Communication apparatus and method

Abstract

A first communication device configured to operate as an initiator and to communicate with a second communication device configured to operate as a responder. A first communication device includes circuitry configured to: connect to a second communication device via at least two links including a non-millimeter wave link and a millimeter wave link; transmitting a beamforming (BF) request frame to a second communication device via the non-millimeter wave link; performing BF training (BFT) with the second communication device by subsequently transmitting a plurality of sector scan (SSW) frames and training fields in different transmission sectors via the millimeter wave link; and if the non-millimeter wave link is not busy at the end of the BFT, receiving a BFT feedback frame from the second communication device via the non-millimeter wave link at the end of the BFT.

Description

Background Art Technical Field

[0001] The present disclosure relates to a first communication device and a second communication device serving as an initiator and a responder, and also relates to a corresponding first communication method and a corresponding second communication method.

[0002] Description of Related Technology

[0003] In the IEEE 802.11 standard, beamforming (BF) is required before transmitting data on a millimeter wave link to establish a link with sufficient quality. Although there are many BF variants, these known BF variants usually consume a lot of time, which is not ideal for low-latency and high-throughput applications.

[0004] The "background" description provided herein is for the purpose of generally presenting the context of the present disclosure. The work of the presently named inventors is neither explicitly nor implicitly admitted to be prior art with respect to the present disclosure to the extent described in this background section and insofar as it may not have been described as prior art at the time of filing. Summary of the Invention

[0005] The purpose is to reduce the amount of time required to establish a link between two communication devices for data exchange in low-latency and high-throughput applications. Another object of the present invention is to provide a corresponding communication device and method, as well as a corresponding computer program and a non-transitory computer-readable recording medium for implementing the communication method.

[0006] According to one aspect, there is provided a first communication device configured to operate as an initiator and communicate with a second communication device configured to operate as a responder, the first communication device comprising circuitry configured to:

[0007] - connecting to a second communication device via at least two links including a non-millimeter wave link and a millimeter wave link;

[0008] - sending a beamforming (BF) request frame to the second communication device via the non-millimeter wave link;

[0009] - performing BF training (BFT) with the second communication device by subsequently transmitting a plurality of sector sweep (SSW) frames and training fields in different transmit sectors via the millimeter wave link; and

[0010] - If the non-millimeter wave link is not busy at the end of the BFT, receiving a BFT feedback frame from the second communication device via the non-millimeter wave link at the end of the BFT.

[0011] According to another aspect, there is provided a second communication device configured to operate as a responder and communicate with a first communication device configured to operate as an initiator, the second communication device comprising circuitry configured to:

[0012] - connecting to a first communication device via at least two links including a non-millimeter wave link and a millimeter wave link;

[0013] - receiving a beamforming (BF) request from a first communication device via a non-millimeter wave link;

[0014] - performing BF training (BFT) with the first communication device by subsequently receiving a plurality of sector sweep (SSW) frames and training fields in different transmit sectors over the millimeter wave link, wherein different receive sectors are used during reception of the training fields; and

[0015] If the non-millimeter wave link is not busy at the end of the BFT, sending a BFT feedback frame to the first communication device via the non-millimeter wave link at the end of the BFT.

[0016] According to a further aspect, a computer program comprising a program element and a non-transitory computer-readable recording medium is provided, wherein the program element is used to cause the computer to perform the steps of the method disclosed herein when the computer program is executed on the computer, and the non-transitory computer-readable recording medium stores a computer program product therein, which, when executed by a processor, causes the method disclosed herein to be performed.

[0017] Embodiments are defined in the dependent claims. It should be understood that the disclosed communication method, the disclosed computer program, and the disclosed computer-readable recording medium have further embodiments similar and / or identical to the claimed communication device and as defined in the dependent claims and / or disclosed herein.

[0018] One aspect of the present disclosure is the recognition that BF for asymmetric links takes a long time and is not useful in use cases that require low latency and high throughput because the initiator (also referred to herein as the "first communication device") is traditionally required to wait a certain amount of time with different receiving sectors in the feedback phase. The proposed disclosure applies a faster and more efficient BF method in multi-link operation (MLO) using non-millimeter wave links (e.g., Sub-7 GHz links) and millimeter wave links (e.g., links using 45 GHz, 60 GHz, or 70 GHz). Hereinafter, the proposed BF is also referred to as multi-link assisted BF. An element of the present disclosure is that the feedback information for BF is preferably transmitted on the non-millimeter wave link at the end of BF training (BFT) to make the BF duration shorter.

[0019] Hereinafter, the term "sector" refers to a predetermined beam pattern of a communication device. The term "TX sector" refers to the sector used by the communication device for transmission, and the term "RX sector" refers to the sector used by the communication device for reception. A transmitter may use a TX sector, and a receiver may use an RX sector, to achieve sufficient link quality. The term "beamforming (BF)" refers to the process of determining the optimal TX / RX sectors for a link before data transmission. The term "BF training (BFT)" refers to the training process within beamforming.

[0020] The foregoing paragraphs have been provided by way of general introduction and are not intended to limit the scope of the appended claims.The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] As a more complete appreciation of the present disclosure and many of its attendant advantages become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0022] Figure 1 Schematic diagram showing an example of conventional beamforming for an asymmetric link.

[0023] Figure 2 FIG. 1 is a schematic diagram showing an embodiment of beamforming of an asymmetric link using MLO proposed according to the first case.

[0024] Figure 3 A first implementation of a BFT feedback frame is shown.

[0025] Figure 4 A second embodiment of the BFT feedback frame is shown.

[0026] Figure 5 An implementation of a BFT acknowledgement frame is shown.

[0027] Figure 6 A schematic diagram of a first embodiment of beamforming for asymmetric links using MLO is shown according to the first case and option A.

[0028] Figure 7 A schematic diagram of a second embodiment of beamforming for asymmetric links using MLO is shown according to the first case and option A.

[0029] Figure 8 FIG. 1 is a schematic diagram showing a third embodiment of beamforming for asymmetric links using MLO according to the first case and option A. FIG.

[0030] Figure 9FIG. 4 is a schematic diagram showing a fourth embodiment of beamforming for asymmetric links using MLO according to the first case and option A.

[0031] Figure 10 FIG. 5 is a schematic diagram showing a fifth embodiment of beamforming for asymmetric links using MLO according to the first case and option A. FIG.

[0032] Figure 11 FIG. 1 is a schematic diagram showing a first embodiment of beamforming for asymmetric links using MLO according to the first case and option B. FIG.

[0033] Figure 12 FIG. 1 is a schematic diagram showing a second embodiment of beamforming for asymmetric links using MLO according to the first case and option B. FIG.

[0034] Figure 13 FIG. 4 is a schematic diagram showing an embodiment of beamforming of asymmetric links using MLO proposed according to the second case.

[0035] Figure 14 FIG. 1 is a schematic diagram illustrating an embodiment of beamforming for asymmetric links using MLO according to Case 2 and Option A. FIG.

[0036] Figure 15 FIG. 1 is a schematic diagram illustrating an embodiment of beamforming of asymmetric links using MLO according to Case 2 and Option B. FIG.

[0037] Figure 16 A flow chart illustrating an embodiment of a first communication method according to the present disclosure is shown.

