Frequency alignment method

Abstract

The invention provides a frequency alignment method, which relates to the technical field of wireless communication, is executed by a second communication device, and comprises the following steps: receiving N first signal frames from a first communication device; determining a frequency pre-correction value according to the N first signal frames, wherein the frequency pre-correction value is used for aligning the frequency with the first communication equipment; and sending a second signal frame which needs to be aligned with the first communication equipment in frequency based on the frequency pre-correction value. The first signal frame may include signal frames of different stages, including but not limited to null packet announcement frames, non-null packet announcement frames, Co-BF trigger frames, non-Co-BF trigger frames, Co-SR trigger frames, non-Co-SR trigger frames, etc. According to the invention, multiple estimation and comprehensive processing are carried out by using multiple signal frames, the problem that single estimation is easily influenced by interference is effectively overcome, and the precision and robustness of frequency alignment are remarkably improved, so that the performance of multi-access-point cooperative beam forming, multi-access-point cooperative spatial multiplexing and STA uplink transmission scenes is ensured.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and more specifically, to a frequency alignment method. Background Technology

[0002] With the development of Wireless Local Area Network (WLAN) technology, in order to address the increasingly severe co-channel interference problem in high-density deployment scenarios and further improve system capacity and reliability, the industry is actively developing next-generation Wi-Fi standards (such as IEEE 802.11bn, or Wi-Fi 8). Among them, Multi-AP Coordination (MAPC) technology has become a key evolution direction. Coordinated Beamforming (Co-BF) and Coordinated Spatial Reuse (Co-SR) are important implementation methods of MAPC. Both Co-BF and Co-SR allow multiple access points (APs) to transmit data to a target station (STA) simultaneously on the same time-frequency resources. Co-BF minimizes mutual interference between APs through precoding technology, while Co-SR reduces interference by coordinating the transmit power of multiple APs, thereby significantly improving network throughput, reliability, and reducing latency.

[0003] A typical Co-BF (Co-Band Combination) consists of two main phases: the Co-BF Sounding Phase and the Co-BF Transmission Phase. In the Co-BF Sounding Phase, the APs acquire Channel State Information (CSI) with the target STA by sending probe signals such as null packets (NDPs). This phase can employ various detection methods, including sequential or joint sounding. In the Co-BF Transmission Phase, multiple APs calculate a precoding matrix based on the acquired CSI and simultaneously transmit the precoded data to the target STA. To achieve effective Co-BF transmission, especially to obtain the expected gains in coherent combining or interference cancellation, the multiple APs participating in the coordination must not only synchronize their transmission times but also maintain a high degree of alignment in their carrier frequencies.

[0004] During the Co-SR transmission phase, multiple APs simultaneously transmit data to the target STA by adjusting their transmit power. This process still requires ensuring the alignment of the transmission time and carrier frequency of the multiple APs.

[0005] In cooperative beamforming and cooperative spatial multiplexing, "first AP" refers to the AP that provides the frequency reference, and "second AP" refers to the AP that needs to perform frequency alignment with the first AP. This frequency alignment process relies on the second AP estimating the carrier frequency offset (CFO) of a specific signal frame (such as a cooperative beamforming trigger frame or a cooperative spatial multiplexing trigger frame) transmitted by the first AP, and using this estimate for pre-compensation of its own transmitter frequency. However, in real-world wireless environments with high-density AP deployments, signal transmission faces numerous challenges. The signal frame transmitted by the first AP for CFO estimation may overlap with signals from other adjacent BSSs at the same frequency, causing short-term strong interference for the second AP during reception; or the signal may encounter obstruction or experience deep fading during propagation. These factors can all lead to a lower signal-to-noise ratio (SNR) or transient distortion of the reference signal received by the second AP. In this situation, if the second AP relies solely on the result of a single CFO estimation for frequency pre-compensation, the estimated value may contain significant errors. An inaccurate frequency pre-correction value causes the actual carrier frequency deviation between multiple APs to exceed the tolerance threshold (e.g., 350Hz), which severely disrupts the cooperative beamforming or cooperative spatial multiplexing effect, leading to increased interference between users, decreased system throughput and loss of reliability, and failing to fully realize the potential advantages of multi-AP cooperative technology.

[0006] Similar issues arise when an AP schedules multiple associated STAs to transmit uplink simultaneously, or when STAs use Enhanced Long Range Physical Layer Protocol Data Units (ELR PPDUs) for uplink transmission. For example, when multiple STAs transmit Trigger Based Physical Layer Protocol Data Units (TB PPDUs), frequency alignment with the AP is required. This process relies on the STA performing a Call Forward Frequency (CFO) estimate on the trigger frames transmitted by the AP and using this CFO estimate to pre-compensate its own transmission frequency, ensuring the AP can correctly receive the TB PPDUs transmitted simultaneously by multiple STAs. However, the trigger frames transmitted by the AP for CFO estimation may still overlap with other signals transmitted simultaneously on the same frequency, or the signals may encounter obstruction or experience deep fading during propagation, leading to significant errors in the CFO estimation results when the STA receives the trigger frames.

[0007] Therefore, a more robust frequency alignment method is urgently needed to overcome the unreliability of single CFO estimation in complex wireless environments, and to ensure stable and high-performance transmission in scenarios such as multi-AP cooperative beamforming technology, multi-AP cooperative spatial multiplexing technology, multi-STA simultaneous uplink transmission, and STA uplink transmission ELR PPDU. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a frequency alignment method.

[0009] According to a frequency alignment method provided by the present invention, the scheme is as follows: Firstly, a frequency alignment method is provided, the method comprising: Receive N first signal frames from the first communication device, where N is an integer greater than 1; Based on the N first signal frames, a frequency pre-correction value is determined, which is used to align the frequency with the first communication device; A second signal frame is sent according to the frequency pre-correction value, the second signal frame being a signal frame whose frequency needs to be aligned with the first communication device.

[0010] In one possible implementation, determining a frequency pre-correction value based on the N first signal frames includes: Based on the N first signal frames, determine the N carrier frequency deviation (CFO) estimation results; Based on the N CFO estimation results, the frequency pre-correction value is determined.

[0011] In one possible implementation, determining the N carrier frequency deviation (CFO) estimation results based on the N first signal frames includes any of the following methods: Method A: Each of the N CFO estimation results is determined based on one of the N first signal frames; Method B: Each of the N CFO estimation results is determined based on at least two of the N first signal frames.

[0012] In one possible implementation, determining the frequency pre-correction value based on the N CFO estimation results includes: Based on whether each of the N CFO estimation results exceeds the error threshold, a set of valid CFO estimation results is determined; The frequency pre-correction value is determined based on the set of effective CFO estimation results; The error threshold is predefined, or determined by at least one of the N CFO estimation results; The step of determining the set of valid CFO estimates based on whether each of the N CFO estimates exceeds an error threshold includes: If the nth CFO estimate among the N CFO estimates does not exceed or is less than the error threshold, then the set of valid CFO estimates includes the nth CFO estimate, where 1 ≤ n ≤ N; If the nth CFO estimate among the N CFO estimates exceeds or is not less than the error threshold, then the set of valid CFO estimates does not include the nth CFO estimate, where 1 ≤ n ≤ N.

[0013] In one possible implementation, determining the frequency pre-correction value based on the N CFO estimation results includes: The frequency pre-correction value is determined based on one of the N CFO estimation results or at least two CFO estimation results.

[0014] In one possible implementation, the N first signal frames are all signal frames transmitted during the cooperative beamforming detection phase, and include at least one combination of the following frame types: a) At least two empty data packets announce NDPA frames; b) One NDPA frame and at least one non-NDPA frame; c) All are non-NDPA frames.

[0015] In one possible implementation, the N first signal frames are all signal frames transmitted during the cooperative beamforming transmission phase, and include at least one combination of the following frame types: a) At least two cooperative beamforming trigger frames; b) A cooperative beamforming trigger frame and at least one non-cooperative beamforming trigger frame; c) All are non-cooperative beamforming trigger frames.

[0016] In one possible implementation, the N first signal frames include signal frames transmitted at different stages of cooperative beamforming; the different stages of cooperative beamforming include a detection stage and a transmission stage.

[0017] In one possible implementation, the second signal frame is a signal frame whose frequency needs to be aligned with the first communication device, including at least one of the following: NDPA frames and / or empty data packet NDP frames during the cooperative beamforming detection phase; Cooperative beamforming trigger frame in the cooperative beamforming transmission phase, and / or, cooperative beamforming physical layer protocol data unit (PPDU).

[0018] In one possible implementation, the N first signal frames are signal frames transmitted during the cooperative spatial multiplexing transmission phase, and include at least one combination of the following frame types: a) At least two cooperative spatial multiplexing trigger frames; b) A cooperative spatial multiplexing trigger frame and at least one non-cooperative spatial multiplexing trigger frame; c) All are non-cooperative spatial multiplexing trigger frames.

[0019] In one possible implementation, the N first signal frames include signal frames transmitted in cooperative beamforming and signal frames transmitted in cooperative spatial multiplexing; the signal frames transmitted in cooperative beamforming include signal frames in the cooperative beamforming detection phase and / or signal frames in the cooperative beamforming transmission phase.

[0020] In one possible implementation, the second signal frame is a signal frame whose frequency needs to be aligned with the first communication device, including at least one of the following: Cooperative space multiplexing trigger frame in the cooperative space multiplexing transmission phase, and / or, cooperative space multiplexing physical layer protocol data unit (PPDU).

[0021] In one possible implementation, the N first signal frames are trigger frames and / or non-trigger frames. The trigger frame is a signal frame sent by the first communication device when scheduling multiple stations to perform uplink transmission simultaneously, and the multiple stations include the second communication device.

[0022] In one possible implementation, the second signal frame includes a signal frame of the second communication device responding to a trigger frame sent by the first communication device, and / or an Enhanced Long Distance Physical Layer Protocol Data Unit (ELR PPDU).

[0023] In one possible implementation, the method further includes: When the second communication device establishes a cooperative beamforming relationship and / or a cooperative spatial multiplexing relationship with multiple different first communication devices, an independent historical record of CFO estimation results and frequency pre-correction value are maintained for each first communication device. The second communication device updates the CFO estimation result to the historical record of the CFO estimation result of the communication device corresponding to the first communication device identifier based on the identification information of the first communication device, and determines the frequency pre-correction value corresponding to the communication device.

[0024] In one possible implementation, the method further includes: The second communication device maintains historical records of CFO estimation results for multiple frequency bands and / or multiple channels for the first communication device. The historical records of CFO estimation results for each of the multiple frequency bands are used to determine the frequency pre-correction value for the corresponding frequency band. The historical records of CFO estimation results for each of the multiple channels are used to determine the frequency pre-correction value for the corresponding channel. The plurality of frequency bands include at least two different frequency bands from the following: 2.4G band, 5G band, 6G band, millimeter wave band, and other frequency bands supported in future communication systems. The frequency range or center frequency of the plurality of channels are different.

[0025] In a second aspect, a communication device is provided, configured to operate as a second communication device in the frequency alignment method, comprising: A receiving module is used to receive N first signal frames from a first communication device; The processing module is used to determine N CFO estimation results and one frequency pre-correction value based on the N first signal frames; The storage module is used to store the N CFO estimation results, the frequency pre-correction value, and maintain the historical record of CFO estimation results for different first communication devices and / or different frequency bands and / or different channels; The transmitting module is used to transmit a second signal frame with a frequency aligned with the first communication device according to the frequency pre-correction value.

[0026] In one possible implementation, the processor is specifically configured to perform the following operations: Determine whether each of the N CFO estimation results exceeds the error threshold, determine the set of valid CFO estimation results, and determine the frequency pre-correction value based on the set of valid CFO estimation results; or, determine the frequency pre-correction value based on one or at least two of the N CFO estimation results.

[0027] Thirdly, a wireless communication system is provided, the wireless communication system comprising at least one first communication device and at least one second communication device; the second communication device is used to perform the method of the first aspect or any possible implementation thereof.

