Asymmetric mode of operation in multi-carrier communication systems

A method and system for providing asymmetric modes of operation in multi-carrier wireless communication systems. A method may assign a long code mask (LCM) to an information channel associated with a plurality of forward link carriers to transmit data from an access network to an access terminal; and multiplex the information channel on a reverse link carrier. The information channel may include one of data source channel (DSC), data rate control (DRC) and acknowledgment (ACK) information, and the multiplexing may be code division multiplexing (CDM). The AN may instruct the AT on whether to multiplex the DSC information based on feedback from the AT. The method may further offset the ACK information on the reverse link to reduce the reverse link peak to average, CDM the information channel on an I-branch and on a Q-branch, and transmit the code division multiplexed information channel on the reverse link carrier.

BACKGROUND

The present invention generally relates to wireless communication systems and, in particular, to multi-carrier communication systems providing asymmetric modes of operation.

A communication system may provide communication between a number of base stations and access terminals. Forward link or downlink refers to transmission from a base station to an access terminal. Reverse link or uplink refers to transmission from an access terminal to a base station. Each access terminal may communicate with one or more base stations on the forward and reverse links at a given moment, depending on whether the access terminal is active and whether the access terminal is in soft handoff.

Wireless communication systems are widely deployed to provide various types of communication (e.g., voice, data, etc.) to multiple users. Such systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or other multiple access techniques. CDMA systems offer some desirable features, including increased system capacity. A CDMA system may be designed to implement one or more standards, such as IS-95, cdma2000, IS-856, W-CDMA, TD-SCDMA, and other standards.

In response to the growing demand for multimedia services and high-rate data, multi-carrier modulation has been proposed in wireless communication systems. There remains, for example, a challenge to provide efficient and robust multi-carrier communication systems.

SUMMARY

A method and system for providing asymmetric modes of operation in multi-carrier wireless communication systems. In one mode, a method may assign a long code mask (LCM) to an information channel associated with a plurality of forward link carriers to transmit data from a base station or access network to an access terminal; and multiplex the information channel on a reverse link carrier. The information channel may include at least one of data source channel (DSC) information, data rate control (DRC) information and acknowledgment (ACK) information, and the multiplexing may be code division multiplexing (CDM). The access network may instruct the access terminal whether to multiplex the DSC information or not. In cases where a feedback from the access terminal goes to the same channel card and a serving sector is the same across multiple forward link carriers, the access network may instruct the access terminal not to multiplex the DSC information. The method may further offset the ACK information on the reverse link to reduce the reverse link peak to average. In another mode, a method may code division multiplex the information channel on an I-branch and on a Q-branch, and transmit the code division multiplexed information channel on the reverse link carrier. The DRC and ACK information may be covered with Walsh codewords, and the DRC information may be further combined with DRC cover symbols, which are offset by Walsh codes, on both the I-branch and the Q-branch.

Depending on the hardware, any combination of the modes may be supported. The first mode may achieve 15 forward link carriers and one reverse link carrier with 15 unique long code masks assigned to an access terminal. The first and second modes may also be combined to achieve 15 forward link carriers and one reverse link carrier with 4 unique long code masks assigned to an access terminal.

DETAILED DESCRIPTION

Any embodiment described herein is not necessarily preferable or advantageous over other embodiments. While various aspects of the present disclosure are presented in drawings, the drawings are not necessarily drawn to scale or drawn to be all-inclusive.

FIG. 1illustrates a wireless communication system100, which includes a system controller102, base stations (BSs)104a-104b, and a plurality of access terminals (ATs)106a-106h. The system100may have any number of controllers102, base stations104and access terminals106. Various aspects and embodiments of the present invention described below may be implemented in the system100.

Access terminals106may be mobile or stationary and may be dispersed throughout the communication system100ofFIG. 1. An access terminal106may be connected to or implemented in a computing device, such as a laptop personal computer. Alternatively, an access terminal may be a self-contained data device, such as a personal digital assistant (PDA). An access terminal106may refer to various types of devices, such as a wired phone, a wireless phone, a cellular phone, a laptop computer, a wireless communication personal computer (PC) card, a PDA, an external or internal modem, etc. An access terminal may be any device that provides data connectivity to a user by communicating through a wireless channel or through a wired channel, for example, using fiber optic or coaxial cables. An access terminal may have various names, such as mobile station (MS), access unit, subscriber unit, mobile device, mobile terminal, mobile unit, mobile phone, mobile, remote station, remote terminal, remote unit, user device, user equipment, handheld device, etc.

