U.S. patent application number 16/324761 was filed with the patent office on 2019-06-13 for communication system.
This patent application is currently assigned to NEC CORPORATION. The applicant listed for this patent is NEC CORPORATION. Invention is credited to Robert ARNOTT, Yassin Aden AWAD, Neeraj GUPTA, Chadi KHIRALLAH.
Application Number | 20190182683 16/324761 |
Document ID | / |
Family ID | 56985963 |
Filed Date | 2019-06-13 |
United States Patent
Application |
20190182683 |
Kind Code |
A1 |
KHIRALLAH; Chadi ; et
al. |
June 13, 2019 |
COMMUNICATION SYSTEM
Abstract
A communication system is disclosed in which a base station
serves a communication area, wherein the communication area is
formed by a plurality of directional beams each covering a
respective portion of the communication area and each having a
different respective beam identifier. The base station communicates
control information, for a communication device (UE), using at
least one directional beam associated with that communication
device (e.g. a UE-specific operational beam set).
Inventors: |
KHIRALLAH; Chadi; (Epsom,
GB) ; AWAD; Yassin Aden; (Uxbridge, GB) ;
GUPTA; Neeraj; (Sutton, GB) ; ARNOTT; Robert;
(London, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEC CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
NEC CORPORATION
Tokyo
JP
|
Family ID: |
56985963 |
Appl. No.: |
16/324761 |
Filed: |
August 10, 2017 |
PCT Filed: |
August 10, 2017 |
PCT NO: |
PCT/JP2017/029061 |
371 Date: |
February 11, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 16/28 20130101;
H04B 7/024 20130101; H04W 24/08 20130101; H04B 7/0621 20130101;
H04B 7/0695 20130101 |
International
Class: |
H04W 16/28 20060101
H04W016/28; H04B 7/06 20060101 H04B007/06; H04W 24/08 20060101
H04W024/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2016 |
GB |
1613902.4 |
Claims
1. A base station for a communication system, wherein the base
station comprises: a controller and a transceiver; wherein the
controller is configured to control communication in a
communication area served by the base station, wherein the
communication area is formed by a plurality of directional beams
each covering a respective portion of the communication area served
by the base station and each having a different respective beam
identifier; and wherein the transceiver is configured to
communicate control information, for at least one communication
device, using at least one directional beam associated with the at
least one communication device.
2. The base station according to claim 1, wherein the controller is
configured to control, for each communication device, a respective
operational beam set, OBS, comprising at least one directional beam
associated with that communication device.
3. The base station according to claim 2, wherein the transceiver
is configured to receive from at least one communication device
results of measurements performed on respective reference signals
transmitted, via each beam, and wherein the controller is
configured to determine each beam in said OBS based on the results
of measurements performed on the reference signals.
4. The base station according to claim 3, wherein the transceiver
is configured to receive from at least one communication device
results of OBS specific measurements (e.g. channel state indicator,
CSI, measurements) for beams that are included in the OBS for that
at least one communication device.
5. The base station according to claim 3 or 4, wherein the
controller is configured to control a handover for a particular
communication device based on at least one of: the OBS associated
with that communication device and beam specific reference
signals.
6. The base station according to any one of claims 3 to 5, wherein
the controller is configured to control a co-ordinated multipoint,
CoMP, transmission/reception for a particular communication device
based on at least one of: the OBS associated with that
communication device and beam specific reference signals.
7. The base station according to any one of claims 3 to 6, wherein
the transceiver is configured to transmit, via each beam,
respective control information comprising reference signals.
8. The base station according to claim 7, wherein the respective
reference signals transmitted via each beam are beam specific
reference signals.
9. The base station according to claim 7 or 8, wherein the
transceiver is configured to transmit the respective reference
signals in each beam periodically, using predefined resources (e.g.
time/frequency resources).
10. The base station according to claim 9, wherein the predefined
resources are specific to a particular beam.
11. The base station according to claim 9, wherein the predefined
resources are common to a plurality (e.g. a subset or all)
beams.
12. The base station according to any one of claims 3 to 11,
wherein the respective reference signals transmitted via each beam
depend on the corresponding beam identifier and a cell identifier
associated with the communication area.
13. The base station according to any one of claims 3 to 11,
wherein resources used for transmitting the respective reference
signals via each beam depend on the corresponding beam identifier
and a cell identifier associated with the communication area.
14. The base station according to any one of claims 1 to 13,
wherein the controller is operable to control a beam configuration
associated with the communication area of the base station, and
wherein the transceiver is configured to transmit (e.g. broadcast),
within the communication area, the beam configuration associated
with that communication area.
15. The base station according to claim 14, wherein the beam
configuration defines at least one of: a number of beams in the
communication area, a beam pattern in the communication area, a
respective width associated with each beam, whether a particular
beam is turned on or off, resources used for transmitting a
reference signal (or a set of reference signals) in a particular
beam, resources allocated for random access procedure per beam.
16. The base station according to any one of claims 1 to 15,
wherein the transceiver is configured to communicate respective
beam specific system information using each directional beam.
17. The base station according to any one of claims 1 to 16,
wherein the transceiver is configured to communicate, over each
beam, information identifying resources for random access procedure
signalling over that beam.
18. The base station according to claim 17, wherein the transceiver
is configured to receive, from the at least one communication
device over at least one beam, random access procedure signalling
using the identified resources.
19. The base station according to any one of claims 1 to 18,
wherein the transceiver is configured to apply transmission
diversity, for the at least one communication device, using a
plurality of directional beams associated with the at least one
communication device.
20. The base station according to any one of claims 1 to 19,
wherein the transceiver is configured to transmit, using the
plurality of directional beams associated with the at least one
communication device, signalling which is not specific to the at
least one communication device (e.g. RAR message 2 and message 4,
power control, and/or paging).
21. The base station according to any one of claims 1 to 20,
comprising a massive antenna for forming a plurality of directional
beams.
22. The base station according to any one of claims 1 to 21,
comprising a base station of a next generation, NextGen, radio
access network.
23. A communication device for a communication system comprising a
base station serving a communication area formed by a plurality of
directional beams each covering a respective portion of the
communication area and each having a different respective beam
identifier, wherein the communication device comprises: a
controller and a transceiver; wherein the transceiver is configured
to receive control information, from the base station, using at
least one directional beam associated with the communication
device.
24. The communication device according to claim 23, wherein the at
least one directional beam associated with the communication device
forms part of an operational beam set, OBS, associated with the
communication device in that communication area.
