Technical Field
[0001] The present invention relates to a wireless communication system and devices
[0002]
thereof operating according to the 3rd Generation Partnership Project (3GPP) standards
or equivalents or derivatives thereof. The disclosure has particular but not exclusive
relevance to improvements relating to Ultra-Reliable and Low-Latency Communications
in the so-called '5G' (or 'Next Generation') systems.
Background Art
The latest developments of the 3GPP standards are the so-called '5G' or 'New
Radio' (NR) standards which refer to an evolving communication technology that is
expected to support a variety of applications and services such as Machine Type Communications
(MTC), Internet of Things (loT) communications, vehicular communications
and autonomous cars, high resolution video streaming, smart city services,
and/or the like. 3GPP intends to support 5G by way of the so-called 3GPP Next
Generation (NextGen) radio access network (RAN) and the 3GPP NextGen core
(NGC) network. Various details of 5G networks are described in, for example, the
'NGMN 5G White Paper' Vl.O by the Next Generation Mobile Networks (NGMN)
Alliance, which document is available from
https://www.ngmn.org/5g-white-paper.html.
[0003] End-user communication devices are commonly referred to as User Equipment (UE)
which may be operated by a human or comprise automated (MTC/IoT) devices. Whilst
a base station of a 5G/NR communication system is commonly referred to as a New
Radio Base Station ('NR-BS') or as a 'gNB' it will be appreciated that they may be
referred to using the term 'eNB' (or 5G/NR eNB) which is more typically associated
with Long Term Evolution (LTE) base stations (also commonly referred to as '4G'
base stations). 3GPP Technical Specification (TS) 38.300 V16.2.0 and 3GPP TS
37.340 V16.2.0 define the following nodes, amongst others:
gNB: node providing NR user plane and control plane protocol terminations
towards the UE, and connected via the NG interface to the 5G core network (5GC).
ng-eNB: node providing Evolved Universal Terrestrial Radio Access (E-UTRA)
user plane and control plane protocol terminations towards the UE, and connected via
the NG interface to the 5GC.
En-gNB: node providing NR user plane and control plane protocol terminations
towards the UE, and acting as Secondary Node in E-UTRA-NR Dual Connectivity
(EN-DC).
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[0004]
[0005]
NG-RAN node: either a gNB or an ng-eNB.
3GPP also defined the so-called 'Xn' interface as the network interface between
neighbouring NG-RAN nodes.
The next-generation mobile networks support diversified service requirements, which
have been classified into three categories by the International Telecommunication
Union (ITU): Enhanced Mobile Broadband (eMBB); Ultra-Reliable and Low-Latency
Communications (URLLC); and Massive Machine Type Communications (mMTC).
eMBB aims to provide enhanced support of conventional mobile broadband, with
focus on services requiring large and guaranteed bandwidth such as High Definition
(HD) video, Virtual Reality (VR), and Augmented Reality (AR). URLLC is a requirement
for critical applications such as automated driving and factory automation,
which require guaranteed access within a very short time. MMTC needs to support
massive number of connected devices such as smart metering and environment
monitoring but can usually tolerate certain access delay. It will be appreciated that
some of these applications may have relatively lenient Quality of Service/Quality of
Experience (QoS/QoE) requirements, while some applications may have relatively
stringent QoS/QoE requirements (e.g., high bandwidth and/or low latency).
[0006] The Physical Uplink Control Channel (PUCCH) carries a set of information called
Uplink Control Information (UCI). The format of the PUCCH depends on what kind of
information the UCI carries. The PUCCH format to be used is determined by how
many bits of information should be carried and how many symbols are assigned. The
UCI used in NR (5G) includes one or more of the following information: Channel
State Information (CSI); ACK/NAK; and Scheduling Request (SR). This is generally
the same as in LTE (4G), as will be described in more detail hereinafter.
[0007] The Physical Downlink Control Channel (PDCCH) carries a set of information called
Downlink Control Information (DCI). The DCI used in NR (5G) includes information
indicating resource assignment in uplink (UL) or downlink (DL), for a single Radio
Network Temporary Identifier (RNTI), e.g., a UE, depending on its Format. There are
various DCI formats used in LTE and NR (5G), each of which is a predefined format
in which the downlink control information is packed/formed and transmitted in
PDCCH. The DCI is used to schedule transmissions from the gNB to the UE
(downlink) and from the UE to the gNB (uplink) and provide such scheduling information
to the UE. Accordingly, DCis are further classified into downlink DCI
formats and uplink DCI formats. DCI Formats and their contents are set forth in 3GPP
TS 38.212 V16.2.0, 3GPP TS 38.213 V16.2.0, 3GPP TS 38.214 V16.2.0, and 3GPP
TS 38.331 V16.1.0. For example, Format 0_0 is used to schedule Physical Uplink
Shared Channel (PUSCH) data transmissions in one cell (Uplink (UL) grant) and
Format 1_0 is used to schedule a Physical Downlink Shared Channel (PDSCH) data
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transmission in one cell (Downlink (DL) grant.
