Patent Description:
Communication networks like wireless local area network (WLAN) comprise an access point station (generally referred to as access point (AP), personal basic service set control point (PCP), or collectively PCP/AP) and other terminal stations (STAs). The access point stations like the PCP/AP transmit a beacon signal on a fixed channel to the STAs and the STAs also use the channel to establish connections with the PCP/AP.

Institute of Electrical and Electronics Engineers (IEEE) <NUM> standards are well-known WLAN standards. IEEE <NUM>. 11ad and IEEE <NUM>. 11ay are two examples of multiple amendments to IEEE <NUM> WLAN standards. IEEE <NUM>1ad and <NUM>1ay standards include a sector level sweep (SLS) procedure, and a beam refinement protocol (BRP) procedure. The SLS procedure may be used for transmit beamforming training; the BRP procedure may be used for receive beamforming training, and iterative refinement of both transmit and receive beams. The US patent application <CIT> is about beam training methods for multiple-input multiple-output (MIMO) operation and for multiple antenna beamforming operation and discloses to apply sector level sweeps. The US patent application <CIT> is about beam training methods applying sector sweeps in IEEE <NUM> systems. The document "<NPL>, is a contribution to the specification of IEEE <NUM>, disclosing fragmented transmit sector sweeps.

Devices, methods, and systems are described herein for the scheduling of an enhanced sector level sweep (SLS).

The full duplex radio may include an interference management unit <NUM> to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor <NUM>).

When using the <NUM> ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel.

11af and <NUM>. The channel operating bandwidths, and carriers, are reduced in <NUM> af and <NUM> ah relative to those used in <NUM>. 11n, and <NUM>.

The CN <NUM> shown in <FIG> may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b.

In view of <FIG>, and the corresponding description of <FIG>, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME <NUM>, SGW <NUM>, PGW <NUM>, gNB 180a-c, AMF 182a-ab, UPF 184a-b, SMF 183a-b, DN 185a-b, and/or any other device(s) described herein, may be performed by one or more emulation devices (not shown).

IEEE <NUM>1ad is an amendment to the WLAN standard, which specifies the MAC and PHY layers for very high throughput (VHT) in the <NUM> band. Operating over the unlicensed <NUM> frequency band, it allows devices to communicate without wires at multi-gigabit per second speeds. IEEE <NUM>1ad standard defines a channel access scheme that allows users for near real time data transmission (e.g., up to <NUM> Gbit/s). The <NUM>1ad supports data rates up to <NUM> Gbits/s, supports three different modulation modes, including Control PHY with single carrier and spread spectrum, Single Carrier PHY, and OFDM PHY, and uses the <NUM> unlicensed band, which is available globally. At <NUM>, the wavelength is <NUM>, which makes compact and antenna or antenna arrays possible. Such antennas may create narrow RF beams at both transmitter and receiver, which effectively increase the coverage range and reduce the interference.

IEEE <NUM>1ay aims to support a maximum throughput of at least <NUM> gigabits per second, while maintaining or improving the power efficiency per station. IEEE <NUM>1ay is expected to support multi-input multi-output (MIMO) transmissions like single user (SU) MIMO and multi user (MU) MIMO) and multi-channel transmission (including channel bonding and channel aggregation).

Features and elements described below are discussed based on IEEE <NUM>. 11ad and <NUM>. However, one of ordinary skill in the art will appreciate that the two standards are just examples and the features and elements are not limited to those two standards.

<FIG> is a signal diagram illustrating an exemplary IEEE <NUM>. 11ad/ay beacon interval (BI). In <FIG>, as defined in IEEE <NUM>. 11ad and IEEE <NUM>. 11ay ("<NUM>. 11ad/ay"), the beacon internal (BI) <NUM> may comprise a Beacon Header Interval (BHI) (<NUM> in <FIG>) and a Data Transmission Interval (DTI) <NUM>. The BHI may further comprise a Beacon Transmission Interval (BTI) <NUM>, an Association Beamforming Training (A-BFT) <NUM>, and an Announcement Transmission Interval (ATI) <NUM>.

The BTI <NUM> may comprise multiple beacon frames (<NUM>, <NUM> in <FIG> and <NUM> in <FIG>), each transmitted by the PCP/AP on a different sector of its antenna or antennas to cover all possible transmission directions. The BTI <NUM> may be used for network announcement and beamforming training of the PCP/AP's antenna sectors. Stations train their antenna sectors for communication with the PCP/AP during A-BFT <NUM>. The PCP/AP exchanges management information with associated and beam-trained stations during the ATI <NUM>.

In <FIG>, the DTI <NUM> includes one or more contention-based access periods (CBAPs) or scheduled service periods (SPs) where stations exchange data frames. In each CBAP, multiple stations may contend for the channel according to IEEE <NUM> enhanced distributed coordination function (EDCF). An SP may be assigned in a DTI for communication between a dedicated pair of nodes as a contention free period.

The frame structure of <NUM>. 11ad/ay facilitates a mechanism for beamforming training like discovery and tracking. The beamforming training protocol may include two components: a sector level sweep (SLS) procedure, and a beam refinement protocol (BRP) procedure. The SLS procedure may be used for transmit beamforming training and the BRP procedure may be used for receive beamforming training, and iterative refinement of both transmit and receive beams. Through the BRP procedure, the STA may improve its antenna configuration (e.g., antenna weight vectors) for transmission and/or reception. That is, the BRP procedure is a process in which a STA trains its RX and TX antenna array(s) and improves its TX antenna configuration and RX antenna configuration using an iterative procedure. The BRP may be used regardless of the antenna configuration a STA supports. In an example, packets assigned for the BRP (BRP packets) are used to train the receiver and transmitter antenna of the STA.

<FIG> is a signal diagram illustrating an exemplary sector level sweep (SLS) procedure. The station initiating the SLS <NUM> is referred to as the initiator <NUM> and the other station is referred to as the responder <NUM>. During an Initial Sector Sweep (ISS) <NUM>, the initiator <NUM> transmits one or more Sector Sweep (SSW) frames <NUM> to the responder <NUM>. During a Responder Sector Sweep (RSS), the responder <NUM> transmits its one or more SSW frames <NUM> to the initiator <NUM>. Afterwards, the initiator <NUM> sends a SS Feedback message <NUM> to the responder <NUM>, while the responder <NUM> transmits a SS Ack message <NUM> to the initiator <NUM>, in return.

