U.S. patent application number 16/063118 was filed with the patent office on 2019-10-17 for wireless device, radio network node, and methods performed therein for handling communication in a wireless communication networ.
The applicant listed for this patent is Telefonaktiebolaget LM Ericsson (publ). Invention is credited to Icaro Leonardo J. Da Silva.
Application Number | 20190320355 16/063118 |
Document ID | / |
Family ID | 61832568 |
Filed Date | 2019-10-17 |
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United States Patent
Application |
20190320355 |
Kind Code |
A1 |
Da Silva; Icaro Leonardo
J. |
October 17, 2019 |
WIRELESS DEVICE, RADIO NETWORK NODE, AND METHODS PERFORMED THEREIN
FOR HANDLING COMMUNICATION IN A WIRELESS COMMUNICATION NETWORK
Abstract
Some embodiments herein relate to a method performed by a
wireless device for handling communication of the wireless device
in a wireless communication network, wherein the wireless device is
served by a radio network node. The wireless device performs a beam
tracking of one or more beams for a set of detected neighbour cells
for tracking one or more best beams of respective neighbour cell
based on measured signal strength or measured signal quality. The
wireless device further receives an indication from the radio
network node, wherein the indication indicates a target cell for
the wireless device. When the target cell is in the set of detected
neighbour cells, the wireless device further initiates a random
access procedure associated with a best target beam for the target
cell, wherein the best target beam is selected based on the beam
tracking performed prior to receiving the indication.
Inventors: |
Da Silva; Icaro Leonardo J.;
(Solna, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget LM Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
61832568 |
Appl. No.: |
16/063118 |
Filed: |
March 22, 2018 |
PCT Filed: |
March 22, 2018 |
PCT NO: |
PCT/SE2018/050299 |
371 Date: |
June 15, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62475939 |
Mar 24, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/046 20130101;
H04W 36/06 20130101; H04L 5/0048 20130101; H04W 16/28 20130101;
H04L 41/0668 20130101; H04W 36/0061 20130101; H04W 74/0833
20130101; H04L 1/0026 20130101; H04W 36/0085 20180801; H04W 72/042
20130101; H04L 5/0051 20130101; H04W 24/08 20130101; H04W 76/19
20180201 |
International
Class: |
H04W 36/00 20060101
H04W036/00; H04W 36/06 20060101 H04W036/06; H04W 72/04 20060101
H04W072/04; H04W 74/08 20060101 H04W074/08; H04W 16/28 20060101
H04W016/28; H04L 1/00 20060101 H04L001/00; H04L 5/00 20060101
H04L005/00 |
Claims
1. A method performed by a wireless device for handling
communication of the wireless device in a wireless communication
network, wherein the wireless device is served by a radio network
node, the method comprising: performing a beam tracking of one or
more beams for a set of detected neighbour cells for tracking one
or more best beams of respective neighbour cell based on measured
signal strength or measured signal quality; receiving an indication
from the radio network node, wherein the indication indicates a
target cell for the wireless device; and when the target cell is in
the set of detected neighbour cells, initiating a random access
procedure associated with at least one target beam for the target
cell, wherein the at least one target beam is selected based on the
beam tracking performed prior to receiving the indication.
2. The method according to claim 1, wherein performing the beam
tracking comprises performing measurements on reference signals of
the one or more beams for the set of detected neighbour cells, and
wherein the at least one target beam for the random access
procedure is selected based on the signal strength or quality of
respective beam.
3. The method according to claim 1, wherein the at least one target
beam is selected further based on a list of allowed beams for the
target cell for the wireless device.
4. The method according to claim 1, further comprising selecting
and storing over a time interval the one or more beams for each
neighbour cell based on the performed beam tracking.
5. The method according to claim 4, wherein the beam tracking
comprises performing a full sweep of the one or more beams before
selecting the one or more beams in each neighbour cell.
6. The method according to claim 1, wherein the random access
procedure is associated with the at least one target beam by random
access channel resources allocated for the at least one target
beam.
7. The method according to claim 1, wherein the beam tracking
comprises obtaining additional information, wherein the additional
information is used to perform the random access procedure.
8. The method according to claim 1, wherein an occurrence of a
mobility event triggers the wireless device to initiate the beam
tracking.
9. The method according to claim 1, further comprising receiving
configuration data from the radio network node, wherein the
configuration data indicates that the wireless device is to perform
beam tracking of one or more beams for a set of detected neighbour
cells and upon reception of the indication, to initiate a random
access procedure associated with at least one target beam for a
target cell, wherein the at least one target beam is selected based
on a performed beam tracking prior to receiving the indication,
wherein the indication indicates the target cell for the wireless
device.
10. The method according to claim 1, wherein measurements of the
beam tracking is performed at a different time scale compared to
measurements used for radio resource management, RRM, purposes,
wherein the measurements are snapshots closer in time to one
another than the measurements used for the RRM purposes.
11. A method performed by a radio network node for handling
communication of a wireless device in a wireless communication
network, wherein the radio network node serves the wireless device,
the method comprising: transmitting configuration data to the
wireless device, wherein the configuration data indicates that the
wireless device is to perform beam tracking of one or more best
beams for a set of detected neighbour cells and upon reception of
an indication, to initiate a random access procedure associated
with at least one target beam for a target cell, wherein the at
least one target beam is selected based on a performed beam
tracking prior to receiving the indication, wherein the indication
indicates a target cell for the wireless device.
12. The method according to the claim 11, wherein the configuration
data comprises one or more filter parameters for measurements of
the beam tracking and/or the configuration data defines the
wireless device to monitor more beams of one candidate cell than
for another candidate cell.
13-26. (canceled)
27. A wireless device for handling communication of the wireless
device in a wireless communication network, wherein the wireless
communication network comprises a radio network node being
configured to serve the wireless device, and wherein the wireless
device comprises processing circuitry and a memory, said memory
comprising instructions executable by said processing circuitry
whereby said wireless device is operative to: perform a beam
tracking of one or more beams for a set of detected neighbour cells
for tracking one or more best beams of respective neighbour cell
based on measured signal strength or measured signal quality;
receive an indication from the radio network node, wherein the
indication indicates a target cell for the wireless device; and,
when the target cell is in the set of detected neighbour cells, to
initiate a random access procedure associated with at least one
target beam for the target cell, and wherein the wireless device is
operative to select the at least one target beam based on the beam
tracking performed prior to receiving the indication.
28. The wireless device according to claim 27, wherein the wireless
device is operative to perform the beam tracking by being operative
to perform measurements on reference signals of the one or more
beams for the set of detected neighbour cells, and wherein the
wireless device is operative to select the at least one target beam
for the random access procedure based on the signal strength or
quality of respective beam.
29. The wireless device according to claim 27, wherein the wireless
device is operative to select the at least one target beam further
based on a list of allowed beams for the target cell for the
wireless device.
30. The wireless device according to claim 27, further being
operative to select and store over a time interval the one or more
beams for each neighbour cell based on the performed beam
tracking.
31. The wireless device according to claim 30, wherein the wireless
device is operative to perform the beam tracking by being operative
to perform a full sweep of beams before selecting the one or more
beams in each neighbour cell.
32. The wireless device according to claim 27, wherein the random
access procedure is associated with the at least one target beam by
random access channel resources allocated for the at least one
target beam.
33. The wireless device according to claim 27, wherein the wireless
device is operative to obtain additional information during the
beam tracking, wherein the additional information is used to
perform the random access procedure.
34. The wireless device according to claim 27, wherein the wireless
device is operative to initiate the beam tracking being triggered
by an occurrence of a mobility event.
