Communication apparatus and communication method for channel sounding, and integrated circuit

Abstract

To provide apparatuses and methods for multi-AP based channel sounding.SOLUTION: In a radio communications system, a communication apparatus 300 may be a peer AP (for example, a shared AP), and a radio receiver 304 receives, in operation, a first frame (for example, a Sounding Setup Request frame) from one other communication apparatus (e.g. a sharing AP) comprising a first field which indicates an intended usage of a sounding procedure. Circuitry 314 (for example, at least one receive signal processor 310 of the circuitry 314) processes, in operation, the first frame. A radio transmitter 302 transmits, in operation, a second frame (for example, a Sounding Setup Response frame) to the one other communication apparatus, the second frame comprising a first field which indicates one or more recommended types of the sounding procedure.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present disclosure relates to a communication device and method for channel sounding, and more particularly, to a communication device and method for channel sounding in an EHT WLAN (extremely high throughput wireless local area network).

Background Art

[0002] In the standardization of next-generation wireless local area networks (WLANs), the IEEE 802.11 Working Group has considered a new wireless access technology that necessarily has backward compatibility with IEEE 802.11a / b / g / n / ac / ax technologies, and named it IEEE 802.11be extremely high throughput (EHT) WLAN.

[0003] In 802.11be EHT WLAN, in order to provide a significant increase in peak throughput and capacity beyond 802.11ax high efficiency (HE) WLAN, especially for cell-edge STAs, it has been proposed to enable multi-AP coordination in a multi-access point (multi-AP) system.

[0004] However, there has been little discussion about communication devices and methods for channel sounding, specifically efficient procedures for multi-AP-based sounding.

[0005] Therefore, there is a need for a communication device and method that provide a feasible technical solution for channel sounding in the context of EHT WLAN. Further, other desirable features and characteristics will become apparent by obtaining the following detailed description and the appended claims, along with the accompanying drawings and the background of this disclosure. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0006] Non-limiting and exemplary embodiments facilitate 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 including a receiver that receives a first frame including a first field indicating a target application of a sounding procedure from another communication device, and a circuit that processes the first frame.

[0008] In a second aspect, the present disclosure provides a communication method including receiving a first frame including a first field indicating a target application of a sounding procedure from another communication device, and processing the first frame.

[0009] In a third aspect, the present disclosure provides an integrated circuit that controls a process of receiving a first frame including a first field indicating a target application of a sounding procedure from another communication device, and a process of processing the first frame.

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

[0011] Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. These benefits and / or advantages may be obtained individually by the various embodiments and features of the specification and drawings, and all of these embodiments and features are not necessarily provided to obtain one or more of such benefits and / or advantages.

[0012] From the following description and drawings, which are merely examples, the embodiments of the present disclosure will be better understood and will become readily apparent to those skilled in the art.

Brief Description of the Drawings

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[0014] Those skilled in the art will recognize that the components in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale. For example, in order to assist in the accurate understanding of the present embodiment, the dimensions of some components in the drawings, block diagrams, or flowcharts may be exaggerated relative to other components.

[0015] Some embodiments of the present disclosure will be described by way of example only with reference to the drawings. Similar reference numerals and letters in the drawings indicate similar components or equivalents.

[0016] In the following paragraphs, specific exemplary embodiments will be described with reference to access points (APs) and stations (STAs) for uplink or downlink channel sounding, particularly in multiple-input multiple-output (MIMO) wireless networks.

[0017] In the context of IEEE802.11 (Wi-Fi) technology, a station, also called an STA, is a communication device that can use the 802.11 protocol. Based on the definition of IEEE802.11-2016, an STA can be any device that includes an IEEE802.11-compliant medium access control (MAC) and physical layer (PHY) interface for a wireless medium (WM).

[0018] For example, the STA may be a laptop, 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. The STA may be fixed or movable. In a WLAN environment, the terms "STA", "wireless client", "user", "user device", and "node" are often used interchangeably.

[0019] Similarly, an AP, which may also be referred to as a wireless access point (WAP) in the context of IEEE802.11 (Wi-Fi) technology, is a communication device that enables an STA within a WLAN to connect to a wired network. Usually, the AP is connected to a router as a stand-alone device (via a wired network), but it is also possible for the AP to be integrated with or used within the router.

[0020] As described above, an STA in a WLAN may act as an AP in different cases, and vice versa. This is because a communication device in the context of IEEE802.11 (Wi-Fi) technology may include both STA hardware components and AP hardware components. In this way, the communication device may switch between the STA mode and the AP mode based on the actual WLAN conditions and / or requirements.

[0021] In a MIMO wireless network, "multiple" refers to a plurality of antennas that are simultaneously used for transmission over a wireless channel and a plurality of antennas that are simultaneously used for reception. In this regard, "multiple input" refers to a plurality of transmitter antennas that input a wireless signal into a channel, and "multiple output" refers to a plurality of receiver antennas that receive a wireless signal from a channel and input it into a receiver. For example, in an N×M MIMO network system, N is the number of transmitter antennas and M is the number of receiver antennas, and N may or may not be equal to M. For the sake of brevity, in the present disclosure, there is no further consideration of the number of transmitter antennas and receiver antennas respectively.

[0022] In a MIMO wireless network, for communication between communication devices such as an AP and an STA, for example, single-user (SU) communication and multi-user (MU) communication can be arranged. A MIMO wireless network has the benefit of enabling higher data rates and robustness by using multiple spatial streams such as spatial multiplexing and spatial diversity. According to various embodiments, the term "spatial stream" may be used interchangeably with the term "space-time stream" (or STS).

[0023] Figure 1A shows a schematic diagram of SU communication 100 between AP 102 and STA 104 in a MIMO wireless network. As shown, the MIMO wireless network may include one or more STAs (e.g., STA 104, STA 106, etc.). When SU communication 100 on a certain channel is executed across the entire channel bandwidth, it is called full bandwidth SU communication. When SU communication 100 on a certain channel is executed across 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, AP 102 transmits a plurality of space-time streams using a plurality of antennas (e.g., the four antennas shown in Figure 1A), and all space-time streams are directed to a single communication device, i.e., STA 104. For simplicity, the plurality of space-time streams directed to STA 104 are shown as grouped data transmission arrows 108 directed to STA 104.

[0024] SU communication 100 can be configured for two-way transmission. As shown in Figure 1A, in SU communication 100, STA 104 may transmit a plurality of space-time streams using a plurality of antennas (e.g., the two antennas shown in Figure 1A), and all space-time streams are directed to AP 102. For simplicity, the plurality of space-time streams directed to AP 102 are shown as grouped data transmission arrows 110 directed to AP 102.

[0025] Thus, the SU communication 100 shown in Figure 1A enables both uplink and downlink SU transmissions in a MIMO wireless network.

[0026] FIG. 1B shows 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 can 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 the network at 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 RU(s) within the channel bandwidth via spatial mapping or precoding techniques. When the RU(s) in which OFDMA or MU-MIMO communication occurs occupy the entire channel bandwidth, that OFDMA or MU-MIMO communication is called full-bandwidth OFDMA or MU-MIMO communication. When the RU(s) in which OFDMA or MU-MIMO communication occurs occupy a part of the channel bandwidth (e.g., one or more 20 MHz subchannels within the channel are punctured), that OFDMA or MU-MIMO communication is called 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 simplicity, the two space-time streams directed to STA 118 are shown as a grouped data transmission arrow 124, the space-time stream directed to STA 116 is shown as a data transmission arrow 122, and the space-time stream directed to STA 120 is shown as a data transmission arrow 126.

[0027] To enable uplink MU transmission, trigger-based communication is provided in a MIMO wireless network. In this regard, FIG. 1C shows a schematic diagram of trigger-based uplink MU communication 128 between an AP 130 and a plurality of STAs 132, 134, 136 in a MIMO wireless network.

[0028] Since a plurality of STAs 132, 134, 136 participate in the trigger-based uplink MU communication, the AP 130 needs to coordinate the simultaneous transmissions of the plurality of STAs 132, 134, 136.

[0029] To perform such coordination, as shown in FIG. 1C, the AP 130 simultaneously transmits trigger frames 139, 141, 143 to the STAs 132, 134, 136 to indicate user-specific resource allocation information (e.g., the number of space-time streams, the number of departure STSs, and the allocated RUs) that each STA can use. In response to the trigger frames, the STAs 132, 134, 136 may then simultaneously transmit their respective space-time streams to the AP 130 according to the user-specific resource allocation information indicated in the trigger frames 139, 141, 143. For example, two space-time streams may be directed from the STA 134 to the AP 130, another space-time stream may be directed from the STA 132 to the AP 130, and yet another space-time stream may be directed from the STA 136 to the AP 130. For simplicity, the two space-time streams directed from the STA 134 to the AP 130 are shown as a grouped data transmission arrow 140, the space-time stream directed from the STA 132 to the AP 130 is shown as a data transmission arrow 138, and the space-time stream directed from the STA 136 to the AP 130 is shown as a data transmission arrow 142.

[0030] To enable downlink multi-AP communication, trigger-based communication is also provided in a MIMO wireless network. In this regard, FIG. 1D shows a schematic diagram of downlink multi-AP communication 144 between an STA 150 and a plurality of APs 146, 148 in a MIMO wireless network.

[0031] Since multiple APs 146 and 148 participate in this trigger-based downlink multi-AP MIMO communication, the master AP 146 needs to coordinate the simultaneous transmissions of multiple APs 146 and 148.

[0032] To perform such coordination, as shown in FIG. 1D, the master AP 146 simultaneously transmits trigger frames 147 and 153 to the AP 148 and the STA 150 to indicate the AP-specific resource allocation information (e.g., the number of space-time streams, the number of departure STS streams, and the allocated RUs) available to each AP. In response to the trigger frames, then the multiple APs 146 and 148 may each transmit their respective space-time streams to the STA 150 according to the AP-specific resource allocation information indicated in the trigger frame 147. Then the STA 150 may receive all the space-time streams according to the AP-specific resource allocation information indicated in the trigger frame 153. For example, two space-time streams may be directed from the AP 146 to the STA 150, and another two space-time streams may be directed from the AP 148 to the STA 150. For simplicity, the two space-time streams directed from the AP 146 to the STA 150 are shown as a grouped data transmission arrow 152, and the two space-time streams directed from the AP 148 to the STA 150 are shown as a grouped data transmission arrow 154.

