BR112013007301B1 - Systems and methods for communicating channel state information - Google Patents

Abstract

SYSTEMS AND METHODS FOR COMMUNICATION OF CHANNEL STATUS INFORMATION. Certain aspects of the present description pertain to a technique for communicating Channel State Information (CSI) feedback. In some respects, CSI feedback is communicated over a very high transfer rate (VHT) wireless communication system.

Description

CROSS REFERENCE TO RELATED ORDERS

[001] This order claims the benefit of the U.S. Provisional Order. No. 61/387,542 filed on September 29, 2010; U.S. Provisional Order No. 61/389,495, filed October 4, 2010; U.S. Provisional Order No. 61/405,283, filed on October 21, 2010; U.S. Provisional Order No. 61/422,098, filed on December 10, 2010; U.S. Provisional Order No. 61/432,115, filed on January 12, 2011; U.S. Provisional Order No. 61/405,194, filed on October 20, 2010; and U.S. Provisional Order No. 61/409,645, filed on November 2, 2010; the entire contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

[002] Certain aspects of the present description relate generally to wireless communications and, more specifically, to methods for communicating channel state information (CSI).

DESCRIPTION OF THE PREVIOUS TECHNIQUE

[003] To solve the problem of increasing bandwidth requirements for wireless communication systems, different schemes are being developed to allow multiple user terminals to communicate with a single access point by sharing channel resources while obtaining high data transmission capacities. Multiple Input Multiple Output (MIMO) technology represents an approach that has recently emerged as a popular technique for next-generation communication systems. MIMO technology has been adopted in several emerging wireless communication standards such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. IEEE 802.11 denotes a set of Wireless Local Area Network (WLAN) air interface standards developed by the IEEE 802.11 committee for short-range communications (eg, from tens of meters to a few hundred meters).

[004] A MIMO system employs multiple transmit antennas (NT) and multiple receive antennas (NR) for data transmission. A MIMO channel formed by the transmit antennas NT and the receive antennas NR can be decomposed into NS independent channels, which are also referred to as spatial channels, where NS < min{W, NR}. Each of the independent NS channels corresponds to a dimension. The MIMO system can provide improved performance (eg, superior transmit capability and/or greater reliability) if the additional dimensionalities created by multiple transmit and receive antennas are utilized.

[005] In wireless networks with a single Access Point (AP) and multiple user stations (STAs), simultaneous transmissions can occur on multiple channels to different stations, both in the uplink and downlink directions. Many challenges are present in such systems.

SUMMARY OF THE INVENTION

[006] Certain aspects of the present disclosure provide for a wireless communication method. The method comprises receiving a request for channel state information. The method comprises determining channel state information parameters based on the information included in the request. The method comprises determining channel status information based at least in part on the determined parameters. The method comprises transmitting a frame comprising at least a part of the determined channel state information.

[007] Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus comprises a receiver configured to receive a request for channel status information. The apparatus comprises a processing system configured to determine channel state information parameters based on information included in the request, and to determine channel state information based at least in part on the determined parameters. The apparatus comprises a transmitter configured to transmit a frame comprising at least a portion of the determined channel status information.

[008] Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus comprises mechanisms for receiving a request for channel status information. The apparatus comprises mechanisms for determining channel state information parameters based on information included in the request. The apparatus comprises mechanisms for determining channel status information based at least in part on the determined parameters. The apparatus comprises mechanisms for transmitting a frame comprising at least a part of the determined channel state information.

[009] Certain aspects of the present disclosure provide a computer program product for wireless communication comprising a computer readable medium comprising instructions. The instructions when executed cause a device to receive a request for channel state information. The instructions when executed cause an apparatus to determine the parameters of the channel state information based on the information included in the request. The instructions when executed cause an apparatus to determine channel state information based at least in part on the determined parameters. The instructions when executed cause an apparatus to transmit a frame comprising at least a part of the determined channel state information.

[0010] Certain aspects of the present disclosure provide for an access terminal. The access terminal comprises at least one antenna. The access terminal comprises a receiver configured to receive, via the at least one antenna, a request for channel status information. The access terminal comprises a processing system configured to determine channel state information parameters based on information included in the request, and to determine channel state information based at least in part on the determined parameters. The access terminal comprises a transmitter configured to transmit a frame comprising at least a part of the determined channel status information.

[0011] Certain aspects of the present disclosure provide for a wireless communication method. The method comprises transmitting a request for channel status information to one or more devices, wherein the request comprises a field identifying each of the one or more devices and indicating parameters for each of the one or more devices to be used in determining channel status information. The method comprises receiving a frame comprising channel state information from at least one of the one or more devices in response to the request, the channel state information having been determined based at least in part on the parameters indicated by the request.

[0012] Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus comprises a transmitter configured to transmit a request for channel status information to one or more apparatus, wherein the request comprises a field identifying each of the one or more apparatus and indicating parameters for each of the one or more apparatus to be used when determining channel state information. The apparatus comprises a receiver configured to receive a frame comprising channel state information from at least one of the one or more apparatus in response to the request, the channel state information having been determined based at least in part on the parameters indicated by the request .

[0013] Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus comprises mechanisms for transmitting a request for channel status information to one or more apparatus, wherein the request comprises a field identifying each of the one or more apparatus and indicating parameters for each of the one or more apparatus to be used by the apparatus. determine the channel status information. The apparatus comprises mechanisms for receiving a frame comprising channel state information from at least one of the one or more apparatus in response to the request, the channel state information having been determined based at least in part on the parameters indicated by the request.

[0014] Certain aspects of the present disclosure provide a computer program product for wireless communication comprising a computer readable medium comprising instructions. The instructions when executed cause a device to transmit a request for channel status information to one or more devices, wherein the request comprises a field identifying each of the one or more devices and indicating parameters for each of the one or more devices. to be used when determining channel state information. The instructions when executed cause an apparatus to receive a frame comprising channel state information from at least one of the one or more apparatus in response to the request, the channel state information having been determined based at least in part on the indicated parameters by request.

[0015] Certain aspects of the present description provide an access point. The access point comprises at least one antenna. The access point comprises a transmitter configured to transmit, through the at least one antenna, a request for channel status information to one or more devices, wherein the request comprises a field identifying each of the one or more devices and indicating parameters. for each of the one or more devices to be used when determining channel status information. The access point comprises a receiver configured to receive a frame comprising channel status information from at least one of the one or more apparatus in response to the request, the channel status information having been determined based at least in part on the indicated parameters by request.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order that the manner in which the above-cited features of the present description may be understood in detail, a more specific description, briefly summarized above, may be obtained by referring to the aspects, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only certain typical aspects of this description and, therefore, should not be considered as limiting its scope, since the description may admit other equally effective aspects.

[0017] Figure 1 illustrates a diagram of a wireless communication network in accordance with certain aspects of the present description.

[0018] Figure 2 illustrates a block diagram of an exemplary access point and user terminals in accordance with certain aspects of the present description.

[0019] Figure 3 illustrates a block diagram of an exemplary wireless device in accordance with certain aspects of the present disclosure.

[0020] Figure 4 illustrates an aspect of a Channel State Information (CSI) feedback protocol.

[0021] Figure 5 illustrates one aspect of an NDPA frame.

[0022] Figures 6A-6C illustrate aspects of a STA information field.

[0023] Figures 7A-7C illustrate aspects of STA information included in the STA information field illustrated in Figures 6A-6C.

[0024] Figure 8 illustrates one aspect of an NDPA frame.

[0025] Figures 9A and 9B illustrate aspects of a control envelope.

[0026] Figure 10 illustrates an aspect of a control envelope.

[0027] Figure 11 illustrates an aspect of a CSI inform message for CSI feedback communication.

[0028] Figures 12A-12E illustrate aspects of a control field for sound feedback.

[0029] Figure 13 illustrates an aspect of an access point.

[0030] Figure 14 illustrates one aspect of a communication method.

[0031] Figure 15 illustrates one aspect of a communication method.

[0032] Figure 16 illustrates one aspect of a communication method.

[0033] Figure 17 illustrates an aspect of an access terminal.

[0034] Figure 18 illustrates one aspect of a communication method.

[0035] Figure 19 illustrates one aspect of a communication method.

[0036] Figure 20 illustrates one aspect of a communication method.

[0037] Figure 21 illustrates one aspect of a communication method.

[0038] Figure 22 illustrates one aspect of a communication method.

[0039] Figure 23 illustrates one aspect of a communication method.

[0040] Figure 24 illustrates one aspect of a communication method.

[0041] Figure 25 illustrates a block diagram of an exemplary user terminal in accordance with certain aspects of the present description.

DETAILED DESCRIPTION OF THE INVENTION

[0042] Various aspects of the description are described more fully below with reference to the accompanying drawings. This description, however, can be incorporated in many different forms and should not be considered to be limited to any specific structure or function presented throughout this description. Rather, these aspects are provided so that such description will be thorough and complete, and will fully convey the scope of the description to those skilled in the art. Based on the present teachings those skilled in the art should consider that the scope of the description is intended to cover any aspect of the description described herein, whether implemented independently of, or combined with, any other aspect of the description. For example, an apparatus may be implemented or a method may be practiced using any number of aspects presented herein. Furthermore, the scope of the description is intended to cover such apparatus or method which is practiced using another structure, functionality or structure and functionality in addition to other than the various aspects of the description presented herein. It is to be understood that any aspect of the description described herein may be incorporated by one or more elements of a claim.

[0043] Although specific aspects are described here, many variations and permutations of these aspects are within the scope of the description. While some benefits and advantages of preferred aspects are mentioned, the scope of the description is not intended to be limited to specific benefits, uses or objectives. Rather, aspects of the description are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of preferred aspects. The detailed description and drawings are only illustrative of the description rather than limiting.

EXEMPLARY WIRELESS COMMUNICATION SYSTEM

[0044] The techniques described here can be used for various broadband wireless communication systems, including communication systems that are based on an orthogonal multiplexing scheme. Examples of such communication systems include Space Division Multiple Access (SDMA) system, Time Division Multiple Access (TDMA) system, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single Carrier Frequency (SC-FDMA), and so on. An SDMA system can use sufficiently different directions to simultaneously transmit data belonging to multiple user terminals. A TDMA system can allow multi-user terminals to share the same frequency channel by dividing the transmission signal into different time slices, each time slice being assigned to a different user terminal. An OFDMA system uses orthogonal frequency division multiplexing (OFDMA), which is a modulation technique that divides the total system bandwidth into multiple orthogonal subcarriers. These subcarriers can also be called tones, bands, etc. With OFDM, each subcarrier can be independently modulated with data. An SC-FDMA system can use interleaved FDMA (IFDMA) to transmit on subcarriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent subcarriers, or used FDMA (RFDMA) to transmit on multiple blocks of adjacent subcarriers. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDMA. An SC-FDMA system can implement 3GPP-LTE (Long Term Evolution of 3rd Generation Partnership Project) or other standards.

[0045] The present teachings may be incorporated (e.g. implemented within or performed by) a variety of wired or wireless apparatus (e.g. nodes). In some aspects, a wireless node implemented in accordance with the present teachings may comprise an access point or an access terminal.

[0046] An access point ("AP") may comprise, be implemented as, or known as, Node B, Radio Network Controller ("RNC"), eNodeB, Base Station Controller ("BSC"), Base Station Transceiver ("BTS"), Base Station ("BS"), Function Transceiver ("TF"), Radio Router, Radio Transceiver, Basic Services Suite ("BSS"), Extended Services Suite ("ESS") , Radio Base Station ("RBS"), or some other terminology.

[0047] An access terminal ("AT") may comprise, be implemented as, or known as, an access terminal, a subscriber station, a subscriber unit, a mobile station, a remote station, a remote terminal, a user terminal, a user agent, a user device, a user equipment, a user station, or some other terminology. In some implementations an access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol ("SIP") telephone, a wireless local area network ("WLL") station, a personal digital assistant ( "PDA"), a handheld device having wireless capability, a station ("STA") or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a telephone (e.g. a cell phone or smart phone), a computer (e.g. a laptop), a portable communication device, a portable computing device (e.g. , a personal data assistant), an entertainment device (for example, a music or video device, or a satellite radio), a global positioning system device, or any other suitable device that is configured for communication via a wired or wireless medium. In some respects the node is a wireless node. Such a wireless node may provide, for example, connectivity to a network (for example, a remote area network such as the Internet or a cellular network) over a wired or wireless communication link.

[0048] Figure 1 illustrates a multi-access multiple-input multiple-output (MIMO) system 100 with access points and user terminals. For simplicity, only one access point 110 is shown in Figure 1. An access point is generally a fixed station that communicates with user terminals and may also be referred to as a base station or some other terminology. A user terminal can be fixed or mobile and can also be referred to as a mobile station, a wireless device or some other terminology. Access point 110 may communicate with one or more user terminals 120 at any given time on the downlink and uplink. The downlink (i.e. forward link) is the communication link from the access point to the user terminals, and the uplink (i.e. the reverse link) is the communication link from the user terminals to the access point. A user terminal can also communicate non-hierarchically with another user terminal. A system controller 130 docks and provides coordination and control for the access points.

[0049] Although parts of the following description describe user terminals 120 capable of communicating via Spatial Division Multiple Access (SDMA), for certain aspects, user terminals 120 may also include some user terminals that do not support SDMA. Thus, for such purposes, an AP 110 can be configured to communicate with both SDMA and non-SDMA user terminals. This approach can conveniently allow older versions of user terminals ("legacy" stations) that do not support SDMA to remain installed in an enterprise, extending their lifespan, while allowing newer SDMA user terminals to be introduced as deemed appropriate.

[0050] System 100 employs multiple transmit antennas and multiple receive antennas for uplink and downlink data transmission. Access point 110 is equipped with Nap antennas and represent the multiple inputs (MI) for downlink transmissions and the multiple outputs (MO) for uplink transmissions. A set of K selected user terminals 120 collectively represent the multiple outputs for downlink transmissions and the multiple inputs for uplink transmissions. For pure SDMA, it is desired to have Nap > K > 1 if the data symbol streams for the K user terminals are not code, frequency, or time multiplexed by some means. K can be greater than Nap if data symbol streams can be multiplexed using TDMA technique, different code channels with CDMA, disconnected sets of subbands with OFDM, and so on. Each selected user terminal transmits specific user data to and/or receives specific user data for the access point. In general, each selected user terminal can be equipped with one or multiple antennas (ie Nut > 1. The K selected user terminals can have the same or different number of antennas.

