U.S. patent application number 14/763113 was filed with the patent office on 2015-12-31 for methods and apparatus for vertical beamforming.
This patent application is currently assigned to InterDigital Patent Holdings, Inc.. The applicant listed for this patent is INTERDIGITAL PATENT HOLDINGS, INC.. Invention is credited to Virgil COMSA, Meilong JIANG, Moon-il LEE, Janet A. STERN-BERKOWITZ.
Application Number | 20150382205 14/763113 |
Document ID | / |
Family ID | 50190724 |
Filed Date | 2015-12-31 |
View All Diagrams
United States Patent
Application |
20150382205 |
Kind Code |
A1 |
LEE; Moon-il ; et
al. |
December 31, 2015 |
METHODS AND APPARATUS FOR VERTICAL BEAMFORMING
Abstract
A method and apparatus for determining a vertical beam for
reception are disclosed herein. A method in a wireless
transmit/receive unit (WTRU) includes receiving a broadcast message
from an evolved Node B (eNB) that includes information associated
with a plurality of vertical beams, wherein the information
includes at least one set of Physical Random Access Control Channel
(PRACH) resources associated with each of the plurality of vertical
beams, measuring reference signals transmitted on each of the
plurality of vertical beams to select a reception vertical beam,
transmitting a PRACH preamble in a set of resources associated with
the selected reception vertical beam, and receiving communications
from the eNB using the selected reception vertical beam.
Inventors: |
LEE; Moon-il; (Melville,
NY) ; STERN-BERKOWITZ; Janet A.; (Little Neck,
NY) ; COMSA; Virgil; (Montreal, CA) ; JIANG;
Meilong; (Plainsboro, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERDIGITAL PATENT HOLDINGS, INC. |
Wilmington |
DE |
US |
|
|
Assignee: |
InterDigital Patent Holdings,
Inc.
Wilmington
DE
|
Family ID: |
50190724 |
Appl. No.: |
14/763113 |
Filed: |
January 24, 2014 |
PCT Filed: |
January 24, 2014 |
PCT NO: |
PCT/US2014/012914 |
371 Date: |
July 23, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61756792 |
Jan 25, 2013 |
|
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 52/365 20130101;
H04B 7/0617 20130101; H04B 7/0417 20130101; H04B 7/086 20130101;
H04B 7/088 20130101; H04B 7/061 20130101; H04L 5/0048 20130101;
H04W 74/0833 20130101; H04W 16/28 20130101; H04W 24/10 20130101;
H04B 7/0626 20130101 |
International
Class: |
H04W 16/28 20060101
H04W016/28; H04L 5/00 20060101 H04L005/00; H04W 24/10 20060101
H04W024/10; H04B 7/08 20060101 H04B007/08; H04B 7/06 20060101
H04B007/06; H04W 74/08 20060101 H04W074/08 |
Claims
1. A method for determining a vertical beam for reception in a
wireless transmit/receive unit (WTRU), the method comprising:
receiving a broadcast message from an evolved Node B (eNB) that
includes information associated with a plurality of vertical beams,
wherein the information includes at least one set of Physical
Random Access Control Channel (PRACH) resources associated with
each of the plurality of vertical beams; measuring reference
signals transmitted on each of the plurality of vertical beams to
select a reception vertical beam; transmitting a PRACH preamble in
a set of resources associated with the selected reception vertical
beam; and receiving communications from the eNB using the selected
reception vertical beam.
2. The method of claim 1, wherein the information associated with
the plurality of vertical beams includes a plurality of measurement
configurations.
3. The method of claim 1, wherein the PRACH preamble is transmitted
on an allocated frequency associated with the set of resources.
4. The method of claim 1, wherein the WTRU selects a reception
vertical beam based on a determination that the measured reference
signal is better on at least one vertical beam.
5. The method of claim 1, wherein the WTRU selects a reception
vertical beam based on predetermined criteria.
6. The method of claim 1, wherein the at least one set of PRACH
resources is portioned based on the number of the plurality of
vertical beams.
7. A wireless transmit/receive unit (WTRU) for determining a
vertical beam for reception comprising: a receiver configured to
receive a broadcast message from an evolved Node B (eNB) that
includes information associated with a plurality of vertical beams,
wherein the information includes at least one set of Physical
Random Access Control Channel (PRACH) resource associated with each
of the plurality of vertical beams; a processor configured to
measure reference signals transmitted on each of the plurality of
vertical beams to select a reception vertical beam; a transmitter
configured to transmit a PRACH preamble in a set of resources
associated with the selected reception vertical beam; and the
receiver is further configured to receive communications from the
eNB using the selected reception vertical beam.
8. The WTRU of claim 7, wherein the information associated with the
plurality of vertical beams includes a plurality of measurement
configurations.
9. The WTRU of claim 7, wherein the PRACH preamble is transmitted
on an allocated frequency associated with the set of resources.
10. The WTRU of claim 7, wherein the WTRU selects a reception
vertical beam based on a determination that the measured reference
signal is better on at least one vertical beam.
11. The WTRU of claim 7, wherein the WTRU selects a reception
vertical beam based on predetermined criteria.
12. The WTRU of claim 7, wherein the at least one set of PRACH
resources is portioned based on the number of the plurality of
vertical beams.
13. A method for determining a vertical beam for reception in an
evolved Node B (eNB), the method comprising: transmitting a
broadcast message to a wireless transmit/receive unit (WTRU) that
includes information associated with a plurality of vertical beams,
wherein the information includes at least one set of Physical
Random Access Control Channel (PRACH) resources associated with
each of the plurality of vertical beams; receiving a PRACH preamble
in a set of resources associated with a selected reception vertical
beam, wherein the selected reception vertical beam is determined by
the WTRU based on measured reference signals transmitted on each of
the plurality of vertical beams; and transmitting communications to
the WTRU using the selected reception vertical beam.
14. The method of claim 13, wherein the information associated with
the plurality of vertical beams includes a plurality of measurement
configurations.
15. The method of claim 13, wherein the PRACH preamble is
transmitted on an allocated frequency associated with the set of
resources.
16. The method of claim 13, wherein the selection of a reception
vertical beam is based on a determination that the measured
reference signal is better on at least one vertical beam.
17. The method of claim 13, wherein the selecting of a reception
vertical beam is based on predetermined criteria.
18. The method of claim 13, wherein the at least one set of PRACH
resources is portioned based on the number of the plurality of
vertical beams.
19. A method for determining a vertical beam for transmission in an
evolved Node B (eNB), the method comprising: transmitting a
broadcast message to a wireless transmit/receive unit (WTRU) that
includes two or more Channel State Information-Reference Signal
(CSI-RS) configurations; receiving a first measurement report from
the WTRU including a received signal-to-interference plus noise
ratio (SINR) for a cell-specific CSI-RS in an uplink subframe;
receiving a second measurement report from the WTRU including SINR
for each antenna port in the cell-specific CSI-RS associated with a
vertical beam; and transmitting communications to the WTRU using
vertical beam.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 61/756,792 filed Jan. 25, 2013, the contents
of which is hereby incorporated by reference herein.
BACKGROUND
[0002] A reference signal (RS) may be classified to a wireless
transmit/receive unit (WTRU)-specific reference (WTRU-RS) and a
cell-specific reference signaling (CRS). The WTRU-RS may be used on
for a specific WTRU so that the RS is transmitted for the resources
allocated to the WTRU. On the other hand, the CRS may be shared by
all WTRUs in a cell so that the RS is transmitted in a wideband
manner. In addition, according to the usage of the reference
signal, it may be further differentiated to demodulation reference
signal (DM-RS) and channel-state-information reference signal
(CSI-RS).
[0003] The DM-RS may be used only for a specific WTRU and the RS is
typically precoded to exploit beamforming gain. The CRS may be
defined for all WTRUs in a cell and used for demodulation and
measurement purposes.
SUMMARY
[0004] A method and apparatus for determining a vertical beam for
reception are disclosed herein. A method in a wireless
transmit/receive unit (WTRU) includes receiving a broadcast message
from an evolved Node B (eNB) that includes information associated
with a plurality of vertical beams, wherein the information
includes at least one set of Physical Random Access Control Channel
(PRACH) resources associated with each of the plurality of vertical
beams, measuring reference signals transmitted on each of the
plurality of vertical beams to select a reception vertical beam,
transmitting a PRACH preamble in a set of resources associated with
the selected reception vertical beam, and receiving communications
from the eNB using the selected reception vertical beam.
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. 1C is a system diagram of an example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0009] FIG. 2 is a diagram of a WTRU-specific precoded demodulation
reference signal (DM-RS);
[0010] FIG. 3 is a diagram of a non-precoded cell-specific
reference signal (RS);
[0011] FIG. 4 is a diagram of a WTRU-specific DM-RS for a normal
cyclic prefix (CP);
[0012] FIG. 5 is a diagram of a cell-specific reference signal
(CRS) structure according to the number of antenna ports;
[0013] FIG. 6 is a diagram of a DM-RS pattern supporting up to
eight layers;
[0014] FIG. 7 is a diagram of a channel state information reference
signal (CSI-RS) patterns reuse according to the number of
ports;
[0015] FIG. 8 is a timing diagram of an example of periodic
reporting;
[0016] FIG. 9 is a block diagram of a an active antenna system
(AAS) radio architecture;
[0017] FIG. 10 is a diagram of vertical sectorization with the AAS
radio architecture;
[0018] FIG. 11 is a diagram of WTRU-specific elevation beamforming
using AAS;
[0019] FIG. 12 is a diagram of a contention-based random access
procedure;
[0020] FIG. 13 is a diagram of a downlink beam tracking reference
signal (d-BTRS) using a four port CSI-RS pattern; and
[0021] FIG. 14 is an example method for receiving a reception
vertical beam.