[0028] Fourthly, a chip is provided, comprising a memory and a processor, the memory for storing a computer program; the processor for reading and executing the computer program stored in the memory, wherein when the processor retrieves and runs the computer program from the memory, an electronic device equipped with the chip system performs the method of the first aspect or any possible implementation thereof.

[0029] Fifthly, a non-transitory computer-readable storage medium storing a computer program is provided, wherein when the computer program is executed by a processor, a method is provided for a communication device to implement the first aspect or any possible implementation thereof.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention effectively improves the accuracy of frequency alignment and anti-interference robustness by using multiple signal frames to estimate and synthesize the carrier frequency deviation (CFO). 2. This invention ensures the performance of scenarios such as multi-AP cooperative beamforming, multi-AP cooperative spatial multiplexing, multi-STA simultaneous uplink transmission, and STA uplink transmission ELR PPDU through more precise frequency alignment, directly improving system throughput and transmission reliability; 3. This invention can flexibly utilize multiple signal frames in the detection phase and / or transmission phase, enhancing the system's adaptability and robustness in high-density, dynamic, and complex wireless environments. 4. This invention is mainly implemented at the algorithm level, without the need for expensive hardware upgrades, and achieves high-performance frequency alignment effect close to hardware-level synchronization at a low cost.

[0031] Other beneficial effects of the present invention will be explained in detail through the introduction of specific technical features and technical solutions in specific embodiments. Those skilled in the art should be able to understand the beneficial technical effects brought about by these technical features and technical solutions through the introduction of these technical features and technical solutions. Attached Figure Description

[0032] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the frequency alignment method proposed in this invention; Figures 2a-2b Schematic diagrams showing AP1 and AP2 initiating coordinated beamforming sequential detection, respectively; Figures 3a-3b These are schematic diagrams showing AP1 and AP2 initiating coordinated beamforming joint detection, respectively. Figures 4a-4b A schematic diagram showing AP1 and AP2 initiating coordinated beamforming sequential detection (the access point has a target site supporting dynamic power saving / enhanced multi-link single radio mode); Figures 5a-5b A schematic diagram showing AP1 and AP2 initiating coordinated beamforming joint detection (the access point has a target site supporting dynamic power saving / enhanced multi-link single radio mode); Figure 6A schematic diagram illustrating how AP1 obtains a transmission opportunity and initiates an invitation for ultra-reliable cooperative beamforming transmission; Figure 7 A schematic diagram illustrating how AP2 obtains a transmission opportunity and initiates an invitation for ultra-reliable cooperative beamforming transmission; Figure 8 A schematic diagram of the transmission phase initiating an ultra-reliable cooperative beamforming transmission invitation for AP1 (the access point has a target site that supports dynamic power saving / enhanced multi-link single radio mode, or seeks confirmation from the target site). Figure 9 A schematic diagram of the transmission phase initiating an ultra-reliable cooperative beamforming transmission invitation for AP2 (the access point has a target site that supports dynamic power saving / enhanced multi-link single radio mode, or seeks confirmation from the target site); Figure 10 A schematic diagram of an invitation to AP1 for ultra-reliable collaborative spatial multiplexing transmission; Figure 11 A schematic diagram of AP2 initiating an invitation for ultra-reliable collaborative spatial multiplexing transmission; Figure 12 A schematic diagram of the transmission phase initiating an ultra-reliable collaborative spatial multiplexing transmission invitation for AP1 (the access point has a target site that supports dynamic energy saving / enhanced multi-link single radio mode, or seeks confirmation from the target site); Figure 13 A schematic diagram of the transmission phase initiating an ultra-reliable collaborative spatial multiplexing transmission invitation for AP2 (the access point has a target site that supports dynamic energy saving / enhanced multi-link single radio mode, or seeks confirmation from the target site). Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0034] This invention provides a frequency alignment method applicable to wireless communication systems supporting Multi-AP Coordination (MAPC) technology in Wi-Fi 8 (IEEE 802.11bn) and future standards, particularly in scenarios involving Coordinated Beamforming (Co-BF) and Coordinated Spatial Reuse (Co-SR). This method is also applicable to scenarios supporting simultaneous uplink transmission by multiple STAs in Wi-Fi 6 (IEEE 802.11ax) and later standards, and to scenarios supporting uplink transmission of ELR PPDUs by STAs in Wi-Fi 8 (IEEE 802.11bn) and future standards.

[0035] Cooperative beamforming scenarios typically include multiple access points (such as...) Figure 2a The system includes AP1 and AP2, and their associated stations (STAs). Among these APs, one is negotiated and determined as the frequency reference AP (referred to as "first AP" in this embodiment), and one or more others are designated as frequency alignment APs (referred to as "second AP" in this embodiment). The roles of the first AP and the second AP can be modified. In the cooperative beamforming scenario, the first communication device is the first AP, and the second communication device is the second AP. The second AP needs to perform frequency alignment with the first AP. The goal of frequency alignment is to minimize the carrier frequency deviation (CFO) of the signal frames transmitted by multiple APs during the Co-BF process (e.g., not exceeding 350Hz) to ensure the performance of cooperative transmission. Specifically, the core method flow of the cooperative beamforming scenario is executed by the second AP, combined with... Figure 1 The flowchart of the frequency alignment method shown in Figure 2- Figure 9 The signal interactions shown can be explained in detail below: (1) Receive N first signal frames.

[0036] The second AP listens for and receives N first signal frames (N>1) from the first AP (frequency reference AP). These frames are used by the second AP to determine the frequency pre-correction value. Key implementation details include: Source and type of signal frames: These first signal frames may contain only the detection phase of Co-BF (e.g., Figures 2a-2b , Figures 3a-3b , Figures 4a-4b , Figures 5a-5b The signal frames transmitted in the Co-BF transmission phase, or only containing the Co-BF transmission phase (such as...) Figure 6 , Figure 7 , Figure 8 , Figure 9The signal frames transmitted in the sequential detection phase, or the signal frames transmitted in both the Co-BF detection phase and the Co-BF transmission phase. Figure 2 illustrates the signal frames transmitted in the sequential detection phase, where... Figure 2a This diagram illustrates AP1 initiating a cooperative beamforming sequence detection. In the diagram, AP1 and AP2 obtain channel state information feedback from STA1 associated with AP1. Figure 2b This diagram illustrates AP2 initiating a cooperative beamforming sequence detection. In the diagram, AP1 and AP2 obtain channel state information feedback from STA2 associated with AP2. Figure 2a AP1 sends a Co-BF Sounding Invite frame with a Short Interframe Space (SIFS) interval. AP2 sends a Co-BF Sounding Response frame to negotiate whether to perform Co-BF sounding and to determine the parameters. Then, AP1 sends an Ultra-Reliable Null Packet Announcement (UHR NDP) frame, AP2 sends an Extremely High Throughput Null Packet Announcement (EHT Sounding NDP) frame, AP1 sends a Beamforming Report Polling Trigger (BFRP) frame, and the associated STA1 sends an Extremely High Throughput Compressed Beamforming / CQI (EHT Compressed Beamforming / CQI) frame. This interaction of signal frames is called cross-BSS UHR Co-BF sounding, used by AP2 to obtain channel state information feedback from STA1. Finally, AP1 sends an Extremely High Throughput Null Packet Announcement (EHT NDP) frame. The interaction of these signal frames is called Very High Throughput Triggered Probe Sounding (EHT TB sounding), which is used by AP1 to obtain channel state information feedback from STA1. Figure 2bIn the joint detection phase, AP2 sends a Co-BF Sounding Invite frame, and AP1 sends a Co-BF Sounding Response frame. This is used for AP1 and AP2 to negotiate whether to perform cooperative beamforming detection and to determine the parameters for cooperative beamforming detection. AP2 sends a UHRNDP Announcement frame, AP1 sends an EHT Sounding NDP frame, AP2 sends a BFRP Trigger frame, and the STA2 associated with AP2 sends an EHT Compressed Beamforming / CQI frame. This is used by AP1 to obtain channel state information feedback from STA2. AP2 also sends an EHT NDP Announcement frame, an EHT Sounding NDP frame, a BFRP Trigger frame, and the STA2 associated with AP2 sends an EHT Compressed Beamforming / CQI frame. This is used by AP2 to obtain channel state information feedback from STA2. It should be noted that during the cooperative beamforming sequential detection process, if an AP already has the channel state information of its associated target STA, it can skip the EHT TB sounding procedure. Figure 3 illustrates the signal frames transmitted during the joint detection phase. Figure 3a This is a schematic diagram of AP1 initiating cooperative beamforming joint detection. In the diagram, AP1 and AP2 jointly obtain channel state information feedback from STA1 associated with AP1. Figure 3b This diagram illustrates AP2 initiating a cooperative beamforming joint detection, where AP1 and AP2 jointly acquire channel state information feedback from STA2 associated with AP2. Figure 3a AP1 sends a Co-BF Sounding Invite frame, AP2 sends a Co-BF Sounding Response frame, AP1 sends a UHR NDP Announcement frame, AP1 and AP2 simultaneously send EHT Sounding NDP frames, AP1 sends a BFRP Trigger frame, and STA1 associated with AP1 sends an EHT Compressed Beamforming / CQI frame. Figure 3b AP2 sends a Co-BF Sounding Invite frame, AP1 sends a Co-BF Sounding Response frame, AP2 sends a UHR NDP Announcement frame, AP1 and AP2 simultaneously send EHT Sounding NDP frames, AP2 sends a BFRP Trigger frame, and STA2 associated with AP2 sends an EHT Compressed Beamforming / CQI frame. Figure 6 and Figure 7For example, the signal frames transmitted during the cooperative beamforming transmission stage are illustrated. Figure 6 A schematic diagram illustrating how AP1 obtains a transmission opportunity and initiates an invitation for ultra-reliable cooperative beamforming transmission. Figure 7 A schematic diagram illustrating how AP2 obtains a transmission opportunity and initiates an invitation for ultra-reliable cooperative beamforming transmission. Figure 6 AP1 sends a Co-BF invite frame, AP2 sends a Co-BF response frame, and AP1 sends a Co-BF trigger frame. AP1 and AP2 simultaneously send Co-BF physical layer protocol data units (Co-BF PPDUs). Figure 7 AP2 sends a Co-BF invite frame, AP1 sends a Co-BF response frame, and AP2 sends a Co-BF trigger frame. AP1 and AP2 simultaneously send Co-BF PPDUs. The combination of frame types included in the multiple first signal frames has various possibilities, such as: including multiple NDPA frames, including one NDPA and multiple non-NDPA frames, all non-NDPA frames, including multiple cooperative beamforming trigger frames, including one cooperative beamforming trigger frame and multiple non-cooperative beamforming trigger frames, all non-cooperative beamforming trigger frames, including one NDPA frame and one cooperative beamforming trigger frame, etc. Taking AP1 as the first AP as an example... Figure 2a The Co-BF Sounding Invite frame, UHR NDP Announcement frame, BFRPTrigger frame, EHT NDP Announcement frame, and EHT Sounding NDP frame transmitted by AP1 can all serve as examples of the first signal frame. In the accompanying drawings of this invention, both AP1 and AP2 may be the first AP. There can be one or more STAs associated with an AP; for simplicity, only one STA is shown in the figures.

[0037] Reception conditions: In a preferred embodiment, the second AP receives the first signal frame when the second AP itself has not performed any transmission operation (i.e., is in a silent reception state) during the period when the first AP sends these frames. For example, assuming AP1 is the first AP, when the second AP receives the Co-BF Sounding Invite frame, such as... Figure 2a As shown. This avoids self-interference and yields a cleaner signal for CFO estimation.

[0038] Temporal distribution: The N first signal frames may be distributed across multiple different transmission opportunities (TXOPs), or they may be transmitted at different times within the same TXOP. The second AP needs to receive the first signal frames at different times to perform CFO estimation and processing.

[0039] (2) Determine N CFO estimation results based on N first signal frames.

