CN110034801B

CN110034801B - Method and device for beam training

Info

Publication number: CN110034801B
Application number: CN201810030203.3A
Authority: CN
Inventors: 刘劲楠; 李德建
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-01-12
Filing date: 2018-01-12
Publication date: 2021-10-01
Anticipated expiration: 2038-01-12
Also published as: CN110034801A

Abstract

The application provides a method and a device for beam training, which can adopt a directional antenna to receive and transmit a beam training frame in an outdoor return scene so as to align beams. The method for beam training comprises the following steps: the method comprises the steps that a first device sends at least one first sector scanning SSW frame to at least one second device by adopting a first beam direction and a first Modulation Coding Scheme (MCS), wherein the data rate of the first MCS is greater than or equal to 27.5 Mbps; the first device receives a first sector scanning Feedback (SSW) Feedback frame sent by the second device after the Feedback offset indicated in the first SSW frame; and after receiving the first SSW Feedback frame, the first device sends a first sector scanning acknowledgement (SSW ACK) frame to the second device after the acknowledgement offset indicated in the first SSW frame.

Description

Method and device for beam training

Technical Field

The present application relates to the field of communications, and more particularly, to a method and apparatus for beam training in the field of communications.

Background

The internet of things (IoT) traffic is very decentralized and flexible. If conventional optical fiber backhaul is used between each Access Point (AP), the network deployment cost is high. At this time, when wireless communication connection is adopted among some access points, the requirements of dispersion and flexibility of IoT services can be met, and the deployment cost of the network can be reduced. The millimeter wave frequency band has a large amount of frequency spectrum, and can inherit more antenna elements (elements), and can realize directional transmission, so that the millimeter wave frequency band can be used for a wireless backhaul system. Meanwhile, in the 60GHz millimeter wave band, there is a wireless access device defined by the international Institute of Electrical and Electronics Engineers (IEEE) 802.11 ad. Therefore, as an evolved version of IEEE 802.11ad, a unified protocol architecture may be adopted in a use case defined by the standard of IEEE 802.11ay, while supporting a wireless access scenario and a wireless backhaul scenario.

The IEEE 802.11ay standard has followed the IEEE 802.11ad network architecture, which supports the directional gigabit (DMG) standard. The DMG standard supports a data transmission type based on a scheduled Service Period (SP). The beam training is a specific flow in high-frequency communication, and because the attenuation of a high-frequency channel is large, if the receiving and transmitting parties do not align the beams, the transmission rate is low, and even the communication cannot be performed. Therefore, a communication scenario in which a receiving end misalignment beam is compensated by 32-fold spread spectrum adopted by a Modulation and Coding Scheme (MCS) 0, that is, a scenario in which quasi-omni reception is adopted, is designed in IEEE 802.11 ad. In the beam training process, 3 Beamforming (BF) frames are defined for Sector Level Scan (SLS), which are a Sector Scan (SSW) frame, a Sector scan Feedback (SSW-Feedback) frame, and a Sector scan acknowledgement (SSW ACK) frame.

However, the outdoor backhaul scenario is different from the indoor scenario, and particularly, in the outdoor backhaul scenario, in order to improve coverage and reduce deployment cost, and not limited by the area of the handheld terminal, the antenna gain may be greater than 15 dB. Causing MCS0 in IEEE 802.11ad, which is designed to compensate the link budget of the quasi-omni antenna, to be used for beam training may cause a bottleneck of the system.

On one hand, if the receiving end continues to use the 11ad middle receiving end to receive the beam training frame by adopting the quasi-omnidirectional antenna, the range of the received beam training frame is too small. Assuming a 25dB gain for the main receive beam in the outdoor backhaul scenario, this results in a 10dB higher power for the directional receive MCS1 frame than for the quasi-omni receive MCS0 frame. That is to say, when both the transceiver and the transmitter use the directional antenna to transmit and receive, the two devices may be able to communicate with each other, and the beams cannot be aligned because the beam training frame cannot be received.

Disclosure of Invention

The application provides a method and a device for beam training, which can adopt a directional antenna to receive and transmit a beam training frame in an outdoor return scene so as to align beams.

In a first aspect, a method for beam training is provided, including:

the method comprises the steps that a first device sends at least one first sector scanning SSW frame to at least one second device by adopting a first beam direction and a first Modulation Coding Scheme (MCS), wherein the data rate of the first MCS is greater than or equal to 27.5 Mbps;

the first device receives a first sector scanning Feedback (SSW) Feedback frame sent by the second device after the Feedback offset indicated in the first SSW frame;

and after receiving the first SSW Feedback frame, the first device sends a first sector scanning acknowledgement (SSW ACK) frame to the second device after the acknowledgement offset indicated in the first SSW frame.

Therefore, in this embodiment of the present application, since the data rate of the first MCS is greater than 27.5Mbps, the first device may increase the range of the received beam training frame by sending the first TDD SSW with the first MCS, further reduce the difference between the coverage of the control physical layer PHY and the coverage of the data physical layer PHY, and ensure correct reception of control transmission, so the method for beam training in this embodiment of the present application may be applicable to an outdoor backhaul scenario.

In this embodiment of the present application, the first device is a party initiating beam training, and may also be referred to as an initiator (initiator) or initiator device, and may be, for example, an AP/PCP or an STA. The second device is the other side of the beam training and may also be referred to as a responder (responder) or responder device, which may be an AP/PCP or STA, for example.

Here, the SSW frame may be specifically a TDD SSW frame. Specifically, 3 types of BF frames are defined in the TDD SP, which may be referred to as TDD SSW frame, TDD SSW Feedback frame, and TDD SSW ACK frame. It should be noted that, in order to distinguish the SSW frame in the DTI phase from the SSW frame in the conventional Sector Level Sweep (SLS) process, the SSW frame in the TDD SP phase is referred to as TDD SSW. Similarly, the SSW Feedback frame in the TDD SP phase is referred to as a TDD SSW Feedback frame, and the SSW ACK frame in the TDD SP phase is referred to as an TDD SSW ACK frame.

Specifically, the second device may determine, according to reciprocity, a transmission beam direction for transmitting the first TDD SSW Feedback frame in the process of receiving the first TDD SSW frame. As an embodiment, the first TDD SSW Feedback frame may be transmitted in a receiving beam direction in which the first TDD SSW frame is received, that is, the receiving beam direction in which the first TDD SSW frame is received is the same as the transmitting beam direction in which the first TDD SSW Feedback frame is transmitted. Also, since both the transmit antenna gain and the receive antenna gain are considered during the transceiving of the TDD SSW frame, if it is desired that the TDD SSW Feedback frame be received by the initiator, it is also desired that the initiator employ directional reception. At this time, the initiator may receive the first TDD SSW Feedback frame in the first beam direction. However, before the first TDD SSW Feedback frame, the initiator has not actually received any Feedback from the responder, and therefore, the initiator can only receive the TDD first SSW Feedback frame using the transmit beam direction of the first TDD SSW frame (i.e., the first beam direction) by using channel reciprocity.

Here, the first TDD SSW frame, the first TDD SSW Feedback frame, and the first TDD SSW ACK frame refer to three beam training frames transmitted by both the initiator and the responder during the first handshake. That is, at least one TDD SSW frame of the first TDD SSW frames is received by the responder device. And there is no beam training information between the initiator device and the responder device before the first TDD SSW Feedback frame and the first TDD SSW ACK frame. Therefore, after the first TDD SSW frame, the first TDD SSW Feedback frame, and the first TDD SSW ACK frame are transmitted, the initiator device and the responder device obtain the initial receiving beam direction and transmitting beam direction information.

Optionally, the first modulation and coding scheme MCS is a transmission format with MCS identifier 1 defined in the directional multi-gigabit DMG protocol, that is, MCS 1.

Specifically, in the embodiment of the present application, a preferred embodiment is to transmit the first TDD SSW frame by using MCS1, so that the transmission format defined in the protocol is directly used without redesigning software and hardware. Where MCS1 is used the SNR of control transmission is the same as data transmission. If the L-Header transmission is adopted, the SNR of the control transmission is 3-4 dB lower than that of the data transmission, but the control transmission can be correctly received at the moment. And if the EDMG Header-A transmission format is adopted, the SNR of the control transmission is 2-3 dB lower than that of the data transmission, but the control transmission can be correctly received at the moment. If the MCS0 spreading factor is modified to 8, the SNR of the control transmission is 4-5 dB lower than that of the data transmission, but the control transmission can be correctly received at the moment. Usually, a certain margin is required for the engineering. These designs are acceptable, but according to MCS0, leaving a margin 10dB lower than the SNR of data transmission has a large impact on the coverage, which may cause MCS0 to perform beam training on the node, and MCS1 transmission cannot be used.

Optionally, the first SSW frame includes an indication for indicating the number of the second devices.

The indication may be, for example, a first field. Therefore, in the embodiment of the present application, the first device may perform beam training with multiple second devices at the same time. Furthermore, when the receiving end receives the beam training frame by adopting the directional antenna to perform beam training, one-to-many training can be performed, so that the beam training efficiency is improved.