[0008] In communications, the UE is configured to estimate and report the CSI of a communication
channel between it and the gNB, and this CSI is used in a CSI feedback
framework for, amongst other things, enabling appropriate Modulation and Coding
Scheme (MCS) selection by the gNB based on the channel conditions over all or part
of the bandwidth. The MCS defines the number of useful bits that can be carried by
one symbol or, more accurately in relation to NR (5G), how many useful bits can be
transmitted per Resource Element (RE). MCS depends on radio signal quality in a
wireless link, wherein the better the quality of the link, the higher will be the MCS and
the more useful bits that can be transmitted within a symbol or RE. The allocated MCS
is signalled to the UE using a DCI over the PDCCH, and defines a modulation and
code rate, and three different MCS tables are defined in 3GPP TS 38.214 5G NR
Physical Layer procedures for data.
[0009] Generally, LTE utilises an implicit rank indicator (RI)/Precoding Matrix Indicator
(PMI)/Channel Quality Indicator (CQI) feedback framework for the CSI feedback.
Together, a combination of the RI, PMI, and CQI forms a channel-state report, and the
CSI feedback framework is "implicit" in the form of CQI/PMI/RI (and Channel Rank
Indicator (CRI) in the LTE specification) derived from a codebook. Rank Indicator
(RI) is information relating to a channel rank and indicates the number of streams/
layers that can be received via the same time-frequency resource. Since RI is determined
by long term fading of a channel, it may be generally fed back at a cycle
longer than that of PMI or CQI. PMI Is a value indicating a spatial characteristic of a
channel and indicates a precoding matrix index of the network device (gNB) preferred
by the respective terminal device (UE). CQI is information indicating the strength of a
channel and a reception Signal-to-Interference-plus-Noise Ratio (SINR) when the gNB
uses PMI.

Claims
A method performed by an access network node of a communications
system comprising at least one terminal device configured to
communicate with the access network node via a communications
channel comprising a PDCCH, a PDSCH, a PUCCH and a PUSCH, the
method comprising, for a CSI feedback occasion in respect of the
terminal device:
transmitting a downlink DCI of Downlink DCI format to said
terminal device, said downlink DCI being configured to trigger
generation by the terminal device of CSI reporting data;
wherein said downlink DCI is further configured to schedule either a
PUSCH or a PUCCH data transmission to support transmission of said
CSI reporting data, depending on PUCCH availability when said CSI
feedback occasion is determined.
A method according to claim 1, wherein said CSI feedback occasion
is an aperiodic CSI feedback occasion.
A method according to claim 1 or claim 2, further comprising determining
if a PUSCH data transmission can be scheduled earlier than a
PUCCH data transmission or if a PDSCH data transmission is to be
scheduled; and transmitting the downlink DCI of Downlink DCI format
to said terminal device if it is determined that a PUSCH data
transmission cannot be scheduled earlier than a PUCCH data
transmission or a PDSCH data transmission is to be scheduled.
The method according to any of claims 1 to 3, further comprising, if
a PUSCH data transmission can be scheduled earlier than a PUCCH
data transmission or there is no PDSCH data to be scheduled,
transmitting an uplink DCI of Uplink DCI format to said terminal
device, wherein said uplink DCI is configured to trigger generation by
the terminal device of CSI reporting data and to schedule a PUSCH
data transmission to support transmission of said CSI reporting data.
The method of claim 4, wherein said uplink DCI is configured to
trigger generation by the terminal device of CSI reporting data.
The method according to any of claims 1 to 5, wherein the downlink
DCI comprises a PUCCH resource allocation field that acts to allocate
PUCCH resources intended to support transmission by the terminal
device of HARQ-ACK feedback data, the method further comprising, if
a PUSCH data transmission cannot be scheduled earlier than a PUCCH
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[Claim 7]
[Claim 8]
[Claim 9]
[Claim 10]
[Claim 11]
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data transmission or a PDSCH data transmission is to be scheduled, determining
if sufficient PUCCH resources are allocated by the PUCCH
resource allocation field of the download DCI to support transmission
of multiplexed CSI reporting data and HARQ-ACK feedback data and
wherein said download DCI includes an indicator field to indicate to
the terminal device whether to use the PUCCH resources allocated in
the PUCCH resource allocation field for transmission of the CSI
reporting data or to use PUSCH for transmission of the CSI reporting
data.