[0038] Figure 17 A flow chart illustrating an embodiment of a second communication method according to the present disclosure is shown. DETAILED DESCRIPTION

[0039] For future applications, such as virtual reality (VR), low latency and high throughput may be required simultaneously, where console devices and head-mounted displays have unrestricted connections. According to the IEEE 802.11ad and 802.11ay standards, sector sweep (SSW) is performed before data transmission, and in the SSW phase, two variants of BF can be performed: 1) transmit sector sweep (TXSS) and 2) receive sector sweep (RXSS). Each of TXSS and RXSS can be performed for the sectors of the beamforming initiator and the sectors of the beamforming responder. Typically, in TXSS for the initiator, the initiator sends training signals using different TX sectors, while the responder receives the signal in a quasi-omnidirectional mode. After sending the training signal, the responder feeds back the best (or several best) transmit sectors to the initiator, and vice versa in RXSS for the initiator.

[0040] IEEE 802.11ay also standardizes the beamforming of communication devices with antenna reciprocity. Antenna reciprocity is based on the fact that due to imperfections in the TX / RX circuits within each communication device, the TX and RX sectors are typically different. However, calibration allows the communication device to compensate for this mismatch, ensuring that the TX and RX sectors have the same beam pattern.

[0041] One BF in IEEE 802.11ay that exploits antenna reciprocity is called "beamforming for asymmetric links," in which the link from the initiator to the responder has better quality than the link from the responder to the initiator during the SSW phase. Asymmetric links are essentially caused by the difference in sector gain between the initiator and the responder. For example, if the initiator is a station (STA) with high TX sector gain and the responder is a STA with low TX sector gain, the training signal from the initiator to the responder can be correctly decoded, but the training signal from the responder to the initiator cannot be correctly decoded. This is because the device should set the quasi-omni mode during SSW. Since the initiator sets the quasi-omni mode to receive feedback, the feedback for the initiator's TXSS cannot be decoded at the initiator. In view of the above, both the initiator and the responder set their sectors to beamforming for asymmetric links during the SSW phase.

[0042] Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, Figure 1 A diagram showing an example of conventional beamforming for an asymmetric link. In this example, the initiator's TXSS is performed as part of beacon signaling.

[0043] In the beacon transmission from the initiator, several beacon frames are sent using different TX sectors, and each beacon frame can be appended with a training field (TRN-R). The responder can set and switch the RX sector while receiving each TRN-R, and thus can train the tuple of <initiator's TX sector ID, responder's RX sector ID> to be the best (or better). Figure 1 In the example, the responder sets the RX sectors from RX sector #1 to RX sector #m during reception of each TRN-R. Each communication device has a predetermined sector with a sector ID.

[0044] Because the initiator does not know which initiator's RX sector should be set to receive the feedback signal from the responder, it sends feedback of the best (or better) tuple <initiator's TX sector, responder's RX sector> during the feedback phase. During the feedback phase, the responder sends feedback in a scheduled time slot, using the initiator's RX sector, which the responder estimates as the best TX sector. Scheduling information for the feedback phase (e.g., which initiator's RX sector is set in which time slot) is included in the beacon frame. The responder estimates the link quality using 1) parameters included in the beacon frame from the initiator and 2) the RSSI (Received Signal Strength Indicator) of the beacon frame received at the responder, thereby determining whether the link is asymmetric.

[0045] like Figure 1 As shown, it can be assumed that at the end of the beacon transmission, the responder estimates <initiator's TX sector #N, responder's RX sector #1> as the optimal tuple <initiator's TX sector ID, responder's RX sector ID>. During the feedback phase, as indicated in the beacon frame, the initiator allocates different durations, each of which sets a different RX sector. During the duration in which the initiator sets RX sector #N, the responder sends a feedback frame (in this case, an SSW frame).

[0046] BF for asymmetric links takes a long time and is rarely applicable because conventional communication systems require the initiator to wait for a certain amount of time with different RX sectors during the feedback phase. The method disclosed herein proposes efficient BF using MLO, where both millimeter wave links and non-millimeter wave links are used. Hereinafter, each proposed BF is referred to as multi-link assisted BF. A key element of this disclosure is that BF feedback information is preferably sent on a non-millimeter wave link to shorten the BF duration.

[0047] Two main scenarios are described below, both assuming that the BFT signal is transmitted over a mmWave link: According to scenario 1, the transmission of the training signal is not paused in the middle of the BFT. According to scenario 2, the transmission of the training signal can be paused in the middle of the BFT.

[0048] Figure 2 FIG1 is a schematic diagram showing a first embodiment of beamforming for an asymmetric link using MLO proposed according to Case 1. Two STAs are associated with each other, wherein STA1 operates as an initiator and STA2 operates as a responder. Figure 2 As shown in FIG, STA1 and STA2 both have two links, one of which is a millimeter wave link 10 and the other is a non-millimeter wave link 11, such as a Sub-7 GHz link (e.g., having a center frequency lower than 7.125 GHz). Hereinafter, the non-millimeter wave link is referred to as a Sub-7 GHz link, but essentially it is a link that does not require beamforming for association advertising and / or control message exchange, and other non-millimeter wave links can be used instead of the Sub-7 GHz link.

[0049] In the MLO setup phase 20, STA1 and STA2 exchange their capabilities and establish an association with each other. Capability exchange is typically performed on the Sub-7 GHz link because, in general, mmWave links (especially asymmetric links) require BF to be performed before exchanging information with each other. The MLO setup essentially allows STA1 and STA2 to learn which capabilities they each support (e.g., BF for asymmetric links, number of TX / RX sectors, etc.) and to perform initial configuration, such as which links to use later. An example of capability exchange using MLO is the exchange of STA profile sub-elements. It should be assumed that STA1 and STA2 are configured to use at least one Sub-7 GHz link and one mmWave link for data transmission via the MLO setup below. The MLO setup may also include allocating specific channels for the Sub-7 GHz link to ensure that any other communication devices do not interfere with the link. The link for the MLO setup may be different from the Sub-7 GHz link used to exchange BF requests and responses.

[0050] After the MLO is set up, the BFT request and response phase 21 is executed. STA1 sends a request for BF to STA2 on the Sub-7 GHz link 11 ( Figure 2 After receiving the BF request frame, STA2 sends an optional response to the request to STA1 ( Figure 2 Before sending the BF request frame, an RTS (Request-to-send) frame 212 and a CTS (Clear-to-send) frame 213 may be exchanged on the Sub-7 GHz link 11 ( Figure 2The RTS frame 212 on the Sub-7 GHz link 11 may be the same as the RTS frame according to the IEEE 802.11 standard, and the CTS frame 213 on the Sub-7 GHz link 11 may be the same as the CTS frame according to the IEEE 802.11 standard.

[0051] The BF request frame 210 may include the following indications: the number of STA1's TX sectors to be trained in the following BFT phase 22 on the mmWave link 10, and the number of STA1's TX antennas to be trained in the following BFT phase 22 on the mmWave link 10. The BF response frame to the BF request is sent as an acknowledgment and may include the following request for the following BFT phase 22:

[0052] The number of RX sectors of STA2 to be trained in BFT phase 22 (N Rx_Sector ) and the number of RX antennas of STA2 to be trained in BFT phase 22 (N Rx_ant ).

[0053] Due to the nature of MLO, it is worth noting how to obtain TXOPs on both links. Three exemplary signaling options for the mmWave link are described below. Each signaling occurs concurrently with the exchange of a BF request 210 and a BFT response 211. The RTS frame 212 on the mmWave link can be identical to an RTS frame or a DMG-RTS frame according to the IEEE 802.11 standard, and the CTS frame 213 on the mmWave link can be identical to a CTS frame or a DMG-CTS frame according to the IEEE 802.11 standard.

