Patent Description:
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 nor impliedly admitted as prior art against the present invention.

Future wireless communications networks will be expected to support communications routinely and efficiently with a wider range of devices associated with a wider range of data traffic profiles and types than current systems are optimised to support. For example it is expected future wireless communications networks will be expected to efficiently support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets and so on. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the "The Internet of Things", and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance.

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 <NUM> Gb/s. The requirements for Ultra Reliable & Low Latency Communications (URLLC) services are for a reliability of <NUM> - <NUM>-<NUM> (<NUM> %) or higher for one transmission of a <NUM> byte packet with a user plane latency of <NUM> [<NUM>]. In addition, systems may be expected to support further enhancements related to Industrial Internet of Things (IIoT) in order to support services with new requirements of high availability, high reliability, low latency, and in some cases, high-accuracy positioning.

Industrial automation, energy power distribution and intelligent transport systems are examples of new use cases for Industrial Internet of Things (IIoT). In an example of industrial automation, the system may involve different distributed components working together. These components may include sensors, virtualized hardware controllers and autonomous robots, which may be capable of initiating actions or reacting to critical events occurring within a factory and communicating over a local area network.

The UEs in the network may therefore be expected to handle a mixture of different traffic, for example, associated with different applications and potentially different quality of service requirements (such as maximum latency, reliability, packet sizes, throughput). Some messages for transmission may be time sensitive and be associated with strict deadlines and the communications network may therefore be required to provide time sensitive networking (TSN) [<NUM>].

The increasing use of different types of communications devices associated with different traffic profiles gives rise to new challenges for efficiently handling communications in wireless telecommunications systems that need to be addressed.

<CIT> discloses a method and apparatus for allocating a temporary radio network temporary identifier to a mobile communications terminal as part of a random access procedure in a wireless communications system.

<CIT> discloses a communications device and a method of operating a communications device for receiving a random access response, RAR, message from a network node.

Embodiments of the present technique as defined in the appended claims can provide a method of operating a communications device in a wireless communications network, the method comprising, with the other limitations of claim <NUM>, transmitting a random access message on a wireless access interface, the random access message comprising a selected random access preamble. In some examples the preamble may be followed by transmitting uplink data on communications resources of a shared channel, the communications resources of the shared channel being determined from the transmission of the random access message. In other examples the random access message may comprise only the preamble, which may form a message B of a two-step random access process. The method further comprises receiving a resource allocation message comprising an indication of downlink communications resources allocated for the transmission of a random access response message combined with a radio network terminal identifier which identifies the communications device which transmitted the random access message, determining that the resource allocation message identifies the communications device, and in response to determining that the resource allocation message identifies the communications device, receiving and decoding the signals transmitted using the allocated downlink communications resources. The determining that the resource allocation message identifies the communications device comprises calculating the radio network terminal identifier which is used in the resource allocation message to identify the communications device using an offset, and confirming that the calculated radio network terminal identifier corresponds with the radio network terminal identifier present in the resources allocation message. In some examples the offset is combined with a parameter which is used for calculating the radio network temporary identifier according to a conventional technique, which depends on a time of transmission of the random access message so that the offset can generate a radio network temporary identifier for a communications device performing a two-step random access procedure which is different and distinguished from a radio network temporary identifier directed for another communications device such as one performing a four-step random access procedure at the same time.

According to some examples, one communications device may perform a two-step random access process whereas another communications device may perform a four-step random access process. If both of the communications devices transmit the random access messages in the same time slot, but on different frequencies, then there is a potential for the same radio network temporary identifier to be generated for identifying both of the communications devices leading to ambiguity and a breakdown in these random access processes. If the communications device performing the four-step process is a legacy or conventional communications device, which must be backwardly compatible with existing systems, then no changes in the generation of the radio network temporary identifier can be made. Embodiments can therefore provide for an offset to be introduced when calculating the radio network temporary identifier for the two-step random access which can therefore be used by a communications device performing the two-step random access process to be identified separately from a communications device performing the four-step random access process.

In other examples, a radio network temporary identifier can be calculated with an offset to separate communications devices which are preforming contention free or contention based random access or system information (SI) request.

The network <NUM> includes a plurality of base stations <NUM> connected to a core network part <NUM>. Each base station provides a coverage area <NUM> (e.g. a cell) within which data can be communicated to and from communications devices <NUM>. Data is transmitted from the base stations <NUM> to the communications devices <NUM> within their respective coverage areas <NUM> via a radio downlink. Data is transmitted from the communications devices <NUM> to the base stations <NUM> via a radio uplink. The core network part <NUM> routes data to and from the communications devices <NUM> via the respective base stations <NUM> and provides functions such as authentication, mobility management, charging and so on. Communications devices may also be referred to as mobile stations, user equipment (UE), user terminals, mobile radios, terminal devices, and so forth. Base stations, which are an example of network infrastructure equipment / network access nodes, may also be referred to as transceiver stations / nodeBs / e-nodeBs, g-nodeBs (gNB) and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, example embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems such as <NUM> or new radio as explained below, 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.

