Methods, communications devices, and infrastructure equipment

Abstract

A method of operating a communications device to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment is provided. The method comprises selecting a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment. The method comprises selecting a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated at least one of the plurality of SSBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type. The selecting the RO comprises identifying a set of ROs of the plurality of sets of ROs that is associated with the selected SSB. The selecting the RO comprises selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO. The selecting the RO comprises selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble. The method comprises transmitting the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

Description

[0001] METHODS, COMMUNICATIONS DEVICES, AND INFRASTRUCTURE EQUIPMENT

[0002] BACKGROUND

[0003] Field of Disclosure

[0004] The present disclosure relates to communications devices, infrastructure equipment of a wireless communications network, and methods.

[0005] The present application claims Paris Convention priority from EP patent application number 24204039.2, filed on 1 October 2024, the contents of which are hereby incorporated 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 to efficiently 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 devices, 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 devices, 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 considerations 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, to efficiently support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements. SUMMARY OF THE DISCLOSURE

[0011] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0012] Various aspects and features of the present disclosure are defined in the appended claims.

[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] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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:

[0016] Figure 1 schematically represents some aspects of an LTE-type wireless telecommunication system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0017] Figure 2 schematically represents some aspects of a new radio access technology (RAT) wireless telecommunications system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0018] Figure 3 is a schematic block diagram of an example infrastructure equipment and communications device which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0019] Figure 4 schematically represents a first example of non-overlapping sub-bands for uplink and downlink transmissions for sub-band full duplex (SBFD);

[0020] Figure 5 schematically represents second and third examples of non-overlapping sub-bands for uplink and downlink transmissions for SBFD;

[0021] Figure 6 schematically illustrates the components of a synchronisation signal block (SSB);

[0022] Figure 7 schematically illustrates an SSB burst set transmitted on SSB beams;

[0023] Figure 8 schematically illustrates a physical random access channel (PRACH) occasion (RO) configuration;

[0024] Figures 9A to 9D schematically illustrates valid and invalid ROs;

[0025] Figure 10 schematically illustrates an example of a time division duplexing (TDD) slot format configuration;

[0026] Figure 11 schematically illustrates an example of an SSB to RO mapping in an association period for a TDD slot format;

[0027] Figure 12 schematically illustrates an example of a set of NPRACH = 4 ROs for 4 x PRACH repetitions;

[0028] Figure 13 schematically illustrates an example of an overall SSB-RO association using a single PRACH configuration;

[0029] Figure 14 schematically illustrates an example of an SBFD RO configuration on a separate PRACH configuration;

[0030] Figure 15 is a flow diagram illustrating a method of operating a communications device in accordance with example embodiments;

[0031] Figure 16 schematically illustrates an example of selecting an RO type in accordance with example embodiments;

[0032] Figure 17 schematically illustrates an example of selecting an RO type in accordance with example embodiments;

[0033] Figure 18 schematically illustrates an example of selecting an RO type in accordance with example embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Long Term Evolution Advanced Radio Access Technology (4G)

[0035] Figure 1 provides a schematic diagram illustrating some basic functionality of a mobile telecommunications network / system 6 operating generally in accordance with LTE principles, but which may also support other radio access technologies, and which may be adapted to implement embodiments of the disclosure as described herein. Various elements of Figure 1 and certain aspects of their respective modes of operation are well-known and defined in the relevant standards administered by the 3GPP (RTM) body, and also described in many books on the subject, for example, Holma H. and Toskala A [1], It will be appreciated that operational aspects of the telecommunications networks discussed herein which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to the relevant standards and known proposed modifications and additions to the relevant standards.

[0036] The network 6 includes a plurality of base stations 1 connected to a core network 2. Each base station provides a coverage area 3 (i.e. a cell) within which data can be communicated to and from communications devices 4. Although each base station 1 is shown in Figure 1 as a single entity, the skilled person will appreciate that some of the functions of the base station may be carried out by disparate, inter-connected elements, such as antennas (or antennae), remote radio heads, amplifiers, etc. Collectively, one or more base stations may form a radio access network.

[0037] Data is transmitted from base stations 1 to communications devices 4 within their respective coverage areas 3 via a radio downlink (DL). Data is transmitted from communications devices 4 to the base stations 1 via a radio uplink (UL). The core network 2 routes data to and from the communications devices 4 via the respective base stations 1 and provides functions such as authentication, mobility management, charging and so on. Communications devices may also be referred to as mobile stations, user equipment (UEs), user terminals, mobile radios, mobile terminals, terminal devices, wireless transmit and receive units (WTRUs), and so forth. Services provided by the core network 2 may include connectivity to the internet or to external telephony services. The core network 2 may further track the location of the communications devices 4 so that it can efficiently contact (i.e. page) the communications devices 4 for transmitting downlink data towards the communications devices 4.

[0038] 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.

[0039] New Radio Access Technology (5G)

[0040] Systems incorporating NR technology are expected to support different services (or types of services), which may be characterised by different requirements for latency, data rate and / or reliability. For example, Enhanced Mobile Broadband (eMBB) services are characterised by high capacity with a requirement to support up to 20 Gb / s. The requirements for Ultra Reliable and Low Latency Communications (URLLC) services are for one transmission of a 32 byte packet to be transmitted from the radio protocol layer 2 / 3 SDU ingress point to the radio protocol layer 2 / 3 SDU egress point of the radio interface within 1 ms with a reliability of 1 - 10'5(99.999 %) or higher (99.9999%) [2],

[0041] 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.

[0042] An example configuration of a wireless communications network which uses some of the terminology proposed for and used in NR and 5G is shown in Figure 2. In Figure 2 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (DUs) 41, 42 by a connection interface represented as a line 16. Each of the TRPs 10 is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus, within a range for performing radio communications via the wireless access interface, each of the TRPs 10, forms a cell of the wireless communications network as represented by a circle 12. As such, wireless communications devices 14 which are within a radio communications range provided by the cells 12 can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 41, 42 are connected to a central unit (CU) 40 (which may be referred to as a controlling node) via an interface 46. The central unit 40 is then connected to the core network 20 which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network 20 may be connected to other networks 25.

[0043] The elements of the wireless access network shown in Figure 2 may operate in a similar way to corresponding elements of an LTE network as described with regard to the example of Figure 1. It will be appreciated that operational aspects of the telecommunications network represented in Figure 2, and of other networks discussed herein in accordance with embodiments of the disclosure, which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to currently used approaches for implementing such operational aspects of wireless telecommunications systems, e.g. in accordance with the relevant standards.

[0044] The TRPs 10 of Figure 2 may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly, the communications devices 14 may have a functionality corresponding to the UE devices 4 known for operation with an LTE network. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of a new RAT network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network.

[0045] In terms of broad top-level functionality, the core network 20 connected to the new RAT telecommunications system represented in Figure 2 may be broadly considered to correspond with the core network 2 represented in Figure 1, and the respective central units 40 and their associated distributed units / TRPs 10 may be broadly considered to provide functionality corresponding to the base stations 1 of Figure 1. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may he with the controlling node / central unit and / or the distributed units / TRPs. A communications device 14 is represented in Figure 2 within the coverage area of the first communication cell 12. This communications device 14 may thus exchange signalling with the first central unit 40 in the first communication cell 12 via one of the distributed units / TRPs 10 associated with the first communication cell 12.

[0046] It will further be appreciated that Figure 2 represents merely one example of a proposed architecture for a new RAT based telecommunications system in which approaches in accordance with the principles described herein may be adopted, and the functionality disclosed herein may also be applied in respect of wireless telecommunications systems having different architectures.

[0047] Thus, certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems / networks according to various different architectures, such as the example architectures shown in Figures 1 and 2. It will thus be appreciated the specific wireless telecommunications architecture in any given implementation is not of primary significance to the principles described herein. In this regard, certain embodiments of the disclosure may be described generally in the context of communications between network infrastructure equipment / access nodes and a communications device, wherein the specific nature of the network infrastructure equipment / access node and the communications device will depend on the network infrastructure for the implementation at hand. For example, in some scenarios the network infrastructure equipment / access node may comprise a base station, such as an LTE- type base station 1 as shown in Figure 1 which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a control unit / controlling node 40 and / or a TRP 10 of the kind shown in Figure 2 which is adapted to provide functionality in accordance with the principles described herein.

[0048] A more detailed diagram of some of the components of the network shown in Figure 2 is provided by Figure 3. In Figure 3, a TRP 10 as shown in Figure 2 comprises, as a simplified representation, a wireless transmitter 30, a wireless receiver 32 and a controller or controlling processor 34 which may operate to control the transmitter 30 and the wireless receiver 32 to transmit and receive radio signals to one or more UEs 14 within a cell 12 formed by the TRP 10. As shown in Figure 3, an example UE 14 is shown to include a corresponding transmitter 49, a receiver 48 and a controller 44 which is configured to control the transmitter 49 and the receiver 48 to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP 10 and to receive downlink data as signals transmitted by the transmitter 30 and received by the receiver 48 in accordance with the conventional operation.

[0049] The transmitters 30, 49 and the receivers 32, 48 (as well as other transmitters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency filters and amplifiers as well as signal processing components and devices in order to transmit and receive radio signals in accordance for example with the 5G / NR standard. The controllers 34, 44 (as well as other controllers described in relation to examples and embodiments of the present disclosure) may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc., configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer readable medium. The transmitters, the receivers and the controllers are schematically shown in Figure 3 as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the infrastructure equipment / TRP / base station as well as the UE / communications device will in general comprise various other elements associated with its operating functionality.

[0050] As shown in Figure 3, the TRP 10 also includes a network interface 50 which connects to the DU 42 via a physical interface 16. The network interface 50 therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 40 to the core network 20.

[0051] The interface 46 between the DU 42 and the CU 40 is known as the Fl interface which can be a physical or a logical interface. The Fl interface 46 between CU and DU may operate in accordance with specifications 3GPP TS 38.470 and 3GPP TS 38.473, and may be formed from a fibre optic or other wired or wireless high bandwidth connection. In one example the connection 16 from the TRP 10 to the DU 42 is via fibre optic. The connection between a TRP 10 and the core network 20 can be generally referred to as a backhaul, which comprises the interface 16 from the network interface 50 of the TRP 10 to the DU 42 and the Fl interface 46 from the DU 42 to the CU 40.

[0052] In order for a UE such as UE 4 or 14 to transmit uplink data to the network (e.g. on a Physical Uplink Control Channel (PUCCH) or a Physical Uplink Shared Channel (PUSCH)) to, for example, base station 1 or TRP 10, the UE must first ensure it is synchronised with the network on the uplink. Since a particular eNB or gNB expects to be receiving communications from many UEs, it needs to ensure that it shares a common timing understanding with each of these UEs (i.e. they are synchronised in terms of the starting times of frames and Orthogonal Frequency Division Multiplexing (OFDM) symbols (often referred to simply as “symbols” for brevity)). This is so that the eNB is able to schedule communication with each of them in a manner that avoids collisions and to ensure orthogonality of the uplink signals, such that intersubcarrier interference is avoided or mitigated.

[0053] Although reference is made to 5G networks, the discussions in this specification apply equally to 6G networks (and beyond) where there is expected to be significantly higher throughput, lower latency and higher reliability utilising sub-THz frequencies.