[0040] The physical layer (PHY) baseband processor of the second AP processes each received first signal frame to estimate the instantaneous carrier frequency deviation between the first AP and the second AP. Specific implementations include any of the following methods: a) Each CFO estimation result is determined based on one of the N first signal frames: For the nth first signal frame (e.g., an NDPA frame or a Co-BF trigger frame), a time-domain or frequency-domain CFO estimation algorithm is performed (e.g., CFO estimation is performed using a short or long training field in the preamble, or CFO estimation is performed using the data portion) to determine the nth CFO estimation result. ( ).

[0041] b) Each CFO estimation result is determined based on at least two of the N first signal frames: For the nth first signal frame, a time-domain or frequency-domain CFO estimation algorithm is performed to generate an estimate, which is then combined with at least one previous CFO estimation result to determine the nth CFO estimation result. ( ). For example, when the second AP receives the nth first signal frame, it performs a time-domain or frequency-domain CFO estimation algorithm to generate an estimate. Simultaneously, combining the CFO estimation result of the second AP determined based on the (n-1)th first signal frame before the nth first signal frame, the following is adopted: A filtering algorithm (first-order lag filtering) is used to determine the nth CFO estimate. Let... The value after the nth filtering is initialized. = For i=2 to n, calculate: Determine the nth CFO estimate. Smoothing coefficient (0< ≤1) determines the new observation value The level of trust can be fixed or adaptively adjusted.

[0042] For another example, the second AP receives the nth first signal frame, performs a CFO estimation algorithm in the time domain or frequency domain, and generates an estimated value. , and at the same time, in combination with the m CFO estimation results respectively determined by the second AP according to the m first signal frames before the nth first signal frame, where 0 < m ≤ n - 1, a weighted average algorithm is adopted, that is , 0 < m ≤ n - 1, and , to determine the nth CFO estimation result . Among them, the weight can be allocated according to a preset rule or the received signal strength indication (RSSI), signal-to-noise ratio (SNR), or the newness or oldness of the estimation time of the ith first signal frame (for example, the higher the signal-to-noise ratio and the more recent the time, the greater the weight), and the weight can also be 0.

[0043] The second AP associates the CFO estimation result determined each time with the corresponding first AP identifier (such as AP ID, or BSSID, or MAC address), and stores it in the storage module to form a historical record of the CFO estimation results of this first AP.

[0044] (3) Determine a frequency pre-correction value according to the N CFO estimation results.

[0045] The processor of the second AP (such as the MAC layer or a dedicated control unit) determines a more robust and accurate comprehensive frequency pre-correction value ( , , …, ) according to one CFO estimation result or at least two CFO estimation results among the stored N CFO estimation results. .

[0046] In a possible implementation, the second AP directly uses one CFO estimation result among the N CFO estimation results as the frequency pre-correction value. For example, the second AP uses the Nth CFO estimation result as the frequency pre-correction value. .

[0047] In another possible implementation, the second AP determines a frequency pre-correction value according to at least two CFO estimation results among the N CFO estimation results. For example, according to the Nth CFO estimation result and the N - 1 CFO estimation results before the Nth CFO estimation result, a weighted average algorithm is adopted, that is , 1 ≤ i ≤ N, and = 1, to determine the frequency pre-correction value .

[0048] In another possible implementation, the processor of the second AP first according to the stored N CFO estimation results ( , , …, Post-processing is performed to determine a set of effective CFO estimates, and then a frequency pre-correction value is determined based on the set of effective CFO estimates. For example, the processor in the second AP filters N CFO estimates. The processor sets an error threshold (Threshold) when a CFO estimate is obtained. When this is done, it is compared with a reference value (such as the mean, median, or previous pre-corrected value) calculated based on the first n-1 valid values. If | If the reference value is greater than the Threshold, the estimate is considered unreliable due to sudden interference or deep fading, and is marked as invalid and discarded, not included in the final calculation. A valid CFO set is determined based on the valid CFO estimates, and then a frequency pre-correction value is determined based on the M (1≤M≤N) CFO estimates in the valid CFO estimate set. The threshold can be a fixed value or dynamically adjusted based on the variance of historical CFO estimates.

[0049] (4) Send the second signal frame according to the frequency pre-correction value.

[0050] When the second AP needs to send a second signal frame aligned with the frequency of the first AP (for example, assuming AP1 is the first AP and AP2 is the second AP), Figure 2b The processor will process the UHR NDPA frame sent by AP2 in step (3). As control parameters, they are sent to the radio frequency (RF) front end or the numerically controlled oscillator (NCO).

[0051] Pre-compensation operation: When the second AP generates the carrier of the signal to be transmitted, it will actively pre-compensate (offset) its center frequency by one - For example, if it is estimated that the frequency of the first AP is higher than that of itself. If the frequency is Hz, then the second AP will lower its own transmission frequency before transmitting. Hz.

[0052] After frequency pre-compensation, the second AP transmits the second signal frame. This ensures that when the signal reaches the receiving point (or STA), its carrier frequency is highly aligned with the carrier frequency of the first AP signal, significantly improving the throughput and reliability of subsequent Co-BF transmissions.

[0053] Collaborative space reuse scenarios typically include multiple access points (such as...) Figure 10In the Co-Spatial Multiplexing (Co-SR) scenario, the first communication device is a frequency reference AP (AP1 and AP2) and their associated stations (STAs). The second communication device is a frequency alignment AP (AP) requiring frequency alignment (the "second AP"). The second AP needs to perform frequency alignment with the first AP. The goal of frequency alignment is to minimize the carrier frequency deviation (CFO) of the signal frames (e.g., Co-Spatial Multiplexing Physical Layer Protocol Data Units, Co-SR PPDUs) transmitted by multiple APs during Co-SR (Co-Spatial Multiplexing), ensuring the performance of the cooperative transmission. Specifically, the core method flow executed by the second AP in the Co-Spatial Multiplexing scenario, combined with… Figure 1 The flowchart of the frequency alignment method shown is as follows: Figures 10-13 The signal interactions shown can be explained in detail below: (1) Receive N first signal frames.

[0054] The second AP listens for and receives N first signal frames (N>1) from the first AP (frequency reference AP). These frames are used by the second AP to determine the frequency pre-correction value. Key implementation details include: Source and type of signal frames: These first signal frames may contain Co-SR triggered frames from the Co-SR transmission phase or non-Co-SR triggered frames (such as...). Figures 10-11 ).by Figure 10 and Figure 11 For example, let's illustrate the signal frames used in cooperative spatial multiplexing transmission, where... Figure 10 A schematic diagram illustrating the process of AP1 initiating an invitation for ultra-reliable collaborative spatial multiplexing transmission. Figure 11 A schematic diagram of AP2 initiating an invitation for ultra-reliable collaborative spatial multiplexing transmission. Figure 10 AP1 sends a Co-SR invite frame, AP2 sends a Co-SR response frame, and AP1 sends a Co-SR trigger frame. AP1 and AP2 simultaneously send Co-SR PPDUs. Figure 11 AP2 sends a Co-SR invite frame, AP1 sends a Co-SR response frame, and AP2 sends a Co-SR trigger frame. AP1 and AP2 simultaneously send Co-SR PPDUs. The combination of frame types included in multiple first signal frames can have various possibilities, such as: including multiple cooperative spatial multiplexing trigger frames, including one cooperative spatial multiplexing trigger frame and multiple non-cooperative spatial multiplexing trigger frames, or all non-cooperative spatial multiplexing trigger frames, etc. Taking AP1 as the first AP as an example... Figure 10The Co-SR Invite frame, ICF, and Co-SRtrigger frame sent by AP1 can all serve as examples of the first signal frame. In the accompanying drawings of this invention, both AP1 and AP2 may be the first AP. There can be one or more STAs associated with an AP.

[0055] Reception conditions: In a preferred embodiment, the second AP receives the first signal frame when the second AP itself has not performed any transmission operation (i.e., is in a silent reception state) during the period when the first AP sends these frames. For example, assuming AP1 is the first AP, when the second AP receives the Co-SR Invite frame, such as... Figure 10 As shown. This avoids self-interference and yields a cleaner signal for CFO estimation.

[0056] Temporal distribution: The N first signal frames may be distributed across multiple different transmission opportunities (TXOPs), or they may be transmitted at different times within the same TXOP. The second AP needs to receive the first signal frames at different times to perform CFO estimation and processing.

[0057] (2) Determine N CFO estimation results based on N first signal frames.

[0058] Similar to the cooperative beamforming scenario, it will not be elaborated here.

[0059] (3) Determine a frequency pre-correction value based on N CFO estimation results.

[0060] Similar to the cooperative beamforming scenario, it will not be elaborated here.

[0061] (4) Send the second signal frame according to the frequency pre-correction value.

[0062] When the second AP needs to send a second signal frame aligned with the frequency of the first AP (for example, assuming AP1 is the first AP and AP2 is the second AP), Figure 10 The Co-SR PPDU transmitted by AP2 can be used as a second signal frame. The pre-compensation operation is similar to that of the cooperative beamforming scenario, and will not be described in detail here.

[0063] In a STA uplink transmission scenario, the first communication device is an AP, and the second communication device is a STA. This STA uplink transmission scenario includes scenarios where multiple STAs transmit uplink simultaneously, or scenarios where STAs transmit ELR PPDUs uplink. In this STA uplink transmission scenario, the goal of frequency alignment is to minimize the carrier frequency deviation (CFO) between the signal frames transmitted by the STA and the AP (e.g., no more than 350Hz, or no more than 2kHz, or no more than 15kHz) to ensure the performance of STA uplink transmission. In a scenario where multiple STAs simultaneously transmit uplink, each STA receives N first signal frames. These first signal frames are trigger frames sent by the AP and / or non-trigger frames sent by the AP. The trigger frames are sent by the AP when scheduling multiple stations to transmit uplink simultaneously. The STA determines N CFO estimation results based on the N first signal frames and then determines a frequency pre-correction value based on these N CFO estimation results. This frequency pre-correction value is used for frequency pre-compensation in second signal frames. The second signal frame can be a trigger-based physical layer protocol data unit (TB PPDU) sent by the STA, including High Efficiency Trigger-Based Physical Layer Protocol Data Unit (HETB PPDU), Extremely High Throughput Trigger-Based Physical Layer Protocol Data Unit (EHT TB PPDU), Ultra High Probability Trigger-Based Physical Layer Protocol Data Unit (UHR TB PPDU), or a TB PPDU used for uplink transmission in future communication systems. Any of the PPDUs, or the second signal frame, can be a non-high throughput physical layer protocol data unit (non-HT PPDU) or a non-high throughput duplicate physical layer protocol data unit (non-HT duplicate PPDU) with the trigger response (TRIGGER_RESPONDING) parameter set to True in the transmission vector (TXVECTOR). In the STA uplink transmission ELR PPDU scenario, the STA receives N first signal frames. These first signal frames are signal frames sent by the target AP. The address of the first signal frame can be the address of the STA or the broadcast address. The first signal frame is a signal frame other than UHR NDP Announcement, downlink non-orthogonal frequency division multiple access cooperative beamforming physical layer protocol data unit (DL non-OFDMA Co-BF PPDU), and downlink single user cooperative spatial multiplexing physical layer protocol data unit (DL SU Co-SR PPDU). The STA determines N CFO estimation results based on the N first signal frames and determines a frequency pre-correction value based on the N CFO estimation results. The frequency pre-correction value is used for frequency pre-compensation in the second signal frame, where the second signal frame is the ELR PPDU sent by the STA.

[0064] Specific implementation details also include: The second communication device includes an antenna, radio frequency transceiver circuitry, a baseband processor, a central processing unit / microcontroller, and a storage module (a software module that stores CFO history records, pre-calibration values, associated AP identifiers, etc.). These components are interconnected via a bus and work together to execute the aforementioned methods.

[0065] Wireless Communication System: This system consists of at least one first communication device and at least one second communication device interacting via a network (such as wired backhaul) and an air interface protocol. The first communication device transmits necessary signal frames according to the protocol. The second communication device executes the frequency alignment method of this invention. The system-level effect is that multiple communication devices can achieve sufficiently accurate distributed frequency triggering via air signals without requiring extremely high-precision, high-cost shared clocks. This supports scenarios such as multi-AP cooperative beamforming, multi-AP cooperative spatial multiplexing, simultaneous uplink transmission by multiple STAs, or STA uplink transmission of ELR PPDUs.