25. The communication device according to claim 24, wherein the
controller is configured to perform measurements on respective
reference signals transmitted, via each beam, and wherein the
transceiver is configured to send the results of the measurements
to the base station.
26. The communication device according to claim 25, the controller
is configured to perform measurements (e.g. channel state
indicator, CSI, measurements) for beams that are included in the
OBS for the communication device, and wherein the transceiver is
configured to send the results of the measurements to the base
station.
27. The communication device according to any one of claims 24 to
26, wherein the controller is operable to control a co-ordinated
multipoint, CoMP, transmission/reception via the base station based
on at least one of: the OBS associated with the communication
device in that communication area and beam specific reference
signals.
28. The communication device according to any one of claims 23 to
27, wherein the transceiver is operable to receive, via each beam,
respective control information comprising reference signals.
29. The communication device according to claim 28, wherein the
respective reference signals in each beam depend on the
corresponding beam identifier and a cell identifier associated with
the communication area.
30. The communication device according to claim 28 or 29, wherein
resources used for receiving the respective reference signals via
each beam depend on the corresponding beam identifier and a cell
identifier associated with the communication area.
31. The communication device according to any one of claims 23 to
30, wherein when the base station communicates data using
transmission diversity, the controller is configured to combine
respective data received using each of a plurality of directional
beams before decoding the data.
32. A system comprising the base station according to any one of
claims 1 to 22, and the communication device according to any one
of claims 23 to 31.
33. A method performed by a base station in a communication system,
the method comprising: controlling communication in a communication
area served by the base station, wherein the communication area is
formed by a plurality of directional beams each covering a
respective portion of the communication area served by the base
station and each having a different respective beam identifier; and
communicating control information, for at least one communication
device, using at least one directional beam associated with the at
least one communication device.
34. A method performed by a communication device in a communication
system comprising a base station serving a communication area
formed by a plurality of directional beams each covering a
respective portion of the communication area and each having a
different respective beam identifier, the method comprising:
receiving control information, from the base station, using at
least one directional beam associated with the communication
device.
35. A computer implementable instructions product comprising
computer implementable instructions for causing a programmable
communications device to perform the method according to claim 33
or 34.
Description
TECHNICAL FIELD
[0001] The present invention relates to a communication system. The
invention has particular but not exclusive relevance to wireless
communication systems and devices thereof operating according to
the 3rd Generation Partnership Project (3GPP) standards or
equivalents or derivatives thereof. The invention has particular
although not exclusive relevance to mobility in the so-called `Next
Generation` systems using beamforming.
BACKGROUND ART
[0002] The latest developments of the 3GPP standards are referred
to as the Long Term Evolution (LTE) of Evolved Packet Core (EPC)
network and Evolved UMTS Terrestrial Radio Access Network
(E-UTRAN), also commonly referred as `4G`. In addition, the term
`5G` and `new radio` (NR) refer to an evolving communication
technology that is expected to support a variety of applications
and services. Various details of 5G networks are described in, for
example, the `NGMN 5G White Paper` V1.0 by the Next Generation
Mobile Networks (NGMN) Alliance, which document is available from
https://www.ngmn.org/5g-white-paper.html. 3GPP intends to support
5G by way of the so-called 3GPP Next Generation (NextGen) radio
access network (RAN) and the 3GPP NextGen core network.
[0003] Under the 3GPP standards, a NodeB (or an eNB in LTE, gNB in
5G) is the base station via which communication devices (user
equipment or `UE`) connect to a core network and communicate to
other communication devices or remote servers. For simplicity, the
present application will use the term base station to refer to any
such base stations and use the term mobile device or UE to refer to
any such communication device. The core network (i.e. the EPC in
case of LTE) hosts functionality for subscriber management,
mobility management, charging, security, and call/session
management (amongst others), and provides connection for
communication devices to external networks, such as the
Internet.
[0004] Communication devices might be, for example, mobile
communication devices such as mobile telephones, smartphones, user
equipment, personal digital assistants, laptop/tablet computers,
web browsers, e-book readers and/or the like. Such mobile (or even
generally stationary) devices are typically operated by a user,
although it is also possible to connect so-called `Internet of
Things` (IoT) devices and similar machine-type communication (MTC)
devices to the network. For simplicity, the present application
refers to mobile devices (or UEs) in the description but it will be
appreciated that the technology described can be implemented on any
communication devices (mobile and/or generally stationary) that can
connect to a communications network for sending/receiving data,
regardless of whether such communication devices are controlled by
human input or software instructions stored in memory.
[0005] 3GPP technical report (TR) 23.799 V0.7.0 describes a
possible architecture and general procedures for NextGen (5G)
systems planned for Release 14 of the 3GPP standards. 3GPP also
studied the potential use of frequency bands up to 100 GHz for new
(5G) radio access networks. Directional beamforming and massive
antenna technologies may also be used in order to overcome the
severe channel attenuation characteristics associated with certain
high frequency bands (e.g. mmWave bands). The term `massive
antenna` refers to an antenna having a high number of antenna
elements (e.g. 100 or more) arranged in an array. Effectively, such
a massive antenna may be used to communicate with several users at
the same time, thus facilitating multi-user MIMO (multiple-input
and multiple-output) transmissions. A base station (also referred
to as a transmission and reception point (TRP) in this case) may be
configured to form respective beams for communicating with a
plurality of UEs substantially concurrently and using associated
directional beams.
[0006] 3GPP has agreed on a number of intra-5G mobility related
requirements. Specifically, 3GPP intends to provide one or more
TRPs per new radio (NR) base station (i.e. 5G base station, or
gNB). As baseline, each NR is expected to support a state with
network controlled mobility handling and a state with UE controlled
mobility. The measurement configuration associated with typical
inter-gNB network controlled mobility is kept minimised. Therefore,
each UE is required to perform fewer (and possibly less detailed)
measurements for mobility purposes (e.g. avoid the need to provide
detailed `cell` level information). However, more detailed
information may be requested in some cases. 3GPP also intends to
minimise context move (between base stations) as a consequence of
UE based mobility.
[0007] Network controlled mobility may be either RRC-driven at cell
level (i.e. using appropriate radio resource control (RRC)
signalling between the gNB and the UE to control UE mobility) or
may be provided with zero/minimum RRC involvement (e.g. at MAC/PHY
layer).
SUMMARY OF INVENTION
Technical Problem
[0008] However, especially in high frequency bands, an obstruction
(e.g. by an obstacle) of the direct, line-of-sight (LOS) path
between a transmitter and receiver and/or mobility of the UE may
result in a degradation of the radio link quality for that UE.
