WO2023011853A1

WO2023011853A1 - Methods and communications devices

Info

Publication number: WO2023011853A1
Application number: PCT/EP2022/069105
Authority: WO
Inventors: Shin Horng Wong
Original assignee: Sony Group Corporation; Sony Europe B.V.
Priority date: 2021-08-03
Filing date: 2022-07-08
Publication date: 2023-02-09

Abstract

A method of operating a communications device configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network is provided. The method comprises receiving, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, determining that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device on the first downlink channel within the downlink transmission occasion, determining that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, determining that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, and determining whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within a HARQ buffer of the communications device. If the communications device determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, storing all of the first downlink channel and the at least one other downlink channel within the HARQ buffer. Or, if the communications device determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, dropping, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer. The method then further comprises transmitting all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

Description

METHODS AND COMMUNICATIONS DEVICES

BACKGROUND

Field of Disclosure

The present disclosure relates to communications devices, infrastructure equipment and methods for the reception of data by a communications device in a wireless communications network.

The present application claims the Paris Convention priority of European patent application number EP21189502.4, filed on 3 August 2021, the contents of which are hereby incorporated by reference.

Description of Related Art

The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.

Latest generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture, are able to support a wider range of services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection. The demand to deploy such networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to continue to increase rapidly.

Future wireless communications networks will be expected to routinely and efficiently support communications with an ever-increasing range of devices associated with a wider range of data traffic profiles and types than existing systems are optimised to support. For example, it is expected future wireless communications networks will be expected to efficiently support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets and so on. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the “The Internet of Things”, and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance. Other types of device, for example supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. Other types of device, for example used for autonomous vehicle communications and for other critical applications, may be characterised by data that should be transmitted through the network with low latency and high reliability. A single device type might also be associated with different traffic profiles / characteristics depending on the application(s) it is running. For example, different consideration may apply for efficiently supporting data exchange with a smartphone when it is running a video streaming application (high downlink data) as compared to when it is running an Internet browsing application (sporadic uplink and downlink data) or being used for voice communications by an emergency responder in an emergency scenario (data subject to stringent reliability and latency requirements).

In view of this there is expected to be a desire for future wireless communications networks, for example those which may be referred to as 5G or new radio (NR) systems / new radio access technology (RAT) systems, as well as future iterations / releases of existing systems, to efficiently support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements.

One example of a new service is referred to as Ultra Reliable Low Latency Communications (URLLC) services which, as its name suggests, requires that a data unit or packet be communicated with a high reliability and with a low communications delay. Another example of a new service is Enhanced Mobile Broadband (eMBB) services, which are characterised by a high capacity with a requirement to support up to 20 Gb/s. URLLC and eMBB type services therefore represent challenging examples for both LTE type communications systems and 5G/NR communications systems.

The increasing use of different types of network infrastructure equipment and terminal devices associated with different traffic profiles give rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

SUMMARY OF THE DISCLOSURE

The present disclosure can help address or mitigate at least some of the issues discussed above.

Embodiments of the present technique can provide a method of operating a communications device configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network. The method comprises receiving, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, determining that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device on the first downlink channel within the downlink transmission occasion, determining that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, determining that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ- ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, and determining whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within a HARQ buffer of the communications device. If the communications device determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, storing all of the first downlink channel and the at least one other downlink channel within the HARQ buffer. Or, if the communications device determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, dropping, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer. The method then further comprises transmitting all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

Embodiments of the present technique, which, in addition to methods of operating communications devices, relate to communications devices, circuitry for communications devices, computer programs, and computer-readable storage mediums, can allow for more efficient use of radio resources and buffer storage by a communications device.

Respective aspects and features of the present disclosure are defined in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the present technology. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and wherein:

Figure 1 schematically represents some aspects of an LTE-type wireless telecommunication system which may be configured to operate in accordance with certain embodiments of the present disclosure;

Figure 2 schematically represents some aspects of a new radio access technology (RAT) wireless telecommunications system which may be configured to operate in accordance with certain embodiments of the present disclosure;

Figure 3 is a schematic block diagram of an example infrastructure equipment and communications device which may be configured to operate in accordance with certain embodiments of the present disclosure;

Figure 4 illustrates how multiple Hybrid Automatic Repeat Request Acknowledgement (HARQ-ACK) feedback indications may be multiplexed onto a single Physical Uplink Control Channel (PUCCH); Figure 5 illustrates how a PUCCH Resource Indicator may be used to indicate onto which PUCCH HARQ-ACK feedback indications may be multiplexed;

Figure 6 shows an example of sub-slot based PUCCHs;

Figure 7 illustrates how multiple HARQ-ACK feedback indications for Semi-Persistent Scheduling (SPS) Physical Downlink Shared Channels (PDSCHs) may be multiplexed onto a single PUCCH per sub-slot; Figure 8 shows an example of two HARQ-ACK codebooks having different priority levels;

Figure 9 shows an example of when a HARQ-ACK may be dropped due to a collision with invalid or downlink symbols and retransmitted in a next available PUCCH resource;

Figure 10 shows an example of a collision between HARQ-ACKs having a same HARQ process number (HPN);

Figure 11 shows a part schematic, part message flow diagram representation of a wireless communications system comprising a communications device and an infrastructure equipment in accordance with embodiments of the present technique;

Figure 12 illustrates how a User Equipment (UE) may drop a PDSCH for which a positive acknowledgement (ACK) has been generated and keep a PDSCH for which a negative acknowledgement (NACK) has been generated when those PDSCHs are associated with the same HPN in accordance with embodiments of the present technique;

Figure 13 shows an example of an HPN collision involving three PDSCHs in accordance with embodiments of the present technique;

Figure 14 shows an example of how a UE may drop a successfully decoded PDSCH from a previous SPS occasion prior to decoding a next SPS occasion associated with the same HPN in accordance with embodiments of the present technique;

Figure 15 shows an example of how a UE may drop an unsuccessfully decoded PDSCH from an earliest SPS occasion when there is an HPN collision in accordance with embodiments of the present technique; Figure 16 shows an example of how a UE may drop an unsuccessfully decoded PDSCH from a latest SPS occasion when there is an HPN collision in accordance with embodiments of the present technique; Figure 17 shows an example of how a UE may drop successfully decoded PDSCHs which are received within SPS occasions that fall outside of a time window when there is an HPN collision in accordance with embodiments of the present technique;

Figure 18 shows an example of how a UE may drop an unsuccessfully decoded PDSCH from an earliest SPS occasion prior to decoding a newly received PDSCH when there is an HPN collision between the PDSCHs in accordance with embodiments of the present technique;

Figure 19 shows an example of how a UE may drop an unsuccessfully decoded PDSCH from a latest SPS occasion prior to decoding a newly received PDSCH when there is an HPN collision between the PDSCHs in accordance with embodiments of the present technique;

Figure 20 shows an example of how a UE may drop successfully decoded PDSCHs which are received within SPS occasions that fall outside of a time window if the UE has no space to store a further received PDSCH with a same HPN in its HARQ buffer in accordance with embodiments of the present technique; Figure 21 illustrates an example of how a dynamically granted (DG) PDSCH may be HARQ-combined with an unsuccessfully decoded PDSCH from a latest SPS occasion in accordance with embodiments of the present technique;

Figure 22 illustrates an example of how a dynamically granted (DG) PDSCH may be HARQ-combined with an unsuccessfully decoded PDSCH from an earliest SPS occasion in accordance with embodiments of the present technique; and

Figure 23 shows a flow diagram illustrating a process of communications in a communications system in accordance with embodiments of the present technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Long Term Evolution Advanced Radio Access Technology (4G)

Figure 1 provides a schematic diagram illustrating some basic functionality of a mobile telecommunications network / system 6 operating generally in accordance with LTE principles, but which may also support other radio access technologies, and which may be adapted to implement embodiments of the disclosure as described herein. Various elements of Figure 1 and certain aspects of their respective modes of operation are well-known and defined in the relevant standards administered by the 3GPP (RTM) body, and also described in many books on the subject, for example, Holma H. and Toskala A [1], It will be appreciated that operational aspects of the telecommunications networks discussed herein which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to the relevant standards and known proposed modifications and additions to the relevant standards.

The network 6 includes a plurality of base stations 1 connected to a core network 2. Each base station provides a coverage area 3 (i.e. a cell) within which data can be communicated to and from communications devices 4. Although each base station 1 is shown in Figure 1 as a single entity, the skilled person will appreciate that some of the functions of the base station may be carried out by disparate, inter-connected elements, such as antennas (or antennae), remote radio heads, amplifiers, etc. Collectively, one or more base stations may form a radio access network.

Data is transmitted from base stations 1 to communications devices 4 within their respective coverage areas 3 via a radio downlink. Data is transmitted from communications devices 4 to the base stations 1 via a radio uplink. The core network 2 routes data to and from the communications devices 4 via the respective base stations 1 and provides functions such as authentication, mobility management, charging and so on. Terminal devices may also be referred to as mobile stations, user equipment (UE), user terminal, mobile radio, communications device, and so forth. Services provided by the core network 2 may include connectivity to the internet or to external telephony services. The core network 2 may further track the location of the communications devices 4 so that it can efficiently contact (i.e. page) the communications devices 4 for transmitting downlink data towards the communications devices 4.

Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, gNB and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, certain embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems, and for simplicity certain terminology may be used regardless of the underlying network architecture. That is to say, the use of a specific term in relation to certain example implementations is not intended to indicate these implementations are limited to a certain generation of network that may be most associated with that particular terminology.

New Radio Access Technology (5G)

An example configuration of a wireless communications network which uses some of the terminology proposed for and used in NR and 5G is shown in Figure 2. In Figure 2 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (DUs) 41, 42 by a connection interface represented as a line 16. Each of the TRPs 10 is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus, within a range for performing radio communications via the wireless access interface, each of the TRPs 10, forms a cell of the wireless communications network as represented by a circle 12. As such, wireless communications devices 14 which are within a radio communications range provided by the cells 12 can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 41, 42 are connected to a central unit (CU) 40 (which may be referred to as a controlling node) via an interface 46. The central unit 40 is then connected to the core network 20 which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network 20 may be connected to other networks 30.

The elements of the wireless access network shown in Figure 2 may operate in a similar way to corresponding elements of an LTE network as described with regard to the example of Figure 1. It will be appreciated that operational aspects of the telecommunications network represented in Figure 2, and of other networks discussed herein in accordance with embodiments of the disclosure, which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to currently used approaches for implementing such operational aspects of wireless telecommunications systems, e.g. in accordance with the relevant standards.

The TRPs 10 of Figure 2 may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly, the communications devices 14 may have a functionality corresponding to the UE devices 4 known for operation with an LTE network. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of a new RAT network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network.

In terms of broad top-level functionality, the core network 20 connected to the new RAT telecommunications system represented in Figure 2 may be broadly considered to correspond with the core network 2 represented in Figure 1, and the respective central units 40 and their associated distributed units / TRPs 10 may be broadly considered to provide functionality corresponding to the base stations 1 of Figure 1. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the controlling node / central unit and / or the distributed units / TRPs. A communications device 14 is represented in Figure 2 within the coverage area of the first communication cell 12. This communications device 14 may thus exchange signalling with the first central unit 40 in the first communication cell 12 via one of the distributed units / TRPs 10 associated with the first communication cell 12.

It will further be appreciated that Figure 2 represents merely one example of a proposed architecture for a new RAT based telecommunications system in which approaches in accordance with the principles described herein may be adopted, and the functionality disclosed herein may also be applied in respect of wireless telecommunications systems having different architectures.

Thus, certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems / networks according to various different architectures, such as the example architectures shown in Figures 1 and 2. It will thus be appreciated the specific wireless telecommunications architecture in any given implementation is not of primary significance to the principles described herein. In this regard, certain embodiments of the disclosure may be described generally in the context of communications between network infrastructure equipment / access nodes and a communications device, wherein the specific nature of the network infrastructure equipment / access node and the communications device will depend on the network infrastructure for the implementation at hand. For example, in some scenarios the network infrastructure equipment / access node may comprise a base station, such as an LTE-type base station 1 as shown in Figure 1 which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a control unit / controlling node 40 and / or a TRP 10 of the kind shown in Figure 2 which is adapted to provide functionality in accordance with the principles described herein.

