Link Adaptation Protocol in Wireless Local Area Network (WLAN)

Abstract

The present disclosure provides systems, methods, and apparatus for a link adaptation protocol in a wireless local area network (WLAN), including a computer program encoded on a computer-readable medium. In one aspect, a link adaptation protocol may be used to select a transmission rate option (such as a modulation and coding scheme (MCS)) for communication from a first WLAN device to a second WLAN device based on wireless channel conditions. The present disclosure includes several example message sequences for a link adaptation protocol that may accommodate various uplink or downlink data transmission designs, including single user (SU) and multi-user (MU) transmissions. The example message sequences may be used with orthogonal frequency division multiple access (OFDMA), multiple input multiple output (MIMO), and beamforming transmissions.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. Non-Provisional Patent Application No. 17 / 121,642, filed on December 14, 2020, entitled "LINK ADAPTATION PROTOCOL INA WIRELESS LOCAL AREA NETWORK (WLAN)" and U.S. Provisional Patent Application No. 62 / 952,216, filed on December 20, 2019, entitled "FAST RATE ADAPTATION (FRA) IN A WIRELESS LOCAL AREA NETWORK (WLAN)", and both applications are assigned to the assignee of this application. The disclosures of these prior applications are considered part of this patent application and are incorporated by reference into this patent application. Technical Field

[0003] The present disclosure relates to the field of wireless communications, and more particularly to link adaptation in a wireless local area network (WLAN).

[0004] Related technical description

[0005] A wireless local area network (WLAN) may be formed by one or more access points (APs) that provide a shared wireless communication medium for use by several client devices, also referred to as stations (STAs). The basic building block of a WLAN that complies with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards is a basic service set (BSS), which is managed by an AP and includes one or more wirelessly connected STAs associated with the AP. When a station (STA) has authenticated and established a wireless session with an AP, the STA may have a wireless connection (referred to as a wireless association, or just "association").

[0006] Two or more WLAN devices (such as an AP and a STA) can establish a communication link to communicate with each other via a shared wireless communication medium. Depending on the conditions on the communication link, the WLAN device can adjust transmission parameters to optimize the throughput or reliability of transmission on the communication link. For example, the transmission parameters can be adjusted to account for radio conditions, environmental obstacles, path loss, interference due to signals from other transmitters, sensitivity of the receiver, or power of the transmitter, etc.

[0007] Overview

[0008] The systems, methods, and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0009] An innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by a first wireless local area network (WLAN) device. The method may include transmitting a link adaptation test packet between a first WLAN device and a second WLAN device via a wireless channel. The transmission may include transmitting or receiving. The link adaptation test packet may include one or more test portions, which are formatted to assist in measuring link quality metrics associated with different transmission rate options for the wireless channel. The method may include obtaining link quality metrics associated with different transmission rate options based on the link adaptation test packet. The method may include selecting a selected transmission rate option for transmitting subsequent packets between a first WLAN device and a second WLAN device via a wireless channel based on the link quality metric. The method may include transmitting subsequent packets using the selected transmission rate option.

[0010] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by a first station (STA) of a WLAN. The method may include receiving a link adaptation test packet from an access point (AP) of the WLAN via a wireless channel. The link adaptation test packet may include one or more test portions formatted to assist in measuring link quality metrics associated with different transmission rate options of the wireless channel. The method may include measuring link quality metrics associated with different transmission rate options based on the link adaptation test packet. The method may include transmitting link adaptation feedback to the AP based on the link quality metric. The method may include receiving a subsequent packet formatted according to a transmission rate option selected by the AP based on the link adaptation feedback.

[0011] Another innovative aspect of the subject matter described in the present disclosure may be implemented as an apparatus of a first WLAN device. The apparatus may include at least one modem configured to transfer a link adaptation test packet between a first WLAN device and a second WLAN device via a wireless channel. The link adaptation test packet may include one or more test portions formatted to assist in measuring a link quality metric associated with different transmission rate options of a wireless channel. The apparatus may include at least one processor communicatively coupled to the at least one modem and configured to obtain a link quality metric associated with different transmission rate options based on the link adaptation test packet. The at least one processor may be configured to select a selected transmission rate option for transmitting subsequent packets between the first WLAN device and the second WLAN device via a wireless channel based on the link quality metric. The at least one modem may be configured to transfer subsequent packets using the selected transmission rate option.

[0012] Another innovative aspect of the subject matter described in the present disclosure may be implemented as an apparatus of a second WLAN device. The apparatus may include at least one modem configured to obtain a link adaptation test packet from an access point (AP) of a WLAN via a wireless channel. The link adaptation test packet may include one or more test portions formatted to assist in measuring a link quality metric associated with different transmission rate options of the wireless channel. The apparatus may include at least one processor communicatively coupled to the at least one modem and configured to measure a link quality metric associated with different transmission rate options based on the link adaptation test packet. The at least one modem may be configured to output link adaptation feedback based on the link quality metric for transmission to the AP. The at least one modem may be configured to obtain a subsequent packet from the AP via the wireless channel, the subsequent packet being formatted according to a transmission rate option selected by the AP based on the link adaptation feedback.

[0013] Details of one or more implementations of the subject matter described in the present disclosure are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. It should be noted that the relative sizes of the following drawings may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of an example wireless communication network supporting use of link adaptation test packets is shown.

[0016] Figure 2 An example link adaptation protocol using a link adaptation test packet is shown.

[0017] Figure 3 A schematic diagram of multiple-input multiple-output (MIMO) communication is shown.

[0018] Figure 4 A schematic diagram of beamforming MIMO communication is shown.

[0019] Figure 5A An example conceptual diagram is shown in which an orthogonal frequency division multiplexing (OFDM) symbol includes multiple link adaptation test sections.

[0020] Figure 5B An example conceptual diagram is shown in which multiple OFDM symbols may be used for a link adaptation test packet.

[0021] Figure 5C An example conceptual diagram is shown in which a link adaptation test portion is included in a resource unit of an orthogonal frequency division multiple access (OFDMA) transmission.

[0022] Figure 6An example message flow diagram for a link adaptation protocol using a link adaptation test packet is shown.

[0023] Figure 7 An example mapping between link adaptation characteristics and example corresponding modulation and coding scheme (MCS) options is shown.

[0024] Fig. 8A A first example feedback message format is depicted.

[0025] Figure 8B A second example feedback message format is depicted.

[0026] Fig. 9A A block diagram of an example transmitting WLAN device supporting link adaptation is depicted.

[0027] Fig. 9B A block diagram of an example receiving WLAN device supporting link adaptation is depicted.

[0028] Fig.10 Depicted are example link adaptation test packets using time division for a link adaptation test signal.

[0029] Fig.11A An example link adaptation test packet is depicted in which a set of link adaptation tests are included in a pad section of a data carrying packet.

[0030] Fig. 11B An example link adaptation test packet is depicted in which a set of link adaptation tests are included in a link adaptation portion of a data carrying packet.

[0031] Fig.12 An example link adaptation message sequence for uplink or downlink communications is shown.

[0032] Fig.13 An example link adaptation message sequence with piggybacked link adaptation test packets and link adaptation feedback packets is shown.

[0033] Fig.14 An example link adaptation message sequence for downlink OFDMA is shown.

[0034] Fig.15 An example link adaptation message sequence for downlink OFDMA with piggybacked link adaptation test packets and link adaptation feedback packets is shown.

[0035] Fig.16 An example link adaptation message sequence following a beamforming determination sequence is shown.

[0036] Fig.17An example link adaptation message sequence is shown that includes a link adaptation message sequence in combination with a beamforming determination protocol.

[0037] Fig.18 An example link adaptation message sequence for downlink multi-user (MU) MIMO is shown.

[0038] Fig.19 An example link adaptation message sequence for uplink communications supporting OFDMA and MU-MIMO is shown.

[0039] Fig. 20 Another example link adaptation message sequence for uplink communications supporting OFDMA and MU-MIMO is shown.

[0040] Fig.21 A flow chart illustrating an example process for supporting link adaptation by a transmitting WLAN device is shown.

[0041] Fig. 22 A flow diagram illustrating an example process for supporting link adaptation for uplink communications is shown.

[0042] Fig.23 A block diagram of an example wireless communication device is shown.

[0043] Fig.24A A block diagram of an example access point (AP) is shown.

[0044] Fig. 24B A block diagram of an example station (STA) is shown.

[0045] Like reference numbers and designations in the various drawings indicate like elements.

[0046] Detailed Description

[0047] The following description is directed to certain specific implementations in order to describe the innovative aspects of the present disclosure. However, one of ordinary skill in the art will readily recognize that the teachings herein can be applied in many different ways. The described implementations can be implemented in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the IEEE 802.15 standard, as defined by the Bluetooth Special Interest Group (SIG) The described implementations may be implemented in any device, system, or network capable of transmitting and receiving radio frequency (RF) signals in accordance with one or more of the Long Term Evolution (LTE), 3G, 4G, or 5G (New Radio (NR)) standards, or the like released by the Third Generation Partnership Project (3GPP). The described implementations may be implemented in any device, system, or network capable of transmitting and receiving RF signals in accordance with one or more of the following technologies or techniques: code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), single user (SU) multiple input multiple output (MIMO), and multi-user (MU) MIMO. The described implementations may also be implemented using other wireless communication protocols or RF signals suitable for use in one or more of a wireless personal area network (WPAN), a wireless local area network (WLAN), a wireless wide area network (WWAN), or an Internet of Things (IOT) network.

[0048] A WLAN (sometimes called Wi-Fi) in a home, apartment, business, or other area TM A WLAN network may include one or more WLAN devices. An access point (AP) is a WLAN device that includes a distribution system access function. An AP may provide distribution system access to one or more stations (STAs) associated with the AP. An AP may provide a wireless coverage area for a device to access the WLAN via a wireless channel. A STA may establish a wireless association (also referred to as a wireless link, wireless connection, etc.) via a channel configuration of the AP to access the WLAN. A transmitting WLAN device (which may be an AP or a STA) may establish a communication link with a receiving WLAN device via a wireless channel.

[0049] The condition of the wireless channel may affect the transmission rate or other parameters of the communication link. Link adaptation (sometimes also referred to as rate adaptation) refers to determining the transmission rate (such as selecting a modulation and coding scheme (MCS)) and other parameters for the communication link according to the condition of the wireless channel. In some implementations, link adaptation may include selecting beamforming or spatial stream configuration for MIMO transmission. The traditional process for link adaptation requires a series of packets and packet feedback to converge on the optimal transmission rate (such as the optimal MCS). For example, the transmitting WLAN device may use the first selected MCS when sending one or more first packets. The transmitting WLAN device may select different MCSs for subsequent packets based on feedback about the one or more first packets (such as an acknowledgment (ACK) or a negative acknowledgment (NACK)) or based on a packet error rate (PER) associated with one or more first packets. Therefore, the traditional process of selecting the optimal MCS for the communication link may require an inefficient and iterative process through a series of consecutive adjustments. At the same time, the channel conditions may change before the WLAN device converges on the optimal transmission rate. In addition, different manufacturers and devices may implement different link adaptation procedures. Performance and channel efficiency may be degraded due to traditional ad hoc methods for link adaptation.

[0050] The present disclosure provides systems, methods and apparatus for link adaptation in a wireless local area network, including a computer program encoded on a computer-readable medium. The technology in the present disclosure can be used in a link adaptation protocol to efficiently determine the transmission rate (such as MCS) and other parameters for a communication link based on the conditions of a wireless channel. In some implementations, the link adaptation protocol may be referred to as a fast rate adaptation (FRA) protocol. Various implementations generally involve determining a transmission rate for wireless communication from a transmitting WLAN device to a receiving WLAN device. The transmission rate may be defined by an MCS selected based on channel conditions and other parameters. According to the present disclosure, a link adaptation protocol may include one or more packets exchanged between a transmitting WLAN device and a receiving WLAN device for quickly determining an MCS or other parameters for subsequent communication. For example, a transmitting WLAN device may transmit a first packet (which may also be referred to as a test packet, a link adaptation test packet, a fast rate adaptation test packet, or a FRA test packet) that can be used to determine one or more link quality metrics about a wireless channel. Transmitting a test packet may refer to transmitting a test packet from a transmitting WLAN device to a receiving WLAN device, or may refer to receiving a test packet from a receiving WLAN device. For simplicity, some examples of the present disclosure refer to delivering a test packet by transmitting a test packet to a receiving WLAN device. The receiving WLAN device may observe the test packet to determine the one or more link quality metrics. Examples of link quality metrics may include log likelihood ratio (LLR), signal-to-noise ratio (SNR), signal-to-interference-plus-noise ratio (SINR), error vector magnitude (EVM), block error rate (BLER), bit error rate (BER) or codeword error rate (CWER), etc. In some implementations, link quality may also be referred to as channel quality. In some implementations, link quality may also refer to the impact of interference on one or more tones or spatial streams within a wireless channel. The test packet may be used to determine the quality of the wireless channel to support communication between the transmitting WLAN device and the receiving WLAN device. The receiving WLAN device may provide feedback information (which may be referred to as link adaptation feedback, fast rate adaptation feedback or FRA feedback) to the transmitting WLAN device in response to the test packet. In some implementations, the transmitting WLAN device may use the feedback information to determine the transmission rate option to be used for subsequent packets to the second WLAN device. In some implementations, the receiving WLAN device may determine the selected transmission rate option based on the link quality metric and send the selected transmission rate option in the link adaptation feedback. The transmission rate option may include an MCS option, a number of spatial streams, a spatial stream configuration, or any combination thereof. The techniques of the present disclosure may implement the selection of the transmission rate option using fewer packets than would otherwise be required to converge to an optimal transmission rate option in a conventional link adaptation process.

[0051] In some implementations, the test packet may be a new packet format defined in a standard technical specification (such as IEEE 802.11be). The test packet may be part of a link adaptation protocol specified in a standard technical specification. In some implementations, the test packet may be based on a packet format for a null data packet (NDP). For example, the test packet may be a modified NDP packet specifically for measuring SINR on each OFDM subcarrier or every Nth OFDM subcarrier. Although some examples in the present disclosure include test packets based on an NDP format, other replacement formats for the first packet may be possible. In some implementations, the test packet may be based on a packet format for a data-bearing packet or a contention-based signaling packet (such as a request to send (RTS) packet). In some implementations, the test packet may be based on a traditional packet format including a padding segment so that the padding segment includes a test portion corresponding to different transmission rate options. The test portion (modulated with different MCS options) may be included in a padding segment at the end of a traditional packet format or in a preamble segment of a traditional packet format. The test packet may be formatted to assist in determining a link quality metric. For example, the test packet may include a portion designed to test different MCS options or determine a link quality metric useful for MCS selection. In some implementations, the test packet may include a test signal (such as a predetermined test signal) modulated using a first MCS in a first test portion and modulated using a second MCS in a second test portion. The first packet may be formatted as a MIMO transmission including one or more test portions for signal to interference plus noise (SINR) estimation. The receiving WLAN device may observe the various test portions in the first packet to determine one or more SINR metrics. Thus, the test packet may be used to determine the quality of the wireless channel based on the amount of interference and other noise affecting the MIMO spatial streams in the wireless channel. In some implementations, the test packet may be delivered as an initial packet of a session so that the optimal transmission rate option may be selected for subsequent packets of the session.

