U.S. patent application number 15/888299 was filed with the patent office on 2018-08-09 for mechanism for beam reciprocity determination and uplink beam management.
The applicant listed for this patent is MEDIATEK INC.. Invention is credited to Ming-Po Chang, Jiann-Ching Guey, Chia-Hao Yu.
Application Number | 20180227772 15/888299 |
Document ID | / |
Family ID | 63038162 |
Filed Date | 2018-08-09 |
United States Patent
Application |
20180227772 |
Kind Code |
A1 |
Yu; Chia-Hao ; et
al. |
August 9, 2018 |
Mechanism for Beam Reciprocity Determination and Uplink Beam
Management
Abstract
A method of beam reciprocity state reporting and uplink beam
management in wireless communication systems with beamforming is
proposed. In one novel aspect, a UE determines its UE beam
reciprocity state and sends a "UE beam reciprocity state" message
to a BS, which triggers proper uplink beam management accordingly.
The UE beam reciprocity state message can take place when UE tries
to register to the network. For example, according to factory
setting, UE reports at least "Positive" or "Negative" in this
message. Beam reciprocity state can be updated by a "UE beam
reciprocity state update" message. An auxiliary information can be
transmitted to the BS for UL beam management if UE reports
"Negative" for beam reciprocity state. The auxiliary information
indicates the uncertainty level of UE beams.
Inventors: |
Yu; Chia-Hao; (Hsinchu,
TW) ; Chang; Ming-Po; (Hsinchu, TW) ; Guey;
Jiann-Ching; (Hsinchu, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MEDIATEK INC. |
Hsinchu |
|
TW |
|
|
Family ID: |
63038162 |
Appl. No.: |
15/888299 |
Filed: |
February 5, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62455039 |
Feb 6, 2017 |
|
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62501936 |
May 5, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 7/0617 20130101;
H04W 72/046 20130101; H04W 88/08 20130101; H04W 16/28 20130101;
H04W 88/02 20130101; H04W 24/10 20130101; H04L 5/0048 20130101;
H04L 5/0091 20130101; H04W 72/04 20130101; H04L 5/0023 20130101;
H04B 7/0619 20130101; H04W 76/27 20180201 |
International
Class: |
H04W 16/28 20060101
H04W016/28; H04L 5/00 20060101 H04L005/00; H04W 72/04 20060101
H04W072/04; H04B 7/06 20060101 H04B007/06 |
Claims
1. A method comprising: obtaining a beam reciprocity state by a
user equipment (UE) in a beamforming communication network;
providing the beam reciprocity state to a base station, wherein the
beam reciprocity state indicates a positive or a negative UE beam
reciprocity state; and performing an uplink beam management
procedure when the beam reciprocity state indicates the negative UE
beam reciprocity state, wherein the UE receives resource
configuration and transmits reference signals over the configured
resource using corresponding UE beams.
2. The method of claim 1, wherein the beam reciprocity state is
obtained according to a factory setting.
3. The method of claim 1, wherein the beam reciprocity state is
provided via a beam reciprocity state message or a beam reciprocity
state update message.
4. The method of claim 1, wherein the UE transmits auxiliary
information that comprises an uncertainty level of UE beams to the
base station when the UE reports the negative beam reciprocity
state.
5. The method of claim 4, wherein the auxiliary information is
represented by a bit string, and wherein a value of the bit string
indicates the uncertainly level of the UE beams.
6. The method of claim 1, further comprising: performing a beam
reciprocity determination procedure when the beam reciprocity state
indicates an unsure UE beam reciprocity state.
7. The method of claim 6, wherein the beam reciprocity determining
procedure further involves: receiving resource configuration from
the base station; performing uplink transmission based on the
resource configuration using a selected number of UE beams;
receiving resource indices with stronger metric from the base
station; and determining the beam reciprocity state based on the
received resource indices and downlink beam management results.
8. A User Equipment (UE) comprising: a radio frequency (RF)
transmitter that transmits a beam reciprocity state to a base
station in a beamforming communication network, wherein the UE
obtains the beam reciprocity state that indicates a positive or a
negative UE beam reciprocity state; and a beam management circuit
that performs an uplink beam management procedure when the beam
reciprocity state indicates the negative UE beam reciprocity state,
wherein the UE receives resource configuration and transmits
reference signals over the configured resource using corresponding
UE beams.
9. The UE of claim 8, wherein the beam reciprocity state is
obtained according to a factory setting.
10. The UE of claim 8, wherein the beam reciprocity state is
provided via a beam reciprocity state message or a beam reciprocity
state update message.
11. The UE of claim 8, wherein the UE transmits auxiliary
information that comprises an uncertainty level of UE beams to the
base station when the UE reports the negative beam reciprocity
state.
12. The UE of claim 11, wherein the auxiliary information is
represented by a bit string, and wherein a value of the bit string
indicates the uncertainly level of the UE beams.
13. The UE of claim 8, further comprising: a beam monitoring
circuit that performs a beam reciprocity determination procedure
when the beam reciprocity state indicates an unsure UE beam
reciprocity state.
14. The UE of claim 13, wherein the beam reciprocity determining
procedure further involves receiving resource configuration,
performing uplink transmission based on the resource configuration
using a selected number of UE beams, receiving resource indices
with stronger metric, and determining the beam reciprocity state
based on the received resource indices and downlink beam management
results.