Moreover, some studies suggest that at mmWave frequencies the radio
channel can change very rapidly and this may also result in an
increase in transmission errors and/or the number of handovers for
a particular UE. Therefore, UEs served via directional beams may be
prone to losing connection with their base station and data loss.
Moreover, existing (e.g. LTE) mobility techniques are not
applicable to 5G RANs due to the technological differences and
bandwidths used.
[0009] It is foreseen that the relative unreliability of high
frequencies and directional beams may lead to frequent changes in
the beam used by an active UE and its 5G base station/TRP. This may
result in, for example, increased session interruption (inter-beam
handover), signalling overhead, and/or transmission inefficiencies
(e.g. an increased need for retransmissions).
[0010] Accordingly, preferred example embodiments of the present
invention aim to provide methods and apparatus which address or at
least partially deal with the above issues.
[0011] Although for efficiency of understanding for those of skill
in the art, the invention will be described in detail in the
context of a 3GPP system (5G networks), the principles of the
invention can be applied to other systems.
Solution to Problem
[0012] In one aspect, the invention provides a base station for a
communication system, wherein the base station comprises: a
controller and a transceiver; wherein the controller is configured
to control communication in a communication area served by the base
station, wherein the communication area is formed by a plurality of
directional beams each covering a respective portion of the
communication area served by the base station and each having a
different respective beam identifier; and wherein the transceiver
is configured to communicate control information, for at least one
communication device, using at least one directional beam
associated with the at least one communication device.
[0013] In another aspect, the invention provides a communication
device for a communication system comprising a base station serving
a communication area formed by a plurality of directional beams
each covering a respective portion of the communication area and
each having a different respective beam identifier, wherein the
communication device comprises: a controller and a transceiver;
wherein the transceiver is configured to receive control
information, from the base station, using at least one directional
beam associated with the communication device.
[0014] Aspects of the invention extend to corresponding systems,
methods, and computer program products such as computer readable
storage media having instructions stored thereon which are operable
to program a programmable processor to carry out a method as
described in the aspects and possibilities set out above or recited
in the claims and/or to program a suitably adapted computer to
provide the apparatus recited in any of the claims.
[0015] Each feature disclosed in this specification (which term
includes the claims) and/or shown in the drawings may be
incorporated in the invention independently of (or in combination
with) any other disclosed and/or illustrated features. In
particular but without limitation the features of any of the claims
dependent from a particular independent claim may be introduced
into that independent claim in any combination or individually.
[0016] Example embodiments of the invention will now be described,
by way of example, with reference to the accompanying drawings in
which:
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 illustrates schematically a cellular
telecommunication system to which example embodiments of the
invention may be applied;
[0018] FIG. 2 is a block diagram of a mobile device forming part of
the system shown in FIG. 1;
[0019] FIG. 3 is a block diagram of a base station forming part of
the system shown in FIG. 1;
[0020] FIG. 4 illustrates schematically a sequence of subframes
that may be used for (control and user) data transmission in the
system of FIG. 1;
[0021] FIG. 5 illustrates schematically an example embodiment in
which directional beams may be used;
[0022] FIG. 6 illustrates schematically another example embodiment
in which directional beams may be used; and
[0023] FIG. 7 illustrates schematically a still another example
embodiment in which directional beams may be used.
DESCRIPTION OF EMBODIMENTS
[0024] Overview
[0025] FIG. 1 schematically illustrates a telecommunications
network 1 in which user equipment 3 (mobile telephones and/or other
mobile devices) can communicate with each other via base stations 5
(denoted `gNB`) using an appropriate radio access technology (RAT).
It will be appreciated that in 5G systems base stations are also
referred to as transmit receive points (TRPs). As those skilled in
the art will appreciate, whilst five mobile device 3 and one base
station 5 are shown in FIG. 1 for illustration purposes, the
system, when implemented, will typically include other base
stations and mobile devices.
[0026] Each base station 5 operates one or more associated cells
either via a TRP located at the base station (and/or one or more
remotely located TRPs). In this example, for simplicity, the base
station 5 operates a single cell. The base station 5 is connected
to a core network 7 (e.g. via an appropriate gateway and/or
user-plane/control function) and neighbouring base stations are
also connected to each other (either directly or via an appropriate
base station gateway). The core network 7 may include, amongst
others, a control plane manager entity and a user plane manager
entity, one or more gateways (GWs) for providing a connection
between the base stations 5 and other networks (such as the
Internet) and/or servers hosted outside the core network.
[0027] The mobile device 3 connects to an appropriate cell
(depending on its location and possibly on other factors, e.g.
signal conditions, subscription data, capability, and/or the like)
by establishing a radio resource control (RRC) connection with the
base station 5 operating that cell. The mobile device 3 and base
stations 5 (and other transmission points in the network)
communicate over an appropriate air interface which depends on the
RAT used. The mobile devices 3 communicate with core network nodes
using so-called non-access stratum (NAS) signalling, which is
relayed between the mobile device 3 and the appropriate core
network node by the base station 5/TRP serving the mobile device
3.
[0028] In this example, the base station 5 operates an associated
antenna array (e.g. a massive antenna) for providing a plurality of
directional beams for communicating with the various mobile devices
3 in the base station's 5 cell. Each beam is arranged to span
(transmit) in a different direction (in three dimension, including
elevation angle). Each beam has an associated identifier (e.g. an
appropriated `Beam ID`) which is unique (at least within the
cell).
[0029] The beam configuration used in the cell defines the number
of beams and the associated beam patterns. In this example, the
total number of beams is `N`, i.e. beams #1 though #N are currently
configured for the cell of the base station 5 (`N` being a positive
integer, at least `1`).
[0030] The base station 5 is beneficially configured to transmit in
its cell (or in each cell if the base station operates multiple
cells) a set of beam-specific reference signals (BRS). The mobile
devices 3 may be configured to use the associated BRS for
performing signal strength and channel estimate measurements for
each beam. Such beam specific measurements are used (by the base
station and/or the mobile device 3) for configuring an appropriate
set of (one or multiple) beams for the mobile device 3, which set
is referred to as the Operational Beam Set (OBS) of the mobile
device 3.
[0031] The OBS may be dynamically updated. e.g. depending on signal
conditions, load in the cell, a throughput and/or quality of
service (QoS) required by the mobile device 3. Beneficially, when
the OBS comprises multiple beams, the likelihood of the mobile
device 3 suffering a radio link failure (RLF)--i.e. a loss off
connection with the base station 5--is greatly reduced because in
most situations there is at least one directional beam that the
mobile device 3 can use and/or new beams may be added to the OBS if
needed (at least temporarily).