A more detailed diagram of some of the components of the network shown in Figure 2 is provided by Figure 3. In Figure 3, a TRP 10 as shown in Figure 2 comprises, as a simplified representation, a wireless transmitter 30, a wireless receiver 32 and a controller or controlling processor 34 which may operate to control the transmitter 30 and the wireless receiver 32 to transmit and receive radio signals to one or more UEs 14 within a cell 12 formed by the TRP 10. As shown in Figure 3, an example UE 14 is shown to include a corresponding transmitter 49, a receiver 48 and a controller 44 which is configured to control the transmitter 49 and the receiver 48 to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP 10 and to receive downlink data as signals transmitted by the transmitter 30 and received by the receiver 48 in accordance with the conventional operation.

The transmitters 30, 49 and the receivers 32, 48 (as well as other transmitters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency filters and amplifiers as well as signal processing components and devices in order to transmit and receive radio signals in accordance for example with the 5G/NR standard. The controllers 34, 44 (as well as other controllers described in relation to examples and embodiments of the present disclosure) may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc., configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer readable medium. The transmitters, the receivers and the controllers are schematically shown in Figure 3 as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the infrastructure equipment / TRP / base station as well as the UE / communications device will in general comprise various other elements associated with its operating functionality.

As shown in Figure 3, the TRP 10 also includes a network interface 50 which connects to the DU 42 via a physical interface 16. The network interface 50 therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 40 to the core network 20.

The interface 46 between the DU 42 and the CU 40 is known as the Fl interface which can be a physical or a logical interface. The Fl interface 46 between CU and DU may operate in accordance with specifications 3GPP TS 38.470 and 3GPP TS 38.473, and may be formed from a fibre optic or other wired or wireless high bandwidth connection. In one example the connection 16 from the TRP 10 to the DU 42 is via fibre optic. The connection between a TRP 10 and the core network 20 can be generally referred to as a backhaul, which comprises the interface 16 from the network interface 50 of the TRP 10 to the DU 42 and the Fl interface 46 from the DU 42 to the CU 40. eURLLC and eMBB

Systems incorporating NR technology are expected to support different services (or types of services), which may be characterised by different requirements for latency, data rate and/or reliability. For example, Enhanced Mobile Broadband (eMBB) services are characterised by high capacity with a requirement to support up to 20 Gb/s. The requirements for Ultra Reliable and Low Latency Communications (URLLC) services are for one transmission of a 32 byte packet to be transmitted from the radio protocol layer 2/3 SDU ingress point to the radio protocol layer 2/3 SDU egress point of the radio interface within 1 ms with a reliability of 1 - 10"⁵ (99.999 %) or higher (99.9999%) [2],

Massive Machine Type Communications (mMTC) is another example of a service which may be supported by NR-based communications networks. In addition, systems may be expected to support further enhancements related to Industrial Internet of Things (IIoT) in order to support services with new requirements of high availability, high reliability, low latency, and in some cases, high-accuracy positioning.

Enhanced URLLC (eURLLC) [3] specifies features that require high reliability and low latency, such as factory automation, transport industry, electrical power distribution, etc. in a 5G system. eURLLC is further enhanced as IIoT-URLLC [4], for which one of the objectives is to enhance UE feedback for Hybrid Automatic Repeat Request Acknowledgements (HARQ-ACK) for Physical Downlink Shared Channel (PDSCH) transmissions.

PDSCH HARQ-ACK Feedback

In a Dynamic Grant PDSCH (DG-PDSCH), the PDSCH resource is dynamically indicated by the gNB using a DL Grant carried by Downlink Control Information (DCI) in a Physical Downlink Control Channel (PDCCH). A PDSCH is transmited using HARQ transmission, where for a PDSCH ending in slot n, the corresponding Physical Uplink Control Channel (PUCCH) carrying the HARQ-ACK is transmited in slot n+Ki. Here, in Dynamic Grant PDSCH, the value of K is indicated in the field "PDSCH -io- HARQ feedback timing indicator” of the DL Grant (carried by DCI Format 1 0, DCI Format 1 1 or DCI Format 1 2). Multiple (different) PDSCHs can point to the same slot for transmission of their respective HARQ-ACKs, and these HARQ-ACKs (in the same slot) are multiplexed into a single PUCCH. Hence, a PUCCH can contain multiple HARQ-ACKs for multiple PDSCHs.

An example of this is shown in Figure 4, where three DU Grants are transmited to the UE via DCI#1, DCI#2 and DCI#3 in slot n, n+1 and w+2 respectively. DCI#1, DCI#2 and DCI#3 schedule PDSCH# 1, PDSCH#2 and PDSCH#3 respectively. DCI#1, DCI#2 and DCI#3 further indicate K\ = 3, K\ = 2 and K\ = 1 respectively. Since the Ki values indicate that the HARQ-ACK feedback for PDSCH#1, PDSCH#2 and PDSCH#3 are all to be transmited in slot n+4. the UE multiplexes all of these HARQ-ACKs into a single PUCCH, i.e. PUCCH#1. The PUCCH Multiplexing Window is a time window where PDSCHs can be multiplexed into that single PUCCH, and the size of the PUCCH multiplexing window depends on the range of Ki values. In the example in Figure 4, the PUCCH Multiplexing Window is from Slot n to Slot w+3 (i.e. between time to and time U), which means the max Ki value is 4 slots.

In Rel-15, only one PUCCH per slot is allowed to carry HARQ-ACKs for the same UE, even if the different PUCCHs do not overlap in time. The PUCCH resource is indicated in the "PUCCH Resource Indicator” (PRI) field in the DL Grant. Each DL Grant may indicate a different PUCCH resource, but the UE will follow the PRI indicated in the last PDSCH in the PUCCH Multiplexing Window since the UE only knows the total number of HARQ-ACK bits after the last PDSCH is received.

An example of this is shown in Figure 5, where DCI#1 and DCI#2 indicate PUCCH# 1 for the HARQ- ACKs corresponding to PDSCH# 1 and PDSCH#2, but DCI#3 indicates PUCCH#2 for the HARQ-ACK corresponding to PDSCH#3. Here, PUCCH# 1 and PUCCH#2 do not overlap in time. Since DCI#3 schedules the last PDSCH, i.e. PDSCH#3, in the Multiplexing Window, the UE will use PUCCH#2 to carry the HARQ-ACKs for PDSCH# 1, PDSCH#2 and PDSCH#3. It should be noted here that a PUCCH carrying other UCI such as SR (Scheduling Request) can be transmited separately to a PUCCH carrying HARQ-ACKs within the same slot if they do not overlap in time.

In Rel-16 eURLLC, sub-slot PUCCH is introduced for carrying HARQ-ACKs for URLLC PDSCHs. Sub-slot based PUCCHs allow more than one PUCCH carrying HARQ-ACKs to be transmited within a slot. This gives more opportunity for PUCCHs carrying HARQ-ACKs for PDSCHs to be transmited within a slot, thereby reducing latency for HARQ-ACK feedback. In a sub-slot based PUCCH, the granularity of the Ki parameter (i.e. the time difference between the end of a PDSCH and the start of its corresponding PUCCH) is in units of sub-slots instead of units of slots, where the sub-slot size can be either two symbols or seven symbols.

An example of this is shown in Figure 6, where the sub-slot size equals seven symbols (i.e. half a slot) and the sub-slots are labelled as m, m+1, m+2, etc. PDSCH#1 is transmited in slot n+1 but for sub-slot based HARQ-ACK PUCCH, it is considered to be transmited in sub-slot m+2 and here Ki= 6 which means that the corresponding HARQ-ACK is in sub-slot m+2+Ki = m+H>. PDSCH#2 is transmited in slot n+2 but occupies sub-slots m+4 and m+5. The reference for Ki is relative to the sub-slot where the PDSCH ends, and in this case PDSCH#2 ends in sub-slot m+5. The DL Grant in DCI#2 that schedules PDSCH#2 indicates Kj = 4, which schedules a PUCCH for its HARQ-ACK at sub-slot m+5+Kj = sub-slot m+9. Semi-Persistent Scheduling (SPS)

As is well understood by those skilled in the art, a gNB uses a PDSCH for downlink data transmission to a UE. The PDSCH resources used for the transmission of the PDSCH can be scheduled by a gNB either dynamically, or through the allocation of Semi-Persistent Scheduling (SPS) resources.

Similarly to the use of Configured Grants (CGs) in the uplink, the use of SPS in the downlink reduces latency, particularly for regular and periodic traffic. The gNB is required to explicitly activate and deactivate SPS resources when it determines they may be required. These SPS resources are typically configured via Radio Resource Control (RRC) signalling, and occur periodically where each SPS PDSCH occasion has a pre-configured and fixed duration. This allows the gNB to schedule traffic that has a known periodicity and packet size. The gNB may or may not transmit any PDSCH in any given SPS PDSCH occasion, and so the UE is required to monitor each SPS PDSCH occasion for a potential PDSCH transmission.

In Rel-15 the UE can only be configured with one SPS PDSCH and this SPS PDSCH is activated using an activation DCI (Format 1 0 or 1 1) with the Cyclic Redundancy Code (CRC) scrambled with a Configured Scheduling Radio Network Temporary Identifier (CS-RNTI). Once an SPS PDSCH is activated, the UE will monitor for a potential PDSCH in each SPS PDSCH occasion of the SPS PDSCH configuration without the need for any DL Grant until the SPS PDSCH is deactivated. Deactivation of the SPS PDSCH is indicated via a deactivation DCI scrambled with CS-RNTI. The UE provides a HARQ-ACK feedback for the deactivation DCI, but no HARQ-ACK feedback is provided for an activation DCI.

Similar to DG-PDSCH, the slot containing the PUCCH resource for HARQ-ACK corresponding to SPS PDSCH is indicated using the K value in the field ^PDSCH-to-HARQ^feedback timing indicator” of the activation DCI. Since a dynamic grant is not used for SPS PDSCH, this Ki value is applied for every SPS PDSCH occasion, and can only be updated after it has been deactivated and re-activated using another activation DCI with a different Ki value.

Since there is only one SPS PDSCH, PUCCH Format 0 or 1 is used to carry the HARQ-ACK feedback. If the PUCCH collides with a PUCCH carrying HARQ-ACK feedback for a DG-PDSCH, the HARQ- ACK for SPS PDSCH is multiplexed into the PUCCH corresponding to the DG-PDSCH.

In Rel-16 the UE can be configured with up to eight SPS PDSCHs, where each SPS PDSCH has an SPS Configuration Index that is RRC configured. Each SPS PDSCH is individually activated using a DCI (Format 1 0, 1 1, and 1 2) with the CRC scrambled with CS-RNTI, where the DCI indicates the SPS Configuration Index of the SPS PDSCH to be activated. However, multiple SPS PDSCHs can be deactivated using a single deactivation DCI. Similar to Rel-15, the UE provides a HARQ-ACK feedback for the deactivation DCI, but does not provide one for the activation DCI.

The slot or sub-slot containing the PUCCH resource for HARQ-ACK feedback corresponding to an SPS PDSCH occasion is determined using the K\ value indicated in the activation DCI. Since each SPS PDSCH configuration is individually activated, different SPS PDSCH can be indicated with different Ki values.

Since different Ki values can be used for different SPS PDSCH configurations, it is possible that the HARQ-ACK for multiple SPS PDSCHs point to the same slot or sub-slot, and in such a scenario, these HARQ-ACKs are multiplexed into a single PUCCH. For multiple SPS PDSCH configurations, PUCCH Format 2, 3, and 4 (in addition to PUCCH Format 0 and 1) can be used to carry multiple HARQ-ACKs for SPS PDSCH. Here, the HARQ-ACKs in the PUCCH are sorted in ascending order according to the DL slot for each of the SPS PDSCH Configuration Indices, and then sorted in ascending order of SPS PDSCH Configuration Index. It should be noted here that since typically the Ki value is fixed per SPS PDSCH then it is unlikely to have two or more SPS PDSCH with the same index being multiplexed into a PUCCH.

An example of this is shown in Figure 7, where a UE is configured with three SPS PDSCHs labelled as SPS#1, SPS#2 and SPS#3 with different periodicities that are RRC configured with SPS Configuration Index 1, 2 and 3 respectively. SPS#1, SPS#2 and SPS#3 are activated with Ki = 3, Ki = 4 and Ki = 1 respectively. These Ki values result in the PUCCH for HARQ-ACK feedback corresponding to SPS#2 in Slot n, SPS#1 in Slot «+l and SPS#3 in Slot n+3 being in the same slot, i.e. carried by PUCCH#2 in Slot n+4. PUCCH#2 therefore provides 3 HARQ-ACKs labelled as {ACK#1, ACK#2, ACK#3} for SPS#1, SPS#2 and SPS#3 respectively according to their SPS PDSCH Configuration Indices (it can be seen that, in this example, there is only one unique SPS PDSCH per DE slot that has HARQ-ACK multiplexed into PUCCH#2).

