Methods, communications devices, and infrastructure equipment

Abstract

A method of transmitting uplink data by a communications device to a wireless communications network includes determining a state of conditions for communicating packets of the data via a wireless access interface to the wireless communications network, and selecting one of a plurality of discard timers associated with each packet based on whether the determined state for transmitting data is either a first state or a second state. In some examples the first state of the communication conditions may correspond to the wireless communication network not being congested, whereas the second state may correspond in the wireless communications network being congested and therefore transmission of packets being delayed. The method further comprises storing the packets for transmission in a transmit buffer and starting the selected discard timer when each packet is stored in the transmit buffer, and either transmitting each packet from the transmit buffer when a transmission occasion occurs, or discarding the packet from the transmit buffer if the selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer. According to the example embodiments, if the determined state is the first state, then the selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the discard timer selected is a plurality of priority based discard timers.

Description

[0001] METHODS, COMMUNICATIONS DEVICES, AND INFRASTRUCTURE EQUIPMENT

[0002] BACKGROUND

[0003] Field of Disclosure

[0004] The present disclosure relates to methods of transmitting uplink data, communications devices for transmitting uplink data and infrastructure equipment, as defined in the appended claims.

[0005] The present application claims the Paris Convention priority to EP23200682.2, filed on 28 September 2023, the contents of which are incorporated herein by reference in their entirety.

[0006] Description of Related Art

[0007] 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.

[0008] Previous 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.

[0009] Current and future wireless communications networks are 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 efficiently to support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets, extended Reality (XR) 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).

[0010] In view of this there is expected to be a desire for current wireless communications networks, for example those which may be referred to as 5G or new radio (NR) systems / new radio access technology (RAT) systems, or indeed future 6G wireless communications, as well as future iterations / releases of existing systems, efficiently to support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements.

[0011] 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 extended Reality (XR), which may be provided by various user equipment such as wearable devices. XR combines real- world and virtual environments, incorporating aspects such as augmented reality (AR), mixed reality (MR), and virtual reality (VR), and thus requires high quality and minimised interaction delay. Services such as URLLC and XR therefore represent a challenging example for both LTE type communications systems and 5G / NR communications systems, as well as future generation communications systems.

[0012] 5G NR has continuously evolved and the current work plan includes 5G-NR-advanced in which some further enhancements are expected, especially to support new use-cases / scenarios with higher requirements. The desire to support these new use-cases and scenarios gives rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

[0013] 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.

[0014] SUMMARY OF THE DISCLOSURE

[0015] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0016] According example embodiments, a method of transmitting uplink data by a communications device to a wireless communications network includes determining a state of conditions for communicating packets of the data via a wireless access interface to the wireless communications network, and selecting one of a plurality of discard timers associated with each packet based on whether the determined state for transmitting data is either a first state or a second state. In some examples the first state of the communication conditions may correspond to the wireless communication network not being congested, whereas the second state may correspond in the wireless communications network being congested and therefore transmission of packets being delayed. The method further comprises storing the packets for transmission in a transmit buffer and starting the selected discard timer when each packet is stored in the transmit buffer, and either transmitting each packet from the transmit buffer when a transmission occasion occurs, or discarding the packet from the transmit buffer if the selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer. According to the example embodiments, if the determined state is the first state, then the selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the discard timer selected is one of a plurality of priority based discard timers.

[0017] In some example embodiments, if the state of the communications conditions is determined to be the first state, the selecting the discard timer comprises selecting the reference discard timer as one of the plurality of discard timers associated with each packet, and whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer until the reference discard timer expires. If the determined state of communication conditions is the second state, the selecting the discard timer from one of the plurality of discard timers associated with each packet, comprises determining a relative priority for transmitting the packet, and selecting the discard timer from one of the plurality of priority based discard timers, each of the priority based discard timers providing a discard time of different length according to a priority of transmitting the packet. In some examples, if the communications conditions are determined to be in the second state (e.g. congested), then delay status reports are not transmitted to the communications network. That is to say a delay status report which informs the network of a time remaining for transmitting a packet within its delay budget, to escalate its transmission, is not used / disabled. However in other examples, if the second state is determined, and the discard timer for discarding packets is the priority based discard timer, then a second discard timer being the reference discard timer may be used in order to generate delay status reports so that the network can be informed of packets which are likely to be foreclosed being discarded.

[0018] According to example embodiments, by providing more than one discard timer which can be selected for each packet, and selecting the discard timer based on a current state of communication conditions for transmitting the uplink data as packets, a more flexible arrangement is provided which can provide a more efficient use of communications resources and more efficient communication of the packets. For example, if the network is congested, then a transmission of packets can be prioritised to satisfy a quality of service requirement by selecting one of a plurality of discard timers which matches the priority, and then delay status reporting can be disabled.

[0019] Respective aspects and features of the present disclosure are defined in the appended claims and include a communications device (for example, a UE), and methods for operating the same.

[0020] 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.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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:

[0023] Figure 1 schematically represents some aspects of a 5G / new radio access technology (RAT) wireless communications system which may be configured to operate in accordance with embodiments of the present disclosure;

[0024] Figure 2 is a schematic block diagram of a communications device communicating data to and / or from an infrastructure equipment (gNB) forming part of the wireless communication system shown in Figure 1;

[0025] Figure 3 is a schematic representation of a dedicated radio bearer between a communications device and an infrastructure equipment of the wireless network which carries different data flows having a different quality of service QoS;

[0026] Figure 4 is a schematic representation of a part of a protocol stack for transmitting packet data from the communications device to a wireless communications network in which packets are prioritised in accordance with a discard timer;

[0027] Figure 5 is a message flow diagram illustrating an operation of the protocol stack shown in Figure 4 when prioritising transmission of PDCP packets using a discard timer;

[0028] Figure 6 is a flow diagram illustrating an operation of the protocol stack shown in Figures 4 and 5 when prioritising a transmission of packets based on a discard timer; Figure 7 is a flow diagram illustrating a transmission process in which a packet is either transmitted from a transmit buffer in a transmission occasion or discarded if the packet’s discard timer has expired based on a selected discard timer duration;

[0029] Figure 8 is a schematic representation of a protocol stack corresponding to that shown in Figure 4 but adapted in accordance with the present technique to provide a plurality of selectable discard timers for each packet;

[0030] Figures 9 is an illustrative representation of a transmit buffer in a physical layer of a communications device which includes packets of different priority and each packet having one of a reference discard timer and one of a plurality of priority based discard timers which can be selected in accordance with example embodiments;

[0031] Figure 10 is a flow diagram illustrating a transmission process corresponding to that illustrated in Figure 7 but adapted, according to example embodiments to include a selection of a reference discard timer or a priority based discard timer according to determined conditions for communication;

[0032] Figure 11 is a flow diagram illustrating a process of selecting a discard timer based upon a state of conditions for communicating packets and including in one state generating delay status reports according to example embodiments;

[0033] Figure 12 is a part schematic block diagram, part flow diagram illustrating an operation of a communications device (UE) and an infrastructure equipment (gNB) in which the communications device receives from the network an indication of a reference discard timer and a variety of priority based discard timers which are applied in accordance with the determined state of communicating received from the network according to example embodiments; and

[0034] Figure 13 is a part schematic block diagram, part flow diagram illustrating an operation of a communications device (UE) and an infrastructure equipment (gNB) in which the communications device determines a state of communication conditions based on a buffer occupancy level, the buffer occupancy level for changing state being received from the network with an indication of a reference discard timer for a first state, and a variety of priority based discard timers for a second state according to example embodiments.

[0035] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] Wireless Communications Network Including Radio Access Technology (5G)

[0037] 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 1. In Figure 1 a plurality of transmission and reception points (TRPs) 110 are connected to distributed control units (DUs) 142 by a connection interface represented as a line 116. Each of the TRPs 110 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 110, forms a cell of the wireless communications network as represented by a circle 112. As such, wireless communications devices 114 which are within a radio communications range provided by the cells 112 can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 142 are connected to a central unit (CU) 140 (which may be referred to as a controlling node) via an interface 146. The central unit 140 is then connected to the core network 120 which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network 120 may be connected to other networks 130. As will be appreciated by those acquainted with the wireless communications network according to a 5G standard as shown in Figure 1, the CU 140, DU 142 and TRPs 110 collectively refer to functions which are conventionally performed by a network base station or, in accordance with 5G terminology, a gNodeB (gNB). In terms of broad top-level functionality, 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 DUs and the communications devices may he with the controlling node / central unit and / or the distributed units / TRPs.

[0038] A communications device 114 is represented in Figure 1 within the coverage area of the first communication cell 112. This communications device 114 may thus exchange signalling with the first CU 140 in the first communication cell 112 via one of the distributed units / TRPs 110 associated with the first communication cell 112. The communications devices 114 may be referred to as mobile terminals, terminals or user equipment (UE), which encompasses chip sets and have a functionality corresponding to the UE devices known for operation with wireless communications networks.

[0039] It will further be appreciated that Figure 1 represents merely one example of a proposed architecture for a RAT communications 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 communications systems having different architectures.

[0040] Figure 2 provides a more detailed diagram of components shown in Figure 1. Components shown in Figure 2, which are also shown in Figure 1 bear the same numerical designations and so description of these parts will not be repeated for brevity. In Figure 2, a TRP 110, which corresponds to TRP 110 in Figure 1, comprises, as a simplified representation, a transmitter circuitry 212, a receiver circuitry 214 and a controller circuitry or controlling processor 216 which may operate to control the transmitter circuitry 212 and the receiver circuitry 214 to transmit and receive radio signals to one or more UEs within a cell 112 (not shown in Figure 2 for clarity) provided by the TRP 110. As shown in Figure 2, the TRP 110 is connected to a DU 142 via a physical interface 116, which may be a fibre optic cable, for example. The physical interface 116 therefore provides a communications link for data and signalling traffic from the TRP 110 via the DU 142 and a CU 140 to a core network 400. An interface 146 between the DU 142 and the CU 140 is known as the Fl interface which can be a physical or a logical interface. The Fl interface 146 between the DU 142 and the CU 140 may operate in accordance with specifications 3GPP TS 38.470 [1] and 3GPP TS 38.473 [2], and may be formed from a fibre optic or other wired or wireless high bandwidth connection. The connection between a TRP 110 and the core network 400 can be generally referred to as a backhaul, which comprises the physical interface 116 from the TRP 110 to the DU 142 and the Fl interface 146 from the DU 142 to the CU 140.

