U.S. patent application number 17/575258 was filed with the patent office on 2022-05-05 for wireless device, radio network node, and methods performed therein for communicating in a wireless communication network.
The applicant listed for this patent is TELEFONAKTIEBOLAGET LM ERICSSON (PUBL). Invention is credited to Icaro L.J. DA SILVA, Rui FAN, Janne PEISA, Pradeepa RAMACHANDRA.
Application Number | 20220141739 17/575258 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220141739 |
Kind Code |
A1 |
FAN; Rui ; et al. |
May 5, 2022 |
WIRELESS DEVICE, RADIO NETWORK NODE, AND METHODS PERFORMED THEREIN
FOR COMMUNICATING IN A WIRELESS COMMUNICATION NETWORK
Abstract
Some embodiments herein relate to a method performed by a
wireless device (10) for handling communication of the wireless
device (10) in a wireless communication network (1), wherein a
first radio network node serves the wireless device (10) and the
wireless communication network (1) further comprises a second radio
network node (13). The wireless device receives a handover command
from the first radio network node (12) indicating a handover to a
cell served by the second radio network node (13), the handover
command comprises a beam indication, such as a threshold,
controlling which beam of the cell to select by the wireless device
(10). The wireless device (10) further selects a beam of the cell
based on at least the beam indication.
Inventors: |
FAN; Rui; (Beijing, CN)
; DA SILVA; Icaro L.J.; (Solina, SE) ; PEISA;
Janne; (Espoo, FI) ; RAMACHANDRA; Pradeepa;
(Linkoping, SE) |
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Applicant: |
Name |
City |
State |
Country |
Type |
TELEFONAKTIEBOLAGET LM ERICSSON (PUBL) |
Stockholm |
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SE |
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Appl. No.: |
17/575258 |
Filed: |
January 13, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16607659 |
Oct 23, 2019 |
11252620 |
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PCT/SE2018/050458 |
May 3, 2018 |
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17575258 |
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62501812 |
May 5, 2017 |
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International
Class: |
H04W 36/06 20090101
H04W036/06; H04B 7/08 20060101 H04B007/08; H04W 74/02 20090101
H04W074/02; H04W 72/04 20090101 H04W072/04; H04W 36/30 20090101
H04W036/30; H04W 74/08 20090101 H04W074/08; H04B 7/06 20060101
H04B007/06 |
Claims
1. A method performed by a wireless device for handling
communication of the wireless device in a wireless communication
network, wherein a first radio network node serves the wireless
device and the wireless communication network, the wireless
communication network having a second radio network node; the
method comprising: receiving a handover command from the first
radio network node, the handover command indicating a handover to a
cell served by the second radio network node, the handover command
including a beam indication indicating which beam of the cell to
select by the wireless device, the beam indication includes at
least an indication of a contention-free resource, and a threshold
indicating a threshold for a beam quality for a beam to be selected
by the wireless device; and selecting a beam of the cell based on
at least the beam indication, and prioritizing said beam associated
with the contention-free resource when the measured beam quality is
better than said beam quality threshold wherein.
2. The method according to claim 1, wherein selecting a beam of the
cell based on at least the beam indication comprises: measuring a
beam quality of at least the beam associated with the
contention-free resource.
3. The method according to claim 1, wherein the beam indication
further comprises a list of beams which are not suitable for access
based on load.
4. The method according to claim 1, wherein the beam indication
further comprises a threshold indicating a beam strength for a beam
to be selected by the wireless device.
5. A method performed by a first radio network node for handling
communication of a wireless device in a wireless communication
network, wherein the first radio network node serves the wireless
device and the wireless communication network, the wireless
communication network including a second radio network node, the
method comprising: transmitting a handover command to the wireless
device, the handover command indicating a handover to a cell served
by the second radio network node, wherein the handover command
includes a beam indication indicating which beam of the cell to
select by the wireless device, wherein the beam indication includes
a list of beams which are not suitable for access based on load,
and a threshold indicating a threshold for a beam strength for a
beam to be selected by the wireless device.
6. The method according to claim 5, wherein the beam indication
comprises at least an indication of a contention-free resource and
a beam quality threshold.
7. A wireless device for handling communication of the wireless
device in a wireless communication network, wherein a first radio
network node is configured to serve the wireless device and the
wireless communication network, the wireless communication network
having a second radio network node; wherein the wireless device is
configured to: receive a handover command from the first radio
network node, the handover command indicating a handover to a cell
served by the second radio network node, wherein the handover
command including a beam indication indicating which beam of the
cell to select by the wireless device, the beam indication includes
at least an indication of a contention-free resource, and a
threshold indicating a threshold for a beam quality for a beam to
be selected by the wireless device; and to select a beam of the
cell based on at least the beam indication.
8. The wireless device according to claim 7, wherein the beam
indication indicates an offset value, which offset value is a
threshold value that a beam, configured with a contention based
random access procedure, needs to outperform a beam, configured
with a contention free random access procedure, with to be
selected.
9. The wireless device according to claim 7, wherein the beam
indication comprises at least an indication of a contention-free
resource and a beam quality threshold.
10. The wireless device according to claim 8, wherein the wireless
device is configured to select a beam of the cell based on at least
the beam indication by measuring a beam quality of at least the
beam associated with the contention-free resource; and,
prioritizing said beam associated with the contention-free resource
when the measured beam quality is better than said beam quality
threshold.
11. A first radio network node for handling communication of a
wireless device in a wireless communication network, wherein the
first radio network node is configured to serve the wireless device
and the wireless communication network, the wireless communication
network having a second radio network node, wherein the first radio
network node is configured to transmit a handover command to the
wireless device, the handover command indicating a handover to a
cell served by the second radio network node, wherein the handover
command includes a beam indication indicating which beam of the
cell to select by the wireless device, the beam indication includes
at least an indication of a contention-free resource, and a
threshold indicating a threshold for a beam quality for a beam to
be selected by the wireless device.
12. The first radio network node according to claim 11, wherein the
beam indication indicates an offset value, which offset value is a
threshold value that a beam, configured with a contention based
random access procedure, needs to outperform a beam, configured
with a contention free random access procedure, with to be
selected.
13. The first radio network node according to claim 11, wherein the
beam indication comprises at least an indication of a
contention-free resource and a beam quality threshold.
14. A computer-readable storage medium, having stored thereon a
computer program product comprising instructions which, when
executed on at least one processor, cause the at least one
processor to carry out the method according to claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This Application is a continuation of and claims priority to
U.S. patent application Ser. No. 16/607,659, filed Oct. 23, 2019,
entitled "WIRELESS DEVICE, RADIO NETWORK NODE, AND METHODS
PERFORMED THEREIN FOR COMMUNICATING IN A WIRELESS COMMUNICATION
NETWORK", which claims priority to International Application No.
PCT/SE2018/050458, filed May 3, 2018, entitled "WIRELESS DEVICE,
RADIO NETWORK NODE, AND METHODS PERFORMED THEREIN FOR COMMUNICATING
IN A WIRELESS COMMUNICATION NETWORK", which claims priority to U.S.
Provisional Application No. 62/501,812, filed May 5, 2017 entitled
"WIRELESS DEVICE, RADIO NETWORK NODE, AND METHODS PERFORMED THEREIN
FOR COMMUNICATING IN A WIRELESS COMMUNICATION NETWORK", the
entireties of all of which are incorporated herein by
reference.
TECHNICAL FIELD
[0002] Embodiments herein relate to a wireless device, a first
radio network node and methods performed therein regarding wireless
communication. Furthermore, a computer program product and a
computer-readable storage medium are also provided herein. In
particular, embodiments herein relate to handling communication,
e.g. handling or enabling handover, of the wireless device in a
wireless communication network.
BACKGROUND
[0003] In a typical wireless communication network, wireless
devices, also known as wireless communication devices, mobile
stations, stations (STA) and/or user equipments (UE), communicate
via a Radio access Network (RAN) to one or more core networks (CN).
The RAN covers a geographical area which is divided into service
areas or cell areas, with each service area or cell area being
served by a radio network node such as an access node e.g. a Wi-Fi
access point or a radio base station (RBS), which in some networks
may also be called, for example, a NodeB, a gNodeB, or an eNodeB.