<FIG> is a schematic diagram illustrating a network architecture for a new RAT wireless communications network / system <NUM> based on previously proposed approaches which may also be adapted to provide functionality in accordance with embodiments of the disclosure described herein. The new RAT network <NUM> represented in <FIG> comprises a first communication cell <NUM> and a second communication cell <NUM>. Each communication cell <NUM>, <NUM>, comprises a controlling node (centralised unit) <NUM>, <NUM> in communication with a core network component <NUM> over a respective wired or wireless link <NUM>, <NUM>. The respective controlling nodes <NUM>, <NUM> are also each in communication with a plurality of distributed units (radio access nodes / remote transmission and reception points (TRPs)) <NUM>, <NUM> in their respective cells. Again, these communications may be over respective wired or wireless links. The distributed units <NUM>, <NUM> are responsible for providing the radio access interface for communications devices connected to the network. Each distributed unit <NUM>, <NUM> has a coverage area (radio access footprint) <NUM>, <NUM> where the sum of the coverage areas of the distributed units under the control of a controlling node together define the coverage of the respective communication cells <NUM>, <NUM>. Each distributed unit <NUM>, <NUM> includes transceiver circuitry for transmission and reception of wireless signals and processor circuitry configured to control the respective distributed units <NUM>, <NUM>.

A communications device or UE <NUM> is represented in <FIG> within the coverage area of the first communication cell <NUM>. This communications device <NUM> may thus exchange signalling with the first controlling node <NUM> in the first communication cell via one of the distributed units <NUM> associated with the first communication cell <NUM>. In some cases communications for a given communications device are routed through only one of the distributed units, but it will be appreciated that in some other implementations communications associated with a given communications device may be routed through more than one distributed unit, for example in a soft handover scenario and other scenarios.

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

A more detailed illustration of two UEs/communications devices 270a, 270b is provided in <FIG>. As will be explained below, <FIG> provides an illustration of an example embodiment in which an NR UE, UEa 270a, which may correspond to a communications device such as the communications device <NUM> of <FIG> performs a two step RACH procedure and a second UE, UEb 270b which may be a conventional or legacy UE such as the communications device <NUM> of <FIG> performs a four step RACH procedure. It will be appreciated however that two-step and four-step RACH may be performed by either a conventional/legacy UE or a NR/<NUM> UE. For example a UE may fall-back to a four-step RACH if a two-step RACH fails. Both UEa 270a and UEb 270b transmit signals on an uplink UL and receive signals on a downlink DL from an example network infrastructure equipment <NUM>, which may be thought of as a gNB <NUM> or a combination of a controlling node <NUM> and TRP <NUM>. The UEa 270a and UEb 270b are shown to transmit uplink data to the infrastructure equipment <NUM> via uplink resources UL of a wireless access interface as illustrated generally by arrows 274a, 274b to the infrastructure equipment <NUM>. The UEa 270a and the UEb 270b may similarly be configured to receive downlink data transmitted by the infrastructure equipment <NUM> via downlink resources DL as indicated by arrows 288a, 288b from the infrastructure equipment <NUM> to the UEa 270a and the UEb 270b. As with <FIG> and <FIG>, the infrastructure equipment <NUM> is connected to a core network <NUM> via an interface <NUM> to a controller <NUM> of the infrastructure equipment <NUM>. The infrastructure equipment <NUM> includes a receiver <NUM> connected to an antenna <NUM> and a transmitter <NUM> connected to the antenna <NUM>. Correspondingly, both of the UEa 270a and the UEb 270b include a controller 290a, 290b connected to a receiver 292a, 292b which receives signals from an antenna 294a, 294b and a transmitter 296a, 296b also connected to the antenna 294a, 294b.

The controller <NUM> is configured to control the infrastructure equipment <NUM> and may comprise processor circuitry which may in turn comprise various sub-units / sub-circuits for providing functionality as explained further herein. These sub-units may be implemented as discrete hardware elements or as appropriately configured functions of the processor circuitry. Thus the controller <NUM> may comprise circuitry which is suitably configured / programmed to provide the desired functionality using conventional programming / configuration techniques for equipment in wireless telecommunications systems. The transmitter <NUM> and the receiver <NUM> may comprise signal processing and radio frequency filters, amplifiers and circuitry in accordance with conventional arrangements. The transmitter <NUM>, the receiver <NUM> and the controller <NUM> are schematically shown in <FIG> as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the infrastructure equipment <NUM> will in general comprise various other elements associated with its operating functionality.

Correspondingly, the controller 290a, 290b of the UEa 270a and the UEb 270b is configured to control the transmitter 296a, 296b and the receiver 292a, 292b and may comprise processor circuitry which may in turn comprise various sub-units / sub-circuits for providing functionality as explained further herein. These sub-units may be implemented as discrete hardware elements or as appropriately configured functions of the processor circuitry. Thus the controller <NUM> may comprise circuitry which is suitably configured / programmed to provide the desired functionality using conventional programming / configuration techniques for equipment in wireless telecommunications systems. Likewise, the transmitter <NUM> and the receiver <NUM> may comprise signal processing and radio frequency filters, amplifiers and circuitry in accordance with conventional arrangements. The transmitters 296a, 296b, receivers 292a, 292b and controllers 290a, 290b are schematically shown in <FIG> as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the communications devices 270a, 270b will in general comprise various other elements associated with its operating functionality, for example a power source, user interface, and so forth, but these are not shown in <FIG> in the interests of simplicity.

The controllers <NUM>, 290a, 290b may be 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.