In Rel-16, when the PUCCH for an SPS PDSCH collides with the PUCCH for a DG-PDSCH, their HARQ-ACKs are multiplexed, where the SPS PDSCH HARQ-ACKs are appended after those for DG- PDSCH, if they have the same priority. Otherwise, one of the PUCCHs is prioritised.

Uplink Layer 1 Priority

In Rel-15, there are no priority levels defined at the Physical Layer (i.e. Layer 1, or LI), and so when two UL transmissions collide, their information is multiplexed and transmitted using a single channel. The possible collisions here are PUCCH with PUCCH and PUCCH with PUSCH. Those skilled in the art would understand that priority levels are defined for the MAC layer (i.e. Layer 2, or L2) in Rel-15, where there are sixteen priority levels.

A UE can be configured to provide eMBB and URLLC services. Since eMBB and URLLC have different latency requirements as discussed above, their uplink transmissions may collide. For example, after an eMBB uplink transmission has been scheduled, an urgent URLLC packet may arrive, which would need to be scheduled immediately and thus its transmission may collide with the eMBB transmission. In order to handle such intra-UE collisions with different latency and reliability requirements, two priority levels at the Physical Layer were introduced in Rel-16 for Uplink transmissions, i.e. for PUCCH and PUSCH. In Rel-16 intra-UE prioritisation is used. That is, when two UL transmissions with different Physical Layer priority levels (LI priority) collide, the UE will drop the lower priority transmission. If both UL transmissions have the same LI priority, then the UE reuses Rel- 15 procedures, by multiplexing and transmitting the colliding UL transmissions using the same channel. The gNB indicates the LI priority to the UE in the one-bit "Priority indicator” DCI field, where “0” indicates Low LI priority and “1” indicates High LI priority and:

• For PUSCH, the LI priority is indicated in the UL Grant carried by DCI Format 0 1 and 0 2; and

• For PUCCH (carrying HARQ-ACK feedback for PDSCH), the LI priority is indicated in the DL Grant scheduling a PDSCH, carried by DCI Format 1 1 and 1 2.

Since the PUCCH can have two LI priorities, two HARQ-ACK codebooks of different priorities can be configured for a UE. This allows High LI priority HARQ-ACKs to be multiplexed into a High LI priority HARQ-ACK codebook, and Low LI priority HARQ-ACKs to be multiplexed into a Low LI priority HARQ-ACK codebook. An example is shown in Figure 8, where DCI#1, DCI#2, DCI#3, and DCI#4 schedule PDSCH#1, PDSCH#2, PDSCH#3, and PDSCH#4 respectively. DCI#1 and DCI#2 each schedule a Low LI priority (LP) PUCCH# 1 in sub-slot m+8 which carries a Low LI priority HARQ- ACK codebook to multiplex the HARQ-ACK feedbacks for PDSCH# 1 and PDSCH#2. DCI#3 and DCI#4 schedules a High LI priority (HP) PUCCH#2 in sub-slot m+9 which carries a High LI priority HARQ-ACK codebook to multiplex the HARQ-ACK feedbacks for PDSCH#3 and PDSCH#4. Hence, this provides the gNB with a mechanism to use different PUCCHs that can have different reliabilities to carry HARQ-ACK with different LI priorities.

In TDD operation, a PUCCH carrying one or more HARQ-ACKs may collide with DL symbols or Invalid symbols (symbols which are marked as being invalid by the network), where the colliding PUCCH is dropped. In DG-PDSCH, the gNB has the flexibility to schedule its PUCCHs to avoid DL symbols or Invalid symbols. However, since K\ is fixed after an SPS PDSCH is activated, it is difficult for the gNB to avoid such collisions because it cannot control where PUCCHs are scheduled with respect to SPS occasions. It is observed that for a short SPS PDSCH periodicity (i.e. more frequent SPS occasions), such collisions would occur more often, and this would lead to excessive dropping of PUCCHs and hence unnecessary PDSCH retransmissions.

Recognising this, 3GPP agreed that for Rel-17 URLLC, a UE can defer a dropped SPS HARQ-ACK transmission to the next available PUCCH, should it needs to do so due to a collision with a DL or Invalid symbol for example. An example of such deferment is illustrated by Figure 9, which shows two different SPS PDSCH configurations, SPS#1 and SPS#2 with periodicities of four and two slots respectively, and assigned K\ values of one and two slots (i.e. slot-based PUCCH) respectively. SPS#1 is transmitted in Slot n and, since Ki=l, its corresponding HARQ-ACK is carried by PUCCH P#1 91 in Slot n+1, which collides with a DL symbol and an Invalid symbol between time tf, and tg and is therefore dropped (as indicated in Figure 9 by the cross). The next available PUCCH resource is P#2 92 in Slot n+3, which is reserved for SPS#2 in Slot «+l, and so based on this proposal, the HARQ-ACK for SPS#1 in Slot n is multiplexed with the HARQ-ACK for SPS#2 in Slot n+1 into PUCCH P#2 92.

The HARQ Process ID, also referred to as the HARQ Process Number (HPN), of the PDSCH in an SPS occasion is determined by equation (1) below, as described in [5]:

Where, K_siot, is the number of slot relative to SFN = 0, N_siot-fra_me is the number of slots per frame (which depends on the subcarrier spacing), PSPS is the periodicity of the SPS occasion, NHARQ is the number of configured HARQ Processes for SPS (where the maximum is 16), and OHARQ is a HARQ offset. The parameters N_siot-frame, PSPS, NHARQ and OHARQ are RRC -configured and therefore are fixed. The HPN of the PDSCH of an SPS occasion therefore depends on the slot in which it is transmitted.

It was identified by 3GPP that the HPN associated with a deferred SPS HARQ-ACK may be the same as that of a non-deferred HARQ-ACK associated with a PDSCH in another SPS occasion, where these HARQ-ACKs associated with the same HPN are transmitted together in the same PUCCH [6], It is also feasible that the deferred SPS HARQ-ACK is transmitted together with another HARQ-ACK of a dynamically scheduled PDSCH (i.e. not an SPS HARQ-ACK) have the same HPN. That is, there may be a collision of HARQ-ACKs associated with the same HPN due to SPS HARQ-ACK deferral.

An example of this is illustrated by Figure 10, where the UE is configured with SPS#1 and SPS#2 and both of them have a periodicity of ten slots. The configured number of HARQ Processes for SPS is NHARQ = 16 and the HARQ offset OHARQ = 0. Here, the number of slots per frame (N_siot.fr_ame) = 10. At Slot 51, the UE receives a PDSCH in SPS#1 and, using equation (1) above, the HPN for SPS#1 is 5. The PUCCH carrying HARQ-ACK for SPS#1 (i.e. P#1 101) is dropped (as indicated in Figure 10 by the cross) due to a collision with both DL symbols and an invalid symbol, and the HARQ-ACK with HPN = 5 that was due to be transmitted in P#1 101 is therefore deferred to the next available PUCCH. At Slot 54, the UE receives another PDSCH from SPS#2 and determines, again, that the HPN = 5. The HARQ- ACK of SPS#2 is transmitted in P#2 102 and, since P#2 102 is also the next available PUCCH for the deferred HARQ-ACK of SPS#1, both HARQ-ACKs (of SPS#1 and SPS#2) are multiplexed and transmitted together in PUCCH P#2 102. Since the UE’s HARQ buffer is typically divided into sections associated with each HPN, collisions between HPNs 103 as illustrated by the example of Figure 10 cause ambiguity with respect to how the UE should manage its HARQ buffer in order to store the soft bits of both the PDSCHs. It should be noted that, in accordance with arrangements of embodiments of the present disclosure as described herein, the HARQ buffer may be configured differently, such as having an overflow section not associated with any particular HPN, which can be used to store PDSCHs of colliding HPNs when the section designated for that HPN is full. Such HARQ buffer configurations are down to UE implementation.

In [7], when there is such a collision of HPNs, it is proposed that the UE drops the earlier PDSCH (from the UE’s HARQ buffer), thereby allowing the later PDSCH to overwrite the previous PDSCH. In the example of Figure 10, this would be the PDSCH received in SPS#1. However, in [8] it is proposed to drop the later PDSCH, as dropping the earlier HARQ-ACK would lead to the UE clearing the HARQ buffer of the earlier PDSCH and would therefore impact the HARQ combining gain from retransmission. In the example of Figure 10, this would be the PDSCH received in SPS#2. It is also recognised that the later SPS may not even contain any PDSCH [6] and so dropping the earlier HARQ-ACK/PDSCH on the off-chance that a new PDSCH with the same HPN may be received is not beneficial.

It should be observed that always dropping the earlier PDSCH or the later PDSCH will impact the UE’s retransmission performance, as one of these PDSCHs would be removed from the UE’s HARQ buffer, since the UE would not know which PDSCH requires retransmission apriori. Embodiments of the present disclosure address the technical problem of collisions between PDSCHs having the same HPN, which may be caused due to a deferred SPS HARQ-ACK.

Handling of Same HARQ Process Number Collision for Deferred SPS HARQ-ACKs

Figure 11 shows a part schematic, part message flow diagram representation of a first wireless communications system comprising a communications device 111 and an infrastructure equipment 112 in accordance with at least some embodiments of the present technique. The communications device 111 is configured to transmit signals to and/or receive signals from the wireless communications network, for example, to and from the infrastructure equipment 112. Specifically, the communications device 111 may be configured to transmit data to and/or receive data from the wireless communications network (e.g. to/from the infrastructure equipment 112) via a wireless radio interface provided by the wireless communications network (e.g. the Uu interface between the communications device 111 and the Radio Access Network (RAN), which includes the infrastructure equipment 112). The communications device 111 and the infrastructure equipment 112 each comprise a transceiver (or transceiver circuitry) 111.1, 112.1, and a controller (or controller circuitry) 111.2, 112.2. Each of the controllers 111.2, 112.2 may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc. The communications device 111 further comprises a buffer 111.3 (e.g. a HARQ buffer) e.g. for storing the received downlink data as soft bits, which are stored so as to be combined with soft bits of later-received retransmissions of the downlink data in the case that the downlink data cannot be successfully decoded, in order to benefit from combining gain to successfully decode the downlink data. As shown in the example of Figure 11, the transceiver circuitry 111.1 and the controller circuitry 111.2 of the communications device 111 are configured in combination to receive 113, from the wireless communications network (e.g. from the infrastructure equipment 112), downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions (e.g. SPS occasions), to determine 114 that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device 111 on the first downlink channel within the downlink transmission occasion, to determine 115 that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, to determine 116 that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network (e.g. from the infrastructure equipment 112), wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ- ACK and the at least one other downlink channel, to determine 116 whether the communications device 111 is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer 111.3 of the communications device 111. If the communications device 111 determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer 111.3, the transceiver circuitry 111.1 and the controller circuitry 111.2 of the communications device 111 are configured in combination to store 117 all of the first downlink channel and the at least one other downlink channel within the HARQ buffer 111.3, or if the communications device 111 determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer 111.3, the transceiver circuitry 111.1 and the controller circuitry 111.2 of the communications device 111 are configured in combination to drop 118, in accordance with at least one characteristic of the downlink channels (i.e. of each of the first downlink channel and the one or more other downlink channels), at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer 111.3. Here, the dropped downlink channel may be the first downlink channel only, one (or more) of the at least one other downlink channel only, the first downlink channel and one (or more) of the at least one other downlink channel, or the first downlink channel and all of the at least one other downlink channel. The transceiver circuitry 111.1 and the controller circuitry 111.2 of the communications device 111 are configured in combination to transmit 119 all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

Essentially, embodiments of the present technique propose that should the communications device determines that it has to drop one of a plurality of downlink channels (e.g. PDSCHs) associated with the same HARQ Process Number (HPN), because there is not enough space to store it in the HARQ buffer either for the purpose of decoding or combining with previously or later received PDSCH(s), then the communications device should drop one of the multiple unacknowledged PDSCHs that have the same HPN (i.e. PDSCHs with same HPN collision), dependent upon the status of these PDSCHs.

In some arrangements of embodiments of the present technique, the said PDSCH status is whether the PDSCH is successfully decoded. That is, the UE drops the successfully decoded PDSCH(s), i.e. the UE already knows that it would feed back an ACK for this PDSCH(s). In other words, the at least one characteristic of the downlink channels comprises whether the downlink channels have been successfully decoded by the communications device, the at least one dropped downlink channel having been successfully decoded by the communications device. These arrangements recognise that the UE would not benefit from further HARQ retransmissions of this PDSCH since it has already been successfully decoded, and hence there isn’t any advantage of storing or continuing to store its soft bits in the HARQ buffer. As those skilled in the art would appreciate, a PDSCH that is not yet successfully decoded may require the UE to receive further retransmissions for soft/HARQ combining with the soft bits of the PDSCH, and hence it is beneficial to store these soft bits in the HARQ buffer.