[0054] According to a first option, RTS / CTS frame exchange is performed on the millimeter wave link 10, such as Figure 2As shown in . STA1 sends an RTS frame 212 to STA2 on the millimeter wave link 10 to obtain a TXOP on the millimeter wave link. In the transmission of the RTS frame, at least one of the following conditions may be satisfied: a) the BF request frame also includes an indication to send the RTS frame on the millimeter wave link; b) the RTS frame on the millimeter wave link is sent simultaneously with the transmission of the BF request; and d) each PPDU (PHY data protocol data unit) of the RTS frame on the millimeter wave link and the BF request have substantially the same length through, for example, padding. After receiving the BF request frame 210 from STA1, STA2 sends a CTS frame 213 on the millimeter wave link. When transmitting the CTS frame 213 on the millimeter wave link, at least one of the following conditions may be satisfied: a) the CTS frame on the millimeter wave link is sent simultaneously with the response to the BF request; and b) each PPDU of the response and the CTS frame have substantially the same length through, for example, padding. If the inter-frame space (IFS) between the RTS frame and the CTS frame on the mmWave link is different from the IFS between the BF request frame and the response frame on the Sub-7 GHz link, the RTS / CTS frame exchange should not be performed.

[0055] According to the second option, the CTS frame and the BF request frame are sent from STA1 simultaneously on the millimeter wave link 10 ( Figure 2 In this case, STA1 may include an indication that STA1 sends a CTS frame in a BF request frame on the millimeter wave link.

[0056] According to the third option, no frame exchange is performed on the mmWave link ( Figure 2 (not shown), that is, STA1 does not transmit any frame on the millimeter wave link. In this case, STA1 may include an indication that STA1 does not send any frame on the millimeter wave link in the BF request frame.

[0057] After exchanging BFT requests and BFT responses on the Sub-7 GHz link, BFT phase 22 is executed, where STA1 and STA2 perform BFT on their TX / RX sectors on the mmWave link in the TXOP that established the BFT request and response phase 21. Figure 2 As shown in FIG, STA1 transmits SSW frames 220a to 220N, each of which is appended with a TRN field 221a to 221N.

[0058] A common TX sector is used for the transmission of the SSW frame and the additional TRN field, but different TX sectors may be used for different SSW frames. Each SSW frame may contain one or more of the following indications:

[0059] -Control frame: Indicates which frame the frame is.

[0060] - Length: The number of bits or octets of the frame.

[0061] - RA (Receiving STA Address): Indicates the MAC address of the communication device that is the intended destination of the frame.

[0062] -TA (Transmitting STA Address): Indicates the MAC address of the communication device that transmits the frame.

[0063] -CDOWN: Decrement counter indicating the number of SSW frame transmissions remaining until the end of the training phase.

[0064] - Sector ID: Indicates the TX sector ID used in the transmission of the SSW frame.

[0065] -Antenna ID: Indicates the mmWave antenna the transmitter is currently using for transmission.

[0066] - FCS (Frame Check Sequence): Extra bits used for error detection.

[0067] Each TRN field can contain the same TRN subfields, but all TRN subfields within a TRN field should be transmitted through the common TX sector and mmWave antenna, which are also indicated and used for the preceding SSW frame. The number of TRN subfields can be N Rx_ant ×N Rx_Sector Multiples of . Among them, N Rx_ant and N Rx_Sector The definition of is as above.

[0068] Typically, a known field is added before any frame used for AFC (automatic frequency correction), AGC (automatic gain control), channel estimation, etc. so that the receiver can decode the frame, and the TRN subfield can be the same as the known field used for channel estimation, and STA2 should know the TRN subfield.

[0069] When receiving each SSW frame 220, STA2 sets the sector to the quasi-omni mode, but when receiving each additional TRN field, STA2 sets a different RX sector for each TRN subfield in the TRN field so that STA2 can estimate the best Rx sector. Figure 2 As shown in , STA2 changes the Rx sector from #1 to #m when receiving TRN.

[0070] After the BFT phase 22, the feedback phase 23 is performed. STA2 sends a BFT feedback frame 230 to STA1, and STA1 sends a BFT Ack frame 231 as a response to the BFT feedback frame 230, both of which are performed on the Sub-7 GHz link 11. Figure 2 Typically, a separate TXOP is established on the Sub-7 GHz link 11.

[0071] Figure 3 An embodiment of the BFT feedback frame 230a is shown in FIG. In general, the BFT feedback frame 230 may include one or more of the following indications:

[0072] - Control frame 2301: Indicates which frame the frame is.

[0073] - Length 2302: Number of bits or octets of the frame.

[0074] - RA (Receiving STA Address) 2303: Indicates the MAC address of the communication device that is the intended destination of the frame.

[0075] -TA (Transmitting STA Address) 2304: Indicates the MAC address of the communication device that transmits the frame.

[0076] - Decoding flag 2305: Indicates whether the SSW frame transmitted using the TX sector indicated in the TX sector selection field within the BFT feedback is correctly decoded at STA2.

[0077] - Tx Sector Selection 2306: Indicates which SSW frame was received with the best quality at STA2 in the BFT phase.

[0078] - Antenna Selection 2307: A value indicating the antenna ID of the originator of the SSW frame received with the best quality in the BFT phase.

[0079] RSSI / SNR Report 2308: Indicates the SNR (Signal-to-Noise Ratio) for the selected TX sector. If the Decode Flags field indicates that the SSW frame was correctly decoded, this is estimated based on the Received TRN field for that TX sector, which was received with the best quality during the BFT phase. Otherwise, this indicates the RSSI (Received Signal Strength Indicator) for the selected TX sector. This is estimated based on the Received TRN field, which was received with the best quality during the BFT phase.

[0080] - FCS (Frame Check Sequence) 2309: Extra bits used for error detection.

[0081] Figure 4 Another embodiment of the BFT feedback frame 230b is shown in FIG. The main difference from the BFT feedback frame 230a is that in this case, multiple tuples 2310 <decoding flag, Tx sector selection, antenna selection, RSSI / SNR report> are indicated to let STA1 know the sector and antenna group of the alternative initiator. In this embodiment, the BFT feedback frame 230b includes a decoding flag field 2303, a Tx sector field 2306, an antenna selection field 2307, and an RSSI / SNR report field 2308 (preferably in each tuple). In addition, the following fields are included:

[0082] - Number of Tx sector selections 2311: indicates the number of tuples 2310 <decoding flag, Tx sector selection, antenna selection, RSSI / SNR report> within the frame.

[0083] After receiving the BFT feedback frame 230, STA1 transmits a BFT Ack frame 231 to announce which Tx sector and antenna ID will be used in subsequent transmissions. Figure 5 An embodiment of a BFT Ack frame 231 is shown, which may include one or more of the following indications:

[0084] - Control frame 2310: Indicates which frame the frame is.

[0085] - Length 2311: Number of bits or octets of the frame.

[0086] - RA (Receiving STA Address) 2312: Indicates the MAC address of the communication device that is the intended destination of the frame.

[0087] -TA (Transmitting STA Address) 2313: Indicates the MAC address of the communication device that transmits the frame.

[0088] -Tx Sector Select 2314: Indicates which initiator's sector to use in subsequent transmissions

[0089] - Antenna Selection 2315: Indicates the value of the antenna ID of the originator to be used in subsequent transmissions.

[0090] - FCS (Frame Check Sequence) 2316: Extra bits used for error detection.

[0091] like Figure 2 As shown in FIG, the BFT feedback frame 230 and the BFT Ack frame 231 are transmitted on the Sub-7 GHz link 11, but several options can be assumed. Figures 6 to 10 ), STA1 sends data to STA2 on the Sub-7 GHz link 11 during the BFT phase. Figure 11 and Figure 12 ), the Sub-7 GHz link 11 is busy due to other transmissions at least during the feedback phase. In other words, according to the present disclosure, if the non-millimeter wave link 11 is not busy at the end of the BFT, the BFT feedback is transmitted via the non-millimeter wave link at the end of the BFT.

