HK1212116B - Method,apparatus,and medium for codebook exchange in a multiple access wireless communication system - Google Patents

Description

Codebook exchange method, apparatus, and medium in multiple access wireless communication system

The present application is a divisional application entitled "method and apparatus for exchanging codebooks in a multiple access wireless communication system" filed 26/10/2007 with application number 200780039490.4.

The benefit of U.S. provisional patent application 60/854,898 entitled "A METHOD AND APPARATUS FOR CONTRODOOK EXCHANGE IN A WIRELESS COMMUNICATION SYSTEM" filed on 26.10.2006 AND U.S. provisional patent application 60/863,313 entitled "A METHOD AND APPARATUS FOR CONTRODOOK EXCHANGE IN A WIRELESS COMMUNICATION SYSTEM" filed on 27.10.2006 are hereby incorporated by reference in their entirety.

Technical Field

The present disclosure relates to wireless communications. In particular, the present disclosure relates to codebook exchange in wireless communication systems, especially multiple access communication systems.

Background

Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of communicating with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA), third generation partnership project-long term evolution (3GPP LTE) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.

Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more access networks, referred to herein as access points or base stations, via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the access network to the terminals. The reverse link (or uplink) refers to the communication link from the terminals to the access network. Such communication links may be established by single-input single-output, multiple-input single-output, or multiple-input multiple-output (MIMO) systems.

MIMO System Using multiple (N)_T) A transmitting antenna and a plurality of (N)_R) And the receiving antennas are used for data transmission. Will be composed of N_TA transmitting antenna and N_RDecomposition of MIMO channel formed by multiple receiving antennas into N_SIndividual channels, also called spatial channels, in which N_S≤min{N_T,N_R}。N_SEach of the individual channels corresponds to a spatial dimension. MIMO systems can improve performance (e.g., higher peak rates and/or coverage) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.

MIMO may be used for Time Division Duplex (TDD) and Frequency Division Duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency range, so an estimate of the forward link channel can be made from the reverse link channel according to the reciprocity principle. In this way, the access network is able to obtain transmit beamforming gain on the forward link when multiple antennas are available to the access network.

Spatial Division Multiple Access (SDMA) systems rely on multiple antennas at the transmitter. SDMA relies on spatial information of users and classifies users based on their spatial location. SDMA is compatible with any multiple access scheme such as TDMA, FDMA, CDMA, etc.

Parallel high-capacity spatial pipes can be obtained by spatial multiplexing using Spatial Division Multiple Access (SDMA), thereby providing superior performance in a radio multiple access wireless communication system. SDMA techniques have been developed using MIMO techniques and using spatial location information of mobile units within a cell. The receive and transmit radiation patterns of the access network are adjusted for each user so that the highest gain is obtained in the direction of the mobile user. This is often achieved using phased array technology.

Precoding is one way to achieve generalized beamforming in MIMO systems. Precoding allows independent and appropriate weighting of the multiple streams of signals from the transmit antennas to maximize the link throughput at the receiver output.

Precoding defines the mapping from the physical antennas to the signals transmitted to a particular user, although the user has no knowledge of the physical antenna pattern, and the received signals are from the effective antennas defined by the precoder. The specific mapping is defined by a precoding matrix. The columns of the precoding matrix give a definition of the set of spatial beams that the access network can use. In single-input single-output (SISO) transmission, the access network uses only one column of the precoding matrix (e.g., one active antenna), and uses multiple columns (e.g., multiple active antennas) in MIMO transmission.

The determination of the active antennas and thus the precoding matrix depends on the implementation and deployment. Deployment involves many transient factors such as the location of the access terminal, environmental conditions, which time of day it is at, etc. Thus, several sets of different precoding matrices may be required for each deployment. Network topology, physical topography, etc. all affect the selection of the set of precoding matrices. The set of such precoding matrices forms a codebook.

At least from the foregoing, there is a need for a system and/or method to efficiently and effectively exchange codebooks between an access network and an access terminal.

Disclosure of Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding of the disclosed aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of those aspects nor delineate the scope of such aspects. Its sole purpose is to present some disclosed aspects in a simplified form as a prelude to the more detailed description that is presented later.

In one aspect, a method of codebook exchange in a multiple access wireless communication system, such as Spatial Division Multiple Access (SDMA), is defined. Such a method comprises providing a plurality of preferred precoding matrices and generating a codebook in an access network (or access network as referred to herein as an access point or base station). The codebook includes a plurality of preferred precoding matrices. The method also includes communicating the codebook to one or more access terminals.

In another aspect, the step of generating the codebook further comprises generating the codebook including a codebook identifier assigned by the access network. More specifically, such a codebook identifier may be 16 bits long for identifying the codebook in the access terminal codebook cache for purposes of verifying that the codebook is received and for codebook assignment.

In one aspect, delivering the codebooks further comprises querying one or more access terminals to determine the identity of the one or more codebooks currently stored in each access terminal; receiving a codebook status response from each of the one or more access terminals, the codebook status response indicating an identity of one or more codebooks stored in each of the one or more access terminals; and if the codebook status response indicates that the codebook is not currently stored in one or more access terminals, communicating the codebook to the one or more access terminals. The identity of each codebook may be defined by a codebook identifier. In one aspect, the codebook identifier is further defined by a 16-bit codebook identifier, although other codebook identifiers having different bit lengths are possible and within the scope of the aspects disclosed.

In another aspect, the method assigns a codebook to one or more access terminals in a predetermined sector in an active set of communication links. Assigning codebooks to predetermined sectors within an active set of a communication link may comprise querying the one or more access terminals to determine the identity of one or more codebooks currently stored at each access terminal; receiving a codebook status response from each of the one or more access terminals, the codebook status response indicating an identity of one or more codebooks stored in each of the one or more access terminals; and assigning the codebook to one or more access terminals in a predetermined sector in the active set of the communication link if the codebook status response for the one or more access terminals indicates that the codebook is currently stored in the one or more access terminals.

Additionally, the method generates a codebook that includes an identification of one or more clusters. The clusters identify a set of the precoding matrices and a set of beams in the cluster. Thus, these clusters may identify a starting beam index and an ending beam index. The method also generates a codebook that includes an overlapping cluster map that indicates one or more clusters that are authorized to potentially overlap.