During the SLS <NUM>, different combinations of initiator antenna sectors and responder antenna sectors are tested to find a satisfactory combination. The SLS training may be performed using a beacon frame or an SSW frame <NUM>. For example, SSW frames <NUM> are emitted sequentially by the different sectors of the initiator antenna.

When a beacon frame is used for the SLS training, the PCP/AP repeats the beacon frame over multiple beams/sectors within each Beacon Interval (BI) and multiple STAs may perform Beamforming (BF) training simultaneously. However, due to the size of the beacon frame, it may not be guaranteed that the PCP/AP may sweep all the sectors/beams within one Bl. Thus a STA may need to wait multiple Bls to complete Initial Sector Sweep (ISS) training, and thus latency may be an issue.

<FIG> is a block diagram illustrating an exemplary Sector Sweep (SSW) frame format by octet. The sector sweep (SSW) frame, as defined in <NUM>. 11ad standard, may comprise a Frame control field <NUM>, a Duration field <NUM>, a RA field <NUM>, a TA field <NUM>, a SSW field <NUM>, a SSW Feedback field <NUM>, and FCS field <NUM>.

The Frame control field <NUM> may contain protocol version, type, sub type, control frame extension, power management, data, WEP, and order. The Duration field <NUM> is set to the time until the end of the SSW frame transmission that has the CDOWN subfield within the SSW field <NUM> equal to <NUM> or until the end of the current allocation. The RA field <NUM> contains the MAC address of the STA that is the intended receiver of the sector sweep. The TA field <NUM> contains the MAC address of the transmitter STA of the sector sweep frame. The SSW frame <NUM> may be utilized for point-to-point BF training and may be transmitted using control PHY.

<FIG> is a block diagram illustrating an exemplary SSW field of the SSW frame by bits. It depicts the SSW field <NUM> of the SSW frame <NUM> in <FIG>, which is also defined in <NUM>. The SSW field <NUM> may comprise a Direction field <NUM>, a CDOWN field, <NUM>, a Sector ID field <NUM>, a DMG Antenna ID field <NUM>, and a RXSS Length field <NUM>.

The Direction field <NUM> may be set to <NUM> to indicate that the frame is transmitted by the beamforming initiator and set to <NUM> to indicate that the frame is transmitted by the beamforming responder. The CDOWN field <NUM> may be a down-counter indicating the number of remaining DMG Beacon frame transmissions to the end of the TXSS, or the number of remaining SSW frame transmissions to the end of the TXSS/RXSS. This field may be set to <NUM> in the last frame DMG Beacon and SSW frame transmission. The Sector ID field <NUM> may be set to indicate the sector number through which the frame containing this SSW field is transmitted. The DMG Antenna ID field <NUM> indicates the DMG antenna the transmitter may be currently using for this transmission. The RXSS Length field <NUM> is valid only when transmitted in a CBAP and is reserved otherwise.

<FIG> are block diagrams illustrating the SSW Feedback field <NUM> of the SSW frame <NUM> in <FIG>. <FIG> depicts the format of the SSW Feedback field <NUM> that is transmitted as part of an ISS, which may comprise any one or the combination of the following subfields; a Total Sectors in ISS <NUM>, a Number of RX DMG Antennas <NUM>, a Poll Required <NUM>, and Reserved fields <NUM>, <NUM>. Meanwhile, <FIG> depicts another format of the SSW Feedback field <NUM> when it is not transmitted as part of an ISS, which may contain some different subfields; a Sector Select <NUM>, a DMG Antenna Select <NUM>, a SNR Report <NUM>, a Poll Required <NUM>, and a Reserved field <NUM>.

The Total Sectors in ISS subfield <NUM> in <FIG> indicates the total number of sectors that the initiator uses in the ISS, including any repetition performed as part of multi-antenna beamforming. The Number of RX DMG Antennas subfield <NUM> indicates the number of receive DMG antennas the initiator uses during the following RSS.

The Sector Select subfield <NUM> in <FIG> contains the value of the Sector ID subfield of the SSW field within the frame that was received with best quality in the immediately preceding sector sweep. The DMG Antenna Select subfield <NUM> indicates the value of the DMG Antenna ID subfield of the SSW field within the frame that was received with best quality in the immediately preceding sector sweep. The SNR Report subfield is set to the value of the SNR from the frame that was received with best quality during the immediately preceding sector sweep, and which is indicated in the sector select subfield.

The Poll Required subfield <NUM> is set to <NUM> by a non-PCP/non-AP STA to indicate that it requires the PCP/AP to initiate communication with the non-PCP/non-AP.

In an example of the Beam Refinement Protocol (BRP), there may be two types of BRP packets: BRP-RX packets and BRP-TX packets. <FIG> illustrates an example of a Protocol Data Unit (PPDU), such as a Directional Multi-Gigabit (DMG) Physical Layer Convergence Procedure (PLCP) Protocol Data Unit (PPDU), which may comprise a PLCP Header (Packet Type Training Length Fields N) <NUM>, a BRP packet <NUM>, a training field containing an Automatic Gain Control (AGC) field <NUM> and a transmitter or receiver training field <NUM>.

A value of N in <FIG> is the Training Length given in the header field, which indicates that the AGC <NUM> has 4N subfields and that the receive and/or transmit training (TRN-RX or alternatively TRN-R) field <NUM> has 5N subfields.

The BRP MAC frame <NUM> in <FIG> is an Action No ACK frame, which may include the following fields: Category; Unprotected DMG Action; Dialog Token; BRP Request field; DMG Beam Refinement element; and fields for Channel Measurement Feedback element <NUM> through Channel Measurement Feedback element k.

A TRN-RX field <NUM> may be appended to the DMG beacon frame, which allows enhanced directional multi-gigabit (EDMG) STAs to perform RX training using beacon frames.

<FIG> is a block diagram illustrating signaling for coexistence with legacy devices. In <FIG>, the Beamforming Training Allocation (BTA) <NUM> is a part of the Data Transmission Interval (DTI) <NUM>. The BTA <NUM> may be scheduled using one or more Enhanced Directional Multi-Gigabit (EDMG) Extended Schedule Element(s), which may define the channel scheduling for an EDMG BSS. The EDMG Extended Schedule Element <NUM> may be a part of the DMG beacon frame <NUM>, as illustrated in <FIG>.

