Patent Description:
In many telecommunication systems, communications networks are used to exchange messages among several interacting spatially-separated devices. Networks may be classified according to geographic scope, which could be, for example, a metropolitan area, a local area, or a personal area. Such networks may be designated respectively as a wide area network (WAN), metropolitan area network (MAN), local area network (LAN), or personal area network (PAN). Networks also differ according to the switching, routing technique used to interconnect the various network nodes and devices (e.g., circuit switching vs. packet switching), the type of physical media employed for transmission (e.g., wired vs. wireless), and the set of communication protocols used (e.g., Internet protocol suite, Synchronous Optical Networking (SONET), Ethernet, etc.).

Wireless networks are often preferred when the network elements are mobile and thus have dynamic connectivity needs, or if the network architecture is formed in an ad hoc, rather than fixed, topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in the radio, microwave, infra-red, optical, etc. frequency bands. Wireless networks advantageously facilitate user mobility and rapid field deployment when compared to fixed wired networks.

In order to address the issue of increasing bandwidth requirements that are demanded for wireless communications systems, different schemes are being developed to allow multiple access terminals to communicate with a single access point by sharing the channel resources while achieving high data throughputs. With limited communication resources, it is desirable to reduce the amount of traffic passing between the access point and the multiple terminals. For example, when multiple terminals send uplink communications to the access point, it is desirable to minimize the amount of traffic to complete the uplink of all transmissions. Thus, there is a need for improved methods and apparatuses for multiple user communications in wireless networks.

Attention is drawn to document <CIT> which relates to a method for transmitting an uplink in a WLAN which comprises the steps of: a first STA transmitting to an AP each of a plurality of RTS frames through at least one channel from among a plurality of first channels; the first STA receiving from the AP at least one CTS frame through at least one channel from among the plurality of channels which have received the RTS frames; and a second STA receiving from the AP at least one CTS frame through at least one channel from among a plurality of second channels, wherein the at least one CTS frame includes STA identifier information and channel information, the STA identifier information includes information for indicating the first STA and the second STA, and wherein the channel information may include information on a first uplink channel allocated for transmitting a first data frame of the first STA and information on a second uplink channel allocated for transmitting a second data frame of the second STA.

Further attention is drawn to document <CIT> which relates wireless communication in a wireless network which comprises a wireless station obtaining a transmission opportunity period (TXOP) for communicating with an access point (AP) over a wireless communication channel. The wireless station sends an announcement to the AP to share the transmission opportunity period with at least another wireless station, as a multi-user transmission opportunity period for simultaneously transmitting data from said wireless stations to the AP on multiple uplink (UL) spatial streams over the wireless channel.

Various aspects of the novel systems, apparatuses, and methods are described more fully hereinafter with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the novel systems, apparatuses, and methods disclosed herein, whether implemented independently of or combined with any other aspect of the application. In addition, the scope of the application is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects set forth herein. It should be understood that any aspect disclosed herein may be embodied by one or more elements of a claim.

Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, or objectives. Rather, aspects of the disclosure 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 the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof.

Wireless network technologies may include various types of wireless local area networks (WLANs). A WLAN may be used to interconnect nearby devices together, employing widely used networking protocols. The various aspects described herein may apply to any communication standard, such as Wi-Fi or, more generally, any member of the IEEE <NUM> family of wireless protocols.

In some aspects, wireless messages may be transmitted according to a high-efficiency <NUM> protocol using orthogonal frequency division multiplexing (OFDM), direct-sequence spread spectrum (DSSS) communications, a combination of OFDM and DSSS communications, or other schemes. Aspects of the high-efficiency <NUM> protocol may be used for Internet access, sensors, metering, smart grid networks, or other wireless applications. Advantageously, aspects of certain devices implementing this particular wireless protocol may consume less power than devices implementing other wireless protocols, may be used to transmit wireless messages across short distances, and/or may be able to transmit messages less likely to be blocked by objects, such as humans.

In some aspects, a WLAN includes various devices which are the components that access the wireless network. For example, there may be two types of devices: access points ("APs") and clients (also referred to as access terminals, or "access terminals"). In general, an access point serves as a hub or base access terminal for the WLAN and an access terminal serves as a user of the WLAN. For example, an access terminal may be a laptop computer, a personal digital assistant (PDA), a mobile phone, etc. In an example, an access terminal connects to an access point via a Wi-Fi (e.g., IEEE <NUM> protocol such as <NUM>. 11ah) compliant wireless link to obtain general connectivity to the Internet or to other wide area networks. In some aspects an access terminal may also be used as an AP.

The techniques described herein may 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 Spatial Division Multiple Access (SDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems, and so forth. An SDMA system may utilize sufficiently different directions to simultaneously transmit data belonging to multiple access terminals. A TDMA system may allow multiple access terminals to share the same frequency channel by dividing the transmission message into different time slots, each time slot being assigned to a different access terminal. A TDMA system may implement global system for moble communications (GSM) or some other standards known in the art. An OFDMA system utilizes orthogonal frequency division multiplexing (OFDM), which is a modulation technique that partitions the overall system bandwidth into multiple orthogonal sub-carriers. These sub-carriers may also be called tones, bins, etc. With OFDM, each sub-carrier may be independently modulated with data. An OFDM system may implement IEEE <NUM> or some other standards known in the art. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on sub-carriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent sub-carriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent sub-carriers. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDMA. A SC-FDMA system may implement 3GPP-LTE (3rd Generation Partnership Project Long Term Evolution) or other standards.

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

An access point ("AP") may comprise, be implemented as, or known as a NodeB, Radio Network Controller ("RNC"), eNodeB, Base Access terminal Controller ("BSC"), Base Transceiver Access terminal ("BTS"), Base Access terminal ("BS"), Transceiver Function ("TF"), Radio Router, Radio Transceiver, Basic Service Set ("BSS"), Extended Service Set ("ESS"), Radio Base Access terminal ("RBS"), or some other terminology.

An access terminal "access terminal" may also comprise, be implemented as, or known as an access terminal ("AT"), a subscriber access terminal, a subscriber unit, a mobile access terminal, a remote access terminal, a remote terminal, a user agent, a user device, user equipment, a user terminal or some other terminology, such as device, or plurality of devices. In some aspects an access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol ("SIP") phone, a wireless local loop ("WLL") access terminal, a personal digital assistant ("PDA"), a handheld device having wireless connection 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 phone (e.g., a cellular phone or smartphone), a computer (e.g., a laptop), a portable communication device, a headset, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a gaming device or system, a global positioning system device, or any other suitable device that is configured to communicate via a wireless medium.

<FIG> illustrates a multiple-access multiple-input multiple-output (MIMO) system <NUM> with access points and access terminals useful for understanding the invention. For simplicity, only one access point <NUM> is shown in <FIG>. An access point is generally a fixed access terminal that communicates with the access terminals and may also be referred to as a base access terminal or using some other terminology. An access terminal or access terminal may be fixed or mobile and may also be referred to as a mobile access terminal or a wireless device, or using some other terminology. The access point <NUM> may communicate with one or more access terminals 120A, 120B, 120C, 120d, 120e, 120f, <NUM>, <NUM>, 120i (hereinafter access terminal <NUM> or, when referring to more than one, access terminals <NUM>) at any given moment on the downlink and uplink. The downlink (i.e., forward link) is the communication link from the access point to the access terminals, and the uplink (i.e., reverse link) is the communication link from the access terminals to the access point. An access terminal may also communicate peer-to-peer with another access terminal. A system controller <NUM> couples to and provides coordination and control for the access points.

While portions of the following disclosure will describe access terminals <NUM> capable of communicating via Spatial Division Multiple Access (SDMA), for certain aspects, the access terminals <NUM> may also include some access terminals that do not support SDMA. Thus, for such aspects, the access point <NUM> may be configured to communicate with both SDMA and non-SDMA access terminals. This approach may conveniently allow older versions of access terminals ("legacy" access terminals) that do not support SDMA to remain deployed in an enterprise, extending their useful lifetime, while allowing newer SDMA access terminals to be introduced as deemed appropriate.

The system <NUM> employs multiple transmit and multiple receive antennas for data transmission on the downlink and uplink. The access point <NUM> is equipped with Nap antennas and represents the multiple-input (MI) for downlink transmissions and the multiple-output (MO) for uplink transmissions. A set of K selected access terminals <NUM> collectively represents the multiple-output for downlink transmissions and the multiple-input for uplink transmissions. For pure SDMA, it is desired to have Nap ≤ K ≤ <NUM> if the data symbol streams for the K access terminals are not multiplexed in code, frequency or time by some means. K may be greater than Nap if the data symbol streams can be multiplexed using TDMA technique, different code channels with CDMA, disjoint sets of sub-bands with OFDM, and so on. Each selected access terminal may transmit user-specific data to and/or receive user-specific data from the access point. In general, each selected access terminal may be equipped with one or multiple antennas (i.e., Nut ≥ <NUM>). The K selected access terminals can have the same number of antennas, or one or more access terminals may have a different number of antennas.