In another aspect, a network access apparatus, such as SDMA, for generating and communicating codebooks in a multiple access wireless communication system is disclosed. The network access device includes at least one processor; a memory coupled to the at least one processor. The apparatus also includes a codebook generator stored in the memory and executable by the at least one processor. The codebook generator is configured to provide a plurality of preferred precoding matrices and generate a codebook comprising the plurality of preferred precoding matrices. The apparatus also includes a codebook switch stored in the memory and executable by the at least one processor. The codebook switch is configured to communicate the codebook to the one or more access terminals.

In yet another aspect, an apparatus for generating and communicating codebooks in a multiple access wireless communication system (e.g., SDMA, etc.) is disclosed. Such an apparatus comprises a providing module for providing a plurality of preferred precoding matrices; and the generating module is used for generating the code book in the access network. The codebook includes a plurality of preferred precoding matrices. The apparatus can also include a means for communicating the codebook therein to one or more access terminals.

Yet another aspect relates to a computer-readable medium. Such a medium includes providing code for causing a computer to provide a plurality of preferred precoding matrices; code is generated for causing a computer to generate a codebook in an access network. The generated codebook includes a plurality of preferred precoding matrices. The medium further includes code for causing a computer to communicate the codebook to one or more access terminals.

Another aspect is an integrated circuit that executes computer-executable instructions for generating and communicating codebooks in a multiple access wireless communication system (e.g., SDMA). The instructions include providing a plurality of preferred precoding matrices; a codebook is generated in the access network. This codebook comprises a plurality of preferred precoding matrices. The instructions also include communicating the codebook to one or more access terminals.

In one aspect, a method of receiving a codebook associated with a multiple access wireless communication system (e.g., SDMA) is defined. The method includes receiving a codebook from an access network and storing the received codebook in a codebook cache. The codebook includes one or more preferred precoding matrices.

In another aspect, an access terminal apparatus for receiving and storing codebooks for a multiple access wireless communication system is defined. The apparatus includes at least one processor and a memory coupled to the at least one processor. The apparatus also includes a codebook module stored in the memory and executable by the at least one processor. The codebook module is configured to receive a codebook from an access network. This codebook includes one or more preferred precoding matrices. The apparatus also includes a codebook cache stored in the memory and operable to store the received codebook.

In another aspect, an apparatus receives and stores codebooks in a multiple access wireless communication system. The apparatus includes a receiving module for receiving a codebook from an access network. The codebook includes one or more preferred precoding matrices. The apparatus also includes a storage module for storing the received codebook in a codebook cache.

Yet another aspect relates to a computer-readable medium. Such a medium includes receiving code for causing a computer to receive a codebook from an access network. The codebook includes one or more preferred precoding matrices. The medium further includes code for causing a computer to store the received codebook in a codebook cache.

Another aspect is an integrated circuit. The integrated circuit executes instructions for receiving and storing codebooks in a multiple access wireless communication system. The instructions include receiving a codebook from an access network and storing the received codebook in a codebook cache. The codebook includes one or more preferred precoding matrices.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the disclosure. These aspects are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed. Moreover, the disclosed aspects are intended to include all such aspects and their equivalents.

Drawings

Fig. 1 illustrates a wireless communication system in various aspects presented herein.

FIG. 2 is a block diagram of an exemplary codebook detailing various parameters in various aspects presented herein.

Fig. 3 is a flow diagram illustrating aspects of a method for generating and exchanging codebooks in a multiple access wireless communication system in accordance with various aspects set forth herein.

Fig. 4 is a flow diagram that illustrates a method for codebook exchange and assignment in a multiple access wireless communication system in accordance with various aspects set forth herein.

Fig. 5 is a block diagram illustrating a network access device for generating and exchanging codebooks in various aspects presented herein.

Fig. 6 is a block diagram illustrating a network access device for generating and exchanging codebooks in various aspects presented herein.

Fig. 7 is a flow diagram that illustrates a methodology for receiving and storing codebooks in an access terminal in accordance with the various aspects presented herein.

Fig. 8 is a flow diagram that illustrates a methodology for receiving, storing, and allocating codebooks in an access terminal in one aspect presented herein.

Fig. 9 is a block diagram illustrating an access terminal for receiving and storing codebooks in various aspects presented herein in a multiple access wireless communication system.

Fig. 10 is a block diagram illustrating an access terminal for receiving and storing codebooks in various aspects presented herein in a multiple access wireless communication system.

Fig. 11 is a block diagram illustrating a Single Codeword (SCW) multiple-input multiple-output (MIMO) transmitter in various aspects presented herein.

Fig. 12 is a block diagram illustrating a Single Codeword (SCW) multiple-input multiple-output (MIMO) receiver in various aspects presented herein.

Fig. 13 illustrates a multiple access wireless communication system in various aspects presented herein.

Fig. 14 illustrates a transmitter and a receiver in a multiple access wireless communication system in various aspects presented herein.

Fig. 15 is a block diagram illustrating a system that coordinates generation and transmission of acquisition information in various aspects presented herein.

Fig. 16 is a block diagram that illustrates a system that coordinates signal acquisition in a wireless communication environment in various aspects presented herein.

Detailed Description

Various aspects are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident, however, that such aspect(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more aspects.

As used in this application, the terms "component," "module," and "system" and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, or software in execution. For example, a component may be, but is not limited to: a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. For example, both an application running on a computing device and the computing device itself can be a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from such components interacting with other components in a local system, distributed system, and/or across a network such as the internet with other components by way of the signal).

Moreover, various aspects are described in connection with an access terminal and an access network. An access terminal may refer to a device that provides voice and/or data and connects to a user. An access terminal may be connected to a computing device, such as a laptop computer or desktop computer, or may be a self-contained device, such as a cellular telephone. An access terminal can also be called a system, subscriber unit, subscriber station, mobile device, remote station, remote terminal, radio access network, wireless terminal, user agent, user device, or user equipment. A wireless terminal may be a subscriber station, wireless device, cellular telephone, PCS telephone, cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, or other processing device connected to a wireless modem. An access network, which may also be referred to as an access point, base station, and/or Base Station Controller (BSC), may refer to a device in the access network that communicates over the air-interface, through one or more sectors, with wireless terminals. The access network may act as a router between the wireless terminal and the rest of the access network, including an Internet Protocol (IP) network, by converting received air-interface frames to IP packets. The access network also coordinates management of air interface attributes.

