U.S. patent application number 15/934442 was filed with the patent office on 2018-07-26 for millimeter wave beam tracking.
This patent application is currently assigned to IDAC Holdings, Inc.. The applicant listed for this patent is IDAC Holdings, Inc.. Invention is credited to Philip J. Pietraski, Ravikumar V. Pragada, Arnab Roy, Bharath Viswanathan.
Application Number | 20180213413 15/934442 |
Document ID | / |
Family ID | 49151350 |
Filed Date | 2018-07-26 |
United States Patent
Application |
20180213413 |
Kind Code |
A1 |
Roy; Arnab ; et al. |
July 26, 2018 |
MILLIMETER WAVE BEAM TRACKING
Abstract
A wireless transmit/receive unit (WTRU) may receive a request to
perform directional signal measurements for received signals. The
WTRU may transmit, based on the request and position information
associated with the WTRU, directional signal measurements to
facilitate generation of a directional radio environment map
(DREM). The WTRU may receive a request to switch beams based on the
DREM.
Inventors: |
Roy; Arnab; (Phoenixville,
PA) ; Pragada; Ravikumar V.; (Warrington, PA)
; Pietraski; Philip J.; (Jericho, NY) ;
Viswanathan; Bharath; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IDAC Holdings, Inc. |
Wilmington |
DE |
US |
|
|
Assignee: |
IDAC Holdings, Inc.
Wilmington
DE
|
Family ID: |
49151350 |
Appl. No.: |
15/934442 |
Filed: |
March 23, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15488146 |
Apr 14, 2017 |
9961565 |
|
|
15934442 |
|
|
|
|
14423362 |
Feb 23, 2015 |
9629171 |
|
|
PCT/US2013/057101 |
Aug 28, 2013 |
|
|
|
15488146 |
|
|
|
|
61774979 |
Mar 8, 2013 |
|
|
|
61694162 |
Aug 28, 2012 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 64/00 20130101;
H04B 7/0695 20130101; H04W 64/003 20130101; H04B 7/088 20130101;
H04W 36/30 20130101; H04W 24/08 20130101; H04W 88/08 20130101; H04W
16/28 20130101; H04W 36/0094 20130101; H04W 72/048 20130101; H04W
72/085 20130101; H04W 36/0083 20130101 |
International
Class: |
H04W 16/28 20090101
H04W016/28; H04W 24/08 20090101 H04W024/08; H04W 64/00 20090101
H04W064/00 |
Claims
1. A wireless transmit/receive unit (WTRU) comprising: a receiver
configured to receive, from a base station (BS), a first request to
perform directional signal measurements for a plurality of received
signals; the receiver further configured to receive, from the BS, a
second request to provide position information associated with the
WTRU; a transmitter configured to transmit, based on the first
request and the position information associated with the WTRU,
directional signal measurements to facilitate generation of a
directional radio environment map (DREM); and the receiver further
configured to receive a third request to switch beams based on the
DREM.
2. The WTRU of claim 1 further comprising: the receiver further
configured to receive a request from the BS to provide orientation
data associated with the WTRU; and the transmitter further
configured to transmit the orientation data.
3. The WTRU of claim 1 further comprising: the transmitter further
configured to transmit historical data on beams used by the
WTRU.
4. The WTRU of claim 1, wherein the directional signal measurements
are performed on inter-cell signals.
5. The WTRU of claim 1 further comprising: the receiver further
configured to receive position data associated with the BS.
6. The WTRU of claim 1 further comprising: a processor configured
to filter the directional signal measurements based on time and GPS
coordinates.
7. A method performed by a wireless transmit/receive unit (WTRU),
the method comprising: receiving, from a base station (BS), a first
request to perform directional signal measurements for a plurality
of received signals; receiving, from the BS, a second request to
provide position information associated with the WTRU;
transmitting, based on the first request and the position
information associated with the WTRU, directional signal
measurements to facilitate generation of a directional radio
environment map (DREM); and receiving a third request to switch
beams based on the DREM.
8. The method of claim 7 further comprising: receiving, from the
BS, a request to provide orientation data associated with the WTRU;
and transmitting, by the WTRU, the orientation data.
9. The method of claim 7 further comprising: transmitting
historical data on beams used by the WTRU.
10. The method of claim 7, wherein the directional signal
measurements are performed on inter-cell signals.
11. The method of claim 7 further comprising: receiving, by the
WTRU, position data associated with the BS.
12. The method of claim 7 further comprising: filtering, by the
WTRU, the directional signal measurements based on time and GPS
coordinates.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Non-Provisional
application Ser. No. 15/488,146 filed Apr. 14, 2017, which is a
continuation of U.S. Non-Provisional application Ser. No.
14/423,362 filed Feb. 23, 2015, which issued as U.S. Pat. No.
9,629,171 on Apr. 18, 2017, which is the U.S. National Stage, under
35 U.S.C. .sctn. 371, of International Application No.
PCT/US2013/057101 filed Aug. 28, 2013, which claims the benefit of
U.S. Provisional Application Ser. No. 61/694,162 filed Aug. 28,
2012 and U.S. Provisional Application Ser. No. 61/774,979 filed
Mar. 8, 2013, the contents of which are hereby incorporated by
reference herein.
BACKGROUND
[0002] High frequencies offer the potential of wide bandwidths. The
narrow beamforming enabled at these frequencies (along with high
penetration losses) provides high spatial containment of the
transmitted signals. These frequencies may be referred to as
millimeter wave (mmW) frequencies. The precise frequency range may
range from approximately 28 GHz to 160 GHZ or 300 GHz with a
special interest in the unlicensed V-band (60 GHz band) and E-band
(70/80/90 GHz point-to-point band). Even higher frequencies,
(sometimes referred to as terahertz (THz)), may be used and may be
are applicable. The V-band is of particular interest due to the
.about.7 GHz, (depending on country) of unlicensed spectrum
available and the growing ecosystem of under-development standards
such as WiGig, WirelessHD and the like. Existing 60 GHz standards
such as Institute of Electrical and Electronics Engineers (IEEE)
802.11ad and IEEE 802.15.3c specify procedures for initial beam
acquisition and subsequent beam tracking. However, these procedures
are inadequate to address more challenging wireless
transmit/receive unit (WTRU) mobility scenarios in outdoor
applications. Moreover, they do not leverage measurements from
neighboring cells to aid WTRU tracking.
SUMMARY
[0003] Methods and apparatuses are described herein to perform and
improve mmW beam tracking. Described herein are localization
methods to improve predictions of the position of a WTRU, which may
allow a millimeter wave base station (mB) to appropriately select a
modified beam without having to perform beam acquisition every
single time a WTRU moves. Localization techniques in which an mB
may control a directional measurement campaign in order to generate
a directional radio environment map (DREM) are described herein.
The mB may request associated WTRUs to perform directional signal
strength measurements, which may then be reported back to the mB.
The mB may then generate a DREM based on the directional signal
strength measurement reports, which may be used to identify
secondary links when a primary link fails. Another application of
the DREM is to determine possibilities for multiple simultaneous
transmissions to different WTRUs. The mB may store the DREM in a
database for network access by other mBs and for secondary link
selection.