[0033] For packet / PPDU (physical layer protocol data unit)-based transmission and distributed MAC (medium access control) schemes in 802.11 WLANs, there is no time scheduling (e.g., periodic time slot allocation for data transmission similar to TDMA (time division multiple access)) in 802.11 WLANs. Frequency and spatial resource scheduling are performed on a packet basis. In other words, the resource allocation information is PPDU-based.

[0034] According to various embodiments, an EHT WLAN supports non-trigger-based communication as shown in FIGS. 1A and 1B and trigger-based communication as shown in FIGS. 1C and 1D. In non-trigger-based communication, a communication device spontaneously transmits a PPDU to one or more other communication devices. In trigger-based communication, a communication device transmits a PPDU to one or more other communication devices only after receiving a soliciting trigger frame.

[0035] Figure 2A shows a single-AP-based sounding procedure 200 between two STAs 202, 204 in an 11ax HE WLAN. The single-AP-based sounding procedure 200 may be initiated when an STA1 202, such as an AP, generates a HE NDP (null data packet) announcement frame 206 for a target STA, such as an STA2 204. The HE NDP announcement frame 206 includes per-STA requested sounding feedback parameters, 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 sounding feedback information includes compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the requested sounding feedback information includes CQI information for each subcarrier or subcarrier group. In an IEEE 802.11 network, the short interframe spacing (SIFS) is the time interval before the transmission of an acknowledgment response by an STA. When transmitting the HE NDP announcement frame 206, the SIFS 207 may be enabled, and at 208, the STA1 202 may transmit a HE sounding NDP 210 to the STA2 204. The HE sounding NDP 210 may include a HE Long Training Field (HE-LTF) for CSI (channel state information) estimation.

[0036] After the last symbol of the HE sounding NDP210 is transmitted, SIFS211 may become active, and at 212, STA2 204 may transmit to STA1 202 an HE compressed beamforming / CQI frame 214 including sounding feedback information. In some embodiments, the sounding feedback information may be derived by STA2 204 from CSI, which is estimated from the HE-LTF field of the HE sounding NDP210 and prepared according to its own required sounding feedback parameters indicated in the HE NDP announcement frame 206. Based on the sounding feedback information received from STA2 204, STA1 202 may determine a steering matrix and / or allocate appropriate resource units (RUs) for subsequent transmissions to STA2 204.

[0037] Figure 2B shows a single-AP-based sounding procedure 220 between an AP 222 and a plurality of STAs 224, 226 in an 11ax HE WLAN. The single-AP-based sounding procedure 220 may be initiated when the AP 222 generates a HE NDP announcement frame 228 for target STAs such as, for example, STA1 224 and STA2 226. The HE NDP announcement frame 228 includes the required 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 required sounding feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the required sounding feedback information includes the CQI information for each subcarrier or subcarrier group. When transmitting the HE NDP announcement frame 228, SIFS 229 may be enabled, and at 230, the AP 222 may transmit a HE sounding NDP 232 to STA1 224 and STA2 226.

[0038] After the HE sounding NDP 232 is transmitted, SIFS 233 may be enabled, and at 234, the AP 222 may transmit a beamforming report poll (BFRP) trigger frame 236 to solicit simultaneous transmission of sounding feedback information from STA1 224 and STA2 226.

[0039] After the last symbol of the BFRP trigger frame 236 is transmitted, SIFS 237 may become active, and at 238, STA1 224 and STA2 226 may simultaneously transmit their respective HE compressed beamforming / CQI frames 240, 242 to AP 222, each including respective sounding feedback information. In some embodiments, the sounding feedback information may be derived from the respective CSI by STA1 224 and STA2 226, which is estimated from the HE-LTF field of the HE sounding NDP 232 and prepared according to the respective sounding feedback parameters indicated in the HE NDP announcement frame 228. Based on the sounding feedback information received from STA1 224 and STA2 226, AP 222 may determine a steering matrix and / or may be able to allocate appropriate RUs for each of STA1 224 and STA2 226 for subsequent transmissions to STA1 224 and / or STA2 226.

[0040] Note that in an 11ax HE WLAN, an AP and STA(s) engaged in a single-AP-based sounding procedure belong to a single BSS (basic service set). Thus, to improve throughput in an 11be EHT WLAN over an 11ax HE WLAN, the object of the present disclosure is to substantially overcome the existing problem of providing a communication device and method for channel sounding that enables multi-AP coordination in a multi-AP system.

[0041] According to the present disclosure, for the formation of a multi-AP adjustment candidate set, a multi-AP adjustment set-up procedure is performed among APs. The multi-AP adjustment candidate set includes a sharing AP and one or more shared APs. In the multi-AP adjustment set-up, an AP set identifier (ID: identifier) is assigned to the multi-AP adjustment candidate set, and here an AP ID may be assigned to each AP of the multi-AP adjustment candidate set. Using this AP ID together with the AP set ID, a specific AP in the multi-AP adjustment candidate set is uniquely identified. In an embodiment, in the multi-AP adjustment set-up, capability negotiation may be performed among the APs of the multi-AP adjustment candidate set. Alternatively, the capability negotiation among the APs of the multi-AP adjustment candidate set may be performed, for example, using a backhaul or the like, before the multi-AP adjustment set-up procedure. In an embodiment, in the multi-AP adjustment set-up, the target STA may indicate a preferred AP of the multi-AP adjustment candidate set for the multi-AP adjustment operation.

[0042] After the multi-AP adjustment set-up procedure is completed, each AP of the multi-AP adjustment candidate set may indicate, in a beacon frame or the like, multi-AP adjustment related information such as multi-AP adjustment candidate set information, the AP sounding capability, and the capabilities of the AP including the multi-AP adjustment capability.

[0043] In various embodiments, before starting the sounding procedure for the multi-AP operation, the sharing AP of the multi-AP adjustment candidate set may start a sounding set-up procedure together with each shared AP (singular or plural) of the multi-AP adjustment candidate set to make preparations necessary for the sounding procedure.

[0044] FIG. 3A shows a partially divided schematic view of a communication device 300 according to the present disclosure. The communication device 300 may also be implemented as an AP or a STA.

[0045] As shown in FIG. 3A, the communication device 300 may include a circuit 314, at least one wireless transmitter 302, at least one wireless receiver 304, and at least one antenna 312 (for the sake of simplicity, only one antenna is shown in FIG. 3A for illustrative purposes). The circuit 314 may include at least one controller 306, and this controller 306 is used to assist software and hardware in executing tasks designed to be performed by this at least one controller 306, including controlling communication with one or more other communication devices in a MIMO wireless network. The circuit 314 may further include at least one transmission signal generator 308 and at least one reception signal processor 310. The at least one controller 306 may control the at least one transmission signal generator 308 to generate MAC frames (such as EHT action frames, etc.) and PPDUs (for example, when the communication device 300 is an AP, the PPDU used for non-trigger-based communication or the PPDU used for trigger-based multi-AP joint transmission, and for example, when the communication device 300 is a STA, the PPDU used for non-trigger-based communication or the PPDU used for trigger-based uplink transmission, etc.), and transmit them to one or more other communication devices through the at least one wireless transmitter 302, and may control the at least one reception signal processor 310 to process MAC frames (such as EHT action frames) and PPDUs (for example, when the communication device 300 is an AP, the PPDU used for non-trigger-based communication or the PPDU used for trigger-based uplink transmission, and for example, when the communication device 300 is a STA, the PPDU used for non-trigger-based communication or the PPDU used for trigger-based multi-AP joint transmission) received from one or more other communication devices through the at least one wireless receiver 304 under the control of this at least one controller 306.As shown in FIG. 3A, at least one transmission signal generator 308 and at least one reception signal processor 310 may be stand-alone modules of a communication device 300 that communicate with at least one controller 306 for the above-described functions. Alternatively, at least one transmission signal generator 308 and at least one reception signal processor 310 may be included in at least one controller 306. Those skilled in the art can recognize that the arrangement of these functional modules is flexible and may vary according to actual needs and / or requirements. Data processing, storage, and other related control devices may be provided on a suitable circuit board and / or within a chipset. In various embodiments, during operation, at least one wireless transmitter 302, at least one wireless receiver 304, and at least one antenna 312 may be controlled by at least one controller 306.

[0046] During operation, the communication device 300 provides the functions necessary for single-AP or multi-AP based channel sounding. For example, the communication device 300 may be an AP (such as a shared source AP, etc.), and the circuit 314 (such as at least one transmission signal generator 308 of the circuit 314, etc.) may generate a first frame (such as a sounding setup request frame, etc.) including a first field indicating the target application of the sounding procedure during operation. The wireless transmitter 302 may transmit the first frame to each of one or more peer communication devices (such as a shared destination AP, etc.) during operation. In an embodiment, the wireless receiver 304 may receive a second frame (such as a sounding setup response frame, etc.) from each of one or more peer communication devices during operation, and this second frame 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 transmission signal generator 308 of the circuit 314, etc.) may further generate a third frame (such as an EHT NDP announcement frame, etc.) to start the sounding procedure during operation.

[0047] The communication device 300 may be a peer AP (such as a sharing destination AP, etc.). During operation, the wireless receiver 304 may receive a first frame (such as a sounding setup request frame, etc.) including a first field indicating the target application of the sounding procedure from one other communication device (e.g., a sharing source AP). The circuit 314 (such as at least one receiving signal processor 310 of the circuit 314, etc.) may process the first frame during operation. In an embodiment, during operation, the wireless transmitter 302 may transmit a second frame (such as a sounding setup response frame, etc.) to that one other communication device, and this second frame includes a first field indicating one or more recommended types of the sounding procedure.

[0048] FIG. 3B shows a flowchart illustrating a communication method according to the present disclosure. In step 318, a step of generating a first frame for a sounding procedure is executed. In step 320, a step of transmitting the first frame to each of one or more peer communication devices is executed, where the first frame includes a first field indicating the target application of the sounding procedure.

[0049] In an embodiment, the first frame may include a second field indicating the target type of the sounding procedure. In another embodiment, the first frame may include a third field indicating one or more target communication devices (such as a STA, etc.) that will engage in the sounding procedure.

[0050] Figure 4 shows a flowchart illustrating a sounding set-up procedure 400 between two APs, specifically between a source AP 402 and a destination AP 404, according to the present disclosure. For example, contention-based channel access procedures such as enhanced distributed channel access (EDCA) procedures are shown by blocks 405, 413, and in addition, SIFS 409, 417 are shown. The sounding set-up procedure includes sounding set-up request and response frames exchanged between the source AP of the multi-AP adjustment candidate set and each destination AP (singular or plural). The sounding set-up request or response frame is an EHT action frame. In particular, the source AP 402 may generate a first frame 408, such as an EHT action frame (hereinafter referred to as a "sounding set-up request frame") including a sounding set-up request, for example, to initiate the sounding set-up procedure 400. The wireless transmitter of the source AP 402 may transmit the sounding set-up request frame 408 to the destination AP 404.