[0054] Full Duplex Time Division Duplex (FD-TDD)

[0055] NR / 5G networks can operate using Time Division Duplex (TDD), where an entire frequency band or carrier is switched to either downlink or uplink transmissions for a time period and can be switched to the other of downlink or uplink transmissions at a later time period. Currently, TDD operates in Half Duplex mode (HD-TDD) where the gNB or UE can, at a given time, either transmit or receive packets, but not both at the same time. As wireless networks transition from NR to 5G-Advanced networks, a proposed new feature of such networks is to enhance duplexing operation for Time Division Duplex (TDD) by enabling Full Duplex operation in TDD (FD-TDD) [3], [4],

[0056] In FD-TDD, a gNB can transmit and receive data to and from the UEs at the same time on the same frequency band. In addition, a UE can operate either in HD-TDD or FD-TDD mode, depending on its capability. For example, when UEs are only capable of supporting HD-TDD, FD-TDD is achieved at the gNB by scheduling a DL transmission to a first UE and scheduling an UL transmission from a second UE within the same OFDM symbol (i.e. at the same time). Conversely, when UEs are capable of supporting FD-TDD, FD-TDD is achieved both at the gNB and the UE, where the gNB can simultaneously schedule this UE with DL and UL transmissions within the same OFDM symbol by scheduling the DL and UL transmissions at different frequencies (e.g. physical resource blocks (PRBs)) of the system bandwidth. A UE supporting FD-TDD requires more complex hardware than a UE that only supports HD-TDD. Development of current 5G networks is focused primarily on enabling FD-TDD at the gNB with UEs operating in HD-TDD mode.

[0057] Motivations for enhancing duplexing operation for TDD include an improvement in system capacity, reduced latency, and improved uplink coverage. For example, in current HD-TDD systems, OFDM symbols are allocated only for either a DL or UL direction in a semi-static manner. Hence, if one direction experiences less or no data, the spare resources cannot be used in the other direction, or are, at best, underutilised. However, if resources can be used for DL data and UL data (as in FD-TDD) at the same time, the resource utilisation in the system can be improved. Furthermore, in current HD-TDD systems, a UE can receive DL data, but cannot transmit UL data at the same time, which causes delays. If a gNB or UE is allowed to transmit and receive data at the same time (as with FD-TDD), the traffic latency will be improved. In addition, UEs are usually coverage limited in their UL transmissions when located close to the edge of a cell. While the UE coverage at the cell-edge can be improved if more time domain resources are assigned to UL transmissions (e.g. repetitions), for HD-TDD systems, if the UL direction is assigned more time resources, fewer time resources can be assigned to the DL direction, which can lead to system imbalance. In contrast, in FD-TDD, continuous UL resources can be assigned for repetition opportunities whilst allowing DL traffic to occur in those resources, thereby UL enhancing coverage without causing system imbalance.

[0058] A Rel-19 Work Item (WI) [5] on Duplex Evolution is therefore agreed to specify the requirements for FD- TDD. In Rel-19 Duplex Evolution, FD-TDD is performed at the gNB, where the gNB can transmit and receive data / signals to / from the UEs at the same time on the same frequency band, whilst the UE is maintained as HD-TDD. That is, full duplex TDD is achieved at the gNB by scheduling a UE in the DL and scheduling another UE in the UL within the same OFDM symbol. One of the objectives of the Rel-19 Duplex Evolution WI [5] is to support RACH operation in Sub-band Full Duplex (SBFD) OFDM symbols.

[0059] Sub-band Full Duplex (SBFD)

[0060] In SBFD, the frequency resource of a TDD system bandwidth or Bandwidth Part (BWP) (i.e. at the UE / gNB) is divided into two or more non-overlapping sub-bands, where each sub-band can be DL or UL [6], Guard sub-bands may be used between DL and UL sub-bands to reduce inter sub-band interference. In the current 5G system, only one UL sub-band can be configured in an OFDM symbol.

[0061] An example is shown in Figure 4, where simultaneous DL and UL transmissions occur in three different non-overlapping sub-bands 61 to 63, i.e. in different sets of frequency Resource Blocks (RB): Sub-band# 1

[0062] 61, Sub-band#2 62, Sub-band#3 63. The example of Figure 4 is referred to as {DUD}, because two subbands, Sub-band# 1 61 and Sub-band#3 63, are used for DL transmissions whilst one sub-band, Sub-band#2

[0063] 62, is used for UL transmissions. To reduce leakage from one sub-band 61 to 63 to another, a guard subband 64 may be configured between UL and DL sub-bands 61 to 63. Guard sub-bands 64 are configured between DL Sub-band#3 63 and UL Sub-band#2 62 and between UL Sub-band#2 62 and DL Sub-band# 1 61.

[0064] Figure 5 shows two further examples with a DL and UL sub-band separated by a guard sub-band, where here, the UL sub-band can be configured to occupy the lower frequency portion of the BWP whilst the DL sub-band occupies higher frequency portion of the BWP {UD} or the UL sub-band occupies the higher frequency portion of the BWP whilst the DL sub-band occupies lower frequency portion of the BWP {DU} . Here, on the left-side of Figure 5, an UL sub-band# 1 71 is separated from a DL sub-band#2 73 by a guard sub-band 72 - this sub-band arrangement is referred to as {UD}. In this case, the DL sub-band#2 73 occupies a higher frequency portion of the system bandwidth than the UL sub-band# 1 71. On the rightside of Figure 5, a DL sub-band# 1 81 is separated from an UL sub-band#2 83 by a guard sub-band 82 - this sub-band arrangement is referred to as {DU}. In this case, the UL sub-band#2 83 occupies a higher frequency portion of the system bandwidth than the DL sub-band# 1 81.

[0065] While Figures 4 and 5 show the system bandwidth as being divided into either two or three sub-bands, those skilled in the art would appreciate that the concept of SBFD may (in further releases of the 3GPP specifications, for example) be extended such that any number of sub-bands could be used, if deemed beneficial. For example, the system bandwidth may be divided into four sub-bands, which may, using the example of Figure 4, include the two downlink sub-bands 61, 63, the uplink sub-band 62 and another uplink sub-band, though other sub-band arrangements are envisioned. Guard sub-bands may be used in substantially any sub-band arrangement.

[0066] Synchronisation Signal Block

[0067] As will be known to one skilled in the art, the Synchronisation Signal Block (SSB) is used for initial access and cell reselection. An example of an SSB is schematically illustrated in Figure 6.

[0068] As shown in Figure 6, the SSB comprises of a Primary Synchronisation Signal (PSS), a Secondary Synchronisation Signal (SSS) and a Physical Broadcast Channel (PBCH). The SSB comprises information for a communications device, such as a UE, to detect, measure and access a cell. The SSB shown in Figure 6 comprises four OFDM symbols and 240 subcarriers. The PSS and SSS each occupy 127 subcarriers. The PBCH occupies two OFDM symbols of 240 subcarriers and also two blocks of 48 subcarriers at the top and bottom of the SSS. The SSB may be configured with a periodicity, PSSB, of between 5 ms and 160 ms.

[0069] An SSB burst set comprises a set of one or more time -multiplexed SSBs. Each SSB is transmitted in a burst set using a different downlink beam, thereby enabling beam sweeping to be implemented for SSB. An SSB burst set may be confined within 5 ms and may comprise up to 4, 8 and 64 SSBs for frequency bands below 3 GHz, between 3 GHz - 6 GHz and for FR2 respectively. As will be understood by one skilled in the art, SSB burst sets may be periodically transmitted.

[0070] An example SSB burst set in the case of 3 GHz - 6 GHz frequency is shown in Figure 7. The SSB burst set shown in Figure 7 comprises eight SSBs labelled as SSB#1, SSB#2, SSB#3, SSB#4, SSB#5, SSB#6, SSB#7 and SSB#8 respectively. Each of the SSBs in the burst set is transmitted using a different downlink beam. In this example, two SSBs are configured per slot within four slots. Furthermore, the burst set is transmitted with a periodicity, PSSB, of 20 ms. Although not shown in Figure 7, the SSB burst set is transmitted by infrastructure equipment of a wireless communications network (such as a gNB) and received by a communications device (such as a UE).

[0071] The UE measures a signal quality of each SSB in the SSB burst set. The UE may then select one of the downlink beams based on the measured signal quality. For example, the UE may select the downlink beam with the highest measured signal quality provided that the measure signal quality is above a threshold (such as RSRP threshold). Then, the UE determines an uplink beam corresponding to the downlink beam to use for synchronisation with the infrastructure equipment. As will be appreciated by one skilled in the art, corresponding uplink and downlink beams form beam pairs which overlap. Therefore, the measurements of the signal quality of a downlink beam are an indication of the signal quality of the corresponding uplink beam in the beam pair. In initial access, the UE transmits RACH on the determined uplink beam. In one example, the measured signal quality of an SSB is an RSRP of the SSB. The UE may measure the RSRP of each SSB in the SSB burst set and select the downlink beam on which the SSB with the highest RSRP was transmitted provided this measured RSRP is above a threshold (such as rsrp-ThresholdSSB). Then, the UE transmits its RACH using the corresponding uplink beam.

[0072] The measurement of the RSRP of an SSB may be referred to as “SS-RSRP”. The measurement of the RSRP of an SSB may comprise measuring the RSRP on resource elements where SSS is transmitted. Alternatively, or in addition, the measurement of the RSRP of an SSB may comprise measuring the RSRP on resource elements where PBCH Demodulation Reference Signals (DMRS) are transmitted.

[0073] In other examples, the measured signal quality of an SSB may be a Reference Signal Received Quality (SS- RSRQ) of the SSB. The SS-RSRQ is defined as the ratio of N x SS-RSRP / RSSI (Received Signal Strength Indicator), where N is the number of resource blocks. For example, the RSSI in NR is measured in one or more OFDM symbols in a SS / PBCH Block Measurement Time Configuration (SMTC). The SMTC is a configuration to the UE to set time window for measurement by using SSB. The OFDM symbols used for RSSI measurement can be configured by higher layers.

[0074] PRACH Occasions

[0075] As will be understood by a person skilled in the art, a Physical Random Access (PRACH) configuration comprises a plurality of PRACH Occasions (RO) configured in uplink communications resources of a wireless access interface. The ROs in a PRACH configuration may be periodically repeating. The ROs represent transmission opportunities for a UE to transmit a PRACH. Each RO may be configured to support up to 64 preambles. In this case, each RO may support a PRACH transmission of up to 64 UEs if each UE uses a different preamble for its PRACH transmission. The ROs may be Frequency Division Multiplexed (FDM) where infrastructure equipment of a wireless communications network can configure { 1, 2, 4, 8} FDM ROs for UEs.

[0076] As mentioned above, ROs are configured in communications resources of a wireless access interface. Communications resources are comprised of time resources and frequency resources. The time resources of the ROs in a PRACH Occasion configuration are determined by a “PRACH Configuration Index”, which is an index to Tables 6.3.3.2-2, 6.3.3.2-3 and 6.3.3.2-4 in [7], which is hereby incorporated by reference in its entirety. There are 256, 263 and 256 PRACH configurations for FR1 FDD, FR1 TDD and FR2 respectively. The PRACH configuration index indicates a PRACH preamble format, a PRACH periodicity (known as a “PRACH Configuration Period”), a number of PRACH Occasions within a PRACH period, the starting symbol of the PRACH Occasion in a slot, and a duration of the PRACH Occasion.