An EDMG Extended Schedule Element may include an indication of which channels an allocation is scheduled on. The format of the EDMG Extended Schedule Element may include one or more of the following fields: an Element ID, a Length, an Element ID Extension, an EDMG Allocation Control, Number of Allocations, Channel Allocations <NUM> - N, and reserved fields. As defined in the IEEE standards, the contents of the Element ID identify each <NUM> element. The Length field specifies the number of octets following the Length field. The EDMG Allocation Control comprises a Distributed Scheduling Enabled subfield, which is set to one to indicate that the distributed scheduling mechanism. The Number of Allocations field indicates the number, N, of Channel Allocation fields following it. Each Channel Allocation field may start with a Scheduling Type subfield, which defines the format of the remaining of the Channel Allocation field. The Channel Allocation field may also include the Asymmetric Beamforming Training subfield, which is set to <NUM> to indicate that this EDMG Extended Schedule Element schedules and allocates a Beamforming Training Allocation (BTA) in a Data Transfer Interval (DTI). The reserved fields included in the EDMG Extended Schedule Element may be used for new purposes.

In <FIG>, during the BTI <NUM>, the Initiator-AP <NUM> transmits DMG beacon frames <NUM>, <NUM>, <NUM> to the Responders <NUM>, <NUM>, <NUM>, <NUM>. During the A-BFT <NUM>, the Responders are training their antenna sectors for communication with the Initiator-AP <NUM>.

In this allocation, a PCP/AP may repeat the Sector Sweep in the same order as in the BTI while in the RX mode. For example, the BTA <NUM> allocated in the DTI <NUM> may have multiple space time slots <NUM>. The receive sector for the first set of space time slots may be the same as the transmit sector used to transmit the first DMG Beacon frame. The receive sector for the second set of space time slots may be same as transmit sector used to transmit the second DMG Beacon frame.

The STAs may respond in the sector which corresponds to best sector found in transmit sector sweep (TXSS) during the BTI. For example, STA X <NUM> may find the second sector <NUM> from the AP <NUM>, which results the best receive performance in BTI <NUM>. It may respond in one or more slots <NUM> in the second space time slot set on which the Initiator-AP <NUM> may use the second sector <NUM> to receive. The Responder-EDMG STA Y <NUM> may find the last sector <NUM> from the AP <NUM>, which results the best receive performance in BTI <NUM>. It may respond in one or more slots <NUM> in the last space time slot set on which the Initiator-AP <NUM> may use the last sector to receive.

A Sector ACK frame <NUM> may be transmitted from the PCP/AP in each sector. The elements <NUM>, <NUM>, and <NUM> may indicate that A-BFT slots <NUM>, which the Initiator-AP <NUM> may receive, use quasi-Omni mode. The Responder EDMG-STAs <NUM>, <NUM>, <NUM>, <NUM> may randomly select one to transmit.

The Space Time Slots <NUM> may be slots allocated for STAs <NUM>, <NUM>, <NUM> to transmit frames back to the Initiator-AP <NUM>. For each slot, the Initiator-AP <NUM> may have a receive sector dedicated to each of the STAs <NUM>, <NUM>, <NUM>.

The time slots <NUM>, <NUM>, and <NUM> may indicate that the Responder-STAs may try to perform TXSS trainings using legacy A-BFT <NUM>. The R-TXSS <NUM> may indicate that the Responder-DMG STA L performs transmit sector sweep when the Initiator-AP <NUM> receive beams in the quasi-Omni mode. The slots <NUM> and <NUM> show that STAs, which may be associated with the same AP sector, may transmit in the same set of space time slots. The STAs may randomly choose one or more slots in the set to transmit. The slots <NUM>, <NUM>, <NUM>, and <NUM> may indicate that STAs may use the space time slot to transmit frames back to the AP. The transmission from STAs may or may not collide. The slots <NUM>, <NUM> and <NUM> may indicate that STAs, which may transmit in the BTA, expect to receive sector ACKs <NUM> from the PCP/AP.

The BTA <NUM> may include two sub-phases; in a responding sub-phase, STAs may transmit responding frames to the PCP/AP and, in an acknowledgement sub-phase, the PCP/AP may transmit acknowledgement to the STAs. The PCP/AP's receive sector is specified in the DTI <NUM>, and the PCP/AP will use this receive sector to listen during the allocation.

The PCP/AP may fragment the initiator TXSS over multiple consecutive BTIs by not transmitting a beacon frame through all sectors available to the PCP/AP in a BTI. For example, the PCP/AP may transmit a beacon frame over a subset of all sectors available to the PCP/AP in a BTI. The PCP/AP may transmit another beacon frame over another subset of all sectors available to the PCP/AP in a different BTI, and so forth. For example, this fragmentation may spread over a greater number of BTIs if multiple antennas and/or multiple channels are available and used for transmission and accordingly more TX sectors are available at the PCP/AP. By transmitting a beacon frame over only a subset of all sectors available to the PCP/AP, a STA may identify (and may select) a TX sector which has acceptable performance (e.g., a beacon frame received over that sector is detected and successfully decoded) in a single BTI. The TX sector identified by the STA may not, however, have the best performance of all sectors available to the PCP/AP. Alternately, the STA may wait until the end of total TXSS (possibly over several BTIs) to find the best TX sector.

IEEE <NUM>. 11ay adopts an enhanced SLS procedure that allows EDMG STAs to perform receiving (RX) training using beacon frames in the BTI. In the enhanced SLS procedure, the BTA may be scheduled using an EDMG Extended Schedule Element, which may be carried in DMG beacon frames transmitted in a Bl. In order to receive an EDMG Extended Schedule element, the non-PCP/AP STA may need to receive at least one directional beacon frame in a current Bl.

If a feedback of the optimal TX sector (i.e., the best TX sector of all sectors available to the PCP/AP) may be preferred, it may be desirable for the non-PCP/AP STA to send feedback information in the BI where the last TXSS fragment was transmitted. However, the optimal TX sector may not have been covered by the TX sectors swept in the last Bl. Thus, the non-PCP/AP STA may not notice the EDMG Extended Schedule Element carried in the last BI and it may not be able to learn the BTA.