The service area or cell area is a geographical area where radio
coverage is provided by the access node. The access node operates
on radio frequencies to communicate over an air interface with the
wireless devices within range of the access node. The access node
communicates over a downlink (DL) to the wireless device and the
wireless device communicates over an uplink (UL) to the access
node.
[0004] A Universal Mobile Telecommunications System (UMTS) is a
third generation telecommunication network, which evolved from the
second generation (2G) Global System for Mobile Communications
(GSM). The UMTS terrestrial radio access network (UTRAN) is
essentially a RAN using wideband code division multiple access
(WCDMA) and/or High-Speed Packet Access (HSPA) for communication
with user equipments. In a forum known as the Third Generation
Partnership Project (3GPP), telecommunications suppliers propose
and agree upon standards for present and future generation networks
and UTRAN specifically, and investigate enhanced data rate and
radio capacity. In some RANs, e.g. as in UMTS, several access nodes
may be connected, e.g., by landlines or microwave, to a controller
node, such as a radio network controller (RNC) or a base station
controller (BSC), which supervises and coordinates various
activities of the plural access nodes connected thereto. The RNCs
are typically connected to one or more core networks.
[0005] Specifications for the Evolved Packet System (EPS) have been
completed within the 3.sup.rd Generation Partnership Project (3GPP)
and this work continues in the coming 3GPP releases, such as 4G and
5G networks. The EPS comprises the Evolved Universal Terrestrial
Radio Access Network (E-UTRAN), also known as the Long-Term
Evolution (LTE) radio access network, and the Evolved Packet Core
(EPC), also known as System Architecture Evolution (SAE) core
network. E-UTRAN/LTE is a 3GPP radio access technology wherein the
access nodes are directly connected to the EPC core network. As
such, the Radio Access Network (RAN) of an EPS has an essentially
"flat" architecture comprising access nodes connected directly to
one or more core networks.
[0006] With the emerging 5G technologies, the use of very many
transmit- and receive-antenna elements is of great interest as it
makes it possible to utilize beamforming, such as transmit-side and
receive-side beamforming. Transmit-side beamforming means that the
transmitter can amplify the transmitted signals in a selected
direction or directions, while suppressing the transmitted signals
in other directions. Similarly, on the receive-side, a receiver can
amplify signals from a selected direction or directions, while
suppressing unwanted signals from other directions.
[0007] Beamforming allows the signal to be stronger for an
individual connection. On the transmit-side this may be achieved by
a concentration of the transmitted power in the desired
direction(s), and on the receive-side this may be achieved by an
increased receiver sensitivity in the desired direction(s). This
beamforming enhances throughput and coverage of the connection. It
also allows reducing the interference from unwanted signals,
thereby enabling several simultaneous transmissions over multiple
individual connections using the same resources in the
time-frequency grid, so-called multi-user Multiple Input Multiple
Output (MIMO).
[0008] Scheduled reference signals, called channel-state
information reference signals (CSI-RS), are transmitted when needed
for a particular connection. CSI comprises Channel Quality
Indicator (CQI), Precoding Matrix Indicator (PMI), and Rank
Indicator (RI). The CQI is reported by wireless device to the radio
network node. The wireless device indicates modulation scheme and
coding scheme to the radio network node. To predict the downlink
channel condition, CQI feedback by the wireless device may be used
as an input. CQI reporting can be based on PMI and RI. PMI is
indicated by the wireless device to the radio network node, which
precoding matrix may be used for downlink transmission which is
determined by RI. The wireless device further indicates the RI to
the radio network node, i.e. the number of layers that should be
used for downlink transmission to the wireless device. The decision
when and how to transmit the CSI-RS is made by the radio network
node and the decision is signalled to the involved wireless devices
using a so-called measurement grant. When the wireless device
receives a measurement grant it measures on a corresponding CSI-RS.
The radio network node may choose to transmit CSI-RSs to a wireless
device only using beam(s) that are known to be strong for that
wireless device, to allow the wireless device to report more
detailed information about those beams. Alternatively, the radio
network node may choose to transmit CSI-RSs also using beam(s) that
are not known to be strong for that wireless device, for instance
to enable fast detection of new beam(s) in case the wireless device
is moving.
[0009] The radio network nodes of a New Radio (NR) network transmit
other reference signals as well. For instance, the radio network
nodes may transmit so-called demodulation reference signals (DMRS)
when transmitting control information or data to a wireless device.
Such transmissions are typically made using beam(s) that are known
to be strong for that wireless device.
[0010] In LTE, the main goal of CSI-RSs is to obtain channel state
feedback for up to eight transmit antenna ports to assist the radio
network node in its precoding operations. Release 10 supports
transmission of CSI-RS for 1, 2, 4 and 8 transmit antenna ports.
CSI-RSs also enable the wireless device to estimate the CSI for
multiple cells rather than just its serving cell, to support future
multi-cell cooperative transmission schemes. Notice that the
purpose of CSI-RS measurements in LTE is not to support mobility
across cells.
[0011] The CSI-RS resource allocation for a given subframe is shown
in FIG. 1. Code Division Multiplexing (CDM) codes of length two are
used, so that CSI-RSs on two antenna ports share two resource
elements (RE) on a given subcarrier. The resource elements used in
the case of two CSI-RS antenna ports are a subset of those used for
four and eight antenna ports; this helps to simplify the
implementation. The total number of supported antenna ports is
forty, which can be used to give a frequency-reuse factor of five
between cells with eight antenna ports per cell, or a factor of
twenty in the case of two antenna ports.
[0012] The CSI-RS configuration is wireless device-specific i.e.
provided via dedicated Radio Resource Control (RRC) signalling.
When configured, CSI-RSs are present only in some subframes
following a given duty cycle and subframe offset. The duty cycle
and offset of the subframes containing CSI-RSs and the CSI-RS
pattern used in those subframes are provided to a Release 10
wireless device through RRC signaling, e.g. see FIG. 2. The duty
cycle and subframe offset are jointly coded, while the CSI-RS
pattern is configured independently of these two parameters.
[0013] In summary, the CSI-RS configuration comprises the following
(at least until Rel-10): [0014] The number of CSI-RS: 1, 2, 4 or 8;
[0015] The CSI-RS periodicity: 5 ms, 10 ms, 20 ms, 40 ms or 80 ms;
[0016] The CSI-RS subframe offset within the CSI-RS period; [0017]
The exact CSR-RS configuration within a resource-block pair--that
is exactly what resource elements from the 40 possible REs are used
for the up to eight CSI-RS in a resource-block pair.
[0018] In the context of cooperative MIMO, it may be possible to
improve the performance of channel estimation, and especially
interference estimation, by coordinating CSI-RS transmissions
across multiple service areas. In Release 10 it is therefore
possible to `mute` a set of REs in data transmissions from a
service area. The locations of these REs, known as the `muting
pattern`, can be chosen to avoid colliding with CSI-RS
transmissions from other service areas and hence improve the
inter-cell measurement quality. Notice that in the multi-cell case,
there can be some level of coordination so that CSI-RS resource
allocation tries to avoid the interference across Transmission and
Reception Points (TRP)/service areas, as shown in the FIG. 3 where
CSI-RS configuration 0 differs from CSI-RS configuration 1 that
also differs from CSI-RS configuration 2. Another important aspect
relates to how the wireless device receiver handle the CSI-RS. In
LTE, Time and Frequency (T/F) synchronization is obtained from
Primary Synchronization Signal (PSS)/Secondary Synchronization
Signal (SSS)/Cell Specific Reference Signal (CRS) and Fast Fourier
Transform (FFT) is applied to relevant CSI-RS symbols and removes
the embedded own-cell ID or RRC configured virtual cell ID (504
possibilities).
[0019] The work on Rel-13 FD-MIMO specification in LTE primary
includes the support for beamforming in LTE. The wireless device
can be configured with a set of CSI-RS processes that can be
associated at the network side to different Downlink (DL) beams,
which can be different for the different subframes. With beamformed
CSI-RS, the wireless device should measure CSI on CSI-RS resources
that are beamformed towards different directions, see FIG. 4.
