U.S. patent application number 17/473506 was filed with the patent office on 2021-12-30 for beamforming methods and methods for using beams.
This patent application is currently assigned to INTERDIGITAL PATENT HOLDINGS, INC.. The applicant listed for this patent is INTERDIGITAL PATENT HOLDINGS, INC.. Invention is credited to Monisha Ghosh, Hanqing Lou, Robert L. Olesen, Oghenekome Oteri, Pengfei Xia.
Application Number | 20210409969 17/473506 |
Document ID | / |
Family ID | 1000005836371 |
Filed Date | 2021-12-30 |
United States Patent
Application |
20210409969 |
Kind Code |
A1 |
Lou; Hanqing ; et
al. |
December 30, 2021 |
BEAMFORMING METHODS AND METHODS FOR USING BEAMS
Abstract
A method, apparatus, system, and computer readable medium may be
used to perform beamforming. The method may include a first
communication device sending a first plurality of beamforming
training frames to a second communication device using a first
beamforming weight vector; the first communication device receiving
from the second communication device a second beamforming weight
vector; and the first communication device sending a second
plurality of beamforming training frames to the second
communication device using the second beamforming weight vector.
The apparatus, method, system, and computer readable media may use
spatial diversity with beam switching, spatial diversity with a
single beam, weighted multipath beamforming training, single user
spatial multiplexing, and beamforming training for beam division
multiple access (BDMA).
Inventors: |
Lou; Hanqing; (Syosset,
NY) ; Xia; Pengfei; (San Diego, CA) ; Ghosh;
Monisha; (Chicago, IL) ; Oteri; Oghenekome;
(San Diego, CA) ; Olesen; Robert L.; (Huntington,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERDIGITAL PATENT HOLDINGS, INC. |
Wilmington |
DE |
US |
|
|
Assignee: |
INTERDIGITAL PATENT HOLDINGS,
INC.
Wilmington
DE
|
Family ID: |
1000005836371 |
Appl. No.: |
17/473506 |
Filed: |
September 13, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14441237 |
May 7, 2015 |
11122444 |
|
|
PCT/US13/69265 |
Nov 8, 2013 |
|
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17473506 |
|
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|
61724679 |
Nov 9, 2012 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 16/28 20130101;
H04W 88/08 20130101; H04B 7/0452 20130101; H04B 7/0413 20130101;
H04W 72/0453 20130101; H04B 7/0417 20130101; H04B 7/0634 20130101;
H04B 7/0408 20130101 |
International
Class: |
H04W 16/28 20060101
H04W016/28; H04B 7/0408 20060101 H04B007/0408; H04B 7/0452 20060101
H04B007/0452; H04B 7/06 20060101 H04B007/06; H04B 7/0417 20060101
H04B007/0417; H04B 7/0413 20060101 H04B007/0413; H04W 72/04
20060101 H04W072/04 |
Claims
1. A method performed by a first station (STA) comprising a
plurality of antennas, the method comprising: partitioning the
plurality of antennas into at least a first group of antennas and a
second group of antennas, wherein the first group of antennas is
associated with a first sector to a second STA, and the second
group of antennas is associated with a second sector to the second
STA; transmitting, to the second STA, a plurality of beamforming
training frames using the first group of antennas and the second
group of antennas; receiving, from the second STA, a first
beamforming weight vector for sending signals on the first group of
antennas; and receiving, from the second STA, a second beamforming
weight vector for sending signals on the second group of antennas.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/441,237, filed May 7, 2015, which is a
national stage entry of PCT/US2013/69265, filed Nov. 8, 2013 which
claims the benefit of U.S. Provisional Application No. 61/724,679
filed on Nov. 9, 2012, which are incorporated by reference as if
fully set forth herein.
BACKGROUND
[0002] Some wireless communication networks support operation at
very high and even extremely high carrier frequencies such as 60
GHz and millimeter wave (mmW) frequency bands. These extremely high
carrier frequencies may support very high throughput such as up to
6 gigabits per second (Gbps). One of the challenges for wireless
communication at very high or extremely high carrier frequencies is
that a significant propagation loss may occur due to the high
carrier frequency. As the carrier frequency increases, the carrier
wavelength may decrease, and the propagation loss may increase as
well.
[0003] At mmW frequency bands, the propagation loss may be severe.
For example, the propagation loss may be on the order of 22 to 27
dB, relative to that observed in either the 2.4 GHz, or 5 GHz
bands. Since the available spectrum is limited, however, and since
users continue to demand more bandwidth, there is a need for
effectively using very high and extremely high carrier frequencies
for communication networks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1A is a system diagram of an example communications
system in which one or more disclosed embodiments may be
implemented;
[0005] FIG. 1B is a system diagram of an example wireless
transmit/receive unit (WTRU) that may be used within the
communications system illustrated in FIG. 1A;
[0006] FIG. 1C is a system diagram of an example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0007] FIG. 1D is a diagram of an example WLAN with an AP and STA
forming a BSS, and beamforming with multipath channels;
[0008] FIG. 1E is a diagram of another example WLAN with an AP and
STA forming a BSS, and beamforming with multiple channels;
[0009] FIG. 2 is a diagram of an example of a method using two STAs
to perform a multi-path beamforming method;
[0010] FIG. 3 is a diagram of an example of one iteration of the
multi-path beamforming method using BRP transactions;
[0011] FIG. 4 is a diagram of an example frame format of a BRP
packet;
[0012] FIG. 5 is a diagram of an example format of a BRP frame
Action field;
[0013] FIG. 6 is a diagram of an example modified channel
measurement feedback element;
[0014] FIG. 7 is a diagram of an example AP configured to perform a
transmission using full size beamforming with STBC;
[0015] FIG. 8 is a diagram of an example AP configured to perform a
transmission using partial size beamforming with STBC;
[0016] FIG. 9 is a diagram of an example transceiver
architecture;
[0017] FIG. 10 is a diagram of another example transceiver
architecture;
[0018] FIG. 11 is a diagram of an example beam division multiple
access (BDMA) architecture;
[0019] FIG. 12 is a diagram of an example beamforming training
method for BDMA;
[0020] FIG. 13 is a diagram of an example modified BRP procedure to
implement a multi-stage iterative beamforming training method for
BDMA;
[0021] FIG. 14 is a diagram of an example PHY layer frame
format;
[0022] FIG. 15 is a diagram of an example beamforming training
procedure using Eigen-beamforming based spatial multiplexing where
the communication devices may be configured to calibrate multiple
transmit RF chains;
[0023] FIG. 16 is a diagram of an example beamforming training
method for Type I devices and for Type II devices without
calibration;
[0024] FIG. 17 is a diagram of an example beamforming training
method for beam sweep based spatial multiplexing for Type I devices
with calibration between two TX chains;
[0025] FIG. 18 is a diagram of an example beamforming training
method for beam sweep based spatial multiplexing Type II devices
and Type I devices without calibration;
[0026] FIG. 19 is a diagram of an example modified FBCK-TYPE
subfield;
[0027] FIG. 20A is a diagram of an example PHY layer frame
format;
[0028] FIG. 20B is a diagram of another example PHY layer frame
format;
[0029] FIG. 20C is a diagram of another example PHY layer frame
format;
[0030] FIG. 21 is a diagram of an example modified SSW training
frames and sequence;
[0031] FIG. 22 is a diagram of an example SSWA frame format;
[0032] FIG. 23 is a diagram of an example early termination of the
SLS training procedure; and
[0033] FIG. 24 is a diagram of an example multi-beam multi-DMG
antenna SLS feedback method.
SUMMARY
[0034] A first communication device for beamforming may include a
plurality of antennas and a processor. The processor may be
configured to partition the antenna into at least a first group of
antennas and a second group of antennas. The processor may be
further configured to send a plurality of beamforming training
frames to a second communication device using the first group of
antennas and the second group of antennas. The processor and/or a
receiver may be configured to receive, from the second
communication device, a first beamforming weight vector for sending
signals on the first group of antennas and to receive a second
beamforming weight vector for sending signals on the second group
of antennas.
[0035] A method of beamforming training for beam division multiple
access (BDMA) may include an AP transmitting Nt sequences modulated
using Nt beamforming vectors. A first station may use a first
previous beamforming vector to receive the Nt sequences and
determine a first transmit beamforming weight from the AP to the
first station based on the first previous beamforming vector and
the received Nt sequences. The first station may send the
determined first transmit beamforming weight to the AP. A second
station may use a second previous beamforming vector to receive the
Nt sequences and determine a second transmit beamforming weight
from the AP to the first station based on the second previous
beamforming vector and the received Nt sequences. The second
station may send the determined second transmit beamforming weight
to the AP, and the AP may transmit one or more sequences modulated
based on the first transmit beamforming weight and the second
transmit beamforming weight.
[0036] A method and apparatus may be used for spatial diversity
with beam switching, spatial diversity with a single beam, weighted
multipath beamforming training, single user spatial multiplexing,
and for reduced beamforming training overhead.
DETAILED DESCRIPTION
[0037] FIG. 1A is a diagram of an example communications system 100
in which one or more disclosed embodiments may be implemented. The
communications system 100 may be a multiple access system that
provides content, such as voice, data, video, messaging, broadcast,
etc., to multiple wireless users. The communications system 100 may
enable multiple wireless users to access such content through the
sharing of system resources, including wireless bandwidth. For
example, the communications systems 100 may employ one or more
channel access methods, such as code division multiple access
(CDMA), time division multiple access (TDMA), frequency division
multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier
FDMA (SC-FDMA), and the like.
[0038] As shown in FIG. 1A, the communications system 100 may
include wireless transmit/receive units (WTRUs) 102a, 102b, 102c,
102d, a radio access network (RAN) 104, a core network 106, a
public switched telephone network (PSTN) 108, the Internet 110, and
other networks 112, though it will be appreciated that the
disclosed embodiments contemplate any number of WTRUs, base
stations, networks, and/or network elements. Each of the WTRUs
102a, 102b, 102c, 102d may be any type of device configured to
operate and/or communicate in a wireless environment. By way of
example, the WTRUs 102a, 102b, 102c, 102d may be configured to
transmit and/or receive wireless signals and may include user
equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a smartphone, a laptop, a netbook, a personal computer, a
wireless sensor, consumer electronics, and the like.
[0039] The communications systems 100 may also include a base
station 114a and a base station 114b. Each of the base stations
114a, 114b may be any type of device configured to wirelessly
interface with at least one of the WTRUs 102a, 102b, 102c, 102d to
facilitate access to one or more communication networks, such as
the core network 106, the Internet 110, and/or the networks 112. By
way of example, the base stations 114a, 114b may be a base
transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a
Home eNode B, a site controller, an access point (AP), a wireless
router, and the like. While the base stations 114a, 114b are each
depicted as a single element, it will be appreciated that the base
stations 114a, 114b may include any number of interconnected base
stations and/or network elements.
[0040] The base station 114a may be part of the RAN 104, which may
also include other base stations and/or network elements (not
shown), such as a base station controller (BSC), a radio network
controller (RNC), relay nodes, etc. The base station 114a and/or
the base station 114b may be configured to transmit and/or receive
wireless signals within a particular geographic region, which may
be referred to as a cell (not shown). The cell may further be
divided into cell sectors. For example, the cell associated with
the base station 114a may be divided into three sectors. Thus, in
one embodiment, the base station 114a may include three
transceivers, i.e., one for each sector of the cell. In another
embodiment, the base station 114a may employ multiple-input
multiple output (MIMO) technology and, therefore, may utilize
multiple transceivers for each sector of the cell.
[0041] The base stations 114a, 114b may communicate with one or
more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116,
which may be any suitable wireless communication link (e.g., radio
frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible
light, etc.). The air interface 116 may be established using any
suitable radio access technology (RAT).
[0042] More specifically, as noted above, the communications system
100 may be a multiple access system and may employ one or more
channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA,
and the like. For example, the base station 114a in the RAN 104 and
the WTRUs 102a, 102b, 102c may implement a radio technology such as
Universal Mobile Telecommunications System (UMTS) Terrestrial Radio
Access (UTRA), which may establish the air interface 116 using
wideband CDMA (WCDMA). WCDMA may include communication protocols
such as High-Speed Packet Access (HSPA) and/or Evolved HSPA
(HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA)
and/or High-Speed Uplink Packet Access (HSUPA).
[0043] In another embodiment, the base station 114a and the WTRUs
102a, 102b, 102c may implement a radio technology such as Evolved
UMTS Terrestrial Radio Access (E-UTRA), which may establish the air
interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced
(LTE-A).
[0044] In other embodiments, the base station 114a and the WTRUs
102a, 102b, 102c may implement radio technologies such as IEEE
802.16 (i.e., Worldwide Interoperability for Microwave Access
(WiMAX)), CDMA2000, CDMA2000 1.times., CDMA2000 EV-DO, Interim
Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim
Standard 856 (IS-856), Global System for Mobile communications
(GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE
(GERAN), and the like.
[0045] The base station 114b in FIG. 1A may be a wireless router,
Home Node B, Home eNode B, or access point, for example, and may
utilize any suitable RAT for facilitating wireless connectivity in
a localized area, such as a place of business, a home, a vehicle, a
campus, and the like. In one embodiment, the base station 114b and
the WTRUs 102c, 102d may implement a radio technology such as IEEE
802.11 to establish a wireless local area network (WLAN). In
another embodiment, the base station 114b and the WTRUs 102c, 102d
may implement a radio technology such as IEEE 802.15 to establish a
wireless personal area network (WPAN). In yet another embodiment,
the base station 114b and the WTRUs 102c, 102d may utilize a
cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.)
to establish a picocell or femtocell. As shown in FIG. 1A, the base
station 114b may have a direct connection to the Internet 110.
Thus, the base station 114b may not be required to access the
Internet 110 via the core network 106.
[0046] The RAN 104 may be in communication with the core network
106, which may be any type of network configured to provide voice,
data, applications, and/or voice over internet protocol (VoIP)
services to one or more of the WTRUs 102a, 102b, 102c, 102d. For
example, the core network 106 may provide call control, billing
services, mobile location-based services, pre-paid calling,
Internet connectivity, video distribution, etc., and/or perform
high-level security functions, such as user authentication.
Although not shown in FIG. 1A, it will be appreciated that the RAN
104 and/or the core network 106 may be in direct or indirect
communication with other RANs that employ the same RAT as the RAN
104 or a different RAT. For example, in addition to being connected
to the RAN 104, which may be utilizing an E-UTRA radio technology,
the core network 106 may also be in communication with another RAN
(not shown) employing a GSM radio technology.
[0047] The core network 106 may also serve as a gateway for the
WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet
110, and/or other networks 112. The PSTN 108 may include
circuit-switched telephone networks that provide plain old
telephone service (POTS). The Internet 110 may include a global
system of interconnected computer networks and devices that use
common communication protocols, such as the transmission control
protocol (TCP), user datagram protocol (UDP) and the internet
protocol (IP) in the TCP/IP internet protocol suite. The networks
112 may include wired or wireless communications networks owned
and/or operated by other service providers. For example, the
networks 112 may include another core network connected to one or
more RANs, which may employ the same RAT as the RAN 104 or a
different RAT.
[0048] Some or all of the WTRUs 102a, 102b, 102c, 102d in the
communications system 100 may include multi-mode capabilities,
i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple
transceivers for communicating with different wireless networks
over different wireless links. For example, the WTRU 102c shown in
FIG. 1A may be configured to communicate with the base station
114a, which may employ a cellular-based radio technology, and with
the base station 114b, which may employ an IEEE 802 radio
technology.
[0049] FIG. 1B is a system diagram of an example WTRU 102. As shown
in FIG. 1B, the WTRU 102 may include a processor 118, a transceiver
120, a transmit/receive element 122, a speaker/microphone 124, a
keypad 126, a display/touchpad 128, non-removable memory 106,
removable memory 132, a power source 134, a global positioning
system (GPS) chipset 136, and other peripherals 138. It will be
appreciated that the WTRU 102 may include any sub-combination of
the foregoing elements while remaining consistent with an
embodiment.
[0050] The processor 118 may be a general purpose processor, a
special purpose processor, a conventional processor, a digital
signal processor (DSP), a plurality of microprocessors, one or more
microprocessors in association with a DSP core, a controller, a
microcontroller, Application Specific Integrated Circuits (ASICs),
Field Programmable Gate Array (FPGAs) circuits, any other type of
integrated circuit (IC), a state machine, and the like. The
processor 118 may perform signal coding, data processing, power
control, input/output processing, and/or any other functionality
that enables the WTRU 102 to operate in a wireless environment. The
processor 118 may be coupled to the transceiver 120, which may be
coupled to the transmit/receive element 122. While FIG. 1B depicts
the processor 118 and the transceiver 120 as separate components,
it will be appreciated that the processor 118 and the transceiver
120 may be integrated together in an electronic package or
chip.
