Methods, communications devices, and infrastructure equipment

Abstract

A method of operating a communications device to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment is provided. The method comprises transmitting, to the infrastructure equipment, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH. The transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment. The trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB). The on-demand SIB comprises at least information required by the communications device to perform an initial access procedure with the infrastructure equipment. Alternatively, the trigger indication comprises an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB. The already-on SIB comprises at least information required for the communications device to perform the initial access procedure with the infrastructure equipment. The method comprises receiving the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructure equipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

Description

[0001] METHODS, COMMUNICATIONS DEVICES, AND INFRASTRUCTURE EQUIPMENT

[0002] BACKGROUND Field of Disclosure

[0003] The present disclosure relates to communications devices and infrastructure equipment of wireless communications networks and methods of operating such communications devices and infrastructure equipment.

[0004] The present application claims Paris Convention priority from EP patent application number 24158109.9, filed on 16 February 2024, the contents of which are hereby incorporated by reference in their entirety.

[0005] Description of Related Art

[0006] 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.

[0007] 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.

[0008] 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 device, for example supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. Other types of device, for example used for autonomous vehicle communications and for other critical applications, may be characterised by data that should be transmitted through the network with low latency and high reliability. A single device type might also be associated with different traffic profiles / characteristics depending on the application(s) it is running. For example, different consideration may apply for efficiently supporting data exchange with a smartphone when it is running a video streaming application (high downlink data) as compared to when it is running an Internet browsing application (sporadic uplink and downlink data) or being used for voice communications by an emergency responder in an emergency scenario (data subject to stringent reliability and latency requirements).

[0009] 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. The desire to support these new use-cases and scenarios gives rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

[0010] SUMMARY OF THE DISCLOSURE

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

[0012] Respective 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 an NR-type 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 is a message flow diagram showing a typical four-step random access (RACH) procedure;

[0020] Figure 5 is a message flow diagram showing a typical two-step RACH procedure;

[0021] Figure 6 schematically illustrates the components of an SSB;

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

[0023] Figure 8 illustrates a part schematic, part message flow diagram representation of a wireless communications system comprising a communications device and infrastructure equipment in accordance with embodiments;

[0024] Figure 9 schematically illustrates an example of a master information block (MIB) in accordance with example embodiments;

[0025] Figure 10 schematically illustrates an example of an Abstract Syntax Notation One (ASN1) message carried in a Broadcast Channel (BCH) in accordance with example embodiments;

[0026] Figure 11 is a flow diagram illustrating a method of operating a communications device in accordance with example embodiments;

[0027] Figure 12 is a flow diagram illustrating a method of operating infrastructure equipment of a wireless communications network in accordance with example embodiments.

[0028] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] Long Term Evolution Advanced Radio Access Technology (4G)

[0030] 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.

[0031] The network 6 includes a plurality of base stations 1 connected to a core network 2, which may be for example an Evolved Packet Core (EPC). 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.

[0032] 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 (UE), user terminal, mobile radio, communications device, and so forth. Services provided by the core network 2 may include connectivity to the internet or to external telephony services. The core network 2 may further track the location of the communications devices 4 so that it can efficiently contact (i.e., page) the communications devices 4 for transmitting downlink data towards the communications devices 4.

[0033] Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, eNodeBs, eNB, gNodeBs, 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.

[0034] New Radio Access Technology (5G)

[0035] 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],

[0036] 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 be for example referred to as 5GC) which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network 20 may be connected to other networks 30.

[0037] 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.

[0038] 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.

[0039] In terms of broad top-level functionality, the core network 20 connected to the new RAT telecommunications system represented in Figure 2 may be broadly considered to correspond with the core network 2 represented in Figure 1, and the respective central units 40 and their associated distributed units / TRPs 10 may be broadly considered to provide functionality corresponding to the base stations 1 of Figure 1. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the controlling node / central unit and / or the distributed units / TRPs. A communications device 14 is represented in Figure 2 within the coverage area of the first communication cell 12. This communications device 14 may thus exchange signalling with the first central unit 40 in the first communication cell 12 via one of the distributed units / TRPs 10 associated with the first communication cell 12.

[0040] It will further be appreciated that Figure 2 represents merely one example of a proposed architecture for a new RAT based telecommunications system in which approaches in accordance with the principles described herein may be adopted, and the functionality disclosed herein may also be applied in respect of wireless telecommunications systems having different architectures. Thus, certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems / networks according to various different architectures, such as the example architectures shown in Figures 1 and 2. It will thus be appreciated the specific wireless telecommunications architecture in any given implementation is not of primary significance to the principles described herein. In this regard, certain embodiments of the disclosure may be described generally in the context of communications between network infrastructure equipment / access nodes and a communications device, wherein the specific nature of the network infrastructure equipment / access node and the communications device will depend on the network infrastructure for the implementation at hand. For example, in some scenarios the network infrastructure equipment / access node may comprise a base station, such as an LTE-type base station 1 as shown in Figure 1 which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a control unit / controlling node 40 and / or a TRP 10 of the kind shown in Figure 2 which is adapted to provide functionality in accordance with the principles described herein.

[0041] 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.

[0042] 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.

[0043] As shown in Figure 3, the TRP 10 also includes a network interface 50 which connects to the DU 42 via a physical interface 16. The network interface 50 therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 40 to the core network 20. The interface 46 between the DU 42 and the CU 40 is known as the F 1 interface which can be a physical or a logical interface. The Fl interface 46 between CU and DU may operate in accordance with 3GPP technical specifications [3] and [4], 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.

[0044] As will be appreciated by those acquainted with 5G architecture, the CU 40 may be a logical node which hosts Radio Resource Control (RRC) protocols, Service Data Adaptation Protocols (SDAP), and Packet Data Convergence Protocols (PDCP) of a gNB. Alternatively, the CU 40 may be a logical node which hosts RRC and PDCP protocols of an en-gNB (which is a gNB that is able to connect with both EPC and eNBs and can be understood as being, for example, a secondary node (SgNB) used in dual connectivity scenarios). The CU 40 partly controls the operation of one or more DUs 40 and terminates the Fl interface 46 for the DUs that it controls. The DU 42 may be a logical node which hosts Radio Eink Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of a gNB or en-gNB. The operation of the DU 42 is partly controlled by the CU 40 for which the DU 42 terminates the Fl interface 46.

[0045] Although not shown in Figures 2 or 3, it will be familiar to those acquainted with 5G architecture that the CU 40 may be further split into a CU-CP which performs the control plane functions of the CU 40 and a CU-UP which performs the user plane functions of the CU 40 (see for example, [5]). In more detail, the CU-CP may be a logical node hosting an RRC protocol and a control plane part of a PDCP protocol of the CU 40 for the gNB or en-gNB. The CU-CP terminates an El interface connected with the CU-UP and an Fl-C interface connected with the DU 42. As will be appreciated, the Fl-C interface carries control plane signalling of the Fl interface 46. The CU-UP may be a logical node which hosts a user plane part of a PDCP protocol of the CU 40 for an en-gNB. Alternatively, the CU-UP may be a logical node which hosts a user plane part of the PDCP protocol and an SDAP protocol of the CU 40 for a gNB. The CU-UP terminates an El interface connected with the CU-CP and an Fl-U interface connected with the DU 42. As will be appreciated, the Fl-U interface carries user plane signalling of the Fl interface 46.

[0046] Random Access (RACH) Procedures

[0047] In wireless communications networks, such as LTE and NR type networks, a random access procedure may be used by communications devices to perform initial access with the wireless communications network. The random access procedure involves the communications device transmitting a preamble on a physical random access channel (PRACH), and so the procedure is commonly referred to as a RACH or PRACH procedure / process. The RACH procedure may be a two-step RACH procedure or a four-step RACH procedure as described in more detail below.

[0048] In addition, there exists Radio Resource Control (RRC) modes for communications devices. For example, it is common to support an RRC idle mode (RRC IDLE) and an RRC connected mode (RRC CONNECTED). A communications device in the RRC IDLE mode may transition to RRC CONNECTED mode, for example because it needs to transmit uplink data or respond to a paging request, by undertaking a random access procedure.

[0049] In addition to a communications device deciding itself to initiate a random access procedure to connect to the wireless communications network, it is also possible for the wireless communications network, e.g. a base station, to instruct a communications device in an RRC CONNECTED mode to initiate a random access procedure by transmitting to the communications device an instruction to do so. Such an instruction is sometimes referred to as a PDCCH order (Physical Downlink Control Channel order). There are various scenarios in which a network-triggered RACH procedure (PDCCH order) may arise.