The system <NUM> may 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 system <NUM> may also utilize a single carrier or multiple carriers for transmission. Each access terminal may be equipped with a single antenna (e.g., in order to keep costs down) or multiple antennas (e.g., where the additional cost can be supported). The system <NUM> may also be a TDMA system if the access terminals <NUM> share the same frequency channel by dividing transmission, reception into different time slots, where each time slot may be assigned to a different access terminal <NUM>.

<FIG> illustrates a block diagram of the access point <NUM> and two access terminals 120A and 120i in system <NUM> which is useful for understanding the invention. The access point <NUM> is equipped with Nt antennas 224a through 224ap. The access terminal 120A is equipped with Nut,m antennas <NUM>ma through <NUM>mu, and the access terminal 120i is equipped with Nut,x antennas <NUM>xa through <NUM>xu. The access point <NUM> is a transmitting entity for the downlink and a receiving entity for the uplink. The access terminal <NUM> is a transmitting entity for the uplink and a receiving entity for the downlink. As used herein, a "transmitting entity" is an independently operated apparatus or device capable of transmitting data via a wireless channel, and a "receiving entity" is an independently operated apparatus or device capable of receiving data via a wireless channel. In the following description, the subscript "dn" denotes the downlink, the subscript "up" denotes the uplink, Nup access terminals are selected for simultaneous transmission on the uplink, and Ndn access terminals are selected for simultaneous transmission on the downlink. Nup may or may not be equal to Ndn, and Nup and Ndn may be static values or may change for each scheduling interval. Beam-steering or some other spatial processing technique may be used at the access point <NUM> and/or the access terminal <NUM>.

On the uplink, at each access terminal <NUM> selected for uplink transmission, a TX data processor <NUM> receives traffic data from a data source <NUM> and control data from a controller <NUM>. The TX data processor <NUM> processes (e.g., encodes, interleaves, and modulates) the traffic data for the access terminal based on the coding and modulation schemes associated with the rate selected for the access terminal and provides a data symbol stream. A TX spatial processor <NUM> performs spatial processing on the data symbol stream and provides Nut,m transmit symbol streams for the Nut,m antennas. Each transmitter (TMTR) unit <NUM> receives and processes (e.g., converts to analog, amplifies, filters, and frequency upconverts) a respective transmit symbol stream to generate an uplink message. Nut,m transmitters within respective transceiver units <NUM> provide Nut,m uplink messages for transmission from Nut,m antennas <NUM>, for example to transmit to the access point <NUM>.

Nup access terminals may be scheduled for simultaneous transmission on the uplink. Each of these access terminals may perform spatial processing on its respective data symbol stream and transmit its respective set of transmit symbol streams on the uplink to the access point <NUM>.

At the access point <NUM>, Nup antennas 224a through <NUM>ap receive the uplink messages from all Nup access terminals transmitting on the uplink. Each antenna <NUM> provides a received message to a respective receiver (RCVR) unit within a transceiver unit <NUM>. Each transceiver unit <NUM> performs processing complementary to that performed by a transceiver unit <NUM> and provides a received symbol stream. An RX spatial processor <NUM> performs receiver spatial processing on the Nup received symbol streams from Nup receiver units within the respective transceiver units <NUM> and provides Nup recovered uplink data symbol streams. The receiver spatial processing may be performed in accordance with the channel correlation matrix inversion (CCMI), minimum mean square error (MMSE), soft interference cancellation (SIC), or some other technique. Each recovered uplink data symbol stream is an estimate of a data symbol stream transmitted by a respective access terminal. An RX data processor <NUM> processes (e.g., demodulates, deinterleaves, and decodes) each recovered uplink data symbol stream in accordance with the rate used for that stream to obtain decoded data. The decoded data for each access terminal may be provided to a data sink <NUM> for storage and/or a controller <NUM> for further processing.

On the downlink, at the access point <NUM>, a TX data processor <NUM> receives traffic data from a data source <NUM> for Ndn access terminals scheduled for downlink transmission, control data from a controller <NUM>, and possibly other data from a scheduler <NUM>. The various types of data may be sent on different transport channels. TX data processor <NUM> processes (e.g., encodes, interleaves, and modulates) the traffic data for each access terminal based on the rate selected for that access terminal. The TX data processor <NUM> provides Ndn downlink data symbol streams for the Ndn access terminals. A TX spatial processor <NUM> performs spatial processing (such as a precoding or beamforming) on the Ndn downlink data symbol streams, and provides Nup transmit symbol streams for the Nup antennas. Each transceiver unit <NUM> receives and processes a respective transmit symbol stream to generate a downlink message. Nup transmitters within the respective transceiver units <NUM> may provide Nup downlink messages for transmission from Nup antennas <NUM>, for example to transmit to the access terminals <NUM>.

At each access terminal <NUM>, Nut,m antennas <NUM> receive the Nup downlink messages from the access point <NUM>. Each transceiver unit <NUM> processes a received message from an associated antenna <NUM> and provides a received symbol stream. An RX spatial processor <NUM> performs receiver spatial processing on Nut,m received symbol streams from Nut,m transceiver units <NUM> and provides a recovered downlink data symbol stream for the access terminal <NUM>. The receiver spatial processing may be performed in accordance with the CCMI, MMSE, or some other technique. An RX data processor <NUM> processes (e.g., demodulates, deinterleaves and decodes) the recovered downlink data symbol stream to obtain decoded data for the access terminal.

At each access terminal <NUM>, a channel estimator <NUM> estimates the downlink channel response and provides downlink channel estimates, which may include channel gain estimates, SNR estimates, noise variance and so on. Similarly, a channel estimator <NUM> estimates the uplink channel response and provides uplink channel estimates. Controller <NUM> for each access terminal typically derives the spatial filter matrix for the access terminal based on the downlink channel response matrix Hdn,m for that access terminal. Controller <NUM> derives the spatial filter matrix for the access point based on the effective uplink channel response matrix Hup,eff. The controller <NUM> for each access terminal may send feedback information (e.g., the downlink and/or uplink eigenvectors, eigenvalues, SNR estimates, and so on) to the access point <NUM>. The controllers <NUM> and <NUM> may also control the operation of various processing units at the access point <NUM> and access terminal <NUM>, respectively.

<FIG> illustrates various components that may be utilized in a wireless device <NUM> that may be employed within the wireless communication system <NUM> of <FIG> and which is useful for understanding the invention. The wireless device <NUM> is an example of a device that may be configured to implement the various methods described herein. The wireless device <NUM> may comprise an access point <NUM> or an access terminal <NUM>.

The wireless device <NUM> may include a processing system <NUM> which controls operation of the wireless device <NUM>. The processing system <NUM> may also be referred to as a central processing unit (CPU), hardware processor, or processor. Memory <NUM>, which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processing system <NUM>. A portion of the memory <NUM> may also include non-volatile random access memory (NVRAM). The processing system <NUM> may perform logical and arithmetic operations based on program instructions stored within the memory <NUM>. The instructions in the memory <NUM> may be executable to implement the methods described herein.

The processing system <NUM> may be implemented with one or more processors. The one or more processors may be implemented with any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that can perform calculations or other manipulations of information.

The processing system may also include a computer readable medium encoded thereon with instructions that when executed cause the wireless device <NUM> to perform a method of wireless communication. Such instructions shall be construed broadly to mean any type of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code).

The wireless device <NUM> may also include a housing <NUM> that may include a transmitter <NUM> and a receiver <NUM> to allow transmission and reception of data between the wireless device <NUM> and a remote location. The transmitter <NUM> and receiver <NUM> may be combined into a transceiver <NUM>. A single or a plurality of transceiver antennas <NUM> may be attached to the housing <NUM> and electrically coupled to the transceiver <NUM>. The wireless device <NUM> may also include (not shown) multiple transmitters, multiple receivers, and multiple transceivers.

The wireless device <NUM> may also include a signal detector <NUM> that may be used in an effort to detect and quantify the level of messages received by the transceiver <NUM>. The signal detector <NUM> may detect such messages as total energy, energy per subcarrier per symbol, power spectral density and other messages. The wireless device <NUM> may also include a digital signal processor (DSP) <NUM> for use in processing messages.

The various components of the wireless device <NUM> may be coupled together by a bus system <NUM>, which may include a power bus, a control frame bus, and a status message bus in addition to a data bus. In some aspects, the processing system <NUM> alone or in conjunction with the bus system <NUM> may comprise an interface (e.g., hardware or software) configured to connect two or more components together such that data or information may be communicated between the two or more components. For example, in some aspects, an interface may receive information or communications from a component of the wireless device <NUM> or from another device. In some aspects, the interface may be configured to output information for transmission to another component of the wireless device <NUM> or to another device.

