WO2016068521A1

WO2016068521A1 - Method and apparatus for multiuser beamforming in wireless communication systems

Info

Publication number: WO2016068521A1
Application number: PCT/KR2015/010812
Authority: WO
Inventors: Sridhar Rajagopal; Rakesh Taori
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2014-10-27
Filing date: 2015-10-14
Publication date: 2016-05-06

Abstract

A method of providing multiple station beam refinement in a wiereless communication system comprising an access point (AP) and a plurality of terminals is provided. The method for operating a control node in wireless communication system, the method includes transmitting a control information on beam refinements for a plurality of terminals, and transmitting frames for the beam refinements, Herein, the frames are beamformed with at least one beam, and wherein the at least one beam comprises optimal beams for the plurality of terminals.

Description

METHOD AND APPARATUS FOR MULTIUSER BEAMFORMING IN WIRELESS COMMUNICATION SYSTEMS

The present disclosure relates generally to a wireless communication system and, more specifically, to a multi-user beamforming in the wireless communication system.

Some beamformed millimeter Wave (mmWave) wireless networks are configured around accommodating a small number of users or station (STAs). In some beamformed mmWave wireless networks, beam refinement for multiple STAs can be a time and power consuming process as a function of an inefficient beam refinement procedure. In some beamformed mmWave wireless networks, the above-described time and power inefficiencies can be made worse as the number of STAs in the network is increased.

A primary aspect of the present disclosure is to provide an apparatus and a method for multiple user beamforming in a wireless communication system.

Another aspect of the present disclosure is to provide an apparatus and a method for a beam refinement in a wireless communication system.

Yet another aspect of the present disclosure is to provide an apparatus and a method for reducing a latency for the beam refinement in a wireless communication system.

Still another aspect of the present disclosure is to provide an apparatus and a method for providing control information for beam refinement of a plurality of terminals in a wireless communication system.

In certain embodiments, a method for operating a control node in wireless communication system is proviced. The method includes transmitting control information on beam refinements for a plurality of terminals, and transmitting frames for the beam refinements. Herein, the frames are beamformed with at least one beam, and the at least one beam comprises optimal beams for the plurality of terminals.

In certain embodiments, an apparatus for a control node in wireless communication system, the apparatus includes a transmitter configured to transmit a control information on beam refinements for a plurality of terminals, and to transmit frames for the beam refinements. Herein, the frames are beamformed with at least one beam, and the at least one beam comprises optimal beams for the plurality of terminals

In certain embodiments, a method for operating a terminal in wireless communication system, the method includes receiving a control information on beam refinements for a plurality of terminals including the terminal, and receiving frames for the beam refinements, Herein, the frames are beamformed with at least one beam, and the at least one beam comprises optimal beams for the plurality of terminals.

In certain embodiments, an apparatus for a terminal in wireless communication system, the apparatus includes a receiver configured to receive a control information on beam refinements for a plurality of terminals including the terminal, and to receive frames for the beam refinements. Herein, the frames are beamformed with at least one beam, and the at least one beam comprises optimal beams for the plurality of terminals.

Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “transmit,” “receive,” and “communicate,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” means any device, system or part thereof that controls at least one operation. Such a controller can be implemented in hardware or a combination of hardware and software and/or firmware. The functionality associated with any particular controller can be centralized or distributed, whether locally or remotely. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items can be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.

For a more complete understanding of this disclosure and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 illustrates an example wireless network according to this disclosure;

FIGURE 2 illustrates an example station according to this disclosure;

FIGURE 3 illustrates an example access point according to this disclosure;

FIGURE 4 illustrates an example beamforming procedure in a wireless communication system according to this disclosure;

FIGURE 5 illustrates an example DMG beaconing procedure in a wireless communication system according to this disclosure;

FIGURE 6 illustrates an example association procedure using A-BFT in a wireless communication system according to this disclosure;

FIGURE 7 illustrates an example sector sweep procedure in a wireless communication system according to this disclosure;

FIGURE 8 illustrates an example announcement transmission interval (ATI) procedure in a wireless communication system according to this disclosure;

FIGURE 9 illustrates an example beam refinement protocol in a wireless communication system according to this disclosure;

FIGURE 10 illustrates an example comparison between a sequential beam refinement procedure and a multiple station beam (Multi-STA) refinement procedure according to this disclosure;

FIGURE 11 illustrates an example of beam refinement phases according to this disclosure;

FIGURE 12 illustrates example multiuser beam refinement modes according to this disclosure;

FIGURE 13 illustrates an example Multi-STA beamforming procedure according to this disclosure;

FIGURE 14 illustrates an example Multi-STA BRP operation according to this disclosure;

FIGURE 15 illustrates an example Multi-STA BRP operation with parallel feedback according to this disclosure;

FIGURE 16 illustrates an example coarse beam refinement procedure where all stations have the same best sector ID according to this disclosure;

FIGURE 17 illustrates an example coarse beam refinement procedure where all stations have the same best sector ID and a station indicates a need for additional beam training according to this disclosure;

FIGURE 18 illustrates an example coarse beam refinement procedure where stations have different best sector IDs according to this disclosure;

FIGURE 19 illustrates an example coarse beam refinement procedure where stations have different best sector IDs and a station indicates a need for additional beam training according to this disclosure;

FIGURE 20 illustrates an example AP receive beamforming procedure according to this disclosure;

FIGURE 21 illustrates an example message sequence chart for the AP receive beamforming procedure of FIGURE 20;

FIGURE 22 illustrates an example Multi-STA beam tracking protocol operation for a transmitting PCP/AP and receiving STAs according to this disclosure;

FIGURE 23 illustrates an example message sequence chart for the beamforming procedure of FIGURE 22;

FIGURE 24 illustrates an example Multi-STA beam tracking protocol operation for a receiving PCP/AP and transmitting STAs according to this disclosure;

FIGURE 25 illustrates an example message sequence chart for the beamforming procedure of FIGURE 24;

FIGURE 26 illustrates an example A-BFT structure in a wireless communication system according to this disclosure;

FIGURE 27 illustrates a Multi-STA BRP method according to this disclosure;

FIGURE 28 illustrates a matrix of possible Multi-STA BRP cases according to this disclosure;

FIGURE 29 illustrates an operation of a control node in a wireless communication system according to this disclosure;

FIGURE 30 illustrates a differnt operation of a control node in a wireless communication system according to this disclosure;

FIGURE 31 illustrates an operation of a terminal in a wireless communication system according to this disclosure; and

FIGURE 32 illustrates a different operation of a terminal in a wireless communication system according to this disclosure.

FIGURES 1 through 32, discussed below, and the various embodiments used to describe the principles of the present disclosure are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of this disclosure can be implemented in any suitably arranged device or system.

Exemplary embodiments of the present disclosure provide a technique for providing a multi-user beamforming in a wireless communication system.

Hereinafter, a term for referring control information, terms for referring procedures of beam controls, terms for referring network entities, terms for referring messages, and terms for referring elements of an apparatus or a device are used to ease the understanding. Accordingly, the present disclosure is not limited to those terms to be explained and can adopt other terms of technically equivalent meanings.

To ease the understanding, the present disclosure uses, but not limited to, terms and names defined in Institute of Electrical and Electronical Engineers (IEEE) 802.11 standard. The present disclosure can be equally applied to systems conforming to other standards.

Now, the present disclosure provides multiple connections using a Wireless Local Area Network (WLAN) technology in a cellular communication system. Notably, the present disclosure can employ other radio access technology (RAT), for example, Bluetooth and Bluetooth Low Energy (BLE) besides the WLAN.