An example is shown in Figure 12, where UE receives a PDSCH with HPN = 5 from SPS#1 at time to but its HARQ-ACK is deferred since the scheduled PUCCH, P#l, collides (as indicated in Figure 12 by the cross) with DL & invalid symbols between h and t$. The UE successfully decoded PDSCH SPS#1 and stores the soft bits in its HARQ buffer (for example in a portion of the buffer - shaded in the example of Figure 12 - which is designated for soft bits for PDSCHs with HPN = 5) after or at time h. In this example we assume sixteen HARQ Processes are configured for the UE. At time I . the UE receives another PDSCH with HPN = 5 from SPS#2, where its HARQ-ACK is scheduled in PUCCH P#2, but the UE fails to decode the PDSCH in SPS#2. Since the PDSCHs in SPS#1 and SPS#2 have the same HPN, a same HPN collision occurs. As per such arrangements, in the example of Figure 12, the UE drops the PDSCH in SPS#1 since this PDSCH has been successfully decoded, and replaces the PDSCH for SPS#1 with the soft bits for SPS#2 into its HARQ buffer for HPN = 5 at or after time to. The UE can therefore perform soft combining for SPS#2 when the gNB retransmits the PDSCH. Since P#2 is the first available PUCCH for the deferred HARQ-ACK corresponding to SPS#1, the HARQ-ACKs for SPS#1 and SPS#2 are transmitted in this PUCCH.

It should be appreciated that the solutions defined by embodiments of the present disclosure are applicable for cases where there are more than two PDSCHs in a same HPN collision. For example, with regard to the example wireless communications system of Figure 11, the at least one other downlink channel comprises a plurality of other downlink channels.

An example is shown in Figure 13, where the UE is configured with sixteen HARQ Processes and three SPS configurations, labelled as SPS#1, SPS#2 and SPS#3. A PDSCH transmitted in SPS#1 at time to is assigned HPN = 3 and its soft bits are stored in the UE HARQ buffer. The UE successfully decodes the PDSCH in SPS#1 and is scheduled to feedback its ACK#1 in PUCCH P#l, which is dropped due to collision (as indicated in Figure 13 by the left-most cross) with DL & Invalid symbols and therefore it is deferred. The UE receives another PDSCH in SPS#2 with HPN = 3 which causes an HPN collision. The UE fails to decode the PDSCH in SPS#2, as per embodiments of the present disclosure, the UE drops the soft bits of the PDSCH in SPS#1 that was successfully decoded and replaces it with the PDSCH soft bits from SPS#2. The HARQ-ACK feedback for SPS#2, NACK#2 is scheduled to be transmitted in PUCCH P#2 but P#2 also collides (as indicated in Figure 13 by the right-most cross) with Invalid symbols and is therefore dropped. The HARQ-ACKs for SPS#1 and SPS#2 are therefore deferred again. The UE receives another PDSCH in SPS#3 with the same HPN, i.e. HPN = 3 and successfully decodes it. The UE therefore, in the example of Figure 13, drops the decoded PDSCH from SPS#3 from its HARQ buffer since it has been successfully decoded, and continues to store the PDSCH from SPS#2 in its buffer. The UE the finally transmits the feedback for deferred HARQ-ACKs together with the HARQ-ACK from SPS#3 in PUCCH P#3.

In some arrangements of embodiments of the present technique, the said PDSCH status is the LI priority of the corresponding PUCCH carrying its HARQ-ACK. The PDSCH with the corresponding lower LI priority PUCCH is dropped. In other words, the at least one characteristic of the downlink channels comprises a priority level of uplink channels associated with the downlink channels, the at least one dropped downlink channel being associated with an uplink channel which has a lowest priority level. The activation DCI for an SPS also schedules its corresponding PUCCH to carry its HARQ-ACK and the activation DCI can also indicates the LI priority for this PUCCH. Those skilled in the art would appreciate that the PDSCH or SPS itself does not have any LI priority, but rather that it is the corresponding PUCCH (which is associated with this PDSCH/SPS instance) that has an LI priority.

It should be noted that, typically, the UE only flushes its HARQ buffer for an HPN (i.e. drops a PDSCH corresponding to that HPN) if it has sent the corresponding HARQ-ACK feedback or it has received a DL Grant with the New Data Indicator (NDI) bit being toggled. In solutions defined herein by the arrangements of embodiments of the present technique discussed above and discussed below however, the UE may drop a PDSCH for which an ACK has been generated, prior to that HARQ-ACK actually being transmitted. Also, in contrast to known solutions, when a PDSCH is dropped, instead of always dropping the earlier or the later PDSCH such as is defined in [7] and [8], solutions defined by arrangements of the present disclosure propose that the UE drops PDSCH(s) that are less likely to impact the PDSCH HARQ combining.

In some arrangements of embodiments of the present technique, the UE only drops a PDSCH if the number of PDSCHs with same HPN collision is greater than a threshold NPDSCH. In other words, the communications device may be configured to determine that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on the number of the first downlink channel and the at least one other downlink channel being greater than a threshold number. Such arrangements recognise that the PDSCHs may not fully occupy the HARQ buffer for an HPN and hence, the UE may have sufficient space to store the soft bits for these colliding PDSCHs, provided that there are not too many colliding PDSCHs.

Here, the parameter NPDSCH can be RRC configured by the network. That is, the threshold number may be indicated to the communications device via Radio Resource Control, RRC, signalling received from the wireless communications network.

Alternatively (or in addition), the parameter NPDSCH can be indicated in the SPS activation DCI. That is, the threshold number may be indicated to the communications device within one of an activation downlink control information, DCI, received from the wireless communications network which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

Alternatively (or in addition), the parameter NPDSCH can be fixed in the specifications, e.g. determined based on the sizes of the PDSCHs with colliding HPN. That is, the threshold number may be predetermined and known to the communications device. Here, the threshold number may depend on the sizes of the first downlink channel and the at least one other downlink channel. Those skilled in the art would appreciate that this may also be the case for when the parameter NPDSCH is indicated via RRC or DCI signalling - in such a case, the network bases the parameter NPDSCH on the relative sizes of the PDSCHs with the colliding HPN.

In an implementation of such arrangements of embodiments of the present technique, the said NPDSCH threshold is two (NPSDCH = 2). That is, the UE can store at most two PDSCHs with a colliding HPN in its HARQ buffer. Such an implementation recognises that the UE can be configured to store two PDSCHs for DL spatial multiplexing (i.e. for Multiple -Input and Multiple-Output (MIMO) purposes) and hence the same mechanism can be used to partition its HARQ buffer to store NPDSCH = 2 PDSCHs with a colliding HPN. Here, the UE only needs to drop a PDSCH if there are three or more PDSCHs with a colliding HPN.

The UE may not have sufficient soft buffer space or memory to store a previously received one or two (or more) PDSCHs having a particular HPN, and also to decode a newly received PDSCH of the same HPN. That is, the UE may need memory to store the soft bits for a new or an ongoing PDSCH decoding in its HARQ buffer, and so it cannot store soft bits for the previous PDSCHs. In other words, in some arrangements of embodiments of the present technique, the communications device may determine that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining, prior to attempting to decode at least one of the other downlink channels, that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

In one such arrangement of embodiments of the present technique, when a same HPN collision occurs with a new PDSCH, which has not been decoded yet (or prior to requiring storage of the soft bits), the UE drops a successfully decoded PDSCH in a previous SPS occasion in its HARQ buffer. That is, the UE will make room in its soft buffer or memory to decode the new PDSCH by dropping a PDSCH sharing the same HPN that has already been successfully decoded. In other words, the at least one downlink channel has been successfully decoded by the communications device. This is beneficial since the new PDSCH may not be successfully decoded and hence needs to be stored in the HARQ buffer for soft combining with potential PDSCH retransmissions.

An example is shown in Figure 14, where the PDSCH in SPS#1 at time to is assigned to HPN = 5, and its corresponding HARQ-ACK is deferred because the scheduled PUCCH P#1 collides (as indicated in Figure 14 by the cross) with DL & Invalid symbols between time h and t$. At time /x. the UE monitors SPS#2 for a potential PDSCH and in this example, the UE requires memory to store the soft bits for SPS#2 decoding. As per this arrangement, the UE clears the HARQ buffer for HPN = 5, which contains the soft bits for SPS#1 (i.e. the UE drops SPS#1) since the PDSCH received in SPS#1 has been successfully decoded, so that it can start decoding SPS#2. In this example as shown by Figure 14, the UE successfully decodes SPS#2 as well and therefore feeds back two ACKs {ACK#1, ACK#2} for SPS#1 and SPS#2 respectively in PUCCH P#2.

It should be noted that at the point of dropping the soft bits of SPS#1 in the example of Figure 14, the UE does not know whether or not SPS#2 would be decoded successfully. Furthermore, differently to the example of Figure 14, the UE can actually also clear the HARQ buffer containing SPS#1 prior to time tx (i.e. between time ti and tx) before receiving the PDSCH in SPS#2, since the UE may already foresee a same HPN collision and knows that the PDSCH in SPS#3 has been successfully decoded and hence does not need to be retained in the buffer. However, this can be up to UE implementation.

However, in some arrangements of embodiments of the present disclosure, when a same HPN collision occurs with a new PDSCH, which has not been decoded yet, and there is no successfully decoded PDSCH from any previous SPS occasions or there are still failed PDSCH in previous SPS occasions, the UE will select one of the colliding failed PDSCHs to drop. In other words, the at least one dropped downlink channel may be from among the at least one other downlink channel, and wherein none of the at least one other downlink channel have been successfully decoded. Alternatively, the UE may have one or more successfully decoded PDSCHs to drop, but after dropping them, determines that there is still not enough space in the HARQ buffer to decode the new PDSCH. Here, the UE then makes a determination that it also has to drop at least one of the other PDSCHs which has not been successfully decoded. In other words, the communications device may be configured to determine, after dropping one or more successfully decoded downlink channels, that the HARQ buffer still does not have enough space to store all of the first downlink channel and the at least one other downlink channel that have not been dropped, wherein the at least one dropped downlink channel is from among the remaining at least one other downlink channel, and wherein none of the remaining at least one other downlink channel have been successfully decoded.

For such arrangements of embodiments of the present disclosure, it is trivial when the HPN of the new undecided PDSCH collides with that of just one other PDSCH and the (full) portion of the buffer associated that that HPN comprises the soft bits of only that other PDSCH; i.e. the other PDSCH is dropped from the HARQ buffer. However, for cases where the same HPN collision involves more than two SPS occasions, and/or the HARQ buffer comprises soft bits of PDSCHs of those SPS occasions or other PDSCHs which have not yet been successfully decoded, the UE is required to make a decision regarding which SPS PDSCH should be dropped for each new SPS occasion that has an HPN collision. That is, it is possible that the UE may have to select one or more colliding PDSCHs to drop in an HPN collision. For example, a decision will have to be made if none of the PDSCHs are successfully decoded (all NACKs selection), or if there is more than one successfully decoded PDSCH to choose from (multiple ACKs selection) such as described above with reference to the example of Figure 12.

Some cases in which the UE has insufficient soft buffer memory to store an undecoded PDSCH, i.e. a PDSCH that it is going to decode or is currently decoding) are discussed below, and with reference to the examples of Figures 15, 16, and 17. Here, arrangements of embodiments of the present disclosure provide solutions to how the UE may to discard a PDSCH in its HARQ buffer in order to perform decoding of a new PDSCH.

In an arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process and to decode a newly received PDSCH with that same HPN, the UE drops the failed PDSCH(s) with a corresponding PUCCH of lower LI priority. In other words, the at least one dropped downlink channel may be that which has a lowest priority level.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process and to decode a newly received PDSCH with that same HPN, the UE drops the failed PDSCH(s) that it has attempted decoding from the earliest SPS. In other words, the at least one dropped downlink channel may be that which was received earliest. That is, the UE will ensure there is space in the HARQ buffer to decode the new PDSCH. If dropping the failed PDSCH from the earliest SPS does not provide sufficient HARQ buffer space, the UE drops the failed PDSCH from the second earliest SPS and so on. Here, the UE may have successfully decoded colliding PDSCHs and after dropping them (as per previously described arrangements of embodiments of the present technique) it still does not have sufficient HARQ buffer space.

