Link Adaptation Using Link Quality Estimate Sequences

Abstract

The present disclosure provides systems, methods and apparatus for link adaptation in a wireless local area network (WLAN). A link adaptation test packet from a first WLAN device to a second WLAN device may be formatted as a multiple-input multiple-output (MIMO) transmission and may include one or more test portions for link quality estimation of the MIMO transmission. The link quality estimation portion of the test packet may allow measurement of link quality of various spatial streams for MIMO transmission. The link adaptation test packet may implement fast rate adaptation of a communication link based on the impact of interference on various spatial streams. The second WLAN device may provide feedback information about the one or more test portions. The feedback information may be used to determine a transmission rate for subsequent transmissions from the first WLAN device to the second WLAN device based on wireless channel conditions.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. Non-Provisional Patent Application No. 17 / 105,349, filed on November 25, 2020, entitled "LINK ADAPTATION USING A LINKQUALITY ESTIMATION SEQUENCE", and U.S. Provisional Patent Application No. 62 / 944,094, filed on December 5, 2019, entitled "LINK ADAPTATION WITH SIGNAL-TO-INTERFERENCE-PLUS-NOISE RATIO (SINR) ESTIMATION", and both applications are assigned to the assignee of this application. The disclosure of the prior application is considered a part of this patent application and is incorporated into this patent application by reference. 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). Background Art

[0004] 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").

[0005] 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. Summary of the invention

[0006] 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.

[0007] Innovative aspects 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 transmitting a first packet from the first WLAN device to a second WLAN device via a wireless channel. The first packet may be formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation. The method may include receiving feedback information from the second WLAN device based on the link quality estimation of the one or more test portions of the first packet. The method may include determining a selected transmission rate option for transmitting a subsequent packet to the second WLAN device via the wireless channel based on the feedback information.

[0008] In some implementations, the one or more test portions for link quality estimation include a link quality estimation sequence for measuring a link quality metric for each of a plurality of spatial streams in a MIMO transmission.

[0009] In some implementations, the feedback information includes a plurality of link quality metrics based on signal to interference plus noise (SINR) or error vector magnitude (EVM) measurements for one or more test portions.

[0010] In some implementations, the first packet includes a first portion for signal and noise estimation and a second portion for interference estimation.

[0011] In some implementations, the second portion includes one or more orthogonal frequency division multiplexing (OFDM) symbols for link quality estimation.

[0012] In some implementations, the one or more OFDM symbols of the second portion include at least one null symbol that provides an idle measurement period during the first packet.

[0013] In some implementations, the one or more OFDM symbols of the second portion include at least a first OFDM symbol having a null value on a first subset of tones in a first OFDM symbol.

[0014] In some implementations, the second portion includes at least a second OFDM symbol having null values ​​on a second subset of tones in the second OFDM symbol, the second subset of tones being different from a first subset of tones in the first OFDM symbol.

[0015] In some implementations, the first subset of tones includes every other tone and the second subset of tones includes another tone that is every other tone.

[0016] In some implementations, the one or more OFDM symbols of the second portion include a first OFDM symbol having a first predetermined sequence and at least a second OFDM symbol having the same first predetermined sequence or a second predetermined sequence.

[0017] In some implementations, the one or more OFDM symbols of the second portion include a plurality of OFDM symbols having a same predetermined sequence.The number of the plurality of OFDM symbols may be based on the number of spatial streams in the MIMO transmission.

[0018] In some implementations, the first packet includes instructions to cause the second WLAN device to perform link quality estimation of the one or more test portions and to provide feedback information based on the link quality estimation.

[0019] In some implementations, the indication is included in a preamble of the first packet.

[0020] In some implementations, the first packet includes upper layer data for the second WLAN device in addition to one or more test portions for link quality estimation.

[0021] In some implementations, the one or more test portions for link quality estimation are included in a separate portion of the first packet from the one or more test portions.

[0022] In some implementations, the feedback information includes a field indicating a selected transmission rate option selected by the second WLAN device based on the link quality estimate.

[0023] In some implementations, the feedback information includes one or more link quality metrics associated with one or more test portions for link quality estimation.The method may include determining, by the first WLAN device, the selected transmission rate option based on the one or more link quality metrics.

[0024] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by a second WLAN device. The method may include receiving a first packet from a first WLAN device via a wireless channel, the first packet being formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation. The method may include transmitting feedback information to the first WLAN device based on the link quality estimation of the one or more test portions in the first packet. The feedback information may be used by the first WLAN device to determine a selected transmission rate option for transmitting a subsequent packet for transmission from the first WLAN device via the wireless channel.

[0025] In some implementations, the one or more test portions for link quality estimation include a link quality estimation sequence for measuring a link quality metric for each of a plurality of spatial streams in a MIMO transmission.

[0026] In some implementations, the feedback information includes a plurality of link quality metrics based on signal to interference plus noise (SINR) or error vector magnitude (EVM) measurements for one or more test portions.

[0027] In some implementations, the multiple link quality metrics correspond to multiple spatial streams in a MIMO transmission.

[0028] In some implementations, the method may include determining a selected transmission rate option for a plurality of spatial streams in a MIMO transmission based on the link quality estimate.The feedback information may include a field indicating the selected transmission rate option.

[0029] 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 output a first packet for transmission from the first WLAN device to a second WLAN device via a wireless channel. The first packet may be formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation. The at least one modem may be configured to obtain feedback information from the second WLAN device based on the link quality estimation of the one or more test portions of the first packet. The apparatus may include at least one processor communicatively coupled to the at least one modem and configured to determine a selected transmission rate option for transmitting a subsequent packet to the second WLAN device via the wireless channel based on the feedback information.

[0030] In some implementations, the one or more test portions for link quality estimation include a link quality estimation sequence for measuring a link quality metric for each of a plurality of spatial streams in a MIMO transmission.

[0031] In some implementations, the feedback information includes a plurality of link quality metrics based on signal to interference plus noise (SINR) or error vector magnitude (EVM) measurements for one or more test portions.

[0032] In some implementations, the first packet includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols for link quality estimation. The plurality of OFDM symbols may have the same predetermined sequence. The number of the plurality of OFDM symbols may be based on the number of spatial streams in the MIMO transmission.

[0033] In some implementations, the apparatus may include at least one transceiver coupled to the at least one modem, and 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.