15. A method, comprising: receiving a beam reciprocity state from a
user equipment (UE) by a base station in a beamforming
communication network, wherein the beam reciprocity state indicates
a positive or a negative UE beam reciprocity state; and triggering
an uplink beam management procedure when the beam reciprocity state
indicates the negative UE beam reciprocity state, wherein the beam
management procedure involves configuring resource and receiving
reference signals over the configured resource with corresponding
UE beams.
16. The method of claim 15, wherein the base station receives the
beam reciprocity state via a beam reciprocity state message or a
beam reciprocity state update message.
17. The method of claim 15, wherein the base station receives
auxiliary information that comprises an uncertainty level of UE
beams when the beam reciprocity state is negative.
18. The method of claim 17, wherein the auxiliary information is
represented by a bit string, and wherein a value of the bit string
indicates the uncertainly level of UE beams.
19. The method of claim 15, wherein the base station triggers a
beam reciprocity determination procedure when the beam reciprocity
state indicates an unsure UE beam reciprocity state.
20. The method of claim 19, wherein the beam reciprocity
determining procedure further involves configuring resource to the
UE and transmitting resource indices with stronger metric from the
base station.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn. 119
from U.S. Provisional Application No. 62/455,039, entitled
"Mechanism for Beam Reciprocity Determination and UL Beam
Management," filed on Feb. 6, 2017; U.S. Provisional Application
No. 62/501,936, entitled "Method for Beam Management for Wireless
Communication System with Beamforming," filed on May 5, 2017, the
subject matter of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The disclosed embodiments relate generally to wireless
communication, and, more particularly, to beam reciprocity
determination and uplink beam management in a Millimeter Wave (mmW)
beamforming system.
BACKGROUND
[0003] The bandwidth shortage increasingly experienced by mobile
carriers has motivated the exploration of the underutilized
Millimeter Wave (mmWave) frequency spectrum between 3G and 300G Hz
for the next generation broadband cellular communication networks.
The available spectrum of mmWave band is two hundred times greater
than the conventional cellular system. The mmWave wireless network
uses directional communications with narrow beams and can support
multi-gigabit data rate. The underutilized bandwidth of the mmWave
spectrum has wavelengths ranging from 1 mm to 100 mm. The very
small wavelengths of the mmWave spectrum enable large number of
miniaturized antennas to be placed in a small area. Such
miniaturized antenna system can produce high beamforming gains
through electrically steerable arrays generating directional
transmissions. With recent advances in mmWave semiconductor
circuitry, mmWave wireless system has become a promising solution
for real implementation. However, the heavy reliance on directional
transmissions and the vulnerability of the propagation environment
present particular challenges for the mmWave network with
beamforming.
[0004] For beamformed access, both ends of a link, e.g., both base
station (BS) and user equipment (UE), need to know which
beamformers to use. In downlink DL-based beam management, the BS
side provides opportunities for UE to measure beamformed channel of
different combinations of BS beams and UE beams. For example, BS
performs periodic beam sweeping with reference signal (RS) carried
on individual BS beams. UE can collect beamformed channel state by
using different UE beams, and UE then report the collect
information to BS. Similarly, in uplink UL-based beam management,
the UE side provides opportunities for BS to measure beamformed
channel of different combinations of UE beams and BS beams. For
example, UE performs periodic beam sweeping with reference signal
(RS) carried on individual UE beams. BS can collect beamformed
channel state by using different BS beams, and BS then report the
collect information to UE.
[0005] UE Beam reciprocity state affects whether additional
UL-based beam management is required. Beam reciprocity at BS holds
if BS is able to determine a BS RX beam for the UL reception based
on UE's DL measurement on BS's one or more TX beams, and if BS is
able to determine a BS TX beam for the DL transmission based on
BS's UL measurement on BS's one or more RX beams. Similarly,
reciprocity at UE holds if UE is able to determine a UE RX beam for
the DL reception based on BS's UL measurement on UE's one or more
TX beams, and if UE is able to determine a UE TX beam for the UL
transmission based on UE's DL measurement on UE's one or more RX
beams.
[0006] UL beam management consumes additional resources heavily and
should be minimized. With beam reciprocity or partial beam
reciprocity at UE, UL beam management overhead can be reduced.
Therefore, it is desirable for UE to report its beam reciprocity to
the network for proper UL beam management.
SUMMARY
[0007] A method of beam reciprocity state reporting and uplink beam
management in wireless communication systems with beamforming is
proposed. In one novel aspect, a UE determines its UE beam
reciprocity state and sends a "UE beam reciprocity state" message
to a BS, which triggers proper uplink beam management accordingly.
The UE beam reciprocity state message can take place when UE tries
to register to the network. For example, according to factory
setting, UE reports at least "Positive" or "Negative" in this
message. Beam reciprocity state can be updated by a "UE beam
reciprocity state update" message. An auxiliary information can be
transmitted to the BS for UL beam management if UE reports
"Negative" for beam reciprocity state. The auxiliary information
indicates the uncertainty level of UE beams.
[0008] In one embodiment, a user equipment (UE) obtains a beam
reciprocity state in a beamforming communication network. The UE
provides the beam reciprocity state to a base station. The beam
reciprocity state indicates a positive or negative UE beam
reciprocity state. The UE performs an uplink beam management
procedure when the beam reciprocity state indicates the negative
beam reciprocity state. The UE receives resource configuration from
the base station and transmits reference signals over the
configured resource using corresponding UE beams for uplink beam
management.