[0050] Figure 4 shows atypical four-step RACH procedure used in LTE systems such as that described by reference to Figure 1 which could also be applied to an NR wireless communications system such as that described by reference to Figure 2. A communications device (or UE), which may be in an RRC IDLE mode for example, may have some data which it needs to send to the network. To do so, the UE sends a random access preamble 51 (message 1) to a gNB. This random access preamble 51 indicates the identity of the communications device to the gNB, such that the gNB can address the communications device during later stages of the RACH procedure. Assuming the random access preamble 51 is successfully received by the gNB, the gNB will transmit a random access response 52 message (message 2) to the communications device(s) based on the identity indicated in the received random access preamble 51. The random access response 52 message carries a further identity which is assigned by the gNB to identify the communications device, as well as a timing advance value such that the communications device can change its timing to compensate for the round trip delay caused by its distance from the gNB and grant uplink resources for the communications device to transmit the data in.

[0051] Following the reception of the random access response message 52, the communications device transmits the scheduled transmission of data 53 to the gNB (message 3), using the identity assigned to it in the random access response message 52. Assuming there are no collisions with other UEs, which may occur if another UE and the communications device send the same random access preamble 51 to the gNB at the same time and using the same frequency resources, the scheduled transmission of data 53 is successfully received by the gNB. The gNB will respond to the scheduled transmission 53 with a contention resolution message 54 (message 4).

[0052] In 5G / NR systems, an “inactive” RRC mode (RRC INACTIVE) may be used, where a UE is able to start data transfer with a low delay in the RRC INACTIVE mode without transition to the RRC CONNECTED mode. Various possible solutions have been proposed to permit this, one of which is a two-step RACH procedure. As will be appreciated, compared with the four-step RACH process, the two-step RACH process can provide a facility for transmitting data more quickly. Accordingly, it has been proposed to develop general MAC procedures covering both physical layer and higher layer aspects for the two-step RACH process. In general, the benefit of the two-step RACH procedure compared with the four-step RACH procedure is to reduce the time it takes for connection setup / resume procedure. For example, in an ideal situation, the two-step RACH will reduce the latency by halving the number of steps from four to two for initial access UEs. In addition, it is considered that a two-step RACH procedure has potential benefits for channel access in NR unlicensed spectrum (NR-U).

[0053] Broadly, the two-step RACH allows the combination of the transmission of the random access preamble 51 with the transmission of data 53 of Figure 4 as an initial transmission (“Message A” or “MsgA”), and similarly the combination of the transmission of the random access response 52 and contention resolution message 54 as a response (“Message B”, or “MsgB”). A fallback procedure may be provided to allow a RACH procedure which is started according to the specifications for a two-step RACH to instead proceed according to the four-step RACH procedure. Two-step RACH may be performed by communications devices in the RRC IDLE, RRC INACTIVE or RRC CONNECTED modes.

[0054] A message flow diagram illustrating the two-step RACH process is shown in Figure 5. As its name suggests, in the two-step RACH process, there are only two-steps as noted above. In the first step, the UE transmits a Message A 55 which comprises a RACH preamble 56 and data 57. The data 57 is transmitted on a shared uplink channel, such as a physical uplink shared channel, PUSCH that in a four-step RACH procedure would be transmited in Message 3. More specifically, the choice of a particular preamble 56 may pre-configure the communications device to transmit the data 57 in pre-configured resources of the uplink shared channel. In the second step, the base station, having successfully received the Message A 55, responds with a Message B 58 which incorporates both a RAR, as would be carried by message 2 of the four-step RACH procedure described above, and the corresponding contention resolution and / or data (PDSCH) that in a four-step RACH procedure would be transmited in Message 4.

[0055] Synchronisation Signal Block (SSB)

[0056] As will be known to one skilled in the art, the Synchronisation Signal Block (SSB) (also called as SS / PBCH block) is used for initial access and cell reselection. An example of an SSB is schematically illustrated in Figure 6.

[0057] 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 4 OFDM symbols and 240 subcarriers. The PSS and SSS each occupy 127 subcarriers. The PBCH occupies two OFDM symbols of 240 subcarriers and also 2 blocks of 48 subcarriers at the top and botom of the SSS. The SSB may be configured with a periodicity, PSSB, of between 5 ms and 160 ms. For initial cell selection, the UE assumes a periodicity of 20ms.

[0058] An SSB burst set comprises a set of one or more time-multiplexed SSBs. Each SSB is transmited 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 transmited.

[0059] 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 8 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 transmited using a different downlink beam. In this example, 2 SSBs are configured per slot within 4 slots. Furthermore, the burst set is transmited with a periodicity, PSSB, of 20 ms. Although not shown in Figure 7, the SSB burst set is transmited by infrastructure equipment of a wireless communications network (such as a gNB) and received by a communications device (such as a UE).

[0060] 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.

[0061] 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 transmited provided this measured RSRP is above a threshold (such as rsrp-ThresholdSSB).

[0062] 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 transmited. Alternatively, or in addition, the measurement of the RSRP of an S SB may comprise measuring the RSRP on resource elements where PBCH DMRS is transmitted.

[0063] 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.

[0064] In initial access, after determining the uplink beam, the UE initiates a RACH procedure by transmitting PRACH on the determined uplink beam. For example, the UE may transmit message 51 or message 55 on the determined uplink beam. The PRACH may be transmitted on PRACH resources which have been configured for the UE to transmit the PRACH as part of initial access (an example of “legacy PRACH resources”). For example, the PRACH may be transmitted in one of a periodicity configuration of PRACH Occasions (ROs) configured for transmitting the PRACH.

[0065] Network Energy Saving (NES)

[0066] 3GPP is currently discussing network energy saving (NES). By reducing energy consumption in wireless communications networks, the impact of wireless communications on the environment can be reduced. For example, if less energy is consumed in wireless communications networks, fewer fossil fuels are burned, there are fewer greenhouse gas emissions and therefore environmental sustainability is improved. Furthermore, the reduction of energy consumption in wireless communications networks can reduce costs incurred by network operators.

[0067] 5G / NR can handle advanced services and applications requiring very high data rates (for example, XR). Additionally, 5G / NR networks are becoming denser, using more antennas, and utilising larger bandwidths and an increasing number of frequency bands. Therefore, in at least some cases, energy consumption in 5G / NR is increasing. Since 5G / NR is becoming increasingly pervasive across various industries and geographical areas, it is becoming increasingly important to reduce the environmental impact of 5G / NR networks. NES solutions are therefore required.

[0068] In addition, energy consumption has become a key part of the operating expenses (OPEX) for network operators. According to a report from the Global System for Mobile Communications (GSMA) [6], the energy cost of mobile networks accounts for approximately 23% of total operator cost. Most of the energy consumption comes from the radio access network and in particular from the Active Antenna Unit (AAU), with data centres and fibre transport accounting for a smaller share of the energy consumption. The energy consumption of a radio access network can be split into two parts: (1) a dynamic part which is only consumed when data transmission / reception is ongoing, and (2) a static part which is consumed all the time to maintain the necessary operation of the radio access network equipment, even when data transmission / reception is not on-going. Further details on NES can be found in [7],

[0069] In Release 19 of the 3GPP standards, an NES work item has been approved ([8]). The objectives of the work item are the following:

[0070] 1. Specify procedures and signaling method(s) to support on-demand SSB SCell operation for UEs in connected mode configured with CA, for both intra- / inter-band CA.

[0071] 2. Study procedures and signaling method(s) to support on-demand SIB1 for UEs in idle / inactive mode, including:

[0072] 3. Specify adaptation of common signal / channel transmissions. NES System Information (SI)

[0073] As will be understood by a person skilled in the art, system information is transmitted by infrastructure equipment of a wireless communications network to communications devices in a cell provided by the infrastructure equipment. The system information informs the communications devices on how to access services provided by the wireless communications network. The system information comprises a master information block (MIB), system information block type 1 (SIB1) and a plurality of other system information blocks (SIBs). The MIB is broadcasted in the PBCH in each SSB. The MIB comprises information required to decode SIB1. SIB1 comprises information required for performing initial access (for example, random access parameters such as time / frequency resources for PRACH (e.g an RO configuration), preambles, or barring parameters). Therefore, MIB and SIB1 together provide all the information which is required for initial access Accordingly, SIB 1 is defined as the “remaining minimum SI”. SIB1 may comprise scheduling information of the other SIBs (for example, mapping of SIBs to SI message, periodicity of other SIBs and Sl-window size). SIB1 is periodically broadcasted over a downlink shared channel (DL-SCH), but may be provided on-demand as explained below. Periodically broadcasted SIB1 is typically an “always-on” signal. The information comprised in the other SIBs is not required for initial access SIB1 may comprise an indication of whether the other SIBs are provided on- demand, in which case, SIB 1 may also comprise an indication of a PRACH configuration for use by the UE to request the other SIBs. SIB1 may also comprise radio resource configuration information common to all communications devices in the cell in which the SIB 1 is transmitted. SIB 1 may also comprise cell barring information.

[0074] The other SIBs may comprise one or more of: SIB2-SIB18 and SIBpos.