<FIG> provides a simplified representation of an uplink structure of a wireless access interface with time divided units which may be used for a NR wireless access interface structure. Whilst the terms "frames" and "sub-frames" used in <FIG> are terms which have been used in LTE, 3GPP standards adopted for <NUM>/NR may be different and so it will be appreciated that <FIG> is provided for illustration only to assist in the explanation of the example embodiments. Current proposals for a time divided structure for <NUM>/NR include that one slot providing a time divided structure of the wireless access interface consists of <NUM> OFDM symbols <NUM>, and one sub-frame is defined by <NUM>. The term slot is used in this description to refer to a time slot or time divided unit and time slot and slot may be used interchangeably. As such, the time divided structure of the wireless access interface of <FIG> shows an example in which one sub-frame <NUM> has two slots <NUM>, <NUM> and twenty eight symbols. As shown in <FIG>, the uplink of the wireless access interface is shown to comprise frames <NUM> with respect to which the UE <NUM> transmits to the infrastructure equipment <NUM>. The uplink comprises, in each frame, <NUM> ten sub-frames <NUM>. A frame <NUM> is defined by <NUM>, a sub-frame <NUM> is defined by <NUM>, and a slot <NUM> is defined by fourteen OFDM symbols <NUM>, irrespective of subcarrier spacing. An expanded view of the components of a sub-frame <NUM> are shown to be formed from two consecutive slots n-<NUM>, n <NUM>, <NUM>, which include physical resources of a shared channel as well as control channels. According to the example embodiments explained below, one or more of the time slots may include one or more Physical Random Access Channels (PRACH) providing one or more RACH occasions in which a UE can transmit a random access preamble. An RNTI can therefore be defined to identify the UE which transmitted the preamble based on the slot and OFDM symbol of the RACH occasion in which the preamble was transmitted.

In wireless telecommunications networks, such as LTE type networks, there are different Radio Resource Control (RRC) modes for terminal devices. For example, it is common to support an RRC idle mode (RRC_IDLE) and an RRC connected mode (RRC_CONNECTED). A terminal device in the idle mode may transition to connected mode, for example because it needs to transmit uplink data or respond to a paging request, by undertaking a random access procedure. The random access procedure involves the terminal device transmitting a preamble on a physical random access channel and so the procedure is commonly referred to as a RACH or PRACH procedure / process.

In addition to a terminal device deciding itself to initiate a random access procedure to connect to the network, it is also possible for the network, e.g. a base station, to instruct a terminal device in connected mode to initiate a random access procedure by transmitting to the terminal device an instruction to do so. Such an instruction is sometimes referred to as a PDCCH order (Physical Downlink Control Channel order), see, for example, Section <NUM>. <NUM> in ETSI TS <NUM><NUM> V13. <NUM> (<NUM>-<NUM>) / 3GPP TS <NUM> version <NUM>. <NUM> Release <NUM> [<NUM>]. There are various scenarios in which a network triggered RACH procedure (PDCCH order) may arise.

<FIG> shows a typical RACH procedure used in LTE systems such as that described by reference to <FIG> which could also be applied to an NR wireless communications system such as that described by reference to <FIG>. A communications device (or UE) 270b, which could be in an inactive or idle mode, may have some data which it needs to send to the network. To do so, the UE sends a random access preamble <NUM> (message <NUM>) to a gNodeB <NUM>. This random access preamble <NUM> indicates the identity of the communications device <NUM> to the gNodeB <NUM>, such that the gNodeB <NUM> can address the communications device <NUM> during later stages of the RACH procedure. Assuming the random access preamble <NUM> is successfully received by the gNodeB <NUM>, the gNodeB <NUM> will transmit a random access response <NUM> message (message <NUM>) to the communications device <NUM> based on the identity indicated in the received random access preamble <NUM>. The random access response <NUM> message carries a further identity which is assigned by the gNodeB <NUM> to identify the communications device <NUM>, as well as a timing advance value (such that the communications device <NUM> can change its timing to compensate for the round trip delay caused by its distance from the gNodeB <NUM>) and grant uplink resources for the communications device <NUM> to transmit the data in.

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

In <NUM>/NR systems, an "inactive" RRC state may be used, where a UE is able to start data transfer with a low delay in the inactive state without transition to a connected state. Various possible solutions have been proposed to permit this.

A development to transmit data more quickly for particular applications is known as a two-step RACH [<NUM>]. 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 PRACH 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) (see e.g. [<NUM>]).

Broadly, the two-step RACH allows the combination of the transmission of the random access preamble <NUM> with the transmission of data <NUM> of <FIG> as an initial transmission ("Message A" or "MsgA"), and similarly the combination of the transmission of the random access response <NUM> and contention resolution message <NUM> 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 applicable for communications devices in the RRC_INACTIVE , RRC_CONNECTED and RRC IDLE states.

A message flow diagram illustrating the two-step RACH process is shown in <FIG>. As its name suggests, in the two-step RACH process, there are only two steps as follows:.

Downlink messages (i.e. messages transmitted by the base station <NUM>), such as the Message B (MsgB) or the Message <NUM>, may be preceded by a transmission of downlink control information (DCI) as a resource allocation message to indicate downlink communications resources on which the downlink message is to be transmitted.

A communications device which has recently transmitted either a Message A or a random access request may therefore monitor a downlink control channel on which the DCI may be transmitted. The communications device may determine that the DCI allocates resources for a message transmitted as part of the RACH procedure based on a temporary identity used to encode the DCI. For example, the DCI may be encoded using a random access radio network temporary identity (RA-RNTI), specifically pre-allocated for the purpose of encoding a DCI which allocates resources for a random access response (RAR) message.

If the communications device detects that a DCI has been encoded using the RA-RNTI, then it may proceed to attempt to decode signals transmitted using the communications resources allocated by the DCI to recover the random access response message (e.g. Message B or Message <NUM>).

During the RACH procedure (either two-step or four-step), various means may be made to identify a communications device, to avoid the possibility that a communications device considers that a downlink message was intended for it, when in fact the message was intended for or was in response to a different communications device.