[0004] Also described herein are additional localization techniques
using internal/external information for prediction. The information
may be time-stamping, signal strength measurement, location
information (global positioning system (GPS) coordinates), and
inputs from internal devices such as gyroscopes, accelerometers,
and the like. Another example method may use the previous history
of used beams and other historical data such as mapped terrain
information. In yet another example, data obtained from mB-mB
cooperation including feedback information and reference signaling
information may be used. Using group movement of WTRUs to perform
beam tracking of a WTRU group is also described. Beam tracking for
directional relays and initial beam training optimization methods
are also described. Finally, WTRU localization precision
improvement, beamwidth adaptation, and assisted beam tracking and
handover methods are disclosed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] A more detailed understanding may be had from the following
description, given by way of example in conjunction with the
accompanying drawings wherein:
[0006] FIG. 1A is a system diagram of an example communications
system in which one or more disclosed embodiments may be
implemented;
[0007] 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;
[0008] FIG. 10 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;
[0009] FIG. 2A is a high level flow chart in which the mB may
control a directional measurement campaign in order to generate a
directional radio environment map (DREM);
[0010] FIG. 2B is an example of a first phase of mB controlled
directional measurements;
[0011] FIG. 2C is an example of a second phase of mB controlled
directional measurements;
[0012] FIG. 2D is an example of a third phase of mB controlled
directional measurements;
[0013] FIG. 2E is an example of a fourth phase of mB controlled
directional measurements;
[0014] FIG. 2F is an example of secondary link discovery at a WTRU
following directional signal strength measuring and reporting;
[0015] FIG. 2G is an example of a Directional Measurement
frame;
[0016] FIG. 3A is an example of using data from other sources for
tracking the movement of a WTRU to generate a DREM;
[0017] FIG. 3B is a second example of using data from other sources
for tracking the movement of a WTRU to generate a DREM;
[0018] FIG. 4A is a call flow diagram for an example intra
cell/basic service set (BSS) directional measurement procedure for
DREM generation;
[0019] FIG. 4B is a call flow diagram for an example inter
cell/basic service set (BSS) directional measurement procedure for
DREM generation;
[0020] FIG. 5 is an example of secondary beam activation ;
[0021] FIG. 6A is an example call flow of a procedure in which an
implicit intra-cell switch is made to a secondary beam;
[0022] FIG. 6B is an example call flow of a procedure in which an
explicit inter-cell switch is made to a secondary beam;
[0023] FIG. 7A is an example in which an mB has two beams and may
select a beam based on WTRU movement;
[0024] FIG. 7B is an example of how location information may be
used for improved handover decisions;
[0025] FIG. 8 is an example in which a WTRU may be tracked using
historical data;
[0026] FIG. 9 is an example in which a WTRU may be tracked by
multiple mBs;
[0027] FIG. 10A an example of a WTRU providing data feedback from
multiple mBs to the serving mB;
[0028] FIG. 10B is an example of mB to mB communication
signaling;
[0029] FIG. 11A is an example of the current IEEE 802.11ad Sector
Level Sweep (SLS) procedure;
[0030] FIG. 11B is an example of a revised SLS procedure;
[0031] FIG. 11C is a continuation of the example revised SLS
procedure of FIG. 11B;
[0032] FIG. 12 is an example of improved method for geo-location
precision;
[0033] FIG. 13 is an example of direct and indirect mB-WTRU
links;
[0034] FIG. 14A is an example of beam tracking on the R-WTRU-WTRU
link triggered by WTRU movement;
[0035] FIG. 14B is an example of how an mB may provide relay beam
tracking information to a relay WTRU and may schedule a SP for
WTRU-R-WTRU beam tracking;
[0036] FIG. 14C is an example of a relay beam-tracking field that
may be provided by the mB to the R-WTRU;
[0037] FIG. 15 is an example of beam tracking via omni-directional
band (OBand) signaling;
[0038] FIG. 16 is an example of the use of variable beamwidths;
and
[0039] FIG. 17 is an example of a receiver beam adaptation
procedure.
DETAILED DESCRIPTION
[0040] 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.
[0041] 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.
[0042] 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 other 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.
[0043] 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.
[0044] 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).
[0045] 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).
[0046] 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).
[0047] 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 1x, 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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 130,
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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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 130 and/or the removable memory 132. The
non-removable memory 130 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).
[0058] 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.
[0059] 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.
[0060] 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.
[0061] FIG. 1C is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. The RAN 104 may be an
access service network (ASN) that employs IEEE 802.16 radio
technology to communicate with the WTRUs 102a, 102b, 102c over the
air interface 116. As will be further discussed below, the
communication links between the different functional entities of
the WTRUs 102a, 102b, 102c, the RAN 104, and the core network 106
may be defined as reference points.
[0062] As shown in FIG. 1C, the RAN 104 may include base stations
140a, 140b, 140c, and an ASN gateway 142, though it will be
appreciated that the RAN 104 may include any number of base
stations and ASN gateways while remaining consistent with an
embodiment. The base stations 140a, 140b, 140c may each be
associated with a particular cell (not shown) in the RAN 104 and
may each include one or more transceivers for communicating with
the WTRUs 102a, 102b, 102c over the air interface 116. The base
stations 140a, 140b, 140c 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.
In one embodiment, the base stations 140a, 140b, 140c may implement
MIMO technology. Thus, the base station 140a, for example, may use
multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a. The base stations 140a, 140b,
140c may also provide mobility management functions, such as
handoff triggering, tunnel establishment, radio resource
management, traffic classification, quality of service (QoS) policy
enforcement, and the like. The ASN gateway 142 may serve as a
traffic aggregation point and may be responsible for paging,
caching of subscriber profiles, routing to the core network 106,
and the like.
[0063] The air interface 116 between the WTRUs 102a, 102b, 102c and
the RAN 104 may be defined as an R1 reference point that implements
the IEEE 802.16 specification. In addition, each of the WTRUs 102a,
102b, 102c may establish a logical interface (not shown) with the
core network 106. The logical interface between the WTRUs 102a,
102b, 102c and the core network 106 may be defined as an R2
reference point, which may be used for authentication,
authorization, IP host configuration management, and/or mobility
management.
[0064] The communication link between each of the base stations
140a, 140b, 140c may be defined as an R8 reference point that
includes protocols for facilitating WTRU handovers and the transfer
of data between base stations. The communication link between the
base stations 140a, 140b, 140c and the ASN gateway 142 may be
defined as an R6 reference point. The R6 reference point may
include protocols for facilitating mobility management based on
mobility events associated with each of the WTRUs 102a, 102b,
102c.
[0065] As shown in FIG. 10, the RAN 104 may be connected to the
core network 106. The communication link between the RAN 104 and
the core network 106 may defined as an R3 reference point that
includes protocols for facilitating data transfer and mobility
management capabilities, for example. The core network 106 may
include a mobile IP home agent (MIP-HA) 144, an authentication,
authorization, accounting (AAA) server 146, and a gateway 148.
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.
[0066] The MIP-HA 144 may be responsible for IP address management,
and may enable the WTRUs 102a, 102b, 102c to roam between different
ASNs and/or different core networks. The MIP-HA 144 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. The AAA server 146
may be responsible for user authentication and for supporting user
services. The gateway 148 may facilitate interworking with other
networks. For example, the gateway 148 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.
[0067] In addition, the gateway 148 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.
[0068] Although not shown in FIG. 10, it will be appreciated that
the RAN 104 may be connected to other ASNs and the core network 106
may be connected to other core networks. The communication link
between the RAN 104 and the other ASNs may be defined as an R4
reference point, which may include protocols for coordinating the
mobility of the WTRUs 102a, 102b, 102c between the RAN 104 and the
other ASNs. The communication link between the core network 106 and
the other core networks may be defined as an R5 reference, which
may include protocols for facilitating interworking between home
core networks and visited core networks.
[0069] An access router (AR) 165 of a wireless local area network
(WLAN) 160 may be in communication with other networks 112
including the Internet 110 via the core network 106. The AR 165 may
facilitate communications between APs 170a and 170b. The APs 170a
and 170b may be in communication with WTRU 102d, which may provide
the WTRU 102d with access to packet-switched networks, such as the
Internet 110, to facilitate communications between the WTRUs 102a,
102b, 102c and IP-enabled devices.
[0070] Communication systems using highly directional links require
their beams to be oriented in a way such that they point towards
each other. This process is generally referred as beam acquisition.
This may use the exchange of special signal bursts or sounding
frames between the nodes. Beam acquisition establishes the initial
beam configuration between corresponding nodes, enabling them to
initiate communications. However, the initial antenna configuration
discovered after beam acquisition may be rendered non-optimum due
to substantial relative motion between the communicating nodes.
Therefore, the optimum pair of beams between the nodes may be
improved by being constantly updated based on their relative
motion. This process is called beam tracking and is usually a
simpler procedure than initial beam acquisition, with the beam
search space restricted to a few candidates that are closely
related to the last known optimum beam in some sense. Beam tracking
enhancements that involve directional measurements and message
exchanges between the millimeter wave base station (mB) and WTRU
and between mBs are described herein.
[0071] Beam tracking enables directional communications between
nodes while subject to relative motion and orientation data changes
and follows initial beam acquisition, where initial beam
orientation between nodes is determined. The aim of the beam
tracking function is to adapt the transmission and reception beam
patterns at both ends of a communication link, starting from the
initial beamforming training configuration. Enhancements to the
IEEE 802.11ad standard to suit high-mobility outdoor deployments of
future millimeter wave systems are described herein as an example.
However, the described procedures can be applied to any other
directional communication system. The terms millimeter wave Base
station (mB) and WTRU used herein correspond to an access point
(AP) and station (STA) in IEEE 802.11ad standard, respectively.
Alternately, it could refer to Piconet Controller (PNC) and Device
(DEV) in an IEEE 802.15.3c system, respectively. An mB may also be
any type of wireless device capable of operating AP/BS likes
features. For example, an mB may refer to a WTRU used for tethering
so that other mobile devices may share an internet connection with
the WTRU. An mB may also refer to any WTRU used as a mobile
hotspot.
[0072] Localization methods to improve the prediction of the
positions of a WTRU, which may allow an mB to appropriately select
a modified beam, are described herein in accordance with one
embodiment. The methods described may be applied to determine the
location of the WTRU and to help track the WTRUs movement without
having to perform beam acquisition every single time a WTRU moves.