[0020] Rel-13 FD-MIMO specification in LTE supports an enhanced
CSI-RS reporting called Class B for beamformed CSI-RS. Therein, an
LTE RRC_CONNECTED wireless device can be configured with K beams
(where 8>K>1) where it can be 1,2,4 or 8 port number for each
beam. For feedback purposes such as PMI, RI and CQI there is a
CSI-RS Resource Indicator (CRI) per CSI-RS. The wireless device
reports CRI to indicate the preferred beam where the CRI is
wideband, RI/CQI/PMI is based on legacy codebook (i.e. Rel-12) and
CRI reporting period is an integer multiple of the RI. For Rel-14
enhancements in Full Dimension (eFD)-MIMO, the following is being
considered as potential enhancements such as the extension of
CSI-RS antenna port number up to 32 i.e. {20, 24, 28, 32} CSI-RS
ports and the introduction of aperiodic CSI-RS, see FIG. 5.
[0021] According to the TS 36.331 the CSI-RS configuration (encoded
in the CSI-RS-Config IE) can either be transmitted in the
RRCConnectionSetup, RRCConnectionResume or the RRC Connection
Reconfiguration, with or without mobility Control Information (i.e.
in a handover command). See FIG. 6.
[0022] It has been agreed in RAN1 that CSI-RS is going to be the
primary RS for beam management. Compared to the beamformed CSI-RS
in LTE, perhaps the main additional use case would be the analog
beam sweep, possibly also used for fine T/F tracking. Hence, more
flexibility for the NR CSI-RS in New Radio (NR) is also envisioned
such as: [0023] Possibly transmitted within 1, 2 or 4 symbols;
[0024] Configurable bandwidth (i.e. not always full system as in
LTE); [0025] Orthogonal Frequency Division Multiplexing (OFDM)
symbol can carry CSI-RS only; [0026] Aperiodic, semi-persistent and
periodic transmissions;
[0027] Note: Most of the usage of CSI-RS in LTE and so far,
mentioned in NR are related to measurement to support beam
management. In addition to that, RAN1 and RAN2 have also agreed
that CSI-RS can be used for Radio Resource Management (RRM)
measurements to support inter-cell mobility, although details have
not been defined.
[0028] In the following, the mobility in LTE and in particular the
handover preparation between eNodeBs (eNB) is described.
[0029] In LTE, the handover of a wireless device in RRC_CONNECTED
state is a wireless device-assisted network-controlled Handover
(HO), with HO preparation signalling in E-UTRAN: [0030] Part of the
HO command comes from the target eNB and is transparently forwarded
to the wireless device by the source eNB; [0031] To prepare the HO,
the source eNB passes all necessary information to the target eNB
(e.g. E-Radio Access Bearer (RAB) attributes and RRC context);
[0032] Both the source eNB and the wireless device keep some
context, e.g. Cell-Radio Network Temporary Identifier (C-RNTI), to
enable the return of the wireless device in case of HO failure;
[0033] The wireless device accesses the target cell via Random
Access Channel (RACH) following a contention-free procedure using a
dedicated RACH preamble or following a contention-based procedure
if dedicated RACH preambles are not available; the wireless device
uses the dedicated preamble until the handover procedure is
finished (successfully or unsuccessfully); [0034] If the RACH
procedure towards the target cell is not successful within a
certain time, the wireless device initiates radio link failure
recovery using a suitable cell; [0035] No Robust Header Compression
(ROHC) context is transferred at handover; [0036] ROHC context can
be kept at handover within the same eNB.
[0037] The preparation and execution phase of the HO procedure is
performed without CN involvement (EPC in the case of LTE), i.e.
preparation messages are directly exchanged between the eNBs. The
release of the resources at the source side during the HO
completion phase is triggered by the eNB. The FIG. 7 depicts the
basic handover scenario where neither Mobility Management Entity
(MME) nor Serving Gateway changes:
[0038] Handover preparation in LTE is further described i.e.
actions 3, 4, 5 and 6 in FIG. 7. The Handover preparation is
initiated by the serving eNodeB that makes decision for a handover,
possibly based on MEASUREMENT REPORT and RRM information to hand
off the wireless device, see action 3. Then the follow steps occur:
[0039] Action 4: The source eNB issues a HANDOVER REQUEST message
to the target eNB passing necessary information to prepare the HO
at the target side (wireless device X2 signalling context reference
at source eNB, wireless device S1 EPC signalling context reference,
target cell ID, KeNB*, RRC context including the C-RNTI of the
wireless device in the source eNB, AS-configuration, enhanced Radio
access bearer (E-RAB) context and physical layer ID of the source
cell+short Medium Access Control (MAC)-I for possible Radio Link
Failure (RLF) recovery). Wireless device X2/wireless device S1
signalling references enable the target eNB to address the source
eNB and the EPC. The E-RAB context includes necessary Radio Network
Layer (RNL) and Transport Network Layer (TNL) addressing
information, and Quality Of Service (QoS) profiles of the E-RABs.
[0040] Action 5: Admission Control may be performed by the target
eNB dependent on the received E-RAB QoS information to increase the
likelihood of a successful HO, if the resources can be granted by
target eNB. The target eNB configures the required resources
according to the received E-RAB QoS information and reserves a
C-RNTI and optionally a RACH preamble. The AS-configuration to be
used in the target cell can either be specified independently (i.e.
an "establishment") or as a delta compared to the AS-configuration
used in the source cell (i.e. a "reconfiguration"). [0041] Action
6: The target eNB prepares HO with Layer 1 (L1)/Layer 2 (L2) and
sends the HANDOVER REQUEST ACKNOWLEDGE to the source eNB. The
HANDOVER REQUEST ACKNOWLEDGE message includes a transparent
container to be sent to the wireless device as an RRC message to
perform the handover. The container includes a new C-RNTI, target
eNB security algorithm identifiers for the selected security
algorithms, may include a dedicated RACH preamble, and possibly
some other parameters i.e. access parameters, System Information
Blocks (SIB), etc. The HANDOVER REQUEST ACKNOWLEDGE message may
also include RNL/TNL information for the forwarding tunnels, if
necessary.
[0042] NOTE: As soon as the source eNB receives the HANDOVER
REQUEST ACKNOWLEDGE, or as soon as the transmission of the handover
command is initiated in the downlink, data forwarding may be
initiated.
[0043] Handover preparation in NR is mainly a RAN3 issue in
standardization and work related to intra-NR mobility has not
started. On the other hand, in the RAN2 TR, a similar inter-node
signalling as in LTE has been agreed as baseline. Hence, it is
expected a similar Xn signalling exchanged between gNodeBs i.e. a
Handover Request from serving to target, followed by a Handover
Request Ack once admission control occurs in the target.
[0044] Thus, in LTE, a handover occurs from the serving cell to the
neighbor cell. In order to assist the network, the wireless device
is configured to perform RRM measurements for its own cell and
compare with the quality of neighbor cells. In other words, the
wireless device needs to measure the quality of neighbor cell,
report these to the radio network node so a decision can be
made.
[0045] The network may decide to handover the wireless device from
a serving cell to possibly one of the neighbor cell candidates that
have been reported. Then, the handover command follows (in LTE this
is the RRCConnectionReconfiguration with the IE
mobilityControlInformation) containing among other parameters the
RACH configuration the wireless device should use the access the
target cell such as the Physical Random Access Channel (PRACH) time
and frequency resources the wireless device should transmit the
preamble (possibly also dedicated and allocated in the same
message).
[0046] Since handover is a costly procedure in terms of radio
signalling, and, in some cases (inter-gNodeB) network signalling,
too frequent handovers and ping-pong handover should be avoided or
at least minimized (especially because they may also increase the
chances of failure). In addition, for battery saving reasons and
load, too frequent measurement reports should be avoided or
minimized. Hence, event-triggered reports based on filtered
measurements are defined per cell in LTE. RAN4 then define
requirements on evaluation period of 200 ms for a certain accuracy
and wireless device implementation typically picks a snapshot of 40
ms to perform some coherence and on-coherent average over time and
frequency.