FIGURE 1 illustrates an example wireless network 100 according to this disclosure. The embodiment of the wireless network 100 shown in FIGURE 1 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

The wireless network 100 includes an access point (AP) 102 and a plurality of stations (STAs) configured to wirelessly communicate with the AP 102. In the example illustrated in FIGURE 1, the wireless network 100 includes a first station 104, a second station 106, a third station 108, a fourth station 110, and a fifth station 112. However, the wireless network 100 can include more or fewer stations. The wireless network 100 can be configured according to one or more 802.11 based communication standards. Each station transmits uplink signals to the AP 102 and receives downlink signals from the AP 102.

Depending on the network type, other well-known terms may be used instead of AP, such as “eNodeB” or “eNB,” or “base station.” For the sake of convenience, the term “AP” is used in this patent document to refer to network infrastructure components that provide wireless access to remote terminals. Also, depending on the network type, other well-known terms may be used instead of STA, such as “terminal’, “user equipment” or “UE,” “mobile station,” “subscriber station,” “remote terminal,” “wireless terminal,” or “user device.” For the sake of convenience, the term “STA” is used in this patent document to refer to remote wireless equipment that wirelessly accesses an AP, whether the UE is a mobile device (such as a mobile telephone or smartphone) or is normally considered a stationary device (such as a desktop computer or vending machine).

The AP 102 provides wireless fidelity (WiFi) access, such as 802.11 based communications, to a network, such as the Internet, for the first STA 104, the second STA 106, the third STA 108, the fourth STA 110, and the fifth STA 112. The AP 102 can be located one of: a small business (SB); an enterprise (E); in a WiFi hotspot (HS); in a first residence (R); in a second residence (R); and a mobile device (M) like a cell phone, a wireless laptop, a wireless PDA, or the like. In certain embodiments, one or more of the AP 102 or the

STAs

104, 106, 108, 112 and 114 are configured to support beam refinement in mmWave wireless systems.

FIGURE 2 illustrates an example STA 104 according to this disclosure. The embodiment of the STA 104 illustrated in FIGURE 2 is for illustration only, and the STAs 106-112 of FIGURE 1 could have the same or similar configuration. However, STAs come in a wide variety of configurations, and FIGURE 2 does not limit the scope of this disclosure to any particular implementation of a STA.

The STA 104 includes an antenna 205, a radio frequency (RF) transceiver 210, transmit (TX) processing circuitry 215, a microphone 220, and receive (RX) processing circuitry 225. The STA 104 also includes a speaker 230, a main processor 240, an input/output (I/O) interface (IF) 245, a keypad 250, a display 255, and a memory 260. The memory 260 includes a basic operating system (OS) program 261 and one or more applications 262.

The RF transceiver 210 receives, from the antenna 205, an incoming RF signal transmitted by an AP 102 of the network 100. The RF transceiver 210 down-converts the incoming RF signal to generate an intermediate frequency (IF) or baseband signal. The IF or baseband signal is sent to the RX processing circuitry 225, which generates a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. The RX processing circuitry 225 transmits the processed baseband signal to the speaker 230 (such as for voice data) or to the main processor 240 for further processing (such as for web browsing data).

The TX processing circuitry 215 receives analog or digital voice data from the microphone 220 or other outgoing baseband data (such as web data, e-mail, or interactive video game data) from the main processor 240. The TX processing circuitry 215 encodes, multiplexes, and/or digitizes the outgoing baseband data to generate a processed baseband or IF signal. The RF transceiver 210 receives the outgoing processed baseband or IF signal from the TX processing circuitry 215 and up-converts the baseband or IF signal to an RF signal that is transmitted via the antenna 205.

The main processor 240 can include one or more processors or other processing devices and execute the basic OS program 261 stored in the memory 260 in order to control the overall operation of the STA 104. For example, the main processor 240 could control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceiver 210, the RX processing circuitry 225, and the TX processing circuitry 215 in accordance with well-known principles. In some embodiments, the main processor 240 includes at least one microprocessor or microcontroller.

The main processor 240 is also capable of executing other processes and programs resident in the memory 260, such as operations to support beam refinement in mmWave wireless systems. The main processor 240 can move data into or out of the memory 260 as required by an executing process. In some embodiments, the main processor 240 is configured to execute the applications 262 based on the OS program 261 or in response to signals received from AP 102 or an operator. The main processor 240 is also coupled to the I/O interface 245, which provides the STA 104 with the ability to connect to other devices such as laptop computers and handheld computers. The I/O interface 245 is the communication path between these accessories and the main controller 240.

The main processor 240 is also coupled to the keypad 250 and the display unit 255. The operator of the STA 104 can use the keypad 350 to enter data into the STA 104. The display 255 may be a liquid crystal display or other display capable of rendering text and/or at least limited graphics, such as from web sites.

The memory 260 is coupled to the main processor 240. Part of the memory 260 could include a random access memory (RAM), and another part of the memory 260 could include a Flash memory or other read-only memory (ROM).

Although FIGURE 2 illustrates one example of STA 104, various changes may be made to FIGURE 2. For example, various components in FIGURE 2 could be combined, further subdivided, or omitted and additional components could be added according to particular needs. As a particular example, the main processor 240 could be divided into multiple processors, such as one or more central processing units (CPUs) and one or more graphics processing units (GPUs). Also, while FIGURE 2 illustrates the STA 104 configured as a mobile telephone or smartphone, STAs could be configured to operate as other types of mobile or stationary devices.

FIGURE 3 illustrates an example AP according to this disclosure. The embodiment of the AP 102 shown in FIGURE 3 is for illustration only, and other APs in embodiments of the present disclosure could have the same or similar configuration. However, APs come in a wide variety of configurations, and FIGURE 3 does not limit the scope of this disclosure to any particular implementation of an AP.

The AP 102 includes multiple antennas 305a-305n, multiple RF transceivers 310a-310n, transmit (TX) processing circuitry 315, and receive (RX) processing circuitry 320. The AP 102 also includes a controller/processor 325, a memory 330, and a backhaul or network interface 335.

The RF transceivers 310a-310n receive, from the antennas 305a-305n, incoming RF signals, such as signals transmitted by STAs or other APs. The RF transceivers 310a-310n down-convert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are sent to the RX processing circuitry 320, which generates processed baseband signals by filtering, decoding, and/or digitizing the baseband or IF signals. The RX processing circuitry 320 transmits the processed baseband signals to the controller/ processor 425 for further processing.

The TX processing circuitry 315 receives analog or digital data (such as voice data, web data, e-mail, or interactive video game data) from the controller/processor 325. The TX processing circuitry 315 encodes, multiplexes, and/or digitizes the outgoing baseband data to generate processed baseband or IF signals. The RF transceivers 310a-310n receive the outgoing processed baseband or IF signals from the TX processing circuitry 315 and up-converts the baseband or IF signals to RF signals that are transmitted via the antennas 305a-305n.

The controller/processor 325 can include one or more processors or other processing devices that control the overall operation of the AP 102. For example, the controller/processor 325 could control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceivers 310a-310n, the RX processing circuitry 320, and the TX processing circuitry 315 in accordance with well-known principles. The controller/processor 325 could support additional functions as well, such as more advanced wireless communication functions. Any of a wide variety of other functions could be supported in the AP 102 by the controller/processor 325. In some embodiments, the controller/ processor 325 includes at least one microprocessor or microcontroller.

The controller/processor 325 is also capable of executing programs and other processes resident in the memory 330, such as a basic OS. The controller/processor 325 can move data into or out of the memory 330 as required by an executing process.

The controller/processor 325 is also coupled to the backhaul or network interface 335. The backhaul or network interface 335 allows the AP 102 to communicate with other devices or systems over a backhaul connection or over a network. The interface 335 could support communications over any suitable wired or wireless connection(s). For example, when the AP 102 is implemented as part of a cellular communication system (such as one supporting 5G, Long Term Evolution (LTE), or LTE-Advanced (LTE-A)), the interface 335 could allow the AP 102 to communicate with eNBs over a wired or wireless backhaul connection. When the AP 102 is implemented as an access point, the interface 335 could allow the AP 102 to communicate over a wired or wireless local area network or over a wired or wireless connection to a larger network (such as the Internet). The interface 335 includes any suitable structure supporting communications over a wired or wireless connection, such as an Ethernet or RF transceiver.