[0041] As shown in Figure 2, the TRP 110 may be configured to transmit downlink radio signals and receive uplink radio signals from a UE 114 via a direct wireless communications link 200 which may be a Uu interface in one example. The UE 114 is shown to include a transmitter circuitry 222, a receiver circuitry 224 and a controller circuitry 226 which is configured to control the transmitter circuitry 222 and the receiver circuitry 224 to transmit uplink signals to the TRP 110 and to receive downlink signals from the TRP 110 over the wireless communications link 200 formed between the UE 114 and the TRP 110. The transmiter circuitry 212, 222 and the receiver circuitry 214, 224, as well as other transmiters, receivers and transceivers described in relation to examples and embodiments of the present disclosure may include radio frequency fdters and amplifiers as well as signal processing components, circuitry and devices in order to transmit and receive radio signals in accordance for example with the 5G / NR standard. The controller circuitry 216, 226, 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 transmiters, the receivers and the controllers are schematically shown in Figure 2 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).

[0042] As mentioned above, the TRP 110, DU 142 and the CU 140 may collectively form the gNB 242, which is an example of infrastructure equipment of a radio access network of a wireless communications network. Therefore, references to the UE 114 communicating with the TRP 110 can alternatively be considered as references to the UE 114 communicating with the gNB 242. Furthermore, it will be appreciated that the UE 114 is an example of a communications device or wireless transceiver unit. As will be appreciated the infrastructure equipment / TRP / base station / gNB as well as the UE / communications device will in general comprise various other elements associated with its operating functionality.

[0043] Uplink Transmission of Data from Different Applications

[0044] 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. A requirement for Ultra Reliable and Low Latency Communications (URLLC) services is that one transmission of a 32 byte packet is required to be transmited 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.

[0045] Enhanced URLLC (eURLLC) [3] [4] specifies features that require high reliability and low latency, such as factory automation, transport industry, electrical power distribution, etc. It should be appreciated that the Uplink Control Information (UCI) for URLLC and eMBB will have different requirements.

[0046] Another such service incorporating NR technology is 5G NR in Unlicensed Spectrum (NR-U) [5], which enable devices to make use of shared and unlicensed spectrum bandwidth. Such features as Listen Before Talk (LBT), as specified by [5], is incorporated into the NR frame structure for NR-U operation in unlicensed bands. extended Reality (XR) and Cloud Gaming refer to various types of augmented, virtual, and mixed environments, where human-to-machine and human-to-human communications are performed with the assistance of handheld and wearable end user devices (UEs). XR and Cloud Gaming are two more recently developed applications, that are considered important for NR Rel-18 and beyond (also known as 5G Advanced) [6],

[0047] XR traffic is rich in video, especially in the downlink, with a typical frame rate of 60 Hz [7], which leads to a data transmission with non-integer periodicity in NR, i.e. the periodicity is not an integer number of subframes and in this example, the periodicity is 16.67 ms. Due to varying frame encoding delay and network transfer time, the packet arrival at the gNB may experience random jitter. The noninteger and jitter characteristics of XR traffic is known as quasi-periodic traffic. In addition to jitter, the packet size also varies within a range; that is the packet size in each period is random.

[0048] As will be appreciated, given the different types of application supported by communicating different types of data, there can be a variety of requirements for data being communicated. For uplink communication, the UE must request resources from the wireless indications network in order to transmit the uplink data. The transmission of the uplink data may have different quality of service requirements as illustrated in Figure 3.

[0049] As shown in Figure 3, a dedicated radio bearer (DRB), 300 is formed between a UE 114 and gNodeB 242 according to radio resource control of the wireless access interface, which may broadly correspond to the wireless access interface 202 shown in Figure 2. As shown in Figure 3, the Dedicated Radio Bearer (DRB) is configured to support different quality of service (QoS) requirements for a plurality of different QoS flows. As explained below, transmission of packets via the DRB 312 may be in accordance with a prioritisation to satisfy a packet delay as well as other parameters. The packet delay may be determined in accordance with a packet delay budget or a PDU Set Delay Budget (PSDB) which determines a transmission delay for a set of packets. Different applications require communication of packets according to a different delay budgets and accordingly each of the QoS flows may establish a different delay budget, which may be set in accordance with a priority for communicating packets from different applications. A better appreciation will be gained from a description in the following paragraphs of different protocol layers for communicating packets on the uplink via a dedicated radio bearer 300.

[0050] Uplink Data Communication

[0051] Data may be transmitted from various applications on the uplink according to a protocol stack, in which the data is formed into packets for transmission to a corresponding entity within the network sometimes referred to as a Access Stratum (AS) communication. Figure 4 illustrates a portion 401 of a protocol stack, which is formed and processed by the control circuitry 226 within the communications device (UE) 114 for transmitting uplink data. The protocol stack portion 401 corresponds generally to layer 2, L2, and comprises a Service Data Adaptation Protocol (SDAP) layer 450, a packet data convergence protocol (PDCP) layer 452 and a radio link control (RLC) and amedia access control (MAC) layer shown as a combined layer 454. Logically below the RLC / MAC layer may be a physical layer (PHY) or layer 1, LI, responsible for forming the data into signals for transmission on a wireless access interface, which in a general sense is formed by the transmitter circuitry 222.

[0052] Each of the layers 450, 452, 454 may comprise one or more protocol entities, each protocol entity operating in accordance with a protocol specification.

[0053] In Figure 4, the SDAP layer 450 comprising an SDAP entity 450 may be configured for use only when the communications device is connected to a 5G core network, such as the core network 400 of Figure 2. The SDAP layer comprising the SDAP entity 450 may be configured for use when the communications device is connected to a 5G core network, irrespective of whether the communications device communicates with the peer communications device via a 5G / NR wireless access interface or via an LTE wireless access interface.

[0054] The RLC / MAC layer 454 comprises a combined radio link control (RLC) / media access control (MAC) entity 454 carrying out the functions of the RLC protocol and the MAC protocol. The PHY layer, which may comprise a PHY entity corresponds to the operations performed by the transmitter circuitry 222.

[0055] Together, the SDAP entity 450, the PDCP entity 452, the combined RLC / MAC protocol entity 454 and the PHY entity may form an access stratum (AS) portion of a user plane; that is, the series of protocol entities which process user plane data immediately prior to, or immediately after, transmission via a wireless access interface.

[0056] These entities are referred to as “access stratum” entities because they may operate in a manner specific to the wireless access interface. For example, they may operate in a specific manner when the wireless access interface is a Uu interface provided by a New Radio (NR) wireless access interface.

[0057] Above the SDAP entity 450 may be one or more Non-Access Stratum (NAS) protocol entities, which operate substantially independently of the specific wireless access interface being used for the transmission of the data.

[0058] Data for transmission conventionally passes from ‘higher’ layers to Tower’ layers via service access points, while received data passes from lower layers to upper layers. A portion of data received by at a service access point (SAP) of a protocol entity from a higher layer may be referred to as a service data unit (SDU) 406 of that protocol, while a portion of data generated by a protocol entity and transferred to a SAP of a protocol entity in a lower layer may be referred to as a protocol data unit (PDU) 408.

[0059] For example, the SDAP entity 450 may receive at an SDAP SAP a portion of data 402 from a higher layer protocol entity, such as a NAS entity or application layer. The portion of data 402 may thus be referred to as a first SDAP SDU 402. The portion of data 402 may comprise an internet protocol (IP) packet.

[0060] After processing by the SDAP entity 450, the data portion 402 forming the first SDAP SDU 402 may be formed into a first SDAP PDU 406, which may comprise the first SDAP SDU 402 and (optionally) an SDAP header 404. The SDAP PDU 406 is passed to the PDCP entity 452 as a PDCP SDU.

[0061] After processing by the PDCP entity 452, the first SDAP PDU / PDCP SDU 406 is delivered to the RLC / MAC protocol entity 454 in the form of a PDCP PDU 408, comprising the PDCP SDU 406 and a PDCP header 407.

[0062] Processing by a protocol entity of an SDU may comprise one or more of a segmentation step, an encryption step, a concatenation or bundling step (i.e. where the PDU comprises some or all of more than one SDU). A protocol entity may buffer and / or re-order data. Protocol entities may communicate with peer entities (that is to say, protocol entities operating according to the same protocol in the peer communications device), for example, by means of indications within headers or by the generation and transmission of control protocol data units.

[0063] In the example described above, it is assumed that the first SDAP SDU 402 is not segmented by the SDAP entity 450 or the PDCP entity 452. However, this need not be the case.

[0064] The transfer of a PDU from one protocol entity to an adjacent entity within the stack may be triggered by the sending protocol entity or the receiving protocol entity. For example, the RLC / MAC protocol entity 454 may poll the PDCP entity 452 for a PDCP PDU in response to receiving a grant of communication resources on the wireless access interface for uplink data transmission.

[0065] Although Figure 4 shows the processing of data for transmission, it will be readily apparent that received data may be processed in a substantially symmetric manner i.e. by the sequential processing of received data by (in order) the RLC / MAC protocol entity 454, the PDCP entity 452 and the SDAP entity 450. As will be appreciated in some circumstances the data may be processed in a different order.