[0077] An example PRACH Occasion configuration for an FR1 FDD system is shown Figure 8. The PRACH Occasion is configured with FDM = 2 and with a PRACH Configuration Index = 184. The time resources of the ROs in the PRACH Occasion can be obtained from Table 6.3.3.2-2 of [7] : The PRACH Configuration Period = 20 ms since an RO occurs in every even numbered system frame number (SFN) (x = 2 and y = 0). In each even numbered SFN, subframe 4 and 9 contain a slot with ROs, i.e., PRACH slot. In this example a 15 kHz subcarrier spacing is assumed and so each subframe which is 1 ms contains 1 slot. In each PRACH slot (i.e. in subframe 4 and 9), there are seven sets of time domain ROs where each RO is two OFDM symbols long. Since FDM = 2, each time domain RO has two ROs, and this gives 14 ROs in a PRACH slot as shown in Figure 8. There are therefore 28 ROs in a PRACH Configuration Period of 20 ms (2 PRACH slots in 20ms x 7 time domain ROs x 2 FDM = 28 ROs). SSB to PRACH Occasion Association

[0078] A UE may select an SSB received on a DL beam and transmit a PRACH using a corresponding UL beam. The gNB needs to know which SSB the UE has selected so that it can transmit a Random Access Response (RAR) to the UE using the same SSB beam selected by the UE, or a beam derived from the UE selected SSB beam. Since the UE uses an UL beam, the gNB may maximise its reception by tuning its receiver panels towards the direction of the UL beam. Since ROs and SSBs are configured independently, an SSB- RO association is used for the gNB to determine the UE selected SSB, so that the gNB can determine the SSB selected by the UE based on the RO and preamble used for the UE’s PRACH transmission.

[0079] In SSB-RO association, each SSB is associated with one or more ROs and preambles. Infrastructure equipment of a wireless communications network (such as a gNB) transmits an indication of a number of SSBs associated with each RO and a number of preambles associated with each SSB. For example, the infrastructure equipment may transmit the following RRC parameter to the UE: ssb-perRACH- OccasionAndCB-PreamblesPerSSB . The values for SSB to RO association may be { 1 / 8, 1 / 4, 1 / 2, 1, 2, 4, 8, 16} . In other words, SSB may be associated with 8, 4, 2 or 1 ROs, and an RO may be associated with 2, 4, 8 or 16 SSBs. In each RO, the SSB may be configured to associate with a subset of the 64 preambles or all of the 64 preambles. For the case where an RO is associated with 2, 4, 8 or 16 SSBs, each SSB may only be associated with a subset of the preambles in an RO. For example, if an RO is associated with two SSBs, then each SSB can occupy at most 32 preambles in that RO. For the case where an SSB is associated with one or more ROs, the SSB can occupy all of the 64 preambles although it can be configured to occupy fewer than 64 preambles.

[0080] Once the SSB parameters, RO parameters and SSB-RO association parameters are configured, the UE may then perform the following steps in sequential order:

[0081] 1. Valid ROs determination;

[0082] 2. Indexing the valid ROs; and

[0083] 3. Perform SSB-RO mapping.

[0084] Valid ROs Determination

[0085] For FDD all configured ROs are valid. However, for TDD, the following three legacy validity conditions must be met for an RO to be valid:

[0086] • A valid RO is contained fully in UL OFDM symbols since PRACH cannot be transmitted in DL OFDM symbols;

[0087] • In addition to being fully contained in UL OFDM symbols, there also needs to be a gap of NgapOFDM symbols between the end of an SSB and the start of the valid RO. The value of Ngapdepends on the subcarrier spacing of the PRACH and it is defined in [8], the contents of which are hereby incorporated by reference in their entirety; and

[0088] • If an RO and an SSB falls within a PRACH slot, the RO is invalid if it precedes the SSB.

[0089] Examples of valid and invalid ROs are shown in Figures 9A to 9D. The valid RO shown in Figure 9A meets all three validity conditions as detailed above. However, the invalid ROs as shown in Figures 9B, 9C, and 9D each fail to meet one of these validity conditions. The RO of Figure 9B is invalid because it falls within DL OFDM symbols. The RO of Figure 9C is invalid because there is an insufficient gap between the SSB and the RO. The RO of Figure 9D is invalid because the RO precedes the SSB within the PRACH slot.

[0090] RO Indexing

[0091] Once the valid ROs are determined, they are indexed in the following order: 1. First, in increasing order of preamble indexes within a single RO;

[0092] 2. Second, in increasing order of frequency resource indexes for frequency multiplexed RO;

[0093] 3. Third, in increasing order of time resource indexes for time multiplexed PRACH occasions within a PRACH slot; and

[0094] 4. Fourth, in increasing order of indexes for PRACH slots.

[0095] SSB-RO Mapping

[0096] The SSBs are then mapped to the indexed ROs sequentially by RO index. This mapping is repeated every “SSB-RO Association Period”. The SSB-RO association period is the smallest integer number of PRACH Configuration Periods required for all the SSBs in an SSB burst set to fully map to RO(s) at least once. In an SSB-RO association period, if any remaining ROs cannot fully map all the SSBs of an SSB burst set, they are invalid ROs and are not used for PRACH transmissions. The allowed SSB-RO association periods for each PRACH Configuration Period are listed in Table 8.1-1 of [8], which is reproduced below as Table I.

[0097] Table I: PRACH ( 'onfiguralion Period and SSB-RO association period (reproduced from / / )

[0098] An example of an SSB to RO mapping for an SSB-RO association period will now be explained. Figure 10 illustrates a legacy TDD slot format {DDDDU}, consisting of four DL slots followed by an UL slot as shown in Figure 10, and operating in 15 kHz subcarrier spacing. SSB and PRACH are configured as follows:

[0099] • SSB burst set has 5 SSBs {SSB#1, SSB#2, SSB#3, SSB#4, SSB#5};

[0100] • SSB per RO = 1 / 2; i.e., each SSB is mapped to two ROs;

[0101] • Preambles per SSB = 64, i.e., all preambles in an RO are fully mapped to an SSB;

[0102] • FDM RO = 2; and

[0103] • PRACH Configuration Index = 129 for FR1 TDD.

[0104] Using the lookup table in Table 6.3.3.2-3 of [7], the time resource configuration for PRACH Configuration Index = 129 has a PRACH Configuration Period = 10 ms. This is shown in Table II below, which reproduces a portion of this lookup table in Table 6.3.3.2-3 of [7],

[0105] Table IT: PRACH Configuration Index 129 (reproduced from [7])

[0106] Figure 11 shows an example of SSB to RO mapping in an association period for the legacy TDD slot format, corresponding to PRACH configuration index 129 as shown in Table II above. Here, in each PRACH Configuration Period, Subframe 3, 4, 8 and 9 contain PRACH slots, and in each PRACH slot, there are two time domain ROs with duration six OFDM symbols each, which leads to 16 ROs in a PRACH Configuration Period (four PRACH slots x two time domain ROs per PRACH slot x two FDM ROs). Since a valid RO can only reside in UL OFDM symbols, only subframes 4 and 9 have valid ROs, and the ROs in subframes 3 and 8 are invalid ROs. Hence, each PRACH Configuration Period has eight valid ROs.

[0107] For a PRACH Configuration Period = 10 ms, referring to Table I as reproduced above (i.e., from Table 8.1-

[0108] 1 of [8]), the required SSB-RO association Period to fully map all five SSBs with SSB per RACH = 1 / 2 is

[0109] 2 x PRACH Configuration period (20 ms), giving 2 x 8 = 16 valid ROs. The 16 valid ROs in the 20 ms SSB-RO association period are indexed firstly by preamble, secondly by frequency, thirdly by time, and lastly by PRACH slot as shown in Figure 11. The SSBs are then mapped to the indexed ROs sequentially; e.g., since SSB per RO = 1 / 2, SSB#1 is mapped to RO#1 and RO#2, followed by SSB#2 being mapped to RO#3 and RO#4, etc. The five SSBs are fully mapped to the ROs once in the SSB-RO association period, leaving six remaining ROs: RO#11, RO# 12, RO# 13, RO# 14, RO# 15 and RO# 16 that cannot fully map to another set of five SSBs. Hence these six remaining ROs are Invalid ROs, and are not used for PRACH transmissions.

[0110] PRACH Repetitions

[0111] The concept of using PRACH repetitions is introduced in Rel-18 to enhance the uplink coverage of PRACH The PRACH repetition factor is NPRACH = {2, 4, 8}, where the PRACH is transmitted multiple times in different ROs using the same transmission beam and the same preamble. The set of ROs used for a specific PRACH repetition NPRACH consists of valid ROs that are associated with one SSB (i.e., the selected SSB) and uses the same frequency resources.

[0112] Figure 12 is an example of a set of NPRACH ROS for a PRACH repetition of four, i.e. NPRACH = 4, using the PRACH configurations as described in Figure 11. Figure 12 shows four SSB-RO association periods (each lasting 20 ms), spanning eight radio frames from SFN k to SFN k + ~I. where in each SSB-RO association period, the five SSBs are mapped to ten ROs. Assuming the UE selected SSB#2, and requires 4 x PRACH repetitions, it has a choice between two sets of NRRACH=^ ROS, i.e. one that starts with RO#3 (the lower frequency RO) in SFN k and another that starts with RO#4 (the higher frequency RO) in SFN k. Here, the UE selects RO#3 in SFN k as the start of the PRACH repetition. The remaining ROs in the set of NRRACH=^ ROs are associated with the same SSB#2 and located in the same frequency; that is, the set of NPRACH =4 ROs are RO#3 in SFN k, SFN k + 2, SFN k + 4 and SFN k + 6, which are outlined in dashed boxes in the example of Figure 12.

[0113] The first set of NPRACH ROS starts from SFN 0 and there may be a gap of TimeOffsetBetweenStartingRO valid ROs between each set of NPRACH ROS. The value of TimeOffsetBetweenStartingRO is configured by the network.

[0114] SBFD ROs

[0115] In the current system, there are two methods to configure ROs for SBFD (i.e. ROs that can be configured partially or fully in SBFD sub-bands and hence are usable by SBFD-capable UEs), which are also described in co-pending European patent application number EP24155834.5 [9], the contents of which are hereby incorporated by reference. That is:

[0116] • Single PRACH Configuration: SBFD ROs and legacy ROs are configured in a single PRACH configuration; and

[0117] • Additional PRACH Configurations: SBFD ROs and legacy ROs are configured in separate PRACH configurations, i.e., an additional / separate PRACH configuration is used for SBFD ROs. For each of these SBFD RO configuration methods, SBFD UEs will need to perform the SSB-RO association twice, where the first of these is performed on valid ROs that are validated using legacy RO validation rules, and the second SSB-RO association for SBFD RO is performed using new RO validation rules. Such new RO validation rules for SBFD RO may include that a valid RO must not overlap with SSB. Such new validation rules may include that a valid RO must reside fully within an UL sub-band (or alternatively the validation rules may include that an RO is valid if at least part of the RO resides in the UL subband and the other part of the RO (if any) resides in UL OFDM symbols).