[0092] Figure 6A schematic diagram of a first embodiment of beamforming for an asymmetric link with MLO according to the first case and option A is shown. The MLO setup phase 20 is not shown in this figure. According to this embodiment, data frames 223, 224 (PPDUs in this example) are sent from STA1 to STA2 on the Sub-7 GHz link 11. The last PPDU 224 ends simultaneously with the BFT phase 22. If the data size of the PPDU 223, 224 is so large that the estimated transmission time exceeds the end of the BFT phase 22, STA1 sends partial data so that the BFT feedback frame and the BFT Ack frame can be exchanged on the Sub-7 GHz link 11 immediately after the BFT phase. STA2 can acknowledge the reception of the data frames 223, 224 by sending an acknowledgment (Ack) frame 225. The acknowledgment of at least the last PPDU 224 can be transmitted separately (not shown) or in combination with the BFT feedback frame 230a, for example as part of the BFT feedback frame (e.g., Figure 6 ) or attached to the BFT feedback frame.

[0093] Figure 7 A schematic diagram of a second embodiment of beamforming for asymmetric links using MLO is shown according to the first case and option A. Figure 6 The main difference of the second embodiment shown in FIG is that STA1 obtains TXOP 24 on the Sub-7 GHz link 11 by exchanging RTS and CTS frames 214 and 215 until the end of the feedback phase 23 before transmitting the BFT request frame 210. This scenario can be considered based on the following assumption: data is already queued before the RTS frame 214 is transmitted on the Sub-7 GHz link 11. In addition, the data size is sufficient to ensure that the transmission time is substantially the same as or longer than the BFT phase 22 using the worst-case code rate of the candidate MCS (modulation and coding scheme). In addition, due to low latency requirements, TXOP 24 should be guaranteed during the feedback phase 23.

[0094] According to this embodiment, the RTS frame 214 and / or the CTS frame 215 indicates that the TXOP 24 has a duration such that the TXOP 24 covers at least the estimated feedback phase 23. To ensure that the time of the feedback phase 23 is fixed before sending the BF request, the BF request frame 210 may indicate at least one of the following: a) the number of RX sectors and antennas of STA2 to be trained in the BFT phase 22; b) an indication that the response frame 211 to the BF request frame 210 should not include a request for the number of RX sectors and antennas of STA2 to be trained in the BFT phase 22; and c) an indication that STA1 does not consider STA2's request for the number of RX sectors and antennas of STA2 to be trained in the BFT phase 22.

[0095] Figure 8 A schematic diagram shows a third embodiment of beamforming for asymmetric links using MLO according to the first case and option A. According to this embodiment, separate TXOPs are obtained. For example, there are two TXOPs 25 and 26, the first TXOP 24 having a duration from the RTS / CTS exchange to the end of the BFT phase 22, and the second TXOP 25 covering the feedback phase 23. In this case, another RTS / CTS exchange of an RTS frame 232 and a CTS frame 233 may occur before the feedback phase 23, as shown in FIG. Figure 8 As shown in .

[0096] According to another embodiment, the first TXOP 25 may cover the transmission of the Ack+BFT feedback frame 230 a , and the second TXOP 26 may cover only the BFT Ack transmission 231 . Figure 9 A fourth embodiment of beamforming of asymmetric links with MLO proposed according to the first case and option A is shown.

[0097] The above embodiment assumes that the PPDU is transmitted during the BFT phase 22 , but it can be considered that STA1 does not have sufficient traffic, so that the PPDU transmitted on the Sub-7 GHz link 11 may not occupy the link until the BFT phase 22 ends. Figure 10 A schematic diagram illustrates a fifth embodiment of beamforming for asymmetric links using MLO, according to the first scenario and Option A. According to this embodiment, the PPDU 223 is transmitted during the BFT phase 22, but the PPDU does not occupy the entire duration of the BFT phase 22. In this case, another RTS / CTS exchange of the RTS frame 226 and the CTS frame 227 may be performed to ensure that the BFT feedback 230 can be transmitted after the BFT phase 22. The end time of the CTS frame 227 may be aligned with the end time of the last TRN field 221N.

[0098] The CTS frame 227 may be received earlier than the last TRN field 221N (T IFS +T CTS -T1) transmission, where T IFS is the inter-frame space (IFS) between the CTS frame 227 and the BFT feedback frame 230, T CTS is the duration of the CTS frame 227, and T1 is the duration between the reception of the last TRN field 221N and the transmission of the BFT feedback frame 230, as shown in FIG. Figure 10 As shown in T IFS It may be the same as SIFS (Short IFS) defined in the IEEE 802.11 standard.

[0099] Figure 11The diagram shows a first embodiment of beamforming for an asymmetric link using MLO according to the first scenario and Option B. According to this embodiment, STA2 assesses that the channel on the Sub-7 GHz link 11 is busy due to other transmissions at least during the feedback phase 23. Therefore, STA2 cannot send a BFT feedback frame to STA1 during the busy state. Instead, STA2 sends a BFT feedback frame 230a after assessing that the channel is idle.

[0100] Figure 12 A schematic diagram illustrates a second embodiment of beamforming for asymmetric links using MLO, according to the first scenario and Option B. In this embodiment, BFT feedback 230 is transmitted over the mmWave link. In the asymmetric link scenario, STA1 cannot decode any signals from STA2 unless the optimal sector is set at both STA1 and STA2, and feedback phase 23 is performed over the mmWave link, as defined in "BF for Asymmetric Links" in IEEE 802.11ay, in which STA1 sets a specific RX sector in a predetermined time slot.

[0101] STA1 and STA2 decide whether to perform this process. If STA1 sends the last TRN field to STA2 for a certain duration T thr STA1 does not receive any signal from STA2 within 1 second, then STA1 recognizes that STA2 estimates the channel is busy. In addition, since STA2 estimates the busy state for a certain duration T thr , STA2 attempts to send a BF feedback frame 230 to STA1 on the millimeter wave link 10.

[0102] exist Figure 12 In the embodiment shown in FIG, STA2 estimates <Tx sector #2, Rx sector #1> as the optimal tuple <Tx sector ID, Rx sector ID>, and BFT feedback is transmitted on STA2's Tx sector #1 in the time slot in which STA1 sets Rx sector #2. After receiving the BFT feedback, STA1 sends a BFT Ack to STA2, and feedback phase 23 terminates. Although the time slot for each Tx sector of STA1 is shown as one, the number of time slots for each Rx sector of STA1 may be more than one.

[0103] The BF request frame 210 may also include a) an indication of potential scheduling information for a time slot and / or b) T thr The scheduling information within the BF request 210 may include a) the duration and start time of each time slot and / or b) the Rx sector ID and antenna ID of the initiator used in each time slot.

[0104] refer to Figures 2 to 12, illustrates a different embodiment of Case 1, according to which the transmission of the training signal is not suspended in the middle of the BFT. Figures 13 to 15 , a different implementation of Case 2 will be described, according to which the transmission of the training signal can be suspended in the middle of the BFT.

[0105] Figure 13 FIG2 is a schematic diagram illustrating an embodiment of beamforming for asymmetric links using MLO according to Case 2. In this embodiment, BFT transmission is suspended in BFT phase 22. The main difference from the embodiment according to Case 1 is that BFT is suspended after STA1 receives a BFT feedback indication 230 from STA2 on Sub-7 GHz link 11.