[0034] Another innovative aspect of the subject matter described in the present disclosure can be implemented as an apparatus of a second WLAN device. The apparatus may include at least one modem configured to obtain a first packet from a first WLAN device via a wireless channel, the first packet being formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation. The apparatus may include at least one processor, the at least one processor being communicatively coupled to the at least one modem and configured to: determine feedback information based on the link quality estimation of the one or more test portions in the first packet, the feedback information being usable by the first WLAN device to determine a selected transmission rate option for transmitting a subsequent packet for transmission from the first WLAN device via the wireless channel. The at least one modem may be configured to output the feedback information for transmission to the first WLAN device.

[0035] In some implementations, the feedback information includes a plurality of link quality metrics based on signal to interference plus noise (SINR) or error vector magnitude (EVM) measurements for one or more test portions. The plurality of link quality metrics may correspond to a plurality of spatial streams in a MIMO transmission.

[0036] In some implementations, the apparatus may include at least one transceiver coupled to the at least one modem, and 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.

[0037] 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 methods described above.

[0038] Another innovative aspect of the subject matter described in this disclosure can be implemented as a system including means for implementing any of the above-described methods.

[0039] 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

[0040] Figure 1 A schematic diagram of an example wireless communication network supporting use of link adaptation test packets is shown.

[0041] Figure 2AA conceptual diagram of an example link adaptation test packet having a link quality estimation portion with one or more orthogonal frequency division multiplexing (OFDM) symbols used for link quality estimation is shown.

[0042] Figure 2B A conceptual diagram showing an example link adaptation test packet having more than one spatial stream for link quality estimation is shown.

[0043] Figure 3 A schematic diagram of multiple-input multiple-output (MIMO) communication is shown.

[0044] Figure 4 A schematic diagram of beamforming MIMO communication is shown.

[0045] Figure 5 An example link adaptation protocol using a link adaptation test packet is shown.

[0046] Figure 6 An example message flow diagram for a link adaptation protocol using a link adaptation test packet is shown.

[0047] Figure 7 An example mapping between average link quality metrics and example corresponding modulation and coding scheme (MCS) options is shown.

[0048] Fig. 8A A first example feedback message format is depicted.

[0049] Figure 8B A second example feedback message format is depicted.

[0050] Fig.9A A block diagram of an example transmitting WLAN device supporting link adaptation is depicted.

[0051] Fig. 9B A block diagram of an example receiving WLAN device supporting link adaptation is depicted.

[0052] Fig.10 An example link adaptation test packet using time division for a SINR estimation signal is depicted.

[0053] Fig.11A An example link adaptation test packet is depicted in which a set of link quality estimation tests are included in a pad section of a data carrying packet.

[0054] Fig. 11B An example link adaptation test packet is depicted in which a set of link quality estimation tests are included in a link quality estimation portion of a data carrying packet.

[0055] Fig.12A flow chart illustrating an example process for supporting link adaptation by a transmitting WLAN device is shown.

[0056] Fig.13 A flow chart illustrating an example process for supporting link adaptation by a receiving WLAN device is shown.

[0057] Fig.14 A block diagram of an example wireless communication device is shown.

[0058] Fig.15A A block diagram of an example access point (AP) is shown.

[0059] Fig. 15B A block diagram of an example station (STA) is shown.

[0060] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0061] 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 a manner that is capable of being implemented in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the IEEE 802.15 standard, the Bluetooth Special Interest Group (SIG), or the like. The described implementations may be implemented in any device, system, or network capable of transmitting and receiving radio frequency (RF) signals according to 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 according to 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.

[0062] A WLAN (sometimes called Wi-Fi) in a home, apartment, business, or other area TMA 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.

[0063] 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 acknowledgment or negative acknowledgment) or based on a packet error rate (PER) associated with the one or more first packets. Therefore, the traditional process of selecting the best 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.

[0064] Some conventional techniques for link adaptation 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 a transmission rate 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 (including 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. The wireless channel may not be used during the idle measurement period. Therefore, conventional techniques for rate adaptation based on an idle measurement period may result in delays and degrade the capacity of the wireless channel. In addition, conventional techniques for interference measurement may not support signal to interference plus noise ratio (SINR) estimation for MIMO transmission. MIMO refers to the use of multiple transmit antennas or multiple receive antennas or both to create multiple spatial streams between the transmitting WLAN device and the receiving WLAN device. Although MIMO can increase the capacity or reliability of transmission, interference from other signals may affect the various spatial streams in different ways. SNR measurements are generally not sufficient to estimate the SINR of the various spatial streams because they do not take into account the impact of interference on the various spatial streams.

[0065] 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 fast rate adaptation (FRA) 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. Various implementations generally involve determining a transmission rate for wireless communication from a transmitting WLAN device to a receiving WLAN device. The transmission rate can be defined by an MCS selected based on channel conditions and other parameters. WLAN can support different transmission rate options depending on channel conditions. According to the present disclosure, a transmitting WLAN device can send a first packet as part of a fast rate adaptation protocol. The first packet can also be referred to as a link adaptation test packet (or simply a "test packet"). The test packet may include a link quality estimation sequence, which can be used to determine the channel conditions at various frequencies of a wireless channel. For example, the link quality estimation sequence can be used to determine the signal quality and interference (such as SINR estimation) of a specific frequency tone or frequency tone set within a wireless channel. The test packet can be formatted as a MIMO transmission including one or more parts of various spatial streams for link quality estimation. The receiving WLAN device may observe a sequence of link quality estimates in various spatial streams to determine one or more link quality metrics. In some implementations, the link quality estimation sequence is constructed to implement measurements of link quality metrics such as log likelihood ratio (LLR), signal-to-noise ratio (SNR), signal-to-interference plus noise (SINR), error vector magnitude (EVM), bit error rate (BER) or block error rate (BLER), etc. Therefore, the test packet may be used to determine the quality of the wireless channel taking into account the amount of interference and other noise affecting the MIMO spatial stream. The receiving WLAN device may provide feedback information to the transmitting WLAN device based on the link quality metric. The transmitting WLAN device may use the feedback information to determine a transmission rate option to be used for subsequent packets to the second WLAN device. The transmission rate option may include an MCS option, a number of spatial streams, a spatial stream configuration, or any combination thereof. The technology in the present disclosure may use the test packet instead of a traditional link adaptation process that would otherwise need to converge on the best transmission rate option to implement the selection of the transmission rate option.