The memory 330 is coupled to the controller/processor 325. Part of the memory 330 could include a RAM, and another part of the memory 330 could include a Flash memory or other ROM.

As described in more detail below, the transmit and receive paths of the AP 102 (implemented using the RF transceivers 310a-310n, TX processing circuitry 315, and/or RX processing circuitry 320) support communication operations in mmWave wireless. The transmit and receive paths of the AP 102 are configured to support beam refinement in mmWave wireless systems.

Although FIGURE 3 illustrates one example of an AP 102, various changes may be made to FIGURE 3. For example, the AP 102 could include any number of each component shown in FIGURE 3. As a particular example, an access point could include a number of interfaces 335, and the controller/processor 325 could support routing functions to route data between different network addresses. As another particular example, while shown as including a single instance of TX processing circuitry 315 and a single instance of RX processing circuitry 320, the AP 102 could include multiple instances of each (such as one per RF transceiver).

FIGURE 4 illustrates an example beamforming procedure in a communication system according to this disclosure. For example, the communication system may employ IEEE 802.11ad standard. The communication system may be a mmWave communication system. The embodiment of the beamforming procedure shown in FIGURE 4 is for illustration only, and other beamforming procedures in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 4 illustrates an example beamforming (BF) procedure 400 used in IEEE 802.11ad for a node 402 such as an Access Point (AP), personal basic service set (PBSS) control point (PCP) or a station (STA)) to initiate the attachment with another STA 404. In this case, the node 402 includes an AP 102 and the STA 404 includes a STA2 106. The BF procedure includes a bidirectional sequence of BF training frame transmissions that uses sector sweep and provides the necessary signaling to allow each STA to determine appropriate antenna system settings for both transmission and reception. BF training starts with a sector level sweep (SLS) 406 from the initiator. In this case, the initiator is the node 402. The purpose of the SLS 406 phase is to enable communications between the two participating STAs at the control physical (PHY) rate or higher modulation and coding scheme (MCS). Normally, the SLS 406 phase provides only transmit BF training. At the start of the transmit sector sweep 408, the responder, in this case station 404, should have its receiving antenna configured to a wide beam (e.g. quasi-omni) pattern, followed by transmit sector sweep 410 by the responder. At the end of the sector sweep phase, both the node 402 and the STA2 402 (e.g. AP/PCP and STA) will have completed the transmit beamforming and the best sector is fed back for use in data communication. In this case, the sector sweep phase is followed by the node 402 transmitting a sector sweep feedback 412 to which the STA 404 responds by transmitting a sector sweep acknowledgement (ACK) 414. A beam refinement protocol (BRP) may follow, if requested by either the initiator or the responder.

FIGURE 5 illustrates an example beaconing procedure in a communication system according to this disclosure. For example, the communication system may employ IEEE 802.11ad standard. The communication system may be a mmWave communication system. The embodiment of the beaconing procedure shown in FIGURE 5 is for illustration only, and other beaconing procedures in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 5 illustrates an example beaconing procedure 500 used in IEEE 802.11ad to start the STA association procedure. Though the terms AP/PCP and STA are used for nodes of the beaconing procedure 500, for purposes of discussion of FIGURE 5, the terms can be used interchangeably. In certain embodiments a node 502 includes an AP 102, a node 504 includes a STA1 104, and a node 506 includes a STA2 106.

The AP/PCP or node 502 starts transmitting beacons, in this case, directional multi-gigabit (DMG) beacons 508, using a transmit sector sweep during the beacon transmission interval (BTI) 510. All STAs, such as

nodes

504 and 506, that wish to associate with the PCP/AP are in their receive mode during this transmission using a wide pattern 514 or quasi-omni pattern. Each STA, namely

nodes

504 and 506, record the best directions for reception from the PCP/AP or node 502 and feeds back the direction information to the PCP/AP or node 502 during the association process.

FIGURE 6 illustrates an association procedure in a wireless communication system according to this disclosure. For example, the communication system may employ IEEE 802.11ad standard. The communication system may be a mmWave communication system. The embodiment of the association procedure shown in FIGURE 6 is for illustration only, and other association procedures in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 6 illustrates an example association procedure 600 using an association beamforming training (A-BFT) period 602 of a beacon interval 604. In the A-BFT period 602, time is divided into multiple association slots (called sector sweep slots or SSW slots) determined by the beacon (up to a maximum of 8 slots in IEEE 802.11ad). A SSW slot m 606 and a SSW slot n 608 are included in this embodiment. Each STA, such as nodes 610 (labeled STA i) and 612 (labeled STA j) randomly picks one of the

SSW slots

606 and 608 slots for transmission to the node 614 (labeled PCP/AP). The stations perform their own sector sweeps during the slot time where it transmits multiple SSW frames with different sector IDs. For example, node 612 performs a responder sector sweep 616 during the duration of the SSW slot m 606 and node 610 performs a responder sector sweep 618 during the duration of the SSW slot n 608. During the transmission of the responder sector sweep 616, the node 614 utilizes a quasi-omni antenna pattern or a wide beam 620 antenna pattern and the node 614 records the best sector to receive transmission from the node 616. The node 614 or PCP/AP then transmits and feeds back the best sector ID to the node 612 using a SSW feedback 622 while the node 612 utilizes a wide beam 624 antenna pattern. If there is a collision at the node 614, which is detected by lack of SSW feedback from the PCP/AP to the STA requesting association, the STA retries during the next beacon interval. During the SSW slot n 608, the above-described process is repeated, but between the node 610 and the node 614 utilizing the responder sector sweep 618, the wide beam 626, the sector sweep feedback 628, and the wide beam 630. It is clear that each node such as nodes 610 and 612 attempting to associate with node 614 takes a turn in attempting association and the attempt to associate occur sequentially within the A-BFT 602 using one SSW slot per node or STA attempting to associate.

FIGURE 7 illustrates an example sector sweep procedure for association in a communication system according to this disclosure. For example, the communication system may employ IEEE 802.11ad standard. The communication system may be a mmWave communication system. The embodiment of the sector sweep procedure for association shown in FIGURE 7 is for illustration only, and other sector sweep procedures for association in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 7 illustrates an example sector sweep procedure 700 for association in IEEE 802.11ad. The PCP/AP 702 transmits in multiple directions using a countdown (CDOWN) 704 reporting sector ID 706 during beacon transmissions. That is, the PCT/AP 702 transmits the pairs of the CDOWN 704 and the sector ID 705 in a beacon transmission interval. The STAs STA i 708 and STA j 710 are in a wide beam (e.g. quasi-omni) mode during this time (e.g. the beacon transmissions) and record the best transmit sector ID from the PCP/AP 702 for reception. In this example, STA i 708 finds sector ID = 14 as the best sector ID from PCP/AP 702 while STA j 710 finds sector ID = 10 as the best sector ID from the PCP/AP 702. During the A-BFT interval 712, STA i 708 finds the first transmission SSW slot 714 within the A-BFT 712 and STA j 710 finds the second transmission SSW slot 716 within the A-BFT 712. The PCP/AP 702 is in the wide beam (e.g. quasi-omni) mode during the first and second transmission SSW slots 716, 718. The PCP/AP 702 finds sector ID = 7 as the best ID for STA i 708 and sector ID = 14 as the best ID for STA j 710. Thus, at the end of the SSW, all

STAs

708, 710 and the PCP/AP 702 know the best transmit sector ID. Table 1 below summarizes which best transmit sector IDs are transmitted during SLS.