[0106] In the MLO setup phase 120, STA1 and STA2 exchange their capabilities and establish an association with each other. This phase is similar or identical to the MLO setup phase 20 in Case 1, but STA1 and STA2 may exchange capabilities as follows: Initially, if STA1 receives an indication from STA2 that it is using at least one of the specific link quality estimation tuples <STA1's TX sector ID, STA2's RX sector ID>, STA1 may suspend BFT. Subsequently, STA2 may send feedback information to STA1 during BFT transmission on the Sub-7 GHz link 11. The feedback information may also be preliminary feedback and an indication that STA1 may stop BFT.

[0107] After MLO is set up, in the BF request and response phase 21, if STA1 obtains a TXOP on the Sub-7 GHz link, STA1 sends a request 210 for BFT to STA2 on the Sub-7 GHz link 11. STA2 sends a response 211 in response to the BF request frame 210. Therefore, the BF request and response phase 21 may be similar or identical to the BF request and response phase 21 in Case 1, but may include additional information as described below.

[0108] To allow STA2 to estimate the link quality, the BF request frame 210 may include one or more of the following indications:

[0109] -When STA2 sends STA2 estimated link quality S link quality When at least one of the tuples <TX sector ID of STA1, RX sector ID of STA2> is indicated, the corresponding BFT indication may be suspended;

[0110] - the parameters of the specific link quality mentioned above, which may indicate the minimum required RSSI, the minimum required estimated SNR of the link from STA1 to STA2, or the required estimated SNR of the link from STA2 to STA1;

[0111] - Indicates the specific link quality S link quality is one of the following: the required RSSI estimated by STA2, the required SNR of the link from STA1 to STA2, or the required SNR of the link from STA2 to STA1.

[0112] If the BF request frame 210 includes the above indication a) or b), STA2 estimates the RSSI of the received SSW frame 220 or the SNR of the received SSW frame 220 in the BFT phase 22. If the BF request frame 210 includes the above indication c), STA2 may calculate the estimated SNR of the link from STA2 to STA1 as follows:

[0113] SNR est =P STA2 +G STA2-Tx +(RSSI-CG STA2-Rx ), (1)

[0114] Among them, SNR est is STA2’s estimate of the expected SNR of STA1 receiving STA2’s transmission, P STA2 and G STA2-Tx is the transmit power and antenna gain of the expected STA2 transmission, RSSI is the power measured by STA2 during the reception of the TRN field in the BFT phase 22, and C is the value contained in the SSW frame 220 received in the BFT phase. The indicated value of C can be set as follows:

[0115] C=P STA1 +G STA1-Tx +P Noise , (2)

[0116] Among them, P STA1 and G STA1-TX are the transmit power and antenna gain used in SSW frame transmission, and P Noise is the noise power level estimated by STA1. The unit of each of the above parameters is dB or dBm.

[0117] After exchanging BF requests and responses on the Sub-7 GHz link 11, STA1 and STA2 perform BF training for their TX / RX sectors in BFT phase 122. The BFT can be similar or identical to BFT phase 22 in Case 1, i.e., STA1 transmits SSW frames 220a to 220K+1, each with a TRN field 221a to 221K+1 appended. The SSW frame and TRN field can be similar or identical to those in Case 1, but the SSW frame can additionally include the aforementioned parameter C.

[0118] During the BFT phase 122, STA2 estimates the link quality indicated in the BF request frame 210, i.e., RSSI, SNR of the link from STA1 to STA2, or SNR of the link from STA2 to STA1. If the estimated link quality is equal to or greater than a threshold S that may be included in the BF request frame 210, link quality , STA2 sends a BFT feedback frame 230 to STA1. As an example, Figure 13 It is shown that STA1 transmits K+1 SSW frames, but STA2 estimates that at least one of the sector IDs #1 to #K used for the first K SSW frames satisfies the link quality equal to or greater than S. link quality If STA2 receives SSW frames after STA2 sends the BFT feedback frame 230, STA2 does not have to decode these SSW frames.

[0119] Figure 13 Although not shown, STA1 may stop transmitting the (K+1)th SSW frame 220K+1 to which the TRN field 221K+1 is appended during the frame transmission period, during which STA1 receives the BFT feedback frame 230 .

[0120] In the feedback phase 123, STA1 may send a BFT end frame 234 on the Sub-7 GHz link 11, which includes an indication of which Tx sector and antenna ID will be used in the following transmission, and an indication of the end of the BFT phase 122 on the mmWave link 10. CF (Content Free) End Frame ( Figure 13 The BFT end frame 234 may be transmitted on the Sub-7 GHZ link 11 after the BFT end frame 234 or may be included in the BFT end frame 234.

[0121] STA2 can also send a BFT Ack frame ( Figure 13 (not shown) simultaneously or after the current SSW frame transmission, a CF end frame 235 is sent on the mmWave link 10 to announce the end of the TXOP on the mmWave link 10. The CF end frame may be similar to or the same as that described in the IEEE 802.11 standard.

[0122] like Figure 13 As shown in , BFT feedback and BFT end frames are transmitted on the Sub-7 GHz link 11, but in the case that the Sub-7 GHz link is occupied by another transmission, several options can be assumed as follows: according to option A, STA1 sends data to STA2 on the Sub-7 GHz link during the BFT phase 122, and according to option B, the Sub-7 GHz link 11 is busy due to other transmissions at least during the feedback phase 123.

[0123] Figure 14 FIG2 is a schematic diagram showing an embodiment of beamforming for asymmetric links using MLO according to the second scenario and option A. According to this embodiment, data frames 223 and 224 are sent from STA1 to STA2 on the Sub-7 GHz link 11. Figure 14 , it is also shown that the last PPDU 225 ends when or after the Nth SSW frame 220N is fully transmitted on the mmWave link 10. In this case, STA2 sends a BFT feedback frame 230a to STA1 after the PPDU transmission. The Ack frame to the PPDU can be sent alone (as an Ack frame 225) or can be sent together with the BFT feedback frame 230a.

[0124] To allow STA2 to send a BFT feedback frame 230a on the Sub-7 GHz link 11 while STA1 obtains a TXOP on the Sub-7 GHz link 11, STA1 may include a Reverse Direction Grant (RDG) in the PPDUs 223 and 224 on the Sub-7 GHz link 11 during the BFT phase 122. The RDG may be similar to or the same as that described in the IEEE 802.11 standard.

[0125] If the data size is so large that the estimated transmission time exceeds the end time of the Mth SSW frame transmission (where M is the maximum number of SSW frames to be transmitted in the BFT phase), STA1 may transmit only part of the data so that the BFT feedback frame 230a can be transmitted on the Sub-7 GHz link 11 at the latest after the Mth SSW transmission.

[0126] Even if STA2 has estimated at least one of the tuples <STA1's Tx sector ID, STA2's Rx sector ID> with required link quality, STA2 may decode the SSW frame and estimate the link quality up to BFT feedback transmission.

[0127] Figure 15A schematic diagram illustrates an embodiment of beamforming for asymmetric links using MLO, according to Case 2 and Option B. According to this embodiment, at least during the feedback phase 123, the Sub-7 GHz link at STA2 is busy due to other transmissions. While busy, STA2 cannot send a BFT feedback frame 230 to STA1. Instead, it sends a BFT feedback frame 230 after STA2 assesses that the channel on Sub-7 GHz link 11 is idle. After receiving the BFT feedback frame 230 from STA2, STA1 sends a BFT end frame 234 on Sub-7 GHz link 11 and, optionally, a CF end frame 235 on mmWave link 10. Another exemplary scenario involves BFT feedback frame 230 being transmitted on mmWave link 10. This scenario is similar or identical to the scenario described above with reference to Case 1.

