U.S. patent application number 15/757345 was filed with the patent office on 2020-07-23 for configuration of spatially qcl reference signal resources for transmissions in communication equipment having multiple antenna p.
The applicant listed for this patent is Telefonaktiebolaget LM Ericsson (publ). Invention is credited to Andreas NILSSON.
Application Number | 20200235802 15/757345 |
Document ID | / |
Family ID | 61521475 |
Filed Date | 2020-07-23 |
View All Diagrams
United States Patent
Application |
20200235802 |
Kind Code |
A1 |
NILSSON; Andreas |
July 23, 2020 |
CONFIGURATION OF SPATIALLY QCL REFERENCE SIGNAL RESOURCES FOR
TRANSMISSIONS IN COMMUNICATION EQUIPMENT HAVING MULTIPLE ANTENNA
PANELS
Abstract
Spatially Quasi Co-Located (QCL) reference signal resources are
configured in a wireless communication device having a plurality of
antenna panels. Information indicating a number of antenna panels
in the wireless communication device is obtained, and a
corresponding number of reference signal resource sets is selected
that are to be used in a reference signal resource selection
process, wherein each reference signal resource set includes
identities of one or more reference signal resources to be used by
the wireless communication device when transmitting a sounding
reference signal. The wireless communication device is informed
about which reference signal resource sets have been selected. From
each of the antenna panels, the sounding reference signal is
received on each one of a plurality of transmissions, each
performed by the antenna panel using a different one of the
reference signal resources of the reference signal resource set
selected for the antenna panel. For each reference signal resource
set, the received transmissions from the antenna panels are
assessed, and a best transmission is selected therefrom based on
predefined transmission selection criteria, and for each best
transmission a corresponding reference signal resource is selected
that was used in performance of the best transmission. Information
indicating the selected reference signal resources is sent in one
higher layer data structure. The wireless communication device used
this information to update a sounding reference signal resource set
this is to be used for subsequent transceiver operations.
Inventors: |
NILSSON; Andreas; (Goteborg,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget LM Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
61521475 |
Appl. No.: |
15/757345 |
Filed: |
February 13, 2018 |
PCT Filed: |
February 13, 2018 |
PCT NO: |
PCT/EP2018/053573 |
371 Date: |
March 2, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 7/088 20130101;
H04L 5/0051 20130101; H04B 7/0695 20130101; H04B 7/063 20130101;
H04W 80/02 20130101; H04L 25/0226 20130101; H04W 76/27
20180201 |
International
Class: |
H04B 7/08 20060101
H04B007/08; H04B 7/06 20060101 H04B007/06; H04L 25/02 20060101
H04L025/02; H04L 5/00 20060101 H04L005/00; H04W 76/27 20060101
H04W076/27; H04W 80/02 20060101 H04W080/02 |
Claims
1. A method of configuring spatially Quasi Co-Located (QCL)
reference signal resources in a wireless communication device
having a plurality of antenna panels, wherein the method is
performed by one or more communication network elements
communicating with the wireless communication device, and the
method comprises: obtaining information that directly or implicitly
indicates a number of antenna panels in the wireless communication
device; selecting, for the antenna panels, a corresponding number
of reference signal resource sets to be used in a reference signal
resource selection process, wherein each reference signal resource
set comprises identities of one or more reference signal resources
to be used by the wireless communication device when transmitting a
sounding reference signal; informing the wireless communication
device about which reference signal resource sets have been
selected for the plurality of antenna panels; receiving, from each
of the antenna panels, the sounding reference signal on each one of
a plurality of transmissions, each transmission being performed by
the antenna panel using a different one of the reference signal
resources of the reference signal resource set selected for the
antenna panel; for each one of the antenna panels, assessing the
received transmissions from said one of the antenna panels, and
selecting as a best transmission from said one of the antenna
panels, one of the assessed transmissions based on one or more
predefined transmission selection criteria, and for each best
transmission selecting a corresponding reference signal resource
that was used in performance of the best transmission; and sending
in one higher layer data structure, information indicating the
selected reference signal resources for the plurality of antenna
panels.
2. The method of claim 1, wherein the one data structure is a
Medium Access Control (MAC) Control Element (CE).
3. The method of claim 1, wherein the one data structure is a Radio
Resource Control (RRC) message.
4. The method of claim 1, wherein the one data structure is an
SRS-SpatialRelationInfo parameter of an SRS resource set.
5. A method of configuring spatially Quasi Co-Located (QCL)
reference signal resources in a wireless communication device
having a plurality of antenna panels, the method performed by the
wireless communication device and comprising: communicating to one
or more communication network elements communicating with the
wireless communication device, information that directly or
implicitly indicates a number of antenna panels in the wireless
communication device; receiving, from the one or more communication
network elements, information about which reference signal resource
sets have been selected, wherein each reference signal resource set
comprises identities of one or more reference signal resources to
be used by the wireless communication device when transmitting a
sounding reference signal; mapping a different one of the selected
resource sets to respective ones of the antenna panels; for each
one of the antenna panels, performing a plurality of transmissions
from said one of the antenna panels, each transmission including a
sounding reference signal and being transmitted using a different
one of the reference signal resources included in the reference
signal resource set that was mapped to said one of the antenna
panels; receiving in one higher layer data structure, from the one
or more communication network elements, information indicating the
selected reference signal resources for the plurality of antenna
panels; and using the received information indicating the selected
reference signal resources for the plurality of antenna panels to
update a reference signal resource set to be used when performing
codebook-based transmissions.
6. The method of claim 5, wherein the one data structure is a
Medium Access Control (MAC) Control Element (CE).
7. The method of claim 5, wherein the one data structure is a Radio
Resource Control (RRC) message.
8. The method of claim 5, wherein the one data structure is an
SRS-SpatialRelationInfo parameter of an SRS resource set.
9. The method of claim 5, comprising: performing a codebook-based
transmission using the updated reference signal resource set.
