Patent Description:
The present application claims the Paris Convention priority of European patent application number <CIT>.

Latest generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture, are able to support a wider range of services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. The demand to deploy such networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to continue to increase rapidly.

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

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

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

Document <CIT> discloses mechanisms on response of pre-allocated resource based PUSCH transmission.

Embodiments of the present technique can provide a method of operating a communications device configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network. The method comprises, while the communications device is operating in an inactive state, receiving, from the wireless communications network, a small data transmission, SDT, within a set of downlink resources of the wireless radio interface, determining, based on a configuration indicated by signalling information received from the wireless communications network previously to the SDT, a set of uplink resources of the wireless radio interface, and transmitting, to the wireless communications network in the determined set of uplink resources, a feedback signal in response to the received SDT.

Embodiments of the present technique, which, in addition to methods of operating communications devices, relate to methods of operating infrastructure equipment, communications devices and infrastructure equipment, and circuitry for communications devices and infrastructure equipment, allow for more efficient use of radio resources by a communications device.

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

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

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

3GPP has completed the basic version of <NUM> in Rel-<NUM>, known as the New Radio Access Technology (NR). In addition, enhancements have been made in Rel-<NUM>, incorporating new features such as the <NUM>-step RACH procedure [<NUM>], Industrial Internet of Things (IIoT) [<NUM>] and NR-based Access to Unlicensed Spectrum (NR-U) [<NUM>].

Further enhancements have been agreed for Rel-<NUM>, such as small data transmissions (SDT) in the uplink while the transmitting UE is in the RRC_INACTIVE state, as well as Multicast and Broadcast Services (MBS) and positioning enhancements. With reference to [<NUM>], some specific examples of mobile originated small data transmission (MO SDT) and infrequent data traffic may include the following use cases:.

In addition, based on [<NUM>] as mentioned above, uplink small data transmissions have been enabled for UEs in the RRC_INACTIVE state (i.e. without the UE moving to a fully connected state with the network) in order to reduce the signalling overheads as well as power consumption at the UE, and primarily being for infrequent data traffic. SDT transmission on the uplink for UEs in the RRC_INACTIVE state has been agreed for both RACH based schemes (i.e. <NUM>-step and <NUM>-step RACH) - known as Random Access SDT (RA-SDT) - and configured grant (CG) based schemes (CG-SDT), each of which is discussed in greater detail below. This includes general procedures to enable user plane data transmissions for small data packets on the uplink in the inactive state (for example using either MsgA of the <NUM>-step RACH procedure or Msg3 of the <NUM>-step RACH procedure), and enables flexible payload sizes larger than the Rel-<NUM> Common Control Channel (CCCH) message size that is possible currently for a UE in the RRC_INACTIVE state to transmit small data in MsgA or Msg3 to support user plane data transmission in the uplink.

The NR radio access system employs Orthogonal Frequency Division Multiple Access (OFDMA), where different users are scheduled in different subsets of sub-carriers simultaneously. However, OFDMA requires tight synchronisation in the uplink transmissions in order to achieve orthogonality of transmissions from different users. In essence, the uplink transmissions from all users must arrive at the same time (i.e. they must be synchronised) at the gNB receiver. A UE that is far from the gNB must therefore transmit earlier than a UE closer to the gNB, due to different RF propagation delays. In NR, timing advance commands are applied to control the uplink transmission timing for individual UEs, mainly for Physical Uplink Shared Channels (PUSCHs), Physical Uplink Control Channels (PUCCHs) and Sounding Reference Signals (SRS). The timing advance usually comprises twice the one-way propagation delay between the UE and gNB, thus representing both downlink and uplink delays.

An example configuration of a wireless communications network which uses some of the terminology proposed for and used in NR and <NUM> is shown in <FIG>. In <FIG> a plurality of transmission and reception points (TRPs) <NUM> are connected to distributed control units (DUs) <NUM>, <NUM> by a connection interface represented as a line <NUM>. Each of the TRPs <NUM> is arranged to transmit and receive signals via a wireless access interface (i.e. a radio interface for wireless access) 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 <NUM>, forms a cell of the wireless communications network as represented by a circle <NUM>. As such, wireless communications devices <NUM> which are within a radio communications range provided by the cells <NUM> can transmit and receive signals to and from the TRPs <NUM> via the wireless access interface. Each of the distributed units <NUM>, <NUM> are connected to a central unit (CU) <NUM> (which may be referred to as a controlling node) via an interface <NUM>. The central unit <NUM> is then connected to the core network <NUM> which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network <NUM> may be connected to other networks <NUM>.