<FIG> is a signal diagram illustrating an example of a fragmented TXSS <NUM>. For example, in <FIG>, the PCP/AP may have a total of <NUM> available TX sectors. In each BI, the TX may sweep <NUM> sectors. Accordingly, <NUM> Bls <NUM>, <NUM>, and <NUM> are needed to complete the TXSS training for all <NUM> available TX sectors. For example, a STA may receive a beacon frame <NUM> transmitted on a sector during the second BI <NUM> with a receive quality above a pre-defined/pre-determined threshold. It may be desired, however, for the receiving STA to find the best sector among the <NUM> available TX sectors. Thus, the receiving STA may wait for the end of entire TXSS (i.e., <NUM> Bls). If the STA does not find a better sector during the third BI <NUM> (i.e., does not receive a beacon frame with a receive quality above the pre-defined/pre-determined threshold), the STA will have missed the chance to use the BTA scheduled in the second BI <NUM>.

For example, a STA may determine that one of the TX sectors detected during the BTI <NUM> has a receive quality above a pre-defined/pre-determined threshold. But, the STA may not know whether that sector is the best one until the PCP/AP sweeps all the sectors. Thus, the STA may not use the allocated Beamforming Training Allocation (BTA) <NUM> in this BI <NUM>. During the BI <NUM>, the PCP/AP may finish the TX sweeping, but the STA may not receive anything during this interval, thus it may not use the allocated BTA <NUM>. The arrows <NUM>, <NUM>, and <NUM> may indicate that the TX sectors detected during the BTls <NUM>, <NUM>, <NUM> may be used for beamforming trainings during the corresponding training periods, BTAs <NUM>, <NUM>, <NUM>. Accordingly, it may be desired to adopt a more flexible procedure to schedule enhanced SLS allocations.

One approach to enhanced SLS may have the following steps. First, a PCP/AP's TX beams/sectors and receiver's RX beams/sectors may be trained using a unified frame like the DMG beacon frame. Then, STAs may communicate with a PCP/AP during a Beamforming Training Allocation (BTA), which may be allocated by the DMG beacon frame. This may facilitate improved communications since the PCP/AP may sweep the receive beams/sectors during the BTA and receive communications signals directionally.

A PCP/AP may fragment the initiator TXSS over multiple BTIs <NUM>, <NUM>, <NUM>. In other words, in each BTI, a subset of the TX sectors available to the PCP/AP may be used to carry beacon frames. This may be used to facilitate a sub-optimal TXSS training.

For example, the sub-optimal TXSS training field may be set to allow the sub-optimal TXSS or immediate feedback. In the sub-optimal TXSS training, a non-PCP/AP STA may identify (and may select) one of the TX sectors in BTI <NUM>, which has acceptable performance (e.g., the beacon frame received over that sector is detected and successfully decoded, or the beacon frame is successfully detected with a signal to noise ratio (SNR) above a desired threshold) in a single BTI <NUM>. The identified TX sector may not, however, have the best performance of all sectors available to the PCP/AP.

In an EDMG Extended Schedule Element, a field may be set to indicate that sub-optimal TXSS or immediate feedback is allowed. For example, at least one field of the Extended Schedule Element such as Channel Allocations fields or reserved fields may indicate that the sub-optimal TXSS or the immediate feedback is set or allowed.

If the non-PCP/AP STA detects the beacon frame carrying an EDMG Extended Schedule Element and found that the EDMG Extended Schedule Element indicates that sub-optimal TXSS or immediate feedback is allowed, it may prepare a transmission for the scheduled BTA. Instead of waiting for the end of the entire TXSS sweeping, the non-PCP/AP may then use the assigned BTA to feedback and communicate with the PCP/AP.

<FIG> is a flow chart illustrating an example non-PCP/AP STA procedure for TXSS training. In a first step <NUM>, a non-PCP/AP STA monitors beacon frames which are part of a fragmented TXSS, e.g., beacon frames having a fragmented TXSS field set to <NUM>.

In some cases, the non-PCP/AP STA may continue detecting beacon frames until it successfully detects at least one beacon frame within a BI, which has a signal quality above a pre-defined or pre-determined threshold. (step <NUM>). In the following step, it determines whether the sub-optimal field is set. (step <NUM>). If so, the non-PCP/AP STA use the BTA to communicate with the PCP/AP. (step <NUM>). When the sub-optimal TXSS training is done for all the sectors (step <NUM>), the non-PCP/AP STA procedure will be finished.

The received signal quality being measured may include signal-to-noise ratio (SNR), signal-to-interference-and-noise ratio (SINR), received signal strength indication (RSSI) or any other suitable type of signal quality measurement. In some cases, the threshold may be signaled explicitly to the non-PCP/AP STA in the beacon frame. In other cases, the received signal quality may be measured if the STA uses an omni-directional (or pseudo omnidirectional) beam to receive. In yet another case, the received signal quality may be measured if the STA sweeps its receive beams and records the measurements from best received beam or beams.

In some cases, the non-PCP/AP STA may detect one beacon frame meeting the signal quality threshold requirement, but instead of stopping its attempts to detect further beacon frames, it may continue monitoring for the period covered by the duration field in that beacon frame. In other words, the non-PCP/AP STA may monitor the transmission medium until the end of the Beacon Transmission Interval. The non-PCP/AP STA may determine one beacon frame transmitted to the non-PCP/AP STA by the PCP/AP STA on one TX sector with the best received signal quality, above the threshold, among all the beacon frames transmitted to the non-PCP/AP STA by the PCP/AP STA during the Bl.

The non-PCP/AP STA may use the appended TRN-RX field to train its received beams. The non-PCP/AP STA may detect an EDMG Extended Schedule Element in the beacon frame, which may allocate a BTA in the following DTI within the same Bl. A sub-optimal or immediate feedback field may be contained in the EDMG Extended Schedule Element, or other elements or fields in the beacon frame. For example, <FIG> illustrates examples of the beacon frame <NUM>, an EDMG Extended Schedule Element <NUM>, a sub-optimal field <NUM>, and an immediate feedback field <NUM>. In some cases, only STAs receiving at least one beacon frame in the BI are allowed to transmit in the BTA. In this allocation (i.e., during the allocated BTA), the PCP/AP STA may repeat a fragmented sector sweep in the same order as in the BTI in the same BI, but in the RX mode. The number of sectors swept and order of the sectors may be implicit, unless otherwise signaled explicitly in an EDMG Extended Schedule Element.