[0066] Parameter adaptation: parameter N (the number of first signal frames used to estimate the CFO result) and coefficients in the algorithm (such as smoothing coefficients). Thresholds (or thresholds) do not need to be fixed. They can be adaptively adjusted based on the stability (such as variance) of historical CFO estimates, the operating temperature of the equipment, or the runtime, to balance convergence speed and estimation accuracy.

[0067] Multi-band and / or multi-channel management: The storage module of the second communication device can maintain a frequency alignment table. This table records the historical CFO estimation results and the current frequency pre-correction value for each frequency band and / or channel of the first communication device. .

[0068] The present invention will now be described in more detail.

[0069] In multi-AP cooperative beamforming scenarios, to address the issue of significant carrier frequency deviations between multiple access points caused by the second AP using only a single CFO estimation result for pre-compensation due to interference or low signal-to-noise ratio, a frequency alignment method is proposed, as follows: The second AP receives N first signal frames sent by the first AP, where N is an integer greater than 1; The second AP determines a frequency pre-correction value based on N first signal frames, and this frequency pre-correction value is used to align with the frequency of the first AP. The second AP sends a second signal frame based on the aforementioned frequency pre-correction value. This second signal frame is a signal frame whose frequency needs to be aligned with that of the first AP.

[0070] The N first signal frames are signal frames used by the second AP to determine the frequency pre-correction value, and include any one of the following: (1) The N first signal frames contain at least two NDPA frames in the detection phase, or contain one NDPA frame and at least one non-NDPA frame, or contain only non-NDPA frames; (2) The N first signal frames contain at least two cooperative beamforming trigger frames in the cooperative beamforming transmission phase, or contain one cooperative beamforming trigger frame and at least one non-cooperative beamforming trigger frame, or contain only non-cooperative beamforming trigger frames. (3) The N first signal frames contain signal frames transmitted at different stages of cooperative beamforming, including at least one signal frame in the detection stage and at least one signal frame in the transmission stage.

[0071] Regarding the first signal frame, possible implementation methods are as follows: (1) The N first signal frames contain at least two NDPA frames in the detection phase, or contain one NDPA frame and at least one non-NDPA frame, or contain only non-NDPA frames; It should be noted that NDPA frames are UHR NDPA frames or EHT NDPA frames, or NDPA frames with other names in future communication systems.

[0072] The following combination Figures 2a-2b and Figures 4a-4b This serves as a schematic diagram of sequential detection. Figures 3a-3b and Figures 5a-5b As a schematic diagram of joint detection, a more specific explanation is provided for NDPA frames and non-NDPA frames. Figure 2a and Figure 2b This is a schematic diagram of sequential detection. Figure 4a and Figure 4b This diagram illustrates the sequential detection of a target STA (STA) with Dynamic Power Save (DPS) enabled by the AP, or a target STA operating in enhanced Multi-Link-Single-Radio (eMLSR) mode. Figure 3a and Figure 3b This is a schematic diagram of the joint exploration. Figure 5a and Figure 5b This diagram illustrates joint detection of a target STA with DPS enabled by AP, or a target STA operating in eMLSR mode. During the detection phase, AP1 and AP2 are APs co-beamforming. It should be noted that... Figures 2a-2b and Figures 4a-4b , Figures 3a-3b and Figures 5a-5bThis is merely an illustrative diagram of the detection process for ease of understanding. The actual signal frames transmitted during the detection process may include more than just those shown in the diagram; they may also include other signal frames. Alternatively, the names of the actual transmitted signal frames may differ from those shown in the diagram but may perform the same or similar functions. This invention does not impose specific limitations in this regard. Furthermore, it should be noted that in the following examples, the N first signal frames may not be within the same transmission opportunity (TXOP).

[0073] The first AP is the frequency reference AP, and the second AP is the frequency alignment AP.

[0074] Taking sequential detection with AP1 as the first AP as an example, where AP1 is the AP initiating the Co-BF Sounding Invite, the NDPA frame can be a UHR NDP Announcement or EHT NDP Announcement frame sent by AP1, such as... Figure 2a As shown.

[0075] Taking sequential detection with AP2 as the first AP as an example, where AP2 is the AP initiating the Co-BF Sounding Invite, the NDPA frame can be a UHR NDP Announcement or EHT NDP Announcement frame sent by AP2, such as... Figure 2b As shown.

[0076] Taking joint detection with AP1 as the first AP as an example, where AP1 is the AP initiating the Co-BF Sounding Invite, the NDPA frame can be a UHR NDP Announcement frame sent by AP1, such as... Figure 3a As shown.

[0077] Taking joint detection with AP2 as the first AP as an example, where AP2 initiates the Co-BF Sounding Invite, the NDPA frame can be a UHR NDP Announcement frame sent by AP2, such as... Figure 3b As shown.

[0078] It should be noted that non-NDPA frames include Co-BF Sounding Invite frames, Co-BF Sounding Response frames, EHT sounding NDP frames, BFRP Trigger frames, initial control frames (ICF), or any non-NDPA frame sent by the first AP during the probe phase in a future communication system.

[0079] Taking sequential detection and AP1 as the first AP as an example, the non-NDPA frame can be one or more of the following signal frames: The Co-BF Sounding Invite frame sent by AP1, such as Figure 2a As shown; The Co-BF Sounding Response frame sent by AP1, such as Figure 2b As shown; In EHT TB sounding, the EHT sounding NDP frame sent by AP1, such as Figure 2a As shown; In cross-BSS UHR Co-BF sounding, the EHT sounding NDP frame sent by AP1, such as Figure 2b As shown; The BFRP Trigger frame sent by AP1, such as Figure 2a As shown; If AP1 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, non-NDPA frames can also be ICFs sent by AP1 during the sequential probe phase, such as... Figure 4a As shown.

[0080] Taking sequential detection and AP2 as the first AP as an example, the non-NDPA frame can be one or more of the following signal frames: The Co-BF Sounding Invite frame sent by AP2, such as Figure 2b As shown; The Co-BF Sounding Response frame sent by AP2, such as Figure 2a As shown; In EHT TB sounding, the EHT sounding NDP frame sent by AP2, such as Figure 2b As shown; In cross-BSS UHR Co-BF sounding, the EHT sounding NDP frame sent by AP2, such as Figure 2a As shown; BFRP Trigger frames sent by AP2, such as Figure 2b As shown; If AP2 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, non-NDPA frames can also be ICFs sent by AP2 during the sequential probe phase, such as... Figure 4b As shown.

[0081] Taking joint detection and AP1 as the first AP as an example, the non-NDPA frame can be one or more of the following signal frames: The Co-BF Sounding Invite frame sent by AP1, such as Figure 3a As shown; The Co-BF Sounding Response frame sent by AP1, such as Figure 3b As shown; The BFRP Trigger frame sent by AP1, such as Figure 3a As shown; If AP1 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, non-NDPA frames can also be ICFs sent by AP1 during the joint detection phase, such as... Figure 5a As shown.

[0082] Taking joint detection and AP2 as the first AP as an example, the non-NDPA frame can be one or more of the following signal frames: The Co-BF Sounding Invite frame sent by AP2, such as Figure 3b As shown; The Co-BF Sounding Response frame sent by AP2, such as Figure 3a As shown; BFRP Trigger frames sent by AP2, such as Figure 3b As shown; If AP2 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, non-NDPA frames can also be ICFs sent by AP2 during the joint detection phase, such as... Figure 5b As shown.

[0083] Among them, N first signal frames contain at least two NDPA frames from the detection phase: One possible implementation is that the N first signal frames include UHR NDPA frames for cross-BSS UHR Co-BF sounding and EHT NDPA frames for trigger-based sounding during the sequential sounding phase. Taking AP1 as the first AP as an example, the N first signal frames include UHR NDP Announcement and EHT NDP Announcement frames transmitted by AP1, such as... Figure 2aAs shown, in addition, the N first signal frames may also include non-NDPA frames as described above, exemplified by sequential detection with AP1 as the first AP. Alternatively, taking AP2 as the first AP as an example, the N first signal frames may include UHR NDP Announcement and EHT NDP Announcement frames transmitted by AP2, such as... Figure 2b As shown, in addition, the N first signal frames may also include non-NDPA frames as described above, taking sequential detection and AP2 as the first AP as an example.

[0084] Another possible implementation is that the N first signal frames include at least two UHR NDPA frames from the joint detection phase of cooperative beamforming joint sounding (Co-BF joint sounding). Taking AP1 as the first AP, refer to... Figure 3a Taking AP1 initiating a Co-BF joint detection as an example, AP1 initiates at least two joint detections. The N first signal frames contain at least two UHR NDPA frames with Co-BF joint sounding. Furthermore, the N first signal frames may also include non-NDPA frames as described above, assuming joint detection and AP1 as the first AP. Alternatively, taking AP2 as the first AP as an example, refer to... Figure 3b The N first signal frames include at least two UHR NDPA frames sent by AP2. In addition, the N first signal frames may also include non-NDPA frames in the above description, taking joint detection and AP2 as the first AP as an example.

[0085] Another possible implementation is that the N first signal frames include at least one NDPA frame from the cross-BSS UHRCo-BF sounding (UHR NDPA frame) and EHT TB sounding (EHT NDPA frame) during the sequential detection phase, and at least one UHR NDPA frame during the joint detection phase. Taking AP1 as the first AP as an example, the N first signal frames include the UHR NDP Announcement frame transmitted by AP1 in the cross-BSS UHR Co-BF sounding, such as... Figure 2a As shown, the UHR NDP Announcement frame transmitted by AP1 in Co-BF joint sounding, as... Figure 3a As shown, in addition, the N first signal frames may also include non-NDPA frames as described above, exemplified by sequential detection with AP1 as the first AP, and / or non-NDPA frames as described above, exemplified by joint detection with AP1 as the first AP. Alternatively, taking AP2 as the first AP as an example, the N first signal frames may include EHT NDP Announcement frames transmitted by AP2 in EHT TB sounding, such as... Figure 2b As shown, the UHR NDP Announcement frame sent by AP2 in Co-BFjoint sounding, such as Figure 3b As shown, in addition, the N first signal frames may also include non-NDPA frames in the above description, taking sequential detection as an example and AP2 as the first AP, and / or non-NDPA frames in the above description, taking joint detection as an example and AP2 as the first AP.

[0086] The N first signal frames include one NDPA frame and at least one non-NDPA frame from the detection phase: One possible implementation is that the N first signal frames include one NDPA frame from either the UHR NDP Announcement frame in cross-BSS UHR Co-BF sounding or the EHT NDP Announcement frame in EHT TB sounding during sequential probing, and at least one non-NDPA frame from sequential probing. Taking AP1 as the first AP as an example, the N first signal frames include the UHR NDP Announcement frame transmitted by AP1 in cross-BSS UHR Co-BF sounding, such as... Figure 2a As shown, the N first signal frames also include at least one non-NDPA frame, as described above in the example of sequential detection with AP1 as the first AP. Alternatively, taking AP2 as the first AP as an example, the N first signal frames include the UHR NDP Announcement frame transmitted by AP2 in cross-BSS UHR Co-BF sounding, such as... Figure 2b As shown, the N first signal frames also include at least one non-NDPA frame, as described above with sequential detection and AP2 as the first AP.

[0087] Another possible implementation is that the N first signal frames include a UHR NDP Announcement frame from the Co-BF joint sounding and at least one non-NDPA frame from the joint sounding. Taking AP1 as the first AP as an example, the N first signal frames include the UHR NDP Announcement frame sent by AP1, such as... Figure 3a As shown, the N first signal frames also include at least one non-NDPA frame, as described above in the example of joint detection with AP1 as the first AP. Alternatively, taking AP2 as the first AP as an example, the N first signal frames include a UHR NDP Announcement frame sent by AP2, such as... Figure 3b As shown, the N first signal frames also include at least one non-NDPA frame, as described above with joint detection and AP2 as the first AP.