[0051] The SDMA 100 system can be a time division duplex (TDD) system or a frequency division duplex (FDD) system. For a TDD system, the downlink and uplink share the same frequency band. For an FDD system, the downlink and uplink use different frequency bands. The MIMO system 100 can also use a single carrier, or multiple carriers, for transmission. Each user terminal can be equipped with a single antenna (eg to keep costs down) or multiple antennas (eg where additional cost can be borne). System 100 can also be a TDMA system if user terminals 120 share the same frequency channel by dividing transmit/receive into different time slices, with each time slice being assigned to different user terminal 120.

[0052] Figure 2 illustrates a block diagram of access point 102 and two user terminals 120m and 120x in MIMO system 100. Access point 110 is equipped with Nt antennas 224a to 224t. The 120m user terminal is equipped with Nut,m antennas 252ma to 252mu, and the 120x user terminal is equipped with Nut,x antennas 252xa to 252xu. Access point 110 is a transmitting entity for the downlink and a receiving entity for the uplink. Each user terminal 120 is a transmit entity for the uplink and a receive entity for the downlink. As used herein, a "transmitting entity" is an independently operated apparatus or device capable of transmitting data over a wireless channel, and a "receiving entity" is an independently operated apparatus or device capable of receiving data over a wireless channel. wireless channel. In the description that follows, the subscript "dn" denotes the downlink, the subscript "up" denotes the uplink, Nup user terminals are selected for simulcast on the uplink, Ndn user terminals are selected for simulcast on the uplink descending, Nup may or may not equal Ndn, and Nup and Ndn may be static values or may change for each schedule interval. Beam steering or some other spatial processing technique may be used at the access point and/or user terminal 120.

[0053] On the uplink, at each user terminal 120 selected for uplink transmission, a TX data processor 288 receives traffic data from a data source 286 and control data from a controller 280 The TX data processor 288 processes (e.g., encodes, interleaves, and modulates) the traffic data for the user terminal based on the coding and modulation schemes associated with the selected rate to the user terminal and provides a stream of data symbols. A TX spatial processor 290 performs spatial processing on the data symbol stream and provides Nut,m transmission symbol streams to the Nut,m antennas. Each transmission unit (TMTR) 254 receives and processes (e.g., converts to analog, amplifies, filters, and upconverts a respective stream of transmit symbols to generate an uplink signal. Nut,m transmission units 254 provides Nut,m uplink signals for transmission from Nut,m antennas 252 to access point 110.

[0054] Nup user terminals can be programmed for simultaneous transmission on the uplink. Each of these user terminals performs spatial processing on its data symbol stream and transmits its set of uplink transmission symbol streams to the access point 110.

[0055] At access point 110, Nup antennas 224a to 224ap receive the uplink signals from all Nup user terminals transmitting on the uplink. Each antenna 224 provides a received signal to a respective receiving unit (RCVR) 222. Each receiving unit 222 performs processing complementary to that performed by the transmitting unit 254 and provides a stream of received symbols. An RX spatial processor 240 performs receiver spatial processing on Nap symbol streams received from Nap receiving units 222 and provides Nup retrieved uplink data symbol streams. Receiver spatial processing is performed according to channel correlation matrix inversion (CCMI); least mean square error (MMSE); soft interference cancellation (SIC); or some other technique. Each retrieved uplink data symbol stream is an estimate of a data symbol stream transmitted by a respective user terminal. An RX data processor 242 processes (e.g., demodulates, deinterleave, and decodes) each stream of retrieved uplink data symbols according to the rate used for that stream to obtain the decoded data. The decoded data for each user terminal may be provided to a data warehouse 244 for storage and/or to a controller 230 for further processing.

[0056] On the downlink, an access point 110, a TX data processor 210 receives traffic data from a data source 280 to Ndn user terminals programmed for downlink transmission, control data from from a controller 230, and possibly other data from a scheduler 234. Different types of data may be sent on different transport channels. The TX data processor 210 processes (e.g., encodes, interleaves, and modulates) the traffic data for each user terminal based on the rate selected for that user terminal. The TX data processor 210 provides Ndn downlink data symbol streams to the Ndn user terminals. A TX spatial processor 220 performs spatial processing (such as precoding or beamforming, as described herein) on the Ndn downlink data symbol streams, and provides Nap transmit symbol streams to the Nap antennas. . Each transmission unit 222 receives and processes a respective stream of transmission symbols to generate a downlink signal. Nap transmission units 222 can provide Nap downlink signals for transmission from Nap antennas 224 to user terminals 120.

[0057] At each user terminal 120, Nut,m antennas 252 receive the Nap downlink signals from the access point 110. Each receiving unit 254 processes a signal received from an associated antenna 252 and provides a stream of symbols, received. An RX spatial processor 260 performs receiver spatial processing on Nut,m received symbol streams from Nut,m receiving units 254 and provides a retrieved downlink data symbol stream to the user terminal. Receiver spatial processing is performed according to CCMI, MMSE or some other technique. An RX data processor 270 processes (e.g., demodulates, deinterleave, and decodes) the retrieved downlink data symbol stream to obtain the decoded data for the user terminal.

[0058] At each user terminal 120, a channel estimator 278 estimates the downlink channel response and provides downlink channel estimates, which may include channel gain estimates, SNR estimates, noise variance, and so on. on. Similarly, a channel estimator 228 estimates the uplink channel response and provides uplink channel estimates. Controller 280 for each user terminal typically derives the spatial filter matrix for the user terminal based on the downlink channel response matrix Hdn,m for that user terminal. Controller 230 derives the spatial filter matrix for the access point based on the effective uplink channel response matrix Hup.θ/y. Controller 280 for each user terminal may send feedback information (e.g., downlink and/or uplink eigenvectors, eigenvalues, SNR estimates, and so on) to the access point. Controllers 230 and 280 also control the operation of the various processing units at access point 110 and user terminal 120, respectively.

[0059] Figure 3 illustrates various components that can be used in a wireless device 302 that can be employed within the wireless communication system 100. The wireless device 302 is an example of a device that can be configured to implement the various methods described here. Wireless device 302 may implement an access point 110 or a user terminal 120.

[0060] Wireless device 302 may include a processor 304 which controls the operation of wireless device 302. Processor 304 may also be referred to as a central processing unit (CPU). Memory 306, which may include both read-only memory (ROM) and random access memory (RAM), provides data instructions to processor 304. A portion of memory 306 may also include non-volatile random access memory (NVRAM). Processor 304 typically performs arithmetic and logic operations based on program instructions stored in memory 306. Instructions in memory 306 may be executable to implement the methods described herein.

[0061] Processor 304 may comprise or be a component of a processing system implemented with one or more processors. The one or more processors can be implemented with any combination of commonly used microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDS), controllers, state machines, controlled logic, discrete hardware components, unique hardware finite state machines, or any other suitable entities that can perform calculations or other manipulations of information.

[0062] The processing system may also include machine-readable media for storing software. Software should be considered in the broadest sense to mean any kind of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (eg, in source code format, binary code format, executable code format, or any other suitable code format). Instructions, when executed by one or more processors, cause the processing system to perform the various functions described here.

[0063] The wireless device 302 may also include a housing 308 which may include a transmitter 310 and a receiver 312 to allow transmission and reception of data between the wireless device 302 and a remote location. Transmitter 310 and receiver 312 may be combined in a transceiver 314. A single antenna or a plurality of transmit antennas 316 may be attached to housing 308 and electrically coupled to transceiver 314. Wireless device 302 may also include (not shown ) multiple transmitters, multiple receivers, and multiple transceivers.

[0064] Wireless device 302 may also include a signal detector 318 which may be used in an effort to detect and quantify the level of signals received by transceiver 314. Signal detector 318 may detect such signals as total power, power per subcarrier per symbol, power spectral density and other signals. Wireless device 302 may also include a digital signal processor (DSP) 320 for use in signal processing.

[0065] The various components of the wireless device 302 may be coupled together through a bus system 322, which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus.

[0066] In some respects, the wireless system 100 illustrated in Figure 1 operates in accordance with the IEEE 802.11ac wireless communication standard. IEEE 802.11ac represents an amendment to IEEE 802.11 that allows for higher throughput in IEEE 802.11 wireless networks. Higher throughput can be realized through various measures, for example, parallel transmissions to multiple stations (STAs) at once. In some respects, a wider channel bandwidth (eg 800 MHz or 160 MHz) is used. The IEEE 802.11ac standard is also sometimes referred to as the Very High Throughput (VHT) wireless communication standard.

[0067] Certain aspects of the present description support a low-overhead method of Channel State Information (CSI) communication or feedback accordingly. For example, such information may be communicated between user terminals 120 and access point 110 in wireless system 100. Certain aspects of the present disclosure further support packet formats for a Null Data Packet Announcement (NDPA), CSI poll. , and CSI feedback. Some aspects support a communication indicating whether the CSI was received and/or stored, for example, by an AP or on an AP. This information can be used by an STA, for example, to determine whether to send additional CSI and/or to set parameters to transmit the CSI. Some aspects support a communication indicating whether the CSI is being transmitted, for example by an STA. This information can be used by an AP, for example, to determine how to transmit requests to CSI and/or whether to adjust parameters to transmit requests to CSI. In some cases, the CSI feedback may be too large to be loaded onto a single Media Access Control (MAC) protocol data unit (MPDU) or a Physical Layer (PHY) protocol data unit (PPDU). ). Certain aspects of the present disclosure further support a protocol for CSI feedback segmentation. In the following description, reference is made to a user station (STA). As described above, an STA may comprise a user terminal, for example, user terminal 120 or wireless device 302.

CHANNEL STATUS INFORMATION

[0068] Figure 4 illustrates an aspect of a Channel State Information (CSI) feedback protocol 400. An Access Point (AP) may transmit to one or more User Stations (STAs) a Packet Announcement frame. Null Data Frame (NDPA) 402 followed by a Null Data Packet (NDP) frame 404 after a Symbol Short Intermediate Frame (SIFS) period 406. The NDPA frame 402 may comprise association identifiers (AIDs) of the STAs that must transmit computed CSI feedback messages to the AP, as will be described in further detail below.

[0069] Those STAs that are not identified in the NDPA may ignore the next NDP frame 404. The NDP frame 404 may comprise a sound frame used by each of the STAs to compute corresponding CSI feedback. A first related STA within the NDPA frame 402 may transmit CSI feedback 408 subsequent to a SIFS period after the transmission of the NDP frame 404, as illustrated in Figure 4. In some aspects, the CSI feedback 408 comprises only a portion of the feedback from Complete CSI for the first related STA. For example, when the complete CSI feedback is too large to be transmitted in a data unit such as an MPDU or a PPDU, the portion included in the CSI 408 feedback may be small enough for transmission in the data unit. In these respects, the AP may transmit a CSI Probe 412 to request an additional portion of the complete CSI feedback from the first related STA. The first related STA may then transmit another part such as CSI feedback 414 in response to the CSI poll 412. This process of polling an STA may continue until all parts of the complete CSI feedback have been received.

[0070] In some aspects, a CSI Probe may be sent by the AP to another STA listed in the NDPA frame to request the other STA to send the CSI feedback. For example, if the first STA listed in the NDPA frame 402 divides its full CSI feedback into the two parts of CSI Feedback 408, 414, then the AP can request another STA listed in the NDPA frame 402 to begin transmitting CSI feedback with CSI 416 polling. In response, the other STA may transmit CSI feedback 418, which may be full CSI feedback or a part of the full CSI feedback to the other STA. Any number of STAs may be identified in the NDPA frame 402, as will be discussed in further detail below, and the AP may transmit any number of CSI probes and/or receive any number of CSI feedbacks or parts thereof.

[0071] After the NDPA 402 frame is transmitted, the AP may transmit a second NDPA 422 frame to request CSI feedback again. The STAs from which CSI feedback is requested by the NDPA 422 frame can be different or the same STAs from which CSI feedback is requested by the NDPA 402 frame. The number of STAs from which CSI feedback is requested is requested in NDPA frames 402, 422 may be the same or may vary.

[0072] In some aspects, the NDPA 422 frame is transmitted after the CSI feedback has been received from all STAs identified in the NDPA 402 frame. In some aspects, the NDPA 422 frame is transmitted a certain period of time after the NDPA frame 402, regardless of whether CSI feedback was received from all STAs identified in the NDPA frame 402. In some aspects, the NDPA frame 422 is transmitted after a poll message such as a CSI poll has been sent for all STAs identified in the NDPA 402 frame. In some respects, the NDPA 402 frame may identify one or more STAs that are not identified in the NDPA 402 frame, or it may identify a subset of the STAs that are identified in the NDPA 402 frame. the AP may request CSI feedback from an STA with the NDPA 422 frame while still receiving CSI feedback from one or more STAs identified in the NDPA 402 frame. In some respects, the quad The NDPA 422 frame may be transmitted by the AP in response to a certain event, or the transmission of the NDPA frame 422 may be triggered by an action by the AP or another device.

[0073] Figure 5 illustrates one aspect of an NDPA frame, for example the NDPA 422 frame. In some respects, the NDPA 422 frame may be referred to as a CSI request message, which may be of the NDPA frame type. control. The NDPA frame 422 may comprise one or more of a frame control field 502, a duration field 504, an RA transmission field 506, a TA field 508, a CSI sequence field 512, a STA information field 514, and a CRC field 516. The NDPA frame 422 may be transmitted or broadcast by the AP as described above. The NDPA 402 frame can be formatted or configured similarly to the NDPA 422 frame.

[0074] In the illustrated aspect, the frame control field 502 comprises 16 bits. Also in the illustrated aspect, duration field 504 comprises 16 bits, and may include an NDPA frame length 422. CRC field 516 in the illustrated aspect comprises 32 bits and may comprise data for determining a cyclic redundancy check (CRC).

[0075] In the illustrated aspect, the RA transmission field 506 comprises 48 bits. RA broadcast field 506 may comprise a broadcast/multicast address for multiple STAs. For example, the RA broadcast field 506 may include a group address, where multiple STAs belong to the group. In one aspect, each STA can identify whether it is being addressed based on the group address. In other aspects, the RA transmit field 506 may instead identify a single STA, for example, by indicating a MAC address of an intended STA. In some aspects, the RS 506 transmit field may instead comprise or be referred to as a DA (destination address) field.