[0066] In some implementations, the link quality metric may be a SINR measurement. Based on a comparison of a received link quality estimate sequence with an expected link quality estimate sequence, the SINR measurement may be an indicator of the impact of interference on a wireless channel. In another example, the link quality metric may be based on an EVM measurement. EVM is a measure of how far a modulated constellation point is relative to the constellation plan. Interference (such as noise, distortion, and spurious signals) may degrade the EVM. Therefore, in some implementations, the EVM measurement may be a proxy indicator of link quality that takes into account interference affecting a particular tone or set of tones. The link quality metric may also be referred to as a quality metric or a transmission rate quality metric. Some examples in the present disclosure are based on SINR metrics for teaching purposes.

[0067] In some implementations, the test packet may be formatted to include a link quality estimation portion having one or more link quality estimation sequences. For example, the test packet may be a new packet format defined for the fast rate adaptation (FRA) protocol in a standard technical specification for WLAN (such as IEEE802.11be). In some implementations, the test packet may be based on a packet format for a null data packet (NDP). In some implementations, the test packet may be based on a packet format for a data carrying 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. The link quality estimation portion may be included in a padding segment at the beginning or end of a traditional packet format. For example, in some implementations, the link quality estimation portion may be included after the preamble and before other segments of the traditional packet format. Alternatively, the link quality estimation portion may be included in a padding segment after the data payload of the packet. In some implementations, the test packet may be communicated as an initial packet of a session so that the best transmission rate option may be selected for subsequent packets of the session. Other alternative formats for the test packet may be possible.

[0068] In some implementations, the link quality estimation portion may include a first portion for estimating signal and noise, 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 frequency tones) of the OFDM symbols. The null values ​​may provide an idle measurement period during the test 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 leave specific subcarriers blank. 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 can 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 the test packet.

[0069] In some implementations, a test packet may be used to estimate the link quality of various spatial streams for MIMO transmission from a transmitting WLAN device to a receiving WLAN device. For example, a link quality metric may indicate the effect of interference on a specific spatial stream in a MIMO transmission. Conventional techniques for estimating signals and noise may use conventional sounding packets, which do not use the same spatial stream as a subsequent MIMO transmission. Therefore, conventional sounding packets can only provide a rough estimate of signals and noise. In some implementations of the present disclosure, a test packet may include a test portion for estimating interference on multiple spatial streams to be used in subsequent MIMO transmissions. Therefore, in some implementations, a single test packet may be used to determine the link quality for various MIMO spatial streams so that the best transmission rate option may be selected for subsequent MIMO transmissions. In some implementations, a test packet may include a series of OFDM symbols with a link quality estimation sequence. In some implementations, the link quality estimation sequence may be adjusted in the series of OFDM symbols according to the MIMO spatial stream so that the receiving WLAN device can measure the effect of interference on MIMO transmissions in a wireless channel. The number of OFDM symbols used for link quality estimation may be based on the number of spatial streams in the MIMO transmission.

[0070] In some implementations, the test packet may include an indicator or field indicating that the test packet includes one or more portions for link quality estimation. For example, a flag or indicator in a header of the test packet may cause a receiving WLAN device to determine a link quality metric based on a link quality estimation sequence in the test packet. Alternatively or additionally, a previous packet immediately preceding the test packet may inform the receiving WLAN device that a test packet for link quality estimation will follow the previous packet.

[0071] In some implementations, the feedback may include one or more link quality metrics so that the transmitting WLAN device may select an optimal transmission rate option for subsequent transmissions. Alternatively or additionally, the feedback may include a transmission rate indicator indicating a transmission rate selected by the receiving WLAN device. For example, the receiving WLAN device may select an optimal transmission based on the one or more link quality metrics and include an indicator related to the selected transmission rate option in the feedback to the transmitting WLAN device.

[0072] 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 transmission rate adjustments to converge on the 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 the optimal MCS may preserve air time resources that would otherwise be available to other WLAN devices.

[0073] Figure 1 A 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 can 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 can be a network that implements at least one of the IEEE 802.11 family of wireless communication protocol standards (such as the 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 can provide access to other networks 160. For example, the AP 102 can be connected to a gateway device (not shown) that provides connectivity to the other networks 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.

[0074] 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.

[0075] 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 1 Additionally 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 access to external networks to various STAs 104 in the WLAN via corresponding communication links 106 .

[0076] 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.

[0077] 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).

[0078] 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 a self-organizing (ad hoc) network (or wireless self-organizing network). Self-organizing networks may alternatively be referred to as mesh networks or peer-to-peer (P2P) networks. In some cases, self-organizing networks may be implemented within larger wireless networks (such as WLAN 100). In such implementations, although STA 104 may be able to communicate with each other through AP 102 using communication link 106, STA 104 may also communicate directly with each other via direct wireless links. In addition, two STA 104 may communicate via a direct communication link, regardless of whether the two STA 104 are associated with the same AP 102 and served by the same AP 102. In such a self-organizing system, one or more STA 104 may assume the role played by AP 102 in the BSS. Such STA 104 may be referred to as a group master (GO) and may coordinate transmission within the self-organizing network. Examples of direct wireless links include Wi-Fi Direct connections, connections established by using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, and other P2P group connections.

[0079] 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.

[0080] Each frequency band may include multiple sub-bands or frequency channels. For example, PPDUs compliant 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. As such, 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.

[0081] 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 copied 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.

[0082] 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 communicating 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.

[0083] Figure 1 Also 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. The code rate may refer to how much data stream is actually used to transmit available data. 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. 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 with 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.

[0084] 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. For brevity, reference is made to FIG. Figure 1The described link adaptation test packet 172 is formatted for MIMO transmission and may include one or more parts of link quality estimation for spatial streams of MIMO transmission. Therefore, a single link adaptation test packet 172 can support link quality estimation for different spatial streams based on current channel conditions. One or more parts for link quality estimation may include a link quality estimation sequence (which may also be referred to as a link quality estimation signal). The link quality estimation sequence may implement measurement of signal quality relative to interference. For example, the link quality estimation signal may include a null value on a subcarrier to permit the second WLAN device 120 to measure potential interference 142 from an external transmitter 140. In some implementations, the link quality estimation signal may create all or part of an idle measurement period during one or more OFDM symbols. In some implementations, the link adaptation test packet may be modified to include an explicit instruction (e.g., a predefined instruction type value in a type field) to cause the link adaptation test packet processing unit 162 in the second WLAN device 120 to measure the SINR or EVM metric during the one or more OFDM symbols. Alternatively or additionally, the one or more OFDM symbols may include a predetermined link quality estimation sequence (such as a bit sequence or pattern). The link adaptation test packet 172 may include a link quality estimation portion including one or more OFDM symbols used for SINR estimation. In some implementations, the link adaptation test packet 172 may also carry data in portions other than the link quality estimation portion.

