First device, first reader, and method thereof

Abstract

A wireless communication system is described that consists of at least one 'Ambient' Internet-of-Things (A-IoT) device, at least one A-IoT device reader, and optionally a RAN node that are mutually configured for the implementation of resource allocation and extension for a third message (e.g., contention resolution-type message / 'Msg3') in an access procedure between an A-IoT device reader and one or more A-IoT devices.

Description

FIRST DEVICE, FIRST READER, AND METHOD THEREOF

[0001] The present disclosure relates to a communication system and to parts thereof. The disclosure has particular but not exclusive relevance to wireless communication systems and devices thereof operating according to the 3rd Generation Partnership Project (3GPP) standards, equivalents, or derivatives thereof (including Long-Term Evolution (LTE)-Advanced, Next Generation or 5G networks, future generations, and beyond). The present disclosure relates, in particular but not exclusively, to ambient Internet-of-Things (A-IoT) systems and the allocation of resources for a third message (e.g., contention resolution-type message / 'Msg3') in an access procedure between an A-IoT device reader and one or more A-IoT devices.

[0002] Earlier developments of the 3GPP standards were referred to as the Long-Term Evolution (LTE) of Evolved Packet Core (EPC) network and Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), also commonly referred as '4G'. More recently, the term '5G' and 'new radio' (NR) is used to refer to an evolving communication technology that supports a variety of applications and services. Various details of 5G networks are described in, for example, the 'NGMN 5G White Paper' V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which document is available from https: / / www.ngmn.org / 5g-white-paper.html. 3GPP intends to support 5G by way of the so-called 3GPP Next Generation (NextGen) radio access network (RAN) and the 3GPP NextGen core network.

[0003] Under the 3GPP standards, a NodeB (or an eNB in LTE, and gNB in 5G) is the radio access network (RAN) node (or simply 'access node', 'access network node' or 'base station') via which communication devices (user equipments or 'UEs') connect to a core network and communicate with other communication devices or remote servers. For simplicity, the present application may use the term access network node, RAN node (or simply RAN) or base station to refer to any such access nodes.

[0004] For simplicity, the present application will use the term mobile device, user device, UE, or IoT device, to refer to any communication device that is able to connect to the core network via one or more base stations. Although the present application may refer to mobile devices in the description, it will be appreciated that the technology described can be implemented on any communication devices (mobile and / or generally stationary) that can connect to a communication network for sending / receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory. An IoT device may, for example, be any UE equipped with appropriate electronics, software, sensors, network connectivity, and / or the like, which enable these devices to collect and exchange data with each other and with other communication devices. IoT devices may, for example, be in the form of automated equipment that may operate without requiring human supervision or interaction.

[0005] In the current 5G architecture, the base station structure may be split into two or more parts. In some RAN implementations there are two parts, known as the Central Unit (CU or gNB-CU) - sometimes referred to as a 'control unit' - and the Distributed Unit (DU or gNB-DU), connected by a CU-DU interface (e.g., an F1 interface). This enables the use of a 'split' architecture in which the typically 'higher' CU layers (for example, but not necessarily or exclusively, Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC) layers) and the, 'lower' DU layers (for example, but not necessarily or exclusively, Radio Link Control (RLC), Media (sometimes referred to as 'Medium') Access Control (MAC), and Physical (PHY) layers) are separated between a particular CU, and one or more DUs that are connected to and controlled by that CU via the CU-DU interface. Thus, for example, the higher layer CU functionality for a number of base stations may be implemented centrally (for example, by a single processing unit, or in a cloud-based or virtualised system), whilst retaining the lower layer DU functionality locally separately for each base station.

[0006] In 5G, core network entities comprise logical nodes (or 'functions') including control plane functions (CPFs) and one or more user plane functions (UPFs). The CPFs include, amongst other things, one or more Access and Mobility Management Functions (AMFs), a session management function (SMF), and one or more location management functions (LMFs). The AMF generally corresponds to the MME in 4G and performs many of the functions performed by the MME. Each UPF combines functionality of both the S-GW and P-GW - specifically user plane functionality of the S-GW (SGW-U) and user plane functionality of the P-GW (PGW-U). The SMF provides session management functionality (that formed part of MME functionality in 4G). The SMF also combines the some of the functionality provided by the S-GW and P-GW - specifically control plane functionality of the S-GW (SGW-C) and control plane functionality of the P-GW (PGW-C). The SMF also allocates IP addresses to each UE.

[0007] When a UE wishes to access a cell (and / or a beam) it may attempt to access that cell and / or beam using a random access (RACH) procedure that historically involved four distinct steps. More recently, a simplified access procedure has been developed by which a UE may attempt to access that cell and / or beam using a two-step RACH procedure. Both the four-step and two-step RACH procedures are well known to those skilled in the art.

[0008] In summary, the four-step procedure typically involves the UE selecting random access resources (including, for example, a preamble) that it uses to initiate the RACH procedure. The UE sends the selected preamble in a first message ('Msg1') to a base station over a physical random-access channel (PRACH). In response, the base station responds with a random-access response (RAR) (or 'Msg2'). The RAR indicates reception of the preamble and includes, amongst other things, an uplink grant field indicating resources to be used in the uplink for a physical uplink shared channel (PUSCH). The UE then sends a third message ('Msg3') to the network over a physical uplink shared channel (PUSCH) based on the information in the RAR. The specific message sent by the UE in this step, and the content of the message, depends on the context in which the random-access procedure is being used. For initial RRC connection setup, for example, Msg3 typically comprises an RRC Setup request or similar message carrying a temporary randomly generated UE identifier. The network responds with a fourth message ('Msg4') which carries the randomly generated UE identifier received in Msg3 for contention purposes to resolve any collisions between different UEs using the same preamble sequence. When successful, Msg4 also transfers the UE to a connected state.

[0009] As those skilled in the art will appreciate, while a contention based random access (CBRA) procedure is described, a non-contention based (or 'contention free') procedure may also be used, e.g., in which a dedicated preamble is assigned by the base station to the UE. The two-step procedure is similar in terms of the information transferred but involves one UE to base station message ('MsgA') and one base station to UE message ('MsgB'). MsgA, in effect, combines Msg1 and Msg3 of the four-step procedure, and MsgB, in effect, combines Msg2 and Msg4 of the four-step procedure.

[0010] It will be appreciated that random access procedures such as those mentioned above may also be used in other contexts including, for example, handover, connection reestablishment, requesting uplink (UL) scheduling where no dedicated resource for a scheduling-request has been configured for the UE, etc.

[0011] Recently, IoT has attracted much attention in the wireless communication world, and as IoT develops and grows, more 'things' are expected to be interconnected to improve productivity efficiency and increase the comforts of life. In this vein efforts have been made to try to reduce the size, complexity, and power consumption of IoT devices to enable the deployment of tens or even hundreds of billions of IoT devices for various applications. Typically, such IoT devices are powered by batteries that need to be replaced or recharged manually. Thus, as the number of IoT devices deployed grows apace, there is an increasingly negative impact from such devices as the need to replace them leads to increasingly high maintenance costs, serious environmental issues, and even safety hazards for some use cases, for example, for the use of wireless sensors in electrical power, and petroleum industries.

[0012] 'Ambient' IoT (A-IoT) attempts to address some of the above issues and relies on ultra-low complexity devices with ultra-low power.

[0013] A-IoT devices (which may also be referred to simply as IoT devices for simplicity) make use of 'backscatter' or 'reflected' communication to communicate with an A-IoT device reader which may be a cellular RAN node (base station), or other device connected to a cellular communication network. Specifically, A-IoT devices transmit data by reflecting or backscattering radio frequency (RF) signals from the A-IoT device reader without necessarily having to actively generate their own RF signals. Instead, A-IoT devices effectively modulate their impedance or reflectivity in response to an incoming RF signal (known as an 'unmodulated carrier' or 'unmodulated carrier signal'), which causes the signal to be reflected to a receiver. The backscattered signals (also referred to as 'reflected' signals) carry information, encoded by the modulation, of the impedance or reflectivity of the A-IoT device.

[0014] Such backscattered signals are typically transmitted on the same frequency as the unmodulated carrier signal from which it originated, but alternatively, the backscattered signals may undergo additional processing such that the backscattered signals have an offset from the frequency of the unmodulated carrier signal.

[0015] It can be seen that A-IoT devices and associated A-IoT device readers have much in common with radio frequency identification (RFID) tags and associated RFID readers. However, A-IoT devices need to be able to operate successfully in a conventional, orthogonal frequency-division multiplexing (OFDM) based, cellular communication system, and to co-exist with more complex conventional UEs (such as smart phones, conventional IoT devices, and the like). Accordingly, compared to conventional RFID devices, A-IoT devices and associated A-IoT device readers are typically subject to additional constraints and need to be able to support additional functionality.

[0016] A-IoT devices may be categorised as follows: 　　- Type 1 devices: A-IoT devices that have means of energy storage but no independent signal generation or downlink (DL) / uplink (UL) amplification capabilities. Such devices rely solely on backscatter communication to communicate in the uplink with other devices. Type 1 devices typically have an initial sampling frequency offset (SFO) up to 10Xppm (where the value of X is still to be agreed but may, for example, be 4 or 5). 　　- Type 2a devices: A-IoT devices that have means of energy storage, and no independent signal generation capabilities, but that do have both DL and UL amplification capabilities. Such devices similarly rely on backscatter communication in the uplink to communicate with other devices. For example, the device can use stored energy to amplify signals backscattered on a carrier wave provided externally. Type 2a devices similarly have a typical initial SFO up to 10Xppm (where the value of X is still to be agreed but may, for example, be 4 or 5). 　　- Type 2b devices: A-IoT devices that have means of energy storage and independent signal generation, i.e., the device has active radio frequency (RF) components that can generate signals for transmission. Hence, UL transmissions may be generated internally by the device or may be backscattered on a carrier wave provided externally. Type 2b devices also have both DL and UL amplification capabilities. For example, the device can use its stored energy to amplify signals backscattered on the carrier wave provided externally. Type 2b devices similarly have a typical initial SFO up to 10Xppm (where the value of X is still to be agreed but may, for example, be 4 or 5).

[0017] It will be appreciated that type 1, 2a, and 2b, are only examples of possible ambient IoT device categories and that other categories and / or types of ambient IoT devices are possible. For example, the term 'type A' device is also sometimes used to refer to an ambient IoT device that has no means of energy storage and no independent signal generation / amplification capabilities. Such devices also rely on backscatter communication to communicate with other devices.

[0018] Typically, type 1, 2a, and 2b devices each have their own set of power consumption targets, complexity targets, latency targets, data rate targets, and the like.

[0019] For example, the power consumption target for type 1 devices during transmitting / receiving is typically set to less than or equal to 1 microwatts (μW), while for both type 2a and 2b devices the power consumption target during transmitting / receiving is typically set to less than or equal to a few hundred microwatts (μW).

[0020] It will be appreciated that the requirement for the power consumption target to be less than or equal to a 'few hundred μW' mentioned here means that a specific value does not need to be set. It is, therefore, open to discussion to ascertain whether a given design has a corresponding power consumption that satisfies this requirement.

[0021] It is envisaged that a coverage design target for A-IoT devices will have a maximum distance of between 10m and 50m when the devices are indoors. It will be appreciated that the maximum distance for such A-IoT devices may be sub-selected within the range of 10m to 50m.

[0022] Typically, where such ambient IoT devices are implemented in a communication network / system (also referred to as an ambient IoT network) a maximum connection density target may also be set to ensure optimal performance of the network. Typically, such maximum connection density is set at 150 devices per 100 m2for indoor scenarios, and 20 devices per 100 m2for outdoor scenarios.