[0051] The transmit/receive element 122 may be configured to
transmit signals to, or receive signals from, a base station (e.g.,
the base station 114a) over the air interface 116. For example, in
one embodiment, the transmit/receive element 122 may be an antenna
configured to transmit and/or receive RF signals. In another
embodiment, the transmit/receive element 122 may be an
emitter/detector configured to transmit and/or receive IR, UV, or
visible light signals, for example. In yet another embodiment, the
transmit/receive element 122 may be configured to transmit and
receive both RF and light signals. It will be appreciated that the
transmit/receive element 122 may be configured to transmit and/or
receive any combination of wireless signals.
[0052] In addition, although the transmit/receive element 122 is
depicted in FIG. 1B as a single element, the WTRU 102 may include
any number of transmit/receive elements 122. More specifically, the
WTRU 102 may employ MIMO technology. Thus, in one embodiment, the
WTRU 102 may include two or more transmit/receive elements 122
(e.g., multiple antennas) for transmitting and receiving wireless
signals over the air interface 116.
[0053] The transceiver 120 may be configured to modulate the
signals that are to be transmitted by the transmit/receive element
122 and to demodulate the signals that are received by the
transmit/receive element 122. As noted above, the WTRU 102 may have
multi-mode capabilities. Thus, the transceiver 120 may include
multiple transceivers for enabling the WTRU 102 to communicate via
multiple RATs, such as UTRA and IEEE 802.11, for example.
[0054] The processor 118 of the WTRU 102 may be coupled to, and may
receive user input data from, the speaker/microphone 124, the
keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal
display (LCD) display unit or organic light-emitting diode (OLED)
display unit). The processor 118 may also output user data to the
speaker/microphone 124, the keypad 126, and/or the display/touchpad
128. In addition, the processor 118 may access information from,
and store data in, any type of suitable memory, such as the
non-removable memory 106 and/or the removable memory 132. The
non-removable memory 106 may include random-access memory (RAM),
read-only memory (ROM), a hard disk, or any other type of memory
storage device. The removable memory 132 may include a subscriber
identity module (SIM) card, a memory stick, a secure digital (SD)
memory card, and the like. In other embodiments, the processor 118
may access information from, and store data in, memory that is not
physically located on the WTRU 102, such as on a server or a home
computer (not shown).
[0055] The processor 118 may receive power from the power source
134, and may be configured to distribute and/or control the power
to the other components in the WTRU 102. The power source 134 may
be any suitable device for powering the WTRU 102. For example, the
power source 134 may include one or more dry cell batteries (e.g.,
nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride
(NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and
the like.
[0056] The processor 118 may also be coupled to the GPS chipset
136, which may be configured to provide location information (e.g.,
longitude and latitude) regarding the current location of the WTRU
102. In addition to, or in lieu of, the information from the GPS
chipset 136, the WTRU 102 may receive location information over the
air interface 116 from a base station (e.g., base stations 114a,
114b) and/or determine its location based on the timing of the
signals being received from two or more nearby base stations. It
will be appreciated that the WTRU 102 may acquire location
information by way of any suitable location-determination method
while remaining consistent with an embodiment.
[0057] The processor 118 may further be coupled to other
peripherals 138, which may include one or more software and/or
hardware modules that provide additional features, functionality
and/or wired or wireless connectivity. For example, the peripherals
138 may include an accelerometer, an e-compass, a satellite
transceiver, a digital camera (for photographs or video), a
universal serial bus (USB) port, a vibration device, a television
transceiver, a hands free headset, a Bluetooth.RTM. module, a
frequency modulated (FM) radio unit, a digital music player, a
media player, a video game player module, an Internet browser, and
the like.
[0058] FIG. 1C is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. As noted above, the RAN 104
may employ an E-UTRA radio technology to communicate with the WTRUs
102a, 102b, 102c over the air interface 116. The RAN 104 may also
be in communication with the core network 106.
[0059] The RAN 104 may include eNode-Bs 140a, 140b, 140c, though it
will be appreciated that the RAN 104 may include any number of
eNode-Bs while remaining consistent with an embodiment. The
eNode-Bs 140a, 140b, 140c may each include one or more transceivers
for communicating with the WTRUs 102a, 102b, 102c over the air
interface 116. In one embodiment, the eNode-Bs 140a, 140b, 140c may
implement MIMO technology. Thus, the eNode-B 140a, for example, may
use multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a.
[0060] Each of the eNode-Bs 140a, 140b, 140c may be associated with
a particular cell (not shown) and may be configured to handle radio
resource management decisions, handover decisions, scheduling of
users in the uplink and/or downlink, and the like. As shown in FIG.
1C, the eNode-Bs 140a, 140b, 140c may communicate with one another
over an X2 interface.
[0061] The core network 106 shown in FIG. 1C may include a mobility
management gateway (MME) 142, a serving gateway 144, and a packet
data network (PDN) gateway 146. While each of the foregoing
elements are depicted as part of the core network 106, it will be
appreciated that any one of these elements may be owned and/or
operated by an entity other than the core network operator.
[0062] The MME 142 may be connected to each of the eNode-Bs 142a,
142b, 142c in the RAN 104 via an S1 interface and may serve as a
control node. For example, the MME 142 may be responsible for
authenticating users of the WTRUs 102a, 102b, 102c, bearer
activation/deactivation, selecting a particular serving gateway
during an initial attach of the WTRUs 102a, 102b, 102c, and the
like. The MME 142 may also provide a control plane function for
switching between the RAN 104 and other RANs (not shown) that
employ other radio technologies, such as GSM or WCDMA.
[0063] The serving gateway 144 may be connected to each of the
eNode Bs 140a, 140b, 140c in the RAN 104 via the S1 interface. The
serving gateway 144 may generally route and forward user data
packets to/from the WTRUs 102a, 102b, 102c. The serving gateway 144
may also perform other functions, such as anchoring user planes
during inter-eNode B handovers, triggering paging when downlink
data is available for the WTRUs 102a, 102b, 102c, managing and
storing contexts of the WTRUs 102a, 102b, 102c, and the like.
[0064] The serving gateway 144 may also be connected to the PDN
gateway 146, which may provide the WTRUs 102a, 102b, 102c with
access to packet-switched networks, such as the Internet 110, to
facilitate communications between the WTRUs 102a, 102b, 102c and
IP-enabled devices. An access router (AR) 150 of a wireless local
area network (WLAN) 155 may be in communication with the Internet
110. The AR 150 may facilitate communications between APs 160a,
160b, and 160c. The APs 160a, 160b, and 160c may be in
communication with STAs 170a, 170b, and 170c.
[0065] The core network 106 may facilitate communications with
other networks. For example, the core network 106 may provide the
WTRUs 102a, 102b, 102c with access to circuit-switched networks,
such as the PSTN 108, to facilitate communications between the
WTRUs 102a, 102b, 102c and traditional land-line communications
devices. For example, the core network 106 may include, or may
communicate with, an IP gateway (e.g., an IP multimedia subsystem
(IMS) server) that serves as an interface between the core network
106 and the PSTN 108. In addition, the core network 106 may provide
the WTRUs 102a, 102b, 102c with access to the networks 112, which
may include other wired or wireless networks that are owned and/or
operated by other service providers.
[0066] FIG. 1D is a diagram of an example use of beamforming in a
WLAN 185. The WLAN 185 may include an AP 190 and an STA 192 forming
a BSS. FIG. 1E is a diagram of an example use of beamforming using
spatial diversity or multipath diversity in the WLAN 185. The WLAN
185 may include an AP 190 and an STA 192 forming a BSS. A WLAN in a
Infrastructure Basic Service Set (BSS) mode has an Access Point
(AP) 190 for the BSS and one or more stations (STAs) 192 associated
with the AP. The AP 190 may have an access, or interface, to a
Distribution System (DS) 195, or another type of wired/wireless
network that carries traffic in and out of the BSS. Traffic to STAs
that originates from outside the BSS may arrive through the AP to
be delivered to the STAs. Traffic originating from STAs to
destinations outside the BSS may be sent to the AP to be delivered
to the respective destinations. Traffic between STAs within the BSS
may also be sent through the AP where the source STA may send
traffic to the AP and the AP may deliver the traffic to the
destination STA. Such traffic between STAs within a BSS may be
peer-to-peer traffic. Such peer-to-peer traffic may also be sent
directly between the source and destination STAs with a direct link
setup (DLS) using an 802.11e DLS or an 802.11z tunneled DLS (TDLS).
A WLAN using an Independent BSS (IBSS) mode has no AP, and/or STAs,
communicating directly with each other. This mode of communication
may be referred to as an "ad-hoc" mode of communication.
[0067] As used herein an STA 192 may include, but is not limited
to, a WTRU 102, an AP, or a communication device. Using the 802.11
infrastructure mode of operation, the AP 190 may transmit a beacon
on a fixed channel, usually the primary channel. This channel may
be 20 MHz wide, and may be the operating channel of the BSS. This
channel may also be used by the STAs to establish a connection with
the AP. The fundamental channel access mechanism in an 802.11
system may be Carrier Sense Multiple Access with Collision
Avoidance (CSMA/CA). In this mode of operation, every STA,
including the AP, may sense the primary channel. If the channel is
detected to be busy, the STA may back off. Hence only one STA may
transmit at any given time in a given BSS.
[0068] In an 802.11n example, High Throughput (HT) STAs may also
use a 40 MHz wide channel for communication. This 40 MHz wide
channel may be achieved by combining the primary 20 MHz channel,
with an adjacent 20 MHz channel to form a 40 MHz wide contiguous
channel. 802.11n may operate on the 2.4 GHz, and 5 GHz ISM
bands.
[0069] In an 802.11ac example, Very High Throughput (VHT) STAs may
support 20 MHz, 40 MHz, 80 MHz, and 160 MHz wide channels. The 40
MHz, and 80 MHz, channels may be formed by combining contiguous 20
MHz channels similar to 802.11n described above. A 160 MHz channel
may be formed either by combining 8 contiguous 20 MHz channels, or
by combining two non-contiguous 80 MHz channels, this may also be
referred to as an 80+80 configuration. For the 80+80 configuration,
the data, after channel encoding, is passed through a segment
parser that may divide it into two streams. IFFT and time domain
processing are done on each stream separately. The streams may then
be mapped on two channels, and the data may be transmitted. At the
receiver, this process may be reversed, and the combined data may
be sent to the MAC. 802.11ac may operate only on the 5 GHz ISM
band, and consequently may not be backward compatible with 802.11n
modes of operation in the 2.4 GHz ISM band. For the examples
described herein, any combination of channels may be used, and
should not be limited to contiguous and non-contiguous
channels.
[0070] Sub 1 GHz modes of operation may be supported by 802.11af,
and 802.11ah. For these specifications the channel operating
bandwidths may be reduced relative to those used in 802.11n, and
802.11ac. 802.11af may support 5 MHz, 10 MHz and 20 MHz bandwidths
in the TV White Space (TVWS) spectrum, and 802.11ah may support 1
MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using a non-TVWS
spectrum. A possible use case for 802.11ah may support Meter Type
Control (MTC) devices in a macro coverage area. MTC devices may
have limited capabilities including only support for limited
bandwidths, but also may include a requirement for a very long
battery life. 802.11ah may also be used for macro coverage as
support for cellular offload to WiFi.
[0071] In 802.11ad, wide bandwidth spectrum at 60 GHz may be
available, thus enabling very high throughput operation. 802.11ad
may support up to 2 GHz operating bandwidths and the data rate may
reach up to 6 Gbps. Since the propagation loss at 60 GHz may be
more significant than at the 2.4 GHz, and 5 GHz bands, beamforming
may be adopted in 802.11ad as a means to extend the coverage range.
To support the receiver requirements for this band, the 802.11ac
MAC layer may be modified in several areas. An important
modification for the 802.11ad MAC layer may include procedures that
allow channel estimation and training. These procedures may include
omni, and beamformed modes of operation which do not exist in
802.11ac.
[0072] WLAN systems that support multiple channels and channel
widths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, may
include a channel designated as the primary channel. The primary
channel may, but not necessarily, have a bandwidth equal to the
largest common operating bandwidth supported by all STAs in the
BSS. The bandwidth of the primary channel may therefore be limited
by the STA, of all the STAs operating in a BSS, which supports or
enables the use of the smallest bandwidth operating mode. In the
example of 802.11ah, the primary channel may be 1 MHz wide if there
are STAs, for example, MTC type devices that only support a 1 MHz
mode, even if the AP, and other STAs in the BSS, may support a 2
MHz, 4 MHz, 8 MHz, 16 MHz, or other channel bandwidth operating
modes. All carrier sensing and NAV settings may depend on the
status of the primary channel. For example, if the primary channel
is busy due to a STA supporting only a 1 MHz operating mode, then
the entire available frequency bands may be considered busy even
though a majority of the frequency bands remain idle and
available.
[0073] In the United States, for example, the available frequency
bands that may be used by 802.11ah are from 902 MHz to 928 MHz. In
Korea, for example, the available frequency bands may be from 917.5
MHz to 923.5 MHz, and in Japan, it may be from 916.5 MHz to 927.5
MHz. The total bandwidth available for 802.11ah may be 6 MHz to 26
MHz depending on the country.
[0074] One of the challenges for wireless communication over 60 GHz
may include significant propagation loss due to the high frequency.
As the wavelength decreases, the free space propagation loss may
increase. To address the range limitation due to this propagation
loss, 802.11ad may use beamforming to increase the Effective
Radiated Power (ERP) of the transmissions. Since the wavelength is
small, it may be possible to use a large antenna array to get a
very high beamformed antenna gain. The beam in 802.11ad may be
electronically steered to a particular STA, or group of STAs,
during association with the STAs.
[0075] In order to support beamforming, the 802.11ad PHY and MAC
specifications may be modified to support directional
transmissions, and millimeter wave (mmW) antenna training
procedures. A comprehensive beamforming training protocol may be
defined in 802.11ad. The beamforming training protocol may include
two components, for example 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 enable receive beamforming training and iterative refinement of
both the transmit and receive beams.
[0076] In order to reduce implementation complexity, 802.11ad may
support beam switching at both the AP and the STA. The beam
switching at both the AP and the STA may be in contrast to more
advanced multi-antenna schemes, and may assume that a single RF
front-end is available at both ends. Problems related to link
robustness and spectral efficiency may be of importance for
enabling 802.11ad+ to address the current trend for a Carrier Grade
WiFi service. A Carrier Grade WiFi service may be referred to as 5G
Carrier Grade WiFi, may provide high air interference efficiency
for multiple users, and a stable "cellular-like" quality. A 5G
Carrier Grade WiFi system may support robust and dynamic
deployments, for example dense deployments and flash crowds.
[0077] Although 802.11ad may address the need for a very high peak
throughput, limitations due to the propagation environment are not
adequately addressed in 802.11ad.
[0078] For mmW communications it may be necessary to handle a
propagation loss due in part to the high free space propagation
loss which may occur at mmW frequencies. For example, blockage of
transmissions by the human body may attenuate a signal by 15 to 25
dB for hundreds of milliseconds.
[0079] While propagation loss of walls and other indoor obstacles
may prevent the propagation of mmW through them, indoor Line of
Site (LOS) propagation may occur indoors. LOS propagation may occur
indoors either due to a direct line of sight transmission, or due
to reflections off walls and other obstacles. It should be noted
that non-negligible propagation loss at mmW frequencies may occur
due to walls and other environmental factors. Beam switching may be
used in 802.11ad to utilize signal diversity due to these
reflections.
[0080] Some mmW communications may utilize a single beam for
communications, for example, in 802.11ad. MIMO techniques, such as
spatial multiplexing, may be employed to improve the spectral
efficiency of the system, however it may be difficult to use these
techniques in mmW systems due to the need for multiple symbol
generation. Methods that improve the spectral efficiency of mmW
systems, such as methods that enable the use of spatial
multiplexing, may be needed in future mmW specifications which for
example may be based on 802.11ad, and/or in mmW systems in
general.
[0081] Beamforming training protocols, such as SLS and BRP, may be
used to perform transmit/receive beamforming training and iterative
beam refinement training. The beamforming training overhead and
latency of these procedures, however, may be significant. For
example, with the transmit beamforming training defined in SLS, the
transmitter may need to transmit multiple sector sweep (SSW) frames
that may be modulated by different beamforming sectors. Each device
may have up to 64 different beam sectors. Each SSW frame may
include a full PLCP header, which may include a preamble, one or
more header blocks, and a MAC frame. In order to fully exploit the
beamforming gain, transmit and receive training procedures at both
peer devices may be required, and an iterative beam refinement may
also be needed. These procedures may represent a significant
overhead and hence methods that reduce this overhead may be needed
in part to allow for a better user experience in mmW systems.