[0128] Figure 16 A flowchart of an embodiment of a first communication method 300 is shown, which can be performed by a first communication device (STA1) operating as an initiator and communicating with a second communication device (STA2) operating as a responder. In a first step 301, the first communication device connects to a second communication device via at least two links including a non-millimeter wave link and a millimeter wave link. In a second step 302, it sends a BF request frame to the second communication device via the non-millimeter wave link. In a third step 303, it performs BF training with the second communication device by subsequently sending multiple SSW frames and training fields in different transmission sectors via the millimeter wave link. In a fourth step 304, if it (the non-millimeter wave link) is not busy at the end of the BFT, it receives a BFT feedback frame from the second communication device via the non-millimeter wave link at the end of the BFT.

[0129] Figure 17 A flowchart of an embodiment of a second communication method 400 is shown, which can be performed by a second communication device (STA2) operating as a responder. In a first step 401, the second communication device is connected to the first communication device via at least two links including a non-millimeter wave link and a millimeter wave link. In a second step 402, it receives a BF request from the first communication device via the non-millimeter wave link. In a third step 403, it performs BF training with the first communication device by subsequently receiving multiple SSW frames and training fields in different transmission sectors via the millimeter wave link, wherein different reception sectors are used during the reception of the training field. In a fourth step, if it (the non-millimeter wave link) is not busy at the end of the BFT, it sends a BFT feedback frame to the first communication device via the non-millimeter wave link at the end of the BFT.

[0130] In summary, the present disclosure is directed to fast beamforming for multi-link operation using non-millimeter wave (e.g., Sub-7 GHz) and millimeter wave links. In order to establish data communication links of sufficient quality without consuming a large amount of time, there is a mechanism to utilize the shorter beamforming time of MLO, especially in the case of asymmetric links in millimeter waves, especially for low-latency and high-throughput applications.

[0131] Therefore, the foregoing discussion discloses and describes only exemplary embodiments of the present disclosure. As will be appreciated by those skilled in the art, the present disclosure may be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the disclosure of the present disclosure is intended to be illustrative and not to limit the scope of the present disclosure and other claims. The present disclosure (including any readily discernible variations of the teachings herein) partially defines the scope of the aforementioned claim terms, such that no inventive subject matter is dedicated to the public.

[0132] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0133] To the extent that embodiments of the present disclosure have been described as being implemented at least in part by a data processing device controlled by software, it will be understood that non-transitory machine-readable media (such as optical disks, magnetic disks, semiconductor memories, etc.) carrying such software are also considered to represent embodiments of the present disclosure. In addition, such software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0134] Elements of the disclosed apparatuses, devices, and systems can be implemented by corresponding hardware and / or software elements (e.g., appropriate circuitry). A circuit is a structural assembly of electronic components including conventional circuit elements, integrated circuits including application-specific integrated circuits, standard integrated circuits, application-specific standard products, and field-programmable gate arrays. Furthermore, a circuit includes a central processing unit, a graphics processing unit, and a microprocessor that are programmed or configured according to software code. A circuit does not include pure software, but rather includes hardware that executes the software as described above.

[0135] The following is a list of additional embodiments of the disclosed subject matter:

[0136] 1. A first communication device (STA1) configured to operate as an initiator and communicate with a second communication device (STA2) configured to operate as a responder, the first communication device comprising circuitry configured to:

[0137] - connecting (20) to a second communication device via at least two links including a non-millimeter wave link (11) and a millimeter wave link (10);

[0138] - sending (21) a beamforming (BF) request frame (210) to a second communication device via a non-millimeter wave link;

[0139] - performing (22) BF training (BFT) with the second communication device by subsequently transmitting a plurality of sector sweep (SSW) frames (220A...220N) and training fields (221A...221N) in different transmission sectors via the millimeter wave link; and

[0140] - If the non-millimeter wave link is not busy at the end of the BFT, receiving (23) a BFT feedback frame (230) from the second communication device via the non-millimeter wave link at the end of the BFT.

[0141] 2. The first communication device according to any one of the preceding embodiments,

[0142] The circuitry is configured to use the same beam pattern for transmission and reception in a millimeter wave link, wherein transmit / receive sectors are defined by specific beam patterns.

[0143] 3. The first communication device according to any one of the preceding embodiments,

[0144] The circuit is configured to include a plurality of training subfields in the training field.

[0145] 4. The first communication device according to any one of the preceding embodiments,

[0146] The circuit is configured to send a BFT confirmation frame to the second communication device via the non-millimeter wave link in response to a BFT feedback frame received from the second communication device via the non-millimeter wave link.

[0147] 5. The first communication device according to any one of the preceding embodiments,

[0148] Wherein the circuit is configured to include one or more of the following in the BFT acknowledgement frame:

[0149] -Control frame indication, indicating that the frame is a BFT confirmation frame;

[0150] - Length indication, indicating the number of bits or octets of the BFT acknowledgment frame;

[0151] - Destination indication, indicating the communication device to which the BFT confirmation frame is addressed;

[0152] - a source indication, indicating the first communication device;

[0153] - a sector selection indication indicating which transmit sector to use in subsequent transmissions over the mmWave link;

[0154] - an antenna selection indication, indicating which antenna to use in subsequent transmissions over the mmWave link; and

[0155] - Frame Check Sequence (FCS) for error detection.

[0156] 6. The first communication device according to any one of the preceding embodiments,

[0157] Wherein the circuit is configured to include one or more of the following in the SSW frame:

[0158] -Control frame indication, indicating that the frame is an SSW frame;

[0159] - length indication, indicating the number of bits or octets of the SSW frame;

[0160] - Destination indication, indicating the communication device to which the SSW frame is addressed;

[0161] - a source indication, indicating the first communication device;

[0162] - a counter indicating the number of remaining SSW frames to be sent by the end of the BFT;

[0163] - Sector selection indication, indicating which transmission sector has been used for SSW frame transmission;

[0164] -Antenna selection indication, indicating which antenna has been used for SSW frame transmission; and

[0165] - Frame Check Sequence (FCS) for error detection.

[0166] 7. The first communication device according to any one of the preceding embodiments,

[0167] The circuit is configured to use a Sub-7 GHz link as a non-millimeter wave link, where the Sub-7 GHz link has a center frequency lower than 7.125 GHz.

[0168] 8. The first communication device according to any one of the preceding embodiments,

[0169] The circuit is configured to send one or more data frames to the second communication device via the non-millimeter wave link during the BFT, wherein the transmission of the data frames ends at the latest when the BFT ends.

[0170] 9. The first communication device according to embodiment 8,

[0171] wherein the circuit is configured to transmit via a non-millimeter wave link

[0172] i) No Ready to Send (RTS) frame, or

[0173] ii) RTS frame

[0174] - before sending a BF request, and / or

[0175] - before, during and / or after receiving a BFT feedback frame, and / or

[0176] -During the BFT period.

[0177] 10. The first communication device according to any one of the preceding embodiments,

[0178] wherein the circuit is configured to send to the second communication device prior to the BFT, in particular as part of a BF request frame,

[0179] - clearing period information indicating a clearing period for the second communications device to use in deciding whether to send a BFT feedback frame via the mmWave link if the non-mmWave link does not become idle within the clearing period, and / or

[0180] - Link quality information, indicating a link quality threshold, for use by the second communications device in deciding whether to send a BFT feedback frame during the BFT period.