The system100provides communication for a number of cells, where each cell is serviced by one or more base stations104. A base station104may also be referred to as a base station transceiver system (BTS), an access point, a part of an access network (AN), a modem pool transceiver (MPT), or a Node B. Access network refers to network equipment providing data connectivity between a packet switched data network (e.g., the Internet) and the access terminals106.

Forward link (FL) or downlink refers to transmission from a base station104to an access terminal106. Reverse link (RL) or uplink refers to transmission from an access terminal106to a base station104.

A base station104may transmit data to an access terminal106using a data rate selected from a set of different data rates. An access terminal106may measure a signal-to-noise-and-interference ratio (SINR) of a pilot signal sent by the base station104and determine a desired data rate for the base station104to transmit data to the access terminal106. The access terminal106may send data request channel or data rate control (DRC) messages to the base station104to inform the base station104of the desired data rate.

The system controller102(also referred to as a base station controller (BSC)) may provide coordination and control for base stations104, and may further control routing of calls to access terminals106via the base stations104. The system controller102may be further coupled to a public switched telephone network (PSTN) via a mobile switching center (MSC), and to a packet data network via a packet data serving node (PDSN).

The communication system100may use one or more communication techniques, such as code division multiple access (CDMA), IS-95, high rate packet data (HRPD), also referred to as high data rate (HDR), as specified in “cdma2000 High Rate Packet Data Air Interface Specification,” TIA/EIA/IS-856, CDMA 1x evolution data optimized (EV-DO), 1xEV-DV, wideband CDMA (W-CDMA), universal mobile telecommunications system (UMTS), time division synchronous CDMA (TD-SCDMA), orthogonal frequency division multiplexing (OFDM), etc. The examples described below provide details for clarity of understanding. The ideas presented herein are applicable to other systems as well, and the present examples are not meant to limit the present application.

A “multi-carrier” system described herein may use frequency division multiplex, wherein each “carrier” corresponds to a radio frequency range. For example, a carrier may be 1.25 Megahertz wide, but other carrier sizes may be used. A carrier may also be called a CDMA carrier, a link or a CDMA channel.

Data flow requirements may be biased towards heavier usage of a forward or reverse link. The description below relates to de-coupling forward link and reverse link assignment in a multi-carrier wireless communication system. The system100may assign M forward links (or carriers) and N reverse links (or carriers) to an access terminal106, where M and N may not be equal. The description below describes mechanisms for overhead channel transmissions to reduce reverse link overhead.

The base stations, BSCs or MSC may determine a number of FL carriers assigned for an access terminal. The base stations, BSCs or MSC may also change the number of FL carriers assigned for an access terminal depending on conditions, such as channel conditions, available data for the terminal, terminal power amplifier headroom, and application flows.

The access terminals106may run applications, such as Internet applications, video conferencing, movies, games, etc., which may use voice, image files, video clips, data files, etc., transmitted from the base stations104. The applications may include two types:1. Delay-tolerant, high forward link throughput and low reverse link throughput; and2. Delay-sensitive, low forward link throughput and low reverse link throughput. Other types of applications may also exist.

If the system100uses multiple carriers on the forward link to achieve high throughput or maximize spectral efficiency, an access terminal106may avoid transmission on all associated carriers on the reverse link to improve reverse link efficiency.

For type1applications where a slower DRC update is acceptable, an access terminal106may:a) transmit a continuous pilot signal on a primary reverse link carrier;b) transmit data only on the primary reverse link carrier;c) transmit DRC for each FL carrier as time-division multiplexed on the primary reverse link carrier, which assumes slower DRC channel update is acceptable; andd) transmit acknowledgment (ACK) or negative acknowledgment (NAK) messages for each FL carrier as needed. An access terminal106can transmit a gated pilot (at the same power level as the pilot on the primary RL carrier) on secondary carriers when transmitting ACK channel, e.g., ½ slot skirt around ACK transmission for pilot filter warm-up.

