Communication device and communication method for channel sounding

Abstract

The present disclosure provides a communication device, comprising: a circuit that generates a first frame for a discovery procedure; and a transmitter that transmits the first frame to each of one or more peer communication devices, the first frame including a first field indicating an intended use of the discovery procedure.

Description

Technical Field

[0001] The present disclosure relates to communication devices and methods for channel sounding, and more particularly, to communication devices and methods for channel sounding in an EHT WLAN (Extremely High Throughput Wireless Local Area Network). Background Art

[0002] In the standardization of the next-generation wireless local area network (WLAN), new radio access technologies that must be backward compatible with IEEE 802.11a / b / g / n / ac / ax technologies have been discussed in the IEEE 802.11 working group, and this technology is named IEEE 802.11be Extremely High Throughput (EHT) WLAN.

[0003] In 802.11be EHT WLAN, in order to provide significantly increased peak throughput and capacity over 802.11ax High-Efficiency (HE) WLAN (especially for cell-edge STAs), enabling multi-AP coordination in a multi-access point (multi-AP) system has been proposed.

[0004] However, there has not been much discussion about communication devices and methods for channel sounding (especially about efficient procedures for multi-AP-based sounding).

[0005] Therefore, there is a need for communication devices and methods that provide viable technical solutions for channel sounding in the context of EHT WLAN. Additionally, other desired features and characteristics will become apparent from the subsequent detailed description and the appended claims in conjunction with the accompanying drawings and the background of the present disclosure. Summary of the Invention

[0006] Non-limiting and exemplary embodiments contribute to providing a communication device and a communication method for channel sounding in the context of EHT WLAN.

[0007] In a first aspect, the present disclosure provides a communication device, comprising: a circuit that generates a first frame for a sounding procedure; and a transmitter that transmits the first frame to each of one or more peer communication devices, the first frame including a first field indicating an intended use of the sounding procedure.

[0008] In a second aspect, the present disclosure provides a peer communication device, comprising: a receiver that receives a first frame for a sounding procedure from the communication device; and a circuit that processes the first frame, the first frame including a first field indicating an intended use of the sounding procedure.

[0009] In a third aspect, the present disclosure provides a communication method, which includes: generating a first frame for a sounding procedure; and transmitting the first frame to each of one or more peer communication devices, the first frame including a first field indicating an intended use of the sounding procedure.

[0010] It should be noted that the general or specific embodiments can be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

[0011] Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and the drawings. The benefits and / or advantages can be obtained individually through the various embodiments and features of the specification and the drawings, and it is not necessary to provide all these embodiments and features in order to obtain one or more such benefits and / or advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] By way of example only, through the following written description and in conjunction with the drawings, the embodiments of the present disclosure will be better understood and apparent to those skilled in the art, wherein:

[0013] Figure 1A A schematic diagram depicting uplink and downlink single-user (SU) MIMO communications between an access point (AP) and a station (STA) in a multiple-input multiple-output (MIMO) wireless network.

[0014] Figure 1B A schematic diagram depicting downlink multi-user (MU) communications between an AP and multiple STAs in a MIMO wireless network.

[0015] Figure 1C A schematic diagram depicting trigger-based uplink MU communications between an AP and multiple STAs in a MIMO wireless network.

[0016] Figure 1D A schematic diagram depicting trigger-based downlink multi-AP communications between multiple APs and STAs in a MIMO wireless network.

[0017] Figure 2A A schematic diagram depicting a single-AP-based sounding procedure between two STAs in an 11ax HE WLAN.

[0018] Figure 2B A schematic diagram depicting a single-AP-based sounding procedure between an AP and multiple STAs in an 11ax HE WLAN.

[0019] Figure 3A A schematic example of a communication device according to various embodiments is shown. According to the present disclosure, the communication device can be implemented as an AP or an STA and is used for channel sounding.

[0020] Figure 3B Shows a flowchart illustrating a communication method according to the present disclosure.

[0021] Figure 4 Depicts a flowchart illustrating a probe establishment procedure according to an embodiment.

[0022] Figure 5A Depicts an example format of an EHT action frame.

[0023] Figure 5B Depicts an example format of a probe establishment element field of an EHT action frame.

[0024] Figure 5C Depicts another example format of a probe establishment element field of an EHT action frame.

[0025] Figure 6A Depicts a flowchart illustrating a single-AP-based explicit probe procedure between two STAs in an 11be EHT WLAN according to an embodiment.

[0026] Figure 6B Depicts a flowchart illustrating a single-AP-based explicit probe procedure between an AP and multiple STAs in an 11be EHT WLAN according to another embodiment.

[0027] Figure 7A Depicts a flowchart illustrating a single-AP-based implicit sequential probe procedure according to an embodiment.

[0028] Figure 7B Depicts a flowchart illustrating a single-AP-based implicit sequential probe procedure according to another embodiment.

[0029] Figure 8 Depicts a flowchart illustrating a single-AP-based implicit joint probe procedure according to an embodiment.

[0030] Figure 9 Depicts a flowchart illustrating a multi-AP-based explicit sequential probe procedure according to an embodiment.

[0031] Figure 10 Depicts a flowchart illustrating a multi-AP-based explicit joint probe procedure according to an embodiment.

[0032] Figure 11A Depicts a flowchart illustrating a multi-AP-based implicit sequential probe procedure according to an embodiment.

[0033] Figure 11B Depicts a flowchart illustrating a multi-AP-based implicit sequential probe procedure according to another embodiment.

[0034] Figure 12 Depicts a flowchart illustrating a multi - AP - based implicit joint detection procedure according to an embodiment.

[0035] Figure 13A Depicts a flowchart illustrating a multi - AP - based hybrid sequential detection procedure according to an embodiment.

[0036] Figure 13B Depicts a flowchart illustrating a multi - AP - based hybrid sequential detection procedure according to another embodiment.

[0037] Figure 14A Depicts a flowchart illustrating a multi - AP - based hybrid joint detection procedure according to an embodiment.

[0038] Figure 14B Depicts a flowchart illustrating a multi - AP - based hybrid joint detection procedure according to another embodiment.

[0039] Figure 15 Depicts an example format of an EHT Null Data Packet (NDP) announcement frame.

[0040] Figure 16A Depicts an example format of the STA feedback information field when the probe type field refers to single - AP - based explicit probing.

[0041] Figure 16B Depicts an example format of the STA probe information field when the probe type field refers to single - AP - based implicit probing.

[0042] Figure 16C Depicts an example format of the AP - STA explicit probe information field when the probe type field refers to multi - AP - based explicit probing.

[0043] Figure 17 Illustrates the configuration of a communication device (e.g., an AP) according to the present disclosure.

[0044] Figure 18 Illustrates the configuration of a communication device (e.g., an STA) according to the present disclosure.

[0045] Those skilled in the art will understand that the elements in the drawings are illustrated for clarity and simplicity and are not necessarily drawn to scale. For example, the dimensions of some elements in the illustrations, block diagrams, or flowcharts may be exaggerated relative to other elements to aid in the accurate understanding of the present embodiment. Detailed Description

[0046] By way of example only, some embodiments of the present disclosure will be described with reference to the accompanying drawings. Like reference numerals and characters in the drawings refer to like elements or equivalents.

[0047] In the following paragraphs, certain exemplary embodiments are explained with reference to an access point (AP) and a station (STA) for uplink or downlink channel sounding, particularly in a multiple-input multiple-output (MIMO) wireless network.

[0048] In the context of IEEE 802.11 (Wi-Fi) technology, a station (which may be interchangeably referred to as an STA) is a communication device capable of using the 802.11 protocol. Based on the IEEE 802.11-2016 definition, an STA can be any device that includes a media access control (MAC) compliant with IEEE 802.11 and a physical layer (PHY) interfacing to the wireless medium (WM).

[0049] For example, an STA can be a laptop computer, a desktop personal computer (PC), a personal digital assistant (PDA), an access point, or a Wi-Fi phone in a wireless local area network (WLAN) environment. An STA can be fixed or mobile. In a WLAN environment, the terms "STA", "wireless client", "user", "user equipment", and "node" are often used interchangeably.

[0050] Similarly, an AP (which may be interchangeably referred to as a wireless access point (WAP) in the context of IEEE 802.11 (Wi-Fi) technology) is a communication device that allows STAs in a WLAN to connect to a wired network. An AP is typically connected to a router (via a wired network) as a stand-alone device, but it can also be integrated with or used within a router.

[0051] As described above, an STA in a WLAN can act as an AP on different occasions, and vice versa. This is because, in the context of IEEE802.11 (Wi-Fi) technology, a communication device can include both STA hardware components and AP hardware components. In this way, the communication device can switch between STA mode and AP mode based on actual WLAN conditions and / or requirements.

[0052] In a MIMO wireless network, "multiple" refers to multiple antennas that are simultaneously used for transmission on a radio channel and multiple antennas that are simultaneously used for reception. In this regard, "multiple-input" refers to multiple transmitter antennas that input radio signals into the channel, and "multiple-output" refers to multiple receiver antennas that receive radio signals from the channel and input them into the receiver. For example, in an N×M MIMO network system, N is the number of transmitter antennas, M is the number of receiver antennas, and N can be equal to or not equal to M. For the sake of simplicity, the respective numbers of transmitter antennas and receiver antennas are not further discussed in this disclosure.

[0053] In a MIMO wireless network, single-user (SU) communication and multi-user (MU) communication can be deployed for communication between communication devices such as an AP and an STA. The MIMO wireless network has benefits such as spatial multiplexing and spatial diversity, which achieve higher data rates and robustness by using multiple spatial streams. According to various embodiments, the term "spatial stream" can be used interchangeably with the term "space-time stream" (or STS).

[0054] Figure 1A FIG. depicts a schematic diagram of SU communication 100 between an AP 102 and an STA 104 in a MIMO wireless network. As shown, the MIMO wireless network can include one or more STAs (e.g., STA 104, STA 106, etc.). If the SU communication 100 in the channel is carried out over the entire channel bandwidth, it is called full-bandwidth SU communication. If the SU communication 100 in the channel is carried out over a part of the channel bandwidth (e.g., one or more 20 MHz sub-channels within the channel are punctured), it is called punctured SU communication. In SU communication 100, the AP 102 uses multiple antennas (e.g., four antennas as shown) to transmit multiple space-time streams, where all the space-time streams are directed to a single communication device, i.e., STA 104. For simplicity, the multiple space-time streams directed to STA 104 are illustrated as grouped data transmission arrows 108 directed to STA 104. Figure 1A The SU communication 100 can be two-way. As shown, in the SU communication 100, the STA 104 can use multiple antennas (e.g., two antennas as shown) to transmit multiple space-time streams, where all the space-time streams are directed to the AP 102. For simplicity, the multiple space-time streams directed to the AP 102 are illustrated as grouped data transmission arrows 110 directed to the AP 102.

[0055] SU communication 100 can be two-way. As Figure 1A shown, in the SU communication 100, the STA 104 can use multiple antennas (e.g., two antennas as shown) to transmit multiple space-time streams, where all the space-time streams are directed to the AP 102. For simplicity, the multiple space-time streams directed to the AP 102 are illustrated as grouped data transmission arrows 110 directed to the AP 102. Figure 1A shown, in the SU communication 100, the STA 104 can use multiple antennas (e.g., two antennas as shown) to transmit multiple space-time streams, where all the space-time streams are directed to the AP 102. For simplicity, the multiple space-time streams directed to the AP 102 are illustrated as grouped data transmission arrows 110 directed to the AP 102.

[0056] Thus, Figure 1A the SU communication 100 depicted in FIG. achieves both uplink and downlink SU transmissions in the MIMO wireless network.