[0009] In another embodiment, a base station (BS) receives a beam
reciprocity state from a user equipment (UE) in a beamforming
communication network. The beam reciprocity state indicates
positive, negative, or unsure UE beam reciprocity. The BS triggers
an uplink beam management procedure when the beam reciprocity state
indicates negative UE beam reciprocity. The beam management
procedure involves configuring resource and receiving reference
signals over the configured resource with corresponding UE
beams.
[0010] In one novel aspect, a BS configures one or more resource
sets to a UE for uplink beam management. The one or more resource
sets are allocated for UE to transmit UL reference signal using a
number of UE beams. The number of UE beams to be trained is
reported by the UE, e.g., via the "UE beam reciprocity state
(update)" message. The BS also indicates whether a fixed UE TX beam
or which UE TX beam is used for transmission, or indicates whether
different UE TX beams are used for transmission of different
resources in a resource set. The BS then feedback measurement
results for UE to choose a proper TX beam.
[0011] In one embodiment, a UE obtains resource configuration from
a base station in a beamforming communication network. The resource
configuration allocates one or more resource sets in time and
frequency domain to train a number of UE beams for uplink beam
management. The UE obtains beam configuration indicating one or
more UE beams to be used for uplink transmission. The UE transmits
reference signals over one or more activated resource sets. The UE
maps the activated resource set(s) to the one or more UE beams. The
UE receives measurement results of the reference signals and
thereby determining a proper UE beam for uplink transmission.
[0012] In another embodiment, a BS provides resource configuration
to a user equipment (UE) in a beamforming communication network.
The resource configuration allocates one or more resource sets in
time and frequency domain to train a number of UE beams for uplink
beam management. The BS activates one or more resource sets and
providing beam configuration with one or more UE beams to be used
for uplink transmission. The BS performs measurements on reference
signals received from the UE over the activated resource set(s).
The BS transmits measurement results to the UE for determining a
proper UE beam for uplink transmission.
[0013] Other embodiments and advantages are described in the
detailed description below. This summary does not purport to define
the invention. The invention is defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, where like numerals indicate like
components, illustrate embodiments of the invention.
[0015] FIG. 1 illustrates a beamforming wireless communication
system supporting beam reciprocity reporting and corresponding
uplink beam management in accordance with one novel aspect.
[0016] FIG. 2 is a simplified block diagram of a base station and a
user equipment that carry out certain embodiments of the present
invention.
[0017] FIG. 3 illustrates definition of beam reciprocity using
communication between BS and UE.
[0018] FIG. 4 illustrates calibrated RX and TX RF paths and beam
reciprocity.
[0019] FIG. 5 illustrates a first embodiment of beam reciprocity
state indication and update in accordance with a novel aspect.
[0020] FIG. 6 illustrates a second embodiment of beam reciprocity
state indication and update in accordance with a novel aspect.
[0021] FIG. 7 illustrates a third embodiment of beam reciprocity
state indication and update in accordance with a novel aspect
[0022] FIG. 8 illustrates a beam reciprocity state determination
procedure in accordance with one novel aspect.
[0023] FIG. 9 is a flow chart of a method of beam reciprocity
indication from UE perspective in a beamforming system in
accordance with one novel aspect.
[0024] FIG. 10 is a flow chart of a method of beam reciprocity
indication from BS perspective in a beamforming system in
accordance with one novel aspect.
[0025] FIG. 11 illustrates an uplink beam management procedure in
accordance with one novel aspect.
[0026] FIG. 12 illustrates a first example of resource
configuration for UL beam management.
[0027] FIG. 13 illustrates a second example of resource
configuration for UL beam management.
[0028] FIG. 14 illustrates a third example of resource
configuration for UL beam management.
[0029] FIG. 15 illustrates embodiments of configuring different
sets of resources for UL RS transmission via RRC signaling.
[0030] FIG. 16 illustrates embodiments of activating one or subset
of the configured resource sets for UL RS transmission via DCI.
[0031] FIG. 17 is a flow chart of a method of uplink beam
management from UE perspective in a beamforming system in
accordance with one novel aspect.
[0032] FIG. 18 is a flow chart of a method of uplink beam
management from base station perspective in a beamforming system in
accordance with one novel aspect.
DETAILED DESCRIPTION
[0033] Reference will now be made in detail to some embodiments of
the invention, examples of which are illustrated in the
accompanying drawings.
[0034] FIG. 1 illustrates a beamforming wireless communication
system 100 supporting beam reciprocity reporting and corresponding
uplink beam management in accordance with one novel aspect.
Beamforming mmWave mobile communication network 100 comprises a
base station BS 101 and a user equipment UE 102. The mmWave
cellular network uses directional communications with narrow beams
and can support multi-gigabit data rate. Directional communications
are achieved via digital and/or analog beamforming, wherein
multiple antenna elements are applied with multiple sets of
beamforming weights to form multiple beams. In the example of FIG.
1, BS 101 is directionally configured with multiple TX/RX BS beams,
e.g., #B1, #B2, #B3, #B4, and #B5 to cover a service area.
Similarly, UE 102 may also apply beamforming to form multiple UE
beams, e.g., #U1 and #U2.
[0035] The set of BS beams may be periodically configured or occur
indefinitely and repeatedly in order known to the UEs. Each BS beam
broadcasts minimum amount of cell-specific and beam-specific
information similar to System Information Block (SIB) or Master
Information Block (MIB) in LTE systems. Each BS beam may also carry
UE-specific control or data traffic. Each BS beam transmits a set
of known reference signals for the purpose of initial
time-frequency synchronization, identification of the beam that
transmits the signals, and measurement of radio channel quality for
the beam that transmits the signals. In one example, a hierarchical
control beam and dedicated data beam architecture provides a robust
control-signaling scheme to facilitate the beamforming operation in
mmWave cellular network systems.