[0085] As described above, in some implementations, one or more OFDM symbols in the link quality estimation portion of the first packet may create an idle measurement period (also referred to as a silent period) during the first packet. The idle measurement period may be used by the second WLAN device 120 to measure interference or perform an idle circuit calibration procedure. Figure 1 In the example of , the first WLAN device 110 can detect the presence of interference 142 from the external transmitter 140. The average interference or noise floor can be defined as the median of all measured values ​​of radio energy in a set of subcarriers. However, in order to accurately determine the average interference or noise floor, the wireless channel should not have data communication signals during the measurement. When one or more OFDM symbols in the link quality estimation portion of the link adaptation test packet 172 include null values ​​in some or all subcarriers, those subcarriers can create an inactive idle measurement period for the second WLAN device 120 to detect the presence of interference or perform channel characteristic measurements. In addition, using the portion of the first packet that includes data signaling for MIMO transmission, the second WLAN device 120 can determine the signal strength (or SNR). The SINR metric can be based on the measured SNR and the measured interference. Therefore, the same link adaptation test packet 172 can be used to determine the SINR metric that can be used for link adaptation.

[0086] 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 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. Additionally or alternatively, the feedback information 174 may include an MCS indicator indicating an MCS option selected by the second WLAN device 120 based on the link adaptation test packet 172. After the selected MCS 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 an MCS option, the transmission rate option selected by the link adaptation unit 154 may be any parameter to adapt the transmission rate based on current channel conditions. The data transmission unit 156 in the first WLAN device 110 may modulate the 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 .

[0087] 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 link quality metrics for various link quality estimation sequences in the link adaptation test packet 172. For example, the link adaptation test packet processing unit 162 may separately process each link quality estimation sequence in each spatial stream to determine a link quality metric for each spatial stream.

[0088] 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.

[0089] 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 quality metric determined by the link adaptation test packet processing unit 162. Alternatively, the feedback unit 164 may prepare a feedback message including the 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.

[0090] Figure 2A A conceptual diagram of an example link adaptation test packet 210 having a link quality estimation portion having one or more OFDM symbols for link quality estimation is shown. The link adaptation test packet 210 is provided as an illustrative example of how OFDM symbols can support link quality estimation. The link adaptation test packet 210 may include one or more preamble OFDM symbols (such as preamble 211) followed by a link quality estimation portion 250. The link quality estimation portion 250 may include one or more OFDM symbols 212, 213, 214, 215, and 216 for link quality estimation (such as measurement of SINR or EVM). In some implementations, the link adaptation test packet 210 may include a physical layer header (not shown) between the preamble 211 and the link quality estimation portion 250.

[0091] In some implementations, the one or more OFDM symbols may include a predetermined sequence (such as an LTF). For example, the LTF may be repeated in the first and second OFDM symbols 212 and 213. In some implementations, one or more of the OFDM symbols may have a null value. For example, an OFDM symbol (such as the third OFDM symbol 214) may cause all or some subcarriers in the OFDM symbol to be nulled to create idle subcarriers during a predictable time associated with the OFDM symbol. In some implementations, if all subcarriers are nulled, the receiving WLAN device may lose synchronization. Therefore, in some implementations, one OFDM symbol 214 may cause a first subset of subcarriers to be nulled, and another OFDM symbol 215 may cause a different subset of subcarriers to be nulled. The receiving WLAN device may measure the signal strength for the subcarriers having a signal and the interference for the nulled subcarriers. Over the course of several OFDM symbols, the receiving WLAN device may determine the link quality (such as SINR or EMV) for all subcarriers (or groups of subcarriers) in the coherence bandwidth of the wireless channel.

[0092] Figure 2BA conceptual diagram of an example link adaptation test packet 220 having more than one spatial stream for link quality estimation is shown. For example, the link adaptation test packet 220 may be formatted for MIMO transmission from a first transmitter (TX1) and a second transmitter (TX2) of a first WLAN device. In MIMO, some or all portions of the link adaptation test packet 220 may be different based on spatial stream encoding. In some implementations, the waveforms transmitted by both TX1 and TX2 are based at least in part on the same packet stream data or different packet stream data. The receiving WLAN device may determine a link quality metric (such as SINR or EVM) based on the link quality estimation sequence for each spatial stream. The link quality metric may enable MCS selection for MIMO transmission with multiple spatial streams. Figure 2A Similar to the example in , the link adaptation test packet 220 may include a preamble followed by a link quality estimation portion 250 including one or more OFDM symbols used for link quality estimation.

[0093] The fast link adaptation techniques in the present disclosure may be applied to open-loop or beamformed transmissions. In some implementations, the fast link adaptation techniques may also be applied to beamformed communications. In some implementations, the same packet stream data may be beamformed to obtain two or more waveforms obtained by applying a set of beamforming coefficients to the packet stream data. Thus, the waveforms may be the same or may not be the same, although they may carry the same information. In one example, the same waveform may be transmitted from two transmitters. In another example, different waveforms (processed from the same packet data stream) are generated and sent via the two transmitters. If the link adaptation test packet 220 is beamformed, the link quality metric (and the resulting selected MCS) will be applied to subsequent packets that are beamformed using the same beamforming configuration.

[0094] 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.

[0095] 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 Tx If 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 .

[0096] 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 TxIn 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.

[0097] 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.

[0098] 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 4The 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.

[0099] 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 N channel sounding procedures corresponding to all transmit antenna and receive antenna pairs based on the sounding signals. Tx xN Rx 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.

[0100] In some implementations, the channel sounding procedure for beamforming can be extended or modified to support link quality estimation. For example, a sounding signal (such as an NDP) can be modified to include or add a link quality estimation portion so that one or more OFDM symbols are added to the NDP for link quality 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 estimation accurately measures the SINR 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.

[0101] Figure 5 An example link adaptation protocol using a link adaptation test packet is depicted. The example link adaptation protocol 500 may begin with a first packet 510 from a first WLAN device 110 to a second WLAN device 120. The first packet 510 may include an indicator indicating that the first packet includes one or more portions 570 for link quality estimation. For example, in some implementations, the first packet 510 may include a link adaptation test capability or enablement indicator indicating that the first packet 510 is formatted for the link adaptation protocol 500. Alternatively or additionally, an announcement packet (not shown) may precede the first packet 510. In some implementations, a test header in the first packet 510 may indicate a configuration of the one or more portions 570 for link quality estimation. For example, the test header may indicate a predetermined sequence of OFDM symbols, a null pattern or number, etc. The one or more portions 570 for link quality estimation may include a link quality estimation sequence that enables the second WLAN device 120 to determine a link quality metric that takes into account interference to various tones or sets of tones.