With the development of New Radio (NR) for <NUM>, it has been proposed to enhance the two-step RACH process [<NUM>], to assist with and to further develop applications such as the Industrial Internet of Things (IIoT) [<NUM>] and an NR-based Access to Unlicensed Spectrum [<NUM>]. The enhancements to the two-step RACH process are aimed at specifying general Medium Access Control (MAC) procedures covering both physical layer and higher layer aspects. In general, benefits of the two-step RACH is to reduce a time taken 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 <NUM> to <NUM> for initial access UEs. It was concluded that a two-step RACH procedure has potential benefits for channel access in NR unlicensed spectrum (NR-U). In addition, two-step RACH procedure has been proposed to enable small data transmissions for UEs in RRC connected mode without UL synchronization as well as UEs in inactive state.

As part of a proposal to enhance the two-step RACH a process followed by the UE and the gNB differs depending on whether the UE already has a Radio Network Terminal Identifier (RNTI). Those acquainted with 3GPP protocols will be aware that there are various RNTIs which are used to identify UEs at various points where the UE needs to be identified during some interaction with the network or performing a protocol. According to one proposal if the UE has an RNTI for the cell in which it is communicating with the gNB, which is a Cell RNTI (C-RNTI) then:.

On the other hand if the UE does not have a C-RNTI then:.

A technical problem therefore exists in providing a two-step RACH procedure in which a UE performing the two-step RACH procedure will be able to identify a MsgB using an RNTI, which will not be confused by a legacy or conventional UE if performing a four-step RACH. This is because, whilst it is being proposed to design a new RNTI of MsgB for the two-step RACH, it is assumed that a search space or control channel resources (i.e. PDCCH search space) in the downlink where MsgB and legacy RAR messages are transmitted can be the same for both two-step RACH and four-step RACH. In addition, the uplink PRACH resources (i.e. occasion) for two-step RACH and four-step RACH can be mostly multiplexed either in time domain or frequency domain with Frequency Division Multiplexing (FDM). If time domain multiplexing is employed (i.e. in different time slots), the legacy RNTI for four-step RACH can be also used for two-step RACH because the equation for RNTI includes slot index, therefore there is no issue of RNTI collision or ambiguity, because separating different PRACH transmissions (preamble) will produce different RNTIs in the response. However, for the case of FDM multiplexing or shared PRACH resources on the same slot where starting OFDM symbols are the same, the RNTI collision or ambiguity will occur. Note that in case of shared PRACH resources, the PRACH preambles are portioned into two groups, one for four-step RACH and the other for two-step RACH UEs.

An example illustration of a FDM of a PRACH in which a two-step RACH and a four-step RACH are multiplexed in frequency and so transmitted at the same time is shown in <FIG>. In <FIG> a bandwidth part (BWP) <NUM> of a wireless access interface is divided in time according to a proposal for NR in which communications resources of the wireless access interface are divided in time into a plurality of time slots, each of which comprises fourteen OFDM symbols <NUM>. Each of the OFDM symbols is given a symbol index <NUM>. The frequency domain is also divided into a plurality of sub-carriers, in this example one hundred, each of which is given a physical resource block ((PRB) index <NUM>. As shown in <FIG> the resource of the bandwidth part <NUM> are divided in frequency in the time slot <NUM> to provide a first PRACH from PRBs <NUM>, <NUM> and <NUM> allocated as a four-step RACH occasion <NUM> and a second PRACH from PRBs <NUM>, <NUM>, <NUM> allocated as a two-step RACH occasion <NUM>. As such two different UEs one a conventional or legacy UE and one a NR/<NUM> UE could transmit contemporaneously a PRACH preamble and MsgB respectively. The network therefore needs to respond to both using an RNTI which will be recognised by both unambiguously and not confused with each other. Hence the issue is how to differentiate RNTIs for two-step RACH and four-step RACH when two or more UEs transmit PRACH preambles on the same slot in the uplink for initial access procedure, specifically for FDM multiplexing or shared PRACH resources where starting OFDM symbols are the same for both two-step RACH and four-step RACH on a bandwidth part (BWP) of a cell.

Embodiments of the present technique can provide, on the UE side, a method of operating a communications device in a wireless communications network, the method comprising transmitting a random access message on a wireless access interface, the random access message comprising a selected random access preamble and transmitting uplink data on communications resources of a shared channel, the communications resources of the shared channel being determined from the transmission of the random access message. The method further comprises receiving a resource allocation message comprising an indication of downlink communications resources allocated for the transmission of a random access response message combined with a radio network terminal identifier which identifies the communications device which transmitted the random access message, determining that the resource allocation message identifies the communications device, and in response to determining that the resource allocation message identifies the communications device, receiving and decoding the signals transmitted using the allocated downlink communications resources. The determining that the resource allocation message identifies the communications device comprises calculating the radio network terminal identifier which is used in the resource allocation message to identify the communications device using an offset, and confirming that the calculated radio network terminal identifier corresponds with the radio network terminal identifier present in the resources allocation message.

Embodiments of the present technique can differentiate between RNTIs for two-step RACH and four-step RACH when two or more UEs transmit PRACH preambles on the same slot in the uplink for initial access procedure. In other words, differentiating between legacy RA-RNTI and MsgB-RNTI where both two-step RACH and four-step RACH are supported on the same bandwidth part (BWP) of a cell.

According to one embodiment some un-used RNTIs from legacy RA-RNTI space are used for MsgB-RNTI of two-step RACH. The assumption here is that DCI size for two-step RACH and four-step RACH are same. A conventional or legacy RA-RNTI (compatible for a four-step RACH) is calculated according to the following equation from [<NUM>]: <MAT>.