[0088] Another possible implementation is that the N first signal frames include any one NDPA frame from the following: a UHR NDP Announcement frame in cross-BSS UHR Co-BF sounding during sequential detection, an EHT NDP Announcement frame in EHT TB sounding, or a UHR NDP Announcement frame in Co-BF joint sounding during joint detection; and at least one non-NDPA frame from sequential detection and / or joint detection. Taking AP1 as the first AP as an example, the N first signal frames include the EHT NDP Announcement frame transmitted by AP1 in EHT TB sounding, such as... Figure 2a As shown, the N first signal frames also include at least one non-NDPA frame in the above description, taking sequential detection as an example with AP1 as the first AP, and / or at least one non-NDPA frame in the example of joint detection with AP1 as the first AP. Alternatively, taking AP2 as the first AP as an example, the N first signal frames include the UHR NDP Announcement frame transmitted by AP2 in cross-BSS UHR sounding, such as... Figure 2b As shown, the N first signal frames also include at least one non-NDPA frame from the non-NDPA frames described above, taking joint detection and AP2 as the first AP as an example.

[0089] Among them, N first signal frames contain only non-NDPA frames: One possible implementation is that the N first signal frames contain only non-NDPA frames from the sequential probe phase and no NDPA frames. For example, the N first signal frames contain only at least one non-NDPA frame as described above, taking sequential probe with AP1 as the first AP. Or, for example, the N first signal frames contain only at least one non-NDPA frame as described above, taking sequential probe with AP2 as the first AP.

[0090] Another possible implementation is that the N first signal frames contain only non-NDPA frames from the joint detection sequence, and do not contain NDPA frames. For example, the N first signal frames contain only at least one non-NDPA frame in the above description, taking joint detection and AP1 as the first AP. Or, for example, the N first signal frames contain only at least one non-NDPA frame in the above description, taking joint detection and AP2 as the first AP.

[0091] Another possible implementation is that the N first signal frames contain only non-NDPA frames from the sequential detection and joint detection phases, and exclude NDPA frames from the sequential detection and joint detection phases. For example, the N first signal frames contain only the non-NDPA frames described above, assuming sequential detection and AP1 as the first AP, and the non-NDPA frames described above, assuming joint detection and AP1 as the first AP. Or, for example, the N first signal frames contain only the non-NDPA frames described above, assuming sequential detection and AP2 as the first AP, and the non-NDPA frames described above, assuming joint detection and AP2 as the first AP.

[0092] (2) The N first signal frames contain at least two cooperative beamforming trigger frames in the cooperative beamforming transmission phase, or contain one cooperative beamforming trigger frame and at least one non-cooperative beamforming trigger frame, or contain only non-cooperative beamforming trigger frames. It should be noted that the cooperative beamforming trigger frame is a signal frame used to align transmission time and carrier frequency when multiple APs simultaneously transmit Co-BF PPDUs during the cooperative beamforming transmission phase. The cooperative beamforming trigger frame can also be called the cooperative beamforming synchronization frame.

[0093] The following combination Figure 6 , Figure 7 , Figure 8 and Figure 9 As a schematic diagram of the cooperative beamforming transmission phase, a more detailed explanation is provided for cooperative beamforming trigger frames and non-cooperative beamforming trigger frames. AP1 and AP2 are APs for cooperative beamforming. Figure 6 This diagram illustrates the Co-BF PPDU transmission initiated by AP1 upon obtaining TXOP. Figure 8 This diagram illustrates a Co-BFPPDU transmission where AP1 obtains a TXOP, and either AP1 or AP2 has an enabled DPS or a target STA operating in eMLSR mode, or an AP requests confirmation from its associated target STA. Figure 7 This diagram illustrates AP2 obtaining a TXOP and initiating a Co-BF PPDU transmission. Figure 9 This diagram illustrates a Co-BF PPDU transmission where AP2 obtains a TXOP, and either AP1 or AP2 has an enabled DPS or a target STA operating in eMLSR mode, or an AP requests confirmation from its associated target STA. It should be noted that... Figure 6 , Figure 7 , Figure 8 and Figure 9This is merely an illustrative diagram of the cooperative beamforming transmission stage for ease of understanding. The actual transmitted signal frames may include more than just those shown in the diagram; they may also include other signal frames. Alternatively, the names of the actual transmitted signal frames may differ from those shown in the diagram but may perform the same or similar functions. This invention does not impose specific limitations in this regard. Furthermore, it should be noted that in the following examples, the N first signal frames may not be within the same transmission opportunity (TXOP).

[0094] Taking AP1 as the first AP, and AP1 receiving the TXOP and initiating the Co-BF invite frame as an example, the cooperative beamforming trigger frame is the Co-BF trigger frame sent by AP1, such as... Figure 6 As shown.

[0095] Taking AP2 as the first AP, and AP2 receiving the TXOP and initiating the Co-BF invite frame as an example, the cooperative beamforming trigger frame is the Co-BF trigger frame sent by AP2, such as... Figure 7 As shown.

[0096] It should be noted that non-cooperative beamforming trigger frames include Co-BFinvite frames, Co-BF response frames, ICF frames, Multi-User Block ACK Request (MU-BAR) frames in the cooperative beamforming transmission phase, or any non-cooperative beamforming trigger frame sent by the first AP in the cooperative beamforming transmission phase of a future communication system.

[0097] Taking AP1 as the first AP and AP1 receiving a TXOP to initiate a Co-BF invite as an example, the non-cooperative beamforming trigger frame can be one or more of the following signal frames: The Co-BF invite frame sent by AP1, such as Figure 6 As shown; The MU-BAR frame sent by AP1, such as Figure 8 As shown; If AP1 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative beamforming trigger frame can also be an ICF sent by AP1, for example. Figure 8 As shown.

[0098] Taking AP1 as the first AP, AP2 receiving the TXOP and initiating a Co-BF invite, and AP1 responding with a Co-BF response frame as an example, the non-cooperative beamforming trigger frame can be one or more of the following signal frames: The Co-BF response frame sent by AP1, such as Figure 7 As shown; The MU-BAR frame sent by AP1, such as Figure 9 As shown; If AP1 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative beamforming trigger frame can also be an ICF sent by AP1, for example. Figure 9 As shown.

[0099] Taking AP2 as the first AP and AP2 receiving a TXOP to initiate a Co-BF invite as an example, the non-cooperative beamforming trigger frame can be one or more of the following signal frames: The Co-BF invite frame sent by AP2, such as Figure 7 As shown; MU-BAR frames sent by AP2, such as Figure 9 As shown; If AP2 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative beamforming trigger frame can also be an ICF sent by AP2, for example. Figure 9 As shown.

[0100] Taking AP2 as the first AP, AP1 receiving the TXOP and initiating a Co-BF invite, and AP2 responding with a Co-BF response frame as an example, the non-cooperative beamforming trigger frame can be one or more of the following signal frames: The Co-BF response frame sent by AP2, such as Figure 6 As shown; MU-BAR frames sent by AP2, such as Figure 8 As shown; If AP2 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative beamforming trigger frame can also be an ICF sent by AP2, for example. Figure 8 As shown.

[0101] Among them, N first signal frames contain at least two cooperative beamforming trigger frames in the cooperative beamforming transmission phase: One possible implementation is to take AP1 as the first AP initiating a Co-BF PPDU transmission as an example, referring to... Figure 6When AP1 initiates multiple Co-BF PPDU transmissions, the N first signal frames include at least two Co-BF trigger frames sent by AP1. These at least two Co-BF trigger frames can be trigger frames transmitted after AP1 sends a Co-BF invite frame, or trigger frames transmitted after each of multiple Co-BF invite frames sent by AP1. The N first signal frames may also include non-cooperative beamforming trigger frames, exemplified by AP1 being the first AP and AP1 initiating a Co-BF invite frame upon receiving a TXOP, and / or non-cooperative beamforming trigger frames, exemplified by AP1 being the first AP, AP2 initiating a Co-BF invite upon receiving a TXOP, and AP1 responding with a Co-BF response frame. Alternatively, exemplified by AP2 being the first AP initiating a single Co-BF PPDU transmission, refer to [reference needed]. Figure 7 The N first signal frames include at least two Co-BF trigger frames sent by AP2. These at least two Co-BF trigger frames can be trigger frames transmitted after AP2 sends a Co-BF invite frame, or trigger frames transmitted after each of multiple Co-BF invite frames sent by AP2. The N first signal frames may also include non-cooperative beamforming trigger frames, exemplified by AP2 being the first AP and AP2 receiving a Co-BF invite frame initiated by TXOP, and / or non-cooperative beamforming trigger frames, exemplified by AP2 being the first AP, AP1 receiving a Co-BF invite frame initiated by TXOP, and AP2 responding with a Co-BF response frame.

[0102] The N first signal frames include one cooperative beamforming trigger frame and at least one non-cooperative beamforming trigger frame in the cooperative beamforming transmission phase: One possible implementation is that the N first signal frames include Co-BF trigger frames and non-cooperative beamforming trigger frames. For example, the N first signal frames include a Co-BF trigger frame where AP1 is the first AP and AP1 receives a Co-BF invite frame initiated by TXOP; the N first signal frames also include at least one non-cooperative beamforming trigger frame where AP1 is the first AP and AP1 receives a Co-BF invite frame initiated by TXOP; and / or, the N first signal frames also include at least one non-cooperative beamforming trigger frame where AP1 is the first AP, AP2 receives a Co-BF invite frame initiated by TXOP, and AP1 responds with a Co-BF response frame. Alternatively, for example, the N first signal frames include a Co-BF trigger frame, where AP2 is the first AP and AP2 receives a Co-BF invite frame initiated by TXOP; the N first signal frames also include at least one non-cooperative beamforming trigger frame, where AP2 is the first AP and AP2 receives a Co-BF invite frame initiated by TXOP; and / or, the N first signal frames also include at least one non-cooperative beamforming trigger frame, where AP2 is the first AP, AP1 receives a Co-BF invite frame initiated by TXOP, and AP2 responds to a Co-BF response frame.

[0103] Among them, N first signal frames contain only non-cooperative beamforming trigger frames in the cooperative beamforming transmission phase: One possible implementation is that the N first signal frames contain only non-cooperative beamforming trigger frames from the cooperative beamforming transmission phase, and do not contain cooperative beamforming trigger frames. For example, the N first signal frames may contain only non-cooperative beamforming trigger frames, exemplified by AP1 being the first AP, AP2 receiving a TXOP and initiating a Co-BF invite, and AP1 responding with a Co-BF response frame. Alternatively, for example, the N first signal frames may contain only non-cooperative beamforming trigger frames, exemplified by AP2 being the first AP, AP1 receiving a TXOP and initiating a Co-BF invite, and AP2 responding with a Co-BF response frame.

[0104] (3) The N first signal frames contain signal frames transmitted at different stages of cooperative beamforming, including at least one signal frame in the cooperative beamforming detection stage and at least one signal frame in the cooperative beamforming transmission stage: One possible implementation is that the N first signal frames include NDPA frames in the sequential detection cross-BSS UHR Co-BF sounding and trigger frames in the cooperative beamforming transmission phase. Taking AP1 as the first AP, and AP1 receiving the TXOP-initiated Co-BF invite frame as an example, the N first signal frames include the UHR NDP Announcement frame sent by AP1 in the cross-BSS UHR Co-BF sounding, such as... Figure 2a As shown, and the Co-BF trigger frame sent by AP1, as... Figure 6 As shown. The N first signal frames may also include EHT NDP Announcement frames transmitted by AP1 in EHT TB sounding, and / or, the N first signal frames may also include non-NDPA frames with sequential detection and AP1 as the first AP, and / or, the N first signal frames may also include non-cooperative beamforming trigger frames with AP1 as the first AP in the cooperative beamforming transmission phase, and / or, the N first signal frames may also include non-cooperative beamforming trigger frames with AP1 receiving a TXOP and initiating a Co-BF invite frame, and / or, the N first signal frames may also include non-cooperative beamforming trigger frames with AP1 as the first AP, AP2 receiving a TXOP and initiating a Co-BF invite, and AP1 responding with a Co-BF response frame.