10. An apparatus for configuring spatially Quasi Co-Located (QCL)
reference signal resources in a wireless communication device
having a plurality of antenna panels, wherein the apparatus
controls one or more communication network elements communicating
with the wireless communication device, and the apparatus
comprises: circuitry configured to obtain information that directly
or implicitly indicates a number of antenna panels in the wireless
communication device; circuitry configured to select, for each of
the antenna panels, a corresponding number of reference signal
resource sets to be used in a reference signal resource selection
process, wherein each reference signal resource set comprises
identities of one or more reference signal resources to be used by
the wireless communication device when transmitting a sounding
reference signal; circuitry configured to inform the wireless
communication device about which reference signal resource sets
have been selected for the plurality of antenna panels; circuitry
configured to receive, from each of the antenna panels, the
sounding reference signal on each one of a plurality of
transmissions, each transmission being performed by the antenna
panel using a different one of the reference signal resources of
the reference signal resource set selected for the antenna panel;
circuitry configured to assess, for each one of the antenna panels,
the received transmissions from said one of the antenna panels, and
to select as a best transmission from said one of the antenna
panels, one of the assessed transmissions based on one or more
predefined transmission selection criteria, and for each best
transmission to select a corresponding reference signal resource
that was used in performance of the best transmission; and
circuitry configured to send in one higher layer data structure,
information indicating the selected reference signal resources for
each of the antenna panels.
11. The apparatus of claim 10, wherein the one data structure is a
Medium Access Control (MAC) Control Element (CE).
12. The apparatus of claim 10, wherein the one data structure is a
Radio Resource Control (RRC) message.
13. The apparatus of claim 10, wherein the one data structure is a
SpatialRelationInfo parameter of an SRS resource set.
14. An apparatus for configuring spatially Quasi Co-Located (QCL)
reference signal resources in a wireless communication device
having a plurality of antenna panels, the apparatus comprising:
circuitry configured to communicate to one or more communication
network elements, information that directly or implicitly indicates
a number of antenna panels in the wireless communication device;
circuitry configured to receive, from the one or more communication
network elements, information about which reference signal resource
sets have been selected, wherein each reference signal resource set
comprises identities of one or more reference signal resources to
be used by the wireless communication device when transmitting a
sounding reference signal; circuitry configured to map a different
one of the selected resource sets to respective ones of the antenna
panels; circuitry configured to perform, for each one of the
antenna panels, a plurality of transmissions from said one of the
antenna panels, each transmission including a sounding reference
signal and being transmitted using a different one of the reference
signal resources included in the reference signal resource set that
was mapped to said one of the antenna panels; circuitry configured
to receive in one higher layer data structure, from the one or more
communication network elements, information indicating the selected
reference signal resources for the plurality of antenna panels; and
circuitry configured to use the received information indicating the
selected reference signal resources for the plurality of antenna
panels to update a reference signal resource set to be used when
performing codebook-based transmissions.
15. The apparatus of claim 14, wherein the one data structure is a
Medium Access Control (MAC) Control Element (CE).
16. The apparatus of claim 14, wherein the one data structure is a
Radio Resource Control (RRC) message.
17. The apparatus of claim 14, wherein the one data structure is a
SpatialRelationInfo parameter of an SRS resource set.
18. The apparatus of claim 14, comprising: circuitry configured to
perform a codebook-based transmission using the updated reference
signal resource set.
19. A non-transitory computer readable medium comprising
instructions that, when performed by one or more processors of one
or more communication network elements, cause the one or more
processors to perform a method of configuring spatially Quasi
Co-Located (QCL) reference signal resources in a wireless
communication device having a plurality of antenna panels, wherein
the method is performed by the one or more communication network
elements communicating with the wireless communication device, and
the method comprises: obtaining information that directly or
implicitly indicates a number of antenna panels in the wireless
communication device; selecting, for the antenna panels, a
corresponding number of reference signal resource sets to be used
in a reference signal resource selection process, wherein each
reference signal resource set comprises identities of one or more
reference signal resources to be used by the wireless communication
device when transmitting a sounding reference signal; informing the
wireless communication device about which reference signal resource
sets have been selected for the plurality of antenna panels;
receiving, from each of the antenna panels, the sounding reference
signal on each one of a plurality of transmissions, each
transmission being performed by the antenna panel using a different
one of the reference signal resources of the reference signal
resource set selected for the antenna panel; for each one of the
antenna panels, assessing the received transmissions from said one
of the antenna panels, and selecting as a best transmission from
said one of the antenna panels, one of the assessed transmissions
based on one or more predefined transmission selection criteria,
and for each best transmission selecting a corresponding reference
signal resource that was used in performance of the best
transmission; and sending in one higher layer data structure,
information indicating the selected reference signal resources for
the plurality of antenna panels.
20. A non-transitory computer readable medium comprising
instructions that, when performed by one or more processors of a
wireless communication device having a plurality of antenna panels,
cause the one or more processors to perform a method of configuring
spatially Quasi Co-Located (QCL) reference signal resources in the
wireless communication device, the method comprising: communicating
to one or more communication network elements communicating with
the wireless communication device, information that directly or
implicitly indicates a number of antenna panels in the wireless
communication device; receiving, from the one or more communication
network elements, information about which reference signal resource
sets have been selected, wherein each reference signal resource set
comprises identities of one or more reference signal resources to
be used by the wireless communication device when transmitting a
sounding reference signal; mapping a different one of the selected
resource sets to respective ones of the antenna panels; for each
one of the antenna panels, performing a plurality of transmissions
from said one of the antenna panels, each transmission including a
sounding reference signal and being transmitted using a different
one of the reference signal resources included in the reference
signal resource set that was mapped to said one of the antenna
panels; receiving in one higher layer data structure, from the one
or more communication network elements, information indicating the
selected reference signal resources for the plurality of antenna
panels; and using the received information indicating the selected
reference signal resources for the plurality of antenna panels to
update a reference signal resource set to be used when performing
codebook-based transmissions.
Description
BACKGROUND
[0001] The present invention relates to mobile communications
system equipment having multiple antenna panels that are used for
Multiple Input Multiple Output (MIMO) transmissions, and more
particularly to technology for configuring spatially Quasi
Co-Located (QCL) reference signal resources for use by the mobile
communications system equipment when performing transmissions, such
as codebook based MIMO transmissions.