[0052] The link adaptation protocol may be defined by one or more message sequences. The present disclosure includes various example link adaptation message sequences that may be used depending on different types of communications. For example, a basic link adaptation message sequence may include using a link adaptation null data packet announcement (LA-NDPA) to indicate that a test packet (which may be referred to as a link adaptation null data packet, i.e., LA-NDP) will follow the LA-NDPA. The LA-NDPA may include indicators about which test signals are included in the LA-NDP, and may indicate which receiving WLAN devices should observe the LA-NDP. In some implementations, the LA-NDPA may indicate the format or type of feedback expected from the receiving WLAN device. The receiving device may send feedback information in a link adaptation feedback (LA-FB) message in response to the LA-NDP. Thereafter, the transmitting WLAN device may send data packets using a transmission rate option selected based on the feedback information.

[0053] In addition to the basic link adaptation message sequence described above, the present disclosure also includes link adaptation message sequences for addressing various options and alternatives. For example, in some implementations, the link adaptation message sequence may include data packets modified to support the piggybacked link adaptation test portion included with each transmission so that the transmission rate selection can be refined on a packet-by-packet basis (if necessary). In some implementations, the link adaptation protocol may include different message sequences for supporting OFDMA, MU-MIMO, beamforming, and other communication types. In addition, the present disclosure includes some link adaptation message sequences that can be used when uplink data is scheduled or triggered by the AP receiving the data.

[0054] Certain implementations of the subject matter described in this disclosure may be implemented to achieve one or more of the following potential advantages. Link adaptation test packets may be used to quickly determine optimal transmission rate options (such as MCS options, spatial stream configurations, or both) for subsequent transmissions without requiring a series of repeated transmission rate adjustments to converge on an optimal transmission rate option between a transmitting WLAN device and a receiving WLAN device. Throughput and resiliency may be improved by reducing error rates in transmissions that would otherwise use suboptimal transmission rate settings. In addition to saving time for link adaptation between a pair of WLAN devices, using a single link adaptation test packet to determine an optimal transmission rate option may preserve air time resources that would otherwise be available to other WLAN devices.

[0055] Figure 1A schematic diagram of an example wireless communication network 100 supporting the use of link adaptation test packets is shown. According to some aspects, the wireless communication network 100 may be an example of a wireless local area network (WLAN) such as a Wi-Fi network (and will be referred to as WLAN 100 hereinafter). For example, the WLAN 100 may be a network implementing at least one of the IEEE 802.11 family of wireless communication protocol standards, such as standards defined by the IEEE 802.11-2016 specification or its revisions, including but not limited to 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be. The WLAN 100 may provide access to another network 160. For example, the AP 102 may be connected to a gateway device (not shown) that provides connectivity to the other network 160. WLAN 100 may include numerous wireless communication devices, such as at least one access point (AP) 102 and a plurality of stations (STAs) 104 that may have wireless associations with AP 102. Although only one AP 102 is shown, WLAN network 100 may also include multiple APs 102.

[0056] Each STA 104 may also be referred to as a mobile station (MS), a mobile device, a mobile handset, a wireless handset, an access terminal (AT), a user equipment (UE), a subscriber station (SS), or a subscriber unit, among other possibilities. STA 104 may represent a variety of devices, such as mobile phones, personal digital assistants (PDAs), other handheld devices, netbooks, netbook computers, tablet computers, laptops, display devices (e.g., TVs, computer monitors, navigation systems, etc.), music or other audio or stereo equipment, remote control devices (“remote controls”), printers, kitchen or other home appliances, key fobs (e.g., for passive keyless entry and start (PKES) systems), and other possibilities.

[0057] A single AP 102 and the associated set of STAs 104 may be referred to as a basic service set (BSS), which is managed by the respective AP 102 . Figure 1Additionally shown is an example coverage area 108 of the AP 102, which may represent a basic service area (BSA) of the WLAN 100. The BSS may be identified to users by a service set identifier (SSID) and may also be identified to other devices by a basic service set identifier (BSSID), which may be a media access control (MAC) address of the AP 102. The AP 102 periodically broadcasts a beacon frame (“beacon”) including the BSSID to enable any STA 104 within the wireless range of the AP 102 to “associate” or re-associate with the AP 102 to establish or maintain a corresponding communication link 106 (hereinafter also referred to as a “Wi-Fi link”) with the AP 102. For example, the beacon may include an identification of a primary channel used by the corresponding AP 102 and a timing synchronization function for establishing or maintaining timing synchronization with the AP 102. The AP 102 may provide various STAs 104 in the WLAN with access to external networks via respective communication links 106 .

[0058] To establish a communication link 106 with the AP 102, each STA 104 is configured to perform passive or active scanning operations ("scanning") on frequency channels in one or more frequency bands (eg, 2.4 GHz, 5 GHz, 6 GHz, or 60 GHz bands). To perform a passive scan, the STA 104 listens for beacons transmitted by the corresponding AP 102 at periodic time intervals, referred to as target beacon transmission times (TBTTs), measured in time units (TUs), where one TU may be equal to 1024 microseconds (μs). To perform an active scan, the STA 104 generates probe requests and sequentially transmits these probe requests on each channel to be scanned, and listens for probe responses from the AP 102. Each STA 104 may be configured to identify or select an AP 102 to associate with based on the scan information obtained through passive or active scanning, and perform authentication and association operations to establish a communication link 106 with the selected AP 102. The AP 102 assigns an association identifier (AID) to the STA 104 at the end of the association operation, and the AP 102 uses the AID to track the STA 104.

[0059] As wireless networks become more and more common, STA 104 may have the opportunity to select one of many BSSs within the range of the STA or to select among multiple APs 102 that together form an extended service set (ESS) (including multiple connected BSSs). The extended network station associated with WLAN 100 may be connected to a wired or wireless distribution system that allows multiple APs 102 to be connected in such an ESS. In this way, STA 104 may be covered by more than one AP 102 and may be associated with different APs 102 at different times for different transmissions. Additionally, after associating with AP 102, STA 104 may also be configured to periodically scan its surroundings to find a more suitable AP 102 to associate with. For example, a STA 104 that is moving relative to its associated AP 102 may perform a "roaming" scan to find another AP 102 with more suitable network characteristics (such as a larger received signal strength indicator (RSSI) or a reduced traffic load).

[0060] In some cases, STA 104 may form a network without AP 102 or other equipment other than STA 104 itself. An example of such a network is an ad hoc network (or wireless ad hoc network). An ad hoc network may alternatively be referred to as a mesh network or a peer-to-peer (P2P) network. In some cases, an ad hoc network may be implemented within a larger wireless network (such as WLAN 100). In such an implementation, although STA 104 may be able to communicate with each other through AP 102 using a communication link 106, STA 104 may also communicate directly with each other via a direct wireless link 111. In addition, two STAs 104 may communicate via a direct communication link 111, regardless of whether the two STAs 104 are associated with the same AP 102 and served by the same AP 102. In such an ad hoc system, one or more STAs 104 may assume the role played by AP 102 in a BSS. Such a STA 104 may be referred to as a group master (GO) and may coordinate transmissions within the ad hoc network. Examples of direct wireless link 111 include a Wi-Fi Direct connection, a connection established by using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, and other P2P group connections.

[0061] The AP 102 and the STA 104 may function and communicate (via corresponding communication links 106) in accordance with the IEEE 802.11 family of wireless communication protocol standards, such as those defined by the IEEE 802.11-2016 specification or its revisions, including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be. These standards define WLAN radio and baseband protocols for the PHY and media access control (MAC) layers. The AP 102 and the STA 104 transmit and receive wireless communications (hereinafter also referred to as "Wi-Fi communications") to and from each other in the form of physical layer convergence protocol (PLCP) protocol data units (PPDUs). The AP 102 and STA 104 in the WLAN 100 may transmit PPDUs on an unlicensed spectrum, which may be a portion of a spectrum that includes frequency bands traditionally used by Wi-Fi technology, such as the 2.4 GHz band, the 5 GHz band, the 60 GHz band, the 3.6 GHz band, and the 900 MHz band. Some implementations of the AP 102 and STA 104 described herein may also communicate in other frequency bands, such as the 6 GHz band, that may support both licensed and unlicensed communications. The AP 102 and STA 104 may also be configured to communicate on other frequency bands, such as shared licensed frequency bands, where multiple operators may have licenses to operate in one or more of the same or overlapping frequency bands.

[0062] Each frequency band may include multiple sub-bands or frequency channels. For example, PPDUs that comply with IEEE 802.11n, 802.11ac, and 802.11ax standard revisions may be transmitted on 2.4 GHz and 5 GHz frequency bands, where each frequency band is divided into multiple 20 MHz channels. In this way, these PPDUs are transmitted on a physical channel with a minimum bandwidth of 20 MHz, but larger channels may be formed through channel bonding. For example, a PPDU may be transmitted on a physical channel with a bandwidth of 40 MHz, 80 MHz, 160 MHz, or 320 MHz by bonding multiple 20 MHz channels together.

[0063] Each PPDU is a composite structure including a PHY preamble and a payload in the form of a PLCP service data unit (PSDU). The information provided in the preamble can be used by the receiving device to decode subsequent data in the PSDU. In an instance where the PPDU is transmitted over a bonded channel, the preamble field can be replicated and transmitted in each of a plurality of component channels. The PHY preamble may include both a legacy portion (or "legacy preamble") and a non-legacy portion (or "non-legacy preamble"). Legacy preambles can be used for packet detection, automatic gain control, and channel estimation, as well as other purposes. Legacy preambles can also generally be used to maintain compatibility with legacy devices. The format, decoding, and information provided therein of the non-legacy portion of the preamble are based on the specific IEEE 802.11 protocol to be used to transmit the payload.

[0064] STA 144 is associated with AP 102 and may receive downstream communications from AP 102 or transmit upstream communications to AP 102 via communication link 106. Figure 1 102. To avoid ambiguity, AP 102 may be referred to as first WLAN device 110. Alternatively, first WLAN device 110 may be a wireless communication device in AP 102. Acting as a transmitting WLAN device, first WLAN device 110 is capable of delivering downstream data to second WLAN device 120 (such as STA 144). Second WLAN device 120 may be referred to as a receiving WLAN device. Thus, in Figure 1 In the embodiment of the present invention, the first WLAN device 110 may be referred to as a transmitting WLAN device and the second WLAN device 120 may be referred to as a receiving WLAN device. However, for uplink data (from STA 144 to AP 102), the designation of the transmitting WLAN device and the receiving WLAN device may be reversed. Similarly, the techniques in the present disclosure may be used with a peer-to-peer or mesh network, in which case one WLAN device may be considered a transmitting WLAN device and another WLAN device may be considered a receiving WLAN device.

[0065] Figure 1Also shown is an example of potential interference 142 from an external transmitter 140 (such as a radio broadcast tower, a WWAN, or another WLAN, etc.). Interference 142 may affect the channel conditions of the wireless channel used by the BSS managed by AP 102. Interference 142 may have a greater impact on high transmission rates (such as the first MCS) and may have a smaller impact on low transmission rates (such as the second MCS). In order to provide flexibility in transmission rates, the IEEE 802.11 family of standards specifies various MCS options with different modulation and coding rates. Various modulation schemes may include binary phase shift keying (BPSK) modulation schemes, quadrature phase shift keying (QPSK) modulation schemes, and different types of quadrature amplitude modulation (QAM) modulation schemes, etc. Each MCS option may have a different data rate. The data rate may refer to how much data stream is actually used to transmit available data. A higher data rate means that data transmission is more efficient. At the same time, a lower data rate may result in a more robust transmission because the transmission may include redundant data or error correction data. As described herein, conventional techniques for link adaptation may include an iterative process for sequentially adjusting MCS selection until the WLAN device converges on an optimal transmission rate that balances data throughput and the amount of interference 142. The present disclosure describes fast rate adaptation techniques for determining an optimal MCS between a transmitting WLAN device, such as the first WLAN device 110, and a receiving WLAN device, such as the second WLAN device 120.

[0066] The first WLAN device 110 may include a link adaptation test packet transmission unit 152. The link adaptation test packet transmission unit 152 may be configured to transmit a first packet (which may be referred to as a link adaptation test packet 172) to the second WLAN device 120. In some implementations, the link adaptation test packet 172 may be formatted as a single-user (SU) basic open-loop transmission. Alternatively, the link adaptation test packet 172 may be formatted as a multi-user (MU) transmission, such as an OFDMA or MU-MIMO transmission. In some implementations, the link adaptation test packet 172 may be formatted as a multi-user (MU) transmission. Figure 4. Portions of the link adaptation test packet 172 may include different test signals that can be measured to determine a link quality metric. For example, the link adaptation test packet 172 may include multiple test portions modulated using corresponding multiple MCS options. The first portion may be modulated using a first MCS, and the second portion may be modulated using a second MCS. Thus, a single link adaptation test packet 172 may support testing of several MCS options based on current channel conditions. Alternatively or additionally, the link adaptation test packet 172 is formatted as a MIMO transmission and may include one or more portions of SINR estimates for spatial streams for the MIMO transmission. Thus, a single link adaptation test packet 172 may support SINR estimates for different spatial streams based on current channel conditions. In some implementations, the link adaptation test packet 172 may also carry data in addition to the test portion.

[0067] The first WLAN device 110 may include a link adaptation unit 154 configured to determine a transmission rate or other link configuration for a subsequent packet 176 transmitted to the second WLAN device 120. For example, the link adaptation unit 154 may receive feedback information 174 from the second WLAN device 120 in response to the link adaptation test packet 172. The link adaptation unit 154 may determine a selected MCS or other transmission rate option to be used for the subsequent packet 176 based on the feedback information 174. In some implementations, the feedback information 174 may include a link quality metric (such as SINR or EVM) regarding the link adaptation test packet 172. Alternatively or additionally, the feedback information 174 may include an indicator indicating a transmission rate option selected by the second WLAN device 120 based on the link adaptation test packet 172. After the selected transmission rate option is determined by the link adaptation unit 154, the first WLAN device 110 may transmit the subsequent packet 176 using the selected MCS option. Although described in terms of the MCS option, the transmission rate option selected by the link adaptation unit 154 may be any parameter that adapts the transmission rate based on the current channel conditions. The data transmission unit 156 in the first WLAN device 110 may modulate a subsequent packet 176 using the transmission rate option selected by the link adaptation unit 154 based on the feedback information 174 regarding the link adaptation test packet 172.

[0068] The second WLAN device 120 may include a link adaptation test packet processing unit 162. The link adaptation test packet processing unit 162 may receive the link adaptation test packet 172 and determine a link quality metric for the link adaptation test packet 172 (or each test portion thereof). For example, the link adaptation test packet processing unit 162 may process each portion separately to determine a received test signal for each test portion. The link adaptation test packet processing unit 162 may determine the link quality metric based on a comparison of the received test signal with a predetermined test signal used by the first WLAN device 110 for each test portion. In some implementations, the predetermined test signal may be a known bit sequence or pattern. The link adaptation test packet processing unit 162 may compare the received test signal with a known bit sequence or pattern to determine BER, BLER, SNR, SINR, or EVM, etc.

[0069] In some implementations, the link adaptation test packet processing unit 162 may process a first portion of the link adaptation test packet 172 to determine signal strength, and may process a second portion of the link adaptation test packet 172 to determine noise and interference. The link adaptation test packet processing unit 162 may determine a link quality metric based on measurements during the first portion and the second portion of the link adaptation test packet 172. Furthermore, different link quality metrics may be determined for different spatial streams of the link adaptation test packet 172.

