/8
4,608	3	307.2	32.000	1/5	1	QPSK	++--/+-	27,648	1/6
										4,608	2	460.8	48.000	1/5	1	QPSK	++--/+-	18,432	1/4
4,608	1	921.6	96.000	1/5	1	QPSK	++--/+-	9,216	1/2
										6,144	4	307.2	32.000	1/5	1	QPSK	++--/+-	36,864	1/6
6,144	3	409.6	42.667	1/5	1	QPSK	++--/+-	27,648	2/9
										6,144	2	614.4	64.000	1/5	1	QPSK	++--/+-	18,432	1/3
6,144	1	1228.8	128.000	1/5	1	QPSK	++--/+-	9,216	2/3

In an exemplary embodiment, turbo coding is used for all rates. For the R1/4 code, a similar interleaver to the current cdma2000 reverse link is used, and if the second subpacket is sent, its format is the same as the first subpacket. For the R1/5 code, an interleaver similar to the cdma2000 forward packet data channel is used, and if the second subpacket is transmitted, the sequence of coded and interleaved symbols selected for the second subpacket follows those selected for the first subpacket. At most, transmission of two subpackets is allowed, and if the second subpacket is transmitted, it uses the same data rate as the first subpacket transmission.

The number of bits per encoder packet includes CRC bits and 6 tail bits (tailbits). For an encoder packet size of 192 bits, a 12-bit CRC is used; otherwise, a 16-bit CRC is used. The number of information bits per frame is twice as large as the corresponding rate of cdma 2000. The 5ms slots are assumed to be separated by 15ms to allow time for ACK/NAK responses. If an ACK is received, the remaining slots of the packet are no longer transmitted.

The 5ms subpacket duration and related parameters just described are for example purposes only. Combinations of any number of rates, formats, subpacket repetition selections, subpacket durations, etc., will be apparent to those skilled in the art from the description herein. An alternative 10ms embodiment using 3 ARQ channels can be employed. In one embodiment, a single sub-packet duration or a single frame size is selected. For example, a 5ms or 10ms structure would be selected. In an alternative embodiment, which will be described in further detail below, the system may support multiple frame durations.

F-CACKCH

The forward common acknowledgement channel, or F-CACKCH, is used by the base station to confirm correct reception of the R-ESCH and to extend the existing grant. An Acknowledgement (ACK) on the F-CACKCH indicates that the sub-packet was correctly received. It is no longer necessary for the mobile station to additionally transmit the subpacket. Negative Acknowledgements (NAKs) on the F-CACKCH cause the mobile station to transmit the next subpacket up to the maximum number of subpackets allowed per packet. The third command, ACK-and-Continue, enables the base station to acknowledge the successful receipt of the packet and at the same time allow the mobile station to transmit by using the grant that resulted in the successfully received packet. One embodiment of the F-CAKCH uses a +1 value to represent the ACK symbol, a NULL symbol to represent the NAK symbol, and a-1 value to represent the ACK-and-Continue symbol. In various exemplary embodiments, up to 96 mobile station IDs may be supported on one F-CACKCH, as described in further detail below. Additional F-CACKCH may be employed to support additional mobile station IDs.

A Hadamard encoder is an example of an encoder for mapping onto a set of orthogonal functions. Various other techniques may also be employed. For example, any walsh code or Orthogonal Variable Spreading Factor (OVSF) code generation may be used for encoding. Different users may be transmitted at different power levels if separate gain blocks are employed. The F-CACKCH transmits a dedicated three-value flag for each user. Each user monitors the F-ACKCHs from all base stations in its active set (or alternatively, the signaling may define a reduced active set to reduce complexity).

In various embodiments, detailed below, the two channels are each masked by a 128-chip walsh mask sequence. One channel is transmitted on the I channel and the other on the Q channel. Another embodiment of the F-CACKCH uses a single 128-chip walsh mask sequence to support up to 192 mobile stations simultaneously. This method uses a duration of 10ms for each of the three value flags.

There are several ways to operate the ACK channel. In one embodiment, this may be done so that a "1" is sent for the ACK. Not sent means a NAK, or "off" state. And the transmission of "-1" refers to ACK-and-Continue, i.e. the same grant is repeated to the MS. This saves the overhead of a new grant channel.