[0002] The standardized organization of communications networks, as
well as the designs of individual network elements and other
equipment that form and/or interact with the network, continue to
evolve in response to ever increasing demands for higher
performance and capacity in mobile communications systems. One
aspect of this evolution involves the use of the electromagnetic
spectrum in bands located at higher frequencies than have been used
in earlier generation equipment. This use means, in turn, that
narrow beam transmission and reception schemes will be needed at
higher frequencies to compensate for the high propagation loss
between the User Equipment (UE) and the networks'
Transmission/Reception Point (TRP). As used in this specification,
the term UE can refer to any wireless communication device that is
directly operated by an end user such as, but not limited to, the
following examples: cellular or other wireless telephones, personal
digital assistants, tablets and other personal computing devices
equipped with wireless communication equipment, machine type
communication devices, and the like. Further, as used throughout
this specification, the term TRP can refer to any radio
communication equipment such as, but not limited to, the following
examples: Base Transceiver Stations (BTS), Base Station Controllers
(BSC), relay nodes (RN), Remote Radio Heads (RRH), NodeB, eNodeB,
gNodeB (gNB), and the like, such being defined by the various
communications standards promulgated by standardization bodies
(e.g., Third Generation Partnership Project--3GPP), such as Global
System for Mobile Communication (GSM), Universal Mobile
Telecommunications Service (UMTS), Long Term Evolution (LTE), and
most recently, New Radio (NR). Such network equipment may be
referred to herein as "nodes". Historically, such nodes have been
implemented as processing equipment configured in one location.
More recently, the functionality of a single node may in some, but
not necessarily all, instances be distributed among a plurality of
processing elements that are distributed within the communications
network, and which interact with one another in a seamless way such
that any device interacting with such a virtual node has no way of
knowing whether the functionality is being provided by a single
processing equipment (herein also referred to as "element") or by a
plurality of communication network elements. To facilitate the
discussion, this description will refer to communications between a
UE and a network node. However, it will be understood that the term
"network node" refers to any type of TRP that is capable of
carrying out the described functionality, regardless of
implementation (e.g., the term "network node" can refer to one or
more communication network elements cooperating within the network
to accomplish functions attributed to the "node").
[0003] For a given communication link, beams can be applied at the
network node and also at the UE (one transmitting, the other
receiving), which will herein be referred to as a beam pair link
(BPL). A beam management procedure is performed, whose task is to
establish and maintain beam pair links To illustrate this point,
FIG. 1 depicts a network node 101, a UE 103, and a BPL 105 that
connects them. In order to establish the BPL 105, the network node
may have tried any of the candidate beams 107, before settling on a
best one for use in the BPL 105. The network thereafter maintains
the BPL 105 for further communication between the UE 103 and
network node 101. Both the transmit and receive beams of the BPL
105 are established and monitored by the network using measurements
on downlink reference signals used for beam management. For
example, it has been agreed by the 3GPP in its standardization of
NR, that Channel State Information-Reference Signals (CSI-RS) will
be the beam reference signals. The CSI-RS for beam management can
be transmitted periodically, semi-persistently or aperiodically
(event triggered), and they can be either shared between multiple
UEs or be UE-specific. In order to find a suitable network node
beam, the network node transmits CSI-RS in different network node
transmission (TX) beams on which the UE performs Reference Signal
Received Power (RSRP) measurements, and reports back some number
(N) of the best node TX beams (where N can be configured by the
network). Furthermore, the CSI-RS transmission on a given node beam
can be repeated to allow the UE to evaluate suitable UE beams
(i.e., UE reception--RX--beam training).
[0004] There are primarily three different implementations of
beamforming, both at the network node and at the UE: analog
beamforming, digital beamforming and hybrid beamforming. Each
implementation has its pros and cons. Digital beamforming is the
most flexible solution but also the costliest due to the large
number of required radios and baseband chains. Analog beamforming
is the least flexible but the cheapest to manufacture due to
reduced number of required radio and baseband chains. Hybrid
beamforming is a compromise between the analog and digital
beamforming implementations.
[0005] One type of beamforming antenna architecture that has been
agreed to study in 3GPP for the NR access technology involves the
use of antenna panels, both at the network node side and at the UE.
A panel is an antenna array of single- or dual-polarized elements
with typically one transmit/receive unit (TXRU) per polarization.
An analog distribution network with phase shifters is used to steer
the beam of each panel. FIGS. 2A and 2B illustrate two examples of
dual-polarized panels, with FIG. 2A illustrating a two-dimensional
panel 201, and FIG. 2B illustrating a one-dimensional panel. The
two-dimensional panel 201 has a pair of connection points 205 for
connection to one TXRU (not illustrated), one connection point per
polarization. The one-dimensional panel 203 is similarly configured
with a pair of connection points 207.
Uplink Beam Management
[0006] Some UEs might have analog beamformers without beam
correspondence, which means that Downlink/Uplink (DL/UL)
reciprocity cannot be used to determine the beams for these
beamformers. For such UEs, the UE beam used for UL cannot be
derived from beam management procedures based on DL reference
signals as described above. To handle such UEs, UL beam management
has been included in the NR standard specification for release 19.
The main difference between normal beam management and UL beam
management is that UL beam management utilizes uplink reference
signals instead of DL references signals. The UL reference signals
that have been agreed to be used for UL beam management are
Sounding Reference Signals (SRS). Two UL beam management
procedures, called U2 and U3, have been discussed during the
standardization of NR. These are schematically illustrated in FIGS.
3A and 3B, respectively. Looking first at FIG. 3A, the U2 procedure
is performed by transmitting a burst of SRS resources in one UE TX
beam 301 and letting the network node 303 evaluate different TRP RX
beams 305. And as illustrated in FIG. 3B, the U3 procedure lets the
network node 303 select a suitable ("best") UE TX beam by having
the UE 307 transmit different SRS resources in different UE TX
beams 309, and then assessing the received transmissions based on
one or more predefined transmission selection criteria (e.g.,
comparing the different beams using any of the measurements of
received signal quality that are known in the art).