[0023] Ambient IoT networks may be configured to have any one of several possible connectivity topologies and may be deployed in several different ways. These topologies include: 　　- Topology 1 in which an ambient IoT device reader (in this example a base station or RAN node) and ambient IoT device communicate with one another directly (including the possibility that the base station that transmits to the ambient IoT device is different to the base station that receives from the ambient IoT device). This topology may, therefore, need to support full duplex operation at the base station to enable backscatter communication. This can be a significant challenge if an incoming RF signal (known as an 'unmodulated carrier' or 'unmodulated carrier signal') and reflected (or backscattered) signal are within the same RF band. 　　- Topology 2 in which a base station (or RAN node) and ambient IoT device communicate with one another via an ambient IoT device reader in the form of an intermediate / assisting node (which may be a relay, an integrated access and backhaul (IAB) node, another UE, a repeater and / or the like, which is capable of ambient IoT operation). The intermediate node transfers ambient IoT data and / or signalling between base station and the ambient IoT device. Like Topology 1, this topology may require support of full duplex operation at the intermediate node and hence faces similar associated challenges. 　　- Topology 3 in which the ambient IoT device: receives data / signalling from the base station (or RAN node) directly but transmits data / signalling to the base station indirectly via an assisting node; or transmits data / signalling to the base station (or RAN node) directly but receives data / signalling from the base station indirectly via an assisting node. Accordingly, in this example some IoT device reader functionality is provided by the base station and some IoT device reader functionality is provided by the assisting node. The assisting node may be a relay, an IAB node, another UE, a repeater and / or the like, which is capable of ambient IoT operation. This topology has the benefit that it does not require the base station, or the assisting node, to have full duplex operation. However, the node receiving the reflected signal needs to be able to differentiate between an unmodulated carrier signal and a reflected signal from an ambient IoT device.

[0024] For Topologies 1 and 2, there may be: none of RRC states typical to conventional UEs (e.g., IDLE, CONNECTED, SUSPENDED and / or the like); none of the mobility procedures typical to conventional UEs (e.g., at least no cell selection / re-selection functionality); and / or none of the automatic repeat request (ARQ) and / or hybrid-ARQ (HARQ) typical to conventional UEs.

[0025] Typically, in ambient IoT-based systems the user experienced data rate target is between 0.1 kbps and 5 kbps (with 1 kbps being a typical rate), and the design target of the maximum message size is approximately 1000 bits over both the 'device-to-reader' ('D2R') link, and the 'reader-to-device' ('R2D') link, which is in turn based on the maximum possible application layer packet size. Thus, assuming a 1 kbps data rate, it takes 1s to transmit 1000 bits over the D2R and R2D links. Typically, the D2R link between an A-IoT device reader and one or more A-IoT devices supports both time-division multiple access (TDMA) and frequency-division multiple access (FDMA), whilst the corresponding R2D link may only support TDMA.

[0026] The current view is that R2D transmission will typically comprise an R2D preamble to indicate a start time of the following PRDCH and possibly chip length information. This R2D preamble is followed immediately by the PRDCH transmission (carrying any R2D traffic data and / or any control information). An R2D postamble is transmitted immediately after the PRDCH transmission to indicate an end of the PRDCH transmission. Similarly, for D2R transmissions, it is envisaged that a D2R preamble will be transmitted at the beginning of each D2R transmission, immediately before the PDRCH transmission, to indicate a start time of the PDRCH transmission. A D2R postamble may also be transmitted following the PDRCH transmission to indicate the end of the PDRCH transmission (and possibly provide a final timing correction to the A-IoT device reader). In the context of D2R communication, however, a D2R midamble may be inserted into (sent during) the PDRCH transmission, for facilitating chip-level timing tracking and channel / interference estimation (e.g., depending on the length of that PDRCH transmission).

[0027] Thus, as the R2D preamble is used to indicate the start of each R2D transmission, the R2D postamble implicitly indicates the TBS of the PDRCH transmission by indicating the end of each R2D transmission. Accordingly, there is no need to restrict the timing of the R2D transmission to align with a conventional OFDM slot (e.g., an NR slot in a 5G system). Moreover, given the potential for a large number of small packets to be transmitted via A-IoT communication, flexible and efficient scheduling can be facilitated by not imposing a constraint that the boundary of the R2D transmission should align with that of the OFDM (e.g. NR) slots. Nevertheless, since the R2D transmission waveform is an OFDM-based waveform, the start of a R2D transmission may be aligned with the boundary of an OFDM (e.g., NR) symbol (including any cyclic prefix) when the R2D transmission co-exists with such transmissions) for in-band and guard-band operations.

[0028] Generally, for A-IoT communication, it is envisaged that multiple A-IoT logical channels for communication of upper layer data need not be supported. It is yet to be determined whether the concept of A-IoT logical channels is used (e.g., depending on final modelling issues). It is also envisaged that access stratum (AS) layer (above the PHY layer) RLC-like retransmission / repetition will not be supported for A-IoT. Nevertheless, this does not preclude the reader and device resending the payload again as a new transmission from the perspective of the MAC layer. It is yet to be determined how segmentation is to be handled (if needed).

[0029] Due to the simplicity of A-IoT technology, new random access procedures are being developed for allowing communication between an A-IoT device and the A-IoT device reader. These A-IoT access procedures are typically based on a slotted Additive Links On-line Hawaii Area (slotted-ALOHA) based algorithm / protocol that is widely used for communication between radio frequency identification (RFID) tags and their associated RFID reader. Slotted-ALOHA is a variation of the ALOHA protocol, which will be familiar to those skilled in the art. In slotted-ALOHA, a communication channel is effectively divided into small, fixed-length, time slots. Devices are only able to transmit data at particular times (e.g., during specific transmission occasions).

[0030] For random access in the context of RFID technology, as RFID tags are passive devices, the RFID reader needs to initiate any communication access from the RFID tags to the RFID reader. Specifically, communication between the RFID reader and the RFID tags is performed as part of a procedure called an inventory round. Initially, before the inventory process commences, the RFID reader typically transmits a 'Select' command to all RFID tags in the coverage area of the RFID reader, to select a particular group of the RFID tags that are allowed to respond to the RFID reader in the subsequent procedure. The Select command includes information that allows the RFID tags to identify if they are allowed to respond - for example, a device identifier (optionally with a mask) such as an electronic product code (EPC) (or part of it), and / or part of the information in the RFID tag's memory. Any RFID tag that matches the information in the Select command may respond. The RFID reader then sends a 'Query' command to initiate a random access like identification process and sets the parameters to be used for subsequent RFID tag to RFID reader communication.

[0031] Selected RFID tags (i.e., those that match the parameters in the Select command) then randomly determine a 'random access' slot (or 'reply slot') to reply in based on information in the 'Query' command. This reply slot may be the first slot (slot #0) or a subsequent slot. Selected RFID tags that do not respond immediately to the Query command in the first slot (slot #0) move to an Arbitrate state and wait to receive either a QueryAdjust command (to adjust one or more parameters provided in the original Query command and trigger the affected RFID tags to determine a new slot to reply in) or a QueryRep command (to indicate a transition to the next slot and hence the affected RFID tags to modify (decrease) an associated slot counter indicating a number of slots until the determined reply slot).

[0032] When a given selected RFID tag responds in a corresponding reply slot, that RFID tag does so by sending a 16-bit random number (RN16) to the RFID reader (the sending of this RN16 parameter is analogous to the transmission of Msg1 in conventional cellular random access procedures). This 16-bit random number may be used, for example, for the purposes of contention resolution in the event that a plurality of selected RFID tags selects the same slot for response, and hence respond to the Query command simultaneously.

[0033] Assuming that a single RFID tag has responded to the RFID reader in a given slot, the RFID reader confirms reception of the with an acknowledgement (ACK command) containing the same RN16 value (the sending of this acknowledgement is analogous to the transmission of the RAR / Msg2 in conventional cellular random access procedures). On receipt of the acknowledgement with the same RN16 value, the RFID tag that responded enters an acknowledged state and responds to the RFID reader with an EPC (a unique identifier of the RFID tag), a cyclic-redundancy check (CRC) and a protocol-control (PC) (the sending of this information is analogous to the transmission of Msg3 in conventional cellular random access procedures).

[0034] The RFID reader then sends a QueryAdjust or QueryRep command, triggering the RFID tag that has just communicated with it to return to a Ready state, and triggering the remaining selected RFID tags in the current identification process to decrease their slot counters. If no RFID tags respond in a given slot RFID reader may send another QueryRep command to trigger the remaining selected RFID tags in the current identification process to decrease their slot counters again.

[0035] For random access in the context of A-IoT devices and A-IoT device readers it is envisaged that when a response is expected from multiple devices (e.g., for the purposes of identifying multiple devices in the vicinity of the A-IoT device reader) a contention-based random access procedure may be used. This contention-based random access procedure may, for example, be similar to a conventional four-step RACH procedure or to a conventional two-step RACH procedure and may also have some similarities with the RFID random access procedure.

[0036] In an A-IoT 'four-step' random access procedure, like the RFID random access procedure, random access is triggered by the A-IoT device reader using an appropriate reader-to-device (R2D) trigger message ('A-IoT Msg0') in a manner that is analogous to the Query command of the RFID random access procedure. The A-IoT device reader includes, in this trigger message, the information (appropriate parameters) that one or more A-IoT devices need to respond to the random access trigger. It is possible that this trigger message may trigger initial access by a single device, a group of devices, or all devices in a cell / coverage area.

[0037] When triggered by the R2D trigger message (A-IoT Msg0), the one or more A-IoT devices may send an initial device-to-reader (D2R) message ('A-IoT Msg1') carrying a corresponding identifier (e.g., a random ID generated by A-IoT device), and possibly other information, to the A-IoT device reader. The A-IoT Msg0 that triggers random access between the A-IoT device reader, and the one or more A-IoT devices, also indicates to the one or more A-IoT devices X time domain resources for one or more initial D2R transmissions (e.g., for one or more A-IoT Msg1s; one A-IoT Msg1 per A-IoT device triggered for random access). Each of the one or more A-IoT Msg1s occur in a corresponding time domain resource of the X time domain resources indicated to the one or more A-IoT devices in the Msg0 that triggers the random access procedure between the A-IoT device reader and the one or more A-IoT devices. It will be appreciated that X may be equal to, or greater than 1, and when greater than 1 the maximum value is set considering the implementation complexity of the A-IoT device, the power consumption of the A-IoT device, resource usage efficiency (which may be affected at least by the SFO of the A-IoT device), and inventory latency associated with the A-IoT device.

[0038] The A-IoT device reader echoes the identifier received in the one or more initial D2R messages (one or more A-IoT Msg1s) back to the one or more A-IoT device in one or more R2D response messages (one or more 'A-IoT Msg2') that may include additional useful information where appropriate. For example, the A-IoT device reader, in response to the A-IoT Msg1s received from one or more A-IoT devices, may send a corresponding A-IoT Msg2 to each respective A-IoT device that sent an A-IoT Msg1 to the A-IoT device reader (Msg2 Transmission Option #1). Alternatively, the A-IoT device reader, in response to the A-IoT Msg1s received from one or more A-IoT devices, may send a single (common) A-IoT Msg2 to a group of the A-IoT devices that sent an A-IoT Msg1 to the A-IoT device reader (Msg2 Transmission Option #2).

[0039] In the scenario where the A-IoT device reader sends a corresponding A-IoT Msg2 to each respective A-IoT device that sent an A-IoT Msg1 to the A-IoT device reader, the transport block size (TBS) of each A-IoT Msg2 may be kept small, and the power consumption and complexity of implementation at the A-IoT devices may be less. On the other hand however, the amount of control information that needs to be sent by the A-IoT device reader is large since each A-IoT Msg2 monitoring window is different for each respective A-IoT device, and in that case multiple maximum time intervals between the transmission of the A-IoT Msg1 and the transmission of the A-IoT Msg2 (TD2R_max) may need to be configured when TDMA and / or FDMA is implemented.

[0040] In the scenario where the A-IoT device reader sends a single (common) A-IoT Msg2 to all of the A-IoT devices that sent an A-IoT Msg1 to the A-IoT device reader, the amount of control information that needs to be sent by the A-IoT device reader is small i.e., if one A-IoT Msg2 supports multiple R2D responses, the same value of TD2R_maxcan be used for FDMA. On the other hand, however, the TBS of that A-IoT Msg2 will be large, which in turn increases the power consumption and complexity of implementation at the A-IoT devices. Furthermore, where TDMA is implemented multiple TD2R_maxmay need to be configured.

[0041] Having received an A-IoT Msg2, the one or more A-IoT devices may then send a further D2R message ('A-IoT Msg3') including the A-IoT device's device identifier and / or any other higher layer data (depending on a higher layer request). It will be appreciated that the A-IoT device may consider contention resolution to be successful, if the received response message (A-IoT Msg2) includes the same random identifier that was sent by that A-IoT device in the initial D2R message (A-IoT Msg1). Hence the size of the random identifier needs to be sufficient for effective contention resolution purposes. A further R2D transmission ('A-IoT Msg4') may then be sent by the A-IoT device reader to the A-IoT device after the further D2R message (A-IoT Msg3) but does not always need to be sent. The further R2D transmission (A-IoT Msg4) may, for example, be sent to handle a transmission failure (e.g., a failure of A-IoT Msg3 due to any of a number of different reasons). It will be appreciated that the 'A-IoT Msg' terms (e.g., 'A-IoT Msg4') may or may not be used in practice.