[0105] Another possible implementation is that the N first signal frames include NDPA frames in the Co-BF joint sounding and non-cooperative beamforming trigger frames in the cooperative beamforming transmission phase. Taking AP2 as the first AP, AP1 receiving a TXOP to initiate a Co-BF invite, and AP1 responding with a Co-BF response frame as an example, the N first signal frames include the UHR NDP Announcement frames transmitted by AP2 in the Co-BF joint sounding, such as... Figure 3b As shown, the Co-BF response frame sent by AP2 is as follows: Figure 6 As shown. The N first signal frames may also include non-NDPA frames, such as joint detection with AP2 as the first AP, and / or, the N first signal frames may also include non-cooperative beamforming trigger frames, such as AP2 as the first AP, AP1 receiving a TXOP-initiated Co-BF invite, and AP2 responding to a Co-BF response frame, during the cooperative beamforming transmission phase, and / or, the N first signal frames may also include non-cooperative beamforming trigger frames, such as AP2 as the first AP, and AP2 receiving a TXOP-initiated Co-BF invite.

[0106] In a preferred embodiment, the second AP does not send any signal during the transmission time of the N first signal frames, and the N first signal frames do not include signal frames in which the second AP and the first AP simultaneously send signals. For example, a signal frame in which the second AP and the first AP simultaneously send signals is referred to... Figure 3a and Figure 3b In Co-BF joint sounding, when the first AP and the second AP transmit simultaneously, the EHT sounding NDP frame transmitted by the first AP, or refer to... Figure 6 and Figure 7 During the cooperative beamforming transmission phase, when the first AP and the second AP transmit simultaneously, the first AP transmits the Co-BF PPDU.

[0107] In one possible implementation, the results of N CFOs are contained only in the CFO estimates determined within the same TXOP.

[0108] In another possible implementation, the results of N CFOs are contained in the CFO estimation results determined in different TXOPs.

[0109] The second AP determines a frequency pre-correction value based on N first signal frames. This frequency pre-correction value is used to align with the frequency of the first AP. In one possible implementation, the second AP determines a frequency pre-correction value based on N first signal frames, which includes the second AP determining N carrier frequency deviation (CFO) estimation results based on the N first signal frames and determining the frequency pre-correction value based on the N CFO estimation results. Each of the N CFO estimation results is determined by the second AP based on each of the N first signal frames, or based on at least two of the N first signal frames.

[0110] Each of the N CFO estimation results is determined by the second AP based on each of the N first signal frames. One possible implementation is that the second AP receives the nth first signal frame, performs a time-domain or frequency-domain CFO estimation algorithm, and determines the nth CFO estimation result. ( ).

[0111] Each of the N CFO estimation results is determined by the second AP based on at least two of the N first signal frames. One possible implementation is that the second AP receives the nth first signal frame, performs a time-domain or frequency-domain CFO estimation algorithm, and generates an estimate. Simultaneously, combining the CFO estimation result of the second AP determined based on the (n-1)th CFO of the first signal frames preceding the nth signal, the following is adopted: Filtering (first-order lag filtering) algorithm to determine the nth CFO estimation result , that is:

[0112] where is the filtering output value, is the estimated value obtained from the nth first signal frame estimation, is the smoothing coefficient for the nth time, 0 < ≤ 1, determines the confidence in the new observation value , which can be configured according to a preset rule or adaptively adjusted according to some parameters of the nth first signal frame, such as the received signal strength indication (RSSI).

[0113] Each CFO estimation result among the N CFO estimation results is determined by the second AP based on at least two of the N first signal frames. A possible implementation is that the second AP receives the nth first signal frame, performs a CFO estimation algorithm in the time domain or frequency domain, and generates an estimated value . At the same time, in combination with the m CFO estimation results respectively determined by the second AP based on the m first signal frames before the nth signal, 0 < m ≤ n - 1, a weighted average algorithm is used to calculate the weighted sum of the CFO estimated values to determine the nth CFO estimation result , that is , 0 < m ≤ n - 1, and . Among them, the weight can be assigned according to a preset rule or the received signal strength indication (RSSI), signal-to-noise ratio (SNR), or the newness or oldness of the estimation time of the ith first signal frame (for example, the higher the signal-to-noise ratio and the more recent the time, the greater the weight), and the weight can also be 0.

[0114] Among them, the value of N may be affected by device temperature changes, aging, or moving speed. In a preferred implementation, the value of N can be adaptively adjusted according to the stability of the CFO estimation result, the operating temperature of the device, or the running time.

[0115] Furthermore, the second AP determines the frequency pre-correction value based on the N CFO estimation results, including that the second AP determines a frequency pre-correction value based on one CFO estimation result or at least two CFO estimation results among the N CFO estimation results.

[0116] When the second AP determines a frequency pre-correction value based on one CFO estimation result among the N CFO estimation results, a possible implementation is that the second AP uses the Nth CFO estimation result among the N CFO estimation results as the frequency pre-correction value, .

[0117] The second AP determines a frequency pre-correction value based on at least two of the N CFO estimates. One possible implementation is, for example, using a weighted average algorithm based on the Nth CFO estimate and the N-1 CFO estimates preceding it. , 1≤i≤N, and =1, determine the frequency pre-correction value. .

[0118] In one possible implementation, the second AP first filters the N CFO estimation results, determining a set of valid CFO estimation results based on whether each CFO estimation result exceeds an error threshold. Then, a frequency pre-correction value is determined based on this set of valid CFO estimation results. The error threshold is predefined or determined by at least one of the N CFO estimation results.

[0119] The effective CFO estimation result set is determined based on whether each of the N CFO estimation results exceeds an error threshold. This includes: if the nth CFO estimation result among the N CFO estimation results does not exceed or is less than the error threshold, then the effective CFO estimation result set includes the nth CFO estimation result, where 1 ≤ n ≤ N; if the nth CFO estimation result among the N CFO estimation results exceeds or is not less than the error threshold, then the effective CFO estimation result set does not include the nth CFO estimation result, where 1 ≤ n ≤ N.

[0120] To determine the set of valid CFO estimates, we need to consider whether the nth CFO estimate exceeds an error threshold. One possible approach is to determine a reference value based on the data characteristics of the first n-1 CFO estimates, such as the mean, median, filtered value, or the last valid value. If the absolute value of the deviation between the nth CFO estimate and the reference value is | If the reference value is greater than the preset dynamic or static error threshold, the nth CFO value is determined to be an invalid estimate and is removed. A set of valid CFO estimates is determined based on the valid CFO estimates. Then, a frequency pre-correction value is determined based on the M (1≤M≤N) CFO estimates in the set of valid CFO estimates.

[0121] The error threshold is predefined or determined by at least one of the N CFO estimation results. This means that the error threshold can be a preset fixed value or dynamically adjusted according to the data characteristics of at least one of the N CFO estimation results, such as dynamically adjusting according to the variance of historical CFO estimation results.

[0122] In another possible implementation, the second AP does not filter the N CFO estimation results, but takes all N CFO estimation results as valid CFO estimation results, and then determines a frequency pre-correction value through the N CFO estimation results in the CFO estimation result set.

[0123] In a preferred embodiment, the number N of CFO estimation results used to determine the frequency pre-correction value or the smoothing coefficient in the algorithm can be dynamically adjusted according to changes in ambient temperature, equipment aging, or the stability of the CFO estimation results.

[0124] In a preferred embodiment, when the second AP establishes cooperative beamforming relationships with multiple other APs, it is necessary to remember the AP ID, BSSID, or MAC address of each of the other APs, and when the first signal frame of the AP with the same identifier is received, perform the corresponding CFO estimation and determine the frequency pre-correction value.

[0125] In one possible implementation, after multiple APs terminate the Co-BF relationship, the cached CFO estimation result history is cleared.

[0126] In one possible implementation, after multiple APs terminate the Co-BF relationship, they still retain the historical record of CFO estimation results.

[0127] The second AP transmits a second signal frame based on the aforementioned frequency pre-correction value. This second signal frame is a signal frame whose frequency needs to be aligned with that of the first AP. In a preferred implementation, it includes at least one of the following: NDPA frames and / or empty data packet NDP frames transmitted during the cooperative beamforming detection phase; Cooperative beamforming trigger frames and / or cooperative beamforming physical layer protocol data units (PPDUs) are transmitted during the cooperative beamforming transmission phase.

[0128] Regarding the second signal frame, possible implementation methods are as follows: The second signal frames transmitted by the second AP include, but are not limited to, NDPA frames and / or NDP frames transmitted by the second AP during the Co-BF sounding and Co-BF joint sounding phases of the Co-BF detection phase, Co-BF trigger frames and / or Co-BF PPDUs transmitted by the second AP during the Co-BF transmission phase.

[0129] Taking sequential detection and AP1 as the first AP as an example, the second signal frame can include: When AP1 initiates a Co-BF Sounding Invite, AP2 sends an EHT sounding NDP frame in cross-BSS UHR Co-BF sounding, such as Figure 2a As shown; When AP2 initiates a Co-BF Sounding Invite, the UHR NDP Announcement frame sent by AP2 in the cross-BSS UHR Co-BF sounding, such as... Figure 2b As shown; Taking sequential detection and AP2 as the first AP as an example, the second signal frame can include: When AP1 initiates a Co-BF Sounding Invite, the UHR NDP Announcement frame sent by AP1 in cross-BSS UHR Co-BF sounding, such as... Figure 2a As shown; When AP2 initiates a Co-BF Sounding Invite, AP1 sends an EHT sounding NDP frame in cross-BSS UHR Co-BF sounding, such as Figure 2b As shown; Taking joint detection and AP1 as the first AP as an example, the second signal frame may include: When AP1 initiates a Co-BF Sounding Invite, AP2 sends an EHT sounding NDP frame, as shown in Figure 3a. When AP2 initiates a Co-BF Sounding Invite, AP2 sends a UHR NDP Announcement frame and an EHT Sounding NDP frame, such as Figure 3b As shown.

[0130] Taking joint detection and AP2 as the first AP as an example, the second signal frame may include: When AP1 initiates a Co-BF Sounding invite, AP1 sends a UHR NDP Announcement frame and an EHT Sounding NDP frame, such as Figure 3a As shown; When AP2 initiates a Co-BF Sounding invite, AP1 sends an EHT sounding NDP frame, such as Figure 3b As shown.

[0131] During the cooperative beamforming transmission phase, the second signal frame may include: Taking AP1 as the first AP and AP1 receiving the TXOP and initiating a Co-BF invite frame as an example, the second signal frame contains the Co-BF PPDU sent by AP2, such as... Figure 6 As shown; Taking AP1 as the first AP and AP2 receiving the TXOP and initiating a Co-BF invite frame as an example, the second signal frame includes the Co-BF trigger frame and Co-BF PPDU sent by AP2, such as... Figure 7 As shown; Taking AP2 as the first AP and AP1 receiving the TXOP and initiating a Co-BF invite frame as an example, the second signal frame includes the Co-BF trigger frame and Co-BF PPDU sent by AP1, such as... Figure 6 As shown; Taking AP2 as the first AP and AP2 receiving the TXOP and initiating a Co-BF invite frame as an example, the second signal frame contains the Co-BF PPDU sent by AP1, such as... Figure 7 As shown.

[0132] In a multi-AP cooperative spatial multiplexing scenario, the N first signal frames include any one of the following: at least two cooperative spatial multiplexing trigger frames, or one cooperative spatial multiplexing trigger frame and at least one non-cooperative spatial multiplexing trigger frame, or only a non-cooperative spatial multiplexing trigger frame. It should be noted that the Co-space Multiplexing Trigger Frame is a signal frame used to align transmission time and carrier frequency when multiple APs simultaneously transmit Co-SR PPDUs during the Co-space Multiplexing transmission phase. The Co-space Multiplexing Trigger Frame can also be called the Co-space Multiplexing Synchronization Frame.