Recall that when the MS has a packet to transmit that requires the use of the R-ESCH, the MS transmits a request on the R-REQCH. The base station may respond with permission using the F-CGCH, or F-GCH. However, this operation overhead is somewhat large. To reduce the forward link overhead, the F-CAKCH may send an "ACK-and-Continue" flag that extends the existing grants by the scheduling base station at a low cost. This approach can be used for both private and public licenses. ACK-and-Continue is used according to the granted base station and extends the current grant for one more encoder packet on the same ARQ channel.

Various embodiments are described herein for a common acknowledgement channel (F-CAKCCH). Those skilled in the art will recognize that the principles described herein are applicable to any type of common sequence or other data sequence.

Fig. 5 shows a prior art embodiment of a portion of a command stream transmitter. Command streams to be transmitted to one or more mobile stations may be combined into a shared command channel. In this example, forward link acknowledgement commands for up to 96 mobile stations are passed to multiplexers (mux)510 and 520, where each mux is sent48 command streams. These command streams include acknowledgement commands, which as described above include an Acknowledgement (ACK), a Negative Acknowledgement (NAK), and an acknowledgement and Continue (ACK-and Continue). Multiplexers 510 and 520 select the command sequences one at a time to form TDM sequences, one for in-phase transmission and the other for quadrature transmission. The TDM sequence in this example includes 48 symbols (9.6ksps) every five milliseconds. The TDM sequences are gain controlled in channel gain blocks 530 and 540, respectively. The gain control TDM sequence is masked with an in-phase mask sequence and a quadrature mask sequence in multipliers 550 and 560, respectively. In this example, the mask sequence is a 128-bit Walsh sequence, W_i ¹²⁸. The outputs resulting from multipliers 550 and 560 are the IF-CACKCH output and QF-CACKCH output for transmission at 1.2288 Mcps.

The output of fig. 5 may be combined with other data and/or control signals as appropriate to be masked and transmitted to one or more mobile stations. Thus, a method of TDM on a CDM basis is employed to transmit a plurality of commands to a plurality of mobile stations using a shared CDM channel. One disadvantage of this approach is that for a given error probability, both the peak power requirement and the average power requirement are higher than required by the embodiments of the invention disclosed herein. In the prior art, this technique has been used successfully by increasing the probability of error allowed to provide guarantees for acceptable peak power requirements, as well as average power consumption. This tradeoff may be acceptable in some situations, such as power control loops. In a power control loop it is common for a single bit increase or decrease command to be sent. The power control loop controls the command so that the received power can reach the desired power set point. If the power control command is received with an error, the power control loop will correct the error. However, in other cases, such as the forward link common acknowledgement channel (F-CAKCCH) defined for 1xEV-DV systems described above, the specified performance requirements may be either out of reach or too costly by using a method for TDM on a CDM basis. For example, although a power control command error may cause the transmitted power to be slightly too high for a period of time, thereby using more shared resources than required, or too low for a period of time, thereby causing an error rate to rise, typical power control schemes are designed to counter such a situation with fast power control and quickly restore the transmit power to a desired level, thereby minimizing any undue system performance degradation. Conversely, a false Acknowledgement (ACK) command may cause a packet to be dropped. While NAKs often cause additional subpackets to be sent, potentially resulting in correct reception when combined with previously received subpackets, a false ACK may require the dropped packet to be retransmitted completely, most likely after interference from higher layer protocols, and with significant delay. The wrong ACK-and-Continue has the same problem. An erroneous NAK, meaning that the packet has been received correctly, results in additional subpackets being transmitted unnecessarily. All of these conditions can compromise system performance. As such, in some cases, commands such as HARQ commands may be advantageously transmitted with a lower error rate. If the prior art arrangement shown in fig. 5 is used, this translates into a higher average transmit power and a very high (possibly unreachable) peak power.