An example is shown in Figure 15, where NPDSCH = 2, and so the UE needs to clear the HARQ buffer of an HPN if it needs to decode a new PDSCH with the same HPN. The UE receives a PDSCH with HPN = 12 from SPS#1 at time to but failed to decode it and stores its soft bits into the HARQ buffer. The UE then receives another PDSCH with HPN = 12 from SPS#2 at time and since NPDSCH = 2, it can decode the PDSCH without dropping the PDSCH from SPS#1 in its HARQ buffer. At time tn, the UE starts to monitor SPS#3 where the PDSCH would have an HPN = 12 thereby causing HPN collision with the PDSCHs from SPS#1 and SPS#2 and their HARQ-ACKs are deferred due to their corresponding PUCCHs P#1 and P#2 colliding with DL and Invalid symbols (as indicated in Figure 15 by the crosses). The UE needs to drop a PDSCH’s soft bits from its HARQ buffer in order to decode SPS#3 and, as per this arrangement, the UE drops PDSCH from SPS#1 - as it is the earliest SPS from among the colliding SPS - at time tn (it should be noted that the UE only needs to drop the soft bits of the PDSCH from SPS#1 when it starts to add new soft bits to its HARQ buffer, which may for example be done between tn and tn). The UE successfully decodes PDSCH in SPS#3, and stores its soft bits in its HARQ buffer at time /|2- The UE then transmits the deferred HARQ-ACKs from SPS#1 and SPS#2 together with the HARQ-ACK from SPS#3 in PUCCH P#3.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process and to decode a newly received PDSCH with that same HPN, the UE drops the failed PDSCH(s) that it has attempted decoding from the latest SPS. In other words, the at least one dropped downlink channel may be that which was received latest. That is, the UE will ensure there is space in the HARQ buffer to decode the new PDSCH. If dropping the failed PDSCH from the latest SPS does not provide sufficient HARQ buffer space, the UE drops the failed PDSCH from the second latest SPS and so on.

An example is shown in Figure 16, which has the same scenario as the example in Figure 15, where the PDSCHs from SPS#1, SPS#2 and SPS#3 have an HPN collision. Here, prior to decoding the PDSCH in SPS#3 at time tn (or prior to having to store soft bits for the new decoding between time tn and tn), the UE drops the failed PDSCHs from SPS#2, which is the latest SPS. The UE then successfully decodes SPS#3 and stores the soft bits into its HARQ buffer at time tn- The HARQ-ACKs for SPS#1, SPS#2 and SPS#3 are transmitted together in PUCCH P#3.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process and to decode a newly received PDSCH with that same HPN, the UE drops the failed PDSCH(s) that it has attempted decoding from SPS that are outside a time window TPDSCH. In other words, the at least one dropped downlink channel may be those which were received outside of a specified time window. That is, the UE will ensure there is space in the HARQ buffer to decode the new PDSCH. The said time window TPDSCH can be RRC configured, indicated in an activation DCI or fixed in the specifications.

An example is shown in Figure 17, which illustrates a similar scenario to the examples illustrated by Figures 15 and 16. At time tn, the UE needs to drop failed PDSCHs with HPN = 12 in order to decode a new PDSCH in SPS#3. As per this arrangement, the time window TPDSCH is configured, e.g. one slot relative to SPS#3. Since no SPS falls within TPDSCH, the UE drops all the failed PDSCHs (i.e. those received in SPS#1 and SPS#2) with HPN = 12 in its HARQ buffer. The UE successfully decoded SPS#3 and stores the soft bits in its HARQ buffer. It then sends the HARQ-ACK for SPS#1, SPS#2 and SPS#3 in PUCCH P#3.

In another embodiment, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process, the UE drops the new undecoded SPS. In other words, the at least one of the at least one other downlink channel is dropped prior to being decoded by the communications device. That is, the UE prioritises the failed PDSCHs that it has already attempted to decode. It should be noted that the UE will drop successfully decoded PDSCHs first in order to create HARQ buffer space, as in the example of Figure 13, before considering dropping the new undecoded SPS if this is not possible. In another embodiment, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process, the UE drops the new undecoded SPS if the new undecoded SPS is activated with a corresponding PUCCH of lower LI priority. In other words, the at least one dropped downlink channel may be the at least one of the at least one other downlink channel if the uplink channel associated with the at least one of the at least one other downlink channel has a lowest priority level from among uplink channels associated with each of the first downlink channel and the at least one other downlink channel, and wherein the at least one of the at least one other downlink channel is dropped prior to being decoded by the communications device.

Contrary to those arrangements discussed above, the UE may in fact have sufficient soft buffer space or memory to store an undecoded PDSCH (i.e. a PDSCH that it is going to decode or is decoding) in addition to a previously received one or two (or more) PDSCHs having a particular HPN. As such, the UE does not need to discard PDSCH in its HARQ buffer in order to perform the decoding. However, the UE may need to discard the soft bits of one or more of the PDSCHs from its HARQ buffer following decoding of the newly received PDSCH, for example because it does not have space to store all of the colliding PDSCHs that failed the decoding process, or because it anticipates the reception of a further PDSCH. If possible, the UE drops successfully decoded PDSCHs, but this may not be possible (or sufficient if multiple PDSCHs need to be dropped). The UE might, as described above, have to drop one or more unsuccessfully decoded PDSCHs. In other words, in some arrangements of embodiments of the present disclosure, the communications device may be configured to determine that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining, after decoding at least one of the at least one other downlink channel, that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel. Here, the at least one dropped downlink channel may be from among the first downlink channel and the at least one other downlink channel, and wherein none of the first downlink channel and the at least one other downlink channel have been successfully decoded.

In an arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process, the UE drops the failed PDSCH(s) with a corresponding PUCCH of lower LI priority. In other words, the at least one dropped downlink channel may be that which has a lowest priority level.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process, the UE drops the failed PDSCH(s) from the earliest SPS. In other words, the at least one dropped downlink channel may be that which was received earliest. Here, the UE may have already dropped colliding PDSCHs that has passed the decoding process and still there is not sufficient HARQ buffer space. This is beneficial if the earliest PDSCH may not be able to meet its latency requirement, i.e. it has already exceeded the latency budget. It should be noted that the UE may drop two PDSCHs from the earliest SPS if that SPS is transmitted using MIMO. If dropping the earliest PDSCH still does not provide sufficient HARQ buffer memory, the UE will drop the PDSCH from the second earliest SPS and so on.

An example is shown in Figure 18, where an HPN collision occurs for PDSCHs from SPS#1, SPS#2 and SPS#3. Here it is assumed that the UE can store two PDSCHs with the same HPN in its HARQ buffer, i.e. NPDSCH = . At time tn, the UE needs to decide which colliding PDSCH to drop from its HARQ buffer, as it does not have sufficient room to store all three PDSCHs. As per this arrangement, the failed PDSCH from the earliest SPS is dropped and the UE stores the PDSCHs from SPS#2 and SPS#3 in its HARQ buffer. In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs that failed the decoding process, the UE drops the failed PDSCH(s) from the latest SPS. In other words, the at least one dropped downlink channel may be that which was received latest. If dropping the latest SPS still does not provide sufficient HARQ buffer for the UE to store the remaining (failed) PDSCHs, the UE drops the failed PDSCH from the second latest SPS and so on.

An example is shown in Figure 19, where the PDSCHs received in SPS#1, SPS#2, and SPS#3 have an HPN collision. In SPS#3, the UE is scheduled with MIMO and hence it needs to decode two PDSCHs. The UE HARQ buffer can store only two PDSCHs, i.e. NPSDCH = 2, and after decoding SPS#3, there are four PDSCHs and only two can be stored. As per this arrangement, the UE drops the failed PDSCHs from the latest SPS, i.e. SPS#3, and stores the PDSCH from SPS#1 and SPS#2. The deferred HARQ- ACKs from SPS#1 and SPS#2 are transmitted together with that from SPS#3 in PUCCH P#3.

In another arrangement of embodiments of the present technique, a time window TPDSCH is defined where the UE drops failed PDSCHs in an HPN collision from SPS that are outside TPDSCH. In other words, the at least one dropped downlink channel are those which were received outside of a specified time window. The said time window can be RRC configured, indicated in an activation DCI or fixed in the specifications.

An example is shown in Figure 20, where PDSCHs from SPS#1, SPS#2, and SPS#3 have an HPN collision and the UE determines that it needs to drop a PDSCH. As per this arrangement, a time window TPDSCH is defined/configured between time t to /u. The UE drops any PDSCHs with SPS outside of TPDSCH and only stores PDSCH from SPS#3 in its HARQ buffer.

As described in some arrangements of embodiments of the present technique above, for example with reference to Figures 12, 13, and 14, the UE may be required to drop from its HARQ buffer the soft bits of a successfully decoded PDSCH in order to make room for another PDSCH with the same HPN, or because it cannot store all of the currently decoded PDSCHs with the same HPN in its HARQ buffer. However, it may be the case that there is more than one successfully decoded PDSCH with a same HPN stored in the UE’s HARQ buffer, and so the UE needs to make a decision regarding which one (or more) of these successfully decoded PDSCHs to drop. In other words, at least two of the first downlink channel and the at least one other downlink channel may have been successfully decoded by the communications device. Here, the communications device may be configured to determine that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

In such an arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all PDSCHs in the HPN collision and there are more than one successfully decoded PDSCHs among these colliding PDSCHs, the UE drops all the successfully decoded PDSCHs. In other words, all of the successfully decoded downlink channels may be dropped. This arrangement recognises that there is no benefit in keeping any PDSCHs that have been successfully decoded.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all PDSCHs in the HPN collision and there are more than one successfully decoded PDSCHs among these colliding PDSCHs, the UE drops the successfully decoded PDSCH(s) that has a corresponding PUCCH of lower LI priority. In other words, the one of the successfully decoded downlink channels which is associated with an uplink channel having a lowest priority level may be dropped.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all PDSCHs in the HPN collision and there are more than one successfully decoded PDSCHs among these colliding PDSCHs, the UE drops the successfully decoded PDSCH(s) from the earliest SPS. In other words, the one of the successfully decoded downlink channels which was received earliest may be dropped. If dropping the successfully decoded PDSCH(s) from the earliest SPS does not provide sufficient HARQ buffer space, the UE drops the successfully decoded PDSCH(s) from the second earliest SPS and so on.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all PDSCHs in the HPN collision and there are more than one successfully decoded PDSCHs among these colliding PDSCHs, the UE drops the successfully decoded PDSCH(s) from the latest SPS. In other words, the one of the successfully decoded downlink channels which was received latest may be dropped. If dropping the successfully decoded PDSCH(s) from the latest SPS does not provide sufficient HARQ buffer space, the UE drops the successfully decoded PDSCH(s) from the second latest SPS and so on.

In another arrangement of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all PDSCHs in the HPN collision and there are more than one successfully decoded PDSCHs among these colliding PDSCHs, the UE drops the successfully decoded PDSCH(s) that are outside a time window TPDSCH- In other words, those of the of the successfully decoded downlink channels which were received outside of a specified time window may be dropped. The said time window TPDSCH can be RRC configured, indicated in an activation DCI or fixed in the specifications.

In some arrangements of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all PDSCHs in the HPN collision and there are more than one successfully decoded PDSCHs among these colliding PDSCHs, the UE drops the one or more successfully decoded PDSCHs in this collision prior to having decoded a new colliding PDSCHs. Such arrangements cater for the case where the UE does not have sufficient HARQ buffer space to decode a new PDSCH with the same HPN and therefore needs to clear some HARQ buffer space in that HPN in order to decode the new PDCH. In other words, at least two of the first downlink channel and the at least one other downlink channel may have been successfully decoded by the communications device. Here, the communications device may be configured to determine that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on receiving a new downlink channel which is to be decoded by the communications device, wherein the new downlink channel is associated with the same HPN as the first downlink channel and the at least one other downlink channel.

In such an arrangement of embodiments of the present technique, where the UE drops one or more successfully decoded PDSCHs in an HPN collision prior to decoding a new colliding PDSCH, the PDSCHs that are selected for dropping by the UE are all the successfully decoded PDSCHs. In other words, all of the successfully decoded downlink channels may be dropped. This arrangement recognises that there is no benefit in keeping any PDSCHs that have been successfully decoded. In another arrangement of embodiments of the present technique where the UE drops one or more successfully decoded PDSCHs in an HPN collision prior to decoding a new colliding PDSCH, the PDSCHs that are selected for dropping by the UE is the successfully decoded PDSCH(s) that has a corresponding PUCCH of lower LI priority. In other words, the one of the successfully decoded downlink channels which is associated with an uplink channel having a lowest priority level may be dropped.