[0133] The following combination Figures 10-13 As a schematic diagram of the cooperative space multiplexing transmission phase, a more detailed explanation is provided regarding the cooperative space multiplexing trigger frame and the non-cooperative space multiplexing trigger frame. AP1 and AP2 are APs used for cooperative space multiplexing. Figure 10 A schematic diagram illustrating the AP1 initiating a cooperative spatial multiplexing transmission invitation. Figure 12 This diagram illustrates a Co-SR PPDU transmission where AP1 initiates a cooperative spatial multiplexing transmission invitation, and either AP1 or AP2 has an enabled DPS or a target STA operating in eMLSR mode, or an AP requests confirmation from its associated target STA. Figure 11 A diagram illustrating the AP2 initiating a cooperative spatial multiplexing transmission invitation. Figure 13This diagram illustrates a Co-SR PPDU transmission where AP2 initiates a cooperative spatial multiplexing transmission invitation, and either AP1 or AP2 has an enabled DPS or a target STA operating in eMLSR mode, or an AP requests confirmation from its associated target STA. It should be noted that... Figures 10-13 This is merely an illustrative diagram of the cooperative spatial multiplexing transmission phase for ease of understanding. The actual signal frames transmitted during cooperative spatial multiplexing transmission may include not only those shown in the diagram, but also other signal frames. Alternatively, the names of the actual transmitted signal frames may differ from those shown in the diagram, but they may perform the same or similar functions. This invention does not impose specific limitations in this regard. Furthermore, it should be noted that in the following examples, the N first signal frames may not be within the same transmission opportunity (TXOP).

[0134] Taking AP1 initiating a Co-SR invite frame as an example, the Co-SR trigger frame is the Co-SR trigger frame sent by AP1, such as... Figure 10 As shown.

[0135] Taking AP2 initiating a Co-SR invite frame as an example, the Co-SR trigger frame is the Co-SR trigger frame sent by AP2, such as... Figure 11 As shown.

[0136] It should be noted that the non-cooperative spatial multiplexing trigger frame includes Co-SRinvite frame, Co-SR response frame, ICF, MU-BAR frame in the cooperative spatial multiplexing transmission phase, or any non-cooperative spatial multiplexing trigger frame sent by the first AP in the cooperative spatial multiplexing transmission phase in a future communication system.

[0137] Taking AP1 as the first AP and AP1 initiating a Co-SR invite as an example, the non-cooperative spatial multiplexing trigger frame can be one or more of the following signal frames: The Co-SR invite frame sent by AP1, such as Figure 10 As shown; The MU-BAR frame sent by AP1, such as Figure 12 As shown; If AP1 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative spatial multiplexing trigger frame can also be an ICF sent by AP1, for example... Figure 12 As shown.

[0138] Taking AP1 as the first AP, AP2 initiating a Co-SR invite, and AP1 responding with a Co-SR response frame as an example, the non-cooperative spatial multiplexing trigger frame can be one or more of the following signal frames: The Co-SR response frame sent by AP1, such as Figure 11 As shown; The MU-BAR frame sent by AP1, such as Figure 13 As shown; If AP1 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative spatial multiplexing trigger frame can also be an ICF sent by AP1, for example... Figure 13 As shown.

[0139] Taking AP2 as the first AP and AP2 initiating a Co-SR invite as an example, the non-cooperative spatial multiplexing trigger frame can be one or more of the following signal frames: The Co-SR invite frame sent by AP2, such as Figure 11 As shown; MU-BAR frames sent by AP2, such as Figure 13 As shown; If AP2 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative spatial multiplexing trigger frame can also be an ICF sent by AP2, for example. Figure 13 As shown.

[0140] Taking AP2 as the first AP, AP1 initiating a Co-SR invite, and AP2 responding with a Co-SR response frame as an example, the non-cooperative spatial multiplexing trigger frame can be one or more of the following signal frames: The Co-SR response frame sent by AP2, such as Figure 10 As shown; MU-BAR frames sent by AP2, such as Figure 12 As shown; If AP2 has a target STA with DPS enabled, or a target STA operating in eMLSR mode, the non-cooperative spatial multiplexing trigger frame can also be an ICF sent by AP2, for example. Figure 12 As shown.

[0141] Among them, N first signal frames contain at least two cooperative space multiplexing trigger frames in the cooperative space multiplexing transmission phase: One possible implementation is to take AP1 as the first AP initiating a Co-SR PPDU transmission as an example, referring to... Figure 10When AP1 initiates multiple Co-SR PPDU transmissions, the N first signal frames include at least two Co-SR trigger frames sent by AP1. These at least two Co-SR trigger frames can be trigger frames transmitted after AP1 sends a Co-SR invite frame, or trigger frames transmitted after each of multiple Co-SR invite frames sent by AP1. The N first signal frames can also include non-cooperative spatial multiplexing trigger frames, exemplified by AP1 being the first AP and AP1 initiating a Co-SR invite frame, and / or non-cooperative spatial multiplexing trigger frames, exemplified by AP2 being the first AP and AP1 responding with a Co-SR response frame. Alternatively, exemplified by AP2 being the first AP initiating a single Co-SR PPDU transmission, refer to [reference needed]. Figure 11 The N first signal frames include at least two Co-SR trigger frames sent by AP2. These at least two Co-SR trigger frames can be trigger frames transmitted after AP2 sends a Co-SR invite frame, or trigger frames transmitted after each of multiple Co-SR invite frames sent by AP2. The N first signal frames may also include non-cooperative spatial multiplexing trigger frames, exemplified by AP2 being the first AP and AP2 initiating a Co-SR invite frame, and / or non-cooperative spatial multiplexing trigger frames, exemplified by AP2 being the first AP, AP1 initiating a Co-SR invite, and AP2 responding with a Co-SR response frame.

[0142] The N first signal frames include one cooperative spatial multiplexing trigger frame and at least one non-cooperative spatial multiplexing trigger frame in the cooperative spatial multiplexing transmission phase: One possible implementation is that the N first signal frames include Co-SR trigger frames and non-cooperative spatial multiplexing trigger frames. For example, the N first signal frames include a cooperative spatial multiplexing trigger frame where AP1 is the first AP and AP1 initiates a Co-SR invite frame; the N first signal frames also include at least one non-cooperative spatial multiplexing trigger frame where AP1 is the first AP and AP1 initiates a Co-SR invite frame; and / or, at least one non-cooperative spatial multiplexing trigger frame where AP2 is the first AP and AP1 initiates a Co-SR invite frame, and AP1 responds with a Co-SR response frame. Alternatively, for example, the N first signal frames include a cooperative spatial multiplexing trigger frame where AP2 is the first AP and AP2 initiates a Co-SR invite frame; the N first signal frames also include at least one non-cooperative spatial multiplexing trigger frame where AP2 is the first AP and AP2 initiates a Co-SR invite frame; and / or, at least one non-cooperative spatial multiplexing trigger frame where AP1 is the first AP and AP2 responds with a Co-SR response frame.

[0143] Among them, N first signal frames contain only non-cooperative spatial multiplexing trigger frames: One possible implementation is that the N first signal frames contain only non-cooperative spatial multiplexing trigger frames from the cooperative spatial multiplexing transmission phase, and do not contain cooperative spatial multiplexing trigger frames. For example, the N first signal frames may contain non-cooperative spatial multiplexing trigger frames, exemplified by AP1 being the first AP and AP1 initiating a Co-SR invite, and / or, the N first signal frames may contain non-cooperative spatial multiplexing trigger frames, exemplified by AP2 being the first AP and AP1 responding with a Co-SR response frame. Alternatively, for example, the N first signal frames may contain non-cooperative spatial multiplexing trigger frames, exemplified by AP2 being the first AP and AP2 initiating a Co-SR invite, and / or, the N first signal frames may contain non-cooperative spatial multiplexing trigger frames, exemplified by AP1 being the first AP and AP2 responding with a Co-SR response frame.

[0144] The second AP determines a frequency pre-correction value based on N first signal frames. This process is similar to the cooperative beamforming process and will not be described in detail here.

[0145] The second AP transmits a second signal frame based on the aforementioned frequency pre-correction value. This second signal frame is a signal frame whose frequency needs to be aligned with that of the first AP. In a preferred implementation, it includes at least one of the following: Cooperative space multiplexing trigger frames and / or cooperative space multiplexing physical layer protocol data units (PPDUs) transmitted during the cooperative space multiplexing transmission phase.

[0146] Regarding the second signal frame, possible implementation methods are as follows: During the cooperative spatial multiplexing transmission phase, the second signal frame may include: Taking AP1 as the first AP and AP1 initiating a Co-SR invite frame as an example, the second signal frame contains the Co-SRPPDU sent by AP2, such as... Figure 10 As shown; Taking AP1 as the first AP and AP2 as the initiator of the Co-SR invite frame as an example, the second signal frame includes the Co-SR trigger frame sent by AP2, and / or, the Co-SR PPDU, such as Figure 11 As shown; Taking AP2 as the first AP and AP1 initiating a Co-SR invite frame as an example, the second signal frame includes the Co-SR trigger frame sent by AP1, and / or, a Co-SR PPDU, such as... Figure 10 As shown; Taking AP2 as the first AP and AP2 initiating a Co-SR invite frame as an example, the second signal frame contains the Co-SRPPDU sent by AP1, such as... Figure 11 As shown.

[0147] When the first communication device and the second communication device simultaneously establish a cooperative beamforming relationship and a cooperative spatial multiplexing relationship, the N first signal frames may also include signal frames transmitted in cooperative beamforming and signal frames transmitted in cooperative spatial multiplexing. The signal frames transmitted in cooperative beamforming include signal frames in the cooperative beamforming detection phase and / or signal frames in the cooperative beamforming transmission phase.

[0148] One possible implementation is that the N first signal frames include Co-BF trigger frames in the cooperative beamforming transmission phase and Co-SR trigger frames in the cooperative spatial multiplexing transmission phase. For example, the N first signal frames include a cooperative beamforming trigger frame with AP1 as the first AP and AP1 initiating a Co-BF invite frame upon receiving a TXOP, and the N first signal frames also include a cooperative spatial multiplexing trigger frame with AP1 as the first AP and AP1 initiating a Co-SR invite frame. The N first signal frames may also include, for example, a non-cooperative beamforming trigger frame where AP1 is the first AP and AP1 receives a TXOP-initiated Co-BF invite frame, and / or, a non-cooperative beamforming trigger frame where AP1 is the first AP, AP2 receives a TXOP-initiated Co-BF invite frame, and AP1 responds with a Co-BF response frame, and / or, a non-cooperative spatial multiplexing trigger frame where AP1 is the first AP and AP1 initiates a Co-SR invite frame, and / or, a non-cooperative spatial multiplexing trigger frame where AP1 is the first AP, AP2 initiates a Co-SR invite frame, and AP1 responds with a Co-SR response frame. Alternatively, for example, the N first signal frames may include a cooperative beamforming trigger frame where AP2 is the first AP and AP2 receives a TXOP-initiated Co-BF invite frame, and the N first signal frames may also include a cooperative spatial multiplexing trigger frame where AP2 is the first AP and AP2 initiates a Co-SR invite frame. The N first signal frames may also include non-cooperative beamforming trigger frames, such as AP1 receiving a TXOP and initiating a Co-BF invite frame, with AP2 as the first AP, and / or non-cooperative beamforming trigger frames, such as AP2 receiving a TXOP and initiating a Co-BF invite frame, with AP1 responding to a Co-BF response frame, with AP2 as the first AP, and / or non-cooperative spatial multiplexing trigger frames, such as AP2 receiving a Co-SR invite frame, with AP2 as the first AP, and / or non-cooperative spatial multiplexing trigger frames, such as AP1 receiving a Co-SR invite frame, with AP2 responding to a Co-SR response frame.