[0066] As such, the peer communications device may comprise functionality corresponding to the protocol stack 401, for the purpose of processing data received via the wireless access interface.

[0067] Also shown in Figure 4 is a timer 440 which will be explained in the following which will be referred to in the following description as a discarded timer. Each packet for transmission 408 is queued for transmission in a buffer 406 in which each packet received from the RLC / MAC layer is queued for transmission. Each the packets is then transmitted via a DRB when resources are allocated to the UE 114. As explained below, packets are transmitted in order to comply with QoS requirements which includes transmission within a delay budget according to that QoS. According to some examples therefore a discard timer 440 is provided to monitor a time in which a packet is queued until it is transmitted. If the packet exceeds its discard time than the packet is removed from the buffer 406 and discarded.

[0068] As disclosed in our co-pending European patent application number 19720689.9 filed 3 May 2019, priority which is assigned to a transmission of data in each packet can be used to adapt a discard timer in accordance with that priority. Embodiments of the present disclosure provide enhancement to prioritisation with respect to discard timer as explained below.

[0069] QoS flows, DRBs, Protocol

[0070] As explained above with reference to Figure 3, data for transmission may be grouped according to its associated Quality of Service (QoS) requirements. Data having substantially similar, or identical, QoS requirements may form a QoS flow 312, 314. For example, data received from an application entity by the SDAP entity 450 may comprise data units associated with one or more QoS flows. Data units may be assigned to a QoS flow 312, 314 by comparing one or more characteristics of each data unit (for example, type of service (TOS) bits or a traffic class indication within an internet protocol (IP) header) with a traffic flow template (TFT) associated with each QoS flow.

[0071] Each QoS flow 312, 314 may be associated with a dedicated radio bearer (DRB) 300. One or more QoS flows may be related to a single service or protocol data unit (PDU) session when connected to a 5G core network.

[0072] The SDAP entity 450 may maintain a mapping, or association, between each QoS flow on which it receives data units from an application entity and one or more DRBs which have been established between the communications device and the peer communications device. A DRB may be associated with zero, one or more QoS flows.

[0073] There may be a single PDCP entity for each DRB; as such, a PDCP entity such as the PDCP entity 452 may receive data only for the DRB with which it is associated.

[0074] A description of the functionality of an SDAP entity operating in accordance with conventional techniques may be found in 3GPP TS 37.324 [2], A description of the functionality of an PDCP entity operating in accordance with conventional techniques in a 5G / NR wireless communications network may be found in 3GPP TS 38.323 [3], An adaption of a discard timer in accordance with a priority as disclosed in European patent application 197208689.9 as explained with reference to a part message part flow diagram provided in Figures 5, 6 and 7. Figure 5 presents the protocol stack formed by the controller circuitry 222 of the UE 114 as shown in Figure 4 adapted to illustrate a transmission of packets according to a different priority according to the functions of the SDAP entity 450, the PDCP entity 452 and the RLC / MAC protocol entity 454. The data is transmitted by the transceiver circuitry 222 as packets from the buffer 406 via a wireless access interface 456, which may be, for example, the Uu wireless access interface configured in accordance with specifications for a 5G / New Radio (NR) wireless communications network. The data is transmitted according to the flow diagram of Figure 5 with a prioritisation, which adapts a discard timer 440 according to the explanation in the following paragraphs.

[0075] At step S10 of Figure 5, the SDAP entity 450 receives from an application layer protocol entity a first SDAP SDU 402, for transmission on the wireless access interface 456.

[0076] At step S12, the SDAP entity 450 identifies a QoS flow associated with the first SDAP SDU 402 and, based on the identified QoS flow, associates the first SDAP SDU 402 with a DRB. The SDAP entity 450 determines whether the first SDAP SDU 402 meets one or more criteria associated with a higher priority SDAP SDU, that is, an SDAP SDU having a higher priority, relative to one or more other SDAP SDUs. For example, the first SDAP SDU 402 could be determined to be a higher priority SDAP SDU if it comprises a critical message, such as a fire signal, an emergency shutdown signal, or important packets in a video frame, or contains an indication of a command which needs to be prioritised. On other examples, an RTP header may be modified to include an indication of priority, which is then read by the PDCP layer.

[0077] In this example, the SDAP entity 450 determines that the first SDAP SDU 402 does not meet the criteria associated with a higher priority SDAP SDU and forwards the first SDAP SDU 402 as the first SDAP PDU 406 to the PDCP entity 452 at step S14.

[0078] In some embodiments, an SDAP header 404 is added to the first SDAP SDU 402 to form the first SDAP PDU 406; in some embodiments, the SDAP header 404 is only added to a SDAP SDU (such as the first SDAP SDU 402) if the first SDAP SDU 402 meets one of the one or more criteria associated with the higher priority. In some embodiments, an indication that the first SDAP SDU 402 meets one or more criteria associated with the higher priority is included in the SDAP header 404.

[0079] At step S16, the PDCP entity 452 processes the received first PDCP SDU 406. In the example of Figure 5, the PDCP entity 452 is associated with only a single DRB and there is therefore no need for the PDCP entity 452 to determine the DRB associated with the first PDCP SDU 406 (i.e. on which the data is to be transmitted).

[0080] Alternatively, the DRB associated with the first PDCP SDU 406 may be indicated to the PDCP entity 452 by the SDAP entity 450.

[0081] The PDCP entity 452 may determine whether or not the first PDCP SDU 406 is associated with the higher priority. For example, this may be by evaluating an indication associated with the first PDCP SDU 406 received from the SDAP entity 450, by determining whether the SDAP entity 450 has added the SDAP header 404 to the first SDAP SDU 402 and if so, optionally, by determining whether the SDAP header 404 comprises an indication that the first SDAP SDU 402 meets one or more criteria associated with the higher priority or optionally based on a header field added by application layer protocols like RTP.

[0082] The PDCP entity 452 may form the first PDCP PDU 408 from the first PDCP SDU 406 and the PDCP header 407 comprising a PDCP sequence number. For example, if sequence numbers 1 to 9 (inclusive) have previously been assigned to PDCP PDUs for the same DRB, the first PDCP PDU 408 may be assigned sequence number 10.

[0083] In some examples, header compression (such as in accordance with the internet engineering task force (IETF) robust header compression (RoHC) standard) may be applied to the first PDCP PDU 408. The header compression may be in accordance with the assigned PDCP sequence number.

[0084] The PDCP entity 452 may store the first PDCP PDU 408 in the PDCP buffer 440. The PDCP buffer 440 may be used to store data for which no uplink transmission opportunity has arisen. The PDCP buffer 440 may be specific to the DRB on which the first PDCP PDU 408 is to be transmitted. The PDCP buffer may be a first-in, first-out (FIFO) buffer.

[0085] The PDCP entity 452 may start a first PDCP discard timer, associated with the first PDCP SDU 406. The first PDCP discard timer may define a future time at which, if the first PDCP SDU 406 has not yet been transmitted or otherwise passed to the RLC / MAC protocol entity 454 and / or is still in the PDCP buffer, the PDCP entity 452 will discard the first PDCP SDU 406. The future time may be defined by a timer duration.

[0086] At step SI 8, a second SDAP SDU 412 is received by the SDAP entity 450.

[0087] At step S20, the SDAP entity 450 determines (in this example), based on its QoS flow, that the second SDAP SDU 412 is associated with the same DRB as the first SDAP SDU 402. The SDAP / PDCP entity 450 / 452 determines whether the second SDAP SDU 412 meets the criteria associated with the higher priority. In this example, the SDAP entity 450 determines that the second SDAP SDU 412 meets one or more of the criteria associated with the higher priority. In response to this determination, the SDAP entity 450 may generate an SDAP header comprising an indication that the second SDAP SDU 412 meets one or more of the criteria associated with the higher priority.

[0088] In response to the determination, the SDAP entity 450 may additionally or alternatively indicate to the PDCP entity 452 that the second SDAP SDU 412 is a higher priority SDU.

[0089] In step S22, a second SDAP PDU 416, comprising the second SDAP SDU 412 is passed from the SDAP entity 450 to the PDCP entity 452 as a second PDCP SDU 416.

[0090] At step S24, the PDCP entity 452 processes the received second PDCP SDU 416. Similar to the processing of the first PDCP SDU 406 at step SI 6, this processing may comprise one or more of: determining a DRB associated with the second PDCP SDU 416 (if it is not implicit), determining whether or not the second PDCP SDU 416 is associated with the higher priority, assigning a sequence number for a second PDCP PDU 418 forming the second PDCP PDU 418 from the second PDCP SDU 416, applying header compression to the second PDCP PDU 418 storing the second PDCP PDU 418 in a PDCP buffer, and starting a second PDCP discard timer associated with the second PDCP PDU 418.

[0091] In the example shown in Figure 5, the PDCP entity 452 determines that the second PDCP SDU 416 is associated with the higher priority. In response to this determination, the processing step S24 may differ from the processing step S16 carried out in respect of the first PDCP SDU 406 in accordance with a different priority.

[0092] A PDCP SDU (or a PDCP PDU containing a PDCP SDU) which is determined to have the higher priority (such as the second PDCP SDU 416) has associated with it a discard timer having a longer duration than a discard timer associated with a PDCP SDU not having the higher priority. As such, a PDCP SDU having the higher priority will only be discarded (and therefore not transmitted) if no opportunity for its transmission has arisen within a time period, starting at the time of receipt of the PDCP SDU by the PDCP entity 452, the time period being longer in duration than a corresponding time period associated with a PDCP SDU not having the higher priority. In the example of Figure 5, therefore, the PDCP entity 452 may, at step S24, assign to the second PDCP PDU 418 a discard timer having a shorter time to expiry than the time to expiry of the discard timer assigned to the first PDCP PDU 416.