Optionally, the method further includes:

after sending the first SSW ACK frame, the first device sends a second SSW frame using a second beam, where the second beam includes at least one beam direction;

the first device receives a second SSW Feedback frame sent by the second device after the Feedback offset indicated in the first SSW ACK frame;

and the first equipment sends a second SSW ACK frame to the second equipment after the acknowledgement offset indicated in the first SSW ACK frame.

It should be noted that in the embodiment of the present application, the frame formats of the first SSW frame and the second SSW frame may be the same. The frame formats of the first SSW Feedback frame and the second SSW Feedback frame may be the same. The frame format of the first TDD SSW ACK frame and the second TDD SSW frame may be the same.

When the end of training field indicates that the beam training is not finished, indication information is carried through the first TDD SSW ACK. That is, in addition to the responder Feedback offset field and the initiator acknowledgement offset field included in the TDD SSW frame, the responder Feedback offset field and the initiator acknowledgement offset field are also included in the first TDD SSW ACK frame, where the Feedback offset field is used to indicate the time when the initiator receives the TDD SSW Feedback frame next time (the second time TDD SSW ACK with respect to the first time TDD SSW ACK), and the acknowledgement offset field is used to indicate the time when the initiator transmits TDD SSW ACK frames next time (the second time TDD SSW ACK with respect to the first time TDD SSW ACK). It can be understood that the TDD SSW Feedback frame transmitted next time refers to the first TDD SSW Feedback frame transmitted by the responder after receiving the first TDD SSW ACK frame, and may be referred to as a second TDD SSW Feedback frame. The next transmitted TDD SSW ACK frame refers to the first TDD SSW ACK frame transmitted by the initiator after the first TDD SSW ACK frame and may be referred to as a second TDD SSW Feedback frame.

Alternatively, in the embodiment of the present application, the data rate of the first MCS may also be equal to 27.5Mbps, that is, in this case, the data rate of MCS0 is adopted for the first SSW frame. Unlike the prior art, the first SSW frame may carry an indication that the data rate of the second SSW frame with the second MCS is greater than 27.5 Mbps. After the handshake between the first device and the second device is completed through the first SSW Feedback and the first SSW ACK, the second SSW frame may be transmitted with a higher data amount, and may carry more information, such as management information.

In a particular implementation, the responder device sends a second TDD SSW Feedback frame to the initiator device after receiving the responder Feedback offset after the first TDD SSW ACK frame. Here, the responder feedback offset is the feedback offset indicated by the responder feedback offset field in the first TDD SSW ACK frame. And, if the initiator device receives the second TDD SSW Feedback frame after transmitting the second TDD SSW frame, then a second TDD SSW ACK is transmitted to the responder device after a second time interval after transmitting the first TDD SSW ACK frame, where the second time interval is the sum of the responder Feedback offset and the initiator acknowledgement offset, which is the acknowledgement offset indicated by the initiator acknowledgement offset field in the first TDD SSW ACK frame.

It should be understood that, in the embodiment of the present application, the second TDD SSW frame may also include a responder feedback offset and an initiator acknowledgement offset. And the transmission time of the second TDD SSW Feedback frame indicated by the responder Feedback offset in the second TDD SSW frame coincides with the transmission time of the second TDD SSW Feedback frame indicated by the responder Feedback offset in the first TDD SSW ACK frame. Likewise, the transmission time of the second TDD SSW ACK frame indicated by the initiator acknowledgement offset in the second TDD SSW frame coincides with the transmission time of the second TDD SSW ACK frame indicated by the initiator acknowledgement offset in the first TDD SSW ACK frame. The offset calculations are made with respect to the time instant of the TDD SSW frame and with respect to the time of TDD SSW ACK, respectively.

Further, after the first transceiver obtains the beam information that can be communicated, all the beam training processes may adopt the first TDD SSW Feedback frame and the transmit and receive beam configurations adopted by the first TDD SSW ACK. Therefore, the beam training frame used in the subsequent beam training process may also be referred to as the second frame, for example, the subsequent TDD SSW frame may also be referred to as the second TDD SSW frame, the subsequent TDD SSW Feedback frame may also be referred to as the second TDD SSW Feedback frame, and the subsequent TDD SSW ACK frame may also be referred to as the second TDD SSW ACK frame.

Also, the frame formats of the first TDD SSW ACK frame and the second TDD SSW ACK frame may be the same, then the second TDD SSW ACK frame may also include a responder feedback offset field and an initiator acknowledgement offset field. And, the feedback offset field is used to indicate the time of the first TDD SSW feedback frame received by the initiator after the second TDD SSW ACK frames, and the acknowledgement offset field is used to indicate the time of the first TDD SSW ACK frames transmitted by the initiator after the second TDD SSW ACK frames. For example, the TDD SSW ACK frame sent for the second time may include a first responder Feedback offset field for indicating the time when the initiator receives the TDD SSW Feedback frame for the third time and a first initiator acknowledgement offset field for indicating the time when the initiator sends TDD SSW ACK the third time.

Optionally, the first SSW Feedback frame includes an identifier of a first receive beam and a first signal-to-noise ratio SNR, where the first receive beam is a receive beam of the first SSW frame received by the second device, and the first SNR is an SNR for receiving the first SSW frame using the first receive beam;

the second SSW Feedback frame includes an identifier of a second receive beam and a second signal-to-noise ratio (SNR), where the second receive beam is a receive beam of a training frame of the first SSW frame and the second SSW frame received by the second device, and the second SNR is an SNR for receiving the training frame using the second receive beam;

wherein the first SNR is different from the second SNR or an identity of the first receive beam is different from an identity of the second receive beam.

Since the TDD SSW frame transmission may be divided into multiple segments by the TDD SSW Feedback frames TDD SSW ACK, if the current best beam id and SNR are fed back in each Feedback frame in 11ad/11ay, resources of part of the Feedback frame are wasted (the resources here refer to time-frequency resources and resources transmitted in a certain frequency band within a certain time period). Moreover, since the offset of the TDD SSW Feedback is carried in the TDD SSW frame in the existing mechanism, the second device may not receive the TDD SSW, and therefore, the resource of the pre-allocated TDD SSW Feedback frame is wasted. Similarly, TDD SSW ACK, since the TDD SSW Feedback frame cannot be received, the resource of TDD SSW ACK frames allocated in advance is wasted. While in our design the parameters of TDD SSW Feedback offset and TDD SSW ACK acknowledgement offset are carried in the previous TDD SSW ACK, so the resources of the subsequent pre-allocated TDD SSW Feedback frame and TDD SSW ACK frame are always used for transmission. Therefore, preferably, when the first SNR is different from the second SNR or the identification of the first receiving beam is different from the identification of the second receiving beam, the receiving end can always report the best beam information of the beams that have not been reported, i.e. the identification and SNR of the beams.

Optionally, the first device receives the first SSW Feedback frame and the second SSW Feedback frame in the first beam direction.

Optionally, the first device sends the first SSW ACK frame and the second SSW ACK frame in the first beam direction.

After the first handshake, both the transceiver and the transmitter may determine a transceiving mode in which data transmission may be performed, so as to ensure that the TDD SSW Feedback and TDD SSW ACK may be successfully transmitted in the training process, in the subsequent training process, the initiator may receive a second TDD SSW Feedback frame in the beam direction trained in the first handshake, and/or send a second TDD SSW ACK frame to the responder in the beam direction trained in the first handshake, and the responder may send the second TDD SSW Feedback frame in the beam direction trained in the first handshake, and/or receive the second TDD SSW ACK frame sent by the responder in the beam direction trained in the first handshake.

Optionally, the first SSW frame carries an indication that the data rate of the second SSW frame using the second MCS is greater than 27.5 Mbps.

Since the first SSW frame is an SSW frame sent before the first device and the second device handshake through the first SSW Feedback frame and the first SSW ACK, the beams of the transmitting and receiving parties are not aligned. While beam training efficiency and robustness of beam training may be compromised by indicating whether the second SSW is allowed to transmit at a higher data rate, while the first SSW is still transmitting at MCS 0.

Optionally, the first SSW ACK frame carries an indication that the data rate of the second MCS used by the second SSW frame is greater than 27.5 Mbps.

That is, the data rate or specific MCS level of the second beam may be carried in the first SSW ACK. Therefore, the required transmission rate of the second SSW frame can be estimated by the Feedback information in receiving the first SSW Feedback.

Optionally, in this embodiment of the application, when the first MCS data rate is greater than 27.5Mbps, the first SSW frame may carry management information, where the management information may be a resource scheduling condition in a BSS, for example, information of current TDD SP scheduling. The TDD SP scheduling information may include frame division, Slot division, and information about the transmission direction (uplink, downlink, uncertain, etc.) in each Slot in the TDD SP.

Optionally, in this embodiment of the application, when the second MCS data rate is greater than 27.5Mbps, the second SSW frame may also carry management information, where the management information may be a resource scheduling condition in a BSS, for example, information of current TDD SP scheduling. The TDD SP scheduling information may include frame division, Slot division, and information about the transmission direction (uplink, downlink, uncertain, etc.) in each Slot in the TDD SP.