DETAILED DESCRIPTION
[0022] 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.
[0023] 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.
[0024] The communications systems 100 may also include a base
station 114a and a base station 114b. Each of the base stations
114a, 114b may be any type of device configured to wirelessly
interface with at least one of the WTRUs 102a, 102b, 102c, 102d to
facilitate access to one or more communication networks, such as
the core network 106, the Internet 110, and/or the networks 112. By
way of example, the base stations 114a, 114b may be a base
transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a
Home eNode B, a site controller, an access point (AP), a wireless
router, and the like. While the base stations 114a, 114b are each
depicted as a single element, it will be appreciated that the base
stations 114a, 114b may include any number of interconnected base
stations and/or network elements.
[0025] 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.
[0026] 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).
[0027] 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).
[0028] 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).
[0029] In other embodiments, the base station 114a and the WTRUs
102a, 102b, 102c may implement radio technologies such as IEEE
802.16 (i.e., Worldwide Interoperability for Microwave Access
(WiMAX)), CDMA2000, CDMA2000 1.times., CDMA2000 EV-DO, Interim
Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim
Standard 856 (IS-856), Global System for Mobile communications
(GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE
(GERAN), and the like.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] FIG. 1B is a system diagram of an example WTRU 102. As shown
in FIG. 1B, the WTRU 102 may include a processor 118, a transceiver
120, a transmit/receive element 122, a speaker/microphone 124, a
keypad 126, a display/touchpad 128, non-removable memory 106,
removable memory 132, a power source 134, a global positioning
system (GPS) chipset 136, and other peripherals 138. It will be
appreciated that the WTRU 102 may include any sub-combination of
the foregoing elements while remaining consistent with an
embodiment.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] The processor 118 of the WTRU 102 may be coupled to, and may
receive user input data from, the speaker/microphone 124, the
keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal
display (LCD) display unit or organic light-emitting diode (OLED)
display unit). The processor 118 may also output user data to the
speaker/microphone 124, the keypad 126, and/or the display/touchpad
128. In addition, the processor 118 may access information from,
and store data in, any type of suitable memory, such as the
non-removable memory 106 and/or the removable memory 132. The
non-removable memory 106 may include random-access memory (RAM),
read-only memory (ROM), a hard disk, or any other type of memory
storage device. The removable memory 132 may include a subscriber
identity module (SIM) card, a memory stick, a secure digital (SD)
memory card, and the like. In other embodiments, the processor 118
may access information from, and store data in, memory that is not
physically located on the WTRU 102, such as on a server or a home
computer (not shown).
[0040] 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.
[0041] 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.
[0042] 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.
[0043] FIG. 1C is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. As noted above, the RAN 104
may employ an E-UTRA radio technology to communicate with the WTRUs
102a, 102b, 102c over the air interface 116. The RAN 104 may also
be in communication with the core network 106.
[0044] The RAN 104 may include eNode-Bs 140a, 140b, 140c, though it
will be appreciated that the RAN 104 may include any number of
eNode-Bs while remaining consistent with an embodiment. The
eNode-Bs 140a, 140b, 140c may each include one or more transceivers
for communicating with the WTRUs 102a, 102b, 102c over the air
interface 116. In one embodiment, the eNode-Bs 140a, 140b, 140c may
implement MIMO technology. Thus, the eNode-B 140a, for example, may
use multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a.
[0045] Each of the eNode-Bs 140a, 140b, 140c may be associated with
a particular cell (not shown) and may be configured to handle radio
resource management decisions, handover decisions, scheduling of
users in the uplink and/or downlink, and the like. As shown in FIG.
1C, the eNode-Bs 140a, 140b, 140c may communicate with one another
over an X2 interface.
[0046] The core network 106 shown in FIG. 1C may include a mobility
management gateway (MME) 142, a serving gateway 144, and a packet
data network (PDN) gateway 146. While each of the foregoing
elements are depicted as part of the core network 106, it will be
appreciated that any one of these elements may be owned and/or
operated by an entity other than the core network operator.
[0047] The MME 142 may be connected to each of the eNode-Bs 142a,
142b, 142c in the RAN 104 via an S1 interface and may serve as a
control node. For example, the MME 142 may be responsible for
authenticating users of the WTRUs 102a, 102b, 102c, bearer
activation/deactivation, selecting a particular serving gateway
during an initial attach of the WTRUs 102a, 102b, 102c, and the
like. The MME 142 may also provide a control plane function for
switching between the RAN 104 and other RANs (not shown) that
employ other radio technologies, such as GSM or WCDMA.
[0048] The serving gateway 144 may be connected to each of the
eNode Bs 140a, 140b, 140c in the RAN 104 via the S1 interface. The
serving gateway 144 may generally route and forward user data
packets to/from the WTRUs 102a, 102b, 102c. The serving gateway 144
may also perform other functions, such as anchoring user planes
during inter-eNode B handovers, triggering paging when downlink
data is available for the WTRUs 102a, 102b, 102c, managing and
storing contexts of the WTRUs 102a, 102b, 102c, and the like.
[0049] The serving gateway 144 may also be connected to the PDN
gateway 146, which may provide the WTRUs 102a, 102b, 102c with
access to packet-switched networks, such as the Internet 110, to
facilitate communications between the WTRUs 102a, 102b, 102c and
IP-enabled devices.
[0050] The core network 106 may facilitate communications with
other networks. For example, the core network 106 may provide the
WTRUs 102a, 102b, 102c with access to circuit-switched networks,
such as the PSTN 108, to facilitate communications between the
WTRUs 102a, 102b, 102c and traditional land-line communications
devices. For example, the core network 106 may include, or may
communicate with, an IP gateway (e.g., an IP multimedia subsystem
(IMS) server) that serves as an interface between the core network
106 and the PSTN 108. In addition, the core network 106 may provide
the WTRUs 102a, 102b, 102c with access to the networks 112, which
may include other wired or wireless networks that are owned and/or
operated by other service providers.
[0051] The reference signals (RSs) may be classified to a wireless
transmit/receive unit (WTRU)-specific reference (WTRU-RS) and a
cell-specific reference signaling (CRS). The WTRU-RS may be used
only for a specific WTRU so that the RS is transmitted for the
resources allocated to the WTRU. The CRS may be shared by all WTRUs
in the cell so that the RS is transmitted in a wideband manner.
Reference signals may be further differentiated from a demodulation
reference signal (DM-RS) and a channel-state-information reference
signal (CSI-RS).
[0052] The DM-RS may be used for a specific WTRU and the RS may
typically be precoded to exploit beamforming gain. Since the
WTRU-specific DM-RS is not shared with other WTRUs in the cell, the
DM-RS may be transmitted in the time/frequency resources allocated
for the WTRU. The DM-RS may only be used for demodulation
purposes.
[0053] FIG. 2 is an example of a WTRU-specific precoded DM-RS. FIG.
2 includes a precoding entity 200. Stream 0 201 enters the
precoding entity 200 with a DM-RS 0 202, Stream k-1 203 enters the
precoding entity 200 with a DM-RS K-1 204. Stream 0 201 exits the
precoding entity 200 with CSI-RS 0 205. Stream k-1 203 exits the
precoding entity 200 with CSI-RS Nt-1 206.
[0054] FIG. 2 shows that if a precoded DM-RS is employed, the RS
may be precoded with the same precoding used for data symbols and
the same number of RS sequences corresponding to the number of
layers K is transmitted. Here, K is equal to or smaller than the
number of antenna ports Nt.
[0055] In FIG. 2, the K streams may be allocated for a WTRU or
shared with multiple WTRUs. If multiple WTRUs share the K streams,
the co-scheduled WTRUs may share the same time/frequency resources
at the same time. If a precoded DM-RS is used, a measurement
reference signal such as CSI-RS may be used together for a WTRU to
measure channel state information.
[0056] The CRS may be defined for all WTRUs in a cell and may be
used for demodulation and measurement purposes. Since the CRS is
shared by all WTRUs, a non-precoded RS may typically be employed to
keep the cell coverage uniform. The precoded RS may have different
cell coverage according to the directions due to the beamforming
effect.
[0057] FIG. 3 is an example of a non-precoded cell-specific RS.
FIG. 3 includes a precoding entity 300. Stream 0 301 enters the
precoding entity 300 and exits with a CRS 0 302. Stream k-1 303
enters the precoding entity 300 and exits with a CRS Nt-1 304.
[0058] FIG. 3 shows an example of a multiple input multiple output
(MIMO) transmitter for non-precoded CRS transmission. In some
cases, a WTRU transparent antenna virtualization may be used if the
number of physical antenna elements and logical antenna port is
different. The RS sequences may be transmitted on all antenna ports
irrespective of the number of streams.
[0059] FIG. 4 is an example of a WTRU-specific DM-RS for a normal
CP (port-5). FIG. 4 shows a DM-RS (antenna port-5 400) defined in
an LTE system to support non-codebook based transmission at an
evolved Node B (eNB) and the antenna port-5 400 only supports one
layer transmission. Since the antenna port-5 400 is always
transmitted with CRS, the RS overhead in total may increase
significantly.
[0060] FIG. 5 is an example of a CRS structure according to the
number of antenna ports. FIG. 5 shows the CRS pattern for 1Tx 501,
2Tx 502, and 4Tx 503 antenna ports for a normal cyclic prefix (CP).
The CRS patterns for each antenna ports may be mutually orthogonal
in the time/frequency domain. In FIG. 5, R0 and R1 (for example,
505 and 510, respectively in the 2Tx 502 antenna port) indicate CRS
for antenna port 0 and antenna port 1, respectively. To avoid
interference between CRS antenna ports, the data resource elements
(REs) located at the RE in which any CRS antenna ports is
transmitted may be muted.