For type1applications where a slower DRC update may not be not acceptable, an access terminal106may:a) transmit a continuous pilot signal on all reverse link carrier(s) associated with enabled forward link carriers;b) transmit data only on the primary reverse link carrier; andc) transmit ACK for each FL carrier as needed.

For type2applications, an access terminal106may:a) transmit a continuous pilot on the primary reverse link carrier;b) transmit data only on the primary reverse link carrier;c) transmit DRC for each FL carrier as time-division multiplexed on the primary reverse link carrier, which assumes slower DRC channel update is acceptable; andd) transmit ACK only on the primary reverse link carrier. A base station104may be constrained to ensure no more than one packet is in flight across all forward link carriers. A base station104can determine ACK association based on timing of transmitted FL packet.

Alternatively, an access terminal106may perform an alternate form of ACK channel transmission:a) reduce ACK channel transmit time interval if desired, e.g., if the system100supports additional FL carriers (in an EV-DO system, ACK may be transmitted in ½ slot);b) ACK channel transmission for N forward link carriers within a single ½ slot;c) ACK channel transmit interval is a function of number of enabled forward link carriers; andd) ACK channel transmissions on RL and FL association setup may be implemented via signaling in the medium access control (MAC) layer1400(FIG. 14).
Multi-Carrier Forward Traffic Channel Mac

There may be two modes of carrier assignment: symmetric carrier assignment and asymmetric carrier assignment.

FIG. 2illustrates an example of symmetric carrier assignment with three forward link carriers200A-200C, e.g., used for EV-DO data, and three corresponding reverse link carriers202A-202C. Symmetric carrier assignment may be used for (a) applications with symmetric data rate requirements, and/or (b) applications with asymmetric data rate requirements supported on hardware that enforces symmetric FL/RL operation.

FIGS. 3A and 3Billustrate examples of asymmetric carrier assignment.FIG. 3Ashows three forward link carriers300A-300C and one corresponding reverse link carrier302.FIG. 3Bshows three forward link carriers300A-300C, and two corresponding reverse link carriers304A and304B. Asymmetric carrier assignment may be used for applications with asymmetric data rate requirements such as file transfer protocol (FTP) download. Asymmetric carrier assignment may have (a) reduced reverse link overhead and (b) MAC channels that allow forward link traffic (FLT) carrier assignment to be separate from reverse power control (RPC) carrier assignment.

Asymmetric Forward and Reverse Link Assignment—Multi-Carrier DRC

An access terminal106may time-division multiplex DRC channel transmission for multiple forward link carriers on a single reverse link carrier.

FIG. 14illustrates a time division multiplexer1402for multiplexing DCR information in an access terminal106ofFIG. 1.

A MAC layer1400(FIG. 14) in the access terminal106may provide DRC-to-forward-link association based on DRC transmit time. The number of forward link carriers (for which DRC transmissions are indicated by a single reverse link carrier) may depend on: (i) a maximum acceptable DRC span, which is a time interval required for transmission of DRC for all assigned forward link carriers, e.g., DRC span=max (16 slots, DRCLength (per carrier)×number of carriers); and (ii) number of carriers supported by hardware, such as a 1xEV-DO Rev A channel card. In one embodiment, four FL carriers are associated with a single RL carrier, which may be limited by sending ACKs for the four FL carriers.

In another embodiment, an access terminal106may use a single DRC channel across all carriers. In other words, an access terminal106sends a single DRC to a base station104for all designated FL carriers to transmit data at the DRC-designated rate to that access terminal106.

In another embodiment, an access terminal106may use a combination of (a) a single DRC channel across multiple carriers (same DRC for some FL carriers of the total number of FL carriers) and (b) time-division multiplexed DRC channel.