[0032] Moreover, the OBS may be beneficially used to support
intra-cell mobility for the mobile device 3. Specifically, as the
mobile device 3 changes its location within the base station's 5
coverage area (cell), new beams may be added to the OBS as
necessary (and beams that are no longer needed may be removed).
[0033] The mobile device 3 may be configured to perform and report
more frequent signal measurements (for example, detailed Channel
Status Information (CSI) measurements) for those beams that are
included in the OBS of the mobile device 3 than other beams.
Therefore, when an obstacle is present (e.g. temporarily) between
the mobile device 3 and the base station 5 (blocking line of sight
for a particular directional beam) then it is possible to detect
such change in signal condition (and identify the affected beam)
relatively quickly. The base station 5 can also carry out necessary
adjustments in its transmissions for the mobile device 3 in order
to avoid disruptions and/or radio link failure due to the obstacle.
Beneficially, however, the mobile device 3 will most likely be able
to continue communicating with the base station 5 using any other
suitable (unaffected) beam in its OBS. If the problem affecting a
particular beam in the OBS persists, the base station 5 may remove
that beam from the OBS (e.g. after expiry of a predetermined timer
and/or after receiving a predetermined number of reports indicating
problems with that beam).
[0034] Similarly, the base station 5 may be configured to remove a
beam from the OBS of the mobile device 3 (and replace it with a
different beam) due to mobility of the mobile device 3.
[0035] As can be seen, therefore, the provision of an OBS (and/or
associated beam specific reference signals) provides a number of
benefits such as flexibility in serving the mobile devices via the
base station's cell, improved tolerance for signal propagation
issues (e.g. obstacles) affecting high frequency radio beams, lower
risk for radio link failures due to loss of signal, faster and more
efficient cell/beam acquisition by mobile devices (e.g. whilst
moving within the cell or between different cells).
[0036] Mobile Device
[0037] FIG. 2 is a block diagram illustrating the main components
of the mobile device 3 shown in FIG. 1 (e.g. a mobile telephone or
other user equipment). As shown, the mobile device 3 has a
transceiver circuit 31 that is operable to transmit signals to and
to receive signals from a base station 5 via one or more antenna
33. The mobile device 3 has a controller 37 to control the
operation of the mobile device 3. The controller 37 is associated
with a memory 39 and is coupled to the transceiver circuit 31.
Although not necessarily required for its operation, the mobile
device 3 might of course have all the usual functionality of a
conventional mobile telephone 3 (such as a user interface 35) and
this may be provided by any one or any combination of hardware,
software and firmware, as appropriate. Software may be
pre-installed in the memory 39 and/or may be downloaded via the
telecommunications network or from a removable data storage device
(RMD), for example.
[0038] The controller 37 is configured to control overall operation
of the mobile device 3 by, in this example, program instructions or
software instructions stored within the memory 39. As shown, these
software instructions include, among other things, an operating
system 41, a communications control module 43, a beam configuration
module 44, a mobility module 45, and a signal measurement module
46.
[0039] The communications control module 43 is operable to control
the communication between the mobile device 3 and its serving base
station(s) 5 (and other communication devices connected to the base
station 5, such as further mobile devices and/or core network
nodes).
[0040] The beam configuration module 44 is responsible for managing
the OBS (or respective OBS's) for the mobile device 3 used in the
current serving cell (or cells). This includes, for example, adding
and removing cells (e.g. based on information provided by the base
station 5 and/or the signal measurement module 46).
[0041] The mobility module 45 is responsible for maintaining
network attachment via an appropriate cell (of a base station 5)
whilst the mobile device 3 is moving within the area covered by the
telecommunications network 1. The mobility module 45 maintains
network attachment by performing a cell/beam reselection and/or
handover procedure in dependence on signal conditions and/or the
like. It will be appreciated that the mobility module 45 may
perform a cell/beam reselection and/or handover procedure even when
the mobile device 3 remains stationary, for example, due to changes
in signal conditions, network load in the current cell, and/or the
like. The mobility module 45 also takes into account, for the
current cell and/or potential handover candidate cells, the OBS of
the mobile device 3 and/or the current beam configuration (e.g.
provided by the beam configuration module 44).
[0042] The signal measurement module 46 is responsible for
obtaining signal quality measurements for cells/beams in the
vicinity of the mobile device 3 and to generate and transmit
associated signal measurement reports to the serving base station
5. The signal quality measurements are performed over beam specific
reference signals transmitted by the base station 5 based on an
appropriate measurement configuration provided by the serving base
station 5. The signal quality measurements may include for example,
(detailed) Channel Status Information (CSI) measurements, reference
signal received power (RSRP), reference signal received quality
(RSRQ), received signal-to-noise ratio (SNR), and/or signal to
interference plus noise ratio (SINR) measurements and associated
reporting.
[0043] Base Station
[0044] FIG. 3 is a block diagram illustrating the main components
of a base station 5 shown in FIG. 1. As shown, the base station 5
has a transceiver circuit 51 for transmitting signals to and for
receiving signals from the communication devices (such as mobile
devices 3/user equipment) via one or more antenna 53 (e.g. an
antenna array/massive antenna), and a network interface 55 for
transmitting signals to and for receiving signals from network
nodes (e.g. other base stations and/or nodes in the core network
7). The base station 5 has a controller 57 to control the operation
of the base station 5. The controller 57 is associated with a
memory 59. Software may be preinstalled in the memory 59 and/or may
be downloaded via the telecommunications network 1 or from a
removable data storage device (RMD), for example. The controller 57
is configured to control the overall operation of the base station
5 by, in this example, program instructions or software
instructions stored within the memory 59. As shown, these software
instructions include, among other things, an operating system 61, a
communications control module 63, a beam control module 64, and a
measurement configuration module 66.
[0045] The communications control module 63 is operable to control
the communication between the base station 5 and mobile devices 3
(user equipment) and other network entities that are connected to
the base station 5. The communications control module 63 also
controls the separate flows of downlink user traffic (via
associated data radio bearers) and control data to be transmitted
to communication devices associated with this base station 5
including, for example, control data for core network services
and/or mobility of the mobile device 3 (also including general
(non-UE specific) system information and reference signals).
[0046] The beam control module 64 is responsible for managing the
associated OBS for each mobile device 3 in the cell (or cells) of
the base station 5. This includes, for example, adding and removing
cells (e.g. based on information such as signal measurements
provided by the mobile device 3, mobility of the mobile device 3,
and/or other information relevant to the cell, such as load
information).