[0118] The SSB-RO association for SBFD RO has not yet been specified, but a potential overall SSB-RO association is shown in Figure 13, where the example PRACH configuration as used in the example in Figure 11 is used again here (i.e. corresponding to PRACH configuration index 129 as shown in Table II). Here, an {XXXXU} SBFD slot format is assumed, where “X” is a slot consisting of SBFD OFDM symbols, where in the example in Figure 13, the SBFD slots consists of a {DUD} sub-band arrangement in the frequency domain such as that shown in Figure 4.

[0119] In the example of Figure 13, the UE performs an SSB-RO association using legacy RO validation rules for non-SBFD OFDM symbols, where it maps SSB#1 and SSB#2 to RO#1 and RO#2, and RO#3 and RO#4 respectively in Subframe 4 of SFN k, SSB#3 and SSB#4 to RO#5 and RO#6, and RO#7 and RO#8 respectively in Subframe 9 of SFN k, and SSB#5 to RO#9 and RO# 10 in Subframe 4 of SFN k + 1. The UE performs a second SSB-RO association on SBFD OFDM symbols, where it maps SSB#1 and SSB#2 to RO#1 and RO#2, and RO#3 and RO#4 respectively in Subframe 3 of SFN k, SSB#3 and SSB#4 to RO#5 and RO#6, and RO#7 and RO#8 respectively in Subframe 8 of SFN k, and SSB#5 to RO#9 and RO#10 in Subframe 3 of SFN k + 1. The overall SSB-RO association combining the two SSB-RO associations is shown in Figure 13.

[0120] Table III below shows the parameters for an example SBFD RO using a separate PRACH configuration, i.e. the SBFD UE is configured with two PRACH configurations.

[0121] Table III: Dual PRACH configurations for legacy TDD and SBFD RACH

[0122] Here the SBFD UE also performs two SSB-RO association with different RO validations but on different PRACH configurations, where a first SSB-RO association using legacy RO validation rules on the legacy PRACH configuration (PRACH Configuration Index = 127) and another SSB-RO association using the new SBFD RO validation rules on the additional PRACH configuration with PRACH Configuration Index = 125, as shown in Table IV below. The resultant SSB-RO mapping is shown in Figure 14, where the SBFD ROs occupies different frequency resources from the legacy TDD ROs.

[0123] Table IV: PRACH Configuration Indices 125 and 127 (reproduced from [7])

[0124] Additional PRACH Resource for NES

[0125] In Rel-19 Network Energy Saving (NES)

[0010] , to save standby time for gNB to receive PRACH especially in the case of low load (i.e. few UEs are in a cell), additional PRACH resources have been introduced. Accordingly, PRACH resources are divided into legacy PRACH resources (which are fixed by RRC signalling and cannot be dynamically activated or deactivated) and additional PRACH resources which can dynamically turn to be activated or deactivated. For example, the gNB may send a signal to the UE to dynamically activate or deactivate the additional PRACH resources for the UE.

[0126] If PRACH collisions rarely happens, this implies there are few UEs transmitting PRACH in a cell and that the legacy PRACH resources provide sufficient resources for the UEs. In such scenarios, the additional PRACH resources may be deactivated so that the gNB can enter a low power (e.g. sleep) state during times where the additional PRACH resources are configured.

[0127] On the other hand, if PRACH collisions frequently happen, this implies there are many UEs transmitting PRACH in the cell and that the legacy PRACH resources do not provide sufficient resources for the UEs. In such scenarios, the additional PRACH resources may be activated so that the UEs can use the additional PRACH resources for transmitting PRACH (in addition to the legacy PRACH resources). This helps to reduce the number of PRACH collisions in the cell. In such scenarios, the gNB will wake up and attempt to receive PRACH during times when the additional PRACH resources are configured.

[0128] Technical Challenges

[0129] An SSB selected by an SBFD UE may be associated with two different types of ROs (i.e. SBFD ROs and legacy, non-SBFD ROs). Accordingly, there are two different types of ROs which could be used for the transmission of a PRACH preamble by the UE.

[0130] In co-pending EP patent application number 24187683.8

[0011] , it was proposed a UE to select its preferred RO type if the preferred RO type is within a time window.

[0131] The present inventors have recognized that since non-SBFD UEs are not able to use SBFD ROs (i.e., they can only use non-SBFD ROs) whilst SBFD UEs can use either SBFD ROs or non-SBFD ROs, this may result in under-utilization of SBFD ROs and increased congestion in non-SBFD ROs.

[0132] Similarly, the present inventors have recognized that NES UEs can use ROs from the legacy PRACH configuration and additional PRACH configuration whereas non-NES UEs can only use ROs from the legacy PRACH configuration. This may result in under-utilization of ROs from the additional PRACH configuration and increased congestion in ROs from the additional PRACH configuration.

[0133] Increased congestion may lead to PRACH transmission collisions between different UEs attempting to use the same RO. PRACH transmissions may therefore have to be retransmitted one or more times, therefore leading to an efficient use of communications resources. In view of the above, there is provided methods, communications devices and infrastructure equipment which can provide a more efficient utilization of communications resources.

[0134] Figure 15 is a flow diagram illustrating a method of operating a communications device to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment in accordance with example embodiments.

[0135] In step S 1510, the method comprises selecting a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment.

[0136] In step S1520, the method comprises selecting a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble.

[0137] The plurality of ROs comprise a plurality of sets of ROs. Each of the plurality of sets of ROs are associated with at least one of the plurality of SSBs. Each of the plurality of sets of ROs comprise ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type.

[0138] In some embodiments, each of the plurality of sets of ROs are associated with a respective one of the plurality of SSBs. For example, if the communications device transmits a PRACH in an RO from one of the sets, then this indicates the communications device has selected the SSB associated with that set. In step SI 521, the selecting the RO comprises identifying a set of ROs of the plurality of sets of ROs that is associated with the selected SSB.

[0139] In step S1522, the selecting the RO comprises selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO.

[0140] In some embodiments, the selection probability for each of the plurality of types of RO is greater than zero and less than one. In some embodiments, the first type of RO is an SBFD RO and the second type of RO is a non-SBFD RO. In some embodiments, the selection probability for selecting an SBFD RO is greater than the selection probability for selecting a non-SBFD RO. In other embodiments, the selecting probability for selecting a non-SBFD RO is greater than the selection probability for selecting an SBFD RO.

[0141] The transmission order of the particular PRACH preamble may represent the position of the transmission of the particular PRACH preamble in a sequence of PRACH preamble transmissions by the communications device. In some embodiments, the sequence of PRACH preamble transmissions comprise a transmission of the particular PRACH preamble and one or more retransmissions of the particular PRACH preamble. In some embodiments, the sequence of PRACH preamble transmissions may comprise a transmission of a PRACH preamble when first performing a random access procedure with the infrastructure equipment to enter a connected mode, one or more other transmissions of a PRACH preamble (e.g. a different or the same PRACH preamble) when the communications moves to an idle mode and performs a random access procedure to re-enter the connected mode.

[0142] Advantageously, in some embodiments, the RO type mapping information indicates a mapping of a transmission order of the particular PRACH preamble to only one of the plurality of types of RO, thereby unambiguously identifying the RO type which the communications device should select according to the transmission order of the PRACH preamble.

[0143] In some embodiments, where the RO type mapping information indicates a mapping of a transmission order of the particular PRACH preamble to more than one of the plurality of types of RO, the communications device may randomly select between the more than one of the plurality of types of RO, or use any embodiment discussed herein to select between the more than one type of RO. In step S1523, the selecting the RO comprises selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble.

[0144] Once the RO type has been selected, the selected RO may be selected randomly from among the ROs of the selected type in identified set, for example.

[0145] In step S1530, the method comprises transmitting the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

[0146] By selecting a type of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information, communications resource utilization efficiency can be increased. For example, the selection probability for selecting each of the plurality of types of RO and / or the RO type mapping information can be configured to obtain desired load balancing across different types of ROs.

[0147] Example embodiments will be discussed below with reference to an SBFD RO type and a non-SBFD RO type. This is for ease of explanation only and it should be appreciated that the description below applies generally to a first RO type and a second RO type. An SBFD RO is an RO which is contained within SBFD symbols of the radio access interface, and a non-SBFD RO is an RO which is contained within non-SBFD uplink symbols of the radio access interface. Another example of a first RO type is an RO belonging to a configuration of ROs which can be deactivated or activated for use by the communications device (e.g. additional PRACH resources for NES communications devices). Another example of the second RO type is an RO belonging to a configuration of ROs which are fixed for use by the communications device and cannot be dynamically activated or deactivated (e.g. legacy PRACH resources). In some embodiments, the selection probability for selecting an RO belonging to a configuration of ROs which can be deactivated or activated for use by the communications device is greater than the selection probability for selecting an RO belonging to a configuration of ROs which are fixed for use by the communications device and cannot be dynamically activated or deactivated. In other embodiments, the selection probability for selecting an RO belonging to a configuration of ROs which are fixed for use by the communications device and cannot be dynamically activated or deactivated is greater than an RO belonging to a configuration of ROs which can be deactivated or activated for use by the communications device.

[0148] In some embodiments, the plurality of RO types may comprise more than two types of RO.

[0149] Although the following description will describe processes performed by UEs and gNBs, it will be appreciated that the following description applies generally to processes performed by communications devices and infrastructure equipment of a wireless communications network respectively.

[0150] Selection Probability

[0151] In some embodiments, the communications device selects the RO type based on a selection probability for selecting each of the plurality of types of RO. For example, the selection probability for selecting an SBFD RO may be p and the selection probability for selecting a non-SBFD RO may be q. In some embodiments, p + q = \.

[0152] In some embodiments, the selection probability for selecting the first RO type is higher than the selection probability for selecting the second RO type. For example, p may greater than q, thereby biasing the communications device towards selecting an SBFD RO compared to a non-SBFD RO. Therefore, the communications device is more likely to select an SBFD RO and thus reduce congestion on non-SBFD ROs which may arise because non-SBFD UEs may only use non-SBFD ROs whereas SBFD UEs can use both SBFD ROs and non-SBFD ROs. For example, the infrastructure equipment may configure the communications device with probability q = 0.30, for the selection of non-SBFD ROs, i.e. there is a 30% chance the UE would select a non-SBFD RO, and with probability p = 0.70 for the selection of SBFD ROs, i.e., there is a 70% chance the UE will select a SBFD RO. In some embodiments, the value of p and q are between 0 and 1, i.e., 0.00<p<1.00 and 0.00<q<1.00. In other embodiments, the value of p and q may be one or zero.

[0153] In some embodiments, the selection probability for selecting the first RO type is higher than the selection probability for selecting the second RO type when the number of communications devices in a predefined area (e.g. a cell) of the wireless communications network capable of using the first type of RO is greater than the number of communications devices in the pre-defined area capable of using the second type of RO or vice versa. For example, p may be a large value during early deployment of the SBFD UEs when there are few SBFD UEs, thus biasing the communications device to select SBFD ROs more often than non-SBFD ROs. However, when there are a large number of SBFD UEs, p may be a smaller value (e.g. equal to q).