Fig. 6 shows an embodiment of an encoder for CDM based on CDM, which is used to receive multiple input sequences and combine them using code division multiplexing and transmit the combined signal to one or more mobile stations along with other CDM. This embodiment is shown using the F-CACKCH command stream for 96 mobile stations as an example. Those skilled in the art will recognize that any sequence type, command or data may be used instead. A first set of 48 command streams, identified as addressed to mobile station identification numbers 0 through 47, will be combined and sent onto the I channel. A second set of 48 command streams, identified as addressed to mobile station identification numbers 48 through 96, will be combined and transmitted onto the Q channel. The first set of 48 command streams are each encoded with a mask sequence. In the exemplary embodiment, the command stream is encoded using Hadamard sequence encoders 610A-610N, respectively, of length 48. The Hadamard sequence numbers used in each encoder correspond to mobile station identification numbers. However, the assignment of the sequence is arbitrary and other configurations will be apparent to those skilled in the art. The outputs of Hadamard encoders 610A-610N may be independently gain controlled in channel gain blocks 630A-630N, respectively.

The second set of 48 command streams may also be encoded with a masking sequence. In this example, they are masked using a length 48 Hadamard encoder 620A-620N, respectively, in a manner similar to encoders 610A-610N described above. In addition, the sequence assignment is arbitrary. In a similar manner, the outputs of Hadamard encoders 620A-620N may be independently gain controlled in channel gain blocks 640A-640N, respectively.

The outputs of the channel gain blocks 630A-630N and 640A-640N are passed to be combined in summers 650 and 660, respectively. The outputs of adders 650 and 660 are the I and Q CDM signals, respectively. Each signal includes 48 symbols (9.6ksps) every 5ms for transmission on the I and Q branches. These signals are masked using I and Q masking sequences, collectively W_i ¹²⁸To identify that 1.2288Mcps of IF-CACKCH output and Q F-CACKCH output are generated in multipliers 670 and 680, respectively. These outputs may be combined with other CDM masked signals for transmission to one or more mobile stations. Furthermore, those skilled in the art will recognize that the embodiment shown in fig. 6 is merely an example, and the principle of combining sequences using CDM, and then masking the CDM combined sequences for transmission, may be applied to any control and/or data sequence.

It is further noted that the use of QPSK is only one example, as shown. It has the advantage of allowing two different CDM-based signals to be transmitted by using the orthogonality provided by QPSK. Other modulation formats may also be supported. For example, BPSK may be used instead.

One advantage of using an embodiment such as that shown in fig. 6, as compared to the prior art shown in fig. 5, is that the peak power requirement can be much lower for the desired error rate. In some cases, the embodiment of FIG. 6 may be able to achieve desired specifications that may not be met by an architecture such as that shown in FIG. 5. In addition, the average power required for the embodiment shown in FIG. 6 is also typically much lower.

Fig. 7A and 7B illustrate embodiments of CDM signal combining, CDM, and TDM based techniques. In some cases, CDM-based CDM encoders, such as that depicted in fig. 6, may experience increasing crosstalk interference as the quadrature period increases, where the crosstalk interference is due to input sequences sent to other mobile stations of the F-CACKCH CDM channel. For example, some loss of orthogonality may occur in the 5ms frame given in the above exemplary embodiment due to the effects of multipath. The embodiments shown in fig. 7A and 7B are summarized with respect to the number of input sequences, the length of the encoder, the number of inputs to the adder and multiplexer, and so on. Other embodiments disclosed herein may be generalized in a similar manner, but are described with respect to particular embodiments for clarity of discussion. Those skilled in the art will readily apply the principles described herein to several encoder configurations.

In this example, two signals are generated, one for transmission on the in-phase channel and one for transmission on the quadrature channel. Each signal includes time division multiplexing of multiple CDM channels. The resulting signal is again masked to produce a signal suitable for transmission with other data and/or control signals in CDM form. Thus, a TDM-based CDM signal using CDM-based is substantially generated.

There are N input sequences to be combined onto the common command signal (naturally, non-command sequences can also be combined to form any type of common signal). In some configurations, each input sequence is addressed to a single mobile station. One example of such multiple input sequences is the ACK/NAK/ACK-and-Continue commands, each of which is generated for a unique mobile station, which forms the F-CACKCH as described above. In an alternative embodiment, one or more input sequences may be directed to a single mobile station. To indicate their generality, each input sequence is labeled with a command bit representing a subchannel ID, which varies from 0 to N-1. (the subchannel ID may correspond to the mobile station ID in some embodiments.) M CDM channels are combined over each TDM channel. There are L slots in each TDM channel. Thus, N input sequences are divided over the I and Q channels, with N/2 input sequences for each channel phase. Thus, the relationship between M, N and L can be given by M ═ N/(2 ×) L.