FIGURE 8 illustrates an example announcement time interval in a wireless communication system according to this disclosure. For example, the communication system may employ IEEE 802.11ad standard. The communication system may be a mmWave communication system. The embodiment of the announcement time interval shown in FIGURE 8 is for illustration only, and other announcement time interval in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 8 illustrates an example announcement time interval (ATI) period 800 of the beacon interval 802 in IEEE 802.11ad. During the ATI 800, request 804 and response 806 exchanges occur between a PCP/AP 808 and each associated STA sequentially, namely STA i 810 and STA j 812. The PCP/AP 808 transmits using its best sector ID for each STA while the STA is configured to operate in the quasi-omni pattern mode or wide beam 814 mode. Beam refinement frame messages to set up further beam refinement for a better signal to noise ratio (SNR) for data communication during the data transmission interval (DTI).

FIGURE 9 illustrates an example beam refinement protocol (BRP) in a wireless communication system according to this disclosure. For example, the communication system may employ IEEE 802.11ad standard. The communication system may be a mmWave communication system. The embodiment of the beam refinement protocol shown in FIGURE 9 is for illustration only, and other beam refinement protocols in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 9 illustrates an example beam refinement protocol (BRP) 900 in IEEE 802.11ad. BRP 900 is a process where stations, such as STA i 902 and STA j 904, train transmit (TX) and receive (RX) antenna arrays and improve and refine their beamforming configuration through iterative search to provide increased throughput. This process is performed during the data transmission interval (DTI) 906 part of the beacon interval 908. One of the important goals in the BRP 900 is to provide a finer receiver beam 910 with an aim to provide an increase in receiver beamforming gain, leading to improved data rates. In a first method called multiple sector ID detection (MID), the transmitting node, such as PCP/AP 912 uses a wide beam 914 (e.g. quasi-omni) while the receiving node sweeps through choice antenna weight vectors (AWVs) to determine the RX settings that have the best link quality. In a second method called beam combining (BC), multiple RX AWVs are tested together with multiple TX AWVs. Both methods can be used independently or in together to provide the required beam refinement. The refined beams provide increased SNR to the receiving node, enabling higher data rate communication for data transfer.

FIGURE 10 illustrates an example multiple station beam refinement protocol (Multi-STA BRP) according to this disclosure. The embodiment Multi-STA BRP shown in FIGURE 10 is for illustration only, and other Multi-STA BRPs in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 10 illustrates a comparison between a sequential BRP protocol 1000, such as BRP 900, and a Multi-STA BRP 1002. The sequential BRP 1000 operates in a sequential and per STA basis that requires a significant amount of overhead for beam refinement of multiple STAs. In sequential BRP 1000, during a first time period 1004, a STA1 sector sweep 1006 is performed while a PCP/AP transmission 1008 is performed. Next, in a second time period 1010, a STA1 sector sweep 1012 is performed while a PCP/AP transmission 1014 is performed. This sequential process is repeated n times, once for each STA. However, when utilizing the Multi-STA BRP protocol 1002, while a PCP/AP 1016 is transmitting beam refinement frames in a sector during a first time period 1018, all the STAs, such as STA 1 1018 and STA 2 1020, in that sector utilize the transmission (e.g. transmissions of the beam refinement frames) to refine their beams. This simultaneous multiple station sector sweeping reduces latency and boosts the overall throughput of a network.

FIGURE 11 illustrates an example phases of a beam refinement procedure according to this disclosure. The embodiment of phases of beam refinement shown in FIGURE 11 is for illustration only, and other phases of beam refinement in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 11 illustrates the distinct phases of beam refinement 1100, which iteratively reduce the beamwidth and improve the data communication range and SNR via beamforming with narrower beams. During a coarse beam refinement (CBR) phase 1102, a wide beam 1104 is refined to the accuracy of a sector beam 1106. Next, in a fine beam refinement (FBR) phase 1108, the sector beam 1106 is further refined into a narrow beam 1110. In addition, beam tracking (TR) 1112 is engaged to track the beams at different times to support mobility or temporary blockages. The beam tracking 1112 process does not change the beamwidth but tracks the beams across sectors or across narrow beams, in order to provide the best link quality.

FIGURE 12 illustrates an example of multi-user beam refinement modes according to this disclosure. The embodiments of multi-user beam refinement modes shown in FIGURE 12 is for illustration only, and other multi-user beam refinement modes in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 12 shows multi-user beam refinement modes 1200. In a first mode 1202, with only Tx beam refinement (CBR-Tx) 1204 attained by BTI 1206 and A-BFT 1208, the STAs will operate at a given rate 1 1210 during the DTI 1211. In a second mode 1212, with CBR-Rx 1214 in addition to CBR-Tx 1204, the sector level beams (which are narrower than the wide beams) are obtained at the receiver as well, thereby providing an even higher SNR at the receiver, thereby enabling the STAs to operate at a data rate 2 1216 that is higher than rate 1 1210. In a third mode 1218, with FBR 1220 in addition to CBR-Rx 1214 and CBR-Tx 1204, the beam widths can be further refined to provide a data rate 3 1222 even higher data rate 2 1216. Beam tracking TR 1224 is applied after FBR 1220 in order to track the beams for mobility or temporary blockages to sustain the best data rates that can be obtained at a given level of beam refinement. In a fourth mode 1226, FBR 1220 is conducted after CBR Rx 1214 and without first operating a rate 2 1216.

FIGURE 13 illustrates an example of a Multi-STA beamforming and beam refinement protocol according to this disclosure. A communication system according to this disclosure may be a mmWave communication system. The embodiment of Multi-STA beamforming and beam refinement protocol shown in FIGURE 13 is for illustration only, and other Multi-STA beamforming and beam refinement protocols in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 13 illustrates a multi-STA beamforming and beam refinement protocol 1300. The protocol 1300 includes two stages, a Multi-STA beamforming stage 1302 followed by a Multi-STA multiple input multiple output (MIMO) stage 1304. The multi-STA beamforming stage 1302 starts after the beaconing procedures 1306 and association procedures 1308 are completed. By the end of the association procedures 1308, the transmit beamforming has been completed for the PCP/AP and the associated STAs and thus, the best beams to transmit between the PCP/AP and STAs is known. Next, grouping procedures 1310 are conducted and the PCP/AP first decides on the STAs to group together for transmission. Several factors can be involved in achieving this grouping, including, but not limited to, the link quality between the PCP/AP and the STAs, the best sector ID to transmit to STAs, and the capability of STAs to provide Multi-STA support. Next, a Multi-STA beamforming procedure 1312 is initiated by setting up a multi-STA session 1314 using dedicated time in the service period/contention based access period (SP/CBAP) in the DTI and a Multi-STA BRP frame is utilized to indicate to the STAs that they are now part of a multi-STA BRP session. Next, a multi-STA BRP session 1316 conducts beam refinement for multiple users simultaneously rather than sequentially. At the end of the multi-STA BRP session 1316, the PCP/AP and the STAs know the best directions for transmit and receive beamforming for exchanging data. The beam width of the transmitter and receiver is now fixed for the Multi-STA MIMO stage 1304.

The Multi-STA MIMO stage 1304 follows the Multi-STA BF stage. The Multi-STA MIMO stage 1304 begins by performing channel sounding procedures 1318, during which the channel is sounded for the selected STAs to determine the number of streams to be transmitted to each STA. This can be done in a process similar to the channel sounding performed in IEEE 802.11ac, which uses null data packet (NDP) transmissions or using a staggered preamble to expand the number of long training symbols. The channel sounding is only performed in the directions determined by the Multi-STA BF stage 1302. At 1320, the channel state information is then fed back to the PCP/AP, which makes the decision on the number of streams to be transmitted to each STA in the Multi-STA MIMO transmission. The multi-STA data transmission 1322 and acknowledgements 1324 occur thereafter. Any change in beam width or beam direction requires a new beam refinement and new channel sounding operation to be performed.