[0093] A PDCP PDU formed from a PDCP SDU which is determined to not have the higher priority (such as the first PDCP SDU 406) can be assigned a PDCP sequence number which is the next in sequence for the DRB and which has not been associated with any PDCP PDU (including those currently stored in the PDCP buffer). In contrast, a PDCP PDU formed from a PDCP SDU which is determined to have a higher priority (such as the second PDCP SDU 416) can be assigned a PDCP sequence number which is the next in sequence for the DRB and which has not previously been associated with a PDCP PDU which has already been passed to the RUC / MAC protocol entity 454 for transmission. For example, if PDCP PDUs associated with sequence numbers 1 to 9 inclusive have been transferred to the RUC / MAC protocol entity 454 for transmission, a second PDCP PDU 416 formed from the second PDCP SDU 416 may be assigned the sequence number 10.

[0094] As such, the second PDCP SDU 416 may be assigned a sequence number (10) which has already been assigned to a PDCP PDU (such as the first PDCP PDU 408) associated with the same DRB and which is currently stored in the PDCP buffer. Therefore, in some embodiments, as part of the processing step S24 in respect of a PDCP SDU having the higher priority, the PDCP entity 452 may assign different sequence numbers (i.e. different to those previously assigned) to those PDCP PDUs which belong to the same DRB as the higher priority SDU and are currently stored in the PDCP buffer. For example, the PDCP entity 452 may assign the sequence number 11 to the first PDCP PDU 406.

[0095] In response to determining that the second SDAP PDU 416 is a higher priority SDAP PDU at step S24, the PDCP entity 452 may form the second PDCP PDU 418 and buffer the second PDCP PDU 418 such that it is at the head of the buffer (i.e. will be the next PDCP PDU to be transmitted of all PDCP PDUs in the buffer associated with the same DRB).

[0096] At step S25 the PDCP entity 452 determines that a transmission opportunity exists for a PDCP PDU. This may be, for example, in response to receiving an indication from the MAC protocol entity 454 that a transmission opportunity has arisen for a PDCP PDU belonging to a particular DRB.

[0097] Uplink transmission opportunities may be controlled by a serving infrastructure equipment 242. The MAC protocol entity 454 may determine that a transmission opportunity exists for a PDCP PDU associated with a DRB based on receiving an uplink grant from the serving infrastructure equipment. The uplink grant may indicate the DRB. In response to determining that a transmission opportunity exists for a PDCP PDU of the DRB associated with the first PDCP PDU 408 and the second PDCP PDU 418, the PDCP entity 452 retrieves the second PDCP PDU 418 from the PDCP buffer and transfers it to the RLC / MAC protocol entity for transmission at step S26.

[0098] Subsequently, at step S28, the second PDCP PDU 418 is transmitted on the wireless access interface 456 by the RLC / MAC protocol entity 454. The second PDCP PDU 418 may be processed by the RLC / MAC protocol entity 454 and the PHY entity (not shown) prior to transmission on the wireless access interface 456. The RLC / MAC protocol entity 454 and PHY entity may process the second PDCP PDU 418 in accordance with well-known conventional techniques, such as those specified for the 5G / NR wireless access interface. At steps S30 and S32 the first PDCP PDU 408 is transferred to the RLC / MAC protocol entity 454 and transmitted on the wireless access interface 456, in response to a further identification of an opportunity for transmission via the DRB (not shown).

[0099] Figure 6 is a flow chart illustrating a process corresponding to step S16 and step S24 together with steps S14 and S22 shown in Figure 5 and described above.

[0100] The process starts at step 602 in which a PDCP SDU such as the first PDCP SDU 406 is received from the SDAP entity 450, by the PDCP entity 452. This corresponds to steps S14 and S22 shown in Figure 5. The first PDCP SDU 406 may be accompanied by an indication of the DRB associated with the first PDCP SDU 406, or the DRB indication may be implicit in the selection of the PDCP entity 452 to receive the first PDCP SDU 406. The first PDCP SDU 406 may be accompanied by an indication as to whether the first PDCP SDU 406 is associated with the higher priority or not.

[0101] At step 606 the PDCP entity 452 determines whether the received first PDCP SDU 406 is associated with a higher priority. As described above this may be by means of an indication received from the SDAP entity 450, or by inspecting the SDAP header 404 forming part of the first PDCP SDU 406. If it is determined at step 606 that the received first PDCP SDU 406 is not associated with the higher priority, then flow passes to step 608.

[0102] At step 608 the received first PDCP SDU 406 is assigned the next unused sequence number corresponding to the DRB. That is, the sequence number which is next in sequence and which has not been assigned to any earlier PDCP SDU of the same DRB.

[0103] The process then continues to step 610 in which the PDCP header 407 is generated for the first PDCP SDU 406 in accordance with the assigned sequence number. The first PDCP SDU 406 may be combined with the PDCP header 407 to form the first PDCP PDU 408.

[0104] In step 612 header compression (such as robust header compression) may be applied to the formed first PDCP PDU 408.

[0105] In step 614 the first PDCP PDU 408 is stored at the next available location in the buffer corresponding to the DRB. In other words, the first PDCP PDU 408 is added to the end of a queue of PDCP PDUs waiting for transmission via the DRB.

[0106] At step 616 a PDCP discard timer is started in respect of the formed first PDCP PDU 408. The duration of the timer may be set to a first duration in accordance with the determination at step 606 that the first PDCP PDU 408 is not associated with the higher priority.

[0107] Returning to step 606, if it is determined that the received PDCP SDU is associated with the higher priority (for example, because the received PDCP SDU is the second PDCP SDU 416) then control passes to step 620 in which the second PDCP SDU 416 is assigned a sequence number which is the sequence number of the next PDCP PDU to be transmitted via the DRB. That is, the second PDCP SDU 416 is assigned the lowest sequence number which has not been associated with any PDCP PDU which has already been passed to the RLC / MAC protocol entity for transmission.

[0108] At step 622 the PDCP entity 452 may amend the sequence numbers associated with PDCP PDUs which have previously been generated and stored in the buffer for the DRB. This reflects the possibility that the sequence number which has been assigned to the most recently received second PDCP SDU 416 has previously been assigned to a different PDCP PDU (such as the first PDCP SDU 406) which is currently stored in the PDCP buffer for the DRB.

[0109] At step 624 the PDCP entity 452 may re-form the PDCP headers associated with PDCP PDUs which are stored in the PDCP buffer for the DRB and may subsequently apply header compression to the modified PDCP PDUs. The process continues at step 626 in which the PDCP entity 452 generates the PDCP header 407 for the second PDCP SDU 416 and thus forms the second PDCP PDU 418.

[0110] At step 628, the PDCP entity 452 applies robust header compression to the newly formed second PDCP PDU 418, and at step 630, the newly formed second PDCP PDU 418 is stored at the front of the PDCP buffer for the DRB. That is, the second PDCP PDU 418is to be the next PDCP PDU which is passed to the RLC / MAC entity for transmission on the DRB.

[0111] At step 632 the PDCP entity 452 starts a PDCP discard timer in respect of the newly formed second PDCP PDU 418. Reflecting the determination at step 606 that the received second PDCP SDU 416 which forms the second PDCP PDU 418 is associated with the higher priority, the PDCP discard timer is started with a second duration, which is longer than the first duration which would have been assigned to the PDCP discard timer to a PDCP PDU not having the higher priority, as described above in step 616.

[0112] In Figure 6 the sequence of steps 606, 608, 610, 612, 614, and 616 broadly correspond to the processing carried out at step S16 of Figure 5.

[0113] Similarly, the sequence of steps 606, 620, 622, 624, 626, 628, 630 and 632 broadly correspond to the processing carried out at step S24 of Figure 5.

[0114] In the processes illustrated in Figure 5 and in Figure 6, and described above, the PDCP entity 452 forms PDCP PDUs in response to the receipt of a new PDCP SDU from the SDAP entity 450. As such, the PDCP buffer contains a sequence of one or more PDCP PDUs associated with a DRB, for subsequent transfer to the RLC / MAC entity 454 for transmission on the wireless access interface 456.

[0115] In some examples, the PDCP entity 452 may store PDCP SDUs in the PDCP buffer. The PDCP entity 452 may form the PDCP PDUs, such as the second PDCP PDU 418 and the first PDCP PDU 408, in response to determining that there is a transmission opportunity for a PDCP PDU associated with the DRB.

[0116] It will be appreciated that controlling the sequence number of the PDCP SDU is entirely optional. As such, in one example the step 606 may occur after step 614, i.e. after PDCP PDU is almost ready because transmitting PDCP PDUs out of sequence is permitted from the PDCP layer. Alternatively, the RLC layer can adjust the PDCP sequence number order Furthermore, without operations in which a sequence number is used to prioritise the order of the packets, the flow of operations for the yes branch at step 606 will correspond to the no branch in Figure 6. In addition, RTP header may include an indication of priority and priority is not explicitly indicated in the SDAP header.

[0117] Figure 7 illustrates a process by which the PDCP entity 452 forms PDCP PDUs in which the PDCP buffer is used to store PDCP SDUs.

[0118] The process starts at step 702 and the process continues at step 704 in which it is determined whether or not there is a transmission opportunity for a PDCP PDU of the DRB. If no transmission opportunity is determined to exist then control passes to step 706.

[0119] In step 706 the PDCP entity 452 may determine whether a discard timer has expired in respect of any PDCP SDUs which are stored in the PDCP buffer. As explained in Figure 6, the discard timer is set to a first or a second discard time value 616, 632 according to whether the packet for transmission is a lower priority packet or a higher priority packet. If any discard timers are found to have expired, then control passes to step 708 in which each PDCP SDU associated with an expired timer is discarded, such that it will not be passed to the RLC / MAC entity 454 for transmission on the wireless access interface 456. After step 708 control returns to step 704. Similarly, if at step 706 it is determined that no discard timers associated with PDCP SDUs currently in the PDCP buffer have expired, then control returns to step 704.