[0102] Upon receiving the first packet 510, the second WLAN device 120 may determine one or more link quality metrics (such as SINR or EVM) based on the first packet 510. For example, the link quality metrics may include different SINR metrics for each tone or different sets of tones in an OFDM transmission. In some implementations, the second WLAN device 120 may select a transmission rate option (such as MCS) for subsequent MIMO transmissions based on the link quality metrics. 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 a 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. Alternatively or additionally, the second WLAN device 120 may provide the link quality metrics to the first WLAN device 110 so that the first WLAN device 110 can select a transmission rate option therefrom.

[0103] In response to the first packet 510, the second WLAN device 120 may send a feedback message 530 back to the first WLAN device 110. The feedback message 530 may start after a short interframe space (SIFS) 520, which represents a determinable time period for maintaining synchronization in the WLAN. The feedback message 530 may indicate a link quality metric for the first packet 510 or may indicate a selected transmission rate option based on the link quality metric. Based on the feedback information in the feedback message 530, the first WLAN device 110 may determine a selected transmission rate option for all or part of a second packet 540 to be transmitted from the first WLAN device 110 to the second WLAN device 120.

[0104] 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.

[0105] 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 quality estimation portion. The second WLAN device 120 may process (shown at block 624) the first packet 622 to determine a link quality metric for 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.

[0106] Figure 7 An example mapping between an average 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 channel quality, which would benefit from using a more robust MCS option. A higher average SINR metric may indicate a high channel 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 channel 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).

[0107] Figure 7701 in shows an example MCS option. Graph 701 shows fourteen MCS options (numbered MCS0 to MCS13), 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 graph 701, data throughput may increase as the number of MCS options increases. For example, MCS13 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 SINRs. Therefore, the SINR metric can be used to determine which MCS option results in the best data throughput based on current radio conditions.

[0108] 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, MCS1 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, MCS0 may be selected. If the SINR metric is in a range from 9.5 dB to 12 dB, MCS1 may be selected. If the SINR metric is in a range from 12 dB to 14 dB, MCS2 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 7 The 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.

[0109] 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 quality estimation portion of the link adaptation test packet.

[0110] 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. The link quality metrics 862 may indicate a link quality metric (such as SINR or EVM) for each spatial stream, for each subcarrier, for each subcarrier group, or for a portion of a link adaptation test packet. The selected MCS option indicator 864 may indicate a 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 an SINR 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.

[0111] Fig.9AA 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 transmitting side supporting transmission of user data as well as a link quality estimation signal. 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.

[0112] 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.

[0113] 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.

[0114] The example transmitting WLAN device 900 may include a link adaptation test signal generator 905 configured to send a link quality estimation signal for transmission by the transmitting device. The link quality estimation 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 quality estimation 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 quality estimation signal directly to a TX chain (such as a TX chain 950).

[0115] 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.

[0116] 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.

[0117] 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. 9B In 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] Fig.10An example link adaptation test packet 1000 using time division for a test portion 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 quality estimation 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, the L-LTF 1006, and the 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 quality estimation test set 1012. The link quality estimation test set 1012 may include a test header 1020 for indicating which (or which) link quality estimation signals 1040 are used to prepare the test portions 1021, 1022, and 1023. The link quality estimation signal 1040 may be a known pattern or sequence (e.g., based on an LTF sequence, a pattern with empty subcarriers, or a new link quality test pattern, etc.). The test portions 1021, 1022, and 1023 may be based on the same link quality estimation signal 1040. In some implementations, the link quality estimation 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 quality estimation test set 1012 section of the link adaptation test packet 1000. For example, the link quality estimation signal 1040 may be a test sequence with bit rotation, tone rotation, or other changes so that each test portion may provide some tones of a signal with signal strength measurements and some tones with null values ​​for interference measurements. 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.

[0122] 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 quality estimation 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 quality estimation signals) for supporting fast link adaptation for subsequent packets. The link adaptation test packet 1000 may include more LTF symbols (as link quality estimation 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 based on the number of spatial streams to be included in the subsequent packet. 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 link quality estimation of the channel. In some implementations, the L-SIG 1008 may include an indicator for indicating the number of LTFs (or other link quality estimation signals) included in the link adaptation test packet 1000.

[0123] Fig.11A An example link adaptation test packet 1100 is depicted in which a link quality estimation 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.10 The link quality estimation test packet 1012 is described. For example, all or part of the padding section 1112 may be referred to as the link quality estimation portion of the link adaptation test packet 1000. Fig.11A1010, but in some implementations, the link quality estimation test set 1012 may be included before the data payload 1110. The data payload 1110 may be a separate portion from the link quality estimation test set in the test packet.

[0124] Fig. 11B An example link adaptation test packet 1101 is depicted in which a link quality estimation test set 1012 is included in a link quality estimation portion 1105 of a data carrying packet. The link quality estimation 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 quality estimation 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.

[0125] Fig.12 A flow chart illustrating an example process 1200 of supporting link adaptation by a transmitting WLAN device is shown. In some implementations, the process 1200 may be performed by a first WLAN device, such as the AP 102 described above. In some implementations, the process 1200 starts at block 1210.

[0126] At block 1210, a first WLAN device may transmit a first packet to a second WLAN device via a wireless channel. The first packet may be formatted as a MIMO transmission including one or more test portions for link quality estimation.

[0127] At block 1220 , the first WLAN device may receive feedback information from the second WLAN device based on the link quality estimate of the one or more test portions of the first packet.

[0128] At block 1230, the first WLAN device may determine a selected transmission rate option for transmitting subsequent packets to the second WLAN device via the wireless channel based at least in part on the feedback information.

[0129] Fig.13A flow chart illustrating an example process 1300 of supporting link adaptation by a receiving WLAN device is shown. In some implementations, the process 1300 may be performed by a second WLAN device, such as the second WLAN device 120 described above. In some implementations, the process 1300 begins at block 1310. At block 1310, the second WLAN device may receive a first packet from a first WLAN device via a wireless channel, the first packet formatted as a MIMO transmission including one or more test portions for link quality estimation.