[0075] — SIB2 comprises cell re-selection information, mainly related to the serving cell;

[0076] — SIB3 comprises information about the serving frequency and intra-frequency neighbouring cells relevant for cell re-selection (including cell re-selection parameters common for a frequency as well as cell specific re-selection parameters);

[0077] — SIB4 comprises information about other NR frequencies and inter-frequency neighbouring cells relevant for cell re-selection (including cell re-selection parameters common for a frequency as well as cell specific re-selection parameters), which can also be used for NR idle / inactive measurements;

[0078] — SIB5 comprises information about E-UTRA frequencies and E-UTRA neighbouring cells relevant for cell re-selection (including cell re-selection parameters common for a frequency as well as cell specific re-selection parameters);

[0079] — SIB6 comprises an ETWS primary notification;

[0080] — SIB7 comprises an ETWS secondary notification;

[0081] — SIB8 comprises a CMAS warning notification;

[0082] — SIB9 comprises information related to GPS time and Coordinated Universal Time (UTC);

[0083] — SIB 10 comprises the Human-Readable Network Names (HRNN) of the NPNs listed in SIB1;

[0084] — SIB11 comprises information related to idle / inactive measurements;

[0085] — SIB 15 comprises information related to disaster roaming;

[0086] — SIB 16 comprises slice-based cell reselection information;

[0087] — SIB 17 comprises information related to TRS configuration for UEs in

[0088] RRC IDLE / RRC INACTIVE;

[0089] — SIBpos comprises positioning assistance data as defined in TS 37.355 and TS 38.331; — SIB 18 comprises information related to the Group IDs for Network selection (GINs) associated with SNPNs listed in SIB1.

[0090] Further information regarding existing SI can be found in TS38.300 vl8.0.0, the contents of which are hereby incorporated by reference in their entirety.

[0091] In the NES study phase of Release- 18 of the 3GPP standards, it has been suggested to introduce an on- demand SIB 1. In other words, instead of infrastructure equipment of the wireless communications network periodically broadcasting SIB1, it has been proposed for infrastructure equipment (i.e. NES infrastructure equipment) to broadcast SIB 1 in response to a request (or trigger such as a wake-up signal) from a UE. Since the SIB1 would be transmitted less often, network energy savings would be increased. However, the details of such an on-demand SIB1 have not yet been discussed. Furthermore, existing UEs which do not support NES (also referred to as “non-NES UEs”) are configured to expect the SIB 1 to be periodic. Since non-NES UEs are already deployed in wireless communications networks, it is important that NES solutions do not significantly impact performance for non-NES UEs.

[0092] There is therefore a need for improved methods, communications devices and infrastructure equipment which can provide network energy savings without significantly impacting non-NES communications devices.

[0093] PRACH Resource Trigger for SIB

[0094] Figure 8 shows a part schematic, part message flow diagram representation of a wireless communications system in accordance with example embodiments. The wireless communications system comprises a communications device 62 (e.g. a UE 14) and infrastructure equipment 64 (e.g. a gNB) of a wireless communications network.

[0095] The communications device 62 comprises a transceiver 62.1 (or transceiver circuitry) and a controller 62.2 (or controller circuitry). The infrastructure equipment 64 comprises a transceiver 64.1 (or transceiver circuitry) and a controller 64.2 (or controller circuitry). The transceivers 62. 1, 64. 1 are configured to transmit and receive signals. The transceivers 62.1, 64.1 (or transceiver circuitry) may each comprise a separate transmitter or receiver (or separate transmitter and receiver circuitry), or the transceivers 62. 1, 64.1 (or transceiver circuitry) may each comprise a device (or circuitry) configured to perform both transmission and reception. Each of the controllers may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc.

[0096] The infrastructure equipment 64 provides a wireless access interface for communications with the communications device 62. For example, the wireless access interface may provide communications resources for communications between the infrastructure equipment 64 and the communications device 62.

[0097] As shown in the example of Figure 8, the controller 62.2 of the communications device 62 is configured to control the transceiver 62. 1 of the communications device 62 to transmit 66, to the infrastructure equipment 64, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH.

[0098] The transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment 64. The trigger indication comprises an indication to the infrastructure equipment 64 to start transmitting an on-demand system information block (SIB). The on-demand SIB comprises information required by the communications device 62 to perform an initial access procedure with the infrastructure equipment 64. The on-demand SIB may be one of a plurality of periodic instances of the on-demand SIB transmitted by the infrastructure equipment 64 in response to the infrastructure equipment 64 receiving the PRACH.

[0099] Alternatively, the trigger indication comprises an indication to the infrastructure equipment 64 to increase a frequency with which the infrastructure equipment 64 is transmitting an already-on SIB. In this case, the already-on SIB comprises information required for the communications device 62 to perform the initial access procedure with the infrastructure equipment 64. It will be appreciated that increasing the frequency of the already-on SIB is not referring to a frequency of a radio wave on which the SIB is transmitted but is referring to a frequency of how often the already-on SIB is transmitted. Therefore, increasing the frequency of the already-on SIB means that the already-on SIB is transmitted more often than it was before the frequency was increased. Alternatively stated, increasing the frequency of the already-on SIB may be referred to as reducing a time interval between successive transmissions of the already-on SIB. The frequency with which the already-on SIB is transmitted may therefore be alternatively stated as the number of times the already-on SIB is transmitted in a given period.

[0100] An “already-on” SIB is an SIB which the infrastructure equipment 64 is already transmitting periodically before receiving the PRACH. For example, the already-on SIB may be an “always-on” SIB which is periodically transmitted by the infrastructure equipment 64.

[0101] The communications device 62 may determine to transmit the PRACH because the communications device 62 has determined that it requires information in the SIB 1. The communications device may require information in the SIB1 for a number of reasons including for example: the communications device 62 has uplink data to transmit, the communications device 62 wants to request other SIBs, the communications device 62 moves to another cell and needs the configuration of the new cell. In one example, a user of the communications device 62 may switch on the communications device 62. Then, the communications device 62 scans the cell in which it is located by reading SSB. The communications device 62 may determine, based on the MIB in the SSB, that there is no SIB1 being transmitted in the cell. Therefore, the communications device 62 determines to transmit the PRACH in order to trigger SIB1 transmission.

[0102] As shown in Figure 8, the controller 64.2 of the infrastructure equipment 64 controls the transceiver 64.1 of the infrastructure equipment 64 to receive 66 the PRACH in the PRACH resources. The controller 64.2 of the infrastructure equipment 64 controls the transceiver 64. 1 of the infrastructure equipment 64 to transmit 68 the on-demand SIB to the communications device 62 if the trigger indication comprises the indication to transmit the on-demand SIB. Alternatively, the controller 64.2 of the infrastructure equipment 64 controls the transceiver 64.1 of the infrastructure equipment 64 to transmit 68 the already- on SIB to the communications device 62 with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

[0103] As shown in Figure 8, the controller 62.2 of the communications device 62 controls the transceiver 62.1 of the communications device 62 to receive 68 the on-demand SIB from the infrastructure equipment 64 if the trigger indication comprises the indication to transmit the on-demand SIB. Alternatively, the controller 62.2 of the communications device 62 controls the transceiver 62. 1 of the communications device 62 to receive 68 the already-on SIB from the infrastructure equipment 64 with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

[0104] The SIB (either the on-demand or already-on SIB) provides information required for initial access. In existing systems, the SIB which provides information required for initial access is referred to as “SIB1”. Indeed, example embodiments will be described below with reference to SIB 1. However, example embodiments are not limited to the SIB1 currently defined in 3GPP specifications and are equally applicable to any future SIB which comprises information required for initial access. Therefore, although example embodiments will refer specifically to SIB1, it should be understood that the present disclosure is not so limited and any SIB containing information required for initial access may be used.

[0105] In general, PRACH resources are referring to communications resources of the wireless access interface which are configured for transmitting PRACH. For example, PRACH resources may comprise a periodic configuration of PRACH Occasions (ROs). As will be known to a person skilled in the art, the terms “PRACH occasions” and “RACH occasions” are used interchangeably. Each of the ROs are for transmitting one or more PRACH preambles. In some cases, each RO is associated with a set of one or more PRACH preambles in the sense that only PRACH preambles from the set can be transmitted in that RO. In cases where the PRACH resources comprise a plurality of ROs, the transmission of the PRACH in a PRACH Occasion is referring to transmitting a PRACH preamble in that RO.

[0106] The infrastructure equipment 64 may be configured to start transmitting an on-demand SIB 1 in response to receiving the PRACH.