35. The wireless device according to claim 27, wherein the wireless
device is operative to receive configuration data from the radio
network node, wherein the configuration data indicates that the
wireless device is to perform beam tracking of one or more beams
for a set of detected neighbour cells and upon reception of the
indication to initiate a random access procedure associated with at
least one target beam for a target cell, wherein the at least one
target beam is selected based on a performed beam tracking prior to
receiving the indication, wherein the indication indicates the
target cell for the wireless device.
36. The wireless device according to claim 27, wherein the wireless
device is operative to perform measurements of the beam tracking at
a different time scale compared to measurements used for radio
resource management, RRM, purposes, wherein the measurements are
snapshots closer in time to one another than the measurements used
for the RRM purposes.
37. A radio network node for handling communication of a wireless
device in a wireless communication network, wherein the radio
network node comprises processing circuitry and a memory, said
memory comprising instructions executable by said processing
circuitry whereby said radio network node is operative to serve the
wireless device, and to: transmit configuration data to the
wireless device, wherein the configuration data indicates that the
wireless device is to perform beam tracking of one or more beams
for a set of detected neighbour cells and to, upon reception of an
indication, initiate a random access procedure associated with at
least one target beam for a target cell, wherein the at least one
target beam is selected based on a performed beam tracking prior to
receiving the indication, and wherein the indication indicates the
at least one target cell for the wireless device.
38. The radio network node according to the claim 37, wherein the
configuration data comprises one or more filter parameters for
measurements of the beam tracking and/or the configuration data
defines the wireless device to monitor more beams of one candidate
cell than for another candidate cell.
Description
TECHNICAL FIELD
[0001] Embodiments herein relate to a wireless device, a radio
network node and methods performed therein regarding wireless
communication. Furthermore, a computer program 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
[0002] 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) with 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 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" or "eNodeB" or
"gNodeB". The service area or cell area is a geographical area
where radio coverage is provided by the radio network node. The
radio network node operates on radio frequencies to communicate
over an air interface with the wireless devices within range of the
radio network node. The radio network node communicates over a
downlink (DL) to the wireless device and the wireless device
communicates over an uplink (UL) to the radio network node.
[0003] 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 radio
network 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 radio network nodes connected
thereto. The RNCs are typically connected to one or more core
networks.
[0004] Specifications for the Evolved Packet System (EPS) have been
completed within the 3.sup.rd 3GPP and this work continues in the
coming 3GPP releases, such as 4G and 5G networks such as New Radio
(NR). 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
or LTE is a 3GPP radio access technology wherein the radio network
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 radio network nodes connected directly to
one or more core networks.
[0005] With the emerging 5G technologies such as new radio (NR),
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.
[0006] 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).
[0007] Scheduled reference signals, called channel-state
information reference signals (CSI-RS), are transmitted when needed
for a particular connection. Channel-state information (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. RI indicates 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.
[0008] 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.
[0009] 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.
[0010] 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 may be
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.
[0011] 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 signalling. The duty cycle and subframe
offset are jointly coded, while the CSI-RS pattern is configured
independently of these two parameters.
[0012] In summary, the CSI-RS configuration comprises the
following, at least in LTE: [0013] The number of CSI-RS: e.g. 1, 2,
4 or 8; [0014] The CSI-RS periodicity: e.g. 5 ms, 10 ms, 20 ms, 40
ms or 80 ms; [0015] The CSI-RS subframe offset within the CSI-RS
period; [0016] 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.
[0017] In the context of cooperative MIMO, it may be possible to
improve the performance of channel estimation, see FIG. 2, 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 a `muting
pattern`, may 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) and/or 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 handles the
CSI-RS. In LTE, time and frequency (T/F) synchronization is
obtained from primary synchronization signal (PSS), secondary
synchronization signal (SSS), and/or cell specific reference signal
(CRS), and a fast Fourier transform (FFT) is applied to relevant
CSI-RS symbols and removes the embedded own-cell identity (ID) or
RRC configured virtual cell ID, which are 504 possibilities.
[0018] The work on Rel-13 full dimension (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 may be associated at the network side to different downlink
(DL) beams, which may 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.
[0019] 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 e.g. 8>K>1, and where it may 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, and/or 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.
[0020] According to the TS 36.331 v. 13.0.0 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 wherein the
CSI-RS configuration is transmitted in the RRCConnectionSetup.
[0021] CSI-RS may 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 NR is
also envisioned such as: [0022] Possibly transmitted within 1, 2 or
4 symbols; [0023] Configurable bandwidth, i.e. not always full
system as in LTE; [0024] Orthogonal Frequency Division Multiplexing
(OFDM) symbol may carry CSI-RS only; [0025] Aperiodic,
semi-persistent and periodic transmissions;
[0026] 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, CSI-RS may be used for radio
resource management (RRM) measurements to support inter-cell
mobility i.e. movement between different cells, although details
have not been defined.
[0027] In the following, the mobility in LTE and in particular the
handover preparation between radio network nodes, denoted as
eNodeBs (eNB), is described.
[0028] 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: [0029] Part of the
HO command comes from the target eNB and is transparently forwarded
to the wireless device by the source eNB see actions 6 and 7;
[0030] 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) see action 8; [0031] 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; [0032] 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), see action 9; [0033] 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; [0034] No robust header compression (ROHC) context
is transferred at handover; [0035] ROHC context may be kept at
handover within the same eNB.
[0036] The preparation and execution phase of the HO procedure is
performed without CN involvement, e.g. 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:
[0037] 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,
Action 3, possibly based on MEASUREMENT REPORT and RRM information
to hand off the wireless device. Then the follow steps occur:
[0038] 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, access stratum
(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 signalling and/or 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. [0039] 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"). [0040] Action 6: The target eNB
prepares HO with Layer 1 (L1) and/or 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, and 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
and/or TNL information for the forwarding tunnels, if
necessary.
[0041] NOTE: As soon as the source eNB receives the HANDOVER
REQUEST ACKNOWLEDGE (ACK), or as soon as the transmission of the
handover command is initiated in the downlink, data forwarding may
be initiated.
[0042] A similar inter-node signalling as in LTE may be assumed as
baseline for upcoming generations of telecommunications. Hence, it
is expected a similar Xn signalling exchanged between radio network
nodes, denoted as gNodeBs in NR, i.e. a Handover Request from
serving to target, followed by a Handover Request ACK once
admission control occurs in the target.
[0043] Thus, in LTE, a handover occurs from the serving cell to the
neighbour 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 neighbour cells. In other words, the
wireless device needs to measure the quality of neighbour cell,
report these to the radio network node so a decision can be
made.
[0044] The radio network node may decide to handover the wireless
device from a serving cell to possibly one of the neighbour 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 to 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).
[0045] Since handover is a costly procedure in terms of radio
signalling, and, in some cases (inter-gNodeB i.e. between gNodeBs)
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. There may be
requirements on e.g. 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. Snapshot herein meaning a measurement
taken at a point in time.
[0046] 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,
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 and/or SSS and the
physical broadcast channel (PBCH), see FIG. 8.
[0047] 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.
[0048] In LTE, RACH resources are defined per cell i.e. when the
wireless device receives the Handover (HO) command the wireless
device may 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 beams) 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.
[0049] In that case, solutions being discussed point in two
possible directions: [0050] wireless device receives a HO command
with PRACH mapping to all possible TSS in the target cell; [0051]
wireless device receives a HO command with a subset of PRACH
configurations mapped to a subset of TSS in the target cell.