[0047] In NR, there will be deployment in higher frequencies and
beamforming will be widely used even for the basic control signals
and channels, such as reference signals used for RRM. In addition,
current design principles in 3GPP point to the direction where RACH
resources are portioned per DL beam transmitting RS for RRM and
synchronization, so called a Synchronization Signal (SS) Block
Burst Set. So every SS Block may contain its own RACH configuration
i.e. Time/Frequency (T/F) resources and even preamble sub-set. The
SS Block will contain in its structure some kind of RS that may be
used to indicate the beam, often called tertiary synchronization
sequence (TSS), although it can possibly be transmitted as a
codeword in the SS Block, jointly with the PSS/SSS and the Physical
Broadcast Channel (PBCH), see FIG. 8.
[0048] Even without directional reciprocity, the implementation
enables the target cell to transmit the Random Access Response
(RAR) in the strongest DL beam covering the wireless device thanks
to the mapping between RACH configuration (including the preamble)
and the target cell DL beam. That allows the wireless device to
quickly access a narrow beam in the target right after handover
execution.
[0049] In LTE, RACH resources are defined per cell i.e. when the
wireless device receives the Handover (HO) command the wireless
device can immediately initiate RACH, at least assuming the
wireless device is synchronized (although dedicated resources can
be configured); Meanwhile, in NR, RACH resources are defined per DL
beam (or groups of DL beam) to allow an efficient RACH detection
using analog beamforming (or groups of beams). Hence, the wireless
device may select a DL beam before it initiates random access.
[0050] In that case, current solutions being discussed point in two
possible directions: [0051] wireless device receives a HO command
with PRACH mapping to all possible TSS in the target cell; [0052]
wireless device receives a HO command with a subset of PRACH
configurations mapped to a subset of TSS in the target cell;
[0053] In latest RAN2 #97bis meeting, there are following agreement
made related to HO in NR.
[0054] Agreements [0055] 1 Handover command can contain at least
cell identity of the target cell and RACH configuration(s)
associated to the beams of the target cell. RACH configuration(s)
can include configuration for contention-free random access. [0056]
1b wireless device selects a suitable beam from all beams of the
target cell. [0057] 1c wireless device performs CBRA on the
wireless device's selected beam if Contention Free Random Access
(CFRA) resources are not provided for the wireless device's
selected beam.
[0058] According to this agreement, network (NW) only tell the
wireless device which cell the wireless device should handover to
similar as in LTE. While which beam within the target cell wireless
device should access to is decided by the wireless device
itself.
[0059] The agreement in NR has the advantage that the wireless
device can select a beam with best radio link quality when it needs
to access target cell which might be different from the best beam
that it reported to the NW in a measurement report.
[0060] However, leaving control to the wireless device has some
problems.
[0061] First, some beams with good radio link quality in the target
cell may be loaded from NW perspective, however the wireless device
does not know this. Therefore the wireless device may select those
beam to access target cell. The wireless device may then not get a
good performance.
[0062] Second, sometimes to guarantee the success of random access
in target cell, NW will allocate designated preamble for the
wireless device to use during random access, i.e. contention free
random access (CFRA) procedure. According to current agreement, the
wireless device may not select this beam, then the reservation of
such preamble is a waste and the successfulness of random access in
the target cell may be affected leading to a limited or reduced
performance of the wireless communication network.
SUMMARY
[0063] An object of embodiments herein is to provide a mechanism
that improves the performance of the wireless communication network
when using beamforming in a wireless communication network.
[0064] According to an aspect the object is achieved by providing a
method performed by a wireless device for handling communication of
the wireless device in a wireless communication network. A first
radio network node serves the wireless device and the wireless
communication network further comprises a second radio network
node. The wireless device receives a handover command from the
first radio network node indicating a handover to a cell served by
the second radio network node. The handover command comprises a
beam indication controlling which beam of the cell to select by the
wireless device. The wireless device further selects a beam of the
cell based on at least the beam indication.
[0065] According to another aspect the object is achieved by
providing a method performed by first radio network node for
handling communication of a wireless device in a wireless
communication network. The first radio network node serves the
wireless device and the wireless communication network further
comprises a second radio network node. The first radio network node
transmits a handover command to the wireless device indicating a
handover to a cell served by the second radio network node, wherein
the handover command comprises a beam indication controlling which
beam of the cell to select by the wireless device.
[0066] It is herein also provided a computer program product
comprising instructions, which, when executed on at least one
processor, causes the at least one processor to carry out the
methods herein, as performed by the first radio network node or the
wireless device. Furthermore, it is herein provided a
computer-readable storage medium, having stored thereon a computer
program product comprising instructions which, when executed on at
least one processor, cause the at least one processor to carry out
the methods herein, as performed by the first radio network node or
the wireless device.
[0067] According to yet another aspect the object is achieved by
providing a wireless device for handling communication of the
wireless device in a wireless communication network, wherein a
first radio network node is configured to serve the wireless device
and the wireless communication network is configured to comprise a
second radio network node. The wireless device is configured to
receive a handover command from the first radio network node
indicating a handover to a cell served by the second radio network
node, wherein the handover command comprises a beam indication
controlling which beam of the cell to select by the wireless
device. The wireless device is further configured to select a beam
of the cell based on at least the beam indication.
[0068] According to still another aspect the object is achieved by
providing a first radio network node for handling communication of
a wireless device in a wireless communication network. The first
radio network node is configured to serve the wireless device and
the wireless communication network is configured to comprise a
second radio network node. The first radio network node is
configured to transmit a handover command to the wireless device
indicating a handover to a cell served by the second radio network
node. The handover command comprises a beam indication controlling
which beam of the cell to select by the wireless device.
[0069] According to yet still another aspect the object is achieved
by providing a wireless device comprising processing circuitry
configured to receive a handover command from a first radio network
node indicating a handover to a cell served by a second radio
network node, wherein the handover command comprises a beam
indication controlling which beam of the cell to select by the
wireless device. The processing circuitry is further configured to
select a beam of the cell based on at least the beam
indication.
[0070] According to another aspect the object is achieved by
providing a first radio network node comprising processing
circuitry configured to transmit a handover command to a wireless
device indicating a handover to a cell served by a second radio
network node. The handover command comprises a beam indication
controlling which beam of the cell to select by the wireless
device.
[0071] Embodiments herein enable that the first radio network node
includes the beam indication so that the network can direct the
wireless device which beams the wireless device will select, or
which beams the wireless device 10 should not select. Thus, the
wireless device selects a beam which can meet both a requirement
from the network (NW) and/or a requirement from the wireless
device. Then both NW and the wireless device can experience better
performance during and after a HO. Hence, embodiments herein
improve the performance of the wireless communication network.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] Embodiments will now be described in more detail in relation
to the enclosed drawings, in which:
[0073] FIG. 1 shows CSI-RS resource allocation for a given subframe
and resource block;
[0074] FIG. 2 shows channel estimation of CSI-RS transmissions;
[0075] FIG. 3 shows CSI-RS resource allocation across multiple
coordinated cells;
[0076] FIG. 4 shows CSI-RS support for beam selection in LTE;
[0077] FIG. 5 shows beamformed CSI-RS in LTE;
[0078] FIG. 6 shows a CSI-RS-Config information element;
[0079] FIG. 7 shows a handover process in LTE;
[0080] FIG. 8 shows that each SS Block contains a mapping between
RACH configuration and the strongest DL beam transmitting the SS
Block. In this example, each PRACH occasion/resource is associated
with two SS Block beams;
[0081] FIG. 9a shows a schematic overview depicting a wireless
communication network according to embodiments herein;
[0082] FIG. 9b is a schematic flowchart depicting a method
performed by a wireless device according to embodiments herein;
[0083] FIG. 9c is a schematic flowchart depicting a method
performed by a first radio network node according to embodiments
herein;
[0084] FIG. 10 is a schematic combined flowchart and signalling
scheme according to embodiments herein;
[0085] FIG. 11 is a schematic flowchart according to some
embodiments herein;
[0086] FIG. 12 is a schematic flowchart according to some
embodiments herein;
[0087] FIG. 13 is a schematic flowchart according to some
embodiments herein;
[0088] FIG. 14 is a schematic flowchart according to some
embodiments herein;
[0089] FIG. 15 is a schematic flowchart according to some
embodiments herein;
[0090] FIG. 16 is a block diagram depicting a wireless device
according to embodiments herein; and
[0091] FIG. 17 is a block diagram depicting a first radio network
node according to embodiments herein.