[0076] In the illustrated aspect, the TA field 508 comprises 48 bits. The TA field 508 may comprise an address or identifier of a device transmitting the NDPA frame 422, for example, an address of the transmitting AP. In some aspects, the TA field 508 may instead comprise or be referred to as an SA (source address) field.

[0077] In the illustrated aspect, the CSI sequence field 512 comprises 8 bits. The CSI sequence field 512 may comprise a sequence number for the NDPA frame 422 or other descriptor uniquely identifying the NDPA frame 422.

[0078] In the illustrated aspect, the length of the STA information field 514 may vary. STA information field 514 may include information for each STA from which CSI or other such feedback information is requested.

[0079] Figures 6A-6C illustrate aspects of an STA information field, for example, the STA information field 514. In the aspect illustrated in Figure 6A, when the RA transmission field 506 of the NDPA frame 422 identifies a single STA, the STA information field 514a will include information 602 for only that identified STA. In another aspect illustrated in Figures 6B and 6C, where the RA transmit field 506 of the NDPA frame 422 comprises a broadcast/multicast address for multiple STAs, for example, information for each STA from which the AP is requesting feedback will be included. in the STA information field 514. In Figure 6B, the AP is requesting CSI from STAs 1-4, and information 612-618 for each STA is included in the STA information field 514b. In Figure 6C, in comparison, the AP is requesting SCI only from STAs 5 and 6, and information 622 and 624 is included in the information field of STA 514c. In some aspects, a group or broadcast/multicast address may be included in the RA transmission field 506, but information for only a single STA is included in the STA information field 514. Thus, a broadcast/multicast address may be included in the frame. NDPA 422 for ease of processing and/or uniformity, but a single addressed STA.

[0080] Figures 7A-7C illustrate aspects of STA information included in STA information field 514. Any of the STA information 602-624 illustrated in Figures 6A-6C may be formatted as illustrated in any of Figures 7A-7C. As an example, STA information 612 is illustrated in Figure 7.

[0081] STA information 612 can communicate to a STA the parameters that the STA can use to report CSI. In some respects the CSI returned by the STA is referred to as sound feedback (SF). In such aspects, the STA information 612 may include information or data for the STA to determine and/or calculate SF based on a sound frame included in the NDP frame 404 illustrated in Figure 4, for example. In some aspects, the STA information 612 can be used to determine not to send SF, or to send a form of SF that requires less data.

[0082] In the aspect illustrated in Figure 7A, the STA information 612a may comprise one or more of an AID field 702, an Nss field 704, a Ng field 706, a coefficient field 712, and a codebook field 714, a last received SF field 722, and a last stored SF field 724. In some aspects, the STA information 612a further comprises a reserved field 732 that includes bits in addition to those assigned to fields 702-724 that can be used for either of a variety of purposes. In some respects, fields 702-732 are arranged in an order that differs from the order illustrated in Figure 7A.

[0083] In the illustrated aspect, the AID field 702 comprises 11 bits and may include an AID. As described above, an AID may comprise an Association Identifier of an STA. The AID can comprise any data or descriptor that uniquely identifies the STA. For example, a physical address such as a MAC address may be included in the AID. In some aspects, each of fields 704-724 may include information or data indicating parameters for the STA identified by AID field 702 for use in calculating, determining, or generating the CSI or SF.

[0084] In the illustrated aspect, the field Nss 704 comprises at least 3 bits. Field Nss 704 may indicate a number of spatial channels or CSI feedback streams (e.g. automode) to be computed in the STA identified by AID field 702.

[0085] In the illustrated aspect, the Ng field 706 comprises at least 3 bits. In one aspect, the Ng field 706 comprises at least 2 bits. The Ng field 706 may indicate a grouping of tones in which the STA identified by the AID field 702 serves to generate CSI feedback. For example, tones can correspond to subcarriers in an OFDM system.

[0086] In the illustrated aspect, the coefficient field 712 comprises at least 3 bits. In some aspects, coefficient field 712 comprises one or more bits. Coefficient field 712 may indicate a coefficient size, which may correspond to a quantization used by the STA identified by AID field 702 for CSI matrix entries, as will be described in further detail below. In some respects, the coefficient field 712 is omitted. For example, the NDPA 402 may state that the CSI is formatted as a form of compressed feedback, in which case a coefficient size may not be included.

[0087] In the illustrated aspect, codebook field 714 comprises at least 3 bits. In some aspects, codebook field 714 comprises one or more bits. Codebook field 714 may indicate a quantization for angles that the STA has identified through AID field 702 that is to be used for SF.

[0088] In the illustrated aspect, the last received field SF 722 comprises at least 1 bit. The last received SF field may indicate whether the AP received SF from the STA identified by AID field 702 subsequent to sending a previous NDPA frame. For example, in the aspect discussed with respect to Figure 4, the NDPA frame 402 was transmitted to several STAs to request channel state information. A second STA identified in the NDPA frame 422 transmitted the SCI feedback 418. In the NDPA frame 422, if the AID field 702 in the STA information 612a identifies the second STA, then the last received field SF 722 may indicate whether the AP received the CSI feedback 418 For example, the last received SF field can be set to a value of 0 if CSI 418 feedback has not been received, and can be set to a value of 1 if CSI 418 feedback has been received. In other respects, these values can be inverted. In some aspects, the last received field SF 722 is used as an acknowledgment of the last sound feedback that was polled by the AP.

[0089] In some respects, the last received SF field comprises at least 8 bits and may include a sequence number. In this aspect, the last received SF field indicates the sequence number corresponding to the last transmitted feedback from CSI. For example, the NDPA frame 422 illustrated in Figure 5 includes a sequence number for the NDPA frame 422 or other descriptor uniquely identifying the NDPA frame 422 in the CSI sequence field 512. If SF is received in response to the NDPA frame 422 from an STA - in some aspects, the SF includes the sequence number or other identifier - a following NDPA frame may include the sequence number or other identifier in a last received SF archived from an STA information identifying the STA from which the SF it was received.

[0090] Channel state information transmitted by an STA may not have been received by an AP for any of a variety of reasons. For example, data conflicts, channel interference, or physical obstacles can prevent communication such as a CSI feedback from being received, or reduce the likelihood that the CSI feedback will be received accurately. In some respects, even in situations where the AP receives the CSI from an STA, the last SF field will be set to indicate that the CSI feedback has not been received if the CSI feedback cannot be accurately decoded or processed.

[0091] The last received field SF 722 can be used by the STA identified by field AID 702 for any number of purposes. For example, if the STA transmitted SF in response to the NDPA frame 402, but the last received field SF 722 indicates that the SF was not received by the AP, the STA can determine that there was an error in the transmission. In response, the STA may retransmit the previous SF. As another example, if the STA does not transmit the SF in response to the NDPA frame 402, but the last received field SF 722 indicates that the SF was received, the STA may determine that the received SF is erroneous and may send a communication to the AP instructing the AP to discard received SF.

[0092] In some respects, the last received field SF 722 can be used to adjust a rate used to send SF. For example, when the last received field SF 722 indicates that SF was not received even though the STA has transmitted the SF, the STA may reduce a PHY rate to send a subsequent SF. Similarly, when the last received field SF 722 indicates that a previously transmitted SF was successfully received, the STA may increase a PHY rate to send a subsequent SF. In this way, a rate used to send the SF can be continuously adjusted or tuned for increased performance. In some respects, another parameter or characteristic besides the rate may be adjusted based on whether a previous SF was properly received. For example, a modulation used to send SF may be changed if the previous SF was not received properly.

[0093] In some respects, the STA adjusts the rate only after a series of SFs is received properly, or after a series of SFs is received improperly. For example, the STA may increase a rate after receiving a certain number of NDPA frames having a last received SF field that indicates whether the SF was received properly. In some respects, if a series of SFs has not been received properly, for example, as indicated by the last received fields from CSI in a series of NDPA frames, the STA may transmit a communication to the AP to indicate that the AP should abstain. to submit any additional requests to CSI. In this way, network resources consumed upon transmission from the NDPA to the STA can be conserved when the AP does not appear to be properly receiving any CSI from the STA.

[0094] In some respects, the rate used by the STA to send sound feedback is determined from a rate from a poll message. For example, the rate used to send the CSI 416 probe in the aspect illustrated in Figure 4 can be used to send the CSI 418 feedback. As another example, the rate used to send the CSI 416 probe can be adjusted up or down. based on whether the previous SF was received, as indicated by the last field received from SF, for example.

[0095] Returning to the description of the STA information 612a illustrated in Figure 7, the last stored SF field 724 comprises at least 1 bit. The last stored SF field 724 can indicate whether the AP has stored the last SF received from the STA identified by the AID field 702. Thus, in some aspects, the last stored SF field 724 can indicate whether the AP has stored the SF received from the STA. STA subsequent to sending a previous NDPA frame. For example, in the aspect discussed with respect to Figure 4, the NDPA frame 402 was transmitted to several STAs to request channel state information. A second STA identified in the NDPA frame 422 transmitted feedback from CSI 418. In the NDPA frame 422, if the AID field 702 in the STA information 612a identifies the second STA, then the last stored SF field 724 may indicate whether the AP has stored the feedback. of CSI 418. For example, the last stored SF field can be set to a value of 0 if feedback from CSI 418 has not been stored, and can be set to a value of 1 if feedback from CSI 418 has been stored. In other respects, these values can be reversed.

[0096] In some aspects, the last stored SF field comprises at least 8 bits and may include a sequence number. In this regard, the last stored SF field indicates the sequence number corresponding to the last transmitted CSI feedback. For example, the NDPA frame 422 illustrated in Figure 5 includes a sequence number for the NDPA frame 422 or other descriptor uniquely identifying the NDPA frame 422 in the CSI sequence field 512. If the SF received from an STA was stored subsequent to the NDPA frame 422 - in some aspects, the SF includes the sequence number or other identifier - a subsequent NDPA frame may include the sequence number or other identifier in a last SF stored field of an STA information identifying the STA from from which the SF was received.

[0097] Channel state information transmitted by an STA may not have been stored by an AP for any of a variety of reasons. For example, when the CSI has not been received or is received improperly, the CSI cannot be stored by the AP. In some respects, however, even properly received the CSI may not be stored. For example, an AP may not have enough memory to store the CSI. As another example, the AP may determine not to store the CSI when a specific amount of time has elapsed since the CSI was requested, or when a certain amount of time has elapsed since the CSI was determined by the STA. Therefore, the CSI may have “timed out” and may not be stored. In some respects, the AP can erase the stored CSI that “timed out”. When transmitting the next NDPA, the AP can indicate in the last SF stored field for the STA that transmitted the cleared CSI that the CSI was not stored.

[0098] Last stored SF field 724 can be used by the STA identified by AID field 702 for any number of purposes. For example, if the STA transmitted the SF in response to the NDPA frame 402, but the last stored SF field 724 indicates that the SF was not stored by the AP, the STA may retransmit the previous SF.

[0099] As another example, if the last SF stored field 724 indicates that the previous SF was stored and the STA determines that the channel for which the CSI is requested has changed less than a threshold value, or determines that the CSI has changed less than a threshold value, the STA may determine that the stored CSI and a current CSI are substantially the same and may not send any CSI in response to the NDPA 422 frame. In that circumstance, the STA may instead send a communication to the AP indicating that no CSI will be transmitted, for example as described below. Omitting the CSI can conserve network resources and increase the speed and/or reliability of communications within the network.

[00100] In some aspects where the last SF stored field 724 indicates that the previous SF was stored, the STA may transmit information representing a difference between the stored SF and the current SF. In some respects, complete CSI feedback may comprise a data matrix indicative of the same. In some aspects, the matrix may comprise a plurality of eigenmodes, singular vectors, or singular values. As described above, the STA may determine a spatial filter matrix based on a downlink channel response matrix Hdn,m for that STA. Feedback information (e.g., downlink eigenvectors (eigenvalues, SNR estimates, and so on) may be transmitted in this way, e.g., to the AP. Thus, channel state information and/or SF may be represented as an array. In some respects, a difference between a previous SF and a current SF can also be represented by an array. The difference array, however, may require a smaller number of bytes to represent. Thus, sending a Difference CSI instead of a full CSI can also conserve network resources.

[00101] In some respects, when the last SF received field 722 indicates that the last SF that the AP probed was not received, the last SF received field 724 will always indicate that the AP did not store the last SF probed. For example, when the last SF received field 722 and the last SF stored field 724 are implemented as bits as described above, the last SF stored field 724 will always have a value of 0 when the last SF received field 722 has a value of 0. In other aspects, when the last SF received field 722 indicates that the last SF that the AP probed was not received, the last SF stored field 724 can be used to indicate that a previously stored SF is still being stored by the AP. For example, when the last SF received field 722 and the last SF stored field 724 are implemented as bits as described above and the last SF received field 722 has a value of 0, the last SF stored field 724 can be set to 1 to indicate that a previously stored SF is still being stored and can be toggled to 0 to indicate that a previously stored SF has been deleted or that a complete new SF is requested.

[00102] Some aspects use indicators other than fields 704-724 to indicate parameters for an STA that the STA can use to report to the CSI. In one aspect, a bit or series of bits in the STA information 612a may be used by the STA to query the relevant parameters. The STA may have parameters stored or may retrieve parameters corresponding to one or more of the Nss field 704, Ng field 706, coefficient field 712, and codebook field 714 based on such bits in the STA information 612a.

[00103] Figure 7B illustrates another aspect 612b of the STA information 612. The STA information 612b is illustrated as including fields 702-724 and 732 included in the STA information 612a, as well as a MU-SU field 726. In the illustrated aspect, the MU-SU field 726 comprises at least 1 bit. This field can indicate whether the STA identified by field AID 702 was requested to provide single-user (SU) or multi-user (MU) feedback. In this way, the AP can separately notify each STA identified in the NDPA frame 422 if SU or MU feedback is requested from that respective STA.

