Methods and systems for multi user uplink compatibility with legacy devices

Methods and apparatus for multiple user uplink are provided. In one aspect, a method of transmitting a physical layer convergence protocol data unit on a wireless medium includes generating a first portion and a second portion of the physical layer convergence protocol data unit, transmitting the first portion at a first data rate, the first portion decodable by a first and second sets of devices, and transmitting the second portion at a second data rate higher than the first data rate, the second portion decodable by the second set of devices.

FIELD

Certain aspects of the present disclosure generally relate to wireless communications, and more particularly, to methods and apparatus for multiple user uplink communication in a wireless network.

BACKGROUND

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 user 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 an improved protocol for uplink transmissions from multiple terminals.

SUMMARY

One aspect disclosed is a method of transmitting a physical layer convergence protocol data unit on a wireless medium. The method includes generating a first portion and a second portion of the physical layer convergence protocol data unit, transmitting the first portion at a first data rate, the first portion decodable by a first and second sets of devices; and transmitting the second portion at a second data rate higher than the first data rate, the second portion decodable by the second set of devices. In some aspects, the generating the second portion includes generating an indication of scheduling information for a multi-user transmission. In some aspects, the generating the second portion includes generating an identification of one or more of the second set of devices that will communicate during the multi-user transmission. In some aspects, the generating the identification of the one or more of the second set of devices includes generating at least one of a station identifier, group identifier, and association identifier for each of the one or more second set of devices.

In some aspects, the generating the second portion includes generating an indication of one or more of a modulation and coding scheme (MCS), bandwidth, sub-band, spatial stream information, and length information for the multi-user transmission. In some aspects, the generating the first portion includes generating a duration field, the duration field including a data value greater than a combined length of the first and second portions.

In some aspects, the generating the second portion includes generating an indication of a length of the second portion. In some aspects, the generating the first portion includes generating a signal field for indicating an end position of the second portion.

Another aspect disclosed is an apparatus for transmitting a physical layer convergence protocol data unit on a wireless medium. In some aspects, the apparatus includes a processor configured to generate first and second portions of the physical layer convergence protocol data unit, a transmitter configured to transmit the first portion at a first data rate, the first portion decodable by a first and second sets of devices; and transmit the second portion at a second data rate higher than the first data rate, the second portion decodable by the second set of devices. In some aspects, the generation of the second portion includes generating an indication of scheduling information for a multi-user transmission. In some aspects, the generation of the second portion includes generating an identification of one or more of the second set of devices that will communicate during the multi-user transmission. In some aspects, the generation of the identification of the one or more of the second set of devices includes generating at least one of a station identifier, group identifier, and association identifier for each of the one or more second set of devices.

In some aspects, the generation of the second portion includes generating an indication of one or more of a modulation and coding scheme (MCS), bandwidth, sub-band, spatial stream information, and length information for the multi-user transmission. In some aspects, the generation of the first portion includes generating a duration field storing a value greater than a combined length of the first and second portions. In some aspects, the generation of the second portion includes generating an indication of a length of the second portion. In some aspects, the generation of the first portion includes generating a signal field indicating an end position of the second portion.

Another aspect disclosed is a method of receiving a physical layer convergence protocol data unit on a wireless medium. The method includes receiving, by a wireless device, a first portion of the physical layer convergence protocol data unit, determining, based on the first portion, whether the physical layer convergence protocol data unit includes a second portion transmitted at a higher data rate than the first portion; and receiving the second portion at the higher data rate based on the determining.

In some aspects, the method also includes decoding the second portion for determining scheduling information for a multi-user transmission. In some aspects, the method also includes decoding the second portion for identifying one or more of the second set of devices that will communicate during the multi-user transmission, determining if the wireless device is identified, and communicating during the multi-user transmission based on whether the wireless device is identified.

In some aspects, the method includes identifying the one or more of the second set of devices by decoding one of a station identifier, group identifier, and association identifier for each of the one or more second set of devices from the second portion. In some aspects, the method includes decoding the second portion for determining one or more parameters of the multi-user transmission including one or more of a modulation and coding scheme (MCS), bandwidth, sub-band, spatial stream information, and length information for the multi-user transmission; and performing the multi-user transmission based on the determined one or more parameters.

In some aspects, the method includes decoding the first portion for determining a duration field having a data value greater than a combined length of the first and second portions; and setting a network allocation vector based on the data value of the duration field. In some aspects, the method also includes decoding an indication of a length of the second portion included in the second portion for determining the length of the second portion; and decoding the second portion based on the determined length.

In some aspects, the method also includes decoding a signal field in the first portion for determining an end position of the second portion; and decoding the second portion based on the determined end position.

Another aspect disclosed is an apparatus for receiving a physical layer convergence protocol data unit on a wireless medium. The apparatus includes a receiver configured to receive a first portion of the physical layer convergence protocol data unit; and a processor configured to determine, based on the first portion, whether the physical layer convergence protocol data unit includes a second portion transmitted at a higher data rate than the first portion, wherein the receiver is further configured to receive the second portion at the higher data rate based on the determining.

In some aspects of the apparatus, the processor is further configured to: decode the second portion for determining scheduling information for a multi-user transmission. In some aspects, the processor is further configured to decode the second portion for identifying one or more devices that will communicate during the multi-user transmission, determine if the apparatus is identified; and communicate during the multi-user transmission based on whether the apparatus is identified.

In some aspects of the apparatus, the processor is further configured to identify the one or more of devices by decoding one of a station identifier, group identifier, and association identifier for each of the one or more second set of devices from the second portion. In some aspects of the apparatus, the processor is further configured to decode the second portion for determining one or more parameters of the multi-user communication including a modulation and coding scheme (MCS), bandwidth, sub-band, spatial stream information, and length information for the multi-user transmission, and perform the multi-user transmission based on the determined parameters.

In some aspects of the apparatus, the processor is further configured to decode the first portion for determining a duration field having a data value greater than a combined length of the first and second portions; and set a network allocation vector based on the determined data value of the duration field.

DETAILED DESCRIPTION

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 802.11 family of wireless protocols.