DETAILED DESCRIPTION
[0092] Embodiments herein relate to wireless communication networks
in general. FIG. 9a is a schematic overview depicting a wireless
communication network 1. The wireless communication network 1
comprises one or more RANs and one or more CNs. The wireless
communication network 1 may use one or a number of different
technologies, such as New Radio (NR), Wi-Fi, LTE, LTE-Advanced,
Fifth Generation (5G), Wideband Code-Division Multiple Access
(WCDMA), Global System for Mobile communications/enhanced Data rate
for GSM Evolution (GSM/EDGE), Worldwide Interoperability for
Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to
mention a few possible implementations. Embodiments herein relate
to recent technology trends that are of particular interest in a 5G
context. However, embodiments are also applicable in further
development of the existing wireless communication systems such as
e.g. WCDMA and LTE.
[0093] In the wireless communication network 1, a wireless device
e.g. a wireless device 10 such as a mobile station, a non-access
point (non-AP) STA, a STA, a user equipment and/or a wireless
terminal, communicates via one or more Access Networks (AN), e.g.
RAN, to one or more core networks (CN). It should be understood by
the skilled in the art that "wireless device" is a non-limiting
term which means any terminal, wireless communication terminal,
user equipment, Machine-Type Communication (MTC) device,
Device-to-Device (D2D) terminal, or node e.g. smart phone, laptop,
mobile phone, sensor, relay, mobile tablets or even a small base
station capable of communicating using radio communication with a
network node within an area served by the network node.
[0094] The wireless communication network 1 comprises a first radio
network node 12, also referred to as merely a network node, serving
or providing radio coverage over a geographical area, a first
service area 11 or a first cell, of a first radio access technology
(RAT), such as NR, LTE, Wi-Fi, WiMAX or similar. The first radio
network node 12 may be a transmission and reception point, a radio
network node such as an Mobility Management Entity (MME), a serving
Gateway, a Wireless Local-Area Network (WLAN) access point or an
Access Point Station (AP STA), an access node, an access
controller, a base station, e.g. a radio base station such as a
NodeB, an evolved Node B (eNB, eNode B), gNodeB, a base transceiver
station, a radio remote unit, an Access Point Base Station, a base
station router, a transmission arrangement of a radio base station,
a stand-alone access point or any other network unit or node
capable of communicating with a wireless device within the service
area served by the first radio network node 12 depending e.g. on
the first radio access technology and terminology used. The first
radio network node 12 may be referred to as a serving network node
wherein the first service area may be referred to as a source beam,
and the serving network node serves and communicates with the
wireless device 10 in form of DL transmissions to the wireless
device 10 and UL transmissions from the wireless device 10.
[0095] A second radio network node 13 may further provide radio
coverage over a second service area 14 or a second cell of a second
radio access technology (RAT), such as NR, LTE, Wi-Fi, WiMAX or
similar. The first RAT and the second RAT may be the same or
different RATs. The second radio network node 13 may be a
transmission and reception point e.g. a radio network node such as
a Wireless Local-Area Network (WLAN) access point or an Access
Point Station (AP STA), an access node, an access controller, a
base station, e.g. a radio base station such as a NodeB, an evolved
Node B (eNB, eNode B), gNodeB, a base transceiver station, a radio
remote unit, an Access Point Base Station, a base station router, a
transmission arrangement of a radio base station, a stand-alone
access point or any other network unit or node capable of
communicating with a wireless device within the area served by the
second radio network node 13 depending e.g. on the second radio
access technology and terminology used. The second radio network
node 13 may be referred to as a neighbour network node wherein the
second service area 14 may be referred to as a neighbouring beam or
a target beam.
[0096] It should be noted that a service area may be denoted as a
cell, a beam group, a mobility measurement beam, or similar to
define an area of radio coverage. The radio network nodes transmit
RSs over respective service area in beams. Hence, the first and
second radio network nodes may transmit CSI-RSs or beam reference
signals (BRS), repeatedly, in time, in a large number of different
directions using as many Tx-beams as deemed necessary to cover the
service area of the respective radio network node. Hence the first
radio network node 12 provides radio coverage over the first
service area using a first reference signal, e.g. first CSI-RS, for
the first service area 11 in the wireless communication network 1.
The second radio network node 13 provides radio coverage over the
second service area 14 using a number of beams each with a
reference signal, e.g. one or more second CSI-RSs, in the wireless
communication network.
[0097] During a handover process of the wireless device 10 between
the first and second radio network nodes, according to embodiments
herein, the first radio network node 12 transmits a handover
command to the wireless device 10 indicating a handover to the cell
or service area 14 served by the second radio network node 13. The
handover command further comprises a beam indication controlling or
at least directing which beam of the cell to select by the wireless
device 10, wherein the beam indication may e.g. be a threshold for
a beam quality and/or a list indicating beams allowable or not
allowable. Embodiments herein thus allow the first radio network
node 12 to include some information in an HO command so that the
network can direct the wireless device 10 which beams the wireless
device will select, or which beams the wireless device 10 should
not select.
[0098] In one case, the first radio network node 12 does not
configure Contention Free Random Access (CFRA), i.e. not using
dedicated RACH resources, on any of the beams in the target cell
and in this case, the first radio network node 12 makes sure the
wireless device 10 does not select a beam with radio link quality
worse than a threshold, and may furthermore make sure that the
wireless device 10 does not select a beam that has some issues from
a network perspective, e.g. those beams that are already traffic
loaded. Therefore, in the HO command, the first radio network node
12 may include e.g. a beam quality threshold also referred to as
radio quality threshold (`Min_threshold`) and/or a list of beams
that the network would not want the wireless device 10 to select,
also referred to as a black list of beams.
[0099] The pseudo code for this algorithm may be:
TABLE-US-00001 If (Reference Signal Received Power (RSRP) of SS
block > `Min_threshold` and is not blacklisted by the NW):
Consider beam associated to SS block suitable for access; Else Not
consider beam associated to this SS block for access;
[0100] In another case the first radio network node 12 configures
CFRA, i.e. dedicating RACH resources, on one or more of the beams
in the target cell. Since the first radio network node 12 then
reserves a preamble on one or more beams and expects wireless
device 10 to do CFRA on those beams to ensure reliability of random
access and if the wireless device 10 does not select those beams,
then the beams that the wireless device selects must be better
enough than the one designated by the first radio network node 12
to motivate such a selection. Otherwise, it is a waste of network
resources, and may impact the reliability of random access.
[0101] Therefore, in the HO command, the first radio network node
12 may include at least an offset or offset value compared to a
radio link quality of contention free (CF) beams, which offset
value may be denoted CF_OFFSET.
[0102] The pseudo code for this algorithm is as below.
TABLE-US-00002 if (RSRP of the SS block without CFRA configuration
is "CF offset" better than that of SS block with CFRA
configuration): Consider beam associated to that SS block suitable
for access; Else Not consider beam associated to that SS block
suitable for access; If no beam suitable for access Select beam
with CFRA configured.
[0103] The method actions performed by the wireless device 10 for
handling communication of the wireless device 10 in the
communication network 1 according to embodiments herein will now be
described with reference to a flowchart depicted in FIG. 9b.
Examples of the beam indication are marked with dashed boxes. The
first radio network node 12 serves the wireless device 10 and the
wireless communication network 1 further comprises the second radio
network node.
[0104] Action 901. The wireless device 10 receives the handover
command from the first radio network node 12 indicating a handover
to a cell served by the second radio network node 13. The handover
command comprises a beam indication controlling which beam of the
cell to select by the wireless device 10. The beam indication may
indicate a subset of available beams or a list of preferred beams.
Additionally or alternatively, the beam indication may indicate an
offset value, which offset value is a threshold value that a beam,
configured with a contention based random access procedure, needs
to outperform a beam, configured with a contention free random
access procedure, with to be selected. The beam indication may
comprise a list of beams which are not suitable for access, and/or
a threshold indicating a threshold for a beam quality or a beam
strength for a beam to be selected by the wireless device. Beam
quality may also be referred to as radio link quality and may be
measured in reference signal received quality (RSRQ) or signal to
interference plus noise ratio (SINR). Beam strength may also be
referred to as radio link strength and may be measured in reference
signal received power (RSRP).