Certain aspects of the present disclosure support transmitting an uplink (UL) message from multiple access terminals to an AP. In some aspects, the UL message may be transmitted in a multi-user MIMO (MU-MIMO) system. Alternatively, the UL message may be transmitted in a multi-user FDMA (MU-FDMA) or similar FDMA system. Specifically, <FIG>, <FIG> illustrate UL-MU-MIMO transmissions 410A and 410B (collectively UL-MU-MIMO transmissions <NUM>) that would apply equally to UL-FDMA transmissions. In these aspects, UL-MU-MIMO or UL-FDMA transmissions can be sent simultaneously from multiple access terminals to an access point and may create efficiencies in wireless communication.

An increasing number of wireless and mobile devices put increasing stress on bandwidth requirements that are demanded for wireless communications systems. With limited communication resources, it is desirable to reduce the amount of traffic passing between the access point <NUM> and the multiple access terminals <NUM>. For example, when multiple access terminals <NUM> send uplink communications to the access point <NUM>, it is desirable to minimize the amount of traffic to complete the uplink of all transmissions. Thus, aspects described herein support utilizing communication exchanges, scheduling and certain messages for increasing throughput of uplink transmissions to the access point <NUM>.

<FIG> is a time sequence diagram illustrating an UL-MU-MIMO protocol <NUM> that may be used for UL communications, in accordance with some aspects of the invention. As shown in <FIG> and in conjunction with <FIG>, the access point <NUM> may transmit a clear to transmit (CTX) message <NUM> to the access terminals <NUM> indicating which access terminals may participate in the UL-MU-MIMO scheme, such that a particular access terminal is directed to start an UL-MU-MIMO. In some aspects, the CTX message <NUM> may be transmitted in a payload portion of a physical layer convergence protocol (PLCP) protocol data unit (PPDU). Example CTX message structures are described more fully below with reference to <FIG>. In some aspects, the CTX message may comprise a null data packet (NDP) (e.g., a message comprising a PLCP header and no payload). In such aspects, the CTX message information may be included in one of the fields of the PLCP header. In a PLCP header compatible with the <NUM>. 11ax standard, for example, the information may be included in one of a first high efficiency signal field (HE SIG1), a second high efficiency signal field (HE SIG <NUM>), or a third high efficiency signal field (HE SIG <NUM> field), collectively, a plurality of signal fields. <FIG> illustrate some examples of <NUM>. 11ax NDP CTX messages comprising CTX message information.

Once an access terminal <NUM> receives the CTX message <NUM> from the access point <NUM> where the access terminal is listed, the access terminals <NUM> may transmit the UL-MU-MIMO transmission 410A, 410B (collectively <NUM>). In <FIG>, access terminal 120A and access terminal 120B transmit UL-MU-MIMO transmission 410A and 410B, respectively, containing physical layer convergence protocol (PLCP) protocol data units (PPDUs). Upon receiving the UL-MU-MIMO transmission <NUM>, the access point <NUM> may transmit block acknowledgments (block ACK messages) <NUM> to the access terminals <NUM>.

<FIG> is a time sequence diagram illustrating an UL-MU-MIMO protocol that may be used for UL communications, in accordance with some aspects of the invention. In <FIG>, a CTX message is aggregated in an aggregated MAC protocol data unit (A-MPDU) message <NUM>. The aggregated A-MPDU message <NUM> may provide time to an access terminal <NUM> for processing before transmitting the UL messages or may allow the access point <NUM> to send data to the access terminals <NUM> before receiving uplink data.

Not all access points <NUM> or access terminals <NUM> may support UL-MU-MIMO or UL-FDMA operation. A capability indication from an access terminal <NUM> may be indicated in a high efficiency (HE) wireless capability element that is included in an association request or probe request and may include a bit indicating capability, the maximum number of spatial streams an access terminal <NUM> can use in a UL-MU-MIMO transmission, the frequencies an access terminal <NUM> can use in a UL-FDMA transmission, the minimum and maximum power and granularity in the power backoff, and the minimum and maximum time adjustment an access terminal <NUM> can perform.

A capability indication from an access point may be indicated in a HE wireless capability element that is included in an association response, beacon or probe response and may include a bit indicating capability, the maximum number of spatial streams a single access terminal <NUM> can use in a UL-MU- MIMO transmission, the frequencies a single access terminal <NUM> can use in a UL-FDMA transmission, the required power control granularity, and the required minimum and maximum time adjustment an access terminal <NUM> should be able to perform.

In some aspects, access terminals <NUM> may request to the access point <NUM> to be part of the UL-MU-MIMO (or UL-FDMA) protocol by sending a management message to the access point <NUM> indicating a request for enablement of the use of the UL-MU-MIMO feature. In some aspects, an access point <NUM> may respond by granting the use of the UL-MU-MIMO feature or denying it. Once the use of the UL-MU-MIMO is granted, the access terminal <NUM> may expect a CTX message <NUM> at a variety of times. Additionally, once an access terminal <NUM> is enabled to operate the UL-MU-MIMO feature, the access terminal <NUM> may be subject to follow a certain operation mode. If multiple operation modes are possible, the access point <NUM> may indicate to the access terminal <NUM> which mode to use in a HE wireless capability element, a management message, or in an operation element. In some aspects the access terminals <NUM> can change the operation modes and parameters dynamically during operation by sending a different operating element to the access point <NUM>. In some aspects the access point <NUM> may switch operation modes dynamically during operation by sending an updated operating element or a management message to an access terminal <NUM> or in a beacon. In some aspects, the operation modes may be indicated in the setup phase and may be setup per access terminal <NUM> or for a group of access terminals <NUM>. In some aspects the operation mode may be specified per traffic identifier (TID).

<FIG> is a time sequence diagram that, in conjunction with <FIG>, illustrates an operation mode of a UL-MU-MIMO transmission, in accordance with some aspects of the invention. In such aspects, an access terminal <NUM> receives a CTX message <NUM> from an access point <NUM> and sends an immediate response to the access point <NUM>. The response may be in the form of a clear to send (CTS) message <NUM> or another similar message. In some aspects, requirement to send a CTS message may be indicated in the CTX message <NUM> or may be indicated in the setup phase of the communication. As shown in <FIG>, access terminal 120A and access terminal 120B may transmit a first CTS message 408A and a second CTS message 408B in response to receiving the CTX message <NUM>. The modulation and coding scheme (MCS) of the first CTS message 408A and the second CTS message 408B may be based on the MCS of the CTX message <NUM>. In such aspects, the first CTS message 408A and the second CTS message 408B comprise the same bits and the same scrambling sequence so that they may be transmitted to the access point <NUM> at the same time. The duration field of the CTS messages 408A, 408B may be based on the duration field in the CTX message <NUM> by removing the time for the CTX message PPDU. The UL-MU-MIMO transmissions 410A, 410B are then sent by the access terminals 120A, 120B as listed in the CTX message <NUM> messages. The access point <NUM> may then send an acknowledgment (ACK) message <NUM> to the access terminals 120A, 120B. In some aspects, the ACK messages <NUM> may be serial ACK messages to each access terminal or block ACK messages. In some aspects the ACK messages may be polled. This aspect creates efficiencies by simultaneously transmitting CTS messages 408A, 408B from multiple access terminals to an access point <NUM> instead of sequentially, which saves time and reduces the possibility of interference.

<FIG> is a time sequence diagram that, in conjunction with <FIG>, illustrates another example of an operation mode of a UL-MU-MIMO transmission, in accordance with some aspects of the invention. In these aspects, access terminals 120A, 120B receive a CTX message <NUM> from an access point <NUM> and are allowed to start a UL-MU-MIMO transmission a time (T) <NUM> after the end of the PPDU carrying the CTX message <NUM>. The time (T) <NUM> may be a short interframe space (SIFS), point interframe space (PIFS), or another time potentially adjusted with additional offsets as indicated by an access point <NUM> in the CTX message <NUM> or via a management message. The SIFS and PIFS time may be fixed by a standard or indicated by an access point <NUM> in the CTX message <NUM> or in a management message, a benefit of the time (T) <NUM> may include to improve synchronization or to allow access terminals 120A, 120B time to process the CTX message <NUM> or other messages before transmission. Increasing the interframe space (IFS) beyond PIFS may be risky, since other access terminals may be able to complete their contention and transmit during the IFS time. Where IFS > PIFS, the CTX message legacy preamble may be modified to indicate a PPDU duration that exceeds the actual PPDU duration, hence providing an increased deferral time.

Referring to <FIG>, in conjunction with <FIG>, the UL-MU-MIMO transmission <NUM> may have the same duration. The duration of the UL-MU-MIMO transmission <NUM> for access terminals utilizing the UL-MU-MIMO feature may be indicated in the CTX message <NUM> or during the setup phase. To generate a PPDU of the required duration, an access terminal <NUM> may build a PLCP service data unit (PSDU) so that the length of the PPDU matches the length indicated in the CTX message <NUM>. In some aspects, an access terminal <NUM> may adjust the level of data aggregation in a median access control (MAC) protocol data unit (A-MPDU) or the level of data aggregation in a MAC service data unit (A-MSDU) to approach the target length. In some aspects, an access terminal <NUM> may add end of file (EOF) padding delimiters to reach the target length. In another approach the padding or the EOF pad fields are added at the beginning of the A-MPDU. One of the benefits of having all the UL-MU-MIMO transmissions the same length is that the power level of the transmission will remain constant.

