Traffic separation in a controller based multi-AP network

Certain aspects relate to methods and apparatus for traffic separation in a multi AP (MAP) network. In some cases, a MAP Controller may configure sets of SSIDs to a single VLAN ID in a Traffic Separation Policy and distribute the Traffic Separation Policy information to the MAP Agents.

BACKGROUND

Field

The present disclosure relates generally to communication systems, and more particularly, to methods and apparatus for traffic separation in multi AP (MAP) networks.

Description of Related Art

In order to address the issue of increasing bandwidth requirements that are demanded for wireless communication systems, different schemes are being developed to allow multiple user terminals to communicate with a single access point (AP) or multiple APs by sharing the channel resources while achieving high data throughputs. Multiple Input Multiple Output (MIMO) technology represents one such approach that has recently emerged as a popular technique for the next generation communication systems.

A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≤min{NT, NR}. Each of the NS independent channels corresponds to a dimension. The MIMO system can provide improved performance (such as higher throughput and greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.

In wireless networks with multiple APs and multiple user stations (STAs), concurrent transmissions may occur on multiple channels toward different STAs, both in uplink and downlink directions. Many challenges are present in such systems. For example, the AP may transmit signals using different standards such as the IEEE 802.11n/a/b/g or the IEEE 802.11ac (Very High Throughput (VHT)) standards. A receiver station (STA) may be able to detect a transmission mode of the signal based on information included in a preamble of the transmission packet.

A downlink multi-user MIMO (MU-MIMO) system based on Spatial Division Multiple Access (SDMA) transmission can simultaneously serve a plurality of spatially separated STAs by applying beamforming at the AP's antenna array. Complex transmit precoding weights can be calculated by the AP based on channel state information (CSI) received from each of the supported STAs.

In a distributed MU-MIMO system, multiple APs may simultaneously serve a plurality of spatially separated STAs by coordinating beamforming by the antennas of the multiple APs. For example, multiple APs may coordinate transmissions to each STA.

As the demand for wireless access continues to increase, there exists a desire for further improvements in wireless technology. Preferably, these improvements should be applicable to other multi-access technologies and the communication standards that employ these technologies.

BRIEF SUMMARY

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes a processing system configured to assign virtual local area network (VLAN) identifiers (VIDs) to service set identifiers (SSIDs) supported by a multi access point (MAP) network, generate traffic separation policy information for each SSID, including the assigned VID, and at least one interface configured to output the traffic separation policy information to agents in the MAP network for use in separating traffic.

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes at least one interface configured to obtain traffic separation policy information including virtual local area network (VLAN) identifiers (VIDs) assigned to service set identifiers (SSIDs) supported by a multi access point (MAP) network and a processing system configured to forward traffic in the MAP network, based on the VIDs in the traffic separation policy information.

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes at least one interface configured to obtain traffic separation policy information including virtual local area network (VLAN) identifiers (VIDs) assigned to client STAs in a multi access point (MAP) network that belong to service set identifiers (SSIDs) based on IP addresses and MAC address and a processing system configured to map downlink traffic for the client STAs to the VIDs assigned to the SSIDs based on the IP addresses in the traffic separation policy information.

Aspects generally include methods, apparatus, systems, computer readable mediums, and processing systems, as substantially described herein with reference to and as illustrated by the accompanying drawings. Numerous other aspects are provided.

DETAILED DESCRIPTION

The techniques described herein may be used for various broadband wireless communication systems, including communication systems that are based on a single carrier transmission. Aspects may be, for example, advantageous to systems employing Ultra-Wide Band (UWB) signals including millimeter-wave signals. However, this disclosure is not intended to be limited to such systems, as other coded signals may benefit from similar advantages.

The techniques may be incorporated into (such as implemented within or performed by) a variety of wired or wireless apparatuses (such as nodes). In some implementations, a node includes a wireless node. Such a wireless node may provide, for example, connectivity to or for a network (such as a wide area network (WAN) such as the Internet or a cellular network) via a wired or wireless communication link. In some implementations, a wireless node may include an access point or a user terminal.