[0061] A predefined RS sequence (for example, Pseudo-random noise
(PN) sequence and the like) may be transmitted in the RE location
for the CRS ports to minimize inter-cell interference, thus
improving channel estimation accuracy from CRS. This PN sequence
may be applied at the OFDM symbol level in a subframe and the
sequence may be defined according to the cell-ID, subframe number
and the position of the OFDM symbol. For instance, the number of
CRS antenna ports may be two in an OFDM symbol containing CRS per
physical resource block (PRB) and the number of PRBs in an LTE
system may vary from 6 to 110. In this case, the total number of
CRS for an antenna port in an OFDM symbol containing the RS may be
2.times.N.sub.RB, which may imply that the sequence length should
be 2.times.N.sub.RB.sup.DL. Here, N.sub.RB denotes the number of
RBs corresponding to a bandwidth and the sequence may be binary or
complex. The sequence r(m) shows the complex sequence.
r ( m ) = 1 2 ( 1 - 2 c ( 2 m ) ) + j 1 2 ( 1 - 2 c ( 2 m + 1 ) ) ,
m = 0 , 1 , , 2 N RB DL - 1 Equation 1 ##EQU00001##
[0062] where N.sub.RB.sup.DL denotes the number of RB corresponding
to the maximum bandwidth in the LTE system, therefore
N.sub.RB.sup.DL may be 110 as mentioned above. c denotes a PN
sequence with length-31 and may be defined with Gold-sequence. If a
DM-RS is configured, the following equation may be used:
r ( m ) = 1 2 ( 1 - 2 c ( 2 m ) ) + j 1 2 ( 1 - 2 c ( 2 m + 1 ) ) ,
m = 0 , 1 , , 12 N RB PDSCH - 1 Equation 2 ##EQU00002##
where N.sub.RB.sup.PDSCH denotes the number of RBs allocated for a
specific WTRU. Therefore the sequence length may vary according to
the number of RBs allocated for a WTRU.
[0063] To reduce the overall RS overhead, a DM-RS based downlink
transmission may be introduced in the Release 10 LTE-A system. The
CRS may be a non-precoded RS which is common for all WTRUs in a
cell, therefore the RS sequences for all antenna ports may need to
be transmission always. On the other hand, the DM-RS may be a
WTRU-specific precoded RS and the same precoder used for PDSCH may
be used for the DM-RS. In this case, the RS sequences may be
transmitted only on the antenna ports used for PDSCH transmission,
thus reducing RS overhead as compared with CRS since the used
number of antenna ports may be smaller than or equal to the number
of antenna ports used for CRS according to the number of layers for
the PDSCH transmission.
[0064] FIG. 6 is an example of a DM-RS pattern supporting up to 8
layers. FIG. 6 shows the DM-RS patterns in a PRB for a subframe
with a normal CP as an example. FIG. 6 includes two code division
multiplexing (CDM) groups, CDM group 1 601 and CDM group 2 602.
Also illustrated in FIG. 6 is the 4 layer Walsh covering 603 which
may be used for CDM multiplexing for each CDM group.
[0065] CDM groups may be used for multiplexing up to 4 layers in
each CDM group. Therefore, up to 8 layers may be multiplexed as a
maximum in this pattern. For the CDM multiplexing for each CDM
group, 4.times.4 Walsh spreading may be used.
[0066] Since the DM-RS is only used for demodulation performance, a
time/frequency sparse CSI-RS may be introduced for measurement
purposes. The CSI-RS may be transmitted with a duty cycle {5, 10,
20, 40, 80}ms in the physical downlink shared channel (PDSCH)
region. In addition, up to 20 CSI-RS pattern reuse may be available
in a subframe as shown in FIG. 7.
[0067] FIG. 7 is an example of CSI-RS patterns reuse according to
the number of ports. FIG. 7 shows the CSI-RS patters for 2Tx 701,
4Tx, 702, and 8Tx 703 antenna ports. In FIG. 7, the same shading
implies a set of REs for a particular CSI-RS configuration. The
different shaded regions represent Rel-8 CRS 703, a Physical
Downlink Control Channel (PDCCH) region 705; Rel 9/10 DM-RS 706,
and a Physical Downlink Shared Channel 707.
[0068] Two types of reporting channels may be used, such as the
physical uplink control channel (PUCCH) and the physical uplink
shared channel (PUSCH). The PUCCH reporting channel may provide
robust CSI feedback while allowing limited feedback overhead. The
PUSCH reporting channel may allow a large amount of feedback
overhead with less reliability. Therefore, the PUCCH reporting
channel may be used for periodic CSI feedback for coarse link
adaptation and the PUSCH reporting may be triggered aperiodically
for finer link adaptation.
[0069] Table 1 is an example of reporting modes in LTE/LTE-A.
TABLE-US-00001 TABLE 1 Reporting modes in LTE/LTE-A Periodic CSI
Aperiodic CSI Scheduling Mode reporting channels reporting channel
Frequency non- PUCCH selective Frequency selective PUCCH PUSCH
[0070] CSI feedback may be reported in the format of a rank
indicator (RI), precoder matrix index (PMI) and channel quality
indicator (CQI). The RI and PMI may be calculated at a WTRU
receiver by selecting the rank and the precoding matrix in the
predefined codebook which maximizes WTRU throughput. The PMI and
CQI may be further classified into wideband, subband, and
WTRU-selected subband, while RI is only reported in a wideband
manner.
[0071] Table 2 shows further details aperiodic and periodic for CSI
feedback according to the transmission mode.
TABLE-US-00002 TABLE 2 Rel-8/Rel-9 Details of CSI feedback
according to Transmission Modes Transmission Mode Aperiodic
Feedback Periodic Feedback 1 Mode 2-0: WTRU selected Mode 1-0: WB
CQI 2 sub band CQI: WB CQI + Mode 2-0: WTRU 3 CQI over M best
Selected sub band CQI: 7 subbands. WB CQI + WTRU reports 8 Mode
3-0: high layer(HL) CQI in preferred subband configured subband
CQI: in each BW part, one BW WB CQI + subband CQI. part in each
reporting Notes: opportunity. CQI for first CW only, No Notes: PMI
CQI for first CW only, No PMI 4 Mode 1-2: WB CQI/ Mode 1-1: WB CQI/
6 Multiple PMI: CQI for Single PMI each CW; PMI for each Mode 2-1:
WTRU selected 8 subband. subband CQI/Single Mode 2-2: WTRU selected
PMI (N.sub.RB.sup.DL > 7 only): WB sub band CQI/Multiple CQI/PMI
+ WTRU PMI: CQI per CW and reports CQI in preferred PMI, both over
full BW subband in each BW part and M best subbands. Mode 3-1: HL
configured sub band CQI/Single PMI: WB CQI + subband CQI, both per
CW. 5 Mode 3-1: HL configured sub band CQI/Single PMI (see
above)
[0072] Periodic feedback may be transmitted on the PUCCH, although
it may be transmitted on the PUSCH when that channel exists.
Periodic reporting may use a sequence of different types of
reports; which may be defined as: Type 1: Subband CQI; Type 2:
Wideband CQI/PMI; Type 3: RI; and Type 4: Wideband CQI.
[0073] FIG. 8 is an example of periodic reporting. A typical
reporting sequence is shown in FIG. 8, where the number in each
rectangle corresponds to the report type above. The type 3 RI may
be reported with longest duty cycle which is defined as
H.times.MRI.times.NP subframes where H, MRI, and NP are configured
by higher layers. The type 2 802 wideband CQI/PMI may be reported
with a longer duty cycle over type 1 803 subband CQI since subband
CQI is changed more frequently over time due to its short-term
channel characteristic.
[0074] Aperiodic feedback may be requested by DCI Format 0 or DCI
format 4 when the CQI Request bit is set. It may be transmitted on
the PUSCH.
[0075] In LTE Rel-10, the types of periodic PUCCH feedback may be
further extended to the following for eight transmit antenna ports:
Type 1 report supports CQI feedback for the WTRU selected
sub-bands; Type 1a report supports subband CQI and second PMI
feedback; Type 2, Type 2b, and Type 2c reports support wideband CQI
and PMI feedback; Type 2a report supports wideband PMI feedback;
Type 3 report supports RI feedback; Type 4 report supports wideband
CQI; Type 5 report supports RI and wideband PMI feedback; and Type
6 report supports RI and PTI feedback.
[0076] In a Type 6 report, the precoding type indicator (PTI) may
be used only for 8 transmit antenna ports since the 8-transmit
precoder is defined with a dual codebook.
[0077] An active antenna system (AAS) may be a signal processing
controlled smart antenna system. FIG. 9 is a generic block diagram
of AAS radio architecture. As shown in FIG. 9, an AAS system
consists of three components, namely a digital signal processing
(DSP) controller 901 (also called beam controller), an active
transceiver micro-radio unit 902, and a passive antenna element.
The DSP controller 901 is part of the optical CPRI feeder 904. The
active transceiver micro-radio unit 902 includes a digital upload
converter 905 and a duplexer 906. Through the DSP controller units,
both the amplitude and phase of the RF signal fed into each antenna
may be dynamically adjusted to change the beam direction and
width.
[0078] FIG. 10 is an example concept of vertical sectorization with
AAS radio architecture. FIG. 10 shows examples of 1 vertical sector
1001, 2 vertical sectors 1002, and 3 vertical sectors 1003. The AAS
may be used to form multiple vertical sectors within a cell as
shown in FIG. 10, resulting in cell-splitting gain in spatial
domain. The vertical sectors may be used in either a cell-specific
manner or WTRU-specific manner. The vertical sectors using AAS may
reduce inter-cell interference while improving throughput
performance.