[0154] In some embodiments, the selection probability for selecting the first type of RO is equal to a number of communications devices in the predefined area capable of using the first type of RO divided by the sum of the number of communications devices in the predefined area capable of using the first type of RO and the number of communications devices in the predefined area capable of using the second type of RO. For example, in some embodiments, p = number of SBFD UEs in predefined area / (number of SBFD UEs in predefined area + number of non-SBFD UEs in predefined area).

[0155] In some embodiments, the communications device receives, from the infrastructure equipment, an indication of the selection probability for selecting the first type of RO (e.g. p). In embodiments where there are only two types of RO (e.g. SBFD RO and non-SBFD RO), and where q = 1 -p, the communications device may determine q by inserting the p received from the infrastructure equipment into q = 1 -p. In such embodiments, communications efficiency is increased because only one selection probability is transmitted. In other embodiments, the communications device receives an indication of q from the infrastructure equipment and uses p = 1 - q to obtain p. In other embodiments, the infrastructure equipment transmits an indication of p and an indication of q.

[0156] In some embodiments, an indication of p and / or q is received from the network. For example, the indication of p and / or q may be comprised in a Radio Resource Control (RRC) signal, a Physical Downlink Control Channel (PDCCH) Order instructing the communications device to perform the random access procedure, or in a System Information Block (SIB).

[0157] In some embodiments, the communications device determines the selection probability for selecting each of the plurality of RO types without receiving a signal from the infrastructure equipment of the wireless communications network. For example, the communications device determines the selection probability for selecting the first RO type based on the ratio of the number of ROs of the first type to the number ROs of a second type plus ROs of the first type within a pre-defined period. For example, the probability of selecting the first type of RO may be equal to the ratio. The pre-defined period may be the SSB to RO association period for example.

[0158] Figure 16 schematically illustrates an example of selecting an RO type in accordance with example embodiments. Figure 16 uses the same PRACH configurations as that in the example in Figure 14, i.e., where the SBFD RO is configured in a separate PRACH configuration to that of the non-SBFD RO (labelled “legacy RO” in Figure 16). In Figure 16, the subframes in SFN T and SFN +l are expanded to also show the subframes without any configured ROs (only subframes 0 to 4 SFN +l are shown for clarity). In addition, it is assumed that infrastructure equipment of a wireless communications network configured an SBFD UE with a probability p = 0.7 to select SBFD ROs and with a probability q = 0.3 to select non-SBFD ROs. The SBFD UE selects SSB#3 at Subframe 3 of SFN K. The ROs associated with SSB#3 include an RO of the SBFD RO type (RO#3 in frequency / i) and ROs of the non-SBFD RO type (RO#5 and RO#6 in frequency fi and . The SBFD UE, based on the selection probability for the SBFD RO type and the non- SBFD-RO type, selects the non-SBFD RO type. Once the non-SBFD RO type has been selected, the selection of which of RO#5 and RO#6 to select is up to UE implementation or the selection may be performed randomly with equal probability. In this example, the SBFD UE selects RO#6 despite SBFD RO#3 in frequency / i being the earliest RO associated with SSB#3, because RO#6 is of the selected RO type (i.e. non-SBFD RO type).

[0159] Figure 17 schematically illustrates another example of selecting an RO type in accordance with example embodiments. In Figure 17, the gNB is configured with three SSBs, and the SSB per RO = ! , i.e. each SSB is mapped to four ROs for SBFD ROs and SBFD ROs. In this example, the SBFD UE selects the SBFDO RO type based on the selection probability for the SBFD RO type and the non-SBFD-RO type.

[0160] In this example, a PRACH slot is equivalent to a subframe and the UE selects SSB#1 at Subframe 0 of SFN K. As shown in Figure 17, there are two PRACH slots (in Subframe 2 and Subframe 7) containing SBFD ROs associated with SSB#1, i.e. RO#1 & RO#2 in the PRACH slot in Subframe 2, and RO#3 & RO#4 in Subframe 7 of SFN K. In this case, the UE selects an RO in the PRACH slot in Subframe 2 since it is the earliest PRACH slot of SBFD RO type. The decision of which of RO in the same PRACH slot to select (i.e. RO#1 or RO#2) may be random to avoid congestion compared to if the earliest RO in the PRACH slot (i.e. RO#1) was always selected.

[0161] Cell Edge and Cell Centre UEs

[0162] The present inventors have recognized that UEs near the cell edge may be susceptible to interference for both non-SBFD ROs and SBFD ROs. However, UE-to-UE cross-link interference (CLI) in the adjacent subbands in the cell affects SBFD ROs but not non-SBFD ROs. The high transmission power required in UL subbands that contain SBFD ROs for cell-edge UEs creates interference in adjacent DL subbands and therefore affects the UEs DL coverage.

[0163] In some embodiments, the communications device receives, from the infrastructure equipment, a plurality of candidate selection probabilities for selecting the first RO type and an indication of a downlink signal quality threshold. In such embodiments, the communications device determines which of the plurality of candidate selection probabilities to use for selecting the first type of RO based on a comparison between a measured downlink signal quality and the indicated downlink signal quality threshold.

[0164] The candidate selection probabilities may comprise a probability for selecting the SBFD RO type for cell centre UEs (pCentre) and a probability for selecting the SBFD RO type for cell-edge UEs (pedge), where pcentre and pedge are separately determined or separately configured. In some embodiments, pcentre and pedgeare different from each other. In some embodiments, pcentre is advantageously larger than pedge, thereby giving cell centre UE’s a higher probability of selecting the SBFD RO type compared with cell centre UEs.

[0165] For example, a cell-centre UE may select the SBFD RO type with a selection probability of pcentre = 0.70 (i.e., the UE selects non-SBFD ROs with probability 0.30), and a cell-edge UE may select the SBFD RO type with a selection probability of pedge= 0.20 (i.e., the UE selects non-SBFD ROs with probability 0.80). In other words, the probability of cell-centre UEs using SBFD ROs (p = 0.70) is higher than the probability of the cell-edge UEs using SBFD ROs (p = 0.20). This means that interference for cell-edge UEs can be reduced. Figure 18 schematically illustrates an example of selecting an RO type in accordance with example embodiments. As shown in Figure 18, a gNB is configured to communicate with a cell-centre UE 1804 located within a cell-centre area and a cell-edge UE 1806 located within a cell-edge area. An edge 1808 of the cell centre area and an edge of the cell-edge area 1810 may be determined by downlink signal quality thresholds. For example, the edge 1808 of the cell centre area may be defined by a radius beyond which the downlink signal quality drops below a first threshold and the edge 1810 of the cell edge area may be defined by a radius beyond which the downlink signal quality drops below a second threshold. The downlink signal quality thresholds may be Reference Signal Received Power (RSRP) thresholds, Reference Signal Received Quality (RSRQ) thresholds or Signal to Interference plus Noise Ratio (SINR) thresholds, for example.

[0166] For example, a UE may determine whether it is in the cell-centre area or the cell-edge area by comparing a downlink signal quality measurement made by the UE with the first threshold. For example, the gNB 1802 may configure a UE with an RSRP threshold, TRSRP, where the UE uses probability pcentre if a measured RSRP > TRSRP, otherwise the uses probability pedgefor the selection of SBFD ROs. The threshold information can be provided to the UE, as part as of the overall PRACH configuration. It can be carried in the RRC message, via SIB or unicast message, for example.

[0167] In some embodiments, the edge 1808 of the cell-centre area is defined by a pathloss threshold. Pathloss may be calculated by a UE using: reference Si gnalPow er parameter - measured RSRP, where the referenceSignalPower parameter is provided by higher layers. The gNB 1802 may configure a pathloss threshold TPL where the UE uses probability pcentre if its calculated pathloss < TPL, otherwise it uses probability pedgefor the selection of SBFD ROs.

[0168] In other embodiments, the pathloss may be calculated by a UE using: measured RSRP - referenceSignalPower parameter, where the referenceSignalPower parameter is provided by higher layers. In this case, the gNB 1802 may configure a pathloss threshold TPL where the UE uses probability pcentre if its calculated pathloss > TPL, otherwise it uses probability pedgefor the selection of SBFD ROs.

[0169] The calculated pathloss may be used by the UE to determine PRACH Tx power and therefore CLI caused by high PRACH Tx can be controlled by using pathloss value.

[0170] Probability Mapping Information

[0171] As mentioned above, the transmission order of the particular PRACH preamble may represent the position of the transmission of the particular PRACH preamble in a sequence of PRACH preamble transmissions by the communications device. In some such embodiments, selecting a type of RO of the plurality of types of RO based on the selection probability for selecting each of the plurality of types of RO comprises selecting the type of RO further based on probability mapping information. The probability mapping information indicates a mapping of the transmission order of each of the PRACH preamble transmissions in the sequence to the selection probability for one of the plurality of types of RO.

[0172] For example, for each transmission attempt of a PRACH preamble the RO type is selected based on different set of probabilities. For example, for the first transmission of a PRACH preamble, the probability may be {pi, qi}, where qi = 1 - pi, i.e., the UE has probability pi of selecting SBFD RO and qi of selecting non-SBFD RO. In a second transmission attempt (e.g. a first retransmission), the set of probability is {pg, qf, and for a third transmission attempt (e.g. a second retransmission), the probability set is {pg, qs}, and so on.

[0173] In some embodiments, the probability mapping information indicates that the selection probability for one of the plurality of types of RO should be applied alternately to the first RO type and the second RO type in tandem with the transmission order. For example, for the first transmission attempt of a PRACH preamble, a selection probability p (which may be configured by the infrastructure equipment) represents the probability of selecting the SBFD RO type. For the second transmission attempt (e.g. first retransmission), selection probability p represents the probability of selecting the non-SBFD RO type. The third transmission attempt (e.g. second retransmission) may cycle back to representing the selection probability p as the probability of selecting the SBFD RO type as in the first transmission attempt, and so on.

[0174] In some embodiments, the probability mapping information may comprise a bitmap comprising a sequence of bits. In some embodiments, the sequence of bits may be a sequence of bits in a period such as an S SB to RO association period, for example. In other embodiments, the period is undefined, and the communications device keeps a counter on operating the PRACH transmission following the bitmap. The position of each bit in the sequence represents the transmission order of a PRACH preamble. Each bit in the sequence maps the transmission order represented by that bit to a probability set. For example, a bitmap may comprise a sequence of bits, each of which is either “1” or “0”, where a 1 bit indicates that the probability set to use is {pi, qi} (i.e. indicating to use pi for selecting the SBFD RO and qi for selecting the non-SBFD RO) and and the 0 bit indicates that the probability set to use is {p2, q2} (i.e. indicating to use p2 for selecting the SBFD RO and q2for selecting the non-SBFD RO). In some embodiments, pi = q2and qi = P2. A UE may select the probability set to use by moving along the bitmap in accordance with transmission order. For example, for a bitmap of “01001”, the UE selects to use {p2, q2} (since bit = “0”) for the first transmission of a PRACH preamble by the UE (transmission order =1), the UE selects to use {pi, qi} (since the 2nd bit = “1”) for the second transmission of a PRACH preamble by the UE (transmission order =2), and the UE selects to use {p2, q2} (since the 3rdbit = “0”) for the third transmission of a PRACH preamble by the UE (transmission order = 3) and so on.