[0107] Alternatively, the infrastructure equipment 64 may be configured to increase the transmission frequency of the always-on SIB1 in response to receiving the PRACH. In some embodiments, before receiving the PRACH, the infrastructure equipment 64 transmits the already-on SIB 1 with a frequency which is lower than the frequency at which existing non-NES infrastructure equipment transmit SIB1. For example, existing non-NES infrastructure equipment may transmit SIB1 every 160 ms. By contrast, the infrastructure equipment 64, before receiving the PRACH, may transmit the already-on SIB 1 such that time interval between successive SIB1 transmissions is greater than 160 ms (for example, 320 ms or 640 ms). The infrastructure equipment 64 may be regarded as NES infrastructure equipment because SIB1 can be transmitted less often compared to existing non-NES infrastructure equipment. As mentioned above, the trigger indication may comprise an indication to increase the frequency with which the infrastructure equipment 64 transmits the already-on SIB 1. The increased frequency may be a frequency such that the time interval between successive transmissions of the already-on SIB1 is the same as for existing non- NES infrastructure equipment. For example, the frequency may be increased such that there is 160ms between successive SIB1 transmissions. In some embodiments, the infrastructure equipment 64 may transmit the already-on SIB 1 with the increased frequency for a pre-defined time period. After the predefined time period, the infrastructure equipment 64 may revert to transmitting the already-on SIB 1 with the frequency with which the already-on SIB1 was being transmitted before the PRACH was received. In cases where the infrastructure equipment 64 is configured to transmit an on-demand SIB1, the communications device 62 is configured to trigger and receive SIB 1. In cases where the infrastructure equipment 64 is configured to transmit a already-on SIB 1 with frequency which is lower than existing non-NES infrastructure equipment, the communications device 62 is configured to trigger an increase in the frequency and to receive the SIB1 with the increased frequency. Therefore, in either case, the communications device 62 may be regarded as an NES communications device because it can support NES functions of the infrastructure equipment 64 (such as on-demand SIB 1 or already-on SIB 1 with different periodicity compared to existing non-NES infrastructure equipment).

[0108] The PRACH which is transmitted to provide the trigger indication to the infrastructure equipment 64 may be referred to as a “trigger PRACH” throughout this disclosure. The PRACH resources configured for transmitting the trigger PRACH may be referred to as “trigger PRACH resources”. In some embodiments, the trigger PRACH resources are provided for the communications device 62 in addition to legacy PRACH resources used for transmitting PRACHs for other purposes. Examples of such purposes include transmitting another PRACH as part of initial access, or, if the communications device 62 is in an RRC connected mode, requesting an updated on-demand SIB1. In some embodiments, the legacy PRACH resources are re-used for transmitting the trigger PRACH. In other words, the trigger PRACH resources and the legacy PRACH resources may be the same resources.

[0109] The trigger PRACH resources may be pre-configured for the communications device 62, or the infrastructure equipment 64 may transmit an indication of the trigger PRACH resources to the communications device 62.

[0110] As mentioned previously non-NES gNBs broadcast SIB1 with a relatively high frequency (e.g a 160 ms s time interval between successive transmissions of SIB1). By using PRACH resources to transmit a trigger for an on-demand SIB1, the SIB1 is only transmitted by the infrastructure equipment 64 when it is required by the communications device 62, therefore reducing network energy consumption. In cases where the infrastructure equipment 64 is configured to transmit an already-on SIB1, the transmission of a trigger PRACH triggers the infrastructure equipment 64 to increase the frequency with which the SIB 1 is transmitted. Since the frequency is only increased when the communications device 62 requires the SIB1, the number of SIB Is transmitted by the infrastructure equipment 64 is reduced on average, therefore reducing network energy consumption. Furthermore, the use of PRACH resources for the trigger reduces impact to the performance of non-NES UEs.

[0111] For ease of explanation, embodiments will be described below with reference to UEs and gNBs. However, the present disclosure is not so limited, and references to “UE” may be replaced with “communications device” and references to “gNB” may be replaced with “infrastructure equipment of a wireless communications network”.

[0112] Furthermore, references to “NES UEs” should be understood as generally referring to communications devices supporting on-demand SIB1, or supporting periodic SIB1 where the periodicity can be changed for example, in response to a trigger from the communications device. References to NES gNBs should be understood as generally referring to infrastructure equipment of a wireless communications network supporting on demand-SIBl, or supporting periodic SIB1 transmissions where the frequency of transmission can be changed for example, in response to a trigger from the communications device. UEs and gNBs which do not support either on-demand SIB 1 or a periodic SIB 1 where the frequency of transmission can be changed for example, in response to a trigger from the communications device will be referred to as “non-NES UEs” and “non-NES gNBs”. Non-NES gNBs broadcast only legacy SIB1 with a fixed periodicity whilst non-NES UEs only expect to receive SIB 1 with a fixed periodicity.

[0113] Triggering On-Demand SIB1

[0114] Different Trigger PRACH resources and Legacy PRACH Resources

[0115] In some embodiments, PRACH resources configured for transmitting a PRACH to trigger the on-demand SIB1 transmission (“trigger PRACH resources”) may be configured for an NES UE in addition to PRACH resources used for other purposes (such as initial access) with a NES gNB (“legacy PRACH resources”). In other words, the trigger PRACH resources and the legacy PRACH resources are different. In such embodiments, the trigger PRACH resources may be reserved for transmitting only a trigger PRACH and are not available to transmit a PRACH for other purposes (such as initial access).

[0116] In such embodiments, the trigger PRACH resources may be preconfigured for the NES UE (e.g. hardwired into the NES UE) or the NES UE may receive configuration signalling of the trigger PRACH resources from the NES gNB. The trigger PRACH resources may comprise a periodic configuration of PRACH Occasions (ROs) with each of the ROs associated with a plurality of PRACH preambles.

[0117] The indication of the configuration of the trigger PRACH resources from the NES gNB may indicate:

[0118] 1) A configuration of PRACH occasions (ROs) configured for transmitting the trigger PRACH, a target preamble receiver power level at the gNB, and a number of SSBs per PRACH occasion. The ROs configured for transmitting the trigger PRACH are time / frequency resources in the wireless access interface provided by the gNB for transmitting the trigger PRACH;

[0119] 2) A periodicity of the trigger PRACH configuration; and

[0120] 3) A preamble configuration. For example, a reserved preamble to use for transmitting the trigger PRACH.

[0121] The indication of configuration of the trigger PRACH resources may comprise an indication of a position of the trigger PRACH resources relative to a position of an SSB. For example, the trigger PRACH resources may be indicated as being a particular time and / or frequency offset from a position of an SSB.

[0122] In cases where multiple NES UEs select the same preamble in the same RO for transmitting a trigger PRACH, there may be a collision between the trigger PRACHs transmitted by the NES UEs. This may mean that the NES gNB cannot decode the collided PRACHs, and therefore cannot determine which NES UEs in a cell provided by the NES gNB transmitted the trigger PRACH. In accordance with example embodiments, the trigger PRACH resources may be reserved only for transmitting the trigger PRACH. In such embodiments, the NES gNB may broadcast the on-demand SIB1 in response to detecting energy in the trigger PRACH resources since the NES gNB knows that at least one of the NSE UEs in the cell transmitted a trigger PRACH.

[0123] Common Trigger PRACH resources for Multiple gNBs

[0124] In some embodiments, the trigger PRACH resources may be arranged to be common for a set of cells (such as a set of cells within a particular area having the same area ID or a set of cells in a list of cell IDs).

[0125] In some embodiments, where the trigger PRACH resources are reserved for transmitting a trigger PRACH and the trigger PRACH resources are common for a set of cells, an NES UE in a different cell may receive SIB1 from a non-NES gNB or a NES gNB before. The received SIB1 may comprise an indication of a configuration of trigger PRACH resources common to the set of cells. The NES UE may store the indication of the configuration of the trigger PRACH resources and use the trigger PRACH resources to transmit a trigger PRACH when the NES UE wants to gain access to one of the cells in the set. Such embodiments are particularly advantageous when the cell in which the NES UE received the SIB1 comprising the indication of the configuration of the trigger PRACH resources overlaps with one or more of the set of cells. For example, the cell in which the NES UE receives the SIB1 may be a large cell and the NES UE may use the stored indication of the configuration of the trigger PRACH resources to transmit a trigger PRACH in a small cell underlying the large cell. The indication of the configuration of the PRACH resources may comprise one or more of: a delta SIB 1 of the small cell configuration, a trigger PRACH resource configuration delta of the small cell configuration and the trigger PRACH resource configuration to trigger SIB1 from the small cell.

[0126] In some embodiments, the trigger PRACH resources are the same as the legacy PRACH resources. In some such embodiments, the PRACH resources may be common for a set of cells. In some embodiments, an NES UE in one of the set of cells transmits a trigger PRACH in the PRACH resources. In response to the trigger PRACH, the NES UE receives an on-demand SIB1 from an NES gNB. The NES UE may then store the SIB 1. When the UE attempts to perform initial access with another one of the cells in the set of cells, the NES UE may use the stored SIB1. Since the NES UE does not need to receive SIB1 again in order to access the new cell, the NES UE does not need to transmit a trigger PRACH in the new cell but can transmit a legacy PRACH (e.g. message 1 or message A). After transmitting the legacy PRACH, the NES UE may optionally continue with the legacy PRACH procedure. In some cases, the NES UE may only continue with the initial access procedure until it receives an updated SIB1 from the new cell.

[0127] In some embodiments, where the trigger PRACH resources are the same as legacy PRACH resources, and the PRACH resources comprise a plurality of ROs each associated with a plurality of preambles, then the preambles associated with each RO may be partitioned. The preambles may be partitioned into preambles reserved for transmitting a trigger PRACH and preambles reserved for legacy purposes such as initial access.