[0082] Referring back to FIGS. 1D and 1E, multipath propagation may
be common in indoor communications links. Beam switching based
beamforming algorithms utilized in the current 802.11ad
specification may attempt to point the beam to the strongest path.
As shown in FIG. 1D, a LOS path and a strong reflection path may
exist between AP 190 and STA 192. After the beamforming training
procedure, the beam with the best channel gain may be selected.
This beam may be formed towards the strongest path among multiple
propagation paths. However, human blockage may introduce an average
20 dB loss for 230 ms, which may prevent the 60 GHz radio to
provide multi-Gigabit/sec data transmissions. It is therefore
highly likely that the beamformed link may be dropped, and hence
the transmitted packet during this period would be lost. Moreover,
due to the loss of the packet, the system may have to repeat the
beamforming training and then retransmit the packet over a
potentially new beam.
[0083] Example beamforming schemes may exploit the spatial
diversity such that the transmission is not dependent on only the
strongest path. As shown in FIG. 1E, with two strong propagation
paths, for example, a LOS path and a strong reflection path, a
number of solutions may be possible including fast beam switching,
wider beam and multi-beam methods.
[0084] Spatial diversity may be achieved with fast beam switching.
In order to accomplish fast beam switching when the channel
condition changes, it may be necessary that both AP and STA have an
available list of weight vectors/beam identifiers. Example methods
for obtaining a list of weight vectors/beam identifiers are
disclosed below. There may be two possibilities for fast-beam
switching including in-band signaling and out-of-band signaling.
In-band beam switching may be used in some examples.
[0085] In an in-band beam switching example, the AP may be
communicating with the STA using a beam set (Tx and Rx beams) B1.
The AP and STA may have prioritized the beam sets according to the
received SNR, or SINR, during the SLS and BRP phases. The STA may
monitor one or more of the received SNR, SINR, Bit-Error-Rate (BER)
or Packet Error Rate (PER), acknowledgement (ACK) statistics or a
combination of these parameters. If, at the end of a packet
reception, the STA determines that the channel quality is
deteriorating, it may append a message to the ACK packet requesting
the AP to switch to the next best beam set, for example B2, for the
next transmitted packet. The assumption here is that the channel
condition may be deteriorating, but not to the point that the data
packet cannot be decoded correctly and hence an ACK may be
sent.
[0086] In another example, alternative beam retransmission methods
may be used. In 802.11 systems, and mmW systems in particular, if
no ACK is received, the data packet may be retransmitted. This
retransmission may use the same beam that was used in the prior
transmission. An example for an alternative procedure may be that
if the AP does not receive an ACK, the AP may retransmit the data
packet using the beam set B2 instead of the beam set B1. Since
these beam sets may have been defined prior to this procedure,
possibly during association of the STA with the AP, the procedure
at the STA may use the corresponding receive beam set B2 for
reception of the retransmission from the AP. In an example
procedure, the AP and the STA may define an association of indices
to beam sets, and subsequently use the beam set indices for
identification of beam sets in the aforementioned procedures.
[0087] In an alternative, or additional example, the AP may cycle
the data packet through the N best beam-sets. The STA may then
perform a procedure wherein it receives N packets from the AP, and
perform maximum-ratio-combining, selection combining, or a similar
receive algorithm, on these packets. An ACK may then be determined
and sent to the AP, for example, after all N transmissions have
occurred, or as soon as the packet has been successfully received
and decoded.
[0088] In an alternative, or additional example, the AP may also
transmit the data packet through all of, or a subset of, the N
beam-sets simultaneously. The remainder of the procedure described
in the previous paragraph may then follow in a similar way.
[0089] A beam set may include the identification of a primary beam
within the beam set. The primary beam may be used by transmission
procedures at the AP, STA, or both, as the beam to be used for
initial attempts at wireless communication. Alternatively, the
primary beam may be used exclusively for transmission of control or
scheduling information. More than one primary beam may be used for
more than one STA wherein each primary beam may be associated with
a particular STA.
[0090] In an alternative, or in addition to, the AP may also cycle
through different modes of MIMO operation for each beam set, prior
to proceeding to the next beam set. For example, if the AP does not
receive an ACK on beam set B1 it may select a more robust form of
operation such as Space Time Block Coding (STBC), Space Frequency
Block Coding (SFBC), or Cyclic Delay Diversity (CDD), before
proceeding to transmit on the remaining beam sets B2 through
BN.
[0091] In some examples, a first and second best beam transmission
method may be used. For example, the STA may determine the two best
beams, B1, B2, using a procedure similar to the above, and
recommend these beam indices to the AP. In this example, for the
remainder of the communication interval, the AP and the STA may
assume that either, or both, beam indices may be used for wireless
communication.
[0092] The AP may then determine to transmit on either beam during
a particular transmission time interval (TTI) based on one or more
criteria determined by the AP. Example criteria may include one or
more of the received SNR, or SINR, Bit-Error-Rate (BER), or Packet
Error Rate (PER), acknowledgement (ACK) statistics, or a
combination of these criteria. The STA may respond to a message
from the AP with an indication of the reception quality, or similar
metric, for the beam that it used to receive the message from the
AP. This indication or metric may be indicated in the response by
the beam index.
[0093] Alternatively, if the STA does not provide an indication of
the reception quality in its ACK and/or any other packet to the AP,
the AP may determine that the reception quality was acceptable for
one or more associated beams. If the STA indicates a poor reception
quality to the AP for B1, it may assume that the next transmission
from the AP will use the second best beam B2.
[0094] During communication with the STA, the AP may store the
packet reception quality for each transmission, on each beam, in a
memory, while using either beam. If a particular beam in the pair
becomes unusable for further communication, the AP may identify a
new first, or a second best beam for communication with the STA,
while at the same time continuing communication on the remaining
beam of the original beam pair. Other combinations of the
procedures described in this example may be possible. The above
example is not limited to a pair of beams and may be extended to
support any number of beams greater than one that the system may
simultaneously support.
[0095] Some examples may use out of band beam switching. For
example, the AP and STA may both have multi-band capability. In
this example, the AP and the STA may communicate over either a 2.4
GHz or a 5 GHz link in addition to a directional 60 GHz link. The
AP and the STA may use one or more of the sub-6 GHz links as an
alternate link to signal to each other that the beam set needs to
switch to the next best beam set at the beginning of the next data
packet. This example procedure may allow for a fast beam switch to
occur even if the packet currently being transmitted is not decoded
correctly.
[0096] Some examples may implement spatial diversity using a single
beam. For example, it may be possible that only one RF chain is
available at both transmitter and receiver, such that only one data
stream may be transmitted and received at the same time. This RF
chain arrangement may be used in mmW systems. With one RF chain,
devices may form one beam and transmit the data stream toward the
direction specified by the beam. In this example, the devices may
forming a beam pointing to a propagation path with the strongest
channel gain. Multipath wireless channels, however, may introduce
frequency selectivity. A beamforming weight may benefit some
frequency tones, however, it may have a detrimental effect for one
or more of the other set of frequency tones. Accordingly, there may
be no guarantee that the weight pointing to the strongest
propagation path will introduce the maximum beamforming gain for
the entire frequency channel. Moreover, pointing in one beam
direction may increase the system sensitivity to small changes in
the multipath environment and may fail to provide robust
communication.
[0097] FIG. 2 is a diagram of an example method 200 using two STAs
to perform multi-path beamforming. The method may be a multi-stage
iterative beamforming method as discussed below, and may include
grouping two or more antennas. For example, FIG. 2 shows a first
iteration 201 of the method and a second iteration 202 of the
method.
[0098] The following articles disclose methods for beamforming. P.
Xia, S. K. Yong, J. Oh and C. Ngo, "A practical SDMA protocol for
60 GHz millimeter wave communications", Asilomar, 2008; and, P.
Xia, S. K. Yong, J. Oh and C. Ngo, "Mulit-stage iterative antenna
training for millimeter wave communications", Globecom, 2008, the
entire contents of both are incorporated herein by reference.
[0099] Referring to FIG. 2, STA.sub.1 205 and STA.sub.2 210 are
respectively shown on two time axes 215 and 220. In this example,
STA.sub.1 205 may transmit one or more training beamforming
weights, and STA.sub.2 210 may receive training beamforming weights
230, 240, and transmit beamforming weights 235 to STA.sub.1 205.
STA.sub.1 205 and STA.sub.2 210 may be, for example, WTRU,
stations, electronic communication devices, or access points. The
example in FIG. 2 shows STA.sub.1 205 transmitting 230, 240 to only
STA.sub.2 210, however there may be more than one STA, which are
not shown. STA.sub.1 205 may be an AP or a non-AP STA. STA.sub.2
210 may be an AP or a non-AP STA.
[0100] In each iteration of the method 201, 202, the AP, here
STA.sub.1 205, may transmit one or more training sequences over
multiple time slots 230 and sweep the transmit beamforming weights.
For example, STA.sub.1 205 may be an AP or a non-AP STA. Note that
only two iterations of the method 201, 202 are illustrated, but the
method may have more than two iterations of the method 201, 202.
STA.sub.2 210 may calculate the best transmit beamforming weight
vector according to an estimate of the received channel state. Note
that the calculated transmit beamforming weight may not be one of
the weights the transmitter STA.sub.1 205 originally utilized. The
method at STA.sub.2 210 may then feedback this beamforming weight
vector 235, or the estimated channel state vector, to the AP, here
STA.sub.1 205. The AP, here STA.sub.1 205, may, or may not, update
the transmit beamforming weight it utilizes for a subsequent
transmission to STA.sub.2 210. The method may continue until packet
transmissions are completed for the associated STAs, STA.sub.2
210.
[0101] The AP, here STA.sub.1 205, may group the antenna array into
multiple sub-groups to point the beamforming weight to multiple
paths. For example, if there are 36 antenna units and only the two
strongest paths are used, then each sub-group may have 18 antenna
units. Alternatively, if more antenna gain is anticipated from the
strongest path, more antenna units may be assigned to the strongest
path. The AP, here STA.sub.1 205, may assign other antenna
sub-group partitions depending on the requirements of the system.
For example, more than two strongest paths may be used. The method
in this example may steer the antenna array in the first sub-group
to the strongest path, while the second sub-group may be steered to
the second strongest path, and so on. This antenna group partition
procedure may be performed by the AP, here STA.sub.1 205, or
STA.sub.2 210, or both.
[0102] In another example, antenna group based multi-path
beamforming may be performed. In this example, STA.sub.1 205 may
have Nt transmit antennas and STA.sub.2 210 may have Nr receive
antennas, and only the two strongest paths may be considered.
[0103] The transmitter, for example STA.sub.1 205, may transmit Nt
sequences 230. The Nt sequences 230 may be modulated using Nt
orthogonal beamforming vectors. STA.sub.1 205 may include a
precoder, for example an identity precoder, and may be configured
to transmit the first sequence using the first antenna, and
transmit the second sequence using the second antenna, and so on.
Other orthogonal precoding matrices may be utilized by STA.sub.1
205.
[0104] The receiver, for example STA.sub.2 210, may receive the Nt
sequences using the receive beamforming vector calculated in the
last iteration, W.sub.i-1.sup.r. In some examples, W.sub.i-1.sup.r
may be set to an initial value. STA2 210 may be configured to
determine that the first n time slots correspond to transmit
antenna 1 to antenna n, which may correspond to antenna group 1.
STA2 210 may utilize the training sequence transmitted in each time
slot to estimate the strongest path of the propagation channel, and
may denote the strongest channel path as H1. The received signal
from the first n time slots may be expressed as
y.sub.i.sup.11=W.sub.i-1.sup.r(1:n)Hs+N, where y may be the
received symbol, s may be the sent symbol, N may be the additive
Gaussian noise having a variance, and H may be the channel matrix
between the transmitter STA1 205 and the receiver STA2 210. The
receiver STA2 210 may use the correlation property of the training
sequence to estimate the channel corresponding to the strongest
propagation path, H.sub.1.sup.1. Thus, the receiver STA2 210 may
determine the best transmit beamforming weight corresponding to
antenna group 1 and the strongest path, and may be represented as
(H.sub.1.sup.1)'. The size of the beamforming weight may be
n.times.1.
[0105] The receiver, STA2 210, may be configured to determine that
time slots n+1 to Nt correspond to transmit antenna n+1 to antenna
Nt, and may correspond to antenna group 2 of STA1 205. The
receiver, STA2 210, may utilize the training sequence transmitted
in each time slot to estimate the second strongest path of the
propagation channel, and may be denoted as H2. The received signal
245 from the Nt-(n+1)+1 time slots may be expressed as
y.sub.i.sup.12=W.sub.i-1.sup.r(n+1:Nt)Hs+N Since the signal may be
transmitted using a sequence with a zero auto correlation (ZAC)
property, STA2 210 may use a Rake receiver like method, where the
strongest path may be removed, and the channel of the second
strongest path may be determined. The second strongest path may be
represented by H.sub.2.sup.1. Thus the best transmit beamforming
weight corresponding to antenna group 2 and the second strongest
path may be (H.sub.2.sup.1)'. The size of the transmit beamforming
weight may be (Nt-n).times.1.
[0106] The updated transmit beamforming weight for iteration i may
be expressed as W.sub.i.sup.t=[H.sub.1.sup.1,H.sub.2.sup.1]'. STA2
210 may transmit W.sub.i.sup.t back to STA1 205 at 235. STA1 205
may use the received W.sub.i.sup.t to transmit 240 another set of
beamforming training frames. STA1 205 may transmit Nr repetition of
training frames, where Nr may be the number of antenna(s) at STA2
205. STA2 205 may be configured to use this set of training frames
to update the received beamforming weight. STA2 210 may use Nr
antennas to receive the training frames sequentially. STA2 210 may
also use other orthogonal beamforming weights to receive the Nr
training frames. In this example, at STA2 210, antenna 1 to m may
belong to the first antenna group, and may be used to point to the
strongest propagation path, while antenna m+1 to Nr may belong to
antenna group 2, and may correspond to the second strongest
propagation path.
[0107] In one example, STA1 205 may use a mixed mode to transmit Nr
repetitions of training frames with weight W.sub.i.sup.t. This
example mixed mode method is shown in FIG. 2 as 202. The received
signal through the Nr time slot may be expressed as
y.sub.i=HW.sub.i.sup.ts+n. The received signal from antenna group 1
may be y.sub.i.sup.21=y.sub.i(1:m) STA2 210 may use the correlation
property of the training sequence to estimate the channel with the
strongest propagation path, H.sub.1.sup.2. The received signal from
antenna group 2 may be y.sub.i.sup.22=y.sub.i(m+1:Nr) and STA2 210
may use correlation detection to remove the strongest path. STA2
210 may accordingly determine the estimated channel for the second
strongest path, H.sub.2.sup.2. STA2 210 may update the receive
beamforming weight, which may be represented as,
W.sub.i.sup.r=[H.sub.1.sup.2,H.sub.2.sup.2]'. In FIG. 2, the
reception of the signals is shown in dashed lines as an example
illustration of the receiver operation while receiving a
packet.
[0108] Alternatively, or in addition to, STA1 205 may use a
sequential mode. STA1 205 may transmit m repetitions of training
frames with antenna group 1, i.e.,
W.sub.1.sup.t1=[H.sub.1.sup.1,0]'. During the m training time slot,
the receiver, for example STA2 210, may utilize antenna group 1 to
receive the training frames. For example, STA2 210 may utilize
antenna 1 to receive the first training frame, and antenna m to
receive the mth training frame. The received signal from these m
frames may be expressed as y.sub.i.sup.21=HW.sub.i.sup.t1s+n. STA2
210 may estimate the channel corresponding to the strongest
propagation path H.sub.1.sup.2. STA1 205 may transmit Nr-m
repetitions of training frames with antenna group 2 only, for
example, W.sub.1.sup.t2=[0,H.sub.2.sup.1]'. STA2 210 may utilize
its antenna group 2 to receive the training frames. The received
signal may be y.sub.i.sup.22=HW.sub.i.sup.t2=HW.sub.i.sup.t2s+n.
STA2 210 may use a correlation method to determine the channel
corresponding to the second strongest path, H.sub.2.sup.2. STA2 210
may update the receive beamforming weight
W.sub.i.sup.r=[H.sub.1.sup.2,H.sub.2.sup.2]'. In some examples,
feedback channels corresponding to the strongest paths may be used
directly by STA2 210 or STA1 205. Note that this mode is not
illustrated in FIG. 2.
[0109] STA2 210 may send
W.sub.i.sup.r=[H.sub.1.sup.2,H.sub.2.sup.2]' to STA1 205 (not
illustrated). In addition, the method may repeat for a number of
times up to a threshold or until the method converges which may be
determined by comparing a next value of the beamforming weights
with a previous value of the beamforming weights and determining if
the difference is less than a threshold value.