Therefore, a first set of M input sequences is masked in the encoders 710A-710M by a length-M Hadamard sequence. M different Hadamard sequences can be arbitrarily assigned to the input sequence. In this example, the sequence matches the subchannel ID. The set of M input sequences is assigned until the last M input sequences (M (L-1) through (N/2) -1) assigned to the I channel are transmitted to encoders 720A-720M. It is noted that the assignment of particular Hadamard sequences is arbitrary, although in this example they are assigned in terms of subchannel ID modulo M. The next N/2 input sequence is similarly encoded as shown. The M sequences N/2 through N/2+ M-1 are transmitted to encoders 750A-750M. The assignment continues until the last M sequences (N/2+ M (L-1) through N-1) are sent to encoders 755A-755M. Furthermore, the Hadamard sequence allocation is arbitrary, but in this example it is sub-channel ID modulo M.

Each output of the Hadamard encoder may be modified by channel gains in channel gain blocks 730A-730M through 735A-735M and 760A-760M through 765A-765M, respectively. For each phase (I and Q), there are L adders 740A-740L for the I channel and 770A-770L for the Q channel, each combining their respective M masked input sequences to form 2L CDM sequences. The L in-phase CDM sequences from summers 740A-740L are time division multiplexed in multiplexer 745 to generate a TDM-based CDM signal for the I channel. Similarly, the L orthogonal CDM sequences from summers 770A-770L are time division multiplexed in multiplexer 775 to generate a TDM-based CDM signal for the Q channel. The TDM-based CDM signal is then masked in multipliers 780 and 785, respectivelyThe code sequence (comprising in-phase and quadrature parts) is masked, denoted W_iTo generate I and Q common command signal outputs. These masked signals are then ready to be combined and transmitted in CDM fashion with other data and/or control signals. (again, those skilled in the art will recognize that QPSK is only an option and not mandatory; further, the common signal may include a sequence rather than a command signal; and the shared channel may be sent to and received by any combination of one or more mobile stations.) thus, the general embodiment shown in FIGS. 7A and 7B illustrates the use of a CDM-based TDM-based CDM combination of the input sequences. This technique results in a reduction in peak and average power due to the CDM features, and a potential increase in the number of users and a reduction in orthogonality loss due to the TDM features.

Those skilled in the art will recognize that the embodiments of fig. 7A and 7B are generic and that many combinations of CDM channel numbers M, time slots L, and input sequences N may be utilized. Alternative embodiments also need not include the symmetries described in fig. 7A and 7B. For example, the I and Q signals may be constructed using different parameters. Further, the multiplexer may be configured to time-multiplex the outputs of the summers, each of which may or may not combine the same number of CDM channels. Two exemplary embodiments of the above-described F-CAKCHs are given here for illustration. In a first embodiment, 96 input sequences, including ACK/NAK/ACK-and-Continue commands, sent with a 128 chip walsh mask sequence at 1.2288Mcps to up to 96 mobile stations, are combined by generating an orthogonal period of 1/2400 seconds, using M-4 and L-12, on both the I and Q channels. In the second embodiment, the same input is processed and the output as described in the first embodiment is generated by generating an orthogonal period exceeding 1.25ms using M-12 and L-4. Any number of combinations will be readily devised by those skilled in the art in light of the present invention.