• where s_id is the index of the first OFDM symbol of the PRACH occasion (<NUM> ≤ s_id < <NUM>),
• t id is the index of the first slot of the PRACH occasion in a system frame (<NUM> ≤ t id < <NUM>), where the subcarrier spacing to determine t_id is based on the value of µ specified in subclause <NUM>. <NUM> in TS <NUM> (also shown on Table <NUM> below),
• f id is the index of the PRACH occasion in the frequency domain (<NUM> ≤ f_id < <NUM>), and
• ul carrier id is the UL carrier used for Random Access Preamble transmission (<NUM> for NUL carrier, and <NUM> for SUL carrier).

From the legacy equation, consider an example in which t_id = <NUM>, f_id =<NUM> and ul carrier id = <NUM>. Then the RA-RNTI equation collapses as: <MAT> where <NUM> ≤ s_id < <NUM>.

As can be seen from this example embodiment, there are fourteen OFDM symbols in a slot <NUM> of a PRACH occasion, there are fourteen different RNTIs which can be generated. However, in most of the PRACH configurations, the starting OFDM symbol is only one in every slot/PRACH occasion. This is because the PRACH occasion will typically begin at starting index symbol <NUM>. Examples of possible PRACH occasions are provided for example in Table <NUM>. <NUM>-<NUM> [<NUM>]. This means that typically only one RNTI out of fourteen RNTIs in a slot is used or in other words there typically are up to thirteen unused RNTIs in a slot in most of the cases.

It is also possible to have two or more PRACH occasions on the same slot for four-step RACH with different starting symbols depending on PRACH Configurations, for example see Table <NUM>. <NUM>-<NUM> [<NUM>], also illustrated on <FIG> presents a corresponding example to that of <FIG>, in which a bandwidth part <NUM> provides time and frequency resources of a wireless access interface in which a timeslot <NUM> provides fourteen OFDM symbols with a symbols index <NUM> with sub-carriers having a PRB index <NUM> numbered <NUM> to <NUM>. For the example shown in <FIG>, three PRACH occasions <NUM>, <NUM>, <NUM> are provided with frequency resources <NUM> of PRB <NUM>, <NUM>, <NUM>. Each of the three PRACH occasions <NUM>, <NUM>, <NUM> has a different starting symbol index <NUM>, <NUM>, <NUM> which will correspondingly generate a different RNTI according to the above equation. However, there are a good number of unused RNTIs in a slot. Embodiments of the present technique therefore use these unused RNTIs for two-step RACH.

Legacy RA-RNTI for four-step RACH cannot be changed due to backword compatibility issues, so there is no need to propose a new RNTI. However, for two-step RACH there is a need to specify a new RA-RNTI design for MsgB. In order to reuse the unused RNTIs in a slot for two-step RACH, an offset is introduced from the starting OFDM symbol of the PRACH occasion for two-step RACH. This offset value is only used in the MsgB-RNTI equation (see below) and the actual starting OFDM symbol of the PRACH resource/occasion for two-step RACH is not changed. That is to say that although the offset is used to generate the RNTI for the two-step RACH, this does not represent an offset in the actual transmission of the Message A.

The offset can be fixed or configurable. If configurable, then in one example the offset for performing a two-step RACH in a cell can be communicated using a broadcast transmission for example in System Information Blocks (SIB). Alternatively, the offset can be UE-specifically signalled if in connected mode for example using RRC signalling.

According to example embodiments both the UE and the gNB of the network infrastructure equipment can both generate the proposed MsgB-RNTI transmitted by the gNB and searched for by the UE according to the following formula: <MAT> where s_new_id = (s_id + s_offset) modulus <NUM>, and s_offset is an offset value (<NUM> ≤ s_offset < <NUM>) from the legacy starting OFDM symbol s_id. All other parameters are same as defined by the legacy equation for RA-RNTI.

According to other alternatives the offset may be calculated as follows: <MAT> where <MAT> is defined in Table <NUM>. <MAT> <MAT> <MAT> s_new_id = index of the last OFDM symbol of the PRACH occasion.

According to the above equation, for an example in which FDM multiplexing is used for the two-step and the four-step PRACH on the same time slot where starting OFDM symbols are the same for both two-step RACH and four-step RACH, the RNTI generated for two-step RACH will be different due to the offset value introduced and configured for two-step RACH. In this case, the network can decide and configure an offset value such that the MsgB-RNTI for the two-step RACH would be different from RA-RNTI of the four-step RACH. According to this example there are up to thirteen offset values available in each slot.

In another example embodiment some un-used RNTIs from a legacy RA-RNTI space are used to form a MsgB-RNTI for the two-step RACH by adding an offset to a time slot value in the above mentioned formula. According to this example the above formula for calculating the MsgB RNTI is adapted to become: <MAT>.

In this formula for the MsgB RNTI, a slot offset t_new_id is adapted to become: <MAT> <MAT> when t_id > <NUM>; <MAT> PRACH occasion t_id. where t_offset is an offset value (<NUM> ≤ t offset < <NUM>) from the legacy slot with.

According to this example embodiment an offset to a slot in which the preamble for the RACH process is transmitted is added to the slot in which the preamble was actually transmitted to form an RNTI which will not be confused with an RNTI generated for a UE performing a four step RACH in the same time slot. This is expressed in the above adaptation to the formula for calculating the Message B RNTI (t_new_id).

The slot offset (<NUM> ≤ t_offset < <NUM>) may be communicated to the UE in advance. In some examples, the offset can be UE-specifically signalled if in connected mode, for example by RRC signalling. Accordingly, the gNB and UE are synchronized in respect of how to generate the RNTI based on the slot offset signalled to the UE in advance. The UE would simply input the new parameter "t_new_id" into the equation as explained above.