[0042] Similarly, in an A-IoT 'two-step' random access procedure, like the RFID random access procedure, random access is triggered by the A-IoT device reader using an appropriate reader-to-device (R2D) trigger message ('A-IoT Msg0') in a manner that is analogous to the Query command of the RFID random access procedure.

[0043] In the two-step scenario, however, when triggered by the R2D trigger message (A-IoT Msg0), the A-IoT device may send an initial device-to-reader (D2R) message ('A-IoT Msg1') carrying a corresponding device identifier (e.g., a random ID generated by A-IoT device or some other identifier), and / or any other higher layer data (depending on a higher layer request), to the A-IoT device reader. This initial D2R message may also include other appropriate information. The A-IoT device reader may echo some or all of the information received in the initial D2R message (A-IoT Msg1) back to the A-IoT device in a R2D response message ('A-IoT Msg2') that may include additional useful information where appropriate.

[0044] Nevertheless, whilst progress has been made in the development of appropriate random access procedures for A-IoT as described above, further work is needed with regards to the transmission and reception of the one or more A-IoT Msg3s sent by the A-IoT devices to the A-IoT device reader. In particular, it is yet to be decided how frequency and time domain resources are allocated for Msg3 when FDMA and / or TDMA are to be implemented.

[0045] To-date it has been proposed that frequency and time domain resources may be allocated for Msg3 in the following ways: 　　- Msg3 Resource Allocation Option #1: Each Msg3 may be transmitted using the same time resource and frequency resource as a Msg1. For example, each A-IoT device may be configured to use the same resources to transmit Msg3 to the A-IoT device reader that it used to transmit its Msg1; 　　- Msg3 Resource Allocation Option #2: Each Msg3 sent by a respective A-IoT device may be transmitted over the same frequency resource used by that A-IoT device to transmit Msg1, whilst the time resource for Msg3 is indicated to that A-IoT device in a corresponding Msg2 sent by the A-IoT device reader to that A-IoT device; 　　- Msg3 Resource Allocation Option #2a: Each Msg3 sent by a respective A-IoT device may be transmitted over the same time resource used by that A-IoT device to transmit Msg1, whilst the frequency resource for Msg3 is indicated to that A-IoT device in a corresponding Msg2 sent by the A-IoT device reader to that A-IoT device; or 　　- Msg3 Resource Allocation Option #3: Each Msg3 sent by a respective A-IoT device may be transmitted over time and frequency resources indicated to that A-IoT device in a corresponding Msg2 sent by the A-IoT device reader to that A-IoT device.

[0046] However, each of those options have their own advantages and disadvantages. For example, Msg3 Transmission Option #1 may result in inefficiencies in the A-IoT system since some available resources may be wasted if those resources are not used for a corresponding Msg1 transmission.

[0047] In the case of Msg3 Resource Allocation Option #2, the partial re-use of the frequency resource allocations of Msg1 can partially save on signalling overhead as the frequency of the resource allocations for Msg3 do not need to be signalled again. However, resource utilisation and scheduling efficiencies associated with Msg3 Resource Allocation Option #2 may still not be optimal.

[0048] Similarly in the case of Msg3 Resource Allocation Option #2a. the partial re-use of the time resource allocations of Msg1 can partially save on signalling overhead as the frequency of the resource allocations for Msg3 do not need to be signalled again. However, as with Msg3 Resource Allocation Option #2, resource utilisation and scheduling efficiencies associated with Msg3 Resource Allocation Option #2a may still not be optimal.

[0049] In the case of Msg3 Resource Allocation Option #3, as all of the resource allocations for Msg3 are signalled in a corresponding Msg2, high efficiency can be achieved as the resources can be dynamically allocated. However, the need to signal the resource allocations for each Msg3 increases the overall signalling overhead of the A-IoT system.

[0050] There is therefore still a need to consider the specifics of how resources for Msg3 transmissions in an A-IoT system should be scheduled and signalled to enhance the overall efficiency of the A-IoT system whilst minimising scheduling overhead.

[0051] Additionally, as will be appreciated, in Msg3 Transmission Options #1 #2, and #2a, where the resource allocations for Msg3 are entirely, or partially, based on the resource allocations used for Msg1, issues may arise when the size of the data to be transmitted in Msg3 is larger than the size of the data that was transmitted in the corresponding Msg1. In this scenario, the re-use of all, or some, of the resources of the corresponding Msg1 may not be suitable (or even possible).

[0052] There is therefore a need to develop enhanced mechanisms for allocating resources for use in Msg3 transmission in A-IoT systems.

[0053] Furthermore, it will be appreciated that in the case where either Msg2 Transmission Option #1 (i.e., whereby the A-IoT device reader, in response to the A-IoT Msg1s received from one or more A-IoT devices 3-1, may send a corresponding A-IoT Msg2 to each respective A-IoT device 3-1 that sent an A-IoT Msg1 to the A-IoT device reader) or Msg2 Transmission Option #2 (i.e., whereby the A-IoT device reader, in response to the A-IoT Msg1s received from one or more A-IoT devices, may send a common A-IoT Msg2 to the A-IoT devices 3-1 that sent an A-IoT Msg1 to the A-IoT device reader) is implemented, the A-IoT devices may continue to monitor for A-IoT Msg2 transmissions in perpetuity as they may not be aware of when the A-IoT device reader has sent its last A-IoT Msg2 transmission.

[0054] There is therefore a need to develop enhanced mechanisms for indicating when an A-IoT device reader has finished Msg2 transmissions where Msg2 Transmission Option #1 or Msg2 Transmission Option #2 is implemented.

[0055] The disclosure aims to describe one or more apparatus and / or one or more associated mechanisms / procedures that at least partially addresses or contributes to meeting one or more of the above needs and / or addressing one or more of the above issues.

[0056] Various example described below may be implemented by means of a computer program product comprising computer implementable instructions for causing a programmable computer to carry out any of the methods described below. The computer implementable instructions may be provided as a signal or on a tangible computer readable medium.

[0057] A method performed by a first device according to a first aspect of the present disclosure includes: 　　receiving a first message from a first reader, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　transmitting, to the first reader, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

[0058] A method performed by a first reader according to a second aspect of the present disclosure includes: 　　transmitting a first message to a first device, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　receiving, from the first device, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

[0059] Examples of apparatus and methods will now be described, by way of example, with reference to the accompanying drawings in which:

[0060] Fig. 1 illustrates schematically a mobile (cellular or wireless) communication system to which example embodiments of the disclosure may be applied;Fig. 2A illustrates schematically a first possible arrangement of a first connectivity topology (topology 1) that may be used in the communication system of Fig. 1;Fig. 2B illustrates schematically another possible arrangement of a first connectivity topology (topology 1) that may be used in the communication system of Fig. 1;Fig. 3A illustrates schematically a first possible arrangement second connectivity topology (topology 2) that may be used in the communication system of Fig. 1;Fig. 3B illustrates schematically another possible arrangement second connectivity topology (topology 2) that may be used in the communication system of Fig. 1;Fig. 4A illustrates schematically a first possible arrangement of a third connectivity topology (topology 3) that may be used in the communication system of Fig. 1;Fig. 4B illustrates schematically another possible arrangement of the third connectivity topology (topology 3) of Fig. 4A;Fig. 5 is a simplified sequence diagram of an example A-IoT random access procedure that may be implemented in the communication system of Fig. 1;Fig. 6 illustrates an example of a first resource allocation mechanism that may be implemented, wherein Msg3 uses a Msg1 frequency resource and the time resource for Msg3 is provided in a corresponding Msg2;Fig. 7A illustrates an example of a second resource allocation mechanism that may be implemented wherein Msg3 uses the same frequency resource as Msg1, and the time resource for Msg3 is provided in a corresponding Msg2;Fig. 7B illustrates an example of a second resource allocation mechanism that may be implemented wherein Msg3 uses the same frequency resource as Msg1, and the time resource for Msg3 is provided in a corresponding Msg2;Fig. 7C illustrates an example of a second resource allocation mechanism that may be implemented wherein Msg3 uses the same frequency resource as Msg1, and the time resource for Msg3 is provided in a corresponding Msg2;Fig. 8A illustrates an example of a third resource allocation mechanism that may be implemented when Msg3 uses the same time resource as Msg1, and the frequency resource for Msg3 is provided in a corresponding Msg2;Fig. 8B illustrates an example of a third resource allocation mechanism that may be implemented when Msg3 uses the same time resource as Msg1, and the frequency resource for Msg3 is provided in a corresponding Msg2;Fig. 9 illustrates an example of a first resource allocation mechanism that may be implemented using a single Msg2 transmitted to a plurality of A-IoT devices;Fig. 10 illustrates an example of a second resource allocation mechanism that may be implemented using a single Msg2 transmitted to a plurality of A-IoT devices 2;Fig. 11 illustrates an example of a third resource allocation mechanism that may be implemented t using a single Msg2 transmitted to a plurality of A-IoT devices;Fig. 12A illustrates examples of timing relations between Msg2 and Msg3 transmissions;Fig. 12B illustrates examples of timing relations between Msg2 and Msg3 transmissions;Fig. 13A illustrates more examples of timing relations between Msg2 and Msg3 transmissions;Fig. 13B illustrates more examples of timing relations between Msg2 and Msg3 transmissions;Fig. 14A illustrates an example of timing relations between Msg2 and Msg3 transmissions when the timing relation is indicated by a first Msg2;Fig. 14B illustrates an example of timing relations between Msg2 and Msg3 transmissions when the timing relation is indicated by a first Msg2;Fig. 15 is a simplified block schematic illustrating the main components of a user equipment that may be used in the communication system of Fig. 1;Fig. 16 is a simplified block schematic illustrating the main components of an A-IoT device that may be used in the communication system of Fig. 1;Fig. 17 is a simplified block schematic illustrating the main components of a RAN node that may be used in the communication system of Fig. 1; andFig. 18 is a simplified block schematic illustrating the main components of an intermediate or assisting node that may be used in the communication system of Fig. 1.

[0061] Overview 　　An exemplary communication system will now be described in general terms, by way of example only, with reference to Figs. 1 to 4. 　　Fig. 1 schematically illustrates a mobile ('cellular' or 'wireless') communication system (e.g., communication system 1) to which examples of the present disclosure are applicable.

[0062] In the communication system 1 user equipments (UEs) 3 (3-1, 3-2, 3-3) (e.g., mobile telephones and / or other mobile devices including (ambient) IoT devices) can communicate with each other via a corresponding radio access network (RAN) node 5-1 that operates according to one or more compatible radio access technologies (RATs). In the illustrated example, the RAN node 5-1 comprises a base station operating one or more associated cells. Communication via the RAN node 5-1 is typically routed through a core network 7 (e.g., a 5G / 6G or later generations core network or evolved packet core network (EPC)). As those skilled in the art will appreciate however, a base station 5-1 or 'gNB' 5-1 is an example of a RAN node 5-1 only and that the RAN node 5-1 may be any appropriate RAN node 5-1 (e.g., where appropriate the RAN node 5-1 may be a RAN node that operates using a different RAT than NR / 5G).

[0063] As those skilled in the art will appreciate, whilst three UEs 3, and one RAN node 5-1 are shown in Fig. 1 for illustration purposes, the system, when implemented, will typically include other RAN nodes 5-1 and UEs 3.

[0064] In the illustrated example, the UEs 3 include at least one 'ambient' IoT device 3-1 (A-IoT device 3-1) that is capable of performing backscatter communication and a number of other, non-ambient IoT, UEs 3-2, 3-3 (such as smartphones or the like) that communicate in a conventional manner.

[0065] The A-IoT device 3-1 may, for example, be a Type 1, Type 2a, or Type 2b device as described in the introduction. As described in more detail later, depending on the connectivity topology employed, the A-IoT device 3-1 may be configured for uplink (backscatter) communication and / or downlink communication directly with the RAN node 5-1 and / or may be configured for uplink (backscatter) communication and / or downlink communication indirectly via communication (e.g., 'sidelink' or similar communication) with intermediate, or assisting, node 5-2. It will be appreciated that the intermediate, or assisting, node 5-2 may, in effect, be another node of the RAN, a separate RAN or other type of communication node, or another UE 3 that communicates with the A-IoT device 3-1 via an appropriate device-to-device (D2D) interface (e.g., sidelink, PC5 or the like). The intermediate, or assisting, node 5-2 may, for example, be a relay node (e.g., a dedicated relay or UE-relay), an integrated access and backhaul (IAB) node, a repeater and / or the like, which is capable of ambient IoT operation including receiving backscatter / reflected signals from, and / or transmitting unmodulated carrier signals to, the A-IoT device 3-1.