[0051] Upon receipt of the sounding set-up request frame 408, SIFS 409 may become active, and at 410, the destination AP 404 may transmit an acknowledgement (Ack) frame 412 to the source AP 402 to indicate successful receipt of the sounding set-up request frame 408.

[0052] After the last symbol of the Ack frame 412 is transmitted, the destination AP 404 may generate a second frame 416, which may be, for example, an EHT action frame including a sounding set-up response (hereinafter referred to as a "sounding set-up request frame") to respond to the sounding set-up request frame 408 and indicate whether the destination AP 404 is ready for subsequent sounding procedures.

[0053] Upon receiving the sounding setup response frame 416, SIFS 417 may be enabled, and at 418, the source AP 402 may send an Ack frame 420 to the destination AP 404 to indicate successful reception of the sounding setup response frame 416.

[0054] FIG. 5A shows an example of the format of an EHT action frame 500 that can be used as the sounding setup request frame 408 or the sounding setup response frame 416 shown in FIG. 4. The EHT action frame 500 may include (or consist of) a frame control field, a duration field, three address fields (addresses 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 (addresses 1, 2, and 3 respectively), the sequence control field, and the HT control field may be grouped as a MAC header. The frame body field 502 may further include a category field, an EHT action field, a dialog token field, a sounding setup element field 504, and other elements or fields.

[0055] Figure 5B shows an example of the format of the sounding setup element field 504 of the EHT action frame 500 when the action type field 506 indicates "request" for the sounding setup request frame. The sounding 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 506 indicates "request", the sounding setup element field 502 may further include a target sounding usage field 510, a target sounding type field 512, and a target STA field 514. The AP set ID field 508 identifies a multi-AP adjustment candidate set including the source AP and at least one destination AP. The target STA field 514 indicates one or more STAs that belong to the BSS of the source AP and / or the BSS of at least one destination AP and are considered to participate in subsequent sounding procedures. Note that in an 11be EHT WLAN, the AP(s) and STA(s) participating in single-AP or multi-AP-based sounding procedures may belong to different BSSs. In an 11be EHT WLAN, an STA can be identified by the BSSID (BSS identifier) of the AP to which the STA is associated and its own STA ID. Alternatively, an STA can be identified by the AP ID of the AP to which the STA is associated, the AP set ID of the multi-AP adjustment candidate set including that AP, and the STA ID of that STA. Further details of the target sounding usage field 510 and the target sounding type field 512 are detailed below.

[0056] Figure 5C shows another example of the format of the sounding setup element field 504 for the EHT action frame 500 when the action type field 506 indicates "response" for the sound set up response frame. Similarly, the sounding 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 indicates "response", the sounding setup element field 504 may further include a recommended sounding type field 514 for indicating one or more recommended types of the sounding procedure. Further details of the recommended sounding type field 514 are detailed below.

[0057] The common source AP 402 may determine target sounding parameters, such as a target sounding application and a target sounding type, based on the capability negotiation between APs within the multi-AP adjustment candidate set performed before the sounding setup procedure.

[0058] The target sounding application field 510 indicates the target application of the sounding procedure following the sounding setup procedure (i.e., the target scheme of the multi-AP adjustment that uses the result of the sounding procedure). The target scheme of the multi-AP adjustment is one of the following. · Adjusted spatial reuse · Adjusted orthogonal frequency division multiple access (OFDMA) · Adjusted beamforming, and · Joint beamforming (also known as joint transmission).

[0059] The target sounding type field 512 indicates the target type of the sounding procedure following the sounding setup procedure, which is one of the following. · Single-AP-based explicit sounding, · Single AP-based implicit sequential sounding, · Single AP-based implicit joint sounding, · Multi-AP-based explicit sequential sounding, · Multi-AP-based explicit joint sounding, · Multi-AP-based implicit sequential sounding, · Multi-AP-based implicit joint sounding, · Multi-AP-based hybrid sequential sounding, and · Multi-AP-based hybrid joint sounding.

[0060] Furthermore, in the sounding setup response frame 416, the recommended sounding type field 514 indicates one or more recommended types of sounding procedures following the sounding setup procedure, which is one of the following. · Single AP-based explicit sounding, · Single AP-based implicit sequential sounding, · Single AP-based implicit joint sounding, · Multi-AP-based explicit sequential sounding, · Multi-AP-based explicit joint sounding, · Multi-AP-based implicit sequential sounding, · Multi-AP-based implicit joint sounding, and · Exemption from multi-AP-based sounding is requested.

[0061] When the destination AP 404 makes any recommendation on the sounding type in the recommended sounding type field 514, the destination AP 404 should consider the target scheme for multi-AP adjustment. As an example, the result of multi-AP based sequential sounding cannot be used for joint beamforming. As another example, the result of single-AP based sounding can be used for adjusted spatial reuse and adjusted OFDMA, but cannot be used for adjusted beamforming and joint beamforming.

[0062] After receiving the sounding setup request frame 408 from the source AP 402, the destination AP 404 may determine whether it is necessary to reconfigure its own transmission and reception (TX / RX) chain for subsequent sounding procedures according to the information about the target STA(s) indicated in the sounding setup request frame 408.

[0063] According to an embodiment of the present disclosure, when the destination AP 404 is not ready for the target sounding type indicated in the sounding setup request frame 408, the destination AP 404 may recommend one or more different sounding types in the sounding setup response frame 416, or request to be exempted from subsequent sounding procedures.

[0064] According to another embodiment of the present disclosure, when the destination AP 404 supports single-AP based implicit sounding or multi-AP based implicit sounding and its TX / RX chain has been reconfigured for subsequent sounding procedures, a calibration procedure may be initiated by the destination AP 404 to re-calibrate its TX / RX chain before sending the sounding setup response frame 416 to the source AP 402. However, if the calibration procedure is not successfully completed, the destination AP 404 may not recommend any single-AP based or multi-AP based implicit sounding procedures.

[0065] After the sounding set-up procedure between the source AP of the multi-AP adjustment candidate set and each destination AP (single or multiple) is completed, the sounding procedure may be started. The sounding procedure may be started by transmitting an EHT NDP announcement frame indicating one of the following types of sounding procedures. · Single-AP based explicit sounding, · Single-AP based implicit sequential sounding, · Single-AP based implicit joint sounding, · Multi-AP based explicit sequential sounding, · Multi-AP based explicit joint sounding, · Multi-AP based implicit sequential sounding, · Multi-AP based implicit joint sounding, · Multi-AP based hybrid sequential sounding, and · Multi-AP based hybrid joint sounding.

[0066] The EHT NDP announcement frame for starting the multi-AP based sounding procedure may be transmitted by the source AP.

[0067] Figure 6A shows a flowchart illustrating a single AP-based explicit sounding procedure 600 between two STAs 602, 604 in an 11be EHT WLAN according to an embodiment. The single AP-based explicit sounding procedure 600 may be initiated, for example, when an STA 1 602, which is an AP, transmits an EHT NDP announcement frame 606 to a target STA such as an STA 2 604. The EHT NDP announcement frame 606 includes the required 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, CQI feedback, and calibration feedback. When the feedback type is SU feedback or MU feedback, the required sounding feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the required sounding feedback information includes the CQI information for each subcarrier or subcarrier group. When the feedback type is calibration feedback, the required sounding feedback information includes the compressed CSI for each subcarrier or subcarrier group. Upon receipt of the EHT NDP announcement frame 606, SIFS 607 may be enabled, and at 608, the STA 1 602 may transmit an EHT sounding NDP 610 to the STA 2 604. The EHT sounding NDP 610 may include an EHT-LTF field for CSI estimation.

[0068] After the last symbol of the EHT sounding NDP610 is transmitted, SIFS611 may become active, and at 612, STA2 604 may transmit an EHT compressed beamforming / CQI frame 614 including sounding feedback information to STA1 602. In some embodiments, the sounding feedback information may be derived from CSI by STA2 604, which is estimated from the EHT-LTF field of the EHT sounding NDP610 and prepared according to its own sounding feedback parameters indicated in the EHT NDP announcement frame 606. Based on the sounding feedback information received from STA2 604, STA1 602 may determine a steering matrix and / or may be able to allocate an appropriate RU for subsequent transmissions to STA2 604.

[0069] Figure 6B shows a flowchart illustrating a single-AP-based explicit sounding procedure 620 between an AP622 and a plurality of STAs 624, 626 in an 11be EHT WLAN according to another embodiment. The single-AP-based explicit sounding procedure 620 may be initiated when the AP622 transmits an EHT NDP announcement frame 628 to target STAs such as, for example, STA1 624 and STA2 626. Similarly, the EHT NDP announcement frame 628 may include the required 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, CQI feedback, and calibration feedback. When the feedback type is SU feedback or MU feedback, the required sounding feedback information includes the compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the required sounding feedback information includes the CQI information for each subcarrier or subcarrier group. When the feedback type is calibration feedback, the required sounding feedback information includes the compressed CSI for each subcarrier or subcarrier group. Upon transmission of the EHT NDP announcement frame 628, SIFS 629 may be enabled, and at 630, the AP622 may transmit an EHT sounding NDP 632 to STA1 624 and STA2 626.

[0070] After the EHT sounding NDP632 is transmitted, SIFS633 may become active. At 634, the AP622 may transmit an EHT BFRP trigger frame 636 to request simultaneous transmission of sounding feedback information from STA1 624 and STA2 626. After the last symbol of the EHT BFRP trigger frame 636 is transmitted, SIFS637 may become active. At 638, STA1 624 and STA2 626 may simultaneously transmit their respective EHT compressed beamforming / CQI frames 640, 642 containing the sounding feedback information to the AP622. In some embodiments, the sounding feedback information may be derived from the respective CSI by STA1 624 and STA2 626, which is estimated from the EHT-LTF field of the EHT sounding NDP632 and prepared according to the respective sounding feedback parameters indicated in the EHT NDP announcement frame 628. Based on the sounding feedback information received from STA1 624 and STA2 626, the AP622 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.