In some aspects, wireless signals may be transmitted according to a high-efficiency 802.11 protocol using orthogonal frequency-division multiplexing (OFDM), direct-sequence spread spectrum (DSSS) communications, a combination of OFDM and DSSS communications, or other schemes. Implementations of the high-efficiency 802.11 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 signals across short distances, and/or may be able to transmit signals less likely to be blocked by objects, such as humans.

In some implementations, 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 stations, or “STAs”). In general, an AP serves as a hub or base station for the WLAN and an STA serves as a user of the WLAN. For example, a STA may be a laptop computer, a personal digital assistant (PDA), a mobile phone, etc. In an example, an STA connects to an AP via a Wi-Fi (e.g., IEEE 802.11 protocol such as 802.11ah) compliant wireless link to obtain general connectivity to the Internet or to other wide area networks. In some implementations an STA 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 user terminals. A TDMA system may allow multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots, each time slot being assigned to different user terminal. A TDMA system may implement 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 802.11 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.

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

A station “STA” may also comprise, be implemented as, or known as a user terminal, an access terminal (“AT”), a subscriber station, a subscriber unit, a mobile station, a remote station, a remote terminal, a user agent, a user device, user equipment, or some other terminology. In some implementations an access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (“SIP”) phone, a wireless local loop (“WLL”) station, a personal digital assistant (“PDA”), a handheld device having wireless connection capability, or 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. 1is a diagram that illustrates a multiple-access multiple-input multiple-output (MIMO) system100with access points and user terminals. For simplicity, only one access point110is shown inFIG. 1. An access point is generally a fixed station that communicates with the user terminals and may also be referred to as a base station or using some other terminology. A user terminal or STA may be fixed or mobile and may also be referred to as a mobile station or a wireless device, or using some other terminology. The access point110may communicate with one or more user terminals120at any given moment 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., reverse link) is the communication link from the user terminals to the access point. A user terminal may also communicate peer-to-peer with another user terminal. A system controller130couples to and provides coordination and control for the access points.

While portions of the following disclosure will describe user terminals120capable of communicating via Spatial Division Multiple Access (SDMA), for certain aspects, the user terminals120may also include some user terminals that do not support SDMA. Thus, for such aspects, the AP110may be configured to communicate with both SDMA and non-SDMA user terminals. This approach may conveniently allow older versions of user terminals (“legacy” stations) that do not support SDMA to remain deployed in an enterprise, extending their useful lifetime, while allowing newer SDMA user terminals to be introduced as deemed appropriate.

The system100employs multiple transmit and multiple receive antennas for data transmission on the downlink and uplink. The access point110is equipped with Napantennas and represents the multiple-input (MI) for downlink transmissions and the multiple-output (MO) for uplink transmissions. A set of K selected user terminals120collectively represents the multiple-output for downlink transmissions and the multiple-input 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 multiplexed in code, frequency or time by some means. K may be greater than Napif 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 user terminal may transmit user-specific data to and/or receive user-specific data from the access point. In general, each selected user terminal may be equipped with one or multiple antennas (i.e., Nut≥1). The K selected user terminals can have the same number of antennas, or one or more user terminals may have a different number of antennas.

The SDMA system100may 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 system100may also utilize a single carrier or multiple carriers for transmission. Each user 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 system100may also be a TDMA system if the user terminals120share the same frequency channel by dividing transmission/reception into different time slots, where each time slot may be assigned to a different user terminal120.

FIG. 2illustrates a block diagram of the access point110and two user terminals120mand120xin MIMO system100. The access point110is equipped with Ntantennas224athrough224ap. The user terminal120mis equipped with Nut,mantennas252mathrough252xu, and the user terminal120xis equipped with Nut,xantennas252xathrough252xu. The access point110is a transmitting entity for the downlink and a receiving entity for the uplink. The user terminal120is 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, Nupuser terminals are selected for simultaneous transmission on the uplink, and Ndnuser terminals are selected for simultaneous transmission on the downlink. Nupmay or may not be equal to Ndn, and Nupand Ndnmay be static values or may change for each scheduling interval. Beam-steering or some other spatial processing technique may be used at the access point110and/or the user terminal120.

On the uplink, at each user terminal120selected for uplink transmission, a TX data processor288receives traffic data from a data source286and control data from a controller280. The TX data processor288processes (e.g., encodes, interleaves, and modulates) the traffic data for the user terminal based on the coding and modulation schemes associated with the rate selected for the user terminal and provides a data symbol stream. A TX spatial processor290performs spatial processing on the data symbol stream and provides Nut,mtransmit symbol streams for the Nut,mantennas. Each transmitter unit (TMTR)254receives and processes (e.g., converts to analog, amplifies, filters, and frequency upconverts) a respective transmit symbol stream to generate an uplink signal. Nut,mtransmitter units254provide Nut,muplink signals for transmission from Nut,mantennas252, for example to transmit to the access point110.

Nupuser terminals may be scheduled for simultaneous transmission on the uplink. Each of these user 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 point110.

At the access point110, Nupantennas224athrough224apreceive the uplink signals from all Nupuser terminals transmitting on the uplink. Each antenna224provides a received signal to a respective receiver unit (RCVR)222. Each receiver unit222performs processing complementary to that performed by transmitter unit254and provides a received symbol stream. An RX spatial processor240performs receiver spatial processing on the Nupreceived symbol streams from Nupreceiver units222and provides Nuprecovered 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 user terminal. An RX data processor242processes (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 user terminal may be provided to a data sink244for storage and/or a controller230for further processing.

On the downlink, at the access point110, a TX data processor210receives traffic data from a data source208for Ndnuser terminals scheduled for downlink transmission, control data from a controller230, and possibly other data from a scheduler234. The various types of data may be sent on different transport channels. TX data processor210processes (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 processor210provides Ndndownlink data symbol streams for the Ndnuser terminals. A TX spatial processor220performs spatial processing (such as a precoding or beamforming) on the Ndndownlink data symbol streams, and provides Nuptransmit symbol streams for the Nupantennas. Each transmitter unit222receives and processes a respective transmit symbol stream to generate a downlink signal. Nuptransmitter units222may provide Nupdownlink signals for transmission from Nupantennas224, for example to transmit to the user terminals120.