[0066] The RAN node 5-1 controls one or more associated cells either directly, or indirectly via one or more other nodes (such as home base stations, relays, remote radio heads, distributed units, and / or the like). It will be appreciated that the RAN node 5-1 may be configured to support 4G, 5G, 6G and / or later generation, and / or any other 3GPP or non-3GPP communication protocols.

[0067] The RAN node 5-1 may be a distributed base station comprising at least one distributed unit (DU) (e.g., a gNB-DU or the like), and a central unit (CU) (e.g., a gNB-CU or the like). In such a distributed base station the CU employs a separated control plane and user plane and so is, itself, split between a control plane function (CU-CP) and a user plane function (CU-UP) which respectively communicate, with the DU via an appropriate interface (e.g. F1-C logical interface) and an appropriate interface (e.g. F1-U logical interface) (together forming an F1 interface (or 'reference point')), and with one another via an appropriate interface (e.g. E1 logical interface). It will be appreciated that while the DU may include the physical and virtual elements required to provide the functionality of the lower parts of the PHY layer and hence communicate with the UEs 3 over the air interface, the base station may alternatively (or additionally) include one or more separate radio units (RUs) (e.g., providing this functionality of the lower parts of the PHY layer). It will, nevertheless, be appreciated that the RAN node 5-1 may be a base station may of a non-distributed form, for example as an integrated base station.

[0068] The UEs 3 (and possibly the intermediate or assisting node 5-2 if present) are configured for communication with the RAN node 5-1 via an appropriate air interface (for example a so-called 'Uu' interface and / or the like). It will be appreciated that the A-IoT device 3-1 may, alternatively or additionally, be configured for indirect communication with the RAN node 5-1 via an (air) interface with the intermediate or assisting node 5-2 (if present) and an (air) interface between the intermediate or assisting node 5-2 and the RAN node 5-1. Neighbouring RAN nodes 5-1 may be connected to each other via an appropriate base station to base station interface (such as the so-called 'X2' interface, 'Xn' interface and / or the like - not shown in Fig. 1).

[0069] The core network 7 includes a number of logical nodes (or 'functions') for supporting communication in the communication system 1. In this example, the core network 7 comprises control plane functions (CPFs) 10 and one or more network node entities for the communication of user data (e.g. user plane functions (UPFs) 11). The CPFs 10 include one or more network node entities for the communication of control signalling (e.g. Access and Mobility Management Functions (AMFs) 10-1), one or more network node entities for session management (e.g. Session Management Functions (SMFs) 10-2) and a number of other functions 10-n. Additional functions may include, for example: an Authentication Server Function (AUSF) which facilitates security processes; a Unified Data Management (UDM) entity for managing user specific data (e.g., for access authorisation, user registration, and data network profiles); a Policy Control Function (PCF); an Application Function (AF); a Security Anchor Function (SEAF) which is in a serving network and acts as a "middleman" during an authentication process between the UE 3 and its home network; an Authentication credential Repository and Processing Function (ARPF) which maintains the authentication credentials; and / or the like. It will be appreciated that the nodes or functions may have different names in different systems.

[0070] The RAN node 5-1 is connected to the core network nodes via appropriate interfaces (or 'reference points') such as an N2 reference point between the RAN node 5-1 and the AMF 10-1 for the communication of control signalling, and an N3 reference point between the RAN node 5-1 and each UPF 11 for the communication of user data. At least the non-ambient IoT UEs 3 are each connected to the AMF 10-1 via a non-access stratum (NAS) connection over an appropriate reference point (e.g., N1 reference point (analogous to the S1 reference point in LTE)). It will be appreciated, that N1 communication is routed transparently via the RAN node 5-1.

[0071] One or more UPFs 11 are connected to an external data network 40 (e.g., an IP network such as the internet) via an appropriate reference point (e.g., N6 reference point) for communication of the user data.

[0072] The AMF 10-1 performs mobility management related functions, maintains the NAS connection with at least each non-ambient IoT UE 3-2, 3-3 and manages UE registration. The AMF 10-1 is also responsible for managing paging.

[0073] The SMF 10-2 is connected to the AMF 10-1 via an appropriate reference point (e.g., N11 reference point). The SMF 10-2 provides session management functionality (that formed part of MME functionality in LTE) and additionally combines some control plane functions (provided by the serving gateway and packet data network gateway in LTE). The SMF 10-2 also allocates IP addresses to at least each non-ambient IoT UE 3-2, 3-3. The SMF 10-2 uses user information provided via the AMF 10-1 to determine what session manager would be best assigned to the user. The SMF 10-2 may be considered effectively to be a gateway from the user plane to the control plane of the network. The SMF 10-2 also allocates IP addresses to at least each non-ambient IoT UE 3-2, 3-3.

[0074] Each RAN node 5-1 is also configured for transmission of, and at least the non-ambient IoT UEs 3-2, 3-3 are configured for the reception of, control information and user data via a number of downlink (DL) physical channels and for transmission of a number of physical signals. The DL physical channels correspond to resource elements (REs) carrying information originated from a higher layer, and the DL physical signals are used in the physical layer and correspond to Res which do not carry information originated from a higher layer.

[0075] The physical channels may include, for example, a physical downlink shared channel (PDSCH), a physical broadcast channel (PBCH), and a physical downlink control channel (PDCCH). The PDSCH carries data sharing the PDSCH's capacity on a time and frequency basis. The PDSCH can carry a variety of items of data including, for example, user data, UE-specific higher layer control messages mapped down from higher channels, system information blocks (SIBs), and paging. The PDCCH carries downlink control information (DCI) for supporting a number of functions including, for example, scheduling the downlink transmissions on the PDSCH and also the uplink data transmissions on a physical uplink shared channel (PUSCH). The PBCH provides at least the non-ambient IoT UEs 3-2, 3-3 with the Master Information Block (MIB). It also, in conjunction with the PDCCH, supports the synchronisation of time and frequency, which aids cell acquisition, selection and re-selection.

[0076] The DL physical signals may include, for example, reference signals (RSs) and synchronisation signals (SSs). A reference signal (sometimes known as a pilot signal) is a signal with a predefined special waveform known to both the UE 3 and the RAN node 5-1. The reference signals may include, for example, cell specific reference signals, UE-specific reference signal (UE-RS), downlink demodulation signals (DMRS), and channel state information reference signal (CSI-RS).

[0077] Similarly, at least the non-ambient IoT UEs 3-2, 3-3 are configured for transmission of, and the RAN node 5-1 is configured for the reception of, control information and user data via a number of uplink (UL) physical channels corresponding to REs carrying information originated from a higher layer, and UL physical signals which are used in the physical layer and correspond to REs which do not carry information originated from a higher layer. The physical channels may include, for example, the PUSCH, a physical uplink control channel (PUCCH), and / or a physical random-access channel (PRACH). The UL physical signals may include, for example, demodulation reference signals (DMRS) for a UL control / data signal, and / or sounding reference signals (SRS) used for UL channel measurement.

[0078] Moreover, at least the non-ambient UEs 3-2, 3-3 and the RAN node 5-1 are mutually configured for performing a random-access channel (RACH) procedure for those UEs 3-2, 3-3 to access the network. Specifically, on detection and selection of a cell (and / or a beam) the UE 3 is able to attempt access to that cell and / or beam using an initial radio resource control (RRC) connection setup procedure comprising a random-access procedure with the RAN node 5-1.

[0079] Prior to attempting initial access, at least a non-ambient IoT UE 3-2, 3-3 will choose random access resources (including, for example, a preamble) to use to initiate the RACH procedure. The UE 3 sends the selected preamble (e.g., in 'Msg1') to the RAN node 5-1 over a physical random-access channel (PRACH) for initiating the process to obtain synchronisation in the uplink (UL). In response, the RAN node 5-1 responds with a random-access response (RAR) (or 'Msg2'). The RAR indicates reception of the preamble and includes: a timing-alignment (TA) command for adjusting the transmission timing of the UE 3 based on the timing of the received preamble; an uplink grant field indicating the resources to be used in the uplink for a physical uplink shared channel (PUSCH); a frequency hopping flag to indicate whether the UE 3 is to transmit on the PUSCH with or without frequency hopping; a modulation and coding scheme (MCS) field from which the UE 3 can determine the MCS for the PUSCH transmission; and a transmit power control (TPC) command value for setting the power of the PUSCH transmission. The UE 3 then sends a third message ('Msg3') to the RAN node 5-1 over a physical uplink shared channel (PUSCH) based on the information in the RAR. The specific message sent by the UE 3 in this step, and the content of the message, depends on the context in which the random-access procedure is being used. In the example of initial RRC connection setup, however, Msg3 typically comprises an RRC Setup request or similar message carrying a temporary randomly generated UE identifier. The RAN node 5-1 responds with a fourth message ('Msg4') which carries the randomly generated UE identifier received in Msg3 for contention purposes to resolve any collisions between different UEs 3 using the same preamble sequence. When successful, Msg4 also transfers the UE 3 to a connected state.

[0080] At least the non-ambient UEs 3-2, 3-3 and the RAN node 5-1 are also mutually configured for performing a two-step RACH procedure that involves the UE 3-2, 3-3 sending one message ('MsgA') to the RAN node 5-1 and the RAN node 5-1 sending one message ('MsgB') to the UE 3-1, 3-3. MsgA, in effect, combines Msg1 and Msg 3 of the four-step procedure, and MsgB, in effect, combines Msg2 and Msg4 of the four-step procedure.

[0081] While contention-based RACH procedures are described it will be appreciated that a UE 3 and the RAN node 5-1 may also perform a non-contention based (or 'contention free') procedure in which a dedicated preamble is assigned by the RAN node 5-1 to the UE 3. Moreover, the UE 3 and the RAN node 5-1 may perform a two-step RACH procedure.

[0082] Each A-IoT device 3-1 may be completely passive or may be active and configured with at least a subset of the functionality of the non-ambient IoT UEs 3-2, 3-3. It will be appreciated that the specific functionality with which the A-IoT device 3-1 is configured is dependent on the type of A-IoT device 3-1 as described above. It will, nevertheless, be appreciated that regardless of the non-ambient IoT UE functionality that an A-IoT device 3-1 may be configured with, each A-IoT device 3-1 is respectively configured with A-IoT specific functionality and each RAN node 5-1 is configured with corresponding functionality for communication with A-IoT devices 3-1.

[0083] For example, each A-IoT device reader (e.g., RAN node 5-1 or intermediate node 5-2) is also configured for transmission of, and the A-IoT devices 3-1 are configured for the reception of, control information and data via a physical R2D channel (PRDCH) for R2D communication that will typically carry any higher-layer payload, and any L1 R2D control information (if defined). For example, each R2D transmission may typically comprise an R2D preamble to indicate a start time of the following PRDCH and possibly and chip length (duration) information. This R2D preamble is followed immediately by the PRDCH transmission, which may, for example, be carrying R2D traffic data and / or control information such as indications of time domain resources and / or frequency domain resources scheduled for D2R transmissions. An R2D postamble may be transmitted immediately after the PRDCH transmission to indicate an end of the PRDCH transmission.

[0084] Similarly, each A-IoT device reader is also configured for reception of, and the A-IoT devices 3-1 are configured for the transmission of, control information and data via a physical D2R channel (PDRCH) for D2R communication that will typically carry any higher-layer payload, and any L1 D2R control information (if defined). For example, each D2R transmission may typically comprise a D2R preamble that is transmitted at the beginning of each D2R transmission, immediately before the PDRCH transmission, to indicate a start time of the PDRCH transmission. A D2R postamble may also be transmitted following the PDRCH transmission to indicate the end of the PDRCH transmission (and possibly provide a final timing correction to the A-IoT device reader).

[0085] Additionally, the PDRCH transmission may include one or more midambles. Such midambles may be embedded within a D2R transmission (e.g., between adjacent data segments of the D2R transmission), and may be provided in the PDRCH transmission for the purposes of performing timing / frequency tracking, channel estimation (e.g., depending on the length of that PDRCH transmission), and / or interference estimation. Additionally, such midambles may also be supported in the PDRCH transmission for the purposes of performing SFO estimation, SFO tracking for a PDRCH transmission with a long transmission duration, and / or timing correction procedures. For example, in the case of timing correction procedures, after SFO estimation based on the D2R preamble, a D2R midamble may be used for improving the SFO estimation.