[0128] Target Cell Indication

[0129] In some examples, the trigger RACH transmitted by an NES UE may be received by multiple gNBs. In such cases, each of the gNBs may transmit an on-demand SIB1 to the NES UE. This contributes to network power wastage because the NES UE only requires the SIB1 for one of the cells (i.e. the target cell provided by the gNB with the best RSRP to the NES UE). Therefore, in accordance with example embodiments, a preamble of a trigger PRACH may comprise an indication of a target cell which a UE intends to access. Thus, gNBs receiving a trigger PRACH which incorporates an indication of the target cell will not transmit the on-demand SIB 1 whereas the target gNB providing the target cell will transmit the on-demand SIB1, thus improving network energy savings.

[0130] The NES UE may use indicate the target cell by its choice of PRACH preamble used for the trigger RACH. Since there are 64 possible preambles, the UE may determine the preamble to use to indicate the target cell based on the following equation:

[0131] P idx = Cell lD mod 64

[0132] Where “P idx” is an index of the preamble selected by the UE and “Cell lD” is a cell ID of the target cell. For example, if the target cell has a cell ID of “3”, then the UE selects the preamble with P_idx = 3.

[0133] MIB

[0134] Figure 9 illustrates the fields of an existing MIB which is transmitted in a cell. As will be appreciated from Figure 9, there is a spare bit 92 in the MIB.

[0135] In some embodiments, the spare bit 92 may be configured to indicate whether or not the cell supports on- demand SIB 1. Therefore, a UE receiving the MIB can determine, based on the spare bit 92, whether to monitor for a legacy periodic SIB 1 , or whether to transmit a trigger PRACH to trigger the transmission of an on-demand SIB 1.

[0136] In some embodiments, the spare bit 92 may be configured to indicate whether or not trigger PRACH resources have been configured in addition to legacy PRACH resources for the cell. In such embodiments, a UE will know if additional trigger PRACH resources for triggering the on-demand SIB 1 is supported or not. In this case, an NES UE is configured with trigger PRACH resources in advance (e.g. hard-wired into the UE or indicated by the NES gNB) and then the spare bit 92 indicates whether the configured trigger PRACH resources can be used in this gNB to trigger SIB1 broadcasting. Based on the spare bit 92, the NES UE determines that it can use the trigger PRACH resources to transmit a trigger PRACH to trigger the transmission of the on-demand SIB 1. A time delay between successive instances of trigger PRACH resources in the wireless access interface may be reduced compared with legacy PRACH resources so that on-demand SIB1 can be triggered with reduced delay. For example, the trigger PRACH resources may be a periodic configuration of ROs which has a shorter period than legacy PRACH resources.

[0137] As shown in Figure 9, parameters in the MIB comprise SIB 1 related parameters such as “dmrs-TypeA- Position”, and “pdcch-ConfigSIB”. Since these parameters describe legacy periodic SIB1, they can be reconfigured to provide different information in NES cells which provide on-demand SIB 1.

[0138] In some embodiments, a cell barred bit in MIB may indicate to non-NES UEs that they are barred from accessing cells in which SIB 1 with the reconfigured parameters is transmitted, therefore preventing non- NES UEs from attempting to decode the SIB1 with the reconfigured parameters. NES UEs may be configured to ignore the cell barred bit in the MIB in such embodiments.

[0139] In accordance with example embodiments, the SIB 1 related parameters in the MIB may be configured to indicate PRACH parameters to trigger the on-demand SIB. For example, the SIB1 related parameters may be used to indicate a PRACH preamble and / or indicate a PRACH configuration index of the trigger PRACH resources.

[0140] In accordance with example embodiments, the SIB1 related parameters (such as pdcch-ConfigSIB 1) may indicate an offset of the trigger PRACH resources relative to a configuration of PRACH resources for legacy PRACH from a SIB1 transmitted in a previous cell.

[0141] In some embodiments, the spare bit 92 in MIB indicates to the UE whether or not to interpret the SIB 1 related parameters as indicating information associated with the trigger PRACH resources.

[0142] Secondary MIB

[0143] In some embodiments, the spare bit 92 in the MIB indicates whether or not a second MIB will be transmitted by an NES gNB. If the spare bit 92 indicates that the NES gNB will transmit a second MIB, then a UE will attempt to receive the second MIB. If the spare bit 92 indicates that the NES gNB will not transmit a second MIB, then the UE will follow non-NES UE behaviour. The second MIB may comprise an indication of a configuration of the trigger PRACH resources. The second MIB may be transmitted on different time and / or frequency resources compared with the time and frequency resources used to transmit the SSB carrying the first MIB. The second MIB may be transmitted in another SSB or may be transmitted independently of SSB.

[0144] In some embodiments, the NES gNB may use the spare bit 92 in the MIB to indicate that the second MIB will be transmitted instead of transmitting SIB 1 periodically. On the other hand, if the NES gNB is transmitting the SIB 1, there is no need to transmit the second MIB because in this case, both non-NES UE and UE supporting NES can perform initial access in that cell.

[0145] NES MIB

[0146] Figure 10 illustrates an Abstract Syntax Notation One (ASN1) message in a Broadcast Channel (BCH). As shown in Figure 10, the ASN1 message comprises a choice bit 102. The choice bit 102 may be configured to select MIB (i.e. a legacy MIB transmitted by a non-NES gNB) or messageClassExtension. In existing systems, the choice bit 102 is set to select MIB. However, in accordance with example embodiments, the choice bit 102 may be configured to select messageClassExtension and a new MIB (referred to herein as an “NES MIB”) may be defined on messageClassExtension. The NES MIB may comprise an indication of a configuration of the trigger PRACH resources. In some embodiments, the NES MIB may be carried on a “non-cell defining SSB”.

[0147] Non-cell defining SSBs have been defined as SSBs that are not associated with legacy SIB1. Specifically, MIB in non-cell defining SSBs does not indicate a CORESET for TypeO-PDCCH CSS set which schedules PDSCH resources that carry SIB1. Non-NES UEs assume that an SSB is a non-cell defining SSB if a CORESET subcarrier offset from SSB (kssB) is greater than 23 for FR1 or kssB is greater than 11 for FR2. kssB is determined by 1 bit of PBCH payload and field ssb-SubcarrierOffset in the MIB. The non-NES UE will attempt to search other SSBs if the SSB is determined to be a non-cell defining SSB because non-cell defining SSBs are not associated with CORESET#0 and SIB1. Cell-defining SSBs are defined as SSBs which are associated with SIB1. Cell-defining SSBs may comprise CORESET for TypeO-PDCCH CSS set which schedules PDSCH resources that carry SIB1. Non-cell defining SSBs are typically used for the purposes of time / frequency synchronisation and RRM measurement only.

[0148] In accordance with example embodiments, an NES UE may attempt to search both “cell defining SSBs” and “non-cell defining SSBs” to read legacy MIB and the NES MIB respectively. The NES UE may then transmit a trigger PRACH using the trigger PRACH resources indicated in the NES MIB.

[0149] Compact SIB 1

[0150] In some embodiments, a “compact SIB1” is transmitted from an NES gNB to an NES UE. The compact SIB1 comprises an indication of a configuration of the trigger PRACH resources. A compact SIB1 is compact in the sense that it carries less information than a legacy SIB 1. For example, the compact SIB 1 may exclusively consist of an indication of a configuration of the trigger PRACH resources. In such embodiments, the on-demand SIB 1 may comprise the remaining minimum system information required for initial access which is not carried by the compact SIB 1.

[0151] Legacy SIB1 is transmitted on a physical downlink shared channel (PDSCH). The compact SIB1 uses fewer resource blocks compared to the legacy SIB1. Therefore, in some embodiments, the compact SIB1 may be transmitted on a PDSCH using fewer resource blocks than the legacy SIB 1. In some embodiments, the compact SIB 1 may be transmitted on a physical downlink control channel (PDCCH) in cases where the compact SIB1 is at least as small as downlink control information (DCI). Since the resources required for compact SIB1 transmission are less compared with legacy SIB1 transmission, this may lead to network energy savings.

[0152] In some embodiments, a cell barred bit in MIB may indicate to non-NES UEs that they are barred from accessing cells in which compact SIB 1 is transmitted, therefore preventing non-NES UEs from attempting to decode compact SIB 1. NES UEs may be configured to ignore the cell barred bit in the MIB in such embodiments.

[0153] In some embodiments, an NES UE may obtain a compact SIB 1 in a cell. Then the NES UE may transmit a trigger PRACH to trigger a gNB to transmit SIB 1. If the SIB 1 is transmitted with a legacy configuration (e.g periodicity), then non-NES UEs may access the cell (without needing the compact SIB1).