At each user terminal120, Nut,mantennas252receive the Nupdownlink signals from the access point110. Each receiver unit254processes a received signal from an associated antenna252and provides a received symbol stream. An RX spatial processor260performs receiver spatial processing on Nut,mreceived symbol streams from Nut,mreceiver units254and provides a recovered downlink data symbol stream for the user terminal120. The receiver spatial processing may be performed in accordance with the CCMI, MMSE, or some other technique. An RX data processor270processes (e.g., demodulates, deinterleaves and decodes) the recovered downlink data symbol stream to obtain decoded data for the user terminal.

At each user terminal120, a channel estimator278estimates 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 estimator228estimates the uplink channel response and provides uplink channel estimates. Controller280for each user terminal typically derives the spatial filter matrix for the user terminal based on the downlink channel response matrix Hdn,mfor that user terminal. Controller230derives the spatial filter matrix for the access point based on the effective uplink channel response matrix Hup,eff. The controller280for each user terminal may send feedback information (e.g., the downlink and/or uplink eigenvectors, eigenvalues, SNR estimates, and so on) to the access point110. The controllers230and280may also control the operation of various processing units at the access point110and user terminal120, respectively.

FIG. 3illustrates various components that may be utilized in a wireless device302that may be employed within the wireless communication system100. The wireless device302is an example of a device that may be configured to implement the various methods described herein. The wireless device302may implement an access point110or a user terminal120.

The wireless device302may include a processor304which controls operation of the wireless device302. The processor304may also be referred to as a central processing unit (CPU). Memory306, which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processor304. A portion of the memory306may also include non-volatile random access memory (NVRAM). The processor304may perform logical and arithmetic operations based on program instructions stored within the memory306. The instructions in the memory306may be executable to implement the methods described herein.

The wireless device302may also include a housing308that may include a transmitter310and a receiver312to allow transmission and reception of data between the wireless device302and a remote location. The transmitter310and receiver312may be combined into a transceiver314. A single or a plurality of transceiver antennas316may be attached to the housing308and electrically coupled to the transceiver314. The wireless device302may also include (not shown) multiple transmitters, multiple receivers, and multiple transceivers.

The wireless device302may also include a signal detector318that may be used in an effort to detect and quantify the level of signals received by the transceiver314. The signal detector318may detect such signals as total energy, energy per subcarrier per symbol, power spectral density and other signals. The wireless device302may also include a digital signal processor (DSP)320for use in processing signals.

The various components of the wireless device302may be coupled together by a bus system322, which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus.

Certain aspects of the present disclosure support transmitting an uplink (UL) signal from multiple STAs to an AP. In some embodiments, the UL signal may be transmitted in a multi-user MIMO (MU-MIMO) system. Alternatively, the UL signal may be transmitted in a multi-user FDMA (MU-FDMA) or similar FDMA system. In some embodiments, UL-MU-MIMO or UL-FDMA transmissions can be sent simultaneously from multiple STAs to an AP and may create efficiencies in wireless communication.

FIG. 4is a diagram that illustrates a multiple-access multiple-input multiple-output (MIMO) system100with access points and user terminals. The access point110inFIG. 4is shown communicating with two groups of devices402a-b. The first group of devices402aincludes at least user terminals120a-c. The second group of devices402bincludes at least user terminals120d-f. In some aspects, user terminals120a-cmay have a first set of features or capabilities, while user terminals120d-fmay have a second set of capabilities or features. For example, user terminals120a-cmay have been manufactured before a particular date, and thus their features or capabilities reflect technical standards and or features present at their time of manufacture. In contrast, user terminals120d-fmay have been manufactured after the particular date, and thus their features or capabilities include implementation of technical standards and/or features that post-date the particular date. Alternatively, user terminals120a-cmay be less sophisticated and thus less expensive devices than user terminals120d-f. Due to less expensive design, user terminals120a-cmay be able to provide fewer features and/or capabilities than user terminals120d-f.

As discussed above, certain aspects of the present disclosure support transmitting an uplink (UL) signal from multiple STAs to an access point. Older, legacy devices may not implement multi-user uplink transmissions. Therefore, network messages implementing multi-user uplink transmissions that were defined after the older legacy devices were produced, may not be readily interpreted or decoded by these legacy devices. However, it is still desirable to have these legacy devices refrain from transmissions during a non-contention period associated with multi-user uplink (UL) transmissions. One way to accomplish this would be to transmit two separate PPDUs, with a first PPDU indicating to legacy devices that they should refrain from transmission during a contention free period. A second, separate transmission of a PPDU could then be performed to communicate parameters of a multi-user transmission to select devices that have multi-user uplink capabilities. However, the transmission of two separate messages for the two sets of devices presents inefficiencies in network operation that are undesirable. Thus, methods and systems that communicate contention free periods to all devices, including legacy devices, in an efficient manner are desired, even when the contention free period will be used for multi-user uplink transmissions.

Additionally, devices that are capable of performing multi-user transmissions may also possess additional capabilities beyond those of legacy devices. For example, some of these devices may be capable of transmitting and/or receiving data at higher data rates than legacy devices. Therefore, it is desirable to take advantage of higher transmission and/or receive data rates present in modern devices to improve network throughput.

FIG. 5Aillustrates an exemplary clear to send frame. The clear to send frame500includes a physical layer convergence protocol (PLCP) header501and a Media Access Control Protocol Data Unit (MPDU)503. The PLCP header501includes at least a short training field502, a long training field504, and a signal field506. The Media Access Control Protocol Data Unit (MPDU)503includes a data portion508, that includes a service field510, a physical layer service data unit512, a tail field514, and a pad field516. The service field510includes a scrambler seed field522and other fields524. The physical layer service data unit field512includes a frame control field532, duration field534, address field536, and a frame check sequence field538.

FIG. 6Aillustrates an exemplary message for communicating multi-user uplink transmission information to both legacy and non-legacy devices. The example message600includes fields corresponding to those described with respect toFIG. 5A. In some aspects, frame control field632may substantially conform with the format shown for frame control field532inFIG. 5B. In addition, the message600includes two data portions, MPDU603, shown as data portion608, and also a second data portion609. Data portion608is equivalent to data508described with respect toFIG. 5A. This equivalency enables data portion608to be decoded by both legacy and non-legacy devices. Data portion609may be formatted in a manner that is not decodable by legacy devices. For example, the format of data portion609may not have been defined with some legacy devices were designed and/or produced. In some aspects, data portion609may be transmitted at a different data rate than data portion608, and also at a higher rate than the first portion should inFIG. 6A, which includes the PLCP Header601and data portion608. In some aspects, legacy devices may not be able to decode data portion609because of its higher data transmission rate.