[0110] The initial beamforming weights for STA1 205 and STA2 210
may be set to initial values prior to beginning the method. STA1
205 and STA2 210 may determine the initial values in order to
reduce the number iterations needed for the method to converge. The
example method shown in FIG. 2 may be used for determining the two
strongest paths. However, in other example embodiments, more than
two paths may be determined by the STA1 205 and STA2 210.
[0111] Existing protocols may be modified to perform multi-path
beamforming methods. For example, a multi-path beamforming method
may be used in 802.11 and 802.11ad. For example, the multi-path
beamforming method may be used in 802.11ad by using a modification
of the beam refinement protocol (BRP) as disclosed in IEEE
P802.11ad.TM./D9.0: Part 11, "Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) specifications," the entire contents
of which are herein incorporated by reference. The multi-path
beamforming method may be a multi-iteration multi-path beamforming
training method.
[0112] A beam refinement transaction may be a set of BRP frames
that include one or more beam refinement requests and responses.
The multi-path beamforming method may be implemented by modifying
current beamforming refinement protocols.
[0113] FIG. 3 is a diagram of an example of one iteration of the
multi-path beamforming method 300 using BRP transactions. The
beamforming initiator, STA1 305, may transmit a BRP frame 315 that
indicates that the BRP frame 315 is a Transmit BRP Request frame.
This indication may be performed by setting a field, for example,
TX-TRN-REQ=1. A BRP frame with TX-TRN-REQ=1 315 may include a
transmit training subfield (TRN-T) 320 appended to it. The
responder, STA2 310 may reply with a Transmit BRP Feedback 325, for
example, by setting TX-TRN-RSP=1. Moreover, STA2 310 may request a
receive beamforming training by indicating Receive BRP Request
frame in the same BRP frame, for example, by setting L_RX>0. In
this example, the Receive BRP Request frame may be piggybacked on
the Transmit BRP Response frame. L_RX may be a signal field used to
indicate that the receiver requests a receive BRP training, and the
transmitter may respond with a BRP train response followed by a
TRN-R training field. STA1 305 may transmit a BRP frame 330 with a
BRP train response, for example, by setting RX-TRN-RSP to 1. A BRP
frame that includes an RX-Train-response that equals 1 may include
a receive training subfield (TRN-R) 335 appended to it.
[0114] FIG. 4 is a diagram of an example frame format for a BRP
packet 402. The BRP packet 402 may include a short training field
(STF) 404, a channel estimation (CE) field 406, a Header field 408
and a data field 410. A training field 416 may be
appended/prepended to the BRP packet 402 and may include an AGC
training field 412 and a receiver/transmitter training subfield
(TRN-R/T) 414. A BRP packet 402 may be transmitted using control
PHY. Prior to the RTN-R/T training, there may be a signaling
exchange to aid the training procedure. This is the purpose of
field 404, 406, 408, 410. A Packet Type field may be included in
the PHY header, and it may indicate whether a TRN-R or a TRN-T
subfield 414 is appended to the frame 402. A BRP frame 402 with a
TRN-R/T 414 field appended may be referred to as a BRP-RX/TX packet
402. In a BRP-TX packet 402, the transmitter may change the TX
beamforming weight configuration at the beginning of each AGC
subfield 412. The set of beamforming weights used for the AGC
subfields 412 may be the same as that used for the TRN-T subfield
414. In a BRP-RX packet 402, the transmitter may use the same
transmit beamforming weight as in the preamble and data fields of
the transmission data packet. The BRP frame may be an Action No ACK
frame.
[0115] FIG. 5 is a diagram of an example format of a BRP frame
Action field. The BRP frame Action field 500 may include a Category
field 510, an Unprotected DMG Action field 520, a Dialog Token
field 530, a BRP Request field 540, a DMG Beam Refinement element
550, and one or more Channel Measurement Feedback elements 5601 . .
. 560n.
[0116] An 802.11ad beam refinement protocol may be modified as
follows in order to accommodate a multi-path beamforming algorithm.
For example, an initiator may determine the capabilities of the
responder prior to initiating beamforming training with the
responder. The multi-path multi-stage iterative beamforming
training capability may be indicated in a DMG Capabilities element.
A DMG Capabilities element may be present in Association Request,
Association Response, Reassociation Request, Reassociation
Response, Probe Request and Probe Response frames and may be
present in DMG Beacon and Information request and response frames.
A DMG Antenna Array Support field may include one or more bits that
indicate that the STA is capable of forming sub-antenna groups and
capable of performing the multi-path multi-stage beamforming
training method.
[0117] Partitioning of antenna sub-groups at both initiator and
responder may be signaled. Depending on the antenna grouping
method, the signaling may be different. For example, the antenna
grouping may be performed uniformly or non-uniformly.
[0118] In a uniform antenna grouping example, assuming the total
number of antennas is even, each antenna sub-group may have the
same number of antenna elements, and hence only the number of
antenna groups is required to indicate the partition of antenna
sub-groups. For example if there are four antennas, and two groups,
the number of groups, in this example two, may be sent back since
the number of antennas per group will be known. The mapping between
antenna element indices and sub-group indices may be predetermined
and transmitted explicitly in a field of the BRP frame, for
example, a BRP Request field. If the mapping is explicitly
indicated in the BRP frame, the antenna sub-group index may be
assigned to each antenna element.
[0119] In a non-uniform antenna grouping example, each antenna
sub-group may have a different number of antenna elements. For
example, the system may assign more antenna elements for the
strongest path, so that the antenna gain from this sub-group may be
larger. The mapping between antenna element indices and sub-group
indices may be predetermined and transmitted explicitly in a field
of the BRP frame, for example, in a BRP Request field.
[0120] Mapping between antenna sub-groups and channel propagation
paths/taps may be predetermined. For example, antenna sub-group 1
may always map to the strongest path, and so on. Alternatively, the
mapping may be defined in the BRP Request field.
[0121] The precoding matrix used by the initiator, for example,
STA1 205, in the first part of each iteration may be predetermined
and agreed by both initiator and responder. The first part of each
iteration may be referred to as the transmit beamforming training
part. In one example, a set of unitary precoding matrices may be
predetermined. In this example, the initiator and responder may
negotiate which matrix is utilized before performing the
beamforming training. For example, the precoding matrix index may
be predetermined and transmitted in the BRP Request field.
[0122] The number of antennas at both initiator and responder side
may be signaled. Number of antennas may be signaled, for example,
in the PHY header, MAC header or BRP Request field.
[0123] FIG. 6 is a diagram of an example modified channel
measurement feedback element 600. The channel measurement feedback
element may include a signal-to-noise ratio (SNR) subfield 610, a
channel measurement subfield 620, a tap delay subfield 630, and a
sector ID order subfield 640. The presence of these subfields may
depend on the values defined in the DMG Beam Refinement element.
For example, the channel measurement subfield may be used to feed
back up to Ntap channel measurements that correspond to a common
set of relative tap delays defined in the tap delay subfield.
Without the presence of the tap delay subfield, for example, the
Ntaps channel taps may be interpreted as contiguous time samples,
separated by Tc, where Tc may be the SC PHY chip time, and may be
0.57 ns. In these exemplary multi-path beamforming methods, the
channel measurements of the strongest propagation paths may be sent
to STA1. In the example shown in FIG. 2, the strongest path/tap may
be assigned for the first antenna sub-group, and the second
strongest path/tap may be assigned for the second antenna sub-group
and so on. If the multi-path beamforming method is indicated in the
PHY header, MAC header or MAC body, the interpretation of the
channel measurement may be modified when the tap delay subfield is
not present. Therefore, protocols may be modified to accommodate
examples of the multi-path beamforming method disclosed herein.
[0124] Weighted multi-path beamforming training methods may be
performed. For example, a beamforming method for steering the beam
towards multiple propagation paths may be performed. The strongest
propagation paths/taps may be determined by a STA, and one or more
beamforming weights may be determined to point to one or more of
the propagation paths/taps. The beamforming weight for the kth
strongest propagation path may be represented as Wk, and the final
beamforming weight may be expressed as
W = k = 1 K .times. .alpha. k .times. W k , ##EQU00001##
where K may be the number of channel propagation paths and
.alpha..sub.k may be the weight, with .SIGMA..alpha..sub.k=1.
[0125] Different methods may be used by the STA selecting
.alpha..sub.k in one of the following ways. For example,
propagation path selection may be based on:
.alpha. k = { 1 .times. .times. k = m 0 .times. .times. k .noteq. m
. ##EQU00002##
By this selection, the final beamforming weight vector may equal
the weight vector directed towards the mth propagation path.
[0126] In an 802.11ad example, the channel propagation taps may be
measured and fed back to the beamforming initiator, which may be
STA1 205. According to the channel measurement of each tap, a
channel gain may be estimated by the STA. Channel gain of the kth
propagation path/tap may be represented as .beta..sub.k.
.alpha..sub.k may be represented as
.alpha. k = .lamda. - 1 .beta. k , ##EQU00003##
so that
.alpha. k = 1 , .lamda. = 1 + 1 .times. / .times. .beta. k K
##EQU00004##
may be satisfied. The propagation path with the larger channel gain
may have a larger weight and may be determined by the STA to be the
strongest propagation path.
[0127] A single data stream transmission may be performed with
multi-beam capability devices. For example, multiple RF chains may
be available at the AP. Accordingly, the AP may form multiple beams
simultaneously. In this example, the STA may form only one RF
chain. The AP and the STA may be configured to use an Nx1 virtual
MIMO channel. The AP and the STA may be configured to use diversity
methods, such as, for example, STBC, SFBC and CDD. These example
methods may be performed by more than one AP and more than one STA.
In addition, a STA may be an AP.
[0128] There may be at least two possible transmission procedures
that implement RF front-end beamforming with digital domain STBC.
One example transmission procedure may use full size beamforming
with STBC. Another example transmission procedure may use partial
size beamforming with STBC.
[0129] FIG. 7 is a diagram of an example AP 700 configured to
perform a transmission using full size beamforming with STBC. The
AP 700 may include a coding/modulation unit 702, an STBC encoder
706, a plurality of DAC/upconverters 708, 710, and a plurality of
antennas 716. In this example, the coding/modulation unit 702 may
perform modulation and coding and pass the modulation symbols 704
to the STBC encoder 706. The STBC encoder 706 may generate two data
streams 718, 720. The two data streams 718, 720 then be processed
through two RF chains at the plurality of DAC/upconverters 708,
710, which may separately perform DAC and up conversion to the
operating frequency band. At the RF front-end, two beamforming
weight vectors W1 712 and W2 714 may be generated by AP. Each
weight-vector may be of size Nt.times.1. The first data stream 718
may be multiplied with the first weight vector W1 712, and the
second data stream 720 may be multiplied with the second weight
vector W2 514. The two data streams 718, 720 may then be summed
together and transmitted through the Nt antennas 716. In some
embodiments, the AP may be configured with more than two RF
chains.
[0130] FIG. 8 is a diagram of an example AP 800 configured to
perform a transmission using partial size beamforming with STBC.
The AP 800 may include a coding/modulation unit 802, an STBC
encoder 806, a plurality of DAC/upconverters 808, 810, and a
plurality of sets of antennas 816, 817. In this example, the
coding/modulation unit 802 may perform modulation and coding and
pass the modulation symbols 804 to the STBC encoder 806. The STBC
encoder 806 may generate two data streams 818, 820. The two data
streams 818, 820 may then be processed through two RF chains at the
plurality of DAC/upconverters 808, 810, which may separately
perform DAC and up conversion to the operating frequency band. At
the RF front-end, two beamforming weight vectors W1 812 and W2 814
may be generated. Each weight vector may be of size Nt/2.times.1.
The first data stream 818 may be multiplied with the first weight
vector W1 812, and the second data stream 820 may be multiplied
with the second weight vector W2 814. The first data stream 818 may
be transmitted through the first set of Nt/2 antennas 816 and the
second data stream may be transmitted through the second set of
Nt/2 antennas 817. In embodiments, AP may be configured with more
than two RF chains.
[0131] The AP and/or the STA may be configured to send and receive
multiple data streams. For example, the AP and/or the STA may be
configured with multiple RF chains. In these examples, the AP may
be configured to communicate with multiple STAs simultaneously. The
AP may be configured to distinguish the multiple STAs by spatial
domain beams, thus the method may be referred to as Beam Division
Multiple Access (BDMA). The AP may need multiple RF chains to
perform BDMA. For example, the AP may be configured to use spatial
multiplexing methods for single STA transmission. The AP and STA
may be configured to send more than one data stream at a time,
which may increase the spectral efficiency of the system. Multiple
RF chains may be needed at both AP and STA side.
[0132] FIG. 9 is a diagram of an example of transceiver
architecture 900. The AP and/or STA may be configured as follows.
The transceiver architecture 900 may include a transmitter side 902
and a receiver side 904. The transmitter side 902 may include one
or more coding/modulation units 903, a plurality of
DAC/upconverters 912, 914, a digital controller 917, one or more
power amplifiers (PA)s 920, and a plurality of Nt antennas 925.
Multiple data streams may be modulated and coded at baseband, and
then converted from a digital domain to an analog domain through
the digital controller 917. The streams 908, 910 may be upconverted
to operation frequency band by the DAC/upconverters 912, 914. Two
sets of DACs and upconverters are illustrated here, which implies
that up to two data streams may be supported by the transmitter.
Beamforming weights 915, 916 may be applied prior to applying the
streams to the PAs 920. The beamforming weights 915, 916 may be
prepared in a digital domain.
[0133] The transmitter 902, may be an AP or STA, an may be
configured with Nt antennas 925. The Nt antennas 925 may be shared
by two or more RF chains. When the transmitter 902 has two data
streams {s.sub.1,s.sub.2} to transmit, it may generate two
beamforming weights V.sup.1=(V.sub.1.sup.1, V.sub.2.sup.1, . . . ,
V.sub.Nt.sup.1).sup.T 916 and V.sup.2=(V.sub.1.sup.2,
V.sub.2.sup.2, . . . , V.sub.Nt.sup.2).sup.T 915. The two signal
streams may be combined and transmitted through Nt transmit
antennas 925, s=V.sup.1s.sub.1+V.sup.2s.sub.2. The AP and STA may
be similarly configured on the receiver side if multiple RF chains
are presented. The receiver 904 may generate two sets of receive
beamforming weights U.sup.1=(U.sub.1.sup.1, U.sub.2.sup.1, . . . ,
U.sub.Nr.sup.1).sup.T 936 and U.sup.2=(U.sub.1.sup.2,
U.sub.2.sup.2, . . . , U.sub.Nr.sup.2).sup.T 935 and apply them in
an analog domain. The weighted streams may be applied to a
respective ADC/downconverter. The downconverted streams 908', 910'
may be decoded and demodulated.
[0134] Communication devices, which may be, for example, APs or
STAs, with the transceiver embodiment illustrated in FIG. 9 may be
referred to as Type I. In some embodiments, the AP and/or STA may
be configured with more than two RF chains where FIG. 9 may be
extended to accommodate the more than two RF chains.
[0135] FIG. 10 is a diagram of another example transceiver
architecture 1000. The transceiver architecture 1000 may include a
transmitter side 1002 and a receiver side 1004. In this example,
the AP and or the STA may be configured as follows. Each RF chain
may have its own set of antennas 1048, 1050, respectively. The
antennas may be deemed to have been partitioned or split into
sub-groups based on the number of RF chains. Compared to Type I
devices, in order to achieve the same antenna gain, N antenna
elements may be required. Here N may be the number of RF chains.
Communication devices, which may be, for example, APs or STA, with
the transceiver architecture illustrated in FIG. 10 may be referred
to as Type II. The beamforming weights in FIG. 10, may be tuned as
a group by the digital controller logic, as indicated by the dashed
lines.
[0136] FIG. 11 is a diagram of an example of beam division multiple
access (BDMA) architecture 1100. The AP 1102 may be configured to
transmit two packets to STA1 1106 and STA2 1104 simultaneously. The
STAs 1106, 1104 may be configured to share the time-frequency
resource by different RF front-end beams.
[0137] The AP 1102 may be configured to prepare MAC packets for
both STA1 1106 and STA2 1104. The AP 1102 may encode and modulate
the MAC packets and form separate PHY packets and up convert them
to 60 GHz through separate RF chains. At the RF front-end, the AP
1102 may apply beamforming weight vector W1 to the first data
stream and W2 to the second data stream. The AP transmits a
combination of the two data streams. In this way, multiple RF
chains may share the same set of antennas as shown in FIG. 9.
Alternatively, the AP 1102 may be configured to implementation BDMA
by dividing, grouping, or partitioning the set of antennas to
sub-groups, and each RF chain control may be sent by the AP 1102 on
one antenna sub-group as shown in FIG. 10.