[0007] It will be understood that, as used herein, the term "SRS
resource" refers to a configuration of a number of parameters that
control how one or more SRSs are transmitted, and is exemplified by
SRS resources as defined and discussed in, for example, Section
6.2.1 "UE sounding procedure" of the specification, 3GPP TS 38.214
V15.0.0 (2017-12), "3rd Generation Partnership Project; Technical
Specification Group Radio Access Network; NR; Physical layer
procedures for data (Release 15)", December 2017.
Codebook Based UL Transmission
[0008] In addition to their use for UL beam management as described
above, SRS resources are also used to help normal UL transmissions,
for example when performing a so-called Codebook-based UL
transmission, which has been standardized in NR. Codebook based UL
transmission relies on a multi-antenna configuration to support
uplink MIMO communications with up to 4 layer spatial multiplexing
using up to 4 antenna ports with channel dependent precoding. The
spatial multiplexing mode aims for high data rates in favorable
channel conditions.
[0009] FIG. 4 is an exemplary embodiment of an arrangement 400 for
performing precoded spatial multiplexing when Cyclic
Prefix-Orthogonal Frequency Division Multiplexing (CP-OFDM) is used
on the uplink As seen in the figure, information to be transmitted
partitioned into a number, r, separate Layers, where the number r
is called the "transmission rank." Each Layer 401-x supplies one
symbol to a respective one of r inputs of the precoder matrix W,
forming an information-carrying symbol vector, s. The symbol vector
s is multiplied by an N.sub.T.times.r precoder matrix W, which
serves to distribute the transmit energy in a subspace of the
N.sub.T-dimensional vector space (corresponding to N.sub.T antenna
ports). The precoder matrix W is typically selected from a codebook
of possible precoder matrices, with selection typically being
indicated by means of a transmit precoder matrix indicator (TPMI),
which specifies a unique precoder matrix in the codebook for a
given number of symbol streams The N.sub.T weighted symbols
supplied at the output of the precoder matrix W are supplied to
respective ones of N.sub.T Inverse Fast Fourier Transform (IFFT)
processors 403-x. The outputs of the IFFT processors 403-x are
supplied to respective ones of N.sub.T antenna ports. In this way,
spatial multiplexing is achieved since multiple symbols can be
transmitted simultaneously over the same time/frequency resource
element (TFRE). The number of symbols r is typically adapted to
suit the current channel properties.
[0010] The received N.sub.R.times.1 vector y.sub.n for a certain
TFRE on subcarrier n (or alternatively data TFRE number n) (where
N.sub.R is the number of receiver antennas) is thus modeled by
y.sub.n=H.sub.nWs.sub.n+e.sub.n Equation 1
where e.sub.n is a noise/interference vector obtained as
realizations of a random process. The precoder W can be a wideband
precoder, which is constant over frequency, or frequency
selective.
[0011] The precoder matrix W is often chosen to match the
characteristics of the N.sub.R.times.N.sub.T MIMO channel matrix
H.sub.n, resulting in so-called channel dependent precoding. This
is also commonly referred to as closed-loop precoding and
essentially strives for focusing the transmit energy into a
subspace which is strong in the sense of conveying much of the
transmitted energy to the UE. In addition, the precoder matrix may
also be selected to strive for orthogonalizing the channel, meaning
that after proper linear equalization at the UE, the inter-layer
interference is reduced.
[0012] One example method for a UE to select a precoder matrix W
can be to select the W.sub.k that maximizes the Frobenius norm of
the hypothesized equivalent channel:
max k H ^ n W k F 2 Equation 2 ##EQU00001##
Where
[0013] H.sub.n is a channel estimate, possibly derived from CSI-RS.
[0014] W.sub.k is a hypothesized precoder matrix with index k.
[0015] H.sub.nW.sub.k is the hypothesized equivalent channel.
[0016] In closed-loop precoding for the NR uplink, the network node
decides, based on channel measurements in the reverse link
(uplink), what TPMI the UE should use on its uplink antennas, and
transmits this TPMI to the UE. The gNodeB configures the UE to
transmit the SRS according to the number of UE antennas it would
like the UE to use for uplink transmission, in order to enable the
channel measurements. A single precoder that is supposed to cover a
large bandwidth (wideband precoding) may be signaled. It may also
be beneficial to match the frequency variations of the channel and
instead feed back a frequency-selective precoding report, for
example, several precoders and/or several TPMIs, one per
subband.
[0017] Information other than the TPMI is generally used to
determine the UL MIMO transmission state, such as SRS resource
indicators (SRIs) as well as transmission rank indicators (TRIs).
These parameters, as well as the modulation and coding scheme
(MCS), and the uplink resources where the Physical Uplink Shared
Channel (PUSCH) is to be transmitted, are also determined by
channel measurements derived from SRS transmissions from the UE.
The transmission rank, and thus the number of spatially multiplexed
layers, is reflected in the number of columns of the precoder
matrix, W. For efficient performance, it is important that a
transmission rank that matches the channel properties be
selected.
SRS Resource Set
[0018] The network node needs to signal to the UE various
parameters that control how the SRS transmission should be done.
Such parameters include, for example, which SRS resource to use,
the number of ports per SRS resource, and the like. This is solved
in NR by defining a number of SRS resource sets using higher layer
signaling (e.g., Radio Resource Control--RRC)--and/or Medium Access
Control-Control Element--MAC-CE), where each SRS resource set
contains a list of different SRS resources. For NR release 15, each
UE can be configured to have a number of different SRS resource
sets, including: [0019] one SRS resource set for codebook based UL
transmission, and [0020] multiple SRS resource sets for UL beam
management.
[0021] The different SRS resources within an SRS resource set can
have different time domain behavior. For example in a SRS resource
set consisting of four SRS resources, two SRS resources can be
configured with periodic time domain behavior, while the other two
can be configured with aperiodic time domain behavior. The periodic
SRS resources in an SRS resource set are triggered by using RRC
signaling, the SRS resources with semi-persistent time domain
behavior are triggered by using Medium Access Control/Control
Element (MAC/CE) signaling, and the aperiodic SRS resources are
triggered by using DCI signaling.