[0154] Sensing before transmitting PRACH trigger

[0155] In some embodiments, in TDD or unlicensed spectrum, an NES UE may sense a transmission from another UE before transmitting a trigger PRACH in order to avoid a collision between the trigger PRACH and the transmission of the other UE. Such collisions are more likely, for example, when the trigger PRACH resources are preconfigured for the NES UE and are therefore not controlled by the NES gNB. If the NES UE detects a transmission from another UE, the NEs UE may refrain from transmitting the trigger PRACH. Otherwise, if the NES UE does not detect a transmission from the other UE, the NES UE will transmit the trigger PRACH. In some embodiments, in TDD or unlicensed spectrum, the NES UE may sense another trigger PRACH being transmitted by another NES UE. In such embodiments, the NES UE may refrain from transmitting its trigger PRACH if it detects the other trigger PRACH being transmitted by the other NES UE. Such embodiments are particularly advantageous when the on-demand SIB 1 is broadcasted in a cell in which NES UE and the other NES UE are located because it avoids duplication of trigger PRACHs and therefore promotes energy saving.

[0156] Increasing Frequency of SIB1 Transmission

[0157] Embodiments have been discussed above where the trigger PRACH transmitted in trigger PRACH resources triggers the transmission of an on-demand SIB1. In some embodiments, an NES gNB may be configured to transmit an SIB1 with a lower frequency (i.e. a bigger time gap between SIB1 transmissions) compared with legacy SIB1. The periodicity of a legacy SIB1 is 160 ms, for example. The periodicity of NES gNBs is higher than 160 ms and may be 320 or 640 ms, for example. Since the SIB1 is transmitted less often, network energy savings are promoted.

[0158] In accordance with examples embodiments, the transmission of a trigger PRACH on PRACH resources triggers the NES gNB to increase a frequency with which the NES gNB transmits SIB 1. In some embodiments, the frequency is increased to the frequency of legacy SIB1. Therefore, while the SIB1 is generally transmitted with a lower frequency than the legacy SIB 1, the frequency can be increased so that the UE can receive the SIB1 more quickly when the SIB1 is required by the UE. The gNB may decide by how much to increase the frequency in response to receiving a trigger PRACH from the UE.

[0159] All previously discussed embodiments where the trigger PRACH triggers an on-demand SIB 1 are equally applicable to scenarios where the trigger PRACH triggers the gNB to transmit SIB 1 with an increased frequency.

[0160] For example, in some embodiments, there may be trigger PRACH resources for triggering the gNB to transmit an SIB 1 with increased frequency in addition to legacy PRACH resources for other purposes (such as initial access). In some embodiments, there may be a plurality of sets of trigger PRACH resources for triggering the gNB to transmit an SIB 1 with increased frequency in addition to legacy PRACH resources. In some embodiments, each of the different sets of PRACH resources may be associated with a different SIB 1 periodicity. For example, the transmission of a trigger PRACH in one of the sets of trigger PRACH resources may indicate to the gNB to change the SIB1 periodicity to the legacy periodicity (for example, 160 ms) and the transmission of a trigger PRACH in another set of the trigger PRACH resources may indicate to the gNB to change the SIB 1 periodicity to another periodicity (for example, 320 ms). Therefore, the gNB can determine what value to change the SIB1 periodicity to based on the trigger PRACH resources in which the trigger PRACH was transmitted. Embodiments with a plurality of sets of trigger PRACH resources, each associated with a different SIB 1 periodicity, are particularly advantageous in scenarios where the UE has periodic user data to transmit.

[0161] IDLE and INACTIVE UEs

[0162] In accordance with example, embodiments the UE may be in an idle mode (for example, in RRC IDLE mode) when the UE transmits the trigger PRACH and receives the on-demand, or increased frequency, SIB1 from the gNB. In some embodiments, the UE may also be in the idle mode when it receives the indication of the configuration of the trigger PRACH resources from the gNB. However, in some embodiments, the UE may receive an indication of a configuration of the trigger PRACH resources while the UE is in an inactive mode (for example, UEs in an RRC INACTIVE mode). For example, the inactive UE may receive an RRC release message which transitions the UE from the inactive mode to the idle mode, and the RRC release message may comprise an indication of a configuration of the trigger PRACH resources. Therefore, when the idle UE wishes to transition to the connected mode, the idle UE can transmit a trigger PRACH in the trigger PRACH resources to trigger transmission of the on-demand SIB 1, or to trigger the increase in frequency of SIB 1.

[0163] Methods of operating communications devices and infrastructure equipment in accordance with example embodiments

[0164] Figure 11 is a flow diagram illustrating a method of operating a communications device to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment in accordance with example embodiments. The method starts in step SI.

[0165] In step S2, the method comprises transmitting, to the infrastructure equipment, a Physical Random Access Channel (PRAC in PRACH resources of the wireless access interface configured for the transmission of the PRACH. The transmission of the PRACH in the RACH resources provides a trigger indication to the infrastructure equipment. The trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB). The on- demand SIB comprises at least information required by the communications device to perform an initial access procedure with the infrastructure equipment. Alternatively, the trigger indication comprises an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB. The already-on SIB comprises information required for the communications device to perform the initial access procedure with the infrastructure equipment.

[0166] In step S3, the method comprises receiving the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructure equipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

[0167] The method ends in step S4.

[0168] Figure 12 is a flow diagram illustrating a method of operating infrastructure equipment of a wireless communications network to communicate with a communications device via a wireless access interface provided by the infrastructure equipment in accordance with example embodiments. The method starts in step Si l.

[0169] In step S12, the method comprises receiving, from a communications device, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH. The reception of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment. The trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB). The on-demand SIB comprises at least information required by the communications device to perform an initial access procedure with the infrastructure equipment. Alternatively, the trigger indication comprises an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment transmits an already-on SIB. The already-on SIB comprises at least information required for the communications device to perform the initial access procedure with the infrastructure equipment. In step S 13, the method comprises transmitting the on-demand SIB if the trigger indication comprises the indication to transmit the on-demand SIB. Alternatively, the method comprises transmitting the already- on SIB with the increased frequency if the trigger indication comprises the indication to reduce the increase the frequency of the already-on SIB

[0170] The method ends in step S14.

[0171] Those skilled in the art would further appreciate that such infrastructure equipment and / or communications devices as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and communications devices as herein defined and described may form part of communications systems other than those defined by the present disclosure.

[0172] The following numbered paragraphs provide further example aspects and features of the present technique:

[0173] Paragraph 1. A method of operating a communications device to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment, the method comprising transmitting, to the infrastructure equipment, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, and the method comprises receiving the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructure equipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

[0174] Paragraph 2. A method according to paragraph 1, wherein the PRACH resources pre-configured for the communications device.

[0175] Paragraph 3. A method according to paragraph 1 or paragraph 2, wherein the PRACH resources comprise a periodic configuration of PRACH Occasions (ROs), each of the ROs being associated with one or more preambles, wherein the transmission of the PRACH in the PRACH resources comprises transmitting the PRACH in one of the ROs using a preamble associated with the RO.

[0176] Paragraph 4. A method according to any of paragraphs 1 to 3, comprising receiving an indication of a configuration of the PRACH resources from the infrastructure equipment.

[0177] Paragraph 5. A method according to paragraph 4, wherein the indication of the configuration of the PRACH resources from the infrastructure equipment comprises an indication of a periodic configuration of PRACH Occasions (ROs), each of the ROs being associated with one or more of preambles, wherein the transmission of the PRACH in the PRACH resources comprises transmitting the PRACH in one of the ROs using a preamble associated with the RO.

[0178] Paragraph 6. A method according to any of paragraphs 4 to 5, wherein the method comprises receiving a synchronisation signal block (SSB) from the infrastructure equipment, wherein the indication of the configuration of the PRACH resources received from the infrastructure equipment comprises an indication of a position of the PRACH resources in the wireless access interface relative to a position of the SSB in the wireless access interface.

[0179] Paragraph 7. A method according to any of paragraphs 4 to 5, comprising receiving, from the infrastructure equipment, another system information block comprising the indication of the configuration of the PRACH resources.

[0180] Paragraph 8. A method according to paragraph 7, wherein the other system information block exclusively consists of the indication of the configuration of the PRACH resources.

[0181] Paragraph 9. A method according to any of paragraphs 4 to 6, comprising receiving, from the infrastructure equipment, a master information block (MIB), wherein the MIB comprises information for decoding the received SIB, and the indication of the configuration of the PRACH resources configured for transmitting the PRACH.

[0182] Paragraph 10. A method according to any of paragraphs 4 to 6, comprising receiving, from the infrastructure equipment, a first master information block (MIB) comprising information for decoding the received SIB, wherein the first MIB comprises an indication that a second MIB is to be transmitted by the infrastructure equipment, receiving, from the infrastructure equipment, the second MIB, the second MIB comprising the indication of the configuration of the PRACH resources.

[0183] Paragraph 11. A method according to paragraph 10, wherein the indication that a second MIB is to be transmitted by the infrastructure equipment is a 1 -bit indication in the first MIB.

[0184] Paragraph 12. A method according to any of paragraphs 1 to 11, comprising determining, from the received SIB, the information required for the initial access procedure with the infrastructure equipment, performing the initial access procedure with the infrastructure equipment, the initial access procedure comprising transmitting another PRACH to the infrastructure equipment in other PRACH resources of the wireless access interface configured for the transmission of the other PRACH, the other PRACH resources being different from the PRACH resources in which the PRACH was transmitted. Paragraph 13. A method according to any of paragraphs 12, wherein the transmission of the PRACH is performed in response to determining, based on the PRACH resources, that another communications device is not transmitting a PRACH in the PRACH resources.