Fig. 8 shows an embodiment using pattern repetition. Although this embodiment can be generalized with respect to FIG. 7A and FIG.7B in a similar manner as detailed above, but for illustrative purposes the F-CAKCCH is used again. This embodiment uses a CDM approach with pattern repetition. In this example, the 48 input sequences, F-CACKCH bits for Mobile IDs 0-47, are passed to 48 symbol encoders 810A-810N and 820A-820N for the I and Q channels, respectively. Each 48-symbol encoder uses 2 Hadamard sequences of 24 symbols. The encoded outputs are gain adjusted in channel gain blocks 830A-830N and 840A-840N, respectively. Summer 850 combines the respective gain adjusted coded sequences to generate an I-channel CDM signal. Summer 860 combines the respective gain-adjusted coded sequences to generate a Q-channel CDM signal. (Note that it is not necessary to use both the I and Q channels to transmit signals as before-alternative embodiments may use other modulation schemes within the scope of the invention.) the multipliers 870 and 880 may be implemented by using a complex masking sequence W_i ¹²⁸The I and Q CDM signals are again masked to generate I F-CACKCH outputs and Q F-CACKCH outputs, which are combined with other signals, possibly in CDM, and transmitted to one or more mobile stations. Thus, fig. 8 shows still another embodiment of a CDM-based CDM encoding method.

One advantage of the embodiment shown in fig. 8 is that the quadrature period is reduced from 5ms to 2.5 ms. Thus, there is less crosstalk interference from other possible users of that F-CACKCH. In this example, the repetitions used in encoders 810 and 820 do not repeat the same Hadamard sequence, but use a different sequence for the second transmission. So, for example, if an individual user is transmitting for the first time causing interference to another user, the same user is not transmitting for the second time causing the same interference. This approach reduces peak crosstalk interference and brings it closer to average interference. However, compared to the embodiment of fig. 6, the present embodiment supports only half the number of users.

In one embodiment, the Hadamard sequences selected for encoders 810 and 820 are as follows. The first set of 24 symbols for encoders 810 and 820 is a length-24 Hadamard sequence, identified by mobile station ID modulo 24. The second set of 24 symbols for encoder 810 is a length-24 Hadamard sequence, identified by (mobile station ID +5) modulo 24. The second set of 24 symbols for encoder 820 is a length-24 Hadamard sequence, identified by (mobile station ID +7) modulo 24. There is no particular significance to those values, although they are easily calculated. Those skilled in the art will readily extend these principles to other different repeat sequences. The result is that if a particular user causes interference to another user in a first transmission, the same user will not cause the same interference in a second transmission. This reduces peak crosstalk interference and makes the interference closer to average interference.

In an alternative embodiment, the values of the Hadamard sequences are assigned in a time-varying manner. In the first embodiment just described, with two repetitions including the pattern described, the peak crosstalk interference over two transmissions (i.e., one frame) may be much higher than the average interference. If two users are allocated such that such peak interference occurs, it may occur every frame. With the time-varying approach, even if the crosstalk interference of one frame is severe, the same user will not have the same severe crosstalk interference in the following frames because the Hadamard sequences are allocated in a time-varying manner.

Various other alternatives are also envisaged. Additional repetitions may be introduced if more orthogonality protection is required. Furthermore, the repetition technique described with respect to fig. 8 may be combined with the TDM approach introduced in the embodiments of fig. 7A and 7B. Many combinations will be readily configured by those skilled in the art in light of the principles disclosed herein.

The wireless communication device 106 described above with respect to fig. 3 may be operable to receive and demodulate any of the different CDM transmission signals described above. Demodulator 305 may be configured to perform de-masking (decover) and de-multiplexing of the different TDM and CDM signals described to extract the symbols of the desired sequence transmitted from base station 104. In some of the above examples, those symbols would be the bits of the F-CAKCCH assigned to a particular mobile station 106.

It should be noted that in all the embodiments described above, method steps can be interchanged without departing from the scope of the invention. The description disclosed herein refers in some cases to symbols, parameters, and steps that comply with the 1xEV-DV standard, although the scope of the invention is not so limited. Those skilled in the art will readily apply the principles herein to various other communication systems. These and other modifications will be apparent to those of ordinary skill in the art.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) and other programmable logic devices, discrete gate and transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside directly in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside as discrete components in an ASIC.

Furthermore, the previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (44)

1. An apparatus, comprising:

a first encoder for receiving a plurality of symbol streams and encoding each of the symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

an adder for accumulating the plurality of masked sequences to form a first Code Division Multiplexed (CDM) signal; and

a second encoder for masking the first CDM signal with a masking sequence to form a first masked CDM signal.

2. The apparatus of claim 1, further comprising one or more channel gain blocks for receiving a plurality of gain values and multiplying the plurality of masked sequences by the plurality of gain values, respectively, before transmission to the summer.