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

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

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

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

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

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

As shown in <FIG>, the TRP <NUM> also includes a network interface <NUM> which connects to the DU <NUM> via a physical interface <NUM>. The network interface <NUM> therefore provides a communication link for data and signalling traffic from the TRP <NUM> via the DU <NUM> and the CU <NUM> to the core network <NUM>.

The interface <NUM> between the DU <NUM> and the CU <NUM> is known as the F1 interface which can be a physical or a logical interface. The F1 interface <NUM> between CU and DU may operate in accordance with specifications 3GPP TS <NUM> and 3GPP TS <NUM>, and may be formed from a fibre optic or other wired or wireless high bandwidth connection. In one example the connection <NUM> from the TRP <NUM> to the DU <NUM> is via fibre optic. The connection between a TRP <NUM> and the core network <NUM> can be generally referred to as a backhaul, which comprises the interface <NUM> from the network interface <NUM> of the TRP10 to the DU <NUM> and the F1 interface <NUM> from the DU <NUM> to the CU <NUM>.

In a Dynamic Grant Physical Downlink Shared Channel (DG-PDSCH), the PDSCH resource is dynamically indicated by the gNB using a DL Grant carried by Downlink Control Information (DCI) in a Physical Downlink Control Channel (PDCCH).

A PDSCH is transmitted using HARQ transmission, where for a PDSCH ending in slot n, the corresponding Physical Uplink Control Channel (PUCCH) carrying the HARQ-ACK is transmitted in slot n+K<NUM>. Here, in Dynamic Grant PDSCH, the value of K<NUM> is indicated in the field "PDSCH-to-HARQ_feedback timing indicator" of the DL Grant (carried by DCI Format 1_0, DCI Format 1_1 or DCI Format 1_2). Multiple (different) PDSCHs can point to the same slot for transmission of their respective HARQ-ACKs, and these HARQ-ACKs (in the same slot) are multiplexed into a single PUCCH. Hence, a PUCCH can contain multiple HARQ-ACKs for multiple PDSCHs.

A communications device and an infrastructure equipment, such as the communications device <NUM> and infrastructure equipment <NUM> of <FIG> or the communications device <NUM> and infrastructure equipment (TRP) <NUM> of <FIG>, are configured to communicate via a wireless access interface. The wireless access interface may comprise one or more carriers, each providing, within a range of carrier frequencies, communications resources for transmitting and receiving signals according to a configuration of the wireless access interface. The one or more carriers may be configured within a system bandwidth provided for the wireless communications network of which the infrastructure equipment <NUM>, <NUM> forms part. Each of the carriers may be divided in a frequency division duplex scheme into an uplink portion and a downlink portion and may comprise one or more bandwidth parts (BWPs). A carrier may be configured therefore with a plurality of different BWP for a communications device to transmit or receive signals. The nature of the wireless access interface may be different amongst the different BWPs. For example, where the wireless access interface is based on orthogonal frequency division multiplexing, different BWPs may have different numerologies - i.e. values of parameters including sub-carrier spacing, symbol periods, bandwidths, and/or cyclic prefix lengths.

As described, there are three schemes agreed by 3GPP for the initiation of SDT transmissions on the uplink, originating from a mobile UE in the inactive state. These are:.

<FIG> shows an example of the <NUM>-step RACH based scheme, and shows how MO SDTs can be initiated by such a scheme. When a UE has an UL SDT ready for transmission, it may start a <NUM>-step RACH procedure as shown in <FIG>, which comprises the following steps:.