[0079] FIG. 11 is an example of a WTRU specific elevation
beamforming using AAS. In addition to the vertical sectorization,
the AAS 1100 may provide WTRU-specific elevation beamforming gain
by using the best elevation beam for a specific WTRU as shown in
FIG. 11. From the WTRU-specific elevation beamforming, the cell
coverage or WTRU throughput performance may be significantly
improved.
[0080] In LTE, the Random Access (RA) procedure may be used in
certain situations, for example, one or more of the following: 1.)
For an RRC Connection Request, such as for initial access or to
register; 2.) For RRC Connection re-establishment, such as
following radio link failure; 3.) During the Handover to access the
target cell; 4.) To obtain uplink (UL) synchronization, such as
when UL synchronization is lost and downlink (DL) data arrives or
there is UL data to transmit; 5.) When the WTRU has UL data to
transmit and there are no dedicated resources (for example, no
PUCCH resources have been assigned to the WTRU); and 6.) For
positioning purposes, such as when a timing advance is needed for
WTRU positioning.
[0081] There may be two forms of the RA procedure: Contention-based
(which may also be called common), which may apply to the first
five events above, and non-contention based (which may also be
called contention free or dedicated), which may apply or only apply
to handover, DL data arrival, and positioning.
[0082] When using a contention-based RA procedure, the WTRU may
initiate the process by transmitting a RA preamble randomly chosen
from a common pool of preambles which may be communicated to the
WTRU by the network, for example, via broadcasted system
information. The WTRU may transmit the preamble on a PRACH resource
(for example, a resource in time and frequency) that the WTRU
chooses from a set of allowed resources, which may be communicated
to the WTRU by the network, for example, via broadcasted system
information. This set of allowed PRACH resources may be referred to
as the cell's configured set of PRACH resources. The unit of time
for the PRACH resource may be a subframe. The subframe the WTRU
chooses for the PRACH resource may be the next subframe configured
for PRACH in which the WTRU may transmit the PRACH (for example,
based on timing, measurement, and other WTRU constraints). The
frequency aspect of the PRACH resource (for example, the resource
blocks (RBs)) the WTRU chooses in the selected subframe may be
based on parameters communicated to the WTRU by the network, for
example, via broadcasted system information. In certain cases, for
example, for frequency division duplex (FDD), there may be one
frequency resource allowed for PRACH in any subframe. The frequency
resource may be defined by a starting (lowest) RB number which may
be provided by the network, for example, prach-FrequencyOffset, and
may have a fixed bandwidth, such as 6RBs.
[0083] When a contention-based RA procedure is used, it may be
possible that at least two WTRUs select the same resources
(preamble and PRACH resource) for random access, and therefore the
contention situation may need to be resolved.
[0084] When using a non-contention based RA procedure, the WTRU may
transmit a RA preamble explicitly signaled to the WTRU by the
network, for example, ra-PreambleIndex. The WTRU may transmit the
preamble on a PRACH resource chosen from a specific subset of the
cell's configured PRACH resources. The subset (for example, the
mask) may be explicitly signaled to the WTRU by the network, for
example, ra-PRACH-MaskIndex. In the case the subset includes only
one choice, the WTRU may use the indicated resource.
[0085] In some cases which may be applicable to one or both of the
RA procedure types, the preamble transmission may span or be
repeated over more than one subframe. In this case, the selected
subframe may be the starting subframe for the transmission.
[0086] The terms RACH resources and PRACH resources may be used
interchangeably.
[0087] FIG. 12 is an example of a contention-based RA procedure.
The steps of the contention-based RA procedure may be as
follows.
[0088] The WTRU 1201 may transmit 1203 the selected RA preamble on
the selected PRACH resource to an eNB 1202. After transmitting the
preamble, the WTRU 1201 may read the physical downlink control
channel (PDCCH) and look for the Random Access Radio Network
Temporary ID (RA-RNTI) corresponding to the first subframe on which
it transmitted the preamble. If it is not received in the response
monitoring window, the WTRU 1201 may ramp up the power, select
another resource (possibly after some backoff time), and try again.
The RA-RNTI may be determined according to:
RA-RNTI=1+t_id+10.times.f_id, where t_id may be the index of the
first subframe of the PRACH used for preamble transmission (for
example, 0.ltoreq.t_id<10), and f_id may be the index of the
PRACH used for preamble transmission within that subframe, in
ascending order of frequency domain (for example,
0.ltoreq.f_id<6). For the case of one frequency resource per
subframe, for example, for FDD, f_id may be 0.
[0089] Random Access Response (RAR) 1204 may consist of a network,
for example the eNB 1202, transmitting a timing advance command to
adjust the terminal transmit timing to the WTRU 1201. The network
1202 may also allocate uplink resources for the WTRU 1201 and may
transmit a response on the downlink control channel (PDCCH) using
the RA-RNTI to identify which WTRU group the allocation is for.
Within each group, the RA preamble identifier (RAPID) may be used
to narrow down further (for example, at the medium access control
(MAC) level) the WTRU group specified by the RA-RNTI to the subset
of WTRUs which have used the same preamble during step 1 of the RA
procedure. The RAR 1204 may include one or more of the index of the
RA preamble sequences the network 1202 detected and for which the
response is valid, the timing correction calculated by the RA
preamble receiver, a scheduling grant, or a temporary cell identity
(TC-RNTI).
[0090] For scheduled transmission 1205, the WTRU 1201 may use the
allocated resources indicated by the scheduling grant to transmit
1205 its message (such as RRC Connection Request) to the eNB 1202.
If the terminal is connected to a known cell (for example, in the
RRC_CONNECTED state), the terminal may have a C-RNTI (Cell RNTI)
which it may include in the UL message. Otherwise a core network
terminal identifier may be used. The UL transmission (UL SCH) may
be scrambled by the WTRU 1201 using the temporary TC-RNTI received
in the RAR 1204. The scheduled transmission 1205 may be referred to
as Message 3 (Msg3).
[0091] For contention resolution 1206, the network (eNodeB) 1202
may transmit 1206 a contention resolution message on the DL based
either on the C-RNTI on the PDCCH or a WTRU contention resolution
identity on the DL-SCH, for example, the core network terminal
identifier transmitted by the terminal in the scheduled
transmission 1205, to the WTRU 1201. Only the terminal which
observes a match between the identity received in the contention
resolution 1206 and the identity transmitted as part of the
scheduled transmission 1205 may declare the RA procedure
successful. Contention between WTRUs that chose both the same PRACH
time-frequency resource and the same preamble may be resolved by
the contention resolution 1206.
[0092] For contention-based RA, the WTRU may derive the common pool
of preambles from parameters provided by the network. From these
parameters, the WTRU may derive a full set of preambles, for
example, a certain number such as 64 preambles, which may be based
on one or more root Zadoff-Chu sequences. A parameter which may
designate the sequence or sequences to use may be
rootSequenceIndex. The WTRU may receive additional parameters
indicating a subset of the preambles which may be used by the WTRU
and how to divide this subset into two groups, A and B. For
example, numberOfRA-Preambles may define the subset of preambles.
The first sizeOfRA-PreamblesGroupA may be in Group A (for example,
preambles 0 to sizeOfRA-PreamblesGroupA-1), and the remaining
preambles in the subset, if any (for example,
sizeOfRA-PreamblesGroupA to numberOfRA-Preambles-1), may be in
Group B. When to use a Group A versus a Group B preamble may be
known to the WTRU. The decision may be based on criteria such as
the size of Msg3 and/or pathloss. Preambles in the full set which
are not in Group A or B may be used by the network when it assigns
dedicated preambles.
[0093] A PRACH Configuration Index, for example, prach-ConfigIndex,
may be used by the network to tell the WTRU which of a preset list
of possible configurations it is choosing for the cell's configured
set of PRACH resources. The preset configurations may define, for
example for FDD, one or more of the preamble formats, which may
define the time for the preamble cyclic prefix (CP) and the time
for the preamble sequence, the system frame numbers (SFNs) in which
the PRACH is allowed (for example, any, even only, odd only), and
the subframes of the allowed SFNs (for example, a specific 1, 2, 3,
4, 5, or all 10 subframes) in which the PRACH is allowed.
[0094] A Power Headroom Report (PHR) may be triggered by a WTRU if
any of the following events occur.
[0095] A PHR may be triggered if a prohibitPHR-Timer expires or has
expired and the path loss has changed more than dl-PathlossChange
dB for at least one activated Serving Cell which is used as a
pathloss reference since the last transmission of a PHR when the
WTRU has UL resources for new transmission.
[0096] A PHR may be triggered if a periodicPHR-Timer expires.
[0097] A PHR may be triggered upon configuration or reconfiguration
of the power headroom reporting functionality by upper layers,
which is not used to disable the function.
[0098] A PHR may be triggered upon activation of a serving cell
(SCell) with configured UL.
[0099] A PHR may be triggered if: 1) a prohibitPHR-Timer expires or
has expired, 2) when the WTRU has UL resources for new
transmission, and 3) when the following in this transmission time
interval (TTI) for any of the active SCells with configured UL is
true: there are UL resources allocated for transmission or there is
a PUCCH transmission on this cell, and the required power backoff
due to power management (as allowed by P-MPR.sub.c) for this cell
has changed more than dl-PathlossChange dB since the last
transmission of a PHR when the WTRU had UL resources allocated for
transmission or PUCCH transmission on this cell.