[0052] Regardless which case is finally captured in the standards,
or even if both are possible, the handover performance could be
negatively affected in the case the beam selection in the target
cell takes too long time. As described in the baseline, and in the
LTE specifications, the wireless device would synchronize with the
target only after receiving the HO command and at that time it
would select the best DL beam to map to the received RACH
resources. However, since transmissions are sparse in time,
differently from LTE where CRS is always available in every
subframe, at least 10 or 20 ms could be needed until the first
possible beam is detected. That could be even worse in analog
beamforming, depending on the duration of a full SS Block Burst
Set, e.g. intervals longer than 20 ms, which can make handover
non-seamless as required in many NR services, such as
ultra-reliable low-latency communications (URLLC) or even some
mobile broadband (MBB) services. Thus, this may reduce or limit the
performance of the wireless communication network.
SUMMARY
[0053] 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.
[0054] 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. The
wireless device is served by a radio network node. The wireless
device performs a beam tracking of one or more beams for a set of
detected neighbour cells for tracking one or more best beams of
respective neighbour cell based on measured signal strength or
measured signal quality. The wireless device receives an indication
from the radio network node, wherein the indication indicates a
target cell for the wireless device; and when the target cell is in
the set of detected neighbour cells. The wireless device further
initiates a random access procedure associated with at least one
target beam for the target cell, wherein the at least one target
beam is selected based on the beam tracking performed prior to
receiving the indication.
[0055] Upon receiving the indication such as a handover command,
e.g. RRCConnectionReconfiguration with mobilityControlInformation
or equivalent such as RRCReconfiguration with synchronization
indication, secondary cell group (SCG) change, SCG addition, etc.,
that is to be used to trigger a handover or an establishment of a
secondary cell, the wireless device may thus use up-to-date or
latest information from the beam tracking to initiate random access
procedure with e.g. a second radio network node, without
necessarily waiting to perform additional measurements to select
the best DL beam to map to its configured RACH resources.
[0056] According to another aspect the object may be achieved by
providing a method performed by a radio network node for handling
communication of a wireless device in a wireless communication
network. The radio network node serves the wireless device. The
radio network node transmits configuration data to the wireless
device, wherein the configuration data indicates that the wireless
device is to perform beam tracking of one or more beams for a set
of detected neighbour cells and to initiate a random access
procedure associated with at least one target beam for a target
cell, wherein the at least one target beam is selected based on a
performed beam tracking prior to receiving an indication, wherein
the indication indicates a target cell for the wireless device.
[0057] 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. The wireless
communication network comprises a radio network node being
configured to serve the wireless device. The wireless device is
configured to perform a beam tracking of one or more beams for a
set of detected neighbour cells for tracking one or more best beam
of respective neighbour cell based on measured signal strength or
measured signal quality. The wireless device is further configured
to receive an indication from the radio network node, wherein the
indication indicates a target cell for the wireless device. When
the target cell is in the set of detected neighbour cells, the
wireless device is configured to initiate a random access procedure
associated with at least one target beam for the target cell, and
the wireless device is configured to select the at least one target
beam based on the beam tracking performed prior to receiving the
indication.
[0058] According to still another aspect the object is achieved by
providing a radio network node handling communication of a wireless
device in a wireless communication network. The radio network node
is configured to serve the wireless device, and to transmit
configuration data to the wireless device. The configuration data
indicates that the wireless device is to perform beam tracking of
one or more beams for a set of detected neighbour cells and to,
upon reception of an indication, initiate a random access procedure
associated with at least one target beam for a target cell, wherein
the at least one target beam is selected based on a performed beam
tracking prior to receiving the indication, and wherein the
indication indicates the target cell for the wireless device.
[0059] It is herein also provided a computer program 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 radio network node or the wireless device.
Furthermore, it is herein provided a computer-readable storage
medium, having stored thereon a computer program 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 radio network node or the wireless device.
[0060] According to yet still another aspect the object is achieved
by providing a wireless device for handling communication of the
wireless device in a wireless communication network. The wireless
communication network comprises a radio network node being
configured to serve the wireless device. The wireless device
comprises processing circuitry and a memory, said memory comprising
instructions executable by said processing circuitry whereby said
wireless device is operative to perform a beam tracking of one or
more beams for a set of detected neighbour cells for tracking one
or more best beams of respective neighbour cell based on measured
signal strength or measured signal quality. The wireless device is
further operative to receive an indication from the radio network
node, wherein the indication indicates a target cell for the
wireless device; and, when the target cell is in the set of
detected neighbour cells, to initiate a random access procedure
associated with at least one target beam for the target cell. The
wireless device is operative to select the at least one target beam
based on the beam tracking performed prior to receiving the
indication.
[0061] According to another aspect the object is achieved by
providing a radio network node for handling communication of a
wireless device in a wireless communication network, wherein the
radio network node comprises processing circuitry and a memory. The
memory comprises instructions executable by said processing
circuitry whereby said radio network node is operative to serve the
wireless device, and to transmit configuration data to the wireless
device. The configuration data indicates that the wireless device
is to perform beam tracking of one or more beams for a set of
detected neighbour cells and to, upon reception of an indication,
initiate a random access procedure associated with at least one
target beam for a target cell. The at least one target beam is
selected based on a performed beam tracking prior to receiving the
indication, and wherein the indication indicates the at least one
target cell for the wireless device.
[0062] Embodiments herein enable the wireless device to access a
target cell, during e.g. a handover and/or establishment a
secondary cell, much faster, immediately after the indication is
received. This is particularly important in carriers where the
signals used for beam selection for random access, in e.g. NR,
these will be the signals transmitted in the so called SS Block
Burst Set, are sparser in time, which may be the case in
non-standalone carriers, where periodicities could be up to 160 ms,
and/or the cases where, in e.g. analog beamforming, directions are
multiplexed over multiple SS Burst so that it may take time for the
wireless device to detect its target beam. Hence, embodiments
herein improve the performance of the wireless communication
network since the wireless device connects quicker to a beam of the
target cell.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] Embodiments will now be described in more detail in relation
to the enclosed drawings, in which:
[0064] FIG. 1 shows CSI-RS resource allocation for a given subframe
and resource block;
[0065] FIG. 2 shows channel estimation of CSI-RS transmissions;
[0066] FIG. 3 shows CSI-RS resource allocation across multiple
coordinated cells;
[0067] FIG. 4 shows CSI-RS support for beam selection in LTE;
[0068] FIG. 5 shows beamformed CSI-RS in LTE;
[0069] FIG. 6 shows a CSI-RS-Config information element;
[0070] FIG. 7 shows a handover process in LTE;
[0071] 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 and/or PRACH resource
is associated with two SS Blocks;
[0072] FIG. 9a shows a schematic overview depicting a wireless
communication network according to embodiments herein;
[0073] FIG. 9b shows a schematic flowchart depicting a method
performed by a wireless device according to embodiments herein;
[0074] FIG. 9c shows a schematic flowchart depicting a method
performed by a radio network node according to embodiments
herein;
[0075] FIG. 9d is a schematic combined flowchart and signalling
scheme according to some embodiments herein;
[0076] FIG. 10 is a schematic combined flowchart and signalling
scheme according to embodiments herein;
[0077] FIG. 11 is a block diagram depicting a wireless device
according to embodiments herein; and
[0078] FIG. 12 is a block diagram depicting a radio network node
according to embodiments herein.
DETAILED DESCRIPTION
[0079] 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.
[0080] In the wireless communication network 1, wireless devices
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, communicate 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.
[0081] The wireless communication network 1 comprises a first radio
network node 12, also referred to as merely the radio network node,
providing radio coverage over a geographical area, a first service
area 11 or a first beam or beam group, 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 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 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 serving cell with a number of beams,
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.
[0082] A second radio network node 13 may further provide radio
coverage over a second service area 14 or a second beam or beam
group 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
target beam.