[0120] If at step 704 it is determined that there is a transmission opportunity for a PDCP PDU via the DRB, then control passes to step 710. In step 710, the PDCP entity retrieves the PDCP SDU (such as the first PDU SDU 406) which is the next to be transmitted from the PDCP buffer. At step 712, the first PDCP SDU 406 is assigned the next sequence number, that is to say the lowest sequence number which has not yet been used for any PDCP PDU which has been transmitted via the DRB.

[0121] At step 714 the PDCP entity forms the PDCP header 407 and thereby constructs the first PDCP PDU 408 comprising the first PDCP SDU 406 which has been retrieved from the buffer and the header 407 indicating the assigned sequence number. At step 716 header compression is applied to the first PDCP PDU 408, and in step 718 the first PDCP PDU 408 is passed to the RUC / MAC protocol entity 454 for transmission on the wireless access interface 456.

[0122] In accordance with the process illustrated in Figure 7 and described above, the process illustrated in Figure 6 may be accordingly modified so that there is no need to assign a sequence number, or to construct the PDCP header 407 or to form the first PDCP PDU 408 at the time when the first PDCP SDU 406 is received from the SDAP entity 450. As such, in some embodiments, and as indicated above, the process of Figure 6 may be modified in accordance with the process of Figure 7 by the omission of steps 608, 610, 612 in respect of PDCP SDUs not determined to be associated with the higher priority, and by the omission of steps 620, 622, 624, 626 and 628 in respect of PDCP SDUs which are determined to be associated with the higher priority. Such a modified process may operate substantially concurrently with the process of Figure 7.

[0123] Alternatively, in accordance with the process illustrated in Figure 6 and described above, the process illustrated in Figure 7 may be accordingly modified so that at step 710, a next PDCP PDU is retrieved from the PDCP buffer, and steps 714, 716 and 718 may be omitted. Such a modified process may operate substantially concurrently with the process of Figure 6.

[0124] According to the above explanation, one or more of the process steps of Figure 5, Figure 6 and Figure 7 may be omitted, and / or one or more of the process steps may occur in a different order from that shown in a Figure and described above.

[0125] Example Embodiments

[0126] As explained above with reference to Figures 4, 5, 6 and 7, our co-pending European patent application number 197208689.9 [3] discloses a technique for prioritising transmission of packets within a DRB based on a discard timer. One of the disclosed options is to use a different discard timer for each packet depending on priority, so that with two priority levels are used, two separate and different PDCP discard timers can be used to give effect to the different priority levels of transmission to meet different QoS requirements. A PDCP discard timer is set by RRC pdcp-config information element (IE) inside an RRC Reconfiguration message, which is normally set to a value equal to Packet Delay Budget (PDB) by the gNB. PDB value is related to the QoS profile of a QoS flow, which is mapped to a DRB. Generally, as explained with reference to Figure 3, one or more QoS flows of similar QoS characteristics can be mapped to a single DRB.

[0127] Current wireless communications techniques such as those discussed in 3GPP for Rel-18 are considering capacity enhancements, which may for example assist in the transmission of XR (extended Reality) traffic. This is because any packet losses in XR, which uses heavy compression and spatial-temporal prediction, and in video generally, can result in degradation of a user-perceived quality of experience. Hence, video applications generally benefit from packet loss being minimised. Proposed enhancements to packet communications include consideration of network congestion, and include discarding packets with a lower priority in preference to higher priority packets. For packets with a higher priority, discarding should be avoided and packets discarded only if necessary. Under normal operation, when for example the network is not congested, transmission of packets from a transmit buffer can be prioritised as explained above with reference to Figures 4 to 7.

[0128] An alternative to prioritising packet discard using different discard timers as disclosed in EP 197208689.9 [3] is to use a threshold based approach to discarding packets. According to the threshold based approach, a certain number of packets can be discarded when a number of packets in a UE’s transmit buffer are above a certain threshold. However, a disadvantage to this approach is that packet discarding can be indiscriminate and therefore applications such as XR can suffer a disproportionate loss of service. Therefore, using discard timers separately configured in accordance with priority can provide a flexible technique for discarding packets in accordance with priority when a network is congested. That said, a technical problem with this approach concerns a technique for warning a communications network that a packet is approaching a limit of its delay budget or Packet Set Delay Budget (PSDB), so that its transmission from the UE’s transmit buffer should be escalated. This technique is referred to as Delay Status Reporting (DSR).

[0129] Delayed Status Reporting (DSR) is triggered by the UE if packets in the UE’s transmit buffer run a risk of overrunning their delay budget (PSDB). As a time in the UE’s transmit buffer approaches the delay budget, the UE transmits a DSR to the communications network to escalate transmission, so that the network can more urgently schedule resources and transmission opportunities for the UE. According to this arrangement, a UE triggers DSR and informs the communications network of a remaining amount of time for which the data in the UE buffer is still relevant i.e., delay is within PDB / PSDB limits. This remaining time can be calculated according to: remaining time = [discard timer value (the value of this timer is normally linked to PDB in gNB implementation)- time spent in UE buffer]. However, under some communications conditions, such as network congestion, packets may more frequently be delayed and if a shorter discard timer value is used for such packets then doing so will trigger DSR at a time when the UE of the network cannot transmit packets, which increases consumption of resources without increasing a likelihood of transmitting the packets.

[0130] There is another related concept of PDU Size Importance (PSI) value. A PSI value for a packet or set of packets is assigned by an application layer. It is currently envisaged within 3GPP that there are 16 PSI levels with corresponding values. A higher value implies that the packet is important. Under congestion, packets assigned with a low priority / importance value should be discarded so that congestion situation eases in the network.

[0131] As will be appreciated, from the solution proposed in EP197208689.9 [3], setting a higher discard timer for more important packets can result in more important packets being transmitted and lower important packets being discarded. However, using a shorter discard timer can have an effect of causing a UE to transmit more DSR because the packet is more likely to approach its expiry of new shorter discard timer value. As mentioned above, increasing transmission of DSR where network is congested has a disadvantage of consuming communications resources and power for a UE.

[0132] Embodiments of the present technique can provide, a communications device and methods of transmitting uplink data by a communications device to a wireless communications network by forming the data into packets for transmission and determining a state of conditions for communicating the packets via a wireless access interface to the wireless communications network, and selecting one of a plurality of discard timers associated with each packet based on whether the determined state for transmitting data is either a first state or a second state. The first state of the communication conditions may correspond to the wireless communication network not being congested, whereas the second state may correspond to the network being congested and therefore transmission of packets being more likely to be delayed. The method further comprises storing the packets for transmission in a transmit buffer and starting the selected discard timer when each packet is stored in the transmit buffer, and either transmitting each packet from the transmit buffer when a transmission occasion occurs, or discarding the packet from the transmit buffer if the selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer. According to the example embodiments, if the determined state is the first state, then the selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the discard timer selected is a plurality of priority based discard timers. If the state of the communications conditions is determined to be the first state, then the selecting the discard timer may comprise selecting the reference discard timer as one of the plurality of discard timers associated with each packet, and whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer until the reference discard timer expires. If the determined state of communication conditions is the second state, the selecting the discard timer from one of the plurality of discard timers associated with each packet, comprises determining a relative priority for transmitting the packet, and selecting the discard timer from one of the plurality of priority based discard timers, each of the priority based discard timers providing a discard time of different length according to a priority of transmitting the packet. In some examples, if the communications conditions are determined to be in the second state, the one or more delay status reports are not transmitted to the communications network. In some embodiments, if the determined state of communication conditions is the second state then both the priority based discard timer may be used and the reference discard timer may be used, the priority based discard timer being used to discard the packet if it has not been transmitted by the time the discard timer expires, and the reference discard timer is started and used to transmit delay status reports (DSR) to inform the network of the packets which are being more likely not to be discarded. Therefore, if the second state is selected then to discard timers are selected and run, the priority based discard timer being used for discarding packets in accordance with their priority and the reference discard timer being used to generate DSR.

[0133] According to example embodiments, two separate discard timers are applied per packet. A normal / reference discard timer value is applied for discarding packets in one state such as if there is no congestion and for triggering DSR. In another state in which the network is congested, a different priority based timer is applied for discarding packets, and in which no DSR is triggered. The reference discard timer, which is linked to delay budget (PSDB), is always applied for triggering DSR.

[0134] Figure 8 provides an example illustration, which corresponds to the protocol stack shown in Figure 4 with adaptation according to example embodiments. Parts shown in Figure 8 correspond to those shown in Figure 4, in which the same elements have the same reference numerals. In contrast to Figure 4, in Figure 8, the PDU packet from the PDCP layer includes a plurality of discard timers 840 each of which is selected in accordance with conditions for communicating the PDU from the uplink transmit buffer 406. In some examples more than one discard timer may be selected and used, one for discarding packets according to their priority and one for generating delay status reports. A more detailed illustration is provided in Figure 9, which shows the UE transmit buffer 406 of the transmitter circuitry containing a plurality of PDU packets 850 for transmission in the uplink via the DRB 300. For the present example, each of the packets 850 may be either lower priority packet or higher priority packet as shown in Figure 9 indicated by a different shading. The UE transmit buffer 406 is illustrated as including packets having different priorities and assumes a FIFO operation, and illustrates a case in which a low priority packet stuck in the queue is blocking a high importance packet. Figures 8 and 9 show different importance values assigned to different packets. For simplicity, only two PSI values are shown / assigned, although it will be appreciated that a plurality of different priorities can be used in accordance with example embodiments a different discard timer value can be assigned to each of the plurality of priorities.