A multi-STA BRP announcement frame is transmitted from the PCP/AP to indicate to the STAs that STAs are a part of the Multi-STA BRP. The content of an example Multi-STA BRP announcement frame is shown in Table 2. The multi-STA BRP announcement frame includes the SSW sweep duration and the duration of each BRP-FBCK, the PCP/AP information (e.g. association ID (AID), best sector ID and so forth), the list of STAs involved in the Multi-STA BRP, the number of times the AP will repeat its SSW, the refinement type such as CBR, FBR or TR and the best narrow beam ID for fine refinement (if needed). Table 2 shows an example of a structure for the multi-STAT BRP announcement frame.

FIGURE 14 illustrates an example of a Multi-STA BRP operation according to this disclosure. A communication system according to this disclosure may be a mmWave communication system. The embodiment of Multi-STA BRP operation shown in FIGURE 14 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

In the example shown in FIGURE 14, the Multi STA BRP operation 1400 begins with a parallel multi-station beam refinement procedure 1402 using sector sweep. The operation 1402 has a duration equal to aSSDuration*aSSRep. During the operation 1402, an AP (or multi-STA) sweeps the beam over multiple repetitions while the multi-STA (or AP) beams remain fixed at a given direction for receive beam refinement. After the operation 1402, the multi-STA (or AP) sends feedback, such as STA 1 SSW-FBCK 1404 and STA 2 SSW-FBCK 1406, on whether the beam refinement was successful and whether any additional beam training is needed. Each feedback has a duration equal to aSSWFBCKDuration. Accordingly, the entire operation 1400 has a time duration, aMultiSTABRPDuration, equal to aSSDuration*aSSRep+LBIFS+(n-1)*SBIFS+n*aSSWFBCKDuration.

FIGURE 15 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 15 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 15 illustrates a Multi-STA BRP operation 1500 in which feedback, such as STA1 SSW-FBCK 1502 and STA2 SSW-FBCK 1504, are sent in parallel because the AP determined that the feedback will not have collisions. This is possible for cases such as space division multiple access (SDMA) where multiple transmissions in different directions could occur without collisions. In this case, the operation 1500 begins with a parallel multi-station beam refinement procedure 1506 using sector sweep. The operation 1506 has a duration equal to aSSDuration*aSSRep. During the procedure 1506, an AP (or multi-STA) sweeps the beam over multiple repetitions while the multi-STA (or AP) beams remain fixed at a given direction for receive beam refinement. After the procedure 1506, the multi-STA (or AP) sends STA1 SSW-FBCK 1502 and STA2 SSW-FBCK 1504 on whether the beam refinement was successful and whether any additional beam training is needed. Since the feedback in this example is sent simultaneously, the feedback collectively has a duration equal to aSSWFBCKDuration. Accordingly, the entire operation 1500 has a time duration, aMultiSTABRPDuration, equal to aSSDuration*aSSRep+LBIFS+aSSWFBCKDuration.

Three examples of multi-STA BRP operation are described below. A first case where AP is transmitting BRP to multiple STAs with same sector ID (see FIGURE 16), a second case where an AP is transmitting BRP to multiple STAs with different sector IDs (see FIGURE 17), and a third case where multi-STAs are transmitting BRP to an AP (see FIGURE 18). In each of these cases, it is assumed that the STA capability is not changed and the multi-STA operation by the AP is made transparent to the STA (i.e., the STA need not know). The cases also assume that Tx BRP is done via sector level sweep (SLS) during beacon and association periods.

FIGURE 16 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 16 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 16 illustrates an example Multi-STA BRP operation 1600 for station receive coarse beam refinement where all STAs, such as STA i 1602 and STA j 1604, have the same best sector ID of a PCP/AP 1606. Using the best sector ID, a PCP/AP 1606 send announcement 1608 to the desired STAs, STA i 1602 and STA j 1604, that it will perform BRP. STAs that have been informed about Rx BRP, will perform Rx SS 1610 during this transmission (e.g. transmissions of BRP frames). In response, STAs will provide feedback, such as feedback 1612 STA i 1602 and feedback 1614 of STA j 1604, to the PCP/AP 1606 regarding whether the Rx BRP was sufficient and whether further Rx BRP is required. Feedback, such as

feedback

1612 and 1614, will be sent in the direction of best Tx sector ID for transmission to the PCP/AP 1606. The SSW can be repeated aSSRep times to improve the Rx BRP. While

feedback

1612 and 1614 are shown as being transmitted sequentially, in certain embodiments where the PCP/AP 1606 can ensure collision avoidance, feedback such as

feedback

1612 and 1614 can be transmitted in parallel.

FIGURE 17 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 17 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 17 illustrates an example of Multi-STA BRP operation 1700 for receive beam refinement where during a first iteration 1702 of the operation 1700, a STA i 1704 provides an indication 1706 of a need for additional beamforming training and a STA j 1708 provides an indication 1710 of no need for additional training. Referring FIGURE 17, during the first iteration 1702, AP/STA 1712 transmits a BRP announcement. For example, the BRP announcement may includes at least one of parameters in Table 2. Then, according to the BRP announcement, AP/STA 1712 transmits BRP frames through an optimal Tx sector. After that, STAi 1704 transmits a feedback 1706 informing that an additional beam training is required. Because STA i 1704 provided indication 1706 to AP/STA 1712, the AP/STA 1712 conducts a subsequent or second iteration 1714 of the Multi-STA BRP operation 1700 with STA j 1708.

FIGURE 18 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 18 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 18 illustrates an example Multi-STA BRP operation 1800 for station receive coarse beam refinement where STAs, such as STA i 1802 and STA j 1804, have different best sector IDs of a PCP/AP 1808. One method to do this would be to cycle through each sector with the process as described above with regard to FIGURES 16 and 17. However, for MU-MIMO/SDMA operation, multiple RF chains are assumed, which enables the PCP/AP 1808 to generate a multi-sector pattern. In such a case, the PCP/AP 1808 can transmit using a multi-sector antenna pattern 1810. The multi-sector pattern 1810 includes a best sector transmission 1812 for STA i 1802 and a best sector transmission 1812 for STA j 1804. The multi-sector antenna pattern 1810 is to generate a combination of two (2) or more beams. All STAs that have been informed about Rx BRP perform Rx SS 1 during this multi-sector antenna pattern 1810 transmission. This ability to generate a multi-sector antenna pattern 1810 can be set as a requirement for MU-MIMO/SDMA operation by the PCP/AP 1808, and the PCP/AP 1808 announces multiple best sector IDs of requesting Rx BRP to the appropriate STAs. Transmitting the multi-sector antenna pattern 1810 can require additional hardware capability (the ability to generate multiple sector patterns without loss in power in each direction) at the AP 1808. In response, STAs provide feedback, such as feedback 1818 of STA i 1802 and feedback 1820 of STA j 1804, to the PCP/AP 1808 regarding whether the Rx BRP was sufficient and whether further Rx BRP is required. Feedback, such as

feedback

1818 and 1820, will be sent in the direction of best Tx sector ID for transmission to the PCP/AP 1808. The SSW can be repeated aSSRep times to improve the Rx BRP. While

feedback

1818 and 1820 are shown as being transmitted sequentially, in certain embodiments where the PCP/AP 1808 can ensure collision avoidance, feedback such as

feedback

1818 and 1820 can be transmitted in parallel.