[0047] The measurement configuration module 66 is responsible for
configuring mobile devices 3 for performing and reporting signal
quality measurements for cells and/or beams in the vicinity of the
mobile devices 3 (e.g. cells/beams operated by this base station 5
and/or a neighbouring base station). The measurement configuration
module 66 obtains signal quality measurements by generating and
sending an appropriate measurement configuration to a particular
mobile device 3 and by receiving an associated measurement report.
The measurement report may be used, for example, when performing a
mobility and/or beam configuration procedure involving the mobile
device 3 that provided the report.
[0048] In the above description, the mobile device 3 and the base
station 5 are described for ease of understanding as having a
number of discrete modules (such as the communications control
modules and the beam configuration/control modules). Whilst these
modules may be provided in this way for certain applications, for
example where an existing system has been modified to implement the
invention, in other applications, for example in systems designed
with the inventive features in mind from the outset, these modules
may be built into the overall operating system or code and so these
modules may not be discernible as discrete entities. These modules
may also be implemented in software, hardware, firmware or a mix of
these.
[0049] A more detailed description will now be given (with
reference to FIGS. 4 to 7) of some ways in which directional
beams/OBS may be used for communicating between user equipment and
TRPs (base stations) in a network.
[0050] Operation
[0051] The base station 5 is beneficially configured to transmit in
its cell (or in each cell if the base station operates multiple
cells) a set of beam-specific reference signals (BRS). For example,
the base station 5 may transmit one BRS per Beam ID. The mobile
devices 3 may use the associated BRS for performing signal strength
and channel estimate measurements for each beam. The BRS is
transmitted (e.g. periodically) using predefined time/frequency
resources using the beam pattern of the corresponding beam. It will
be appreciated that different BRS's may be transmitted in the same
time/frequency resources or in different time/frequency resources
(for example, when `beam scanning` is employed). Preferably, the
various BRS's within the same cell are orthogonal to each other
(over the set of time/frequency resources in which they are
transmitted), whilst BRS's in different cells have low
cross-correlation with each other. The BRS corresponding to a given
Beam ID may be determined (by the mobile device 3) based on the
Beam ID and the Cell ID. In other words, the mobile device 3 may be
able to construct the BRS for a particular beam (including the set
of time/frequency resources in which the BRS is transmitted) based
on the associated Beam ID and Cell ID.
[0052] Idle Mode and Initial Cell Selection
[0053] When the mobile device 3 is in idle mode, it may perform an
initial cell search using appropriate synchronisation signals
transmitted by the base station (via each of the multiple beams
configured in the cell/coverage area of the base station).
[0054] FIG. 4 illustrates schematically an exemplary sequence of
subframes (in this example, downlink subframes) transmitted by the
base station in each of its beams. As can be seen, the subframes
comprise a number of (downlink) data subframes 80 in the base
station 5 may transmit data to the mobile devices 3 in its cell
(and served via this particular beam). It will be appreciated that
(although not shown in FIG. 4 for simplicity) each data subframe 80
may also carry control signals (e.g. scheduling information) and/or
reference signals (for signal measurements).
[0055] Beneficially, the base station is configured to transmit
(periodically) appropriately formatted synchronisation signals in
specific subframes (herein referred to as synchronisation subframes
81). For example, such synchronisation subframes 81 may be
transmitted in a subframe preceding the subframe in which system
information (SI) broadcast is transmitted (denoted SI info subframe
82 in FIG. 4). Therefore, using the synchronisation signals, the
mobile device 3 is able to adapt its transceiver to use the correct
time/frequency resources in that particular beam before it proceeds
to receiving the system information broadcast. This beneficially
allows the mobile device 3 to find and connect to the base station
5 via that beam in a quick and efficient manner.
[0056] Specifically, the following options may be used in order to
facilitate the mobile device 3 carrying out beam searching for
initial access (by performing a random access procedure): [0057] a)
Beamformed downlink (DL) synchronisation signals--the mobile device
may be configured to detect the cell ID from the synchronisation
signals, and possibly detects the associated beam ID from beam
reference signal (BRS) transmitted in a particular beam; [0058] b)
Beamformed DL system information--the mobile device 3 may be
configured to acquire necessary system information from the cell
and possibly some beam specific system information for
communication via a particular beam; [0059] c) Beamformed UL
physical random access channel (PRACH) transmission (msg1)--PRACH
resources may be configured using the system information which the
mobile device acquires in advance (i.e. prior to initiating a
random access procedure by sending a so-called `msg1` transmission
via a particular beam); and [0060] d) Beamformed DL random access
messages (msg2/4)--PRACH resources for transmitting msg2/4 (via a
particular beam) may be configured using the system
information.
[0061] <Connected Mode Intra-Cell Mobility>
[0062] It will be appreciated that while in connected mode (e.g.
after performing an appropriate beam searching and random access
procedure), the mobile device 3 may connect to its serving cell
using one or multiple beams, referred to as the Operational Beam
Set (OBS) for that mobile device 3. Such an OBS may comprise a
(typically small) sub-set of the beams within the base station's
cell, which sub-set is selected for communication with that mobile
device 3 while it remains within the cell of the base station
5.
[0063] However, in order to account for mobility of the mobile
device 3 within the cell (and/or for changes in signal conditions)
within the cell, the base station 5 may modify the OBS of the
mobile device 3 by adding or removing beams based on at least one
of, for example: [0064] beam measurements (performed and reported
by the mobile device 3 and/or derived by the base station 5 from UL
transmissions by that mobile device 3); [0065] beam load (traffic
congestion); and [0066] beam priority (which may be set by, for
example, higher layers for inter-cell interference coordination
and/or the like).
[0067] <OBS Measurements for Intra-Cell Mobility>
[0068] In order to account for mobility of the mobile device 3
within the cell, the base station 5 may also use beam measurements
(performed and reported by the mobile device 3 and/or derived by
the base station 5 from UL transmissions by that mobile device
3).
[0069] In this case, the beam measurements reported by the mobile
device 3 may comprise, for example, a reference signal received
power (RSRP) and/or a signal to interference plus noise ratio
(SINR) associated with each beam (measured using the respective BRS
on each beam).
[0070] The mobile device 3 may be configured (by the serving base
station 5 via appropriate measurement configuration signalling) to
report the measurements periodically and/or in an event-triggered
manner. For example a report may be triggered when the RSRP of a
beam goes above or below a predetermined threshold (either absolute
or relative to another beam) for a certain amount of time. This is
similar to handover measurements in LTE.