In some aspects, an access terminal <NUM> may have data to upload to the access point <NUM> but the access terminal <NUM> has not received a CTX message <NUM> or other message indicating that the access terminal <NUM> may start a UL-MU-MIMO transmission.

In one operation mode, the access terminals <NUM> may not transmit outside an UL-MU-MIMO transmission opportunity (TXOP) (e.g., after the CTX message <NUM>). In another operation mode, access terminals <NUM> may transmit messages to initialize a UL-MU-MIMO transmission, and then may transmit during the UL-MU-MIMO TXOP, if for example, they are instructed to do so in a CTX message <NUM>. In some aspects, the message to initialize a UL-MU-MIMO transmission may be a request to transmit (RTX), message which is specifically designed for this purpose (an example of a RTX message structure is described more fully below with reference to <FIG> and <FIG>). The RTX messages may be the only messages an access terminal <NUM> is allowed to use to initiate a UL-MU-MIMO TXOP. In some aspects, the access terminal may not transmit outside an UL-MU-MIMO TXOP other than by sending an RTX message. In some aspects, a message to initialize an UL-MU-MIMO transmission may be any message which indicates to an access point <NUM> that an access terminal <NUM> has data to send. It may be pre-negotiated that these messages indicate a UL-MU-MIMO TXOP request. For example, the following may be used to indicate that an access terminal <NUM> has data to send and is requesting an UL-MU-MIMO TXOP: a request to send (RTS) message, a data frame or QoS Null frame with bits <NUM>-<NUM> of the QoS control frame set to indicate more data, or a PS poll message. In some aspects, the access terminal may not transmit outside an UL-MU-MIMO TXOP other than by sending messages to trigger this TXOP, where this message may be an RTS message, PS poll message, or quality of service (QOS) null frame. In some aspects, the access terminal <NUM> may send single user uplink data as usual, and may indicate a request for a UL-MU-MIMO TXOP by setting bits in the QoS control frame of its data packet.

<FIG> is a time sequence diagram useful for understanding the invention, illustrating, in conjunction with <FIG>, initializing a UL-MU-MIMO utilizing a RTX message <NUM>. In such aspects the access terminal <NUM> sends to the access point <NUM> a RTX message <NUM> that includes information regarding the UL-MU-MIMO transmission. As shown in <FIG>, the access point <NUM> may respond to the RTX message <NUM> with a CTX message <NUM> granting an UL-MU-MIMO TXOP to send the UL-MU-MIMO transmission <NUM> immediately following the CTX message <NUM>. In some aspects, the access point <NUM> may respond with a CTS message (not shown) that grants a single-user (SU) UL TXOP. In some aspects, the access point <NUM> may respond with a message (e.g., ACK message or CTX message with a special indication, not shown) that acknowledges the reception of the RTX message <NUM> but does not grant an immediate UL-MU-MIMO TXOP. In some aspects, the access point <NUM> may respond with a message (not shown) that acknowledges the reception of the RTX message <NUM>, does not grant an immediate UL-MU-MIMO TXOP, but grants a delayed UL-MU-MIMO TXOP and may identify the time of the TXOP that is granted. In such aspects, the access point <NUM> may send a CTX message <NUM> to start the UL-MU-MIMO at the granted time.

In some aspects, the access point <NUM> may respond to the RTX message <NUM> with an ACK message or other response message which does not grant the access terminal <NUM> an UL-MU-MIMO transmission but indicates that the access terminal <NUM> shall wait for a time (T) before attempting another transmission (e.g., sending another RTX). In such aspects the time (T) may be indicated by the access point <NUM> in the setup phase or in the response message. In some aspects an access point <NUM> and an access terminal <NUM> may agree on a time which the access terminal <NUM> may transmit a RTX message <NUM>, RTS message, a power save (PS)-Poll message, or any other request for a UL-MU-MIMO TXOP.

In another operation mode, access terminals <NUM> may transmit requests for UL-MU-MIMO transmissions <NUM> in accordance with regular contention protocols. In some aspects, the contention parameters for access terminals <NUM> using UL-MU-MIMO are set to a different value than for other access terminals that are not using the UL-MU-MIMO feature. In such aspects, the access point <NUM> may indicate the value of the contention parameters in a beacon, association response, or through a management message. In some aspects, the access point <NUM> may provide a delay timer that prevents an access terminal <NUM> from transmitting for a certain amount of time after each successful UL-MU-MIMO TXOP or after each RTX message, RTS message, PS-Poll message, or QoS null frame. The timer may be restarted after each successful UL-MU-MIMO TXOP. In some aspects, the access point <NUM> may indicate the delay timer to access terminals <NUM> in the setup phase or the delay timer may be different for each access terminal <NUM>. In some aspects, the access point <NUM> may indicate the delay timer in the CTX message <NUM> or the delay timer may be dependent on the order of the access terminals <NUM> in the CTX message <NUM>, and may be different for each terminal.

In another operational mode, the access point <NUM> may indicate a time interval during which the access terminals <NUM> are allowed to transmit a UL-MU-MIMO transmission. In some aspects, the access point <NUM> indicates a time interval to the access terminals <NUM> during which the access terminals are allowed to send a RTX or RTS message or other request to the access point <NUM> to ask for an UL-MU-MIMO transmission. In such aspects, the access terminals <NUM> may use regular contention protocols. In some aspects, the access terminals <NUM> may not initiate a UL-MU-MIMO transmission during the time interval but the access point <NUM> may send a CTX message <NUM> or other message to the access terminals <NUM> to initiate the UL-MU-MIMO transmission.

In certain aspects, an access terminal <NUM> enabled for UL-MU-MIMO may indicate to an access point <NUM> that it requests an UL-MU-MIMO TXOP because it has data pending for UL. In some aspects, the access terminal <NUM> may send a RTS message or a PS-poll message to request a UL-MU-MIMO TXOP. In some aspects, the access terminal <NUM> may send any data frame, including a quality of service (QoS) null data frame, where the bits <NUM>-<NUM> of the QoS control field indicate a non-empty queue. In such aspects the access terminal <NUM> may determine during the setup phase which data frames (e.g., RTS message, PS-Poll message, QoS null frame, etc.) will trigger a UL-MU-MIMO transmission when the bits <NUM>-<NUM> of the QoS control field indicate a non-empty queue. In some aspects, the RTS message, PS-Poll message, or QoS null frames may include a <NUM> bit indication allowing or disallowing the access point <NUM> to respond with a CTX message <NUM>. In some aspects, the QoS null frame may include TX power information and a per TID queue information. The TX power information and per TID queue information may be inserted in the two bytes of the sequence control and QoS controls fields in a QoS null frame and the modified QoS null frame may be sent to the access point <NUM> to request a UL-MU-MIMO TXOP. In some aspects, referring to <FIG> and <FIG>, the access terminal <NUM> may send a RTX message <NUM> to request a UL-MU-MIMO TXOP.

In response to receiving an RTS message, RTX message, PS-poll or QoS null frame, or other trigger message as described above, an access point <NUM> may send a CTX message <NUM>. In some aspects, also referring to <FIG>, after the transmission of the CTX message <NUM> and the completion of the UL-MU-MIMO transmissions 410A and 410B, TXOP returns to the access terminals 120A, 120B which can decide on how to use the remaining TXOP. In some aspects, referring to <FIG>, after the transmission of the CTX message <NUM> and the completion of the UL-MU-MIMO transmissions 410A and 410B, TXOP remains with the access point <NUM> and the access point <NUM> may use the remaining TXOP for additional UL-MU-MIMO transmissions by sending another CTX message <NUM> to either access terminals 120A, 120B or to other access terminals.

<FIG> is a message timing diagram of multi-user uplink communication, in accordance with some aspects of the invention. Message exchange <NUM> shows communication of wireless messages between an access point <NUM> and three access terminals 120A-120C. Message exchange <NUM> indicates that each of access terminals 120A-120C transmits a request to transmit (RTX) message 802A-802C to the access point <NUM>. Each of RTX messages 802A-802C indicate that the transmitting access terminal 120A-120C has data available to be transmitted to the access point <NUM>.

After receiving each of RTX messages 802A-802C, the access point <NUM> may respond with a message indicating that the access point <NUM> has received the RTX message. As shown in <FIG>, the access point <NUM> transmits ACK messages 803A-803C in response to each of the RTX messages 802A-802C. In some aspects, the access point <NUM> may transmit a message (e.g., a CTX message) indicating that each of the RTX messages 802A-802C has been received but that the access point <NUM> has not granted a transmission opportunity for the access terminals 120A-120C to transmit uplink data. In <FIG>, after sending ACK message 803C, the access point <NUM> transmits a CTX message <NUM>. In some aspects, the CTX message <NUM> is transmitted to at least the access terminals 120A-120C. In some aspects, the CTX message <NUM> is broadcast. In some aspects, the CTX message <NUM> indicates which access terminals are granted permission to transmit data to the access point <NUM> during a transmission opportunity. The starting time of the transmission opportunity and its duration may be indicated in the CTX message <NUM> in some aspects. For example, the CTX message <NUM> may indicate that the access terminal 120A-120C should set their network allocation vectors to be consistent with network allocation vector (NAV) <NUM>.