Moreover, various aspects or features described herein can be implemented as a method, apparatus, or article of manufacture using standard programming and/or engineering techniques. The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer-readable media include, but are not limited to, magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks (e.g., CD, DVD, etc.), smart cards and flash memory devices (e.g., card, stick, key drive, etc.), and integrated circuits such as read-only memory, programmable read-only memory, and electrically erasable programmable read-only memory.

Various aspects will be described in terms of systems that may include a number of devices, component modules, and the like. It is to be understood that such systems may include additional devices, components, modules, etc. and/or may include all of the devices, components, modules etc. described in connection with the figures. Combinations of these approaches may also be used.

Referring now to fig. 1, fig. 1 illustrates a wireless communication system 100 in various aspects described herein. Communications in wireless system 100 may be improved in various ways, including precoding, SDMA, multiple-input multiple-output (MIMO), and transmit/receive diversity. As shown, an access terminal 102 is in wireless communication with an access network 104. It should be appreciated that although only one access terminal 102 and one access network 104 are depicted for simplicity, there may be more than one of them.

The access network 104 includes transmit antennas that are capable of generating beams covering a predetermined area, resulting in a fixed beam pattern. The access network 104 supports multiple technologies such as precoding, SDMA, and/or MIMO. Regardless of the technology employed, the access network 104 pre-processes the technology employed. For example, for precoding, a particular vector may be employed to modulate all transmissions of a user over a period of time. For MIMO precoding, the transmission from the access network 104 may be modulated with a set of vectors.

The codebook 106 includes several entries (entries) of different vectors and/or matrices, which may correspond to multiple transmission modes, which information may be predefined. Each entry may correspond to a transmission mode or a form of spatial processing (e.g., precoding, SDMA, MIMO, etc.). For example, codebook 106 may contain a set of 64 entries. However, there may be any number of items, 64 being just one number arbitrarily chosen. According to these aspects, the codebook 106 can be customized for an access network 104 or sector or access terminal 102 in communication with the access network 104. By way of example and not limitation, codebook 106 may support multiple users employing multiple transmission modes. It should be noted that although only one codebook 106 is depicted here, there may be more than one codebook in the system 100 and more than one codebook 106 may be associated with a given deployment.

The access terminal 102 may inform the access network 104 of the codebook entries preferred by the access terminal 102. The codebook 106 can be known by either the access terminal 102 or the access terminal 104, or both, depending on the communication system requirements. In systems in these aspects, the codebook 106 will be generated by the access network 104 and communicated to the access terminal 102 for storage in the access terminal cache (i.e., temporary storage). Thus, in these aspects, the codebook 106 is known by both the access network 104 and the access terminal 102. As the access terminal 102 moves between different access networks 104, the access terminal 102 may acquire and use different codebooks 106 associated with the access networks 104 in a particular geographic area. The acquisition and/or allocation of the new codebook 106 may be performed autonomously by the access terminal 102 (e.g., by a processor accessing a different codebook) or the access terminal 102 may be informed of the new allocation by the access network 104.

In SDMA, multiple users whose spatial signatures can be distinguished can be scheduled simultaneously on the same time-frequency resource. In SDMA, a sector is split into several virtual sectors, so that user equipments in different areas share the same channel resources, thereby obtaining a higher spatial reuse rate. Thus, in SDMA, there may be different transmission modes that can provide robust signaling. Control and/or broadcast data may be transmitted in this transmission mode. Each virtual sector may be further subdivided into a set of narrower spatial beams, and a particular beam (or linear combination of beams) in a virtual sector may be applied to a particular user device to increase antenna gain to the user device and limit the spatial spread of the interference caused by the transmission.

SDMA is useful when the capacity is close to the nonlinear region in case of high SNR. In these aspects, overlapping multiple users can increase the number (dimension) of available channels at the cost of reduced SNR per user. This approach can increase system capacity, assuming that users are in the non-linear capacity region when SNR is high. On the other hand, in regions where the SNR is low (linear region of the capacity curve), it is often not beneficial to reduce the power of the user while increasing the dimensionality. In these aspects, it may be beneficial to improve the SNR of the user through techniques, such as precoding techniques. The precoding therein may be for multiple streams or for several information streams (MIMO precoding). These aspects employ predefined sets of beams to transmit to users. In a MIMO scheme, there are multiple streams transmitted to the same user, where data can be sent along multiple eigenvector directions.

With the disclosed techniques, multiple-input single-output/multiple-input multiple-output (MISO/MIMO) precoding and seamless operation of SDMA are enabled by precoding in the beam space of SDMA beams. In particular, if there are a small number of virtual sectors employing SDMA, each such region also includes a set of narrow spatial beams. These narrow beams form the basis of transmission in the virtual sector.

The decision of which mode (precoding, SDMA, MIMO, or a combination thereof) to use may be based on one or more channel conditions. Channel Quality Indicator (CQI) techniques may be utilized to decide which vector to use, e.g., provide a maximum or minimum value. For precoding, a specific entry that preprocesses the user's transmission may be utilized. For MIMO precoding, a set of vectors may be used to pre-process transmissions for an access network. Precoding provides higher SNR, possibly leading to higher peak rates and better coverage.

Referring to FIG. 2, in accordance with these aspects, a block diagram depicting an exemplary structure of codebook 200 is depicted. Codebook 200 may include some, but not all, of the following parameters. For example, codebook 200 can include a codebook identifier 202 that is used to distinguish the codebook from other codebooks. In some aspects, the codebook identifier 202 may be a 16-bit identifier assigned by the access network. A 16-bit codebook identifier can ensure that there is a minimal likelihood of codebook identification collisions between different vendors. However, the aspects disclosed herein are not limited to a 16-bit codebook identifier structure, and may be identifiers of other bit lengths, which are also within the scope of the aspects disclosed. As will be described in detail, the codebook identifier 202 may be used during codebook swapping and assignment to verify the codebook and extract the necessary codebook from the access terminal cache.