The methods described herein may be applied in collaboration in
order to increase the accuracy of the predictions of the position
of the WTRU and therefore improve secondary beam selection.
[0073] Measuring signal strength for example may be one technique
used for improving beam tracking. The measurement of signal
strength of a beacon signal may be done using factors including but
not limited to the frequency and power of a signal. The concept of
the Doppler Effect may be used to accomplish this task. The Doppler
Effect occurs when an object, such as a WTRU, moves with respect to
another stationary object (mB). The received frequency of the waves
emitted from the stationary object change according to the moving
object's motion. As a result, when a WTRU moves with respect to a
stationary object, the frequency of the waves transmitted from the
WTRU may change. These relative changes in frequency occur because
as the WTRU is moving toward a stationary observer, each successive
wave crest may be emitted from a position closer to the stationary
observer than the previous wave and may take less time to reach the
observer than the previous wave. This reduction in the time between
the arrivals of successive wave crests may cause an increase in the
frequency. While the WTRU is moving, the distance between
successive wave fronts may be reduced, so the waves appear to bunch
together. Similarly, if the WTRU is moving away from the stationary
observer, each wave may be emitted from a position farther from the
stationary observer than the previous wave, and as a result, the
arrival time between successive waves is increased, which reduces
the frequency. The distance between successive wave fronts is
increased, so the waves appear to spread out.
[0074] An observation similar to the Doppler Effects may be made
when the power of beacon signals received from an mB is observed.
When the moving WTRU gets closer to the stationary mB, the measured
power of the signal may increase, and as the WTRU moves away, the
power may decrease because the signal has travelled a longer
distance to reach the WTRU and may have deteriorated. The WTRU may
also measure the power of any other mBs within listening range, and
the WTRU may then use for example, a triangulation technique with
the collected information to determine its location.
[0075] By measuring the difference in power due to the movement of
the WTRU with respect to all the possible mBs in range, the
movement of the WTRU may be tracked. The beam direction may be
changed accordingly to facilitate the strongest link between the
WTRU and mB. Therefore, measurement, reporting, and prediction
techniques may be used to establish the strongest link at various
positions of the WTRU in movement. The WTRU may make measurements
that record changes in the frequency or power of a received signal
that may be used by the mB to determine the position of the
WTRU.
[0076] FIG. 2A provides a high level flow chart in which the mB may
control a directional measurement campaign in order to generate a
directional radio environment map (DREM) for use in improved beam
tracking and simplified handovers in accordance with one embodiment
200. The mB may request associated WTRUs to perform directional
signal strength measurements 201 on signals addressed to them. An
mB may also request that associated WTRUs report directional signal
measurements 201 on messages addressed to other WTRUs. The mB may
either specify the receive directions from which to request
measurements 201, and also the associated antenna configuration
(beamwidth, gain, and the like) to use, or may let the WTRU decide
the measurement directions. Alternatively or additionally, the mB
may request the WTRU perform directional signal strength
measurements 201 when nodes such as other WTRUs and/or mBs
belonging to other networks are transmitting. These directional
signal strength measurements 201 may apply to the broadcast beacon
messages in the IEEE 802.11ad standard, 802.11aj, 802.15.3c or
other similar standards. The WTRU directional signal strength
measurements 201 may be performed either using a quasi-omni antenna
pattern corresponding to Control PHY reception or with directional
reception if it is already associated.
[0077] The mB may also provide a transmission schedule 202 to the
WTRU. This may include the measurement schedule (including but not
limited to time and frequency information) and the direction and
antenna configuration for these measurements. This may enable the
WTRU to make multiple directional signal strength measurements when
data transmission is scheduled between another WTRU in the network
and the mB.
[0078] The mB then may receive directional signal strength
measurement reports 203 from the WTRU. The WTRU may report 203 the
measured signal strength of received transmissions from the mB in
terms of a Received Signal Strength Indicator (RSSI). This may be
time-averaged over an appropriate duration to counter signal
fading. The averaging interval used may capture WTRU dynamics when
it is short enough. Additionally, the WTRU may be required to
report 203 its antenna configuration such as receive beamwidth,
antenna gain, and the like to the mB along with measurement
results. The WTRU may report 203 the measurement results either to
its serving mB or to neighbor mBs if it is associated with them.
Also, when the WTRU determines the measuring directions, the
measurement report 203 may include the directions covered and the
antenna configuration used along with the measurements. From the
signal strength measurement reports 203, the serving mB may
estimate the WTRU range and may modify its associated beam.
[0079] The mB may then generate 204 a directional radio environment
map (DREM) based on the directional signal strength measurement
reports. The measurement reports may enable the mB to generate 204
DREM, which may include data about its surroundings including
measurements on intra-cell and inter-cell signals. Note that DREM
may also include historical information gathered from previous
measurement reports and possibly from different WTRUs. Antenna
configurations resulting in received signal strength at the WTRU
larger than a configurable or predetermined threshold may be
retained as secondary WTRU-mB1 links that may get activated when
the primary line-of-sight (LoS) link may become obstructed or
experiences interference without conducting a complete beam
training procedure. Based on these reports the mB may perform beam
tracking and identification of non line-of-sight (nLoS)
communication possibilities. Another application of the DREM is to
determine possibilities for multiple simultaneous transmissions to
different WTRUs. The mBs may be expected to have capabilities to
transmit to multiple WTRUs at the same time, either in the same
direction or in distinct directions using Space Division
Multiplexing (SDM) and Multi-User Multiple Input Multiple Output
(MU-MIMO) techniques. Multiple simultaneous transmissions based on
SDM techniques may identify WTRUs with small cross-interference
between their individual beams. WTRUs in MU-MIMO systems sharing
the same mB beam may also identify the WTRUs.
[0080] The mB may store 205 the DREM in a database for network
access by other mBs or a central network entity and for secondary
link selection. The mB may then identify 206 secondary beams for
WTRUs based on the DREM. The mB may handover from the primary beam
to the secondary beams based on the DREM when the primary beam
becomes disrupted.
[0081] FIGS. 2B-2F provide an example of mB controlled directional
measurements that may be used to generate a DREM, in which an mB
directs a WTRU to make directional signal strength
measurements.
[0082] FIG. 2B provides an example of a first phase of mB
controlled directional measurements. WTRU1 210 may be communicating
with mB 212 over a direct LoS link with receive beam 213a and
transmit beam 213b. WTRU2 211 may not be communicating.
[0083] FIG. 2C provides an example of a second phase of mB
controlled directional measurements. In this phase, mB 222 may not
have a direct LoS link with WTRU1 220, but a viable alternate
reflected link may exist 223. WTRU2 221 may be communicating over a
direct LoS link with receive beam 224a and transmit beam 224b.
[0084] FIG. 2D provides an example of a third phase of mB
controlled directional measurements. To identify any existing
secondary links, mB 232 may request WTRU1 230 make directional
signal strength measurements while communicating over a direct LoS
link with receive beam 233a and transmit beam 233b. WTRU2 231 may
not be communicating. mB 232 may also direct WTRU1 230 to make
multiple directional signal strength measurements when data
transmission is scheduled on the mB1 232 to WTRU2 231 link.
[0085] FIG. 2E provides an example of a fourth phase of mB
controlled directional measurements. Following the request to make
directional signal strength measurements, WTRU1 240 may perform
measurements in the requested directions 245a, 245b, and 245c and
may report results to mB 242. This may include making measurements
when data transmission is scheduled on the mB 242 to WTRU2 241
link. In this phase, WTRU1 240 may have an indirect or reflected
link 243 with mB 242. WTRU2 241 may be communicating with mB 242
over a direct LoS link with receive beam 244a and transmit beam
244b.
[0086] FIG. 2F provides an example of secondary link discovery at a
WTRU following directional signal strength measuring and reporting.
WTRU1 250 may communicate with mB 252 over a direct LoS link with
receive beam 253a and transmit beam 253b. Alternatively, WTRU1 250
may communicate over a non-LoS link comprising receive beam 254a
and transmit beam 254b which may have been established based on the
directional signal strength measurements. Communication between
WTRU2 251 and mB 252 over a direct LoS link with receive beam 255a
and transmit beam 255b may remain undisturbed.
[0087] mB controlled directional measurements for generating a DREM
and determining WTRU location may also involve sending extra data
in beacon frames. FIG. 2G shows an example of a Directional
Measurement frame, which may contain a directional measurement
request 263 field, a directional measurement report 273 field, and
a beam switch 282 field.
[0088] The directional measurement request 263 field may include
but is not limited to the following information: a start time 261,
measurement interval 262, measurement count 264, start azimuth 265,
start elevation 266, azimuth step 267, elevation step 268, and
measurement control 269.
[0089] The directional measurement report 273 field shown in FIG.