[0175] In some embodiments, where the transmission order (m) of a PRACH preamble is greater than the number of bits (n), the bit representing the mthtransmission order is the bit at the xthposition in the sequence of bits where x = remainder of m / n. This has the effect that the UE cycles back to the beginning of the bitmap. For example, for the fifth transmission of a PRACH preamble by the UE (transmission order = 5), the UE selects to use {pi, qi} since the 5thbit = “1”, and, for the sixth transmission of a PRACH preamble (transmission order = 6), the UE selects to use {p2, q2} since the UE cycles back to the beginning of the bitmap where the 1stbit = “0”. In other words, for transmission order =6, x = remainder (6 / 5) = 1stbit.

[0176] In some embodiments, the communications device may be preconfigured to know the probability mapping information. In some embodiments, the infrastructure equipment of the wireless communications network may transmit an indication of the probability mapping information to the communications device. The indication may be transmitted in an RRC signal, for example.

[0177] RO Type Mapping Information

[0178] In some embodiments, the communications device selects the type of RO based on RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to one of the plurality of types of RO.

[0179] In some embodiments, the communications device may be preconfigured to know the RO type mapping information. In some embodiments, the infrastructure equipment of the wireless communications network may transmit an indication of the RO type mapping information to the communications device. The indication may be transmitted in an RRC signal, for example.

[0180] Bitmap(s)

[0181] In some embodiments, the RO type mapping information comprises a bitmap comprising a sequence of bits. In some embodiments, the sequence of bits may be a sequence of bits in a pre-defined period such as an SSB to RO association period, for example. In other embodiments, the period is undefined, and the communications device keeps a counter on operating the PRACH transmission following the bitmap. The position of each bit in the sequence represents the transmission order of a PRACH preamble. Each bit in the sequence maps the transmission order represented by that bit to one of the plurality of RO types.

[0182] For example, a bitmap may comprise a sequence of bits, each of which is either “1” or “0”, where a 1 bit indicates that the non-SBFD RO type must be selected, and the 0 bit indicates that the SBFD RO type must be selected. A UE may select an RO type by moving along the bitmap in accordance with transmission order. For example, a bitmap of “01001” the UE selects the SBFD RO type (since bit = “0”) for the first transmission of a PRACH preamble by the UE (transmission order =1), the UE selects the non-SBFD RO type (since the 2nd bit = “1”) for the second transmission of a PRACH preamble by the UE (transmission order =2), and the UE selects the SBFD RO type (since the 3rdbit = “0”) for the third transmission of a PRACH preamble by the UE (transmission order = 3) and so on.

[0183] In some embodiments, where the transmission order (m) of a PRACH preamble is greater than the number of bits (n), the bit representing the mthtransmission order is the bit at the xthposition in the sequence of bits where x = remainder of m / n. This has the effect that the UE cycles back to the beginning of the bitmap. For example, for the fifth transmission of a PRACH preamble by the UE (transmission order = 5), the UE selects the non-SBFD type since the 5thbit = “1”, and, for the sixth transmission of a PRACH preamble (transmission order = 6), the UE selects the SBFD RO type since the UE cycles back to the beginning of the bitmap where the 1stbit = “0”. In other words, for transmission order =6, x = remainder (6 / 5) = 1stbit.

[0184] The bitmap can be configured to obtain load balancing across SBFD ROs and non-SBFD ROs. For example, it will be appreciated that a bitmap of 01 or 10 could be used to so that non-SBFD ROs are used in 50% of transmission instances and SBFD ROs are used in the other 50% of transmission instances.

[0185] In some embodiments, the RO type mapping information comprises a plurality of bitmaps including a first bitmap comprising a sequence of bits and a second bitmap comprising a sequence of bits. In some embodiments, the sequence of bits in the first bitmap and the second bitmap is a sequence of bits in a predefined period such as an SSB to RO association period, for example. In some embodiments, the period is undefined, the communications device keeps a counter on operating the PRACH preamble transmission following the first bitmap and the second bitmap. In such embodiments, the position of each bit in each sequence represents the transmission order of a PRACH preamble. Each bit in the sequence of bits in the first bitmap indicates whether a PRACH preamble with the transmission order represented by that bit can be transmitted in an RO of the first type (e.g. SBFD RO type) and each bit in the sequence of bits in the second bitmap indicates whether a PRACH preamble with the transmission order represented by that bit can be transmitted in an RO of the second type (SBFD RO type). For example, the first bitmap may comprise a bit sequence comprising Is and 0s where a 1 bit indicates a SBFD RO type can be selected, and a 0 bit indicates an SBFD RO type cannot be selected. The second bitmap may comprise a bit sequence comprising Is and 0s where a 1 bit indicates a non-SBFD RO type can be selected, and a 0 bit indicates a non-SBFD RO type cannot be selected.

[0186] In some embodiments, where the multiple bitmaps are comprised in RO type mapping information, the communications device may determine, based on the transmission order of the particular PRACH preamble, which of the bits in the first bitmap and the second bit map represents the transmission order for the particular PRACH preamble. The communications device may then determine, based on the determined bit in the first bitmap and the second bitmap, that the particular PRACH preamble can be transmitted in one of the first type of RO or the second type of RO. The communications device may select the type of RO in which the particular PRACH preamble can be transmitted.

[0187] In some embodiments, the first and second bitmaps indicate that the particular PRACH preamble can be transmitted using either the first or second type of RO. In such cases, the communications device may randomly select between the first and second type of RO, or may utilise any other embodiment discussed herein for selecting the type of RO from the first and second type of RO.

[0188] RO Type selection for retransmission ROs

[0189] As mentioned above, in some embodiments, the transmission order of the particular PRACH preamble may represent the position of the transmission of the particular PRACH preamble in a sequence of PRACH preamble transmissions by the communications device and the sequence of PRACH preamble transmissions comprises a transmission of the particular PRACH preamble and one or more retransmissions of the particular PRACH preamble.

[0190] In some such embodiments, the RO type mapping information indicates a mapping of a transmission order of each of the PRACH preamble transmissions in the sequence to one of the plurality of types of RO. The first transmission of the particular PRACH preamble is mapped to the first type of RO and the first retransmission of the particular PRACH preamble is mapped to the second type of RO. For example, for a first transmission of the PRACH preamble, the SBFD RO type may be selected, and for the second transmission of the PRACH preamble (first retransmission), the non-SBFD RO type may be selected or vice versa. For the third transmission of the PRACH preamble (second retransmission), the UE may cycle back to the type selected for the first PRACH preamble transmission, and so on.

[0191] Conditions

[0192] In some embodiments, selecting the type of RO based on a selection probability for each of the plurality of types of RO or RO type mapping information may only be permitted if one or more conditions are met. In one example, if a condition is met, then the RO type may be selected based on either of the selection probability and RO type mapping information. In another example, if a condition is met, then the RO type may be selected based on the selection probability but not the RO type mapping information and vice versa.

[0193] The one or more conditions may specify that a particular type of random access must be used such as Contention Based Random Access (CBRA) only or Contention Free Random Access (CFRA) only. For example, in a CFRA, the gNB may explicitly indicate the RO type the UE should use in a PDCCH order.

[0194] In another embodiment, the one or more conditions may require that the UE does not specifically ask to use a given RO (or RO type) or that the infrastructure equipment does not specifically ask the UE to use a given RO (or RO type). For example, if based on the selection probability the UE determines that it should use a non-SBFD RO, but the UE receives signalling from the infrastructure equipment to use an SBFD RO, then the UE uses the SBFD RO. In other words, if the UE receives an instruction from the gNB to select a particular type of RO, the UE may skip the step of determining which of the types of RO to select based on the selection probability for each of the plurality of types of RO or the RO type mapping information. Alternatively, if the UE has already determined which of the types of RO to select based on the selection probability for each of the plurality of types of RO or the RO type mapping information, the instruction received from the infrastructure equipment may override this selection, so that the UE selects the RO type instructed by the infrastructure equipment.

[0195] In another embodiment, the one or more conditions may comprise a condition that the transmission is not a retransmission of the PRACH preamble. In such embodiments, the communications device may always use the same type of RO for retransmissions (e.g. the communications device may always use the SBFD RO type for retransmissions).

[0196] Those skilled in the art would further appreciate that methods, infrastructure equipment and / or communications devices as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and communications devices as herein defined and described may form part of communications systems other than those defined by the present disclosure, provided that these are within the scope of the claims.

[0197] The methods described herein may also be embodied or encoded in a computer-readable medium, such as a computer-readable storage medium, containing instructions. Instructions embedded or encoded in a computer-readable medium may cause a programmable processor, or other processor, to perform the method, e.g., when the instructions are executed. Computer-readable media may include non-transitory computer-readable storage media and transient communication media. Computer readable storage media, which is tangible and non-transitory, may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a CD- ROM, a floppy disk, a cassette, magnetic media, optical media, or other computer-readable storage media. The term “computer-readable storage media” refers to physical storage media, and not signals, carrier waves, or other transient media. As noted above, computer readable media may include transient communication media. Such communication media may occur within a single computer system or between multiple computer systems, and may take the form of transient signal-conveying media such as carrier waves and transmission signals.

[0198] Particular examples of the present disclosure are set forth in the following numbered paragraphs:

[0199] Paragraph 1. A method of operating a communications device to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment, the method comprising selecting a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment, selecting a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated at least one of the plurality of S SBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein selecting the RO comprises identifying a set of ROs of the plurality of sets of ROs that is associated with the selected SSB, selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO, selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble, and the method comprises transmitting the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

[0200] Paragraph 2. A method according to paragraph 1, comprising receiving, from the infrastructure equipment, an indication of the selection probability (p) for selecting the first type of RO.

[0201] Paragraph 3. A method according to paragraph 2, wherein the indication of the selection probability for the first RO type is comprised in a Radio Resource Control (RRC) signal, or a Physical Downlink Control Channel (PDCCH) Order instructing the communications device to perform the random access procedure, or in a System Information Block (SIB).

[0202] Paragraph 4. A method according to paragraph 2 or paragraph 3, comprising determining, based on the selection probability (p) for selecting the first type of RO, the selection probability for selecting the second type of RO (q), wherein the plurality of types of ROs consist of the first type of RO and the second type of RO.

[0203] Paragraph 5. A method according to paragraph 2 or paragraph 3, comprising receiving, from the infrastructure equipment, an indication of the probability (q) for selecting the second type of RO.

[0204] Paragraph 6. A method according to any of paragraphs 2 to 5, wherein the receiving the indication of the selection probability for selecting the first type of RO comprises receiving, from the infrastructure equipment, a plurality of candidate selection probabilities for selecting the first RO type and an indication of a downlink signal quality threshold, and the method comprises determining which of the plurality of candidate selection probabilities to use for selecting the first type of RO based on a comparison between a measured downlink signal quality and the indicated downlink signal quality threshold.

[0205] Paragraph 7. A method according to paragraph 6, wherein the indication of the downlink signal quality threshold is received in a Radio Resource Control (RRC) Signal from the infrastructure equipment.

[0206] Paragraph 8. A method according to paragraph 6 or paragraph 7, wherein the downlink signal quality threshold is a Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ) or Signal to Interference plus Noise Ratio (SINR) threshold.