3. The apparatus of claim 1, wherein the first encoder comprises one or more Hadamard encoders.

4. The apparatus of claim 1, further comprising a transmitter to receive the first masked CDM signal and one or more additional masked signals, to combine the first masked CDM signal with the one or more additional masked signals to form a combined CDM signal, and to transmit the combined CDM signal to a remote station.

5. The apparatus of claim 1, further comprising:

a third encoder for receiving a second plurality of symbol streams and encoding each of the symbol streams with the plurality of mask sequences to form a second plurality of masked sequences;

a second adder for accumulating the second plurality of masked sequences to form a second Code Division Multiplexed (CDM) signal;

a fourth encoder for masking the second CDM signal with a masking sequence to form a second masked CDM signal; and

a transmitter to send the first masked CDM signal onto an in-phase channel and the second masked CDM signal onto a quadrature channel.

6. The apparatus of claim 1, wherein one or more of the plurality of symbol streams includes a command value indicating an acknowledgement, a negative acknowledgement, or an acknowledgement and continue.

7. The apparatus of claim 1, wherein the encoder divides the encoding time into two or more segments and masks each of the plurality of symbol streams with two or more sequences, each sequence being used for masking during the two or more segments, respectively, and the sequence that masks each symbol stream during one segment is unique to each symbol stream.

8. The apparatus of claim 7, wherein the first sequence is selected as a Hadamard sequence corresponding to the remote station identifier and the second sequence is selected as the remote station identifier plus five modulo half of a number of symbol streams in the plurality of symbol streams.

9. The apparatus of claim 7, wherein the first sequence is selected as a Hadamard sequence corresponding to the remote station identifier and the second sequence is selected as the remote station identifier plus seven modulo half of a number of symbol streams in the plurality of symbol streams.

10. The apparatus of claim 7, wherein each sequence is assigned in a time-varying manner.

11. An apparatus, comprising:

a plurality of CDM encoders for receiving a plurality of symbol streams and generating a plurality of masked CDM signals, each CDM encoder comprising:

a first encoder for receiving the plurality of symbol streams and encoding each of the symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

a summer for accumulating the plurality of masked sequences to form a CDM signal;

a time multiplexer to receive the plurality of masked CDM signals and form a Time Division Multiplexed (TDM) signal comprising the plurality of masked CDM signals; and

a second encoder for masking the TDM signal with a masking sequence to form a masked TDM/CDM signal.

12. The apparatus of claim 11, wherein each CDM encoder further comprises one or more channel gain blocks for receiving a plurality of gain values and multiplying the plurality of masked sequences with the plurality of gain values, respectively, before transmission to the summer.

13. The apparatus of claim 11, further comprising a transmitter to receive the masked TDM/CDM signal and one or more additional masked signals, to combine the masked TDM/CDM signal with one or more additional masked signals to form a combined CDM signal, and to transmit the combined CDM signal to a remote station.

14. An apparatus, operable with a CDM signal, covered with a first covering sequence, comprising one or more sub-CDM signals, each of the one or more sub-CDM signals comprising a plurality of symbol sequences covered by a second plurality of covering sequences, respectively, the apparatus comprising:

a receiver for receiving the CDM signal;

a first despreader for despreading the received CDM signal with the first mask sequence to generate a despread CDM signal; and

a second despreader for despreading the despread CDM signal with one of the second mask sequences to generate a recovered symbol sequence.

15. The apparatus of claim 14, wherein the second despreader further despreads the despread CDM signal with one or more additional second masking sequences to generate one or more additional recovered symbol sequences.

16. An apparatus, operable with a CDM signal, covered with a first covering sequence, comprising one or more TDM signals, each of the one or more TDM signals comprising one or more sub-CDM signals, each of the one or more sub-CDM signals comprising a plurality of symbol sequences covered by a second plurality of covering sequences, respectively, the apparatus comprising:

a receiver for receiving the CDM signal;

a first despreader for despreading the received CDM signal with the first mask sequence to generate a despread CDM signal;

a demultiplexer for selecting one of the TDM signals from the despread CDM signal; and

a second despreader for despreading the selected TDM signal with one of the second mask sequences to generate a recovered symbol sequence.