2G may include but is not limited to the following information:
azimuth 271, elevation 272, received channel power indicator
(RCPI)/received signal to noise indicator (RSNI) 274, and Rx
antenna gain 275.
[0090] The beam switch 282 field shown in FIG. 2G may include but
is not limited to the following information: switch trigger 281,
azimuth offset 283, elevation offset 284, traffic specification
(TSPEC)/QoS specification 285, signal strength loss 286, switch
time 287, switch control 288, handover (HO) address 289, and HO
parameters 290.
[0091] As stated above the directional measurement request 263
field includes a start time 261 timestamp, which may define the
exact time of the frame. This start time 261 timestamp may also be
used to calculate the Round Trip Time (RTT) after the
acknowledgement (ACK) is sent back. By obtaining the RTT, the
location of a WTRU may be identified independently from the
directional signal strength measurements reported by the WTRU by
calculating the distance travelled by the beacon to reach the WTRU.
Calculating the distance travelled by the beacon to reach the WTRU
using Time of Arrival (ToA) or Time Difference of Arrival (TDoA)
may also be performed when system clocks are synchronized. The
accuracy of the WTRU's position may be improved by calculating the
distance of the WTRU from more than one mB.
[0092] The WTRU may receive periodic beacons from a mB as shown in
the example of FIG. 2G. The WTRU may then synchronize its internal
clock based on the received start time 261 timestamp. The WTRU may
then respond to the mB with a control message containing the exact
transmission instant of the WTRU response. From the timestamp
received from the WTRU, the mB may estimate the range of the WTRU
using time-of-flight calculations. Based on the range estimate and
other received information, the mB may determine the best beam to
use for communicating with the WTRU. The mB may also transmit the
range estimate to the WTRU.
[0093] The WTRU may respond with its timing response upon receiving
the beacon or some other message from the mB with a timestamp to
avoid timing errors due to clock drift. For an mB with multiple
associated WTRUs, a schedule for collecting WTRU timing responses
may be established by the mB, and should shortly follow the beacon
transmissions.
[0094] FIGS. 3A-3B provide examples of using data from other
sources for tracking the movement of a WTRU to generate a DREM and
perform beam tracking 300. In FIG. 3A, the WTRU 310 may have a
communication link with mB 315 using beam 312, but WTRU 310 may
also know the signal strengths of beams 311, 313, and 314. This
information may be used to determine which beam would be the best
to use in the event that the orientation data of WTRU 310
changes.
[0095] In FIG. 3B, it is shown that once the orientation data of
WTRU 320 may have changed, the WTRU 320 may start using beam 323 to
sustain the communication link with mB 325. After the beam has been
adjusted, WTRU 320 may contact mB 325 to notify mB 325 that because
the orientation of WTRU 320 has changed, beam 323 may be used in
case beam 322 is no longer strong enough to sustain the
communication link. Consequently, mB 325 may update the current
beam orientation and DREM associated with WTRU 320. If WTRU 320
changes orientation drastically a different mB may be used to
continue the connection. Alternatively or additionally, WTRU 320
and mB 325 may feed back the alternative beam 323 to an eNB, either
through the overlaying LTE connection or a viable mmW link.
[0096] WTRU 320 may use various methods to determine and report its
movement and/or changed orientation to the mB 325. One approach is
for the WTRU 320 to use internal compass signals. Additionally, the
orientation change signaled by the internal sensors may be used by
WTRU 320 to maintain its beam orientation towards mB 325, by
modifying its beam configuration to use alternative beam 323.
[0097] In another example, GPS coordinates may be used to track the
movement of WTRU 320. Coordinates may be obtained using GPS,
Assisted-GPS (A-GPS) or the like. This method may reduce the
resources used for beam acquisition and training because the
location of WTRU 320 may be established within a smaller range as
the mB filters the directional signal strength measurements
received based on the GPS coordinates or time information. GPS is a
space-based satellite navigation system that provides location and
time information in all weather and anywhere on or near the Earth
where there may be an unobstructed line of sight to four or more
GPS satellites. Using these coordinates may enable the
identification of the position of WTRU 320 with the accuracy of 10
meters or less. This may be used by mB 325 in order to perform a
beam training procedure within a particular area (of a 10 meter
radius) rather than the wider range. After mmW links are formed
regular feedback may be sent with the position of WTRU 320
according to the GPS coordinates to mB 325 and additionally to the
eNB. For efficiency, WTRU 320 may report only the change in
readings from the previous instance. Using this information, a
prediction may be made as to which direction WTRU 320 may be moving
and with what speed, narrowing the possibilities of beams that may
be used to make a link, which may enable mB 325 to determine the
best beam 323 for communicating with WTRU 320.
[0098] Another approach for performing beam tracking of WTRU 320
may include the use of other devices internal to WTRU 320 such as
by using a gyroscope/accelerometer. A gyroscope is a device that
may be used for measuring orientation using angular momentum,
thereby allowing it to maintain the orientation. A gyroscope may
comprise a spinning wheel or disk in which the axle is free to
assume any orientation. This orientation, which is not fixed, may
keep changing in response to an external torque much less and in a
different direction than it would without the large angular
momentum associated with the disk's high rate of spin and moment of
inertia. When the device is mounted on gimbals, external torque is
minimized, but its orientation remains nearly fixed, regardless of
any motion of the platform on which it is mounted. Because
gyroscopes allow the calculation of orientation and rotation
designers have incorporated them into many devices. The integration
of the gyroscope has allowed for more accurate recognition of
movement within a 3D space than previous methods using a lone
accelerometer within a number of smart phones. A further recent
innovation is an electronic gyroscope, which is present in vehicles
like Segway scooters and the Honda UNI-CUB, which ensures that the
vehicle remains upright and balanced.
[0099] WTRU 320 may have an integrated gyroscope, accelerometer,
compass and other orientation sensing devices. Outputs from such
internal sensors may be fed back to mB 325 to facilitate beam
tracking. These readings, when available with high precision, along
with other information, may enable mB 325 to determine the precise
location and orientation of WTRU 320. For efficiency, WTRU 320 may
report only the change in readings from the previous instance.
These devices may also be used advantageously by measuring the
signal strength readings from the beacons, such that whatever
position WTRU 320 is in WTRU 320 remains in contact with the
strongest beam.
[0100] Group movement of WTRUs may also be tracked using the
methods described above. This situation may apply when multiple
WTRUs move together in the same direction, for example, in a
vehicle. The WTRU tracking may be aided in such a situation because
multiple measurements covering several WTRUs may be leveraged for
WTRU location estimation. A collection of WTRUs covered by the same
or adjoining mB beams constitute a group. Members of a group
maintain a constant spatial relation with respect to each other,
which facilitates efficient tracking. This enhancement may manifest
itself in several ways including but not limited to the following:
the mB may reduce WTRU tracking measurements by denoting one or a
few of the WTRUs in the group, identifying one or more of the WTRUs
as a group head or heads and using those measurements for the
entire group, or it may manifest itself in the form of a denser
sampling of WTRU tracking measurements leading to better location
prediction.
[0101] For tracking purposes, a group may comprise of WTRUs sharing
the same mB beam. A feature of a group may include that the members
maintain a constant spatial relation with respect to each other,
which facilitates efficient tracking. This may allow group members
to reduce their location reporting periodicity. The WTRUs may be
informed of group membership or may infer group membership using
methods including but not limited to the following: the mB may
inform the WTRU about group membership and a lower location
reporting periodicity, or the WTRU may determine group membership
via monitoring location information of other WTRUs reported via
OBand signaling. In the second case, the WTRU may infer that it is
part of a group when it finds other WTRUs with similar coordinates,
and may automatically reduce its position reporting
periodicity.
[0102] FIG. 4A is a call flow diagram for an example intra
cell/basic service set (BSS) directional measurement procedure for
DREM generation 400. Serving mB 401 may transmit a measurement
schedule 410a, 410b, and 410c to WTRU1 402a, WTRU2 402b, and WTRU3
402c respectively. The schedule may be transmitted in a beacon
frame as described above. Serving mB 401 may then transmit
directional measurement request 411a to WTRU1 402a and directional
measurement request 411b to WTRU3 402c. WTRU1 402a and WTRU3 402c
may respond by transmitting ACK 412a and 412b respectively to
serving mB 401. Then while serving mB 401 is transmitting data 413
to WTRU2 402b, WTRU1 402a and WTRU3 402c may make directional
measurements 414a and 414b. WTRU3 402c may then transmit a
directional measurement report 415a to serving mB 401, which
transmits an ACK 415b back to WTRU3 402c in response. Similarly
WTRU1 402a may then transmit directional measurement report 416a to
serving mB 401, which transmits an ACK 416b back to WTRU1 402a in
response.