[0100] A PHR may be transmitted by a WTRU in a particular TTI
(which may correspond to a particular subframe) if the WTRU has UL
resources allocated for new transmission for this TTI (or subframe)
and the following applies: the Power Headroom reporting procedure
determines that at least one PHR has been triggered and not
cancelled, and the allocated UL resources may accommodate a PHR MAC
control element plus its subheader if extendedPHR is not
configured; or the Extended PHR MAC control element plus its
subheader if extendedPHR is configured, as a result of logical
channel prioritization.
[0101] A WTRU may transmit a sounding reference signal (SRS) to the
eNB when configured or triggered to do so. The WTRU may transmit
SRS in the last symbol of a subframe.
[0102] SRS transmission by a WTRU may be periodic or aperiodic.
Periodic SRS transmission may be configured by the eNB. Aperiodic
SRS transmissions may be triggered by the eNB, for example, by
including a request for aperiodic SRS along with an UL grant.
[0103] Cell-specific SRS subframes may be subframes in which the
SRS may be transmitted in a given cell. The configuration of
cell-specific subframes may be provided in signaling such as
broadcast or dedicated radio resource control (RRC) signaling.
[0104] WTRU-specific SRS subframes may be subframes in which the
SRS may be transmitted by a certain WTRU, which may be a subset of
the cell-specific SRS subframes. The configuration of WTRU-specific
subframes may be provided to a WTRU in signaling, such as dedicated
RRC signaling. There may be separate WTRU-specific subframes
configured for a WTRU for periodic and aperiodic SRS.
[0105] When aperiodic SRS is triggered in subframe n, the WTRU may
transmit the SRS in the next aperiodic WTRU-specific SRS subframe
n+k, where k satisfies a certain criteria, for example,
k>=4.
[0106] When one SRS (periodic or aperiodic SRS) and another SRS or
channel are both scheduled to be transmitted in the same subframe,
rules and/or configuration parameters may govern whether or not the
WTRU may transmit the scheduled SRS.
[0107] The aperiodic SRS trigger and the aperiodic SRS request may
be used interchangeably.
[0108] The eNB receiver may estimate a proper downlink vertical
beam (for example, transmit vertical beam) for a specific WTRU
based on the uplink vertical beam (for example, receive vertical
beam), thus requiring a SRS for the receive vertical beam
convergence. Since the UL coverage may be different, more than 6 dB
between before and after the receive vertical beam adjustment.
Therefore, faster receive vertical convergence may reduce
interference and increase UL throughput. However, current SRS
design may not allow the faster receive vertical beam convergence,
as its transmission has a duty cycle and/or a single subframe
transmission is only possible at a time.
[0109] To allow efficient vertical beam adjustment, a WTRU
reporting assisted vertical beam selection may be used at the eNB.
Since the vertical antenna elements may not be seen by the WTRU,
multiple DL reference signals may be used for a WTRU to select the
best vertical beam associated with a specific reference signal.
However, current DL reference signal structure may not allow
multiple DL reference signals or the overhead of multiple DL
reference signals may be excessive.
[0110] Since the SRS transmission is only available after initial
cell access, the PRACH process may not enjoy the benefit of the
active antenna system (AAS). In addition, the UL coverage of the
PRACH may be worse than before, as the appropriate UL vertical beam
for a specific WTRU may not be estimated at the eNB receiver.
Therefore, the PRACH may not have enough coverage in an AAS as
compared with other UL/DL channels.
[0111] For the RA procedure, such as the initial RA procedure, to
gain initial access or transmit the RRC Connection request, it may
be desirable to improve performance by using vertical beamforming.
Methods and procedures may be needed to enable the WTRU to
determine a vertical beam for transmission and for the eNB to know
what vertical beam to use for reception.
[0112] After receive beam convergence, the power headroom reporting
may be updated immediately since there may be more than a 6 dB
difference between before and after the receive beam convergence.
Current power headroom reporting behavior may not support this
case. It may be useful for the eNB to receive a PHR for a WTRU as
soon as possible after the vertical beam it has selected for the
WTRU has converged. Methods and procedures may be needed to
accomplish this.
[0113] Since a WTRU moves in a cell across multiple vertical
sectors/beams, the best vertical beam for the WTRU may be changed
frequently over time. To provide appropriate coverage in vertical
sectorized cell, WTRU mobility may be taken into account even
within a cell. Current LTE/LTE-A systems may not be flexible to
support WTRU mobility across multiple vertical beams within a
cell.
[0114] A new UL reference signal may be defined for better receive
beam convergence and the reference signal may be similar to the
sounding reference signal (SRS). The UL reference signal for
receive beam convergence may be defined as the Uplink Beam Tracking
Reference Signal (u-BTRS).
[0115] In a first example, the u-BTRS may be defined in a PUSCH
region only, where the PUSCH region implies that the PRBs are not
used for the PUCCH in a subframe. In this case, one or more of
following may apply.
[0116] The u-BTRS may be transmitted in the subframe configured for
cell-specific u-BTRS subframe and the last single carrier frequency
division multiple access (SC-FDMA) symbol, as for SRS. In an
example, the cell-specific u-BTRS subframes may be equivalent to
the cell-specific SRS subframe. In another example, the
cell-specific u-BTRS subframes may be independently configured and
the subframes may be mutually exclusive from the cell-specific SRS
subframes. Alternatively, the cell-specific u-BTRS subframes may be
independently configured from cell-specific SRS subframes while
subframes may fully or partially be overlapped between u-BTRS and
SRS. In the case of overlapping, at least one of following may be
applied: the u-BTRS transmission has a higher priority, so that all
SRS transmissions in the subframes may be dropped; the SRS
transmission has a higher priority, so that all u-BTRS
transmissions in the subframes may be dropped; and the subframe may
be used either for u-BTRS transmission or for SRS transmission. If
both transmissions are triggered and/or scheduled in the subframe,
the u-BTRS may have a higher priority and SRS may be dropped, or
vice versa.
[0117] The u-BTRS may be transmitted in the subframe configured for
cell-specific u-BTRS subframe (other than the last SC-FDMA symbol),
thus allowing multiplexing of u-BTRS and SRS in the same subframe
if scheduled. In this case, one or more of following may apply: the
second to last SC-FDMA symbol may be used for the u-BTRS subframe;
one of SC-FDMA symbols used for DM-RS may be used for the u-BTRS
transmission; the last SC-FDMA symbol in the first slot may be used
for the u-BTRS transmission in the subframe; and a SC-FDMA symbol
for u-BTRS may be configured by a broadcasting channel (for
example, SIB-x).
[0118] In a cell-specific u-BTRS subframe, even though SRS may be
transmitted in all system bandwidth, the u-BTRS may only be
transmitted in the PUSCH region. Therefore, the frequency bandwidth
for the u-BTRS in a subframe may be smaller than the SRS. For
instance, if a system has 50 PRBs in UL the SRS may be transmitted
in any location of the 50 PRBs according to the configuration. The
u-BTRS may only be transmitted in the center N.sub.PUSCH PRBs for
the PUSCH. In this case, at least one of following may be applied:
N.sub.PUSCH and N.sub.uBTRS may be used interchangeably, where
N.sub.uBTRS denotes the PRBs configured for u-BTRS transmission
which may be defined irrespective of the PUSCH region; the
N.sub.PUSCH may be configured by higher layers, for the indication
of N.sub.PUSCH, the starting PRB number may be indicated; and
N.sub.PUSCH may be indicated dynamically in each trigger of
u-BTRS.
[0119] In second example, multiple SC-FDMA symbols may be used for
the u-BTRS in a subframe. If multiple SC-FDMA symbols are used for
the u-BTRS transmission, the receive beam convergence time may be
reduced. For u-BTRS transmission in multiple SC-FDMA symbols, one
or more of following may apply.
[0120] The multiple SC-FDMA symbols in a subframe for u-BTRS
transmission may be located within a center N.sub.PUSCH/N.sub.uBTRS
PRBs.
[0121] The last N.sub.uBTRS SC-FDMA symbols in a subframe may be
used for u-BTRS transmission and at least one of following may be
used. The N.sub.uBTRS may be defined as a predefined integer
number. For example, N.sub.uBTRS=2 or N.sub.uBTRS=3 may be used.
The N.sub.uBTRS may be configured by the eNB via a broadcasting
channel (for example, MIB or SIB-x) or higher layer signaling.
[0122] Among the multiple SC-FDMA symbols for u-BTRS transmission,
if one SC-FDMA symbol collides with the SC-FDMA symbol for SRS
transmission, the colliding SC-FDMA symbol may not be used for the
u-BTRS transmission in the subframe while the other SC-FDMA symbols
may be used.
[0123] When multiple SC-FDMA symbols are used for the u-BTRS
transmission, the u-BTRS in a SC-FDMA symbol may be repetitively
transmitted in the other SC-FDMA symbols in the same frequency
locations.
[0124] In a solution for PUSCH transmission, if a WTRU capable for
u-BTRS transmission is scheduled for PUSCH transmission in the
cell-specific u-BTRS subframe, at least one of following WTRU
behaviors may apply. A WTRU may transmit the PUSCH and rate-match
around the cell-specific u-BTRS resource in the subframe. A WTRU
may transmit the PUSCH if the WTRU is not scheduled to transmit the
u-BTRS in that subframe. Otherwise, the WTRU may drop the PUSCH and
transmit the u-BTRS in that subframe. Alternatively, the WTRU may
drop the u-BTRS transmission and transmit the PUSCH in that
subframe.
[0125] A DL beam tracking reference signal (d-BTRS) may be defined
for the purpose of vertical beam measurement so that a WTRU may
measure multiple vertical beams from the d-BTRS associated with the
vertical beams. Assuming that N.sub.vertical beams are used in a
cell, N.sub.vertical d-BTRS may be configured so that one d-BTRS
may correspond to one vertical beam. In an example, multiple CSI-RS
may be used as d-BTRS for multiple vertical beam tracking. In this
case, one or more of following may apply.