Multiple APs may transmit to multiple receiving user terminals at a time by using distributed multi-user multiple input multiple output (MU-MIMO). For example, multiple APs may transmit data to a given user terminal at a time, meaning the transmission of data to the user terminal is distributed between the multiple APs. The multiple APs may utilize beamforming to steer signals spatially to the user terminal. In some implementations, for the multiple APs to perform distributed MU-MIMO, the multiple APs coordinate the beamforming performed by each AP to reduce interference for transmitting data to the user terminal. In some implementations, the multiple APs perform a procedure to form a group of APs to transmit to the user terminal, as discussed herein. Further, in some implementations, to coordinate the beamforming between the multiple APs, the multiple APs perform a sounding procedure to gather feedback information from the user terminal about wireless channels between the multiple APs and the user terminal, as discussed herein. The multiple APs may utilize the feedback information to perform beamforming.

Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. For example, APs are able to form a group for transmitting to a user terminal using over the air signaling as opposed to communicating over a backhaul. This may reduce data congestion on the backhaul. Additionally, the sounding procedures may allow for coordinated gathering of feedback information by multiple APs from user terminals. Accordingly, the feedback information for the multiple APs may include channel conditions for each of the multiple APs coordinated in time, which may improve the accuracy of the beamforming based on the feedback information. Furthermore, the sounding procedures may limit the amount of data exchanged wirelessly to perform the sounding procedures, which may reduce bandwidth usage of wireless channels.

Example Wireless Communication System

FIG. 1illustrates a multiple-access point (multi-AP or MAP) network100with access points110and user terminals120. For simplicity, only two access points110(e.g., APs1101and1102) are shown inFIG. 1. APs1101and1102may coordinate to route traffic between each other and to serve multiple UTs120, in accordance with techniques described herein.

An access point (AP) is generally a fixed station that communicates with the user terminals and also may be referred to as a base station or some other terminology. A user terminal may be fixed or mobile and also may be referred to as a mobile station, a station (STA), a client, a wireless device, or some other terminology. A user terminal may be a wireless device, such as a cellular phone, a personal digital assistant (PDA), a handheld device, a wireless modem, a laptop computer, a personal computer, etc.

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 also may communicate peer-to-peer with another user terminal.

The MAP network100employs multiple transmit and multiple receive antennas for data transmission on the downlink and uplink. The access point110is equipped with a number Napof antennas and represents the multiple-input (MI) for downlink transmissions and the multiple-output (MO) for uplink transmissions. A set Nuof selected user terminals120collectively represents the multiple-output for downlink transmissions and the multiple-input for uplink transmissions. In some implementations, it may be desirable to have Nap≥Nu≥1 if the data symbol streams for the Nuuser terminals are not multiplexed in code, frequency or time by some means. Numay be greater than Napif the data symbol streams can be multiplexed using different code channels with CDMA, disjoint sets of sub-bands with OFDM, and so on. Each selected user terminal transmits user-specific data to and receives 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 Nuselected user terminals can have the same or different number of antennas.

The MAP network100may 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 MAP network100also may utilize a single carrier or multiple carriers for transmission. Each user terminal may be equipped with a single antenna (such as in order to keep costs down) or multiple antennas (such as where the additional cost can be supported). The MAP network100may represent a high speed Wireless Local Area Network (WLAN) operating in a 60 GHz band.

FIG. 2illustrates example components of the access point110and station120illustrated inFIG. 1, which may be used to implement aspects of the present disclosure. One or more components of the access point110and station120may be used to practice aspects of the present disclosure. For example, antenna224, transmitter/receiver unit222, processors210,220,240,242, and/or controller230or antenna252, transmitter/receiver254, processors260,270,288, and290, and/or controller280may be used to perform the operations described herein and illustrated with reference toFIGS. 7, 7A, 8, 8A, 15, and 15A.