[0036] For beamformed access, both ends of a link need to know
which beamformers to use, e.g., a beam pair link (BPL). In downlink
DL-based beam management, the BS side provides opportunities for
the UE side to measure beamformed channel of different combinations
of BS beams and UE beams. For example, BS 101 performs periodic
beam sweeping with reference signal (RS) carried on individual BS
beams. UE 102 can collect beamformed channel state by using
different UE beams, and UE 102 then report the collect information
to BS 101. Beam reciprocity state of UE affects whether additional
uplink UL-based beam management is required. UL beam management
consumes additional resources heavily and should be minimized. With
beam reciprocity or partial beam reciprocity at UE, UL beam
management overhead can be reduced.
[0037] In according with one novel aspect, UE 102 determines its UE
beam reciprocity state and sends a "UE beam reciprocity state"
message to BS 101, which triggers proper uplink beam management
accordingly. The UE beam reciprocity state message can take place
when UE 102 tries to register to the network. For example, this
message is transmitted in Radio Resource Control (RRC) signaling.
According to factory setting, UE 102 reports at least "Positive" or
"Negative" in this message. Beam reciprocity state can be updated
by a "UE beam reciprocity state update" message. An auxiliary
information can be transmitted to the network for UL beam
management if UE reports "Negative" for beam reciprocity state. The
auxiliary information indicates the uncertainty level of the UE
beams.
[0038] For UL beam management, BS 101 configures one or more
resource sets to UE 102 for uplink beam management. The one or more
resource sets are allocated for UE 102 to transmit UL reference
signal using a number of UE beams. The number of UE beams to be
trained is reported by UE 102, e.g., via the "UE beam reciprocity
state (update)" message with auxiliary information. BS 101 also
indicates whether a fixed UE TX beam or which UE TX beam is used
for transmission, or indicates whether different UE TX beams are
used for transmission of different resources in a resource set. BS
101 then feedback measurement results for UE 102 to choose a proper
TX beam.
[0039] FIG. 2 is a simplified block diagram of a base station and a
user equipment that carry out certain embodiments of the present
invention. BS 201 has an antenna array 211 having multiple antenna
elements that transmits and receives radio signals, one or more RF
transceiver modules 212, coupled with the antenna array, receives
RF signals from antenna 211, converts them to baseband signal, and
sends them to processor 213. RF transceiver 212 also converts
received baseband signals from processor 213, converts them to RF
signals, and sends out to antenna 211. Processor 213 processes the
received baseband signals and invokes different functional modules
to perform features in BS 201. Memory 214 stores program
instructions and data 215 to control the operations of BS 201. BS
201 also includes multiple function modules and circuits that carry
out different tasks in accordance with embodiments of the current
invention.
[0040] Similarly, UE 202 has an antenna 231, which transmits and
receives radio signals. A RF transceiver module 232, coupled with
the antenna, receives RF signals from antenna 231, converts them to
baseband signals and sends them to processor 233. RF transceiver
232 also converts received baseband signals from processor 233,
converts them to RF signals, and sends out to antenna 231.
Processor 233 processes the received baseband signals and invokes
different functional modules to perform features in UE 202. Memory
234 stores program instructions and data 235 to control the
operations of UE 202. UE 202 also includes multiple function
modules and circuits that carry out different tasks in accordance
with embodiments of the current invention.
[0041] The functional modules and circuits can be implemented and
configured by hardware, firmware, software, and any combination
thereof. Each module or circuit may comprise a processor with
corresponding program codes. For example, BS 201 comprises a beam
management module 220, which further comprises a beamforming
circuit 221, a beam monitor 222, and a beam resource configuration
circuit 223. Beamforming circuit 221 may belong to part of the RF
chain, which applies various beamforming weights to multiple
antenna elements of antenna 211 and thereby forming various beams.
Beam monitor 222 monitors received radio signals and performs
measurements of the radio signals over the various beams. Beam
resource configuration circuit 223 allocates radio resources and
corresponding TX beams to be used for UL beam management.
[0042] Similarly, UE 202 comprises a beam management module 240,
which further comprises a beamforming circuit 241, a beam monitor
242, a beam reciprocity reporting module 243, and a beam
configuration circuit 244. Beamforming circuit 241 may belong to
part of the RF chain, which applies various beamforming weights to
multiple antenna elements of antenna 231 and thereby forming
various beams. Beam monitor 242 monitors received radio signals and
performs measurements of the radio signals over the various beams.
Beam reciprocity indication circuit 243 determines UE beam
reciprocity and sends out UE beam reciprocity state message to BS
201. Beam configuration circuit 244 receives resource and beam
configuration from BS 201, such configuration is based on the
received UE beam reciprocity state from UE 201 for uplink beam
management to achieve reduced overhead.
UE Beam Reciprocity Indication
[0043] FIG. 3 illustrates definition of beam reciprocity using
communication between BS and UE. It is sometimes assumed that the
downlink channel and the uplink channel is spatially reciprocal in
the beamforming system. Under spatially reciprocal beamforming, the
same beamformed antenna pattern is used for reception and
transmission. TX/RX beam reciprocity at BS holds if BS is able to
determine a BS Rx beam for the UL reception based on UE's DL
measurement on BS's one or more TX beams, and BS is able to
determine a BS TX beam for the DL transmission based on BS's UL
measurement on BS's one or more RX beams. Similarly, for UE. As
illustrated in FIG. 3, for downlink transmission, the BS applies TX
beamforming vector V.sub.BS,TX and the UE applies RX beamforming
vector V.sub.UE,RX. For uplink transmission, the BS applies RX
beamforming vector V.sub.Bs,RX and the UE applies TX beamforming
vector V.sub.UE,TX. Under spatially reciprocal beamforming, the
beamforming vectors for downlink and uplink are the same, e.g.,
(V.sub.BS,TX, V.sub.UE,RX)=(V.sub.BS, RX, V.sub.UE,TX).