[0057] Figure 1BFIG. depicts a schematic diagram of downlink MU communication 112 between an AP 114 and multiple STAs 116, 118, 120 in a MIMO wireless network. The MIMO wireless network may include one or more STAs (e.g., STA 116, STA 118, STA 120, etc.). The MU communication 112 may be OFDMA (Orthogonal Frequency Division Multiple Access) communication or MU-MIMO communication. For OFDMA communication in a channel, the AP 114 simultaneously transmits multiple streams to the STAs 116, 118, 120 in different resource units (RUs) within the channel bandwidth. For MU-MIMO communication in a channel, the AP 114 uses multiple antennas to simultaneously transmit multiple streams to the STAs 116, 118, 120 at the same (one or more) RUs within the channel bandwidth via spatial mapping or precoding techniques. If the (one or more) RUs where OFDMA or MU-MIMO communication occurs occupy the entire channel bandwidth, then the OFDMA or MU-MIMO communication is referred to as full-bandwidth OFDMA or MU-MIMO communication. If the (one or more) RUs where OFDMA or MU-MIMO communication occurs occupy a part of the channel bandwidth (e.g., one or more 20 MHz sub-channels within the channel are punctured), then the OFDMA or MU-MIMO communication is referred to as punctured OFDMA or MU-MIMO communication. For example, two space-time streams may be directed to STA 118, another space-time stream may be directed to STA 116, and yet another space-time stream may be directed to STA 120. For the sake of simplicity, the two space-time streams directed to STA 118 are illustrated as grouped data transmission arrows 124, the space-time stream directed to STA 116 is illustrated as a data transmission arrow 122, and the space-time stream directed to STA 120 is illustrated as a data transmission arrow 126.

[0058] To enable uplink MU transmission, trigger-based communication is provided to the MIMO wireless network. In this regard, Figure 1C FIG. depicts a schematic diagram of trigger-based uplink MU communication 128 between an AP 130 and multiple STAs 132, 134, 136 in a MIMO wireless network.

[0059] Since there are multiple STAs 132, 134, 136 participating in the trigger-based uplink MU communication, the AP 130 needs to coordinate the simultaneous transmissions of the multiple STAs 132, 134, 136.

[0060] To do so, as Figure 1CAs shown, AP 130 simultaneously sends trigger frames 139, 141, 143 to STAs 132, 134, 136 to indicate user - specific resource allocation information (e.g., the number of space - time streams, the starting STS number, and the allocated RUs) that each STA can use. In response to the trigger frames, STAs 132, 134, 136 can then simultaneously send their respective space - time streams to AP 130 according to the user - specific resource allocation information indicated in trigger frames 139, 141, 143. For example, two space - time streams can point from STA 134 to AP 130, another space - time stream can point from STA 132 to AP 130, and yet another space - time stream can point from STA 136 to AP 130. For the sake of simplicity, the two space - time streams pointing from STA 134 to AP 130 are illustrated as grouped data - sending arrows 140, the space - time stream pointing from STA 132 to AP 130 is illustrated as data - sending arrow 138, and the space - time stream pointing from STA 136 to AP 130 is illustrated as data - sending arrow 142.

[0061] Trigger - based communication is also provided to a MIMO wireless network to enable downlink multi - AP communication. In this regard, Figure 1D FIG. depicts a schematic diagram of downlink multi - AP communication 144 between STA 150 and multiple APs 146, 148 in a MIMO wireless network.

[0062] Since multiple APs 146, 148 are involved in trigger - based downlink multi - AP MIMO communication, the primary AP 146 needs to coordinate the simultaneous transmissions of multiple APs 146, 148.

[0063] To do so, as Figure 1D shown, the primary AP 146 simultaneously sends trigger frames 147, 153 to AP 148 and STA 150 to indicate AP - specific resource allocation information (e.g., the number of space - time streams, the starting STS stream number, and the allocated RUs) that each AP can use. In response to the trigger frames, multiple APs 146, 148 can then send their respective space - time streams to STA 150 according to the AP - specific resource allocation information indicated in trigger frame 147; and STA 150 can then receive all the space - time streams according to the AP - specific resource allocation information indicated in trigger frame 153. For example, two space - time streams can point from AP146 to STA 150, and another two space - time streams can point from AP 148 to STA 150. For the sake of simplicity, the two space - time streams pointing from AP 146 to STA 150 are illustrated as grouped data - sending arrows 152, and the two space - time streams pointing from AP 148 to STA 150 are illustrated as grouped data - sending arrows 154.

[0064] Due to the packet / PPDU (Physical Layer Protocol Data Unit)-based transmission and distributed MAC (Media Access Control) scheme in 802.11 WLAN, there is no time scheduling (e.g., TDMA (Time Division Multiple Access)-like periodic time slot allocation for data transmission) in 802.11 WLAN. Frequency and spatial resource scheduling are performed on a packet basis. In other words, resource allocation information is PPDU-based.

[0065] According to various embodiments, the EHT WLAN supports non-trigger-based communication as illustrated in Figure 1A and Figure 1B and trigger-based communication as illustrated in Figure 1C and Figure 1D In non-trigger-based communication, a communication device sends a PPDU to one or more other communication devices in an unsolicited manner. In trigger-based communication, a communication device sends a PPDU to one or more other communication devices only after receiving a request trigger frame.

[0066] Figure 2A Depicts a single-AP-based probing procedure 200 between two STAs 202, 204 in an 11ax HE WLAN. When STA1 202 (e.g., an AP) generates a HE NDP (Null Data Packet) announcement frame 206 to an intended STA (e.g., STA2 204), the single-AP-based probing procedure 200 can be initiated. The HE NDP announcement frame 206 includes the requested probing feedback parameters for each STA, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns of the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, and CQI (Channel Quality Indicator) feedback. When the feedback type is SU feedback or MU feedback, the requested probing feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the requested probing feedback information includes the CQI information for each subcarrier or subcarrier group. In an IEEE 802.11 network, the Short Inter-Frame Space (SIFS) is the time interval before a STA sends an acknowledgment. When sending the HE NDP announcement frame 206, the SIFS 207 can take effect, and at 208, STA1 202 can send a HE probing NDP 210 to STA2 204. The HE probing NDP 210 can include a HE Long Training Field (HE-LTF) for CSI (Channel State Information) estimation.

[0067] After sending the last symbol of the HE sounding NDP 210, the SIFS 211 can become effective, and at 212, the STA2 204 can send a HE compressed beamforming / CQI frame 214 including sounding feedback information to the STA1 202. In one embodiment, the sounding feedback information can be derived by the STA2 204 from the CSI estimated from the HE-LTF field of the HE sounding NDP 210 and prepared according to the requested sounding feedback parameters indicated in the HE NDP announcement frame 206. Based on the sounding feedback information received from the STA2 204, the STA1 202 can determine the steering matrix and / or allocate appropriate resource units (RUs) for subsequent transmissions to the STA2 204.

[0068] Figure 2B Depicts a single-AP based sounding procedure 220 between an AP 222 and multiple STAs 224, 226 in an 11ax HE WLAN. The single-AP based sounding procedure 220 can be initiated when the AP 222 generates an NDP announcement frame 228 to the intended STAs such as STA1 224 and STA2 226. The HE NDP announcement frame 228 includes the requested sounding feedback parameters for each STA, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns of the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, and CQI feedback. When the feedback type is SU feedback or MU feedback, the requested sounding feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the requested sounding feedback information includes the CQI information for each subcarrier or subcarrier group. When the HE NDP announcement frame 228 is sent, the SIFS 229 can become effective, and at 230, the AP 222 can send a HE sounding NDP 232 to the STA1 224 and the STA2 226.

[0069] After sending the HE sounding NDP 232, the SIFS 233 can become effective, and at 234, the AP 222 can send a beamforming report poll (BFRP) trigger frame 236 to request simultaneous transmission of sounding feedback information from the STA1 224 and the STA2 226.

[0070] After sending the last symbol of the BFRP trigger frame 236, the SIFS 237 can take effect, and at 238, STA1 224 and STA2 226 can simultaneously send respective HE compressed beamforming / CQI frames 240, 242 including their respective probe feedback information to the AP 222. In one embodiment, the probe feedback information can be derived by STA1 224 and STA2 226 from their respective CSIs, which are estimated based on the HE-LTF fields of the HE probe NDP 232 and are prepared according to the respective probe feedback parameters indicated in the HE NDP announcement frame 228. Based on the probe feedback information received from STA1 224 and STA2 226, the AP 222 can determine the steering matrix and / or allocate an appropriate RU for each of STA1 224 and STA2 226 for subsequent transmissions to STA1 224 and / or STA2 226.

[0071] Note that in an 11ax HE WLAN, the AP and the (one or more) STAs participating in the single-AP-based probe procedure belong to a single BSS (basic service set). Thus, to improve the throughput of an 11be EHT WLAN relative to an 11ax WLAN, an object of the present disclosure is to substantially overcome existing challenges to provide communication apparatuses and methods for channel probing that achieve multi-AP coordination in a multi-AP system.

[0072] According to the present disclosure, a multi-AP coordination establishment procedure is performed among APs for forming a multi-AP coordination candidate set. The multi-AP coordination candidate set includes a shared AP and one or more shared APs. In multi-AP coordination establishment, an AP set identifier (ID) is assigned to the multi-AP coordination candidate set, where each AP in the multi-AP coordination candidate set can be assigned an AP ID, which is used together with the AP set ID to uniquely identify a specific AP in the multi-AP coordination candidate set. In one embodiment, in multi-AP coordination establishment, a capability negotiation can be performed among the APs in the multi-AP coordination candidate set. Alternatively, the capability negotiation among the APs in the multi-AP coordination candidate set can be performed before the multi-AP coordination establishment procedure, for example, using a backhaul. In one embodiment, in multi-AP coordination establishment, an expected STA can indicate a preferred AP in the multi-AP coordination candidate set for multi-AP coordination operation.

[0073] After the multi-AP coordination establishment procedure is completed, each AP in the multi-AP coordination candidate set can indicate multi-AP coordination-related information, such as multi-AP coordination candidate set information, AP capabilities including AP probing capabilities and multi-AP coordination capabilities, etc., in a beacon frame or the like.

[0074] In various embodiments, before initiating a probing procedure for multi-AP operation, a shared AP in a multi-AP coordination candidate set may initiate a probing establishment procedure with each of the shared (one or more) APs in the multi-AP coordination candidate set to make necessary preparations for the probing procedure.

[0075] Figure 3A FIG. shows a schematic partial cross-sectional view of a communication device 300 according to the present disclosure. The communication device 300 may also be implemented as an AP or an STA.