[0083] It should be noted that a service area may be denoted as a
cell, a beam, a mobility measurement beam, a beam group or similar
to define an area of radio coverage. The radio network nodes
transmit RSs over respective service area. 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 an
operational 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 or first beam in the wireless
communication network 1. The second radio network node 13 provides
radio coverage over the second service area 14 using a second
reference signal, e.g. second CSI-RS, for the second service area
14 or second beam in the wireless communication network.
[0084] Wireless devices may store cell based measurements taking
into account best beam and/or N1 best beams. However, beams are
much more unstable than the cell measurements i.e. the measurements
associated to the best N beams detected and filtered at the moment
the wireless device has performed may be completely outdated at the
moment the wireless device receives the HO command. Hence, using
these could simply lead to a wrong HO decision, which may reduce or
limit the performance of the wireless communication network. I.e.
using previously reported measurements instead of up-to-date
measurements obtained due to beam tracking may simply lead to a
wrong HO decision, i.e. selecting a wrong beam during HO. This may
reduce or limit the performance of the wireless communication
network. Tracking means that the measurements are not discarded and
may ay be used later for RACH.
[0085] According to embodiments herein the wireless device 10
instead performs beam tracking of one or more beams, e.g. N2 best
beams, associated with a set of detectable neighbour cells, e.g.
based on signal to interference plus noise ratio (SINR) or
equivalent above a certain threshold, which could be potential
candidates as target cells, depending on a reception of a handover
command, or equivalent, from the wireless communication network.
Herein N2 may be larger than N1, as a typical N1 configuration is
N1=1. A set of neighbour cells may comprise one or more neighbour
cells such as the second service area 14. Hence, a best beam may be
a beam with a measured signal strength or quality above e.g. the
threshold or above signal strength or quality of other beams of
that cell. Upon reception of an indication, such as a handover
command or a secondary cell establishment command, indicating a
target cell, the wireless device 10 initiates a random access
procedure associated with at least one target beam for the target
cell, wherein the at least one target beam is selected based on the
beam tracking performed prior to receiving the indication. Since
the target cell is one of the neighbor cells for which beam
tracking has been performed, the at least one target beam for the
target cell is the best or one of the best beams for that neighbor
cell. Hence, embodiments herein improve the performance of the
wireless communication network since the wireless device connects
quicker to a beam of the target cell, wherein the beam is selected
based on more recent measurements.
[0086] The method actions performed by the wireless device 10 for
handling communication of the wireless device 10 in the wireless
communication network 1 according to embodiments herein will now be
described with reference to a flowchart depicted in FIG. 9b. The
actions do not have to be taken in the order stated below, but may
be taken in any suitable order. Actions performed in some
embodiments are marked with dashed boxes. The wireless device 10 is
served by a radio network node exemplified herein as the first
radio network node 12.
[0087] Action 901. The wireless device 10 may receive configuration
data from the first radio network node 12, wherein the
configuration data indicates that the wireless device 10 is to
perform beam tracking of one or more beams for a set of detected
neighbour cells and upon reception of the indication, to initiate a
random access procedure associated with at least one target beam
for a target cell, wherein the at least one target beam is selected
based on a performed beam tracking prior to receiving an
indication, wherein the indication indicates a target cell for the
wireless device. The configuration data may comprise one or more
filter parameters for measurements of the beam tracking and/or the
configuration data defines the wireless device to monitor more
beams of one candidate cell than for another candidate cell. Filter
parameters may be an evaluation period of measurements, a snapshot
periodicity, and average over time and frequency parameters.
Furthermore, information regarding random access resources, such as
preamble, or time and frequency, to use may be provided in a
message such as measConfig or in the configuration data.
[0088] Action 902. The wireless device 10 performs the beam
tracking of one or more beams for the set of detected neighbour
cells for tracking the one or more best beams of respective
neighbour cell based on measured signal strength or measured signal
quality. The one or more beams may be larger than the number of
beams used for a cell quality derivation. The beam tracking may
comprise obtaining additional information, wherein the additional
information, such as preamble and/or radio resources, is used to
perform the random access procedure. An occurrence of a mobility
event such as any of the events A1-A6 or a wireless device movement
and/or a wireless device with a speed above a speed threshold, may
trigger the wireless device 10 to initiate the beam tracking.
Measurements of the beam tracking may be performed at a different
time scale compared to measurements used for RRM purposes. E.g. the
measurements may be snapshots closer in time to one another than
the measurements used for the RRM purposes, thus performed at a
different time scale. Since the measurements may be snapshots
closer in time to one another the measurements are collected
recently. Measurements of the beam tracking may use a different
time domain filtering and/or a frequency domain filtering; or the
measurements of the beam tracking may be performed on a different
reference signal compared to the measurements used for RRM
purposes. It should be noted that the tracking can be triggered by
the wireless device 10 even without received configuration data for
beam reporting.
[0089] Action 903. The wireless device 10 may select and store over
a time interval the one or more beams for each neighbour cell based
on the performed beam tracking. This results in having recent
updated one or more beams and not based on an outdated measurement.
The wireless device 10 may perform a full sweep of beams before
selecting the one or more beams in each neighbour cell. This is in
order to get select an beam or beams as accurate as possible.
[0090] Action 904. The wireless device 10 receives the indication
from the first radio network node 12, wherein the indication
indicates the target cell for the wireless device 10. The
indication may be a handover command or similar in an RRC
message.
[0091] Action 905. The wireless device 10, when the target cell is
in the set of detected neighbour cells, initiates the random access
procedure associated with the at least one target beam for the
target cell, wherein the at least one target beam is selected based
on the beam tracking performed prior to receiving the indication.
The wireless device 10 may select, in addition to the measured
signal strength or measured signal quality, the at least one target
beam further based on a list of allowed beams, i.e. to avoid black
list beams, for the target cell for the wireless device 10. The
random access procedure may be associated with the at least one
target beam by random access channel resources allocated for the at
least one target beam. E.g. certain random access resources such as
preamble and/or time and frequency resources are allocated for a
certain beam. In some embodiments, the wireless device 10 may
perform measurements on reference signals, such as CSI-RS and/or
SSBs, of the one or more beams for the set of detected neighbour
cells, and wherein the at least one target beam for the random
access procedure is selected based on the signal strength or
quality of respective beam. E.g. strongest beam or the beam
providing shortest RACH delay i.e. the first to appear.
[0092] The method actions performed by the radio network node,
exemplified herein as the first radio network node 12, for handling
communication of the wireless device in a wireless communication
network 1 according to some embodiments will now be described with
reference to a flowchart depicted in FIG. 9c. The actions do not
have to be taken in the order stated below, but may be taken in any
suitable order. Actions performed in some embodiments are marked
with dashed boxes. The first radio network node 12 serves the
wireless device 10. The wireless communication network 1 may
further comprise the second radio network node 13.
[0093] Action 911. The first radio network node 12 may in order to
configured the wireless device transmit configuration data to the
wireless device 10, wherein the configuration data indicates that
the wireless device is to perform beam tracking of one or more
beams for a set of detected neighbour cells and to, upon reception
of the indication, initiate a random access procedure associated
with at least one target beam for a target cell, wherein the at
least one target beam is selected based on a performed beam
tracking prior to receiving the indication, wherein the indication
indicates the target cell for the wireless device 10. The
configuration data may comprise one or more filter parameters for
measurements of the beam tracking and/or the configuration data
defines the wireless device 10 to monitor more beams of one
candidate cell than for another candidate cell. Hence, there can be
an configuration indication telling the wireless device 10 to
perform beam tracking so that at the moment the wireless device 10
receives the indication to perform random access (and then beam
selection before triggering random access) the wireless device 10
uses beam tracking information that it has been previously
configured to perform.