FIG. 2shows a block diagram of the access point/base station110and two user terminals/user equipments120mand120xin a MAP network100. The access point110is equipped with Napantennas224athrough224ap. The user terminal120mis equipped with Nut,mantennas252mathrough252mu, and the user terminal120xis equipped with Nut,xantennas252xathrough252xu. The access point110is a transmitting entity for the downlink and a receiving entity for the uplink. Each 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 frequency channel, and a “receiving entity” is an independently operated apparatus or device capable of receiving data via a frequency 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. Moreover, Nupmay or may not be equal to Ndn, and Nup, and Ndnmay include static values or can change for each scheduling interval. Beamforming (such as beam-steering) or some other spatial processing techniques may be used at the access point and user terminal.

On the uplink, at each user terminal120selected for uplink transmission, a TX data processor288receive traffic data from a data source286and control data from a controller280. The controller280may be coupled with a memory282. The TX data processor288processes (such as encodes, interleaves, and modulates) the traffic data {dup,m} 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 {sup,m}. A TX spatial processor290performs spatial processing on the data symbol stream {sup,m} and provides Nut,mtransmit symbol streams for the Nut,mantennas. Each transmitter unit (TMTR)254receives and processes (such as converts to analog, amplifies, filters, and frequency upconverts) a respective transmit symbol stream to generate an uplink signal. The Nut,mtransmitter units254provide Nut,muplink signals for transmission from the Nut,mantennas252to the access point110.

A number Nupof user terminals may be scheduled for simultaneous transmission on the uplink. Each of these user terminals performs spatial processing on its data symbol stream and transmits its set of transmit symbol streams on the uplink to the access point.

At the access point110, the Napantennas224athrough224apreceive 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 the transmitter unit254and provides a received symbol stream. An RX spatial processor240performs receiver spatial processing on the Napreceived symbol streams from the Napreceiver units222and provides Nuprecovered uplink data symbol streams. The receiver spatial processing is performed in accordance with the channel correlation matrix inversion (CCMI), minimum mean square error (MMSE), successive interference cancellation (SIC), or some other technique. Each recovered uplink data symbol stream {sup,m} is an estimate of a data symbol stream {sup,m} transmitted by a respective user terminal. An RX data processor242processes (such as demodulates, de-interleaves, and decodes) each recovered uplink data symbol stream {sup,m} 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 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. The TX data processor210processes (such as 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 on the Ndndownlink data symbol streams, and provides Naptransmit symbol streams for the Napantennas. Each transmitter unit (TMTR)222receives and processes a respective transmit symbol stream to generate a downlink signal. The Naptransmitter units222provide Napdownlink signals for transmission from the Napantennas224to the user terminals. The decoded data for each STA may be provided to a data sink272for storage and/or a controller280for further processing.

At each user terminal120, the Nnt,mantennas252receive the Napdownlink signals from the access point110. Each receiver unit (RCVR)254processes 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 the Nut,mreceiver units254and provides a recovered downlink data symbol stream {sdn,m} for the user terminal. The receiver spatial processing can be performed in accordance with the CCMI, MMSE, or other known techniques. An RX data processor270processes (such as demodulates, de-interleaves, and decodes) the recovered downlink data symbol stream to obtain decoded data for the user terminal.

At each user terminal120, the Nut,mantennas252receive the Napdownlink signals from the access point110. Each receiver unit (RCVR)254processes 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 the Nut,mreceiver units254and provides a recovered downlink data symbol stream {sdn,m} for the user terminal. The receiver spatial processing is performed in accordance with the CCMI, MMSE, or some other technique. An RX data processor270processes (such as demodulates, de-interleaves, and decodes) the recovered downlink data symbol stream to obtain decoded data for the user terminal.

FIG. 3illustrates various components that may be utilized in a wireless device302that may be employed within the MAP network100. The wireless device302is an example of a device that may be configured to implement the various methods described herein. The wireless device302may be an access point110or a user terminal120.