[0076] As Figure 3A shown, the communication device 300 may include a circuit 314, at least one radio transmitter 302, at least one radio receiver 304, and at least one antenna 312 (for the sake of simplicity and for illustrative purposes, only one antenna is depicted in Figure 3A ). The circuit 314 may include at least one controller 306 for operating, with software and hardware assistance, tasks that the at least one controller 306 is designed to perform, including controlling communication with one or more other communication devices in an MIMO wireless network. The circuit 314 may also include at least one transmit signal generator 308 and at least one receive signal processor 310. The at least one controller 306 may control the at least one transmit signal generator 308 to generate MAC frames (e.g., EHT action frames) and PPDUs (e.g., if the communication device 300 is an AP, a PPDU for non-trigger-based communication or a PPDU for trigger-based multi-AP joint transmission, and e.g., if the communication device 300 is an STA, a PPDU for non-trigger-based communication or a PPDU for trigger-based uplink transmission) to be transmitted to one or more other communication devices via the at least one radio transmitter 302; and the at least one receive signal processor 310, under the control of the at least one controller 306, is configured to process MAC frames (e.g., EHT action frames) and PPDUs received from one or more other communication devices via the at least one radio receiver 304 (e.g., if the communication device 300 is an AP, a PPDU for non-trigger-based communication or a PPDU for trigger-based uplink transmission, and e.g., if the communication device 300 is an STA, a PPDU for non-trigger-based communication or a PPDU for trigger-based multi-AP joint transmission). As Figure 3AAs shown, the at least one transmit signal generator 308 and the at least one receive signal processor 310 can be separate modules of the communication device 300, which communicate with the at least one controller 306 to implement the above functions. Alternatively, the at least one transmit signal generator 308 and the at least one receive signal processor 310 can be included in the at least one controller 306. For those skilled in the art, it is obvious that the arrangement of these functional modules is flexible and can vary according to actual needs and / or requirements. Data processing, storage, and other related control devices can be provided on appropriate circuit boards and / or chip sets. In various embodiments, the at least one radio transmitter 302, the at least one radio receiver 304, and the at least one antenna 312 can be controlled by the at least one controller 306.

[0077] The communication device 300 provides the functions required for single-AP or multi-AP based channel sounding. For example, the communication device 300 can be an AP (such as a shared AP), and the circuit 314 (such as at least one transmit signal generator 308 of the circuit 314) can generate a first frame (such as a probe setup request frame), which includes a first field indicating the intended use of the sounding procedure. The radio transmitter 302 can send the first frame to each of one or more peer communication devices (such as the shared AP). In one embodiment, the radio receiver 304 can receive a second frame (such as a probe setup response frame) from each of one or more peer communication devices, which includes a first field indicating one or more recommended types of the sounding procedure. In another embodiment, the circuit 314 (such as at least one transmit signal generator 308 of the circuit 314) can also generate a third frame (such as an EHT NDP announcement frame) to initiate the sounding procedure.

[0078] The communication device 300 can be a peer AP (such as a shared AP), and the radio receiver 304 can receive a first frame (such as a probe setup request frame) from another communication device (such as a shared AP), which includes a first field indicating the intended use of the sounding procedure. The circuit 314 (such as at least one receive signal processor 310 of the circuit 314) can process the first frame. In one embodiment, the radio transmitter 302 can send a second frame (such as a probe setup response frame) to another communication device, which includes a first field indicating one or more recommended types of the sounding procedure.

[0079] Figure 3BA flowchart illustrating a communication method according to the present disclosure is shown. In step 318, a step of generating a first frame for a probing procedure is performed. In step 320, a step of sending the first frame to each of one or more peer communication devices is performed, where the first frame includes a first field indicating the intended use of the probing procedure.

[0080] In one embodiment, the first frame may include a second field indicating the intended type of the probing procedure. In another embodiment, the first frame may include a third field indicating one or more intended communication devices (e.g., STAs) that will participate in the probing procedure.

[0081] Figure 4 A flowchart depicting a probing establishment procedure 400 between two APs according to the present disclosure, specifically between a shared AP 402 and a shared AP 404, is shown. A contention-based channel access procedure (e.g., an Enhanced Distributed Channel Access (EDCA) procedure) is illustrated by blocks 405, 413, and SIFSs 409, 417 are shown. The probing establishment procedure includes probing establishment request and response frames exchanged between each of the (one or more) shared APs in the multi-AP coordination candidate set and the shared AP. The probing establishment request or response frame is an EHT action frame. Specifically, the shared AP 402 may generate a first frame 408, e.g., an EHT action frame including a probing establishment request (hereinafter referred to as a "probing establishment request frame"), to initiate the probing establishment procedure 400. The radio transmitter of the shared AP 402 may send the probing establishment request frame 408 to the shared AP 404.

[0082] When the probing establishment request frame 408 is received, the SIFS 409 may take effect, and at 410, the shared AP 404 may send an acknowledgement (Ack) frame 412 to the shared AP 402 to indicate successful reception of the probing establishment request frame 408.

[0083] After the last symbol of the Ack frame 412 is sent, the shared AP 404 may generate a second frame 416, e.g., an EHT action frame including a probing establishment response (hereinafter referred to as a "probing establishment request frame"), to respond to the probing establishment request frame 408 and indicate whether the shared AP 404 is ready for a subsequent probing procedure.

[0084] When the probing establishment response frame 416 is received, the SIFS 417 may take effect, and at 418, the shared AP 402 may send an Ack frame 420 to the shared AP 404 to indicate successful reception of the probing establishment response frame 416.

[0085] Figure 5ADepicts an example format of an EHT action frame 500, which can be used as the probe setup request frame 408 or the probe setup response frame 416 as illustrated in Figure 4 The EHT action frame 500 can include (or consist of) a frame control field, a duration field, three address fields (Address 1, 2, and 3 respectively), a sequence control field, an HT (High Throughput) control field, a frame body field 502, and an FCS (Frame Check Sequence) field. The frame control field, the duration field, the three address fields (Address 1, 2, and 3 respectively), the sequence control field, and the HT control field can be grouped as the MAC header. The frame body field 502 can also include a category field, an EHT action field, a dialogue token field, a probe setup element field 504, and other elements or fields.

[0086] Figure 5B Depicts an example format of the probe setup element field 504 of the EHT action frame 500 when the action type field 506 refers to "Request" which indicates a probe setup request frame. The probe setup element field 504 can include (or consist of) an element ID field, a length field, an extended element ID field, an action type field 506, and an AP set ID field 508. When the action type field 506 refers to "Request", the probe setup element field 502 can also include an expected probe usage field 510, an expected probe type field 512, and an expected STA field 514. The AP set ID field 508 identifies a multi-AP coordination candidate set including a shared AP and at least one shared AP. The expected STA field 514 indicates one or more STAs that belong to the BSS of the shared AP and / or the BSS of at least one shared AP and should participate in the subsequent probe procedure. Note that in an 11be EHT WLAN, the (one or more) APs and (one or more) STAs participating in a single-AP or multi-AP based probe procedure can belong to different BSSs. In an 11be EHT WLAN, an STA can be identified by the BSSID (BSS Identifier) of the AP associated with the STA and its STAID. Alternatively, the AP ID of the AP associated with the STA, together with the AP set ID of the multi-AP coordination candidate set including the AP and the STA ID of the STA, can identify the STA. Further details of the expected probe usage field 510 and the expected probe type field 512 will be elaborated below.

[0087] Figure 5CDepicts another example format of the probe setup element field 504 of the EHT action frame 500 when the action type field 506 refers to "response" indicating a probe setup response frame. Similarly, the probe setup element field 504 may include (or consist of) an element ID field, a length field, an extended element ID field, an action type field 506, and an AP set ID field 508. When the action type field refers to "response", the probe setup element field 504 may further include a recommended probe type field 514 to indicate one or more recommended types of the probe procedure. Further details of the recommended probe type field 514 will be elaborated below.

[0088] The shared AP 402 may determine the expected probe parameters, such as the expected probe usage and the expected probe type, based on the capability negotiation among the APs in the multi-AP coordination candidate set performed before the probe setup procedure.

[0089] The expected probe usage field 510 indicates the expected usage of the probe procedure after the probe setup procedure (i.e., the expected scenario of multi-AP coordination using the results of the probe procedure). The expected scenario of multi-AP coordination is one of the following scenarios:

[0090] · Coordinated spatial reuse

[0091] · Coordinated orthogonal frequency division multiple access (OFDMA)

[0092] · Coordinated beamforming; and

[0093] · Joint beamforming (also known as joint transmission)

[0094] The expected probe type field 512 indicates the expected type of the probe procedure after the probe setup procedure, which is one of the following:

[0095] · Single-AP-based explicit probing;

[0096] · Single-AP-based implicit sequential probing;

[0097] · Single-AP-based implicit joint probing;

[0098] · Multi-AP-based explicit sequential probing;

[0099] · Multi-AP-based explicit joint probing;

[0100] · Multi-AP-based implicit sequential probing;

[0101] · Multi-AP-based implicit joint probing;

[0102] · Multi-AP-based hybrid sequential probing; and

[0103] · Multi-AP-based hybrid joint probing

[0104] In addition, in the probe setup response frame 416, the recommended probe type field 514 indicates one or more recommended types of probe procedures after the probe setup procedure, which are one of the following:

[0105] · Single-AP based explicit probing;

[0106] · Single-AP based implicit sequential probing;

[0107] · Single-AP based implicit joint probing;

[0108] · Multi-AP based explicit sequential probing;

[0109] · Multi-AP based explicit joint probing;

[0110] · Multi-AP based implicit sequential probing;

[0111] · Multi-AP based implicit joint probing; and

[0112] · Request for exemption from multi-AP based probing.

[0113] Note that when the shared AP 404 makes any recommendation on the probe type in the recommended probe type field 514, the shared AP 404 should consider the expected scenario of multi-AP coordination. For example, the results of multi-AP based sequential probing cannot be used for joint beamforming. For another example, the results of single-AP based probing can be used for coordinated spatial reuse and coordinated OFDMA, but cannot be used for coordinated beamforming and joint beamforming.

[0114] After receiving the probe setup request frame 408 from the shared AP 402, the shared AP 404 can determine whether its transmit and receive (TX / RX) chains need to be reconfigured for subsequent probe procedures based on the information about the expected STA(s) indicated in the probe setup request frame 408.

[0115] According to an embodiment of the present disclosure, when the shared AP 404 is not ready for the expected probe type indicated in the probe setup request frame 408, the shared AP 404 can recommend one or more different probe types or requests to exempt subsequent probe procedures in the probe setup response frame 416.

[0116] According to another embodiment of the present disclosure, when the shared AP 404 supports single-AP-based implicit probing or multi-AP-based implicit probing and its TX / RX chain is reconfigured for a subsequent probing procedure, the shared AP 404 may initiate a calibration procedure to recalibrate its TX / RX chain before it sends a probe setup response frame 416 to the shared AP 402. However, if the calibration procedure is not successfully completed, the shared AP 404 may not recommend any single-AP-based or multi-AP-based implicit probing procedures.

[0117] After the probe setup procedure is completed between each of the (one or more) shared APs in the multi-AP coordination candidate set and the shared AP, the probing procedure may be initiated. The probing procedure may start by sending an EHT NDP announcement frame, which indicates one of the following types of probing procedures:

[0118] · Single-AP-based explicit probing;

[0119] · Single-AP-based implicit sequential probing;

[0120] · Single-AP-based implicit joint probing;

[0121] · Multi-AP-based explicit sequential probing;

[0122] · Multi-AP-based explicit joint probing;

[0123] · Multi-AP-based implicit sequential probing;

[0124] · Multi-AP-based implicit joint probing;

[0125] · Multi-AP-based hybrid sequential probing; and

[0126] · Multi-AP-based hybrid joint probing.

[0127] The EHT NDP announcement frame that initiates the multi-AP-based probing procedure may be sent by the shared AP.

[0128] Figure 6AFIG. 0 depicts a flowchart of a single-AP based explicit probing procedure 600 between two STAs 602, 604 in an 11be EHT WLAN according to an embodiment. The single-AP based explicit probing procedure 600 may be initiated when STA1 602 (e.g., an AP) sends an EHT NDP announcement frame 606 to an intended STA (e.g., STA2 604). The EHT NDP announcement frame 606 includes the requested probing feedback parameters for each STA, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns of the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, CQI feedback, and calibration feedback. When the feedback type is SU feedback or MU feedback, the requested probing feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the requested probing feedback information includes the CQI information for each subcarrier or subcarrier group. When the feedback type is calibration feedback, the requested probing feedback information includes the compressed CSI for each subcarrier or subcarrier group. Upon receiving the EHT NDP announcement frame 606, SIFS 607 may become effective, and at 608, STA1 602 may send an EHT probe NDP 610 to STA2 604. The EHT probe NDP 610 may include an EHT-LTF field for CSI estimation.