[0044] FIG. 4 illustrates calibrated RX and TX RF paths and beam
reciprocity. To form desired beam pattern, a relative complex gain
between individual RF paths need to be controlled. Individual RF
paths are calibrated in phase/magnitude, thus considered coherent.
Absolute complex gain is not important for beam pattern. This
applies for either TX paths or for RX paths. To claim beam
reciprocity, the calibrated complex gain of TX path i (d.sub.TXi)
and RX path i (d.sub.RXi) can be subject to a fixed complex gain.
As depicted in FIG. 4, beam reciprocity of the illustrated array is
maintained under the fixed complex value .alpha., e.g.,
d.sub.TXi=.alpha. d.sub.RXi. Component response of individual RF
paths is subject to variation during manufacturing. With factory
calibration to assure aligned response, RF component response is
also affected by temperature and aging. Partial beam reciprocity is
a sensible assumption. RF component variation introduces difference
between TX and RX responses. For a coarse beam, beam reciprocity
can be treated as hold. For a refined beam, beam reciprocity is not
necessarily true. Beam reciprocity state of UE affects whether
additional uplink UL-based beam management is required.
Furthermore, with partial beam reciprocity at UE, UL beam
management overhead can be reduced.
[0045] In accordance with one novel aspect, UE supports a "UE beam
reciprocity state" message and a "UE beam reciprocity state update"
message to the network in facilitating uplink beam management. The
UE beam reciprocity state message can take place when UE tries to
register to the network, e.g., this message is transmitted in RRC
signaling, or during initial access such as in RACH Msg1 or RACH
Msg3. According to factory setting, UE reports at least "Positive"
or "Negative" in this message. If UE cannot decide its state, UE
reports "Negative". Optionally, if UE cannot decide its state, UE
reports "Unsure". The indication can be represented by a bit
string. For example, all "0" bit string indicates "Negative" state,
and all "1" bit string indicates "Positive" state, and other
combinations indicate "Unsure" with extra information (e.g.,
different uncertainty level in terms of beam reciprocity state).
The bit length can be dependent on the number of UE analog beam
capability, e.g., the largest value of the bit string stands for
the number of UE analog beams per antenna panel. There can be
another parameter, e.g., a bit string, in capability signaling to
represent UE analog beam capability, e.g., the number of UL RS
resources needed to train UE beams.
[0046] Beam reciprocity state can be updated by the "UE beam
reciprocity state update" message, which can be UE-initiated or
network-triggered. The signaling takes place in MAC CE or RRC
message, e.g., not part of capability signaling if the state is not
static, but part of capability signal if the state is not changed
frequently. The signaling can take place during initial access to
the network, e.g., in Msg1 or Msg3 in RACH procedure. If beam
resolution selected by UE is coarse for the time being, report
"Positive" state. If beam resolution selected by UE is fine for the
time being, report "Negative" state. If UE cannot decide its beam
reciprocity state, report "Unsure" state. The indication of the "UE
beam reciprocity state update" can be represented by a bit string,
similar to the "UE beam reciprocity state" message. Note that if
there's no additional "beam reciprocity state update" message, then
beam reciprocity state remains unchanged. Furthermore, beam
reciprocity stat is not updated if it is part of capability
signaling.
[0047] FIG. 5 illustrates a first embodiment of beam reciprocity
state indication and update in accordance with a novel aspect. UE
beam reciprocity state is also referred as UE beam correspondence
state. In step 511, UE 501 determines UE beam correspondence state.
UE 501 can determine its beam reciprocity by different mechanisms.
In a first scenario, initial access procedure provides implication
of UE beam reciprocity state. For example, if the implication
indicates positive state and if following transmissions in
CONNECTED mode use same/similar/wider beam resolution as UE beams
used during initial access, then the state is positive. On the
other hand, if the implication indicates positive state and if
following transmissions in CONNECTED mode use narrower (refined)
beam resolution as UE beams used during initial access, then the
state can be negative. If the implication indicates negative state,
then UE reports negative beam reciprocity state. In a second
scenario, if UE is capable of beam reciprocity calibration by its
own, then periodic triggering of the calibration procedure can
ensure positive beam reciprocity state. In a third scenario, If UE
is not aware of its current beam reciprocity state, then UE reports
either "Negative" state or a "Unsure" state. The "Unsure" state can
be represented by, e.g., a series of bits, different bit
combinations indicate different uncertainty level in terms of beam
reciprocity state. In a fourth scenario, UE can retrieve factory
setting for its beam reciprocity state. In step 512, UE 501
transmits the beam reciprocity state message or beam reciprocity
state update message to BS 502, which indicates that the UE beam
reciprocity state is "Positive".