[0022] In case the UE is equipped with one or more analog
beamformers, the SRS resource sets can be configured with a spatial
QCL relation to indicate to the UE which analog UE beam (i.e., BPL)
to use during the SRS transmission. The spatial QCL relation is
configured using the higher layer parameter SRS-SpatialRelationInfo
which can be defined for each SRS resource set. (Multi-layer
communications protocols such as The Open Systems Interconnection
model--OSI model--are well-known, and as used herein, the term
"higher layer" means any layer higher than Layer 1, the Physical
Layer.) The SRS-SpatialRelationInfo can point to a DL reference
signal such as SSB/PBCH or CSI-RS (in case of beam correspondence)
or to UL reference signals such as SRS (in case of no beam
correspondence). So, for example, a UE without beam correspondence
can first perform a U3 procedure by transmitting different SRS
resources in different UE TX beams The network node measures RSRP
of the different SRS resources and determines which SRS resource
gives the highest RSRP. The network node can then use higher layer
signaling to update the SRS-SpatialRelationInfo (for a given SRS
resource set) with the best SRS resource. After this update, the
next time the UE is triggered for SRS transmission for that SRS
resource set, the UE will know which analog UE TX beam to apply
when transmitting the SRS resources.
[0023] One example for periodic SRS transmissions, is published in
the earlier-mentioned specification, 3GPP TS 38.214 V15.0.0
(2017-12), "3rd Generation Partnership Project; Technical
Specification Group Radio Access Network; NR; Physical layer
procedures for data (Release 15)", December 2017: [0024] For a UE
configured with one or more SRS resource configuration(s), and when
the higher layer parameter SRS-ResourceConfigType is set to
`periodic`: p2 if the UE is configured with the higher layer
parameter SRS-SpatialRelationInfo set to `SSB/PBCH`, the UE shall
transmit the SRS resource with the same spatial domain transmission
filter used for the reception of the SSB/PBCH, if the higher layer
parameter SRS-SpatialRelationInfo is set to `CSI-RS`, the UE shall
transmit the SRS resource with the same spatial domain transmission
filter used for the reception of the periodic CSI-RS or of the
semi-persistent CSI-RS, if the higher layer parameter
SRS-SpatialRelationInfo is set to `SRS`, the UE shall transmit the
SRS resource with the same spatial domain transmission filter used
for the transmission of the periodic SRS.
UL Beam Management for Multi-panel UEs
[0025] It is expected that the UE will use two or more antenna
panels, preferably pointing in different directions, in order to
improve the coverage and increase the order of spatial
multiplexing. FIG. 5 illustrates a non-limiting example of a UE 501
having two one-dimensional antenna panels 503, 505 located in
different directions. In order to handle UL beam management for
such UEs in an efficient manner (to minimize overhead), it has been
agreed in the NR standard that the network node can trigger the UE
501 to transmit one SRS resource set per UE antenna panel, where
each SRS resource set consists of a number of SRS resources
(corresponding to the number of candidate beams per UE antenna
panel 503, 505). When so triggered, the UE 501 transmits one SRS
resource per beam per panel while the network node performs RSRP
measurements on the SRS resources. The network node assesses these
measurements and determines the best SRS resource per SRS resource
set and in that way the network node can determine the best UE TX
beam per panel.
[0026] The inventor of the embodiments described herein has
recognized that the existing technology suffers from one or more
problems. For example, conventional technology enables a network
node to use higher layer signaling to cause a UE to configure the
SRS-SpatialRelationInfo parameter for only a single antenna panel.
As a result, a UE having more than one antenna panel but lacking
beam correspondence (i.e., having no ability to use DL/UL
reciprocity to derive a suitable beam for UL transmissions based on
DL reference signals) would still not be able to benefit by the
improved performance that would otherwise be achievable if it could
know which beam to use for more than one of its antenna panels.
[0027] Hence, there is a need for technology that addresses the
above and/or related issues.
SUMMARY
[0028] It should be emphasized that the terms "comprises" and
"comprising", when used in this specification, are taken to specify
the presence of stated features, integers, steps or components; but
the use of these terms does not preclude the presence or addition
of one or more other features, integers, steps, components or
groups thereof.
[0029] Moreover, reference letters may be provided in some
instances (e.g., in the claims and summary) to facilitate
identification of various steps and/or elements. However, the use
of reference letters is not intended to impute or suggest that the
so-referenced steps and/or elements are to be performed or operated
in any particular order.
[0030] In accordance with one aspect of the present invention, the
foregoing and other objects are achieved in technology (e.g.,
methods, apparatuses, nontransitory computer readable storage
media, program means) that configures spatially Quasi Co-Located
(QCL) reference signal resources in a wireless communication device
having a plurality of antenna panels. Some but not all embodiments
encompass aspects performed by one or more communication network
elements communicating with the wireless communication device. The
one or more communication network elements can collectively be the
equivalent of a network node. Such embodiments comprise obtaining
information that directly or implicitly indicates a number of
antenna panels in the wireless communication device, and selecting,
for the antenna panels, a corresponding number of reference signal
resource sets to be used in a reference signal resource selection
process, wherein each reference signal resource set comprises
identities of one or more reference signal resources to be used by
the wireless communication device when transmitting a sounding
reference signal. The one or more network elements then inform the
wireless communication device about which reference signal resource
sets have been selected for the plurality of antenna panels. The
one or more network elements receive, from each of the antenna
panels, the sounding reference signal on each one of a plurality of
transmissions, each transmission being performed by the antenna
panel using a different one of the reference signal resources of
the reference signal resource set selected for the antenna panel.
For each one of the antenna panels, the received transmissions from
said one of the antenna panels are assessed, and a best
transmission is selected from said one of the antenna panels, one
of the assessed transmissions, with selection being based on one or
more predefined transmission selection criteria. For each best
transmission a corresponding reference signal resource is selected
that was used in performance of the best transmission. Then,
information indicating the selected reference signal resources for
the plurality of antenna panels is sent in one higher layer data
structure to the wireless communication device.
[0031] Some but not all other embodiments encompass aspects
performed by the wireless communication device, communicating with
the one or more communication network elements. Such embodiments
comprise the wireless communication device communicating to the one
or more communication network elements, information indicating a
number of antenna panels in the wireless communication device.