When a UE remains in the same cell for a period of time, it is possible that the UE can use some preconfigured UL resources for transmitting data, provided that the UE is UL synchronised, while remaining in the INACTIVE state. Hence in Rel-<NUM>, it is agreed that a network can configure dedicated CG PUSCH resource(s) for SDT on a dedicated BWP or initial BWP, just before a UE moves to the RRC_INACTIVE state. The usage of CG PUSCH resources may be validated based on some criteria; for example, the UL time alignment must not have expired and DL Reference Signal Received Power (RSRP) must not have changed significantly (e.g. by less than a delta value defined by the network). In addition, there is also a DL acknowledgment (i.e. an explicit or implicit HARQ-ACK feedback) for the transmitted CG-SDT. It should be noted that it is also allowed for a UE to be scheduled with a DL PDSCH after an initial transmission using a CG PUSCH (i.e. subsequent UL and DL SDT transmissions are possible).

In the current discussion for Rel-<NUM> [<NUM>], upon arrival of data only for data radio bearer (DRB)/signalling radio bearer(s) (SRB(s)) for which SDT is enabled, the high-level procedure for selection between SDT and non SDT procedure is as follows:.

The criteria for CG-SDT and RA-SDT, as identified in [<NUM>], are as follows:.

While developments for supporting Small Data Transmissions (SDT) for uplink (aka mobile originated (MO) transmissions) in Inactive state are still ongoing for Rel-<NUM>, discussions relating to the need for mobile terminated (MT) transmissions in the downlink for SDT in Rel-<NUM> have also begun, for example for positioning services or infrequent reception of small data at a UE in the Inactive state. Possible triggering mechanisms for MT-SDT (as discussed in greater detail in co-pending European patent application published under number <CIT> [<NUM>], the contents of which are hereby incorporated by reference) may include:.

However, an issue to solve here is how to configure UL feedback resources for HARQ-ACK in response to DL SDT carried on a PDSCH, since the UE may not be UL-synchronised at least after receiving the first DL SDT message as shown in <FIG>. As can be seen in <FIG>, UE#<NUM> is in the Inactive state, and receives DCI#<NUM> which schedules PDSCH#<NUM>. After UE#<NUM> decodes PDSCH#<NUM>, it does not have any UL feedback resources to transmit a HARQ-ACK in as it is not UL-synchronised. Hence, the gNB cannot determine whether PDSCH#<NUM> is successfully received or not. Clearly, this is a problem, since the gNB will not know whether it needs to retransmit the initial SDT carried by PDSCH#<NUM>, or move on to the next SDT if it has more data to transmit.

Furthermore, in the current discussion of Rel-<NUM>, it is agreed that after a first UL SDT, it is allowed for a UE and gNB to engage in subsequent UL and DL SDT transmissions while the UE remains in the INACTIVE state. However, it is not clear where the UL feedback in response to received DL PDSCHs will be transmitted during subsequent DL SDT transmissions - i.e. whether the UL feedback should be transmitted within the existing cell-specific PUCCH or within some dedicated PUCCH resources. If the existing cell-specific PUCCH resources are re-used for both SDT and non-SDT UEs, then there is a concern that due to there being a limited number of PUCCH resources within the cell, this will result collisions between transmissions from SDT UEs and non-SDT UEs accessing the cell (i.e. inter-UEs collisions). Such collisions will prolong the access time for initial access UEs, and result in retransmissions for the SDT UEs - both of which will lead to overall delays and inefficiencies.

As can be seen in the example of <FIG>, a UE#<NUM> receives DCI#<NUM> which schedules PDSCH#<NUM> for use in transmitting initial access messages for performing RACH procedures. After decoding PDSCH#<NUM>, UE#<NUM> transmits UL HARQ-ACK feedback on cell-specific PUCCH#<NUM>. At the same time, a UE#<NUM> which receives DCI#<NUM> which schedules PDSCH#<NUM> for DL SDT, transmits its UL HARQ-ACK feedback on the same cell specific PUCCH#<NUM>. Hence there is a collision between the UL HARQ-ACK feedback transmitted by UE#<NUM> and UE#<NUM>.

A similar issue may occur even when the UE is performing ongoing UL/MO-SDT transmission with the network in the INACTIVE mode and during which it receives a DL/MT-SDT (for example, when the UE is UL-synchronised with the network). While in such cases the gNB may have better knowledge of where it might expect to receive UL feedback, the issue still exists of potential collisions with other UEs, such as those performing initial access.