[0048] FIG. 6 illustrates a second embodiment of beam reciprocity
state indication and update in accordance with a novel aspect. UE
beam reciprocity state is also referred as UE beam correspondence
state. In step 611, UE 601 determines UE beam correspondence state,
similar to step 511 of FIG. 5. In step 612, UE 601 transmits the
beam reciprocity state message or beam reciprocity state update
message to BS 602, which indicates that the UE beam reciprocity
state is "Negative". Indication of negative beam reciprocity state
may result in UL beam management. UE indicates level of "ambiguity"
of its partial beam reciprocity. Along with "Negative" state
indication, UE also includes e.g., number of UE beams to
examine/sweep. The number of UE beams indicated to BS is preferred
to be a subset of all UE beams in the considered resolution.
Indication of "Negative" state and the level of ambiguity can be
aggregated into a bit string. This facilitates the following
resource configuration from the BS for UL beam management
resources. In step 613, BS 602 triggers UL beam management
procedure.
[0049] FIG. 7 illustrates a third embodiment of beam reciprocity
state indication and update in accordance with a novel aspect. UE
beam reciprocity state is also referred as UE beam correspondence
state. In step 711, UE 701 determines UE beam correspondence state,
similar to step 511 of FIG. 5. In step 712, UE 701 transmits the
beam reciprocity state message or beam reciprocity state update
message to BS 702, which indicates that the UE beam reciprocity
state is "Unsure". Indication of "Unsure" state may trigger BS to
initiate a "beam reciprocity state determination procedure" for
determining UE beam reciprocity state. UE indicates level of
"ambiguity" of its partial beam reciprocity. Along with "Unsure"
state indication, UE also includes e.g., number of UE beams to
examine/sweep. The number of UE beams indicated to BS is preferred
to be a subset of all UE beams in the considered resolution.
Indication of "Unsure" state and the level of ambiguity can be
aggregated into a bit string. Indication of "Unsure" state may
trigger BS 702 o initiate a "beam reciprocity state determination"
procedure, as depicted in step 713.
[0050] FIG. 8 illustrates a beam reciprocity state determination
procedure in accordance with one novel aspect. Partial beam
reciprocity implies not all beams of interested beam resolution
level need to be examined/swept for a considered terminal or
network transmission point. The resource configuration for beam
reciprocity state determination procedure considers 1) BS beams
need to be examined/swept, and 2) The number of UE beams to be
examined/swept (the information is reported by UE). For partial
beam reciprocity case, BS beams to be examined is simply a subset
of all BS beams of the interested beam resolution level. The subset
of BS beams to be examined/swept is constrained by DL beam
management results. The subset of BS beams is neighboring beams of
selected DL BS beam(s) based on DL beam management with the
concerned UE. The size of the subset of BS beams depends on BS side
beam reciprocity state, e.g., if BS side beam reciprocity holds and
only one DL beam pair is considered, the size can be one and the
only beam is the same as the selected DL BS beam.
[0051] In FIG. 8 step 811, BS 802 determines resource based on UE
reported number of UE beams, BS beam reciprocity, and DL beam pairs
to consider. In step 812, BS 802 sends resource configuration to UE
801, which indicates UL resources where UL transmission can take
place with the selected number of beams. In step 813, UE 801
performs UL transmission. Individual UE beams may be used for
multiple times for transmission. The transmission is received by BS
802 with the subset of BS beams. Individual BS beams may be used
for multiple times for reception. In step 821, based on the uplink
transmission, BS 802 decides a subset of resources with indices
that correspond to stronger received metric. The metric can be but
are not limited to, e.g., SNR, SINR, RSRP, etc. The size of the
subset of resources depends on, e.g., number of considered DL beam
pairs. For example, if the number of DL beam pair is one, then the
size can be one. In step 822, BS 802 signals the determined
resource indices with stronger received metric to UE 801.
[0052] In step 831, UE 801 determines its beam reciprocity state,
which may involve reciprocity calibration procedure. UE can map the
resource indices to corresponding UE beams used for UL
transmission. UE can compare the corresponding UE beams with UE
beams of considered DL beam pairs. The considered DL beam pairs are
determined based on DL beam management procedure. In step 832, UE
801 signals the determined beam reciprocity state to BS 802. If the
determined state is "Positive", such signaling can reuse the "UE
beam reciprocity state update" message. If the determined state is
"Negative", and if beam reciprocity calibration is supported, then
calibration procedure can be triggered. The calibration procedure
intends to change the state to "Positive" and the updated state is
reported. Otherwise, "Negative" state signaling can reuse the "UE
beam reciprocity state update" message, which triggers UL beam
management procedure.
[0053] FIG. 9 is a flow chart of a method of beam reciprocity
indication from UE perspective in a beamforming system in
accordance with one novel aspect. In step 901, a UE obtains a beam
reciprocity state in a beamforming communication network. In step
902, the UE provides the beam reciprocity state to a base station.
The beam reciprocity state indicates a positive or a negative beam
reciprocity. In step 903, the UE performs an uplink beam management
procedure when the beam reciprocity state indicates the negative
beam reciprocity state. The UE receives resource configuration from
the base station and transmits reference signals over the
configured resource using corresponding UE beams.
[0054] FIG. 10 is a flow chart of a method of beam reciprocity
indication from BS perspective in a beamforming system in
accordance with one novel aspect. In step 1001, a BS receives a
beam reciprocity state from a user equipment (UE) in a beamforming
communication network. The beam reciprocity state indicates a
positive or a negative UE beam reciprocity state. In step 1002, the
BS triggers an uplink beam management procedure when the beam
reciprocity state indicates the negative UE beam reciprocity state.
The beam management procedure involves configuring resource and
receiving reference signals over the configured resource with
corresponding UE beams.