[0135] As shown in Figure 9, each of the low priority packets and the high priority packets includes a discard timer based on priority (T PSI low / T PSI high) and a reference discard time, T ref. According to example embodiments, one of the priority based discard timers T PSI low / high is selected or the reference discard time, T_ref, is selected according to whether conditions for communicating the packets on the uplink are determined to be in a first state or a second state respectively. The first state may for example correspond to a situation in which the wireless communications network is not congested and so the reference discard timer is selected and therefore DSR can be transmitted according to delay budget of the packet in the transmit buffer 406. In the first state only one discard timer namely the reference discard timer is used. The second state may correspond to a state in which the network is congested. Therefore, as illustrated in Figure 9 each packet has a plurality of discard timers, at least one of which is selected for determining whether to discard the packet in accordance with a state of communications conditions. For example, if the network is congested then a prioritisation discard timer (T PSI low / T PSI high) is used where a value of the timer reflects a relative priority for discarding of that packet to satisfy QoS requirements.

[0136] In one example, both the priority discard timer is selected for determining whether to discard the packet from the queue in accordance with its priority and a second discard timer based on the reference discard timer may also be selected, which is started and monitored for the purposes of generating delay status reports. Since the priority based discard timer is shorter than the reference discard timer, then the priority based discard timer will expire before the reference discard timer and so the priority based discard timer will be used to judge discard of the packet. However, in other examples the delay status reporting may be disabled if the second state is determined.

[0137] A further illustration of example embodiments is presented in Figure 10 which shows an adaptation of the flow diagram of Figure 7 for transmitting uplink packets from the UE’s transmit buffer 406 and for discarding a packet from the transmit buffer 406 depending on whether a discard timer has expired. In contrast to Figure 7, Figure 10 includes two further step 1001, 1002, which are for setting a discard time for a packet with respect to which the discard timer is tested at decision point 706. In a determination step 1001, communication conditions for transmitting packets on the uplink are determined or evaluated to identify one of a plurality of states. For example, the communications conditions could be a state of congestion of the wireless communications network which should configure communications resources for transmitting the packets on the uplink and receive the packets transmitted from the uplink buffer 406. The determined communications conditions are fed to a second operation 1002, which selects either a reference discard timer or a priority discard timer to determine whether to discard a packet depending on the communications conditions determined in the previous step 1001. An output of the operation 1002 is to determine a discard time which is fed to the time evaluation decision point 706 which corresponds the operations of the flow diagram in Figure 7.

[0138] As mentioned above, whilst DSR is enabled when the reference discard timer is selected for packet discard, when a priority based discard timer is selected for packet discard, DSR may also be enabled in addition to the priority based discard timer. In this case, a reference discard timer is also selected and started when the packet enters the transmit buffer in order to generate the DSR. Figure 11 is a flow diagram illustrating an operation of selecting the discard timer 1002 in Figure 10 in more detail according to example embodiments. As shown in Figure 11, at decision step 1101, an evaluation or indication is provided of the conditions for communicating uplink data packets from the transmit buffer 406 which is used to determine whether or not the conditions indicate a first state or a second state. For example, the first state may correspond to little or no congestion of the network whereas the second state may correspond to network congestion. However congestion is one example of network conditions and other communications conditions can be a state of the transmission transmit buffer 406, radio communications conditions for transmitting the uplink data, power state of the UE and other conditions which may affect transmission of the uplink data from the buffer 406. If the decision at step 1101 is to determine that communications conditions correspond to a second state, for example network congestion, then flow passes to a second decision 1102 which determines whether the packet (PDCP PDU) has a high priority (PSI) or a low priority (PSI). If the packet has a low priority then in step 1104 the discard timer is set according to a low priority value, T PSI low. On the other hand if the packets are determined to have a high priority then step 1106 the discard timer is set to a value for high priority, T PSI high. Then at step 1108, the discard timer starts and flow then passes to the decision point 706 corresponding to that shown in Figure 7.

[0139] Alternatively, decision point 1101, if the first state is determined (e.g. no congestion), then the discard timer is set, at step 1110, to the reference discard time, T_ref. The reference discard timer may be set according to a packet delay budget or PSDB as mentioned above. The reference discard timer is then started at 1112. Since the first state has been selected which for example may correspond to a low or no congestion state of the network, then because the reference discard timer has been selected, the UE generates DSR 1114 and transmits the DSR to the network in accordance with a remaining time left for the discard timer. That is, a time remaining in the discard timer is determined in DSR proportionately generated in accordance with a proximity to the maximum time of the packet delay budget. Then flow passes to determine whether the discard timer has expired at step 706 corresponding to the operations in Figure 7. An entry point or connection 1008 is shown with respect to Figure 10 and an exit point 1006 shown with respect to Figure 10.

[0140] According to example embodiments a UE may be configured with discard timers including a reference discard timer and priority based discard timers. With the discard timers, the communications network indicates that the reference discard timer value, which is linked to delay budget (PSDB) is used for DSR reporting as well as for discarding packets in a first state. The other priority based discard timer values are configured for discarding packets per priority or PSI value when there is congestion. Figure 12 provides an illustrative example.

[0141] In Figure 12 RRC signalling is exchanged between the gNB 242 of the communications network and a UE 114. The wireless communications network transmits an RRC Reconfig message 1201 from the gNB 242 to the UE 114. As shown in Figure 12, the RRC Reconfig message 1201 includes a reference discard timer value and one or more other discard timer values 1202 to be used by the UE 114 in accordance with different communications conditions. The UE 114 then transmits an RRC Reconfig complete message 1204 to the gNB 242.

[0142] According to example embodiments, for a communications state for example corresponding to the communications network not being congested, then the discard timer is set according to the reference discard timer value 1206 which includes reporting DSR which are based on the reference to discard timer 1208. However the UE 114 may subsequently receive a congestion indication 1210 in which case operation switches to a different state in which the discard timer is set to select one of the discard timer values corresponding to a priority with which the packets are to be transmitted 1212. In one example the congestion indication 1210 includes a data threshold value, which represents an occupancy level of the transmit buffer indicating how full the transmit buffer is, which corresponds a number of packets or data size in the UEs transmit buffer with respect to its total capacity 1214. The congestion indication 1210 may also include different priority based discard timer values to be used when the network is determined to be congested. Accordingly, if the amount of packets in the transmit buffer falls below the data threshold, then the UE may determine that the network is no longer congested and therefore switches the discard timer back to the reference discard timer value. The discard timer value used for DSR reporting is still the reference discard timer value as shown in Figure 9.

[0143] According to example embodiments as illustrated in Figure 12, the network configures two separate discard timer values and UE applies reference discard timer values for reporting DSR. The other value of discard timer is applied in order to discard packets under congestion. The UE 114, may receive a congestion notification from the network, and in response the UE 114 simply applies priority selected discard timer values. The network indication of congestion may be explicit or implicit or a combination of both. For example, as indicated by the example of Figure 12 congestion could be an indication of a UE buffer threshold from the network.

[0144] According to example embodiments, an explicit indication of congestion may not be provided from the network. According to this example, a UE may be able to determine a congested state of the network and apply discard timer values according to priority when it determines that the network is congested. The UE may detect congestion based on the size of its buffer and may be based on explicit buffer size indication from the network as illustrated by the example in Figure 12. Alternatively the UE may itself decide that the network is congested based on its buffer size and currently experienced radio conditions. For example, if radio conditions are good but the UE buffer is above a certain value then the UE may assume that the buffer is becoming full as a result of congestion on the network side. The example embodiment according to this scenario is illustrated in Figure 13.

[0145] As for the example shown in Figure 12, the gNB 242 transmits an RRC reconfig message 1301 which includes reference discard timer value, and a plurality of priority selected discard timer values 1302. However the reconfig message 1301 also includes a data threshold value representing an occupancy threshold of the UEs transmit buffer after which the UE 114 can determine that the network is congested. Following receipt of the RRC reconfig message 1301, the UE transmits an RRC reconfig complete message 1304. Based on the data threshold value and a number of packets in the UEs transmit buffer, the UE may determine that the network is not congested and accordingly apply the reference discard timer value 1306 and transmit DSR 1308. However the UE may then determine that the network is congested as a result of for example a change in radio conditions and based on an amount of packets within the UEs transmit buffer exceeding data threshold 1310. As a result of determining that communications conditions are such as to switch to a state for using the priority based discard timer values, the UE applies the discard timer values and discards those packets for which the discard timer has expired 1302 and does not transmit DSR based on an amount of time it left in the reference discard timer. If however the amount of data within the buffer falls below the data threshold then the UE can switch back to the reference discard timer value.

[0146] As will be appreciated from the above embodiments, the UE is able to adapt a discard timer value in accordance with a state of communicating uplink packets to wireless communications network adaptively using DSR and prioritisation in accordance with discard timer value determined or conditional upon dynamically experience communications conditions.

[0147] In some examples, values configured by network and UE actions: • Longer value (discard timer value, reference discard timer) : DSR and discard when no congestion

[0148] • Shorter value (Discard timer 1, discard timer 2. . . based on PSI): discard when congestion is detected and use the longer reference discard timer for generating DSR

[0149] UE threshold is used when to apply shorter value and resume normal operation (using longer value for both DSR and discard).

[0150] 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.

[0151] 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.

[0152] 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.

[0153] The following numbered paragraphs provide further example aspects and features of the present technique:

[0154] Paragraph 1. A method of transmitting uplink data by a communications device to a wireless communications network, the method comprising forming the data into packets for transmission via a wireless access interface of the wireless communications network, determining a state of communication conditions for communicating the data via the wireless access interface to the wireless communications network, selecting at least one of a plurality of discard timers associated with each packet based on whether the determined state of communication conditions for transmitting data is either a first state or a second state, storing the packets for transmission in a transmit buffer and starting the at least one selected discard timer when each packet is stored in the transmit buffer, and either transmitting each packet from the transmit buffer when a transmission occasion for transmitting the packet via the wireless access interface occurs before the selected discard timer has expired, or discarding the packet from the transmit buffer if the at least one selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer, wherein if the determined state is a first state, then the at least one selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the at least one discard timer selected is one of a plurality of priority based discard timers.