[0094] Action 912. The first radio network node 12 may receive from
the wireless device 10 one or more measurement reports of one or
more of detected neighbour cells such as the second service area
14.
[0095] Action 913. The first radio network node 12 may then select
the target cell for the wireless device 10 based on the measurement
report.
[0096] Action 914. The first radio network node 12 may then
transmit the indication to the wireless device 10, wherein the
indication indicates the target cell for the wireless device
10.
[0097] FIG. 9d is a combined flowchart and signalling scheme
according to embodiments herein wherein the neighbour cells a and b
are provided by the second radio network node 13 and a third radio
network node 15.
[0098] Action 921. The first radio network node 12 may transmit a
beam tracking configuration e.g. a neighbour cell beam tracking
configuration, to the wireless device 10. The neighbour cell beam
tracking information may comprise the set of neighbour cells to
perform beam tracking on as well as beam information such as
reference signals to track i.e. to perform measurements on.
[0099] Action 922. The wireless device 10 may receive the beam
tracking configuration and set up the wireless device for the beam
tracking. The configuration may contain (or comprise): K(i) number
of tracked beams per cell, N number of tracked cells, filter
parameters per beam and/or per neighbour cell, beam tracking
triggering info, CSI-RS configuration per neighbour cell etc. Beam
tracking is performed by continuously measuring signal strength
and/or quality of a beam (or a reference signal of a beam) and
keeping track of the measurements. Filter parameters may be an
evaluation period of measurements, a snapshot periodicity, and
average over time and frequency parameters.
[0100] Action 923. A neighbour cell `a`, e.g. provided by the third
radio network node 15, may transmit beamformed CSI-RSs or SS blocks
for its respective beam, e.g. for beams 1 to M(i) of that neighbour
cell.
[0101] Action 924. The neighbour cell `b`, e.g. provided by the
second radio network node 13, may transmit beamformed CSI-RSs or SS
blocks for respective beam, e.g. for beams 1 to M(i) of that
neighbour cell, e.g. service area 14.
[0102] Action 925. The wireless device 10 performs beam tracking,
also referred to as neighbour cell beam tracking, e.g. beam 2 in
neighbour cell `a` and beam 1 in neighbour cell `b`. For example,
measures signal strength or quality of CSI-RSs or SS blocks for
respective beams of respective cell.
[0103] Action 926. The wireless device 10 continues with the beam
tracking wherein measurement are updated according to e.g. the
filtering configuration, e.g. with a certain periodicity or
similar.
[0104] Action 927. The first radio network node 12 transmits a
handover command to the wireless device 10 indicating the neighbour
cell to handover the wireless device 10 to. E.g. the first radio
network node 12 transmits RRCConnectionReconfiguration with
mobilityControlinformation containing Cell ID and RACH
configuration, e.g. preamble, time and frequency resource, per DL
beam in the neighbour or target cell, e.g. cell `b`.
[0105] Action 928. The wireless device 10 is aware that beam 2 in
cell `b` is the best target beam from the beam tracking.
[0106] Action 929. The wireless device 10 looks up or selects the
RACH configuration for beam 2 in neighbour cell `b` from e.g. the
indication such as the HO command.
[0107] Action 930. The wireless device 10 transmits a random access
preamble, also referred to as RACH preamble, to the second radio
network node 13 based on the RACH configuration for beam 2.
[0108] Action 931. The second radio network node 13 selects the
beam of the RACH configuration. That is, based on the preamble
reception the second radio network node 13, such as a target
gNodeB, knows the best DL narrow beam to transmit e.g. a random
access response (RAR) on e.g. the beam 2.
[0109] Action 932. The second radio network node 13 transmits the
RAR in beam 2 to the wireless device 10.
[0110] Action 933. The wireless device 10 may then transmit an
RRCConnectionReconfiguration complete to the second radio network
node 13 confirming connection to the beam 2.
[0111] It is herein described in relation to the embodiments
herein: [0112] a tracking process, including potential triggers to
reduce the number of measurements needed, see e.g. action 1003;
[0113] reference signals that could be used for tracking, see e.g.
action 1002; [0114] wireless device actions upon receiving the HO
command (or equivalent) with the mapping between RACH and the DL
beam in the target, see e.g. action 1005. [0115] a SON function and
report associated to the SON function [0116] potential network
signalling and/or configuration for the wireless device actions,
see e.g. action 1001.
[0117] FIG. 10 is a schematic combined flowchart and signalling
scheme depicting some embodiments herein. The first radio network
node 12 is serving the wireless device 10 in the wireless
communication network 1, which comprises the second radio network
node 13.
[0118] Action 1001. The first radio network node 12 may transmit an
indication to the wireless device 10 indicating a set of candidate
neighbouring cells. That is, the first radio network node 12 may
configure the wireless device 10 with a set of candidates
neighbouring cells. The first radio network node 12 may further
configure beam-specific tracking filter parameters such as the
number of snapshots per evaluation periods e.g. 40 ms snapshots
within 200 ms.
[0119] The first radio network node 12 may also configure the
wireless device 10 with a 35 number K of best beams to track per
neighbour candidate. The first radio network node 12 may also have
K(i) as a function of specific neighbour cells i.e. for some
candidates the wireless device 10 may track more beams than for
some other neighbour cells. That can be useful, for example, in the
case there is a limitation in the maximum number of beams that
could be tracked and the first radio network node 12 is aware of a
more likely neighbour cell candidate then the wireless device 10
may possibly monitor more beams of this candidate than for another
neighbour cell candidate.
[0120] The first radio network node 12 may also configure the
wireless device 10 with a number M best cells to perform beam
tracking on. In other words, if the wireless device 10 detects a
maximum number of cells, only a subset of these may be candidates
for beam tracking.
[0121] The first radio network node 12 may also configure the
wireless device 10 to use embodiments herein or not, even on a cell
basis. That may depend on the network knowledge about the
periodicity the signals are being transmitted and/or the usage of
beamforming in the neighbour cells.
[0122] The first radio network node 12 may also configure the
wireless device 10 to use a given reference signal or sets of
reference signals for the feature. For example, as described above,
the wireless device 10 could be configured with the CSI-RS for the
tracking and/or signal(s) in the SS Block such as PSS, SSS, TSS
and/or DMRS for PBCH. This is some examples of the action 911 in
FIG. 9c.
[0123] Action 1002. The second radio network node 13 transmits its
beams, i.e. the second radio network node 13 transmits reference
signals (RS) associated with a respective beam, e.g. PSS, SSS, TSS,
DMRS, CSI-RS, BRS, or similar of respective beam.
[0124] Action 1003. The wireless device 10 performs beam tracking
of the N best beams of the set of detected neighbour cell
candidates. The wireless device 10 may track, repeatedly measure on
the reference signals transmitted from the network node, a number
of beams over a set time interval. The beam tracking may be
performed in a different time scale compared to the measurements
used for RRM purposes i.e. measurements to trigger mobility events
to support mobility, carrier aggregation, dual connectivity,
inter-RAT dual connectivity, i.e. dual connectivity from different
RATs such as LTE and NR tight interworking, procedures. E.g. the
measurements of the beam tracking may be performed more often i.e.
with a short periodicity compared to a periodicity of an RRM
measurement.