[0181] 11. The first communication device according to any one of the preceding embodiments,

[0182] The circuit is configured to suspend BFT if a BFT feedback frame is received during the BFT period.

[0183] 12. A second communication device (STA2) configured to operate as a responder and communicate with a first communication device (STA1) configured to operate as an initiator, the second communication device comprising circuitry configured to:

[0184] - connecting (20) to a first communication device via at least two links including a non-millimeter wave link (11) and a millimeter wave link (10);

[0185] - receiving (21) a beamforming (BF) request (210) from a first communication device via a non-millimeter wave link;

[0186] - performing (22) BF training (BFT) with the first communication device by subsequently receiving a plurality of sector sweep (SSW) frames (220A...220N) and training fields (221A...221N) in different transmit sectors via the millimeter wave link, wherein different receive sectors are used during reception of the training fields; and

[0187] - If the non-millimeter wave link is not busy at the end of the BFT, sending (23) a BFT feedback frame (230) to the first communication device via the non-millimeter wave link at the end of the BFT.

[0188] 13. The second communication device according to embodiment 12,

[0189] The circuit is configured to use the same beam pattern for transmission and reception in a millimeter wave link.

[0190] 14. The second communication device according to any one of embodiments 12 to 13,

[0191] The circuit is configured to send a BF response to the first communication device via the non-millimeter wave link in response to a BF request received from the first communication device via the non-millimeter wave link.

[0192] 15. The second communication device according to any one of embodiments 12 to 14,

[0193] The circuit is configured to receive a plurality of training subfields included in the training field, wherein each training subfield is received by a different receiving sector.

[0194] 16. The second communication device according to any one of embodiments 12 to 15,

[0195] The circuit is configured to include in the BFT feedback frame:

[0196] - a decoding flag indicating whether the transmitted SSW frame has been correctly decoded by the second communication device; and / or

[0197] - Two or more decode flag fields indicating two or more alternative transmission sectors for use by the first communication device.

[0198] 17. The second communication device according to embodiment 16,

[0199] The circuit is configured to further include one or more of the following in the BFT feedback frame:

[0200] -Control frame indication, indicating that the frame is a BFT feedback frame;

[0201] - Length indication, indicating the number of bits or octets of the BFT feedback frame;

[0202] - Destination indication, indicating the communication device to which the BFT feedback frame is addressed;

[0203] - a source indication, indicating the second communication device;

[0204] - a decoding flag indicating whether the transmitted SSW frame indicated in the corresponding sector selection indication has been correctly decoded by the second communication device;

[0205] - a sector selection indication indicating which SSW frame was received with the best quality at the second communication device during the BFT phase;

[0206] -Antenna selection indication, indicating the antenna that receives the SSW frame with the best quality during the BFT phase;

[0207] - RSSI / SNR reporting indication, indicating the signal-to-noise ratio (SNR) or received signal strength indicator (RSSI) of the best transmitting sector in the BFT phase; and

[0208] - Frame Check Sequence (FCS) for error detection.

[0209] 18. The second communication device according to any one of embodiments 12 to 17,

[0210] wherein the circuit is configured to transmit a CTS frame via the non-millimeter wave link in response to a ready-to-send (RTS) frame from the first communication device

[0211] - before sending a BF request, and / or

[0212] - before, during and / or after receiving a BFT feedback frame, and / or

[0213] -During the BFT period.

[0214] 19. The second communication device according to any one of embodiments 12 to 18,

[0215] The circuit is configured to, if the non-millimeter wave link is busy at the end of the BFT, send the BFT feedback frame via the non-millimeter wave link once the non-millimeter wave link becomes idle, or if the non-millimeter wave link does not become idle within the clearing period, send the BFT feedback frame via the non-millimeter wave link after the clearing period.

[0216] 20. The second communication device according to embodiment 19,

[0217] Wherein the circuit is configured to, if the non-millimeter wave link is busy at the end of the BFT and does not become idle within the clearing period,

[0218] - estimating the best combination of the best transmission sector of the first communication device and the best reception sector of the second communication device; and

[0219] After the clearing period, at a time slot when the first communication device receives using the reception sector estimated to be the best transmission sector of the first communication device, a BFT feedback frame is transmitted via the millimeter wave link using the transmission sector estimated to be the best reception sector of the second communication device.

[0220] 21. The second communication device according to any one of embodiments 12 to 20,

[0221] Wherein the circuit is configured to send a BFT feedback frame during the BFT period if the estimated link quality becomes equal to or greater than a link quality threshold.

[0222] 22. The second communication device according to any one of embodiments 12 to 21,

[0223] The circuit is configured to send a BFT feedback frame once the first communication device sends the last data frame or the non-millimeter wave link becomes idle if the non-millimeter wave link is busy due to the first communication device sending a data frame to the second communication device or due to other services on the non-millimeter wave link.

[0224] 23. A first communication method of a first communication device configured to operate as an initiator and communicate with a second communication device configured to operate as a responder, the first communication method comprising:

[0225] - connecting to a second communication device via at least two links including a non-millimeter wave link and a millimeter wave link;

[0226] - sending a beamforming (BF) request frame to the second communication device via the non-millimeter wave link;

[0227] - performing BF training (BFT) with the second communication device by subsequently transmitting a plurality of sector sweep (SSW) frames and training fields in different transmit sectors via the millimeter wave link; and

[0228] - If the non-millimeter wave link is not busy at the end of the BFT, receiving a BFT feedback frame from the second communication device via the non-millimeter wave link at the end of the BFT.

[0229] 24. A second communication method of a second communication device configured to operate as a responder and communicate with a first communication device configured to operate as an initiator, the second communication method comprising:

[0230] - connecting to a first communication device via at least two links including a non-millimeter wave link and a millimeter wave link;

[0231] - receiving a beamforming (BF) request from a first communication device via a non-millimeter wave link;

[0232] - performing BF training (BFT) with the first communication device by subsequently receiving a plurality of sector sweep (SSW) frames and training fields in different transmit sectors over the millimeter wave link, wherein different receive sectors are used during reception of the training fields; and

[0233] If the non-millimeter wave link is not busy at the end of the BFT, sending a BFT feedback frame to the first communication device via the non-millimeter wave link at the end of the BFT.

[0234] 25. A non-transitory computer-readable recording medium having a computer program product stored therein, which, when executed by a processor, causes execution of the method according to embodiment 23 or embodiment 24.

[0235] 26. A computer program comprising program code means for causing the computer to execute the steps of the method according to embodiment 23 or embodiment 24 when the computer program is executed on the computer.

Claims

1. A first communication device configured to operate as an initiator and communicate with a second communication device configured to operate as a responder, the first communication device comprising circuitry configured to: - connecting to the second communication device via at least two links including a non-millimeter wave link and a millimeter wave link; - sending a beamforming (BF) request frame to the second communication device via the non-millimeter wave link; - performing BF training (BFT) with the second communication device by subsequently transmitting a plurality of sector sweep (SSW) frames and training fields in different transmission sectors via the millimeter wave link; as well as - If the non-millimeter wave link is not busy at the end of the BFT, receiving a BFT feedback frame from the second communication device via the non-millimeter wave link at the end of the BFT.

2. The first communication device according to claim 1, in, The circuitry is configured to use the same beam pattern for transmission and reception in the millimeter wave link, wherein transmit / receive sectors are defined by a specific beam pattern and / or to suspend BFT if a BFT feedback frame is received during a BFT period.

3. The first communication device according to claim 1, in, The circuitry is configured to include a plurality of training subfields in a training field.