[0149] In the STA uplink transmission scenario, the first communication device is the AP and the second communication device is the STA. The STA uplink transmission scenario includes scenarios where multiple STAs transmit uplink simultaneously, or scenarios where STAs transmit ELR PPDUs uplink. In a scenario where multiple STAs simultaneously transmit uplink, each STA receives N first signal frames. These first signal frames are trigger frames sent by the AP and / or non-trigger frames sent by the AP. The trigger frames are signal frames sent by the AP when scheduling multiple STAs to transmit uplink simultaneously. Each STA determines N CFO estimation results based on the N first signal frames and determines a frequency pre-correction value based on the N CFO estimation results. This frequency pre-correction value is used for frequency pre-compensation in second signal frames. The second signal frame can be a trigger-based physical layer protocol data unit (TB PPDU) sent by the STA, including High Efficiency Trigger-Based Physical Layer Protocol Data Unit (HE TB PPDU), Extremely High Throughput Trigger-Based Physical Layer Protocol Data Unit (EHT TB PPDU), Ultra High Probability Trigger-Based Physical Layer Protocol Data Unit (UHR TB PPDU), or a TB PPDU used for uplink transmission in future communication systems. Any of the PPDUs, or the second signal frame, can be a non-high throughput physical layer protocol data unit (non-HT PPDU) or a non-high throughput duplicate physical layer protocol data unit (non-HT duplicate PPDU) with the trigger response (TRIGGER_RESPONDING) parameter set to True in the transmission vector (TXVECTOR). In the STA uplink transmission ELR PPDU scenario, the STA receives N first signal frames. These first signal frames are signal frames sent by the target AP. The address of the first signal frame can be the STA's address or broadcast address. The first signal frame is a signal frame other than UHR NDP Announcement, downlink non-orthogonal frequency division multiple access cooperative beamforming physical layer protocol data unit (DL non-OFDMA Co-BF PPDU), and downlink single user cooperative spatial multiplexing physical layer protocol data unit (DL SU Co-SR PPDU). The STA determines N CFO estimation results based on the N first signal frames and determines a frequency pre-correction value based on the N CFO estimation results. The frequency pre-correction value is used for frequency pre-compensation in the second signal frame, where the second signal frame is the ELR PPDU sent by the STA.

[0150] In one possible implementation, the second communication device maintains historical records of CFO estimation results for multiple frequency bands and / or multiple channels for the first communication device. The historical records of CFO estimation results for each of the multiple frequency bands are used to determine the frequency pre-correction value for the corresponding frequency band; the historical records of CFO estimation results for each of the multiple channels are used to determine the frequency pre-correction value for the corresponding channel; wherein the multiple frequency bands include at least two different frequency bands among 2.4G, 5G, 6G, millimeter wave, and other frequency bands supported in future communication systems, and the frequency ranges or center frequencies of the multiple channels are different.

[0151] Among these, multiple channels have different frequency ranges and center frequencies. For example, in the 20MHz channel of the 5G band, the center frequency of channel number 36 is 5180MHz, and the frequency range is 5170-5190MHz. Another example is the 20MHz channel of the 2.4G band, where the center frequency of channel number 1 is 2412MHz, and the frequency range is 2402-2422MHz. Or, for example, in the 80MHz channel of the 5G band, four consecutive 20MHz channels are bundled together. One possible implementation is to bundle channels numbered 36, 40, 44, and 48, with a center frequency of 5210MHz and a frequency range of 5170-5250MHz.

[0152] The frequency alignment method provided by this invention can also be applied to a first communication device, wherein the first communication device is a first AP (frequency reference AP) for cooperative beamforming or cooperative spatial multiplexing. In cooperative beamforming, assuming AP1 is the first AP and AP2 is the second AP, the first AP utilizes the UHR NDP Announcement frames (referred to as references respectively) transmitted by the second AP during the cross-BSS UHR Co-BF sounding and / or Co-BF jointsounding phases. Figure 2b , and / or, refer to Figure 3b ), and / or, the Co-BF trigger frame sent by the second AP during the transmission phase (see reference). Figure 7 The CFO results are estimated and stored multiple times, and a frequency precorrection value is determined; in cross-BSS UHR Co-BF sounding, and / or, Co-BF Joint sounding, the first AP estimates the transmitted EHT sounding NDP frames (referencing the frequency precorrection value respectively) based on the frequency precorrection value. Figure 2b , and / or, refer to Figure 3b Pre-compensation is performed, and / or, during the transmission phase, the first AP pre-corrects the transmitted Co-BF PPDU (reference) based on the frequency pre-correction value. Figure 7Pre-compensation is performed. In cooperative space reuse, assuming AP1 is the first AP and AP2 is the second AP, the first AP utilizes the Co-SR trigger frames sent multiple times by the second AP (see reference). Figure 11 The CFO results are estimated and stored multiple times, and a frequency pre-correction value is determined; the first AP adjusts the transmitted Co-SR PPDU (reference) based on the frequency pre-correction value. Figure 11 ) to make pre-compensation.

[0153] This invention provides a frequency alignment method that effectively overcomes the problem of single estimation being susceptible to interference by using multiple signal frames for multiple estimations and comprehensive processing, significantly improving the accuracy and robustness of frequency alignment, thereby ensuring the performance of scenarios such as multi-AP cooperative beamforming, multi-AP cooperative spatial multiplexing, multiple STA simultaneous uplink transmission, and STA uplink transmission ELR PPDU.

[0154] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0155] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A frequency alignment method, characterized in that, Performed by a second communication device, the method includes: Receive N first signal frames from the first communication device, where N is an integer greater than 1; Based on the N first signal frames, a frequency pre-correction value is determined, which is used to align the frequency with the first communication device; A second signal frame is sent according to the frequency pre-correction value, the second signal frame being a signal frame whose frequency needs to be aligned with the first communication device.

2. The frequency alignment method according to claim 1, characterized in that, The step of determining a frequency pre-correction value based on the N first signal frames includes: Based on the N first signal frames, determine the N carrier frequency deviation (CFO) estimation results; Based on the N CFO estimation results, the frequency pre-correction value is determined.

3. The frequency alignment method according to claim 2, characterized in that, The determination of N carrier frequency deviation (CFO) estimation results based on the N first signal frames includes any of the following methods: Method A: Each of the N CFO estimation results is determined based on one of the N first signal frames; Method B: Each of the N CFO estimation results is determined based on at least two of the N first signal frames.

4. The frequency alignment method according to claim 2, characterized in that, The step of determining the frequency pre-correction value based on the N CFO estimation results includes: Based on whether each of the N CFO estimation results exceeds the error threshold, a set of valid CFO estimation results is determined; The frequency pre-correction value is determined based on the set of effective CFO estimation results; The error threshold is predefined, or determined by at least one of the N CFO estimation results; The step of determining the set of valid CFO estimates based on whether each of the N CFO estimates exceeds an error threshold includes: If the nth CFO estimate among the N CFO estimates does not exceed or is less than the error threshold, then the set of valid CFO estimates includes the nth CFO estimate, where 1 ; If the nth CFO estimate among the N CFO estimates exceeds or is not less than the error threshold, then the set of valid CFO estimates does not include the nth CFO estimate, where 1 .

5. The frequency alignment method according to claim 2, characterized in that, The step of determining the frequency pre-correction value based on the N CFO estimation results includes: The frequency pre-correction value is determined based on one of the N CFO estimation results or at least two CFO estimation results.

6. The frequency alignment method according to claim 1, characterized in that, The N first signal frames are all signal frames transmitted during the cooperative beamforming detection phase, and include at least one of the following frame type combinations: a) At least two empty data packets announce NDPA frames; b) One NDPA frame and at least one non-NDPA frame; c) All are non-NDPA frames.

7. The frequency alignment method according to claim 1, characterized in that, The N first signal frames are all signal frames transmitted during the cooperative beamforming transmission phase, and include at least one of the following frame type combinations: a) At least two cooperative beamforming trigger frames; b) A cooperative beamforming trigger frame and at least one non-cooperative beamforming trigger frame; c) All are non-cooperative beamforming trigger frames.

8. The frequency alignment method according to claim 1, characterized in that, The N first signal frames include signal frames transmitted at different stages of cooperative beamforming; the different stages of cooperative beamforming include a detection stage and a transmission stage.

9. The frequency alignment method according to claim 1, characterized in that, The second signal frame is a signal frame that needs to be aligned with the frequency of the first communication device, including at least one of the following: NDPA frames and / or empty data packet NDP frames during the cooperative beamforming detection phase; Cooperative beamforming trigger frame in the cooperative beamforming transmission phase, and / or, cooperative beamforming physical layer protocol data unit (PPDU).

10. The frequency alignment method according to claim 1, characterized in that, The N first signal frames are signal frames transmitted during the cooperative spatial multiplexing transmission phase, and include at least one of the following frame type combinations: a) At least two cooperative spatial multiplexing trigger frames; b) A cooperative spatial multiplexing trigger frame and at least one non-cooperative spatial multiplexing trigger frame; c) All are non-cooperative spatial multiplexing trigger frames.

11. The frequency alignment method according to claim 1, characterized in that, The N first signal frames include signal frames transmitted in cooperative beamforming and signal frames transmitted in cooperative spatial multiplexing; the signal frames transmitted in cooperative beamforming include signal frames in the cooperative beamforming detection phase and / or signal frames in the cooperative beamforming transmission phase.

12. The frequency alignment method according to claim 1, characterized in that, The second signal frame is a signal frame that needs to be aligned with the frequency of the first communication device, including at least one of the following: Cooperative space multiplexing trigger frame in the cooperative space multiplexing transmission phase, and / or, cooperative space multiplexing physical layer protocol data unit (PPDU).

13. The frequency alignment method according to claim 1, characterized in that, The N first signal frames are trigger frames and / or non-trigger frames. The trigger frame is a signal frame sent by the first communication device when scheduling multiple stations to perform uplink transmission simultaneously. The multiple stations include the second communication device.

14. The frequency alignment method according to claim 1, characterized in that, The second signal frame includes a signal frame from which the second communication device responds to a trigger frame sent by the first communication device, and / or an Enhanced Long Distance Physical Layer Protocol Data Unit (ELR PPDU).

15. The frequency alignment method according to claim 2, characterized in that, The method further includes: When the second communication device establishes a cooperative beamforming relationship and / or a cooperative spatial multiplexing relationship with multiple different first communication devices, an independent historical record of CFO estimation results and frequency pre-correction value are maintained for each first communication device. The second communication device updates the CFO estimation result to the historical record of the CFO estimation result of the communication device corresponding to the first communication device based on the identification information of the first communication device, and determines the frequency pre-correction value corresponding to the communication device.

16. The frequency alignment method according to claim 2, characterized in that, The method further includes: The second communication device maintains historical records of CFO estimation results for multiple frequency bands and / or multiple channels for the first communication device. The historical records of CFO estimation results for each of the multiple frequency bands are used to determine the frequency pre-correction value of the corresponding frequency band; the historical records of CFO estimation results for each of the multiple channels are used to determine the frequency pre-correction value of the corresponding channel. The plurality of frequency bands include at least two different frequency bands from the following: 2.4G band, 5G band, 6G band, millimeter wave band, and other frequency bands supported in future communication systems. The frequency range or center frequency of the plurality of channels are different.

17. A communication device, characterized in that, Configured to operate as a second communication device in the frequency alignment method according to any one of claims 1-16, comprising: A receiving module is used to receive N first signal frames from a first communication device; The processing module is used to determine N CFO estimation results and one frequency pre-correction value based on the N first signal frames; The storage module is used to store the N CFO estimation results, the frequency pre-correction value, and maintain the historical record of CFO estimation results for multiple different first communication devices and / or different frequency bands and / or different channels; The transmitting module is used to transmit a second signal frame with a frequency aligned with the first communication device according to the frequency pre-correction value.

18. The communication device according to claim 17, characterized in that, The processing module is specifically configured to perform the following operations: Determine whether each of the N CFO estimation results exceeds the error threshold, determine the set of valid CFO estimation results, and determine the frequency pre-correction value based on the set of valid CFO estimation results. Alternatively, the frequency pre-correction value may be determined based on one of the N CFO estimation results or at least two CFO estimation results.

19. A wireless communication system, characterized in that, The wireless communication system includes at least one first communication device and at least one second communication device, the second communication device being used to perform the method as described in any one of claims 1-16.

20. A chip or chip system, characterized in that, The chip or chip system includes a processor coupled to a memory for storing programs or instructions that, when executed by the processor, cause the method as described in any one of claims 1-16 to be performed.

21. A non-transitory computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it causes the communication device to implement the frequency alignment method as described in any one of claims 1-16.

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