FIG. 4Aillustrates an example of a DRC reverse link transmission (DRC length=8 slots), which requests a data transmit rate for a single forward link carrier to use.FIGS. 4B-4Fillustrate examples of multi-carrier, time division multiplexed DRC. Specifically,FIG. 4Bshows an example of two DRCs (DRC length=4 slots each; DRC span=8 slots) transmitted on a single reverse link carrier for two forward link carriers.FIG. 4Cshows an example of four DRCs (DRC length=2 slots each; DRC span=8 slots) transmitted on a single reverse link carrier for four forward link carriers.

FIG. 4Dillustrates an example of two interlaced DRCs (DRC length=4 slots each; DRC span=8 slots) transmitted on a single reverse link carrier for two forward link carriers. Interlaced DRC channel transmission may provide additional time diversity for a given DRCLength.FIG. 4Eshows an example of four interlaced DRCs (DRC length=4 slots each; DRC span=16 slots) transmitted on a single reverse link carrier for four forward link carriers.FIG. 4Fshows an example of four interlaced DRCs (DRC length=2 slots each; DRC span=8 slots) transmitted on a single reverse link carrier for four forward link carriers.

Asymmetric Forward and Reverse Link Assignment—Multi-Carrier ACK

In one embodiment or mode of multi-carrier communication operation, when the number of forward link channels is greater than the number of reverse link channels, the DSC, DRC and ACK channels associated with a plurality of forward link channels may be multiplexed onto a single reverse link carrier. In this embodiment or mode, a long code mask (LCM) may be used to facilitate such multiplexing. With this embodiment or mode, the AN may instruct the AT whether to multiplex the DSC or not. In cases where a feedback from the AT goes to the same channel card and a serving sector is the same across multiple forward link carriers, the AN may instruct the AT not to multiplex the DSC. In particular, a unique long code mask may be used to transmit DRC and ACK channels for secondary forward link carriers. Referring toFIG. 5, there is shown a block diagram of a module that may be used to transmit DRC and ACK channels for additional forward link carriers on a primary reverse link using a separate long code mask. As a result, the reverse link peak to average may be reduced by use of offset ACK channels.

Referring toFIG. 6, there is illustrated a peak to average reduction in asymmetric mode of operation of using, for example, more than one long code mask. In particular, a DSC channel may be transmitted per AT as opposed to per carrier. Because the reverse link peak to average reduction may be adversely affected by ACK channel transmission for the secondary forward link carriers (e.g., multiple ACK channels may become overlapping on a power vs. time plot), the DSC channel may be used to transmit half-slot for ACK channel transmission for the secondary forward link carriers, thereby offsetting the ACK channel transmission as illustrated inFIG. 6. As a result, the forward link demodulation and decoding time for multi-carrier ATs may be reduced for some fraction of assigned forward link carriers.

Reverse link peak to average reduction is further illustrated inFIGS. 7A-7E. More specifically, an access terminal106may time division multiplex ACK channel transmission for multiple forward link carriers on a single reverse link carrier, as explained below withFIG. 7E.FIG. 14illustrates a time division multiplexer1404for multiplexing ACK information in an access terminal106ofFIG. 1.

Per carrier ACK channel transmission may be reduced, for example, from 1 slot to ¼ slot (each ACK transmitted for ¼ slot) (instead of ½ slot used in EV-DO Rev. A), which may depend on a number of FL carriers for which ACK channel is transmitted. The MAC layer1400(FIG. 14) at the access terminal106may provide ACK-to-forward-link association based on ACK transmit time.

FIGS. 7A and 7Bshow an example of two DRC channel transmit requests sent from an access terminal106to a base station104for two forward link carriers (carriers1and2) to transmit FL data at two different rates (e.g., 153.6 and 307.2 kbps).FIGS. 7A and 7Bmay show the DRCs decoded by the base station104, butFIGS. 7A and 7Bdo not indicate the method with which the DRCs are time division multiplexed on a single Reverse Link carrier, as inFIGS. 4B-4F.

In response to the DRCs, the base station104transmits forward traffic channel (FTC) sub-packets on the two forward link carriers at the two different rates (e.g., 153.6 and 307.2 kbps) inFIGS. 7C and 7D.