[0105] Action 902. The wireless device 10 may measure beam quality
or beam strength of reference signals such as CSI-RS, SS blocks or
similar of different beams.
[0106] Action 903. The wireless device 10 selects a beam of the
cell based on at least the beam indication. E.g. the wireless
device 10 may select a beam to access and may transmit RACH
resources such as preamble and/or time and frequency associated
with the selected beam. The association may be according to RACH
configuration previously received. The beam indication may comprise
at least an indication of a contention-free resource and a beam
quality threshold. The wireless device 10 may select a beam of the
cell based on at least the beam indication by e.g. measure a beam
quality of at least the beam associated with the contention-free
resource; and prioritize said beam associated with the
contention-free resource when the measured beam quality is better
than said beam quality threshold.
[0107] The method actions performed by the first radio network node
12 for handling communication of the wireless device 10 in the
communication network 1 according to embodiments herein will now be
described with reference to a flowchart depicted in FIG. 9c.
Examples of the beam indication are marked with dashed boxes. The
first radio network node 12 serves the wireless device 10 and the
wireless communication network 1 further comprises the second radio
network node 13.
[0108] Action 911. The first radio network node 12 may determine or
configure the beam indication e.g. indicating preferred beams
and/or the threshold for a beam quality or a beam strength. The
beam indication may comprise at least an indication of a
contention-free resource and a beam quality threshold.
[0109] Action 912. The first radio network node 12 transmits a
handover command to the wireless device 10 indicating the handover
to the cell served by the second radio network node 13, wherein the
handover command comprises the beam indication controlling which
beam of the cell to select by the wireless device 10. The beam
indication may indicate the subset of available beams or the list
of preferred beams. Alternatively or additionally, the beam
indication may indicate the offset value, which offset value is the
threshold value that a beam, configured with a contention based
random access procedure, needs to outperform a beam, configured
with a contention free random access procedure, with to be
selected. Alternatively or additionally, the beam indication may
comprise the list of beams which are not suitable for access,
and/or the threshold indicating a threshold for a beam quality or a
beam strength for a beam to be selected by the wireless device
10.
[0110] FIG. 10 is a combined signaling scheme and flowchart for
handling handover according to embodiments herein.
[0111] Action 1010. The first radio network node 12 may determine
or configure the beam indication indicating preferred beams such as
CSI RS to select and/or conditions to be fulfilled such as strength
or quality thresholds, see FIGS. 11-15 below. This is an example of
action 911 in FIG. 9c.
[0112] Action 1020. During a handover process the first radio
network node 12 transmits the handover command to the wireless
device 10 indicating the handover to the cell served by the second
radio network node. The handover command comprises the beam
indication controlling or informing which beam or beams of the cell
to select by the wireless device 10. Thus the wireless device 10
receives the beam indication indicating preferred or in some
embodiments not preferred beams. The beam indication may be a
threshold value of strength or quality, a list of not wanted beams,
or a list of preferred beams. The beam indication may be a list of
beams which are not suitable for access, or a radio link quality
threshold for a beam to be selected by the wireless device. This is
an example of action 912 in FIG. 9c.
[0113] Action 1030. The wireless device 10 may then select a beam
taking the received beam indication into account. This is an
example of action 903 in FIG. 9b.
[0114] Action 1040. The wireless device 10 may then initiate
handover or access to the selected beam.
[0115] Regarding action 911 above wherein the first radio network
node 12 may determine the beam indication, as an example, the first
radio network node 12 may configure a list of not allowed beams (a
black list) in the target cell. I.e., some beams are not preferred
from a handover point of view (e.g. are currently congested) and
the first radio network node would like to ensure that the wireless
device 10 does not select one of those beams.
[0116] The list of not allowed beams may be e.g. included in the
handover command, may be preconfigured prior to the handover, may
be included in the system information of the source or target cells
or provided to the wireless device using other means.
[0117] The pseudo code for this method is shown below and is
exemplified in FIG. 11.
TABLE-US-00003 111) The wireless device 10 receives a target cell
and a list of black listed cells from the network 112) The wireless
device 10 identifies and selects a suitable beam (e.g. based on the
beam quality also referred herein as radio link quality) in the
target cell 113) The wireless device 10 determines whether the
selected beam is in black list or not. 114) If the selected beam is
not included in the black list - The wireless device 10 considers
beam associated to this SS block suitable for access; Else 115) -
The wireless device 10 determines if more beams from same target
cell available 116) if more beams from same target cell are
available - The wireless device 10 may select another beam from the
same target cell, and compares it to the black list again using
step 113. 117) If no further beams are available, the wireless
device 10 considers the handover to have failed and may declare a
handover failure.
[0118] In another embodiment, the wireless device 10 is allowed to
access using a black listed cell if all the detected beams are
black listed, i.e. overrun the black list.
[0119] The first radio network node 12 may configure a threshold
such as a minimum threshold for the beams in the target cell i.e.
the second service area.
[0120] In this case embodiment, the first radio network node 12 may
need to ensure that the wireless device 10 does not select a too
weak beam, and provides the beam indication e.g. indicating a
minimum allowed quality (threshold) for the beam quality.
[0121] The minimum allowed quality for allowed beams can be e.g.
included in the handover (HO) command, can be preconfigured prior
to the handover or can be included in the system information of the
source or target cells or provided to the wireless device 10 using
other means.
[0122] The pseudo code for this algorithm is as below
TABLE-US-00004 121) The wireless device 10 receives a target cell
and a minimum quality level for allowed beams (Threshold). 122) The
wireless device 10 identifies and selects a suitable beam (e.g.
based on the beam quality also referred herein as radio link
quality) in the target cell 123) The wireless device 10 determines
whether the selected beam is below threshold or not. 124) If (RSRP
of SS block > `Min_threshold`) Consider beam associated to SS
block suitable for access; Else 125) - The wireless device 10
determines if more beams from same target cell available 126) if
more beams from same target cell are available - The wireless
device 10 may select another beam from the same target cell, based
on beam quality. 127) If no further beams are available, the
wireless device 10 considers the handover to have failed and may
declare a handover failure. This procedure is shown in FIG. 12.
[0123] The first radio network node 12 may configure CFRA on one or
more of the beams in the target cell
[0124] In this case, as the first radio network node 12 reserves
preamble on one or more beams and expects the wireless device 10 to
do CFRA on those beams to ensure reliability of random access, if
the wireless device 10 does not select those beams, then the beams
that wireless device 10 select must be better enough than the one
designated by the first radio network node to motivate the wireless
device selection, otherwise, it is a waste of network resources,
and impact the reliability of random access.
[0125] Therefore, in the HO command, it can include at least an
offset compared to radio link quality of Contention Free (CF) beams
denoted as CF_OFFSET.
[0126] The pseudo code for this algorithm is as shown in FIG.
13.
TABLE-US-00005 131) The wireless device 10 receives a target cell
and CFRA for some beams in target cell and the offset value related
to contention free beams (CF_OFFSET) 132) The wireless device 10
identifies and selects a suitable beam (e.g. based on the beam
quality) in the target cell 133) The wireless device 10 determines
whether selected beam have CFRA or not. 134) if selected beam have
CFRA then use this beam specific RA resources for accessing the
target cell; 135) Is this beam's quality better than the best beam
with CFRA by CF_OFFSET? I.e. if (RSRP of the SS block without CFRA
configuration is "CF offset" better than that of SS block with CFRA
configuration) 134) the wireless device 10 considers beam
associated to that SS block suitable for access; Else the wireless
device 10 does not consider beam associated to that SS block
suitable for access; 136) - The wireless device 10 selects another
suitable beam from same target cell available If no beam suitable
for access the wireless device 10 selects beam with CFRA
configured.
[0127] This procedure is shown in FIG. 13.
[0128] The first radio network node 12 may configure CFRA on one or
more of the beams in the target cell plus may blacklist beams in
target cell.
[0129] In this case, then wireless device 10 should select a CFRA
beam unless a beam with an RSRP that is offset better than that of
CFRA beam and not in blacklist in target cell. Otherwise, the
wireless device 10 should select CFRA beam.