[0103] FIG. 4B is a call flow diagram for an example inter
cell/basic service set (BSS) directional measurement procedure for
DREM generation. Serving mB 401 may transmit a downlink schedule
request 421 to neighbor mB 403a. Neighbor mB 403a may then transmit
a measurement schedule 422 to WTRU4 402d. Then neighbor mB 403a may
transmit a downlink schedule request 423 to serving mB 401, which
may include beam orientations. Serving 401 mB may then transmit a
measurement schedule 424a to WTRU1 402a and transmit a measurement
schedule 424b to WTRU2 402b. Serving mB 401 may then transmit
directional measurement request 425a to WTRU1 402a and directional
measurement request 425b to WTRU2 402b. WTRU1 402a and WTRU2 402b
may respond by transmitting ACK 426a and 426b to serving mB 401.
Then while neighbor mB 403a is transmitting data 427a to WTRU4
402d, WTRU1 402a and WTRU2 402b may make directional measurements
427b and 427c. WTRU1 402a may then transmit directional measurement
report 428a to serving mB 401, which may transmit an ACK 429a back
to WTRU1 402a. Similarly WTRU2 402b may then transmit a directional
measurement report 428b to serving mB 401, which transmits an ACK
429b back to WTRU2 402b in response.
[0104] As aforementioned, once an mB has generated a DREM in
accordance with any of the methods described herein, the mB may
identify secondary beams for use by a WTRU. FIG. 5 provides an
example of secondary beam activation 500. FIG. 5 shows the use of
DREM to identify a secondary beam during service period 510. In
this example, mB 501 may transmit data on its primary transmission
(Tx) beam 511a and 511b and may receive on its primary reception
(Rx) beam 512a and 512b while WTRU 502 may be transmitting ACKs on
its primary Tx beam 522a and 522b and may be receiving data on its
primary Rx beam 521a and 521b. When the primary Rx beam 512b of mB
is blocked, mB 501 switches to a secondary beam as identified using
DREM and may continue to transmit data on secondary Tx beam 513a,
513b, and 513c. mB 501 may receive on secondary Rx beam 514a, 514b,
and 514c. Similarly, WTRU 502 is transmitting on its secondary Tx
beam 524a, 524b, and 524c and receives on its secondary Rx beam
523a, 523b, and 523c.
[0105] mB 501 may then test the primary Tx beam 511c, which may
result in WTRU 502 having its primary Rx beam 521c blocked and mB
501 having its primary Rx beam 512c blocked. As a result mB 501 and
WTRU 502 may continue communicating on their respective secondary
beams: mB 501 transmits on its secondary Tx beam 513d and secondary
Rx beam 513e while WTRU 502 transmits on its secondary Tx beam 523d
and secondary Rx beam 524d.
[0106] FIG. 6A shows an example call flow of a procedure in which
an implicit intra-cell switch is made to a secondary beam 600.
Serving mB 601 may identify a secondary beam 611 associated with
WTRU 602 based on DREM which includes but is not limited to
directional measurement reports, WTRU location information, and/or
WTRU orientation based on any of the methods described herein.
While communicating on a primary beam 603, the serving mB 601 may
transmit a schedule 612 to WTRU 602 on its primary beam 605, and
WTRU 602 may be notified of the secondary beam configuration 613.
Serving mB 601 may then send a beam switch 615 to WTRU 602 over
their respective primary beams 603 and 605. Within a short
interframe space (SIFS) 616, WTRU 602 may respond with an ACK 617.
Serving mB 601 may then transmit data 618 to WTRU 602. Again,
within a SIFS 619, WTRU 602 may respond with an ACK 620. Following
SIFS 621, serving mB 601 may transmit data 622 to WTRU 602. WTRU
602 may then respond with an ACK 624, which is blocked and not
received by serving mB 601 during SIFS 623. As a result WTRU 602
may switch to a secondary beam 626, and serving mB 601 may also
switch to a secondary beam 628 following a beam change interval
625. Serving mB 601 may then retransmit data 627 to WTRU 602 on
their respective secondary beams 604 and 606. WTRU 602 may then
respond with an ACK 629. This procedure may occur within a service
period (SP) 614b or within more than one SP such as a previous SP
614a.
[0107] FIG. 6B shows an example call flow of a procedure in which
an explicit inter-cell switch is made to a secondary beam. Serving
mB 601 may identify a secondary beam 631 associated with WTRU 602
based on DREM which includes but is not limited to directional
measurement reports, WTRU location information, and/or WTRU
orientation based on any of the methods described herein. While
communicating on a primary beam, the serving mB 601 may transmit a
schedule 632 to WTRU 602. Serving mB 601 may then transmit a
handover (HO) request 634 to a neighbor mB 607, and the neighbor mB
may respond with a HO response 635 indicating success. The HO
request 634 and HO response 635 exchange may occur over the
distribution system (DS) 633. Serving mB 601 may then send a beam
switch 637a to WTRU 602, and WTRU 602 may learn of the secondary
beam configuration 637b. Within a short interframe space (SIFS)
636a, WTRU 602 may respond with an ACK 638. Serving mB 601 may then
transmit data 639 to WTRU 602. Again, within a SIFS 636b, WTRU 602
may respond with an ACK 640. Following SIFS 636c, serving mB 601
may transmit a beam switch 641 to WTRU 602, which may respond with
ACK 642. Serving mB 601 may then transmit a path switch request 644
to a network controller 608, and the network controller 608 may
respond with a path switch confirmation 645. Then neighbor mB 607
may transmit data 646 to WTRU 602 on a secondary beam, and WTRU 602
may respond with an ACK 647. The message exchange as detailed
herein may occur within the same SP 643c or within more than one SP
643b such as a previous SP 643d. The message exchange between
neighbor mB and WTRU 602 may occur within a separate SP 643a.
[0108] FIG. 7A shows an example in which an mB has two beams and
may select a beam based on WTRU movement 700. The directional
signal strength measurements and location and orientation
information fed back by WTRU 702 in accordance with any of the
methods described herein may enhance the tracking performance at
the mB 701. mB 701 may combine any of the aforementioned
information reported by the WTRU 702 to estimate the position of
WTRU 702 with high accuracy. The information may be used by mB 701
to choose the appropriate beam from its two beams 703 and 704 which
provide overlapping coverage. In this example the WTRU location
uncertainty region 705 is smaller than the beam 703 coverage and
704 respectively. Based on the illustrated WTRU 702 location
estimate, mB 701 may switch from beam 703 to beam 704 for the next
data transmission. Location based beam tracking may also be used in
examples where there is no overlapping coverage between adjoining
beams.
[0109] FIG. 7B shows an example of how location information may be
used for improved handover decisions. Again, the directional signal
strength measurements and location and orientation information fed
back by WTRU 712 in accordance with any of the methods described
herein may enhance the tracking performance at the mB1 711 and mB2
713, which may provide overlapping coverage as in this example.
Also in this example, the location uncertainty region 716 of WTRU
712 is smaller than the beam coverage provided by 714 and 715.
Initially, mB1 711 may be the serving mB. Based on the WTRU 712
location estimate and knowledge of adjacent beam coverage based on
for example the DREM, mB1 711 may determine that handover of WTRU
712 to mB2 713 may be needed. Location based handover decisions may
also be used in examples where there is no overlapping coverage
between adjoining beams.
[0110] In addition to the directional signal strength measurements
and location and orientation information fed back by a WTRU
historical data may also be used for WTRU tracking and may allow
logical predictions to be made as to the direction that a WTRU may
move. FIG. 8 shows an example in which a WTRU may be tracked using
historical data 800. WTRU 801 may be currently communicating with
mB 803 using beam 805, while moving in the direction shown 802. At
the current position, beam 805 may be determined to be in fact the
strongest and thereby, the optimal beam to use. However,
information including the corresponding beam strengths of beams
804, 806, and 807 may also be present. The direction in which WTRU
801 is moving may be calculated using the differences among the
beam strengths of beams 804, 806, and 807 and the rate in which the
beam strengths change. This calculation may further be improved by
using other factors like timestamps, GPS data, gyroscope
measurements, and the like using any of the methods described
herein. Historical data may be maintained in a database such as a
DREM database. This database may contain data such as for example,
recent history of beams used (according to mB and beam ID) by WTRU
801, history of the terrain in which mB 803 is deployed, previous
history of similar movements of WTRU 801, and any related
historical information pertaining to the nearest neighboring mBs of
mB 803. Terrain information in which mB 803 is deployed and the
terrain of neighboring cells may further narrow down predictions as
it may reduce the number of attempts for a beam training procedure
to be performed because the possible paths of movement by WTRU 801
are known. This database may be constantly updated using
information received from WTRU 801. mB 803 may also store the route
in which WTRU 801 is moving in a database. Storing and retrieving
such historical data may enable mB 803 to predict the movement of
WTRU 801 allowing mB 803 to track WTRU 801 more accurately. By
retrieving recent history of previous beams stored in the database
of mB 803, a more accurate prediction may be made to determine the
position of WTRU 802.