Subsequently, the wireless communication device receives, from the
one or more communication network elements, information about which
reference signal resource sets have been selected, wherein each
reference signal resource set comprises identities of one or more
reference signal resources to be used by the wireless communication
device when transmitting a sounding reference signal.
[0032] The wireless communication system maps a different one of
the selected resource sets to respective ones of the antenna
panels. Then, for each one of the antenna panels, the wireless
communication device performs a plurality of transmissions from
said one of the antenna panels, each transmission including a
sounding reference signal and being transmitted using a different
one of the reference signal resources included in the reference
signal resource set that was mapped to said one of the antenna
panels. After those transmissions, the wireless communication
device receives, in one higher layer data structure, from the one
or more communication network elements, information indicating the
selected reference signal resources for the plurality of antenna
panels. The wireless communication device then uses the received
information indicating the selected reference signal resources for
the plurality of antenna panels to update a reference signal
resource set to be used when performing a subsequent transceiver
operation, such as codebook-based UL transmissions or channel
sounding for DL reciprocity.
[0033] In some but not necessarily all embodiments, the wireless
communication device also performs a codebook-based transmission
using the updated reference signal resource set.
[0034] In other aspects, any of the above mentioned embodiments may
be further characterized by the one data structure being a Medium
Access Control (MAC) Control Element (CE).
[0035] Alternatively, any of the above mentioned embodiments may be
further characterized by the one data structure being a Radio
Resource Control (RRC) message.
[0036] And in yet another alternative, any of the above mentioned
embodiments may be further characterized by the one data structure
being an SRS-SpatialRelationInfo parameter of an SRS resource
set.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The objects and advantages of the invention will be
understood by reading the following detailed description in
conjunction with the drawings in which:
[0038] FIG. 1 depicts a network node, a UE, and a BPL that connects
them.
[0039] FIGS. 2A and 2B illustrate two examples of dual-polarized
panels, with FIG. 2A illustrating a two-dimensional panel, and FIG.
2B illustrating a one-dimensional panel.
[0040] FIGS. 3A and 3B schematically illustrate two UL beam
management procedures, respectively called U2 and U3, that have
been discussed during the standardization of NR.
[0041] FIG. 4 is an exemplary embodiment of an arrangement for
performing precoded spatial multiplexing when CP-OFDM is used on
the uplink
[0042] FIG. 5 illustrates a non-limiting example of a UE having two
one-dimensional antenna panels located in different directions.
[0043] FIG. 6A depicts a UE having two dual-polarized antenna
panels with two candidate beams per panel.
[0044] FIG. 6B illustrates an exemplary configuration of three
different SRS resource sets, two used by a UE for beam management,
and a third SRS resource set being used for codebook based UL
transmissions.
[0045] FIGS. 6C and 6D together are a signaling/flowchart of
interactions between the UE and a network node for performing UL
beam management, and codebook based UL transmission.
[0046] FIG. 7 depicts, in one respect, a flow chart of
steps/processes performed by a network node in accordance with some
but not necessarily all exemplary embodiments consistent with the
invention. In another respect, FIG. 7 depicts an arrangement of
various circuitry configured to perform the actions as set out in
the figure.
[0047] FIG. 8 depicts, in one respect, a flow chart of
steps/processes performed by a UE having a plurality of antenna
panels, and operating in a communication system having network
nodes. In another respect, FIG. 8 depicts an arrangement of various
circuitry configured to perform the actions as set out in the
figure.
[0048] FIG. 9 illustrates an exemplary controller of a network node
(single entity or distributed across multiple communication network
elements), in accordance with some but not necessarily all
exemplary embodiments consistent with the invention.
[0049] FIG. 10 illustrates an exemplary controller of a UE in
accordance with some but not necessarily all exemplary embodiments
consistent with the invention.
DETAILED DESCRIPTION
[0050] The various features of the invention will now be described
with reference to the figures, in which like parts are identified
with the same reference characters.
[0051] The various aspects of the invention will now be described
in greater detail in connection with a number of exemplary
embodiments. To facilitate an understanding of the invention, many
aspects of the invention are described in terms of sequences of
actions to be performed by elements of a computer system or other
hardware capable of executing programmed instructions. It will be
recognized that in each of the embodiments, the various actions
could be performed by specialized circuits (e.g., analog and/or
discrete logic gates interconnected to perform a specialized
function), by one or more processors programmed with a suitable set
of instructions, or by a combination of both. The term "circuitry
configured to" perform one or more described actions is used herein
to refer to any such embodiment (i.e., one or more specialized
circuits alone, one or more programmed processors, or any
combination of these). Moreover, the invention can additionally be
considered to be embodied entirely within any form of nontransitory
computer readable carrier, such as solid-state memory, magnetic
disk, or optical disk containing an appropriate set of computer
instructions that would cause a processor to carry out the
techniques described herein. Thus, the various aspects of the
invention may be embodied in many different forms, and all such
forms are contemplated to be within the scope of the invention. For
each of the various aspects of the invention, any such form of
embodiments as described above may be referred to herein as "logic
configured to" perform a described action, or alternatively as
"logic that" performs a described action.
[0052] The inventor of the embodiments described herein has
recognized that existing technology suffers from one or more
problems due to its inability to configure a suitable beam for more
than one antenna panel. As a consequence, even if a UE has multiple
antenna panels, it will receive information about which beam to use
for only one of them, and this leaves functions such as codebook
based UL transmission without the ability to benefit by the use of
multiple antenna panels if there is no beam correspondence that
would otherwise enable the UE to derive a suitable beam for UL
transmissions based on DL reference signals.
[0053] In one aspect, the technology described herein provides a
mechanism whereby a UE can configure beams for more than one of its
antenna panels based on information provided by the network, even
when there is no beam correspondence.
[0054] In another aspect, an SRS Resource Set is configured to
include information indicating which SRS Resource or SRS resources
to use for each antenna panel in a UE having more than one antenna
panel. In some but not all embodiments, SRS-SpatialRelationInfo
parameter in an SRS resource set is configured to identify more
than one SRS resource.