Accordingly, a problem required to be solved is how to configure UL feedback resources for HARQ-ACK transmissions by a UE in response to the UE a DL SDT carried on a PDSCH while the UE is in the RRC_INACTIVE state. Embodiments of the present technique aim to provide solutions to such a problem.

<FIG> shows a part schematic, part message flow diagram representation of a first wireless communications system comprising a communications device <NUM> and an infrastructure equipment <NUM> in accordance with at least some embodiments of the present technique. The communications device <NUM> is configured to transmit signals to and/or receive signals from the wireless communications network, for example, to and from the infrastructure equipment <NUM>. Specifically, the communications device <NUM> may be configured to transmit data to and/or receive data from the wireless communications network (e.g. to/from the infrastructure equipment <NUM>) via a wireless radio interface provided by the wireless communications network (e.g. a Uu interface between the communications device <NUM> and the Radio Access Network (RAN), which includes the infrastructure equipment <NUM>). The communications device <NUM> and the infrastructure equipment <NUM> each comprise a transceiver (or transceiver circuitry) <NUM>, <NUM>, and a controller (or controller circuitry) <NUM>, <NUM>. Each of the controllers <NUM>, <NUM> may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc..

As shown in the example of <FIG>, the transceiver circuitry <NUM> and the controller circuitry <NUM> of the communications device <NUM> are configured in combination, while the communications device is operating in an inactive state, to receive <NUM>, from the wireless communications network (e.g. from the infrastructure equipment <NUM>), a small data transmission, SDT, within a set of downlink resources of the wireless radio interface, determining <NUM>, based on a configuration indicated by signalling information (which may be for example carried by a system information block (SIB)) received <NUM> from the wireless communications network (e.g. from the infrastructure equipment <NUM>) previously to the SDT <NUM>, a set of uplink resources of the wireless radio interface, and transmitting <NUM>, to the wireless communications network (e.g. to the infrastructure equipment <NUM>) in the determined set of uplink resources, a feedback signal in response to the received SDT.

Essentially, embodiments of the present technique propose that the network is to configure an UL feedback resource on a BWP for a UE performing DL SDT in INACTIVE state, e.g. HARQ-ACK feedback (ACK or NACK) corresponding to the DL PDSCH carrying the DL/MT SDT from the network. Such an UL feedback resource may alternatively/additionally be for a UE to feedback channel state information (CSI) if instructed to do so. Broadly, there are two different scenarios that may determine what kind of resources are applicable; when the UE is UL-synchronised with the network, and when the UE is not UL-synchronised with the network.

A UE may not be UL-synchronised with the network when it has just received the first DL SDT (e.g. on a PDSCH). Here, embodiments of the present technique provide solutions to how the UE may transmit HARQ-ACK feedback for the DL SDT in the uplink on a BWP. If a UE is not UL-synchronised, then it cannot generally transmit a PUCCH or PUSCH in the uplink due to the possibility of interference between users transmitting in the uplink. As described above, the principle of OFDMA as utilised by NR systems is that uplink transmissions from all users must arrive at the same time (i.e. they must be synchronised) at the gNB receiver. A UE that is farther from the gNB must transmit earlier than a UE located closer to the gNB to ensure that their transmissions arrive at the same time due to different RF propagation delays.

NR technologies allow for PRACH transmissions when a UE is not UL-synchronised. After receiving a PRACH preamble, the network sends a timing advance command to the UE to control its uplink transmission timing, which as described above is mainly used for PUSCH, PUCCH and SRS. Based on this principle, several feedback methods, described below, using different combinations of channels can be utilised to carry the UL feedback for a DL/MT SDT.