[0070] The second WLAN device 120 may include a feedback unit 164 configured to prepare feedback information 174. The feedback unit 164 may select an MCS option based on the link quality metric determined by the link adaptation test packet processing unit 162. Alternatively, the feedback unit 164 may prepare a feedback message including the link quality metric. The data receiving unit 166 in the second WLAN device 120 may receive and process a subsequent packet 176 based on the selected transmission rate option, such as the selected MCS option.

[0071] Figure 2An example link adaptation protocol using link adaptation test packets is depicted. The example link adaptation protocol 200 may begin with a first packet 210 from a first WLAN device 110 to a second WLAN device 120. The first packet 210 may be a link adaptation test packet and may include an indicator indicating that the first packet includes multiple test portions 201. For example, in some implementations, the first packet 210 may include a link adaptation test capability or enablement indicator to indicate that the first packet 210 is formatted for the link adaptation protocol 200. In some implementations, a test header in the first packet 210 may indicate which transmission rate options are used for the test portion 201. The transmission rate options may be various MCS options. In some implementations, the test header in the first packet 210 may indicate a configuration of one or more portions for SINR estimation. For example, the test header may indicate a predetermined bit sequence of OFDM symbols, a null pattern, or a number of OFDM symbols, etc. In Figure 2 In one example, the first packet 210 may include a first portion 270 modulated using a first MCS option, a second portion 280 modulated using a second MCS option, and a third portion 290 modulated using a third MCS option.

[0072] Upon receiving the first packet 210, the second WLAN device 120 may determine the success rate or error rate of each test portion 201 to determine which MCS option has the highest throughput and quality above a threshold. For example, if both the first portion 270 and the second portion 280 are received with a quality above a threshold, the second WLAN device 120 may determine (for the first portions 270 and 280) which MCS option will result in the highest data throughput. Meanwhile, if the third portion 290 is received with a quality below a threshold (such as a high bit error rate indicating lower quality), the second WLAN device 120 may determine that the third MCS option should not be used for subsequent packets. A low-quality MCS may result in retransmissions, which consumes air time and results in additional processing overhead. Meanwhile, if multiple MCS options result in a quality metric above a quality threshold, the optimal MCS option is the MCS option that will result in the highest throughput while having an acceptable quality above the threshold.

[0073] exist Figure 2In another example, the first packet 210 may include a portion for enabling SINR measurement. Some conventional techniques for selecting an MCS may utilize a signal-to-noise ratio (SNR) as a metric for determining channel quality. The SNR may represent a rough estimate of signal strength compared to noise that may be measured during transmission. For example, a transmitting WLAN device may send a first packet that may be used by a receiving WLAN device to determine a signal (S) strength and a rough noise (N) estimate. The receiving WLAN device (or transmitting WLAN device) may select an MCS based on the S and N estimates. Conventional techniques for determining the SNR may not take into account the effects of interference (I). Interference is conventionally measured during an idle measurement period of a channel, during which the transmitting WLAN device and the receiving WLAN device may measure interference caused by other transmitters (such as those that are not part of the WLAN). The idle measurement period may be predetermined based on a synchronized idle period, or may be triggered by one of the WLAN devices. Because conventional techniques for interference measurement rely on an idle measurement period, conventional techniques may result in delays and may not be suitable for fast link adaptation.

[0074] In some implementations, the first packet may include a first portion for estimating a signal and may include a second portion for interference estimation. For example, the second portion of the packet may include one or more orthogonal frequency division multiplexing (OFDM) symbols for interference estimation. The one or more OFDM symbols of the second portion may include null values ​​on some or all subcarriers (also referred to as tones) of the OFDM symbols. The null values ​​may provide an idle measurement period during the first packet. Alternatively or additionally, the one or more symbols may be filled with a predetermined sequence (such as a repetition of a long training field (LTF)). In some implementations, the sequence may be modified to empty a particular subcarrier. In some implementations, the one or more OFDM symbols may be filled with at least a portion of the same sequence (such as an LTF sequence or other predetermined sequence) that may be interpreted by a receiving WLAN device. Alternatively or additionally, a link quality estimation sequence (such as a repetition of an LTF sequence) may be repeated on two or more OFDM symbols in a test packet.

[0075] Upon receiving the first packet 210, the second WLAN device 120 may determine one or more link quality metrics (such as SINR or EVM) based on the first packet 210. For example, the SINR metric may include different SINR metrics for each subcarrier or different subcarrier groups in OFDM transmission. The second WLAN device 120 may select an MCS option for subsequent MIMO transmission based on the SINR metric. For example, if the average SINR of the wireless channel is above a threshold, the second WLAN device 120 may select a first MCS option with high data throughput. Meanwhile, if the average SINR of the wireless channel is below a threshold, the second WLAN device 120 may select a second MCS option for subsequent packets.

[0076] In response to the first packet 210, the second WLAN device 120 may send a feedback message 230 back to the first WLAN device 110. The feedback message 230 may start after a short interframe space (SIFS) 220, which represents a determinable time period for maintaining synchronization in the WLAN. The feedback message 230 may indicate a link quality metric for the test portion 201 or may indicate an optimal transmission rate option selected by the second WLAN device 120 based on quality and throughput. Based on the feedback information in the feedback message 230, the first WLAN device 110 may determine the selected transmission rate option for all or part of the second packet 240 to be transmitted from the first WLAN device 110 to the second WLAN device 120.

[0077] In some implementations, the first packet may include a test signal in a single orthogonal frequency division multiplexing (OFDM) symbol (or a single resource unit of an orthogonal frequency division multiple access (OFDMA) symbol). For example, the single OFDM symbol may include a first tone (or a first set of tones) having a test signal modulated using a first MCS and a second tone (or a second set of tones) having a test signal modulated using a second MCS. In some implementations, each tone in the OFDM symbol may be modulated using a different MCS. Alternatively or additionally, the predetermined test signal may be modulated using a first MCS for a first OFDM symbol of the first packet and a second MCS for a second OFDM symbol of the first packet. The receiving WLAN device may observe portions of the first packet for the predetermined test signal using different MCSs.

[0078] In some implementations, the first packet may be used to estimate link quality metrics for various spatial streams of a MIMO transmission from a transmitting WLAN device to a receiving WLAN device. For example, the link quality metric may indicate the impact of interference on a specific spatial stream in a MIMO transmission. In some implementations of the present disclosure, the first packet may include portions for estimating link quality metrics for multiple spatial streams to be used in subsequent MIMO transmissions. Thus, in some implementations, a single test packet may be used to determine link quality metrics based on MIMO spatial streams so that an optimal MCS may be selected for subsequent MIMO transmissions. In some implementations, the first packet may include a series of OFDM symbols with a link adaptation estimate bit sequence.

[0079] Figure 3 FIG. 1 shows a schematic diagram of MIMO communication. Figure 3 , the first WLAN device 110 may include four antennas 302, 304, 306, and 308. The second WLAN device 120 may include antennas 312, 314, 316, and 318. The number of antennas in each of the first WLAN device and the second WLAN device 120 is provided as an example only, and other numbers of antennas may be used. In some implementations, the number of antennas in the second WLAN device 120 may be different from the number of antennas in the first WLAN device 110. Spatial diversity may be used by one or both of the transmitting device or the receiving device to improve the robustness of the transmission. For example, in order to implement a transmit diversity scheme, the first WLAN device 110 may redundantly transmit the same data on two or more antennas. WLAN devices including multiple antennas may also support space-time block coding (STBC). Using STBC, the transmitting device also transmits multiple copies of the data stream across several antennas to increase the possibility of decoding the correct data using each received version of the data. More specifically, the data stream to be transmitted is encoded in blocks, which are distributed between spaced antennas and across time. Generally, when the number of transmitting antennas N Tx Exceeding the number of spatial streams N SS When N is used, STBC (described below) can be used. SS The spatial streams can be mapped into N STS space-time streams, which are then mapped to N Tx A transmission chain.

[0080] WLAN devices including multiple antennas may also support spatial multiplexing, which may be used to increase spectral efficiency and the resulting throughput of transmission. To implement spatial multiplexing, the transmitting device divides the data stream into a number N of SS These spatial streams are then encoded separately and passed through a number N TxIf the first WLAN device 110 includes N transmitting antennas, Tx The second WLAN device 120 includes N transmitting antennas. Rx receive antennas, the maximum number of spatial streams that the first WLAN device 110 can simultaneously transmit to the second WLAN device 120 is N SS Limited by N Tx and N Rx The smaller of .

[0081] In some implementations, the first WLAN device 110 and the second WLAN device 120 may be capable of implementing both transmit diversity and spatial multiplexing, such as Figure 3 For example, when the number of spatial streams N SS Less than the number of transmitting antennas N Tx In the example of , the spatial streams can be multiplied by a spatial spreading matrix to achieve transmit diversity. Figure 3 , the first WLAN device 110 transmits a first spatial stream using transmit diversity as a first signal 341 from an antenna 302 of the first WLAN device 110 to an antenna 312 of a second WLAN device 120 and a second signal 342 from an antenna 304 of the first WLAN device 110 to an antenna 314 of the second WLAN device 120. The first signal 341 and the second signal 342 may be redundant copies of the same data. The first WLAN device 110 transmits a second spatial stream using transmit diversity as a third signal 343 from an antenna 306 of the first WLAN device 110 to an antenna 316 of the second WLAN device 120 and a fourth signal 344 from an antenna 308 of the first WLAN device 110 to an antenna 318 of the second WLAN device 120. The third signal 343 and the fourth signal 344 may be redundant copies of the same data. However, the data for the first spatial stream (in the signals 341 and 342) may be different from the data for the second spatial stream (in the signals 343 and 344). The MIMO modulation module 310 in the first WLAN device 110 may determine spatial streams and modulate data for each spatial stream for transmission by antennas 302, 304, 306, and 308. The MIMO processing module 320 of the second WLAN device 120 may process received signals 341, 342, 343, and 344 to recover the spatial streams.

[0082] In some implementations, the test packet may be communicated as a MIMO transmission using signals 341, 342, 343, and 344. The test packet may include a link quality estimation portion occupying one or more OFDM symbols encoded according to the MIMO spatial streams supported between the first WLAN device 110 and the second WLAN device 120. Thus, the test packet may enable the second WLAN device 120 to accurately determine the link quality metric for the MIMO spatial stream. The link quality metric may be used by the second WLAN device 120 or the first WLAN device 110 to determine an optimal transmission rate for a subsequent MIMO transmission using the same spatial stream configuration as the first packet.

[0083] Figure 4 Schematic diagram of beamforming MIMO communication is shown. The technology in the present disclosure can be used with beamforming MIMO communication. Figure 3 As described in Figure 4 The first WLAN device 110 in the embodiment includes four antennas 302, 304, 306 and 308. The second WLAN device 120 includes antennas 312, 314, 316 and 318. APs and STAs including multiple antennas can also support beamforming. Beamforming refers to focusing the energy of the transmission in the direction of the target receiver. Beamforming can be used both in a single-user environment, for example to improve SNR or SINR, and in a multi-user (MU) environment, for example to implement MU multiple-input multiple-output (MIMO) (MU-MIMO) transmission (also known as spatial division multiple access (SDMA)). In order to perform beamforming, a transmitting device (such as the first WLAN device 110), referred to as a beamforming initiator, transmits a signal 440 from each of the multiple antennas 302, 304, 306, 308. The beamforming initiator configures the amplitude and phase shifts between the signals 440 transmitted from the different antennas so that the signals add constructively in a particular direction toward an intended receiver, such as the second WLAN device 120, which is referred to as a beamforming receiver. The beamforming module 410 in the first WLAN device 110 may determine the amplitude and phase shifts of the various signals 440. The manner in which the beamforming initiator configures the amplitude and phase shifts depends on the channel state information (CSI) associated with the wireless channel over which the beamforming initiator intends to communicate with the beamforming receiver.

[0084] In order to obtain CSI for beamforming, the beamforming initiator may perform a channel sounding procedure with the beamforming receiver. For example, the beamforming initiator may transmit one or more sounding signals (e.g., in the form of null data packets (NDPs)) to the beamforming receiver. The beamforming receiver may then perform channel sounding procedures for N corresponding to all transmit antennas and receive antenna pairs based on the sounding signals. Tx x N RxThe beamformer may perform measurements for each of the subchannels. For example, the feedback module 420 of the beamformer receiver may generate a feedback matrix based on the channel measurements and typically compress the feedback matrix before transmitting the feedback to the beamformer initiator. The beamformer initiator may then generate a precoding (or "steering") matrix for the beamformer receiver based on the feedback and use the steering matrix to precode the data stream to configure amplitude and phase shifts for subsequent transmissions to the beamformer receiver.

[0085] In some implementations, the channel sounding procedure for beamforming can be extended or modified to support link adaptation. For example, a sounding signal (such as an NDP) can be modified to include or add a link adaptation measurement signal so that one or more OFDM symbols are added to the NDP for SINR estimation. In some implementations, a channel sounding procedure and CSI feedback can be performed first to determine the beamforming coefficients before transmitting the link adaptation test packet. The link adaptation test packet can be beamformed based on the channel sounding procedure and CSI feedback so that the link quality metric accurately reflects the link quality for each beamformed spatial stream between the first WLAN device 110 and the second WLAN device 120, which will be used for subsequent beamformed MIMO packets.

[0086] Figure 5A An example conceptual diagram is shown in which an OFDM symbol includes multiple link adaptation test portions. The OFDM channel width may include multiple subcarriers. Subcarriers may also be referred to as frequency modulation. A WLAN packet (also referred to as a PPDU) includes data encoded using subcarriers of the channel width. The PPDU may be of different time lengths and include multiple OFDM symbols. In some implementations, a transmitting WLAN device may include an OFDM symbol (such as OFDM symbol 550) having different test portions modulated using a test signal or different MCS. For example, Figure 5A The OFDM symbol 550 in FIG. 5 includes four test parts 512, 522, 532, and 542, which may also be referred to as test part 1 (TP1), TP2, TP3, and TP4, respectively. In some implementations, each test part may be modulated using a different MCS so that a variety of MCS options may be included in the OFDM symbol 550. Each test part may be a group of contiguous subcarriers (e.g., Figure 5A The test portions may be composed of only one subcarrier each. For example, test portions TP1, TP2, TP3, and TP4 may each be one subcarrier. The remaining subcarriers may be used for data or other signaling.

[0087] Figure 5B An example conceptual diagram is shown in which multiple OFDM symbols can be used for a link adaptation test packet. For example, a first OFDM symbol 510 can include a first test portion (TP1) 512. A second OFDM symbol 520 can include a second test portion (TP2) 522. A third OFDM symbol 530 can include a third test portion (TP3) 532. And a fourth OFDM symbol 540 can include a fourth test portion (TP4) 542. Each of the test portions 512, 522, 532, and 542 can be modulated with a different MCS.