17. A wireless communication device, comprising:

a first encoder for receiving a plurality of symbol streams and encoding each of the symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

an adder for accumulating the plurality of masked sequences to form a first Code Division Multiplexed (CDM) signal; and

a second encoder for masking the first CDM signal with a masking sequence to form a first masked CDM signal.

18. A wireless communication device, comprising:

a plurality of CDM encoders for receiving a plurality of symbol streams and generating a plurality of masked CDM signals, each CDM encoder comprising:

a first encoder for receiving the plurality of symbol streams and encoding each of the symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

a summer for accumulating the plurality of masked sequences to form a CDM signal;

a time multiplexer to receive the plurality of masked CDM signals and form a Time Division Multiplexed (TDM) signal comprising the plurality of masked CDM signals; and

a second encoder for masking the TDM signal with a masking sequence to form a masked TDM/CDM signal.

19. A wireless communications device operable with a CDM signal, covered with a first covering sequence, comprising one or more sub-CDM signals, each of the one or more sub-CDM signals comprising a plurality of symbol sequences covered by a second plurality of covering sequences, respectively, the apparatus comprising:

a receiver for receiving the CDM signal;

a first despreader for despreading the received CDM signal with the first mask sequence to generate a despread CDM signal; and

a second despreader for despreading the despread CDM signal with one of the second mask sequences to generate a recovered symbol sequence.

20. A wireless communications device, operable with a CDM signal, covered with a first covering sequence, comprising one or more TDM signals, each of the one or more TDM signals comprising one or more sub-CDM signals, each of the one or more sub-CDM signals comprising a plurality of symbol sequences respectively covered by a second plurality of covering sequences, the apparatus comprising:

a receiver for receiving the CDM signal;

a first despreader for despreading the received CDM signal with the first mask sequence to generate a despread CDM signal;

a demultiplexer for selecting one of the TDM signals from the despread CDM signal; and

a second despreader for despreading the selected TDM signal with one of the second mask sequences to generate a recovered symbol sequence.

21. A wireless communication system comprising a first wireless communication device, the device comprising:

a first encoder for receiving a plurality of symbol streams and encoding each of the symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

an adder for accumulating the plurality of masked sequences to form a first Code Division Multiplexed (CDM) signal; and

a second encoder for masking the first CDM signal with a masking sequence to form a first masked CDM signal.

22. The wireless communication system of claim 21, further comprising a second wireless communication device, the device comprising:

a receiver for receiving the first masked CDM signal;

a first despreader for despreading the received CDM signal with the first mask sequence to generate a despread CDM signal; and

a second despreader for despreading the despread CDM signal with one of the second mask sequences to generate a recovered symbol sequence.

23. A wireless communication system comprising a wireless communication device, the device comprising:

a plurality of CDM encoders for receiving a plurality of symbol streams and generating a plurality of masked CDM signals, each CDM encoder comprising:

a first encoder for receiving the plurality of symbol streams and encoding each of the symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

a summer for accumulating the plurality of masked sequences to form a CDM signal;

a time multiplexer to receive the plurality of masked CDM signals and form a Time Division Multiplexed (TDM) signal comprising the plurality of masked CDM signals; and

a second encoder for masking the TDM signal with a masking sequence to form a masked TDM/CDM signal.

24. The wireless communication system of claim 23, further comprising a second wireless communication device, the device comprising:

a receiver for receiving the TDM/CDM signal;

a first despreader for despreading the received TDM/CDM signal with the first mask sequence to generate a despread CDM signal;

a demultiplexer for selecting one of the TDM signals from the despread CDM signal; and

a second despreader for despreading the selected TDM signal with one of the second mask sequences to generate a recovered symbol sequence.

25. A method of multiplexing a plurality of symbol streams, comprising:

masking each of the plurality of symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

accumulating the plurality of masked sequences to form a first CDM signal; and

the first CDM signal is masked with a masking sequence to form a first masked CDM signal.

26. The method of claim 25, further comprising multiplying the plurality of masked sequences with a plurality of gain values, respectively, prior to accumulating.

27. The method of claim 25, further comprising:

combining the first masked CDM signal with one or more additional masked signals; and

the combined signal is transmitted to one or more remote stations.