One such method, in some arrangements of embodiments of the present technique, comprises the transmission of both a PRACH and a PUCCH. In this case, a UE transmits a PRACH followed by a PUCCH resource (PUCCH#<NUM>) in slot n+<NUM> in the time domain as shown in <FIG>. The network will use the preamble carried by the PRACH to determine the uplink time alignment value that will be used by the UE, and will then itself use this uplink time alignment value for decoding PUCCH#<NUM> when this is received from the UE. It is assumed here that the PRACH resources used by the UE are separately configured from the legacy PRACH resources on a BWP, so that the gNodeB can easily identify "PRACH + PUCCH" for SDT feedback. In other words, the communications device may be configured to receive the signalling information from the wireless communications network (e.g. from an infrastructure equipment) either while the communications device is operating in the inactive state or while the communications device is operating in a connected state and before the communications device transitions to the inactive state, to select, based on the configuration indicated by the signalling information, one of a plurality of preambles, the selected preamble being associated with the determined set of uplink resources and indicating the set of uplink resources in which the feedback signal will be transmitted, and to transmit, to the wireless communications network (e.g. to an infrastructure equipment) before transmitting the feedback signal, the selected preamble, where here, the determined set of uplink resources may be a physical uplink control channel, PUCCH.

The mapping between PRACH preambles and different sets of possible PUCCH resources may be pre-specified in a BWP specific manner. Therefore, when a UE selects a specific preamble index, it also knows which PUCCH resource to use for UL feedback. The periodicity and occasions of the PRACH + PUCCH resources can be predefined in a BWP for all inactive UEs - for example, in the example shown by <FIG>, the periodicity is every three slots (the previous occasions of the PRACH + PUCCH resources are shown in slot n+<NUM>, while the occasions used by the UE for transmitting the preamble and feedback are located in slot n+<NUM> as described above).

Another such method, in some arrangements of embodiments of the present technique, comprises (similar to the <NUM>-step RACH procedure as described above) the transmission by a UE of a PRACH and a PUSCH. In this case, as is shown in the example of <FIG>, the UE transmits a PRACH followed by a PUSCH resource slot n+<NUM> in the time domain as shown in <FIG>. The network will use the preamble carried by the PRACH to determine the uplink time alignment value that will be used by the UE, and will then itself use this uplink time alignment value for decoding the PUSCH when this is received from the UE later in slot n+<NUM>. It is assumed here that the PRACH resources used by the UE are separately configured from the legacy PRACH resources on a BWP so that the gNodeB can identify "PRACH + PUSCH" for SDT feedback. In other words, the communications device may be configured to receive the signalling information from the wireless communications network (e.g. from an infrastructure equipment) either while the communications device is operating in the inactive state or while the communications device is operating in a connected state and before the communications device transitions to the inactive state, to select, based on the configuration indicated by the signalling information, one of a plurality of preambles, the selected preamble being associated with the determined set of uplink resources, and to transmit, to the wireless communications network (e.g. to an infrastructure equipment) before transmitting the feedback signal, the selected preamble, where here, the determined set of uplink resources may be a physical uplink shared channel, PUSCH. In this option, the PUSCH may carry, in addition (or alternatively) to any HARQ-ACK feedback for DL PDSCH response, UL SDT data and/or CSI reports, if it has any to transmit, where the feedback and UL SDT data - if the UE has both to transmit - can be multiplexed into the same PUSCH resource.

Similarly, the above arrangements described with respect to the example <FIG>, the mapping between PRACH preambles and a set of PUSCH resources may be pre-specified in a BWP specific manner. Therefore, when a UE selects a specific preamble index, it also knows which PUSCH resource to use for UL feedback. This could be achieved in the same way as a <NUM>-step RACH procedure, where there is a pre-defined mapping between PRACH preambles and different sets of PUSCH resources in Rel-<NUM>. Again here, the periodicity and occasions of the PRACH + PUSCH resources can be predefined in a BWP for all inactive UEs - for example, in the example shown by <FIG>, the periodicity is again every three slots (the previous occasions of the PRACH + PUSCH resources are shown in slot n+<NUM> while the occasions used by the UE for transmitting the preamble and feedback are located in slot n+<NUM> as described above).

Another such method, in some arrangements of embodiments of the present technique, comprises the transmission by a of a PRACH only, where the PRACH includes a known preamble that also represents the HARQ-ACK feedback for the received DL SDT. Similarly, to those methods as described above with reference to <FIG> and <FIG>, the UE here is configured with PRACH resources in a BWP. The gNB would then try to detect the known preamble at the configured BWP to receive the UE's feedback. In other words, the determined set of uplink resources is a physical random access channel, PRACH, and wherein the transmission of the selected preamble represents/indicates the feedback signal. For example, if the network receives the PRACH preamble, this indicates positive feedback (ACK), whereas if the network does not receive any PRACH preamble, then this implies negative feedback (NACK). Alternatively, the UE may transmit one PRACH preamble to represent an ACK and another to represent a NACK.