[0088] Figure 5C An example conceptual diagram is shown in which a link adaptation test portion is included in a resource unit of OFDMA transmission. IEEE 802.11ax introduces the use of OFDMA in WLAN. OFDMA decomposes the channel width into multiple resource units (RUs). Each RU may include a different number of subcarriers. By using OFDMA, the AP can allocate different RUs to different WLAN devices. For example, PPDU 560 may include different RUs allocated to a first WLAN device, a second WLAN device, a third WLAN device, and a fourth WLAN device. One RU 570 may be allocated to the first WLAN device in PPDU 560, while other RUs 572 and 574 may be allocated to different WLAN devices. The allocation of RUs may also be used to schedule channel access. For example, a trigger message from an AP may indicate which RUs are allocated to a specific STA for uplink traffic after the trigger message in the PPDU.

[0089] exist Figure 5C In the example shown, the first RU 570 may include a link adaptation test portion from a first WLAN device (such as an AP) to a second WLAN device (such as a STA). Therefore, the RU 570 may be divided by frequency division to support different test portions 512, 522, 532, and 542. The test portions 512, 522, 532, and 543 may occupy different tones (or sets of tones) within the RU 570. Each test portion may be modulated using a different MCS option.

[0090] Figure 5A , Figure 5B and Figure 5C The concepts described in are illustrative examples and are not mutually exclusive. For example, when a PPDU includes multiple OFDM symbols, each OFDM symbol may carry user data or other signaling in some subcarriers and carry a test portion in other subcarriers. In addition, a series of OFDM symbols may be used to convey the test portion, which occupies a subset of the subcarriers in each OFDM symbol. Figures 5A-5CThe number and size of the test portions in the may vary and may depend on the number of MCS options being tested in the link adaptation test packet.

[0091] Figure 6 An example message flow diagram of a link adaptation protocol using a link adaptation test packet is depicted. The example message flow 600 shows a first WLAN device 110 (as a transmitting STA) and a second WLAN device 120 (as a receiving STA). The first WLAN device 110 and the second WLAN device 120 can exchange configuration messages 612 to establish a wireless association over a wireless communication medium.

[0092] The first WLAN device 110 may transmit a first packet 622 to the second WLAN device 120. The first packet 622 may include a link adaptation test portion. The second WLAN device 120 may process (shown at block 624) the first packet 622 to determine a link quality metric about the first packet 622, as described above. The second WLAN device 120 may transmit feedback information 626 to the first WLAN device 110 based on the first packet 622. Based on the feedback information 626, the first WLAN device 110 may determine a selected transmission rate option (such as an MCS) to be used for transmitting a subsequent packet 628 to the second WLAN device 120.

[0093] Figure 7 An example mapping between a link quality metric 700 and an example corresponding MCS option is shown. In some implementations, each link quality metric may be used to determine an MCS option for a particular spatial stream or portion of a MIMO transmission. In some other implementations, the link quality metric for the first packet may be averaged to determine an average link quality metric 700 for communication from a first WLAN device to a second WLAN device via a wireless channel. For example, the average link quality metric 700 may represent the overall quality of the communication path between the first WLAN device and the second WLAN device. The average link quality metric 700 may range from low to high. When the link quality metric is based on SINR or EVM, a lower average value indicates poor link quality, while a higher average value indicates better link quality. For example, a lower average SINR metric may indicate poor link quality, which would benefit from using a more robust MCS option. A higher average SINR metric may indicate a high link quality that supports a higher data transmission rate using a higher order MCS. When the link quality metric is based on another measurement, there may be an inverse mapping so that the relationship from low to high can be reversed. For example, a low BER (or BLER) may indicate a high link quality (and may be mapped to a higher order MCS), while a high BER (or BLER) may indicate a low link quality (and may be mapped to a lower order MCS).

[0094] Figure 7 701 in Figure 701 shows an example MCS option. Figure 701 shows fourteen MCS options (numbered MCS0 to MCS 13), each MCS option having a different combination of modulation scheme and forward error correction (FEC) code rate (sometimes referred to as code rate). Various modulation schemes may include binary phase shift keying (BPSK) modulation schemes, quadrature phase shift keying (QPSK) modulation schemes, and different types of quadrature amplitude modulation (QAM) modulation schemes, etc. The forward error correction code rate can affect how much data stream is actually used to transmit available data. For example, a code rate of 5 / 6 means that 83.3% of the transmitted data stream includes actual data (or 5 bits out of every 6 bits are information bits, and the remaining bits are parity bits). A higher code rate means that data transmission is more efficient. At the same time, a lower code rate may result in a more robust transmission because the transmission may include redundant data or error correction data, etc. Based on Figure 701, data throughput may increase as the number of MCS options increases. For example, MCS 13 has a higher data throughput than MCS 0. However, higher numbered MCS options are more susceptible to errors caused by interference or poor radio conditions. Therefore, higher numbered MCS options are more suitable for use in communication channels with higher SINR. Therefore, the SINR metric can be used to determine which MCS option results in the best data throughput based on the current radio conditions.

[0095] In some implementations, one or more thresholds may be used with a link quality metric to determine which MCS option to select. For illustrative purposes, the link quality metric may be based on an average SINR. When the average SINR metric is below a first threshold 710, MCS 0 may be selected. When the average SINR metric is above the first threshold 710 and below a second threshold 720, MCS 1 may be selected. As an illustrative example, consider a communication link using a 2x2 MIMO transmission configuration with 2 streams and IEEE channel model D with non-line of sight (NLOS). For such a communication link, if the SINR metric is below 9.5 dB, MCS 0 may be selected. If the SINR metric is in a range from 9.5 dB to 12 dB, MCS 1 may be selected. If the SINR metric is in a range from 12 dB to 14 dB, MCS 2 may be selected. If the SINR metric is in a range from 14 dB to 17.5 dB, MCS 3 may be selected, and so on. The thresholds and Figure 7The MCS options shown in are provided for illustrative purposes. If the SINR varies from one OFDM subcarrier to the next, the optimal MCS may depend not only on the average SINR, but also on the variation of the SINR. The number of thresholds and the values ​​of the thresholds may depend on the transmitter or receiver capabilities. Alternatively or additionally, the number of thresholds and the values ​​of the thresholds may be based on the system or device configuration.

[0096] Fig. 8A A first example feedback message format is depicted. The first example feedback message format 800 may be based on a legacy preamble associated with a legacy WLAN frame format 802. The feedback message format 800 may include a legacy short training field 804 (L-STF), a legacy long training field 806 (L-LTF), and a legacy signal field 808 (L-SIG). The L-STF and L-LTF are used for detection and synchronization using a predetermined training signal. Therefore, the L-SIG field is the only portion of the legacy preamble that carries data. The L-SIG field includes a set of bits for indicating a rate setting 812 and a set of bits for indicating a length 814 of a legacy WLAN packet that typically follows the legacy preamble. In Fig. 8A In the example of , the feedback message may end with an L-SIG. Therefore, the length 814 may indicate a value of "0". The rate setting 812 may indicate a selected MCS option determined by the receiving WLAN device based on a link quality metric measured for the link adaptation test portion of the link adaptation test packet.

[0097] Figure 8B A second example feedback message format 801 may be based on the legacy preamble (L-STF 804 , L-LTF 806 , and L-SIG 808 ) followed by feedback information 838 . Figure 8B Several example feedback subfields 860 included in the feedback information 838 are shown. The example feedback subfields 860 include one or more link quality metrics 862, selected MCS option indicators 864, and test result bitmaps 866. For example, the link quality metrics 862 may indicate BER, EVM, BLER, SINR, or other metrics for each spatial stream, for each subcarrier, for each subcarrier group, or for a portion of a link adaptation test packet, etc. The selected MCS option indicator 864 may indicate the selected MCS selected by the receiving WLAN device. The test result bitmap 866 may indicate which MCS options are recommended, or which portions of the link adaptation test packet have link quality metrics above a threshold. Fig. 8A and 8B The examples in are intended to be illustrative examples, and other variations are possible. For example, in some implementations, there may be fewer, more, or different subfields in the feedback information 838.

[0098] Fig. 9A A block diagram of an example transmitting WLAN device supporting link adaptation is depicted. The example transmitting WLAN device 900 is one of many designs for a first WLAN device. The example transmitting WLAN device 900 is based on a transmitter supporting transmission of user data as well as link adaptation test signals. The example transmitting WLAN device 900 is designed for binary convolutional coding (BCC) encoding. Another design (not shown) may support low data parity check (LDPC) encoding. Fig. 9A The transmitting WLAN device 900 in FIG. 1 supports the transmission of data 902. The data 902 may be processed by a scrambler 910 and an encoding module 915. The scrambler 910 may scramble the data 902 to reduce the probability of long sequences of zeros or ones. The scrambler 910 may use a seed to determine the scrambled bits. The seed may be known or shared with a receiving WLAN device so that the receiving WLAN device may reverse the scrambling process performed by the scrambler 910. After scrambling, the data may be processed by an encoding module 915.

[0099] The coding module 915 may perform coding for error correction and error detection. For example, the coding module 915 may perform FEC and add redundant or CRC bits to the source data. The encoder may use BCC to encode the data. The encoded data may be sent to the stream parser 920, which divides the encoded data into NSS spatial streams. In some implementations, there may be only one spatial stream and the stream parser 920 may not be used. Examples of spatial stream processing 940 may include an interleaver 930 and a constellation mapper 935. The interleaver 930 interleaves the bits of each spatial stream (changes the order of the bits) to prevent long sequences of adjacent noise bits from entering the BCC decoder. The interleaver 930 may be present in a transmitter design using BCC coding. When LDPC coding (instead of BCC) is used, the interleaver 930 may be omitted. Interleaving is applied only when BCC coding is used. The constellation mapper 935 maps the bit sequence in each spatial stream to a constellation point (complex number). The constellation mapper 935 may perform modulation of the bits. For example, the constellation mapper 935 may determine constellation points for modulation based on the modulation scheme.

[0100] After the spatial streams are processed, the spatial mapping unit 945 can map the space-time streams to the NTX transmit chains (including the TX chain 950). There may be different ways to map the streams to the transmit chains. For example, in direct mapping, the constellation points from each space-time stream can be directly mapped to the transmit chain (one-to-one mapping). Another example can use spatial expansion, where the vectors of constellation points from all space-time streams are expanded via matrix multiplication to produce inputs to all transmit chains. The spatial mapping unit 945 can support beamforming (such as spatial expansion), where each vector of constellation points from all space-time streams is multiplied by a steering vector matrix to produce inputs to the transmit chain.

[0101] The example transmitting WLAN device 900 may include a link adaptation test signal generator 905 configured to send a link adaptation test signal for transmission by the transmitting device. The link adaptation test signal may be sent in place of the data 902 or may be sent as an added portion of the same packet including the data 902. In some implementations, the link adaptation test signal generator 905 may send the link adaptation test signal to the encoding module 915 as part of the source data stream or in place of the source data stream. In some other implementations, the link adaptation test signal generator 905 may send the link adaptation test signal to the spatial mapping unit 945 as part of the NSS spatial streams or in place of the NSS spatial streams. Alternatively or additionally, the link adaptation test signal generator 905 may send the link adaptation test signal directly to the TX chain (such as the TX chain 950).

[0102] Each TX chain 950 may prepare a plurality of OFDM symbols based on a constellation point. For example, the TX chain 950 may include an inverse discrete Fourier transform (IDFT) that converts a constellation point block into a time domain block. The TX chain 950 may include a cyclic shift (CSD), a guard interval inserter, and an analog front end to transmit the OFDM symbol as radio frequency (RF) energy.

[0103] Fig. 9A The transmitting WLAN device 900 described in the figure is only one example of a transmitting device. Other block diagrams may add or remove functional blocks.

[0104] Fig. 9B A block diagram of an example receiving WLAN device supporting link adaptation is depicted. The example receiving WLAN device 901 is one of many possible designs for a second WLAN device. Fig. 9BIn an example of , RF energy may be received by an analog front end of a receive (RX) chain 955. For example, the RX chain 955 may include an antenna and an automatic gain control (AGC) component (not shown). In addition, the RX chain 955 may include a fast Fourier transform (FFT) function for converting a time domain symbol into a frequency domain representation of received data. NRX receive chains may prepare a frequency domain representation of received data associated with each RX chain. Each receive chain may be sent to a spatial parser 960, which converts the frequency domain representation of the received signal into a plurality of spatial streams. As a result, the spatial parser 960 may prepare NSS spatial streams for spatial stream processing. When recovering data from a plurality of spatial streams, spatial stream processing may be used. An example of spatial stream processing 972 may include a deinterleaver 965 and a demodulator 970. If a BCC interleaver is used in the transmitting WLAN device 900, the deinterleaver 965 may perform deinterleaving of a bit stream to restore the original ordering of the bit stream. The demodulator 970 may use LLR calculations to recover the bit stream.

[0105] The example receiving WLAN device 901 may include a link quality measurement unit 995 for processing a received test signal. For example, the link quality measurement unit 995 may receive the test signal from the spatial parser 960 or directly from an RX chain, such as the RX chain 955. In some implementations, the spatial parser 960 may send a spatial stream related to the link quality estimation test signal to the link quality measurement unit 995. The link quality measurement unit 995 may determine one or more link quality metrics, such as SINR or EVM, based on the received test signal.

[0106] If the first packet includes user data, the user data may be recovered by the remaining modules of the example receiving WLAN device 901, such as a stream combiner 975, a decoding module 980, etc. The stream combiner 975 may reverse the processing of the transmitting stream parser 920. For example, the stream combiner 975 may combine bit streams from multiple spatial streams to prepare coded data bits for the decoding module 980. The decoding module 980 may decode the coded bits. In some implementations, the decoding module 980 may use redundant bits in the coded bits to implement error correction.

[0107] In some implementations, the example receiving WLAN device 901 can be configured to receive data 998 in addition to the test signal. The decoding module 980 can send the received data to the descrambler 990. The descrambler 990 can reverse the scrambling performed by the scrambler in the transmitting WLAN device. The descrambler 990 can provide the received data 998 to an upper layer (not shown) of the example receiving WLAN device 901.

[0108] Fig.10An example link adaptation test packet 1000 using time division for a link adaptation test signal is depicted. For example, the link adaptation test packet 1000 may be formatted as a PPDU. As shown, the link adaptation test packet 1000 includes a preamble and a link adaptation test set 1012. For example, the preamble may be a PHY preamble and may include a legacy portion that itself includes a legacy short training field (L-STF) 1004, a legacy long training field (L-LTF) 1006, and a legacy signaling field (L-SIG) 1008. The preamble may also include a non-legacy portion (not shown). The L-STF 1004 generally enables a receiving device to perform automatic gain control (AGC) and coarse timing and frequency estimation. The L-LTF 1006 generally enables a receiving device to perform fine timing and frequency estimation, and also to estimate a wireless channel. The L-SIG 1008 generally enables a receiving device to determine the duration of the PPDU and use the determined duration to avoid transmitting over the PPDU. For example, the L-STF 1004, L-LTF 1006, and L-SIG 1008 may be modulated using a robust MCS option, such as an option using a BPSK modulation scheme. After the preamble, the link adaptation test packet 1000 may include one or more other headers (not shown) and a link adaptation test set 1012. The link adaptation test set 1012 may include a test header 1020 for indicating which (or which) link adaptation test signals 1040 are used to prepare the test portions 1021, 1022, and 1023. The link adaptation test signal 1040 may be a known pattern or bit sequence (e.g., based on an LTF sequence, a pattern with empty subcarriers, or a new SINR test pattern, etc.). The test portions 1021, 1022, and 1023 may be based on the same link adaptation test signal 1040. In some implementations, the link adaptation test signal 1040 may be changed for each test portion. As Fig.10 As shown in , the test portions may be time-division ordered in the link adaptation test set 1012 section of the link adaptation test packet 1000. For example, the link adaptation bit sequence 1040 may have bit rotation, tone rotation, or other changes so that each test portion may provide some tones with signals for signal strength measurement and some tones with null values ​​for interference measurement. In some implementations, each test portion may be one or more OFDM symbols in a series of OFDM symbols constituting the link adaptation test packet 1000.