[0071] According to the present disclosure, when the sounding type shown in the EHT NDP announcement frames 606, 628 is single-AP-based explicit sounding and the feedback type shown 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. On the other hand, when the sounding type shown in the EHT NDP announcement frames 606, 628 is single-AP-based explicit sounding and the feedback type shown 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 variation of the single-AP-based explicit sounding procedure shown in FIGS. 6A and 6B. Advantageously, according to the present disclosure, a single procedure 600, 620 can be used for both calibration and explicit sounding purposes.

[0072] In various embodiments, when the procedure 620 is a single-AP-based calibration procedure, the EHT NDP announcement frame 628 may indicate calibration RU allocation and calibration spatial stream (SS) allocation for each of STA1 624 and STA2 626. In particular, the data RU allocation and data SS allocation for each of STA1 624 and STA2 626 are shown in the corresponding EHT BFRP trigger frame 636. The calibration SS assigned to a STA may include the data SS assigned to that STA. In other words, the number of calibration SSs may be greater than or equal to the number of data SSs. Additionally, the calibration RU assigned to a STA may be the same as the data RU assigned to that STA.

[0073] In various embodiments, when procedures 600, 620 are single-AP-based calibration procedures, the EHT compressed beamforming / CQI frames 614, 640, 642 may include DL compressed CSI information instead of DL compressed beamforming feedback information. Further, each STA, such as STA2 604, STA1 624, STA2 626, etc., transmits multiple SSs on the EHT-LTF field of the EHT PPDU including the EHT compressed beamforming / CQI frames 614, 640, 642, and this EHT-LTF field is used for UL CSI estimation for data demodulation and calibration. In this way, the APs 602, 622 may be able to determine calibration coefficients for each of their TX antennas according to the DL compressed CSI information included in the EHT compressed beamforming / CQI frames 614, 640, 642 and the UL CSI estimation.

[0074] FIG. 7A shows a flowchart illustrating a single AP-based implicit sequential sounding procedure 700 between an AP 702 and a plurality of STAs 704, 706 in an 11be EHT WLAN according to an embodiment (Option 1). The single AP-based implicit sequential sounding procedure 700 may be initiated when the AP 702 transmits a first EHT NDP announcement frame 708 to target STAs such as, for example, STA1 704 and STA2 706. The first EHT NDP announcement frame 708 may indicate STA ordering, and for example, target STAs such as STA1 704 to STA2 706 may transmit an EHT sounding NDP to the AP 702 in this STA ordering. Additionally, the first EHT NDP announcement frame 708 may indicate a sounding RU allocation and a sounding SS allocation for the first STA in the STA ordering. After receiving the EHT NDP announcement frame 708, STAs (one or more) other than the first STA in the STA ordering, such as, for example, STA2 706, may be switched from an awake state to a doze state for power saving. At 711 after SIFS 709, the first STA in the STA ordering, such as, for example, STA1 704, may prepare a first EHT sounding NDP 712 based on its sounding RU allocation and sounding SS allocation and transmit it to the AP 702. The AP 702 may then determine the DL CSI corresponding to STA1 704 by estimating the first UL CSI from the received first EHT sounding NDP 712 and compensating the first UL CSI according to the calibration parameters obtained from the calibration procedure.

[0075] After the last symbol of the first EHT sounding NDP712 is transmitted at 713, STA1 704 may switch from the awake state to the doze state for power saving. At 715 during SIFS714, the next STA in the STA ordering, for example STA2 706, may switch to return from the doze state to the awake state. At 716 after SIFS714, AP702 may transmit a second EHT NDP announcement frame 718, which may indicate a sounding RU allocation and a sounding SS allocation for the next STA in the STA ordering. When transmitting the second EHT NDP announcement frame 718, SIFS719 may become effective, and at 720, STA2 706 may prepare a second EHT sounding NDP722 based on its sounding RU allocation and sounding SS allocation and transmit it to AP702. Then AP702 may estimate a second UL CSI from the received second EHT sounding NDP722 and determine a DL CSI corresponding to STA2 706 by compensating the second UL CSI according to the calibration parameters obtained from the calibration procedure. Further, based on the DL CSI for STA1 704 and STA2 706, AP702 may determine a steering matrix and / or may be able to 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 shown in FIG. 7A may require less sounding overhead than the single-AP-based explicit sounding procedure shown in FIG. 6B because it does not require the transmission of sounding feedback information.

[0076] Figure 7B shows a flowchart of a single-AP-based implicit sequential sounding procedure 730 between an AP 732 and a plurality of STAs 734, 736 in an 11be EHT WLAN according to another embodiment (Option 2). Similarly, the single-AP-based implicit sequential sounding procedure 730 may be initiated when the AP 732 transmits an EHT NDP announcement frame 738 to target STAs such as, for example, STA1 734 and STA2 736. The EHT NDP announcement frame 738 may indicate STA ordering, and the target STAs such as, for example, STA1 734 to STA2 736 may transmit an EHT sounding NDP to the AP 732 in this STA ordering. The EHT NDP announcement frame 738 may indicate a sounding RU assignment and a sounding SS assignment for each of the target STAs. Thus, from the sounding SS assignment for the STA, the duration of the EHT-LTF field of the EHT sounding NDP transmitted by each STA (equivalent to the transmission time of the EHT sounding NDP) can be determined. Based on the transmission times of the EHT sounding NDPs of each STA, a second EHT sounding NDP from the second STA in the STA ordering may follow after the first EHT sounding NDP from the first STA in the STA ordering.

[0077] For example, when transmitting the EHT NDP announcement frame 738, SIFS 739 may be enabled, and during 740 between SIFS 739, STAs other than the first STA in the STA ordering, such as STA2 706, may be switched from the awake state to the doze state for power saving. At 741 after SIFS, the first STA in the STA ordering, such as STA1 734, may transmit the first EHT sounding NDP 742 to the AP 732. Then the AP 732 may estimate the first UL CSI from 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 from the calibration procedure. After the last symbol of the first EHT sounding NDP 742 is transmitted at 743, STA1 734 may be switched from the awake state to the doze state for power saving. SIFS 744 may be enabled, and at 745 between SIFS 744, STA2 736 may be switched from the doze state to the awake state. At 746 after SIFS 744, STA2 736 may transmit the second EHT sounding NDP 748 to the AP 732. Then the AP 732 may estimate the second UL CSI from 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 from the calibration procedure. Further, based on the DL CSI for STA1 734 and STA2 736, the AP 732 may determine the steering matrix and / or may be able to allocate appropriate RUs for each of STA1 734 and STA2 736 for subsequent transmissions to STA1 734 and / or STA2 736. Advantageously, the single-AP-based implicit sequential sounding option 2 shown in FIG. 7B reduces the sounding overhead even further than the single-AP-based implicit sequential sounding option 1 shown in FIG. 7A.

[0078] FIG. 8 shows a flowchart of a single AP-based implicit joint sounding procedure 800 between 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 transmits an EHT NDP announcement frame 808 to target STAs such as, for example, STA1 804 and STA2 806. The EHT NDP announcement frame 808 may indicate a sounding RU assignment and a sounding SS assignment for each of the target STAs. When transmitting the EHT NDP announcement frame 808, SIFS 809 may be enabled. At 810, STA1 804 and STA2 806 may each transmit their respective EHT sounding NDPs 812, 814 to the AP 808 according to their respective sounding RU assignments and sounding SS assignments. The AP 802 may then estimate a first UL CSI from the received EHT sounding NDP 812 and estimate a second UL CSI from the received EHT sounding NDP 814, and determine DL CSIs corresponding to each of STA1 804 and STA2 806 by compensating the first UL CSI and the second UL CSI according to calibration parameters obtained from a calibration procedure. Further, based on the DL CSIs for STA1 804 and STA2 806, the AP 802 may determine a steering matrix and / or may be able to assign appropriate RUs to 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 shown in FIG. 8 may have lower sounding overhead than the single AP-based implicit sequential sounding shown in FIGS. 7A and 7B.

[0079] FIG. 9 shows a flowchart illustrating a multi-AP based explicit sequential sounding procedure 900 between a plurality of APs 902, 904 and a plurality of STAs 906, 908 in an 11be EHT WLAN. The multi-AP based explicit sequential sounding procedure 900 may be initiated when a source-sharing AP 902 transmits a first EHT NDP announcement frame 910 to destination-sharing AP(s) participating in the sounding procedure 1000 and target STAs such as STA1 906 and STA2 908. The first EHT NDP announcement frame 910 may indicate destination-sharing AP ordering, and the destination-sharing AP(s) engaged in the sounding procedure 900 may transmit the EHT NDP announcement frame and the EHT sounding NDP to target STAs such as STA1 906 and STA2 908 in this destination-sharing AP ordering. The first EHT NDP announcement frame 910 may indicate a sounding RU assignment and a sounding SS assignment for each destination-sharing AP(s) engaged in the sounding procedure 900. Each EHT NDP announcement frame may indicate sounding feedback parameters required 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 required sounding feedback information includes compressed beamforming feedback information for each subcarrier or subcarrier group. When the feedback type is CQI feedback, the required sounding feedback information includes CQI information for each subcarrier or subcarrier group. When the feedback type is calibration feedback, the required sounding feedback information includes compressed CSI for each subcarrier or subcarrier group.

[0080] When transmitting the first EHT NDP announcement frame 910, SIFS 911 may be enabled. At 912, the common source AP 902 may transmit the first EHT sounding NDP 914 to STA1 906 and STA2 908. After transmitting the first EHT sounding NDP 914, SIFS 915 may be enabled. At 916, the common source AP 902 may transmit 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 transmitted, SIFS 919 may be enabled. At 920, STA1 906 and STA2 908 may simultaneously transmit their respective first EHT compressed beamforming / CQI frames 922, 924 including sounding feedback information to the common source AP 902. Based on the sounding feedback information received from STA1 906 and STA2 908, the common source AP 902 may determine a steering matrix and / or may be able to allocate appropriate RUs for each of STA1 906 and STA2 908 for subsequent transmissions to STA1 906 and / or STA2 908.