[0111] By using any of the tracking techniques disclosed herein
and/or historical data, mB 803 may more efficiently handover the
signal to a new mB because mB 803 may be able to determine the
closest mB to which WTRU 801 is moving. When the WTRU reaches the
edge of the cell, it is able to listen or communicate with multiple
mBs. mB 803 may then handover the signal to a new mB by immediately
informing the eNB in the network and the new mB the details of the
movement of WTRU 802.
[0112] FIG. 9 shows an example in which a WTRU may be tracked by
multiple mBs 900. In this example, WTRU 901 may be at all times
situated in between mB1 902, mB2 903, and mB3 904. When WTRU 901 is
within listening distance of mB1 902, mB2 903, and mB3 904 as shown
by their respective beams 906, 907, and 905. mB1 902, mB2 903, and
mB3 904 may use tracking information to locate the position of WTRU
901 by performing any of the methods described herein. By using
multiple mBs, the WTRU may be tracked with improved precision or
accuracy using method such as a triangulation technique.
[0113] Data tracked by mB2 903 and mB3 904 may be fed back to mB1
902 when mB 902 is the serving mB. This may allow mB1 902 to know
the details tracked by mB2 903 and mB3 904 from WTRU 901. For
example, by getting the distances of WTRU 901 from mB2 903 and mB3
904, the exact location of WTRU 901 may be determined. The data fed
back to mB1 902 may be of any form such as, for example, GPS
co-ordinates, gyroscope/accelerometer measurements or other mB's
measurements namely, power, time taken, distance, and the like and
may be provided in accordance with any of the methods described
herein.
[0114] According to yet another embodiment, mB1 902, mB2 903, and
mB3 904 may belong to a group, which for example may be called
Group mBs. Coordinated beam tracking between multiple mBs, mB1 902,
mB2 903, and mB3 904 may also enable mBs as a group to identify an
optimal beam to communicate with WTRU 901 or to identify an
alternative beam when a current link fails. This method may also
include a logical controller, which can either be co-located or not
with one of the mBs in the group.
[0115] The Group mBs may share the location of WTRU 901 and
orientation information of WTRU 901 with a controller. In the case
of simultaneous association of WTRU 901 with multiple mBs, each mB
reports the location of WTRU 901 and orientation information of
WTRU 901 to the controller. The controller then determines the best
beam to communicate with mB1 902, mB2 903, or mB3 904. If the
controller determines that the best beam belongs to an mB that is
different than the current serving mB, then it informs the serving
mB to command the WTRU to switch to another Group mB once the
current message exchange is complete. The reported data to the
neighbor mB may include any of the location or orientation related
information listed herein.
[0116] FIG. 10A shows an example of a WTRU providing data feedback
from multiple mBs to the serving mB for multiple mB-aided tracking
in accordance with yet another embodiment 1000. In this example,
WTRU 1001 may get attached to serving mB1 1002 by performing a beam
acquisition procedure and determining the strongest possible mmW
link. The serving mB1 1002 may request WTRU 1001 perform signal
strength measurements on signals originating in other networks.
These networks may be operating either in the same frequency
channel as serving mB 1002 or another channel. In either case a
measurement gap may be configured by serving mB 1002 allow WTRU
1001 to perform measurement procedures that may occur when WTRU
1001 switches channels or receives beam direction for signal
measurements. By setting up a measurement gap, serving mB 1002 may
ensure that no data transmissions are scheduled for WTRU 1001
during the measuring interval.
[0117] In-band measurements may also be used. WTRU 1001 may be
directed by serving mB 1002 to report directional signal strength
measurements for signals received from the neighboring mBs such as
mB2 1003 and mB3 1004. In case of an IEEE 802.11ad system, WTRU
1001 may be directed to report RSSI of directional beacons from the
neighboring mB2 1003 and mB3 1004. In some embodiments, WTRU 1001
may measure the beacon strength of neighboring mB2 1003 and mB3
1004 with an omni or quasi-omni antenna pattern. Alternatively,
WTRU 1001 may measure the beacon strength using a beam directed
towards neighboring mB2 1003 and mB3 1004. This may require
successful completion of a beam training procedure at WTRU 1001,
via Responder-Receive Sector Sweep (R-RXSS) procedure, to identify
optimum receive antenna pattern. If the report of WTRU 1001 also
includes the antenna pattern used for signal measurements, then
serving mB 1002 may estimate the absolute range of WTRU 1001 from
neighboring mB2 1003 and mB3 1004. If the receive antenna
configuration information is not included in the report of WTRU
1001, then serving mB 1002 may estimate relative WTRU 1001
displacement by comparing successive signal strength reports.
[0118] Out-of-band measurements may also be used. Serving mB 1002
may request WTRU 1001 make signal strength measurements in a
different frequency channel, either within the same band or
different. Additionally, serving mB 1002 may provide other
information such as mB identifiers in other channels and their
coordinates. Serving mB 1002 may also establish a measurement gap
for WTRU 1001 making signal strength measurements on a different
frequency channel.
[0119] Alternatively or additionally, WTRU 1001 may report the beam
identifiers of neighboring mB2 1003 and mB3 1004 corresponding to
strongest beacon reception. In general, neighboring mB2 1003 and
mB3 1004 may include the transmit beam identifier in the
transmitted beacon, and this may be reported by WTRU 1001 to the
serving mB 1002 if the packet is successfully decoded.
[0120] During the measurement gap, WTRU 1001 may listen to the
neighboring mBs such as mB2 1003 and mB3 1004 and receive
information from mB2 1003 and mB3 1004. WTRU 1001 may then perform
calculations and measurements. The WTRU may then feed all of these
details back to serving mB1 1002, which may then analyze the
received information, perform calculations, and determine the exact
position of WTRU 1001.
[0121] Reference signaling with respect to multiple mB-aided WTRU
tracking may also be used. A reference signal may be defined as one
that is sent between two entities exclusively in order to measure
or estimate the mmW link quality. A triangulation method or any of
the other methods described herein may be applied. This reference
signal may be include but is not limited to the following:
[0122] 1) A known sequence--this signal may be solely sent for the
purpose of calculating the power of the signal at arrival;
[0123] 2) A time-stamp--this signal may have a timestamp attached
to it to calculate the time taken by either RTT, ToA or TDoA to
determine position; or
[0124] 3) Beam+mB identifier--this signal may have details about
which beam was sent from which mB so that a ranking system may be
established as to which one was the strongest.
[0125] FIG. 10B shows an example of mB to mB communication
signaling in accordance with another embodiment. This method
involves the direct communication of data from the neighboring mB2
1013 to the connected mB 1012. In this process, WTRU 1011 initially
may get attached to serving mB1 1012 by performing a beam
acquisition procedure and determining the strongest possible mmW
link. Serving mB1 1012 may configure a measurement gap and allow
WTRU 1011 to perform measurement procedures. During the measurement
gap, WTRU 1011 may listen to the neighboring mBs such as mB2 1013
and mB3 1014 and receive information from mB2 1013 and mB3 1014.
WTRU 1011 may then perform calculations and measurements. The WTRU
may then feed all of these details back to mB2 1013. mB2 1013 may
either reports these details back to mB1 1012 in raw form or may
analyze the received information, perform calculations and send
processed information to allow mB1 1012 to determine the position
of WTRU 1011.
[0126] WTRU 1011 may also provide feedback to neighbor mB 1013.
Under some conditions WTRU 1011 may want to convey its changed
location or orientation information to its serving mB1 1012 earlier
than its next service period (SP), and when no contention-based
access period (CBAP) is available before its next SP. Then WTRU
1011 may send its location or orientation information to neighbor
mB2 1013, with which it is simultaneously associated. Simultaneous
association as used herein may refer to any kind of multiple
association, such as temporary association, association for control
signaling only, and the like. In this case, data transmissions may
still occur through serving mB1 1012, but WTRU 1011 communicates
with neighbor mB2 1013 for measurement reports and other control
messaging. Neighbor mB2 1013 may forward the received information
to the serving mB1 1012 of WTRU 1011 either through the
distribution system (DS) or via a direct link between mB1 1012 and
mB2 1013, if one is available. This may allow the serving mB1 1012
of WTRU 1011 to proactively adjust its beam towards the WTRU for
the next transmission. This allows the serving mB1 1012 to react to
rapid movement by WTRU 1011 between two successive measurement
report transmissions, which may result in loss of the serving mB1
1012-WTRU 1011 link when the neighbor mB 1013-WTRU 1011 link may
still be operational. This may also enable WTRU 1011 to make better
handover decisions to neighbor mB2 1013 and mB3 1014. The reported
quantities to neighbor mB2 1013 may include any of the location or
orientation related information described herein.