Those skilled in the art would appreciate that the above three methods for UEs that are not UL-synchronised (PRACH+PUCCH, PRACH+PUSCH, PRACH only) may be implemented in either an individual or a combined manner. That is, the network may configure any one of these methods for a UE, where this configuration may change such that another method is configured for the UE at a later time.

In those arrangements described above where the UE is not UL-synchronised with the network, the particular preamble that the UE uses for the feedback can be determined using one or more of the following arrangements of embodiments of the present disclosure:.

In other words, the communications device may be configured to select the selected preamble from the plurality of preambles based on one or more of: the configuration indicated by the signalling information, an indication carried by a downlink control signal, and an identifier of the downlink control signal, where this downlink control signal is received from the wireless communications network prior to receiving the SDT and indicates the set of downlink resources in which the SDT is to be received.

In those arrangements described above where the UE is not UL-synchronised with the network, a UE upon detection of the DCI carried by a PDDCH for triggering SDT at DL slot n may perform PRACH transmission in the first slot from n+k<NUM>, where k<NUM> ≥ x, where a PRACH resource is available, and x is a known value e.g. <NUM> or <NUM> or <NUM> or <NUM>. In other words, the communications device may be configured to transmit the selected preamble within a first available PRACH that is located a specified number of time units of the wireless radio interface from the location of a downlink control signal, where this downlink control signal is received from the wireless communications network prior to receiving the SDT and indicates the set of downlink resources in which the SDT is to be received. It should be noted the timing relationship between the PRACH and the PUCCH/PUSCH may be fixed in the specification based on a pre-defined mapping scheme of PRACH preambles and PUCCH/PUSCH as mentioned earlier.

In another arrangement of embodiments of the present disclosure, the network can configure a UE with two different resources: one for UL feedback only and another for UL feedback plus UL SDT data. Hence if a UE has UL SDT data to transmit, then it can multiplex UL feedback with the SDT data and transmit it in the same resource. In other words, the communications device may be configured to determine the set of uplink resources in accordance with whether or not the communications device has an uplink SDT to transmit to the wireless communications network in addition to the feedback signal. In this case, for example, the resource to use for transmitting only UL feedback could be PRACH+PUCCH, whilst UL feedback plus UL SDT data must be transmitted using PRACH+PUSCH.

A UE may be UL-synchronised with the network in various scenarios; for example, when it already has an ongoing UL SDT being performed with the network. At the same time as this, the UE may receive DL SDT data (via a PDSCH), and then must transmit HARQ-ACK feedback for this DL SDT data in the uplink. When a UE which is required to transmit HARQ-ACK feedback for a DL SDT is UL synchronised, several feedback methods, as described below, may be utilised for the transmission of the UL feedback for this DL/MT SDT.

One such method, in some arrangements of embodiments of the present technique, comprises using a dedicated PUCCH resource for a UE in an inactive state. Here, the network may configure a dedicated PUCCH resource just before the UE moves to the RRC_INACTIVE state (i.e. RRCRelease with suspend) on a dedicated BWP or an initial BWP for a UE to use for UL feedback in the latest serving cell as shown in the example of <FIG>. In other words, the communications device may be configured to receive the signalling information from the wireless communications network while the communications device is operating in a connected state and before the communications device transitions to the inactive state, where here, the determined set of uplink resources is a physical uplink control channel, PUCCH.

In the example of <FIG>, this dedicated PUCCH resource is PUCCH#<NUM>, and it is within PUCCH#<NUM> that the UE transmits the feedback for the DL SDT in slot n+<NUM> in the example of <FIG>. Hence, this resource is valid only if the UE is still in the same cell as before moving to the INACTIVE state, and also if the UE is still UL-synchronised. In order the UE to be considered as UL-synchronised, the time alignment (TA) must be valid, e.g. the TA timer must not have expired. The TA timer is used at both the UE and the network in order to ensure that they are aligned with each other. If the TA timer expires, the PUCCH resources will be released.