The wireless device302may include a processor304which controls operation of the wireless device302. The processor304also may 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 memory306also may include non-volatile random access memory (NVRAM). The processor304typically performs 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 device302also may include a housing308that may include a transmitter310and a receiver312to allow transmission and reception of data between the wireless device302and a remote location. The transmitter310and the receiver312may be combined into a transceiver314. A plurality of transmit antennas316may be attached to the housing308and electrically coupled to the transceiver314. The wireless device302also may include (not shown) multiple transmitters, multiple receivers, and multiple transceivers.

The wireless device302also may 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 device302also may 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.

Example Traffic Separation in Map Networks

Aspects of the present disclosure provide techniques that may help achieve traffic separation in multi AP (MAP) networks. For example, the techniques presented herein may allow for separation of traffic to provide different network accesses for clients of a MAP network, such as owner's network, guest network, and public network.

FIG. 4illustrates an example MAP network400in which MAP devices4101and4102route traffic to and from non-AP STAs4201and4202. In this example, MAP devices4101and4102communicate directly with non AP STAs4201and4202via a wireless fronthaul link, while MAP devices4101and4102communicate with each other via a backhaul link that may be wired or wireless.

As illustrated inFIG. 4, the MAP network400may be central controller based, for example, with a MAP controller residing on a device within the MAP network (e.g., within a gateway device and/or co-located with a MAP agent). In this example, the MAP controller resides on a MAP device4101. The controller may configure (via a MAP control interface) other devices, referred to as agents, to perform traffic routing as described herein. For example, the controller may generate and send traffic separation policy information to MAP network agents residing on MAP devices4101and4102, for use in forwarding traffic, in accordance with aspects of the present disclosure.

FIG. 5illustrates another example MAP network500in which MAP devices5101,5102,5103, and5104route traffic to and from non-AP STAs5201,5202,5203and5204. In this example, MAP devices5101-4communicate directly with non AP STAs5201-4via a wireless fronthaul link. In this case, MAP devices5101and5102communicate with each other via a wireless backhaul link (as do MAP devices5102and5104), while MAP devices5101and5103communicate via a wired backhaul link. As illustrated inFIG. 5, the MAP controller may reside on MAP device5101which, in this case, may be connected to a wide area network (WAN) and may serve as a gateway device.

FIG. 6illustrates yet another example MAP network600in which MAP devices6102,6103, and6104route traffic to and from non-AP STAs6201,6202, and6203. In this example, the MAP controller resides on a separate Multi-AP device6101which, in this case, may be connected to a WAN and may serve as a gateway device. In this example, MAP devices6102-4communicate directly with non AP STAs6201-3via a wireless fronthaul link. In this case, MAP device6102communicates with MAP devices6103-4via a wireless backhaul link, while MAP device6102communicates with MAP device6101via a wired backhaul link. In this arrangement, MAP device6102may obtain control information from MAP device6101and forward the control information to MAP devices6103-4.

As illustrated in the various examples shown inFIGS. 4, 5 and 6, through various wired and/or wireless fronthaul and backhaul connections via various MAP agents, the MAP network may serve to route traffic to and from various non-AP STAs. For example, the MAP agents may be configured to forward uplink and/or downlink traffic in accordance with the traffic separation policy information received from the controller. In some cases, the actual topology for a MAP network may depend on capabilities of the agents in the MAP network. For example, a MAP controller may arrange the topology in such a way that traffic for all VIDs downstream of an Agent can be forwarded by that Agent.

A single Multi-AP (MAP) Network can support multiple SSIDs. The administrator of a MAP network can use these different SSIDs to provide different network accesses for clients, such as owner's network access, guest network access, and public network access.

Aspects of the present disclosure provide a mechanism for separating traffic from different networks supported in a MAP network. For example, aspects of the present disclosure provide a mechanism (protocol) to allow the controller to configure MAP agents so that MAP agents can perform traffic separation.

FIG. 7illustrates example operations700for wireless communications by an apparatus, in accordance with aspects of the present disclosure. For example, operations700may be performed by a controller (any device acting as a controller function) of a MAP network, such as any of the MAP devices (4101,5101or6101) shown inFIGS. 4-6with a resident controller.