[00104] In some aspects, one or more of the fields 702-732 are omitted from the STA information 612. In addition, additional fields may be included in the STA information 612. In some aspects, some of the bits in the STA information 612 are reserved for other uses or for future uses. For example, STA information 612c illustrated in Figure 7C shows appearance including AID field 702, a field 752 having one or more bits that have been reserved for future use, and a previous stored SF field 754. The previous stored SF field may indicate when the AP has stored the last SF it probed from the STA identified in the AID field 702. In some respects, the previous stored SF field 754 may be configured similar to, and/or used similar to, the last stored SF field 724.

[00105] Compared to the aspect illustrated in Figure 7B, another aspect for notifying STAs if MU or SU feedback is requested is illustrated in Figure 8. In the aspect illustrated in Figure 8, a MU/SU field 522 is included in a NDPA 422a frame. The NDPA frame 422a may be formatted or configured similar to the NDPA frame 422, with the exception that the MU/SU field 522 is added to the NDPA frame 422a such that the MU/SU field 522 is separate from the STA information field. 514. The MU/SU field 522 can be used as a “global” indicator to indicate whether SU or MU feedback is requested from all STAs identified in the STA information field 514.

[00106] In some respects, the AP may require or request that the CSI be transmitted using a particular modulation coding scheme (MCS). Figures 9A and 9B illustrate aspects of a frame including information for determining MCS. In the aspect illustrated in Figure 9A, frame 900a comprises an NDPA frame that has been "wrapped" in a control envelope. Thus, frame 900a can be used to request CSI from an STA, for example, in addition to NDPA frame 422 or in place of NDPA frame 422.

[00107] In the illustrated aspect, frame 900a includes frame control field 502, duration field 504, RA transmission field 506, AS field 508, CSI sequence field 512, STA information field 514, and CRC field 516, which are included in NDPA 422. In addition, frame 900a includes a 902 loaded frame control field and an HT 904 control field. In the illustrated aspect, the loaded frame control field 902 comprises at least 2 bits and the HT 904 control field comprises at least 4 bits.

[00108] The HT control field 904 may comprise information indicating an MCS for the STAs identified in the STA information field 514 to use when transmitting SF. In some aspects, the HT control field 604 comprises a link adaptation control field including information that STAs can use to determine the MCS. In some aspects, the link adaptation control field includes a TRQ (Training Request) field, a MAI (Antenna Selection Indication or MCS Request) field, an MFSI (MCS Feedback Sequence Identifier (MFB) field) , and an MFB/ASELC (MCS/Data Feedback and Antenna Selection Command) field. In some respects, frame 900a includes a very high throughput (VHT) control field instead of the high throughput (HT) control field 904. The VHT control field may include information as discussed above with respect to to the HT control field 904. In some aspects, the HT control field 904 or another part of the frame 900a includes information for an STA to determine a rate to transmit the CSI.

[00109] In the aspect illustrated in Figure 9B, frame 900b is illustrated as comprising fields 502-516, 902 and 904 illustrated with respect to frame 900a, as well as an additional field. The additional field may comprise a service set identifier that identifies a network, for example a WLAN. In the illustrated aspect, for example, the BSSID field 912 comprises a Basic Service Set Identifier (BSS) and identifies a BSS. In some aspects, the BSSID 912 field may be set to a MAC address of an AP that transmitted frame 900b.

[00110] Fields 502-516, 902 and 904 illustrated in Figure 9B can be configured as described above with respect to Figure 9A. In some aspects, one or more of these fields comprise additional bits or a smaller number of bits than previously described. In some respects, the BSSID 912 field comprises somewhere between 1-32 octets. In one aspect, the BSSID 912 field comprises 6 octets. In some aspects, fields 502-516 and 902-912 are arranged in an order that differs from the order illustrated in Figure 9A and/or Figure 9B.

[00111] Figure 10 illustrates another aspect of frame 1000 including information for determining MCS. In the aspect illustrated in Figure 10, frame 1000 comprises a CSI probe that has been “wrapped” in a control envelope. Thus, frame 1000 can be used to request at least a part of the CSI from an STA, for example, in addition to or in place of the CSI poll 412.

[00112] In the illustrated aspect, frame 1000 may comprise at least one of: a frame control field 1002, a duration field 1004, a destination address (DA) field 1006, a source address (SA) field ) 1008, a sequence field 1012, a remaining segments field 1014, and a Cyclic Redundancy Check (CRC) field 1016.

[00113] In the illustrated aspect, the frame control field 1002 comprises 16 bits. Also in the illustrated aspect, the duration field 1004 comprises 16 bits and may include a frame length 1000. The CRC field 1016 in the illustrated aspect comprises 32 bits.

[00114] In the illustrated aspect, the DA field 1006 comprises 48 bits. The DA field 1006 may indicate an address of the STA to which the frame 1000 is being transmitted, for example, as discussed above.

[00115] In the illustrated aspect, the SA field 1008 comprises 48 bits. SA field 1008 can indicate an address of the AP that is transmitting frame 1000, for example, as discussed above.

[00116] In the illustrated aspect, the sequence field 1012 comprises 8 bits. Sequence field 1012 may comprise information indicative of the common sequence number for CSI feedback for which the AP is requesting an additional segment. In some aspects, the sequence number indicated by sequence field 1012 is the same as, or is copied from, the sequence number into the immediately preceding NDPA frame. Thus, when frame 1000 is used in place of the CSI poll 412 in Figure 4, the sequence field 1012 can have the same value as the CSI sequence field in the NDPA 402, for example.

[00117] In the illustrated aspect, the remaining segments field 1014 comprises 8 bits. Remaining segments field 1014 indicates the number of CSI feedback segments that the AP expects to receive from the STA addressed by DA field 1006. In some aspects, information included with CSI feedback sent by the STA includes a number of remaining segments left to be transmitted, as will be discussed below. In such aspects, the information in the remaining segments field 1014 may be copied from the remaining segments field of the immediately preceding CSI information. For example, when the AP receives the CSI feedback portion 408 in Figure 4 , the frame 1000 may be sent to the STA that transmitted the CSI feedback portion 408 with the remaining segments field 1014 having a value of 1. In response, the STA may transmit that remaining portion of the CSI 414 feedback.

[00118] Frame 1000 may further comprise loaded frame control field 902 and HT control field 904 described above with respect to Figure 9A. As discussed above, the HT control field 904 may comprise information indicating an MCS or a rate such as a physical layer rate. The STA identified in the DA field 1006 may comprise information indicating an MCS or a rate such as a physical layer rate. The STA indicated in the DA field 1006 can use the information in the HT control field 904 to determine the MCS or rate.

[00119] Figure 11 illustrates one aspect of a CSI inform message to communicate CSI feedback. For example, the CSI inform message can be used to implement the CSI 408 feedback illustrated in Figure 4. The CSI 408 feedback can be determined by an STA in response to an NDPA frame received, for example, the NDPA 402 frame or the NDPA 422 frame described above. As described in further detail below, CSI 408 feedback elements can be generated based on information in the NDPA frame. The CSI inform message may comprise a frame to communicate the CSI feedback.

[00120] In one aspect, the CSI 408 feedback may be generated by one of the STAs identified in the NDPA frame 402 and autonomously transmitted a SIFS period after the NDP frame 404. For example, the first STA identified in an information field STA can generate CSI 408 feedback and autonomously transmit CSI 408 feedback to the AP in a SIFS period after receiving the NDP 404 frame. Other STAs identified in the STA information field can wait for a polling message before transmitting the STA. respective CSI feedback, as discussed above.

[00121] CSI feedback 408 may comprise at least one of: a frame control field 1102, a duration field 1104, a destination address (DA) field 1106, a source address (SA) field 1108 , a CSI 1110 feedback control field, a CSI 1112 feedback field with a computed CSI, or a Cyclic Redundancy Check (CRC) 1114 field. The CSI 408 feedback can be a No Action Confirmation message ( ACK) which may not require an ACK response. In the illustrated aspect, the CSI feedback 408 may comprise a control frame.

[00122] In some respects, instead of the field described above, the CSI 408 feedback may instead comprise a category field, an action field, a sound sequence field, the CSI 1110 feedback control field , and/or a sound report. In such respects, the CSI 408 feedback may comprise an action frame. In some respects, the CSI 1112 feedback field and the sound report contain similar information.

[00123] In some aspects, channel state information and/or SF may be represented as a matrix, as discussed above, and the sound report and/or CSI 1112 feedback field may comprise the matrix or data indicative of the same. As discussed above, the matrix comprises a plurality of eigenmodes, singular vectors, or singular values in some respects.

[00124] There are certain situations in which the STA may determine not to send feedback. For example, SF may not be transmitted if a previous corresponding NDPA/NDP frame has not been received, or if the current SF is substantially similar to the previously transmitted SF. As another example, SF may not be transmitted if the transmission exceeds a transmission opportunity limitation (TXOP) or PPDU. In some respects, the CSI 1112 feedback field is omitted in such situations. Thus, the absence of the CSI 1112 feedback field may indicate that no SF is being transmitted in some respects. For example, if a device such as an AP receives CSI 408 feedback, the device can determine a length of the CSI 408 feedback. The length can be used to determine whether the CSI 1112 feedback field is included, and it can be determined that no SF is passed if the CSI feedback is omitted. In some respects, an indicator in the CSI 1110 feedback control field can signify a reason why SF is not being transmitted.

[00125] Figures 12A-12E illustrate one aspect of a control field for sound feedback, for example, the CSI 1110 feedback control field. In some aspects, the CSI 1110 feedback control field comprises a control field. MIMO with very high throughput (VHT).

[00126] In one aspect illustrated in Figure 12A , the CSI feedback control field 1110a may comprise one or more of a subfield Nc 1202, a subfield Nr 1204, a bandwidth subfield 1206, a subfield Ng 1212, a subfield codebook 1214, a coefficient subfield 1216, a remaining segments subfield 1222, a sequence subfield 1224, a MU/SU subfield 1232, a CSI null subfield 1234, an unreceived NDPA/NDP subfield 1236, and a difference CSI subfield 1238. In some aspects, the CSI feedback control field 1110a further comprises a reserved subfield 1242 that includes bits in addition to those assigned to subfields 1202-1238 that can be used for any of a variety of purposes. In some respects, subfields 1202-1242 are arranged in an order that differs from the order illustrated in Figure 12.

[00127] In the illustrated aspect, subfield Nc 1202 comprises at least 3 bits. Subfield Nc 1202 may indicate a number of columns in the matrix discussed above that represent the CSI for the STA. Using 3 bits provides information regarding at least 5 antennas. In some respects, the 3 bits provide information for 8 antennas.

[00128] In the illustrated aspect, subfield Nr 1204 comprises at least 3 bits. Subfield Nr 1204 can indicate a number of rows in the matrix discussed above. Using 3 bits provides information regarding at least 5 antennas. In some respects, the 3 bits provide information for 8 antennas.

[00129] In some aspects, information from subfield Nss 704 in STA information 612 is used to determine Nc and Nr. In one aspect, the STA sends SF, for example, in the sound inform or CSI feedback field 1112, using exactly the same number of spatial streams (for example, automode) as indicated by the Nss field 704. This can be reflected in Nc and Nr. Using exactly the same number of spatial streams can reduce SF overhead because the SF size will not be larger than the AP determined to be required. This way, resources will not be wasted by sending more feedback than requested by the AP. In other respects, a greater or lesser number of spatial streams may be used by the STA than required by the AP.

[00130] In the aspect illustrated in Figure 12A, the bandwidth subfield 1206 comprises at least 2 bits. Bandwidth subfield 1206 may indicate a CSI feedback bandwidth. For example, the 2 bits can be used to represent 4 different values (i.e. 0, 1, 2 and 3), each of which can correspond to one of the following frequencies: 20 MHz, 40 MHz, 80 MHz and 160 MHz .

[00131] In the aspect illustrated in Figure 12A, subfield Ng 1212 comprises at least 3 bits. Subfield Ng 1212 may indicate a grouping of tones in which the STA generated CSI feedback. Using these 3 bits, 8 different tone group options can be identified. For example, options including DC/band edge tones can be identified. In some aspects, subfield Ng 1212 comprises at least 2 bits.

[00132] In some respects, CSI feedback is generated for each tone being used by the STA. As an example, there can be up to 468 tones when a CSI feedback bandwidth is 160 MHz. Some of the tones, however, can be grouped together such that information is reported on all tones in the group simultaneously. The subfield Ng 1212 can indicate how the tones were grouped and how many tones are in the group. For example, 3-4 tones can be grouped together and the information for those tones averaged to generate CSI feedback.

[00133] In one aspect, the STA sends CSI feedback with tone groups that are no greater than the tone groups indicated by the Ng field 706 in the STA information 612. In some aspects, however, the STA may use a smaller value of Ng than indicated by the Ng 706 field. Using groups that are not larger than the Ng 706 field indicates will decrease the likelihood of MU gains being decreased. This decrease may be due to the AP deciding the Ng indicated in the Ng field 706 based on a MU/SU transmission to use. In other respects, the STA may use tone groups that are larger than the tone groups indicated by field Ng 706.

[00134] In the appearance illustrated in Figure 12A , codebook subfield 1214 comprises at least 3 bits. Codebook subfield 1214 can include information that the AP can use to index into a table indicating how CSI values are quantized. In some aspects, the STA quantizes values using at least as many bits as indicated by codebook field 714 of STA information 612. Using at least as many bits as indicated by codebook field 714 will decrease the probability of that MU gains are diminished. This decrease could be due to the AP having decided on a requested quantization based on whether the AP intends to use SF in a MU or SU protocol. In other aspects, the STA may use fewer bits than indicated by codebook field 714. In some aspects, codebook subfield 1214 comprises one or more bits.

[00135] In the illustrated aspect, the coefficient subfield 1216 comprises at least 3 bits. Coefficient subfield 1216 may indicate a coefficient size, which may correspond to a quantization used by the STA for entries in the matrix described above. In some aspects, coefficient subfield 1216 comprises one or more bits. In some respects, the 1216 coefficient subfield is omitted. For example, SF might be formatted as a compressed feedback, in which case a coefficient size might not be included.

[00136] In some aspects, the STA quantizes the matrix entries using at least as many bits as indicated by coefficient field 712 of STA information 612. Using as many bits as indicated by coefficient field 712 will decrease the probability of that the MU gains are diminished. This decrease could be due to the AP having decided on a requested quantization based on whether the AP intends to use SF for MU or SU. In other aspects, the STA may use fewer bits than indicated by coefficient field 712.