In some aspects, data portion609may comprise information such as downlink data for specific receivers. In some aspects, data portion609may start with or include a Group ID that identifies a group of STAs to which a subsequent portion of data portion609is addressed. In some aspects, the presence of data portion609in frame600may be signaled to a device receiving frame600. This signaling may be designed to not interfere with legacy devices decoding and processing of the first portion600a. For example, in some aspects, a transmitter of frame600may set the address field636of data portion608based on whether the second portion609is present in a frame. When transmitting frame500ofFIG. 5A, a transmitting device may set the address field536to a basic service set identifier (BSSID) of the transmitting device. When transmitting frame600, which includes second portion609, the transmitting device may set the address field636to a multicast version of the basic service set identifier (BSSID). A receiving device decoding the address field536and/or636may determine whether the address is a multicast address or not. If the field536and/or636is multicast, a receiving device may determine data portion609is present in the frame, while if the address is not multicast, the receiving device may determine data portion609is not present (i.e. a frame similar to frame500is being received). Other fields of frames500and600may be used to indicate whether the second portion609is present in a frame. For example, in some aspects, a frame subtype field (not shown) in the frame control field632may indicate whether the second portion609is present. In some aspects, a specific combination of frame type and subtype field (not shown) in the frame control field632may indicate whether the second portion609is present. In some aspects, a specific control subtype may indicate whether the second portion609is present. In some aspects, a specific control frame extension may indicate whether the second portion609is present. In some aspects, a specific extension subtype may indicate whether the second portion609is present. In some aspects, a specific control frame, control frame extension frame, or extension frame indicating the presence of second portion609may comprise the same subfields as a CTS MPDU (i.e. Frame Control, Duration, Address, FCS). In some aspects, the scrambler seed field522and/or622may indicate the presence of the second portion609. In some aspects, a combination of a multicast version of the BSSID and a specific value of (part of) the scrambler seed may indicate the presence of the second portion609. In some aspects, instead of a multicast version of the BSSID a localized version of the BSSID may be used. In some aspects, the L-SIG field506/606may indicate the presence of the data portion609. For example, in some aspects, if the L-SIG field506/506indicates a length that is longer than the PLCP header601and first portion608, a receiver may determine that the second portion609is present.

In some aspects, setting particular bits of the Frame Control (FC) field632included in the PSDU612may indicate the presence of the second portion609. In some aspects, setting to one (1) one of the following subfields of the FC field632may indicate the presence of the second portion609: To DS field (such as field556ofFIG. 5B), From DS field (such as field558ofFIG. 5B), More Frag field (such as field560ofFIG. 5B), Retry field (such as field562ofFIG. 5B), or a Protected Frame field (such as field568ofFIG. 5B). In some aspects, if a combination of these subfields are set to one (1), the frame control field632may indicate the presence of second portion609. In some aspects, a combination of these subfields set to one (1) in combination with particular values of a multicast address field636may indicate the presence of second portion609. In some aspects, a specific value in the scrambler seed field622may also be used in conjunction with the fields discussed above to indicate that second portion609is present. In some aspects, the second portion609contains a second portion type field (not shown), which indicates a type of the second portion609. In some aspects, the PSDU612may be a clear-to-send frame.

FIG. 6Bis an illustration of one embodiment of a second portion609a. In some aspects, second portion609amay start with or include a greenfield VHT PHY header preceding a downlink MU-MIMO transmission. A greenfield VHT PHY header is a VHT PHY header without a legacy OFDM portion699, i.e. a VHT PHY header that starts at VHT SIG-A field688and omits the L-STF682, L-LTF684and L-SIG686fields of the VHT PHY header. In some aspects, second portion609amay comprise a modified greenfield VHT PHY header, which includes uplink (multi-user) transmission information. The uplink (multi-user) transmission may begin after the downlink VHT transmission, for example separated by a SIFS interval.

FIG. 6Cis a simplified illustration of one embodiment of the PLCP Protocol Data Unit600described inFIG. 6A. As shown, the PPDU650includes a signal field606, a MPDU608, and a second portion609. In the aspect shown inFIG. 6C, the L-SIG value defines a length of the MPDU608, which in this case is a clear-to-send frame that is fourteen (14) bytes long. Since the signal field606is indicating a length equivalent to the length of the MPDU608(in this case a clear-to-send frame), a device receiving the PPDU650may determine whether the second portion609is present in the PPDU650based on some other field besides the signal field606. For example, as discussed above, one or more of a subtype field, scrambler seed field, and/or address field may be used to determine whether the second portion609is present in the PPDU650.

FIG. 6Dis a simplified illustration of one embodiment of the PLCP Protocol Data Unit600described inFIG. 6A. As shown, the PLCP Protocol Data Unit675includes a signal field606, a MPDU608, and a second portion609. In the aspect shown inFIG. 6D, the L-SIG value defines a length of the MPDU608which in this case is a clear-to-send frame that is fourteen (14) bytes long, plus an additional amount “z.” The combined length of the MPDU (14) and the amount “z” indicates the transmission time of the PPDU675extends to the end of second portion609. A device receiving the PLCP Protocol Data Unit675may determine whether the second portion609is present in the PPDU675based on the L-SIG field606. For example, if the L-SIG filed606indicates a length greater than the length of the MPDU608, a receiving device may determine the second portion609is present in the PPDU675.

In some aspects, the network allocation vector (NAV) indicated in PPDU675is to be set after a time indicated by the L-SIG value. For example, the PPDU675may indicate that the NAV starts after completion of the transmission of the PPDU675, including both the first portion608and second portion609.

In some aspects, the first portion608may indicate a NAV that extends beyond the length of the second portion, as shown inFIG. 6D. In some aspects, the first portion608may indicate that a multi-user transmission will be performed after transmission of the second portion609. The NAV indicated by the first portion608may provide protection for the multi-user transmission. In some aspects, the length of the second portion609is indicated by the second portion itself. For example, the second portion609may include a length field, perhaps early in the second portion, such that decoding devices can determine the length of the second portion. In some aspects, the L-SIG value606may indicate the length of the second portion as discussed above. In some other aspects, the length of the second portion may be predetermined. For example, in some aspects, the length of the second portion may be fixed. In some other aspects, the length of the second portion may be communicated to one or more receivers via separate message exchanges (not shown).