Additionally, codebook 200 may include beam index parameters 204 that point to beams in the codebook. Thus, the beam index parameter 204 may, for example, indicate one or more of: (1) no preferred precoding or SDMA matrix; (2) SISO (single input single output) precoding or SDMA transmission on spatial beams is preferred; and (3) preferably MIMO (multiple input multiple output) precoding or SDMA transmission over a set of spatial beams (e.g., more than one column of a precoding matrix). The beam index parameter 204 may also indicate one or more sets of allowed overlapping beams.

Codebook 200 may also include a transmit antenna parameter 206, where transmit antenna parameter 206 identifies a maximum number of antennas implemented by the access network. Additionally, codebook 200 can also include supported layer parameters 208, where supported layer parameters 208 identify a maximum number of supported layers in the communication system. The maximum number of layers supported is referred to in the art as the spatial order. The maximum number of antennas and the maximum number of supported layers are used to define the size of the precoding matrix. Thus, the size of the precoding matrix may be defined as the product of the maximum number of transmit antennas and the maximum number of supported layers.

Codebook 200 may also include precoding matrix parameters 210, precoding matrix parameters 210 identifying the number of precoding matrices in the codebook. As described above, the codebook 200 typically includes 64 precoding matrices. However, other numbers of precoding matrices are possible.

In addition, codebook 200 will include a plurality of preferred precoding matrices 212, which plurality of preferred precoding matrices 212 provide a preferred mapping between active antennas and physical antennas.

Codebook 200 may also support clusters. A cluster is defined as a group of precoding matrices (e.g., a set of beams) defined by a coverage space. Columns of the matrix in different clusters are used to form spatial beams that spatially cover different groups of users/access terminals. If the access terminal feeds back the beam index in the cluster, the access network will take this as an indication that it can schedule other access terminals on different clusters, i.e., SDMA is allowed. Thus, codebook 200 can include a cluster parameter 214 that defines the number of clusters in the codebook. Each cluster will have a cluster sub-parameter 216 that identifies the number of beams in the cluster. The number of beams in a cluster may be identified by a starting beam index and an ending beam index.

Additionally, codebook 200 may include a cluster overlap map 218, where cluster overlap map 218 indicates those clusters that are likely to be overlapped by the grant. The cluster overlap map 218 may be formed as a matrix having the following dimensions: the number of precoding matrices is multiplied by the number of precoding matrices. Thus, for a codebook with 64 precoding matrices, the cluster overlap map may have a matrix size of 4096. The overlay map matrix may be formed such that 1 indicates that overlay is allowed and 0 indicates that overlay is not allowed. In addition, the access terminal should take overlapping clusters into account when reporting CQI (channel quality indication) to the access network.

Fig. 3 is a flow diagram of a method 300 of generating and exchanging codebooks in a multiple access wireless communication system. It is to be appreciated that methodology 300 may be implemented by, for example, an access network (e.g., access network 104) and/or any other network entity as appropriate. In block 302, a plurality of preferred precoding matrices are provided. For example, in one aspect, 64 precoding matrices may be provided. Each matrix defines a mapping between active antennas and physical antennas, thus supporting beamforming. The access terminal selects a precoding matrix among a plurality of preferred precoding matrices based on implementation and deployment factors.

In block 304, a codebook is generated in the access network. The codebook includes a plurality of preferred precoding matrices. Additionally, the generated codebook may include a codebook identifier, such as a 16-bit codebook identifier, or any other suitable bit length codebook identifier. The generated codebook may include an identification of clusters, which are defined as groups of precoding matrices. In addition to the number of clusters in the codebook, the codebook may include a cluster beam index indicating the number of beams in the cluster, a start beam index, and an end beam index. In some aspects, the generated codebook may further include a cluster overlap map identifying overlapping clusters.

In block 306, the codebook is communicated to one or more access terminals that are currently within reception range of the access network. In optional block 308, one or more access terminals are assigned codebooks. The delivery of the codebooks may occur simultaneously with the allocation of the codebooks, or the allocation of the codebooks may be independent of the delivery of the codebooks. Fig. 4, which will be described below, provides a detailed method of codebook delivery and allocation.

Fig. 4 is a flow diagram of a method 400 of codebook exchange and allocation in a multiple access wireless communication system in these aspects. It is to be appreciated that methodology 400 can be implemented with, for example, an access network (e.g., base station 104) and/or any other suitable network entity. In block 402, the access network communicates a codebook status query message to the access terminal. The codebook status query message is communicated on the forward link. The codebook status query may be communicated by each new access network added to the active set of access networks.

In block 404, the access network receives a codebook status response indicating the currently stored codebook in the access terminal cache. The codebook status response is communicated on the reverse link and identifies the cached codebook according to the corresponding codebook identifier. By providing each access network, e.g., base station, with the ability to query the access terminal for the current codebook assignment, it is not necessary at all to share the access terminal codebook cache state with other access networks. This enables the size and complexity of the session information that must be shared between the access networks to be reduced.

In decision block 406, the access network determines whether the access terminal currently has an associated codebook in the access terminal cache. This determination is made by examining the access network related codebook identifier in the codebook status response. If the determination is that the access terminal does not currently have a codebook in the access terminal cache, then the access terminal passes the codebook to the access terminal in block 408. The access network may communicate the codebook on the forward link as part of a codebook setup message.

The access network may assign the codebook to the access terminal as soon as the codebook is communicated to the access terminal or upon determining that the codebook is currently stored in the access terminal cache, block 408. Assigning codebooks supports the adoption of codebooks for specific sectors within an active set. The codebook assignments are communicated on the forward link.

Fig. 5 is a block diagram of an access network 500 that generates and exchanges codebooks in a multiple access wireless communication system, in accordance with various aspects. The modules disclosed herein may be implemented using computer readable media (e.g., software) stored in device memory, hardware (e.g., processing subsystems, etc.), or a combination of computer readable media and hardware. The access network 500 comprises a module 502 for providing a plurality of preferred precoding matrices. Each matrix will define a mapping between active and physical antennas, thus supporting beamforming. The access terminal may select a precoding matrix from a plurality of preferred precoding matrices based on deployment and deployment considerations.

The access network 500 further comprises a module 504 for generating a codebook comprising a plurality of preferred precoding matrices. In addition, the generated codebook may include a codebook identifier, such as a 16-bit codebook identifier, or any other bit-length codebook identifier. The generated codebook may include an identification of clusters, which are defined as groups of precoding matrices. In addition to the number of clusters in the codebook, the codebook may include a cluster beam index indicating the number of beams in the cluster, a start beam index, and an end beam index. In some aspects, the generated codebook may additionally include a cluster overlap map identifying overlapping clusters.