[0138] The AP and STA may be configured to perform a beamforming
training method for BDMA. The AP and/or STA may be configured to
perform the beamforming training method sequentially with one or
more STAs in communication with one another. The example
beamforming training methods may be standardized, for example, and
may be used in 802.11ad. The AP and/or STA may be configured to use
orthogonality between training beams.
[0139] FIG. 12 is a diagram of an example beamforming training
method 1200 for BDMA. This example may use a multi-stage iterative
beamforming training algorithm for BDMA. In the example
illustrated, the AP 1202 has Nt antennas, STA1 1204 has M1 antennas
and STA2 1206 has M2 antennas.
[0140] The beamforming training method for BDMA may be performed
iteratively. The AP 1202 may transmit Nt sequences 1208. The Nt
sequences 1208 may be modulated using Nt orthogonal beamforming
vectors. The example shown in FIG. 12 may be performed using a
precoder, for example, an identity precoder. In this example, the
first sequence may be transmitted using a first antenna ("Ant 1")
1208, and a second sequence may be transmitted using the second
antenna, and so on until the Nt antenna ("Ant Nt") 1210. The AP
1202 may be configured to use other orthogonal precoding matrices,
such as, for example, the Walsh Hadamard matrix or FFT matrix.
[0141] STA1 1204 may be configured to utilize the best receive
beamforming vector 1212 calculated through the last iteration,
W.sub.i-1.sup.r1, to receive the signals. In FIG. 12, the reception
of the signals is shown in dashed lines as an example illustration
of the receiver operation while receiving a packet. For example,
the dashed box W.sub.i-1.sup.r1 may indicate that the STA1 1204
should use receive beamforming vector W.sub.i-1.sup.r1 to perform
receive beamforming. Since the AP 1202 may have transmitted the
signal through each antenna sequentially, STA1 1204 may receive a
Nt.times.1 effective MISO channel between AP 1202 and STA1 1204,
W.sub.i-1.sup.r1H.sub.1 at the end of the transmission due to the
use of the receive beamformer. Equivalently, the received signal
may be expressed in a matrix format:
y.sub.11=W.sub.i-1.sup.r1H.sub.1s+n, where y may be the received
signal, s may be the sent signal, n may be Gaussian noise, W may be
the weight used by STA1 1204, and H may be the channel matrix
between AP 1202 and STA1 1204. Based on the received signal, STA1
1204 may calculate or determine the best transmit beamforming
weight from AP 1202 to STA1 1204 which may be represented as
V i r .times. .times. 1 = y 11 .times. s ' y 11 .times. s ' .
##EQU00005##
[0142] Similarly, STA2 1206 may be configured to utilize
W.sub.i-1.sup.r2 to receive the signals, and the received signal
may be expressed as y.sub.12=W.sub.i-1.sup.r2H.sub.2s+n. The best
transmit beamforming weight from AP 1202 to STA2 1206 may be
represented as
V i r .times. 2 = y 1 .times. 2 .times. s ' y 1 .times. 2 .times. s
' , ##EQU00006##
which STA2 1206 may be configured to determine.
[0143] The method may continue with STA1 1204 sending
V.sub.i.sup.r1 1222 to the AP 1202. STA2 1206 may send
V.sub.i.sup.r2 1220 to the AP 1202. STA2 1206 may transmit the
packet immediately after the transmission of STA1 1204, or STA2
1206 may wait for a polling frame transmitted from the AP 1202 (not
illustrated) before transmitting the packet.
[0144] The method may continue with the AP 1202 calculating MU-MIMO
weight W.sub.i.sup.t1 and W.sub.i.sup.t2 based on and
V.sub.i.sup.r2. The AP 1202 may then implement a linear or
non-linear MU-MIMO precoding algorithm for this weight update
1209.
[0145] The method may continue with the AP 1202 transmitting 1230
again with the best beamforming weights and each STA 1204, 1206
receiving with multiple receive antennas.
[0146] The method may continue with one of the following
alternatives. In a first alternative, as illustrated in FIG. 12,
the AP 1202 may transmit
W.sub.i.sup.t1s.sub.1+W.sub.i.sup.t1s.sub.2 for Max(M1,M2) times
1230. s.sub.1 and s.sub.2 may be orthogonal sequences, and may be
known at AP 1202, STA1 1204 and STA2 1206. The AP 1202 may signal
STA1 1204 and STA2 1206 about the assignment of s.sub.1 and
s.sub.2. STA1 1204 may be configured to switch receive antennas to
train the best receive beamforming weight W.sub.i.sup.r1.
Similarly, STA2 1206 may train the best receive beamforming weight
W.sub.i.sup.r2. STA1 1204 may use the orthogonal sequences to
estimate the current signal (via cross correlation with s.sub.1)
and the current interference (via cross correlation with s.sub.2).
Thus, STA1 1204 may train its receive beamforming vectors by
nulling the interference. Similarly, STA2 1206 may use the
orthogonal sequences to estimate the current signal (via cross
correlation with s.sub.2) and the current interference (via cross
correlation with s.sub.1) Then, STA2 1206 may train its receive
beamforming vectors by nulling the interference.
[0147] In a second alternative, the AP 1202 may transmit
W.sub.i.sup.t1s for M1 repetitions. STA1 1204 may switch between
its M1 antennas to receive W.sub.i.sup.t1s, and at the same time,
STA2 may monitor the transmission of W.sub.i.sup.t1s. AP 1202 may
transmit W.sub.i.sup.t2s for M2 repetitions and STA2 may switch
between its M2 antennas to receive W.sub.i.sup.t2s while STA1 1204
monitors the transmission of W.sub.i.sup.t2s.
[0148] The example beamforming training method for BDMA may not be
successful. If the correlation between two STAs 1204, 1206 is high,
the two STAs 1204, 1206 may not be distinguished by beams. This may
lead to an unsuccessful beamforming training for BDMA. In this
example, the AP 1202, and or STAs 1204, 1206, may be configured to
provide information if BDMA may or may not be supported with the
current configuration. The STAs 1204, 1206 may include the report
of beamforming gain when they report V.sub.i.sup.r1 and
V.sub.i.sup.r2 to the AP 1002. The beamforming gain may be defined
as .parallel.y.sub.11s'.parallel..sup.2 and
.parallel.y.sub.12s'.parallel..sup.2. Alternatively, or in
addition, the STAs 1204, 1206 may report signal to interference
ratio (SIR) during or at the end of the method. The STAs 1004, 1006
may determine or calculate the desired signal strength and
interference signal strength with both example alternatives.
[0149] The BDMA training method may include performing BDMA
training on each STA 1204, 1206 sequentially. This example method
may be extended for more than two STAs.
[0150] Examples of the BDMA training method may be standardized.
For example, the BDMA training method may be used with IEEE
802.11ad. In these examples, a service period (SP) may be a time
period scheduled for service from one device to another device. The
transmission during an SP duration may be scheduled by an AP. The
BDMA training method may be scheduled by the AP if it is allocated
in an SP duration. Examples of the BDMA training method may be used
by modifying the BRP procedures.
[0151] FIG. 13 is a diagram of an example modified BRP procedure to
implement a multi-stage iterative beamforming training method for
BDMA 1300. In this example, AP 1302 may transmit a BRP frame 1320
that indicates a Transmit BDMA BRP Request. A Transmit BDMA BRP
Request subfield may be defined in BRP Request field, and may
indicate that the BRP frame is for transmit BDMA BRP training.
Alternatively, a Transmit BRP Request may be used with TX-TRN-REQ=1
to indicate that the BRP frame is for transmit BRP training. A
frame that is utilized for single user beamforming training or BDMA
training may be indicated implicitly or explicitly in the MAC frame
or PHY header.
[0152] STA1 1304 may reply with a Transmit BRP Feedback frame 1322
by setting TX-train-response=1. STA1 1304 may also request a
receive beamforming training by indicating Receive BRP Request in
the same Transmit BRP Feedback frame 1322 by setting L_RX>0.
[0153] AP 1302 may transmit a Polling frame 1324 to STA2 1304 to
request BRP feedback. This step may be skipped if the frame length
of BRP feedback frame is fixed and known by all the devices.
[0154] STA2 1306 may reply with a Transmit BRP Feedback frame 1326
by setting TX-train-response=1. STA2 1306 may also request a
receive beamforming training by indicating Receive BRP Request in
the same Transmit BRP Feedback frame 1326 by setting L_RX>0.
[0155] AP 1302 may transmit a BDMA BRP frame 1328 indicating a BRP
train response by setting RX-Train-response to 1. A BRP frame with
RX-Train-response equal to 1 may include a receive training
subfield TRN-R 1330 appended to it. A BDMA BRP frame 1328 may
indicate multiple receivers explicitly or implicitly in PHY header
or MAC body.
[0156] The example in FIG. 13 shows that one AP 1302 may transmit
to two STAs 1304, 1306. However, the BDMA transmission may be from
one device to two devices irrespective of whether they are APs or
STAs. Moreover, the AP 1302 may transmit to two or more STAs.
[0157] Examples of the method in FIG. 13 may include BDMA
protection mechanisms. The feedback frame 1322 may include not only
the best beam, but also the achievable SINR. If after a certain
number of iterations, the achievable SINR is less than the target
SNR, the BDMA method may be aborted. The number of iterations may
be predetermined, determined statically, dynamically determined
based on previous methods running, or in another way.
[0158] BDMA grouping may be indicated in some examples. The
following examples may enable an indication of BDMA grouping by one
or more communication devices. Using an SP, the BDMA grouping
information may be indicated in an allocation field in an Extended
Schedule Element. The Extended Schedule Element may be transmitted
in a Beacon frame. The tuple, Source AID, Destination AID and
Allocation ID may uniquely identify the allocation. The Source AID
field may be set to the AID of the STA an may initiate channel
access during the SP. The Destination AID field may indicate the
AID of a STA that may be expected to communicate with the source
STA during the allocation. The Allocation ID may identify an
airtime allocation from a Source AID to a Destination AID. With
BDMA transmission, more than one receiver may be indicated. One
method may be to group BDMA transmitters and receivers, and assign
each group a unique BDMA ID. Each STA corresponding to a BDMA ID
may be assigned a User Position Array that may be used to
distinguish the role of the STA. Therefore, the Destination AID may
be replaced by the BDMA ID for BDMA transmissions. Alternatively,
more than one Destination AID may be included in the allocation
field. In this way, the order of the Destination AIDs may imply the
role of one or more STAs in the BDMA transmission.
[0159] Since the BDMA transmission may be within the SP time slot,
the communication device may not need to signal the BDMA
transmission in the PHY header or MAC header. The MCS levels and
Length field for each BDMA receiver may be signaled in PHY
Header.
[0160] FIG. 14 is a diagram of an example PHY layer frame format
1400 that may be used in a BDMA transmission. N may represent the
number of BDMA communication devices that may be signaled in the
allocation field in Extended Schedule Element. The example PHY
layer frame format 1400 may include an STF field 1410, one or more
CE fields 1420, a header 1430, and a data field 1440. The one or
more CE fields 1420 may be transmitted with a weight and a P
matrix. The weight for the one or more CE fields may range from W1
to WN, for example, the first field may be transmitted with a
weight W1, and the last CE field may be transmitted with a weight
WN. The header 1430 and data field 1440 may be transmitted using
BDMA and with all of the weights from W1 to WN.
[0161] Example embodiments may include performing BDMA in a
contention based access period. For example, BDMA transmission
protocols may be used by the communication device. Performing a
BDMA transmission in a contention based access period may utilize
the NDP announcement (NDPA) and NDP sequences for beamforming
training. BDMA transmission may be performed after the NDP sequence
exchanges. Alternatively, or in addition, the BDMA transmission may
be delayed until the BDMA initiator, which may be a STA or an AP,
acquires the media again.
[0162] In one example BDMA transmission procedure, one or more of
the communication devices may be configured to use an NDPA period.
In this example, an AP may transmit a message that indicates which
STAs should participate in BDMA training. The NDPA frame may
contain a STA info field to indicate the individual STA
information. The NDPA frame may reserve a TXOP until the end of
BDMA beamforming training by setting the duration period
accordingly. Alternatively, the NDPA frame may reserve a TXOP until
the end of the BDMA transmission.
[0163] In another example, an NDP period may be configured to allow
training of transmit antennas at the AP. In this example, the STAs
may perform measurements. In another example, a feedback period may
be configured to allow STAs to take turns to feedback the best beam
vectors as well as the achievable SINRs. Moreover, STAs may also
feedback the measured channels or the calculated transmit
beamforming weight vectors.
[0164] In another example, a receiver training period may be
configured to allow an AP to set its beamforming vectors. In this
example, STAs may train their receive antennas.
[0165] In another example, the NDP period, feedback period, and
receiver training period may be repeated for a number of
iterations. A number of stopping criteria may be applied in this
example. For example, if the achievable SINR meets expectation, the
iteration may stop early. In these examples, BDMA transmissions may
begin a certain inter-frame spacing after training is performed.
ACK1 and ACK 2 may each be followed by a SIFs duration after BDMA
transmission is performed.
[0166] In another example, one or more communication devices may be
configured to indicate BDMA grouping. The following is an example
of indicating grouping. BDMA grouping with contention based access
period (CBAP) may be performed by using a BDMA ID. A BDMA ID
management frame may be transmitted from an AP to a STA to indicate
whether the STA belongs to one of the BDMA groups and the user
position of the STA. The BDMA ID management frame may contain a
Membership Status Array field and a User Position Array field. The
BDMA ID may be included in BDMA related frames, such as BDMA
training frames, BDMA transmission frames, or other similar
frames.
[0167] One or more communication devices may be configured to
perform a BDMA transmission method for CBAP that may be similar to
that defined for SP. The BDMA transmission may be performed after
the BDMA initiator, for example the AP, acquires a TXOP in the
CBAP. The PHY layer frame format may be the same as illustrated
FIG. 14. The transmission of BDMA in CBAP may not be scheduled by
the AP. Accordingly, the BDMA ID may be included in the PHY header.
The number of users or communication devices, N, may be indicated
in the sequence exchange to acquire the TXOP before a BDMA
transmission. Alternatively, it may be implicitly indicated using a
short training field (STF) and/or a channel estimation (CE)
field.
[0168] In some examples, the communication devices may be
configured to perform single user spatial multiplexing. In order to
perform spatial multiplexing, both transmitter and receiver may
have multiple RF chains. FIG. 9 and FIG. 10 are example transceiver
configurations to perform single user spatial multiplexing. A
communication device with the transceiver configuration shown in
FIG. 9 may be referred to as a Type I device, i.e., where multiple
RF chains share the same set of antenna elements. A communication
device with the transceiver configuration shown in FIG. 10 may be
referred to as a Type II communication device, i.e., where the
antenna elements may be split into sub-groups, and each sub-group
may correspond to one RF chain.
[0169] The communication devices may be configured to perform
beamforming methods for spatial multiplexing. In this example,
several beamforming methods may be used to perform spatial
multiplexing transmission between a pair of communication devices.
Two types of example beamforming methods may be used. The first
example method may be referred to as Eigen-Beamforming based
spatial multiplexing. In this example, the initiator/responder may
estimate the channel over the air and calculate beamforming weights
accordingly. The second example method may be referred to as beam
sweep based spatial multiplexing. With this method, both initiator
and responder may transmit and receive using pre-defined beam
sectors. The beamforming beams may then be selected from these beam
sectors.
[0170] The communication devices may be configured to perform an
Eigen-Beamforming based spatial multiplexing method, where the
communication devices may be configured as Type I devices with
calibration. Type I devices may have multiple RF chains sharing the
same set of antennas as discussed in conjunction with FIG. 9. If
the communication devices are configured to calibrate the multiple
transmit RF chains, the communication devices may determine that
the multiple RF chains are identical. Examples of non-calibrated or
identical RF chains are discussed below.
[0171] FIG. 15 is a diagram of an example beamforming training
procedure 1500 using Eigen-beamforming based spatial multiplexing
where the Type I communication devices may be configured to
calibrate the multiple transmit RF chains. An iterative example
with two RF chains at both initiator and responder is shown in FIG.
15, however, the method may be extended to any number of RF chains.
In this example, the transmitter (STA1) 1502 may have Nt antenna
elements, and the receiver side (STA2) 1504 may have Nr antenna
elements.
[0172] The beamforming training method may be performed
iteratively. In each iteration, the transmit beamforming training
may be performed and then the receive beamforming training may be
performed. An example of a detailed method for Type I devices with
calibration is described below.
[0173] For iteration i, STA1 1502 may act as an initiator, and may
transmit Nt training sequences 1506 sweeping all the transmit
antenna elements. The transmission may be performed using the first
transmit RF chain (TX1) or the second transmit RF chain (TX2) of
STA1 1502. In some examples, the two RF chains may be identical or
differ by a scalar, or, in other examples, the two TX chains may be
calibrated. Alternatively, STA1 1502 may also use an orthogonal
precoding matrix to transmit the Nt training sequences.