[0129] After the last symbol of the EHT probe NDP 610 has been transmitted, SIFS 611 may become effective, and at 612, STA2 604 may send an EHT compressed beamforming / CQI frame 614 including the probing feedback information to STA1 602. In one embodiment, the probing feedback information may be derived by STA2 604 from the CSI estimated from the EHT-LTF field of the EHT probe NDP 610 and prepared according to its probing feedback parameters indicated in the EHT NDP announcement frame 606. Based on the probing feedback information received from STA2 604, STA1 602 is able to determine the steering matrix and / or allocate an appropriate RU for subsequent transmission to STA2 604.

[0130] Figure 6BDepicts a flowchart of a single-AP based explicit probing procedure 620 between an AP 622 and multiple STAs 624, 626 in an 11be EHT WLAN according to another embodiment. The single-AP based explicit probing procedure 620 can be initiated when the AP 622 sends an EHT NDP announcement frame 628 to the intended STAs such as STA1 624 and STA2 626. Similarly, the EHT NDP announcement frame 628 can include the requested probing feedback parameters for each STA, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns of the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, CQI feedback, and calibration feedback. When the feedback type is SU feedback or MU feedback, the requested probing feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the requested probing feedback information includes the CQI information for each subcarrier or subcarrier group. When the feedback type is calibration feedback, the requested probing feedback information includes the compressed CSI for each subcarrier or subcarrier group. After sending the EHT NDP announcement frame 628, SIFS 629 can take effect, and at 630, the AP 622 can send an EHT probe NDP 632 to STA1 624 and STA2 626.

[0131] After sending the EHT probe NDP 632, SIFS 633 can take effect, and at 634, the AP 622 can send an EHT BFRP trigger frame 636 to request simultaneous sending of probing feedback information from STA1 624 and STA2 626. After the last symbol of the EHT BFRP trigger frame 636 is sent, SIFS 637 can take effect, and at 638, STA1 624 and STA2 626 can simultaneously send their respective EHT compressed beamforming / CQI frames 640, 642 including the probing feedback information to the AP 622. In one embodiment, the probing feedback information can be derived by STA1 624 and STA2 626 from their respective CSIs, which are estimated based on the EHT-LTF field of the EHT probe NDP 632 and prepared according to the respective probing feedback parameters indicated in the EHT NDP announcement frame 628. Based on the probing feedback information received from STA1 624 and STA2 626, the AP 622 can determine the steering matrix and / or allocate appropriate RUs for each of STA1 624 and STA2 626 for subsequent transmissions to STA1 624 and / or STA2 626.

[0132] According to the present disclosure, when the sounding type indicated in the EHT NDP announcement frames 606, 628 is single-AP based explicit sounding and the feedback type indicated in the EHT NDP announcement frames 606, 628 is SU, MU, or CQI feedback, the procedures 600, 620 are normal single-AP based explicit sounding procedures; however, when the sounding type indicated in the EHT NDP announcement frames 606, 628 is single-AP based explicit sounding and the feedback type indicated in the EHT NDP announcement frames 606, 628 is calibration feedback, the procedures 600, 620 are single-AP based calibration procedures. In other words, the single-AP based calibration procedure is a variant of the single-AP based explicit sounding procedure as Figure 6A and 6B illustrated. Advantageously, according to the present disclosure, a single procedure 600, 620 can be used for both calibration and explicit sounding purposes.

[0133] In various embodiments, when the procedure 620 is a single-AP based calibration procedure, the EHT NDP announcement frame 628 can indicate the calibration RU allocation and calibration spatial stream (SS) allocation for each of STA1 624 and STA2 626. Specifically, the data RU allocation and data SS allocation for each of STA1 624 and STA2 626 are indicated in the corresponding EHT BFRP trigger frame 636. The calibration SS allocated to a STA can include the data SS allocated to the STA. In other words, the number of calibration SSs can be equal to or greater than the number of data SSs. Further, the calibration RU allocated to a STA can be the same as the data RU allocated to the STA.

[0134] In various embodiments, when the procedures 600, 620 are single-AP based calibration procedures, the EHT compressed beamforming / CQI frames 614, 640, 642 can contain DL compressed CSI information instead of DL compressed beamforming feedback information. Further, each STA, such as STA2 604, STA1 624, STA2 626, transmits multiple SSs on the EHT-LTF field of the EHT PPDU containing the EHT compressed beamforming / CQI frames 614, 640, 642, where the EHT-LTF field is used for data demodulation and UL CSI estimation for calibration. In this way, the APs 602, 622 are able to determine the calibration coefficients for each of their TX antennas based on the DL compressed CSI information and UL CSI estimation included in the EHT compressed beamforming / CQI frames 614, 640, 642.

[0135] Figure 7ADepicts a flowchart of a single-AP based implicit sequential sounding procedure 700 between an AP 702 and multiple STAs 704, 706 in an 11be EHT WLAN according to an embodiment (Option 1). The single-AP based implicit sequential sounding procedure 700 can be initiated when the AP 702 sends a first EHT NDP announcement frame 708 to expected STAs such as STA1 704 and STA2 706. The first EHT NDP announcement frame 708 can indicate STA ordering, where the expected STAs (e.g., STA1 704 to STA2 706) can send EHT sounding NDPs to the AP 702. The first EHT NDP announcement frame 708 can also indicate the sounding RU allocation and sounding SS allocation for the first STA for STA ordering. After receiving the EHT NDP announcement frame 708, other (one or more) STAs other than the first STA in the STA ordering (e.g., STA2 706) can switch from the wake state to the sleep state to save power. At 711 after SIFS 709, the first STA in the STA ordering (e.g., STA1 704) can prepare a first EHT sounding NDP 712 based on its sounding RU allocation and sounding SS allocation and send it to the AP 702. The AP 702 can then estimate a first UL CSI from the received first EHT sounding NDP 712 and determine the DL CSI corresponding to STA1 704 by compensating the first UL CSI according to the calibration parameters obtained through a calibration procedure.

[0136] After sending the last symbol of the first EHT sounding NDP 712 at 713, for power saving, STA1 704 can switch from the wake state to the sleep state. During the SIFS 714 at 715, the next STA in the STA sorting (e.g., STA2 706) can switch back from the sleep state to the wake state. After the SIFS 714 at 716, the AP 702 can send a second EHT NDP announcement frame 718, which can indicate the sounding RU allocation and sounding SS allocation for the next STA in the STA sorting. When the second EHT NDP announcement frame 718 is sent, the SIFS 719 can take effect, and at 720, STA2 706 can prepare the second EHT sounding NDP 722 based on its sounding RU allocation and sounding SS allocation, and send it to the AP 702. The AP 702 can then estimate the second UL CSI from the received second EHT sounding NDP 722, and determine the DL CSI corresponding to STA2 706 by compensating the second UL CSI according to the calibration parameters obtained through the calibration procedure. In addition, based on the DL CSI of STA1 704 and STA2 706, the AP 702 is able to determine the steering matrix and / or allocate appropriate RUs for each of STA1 704 and STA2 706 for subsequent transmissions to STA1 704 and / or STA2 706. Advantageously, the single-AP-based implicit sequential sounding procedure illustrated in Figure 7A can require less sounding overhead than, for example, Figure 6B the single-AP-based explicit sounding procedure illustrated in

[0137] Figure 7BDepicts a flowchart of a single-AP based implicit sequential sounding procedure 730 between an AP 732 and multiple STAs 734, 736 in an 11be EHT WLAN according to another embodiment (Option 2). Similarly, the single-AP based implicit sequential sounding procedure 730 can be initiated when the AP 732 sends an EHT NDP announcement frame 738 to intended STAs such as STA1 734 and STA2 736. The EHT NDP announcement frame 738 can indicate STA ordering, where the intended STAs (e.g., STA1 734 to STA2 736) can send EHT sounding NDPs to the AP 732. The EHT NDP announcement frame 738 can indicate the sounding RU assignment and the sounding SS assignment for each of the intended STAs. Thus, the duration of the EHT-LTF field of the EHT sounding NDP sent by each STA (equivalent to the transmission time of the EHT sounding NDP) can be determined from the sounding SS assignment of that STA. Based on the transmission time of the EHT sounding NDP of each STA, the first EHT sounding NDP from the first STA in the STA ordering can be followed by the second EHT sounding NDP from the second STA in the STA ordering.

[0138] For example, when the EHT NDP announcement frame 738 is sent, SIFS 739 can take effect. During the SIFS 739 at 740, other STAs (such as STA2 706) other than the first STA in the STA sorting can switch from the wake state to the sleep state to save power. And after the SIFS at 741, the first STA (such as STA1 734) in the STA sorting can send the first EHT sounding NDP 742 to the AP 732. The AP 732 can then estimate the first UL CSI based on the received first EHT sounding NDP 742, and determine the DL CSI corresponding to STA1 734 by compensating the first UL CSI according to the calibration parameters obtained through the calibration procedure. After the last symbol of the first EHT sounding NDP 742 is sent at 743, for power saving, STA1 734 can switch from the wake state to the sleep state. SIFS 744 can take effect. During the SIFS 744 at 745, STA2 736 can switch from the sleep state to the wake state, and after the SIFS at 746, STA2 736 can send the second EHT sounding NDP 748 to the AP 732. The AP 732 can then estimate the second UL CSI based on the received EHT sounding NDP 748, and determine the DL CSI corresponding to STA2 736 by compensating the second UL CSI according to the calibration parameters obtained through the calibration procedure. In addition, based on the DL CSIs of STA1 734 and STA2 736, the AP 732 can determine the pilot matrix and / or allocate appropriate RUs for each of STA1 734 and STA2 736 for subsequent transmissions to STA1 734 and / or STA2 736. Advantageously, as Figure 7B illustrated in Figure 7A the single-AP based implicit sequential sounding option 2 further reduces the sounding overhead compared to

[0139] Figure 8FIG. 0 depicts a flowchart of a single-AP based implicit joint sounding procedure 800 among an AP 802 and multiple STAs 804, 806 in an 11be EHT WLAN according to an embodiment. The single-AP based implicit joint sounding procedure 800 may be initiated when the AP 802 sends an EHT NDP announcement frame 808 to expected STAs such as STA1 804 and STA2 806. The EHT NDP announcement frame 808 may indicate the sounding RU allocation and sounding SS allocation for each of the expected STAs. Upon sending the EHT NDP announcement frame 808, SIFS 809 may take effect, and at 810, STA1 804 and STA2 806 may send their respective EHT sounding NDPs 812, 814 to the AP 808 according to their respective sounding RU allocations and sounding SS allocations. The AP 802 may then estimate a first UL CSI based on the received EHT sounding NDP 812, and estimate a second UL CSI based on the received EHT sounding NDP 814, and determine the DL CSIs corresponding to STA1 804 and STA2 806 respectively by compensating the first UL CSI and the second UL CSI according to the calibration parameters obtained through a calibration procedure. In addition, based on the DL CSIs of STA1 804 and STA2 806, the AP 802 is able to determine the steering matrix and / or allocate appropriate RUs for each of STA1 804 and STA2 806 for subsequent transmissions to STA1 804 and / or STA2 806. Advantageously, the single-AP based implicit joint sounding as illustrated in Figure 8 may provide less sounding overhead than the single-AP based implicit sequential sounding as illustrated in Figure 7A and Figure 7B .