In addition, the access network includes a module 506 for communicating the codebook to one or more access terminals. Delivering the codebook may include querying the access terminal for the codebook status, receiving a response to the codebook status query and delivering the codebook to the access terminal if the response indicates that the codebook is not currently stored in the access terminal memory.

Fig. 6 depicts a block diagram of an access network apparatus 600 in accordance with various aspects. The access network apparatus may be a single device or may be multiple devices that act in concert to achieve the functionality described herein. The access network includes at least one processor 602 and memory 604 coupled to the processor 602. The processor 602 may be an Application Specific Integrated Circuit (ASIC) or other chipset, processor, logic circuit, or other data processing device. Memory 604 may include volatile and nonvolatile memory such as read-only and/or random-access memory (RAM and ROM), EPROM, EEPROM, flash cards, or any memory common to computer platforms. Further, memory 604 may include one or more flash memory cells, and may be any secondary or tertiary storage device, such as magnetic media, optical media, tape, or soft or hard disk.

The access network 600 also includes a codebook generator 606 stored in the memory 604 and executable at least by the processor 602. The codebook generator 606 is used to generate a codebook comprising a plurality of preferred precoding matrices. In addition, the generated codebook may include a codebook identifier, such as a 16-bit codebook identifier, or any other bit-length codebook identifier. The generated codebook may include an identification of clusters, which are defined as groups of precoding matrices. In addition to the number of clusters in the codebook, the codebook may include a cluster beam index indicating the number of beams in the cluster, a start beam index, and an end beam index. In some aspects, the generated codebook may additionally include a cluster overlap map that identifies clusters that are likely to overlap.

The access network 600 also includes a codebook switch 608 that is stored in the memory 604 and executable at least by the processor 602. Codebook switch 608 is configured to communicate codebooks to one or more access terminals. Delivering the codebook may include querying the access terminal for the codebook status, receiving a response to the codebook status query, and delivering the codebook to the access terminal if the response indicates that the codebook is not currently stored in the access terminal memory.

Fig. 7 is a flow diagram illustrating a method 700 for receiving and storing codebooks in an access terminal in a multiple access wireless communication system. It is to be appreciated that methodology 700 can be implemented with, for example, an access terminal and/or any other suitable device that is in wireless communication with an access network. In block 702, an access terminal receives a codebook comprising a plurality of preferred precoding matrices. The codebook may be received through a status query and a subsequent response, as described below with reference to fig. 8. The reception of the codebook may be performed on the forward link.

In block 704, the received codebook is stored in a codebook cache according to a codebook identification included in the codebook. In general, an access terminal can cache a codebook if the access terminal is in an idle state when the codebook is received, or in another aspect, the access terminal can discard codebook cache entries. In addition, the access terminal may also delete codebooks from the cache when the terminal is powered off or experiences power cycling. Also, in the case of a codebook being cached in non-volatile memory, the access terminal may delete the codebook from memory when there is no power (e.g., no battery). In these aspects, restoring power typically requires the access terminal to reacquire the necessary codebooks from the access network to restore the codebook cache as needed.

At optional block 706, a codebook assignment is received for a codebook stored in a codebook cache. This assignment assigns the identified codebook to a predetermined sector within the active set of communication links. The allocation of the codebooks may be performed in conjunction with the delivery of the codebooks, or may be performed at any point in time after the codebooks are delivered and stored at the access terminal. The access terminal is typically configured to maintain (i.e., delete) any cache entries currently allocated by sectors in the active set of the communication link.

Fig. 8 is a flow diagram that illustrates a methodology 800 for receiving and allocating codebooks in an access terminal in a multiple access wireless communication system in accordance with aspects presented herein. It is to be appreciated that methodology 800 can be implemented with, for instance, an access terminal and/or any other suitable device that is in wireless communication with an access network. In block 802, the access terminal receives a codebook status query message communicated from the access network. The codebook status query message may be communicated on the forward link. The codebook status query may be communicated by each new access network added to the active set of access networks.

In block 804, a codebook status response is communicated to the access network indicating the codebook currently stored in the access terminal cache. A codebook status response may be communicated on the reverse link and identify the cached codebook according to the corresponding codebook identifier. By providing each access network, e.g., base station, with the ability to query the access terminal for current codebook assignments, there is no need to share the access terminal codebook cache state with other access networks at all. This enables the size and complexity of the session information that must be shared between the access networks to be reduced.

In block 806, the access terminal receives the codebook if the response to the codebook status query indicates that the codebook associated with the access network that initiated the query is not currently stored in the access terminal's codebook cache. The access terminal may receive the codebook on the forward link as part of a codebook setup message.

Upon receipt of the codebook by the access terminal, the terminal can receive a codebook assignment that assigns the codebook to a particular sector in the active set of the communication link, block 808. The codebook assignments may be communicated on the forward link.

Fig. 9 is a block diagram that illustrates an access terminal 900 for receiving and storing codebooks in various aspects presented herein in a multiple access wireless communication system. The modules disclosed herein may be implemented in computer readable media (e.g., software) stored in device memory, hardware (e.g., processing subsystems, etc.), or a combination of computer readable media and hardware. Access terminal 900 includes a module 902 that module 902 can employ to receive a codebook that includes a plurality of preferred precoding matrices. Each matrix defines a mapping between active antennas and physical antennas, thus supporting beamforming. The access terminal selects a precoding matrix from a plurality of preferred precoding matrices based on system configuration and deployment.

Access terminal 900 further comprises a module 904 for storing the received codebook in a codebook cache. The codebooks may be stored in terms of a codebook identifier included in the codebook (e.g., a 16-bit identifier or any other bit length codebook identifier). The codebook can be stored during an idle state of the access terminal or can be ignored during the idle state. The codebook is typically saved in a codebook cache until the device is powered down or undergoes a power state change.