The base station104may repeat and process data bits of an original data packet into a plurality of corresponding “sub-packets” to transmit to the access terminal106. If the access terminal106experiences a high signal-to-noise ratio signal, the first sub-packet may contain sufficient information for the access terminal106to decode and derive the original data packet. If the access terminal106experiences fading or a low signal-to-noise-ratio signal, the access terminal106may have a relatively low probability of correctly decoding and deriving the original data packet from only the first sub-packet.

If the access terminal106does not successfully decode the first sub-packet, the access terminal106sends a NAK to the base station104. The base station104then sends a second sub-packet. The access terminal106may combine information from the first and second sub-packets to try to decode the original data packet. As the access terminal106receives more sub-packets and combines information derived from each received sub-packet, the probability of decoding and deriving the original data packet increases.

InFIG. 7C, a base station104sends a first sub-packet of an original data packet to the access terminal106in slot1of carrier1. Simultaneously, inFIG. 7D, the base station104sends a first sub-packet of another original data packet to the access terminal106in slot1of carrier2.

The access terminal106tries to decode the two original data packets from the received first sub-packets on carriers1and2, respectively. The access terminal106cannot correctly decode the received first sub-packet on carrier1; sends a NAK on the ACK channel to the base station104inFIG. 7E; cannot correctly decode a received second sub-packet on carrier1; sends a NAK on the ACK channel to the base station104; cannot correctly decode a received third sub-packet on carrier1; sends a NAK on the ACK channel to the base station104; correctly decodes a received fourth sub-packet on carrier1; and sends an ACK on the ACK channel to the base station104.

Also inFIG. 7E, the access terminal106cannot correctly decode the first and second received sub-packets on carrier2and sends NAKs to the base station104. The access terminal106correctly decodes the original second packet (e.g., using a cyclic redundancy check (CRC) or other error detection technique) after receiving and processing the third sub-packet on slot3of carrier2. The access terminal106sends an acknowledgement (ACK) signal to the base station104to not send a fourth sub-packet for the second original packet on carrier2.

The base station104can then send a first sub-packet of a next packet in slot1(n+12) of carrier2. InFIG. 7E, the access terminal106sends ACKs and NAKs on a single ACK/NAK RL channel for the two FL carriers (½ slot ACK/NAK channel transmissions with a ¼ slot per FL carrier).

In another embodiment of a multi-carrier ACK, an access terminal106may use a single RL ACK channel, where RL ACK is associated with FL based on timing of packet reception (also called transmit-time-based-ACK-channel association). This may be used for Voice over Internet Protocol (VoIP)-type traffic. Transmit-time-based-ACK-channel association may add a constraint on a FL scheduler to limit transmission on a single FL carrier to a given access terminal106at a time.

In another embodiment of asymmetric mode for multi-carrier operation,FIGS. 8 and 9illustrate processes and structures for multi-carrier ACK and cover transmission. With this mode, there may be 4 ACK channels for 4 forward link carriers per long code mask, e.g., to transmit ACK on a single reverse link carrier using code division multiplex (CDM) transmission on the I-branch and the Q-branch. Different Walsh covers may be used, e.g., to orthogonalize the I-branch and the Q-branch. In particular,FIG. 8shows a process and structure for preparing multi-carrier ACK transmissions. A first and second ACK Signal Mapping blocks800and802map or encode ACK Channel carriers1and2, respectively (1 bit per slot). Symbol Repetition blocks804and806then repeat a plurality of symbols per half-slot. After repetition, the symbols are channelized by Walsh code/cover W14and W04at Walsh Cover blocks808and810, respectively, to produce 32 binary symbols per half-slot. Gain is then applied to each of the half-slots at ACK Channel Gain blocks812and814. The gains of the half-slots are combined at816and a multiplier818then applies a Walsh covering/code W1232to indicate an ACK channel for the I-phase.