FIGS. 6E-Hare simplified illustrations of embodiments of message exchanges that include provisions for extending the response time for a multi-user uplink transmission.

FIG. 6Eillustrates a message exchange690. The PPDU transmitted as part of message exchange690includes an signal field606that indicates the length of the CTS MPDU608. Extra symbols680are transmitted after the second portion609. In some aspects, the extra symbols680may be transmitted after a cyclic redundancy check field or a frame check sequence field of the second portion609. The presence of these extra symbols680is known by devices that will perform an uplink transmission during the transmission opportunity682. The presence of the extra symbols680enables the uplink transmitting devices to postpone their uplink transmissions until transmission of the extra symbols have been completed, and after the short inter-frame space (SIFS) time681has passed. This additional time between completion of the transmission of second portion609and the beginning of an uplink transmission may provide additional time for Phased Locked Loops (PLLs) to settle at the uplink transmitters.

FIG. 6Fillustrates an alternate message exchange692. Message exchange692does not transmit the extra symbols680ofFIG. 6E. Instead of transmitting extra symbols680and maintaining a consistent short inter-frame space SIFS time681, message exchange692utilizes an extended short inter-frame space (SIFS) time683. The extended short inter-frame space time683functions in a similar manner as the extra symbols and SIFS681, in that it provides additional time after the transmission/reception of second portion609before an uplink transmission during TxOp684begins. In some aspects, the extended SIFS time may or may not be filled with extra (random) symbols. As discussed above, this additional time may provide for Phased Locked Loops (PLLs) to settle at uplink transmitters.

FIG. 6Galso illustrates the use of extra symbols680during a message exchange694. Message exchange694differs from message exchange690in that the signal field606ofFIG. 6Gmay be followed by a CTX MPDU608-ctxinstead of a CTS MPDU608as illustrated inFIG. 6E. In some aspects, the extra symbols may be transmitted after a cyclic redundancy check field or a frame check sequence field of the CTX MPDU608-ctx.

FIG. 6Hillustrates a message exchange696including a CTX MPDU608ctxthat utilizes an extended SIFS time683, instead of the extra symbols680as described above with respect toFIG. 6G. In some aspects, the extended SIFS time may or may not be filled with extra (random) symbols.

FIG. 7is an example of a second portion609bof a PLCP Protocol Data Unit. The second portion includes a control (CTRL) field720, a PLCP Protocol Data Unit duration field725, a STA info field730a-n, and an error check field780. The CTRL field720is a generic field that may include information regarding the format of the remaining portion of the frame (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 user terminals120, and/or an indication of allowed TID. The CTRL field720may also indicate if the multi-user transmission that follows the frame600is 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 field1230. Alternatively, the indication of whether frame600is for UL MU MIMO or for UL FDMA can be based on the value of a subtype field in the frame control field632, for example, as shown with respect to frame control field532ofFIG. 5B, which includes a sub-type field554. Note that UL MU MIMO and UL FDMA operations can be jointly performed by specifying to a STA both the spatial streams to be used and the channel to be used, in which case both fields are present in the second portion; in this case, the Nss indication is referred to a specific tone allocation. The PPDU duration725field indicates the duration of the following UL-MU-MIMO PPDU that the user terminals120are allowed to send. The STA Info fields730a-ncontain information regarding a particular STA and may include a per-STA (per user terminal120) set of information (see STA Info1730aand STA Info N730n). The STA Info fields730a-nmay include an AID or MAC address field732which identifies a STA, a number of spatial streams field (Nss)734field which indicates the number of spatial streams a STA may use (in an UL-MU-MIMO system), a Time Adjustment field736which indicates a time that a STA should adjust its transmission compared to the reception of a trigger frame (frame600in this case), a Power Adjustment field738which indicates a power back-off a STA should take from a declared transmit power, a Tone Allocation field740which indicates the tones or frequencies a STA may use (in a UL-FDMA system), an Allowed TID742field which indicates the allowable TID, an Allowed TX Mode744field which indicates the allowed TX modes. A user terminal120receiving a second portion609with an Allowed TID742indication 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.

FIG. 8illustrates another example of a second portion609cof a PPDU. In this embodiment, the STA Info field830does not contain the AID or MAC Address field (such as field732) and instead the second portion609includes a group identifier (GID)826field which identifies the STAs by a group identifier rather than an individual identifier.

FIG. 9is a message timing diagram for one implementation of multi-user uplink transmission. The diagram begins with the AP110transmitting PPDU600ofFIG. 6A, which includes a first portion608and a second portion609. In some aspects, the first portion may define a contention free period on the wireless medium. For example, in some aspects, the first portion may be a clear-to-send frame. The first portion may be configured such that it can be readily decoded by both legacy and non-legacy devices. For example, the first portion may be decodable by both the devices in device set402aand device set402billustrated inFIG. 4. Therefore, the STAs120aand120d-fshown inFIG. 9can decode the first portion608. In some aspects, the decodability of first portion608relates to its format. For example, in some aspects, both the first and second sets of devices are configured to decode the allocation and values of fields comprising the first portion. In some aspects, the decodability of the first portion608relates to a rate at which the AP110transmits the first portion. For example, in some aspects, the first portion608may be transmitted at 6 Mbps OFDM. In some aspects, all of STAs120aand120d-fmay be able to decode frames transmitted at this rate. In some aspects, the first portion may be decoded by the STA120aand STAs120d-fto indicate how to set a network allocation vector, which defines a contention free period920on the wireless medium.

The second portion609may not be decodable by both the first and second groups of devices illustrated inFIG. 4. For example, the second portion609may be decodable only by the group of devices in group402b. In some aspects, the second portion609is transmitted by the AP110at a higher data rate than the first portion608. For example, in some aspects, the second portion609is transmitted at 12 or 24 Mbps. In some aspects, transmission of the second portion at this rate is conditional on whether intended recipients of the second portion (in this case, STAs120d-f) are near enough to be able to receive frames transmitted at the higher rate.