[0071] Optionally, the mobile device 3 may be configured to sort
the beams in order of preference based on the measurements, and
report the measurements only for the best beams (e.g. a
predetermined number of beams), or report (e.g. as a list) the beam
IDs associated with the best beams for that mobile device 3.
[0072] However, it will also be appreciated that the mobile device
3 may request for a specific beam or beams to be added or removed
from its OBS (even without reporting the actual measurements). This
may reduce the amount of signalling required between the mobile
device 3 and the base station 5. The base station 5 may optionally
specify a sub-set of beams to be measured and reported by the
mobile device 3 (e.g. before adding them to, or removing them from,
the OBS).
[0073] In the case of time division duplex (TDD) transmissions, the
base station 5 may also be configured to exploit channel
reciprocity for selecting the most appropriate beam(s) for the OBS
of a mobile device 3 based on channel measurements derived from UL
transmissions from that mobile device 3.
[0074] Whenever the network (base station 5) modifies the OBS, it
informs the mobile device 3 using appropriately formatted control
signalling (e.g. RRC signalling).
[0075] <UE-Specific Data and Control>
[0076] Beneficially, the OBS may be used for i) UE-specific DL data
transmissions (similarly to how a physical downlink shared channel
or `PDSCH` is transmitted in LTE cells) and ii) UE-specific DL
control transmissions (similarly to enhanced physical downlink
control channel or `E-PDCCH` in LTE).
[0077] OBS may be useful at least for reducing the amount of CSI
signalling and for facilitating open-loop transmit diversity for a
particular mobile device 3.
[0078] Specifically, a reduction in the amount of CSI signalling
may be achieved as follows. Typically, DL beamforming for the
transmission of UE-specific channels is based on CSI reports from
the UE (mobile device 3). However, when using OBS, it is possible
to reduce the overhead of CSI measurement and signalling by
configuring the mobile device to send detailed CSI reports only for
those beams that are in the OBS (using the associated BRS on those
beams for CSI measurement).
[0079] In a particularly beneficial case, the base station 5 may
apply appropriate pre-coding (amplitude and phase weighting) for
its DL transmission across the beams in the OBS, based on the CSI
reports from the mobile device 3. In this case a UE-specific DM-RS
may be included in the transmission so that the mobile device 3
does not need to be aware of the pre-coding weights used by the
network.
[0080] The base station 5 may be configured to apply transmission
diversity over the beams in the OBS. In this case the mobile device
3 can extract the transmitted signal from each beam using the BRS
on each beam and then combine the transmitted signals before
decoding. This scheme has an advantage that no detailed CSI is
required from the mobile device 3.
[0081] <Common Control Signalling>
[0082] The mobile device 3 may need to receive from the network
certain control information which is not specific to that UE and/or
which does not need to be broadcast over the whole cell of the base
station 5. Such control information may include, although not being
limited to, for example: random access response (RAR) message 2 and
message 4, power control signalling, paging.
[0083] The base station 5 may transmit such common control
information on all beams in the OBS (for example using open-loop
transmit diversity as described previously). In this case, the
mobile device 3 may use the BRS on each beam to demodulate the
transmission on that beam and then combine the received data in
order to improve communication reliability.
[0084] <Intra-Cell Mobility>
[0085] FIG. 5(a) illustrates schematically a base station 5
operating a number of directional beams, from which beams #3 and #4
are currently allocated to the OBS of the mobile device 3. The
beams that are included in the OBS are shown using continuous lines
and the beams not included in the OBS are shown in dotted
lines.
[0086] It will be appreciated that the diversity created by using
multiple beams between the base station 5 and the mobile device 3
may significantly reduce the chance of the mobile device 3 losing
connection with the base station 5 due a obstacles and/or mobility
(whilst in the cell of the base station 5) even when the base
station 5 is operating high frequency bands in its cell. That is,
in the case of losing one beam (or more), the mobile device 3 is
still likely to remain connected to at least one beam (or even
multiple beams) of the base station 5, and hence it should be able
to tolerate a loss in received SNR (combined from multiple
beams).
[0087] In more detail, FIG. 5(a) illustrates schematically a
scenario in which the mobile device 3 is currently communicating
with the base station 5 using an OBS comprising beams #3 and #4.
Because these are included in the OBS, the mobile device 3 is
configured to send (relatively frequent) detailed CSI reports for
beams #3 and #4, whilst the mobile device 3 only sends periodic
(less frequent) RSRP measurements for the other beams (and/or RSRP
measurements for beams #3 and #4).
[0088] As generally shown in FIG. 5(b), an obstacle (e.g. a
vehicle) between the mobile device 3 and the base station 5 may
cause in a drop in the RSRP of a beam in the OBS (in this example
beam #4). However, such change in signal condition is beneficially
tracked by the CSI measurement for that beam, and the mobile device
3 is still able to receive DL transmissions via beam #3 (which does
not currently suffer a degradation of signal quality due to the
obstacle). Accordingly, using the CSI measurement for the affected
beam (#4), the base station 5 is able to carry out necessary
adjustments in its transmission (e.g. prioritise beam #3 over beam
#4) for the mobile device 3 (at least temporarily). If the CSI
measurement for the affected beam still indicate poor signal
conditions (e.g. over a predetermined period and/or number of CSI
reports), then the base station 5 may be configured to remove the
affected beam from the OBS of the mobile device 3.
[0089] Similarly, the base station 5 may be configured to remove a
beam from the OBS of the mobile device 3 due to mobility of the
mobile device 3. Such a mobility scenario is generally illustrated
in FIG. 5(c). Specifically, in this example, as the mobile device 3
moves within the cell of the base station 5, the network (and/or
the mobile device 3) monitors (e.g. using the beam RSRP
measurements and/or CSI) the signal conditions for the beams
included in the OBS (and/or signal conditions for adjacent beams)
and decides to update the OBS by removing beam #4 and adding beam
#2 when the mobile device 3 is no longer in the area served by beam
#4.
[0090] <Connected Mode Inter-Cell Mobility>
[0091] In order for the network (base station 5) to decide when to
initiate handover of the mobile device 3 to a neighbour cell, it
may configure the mobile device 3 to perform measurements that take
into account the beamforming gain available from the beams used in
the neighbour cell. Beneficially, therefore, when selecting a
handover target cell for the mobile device 3, the serving base
station 5 is able to select the most suitable beams of the handover
target cell so that the mobile device 3 can continue communicate
via the new cell without experiencing significant data loss and/or
delays.