Operations700begin, at702, by assigning virtual local area network (VLAN) identifiers (VIDs) to service set identifiers (SSIDs) supported by a multi access point (MAP) network. At704, the apparatus generates traffic separation policy information for each SSID, including the assigned VID.

At706, the apparatus outputs the traffic separation policy information to agents in the MAP network for use in separating traffic. For example, the traffic separation policy information may be output for transmission via a type length value (TLV) field. The TLV filed may be included in a message, such as a MAP policy configuration request message or a Wi-Fi simple configuration (WSC) message.

In this manner, the MAP Controller may configure sets of (one or more) SSIDs to a single VLAN ID in a Traffic Separation Policy (e.g., each mapping from one or many SSIDs to one VLAN ID may be indicated in a Traffic Separation Policy TLV such as shown inFIG. 10). As shown inFIG. 4, a MAP Controller may distribute the Traffic Separation Policy information to the MAP Agents.

FIG. 8is a flow diagram of example operations800for wireless communication by an apparatus, in accordance with certain aspects of the present disclosure. Operations800may be performed, for example, by a MAP agent receiving traffic separation information from a MAP controller, such as any of the MAP devices shown inFIGS. 4-6with a resident MAP agent.

The operations800begin, at802, by obtaining information (e.g., traffic separation policy information) including virtual local area network (VLAN) identifiers (VIDs) assigned to service set identifiers (SSIDs) supported by a multi access point (MAP) network. At804, the apparatus forwards traffic in the MAP network, based on the VIDs in the information.

As noted above, the traffic separation policy information may be output for transmission via a TLV field. In some cases, the traffic separation policy information may include a bitmap that indicates how traffic for certain SSIDs is to be filtered. For example, network resource accessibility bitmaps may indicate how traffic for corresponding SSIDs are to be treated. In some cases, a resource accessibility bitmap may indicate traffic for a corresponding SSID is to only be forwarded between a gateway and an agent.

FIG. 9is a flow diagram of example operations800for wireless communication by an apparatus, in accordance with certain aspects of the present disclosure. Operations900may be performed, for example, by a gateway device (e.g., MAP device5101ofFIG. 5 or 6101ofFIG. 6).

The operations900begin, at902, by obtaining information (e.g., traffic separation policy information) including virtual local area network (VLAN) identifiers (VIDs) assigned to client STAs in a multi access point (MAP) network that belong to service set identifiers (SSIDs) based on IP addresses and MAC address.

At904, the apparatus maps downlink traffic for the client STAs to the VIDs assigned to the SSIDs based on the IP addresses in the information. As noted above, the traffic separation policy information may be output for transmission via a TLV field.

As noted above, a MAP network can support multiple SSIDs, which can help support traffic separation to provide different network accesses for clients, such as owner's network, guest network, and public network.

When configured by the Controller to enable multiple SSIDs, a MAP agent may enable multiple SSIDs on its Fronthaul BSSs and may use different BSSs for different SSIDs. In this case, a MAP Agent may provide a Backhaul SSID for a downstream Agent to join the backhaul.

With the traffic separation technique presented herein, traffic belonging to different SSIDs may be separated in a MAP network using virtual local area network (VLAN) identifiers (VIDs). In such cases, each SSID may be mapped to a unique VLAN VID. As described above, with reference toFIG. 7, the assignment of a VLAN VID to a SSID may be determined by a MAP Controller.

Traffic separation may be effectively implemented by configuring a MAP agent such that traffic belonging to one VID is not sent on a BSS belonging to a different VID. This can include broadcast traffic.

In some cases, the traffic forwarding between Agents may not be based on SSID-VLAN VID mapping. Rather, an Agent may be configured to forward traffic as an AP to a Backhaul-STA of its associated Agent or as a STA to the Fronthaul-AP of its associated Agent. When forwarding in this manner, the Agent may maintain the VLAN VID of the incoming traffic.