[0130] At block 1320, the second WLAN device may transmit feedback information to the first WLAN device based on the link quality estimate of the one or more test portions in the first packet, which feedback information may be used by the first WLAN device to determine a selected transmission rate option for transmitting subsequent packets for transmission from the first WLAN device via the wireless channel.

[0131] Fig.14 A block diagram of an example wireless communication device 1400 is shown. In some implementations, the wireless communication device 1400 may be a wireless communication device for a STA (such as the one described above with reference to FIG. Figure 1 In some implementations, the wireless communication device 1400 may be an example of a device in an AP (such as one of the STAs 104 or 144 described above). Figure 1 102). The wireless communication device 1400 may 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 1400 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 may 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 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).

[0132] The wireless communication device 1400 may be or may include a chip, system on chip (SoC), chipset, package, or device including one or more modems 1402 (e.g., Wi-Fi (IEEE 802.11 compliant) modems). In some implementations, one or more modems 1402 (collectively, “modems 1402”) additionally include a WWAN modem (e.g., a 3GPP 4G LTE or 5G compatible modem). In some implementations, the wireless communication device 1400 also includes one or more radios 1404 (collectively, “radios 1404”). In some implementations, the wireless communication device 1400 further includes one or more processors, processing blocks, or processing elements 1406 (collectively, “processors 1406”) and one or more memory blocks or elements 1408 (collectively, “memory 1408”).

[0133] The modem 1402 may include an intelligent hardware block or device (for example, such as an application specific integrated circuit (ASIC)). The modem 1402 is generally configured to implement the PHY layer. For example, the modem 1402 is configured to modulate packets and output the modulated packets to the radio 1404 for transmission on the wireless medium. Similarly, the modem 1402 is configured to obtain the modulated packets received by the radio 1404 and demodulate the packets to provide demodulated packets. In addition to the modulator and demodulator, the modem 1402 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 1406 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 may 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 1404. 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.

[0134] When in receive mode, a digital signal received from the radio 1404 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 1406) for processing, evaluation, or interpretation.

[0135] The radio 1404 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 1400 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 1402 are provided to the radio 1404, which then transmits the codewords via the coupled antenna. Similarly, the codewords received via the antenna are obtained by the radio 1404, which then provides the codewords to the modem 1402.

[0136] The processor 1406 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 1406 processes information received through the radio 1404 and the modem 1402, and processes information to be output by the modem 1402 and the radio 1404 for transmission over a wireless medium. For example, the processor 1406 may 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 1406 may generally control the modem 1402 to cause the modem to perform the various operations described above.

[0137] The memory 1408 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 1408 may also store non-transient processor or computer executable software (SW) code containing instructions that, when executed by the processor 1406, cause the processor to perform various operations for wireless communication described herein, 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.

[0138] Fig.15A 1 shows a block diagram of an example AP 1502. For example, AP 1502 may be a reference Figure 1 An example implementation of the AP 102 is described. The AP 1502 includes a wireless communication device (WCD) 1510 (although the AP 1502 itself may also be generally referred to as a wireless communication device as used herein). For example, the wireless communication device 1510 may be a wireless communication device as described herein. Fig.14An example implementation of the wireless communication device 1400 described. The AP 1502 also includes a plurality of antennas 1520 coupled to the wireless communication device 1510 to transmit and receive wireless communications. In some implementations, the AP 1502 additionally includes an application processor 1530 coupled to the wireless communication device 1510, and a memory 1540 coupled to the application processor 1530. The AP 1502 further includes at least one external network interface 1550, which enables the AP 1502 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 1550 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 1502 further includes a housing that encloses the wireless communication device 1510, the application processor 1530, the memory 1540, and encloses at least a portion of the antenna 1520 and the external network interface 1550.

[0139] Fig. 15B 1 shows a block diagram of an example STA 1504. For example, STA 1504 may be a reference Figure 1 104. STA 1504 includes a wireless communication device 1515 (although STA 1504 itself may also be generally referred to as a wireless communication device as used herein). For example, wireless communication device 1515 may be a wireless communication device. Fig.14 An example implementation of the wireless communication device 1400 described. The STA 1504 also includes one or more antennas 1525 coupled to the wireless communication device 1515 to transmit and receive wireless communications. The STA 1504 additionally includes an application processor 1535 coupled to the wireless communication device 1515, and a memory 1545 coupled to the application processor 1535. In some implementations, the STA 1504 further includes a user interface (UI) 1555 (such as a touch screen or keyboard) and a display 1565, which can be integrated with the UI 1555 to form a touch screen display. In some implementations, the STA 1504 can further include one or more sensors 1575 (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 1504 further includes a housing that encloses the wireless communication device 1515 , the application processor 1535 , the memory 1545 , and encloses at least portions of the antenna 1525 , the UI 1555 , and the display 1565 .

[0140] Figure 1-15BThe 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.

[0141] 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.

[0142] Innovative aspects 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 outputting a first packet for transmission from the first WLAN device to a second WLAN device via a wireless channel, the first packet being formatted as a multiple-input multiple-output (MIMO) transmission including one or more portions for signal-to-interference-plus-noise (SINR) estimation. The method may include receiving feedback information from the second WLAN device based on the SINR estimation of the first packet, the feedback information being usable by the first WLAN device to determine a selected modulation and coding scheme (MCS) to modulate subsequent packets to the second WLAN device via the wireless channel.

[0143] In some implementations, the first packet includes a first portion for signal and noise estimation and a second portion for interference estimation.

[0144] In some implementations, the second portion includes one or more orthogonal frequency division multiplexing (OFDM) symbols used for interference estimation.

[0145] In some implementations, the one or more OFDM symbols of the second portion include at least one null symbol that provides an idle measurement period during the first packet.

[0146] In some implementations, the one or more OFDM symbols of the second portion include at least a first OFDM symbol having a null value on a first subset of tones in a first OFDM symbol.

[0147] In some implementations, the second portion includes at least a second OFDM symbol having null values ​​on a second subset of tones in the second OFDM symbol, the second subset of tones being different from a first subset of tones in the first OFDM symbol.

[0148] In some implementations, the first subset of tones includes every other tone and the second subset of tones includes another tone that is every other tone.

[0149] In some implementations, the one or more OFDM symbols of the second portion include a first OFDM symbol having a first predetermined sequence and at least a second OFDM symbol having a second predetermined sequence.

[0150] In some implementations, the one or more OFDM symbols of the second portion include a first OFDM symbol having a predetermined sequence and at least a second OFDM symbol having the same predetermined sequence.