When the second portion609is transmitted at a higher rate, STA120amay not be able to decode the second portion609. However, the transmission of second portion609does not interfere with STA120a's ability to decode the first portion608. Therefore, STA120ais still able to set its NAV as shown by NAV920.

As discussed above with respect toFIGS. 7 and 8, the second portion may include information defining how a multi-user uplink transmission performed during non-contention period920will be performed. For example, the second portion may indicate to one or more of STAs120d-fthat they may perform a multi-user transmission during the non-contention period920and which multi-user parameters control the transmission (such as which tones should be used in an UL-OFDM transmission or the number of spatial streams used in a UL-MU-MIMO transmission). In some aspects, scheduling information controlling the multi-user transmission included in the second portion may include an indication of one or more stations that should participate in the OFDMA and/or MU-MIMO multi-user transmission (such as station identifiers, MAC addresses, association identifiers, group identifiers, etc). The scheduling information may also define one or more of bandwidth and/or subband information for each device transmitting during the multi-user transmission, how many spatial streams should be included in the multi-user transmission, and/or which device is assigned to which spatial stream, the modulation and coding scheme (MCS) for the multi-user transmission, and the maximum length of the multi-user transmission.

Stations receiving the second portion may then decode the second portion to decode one or more of the scheduling parameters controlling the multi-user transmission, and perform the multi-user transmission as specified by the decoded parameters.

In the illustrated message sequence ofFIG. 9, the second portion indicates to each of STAs120d-fthat they should transmit during the contention free period920. After the PPDU600is transmitted, STA120adefers any pending transmissions during the contention free period920. Since each of STAs120d-fwas provided with an indication to transmit by the second portion609, each of STAs120d-ftransmits data910a-cduring the contention free period920. Each of data transmissions910a-cis based on multi-user uplink transmission parameters provided by the second portion609.

FIG. 10Ais a flowchart of a method for multi-user uplink communication on a wireless network. In some aspects, the method1000may be performed by the AP110and/or the wireless device302.FIG. 10Adescribes a method of controlling a multi-user uplink transmission on a wireless medium that is compatible with devices capable of multi-user uplink transmissions and also with devices that may not be configured to operate in a multi-user uplink environment. For example, legacy devices may not have programming logic so as to decode and properly interpret multi-user control data, such as that described above with respect to the second portion609. By transmitting a physical layer convergence protocol data unit that includes two portions, compatibility with both legacy devices, and devices that support multi-user uplink transmissions may be achieved.

In block1005, first and second portions of a physical layer convergence protocol data unit are generated. In some aspects, the first portion is generated to indicate a duration of a contention free period on the wireless medium. For example, in some aspects, the first portion includes a clear-to-send frame.

In some aspects, the first portion is generated to indicate the presence of the second portion in the PPDU. In some aspects, the first portion is generated to include a signal field storing a value indicating a length greater than a length of the first portion. For example, in some aspects, the L-SIG field606of PPDU600may be generated to store a value indicating a length greater than the length of first portion608. In some aspects, the first portion is generated to include a duration field, the duration field indicating a length greater than a length of the first portion. This may indicate to receiving devices that the second portion is present in some aspects.

In some aspects, a specific value greater than the length of first portion608may be used to indicate the presence of a second portion609in the physical layer convergence protocol data unit. For example, in some aspects, a length value of 0xFFFF may indicate the presence of the second portion.

In some aspects the first portion may be generated to include a scrambler seed value, with the scrambler seed value indicating the presence or absence of the second portion. For example, in some aspects, scrambler seed field622may be generated with a value that indicates the presence or absence of the second portion. In some aspects, the scrambler seed value is used in combination with the L-SIG field described above to indicate the presence or absence of the second portion.

In some aspects, the first portion may be generated to include a type field and a subtype field. For example, the frame control field632may include a type and subtype field, for example, as shown with respect to frame control field532ofFIG. 5B, which includes a type field552and sub-type field554. In some aspects, the subtype field554may be generated with a value that indicates the presence or absence of the second portion.

In some aspects, the first portion may be generated to set one or more combinations of fields in a frame control field, such as frame control field632illustrated inFIG. 6A, to indicate whether a second portion is present. For example, one or more of a “To DS” field, “From DS” field, “More Frag” field, “Retry” field, or “Protected Frame” field may be generated to have a value of one (1) to indicate the second portion is present, while generating the frame control field to have one or more of these fields with a value of zero (0) may indicate a second portion is not present.

In some aspects, one or more fields of a frame control field, along with one or more of a scrambler seed field, such as scrambler seed field622, and/or an address field, such as address field636may be generated to indicate whether the second portion is present. For example, if the address field636is generated to indicate a multicast address, and one or more particular fields of the frame control field632are generated to have a value of one (1), this may indicate that the second portion is present in some aspects.

In some aspects, the first portion may be generated to include an address field, such as address field636. In some aspects, the address field may be generated to include a value that indicates the presence or absence of the second portion. For example, in some aspects, whether the address field includes a multicast address or a non-multicast address may indicate whether the second portion is present in the physical layer convergence protocol data unit. In some aspects, whether the address field includes a localized address or a non-localized address may indicate whether the second portion is present in the physical layer convergence protocol data unit.

In some aspects, the second portion is generated to include an error check value for the second portion. For example, in some aspects, the second portion may be generated to include a parity bit and/or cyclic redundancy check (CRC) value for the second portion.

In some aspects, the second portion is generated to indicate control data for a multi-user uplink transmission. For example, the second portion may be generated to identify a plurality of devices. In some aspects, the plurality of devices are each identified by their station address or their association identifier. In some aspects, the second portion may specify a group identifier, which identifies a group of devices that may perform a multi-user uplink transmission following transmission of the first and second portions.

In some aspects, the second portion is also generated to indicate a plurality of indications of multi-user transmission opportunities corresponding to each of the association identifiers. For example, for each device identified in the second portion as performing a portion of the multi-user uplink transmission, transmission parameters for that device's transmission may be included in the second portion. As described with respect toFIGS. 7 and 8, transmission parameters such as tone allocations (field740and840) and/or the number of spatial streams (fields734and834) may be indicated in the second portion. Other fields shown in the embodiment of second portions609a-cofFIG. 6B, 8, or9may be included in the second portion. In some aspects, the second portion may include multi-user transmission scheduling information such as bandwidth and/or subband assignments for one or more of the devices participating in the defined multi-user communication, how many spatial streams will be utilized by the multi-user transmission, the modulation and coding scheme (MCS) to be used by each device participating in the multi-user transmission and/or the length of the multi-user transmission.