[0055] These and other aspects will now be described further in the
following, in conjunction with the figures.
[0056] Aspects of embodiments consistent with the invention will
now be described with reference to FIGS. 6A, 6B, 6C, and 6D. For
the sake of example, and without limitation, it will be assumed
that a UE is configured like the UE 601 depicted in FIG. 6A, having
two dual-polarized antenna panels 603, 605 with two candidate beams
607-A, 607-B, 609-A, 609-B per panel. The UE 601 also includes a
transceiver 611, a controller 613, and a plurality of SRS Resource
Sets 615. The UE 601 also includes other components, as are known
in the art, but these are not depicted. As illustrated in FIG. 6B,
and for the sake of this example, it is assumed that the network
node has configured the UE 601 with three different SRS resource
sets 615, two used for beam management (a first SRS resource set
617, and a second SRS resource set 619) and a third SRS resource
set 621 for codebook based UL transmissions.
[0057] FIGS. 6C and 6D together are a signaling/flowchart of
interactions between the UE 601 and a network node 625 for
performing UL beam management, and codebook based UL transmission.
The illustrated functions start with the network node 625
triggering 651 the UE 601 with aperiodic SRS transmission by
signaling, by means of Downlink Control Information (DCI) a pointer
to the two SRS resource sets 617, 619 configured for beam
management (SRS set 1 and 2 ). The UE 601 then transmits 653 one
SRS per panel, with plural transmissions from the first panel 603
being according to the SRS resources specified by the first SRS
resource set 617, and transmissions from the second panel 605 being
according to the SRS resources specified by the second SRS resource
set 619. Both SRS resource sets in this example consist of two SRS
resources, one per beam per panel. As can be seen, each antenna
panel 603, 605 consists of two ports (one per polarization), hence
each SRS resource consists of two ports. In other examples in which
the antenna panels have only one port (e.g., if they comprise only
single polarized elements), the SRS resources will correspondingly
have one SRS port.
[0058] The network node 625 then measures and assesses the RSRP on
the different SRS resources and determines a preferred SRS resource
per SRS resource set (step 655), which in this example is assumed
to be SRS resource 1 for the first SRS set 617 and SRS resource 3
for the second SRS resource set 619. The network node 625 then
updates 657 the SRS-SpatialRelationInfo parameter for the third SRS
resource set 621 by means of higher layer signaling (e.g.,
signaling in RRC or MAC/CE) to the UE 601 about the updates. The UE
601 then updates 659 the SRS-SpatialRelationInfo located in the
third SRS resource set 621 to indicate the selected resources, SRS
resource 1 and SRS resource 3.
[0059] Next, the network node 625 triggers an aperiodic SRS
transmission of the third SRS resource set 621 (step 661) in order
to initiate codebook based UL transmission. In response, the UE 601
transmits 663 SRS resources indicated by the third SRS resource set
621 using the analog beams indicated in the SRS-SpatialRelationInfo
parameter of the third SRS resource set 621.
[0060] The network node 625 then selects a TPMI and MCS to apply
for the PUSCH transmission and signals 665 this back to the UE 601.
When the UE 601 transmits 667 the PUSCH using the TPMI signaled
from the network node 625, the UE 601 will use the same analog UE
beam as was used for transmitting SRS resource set 3, since the
port number is the same for the SRS and DMRS used for the PUSCH
transmission.
[0061] Further aspects of embodiments consistent with the invention
will now be described with reference to FIG. 7, which depicts, in
one respect, a flow chart of steps/processes performed by a network
node 625 in accordance with some but not necessarily all exemplary
embodiments consistent with the invention. In another respect, FIG.
7 also depicts an arrangement 700 of various circuitry configured
to perform the actions as set out in the figure, and as further
described herein, such circuitry being comprised in a network node
(e.g., one or more communications network elements, such as
processors).
[0062] The aim of the depicted process is to configure spatially
QCL reference signal resources in a UE 601 having more than one
antenna panel. The exemplary embodiment begins with the network
node 625 obtaining information that directly or implicitly
indicates a number of antenna panels in the UE 601 (i.e., how many
antenna panels the UE 601 has) (step 701). The network node 625
then selects (step 703) from the groups of SRS resource sets 615, a
number of SRS resource sets in correspondence with the number of
antenna panels in the wireless communication device, wherein each
reference signal resource set comprises identities of one or more
reference signal resources to be used by the wireless communication
device when transmitting a sounding reference signal from one of
its antenna panels (503, 505, 603, 605). The reference signal
resources sets were illustrated earlier as the first SRS resource
set 617, the second SRS resource set 619, and the third SRS
resource set 621. Making selections for each of the antenna panels
can be performed in any number of ways, the particular way not
being an essential aspect of the technology.
[0063] The network node 625 informs the UE 601 about which
reference signal resource sets have been selected (step 705), and
consequently then expects that the selected SRS resource sets will
be assigned by the UE 601 to different antenna panels (503, 505,
603, 605) and used in a reference signal resource selection
process. The network node 625 accordingly receives, from each of
the antenna panels, the sounding reference signal on each one of a
plurality of transmissions (step 707), each transmission being
performed by the antenna panel using a different one of the
reference signal resources of the reference signal resource set
selected for the antenna panel. Then, for each one of the selected
SRS resource sets 617, 619, the network node 625 assesses the
received transmissions from the antenna panel, and selects as a
best transmission from that antenna panel, one of the assessed
transmissions based on one or more predefined transmission
selection criteria (e.g., best RSRP), and for each best
transmission selects a corresponding reference signal resource that
was used in performance of the best transmission (step 709).
[0064] The network node then uses higher layer signaling (e.g., RRC
or MAC/CE) to send in one higher layer data structure, information
indicating the selected reference signal resources for each of the
SRS resource sets (step 711). The intention of this signaling is to
cause the UE 601 to update the SRS-SpatialRelationInfo parameter
(or equivalent in other embodiments) to include a selected SRS
resource, one for each of its antenna panels.
[0065] Further aspects of embodiments consistent with the invention
will now be described with reference to FIG. 8, which depicts, in
one respect, a flow chart of steps/processes performed by a UE 601
having a plurality of antenna panels, and operating in a
communication system having network nodes. In another respect, FIG.