28. The method of claim 25, further comprising:

masking each of a second plurality of symbol streams with one of the plurality of masking sequences to form a second plurality of masked sequences;

accumulating the second plurality of masked sequences to form a second CDM signal;

masking the second CDM signal with a masking sequence to form a second masked CDM signal;

transmitting the first masked CDM signal onto an in-phase channel; and

transmitting the second masked CDM signal onto an orthogonal channel.

29. The method of claim 25, wherein one or more of the plurality of symbol streams includes a command value indicating an acknowledgement, a negative acknowledgement, or an acknowledgement and continue.

30. The method of claim 25, wherein masking each of the plurality of symbol streams comprises:

partitioning the encoding time into two or more segments;

masking each of the plurality of symbol streams with two or more sequences, each sequence for masking during the two or more segments, respectively, and the sequence that masks each symbol stream during a segment is unique to the respective symbol stream.

31. The method of claim 30, wherein the two or more sequences are Hadamard sequences.

32. The method of claim 30, wherein the two or more sequences are assigned in a time-varying manner.

33. A method of multiplexing a plurality of symbol streams, comprising:

masking each of the plurality of symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

accumulating a subset of the plurality of masked sequences to form a plurality of CDM signals;

time-division multiplexing the plurality of CDM signals to form a TDM signal; and

the first TDM signal is masked with a masking sequence to form a masked TDM/CDM signal.

34. The method of claim 33, further comprising:

combining the first masked TDM/CDM signal and one or more additional masked signals; and

transmitting the combined signal to one or more remote stations.

35. A method of decoding a sequence of symbols, comprising:

receiving a CDM signal;

despreading the received CDM signal with a first masking sequence; and

despreading the despread received CDM signal with a second masking sequence to generate a decoded symbol sequence.

36. A method of decoding a sequence of symbols, comprising:

receiving a CDM signal;

despreading the received CDM signal with a first masking sequence;

time demultiplexing the despread received CDM signal to select a TDM signal; and

despreading the selected TDM signal with a second masking sequence to generate a decoded symbol sequence.

37. An apparatus, comprising:

means for masking each of the plurality of symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

means for accumulating the plurality of masked sequences to form a first CDM signal;

means for masking the first CDM signal with a masking sequence to form a first masked CDM signal.

38. An apparatus, comprising:

means for masking each of the plurality of symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

means for accumulating a subset of the plurality of masked sequences to form a plurality of CDM signals;

means for time division multiplexing the plurality of CDM signals to form a TDM signal; and

means for masking the first TDM signal with a masking sequence to form a masked TDM/CDM signal.

39. An apparatus, comprising:

means for receiving a CDM signal;

means for despreading the received CDM signal with a first masking sequence; and

means for despreading the despread received CDM signal with a second masking sequence to generate a decoded symbol sequence.

40. An apparatus, comprising:

means for receiving a CDM signal;

means for despreading the received CDM signal with a first masking sequence;

means for time demultiplexing the despread received CDM signal to select a TDM signal; and

means for despreading the selected TDM signal with a second masking sequence to generate a decoded symbol sequence.

41. A processor-readable medium operable to perform the steps of:

masking each of the plurality of symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

accumulating the plurality of masked sequences to form a first CDM signal; and

the first CDM signal is masked with a masking sequence to form a first masked CDM signal.

42. A processor-readable medium operable to perform the steps of:

masking each of the plurality of symbol streams with one of a plurality of masking sequences to form a plurality of masked sequences;

accumulating a subset of the plurality of masked sequences to form a plurality of CDM signals;

time division multiplexing the plurality of CDM signals to form a TDM signal; and

the first TDM signal is masked with a masking sequence to form a masked TDM/CDM signal.

43. A processor-readable medium operable to perform the steps of:

receiving a CDM signal;

despreading the received CDM signal with a first masking sequence; and

despreading the despread received CDM signal with a second masking sequence to generate a decoded symbol sequence.

44. A processor-readable medium operable to perform the steps of:

receiving a CDM signal;

despreading the received CDM signal with a first masking sequence;

time demultiplexing the despread received CDM signal to select a TDM signal; and

despreading the selected TDM signal with a second masking sequence to generate a decoded symbol sequence.