The method according to claim 5, wherein a PUSCH resource allocation
is preconfigured for the download DCI.
The method according to claim 5, wherein the download DCI format
includes a PUSCH resource allocation field which, when populated,
acts to allocate PUSCH resources intended to support transmission by
the terminal device of CSI reporting data.
The method according to any of any of claims 5 to 8, wherein said
indicator field is configured to hold a first value to indicate, to the
terminal device, that PUCCH data transmission is to be used to transmit
the CSI reporting data, and a second value if PUSCH is to be used to
transmit the CSI reporting data.
An access network node of a communication system, the access
network node being configured to communicate with a terminal device
via a communications channel comprising a PDCCH, a PDSCH, a
PUCCH and a PUSCH, and comprising:
means for triggering a CSI occasion in respect of a communicably
coupled terminal device, configured to transmit a downlink DCI of
Downlink DCI format to said terminal device, said downlink DCI being
configured to trigger generation by the terminal device of CSI reporting
data;
wherein said downlink DCI is further configured to schedule either a
PUSCH or a PUCCH data transmission to support transmission of said
CSI reporting data, depending on PUCCH availability when said CSI
feedback occasion is determined.
An access network node according to claim 10, further comprising
means for determining if a PUSCH data transmission can be scheduled
earlier than a PUCCH data transmission or if a PDSCH data
transmission is to be scheduled; and transmit the downlink DCI of
Downlink DCI format to said terminal device, if said determining
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[Claim 12]
[Claim 13]
[Claim 14]
[Claim 15]
[Claim 16]
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means determines that a PUSCH data transmission cannot be scheduled
earlier than a PUCCH data transmission or a PDSCH data transmission
is to be scheduled.
An access network node according to claim 10 or claim 11, wherein
said download DCI includes an indicator field to indicate to the
terminal device whether to use the PUCCH resources allocated in the
PUCCH resource allocation field for transmission of the CSI reporting
data or to use PUSCH for transmission of the CSI reporting data.
An access network node according to claim 11, wherein the
download DCI includes a PUSCH resource allocation field and the
access network node is configured to allocate PUSCH resources in the
PUSCH resource allocation field only for scheduling PUSCH data
transmission only if the download DCI indicates that PUSCH data
transmission is to be used to support transmission of said CSI reporting
data.
An access network node according to claim 11, being preconfigured
with a PUSCH resource allocation to be used only if the downlink DCI
indicates that PUSCH data transmission is to be used to support
transmission of said CSI reporting data.
A method performed by a terminal device configured to communicate
with an access network node of a communications system via
a communications channel comprising a PDCCH, a PDSCH, a PUCCH
and PUSCH, the method comprising:
receiving a downlink DCI of downlink DCI format, said downlink
DCI being configured to trigger generation by the terminal device of
CSI reporting data; wherein said downlink DCI is further configured to
schedule either a PUSCH or a PUCCH data transmission to support
transmission of said CSI reporting data; and
transmitting CSI reporting data to said access network node by
means of a PUCCH or PUSCH data transmission, depending on a respective
resource allocation in said received downlink DCI.
A terminal device of a communications system comprising at least
one access network node configured to communicate with said terminal
device via a communications channel comprising a PDCCH, a PDSCH,
a PUCCH and a PUSCH, the terminal device comprising:
means for receiving a downlink DCI of downlink DCI format, said
downlink DCI being configured to trigger generation by the terminal
device of CSI reporting data; wherein said downlink DCI is further
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[Claim 17]
[Claim 18]
[Claim 19]
[Claim 20]
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configured to schedule either a PUSCH or a PUCCH data transmission
to support transmission of said CSI reporting data; and
means for transmitting CSI reporting data to said access network
node by means of a PUCCH or PUSCH data transmission, depending
on a respective resource allocation in said received downlink DCI.
A communication system comprising a core network device, an
access network node according to any of claims 10 to 14 and at least
one terminal device configured to communicate therewith via a communications
channel comprising a PDCCH, a PDSCH, a PUCCH and a
PUSCH.
A communication system comprising a core network device, an
access network node, and a terminal device according to claim 16
configured to communicate therewith via a communications channel
comprising a PDCCH, a PDSCH, a PUCCH and a PUSCH.
A computer implementable instructions product comprising
computer implementable instructions for causing a programmable communications
device to perform the method according to any of claims 1
to 9.
A computer implementable instructions product comprising
computer implementable instructions for causing a programmable communications
device to perform the method according to claim 15.