[0140] Figure 9FIG. 0 depicts a flowchart of a multi-AP based explicit sequence sounding procedure 900 among multiple APs 902, 904 and multiple STAs 906, 908 in an 11be EHT WLAN according to an embodiment. The multi-AP based explicit sequence sounding procedure 900 may be initiated when a shared AP 902 transmits a first EHT NDP announcement frame 910 to the shared (one or more) APs participating in the sounding procedure 1000 and to expected STAs such as STA1 906 and STA2 908. The first EHT NDP announcement frame 910 may indicate the ranking of the shared AP, where the shared (one or more) APs participating in the sounding procedure 900 may transmit an EHT NDP announcement frame and an EHT sounding NDP to expected STAs such as STA1 906 and STA2 908. The first EHT NDP announcement frame 910 may indicate the sounding RU allocation and the sounding SS allocation for each of the shared (one or more) APs participating in the sounding procedure 900. Each EHT NDP announcement frame may indicate the sounding feedback parameters requested by each STA, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns of the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, CQI feedback, and calibration feedback. When the feedback type is SU feedback or MU feedback, the requested sounding feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the requested sounding feedback information includes the CQI information for each subcarrier or subcarrier group. When the feedback type is calibration feedback, the requested sounding feedback information includes the compressed CSI for each subcarrier or subcarrier group.

[0141] When the first EHT NDP announcement frame 910 is sent, SIFS 911 can take effect, and at 912, the shared AP 902 can send the first EHT sounding NDP 914 to STA1 906 and STA2 908. After the first EHT sounding NDP 914 is sent, SIFS 915 can take effect, and at 916, the shared AP 902 can send an EHT BFRP trigger frame 918 to request simultaneous transmission of sounding feedback information from STA1 906 and STA2 908. After the last symbol of the EHT BFRP trigger frame 918 is sent, SIFS 919 can take effect, and at 920, STA1 906 and STA2 908 can simultaneously send their respective first EHT compressed beamforming / CQI frames 922, 924 including the sounding feedback information to the shared AP 902. Based on the sounding feedback information received from STA1 906 and STA2 908, the shared AP 902 can determine the steering matrix and / or allocate appropriate RUs for each of STA1 906 and STA2 908 for subsequent transmission to STA1 906 and / or STA2 908.

[0142] When the first EHT compressed beamforming / CQI frames 922, 924 are sent, SIFS 925 can take effect, and at 926, the next AP in the AP ranking (e.g., the shared AP 904) can send a second EHT NDP announcement frame 928 to STA1 906 and STA2 908. When the second EHT NDP announcement frame 928 is sent, SIFS 929 can take effect, and at 930, the shared AP 904 can send a second EHT sounding NDP 932 to STA1 906 and STA2 908. Similarly, after the second EHT sounding NDP 932 is sent, SIFS 933 can take effect, and at 934, the shared AP 904 can send an EHT BFRP trigger frame 918 to request simultaneous transmission of sounding feedback information from STA1 906 and STA2 908. After the last symbol of the EHT BFRP trigger frame 936 is sent, SIFS 937 can take effect, and at 938, STA1 906 and STA2 908 can simultaneously send their respective second EHT compressed beamforming / CQI frames 940, 942 including the sounding feedback information to the shared AP 904. Based on the sounding feedback information received from STA1 906 and STA2 908, the shared AP 904 can determine the steering matrix and / or allocate appropriate RUs for each of STA1 906 and STA2 908 for subsequent transmission to STA1 906 and / or STA2 908.

[0143] According to the present disclosure, when the detection type indicated in the EHT NDP announcement frame 910, 1010 is explicit detection based on multiple APs, and the feedback type indicated in the EHT NDP announcement frame 910, 1010 is SU, MU or CQI feedback, the procedures 900, 1000 are normal explicit detection procedures based on multiple APs; however, when the detection type indicated in the EHT NDP announcement frame 910, 1010 is explicit detection based on multiple APs, and the feedback type indicated in the EHT NDP announcement frame 910, 1010 is calibration feedback, the procedures 900, 1000 are calibration procedures based on multiple APs. In other words, the calibration procedure based on multiple APs is as follows Figure 9 Neutralization Figure 10 Advantageously, in accordance with the present disclosure, a single procedure 900, 1000 may be used for both calibration and explicit sounding purposes.

[0144] In various embodiments, when the procedures 900 and 1000 are multi-AP-based calibration procedures, the EHT NDP announcement frames 910, 928, and 1010 may indicate the calibration RU allocation and calibration SS allocation of each STA (e.g., STA1 906, STA2 908, STA1 1006, and STA2 1008). Specifically, the data RU allocation and data SS allocation of each STA are indicated in the corresponding EHT BFRP trigger frames 918, 936, and 1020. The calibration SS allocated to the STA may include the data SS allocated to the STA. In other words, the number of calibration SSs may be equal to or greater than the number of data SSs. The calibration RU allocated to the STA may be the same as the data RU allocated to the STA.

[0145] In various embodiments, when the procedures 900, 1000 are multi-AP based calibration procedures, the EHT Compressed Beamforming / CQI frames 922, 924, 940, 942, 1024, 1026 may contain DL compressed CSI instead of DL compressed beamforming feedback information. In addition, each STA, such as STA1 906, STA2 908, STA1 1006, STA2 1008, transmits multiple SSs on the EHT-LTF field of the EHT PPDU containing the EHT Compressed Beamforming / CQI frames 922, 924, 940, 942, 1024, 1026, wherein the EHT-LTF field is used for UL CSI estimation for data demodulation and calibration. In this manner, the AP 902 , 904 , 1002 , 1004 can determine calibration coefficients for each of its TX antennas based on the DL compressed CSI and UL CSI estimates included in the EHT compressed beamforming / CQI frames 922 , 924 , 940 , 942 , 1024 , 1026 .

[0146] In various embodiments, there are two options for the STA to send EHT compressed beamforming / CQI frames in a multi-AP sequential calibration procedure: i) The STA can send the same SS on the EHT-LTF fields of multiple EHT PPDUs containing EHT compressed beamforming / CQI frames; or ii) The STA can send different SSs on the EHT-LTF fields of multiple EHT PPDUs containing EHT compressed beamforming / CQI frames, as a result of which it can advantageously reduce the EHT-LTF overhead. For example, assume that STA1 906 or STA2 908 has four TX antennas and sends two EHT compressed beamforming / CQI frames. Under Option 1, STA1 904 and STA2 908 can use the P 8x8 matrix to send four SSs on the eight EHT-LTF symbols of the EHT PPDUs containing EHT compressed beamforming / CQI frames 922, 924, 940, 942; while under Option 2, STA1 906 and STA2 908 can use the P 4x4 matrix to send two SSs on the four EHT-LTF symbols of the EHT PPDU containing the first EHT compressed beamforming / CQI frames 922, 924, and STA1 906 and STA2 908 can use the P 4x4 matrix to send two additional SSs on the four EHT-LTF symbols of the EHT PPDU containing the second EHT compressed beamforming / CQI frames 940, 942.

[0147] Figure 10Depicts a flowchart of a multi-AP based explicit joint sounding procedure 1000 among multiple APs 1002, 1004 and multiple STAs 1006, 1008 in an 11be EHT WLAN according to an embodiment. The multi-AP based explicit joint sounding procedure 1000 can be initiated when a shared AP 1002 sends an EHT NDP announcement frame 1010 to the shared (one or more) APs participating in the sounding procedure 1000 and to the intended STAs such as STA1 1006 and STA2 1008. The EHT NDP announcement frame 1010 can indicate the sounding RU allocation and the sounding SS allocation of each shared AP participating in the sounding procedure 1000. The EHT NDP announcement frame 1010 can indicate the requested sounding feedback parameters for each pair of STA and AP among the shared AP 1002, the shared APs 1004 and the intended STAs 1006, 1008. The requested sounding feedback parameters for each AP-STA pair can include AP-dependent sounding feedback parameters such as the feedback bandwidth and the number of columns of the compressed beamforming feedback matrix; and AP-independent sounding feedback parameters such as the feedback type, the subcarrier grouping and the quantization resolution, wherein, in terms of the sounding results for joint beamforming, for a STA, for all AP-STA pairs in the EHT NDP announcement frame 1010, each AP-independent sounding feedback parameter can be set to the same value; however, for each AP-STA pair in the EHT NDP announcement frame 1010, each AP-dependent sounding feedback parameter can be set to a different value.

[0148] When the EHT NDP announcement frame 1010 is sent, SIFS 1011 can take effect, and at 1012, all APs participating in the sounding procedure 1000 (such as the sharing AP 1002 and the shared AP 1004) can simultaneously send their respective EHT sounding NDPs 1014, 1016 to all expected STAs (such as STA1 1006 and STA2 1008). After the EHT sounding NDPs 1014, 1016 are sent, SIFS 1017 can take effect, and at 1018, the AP 1002 can send an EHT BFRP trigger frame 1020 to request the simultaneous transmission of sounding feedback information from STA1 1006 and STA2 1008. After the last symbol of the EHT BFRP trigger frame 1020 is sent, SIFS 1021 can take effect, and at 1022, STA1 1006 and STA2 1008 can simultaneously send their respective EHT compressed beamforming / CQI frames 1024, 1026 including the requested sounding feedback information to the APs 1002, 1004. Based on the sounding feedback information received from STA1 1006 and STA2 1008, the APs 1002, 1004 can determine the steering matrix and / or allocate appropriate RUs for each of STA1 1006 and STA2 1008 for subsequent transmissions to STA1 1006 and / or STA2 1008. Alternatively, the sharing AP 1002 can determine the steering matrix and / or allocate appropriate RUs for each AP-STA pair. The sharing AP 1002 can then notify the shared AP 1004 of the corresponding steering matrix and / or RU allocation for STA1 1006 and STA2 1008 for subsequent transmissions to STA1 1006 and / or STA2 1008. Advantageously, as Figure 10 explicit joint multi-AP sounding as illustrated in Figure 9 explicit sequential multi-AP sounding as illustrated in has less sounding overhead.

[0149] Figure 11ADepicts a flowchart of a multi-AP based implicit sequential sounding procedure 1100 among multiple APs 1102, 1104 and multiple STAs 1106, 1108 in an 11be EHT WLAN according to an embodiment (Option 1). The multi-AP based implicit sequential sounding procedure 1100 can be initiated when a shared AP 1102 sends a first EHT NDP announcement frame 1110 to the shared (one or more) APs participating in the sounding procedure 1100 and to expected STAs such as STA1 1106 and STA2 1108. The first EHT NDP announcement frame 1110 can indicate the shared (one or more) APs participating in the sounding procedure 1100, such as the shared AP 1104. The first EHT NDP announcement frame 1110 can also indicate STA ordering, where the expected STAs (e.g., STA1 1106 to STA2 1108) can send EHT sounding NDPs to the shared AP 1102 and all the shared APs participating in the sounding procedure 1100. Each EHT NDP announcement frame 1110, 1120 can indicate the sounding RU allocation and sounding SS allocation for the corresponding STA. When the first EHT NDP announcement frame 1110 is sent, SIFS 1111 can take effect. During SIFS 1111 at 1112, other (one or more) STAs other than the first STA in the STA ordering (e.g., STA2 1108) can switch from the wake state to the sleep state to save power, and after SIFS at 1113, the first STA in the STA ordering (e.g., STA1 1106) can send a first EHT sounding NDP 1114 to the shared AP 1102 and the shared AP 1104. The shared AP 1102 and the shared AP 1104 can then estimate the UL CSI based on the received first EHT sounding NDP 1114, and determine the DL CSI of STA1 1106 by compensating the UL CSI according to the calibration parameters obtained through a calibration procedure. In addition, based on the DL CSI of STA1 1106, the shared AP 1102 and the shared AP 1104 are able to determine the steering matrix and / or allocate an appropriate RU for subsequent transmission to STA1 1106.