[0151] In some implementations, the one or more OFDM symbols of the second portion include a plurality of OFDM symbols having a same predetermined sequence.The number of the plurality of OFDM symbols may be based on the number of spatial streams in the MIMO transmission.

[0152] In some implementations, the first packet is a link adaptation test packet defined in a technical standard specification.

[0153] In some implementations, the first packet is formatted according to a multi-user (MU) MIMO packet format.

[0154] In some implementations, the first packet has a format based on a Null Data Packet (NDP) defined for a WLAN.

[0155] In some implementations, the first packet includes at least one indicator requesting feedback information.

[0156] In some implementations, the first packet includes upper layer data for the second WLAN.One or more portions for SINR estimation can be included in the first packet with the upper layer data.

[0157] In some implementations, the one or more portions used for SINR estimation are appended as padding sections after the upper layer data in the first packet.

[0158] In some implementations, the first packet includes an indicator that causes the second WLAN device to determine one or more SINR metrics based on one or more portions of the first packet used for SINR estimation.

[0159] In some implementations, the feedback information includes a field indicating a selected MCS selected by the second WLAN device based on the SINR estimate.

[0160] In some implementations, the feedback information includes one or more SINR metrics associated with one or more portions used for SINR estimation.The method may include determining, by the first WLAN device, the selected MCS based on the one or more SINR metrics.

[0161] In some implementations, receiving the feedback information includes receiving an acknowledgement (ACK) message in response to the first packet. The ACK message may include a field populated with the feedback information.

[0162] In some implementations, the first packet is a request to send (RTS) packet.

[0163] In some implementations, receiving the feedback information includes receiving a clear to send (CTS) message in response to the first packet. The CTS message may include a field populated with the feedback information.

[0164] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a method performed by a second WLAN device. The method may include receiving a first packet from a first WLAN device via a wireless channel, the first packet being formatted for a multiple-input multiple-output (MIMO) transmission including one or more portions for signal to interference plus noise (SINR) estimation. The method may include outputting feedback information in response to the first packet for transmission to the first WLAN device, the feedback information being usable by the first WLAN device to determine a selected modulation and coding scheme (MCS) to modulate a subsequent packet for transmission from the first WLAN device via the wireless channel.

[0165] In some implementations, the method may include determining one or more SINR metrics based on the one or more portions used for SINR estimation.

[0166] In some implementations, the method may include determining feedback information based on the one or more SINR metrics.The feedback information may include a plurality of SINR metrics corresponding to a plurality of spatial streams in a MIMO transmission.

[0167] In some implementations, the method may include determining a selected MCS based on the one or more SINR metrics.The feedback information may include a field indicating the selected MCS.

[0168] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a system. The system may include a first WLAN device configured to transmit a first packet from the first WLAN device to a second WLAN device via a wireless channel, the first packet being formatted as a multiple input multiple output (MIMO) transmission including at least a first portion for signal and noise estimation and a second portion for interference estimation. The second WLAN device may be configured to receive the first packet. The second WLAN device may be configured to determine one or more signal and interference plus noise (SINR) metrics for MIMO transmission based on the first packet. The second WLAN device may be configured to determine a selected MCS for the first WLAN device to modulate a subsequent packet to the second WLAN device via the wireless channel, the selected MCS being based on the one or more SINR metrics. The second WLAN device may be configured to transmit a feedback message to the first WLAN device, the feedback message including a field filled with the selected MCS. The first WLAN device may be configured to receive the feedback message and transmit subsequent packets using the selected MCS.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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 in a wireless local area network (WLAN), comprising: transmitting a first packet from a first WLAN device to a second WLAN device via a wireless channel, the first packet being formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation, wherein the one or more test portions are included in a padding section following a data payload of the first packet; as well as receiving feedback information from the second WLAN device based on the link quality estimate of the one or more test portions of the first packet; as well as Subsequent packets are transmitted to the second WLAN device via the wireless channel using a transmission rate option based at least in part on the feedback information.

2. The method of claim 1, wherein the one or more test portions for link quality estimation include a link quality estimation sequence for measuring a link quality metric for each of a plurality of spatial streams in the MIMO transmission.

3. The method of claim 1, wherein the feedback information comprises a plurality of link quality metrics based on signal to interference plus noise ratio (SINR) or error vector magnitude (EVM) measurements for the one or more test portions.

4. The method of claim 1, wherein the first packet comprises a first portion for signal and noise estimation and a second portion for interference estimation.

5. The method of claim 4, wherein the second portion comprises one or more Orthogonal Frequency Division Multiplexing (OFDM) symbols used for the link quality estimation.

6. The method of claim 5, wherein the one or more OFDM symbols of the second portion include at least one null symbol that provides an idle measurement period during the first packet.

7. The method of claim 5, wherein the one or more OFDM symbols of the second portion include at least a first OFDM symbol having a null value at a first frequency tone subset in the first OFDM symbol.

8. The method of claim 7, wherein the second portion comprises at least a second OFDM symbol having a null value at a second subset of frequency tones in the second OFDM symbol, the second subset of frequency tones being different from the first subset of frequency tones in the first OFDM symbol.

9. The method of claim 8, the first subset of frequency tones comprising every other frequency tone and the second subset of frequency tones comprising another frequency tone of every other frequency tone.

10. The method of claim 5, wherein the one or more OFDM symbols of the second portion include a first OFDM symbol having a first predetermined sequence and at least a second OFDM symbol having the same first predetermined sequence or a second predetermined sequence.

11. The method of claim 5, wherein the one or more OFDM symbols of the second portion comprises a plurality of OFDM symbols having a same predetermined sequence, wherein a number of the plurality of OFDM symbols is based on a number of spatial streams in the MIMO transmission.

12. The method of claim 1, wherein the first packet includes instructions to cause the second WLAN device to perform link quality estimation of the one or more test portions and to provide the feedback information based on the link quality estimation.

13. The method of claim 12, wherein the indication is included in a preamble of the first packet.

14. The method of claim 1, wherein the first packet further comprises upper layer data for the second WLAN device in addition to the one or more test portions for the link quality estimation.

15. The method of claim 14, wherein the one or more test portions used for the link quality estimation are included in a separate portion of the first packet from the one or more test portions.

16. The method of claim 1, wherein the feedback information includes a field indicating the transmission rate option.

17. The method of claim 1, wherein the feedback information comprises one or more link quality metrics associated with the one or more test portions used for the link quality estimation.