In a second aspect, a method for beam training is provided, including:

the method comprises the steps that a second device receives a first SSW frame sent by a first device, wherein the first SSW frame is sent by adopting a first Modulation and Coding Scheme (MCS), and the data rate of the first MCS is greater than or equal to 27.5 Mbps;

the second device sends a first sector sweep feedback SSW feedback to the first device according to the feedback offset indicated in the first SSW frame;

and the second device receives a first sector scanning acknowledgement (SSW ACK) frame sent by the first device after the acknowledgement offset indicated in the first SSW frame.

Optionally, the first MCS is a transmission format with MCS identifier 1 defined in a directional multi-gigabit DMG protocol.

Optionally, the method further includes:

the second device receives a second SSW frame sent by the first device, wherein the second SSW frame is sent by the first device after the first SSW ACK frame is sent;

the second device sends a second SSW Feedback frame to the first device according to the Feedback offset indicated in the first SSW ACK frame;

and the second device receives a second SSW ACK frame sent by the first device after the acknowledgement offset indicated in the first SSW ACK frame.

Since the TDD SSW frame transmission may be divided into multiple segments by the TDD SSW Feedback frames TDD SSW ACK, if the current best beam id and SNR are fed back along each Feedback in 11ad/11ay, the resources of part of the Feedback frame are wasted. Moreover, since the offset of the TDD SSW Feedback is carried in the TDD SSW frame in the existing mechanism, the second device may not receive the TDD SSW, and therefore, the resource of the pre-allocated TDD SSW Feedback frame is wasted. Similarly, TDD SSW ACK, since the TDD SSW Feedback frame cannot be received, the resource of TDD SSW ACK frames allocated in advance is wasted. While in our design the parameters of TDD SSW Feedback offset and TDD SSW ACK acknowledgement offset are carried in the previous TDD SSW ACK, so the resources of the subsequent pre-allocated TDD SSW Feedback frame and TDD SSW ACK frame are always used for transmission. Therefore, preferably, when the first SNR is different from the second SNR or the identification of the first receiving beam is different from the identification of the second receiving beam, the receiving end can always report the best beam information of the beams that have not been reported, i.e. the identification and SNR of the beams.

Optionally, the first SSW frame carries an indication that the data rate of the second MCS allowed to be used by the second SSW frame is greater than 27.5 Mbps.

Optionally, when the second modulation and coding strategy MCS data rate is greater than 27.5Mbps, the first SSW frame carries management information.

In a third aspect, an apparatus for beam training is provided, configured to perform the method in the first aspect or any possible implementation manner of the first aspect. In particular, the apparatus for beam training comprises means for performing the method of the first aspect described above or any possible implementation manner of the first aspect.

In a fourth aspect, an apparatus for beam training is provided to perform the method of the second aspect or any possible implementation manner of the second aspect. In particular, the apparatus for beam training comprises means for performing the method of the second aspect described above or any possible implementation manner of the second aspect.

In a fifth aspect, an apparatus for beam training is provided, where the apparatus for beam training includes: a transceiver, a memory, a processor, and a bus system. Wherein the transceiver, the memory and the processor are connected by the bus system, the memory is configured to store instructions, and the processor is configured to execute the instructions stored by the memory to control the transceiver to receive and/or transmit signals, and when the processor executes the instructions stored by the memory, the execution causes the processor to perform the method of the first aspect or any possible implementation manner of the first aspect.

In a sixth aspect, an apparatus for beam training is provided, which includes: a transceiver, a memory, a processor, and a bus system. Wherein the transceiver, the memory and the processor are connected by the bus system, the memory is used for storing instructions, the processor is used for executing the instructions stored by the memory to control the transceiver to receive and/or transmit signals, and when the processor executes the instructions stored by the memory, the execution causes the processor to execute the method of the second aspect or any possible implementation manner of the second aspect.

In a seventh aspect, a computer-readable medium is provided for storing a computer program comprising instructions for performing the method of any possible implementation of the first aspect.

In an eighth aspect, there is provided a computer readable medium for storing a computer program comprising instructions for performing the method of any possible implementation of the first aspect described above.

In a ninth aspect, there is provided a computer program product, the computer program product comprising: computer program code which, when executed by a communication unit, processing unit or transceiver, processor of a communication device (e.g. a beam training apparatus), causes the beam training apparatus to perform the method of any possible implementation of the first aspect described above.

In a tenth aspect, there is provided a computer program product comprising: computer program code which, when executed by a communication unit, processing unit or transceiver, processor of a communication device (e.g. a beam training apparatus), causes the beam training apparatus to perform the method of any possible implementation of the second aspect described above.

Drawings

Fig. 1 is a diagram illustrating a wireless backhaul system according to an embodiment of the present application.

Fig. 2 shows a schematic diagram of a Beacon Interval (BI) defined by the DMG standard.

Fig. 3 shows a schematic flow chart of a method for beam training provided in an embodiment of the present application.

Fig. 4 shows a schematic diagram of a frame format of a TDD SSW frame.

Fig. 5 is a schematic diagram illustrating an apparatus for beam training according to an embodiment of the present application.

Fig. 6 is a schematic diagram illustrating another beam training apparatus provided in an embodiment of the present application.

Fig. 7 is a schematic diagram illustrating another beam training apparatus according to an embodiment of the present application.

Fig. 8 is a schematic diagram illustrating another beam training apparatus according to an embodiment of the present application.

Detailed Description

The technical solution in the present application will be described below with reference to the accompanying drawings.

It should be understood that the embodiments of the present application may be applied to a Wireless Local Area Network (WLAN), and the embodiments of the present application may be applied to any one of the international Institute of Electrical and Electronics Engineers (IEEE) 802.11 series protocols currently adopted in the WLAN. A WLAN may include one or more Basic Service Sets (BSSs), with network nodes in the BSS including Access Points (APs) and Stations (STAs). Based on the original BSS, IEEE 802.11ad introduces a Personal Basic Service Set (PBSS) and a personal basic service set control node (PCP). Each personal basic service set may contain one AP/PCP and a plurality of STAs associated with the AP/PCP.

Fig. 1 is a diagram illustrating a wireless backhaul system in which at least some transmission nodes are connected via wireless communication according to an embodiment of the present application. Specifically, the telegraph pole is provided with millimeter wave transmission nodes 101 to 106, and the transmission nodes can provide wireless access for pedestrians on the road or surrounding households. There are wireless connections between transmission nodes on multiple utility poles and data in the network is transmitted back to a node (e.g., transmission node 106) with an optical fiber connection to provider network 107 via one or more hop wireless connections.

It should be understood that the transmission node in the embodiment of the present application may be an AP/PCP in a WLAN, and the AP/PCP may be configured to communicate with an access terminal through a wireless local area network and transmit data of the access terminal to a network side or transmit data from the network side to the access terminal. An access terminal may be a Station (STA) in a WLAN, which may also be referred to as a system, subscriber unit, access terminal, mobile station, remote terminal, mobile device, user terminal, wireless communication device, user agent, user device, or User Equipment (UE). The STA may be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless local area network (e.g., Wi-Fi) communication capabilities, a computing device, or other processing device connected to a wireless modem.

The network architectures of IEEE 802.11ay and IEEE 802.11ad include APs/PCPs and STAs that support the DMG protocol. Fig. 2 shows a schematic diagram of a Beacon Interval (BI) defined by the DMG standard. The BI includes a Beacon Transmission Interval (BTI), associated beam training (a-BFT), Announcement Time Interval (ATI), and a Data Transmission Interval (DTI). In the BTI, all STAs other than the PCP and the AP detect the beacon. The A-BFT is used for the STA and the AP/PCP to carry out beam training. ATI is used for initiating requests and responses between AP/PCP and STA. The DTI may include two types of data transmission, one is a Service Period (SP) based on scheduling, and the other is a CBAP (Contention based Access Period) based on Contention. Also, BTI, A-BFT, ATI may optionally occur at the BI, while DTI may include multiple SPs and/or multiple CBAPs.

In the embodiment of the application, in order to be compatible with existing DMG STA equipment, the equipment based on the outdoor scene is divided into separate time periods, and the existing scheduling mechanism in DTI is multiplexed. A special SP is identified and may be referred to as a schedule-based SP as a Time Division Duplex (TDD) SP.

Fig. 3 shows a schematic flow diagram of a method of beam training in TDD SP. When the TDD Applicable SP field in the scheduling signaling is set to 1, the transmission and reception scheduling resources of the STA in the source address and the STA in the destination address are explicitly defined, where the scheduling resources are scheduling resources in the time domain and/or the frequency domain.

Specifically, in this embodiment of the present application, the first device is a party initiating beam training, and may also be referred to as an initiator (initiator) or initiator device, and may be, for example, the AP/PCP or the STA in the foregoing. The second device is another party of beam training and may also be referred to as a responder (responder) or responder device, and may be, for example, an AP/PCP or STA as described above.

In the beam training process, the transmitting and receiving beam configurations that the transmitting and receiving parties can communicate, such as the transmitting beam number, the receiving beam number, and the corresponding Signal-to-noise ratio (SNR), can be obtained by the transmitting and receiving parties using different beam configurations to transmit and receive training frames.