[0174] STA2 (responder) 1504 may have two receive beamforming
weights trained from previous iterations, and may be represented by
w.sub.t-1.sup.r1 and W.sub.i-1.sup.r2. If this is the first
iteration of the method, STA2 1504 may randomly select two
beamforming weights, or use Omni weights, or may determine the two
beamforming weights in an alternate method. The first RF chain
(RX1) may receive a signal that is the weighted combination of
signals received from all the receive antenna elements. This weight
may be the first receive beamforming weight W.sub.i-1.sup.r1.
Similarly, the second RF chain (RX2) may receive a signal that is
the weighted combination of signals received from all the receive
antenna elements. This weight may be the second receive beamforming
weight W.sub.i-1.sup.r2. In FIG. 15, the reception of the signals
is shown in dashed lines as an example illustration of the receiver
operation while receiving a packet. For example, the dashed box
W.sub.i-1.sup.r1 may indicate that the STA1 1504 should use receive
beamforming vector W.sub.i-1.sup.r1 to perform receive beamforming.
After conversion to the digital domain, STA2 1504 may estimate the
effective channel by comparing the received sequence with the known
transmitted sequence. For time slot k, STA2 1504 may estimate two
channels using two RF chains
[ G k .times. 1 G k .times. 2 ] . ##EQU00007##
With Nt time slots, STA2 1504 may receive
[ G 1 .times. 1 G N .times. t .times. 1 G 1 .times. 2 G N .times. t
.times. 2 ] . ##EQU00008##
Applying the inverse of the orthogonal precoding matrix, STA2 1504
may obtain the channel from Nt transmit antenna elements to two RF
chains as
H = [ H 1 .times. 1 H N .times. t .times. 1 H 1 .times. 2 H N
.times. t .times. 2 ] . ##EQU00009##
[0175] STA2 1504 may feedback the channel information or
beamforming weights for multiple data streams to STA1 1502. STA2
1504 may calculate the transmit beamforming weights for spatial
multiplexing and feedback 1508 the weights to STA1 1502. STA2 1504
may feedback the channel H to STA1 1502, and STA1 1502 then may
determine or calculate the transmit beamforming weights 1510.
[0176] In some examples, the transmit beamforming weight method may
be implementation dependent. For example, STA1 1502 and/or STA2
1504 may use linear or non-linear precoding algorithms.
[0177] The updated transmit beamforming weights for the ith
iteration may be denoted as (W.sub.i.sup.t1,W.sub.i.sup.t2). STA1
1502 may transmit a training sequence Nr times with beamforming
weight W.sub.i.sup.t1 1512. STA2 1504 may sweep through Nr receive
antennas 1514, or apply an orthogonal matrix. STA2 1504 then passes
the received signal through the two RF chains. STA1 1502 may
transmit training sequences again Nr times with beamforming weight
W.sub.i.sup.t2 1516. STA2 1504 may repeat a similar procedure with
both RF chains 1518. The sweeping of the Nr receive antennas 1514
and 1518 is shown in dashed lines as an example illustration of
receiver operation. For example, to receive Nr packets from the
transmitter, the receiver may receive a first packet with the first
receive antenna, a second packet with the second receive antenna,
and so on, until it receives a last packet with the last receive
antenna. STA2 1504 may estimate the channel and update the receive
beamforming weight accordingly (not shown). The receive beamforming
weight method may be implementation dependent.
[0178] The above method may be repeated until the method converges
or certain criteria have been met that indicate that spatial
multiplexing is not suitable for the pair of devices, for example,
a set of failure criteria). There may be several ways to define
failure criteria that indicate that the pair of devices are not
suitable for spatial multiplexing. A first example of failure
criteria may be that STA2 monitors the rank or condition number of
a channel matrix while selecting a beamforming weight, and may
feedback this information to STA1. A second example of failure
criteria may be that STA2 monitors the rank or condition number of
channel matrix while sweeping through Nr receive antennas or
applying an orthogonal matrix, and feeds back this information to
STA1. If the rank is less than the number of data streams expected
to be supported, or the condition number is greater than a certain
threshold, both STA1 and STA2 may determine that the maximum number
of data streams supported may not meet the desired number. In this
example, the pair of devices may determine to complete the training
procedure, and perform RF selection at both transmitter and
receiver later. For example, the pair of devices may terminate the
training with a full set of RF chains, and return to perform
beamforming training with a lesser number of RF chains. For
example, after training, the devices may transmit with a lesser
number of spatial streams.
[0179] A method of Eigen-beamforming for spatial multiplexing may
be performed. The method may be for communication devices that are
of Type I or Type II as discussed in conjunction with FIG. 9.
[0180] Type I devices may perform transmit RF chain training
sequentially if the RF chains are not calibrated. Even though the
RF chains share the same set of antenna elements and the physical
channels over the air may be the same, the effective channels,
which may be the combination of channel over the air and
transmit/receive RF chains, may be measured and estimated.
[0181] Type II devices may split the antenna elements into
sub-groups, and each sub-group has an RF chain. In these examples,
there may be two RF chains and two sub-groups of antennas. The
physical channel corresponding to RF chain 1 may be transmitted
with antenna sub-group I, which may be different from that
corresponding to RF chain 2 that may be transmitted with the other
antenna sub-group. Because of this, the training for multiple
transmit RF chains may be performed sequentially.
[0182] FIG. 16 is a diagram of an example beamforming training
method 1600 for Eigen-beamforming based spatial multiplexing for
Type I devices and for Type II devices without calibration. For
iteration i, STA1 1602 (initiator) may transmit Nt repetitions of
training sequences sweeping all the transmit antenna elements in a
first antenna sub-group using the first transmit RF chain (TX1)
1606. Then STA1 1602 may transmit Nt repetitions of training
sequences sweeping all the transmit antenna elements in the second
antenna sub-group using the first transmit RF chain (TX2) 1608.
STA1 1602 may also use an orthogonal precoding matrix to transmit
the Nt repetitions of training sequences. The first antenna
sub-group may be the same as the second antenna sub-group for Type
I devices, STA1 1602; while for Type II devices, STA1 1602, they
may correspond to different antenna elements.
[0183] STA2 (responder) 1604 may have the two receive beamforming
weights trained from the previous iterations. If this is the first
iteration, STA2 1604 may randomly select two beamforming weights,
use Omni weights, or select the weights in an alternate manner. The
first receive RF chain (RX1) may obtain a signal as the weighted
combination of signals received from all antenna elements. The
weight may be the first receive beamforming weight
w.sub.i-1.sup.r1. Similarly, the second receive RF chain (RX2) may
obtain a signal as the weighted combination of signals received
from all the antenna elements. The weight may be the second receive
beamforming weight W.sub.i-1.sup.r2. The sweeping of the Nr receive
antennas 1616 and 1618 is shown in dashed lines as an example
illustration of receiver operation. For example, to receive Nr
packets from the transmitter, the receiver may receive a first
packet with the first receive antenna, a second packet with the
second receive antenna, and so on, until it receives a last packet
with the last receive antenna. After converting them to baseband
and digital domain, STA2 1604 may estimate the effective channel by
comparing the received sequence with the known transmitted
sequence. For time slot k, STA2 1604 may estimate two channels
using two RF chains
[ G k .times. 1 G k .times. 2 ] . ##EQU00010##
With 2Nt time slot, STA2 may receive
[ G 1 .times. 1 G 2 .times. N .times. t .times. 1 G 1 .times. 2 G 2
.times. N .times. t .times. 2 ] .times. . ##EQU00011##
The first half of the G matrix,
G T .times. X .times. 1 = [ G 1 .times. 1 G N .times. t .times. 1 G
1 .times. 2 G N .times. t .times. 2 ] , ##EQU00012##
may correspond to TX1, and the second half of the G matrix,
G T .times. X .times. 2 = [ G ( Nt + 1 ) .times. 1 G 2 .times. N
.times. t .times. 1 G ( Nt + 1 ) .times. 2 G 2 .times. N .times. t
.times. 2 ] , ##EQU00013##
may correspond to TX2. Applying the inverse of the orthogonal
precoding matrix to the first half and second half of G matrix
respectively, STA2 1604 may obtain the channel from Nt transmit
antenna elements with two transmit RF chains to two receive RF
chains
H = [ H 1 .times. 1 H 2 .times. N .times. t .times. 1 H 1 .times. 2
H 2 .times. N .times. t .times. 2 ] . ##EQU00014##
[0184] STA2 1604 may transmit channel information or beamforming
weights for multiple data streams 1610 to STA1 1602. STA2 1604 may
calculate the transmit beamforming weights to perform spatial
multiplexing for STA1 1602, and transmit the weights 1610 to STA1
1602. STA2 1604 may transmit the channel H 1610 to STA1 1602, and
STA1 1602 then may determine or calculate the transmit beamforming
weights for itself 1620.
[0185] For example, the transmit beamforming weight method may be
implementation dependent, and linear or non-linear precoding
methods may be used. The updated transmit beamforming weights for
ith iteration may be denoted as (W.sub.i.sup.t1,W.sub.i.sup.t2).
STA1 1602 may transmit training sequences Nr times with beamforming
weight W.sub.i.sup.t1 1612. STA2 1604 may sweep through Nr receive
antennas 1616, or apply an orthogonal matrix. STA2 1604 may pass
the received signal to two RF chains. STA1 1602 may transmit
training sequences 1614 again for Nr times with beamforming weight
W.sub.i.sup.t2. STA2 1604 may repeat the same procedure with both
RF chains 1618. The sweeping of the Nr receive antennas 1616 and
1618 is shown in dashed lines as an example illustration of
receiver operation. For example, to receive Nr packets from the
transmitter, the receiver may receive a first packet with the first
receive antenna, a second packet with the second receive antenna,
and so on, until it receives a last packet with the last receive
antenna. STA2 1604 may estimate the channel and update the receive
beamforming weight 1622 accordingly.
[0186] For example, the receive beamforming weight method may be
implementation dependent, and may be repeated for several
iterations until the algorithm converges or certain criteria have
been met that indicate that spatial multiplexing is not suitable
for the pair of devices, STA1 1602 and STA2 1604.
[0187] There may be several ways to define failure criteria to
indicate that the pair of devices are not suitable for spatial
multiplexing. For example, the failure criteria may include STA2
monitoring the rank or condition number of channel matrix when
selecting beamforming weights, and feeding back this information to
STA1. A second example of a failure criteria may include STA2
monitoring the rank or condition number of channel matrix while
sweeping through Nr receive antennas or applying an orthogonal
matrix, and feeding back this information to STA1.
[0188] If the rank is less than the number of data streams expected
to be supported, or the condition number is greater than a certain
threshold, both STA1 and STA2 may determine that the maximum number
of data streams that may be supported does not meet the
requirements. In this example, the pair of devices may determine to
complete the training procedure, and perform RF selection at both
transmitter and receiver later. Alternatively, the pair of devices
may terminate the training with full set of RF chains, and return
to performing beamforming training with a fewer number of RF
chains. After training, they may transmit with a fewer number of
spatial streams.
[0189] In some examples, methods for beam sweep based spatial
multiplexing for Type I devices with calibration may be performed.
For example, the method of beam sweep based spatial multiplexing
may be similar to Eigen-Beamforming based spatial multiplexing.
Examples using Eigen-Beamforming based spatial multiplexing may
require that the channel estimate and the transmit/receive weights
for spatial multiplexing may be determined based on the estimated
channel, which may not necessarily be the same as one of the beams
used for beamforming training. In beam sweep based spatial
multiplexing, there may be no requirement for channel estimation.
The device may select one or multiple beams from the set of beams
used for beam sweep training. For example, implementation of beam
sweep based beamforming may be easier than Eigen-Beamforming based
beamforming. The performance of the beam sweep based methods may be
sub-optimum compared to the Eigen-beamforming based methods.
[0190] FIG. 17 is a diagram of an example beamforming training
method 1700 for beam sweep based spatial multiplexing for Type I
devices with calibration between two TX chains. Referring to FIG.
17, for iteration i, STA1 (initiator) 1702 may transmit N
repetitions of training sequences 1706 sweeping the transmit beams
it intends to train. In these examples, N may not necessarily be
related to the number of transmit antennas. The transmission 1706
may be performed using the first transmit RF chain (TX1) or the
second transmit RF chain (TX2). The two RF chains may be identical
or different by a scalar. In some examples, the two TX chains may
have been calibrated.
[0191] STA2 (responder) 1704 may have the two receive beams trained
from the previous iterations. If this is the first iteration, STA2
1704 may randomly select two beams, use Omni weights, or select
initial values in an alternate manner. The first receive RF chain
(RX1) of STA2 1704 may obtain a signal as the weighted combination
of signals received from all antenna elements. The weight may be
the first receive beamforming weight W.sub.t-1.sup.r1. Similarly,
the second receive RF chain (RX2) of STA2 1704 may obtain a signal
as the weighted combination of signals received from all the
antenna elements. The weight may be the second receive beamforming
weight W.sub.i-1.sup.r2. {W.sub.i-1.sup.r1,W.sub.i-1.sup.r2} may be
the weights corresponding to beam indices
{ID.sub.i-1.sup.r1,ID.sub.i-1.sup.r2}. After converting them to
baseband and digital domain, STA2 1704 may measure the effective
SNR or equivalent parameters. For time slot k, STA2 1704 may
perform SNR measurements using two receive RF chains
[ S .times. N .times. R k .times. 1 S .times. N .times. R k .times.
2 ] . ##EQU00015##
With N time slots, STA2 1704 may receive
[ S .times. N .times. R 1 .times. 1 S .times. N .times. R N .times.
1 S .times. N .times. R 1 .times. 2 S .times. N .times. R N .times.
2 ] . ##EQU00016##
In FIG. 17, the reception of the signals is shown in dashed lines
as an example illustration of the receiver operation while
receiving a packet.
[0192] STA2 1704 may feedback two beam indices to STA1 1702. The
beam selection method may be implementation dependent. For example,
the STA2 1704 may choose the pair of indices
(ID.sub.i.sup.t1,ID.sub.i.sup.t2) which may satisfy
ID.sub.i.sup.t1=arg max.sub.k(SNR.sub.k1.sup.TX-SNR.sub.k2.sup.TX),
and ID.sub.i.sup.t2=arg
max.sub.k(SNR.sub.k2.sup.TX-SNR.sub.k1.sup.TX).
[0193] The updated transmit beam indices for the ith iteration may
be (ID.sub.i.sup.t1, ID.sub.i.sup.t2) STA1 1702 may transmit a
training sequence for M times with beam ID.sub.i.sup.t2 1720. STA2
1704 may sweep through M receive beams with both receive RF chains
(RX1 and RX2) 1722. STA1 1702 may transmits a training sequence
again for M times with beamforming weight ID.sub.i.sup.t2 1724.
STA2 1704 may repeat the similar procedure with both RF chains
1726. The sweeping of the receive antennas 1722 and 1726 is shown
in dashed lines as an example illustration of receiver operation.
For example, to receive packets from the transmitter, the receiver
may receive a first packet with the first receive antenna, a second
packet with the second receive antenna, and so on, until it
receives a last packet with the last receive antenna. STA2 1704 may
measure the SNR or equivalent parameters and update the receive
beam index accordingly. The receive beam selection method may be
implementation dependent. For example, M may be the number of
receive beams STA2 1704 intends to train and it may not necessarily
be related to a number of receive antennas at STA2 1704. The method
may be repeated until the method converges or certain criteria have
been met that indicates that spatial multiplexing is not suitable
for the pair of devices.
[0194] Failure criteria may be defined in several different ways.
For example, failure criteria may indicate that the pair of devices
is not suitable for spatial multiplexing. In one example, the
failure criteria may be defined as when STA2 1704 may record
.DELTA..sub.11.sup.SNR=max.sub.k(SNR.sub.k1.sup.TX-SNRk.sub.k2.sup.TX)
and
.DELTA..sub.12.sup.SNR=max.sub.k(SNR.sub.k2.sup.TX-SNR.sub.k1.sup.TX)
when selecting beams, and feedback this information to STA1 1702.
In another example, STA2 1704 may record
.DELTA..sub.21.sup.SNR=max.sub.1.ltoreq.k.ltoreq.N(SNR.sub.k1.sup.RX-SNR.-
sub.k2.sup.RX) and
.DELTA..sub.22.sup.SNR=max.sub.N<k.ltoreq.2N(SNR.sub.k2.sup.RX-SNR.sub-
.k1.sup.RX) when sweeping beams, and feedback this information to
STA1 1702.