[0092] In order to facilitate inter-cell mobility, the mobile
device 3 may be configured to measure the respective signal
strengths of each beam in one or more neighbouring cells (at least
those cells/beams that the current base station requests to be
measured). For example, the mobile device 3 may be configured to
scan each beam ID (unique BRS) transmitted in the neighbour
cell(s), and for each measured neighbour cell, report the ID of the
strongest beam (or beams) to the serving base station 5. If the
serving base station 5 determines that a handover is required for
the mobile device 3, then the serving base station 5 may provide,
to the target cell during the handover procedure, information
identifying the most suitable beam(s) for the mobile device 3 in
the target cell. If available from the mobile device 3, the serving
base station 5 may also provide detailed measurements for such
beams.
[0093] FIG. 6 illustrates schematically a scenario in which the
mobile device 3 performs a handover between a cell (`Cell1`)
operated by its current serving base station 5A and a neighbour
cell (`Cell2`) operated by base station 5B.
[0094] As can be seen, both base stations 5A and 5B operate a
number of directional beams. Initially, the mobile device 3 is
communicating with its serving base station 5A using an OBS
comprising beams #5 and #6 of Cell1. The mobile device 3 performs
appropriate handover measurements on one or more neighbour cells
(including Cell2) by measuring RSRP for all beams in that cell. In
this example, the mobile device 3 reports strong RSRP for beams #2
and #3 in Cell2. Therefore, when selecting Cell2 as a handover
target cell, the current serving base station 5A is beneficially
able to control handover of the mobile device 3 to beams 2# and #3
of Cell2 as the most suitable beams in that cell.
[0095] Thus, when the mobile device 3 performs a handover to the
Cell2, it is potentially able to connect via the most suitable
beams in that cell (assuming that those beams are available for the
mobile device 3). Even if not all beams in Cell2 having good signal
conditions are available for the mobile device 3 (e.g. due to load
in the Cell2 and/or the like), the new base station 5B is still
able to start serving the mobile device 3 via at least some of the
suitable candidate beams (and potentially add other beams to the
OBS as the mobile device 3 moves around in the area covered by
Cell2).
[0096] <OBS in CoMP>
[0097] FIG. 7 illustrates schematically a scenario in which the
mobile device 3 communicates concurrently via Cell1 operated by
base station 5A and Cell2 operated by base station 5B. This
scenario is effectively a variant of a Coordinated Multipoint
(CoMP) transmission and reception scenario specified for LTE.
However, in this case the base stations 5 are configured to
allocate specific beams for the mobile device 3 rather than entire
component carriers. Such concurrent transmission/reception may be
feasible, for example, when the mobile device 3 is located in a
cell-edge region and/or when the cells of neighbouring base
stations overlap. In such situations, therefore, the mobile device
3 may be able to receive signals from multiple cells (and transmit
signals via multiple cells) thereby significantly improving
downlink (or uplink) performance. The concurrent
transmission/reception (CoMP) may be used for two main purposes: i)
to improve signal quality (by transmitting/receiving the same
signal via two or more cells); and ii) to improve throughput (by
transmitting different data via different cells thus achieving a
higher overall data rate than what would be possible using a single
cell only).
[0098] In the scenario shown in FIG. 7, the mobile device 3 has a
respective OBS for each cell in its CoMP measurement set (in this
example, Cell1 and Cell2), and it is configured to measure and
report per-beam CSI for each beam in each OBS. Specifically, in
this example, the OBS for the mobile device 3 in Cell1 includes
beams #5 and #6 of that cell, and the OBS for the same mobile
device 3 in Cell2 includes beams #2 and #3 of Cell2. Therefore, the
mobile device 3 is configured to perform per-beam CSI measurements
and reporting for beams #5 and #6 of Cell1 and beams #2 and #3 of
Cell2.
[0099] It will be appreciated that the per-beam CSI measurement may
be reported to the same (e.g. a master) base station 5 regardless
of which base station operates that beam and/or the CSI measurement
may be reported to the base station that operates that particular
beam. Regardless which base station 5 the mobile device 3 reports
to, the base stations 5 may be configured to exchange CoMP related
signalling with each other via an appropriate base station to base
station interface provided between them. The CoMP related
signalling may include, for example, per-beam CSI and similar
information associated with the OBS of the mobile device 3 (e.g.
beam IDs included in the OBS).
[0100] Moreover, when concurrent transmission/reception is used,
decisions to add/remove cells to/from the mobile device's 3 CoMP
measurement set may be based on associated per-beam RSRP
measurements (which may be obtained as described above).
Beneficially, therefore, it is possible to improve signal
conditions for mobile devices (whilst using narrow, high frequency
directional beams) and/or improve throughput (by communicating via
multiple cells) using beam specific reference signals and
respective OBS configurations in each cell, together with
appropriate coordination between the serving base stations.
[0101] Modifications and Alternatives
[0102] Detailed example embodiments have been described above. As
those skilled in the art will appreciate, a number of modifications
and alternatives can be made to the above example embodiments
whilst still benefiting from the inventions embodied therein. By
way of illustration only a number of these alternatives and
modifications will now be described.
[0103] It will be appreciated that the beam configuration may be
different for different cells, depending on the coverage/throughput
requirements for a particular cell. For example, a high number of
very narrow beams may be used for a large cell radius, whilst fewer
and relatively wider beams may be used to facilitate fast cell
acquisition and reduce the overhead for transmission of
beam-specific reference signals. In some cases, the beam
configuration may consist of a single beam, defining the coverage
of the whole cell (similarly to legacy cells).
[0104] It will also be appreciated that the beam configuration of a
given cell may change semi-statically, e.g. for the purposes of
self-organising network (SON) adaptation such as Capacity and
Coverage Optimisation (CCOpt) and/or the like. In this case,
reconfiguration of a particular beam configuration may include
changing the beam-width of one or more beams and/or changing the
number of beams (e.g. switching beams on or off).
[0105] When preparing for handover between cells, if such
information is available, the serving base station may inform the
mobile device of the number of beams currently operated in the
neighbour cell, so that the mobile device knows the range of beam
IDs it needs to scan/measure. However, if such information is not
available or not sent to the mobile device, the mobile device may
be configured to perform beam measurement assuming that the
neighbour cell has the maximum possible number of beams. In any
case, using the information identifying the most suitable beams of
the target cell, there is no need to perform extensive beam
measurements upon entering the target cell because the mobile
device already has a potential set of beams that can be considered
for its OBS in the target cell.