[0125] The tracking process can be performed as a filtering process
for filtering out beams with too low measured signal strength or
quality, which could either be configured by the network or done
via wireless device implementation. The wireless device 10 may
collect snapshots of the RSs transmitted in DL beams by the
neighbour cell candidates and may perform coherent and non-coherent
averages per beams. Filtering may occur in the time domain, the
frequency domain or both time and frequency domain. The N best
beams per snapshot may be detected based e.g. on peaks in the
signal to interference plus noise ratio (SINR), reference signal
received power (RSRP) or reference signal received quality (RSRQ),
and identified via some implicit or explicit beam identification in
the RS, e.g. time/frequency resources or even some identifier e.g.
TSS. For the beam tracking purpose, the snapshot may not combine
beam values, e.g. average, with each other but instead separate
them. The N best beams may e.g. be the instantaneous beam values at
time t(n-1).
[0126] Subsequent snapshots could be taken, e.g. not far apart from
each other. The wireless device 10 may collect multiple samples of
the same beam in the target cell and possibly combine them to form
some average per beam SINR or RSRP. If N varies from one snapshot
to another the wireless device 10 may discard or at least separate
beams with less samples. In the case subsequent samples are used,
the timing may be different compared to the timing used for the
cell level measurements since for the snapshots need to be much
closer in time otherwise these will be outdated measurements at the
moment of the handover.
[0127] The wireless device 10 may constantly perform this tracking
process for each detected neighbour cell (or explicitly configured
neighbour cell by the first radio network node). The wireless
device 10 may perform the beam tracking right after detecting that
a given cell is a neighbour cell candidate. The advantage of
triggering the beam tracking even before any report is transmitted
is that the network may trigger blind or semi-blind handovers or
blind or semi-blind establishment of dual connectivity or carrier
aggregation or tight interworking with LTE via dual connectivity
i.e. at that time the wireless device 10 would already have these
per beam measurements. Alternatively, the wireless device 10 may
start the beam tracking (tracking process) only after triggering
one of the configured mobility events (such as events similar to
the events A1, A2, . . . , A6 in LTE) or after sending one of these
in measurement reports. That may relax the wireless device 10
constraint to not have to perform per beam measurements and store
them.
[0128] The wireless device 10 may be configured with a special
mobility event that triggers the wireless device 10 to initiate per
beam measurements. The special mobility events may be a conditional
event i.e. only triggered after one of the mobility events like
events A1, A2, . . . , A6 in LTE are triggered. Alternatively, that
is simply done via threshold adjustment or alignment of the
events.
[0129] The wireless device 10 may be configured by the first radio
network node 12 to initiate the beam tracking for a set of specific
target cells, possibly previously reported as good candidates or
known by the first radio network node 12 as possibly detectable by
the wireless device 10.
[0130] The beam tracking or tracking procedure may also contain
aspects related to the beamforming of the wireless device 10, both
in terms of wireless device reception beamforming to detect the
strongest DL beam or/and wireless device transmission beamforming
to transmit the RACH preamble associated to the strongest being the
best DL beam in the target. For example, the wireless device 10 may
perform a full sweep of its Reception (Rx) beamforming, i.e.
measuring on all possible beams of each cell, before selecting the
best beam in each target candidate cell. That may provide
additional information, especially in the case the measurements per
beam have low SINR, RSRP, or RSRQ. The wireless device 10 may use
the additional information to improve its PRACH preamble
transmission i.e. to send the equivalent direction. This would be a
tracking of the best Transmission (Tx) beam of the wireless device
10 to transmit the RACH in the target.
[0131] Other potential triggers of the beam tracking may be related
to the wireless device movements or wireless device speed where
beam tracking becomes even more important.
[0132] The wireless device 10 may perform beam tracking on always
on or periodic reference signals that are transmitted in DL beam by
the neighbour cells. These could be any signal in the SS Block,
such as the PSS, the SSS, the TSS and/or DMRSs defined for the PBCH
demodulation. In that case, the neighbour cell identification may
be done via the PSS and/or SSS, while the TSS may be used to
distinguish the beams, if subsequent snapshots are needed.
[0133] The wireless device 10 perform beam tracking on, in addition
and/or instead, CSI-RSs. These CIS-RSs may be configured per
neighbour cell e.g. after measurement reports are transmitted by
the wireless device 10 indicating the best cells. In the case the
wireless device 10 reports best beams per cell (e.g. based on the
long term averages done per cell) the network can use that
information to trigger narrow CSI-RS beams to be monitored instead
of a full sweep for the target cell candidates, i.e. the number of
RS searched for may be reduced. The wireless device 10 may be aware
of the CSI-RS transmissions in the target cell, e.g. the
time/frequency resources that are transmitted, the bandwidth,
sequences to search for, etc.). That could have been previously
configured by the network as part of the measurement configuration
in the serving cell. These are examples of the action 902 in FIG.
9b.
[0134] Action 1004. The first radio network node 12 may decide to
request a handover for the wireless device 10 (or a set of wireless
devices) to a specific candidate target service area associated to
the second radio network node 13. The first radio network node 12
then transmits, to the wireless device 10, a handover command or a
message indicating a handover of the wireless device to the second
radio network node 13 being examples of the indication in action
904 in FIG. 9b and action 914 in FIG. 9c.
[0135] Action 1005. Upon receiving the indication such as the
handover command (e.g. RRCConnectionReconfiguration with
mobilityControlInformation or equivalent), that indication is to be
used to trigger a handover or the establishment of a secondary
cell, the wireless device 10 uses the result of the beam tracking
(up-to-date information) to initiate random access procedure with
the target, i.e. the second radio network node 13, without
necessarily waiting to perform additional measurements to select
the best DL beam to map to its configured RACH resources.
[0136] The wireless device 10 has up-to-date information about the
best DL beam for a set or subset of the neighbour cells. If the
target cell indicated in the HO command is within the set of the
neighbour cells for which the wireless device 10 has up-to-date
measurements concerning the best beam (where up-to-date can be
defined by the network or via implementation, although that may
probably be defined as some time elapsed from the latest snapshot
to the time the HO command is received) and the best beam is in a
list of allowed beams for the target (jointly with the RACH
configuration per beam) the wireless device 10 may initiate a
random access procedure to the radio network node associated with
the best beam by sending a preamble in the HO command per DL
matching the best beam. In other words, the wireless device 10 may
send the configured preamble in the time-frequency resources
matching the best DL beam in the target cell based on the performed
beam tracking.
[0137] If the target cell indicated in the HO command is within the
set of the neighbour cells for which the wireless device 10 has
up-to-date measurements concerning the best beam (where up-to-date
can be defined by the network or via implementation, although that
would be some time elapsed from the latest snapshot to the time the
HO command is received) but the best beam is not in the list of
allowed beams for the target (jointly with the RACH configuration
per beam) the wireless device 10 may check the availability of the
second best beam associated to that target. Notice that
availability may depend whether the wireless device 10 has
performed measurement for the best or also for the other K-1 best
beams per target. On the network side, K best beams for tracking
could have been configured when it is known that target cells might
be overloaded so that it is might be good if the wireless device 10
has some alternative beams to access. If the HO command contains
one of the tracked K-1 best beams the wireless device 10 initiates
a random access procedure assuming that one as the best beam by
sending a preamble in the HO command per DL matching the best beam.
In other words, the wireless device 10 may send the configured
preamble in the time-frequency resources matching the k-th best DL
beam in the target cell based on the tracking depending on the
availability of measurements.
[0138] If the target cell indicated in the HO command is within the
set of the neighbour cells for which the wireless device 10 has
up-to-date measurements concerning the best beam (where up-to-date
can be defined by the network or via implementation, although that
would be some time elapsed from the latest snapshot to the time the
HO command is received) but is any of the available k-th best beam
in the list of allowed beams for the target (jointly with the RACH
configuration per beam) the wireless device 10 may trigger a
fallback procedure and wait to select the best beam in the target
cell before initiating random access.