[0127] Initial beam training optimization is also described herein
in accordance with yet another embodiment. The current IEEE
802.11ad beam training procedure specifies quasi-omni reception at
the responder/STA for device discovery, followed by beamforming
training involving signal strength measurements on multiple
candidate beams to arrive at the optimum pair of transmit and
receive beams at the initiator/AP and responder/STA. The
beamforming training procedure may be simplified with location and
orientation information as described herein.
[0128] FIG. 11A shows an example of the current IEEE 802.11ad
Sector Level Sweep (SLS) procedure 1100. At the end of the SLS
procedure, the initiator 1111 and the responder 1112 normally
identify their best transmit sectors by exchanging sector sweep
frames. The procedure begins with the initiator 1111 (personal
basic service set (PBSS) control point/access point (PCP/AP))
transmitting sector sweep frames 1120 or beacons in multiple
directions with a sectorized antenna pattern, while the responder
1112 (STA) receives with a quasi-omni antenna pattern 1122. Each of
these messages 1121a, 1121b, and 1121c contains a unique countdown
field and a sector identifier. This phase is called Initiator
Sector Sweep (ISS) 1123. This is followed by the Responder Sector
Sweep (RSS) 1124a that normally consists of the Receive Sector
Sweep (RXSS), called Responder-Receive Sector Sweep (R-RXSS). In
this phase, the responder transmits multiple sector sweep 1124b
frames in different directions using sectorized antenna patterns,
while the initiator receives with a quasi-omni antenna pattern
1129. Each sector sweep frame 1125a, 1125b, and 1125c transmitted
by the responder contains unique countdown and sector identifier
fields, and also the initiators best sector identifier. Therefore,
at the end of the SLS procedure, the initiator and responder
identify their optimal transmit sectors 1126a while receiving with
a quasi-omni antenna pattern 1126b and 1127a.
[0129] FIG. 11B shows an example of a revised SLS procedure in
accordance with yet another embodiment. In this procedure nodes
exchange their coordinates leading to discovery of optimum transmit
and receive sectors at the initiator and the responder. The nodes,
initiator 1111 and responder 1112, may identify their coordinates
with high accuracy using any of the procedures described herein.
The accuracy of the location information naturally affects the
performance and the time required to converge to the optimum
sectors, but the procedure is flexible enough to accommodate
different input accuracy levels. Moreover, the described procedure
is backward compatible with IEEE 802.11ad SLS procedure, such that
legacy devices are also accommodated.
[0130] The first phase, ISS 1133, begins with the initiator 1111
transmitting multiple sector sweep 1130 frames or beacons in
different directions. However, the initiator now may include its
precise coordinates in the transmitted frames 1131a, 1131b, and
1131c while the responder 1112 may receive with a quasi-omni
antenna pattern 1132. Legacy devices that receive one of the
transmitted frames may discard the coordinate information and
proceed normally to the next phase.
[0131] The second SLS phase, RSS 1134a, may use the location
information transmitted by the initiator 1111. Now, any responder
1112 that is able to successfully decode one of the sector sweep or
beacon frames, 1131a, 1131b, and 1131c, may identify the precise
coordinates of the initiator 1111. Based on the knowledge of its
own location, previously acquired by any of the options described
earlier, the responder 1112 may determine the optimum sector to use
for sector sweep frame transmission. Depending on the accuracy of
the location information, the responder may identify one optimum
sector or a set of candidate sectors to try out in the second
phase. It then may transmit the sector sweep 1134b frames 1135a and
1135b through the identified sectors while the initiator 1111 may
modify the countdown field to reflect the number of transmit
sectors under test. The responder 1112 may also include its own
coordinates in all the transmissions. During this time the
initiator 1111 may receive with a quasi-omni antenna pattern 1136.
In the case of a response received from a legacy device, the
initiator 1111 may proceed to the next stage according to the
standardized procedure. If however, the received response contains
the coordinate field, the initiator 1111 may switch to the modified
third phase as described below.
[0132] At the end of the second phase (RSS), the initiator 1111 may
also learn the coordinates of the responder 1112 and may switch to
transmit mode to transmit sector sweep frames 1138a, 1138b, 1138c,
1138d through a small set of transmit sectors, identified based on
the coordinates of the initiator 1111 and the responder 1112. In
the first sub-phase, the initiator 1111 may transmit sector sweep
frames 1138a, 1138b, 1138c, 1138d through some sectors while the
responder 1112 may receive through its receive sectors 1139a,
1139b, 1139c, and 1139d that were identified earlier, at the end of
ISS. At the end of this sub-phase, the responder 1112 may also be
able to uniquely identify the optimum sector. Then the responder
1112 may transmit sector sweep frames 1140b and 1140d through the
optimum sector while the initiator 1111 may receive through its
identified sectors 1140a and 1140c. At the end of this sub-phase,
the initiator 1111 also may identify the optimum sector. Therefore,
both nodes may be able to identify optimum sectors, aided by
location information. By having an mB include location information,
a WTRU may get additional location and directional information of
the mB. Furthermore, because the WTRU may include its location
information in the procedure described herein, the mB may estimate
the location of the WTRU more accurately. These sectors may be used
as starting points for fine beam training in the Beam Refinement
Protocol (BRP) procedure. If the initiator 1111 determines that it
may not finish the modified SLS procedure in the current
Association-Beam Forming Training (A-BFT) period, then the
procedure may be split into multiple A-BFT periods or the remaining
steps completed in a SP or CBAP.
[0133] FIG. 12 shows an example of improved method for geo-location
precision 1200. mB 1201 may improve geo-location precision by using
beam tagging. A WTRU's location may be estimated using GPS or
related technologies as described using any of the methods
described herein. However, there may be error in some of these
calculations due to factors including but not limited to
environmental conditions, such as the terrain in dense urban areas.
To mitigate any estimation errors, mB 1201 may create a narrow beam
that illuminates a small area with radio waves using a highly
directional antenna. The area covered by a directional beam 1202
may be smaller than the uncertainty region 1203 of a localization
technique such as GPS or any of the other methods described herein,
especially when the WTRU is close to mB 1201. This method may be
used to correct localization errors and refine such estimates.
[0134] In this method, mB 1201 may continuously collect the
reported coordinates of associated WTRUs over a period of time. The
WTRU then may filter the reported coordinates according to the
associated beams. By time-averaging the reported coordinates of
WTRUs served by a particular beam, mB 1201 may estimate the precise
coordinates of the centroid of the area illuminated by the beam
1202 on the ground. Therefore, by collecting the coordinates of
WTRUs associated with different beams, mB 1201 may precisely
estimate the coordinates associated with each beam, i.e., mB 1201
may tag each beam with a GPS coordinate. The coordinates associated
with a beam may be transmitted to a WTRU using that beam to improve
its location estimate. This may improve the handover performance of
the WTRU, due to an improved location estimate. Additionally, mB
1201 may supply location information to WTRUs that lack secondary
localization capabilities such as GPS. Such low-capability devices
may take advantage of location estimates supplied by serving mB
1201 for improved beam-tracking and better handover
performance.
[0135] Beam tracking methods for indirect links may be performed in
accordance with yet another embodiment. Beam tracking via in-band
signaling is one technique described herein. FIG. 13 shows an
example of direct and indirect mB-WTRU links 1300. WTRU 1301 has a
direct communication link with mB 1302 and also indirect links to
mB 1302 via Relay WTRUs, R-WTRU1 1303b and R-WTRU2 1303a. R-WTRU1
1303b and R-WTRU2 1303a may perform beam tracking on the WTRU
1301-R-WTRU1 1303b link and WTRU 1301-R-WTRU2 1303a link. R-WTRU1
1303b and R-WTRU2 1303a may perform beam tracking for the relay
link without direct communication with the WTRU.
[0136] In one method in accordance with this embodiment, WTRU 1301
may report its location information to serving mB 1302. These
reports may be sent periodically, may be trigger-based, or may be
sent in response to mB 1302 requests. Location information of WTRU
1301 may be used by mB 1302 to update the associated beam.
Additionally, location information of WTRU 1301 may be sent to
R-WTRU1 1303b and R-WTRU2 1303a that may be registered with mB 1302
as relays for WTRU 1301. Based on location information of WTRU 1301
received from mB 1302, R-WTRU1 1303b and R-WTRU2 1303a may update
their respective beams to point towards WTRU 1301. Additionally,
location information supplied by R-WTRU1 1303b and R-WTRU2 1303a
may be forwarded by mB 1302 to WTRU 1301, so that WTRU 1301 may
maintain appropriate beams for relay links. In accordance with any
of the location-related feedback methods described herein, the beam
orientation relative to a global reference may also be transmitted
by WTRU 1301, R-WTRU1 1303b and R-WTRU2 1303a, or mB 1302 to enable
tracking in the other link. For example, beam orientation for the
direct link, (such as orientation with respect to geographic
North), may be transmitted by WTRU 1301 to mB 1302 and this may be
forwarded to R-WTRU1 1303b and R-WTRU2 1303a to assist it in
tracking WTRU 1301. Similar feedback from R-WTRU1 1303b and R-WTRU2
1303a to assist WTRU 1301 may also possible.