In block1010, the first portion is transmitted at a first data rate. As discussed above with respect toFIG. 9, the first portion is configured and transmitted to be decodable by both a first and second sets of devices. For example, the first portion may be decodable by legacy devices that are not configured to support multi-user uplink transmissions. The first portion may be transmitted at a data rate decodable by these legacy devices. For example, the first portion may be transmitted at six (6) Mbps OFDM.

In block1015, the second portion is transmitted at a second data rate higher than the first data rate. The second portion is configured and transmitted such that it may be decoded by a second set of devices. The second set of devices and the first set of devices do not overlap. In some aspects, the second portion is transmitted at 12 or 24 Mbps.

Some aspects of process1000also include receiving a network message. The network message may indicate the data rate at which the second portion and/or the first portions should be sent. In some aspects the first and/or second portions are then transmitted at the appropriate data rate(s) indicated by the network message. In some aspects, the network message is received from an access point or a station. In some aspects, the received network message is a management frame.

In some aspects, process1000includes transmitting one or more additional symbols after transmission of the second portion. In some aspects, the additional symbols may be transmitted after a CRC or FCS covering the second portion is transmitted (as part of the second portion at least in some aspects). In some aspects, these additional symbols provide time for a receiving device's phase locked loop (PLL) to settle before a multi-user uplink transmission begins. In some aspects, the additional symbols may contain no information that needs to be received by any devices that will perform a multi-user uplink transmission during the upcoming transmission opportunity. In some aspects, the additional symbols are transmitted to contain random data. In some aspects, a multi-user uplink transmission is then received short inter-frame space time (SIFS) after transmission of the additional symbols completes.

In some other aspects, process1000includes receiving a multi-user uplink transmission after an extended short inter-frame space (SIFS) time that is longer than the standard SIFS time. This extended SIFS time also provides additional PLL (Phase locked Loop) settlement time for a device performing a multi-user uplink transmission during the transmission opportunity following the extended SIFS.

FIG. 10Bis a functional block diagram of an apparatus1050for wireless communication, in accordance with certain embodiments described herein. In some aspects, the apparatus1050is the device302. Those skilled in the art will appreciate that the apparatus1050may have more components than the simplified block diagrams shown inFIG. 10B.FIG. 10Bincludes only those components useful for describing some prominent features of implementations within the scope of the claims.

The apparatus1050comprises a PLCP Protocol Data Unit generation circuit1055. In some aspects, the PLCP Protocol Data Unit generation circuit1055may be configured to perform one or more of the functions described above with respect to block1005. In some aspects, the PLCP Protocol Data Unit generation circuit1055may include the processor304. The apparatus1050further comprises a transmission circuit1060. In some aspects, the transmission circuit1060may be configured to perform one or more of the functions described above with respect to block1010and/or1015. In some aspects, the transmission circuit1060may include the transmitter310.

FIG. 11Ais a flowchart of a method for multi-user uplink communication on a wireless network. In some aspects, the method1100may be performed by the stations120d-fillustrated inFIG. 4and/orFIG. 9, and/or the wireless device302.FIG. 11Adescribes a method of receiving control information for a multi-user uplink transmission on a wireless medium that is compatible with devices that may not be configured to operate in a multi-user uplink environment. For example, a first set of devices, such as legacy devices, may not have hardware and/or programming logic so as to decode and properly interpret multi-user uplink transmission control data, such as that described above with respect to the second portion609. By first receiving a first portion of a physical layer convergence protocol data unit that is decodable by a first and second sets of devices, certain information relating to a non-contention period may be received by both a first and second sets of devices (for example, legacy and non-legacy devices). For example, a duration of a non-contention period may be determined from the first portion such that a network allocation vector may be properly set by both the first and second sets of devices operating on the wireless medium. For example, the first portion may be decoded by the first and second sets of devices as a clear-to-send frame, which is understood by these devices to set a duration of a network allocation vector that defines a non-contention or contention free period on the wireless network. In some aspects, the value of the duration field may indicate to a receiving device whether the second portion is present in the received frame. For example, if the duration field stores a value that is greater than a threshold, it may indicate the second portion is present. Alternatively, if the duration field stores a value that is greater than a length of the first portion plus an additional threshold then it may indicate the second portion is present. Correspondingly, if the duration field does not exceed the parameters discussed above then the duration field may indicate no second portion is present.

Those devices capable of multi-user uplink transmissions (for example, the second set of devices discussed above) may then receive and decode a second portion of the PPDU that includes control information relating to the multi-user uplink transmission to occur during the contention free period. The second set of devices may be configured to determine whether the second portion is present in the PPDU based on one or more fields of the first portion, as discussed above and below.

The second portion may also be sent at a different data rate than the first portion because, in some aspects, the second set of devices have improved receive capabilities relative to the first set of devices. This improved set of capabilities may include the ability to receive data at a higher data rate(s) than can be supported by the first set of, possible legacy, devices. Transmitting/receiving the second portion at a higher data rate may improve network utilization and efficiency. While method1100is illustrated as including several blocks, it should be understood that not all blocks are performed in all aspects of method1100.

In block1105, a first portion of a PLCP Protocol Data Unit is received by a first device at a first data rate. In some aspects, the first device is a station, such as any of stations120d-fdiscussed above. In block1110, the first portion is decoded to determine a duration of a contention free period. For example, as discussed above with respect toFIG. 9, the first portion may be decoded to set a network allocation vector, which defines a contention free period920. In some aspects, the first portion is decoded as a clear-to-send frame.

In block1115, the first portion is decoded to determine whether a second portion of the PPDU is present. In some aspects, a signal field, such as signal field606is decoded for determining the presence of the second portion. For example, if the signal field indicates a length of the PPDU that is greater than the length of the first portion, process1100may determine that the second portion is present. Alternatively, if the length indicated by the signal field is a specific value, with the specific value also being greater than the length of the first portion, then process1100may determine the second portion is present. In some aspects, a duration field of the first portion may be decoded for determining whether the second portion is present. For example, if the duration field is greater than a threshold, the second portion may be determined to be present. Alternatively, if the duration field stores a value that is greater than a length of the first portion and an additional threshold or offset period of time then the duration may indicate the second portion is present. Correspondingly, if the duration field does not exceed the parameters discussed above then the duration field may indicate no second portion is present.