Uplink Beam Management
[0055] FIG. 11 illustrates an uplink (UL) beam management procedure
in accordance with one novel aspect. With partial UE beam
reciprocity, uplink UL-based beam management is needed. Partial
beam reciprocity implies not all beams of interested beam
resolution level are examined/swept for a considered terminal or
network transmission point. In UL beam management, the UE side
provides opportunities for BS to measure beamformed channel of
different combinations of UE beams and BS beams. For example, UE
performs periodic beam sweeping with reference signal (RS) carried
on individual UE beams. BS can collect beamformed channel state by
using different BS beams, and BS then report the collect
information and measurement results to UE such that UE can
determine the UL beam pair to be used for UL communication.
[0056] In step 1111, UE 1101 transmits a UE beam reciprocity
state="Negative" message to BS 1102 together with "auxiliary
information". The auxiliary information indicates uncertainty level
of UE beams. In one example, it indicates the number of UE beams to
be trained in order to select the most proper UL transmit beam. In
another example, it indicates the number of UL RS resources that is
needed to resolve the uncertainty of UE beams for determining
proper UL transmit beam. The auxiliary information can be
transmitted together with "UE beam reciprocity state" message or
"UE beam reciprocity state update" message. The auxiliary
information can be in MAC CE or RRC message. In one example, it can
be part of UE capability report. In another example, it can be
carried in Msg1 or Msg3 in RACH procedure during initial access to
the network. The "negative" state indication and auxiliary
information can be represented by a bit string. For example, all
"0" bit string indicates "negative" state, and all "1" bit string
indicates "positive" state, and other combinations indicate "not
sure" with extra information (e.g., different uncertainty level in
terms of beam reciprocity state). The bit length can be dependent
on the number of UE analog beam capability, e.g., the largest value
of the bit string stands for the number of UE analog beam per
antenna panel. There can be another parameter e.g., bit string, in
capability signal to represent UE analog beam capability, e.g., the
number of UL RS resources needed to train UE beams.
[0057] In step 1112, BS 1102 configure several resource sets to UE
1101 for UL reference signal (RS) transmission. The resource
configuration for UL beam management considers the following
factors: 1) BS beams need to be examined or swept and 2) The number
of UE beams to be examined or swept that is reported by UE. For the
BS beams, for partial beam reciprocity case, BS beams to be
examined is simply a subset of all BS beams of the interested beam
resolution level. The size of the subset of BS beams depends on BS
side beam reciprocity state. For example, if BS side beam
reciprocity holds and only one DL beam pair is considered, the size
can be one and the only beam is the same as the selected DL BS
beam. The subset of BS beams is constrained by serving BS beam(s)
determined from DL beam management results. For the number of UE
beams, BS can reuse the content included in "Negative beam
reciprocity state update" or in "Unsure beam reciprocity state
update"; UE can indicate the number of UE beams in a separate
report; or BS acquires the number of UE beams from the "auxiliary
information" reported by UE when UE reports "Negative" for UE beam
reciprocity state. In step 1113, BS 1102 activates one resource set
and configures UE 1101 to train the number of UE beams.
[0058] In step 1121, UE 1101 transmits UL reference signal to BS
1102 over the allocated resources. The resource configuration can
include periodic resources for UE to transmit reference signal with
the set of reported ambiguous beams. Additional transmissions can
also be configured and triggered aperiodically whenever needed.
Individual UE beams may be used for multiple times for transmission
in a transmission round. The resource configuration supports a
configuration that provides UE to transmit UL reference signal for
multiple times by using a same UE beam in a transmission round. The
same UE beam can be UE beam used for UL data transmission. The
resource configuration supports a configuration that provides UE to
transmit UL reference signal for multiple times by using multiple,
and optionally different, UE TX beams, respectively in a
transmission round. Furthermore, the association of the resources
and UE/BS beams can be changed dynamically without additional
signaling. BS 1102 adapts its receiving beams for UL beam
management receptions based on the selected DL BS beam(s) from DL
beam management with UE 1101. Similarly, UE 1101 adapts its
transmitting beams for UL beam management transmissions based on
the selected DL BS beam(s) from DL beam management with UE 1101. In
step 1122, UE 1101 follows mapping between resource and beam for UL
RS transmission. In step 1123, BS 1102 selects its RX beam that is
transparent to UE. Finally, in step 1131, BS 1102 feedback UL RS
measurement result to UE 1101 for determining the proper UE TX
beam.
[0059] FIG. 12 illustrates a first example of resource
configuration for UL beam management. According to UE capability,
network can configure more than one resource per time unit. The use
of UE beam on a specific resource can be selected by UE. In the
example of FIG. 12, in time unit #1, network configures resources
#1 and #2 for UE beams #1 and #2, respectively. In time unit #2,
network configures resources #3 and #4 for UE beams #3 and #4,
respectively. In time unit #3, network configures resources #5 and
#6 for UE beams #5 and #6, respectively. In time unit #4, network
configures resources #7 and #8 for UE beams #7 and #8,
respectively.
[0060] FIG. 13 illustrates a second example of resource
configuration for UL beam management. Network can configure
multiple resources in multiple time units with different UE beams.
In the example of FIG. 13, network configures resource #1 for UE
beam #1 in time unit #1, resource #2 for UE beam #2 in time unit
#2, resource #3 for UE beam #3 in time unit #3, and resource #4 for
UE beam #4 in time unit #4.
[0061] FIG. 14 illustrates a third example of resource
configuration for UL beam management. Network can configure
multiple resources in multiple time units with the same UE beam. In
the example of FIG. 14, network configures resource #1 for UE beam
#1 in time unit #1, resource #2 for UE beam #1 in time unit #2,
resource #3 for UE beam #2 in time unit #3, and resource #4 for UE
beam #2 in time unit #4.