[0155] Paragraph 2. A method of paragraph 1, wherein if the state of the communications conditions is determined to be the first state the selecting the at least one discard timer comprises selecting the reference discard timer as one of the plurality of discard timers associated with each packet, and whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer until the reference discard timer expires.

[0156] Paragraph 3. A method of paragraph 1 or 2, wherein if the determined state of communication conditions is the second state, then the selecting the at least one discard timer from one of the plurality of discard timers associated with each packet, comprises determining a relative priority for transmitting the packet, and selecting the at least one discard timer from one of the plurality of priority based discard timers, each of the priority based discard timers providing a discard time of different length according to a priority of transmitting the packet.

[0157] Paragraph 4. A method of paragraph 1, 2 or 3, wherein if the communications conditions are determined to be in the second state, not transmitting one or more delay status reports to the communications network.

[0158] Paragraph 5. A method of paragraph 1, wherein if the determined state of communication conditions is the second state, then the selecting the at least one of the plurality of discard timers associated with each packet, comprises selecting a discard timer from one of the plurality of priority based discard timers according to a priority for transmitting the packet, and selecting the reference discard timer, and the starting the at least one selected discard timer when each packet is stored in the transmit buffer comprises starting the selected priority based discard timer and the reference discard timer, whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer, and either transmitting the packet or discarding the packet if the priority based packet has expired.

[0159] Paragraph 6. A method of any of paragraphs 1 to 5, comprising receiving from the wireless communications network an indication of the reference discard timer to be used in the first state of communication conditions and with the delay status reporting.

[0160] Paragraph 7. A method of any of paragraphs 1 to 6, comprising receiving from the wireless communications network an indication of the plurality of priority based discard timers to be used in the second state of communication conditions.

[0161] Paragraph 8. A method of any of paragraphs 1 to 7, comprising receiving from the wireless communications network an indication of the first state of communication conditions and the second state of communication conditions based on a threshold value of a packet occupancy in the transmit buffer. Paragraph 9. A method of paragraph 8, wherein the indication from the wireless communications network of the second state provides the threshold level of buffer capacity being exceeded and for the second state the indication of the plurality of priority based discard timers to be used in the second state of communication conditions.

[0162] Paragraph 10. A method of paragraph 6, 7 or 8, wherein the indication is received in a Radio Resource Control, RRC, reconfig message.

[0163] Paragraph 11. A method of any of paragraphs 1 to 5, wherein the determining the state of communication conditions for communicating the data being the first state or the second state comprises determining a radio communications conditions, and based on the determined radio communication conditions and an occupancy level of the transmit buffer determining by the communications device whether the state of communication condition is the second state.

[0164] Paragraph 12. A method of any of paragraphs 1 to 11, wherein the first state of communication conditions represents a state in which there is no congestion of data being communicated from the communications device via the wireless communications network.

[0165] Paragraph 13. A method of any of paragraphs 1 to 12, wherein the second state of communication conditions represents a state of congestion for data being communicated from the communications device via the wireless communications network.

[0166] Paragraph 14. A method of operating an infrastructure equipment in a wireless communications network, the method comprising transmitting information for controlling a discard timer for discarding packets by one or more communications devices, when the communications devices are transmitting uplink data packets via a wireless access interface provided by the wireless communications network, the information comprising a reference discard timer based on a packet delay budget for transmitting the packets for use in a first state for communicating via the wireless communications network and a plurality of priority based discard timers for use in a second state for communicating via the wireless communications network.

[0167] Paragraph 15. A method of paragraph 14, wherein the information includes athreshold of an occupancy level of a transmit buffer of the communications devices, the transmit buffer for storing the packets before transmission, the threshold indicating an occupancy level for use by the communications devices to determine whether the conditions for communicating via the wireless communications network are in the first state or the second state.

[0168] Paragraph 16. A method of paragraph 14 or 15, wherein the first state of communication conditions represents a state in which there is no congestion of data being communicated from the communications device via the wireless communications network.

[0169] Paragraph 17. A method of any of paragraphs 14 to 16, wherein the second state of communication conditions represents a state of congestion for data being communicated from the communications device via the wireless communications network.

[0170] Paragraph 18. A method of any of paragraphs 14 to 17, comprising transmitting to one or more of the communications devices an indication that communication conditions via the wireless communications network are congested. Paragraph 19. A method of any of paragraphs 14 to 18, wherein the information is transmitted as part of radio resource control signalling.

[0171] Paragraph 20. A communications device for communicating uplink data via a wireless communications, the communications device comprising transmitter circuitry configured to transmit the uplink data to the wireless communications network via a wireless access interface provided by the wireless communications network, receiver circuitry configured to receive from the wireless communications network, and controller circuitry configure to control the transmitter circuitry and the receiver circuitry, wherein the controller circuitry is configured to form the uplink data into packets for transmission via a wireless access interface of the wireless communications network, to determine a state of communication conditions for communicating the data via the wireless access interface to the wireless communications network, to select at least one of a plurality of discard timers associated with each packet based on whether the determined state of communication conditions for transmitting data is either a first state or a second state, to store the packets for transmission in a transmit buffer and to start the at least one selected discard timer when each packet is stored in the transmit buffer, and either to transmit each packet from the transmit buffer when a transmission occasion for transmitting the packet via the wireless access interface occurs before the selected discard timer has expired, or to discard the packet from the transmit buffer if the at least one selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer, wherein if the determined state is a first state, then the at least one selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the at least one discard timer selected is one of a plurality of priority based discard timers.

[0172] Paragraph 21. A communications device of paragraph 20, wherein the controller circuitry is configured to select the at least one discard timer by, if the state of the communications conditions is determined to be the first state, selecting the reference discard timer as one of the plurality of discard timers associated with each packet, and whilst the packet is stored in the transmit buffer, to transmit one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer until the reference discard timer expires.

[0173] Paragraph 22. A communications device of paragraph 20 or 21, wherein the controller circuitry is configured to select the at least one discard timer from one of the plurality of discard timers associated with each packet, if the determined state of communication conditions is the second state, by determining a relative priority for transmitting the packet, and selecting the at least one discard timer from one of the plurality of priority based discard timers, each of the priority based discard timers providing a discard time of different length according to a priority of transmitting the packet. Paragraph 23. A communications device of paragraph 20, 21 or 22, wherein the controller circuitry is configured not to transmit one or more delay status reports to the communications network to if the communications conditions are determined to be in the second state.

[0174] Paragraph 24. A communications device of paragraph 20, wherein the controller circuitry is configured if the determined state of communication conditions is the second state, to select the at least one of the plurality of discard timers associated with each packet by selecting a discard timer from one of the plurality of priority based discard timers according to a priority for transmitting the packet, and selecting the reference discard timer, starting the selected priority based discard timer and the reference discard timer, whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer, and either transmitting the packet or discarding the packet if the priority based packet has expired.

[0175] Paragraph 25. An infrastructure equipment for forming part of a wireless communications network, the infrastructure equipment comprising transmitter circuitry configured to transmit the uplink data to the wireless communications network via a wireless access interface provided by the wireless communications network, receiver circuitry configured to receive from the wireless communications network, and controller circuitry configure to control the transmitter circuitry and the receiver circuitry, wherein the controller circuitry is configured to transmit information for controlling a discard timer for discarding packets by one or more communications devices, when the communications devices are transmitting uplink data packets via a wireless access interface provided by the wireless communications network, the information comprising a reference discard timer based on a packet delay budget for transmitting the packets for use in a first state for communicating via the wireless communications network and a plurality of priority based discard timers for use in a second state for communicating via the wireless communications network.

[0176] Paragraph 26. An infrastructure equipment of paragraph 25, wherein the information includes a threshold of an occupancy level of a transmit buffer of the communications devices, the transmit buffer for storing the packets before transmission, the threshold indicating an occupancy level for use by the communications devices to determine whether the conditions for communicating via the wireless communications network are in the first state or the second state.

[0177] Paragraph 27. An infrastructure equipment of paragraph 25 or 26, wherein the first state of communication conditions represents a state in which there is no congestion of data being communicated from the communications device via the wireless communications network.

[0178] Paragraph 28. An infrastructure equipment of any of paragraphs 25 to 27, wherein the second state of communication conditions represents a state of congestion for data being communicated from the communications device via the wireless communications network.

[0179] Paragraph 29. An infrastructure equipment of any of paragraphs 25 to 28, wherein the controller circuitry is configured to transmit to one or more of the communications devices an indication that communication conditions via the wireless communications network are congested. Paragraph 30. An infrastructure equipment of any of paragraphs 25 to 30, wherein the information is transmitted as part of radio resource control signalling.

[0180] REFERENCES [1] 3GPP TS 38.470

[0181] [2] 3GPP TS 38.473

[0182] [3] European patent application number EP18172380.0

Claims

CLAIMS1. A method of transmitting uplink data by a communications device to a wireless communications network, the method comprising forming the data into packets for transmission via a wireless access interface of the wireless communications network, determining a state of communication conditions for communicating the data via the wireless access interface to the wireless communications network, selecting at least one of a plurality of discard timers associated with each packet based on whether the determined state of communication conditions for transmitting data is either a first state or a second state, storing the packets for transmission in a transmit buffer and starting the at least one selected discard timer when each packet is stored in the transmit buffer, and either transmitting each packet from the transmit buffer when a transmission occasion for transmitting the packet via the wireless access interface occurs before the selected discard timer has expired, or discarding the packet from the transmit buffer if the at least one selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer, wherein if the determined state is a first state, then the at least one selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the at least one discard timer selected is one of a plurality of priority based discard timers.