In some aspects, a scrambler seed value, such as scrambler seed622illustrated inFIG. 6Amay be decoded for determining whether the second portion is present. For example, if particular bits or combinations of bits are set to particular values, process1100may determine the second portion is present. In some aspects, a combination of particular scrambler seed values and signal field values may be used for determining whether the second portion is present.

In some aspects, a control frame included in the first portion may include a frame control field, the frame control field defining a type field and a subtype field. In some aspects, specific values of the subtype field may indicate the presence or absence of the second portion in the PPDU. In some aspects, one or more combinations of fields in a frame control field, such as frame control field632illustrated inFIG. 6A, may be decoded for determining whether a second portion is present. For example, one or more of a “To DS” field, “From DS” field, “More Frag” field, “Retry” field, or “Protected Frame” field may be decoded for determining whether the second portion is present. In some aspects, one or more fields of a frame control field, along with one or more of a scrambler seed field, such as scrambler seed field622, and/or an address field, such as address field636may be decoded for determining whether the second portion is present. For example, if the address field636represents a multicast address, and one or more particular fields of the frame control field632are set to one (1), this may indicate that the second portion is present in some aspects.

In some aspects, an address field of the first portion may be decoded for determining whether the second portion is present in the PPDU. For example, if the address field is a multicast address or a localized address, method1100may determine the second portion is present. In some aspects, if the address field is both multicast and localized, the method1100may determine the second portion is present, but otherwise the second portion may be determined not to be present.

If the second portion is not present, decision block1120takes the “No” branch, and processing continues. If the second portion is present, process1100moves to block1125, where, at least non-legacy devices capable of receiving at a second data rate do receive the second portion at the second data rate, which is higher than the first data rate. In some aspects, the second portion may be received at the same data rate as the first portion. However, even when the first and second portions are received at the same data rate, the conditional processing described above with respect to block1115, where the first device determines whether the second portion is still present, may still be performed.

In block1130, the second portion is decoded for determining whether permission is granted for the first device to transmit as part of a multi-user uplink transmission during the non-contention period. In other words, multiple devices may transmit during the non-contention period, with each device transmitting using at least some differing transmission parameters. Thus, any individual transmitting device represents only a portion of the total multi-user transmission occurring during the non-contention period.

In some aspects, whether permission is granted is based on whether the first device is identified in the second portion of the PPDU via the first devices's address, AID, or a group identifier associated with the first device (as shown and discussed above with respect toFIGS. 7-8). If the first device is not identified in the second portion, decision block1135takes the “No” branch, and processing continues. If the first device is identified, block1140decodes the second portion for determining parameters for the uplink transmission during the non-contention period. In some aspects, these parameters may include one or more of the parameters discussed above with respect toFIGS. 7 and/or 8. In some aspects, the parameters or scheduling information may include one or more of bandwidth and/or subband assignments for one or more devices participating in the multi-user transmission, how many spatial streams are utilized in the multi-user transmission, the modulation and coding scheme (MCS) used by each device participating in the multi-user transmission, and a maximum length of the multi-user transmission. In block1145, the first device performs part of a multi-user uplink transmission during the non-contention period based on the decoded transmission parameters.

In some aspects, once the second portion is determined to be present, and is received by method1100in block1125, an error check value may be decoded from the second portion. The error check value could be, in various aspects, a parity bit or a cyclic redundancy check (CRC) or any other error check value known in the art. An error detection method may then be performed on the second portion based on the error check value included in the second portion. If an error is detected, the second portion may be ignored by method1100and not processed further.

In some aspects of method1100, a separate network message is received by the first device indicating a transmission data rate of the second portion. This indicated transmission data rate may be stored by the first device and relied on to determine a receiving and/or decoding rate of second portions received subsequent to the separate network message.

Therefore, the receiving and/or decoding of the second portion may then be based on the data rate indicated by the network message. In some aspects, the network message is a management frame, perhaps transmitted by an access point. In some aspects, the network message is not separate, but instead may be just the first portion.

In some aspects, process1100includes receiving one or more additional symbols after reception of the second portion. The received additional symbols may contain random information in some aspects. In some aspects, the additional symbols may be received after a CRC or FCS covering the second portion is received. In some aspects, these additional symbols provide time for a phase locked loop (PLL) of a receiving device (for example, a device performing process1100) to settle before a multi-user uplink transmission begins. In some aspects, a multi-user uplink transmission is then initiated (performed) short inter-frame space time (SIFS) after reception of the additional symbols completes.

In some other aspects, process1100includes transmitting a multi-user uplink transmission after an extended short inter-frame space (SIFS) time that is longer than the standard SIFS time. This extended SIFS time also provides additional PLL (Phase locked Loop) settlement time for a device performing a multi-user uplink transmission during the transmission opportunity following the extended SIFS.

FIG. 11Bis a functional block diagram of an apparatus1150for wireless communication, in accordance with certain embodiments described herein. In some aspects, the apparatus1150is the device302. Those skilled in the art will appreciate that the apparatus1150may have more components than the simplified block diagrams shown inFIG. 11B.FIG. 11Bincludes only those components useful for describing some prominent features of implementations within the scope of the claims.

The apparatus1150includes a receive circuit1155. The receive circuit1155may be configured to perform one or more of the functions discussed above with respect to blocks1105and/or1125. In some aspects, the receive circuit1155includes the receiver312. The apparatus1150also includes a decoding circuit1160. The decoding circuit1160may be configured to perform one or more of the functions discussed above with respect to blocks1110,1115,1120,1130,1135, and/or1140. In some aspects, the decoding circuit1160may include the processor304. The device1150also includes a multi-user uplink transmission circuit1165. In some aspects, the multi-user uplink transmission circuit1165may be configured to perform one or more of the functions discussed above with respect to block1145. In some aspects, the multi-user uplink transmission circuit1165may include the transmitter310.

A person/one having ordinary skill in the art would understand that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, 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.

Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations 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.