[0109] In some implementations, the legacy preamble of the link adaptation test packet 1000 may include a repetition of an L-LTF (RL-LTF) symbol after the L-LTF 1006 or L-SIG 1008 (not shown). The L-LTF and RL-LTF may be used for noise estimation (rather than interference estimation) for single-stream transmission. Therefore, the link adaptation test packet 1000 may include a link adaptation test set 1012 for implementing interference estimation for multiple spatial streams. For example, the link adaptation test packet 1000 may include more LTF symbols (as link adaptation test signals) for supporting link adaptation for subsequent packets. The link adaptation test packet 1000 may include more LTF symbols (as link adaptation test signals) than originally required for the current packet. For example, in a normal packet, only two LTFs (L-LTF and RL-LTF) will be required for MIMO transmission with two spatial streams. However, the link adaptation test packet 1000 may include additional LTFs (such as within the preamble, in a designated test portion of the packet, at the end of the packet, etc.) to facilitate the determination of the link quality metric based on the spatial stream configuration. In some implementations, the number of additional LTFs may be based on the number of spatial streams to be included in subsequent packets. As an example, if the transmitting WLAN device will include 8 spatial streams in subsequent packets, the transmitting WLAN device may include 8 LTFs in the link adaptation test packet 1000 to support the determination of the link quality metric of the channel. In some implementations, the L-SIG 1008 may include an indicator for indicating the number of LTFs (or other link adaptation test signals) included in the link adaptation test packet 1000.

[0110] Fig.11A An example link adaptation test packet 1100 is depicted in which a link adaptation test set is included in a padding section of a data carrying packet. Similar to the link adaptation test packet 1000, the link adaptation test packet 1100 may include a preamble (such as L-STF 1004, L-LTF 1006, and L-SIG 1008). However, unlike the link adaptation test packet 1000, the link adaptation test packet 1100 may be a data carrying packet including a data payload 1110. For example, the data payload 1110 may include data for a second WLAN device. In some implementations, such as when fast link adaptation has not yet been performed, the data payload 1110 may be modulated by a suboptimal MCS option or may be modulated based on a previously selected MCS option. After the data payload 1110, typically the PPDU will include a padding section 1112. However, in some implementations, the padding section 1112 may be filled with a suboptimal MCS option as described in reference to FIG. Fig.10The link adaptation test packet 1012 is described. For example, all or part of the fill section 1112 may be referred to as the link adaptation portion of the link adaptation test packet 1000. Fig.11A 110, but in some implementations, the link adaptation test set 712 may be included before the data payload 1110. The data payload 1110 may be a separate portion from the link adaptation test set in the test packet.

[0111] Fig. 11B An example link adaptation test packet 1101 is depicted in which a set of link adaptation tests are included in a link adaptation portion 1105 of a data carrying packet. The link adaptation portion 1105 may be populated with Fig.10 The described link quality estimation test set 1012. Fig. 11B 1008). In some implementations, the data carrying packet may include other preambles (not shown), such as a High Efficiency (HE) preamble (defined in IEEE 802.11ax), an Extremely High Throughput (EHT) preamble (defined in IEEE 802.11be), or other preambles before the data payload 1110. The link adaptation portion 1105 may be after the preamble and before the data payload 1110. In some implementations, the link quality estimation portion 1105 may be after the L-LTF 1006 and before the L-SIG 1008.

[0112] Example message sequence for the link adaptation protocol

[0113] The present disclosure includes several example link adaptation message sequences that can be used for different communication types. These link adaptation message sequences are illustrative in nature and can be combined or modified within the scope of the present disclosure. For the sake of brevity, the example link adaptation message sequences use some terms, such as LA-NDPA, LA-NDP, LA-FB packets, which may have different names and different packet formats as described herein. Table 1 includes a list of how some of the example link adaptation message sequences can be used for different communication types, whether for uplink or downlink transmissions.

[0114]

[0115] Table 1. Example link adaptation message sequences for different communication types

[0116] Fig.12An example link adaptation message sequence for uplink or downlink communication is shown. The example link adaptation message sequence 1200 may be used for single user (SU) uplink or downlink communication. The first WLAN device 110 may send a LA-NDPA 1205 to indicate the start of the link adaptation message sequence and the LA-NDP 1210 will follow. The LA-NDP 1210 is an example of a link adaptation test packet that enables the second WLAN device 120 to determine a link quality metric (such as SINR, EVM, BER, BLER, etc.). The second WLAN device 120 may respond with a LA-FB packet 1230 to indicate the link quality metric or a transmission rate option (such as MCS) selected based on the link quality metric. If the LA-FB packet 1230 includes a link quality metric, the first WLAN device 110 may select a transmission rate option based on the link quality metric. Otherwise, the first WLAN device 110 may determine the selected transmission rate option indicated in the LA-FB packet 1230. Thereafter, the first WLAN device 110 may send a data packet 1240 modulated based on the selected transmission rate option. The second WLAN device 120 may send an acknowledgment packet 1260. In some implementations, the acknowledgment packet 1260 is a block acknowledgment (BA) feedback packet.

[0117] Fig.13 An example link adaptation message sequence with piggybacked link adaptation test packets and link adaptation feedback packets is shown. The example link adaptation message sequence 1300 may be used for single user (SU) uplink or downlink communications. The link adaptation message sequence 1300 is similar to Fig.12 1200, except that the WLAN device may use the piggybacked test packets to continuously monitor and adjust the transmission rate options for subsequent packets. For example, LA-NDPA 1205, LA-NDP 1210, LA-FB packet 1230, and data packet 1240 may be associated with Fig.121301. The first WLAN device 110 may transmit another LA-NDP 1345 after (or as part of) the data packet 1240. When the second WLAN device 120 transmits an acknowledgment packet 1360 (regarding the data packet 1240), the second WLAN device 120 may include another LA-FB packet 1365 (in addition to or as part of the acknowledgment packet 1360). The data packet 1240, the LA-NDP 1345, the acknowledgment packet 1360, and the LA-FB packet 1365 may be considered together as one cycle 1301 of the link adaptation transmission sequence. Thereafter, the first WLAN device 110 may begin another cycle 1302 during which the first WLAN device 110 may transmit another data packet 1370 modulated based on the transmission rate option selected according to the LA-FB packet 1365. This process may continue for each subsequent data packet, such as the data packet 1370. In some implementations, if the data packet 1370 is the last data packet for the session (as determined by the completion of the data traffic in the queue sent from the first WLAN device 110 to the second WLAN device 120), the LA-NDP 1375 may be omitted. The use of piggybacked link adaptation packets and feedback may permit the WLAN device to continuously monitor and optimize the transmission rate selection for the session, which may include multiple data transmission cycles. Each cycle may include an LA-FB that may cause an adjustment to be made for the next cycle. Although the LA-NDP 1345 and the data packet 1240 are illustrated and described as separate packets, they may be combined together in a single packet, such as with reference to each. Fig.11A and 11B Link adaptation test packets 1100 and 1101 are described.

[0118] Fig.14An example link adaptation message sequence for downlink OFDMA is shown. The example link adaptation message sequence 1400 may be used for OFDMA downlink communications. The first WLAN device 110 may send a LA-NDPA 1405 to indicate the start of the link adaptation message sequence and that a LA-NDP 1410 will follow. In OFDMA, since the first WLAN device 110 (such as an AP) manages channel usage, the trigger frame 1420 (or LA-NDPA 1405) may indicate which RUs are for STAs (such as the second WLAN device 120 and the third WLAN device 130) to monitor or which RUs are for the STAs to use for uplink feedback. The second WLAN device 120 and the third WLAN device 130 may respond with LA-FB packets 1430 and 1432, respectively, to indicate a link quality metric or a transmission rate option selected based on the link quality metric. Although the LA-FB packets 1430 and 1432 are not transmitted in the OFDMA protocol, the LA-NDPA 1405 may be transmitted in the OFDMA protocol. Fig.14 14 is illustrated as a concurrent multi-user (MU) OFDMA transmission, but in some implementations, the LA-FB packets may be sent sequentially by the second WLAN device 120 and the third WLAN device 130. In some implementations, the trigger frame 1420 may indicate a timing or sequential list for the WLAN devices 120 and 130 to send the LA-FB packets.

[0119] In some implementations, the STAs (the second WLAN device 120 and the third WLAN device 130) may observe the full channel of the LA-NDP 1410 and the LA-FB packets 1430 and 1432 may include link quality metrics for portions of the full channel. In such implementations, the first WLAN device 110 (in addition to the selected transmission rate) may also determine RU allocations for the STAs based on the link quality metrics. Thus, subsequent packets 1440 (which may be DL OFDMA transmissions) may indicate specific RUs for each STA to optimize RU allocations and transmission rate options.

[0120] After the subsequent packet 1440 , the first WLAN device 110 may send a block acknowledgment request (BAR) message 1470 as a trigger to cause the STA to send acknowledgments 1480 and 1482 .

[0121] Fig.15 An example link adaptation message sequence 1500 for downlink OFDMA with piggybacked link adaptation test packets and link adaptation feedback packets is shown. Fig.14As described in the embodiment of the present invention, the link adaptation message sequence 1500 may start with the LA-NDPA 1405, the trigger frame 1420, the trigger frame 1420, the LA-FB packet 1430, and the LA-FB packet 1432. In the first cycle 1501, the first WLAN device 110 may send a data packet 1440 modulated based on the selected transmission rate option determined based on the LA-FB packets 1430 and 1432. The first WLAN device 110 may utilize the subsequent packet 1440 and append or include another LA-NDP 1545 before sending the BAR 1450. When the STAs (the second WLAN device 120 and the third WLAN device 130) send acknowledgment packets 1560 and 1562, respectively, these acknowledgment packets may include another LA-FB packet 1565 and 1567, respectively. Therefore, during the next cycle 1502, the first WLAN device 110 may adapt the transmission rate based on the new LA-FB packets 1565 and 1567. The next cycle 1502 may include a new data packet 1570 , optionally followed by another LA-NDP 1575 and BAR 1590 .

[0122] Fig.16 An example link adaptation message sequence 1600 is shown following a separate beamforming determination sequence. Prior to executing the link adaptation message sequence 1600, the first WLAN device 110 and the second WLAN device 120 may determine a beamforming configuration for a channel. For example, the first WLAN device 110 may send a conventional NDPA 1605 and NDP 1610 intended to solicit a beamforming report 1630 from the second WLAN device 120. The beamforming report 1630 may include beamforming information for determining a beamforming configuration for a plurality of antennas of the first WLAN device 110, among other configurations. Thereafter, the link adaptation message sequence 1600 may use beamformed transmissions from the first WLAN device 110 to the second WLAN device 120 based on the beamforming configuration. The example link adaptation message sequence 1600 may be similar to Fig.12 , 13, 14, or 15. For example, the first WLAN device 110 may send a LA-NDPA 1205 to indicate the start of a link adaptation message sequence and that a LA-NDP 1210 will follow. The LA-NDP 1210 is an example of a fast link adaptation test packet that enables the second WLAN device 120 to determine a link quality metric (such as SINR, BER, BLER, etc.). The second WLAN device 120 may respond with a LA-FB packet 1230 to indicate a link quality metric or a transmission rate option selected based on the link quality metric. If the LA-FB packet 1230 includes a link quality metric, the first WLAN device 110 may select a transmission rate option based on the link quality metric. Otherwise, the first WLAN device 110 may determine the selected transmission rate option indicated in the LA-FB packet 1230. Thereafter, the first WLAN device 110 may send a data packet 1240 modulated based on the selected transmission rate option. The second WLAN device 120 may send an acknowledgment packet 1260. In some implementations, the acknowledgment packet 1260 is a block acknowledgment (BA) feedback packet.

[0123] Fig.17 An example link adaptation message sequence 1700 including a combination of a link adaptation message sequence and a beamforming determination sequence is shown. The first WLAN device 110 may send a combined NDP and LA-NDPA 1705 to indicate the start of the link adaptation message sequence and a combined NDP and LA-NDP 1710 will follow. The combined NDP and LA-NDP 1710 may enable the second WLAN device 120 to determine the beamforming information and link quality metrics in the same test packet. The second WLAN device 120 may respond with a combined BF report and LA-FB 1730. The beamforming information is used to determine the beamforming configuration for multiple antennas of the first WLAN device 110, among other configurations. The LA-FB is used to select a transmission rate option for a subsequent packet 1760. Thereafter, the first WLAN device 110 may send a data packet 1760 modulated based on the selected transmission rate option and beamformed based on the beamforming configuration. The second WLAN device 120 may send an acknowledgment packet 1780.

[0124] Fig.18An example link adaptation message sequence 1800 for downlink multi-user (MU) MIMO is shown. The traditional NDPA 1805 and the traditional NDP 1810 are followed by a trigger frame 1820 to prompt the second WLAN device 120 and the third WLAN device 130 to send BF reports 1830 and 1832, respectively. These messages are used to determine the beamforming configuration for DL ​​MU-MIMO transmission 1860. Before sending the DL MU-MIMO transmission 1860, the first WLAN device 110 can send LA-NDPA 1835 and LA-NDP 1840 for the STA to use to determine the link quality metric. The LA-NDP 1840 in this example can also be used as a trigger frame for LA-FB packets 1850 and 1852 from the second WLAN device 120 and the third WLAN device 130, respectively. Based on the LA-FB packets 1850 and 1852, the first WLAN device 110 can determine the transmission rate option for each STA. The BAR 1870 may follow the MU-MIMO transmission 1860 and cause the STA to send back acknowledgments 1880 and 1882 .

[0125] Fig.19 An example link adaptation message sequence 1900 for uplink communication supporting OFDMA and MU-MIMO is shown. In OFDMA and MU-MIMO, the first WLAN device 110 (such as an AP) can control channel usage based on a trigger frame or other scheduling messages. Fig.19 In the example of FIG. 1 , the first WLAN device 110 may send a link adaptation null data packet request (LA-NDPR) packet 1905 to cause the STAs (the second WLAN device 120 and the third WLAN device 130) to send LA-NDPs 1910 and 1912. The LA-NDPs 1910 and 1912 may be sent sequentially (eg, Fig.19 as shown) or concurrently (as shown Fig. 20 1905 may be sent. In some implementations, the packet 1905 may indicate a sequential order for the LA-NDPs 1910 and 1912. Thereafter, the first WLAN device 110 may send a trigger frame 1920 to prompt the STA to send an UL OFDMA transmission with data 1940 and 1942 from the second WLAN device 120 and the third WLAN device 130, respectively. The trigger frame 1920 may include RU allocation, transmission rate option selection, or other link adaptation information used by the second WLAN device 120 and the third WLAN device 130 to optimize the transmission rate selected for the uplink data transmission. The first WLAN device 110 may send an acknowledgment 1960 after receiving and processing the UL OFDMA transmission.

[0126] Fig. 20Another example link adaptation message sequence for uplink communications supporting OFDMA and MU-MIMO is shown. Fig. 20 Similar to Fig.19 , except that LA-NDP packets 1910 and 1912 may be transmitted concurrently using OFDMA or MU-MIMO.