FIGURE 19 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 19 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 19 illustrates an example Multi-STA BRP operation 1900 for station receive coarse beam refinement where STAs, such as STA i 1902 and STA j 1904, have different best sector IDs of a PCP/AP 1908. In certain embodiments, during a first iteration 1902, AP/STA 1908 transmits a BRP announcement. For example, the BRP announcement may includes at least one of parameters in Table 2. Then, the PCP/AP 1908 generates a multi-sector pattern 1910 and transmits a first BRP frame 1912 to STA i 1914 along a best sector for STA i 1914. While transmitting the first BRP frame 1912, the PCP/AP 1908 also transmits a second BRP frame 1916 to STA j 1904 along a best sector for STA j 1904. Thereafter, STA i 1902 transmits feedback 1916 to the PCP/AP 1908 indicating that additional training is needed. Following feedback 1916, STA j 1904 transmits feedback 1918 to the PCP/AP 1908 indicating that no additional training is needed. The

feedback

1916 and 1918 are each transmitted via a best transmits sectors for STA i 1902 and STA j 1904, respectively. While

feedback

1916 and 1918 are shown as being transmitted sequentially, in certain embodiments where the PCP/AP 1808 can ensure collision avoidance, feedback such as

feedback

1916 and 1918 can be transmitted in parallel or at least partially simultaneously. In certain embodiments, because STA i 1902 indicated a need for additional training in feedback 1916 during a first iteration 1920 of beam refinement training, a second iteration of beam refinement training 1922 is conducted that ultimately concludes with STA i 1902 sending a feedback 1924 to the AP/STA 1908 indicating that no additional training is needed.

FIGURE 20 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 20 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 20 illustrates an example Multi-STA BRP operation 2000 in which the PCP/AP 2002 performs Rx BRP with multiple STAs, such STA i 2004 and STA j 2006. The PCP/AP 2002 announces to desired required STAs of a need for Rx BRP with the STAs. PCP/AP 2002 performs Rx SSW with single or multiple sector patterns. Multiple sweeps will be required to cover all n STAs determined by aSSRep. Each STA will transmit in their best sector ID sequentially for a time aSSDuration (where aSSDuration = m, aSSRep ≥ n, if aSSRep >n, repeat cycle) determined by the PCP/AP 2002. In this case, STA i 2004 provides best sector information in a transmission 2008 in response to a first sector sweep 2010. Also in this case, STA j 2006 provides best sector information in a transmission 2012 in response to a second sector sweep 2014. Table 3 shows the time taken for sector sweeps with M RF chains.

Multiple sector patterns can require hardware capability support and can help reduce sweep time. (aSSDuration = m, aSSRep ≥ n/M, if aSSRep >n/M, repeat cycle). Partial sweeps are also possible to reduce sweep time if the PCP/AP 2002 has some prior indication of direction from previous sweeps (aSSDuration = k, k<m, aSSRep ≥ n/M, if aSSRep >n/M, repeat cycle). The PCP/AP 2002 informs STA i 2004 via a feedback 2016 as to whether the Rx BRP was sufficient or whether further Rx BRP is required for STA i 2004. After transmitting feedback 2016, PCP/AP 2002 informs STA j 2006 via a feedback 2018 as to whether the Rx BRP was sufficient or whether further Rx BRP is required for STA j 2006.

Feedback

2004 and 2006 are sent in the direction of best Tx sector ID for transmission to STA i 2004 and STA j 2006, respectively. While

feedback

2004 and 2006 are sent sequentially or in series, in alternative embodiments, the feedback can be sent in parallel or at least partially simultaneously if PCP/AP 2002 includes mechanisms, such as multiple sector transmission capability, to ensure there are no collisions.

FIGURE 21 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 21 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 21 illustrates an example Multi-STA BRP operation 2100 for AP Rx BRP. In certain embodiments, the AP/STA 2102 transmits a BRP announcement 2104 to each of a STA i 2106 and a STA j 2108. For example, the BRP announcement 2104 may includes at least one of parameters in Table 2. In response to the BRP announcement 2104, STA i 2106 transmits best Tx sector information 2110 while the AP/STA 2102 performs SSWs 2112. Also in response to the BRP announcement 2104 and after the STA i 2106 transmits best Tx sector information 2110, the STA j 2108 transmits best Tx sector information 2114 while the AP/STA 2102 performs SSWs 2116. Next, AP/STA 2102 transmits best Tx sector feedback 2118 to STA i 2106 via the best transmit sector to STA i 2106. Next, AP/STA 2102 transmits best Tx sector feedback 2120 to STA i 2108 via the best transmit sector to STA i 2108. While

feedback

2118 and 2120 are shown as being transmitted sequentially, in certain embodiments where the AP/STA 2102 can ensure collision avoidance, feedback such as

feedback

2118 and 2120 can be transmitted in parallel or at least partially simultaneously.

Fine beam refinement (FBR) assumes that coarse beam refinement has been performed. FBR follows substantially similar procedures as the above-described coarse beam refinement BRPs with the exceptions that wide beams are replaced by best Tx and Rx sector beams obtained during coarse beam refinement and sector beams are replaced by narrow beams. In certain embodiments, wide beams are broader than fine beams and fine beams are broader than narrow beams. At the end of a fine beam refinement phase, the best narrow beam IDs are known for Tx and Rx.

In certain embodiments, Multi-STA joint Tx-Rx beam tracking is used when multi-sector patterns are used for the purpose of future MU-MIMO/SDMA operation and STAs are in different sectors for AP Tx-Rx. Beam tracking is used in MU-MIMO when mobility or interference cause the currently selected beams to no longer be optimum, thereby requiring an adaptation of the beam patterns. In certain cases, a first order estimate of both Tx and Rx best beams (SECTOR/NARROW) from the AP and STA can be assumed to be available. There are two cases for discussion, namely, a case of joint AP Tx & STA Rx tracking and a case of joint AP Rx & STA Tx tracking.

FIGURE 22 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 22 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 22 illustrates an example Multi-STA beams tracking protocol operation 2200 for beam tracking for transmitting PCP/AP 2202 and receiving STAs, STA i 2204 and STA j 2206. In certain embodiments, the multi-STA beam tracking protocol utilizes a message sequence chart for the case while the PCP/AP 2202 is transmitting and the Rx beams of STA i 2204 and STA j 2206 are being tracked. The PCP/AP 2202 sweeps current multi-sector pattern 2208 in aSSDuration while STA i 2204 and STA j 2206 maintain

best Rx patterns

2210 and 2212, respectively. The multi-sector pattern may be used to reduce a processing time for the beam refinement. By using the multi-sector pattern, the PCP/AP 2202 may steer beams in different directions. Next, the PCP/AP 2202 sweeps repeat aSSRep times, such as sweep 2214, while STA i 2204 and STA j 2206 try

other Rx patterns

2216 and 2218, respectively. Next, STA i 2204 and STA j 2206 transmit

best sector choices

2220 and 2222, respectively, back to the PCP/AP 2202 that receives the

best sector choices

2220, 2222 via the previously determined best sectors 2224 for each of STA i 2204 and STA j 2206. After receiving the

best sector choices

2220, 2222, the PCP/AP 2202 looks at all the reports and makes a decision on the beam pattern and whether to continue supporting MU-MIMO operation. The PCP/AP 2208 can also request further beam tracking. (aSSRep ≥ k. if > k, repeat cycle).