18. A method for wireless communication in a wireless local area network (WLAN), comprising: receiving a first packet from a first WLAN device via a wireless channel, the first packet formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation, wherein the one or more test portions are included in a padding section following a data payload of the first packet; as well as Feedback information is transmitted to the first WLAN device based on the link quality estimate of the one or more test portions in the first packet, the feedback information being usable by the first WLAN device to determine a transmission rate option for transmission of subsequent packets from the first WLAN device via the wireless channel.

19. The method of claim 18, wherein the one or more test portions for link quality estimation include a link quality estimation sequence for measuring a link quality metric for each of a plurality of spatial streams in the MIMO transmission.

20. The method of claim 18, wherein the feedback information comprises a plurality of link quality metrics based on signal to interference plus noise ratio (SINR) or error vector magnitude (EVM) measurements for the one or more test portions.

21. The method of claim 20, wherein the plurality of link quality metrics correspond to a plurality of spatial streams in the MIMO transmission.

22. The method of claim 18, further comprising: The transmission rate option for a plurality of spatial streams in the MIMO transmission is determined based on a link quality estimate, wherein the feedback information includes a field indicating the transmission rate option.

23. An apparatus of a first wireless local area network (WLAN) device, comprising: at least one processor; as well as at least one modem, the at least one modem coupled to the at least one processor, the at least one modem and the at least one processor configured to: outputting a first packet for transmission from the first WLAN device to a second WLAN device via a wireless channel, wherein the first packet is formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation, wherein the one or more test portions are included in a padding section following a data payload of the first packet, and obtaining feedback information from the second WLAN device based on a link quality estimate of the one or more test portions of the first packet; as well as Subsequent packets are output for transmission from the first WLAN device to the second WLAN device via the wireless channel using a transmission rate option based at least in part on the feedback information.

24. The apparatus of claim 23, wherein the one or more test portions for link quality estimation include a link quality estimation sequence for measuring a link quality metric for each of a plurality of spatial streams in the MIMO transmission.

25. The apparatus of claim 23, wherein the feedback information comprises a plurality of link quality metrics based on signal to interference plus noise ratio (SINR) or error vector magnitude (EVM) measurements for the one or more test portions.

26. The device of claim 23, wherein the first packet includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols for link quality estimation, wherein the plurality of OFDM symbols have the same predetermined sequence, and The number of the plurality of OFDM symbols is based on the number of spatial streams in the MIMO transmission.

27. 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, the at least one transceiver configured to receive the feedback information via the plurality of antennas and to transmit the first packet and the subsequent packets via the plurality of antennas; 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.

28. The apparatus of claim 23, wherein the first packet comprises a first portion for signal and noise estimation and a second portion for interference estimation.

29. The apparatus of claim 28, wherein the second portion comprises one or more Orthogonal Frequency Division Multiplexing (OFDM) symbols used for the link quality estimation.

30. The apparatus of claim 29, wherein the one or more OFDM symbols of the second portion include at least one null symbol that provides an idle measurement period during the first packet.

31. The apparatus of claim 29, wherein the one or more OFDM symbols of the second portion include at least a first OFDM symbol having a null value at a first tone subset in the first OFDM symbol.

32. An apparatus as claimed in claim 31, wherein the second part includes at least a second OFDM codeword, and the second OFDM codeword has a null value on a second frequency tone subset in the second OFDM codeword, and the second frequency tone subset is different from the first frequency tone subset in the first OFDM codeword.

33. The apparatus of claim 32, wherein the first subset of frequency tones includes every other frequency tone and the second subset of frequency tones includes another frequency tone that is every other frequency tone.

34. The apparatus of claim 29, wherein the one or more OFDM symbols of the second portion include a first OFDM symbol having a first predetermined sequence and at least a second OFDM symbol having the same first predetermined sequence or a second predetermined sequence.

35. The apparatus of claim 29, wherein the one or more OFDM symbols of the second portion comprises a plurality of OFDM symbols having a same predetermined sequence, wherein a number of the plurality of OFDM symbols is based on a number of spatial streams in the MIMO transmission.

36. The apparatus of claim 23, wherein the first packet includes instructions to cause the second WLAN device to perform link quality estimation of the one or more test portions and to provide the feedback information based on the link quality estimation.

37. The apparatus of claim 36, wherein the indication is included in a preamble of the first packet.

38. The apparatus of claim 23, wherein the first packet further comprises upper layer data for the second WLAN device in addition to the one or more test portions for the link quality estimation.

39. The apparatus of claim 38, wherein the one or more test portions used for the link quality estimation are included in a separate portion of the first packet that is different from the one or more test portions.

40. The apparatus of claim 23, wherein the feedback information includes a field indicating the transmission rate option.

41. The apparatus of claim 23, wherein the feedback information comprises one or more link quality metrics associated with the one or more test portions used for the link quality estimation.

42. An apparatus for a second wireless local area network (WLAN) device, comprising: at least one processor; as well as at least one modem, the at least one modem coupled to the at least one processor, the at least one modem and the at least one processor configured to: obtaining a first packet from a first WLAN device via a wireless channel, the first packet being formatted as a multiple-input multiple-output (MIMO) transmission including one or more test portions for link quality estimation, wherein the one or more test portions are included in a padding section following a data payload of the first packet; as well as Feedback information is output for transmission to the first WLAN device, the feedback information being based on the link quality estimate of the one or more test portions in the first packet and being usable by the first WLAN device to determine a transmission rate option for transmission of subsequent packets from the first WLAN device via the wireless channel.

43. An apparatus as described in claim 42, wherein the feedback information includes multiple link quality metrics based on signal to interference plus noise ratio (SINR) or error vector magnitude (EVM) measurements for the one or more test portions, and wherein the multiple link quality metrics correspond to multiple spatial streams in the MIMO transmission.

44. The apparatus of claim 42, further comprising: at least one transceiver coupled to the at least one modem; a plurality of antennas coupled to the at least one transceiver, the at least one transceiver configured to receive the first packet via the plurality of antennas and to transmit the feedback information via the plurality of antennas; 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.

45. The apparatus of claim 42, wherein the one or more test portions for link quality estimation include a link quality estimation sequence for measuring a link quality metric for each of a plurality of spatial streams in the MIMO transmission.

46. ​​The apparatus of claim 42, wherein the at least one processor is further configured to: The transmission rate option for a plurality of spatial streams in the MIMO transmission is determined based on a link quality estimate, wherein the feedback information includes a field indicating the transmission rate option.

Images