[0126] Multiple CSI-RS may be configured in a cell-specific manner
and each CSI-RS may be associated with a vertical beam. To
configure the cell-specific CSI-RS as d-BTRS, at least one of
following may be used. Two or more CSI-RS configurations may be
informed to a WTRU via a broadcasting channel (for example, MIB or
SIB-x) and the CSI-RS configurations may include at least one of:
number of antenna ports, duty cycle, pattern, or subframe offset.
The number of antenna ports for each cell-specific CSI-RS
configuration may be limited to one or two antenna ports, which may
be independent from the WTRU-specific CSI-RS configuration. The
cell-specific CSI-RS may be transmitted in a subset of PRBs. For
instance, the cell-specific CSI-RS may be transmitted in
even-numbered PRBs or odd-numbered PRBs. The subset of PRBs for the
cell-specific CSI-RS may be informed to a WTRU as a part of CSI-RS
configuration.
[0127] A vertical beam measurement reporting procedure may be
defined based on the multiple cell-specific CSI-RS for better DL
vertical beam tracking at the eNB transmitter. For the vertical
beam measurement reporting procedure, WTRU behavior may be defined
as at least one of the following. A WTRU may measure two or more
cell-specific CSI-RS and measure the received signal to noise
ration (SNR) received signal to interference plus noise ratio
(SINR), which may be considered as reference signal received power
(RSRP), pathloss, wideband CQI, or subband CQI. A WTRU may report
the measured received SINR for each cell-specific CSI-RS in a
specific UL subframe if scheduled to report or triggered in the
subframe.
[0128] An antenna port in a cell-specific CSI-RS may correspond to
a specific vertical beam. A single cell-specific CSI-RS may be
configured with two or more antenna ports and each antenna port may
be associated with a specific vertical beam. A WTRU may measure the
received SINR for each antenna port in the cell-specific CSI-RS and
report the measured SINRs in a specific UL subframe if scheduled to
report or triggered in the subframe.
[0129] In another example, a new measurement RS may be defined as
d-BTRS for better measurement accuracy as compared with that of
CSI-RS.
[0130] The new measurement RS (d-BTRS) may be defined with one or
more of the following properties. A single antenna port may be
defined with 3 or 6 subcarrier spacing. An orthogonal frequency
division multiplexing (OFDM) symbol in a subframe may be used as a
reference signal, resulting in 1 subcarrier spacing in the
frequency domain. The CSI-RS patterns may be reused with
modification.
[0131] FIG. 13 is an example of a downlink beam tracking reference
signal (d-BTRS) using a four port CSI-RS pattern. For example, a
4-port CSI-RS pattern may be used as a 2-port d-BTRS pattern 1300
as shown in FIG. 13. Therefore, a larger port CSI-RS pattern may be
used and modified for a smaller port d-BTRS pattern for a denser RS
pattern in the frequency domain from an antenna port perspective
that may include an 8-port CSI-RS pattern used for a 2-port d-BTRS
pattern and a 2-port CSI-RS pattern used for a 1-port d-BTRS
pattern. For example, by using a 4 port CSI-RS pattern for 2-port
d-BTRS as shown in FIG. 13, the frequency spacing of an antenna
port of d-BTRS is 6 subcarriers. However, if 2-port CSI-RS pattern
is used for a 2-port d-BTRS, the frequency spacing of an antenna
port of d-BTRS is 12 subcarriers.
[0132] Selection or determination of an RA resource may include
selection/determination of one or more of an RA preamble, an RA
preamble format, and a PRACH resource which may include the
selection/determination of the time and/or frequency aspect (for
example, allocation) of the resource. A WTRU may select or
otherwise determine one or more RA resources based on at least one
measurement.
[0133] The eNB may provide and the WTRU may receive one or more
measurement configurations where each measurement configuration may
correspond to a signal the eNB may transmit with one or more
certain characteristics. For example, the signal may include a
certain vertical (or DL vertical) beam.
[0134] In the descriptions herein, vertical and DL vertical beams
are example characteristics. Any other characteristics may be used
and still be consistent with this description.
[0135] The configuration may be signaled by the eNB to the WTRU via
higher layer signaling such as broadcast or dedicated RRC
signaling.
[0136] A measurement configuration may include the parameters
needed by the WTRU to make the measurements, such as: the time
schedule of the measurement (for example, which frames and
subframes), frequency location, measurement identifier, the type of
measurement, or other parameters specific to the type of
measurement.
[0137] Separate from, or as part of, a measurement configuration,
the eNB may indicate an association of a measurement (or
measurement configuration), which may correspond to a certain
transmission characteristic such as a vertical beam, with a certain
set of RA resources or RA parameters.
[0138] The RA resources or RA parameters may include or may enable
the WTRU to determine: a set of one or more RA preambles, the
preamble format for the RA preambles, or a set of one or more PRACH
resources which may include an allocation in frequency and/or time.
This indication may be signaled by the eNB to the WTRU via higher
layer signaling such as broadcast or dedicated RRC signaling.
[0139] The indication may include any parameters necessary to
convey the certain set of RA parameters. For example, the
parameters may include: one or more indices into one or more tables
with predefined configurations which may, for example, define the
frames and/or subframes to use; one or more masks to use with
another configuration (or configurations) that define a larger set
of resources; specific preamble number (or index); starting
preamble number (or index); number of preambles; frequency offset
for first RB; or Number of RBs.
[0140] Indication of association and/or random access or other
related parameters may be provided for individual measurements (or
measurement configurations) and/or groups of measurements (or
measurement configurations).
[0141] A set of RA resources may currently be provided in a cell
for contention-based RA. Since all WTRUs may use these resources
and the eNB may not have certain information about these WTRUs, the
eNB may not be able to treat reception of RA preambles from
different WTRUs differently even if it may be desirable to do
so.
[0142] One way to enable the eNB to recognize a certain purpose or
characteristic of the WTRU transmitting a preamble may be to
designate certain RA resources to be used by WTRUs for a certain
purpose or with a certain characteristic. For example, the certain
characteristic may be a preferred or selected beam direction. The
eNB may designate certain RA resources, for example, certain RA
preambles and/or PRACH resources, to be used by WTRUs that prefer
or select a certain one or more vertical beam directions in the UL
and/or DL. For reception of these preambles and/or resources, the
eNB may use a specific UL vertical beam that may achieve better
reception performance.
[0143] As another example, the certain characteristic may be that
the WTRU has determined that a measurement it makes warrants use of
a certain set of RA resources (for example, certain RA preambles
and/or PRACH resources). For example, if a measurement a WTRU makes
meets a certain criteria, the WTRU may choose and/or use an RA
resource (for example, RA preamble and/or PRACH resource) in a set
of RA resources (for example, RA preambles and/or PRACH resources)
associated with that measurement or the configuration of the
measurement.
[0144] A set of RA resources may be allocated by the eNB and/or
used by a WTRU for RA transmission when the WTRU has a certain
characteristic or purpose.
[0145] A set of RA resources associated with a certain
characteristic or purpose may include a set of RA preambles and/or
PRACH resources which may have one or more of the following aspects
different from the RA preambles and PRACH resources designated in
the cell for contention-based RA: preambles, time aspect (or
allocation) of the PRACH resources, or frequency aspect (or
allocation) of the PRACH resources.
[0146] When selecting RA resources, a WTRU with a certain purpose
or characteristic may (or may only) choose an RA resource (for
example, including preamble and PRACH resource in time and
frequency) which is in the set of RA resources allowed or
designated for use for the certain purpose or characteristic.
[0147] For the set of RA preambles which may be used for a certain
purpose or characteristic, one or more of the following may
apply.
[0148] The set of RA preambles may be a designated subset of the
cell's existing full set of preambles. The set may be within the
subset of the full set that is not part of Group A or Group B.
[0149] The set of RA preambles may be a separate set of preambles
from the cell's existing full set of preambles. The set may have
its own root Zadoff-Chu sequence or sequences. Given multiple
purposes or characteristics, for example, vertical beams or
measurement configurations, there may be a set (or multiple sets)
of preambles separate from the cell's existing full set of
preambles and each purpose or characteristic may be associated with
a subset of that set (or one of those sets).
[0150] One set of preambles may be designated for a group of
purposes or characteristics, for example, a group of vertical beams
or measurements (or measurement configurations). Given N purposes
or characteristics in the group, the set of preambles may be
divided, for example, equally, among the group with understanding
between the WTRU and eNB, for example, based on explicit or
implicit configuration, as to which preambles correspond to which
member of the group. When measurements are the characteristic, the
understanding may, for example, be based on the measurement
identity or the order of the measurement configurations, such that
if a WTRU chooses a RA preamble based on a particular measurement
meeting a criteria, it knows from which set of preambles to
choose.
[0151] The set of RA preambles may be the preambles in the existing
Group A and/or B. In this case, preamble may not be used by the eNB
to understand the purpose or characteristic.
[0152] The RA preamble format for the set of preambles may be
different. For example, one or more certain CP lengths, for
example, longer than currently used for a given preamble format,
may be used for a certain purpose or characteristic.
[0153] For the set of PRACH resources which may be used for a
certain purpose or characteristic, one or more of the following may
apply.
[0154] The frequency allocation of the PRACH resources may be
separate or different from the frequency allocation for the cell's
existing set of PRACH resources. Each purpose or characteristic may
have its own frequency resource where the starting RB may be
designated. One new frequency resource may be designated for a
group of purposes or characteristics, for example, all vertical
beams or all of a certain type of measurement.