FIGURE 23 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 23 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 23 illustrates an example Multi-STA beams tracking protocol operation 2300 for beam tracking beam tracking for transmitting AP/STA 2302 and receiving STAs, STA i 2304 and STA j 2306. The AP/STA 2302 sends a Rx BRP announcement 2308 to STA i 2304 and STA j 2306. For example, the BRP announcement 2308 may includes at least one of parameters in Table 2. After the announcement 2308, the multi-STA beam tracking protocol utilizes a message sequence chart while the PCP/AP 2302 is transmitting BRP frames 2310 and the Rx beams of STA i 2304 and STA j 2306 are being tracked to determine best

Rx sector information

2312 and 2314, respectively. In a first iteration 2316, the PCP/AP 2302 sweeps current multi-sector pattern in aSSDuration while STA i 2304 and STA j 2306 maintain best Rx patterns. During a second iteration 2318, the PCP/AP 2302 sweep repeats while STA i 2304 and STA j 2306 try other Rx patterns. During the second iteration 2318, the PCP/AP 2302 transmits BRP frames 2320 and STA i 2304 and STA j 2306 determine new

best Rx sectors

2322 and 2324, respectively. Next, the STA i 2304 and STA j 2306 transmit best

Tx sector information

2326 and 2328, respectively, back to the PCP/AP 2302 using feedback 2330 and 2332, respectively. The AP/STA 2302 receives the feedback 2330 and 2332 using multiple best Rx sectors 2334. After receiving the

best sectors

2326, 2328, the PCP/AP 2302 looks at all the reports and makes a decision on the beam pattern and whether to continue supporting MU-MIMO operation. The PCP/AP 2308 can also request further beam tracking. (aSSRep ≥ k. if > k, repeat cycle).

FIGURE 24 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 24 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 24 illustrates an example Multi-STA beam tracking protocol operation 2400 for beam tracking beam tracking for receiving PCP/AP 2402 and transmitting STAs, STA i 2404 and STA j 2406. This embodiment is substantially similar to the embodiment of FIGURE 22 but with the roles of the STAs and the PCP/AP reversed.

FIGURE 25 illustrates another example of a Multi-STA BRP operation according to this disclosure. The embodiment of Multi-STA BRP operation shown in FIGURE 25 is for illustration only, and other Multi-STA BRP operations in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 25 illustrates an example Multi-STA beams tracking protocol operation 2500 for beam tracking beam tracking receiving AP/STA 2502 and transmitting STAs, STA i 2504 and STA j 2506. The AP/STA 2502 sends a Rx BRP announcement 2508 to STA i 2504 and STA j 2506. For example, the BRP announcement 2508 may includes at least one of parameters in Table 2. After the announcement 2508, the multi-STA beam tracking protocol utilizes a message sequence chart while the STA i 2504 and STA j 2506 transmit

BRP frames

2510 and 2512, respectively. In a first iteration 2516, the AP/STA 2502 sweeps current multi-sector pattern in aSSDuration while STA i 2504 and STA j 2506 maintain best Tx patterns. During a second iteration 2518, the PCP/AP 2502 repeats sweep while STA i 2504 and STA j 2506 try other Tx patterns. During the second iteration 2518, the STA i 2504 and STA j 2506 transmit

BRP frames

2520 and 2522, respectively, and AP/STA 2502 determines new best Tx sectors. Next, the PCP/AP 2502 transmit best

Rx sector information

2524 and 2526, respectively, back to the STA i 2504 and STA j 2506 using

feedback

2528 and 2530, respectively. The AP/STA 2502 transmits the

feedback

2528 and 2530 using multiple best Tx sectors.

FIGURE 26 illustrates an example A-BFT structure in a wireless communication system according to this disclosure. For example, the communication system may employ IEEE 802.11ad standard. The embodiment of A-BFT structure shown in FIGURE 26 is for illustration only, and other A-BFT structures in embodiments of the present disclosure could have the same or similar configuration.

FIGURE 26 illustrates an IEEE 802.11ad initial beamforming training (A-BFT) structure 2600 for association. The A-BFT structure 2600 occupies a portion of a beacon interval 2602 and follows a beacon transmission interval (BTI) 2604 of the beacon interval 2602. The A-BFT structure 2600 precedes an announcement transmission interval (ATI) 2606 of the beacon interval 2602. A data transmission interval (DTI) 2608 follows the ATI 2606. The A-BFT structure 2600 includes an aSSSlotTime 2610 that includes a first portion 2612 and a subsequent SSW feedback 2614. The first portion 2612 includes a SSW 2616 followed by short beamforming interframe spacing (SBIFS) 2618. The aSSSlotTime 2610 can also be explained as including aAirPropogationTime 2620, followed by an aSSDuration 2622 (including responder TxSS and RxSS), followed by a medium beamforming interframe spacing (MBIFS) 2624, followed by an aSSFBDuration 2626 (including SSW Feedback 2614), followed by another MBIFS 2624.

FIGURE 27 illustrates a flowchart of a Multi-STA BRP method 2700 according to this disclosure. While the flow chart depicts a series of sequential steps, unless explicitly stated, no inference should be drawn from that sequence regarding specific order of performance, performance of steps or portions thereof serially rather than concurrently or in an overlapping manner, or performance of the steps depicted exclusively without the occurrence of intervening or intermediate steps. The process depicted in the example depicted is implemented by a processing circuitry in, for example, an AP or a STA.

In certain embodiments, the Multi-STA BRP method 2700 begins at step 2702 by the AP collecting BRP requirements from stations. At step 2704, the AP informs selected stations of Multi-STA BRP, such as by sending an announcement. Next at step 2706, the AP allocates DTI time for Multi-STA BRP. At step 2708, the AP performs the above-described multiple station BRP. Next at step 2710, the AP provides group feedback regarding BRP status. At step 2712, the AP determines whether BRP is complete. If BRP is complete, the method 2700 ends. If the BRP is determined at step 2712 to not be complete, the method 2700 progresses to step 2714 and the AP reschedules BRP for stations that require further BRP. From step 2714, the method 2700 progresses back to step 2704.

FIGURE 28 illustrates a matrix 2800 of possible Multi-STA BRP cases and provides reference between the cases and the related figures of this disclosure. The embodiment of the matrix 2800 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

FIGURE 29 illustrates an operation of a control node in a wireless communication system according to this disclosure. FIGURE 29 exemplifies a method for operating an AP or a terminal functioning as the AP (i.e., a PCP).

Referring FIGURE 29, in step 2901, the control node transmits a control information on beam refinements for a plurality of terminals. The control information may includes at least one of a duration per frame, a duration for a feedback, an identification of the control node, identifications of the terminals, a number of frame transmissions, and a type of the beam refinements. The control information is transmitted to change a wide beam into a sector beam, the sector beam into a narrow beam, or a current beam into different beam. That is, the beam refinements comprises one of narrowing a beam width, and changing a current beam into different beam having same beam width.

In step 2903, the control node transmits frames for the beam refinements. The frames are beamformed with at least one beam which includes optimal beams for the plurality of terminals. At this time, if the optimal beams are different from each other, then the frames are multiple transmit-beamformed with a plurality transmit-beams. That is, the control node may form a plurality of transmit-beams simultaneously. Accordingly, a plurality of terminal may perform the beam refinements in parallel.

An embodiment described in conjunction with FIGURE 29 is related to beam refinements for the terminals. In another embodiment, similar procedure is utilized for a beam refinements for the control node. Specifically, the control information transmitted in step 2901 includes information on frames to be transmitted by the terminals. Further, in step 2903, the control node may receive the frames that are repeatedly transmitted by each of the terminals. During receiving the frames, the control node may sweep receive-beams. In another embodiment, similar procedure is utilized for a beam tracking.

FIGURE 30 illustrates a differnt operation of a control node in a wireless communication system according to this disclosure. FIGURE 30 exemplifies a method for operating an AP or a terminal functioning as the AP (i.e., a PCP).

Referring FIGURE 30, in step 3001, the control node determines a set of terminals for a multi-terminal (e.g., multi-STA) beam refinement. The set of terminals may be determined based on various criteria. For example, the control node may determines the set of terminal based on at least one of optimal sectors for transmission to the terminals, and capabilities of the terminals to provide multi-terminal support.

In step 3003, the control node transmits a control information on beam refinements for a plurality of terminals. The control information may includes at least one of a duration per frame, a duration for a feedback, an identification of the control node, identifications of the terminals, a number of frame transmissions, and a type of the beam refinements.