TABLE-US-00006 141) The wireless device 10 receives a target cell
and CFRA for some beams in target cell, a contention free beams
related offset (CF_OFFSET) and a list of not allowed beams
(blacklist). 142) The wireless device 10 identifies and selects a
suitable beam (e.g. based on the beam quality) in the target cell.
143) The wireless device 10 determines whether selected beam is in
the blacklist. 144) If the beam is not in the blacklist the
wireless device determines whether the selected beam has CFRA. 145)
If not CFRA it is determined whether the selected beam's quality is
better than the best beam with CFRA by CF_OFFSET? I.e. if (RSRP of
the SS block without CFRA configuration is "CF offset" better than
that of SS block with CFRA configuration & SS block is not in
blacklist of target cell) 146) the wireless device 10 considers
beam associated to that SS block suitable for access i.e. use this
beam specific RA resources for accessing the target cell; Else the
wireless device 10 does not consider beam associated to that SS
block suitable for access. 147) The wireless device 10 may select
another beam from the same target cell, based on beam quality. If
no beam suitable for access the wireless device 10 may select beam
with CFRA configured. 148) If no further beams are available, the
wireless device 10 considers the handover to have failed and may
declare a handover failure.
[0130] The process is shown in FIG. 14.
[0131] The first radio network node 12 may also configure a
whitelist of beams.
[0132] The white listed beams are the one or ones that the first
radio network node 12 suggests the wireless device to choose. But
in order to make sure that a beam in whitelist does not have too
bad radio link quality, the first radio network node 12 may also
configure a WHITELIST_OFFSET, which indicate how much worse white
list beam can be compared to best beam. Unless beam in whitelist is
not offset worse than best beam, the wireless device may select
them, otherwise, the wireless device 10 will not select them. CFRA
beam can be seen as a whitelist beam.
TABLE-US-00007 151) The wireless device 10 receives a target cell
and a list of whitelisted beams and a WHITELIST_OFFSET 152) The
wireless device 10 identifies and selects a suitable beam (e.g.
based on the beam quality) from the whitelist. 153) The wireless
device 10 determines whether selected beam is within whitelist
offset. 154) If yes, use this beam specific RA resources for
accessing the target cell. 155) if no, determine if any other
Whitelist beams from same target cell is available? 156) if
available, the wireless device 10 may select another suitable
whitelisted beam from the same target cell (e.g. based on beam
quality); 157) if not available, the wireless device 10 may
determine if another beam is available 158) If another beam is
available the wireless device 10 may select the beam (e.g. based on
beam quality) (and proceed to 159). 159) If no further beams are
available, the wireless device 10 considers the handover to have
failed and may declare a handover failure. The pseudo code may be
as below if (RSRP of the SS block within whitelist is not
WHITELIST_OFFSET worse than best SS block) The first radio network
node 12 considers the beam associated to that SS block in whitelist
suitable for access; If no beam in whitelist suitable for access
the first radio network node 12 selects beam not in whitelist.
[0133] The process is shown in FIG. 15.
[0134] Various embodiments can also be combined to create further
embodiments. For example, FIG. 13 shows how embodiments in FIGS. 11
and 12 may be combined to allow the network to control both the
allowed beams and set a minimum suitable level for suitable cells.
Similar combinations of other embodiments are also possible.
[0135] The previously describe embodiment associate the beam
selection at the wireless device side based on e.g. a RS within an
SS Block, such as the RACH association provided by the network. In
addition to it, a set of equivalent embodiments could be defined
when CSI-RS resources are configured for RRM measurement or
handover optimization. In that case, each CSI-RS resource, such as
time, frequency and sequence, may be associated to a beam in the
DL. The wireless device 10 may also be configured with a notion of
group in such a way that it knows which CSI-RSs are associated with
which resources. Hence, assuming that the HO command may contain a
RACH to CSI-RS association, just as we described for the SS Blocks,
the concept of blacklist of beam or whitelist of beams can also be
applied herein.
[0136] Alternatively, a network implementation may be achieved by
not configuring the wireless device 10 to access a target area via
SS blocks but by using CSI-RS association to RACH and only
configuring CSI-RSs for that access in the allowed area e.g. the
areas associated to beams the network is aware of not being
overloaded. Hence, the network can simply configure a subset of
CSI-RS out of all possible CSI-RSs covering the whole cell and
provide RACH resources for the subset.
[0137] It should be noted that in a general scenario the term
"radio network node" can be substituted with "transmission and
reception point". The key observation is that it must be possible
to make a distinction between the transmission reception points
(TRPs), typically based on RSs or different synchronization signals
and BRSs transmitted. Several TRPs may be logically connected to
the same radio network node but if they are geographically
separated, or are pointing in different propagation directions, the
TRPs will be subject to the same issues as different radio network
nodes. In subsequent sections, the terms "radio network node" and
"TRP" can be thought of as interchangeable.
[0138] It should further be noted that a wireless communication
network may be a virtually network sliced into a number of
Network/RAN slices, each Network/RAN slice supports one or more
type of wireless devices and/or one or more type of services i.e.
each network slice supports a different set of functionalities.
Network slicing introduces the possibility that the network/RAN
slices are used for different services and use cases and these
services and use cases may introduce differences in the
functionality supported in the different network slices. Each
network/RAN slice may comprise one or more network nodes or
elements of network nodes providing the services/functionalities
for the respective network slice. Each network/RAN slice may
comprise a network node such as a RAN node and/or a core network
node.
[0139] FIG. 16 is a block diagram depicting the wireless device 10
according to embodiments herein for handling communication of the
wireless device 10 in the wireless communication network 1. The
wireless communication network 1 is configured to comprise the
second radio network node 13. The first radio network node 12 is
configured to serve the wireless device 10 and the wireless
communication network 1 further comprises the second radio network
node 13.
[0140] The wireless device 10 may comprise processing circuitry
1601, e.g. one or more processors, configured to perform the
methods herein.
[0141] The wireless device 10 may comprise a receiving module 1602,
e.g. a receiver or transceiver. The wireless device 10, the
processing circuitry 1601, and/or the receiving module 1602 is
configured to receive the handover command from the first radio
network node 12 indicating a handover to a cell served by the
second radio network node 13, wherein the handover command
comprises a beam indication controlling which beam of the cell to
select by the wireless device 10. E.g. the handover command further
comprises the beam indication controlling or indicating which beam
of the cell to select by the wireless device. The indication may be
a list of beams which are not suitable to access, or a radio link
quality threshold.
[0142] The wireless device 10 may comprise a selecting module 1603.
The wireless device 10, the processing circuitry 1601, and/or the
selecting module 1603 is configured to select a beam of the cell
based on at least the beam indication. The wireless device 10, the
processing circuitry 1601, and/or the selecting module 1603 may be
configured to measure strength or quality of beams and take this
into account as well. The beam indication may comprise at least an
indication of a contention-free resource and a beam quality
threshold. The wireless device 10, the processing circuitry 1601,
and/or the selecting module 1603 may be configured to select a beam
of the cell based on at least the beam indication by e.g. measure a
beam quality of at least the beam associated with the
contention-free resource; and prioritize said beam associated with
the contention-free resource when the measured beam quality is
better than said beam quality threshold. The beam indication may
indicate a subset of available beams or a list of preferred beams.
The beam indication may indicate an offset value, which offset
value is a threshold value that a beam, configured with a
contention based random access procedure, needs to outperform a
beam, configured with a contention free random access procedure,
with to be selected. The beam indication may comprise a list of
beams which beams are not suitable for access, and/or a threshold
indicating a threshold for a beam quality or a beam strength for a
beam to be selected by the wireless device.
[0143] The wireless device 10 further comprises a memory 1604. The
memory comprises one or more units to be used to store data on,
such as strengths qualities, indications, beams, CSI-RSs,
thresholds, applications to perform the methods disclosed herein
when being executed, and similar.