For example, if the sub-optimal field or immediate feedback field is set in an EDMG Extended Schedule Element, the STA may communicate with the PCP/AP during the BTA. Even if sub-optimal training or immediate feedback is indicated in other ways, the STA may communicate with the PCP/AP, too. For example, a sub-optimal or immediate feedback indication may be carried in the response frame transmitted from the STA to the AP to indicate that the TX sector selected by the STA may not be optimal. Further, the non-PCP/AP STA may report received channel quality corresponding to the TX sector to the PCP/AP during the BTA.

The non-PCP/AP STA may continue monitoring the remaining beacon frames in the following Bls until a countdown (CDOWN) reaches <NUM>. In this case, the CDOWN tracks the number of remaining beacon frames in the TXSS. For example, if a PCP/AP STA has <NUM> transmit sectors, it may sweep <NUM> sectors with the beacon frame during the first Bl. After the first beacon frame is transmitted, CDOWN will be <NUM> when the initial value of the CDOWN is <NUM>. In other words, the non-PCP/AP STA may monitor all the fragmented TXSS beacon frames carried in consecutive Bls and may discover a better sector (e.g., a sector in which a Beacon is received with a higher receive quality, lower SNR, etc.) in a later Bl. The non-PCP/AP STA may use the corresponding BTA in the same BI to communicate with the PCP/AP STA using the updated TX sector. A sub-optimal indication may be set in a response frame from the non-PCP/AP STA to the PCP/AP STA to indicate the updated TX sector is a sub-optimal sector if more Bls need to be monitored. Otherwise, the sub-optimal indication may be set (or may be not set) to indicate an optimal TX sector. Further, the received channel quality corresponding to the TX sector may be reported to the PCP/AP STA in the response frame from the non-PCP/AP STA to the PCP/AP STA.

The non-PCP/AP STA may not transmit any BTA if the fragmented TXSS is not completed. In other words, the STA may complete the TXSS and find an optimal sector and store a record of the optimal sector. The non-PCP/AP STA may communicate the optimal sector to the PCP/AP STA at a later opportunity (e.g., in a BTA or an A-BFT, or other type of allocation).

If the sub-optimal field is not set (or is set to indicate non-sub-optimal training), the non-PCP/AP STA may continue monitoring the following beacon frames until the CDOWN reaches <NUM>. In some cases, the non-PCP/AP STA may learn the number of Bls required for the PCP/AP to complete the TXSS training by checking the TXSS Span field. The non-PCP/AP STA may thus monitor all the beacon frames in the indicated Bls. The non-PCP/AP STA may discover an optimal TX sector from the PCP/AP STA.

The non-PCP/AP STA may transmit one or more SSW frames in the first BTA or A-BFT it detects after the completion of the fragmented TXSS. Otherwise, if no BTA allocated in the Bl, the non-PCP/AP STA may wait for next BTA, or may use a legacy A-BFT to feedback a sub-optimal TX sector and train its transmit sectors.

In some cases, other non-PCP/AP STA procedures may be used. For example, sub-optimal field set <NUM> in <FIG> may be replaced with a scheduled block.

<FIG> is a signal diagram illustrating an exemplary flexible scheduling procedure for scheduling a Beamforming Training Allocation (BTA) <NUM> in a later BI <NUM> by introducing a Next Allocation field <NUM> or a Periodic Allocation field <NUM>, to an EDMG Extended Schedule Element <NUM> included in a beacon frame <NUM>.

The Next Allocation field <NUM> or the Periodic Allocation field <NUM> may be included in the EDMG Extended Schedule Element <NUM>. If a BTA is allocated in a later BI <NUM>, the reception beams/sectors may not be exactly the same as that used in the same BTI. Thus, reception beams/sectors may need to be explicitly or implicitly signaled or pre-defined.

As shown in <FIG>, the scheduling procedure may include a first BI <NUM> and a later BI <NUM>. The first BI <NUM> may include any one or a combination of the following fields: a BTI field <NUM>, an A-BFT field <NUM>, an ATI field <NUM>, and a DTI field <NUM>. The later BTI <NUM> may include any one or a combination of the following fields: a BTI field <NUM>, an A-BFT field <NUM>, an ATI field <NUM>, a BTA field <NUM>, and DTI field <NUM>.

As described earlier, the BTI <NUM> may comprise multiple beacon frames <NUM>, each transmitted by the PCP/AP on a different sector of its antenna or antennas to cover all possible transmission directions. The BTI <NUM> may be used for network announcement and beamforming training of the PCP/AP's antenna sectors. Stations train their antenna sectors for communication with the PCP/AP during A-BFT <NUM>. The PCP/AP exchanges management information with associated and beam-trained stations during the ATI <NUM>.

The Next Allocation field <NUM> or the Periodic Allocation field <NUM> may be changed or deleted before the allocation. However, if the allocation is scheduled for multiple STAs for uplink transmission, the modification of the allocation may need to be transmitted over multiple beams to reach multiple STAs.

Any one or a combination of the following rules may be applied in order to allow the PCP/AP STA to schedule an allocation, including a BTA, in a later Bl. The Next Allocation field <NUM> or the Periodic Allocation field <NUM> may be used to allocate SP(s)/CBAP(s)/BTA(s) in a future Bl. The Next Allocation field <NUM> or the Periodic Allocation field <NUM> may be signaled in an EDMG Extended Schedule Element <NUM> or in a legacy Extended Schedule Element. If The Next Allocation field <NUM> or the Periodic Allocation field <NUM> is allocating a BTA, it may be signaled using an EDMG Extended Schedule Element <NUM>.