[0195] If .DELTA..sub.ij.sup.SNR is smaller than a certain
threshold, both STA1 1702 and STA2 1704 may determine that the
channel cannot provide enough spatial diversity to support two data
streams. In this example, STA1 1702 and STA2 1704 may determine to
complete the training procedure, and perform RF selection at both
transmitter and receiver. STA1 1702 and STA2 1704 may terminate the
training with two RF chains, and return to performing beamforming
training with one RF chain. After training, they may transmit with
a fewer number of spatial streams. For example, more than two data
streams may be determined.
[0196] Beam sweep based spatial multiplexing for Type II devices
and Type I devices without calibration may be performed. FIG. 18 is
a diagram of an example beamforming training method 1800 for beam
sweep based spatial multiplexing Type II devices and Type I devices
without calibration.
[0197] For iteration i, STA1 (initiator) 1802 may transmit N
repetition of training sequences sweeping all the transmit beams it
intends to train using the first transmit RF chain (TX1) 1806. Then
STA1 1802 may repeat the same procedure with the second RF chain
(TX2) 1808. N may not necessarily be related to the number of
transmit antennas. For example, the beam pattern used for TX1 may
not be the same as that for TX2.
[0198] STA2 (responder) 1804 may have the two receive beams trained
from the previous iterations. If this is the first iteration, STA2
1804 may randomly select two beams, use Omni weights, or select the
two beams in a different way. The first receive RF chain (RX1) 1810
may obtain a signal as the weighted combination of signals received
from all antenna elements. The weight may be the first receive
beamforming weight W.sub.i-1.sup.r1. The second receive RF chain
(RX2) 1812 may obtain a signal as the weighted combination of
signals received from all the antenna elements. The weight may be
the second receive beamforming weight W.sub.i-1.sup.r2. For
example, {W.sub.i-1.sup.r1,W.sub.i-1.sup.r2} may be the weights
that correspond to beam indices
{ID.sub.i-1.sup.r1,ID.sub.i-1.sup.r2}. After converting them to
baseband and digital domain, STA2 1804 may measure the effective
SNR or equivalent parameters. For time slot k, STA2 1804 may
perform SNR measurements using two receive RF chains
[ S .times. N .times. R k .times. 1 S .times. N .times. R k .times.
2 ] . ##EQU00017##
With the first N time slot, STA2 1804 may receive
[ S .times. N .times. R 1 .times. 1 S .times. N .times. R N .times.
1 S .times. N .times. R 1 .times. 2 S .times. N .times. R N .times.
2 ] , ##EQU00018##
which may correspond to TX1 of STA1 1802. With the last N time
slots, STA2 1804 may receive
[ S .times. N .times. R ( N + 1 ) .times. 1 S .times. N .times. R 2
.times. N .times. 1 S .times. N .times. R ( N + 1 ) .times. 2 S
.times. N .times. R 2 .times. N .times. 2 ] , ##EQU00019##
which may correspond to TX2 of STA1 1802. In FIG. 18, the reception
of the signals is shown in dashed lines as an example illustration
of the receiver operation while receiving a packet.
[0199] STA2 1804 may feedback two beam indices 1814 to STA1 1802.
The beam selection method may be implementation dependent. For
example, the STA2 1804 may select the pair of indices
(ID.sub.i.sup.t1,ID.sub.i.sup.t2) which may satisfy
ID.sub.i.sup.t1=arg
max.sub.1.ltoreq.k.ltoreq.N(SNR.sub.k1.sup.TX-SNR.sub.k2.sup.TX)
and ID.sub.i.sup.t2=arg
max.sub.N<k.ltoreq.2N(SNR.sub.k2.sup.TX-SNR.sub.k1.sup.TX).
[0200] The updated transmit beam indices for ith iteration may be
(ID.sub.i.sup.t1,ID.sub.i.sup.t2). STA1 1802 may transmit a
training sequence M times with beam ID.sub.i.sup.t1 1816. STA2 1804
may sweep through M receive beams with both receive RF chains (RX1
and RX2) 1818. STA1 1802 may transmit a training sequence again M
times with beamforming weight ID.sub.i.sup.t2 1820. STA2 1804 may
repeat the same procedure with both RF chains 1822. The sweeping of
the receive antennas 1818 and 1822 is shown in dashed lines as an
example illustration of receiver operation. For example, to receive
packets from the transmitter, the receiver may receive a first
packet with the first receive antenna, a second packet with the
second receive antenna, and so on, until it receives a last packet
with the last receive antenna. STA2 1804 may measure the SNR or
equivalent parameters and update the receive beam index
accordingly. The receive beam selection method may be
implementation dependent. For example, M may be the number of
receive beams STA2 1804 intends to train and may not necessarily be
related to the number of receive antennas at STA2 1804.
[0201] The procedure may be repeated for several iterations until
the method converges or certain criteria have been met that
indicates that spatial multiplexing is not suitable for STA1 1802
and STA2 1804.
[0202] There may be several ways to define failure criteria that
indicate that the pair of devices are not suitable for spatial
multiplexing. For example, the failure criteria may be defined as
when STA2 1804 may record
.DELTA..sub.11.sup.SNR=max.sub.1.ltoreq.k.ltoreq.N(SNR.sub.k1.sup.TX-SNR.-
sub.k2.sup.TX) and
.DELTA..sub.12.sup.SNR=max.sub.N<k.ltoreq.2N(SNR.sub.k2.sup.TX-SNR.sub-
.k1.sup.TX) in when selecting beams, and feedback this information
to STA1 1802. In another example failure criteria, STA2 1804 may
record
.DELTA..sub.21.sup.SNR=max.sub.1.ltoreq.k.ltoreq.N(SNR.sub.k1.sup.RX-SNR.-
sub.k2.sup.RX) and
.DELTA..sub.22.sup.SNR=max.sub.N<k.ltoreq.2N(SNR.sub.k2.sup.RX-SNR.sub-
.k1.sup.RX) in when sweeping beams, and feedback this information
to STA1 1802.
[0203] If .DELTA..sub.ij.sup.SNR is smaller than a threshold, both
STA1 1802 and STA2 1804 may determine that the channel cannot
provide enough spatial diversity to support two data streams. In
this example, the pair of devices may determine to complete the
training procedure, and perform RF selection at both transmitter
and receiver. Alternatively, the pair of devices may terminate the
training with two RF chains, and return to performing beamforming
training with one RF chain. After training, the pair of devices may
transmit with a fewer number of spatial streams.
[0204] The beam refinement transaction discussed in conjunction
with FIG. 3 may be used for Eigen-beamforming based spatial
multiplexing methods disclosed above. Modifications may be applied
to support spatial multiplexing. For example, a number of spatial
streams may be defined. The number of data streams may be defined
in a DMG beam refinement element. The FBCK-TYPE subfield in the DMG
beam refinement element may be modified.
[0205] FIG. 19 is a diagram of an example modified FBCK-TYPE
subfield 1900. The modified FBCK-TYPE subfield 1900 may be included
in a DMG refinement element. The modified FBCK-TYPE subfield 1900
may include a SNR present field 1910, a channel measurement present
field 1920, a tap delay present field 1930, a number of taps
present field 1940, a number of measurement field 1950, a number of
spatial streams field 1960, a sector ID order present field 1970,
and a number of beams field 1980.
[0206] An initiator may determine the capabilities of the responder
prior to initiating beamforming training with the responder by
using an Eigen-beamforming based spatial multiplexing capability.
The Beam sweep based spatial multiplexing capability may be
indicated in a DMG capabilities element. The DMG capabilities
element may be present in an association request, association
response, re-association request, re-association response, probe
request and probe response frames and may be present in DMG beacon
and information request and response frames. One bit of
Eigen-beamforming based spatial multiplexing indication and one bit
of beam sweep spatial multiplexing capability may be used to
indicate that the STA is capable of performing Eigen-beamforming
based spatial multiplexing.
[0207] The type of beamforming training algorithm, such as
Eigen-beamforming based and beam sweep based, may be indicated in
DMG beam refinement element. In addition, transceiver architecture
type, such as Type I and Type II may be indicated in a DMG
capabilities element.
[0208] A precoding matrix utilized by the initiator in the first
part of each iteration may be predefined and agreed on by both
initiator and responder if Eigen-beamforming based spatial
multiplexing is implemented. In this example, the initiator and
responder may negotiate which matrix to utilize before the
beamforming training. For example, the precoding matrix index may
be defined and transmitted in a BRP request field. In addition, a
set of unitary precoding matrices may be predetermined.
[0209] A number of antennas at both initiator and responder may be
signaled if Eigen-beamforming based spatial multiplexing is
implemented. The number of antennas may be signaled in the PHY
header, MAC header or a BRP Request field.
[0210] A spatial multiplexing frame format may be implemented. For
example, when a packet is transmitted using spatial multiplexing,
an indication may be sent to inform the packet recipients that
multiple streams were transmitted. The MCS may be redefined for a
modulation/coding scheme and the number of spatial streams. In
802.11ad, for example, MCS 0 may be the Control PHY; MCS 1-12 may
be utilized for single carrier (SC) PHY; MCS 13-24 may be for OFDM
PHY; and MCS 25-31 may be for low power SC PHY.
[0211] In examples with two data stream transmissions, the
following may be defined for use by the communication devices. For
example, MCS 32-43 may be for SC PHY, MCS 44-55 may be for OFDM
PHY, and 56-62 may be for low power SC PHY. In some examples, the
MCS mapping may not be the same as defined above.
[0212] Alternatively, the number of spatial streams may be
indicated in a PHY header. In order to support multiple data
streams, the PHY layer frame format may need to be modified.
[0213] FIGS. 20A, 20B, and 20C are diagrams of example PHY layer
frame formats. With SC PHY, the data field may be composed of
symbol blocks, while with OFDM PHY, the data field may be composed
of OFDM symbols. The frame may be appended with TRN-T/R subfields,
and may be utilized for beam refinement protocol.
[0214] Referring to FIG. 20A, short training field (STF) 2010,
channel estimation field (CE) 2020 and PHY headers 2030 may be
transmitted with a weight, W1 2040. The number of data streams
supported, N, may be indicated in the PHY header. If more than one
data stream will be transmitted, additional CE field(s) may be
included. With N data streams, an extra N-1 CE field 2050 may be
transmitted and weights W2 2060, . . . , WN 2070 may be applied to
each CE field. An orthogonal mapping matrix, such as the P matrix
defined in 802.11n/ac, may be applied. If a cyclic shift delay
(CSD) scheme is applied to spatial multiplexing, the same CSD
parameters may be applied to the CE fields. The data field 2080
that follows may be transmitted using the spatial multiplexing
scheme, and all of the weights (W1, . . . , WN) 2090 may be
applied.
[0215] FIG. 20B is a diagram of another example preamble format for
spatial multiplexing transmissions. This format is similar to FIG.
20A except that an AGC field 2015 may be inserted after additional
CE fields and before the data field 2080. The AGC field 2015 may
use the same sequence as an LTF field, or it may be redesigned. The
purpose of this AGC field 2015 may be for automatic gain control.
The transmission of the AGC field 2015 may be in the same format as
the data field 2080, i.e., weights (W1, . . . , WN) 2090 may be
applied. The same CSD parameters may be applied to AGC field 2015
if CSD is utilized for data transmissions.
[0216] FIG. 20C is a diagram of another example preamble format for
spatial multiplexing transmissions in which the number of data
streams may be signaled implicitly. STF 2010 may be transmitted
using all the weights (W1, . . . , WN) 2025. The first CE field
2020 following STF 2010 may be transmitted using the first weight
W1 2040. The number of data streams may be implicitly indicated by
using STF 2010 and the first CE field 2020. For example, several CE
sequences may be defined, and each sequence may correspond to a
certain number of data streams. Additional N-1 CE fields 2050 may
follow the first CE field 2020 and transmitted with weights W2 2060
to WN 2070. The header 2035 may be transmitted with one of the
weights or a combination of the weights similar to STF 2010. The
spatial multiplexing transmission may be transmitted following the
additional CE fields.
[0217] Beamforming training overhead and latency may be reduced.
For example, sector sweep (SSW) frames and related training methods
may be modified.
[0218] In the SLS procedures, SSW frames may be utilized for
transmit and receive beamforming training. For example, the SSW
frames may be transmitted in N time slots. For transmit beamforming
training, SSW frames may be transmitted and multiple antenna
sectors may be swept. The receiver may receive the SSW frames with
the same antenna sector and feedback the best transmit sector ID to
the transmitter. For example, for receive beamforming training, the
same SSW frames may be repeated N times, and the receiver may sweep
over multiple antenna sectors to receive. After the receive
beamforming training, the receiver may select the best receive
sector.
[0219] Each SSW frame may comprise a full PLCP header that may
include a preamble, one or more header blocks, and a MAC frame.
Since the SSW frames may be utilized for beamforming training, they
may be transmitted using the lowest data rate, for example, control
PHY or MCSO in 802.11ad. SSW frames may not contain data traffic,
therefore SSW frame sequences may be beamforming training
overhead.
[0220] FIG. 21 is a diagram of an example modified SSW training
frames and sequence 2100. In this example, modified SSW training
sequences may be utilized. A SSW announcement (SSWA) frame 2110 may
be transmitted at the beginning of the SSW training sequences. The
SSWA frame 2110 may contain all the information used to transmit by
SSW frames. One or more N null SSW (NSSW) frames 2120 may follow
the SSWA frame 2110 with a certain inter-frame spacing. NSSW frames
2120 may contain only preamble and PHY headers, and no MAC
frame.
[0221] FIG. 22 is a diagram of an example SSWA frame format 2200.
The SSWA frame format 2200 may include a frame control field 2205,
a duration field 2210, an RA field 2215, a TA field 2220, an SSW
field 2225, an SSW feedback (FB) field 2230, and an FCS field 2235.
The SSW field 2225 may include a direction subfield 2240, a DMG
antenna ID 1 subfield 2245, a sector ID 1 subfield 2250, a sector
ID N subfield 2255, a DMG antenna ID 2 subfield 2260, a sector ID 1
subfield 2265, a sector ID N2 subfield 2270, and an RXSS length
subfield 2275. In this example, sector ID 1 subfield 2250 may be
for DMG antenna ID 1, and sector ID 1 subfield 2265 may be for DMG
antenna ID 2.
[0222] The direction subfield 2240 and the RXSS length subfield
2275 may be the same as in IEEE 802.11ad. The direction subfield
2240 may be set to 0 to indicate that the frame is transmitted by
the beamforming initiator and set to 1 to indicate that the frame
is transmitted by the beamforming responder. The RXSS Length
subfield 2275 may be valid only when transmitted in a CBAP and may
be reserved otherwise. The RXSS Length subfield 2275 may specify
the length of a receive sector sweep as required by the
transmitting STA, and may be defined in units of an SSW frame. The
value of this field is in the range 0-62, with odd values being
reserved.
[0223] DMG Antenna IDs and Sector IDs may be utilized to indicate
the antenna pattern for the following NSSW frames. For example, the
first NSSW frame may utilize DMG Antenna ID 1 and Sector ID 1 to
transmit, and the second NSSW frame may utilize DMG Antenna ID 1
and Sector ID 2 to transmit, and so on. With DMG antenna ID k,
there may be Nk sectors swept for this round of beamforming
training. The total number of NSSW frames following this SSWA frame
may be
k = 1 K .times. N k . ##EQU00020##
K may be the number of DMG antennas trained with these SSWA-NSSW
sequences.
[0224] The SSWA may be transmitted as follows. For example, the
SSWA frame may carry all the MAC information necessary for
beamforming training. It may be important that the receiver decodes
the SSWA frame correctly. The SSWA frame may be transmitted using
one of the following methods. For example, if the beamforming
training is between two non-AP/PCP devices, the SSWA frame may be
transmitted from AP to the two devices. In another example, if both
the beamforming initiator and responder are multi-band capable,
they may operate on multiple frequency bands simultaneously, and
the SSWA frame may be transmitted on another frequency band. The
SSWA frame may be transmitted with low data rate, spreading codes,
or repetition schemes.
[0225] Some examples may use sub-optimum SLS training methods. In
these examples, SLS training methods may be terminated early.