[0081] When transmitting the first EHT compressed beamforming / CQI frames 922, 924, SIFS 925 may be enabled. At 926, the next AP in the AP ordering, for example, the destination AP 904, may transmit the second EHT NDP announcement frame 928 to STA1 906 and STA2 908. When transmitting the second EHT NDP announcement frame 928, SIFS 929 may be enabled. At 930, the destination AP 904 may transmit the second EHT sounding NDP 932 to STA1 906 and STA2 908. Similarly, after the second EHT sounding NDP 932 is transmitted, SIFS 933 may be enabled. At 934, the destination AP 904 may transmit the 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 transmitted, SIFS 937 may be enabled. At 938, STA1 906 and STA2 908 may simultaneously transmit their respective second EHT compressed beamforming / CQI frames 940, 942 containing the sounding feedback information to the destination AP 904. Based on the sounding feedback information received from STA1 906 and STA2 908, the destination AP 904 may determine the steering matrix and / or may be able to allocate appropriate RUs to each of STA1 906 and STA2 908 for subsequent transmissions to STA1 906 and / or STA2 908.

[0082] According to the present disclosure, when the sounding type shown in the EHT NDP announcement frames 910, 1010 is multi-AP-based explicit sounding and the feedback type shown in the EHT NDP announcement frames 910, 1010 is SU, MU, or CQI feedback, procedures 900, 1000 are normal multi-AP-based explicit sounding procedures. On the other hand, when the sounding type shown in the EHT NDP announcement frames 910, 1010 is multi-AP-based explicit sounding and the feedback type shown in the EHT NDP announcement frames 910, 1010 is calibration feedback, procedures 900, 1000 are multi-AP-based calibration procedures. In other words, the multi-AP-based calibration procedure is a variation of the multi-AP-based explicit sounding procedure shown in FIGS. 9 and 10. Advantageously, according to the present disclosure, a single procedure 900, 1000 can be used for both calibration and explicit sounding purposes.

[0083] In various embodiments, when procedures 900, 1000 are multi-AP-based calibration procedures, the EHT NDP announcement frames 910, 928, 1010 may indicate calibration RU assignments and calibration SS assignments for each STA such as STA1 906, STA2 908, STA1 1006, STA2 1008, etc. In particular, the data RU assignments and data SS assignments for each STA are shown in the corresponding EHT BFRP trigger frames 918, 936, 1020. The calibration SS assigned to a STA may include the data SS assigned to that STA. In other words, the number of calibration SSs may be greater than or equal to the number of data SSs. The calibration RU assigned to a STA may be the same as the data RU assigned to that STA.

[0084] In various embodiments, when procedures 900, 1000 are multi-AP based calibration procedures, the EHT compressed beamforming / CQI frames 922, 924, 940, 942, 1024, 1026 may include DL compressed CSI instead of DL compressed beamforming feedback information. Further, each STA, such as STA1 906, STA2 908, STA1 1006, STA2 1008, etc., transmits a plurality of SSs on the EHT-LTF field of an EHT PPDU including the EHT compressed beamforming / CQI frames 922, 924, 940, 942, 1024, 1026, where the EHT-LTF field is used for UL CSI estimation for data demodulation and calibration. In this way, the APs 902, 904, 1002, 1004 may be able to determine calibration coefficients for each of their TX antennas according to the DL compressed CSI included in the EHT compressed beamforming / CQI frames 922, 924, 940, 942, 1024, 1026 and the UL CSI estimation.

[0085] In various embodiments, the options for a STA to transmit an EHT compressed beamforming / CQI frame in a multi-AP based sequential calibration procedure are the following two. i) The STA may transmit the same SS on the EHT-LTF fields of a plurality of EHT PPDUs including the EHT compressed beamforming / CQI frame, or ii) the STA may transmit different SSs on the EHT-LTF fields of a plurality of EHT PPDUs including the EHT compressed beamforming / CQI frame, and as a result, the EHT-LTF overhead may be advantageously reduced. For example, assuming that STA1 906 or STA2 908 has four TX antennas and transmits two EHT compressed beamforming / CQI frames, in option 1, STA1 904 and STA2 908 may transmit four SSs on eight EHT-LTF symbols of an EHT PPDU including the EHT compressed beamforming / CQI frames 922, 924, 940, 942 using a P 8x8 matrix, while in option 2, STA1 906 and STA2 908 may transmit a P 4x4Two SUs may be transmitted on four EHT-LTF symbols of an EHT PPDU including first EHT compressed beamforming / CQI frames 922, 924 using a matrix, and STAs 1 906 and 2 908 may be P 4x4 Another two SUs may be transmitted on four EHT-LTF symbols of an EHT PPDU including second EHT compressed beamforming / CQI frames 940, 942 using a matrix.

[0086] FIG. 10 shows a flowchart illustrating a multi-AP-based explicit joint sounding procedure 1000 among a plurality of APs 1002, 1004 and a plurality of STAs 1006, 1008 in an 11be EHT WLAN. The multi-AP-based explicit joint sounding procedure 1000 may be initiated when a source-sharing AP 1002 transmits an EHT NDP announcement frame 1010 to destination-sharing AP(s) participating in the sounding procedure 1000 and target STAs such as STA1 1006 and STA2 1008. The EHT NDP announcement frame 1010 may indicate a sounding RU assignment and a sounding SS assignment for each destination-sharing AP engaged in the sounding procedure 1000. The EHT NDP announcement frame 1010 may indicate sounding feedback parameters required for each pair of the STA and the AP among the source-sharing AP 1002, the destination-sharing AP 1004, and the target STAs 1006, 1008. The sounding feedback parameters required for each AP-STA pair may include AP-dependent sounding feedback parameters such as a feedback bandwidth and the number of columns of a compressed beamforming feedback matrix, and AP-independent sounding feedback parameters such as a feedback type, subcarrier grouping, and quantization resolution. Here, in terms of the sounding results used for joint beamforming, for the STA, each AP-independent sounding feedback parameter may be set to the same value for all AP-STA pairs in the EHT NDP announcement frame 1010, while each AP-dependent sounding feedback parameter may be set to a different value for each AP-STA pair in the EHT NDP announcement frame 1010.

[0087] When transmitting the EHT NDP announcement frame 1010, SIFS 1011 may be enabled. At 1012, for example, all APs engaged in the sounding procedure 1000, such as the source-sharing AP 1002 and the destination-sharing AP 1004, may simultaneously transmit their respective EHT sounding NDPs 1014, 1016 to all target STAs, such as STA1 1006 and STA2 1008. After the EHT sounding NDPs 1014, 1016 are transmitted, SIFS 1017 may be enabled. At 1018, AP 1002 may transmit 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 transmitted, SIFS 1021 may be enabled. At 1022, STA1 1006 and STA2 1008 may simultaneously transmit their respective EHT compressed beamforming / CQI frames 1024, 1026 containing the requested sounding feedback information to APs 1002, 1004. Based on the sounding feedback information received from STA1 1006 and STA2 1008, APs 1002, 1004 may determine the steering matrix and / or may be able to allocate appropriate RUs to each of STA1 1006 and STA2 1008 for subsequent transmissions to STA1 1006 and / or STA2 1008. Alternatively, the source-sharing AP 1002 may determine the steering matrix and / or may be able to allocate appropriate RUs to each AP-STA pair. The source-sharing AP 1002 may then notify the destination-sharing AP 1004 of the corresponding steering matrix and / or the RU allocation to STA1 1006 and / or STA2 1008 for subsequent transmissions to STA1 1006 and STA2 1008. Advantageously, the multi-AP-based explicit joint sounding shown in FIG. 10 has less sounding overhead than the multi-AP-based explicit sequential sounding shown in FIG. 9.

[0088] FIG. 11A shows a flowchart of a multi-AP based implicit sequential sounding procedure 1100 between a plurality of APs 1102, 1104 and a plurality of STAs 1106, 1108 in an 11be EHT WLAN according to an embodiment (Option 1). The multi-AP based implicit sequential sounding procedure 1100 may be started when the source-sharing AP 1102 transmits a first EHT NDP announcement frame 1110 to the destination-sharing AP(s) participating in the sounding procedure 1100 and target STAs such as STA1 1106 and STA2 1108. The first EHT NDP announcement frame 1110 may indicate the destination-sharing AP(s) participating in the sounding procedure 1100, such as the destination-sharing AP 1104. The first EHT NDP announcement frame 1110 may also indicate the STA ordering. For example, the target STAs such as STA1 1106 to STA2 1108 may transmit the EHT sounding NDP to the source-sharing AP 1102 and all the destination-sharing APs participating in the sounding procedure 1100 in this STA ordering. Each EHT NDP announcement frame 1110, 1120 may indicate the sounding RU assignment and the sounding SS assignment for the corresponding STA. When transmitting the first EHT NDP announcement frame 1110, SIFS 1111 may be enabled. During 1112 between SIFSs, one or more STAs other than the first STA in the STA ordering, such as STA2 1108, may be switched from the awake state to the doze state for power saving, and at 1113 after the SIFS, the first STA in the STA ordering, such as STA1 1106, may transmit the first EHT sounding NDP 1114 to the source-sharing AP 1102 and the destination-sharing AP 1104. Then, the source-sharing AP 1102 and the destination-sharing AP 1104 may determine the DL CSI for STA1 1106 by estimating the UL CSI from the received first EHT sounding NDP 1114 and compensating the UL CSI according to the calibration parameters obtained from the calibration procedure.Furthermore, based on the DL CSI for STA1 1106, the source AP 1102 and the destination AP 1104 may determine a steering matrix and / or may allocate an appropriate RU for STA1 1106 for subsequent transmissions to STA1 1106.

[0089] After the last symbol of the first EHT sounding NDP 1114 is transmitted at 1115, STA1 1106 may switch from the awake state to the doze state for power saving. SIFS 1116 may become active, and at 1117 during SIFS 1116, the next STA in the STA ordering, for example STA2 1108, may switch from the doze state to the awake state. At 1118 after SIFS 1116, AP1102 may transmit a second EHT NDP announcement frame 1120. When transmitting the second EHT NDP announcement frame 1120, SIFS 1121 may become active, and at 1122, STA2 1108 may transmit a second EHT sounding NDP 1124 to the source AP 1102 and the destination AP 1104. The source AP 1102 and the destination AP 1104 then estimate the UL CSI from the received second EHT sounding NDP 1124 and determine the DL CSI for STA2 1108 by compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Furthermore, based on the DL CSI for STA2 1108, the source AP 1102 and the destination AP 1104 may determine a steering matrix and / or may allocate an appropriate RU for STA2 1108 for subsequent transmissions to STA2 1108. Advantageously, the multi-AP based implicit sequential sounding procedure shown in FIG. 11A may require less sounding overhead than the multi-AP based explicit sounding procedure shown in FIG. 9 or FIG. 10 because there is no need to transmit sounding feedback information.