The Next Allocation field <NUM> may be signaled as an offset from the current BI in units of Bl. For example, the Next Allocation = <NUM> may indicate that the allocation is scheduled during the current BI, while the Next Allocation = <NUM> may indicate that the allocation is scheduled for the following Bl. The Next Allocation field <NUM> may be used to signal up to a dot11MaxNextBeacons BI following the last received EDMG Extended Schedule Element containing next allocation. An EDMG Extended Schedule Element carried in a BI may schedule a transmission in one or more of the following Bls. The dot11MaxNextBeacons is the maximum number of beacon intervals allowed for An EDMG Extended Schedule Element to schedule a transmission over subsequent Bls. For example, if, an EDMG Extended Schedule Element in nth beacon interval may carry scheduling information for n+kth beacon intervals. Then, k may be less than or equal to dot11MaxNextBeacons. The dot11MaxNextBeacons may be a number pre-defined or pre-determined to indicate the maximum number the Next Allocation field may use.

An allocation Start field may be signaled in an EDMG Extended Schedule Element or legacy Extended Schedule Element. With the Next Allocation field greater than <NUM>, the Allocation Start field may indicate the time offset relative to the TBTT in that Bl.

The PCP/AP STA may change the Next Allocation field by transmitting an additional EDMG Extended Schedule Element before the Next Allocation field. If the Next Allocation field is a CBAP, or if the Source AID is a broadcast/multicast AID, an EDMG Extended Schedule Element, which may change the Next Allocation field, may be repeated and transmitted by sweeping multiple beams/sectors. The PCP/AP STA may delete the Next Allocation field by transmitting an additional EDMG Extended Schedule Element before the Next Allocation field. If the Next Allocation field is a CBAP, or if the Source AID is a broadcast/multicast AID, an EDMG Extended Schedule Element, which may delete the Next Allocation field, may be repeated and transmitted by sweeping multiple beams/sectors.

<FIG> is a flow chart illustrating an example non-PCP/AP STA procedure for beamforming training where the PCP/AP STA performs optimal TXSS by scheduling a BTA in a later Bl.

In a first step, a non-PCP/AP STA monitors beacon frames which are part of a fragmented TXSS (e.g., beacon frames having a fragmented TXSS field set to <NUM>) (step <NUM>). Thereafter, the non-PCP/AP STA may successfully detect at least one of the beacon frames within a BI (step <NUM>). The non-PCP/AP STA may then detect an EDMG Extended Schedule Element in the beacon frames, which may allocate a BTA in a future BI (step <NUM>).

Next, a determination is made regarding whether the detected EDMG Extended Schedule Element includes an updated BTA allocation (step <NUM>). If an updated BTA allocation is not found, the non-PCP/AP STA may record the receive signal quality of the beacon frame (step <NUM>). The non-PCP/AP STA may use the appended TRN-RX field to train its received beams. A TRN-RX field may be appended to a beacon frame, which allows enhanced directional multi-gigabit (EDMG) STAs to perform RX training using beacon frames. The non-PCP/AP STA may measure the received signal quality of the beacon frame when the non-PCP/AP STA uses directional beam to receive the beacon frame. The non-PCP/AP STA may continue monitoring the beacon frames and searching for best one or more TX sectors/beams (step <NUM>).

If the updated BTA allocation is found, the non-PCP/AP STA may receive an EDMG Extended Schedule Element with an updated or modified BTA allocation and the updated or modified allocation may overwrite the old allocation (step <NUM>). Then, the non-PCP/AP STA may record the receive signal quality of the beacon frame (step <NUM>) and the non-PCP/AP STA may continue monitoring the beacon frames and searching for best TX one or more sectors/beams (step <NUM>).

The non-PCP/AP STA may prepare a transmission on the allocated BTA. The non-PCP/AP STA may obtain the receive beam/sector order of the PCP/AP, implicitly or explicitly, from an EDMG Extended Schedule Element. The non-PCP/AP STA may transmit in a time slot where the receive beam from the PCP/AP STA is associated with the best transmit beam from the PCP/AP STA identified by the non-PCP/AP STA using the beacon frames.

The PCP/AP STA receives beam allocation in a future BTA, which may be implicit and may be in the same order of fragmented TXSS in consecutive Bls. The PCP/AP receives beam allocation in a future BTA, which may be explicitly signaled in legacy Extended Schedule Element or EDMG Extended Schedule Element.

In a flexible scheduling procedure, a BTA may be allocated in a future BI and sub-optimal TXSS may be allowed. The non-PCP/AP STA procedure may be changed from the flexible scheduling procedure described with respect to <FIG>. However, the rules and beam/sector allocation, which PCP/AP STA receives, described with respect to that procedure may be the same.

The following describes an example of a flexible non-PCP/AP STA scheduling procedure with sub-optimal TXSS. A non-PCP/AP STA monitors the beacon frames, which is part of the fragmented TXSS, i.e., has the Fragmented TXSS field set to <NUM>.

The non-PCP/AP STA may successfully detect at least one beacon frame within a Bl. The non-PCP/AP STA may further detect an EDMG Extended Schedule Element in the Beacon Frame, and the received signal quality may be over a pre-defined or pre-determined threshold. The EDMG Extended Schedule Element may allocate a BTA in a future BI, and may set a sub-optimal field in EDMG Extended Schedule Element or other element/field carried by the beacon frame to indicate that sub-optimal TXSS training is allowed.

The non-PCP/AP STA may record the received signal quality of the beacon frame. The non-PCP/AP STA may use the appended TRN-R (alternatively, TRN-RX) field to train its receive beams. The received signal quality may be measured when the non-PCP/AP STA may use directional beam to receive.

The non-PCP/AP STA may enter a sleep, doze, or power saving mode if the non-PCP/AP STA has not yet associated with a PCP/AP STA and the non-PCP/AP STA needs to wait for BTA to associate with the PCP/AP STA. The non-PCP/AP STA may also enter a sleep, doze, or power saving mode if the current beams trained for the non-PCP/AP STA do not work and the non-PCP/AP STA needs to wait for BTA to complete the beam training. The non-PCP/AP STA may further enter a sleep, doze, or power saving mode if the non-PCP/AP STA does not have traffic to send to the AP and/or the non-PCP/AP STA does not have buffered traffic from AP.

The non-PCP/AP STA may wake up before the BTA and prepare transmission in the allocated BTA. The non-PCP/AP STA may know the receive beam/sector order of the PCP/AP STA implicitly or explicitly from an EDMG Extended Schedule Element. The non-PCP/AP STA may transmit in a time slot where the receive beam from PCP/AP STA may be associated with the best transmit beam from the PCP/AP STA identified by the non-PCP/AP STA using the beacon frames.