[0185] Paragraph 14. A method according to any of paragraphs 12 to 13, wherein the PRACH resources configured are exclusively reserved for transmitting the PRACH comprising the trigger indication. Paragraph 15. A method according to any of paragraphs 1 to 11, comprising determining, from the received SIB, the information required for the initial access procedure with the infrastructure equipment, performing the initial access procedure with the infrastructure equipment, the initial access procedure comprising transmitting another PRACH to the infrastructure equipment in the PRACH resources of the wireless access interface configured for the transmission of the PRACH. Paragraph 16. A method according to any of paragraphs 1 to 15, wherein the wireless access interface provided by the infrastructure equipment is for a cell provided by the infrastructure equipment in which the communications device is located when the communications device transmits the PRACH, and one or more other infrastructure equipment of the wireless communications network provide one or more wireless access interfaces for one or more cells provided by the one or more other infrastructure equipment, and the PRACH resources in the wireless access interface for the cell provided by the infrastructure equipment are also configured in the one or more wireless access interfaces for the one or more cells provided by the one or more other infrastructure equipment, or a sub-set of the PRACH resources in the wireless access interface for the cell provided by the infrastructure equipment are configured in the one or more wireless access interfaces for the one or more cells provided by the one or more other infrastructure equipment.

[0186] Paragraph 17. A method according to paragraph 16, wherein the cell provided by the infrastructure equipment and the one or more cells provided by the one or more other infrastructure equipment have the same area ID, or belong to the same list of cell IDs.

[0187] Paragraph 18. A method according to paragraph 16 or paragraph 17, wherein the PRACH resources comprise a plurality of RACH Occasions (ROs), each of the ROs being associated with a plurality of preambles, wherein the preambles associated with each RO are partitioned into preambles reserved for transmitting the PRACH and preambles reserved for transmitting another PRACH, and the transmission of the PRACH in the PRACH resources comprises transmitting the PRACH in one of the ROs using a preamble reserved for transmitting the PRACH.

[0188] Paragraph 19. A method according to any of paragraphs 1 to 18, wherein an index of a preamble of the PRACH is derived from an identification of a target cell from which the communications device is seeking to receive the SIB.

[0189] Paragraph 20. A method according to any of paragraphs 1 to 19, comprising receiving, from the infrastructure equipment, a master information block (MIB) comprising information for decoding the received SIB, wherein the MIB comprises an indication of whether or not the on-demand SIB is supported by the infrastructure equipment.

[0190] Paragraph 21. A method according to paragraph 20, wherein the indication of whether or not the on- demand SIB is supported by the infrastructure comprises an indication of whether other PRACH resources are configured in the wireless access interface for performing the initial access procedure in addition to the PRACH resources configured for the transmission of the PRACH.

[0191] Paragraph 22. A method according to any of paragraphs 20 or paragraph 21 wherein the indication of whether or not on-demand SIB is supported by the infrastructure equipment is a 1 -bit indication in the MIB.

[0192] Paragraph 23. A method according to any of paragraphs 1 to 21, wherein the PRACH resources configured for the transmission of the PRACH comprise a first set of PRACH resources and a second set of PRACH resources, and the PRACH is transmitted in the first set of PRACH resources, and the transmission of the PRACH in the first set of PRACH resources provides the indication to the infrastructure equipment to transmit the on-demand SIB, or the PRACH is transmitted in the second set of PRACH resources, and the transmission of the PRACH in the second set of PRACH resources provides the indication to the infrastructure equipment to increase the frequency of the already-on SIB.

[0193] Paragraph 24. A method according to any of paragraphs 1 to 23, wherein the trigger indication comprises the indication to increase the frequency of the already-on SIB, and the PRACH resources configured for the transmission of the PRACH comprise a plurality of sets of PRACH resources, wherein the set of the PRACH resources in which the PRACH is transmitted indicates a frequency value which the frequency of the already-on SIB should be increased to.

[0194] Paragraph 25. A method according to any of paragraphs 1 to 24, wherein the on-demand SIB is system information block type 1 (SIB1).

[0195] Paragraph 26. A method according to any of paragraphs 1 to 25, wherein the already-on SIB is system information block type 1 (SIB1).

[0196] Paragraph 27. A method according to any of paragraphs 1 to 26, wherein the method comprises when the communications device is in a Radio Resource Control (RRC) connected state, transmitting, to the infrastructure equipment, an RRC message comprising a request for an updated on-demand SIB 1.

[0197] Paragraph 28. A method according to any of paragraphs 1 to 27, wherein the PRACH transmitted by the communications device comprises a PRACH preamble.

[0198] Paragraph 29. A method of operating infrastructure equipment of a wireless communications network to communicate with a communications device via a wireless access interface provided by the infrastructure equipment, the method comprising receiving, from a communications device, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the reception of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the method comprises if the trigger indication comprises the indication to transmit the on-demand SIB, transmitting the on-demand SIB, or if the trigger indication comprises the indication to increase the frequency of the already-on SIB, transmitting the already-on SIB with the increased frequency.

[0199] Paragraph 30. A communications operable to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment, the communications device comprising a transceiver configured to transmit and to receive signals, and a controller configured in combination with the transceiver to transmit, to the infrastructure equipment, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller is configured in combination with the transceiver to receive the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructure equipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

[0200] Paragraph 31. Infrastructure equipment for a wireless communications network operable to communicate with a communications device via a wireless access interface provided by the infrastructure equipment, the infrastructure equipment comprising a transceiver configured to transmit and to receive signals, and a controller configured in combination with the transceiver to receive, from a communications device, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the reception of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller is configured in combination with the transceiver to if the trigger indication comprises the indication to transmit the on-demand SIB, transmitting the on-demand SIB, or if the trigger indication comprises the indication to increase the frequency of the already-on SIB, transmitting the already-on SIB with the increased frequency.

[0201] Paragraph 32. Circuitry for a communications operable to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment, the circuitry comprising transceiver circuitry configured to transmit and to receive signals, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the infrastructure equipment, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller circuitry is configured in combination with the transceiver circuitry to receive the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructure equipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

[0202] Paragraph 33. Circuitry for Infrastructure equipment of a wireless communications network operable to communicate with a communications device via a wireless access interface provided by the infrastructure equipment, the infrastructure equipment comprising transceiver circuitry configured to transmit and to receive signals, and controller circuitry configured in combination with the transceiver circuitry to receive, from a communications device, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the reception of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller circuitry is configured in combination with the transceiver circuitry to if the trigger indication comprises the indication to transmit the on-demand SIB, transmitting the on-demand SIB, or if the trigger indication comprises the indication to increase the frequency of the already-on SIB, transmitting the already-on SIB with the increased frequency.

[0203] Paragraph 34. A computer program which, when the program is executed by a computer, cause the computer to perform the method of any of paragraphs 1 to 29.

[0204] Paragraph 35. A non-transitory computer-readable storage medium storing a computer program according to paragraph 34.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] References

[0209] [1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radio access”, John Wiley and Sons, 2009.

[0210] [2] TR 38.913, “Study on Scenarios and Requirements for Next Generation Access Technologies (Release 14)”, 3rd Generation Partnership Project, vl4.3.0, August 2017.

[0211] [3] TS 38.470, “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Fl general aspects and principles (Release 17)”, 3GPP, V17.4.0, March 2023.

[0212] [4] TS 38.473, “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Fl application protocol (F1AP) (Release 17)”, 3GPP, V17.4.1, April 2023.

[0213] [5] TS 38.401, “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Architecture description (Release 17)”, 3GPP, V17.4.0, March 2023.

[0214] [6] RP-234065, “New WID: Enhancements of network energy savings for NR,” 3GPP TSG RAN Meeting# 102, Edinburgh, Scotland, December 11th- 15th, 2023 [7] GSMA, 5G energy efficiencies: Green is the new black, https: / / data.gsmaintelligence.com / api- web / v2 / research-file-download?id=54165956&file=241120-5G-energy.pdf

[0215] [8] 3GPP TR 38.864 V18. 1.0 Study on network energy savings for NR

Claims

CLAIMSWhat is claimed is:

1. A method of operating a communications device to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment, the method comprising transmitting, to the infrastructure equipment, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, and the method comprises receiving the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructure equipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

2. A method according to claim 1, wherein the PRACH resources pre-configured for the communications device.

3. A method according to claim 1, wherein the PRACH resources comprise a periodic configuration of PRACH Occasions (ROs), each of the ROs being associated with one or more preambles, wherein the transmission of the PRACH in the PRACH resources comprises transmitting the PRACH in one of the ROs using a preamble associated with the RO.

4. A method according to claim 1, comprising receiving an indication of a configuration of the PRACH resources from the infrastructure equipment.