In another arrangement of embodiments of the present technique, where the UE drops one or more successfully decoded PDSCHs in an HPN collision prior to decoding a new colliding PDSCH, the PDSCHs that are selected for dropping by the UE are the PDSCHs from the earliest SPS. In other words, the one of the successfully decoded downlink channels which was received earliest may be dropped. If dropping the PDSCH(s) from the earliest SPS does not provide sufficient HARQ buffer space, the UE drops the PDSCH(s) from the second earliest SPS and so on.

In another arrangement of embodiments of the present technique, where the UE drops one or more successfully decoded PDSCHs in an HPN collision prior to decoding a new colliding PDSCH, the PDSCHs that are selected for dropping by the UE are the PDSCHs from the latest SPS. In other words, the one of the successfully decoded downlink channels which was received latest may be dropped. If dropping the PDSCH(s) from the latest SPS does not provide sufficient HARQ buffer space, the UE drops the PDSCH(s) from the second latest SPS and so on.

In another arrangement of embodiments of the present technique, where the UE drops one or more successfully decoded PDSCHs in an HPN collision prior to decoding a new colliding PDSCH, the PDSCHs that are selected for dropping by the UE are the PDSCHs from SPS that are outside of a time window TPDSCH. In other words, those of the of the successfully decoded downlink channels which were received outside of a specified time window may be dropped. The said time window TPDSCH can be RRC configured, indicated in an activation DCI or fixed in the specifications.

In some arrangements of embodiments of the present technique, when a same HPN collision occurs and the UE does not have sufficient HARQ buffer to store all the colliding PDSCHs, the subset of SPS with colliding HPN that are selected for dropping may be explicitly indicated by the network. In other words, the communications device may be configured to determine that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel, and wherein the communications device determines the at least one dropped downlink channel based on an indication received from the wireless communications network. Here this subset can include SPS that have failed PDSCHs and successfully decoded PDSCHs.

In another arrangement of embodiments of the present technique, the said subset includes only SPS where the UE has failed to decode its PDSCH(s). In other words, the at least one dropped downlink channel indicated by the indication are those which have not been successfully decoded. Here it is assumed that the PDSCHs from successfully decoded SPS are already dropped and there are still not sufficient HARQ buffer space to store the failed PDSCHs from the remaining SPS. Here the network can indicate whether to drop the earliest or latest SPS.

In another arrangement of embodiments of the present technique, the said subset includes only SPS where the UE has successfully decoded its PDSCH(s). In other words, the at least one dropped downlink channel indicated by the indication are those which have been successfully decoded. The network can indicate which among these SPS that the UE needs to drop. In another arrangement of embodiments of the present technique, the said subset excludes an undecoded PDSCH in a new SPS with colliding HPN. In other words, prior to the communications device attempting to decode the first downlink channel, the at least one dropped downlink channel indicated by the indication may be from among the at least one other downlink channel. That is, the UE may drop one or more PDSCHs with a colliding HPN to create HARQ buffer space in order to decode a new SPS with the same HPN. This indicator also allows the gNB to decide whether to prioritise an undecoded PDSCH in a new SPS or not; i.e. if it is excluded then the new SPS is prioritised, otherwise it is included in the subset for dropping.

In another arrangement of embodiments of the present technique, the said indication is RRC signaled by the network. In other words, the indication may be received the by the communications device via RRC signalling received from the wireless communications network. In an example implementation, for each SPS index, the gNB can indicate via configuration, whether the SPS index is dropped or not. The gNB can further configure an order in which each SPS index is to be dropped. For example, the gNB can configure four SPS instances, e.g. SPS#1, SPS#2, SPS#3 an SPS#4, and configure that the order of dropping is {SPS#3, SPS#2, SPS#4, SPS#1}; that is UE drops SPS#3 first if there is an HPN collision regardless if it is the earliest or the latest, and if there is not HARQ buffer space, drop SPS#2 and so on.

In another arrangement of embodiments of the present technique, the said indication is dynamically indicated in an activation DCI. In other words, the indication may be received by the communications device within one of an activation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

It should be appreciated by those skilled in the art that the network can configure more than one subset for the UE. For example, the network can configure a subset that includes only failed SPS and another subset that includes only SPS with successfully decoded PDSCH. The network may then indicate separately which SPS in each subset the UE should drop.

While arrangements of embodiments of the present technique, and the examples of Figures 12 to 20, described above the examples refer to PDSCHs with same HPN collision all being received within SPS instances (i.e., the at least one other downlink channel is received within at least one of the plurality of downlink transmission occasions), those skilled in the art would also appreciate that it is possible that one or more of the colliding PDSCHs are dynamically scheduled using a DL Grant in a DCI. That is, in other words, in some arrangements of embodiments of the present disclosure at least one of the at least one other downlink channel may be received within at least one set of downlink resources indicated to the communications device by a dynamic grant carried by DCI signalling received from the wireless communications network. While a PUCCH for a DG-PDSCH can be rescheduled if, for example, it collides with a DL or invalid symbol, a PUCCH for an SPS-PDSCH cannot due to the fixed nature of parameters such as Ki. That means that while it is unlikely for a HARQ-ACK for a DG-PDSCH to have to be delayed to a next available PUCCH, it is possible (as described above) for a HARQ-ACK for an SPS-PDSCH to have to be delayed to a next available PUCCH. Such arrangements of embodiments of the present disclosure are therefore considered in view of such a next available PUCCH (to carry the HARQ-ACK for an SPS-PDSCH) to already carry (at least) a HARQ-ACK for a DG-PDSCH, where the HPNs of the DG-PDSCH and SPS-PDSCH collide. In some arrangements of embodiments of the present technique, it may be the DG-PDSCH that is dropped from the HARQ buffer of the UE - either due to it being a DG-PDSCH, or because it satisfied some other criteria or characteristic as described herein (e.g. its associated PUCCH has a lower LI priority than the other HPN-colliding SPS-PDSCHs). In other words, the at least one dropped downlink channel comprises the at least one dynamically granted downlink channel.

In such an arrangement of embodiments of the present technique, the network indicates whether a dynamically scheduled PDSCH with HPN colliding with one or more SPS is a retransmission or a new data. In other words, the communications device may be configured to receive an indication from the wireless communications network of whether the downlink data carried by the at least one dynamically granted downlink channel is new data or is retransmitted data.

In another arrangement of embodiments of the present technique, the said retransmission or new data indicator is RRC configured. In other words, the indication may be received the by the communications device via RRC signalling received from the wireless communications network.

In another embodiment, the said retransmission or new data indicator is dynamically indicated in the DCI, e.g. SPS activation DCI of one or more of the SPS or the DL Grant of the dynamic PDSCH. In other words, the indication may be received the by the communications device via DCI signalling received from the wireless communications network. Here, the DCI signalling carrying the indication may be one of an activation DCI which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network. Alternatively, the DCI signalling carrying the indication may be the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel.

In another arrangement of embodiments of the present technique, the said dynamic retransmission or new data indicator is the NDI bit in the DL Grant. In other words, the indication may be carried by a new data indicator, NDI, bit of the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel. If the NDI bit is toggled, it means that the dynamically scheduled PDSCH is a retransmission for one of the colliding SPS. If the NDI bit is not toggled, it means that the dynamically scheduled PDSCH is a new data.

In another arrangement of embodiments of the present technique, whether an HPN-colliding dynamic PDSCH is a retransmission or a new data is fixed in the specifications. In other words, it may be predetermined and known to the communications device whether the downlink data carried by the at least one dynamically granted downlink channel is new data or is retransmitted data. That is, here, solutions as defined by the present technique may be employed for cases only where an HPN-colliding DG-PDSCH is a retransmission, or only for cases where an HPN-colliding DG-PDSCH carries new data. In such cases, if the colliding HPN-colliding PDSCHs are all SPS-PDSCHs, then such a restriction will not apply.

In some arrangements of embodiments of the present disclosure, when the dynamic PDSCH with HPN colliding with one or more SPS PDSCHs is determined (e.g. via indication as described above) to be a retransmission, the UE may perform HARQ combining (i.e. soft combining) using the dynamically scheduled PSDCH with one of its colliding PDSCHs. In other words, the downlink data carried by the at least one dynamically granted downlink channel is retransmitted data, and wherein the communications device is configured to combine the downlink data carried by the dynamically granted downlink channel with downlink data carried by a selected at least one of the first downlink channel and - if there are further colliding downlink channels to the first downlink channel and the at least one dynamically granted downlink channel - the at least one other downlink channel (that isn’t the at least one dynamically granted downlink channel).

The following arrangements describe which colliding SPS the UE should perform HARQ combining on for the case where they are more than one colliding SPS. If there is only one colliding SPS (i.e. an HPN collision involving a single SPS PDSCH and a single dynamic PDSCH) then it is clear that the UE will HARQ combine the only colliding SPS with the dynamic PDSCH.

It should be noted that, in the absence of any HARQ-ACK feedback, the gNB does not know which SPS the UE has failed to decode. Hence, this is a blind attempt from the gNB to schedule a retransmission to the UE.

In an arrangement of embodiments of the present technique, the said colliding PDSCHs that is selected for HARQ combining is the PDSCH from the latest SPS. In other words, the selected downlink channel may be the latest received downlink channel from among the first downlink channel and the at least one other downlink channel. An example is shown in Figure 21, where PDSCHs from SPS#1 and SPS#2 have the same HPN therefore causing a collision. Here NPDSCH = . The UE fails to decode SPS# I and SPS#2 and their NACKs are deferred due their corresponding PUCCH, P#1 and P#2 respectively, colliding with DL and Invalid symbols (as indicated in Figure 21 by crosses). At time fio, the UE receives DCI#3 containing a DL Grant scheduling PDSCH#3 and a corresponding PUCCH P#3. The DL Grant indicates an HPN = 3 which is the same as the colliding HPN for the already colliding SPS and the NDI bit is not toggled, indicating a retransmission. As per this arrangement, the UE HARQ combines PDSCH#3 with SPS#2, which is the latest colliding SPS and in this example, it successfully decodes the PDSCH. The UE stores the soft bits for SPS# I and the HARQ combined soft bits of PDSCH#3 and SPS#2 in its HARQ buffer. The UE then feeds back NACK#1 and ACK#2 using PUCCH P#3.

In another arrangement of embodiments of the present technique, the said colliding PDSCHs that is selected for HARQ combining is the PDSCH from the earliest SPS. In other words, the selected downlink channel may be the earliest received downlink channel from among the first downlink channel and the at least one other downlink channel. An example is shown in Figure 22, which illustrates a similar scenario to the example in Figure 21. However, as per this arrangement, the dynamically scheduled PDSCH#3 is HARQ combined with the PDSCH in SPS#1, which is the earliest SPS. Here the UE successfully decodes SPS# I and feeds back an ACK#1 in P#3 together with the deferred NACK#2 from SPS#2.

In another arrangement of embodiments of the present technique, the network indicates which PDSCH with colliding HPN the UE should HARQ combine with the colliding dynamic PDSCH. In other words, the communications device may be configured to receive an indication from the wireless communications network of the selected downlink channel.

In another arrangement of embodiments of the present technique, the said colliding PDSCH indication for HARQ combining is RRC configured. In other words, the indication may be received the by the communications device via RRC signalling received from the wireless communications network. That is, the gNB can configure one or more SPS indices where if present in an HPN collision would HARQ combining with a colliding dynamic PDSCH. If the gNB configures more than one SPS indices for HARQ combining with a colliding dynamic PDSCH, any suitable arrangement of embodiments of the present technique as described above can be utilised, e.g. the latest or earliest SPS among those configured for HARQ combining.

In another arrangement of embodiments of the present technique, the said colliding PDSCH indication for HARQ combining is dynamically indicated. In other words, the indication may be received the by the communications device via DCI signalling received from the wireless communications network. The dynamic indicator can be:

• The DL Grant scheduling the colliding dynamic PDSCH. In other words, the DCI signalling carrying the indication may be the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel. The indicator can point to an SPS index, or it can be a simple 1 bit indicating either earliest or latest colliding SPS; or

• The SPS activation DCI, where an SPS upon being activate will also be indicated whether it should combine with a colliding dynamic PDSCH. In other words, the DCI signalling carrying the indication may be one of an activation DCI which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

In an arrangement of embodiments of the present technique, if the colliding dynamic PDSCH is determined, e.g. via indication, as a new data, the UE may perform dropping of one or more colliding PDSCH from its HARQ buffer if there is no available space in the HARQ buffer to store the dynamic PDSCH soft bits. The UE can utilise one or more of the previous arrangements of embodiments of the present disclosure in deciding which colliding PDSCH (including the dynamically PDSCH) to drop. In other words, the downlink data carried by the at least one dynamically granted downlink channel may be new data, and the communications device may be configured to determine that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel, wherein the at least one dropped downlink channel is one of the first downlink channel and the at least one other downlink channel other than the dynamically granted downlink channel.