<FIG> illustrates an exemplary flow chart of sector ranking procedure, which may be used for a non-PCP/AP STA to provide feedback in fragmented TXSS. A non-PCP/AP STA may monitor beacon frames (step <NUM>). A non-PCP/AP STA may monitor the wireless medium continuously for beacon frames transmitted from a PCP/AP STA. For example, a non-PCP/AP STA, which is already associated with a PCP/AP STA, may monitor the wireless medium for beacon frames at the beginning of a BI, when the BI contains a beacon transmission period (interval) or A-BFT period. A STA may also begin to monitor the wireless medium for beacon frames at the start of a BTI if it has received one or more beacons previously from a PCP/AP STA, which indicate that the beacon frame is a part of a fragmented TXSS, (e.g., the beacon frame has a Fragmented TXSS field set to <NUM>) and the start of the following BI may be derived from that beacon.

If the non-PCP/AP receives one or more beacons during the BTI (step <NUM>), the non-PCP/AP may compile a list of sectors in which it has received a beacon from the PCP/AP (step <NUM>). A WTRU or a STA may rank the sectors in the list based on their measured characteristics like RSSI, SNR, SINR or others. If the received beacon is a part of a fragmented TXSS, (e.g., as indicated by its Fragmented TXSS field), the STA may compile the one or more sectors in which the STA has received beacon in addition to the list of sectors in which it has received beacons in the same fragmented TXSS. The list of sectors may be ranked by RSSI, SNR, SINR or other measurements (step <NUM>). Alternatively or additionally, the list of ranked sectors may only contain one or more best sectors in terms of the measurements. Then, the non-PCP/AP STA may transmit the list to the PCP/AP STA (step <NUM>). The process may then either continue monitoring beacon frames (step <NUM>) or end (step <NUM>).

The non-PCP/AP STA may conduct receive-beam training using the TRN-R fields attached to a beacon which it has received. The non-PCP/AP STA may record the appropriate receive one or more beams/sectors to use when communicating with the PCP/AP using the sector in which it received a beacon from the PCP/AP STA. The non-PCP/AP STA may include the receive sector(s) in the ranked list of the PCP/AP sector in which it has received a beacon.

If non-PCP/AP STA has already associated with a PCP/AP STA, and if it has detected, after the BTI, that its sector has changed (e.g., one of the one or more sectors in its list of sectors in which it has not received a beacon), it may remove the obsolete sector from its ranked list. It may also include an indication in its ranked list of sectors that changes has been made compared to previous version of the ranked list of sectors. If the ranking of sectors has changed, the change may also be indicated in the ranked list. Alternatively or additionally, the list may include change indications (e.g., "sector entry changed", "sector entry added", "sector entry removed", "sector ranking changed" etc., or entries to that effect).

The non-PCP/AP STA may provide the list of ranked sectors to the PCP/AP STA in a modified SSW frame, short SSW frame, (short) SSW Feedback frame, (short) SSW ACK frame, or any other suitable type of frame by transmitting one or more such frames using one or more sectors in the top of the list. Such a list of ranked sectors may also include a power measurement, such as RSSI, indicating at which level the beacon was received. The ranked sectors may also include the receive/transmit sectors which the non-PCP/AP STA may use, or should preferable use, when transmitting to or receiving from the PCP/AP STA when the PCP/AP STA uses one of the ranked sectors. In some cases, the list of ranked sectors may only contain one or more best sectors in terms of some criteria, such as the best one or more sectors in terms of a desired criterion such as RSSI. To make the received power measurements comparable, the transmit power of the beacon frames through multiple directions using fragmented TXSS may be the same. Or, the transmit power or power adjustment for beacon frames may be explicitly signaled.

Such feedback list of ranked sectors may be provided during the A-BFT period, or alternatively be provided in BTA periods, as announced by the received beacon frame or announcement frame (or any other suitable type of frames) during the DTI period.

A PCP/AP STA may provide multi-channel Sector level Sweep (SLS) using its beacons or SSW frames. The following describes an example of multi-channel SLS procedure using beacons. A PCP/AP STA may indicate that a BTI is a multi-channel BTI or multi-channel SLS, either in a previous beacon or beacons, or by an announcement frame, a frame containing extended schedule element, or any other type of frames. Due to channel bonding capabilities, the targeted non-PCP/AP STAs for multi-channel SLS may be or include EDMG STAs. Without loss of generality, a multi-channel BTI or multi-channel SLS may be referred to as a multi-channel beamforming training period (MCBFT).

A PCP/AP STA may transmit beacons or SSW frames concurrently during the MCBFT on all or the subset of available channels, in the BTI or DTI period. The beacons and/or SSW frames may overlap completely in time. Prior to the MCBFT, the PCP/AP STA may transmit clear-to-send (CTS)-to-self, or other types of frames providing NAV protections for the multi-channel training. The beacon frames or SSW frames may be sent sequentially in one or more sectors on each of the channels. These multi-channel beacon frames or SSW frames may contain an indication of the primary channel of the PCP/AP STA. The beacon frames or SSW frames may contain an extended schedule element, by which STAs may report the results of their multi-channel feedback. The extended schedule element may include the channel (such as the primary channel), time slots (such as SSW slot in A-BFT, or BTA or SP in DTI). Alternatively or additionally, frames like announcement frames, sent by the PCP/AP STA during the ATI, may contain extended schedule element which may indicate the channel/schedule at which the non-PCP/AP STA should report the results of the multi-channel SLS feedback. For example, the extended schedule element may schedule the feedback of STAs on a particular channel in a particular BTA, e.g., there will be a primary channel BTA, Channel <NUM> BTA, channel <NUM> BTA, etc. Such specific channel BTAs may be scheduled for the A-BFT, BTA and/or DTI periods, and may be scheduled solely on the primary channel, and/or on the specified channels.

Multiple TRN-R fields may be appended to the beacon frames or SSW frames. These TRN-R fields may provide receive beamforming training for STAs that have received the beacons or SSW frames in a particular sector on a particular channel. For example, the initiator may repeat the TRN-R fields, while the responder sweeps its receive beam to be trained.