[0090] FIG. 11B shows a flowchart of a multi-AP based implicit sequential sounding procedure 1130 between a plurality of APs 1132, 1134 and a plurality of STAs 1136, 1138 in an 11be EHT WLAN according to another embodiment (Option 2). Similarly, the multi-AP based implicit sequential sounding procedure 1130 may be started when the AP 1132 transmits an EHT NDP announcement frame 1140 to a shared destination AP(s) participating in the sounding procedure 1130 and target STAs such as, for example, STA1 1136 and STA2 1138. The EHT NDP announcement frame 1140 indicates a shared destination AP(s) participating in the sounding procedure 1130, such as, for example, the shared destination AP 1134. The EHT NDP announcement frame 1140 may indicate an STA ordering, and target STAs such as, for example, STA1 1136 to STA2 1138 may transmit an EHT sounding NDP to the AP 1132 and a shared destination AP(s) participating in the sounding procedure 1130 in this STA ordering. The EHT NDP announcement frame 1140 may further indicate a sounding RU assignment and a sounding SS assignment for each STA. Thus, the EHT-LTF field duration of the EHT sounding NDP transmitted by each STA (equivalent to the transmission time of the EHT sounding NDP) can be determined from the SS assignment for that STA. Based on the transmission time of the EHT sounding NDP of each STA, a second EHT sounding NDP from a second STA in the STA ordering can follow after the first EHT sounding NDP from the first STA in the STA ordering.

[0091] For example, when transmitting the EHT NDP announcement frame 1140, SIFS 1141 may be enabled. During 1142 between SIFS 1141, a STA other than the first STA in the STA ordering, such as STA2 1138, may be switched from the awake state to the doze state for power saving. At 1143 after SIFS, the first STA in the STA ordering, such as STA1 1136, may transmit the first EHT sounding NDP 1144 to the source AP 1132 and the destination AP 1134. Then, the source AP 1132 and the destination AP 1134 may estimate the UL CSI from the received first EHT sounding NDP 1144 and determine the DL CSI for STA1 1136 by compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. At 1145, after transmitting the last symbol of the first EHT sounding NDP 1144, STA1 1136 may be switched from the awake state to the doze state for power saving. SIFS 1148 may be enabled. During 1147 between SIFS 1148, STA2 1138 may be switched back from the doze state to the awake state. At 1148 after SIFS 1146, STA2 1138 may transmit the second EHT sounding NDP 1150 to the source AP 1132 and the destination AP 1134. Then, the source AP 1132 and the destination AP 1134 may estimate the UL CSI from the received second EHT sounding NDP 1150 and determine the DL CSI for STA2 1138 by compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Further, based on the DL CSI for STA1 1136 and STA2 1138, the source AP 1132 and the destination AP 1134 may determine the steering matrix and / or may be able to allocate appropriate RUs for each of STA1 1136 and STA2 1138 for subsequent transmissions to STA1 1136 and / or STA2 1138.Advantageously, the multi-AP based implicit sequential sounding option 2 shown in FIG. 11B further reduces the sounding overhead as compared to the multi-AP based implicit sequential sounding option 1 shown in FIG. 11A.

[0092] FIG. 12 shows a flowchart illustrating a multi-AP based implicit joint sounding procedure 1200 between a plurality of APs 1202, 1204 and a plurality of STAs 1206, 1208 in an 11be EHT WLAN. The multi-AP based implicit joint sounding procedure 1200 may be initiated when a source AP 1202 transmits an EHT NDP announcement frame 1210 to a destination AP (s) participating in the sounding procedure 1200, such as the destination AP 1204, and target STAs, such as STA1 1206 and STA2 1208. The EHT NDP announcement frame 1210 may indicate the destination AP (s) participating in the sounding procedure 1200, and in addition, may indicate a sounding RU allocation and a sounding SS allocation for each STA. When transmitting the EHT NDP announcement frame 1210, SIFS 1211 may be enabled, and at 1212, STA1 1206 and STA2 1208 may transmit their respective EHT sounding NDPs 1214, 1216 to the source AP 1202 and the destination AP 1204. Then, the source AP 1202 and the destination AP 1204 may estimate a first UL CSI from the received EHT sounding NDP 1214 and compensate the first UL CSI according to the calibration parameters obtained from the calibration procedure to determine the DL CSI for STA1 1206. Similarly, the source AP 1202 and the destination AP 1204 may estimate a second UL CSI from the received EHT sounding NDP 1216 and compensate the second UL CSI according to the calibration parameters obtained from the calibration procedure to determine the DL CSI for STA2 1208. Further, based on the DL CSI for STA1 1206 and STA2 1208, the source AP 1202 and the destination AP 1204 may determine a steering matrix and / or may be able to allocate appropriate RUs for each of STA1 1206 and STA2 1208 for subsequent transmissions to STA1 1206 and / or STA2 1208.Advantageously, the multi-AP based implicit joint sounding shown in FIG. 12 may require less sounding overhead than the multi-AP based implicit sequential sounding shown in FIGS. 11A and 11B.

[0093] According to the present disclosure, the source AP and the destination AP(s) engaged in the multi-AP based hybrid sounding procedure are divided into two groups, and the APs in Group 1 include the AP(s) participating in the explicit sounding part of the multi-AP based hybrid sounding procedure, and the APs in Group 2 include the AP(s) participating in the implicit sounding part of the multi-AP based hybrid sounding procedure.

[0094] Figure 13A shows a flowchart illustrating a multi-AP based hybrid sequential sounding procedure 1300 between a plurality of destination APs 1302, 1304, 1306 and a STA 1308 in an 11be EHT WLAN according to an embodiment. In this embodiment, the source AP 1302 and the destination AP1 1304 are APs of group 1, while the destination AP2 1306 is an AP of group 2. The multi-AP based hybrid sequential sounding procedure 1300 may start when the source AP 1302 transmits a first EHT NDP announcement frame 1310 to all destination APs (singular or plural) (e.g., destination APs 1304, 1306) participating in the sounding procedure 1300 and the target STA 1308. The first EHT NDP announcement frame 1310 may indicate the ordering of group 2 APs and group 1 APs, and each of the group 1 APs may transmit an EHT NDP announcement frame and an EHT sounding NDP to the target STA in this ordering. The first EHT NDP announcement frame 1310 may indicate a sounding RU allocation and a sounding SS allocation for each of the group 1 APs. Each EHT NDP announcement frame may indicate a sounding RU allocation and a sounding SS allocation for the target STA 1308. Each EHT NDP announcement frame may indicate requested sounding feedback parameters for the target STA 1308, 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 transmitting the first EHT NDP announcement frame 1310, SIFS 1311 may be enabled, and at 1312, the source AP 1302 may transmit the first EHT sounding NDP 1314 to the STA 1308.After the last symbol of the first EHT sounding NDP1314 is transmitted, SIFS1315 may become active, and at 1316, STA1308 transmits a first EHT compressed beamforming / CQI frame 1318 containing sounding feedback information to the source AP1302. Note that the EHT-LTF field of the EHT PPDU containing the first EHT compressed beamforming / CQI frame 1318 may also be used for CSI estimation for implicit sounding by APs (single or multiple) in group 2, such as destination AP2 1306. Based on the sounding feedback information received from STA1308, the source AP1302 may determine a steering matrix and / or may allocate an appropriate RU to STA1308 for subsequent transmissions to STA1308.

[0095] When transmitting the first EHT compressed beamforming / CQI frame 1318, SIFS 1319 may be enabled. At 1320, the next AP in the ordering of the APs in group 1, for example, the destination-sharing AP1 1304, may transmit the second EHT NDP announcement frame 1322 to the STA 1308. When transmitting the second EHT NDP announcement frame 1322, SIFS 1323 may be enabled. At 1324, the destination-sharing AP1 1304 may transmit the second EHT sounding NDP 1326 to the STA 1308. Similarly, after the second EHT sounding NDP 1326 is transmitted, SIFS 1327 may be enabled. At 1328, the STA 1308 may transmit the second EHT compressed beamforming / CQI frame 1330 including sounding feedback information to the destination-sharing AP1 1304. Note that the EHT-LTF field of the EHT PPDU including the second EHT compressed beamforming / CQI frame 1330 may also be used for implicit sounding by the APs (single or multiple) in group 2, such as the destination-sharing AP2 1306. Based on the sounding feedback information received from the STA 1308, the source-sharing AP 1304 may determine the steering matrix and / or may allocate an appropriate RU to the STA 1308 for subsequent transmissions to the STA 1308. Further, the destination-sharing AP2 1306 may estimate the UL CSI from the EHT-LTF field of the EHT PPDU including the first and second EHT compressed beamforming / CQI frames 1318 and 1330, and may determine the DL CSI corresponding to the STA 1308 by compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Then, the destination-sharing AP1306 may determine the steering matrix and / or may allocate an appropriate RU to the STA 1308 based on the DL CSI for subsequent transmissions to the STA 1308.

[0096] FIG. 13B shows a flowchart of a multi-AP-based hybrid sequential sounding procedure 1340 between a plurality of destination APs 1342, 1344, 1346 and a plurality of STAs 1348, 1350 in an 11be EHT WLAN according to an embodiment. In this embodiment, the source AP 1342 and the destination AP1 1344 are APs of group 1, while the destination AP2 1346 is an AP of group 2. The multi-AP-based hybrid sequential sounding procedure 1340 may be started when the source AP 1342 transmits a first EHT NDP announcement frame 1352 to all destination APs (singular or plural) (e.g., destination APs 1344, 1346) participating in the sounding procedure 1340 and the target STAs 1348, 1350. The first EHT NDP announcement frame 1352 may indicate the ordering of the APs in group 2 and the APs in group 1, and each of the APs in group 1 may transmit an EHT NDP announcement frame and an EHT sounding NDP to the target STAs in this ordering. The first EHT NDP announcement frame 1352 may indicate a sounding RU allocation and a sounding SS allocation for each of the APs in group 1. Each EHT NDP announcement frame may indicate a sounding RU allocation and a sounding SS allocation for each of STA1 1348 and STA2 1350. In particular, 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 may include the data SS. In other words, the number of sounding SSs may be greater than or equal to the number of data SSs. The data RU allocation may be the same as the sounding RU allocation for each STA. Each EHT NDP announcement frame may indicate request sounding feedback parameters for each of the target STAs 1348, 1350, 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 transmitting the first EHT NDP announcement frame 1352, SIFS1353 may be enabled, and at 1354, the source AP1342 may transmit the first EHT sounding NDP1356 to STA1 1348 and STA2 1350. After the last symbol of the first EHT sounding NDP1356 is transmitted, SIFS1357 may be enabled, and at 1358, the source AP1342 may transmit an EHT BFRP trigger frame 1360 to request the simultaneous transmission of sounding feedback information from STA1 1348 and STA2 1350. When receiving the EHT BFRP trigger frame 1360, SIFS1361 may be enabled, and at 1362, STA1 1348 and STA2 1350 may simultaneously transmit their respective first EHT compressed beamforming / CQI frames 1364, 1366 including the sounding feedback information to the source AP1342. Note that the EHT-LTF field of the EHT PPDU including the first EHT compressed beamforming / CQI frames 1364, 1366 can also be used for CSI estimation for implicit sounding by APs (one or more) in group 2, such as the destination AP2 1346. Based on the sounding feedback information received from STA1 1348 and STA2 1350, the source AP1342 may determine the steering matrix and / or may be able to allocate appropriate RUs for each of STA1 1348 and STA2 1350 for subsequent transmissions to STA1 1348 and STA2 1350.