[0150] After sending the last symbol of the first EHT sounding NDP 1114 at 1115, for power saving, the STA 11106 can switch from the wake state to the sleep state. The SIFS 1116 can take effect. During the SIFS 1116 at 1117, the next STA in the STA sorting (e.g., STA2 1108) can switch from the sleep state to the wake state, and after the SIFS 1116 at 1118, the AP 1102 can send the second EHT NDP announcement frame 1120. When the second EHT NDP announcement frame 1120 is sent, the SIFS 1121 can take effect, and at 1122, the STA2 1108 can send the second EHT sounding NDP 1124 to the shared AP 1102 and the shared AP 1104. The shared AP 1102 and the shared AP 1104 then estimate the UL CSI based on the received second EHT sounding NDP 1124 and determine the DL CSI of the STA2 1108 by compensating the UL CSI according to the calibration parameters obtained through the calibration procedure. In addition, based on the DL CSI of the STA2 1108, the shared AP 1102 and the shared AP 1104 can determine the pilot matrix and / or allocate an appropriate RU for subsequent transmission to the STA2 1108. Advantageously, as Figure 11A illustrated, the multi-AP based implicit sequential sounding procedure can, for example Figure 9 in or Figure 10 illustrated, the multi-AP based explicit sounding procedure requires less sounding overhead because it does not need to send sounding feedback information.

[0151] Figure 11BA flowchart depicting a multi-AP based implicit sequential sounding procedure 1130 among multiple APs 1132, 1134 and multiple STAs 1136, 1138 in an 11be EHT WLAN according to another embodiment (Option 2) is shown. Similarly, when AP 1132 sends an EHT NDP announcement frame 1140 to the shared (one or more) APs participating in the sounding procedure 1130 and expected STAs such as STA1 1136 and STA2 1138, the multi-AP based implicit sequential sounding procedure 1130 can be initiated. The EHT NDP announcement frame 1140 indicates the shared (one or more) APs participating in the sounding procedure 1130, such as the shared AP 1134. The EHT NDP announcement frame 1140 can indicate STA ordering, where the expected STAs (e.g., STA1 1136 to STA2 1138) can send EHT sounding NDPs to AP 1132 and the shared (one or more) APs participating in the sounding procedure 1130. The EHT NDP announcement frame 1140 can also indicate the sounding RU assignment and sounding SS assignment for each STA. Thus, the duration of the EHT-LTF field of the EHT sounding NDP sent by each STA (equivalent to the transmission time of the EHT sounding NDP) can be determined from the SS assignment of that STA. Based on the transmission time of the EHT sounding NDP of each STA, the first EHT sounding NDP from the first STA in the STA ordering can be followed by the second EHT sounding NDP from the second STA in the STA ordering.

[0152] For example, when sending the EHT NDP announcement frame 1140, SIFS 1141 can take effect. During the SIFS 1141 at 1142, other STAs (such as STA2 1138) other than the first STA in the STA sorting can switch from the wake state to the sleep state to save power, and after the SIFS at 1143, the first STA (such as STA1 1136) in the STA sorting can send the first EHT sounding NDP 1144 to the shared AP 1132 and the shared AP 1134. The shared AP 1132 and the shared AP 1134 can then estimate the UL CSI based on the received first EHT sounding NDP 1144, and determine the DL CSI of STA1 1136 by compensating the UL CSI according to the calibration parameters obtained through the calibration procedure. After the last symbol of the first EHT sounding NDP 1144 is sent at 1145, for power saving, STA1 1136 can switch from the wake state to the sleep state. SIFS 1148 can take effect. During the SIFS 1148 at 1147, STA2 1138 can switch back from the sleep state to the wake state, and after the SIFS at 1148, STA2 1138 can send the second EHT sounding NDP 1150 to the shared AP 1132 and the shared AP 1134. The shared AP 1132 and the shared AP 1134 can then estimate the UL CSI based on the received second EHT sounding NDP 1150, and determine the DL CSI of STA2 1138 by compensating the UL CSI according to the calibration parameters obtained through the calibration procedure. In addition, based on the DL CSI of STA1 1136 and STA2 1138, the shared AP1132 and the shared AP 1134 can determine the pilot matrix and / or allocate appropriate RUs for each of STA1 1136 and STA2 1138 for subsequent transmissions to STA1 1136 and / or STA2 1138. Advantageously, Figure 11B the multi-AP based implicit sequential sounding option 2 illustrated in Figure 11A reduces the sounding overhead further than the multi-AP based implicit sequential sounding option 1 illustrated in

[0153] Figure 12FIG. 0 depicts a flowchart of a multi-AP based implicit joint sounding procedure 1200 among multiple APs 1202, 1204 and multiple STAs 1206, 1208 in an 11be EHT WLAN according to an embodiment. The multi-AP based implicit joint sounding procedure 1200 may be initiated when a shared AP 1202 sends an EHT NDP announcement frame 1210 to the shared (one or more) APs (e.g., the shared AP 1204) and the intended STAs (e.g., STA1 1206 and STA2 1208) participating in the sounding procedure 1200. The EHT NDP announcement frame 1210 may indicate the shared (one or more) APs participating in the sounding procedure 1200, and may also indicate the sounding RU allocation and the sounding SS allocation for each STA. When the EHT NDP announcement frame 1210 is sent, SIFS 1211 may take effect, and at 1212, STA1 1206 and STA2 1208 may send their respective EHT sounding NDPs 1214, 1216 to the shared AP 1202 and the shared AP 1204. The shared AP 1202 and the shared AP 1204 may then estimate a first UL CSI based on the received EHT sounding NDP 1214, and determine the DL CSI of STA1 1206 by compensating the first UL CSI according to the calibration parameters obtained through a calibration procedure. Similarly, the shared AP 1202 and the shared AP 1204 may estimate a second UL CSI based on the received EHT sounding NDP 1216, and determine the DL CSI of STA2 1208 by compensating the second UL CSI according to the calibration parameters obtained through a calibration procedure. In addition, based on the DL CSIs of STA1 1206 and STA2 1208, the shared AP 1202 and the shared AP 1204 are able to determine a steering matrix and / or allocate appropriate RUs for each of STA1 1206 and STA2 1208 for subsequent transmissions to STA1 1206 and / or STA2 1208. Advantageously, as Figure 12 illustrated in Figure 11A and Figure 11B the multi-AP based implicit joint sounding illustrated in

[0154] requires less sounding overhead than the multi-AP based implicit sequential sounding illustrated in

[0155] Figure 13A Depicts a flowchart of a multi-AP based hybrid order sounding procedure 1300 among multiple APs 1302, 1304, 1306 and STA 1308 in an 11be EHT WLAN according to an embodiment. In this embodiment, the shared AP 1302 and the shared AP1 1304 are group 1 APs, while the shared AP2 1306 is a group 2 AP. The multi-AP based hybrid order sounding procedure 1300 can be initiated when the shared AP 1302 sends a first EHT NDP announcement frame 1310 to all the shared (one or more) APs (e.g., shared APs 1304, 1306) and the intended STA 1308 participating in the sounding procedure 1300. The first EHT NDP announcement frame 1310 can indicate the ordering of the group 2 AP and the group 1 APs, where each of the group 1 APs can send an EHT NDP announcement frame and an EHT sounding NDP to the intended STA. The first EHT NDP announcement frame 1310 can indicate the sounding RU allocation and sounding SS allocation for each of the group 1 APs. Each EHT NDP announcement frame can indicate the sounding RU allocation and sounding SS allocation for the intended STA 1308. Each EHT NDP announcement frame can indicate the requested sounding feedback parameters for the intended STA 1308, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns in the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, and CQI feedback. When the first EHT NDP announcement frame 1310 is sent, SIFS 1311 can take effect, and at 1312, the shared AP 1302 can send a first EHT sounding NDP 1314 to the STA 1308. After the last symbol of the first EHT sounding NDP 1314 is sent, SIFS 1315 can take effect, and at 1316, the STA 1308 sends a first EHT compressed beamforming / CQI frame 1318 including sounding feedback information to the shared AP 1302. Note that the EHT-LTF field of the EHT PPDU containing the first EHT compressed beamforming / CQI frame 1318 can also be used for CSI estimation for the implicit sounding of the group 2 AP (e.g., shared AP2 1306). Based on the sounding feedback information received from the STA 1308, the shared AP 1302 can determine the steering matrix and / or allocate an appropriate RU for the STA 1308 for subsequent transmissions to the STA 1308.

[0156] When the first EHT compressed beamforming / CQI frame 1318 is sent, SIFS 1319 can take effect, and at 1320, the next AP in the ranking of group 1 APs (e.g., the shared AP1 1304) can send a second EHT NDP announcement frame 1322 to the STA 1308. When the second EHT NDP announcement frame 1322 is sent, SIFS 1323 can take effect, and at 1324, the shared AP1 1304 can send a second EHT sounding NDP 1326 to the STA 1308. Similarly, after the second EHT sounding NDP 1326 is sent, SIFS 1327 can take effect, and at 1328, the STA 1308 can send a second EHT compressed beamforming / CQI frame 1330 including sounding feedback information to the shared AP1 1304. Note that the EHT-LTF field of the EHT PPDU containing the second EHT compressed beamforming / CQI frame 1330 can also be used for implicit sounding of group 2 APs (e.g., the shared AP2 1306). Based on the sounding feedback information received from the STA 1308, the shared AP 1304 can determine the steering matrix and / or allocate an appropriate RU for subsequent transmission to the STA 1308. In addition, the shared AP2 1306 can estimate the UL CSI according to the EHT-LTF field of the EHT PPDU containing the first and second EHT compressed beamforming / CQI frames 1318, 1330, and determine the corresponding DL CSI of the STA 1308 by compensating the UL CSI according to the calibration parameters obtained through the calibration procedure, and then the shared AP 1306 can determine the steering matrix and / or allocate an appropriate RU for subsequent transmission to the STA 1308 based on the DL CSI.

[0157] Figure 13BDepicts a flowchart of a multi-AP based hybrid sequential sounding procedure 1340 among multiple APs 1342, 1344, 1346 and multiple STAs 1348, 1350 in an 11be EHT WLAN according to an embodiment. In this embodiment, the shared AP 1342 and the shared AP1 1344 are group 1 APs, while the shared AP2 1346 is a group 2 AP. When the shared AP 1342 sends a first EHT NDP announcement frame 1352 to all the shared (one or more) APs (e.g., shared APs 1344, 1346) and the expected STAs 1348, 1350 participating in the sounding procedure 1340, the multi-AP based hybrid sequential sounding procedure 1340 can be initiated. The first EHT NDP announcement frame 1352 can indicate the ordering of the group 2 AP and the group 1 APs, where each of the group 1 APs can send an EHT NDP announcement frame and an EHT sounding NDP to the expected STAs. The first EHT NDP announcement frame 1352 can indicate the sounding RU allocation and the sounding SS allocation for each of the group 1 APs. Each EHT NDP announcement frame can indicate the sounding RU allocation and the sounding SS allocation for each of STA1 1348 and STA2 1350. Specifically, the data RU allocation and the data SS allocation for each of STA1 1348 and STA2 1350 are indicated in the corresponding EHT BFRP trigger frame. The sounding SS can include the data SS. In other words, the number of sounding SSs can be equal to or greater than the number of data SSs. The data RU allocation can be the same as the sounding RU allocation for each STA. Each EHT NDP announcement frame can indicate the requested sounding feedback parameters for each expected STA 1348, 1350, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns in the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, and CQI feedback. When the first EHT NDP announcement frame 1352 is sent, the SIFS 1353 can become effective, and at 1354, the shared AP 1342 can send a first EHT sounding NDP 1356 to STA1 1348 and STA2 1350. After the last symbol of the first EHT sounding NDP 1356 is sent, the SIFS 1357 can become effective, and at 1358, the shared AP 1342 can send an EHT BFRP trigger frame 1360 to request the simultaneous transmission of sounding feedback information from STA1 1348 and STA2 1350. When the EHT BFRP trigger frame 1360 is received, the SIFS 1361 can become effective, and at 1362, STA1 1348 and STA2 1350 simultaneously send their respective first EHT compressed beamforming / CQI frames 1364, 1366 including the sounding feedback information to the shared AP 1342.Note that the EHT-LTF fields of the EHT PPDU containing the first EHT compressed beamforming / CQI frames 1364, 1366 can also be used for CSI estimation for implicit probing of Group 2 APs (e.g., the shared AP2 1346). Based on the probing feedback information received from STA1 1348 and STA2 1350, the shared AP 1342 can determine the steering matrix and / or allocate appropriate RUs for each of STA1 1348 and STA2 1350 for subsequent transmissions to STA1 1348 and / or STA2 1350.