[0086] The PRDCH may include any appropriate information. For the purposes of D2R scheduling, for example, the R2D control information may include time domain resources; frequency domain resources; modulation and coding scheme (MCS) like information; chip duration; one or more identifiers (IDs) associated with one or more A-IoT devices; an indication of a number of repetitions; and / or midamble related information.

[0087] The midamble related information may be provided explicitly and / or implicitly and may include, for example, information such as: an indication of the required / requested presence (or absence of) one or more midambles in a D2R transmission; an indication of the number of midambles that are to be included per D2R transmission; an indication of the position / location of the midamble / midambles (e.g., with respect to the preamble, data, and / or postamble in the D2R transmission); an indication of the length of the midamble / midambles; and / or the like. Nevertheless, it will be appreciated that the number of midambles that are to be included per D2R transmission, and the position / location and / or length of those midambles may alternatively be predefined by a preconfigured rule (e.g., the number and position of the midambles may be fixed and the same for every D2R transmission).

[0088] It will be appreciated that, as one or more midambles may be used to perform a number of different procedures such as those highlighted above, the design / format / length of such midambles may need to vary depending on their specific purpose. Accordingly, the midamble related information may also (or alternatively), beneficially include an explicit and / or implicit indication of one or more specific purposes for which the midamble (or plurality of midambles) is intended.

[0089] Connectivity Topologies 　　The A-IoT device 3-1 may form part of an ambient IoT network having any one of the possible connectivity topologies referred to in the introduction and may be deployed in any of several different ways. Possible connectivity topologies and their deployment will now be described in more detail with reference to Figs. 2A, 2B, 3A, 3B, 4A, and 4B.

[0090] Topology 1: RAN node <-> IoT device: 　　Fig. 2A illustrates schematically a first possible arrangement of a first connectivity topology (topology 1) that may be used in the communication system 1.

[0091] As shown in Fig. 2A, in the first possible arrangement of topology 1 the functionality of an A-IoT device reader is implemented as part of a RAN node 5-1. An A-IoT device 3-1 and the RAN node 5-1 engage in direct communication with one another (i.e., without the presence of an assisting or intermediate node 5-2). Specifically, as shown, the A-IoT device 3-1 directly and bidirectionally communicates with the RAN node 5-1. The communication between the RAN node 5-1 and the A-IoT device 3-1 may, for example, include ambient IoT data and / or other ambient IoT signalling (e.g., control signals or the like). The communication between the RAN node 5-1 and the A-IoT device 3-1 may occur over an appropriate air interface such as the Uu air interface, a dedicated interface for ambient IoT, or the like.

[0092] In this example, the RAN node 5-1 is responsible for transmission of an unmodulated carrier signal 20-1 to the A-IoT device 3-1; also known as the 'Carrier Wave' signal (CW). That unmodulated carrier signal 20-1 (or CW) may be transmitted by the RAN node 5-1 to the A-IoT device 3-1 to provide the A-IoT device 3-1 with a signal and / or energy upon which modulated and backscattered / reflected information can be sent. For example, upon receiving a reader-to-device (R2D) signal 20-2 from the RAN node 5-1, the A-IoT device 3-1 may modulate the unmodulated carrier signal 20-1 (or CW) it received based on the R2D signal 20-2 it received and backscatter / reflect that modulated signal as a backscattered device-to-reader (D2R) signal 20-3, to the RAN node 5-1.

[0093] Such transmission of an unmodulated carrier, and receipt of backscattering by the same RAN node (base station) 5-1 may, for example, be supported by topology 1 where full duplex operation is supported at that RAN node 5-1.

[0094] Nevertheless, while Fig. 2A shows the unmodulated carrier signal 20-1 (or CW) and the R2D signal 20-2 as originating from the same RAN node; namely RAN node 5-1, it will be appreciated that topology 1 also allows for the possibility that the RAN node 5-1 (in this case the 'IoT device reader') that communicates with the A-IoT device 3-1 may be a different communication node than a communication node that provides the unmodulated carrier signal 20-1 (or CW).

[0095] For example, as shown in Fig. 2B, which illustrates schematically a second possible arrangement of the first connectivity topology (topology 1) that may be used in the communication system 1, a separate communication node 6 may transmit the unmodulated carrier signal 20-1 (or CW) to the A-IoT device 3-1 to provide the A-IoT device 3-1 with a signal and / or energy based upon which modulated and backscattered / reflected information can be sent. The RAN node 5-1 acting as the IoT device reader may then provide the R2D signals 20-2 to the A-IoT device 3-1. Upon receiving an R2D signal 20-2, the A-IoT device 3-1 modulates the unmodulated carrier signal 20-1 (or CW) it received (e.g., based on an R2D signal 20-2 it received) and backscatter / reflect that modulated signal as a backscattered D2R signal 20-3 to the RAN node 5-1.

[0096] Topology 1 may typically be deployed for indoor scenarios, with a type 1, 2a, and / or 2b A-IoT device and the RAN node 5-1 (IoT device reader) being located in an indoor environment. In this scenario the RAN node 5-1 typically supports one or more small cells (e.g., micro-, and pico- cells) used for voice, video, and data transmission, which are designed to provide network coverage to small areas and operate on either licensed frequency division duplex (FDD), licensed time division duplex (TDD), or unlicensed parts of the spectrum.

[0097] Alternatively, topology 1 may be deployed for scenarios where the A-IoT device 3-1 is in an indoor environment but the RAN node 5-1 is located in an outdoor environment. In this case, the RAN node 5-1 may be configured to support one or more small cells (e.g., micro-cells) used for voice, video, and data transmission, which are designed to provide network coverage to small areas and operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum. Alternatively, the RAN node 5-1 may support one or more larger cells (e.g., macro- cells) providing radio coverage to a large area, and that operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum.

[0098] Topology 1 may also be deployed for outdoor scenarios with one or more A-IoT devices 3-1 and the RAN node 5-1 are located in an outdoor environment. In such scenarios the RAN node 5-1 may support one or more small cells (e.g., micro-cells) used for voice, video, and data transmission, which are designed to provide network coverage to small areas and operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum. Alternatively (or additionally), the RAN node 5-1 may support larger cells (e.g., macro- cells) providing radio coverage to a large area, and that operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum.

[0099] This topology may, for example, be appropriate for a situation in which the RAN node 5-1 needs to fetch data (e.g., a meter record, a sensor reading, an error code and / or the like) from the A-IoT device 3-1. The RAN node 5-1 will send an unmodulated carrier signal as a 'stimulus' signal to the A-IoT device 3-1 which will automatically respond with the required data encoded in the resulting backscattered / reflected signal.

[0100] Topology 2: RAN node <-> Intermediate node <-> IoT device: 　　Fig. 3A illustrates schematically a first possible arrangement of a second connectivity topology (topology 2) that may be used in the communication system 1.

[0101] As shown in Fig. 3A, in the first possible arrangement of topology 2 the functionality of an IoT device reader is implemented as part of an intermediate node 5-2. Specifically, an A-IoT device 3-1 and a RAN node 5-1 engage in communication with one another via the intermediate node 5-2 (which may also be referred to as an assisting node / IoT device reader) to transfer ambient IoT data and / or signalling between the RAN node 5-1 and the A-IoT device 3-1. It will be appreciated that while the intermediate node 5-2 is depicted in Fig. 3A as being a type of base station, the intermediate node 5-2 may in fact be any one of an IAB node, a UE 3, a repeater, or the like, or any other appropriate device, as described above, that can act as an intermediary between the RAN node 5-1 and the A-IoT device 3-1 and that is capable of supporting ambient IoT signalling.

[0102] In this example, the A-IoT device 3-1 communicates bidirectionally with the intermediate node 5-2, which is located between the A-IoT device 3-1 and the RAN node 5-1, and which is able to transfer ambient IoT data and / or signalling between the RAN node 5-1 and the A-IoT device 3-1.

[0103] Specifically, the communication between the intermediate node 5-2 and the A-IoT device 3-1 may occur over an appropriate air interface. For example, they may communicate over a Uu, a dedicated interface for A-IoT, or any other appropriate interface (e.g., a sidelink-like interface, Proximity-based Services (ProSe) interface, PC5 interface, or the like where the intermediate node 5-2 is a UE 3).

[0104] In a first (downlink) direction (RAN node 5-1 -> intermediate node 5-2 -> A-IoT device 3-1) a downlink signal may be transmitted from the RAN node 5-1 to the intermediate node 5-2 as part of communication 20-4 between the RAN node 5-1 and the intermediate node 5-2. The downlink signal, once received by the intermediate node 5-2, may trigger transmission of an unmodulated carrier signal / CW 20-1 to the A-IoT device 3-1 (e.g., on a 'sidelink' or similar interface where the intermediate node 5-2 is a UE 3). The downlink signal may be (or may carry) the unmodulated carrier signal 20-1 that is to be transmitted (e.g. relayed) by the intermediate node 5-2 to the A-IoT device 3-1 or may be a trigger signal for triggering transmission of the unmodulated carrier signal 20-1 to provide the A-IoT device 3-1 with an unmodulated carrier signal 20-1 (or CW) based upon which modulated and backscattered / reflected information can be sent. For example, upon receiving an R2D signal 20-2 from the intermediate node 5-2, the A-IoT device 3-1 may modulate the unmodulated carrier signal 20-1 (or CW) it received (e.g., based on the R2D signal 20-2) and backscatter / reflect that modulated signal as a backscattered D2R signal 20-3, to the intermediate node 5-2.

[0105] That is to say, in a second (uplink) direction (A-IoT device 3-1 -> intermediate node 5-2 -> RAN node 5-1) the intermediate node 5-2 is responsible for receiving a modulated backscattered (D2R) signal 20-3 from A-IoT device 3-1 (e.g., on a 'sidelink' or similar interface where the intermediate node 5-2 is a UE 3). Specifically, the uplink communication may comprise a modulated backscattered signal 20-3 from the A-IoT device 3-1 to the intermediate node 5-2 that is transmitted (e.g., on a 'sidelink' or similar interface where the intermediate node 5-2 is a UE 3) in using the unmodulated carrier signal 20-1 from the intermediate node 5-2. This modulated backscattered D2R signal 20-3 (or at least the information encoded in it), once received by the intermediate node 5-2, may be relayed / forwarded (transmitted) to the RAN node 5-1 in an uplink signal as part of the communication 20-4 between the intermediate node 5-2 and the RAN node 5-1. The modulated backscattered D2R signal 20-3 may be processed before being relayed by the intermediate node 5-2 to the RAN node 5-1. For example, the modulated D2R backscattered D2R signal 20-3 may be processed by the intermediate node 5-2 to extract information encoded in the modulated D2R backscattered signal, and to encapsulate the extracted information into an appropriate message format (e.g., in accordance with a corresponding application protocol) for communication with the RAN node 5-1. Alternatively, the modulated backscattered D2R signal may itself be processed by the intermediate node 5-2 (without extracting any data encoded in it) to encapsulate it into an appropriate message format (e.g., in accordance with a corresponding application protocol) for communication with the RAN node 5-1.

[0106] Such transmission of an unmodulated carrier, and receipt of backscattering by the same intermediate node 5-2 may, for example, be supported by topology 2 where full duplex operation is supported at that intermediate node 5-2.

[0107] Communication 20-4 between the RAN node 5-1 and the intermediate node 5-2 may occur over any appropriate interface. For example, the RAN node 5-1 and intermediate node 5-2 may communicate over an air interface (such as the Uu interface or the like), for example where the intermediate node 5-2 is a UE 3 (or at least acts like a UE 3 in its communication with the RAN node 5-1). The RAN node 5-1 and intermediate node 5-2 may communicate over a direct base station to base station interface (such as X2 or Xn), for example where the intermediate node 5-2 is a base station (or at least acts like a base station in its communication with the RAN node 5-1). The RAN node 5-1 and intermediate node 5-2 may communicate over an appropriate IAB interface (such as F1), for example where the RAN node 5-1 acts as an IAB donor base station and the intermediate node 5-2 is an IAB node. Nevertheless, the RAN node 5-1 and the intermediate node 5-2 may communicate over a dedicated interface for the purpose of ambient IoT.

[0108] Nevertheless, while Fig. 3A shows the unmodulated carrier signal 20-1 (or CW) and the R2D signal 20-2 as originating from the same node; namely the intermediate node 5-2, it will be appreciated that topology 2 also allows for the possibility that the intermediate node 5-2 (in this case the 'IoT device reader') transmitting to and receiving from the A-IoT device 3-1 is a different communication node than a communication node that provides the unmodulated carrier signal 20-1 (or CW).