[00137] In the illustrated aspect, the remaining segments subfield 1222 may comprise at least 5 bits. Remaining segments subfield 1222 may indicate a number of segments that must still be transmitted with respect to the CSI feedback to the STA, as discussed above.

[00138] For example, a number of bytes for CSI feedback may be large. For example, in the case of 800 MHz 8x3 uncompressed bandwidth, the number of bytes for the CSI feedback can be approximately equal to 12K. A large CSI feedback may not fit into a MAC Protocol Data Unit (MPDU) due to MPDU size limitations. A maximum MPDU size of approximately 8K can be obtained from the Aggregate MPDU Delimiter Indication (A-MPDU). Additionally, an MPDU size capacity can be even smaller once it is negotiated.

[00139] CSI feedback can be segmented into multiple MPDUs. For example, CSI feedback segments can be transmitted within multiple MPDUs of an A-MPDU. Thus, the remaining segments subfield 1222 may indicate a number of remaining segments of the CSI or SF feedback that must still be transmitted after the current MPDU.

[00140] In the aspect illustrated in Figure 12A, the sequence subfield 1224 can comprise at most 8 bits. Sequence subfield 924 may comprise information indicative of a sequence number that is common among all segments of a CSI feedback transmitted by the STA. In some aspects, the sequence number indicated by sequence field 1224 is the same as, or is copied from, the sequence number from a preceding NDPA frame, for example, from a CSI sequence field.

[00141] In the illustrated aspect, the CSI feedback control field 1110a includes the MU/SU subfield 1232 to indicate whether the associated CSI feedback has been computed for MU or SU. In some aspects, the CSI feedback is determined in accordance with the MU/SU field in an NDPA frame, for example, as illustrated in Figure 7B or 8. In other aspects, the STA determines whether to compute the CSI for SU or MU . In some respects, the calculated feedback for SU can be determined with less resolution. Thus, determining SU feedback instead of MU feedback can reduce processing complexity in the STA or can reduce the amount of network resources used to send feedback. In the illustrated aspect, the MU/SU field comprises at least 1 bit.

[00142] In the illustrated aspect, the null CSI subfield 1234 comprises at least 1 bit. The null CSI subfield 1234 can be used to indicate whether the CSI will be transmitted by the STA. For example, the null CSI subfield 1234 can be set to a value of 0 if no CSI will be transmitted, and can be set to a value of 1 if CSI will be transmitted. In other respects, these values can be inverted. In some respects, the null CSI subfield 1234 may be omitted, and the extent of the CSI feedback 408 is used to determine whether the CSI is being transmitted. In such respects, if it is determined that the CSI is not being transmitted, the CSI feedback control field 1110a may include an indicator which means that the CSI is not being transmitted because a transmission limitation would be exceeded. For example, the CSI feedback control field 1110a may comprise a 1-bit field indicating whether the CSI transmission would exceed a PPDU or TXOP limitation. Exceeding the PPDU or TXOP limitation could occur if a frame containing the CSI is too long to be transmitted, for example.

[00143] In the illustrated aspect, the unreceived NDPA/NDP subfield 1236 comprises at least 1 bit. When the null CSI subfield 1234 indicates that the CSI will not be transmitted, the NDPA/NDP not received field 1236 can be used to indicate a condition that caused the CSI not to be transmitted. In one aspect, a value of 0 in NDPA/NDP not received subfield 1236 indicates that a corresponding NDPA frame was not received, while a value of 1 in NDPA/NDP not received subfield 1236 indicates that a corresponding NDP frame was not received.

[00144] In another aspect, a single value of subfield NDPA/NDP not received 1236 is used to indicate whether an NDPA or an NDP corresponding to an identifier in sequence field 1224 has not been received. For example, a value of 0 can be used to indicate this condition. The other value, which in this example is 1, can be used to indicate that no CSI is being transmitted because the current CSI is within a threshold of a previously transmitted CSI. For example, when an NDPA last stored SF field indicates that the last SF transmitted by the STA was stored, the STA may refrain from sending the current SF if the current SF is substantially similar to the stored SF. In this situation, the unreceived NDPA/NDP subfield 1236 may be set to a value to indicate that the channel has not changed sufficiently to authorize the transmission of additional SF.

[00145] In the illustrated aspect, the difference CSI subfield 1238 comprises at least 1 bit. When the null CSI subfield 1234 indicates that the CSI is being transmitted, the difference CSI subfield can be used to indicate whether the complete CSI is being transmitted or if information representative of a difference is being transmitted. For example, a value of 0 in the difference CSI subfield 1238 may indicate that complete CSI information is being transmitted. A value of 1 in difference CSI subfield 1238, however, may indicate that information representative of a difference between a previously transmitted CSI and the current CSI is being transmitted. For example, when an NDPA's last stored SF field indicates that the STA's last SF was stored in an AP, the STA can calculate and transmit a difference between the current SF and the stored SF, and indicate these actions to the AP using the difference CSI subfield 1238. As discussed above, the difference can in certain respects be represented using a smaller number of bits, and thus can reduce overhead.

[00146] An AP receiving the feedback control field from CSI 1110a can use information there to determine a CSI. In some aspects, such as aspects where the CSI is not transmitted by the STA as indicated by null CSI subfield 1234, the AP may use the previously received or stored CSI. In other respects, the CSI may receive full CSI from the AP, or it may receive data representative of a difference and later calculate the current CSI from the difference and a previously stored CSI, for example, as indicated by the CSI subfield of difference 1238.

[00147] In some aspects, the AP may adjust the parameters to send information to the STA based on information in the CSI feedback control field 1110a. For example, when the NDPA/NDP not received subfield 1236 indicates that a previously transmitted NDPA or NDP was not received, the AP may retransmit the NDPA or NP, or it may reduce a rate such as a PHY rate used to send future NDPAs. and/or NDPs. If the unreceived NDPA/NDP subfield 1236 indicates that a previously transmitted NDPA and NDP have been received, the AP may increase the rate or may adjust another parameter such as a modulation scheme. Additionally, if the CSI feedback control field 1110a indicates that a channel has not changed or has changed very little, for example, using unreceived NDPA/NDP subfield 1236 and/or difference CSI subfield 1238, the AP may decrease the frequency. in which it requests CSI from the STA. Similarly, if the AP receives full CSI each time, or if the channel appears to be changing rapidly, the AP can increase the frequency at which it requests CSI from the STA.

[00148] In some respects, one or more of the fields 1202-1242 are omitted from the feedback control field of CSI 1110. Additionally, additional fields may be included in the feedback control field of CSI 1110. In some respects, some of the bits in the STA information 612 are reserved for other or future uses. For example, the CSI feedback control field 1110b illustrated in Figure 12B shows an aspect including subfield Nc 1202, subfield Nr 1204, bandwidth subfield 1206, remaining segments subfield 1222, sequence number subfield 1224, and optionally the MU/SU subfield 1232. In addition, the CSI feedback control field 1110b includes a null SF subfield 1252 and a previous SF utilize subfield 1254.

[00149] In the illustrated aspect, the null SF subfield 1252 comprises at least 1 bit. Null SF subfield 1252 can indicate whether SF is being transmitted by the STA. In some respects, the null SF subfield is configured similar to, and/or used similar to, the null CSI subfield 1234.

[00150] In the illustrated aspect, the subfield using SF prior to 1254 comprises at least 1 bit. The subfield use previous SF 1254 can indicate whether the SF previously stored in the AP should be used. For example, when a previous SF field stored in an NDPA indicates that the previously transmitted SF was stored in the AP, the subfield use previous SF 1254 can be used to indicate that the stored SF should be used as the current SF, or to indicate that the stored SF must be combined with the difference data being transmitted by the STA. In some aspects, if the null SF subfield 1252 and the previous SF subfield 1254 indicate that no SF is being transmitted, the AP can infer that a previous NDPA frame and/or an NDP frame was not received. Thus, the null SF subfield 1252 may indicate that no CSI is being transmitted, while the use previous SF subfield 1254 indicates a condition that caused the CSI not to be transmitted, such as channel information being absent or a difference between current SF and previous SF being insignificant. A table summarizing one aspect of possible values of the null SF subfield 1252 and the use previous SF subfield 1254 is included below. The table shows how the values correspond to a potential CSI transmission.

[00151] The CSI feedback control field 1110c illustrated in Figure 12C shows an aspect including the Nc subfield 1202, the Nr subfield 1204, the bandwidth subfield 1206, the remaining segments subfield 1222, the Ng subfield 1212, the codebook subfield 1214, coefficient subfield 1216, remaining segments subfield 1222, sequence number subfield 1224, and optionally MU/SU subfield 1232 and/or reserved subfield 1242. Each of these subfields may be configured as described with respect to Figure 12A.

[00152] In comparison to the feedback control field CSI 1110a illustrated in Figure 12A, however, the feedback control field CSI 1110c omits the null CSI subfield 1234 and instead includes a first segment subfield 1262. illustrated, first segment subfield 1262 comprises at least 1 bit. First segment subfield 1262 may be used to indicate whether the CSI feedback being transmitted is the first segment of that CSI. If an AP receives a CSI segment from a new CSI, but the first segment subfield 1262 does not indicate that the received segment is the first segment from the new CSI, then the AP can determine that it has lost at least one previously transmitted segment from the new CSI . The CSI can be identified as new using the sequence number subfield 1224 and/or using the remaining segments subfield 1222. For example, if the remaining segments subfield 1222 associated with a previous CSI segment indicated that the segment was the last segment, any CSI segments that are received in the future can be determined to be associated with the new CSI.

[00153] Additionally, the unreceived NDPA/NDP subfield 1236 and difference CSI subfield 1238 illustrated in Figure 12A have been replaced by a single null and difference CSI subfield 1264 in the CSI feedback control field 1110c. In the illustrated aspect, the null and difference CSI subfield 1264 comprises at least 2 bits. Implementing the null and difference CSI subfield 1264 thus allows the CSI feedback control field 1110c to be implemented using the same number of bits as the CSI feedback control field 1110a. The null and difference CSI subfield 1264 can indicate if regular SF is being transmitted, if a difference between current SF and previous SF is insignificant, and/or if SF is not available. In one respect, SF may not be available if a corresponding NDP or NDPA frame has not been received. Those skilled in the art will appreciate that the null and difference CSI subfield 1264 may be used to indicate the same or similar information as indicated by one or more of the null CSI subfield 1234, subfield NDPA/NDP not received 1236, subfield CSI of difference 1238, SF null subfield 1252 and subfield use previous SF 1254. One aspect of possible values of null CSI subfield and difference 1264 is summarized in the table below. The table illustrates how the values correspond to a potential transmission of CSI.

[00154] Those skilled in the art consider that other values or combinations of values may correspond to the related actions. For example, the actions associated with “0 1” and “1 1” can be reversed in the table above.

[00155] In the table above, values of “1 1” can be used to indicate that the CSI feedback being transmitted is a difference CSI. In other respects, values of “1 1” may be reserved. In some respects, values of “1 1” can be used to indicate that CSI is not being included because the transmission of the CSI feedback would exceed a transmission limitation, such as a PPDU limitation or a TXOP limitation. For example, if a CSI feedback extension, such as the CSI 408 feedback, indicates that no SF is being transmitted, values of “1 1” may indicate that the condition that caused the non-transmission is a TPDU limitation or TXOP

[00156] In some respects, if the extent of the CSI 408 feedback indicates that no SF is being transmitted, one or more of the indicators or subfields discussed above may be used to indicate a condition that caused the SF not to be transmitted. For example, the NDPA/NDP not received subfield 1236, the difference CSI subfield 1238, the use previous SF subfield 1254, and/or the null and difference CSI subfield 1264 can signify what the condition is. In other respects, a new field can be defined to indicate the condition. In still other aspects, one or more bits that would be used for another purpose when the CSI is being transmitted may be used to provide that indication. For example, one or more of the bits in the remaining segments field 1222 can be used to indicate the condition if a length of CSI feedback 408 indicates that SF is not being transmitted.

[00157] CSI feedback control field 1110d illustrated in Figure 12D shows an aspect including subfield Nc 1202, subfield Nr 1204, bandwidth subfield 1206, subfield Ng 1212, codebook subfield 1214 , sequence number subfield 1224, and MU/SU subfield 1232. In the illustrated aspect, however, bandwidth subfield 1206 is illustrated as a channel width subfield. Additionally, subfield Ng 1212 is illustrated as a grouping subfield. Additionally, the MU/SU subfield 1232 is illustrated as a feedback type subfield, and the sequence number subfield 1224 is illustrated as a sound sequence subfield. Each of these subfields can be configured as described with respect to Figure 12A.

[00158] CSI feedback control field 1110d further includes reserved subfield 1242. In the appearance illustrated in Figure 12D, reserved subfield 1242 can be used to indicate whether CSI will be transmitted. Thus, reserved subfield 1242 may indicate that the CSI feedback frame 408 is a null feedback frame, for example, omitting information from the CSI feedback field 1112 or omitting the CSI feedback field 1112 entirely. reserved 1242, therefore, can be used in some respects to indicate information similar to the null CSI subfield 1234, discussed above.

[00159] In the appearance illustrated in Figure 12D, reserved subfield 1242 may instead or additionally be used to indicate whether the CSI feedback being transmitted is the first segment of that CSI. The reserved subfield 1242, therefore, can be used in some respects to indicate information similar to the first segment subfield 1262 discussed above.

[00160] In the aspect illustrated in Figure 12D, reserved subfield 1242 may instead or additionally be used to indicate a number of remaining segments of the CSI or SF feedback that must be transmitted after the current MPDU. The reserved subfield 1242, therefore, can be used in some respects to indicate information similar to the remaining segments subfield 1222 discussed above. Thus, reserved subfield 1242 can indicate which of a plurality of feedback segments is first and how many feedback segments are missing. The first segment and remaining segments indication can alert a receiver, such as an AP, as to how many segments to expect and whether all segments have been received.

[00161] In the appearance shown in Figure 12D, reserved subfield 1242 is illustrated as comprising 4 bits. In one aspect, one of the 4 bits can be used to indicate whether a segment of the feedback being transmitted is a first segment. For example, a bit value of “1” can be used to indicate that the segment is a first segment, and a bit value of “0” can indicate that the segment is not a first segment. In some respects, B15 is used as bit one.