[0155] The time allocation of the PRACH resources may be separate
or different from the time allocation for the cell's existing set
of PRACH resources. Each purpose or characteristic may have its own
time allocation. One new time allocation may be designated for a
group of purposes or characteristics, for example, all vertical
beams. The time allocation for one or a group of purposes or
characteristics may be accomplished by designation of a specific
PRACH configuration index and/or PRACH Mask index where the
configurations and masks corresponding to these indices may be
those which currently exist, for example, for all
purposes/characteristics and/or new configurations and masks may be
used. For the case of a group of purposes or characteristics, if
one PRACH configuration index is provided, the WTRU may understand
how to divide the time resources among the members of the group
based on, for example, certain configuration information it may
receive such as beam or measurement identities or the order of
beams or measurements configured or in a configuration. To minimize
impact to a system when there may be a number of purposes or
characteristics, the time allocation for a purpose or
characteristic may be sparser than currently allowed, for example,
sparser than every other frame.
[0156] A WTRU may select or otherwise determine a RA resource to
use for RA transmission, or a set of RA resources which may be used
for RA transmission, based on at least one of the following: one or
more measurements; WTRU determination that one or more measurements
meet a certain criteria; the result of a comparison made by the
WTRU of at least one measurement against one or more quality
criteria or thresholds; the result of a comparison of two or more
measurements; WTRU selection of a measurement based on certain
criteria being met and/or the results of comparison with one or
more other measurements; and the association of a measurement with
one or a set of RA resources.
[0157] The result of a comparison made by the WTRU of at least one
measurement against one or more quality criteria or thresholds. For
example, the selection or determination may be based on the WTRU
determining that a measurement is better (or worse) than a
threshold. Better may mean greater in value and worse may mean
lower in value. For example, the WTRU may make an RSRP measurement
using the CRS of the cell and if that measurement is above a
threshold, the WTRU may determine that the cell's existing set of
RA resources (for example, RA resources which may not be associated
with a certain purpose or characteristic such as vertical
beamforming) may be used.
[0158] The result of a comparison of two or more measurements. For
example, the selection or determination may be based on the WTRU
determining that a measurement is better (or worse) than at least
one other measurement. For example, the selection or determination
may be based on the WTRU determining a measurement is the best of a
set of measurements. Better may mean greater in value, for example
by at least a certain threshold. Worse may mean lower in value, for
example by at least a certain threshold. Other quality criteria
instead of or, in addition to, value may be used to determine
whether one measurement is better (or worse) than another
measurement. At least one of the measurements may need to meet
certain other criteria, for example, quality criteria, to be
included in the comparison. For example, a measurement value may
need to exceed a threshold in order to be included in the
comparison.
[0159] WTRU selection of a measurement based on certain criteria
being met and/or the results of comparison with one or more other
measurements. For example, WTRU selection of a certain measurement
as the best measurement which may correspond to the WTRU selection
of the best vertical beam.
[0160] The association of a measurement with one or a set of RA
resources. The association of measurements with RA resources may be
configured by the eNB, for example, as described elsewhere
herein.
[0161] The one or more measurements may be configured by the eNB,
which may mean signaled to the WTRU via higher layer signaling,
such as broadcast or dedicated RRC signaling. Such configuration
may be as described elsewhere herein.
[0162] Any thresholds a WTRU may use may be signaled to the WTRU by
the eNB, for example by broadcast or dedicated signaling.
[0163] The one or more measurements may be made by the WTRU. The
comparisons may be performed by the WTRU. The determination as to
whether criteria are met may be performed by the WTRU.
[0164] When the selection/determination is of a set of RA resources
which may be used for transmission, the WTRU may choose the
specific RA resource based on rules similar to the existing rules
or new rules may be defined.
[0165] For example, if there are multiple preambles to choose from,
the WTRU may choose one randomly. If there are different preambles
to choose from with certain criteria to be met such as for the
current Group A and B preambles, the WTRU may choose a preamble
taking into account those criteria. If there are multiple frequency
resources to choose from, the WTRU may choose one randomly. For the
time aspect, the WTRU may choose the first available subframe in
the set of RA resources in which it is permitted to transmit the
preamble and may meet its time constraints.
[0166] In one example, a WTRU may make at least two measurements.
The WTRU may compare the measurements and determine which
measurement is best. The WTRU may select or determine the set of RA
resources associated with the determined best measurement. The WTRU
may then select or determine an RA resource from within the
determined set of RA resources and the WTRU may use that resource
for RA transmission.
[0167] In another example, the WTRU may first determine if the
measurements meet a certain quality criteria such as whether they
exceed a threshold. The WTRU may or may only include measurements
in the comparison if they meet the certain criteria. If only one
measurement may meet the quality criteria, then that measurement
may be considered the best measurement by the WTRU.
[0168] In another example, the WTRU may first determine whether a
certain criteria is met, such as whether the RSRP of the cell
exceeds a threshold. If that criteria is met, then the WTRU may use
the legacy RA resources for RA transmission. If the criteria is not
met, then the WTRU may determine which RA resources to use based on
the results of comparisons of measurements associated with RA
resources.
[0169] The measurement may be a reference signal (RS), where the
reference signal may be: a cell-specific RS (CRS), a channel-state
information (CSI) RS, a vertical beam (VB) RS, or any other RS or
known signal which may be received by the WTRU or transmitted by an
eNB.
[0170] If measurements of different types are to be compared by the
WTRU, the eNB may provide parameters to the WTRU to enable the WTRU
to adjust one or more of the measurements prior to comparison, for
example, to better correlate the measurements.
[0171] The WTRU may make and compare measurements that are for all
purposes and characteristics (for example, existing or legacy
measurements) with measurements which may be associated with
certain purposes or characteristics.
[0172] The WTRU may do this without additional configuration from
the eNB regarding the existing/legacy measurements. The WTRU may
understand that these are associated with existing/legacy RA
resources.
[0173] The WTRU may be provided with multiple, for example, one or
more sets of RA resources that the WTRU may understand are to be
used for certain purposes or characteristics. For example, the WTRU
may understand that each RA resource set corresponds to a different
vertical beam (where the WTRU may or may not know what each beam
direction is), measurement, or measurement configuration. One of
these sets may be the RA resource set which may be used for
existing/legacy purposes.
[0174] The WTRU may, for example, if it has no knowledge of which
set of resources may be better, do one or more of the following:
choose, for example, randomly, one set from the multiple RA
resource sets; select a RA resource within the set according to the
selection rules (for example, random selection of preamble in the
set, first available subframe in the set that may meet the physical
timing constraints, and the like); perform the RA procedure (which
may include transmitting the selected preamble at a certain power);
wait for a RAR; and if no reply is received, the WTRU may ramp the
power up and try again, which may include repeating the RA resource
selection from the currently selected RA resource set and ramping
power until it receives an RAR or reaches the maximum allowed power
ramping or ramping attempts.
[0175] If the WTRU reaches the maximum allowed power ramping or
ramping attempts, the WTRU may then select, for example, randomly,
another set of RA resources if one exists and then try again.
[0176] The order in which the WTRU chooses a set of RA resources
may be according to one or more of the following.
[0177] The WTRU may select the RA set to be used for
existing/legacy purposes first. The WTRU may determine to select
the RA set to be used for existing/legacy purposes first if it
determines a measurement, such as a RSRP measurement, exceeds a
certain threshold.
[0178] The WTRU may select an RA resource set randomly from the
multiple sets provided.
[0179] Each time a WTRU selects an RA set, it may select the set
randomly from the multiple sets provided or from the subset of the
multiple sets that does not include a set already tried.
[0180] The WTRU may select an RA resource set according to an order
configured by the eNB where such configuration may be signaled to
the WTRU by the eNB via signaling, such as broadcast or dedicated
RRC signaling.
[0181] The WTRU may use measurements to determine which RA resource
set to try first or the order in which to try the RA resource sets.
When measurements are used, the WTRU may select the RA resource set
that corresponds to the measurement or measurement configuration
that meets a certain criteria.
[0182] An eNB may use measurements of SRS transmissions from a WTRU
to determine a preferred beam direction for UL reception from
and/or DL transmission to the WTRU.
[0183] The eNB may use aperiodic SRS to cause the WTRU to transmit
SRS at specific time.
[0184] To enable the eNB to get a number of SRS transmissions, for
example to enable convergence of the beam direction, the eNB may
trigger aperiodic SRS a number of times, where such triggers may be
closely spaced in time. For example, the eNB may trigger N
aperiodic SRS for a WTRU such that the WTRU is scheduled to
transmit and/or transmits SRS in N consecutive WTRU-specific SRS
subframes. Consecutive WTRU-specific SRS subframes may not be
consecutive subframes, since only certain subframes may be
WTRU-specific SRS subframes.
[0185] To enable the eNB to get a number of SRS transmissions, for
example to enable convergence of the beam direction, the eNB may
trigger a multi-shot aperiodic SRS which may yield the result that
the WTRU is scheduled to transmit and/or transmits SRS in N
consecutive WTRU-specific SRS subframes. The first subframe in
which the WTRU transmits SRS may be the first WTRU-specific
subframe that is at least k subframes after the subframe in which
the trigger is received, where k may be 4. N may be a known value,
a configured value, or a value provided with the trigger.
[0186] It may be useful for the eNB to receive a PHR after the
vertical beam has converged.
[0187] To accomplish this, the WTRU, for example, may trigger a PHR
according to at least one of the following: upon receipt of an
aperiodic SRS request which may also include a PHR request; a
certain time T, or a number of TTIs or subframes S, after receiving
an aperiodic SRS request; a certain time T, or a number of TTIs or
subframes S, after transmitting an aperiodic SRS; a certain time T,
or a number of TTIs or subframes S, after transmitting the last of
the N SRS transmissions triggered by a multi-shot aperiodic SRS
request; and a certain time T, or a number of TTIs or subframes S,
after receiving a group of closely spaced aperiodic SRS requests.