[0106] In the above example embodiments the base station is
described to transmit a plurality of directional beams. It will be
appreciated that data may be transmitted substantially concurrently
via the plurality of beams. However, in some cases, for example
when a hybrid (part analogue and part digital) beamforming is used,
it may not be possible to transmit all beams at once. It will be
appreciated that in this case a technique referred to as `beam
sweeping` (i.e. transmitting one beam at a time) may be used.
[0107] It will be appreciated that, instead of the network (base
station) deciding on the OBS based on measurements from the mobile
device, the mobile device may be configured to choose the beams for
its own OBS and (unless configured differently) report the Channel
Status Information (CSI) only for the beams chosen by the mobile
device 3 for its OBS. In this case, beneficially, the network is
able to determine the OBS implicitly from the beams (Beam IDs)
included in the CSI reports. Since CSI reports for beams in the OBS
are likely to be needed anyway, this method has the advantage that
no additional signalling is required when the mobile device is
updating its OBS.
[0108] In the above example embodiments, the base station uses a
3GPP radio communications (radio access) technology to communicate
with the mobile device. However, any other radio communications
technology (i.e. WLAN, Wi-Fi, WiMAX, Bluetooth, etc.) can be used
between the base station and the mobile device in accordance with
the above embodiments. The above example embodiments are also
applicable to `non-mobile` or generally stationary user
equipment.
[0109] In the above description, the mobile device and the base
station are described for case of understanding as having a number
of discrete functional components or modules. Whilst these modules
may be provided in this way for certain applications, for example
where an existing system has been modified to implement the
invention, in other applications, for example in systems designed
with the inventive features in mind from the outset, these modules
may be built into the overall operating system or code and so these
modules may not be discernible as discrete entities.
[0110] In the above example embodiments, a number of software
modules were described. As those skilled in the art will
appreciate, the software modules may be provided in compiled or
un-compiled form and may be supplied to the base station, to the
mobility management entity, or to the mobile device as a signal
over a computer network, or on a recording medium. Further, the
functionality performed by part or all of this software may be
performed using one or more dedicated hardware circuits. However,
the use of software modules is preferred as it facilitates the
updating of the base station or the mobile device in order to
update their functionalities.
[0111] Each controller may comprise any suitable form of processing
circuitry including (but not limited to), for example: one or more
hardware implemented computer processors: microprocessors; central
processing units (CPUs); arithmetic logic units (ALUs);
input/output (IO) circuits; internal memories/caches (program
and/or data); processing registers; communication buses (e.g.
control, data and/or address buses); direct memory access (DMA)
functions: hardware or software implemented counters, pointers
and/or timers; and/or the like.
[0112] The controller of the base station may be operable to
control, for each communication device, a respective operational
beam set (OBS) comprising at least one directional beam associated
with that communication device.
[0113] The transceiver of the base station may be operable to
receive from at least one communication device results of
measurements performed on respective reference signals transmitted,
via each beam, and the controller may be operable to determine each
beam in said OBS based on the results of measurements performed on
the reference signals.
[0114] The transceiver of the base station may be operable to
receive from at least one communication device results of OBS
specific measurements (e.g. channel state indicator. CSI,
measurements) for beams that are included in the OBS for that at
least one communication device.
[0115] The controller of the base station may be operable to
control a handover for a particular communication device based on
at least one of: the OBS associated with that communication device
and beam specific reference signals.
[0116] The controller of the base station may be operable to
control a co-ordinated multipoint (CoMP) transmission/reception for
a particular communication device based on at least one of: the OBS
associated with that communication device and beam specific
reference signals.
[0117] The transceiver of the base station may be operable to
transmit, via each beam, respective control information comprising
reference signals. In this case, the respective reference signals
transmitted via each beam may be beam specific reference signals.
The transceiver of the base station may be configured to transmit
the respective reference signals in each beam periodically, using
predefined resources (e.g. time/frequency resources). The
predefined resources may be specific to a particular beam.
Alternatively, the predefined resources may be common to a
plurality (e.g. a subset or all) beams.
[0118] The respective reference signals transmitted via each beam
may depend on the corresponding beam identifier and a cell
identifier associated with the communication area and/or the
resources used for transmitting the respective reference signals
via each beam may depend on the corresponding beam identifier and a
cell identifier associated with the communication area.
[0119] The controller of the base station may be operable to
control a beam configuration associated with the communication area
of the base station, and the transceiver of the base station may be
operable to transmit (e.g. broadcast), within the communication
area, the beam configuration associated with that communication
area. The beam configuration may define at least one of: a number
of beams in the communication area, a beam pattern in the
communication area, a respective width associated with each beam,
whether a particular beam is turned on or off, resources used for
transmitting a reference signal (or a set of reference signals) in
a particular beam, resources allocated for random access procedure
per beam.
[0120] The transceiver of the base station may be operable to
communicate respective beam specific system information using each
directional beam. The transceiver of the base station may be
operable to communicate, over each beam, information identifying
resources for random access procedure signalling over that beam.
The transceiver of the base station may be operable to receive,
from the at least one communication device over at least one beam,
random access procedure signalling using the identified
resources.
[0121] The transceiver of the base station may be operable to apply
transmission diversity, for the at least one communication device,
using a plurality of directional beams associated with the at least
one communication device. In this case, the processor of the
communication device may be operable to combine respective data
received using each of a plurality of directional beams before
decoding the data.
[0122] The transceiver of the base station may be operable to
transmit, using the plurality of directional beams associated with
the at least one communication device, signalling which is not
specific to the at least one communication device (e.g. RAR message
2 and message 4, power control, and/or paging).
[0123] The base station may comprise a massive antenna for forming
a plurality of directional beams. The base station may be a base
station of a next generation (NextGen or 5G) radio access
network.
[0124] The controller of the communication device may be operable
to perform measurements on respective reference signals
transmitted, via each beam, and the transceiver of the
communication device may be operable to send the results of the
measurements to the base station. The controller of the
communication device may be operable to perform measurements (e.g.
channel state indicator, CSI, measurements) for beams that are
included in the OBS for the communication device, and the
transceiver of the communication device may be operable to send the
results of the measurements to the base station.
[0125] The controller of the communication device may be operable
to control a coordinated multipoint, CoMP, transmission/reception
via the base station based on at least one of: the OBS associated
with the communication device in that communication area and beam
specific reference signals.
[0126] Various other modifications will be apparent to those
skilled in the art and will not be described in further detail
here.
[0127] This application is based upon and claims the benefit of
priority from United Kingdom patent application No. 1613902.4,
filed on Aug. 12, 2016, the disclosure of which is incorporated
herein in its entirety by reference.
* * * * *
References