[00162] In such respects, one or more bits remaining in reserved subfield 1242 may be used to indicate a number of segments that are yet to be transmitted. For example, if bit B15 is used to indicate whether the segment being transmitted is a first segment, bits B12-B14 can be used to indicate the number of segments remaining. A value of “111” might indicate that there are still seven segments left, a value of “110” might indicate that there are still six segments left, and so on. If a single segment is being transmitted, the first segment bit can be set to “1” and the remaining segment bits are all set to “0”. If B12-B14 indicates the number of segments remaining, and B15 indicates that the segment is a first segment, then reserved subfield 1242 can have a value of “0001” to indicate that a single feedback segment is being transmitted.

[00163] In some respects, the feedback can be divided into no more than eight segments. In these respects, there can be a maximum of seven segments remaining. Seven segments can be left, however, only if the segment being transmitted is the first segment. Thus, there would be no circumstance in which a segment that is not the first segment would indicate that seven segments are left. In such respects, the first segment bit can be set to “0” and the remaining segment bits all set to “1” to indicate that the CSI is not being transmitted. If B12-B14 indicates the number of segments remaining and B15 indicates whether the segment is a first segment, then reserved subfield 1242 can have a value of “1110” to indicate that a null feedback frame is being transmitted. Thus, an indication that the first segment is not being transmitted in combination with an indication that the maximum number of segments remaining must still be transmitted can alert a receiver, such as an AP, that no CSI is being transmitted.

[00164] In some respects, if reserved subfield 1242 indicates that no CSI is being transmitted, all bits preceding reserved subfield 1242 may be used as reserved bits. Thus, if a null feedback frame is transmitted, bits B0-B11 can be reserved. In some respects, one or more of these bits may be used to indicate a condition that caused the CSI not to be transmitted.

[00165] For example, bits B10-B11 may be used for a reason that feedback is missing. The reason may relate to the reception of sound information, a transmission limitation, or calculated CSI, among other reasons. In some respects, B10-B11 are set to a value of “00” if sound information is missing, for example, if an NDPA or NDP frame was not received or was received incorrectly. In some respects, B10-B11 are set to a value of “01” if feedback cannot be sent due to a TXOP limitation. In some respects, B10-B11 are set to a value of “10” if feedback cannot be sent due to a PPDU limitation. In some aspects, B10-B11 are set to a value of "11" if previously transmitted channel state information is substantially similar to the current channel state information. In some respects, the value of “11” is reserved for B10-B11.

[00166] In the appearance illustrated in Figure 12D, the coefficient size subfield is omitted. Additionally, subfield MU/SU 1232 is disposed before any remaining segments, first segment, and null feedback information or indicators. Additionally, sequence number subfield 1224 is arranged after such information or pointers and therefore after reserved field 1242.

[00167] Figure 12E illustrates an aspect of the CSI feedback control field 1110e showing the reserved subfield 1242 being divided into a remaining segments subfield 1272 and a first segment subfield 1274. In the illustrated aspect, the remaining segments subfield 1272 comprises bits B12-B14 of field 1110c and subfield first segment 1274 comprises bit B15 of field 1110e. The segments remaining subfield 1272 may be used to transmit similar information, or may be configured similar to the segments remaining subfield 1222 discussed above. First segment subfield 1274 may be used to transmit information similar or configured similar to first segment subfield 1262 discussed above. When considered together, the remaining segments subfield 1272 and the first segment subfield 1274 can be used to transmit information similar to that of the null CSI subfield 1234 and/or the null SF subfield 1252, discussed above.

[00168] Remaining segments subfield 1272 and first segment subfield 1274 may be set to various values as described above with respect to bits B12-B14 and B15, respectively, to indicate CSI feedback information. Exemplary values of these subfields, as well as the remaining subfields 1202-1232 of field 1110c, are enumerated in the table below. The values below are illustrative only and are not intended to be limiting. Those of ordinary skill in the art will appreciate that other values may be used or other information may be indicated by the illustrated values.

[00169] Figure 13 illustrates an aspect of an access point (AP) 1300 for use within system 100. The AP 1300 may comprise the AP 110 illustrated in Figure 1 or Figure 2. As discussed above, the AP 1300 may be implemented as a wireless device, for example, as a wireless device 302 illustrated in Figure 3. The AP 1300 can be used to communicate with a user terminal or STA as described above with respect to Figures 4-12.

[00170] The AP 1300 may comprise an NDPA module 1302 to generate an NDPA frame, for example, the NDPA frame 402 or 422. By generating an NDPA frame, the NDPA module 1202 may determine whether SF has been received from an STA in response to a previous NDPA frame or in response to a polling message. The SF may be received by a receiving module 1204, for example, and an NDPA frame may have been transmitted by a transmitting module 1206. The polling message may be generated by a polling module 1208. The result of this determination may be included in the NDPA frame, for example in a Last Received SF field as discussed above.

[00171] The NDPA module 1302 can further determine whether the last SF probed by the poll module 1308 has been stored, e.g. stored in a memory 1312. The result of this determination can be included in the NDPA frame, e.g. in a last field SF stored or a previous SF field stored as discussed above.

[00172] In some respects, the NDPA module 1302 is configured to envelop an NDPA frame in a control envelope, for example, as shown in Figure 9A or Figure 9B. In these respects, the NDPA module 1302 may be configured to determine an HT and/or MCS control field for an STA to send the requested CSI. The NDPA 1302 module can also determine a rate at which the STA should use to send the requested CSI. The result of this determination can be included in the enveloped NDPA framework.

[00173] The NDPA 1202 module can be configured to determine one or more STAs from which CSI feedback information is being requested. Information identifying these STAs may be included in an STA information field, as described above with respect to Figures 6A-6C.

[00174] The NDPA 1302 module can be configured to assign parameters to each of the STAs for use in CSI feedback reporting. For example, the NDPA module 1202 can determine whether each STA or all STAs collectively should compute CSI for SU or MU. The NDPA 1302 module can additionally be configured to determine a number of spatial channels or streams (e.g. auto modes) of CSI feedback to be computed in the STAs, a grouping of tones in which the STAs must generate CSI feedback, a size of coefficient corresponding to a quantization used by STAs for matrix entries of CSI feedback, and/or codebook information indicating a quantization for angles that STAs should use for CSI feedback, as described above with respect to Figure 7. In some respects, the NDPA 1302 module is configured to determine one or more of the above parameters based on whether the CSI feedback will be used for MU or SU.

[00175] In some respects, the NDPA module 1302 is configured to determine a frequency for sending NDPA frames, for example, based at least in part on the CSI or changing channel conditions indicated in the CSI feedback, as discussed above. The NDPA 1302 module can be further configured to generate or determine any of the other information described above with respect to the NDPA 422 frame. In some aspects, the functionality of the NDPA 1302 module is implemented using at least the 230 controller illustrated in Figure 2.

[00176] Receive module 1304 may be used to receive control information, CSI feedback, and/or other communications from a STA such as communications indicating that no CSI feedback will be transmitted from the STA. The received data may be demodulated, downconverted, or otherwise processed by the receiving module 1304 or other module. Receive module 1304 may be implemented using one receiver, for example, receiver 312 illustrated in Figure 3, or a combination of receivers, for example, receivers 222a-222ap illustrated in Figure 2. Receive module 1304 may be implemented in a transceiver, and may comprise a demodulator and/or a receive data processor, for example the RX data processor 242. In some aspects, the receive module 1304 comprises an antenna and a transceiver, for example the antenna 224 and transceiver 222. The transceiver may be configured to demodulate incoming wireless messages. Messages can be received through the antenna.

[00177] Transmission module 1306 can be used to transmit NDPA frames and/or polling messages. In some aspects, the transmission module 1306 is configured to wirelessly transmit the NDPA frame, for example, to the user terminal 120. The transmission module 1306 may be implemented using a transmitter, for example, the transmitter 310 illustrated in Figure 3, or a combination of transmitters, for example, the transmitters 222a-222ap illustrated in Figure 2. The transmission module 1306 may be implemented in a transceiver, and may comprise a modulator and/or a transmission data processor, for example. , the TX data processor 210. In some aspects, the transmission module 1306 comprises an antenna and a transceiver, for example, antenna 224 and transceiver 222. The transceiver may be configured to modulate outgoing wireless messages following to a user terminal or STA. Messages can be transmitted via the antenna.

[00178] The polling module 1308 can be used to generate polling messages for transmission to the STAs, e.g. any of the CSI polls 412, 416. The polling module can determine which STA to transmit a polling message with based on information received through the reception module 1304. For example, remaining segment information received in a control or field message through the reception module 1304 can be used by the polling module 1308 to generate a polling message.

[00179] In some respects, the 1308 polling module is configured to envelop a polling message in a control envelope, for example, as shown in Figure 10. In these respects, the 1308 polling module may be configured to determine a field of HT and/or MCS control for an STA to send the requested CSI. The result of this determination can be included in the enveloped polling message.

[00180] The poll module 1308 can be further configured to generate or determine any of the other information described above with respect to polling messages such as the CSI 412 poll or the CSI 416 poll, or the frame 1000, for example , to include the sequence number of an NDPA frame. In some aspects, the functionality of the probe module 1308 is implemented using at least the controller 230 and/or the programmer 234 illustrated in Figure 2.

[00181] Memory 1312 may be configured to store CSI information received from one or more STAs, for example via the receive module 1304. As described above, the CSI may be represented as an array, which may be stored in memory 1312. Other formats for representing the CSI may additionally be stored in memory 1312. In some respects, CSI that has timed out or expired may be periodically erased from memory 1312. Memory 1312 may be volatile or non-volatile , or it can be a combination of both. In some aspects, the functionality of memory 1312 is implemented using at least memory 232 illustrated in Figure 2 or memory 306 illustrated in Figure 3.

[00182] The AP 1300 may further comprise the CSI processing module 1314 for processing received CSI feedback, e.g. received using the receiving module 1304. The CSI processing module 1314 may be configured to process feedback from CSI using one or more of the parameters indicated in a received message, for example according to SU or MU. The CSI processing module 1314 can also be configured to process CSI feedback using one or more of the parameters indicated in a previously transmitted frame, for example, using MCS transmitted in an enveloped frame.

[00183] In some aspects, the CSI processing module 1314 is configured to determine if a communication is received from an STA indicating that the STA has no CSI feedback to transmit. For example, a null CSI field may be received in a CSI feedback indicating that no CSI will be received, or one or more values in a reserved field, such as a first segments field and a remaining segments field, may indicate that no CSI will be received. The CSI processing module can be configured to determine whether previously stored CSI should be used, for example by evaluating a null SF field and a field using previous SF. In some aspects, the CSI processing field is configured to change a rate or modulation to transmit CSI requests based on information received in the CSI feedback, as described above. In some respects, the 1314 CSI processing module may determine that no CSI will be received based on an extension of the communication. The 1314 CSI Processing Module can also be configured to determine a condition that caused the CSI not to be received.

[00184] In some respects, the CSI processing module 1314 is configured to generate the CSI from a received difference in a CSI feedback. For example, when a difference CSI field or a field using previous SF indicates that data representative of a difference between a current CSI and a previously stored CSI is being transmitted, the CSI processing module 1314 can determine the current CSI using the difference and CSI data stored in memory 1312.

[00185] In some respects, the CSI processing module 1314 is configured to analyze the received CSI feedback to determine a frequency to send NDPA frames, for example, based at least in part on CSI or changing channel conditions indicated in CSI feedback. This information may be communicated to the NDPA module 1302. In some aspects, the functionality of the CSI processing module 1210 is implemented using at least the controller 230 and/or the RX data processor 242 illustrated in Figure 2.

[00186] Those of skill in the art will consider various circuits, chips, modules and/or components, which may comprise software or hardware, or both, that may be used to implement the modules described above with respect to the AP 1300. One or more of the AP 1300 modules can be implemented partially or fully in the 304 processor illustrated in Figure 3.

[00187] Figure 14 illustrates an aspect 1400 of a method for communication. The method may be implemented by the AP 1200, for example, to request channel status information from an STA and to optionally inform the STA as to whether the previous SF was received from the STA and/or stored in the AP. Although the method below is described with respect to the elements of the AP 1200, those of skill in the art will appreciate that other components can be used to implement one or more of the steps described herein.

[00188] In step 1402, a first request for channel status information is transmitted, for example, using transmission module 1204. The first request may comprise a null data packet advertisement or a polling message, for example. The NDPA module 1302 or the probe module 1308 can be used to generate the request.

[00189] Proceeding to step 1404, it is determined whether channel state information was received in response to the first request or whether channel state information was stored subsequent to transmission. This determination can be performed by the CSI 1314 processing module, for example. Channel status information may be received at the receiving module 1304, or may be stored in memory 1312.

[00190] Moving to step 1406, a second request comprising an indicator signifying a result of the determination is transmitted, for example, using transmission module 1306. The second request may comprise an NDPA frame, for example. In some respects, the result of the determination is indicated in a last SF received field, a last SF stored field, a previous SF stored field, as discussed above with respect to Figure 7. The NDPA 1302 module and/or the CSI processing module 1314 can be used in creating the second request.

[00191] Figure 15 illustrates an aspect 1500 of a method for communication. The method may be implemented by the AP 1200, for example, to receive data representative of a part of the channel state information, or to receive notice that the channel state information will not be transmitted. In some aspects, method 1500 may be used to determine why channel state information is not being transmitted from an STA. Although the method below is described with respect to the elements of the AP 1200, those skilled in the art will appreciate that other components may be used to implement one or more of the steps described herein.

[00192] In step 1502, a request for channel status information is transmitted, for example, by transmission module 1306. Later, in step 1504, a communication is received. The communication may comprise a first indicator and a second indicator signifying that channel status information is included in the communication. If the first indicator and/or the second indicator means that channel state information is included, the first indicator and/or the second indicator further means that the channel state information comprises information representative of a difference between current channel and previously received channel status information. The first and second indicators may comprise two or more of a null CSI field, an unreceived NDPA/NDP field, a null SF field, a use previous SF field, and/or a null and difference CSI field, as described above with reference to Figure 12 . Communication may be received using, for example, a receive module 1304. Communication may be processed by the CSI processing module 1314, for example, to determine whether CSI information is included and/or to determine if CSI stored in the AP will be used.