Example embodiments of the present technique can take advantage of used parts of an RNTI space defined in specifications such as those defined by possible PRACH occasions defined for example in TS <NUM> V15. <NUM> [<NUM>]. This is because it can be observed that not all slots (<NUM> ≤ t_id < <NUM>) within a system radio frame have PRACH occasions in most of the PRACH configurations as captured in TS <NUM> V15. <NUM> Table <NUM>. <NUM>-<NUM>, Table <NUM>. <NUM>-<NUM> and Table <NUM>. <NUM>-<NUM> [<NUM>].

For example in Table <NUM>. <NUM>-<NUM>, PRACH configuration index <NUM> has slot indices <NUM>,<NUM>,<NUM>,<NUM>,<NUM> with PRACH occasions as shown in <FIG>. As shown in <FIG> and according to the example PRACH configuration of index <NUM> in Table <NUM>. <NUM>-<NUM> [<NUM>] there are PRACH occasions <NUM> specified for slots <NUM>, <NUM>, <NUM>, <NUM>, <NUM> according to the slot index <NUM> of the radio frame <NUM>, but there are no PRACH occasions for slot indices <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. Accordingly an RNTI can be generated with an offset to point to these slots indices <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in which there is no PRACH occasion specified. As a result, two UEs, one performing a two-step RACH and another performing a four-step RACH will have different RNTIs generated even if they transmit a RACH preamblke in the same PRACH occasion according to this index <NUM>, because the UE performing the two-step RACH will include an offset in the slot index, which points to a slot in which there is no PRACH occasion. Accordingly embodiment of the present technique provide an arrangement for generating an RNTI which is related to a location in the wireless access interface in which a RACH preamble was transmitted but adapted to represent a location where a RACH preamble will not have been transmitted according to specifications for the wireless access interface.

In example embodiments, other parameters in the above equation can also be exploited, for example when some of the values of PRACH frequency-domain index (<NUM> ≤ f id < <NUM>) or uplink carrier index (ul_carrier_id: <NUM> for NUL carrier, and <NUM> for SUL carrier) are not used for Contention Based Random Access (CBRA) of a two-step RACH within a cell. An offset of f_id or ul carrier id can be signalled to the UE for generating the RNTI for Contention Free Random Access (CFRA) for a two-step RACH.

Hence, embodiments of the present technique can exploit any one of the parameters (i.e. s_id, t_id, f_id and ul_carrier_id) in the equation above equation for generating the RNTI of Message B or combination of these parameters to generate a different RNTI for CFRA of <NUM>-step RACH than the RNTI for CBRA of <NUM>-step RACH. Embodiments of the present technique can be used to differentiate between CFRA RNTI (contention-free random access) and CBRA RNTI (contention-based random access) regardless of which type of PRACH (<NUM>-step or <NUM>-step) a UE performs by employing an offset for a slot index or PRACH frequency domain index or uplink carrier index or combination of these offsets when both (CFRA and CBRA) are supported on the same slot of the same bandwidth part (BWP) of a cell.

Example embodiments therefore provide an arrangement in which different RNTIs can be provided for contemporaneously transmitted preamble/Message A transmissions for MsgB, which does not increase the range of the RNTI-spaces by re-using some of the unused RNTIs within the existing RNTI-space of four-step RACH.

<FIG> provides a part message exchange diagram part flow diagram illustrating an example embodiment. As for the example shown in <FIG>, two UEs, UEa 270a, UEb 270b, perform respectively a two-step and four-step RACH process with a gNB <NUM>. As for the example embodiments explained above, the UEa 270a and the UEb 270b transmit respectively a MsgA <NUM> and a Message <NUM><NUM> according to a two-step and four-step RACH processes respectively using frequency multiplexed resources of the same time slot as shown in <FIG> for example. For this example the MsgA and Message <NUM> comprising a preamble both transmit in the PRACH resources of the time slot starting at the same OFDM symbol index.

From the explanation of the example embodiments provided above, it will be appreciated that the UEb 270b performs a conventional four-step RACH by exchanging messages with the gNB <NUM> as represented as message <NUM><NUM>, message <NUM><NUM>, message <NUM><NUM> and message <NUM><NUM> as illustrated and explained above with reference to <FIG> and so a detailed explanation will not be repeated. As will be appreciated however, after receiving the RACH preamble of message <NUM><NUM>, the gNB <NUM> in a first process step S801 generates the RA-RNTI according to a conventional operation, which then forms part of the Message <NUM><NUM> and continues in step S803 with the four-step random access process. Accordingly operations of the UEb 270b will not be provided in detail because these conform to the legacy or conventional operation as explained with reference to <FIG>. However it will be appreciated that the RA-RNTI is generated without reference to an RNTI generated for UEa 270a for the two-step RACH which it is performing.

When performing the two-step RACH, UEa 270a generates MsgA <NUM> in a step S805 and, as explained above, transmits the MsgA <NUM> in the same time slot at the same starting symbol as the preamble of the Message <NUM><NUM> transmitted by the UEb 270b. A conventional way of generating the RNTI would therefore produce the same RNTI as that generated in step S801 and would therefore conflict with the message <NUM><NUM> transmitted by the gNB <NUM> to UEb 270b. According to the example embodiments therefore the UEa 270a in step S807 generates an RNTI based on an offset according to the above equation and the gNB <NUM> also generates an RNTI according to the same equation using the same offset in step S809. The offset used in steps S807 and S809 may be signalled in advance using either broadcast signalling such as in System Information Blocks (SIB) or using RRC signalling.