In some cases, a STA acting as an ingress Agent may map uplink traffic from a non-Agent STA that is associated with a SSID to the VLAN VID that is assigned that SSID. An ingress agent generally refers to a device that is a first point of entry to a MAP network for a non-AP STA (e.g., MAP device4102ofFIG. 4may be considered an ingress Agent for non-AP STA4202).

In some cases, an ingress Agent may add the VID to an ingress packet (e.g., an 802.1Q C-TAG with a VLAN ID) as specified in the Traffic Separation Policy. In such cases, an egress agent (forwarding a packet out of the MAP network) may remove the VLAN ID (e.g., remove the 802.1Q C-TAG with the VLAN ID). In this manner, the traffic belonging to each VLAN may be distinguished using the unique VLAN ID (e.g., in an 802.1Q C-TAG).

The Gateway (e.g., an agent that provides a gateway to a wide area network such as MAP device5101ofFIG. 5 or 6101ofFIG. 6) may map the downlink traffic for an end client STA to the VLAN VID assigned to the SSID the end client STA joins based, on the STA's IP address in the MAP network (which may be provided in the traffic separation policy information).

FIG. 10illustrates an example traffic separation policy TLV format. As noted above, in some cases, a Network Resource Accessibility bitmap in the SSID Traffic Separation Policy TLV (as illustrated in the second to last row of the example format shown inFIG. 10) for an SSID may indicate that the traffic is to be forwarded only between the Gateway and an Agent. In such cases, upon receiving a MAC service data unit (MSDU) of a VLAN VID that belongs to that SSID, the Agent should discard the MSDU, if neither the destination address nor the source address is the Gateway address.

Based on the SSID Traffic Separation configuration at the Controller, the Controller may be configured to send the traffic separation policy information of each SSID to Agents and to the Gateway, as shown inFIG. 4. The traffic separation policy information may be sent using SSID Traffic Separation Policy type length value (TLV), such as the example TLV format shown inFIG. 10. As noted above, such a TLV may be enclosed in the Multi-AP Policy Configuration Request message.

As described herein, SSID Traffic Separation Policy information for Agents of a MAP network may be directly based on SSID. In contrast, SSID Traffic Separation Policy information for the Gateway may be based on the IP addresses of the Agents and STAs associated with a SSID.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). As used herein, including in the claims, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” For example, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form. Unless specifically stated otherwise, the term “some” refers to one or more. Moreover, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase, for example, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, for example the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering. For example, operations700,800, and900illustrated inFIGS. 7, 8, and 9correspond to means700A,800A, and900A illustrated inFIG. 7A, 8A, and 9A, respectively.

For example, means for transmitting (or means for outputting for transmission) may comprise a transmitter (e.g., the transmitter unit222) and/or an antenna(s)224of the access point110or the transmitter unit254and/or antenna(s)252of the station120illustrated inFIG. 2. Means for receiving (or means for obtaining) may comprise a receiver (e.g., the receiver unit222) and/or an antenna(s)224of the access point110or the receiver unit254and/or antenna(s)252of the station120illustrated inFIG. 2. Means for processing, means for extracting, means for performing channel estimation, means for demultiplexing, means for obtaining, means for generating, means for selecting, means for decoding, means for deciding, means for demultiplexing, means for discarding, means for forwarding, means for mapping, or means for determining, may comprise a processing system, which may include one or more processors, such as the RX data processor242, the TX data processor210, the TX spatial processor220, and/or the controller230of the access point110or the RX data processor270, the TX data processor288, the TX spatial processor290, and/or the controller280of the station120illustrated inFIG. 2.

In some cases, rather than actually transmitting a frame a device may have an interface to output a frame for transmission (a means for outputting). For example, a processor may output a frame, via a bus interface, to a radio frequency (RF) front end for transmission. Similarly, rather than actually receiving a frame, a device may have an interface to obtain a frame received from another device (a means for obtaining). For example, a processor may obtain (or receive) a frame, via a bus interface, from an RF front end for reception.