At a time indicated by the CTX message <NUM>, the three access terminals 120A-120C transmit data 806A-806C to the access point <NUM>. The data 806A-806C are transmitted at least partially concurrently during the transmission opportunity (e.g., at least <NUM> of the access terminals 120A, 120B, 120C are transmitting at a same time). The transmissions of data 806A-806C may utilize uplink multi-user multiple input, multiple output transmissions (UL-MU-MIMO) or uplink frequency division multiple access (UL-FDMA).

In some aspects, access terminals 120A-120C may transmit pad data such that the transmissions of each access terminal transmitting during a transmission opportunity are of approximately equal duration. Message exchange <NUM> shows access terminal 120A transmitting pad data 808A while access terminal 120C transmits pad data 808C. The transmission of pad data ensures that the transmissions from each of the access terminals 120A-120C complete at approximately the same time. This may provide for a more equalized transmission power over the entire duration of the transmission, optimizing access point <NUM> receiver efficiencies.

After the access point <NUM> receives the data transmissions 806A-806C, the access point <NUM> transmits acknowledgments 810A-810C to each of the access terminals 120A-120C. In some aspects, the acknowledgments 810A-810C may be transmitted at least partially concurrently using either DL-MU-MIMO or DL-FDMA.

<FIG> shows a diagram of a RTX message <NUM>, useful for understanding the invention. The RTX message <NUM> includes a message control (FC) field <NUM>, a duration field <NUM> (optional), a transmitter address (TA) or allocation identifier (AID) field <NUM>, a receiver address (RA) or a basic service set identifier (BSSID) field <NUM>, a TID field <NUM>, an estimated transmission (TX) time field <NUM>, and a TX power field <NUM>. The FC field <NUM> indicates a control subtype or an extension subtype. The duration field <NUM> indicates to any receiver of the RTX message <NUM> to set the NAV. In some aspects, the RTX message <NUM> may not have a duration field <NUM>. The TA or AID field <NUM> indicates the source address which can be an AID or a full MAC address. The RA or BSSID field <NUM> indicates the RA or BSSID, respectively. In some aspects the RTX message <NUM> may not contain a RA or BSSID field <NUM>. The TID field <NUM> indicates the access category (AC) for which the user has data. The Estimated TX time field <NUM> indicates the time requested for the UL-TXOP and may be the time required for an access terminal <NUM> to send all the data in its buffer at the current planned MCS. The TX power field <NUM> indicates the power at which the message is being transmitted and can be used by the access point to estimate the link quality and adapt the power backoff indication in a CTX message.

In some aspects, before an UL-MU-MIMO communication can take place, an access point <NUM> may collect information from the access terminals <NUM> that may participate in the UL-MU-MIMO communication. An access point <NUM> may optimize the collection of information from the access terminals <NUM> by scheduling the transmissions from the access terminals <NUM>.

As discussed above, the CTX message <NUM> may be used in a variety of communications. <FIG> is a diagram of a clear to transmit (CTX) message <NUM>, in accordance with some aspects of the invention. The CTX message <NUM> is a control frame that includes a message control (FC) field <NUM>, a duration field <NUM>, a transmitter address (TA) field <NUM>, a control (CTRL) field <NUM>, a PPDU duration field <NUM>, a station (STA) info field <NUM>, and a message check sequence (FCS) field <NUM>. The FC field <NUM> indicates a control subtype or an extension subtype. The duration field <NUM> indicates to any receiver of the CTX message <NUM> to set the NAV. The TA field <NUM> indicates the transmitter address or a BSSID. The control field <NUM> is a generic field that may include information regarding the format of the remaining portion of the message (e.g., the number of STA info fields and the presence or absence of any subfields within a STA info field), indications for rate adaptation for the access terminals <NUM>, indication of allowed TID, and indication that a CTS message must be sent immediately following the CTX message <NUM>. The control field <NUM> may also indicate if the CTX message <NUM> is being used for UL-MU-MIMO or for UL FDMA or both, indicating whether a Nss or Tone allocation field is present in the STA info field <NUM>.

Alternatively, the indication of whether the CTX message <NUM> is for UL-MU-MIMO or for UL FDMA can be based on the value of the subtype. Note that UL-MU-MIMO and UL FDMA operations can be jointly performed by specifying to an access terminal <NUM> both the spatial streams to be used and the channel to be used, in which case both fields are present in the CTX message <NUM>; in this case, the Nss indication is referred to as a specific tone allocation. The PPDU duration field <NUM> indicates the duration of the following UL-MU-MIMO PPDU that the access terminals <NUM> are allowed to send. The STA info field <NUM> contains information regarding a particular access terminal <NUM> and may include a per-access terminal set of information (see STA info <NUM><NUM> and STA info N <NUM>). The STA info field <NUM> may include an AID or MAC address field <NUM> which identifies an access terminal <NUM>, a number of spatial streams field (Nss) field <NUM> which indicates the number of spatial streams an access terminal <NUM> may use (in an UL-MU-MIMO system), a Time Adjustment field <NUM> which indicates a time that an access terminal <NUM> should adjust its transmission compared to the reception of a trigger message (the CTX message <NUM> in this case), a Power Adjustment field <NUM> which indicates a power backoff an access terminal <NUM> should take from a declared transmit power, a Tone Allocation field <NUM> which indicates the tones or frequencies an access terminal <NUM> may use (in a UL-FDMA system), an Allowed TID field <NUM> which indicates the allowable TID, an Allowed TX Mode field <NUM> which indicates the allowed TX modes, a MCS field <NUM> which indicates the MCS the access terminal <NUM> should use, and a TX start time field <NUM> which indicates a start time for the access terminal <NUM> to transmit uplink data. In some aspects, the allowed TX modes may include a short, long guard interval (GI) or cyclic prefix mode, a binary convolutional code (BCC), low density parity check (LDPC) mode (generally, a coding mode), or a space-time block coding (STBC) mode.

In some aspects, the STA info fields <NUM>-<NUM> may be excluded from the CTX message <NUM>. In these aspects, the CTX message <NUM> with the missing STA info fields may indicate to the access terminals <NUM> receiving the CTX message <NUM> that a request message to uplink data (e.g., RTS message, RTX message or QoS Null frame) has been received but a transmission opportunity has not been granted. In some aspects, the control field <NUM> may include information regarding the requested uplink. For example, the control field <NUM> may include a waiting time before sending data or another request, a reason code for why the request was not granted, or other parameters for controlling medium access from the access terminal <NUM>. A CTX message with missing STA info fields may also apply to CTX messages <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> described below.

In some aspects, an access terminal <NUM> receiving the CTX message <NUM> with a Allowed TID field <NUM> indication may be allowed to transmit data only of that TID, data of the same or higher TID, data of the same or lower TID, any data, or only data of that TID first, then if no data is available, data of other TIDs. The FCS field <NUM> indicates the carries an FCS value used for error detection of the CTX message <NUM>.

<FIG> is another diagram of a CTX message <NUM>, in accordance with some aspects of the invention. In such aspects and in conjunction with <FIG>, the STA info <NUM> field does not contain the AID or MAC Address field <NUM> and instead the CTX message <NUM> includes a group identifier (GID) field <NUM> which identifies the access terminals by a group identifier rather than an individual identifier. <FIG> is another diagram of a CTX message <NUM>, in accordance with some aspects of the invention. In such aspects and in conjunction with <FIG>, the GID field <NUM> is replaced with a receiver address (RA) field <NUM> which identifies a group of access terminals through a multicast MAC address.

<FIG> is another diagram of a CTX message <NUM>, in accordance with some aspects of the invention. In such aspects, the CTX message <NUM> is a management message that includes a Management MAC Header field <NUM>, a Body field <NUM>, and a FCS field <NUM>. The Body field <NUM> includes an information element (IE) identifier (ID) field <NUM> which identifies an information element (IE), a length (LEN) field <NUM> which indicates the length of the CTX message <NUM>, a CTRL field <NUM> which includes the same information as the control field <NUM>, a PPDU Duration field <NUM> which indicates the duration of the following UL-MU-MIMO PPDU that the access terminals <NUM> are allowed to send, a STA info <NUM> field <NUM> and a MCS field <NUM> which can indicate the MCS for all the access terminals to use in the following UL-MU-MIMO transmission, or an MCS backoff for all the access terminals to use in the following UL-MU-MIMO transmission. The STA info <NUM> field <NUM> (along with STA info N field <NUM>) represent a per access terminal field that includes AID field <NUM> which identifies an access terminal, a number of spatial streams field (Nss) field <NUM> which indicates the number of spatial streams an access terminal may use (in an UL-MU-MIMO system), a Time Adjustment field <NUM> which indicates a time that an access terminal should adjust its transmission time compared to the reception of a trigger message (the CTX message in this case), a Power Adjustment field <NUM> which indicates a power backoff an access terminal <NUM> should take from a declared transmit power, a Tone Allocation field <NUM> which indicates the tones or frequencies an access terminal <NUM> may use (in a UL-FDMA system), an Allowed TID field <NUM> which indicates the allowable TID, and a TX start time field <NUM> which indicates a start time for the access terminal to transmit uplink data.