Similarly toFIG. 8,FIG. 9illustrates a process and structure for multi-carrier ACK and cover transmission for ACK Channel carriers3and4. A third and fourth ACK Signal Mapping blocks900and902map or encode ACK Channel carriers3and4, respectively (1 bit per slot). Symbol Repetition blocks904and906then repeat a plurality of symbols per half-slot. After repetition, the symbols are channelized by Walsh code/cover W34and W24at Walsh Cover blocks908and910, respectively, to produce 32 binary symbols per half-slot. Gain is then applied to each of the half-slots at ACK Channel Gain blocks912and914. The gains of the half-slots are combined at916and a multiplier918then applies a Walsh covering/code W1232to indicate an ACK channel for the Q-phase.

In yet another embodiment of asymmetric mode for multi-carrier operation,FIG. 10illustrates a process and structure for preparing enhanced multi-carrier DRC channels for transmission. In this mode, there may be 4 DRC channels (one per forward link carrier) per long code mask, e.g., to transmit DRC rate on a single reverse link carrier using code division multiplex transmission on the I-branch and the Q-branch. For DRC transmissions using the same Codeword Walsh cover, the DRC cover value for one forward carrier may be offset relative to that of the other forward carrier such that the DRC covers are distinct. For example, if carrier #1uses DRC cover=0x 1, carrier #3may use a DRC cover value offset relative to 0x 1.

More specifically, referring toFIG. 10, a first and a second Bi-Orthogonal Encoders1000and1002encode DRC channels (e.g., one 4-bit symbol per active slot) for each of carriers1and2, respectively, and produce 8 binary symbols per active slot. Each of codeword Walsh covers W12and W02in cover blocks1004and1006, respectively, then produces 16 binary symbols per active slot. A first and a second signal point mapping blocks1012and1014then map 0s and 1s to +1 and −1 per actively slot, respectively. After gain is applied to each of the slots at DRC Channel Gain blocks1012and1014, multipliers1020and1022then combine the output of gains1012and1014, respectively, with DRC Cover Symbols (e.g., one 3-bit symbol per active slot) for carriers1and2, respectively.

In another embodiment of asymmetric mode for multi-carrier operation, the DRC Cover Symbols for carriers1and2are channelized by Walsh cover blocks (Wi8(i=0,1, . . . 7))1016and1018, respectively. The output of multipliers1020and1022are then added at1024, which are then multiplied at1026applying a Walsh covering code W816to indicate a DRC channel for the Q-phase.

Similarly toFIG. 10,FIG. 11illustrates a process and structure for preparing enhanced multi-carrier DRC channels for transmission for carriers3and4. A third and a fourth Bi-Orthogonal Encoders1100and1102encode DRC channels (e.g., one 4-bit symbol per active slot) for each of carriers3and4, respectively, and produce 8 binary symbols per active slot. Each of codeword Walsh covers W12and W02in codeword cover blocks1104and1106, respectively, then produces 16 binary symbols per active slot. A first and a second signal point mapping blocks1112and1114then maps 0s and 1s to +1 and −1 per actively slot, respectively. After gain is applied to each of the slots at DRC Channel Gain blocks1112and1114, multipliers1020and1022then combine the output of gains1112and1114, respectively, with DRC Cover Symbols (e.g., one 3-bit symbol per active slot) for carriers3and4, respectively.

In another embodiment of asymmetric mode for multi-carrier operation, the DRC Cover Symbols for carriers3and4are channelized by Walsh cover blocks (Wi8(i=0,1, . . . 7)) at cover blocks1116and1118, respectively. The output of multipliers1120and1122are then added at1124, which are then multiplied at1126applying a Walsh covering code W816to indicate a DRC channel for the I-phase.

It is appreciated that in any of the above-described embodiments of asymmetric mode for multi-carrier operation, the ACK and DRC channels may be transmitted for up to four (4) forward link carriers on a single reverse link carrier using code division multiplex transmission on the I-branch and the Q-branch. In the event that the there are equal numbers of forward link and reverse link channels, the aforementioned scheme may also allow an AT to autonomously turn off the pilot and traffic channels, e.g., on some reverse link frequencies on which the AT chooses not to transmit (e.g., when the AT is short of transmission power headroom). Furthermore, for DRC transmissions using the same codeword Walsh cover, the DRC cover value for one forward carrier may be offset relative to that of the other forward link carrier. Stated another way, with this aspect of the invention, the ACK and DRC channels may be transmitted for the first 4-carriers using I/Q phases (in-phase (I), quadrature (Q)) of Walsh code W(16,8) and I/Q-phases of W(16,8). If additional DRC channel transmissions are required for additional FL carriers, the access terminal106can use ½ slot DRC on each of the phases of W(16,8). Thus, the access terminal106may support DRCs for up to 4 FL carriers with a single RL carrier.