[0097] When transmitting the first EHT compressed beamforming / CQI frames 1364, 1366, SIFS 1367 may be enabled. At 1368, the next AP in the ordering of the APs in group 1, for example, the destination sharing AP1 1344, may transmit the second EHT NDP announcement frame 1370 to STA1 1348 and STA2 1350. When transmitting the second EHT NDP announcement frame 1370, SIFS 1371 may be enabled. At 1372, the destination sharing AP1 1344 may transmit the second EHT sounding NDP 1374 to STA1 1348 and STA2 1350. Similarly, after the second EHT sounding NDP 1374 is transmitted, SIFS 1375 may be enabled. At 1376, the source sharing AP 1342 may transmit the EHT BFRP trigger frame 1378 to request the simultaneous transmission of sounding feedback information from STA1 1348 and STA2 1350. When receiving the EHT BFRP trigger frame 1378, SIFS 1379 may be enabled. At 1380, STA1 1348 and STA2 1350 simultaneously transmit their respective second EHT compressed beamforming / CQI frames 1382, 1384 including the sounding feedback information to the source sharing AP 1344. Note that the EHT-LTF field of the EHT PPDU including the second EHT compressed beamforming / CQI frames 1382, 1384 can also be used for CSI estimation for implicit sounding by the APs (singular or plural) in group 2, such as the destination sharing AP2 1346. Based on the sounding feedback information received from STA1 1348 and STA2 1350, the destination sharing AP 1344 may determine the steering matrix and / or may be able to allocate appropriate RUs for each of STA1 1348 and STA2 1350 for subsequent transmissions to STA1 1348 and STA2 1350.Furthermore, the destination AP2 1346 may be able to determine the DL CSI for the STA1 1348 by estimating the UL CSI from the EHT-LTF field of the EHT PPDU including the first and second EHT compressed beamforming / CQI frames 1364, 1382 and compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Then, the destination AP2 1346 may determine the steering matrix and / or may be able to allocate an appropriate RU for the STA1 1348 based on the DL CSI for subsequent transmissions to the STA1 1348. Similarly, the destination AP2 1346 may be able to determine the DL CSI for the STA2 1350 by estimating the UL CSI from the EHT-LTF field of the EHT PPDU including the first and second EHT compressed beamforming / CQI frames 1366, 1384 and compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Then, the destination AP2 1346 may determine the steering matrix and / or may be able to allocate an appropriate RU for the STA2 1350 based on the DL CSI for subsequent transmissions to the STA2 1350.

[0098] FIG. 14A shows a flowchart of a multi-AP-based hybrid joint sounding procedure 1400 between a plurality of destination APs 1402, 1404, 1406 and a STA 1408 in an 11be EHT WLAN according to an embodiment. In this embodiment, the source AP 1402 and the destination AP1 1404 are APs of group 1, while the destination AP2 1406 is an AP of group 2. The multi-AP-based hybrid sequential sounding procedure 1400 may be started when the source AP 1402 transmits an EHT NDP announcement frame 1410 to all destination AP(s) (e.g., destination APs 1404, 1406) participating in the sounding procedure 1400 and the target STA 1408. The EHT NDP announcement frame 1410 may indicate the ordering of the group 2 APs and the group 1 APs, where each of the group 1 APs may transmit an EHT sounding NDP to the target STA. The EHT NDP announcement frame 1410 may indicate the sounding RU allocation and the sounding SS allocation for each of the group 1 APs. The EHT NDP announcement frame may indicate the sounding RU allocation and the sounding SS allocation for the target STA 1408. The EHT NDP announcement frame may indicate the requested sounding feedback parameters for each pair of the target STA 1408 and the group 1 APs, 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 transmitting the EHT NDP announcement frame 1410, SIFS 1411 may be enabled, and at 1412, the source AP 1402 and the destination AP 1404 may simultaneously transmit their respective EHT sounding NDPs 1414, 1416 to the STA 1408.After the last symbol of the EHT sounding NDP1414, 1416 is transmitted, SIFS1417 may become effective. At 1418, STA1408 transmits an EHT compressed beamforming / CQI frame 1419 containing sounding feedback information to the source AP1402 and the destination 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 for implicit sounding by APs (single or multiple) in group 2, such as the destination AP2 1406. Based on the sounding feedback information received from STA1408, the source AP1402 and the destination AP1 1404 can determine the steering matrix and / or can allocate an appropriate RU to STA1408 for subsequent transmissions to STA1408. Further, the destination AP2 1406 may be able to determine the DL CSI for STA1408 by estimating the UL CSI from the EHT-LTF field of the EHT PPDU containing the EHT compressed beamforming / CQI frame 1419 and compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Then, the destination AP2 1406 can determine the steering matrix and / or can allocate an appropriate RU to STA1408 based on the DL CSI for subsequent transmissions to STA1408.

[0099] Figure 14B shows a flowchart illustrating a multi-AP based hybrid joint sounding procedure 1420 among a plurality of destination APs 1422, 1424, 1426 and a plurality of STAs 1428, 1430 in an 11be EHT WLAN according to an embodiment. In this embodiment, the source AP 1422 and the destination AP1 1424 are APs of group 1, while the destination AP2 1426 is an AP of group 2. The multi-AP based hybrid joint sounding procedure 1420 may be initiated when the source AP 1422 transmits an EHT NDP announcement frame 1432 to all destination APs (singular or plural) (e.g., destination APs 1424, 1426) participating in the sounding procedure 1420 and the target STAs 1428, 1430. The EHT NDP announcement frame 1432 may indicate the ordering of the APs of group 2 and the APs of group 1, where each of the APs of group 1 may transmit an EHT sounding NDP to the target STA1 1428 and STA2 1430. The EHT NDP announcement frame 1432 may indicate a sounding RU allocation and a sounding SS allocation for each of the APs of group 1. The EHT NDP announcement frame 1432 may indicate a sounding RU allocation and a sounding SS allocation for each of the STAs 1428 and 1430. In particular, the data RU allocation and the data SS allocation for each of the STAs 1428 and 1430 are indicated in the corresponding EHT BFRP trigger frame 1442. The sounding SS may include the data SS. In other words, the number of sounding SSs may be greater than or equal to the number of data SSs. The data RU allocation may be the same as the sounding RU allocation for each STA. The EHT NDP announcement frame 1432 may indicate request sounding feedback parameters for each of the target STAs 1428, 1430, such as feedback bandwidth, feedback type, subcarrier grouping, quantization resolution, and the number of columns of the compressed beamforming feedback matrix, etc.The feedback type is one of SU feedback, MU feedback, and CQI feedback. When transmitting the EHT NDP announcement frame 1432, SIFS 1433 may be enabled. At 1434, the source AP 1422 and the destination AP1 1424 may each transmit their EHT sounding NDPs 1436, 1438 to STA1 1428 and STA2 1430. After the last symbol of the EHT sounding NDPs 1436, 1438 is transmitted, SIFS 1439 may be enabled. At 1440, the source AP 1422 may transmit an EHT BFRP trigger frame 1442 to request the simultaneous transmission of sounding feedback information from STA1 1428 and STA2 1430. When receiving the EHT BFRP trigger frame 1442, SIFS 1443 may be enabled. At 1444, STA1 1428 and STA2 1430 simultaneously transmit their respective EHT compressed beamforming / CQI frames 1446, 1448 containing the sounding feedback information to the source AP 1422 and the destination AP1 1424. Note that the EHT-LTF field of the EHT PPDU including the EHT compressed beamforming / CQI frames 1446, 1448 can also be used for CSI estimation for implicit sounding by APs (single or multiple) in group 2, such as the destination AP2 1426. Based on the sounding feedback information received from STA1 1428 and STA2 1430, the source AP 1422 and the destination AP1 1424 may determine the steering matrix and / or may be able to allocate appropriate RUs for each of STA1 1428 and STA2 1430 for subsequent transmissions to STA1 1428 and / or STA2 1430.Furthermore, the destination AP2 1426 may be able to determine the DL CSI for the STA1 1428 by estimating the UL CSI from the EHT-LTF field of the EHT PPDU including the EHT compressed beamforming / CQI frame 1446 and compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Then, the destination AP2 1426 may determine the steering matrix and / or may be able to allocate an appropriate RU for the STA1 1428 based on the DL CSI for subsequent transmissions to the STA1 1428. Similarly, the destination AP2 1426 may be able to determine the DL CSI for the STA1430 by estimating the UL CSI from the EHT-LTF field of the EHT PPDU including the EHT compressed beamforming / CQI frame 1448 and compensating the UL CSI according to the calibration parameters obtained from the calibration procedure. Then, the destination AP2 1426 may determine the steering matrix and / or may be able to allocate an appropriate RU for the STA1430 based on the DL CSI for subsequent transmissions to the STA1430.

[0100] FIG. 15 shows an example of the format of the EHT NDP announcement frame 1500. The EHT NDP announcement frame 1500 may include (or consist of) a frame control field, a duration field, an RA (recipient STA address) field, a TA (transmitting STA address) field, a sounding dialog token field, a sounding 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 may be grouped as a MAC header.

[0101] When the sounding type field 1502 indicates single AP-based explicit sounding, the AP-STA information field 1504 for single AP-based explicit sounding may include one or more STA feedback information fields 1602 as shown in FIG. 16A. The STA feedback information field 1602 may include (or consist of) a target STA field, a feedback bandwidth field, a feedback type field, a subcarrier grouping field, a quantization resolution field, and a number of columns field of the compressed beamforming feedback matrix. In some embodiments, the STA feedback information field is used to indicate the sounding feedback parameters required for the STA indicated in the target STA field.