In some aspects, the CTX message <NUM> or the CTX message <NUM> may be aggregated in an A-MPDU to provide time to an access terminal <NUM> for processing before transmitting the UL messages. In such aspects, padding or data may be added after the CTX message to allow an access terminal <NUM> additional time to process the forthcoming packet. One benefit to padding a CTX message may be to avoid possible contention issues for the UL messages from other access terminals <NUM>, as compared to increasing the interframe space (IFS) as described above. In some aspects, if the CTX message is a management message, additional padding information elements (IEs) may be sent. In some aspects, if the CTX message is aggregated in a A-MPDU, additional A-MPDU padding delimiters may be included. Padding delimiters may include EoF delimiters (4Bytes) or other padding delimiters. In some aspects, the padding may be achieved by adding data, control or Management MPDPUs, as long as they are not required to be processed within the IFS response time. In such a case it may be beneficial for the receiver to know which MPDUs are padded and not require an immediate response. The padded MPDUs may be preceded by an indication in a delimiter field, for example setting the EoF bit = <NUM>, when the length is greater than <NUM>. The MPDUs may include an indication to the receiver that no immediate response is required and will not be required by any of the following MPDUs. In some aspects, the access terminals <NUM> may request of an access point <NUM> a minimum duration or padding for the CTX message <NUM>. In some aspects, the padding may be achieved by adding physical layer (PHY) OFDMA symbols, which may include undefined bits not carrying information, or may include bit sequences that carry information, as long as they do not need to be processed within the IFS time. The presence and/or duration of the PHY padding may be a function of or indicated by one or more transmission parameters, such as the modulation and coding scheme (MCS), the guard interval (GI), a coding type, and/or a packet duration. In some aspects, access terminals <NUM> may have different reception capabilities. Accordingly, the access terminals <NUM> may indicate to the access point <NUM> for which messages and under which transmission conditions the padding should be used, and how long the padding should be.

In some aspects, the padding may be performed by the responding access terminal <NUM>. The access terminal <NUM> may be able to decode the CTX message <NUM> information and access start the transmission of the UL MU response PPDU at the requested time. The access terminal <NUM> may instead need more time to process the data to be included in the payload of the UL MU PPDU (fetch the data from queues, encryption etc.). Accordingly, the access terminal <NUM> may add some pre-padding to gain more time to process the data. The pre-padding may be in the form of A-MPDU delimiters including a length=<NUM> indication.

In some aspects of the invention, the CTX message <NUM> may have a format as shown in <FIG> is a diagram of a CTX message <NUM>, in accordance with some aspects. In these aspects, the CTX message <NUM> is a broadcast control frame that comprises a protocol version <NUM> (PV1) MAC header <NUM> including a message control (FC) field <NUM>, a local address or local identifier (A1) field <NUM>, and a second address (A2) field <NUM> (e.g., three fields). As shown, the FC field <NUM> may have a length of <NUM> bytes (octets) and may comprise a plurality of bits (e.g., <NUM> bits that are not shown) reserved for indicating the "protocol version <NUM>", as well as a type field (not shown) indicating the "CTX message" message type. The local address or local identifier (A1) field <NUM> may also have a length of <NUM> bytes, as opposed to <NUM> bytes, for example. In some aspects, the local address field <NUM> includes a local MAC address. The term "local address" or "local identifier" may correspond to a non-unique <NUM>-byte MAC address assigned to one or more access terminals <NUM> in the basic service set (BSS) by the associated access point <NUM>. Since the local address field <NUM> is <NUM> bytes in length rather than <NUM> bytes (as is a full length, unique MAC address) the difference in overhead of <NUM> bytes may be saved to improve efficiency of data throughput. In some aspects, the local MAC address included in the local address field <NUM> may be a broadcast association identifier (AID), (e.g., the broadcast AID including all zeros). In some aspects, the local address may comprise a group ID corresponding to or identifying two or more access terminals as intended recipients of the message <NUM>. The second address (A2) field <NUM> may have a length of <NUM> bytes and may comprise a full, <NUM> byte unique MAC address. In some aspects, the second address field <NUM> may include a BSSID of the access point <NUM> that currently serves the associated BSS.

The CTX message <NUM> may additionally include a plurality of STA info fields <NUM>, <NUM>. For example, as shown in <FIG>, the CTX message <NUM> may include a first STA info field <NUM>, an Nth STA info field <NUM>, and any STA info fields between the first and Nth STA info fields (not shown). The present application contemplates at least two variations for STA info field format: a <NUM> byte (octet) variant <NUM> and a <NUM> byte (octet) variant <NUM>. Each of the variants may comprise an address field <NUM> for indicating which of the plurality of access terminals indicated in the A1 field <NUM> the particular STA info field <NUM>, <NUM> corresponds to, a number of spatial streams field (Nss) field <NUM> which indicates the number of spatial streams an access terminal may use (in an UL-MU-MIMO system), a time adjustment field <NUM> which indicates a time that an access terminal should adjust its transmission compared to the reception of a trigger message (the CTX message <NUM> in this case), a power adjustment field <NUM> which indicates a power backoff that an access terminal should take from a declared transmit power, an allowed TID field <NUM> which indicates the allowable TID, and a modulation and coding scheme (MCS) field <NUM> which indicates the MCS the access terminal should use. The <NUM> byte variant <NUM> may have field lengths for each of the fields <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> of <NUM> bits, <NUM> bits, <NUM> bits, <NUM> bits, <NUM> bits and <NUM> bits, respectively. By contrast, in the <NUM> byte variant <NUM>, all field lengths may be the same as the <NUM> byte variant <NUM> except the MCS field <NUM> may have a length of <NUM> bit rather than <NUM> bits, reducing the total length by <NUM> bits (one byte).

The CTX message <NUM> further comprises an FCS field <NUM>, which carries an FCS value used for error detection of the CTX message <NUM> and may have a length of <NUM> bytes. It should be noted that the PV1 MAC header <NUM> does not include a duration field, further reducing the overhead required to transmit the CTX message <NUM> and further increasing efficiency of data throughput.

In some aspects, where the CTX message <NUM> is a unicast PV1 CTX message, the CTX message <NUM> may have a format as shown in <FIG> is a diagram of a unicast CTX message <NUM>, in accordance with some aspects of the invention. In these aspects, the unicast PV1 CTX message <NUM> comprises a protocol version <NUM> MAC header <NUM> as previously described in connection with <FIG>, including a message control (FC) field <NUM>, a local address or local identifier (A1) field <NUM>, and a second address (A2) field <NUM> (e.g., three fields). The FC field <NUM> and the second address (A2) field <NUM> may be as previously described in connection with <FIG>. However, rather than including a broadcast MAC address (e.g., AID) in the local address (A1) field <NUM>, local address field <NUM> includes a local address for a single access point (access terminal) having a length of <NUM> bytes.

The CTX message <NUM> may additionally include a single STA info field <NUM>, which may include substantially the same fields as previously described in connection with either of the <NUM> byte variant <NUM> and/or the <NUM> byte variant <NUM> in <FIG>. In some aspects, since the local address (A1) field <NUM> includes only one address, the STA info field <NUM> may not include the address field <NUM>, as previously described in connection with <FIG>. In such aspects, the <NUM> byte variant <NUM> may be a <NUM> byte variant and the <NUM> byte variant <NUM> may be a <NUM> byte variant. The CTX message <NUM> further comprises an FCS field <NUM> having the same characteristics as the FCS field <NUM> of <FIG>. Since the local address field <NUM> includes a local MAC address for only one device, where multiple devices are to transmit substantially simultaneously in a MU mode, multiple CTX messages <NUM> indicating a same transmission time may be transmitted, one addressed to each of the multiple devices.

In some aspects of the invention, the unicast PV1 CTX message may be included in a multi-user (MU) PPDU having a format as shown in <FIG> is a diagram of a MU PPDU <NUM> comprising an OFDMA PHY header <NUM> and one or more per-access terminal physical layer service data units (PSDUs). Each of the one or more per-access terminal PSDUs may include an MPDU <NUM> comprising the unicast CTX message <NUM> of <FIG>. The one or more per-access terminal PSDU additionally includes a service field <NUM> before the MPDU <NUM>, having a length of <NUM> bytes. In some aspects, the OFDM PHY header <NUM> may be transmitted in approximately <NUM>, while the service field <NUM> and the MPDU <NUM> may be transmitted at an increased data rate, as compared to the OFDMA PHY header <NUM>, based on an indicated MCS.