[0109] For example, as shown in Fig. 3B, which illustrates schematically a second possible arrangement of a second connectivity topology (topology 2) that may be used in the communication system 1, a separate communication node 6 may transmit an unmodulated carrier signal 20-1 (or CW) to the A-IoT device 3-1 to provide the A-IoT device 3-1 with a signal and / or energy based upon which modulated and backscattered / reflected information can be sent. Upon receiving an R2D signal 20-2 from the intermediate node 5-2 (which may be triggered in response to the intermediate node 5-2 receiving a DL transmission 20-4 from the RAN node 5-1) the A-IoT device 3-1 may modulate the unmodulated carrier signal 20-1 (or CW) that it received (e.g., based on the R2D signal 20-2 it received) and backscatter / reflect that modulated signal as a backscattered D2R signal 20-3, to the intermediate node 5-2.

[0110] Similarly to in Fig. 3A, the intermediate node 5-2 may then send / relay the modulated backscattered D2R signal 20-3 it receives from the A-IoT device 3-1 (or at least the information encoded in it), to the RAN node 5-1 in an uplink signal as part of the communication 20-4 between the intermediate node 5-2 and the RAN node 5-1. The modulated backscattered D2R signal 20-3 may be processed before being relayed by the intermediate node 5-2 to the RAN node 5-1. For example, the modulated backscattered D2R signal 20-3 may be processed by the intermediate node 5-2 to extract information encoded in the modulated backscattered D2R signal, and to encapsulate the extracted information into an appropriate message format (e.g., in accordance with a corresponding application protocol) for communication with the RAN node 5-1. Alternatively, the modulated backscattered D2R signal may itself be processed by the intermediate node 5-2 (without extracting any data encoded in it) to encapsulate it into an appropriate message format (e.g., in accordance with a corresponding application protocol) for communication with the RAN node 5-1.

[0111] It will be appreciated that in the arrangement of Fig. 3A and Fig. 3B, the intermediate node 5-2 may be of a type that attempts to demodulate the received backscattered signal for subsequent forwarding of the data to the RAN node 5-1 (e.g., a layer-2 (L2) relay device that attempts to demodulate any layer-1 (L1) signals that it receives). Such an intermediate node 5-2 may be referred to as be a layer 2 ('L2') type intermediate node 5-2. Nevertheless, the intermediate node 5-2 may be of a type that blindly forwards a received signal without attempting to demodulate it and hence, on receipt of the backscattered signal no attempt is made to demodulate it (e.g., an L1 repeater device or a network-controlled repeater (NCR) node). Such an intermediate node 5-2 may be referred to as be a layer 1 ('L1') type intermediate node 5-2.

[0112] Topology 2 may be deployed for scenarios with a type 1, 2a, and / or 2b A-IoT device 3-1, in which the A-IoT device 3-1 is in an indoor environment but the RAN node 5-1 is located in an outdoor environment. In this scenario the RAN node 5-1 may support one or more small cells (e.g., micro-cells) used for voice, video, and data transmission, which are designed to provide network coverage to small areas and operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum. Alternatively, the RAN node 5-1 may support one or more larger cells (e.g., macro- cells) providing radio coverage to a large area, and that operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum. In this scenario, the assisting node 5-2 may be located in an indoor or an outdoor environment.

[0113] Topology 2 may also be deployed for indoor scenarios with a type 1, 2a, and / or 2b A-IoT device 3-1, intermediate node 5-2 and RAN node 5-1 are located in an indoor environment. In this scenario the RAN node 5-1 typically supports one or more small cells (e.g., micro-, and pico- cells) used for voice, video, and data transmission, which are designed to provide network coverage to small areas and operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum.

[0114] Topology 2 may also be deployed for outdoor scenarios with a type 1, 2a or 2b IoT device A-3-1, RAN node 5-1 and intermediate (or assisting) node 5-2 being located in an outdoor environment. In this scenario the RAN node 5-1 may support one or more small cells (e.g., micro-cells) used for voice, video, and data transmission, which are designed to provide network coverage to small areas and operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum. Alternatively, the RAN node 5-1 may support one or more larger cells (e.g., macro- cells) providing radio coverage to a large area, and that operate on either licensed FDD, licensed TDD, or unlicensed parts of the spectrum.

[0115] This topology may, for example, be appropriate for a situation in which a RAN node 5-1 needs to fetch data (e.g., a meter record, a sensor reading, an error code and / or the like) from the A-IoT device 3-1. The RAN node 5-1 will trigger the intermediate node 5-2 to send an unmodulated carrier signal as a 'stimulus' signal to the A-IoT device 3-1 which will automatically respond with the required data encoded in the resulting backscattered / reflected signal. The resulting backscattered / reflected signal (or at least the data encoded in it) will then be forwarded / relayed to the RAN node 5-1.

[0116] Topology 3: RAN node <-> Assisting node <-> A-IoT device <-> RAN node: 　　Figs. 4A and 4B illustrate schematically a third connectivity topology (topology 3) of a mobile (cellular or wireless) communication system 1.

[0117] As shown in Figs. 4A and 4B, in topology 3 part of the functionality of an A-IoT device reader is implemented as part of an assisting node 5-2 and part of the functionality of the A-IoT device reader is implemented as part of a RAN node 5-1. Specifically, an A-IoT device 3-1 and the RAN node 5-1 engage in communication with one another via the assisting node 5-2 (which may also be referred to as an intermediate node). It will be appreciated that while the assisting node 5-2 is depicted in Fig. 4A and Fig. 4B as a type of base station, the assisting node 5-2 may in fact be any one of an IAB node, a UE 3, a repeater, or the like, or any other appropriate device that can act as an intermediary between a RAN node 5-1 and an A-IoT device 3-1.

[0118] It will be appreciated that the assisting node 5-2 may be of a type that attempts to demodulate the received backscattered signal for subsequent forwarding of the data to the RAN node 5-1 (e.g., a layer-2 (L2) relay device that attempts to demodulate any layer-1 (L1) signals that it receives). Such an assisting node may be referred to as be a layer 2 ('L2') type assisting node 5-2. Nevertheless, the assisting node 5-2 may be of a type that blindly forwards a received signal without attempting to demodulate it (e.g., an L1 repeater device or a network-controlled repeater (NCR) node) and hence, on receipt of the backscattered signal no attempt is made to demodulate it. Such an assisting node may be referred to as be a layer 1 ('L1') type assisting node 5-2.

[0119] As shown in Fig. 4A, the A-IoT device 3-1 may communicate with a RAN node 5-1 in a downlink direction and an assisting (intermediate) node 5-2 in an uplink direction (e.g., on a 'sidelink' or similar). The communication between the RAN node 5-1 and the A-IoT device 3-1, or the communication between the assisting node 5-2 and the A-IoT device 3-1 respectively may occur over an appropriate air interface. For example, they may communicate over a Uu or dedicated 'sidelink' interface.

[0120] In this example the RAN node 5-1 (base station / cell) is responsible for transmission of an unmodulated carrier signal 20-1 (or CW) to the A-IoT device 3-1 to provide the A-IoT device 3-1 with a signal and / or energy based upon which modulated and backscattered / reflected information can be sent. Upon receiving an R2D signal 20-2 from the RAN node 5-1, the unmodulated carrier signal 20-1 may be modulated (e.g., based on the received R2D signal 20-2) and backscattered, as a modulated backscattered D2R signal 20-3, from the A-IoT device 3-1 and received at the assisting node 5-2. That is, the assisting node 5-2 is responsible for receiving the backscattered D2R signal 20-3 from the A-IoT device 3-1. The modulated backscattered D2R signal 20-3 (or at least the information encoded in it), once received by the assisting node 5-2, may be relayed (forwarded / transmitted) to the RAN node 5-1 in another signal 20-3'. The modulated backscattered D2R signal 20-3 may be processed before being relayed / forwarded by the assisting node 5-2 to the RAN node 5-1. For example, the modulated backscattered 20-3 signal may be processed by the assisting node 5-2 to extract information encoded in the modulated backscattered signal, and to encapsulate the extracted information into an appropriate message format (e.g., in accordance with a corresponding application protocol) for communication with the RAN node 5-1 over an appropriate signal 20-3'. Alternatively, the modulated backscattered D2R signal 20-3 may itself be processed by the assisting node 5-2 (without extracting any data encoded in it) to encapsulate it into an appropriate message format (e.g., in accordance with a corresponding application protocol) for communication with the RAN node 5-1 over an appropriate signal 20-3'.

[0121] The communication 20-3' between the RAN node 5-1 and the assisting node 5-2 occurs over an appropriate interface. For example, the RAN node 5-1 and the assisting node 5-2 may communicate over an air interface (such as the Uu interface or the like), for example where the assisting node 5-2 is a UE 3 (or at least acts like a UE in its communication with the RAN node 5-1). The RAN node 5-1 and assisting node 5-2 may communicate over an appropriate IAB interface (such as F1), for example where the RAN node 5-1 acts as an IAB donor base station and the assisting node 5-2 is an IAB node. Nevertheless, the RAN node 5-1 and the assisting node 5-2 may communicate over a dedicated interface for the purpose of ambient IoT. The communication, comprising the modulated backscattered signal 20-2 received at the assisting node 5-2 from the A-IoT device 3-1, also occurs over an appropriate air interface. For example, they may communicate over a Uu or a dedicated interface.

[0122] This topology may, for example, be appropriate for a situation in which a RAN node 5-1 needs to fetch data (e.g., a meter record, a sensor reading, an error code and / or the like) from the A-IoT device 3-1. The RAN node 5-1 will send an unmodulated carrier signal as a 'stimulus' signal to the A-IoT device 3-1 which will automatically respond with the required data encoded in the resulting backscattered / reflected signal sent to the assisting node 5-2 for relaying / forwarding to the RAN node 5-1.

[0123] Alternatively, as shown in Fig. 4B, the A-IoT device 3-1 may communicate with the RAN node 5-1 in an uplink direction and the assisting (intermediate) node 5-2 in a downlink direction (e.g., on a 'sidelink' or similar). The communication between the RAN node 5-1 and A-IoT device 3-1, and the communication between the assisting node 5-2 and the A-IoT device 3-1, respectively occur over an appropriate air interface. For example, they may communicate over a Uu or dedicated 'sidelink' interface.

[0124] In this example the assisting node 5-2 is responsible for transmission of an unmodulated carrier signal 20-1 to the A-IoT device 3-1 to provide the A-IoT device 3-1 with a signal and / or energy based upon which modulated and backscattered / reflected information can be sent. Upon receiving an R2D signal 20-2 from the assisting node 5-2, the unmodulated carrier signal 20-1 may be modulated (e.g., based on the received R2D signal 20-2) and backscattered, as a modulated backscattered D2R signal 20-3, from the A-IoT device 3-1 and received at the RAN node 5-1. That is, the RAN node 5-1 (base station / cell) is responsible for receiving the backscattered D2R signal 20-3 from the A-IoT device 3-1. The transmission of the unmodulated carrier signal 20-1 may be triggered by a downlink signal 20-2' received by the assisting node 5-2 from the RAN node 5-1. For example, the downlink signal 20-2' may be (or may carry) the unmodulated carrier signal 20-1 that is to be transmitted (e.g. relayed) by the assisting node 5-2 to the A-IoT device 3-1 or may be a trigger signal for triggering transmission of the unmodulated carrier signal 20-1.

[0125] This topology may, for example, be appropriate for a situation in which a RAN node 5-1 needs to fetch data (e.g., a meter record, a sensor reading, an error code and / or the like) from the A-IoT device 3-1. The RAN node 5-1 will send an unmodulated carrier signal as a 'stimulus' signal to the IoT device 3-1 which will automatically respond with the required data encoded in the resulting backscattered / reflected signal sent to the assisting node 5-2. The resulting backscattered / reflected signal (or at least the data encoded in it) will then be forwarded / relayed to the RAN node 5-1 by the assisting node 5-2.

[0126] Similarly to Fig. 4A, in Fig. 4B the communication 20-2' between the RAN node 5-1 and the assisting node 5-2 occurs over an appropriate interface. For example, the RAN node 5-1 and the assisting node 5-2 may communicate over an air interface (such as the Uu interface or the like), for example where the assisting node 5-2 is a UE (or at least acts like a UE in its communication with the RAN node 5-1). The RAN node 5-1 and assisting node 5-2 may communicate over an appropriate IAB interface (such as F1), for example where the RAN node 5-1 acts as an IAB donor base station and the assisting node 5-2 is an IAB node. Nevertheless, the RAN node 5-1 and the assisting node 5-2 may communicate over a dedicated interface for the purpose of ambient IoT. The downlink communication, comprising the unmodulated carrier signal 20-1 sent from the assisting node 5-2 to the A-IoT device 3-1, also occurs over an appropriate air interface. For example, they may communicate over a Uu or a dedicated interface.