[0127] Fig.21 A flow chart illustrating an example process 2100 of supporting link adaptation by a transmitting WLAN device is shown. In some implementations, the process 2100 may be performed by a first WLAN device (such as the AP 102, the first WLAN device 110, the second WLAN device 120, the STA 144, the wireless communication device 2300, the AP 2402, or the STA 2404 described herein).

[0128] In block 2110, the first WLAN device may communicate a link adaptation test packet between the first WLAN device and a second WLAN device via a wireless channel, the link adaptation test packet including one or more test portions formatted to facilitate measurement of link quality metrics associated with different transmission rate options of the wireless channel.

[0129] At block 2120, the first WLAN device may obtain link quality metrics associated with different transmission rate options based on the link adaptation test packet.

[0130] At block 2130 , the first WLAN device may select a selected transmission rate option for communicating subsequent packets between the first WLAN device and the second WLAN device via the wireless channel based at least in part on the link quality metric.

[0131] At block 2140, the first WLAN device may communicate the subsequent packet using the selected transmission rate option.

[0132] Fig. 22 A flow chart illustrating an example process 2200 of supporting link adaptation for uplink communication is shown. In some implementations, the process 2100 may be performed by a receiving WLAN device, such as the second WLAN device 120, the STA 144, the wireless communication device 2300, or the STA 2404 described herein.

[0133] At block 2210, a receiving WLAN device may receive a link adaptation test packet from an access point (AP) of the WLAN via a wireless channel. The link adaptation test packet may include one or more test portions formatted to facilitate measurement of link quality metrics associated with different transmission rate options of the wireless channel.

[0134] At block 2220, the receiving WLAN device may measure link quality metrics associated with different transmission rate options based on the link adaptation test packet.

[0135] At block 2230, the receiving WLAN device may transmit link adaptation feedback to the AP based at least in part on the link quality metric.

[0136] At block 2240, the receiving WLAN device may receive subsequent packets formatted according to the transmission rate option selected by the AP based on the link adaptation feedback.

[0137] Fig.23 2300. In some implementations, the wireless communication device 2300 may be a wireless communication device for a STA (such as the one described above). Figure 1 In some implementations, the wireless communication device 2300 may be an example of a device in an AP (such as one of the STAs 104 or 144 described above). Figure 1 The wireless communication device 2300 is an example of a device in the AP 102 described above. The wireless communication device 2300 can be used as a transmitting WLAN device or a receiving WLAN device (such as the first WLAN device 110 and the second WLAN device 120, respectively). The wireless communication device 2300 is capable of transmitting (or outputting for transmission) and receiving wireless communications (e.g., in the form of wireless packets). For example, the wireless communication device can be configured to: transmit and receive packets in the form of physical layer convergence protocol (PLCP) protocol data units (PPDUs) and media access control (MAC) protocol data units (MPDUs) that comply with IEEE 802.11 wireless communication protocol standards (such as standards defined by the IEEE802.11-2016 specification or its revisions, including but not limited to 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be).

[0138] The wireless communication device 2300 may be or may include a chip, system on chip (SoC), chipset, package, or device including one or more modems 2302 (e.g., Wi-Fi (IEEE 802.11 compliant) modems). In some implementations, one or more modems 2302 (collectively, "modems 2302") additionally include a WWAN modem (e.g., a 3GPP 4G LTE or 5G compatible modem). In some implementations, the wireless communication device 2300 also includes one or more radios 2304 (collectively, "radios 2304"). In some implementations, the wireless communication device 2300 further includes one or more processors, processing blocks, or processing elements 2306 (collectively, "processors 2306") and one or more memory blocks or elements 2308 (collectively, "memory 2308").

[0139] The modem 2302 may include an intelligent hardware block or device (for example, such as an application specific integrated circuit (ASIC)). The modem 2302 is generally configured to implement the PHY layer. For example, the modem 2302 is configured to modulate packets and output the modulated packets to the radio 2304 for transmission on the wireless medium. Similarly, the modem 2302 is configured to obtain the modulated packets received by the radio 2304 and demodulate the packets to provide demodulated packets. In addition to the modulator and demodulator, the modem 2302 may further include a digital signal processing (DSP) circuit system, an automatic gain control (AGC), an encoder, a decoder, a multiplexer, and a demultiplexer. For example, when in the transmission mode, the data obtained from the processor 2306 is provided to the encoder, which encodes the data to provide coded bits. The coded bits are then mapped to points in the modulation constellation (using the selected MCS) to provide modulated symbols. Subsequently, the modulated symbols can be mapped to a number of NSS spatial streams or a number of NSTS space-time streams. The modulated symbols in the corresponding spatial streams or space-time streams may then be multiplexed, transformed via an inverse fast Fourier transform (IFFT) block, and then provided to the DSP circuitry for Tx windowing and filtering. The digital signal may then be provided to a digital-to-analog converter (DAC). The resulting analog signal may then be provided to an upconverter and ultimately to the radio 2304. In an implementation involving beamforming, the modulated symbols in the corresponding spatial streams are precoded via a steering matrix before being provided to the IFFT block.

[0140] When in receive mode, a digital signal received from the radio 2304 is provided to a DSP circuit system that is configured to acquire the received signal, for example, by detecting the presence of the signal and estimating the initial timing and frequency offset. The DSP circuit system is further configured to digitally condition the digital signal, for example, using channel (narrowband) filtering, analog impairment conditioning (such as correcting I / Q imbalance), and applying digital gain to ultimately acquire a narrowband signal. Subsequently, the output of the DSP circuit system may be fed to an AGC that is configured to use information extracted from the digital signal (e.g., in one or more received training fields) to determine an appropriate gain. The output of the DSP circuit system is also coupled to a demodulator that is configured to extract modulated symbols from the signal and, for example, calculate a log-likelihood ratio (LLR) for each bit position of each subcarrier in each spatial stream. The demodulator is coupled to a decoder that may be configured to process the LLRs to provide decoded bits. Subsequently, the decoded bits from all spatial streams are fed to a demultiplexer for demultiplexing. The demultiplexed bits may then be descrambled and provided to the MAC layer (processor 2306) for processing, evaluation, or interpretation.

[0141] The radio 2304 generally includes at least one radio frequency (RF) transmitter (or "transmitter chain") and at least one RF receiver (or "receiver chain"), which can be combined into one or more transceivers. For example, the RF transmitter and receiver may include various DSP circuit systems, including at least one power amplifier (PA) and at least one low noise amplifier (LNA), respectively. The RF transmitter and receiver may in turn be coupled to one or more antennas. For example, in some implementations, the wireless communication device 2300 may include or be coupled to multiple transmit antennas (each having a corresponding transmit chain) and multiple receive antennas (each having a corresponding receive chain). The codewords output from the modem 2302 are provided to the radio 2304, which then transmits the codewords via the coupled antenna. Similarly, the codewords received via the antenna are obtained by the radio 2304, which then provides the codewords to the modem 2302.

[0142] The processor 2306 may include an intelligent hardware block or device designed to perform the functions described herein, such as, for example, a processing core, a processing block, a central processing unit (CPU), a microprocessor, a microcontroller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a programmable logic device (PLD) (such as a field programmable gate array (FPGA)), discrete gate or transistor logic, discrete hardware components, or any combination thereof. The processor 2306 processes information received through the radio 2304 and the modem 2302, and processes information to be output by the modem 2302 and the radio 2304 for transmission over a wireless medium. For example, the processor 2306 can implement a control plane and a MAC layer, which is configured to perform various operations related to the generation and transmission of MPDUs, frames, or packets. The MAC layer is configured to perform or facilitate encoding and decoding of frames, spatial multiplexing, space-time block decoding (STBC), beamforming, and OFDMA resource allocation and other operations or techniques. In some implementations, the processor 2306 can generally control the modem 2302 to cause the modem to perform the various operations described above.

[0143] The memory 2308 may include a tangible storage medium, such as a random access memory (RAM) or a read-only memory (ROM) or a combination thereof. The memory 2308 may also store non-transient processor or computer executable software (SW) code containing instructions that, when executed by the processor 2306, cause the processor to perform various operations described herein for wireless communication, including generation, transmission, reception, and interpretation of MPDUs, frames, or packets. For example, the various functions of the various components disclosed herein or the various blocks or steps of the methods, operations, processes, or algorithms disclosed herein may be implemented as one or more modules of one or more computer programs.

[0144] Fig.24A A block diagram of an example AP 2402 is shown. For example, the AP 2402 may be a reference Figure 1 An example implementation of the AP 102 is described. The AP 2402 includes a wireless communication device (WCD) 2410 (although the AP 2402 itself may also be generally referred to as a wireless communication device as used herein). For example, the wireless communication device 2410 may be a wireless communication device as described herein. Fig.23An example implementation of the wireless communication device 2300 described. The AP 2402 also includes a plurality of antennas 2420 coupled to the wireless communication device 2410 to transmit and receive wireless communications. In some implementations, the AP 2402 additionally includes an application processor 2430 coupled to the wireless communication device 2410, and a memory 2440 coupled to the application processor 2430. The AP 2402 further includes at least one external network interface 2450, which enables the AP 2402 to communicate with a core network or a backhaul network to obtain access to an external network including the Internet. For example, the external network interface 2450 may include one or both of a wired (e.g., Ethernet) network interface and a wireless network interface (such as a WWAN interface). Components in the aforementioned components may communicate directly or indirectly with other components in these components on at least one bus. The AP 2402 further includes a housing that encloses the wireless communication device 2410, the application processor 2430, the memory 2440, and encloses at least a portion of the antenna 2420 and the external network interface 2450.

[0145] Fig. 24B A block diagram of an example STA 2404 is shown. For example, STA 2404 may be a reference Figure 1 104. STA 2404 includes a wireless communication device 2415 (although STA 2404 itself may also be generally referred to as a wireless communication device as used herein). For example, wireless communication device 2415 may be a wireless communication device. Fig.23 An example implementation of the wireless communication device 2300 described. The STA 2404 also includes one or more antennas 2425 coupled to the wireless communication device 2415 to transmit and receive wireless communications. The STA 2404 additionally includes an application processor 2435 coupled to the wireless communication device 2415, and a memory 2445 coupled to the application processor 2435. In some implementations, the STA 2404 further includes a user interface (UI) 2455 (such as a touch screen or keyboard) and a display 2465, which can be integrated with the UI 2455 to form a touch screen display. In some implementations, the STA 2404 can further include one or more sensors 2475 (such as one or more inertial sensors, accelerometers, temperature sensors, pressure sensors, or altitude sensors, for example). Components of the foregoing components can communicate with other components of these components directly or indirectly on at least one bus. STA 2404 further includes a housing that encloses the wireless communication device 2415 , the application processor 2435 , the memory 2445 , and encloses at least a portion of the antenna 2425 , the UI 2455 , and the display 2465 .

[0146] Figure 1-24BThe operations described herein are examples intended to aid in understanding example implementations and should not be used to limit potential implementations or to limit the scope of the claims. Some implementations may perform additional operations, perform fewer operations, perform operations in parallel or in a different order, and perform some operations differently.

[0147] Although various aspects of the present disclosure have been described in the form of various examples, any combination of aspects from any one of these examples is also within the scope of the present disclosure. The examples in the present disclosure are provided for teaching purposes. As an alternative or supplement to other examples described herein, examples include any combination of the following implementation options.

[0148] One innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by a first wireless local area network (WLAN) device. The method may include transmitting a link adaptation test packet between a first WLAN device and a second WLAN device via a wireless channel. The link adaptation test packet may include one or more test portions formatted to assist in measuring link quality metrics associated with different transmission rate options for the wireless channel. The method may include obtaining link quality metrics associated with different transmission rate options based on the link adaptation test packet. The method may include selecting a selected transmission rate option for transmitting subsequent packets between the first WLAN device and the second WLAN device via the wireless channel based on the link quality metric. The method may include transmitting subsequent packets using the selected transmission rate option.

[0149] In some implementations, communicating refers to transmitting the link adaptation test packet and the subsequent packet from the first WLAN device to the second WLAN device. In some implementations, communicating refers to receiving the link adaptation test packet and the subsequent packet from the second WLAN device.

[0150] In some implementations, obtaining the link quality metric includes receiving feedback information from the second WLAN device in response to the link adaptation test packet.

[0151] In some implementations, the link adaptation test packet is formatted as a Link Adaptation Null Data Packet (LA-NDP) and the feedback information is received in a Link Adaptation Feedback (LA-FB) packet.

[0152] In some implementations, the feedback information includes a field indicating a modulation and coding scheme (MCS) option selected by the second WLAN device based on the link quality metric.The selected transmission rate option may be based on the MCS option selected by the second WLAN device.

[0153] In some implementations, the link adaptation test packet is part of a sequence of messages defined for the link adaptation protocol.

[0154] In some implementations, the method includes selecting a message sequence from among a plurality of message sequences based on a transmission type for a subsequent packet, the plurality of message sequences including different message sequences when the transmission type is one of a group including a single user (SU) transmission, an orthogonal frequency division multiple access (OFDMA) transmission, and a multi-user (MU) multiple input multiple output (MU-MIMO) transmission type. The method may include formatting a link adaptation test packet based at least in part on the selected message sequence.

[0155] In some implementations, the selected message sequence includes the first WLAN device transmitting a Link Adaptation Null Data Packet Announcement (LA-NDPA) or a Link Adaptation Feedback Request prior to delivering the link adaptation test packet, the LA-NDPA or the Link Adaptation Feedback Request being formatted to cause the second WLAN device to provide link quality metrics regarding the link adaptation test packet.

[0156] In some implementations, the link adaptation test packet is part of a link adaptation message sequence that includes transmitting the link adaptation test packet as a piggybacked link adaptation portion of a data carrying packet from a first WLAN device to a second WLAN device, and receiving a link quality metric as part of a block acknowledgment (BA) feedback message from the second WLAN device.

[0157] In some implementations, the method may include communicating a plurality of link adaptation test packets from the first WLAN device to the second WLAN device in a corresponding plurality of data carrying packets. The method may include adjusting the selected transmission rate option based on feedback from the second WLAN device in response to one or more of the link adaptation test packets.

[0158] In some implementations, communicating the link adaptation test packet includes transmitting the link adaptation test packet from the first WLAN device to the second WLAN device as a downlink (DL) orthogonal frequency division multiple access (OFDMA) transmission. The method may include transmitting a trigger frame to cause at least the second WLAN device to provide a link quality metric in a trigger-based protocol data unit (TB PPDU).

[0159] In some implementations, the method may include determining that a subsequent packet will be a beamformed transmission. The method may include adjusting a format of a link adaptation test packet when the subsequent packet will be a beamformed transmission so that the link adaptation test packet is formatted to facilitate measurement of beamforming characteristics of a wireless channel.

[0160] In some implementations, the method may include transmitting a null data packet announcement (NDPA) to indicate that a combined null data packet (NDP) including a link adaptation test packet is to be used for beamforming estimation and link adaptation. The method may include transmitting the combined NDP from the first WLAN device to the second WLAN device. The method may include receiving a response to the combined NDP. The response may include beamforming feedback based on the beamforming estimation and link adaptation feedback based on a link quality metric of the wireless channel.