[0158] When the first EHT compressed beamforming / CQI frames 1364, 1366 are sent, the SIFS 1367 can take effect, and at 1368, the next AP in the ranking of group 1 APs (e.g., the shared AP1 1344) can send a second EHT NDP announcement frame 1370 to STA1 1348 and STA2 1350. When the second EHT NDP announcement frame 1370 is sent, the SIFS 1371 can take effect, and at 1372, the shared AP1 1344 can send a second EHT sounding NDP 1374 to STA1 1348 and STA2 1350. Similarly, after the second EHT sounding NDP 1374 is sent, the SIFS 1375 can take effect, and at 1376, the shared AP 1342 can send an EHT BFRP trigger frame 1378 to request STA1 1348 and STA2 1350 to send sounding feedback information simultaneously. When the EHT BFRP trigger frame 1378 is received, the SIFS 1379 can take effect, and at 1380, STA1 1348 and STA2 1350 simultaneously send their respective second EHT compressed beamforming / CQI frames 1382, 1384 including the sounding feedback information to the shared AP 1344. Note that the EHT-LTF field of the EHT PPDU containing the second EHT compressed beamforming / CQI frames 1382, 1384 can also be used for CSI estimation for implicit sounding of group 2 APs (e.g., the shared AP2 1346). Based on the sounding feedback information received from STA1 1348 and STA2 1350, the shared AP1 1344 can determine the steering matrix and / or allocate appropriate RUs for each of STA1 1348 and STA2 1350 for subsequent transmissions to STA1 1348 and / or STA2 1350. In addition, the shared AP2 1346 can estimate the UL CSI according to the EHT-LTF field of the EHT PPDU containing the first and second EHT compressed beamforming / CQI frames 1364, 1382, and determine the DL CSI of STA1 1348 by compensating the UL CSI according to the calibration parameters obtained through the calibration procedure; and then, the shared AP2 1346 can determine the steering matrix and / or allocate an appropriate RU for STA1 1348 for subsequent transmissions to STA1 1348 based on the DL CSI.Similarly, the shared AP2 1346 can estimate the UL CSI based on the EHT-LTF field of the EHT PPDU including the first and second EHT compressed beamforming / CQI frames 1366, 1384, and determine the DL CSI of the STA2 1350 by compensating the UL CSI according to the calibration parameters obtained through the calibration procedure; and then, the shared AP2 1346 can determine the steering matrix based on the DL CSI and / or allocate an appropriate RU for subsequent transmission to the STA2 1350 for the STA2 1350.

[0159] Figure 14ADepicts a flowchart of a multi-AP based hybrid joint sounding procedure 1400 among multiple APs 1402, 1404, 1406 and a STA 1408 in an 11be EHT WLAN according to an embodiment. In this embodiment, the shared AP 1402 and the shared AP1 1404 are group 1 APs, while the shared AP2 1406 is a group 2 AP. When the shared AP 1402 sends an EHT NDP announcement frame 1410 to all the shared (one or more) APs (e.g., shared APs 1404, 1406) and the intended STA 1408 participating in the sounding procedure 1400, the multi-AP based hybrid sequential sounding procedure 1400 can be initiated. The EHT NDP announcement frame 1410 can indicate the group 2 AP and the group 1 APs, where each of the group 1 APs can send an EHT sounding NDP to the intended STA. The EHT NDP announcement frame 1410 can indicate the sounding RU allocation and the sounding SS allocation for each of the group 1 APs. The EHT NDP announcement frame can indicate the sounding RU allocation and the sounding SS allocation for the intended STA 1408. The EHT NDP announcement frame can indicate the requested sounding feedback parameters for each pair of the intended STA1408 and the group 1 APs, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns in the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, and CQI feedback. When the EHT NDP announcement frame 1410 is sent, SIFS 1411 can take effect, and at 1412, the shared AP 1402 and the shared AP1404 can simultaneously send their respective EHT sounding NDPs 1414, 1416 to the STA 1408. After the last symbol of the EHT sounding NDPs 1414, 1416 is sent, SIFS 1417 can take effect, and at 1418, the STA 1408 sends an EHT compressed beamforming / CQI frame 1419 including sounding feedback information to the shared AP 1402 and the shared AP1 1404. Note that the EHT-LTF field of the EHT·PPDU containing the EHT compressed beamforming / CQI frame 1419 can also be used for CSI estimation of the implicit sounding of the group 2 AP (e.g., the shared AP2 1406). Based on the sounding feedback information received from the STA 1408, the shared AP1402 and the shared AP1 1404 are able to determine the steering matrix and / or allocate an appropriate RU for the STA1408 for subsequent transmissions to the STA1408.In addition, the shared AP2 1406 can estimate the UL CSI based on the EHT-LTF field of the EHT PPDU including the EHT compressed beamforming / CQI frame 1419, and determine the DL CSI of the STA 1408 by compensating the UL CSI according to the calibration parameters obtained through the calibration procedure; and then, the shared AP2 1406 can determine the steering matrix based on the DL CSI and / or allocate an appropriate RU for subsequent transmission to the STA 1408 for the STA 1408.

[0160] Figure 14BDepicts a flowchart of a multi-AP based hybrid joint sounding procedure 1420 among multiple APs 1422, 1424, 1426 and multiple STAs 1428, 1430 in an 11be EHT WLAN according to an embodiment. In this embodiment, the shared AP 1422 and the shared AP1 1424 are group 1 APs, and the shared AP2 1426 is a group 2 AP. When the shared AP 1422 sends an EHT NDP announcement frame 1432 to all the shared (one or more) APs (e.g., the shared APs 1424, 1426) and the expected STAs 1428, 1430 participating in the sounding procedure 1420, the multi-AP based hybrid joint sounding procedure 1420 can be initiated. The EHT NDP announcement frame 1432 can indicate the group 2 AP and the group 1 APs, where each of the group 1 APs can send an EHT sounding NDP to the expected STA1 1428 and STA2 1430. The EHT NDP announcement frame 1432 can indicate the sounding RU allocation and the sounding SS allocation for each of the group 1 APs. The EHT NDP announcement frame 1432 can indicate the sounding RU allocation and the sounding SS allocation for each of the STA1 1428 and STA2 1430. Specifically, the data RU allocation and the data SS allocation for each of the STA1 1428 and STA2 1430 are indicated in the corresponding EHT BFRP trigger frame 1442. The sounding SS can include the data SS. In other words, the number of sounding SSs can be equal to or greater than the number of data SSs. For each STA, the data RU allocation can be the same as the sounding RU allocation. The EHT NDP announcement frame 1432 can indicate the request sounding feedback parameters for each of the expected STAs 1428, 1430, such as the feedback bandwidth, the feedback type, the subcarrier grouping, the quantization resolution, and the number of columns in the compressed beamforming feedback matrix. The feedback type is one of SU feedback, MU feedback, and CQI feedback. When the EHT NDP announcement frame 1432 is sent, SIFS 1433 can take effect, and at 1434, the shared AP 1422 and the shared AP1 1424 can send their respective EHT sounding NDPs 1436, 1438 to the STA1 1428 and STA2 1430. After the last symbol of the EHT sounding NDPs 1436, 1438 is sent, SIFS 1439 can take effect, and at 1440, the shared AP 1422 can send an EHT BFRP trigger frame 1442 to request the sounding feedback information to be sent simultaneously from the STA1 1428 and STA2 1430.When the EHT BFRP trigger frame 1442 is received, the SIFS 1443 can take effect, and at 1444, STA1 1428 and STA2 1430 simultaneously send their respective EHT compressed beamforming / CQI frames 1446, 1448 including probe feedback information to the shared AP 1422 and the shared AP1 1424. Note that the EHT-LTF field of the EHT PPDU containing the EHT compressed beamforming / CQI frames 1446, 1448 can also be used for CSI estimation for implicit probing of group 2 APs (e.g., the shared AP2 1426). Based on the probe feedback information received from STA1 1428 and STA2 1430, the shared AP 1422 and the shared AP1 1424 can determine the steering matrix and / or allocate appropriate RUs for each of STA1 1428 and STA2 1430 for subsequent transmissions to STA1 1428 and / or STA2 1430. In addition, the shared AP2 1426 can estimate the UL CSI according to the EHT-LTF field of the EHT PPDU containing the EHT compressed beamforming / CQI frame 1446, and compensate the UL CSI according to the calibration parameters obtained through the calibration procedure, so as to determine the DL CSI of STA11428; and then, the shared AP2 1426 can determine the steering matrix and / or allocate an appropriate RU for STA11428 for subsequent transmissions to STA1 1428 based on the DL CSI. Similarly, the shared AP2 1426 can estimate the UL CSI according to the EHT-LTF field of the EHT PPDU containing the EHT compressed beamforming / CQI frame 1448, and compensate the UL CSI according to the calibration parameters obtained through the calibration procedure, so as to determine the DL CSI of STA 1430; and then, the shared AP2 1426 can determine the steering matrix and / or allocate an appropriate RU for STA 1430 for subsequent transmissions to STA 1430 based on the DL CSI.

[0161] Figure 15 An example format of the EHT NDP announcement frame 1500 is depicted. The EHT NDP announcement frame 1500 can include (or consist of) a frame control field, a duration field, an RA (receiver STA address) field, a TA (sender STA address) field, a probe conversation token field, a probe type field 1502, an AP-STA information field 1504, and an FCS field. The frame control field, the duration field, the RA field, and the TA field can be grouped as the MAC header.

[0162] When the probe type field 1502 refers to single-AP explicit probing. For single-AP explicit probing, the AP-STA information field 1504 may include one or more STA feedback information fields 1602 as shown in Figure 16A . The STA feedback information field 1602 may include (or consist of) the expected STA field, the feedback bandwidth field, the feedback type field, the subcarrier group field, the quantization resolution field, and the number of columns of the compressed beamforming feedback matrix field. In one embodiment, the STA feedback information field is used to indicate the requested probe feedback parameters for the STA indicated in the expected STA field.

[0163] When the probe type field 1502 refers to single-AP implicit probing. For single-AP implicit probing, the AP-STA information field 1504 may include one or more STA probe information fields 1604 as shown in Figure 16B . The STA probe information field 1604 may include (or consist of) the expected STA field, the STA probe RU allocation field, and the STA probe SS allocation field. In one embodiment, the STA probe information field is used to indicate the probe RU allocation and the probe SS allocation for the STA indicated in the expected STA field.