[0127] This topology may, for example, be appropriate for a situation in which a RAN node 5-1 needs to fetch data (e.g., a meter record, a sensor reading, an error code and / or the like) from the A-IoT device 3-1. The RAN node 5-1 will trigger the assisting node 5-2 to send an unmodulated carrier signal as a 'stimulus' signal to the A-IoT device 3-1 which will automatically respond with the required data encoded in the resulting backscattered / reflected signal sent to the RAN node 5-1.

[0128] In either scenario (illustrated in Fig. 4A or 4B), backscattering may be supported even if the RAN node 5-1 and / or the assisting node 5-2 do not support full duplex operation.

[0129] A-IoT Four-Step Random Access Procedures 　　The A-IoT device reader (e.g., RAN node 5-1 or assisting / intermediate node 5-2) and the A-IoT device 3-1 of the communication system 1 are mutually configured for supporting A-IoT specific random access between the A-IoT device reader and the A-IoT device 3-1.

[0130] Specifically, the A-IoT device reader (e.g., RAN node 5-1 or assisting / intermediate node 5-2) and the A-IoT device 3-1 of the communication system 1 are mutually configured to support an A-IoT 'four-step' RA procedure. It will be appreciated that the term 'four-step' is used because the procedure is respectively analogous to (and serve a similar purpose to), a conventional four-step RACH procedure. Nevertheless, the A-IoT four-step RA procedure is different to their conventional cellular counterparts. For example, there may be more than four messages sent during an A-IoT four-step RA procedure. An A-IoT 'four-step' RA procedure may also be called as 'three-step' RA procedure, since sometimes, one or more steps may be skipped during random access for A-IoT device.

[0131] Fig. 5 is a simplified sequence diagram of an example A-IoT 'four-step' random access procedure that may be implemented in the communication system 1.

[0132] As seen in Fig. 5, the A-IoT four-step random access (RA) procedure is triggered, at S502, by the A-IoT device reader sending an appropriate reader-to-device (R2D) initial trigger message ('A-IoT Msg0') targeted at or more A-IoT devices 3-1. The A-IoT device reader includes, in the initial trigger message, information (appropriate parameters) that a recipient A-IoT device 3-1 needs to respond to the random access trigger. The initial trigger message (A-IoT Msg0) may be configured to trigger initial access by a single A-IoT device 3-1 or a specific group of A-IoT devices 3-1 in a cell / coverage area. The information may comprise, for example, information indicating: a specific targeted / selected device (e.g. a device identifier); a specific targeted / selected group of one or more A-IoT devices (e.g. a (sub)group identifier and / or one or more device identifiers); a targeted / selected device type; a device or device group that are not targeted / selected (e.g., masking information and / or a group identifier); and / or the like). Nevertheless, the initial trigger message may be configured as a 'blind' request or the like to trigger initial access by all recipient A-IoT devices 3-1 within the cell / coverage area (e.g., by omitting information targeting a specific device, or group of A-IoT devices 3-1, by including information that is common to all A-IoT devices 3-1 within the cell / coverage area, and / or by including an indicator that any recipient device should respond). The information may also comprise, for example, information indicating one or more time and / or frequency resources of one or more RA occasions (e.g., including frequency information, time / frequency resource location, length of the slots for all RA occasions, slot length for each RA occasion, and or the like). The information may also comprise, for example, information indicating the number of RA occasions and / or the availability of each RA occasion. The information may also comprise, for example, an indication that the following access cycle / RA procedure is a repetition and forms part of the current (same) access round (e.g., like a QueryRep command in RFID), or is the start (first access cycle / RA procedure) of a new access round.

[0133] It will be appreciated that all the A-IoT devices 3-1 within the cell / coverage area of the A-IoT device reader may receive the initial trigger message (A-IoT Msg0) (subject to local radio conditions, any interference, and / or the like that may result in a failure to receive the message). However, only those specifically targeted / selected by the initial trigger message (A-IoT Msg0) will be triggered to initiate random access. To facilitate this when an A-IoT device 3-1 receives the initial trigger message (A-IoT Msg0), that A-IoT device 3-1 will determine whether that A-IoT device 3-1 is targeted / selected by the initial trigger message (A-IoT Msg0) by checking (at S504) whether or not information stored locally at the A-IoT device 3-1 (e.g., a device identity (or part of such an identity), a (sub)group identity, a device type indication, or the like) matches corresponding information in the initial trigger message (A-IoT Msg0). When the device (type) matches a device (type) targeted / selected by the initial trigger message (A-IoT Msg0) the A-IoT device 3-1 performs RA resource selection as seen at S504. This RA resource selection involves selecting a specific RA occasion comprising resources to be used for a subsequent D2R transmission (e.g., of A-IoT Msg1). The resources forming each RA occasion may be divided (and hence selectable) in the time and / or frequency domain.

[0134] Having been triggered by an R2D initial trigger message (A-IoT Msg0), the A-IoT device 3-1 sends, at S506, an initial device-to-reader (D2R) message ('A-IoT Msg1') using the selected RA occasion (time / frequency resources). The initial D2R message (A-IoT Msg1) carries a corresponding identifier (e.g., a random number / random ID generated by A-IoT device 3-1), and possibly other information, to the A-IoT device reader. The identifier may, for example, be a 16-bit random number (RN16) as used in RFID access procedures but may be some other form of (random) identifier.

[0135] If the initial D2R message (A-IoT Msg1) is received successfully at the A-IoT device reader (e.g., because there is no contention or other interference that causes a reception failure), then the A-IoT device reader echoes, at S508, the identifier received in the initial D2R message (A-IoT Msg1) back to the A-IoT device 3-1 in an appropriate R2D access response message ('A-IoT Msg2') that may include additional useful information where appropriate. The R2D access response message (A-IoT Msg2) effectively serves as contention resolution - the A-IoT device 3-1 assumes contention resolution to have been successful, if a received R2D response message (A-IoT Msg2) includes the same random identifier that was sent by that A-IoT device 3-1 in the initial D2R message (A-IoT Msg1).

[0136] The A-IoT device 3-1 then sends, at S510, a further D2R message (A-IoT Msg3) including that A-IoT device's A-IoT device identifier (or possibly a short version of that identifier) (and / or a (sub)group identifier) and / or any other higher layer data (e.g., depending on a higher layer request). The A-IoT device's A-IoT device identifier may be at least locally unique and / or may be a temporary identifier allocated by the network.

[0137] An R2D data transmission / message ('A-IoT Msg4') may then be sent by the A-IoT device reader to the A-IoT device 3-1 (as seen at S512), after the further D2R message (A-IoT Msg3) has been received, that may, for example, comprise an inventory command or inventory request (or possibly an upper layer configuration). It will be appreciated that an inventory command may be used to configure the device (in which case there may be no follow-up message from the A-IoT device reader and so that access cycle / RA procedure may end). An inventory request, on the other hand requests a response from the A-IoT device 3-1 and so there will be a follow-up D2R message ('A-IoT Msg3').

[0138] If an R2D data transmission (A-IoT Msg4) is received by the A-IoT device 3-1, from the A-IoT device reader, then the A-IoT device 3-1 may respond appropriately (as seen at S514). For example, the A-IoT device 3-1 may send a D2R data transmission / message ('A-IoT Msg5') to the A-IoT device reader, for example, to provide an inventory response transmission (or the like) - for example to respond to an inventory request if provided with the previous R2D data transmission (A-IoT Msg4).

[0139] Allocation of Resources for Msg3 Transmission 　　Beneficially, as described in more detail later, each A-IoT device 3-1 and each A-IoT device reader of the communication system 1 are mutually configured for implementing one or more procedures / mechanisms for supporting allocation of resources for Msg3 transmission.

[0140] Beneficially, for example, as described in more detail later, each A-IoT device 3-1 and each A-IoT device reader of the communication system 1 may be configured to support one or more mechanisms to allocate extended resources for Msg3s transmitted in an A-IoT random access procedure in via at least partial indication of resources in a Msg2 wherein that Msg2 is transmitted in response to a corresponding Msg1 received from an A-IoT device 3-1.

[0141] Beneficially, for example, as described in more detail later, each A-IoT device 3-1 and each A-IoT device reader of the communication system 1 may be configured to support one or more mechanisms to allocate extended resources for Msg3s transmitted in an A-IoT random access procedure in via at least partial indication of resources in a Msg2 wherein that Msg2 is transmitted in response to plurality of Msg1s received from a corresponding plurality of A-IoT devices 3-1.

[0142] Beneficially, for example, as described in more detail later, each A-IoT device 3-1 and each A-IoT device reader of the communication system 1 may be configured to support one or more mechanisms to indicate timing relations between Msg2 and Msg3 transmitted in an A-IoT random access procedure.

[0143] Enhanced Mechanisms for Msg3 Resource Allocation using Msg2 Transmitted in Response to a Corresponding Msg1 Received from an A-IoT Device Resource Allocation for Msg3 - Use Frequency Domain Resources Allocated for Msg1, Indicate Time Domain Resources 　　As described above, in Msg3 Resource Allocation Option #2 each Msg3 sent by a respective A-IoT device 3-1 may be transmitted over frequency resources allocated for / applied by Msg1, whilst the time resources used for each Msg3 is indicated to that respective A-IoT device 3-1 in a corresponding Msg2 sent by the A-IoT device reader to that respective A-IoT device 3-1. For example, in a scenario where the A-IoT system is configured such that the A-IoT device reader sends a respective Msg2 to each A-IoT device 3-1 in response to receiving a Msg1 from that A-IoT device 3-1 (Msg2 Transmission Option #1), the time resources to be used for Msg3 transmission performed by each respective A-IoT device 3-1 may be signaled to that A-IoT device 3-1 in a respective Msg2 transmitted by the A-IoT device reader to that A-IoT device 3-1.

[0144] However, as also described above, whilst allocating resources for Msg3 in accordance with Msg3 Resource Allocation Option #2 (i.e., each Msg3 sent by a respective A-IoT device 3-1 may be transmitted over Msg1 frequency resources, whilst the time resource for Msg3 is indicated to that A-IoT device 3-1 in a corresponding Msg2 sent by the A-IoT device reader to that A-IoT device 3-1) partially saves on signalling overhead, there is still a risk that the resources allocated for Msg3 may not be sufficient if the amount of data to be transmitted in Msg3 is greater than that transmitted in the Msg1 whose resources are being re-used.

[0145] Several different mechanisms for allocating resources for Msg3 in a manner that beneficially facilitates a reduction in the amount of control information that needs to be included in Msg2, and which may be implemented in the case where Msg2 is transmitted by the A-IoT device reader to A-IoT devices 3-1 in accordance with Msg2 Transmission Option #1, will now be described, by way of example only. In particular, there now follows description of several different mechanisms for allocating resources for Msg3 in the case where Msg3 Resource Allocation Option #2 is implemented in the communication system 1.

[0146] Msg3 Resources Allocated Using a Time Domain Resource Allocation (TDRA) Indication Table 　　Fig. 6 illustrates an example of a first resource allocation mechanism that may be implemented wherein Msg3 uses a Msg1 frequency resource and the time resource for Msg3 is provided in a corresponding Msg2.

[0147] In this example, a Msg3 time-domain resource allocation (TDRA) mapping table is implemented by the A-IoT device reader and (pre)configured or predefined at A-IoT devices 3-1. The TDRA mapping table is used to indicate allocations of Msg3 resources in the time domain that should be applied by one or more A-IoT devices 3-1 when an appropriate index is indicated by the A-IoT device reader to those one or more A-IoT devices 3-1.

[0148] As shown in Fig. 6, the Msg3 TDRA mapping table includes a plurality of indices (e.g., 1…N), and each index in the Msg3 TDRA mapping table is mapped to a corresponding 'Start of Resources' value ('S') and 'Duration / Length of Resources' value ('L').

[0149] S indicates the starting point in time of the allocated resources, which may be defined as an offset value with respect to a reference point for Msg3. That reference point for Msg3 corresponds to the end of a minimum time period between when Msg2 is received by the A-IoT device 3-1 and when the A-IoT device 3-1 can send Msg3 to the A-IoT device reader (T_R2DMin). T_R2DMinmay also be referred to as 'timing relations between Msg2 and Msg3' and may be (pre)configured / predefined at the A-IoT device 3-1. Alternatively, T_R2DMinmay be indicated to the A-IoT device 3-1 in Msg2.