[0137] Alternatively or additionally, mB 1302 may send test signals
using different transmit beams and request WTRU 1301 to report
signal strength measurements on the test signals. This may allow mB
1302 to identify the best beam to associate with a particular WTRU.
mB 1302 may use a logical numbering scheme for its beams linked to
geographical orientation, or some other commonly known basis. Upon
receiving the feedback from WTRU 1301 about the best beam, mB 1302
may forward the optimum beam identifier to the active relays,
R-WTRU1 1303b and R-WTRU2 1303a associated with WTRU 1301. From the
reported mB 1302 beam identifier, R-WTRU1 1303b and R-WTRU2 1303a
may estimate the relative position of WTRU 1301 and may accordingly
adjust their beams associated with the relay link.
[0138] FIG. 14A shows an example of beam tracking on the
R-WTRU-WTRU link triggered by WTRU movement 1400. When WTRU 1402
moves 1404, R-WTRU 1403 adjusts its beam pointing direction from
the initial beam pointing direction to its final beam pointing
direction 1405. Similarly, WTRU 1402 adjusts its beam pointing
direction from the initial beam pointing direction 1407 to its
final beam pointing direction 1406 with mB 1401. As shown in FIG.
14A, beam tracking on the WTRU 1402 to R-WTRU 1403 link is
triggered by the WTRU 1402 motion.
[0139] FIG. 14B shows an example of how an mB may provide relay
beam tracking information to a relay WTRU and may schedule a SP for
WTRU-R-WTRU beam tracking. Following beacon 1421, data 1422b and
1422d and training (TRN) fields 1422c and 1422e may be sent between
the mB and WTRU in SP 1422a. The mB may then provide relay and beam
tracking information to the R-WTRU in 1423b followed by an ACK
1423c during SP 1423a.
[0140] The mB may then schedule an SP for WTRU-R-WTRU beam tracking
1424. Following beam refinement protocol (BRP) fields 1425b and
1425c and TRN fields 1425d and 1425e during SP 1425a, the WTRU and
mB may transmit data 1426b, 1426c, and 1426d with a following ACK
1426e during SP 1426a. Similarly, during SP 1427a, the mB and
R-WTRU may transmit data 1427b and a following ACK 1427c to provide
beam tracking and correction information.
[0141] FIG. 14C shows an example of a relay beam-tracking field
that may be provided by the mB to the R-WTRU. A relay beam-tracking
field 1430 may include but is not limited to the following
information: an azimuth correction 1431, elevation correction 1432,
R-WTRU L-Tx 1433, and WTRU L-Tx 1434.
[0142] FIG. 15 shows an example of beam tracking via
omni-directional band (OBand) signaling 1500. For example, in
addition to communicating in the mmW band in accordance with any of
the methods described herein, WTRU 1504, R-WTRU1 1505, R-WTRU2
1506, and mB 1503 may also simultaneously be connected in the mB's
OBand coverage 1501 and the WTRU's OBand coverage 1502. Several
methods for WTRU-RWTRU link beam tracking via OBand signaling are
described herein as examples.
[0143] In a first method, WTRU 1504 may report its location
information to serving mB 1503, via OBand signaling. These reports
may be sent periodically, be trigger-based or sent in response to
mB 1503 requests. WTRU 1504 location information may be used by mB
1503 to update the associated beam. Additionally, R-WTRU1 1505 and
R-WTRU2 1506 within the OBand transmission range of WTRU 1504 may
also obtain the location information, and adjust their associated
beams to point towards WTRU 1504. Conversely, R-WTRU1 1505 and
R-WTRU2 1506 may report their location information to serving mB
1503 using OBand signaling, and this may be simultaneously heard by
WTRU 1504. Based on the received R-WTRU1 1505 and R-WTRU2 1506
location information, WTRU 1503 may modify its beam associated with
R-WTRU1 1505 and R-WTRU2 1506.
[0144] Alternatively or additionally, mB 1503 may send test signals
using different transmit beams and request WTRU 1504 to report
signal strength measurements on the test signals via OBand
signaling. This may allow mB 1503 to identify the best beam to
associate with a WTRU 1504. mB 1503 may use a logical numbering
scheme for its beams linked to geographical orientation, or some
other commonly known basis. Upon receiving the feedback from WTRU
1504 about the best beam, mB 1503 may use that particular beam for
the next communication with WTRU 1504. Simultaneously, when R-WTRU1
1505 and R-WTRU2 1506 are within transmission range of WTRU 1504,
R-WTRU1 1505 and R-WTRU2 1506 may also receive optimum mB 1503 beam
feedback. From the reported mB 1503 beam identifier, R-WTRU1 1505
and R-WTRU2 1506 may estimate the relative position of WTRU 1504
and may accordingly adjust their beams associated with the relay
link. Alternately or additionally, mB 1503 may echo the beam choice
of WTRU 1504 via OBand signaling, so that any R-WTRUs that are
outside the OBand transmission range of WTRU 1504, but within range
of mB 1503 transmissions, may still obtain WTRU 1504 position
information.
[0145] OBand signaling may also be used for beam tracking of WTRUs
with less traffic or non-periodic/bursty traffic. For these
inactive WTRUs there may be long periods of time between successive
packet transmission and reception. This may lead to larger beam
misalignment with their peer nodes than what may be corrected by
beam-tracking procedures. So, some tracking related signaling may
need to be exchanged to track user mobility between packet
transmissions.
[0146] In IEEE 802.11ad, beam tracking packets may be appended to
regular data packets exchanged between a WTRU and an mB. However,
in the absence of regular data packet transmissions, the mB may set
up a schedule for regular exchange of location information between
the mB and the WTRU. Alternatively, OBand signaling may be used for
beam tracking for inactive WTRUs. Then WTRU or mB may signal on the
OBand when the data packet arrives in its buffer, addressed to the
other node. Then, location information or beam tracking packets may
be exchanged to correct any beam misalignment since last
transmission, before regular packet exchange is attempted.
[0147] Due to user mobility, beamwidth adaptation may be necessary.
FIG. 16 shows an example of the use of variable beamwidths 1600.
Beam tracking according to IEEE 802.11ad procedures involves some
control message overhead. This involves transmission of training
fields for transmitter or receiver beam evaluation. These training
fields are transmitted using different transmit beams for
transmitter training, and received using different receive beams
for receiver training. If user mobility is high, then more frequent
exchange of the training fields may be used. For high user
mobility, wider beamwidths may be used, which may require less
frequent updates. Each node (mB/WTRU) may maintain a mapping of
beams of varying beamwidths that are related to each other as shown
in FIG. 16. WTRU 1601 may maintain a mapping of narrow beams 1603
and wide beams 1602. Similarly, mB 1604 may maintain a mapping of
narrow beams 1607, intermediate beams 1606, and wide beams 1605.
For example, mB 1604 and WTRU 1601 may know that a set of narrow
beams and a wider beam all point in the same direction, and that
the wider beam may be used if contact is lost or performance is
degrading while using one of the narrow beams belonging to the set.
Alternatively, the node (mB/WTRU) may decide to switch to the wider
beam to reduce the beam tracking overhead. The decision to switch
to the wider beam may be communicated from mB 1604 to WTRU 1601 or
from WTRU 1601 to mB 1604 so that SP allocation and Modulation and
Coding Scheme (MCS) selection may be changed.
[0148] FIG. 17 illustrates a receiver beam adaptation procedure
1700. The WTRU and mB start communicating and transmitting data
1701 in the SP using the beams identified earlier in accordance
with any of the methods described herein. However, due to relative
motion, the beams may no longer be aligned correctly. Therefore,
timing synchronization fails at the receiver (mB), and upon
detecting the failure the receiver may switch to a wider beam
pointing in the same direction to detect the end of packet
transmission 1702. Packet transmission may be detected via energy
detection. Then, the mB may send a re-transmission request 1704 to
the WTRU after a SIFS 1703 duration following end of packet
transmission. The re-transmission request may also contain a
request for a new MCS due to a changed receive antenna
configuration, or may contain information related to the new
antenna configuration itself, such as beamwidth or gain. The WTRU
may attempt packet retransmission 1705 using the MCS level
requested by the mB or by selecting the appropriate MCS based on a
new receive antenna configuration reported by the mB, which then
may send an ACK 1706.
[0149] 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.
* * * * *