[0226] FIG. 23 is a diagram of an example early termination of the
SLS training procedure. In this example, the initiator 2302 may
have 4 beam sectors to train, and the countdown (CDOWN) number may
equal 3 in the first training frame. In this example, sector 3 is
shaded to illustrate that the initiator may use sector 3 for
transmission in a first period, and sector 4 is shaded to
illustrate that the initiator may use sector 4 for transmission in
the second period. The initiator 2302 may continue transmitting
training frames which are separated by inter-frame space duration
2T, for example. The responder 2304 may monitor the received
training frames 2306. The dashed "omni" circles in FIG. 23 are
shown to illustrate that the receiver/responder may be in an
omni-receiving mode. An omni-receiving mode may be enabled by an
omni-directional receiving antenna. The first two "omni" circles
are shown in dashed lines to illustrate that they are example
receiver operations. The last "omni" circle is shown in indicating
solid line to illustrate that this is an example transmitter
operation, i.e., the feedback packet may be transmitted in an
omni-transmitting mode, which may be enabled by an omni-directional
transmitting antenna. Once the received SNR (or other parameters)
is greater than a certain threshold, the responder 2304 may
determine to terminate the training procedure by transmitting a
feedback frame 2308. The feedback frame 2308 may be transmitted
after a T duration from the end of a training frame transmitted by
the initiator 2302. Thus the initiator 2302 may detect the
transmission of this feedback and stop transmitting more training
frames. This example may be used for both transmit and receive
beamforming training.
[0227] A group based SLS training method may be performed. In this
example, a STA may divide its sectors to groups. The partition of
sectors may be implementation dependent. For example, the partition
may be based on the direction of the sectors. The beamforming
initiator may select one group to perform SLS training and wait for
the feedback from the responder. Once the feedback from responder
meets the expectation of the initiator, the beamforming initiator
may determine to stop the beamforming training. Otherwise, the
initiator may select another group to perform SLS training until
one beam is selected or all the beams are swept.
[0228] Multi-beam, multi-DMG antenna sector level sweep feedback
may be performed. In examples of the sector level sweep method, the
receiver STA may report back the best beam only, for example, one
sector of one DMG antenna. For example, a list of the best beams,
such as multiple beams of multiple antennas may be reported. This
may enable the communication link to track the relative performance
of the beams over time and, if necessary, switch to a better beam
without the need for retraining.
[0229] FIG. 24 is a diagram of an example multi-beam multi-DMG
antenna SLS feedback method 2400. The following method 2400 may use
a sector level sweep method that may report a list of best beams.
In this example, the DMG transmitting STA1 2402 and receiving STA2
2404 may indicate their capability to support multi-sector,
multi-DMG antenna Sector Sweep (SSW) feedback. This capability may
be indicated by a bit in the DMG STA Capability Information field.
STAs that do not have the capability may fall back to legacy
transmission.
[0230] The STA initiating the sector sweep, for example STA1 2402,
may transmit information to the responder STA, for example STA2
2404, indicating the number of beams to be fed back. The responder
STA 2404 may also transmit information to initiator STA 2402 on the
number of beams to be fed back. The metric to decide on the best
beams may be implementation dependent. One signaling method may use
a Transmit Sector Sweep frame for both the initiator and the
responder may contain the number of beams to be fed back. A second
signaling method may use a DMG beacon that may contain a field that
indicates the number of beams to be fed back for all SSW feedback
2420. In a third signaling method, before a Sector Level Sweep
procedure, the initiator and responder may exchange SLS setup
frames indicating the number of beams to feed back. Quasi-omni may
refer to a near omni-directional transmission or reception. For
example, quasi-omni transmissions may be enabled by repeatedly
transmitting the same information using multiple directional
transmissions, as if it were transmitted using an omni-directional
transmit antenna. Similarly, quasi-omni receptions may be enabled
by repeatedly receiving the same packet using multiple directional
receptions, as if it were received using an omni-directional
receiving antenna.
[0231] Both STAs may implement the legacy initiator and responder
sector level sweep procedures. The transmitter may feedback the
best N beams. This may be by one of the following example methods.
In a first example method, multiple SSW Feedback fields may be
aggregated within an SSW feedback frame 2420. In a second example,
a single SSW Feedback field may be modified to enable feedback of
multiple beams and DMG antennas and corresponding SNR Reports. In a
third example, the best beam/antenna may be fed back during the SLS
procedure and subsequent feedback of the additional N-1 beams with
other transmissions, for example an ACK. In these examples, the
number of antenna may be larger than the number radio frequency
(RF) chains. In some examples, the number of antenna may be much
larger than the number of RF chains.
EMBODIMENTS
[0232] 1. A first communication device comprising: [0233] a
plurality of antennas; [0234] a processor configured to partition
the plurality of antennas; [0235] a transmitter configured to
transmit a plurality of frames to a second communication device;
[0236] and a receiver.
[0237] 2. The first communication device of embodiment 1, wherein
the processor is configured to partition the plurality of antennas
into at least a first group of antennas and a second group of
antennas.
[0238] 3. The first communication device of embodiment 2, wherein
the first group of antennas is associated with a first beam to a
first station (STA).
[0239] 4. The first communication device of embodiment 2 or 3,
wherein the second group of antennas is associated with a second
beam to a second station (STA).
[0240] 5. The first communication device of any one of embodiments
2-4, wherein the first group of antennas is associated with a first
beam to a first plurality of stations (STAs).
[0241] 6. The first communication device of any one of embodiments
2-5, wherein the second group of antennas is associated with a
second beam to a second plurality of stations (STAs).
[0242] 7. The first communication device of any preceding
embodiment, wherein the plurality of frames transmitted are
beamforming training frames.
[0243] 8. The first communication device of any preceding
embodiment, wherein the plurality of frames are transmitted using
the first group of antennas.
[0244] 9. The first communication device of any preceding
embodiment, wherein the plurality of frames are transmitted using
the second group of antennas.
[0245] 10. The first communication device of any preceding
embodiment, wherein the receiver is configured to receive a first
beamforming weight vector from the second communication device.
[0246] 11. The first communication device of embodiment 10, wherein
the first beamforming weight vector is for sending signals on the
first group of antennas.
[0247] 12. The first communication device of any preceding
embodiment, wherein the receiver is configured to receive a second
beamforming weight vector from the second communication device.
[0248] 13. The first communication device of embodiment 12, wherein
the second beamforming weight vector is for sending signals on the
second group of antennas.
[0249] 14. The first communication device of any one of embodiments
10-13, wherein the first beamforming weight vector is a strongest
beam between the first communication device and the second
communication device.
[0250] 15. The first communication device of any one of embodiments
12-14, wherein the second beamforming weight vector is for a second
strongest beam between the first communication device and the
second communication device.
[0251] 16. The first communication device of any preceding
embodiment, wherein the first communication device is a wireless
transmit/receive unit (WTRU).
[0252] 17. The first communication device of any one of embodiments
1-15, wherein the first communication device is a station
(STA).
[0253] 18. The first communication device of any one of embodiments
1-15, wherein the first communication device is an access point
(AP).
[0254] 19. The first communication device of any one of embodiments
1-15, wherein the first communication device is a base station.
[0255] 20. The first communication device of any preceding
embodiment, wherein the second communication device is a wireless
transmit/receive unit (WTRU).
[0256] 21. The first communication device of any one of embodiments
1-19, wherein the second communication device is a station
(STA).
[0257] 22. The first communication device of any one of embodiments
1-19, wherein the second communication device is an access point
(AP).
[0258] 23. The first communication device of any one of embodiments
1-19, wherein the second communication device is a base
station.
[0259] 24. The first communication device of any one of embodiments
7-23, wherein the beamforming training frames are orthogonal
beamforming vectors.
[0260] 25. The first communication device of any preceding
embodiment, wherein the transmitter is further configured to
transmit a second set of beamforming training frames.
[0261] 26. The first communication device of embodiment 25, wherein
the second set of beamforming training frames is transmitted using
the received first beamforming weight vector.
[0262] 27. The first communication device of embodiment 25 or 26,
wherein the second set of beamforming training frames is
transmitted using the received second beamforming weight
vector.
[0263] 28. The first communication device of any preceding
embodiment, wherein the receiver is further configured to receive a
modified first beamforming weight vector.
[0264] 29. The first communication device of embodiment 28, wherein
the modified first weight vector is for sending signals on the
first group of antenna.
[0265] 30. The first communication device of any preceding
embodiment, wherein the receiver is further configured to receive a
modified second beamforming weight vector.
[0266] 31. The first communication device of embodiment 30, wherein
the modified second weight vector is for sending signals on the
second group of antenna.
[0267] 32. The first communication device of any preceding
embodiment, wherein the first communication device comprises one or
more radio frequency (RF) chains.
[0268] 33. The first communication device of any preceding
embodiment, wherein a number of the antenna is larger than a number
of one or more radio frequency (RF) chains.
[0269] 34. A first communication device comprising: [0270] a
plurality of antennas; [0271] a receiver configured to receive a
set of beamforming training frames; [0272] a processor; and [0273]
a transmitter.
[0274] 35. The first communication device of embodiment 34, wherein
the processor is configured to determine a first transmit
beamforming weight vector.
[0275] 36. The first communication device of embodiment 35, wherein
the first transmit beamforming weight vector corresponds to a first
antenna group.
[0276] 37. The first communication device of embodiment 36, wherein
the first antenna group is for a second communication device.
[0277] 38. The first communication device of any one of embodiments
34-37, wherein the processor is configured to determine a second
transmit beamforming weight vector.
[0278] 39. The first communication device of embodiment 38, wherein
the second transmit beamforming weight vector corresponds to a
second antenna group.
[0279] 40. The first communication device of embodiment 39, wherein
the second antenna group is for a second communication device.
[0280] 41. The first communication device of any one of embodiments
34-40, wherein the transmitter is configured to transmit data using
the first transmit beamforming weight vector to the second
communication device to the second communication device.
[0281] 42. The first communication device of any one of embodiments
34-41, wherein the transmitter is configured to transmit data using
the second transmit data using the second transmit beamforming
weight vector to the second communication device.
[0282] 43. The first communication device of any one of embodiments
34-42, wherein the first communication device is a wireless
transmit/receive unit (WTRU).
[0283] 44. The first communication device of any one of embodiments
34-42, wherein the first communication device is a station
(STA).
[0284] 45. The first communication device of any one of embodiments
34-42, wherein the first communication device is an access point
(AP).
[0285] 46. The first communication device of any one of embodiments
34-42, wherein the first communication device is a base
station.
[0286] 47. The first communication device of any one of embodiments
34-46, wherein the second communication device is a wireless
transmit/receive unit (WTRU).
[0287] 48. The first communication device of any one of embodiments
34-46, wherein the second communication device is a station
(STA).
[0288] 49. The first communication device of any one of embodiments
34-46, wherein the second communication device is an access point
(AP).
[0289] 50. The first communication device of any one of embodiments
34-46, wherein the second communication device is a base
station.
[0290] 51. The first communication device of any one of embodiments
34-50, wherein the received beamforming training frames are
orthogonal beamforming vectors.
[0291] 52. The first communication device of any one of embodiments
34-51, wherein the transmitted beamforming weight vectors are
orthogonal beamforming vectors.
[0292] 53. A method for beamforming training for beam division
multiple access (BDMA), the method comprising: [0293] receiving a
first transmit beamforming weight from a first station (STA), and
receiving a second transmit beamforming weight from a second (STA);
[0294] transmitting Nt sequences modulated using Nt beamforming
vectors, wherein the Nt sequences are modulated based on the first
transmit beamforming weight and the second transmit beamforming
weight.
[0295] 54. The method of embodiment 53, wherein the Nt beamforming
vectors are orthogonal.
[0296] 55. A method for beamforming training for beam division
multiple access (BDMA), the method comprising: [0297] receiving a
plurality of Nt sequences using a first previous beamforming
vector; [0298] determining a first transmit beamforming weight from
an access point (AP) based on the first previous beamforming vector
and the received plurality of Nt sequences; and [0299] transmitting
the determined first transmit beamforming weight to the AP.
[0300] 56. A method for beamforming training for spatial
multiplexing, the method comprising: [0301] an initiator station
having two radio frequency (RF) chains and having transmit antenna
elements, the initiator station transmitting Nt known training
sequences sweeping the transmit antenna elements; [0302] a
responder station having a first and a second RF chain and having
receive antenna elements, and having a first and a second receive
beamforming weight, the responder station receiving the first RF
chain and receiving the second RF chain; and [0303] the responder
station estimating at least two channels by comparing the received
first RF chain and the second RF chain to the Nt known training
sequences.
[0304] 57. The method of embodiment 56, wherein the first RF chain
is the combination of signals received from the receive antenna
elements weighted by the first receive beamforming weights
[0305] 58. The method of embodiment 57, wherein the second RF chain
is the combination of signals received from the receive antenna
elements weighted by the second receive beamforming weights.
[0306] 59. The method of any one of embodiments 56-58, wherein the
transmitting Nt training sequences further comprises transmitting
Nt training sequences over a first RF chain of the initiator.
[0307] 60. The method of any one of embodiments 56-58, wherein the
transmitting Nt training sequences further comprises transmitting
Nt training sequences over a second RF chain of the initiator.
[0308] 61. The method of any one of embodiments 56-58, wherein the
transmitting Nt training sequences further comprises transmitting
Nt training sequences over the first RF chain and the second RF
chain.
[0309] 62. The method of embodiment 61, wherein the first RF chain
and the second RF chain are calibrated.
[0310] 63. The method of any one of embodiments 56-62, wherein the
transmitting Nt known training sequences sweeping the transmit
antenna elements comprises the initiator station having two RF
chains and having transmit antenna elements, transmitting Nt known
training sequences sweeping the transmit antenna elements, wherein
a number of the transmit antenna elements is larger than a number
of RF chains.
[0311] 64. The method of any one of embodiments 56-63, wherein the
number of transmit antenna elements is at least six times larger
than a number of RF chains.
[0312] 65. The method of any one of embodiments 56-64 further
comprising the responder transmitting the estimated two channels to
the initiator.
[0313] 66. A method for beamforming training for spatial
multiplexing, the method comprising: [0314] an initiator station
having two or more radio frequency (RF) chains and having transmit
antenna elements, the initiator station transmitting Nt known
sequences sweeping the transmit antenna elements; [0315] a
responder station having a first and a second RF chain and having
receive antenna elements, and having a first and a second receive
beamforming weight, the responder station receiving the first RF
chain and receiving the second RF chain; and [0316] the responder
estimating at least two channels by comparing the received first RF
chain and the second RF chain to the known Nt training
sequences.
[0317] 67. The method of embodiment 66, wherein the first RF chain
is a combination of signals received from the receive antenna
elements weighted by the first receive beamforming weights.
[0318] 68. The method of embodiment 66 or 67, wherein the second RF
chain is the combination of signals received from the receive
antenna elements weighted by the second receive beamforming
weights.
[0319] 69. A method for performing beamforming, the method
comprising: [0320] a first communication device transmitting a
first plurality of beamforming training frames to a second
communication device using a first beamforming vector; [0321] the
first communication device receiving from the second communication
device a second beamforming weight vector; and [0322] the first
communication device transmitting a second plurality of beamforming
training frames to the second communication device using the second
beamforming vector.
[0323] 70. The method of embodiment 69, wherein the first
communication device transmits the first plurality of beamforming
training frames to the second communication device using a first
beamforming weight vector.
[0324] 71. The method of embodiment 69 or 70, wherein the first
communication device transmits a first portion of the first
plurality of beamforming training frames using a first group of
antenna and a first portion of the beamforming weights.
[0325] 72. The method of any one of embodiments 69-71, wherein the
first communication device transmits a second portion of the first
plurality of beamforming training frames using a second group of
antenna and a second portion of the beamforming weights.
[0326] 73. A base station configured to perform any one of
embodiments 53-72.
[0327] 74. A base station configured to perform any portion of
embodiments 53-72.
[0328] 75. An integrated circuit configured to perform any one of
embodiments 53-72.
[0329] 76. An integrated circuit configured to perform any portion
of embodiments 53-72.
[0330] 77. A station (STA) configured to perform any one of
embodiments 53-72.
[0331] 78. A station (STA) configured to perform any portion of
embodiments 53-72.
[0332] 79. An access point (AP) configured to perform any one of
embodiments 53-72.
[0333] 80. An access point (AP) configured to perform any portion
of embodiments 53-72.
[0334] 81. A wireless transmit/receive unit (WTRU) configured to
perform any one of embodiments 53-72.
[0335] 82. A wireless transmit/receive unit (WTRU) configured to
perform any portion of embodiments 53-72.
[0336] Although features and elements are described above in
particular combinations, one of ordinary skill in the art will
appreciate that each feature or element can be used alone or in any
combination with the other features and elements. In addition, the
methods described herein may be implemented in a computer program,
software, or firmware incorporated in a computer-readable medium
for execution by a computer or processor. Examples of
computer-readable media include electronic signals (transmitted
over wired or wireless connections) and computer-readable storage
media. Examples of computer-readable storage media include, but are
not limited to, a read only memory (ROM), a random access memory
(RAM), a register, cache memory, semiconductor memory devices,
magnetic media such as internal hard disks and removable disks,
magneto-optical media, and optical media such as CD-ROM disks, and
digital versatile disks (DVDs). A processor in association with
software may be used to implement a radio frequency transceiver for
use in a WTRU, UE, terminal, base station, RNC, or any host
computer.
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