The first device sends at least one first sector sweep, SSW, frame to the second device using a first beam direction and a first Modulation and Coding Scheme (MCS), 310. Wherein a data rate (transmission rate) of the first MCS is greater than or equal to 27.5 Mbps.

It is to be understood that the above-described terminology is used for the purpose of convenience in differentiation only and is not intended to be limiting. Of course, the scheduling-based SP in the DTI phase may have other names, and is not limited to being a TDD SP. Accordingly, the BF frame in the DTI phase may also have other names without being limited to a TDD BF frame. For example, in this embodiment, the SSW Frame in the special SP scheduled in the DTI phase may be referred to as a Slot-Based SSW Frame or a Frame-Based SSW Frame, the SSW feed Frame in the special SP scheduled in the DTI phase may be referred to as a Slot-Based SSW feed Frame or a Frame-Based SSW feed Frame, and the SSW ACK Frame in the special SP scheduled in the DTI phase may be referred to as a Slot-Based SSW ACK Frame or a Frame-Based SSW ACK Frame, which are not limited in this embodiment.

Fig. 4 shows a format of a TDD SSW frame, which includes a frame control (frame control), duration (duration), receiving node address (RA), transmitting node address (TA), TDD beam training control (BF control) field, frame body (frame body), and check bits (FCS). The FCS may use a 32-bit CRC check. Wherein the TDD BF control field can indicate a type of each TDD BF frame. Specifically, the TDD BF control field includes indications of subtypes TDD SSW, TDD SSW Feedback, and TDD SSW ACK. In addition, an End of training field (End of training) is also included in the control frame, and may be used to indicate whether to End the training process. For example, when the field is 0, it indicates that training is not finished, and then the TDD SSW frame continues to be transmitted; when the field is 1, it indicates that training is finished, and the TDD SSW frame is not continuously transmitted subsequently.

Specifically, the frame body field in the TDD SSW frame includes fields such as a transmit Beam identification (TX Beam Index), a Responder Feedback Offset (Responder Feedback Offset), and an Initiator ACK Offset (Initiator ACK Offset). Wherein, the transmitting beam identifier is used for indicating the beam identifier used by the initiator to transmit the TDD SSW frame. The responder Feedback offset, which may also be referred to as a Feedback offset for short, is used to indicate the time when the responder device sends the TDD SSW Feedback frame to the initiator device after receiving the TDD SSW frame. The initiator acknowledgement offset, which may also be referred to simply as an acknowledgement offset, indicates the time the initiator device sent TDD SSW ACK to the responder device after receiving the TDD SSW Feedback frame. Optionally, all the time parameters may be in units of milliseconds, or in units of time carrying feedback offset and/or acknowledgement offset in TDD SSW frames.

In a specific implementation, the responder device sends the TDD SSW Feedback frame to the initiator device after receiving the responder Feedback offset after the TDD SSW frame. Here, the responder feedback offset is the feedback offset indicated by the responder feedback offset field in the TDD SSW frame. And if the initiator device receives the TDD SSW Feedback frame after transmitting the TDD SSW frame, the initiator device sends TDD SSW ACK to the responder device after a first time interval after transmitting the TDD SSW frame, where the first time interval is a sum of the responder Feedback offset and the initiator acknowledgement offset, and the initiator acknowledgement offset is an acknowledgement offset indicated by the initiator acknowledgement offset field in the TDD SSW frame.

In the prior art, for an indoor backhaul scenario, MCS0 is used to transmit a TDD SSW frame. MCS0 is a transport format identified as 0 by the MCS defined in the DMG protocol. Wherein the transmission data rate of MCS0 is equal to 27.5 Mbps. At this time, MCS0 is adopted, which is designed according to that the receiving end adopts the quasi-omni-directional receiving main beam (the main beam) gain and the directional receiving main beam gain are not more than 15 dB. However, in an outdoor scenario, each node for backhaul may have an antenna gain higher than or equal to that of the AP/PCP configuration in an indoor scenario, for example, the receiving end employs a quasi-omni receiving main beam gain and a directional receiving main beam gain greater than or equal to 25 dB. Therefore, in the outdoor backhaul scenario, if the TDD SSW frame is still transmitted using MCS0, the coverage of the control physical layer PHY (using MCS 0) and the data physical layer PHY (using MCS 1) may be inconsistent. That is, when the node performs beam training through MCS0, the receiving end may not receive the TDD SSW. However, if the receiving end employs directional reception, MCS1 may be used for data transmission, so that the range of deployed data transmission is limited by MCS 0.

In order to solve the above problem, in the process of beam training in TDD SP, an initiating device may send a TDD SSW frame to a responder (i.e., a second device) by using a first MCS, where a data rate of the first MCS is greater than 27.5 Mbps. That is, here, the data rate of the first MCS may be greater than the data rate of MCS 0. Specifically, the first MCS may be any MCS with a data rate greater than MCS0 defined in the DMG protocol, or any MCS obtained based on modification of a transmission scheme with a data rate greater than MCS 0.

It is noted that here, each MCS includes coding and modulation, and framing procedures. Generally, given a coding mode, a code rate and a modulation mode, a transmission format is basically determined.

Specifically, the PPDU in the TDD SSW frame includes a preamble (preamble), a header (header), and data (data). The preamble includes a Short Training Field (STF) and a Channel Estimation Field (CEF), wherein the CEF includes Gu512 and Gv512, and Gv 128. And Gu512 ═ Gb128, -Ga128, Gb128, -Ga128 ]; gu512 [ -Gb128, Ga128, -Gb128, -Ga128 ]; gv128 is-Gb 128. With STF having two options. The STF in the first TDD SSW frame may be of the same design as the STF in the data frame, including 16 repeated Ga128, suffix-Ga 128 sequence. Or the same design as the STF of MCS0 is adopted, including 48 repeated Gb128 sequences followed by-Gb 128 and-Ga 128 sequences. Here, GaN denotes an N-bit long Ga gray sequence, and GbN denotes an N-bit long Gb gray sequence, where (GaN, GbN) forms a gray complementary pair.

The first TDD SSW frame header may use L-header transmission, MCS0 transmission, or MCS0 transmission. Specifically, the transmission modes of the L-header and the MCS0 can be referred to the following description. L-Header denotes a DMG Header, and in 11ay, the Header of 11ad is called a legacy Header (L-Header).

In this embodiment, the data may adopt a transmission mode of the first MCS. The following describes four transmission schemes of the first MCS provided in the embodiment of the present application, except that MCS0 may be adopted, but the embodiment of the present application is not limited thereto. In addition, the following four modes can multiplex the existing transmission format to the maximum extent, and the complexity of software and hardware design is reduced.

1) The first MCS may be a transport format identified as 1 by an MCS defined in the directional multi-gigabit DMG protocol, i.e., MCS 1. The data rate of MCS1 may reach 385 Mbs. Specifically, pi/2-BPSK modulation, LDPC coding, R-1/2 code rate, and repetition of ρ -2 may be performed.

In the LDPC encoding process, the number Ncw of LDPC code blocks is first calculated:

Ncw＝ceil(length*8/((Lcw/ρ)*R))

wherein, Length represents the Length of the PSDU in the packet, and the unit is byte; 672 parts Lcw; ceil denotes rounding up.

Data is divided into a plurality of Lz-Lcw/2 p codewords (b)₁,b₂,…,b_Lz). Here, 168 long code words are taken in turn, and each Lz long code word is followed by Lz zeros, forming a 2 x Lz long sequence (b)₁,b₂,…,b_Lz,0₁,0₂,…,0_Lz). 336 check bits are obtained after LDPC coding, and a sequence c ═ b (b) with the length of 2Lz +336 is formed₁,b₂,…,b_Lz,0₁,0₂,…,0_Lz,P₁,P₂,…,P₃₃₆) So that Hc^T0, where H is parity check matrix (parity check matrix) of LDPC code rate 1/2 (+)^TRepresenting a transpose operation of the matrix. Replacing zero in Lz +1 to 336 by b₁,b₂,…,b_LzThe scrambled data. The above process is then repeated to form a plurality of LDPC code blocks. Then, through pi/2-BPSK modulation, one single-carrier block is formed every 448 modulation symbols, plus a sequence of Ga 64. A single carrier block of less than 448 modulation symbols is filled by padding zeros. Also, scrambling is required before code modulation.

2) The first MCS may be a transmission format in an L-Header MCS-like manner using a single carrier or OFDM mode. Since the L-Header only has 64 bits, the modification is carried out here, the following operation is adopted for every 64 bits to obtain two continuous single carrier blocks, and zero padding is carried out for less than 64 bits. The following operations are repeated continuously:

64 information bits per LH (q)₁,q₂,...,q_LH) Using LDPC coding to fill 504 zeros, using 3/4 LDPC coding matrix to obtain check 168 bits (p)₁,p₂,...,p₁₆₈) Form cs1 ═ q (q)₁,q₂,...,q_LH,p₁,p₂,...,p₁₅₂,p₁₆₁,p₁₆₂,...,p₁₆₀) Obtaining cs2 ═ (q)₁,q₂,...,q_LH,p₁,p₂,...,p₁₅₂,p₁₆₁,p₁₆₂,...,p₁₆₈) And carrying out pi/2 BPSK modulation on the code block (cs1, cs2) with 448 bits, and adding a guard interval Ga64 to form a single carrier block. The second single carrier block, the information of 448 bits in the previous single carrier block is inverted.