4. The first communication device according to claim 1, in, The circuitry is configured to, in response to a BFT feedback frame received from the second communication apparatus via the non-millimeter wave link, send a BFT confirmation frame to the second communication apparatus via the non-millimeter wave link, and / or include one or more of the following in the BFT confirmation frame: -Control frame indication, indicating that the frame is a BFT confirmation frame; - Length indication, indicating the number of bits or octets of the BFT acknowledgment frame; - Destination indication, indicating the communication device to which the BFT confirmation frame is addressed; - a source indication, indicating the first communication device; - a sector selection indication indicating which transmit sector to use in subsequent transmissions via the millimeter wave link; - an antenna selection indication indicating which antenna to use in subsequent transmissions via the millimeter wave link; as well as - Frame Check Sequence (FCS) for error detection.

5. The first communication device according to claim 1, in, The circuitry is configured to include one or more of the following in an SSW frame: -Control frame indication, indicating that the frame is an SSW frame; - length indication, indicating the number of bits or octets of the SSW frame; - Destination indication, indicating the communication device to which the SSW frame is addressed; - a source indication, indicating the first communication device; - a counter indicating the number of remaining SSW frames to be sent by the end of the BFT; - Sector selection indication, indicating which transmission sector has been used for SSW frame transmission; -Antenna selection indication, indicating which antenna has been used for SSW frame transmission; and - Frame Check Sequence (FCS) for error detection. The first communication device according to claim 1 , in, The circuit is configured to use a Sub-7 GHz link as a non-millimeter wave link, the Sub-7 GHz link having a center frequency lower than 7.125 GHz.

7. The first communication device according to claim 1, in, The circuit is configured to transmit one or more data frames to the second communication device via the non-millimeter wave link during a BFT, wherein transmission of the data frames ends at the latest when the BFT ends.

8. The first communication device according to claim 7, in, The circuit is configured to transmit via the non-millimeter wave link i) No Ready to Send (RTS) frame, or ii) RTS frame - before sending a BF request, and / or - before, during and / or after receiving a BFT feedback frame, and / or -During the BFT period.

9. The first communication device according to claim 1, in, The circuit is configured to send to the second communication device before the BFT, in particular as part of a BF request frame, - clearing period information indicating a clearing period for use by the second communication device in determining whether a BFT feedback frame should be sent via the millimeter wave link if the non-millimeter wave link does not become idle within the clearing period, and / or - Link quality information, indicating a link quality threshold, for use by the second communication device in deciding whether a BFT feedback frame should be sent during the BFT period.

10. A second communication device configured to operate as a responder and communicate with a first communication device configured to operate as an initiator, the second communication device comprising circuitry configured to: - connecting to the first communication device via at least two links including a non-millimeter wave link and a millimeter wave link; - receiving a beamforming (BF) request from the first communication device via the non-millimeter wave link; - performing BF training (BFT) with the first communication device by subsequently receiving a plurality of sector sweep (SSW) frames and training fields in different transmit sectors via the millimeter wave link, wherein, using different receive sectors during reception of a training field; as well as - If the non-millimeter wave link is not busy at the end of the BFT, sending a BFT feedback frame to the first communication device via the non-millimeter wave link at the end of the BFT.

11. The second communication device according to claim 10, in, The circuit is configured to transmit and receive using the same beam pattern in the millimeter wave link and / or to send a BF response to the first communication device via the non-millimeter wave link in response to a BF request received from the first communication device via the non-millimeter wave link.

12. The second communication device according to claim 10, in, The circuit is configured to receive a plurality of training subfields included in a training field, wherein each training subfield is received by a different receiving sector.

13. The second communication device according to claim 10, in, The circuit is configured to include in a BFT feedback frame: - a decoding flag indicating whether the transmitted SSW frame has been correctly decoded by the second communication device; and / or - Two or more decoding flag fields indicating two or more alternative transmission sectors for use by said first communication device.

14. The second communication device according to claim 13, in, The circuitry is configured to also include one or more of the following in the BFT feedback frame: -Control frame indication, indicating that the frame is a BFT feedback frame; - Length indication, indicating the number of bits or octets of the BFT feedback frame; - Destination indication, indicating the communication device to which the BFT feedback frame is addressed; - a source indication, indicating the second communication device; - a decoding flag indicating whether the transmitted SSW frame indicated in the corresponding sector selection indication has been correctly decoded by the second communication device; - a sector selection indication indicating which SSW frame was received with the best quality at the second communication device during the BFT phase; -Antenna selection indication, indicating the antenna that receives the SSW frame with the best quality during the BFT phase; - RSSI / SNR reporting indication, indicating the signal-to-noise ratio (SNR) or received signal strength indicator (RSSI) of the best transmitting sector in the BFT phase; and - Frame Check Sequence (FCS) for error detection.

15. The second communication device according to claim 10, in, The circuit is configured to transmit a ready-to-send (CTS) frame via the non-millimeter wave link in response to a ready-to-send (RTS) frame from the first communication device. - before sending a BF request, and / or - before, during and / or after receiving a BFT feedback frame, and / or -During the BFT period.

16. The second communication device according to claim 10, in, The circuit is configured to, if the non-millimeter wave link is busy at the end of the BFT, send the BFT feedback frame via the non-millimeter wave link once the non-millimeter wave link becomes idle, or if the non-millimeter wave link does not become idle within the clearing period, send the BFT feedback frame via the non-millimeter wave link after the clearing period, specifically, if the non-millimeter wave link is busy at the end of the BFT and does not become idle within the clearing period, - estimating the best combination of the best transmission sector of the first communication device and the best reception sector of the second communication device; as well as After the clear period, at a time slot when the first communication device receives using the reception sector estimated to be the best transmission sector for the first communication device, sending a BFT feedback frame via the millimeter wave link using the transmission sector estimated to be the best reception sector for the second communication device.

17. The second communication device according to claim 10, in, The circuit is configured to send a BFT feedback frame a) During the BFT period, if the estimated link quality becomes equal to or greater than the link quality threshold, and / or b) If the non-millimeter wave link is busy due to the first communication device sending a data frame to the second communication device or due to other services on the non-millimeter wave link, once the first communication device sends the last data frame or the non-millimeter wave link becomes idle.

18. A first communication method of a first communication device, the first communication device being configured to operate as an initiator and communicate with a second communication device being configured to operate as a responder, the first communication method comprising: - connecting to the second communication device via at least two links including a non-millimeter wave link and a millimeter wave link; - sending a beamforming (BF) request frame to the second communication device via the non-millimeter wave link; - performing BF training (BFT) with the second communication device by subsequently transmitting a plurality of sector sweep (SSW) frames and training fields in different transmission sectors via the millimeter wave link; as well as - If the non-millimeter wave link is not busy at the end of the BFT, receiving a BFT feedback frame from the second communication device via the non-millimeter wave link at the end of the BFT.

19. A second communication method for a second communication device, the second communication device being configured to operate as a responder and communicate with a first communication device being configured to operate as an initiator, the second communication method comprising: - connecting to the first communication device via at least two links including a non-millimeter wave link and a millimeter wave link; - receiving a beamforming (BF) request from the first communication device via the non-millimeter wave link; - performing BF training (BFT) with the first communication device by subsequently receiving a plurality of sector sweep (SSW) frames and training fields in different transmit sectors via the millimeter wave link, wherein different receive sectors are used during reception of the training fields; as well as - If the non-millimeter wave link is not busy at the end of the BFT, sending a BFT feedback frame to the first communication device via the non-millimeter wave link at the end of the BFT. 20 . A non-transitory computer-readable recording medium in which a computer program product is stored, which, when executed by a processor, causes the method according to claim 18 or claim 19 to be performed.

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