2. A method of claim 1, wherein if the state of the communications conditions is determined to be the first state the selecting the at least one discard timer comprises selecting the reference discard timer as one of the plurality of discard timers associated with each packet, and whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer until the reference discard timer expires.

3. A method of claim 1, wherein if the determined state of communication conditions is the second state, then the selecting the at least one discard timer from one of the plurality of discard timers associated with each packet, comprises determining a relative priority for transmitting the packet, and selecting the at least one discard timer from one of the plurality of priority based discard timers, each of the priority based discard timers providing a discard time of different length according to a priority of transmitting the packet.

4. A method of claim 1, wherein if the communications conditions are determined to be in the second state, not transmitting one or more delay status reports to the communications network.

5. A method of claim 1, wherein if the determined state of communication conditions is the second state, then the selecting the at least one of the plurality of discard timers associated with each packet, comprises selecting a discard timer from one of the plurality of priority based discard timers according to a priority for transmitting the packet, and selecting the reference discard timer, and the starting the at least one selected discard timer when each packet is stored in the transmit buffer comprises starting the selected priority based discard timer and the reference discard timer, whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer, and either transmitting the packet or discarding the packet if the priority based packet has expired.

6. A method of claim 1, comprising receiving from the wireless communications network an indication of the reference discard timer to be used in the first state of communication conditions and with the delay status reporting.

7. A method of claim 1, comprising receiving from the wireless communications network an indication of the plurality of priority based discard timers to be used in the second state of communication conditions.

8. A method of claim 1, comprising receiving from the wireless communications network an indication of the first state of communication conditions and the second state of communication conditions based on a threshold value of a packet occupancy in the transmit buffer.

9. A method of claim 8, wherein the indication from the wireless communications network of the second state provides the threshold level of buffer capacity being exceeded and for the second state the indication of the plurality of priority based discard timers to be used in the second state of communication conditions.

10. A method of claim 6, wherein the indication is received in a Radio Resource Control, RRC, reconfig message.

11. A method of claim 1, wherein the determining the state of communication conditions for communicating the data being the first state or the second state comprises determining a radio communications conditions, and based on the determined radio communication conditions and an occupancy level of the transmit buffer determining by the communications device whether the state of communication condition is the second state.

12. A method of claim 1, wherein the first state of communication conditions represents a state in which there is no congestion of data being communicated from the communications device via the wireless communications network.

13. A method of claim 1, wherein the second state of communication conditions represents a state of congestion for data being communicated from the communications device via the wireless communications network.

14. A method of operating an infrastructure equipment in a wireless communications network, the method comprising transmitting information for controlling a discard timer for discarding packets by one or more communications devices, when the communications devices are transmitting uplink data packets via a wireless access interface provided by the wireless communications network, the information comprising a reference discard timer based on a packet delay budget for transmitting the packets for use in a first state for communicating via the wireless communications network and a plurality of priority based discard timers for use in a second state for communicating via the wireless communications network.

15. A method of claim 14, wherein the information includes a threshold of an occupancy level of a transmit buffer of the communications devices, the transmit buffer for storing the packets before transmission, the threshold indicating an occupancy level for use by the communications devices to determine whether the conditions for communicating via the wireless communications network are in the first state or the second state.

16. A method of claim 14, wherein the first state of communication conditions represents a state in which there is no congestion of data being communicated from the communications device via the wireless communications network.

17. A method of claim 14, wherein the second state of communication conditions represents a state of congestion for data being communicated from the communications device via the wireless communications network.

18. A method of claim 14, comprising transmitting to one or more of the communications devices an indication that communication conditions via the wireless communications network are congested.

19. A method of claim 14, wherein the information is transmitted as part of radio resource control signalling.

20. A communications device for communicating uplink data via a wireless communications, the communications device comprising transmitter circuitry configured to transmit the uplink data to the wireless communications network via a wireless access interface provided by the wireless communications network, receiver circuitry configured to receive from the wireless communications network, and controller circuitry configure to control the transmitter circuitry and the receiver circuitry, wherein the controller circuitry is configured to form the uplink data into packets for transmission via a wireless access interface of the wireless communications network, to determine a state of communication conditions for communicating the data via the wireless access interface to the wireless communications network, to select at least one of a plurality of discard timers associated with each packet based on whether the determined state of communication conditions for transmitting data is either a first state or a second state, to store the packets for transmission in a transmit buffer and to start the at least one selected discard timer when each packet is stored in the transmit buffer, and either to transmit each packet from the transmit buffer when a transmission occasion for transmitting the packet via the wireless access interface occurs before the selected discard timer has expired, or to discard the packet from the transmit buffer if the at least one selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer, wherein if the determined state is a first state, then the at least one selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the at least one discard timer selected is one of a plurality of priority based discard timers.

21. A communications device of claim 20, wherein the controller circuitry is configured to select the at least one discard timer by, if the state of the communications conditions is determined to be the first state, selecting the reference discard timer as one of the plurality of discard timers associated with each packet, and whilst the packet is stored in the transmit buffer, to transmit one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer until the reference discard timer expires.

22. A communications device of claim 20, wherein the controller circuitry is configured to select the at least one discard timer from one of the plurality of discard timers associated with each packet, if the determined state of communication conditions is the second state, by determining a relative priority for transmitting the packet, and selecting the at least one discard timer from one of the plurality of priority based discard timers, each of the priority based discard timers providing a discard time of different length according to a priority of transmitting the packet.

23. A communications device of claim 20, wherein the controller circuitry is configured not to transmit one or more delay status reports to the communications network to if the communications conditions are determined to be in the second state.

24. A communications device of claim 20, wherein the controller circuitry is configured if the determined state of communication conditions is the second state, to select the at least one of the plurality of discard timers associated with each packet by selecting a discard timer from one of the plurality of priority based discard timers according to a priority for transmitting the packet, and selecting the reference discard timer, starting the selected priority based discard timer and the reference discard timer, whilst the packet is stored in the transmit buffer, transmitting one or more delay status reports to the communications network as a function of a time remaining of the reference discard timer, and either transmitting the packet or discarding the packet if the priority based packet has expired.

25. An infrastructure equipment for forming part of a wireless communications network, the infrastructure equipment comprising transmitter circuitry configured to transmit the uplink data to the wireless communications network via a wireless access interface provided by the wireless communications network, receiver circuitry configured to receive from the wireless communications network, and controller circuitry configure to control the transmitter circuitry and the receiver circuitry, wherein the controller circuitry is configured to transmit information for controlling a discard timer for discarding packets by one or more communications devices, when the communications devices are transmitting uplink data packets via a wireless access interface provided by the wireless communications network, the information comprising a reference discard timer based on a packet delay budget for transmitting the packets for use in a first state for communicating via the wireless communications network and a plurality of priority based discard timers for use in a second state for communicating via the wireless communications network.

26. An infrastructure equipment of claim 25, wherein the information includes a threshold of an occupancy level of a transmit buffer of the communications devices, the transmit buffer for storing the packets before transmission, the threshold indicating an occupancy level for use by the communications devices to determine whether the conditions for communicating via the wireless communications network are in the first state or the second state.

27. An infrastructure equipment of claim 25, wherein the first state of communication conditions represents a state in which there is no congestion of data being communicated from the communications device via the wireless communications network.

28. An infrastructure equipment of claim 25, wherein the second state of communication conditions represents a state of congestion for data being communicated from the communications device via the wireless communications network.

29. An infrastructure equipment of claim 25, wherein the controller circuitry is configured to transmit to one or more of the communications devices an indication that communication conditions via the wireless communications network are congested.

30. An infrastructure equipment of claim 25, wherein the information is transmitted as part of radio resource control signalling.

31. Circuitry for communicating uplink data via a wireless communications, the circuitry comprising transmitter circuitry configured to transmit the uplink data to the wireless communications network via a wireless access interface provided by the wireless communications network, receiver circuitry configured to receive from the wireless communications network, and controller circuitry configure to control the transmitter circuitry and the receiver circuitry, wherein the controller circuitry is configured to form the uplink data into packets for transmission via a wireless access interface of the wireless communications network, to determine a state of communication conditions for communicating the data via the wireless access interface to the wireless communications network, to select at least one of a plurality of discard timers associated with each packet based on whether the determined state of communication conditions for transmitting data is either a first state or a second state, to store the packets for transmission in a transmit buffer and to start the at least one selected discard timer when each packet is stored in the transmit buffer, and either to transmit each packet from the transmit buffer when a transmission occasion for transmitting the packet via the wireless access interface occurs before the selected discard timer has expired, or to discard the packet from the transmit buffer if the at least one selected discard timer for the packet expires before the packet has been transmitted from the transmit buffer, wherein if the determined state is a first state, then the at least one selected discard timer is a reference discard timer based on a packet delay budget and if the determined state is the second state then the at least one discard timer selected is one of a plurality of priority based discard timers.

32. Circuitry for forming part of a wireless communications network, the circuitry comprising transmitter circuitry configured to transmit the uplink data to the wireless communications network via a wireless access interface provided by the wireless communications network,receiver circuitry configured to receive from the wireless communications network, and controller circuitry configure to control the transmitter circuitry and the receiver circuitry, wherein the controller circuitry is configured to transmit information for controlling a discard timer for discarding packets by one or more communications devices, when the communications devices are transmitting uplink data packets via a wireless access interface provided by the wireless communications network, the information comprising a reference discard timer based on a packet delay budget for transmitting the packets for use in a first state for communicating via the wireless communications network and a plurality of priority based discard timers for use in a second state for communicating via the wireless communications network.

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