3) The first MCS may be an EDMG Header a (Enhanced DMG Header-a) MCS-like transmission format using a single carrier or OFDM mode. Since EDMG Header-A has only 128 bits, and TDD SSW may be more than 128 bits long, the adaptation is made accordingly. Specifically, the following operation can be adopted for every 64 bits to obtain a single carrier block, and the insufficient bits are filled with zero. And, the following operations are repeated continuously: 64 information bits per LH (q)₁,q₂,...,q_LH) Using LDPC coding to fill 504 zeros, using 3/4 LDPC coding matrix to obtain check 168 bits (p)₁,p₂,...,p₁₆₈) Form cs1 ═ q (q)₁,q₂,...,q_LH,p₁,p₂,...,p₁₅₂,p₁₆₁,p₁₆₂,...,p₁₆₀) Obtaining cs2 ═ (q)₁,q₂,...,q_LH,p₁,p₂,...,p₁₅₂,p₁₆₁,p₁₆₂,...,p₁₆₈) And carrying out pi/2 BPSK modulation on the code block (cs1, cs2) with 448 bits, and adding a guard interval Ga64 to form a single carrier block. Scrambling is also required before code modulation.

4) The first MCS may be a transmission format using a spreading code similar to MCS0 but shorter, for example using Ga8, to modify the spreading factor to 8.

Specifically, similar to the MCS0 transmission method, the header and the data in the TDD SSW frame are also encoded by the same encoding. First, the number Ncw of LDPC code blocks is calculated:

Ncw＝1+ceil((length-6)*8/168))

wherein, Length is the Length of the PSDU in the packet, and the unit is byte; ceil denotes rounding up.

Specifically, the first LDPC codeword may transmit 6 bytes and 88 bytes in addition to the packet header. Followed byThe last LDPC code word except the transmission bit number L of the last LDPC code word_DPCWCeil ((length-6) × 8/((Ncw-1)), the last LDPC codeword may transmit a number of bits L_DPLCW＝(length-6)*8-(Ncw-2)*L_DPCWIn which L is_DPCW，L_DPLCWThe value is 120-168 bits, wherein ceil represents rounding up. Each codeword is padded with zeros to 504 bits, and a code rate 3/4 LDPC check matrix is used to generate check bits. And deleting all the middle zeros, and only taking information bits and check bits. Then, modulation is performed, and the encoded bit stream is subjected to dbpsk (differential binary phase shift keying). The Ga8 sequence was then used for spreading. In addition, the Data field needs to be scrambled before entering LDPC encoding. Using S (x) ═ x⁷+x⁴+1, cyclic shifter, scrambling. A cyclic shifter, a low 4-bit initial value and given in the Scramble field in the Header. Specifically, in MCS0, the spreading sequence is Ga32, and in order to reduce the difficulty of implementation of the apparatus, the spreading sequence may be selected from 8 in Ga32, and the first 8 or the last 8 may be generally used and is denoted as G8. It can be understood that G8 is substituted for Ga32 in the original MCS 0.

Therefore, the preferred embodiment is to use MCS1 to send the first TDD SSW frame, so that the transmission format defined in the protocol is directly used without redesigning hardware and software. Where MCS1 is used the SNR of control transmission is the same as data transmission. If the L-Header transmission is adopted, the SNR of the control transmission is 3-4 dB lower than that of the data transmission, but the control transmission can be correctly received at the moment. And if the EDMG Header-A transmission format is adopted, the SNR of the control transmission is 2-3 dB lower than that of the data transmission, but the control transmission can be correctly received at the moment. If the MCS0 spreading factor is modified to 8, the SNR of the control transmission is 4-5 dB lower than that of the data transmission, but the control transmission can be correctly received at the moment. Usually, a certain margin is required for the engineering. These designs are acceptable, but according to MCS0, leaving a margin 10dB lower than the SNR of data transmission has a large impact on the coverage, which may cause MCS0 to perform beam training on the node, and MCS1 transmission cannot be used.

Optionally, in this embodiment of the application, when the first MCS data rate is greater than 27.5Mbps, the first SSW frame may carry management information, where the management information may be a resource scheduling condition in a BSS, for example, information of current TDD SP scheduling. The TDD SP scheduling information may include frame division, Slot division, and information about the transmission direction (uplink, downlink, uncertain, etc.) in each Slot in the TDD SP. Since the length of the beam frame can be increased when the data rate of the first MCS is greater than 27.5 Mbps. For example, when the first MCS is MCS1, the number of bytes in the first SSW frame is not limited by 27 bytes. Therefore, management information may be carried in the first SSW frame. Unlike the conventional technique, the last TDD SSW ACK indicates the resources of the first device and the second device for transmitting the management frame, in which the management information, such as the TDD SP scheduling information, is carried, after the beam training is finished.

Optionally, in this embodiment of the application, the first TDD SSW frame may include an indication for indicating the number of the second devices, and the indication may be, for example, a first field. That is to say, in the embodiment of the present application, the first device may perform beam training with multiple second devices at the same time. At this time, the first device may add the first field in the first TDD SSW frame. Specifically, the first field may have 2 to 3 bits.

Due to the embodiment of the present application, when the first device transmits the first TDD SSW using MCS0 or a transmission format similar to MCS0, the length of the TDD SSW frame is limited. The first TDD SSW frame may include only one RA address, one feedback offset, and an acknowledgement offset corresponding to the second device. Thus, after the device corresponding to the RA address in the first TDD SSW frame receives the first TDD SSW frame, the device can perform feedback according to the indication of the feedback offset, and receive the acknowledgement frame according to the indication of the acknowledgement offset. And if the other device also receives the first TDD SSW frame, the other device may count the number of the second devices indicated by the first field as NU, calculate its feedback time, and further may randomly backoff feedback in the subsequent NU feedback unit times. The feedback unit time may be the sum of a interframe space (SIFS) and a duration occupied by a TDD SSW feedback frame. And the first device feeds TDD SSW ACK frames back to the device receiving the TDD SSW Feedback frame correspondingly at the time after the confirmation offset.

Alternatively, when the first device transmits the first TDD SSW using another MCS (e.g., MCS1 or another MCS with a higher data rate), the first TDD SSW frame may include RA addresses corresponding to a plurality of second devices, a plurality of feedback offsets, and an acknowledgement offset. Thus, when the plurality of second devices receive the first TDD SSW frame, each of the plurality of second devices may perform feedback according to the indication of the feedback offset, and receive an acknowledgement frame according to the indication of the acknowledgement offset.

Therefore, when the receiving end receives the beam training frame by adopting the directional antenna to perform the beam training, one-to-many training can be performed, and the beam training efficiency is further improved.

320, after the Feedback offset indicated in the first SSW frame, the first device receives a first beam scanning Feedback SSW Feedback frame sent by the second device. Here, the first SSW Feedback frame may also be referred to as a first TDD SSW Feedback frame, that is, the first SSW Feedback frame is a SSW Feedback frame in a TDD SP phase.

In this embodiment of the application, after receiving at least one first TDD SSW frame through receiving beam scanning, according to Feedback offset information in the received first TDD SSW, the second device sends a fed-back TDD SSW Feedback, which is referred to as a first TDD SSW Feedback frame.

Specifically, the frame body field of the TDD SSW Feedback frame includes a transmit Beam identifier (TX Beam Index, txbeam id), a receive Beam identifier (RX Beam Index, rxbeam id), and a signal-to-noise ratio report (SNR report), where SNR report may be referred to as SNR. The transmitting beam identifier is used for indicating the identifier of the transmitting beam adopted by the SSW frame received from the initiator, the receiving beam identifier is the identifier of the receiving beam adopted by the SSW frame received by the responder, and the SNR is the SNR of the SSW frame received by the receiving beam.

Accordingly, the length of the frame body field of the first TDD SSW Feedback frame is not particularly limited in the present invention, and the frame body field includes the first transmit beam id, the first receive beam id, and the first SNR. The first sending beam identifier is used for indicating an identifier of a sending beam adopted by a first SSW frame received from an initiator, the first receiving beam identifier is a receiving beam adopted by a responder to receive the first SSW frame, and the first SNR is an SNR for receiving the first SSW frame by adopting the receiving beam.

Specifically, when the first device transmits at least one SSW frame, the second device scans the SSW frame using multiple receive beams. And when the second device receives the first SSW frame by adopting the first receiving beam, the second device transmits the first TDD SSW Feedback by utilizing reciprocity. Specifically, the second device may determine, according to reciprocity, a transmission beam direction for transmitting the first TDD SSW Feedback frame in the process of receiving the first TDD SSW frame. As an embodiment, the first TDD SSW Feedback frame may be transmitted in a receiving beam direction in which the first TDD SSW frame is received, that is, the receiving beam direction in which the first TDD SSW frame is received is the same as the transmitting beam direction in which the first TDD SSW Feedback frame is transmitted.