In some aspects, the CTX message <NUM> may be a null data packet (NDP) (i.e., a PPDU comprising the PLCP header and no PSDU). The PLCP header comprises one or more fields that may carry the information for the CTX message functionalities. In some aspects, the NDP CTX message may have a format as shown in <FIG>.

<FIG> is a diagram of an NDP CTX message <NUM>, in accordance with some aspects of the invention. The NDP CTX message <NUM> may be a broadcast CTX message, similar to that previously described in connection with <FIG>. The NDP CTX message <NUM> may include a non-legacy portion having a repetition legacy message (RL-SIG) field <NUM>, a first high efficiency message (HE-SIG1) field <NUM>, a second high efficiency message (HE-SIG2) field <NUM>, a high efficiency short training (HE-STF) field <NUM>, a high efficiency long training (HE-LTF) field <NUM> and a third high efficiency message (HE-SIG3) field <NUM>.

The RL-SIG field <NUM> may be a repetition of an L-SIG field from a legacy preamble portion of the NDP CTX message <NUM> (not shown). The reliability of the NDP CTX message <NUM> may be improved by repeating the L-SIG (not shown) in the non-legacy portion. In some examples, the RL-SIG field <NUM> may be approximately <NUM> long. In other examples, the RL-SIG field <NUM> may have other durations.

The HE-SIG1 field <NUM> may be an information field that includes information related to the format of the PPDU that is intended to be decoded by all recipients of the NDP CTX message <NUM>. In some examples, the HE-SIG1 field <NUM> is a fixed length. In one such example, the HE-SIG1 field <NUM> has a length of <NUM>, plus the length of a guard interval. In other examples, the HE-SIG1 field <NUM> may have different lengths.

The HE-SIG2 field <NUM> may be an information field that includes extended information related to the format of the packet or additional operational indications. The HE-SIG2 field <NUM> may also be intended to be received and decoded by all recipients of the NDP CTX message <NUM>. In some examples, the HE-SIG2 field <NUM> is a variable length. In other examples, the HE-SIG2 field <NUM> may be a fixed length.

The HE-STF field <NUM> and the field HE-LTF <NUM> may be training symbols that include information for refreshing channel estimation and synchronization. The HE-STF field <NUM> and the HE-LTF field <NUM> may include per-STA information and may be transmitted only on a specific sub-band or spatial stream for that access terminal. In one example, the HE-STF field <NUM> may have a duration of approximately <NUM> to <NUM>. A duration of the HE-LTF field <NUM> may be dependent on the number of spatial time streams (NSTS) used in the wireless communication system. In other examples, the durations of the HE-STF field <NUM> and the HE-LTF field <NUM> may differ from the specific examples described herein.

The non-legacy portion of the NDP CTX message <NUM> may also include the HE-SIG3 field <NUM>. The HE-SIG3 field <NUM> may include per-STA information and may have variable length. In some examples, the HE-SIG3 field <NUM> may be sent only in a sub-band for a specific access terminal or on a specific spatial stream for the specific access terminal.

The RL-SIG field <NUM>, HE-SIG1 field <NUM>, and HE-SIG2 field <NUM> may include information for each recipient of the NDP CTX message <NUM>. That is, the information may be transmitted on each relevant channel, such as every <NUM> channel of a <NUM> or <NUM> bandwidth. In other examples, other channels and bandwidths may be used. In contrast, the HE-STF field <NUM>, HE-LTF field <NUM>, and HE-SIG3 field <NUM> may be a per-access terminal portion. That is, those fields may contain information relevant to only one access terminal. In that case, different HE-STF field <NUM>, HE-LTF field <NUM>, and HE-SIG3 field <NUM> may be transmitted on a separate channel for each access terminal.

The HE-SIG1 field <NUM> and/or the HE-SIG2 field <NUM> may comprise several fields, including a type field <NUM>, an information field <NUM>, and a cyclic redundancy check (CRC) field <NUM>. The type field <NUM> may describe the type of message or the function of the message. In one example, the type field <NUM> is <NUM> bits. The CRC field <NUM> indicates information related to a cyclic redundancy check. In particular, the CRC field <NUM> may include <NUM> bits that force a checksum to a known constant in order to check for transmission errors. In other examples, other fields and bit lengths may be used.

The information field <NUM> may further comprise additional fields, including a transmitter address field <NUM>, a control (CTRL) field <NUM>, a PPDU duration field <NUM>, and multiple STA information fields <NUM> and <NUM>. In this example, the HE-SIG2 field <NUM> includes N STA information fields (e.g., access terminal <NUM> information field <NUM> through access terminal N information field <NUM>). A STA information field may include additional sub-fields as will be described in more detail below.

The address field <NUM> may indicate a transmitter address or a BSSID. In some aspects, the address field <NUM> may also comprise a "local address" or "local identifier" which, as described in connection with <FIG>, may be a non-unique MAC address having a shortened length as compared to a full length MAC address (e.g., <NUM> bytes versus <NUM> bytes). The CTRL field <NUM> may be a generic field that may include information relating to a format of the remaining portion of the NDP CTX message, indication of rate adaptations, indication of allowed traffic identifier (TID), and an indication that a clear to send messages must be sent responsive to the NDP CTX message <NUM>. For example, the CTRL field <NUM> may include a number of STA information fields present and whether any sub-fields are included in the STA information fields. The CTRL field <NUM> may also include additional control information.

Each STA information field may include a per-access terminal set of information. Sub-fields of a STA information field may include an association identifier (AID) or MAC address field <NUM>, a number of spatial streams (Nss) field <NUM>, a time adjustment field <NUM>, a power adjustment field <NUM>, an allowed TID field <NUM>, and a modulation and coding scheme (MCS) field <NUM>. Each of the fields <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may correspond to the fields <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of <FIG>, respectively. In some examples, not all of the described sub-fields are included in the HE-SIG2 field <NUM> for an NDP CTX message with a broadcast CTX message. In some examples, for each channel (e.g., a <NUM> channel), the trigger information may refer to a different group of access terminals. A per-access terminal portion may or may not be included in an NDP CTX message with a broadcast CTX message.

In an example of an NDP CTX message for multiple user unicast CTX message, the information described being included in the HE-SIG2 field <NUM> may be located in an HE-SIG3 field for each different access terminal. In such an example, the information field <NUM> may include only a single STA information field.

<FIG> is another diagram of a unicast NDP CTX message <NUM>, in accordance with some aspects of the invention. The NDP CTX message <NUM> may be used for individual access terminals, similar to that previously described in connection with <FIG>. The unicast NDP CTX message <NUM> may include fields as discussed above with respect to <FIG>. For example, the unicast NDP CTX message <NUM> may include a RL-SIG field <NUM>, an HE-SIG1 field <NUM>, an HE-SIG2 field <NUM>, an HE-STF field <NUM>, an HE-LTF field <NUM>, and an HE-SIG3 field <NUM>.

The HE-SIG3 <NUM> may include a type field <NUM>, an information field <NUM>, and a CRC field <NUM>. The type field <NUM> and the CRC field <NUM> may be an example of one or more aspects of the type field <NUM> and the CRC field <NUM> of <FIG>. The information field <NUM> may further include an access terminal ID or access point ID field <NUM>, a TID field <NUM>, a sequence number field <NUM>, and a bitmap field <NUM>. The access terminal ID or access point ID field <NUM> may identify the access terminal or access point and may comprise a "local address" or "local identifier," as previously described in connection with <FIG>, having a length shorter than a full MAC address (e.g., <NUM> bytes versus <NUM> bytes). The TID field <NUM> may indicate an access category (AC) for which the access terminal or access point has data. The sequence number field <NUM> acts as a modulo-counter for higher-level messages. The bitmap <NUM> may include bits for acknowledging or not acknowledging messages.

<FIG> is another diagram of a NDP CTX message <NUM>, in accordance with some aspects of the invention. The NDP CTX message <NUM> may include fields as discussed above with respect to <FIG>. For example, the NDP CTX message <NUM> may include a RL-SIG field <NUM>, an HE-SIG1 field <NUM>, an HE-SIG2 field <NUM>, an HE-STF field <NUM>, an HE-LTF field <NUM>, and an HE-SIG3 field <NUM>.

The HE-SIG1 field <NUM> and an HE-SIG2 field <NUM> may include a type field <NUM>, an address field <NUM>, an information field <NUM>, and a CRC field <NUM>. The type field <NUM> and the CRC field <NUM> may be an example of one or more aspects of the type fields <NUM>, <NUM> and the CRC fields <NUM>, <NUM> of <FIG> and <FIG>.