Having calculated the RNTI using the offset and the above equation, the gNB <NUM> generates and transmits in step S811 a DCI for signalling the resources of the PDSCH in which the MsgB will be transmitted. The DCI <NUM> is masked with the calculated RNTI and transmitted by the gNB <NUM> in the PDCCH in a search space known to the UEa 270a according to a conventional operation of the two-step RACH process. The UEa 270a is therefore able in step S813 to detect the DCI <NUM> indicating the resources of the PDSCH in which the MsgB will be transmitted, using the calculated RNTI with the determined offset.

The gNB <NUM> in step S815 then transmits the MsgB in the resources of the PDSCH indicated by the DCI <NUM>, which is detected by the UEa 270a in step S817.

Although the above proposed solution is tailored for differentiating between MsgB-RNTI for two-step RACH and RA-RNTI for four-step RACH in Rel-<NUM>, the concept can be equally applied to the case where there are CFRA (contention-free random access) and CBRA (contention-based random access) resources on the same slot and their starting OFDM symbols are the same. These CFRA and CBRA resources can belong either to four-step RACH or two-step RACH or their combinations on the same bandwidth part (BWP) of a cell. In addition, there are other cases where CBRA and SI request using PRACH resources are configured separately in the same slot on the same BWP of a cell, hence, this concept can be applied as well.

Furthermore, for the case that there are two or more PRACH resources/occasions on the same slot for four-step RACH or if there are two or more PRACH resources/occasions on the same slot for two-step RACH depending on PRACH Configurations, more than one offset value can be configured and broadcasted via system information (SIB) for two-step RACH, possibly one offset for each PRACH resource/occasion.

According to another example embodiment different sizes of DCI can be used for a RAR message of legacy four-step RACH and MsgB of two-step RACH. As the payload of the legacy DCI cannot be changed due to backward compatibility issues, a new DCI format with smaller payload size (i.e. by removing some fields) or larger payload size (i.e. by adding a new set of fields) for two-step RACH can be used according to some example embodiments. This is possible because there are currently up to 16bits that are not used for the DCI scheduling the RAR message of a conventional four-step RACH. UEs can be configured according to example embodiments with two-step RACH to detect a new shorter DCI format on the PDCCH search space. However, the RNTI will be calculated in accordance with the same technique as with a conventional/legacy four-step RACH.

An example according to this embodiment is illustrated in <FIG>, which corresponds to the example shown in <FIG> and so only the differences will be explained. For example the operation of the second UEb 272b performing the four-step RACH has not been shown in <FIG> and will not be repeated although it will be appreciated that a technical problem of separating random access response messages and DCI transmissions using different RNTIs remains the same as that for the embodiment shown in <FIG>. In <FIG> as for the example in <FIG>, the first UEa 270a generates MsgA <NUM> in a step S905 and transmits MsgA <NUM>, which includes a preamble <NUM> and may also include data transmitted in shared resources of the uplink, which represents a transmission of MsgA.

According to this example embodiment the UEa 270a in step S907 generates an RNTI based on a conventional calculation for an RNTI. Correspondingly the gNB <NUM> after detecting the mMsgA preamble in step S903 also calculates an RNTI in step S909 according to a conventional four-step RACH. The calculation of the RNTI in both the UEa 270a in step S905 and the gNB <NUM> in step S909 is according to the equation: <MAT>.

This equation is explained above. According to this example embodiment this RNTI is then formed into shortened DCI by the gNB <NUM> in step S910. According to this example the DCI is formed according to a conventional arrangement except that the payload is shortened from <NUM>-bits for example to <NUM>-bits, which is enough to carry the downlink resource allocation which may be <NUM>-bits. A CRC is then generated and both the information payload representing the downlink resource allocation and the CRC are masked with the RNTI. This therefore forms a shortened DCI <NUM>, which includes the resources of the PDSCH <NUM>. The gNB <NUM> then transmits the shortened DCI in step S911 for signalling the resources of the PDSCH in which the MsgB will be transmitted. The shortened DCI <NUM> is masked with the calculated RNTI <NUM> and transmitted by the gNB <NUM> in the PDCCH in a search space known to the UEa 270a according to a conventional operation of the two-step RACH process. The UEa 270a is therefore able in step S913 to detect the shortened DCI <NUM> indicating the resources of the PDSCH in which the MsgB will be transmitted, using the calculated RNTI with the masked on the shortended payload. The gNB <NUM> in step S915 then transmits the MsgB in the resources of the PDSCH indicated by the DCI <NUM>, which is detected by the UEa 270a in step S917.

According to this example embodiment the second UEb 270b is unable to detect and decode the shorter DCI <NUM> and will not be able to detect the RNTI even though it may calculate the same RNTI if both of the UEa 270a and UEb 270b transmit preambles in the same time slot. This is because the DCI carrying the RNTI has a different size and so the legacy UE will not be able to correctly detect the RNTI because the DCI has a different siz from that which it expecting. Since the second UEb 270b will not be able to detect the DCI it will not recover the resources of the PDSCH in which the MsgB random access response message is transmitted. Accordingly the RAR messages in Message <NUM> and MsgB can be separated.