8 also depicts an arrangement 800 of various circuitry configured
to perform the actions as set out in the figure, and as further
described herein, such circuitry being comprised in a network node
(e.g., one or more communications network elements, such as
processors).
[0066] The aim of the depicted process is to configure spatially
QCL reference signal resources in the UE 601 having more than one
antenna panel. The exemplary embodiment begins with the UE 601
communicating, to one or more communication network elements
(hereinafter, "network node" in order to ease the discussion),
information indicating a number of antenna panels in the UE 601
(i.e., information directly or indirectly--e.g. by specifying a
particular number of SRS resource sets to be selected--telling the
network node how many antenna panels the UE 601 has) (step
801).
[0067] The UE 601 then receives, from the network node, information
about which reference signal resource sets have been selected (step
803), wherein each reference signal resource set comprises
identities of one or more reference signal resources to be used by
the wireless communication device when transmitting a sounding
reference signal. In this exemplary embodiment, the network node
625 does not inform the UE about which SRS resource set goes with
which antenna panel; that allocation is entirely up to the UE 601.
Consequently, the UE 601 maps a different one of the selected
resource sets to respective ones of the antenna panels (step 805),
and for each one of the antenna panels, performs a plurality of
transmissions from the antenna panel (step 807), each transmission
including a sounding reference signal and being transmitted using a
different one of the reference signal resources included in the
reference signal resource set that was mapped to that antenna
panel. The UE 601 can adopt any strategy for performing the
mapping, including arbitrary pairing of antenna panels with
reference signal resource sets.
[0068] Following these transmissions, the UE 601 receives via
higher layer signaling from the network node, a higher layer data
structure containing information indicating the selected reference
signal resources to be allocated to the antenna panels (step 809).
The UE 601 then uses the received information indicating the
selected reference signal resources to update a reference signal
resource set to be used when performing codebook-based
transmissions (step 811). The update can be, for example, updating
the SRS-SpatialRelationInfo parameter to include an SRS resource
for each of the antenna panels. In one embodiment, the UE 601
assigns each selected SRS resource to a respective one of the
antenna panels based on its knowledge of the mapping that it
applied earlier. In alternative embodiments, the network node could
itself directly or indirectly indicate which SRS resource is to be
assigned to which antenna panel.
[0069] At this point, the UE 601 is now configured, and sometime
later can (e.g., when triggered by the network node) perform a
transmission (e.g., a codebook-based transmission, or channel
sounding for DL reciprocity) using the updated reference signal
resource set (step 813). In this way, each antenna panel transmits
a beam that is best suited for transmission to the network
node.
[0070] Other aspects of an exemplary station network node are shown
in FIG. 9, which illustrates an exemplary controller 901 of a
network node (single entity or distributed), in accordance with
some but not necessarily all exemplary embodiments consistent with
the invention. In particular, the controller includes circuitry
configured to carry out any one or any combination of the various
functions described above with respect to the network node 625.
Such circuitry could, for example, be entirely hard-wired circuitry
(e.g., one or more Application Specific Integrated
Circuits--"ASICs"). Depicted in the exemplary embodiment of FIG. 9,
however, is programmable circuitry, comprising a processor 903
coupled to one or more memory devices 905 (e.g., Random Access
Memory, Magnetic Disc Drives, Optical Disk Drives, Read Only
Memory, etc.) and to an interface 907 that enables bidirectional
communication with other elements/components of the network node.
The memory device(s) 905 store program means 909 (e.g., a set of
processor instructions) configured to cause the processor 903 to
control other network node elements so as to carry out any of the
aspects described above, such as but not limited to those described
with reference to FIGS. 6B, 6C, 6D, and 7. The memory device(s) 905
may also store data (not shown) representing various constant and
variable parameters as may be needed by the processor 903 and/or as
may be generated when carrying out its functions such as those
specified by the program means 909.
[0071] Other aspects of an exemplary UE (wireless communication
device) are shown in FIG. 10, which illustrates an exemplary
controller 1001 of a UE, in accordance with some but not
necessarily all exemplary embodiments consistent with the
invention. The exemplary controller 1001 could be, for example, a
controller 507 as shown in FIG. 5, and/or the controller 613 as
shown in FIG. 6A. In particular, the controller 1001 includes
circuitry configured to carry out any one or any combination of the
various functions described above with respect to the UE 601. Such
circuitry could, for example, be entirely hard-wired circuitry
(e.g., one or more Application Specific Integrated
Circuits--"ASICs"). Depicted in the exemplary embodiment of FIG.
10, however, is programmable circuitry, comprising a processor 1003
coupled to one or more memory devices 1005 (e.g., Random Access
Memory, Magnetic Disc Drives, Optical Disk Drives, Read Only
Memory, etc.) and to an interface 1007 that enables bidirectional
communication with other elements/components of the UE 601. The
memory device(s) 1005 store program means 1009 (e.g., a set of
processor instructions) configured to cause the processor 1003 to
control other UE elements so as to carry out any of the aspects
described above, such as but not limited to those described with
reference to FIGS. 6B, 6C, 6D, and 8. The memory device(s) 905 may
also store data (not shown) representing various constant and
variable parameters as may be needed by the processor 1003 and/or
as may be generated when carrying out its functions such as those
specified by the program means 1009.
[0072] The herein-described technology provides a number of
advantages over conventional technology. For example, and without
limitation, UEs having multiple antenna panels and no beam
correspondence can use UL beam management for all panels and not
just for one of the panels, and this in turn provides improved UE
performance (e.g., by enabling multiple antenna panels to be used
for codebook based UL transmissions).
[0073] The invention has been described with reference to
particular embodiments. However, it will be readily apparent to
those skilled in the art that it is possible to embody the
invention in specific forms other than those of the embodiment
described above. Thus, the described embodiments are merely
illustrative and should not be considered restrictive in any way.
The scope of the invention is further illustrated by the appended
claims, rather than only by the preceding description, and all
variations and equivalents which fall within the range of the
claims are intended to be embraced therein.
* * * * *