[0144] The methods according to the embodiments described herein
for the wireless device 10 are respectively implemented by means of
e.g. a computer program product 1605 or a computer program,
comprising instructions, i.e., software code portions, which, when
executed on at least one processor, cause the at least one
processor to carry out the actions described herein, as performed
by the wireless device 10. The computer program product 1605 may be
stored on a computer-readable storage medium 1606, e.g. a disc, a
universal serial bus (USB) stick or similar. The computer-readable
storage medium 1606, having stored thereon the computer program
product, may comprise the instructions which, when executed on at
least one processor, cause the at least one processor to carry out
the actions described herein, as performed by the wireless device
10. In some embodiments, the computer-readable storage medium may
be a non-transitory computer-readable storage medium. It is herein
disclosed a wireless device comprising processing circuitry
configured to receive a handover command from a first radio network
node indicating a handover to a cell served by a second radio
network node, wherein the handover command comprises a beam
indication controlling which beam of the cell to select by the
wireless device; and to select a beam of the cell based on at least
the beam indication.
[0145] FIG. 17 is a block diagram depicting the first radio network
node 12, such as a gNB, MME or similar, according to embodiments
herein for handling communication of the wireless device 10 in the
wireless communication network. The first radio network node 12 is
configured to serve the wireless device 10 and the wireless
communication network 1 is configured to comprise a second radio
network node e.g. further comprises the second radio network node
13.
[0146] The first radio network node 12 may comprise processing
circuitry 1701, e.g. one or more processors, configured to perform
the methods herein.
[0147] The first radio network node 12 may comprise a configuring
module 1702. The first radio network node 12, the processing
circuitry 1701, and/or the configuring module 1702 may be
configured to determine or configure the beam indication.
[0148] The first radio network node 12 may comprise a transmitting
module 1703, e.g. a transmitter or a transceiver. The first radio
network node 12, the processing circuitry 1701, and/or the
transmitting module 1703 is configured to transmit the handover
command to the wireless device 10 indicating a handover to a cell
served by the second radio network node 13, wherein the handover
command comprises a beam indication controlling which beam of the
cell to select by the wireless device. The first radio network node
12, the processing circuitry 1701, and/or the transmitting module
1703 may be configured to transmit the beam indication to the
wireless device 10. The handover command comprises the beam
indication controlling which beam of the cell to select by the
wireless device. The beam indication may indicate a subset of
available beams or a list of preferred beams. The beam indication
may indicate an offset value, which offset value is a threshold
value that a beam, configured with a contention based random access
procedure, needs to outperform a beam, configured with a contention
free random access procedure, with to be selected. The beam
indication may comprise a list of beams which are not suitable for
access, and/or a threshold indicating a threshold for a beam
quality or a beam strength for a beam to be selected by the
wireless device. The beam indication may comprise at least an
indication of a contention-free resource and a beam quality
threshold. The first radio network node 12 further comprises a
memory 1704. The memory comprises one or more units to be used to
store data on, such as beam indications, strengths qualities,
thresholds, beams, cells, applications to perform the methods
disclosed herein when being executed, and similar.
[0149] The methods according to the embodiments described herein
for the first radio network node 12 are respectively implemented by
means of e.g. a computer program product 1705 or a computer
program, comprising instructions, i.e., software code portions,
which, when executed on at least one processor, cause the at least
one processor to carry out the actions described herein, as
performed by the first radio network node 12. The computer program
product 1705 may be stored on a computer-readable storage medium
1706, e.g. a disc, a USB stick, or similar. The computer-readable
storage medium 1706, having stored thereon the computer program
product, may comprise the instructions which, when executed on at
least one processor, cause the at least one processor to carry out
the actions described herein, as performed by the first radio
network node 12. In some embodiments, the computer-readable storage
medium may be a non-transitory computer-readable storage
medium.
[0150] It is herein disclosed a first radio network node comprising
processing circuitry configured to transmit a handover command to a
wireless device indicating a handover to a cell served by a second
radio network node, wherein the handover command comprises a beam
indication controlling which beam of the cell to select by the
wireless device.
[0151] It is herein disclosed a method performed by the wireless
device for handling communication of the wireless device in the
wireless communication network. The first radio network node serves
the wireless device and the wireless communication network further
comprises the second radio network node. The wireless device
receives the handover command from the first radio network node
indicating a handover to a cell served by the second radio network
node, the handover command further comprises the beam indication
controlling which beam of the cell to select by the wireless
device. For example, the handover command may comprise some
information to control which beam the wireless device selects
during HO, such information may be a list of beams which are not
suitable for access, or a radio link quality threshold for a beam
to be selected by the wireless device. For example, measured link
quality of a beam for selection should be better than that radio
link quality threshold. The wireless device then selects a beam of
the cell based on at least the beam indication.
[0152] It is furthermore herein disclosed a method performed by the
first radio network node, also referred to as network node, for
handling communication of the wireless device in the wireless
communication network. The first radio network node serves the
wireless device and the wireless communication network further
comprises the second radio network node. The radio network node
transmits the handover command to the wireless device indicating a
handover to a cell served by the second radio network node. The
handover command further comprises the beam indication controlling
which beam of the cell to select by the wireless device.
[0153] Furthermore, a first radio network node and a wireless
device configured to perform the methods herein are also
provided.
[0154] In some embodiments a more general term "radio network node"
is used and it can correspond to any type of radio network node or
any network node, which communicates with a wireless device and/or
with another network node. Examples of network nodes are NodeB,
Master eNB, Secondary eNB, a network node belonging to Master cell
group (MCG) or Secondary Cell Group (SCG), base station (BS),
multi-standard radio (MSR) radio node such as MSR BS, eNodeB,
network controller, radio network controller (RNC), base station
controller (BSC), relay, donor node controlling relay, base
transceiver station (BTS), access point (AP), transmission points,
transmission nodes, Remote Radio Unit (RRU), Remote Radio Head
(RRH), nodes in distributed antenna system (DAS), core network node
e.g. Mobility Switching Centre (MSC), Mobile Management Entity
(MME) etc, Operation and Maintenance (O&M), Operation Support
System (OSS), Self-Organizing Network (SON), positioning node e.g.
Evolved Serving Mobile Location Centre (E-SMLC), Minimizing Drive
Test (MDT) node etc.
[0155] In some embodiments the non-limiting term wireless device or
user equipment (UE) is used and it refers to any type of wireless
device communicating with a network node and/or with another UE in
a cellular or mobile communication system. Examples of UE are
target device, device-to-device (D2D) UE, proximity capable UE (aka
ProSe UE), machine type UE or UE capable of machine to machine
(M2M) communication, PDA, PAD, Tablet, mobile terminals, smart
phone, laptop embedded equipped (LEE), laptop mounted equipment
(LME), USB dongles etc.
[0156] The embodiments are described for 5G. However the
embodiments are applicable to any RAT or multi-RAT systems, where
the UE receives and/or transmit signals (e.g. data) e.g. LTE, LTE
FDD/TDD, WCDMA/HSPA, GSM/GERAN, Wi Fi, WLAN, CDMA2000 etc.
[0157] Antenna node: As used herein, an "antenna node" is a unit
capable of producing one or more beams covering a specific service
area or direction. An antenna node can be a base station, or a part
of a base station.
[0158] As will be readily understood by those familiar with
communications design, that functions means or modules may be
implemented using digital logic and/or one or more
microcontrollers, microprocessors, or other digital hardware. In
some embodiments, several or all of the various functions may be
implemented together, such as in a single application-specific
integrated circuit (ASIC), or in two or more separate devices with
appropriate hardware and/or software interfaces between them.
Several of the functions may be implemented on a processor shared
with other functional components of a wireless device or network
node, for example.
[0159] Alternatively, several of the functional elements of the
processing means discussed may be provided through the use of
dedicated hardware, while others are provided with hardware for
executing software, in association with the appropriate software or
firmware. Thus, the term "processor" or "controller" as used herein
does not exclusively refer to hardware capable of executing
software and may implicitly include, without limitation, digital
signal processor (DSP) hardware, read-only memory (ROM) for storing
software, random-access memory for storing software and/or program
or application data, and non-volatile memory. Other hardware,
conventional and/or custom, may also be included. Designers of
communications devices will appreciate the cost, performance, and
maintenance tradeoffs inherent in these design choices.
[0160] It will be appreciated that the foregoing description and
the accompanying drawings represent non-limiting examples of the
methods and apparatus taught herein. As such, the apparatus and
techniques taught herein are not limited by the foregoing
description and accompanying drawings. Instead, the embodiments
herein are limited only by the following claims and their legal
equivalents.
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