[00193] Figure 16 illustrates an aspect 1600 of a method for communication. The method may be implemented by the AP 1200, for example, to notify an MCS STA to transmit the CSI. Although the method below is described with respect to the elements of the AP 1200, those skilled in the art will appreciate that other components may be used to implement one or more of the steps described herein.

[00194] In step 1602, the modulation coding scheme (MCS) or a rate for receiving channel status information is determined. In some respects, the NDPA 1302 module can perform the determination. In other aspects, the probe module 1308 may determine to perform the determination. In some aspects, the CSI processing module 1312 may be configured to perform some or all of the determination, for example, based on communications received from an STA such as whether a state of a channel is changing. Communications may be received using receive module 1304, for example.

[00195] Next, in step 1604, an envelope frame is transmitted. The envelope frame may comprise a control field indicating the determined MCS or rate and at least one field indicating that at least a part of the channel state information is requested. The envelope frame may comprise an enveloped NDPA frame, as discussed above with respect to Figure 9A, or an enveloped poll message, as described above with respect to Figure 10. The envelope frame may be transmitted by transmission module 1306, for example.

[00196] Figure 17 illustrates an aspect of a station (STA) 1700 for use within the system 100. The STA 1700 may comprise any of the user terminals 120 illustrated in Figure 1 or Figure 2. As discussed above, the STA 1700 may be implemented as a wireless device, for example, as a wireless device 302 illustrated in Figure 3. The STA 1700 may be used to communicate with an AP as described above with respect to Figures 4-12.

[00197] The STA 1700 may comprise a receive module 1702 for receiving an NDPA frame and/or a CSI probe. For example, receive module 1702 can be configured to receive NDPA frame 402 or 422 and/or any of the CSI probes 412, 416. Additionally, receive module 1702 can be configured to receive an NDP frame and frames that comprise enveloped NDPA frames or enveloped polling messages. The received data may be demodulated, down-converted, or otherwise processed by the receiving module 1702 or other module. Receiver module 1702 may be implemented using a receiver, for example, receiver 312 illustrated in Figure 3, or a combination of receivers, for example, 254m-254-mu or 254xa-254xu receivers illustrated in Figure 2. A module receiver 1702 may be implemented in a transceiver, and may comprise a demodulator and/or a receive data processor, for example, the RX data processor 270. In some aspects, the receive module 1702 comprises an antenna and a transceiver, for example antenna 252 and transceiver 254. The transceiver may be configured to demodulate incoming wireless messages. Messages can be received through the antenna.

[00198] The STA 1700 may further comprise a CSI feedback module 1704 for determining CSI feedback. The CSI Feedback Module 1704 can be configured to determine CSI feedback based on a received NDP frame associated with an received NDPA frame. The CSI can be represented as a matrix, as discussed above. CSI feedback parameters can be determined in some respects by the 1704 CSI feedback module. In some respects, the CSI feedback module is configured to determine the MCS from communication such as a control envelope received through the module. 1702. For example, the CSI feedback module can determine the MCS to CSI from an HT control field included in an enveloped NDPA frame, as described above with respect to Figure 9A.

[00199] The CSI 1704 feedback module can be configured to determine whether to compute the regular/full CSI, or whether to compute a difference between a previous CSI and the current CSI. For example, the CSI 1704 feedback module can evaluate a last SF field stored or a previous SF field stored in an NDPA, as well as the conditions of a channel, as discussed above. If a channel condition is substantially similar to a condition when a previous SF was stored, the CSI 1704 feedback module can determine not to send any CSI. In some aspects, the CSI 1704 feedback module can determine that the SF has been stored in an AP, and it can compute the difference data to send to the AP to calculate the current SF. CSI 1704 feedback module determinations may be included in the CSI feedback, for example, the CSI 408 feedback illustrated in Figures 11 and 12. In some aspects, the determinations may be indicated by a null CSI field, a CSI field of difference, a null SF field, a use previous SF field, a null and difference CSI field, and/or one or more values in a reserved field such as a first segments field and a remaining segments field. A reason that the CSI feedback module 1704 did not send CSI could be indicated by an unreceived NDPA/NDP field, a difference CSI field, a null SF field, a use previous SF field, a null CSI field, and difference, and/or in fields that became reserved when it was determined that no CSI was transmitted, for example, in a CSI feedback communication transmitted to the AP. In some aspects, the CSI feedback module 1704 is configured to generate a CSI feedback communication having an extension that indicates that the CSI will not be transmitted. In some aspects, the CSI feedback module 1704 may determine that the CSI feedback will not be transmitted due to a transmission limitation, such as a PPDU or TXOP limitation.

[00200] The CSI 1704 Feedback Module may be additionally configured to generate or determine any of the other information described above regarding the CSI 408 Feedback. In some respects, the functionality of the CSI 1704 Feedback Module is implemented using the minus the controller 280 and/or the channel estimator 278. In some aspects, the CSI feedback module 1704 comprises a quantizer for quantizing angles and/or inputs in a matrix representing the CSI.

[00201] The STA 1700 may further comprise a rate adjustment module 1706 for determining a rate adjustment used for sending the CSI feedback determined by the CSI feedback module 1704. For example, the rate adjustment module 1706 may increase a PHY rate for sending the CSI feedback when a last received SF field in one or more received NDPA frames indicates that the CSI feedback that the STA 1700 has been transmitting has been successfully received. Similarly, rate adjusting module 1706 may decrease a rate such as a PHY rate if a last received SF field, a last stored SF field, or a previously stored SF field indicates that a previously transmitted SF was not received or could not be stored. In some aspects, the rate adjustment module 1706 can adjust other parameters of the CSI feedback, for example, a modulation of the CSI feedback. The rate adjustment module 1706 can determine or adjust a rate based on a control field in an envelope, as discussed above. Rate adjusting module 1706 may also be configured to determine a rate at which a message, e.g., a polling message, is received, e.g., at receiving module 1702.

[00202] The 1706 Rate Tuning Module can be configured to perform any of the Rate Tuning procedures described above with respect to Figure 7. In some respects, the 1706 Rate Tuning module functionality is implemented using at least the controller 280. In some aspects, rate adjustment module 1706 queries values or parameters in a memory, such as memory 282, for example, to determine an appropriate rate or adjustment.

[00203] The STA 1700 further comprises a transmission module 1708 for transmitting CSI feedback. For example, the 1708 transmit module can be configured to transmit the CSI feedback determined by the 1704 CSI feedback module. The transmit module can be configured to transmit at a rate determined by the 1706 rate adjustment module or use another parameter determined by the rate adjustment module 1706. In some aspects, the transmission module 1708 is configured to wirelessly transmit the CSI feedback, for example, to the AP 110. The transmission module 1708 may be implemented using a transmitter, for example the transmitter 310 illustrated in Figure 3, or a combination of transmitters, for example the 254m-254mu or 254xa-254xu transmitters illustrated in Figure 2 . The transmission module 1708 may be implemented in a transceiver and may comprise a modulator and/or a transmission data processor, for example, the TX data processor 288. In some aspects, the transmission module 1708 comprises a antenna and a transceiver, for example antenna 252 and transceiver 254. The transceiver can be configured to modulate outgoing wireless messages going to an AP. Messages can be transmitted via the antenna.

[00204] Those of skill in the art will consider various circuits, chips, modules and/or components, which may comprise software or hardware or both, which may be used to implement the modules described above with respect to the STA 1700. One or more of the STA modules 1700 may be partially or fully implemented in the processor 304 illustrated in Figure 3.

[00205] Although described separately, it should be noted that the functional blocks described with respect to the AP 1300 and STA 1700 need not be separate structural elements. Similarly, one or more of the function blocks or parts of the functionality of the various blocks may be incorporated into a single chip. Alternatively, the functionality of a specific block can be implemented on two or more chips. In addition, additional modules or functionality may be implemented in the AP 1300 and STA 1700. Similarly, a smaller number of modules or functionality may be implemented in the AP 1300 and STA 1700, and the components of the AP 1300 and/or the STA 1700 may be arranged in any of a plurality of configurations. Additional couplings or a smaller number of couplings between the various modules illustrated in Figures 2, 3, 13 and 17 or between additional modules can be implemented.

[00206] Figure 18 illustrates an aspect 1800 of a method for communication. The method may be implemented by the STA 1700, for example, to determine whether transmitted SF has been received and/or stored at an AP. Although the method below is described with respect to the elements of the STA 1700, those skilled in the art will appreciate that other components may be used to implement one or more of the steps described herein.

[00207] In step 1802, a first request for channel state information is received, for example, using the receive module 1702. The first request may comprise a null data packet advertisement or a polling message, for example.

[00208] In step 1804, a frame comprising channel state information is transmitted. Channel status information may be determined using the CSI feedback module 1704, for example, and may be transmitted using the transmission module 1708, for example. The CSI feedback can be determined using the first request received in step 1802.

[00209] Proceeding to step 1806, a second request is received. The second request comprises a first indicator signifying that channel state information was received in response to the first request or that channel state information was stored subsequent to transmission. The second request may be received using receive module 1702, for example. The second request may comprise an NDPA frame. In some respects, the second request is processed by the CSI feedback module 1704 and/or the rate adjustment module 1706 to determine whether to send CSI feedback or to adjust a parameter such as a rate used to send the CSI.

[00210] Figure 19 illustrates an aspect 1900 of a method for communication. The method may be implemented by the STA 1700, for example, to determine whether to transmit the CSI, and in some aspects to indicate to an AP whether the transmitted CSI comprises a difference CSI. Although the method below is described with respect to the elements of the STA 1700, those of skill in the art will appreciate that other components can be used to implement one or more of the steps described herein.

[00211] In step 1902, a message indicating that channel state information is requested is received, for example, using the receive module 1702. In some aspects, the message comprises an NDPA frame or a polling message. The message can indicate whether the previously transmitted SF is stored on an AP.

[00212] Subsequently, in step 1904 it is determined whether to transmit channel status information. The determination can be performed by the CSI 1704 feedback module, for example. The CSI feedback module 1704 can assess whether a channel condition has changed, and whether CSI is stored in the AP, for example, as described above.

[00213] Moving to step 1906, a communication is transmitted. The communication may comprise a first indicator and a second indicator signifying a result of the determination. If the first indicator and/or the second indicator means that the channel state information will be transmitted, the first indicator and/or the second indicator can mean that the channel state information comprises information representative of a difference between the state information current channel status and previously transmitted channel status information. The first indicator may comprise a null CSI field, a null SF field and/or a part of a null and difference CSI field, for example. The second indicator may comprise a difference CSI field, a previous use SF field, and/or a part of a difference and null CSI field, for example. Indicators can be determined by the CSI 1704 feedback module, for example. The communication may comprise CSI feedback, for example, CSI 408 feedback, or other communication indicating whether the CSI will be transmitted. Communication can be transmitted using transmission module 1708, for example.

[00214] Figure 20 illustrates an aspect 2000 of a method for communication. The method may be implemented by the STA 1700, for example, to determine MCS for transmit CSI. Although the method below is described with respect to the elements of the STA 1700, those skilled in the art will appreciate that other components may be used to implement one or more of the steps described herein.

[00215] In step 2002, an envelope frame is received, for example, using the reception module 1702. The envelope frame may comprise a control field indicating a modulation coding scheme (MCS) for transmitting frame state information. channel, and at least one field indicating that at least some of the channel state information is requested. The envelope frame may comprise an enveloped NDPA frame, as discussed above with respect to Figure 9A, or an enveloped solder message, as described above with respect to Figure 10.

[00216] Subsequently, in step 2004, at least that part of the channel state information requested by the frame is transmitted, for example, using the transmission module 1708. The CSI feedback module 1704 and/or the adjustment module of rate can extract MCS from the control field in the received envelope frame to determine how to send the CSI. Channel status information may be transmitted as CSI feedback such as CSI feedback 408. Channel status information may be determined by the CSI feedback module 1704, for example, as described above.

[00217] Figure 21 illustrates an aspect 2100 of a method for communication. The method may be implemented by the AP 1200, for example, to determine that channel state information will not be received, and to determine why channel state information is not being transmitted from the STA. Although the method below is described with respect to the elements of the AP 1200, those of skill in the art will appreciate that other components can be used to implement one or more of the steps described herein.

[00218] In step 2102, a request for channel status information is transmitted, for example, via transmission module 1306. Later, in step 2104, a communication is received. Communication can comprise an indicator. Communication may be received using receive module 1304, for example.

[00219] Upon receipt of the communication, it is determined whether the communication does not include channel status information based on an extension of the communication in step 2106. Additionally, in step 2108, a condition that caused the channel status information to not was received is determined based on an indicator value. The indicator may comprise an unreceived NDPA/NDP field, a use previous SF field, and/or a null and difference CSI field, as described above with respect to Figure 12. The indicator may further comprise a bit, field, or other significant indicative of whether a transmission limitation would be exceeded upon transmission of channel state information. The determination at step 2106 and/or step 2108 can be performed by the CSI processing module 1314, for example.

[00220] Figure 22 illustrates an aspect 2200 of a method for communication. The method may be implemented by the STA 1700, for example, to determine whether to transmit the CSI, and to indicate to an AP a reason why the CSI is not being transmitted. Although the method below is described with respect to the elements of the STA 1700, those of skill in the art will appreciate that other components can be used to implement one or more of the steps described herein.

[00221] In step 2202, a message indicating that channel state information is requested is received, for example, using reception module 1702. In some aspects, the message comprises an NDPA frame or a polling message. The message can indicate whether the previously transmitted SF is stored on an AP.

[00222] Subsequently, in step 2204, the non-transmission of channel status information is determined. The determination can be performed by the CSI 1704 feedback module, for example. The CSI feedback module 1704 can assess whether a channel condition has changed, whether CSI is stored in the AP, and/or whether a frame including the CSI would be too long for transmission, for example, as described above.

[00223] Moving to step 2206, a communication comprising an indicator is generated. A communication extension is based on the determination in step 2204. For example, the CSI feedback field can be omitted to make the communication of a certain extension. Also, an indicator value is based on a condition that caused channel state information not to be transmitted. The indicator may comprise a difference CSI field, a previous use SF field, and/or a part of a difference and null CSI field, for example. The indicator may further comprise a bit, field, or other signifier indicative of whether a transmission limitation would be exceeded upon transmission of the channel status information. The generation and/or determination of the extent or value of the indicator can be determined by the CSI 1704 feedback module, for example. Communication may comprise CSI feedback, for example, CSI 408 feedback, or other communication indicating whether the CSI will not be transmitted. The indicator can be included in a CSI feedback control field.