Fig. 10 is a block diagram of an access terminal 1000 in accordance with various aspects. An access terminal may comprise any type of computerized, communication device, such as a cellular telephone, a Personal Digital Assistant (PDA), a two-way text pager, a portable computer, or even a separate computer platform that has a wireless communication portal, and which also has a wired connection to a network or the internet. The access terminal may be a remote-slave device or other device that does not have an end-user but simply communicates data over a wireless network, such as remote sensors, diagnostic tools, data relays, and the like. The apparatus and methods may thus be implemented on any form of wireless communication device or wireless computer module, including a wireless communication portal, including without limitation, wireless modems, PCMCIA cards, wireless devices, or any combination or sub-combination thereof.

Access terminal 1000 includes at least one processor 1002 and memory 1004 coupled to processor 1002. The processor 1002 may be an Application Specific Integrated Circuit (ASIC), but may also be another chipset, processor, logic circuit, or other data processing device. Memory 1004 may include volatile and nonvolatile memory such as read-only and/or random-access memory (RAM and ROM), EPROM, EEPROM, flash cards, or any memory common to computer platforms. Further, memory 1004 may include one or more flash memory cells, and may be any secondary or tertiary storage device, such as magnetic media, optical media, tape, or soft or hard disk.

The access terminal 1000 further includes a codebook module 1006 stored in memory 1004 that can be executed by at least one processor 1002. Codebook module 1006 is configured to receive a codebook comprising a plurality of preferred precoding matrices. Additionally, codebook module 1006 may be configured to receive a codebook query and, in response thereto, communicate the currently stored codebook to the access network. Also, codebook module 1006 can be used to assign one of the cached codebooks to a predetermined sector within the active set of communication links.

The access terminal 1000 can further include a codebook cache 1008 stored in the memory 1004 that can be executed by the at least one processor 1002. Codebook cache 1008 is used to store the received codebooks in memory. As described above, during power-up, the received codebook will be stored in the cache, and it can be placed in the cache in an idle state. The access terminal may also be configured to delete codebooks based on the access terminal location or the maximum time setting. However, the allocated codebook is typically not deleted from the cache.

Fig. 11 is a block diagram representation of a transmitter 1100 (e.g., an access network) in Single Codeword (SCW) Multiple Input Multiple Output (MIMO) according to the present aspects. The input data stream is communicated to a turbo encoder 1102, and the turbo encoder 1102 uses the selected code rate input from a rate prediction module 1106. The turbo encoded data stream is then mapped to a selected QAM (quadrature amplitude modulation) constellation in QMA mapping module 1104. The stream of modulation symbols is then demultiplexed into parallel sub-streams in demultiplexer 1108. The M substreams (M defined by receiver 1118) output by demultiplexer 1108 are mapped to physical antennas using active antenna signaling module 1110 to adjust the rate and rank to the channel realization. The sub-streams are then subjected to a single Orthogonal Frequency Division Multiplexing (OFDM) modulation in respective OFSM modulators 112, 114 and 116. Upon completion of the modulation, the substreams are transmitted over corresponding antennas 1120, 1122, and 1124.

Fig. 12 is a block diagram representation of a receiver 1200 (e.g., an access terminal) in Single Codeword (SCW) Multiple Input Multiple Output (MIMO) according to the present aspects. The transmitted sub-streams are received via antennas 1202, 1204, and 1206, and undergo OFDM demodulation in corresponding OFDM demodulators 1206, 1208, and 1208. The demodulated substreams are then passed to an MMSE (minimum mean square error) module 1212, and the MMSE module 1212 applies a linear MMSE filter to the received demodulated substreams. The result of the linear MMSE filtering is passed to a rank prediction CQI quantization module 1214 for rank and CQI determination. In conjunction with parallel-to-serial module 1216, MMSE module 1212 decouples the incoming M substreams and provides soft estimates of the modulation symbols. The soft estimates of the modulation symbols are then passed to an LLR computer 1218 and the output to a turbo decoder 1220, resulting in decoded bits. The receiver may employ a more complex detector, but the complexity may be lower if only linear MMSE is employed.

Fig. 13 illustrates an exemplary multiple access wireless communication system. The multiple access wireless communication system 1300 includes multiple cells, such as cells 1302, 1304, and 1306. In the exemplary system illustrated in fig. 13, each cell 1302, 1304, and 1306 can include an access point 1350, and access point 1350 can include multiple sectors. The multiple sectors are formed by groups of antennas, each group of antennas being responsible for communication with access terminals in a portion of the cell. In cell 1302, antenna groups 1312, 1314, and 1316 each correspond to a different sector. Antenna groups 1318, 1320, and 1322 each correspond to a different sector in cell 1304. In cell 1306, antenna groups 1324, 1326, and 1328 each correspond to a different sector.

Each cell includes several access terminals that communicate with one or more sectors in each access network. For example, access terminals 1330 and 1332 can communicate with an access point (or base station) 1342, access terminals 1334 and 1336 can communicate with an access network 1344, and access terminals 1338 and 1340 can communicate with an access network 1346.

As shown in fig. 13, each access terminal 1330, 1332, 1334, 1336, 1338, and 1340 is in a different portion of its respective cell than every other access terminal in the same cell. Moreover, each access terminal may be a different distance from the corresponding antenna group with which it is communicating. These two factors, as well as environmental factors and other factors in the cell, cause different channel conditions to exist between each access terminal and the corresponding antenna group with which it is communicating.

As used herein, an access point may be a fixed station used for communicating with the terminals and may also be referred to as, and include some or all the functionality of, a base station, a node B, etc. An access terminal may also be referred to as and include some or all the functionality of a User Equipment (UE), a wireless communication device, terminal, mobile station, access terminal, or the like.

In one example, a set of known beams can be utilized at a base station to provide SDMA, e.g., fixed or adaptive sectors. If the access network knows the best beam for each user, it can allocate the same channel to different users if they receive data on different beams. In another example, system 1300 can comprise omni-directional beams that do not correspond to any precoding. The access network uses this beam to broadcast or multicast transmissions. In another example, system 1300 can utilize precoding without SDMA if such channel information is reported to the user.

The access terminal may utilize this channel information to calculate the beam it prefers and inform the access network of this beam. Knowing the channel at the transmitter can increase the capacity even without power allocation, especially for the number of transmit antennas T_MGreater than the number of receiving antennas R_MThose systems of (1). The capacity improvement is obtained by transmitting along the direction of the channel eigenvectors. Feedback on the channel requires overhead.