Furthermore, the DCI that schedules the PDSCH which carries the DL SDT can indicate explicitly which PUCCH resource (if there are multiple PUCCH resources available, or a particular occasion of a PUCCH resource with a certain periodicity) to use at any given time, e.g. using the K<NUM> value where the value of K<NUM> is indicated in the field "PDSCH-to-HARQ_feedback timing indicator" of the DL DCI that schedules the PDSCH. In other words, the PUCCH may be one of a plurality of available PUCCH resources and which is (either explicitly or implicitly) indicated by a downlink control signal received from the wireless communications network prior to receiving the SDT, wherein the downlink control signal indicates the set of downlink resources in which the SDT is to be received. Here, this plurality of available PUCCH resources may have been indicated by the configuration indicated by the signalling information (e.g. SIB) upon the basis of which the communications device determined the set of uplink resources.

Another such method, in some arrangements of embodiments of the present technique, comprises using a dedicated CG-PUSCH resource for a UE in an inactive state. In the current SDT discussions in Rel-<NUM>, it has already been agreed that a network is to configure a dedicated CG-PUSCH resource(s) for SDT just before a UE moves to the RRC Inactive state (i.e. RRCRelease with suspend). This dedicated CG-PUSCH resource(s) can be configured on a dedicated BWP or initial BWP and it is a known solution for this to be used for uplink SDT transmission. However, presently, such a dedicated CG-PUSCH resource(s) has not been proposed to carry any feedback for DL-SDT data. Hence, in such arrangements of embodiments of the present technique, a dedicated CG-PUSCH resource can be configured to carry UL feedback in the latest serving cell as shown in <FIG> (here, in this example, this resource is the CG-PUSCH transmitted in slot n+<NUM>); again, as long as the TA is valid in the same manner as described above with respect to the example described with reference to <FIG>. In other words, the communications device may be configured to receive the signalling information from the wireless communications network while the communications device is operating in a connected state and before the communications device transitions to the inactive state, where here, the determined set of uplink resources is a configured grant physical uplink shared channel, CG-PUSCH.

Assuming the UE has UL SDT data to transmit, this data and the UL feedback for the DL SDT can be multiplexed together in one or more of the available CG-PUSCHs. In other words, the communications device may be configured to transmit both the feedback signal and an uplink SDT to the wireless communications network within the CG-PUSCH. This feedback may be, for example, carried in the form of a CG-UCI. However, if only UL feedback is available, the CG-PUSCH can still carry this feedback information alone.

If more than one CG-PUSCH is available, then it must be specified which one of these is to carry the UL feedback, so that the UE and the network are aligned in their understanding of the location of the UL feedback information. Some methods to define which CG resource may carry the UL feedback, in accordance with arrangements of embodiments of the present disclosure are as follows:.

In other words, the determined CG-PUSCH is one of a plurality of available CG-PUSCHs, and the determined CG-PUSCH may be one or more of: the earliest available CG-PUSCH from among the plurality of available CG-PUSCHs following reception of the SDT, that which has a lowest index value from among the plurality of available CG-PUSCHs, that which has a highest index value from among the plurality of available CG-PUSCHs, that which has a lowest periodicity from among the plurality of available CG-PUSCHs, that which has a highest periodicity from among the plurality of available CG-PUSCHs, that which is formed from the largest amount of resources from among the plurality of available CG-PUSCHs, that which is indicated by a downlink control signal received from the wireless communications network prior to receiving the SDT, wherein the downlink control signal indicates the set of downlink resources in which the SDT is to be received, that which is indicated by Radio Resource Control, RRC, signalling received from the wireless communications network, and that which contains uplink data. Here, alternatively or in addition to any of the above methods, the communications device may be configured to repeat transmission of the feedback signal in one or more subsequent CG-PUSCHs of the plurality of available CG-PUSCHs following the determined CG-PUSCH.