For example, if a WTRU receives an aperiodic SRS request in the
span of less than B ms, the WTRU may trigger PHR C ms or TTIs or
subframes after the last trigger or after the last SRS it transmits
in that time span.
[0188] The time T or number of subframes S may be at least one of:
a known value, for example, by a rule; configured such as by higher
layer signaling; included with the aperiodic SRS request; selected,
such as from a set of known or configured values, by an indication
which may be included in the aperiodic SRS request; or greater than
or equal to 0.
[0189] PHR may or may only be triggered based on receipt of an
aperiodic SRS request if the aperiodic SRS request includes a PHR
request.
[0190] If it is not possible for the WTRU to transmit the PHR, for
example if there are no UL resources allocated for new transmission
in which the PHR may fit, when the PHR is triggered, the WTRU may
transmit the PHR at the soonest later time when transmitting a PHR
is possible.
[0191] Once the criteria for triggering an aperiodic SRS related
PHR has been met, the WTRU may continue to trigger this PHR until
the PHR is transmitted or able to be transmitted.
[0192] For the DL, an eNB with 3D-MIMO/3D-beamforming capabilities
in general may require DL CSI to precisely shape the beam for a
specific WTRU, which may be called WTRU-specific beamforming. The
DL CSI may be obtained with the above proposed CSI feedback
including PMI/CQI/RI/RSRP/PTI/CPI and the like. The eNodeB may also
predefine a set of vertical beams (within a single horizontal
cell). As mentioned above, each vertical beam may be associated
with a specific CSI-RS configuration. To support N.sub.v vertical
beams, N.sub.v CSI-RS configurations may be used for a WTRU to
measure the multiple vertical beams. A WTRU may measure and report
channel state information (CSI) based on a single or multiple
CSI-RS configurations. The CSI-RS and d-BTRS may be interchangeably
used herein. Therefore multiple CSI-RS configurations may be
equivalent to the multiple d-BTRS. In addition, the d-BTRS may be
whole or a subset of the antenna ports in a CSI-RS configuration,
which may include the solution that a single CSI-RS configuration
with N-ports may be divided into multiple subsets and each subset
corresponding to a d-BTRS.
[0193] As a WTRU moves from one location to another location (in
the vertical and/or horizontal domain), the desired WTRU-specific
3-D beam (vertical and/or horizontal) may have changed in either
the vertical domain, the horizontal domain, or both. Thus the
desired WTRU-specific beam may need to be updated either through a
WTRU or an eNodeB triggered event. To support WTRU-specific 3D
beamforming, one or more of following may apply.
[0194] For any given TTI, a WTRU may measure all the CSI-RS
configurations and report the multiple CSI information
(representing the vertical beam quality). This may introduce
excessive feedback overhead. Alternatively, a WTRU autonomous
behavior may be needed to report the best or preferred vertical
beam when the desired vertical beam of the WTRU changes due to
movement.
[0195] The procedure may be defined as follows. A WTRU k may
calculate its wideband SINR .gamma..sub.k(H.sub.k,V.sub.k) as a
function of channel state information and applied vertical
beamforming (reflected in a current active CSI-RS port). The WTRU
may measure all the configured CSI-RS ports and calculate the
SINRs. Once the SINR of the current active CSI-RS port
(corresponding to current vertical beam) drops more than a defined
threshold compared to other configured CSI-RS ports (representing
different vertical beams), for example:
.gamma..sub.k.sup.1(H.sub.k.sup.1,V.sub.k.sup.1)-.gamma..sub.k.sup.0(H.s-
ub.k.sup.0,V.sub.k.sup.0>.GAMMA..sub.th [0196]
.gamma..sub.k.sup.0: SINR at an original location measured on
current active CSI-RS port [0197] .gamma..sub.k.sup.1: SINR at a
new location measured on any other configured CSI-RS port [0198]
.GAMMA..sub.th: SINR threshold for beam reselection the WTRU may
then report back the strongest CSI-RS port associated with the
measured strongest SINR along with an indication of beam update.
The eNB may accordingly update the active vertical beam for the
WTRU for future transmission. The active vertical beam update may
include reconfiguration of the active CSI-RS port. The SINR metric
may be replaced with RSRP or RSRQ with the same procedure. Either
subband or wideband CSI may be used.
[0199] A WTRU may be triggered to report the preferred CSI-RS
configuration among the multiple CSI-RS configurations by one or
more of following.
[0200] The preferred CSI-RS configuration may be defined as at
least one of: the CSI-RS configuration having the highest wideband
CQI (or RSRP) value among the set of CSI-RS configurations, or the
CSI-RS configuration a WTRU preferred to report for CSIs including
CQI/PMI and/or RI.
[0201] An eNB may trigger to report the preferred CSI-RS
configuration among the multiple CSI-RS configurations from a DCI.
A triggering bit may be included in the DCI and if the triggering
bit indicates `0`, the WTRU may not report the preferred CSI-RS
configuration and if the triggering bit indicates `1`, the WTRU may
report the preferred CSI-RS configuration in the corresponding UL
subframe. The corresponding UL subframe may be n+4, where n is the
subframe index where the WTRU received the triggering.
[0202] A WTRU may report the preferred CSI-RS configuration if at
least one of following conditions is satisfied. The previous
preferred CSI-RS configuration has a lower wideband CQI (or RSRP)
than any of the other CSI-RS configurations in a subframe k and the
gap between the best CSI-RS configuration and the previous
preferred CSI-RS configuration is larger than a predefined
threshold value. The CSI-RS configuration having the highest
wideband CQI (or RSRP) is changed and the gap is larger than a
predefined threshold.
[0203] A WTRU may be configured to report the preferred CSI-RS
configuration periodically. For instance, in every N.sub.cycle
[ms], a WTRU may report a preferred CSI-RS configuration. In this
case, one or more of following may apply:
[0204] The preferred CSI-RS configuration may be reported as
V.sub.index and the V.sub.index may be reported by any one of:
separately from PMI/RI/CQI and/or PTI, or via the PUCCH using PUCCH
format 2/2a/2b.
[0205] The preferred CSI-RS configuration (for example,
V.sub.index) may be reported via the PUSCH in a piggybacked manner.
In this case, the location of the V.sub.index may be the same as
the RI.
[0206] A WTRU may be configured with multiple CSI-RS configurations
while the CSI reporting (for example, CQI/PMI/RI and/or PTI) may be
based on an associated CSI-RS configuration, where the associated
CSI-RS configuration may be informed by the eNB. In this case, one
or more of following may apply:
[0207] The associated CSI-RS configuration may be informed via
higher layer signaling. The associated CSI-RS configuration may be
indicated in a DCI for UL grant if aperiodic CSI reporting is used.
A WTRU may report the preferred CSI-RS configuration via higher
layer signaling. The associated CSI-RS configuration may be
informed implicitly by confirming that the eNB received the
preferred CSI-RS configuration reporting. Thus, right after the
confirmation, the WTRU may measure CSI based on the reported
preferred CSI-RS configuration. The multiple CSI-RS configurations
may be measured only for reporting the preferred CSI-RS
configuration.
[0208] The multiple CSI-RS configurations are cell-specific, which
is different from WTRU-specific CSI-RS configuration. A WTRU may
measure cell-specific CSI-RS configurations (for example, d-BTRS)
for reporting preferred CSI-RS configuration, while the WTRU may
measure WTRU-specific CSI-RS configurations for CSI reporting for
one or more transmission points. In this case, one or more of
following may apply:
[0209] A WTRU may report based on cell-specific CSI-RS
configurations if one or more of following conditions are met. The
previous preferred cell-specific CSI-RS configuration has a lower
wideband CQI (or RSRP) than any of other cell-specific CSI-RS
configurations in a subframe k and the gap between the best
cell-specific CSI-RS configuration and the previous preferred
cell-specific CSI-RS configuration is larger than a predefined
threshold value. The cell-specific CSI-RS configuration the having
highest wideband CQI (or RSRP) is changed and the gap is larger
than a predefined threshold.
[0210] A WTRU may report based on WTRU-specific CSI-RS
configurations if the eNB configures periodic CSI reporting or
triggers aperiodic CSI reporting.
[0211] In the case of line of sight (LoS), the above beam
reselection may be complemented with a direction of
arrival-triggered beam update. The eNB may decide and change the
beam for the WTRU based on qualified trigger events. This case is
suitable for the LoS case only and low mobility.
[0212] The eNB may detect the direction of arrival (DoA) for both
azimuth and elevation from each WTRU. Once the measured DoA change
from a WTRU reaches a threshold, the eNB may adjust the WTRU to a
new direction-based predefined vertical beam.
[0213] FIG. 14 is an example method for receiving a reception
vertical beam. A wireless transmit/receive unit (WTRU) 1401 may
receive 1403 a broadcast message from an evolved Node B (eNB) 1402
that includes information associated with a plurality of vertical
beams, wherein the information includes at least one set of
Physical Random Access Control Channel (PRACH) resources associated
with each of the plurality of vertical beams. The WTRU 1401 may
measure 1404 reference signals transmitted on each of the plurality
of vertical beams to select a reception vertical beam. The WTRU
1401 may transmit 1405 a PRACH preamble in a set of resources
associated with the selected reception vertical beam. The WTRU 1401
may receive 1406 communications from the eNB 1402 using the
selected reception vertical beam.
[0214] Although features and elements are described above in
particular combinations, one of ordinary skill in the art will
appreciate that each feature or element may 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 non-transitory
computer-readable medium for execution by a computer or processor.
Examples of non-transitory 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.
* * * * *