SDMA provides a sufficiently rich set of beams at the transmitter to allow full flexibility in scheduling. The user is scheduled on a beam that is told to the access network through some feedback mechanism. For efficient scheduling, if a specific beam is used for scheduling users, the transmitter should have channel quality information of each user.

Fig. 14 illustrates a transmitter and a receiver in a multiple access wireless communication system 1400 in accordance with various aspects set forth herein. For simplicity, the wireless communication system 1400 depicts only one access network and one user terminal. It should be understood that this system may include more than one access network and/or more than one user device, where additional access networks and/or user devices may be substantially similar or different from the exemplary access networks and user devices described below. In addition, it is to be appreciated that the access network and/or the user equipment can employ the systems and/or methods described herein for wireless communication therebetween.

In transmitter system 1410, traffic data for a number of data streams is provided from a data source 1412 to a Transmit (TX) data processor 1414, wherein data source 1412 comprises a codebook for these aspects. In some aspects, each data stream is transmitted over a respective transmit antenna. Transmit data processor 1414 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data. In some aspects, transmit data processor 1414 applies beamforming weights to the symbols of the data streams based on which user the symbol is to be transmitted to and from which antenna. In some aspects, the beamforming weights may be generated based on channel response information indicative of transmission path conditions between the access network and the access terminal. The channel response information may be generated using user-provided CQI (channel quality indicator) information or channel estimates. Further, in those cases where transmission is scheduled, transmit data processor 1414 can select a packet format based on rank information sent from the user.

The coded data for each data stream can be multiplexed with pilot data using OFDM (orthogonal frequency division multiplexing) techniques. The pilot data is typically processed in a known manner and can be used in the receiver system to estimate a known data pattern of the channel response. The multiplexed pilot and coded data for each data stream is then modulated (e.g., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream can be determined by instructions performed or provided by processor 1430. In some aspects, the number of parallel spatial streams may be varied according to rank information sent from the user.

The modulation symbols for the data streams are provided to a transmit MIMO processor 1420, which may further process the modulation symbols (e.g., for OFDM). Transmit MIMO processor 1420 provides NT symbol streams to NT transmitters (TMTR)1422a through 1422 t. In some aspects, transmit MIMO processor 1420 applies beamforming weights to the symbols of the data streams based on the user channel response information, depending on which user the symbol is to be transmitted to and from which antenna.

Each transmitter 1422 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. NT modulated signals from transmitters 1422a through 1422t are transmitted through NT antennas 1424a through 1424t, respectively.

At receiver system 1450, the transmitted modulated signals are received by NR antennas 1452a through 1452r and the received signal from each antenna 1452 is provided to a respective receiver (RCVR) 1454. Each receiver 1454 conditions a respective received signal (e.g., filters, amplifies, and downconverts), digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

A rx data processor 1460 then receives and processes the NR received symbol streams from NR receivers 1454 based on a particular receiver processing technique. The processing of the receive data processor 1460 is described in more detail below. Each detected symbol stream includes symbols that are estimates of the modulation symbols transmitted for the corresponding data stream. Rx data processor 1460 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by rx data processor 1460 is complementary to that performed by transmit MIMO processor 1420 and transmit data processor 1414 in transmitter system 1410.

The channel response estimate generated by receive processor 1460 may be used for space, space/time processing at the receiver, adjusting power levels, changing modulation rates or schemes, and so forth. The receive processor 1460 may also estimate the signal-to-noise-and-interference ratios (SNRs) of the detected symbol streams, and possibly other channel characteristics, and provide these quantities to a processor 1470. Rx data processor 1460 or processor 1470 can also derive an estimate of the "effective" SNR for the system. Processor 1470 can then provide estimated channel information (CSI), which can comprise various information regarding the communication link and/or the received data stream. For example, the CSI may include only the operating SNR and/or rank. The CSI is then processed by a transmit data processor 1418, which also receives traffic data for a number of data streams from a data source 1416, modulated by a modulator 1480, conditioned by transmitters 1454a through 1454r, and transmitted back to transmitter system 1410.

At transmitter system 1410, the modulated signals from receiver system 1450 are received by antennas 1424, conditioned by receivers 1422, demodulated by a demodulator 1440, and processed by a rx data processor 1442 to recover the CSI reported by the receiver system. The reported CSI is then provided to processor 1430 and used to (1) determine the data rates and coding and modulation schemes to be used for the data streams and (2) generate various controls for transmit data processor 1414 and transmit MIMO processor 1420.

At the receiver, the received NR signals may be processed using various processing techniques to detect the transmitted NT symbol streams. These receiver processing techniques can be divided into two main types: (1) spatial and space-time receiver processing techniques (also referred to as equalization techniques); and (2) "successive nulling/equalization and interference cancellation" receiver processing techniques (which are also referred to as "successive interference cancellation" or "successive cancellation" receiver processing techniques).

A MIMO channel formed by NT transmit antennas and NR receive antennas can be decomposed into N_SA separate channel of which N_S<＝min{N_T,N_R}. N may also be substituted_SEach of the independent channels is referred to as a spatial subchannel (or a transmission channel) of the MIMO channel, and each of these corresponds to one dimension.

Fig. 15 illustrates a codebook exchange system in accordance with various aspects in a wireless communication environment. System 1500 includes an access network 1502 having a receiver 1510 that receives signal(s) from one or more user devices 1504 (e.g., access terminals) via one or more receive antennas 1506 and transmits to the one or more user devices 1504 via a plurality of transmit antennas 1508. In one or more aspects, receive antennas 1506 and transmit antennas 1508 can be implemented with a single set of antennas. The receiver 1510 may receive information from the receive antennas 1506 and is connected to a demodulator 1512 that demodulates received information. Receiver 1510 may be, for example, a rake receiver (e.g., a technique that separately processes multipath signal components using multiple baseband correlators), an MMSE (minimum mean square error) -based receiver, or some other suitable receiver for separating assigned user devices, as will be appreciated by those skilled in the art. According to various aspects, multiple receivers (e.g., one for each receive antenna) may be employed, and such receivers may communicate with each other to provide improved estimates of user data. The demodulated symbols are analyzed by a processor 1514 (this processor 1514 is similar to the processor described with reference to fig. 16), and connected to a memory 1516. The memory 1516 stores information related to user equipment allocation, a lookup table related thereto, and the like.