[0161] In some implementations, the method may include determining that a subsequent packet will be a beamformed transmission. The method may include, prior to delivering a link adaptation test packet: transmitting a legacy null data packet announcement (NDPA) from a first WLAN device to a second WLAN device; and transmitting a legacy null data packet (NDP) from the first WLAN device to the second WLAN device. The NDP may be used by the second WLAN device to determine beamforming feedback. The method may include receiving a beamforming (BF) report packet including beamforming feedback from the second WLAN device. The method may include transmitting a link adaptation test packet using a beamforming configuration based on the beamforming feedback.

[0162] In some implementations, the link adaptation test packet is received by the first WLAN device from the second WLAN device.In some implementations, obtaining the link quality metric includes measuring the link quality metric based on the link adaptation test packet.

[0163] In some implementations, the method may include transmitting a link adaptation request packet including an identifier associated with the second WLAN device and the third WLAN device. The link adaptation request packet may be configured to cause the second WLAN device and the third WLAN device to concurrently provide a link adaptation test packet to the first WLAN device. The method may include receiving the link adaptation test packet from the second WLAN device and the third WLAN device via a wireless channel. The method may include determining a first selected transmission rate option for the second WLAN device and a second selected transmission rate option for the third WLAN based at least in part on the link adaptation test packet.

[0164] In some implementations, delivering the subsequent packet includes transmitting the subsequent packet as a multi-user (MU) DL transmission. The MU DL transmission may include a first portion for the second WLAN device modulated according to the first selected transmission rate option and may include a second portion for the third WLAN device modulated according to the second selected transmission rate option.

[0165] In some implementations, the method may include transmitting a trigger frame to cause the second WLAN device and the third WLAN device to transmit a multi-user (MU) uplink (UL) transmission. The trigger frame may include an indication of a first selected transmission rate option for use by the second WLAN device in the MU UL transmission and a second selected transmission rate option for use by the third WLAN device in the MU UL transmission.

[0166] In some implementations, the MU UL transmission is formatted according to a multi-user (MU) multiple-input multiple-output (MIMO) transmission or an orthogonal frequency division multiple access (OFDMA) transmission.

[0167] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by a first station (STA) of a WLAN. The method may include receiving a link adaptation test packet from an access point (AP) of the WLAN via a wireless channel. The link adaptation test packet may include one or more test portions, which are formatted to assist in measuring link quality metrics associated with different transmission rate options of the wireless channel. The method may include measuring link quality metrics associated with different transmission rate options based on the link adaptation test packet. The method may include transmitting link adaptation feedback to the AP based at least in part on the link quality metric. The method may include receiving a subsequent packet formatted according to a transmission rate option selected by the AP based on the link adaptation feedback.

[0168] In some implementations, the method may include receiving a Link Adaptation Null Data Packet Announcement (LA-NDPA) prior to receiving the Link Adaptation Test Packet. The LA-NDPA may instruct the first STA to measure a link quality metric.

[0169] In some implementations, the method may include receiving a trigger frame. Link adaptation feedback may be transmitted in response to the trigger frame.

[0170] In some implementations, the link adaptation test packet is a multi-user (MU) multiple-input multiple-output (MIMO) transmission or an orthogonal frequency division multiple access (OFDMA) transmission formatted to solicit link adaptation feedback from the first STA and the second STA of the WLAN.

[0171] Another innovative aspect of the subject matter described in the present disclosure may be implemented as an apparatus of a first WLAN device. The apparatus may include at least one modem configured to transfer a link adaptation test packet between a first WLAN device and a second WLAN device via a wireless channel. The link adaptation test packet may include one or more test portions formatted to assist in measuring a link quality metric associated with different transmission rate options of the wireless channel. The apparatus may include at least one processor communicatively coupled to the at least one modem and configured to obtain a link quality metric associated with different transmission rate options based on the link adaptation test packet. The at least one processor may be configured to select a selected transmission rate option for transmitting subsequent packets between the first WLAN device and the second WLAN device via the wireless channel based at least in part on the link quality metric. The at least one modem may be configured to transfer subsequent packets using the selected transmission rate option.

[0172] In some implementations, the link adaptation test packet is output from the first WLAN device to the second WLAN device.The at least one processor may be configured to obtain the link quality metric from feedback information obtained by the at least one modem from the second WLAN device in response to the link adaptation test packet.

[0173] In some implementations, the link adaptation test packet is part of a message sequence defined for a link adaptation protocol. The at least one processor may be configured to select a message sequence from among a plurality of message sequences based on a transmission type for a subsequent packet, the plurality of message sequences including different message sequences when the transmission type is one of a group including a single user (SU) transmission, an orthogonal frequency division multiple access (OFDMA) transmission, and a multi-user (MU) multiple input multiple output (MU-MIMO) transmission type. The at least one processor may be configured to cause the at least one modem to format the link adaptation test packet based at least in part on the selected message sequence.

[0174] In some implementations, the at least one processor is further configured to determine that a subsequent packet will be a beamformed transmission, and to cause the at least one modem to adjust a format of a link adaptation test packet when the subsequent packet will be a beamformed transmission so that the link adaptation test packet is formatted to facilitate measurement of beamforming characteristics of the wireless channel.

[0175] In some implementations, the at least one modem may be configured to output a null data packet announcement (NDPA) for transmission to the second WLAN to indicate that a combined null data packet (NDP) including a link adaptation test packet is to be used for beamforming estimation and link adaptation. The at least one modem may be configured to output a combined NDP for transmission from the first WLAN device to the second WLAN device via the wireless channel. The at least one modem may be configured to obtain a response to the combined NDP. The response may include beamforming feedback based on the beamforming estimation and link adaptation feedback based on a link quality metric of the wireless channel.

[0176] In some implementations, the apparatus may include at least one transceiver coupled to the at least one modem. The apparatus may include a plurality of antennas coupled to the at least one transceiver to wirelessly transmit signals output from the at least one transceiver. The apparatus may include a housing enclosing the at least one modem, the at least one processor, the at least one transceiver, and at least a portion of the plurality of antennas.

[0177] Another innovative aspect of the subject matter described in the present disclosure may be implemented as an apparatus of a second WLAN device. The apparatus may include at least one modem configured to obtain a link adaptation test packet from an access point (AP) of a WLAN via a wireless channel. The link adaptation test packet may include one or more test portions formatted to assist in measuring a link quality metric associated with different transmission rate options of the wireless channel. The apparatus may include at least one processor communicatively coupled to the at least one modem and configured to measure a link quality metric associated with different transmission rate options based on the link adaptation test packet. The at least one modem may be configured to output link adaptation feedback based at least in part on the link quality metric for transmission to the AP. The at least one modem may be configured to obtain a subsequent packet from the AP via the wireless channel, the subsequent packet being formatted according to a transmission rate option selected by the AP based on the link adaptation feedback.

[0178] In some implementations, the apparatus may include at least one transceiver coupled to the at least one modem. The apparatus may include a plurality of antennas coupled to the at least one transceiver to wirelessly transmit signals output from the at least one transceiver. The apparatus may include a housing enclosing the at least one modem, the at least one processor, the at least one transceiver, and at least a portion of the plurality of antennas.

[0179] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by a first WLAN device. The method may include determining data to be sent from the first WLAN device to a second WLAN device via a wireless channel. The method may include, before sending the data, outputting a first packet for transmission from the first WLAN device to the second WLAN device via the wireless channel. The first packet may be formatted for the second WLAN device to determine a link quality metric of the wireless channel. The method may include receiving feedback information from the second WLAN device based on the link quality metric of the wireless channel. The feedback information may be used by the first WLAN device to determine an MCS (or other transmission rate option) to encode and modulate subsequent packets to the second WLAN device via the wireless channel. The method may include outputting at least a portion of the data in the subsequent packet using the selected MCS.

[0180] In some implementations, the first packet may be a fast rate adaptation (FRA) test packet.The feedback information may be link adaptation feedback specific to the MCS selection.

[0181] In some implementations, the feedback information includes a field indicating a selected MCS selected by the second WLAN device based on the link quality metric.

[0182] In some implementations, the feedback information includes a link quality metric.The method may include determining, by the first WLAN device, the selected MCS based on the link quality metric.

[0183] In some implementations, the first packet may be formatted as a MIMO transmission including one or more portions for SINR estimation, and the feedback information may be based on the SINR estimation.

[0184] In some implementations, the first packet includes multiple portions modulated using corresponding multiple MCS options, including at least a first portion modulated using a first MCS and a second portion modulated using a second MCS. The feedback information may be based on multiple MCS options.

[0185] In some implementations, the first packet may be part of a fast rate adaptation (FRA) message sequence.

[0186] In some implementations, the first packet may be a LA-NDP, and the feedback information may be received in a LA-FB packet.

[0187] In some implementations, the method may include determining a transmission type for a subsequent packet from among a plurality of transmission types including SU transmission, OFDMA transmission, and MU-MIMO transmission types. The method may include selecting a link adaptation sequence from among a plurality of link adaptation sequences corresponding to the plurality of transmission types.

[0188] In some implementations, the method may include determining whether a subsequent packet will be a beamformed transmission of the determined transmission type.The method may include adjusting a link adaptation sequence based on whether a subsequent packet will be a beamformed transmission.

[0189] In some implementations, the link adaptation sequence includes the first WLAN device outputting the LA-NDPA before outputting the LA-NDP.

[0190] In some implementations, the LA-NDPA includes instructions for the second WLAN device to send the feedback information.

[0191] In some implementations, the LA-NDPA includes an indicator that identifies a link adaptation sequence.

[0192] In some implementations, the LA-FB packet includes an array of link quality metrics based on a subset of the LA-NDP or based on a bandwidth subset for the wireless channel.

[0193] In some implementations, the first packet may be part of a fast rate adaptation (link adaptation) sequence. The link adaptation sequence may include outputting a LA-NDPA from the first WLAN device to the second WLAN device. The link adaptation sequence may include outputting a first packet from the first WLAN device to the second WLAN device. The first packet may be a LA-NDP. The link adaptation sequence may include receiving a LA-FB packet including feedback information from the second WLAN device. The link adaptation sequence may include outputting a subsequent packet. The link adaptation sequence may include receiving a block acknowledgment (BA) feedback message from the second WLAN device. The BA feedback message may be used by the first WLAN device to determine whether to retransmit at least a portion of the data in the subsequent packet.

[0194] In some implementations, the link adaptation sequence permits piggybacked rate adaptation information. The link adaptation sequence may further include an additional LA-NDP included as part of a subsequent packet. The link adaptation sequence may include receiving an additional LA-FB as part of a BA feedback message from the second WLAN device. In some implementations, the additional LA-FB may be used by the first WLAN device to determine a newly selected MCS to modulate a next packet after the subsequent packet. The link adaptation sequence may include outputting the next packet using the newly selected MCS.

[0195] In some implementations, the link adaptation sequence may be used for DL ​​OFDMA transmission. The link adaptation sequence may include, after outputting the LA-NDP, outputting a trigger frame to cause at least the second WLAN device to send a LA-FB. The LA-FB may be a TB PPDU. In some implementations, outputting the subsequent packet includes outputting a DL OFDMA transmission including the subsequent packet.

[0196] In some implementations, the link adaptation sequence may further include outputting a BA request (BAR) packet to cause at least the second WLAN device to send a BA feedback message.

[0197] In some implementations, the link adaptation sequence permits piggybacked rate adaptation information. The link adaptation sequence may further include including an additional LA-NDP as part of a DL OFDMA transmission, and outputting a BAR packet to cause at least a second WLAN device to send a BA feedback message and a LA-FB. The link adaptation sequence may include receiving an additional LA-FB as part of a BA feedback message from the second WLAN device. The additional LA-FB may be used by the first WLAN device to determine a newly selected MCS to modulate a next packet after a subsequent packet. The link adaptation sequence may include outputting a next packet as a next DL OFDMA transmission using the newly selected MCS.

[0198] In some implementations, the method includes determining that a subsequent packet is to be beamformed. The method may include performing a beamforming determination sequence before a link adaptation sequence. The beamforming determination sequence may include outputting a traditional NDPA from a first WLAN device to a second WLAN device. The beamforming determination sequence may include outputting a traditional NDP from a first WLAN device to a second WLAN device, wherein the NDP may be used by the second WLAN device to determine beamforming feedback. The beamforming determination sequence may include receiving a beamforming (BF) report packet including beamforming feedback from the second WLAN device. The beamforming determination sequence may include determining a beamforming configuration based on the beamforming feedback. The beamforming configuration may be used for LA-NDPA, LA-NDP, and subsequent packets.

[0199] In some implementations, the method may include determining that a subsequent packet is to be beamformed. The method may include executing a link adaptation sequence in conjunction with a beamforming determination sequence. The link adaptation sequence in conjunction with the beamforming determination sequence may include outputting a combined NDPA to indicate that the combined NDP will be used for beamforming estimation and link quality metrics. The link adaptation sequence in conjunction with the beamforming determination sequence may include outputting a combined NDP from a first WLAN device to a second WLAN device. The combined NDP may be used by the second WLAN device to determine beamforming feedback and link quality metrics. The link adaptation sequence in conjunction with the beamforming determination sequence may include receiving a response to the combined NDP. The response may include beamforming feedback and feedback information based on a link quality metric of a wireless channel. The link adaptation sequence in conjunction with the beamforming determination sequence may include determining a beamforming configuration based on the beamforming feedback and an MCS selected based on the link quality metric. The beamforming configuration and the selected MCS may be used for subsequent packets.

[0200] In some implementations, the link adaptation sequence may be used for DL ​​MU-MIMO transmission and beamforming. The beamforming determination sequence may include, after outputting a traditional NDP, outputting a trigger frame to cause at least a second WLAN device to send a BF report packet. Outputting a subsequent packet may include outputting a DL MU-MIMO transmission including a subsequent packet.

[0201] In some implementations, the first WLAN device may be an AP and the second WLAN device may be a STA, such that the subsequent packet is a downlink transmission.

[0202] In some implementations, the first WLAN device may be a STA and the second WLAN device may be an AP, such that the subsequent packet is an uplink transmission.

[0203] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by an apparatus of an AP. The method may include determining that a first STA has data to be sent from the first STA to the AP via a wireless channel. The method may include outputting a fast rate adaptation (FRA) request packet before causing the STA to send data. The link adaptation request packet may be configured to cause the first STA to send a link adaptation test packet to the AP. The method may include receiving a link adaptation test packet from the first STA via a wireless channel. The link adaptation test packet may be formatted for the AP to determine a link quality metric of the wireless channel. The method may include determining a first selected MCS (or other transmission rate option) for an uplink transmission including data for the first STA, the first selected MCS being based on a link quality metric of the wireless channel. The method may include outputting a trigger frame configured to cause the first STA to use the first selected MCS in an uplink transmission including data. The trigger frame may prompt the first STA to send an uplink transmission to the AP.

[0204] In some implementations, the uplink transmission may be an OFDMA transmission that includes data from the first STA and other data from the second STA.

[0205] In some implementations, the link adaptation request packet may be formatted as a LA-NDPR and the link adaptation test packet may be formatted as a LA-NDP.

[0206] In some implementations, the link adaptation request packet indicates which STAs are to send link adaptation test packets.