[0207] Paragraph 9. A method according to any of paragraphs 6 to 8, wherein the determining which of the candidate selection probabilities to use for selecting the first type of RO based on a comparison between a measured downlink signal quality and the indicated downlink signal quality threshold comprises determining that the measured downlink signal quality is above the indicated downlink signal quality threshold, and in response, selecting to use a first of the candidate selection probabilities for selecting the first type of RO.

[0208] Paragraph 10. A method according to any preceding paragraph, comprising determining the selection probability for selecting the first RO type based on a ratio of the number of ROs of the first RO type to the number of ROs of the second RO type plus the number of ROs of the first type within a pre-defined period.

[0209] Paragraph 11. A method according to any of paragraphs 1 to 10, wherein the mapping RO type mapping information comprises a bitmap comprising a sequence of bits, the position of each bit in the sequence representing the transmission order of a PRACH preamble, each bit in the sequence mapping the transmission order represented by that bit to one of the plurality of RO types, wherein the selecting a type of RO of the plurality of types of RO based on the RO type mapping information comprises determining, based on the transmission order of the particular PRACH preamble, which of the bits represents the transmission order for the particular PRACH preamble, and selecting the RO type mapped to the determined bit.

[0210] Paragraph 12. A method according to paragraph 11, wherein the sequence of bits comprises n bits, the transmission order of the particular PRACH preamble is m, where m>n, and the bit representing the mthtransmission order is the bit at the xthposition in the sequence of bits where x = remainder of m / n.

[0211] Paragraph 13. A method according to any of paragraphs 1 to 10, wherein the RO type mapping information comprises a plurality of bitmaps including a first bitmap comprising a sequence of bits and a second bitmap comprising a sequence of bits, wherein the position of each bit in each sequence represents the transmission order of a PRACH preamble, each bit in the sequence of bits in the first bitmap indicating whether a PRACH preamble with the transmission order represented by that bit can be transmitted in an RO of the first type and each bit in the sequence of bits in the second bitmap indicating whether a PRACH preamble with the transmission order represented by that bit can be transmitted in an RO of the second type, wherein the selecting a type of RO of the plurality of types of RO based on the RO type mapping information comprises determining, based on the transmission order of the particular PRACH preamble, which of the bits in the first bitmap and the second bit map represents the transmission order for the particular PRACH preamble, determining, based on the determined bit in the first bitmap and the second bitmap, that the particular PRACH preamble can be transmitted in one of the first type of RO or the second type of RO, selecting the type of RO in which the particular PRACH preamble can be transmitted.

[0212] Paragraph 14. A method according to any of paragraphs 1 to 13, wherein the transmission order of the particular PRACH preamble represents the position of the transmission of the particular PRACH preamble in a sequence of PRACH preamble transmissions by the communications device.

[0213] Paragraph 15. A method according to paragraph 14, wherein the sequence of PRACH preamble transmissions comprise a transmission of the particular PRACH preamble and one or more retransmissions of the particular PRACH preamble.

[0214] Paragraph 16. A method according to paragraph 15, wherein the RO type mapping information indicates a mapping of a transmission order of each of the PRACH preamble transmissions in the sequence to one of the plurality of types of RO, wherein the first transmission of the particular PRACH preamble in the sequence is mapped to the first type of RO and the first retransmission of the particular PRACH preamble in the sequence is mapped to the second type of RO.

[0215] Paragraph 17. A method according to paragraph 14 or 15, wherein selecting a type of RO of the plurality of types of RO based on the selection probability for selecting each of the plurality of types of RO comprises selecting the type of RO further based on probability mapping information, wherein the probability mapping information indicates a mapping of the transmission order of each of the PRACH preamble transmissions in the sequence to the selection probability for one of the plurality of types of RO.

[0216] Paragraph 18. A method according to paragraph 17, wherein the probability mapping information indicates that the selection probability for one of the plurality of types of RO should be applied alternately to the first RO type and the second RO type in tandem with the transmission order.

[0217] Paragraph 19. A method according to any preceding paragraph, wherein the method comprises determining that the random access procedure is a contention based random access procedure (CBRA), or determining that the random access procedure is a contention free random access procedure (CFRA).

[0218] Paragraph 20. A method according to any preceding paragraph, wherein the selecting a type of RO of the plurality of types of RO comprises selecting the first type of RO based on the selection probability for selecting each of the plurality of types of RO or the RO type mapping information, receiving, from the infrastructure equipment, an indication to select the second type of RO, and overriding the selection of the first type of RO to select the second type of RO .

[0219] Paragraph 21. A method according to any preceding paragraph, wherein the selecting a type of RO of the plurality of types of RO based on the selection probability for selecting each of the plurality of types of RO or the RO type mapping information comprises determining that the communications device has not received an instruction from the infrastructure equipment to select a particular type of RO.

[0220] Paragraph 22. A method according to any preceding paragraph, wherein the selecting a type of RO of the plurality of types of RO comprises determining that the transmission of the particular PRACH preamble is a not a retransmission of the particular PRACH preamble.

[0221] Paragraph 23. A method according to any preceding paragraph, wherein the selection probability for selecting the first RO type is higher than the selection probability for selecting the second RO type.

[0222] Paragraph 24. A method according to paragraph 23, wherein the selection probability for selecting the first type of RO is equal to a number of communications devices in a predefined area capable of using the first type of RO divided by the sum of the number of communications devices in the predefined area capable of using the first type of RO and the number of communications devices in the predefined area capable of using the second type of RO.

[0223] Paragraph 25. A method according to paragraph 24, wherein the pre-defined area is defined by a cell provided by the infrastructure equipment of the wireless communications network.

[0224] Paragraph 26. A method according to any preceding paragraph, wherein the first RO type is an SBFD RO which is partially or fully contained within SBFD symbols of the radio access interface, and the second RO type is a non-SBFD RO which is contained within non-SBFD uplink symbols of the radio access interface, or vice versa. Paragraph 27. A method according to any preceding paragraph, wherein the first RO type is an RO belonging to a configuration of ROs which can be deactivated or activated for use by the communications device, and the second RO type is an RO belonging to a configuration of ROs which cannot be dynamically activated or deactivated, or vice versa.

[0225] Paragraph 28. A method of operating infrastructure equipment of a wireless communications network configured to communicate with a communications device via a radio access interface between the communications device and the infrastructure equipment, the method comprising transmitting, for receipt by the communications device, a plurality of synchronisation signal blocks (SSBs); and receiving a particular PRACH preamble from the communications device as part of a random access procedure between the communications device and the infrastructure equipment, wherein the PRACH preamble is received in a selected physical random access channel (PRACH) occasion (RO) associated with a selected SSB of the plurality of SSBs, wherein the RO is one of a plurality of ROs, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated with at least one of the plurality of SSBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the type of the selected RO is selected based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO.

[0226] Paragraph 29. A communications device configured to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment, the communications device comprising a transmitter configured to transmit signals, a receiver configured to receive signals, and a controller configured in combination with the transmitter and the receiver to select a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment, select a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated at least one of the plurality of S SBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the controller is configured in combination with the transmitter and the receiver to select the RO by identifying a set of ROs of the plurality of sets of ROs that is associated with the selected SSB, selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO, selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble, wherein the controller is configured in combination with the transmitter and the receiver to transmit the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

[0227] Paragraph 30. Infrastructure equipment for a wireless communications network configured to communicate with a communications device via a radio access interface between the communications device and the infrastructure equipment, the infrastructure equipment comprising a transmitter configured to transmit signals, a receiver configured to receive signals, and a controller configured in combination with the transmitter and the receiver to transmit, for receipt by the communications device, a plurality of synchronisation signal blocks (SSBs); and receive a particular PRACH preamble from the communications device as part of a random access procedure between the communications device and the infrastructure equipment, wherein the PRACH preamble is received in a selected physical random access channel (PRACH) occasion (RO) associated with a selected SSB of the plurality of SSBs, wherein the RO is one of a plurality of ROs, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated with at least one of the plurality of SSBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the type of the selected RO is selected based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO.

[0228] Paragraph 31. Circuitry for a communications device configured to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment, the circuitry comprising transmitter circuitry configured to transmit signals, receiver circuitry configured to receive signals, and controller circuitry configured in combination with the transmitter circuitry and the receiver circuitry to select a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment, select a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated at least one of the plurality of S SBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the controller circuitry is configured in combination with the transmitter circuitry and the receiver circuitry to select the RO by identifying a set of ROs of the plurality of sets of ROs that is associated with the selected

[0229] SSB, selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO, selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble, wherein the controller circuitry is configured in combination with the transmitter circuitry and the receiver circuity to transmit the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

[0230] Paragraph 32. Circuitry for Infrastructure equipment of a wireless communications network configured to communicate with a communications device via a radio access interface between the communications device and the infrastructure equipment, the circuitry comprising transmitter circuitry configured to transmit signals, receiver circuitry configured to receive signals, and controller circuitry configured in combination with the transmitter circuitry and the receiver circuitry to transmit, for receipt by the communications device, a plurality of synchronisation signal blocks (SSBs); and receive a particular PRACH preamble from the communications device as part of a random access procedure between the communications device and the infrastructure equipment, wherein the PRACH preamble is received in a selected physical random access channel (PRACH) occasion (RO) associated with a selected SSB of the plurality of SSBs, wherein the RO is one of a plurality of ROs, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated with at least one of the plurality of SSBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the type of the selected RO is selected based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO.

[0231] Paragraph 33. A computer program which, when the program is executed by a computer, cause the computer to perform the method of any one of paragraphs 1 to 28.

[0232] Paragraph 34. A non-transitory computer-readable storage medium storing a computer program according to paragraph 33.

[0233] It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and / or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and / or processors may be used without detracting from the embodiments. Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and / or processors.

[0234] 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.

[0235] References

[0236] [1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radio access”, John Wiley and Sons, 2009.

[0237] [2] TR 38.913, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; Study on Scenarios and Requirements for Next Generation Access Technologies (Release 14)”, 3GPP, V14.3.0, August 2017.

[0238] [3] RP -213591, “New SI: Study on evolution of NR duplex operation,” CMCC, RAN#94e, December

[0239] 2021.

[0240] [4] RP -220633, “Revised SID: Study on evolution of NR duplex operation,” CMCC, RAN#95e, March

[0241] 2022.

[0242] [5] RP-234035, “New WID: Evolution of NR duplex operation: Sub-band full duplex (SBFD),” CMCC, RAN# 102, December 2023.

[0243] [6] European Patent No. 3545716.

[0244] [7] TS 38.211 “Physical channels and modulation (Rel-18),” 3GPP, vl8.3.0, June 2024.

[0245] [8] TS 38.213, “Physical layer procedures for control (Rel-18),” 3GPP, vl8.3.0, June 2024.

[0246] [9] European patent application number EP24155834.5.

[0247]

[0010] RP-241650, “Revised WID: Enhancements of network energy savings for NR,” Ericsson, Apple, June 2024.

[0248]

[0011] European patent application number 24187683.8.