[0139] If the target cell indicated in the HO command is not within
the set of the neighbour cells for which the wireless device 10 has
up-to-date measurements concerning the best beam (where up-to-date
can be defined by the network or via implementation, although that
would be some time elapsed from the latest snapshot to the time the
HO command is received) then the wireless device 10 triggers the
fallback procedures as described in the previous paragraph i.e.
wait to select the best beam in the configured target cell before
initiating random access. In that particular case synchronization
may be needed.
[0140] These are examples of the action 905 in FIG. 9b.
[0141] Action 1006. The wireless device 10 then sends the RACH
preamble to the second radio network node 13 e.g. transmit the
configured preamble in the time-frequency resources matching the
best DL beam in the target cell based on the performed beam
tracking.
[0142] Action 1007. Upon the reception of the RACH preamble in the
time/frequency resource that maps to a given DL beam, the second
radio network node 13 detects what is the strongest DL narrow beam
covering the wireless device 10.
[0143] Action 1008. The second radio network node 13 may then
respond to the wireless device with a random access response (RAR)
to the wireless device 10. This may be transmitted using the
detected beam or another beam.
[0144] Action 1009. The second radio network node 13 may then
perform user plane (UP) communication (DL or UL) with the wireless
device 10 using the narrow beam associated with the RACH
configuration of the random access procedure performed by the
wireless device 10.
[0145] Thus, embodiments herein disclose the wireless device 10
tracking beams of the target neighbour cell candidates to improve
the handover performance in terms of latency.
[0146] It is herein disclosed 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 performs
a beam tracking of one or more best beams for (or of) a set of
detected neighbour cells (candidates). The wireless device further
receives an indication, e.g. a handover command, from the first
radio network node, which indication indicates a handover of the
wireless device to a neighbour cell. When the neighbour cell is in
the set of detected neighbour cells, the wireless device initiates
a random access procedure associated with the best beam according
to the beam tracking for that neighbour cell.
[0147] It is herein disclosed a method performed by a 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 configuration data i.e. configures the wireless device
with data, which data indicates that the wireless device is to
perform beam tracking of one or more best beams for (or of) a set
of detected neighbour cells.
[0148] According to embodiments herein the wireless device performs
beam tracking of N best beams of (or from) a set of detected
neighbour cell candidates. That can be performed in a different
time scale compared to the measurements used for RRM purposes i.e.
to trigger mobility events to support mobility, carrier
aggregation, dual connectivity, inter-RAT dual connectivity (LTE/NR
tight interworking) procedures.
[0149] The previous embodiments describe the DL beam selection
performed on neighbour cells to speed up the handover execution. In
this embodiment the wireless device 10 may perform a DL beam
selection on its serving cell to speed up beam recovery procedure
where the wireless device 10 sends an UL message to inform the
first radio network node which DL wide beams should be used to
transmit to the wireless device 10 its DL control channel e.g.
Physical Downlink Control Channel (PDCCH). If the embodiment is not
implemented, the wireless device 10 would need to detect the
failure based on narrow beamformed DL signals (such as CSI-RS),
wait for the next occurrence of cell based wide beam transmissions
in an SS Block Set and, based on that DL reference transmits an UL
message (e.g. a scheduling request on Physical Uplink Control
Channel (PUCCH) or RACH preamble on PRACH). In any case beam
recovery relies on the wireless device 10 detecting the best
available DL beam as timing reference so the network, the first
radio network node, can be detecting the right direction (e.g. with
analog beamforming).
[0150] The proposed tracking for the serving cell in this
embodiment for beam recovery occurs as follows: the L1 of the
wireless device 10 collects a snapshot and/or sample of SS Block
Burst and/or Burst Set and provide cell level quality to L3. The
wireless device 10 then stores the values of the N best beams that
will be filtered every measurement window period. These are
constantly stored at the wireless device 10 and updated according
to a beam-based filter, which could be configured by the network.
When a beam failure process is detected, such as based on PDCCH
failure and/or narrow DL beam failure, the wireless device 10 may
try to choose a DL reference in a wide beam. Thanks to beam
tracking, immediately after the detection of narrow beam failure
the wireless device 10 can trigger the beam recovery i.e. without
waiting for the next occurrence of an SS Block Set which may take
160 ms in some scenarios. At the network side e.g. the first radio
network node 12, the detection of the UL signal allows the network
to transmit in a wide beam the PDCCH for that wireless device 10 to
either schedule data or confirm a successful recovery. The wireless
device has the N best, so if a confirmation is expected during some
kind of window (e.g. beam recovery RAR window) the wireless device
10 may transmit the request associated to the second best and so
on.
[0151] Embodiments herein also cover a possible Self Organizing
Network (SON) function to optimize the procedure.
[0152] SON Function and Report Associated to the SON Function
[0153] In the fallback case, e.g. when the target cell indicated in
the HO command is not within the set of the neighbour cells
mentioned in action 1004, the wireless device 10 may have been
previously configured by the network to store the information that
a "failure" has occurred i.e. none of the best beams were in the
subset allowed by the target. That may be reported in a message
such as a HO complete message, or equivalent in the case of dual
connectivity (DC), in the target and forwarded to the serving cell,
via an inter-node interface like Xn in NR. That can be used as an
input to SON functions so in future configurations the serving and
target cells may allow that beam to be accessed and/or trigger the
CSI-RS beams associated to that best beam(s) in the target(s). The
message indicating failure may also be requested by the network
e.g. a network node such as a MME or similar, after the wireless
device 10 is connected to the second radio network node 13.
[0154] The message may be stored at least in one of these two
cases, with the following information: [0155] HO command contains a
cell that was not in the set such as a list of neighbour cells on
which the wireless device 10 was performing beam tracking. In that
case the message, also referred to as a report, may contain the
target cell ID, the serving cell ID, the beams tracked in each
neighbour candidate and their RSRP (or equivalent) values. [0156]
HO command contains a cell that was in the list the wireless device
10 was performing neighbour cell beam tracking, however, any of the
beams tracked for that neighbour cell were not in the allowed list
of accessible beams. In that case, the wireless device 10 stores
and reports target cell ID, the serving cell ID, the beams tracked
in each neighbour candidate and their RSRP (or equivalent) values.
Other information is not precluded.
[0157] The message may be a single report or different reports for
different failures i.e. the two cases.
[0158] The purpose of these reports could be to either allow the
network such as the network node to activate more beams for certain
target cells in the future, enable target cells to trigger specific
DL beams to transmit CSI-RS to assist CSI-RS based handovers and/or
RRM measurements (on demand), etc.
[0159] FIG. 11 is a block diagram depicting two embodiments of the
wireless device 10 according to embodiments herein for handling
communication of the wireless device 10 in the wireless
communication network 1, wherein the wireless communication network
1 comprises the radio network node such as the first radio network
node 12 being configured to serve the wireless device 10. The
wireless communication network 1 may further comprise the second
radio network node 13.
[0160] The wireless device 10 may comprise processing circuitry
1101, e.g. one or more processors, configured to perform the
methods herein.
[0161] The wireless device 10 may comprise a beam tracking module
1102. The wireless device 10, the processing circuitry 1101, and/or
the beam tracking module 1102 is configured to perform the beam
tracking of one or more beams for the set of detected neighbour
cells for tracking one or more best beam of respective neighbour
cell based on measured signal strength or measured signal quality.