[0207] In some implementations, the method may include determining that the second STA has data to be sent from the second STA to the AP via a wireless channel. The method may include including identifiers associated with the first STA and the second STA in a link adaptation request packet. The link adaptation request packet may be configured to cause the first STA and the second STA to concurrently send a link adaptation test packet to the AP. The method may include receiving a link adaptation test packet from the first STA and the second STA via a wireless channel. The method may include determining a first selected MCS for concurrent uplink transmissions by the first STA and a second selected MCS for concurrent uplink transmissions by the second STA, the first selected MCS and the second selected MCS being based on the link adaptation test packet. The method may include including an indication of the first selected MCS and the second selected MCS in a trigger frame so that the first STA uses the first selected MCS for concurrent uplink transmissions and the second STA uses the second selected MCS for concurrent uplink transmissions. The method may include receiving data from the first STA and the second STA in concurrent uplink transmissions.

[0208] In some implementations, concurrent uplink transmissions may be formatted according to MU-MIMO transmissions.

[0209] In some implementations, concurrent uplink transmissions may be formatted according to OFDMA transmissions.

[0210] Another innovative aspect of the subject matter described in the present disclosure can be implemented as a device. The device may include a modem and at least one processor communicatively coupled to at least one modem. The processor together with the modem can be configured to perform any of the above methods or features described herein.

[0211] Another innovative aspect of the subject matter described in this disclosure can be implemented as a computer-readable medium having stored therein instructions that, when executed by a processor, cause the processor to perform any of the above methods or features described herein.

[0212] Another innovative aspect of the subject matter described in this disclosure can be implemented as a system having means for implementing any of the above methods or features described herein.

[0213] As used herein, a phrase referring to "at least one of" or "one or more of" a list of items refers to any combination of those items, including single members. For example, "at least one of a, b, or c" is intended to cover the following possibilities: only a, only b, only c, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a, b, and c.

[0214] The various illustrative components, logic, logic blocks, modules, circuits, operations, and algorithmic processes described in conjunction with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or a combination of hardware, firmware, or software, including the structures disclosed in this specification and their structural equivalents. This interchangeability of hardware, firmware, and software has been generally described in terms of their functionality and is illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the specific application and the design constraints imposed on the overall system.

[0215] The hardware and data processing apparatus for implementing the various illustrative components, logic, logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented or executed with a general purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). In some implementations, specific processes, operations, and methods may be performed by circuit systems dedicated to a given function.

[0216] As described above, in some aspects, the realization of the subject matter described in this specification can be implemented as software.For example, each function of each component disclosed herein or each frame or step of the method, operation, process or algorithm disclosed herein can be implemented as one or more modules of one or more computer programs.Such computer programs may include non-transient processors or computer executable instructions encoded on one or more tangible processors or computer-readable storage media, which are used to perform or control the operation of the data processing device by the data processing device including the components of the device described herein.As an example and not a limitation, this storage medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, or any other medium that can be used to store program codes in the form of instructions or data structures.The above combination should also be included in the scope of storage media.

[0217] Various modifications to the implementations described in this disclosure may be apparent to those of ordinary skill in the art, and the universal principles defined herein may be applied to other implementations without departing from the spirit or scope of the disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but should be granted the widest scope consistent with the disclosure, the principles and novel features disclosed herein.

[0218] In addition, various features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations separately or in any suitable subcombination. Thus, while features may be described above as functioning in a particular combination and even initially claimed as such, one or more features from a claimed combination may in some cases be removed from the combination, and a claimed combination may be directed to a subcombination, or a variation of a subcombination.

[0219] Similarly, although operations are depicted in a particular order in the accompanying drawings, this should not be understood as requiring such operations to be performed in the particular order shown or in a sequential order, or to perform all the operations described in order to achieve the desired result. In addition, the accompanying drawings may schematically depict one or more example processes in the form of a flow chart or a flow diagram. However, other operations not depicted may be incorporated into the example processes schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously or between any of the illustrated operations. In some environments, multitasking and parallel processing may be advantageous. In addition, the separation of various system components in the implementation described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations also fall within the scope of the appended claims. In some cases, the actions described in the claims may be performed in different orders and still achieve the desired result.

Claims

1. A method for wireless communication by a first wireless local area network (WLAN) device, comprising: communicating a link adaptation test packet between the first WLAN device and the second WLAN device via a wireless channel, the link adaptation test packet comprising a first test portion modulated using a first modulation and coding scheme (MCS) and a second test portion modulated using a second MCS, wherein the first MCS is different from the second MCS; obtaining a first link quality metric associated with the first MCS and a second link quality metric associated with the second MCS based on the link adaptation test packet; as well as Subsequent packets are communicated between the first WLAN device and the second WLAN device via the wireless channel using the first MCS or the second MCS based at least in part on the first link quality metric and the second link quality metric.

2. The method of claim 1 , wherein communicating the link adaptation test packet comprises transmitting the link adaptation test packet from the first WLAN device to the second WLAN device, and wherein obtaining the first link quality metric and the second link quality metric comprises receiving feedback information from the second WLAN device in response to the link adaptation test packet.

3. The method of claim 2, wherein the link adaptation test packet is formatted as a link adaptation null data packet (LA-NDP) and the feedback information is received in a link adaptation feedback (LA-FB) packet.

4. The method of claim 2, wherein the feedback information includes a field indicating an MCS option selected by the second WLAN device based on the first link quality metric and the second link quality metric, and wherein delivering the subsequent packet using the first MCS or the second MCS is based on the MCS option selected by the second WLAN device.

5. The method of claim 1, wherein the link adaptation test packet is part of a message sequence defined for a link adaptation protocol.

6. The method of claim 5, further comprising: selecting the message sequence from among a plurality of message sequences based on a transmission type for the subsequent packet, the plurality of message sequences comprising different message sequences when the transmission type is one of a group including single user (SU) transmission, orthogonal frequency division multiple access (OFDMA) transmission, and multi-user (MU) multiple input multiple output (MU-MIMO) transmission types; and The link adaptation test packet is formatted based at least in part on the selected message sequence.

7. The method of claim 6, wherein the selected message sequence comprises the first WLAN device transmitting a Link Adaptation Null Data Packet Announcement (LA-NDPA) or a Link Adaptation Feedback Request prior to delivering the link adaptation test packet, the LA-NDPA or Link Adaptation Feedback Request being formatted to cause the second WLAN device to provide the first link quality metric and the second link quality metric with respect to the link adaptation test packet.

8. The method of claim 1, wherein the link adaptation test packet is part of a link adaptation message sequence, the link adaptation message sequence comprising: transmitting, from the first WLAN device to the second WLAN device, the link adaptation test packet as a piggybacked link adaptation part of a data carrying packet; as well as The first link quality metric and the second link quality metric are received from the second WLAN device as part of a block acknowledgment (BA) feedback message.

9. The method of claim 8, further comprising: transmitting, from the first WLAN device to the second WLAN device, a plurality of link adaptation test packets in the corresponding plurality of data carrying packets; as well as The first MCS or the second MCS is selected based on feedback from the second WLAN device in response to one or more of the link adaptation test packets.

10. The method of claim 1, wherein communicating the link adaptation test packet comprises: transmitting the link adaptation test packet from the first WLAN device to the second WLAN device as a downlink (DL) orthogonal frequency division multiple access (OFDMA) transmission; as well as A trigger frame is transmitted to cause at least the second WLAN device to provide the first link quality metric and the second link quality metric in a trigger-based physical layer convergence protocol (PLCP) protocol data unit (TB PPDU).

11. The method of claim 1, further comprising: determining that the subsequent packet is to be a beamformed transmission; as well as The format of the link adaptation test packet is adjusted when the subsequent packet is to be a beamformed transmission such that the link adaptation test packet is formatted to facilitate measurement of beamforming characteristics of the wireless channel.

12. The method of claim 11, further comprising: transmitting a null data packet announcement (NDPA) to indicate that a combined null data packet (NDP) including the link adaptation test packet is to be used for beamforming estimation and link adaptation; transmitting the combined NDP from the first WLAN device to the second WLAN device; as well as A response to the combined NDP is received, wherein the response comprises beamforming feedback based on the beamforming estimate and link adaptation feedback based on the first link quality metric and the second link quality metric of the wireless channel.

13. The method of claim 1, further comprising: determining that the subsequent packet is to be a beamformed transmission; Before delivering the link adaptation test packet: transmitting a legacy null data packet announcement (NDPA) from the first WLAN device to the second WLAN device, transmitting a legacy null data packet (NDP) from the first WLAN device to the second WLAN device, wherein the NDP can be used by the second WLAN device to determine beamforming feedback, and receiving a beamforming (BF) report packet including the beamforming feedback from the second WLAN device; as well as The link adaptation test packet is transmitted using a beamforming configuration based on the beamforming feedback.

14. The method of claim 1, wherein the link adaptation test packet is received by the first WLAN device from the second WLAN device, and wherein obtaining the first link quality metric and the second link quality metric comprises measuring the first link quality metric and the second link quality metric based on the link adaptation test packet.

15. The method of claim 14, further comprising: transmitting a link adaptation request packet, the link adaptation request packet including identifiers associated with the second WLAN device and the third WLAN device, wherein the link adaptation request packet is configured to cause the second WLAN device and the third WLAN device to concurrently provide link adaptation test packets to the first WLAN device; receiving the link adaptation test packet from the second WLAN device and the third WLAN device via the wireless channel; The first MCS or the second MCS is determined as a first selected transmission rate option for the second WLAN device and the first MCS or the second MCS is determined as a second selected transmission rate option for the third WLAN based at least in part on the link adaptation test packet.

16. The method of claim 15, wherein delivering the subsequent packet comprises: The subsequent packet is transmitted as a multi-user (MU) DL transmission, the MU DL transmission including a first portion for the second WLAN device modulated according to the first selected transmission rate option and further including a second portion for the third WLAN device modulated according to the second selected transmission rate option.

17. The method of claim 15, further comprising: transmitting a trigger frame to cause the second WLAN device and the third WLAN device to transmit a multi-user (MU) uplink (UL) transmission, wherein the trigger frame includes an indication of the first selected transmission rate option for use by the second WLAN device in the MU UL transmission and the second selected transmission rate option for use by the third WLAN device in the MU UL transmission.

18. The method of claim 17, wherein the MU UL transmission is formatted according to a multi-user (MU) multiple-input multiple-output (MIMO) transmission or an orthogonal frequency division multiple access (OFDMA) transmission.

19. A method for wireless communication by a first station (STA) of a wireless local area network (WLAN), comprising: receiving a link adaptation test packet from an access point (AP) of the WLAN via a wireless channel, the link adaptation test packet comprising a first test portion modulated using a first modulation and coding scheme (MCS) and a second test portion modulated using a second MCS, wherein the first MCS is different from the second MCS; measuring a first link quality metric associated with the first MCS and a second link quality metric associated with the second MCS based on the link adaptation test packet; transmitting link adaptation feedback to the AP based at least in part on the first link quality metric and the second link quality metric; as well as Receiving subsequent packets formatted according to the first MCS or the second MCS selected by the AP based on the link adaptation feedback.

20. The method of claim 19, further comprising: A Link Adaptation Null Data Packet Announcement (LA-NDPA) is received prior to receiving the link adaptation test packet, wherein the LA-NDPA instructs the first STA to measure the first link quality metric and the second link quality metric.

21. The method of claim 20, further comprising: A trigger frame is received, wherein the link adaptation feedback is transmitted in response to the trigger frame.

22. The method of claim 19, wherein the link adaptation test packet is a multi-user (MU) multiple-input multiple-output (MIMO) transmission or an orthogonal frequency division multiple access (OFDMA) transmission formatted to solicit link adaptation feedback from the first and second STAs of the WLAN.

23. An apparatus of a first wireless local area network (WLAN) device, comprising: at least one modem configured to communicate a link adaptation test packet between the first WLAN device and a second WLAN device via a wireless channel, the link adaptation test packet comprising a first test portion modulated with a first modulation and coding scheme (MCS) and a second test portion modulated with a second MCS, wherein the first MCS is different from the second MCS; at least one processor communicatively coupled to the at least one modem and configured to: obtaining a first link quality metric associated with the first MCS and a second link quality metric associated with the second MCS based on the link adaptation test packet; as well as The at least one modem is configured to communicate subsequent packets between the first WLAN device and the second WLAN device via the wireless channel using the first MCS or the second MCS based at least in part on the first link quality metric and the second link quality metric.

24. The apparatus of claim 23, wherein the link adaptation test packet is output from the first WLAN device to the second WLAN device, and wherein the at least one processor is configured to obtain the first link quality metric and the second link quality metric from feedback information obtained by the at least one modem from the second WLAN device in response to the link adaptation test packet.

25. The device according to claim 23, wherein the link adaptation test packet is part of a message sequence defined for the link adaptation protocol, wherein the at least one processor is configured to: selecting the message sequence from among a plurality of message sequences based on a transmission type for the subsequent packet, the plurality of message sequences comprising different message sequences when the transmission type is one of a group including single user (SU) transmission, orthogonal frequency division multiple access (OFDMA) transmission, and multi-user (MU) multiple input multiple output (MU-MIMO) transmission types; and The at least one modem is caused to format the link adaptation test packet based at least in part on the selected message sequence.

26. The apparatus of claim 23, wherein the at least one processor is further configured to: determining that the subsequent packet is to be a beamformed transmission; and The at least one modem is caused to adjust a format of the link adaptation test packet when the subsequent packet is to be a beamformed transmission such that the link adaptation test packet is formatted to facilitate measurement of beamforming characteristics of the wireless channel.

27. The apparatus of claim 23, further comprising: The at least one modem is further configured to: outputting a null data packet announcement (NDPA) for transmission to the second WLAN to indicate that a combined null data packet (NDP) including the link adaptation test packet is to be used for beamforming estimation and link adaptation; outputting the combined NDP for transmission from the first WLAN device to the second WLAN device via the wireless channel; as well as A response to the combined NDP is obtained, wherein the response comprises beamforming feedback based on the beamforming estimate and link adaptation feedback based on the first link quality metric and the second link quality metric of the wireless channel.

28. The apparatus of claim 23, further comprising: at least one transceiver coupled to the at least one modem; a plurality of antennas coupled to the at least one transceiver to wirelessly transmit signals output from the at least one transceiver; as well as A housing enclosing the at least one modem, the at least one processor, the at least one transceiver, and at least a portion of the plurality of antennas.

29. An apparatus of a second wireless local area network (WLAN) device, comprising: at least one modem configured to obtain a link adaptation test packet from an access point (AP) of the WLAN via a wireless channel, the link adaptation test packet comprising a first test portion modulated using a first modulation and coding scheme (MCS) and a second test portion modulated using a second MCS, wherein the first MCS is different from the second MCS; at least one processor communicatively coupled to the at least one modem and configured to measure a first link quality metric associated with the first MCS and a second link quality metric associated with the second MCS based on the link adaptation test packet; the at least one modem configured to output link adaptation feedback for transmission to the AP based at least in part on the first link quality metric and the second link quality metric; as well as The at least one modem is configured to obtain subsequent packets from the AP via the wireless channel, the subsequent packets being formatted according to the first MCS or the second MCS selected by the AP based on the link adaptation feedback.

30. The apparatus of claim 29, further comprising: at least one transceiver coupled to the at least one modem; a plurality of antennas coupled to the at least one transceiver to wirelessly transmit signals output from the at least one transceiver; as well as A housing enclosing the at least one modem, the at least one processor, the at least one transceiver, and at least a portion of the plurality of antennas.

Images