[0102] When the sounding type field 1502 indicates single AP-based implicit sounding, the AP-STA information field 1504 for single AP-based implicit sounding may include one or more STA sounding information fields 1604 as shown in FIG. 16B. The STA sounding information field 1604 may include (or consist of) a target STA field, an STA sounding RU allocation field, and an STA sounding SS allocation field. In some embodiments, the STA sounding information field is used to indicate the sounding RU allocation and sounding SS allocation for the STA indicated in the target STA field.

[0103] When the sounding type field 1502 indicates multi-AP-based explicit sounding, the AP-STA information field 1504 for the multi-AP-based explicit sounding may include one or more AP-STA explicit sounding information fields 1606 as shown in FIG. 16C. The AP-STA explicit sounding information field 1606 may include (or consist of) an AP sounding information field 1608 and one or more STA feedback information fields 1602 as shown in FIG. 16A. The AP sounding information field 1608 may further include a target AP field, an AP sounding RU allocation field, and an AP sounding SS allocation field. In some embodiments, the AP-STA explicit sounding information field is used to indicate the sounding RU allocation and sounding SS allocation for the AP indicated in the target AP field and the corresponding sounding feedback parameters for each STA.

[0104] When the sounding type field 1502 indicates multi-AP-based implicit sounding, the AP-STA information field 1504 for the multi-AP-based implicit sounding may include one or more target AP fields and one or more STA sounding information fields 1604 as shown in FIG. 16B. In one embodiment, the one or more target AP fields are used to indicate the shared destination AP(s) participating in the multi-AP-based implicit sounding, and the one or more STA sounding information fields are used to indicate the sounding RU allocation and sounding SS allocation for each target STA.

[0105] Furthermore, when the sounding type field 1502 indicates multi-AP-based hybrid sounding, the AP-STA information field 1504 may include one or more AP-STA explicit sounding information fields 1606 as shown in FIG. 16C, indicating information necessary for the explicit sounding part of the multi-AP-based hybrid sounding, one or more target AP fields indicating information necessary for the implicit sounding part of the multi-AP-based hybrid sounding, and one or more STA sounding information fields 1604 as shown in FIG. 16B.

[0106] FIG. 17 shows the configuration of a communication device such as an AP according to the present disclosure. Similar to the schematic example of the communication device 300 shown in FIG. 3A, the communication device 1700 includes a circuit 1702, at least one wireless transmitter 1710, at least one wireless receiver 1712, and at least one antenna 1714 (only one antenna is shown in FIG. 17 for simplicity). The circuit 1702 may include at least one controller 1708, and this controller 1708 is used for the execution assisted by the software and hardware of the tasks for which it is designed to perform communication for channel sounding. The circuit 1702 may further include a transmission signal generator 1704 and a reception signal processor 1706. The at least one controller 1708 may control the transmission signal generator 1704 and the reception signal processor 1706. The transmission 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, for example, an EHT NDP announcement frame, an EHT action frame, or an EHT BFRP trigger frame. The control signaling generator 1724 may generate a 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 NDP announcement frame, the EHT action frame, or the EHT BFRP trigger frame). The PPDU generator 1726 may generate a PPDU (e.g., the EHT sounding NDP, or the EHT PPDU including the EHT NDP announcement frame, the EHT action frame, or the EHT BFRP trigger frame).

[0107] The received 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 fields of an EHT PPDU including an EHT NDP announcement frame, an EHT action frame, or an EHT BFRP trigger frame). The received signal processor 1706 may further 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 downlink SU or MU transmission allocations, and trigger information for uplink MU transmission allocations. The control signal parser 1742 may analyze the control signaling portion of the received signal and the trigger information for uplink MU transmission allocations shared by the scheduler 1744 to assist the data demodulator and decoder 1732 in demodulating and decoding the data portion of the received signal (e.g., the data fields of an EHT PPDU including an EHT compressed beamforming / CQI frame).

[0108] FIG. 18 shows the configuration of a communication device such as a STA according to the present disclosure. Similar to the schematic example of the communication device 300 shown in FIG. 3A, the communication device 1800 includes a circuit 1802, at least one wireless transmitter 1810, at least one wireless receiver 1812, and at least one antenna 1814 (only one antenna is shown in FIG. 18 for simplicity). The circuit 1802 may include at least one controller 1808, and this controller 1808 is used for the execution assisted by the software and hardware of the tasks for which it is designed to perform communication for channel sounding. The circuit 1802 may further include a received signal processor 1806 and a transmitted signal generator 1804. The at least one controller 1808 may control the received signal processor 1806 and the transmitted signal generator 1804. The received signal processor 1806 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 portion 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 portion 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 the RU information and its assigned user-specific assignment information.

[0109] 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 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 NDP announcement frame or an EHT BFRP trigger frame) to assist the data demodulator and decoder 1832 in demodulating and decoding the data portion of the received signal (e.g., the data field of an EHT PPDU including an EHT NDP announcement frame or an EHT BFRP trigger frame). The trigger information parser 1848 may analyze trigger information for its uplink allocation from the received trigger frame included in the data portion of the received signal. The transmission 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 an EHT sounding NDP, or the EHT-SIG field of an EHT PPDU including an EHT compressed beamforming / CQI frame). The transmission signal generator 1804 may further include a PPDU generator 1826, which generates a PPDU (e.g., an EHT PPDU including an EHT sounding NDP or an EHT compressed beamforming / CQI frame). The transmission signal generator 1804 may further include a frame generator 1822, which may generate a MAC frame such as an EHT compressed beamforming / CQI frame.

[0110] As described above, embodiments of the present disclosure provide an advanced communication system, communication method, and communication device for channel sounding in a MIMO WLAN network to improve spectral efficiency in the MIMO WLAN network.

[0111] The present disclosure can be implemented by software, hardware, or software cooperating with hardware. Each functional block used in the description of each of the above embodiments can be partially or entirely realized by an LSI such as an integrated circuit, and each process described in each embodiment can be partially or entirely controlled by the same LSI or a combination of LSIs. The LSI may be formed as an individual chip, or may be formed such that one chip includes part or all of the functional blocks. The LSI may include a data input and an output coupled to the data input. The LSI in this specification may sometimes be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the technology for realizing the integrated circuit is not limited to the LSI, and may be realized by using a dedicated circuit, a general-purpose processor, or a specific-purpose processor. In addition, an FPGA (Field Programmable Gate Array) that can be programmed after the manufacture of the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells arranged inside the LSI may be used. The present disclosure can be realized as digital processing or analog processing. In future integrated circuit technology, when LSIs are no longer used as a result of the progress of semiconductor technology or other derivative technologies, the functional blocks can be integrated using future integrated circuit technology. Biotechnology may also be applied.

[0112] The present disclosure can be implemented by any type of device, apparatus, or system having a communication function, referred to as a communication device.

[0113] The communication device may include a transceiver and a processing / control circuit. The transceiver may include a receiver and a transmitter, and / or may function as a receiver and a transmitter. The transceiver may include, as a transmitter and a receiver, an RF module including an amplifier and an RF (radio frequency) modulator / demodulator, etc., and one or more antennas.

[0114] Some non-limiting examples of such communication devices include telephones (e.g., cellular (cell) phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, telemedicine / teletherapy (remote medical and treatment) devices, and vehicles that provide communication capabilities (e.g., automobiles, airplanes, ships), as well as various combinations thereof.

[0115] The communication device is not limited to being portable or movable, and may also include any type of non-portable or fixed device, apparatus, or system, such as smart home devices (e.g., appliances, lighting, smart meters, control panels), vending machines, and any other "things" in the network of the "Internet of Things (IoT)".

[0116] Communication may include exchanging data through, for example, cellular systems, wireless LAN systems, satellite systems, etc., and various combinations thereof.

[0117] The communication device may include a device such as a controller or sensor 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 sensor that generates a control signal or data signal used by the communication device of the communication device to perform its communication functions.

[0118] In addition, the communication device may include infrastructure facilities such as any other device, apparatus, or system that communicates with or controls devices such as base stations, access points, and those in the above non-limiting examples.

[0119] Reference has been made to devices to describe some features of various embodiments, and it will be understood that the corresponding features also apply to the methods of the various embodiments, and vice versa.

[0120] Those skilled in the art will recognize that numerous changes and / or modifications may be made to the present disclosure as shown in the specific embodiments without departing from the spirit or scope of the disclosure as broadly described. Accordingly, the present embodiments are to be considered in all respects as illustrative and not restrictive.

Claims

1. a receiver for receiving a first frame from another communication device, the first frame including a first field indicating a target use of the sounding procedure; a circuit for processing the first frame; A communication device comprising:

2. the first frame includes a second field indicating a target type of the sounding procedure; The communication device according to claim 1 .

3. the first frame includes a third field indicating one or more target communication devices that will be engaged in the sounding procedure. The communication device according to claim 1 .

4. a transmitter for transmitting a second frame including a first field indicating one or more recommended types of the sounding procedure. The communication device according to claim 1 .

5. the first field of the second frame indicating that the communication device should be excluded from the sounding procedure. The communication device according to claim 4.

6. The receiver further receives a third frame that initiates the sounding procedure. The communication device according to claim 1 .

7. the third frame includes a first field indicating a type of the sounding procedure; a second field indicating a type of sounding feedback; The communication device according to claim 6.

8. When the type of the sounding procedure indicates an explicit sounding procedure and the type of the sounding feedback indicates a calibration feedback, the sounding procedure includes a calibration procedure. The communication device according to claim 7.

9. the other communication device transmits the first frame to one or more communication devices including the communication device, and when the sounding procedure is a hybrid sounding procedure including an explicit sounding portion and an implicit sounding portion, at least one communication device among the one or more communication devices and the other communication devices is configured to engage in the explicit sounding portion of the sounding procedure, and the remaining communication devices among the one or more communication devices and the other communication devices other than the at least one communication device are configured to engage in the implicit sounding portion of the sounding procedure. The communication device according to claim 1 .

10. the third frame is a Null Data Packet (NDP) announcement frame; The communication device according to claim 6.

11. receiving a first frame from another communication device, the first frame including a first field indicating a target use of the sounding procedure; Processing the first frame. Communication methods.

12. receiving a first frame from another communication device, the first frame including a first field indicating a target use of the sounding procedure; Processing the first frame; and controlling the processing. Integrated circuits.

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