[0164] When the probe type field 1502 refers to multi-AP explicit probing. For multi-AP explicit probing, the AP-STA information field 1504 may include one or more AP-STA explicit probing information fields 1606 as shown in Figure 16C . The AP-STA explicit probing information field 1606 may include (or consist of) the AP probe information field 1608 and one or more STA feedback information fields 1602 as shown in Figure 16A . The AP probe information field 1608 may further include the expected AP field, the AP probe RU allocation field, and the AP probe SS allocation field. In one embodiment, the AP-STA explicit probing information field is used to indicate the probe RU allocation and the probe SS allocation for the AP indicated in the expected AP field and the corresponding probe feedback parameters for each STA.

[0165] When the probe type field 1502 refers to multi-AP implicit probing. For multi-AP implicit probing, the AP-STA information field 1504 may include one or more expected AP fields and as shown in Figure 16BOne or more STA probe information fields 1604 illustrated therein. In one embodiment, one or more expected AP fields are used to indicate the shared AP(s) participating in multi-AP based implicit probing, and one or more STA probe information fields are used to indicate the probe RU allocation and probe SS allocation for each expected STA.

[0166] In addition, when the probe type field 1502 refers to multi-AP based hybrid probing, the AP-STA information field 1504 may include one or more AP-STA explicit probe information fields 1606 as shown in Figure 16C which indicate the necessary information for the explicit probe part of the multi-AP based hybrid probing; may include one or more expected AP fields and one or more STA probe information fields as shown in Figure 16B which indicate the necessary information for the implicit probe part of the multi-AP based hybrid probing.

[0167] Figure 17 Shows a configuration of a communication device (e.g., an AP) according to the present disclosure. Similar to the schematic example of the communication device 300 shown in Figure 3A the communication device 1700 includes a circuit 1702, at least one radio transmitter 1710, at least one radio receiver 1712, and at least one antenna 1714 (for the sake of simplicity, Figure 17 only one antenna is depicted therein). The circuit 1702 may include at least one controller 1708 for operating with software and hardware assistance. The controller 1708 is designed to perform tasks for communication for channel probing. The circuit 1702 may also include a transmit signal generator 1704 and a receive signal processor 1706. The at least one controller 1708 may control the transmit signal generator 1704 and the receive signal processor 1706. The transmit signal generator 1704 may include a frame generator 1722, a control signaling generator 1724, and a PPDU generator 1726. The frame generator 1722 may generate MAC frames, such as EHT NDP announcement frames, EHT action frames, or EHT BFRP trigger frames. The control signaling generator 1724 may generate the control signaling fields of the PPDU to be generated (e.g., the EHT-SIG field of the EHT probe NDP or the EHT-SIG field of the EHT PPDU including the EHT NDP announcement frame, EHT action frame, or EHT BFRP trigger frame). The PPDU generator 1726 may generate a PPDU (e.g., an EHT PPDU including the EHT NDP announcement frame, EHT action frame, or EHT BFRP trigger frame or an EHT probe NDP).

[0168] The receive signal processor 1706 may include a data demodulator and decoder 1734, which may demodulate and decode the data portion of the received signal (e.g., the data field of an EHT PPDU including an EHT NDP announcement frame, an EHT action frame, or an EHT BFRP trigger frame). The receive signal processor 1706 may also include a control demodulator and decoder 1734, which may demodulate and decode the control signaling portion of the received signal (e.g., the EHT-SIG field of an EHT sounding NDP or the EHT-SIG field of an EHT PPDU including an EHT compressed beamforming / CQI frame). At least one controller 1708 may include a control signal parser 1742 and a scheduler 1744. The scheduler 1744 may determine RU information and user-specific allocation information for the allocation of downlink SU or MU transmissions and trigger information for the allocation of uplink MU transmissions. The control signal parser 1742 may analyze the control signaling portion of the received signal and the trigger information for the allocation of uplink MU transmissions shared by the scheduler 1744 and assist the data demodulator and decoder 1732 in demodulating and decoding the data portion of the received signal (e.g., the data field of an EHT PPDU including an EHT compressed beamforming / CQI frame).

[0169] Figure 18 shows a configuration of a communication device (e.g., STA) according to the present disclosure. Similar to Figure 3A the schematic example of the communication device 300 shown in, the communication device 1800 includes circuitry 1802, at least one radio transmitter 1810, at least one radio receiver 1812, at least one antenna 1814 (for the sake of brevity, Figure 18(only one antenna is depicted). Circuit 1802 may include at least one controller 1808, which is designed to perform tasks for communication for channel sounding with the assistance of software and hardware. Circuit 1802 may also include a received signal processor 1804 and a transmitted signal generator 1806. The at least one controller 1808 may control the received signal processor 1804 and the transmitted signal generator 1806. The received signal processor 1804 may include a data demodulator and decoder 1832 and a control demodulator and decoder 1834. The control demodulator and decoder 1834 may demodulate and decode the control signaling part of the received signal (e.g., the EHT-SIG field of the EHT sounding NDP or the EHT-SIG field of the EHT PPDU including the EHT NDP announcement frame or the EHT BFRP trigger frame). The data demodulator and decoder 1032 may demodulate and decode the data part of the received signal (e.g., the data field of the EHT PPDU including the EHT NDP announcement frame or the EHT BFRP trigger frame) according to its own allocated RU information and user-specific allocation information.

[0170] The at least one controller 1808 may include a control signal parser 1842, a scheduler 1844, and a trigger information parser 1846. The control signal parser 1842 may analyze the control signaling part of the received signal (e.g., the EHT-SIG field of the EHT sounding NDP or the EHT-SIG field of the EHT PPDU including the EHT NDP announcement frame or the EHT BFRP trigger frame), and assist the data demodulator and decoder 1832 in demodulating and decoding the data part of the received signal (e.g., the data field of the EHT PPDU including the EHT NDP announcement frame or the EHT BFRP trigger frame). The trigger information parser 1848 may analyze the trigger information for its own uplink allocation from the received trigger frame contained in the data part of the received signal. The transmitted signal generator 1804 may include a control signaling generator 1824, which may generate the control signaling field of the PPDU to be generated (e.g., the EHT-SIG field of the EHT sounding NDP or the EHT-SIG field of the EHT PPDU including the EHT compressed beamforming / CQI frame). The transmitted signal generator 1804 may also include a PPDU generator 1826, which generates a PPDU (e.g., the EHT PPDU including the EHT compressed beamforming / CQI frame or the EHT sounding NDP). The transmitted signal generator 1804 may also include a frame generator 1822, and the frame generator 1822 may generate MAC frames, such as the EHT compressed beamforming / CQI frame.

[0171] As described above, embodiments of the present disclosure provide an advanced communication system, communication method, and communication apparatus for channel sounding in a MIMO WLAN network, and improve the spectral efficiency in the MIMO WLAN network.

[0172] The present disclosure can be implemented by software, hardware, or a cooperation of software and hardware. Each functional block used in the description of each of the above embodiments can be partially or fully implemented by an LSI such as an integrated circuit, and each process described in each embodiment can be partially or fully controlled by the same LSI or a combination of LSIs. The LSI can be formed as a chip alone, or one chip can be formed to include part or all of the functional blocks. The LSI can include data input and output coupled thereto. Depending on the degree of integration, the LSI here can be referred to as an IC, system LSI, super LSI, or ultra LSI. However, the technology for implementing the integrated circuit is not limited to the LSI, and can be implemented by using dedicated circuits, general-purpose processors, or dedicated processors. In addition, an FPGA (field programmable gate array) that can be programmed after the manufacture of the LSI, or a reconfigurable processor in which the connection and setting of circuit units arranged inside the LSI can be reconfigured, can be used. The present disclosure can be implemented as digital processing or analog processing. If future integrated circuit technology replaces the LSI due to the progress of semiconductor technology or other derivative technologies, future integrated circuit technology can be used to integrate the functional blocks. Biotechnology can also be applied.

[0173] The present disclosure can be implemented by any kind of apparatus, device, or system having a communication function, which is referred to as a communication apparatus.

[0174] The communication apparatus can include a transceiver and a processing / control circuit. The transceiver can include and / or act as a receiver and a transmitter. As a transmitter and a receiver, the transceiver can include an RF (radio frequency) module, which includes an amplifier, an RF modulator / demodulator, etc., and one or more antennas.

[0175] Some non-limiting examples of such communication apparatuses include telephones (e.g., cellular phones, smart phones), tablet computers, personal computers (PCs) (e.g., laptops, desktop computers, netbooks), cameras (e.g., digital cameras / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), game consoles, digital book readers, remote health / telemedicine devices, and transportation means providing a communication function (e.g., cars, airplanes, ships), and various combinations thereof.

[0176] The communication device is not limited to being portable or movable, and may also include any kind of non-portable or fixed device, equipment or system, such as smart home devices (e.g., appliances, lighting, smart meters, control panels), vending machines, and any other "things" in the "Internet of Things (IoT)" network.

[0177] Communication may include exchanging data through, for example, cellular systems, wireless LAN systems, satellite systems, etc. and their various combinations.

[0178] The communication device may include devices such as a controller or a sensor, which are coupled to a communication device that performs the communication functions described in the present disclosure. For example, the communication device may include a controller or a sensor that generates control signals or data signals used by the communication device that performs the communication functions of the communication device.

[0179] The communication device may also include infrastructure, such as base stations, access points, and any other device, equipment or system that communicates with or controls the devices in the above non-limiting examples.

[0180] It should be understood that although some attributes of various embodiments have been described with reference to devices, the corresponding attributes also apply to the methods of various embodiments, and vice versa.

[0181] Those skilled in the art will understand that various changes and / or modifications can be made to the present disclosure shown in specific embodiments without departing from the spirit or scope of the present disclosure as broadly described. Therefore, the presented embodiments are considered illustrative rather than restrictive in all aspects.

Claims

1. A first access point, comprising: A circuit that generates a first frame for a sounding procedure; and A transmitter that sends the first frame to each of one or more second access points, the first frame including a first field indicating an intended use of the sounding procedure, wherein at least one of the first access point and the one or more second access points sends a Null Data Packet (NDP) announcement frame after the sending of the first frame.

2. The first access point according to claim 1, wherein the first frame comprises a second field, and the second field indicates an expected type of the probing procedure.

3. The first access point according to claim 1, wherein the first frame comprises a third field, and the third field indicates one or more expected communication devices that will participate in the probing procedure.

4. The first access point according to claim 1, further comprising: A receiver that receives a second frame from each of the one or more second access points, the second frame including a first field that indicates one or more recommended types of the sounding procedure.

5. The first access point according to claim 4, wherein the first field of the second frame indicates that at least one of the one or more second access points will be exempted from the probing procedure.

6. The first access point according to claim 1, wherein the circuit further generates the NDP announcement frame for initiating the probing procedure.

7. The first access point according to claim 6, wherein the NDP announcement frame comprises a first field indicating a type of the probing procedure and a second field indicating a type of the probing feedback.

8. The first access point according to claim 7, when the type of the probing procedure refers to an explicit probing procedure and the type of the probing feedback refers to a calibration feedback, the probing procedure comprises a calibration procedure.

9. The first access point according to claim 1, when the probing procedure is a hybrid probing procedure comprising an explicit probing part and an implicit probing part, at least one access point among the first access point and the one or more second access points participates in the explicit probing part of the probing procedure, and the remaining access points among the first access point and the one or more second access points except the at least one access point participate in the implicit probing part of the probing procedure.

10. A communication method, comprising: Generate a first frame for a sounding procedure; and Send the first frame to each of one or more second access points, the first frame including a first field indicating an intended use of the sounding procedure, wherein at least one of the first access point and the one or more second access points sends a Null Data Packet (NDP) announcement frame after the sending of the first frame.

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