Claims

1. CLAIMS1. A method of operating a communications device to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment, the method comprising selecting a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment, selecting a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated at least one of the plurality of S SBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein selecting the RO comprises identifying a set of ROs of the plurality of sets of ROs that is associated with the selected SSB, selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO, selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble, and the method comprises transmitting the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

2. A method according to claim 1, comprising receiving, from the infrastructure equipment, an indication of the selection probability (p) for selecting the first type of RO.

3. A method according to claim 2, wherein the indication of the selection probability for the first RO type is comprised in a Radio Resource Control (RRC) signal, or a Physical Downlink Control Channel (PDCCH) Order instructing the communications device to perform the random access procedure, or in a System Information Block (SIB).

4. A method according to claim 2, comprising determining, based on the selection probability (p) for selecting the first type of RO, the selection probability for selecting the second type of RO (q), wherein the plurality of types of ROs consist of the first type of RO and the second type of RO.

5. A method according to claim 2, comprising receiving, from the infrastructure equipment, an indication of the probability (q) for selecting the second type of RO.

6. A method according to claim 2, wherein the receiving the indication of the selection probability for selecting the first type of RO comprisesreceiving, from the infrastructure equipment, a plurality of candidate selection probabilities for selecting the first RO type and an indication of a downlink signal quality threshold, and the method comprises determining which of the plurality of candidate selection probabilities to use for selecting the first type of RO based on a comparison between a measured downlink signal quality and the indicated downlink signal quality threshold.

7. A method according to claim 6, wherein the indication of the downlink signal quality threshold is received in a Radio Resource Control (RRC) Signal from the infrastructure equipment.

8. A method according to claim 6, wherein the downlink signal quality threshold is a Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ) or Signal to Interference plus Noise Ratio (SINR) threshold.

9. A method according to claim 6, wherein the determining which of the candidate selection probabilities to use for selecting the first type of RO based on a comparison between a measured downlink signal quality and the indicated downlink signal quality threshold comprises determining that the measured downlink signal quality is above the indicated downlink signal quality threshold, and in response, selecting to use a first of the candidate selection probabilities for selecting the first type of RO.

10. A method according to claim 1, comprising determining the selection probability for selecting the first RO type based on a ratio of the number of ROs of the first RO type to the number of ROs of the second RO type plus the number of ROs of the first type within a pre-defined period.

11. A method according to claim 1, wherein the mapping RO type mapping information comprises a bitmap comprising a sequence of bits, the position of each bit in the sequence representing the transmission order of a PRACH preamble, each bit in the sequence mapping the transmission order represented by that bit to one of the plurality of RO types, wherein the selecting a type of RO of the plurality of types of RO based on the RO type mapping information comprises determining, based on the transmission order of the particular PRACH preamble, which of the bits represents the transmission order for the particular PRACH preamble, and selecting the RO type mapped to the determined bit.

12. A method according to claim 11, wherein the sequence of bits comprises n bits,the transmission order of the particular PRACH preamble is m, where m>n, and the bit representing the mthtransmission order is the bit at the xthposition in the sequence of bits where x = remainder of m / n.

13. A method according to claim 1, wherein the RO type mapping information comprises a plurality of bitmaps including a first bitmap comprising a sequence of bits and a second bitmap comprising a sequence of bits, wherein the position of each bit in each sequence represents the transmission order of a PRACH preamble, each bit in the sequence of bits in the first bitmap indicating whether a PRACH preamble with the transmission order represented by that bit can be transmitted in an RO of the first type and each bit in the sequence of bits in the second bitmap indicating whether a PRACH preamble with the transmission order represented by that bit can be transmitted in an RO of the second type, wherein the selecting a type of RO of the plurality of types of RO based on the RO type mapping information comprises determining, based on the transmission order of the particular PRACH preamble, which of the bits in the first bitmap and the second bit map represents the transmission order for the particular PRACH preamble, determining, based on the determined bit in the first bitmap and the second bitmap, that the particular PRACH preamble can be transmitted in one of the first type of RO or the second type of RO, selecting the type of RO in which the particular PRACH preamble can be transmitted.

14. A method according to claim 1, wherein the transmission order of the particular PRACH preamble represents the position of the transmission of the particular PRACH preamble in a sequence of PRACH preamble transmissions by the communications device.

15. A method according to claim 14, wherein the sequence of PRACH preamble transmissions comprise a transmission of the particular PRACH preamble and one or more retransmissions of the particular PRACH preamble.

16. A method according to claim 15, wherein the RO type mapping information indicates a mapping of a transmission order of each of the PRACH preamble transmissions in the sequence to one of the plurality of types of RO, wherein the first transmission of the particular PRACH preamble in the sequence is mapped to the first type of RO and the first retransmission of the particular PRACH preamble in the sequence is mapped to the second type of RO.

17. A method according to claim 14, wherein selecting a type of RO of the plurality of types of RO based on the selection probability for selecting each of the plurality of types of RO comprises selecting the type of RO further based on probability mapping information, wherein the probability mapping information indicates a mapping of the transmission order of each of the PRACH preamble transmissions in the sequence to the selection probability for one of the plurality of types of RO.

18. A method according to claim 17, wherein the probability mapping information indicates that the selection probability for one of the plurality of types of RO should be applied alternately to the first RO type and the second RO type in tandem with the transmission order.

19. A method according to claim 1, wherein the method comprises determining that the random access procedure is a contention based random access procedure (CBRA), or determining that the random access procedure is a contention free random access procedure (CFRA).

20. A method according to claim 1, wherein the selecting a type of RO of the plurality of types of RO comprises selecting the first type of RO based on the selection probability for selecting each of the plurality of types of RO or the RO type mapping information, receiving, from the infrastructure equipment, an indication to select the second type of RO, and overriding the selection of the first type of RO to select the second type of RO .

21. A method according to claim 1 , wherein the selecting a type of RO of the plurality of types of RO based on the selection probability for selecting each of the plurality of types of RO or the RO type mapping information comprises determining that the communications device has not received an instruction from the infrastructure equipment to select a particular type of RO.

22. A method according to claim 1 , wherein the selecting a type of RO of the plurality of type s of RO comprises determining that the transmission of the particular PRACH preamble is a not a retransmission of the particular PRACH preamble.

23. A method according to claim 1, wherein the selection probability for selecting the first RO type is higher than the selection probability for selecting the second RO type.

24. A method according to claim 23, wherein the selection probability for selecting the first type of RO is equal to a number of communications devices in a predefined area capable of using the first type of RO divided by the sum of the number of communications devices in the predefined area capable of using the first type of RO and the number of communications devices in the predefined area capable of using the second type of RO.

25. A method according to claim 24, wherein the pre-defined area is defined by a cell provided by the infrastructure equipment of the wireless communications network.

26. A method according to claim 1, wherein the first RO type is an SBFD RO which is partially or fully contained in SBFD symbols of the radio access interface, and the second RO type is a non-SBFD RO which is contained within non-SBFD uplink symbols of the radio access interface, or vice versa.

27. A method according to claim 1, wherein the first RO type is an RO belonging to a configuration of ROs which can be deactivated or activated for use by the communications device, and the second RO type is an RO belonging to a configuration of ROs which cannot be dynamically activated or deactivated, or vice versa.

28. A method of operating infrastructure equipment of a wireless communications network configured to communicate with a communications device via a radio access interface between the communications device and the infrastructure equipment, the method comprising transmitting, for receipt by the communications device, a plurality of synchronisation signal blocks (SSBs); and receiving a particular PRACH preamble from the communications device as part of a random access procedure between the communications device and the infrastructure equipment, wherein the PRACH preamble is received in a selected physical random access channel (PRACH) occasion (RO) associated with a selected SSB of the plurality of SSBs, wherein the RO is one of a plurality of ROs, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated with at least one of the plurality of SSBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the type of the selected RO is selected based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO.

29. A communications device configured to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment, the communications device comprising a transmitter configured to transmit signals, a receiver configured to receive signals, and a controller configured in combination with the transmitter and the receiver to select a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment,select a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated at least one of the plurality of S SBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the controller is configured in combination with the transmitter and the receiver to select the RO by identifying a set of ROs of the plurality of sets of ROs that is associated with the selected SSB, selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO, selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble, wherein the controller is configured in combination with the transmitter and the receiver to transmit the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

30. Infrastructure equipment for a wireless communications network configured to communicate with a communications device via a radio access interface between the communications device and the infrastructure equipment, the infrastructure equipment comprising a transmitter configured to transmit signals, a receiver configured to receive signals, and a controller configured in combination with the transmitter and the receiver to transmit, for receipt by the communications device, a plurality of synchronisation signal blocks (SSBs); and receive a particular PRACH preamble from the communications device as part of a random access procedure between the communications device and the infrastructure equipment, wherein the PRACH preamble is received in a selected physical random access channel (PRACH) occasion (RO) associated with a selected SSB of the plurality of SSBs, wherein the RO is one of a plurality of ROs, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated with at least one of the plurality of SSBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the type of the selected RO is selected based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO.

31. Circuitry for a communications device configured to communicate with infrastructure equipment of a wireless communications network via a radio access interface between the communications device and the infrastructure equipment, the circuitry comprising transmitter circuitry configured to transmit signals, receiver circuitry configured to receive signals, and controller circuitry configured in combination with the transmitter circuitry and the receiver circuitry to select a synchronisation signal block (SSB) of a plurality of SSBs for performing a random access procedure with the infrastructure equipment, select a physical random access channel (PRACH) occasion (RO) of a plurality of ROs in which to transmit a particular PRACH preamble, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated at least one of the plurality of S SBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the controller circuitry is configured in combination with the transmitter circuitry and the receiver circuitry to select the RO by identifying a set of ROs of the plurality of sets of ROs that is associated with the selected SSB, selecting a type of RO of the plurality of types of RO based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO, selecting an RO of the selected type of RO from the identified set of ROs on which to transmit the PRACH preamble, wherein the controller circuitry is configured in combination with the transmitter circuitry and the receiver circuity to transmit the particular PRACH preamble to the infrastructure equipment in the selected RO as part of the random access procedure.

32. Circuitry for Infrastructure equipment of a wireless communications network configured to communicate with a communications device via a radio access interface between the communications device and the infrastructure equipment, the circuitry comprising transmitter circuitry configured to transmit signals, receiver circuitry configured to receive signals, and controller circuitry configured in combination with the transmitter circuitry and the receiver circuitry to transmit, for receipt by the communications device, a plurality of synchronisation signal blocks (SSBs); and receive a particular PRACH preamble from the communications device as part of a random access procedure between the communications device and the infrastructure equipment, wherein the PRACH preamble is received in a selected physical random access channel (PRACH) occasion (RO) associated with a selected SSB of the plurality of SSBs,wherein the RO is one of a plurality of ROs, wherein the plurality of ROs comprise a plurality of sets of ROs, each of the plurality of sets of ROs being associated with at least one of the plurality of SSBs, each of the plurality of sets of ROs comprising ROs of a plurality of different types including one or more ROs of a first RO type and one or more ROs of a second RO type, wherein the type of the selected RO is selected based on a selection probability for selecting each of the plurality of types of RO or RO type mapping information indicating a mapping of a transmission order of the particular PRACH preamble to at least one of the plurality of types of RO.

33. A computer program which, when the program is executed by a computer, cause the computer to perform the method of claim 1.

34. A non-transitory computer-readable storage medium storing a computer program according to claim 33.

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