Those skilled in the art should appreciate that the above-described arrangements of embodiments of the present disclosure can be implemented either individually or in any suitable combined manner. For example, the T PDSCH time window may be configured in combination with the dropping by the UE of the failed PDSCH from the earliest (or indeed latest) SPS, such that the UE firstly drops the failed PDSCH outside the time window TPDSCH and if the UE still needs to drop additional PDSCHs, it considers those within the time window as well, where the UE selects either the earliest or latest SPS for dropping.

In another implementation, for a UE without sufficient memory to store soft bits of an undecoded PDSCH of a new SPS with a HPN collision, a combination of checking if a PDSCH in a previous SPS is successful and dropping the undecoded PDSCH can be utilised. That is:

• If the colliding PDSCH in a previous SPS occasion is successfully decoded by the UE, drop this PDSCH and use the HARQ buffer to decode the undecoded PDSCH in the new SPS occasion; or If the colliding PDSCH in a previous SPS occasion has failed the decoding process, drop the undecoded PDSCH in the new SPS occasion and continue to store the previous (failed) PDSCH in the HARQ buffer.

In another implementation, for a UE without sufficient memory to store soft bits of an undecoded PDSCH of a new SPS with a HPN collision, a combination of checking if a PDSCH in a previous SPS is successful and dropping the undecoded PDSCH, whilst considering priority of the PDSCHs, can be used. That is:

• If the colliding PDSCH in a previous SPS occasion is successfully decoded by the UE, drop this PDSCH and use the HARQ buffer to decode the undecoded PDSCH in the new SPS occasion; or

• If the colliding PDSCH in a previous SPS occasion has failed the decoding, drop the SPS with a corresponding PUCCH of lower LI priority, which can be either the undecoded PDSCH in the new SPS occasion or the failed PDSCH in the previous SPS occasion; or

• If both colliding PDSCHs have corresponding PUCCHs of the same LI priority, drop the undecoded PDSCH.

It would be appreciated by those skilled in the art that the combined implementations described above are merely examples, and are not intended to be limiting in any way. That is, any combination of two or more arrangements of embodiments of the present technique as described herein may be configured for a UE, provided that they are not contradictory.

Figure 23 shows a flow diagram illustrating an example process of communications in a communications system in accordance with embodiments of the present technique. The process shown by Figure 23 is a method of operating a communications device configured to transmit signals to and/or to receive signals from a wireless communications network (e.g. to or from an infrastructure equipment of the wireless communications network).

The method begins in step SI. The method comprises, in step S2, receiving, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions. In step S3, the process comprises determining that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device on the first downlink channel within the downlink transmission occasion. In step S4, the method comprises determining that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel. Then, in step S5, the process comprises determining that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel. The method in step S6 comprises determining whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within a HARQ buffer of the communications device. If the communications device determines in step S6 that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, the method, in step S7, comprises storing all of the first downlink channel and the at least one other downlink channel within the HARQ buffer. On the other hand, if the communications device determines in step S6 that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, the method, in step S8, comprises dropping, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer. Following this, in step S9, the process comprises transmitting all of the HARQ-ACK and the at least one other HARQ- ACK within the next available uplink channel. The process ends in step S10.

Those skilled in the art would appreciate that the method shown by Figure 23 may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in either or both of these methods, or the steps may be performed in any logical order. Though embodiments of the present technique have been described largely by way of the example communications system shown in Figure 11, and further described with respect to the arrangements shown by Figures 12 to 22, it would be clear to those skilled in the art that they could be equally applied to other systems to those described herein.

Those skilled in the art would further appreciate that such infrastructure equipment and/or communications devices as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and communications devices as herein defined and described may form part of communications systems other than those defined by the present disclosure.

The following numbered paragraphs provide further example aspects and features of the present technique:

Paragraph 1. A method of operating a communications device configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network, the method comprising receiving, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, determining that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device on the first downlink channel within the downlink transmission occasion, determining that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, determining that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, determining whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within a HARQ buffer of the communications device, if the communications device determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, storing all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, or if the communications device determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, dropping, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer, and transmitting all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

Paragraph 2. A method according to paragraph 1, wherein the at least one characteristic of the downlink channels comprises whether or not the downlink channels have been successfully decoded by the communications device, the at least one dropped downlink channel having been successfully decoded by the communications device.

Paragraph 3. A method according to paragraph 2, wherein at least two of the first downlink channel and the at least one other downlink channel have been successfully decoded by the communications device.

Paragraph 4. A method according to paragraph 3, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

Paragraph 5. A method according to paragraph 3, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on receiving a new downlink channel which is to be decoded by the communications device, wherein the new downlink channel is associated with the same HPN as the first downlink channel and the at least one other downlink channel. Paragraph 6. A method according to paragraph 3, wherein all of the successfully decoded downlink channels are dropped. Paragraph 7. A method according to paragraph 3, wherein the one of the successfully decoded downlink channels which is associated with an uplink channel having a lowest priority level is dropped. Paragraph 8. A method according to paragraph 3, wherein the one of the successfully decoded downlink channels which was received earliest is dropped.

Paragraph 9. A method according to paragraph 3, wherein the one of the successfully decoded downlink channels which was received latest is dropped.

Paragraph 10. A method according to paragraph 3, wherein those of the of the successfully decoded downlink channels which were received outside of a specified time window are dropped.

Paragraph 11. A method according to paragraph 1, wherein the at least one characteristic of the downlink channels comprises a priority level of uplink channels associated with the downlink channels, the at least one dropped downlink channel being associated with an uplink channel which has a lowest priority level.

Paragraph 12. A method according to paragraph 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on the number of the first downlink channel and the at least one other downlink channel being greater than a threshold number. Paragraph 13. A method according to paragraph 12, wherein the threshold number is indicated to the communications device via Radio Resource Control, RRC, signalling received from the wireless communications network.

Paragraph 14. A method according to paragraph 12, wherein the threshold number is indicated to the communications device within one of an activation downlink control information, DCI, received from the wireless communications network which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

Paragraph 15. A method according to paragraph 12, wherein the threshold number is predetermined and known to the communications device.

Paragraph 16. A method according to paragraph 12, wherein the threshold number depends on the sizes of the first downlink channel and the at least one other downlink channel.

Paragraph 17. A method according to paragraph 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining, prior to attempting to decode at least one of the at least one other downlink channel, that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

Paragraph 18. A method according to paragraph 17, wherein the at least one dropped downlink channel has been successfully decoded by the communications device.

Paragraph 19. A method according to paragraph 17, wherein the at least one dropped downlink channel is from among the at least one other downlink channel, and wherein none of the at least one other downlink channel have been successfully decoded.

Paragraph 20. A method according to paragraph 17, comprising determining, after dropping one or more successfully decoded downlink channels, that the HARQ buffer still does not have enough space to store all of the first downlink channel and the at least one other downlink channel that have not been dropped, wherein the at least one dropped downlink channel is from among the remaining at least one other downlink channel, and wherein none of the remaining at least one other downlink channel have been successfully decoded. Paragraph 21. A method according to paragraph 19 or paragraph 20, wherein the at least one dropped downlink channel is that which has a lowest priority level.

Paragraph 22. A method according to paragraph 19 or paragraph 20, wherein the at least one dropped downlink channel is that which was received earliest.

Paragraph 23. A method according to paragraph 19 or paragraph 20, wherein the at least one dropped downlink channel is that which was received latest.

Paragraph 24. A method according to paragraph 19 or paragraph 20, wherein the at least one dropped downlink channel are those which were received outside of a specified time window.

Paragraph 25. A method according to paragraph 17, wherein at least one of the at least one other downlink channel is dropped prior to being decoded by the communications device.

Paragraph 26. A method according to paragraph 17, wherein the at least one dropped downlink channel is the at least one of the at least one other downlink channel if the uplink channel associated with the at least one of the at least one other downlink channel has a lowest priority level from among uplink channels associated with each of the first downlink channel and the at least one other downlink channel, and wherein the at least one of the at least one other downlink channel is dropped prior to being decoded by the communications device.

Paragraph 27. A method according to paragraph 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining, after decoding the at least one of the at least one other downlink channel, that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

Paragraph 28. A method according to paragraph 27, wherein the at least one dropped downlink channel is from among the first downlink channel and the at least one other downlink channel, and wherein none of the first downlink channel and the at least one other downlink channel have been successfully decoded. Paragraph 29. A method according to paragraph 28, wherein the at least one dropped downlink channel is that which has a lowest priority level.

Paragraph 30. A method according to paragraph 28, wherein the at least one dropped downlink channel is that which was received earliest.

Paragraph 31. A method according to paragraph 28, wherein the at least one dropped downlink channel is that which was received latest.

Paragraph 32. A method according to paragraph 28, wherein the at least one dropped downlink channel are those which were received outside of a specified time window.

Paragraph 33. A method according to paragraph 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel, and wherein the communications device determines the at least one dropped downlink channel based on an indication received from the wireless communications network.

Paragraph 34. A method according to paragraph 33, wherein the at least one dropped downlink channel indicated by the indication are those which have not been successfully decoded.

Paragraph 35. A method according to paragraph 33, wherein the at least one dropped downlink channel indicated by the indication are those which have been successfully decoded.

Paragraph 36. A method according to paragraph 33, wherein, prior to the communications device attempting to decode the first downlink channel, the at least one dropped downlink channel indicated by the indication are from among the at least one other downlink channel.

Paragraph 37. A method according to paragraph 33, wherein the indication is received the by the communications device via RRC signalling received from the wireless communications network. Paragraph 38. A method according to paragraph 33, wherein the indication is received by the communications device within one of an activation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

Paragraph 39. A method according to paragraph 1, wherein the at least one other downlink channel is received within at least one of the plurality of downlink transmission occasions.

Paragraph 40. A method according to paragraph 1, wherein at least one of the at least one other downlink channel is received within at least one set of downlink resources indicated to the communications device by a dynamic grant carried by DCI signalling received from the wireless communications network.

Paragraph 41. A method according to paragraph 40, comprising receiving an indication from the wireless communications network of whether the downlink data carried by the at least one dynamically granted downlink channel is new data or is retransmitted data. Paragraph 42. A method according to paragraph 41, wherein the indication is received the by the communications device via RRC signalling received from the wireless communications network. Paragraph 43. A method according to paragraph 41, wherein the indication is received the by the communications device via DCI signalling received from the wireless communications network. Paragraph 44. A method according to paragraph 43, wherein the DCI signalling carrying the indication is one of an activation DCI which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

Paragraph 45. A method according to paragraph 43, wherein the DCI signalling carrying the indication is the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel.

Paragraph 46. A method according to paragraph 45, wherein the indication is carried by a new data indicator, NDI, bit of the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel.

Paragraph 47. A method according to paragraph 40, wherein it is predetermined and known to the communications device whether the downlink data carried by the at least one dynamically granted downlink channel is new data or is retransmitted data.

Paragraph 48. A method according to paragraph 40, wherein the downlink data carried by the at least one dynamically granted downlink channel is retransmitted data, and wherein the method comprises combining the downlink data carried by the dynamically granted downlink channel with downlink data carried by a selected at least one of the first downlink channel and the at least one other downlink channel.

Paragraph 49. A method according to paragraph 48, wherein the selected downlink channel is the latest received downlink channel from among the first downlink channel and the at least one other downlink channel.

Paragraph 50. A method according to paragraph 48, wherein the selected downlink channel is the earliest received downlink channel from among the first downlink channel and the at least one other downlink channel.

Paragraph 51. A method according to paragraph 48, comprising receiving an indication from the wireless communications network of the selected downlink channel. Paragraph 52. A method according to paragraph 51, wherein the indication is received the by the communications device via RRC signalling received from the wireless communications network. Paragraph 53. A method according to paragraph 51, wherein the indication is received the by the communications device via DCI signalling received from the wireless communications network. Paragraph 54. A method according to paragraph 53, wherein the DCI signalling carrying the indication is one of an activation DCI which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

Paragraph 55. A method according to paragraph 53, wherein the DCI signalling carrying the indication is the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel.

Paragraph 56. A method according to paragraph 40, wherein the at least one dropped downlink channel comprises the at least one dynamically granted downlink channel.