[00224] In step 2208, communication is transmitted. Communication can be transmitted using, for example, transmission module 1708.

[00225] Figure 23 illustrates an aspect 2300 of a method for communication. The method may be implemented by the AP 1200, for example, to determine that channel state information will not be received, and to determine why channel state information is not being transmitted from a STA. While the method below is described with respect to the elements of the AP 1200, those skilled in the art will appreciate that other components may be used to implement one or more of the steps described herein.

[00226] In step 2302, a request for channel status information is transmitted, for example, via transmission module 1306. Subsequently, in step 2304, communication is received. The communication may comprise a first field for indicating whether a first segment of channel state information is being received in the communication, and a second field for indicating a number of segments of channel state information which are yet to be received. The first and second fields can be parts of a reserved field, such as a first segment field and a remaining segment field. Communication can be received using, for example, receive module 1304.

[00227] Upon receipt of the communication, it is determined whether the communication includes channel state information based on the first field and the second field in step 2306. For example, it can be determined that no channel state information is included in the communication if the first field indicates that a first segment of the channel state information is not included in the communication and a value of the second field is at least as large as a maximum number of remaining segments.

[00228] Additionally, in step 2308, a condition that caused the channel state information not to be received is determined if the first field and the second field indicate that the communication does not include channel state information. The condition can be determined based at least in part on two or more bits adjacent to the first field or the second field. For example, bits that can be used for a different purpose can become reserved when the first field and the second field indicate that the communication does not include channel state information, as described above with respect to Figure 12. The determination in step 2306 and/or step 2308 can be performed, for example, by the CSI processing module 1314.

[00229] Figure 24 illustrates an aspect 2400 of a method for communication. The method may be implemented by the STA 1700, for example, to determine whether to transmit the CSI, and to indicate to an AP why the CSI is not being transmitted. Although the method below is described with respect to the elements of the STA 1700, those skilled in the art will appreciate that other components may be used to implement one or more of the steps described herein.

[00230] In step 2402, a message is received indicating that channel status information is requested, for example using reception module 1702. In some aspects, the message comprises an NDPA frame or a polling message. The message may indicate whether previously transmitted SF is stored on an AP.

[00231] Subsequently, in step 2404, a communication is generated. The communication may comprise a first field for indicating whether a first segment of channel state information is being transmitted and a second field for indicating a number of segments of channel state information which are yet to be transmitted. The first and second fields can be parts of a reserved field, such as a first segment field and a remaining segment field. The generation can be performed by the CSI 1704 feedback module, for example. A CSI feedback module 1704 can assess whether a channel condition has changed, whether the CSI is stored on the AP, and/or whether a frame indicating the CSI would be too long for transmission, for example, as described above. Communication may comprise CSI feedback, for example CSI 408 feedback.

[00232] Moving to step 2406, various bits in the communication are set as to whether they signify a condition that caused the channel state information to not be included if the first field and the second field indicated that the communication was not includes channel status information. The various bits could mean that a previous request for channel state information was not received, that current channel state information is substantially similar to previously transmitted channel state information, or that a transmission limitation would be exceeded upon, for example , channel state transmission. The establishment of the plurality of bits can be performed by the CSI feedback module 1704, for example. The various bits can be included in a control field of the CSI feedback.

[00233] In step 2408, communication is transmitted. Communication can be transmitted using, for example, transmission module 1708.

[00234] Those skilled in the art will consider that a simple and clean frame format for CSI feedback communications has been described here. In some respects, STA AIDs may be indicated in the NDPA. There may be no indication of a number of STAs in the NDPA in some respects, although this information can be deduced from the length of the NDPA. In some respects, information regarding whether SF was received or stored on an AP may be included in the NDPA. In some aspects, information regarding whether a STA is transmitting CSI is included in the CSI feedback transmitted to the AP. In some respects, an envelope is used to indicate parameters for an STA to use when transmitting SF.

[00235] In some respects, no field is specified for a “first responder” STA. The first related STA-AID can implicitly represent the first responder in one aspect. NDPA and CSI probe can carry a match sequence number to enable STAs to match a corresponding CSI to NDPA probe. Similarly, the sequence number can be copied into a control field transmitted by the STA.

[00236] The various operations of the methods described above can be performed by any suitable mechanisms capable of performing the corresponding functions. Mechanisms may include various hardware and/or software components and/or module(s), but not limited to a circuit, an application-specific integrated circuit (ASIC), or processor. Generally, where there are operations, module, or steps illustrated in the figures, those operations may have corresponding counterparty mechanisms-plus-function components. For example, a user terminal may comprise mechanisms for receiving a request for channel state information, mechanisms for determining parameters of channel state information based on information included in the request, mechanisms for determining channel state information based on at least in part on the determined parameters, and mechanisms for transmitting a frame comprising at least a part of the determined channel state information.

[00237] Figure 25 illustrates a block diagram of an exemplary user terminal 2500 in accordance with certain aspects of the present disclosure. User terminal 2500 comprises a receive module 2505 that can be configured to perform the functions of the receive mechanisms discussed above. In some aspects, the receiving module may correspond to one or more of the receivers 254 of Figure 2. The user terminal 2500 further comprises a determination module 2510 which may be configured to perform the functions of the determination mechanisms discussed above. In some aspects, the determination module may correspond to the controller 280 of Figure 2. The user terminal 2500 further comprises a transmission module 2515 which may be configured to perform the functions of the transmission mechanisms discussed above. In some respects, the transmission module may correspond to one or more of the 254 transmitters of Figure 2.

[00238] As used here, the term "determining" encompasses a wide variety of actions. For example, "determining" may include calculating, computing, processing, deriving, probing, querying (eg, querying a table, database, or other data structure), ascertaining, and the like. Furthermore, "determining" may include receiving (eg, receiving information), accessing (eg, accessing data in a memory), and the like. Furthermore, "determining" can include resolving, selecting, choosing, establishing and the like.

[00239] As used here, the phrase referring to "at least one of" a list of items refers to any combination of those items, including individual members. As an example, "at least one of: a, b or c" is intended to encompass: a, b, c, a-b, a-c, b-c and a-b-c.

[00240] The various operations of the methods described above can be performed using any mechanisms capable of performing the operations, such as various hardware and/or software components, circuits and/or modules. Generally, any operation illustrated in the Figures can be performed using corresponding functional mechanisms capable of performing the operations.

[00241] The various logic blocks, modules, and illustrative circuits described in connection with the present description can be implemented or realized with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC) , an array of field programmable gates (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. A general purpose processor can be a microprocessor, but alternatively, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors together with a DSP core, or any other such configuration.

[00242] In one or more aspects, the functions described may be implemented in hardware, software, firmware or any combination thereof. If implemented in software, functions may be stored or transmitted through one or more instructions or code on a switch-readable medium. Computer readable media includes both computer storage media and communication media including any medium that facilitates the transfer of a computer program from one location to another. Storage media can be any available media that can be accessed by a computer. By way of example, and not by way of limitation, such computer readable media may comprise RAM, ROM, EEPROM, CD-ROM, or other optical disk storage device, magnetic disk storage or other magnetic storage, or any other medium that may be used to transport or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Furthermore, any connection is aptly termed a computer-readable medium. For example, if the software is transmitted from a network site, server or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared (IR), radio and microwave are included in the definition of medium. Magnetic disc and optical disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disc and Blu-ray® disc where magnetic discs normally reproduce data magnetically, while optical discs reproduce the data optically with laser. Thus, in some respects, computer-readable media may comprise non-transient computer-readable media (eg, tangible media). In addition, for other aspects, computer-readable media may also comprise transient computer-readable media (e.g., a signal). Combinations of the above may also be included in the scope of computer readable media.

[00243] The methods described herein comprise one or more steps or actions to obtain the described method. The steps and/or actions of the method may be interchanged with each other without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or usage of specific steps and/or actions may be modified without departing from the scope of the claims.

[00244] The functions described can be implemented in hardware, software, firmware or any combination thereof. If implemented in software, functions can be stored as one or more instructions on a computer-readable medium. Storage media can be any available media that can be accessed by a computer. By way of example, and not by way of limitation, such computer readable media may comprise RAM, ROM, EEPROM, CD-ROM, or other optical disk storage device; magnetic disk storage or other magnetic storage; or any other means that can be used to transport or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Magnetic disk and optical disk, as used herein, include compact disk (CD); laser disk; optical disc; digital versatile disc (DVD); floppy disk; and Blu-ray® disc; where magnetic disks normally reproduce the data magnetically, while optical disks reproduce the data optically with laser.

[00245] Thus, certain aspects may comprise a computer program product to perform the operations presented herein. For example, such a computer program product may comprise a computer readable medium having instructions stored (and/or encoded) therein, the instructions being executable by one or more processors to perform the operations described herein. For certain aspects, the computer program product may include packaging material.

[00246] Software or instructions may also be transmitted over a transmission medium. For example, if the software is transmitted from a network site, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared , radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of a transmission medium.

[00247] Additionally, it should be considered that modules and/or other mechanisms suitable for carrying out the methods and techniques described herein may be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device may be coupled to a server to facilitate the transfer of mechanisms to carry out the methods described herein. Alternatively, various methods described herein may be provided through storage mechanisms (e.g. RAM, ROM, a physical storage medium such as a laser disk (CD) or floppy disk, etc.) user and/or base station can obtain the various methods from docking or provisioning the storage medium to the device. In addition, any other technique suitable for providing the methods and techniques described herein to a device may be used.

[00248] It should be understood that the claims are not limited to the exact configuration and components illustrated above. Various modifications, alterations and variations may be made to the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

[00249] While the foregoing is directed to aspects of the present description, other and additional aspects of the description may be conceived without departing from its basic scope, and its scope is determined by the appended claims.

Claims (15)

1. Method for wireless communications characterized in that it comprises: receiving a broadcast request for channel status information on a device; determining channel state information parameters based on information included in the request; determining channel status information based at least in part on the determined parameters; and transmitting a frame comprising at least a portion of the determined channel state information, wherein at least one of the parameters comprises a number of columns of a matrix for the channel state information that is requested, and wherein the request comprises a first field indicating the number. 2. Method according to claim 1, characterized in that the request additionally comprises a second field that indicates an identifier of association of a device from which the channel status information is requested; and wherein the second field comprises 12 bits; or wherein the request is received at a first apparatus, and wherein the method further comprises determining that the first apparatus is identified by the association identifier. 3. Method according to claim 1, characterized in that the first field comprises at least 3 bits; and wherein at least a part of the determined channel status information is represented as an array comprising a number of columns equal to the number indicated in the first field. 4. Method according to claim 1, characterized in that the information comprises at least one bit indicating whether the channel state information will be used for a single-user protocol or a multi-user protocol; or wherein the request comprises a null data packet advertisement, the null data packet advertisement comprising a sequence number, and wherein the transmitted frame comprises data indicating the sequence number; or wherein the transmitted frame comprises a control field indicating the determined parameters. 5. Method according to claim 1, characterized in that it additionally comprises determining a bandwidth of the channel state information determined based on the determined parameters; and wherein the request comprises a first indicator meaning whether channel state information is requested for a single user or multi-user, and a second indicator meaning a number of columns of a matrix for the channel state information that is requested; or where the given bandwidth is indicated in the frame. 6. Method according to claim 1, characterized in that it additionally comprises: receiving a polling message requesting an additional part of the determined channel state information; and transmitting an additional frame comprising the additional part of the determined channel state information. 7. Apparatus for wireless communications characterized in that it comprises: mechanisms for receiving a broadcast request for channel state information; mechanisms for determining channel state information parameters based on information included in the request; mechanisms for determining channel state information based at least in part on the determined parameters; and mechanisms for transmitting a frame comprising at least a portion of the determined channel state information, wherein at least one of the parameters comprises a number of columns of a matrix for the channel state information that is requested, and wherein the request comprises a first field indicating the number. 8. Method for wireless communication characterized in that it comprises: transmitting a broadcast request for channel status information to one or more devices, wherein the request comprises a second field identifying each of the one or more devices and indicating parameters for each one of the one or more devices to be used in determining channel status information; and receiving a frame comprising channel state information from at least one of the one or more apparatus in response to the request, the channel state information having been determined based at least in part on the parameters indicated by the request, wherein at least one of the parameters comprises a number of columns of an array for the channel status information that is requested, and wherein the request comprises a first field indicating the number. 9. Method according to claim 8, characterized in that it additionally comprises determining one or more of the parameters indicated by the request based on whether the channel state information will be used for a single-user protocol or a multi-user protocol. 10. Method according to claim 8, characterized in that the second field identifying each device of the one or more devices comprises an association identifier for each device, each association identifier comprising 12 bits; or wherein the first field comprises at least 3 bits; or wherein the request comprises a null data packet advertisement, the null data packet advertisement comprising a sequence number, and wherein the received frame comprises data indicating the sequence number. 11. Method, according to claim 8, characterized in that it additionally comprises processing the received channel status information using the parameters indicated by the transmitted request. 12. Method according to claim 8, characterized in that the received frame comprises a control field indicating parameters of the received channel state information, wherein the parameters indicated in the control field are based at least in part on the parameters indicated by the transmitted request; and further comprises processing the received channel status information using the parameters indicated by the control field. 13. Method according to claim 8, characterized in that it additionally comprises: transmitting a polling message requesting additional channel status information from at least one of the one or more devices; and receiving an additional frame comprising the additional channel state information. 14. Device for wireless communications comprising: mechanisms for transmitting a broadcast request for channel status information to one or more devices, wherein the broadcast request comprises a second field identifying each of the one or more devices and indicating parameters for each of the one or more devices to be used in determining channel status information; and mechanisms for receiving a frame comprising channel state information from at least one of the one or more apparatus in response to the request, the channel state information having been determined based, at least in part, on parameters indicated by the request, in that at least one of the parameters comprises a number of columns of an array for the channel status information that is requested, and wherein the request comprises a first field indicating the number. 15. Computer readable memory for wireless communication comprising instructions stored therein, the instructions being executable by a computer to carry out the steps of the method as defined in any one of claims 1 to 6 or 8 to 13.

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