[0062] When the network configures resources for UE to transmit
uplink reference signal (UL RS), the network can indicate one or
more sets of resources in time and frequency domain (and optionally
antenna port). The configuration of the sets of resources can be
via RRC signaling. The activation of one or a subset of the
resource sets can be via physical layer control channel, e.g.,
downlink control information (DCI) carried in physical downlink
control channel (PDCCH). The number of resources in a resource set
is dependent on the number of UE TX beams to be used for UL RS
transmission. Further, the network can indicate whether a fixed UE
TX beam is used for transmission or not, which of the UE TX beams
is used as the fixed UE TX beam, or whether different UE TX beams
are used for transmission of different resources in a resource
set.
[0063] In one embodiment, the network indicates whether a fixed UE
TX beam is used for transmission or not. The use of fixed UE TX
beam can be indicated together with the resource configuration
i.e., via RRC signaling. The use of fixed UE TX beam can be
indicated in DCI that is used for triggering UL RS transmission.
The indication can be implicit, e.g., when it is not explicitly
indicated otherwise, a fixed TX beam is required. Optionally, which
of UE TX beams is used as the fixed UE TX beam can be indicated.
The indication can be via MAC CE signaling, or in DCI that is used
for triggering UL RS transmission. The indication can refer to the
UE TX beam that is used for previous UL RS transmission resources.
The indication can be via spatial QCL information or can be via
beam pair link tag that is associated with UE TX beam for UL
traffic. If there is no such indication, it is up to UE decision,
when the network demands to use a fixed beam.
[0064] In another embodiment, the number of resources in a resource
set is dependent on the number of UE TX beams to be used for UL RS
transmission. The number of UE TX beams can be decided by the
network based on, e.g., the auxiliary information provided by UE.
Optionally, the network indicates whether different UE TX beams are
used for transmission of different resources, respectively, in a
resource set. The use of different UE TX beams can be indicated
together with the resource configuration i.e., via RRC signaling.
The use of different UE TX beams can be indicated in DCI that is
used for triggering UL RS transmission. The indication can be
implicit, e.g., when it is not explicitly indicated otherwise,
different TX beams are used.
[0065] FIG. 15 illustrates embodiments of configuring different
sets of resources for UL RS transmission via RRC signaling. As
depicted in FIG. 15, the configuration for a first resource set #1
indicates the resource location indices, and the use of a fixed UE
TX beam for UL RS transmission. The configuration for a second
resource set #2 indicates the resource location indices, and the
use of different UE TX beams for UL RS transmission. The
configuration for a third resource set #3 indicates the resource
location indices.
[0066] FIG. 16 illustrates embodiments of activating one or subset
of the configured resource sets for UL RS transmission via DCI. As
depicted in FIG. 16, DCI#1 triggers UL RS transmission using
resource set #1 using the same UE beam, e.g., UL RS transmission
using resource #1 with UE reference beam #1 at time unit #1, UL RS
transmission using resource #2 with UE reference beam #1 at time
unit #2, and UL RS transmission using resource #3 with UE reference
beam #1 at time unit #3. DCI #2 triggers UL RS transmission using
resource set #2 using different UE beams, e.g., UL RS transmission
using resource #1 with UE reference beam #2 at time unit #1, UL RS
transmission using resource #2 with UE reference beam #3 at time
unit #2, and UL RS transmission using resource #3 with UE reference
beam #5 at time unit #3. DCI #3 triggers UL RS transmission using
resource set #3 without UE beam indication so UE determines
different beams for different resources itself, e.g., UL RS
transmission using resource #1 with UE reference beam #2 at time
unit #1, UL RS transmission using resource #2 with UE reference
beam #3 at time unit #2, and UL RS transmission using resource #3
with UE reference beam #5 at time unit #3.
[0067] FIG. 17 is a flow chart of a method of uplink beam
management from UE perspective in a beamforming system in
accordance with one novel aspect. In step 1701, a UE obtains
resource configuration from a base station in a beamforming
communication network. The resource configuration allocates one or
more resource sets in time and frequency domain to train a number
of UE beams for uplink beam management. In step 1702, the UE
obtains beam configuration indicating one or more UE beams to be
used for uplink transmission. In step 1703, the UE transmits
reference signals over one or more activated resource sets. The UE
maps the activated resource set(s) to the one or more UE beams. In
step 1704, the UE receives measurement results of the reference
signals and thereby determining a proper UE beam for uplink
transmission.
[0068] FIG. 18 is a flow chart of a method of uplink beam
management from base station perspective in a beamforming system in
accordance with one novel aspect. In step 1801, the BS providing
resource configuration to a user equipment (UE) in a beamforming
communication network. The resource configuration allocates one or
more resource sets in time and frequency domain to train a number
of UE beams for uplink beam management. In step 1802, the BS
activates one or more resource sets and providing beam
configuration with one or more UE beams to be used for uplink
transmission. In step 1803, the BS performs measurements on
reference signals received from the UE over the activated resource
set(s). In step 1804, the BS transmits measurement results to the
UE for determining a proper UE beam for uplink transmission.
[0069] Although the present invention has been described in
connection with certain specific embodiments for instructional
purposes, the present invention is not limited thereto.
Accordingly, various modifications, adaptations, and combinations
of various features of the described embodiments can be practiced
without departing from the scope of the invention as set forth in
the claims.
* * * * *