E.g. perform beam tracking of one or more best beams from (or of) a
set of detected neighbour cell candidates. The wireless device 10,
the processing circuitry 1101, and/or the beam tracking module 1102
may be configured to select and store over a time interval one or
more beams for each neighbour cell based on the performed beam
tracking. The wireless device 10, the processing circuitry 1101,
and/or the beam tracking module 1102 may be configured to perform
the beam tracking by being configured to perform a full sweep of
beams before selecting the one or more beams in each neighbour
cell. The wireless device 10, the processing circuitry 1101, and/or
the beam tracking module 1102 may be configured to obtain
additional information during the beam tracking, wherein the
additional information is used to perform the random access
procedure. The wireless device 10, the processing circuitry 1101,
and/or the beam tracking module 1102 may be configured to initiate
the beam tracking being triggered by an occurrence of a mobility
event. The wireless device 10, the processing circuitry 1101,
and/or the beam tracking module 1102 may be configured to perform
measurements of the beam tracking at a different time scale
compared to measurements used for RRM purposes. E.g. the
measurements may be snapshots closer in time to one another than
the measurements used for the RRM purposes.
[0162] The wireless device 10 may comprise a receiving module 1103,
e.g. a receiver or a transceiver. The wireless device 10, the
processing circuitry 1101, and/or the receiving module 1103 is
configured to receive the indication from the radio network node
12, wherein the indication indicates the target cell for the
wireless device 10. The indication e.g. a handover command
indicates a handover of the wireless device to a neighbour
cell.
[0163] The wireless device 10 may comprise an initiating module
1104, e.g. a transmitter or a transceiver. The wireless device 10,
the processing circuitry 1101, and/or the initiating module 1104 is
configured to initiate, when the target cell is in the set of
detected neighbour cells, the random access procedure associated
with the at least one target beam for the target cell, and wherein
the wireless device 10, the processing circuitry 1101, and/or the
initiating module 1104 is further configured to select the at least
one target beam based on the beam tracking performed prior to
receiving the indication. The random access procedure may be
associated with the at least one target beam by random access
channel resources allocated for the at least one target beam. The
wireless device 10, the processing circuitry 1101, and/or the
initiating module 1104 may be configured to initiate the random
access procedure based on the received indication and a result of
the beam tracking performed. The wireless device 10, the processing
circuitry 1101, and/or the initiating module 1104 may be configured
to initiate a random access procedure to the radio network node
associated with the best beam for the indicated neighbour cell in
the HO command by sending a preamble per the best beam. The
wireless device 10, the processing circuitry 1101, and/or the beam
tracking module 1102 may be configured to perform the beam tracking
by being configured to perform measurements on reference signals,
such as SSB or CSI-RS, of the one or more beams for the set of
detected neighbour cells, these may be the same or different
compared to measurements for RRM purposes. The wireless device 10,
the processing circuitry 1101, and/or the initiating module 1104
may then be configured to select the at least one target beam for
the random access procedure based on the signal strength or quality
of respective beam. The wireless device 10, the processing
circuitry 1101, and/or the initiating module 1104 may then be
configured to select the at least one target beam further based on
the list of allowed beams for the target cell for the wireless
device 10.
[0164] The wireless device 10 may comprise a configuring module
1105. The wireless device 10, the processing circuitry 1101, and/or
the configuring module 1105 may be configured to receive
configuration data from the radio network node 12. The
configuration data may indicate to the wireless device to perform
the methods herein, i.e. the configuration data indicates that the
wireless device 10 is to perform beam tracking of one or more beams
for a set of detected neighbour cells and upon reception of the
indication to initiate a random access procedure associated with
the at least one target beam for a target cell, wherein the at
least one target beam is selected based on a performed beam
tracking prior to receiving the indication, wherein the indication
indicates the target cell for the wireless device. The
configuration data may further comprise one or more filter
parameters for measurements of the beam tracking and/or the
configuration data may define the wireless device 10 to monitor
more beams of one candidate cell than for another candidate
cell.
[0165] The wireless device 10 further comprises a memory 1106. The
memory comprises one or more units to be used to store data on,
such as RS configurations, mappings, beam tracking, mobility
events, strengths or qualities, set of neighbour cells, parameters,
applications to perform the methods disclosed herein when being
executed, and similar. The wireless device 10 may further comprise
a communication interface 1109 comprising e.g. a transmitter, a
transceiver, a receiver, and/or one or more antennas.
[0166] The methods according to the embodiments described herein
for the wireless device 10 are respectively implemented by means of
e.g. a computer program 1107 or a computer program product,
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 1107 may be stored
on a computer-readable storage medium 1108, e.g. a disc, a
universal serial bus (USB) stick or similar. The computer-readable
storage medium 1108, having stored thereon the computer program,
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 or a transitory
computer-readable storage medium.
[0167] Thus, the wireless device may comprise the processing
circuitry and the memory, said memory comprising instructions
executable by said processing circuitry whereby said wireless
device 10 is operative to perform the methods herein.
[0168] FIG. 12 is a block diagram depicting two embodiments of the
radio network node exemplified as the first radio network node 12
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 may further comprise the
second radio network node 13.
[0169] The first radio network node 12 may comprise processing
circuitry 1201, e.g. one or more processors, configured to perform
the methods herein.
[0170] The first radio network node 12 may comprise a configuring
module 1202, e.g. a transmitter or a transceiver. The first radio
network node 12, the processing circuitry 1201, and/or the
configuring module 1202 is configured to transmit configuration
data to the wireless device 10. The configuration data indicates
that the wireless device 10 is to perform the methods herein i.e.
to perform beam tracking of the one or more beams for the set of
detected neighbour cells and to, upon reception of the indication,
initiate a random access procedure associated with at least one
target beam for a target cell, wherein the at least one target beam
is selected based on a performed beam tracking prior to receiving
the indication, wherein the indication indicates the target cell
for the wireless device 10. The configuration data may further
comprise one or more filter parameters for measurements of the beam
tracking and/or the configuration data defines the wireless device
10 to monitor more beams of one candidate cell than for another
candidate cell.
[0171] The first radio network node 12 may comprise a transmitting
module 1203, e.g. a transmitter or a transceiver. The first radio
network node 12, the processing circuitry 1201, and/or the
transmitting module 1203 may be configured to transmit the
indication, e.g. the handover command, to the wireless device
10.
[0172] The first radio network node 12 further comprises a memory
1204. The memory comprises one or more units to be used to store
data on, such as RS configurations, mappings, indications,
messages, set of neighbour cells, strengths or qualities,
parameters, applications to perform the methods disclosed herein
when being executed, and similar. The first radio network node 12
may further comprise a communication interface 1207 comprising e.g.
a transmitter, a transceiver, a receiver, and/or one or more
antennas.
[0173] 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 1205 or a computer program
product, 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
1205 may be stored on a computer-readable storage medium 1206, e.g.
a disc, a USB stick, or similar. The computer-readable storage
medium 1206, having stored thereon the computer program, 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 or a
transitory computer-readable storage medium.
[0174] Thus, the first radio network node 12 may comprise the
processing circuitry and the memory, said memory comprising
instructions executable by said processing circuitry whereby said
radio network node is operative to perform the methods herein.
[0175] 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.
[0176] It should be noted that in a general scenario the term
"radio network node" can be substituted with "transmission and
reception point". It is allowed 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.
[0177] It should further be noted that a wireless communication
network may be virtually network sliced into a number of Network
(and/or RAN) slices, each Network (and/or 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 (and/or 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 (and/or 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 (and/or RAN) slice may comprise a network node such as a
RAN node and/or a core network node.
[0178] 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.
[0179] 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
Frequency Division Duplex/Time Division Duplex (FDD/TDD),
WCDMA/HSPA, GSM/GERAN, Wi Fi, WLAN, CDMA2000 etc.
[0180] 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.
[0181] 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.
[0182] 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, and the memory may comprise
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.
[0183] 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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