5. A method according to claim 4, wherein the indication of the configuration of the PRACH resources from the infrastructure equipment comprises an indication of a periodic configuration of PRACH Occasions (ROs), each of the ROs being associated with one or more of preambles, wherein the transmission of the PRACH in the PRACH resources comprises transmitting the PRACH in one of the ROs using a preamble associated with the RO.

6. A method according to claim 4, wherein the method comprises receiving a synchronisation signal block (SSB) from the infrastructure equipment, wherein the indication of the configuration of the PRACH resources received from the infrastructure equipment comprises an indication of a position of the PRACH resources in the wireless access interface relative to a position of the SSB in the wireless access interface.

7. A method according to claim 4, comprisingreceiving, from the infrastructure equipment, another system information block comprising the indication of the configuration of the PRACH resources.

8. A method according to claim 7, wherein the other system information block exclusively consists of the indication of the configuration of the PRACH resources.

9. A method according to claim 4, comprising receiving, from the infrastructure equipment, a master information block (MIB), wherein the MIB comprises information for decoding the received SIB, and the indication of the configuration of the PRACH resources configured for transmitting the PRACH.

10. A method according to claim 4, comprising receiving, from the infrastructure equipment, a first master information block (MIB) comprising information for decoding the received SIB, wherein the first MIB comprises an indication that a second MIB is to be transmitted by the infrastructure equipment, receiving, from the infrastructure equipment, the second MIB, the second MIB comprising the indication of the configuration of the PRACH resources.

11. A method according to claim 10, wherein the indication that a second MIB is to be transmitted by the infrastructure equipment is a 1 -bit indication in the first MIB.

12. A method according to claim 1, comprising determining, from the received SIB, the information required for the initial access procedure with the infrastructure equipment, performing the initial access procedure with the infrastructure equipment, the initial access procedure comprising transmitting another PRACH to the infrastructure equipment in other PRACH resources of the wireless access interface configured for the transmission of the other PRACH, the other PRACH resources being different from the PRACH resources in which the PRACH was transmitted.

13. A method according to claim 12, wherein the transmission of the PRACH is performed in response to determining, based on the PRACH resources, that another communications device is not transmitting a PRACH in the PRACH resources.

14. A method according to claim 12, wherein the PRACH resources configured are exclusively reserved for transmitting the PRACH comprising the trigger indication.

15. A method according to claim 1, comprising determining, from the received SIB, the information required for the initial access procedure with the infrastructure equipment, performing the initial access procedure with the infrastructure equipment, the initial access procedure comprising transmitting another PRACH to the infrastructure equipment in the PRACH resources of the wireless access interface configured for the transmission of the PRACH.

16. A method according to claim 1, whereinthe wireless access interface provided by the infrastructure equipment is for a cell provided by the infrastructure equipment in which the communications device is located when the communications device transmits the PRACH, and one or more other infrastructure equipment of the wireless communications network provide one or more wireless access interfaces for one or more cells provided by the one or more other infrastructure equipment, and the PRACH resources in the wireless access interface for the cell provided by the infrastructure equipment are also configured in the one or more wireless access interfaces for the one or more cells provided by the one or more other infrastructure equipment, or a sub-set of the PRACH resources in the wireless access interface for the cell provided by the infrastructure equipment are configured in the one or more wireless access interfaces for the one or more cells provided by the one or more other infrastructure equipment.

17. A method according to claim 16, wherein the cell provided by the infrastructure equipment and the one or more cells provided by the one or more other infrastructure equipment have the same area ID, or belong to the same list of cell IDs.

18. A method according to claim 16, wherein the PRACH resources comprise a plurality of RACH Occasions (ROs), each of the ROs being associated with a plurality of preambles, wherein the preambles associated with each RO are partitioned into preambles reserved for transmitting the PRACH and preambles reserved for transmitting another PRACH, and the transmission of the PRACH in the PRACH resources comprises transmitting the PRACH in one of the ROs using a preamble reserved for transmitting the PRACH.

19. A method according to claim 1, wherein an index of a preamble of the PRACH is derived from an identification of a target cell from which the communications device is seeking to receive the SIB.

20. A method according to claim 1, comprising receiving, from the infrastructure equipment, a master information block (MIB) comprising information for decoding the received SIB, wherein the MIB comprises an indication of whether or not the on-demand SIB is supported by the infrastructure equipment.

21. A method according to claim 20, wherein the indication of whether or not the on-demand SIB is supported by the infrastructure comprises an indication of whether other PRACH resources are configured in the wireless access interface for performing the initial access procedure in addition to the PRACH resources configured for the transmission of the PRACH.

22. A method according to claim 20, wherein the indication of whether or not on-demand SIB is supported by the infrastructure equipment is a 1 -bit indication in the MIB.

23. A method according to claim 1, wherein the PRACH resources configured for the transmission of the PRACH comprise a first set of PRACH resources and a second set of PRACH resources, and the PRACH is transmitted in the first set of PRACH resources, and the transmission of the PRACH in the first set of PRACH resources provides the indication to the infrastructure equipment to transmit the on-demand SIB, or the PRACH is transmitted in the second set of PRACH resources, and the transmission of the PRACH in the second set of PRACH resources provides the indication to the infrastructure equipment to increase the frequency of the already-on SIB.

24. A method according to claim 1, wherein the trigger indication comprises the indication to increase the frequency of the already-on SIB, and the PRACH resources configured for the transmission of the PRACH comprise a plurality of sets of PRACH resources, wherein the set of the PRACH resources in which the PRACH is transmitted indicates a frequency value which the frequency of the already-on SIB should be increased to.

25. A method according to claim 1, wherein the on-demand SIB is system information block type 1 (SIB1).

26. A method according to claim 1, wherein the already-on SIB is system information block type 1 (SIB1).

27. A method according to claim 1, wherein the method comprises when the communications device is in a Radio Resource Control (RRC) connected state, transmitting, to the infrastructure equipment, an RRC message comprising a request for an updated on-demand SIB 1.

28. A method according to claim 1, wherein the PRACH transmitted by the communications device comprises a PRACH preamble.

29. A method of operating infrastructure equipment of a wireless communications network to communicate with a communications device via a wireless access interface provided by the infrastructure equipment, the method comprising receiving, from a communications device, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the reception of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the method comprises if the trigger indication comprises the indication to transmit the on-demand SIB, transmitting the on-demand SIB, or if the trigger indication comprises the indication to increase the frequency of the already-on SIB, transmitting the already-on SIB with the increased frequency.

30. A communications operable to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment, the communications device comprising a transceiver configured to transmit and to receive signals, and a controller configured in combination with the transceiver to transmit, to the infrastructure equipment, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprisesan indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller is configured in combination with the transceiver to receive the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructure equipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

31. Infrastructure equipment for a wireless communications network operable to communicate with a communications device via a wireless access interface provided by the infrastructure equipment, the infrastructure equipment comprising a transceiver configured to transmit and to receive signals, and a controller configured in combination with the transceiver to receive, from a communications device, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the reception of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller is configured in combination with the transceiver to if the trigger indication comprises the indication to transmit the on-demand SIB, transmitting the on-demand SIB, or if the trigger indication comprises the indication to increase the frequency of the already-on SIB, transmitting the already-on SIB with the increased frequency.

32. Circuitry for a communications operable to communicate with infrastructure of a wireless communications network via a wireless access interface provided by the infrastructure equipment, the circuitry comprising transceiver circuitry configured to transmit and to receive signals, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the infrastructure equipment, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the transmission of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller circuitry is configured in combination with the transceiver circuitry to receive the on-demand SIB from the infrastructure equipment if the trigger indication comprises the indication to transmit the on-demand SIB, or receiving the already-on SIB from the infrastructureequipment with the increased frequency if the trigger indication comprises the indication to increase the frequency of the already-on SIB.

33. Circuitry for Infrastructure equipment of a wireless communications network operable to communicate with a communications device via a wireless access interface provided by the infrastructure equipment, the infrastructure equipment comprising transceiver circuitry configured to transmit and to receive signals, and controller circuitry configured in combination with the transceiver circuitry to receive, from a communications device, a Physical Random Access Channel (PRACH) in PRACH resources of the wireless access interface configured for the transmission of the PRACH, wherein the reception of the PRACH in the PRACH resources provides a trigger indication to the infrastructure equipment, wherein the trigger indication comprises an indication to the infrastructure equipment to start transmitting an on-demand system information block (SIB), the on-demand SIB comprising at least information required by the communications device to perform an initial access procedure with the infrastructure equipment, or an indication to the infrastructure equipment to increase a frequency with which the infrastructure equipment is transmitting an already-on SIB, the already-on SIB comprising at least information required for the communications device to perform the initial access procedure with the infrastructure equipment, wherein the controller circuitry is configured in combination with the transceiver circuitry to if the trigger indication comprises the indication to transmit the on-demand SIB, transmitting the on-demand SIB, or if the trigger indication comprises the indication to increase the frequency of the already-on SIB, transmitting the already-on SIB with the increased frequency.

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

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

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