The receiver output for each antenna can be jointly processed by the receiver 1510 and/or the processor 1514. A modulator 1518 can multiplex the signal for transmission by a transmitter 1520 through transmit antennas 1508 to user devices 1504.

Fig. 16 is a block diagram of a system 1600 that coordinates acquisition of signals in a wireless communication environment in accordance with various aspects described herein. In one example, system 1600 includes an access terminal 1602. As shown, access terminal 1602 can receive signal(s) from one or more access networks 1604 and transmit to the one or more access networks 1604 through antenna 1606. In addition, access terminal 1602 can comprise a receiver 1610 that receives information from an antenna 1606. In one example, receiver 1610 can be coupled to a demodulator (Demod)1612 that demodulates received information. The demodulated symbols can then be analyzed by a processor 1614. Processor 1614 can be connected to memory 1616, which can store data and/or program codes related to access terminal 1602. In addition, access terminal 1602 can employ processor 1614 to implement the methodologies described herein and/or other methodologies as appropriate. Access terminal 1602 can additionally comprise a modulator 1618, where modulator 1618 can multiplex a signal for transmission by a transmitter 1620 through an antenna 1606 to one or more access networks 1604.

It is to be understood that the various aspects described herein may be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. When the systems and/or methods are implemented in software, firmware, middleware, microcode, program code or code segments, they may be stored in a machine-readable medium, such as a storage component. A code segment may represent a program, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted using any suitable means including memory sharing, message passing, token passing, network transmission, etc.

For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented in the processor or may be external to the processor. In the latter case, the memory may be connected to the processor by various means.

What has been described above includes examples of one or more aspects. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned aspects. Those skilled in the art will appreciate that many combinations and permutations of various aspects are possible. Accordingly, the inventors intend for the various aspects described herein to include all such alternatives, modifications, and variations as fall within the scope of the claims. Furthermore, the term "or" refers to a "non-exclusive or".

Claims (16)

1. A method for codebook exchange in a multiple access wireless communication system, comprising:

providing a codebook, wherein the codebook comprises a plurality of precoding matrices preferred by an access terminal;

transmitting a first parameter and a second parameter from an access network to the access terminal, wherein the first parameter indicates a subset of the plurality of preferred precoding matrices and the second parameter indicates a set of beams, the subset includes at least two precoding matrices of the plurality of preferred precoding matrices and the subset is used by the access terminal to provide feedback to the access network; and

receiving feedback from the access terminal regarding the selected beam index associated with the set of beams.

2. The method of claim 1, wherein the subset is defined by a coverage space.

3. The method of claim 1, wherein the subset supports a transmission mode of the access terminal.

4. An apparatus for codebook exchange in a multiple access wireless communication system, comprising:

means for providing a codebook, wherein the codebook comprises a plurality of precoding matrices preferred by an access terminal;

means for transmitting first and second parameters from an access network to the access terminal, wherein the first parameter indicates a subset of the plurality of preferred precoding matrices and the second parameter indicates a set of beams, the subset including at least two precoding matrices of the plurality of preferred precoding matrices and the subset being used by the access terminal to provide feedback to the access network; and

means for receiving feedback from the access terminal regarding the selected beam index associated with the set of beams.

5. The apparatus of claim 4, wherein the subset is defined by a coverage space.

6. The apparatus of claim 4, wherein the subset supports a transmission mode of the access terminal.

7. A computer-readable medium having recorded thereon code for codebook exchange in a multiple access wireless communication system, comprising:

code for causing a computer to provide a codebook, wherein the codebook comprises a plurality of precoding matrices preferred by an access terminal;

code for causing the computer to transmit a first parameter and a second parameter from an access network to the access terminal, wherein the first parameter indicates a subset of the plurality of preferred precoding matrices and the second parameter indicates a set of beams, the subset includes at least two precoding matrices of the plurality of preferred precoding matrices and the subset is used by the access terminal to provide feedback to the access network; and

code for causing the computer to receive feedback from the access terminal regarding the selected beam index associated with the set of beams.

8. The computer-readable medium of claim 7, wherein the subset supports a transmission mode of the access terminal.

9. A method for codebook exchange in a multiple access wireless communication system, comprising:

providing a codebook, wherein the codebook comprises a plurality of precoding matrices preferred by an access terminal;

receiving, at the access terminal, a first parameter and a second parameter from an access network, wherein the first parameter indicates a subset of the plurality of preferred precoding matrices and the second parameter indicates a set of beams, the subset including at least two precoding matrices of the plurality of preferred precoding matrices and the subset being used by the access terminal to provide feedback to the access network; and

transmitting, at the access terminal, feedback related to the selected beam index associated with the set of beams.

10. The method of claim 9, wherein the subset is defined by a coverage space.

11. The method of claim 9, wherein the subset supports multiple transmission modes for the access terminal.

12. An apparatus for codebook exchange in a multiple access wireless communication system, comprising:

means for providing a codebook, wherein the codebook comprises a plurality of precoding matrices preferred by an access terminal;

means for receiving, at the access terminal, first and second parameters from an access network, wherein the first parameter indicates a subset of the plurality of preferred precoding matrices and the second parameter indicates a set of beams, the subset including at least two precoding matrices of the plurality of preferred precoding matrices and the subset being used by the access terminal to provide feedback to the access network; and

means for transmitting, at the access terminal, feedback related to the selected beam index associated with the set of beams.

13. The apparatus of claim 12, wherein the subset is defined by a coverage space.

14. The apparatus of claim 12, wherein the subset supports a transmission mode of the access terminal.

15. A computer-readable medium having recorded thereon code for codebook exchange in a multiple access wireless communication system, comprising:

code for causing a computer to provide a codebook, wherein the codebook comprises a plurality of precoding matrices preferred by an access terminal;

code for causing the computer to receive, at the access terminal, a first parameter and a second parameter from an access network, wherein the first parameter indicates a subset of the plurality of preferred precoding matrices and the second parameter indicates a set of beams, the subset including at least two precoding matrices of the plurality of preferred precoding matrices and the subset being used by the access terminal to provide feedback to the access network; and

code for causing the computer to transmit, at the access terminal, feedback related to the selected beam index associated with the set of beams.

16. The computer-readable medium of claim 15, wherein the subset supports a transmission mode of the access terminal.