A non-PCP/AP STA that has not associated with a PCP/AP STA, may use the primary channel indication and the scheduling indicated in the beacon frame/SSW frames to provide its feedback to the PCP/AP. Alternatively, the non-PCP/AP STA may provide feedback for the SLS on the particular channel on which it has received the beacon/SSW. The non-PCP/AP STA may thereafter conduct association on that particular channel. Alternatively, the non-PCP/AP STA may be allocated a SP or CBP during which the non-PCP/AP STA, may conduct SLS on the primary channel with the PCP/AP STA. The non-PCP/AP STA may thereafter conduct association with the PCP/AP STA on the primary channel. If more than one channel has been trained during the multi-channel SLS, the non-PCP/AP may provide a list of one or more such sectors for each of the channels. Such a list of sectors for a particular channel may be ranked by some criteria, such as RSSI. In addition, the list of preferred sectors may be ranked across all channels by some criteria, such as RSSI.

A non-PCP/AP STA that has already been associated with the PCP/AP may use the following multi-channel SLS procedure. The non-PCP/AP may have already associated and conducted SLS with a PCP/AP on the primary channel of the PCP/AP. The PCP/AP STA may schedule one or more associated non-PCP/AP STAs for multi-channel SLS. The scheduled multi-channel SLS may be using beacons or SSW frames or other types of frames, e.g., in the BTI, A-BFT or DTI periods. Such multi-channel SLS may be scheduled using an extended schedule element in a beacon or announcement frame or any other type of frames.

A PCP/AP STA may transmit beacons or SSW frames concurrently during the MCBFT on all or the subset of available channels, in the BTI or DTI period. Prior to the MCBFT, the PCP/AP may transmit CTS-to-self or other type of frames providing NAV protections for the multi-channel training.

For example, the SLS for a particular channel may be scheduled at a particular SP/CBP/BTI. The beacon frames or SSW frames may be sent sequentially in one or more sectors on each of the channels. The beacon frames or SSW frames may contain an extended schedule element for non-PCP/AP STAs to report the results of their multi-channel feedback. Such an extended scheduling element may include the channel, such as the primary channel, time slots, such as SSW slot in A-BFT, or BTA or SP in DTI. Alternatively or additionally, frames like announcement frame, sent by the PCP/AP in the ATI, may include an extended schedule element which may indicate the channel/schedule at which the non-PCP/AP STA should report the results of the multi-channel SLS feedback. For example, the scheduling may schedule the feedback of STAs on a particular channel in a particular BTA, e.g., there will be a primary channel BTA, Channel <NUM> BTA, channel <NUM> BTA, etc. Such specific channel BTA may be scheduled for the A-BFT, BTA and/or DTI periods, and they may be scheduled solely on the primary channel, and/or on the specific channels.

Multiple TRN-R fields may be appended to the beacon frames or SSW frames. These TRN-R fields may provide receive beamforming training for STAs that have received the beacons or SSW frames in a particular sector on a particular channel. If more than one channel has been training during the multi-channel SLS, the non-PCP/AP STA may provide a list of one or more sectors for each of the channels. Such a list of sectors for a particular channel may be ranked by some criteria, such as RSSI. In addition, the list of preferred sectors may be ranked across all channels by some criteria, such as RSSI.

As shown in FIG. 9A, legacy users <NUM>, which may not be able to transmit in the BTA, may use A-BFT <NUM> for feedback and train their antenna sectors. STAs <NUM>, <NUM>, <NUM>, however, may be able to feedback using both A-BFT <NUM> and BTA <NUM>. Mechanisms and signaling may be needed to provide some level of fairness between legacy devices and enhanced devices. Example approaches include allowing an enhanced STA to use BTA only, enabling an enhanced STA to decide whether to use BTA and/or A-BFT, or the choice of whether to use BTA or A-BFT may be determined and configured by the PCP/AP.

The following procedure may be followed to provide for legacy device coexistence. A PCP/AP STA may maintain a list of capabilities of associated non-PCP/AP STAs. The PCP/AP STA may have information regarding the number of BTA capable non-PCP/AP STAs and the number of BTA non-capable non-PCP/AP STAs with which it is associated. The PCP/AP may predict the BTA capable and non-capable STAs in the BSS (including unassociated STAs) based on these numbers. For example, the PCP/AP STA may calculate the predicted numbers based on the ratio of #BTA capable STA/#BTA non-capable STA.

The PCP/AP may determine to allow all of the BTA capable STAs to use BTA only. This option may be signaled in the Beacon Frame. The PCP/AP may alternately determine to allow all of the BTA capable STAs to use A-BFT. This option may be signaled in the Beacon Frame. The PCP/AP may alternately determine to allow some of the BTA capable STAs to use A-BFT. In some cases, the percentage of the BTAs which are allowed to use A-BFT may be signaled. For example, a discrete percentage may be signaled in the Beacon Frame (e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>% <NUM>%). In some cases, a BTA capable STA, which receives the percentage number, may randomly choose a number R_percentage between <NUM> to <NUM>. If this random number is smaller than the given Percentage number, i.e., R_percentage<Percentage, the STA may be able to or choose to transmit using A-BFT. Otherwise the STA may transmit on the BTA. The PCP/AP STA may update the ratio by updating the number of BTA capable and non-capable non-PCP/AP STAs.

Although the various features and elements herein are described in particular combinations, each feature or element may be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present disclosure. Although the solutions described herein are described with respect to IEEE <NUM> specific protocols, it is understood that the solutions described herein are not restricted to IEEE <NUM> applications, but are applicable to other wireless systems and other as well.

Claim 1:
A method for use in a first communication device, the method comprising:
monitoring, by a first communication device, a plurality of beacon frames transmitted within a beacon interval (BI) during a fragmented transmit sector sweep (TXSS) from at least a second communication device associated with the first communication device;
receiving, by the first communication device, the beacon frames over a plurality of transmission sectors during a time interval;
compiling, by the first communication device, a list of the transmission sectors where the beacon frames are received within the BI during the fragmented TXSS;
ranking, by the first communication device, the transmission sectors in the list based on a characteristic of the transmission sectors; and
transmitting, by the first communication device, the ranked list of the transmission sectors over at least one of the plurality of transmission sectors to the second communication device prior to completion of the fragmented TXSS.