Paragraph 57. A method according to paragraph 40, wherein the downlink data carried by the at least one dynamically granted downlink channel is new data, and wherein the method comprises determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel, wherein the at least one dropped downlink channel is one of the first downlink channel and the at least one other downlink channel other than the dynamically granted downlink channel.

Paragraph 58. A communications device comprising transceiver circuitry configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to receive, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, to determine that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device on the first downlink channel within the downlink transmission occasion, to determine that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, to determine that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, to determine whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer of the communications device, if the communications device determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, or if the communications device determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to drop, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer, and to transmit all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

Paragraph 59. Circuitry for a communications device comprising transceiver circuitry configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to receive, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, to determine that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the transceiver circuitry on the first downlink channel within the downlink transmission occasion, to determine that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, to determine that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, to determine whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within a HARQ buffer of the communications device, if the circuitry determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, or if the circuitry determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to drop, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer, and to transmit all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

Paragraph 60. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to paragraph 1.

Paragraph 61. A non-transitory computer-readable storage medium storing a computer program according to paragraph 60. It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and/or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and/or processors may be used without detracting from the embodiments.

Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and/or processors.

Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in any manner suitable to implement the technique.

References

[1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radio access”, John Wiley and Sons, 2009.

[2] TR 38.913, “Study on Scenarios and Requirements for Next Generation Access Technologies (Release 14)”, third Generation Partnership Project, vl4.3.0.

[3] RP- 190726, “Physical layer enhancements for NR ultra-reliable and low latency communication (URLLC)”, Huawei, HiSilicon, RAN#83.

[4] RP-201310, “Revised WID: Enhanced Industrial Internet of Things (loT) and ultra-reliable and low latency communication (URLLC) support for NR,” Nokia, Nokia Shanghai Bell, RAN#88e. [5] TS38.321, “NR: Medium Access Control (MAC) protocol specification (Release 16),” vl6.5.0.

[6] Rl-2104039, “Final moderator summary on HARQ-ACK feedback enhancements for NR Rel-17 URLLC/IIoT,” Moderator (Nokia), RANl#104bis-e.

[7] Rl-2102392, “HARQ-ACK enhancements for Rel-17 URLLC/IIoT,” OPPO, RANl#104bis-e.

[8] Rl-2103236, “On HARQ-ACK reporting enhancements,” Samsung, RANl#104bis-e.

Claims

37 CLAIMS What is claimed is:

1. A method of operating a communications device configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network, the method comprising receiving, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, determining that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device on the first downlink channel within the downlink transmission occasion, determining that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, determining that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, determining whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within a HARQ buffer of the communications device, if the communications device determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, storing all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, or if the communications device determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, dropping, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer, and transmitting all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

2. A method according to Claim 1, wherein the at least one characteristic of the downlink channels comprises whether or not the downlink channels have been successfully decoded by the communications device, the at least one dropped downlink channel having been successfully decoded by the communications device.

3. A method according to Claim 2, wherein at least two of the first downlink channel and the at least one other downlink channel have been successfully decoded by the communications device.

4. A method according to Claim 3, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

5. A method according to Claim 3, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on receiving a new downlink 38 channel which is to be decoded by the communications device, wherein the new downlink channel is associated with the same HPN as the first downlink channel and the at least one other downlink channel.

6. A method according to Claim 3, wherein all of the successfully decoded downlink channels are dropped.

7. A method according to Claim 3, wherein the one of the successfully decoded downlink channels which is associated with an uplink channel having a lowest priority level is dropped.

8. A method according to Claim 3, wherein the one of the successfully decoded downlink channels which was received earliest is dropped.

9. A method according to Claim 3, wherein the one of the successfully decoded downlink channels which was received latest is dropped.

10. A method according to Claim 3, wherein those of the of the successfully decoded downlink channels which were received outside of a specified time window are dropped.

11. A method according to Claim 1, wherein the at least one characteristic of the downlink channels comprises a priority level of uplink channels associated with the downlink channels, the at least one dropped downlink channel being associated with an uplink channel which has a lowest priority level.

12. A method according to Claim 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on the number of the first downlink channel and the at least one other downlink channel being greater than a threshold number.

13. A method according to Claim 12, wherein the threshold number is indicated to the communications device via Radio Resource Control, RRC, signalling received from the wireless communications network.

14. A method according to Claim 12, wherein the threshold number is indicated to the communications device within one of an activation downlink control information, DCI, received from the wireless communications network which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

15. A method according to Claim 12, wherein the threshold number is predetermined and known to the communications device.

16. A method according to Claim 12, wherein the threshold number depends on the sizes of the first downlink channel and the at least one other downlink channel.

17. A method according to Claim 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining, prior to atempting to decode at least one of the at least one other downlink channel, that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

18. A method according to Claim 17, wherein the at least one dropped downlink channel has been successfully decoded by the communications device.

19. A method according to Claim 17, wherein the at least one dropped downlink channel is from among the at least one other downlink channel, and wherein none of the at least one other downlink channel have been successfully decoded.

20. A method according to Claim 17, comprising determining, after dropping one or more successfully decoded downlink channels, that the HARQ buffer still does not have enough space to store all of the first downlink channel and the at least one other downlink channel that have not been dropped, wherein the at least one dropped downlink channel is from among the remaining at least one other downlink channel, and wherein none of the remaining at least one other downlink channel have been successfully decoded.

21. A method according to Claim 19 or Claim 20, wherein the at least one dropped downlink channel is that which has a lowest priority level.

22. A method according to Claim 19 or Claim 20, wherein the at least one dropped downlink channel is that which was received earliest.

23. A method according to Claim 19 or Claim 20, wherein the at least one dropped downlink channel is that which was received latest.

24. A method according to Claim 19 or Claim 20, wherein the at least one dropped downlink channel are those which were received outside of a specified time window.

25. A method according to Claim 17, wherein at least one of the at least one other downlink channel is dropped prior to being decoded by the communications device.

26. A method according to Claim 17, wherein the at least one dropped downlink channel is the at least one of the at least one other downlink channel if the uplink channel associated with the at least one of the at least one other downlink channel has a lowest priority level from among uplink channels associated with each of the first downlink channel and the at least one other downlink channel, and wherein the at least one of the at least one other downlink channel is dropped prior to being decoded by the communications device.

27. A method according to Claim 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining, after decoding the at least one of the at least one other downlink channel, that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel.

28. A method according to Claim 27, wherein the at least one dropped downlink channel is from among the first downlink channel and the at least one other downlink channel, and wherein none of the first downlink channel and the at least one other downlink channel have been successfully decoded.

29. A method according to Claim 28, wherein the at least one dropped downlink channel is that which has a lowest priority level.

30. A method according to Claim 28, wherein the at least one dropped downlink channel is that which was received earliest.

31. A method according to Claim 28, wherein the at least one dropped downlink channel is that which was received latest.

32. A method according to Claim 28, wherein the at least one dropped downlink channel are those which were received outside of a specified time window.

33. A method according to Claim 1, comprising determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel, and wherein the communications device determines the at least one dropped downlink channel based on an indication received from the wireless communications network.

34. A method according to Claim 33, wherein the at least one dropped downlink channel indicated by the indication are those which have not been successfully decoded.

35. A method according to Claim 33, wherein the at least one dropped downlink channel indicated by the indication are those which have been successfully decoded.

36. A method according to Claim 33, wherein, prior to the communications device attempting to decode the first downlink channel, the at least one dropped downlink channel indicated by the indication are from among the at least one other downlink channel.

37. A method according to Claim 33, wherein the indication is received the by the communications device via RRC signalling received from the wireless communications network.

38. A method according to Claim 33, wherein the indication is received by the communications device within one of an activation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI received from the wireless communications network which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

39. A method according to Claim 1, wherein the at least one other downlink channel is received within at least one of the plurality of downlink transmission occasions.

40. A method according to Claim 1, wherein at least one of the at least one other downlink channel is received within at least one set of downlink resources indicated to the communications device by a dynamic grant carried by DCI signalling received from the wireless communications network.

41 A method according to Claim 40, comprising receiving an indication from the wireless communications network of whether the downlink data carried by the at least one dynamically granted downlink channel is new data or is retransmitted data.

42. A method according to Claim 41, wherein the indication is received the by the communications device via RRC signalling received from the wireless communications network.

43. A method according to Claim 41, wherein the indication is received the by the communications device via DCI signalling received from the wireless communications network.

44. A method according to Claim 43, wherein the DCI signalling carrying the indication is one of an activation DCI which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

45. A method according to Claim 43, wherein the DCI signalling carrying the indication is the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel.

46. A method according to Claim 45, wherein the indication is carried by a new data indicator, NDI, bit of the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel.

47. A method according to Claim 40, wherein it is predetermined and known to the communications device whether the downlink data carried by the at least one dynamically granted downlink channel is new data or is retransmitted data.

48. A method according to Claim 40, wherein the downlink data carried by the at least one dynamically granted downlink channel is retransmitted data, and wherein the method comprises combining the downlink data carried by the dynamically granted downlink channel with downlink data carried by a selected at least one of the first downlink channel and the at least one other downlink channel.

49. A method according to Claim 48, wherein the selected downlink channel is the latest received downlink channel from among the first downlink channel and the at least one other downlink channel.

50. A method according to Claim 48, wherein the selected downlink channel is the earliest received downlink channel from among the first downlink channel and the at least one other downlink channel.

51. A method according to Claim 48, comprising receiving an indication from the wireless communications network of the selected downlink channel. 42

52. A method according to Claim 51, wherein the indication is received the by the communications device via RRC signalling received from the wireless communications network.

53. A method according to Claim 51, wherein the indication is received the by the communications device via DCI signalling received from the wireless communications network.

54. A method according to Claim 53, wherein the DCI signalling carrying the indication is one of an activation DCI which indicates that one or more of the downlink transmission occasions are activated and therefore are to be used by the communications device for receiving downlink signals from the wireless communications network, and a deactivation DCI which indicates that one or more of the downlink transmission occasions are deactivated and therefore are not to be used by the communications device for receiving downlink signals from the wireless communications network.

55. A method according to Claim 53, wherein the DCI signalling carrying the indication is the DCI signalling carrying the dynamic grant for the at least one dynamically granted downlink channel.

56. A method according to Claim 40, wherein the at least one dropped downlink channel comprises the at least one dynamically granted downlink channel.

57. A method according to Claim 40, wherein the downlink data carried by the at least one dynamically granted downlink channel is new data, and wherein the method comprises determining that the communications device is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer based on determining that the HARQ buffer does not have enough space to store all of the first downlink channel and the at least one other downlink channel, wherein the at least one dropped downlink channel is one of the first downlink channel and the at least one other downlink channel other than the dynamically granted downlink channel.

58. A communications device comprising transceiver circuitry configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to receive, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, to determine that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the communications device on the first downlink channel within the downlink transmission occasion, to determine that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, to determine that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, to determine whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer of the communications device, 43 if the communications device determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, or if the communications device determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to drop, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer, and to transmit all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

59. Circuitry for a communications device comprising transceiver circuitry configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to receive, from the wireless communications network, downlink data on a first downlink channel within one of a plurality of periodically occurring downlink transmission occasions, to determine that an uplink channel associated with the first downlink channel cannot be used to carry a Hybrid Automatic Repeat Request acknowledgement, HARQ-ACK, the HARQ-ACK indicating whether or not the downlink data has been successfully received by the transceiver circuitry on the first downlink channel within the downlink transmission occasion, to determine that the HARQ-ACK is to be carried by a next available uplink channel instead of the uplink channel associated with the first downlink channel, to determine that the next available uplink channel carries at least one other HARQ-ACK associated with one of at least one other downlink channel each carrying other downlink data received from the wireless communications network, wherein a HARQ process number, HPN, associated with both of the HARQ-ACK and the first downlink channel is the same as a HPN associated with both of the at least one other HARQ-ACK and the at least one other downlink channel, to determine whether the communications device is to store all of the first downlink channel and the at least one other downlink channel within a HARQ buffer of the communications device, if the circuitry determines that it is to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, or if the circuitry determines that it is not to store all of the first downlink channel and the at least one other downlink channel within the HARQ buffer, to drop, in accordance with at least one characteristic of the downlink channels, at least one of: the first downlink channel, and the at least one other downlink channel, from the HARQ buffer, and to transmit all of the HARQ-ACK and the at least one other HARQ-ACK within the next available uplink channel.

60. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to Claim 1.

61. A non-transitory computer-readable storage medium storing a computer program according to Claim 60.