Also, since both the transmit antenna gain and the receive antenna gain are considered during the transceiving of the TDD SSW frame, if it is desired that the TDD SSW Feedback frame be received by the initiator, it is also desired that the initiator employ directional reception. At this time, the initiator may receive the first TDD SSW Feedback frame in the first beam direction. However, before the first TDD SSW Feedback frame, the initiator has not actually received any Feedback from the responder, and therefore, the initiator can only receive the TDD first SSW Feedback frame using the transmit beam direction of the first TDD SSW frame (i.e., the first beam direction) by using channel reciprocity.

330, after receiving the first SSW Feedback frame, the first device sends a first beam scanning acknowledgement SSW ACK frame to the second device after the acknowledgement offset indicated in the first SSW frame. The first SSW ACK frame may also be referred to as a first TDD SSW ACK frame, i.e., the first SSW ACK frame is the SSW ACK frame in the TDD SP phase. In this embodiment, after receiving the first TDD SSW Feedback frame, the first device may refer to an TDD SSW ACK frame sent according to the acknowledgement Feedback offset in the first SSW frame as the first TDD SSW frame.

Specifically, the frame body field in the TDD SSW ACK frame may include the TX Beam Index, SNR, initiator management offset (initiator management offset). A responder management offset (responder management offset) field or the like may also be included. Wherein, the TX Beam Index represents the transmit Beam id fed back by the responder in the TDD Feedback frame, which is acknowledged by the initiator to be received. The SNR represents the SNR that the initiator acknowledges the received responder to feed back in the TDD Feedback frame. The initiator management offset is used to indicate an offset time for the initiator to transmit the management frame and the responder management offset is used to indicate an offset time for the responder to transmit the management frame.

In the embodiment of the present application, the process 310-330 may be referred to as a first handshake process. As can be seen, in the process of the first handshake (i.e., before the first handshake is completed), the transceiver (i.e., the initiator and the responder) must pre-allocate resources for beam scanning Feedback and beam scanning acknowledgement for each TDD SSW in the transmission beam direction, so that the initiator can receive the first TDD SSW Feedback frame using the transmission beam direction of the first TDD SSW frame. The first TDD SSW ACK may also be sent in the sending beam direction of the first TDD SSW frame, and the responder sends the first TDD SSW Feedback frame in the receiving beam direction of the received first TDD SSW frame fed back in the first TDD SSW Feedback frame, so as to ensure that both the transceiver and the transmitter utilize the link budget of the antenna gain.

Therefore, the first TDD SSW frame, the first TDD SSW Feedback frame, and the first TDD SSW ACK frame refer to three beam training frames transmitted by both the initiator and the responder during the first handshake. That is, at least one TDD SSW frame of the first TDD SSW frames is received by the responder device. And there is no beam training information between the initiator device and the responder device before the first TDD SSW Feedback frame and the first TDD SSW ACK frame. Therefore, after the first TDD SSW frame, the first TDD SSW Feedback frame, and the first TDD SSW ACK frame are transmitted, the initiator device and the responder device obtain the initial receiving beam direction and transmitting beam direction information.

In the process of beam training, the BF frame in the process of handshake completion by the first device and the second device through beam training is named as "first", that is, before the first device reserves the feedback resource for the second device, the second device receives the SSW frame from the first device for the first time, which is called as a first SSW frame, and the beam direction adopted by the first SSW frame is called as a first beam direction. When the first device receives the TDD SSW Feedback frame from the second device for the first time, the first device receives the TDD SSW Feedback frame sent by the second device in the first beam direction, which is called a first SSW Feedback frame. And after receiving the first SSW Feedback frame, the first device sends TDD SSW ACK frames, called a first SSW ACK frame, to the second device for the first time. That is, before the first SSW frame, the first device may also send TDD SSW frames in other beam directions, and allocate resources of TDD SSW Feedback and resources of TDD SSW ACK, but since the second device does not receive the TDD SSW frames, the second device will not feed back on the resources of the TDD SSW Feedback frames allocated in advance, (i.e. cannot resolve Feedback offset information in the TDD SSW), and since the first device does not receive the TDD SSW Feedback frames sent by the first device, the first device cannot send TDD SSW ACK frames. Therefore, the first device and the second device cannot establish communication, and handshake is realized.

In addition, the "first time" here is also valid for a certain time, i.e. if a communication has been previously established between the first device and the second device. However, when the first device and the second device do not communicate within the appointed time, it is still possible to complete the process 310 and 330 again, obtain the current transceiving beam information between the first device and the second device, and the TDD SP allocation situation.

Optionally, in this embodiment of the present application, since the beam training of each device may take a long time, and the training of all beam directions cannot be completed at one time on the resource allocated to the user, the end of training field indicates whether or not a subsequent TDD SSW frame is sent.

In the prior art, the TDD SSW, TDD SSW Feedback, TDD SSW ACK procedures in each phase are the same. That is, the first device always receives the TDD SSW Feedback frame after receiving the Feedback offset indicated in the TDD SSW frame on the beam transmitted by the TDD SSW frame in this stage, so that if the parameters carried in the subsequent TDD SSW cannot be correctly received, End of Training becomes 1, and the identifier of the End of beam Training cannot be correctly received. Causing the receiving end not to obtain correct information, such as whether the beam training is finished.

The present application also provides an embodiment that when the end of training field indicates that the beam training is not finished, the indication information is carried through the first TDD SSW ACK. That is, in addition to the responder Feedback offset field and the initiator acknowledgement offset field included in the TDD SSW frame, the responder Feedback offset field and the initiator acknowledgement offset field are also included in the first TDD SSW ACK frame, where the Feedback offset field is used to indicate the time when the initiator receives the TDD SSW Feedback frame next time (the second time TDD SSW ACK with respect to the first time TDD SSW ACK), and the acknowledgement offset field is used to indicate the time when the initiator transmits TDD SSW ACK frames next time (the second time TDD SSW ACK with respect to the first time TDD SSW ACK). It can be understood that the TDD SSW Feedback frame transmitted next time refers to the first TDD SSW Feedback frame transmitted by the responder after receiving the first TDD SSW ACK frame, and may be referred to as a second TDD SSW Feedback frame. The next transmitted TDD SSW ACK frame refers to the first TDD SSW ACK frame transmitted by the initiator after the first TDD SSW ACK frame and may be referred to as a second TDD SSW Feedback frame. That is, the first SSW ACK frame indicates resources of the 1 st second SSW Feedback frame and the 1 st second SSW ACK frame, and resources of the ith second SSW Feedback frame and the ith second SSW ACK frame are carried in the i-1 st second SSW ACK frame, i is a positive integer greater than 1.

Also, the frame formats of the first TDD SSW ACK frame and the second TDD SSW ACK frame may be the same, then the second TDD SSW ACK frame may also include a responder feedback offset field and an initiator acknowledgement offset field. And, the feedback offset field is used to indicate the time of the first TDD SSW feedback frame received by the initiator after the second TDD SSW ACK frames, and the acknowledgement offset field is used to indicate the time of the first TDD SSW ACK frames transmitted by the initiator after the second TDD SSW ACK frames. For example, the TDD SSW ACK frame sent for the second time may include a first responder Feedback offset field for indicating the time when the initiator receives the TDD SSW Feedback frame for the third time and a first initiator acknowledgement offset field for indicating the time when the initiator sends TDD SSW ACK the third time. Specifically, the second TDD SSW ACK frame can be referred to the above description of the first TDD SSW ACK frame, and is not repeated here to avoid repetition.

In one possible implementation, when end of tracking is 0, the following fields may be multiplexed: initiator Management Offset (Initiator Management Offset), Responder Management Offset (Responder Management Offset), periodic, and the like. That is, when End of Training is 0, the bits occupied by these fields are reinterpreted as the responder feedback offset field and the initiator acknowledgement offset field.

In another possible implementation, bits may be directly added, and the newly added bits are defined as a Responder Feedback Offset (Responder Feedback Offset) and an Initiator Ack Offset (Initiator Ack Offset).

Like the conventional art, TDD SSW ACK frames may be transmitted using MCS 0. Since the number of feedback frames is small compared to SSW frames, TDD SSW ACK frames do not cause excessive overhead even if they are transmitted with MCS0 and more than 27 bytes. Similar to TDD SSW, modulation coding at higher data rates may also be used. Therefore, the present invention does not limit whether TDD SSW ACK frames are transmitted in a byte number equal to or less than 27 bytes.

Optionally, in this embodiment of the present application, the method further includes 340 to 360.

340, after transmitting the first SSW ACK frame, the first device transmits at least one second SSW frame using a second beam, where the second beam includes at least one beam direction. And, the second beam may include the first beam direction. Here the second SSW frame is the second TDD SSW frame in the above. Specifically, the second SSW frame is described above, and is not described herein again to avoid repetition.