Referring toFIG. 12, there is shown a correspondence between the forward link and reverse link frequencies in a multi-carrier system. Traffic channel assignment (TCA) may specify such relationship. By way of example, the reverse link frequency “x” may be designated to carry the DSC, DRC and ACK channels for all the forward link frequencies.

In one aspect of the invention, a plurality of (e.g., up to four) additional long code masks may be created for each reverse link frequency using the four (4) most significant bits (MSBs) of the long code mask. In particular, a channel on which the feedback (ACK/DRC) is sent may be identified by a 4-bit identifier, e.g., <LongCodeMaskIndex (2 bits), FeedbackWalshCover (1 bit), IQIdentifier (1 bit)>, may be specified in the TCA.

In another aspect, an AT may set the long code masks for the reverse traffic channel (e.g., MIRTCMACand MQRTCMAC) as follows. For example, a 42-bit mask MIRTCMACassociated with each LongcodeMaskIndex may be specified as shown in Table I below:

TABLE IReverse Traffic Channel Long Code Masks

An AN may assign one or more long code masks to an AT on each of the channels on which the AT may transmit. The long code mask for each of the channels may be identified, e.g., by the value of the LongCodeMaskIndex which is a public data of the Route Update Protocol.

In Table I, Permuted (ATILCM) may be defined as follows:

ATILCM=(A31,A30,A29,…⁢,A0)Permuted⁢⁢(ATILCM)=(A0,A31,A22,A13,A4,A26,A17,A8,A30,A21,A12,A3,A25,A16,A7,A29,A20,A11,A2,A24,A15,A6,A28,A19,A10,A1,A23,A14,A5,A27,A18,A9).
The 42-bit mask MQRTCMACmay be derived from the mask MIRTCMACas follows:

MQRTCMAC⁡[k]=MIRTCMAC⁡[k-1],for⁢⁢k=1,…⁢,41MQRTCMAC⁡[0]=MIRTCMAC⁡[0]⊕MIRTCMAC⁡[1]⊕MIRTCMAC⁡[2]⊕MIRTCMAC⁡[4]⊕MIRTCMAC⁡[5]⊕MIRTCMAC⁡[6]⊕MIRTCMAC⁡[9]⊕MIRTCMAC⁡[15]⊕MIRTCMAC⁡[16]⊕MIRTCMAC⁡[17]⊕MIRTCMAC⁡[18]⊕MIRTCMAC⁡[20]⊕MIRTCMAC⁡[21]⊕MIRTCMAC⁡[24]⊕MIRTCMAC⁡[25]⊕MIRTCMAC⁡[26]⊕MIRTCMAC⁡[30]⊕MIRTCMAC⁡[32]⊕MIRTCMAC⁡[34]⊕MIRTCMAC⁡[41]
where the ⊕ denotes the Exclusive OR operation, and MQRTCMAC[i] and MIRTCMAC[i] denote the ithleast significant bits of MQRTCMACand MIRTCMAC, respectively.
Forward Link Soft-Combining Mode

An access terminal106may use multi-carrier DRC with a forward link soft-combining mode (soft-combining data received across multiple FL carriers). In this mode, the base station104does not have to transmit the packets on the individual forward links at the same time, i.e., the design would support soft handoff across carriers with asynchronous transmissions. An access terminal106may indicate a DRC index based on transmission to the access terminal106in a given slot on multiple FL carriers by the same base station104.

In one embodiment, the system or network100may use general attribute update protocol (GAUP) to indicate that all packet transmissions to a given terminal106will be multi-carrier transmissions for some length of time. The access terminal106may, until instructed otherwise, transmit a DRC based on a combined SINR prediction. The MAC layer1400(FIG. 14) may provide signal mapping.