Those skilled in the art would appreciate that, in the same manner as described above for the methods for UEs that are not UL-synchronised, the above methods for UEs that are UL-synchronised (PUCCH or CG-PUSCH) may be implemented in either an individual or a combined manner. That is, the network may configure either of these methods for a UE, where this configuration may change such that another method is configured for the UE at a later time. Clearly, in this case, the specifications must define the conditions of which option to be used at a given time. For example, in an arrangement of embodiments of the present technique, the specifications may define that a PUCCH resource is always used, except if the PUCCH collides with a CG-PUSCH resource. In this case, if the PUCCH collides with a CG-PUSCH resource, the specifications may define in an arrangement of embodiments of the present technique that the UE must multiplex data and UL feedback in the CG-PUSCH resource. Furthermore, such methods may be implemented for UL-synchronised UEs in either an individual or a combined manner as described here in addition to those methods described above for UEs that are not UL-synchronised. Here, a UE will be configured to transmit UL feedback for DL SDTs in at least two different manners, which it selects from based at least in part on whether it is UL-synchronised or not UL-synchronised. For example, a UE may be configured to send UL feedback via a PRACH and PUSCH if it is not UL-synchronised, but via a CG-PUSCH if it is UL-synchronised. Such configurations may be changed by the network at appropriate times.

In another arrangement of embodiments of the present disclosure, similarly as for non-UL-synchronised UEs as described above, the network can configure an UL-synchronised UE with two different resources: one for UL feedback only and another for UL feedback plus UL SDT data. Hence if a UE has UL SDT data to transmit, then it can multiplex UL feedback with the SDT data and transmit it in the same resource. In other words, the communications device may be configured to determine the set of uplink resources in accordance with whether or not the communications device has an uplink SDT to transmit to the wireless communications network in addition to the feedback signal.

As described above, it is possible that there could be feedback collisions for SDT and non-SDT UEs (i.e. inter-UEs collisions). For example, this might happen when a UE has already an ongoing UL SDT but at the same the UE receives DL SDT data (via a PDSCH) and the UE must transmit HARQ-ACK feedback (for the received PDSCH) in the uplink on the initial BWP. Hence, to avoid the collisions, it is proposed here that a UE - depending on whether or not it is performing SDT with the network while in an inactive mode - is configured with one of the following PUCCH resource candidates (as illustrated in the example of <FIG>):.

In other words, the determined set of uplink resources may be a set of cell-specific uplink resources which is only for use by communications devices operating in the inactive state and performing SDT with the wireless communications network. A different set of dedicated uplink resources which are only for use by communications devices performing initial access/RACH procedures with the wireless communications network will differ to these cell-specific uplink resources, and thus would help mitigate feedback collisions between SDT and non-SDT UEs.

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

The method, which is performed while the communications device is operating in an inactive state, begins in step S1. The method comprises, in step S2, receiving, from the wireless communications network, a small data transmission, SDT, within a set of downlink resources of the wireless radio interface. In step S3, the process comprises determining, based on a configuration indicated by signalling information received from the wireless communications network previously to the SDT, a set of uplink resources of the wireless radio interface. The method then comprises, in step S4, transmitting, to the wireless communications network in the determined set of uplink resources, a feedback signal in response to the received SDT. The process ends in step S5.

Those skilled in the art would appreciate that the method shown by <FIG> may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in this method, or the steps may be performed in any logical order. Though embodiments of the present technique have been described largely by way of the example communications system shown in <FIG>, and described by way of the arrangements shown by <FIG>, it would be clear to those skilled in the art that they could be equally applied to other systems to those described herein.

Those skilled in the art would further appreciate that such infrastructure equipment and/or communications devices as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and communications devices as herein defined and described may, without departing from the scope of the claims, form part of communications systems other than those defined by the present disclosure.

Claim 1:
A method of operating a communications device (<NUM>) configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network, the method comprising, while the communications device is operating in an inactive state,
receiving (<NUM>), from the wireless communications network, a small data transmission, SDT, within a set of downlink resources of the wireless radio interface,
determining (<NUM>), based on a configuration indicated by signalling information received (<NUM>) from the wireless communications network previously to the SDT, a set of uplink resources of the wireless radio interface, wherein the determined set of uplink resources is a set of cell-specific uplink resources which is only for use by communications devices operating in the inactive state and performing SDT with the wireless communications network, and
transmitting (<NUM>), to the wireless communications network in the determined set of uplink resources, a feedback signal in response to the received SDT.