For example, when the first beam is a beam having a TXBeamID of 0, the second beam may include different beams having TXBeamID of 0, TXBeamID of 1, TXBeamID of 2, and the like.

Correspondingly, when the first device sends at least one second TDD SSW frame, the second device scans for the second TDD SSW frame. For example, the responder may scan for a second TDD SSW frame in a second receive beam direction.

Optionally, in this embodiment of the application, the first SSW frame may further include an indication that the data rate of the second SSW frame using the second MCS is greater than 27.5 Mbps.

Optionally, in this embodiment of the application, the first SSW ACK may further include an indication that the data rate of the second MCS used by the second SSW frame is greater than 27.5 Mbps.

As a specific embodiment, the second modulation and coding scheme MCS comprises a transmission format with MCS identification 1 defined in the directional multi-gigabit DMG protocol.

Specifically, the second MCS may refer to the description in the above embodiment that the data rate of the first MCS is greater than 27.5Mbps, and is not described herein again to avoid repetition.

Optionally, in this embodiment of the application, when the second MCS data rate is greater than 27.5Mbps, the second SSW frame may carry management information, where the management information may be information of a resource scheduling condition in a BSS, for example, information of current TDD SP scheduling. The TDD SP scheduling information may include frame division, Slot division, and information about the transmission direction (uplink, downlink, uncertain, etc.) in each Slot in the TDD SP. Since the length of the beam frame can be increased when the data rate of the second MCS is greater than 27.5 Mbps. For example, when the second MCS is MCS1, the number of bytes in the second SSW frame is no longer limited by 27 bytes. Thus, management information may be carried in the second SSW frame.

350, the first device receives the second SSW Feedback frame sent by the second device after the Feedback offset indicated in the first SSW ACK frame. Here, the second SSW Feedback frame is the second TDD SSW Feedback frame in the above. Specifically, the second SSW Feedback frame refers to the description above, and is not described herein again to avoid repetition.

Optionally, in this embodiment of the application, the second device may send the second SSW Feedback frame in a beam direction that is the same as a beam direction used for sending the first SSW Feedback frame.

Optionally, in this embodiment of the application, the first device may receive the first SSW Feedback frame and the second SSW Feedback frame in the first beam direction.

Optionally, in this embodiment of the application, the first device may send the first SSW ACK frame and the second SSW ACK frame in the first beam direction.

Optionally, in this embodiment of the application, the second device may receive the second SSW ACK frame in a beam direction that is the same as a beam direction used for receiving the first SSW ACK frame.

Optionally, in this embodiment of the application, the second SSW Feedback includes an identifier of a second receive beam and a second signal-to-noise ratio SNR, where the second receive beam is a receive beam of a training frame received by the second device in the first SSW frame and the second SSW frame, and the second SNR is an SNR for receiving the training frame by using the second receive beam.

In this embodiment of the present application, the first SSW Feedback includes an identifier of a first receiving beam and a first signal-to-noise ratio SNR, where the first receiving beam is a receiving beam of the second device that receives the first SSW frame, and the first SNR is an SNR that the first receiving beam is used to receive the first SSW frame. Here, the first SNR is different from the second SNR, or the identity of the first receive beam is different from the identity of the second receive beam.

And 360, the first device sends a second SSW ACK frame to the second device after the acknowledgement offset indicated in the first SSW ACK frame. Here the second SSW ACK frame is the second TDD SSW ACK frame above. Specifically, the second SSW ACK frame is described above, and is not described herein again to avoid repetition.

Therefore, when the end of training is 0, the number of the transmit beams for TDD SSW beam scanning training is no longer in one-to-one correspondence with the number of the TDD SSW Feedback frames and TDD SSW ACK frames by indicating the responder Feedback offset and the initiator acknowledgement offset in the SSW ACK frame, that is, the second beam may include at least one beam direction, and further, the subsequent SSW Feedback frames and SSW ACK frames are not required to be transmitted as frequently, thereby improving the efficiency of beam training.

In addition, since the initiator device and the responder device can be guaranteed to complete information interaction in the transmitting and receiving beam directions of the second TDD SSW Feedback and the second TDD SSW ACK, information carried in the second TDD SSW Feedback and the second TDD SSW ACK can also be obtained by the initiator device and/or the responder device. For example, beam training ends (End of training), Initiator Management Offset (Initiator Management Offset), and Responder Management Offset (Responder Management Offset).

The method for beam training provided by the embodiment of the present application is described in detail above with reference to fig. 1 to 4, and the apparatus for beam training provided by the embodiment of the present application is described in detail below with reference to fig. 5 to 8.

Fig. 5 is a schematic block diagram illustrating an apparatus 500 for beam training according to an embodiment of the present application. The apparatus 500 comprises a transmitting unit 510 and a receiving unit 520.

A sending unit 510, configured to send at least one first sector scanning SSW frame to at least one second device by using a first beam direction and a first Modulation and Coding Scheme (MCS), where a data rate of the first MCS is greater than or equal to 27.5 Mbps;

a receiving unit 520, configured to receive a first sector scanning Feedback SSW Feedback frame sent by the second device after the Feedback offset indicated in the first SSW frame;

the sending unit 510 is further configured to send a first sector scanning acknowledgement SSW ACK frame to the second device after receiving the first SSW Feedback frame and after receiving the acknowledgement offset indicated in the first SSW frame.

Here, the SSW frame may be specifically a TDD SSW frame. Therefore, in this embodiment of the present application, since the data rate of the first MCS is greater than 27.5Mbps, the first device may increase the range of the received beam training frame by sending the first TDD SSW with the first MCS, further reduce the difference between the coverage of the control physical layer PHY and the coverage of the data physical layer PHY, and ensure correct reception of control transmission, so the method for beam training in this embodiment of the present application may be applicable to an outdoor backhaul scenario.

Optionally, the first modulation and coding strategy MCS is a transmission format with MCS identifier 1 defined in the directional multi-gigabit DMG protocol.

Optionally, the sending unit 510 is further configured to send a second SSW frame by using a second beam after sending the first SSW ACK frame, where the second beam includes at least one beam direction;

the receiving unit 520 is further configured to receive a second SSW Feedback frame sent by the second device after the Feedback offset indicated in the first SSW ACK frame;

the sending unit 510 is further configured to send a second SSW ACK frame to the second device after the acknowledgement offset indicated in the first SSW ACK frame.

Therefore, when the first SNR is different from the second SNR or the identifier of the first receiving beam is different from the identifier of the second receiving beam, the receiving end can always report the best beam information of the beams which are not reported, namely the identifiers and SNRs of the beams.

Optionally, the receiving unit 520 is specifically configured to receive the first SSW Feedback frame and the second SSW Feedback frame in the first beam direction.

Optionally, the sending unit 510 is specifically configured to send the first SSW ACK frame and the second SSW ACK frame in the first beam direction.

Optionally, when the first modulation and coding strategy MCS data rate is greater than 27.5Mbps, the first SSW frame carries management information.

Optionally, when the second modulation and coding strategy MCS data rate is greater than 27.5Mbps, the second SSW frame carries management information.

It should be noted that, in the embodiment of the present invention, the sending unit 510 and the receiving unit 520 may be implemented by a transceiver. As shown in fig. 6, the apparatus 600 for beam training may include a processor 610, a memory 620, and a transceiver 630. The memory 620 may be used for storing codes and the like executed by the processor 610, and the processor 610 may be used for processing data or programs.

In implementation, the steps of the above method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 610. The steps of a method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software modules in the processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in the memory 620, and the processor 610 reads the information in the memory 620 and performs the steps of the above method in combination with the hardware thereof. To avoid repetition, it is not described in detail here.

The beam training apparatus 500 shown in fig. 5 or the beam training apparatus 600 shown in fig. 6 can implement each process of the foregoing method embodiment corresponding to the first device, specifically, the beam training apparatus 500 or the beam training apparatus 600 may refer to the description above, and is not repeated here to avoid repetition.

Fig. 7 is a schematic block diagram illustrating an apparatus 700 for beam training according to an embodiment of the present application. The apparatus 700 includes a receiving unit 710 and a transmitting unit 720.

A receiving unit 710, configured to receive a first SSW frame sent by a first device, where the first SSW frame is sent by using a first modulation and coding scheme MCS, and a data rate of the first MCS is greater than or equal to 27.5 Mbps;

a sending unit 720, configured to send a first sector sweep feedback SSW feedback to the first device according to the feedback offset indicated in the first SSW frame;

the receiving unit 710 is further configured to receive a first sector scanning acknowledgement SSW ACK frame sent by the first device after the acknowledgement offset indicated in the first SSW frame.

Optionally, the first SSW frame includes an indication for indicating the number of the apparatuses.

Optionally, the receiving unit 710 is further configured to receive a second SSW frame sent by the first device, where the second SSW frame is sent by the first device after the first SSW ACK frame is sent;

the sending unit 720 is further configured to send a second SSW Feedback frame to the first device according to the Feedback offset indicated in the first SSW ACK frame;

the receiving unit 710 is further configured to receive a second SSW ACK frame sent by the first device after the acknowledgement offset indicated in the first SSW ACK frame.