The network may have some flexibility to serve the access terminal106using one carrier or a combination of carriers in that same time interval. This may use individual DRCs per carrier as well as DRCs based on a combined SINR prediction. The network may configure the access terminal106to operate in one of these two modes of DRC reporting. The forward link soft-combining mode may be used, for example, when the access terminal106experiences poor channel conditions for VoIP flows or for all types of flows.

FIG. 13Aillustrates an example of a forward link transmit chain, structure or process, which may be implemented at a base station104ofFIG. 1. The functions and components shown inFIG. 13Amay be implemented by software, hardware, or a combination of software and hardware. Other functions may be added toFIG. 13Ain addition to or instead of the functions shown inFIG. 13A.

In block1302, an encoder encodes data bits using one or more coding schemes to provide coded data chips. Each coding scheme may include one or more types of coding, such as cyclic redundancy check (CRC), convolutional coding, Turbo coding, block coding, other types of coding, or no coding at all. Other coding schemes may include Automatic Repeat Request (ARQ), Hybrid ARQ, and incremental redundancy repeat techniques. Different types of data may be coded with different coding schemes.

In block1304, an interleaver interleaves the coded data bits to combat fading. In block1306, a modulator modulates coded, interleaved data to generate modulated data. Examples of modulation techniques include binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK).

In block1308, a repeater may repeat a sequence of modulated data or a symbol puncture unit may puncture bits of a symbol. In block1310, a spreader (e.g., multiplier) may spread the modulated data with a Walsh cover (i.e., Walsh code) to form data chips.

In block1312, a multiplexer may time-division multiplex the data chips with pilot chips and MAC chips to form a stream of chips. In block1314, a pseudo random noise (PN) spreader may spread the stream of chips with one or more PN codes (e.g., short code, long code). The forward link modulated signal (transmitted chips) is then transmitted via an antenna over a wireless communication link to one or more access terminals106.

FIG. 13Billustrates an example of a forward link receive chain, process or structure, which may be implemented at an access terminal106ofFIG. 1. The functions and components shown inFIG. 13Bmay be implemented by software, hardware, or a combination of software and hardware. Other functions may be added toFIG. 13Bin addition to or instead of the functions shown inFIG. 13B.

One or more antennas1320A-1320B receives the forward link modulated signals from one or more base stations104. Multiple antennas1320A-1320B may provide spatial diversity against deleterious path effects such as fading. Each received signal is provided to a respective antenna receiver filtering block1322, which conditions (e.g., filters, amplifies, downconverts) and digitizes the received signal to generate data samples for that received signal.

A cascaded adaptive linear equalizer1324receives data samples and generates equalized chips to block1325. Block1325may despread the samples with one or more PN codes used in block1314. Block1326may remove pilots time skew and insert blanks. In block1328, a despreader may deWalsh, i.e., despread or remove Walsh codes from the received data samples, with the same spreading sequence used to spread the data in block1310at the base station.

In block1330, a demodulator demodulates the data samples for all received signals to provide recovered symbols. For cdma2000, demodulation tries to recover a data transmission by (1) channelizing the despread samples to isolate or channelize the received data and pilot onto their respective code channels, and (2) coherently demodulating the channelized data with a recovered pilot to provide demodulated data. Demodulate block1330may implement a rake receiver to process multiple signal instances.

Block1334may receive punctured symbol locations and convert symbols to consecutive bits. Block1332may zero log likelihood ratios (LLRs) at punctured bit epochs. Block1336may apply a channel de-interleave.

In block1338, a channel decoder decodes the demodulated data to recover decoded data bits transmitted by the base station104.

The term “information channel” disclosed herein may refer to a DRC channel, an ACK channel, or other channels containing the channel state information.

It is appreciated that the embodiments described herein provide some embodiments of asymmetric mode of operation for multi-carrier communication systems. There are other embodiments and implementations. Various disclosed embodiments may be implemented in an AN, an AT, and other elements in multi-carrier communication systems.

Headings are included herein for reference and to aid in locating certain sections. These headings are not intended to limit the scope of the concepts described therein under, and these concepts may have applicability in other sections throughout the entire specification.