In step 3005, the control node receives feedback signals from the terminals. Each of the feedback signal informs whether an additional frame transmission is required or not. At this time, a terminal among the terminals may request the additional frame transmissions, and another terminal may not request the additional frame transmissions. Whether to request the additional frame transmission depends on a beam width, a number of beams needed to complete receive-beam sweeping and so on.

In step 3007, the control node determines whether the additional frame transmission is required or not. The control node may determines whether the additional frame transmission is required or not based on the feedback signals. For example, if any one of terminals transmits a feedback signal informing the additional frame transmission is required, the control node determined that the additional frame transmission is required. If the additional frame transmission is required, the control node proceeds step 3003 and transmits frames.

FIGURE 31 illustrates an operation of a terminal in a wireless communication system according to this disclosure. FIGURE 31 exemplifies a method for operating a terminal (e.g., a station).

Referring FIGURE 31, in step 3101, the terminal receives control information on beam refinements for a plurality of terminals including the terminal. The control information may includes at least one of a duration per frame, a duration for a feedback, an identification of the terminal, identifications of the terminals, a number of frame transmissions, and a type of the beam refinements. The control information is transmitted to change a wide beam into a sector beam, the sector beam into a narrow beam, or a current beam into different beam. That is, the beam refinements comprises one of narrowing a beam width, and changing a current beam into different beam having same beam width.

In step 3103, the terminal receives frames for the beam refinements from a control node. During receiving the frames, the terminal sweeps receive-beams in different directions. Accordingly the terminal may determine an optimal receive-beam. The frames are transmit-beamformed by the control node with at least one beam which includes optimal beams for the plurality of terminals. If the optimal transmit-beams for the plurality of terminals are different from each other, then the frames are multiple transmit-beamformed with a plurality of transmit-beams.

An embodiment described in conjunction with FIGURE 31 is related to beam refinements for the terminals. In another embodiment, similar procedure is utilized for a beam refinements for the terminal. Specifically, the control information transmitted in step 3101 includes information on frames to be transmitted by the terminals. Further, in step 3103, the terminal may repeatedly transmit the frames. In another embodiment, similar procedure is utilized for a beam tracking.

FIGURE 32 illustrates a different operation of a terminal in a wireless communication system according to this disclosure. FIGURE 32 exemplifies a method for operating a terminal (e.g., a station).

Referring FIGURE 32, the terminal receives frames for the beam refinements of a plurality of terminals including the terminal from a control node. During receiving the frames, the terminal sweeps receive-beams in different directions. Accordingly the terminal may determine an optimal receive-beam. The frames are transmit-beamformed by the control node with at least one beam which includes optimal beams for the plurality of terminals. If the optimal transmit-beams for the plurality of terminals are different from each other, then the frames are multiple transmit-beamformed with a plurality of transmit-beams. Before receiving the frames, the terminal may receive control information on beam refinements for the plurality of terminals. The control information may includes at least one of a duration per frame, a duration for a feedback, an identification of the terminal, identifications of the terminals, a number of frame transmissions, and a type of the beam refinements.

In step 3203, the terminal determines whether an additional frame transmission is required or not. In other words, the terminal determines whether a beam training is completed. Whether to request the additional frame transmission depends on a beam width, a number of beams needed to complete receive-beam sweeping and so on.

if the additional frame transmission is required, in step 3205, the terminal transmits a feedback signal to request the additional frame transmission to the control node. After then, the terminal proceeds step 3201 and further receives at least one frame.

if the additional frame transmission is not required, in step 3207, the terminal transmits a feedback signal informing a completion of the beam refinement to the control node. After then, the terminal proceeds step 3201 and further receives at least one frame. In other words, the terminal transmits the feedback signal informing that additional frame transmission is not required.

Embodiments of the present invention according to the claims and description in the specification can be realized in the form of hardware, software or a combination of hardware and software.

Such software may be stored in a computer readable storage medium. The computer readable storage medium stores one or more programs (software modules), the one or more programs comprising instructions, which when executed by one or more processors in an electronic device, cause the electronic device to perform methods of the present invention.

Such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a Read Only Memory (ROM), whether erasable or rewritable or not, or in the form of memory such as, for example, Random Access Memory (RAM), memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a Compact Disc (CD), Digital Video Disc (DVD), magnetic disk or magnetic tape or the like. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs comprising instructions that, when executed, implement embodiments of the present invention. Embodiments provide a program comprising code for implementing apparatus or a method as claimed in any one of the claims of this specification and a machine-readable storage storing such a program. Still further, such programs may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.

Claims

A method for operating a control node in wireless communication system, the method comprising:

transmitting a control information on beam refinements for a plurality of terminals; and

transmitting frames for the beam refinements,

wherein the frames are beamformed with at least one beam, and

wherein the at least one beam comprises optimal beams for the plurality of terminals.
The method of claim 1, further comprising:

receiving, from the plurality of terminals, feedback signals informing whether an additional frame transmission is required or not.
The method of claim 1, further comprising:

receiving, from the plurality of terminals, frames for a beam refinement of the control node,

wherein the frames are transmit-beamformed with each of optimal transmit-beams of the plurality of terminals, and receive-beamformed with a plurality of beams.
The method of claim 1, further comprising:

transmitting information on different beam refinements for tracking optimal receive-beams for the plurality of terminals, that are determined by the beam refinements;

sweeping a multiple beam patterns for the tracking; and

receiving, from the plurality of terminals, feedbacks informing an optimal transmit-beam of the control node.
An apparatus for a control node in wireless communication system, the apparatus comprising:

a transmitter configured to transmit a control information on beam refinements for a plurality of terminals, and to transmit frames for the beam refinements,

wherein the frames are beamformed with at least one beam, and

wherein the at least one beam comprises optimal beams for the plurality of terminals.
The apparatus of claim 5, further comprising:

a controller configured to control implement a method of one of claims 2 to 4.
A method for operating a terminal in wireless communication system, the method comprising:

receiving a control information on beam refinements for a plurality of terminals including the terminal; and

receiving frames for the beam refinements,

wherein the frames are beamformed with at least one beam, and

wherein the at least one beam comprises optimal beams for the plurality of terminals.
The method of claim 7, further comprising:

transmitting a feedback signal informing whether an additional frame transmission is required or not.
The method of claim 7, further comprising:

transmitting frames for a beam refinement of the control node,

wherein the frames are transmit-beamformed with an optimal transmit-beam of the terminal, and receive-beamformed with a plurality of beams by the control node.
The method of claim 7, further comprising:

receiving information on different beam refinements for tracking optimal receive-beams for the plurality of terminals, that are determined by the beam refinements;

receiving frames beamformed with a multiple beam patterns for the tracking; and

transmitting a feedback informing an optimal transmit-beam of the control node.
An apparatus for a terminal in wireless communication system, the apparatus comprising:

a receiver configured to receive a control information on beam refinements for a plurality of terminals including the terminal, and to receive frames for the beam refinements,

wherein the frames are beamformed with at least one beam, and

wherein the at least one beam comprises optimal beams for the plurality of terminals.
The apparatus of claim 11, further comprising:

a controller configured to control implement a method of one of claims 8 to 10.
The method of claim 1, the apparatus of claim 5, the method of claim 7 or the apparatus of claim 11, wherein the optimal beams are different from each other, and

wherein the frames are multiple transmit-beamformed with a plurality transmit-beams.
The method of claim 1, the apparatus of claim 5, the method of claim 7 or the apparatus of claim 11, wherein the control information comprises at least one of a duration per frame, a duration for a feedback, an identification of the control node, identifications of the terminals, a number of frame transmissions, and a type of the beam refinements.
The method of claim 1, the apparatus of claim 5, the method of claim 7 or the apparatus of claim 11, wherein the beam refinements comprises one of narrowing a beam width, and changing a current beam into different beam having same beam width.