It should be noted that, in the embodiment of the present invention, the receiving unit 710 and the transmitting unit 720 may be implemented by a transceiver. As shown in fig. 8, an apparatus 800 for beam training may include a processor 810, a memory 820, and a transceiver 830. The memory 820 may be used for storing codes and the like executed by the processor 810, and the processor 810 may be used for processing data or programs.

In implementation, the steps of the above method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 810. The steps of a method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software modules in the processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in the memory 820, and the processor 810 reads the information in the memory 820 and combines the hardware to complete the steps of the above method. To avoid repetition, it is not described in detail here.

The beam training apparatus 700 shown in fig. 7 or the beam training apparatus 800 shown in fig. 8 can implement each process of the foregoing method embodiment corresponding to the second device, specifically, the beam training apparatus 700 or the beam training apparatus 800 may refer to the description above, and is not repeated here to avoid repetition.

The embodiment of the present application further provides a computer-readable medium for storing a computer program, where the computer program includes instructions for executing the method corresponding to the first device or the second device in the above method embodiments.

An embodiment of the present application further provides a computer program product, where the computer program product includes: computer program code which, when run by a communication unit, processing unit or transceiver, processor of a communication device (e.g. a terminal device or a network device), causes the communication device to perform a method corresponding to the first device or the second device of any of the above-described method embodiments.

The embodiments in the present application may be used independently or jointly, and are not limited herein.

It should be understood that the Processor mentioned in the embodiments of the present invention may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, a discrete hardware component, and the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

It will also be appreciated that the memory referred to in this embodiment of the invention may be either volatile memory or nonvolatile memory, or may include both volatile and nonvolatile memory. The non-volatile Memory may be a Read-Only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically Erasable PROM (EEPROM), or a flash Memory. Volatile Memory can be Random Access Memory (RAM), which acts as external cache Memory. By way of example, but not limitation, many forms of RAM are available, such as Static random access memory (Static RAM, SRAM), Dynamic Random Access Memory (DRAM), Synchronous Dynamic random access memory (Synchronous DRAM, SDRAM), Double Data Rate Synchronous Dynamic random access memory (DDR SDRAM), Enhanced Synchronous SDRAM (ESDRAM), Synchronous link SDRAM (SLDRAM), and Direct Rambus RAM (DR RAM).

It should be noted that when the processor is a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, the memory (memory module) is integrated in the processor.

It should be noted that the memory described herein is intended to comprise, without being limited to, these and any other suitable types of memory.

It should be understood that the descriptions of the first, second, etc. appearing in the embodiments of the present application are only for illustrating and differentiating the objects, and do not represent a particular limitation to the number of devices in the embodiments of the present application, and do not constitute any limitation to the embodiments of the present application.

It should also be understood that, in the various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method of beam training, comprising:

the method comprises the steps that a first device sends at least one first sector scanning SSW frame to at least one second device by adopting a first beam direction and a first Modulation Coding Scheme (MCS), wherein the data rate of the first MCS is greater than 27.5 Mbps;

2. The method of claim 1, wherein the first Modulation and Coding Scheme (MCS) is a transmission format with a MCS identification of 1 defined in a directional multi-gigabit (DMG) protocol.

3. The method of claim 1 or 2, wherein the first SSW frame comprises an indication indicating the number of the second devices.

4. The method of claim 1, further comprising:

5. The method of claim 4, wherein the first SSW Feedback frame comprises an identification of a first receive beam received by the second device and a first signal-to-noise ratio (SNR), wherein the first SNR is an SNR for receiving the first SSW frame using the first receive beam;

6. The method of claim 4 or 5, wherein the first device receives the first SSW Feedback frame and the second SSW Feedback frame in the first beam direction.

7. The method of claim 4 or 5, wherein the first device sends the first SSW ACK frame and the second SSW ACK frame in the first beam direction.

8. The method of claim 4 or 5, wherein the first SSW frame carries an indication that the data rate of the second SSW frame with the second MCS is greater than 27.5 Mbps.

9. The method of claim 4 or 5, wherein the first SSW ACK frame carries an indication that the data rate of the second MCS employed by the second SSW frame is greater than 27.5 Mbps.

10. The method of claim 4 or 5, wherein the first SSW frame carries management information when the first Modulation and Coding Scheme (MCS) data rate is greater than 27.5 Mbps.

11. The method of claim 4 or 5, wherein the second SSW frame carries management information when the second Modulation and Coding Scheme (MCS) data rate is greater than 27.5 Mbps.

12. A method of beam training, comprising:

the method comprises the steps that a second device receives a first SSW frame sent by a first device, wherein the first SSW frame is sent by adopting a first Modulation and Coding Scheme (MCS), and the data rate of the first MCS is greater than 27.5 Mbps;

13. The method of claim 12, wherein the first MCS is a transport format with an MCS identification of 1 as defined in a directional multi-gigabit DMG protocol.

14. The method of claim 12 or 13, further comprising:

15. The method of claim 14, wherein the first SSW Feedback frame comprises an identification of a first receive beam received by the second device and a first signal-to-noise ratio (SNR), wherein the first SNR is an SNR for receiving the first SSW frame using the first receive beam;

16. An apparatus for beam training, comprising:

a sending unit, configured to send at least one first sector scanning SSW frame to at least one second device by using a first beam direction and a first Modulation and Coding Scheme (MCS), where a data rate of the first MCS is greater than 27.5 Mbps;

a receiving unit, configured to receive a first sector scanning Feedback SSW Feedback frame sent by the second device after the Feedback offset indicated in the first SSW frame;

the sending unit is further configured to send a first sector scanning acknowledgement SSW ACK frame to the second device after receiving the first SSW Feedback frame and after an acknowledgement offset indicated in the first SSW frame.

17. The apparatus of claim 16, wherein the first Modulation and Coding Scheme (MCS) is a transport format with a MCS identification of 1 defined in a directional multi-gigabit (DMG) protocol.

18. The apparatus of claim 16 or 17, wherein the first SSW frame comprises an indication indicating the number of the second devices.

19. The apparatus of claim 16,

the transmitting unit is further configured to transmit a second SSW frame using a second beam after transmitting the first SSW ACK frame, where the second beam includes at least one beam direction;

the receiving unit is further configured to receive a second SSW Feedback frame sent by the second device after the Feedback offset indicated in the first SSW ACK frame;

the sending unit is further configured to send a second SSW ACK frame to the second device after the acknowledgement offset indicated in the first SSW ACK frame.

20. The apparatus of claim 19, wherein the first SSW Feedback frame comprises an identification of a first receive beam received by the second device from the first SSW frame and a first signal-to-noise ratio (SNR), wherein the first SNR is the SNR for receiving the first SSW frame using the first receive beam;

21. The apparatus according to claim 19 or 20, wherein the receiving unit is specifically configured to receive the first SSW Feedback frame and the second SSW Feedback frame in the first beam direction.

22. The apparatus according to claim 19 or 20, wherein the transmitting unit is specifically configured to transmit the first SSW ACK frame and the second SSW ACK frame in the first beam direction.

23. The apparatus of claim 19 or 20, wherein the first SSW frame carries an indication that the data rate that allows the second SSW frame to adopt the second MCS is greater than 27.5 Mbps.

24. The apparatus of claim 19 or 20, wherein the first SSW ACK frame carries an indication that the data rate of the second MCS used by the second SSW frame is greater than 27.5 Mbps.

25. The apparatus of claim 19 or 20, wherein the first SSW frame carries management information when the first Modulation and Coding Scheme (MCS) data rate is greater than 27.5 Mbps.

26. The apparatus of claim 19 or 20, wherein the second SSW frame carries management information when the second Modulation and Coding Scheme (MCS) data rate is greater than 27.5 Mbps.

27. An apparatus for beam training, comprising:

a receiving unit, configured to receive a first SSW frame sent by a first device, where the first SSW frame is sent by using a first Modulation and Coding Scheme (MCS), and a data rate of the first MCS is greater than 27.5 Mbps;

a sending unit, configured to send a first sector sweep feedback SSW feedback to the first device according to the feedback offset indicated in the first SSW frame;

the receiving unit is further configured to receive a first sector scanning acknowledgement SSW ACK frame sent by the first device after the acknowledgement offset indicated in the first SSW frame.

28. The apparatus of claim 27, wherein the first MCS is a transport format with an MCS identification of 1 as defined in a directional multi-gigabit DMG protocol.

29. The apparatus of claim 27 or 28,

the receiving unit is further configured to receive a second SSW frame sent by the first device, where the second SSW frame is sent by the first device after the first SSW ACK frame is sent;

the sending unit is further configured to send a second SSW Feedback frame to the first device according to the Feedback offset indicated in the first SSW ACK frame;

the receiving unit is further configured to receive a second SSW ACK frame sent by the first device after the acknowledgement offset indicated in the first SSW ACK frame.

30. The apparatus of claim 29, wherein the first SSW Feedback frame comprises an identification of a first receive beam received by a second device and a first signal-to-noise ratio (SNR), wherein the first SNR is an SNR for receiving the first SSW frame using the first receive beam;