According to some other example embodiments the gNB and UE are configured to generate an RNTI by appending a bit pattern to the legacy RNTI so that a UE configured to perform a two-step RACH can only decode the DCI scheduling MsgB of two-step RACH. The assumption here is that DCI size for two-step RACH and four-step RACH are same. Currently a length of the RNTI is <NUM> bits and a CRC checksum is <NUM> bits for NR. An increase in the length of the RNTI from <NUM> bits to <NUM> bits for a two-step RACH by appending a fixed known bit pattern of 8bits, for example "<NUM>" can provide an arrangement in which a configured UE which performs the two-step RACH can only use this pattern. As such, legacy UEs will not be able to decode the DCI. This bit pattern is fixed and known in advance between gNB and UEs. An example of this embodiment is shown in <FIG>, which again corresponds to the examples of <FIG> and <FIG> and so only the differences will be discussed. As shown in <FIG>, in step S957 and step S969 the UEa 270a and the gNB <NUM> respectively generate a new fixed field RNTI which comprises a sixteen bit field <NUM> and a fixed field <NUM>. The fixed field <NUM> may be eight bits, which may be <NUM> as shown or may be another predetermined pattern. It will of course ne appreciated that any number of bits can be used for the fixed field. The <NUM>-bit field can be generated according to the conventional operation as explained above. As for the above examples, the gNB <NUM> transmits the DCI with the new fixed field RNTI in step S971 and the MsgB <NUM> in step S975, which is detected by the UEa 270a in steps S973 and S977 respectively.

According to this example embodiment the legacy/conventional UEb 270b is not able to detect the fixed field RNTI and so cannot decode the DCI or the MsgB transmitted to the UEa 270a so that a two-step RACH and a four-step RACH procedures can be separated.

Corresponding communications devices, base stations and methods therefore, and circuitry for a communications device and circuitry for a base station have also been described.

As will be appreciated from the above explanation, example embodiments can provide a method of operating an infrastructure equipment in a wireless communications network, the method comprising receiving a first random access message on a wireless access interface provided by the infrastructure equipment from a first communications device, the first random access message comprising a first random access preamble, receiving uplink data on communications resources of a shared channel from the first communications device, the communications resources of the shared channel being determined from the transmission of the first random access message, receiving a second random access message on a wireless access interface provided by the infrastructure equipment from a second communications device, the second random access message comprising a second random access preamble, transmitting a first resource allocation message to the first communications device, the first resource allocation message comprising an indication of downlink communications resources allocated for the transmission of a first random access response message combined with a first radio network terminal identifier which identifies the first communications device which transmitted the first random access message, transmitting a second resource allocation message to the second communications device, the second resource allocation message comprising an indication of downlink communications resources allocated for the transmission of a second random access response message combined with a second radio network terminal identifier which identifies the second communications device which transmitted the second random access message. The transmitting the first resource allocation message to the first communications device includes calculating a first radio network terminal identifier which is used in the first resource allocation message to identify the communications device using an offset to distinguish the first radio network terminal identifier from a second terminal identifier to identify the second communications device, and transmitting the first resource allocation message to the first communications device.

It may be noted various example approaches discussed herein may rely on information which is predetermined / predefined in the sense of being known by both the base station and the communications device. It will be appreciated such predetermined / predefined information may in general be established, for example, by definition in an operating standard for the wireless telecommunication system, or in previously exchanged signalling between the base station and communications devices, for example in system information signalling, or in association with radio resource control setup signalling, or in information stored in a SIM application. That is to say, the specific manner in which the relevant predefined information is established and shared between the various elements of the wireless telecommunications system is not of primary significance to the principles of operation described herein. It may further be noted various example approaches discussed herein rely on information which is exchanged / communicated between various elements of the wireless telecommunications system and it will be appreciated such communications may in general be made in accordance with conventional techniques, for example in terms of specific signalling protocols and the type of communication channel used, unless the context demands otherwise. That is to say, the specific manner in which the relevant information is exchanged between the various elements of the wireless telecommunications system is not of primary significance to the principles of operation described herein.

It will be appreciated that the principles described herein are not applicable only to certain types of communications device, but can be applied more generally in respect of any types of communications device, for example the approaches are not limited to URLLC / IIoT devices or other low latency communications devices, but can be applied more generally, for example in respect of any type of communications device operating with a wireless link to the communication network.

Claim 1:
A method for operating a communications device in a wireless communications network, the method comprising:
transmitting a random access message (<NUM>, <NUM>, <NUM>) on a wireless access interface, the wireless access interface being divided in time into timeslots, each time slot including a plurality of Orthogonal Frequency Division Multiplexed, OFDM, symbols having in the frequency domain a plurality of sub-carriers, and provides a physical random access channel, PRACH, on an uplink carrier in one or more of the time slots, the random access message (<NUM>, <NUM>, <NUM>) comprising a selected random access preamble, the selected random access preamble being transmitted using time and frequency communications resources corresponding to an occasion of the PRACH,
receiving a resource allocation message (<NUM>, <NUM>) comprising an indication of downlink communications resources allocated for the transmission of a random access response message combined with a radio network terminal identifier which identifies the communications device which transmitted the random access message,
determining that the resource allocation message (<NUM>, <NUM>) identifies the communications device, and
in response to determining that the resource allocation message identifies the communications device, receiving and decoding the signals transmitted using the allocated downlink communications resources, the determining that the resource allocation message (<NUM>, <NUM>) identifies the communications device comprising
calculating the radio network terminal identifier which is used in the resource allocation message to identify the communications device using an offset, and
confirming that the calculated radio network terminal identifier corresponds with the radio network terminal identifier present in the resources allocation message, wherein the calculating the radio network terminal identifier comprises calculating the radio network terminal identifier based on one or more of
an index of a first of a plurality of OFDM symbols of a time slot of the PRACH occasion from which the transmission of the selected random access preamble begins, the selected random access preamble occupying a plurality of the OFDM symbols,
an index of a time slot number in which the selected random access preamble was transmitted in a PRACH occasion in a system frame,
a subcarrier spacing,
an index of the PRACH occasion in the frequency domain, and
an uplink carrier used.