The address field <NUM> may identify an access point. In some aspects, the address field <NUM> may comprise a "local identifier" or "local address," as previously described in connection with <FIG>, having a non-unique shortened MAC address as compared to a full length MAC address (e.g., <NUM> bytes versus <NUM> bytes). The information field <NUM> may further include an access terminal ID or access point ID field <NUM>, a TID field <NUM>, a sequence number field <NUM>, and a bitmap field <NUM>. The information field <NUM> may also include an access terminal ID or access point ID field <NUM>, a TID field <NUM>, a sequence number field <NUM>, and a bitmap field <NUM>. In other examples, the information field <NUM> may include additional sets of fields for multiple other access terminals. The fields <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may correspond to the fields <NUM>, <NUM>, <NUM>, <NUM> of <FIG>, respectively.

In some aspects the preamble structure and information described for the NDP CTX message <NUM> may be used in a non-NDP PPDU. In such a case the non-NDP PPDU would comprise a PLCP Header and one or more PSDUs (one per subchannel or stream). The PLCP header may have the same format as described in relation to <FIG>, while each PSDU may have a format according to the <NUM>. 11ax standard PSDU and may carry additional MPDUs. Such a non-NDP CTX message may be beneficial in that it provides for the carrying of CTX message information in the PLCP Header of a PPDU that also carries data for one or more access terminals, hence reducing the overhead that a transmission of a separate CTX message and Data PPDUs would incur. When the non-NDP CTX message PPDU is used to trigger UL-MU-MIMO, OFDMA transmission from one or more access terminals, the access terminals may send the UL-MU-MIMO or OFDMA PPDUs a short interframe space (SIFS) time after the non-NDP CTX message PPDU is fully received. Note that the CTX message information useful for the access terminals responses are included in the PLCP header, which is the initial portion of the PPDU, followed by additional PSDU transmission, hence allowing for increased time for the access terminals to process the CTX message information.

In accordance with some aspects, the NDP CTX message <NUM> may be an NDP block ACK message that includes a block ACK message bitmap with information per each access terminal in the "per-access terminal" portion of the NDP CTX message <NUM>. In some examples, the bitmap is present for a block ACK message and may not be present for an ACK message. The block ACK message information sent to each access terminal may be a self-contained message. That is, the BA information may include a message type identifier, a source address, or a destination address.

In some aspects, the NDP block ACK message may be an approximately immediate response to an MU data PPDU or to a trigger message, such as a multi-access terminal BAR, which may indicate the structure of the NDP BA response and the allocation of the NDP fields to different access terminals. Such a message may be a SIFS immediate response. In this case, the NDP block ACK message may not need to include certain information in the block ACK message, such as access terminal and access point identifier or type. In some examples, bandwidth or streams per access terminal may be allocated based on the access terminals' resource allocation for the soliciting PPDU. For example, the access terminals may use the same bandwidth or streams as the soliciting PPDU or use equal bandwidth allocation according to a number of access terminals identified in the soliciting PPDU. In some examples, as the NDP block ACK message may be an immediate response, the recipient is already well identified and the type of information carried by the NDP may already be known by the recipient of the NDP.

In some aspects, an access point <NUM> may initiate a CTX message transmission. In some aspects, an access point <NUM> may send a CTX message <NUM> in accordance with regular enhanced distribution channel access (EDCA) contention protocol. In some aspects, an access point <NUM> may send a CTX message <NUM> at scheduled times. In such an aspect, the scheduled times may be indicated by the access point <NUM> to the access terminals <NUM> by using a restricted access window (RAW) indication in a beacon which indicates a time reserved for a group of access terminals <NUM> to access the medium, a target wake time (TWT) agreement with each access terminal <NUM> which indicates to multiple access terminals <NUM> to be awake at the same time to take part in a UL-MU-MIMO transmission, or information in other fields. Outside the RAW and TWT an access terminal <NUM> may be allowed to transmit any message, or only a subset of messages (e.g., non-data frames). It may also be forbidden to transmit certain messages (e.g., it may be forbidden to transmit data frames). The access terminal <NUM> may also indicate that it is in sleep mode. One advantage to scheduling a CTX message is that multiple access terminals <NUM> may be indicated a same TWT or RAW time and may receive a transmission from an access point <NUM>.

<FIG> is a flowchart <NUM> of a method for wireless communication, useful for understanding the invention. A person having ordinary skill in the art will appreciate that the method may be implemented by any suitable device and system. Moreover, although the method of flowchart <NUM> is described herein with reference to a particular order, in various aspects, blocks herein may be performed in a different order, or omitted, and additional blocks may be added.

Operation block <NUM> includes generating a clear to transmit message comprising a header having a local address field therein, the clear to transmit message indicating a transmission opportunity, the clear to transmit message further comprising a request that a plurality of devices concurrently transmit data at a specific time. For example, as previously described in connection with any of <FIG>, the clear to transmit message <NUM>, <NUM> may comprise a PV1 MAC header <NUM>, <NUM> having a local address field <NUM>, <NUM> that may be shorter in length than a full MAC address (e.g., <NUM> bytes versus <NUM> bytes). As previously described in connection with any of <FIG>, the NDP clear to transmit message <NUM>, <NUM>, <NUM> may comprise a PHY header having a local address field <NUM>, <NUM>, <NUM>, <NUM> that may also have the shortened length. This clear to transmit message further comprises a request that a plurality of devices (e.g., access terminals <NUM>, see <FIG>) concurrently transmit data (e.g., data 806a, 806b, 806c) at a specific time.

The flowchart <NUM> may then advance to operational block <NUM>, which includes outputting the clear to transmit message for transmission to the plurality of devices.

In some aspects, an apparatus for wireless communication may perform some of the functions of flowchart <NUM>. The apparatus comprises means for generating a clear to transmit message comprising a header having a local address field therein. The clear to transmit message indicates a transmission opportunity. The clear to transmit message further comprises a request that a plurality of devices concurrently transmit data at a specific time. In some aspects, the means for generating a clear to transmit message may comprise the processing system <NUM> of the wireless device <NUM> of <FIG>, for example. The apparatus may further comprise means for outputting the clear to transmit message for transmission to the plurality of devices. In some aspects, the means for outputting the clear to transmit message for transmission may include an interface comprising the processing system <NUM>, and in some aspects, also at least a portion of the bus system <NUM>.

In some aspects the apparatus may additionally include means for inserting a broadcast MAC address corresponding to the plurality of devices into the local address field, comprising the processing system <NUM>, and in some aspects the memory <NUM>, of the wireless device <NUM> of <FIG>, for example, which may be configured to insert the unicast MAC address corresponding to one of the plurality of devices into the local address field. In some aspects, the apparatus may additionally include means for inserting a unicast MAC address corresponding to one of the plurality of devices into the local address field, comprising the processing system <NUM>, and in some aspects the memory <NUM>, of the wireless device <NUM> of <FIG>, for example. In some aspects, the apparatus may additionally include means for generating a second address field in the header, comprising the processing system <NUM>, and in some aspects the memory <NUM>, of the wireless device <NUM> of <FIG>, for example. In some aspects, the apparatus may additionally include means for generating the header without generating a duration field therein, comprising the processing system <NUM>, and in some aspects the memory <NUM>, of the wireless device <NUM> of <FIG>, for example. In some aspects, the apparatus may additionally include means for generating a first signal field, a second signal field, and a third signal field in the physical layer header of the clear to transmit message and generating the local address field in one of the second signal field and the third signal field. This means may comprise the processing system <NUM>, and in some aspects the memory <NUM>, of the wireless device <NUM> of <FIG>, for example.

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

Various modifications to the aspects described in this disclosure can be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to some aspects without departing from the spirit or scope of this disclosure. Thus, the disclosure is not intended to be limited to the aspects shown herein, but is to be accorded the widest scope consistent with the claims, the principles and the novel features disclosed herein. The word "exemplary" is used exclusively herein to mean "serving as an example, instance, or illustration. " Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over some aspects.

Certain features that are described in this specification in the context of separate aspects also can be implemented in combination in a single aspect. Conversely, various features that are described in the context of a single aspect also can be implemented in multiple aspects separately or in any suitable sub-combination. Moreover, although features can be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination can be directed to a sub-combination or variation of a sub-combination.

The various operations of methods described above may be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures may be performed by corresponding functional means capable of performing the operations.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array message (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 may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller or state machine.

In one or more aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer readable medium may comprise non-transitory computer readable medium (e.g., tangible media).

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by an access terminal and/or base access terminal as applicable. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that an access terminal and/or base access terminal can obtain the various methods upon coupling or providing the storage means to the device.

Claim 1:
A method for wireless communication performed by an access terminal (120a...i), comprising:
receiving, a clear to transmit message (<NUM>) from an access point (<NUM>), wherein the clear to transmit message comprises a header (<NUM>) having a local address field (<NUM>) therein, the clear to transmit message (<NUM>) indicating a transmission opportunity, the clear to transmit message (<NUM>) further comprising a request that a plurality of devices concurrently transmit data at a specific time, the plurality of devices comprising the access terminal (120a...i),
the clear to transmit message further comprising a second address field (<NUM>) in the header (<NUM>), the second address field (<NUM>) including a basic service set identifier of the access point (<NUM>).