[0150] L indicates the length / duration of the allocated resources for Msg3 in time and may be defined in any appropriate time unit (e.g., number of symbols, chip length, bit length, mini-slot, or the like).

[0151] By way of example only, as shown in Fig. 6, when a Msg3 uses frequency domain resources allocated / applied for Msg1, and the time domain resources allocated for Msg3 are indicated in a corresponding Msg2 (i.e., Resource Allocation Option #2), an A-IoT device 3-1 may receive, from the A-IoT device reader, a Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) which may include an indication of time domain resources that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission. For example, the Msg2 may include an index, or the like (e.g., Index = 3), to indicate an allocation of Msg3 resources in the time domain that should be applied by the A-IoT device 3-1 allowing the resources allocated for Msg3 to be greater than the resources that were allocated for Msg1 (if needed).

[0152] In response to receiving that Msg2 transmission, the A-IoT device 3-1 uses resources for the subsequent Msg3 transmission (e.g., Msg3 sent at step S510 of Fig. 5) that include the same frequency resources allocated / applied by that A-IoT device 3-1 to transmit Msg1 (e.g., at step S502 of Fig 5), as well as the time resources indicated to that A-IoT device 3-1 in the Msg2 sent by the A-IoT device reader to that A-IoT device 3-1 (e.g., Msg2 sent at step S508 of Fig. 5). Specifically, based on the index included in the Msg2 transmission (e.g., Index = 3), the A-IoT device 3-1 determines the set of resources in the time domain for transmitting Msg3 to the A-IoT device reader. For example, in the case of index = 3, as shown in Fig. 6, the Msg3 resources to be allocated may start 4 time units away from the reference point for Msg3 and may have a duration of 6 time units.

[0153] In another example (not shown) in the case of Index = 1, the Msg3 resources to be allocated may start zero time units away from the reference point for Msg3 and may have a duration of 8 time units. In yet another example (not shown) in the case of Index = 2, the Msg3 resources to be allocated may start 4 time units away from the reference point for Msg3, and may have a duration of 8 time units, etc.

[0154] It will be appreciated that in this example, whilst the Msg3 TDRA mapping table maps indices to both an S value and an L value, the L value may be omitted from the table in cases where the length of the allocated Msg3 resources are (pre)configured to be normalized to the size of the Msg1 resources. For example, the L value may be omitted if the length of the Msg3 resources is (pre)configured to always be twice / triple / etc. the size of the resources allocated for Msg1.

[0155] It will be appreciated that this example may be more especially applicable to Type 1 A-IoT devices 3-1 as such A-IoT devices 3-1 only support a single carrier frequency for D2R transmissions and thus extending resources in the frequency domain i.e., FDRA, may not be possible.

[0156] Msg3 Resources Allocated Using an Extension-based Scheme in the Time Domain 　　Figs. 7A, 7B, and 7C illustrate an example of a second resource allocation mechanism that may be implemented to allocated Msg3 resources wherein Msg3 uses a frequency resource allocated for Msg1, and the time resource for Msg3 is provided in a corresponding Msg2.

[0157] In this example, a Msg3 Extension Pattern mapping table is implemented by the A-IoT device reader and (pre)configured or predefined at A-IoT devices 3-1 that can be used to indicate extensions of Msg3 resources in the time domain that should be applied, by one or more A-IoT devices 3-1, to one or more time resources indicated by the A-IoT device reader (e.g., using an appropriate index / index pair) for a Msg1 resource allocation.

[0158] As shown in Figs. 7A, 7B, and 7C, the Msg3 Extension Pattern mapping table includes a plurality of indices (e.g., 0…N), and each index in the Msg3 Extension Pattern mapping table is mapped to a corresponding 'extension pattern'. Each extension pattern includes a sequence of one or more '1s' and a single '0'. For each extension pattern, 0 indicates a location in time corresponding to the time domain resources of the indicated Msg1 resource allocation, and a value of 1 indicates a location in time corresponding to extended time domain resources that are being allocated for use in transmission of Msg3.

[0159] By way of example only, as shown in Figs. 7A, 7B, and 7C, when Msg3 Resource Allocation Option #2 is to be implemented, an A-IoT device 3-1 may receive, from the A-IoT device reader, a Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) which includes an indication of time domain resources that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission. That Msg2 may include an extension pattern index, or the like to indicate an extension of Msg3 resources in the time domain that should be used by the A-IoT device 3-1 with respect to an indicated Msg1 resource allocation. For example, as shown in resource allocation diagram (a), a plurality of A-IoT devices 3-1 may each be allocated, for transmission of Msg1, a respective set of one or more resources. Each set of one or more resources is identified by a respective index (or pair of indices) which may be used to indicate a Msg1 resource allocation to the A-IoT device 3-1.

[0160] As shown in resource allocation diagram (b), an extension pattern of resources of [1, 1, 0] (extension pattern index = 4) indicates that two sets of extended resources in the time domain should be allocated and used for the Msg3 transmission that are located in front of the Msg1 resource allocation. Those two sets of extended resources in the time domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be three times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0161] As shown in resource allocation diagram (c), an extension pattern of resources of [1, 0, 1] (extension pattern index = 3) indicates that two sets of extended resources in the time domain should be allocated and used for the Msg3 transmission that are located either side of the Msg1 resource allocation. Those two sets of extended resources in the time domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be three times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0162] Similarly, an extension pattern of resources of [0, 1, 1] (extension pattern index = 2) indicates that two sets of extended resources in the time domain should be allocated and used for the Msg3 transmission that are located after the Msg1 resource allocation. Those two sets of extended resources in the time domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be three times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0163] Similarly, an extension pattern of resources of [0, 1] (extension pattern index = 1) indicates that one set of extended resources in the time domain should be allocated and used for the Msg3 transmission that are located after the Msg1 resource allocation. That set of extended resources in the time domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be twice times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0164] Similarly, an extension pattern of resources of [1, 0] (extension pattern index = 0) indicates that one set of extended resources in the time domain should be allocated and used for the Msg3 transmission that are located before the Msg1 resource allocation. That set of extended resources in the time domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be twice times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0165] Alternatively, rather than implementing a Msg3 Extension Pattern mapping table as described above, whereby an extension pattern index corresponding to an entry in the Msg3 Extension Pattern mapping table is provided in Msg2, each possible extension pattern may have its own associated indication (e.g., a [1, 1, 0] indication, a [1, 0, 1] indication, etc.) which is provided in Msg2 to indicate to the A-IoT device 3-1 the extension pattern of resources that should be additionally allocated for Msg3 transmissions.

[0166] Alternatively, rather than implementing a Msg3 Extension Pattern mapping table as described above, an 'Extension by Number' indication, or the like, and an 'Extension Direction' indication, or the like may be included in Msg2 to indicate to the A-IoT device 3-1 a number of extended resources that should be additionally allocated for Msg3 transmissions, and the position of those resources with respect to the Msg1 resource allocation.

[0167] For example, the Msg2 transmission may include an Extension by Number indication (e.g., Extension by Number = 1, 2, 3, etc.) and an Extension Direction indication (e.g., Extension Direction = 0 or 1) to indicate a number of extended resources that should be additionally allocated for Msg3 transmissions, and the position of those resources with respect to the Msg1 resource allocation. In this case, an Extension Direction indication = 0 may indicate that the extended resources are to be located before the Msg1 resources to be reused (e.g., as in resource allocation diagram (b)), while an Extension Direction indication = 1 may indicate that the extended resources are to be located after the Msg1 resource allocation.

[0168] It will be appreciated that in some examples, the number of extended resources to be allocated may be a fixed number. In this case, the Extension by Number indication may be omitted and instead the presence of an Extension Direction indication may implicitly indicate that extended resources for Msg3 are to be allocated.

[0169] It will also be appreciated that in some examples, the position of such extended resources may be fixed (e.g., they may always be located prior to the indicated Msg1 resource allocation). In this case, the Extension Direction indication may be omitted.

[0170] It will be appreciated that this example may be more especially applicable to Type 1 A-IoT devices 3-1 as such A-IoT devices 3-1 only support a single carrier frequency for D2R transmissions and thus extending resources in the frequency domain i.e., FDRA, may not be possible.

[0171] Msg3 Resources Allocated Using Plural Time Indices Indications 　　In another example, rather than implementing mapping tables which are (pre)configured or predefined at A-IoT devices 3-1, a plurality of indices each corresponding to a respective Msg1 type resource allocation may be indicated in Msg2.

[0172] Specifically, in this example, an A-IoT device 3-1 may receive, from the A-IoT device reader, a Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) which includes a respective index, or pair of indices (e.g., a slot index / sub-slot index / etc.) for each Msg1 resource that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission.

[0173] For example, an A-IoT device 3-1 may receive a Msg2 transmission from the A-IoT device reader that includes a pair of indices, e.g., (0, 1), for the Msg3 resource allocation. In this case, the resources allocated for Msg3 would be a combination of the set of one or more Msg1 resources corresponding to index=0 and the set of one or more Msg1 resources corresponding to index=1. Where index 0 and 1 indicated adjacent sets of one or more Msg1 resources the resources allocated for Msg3 will be continuous (which may be preferable).

[0174] Alternatively, the A-IoT device 3-1 may receive a Msg2 transmission from the A-IoT device reader that includes a different pair of indices (0, 3) that may represent separated sets of one or more Msg1 resources. In this case, the resources allocated for Msg3 may be discontinuous - i.e., a discontinuous combination of the set of one or more Msg1 resources corresponding to index=0 and the set of one or more Msg1 resources corresponding to index=3.

[0175] It will be appreciated that example may be more especially applicable to Type 1 A-IoT devices 3-1 as such A-IoT devices 3-1 only support a single carrier frequency for D2R transmissions and thus extending resources in the frequency domain i.e., FDRA, may not be possible.

[0176] Resource Allocation for Msg3 - Use Time Domain Resources Allocated for Msg1, Indicate Frequency Domain Resources 　　As described above, in Msg3 Resource Allocation Option #2a each Msg3 sent by a respective A-IoT device 3-1 may be transmitted over time resources allocated for Msg1, whilst the frequency resources used for each Msg3 is indicated to that respective A-IoT device 3-1 in a corresponding Msg2 sent by the A-IoT device reader to that respective A-IoT device 3-1. For example, in a scenario where the A-IoT system is configured such that each A-IoT device 3-1 sends a respective Msg2 to the A-IoT device reader in response to receiving a Msg1 from that A-IoT device reader (Msg2 Transmission Option #1), the frequency resources to be used for each Msg3 transmission performed by each respective A-IoT device 3-1 may be signaled to that A-IoT device 3-1 in a respective Msg2 transmitted by the A-IoT device reader to that A-IoT device 3-1.

[0177] However, as also described above, whilst allocating resources for Msg3 in accordance with Msg3 Resource Allocation Option #2a (i.e., each Msg3 sent by a respective A-IoT device 3-1 may be transmitted over Msg1 time resources, whilst the frequency resource for Msg3 is indicated to that A-IoT device 3-1 in a corresponding Msg2 sent by the A-IoT device reader to that A-IoT device 3-1) partially saves on signalling overhead, there is still a risk that the resources allocated for Msg3 may not be sufficient if the amount of data to be transmitted in Msg3 is greater than that transmitted in the Msg1 whose resources are being re-used.

[0178] Several different mechanisms for allocating resources for Msg3 in a manner that beneficially facilitates a reduction in the amount of control information that needs to be included in Msg2, and which may be implemented in the case where Msg2 is transmitted by the A-IoT device reader to A-IoT devices 3-1 in accordance with Msg2 Transmission Option #1, will now be described, by way of example only. In particular, there now follows description of several different mechanisms for allocating resources for Msg3 in the case where Msg3 Resource Allocation Option #2a is implemented in the communication system 1.

[0179] Msg3 Resources Allocated Using an Extension-based Scheme in the Frequency Domain 　　Figs. 8A and 8B illustrate an example of a third resource allocation mechanism that may be implemented wherein Msg3 uses a time resource allocated for Msg1, and the frequency resource for Msg3 is provided in a corresponding Msg2.

[0180] In this example, a Msg3 Extension Pattern mapping table is implemented by the A-IoT device reader and (pre)configured or predefined at A-IoT devices 3-1 that can be used to indicate extensions of Msg3 resources in the frequency domain that should be applied, by one or more A-IoT devices 3-1, frequency resources indicated by the A-IoT device reader (e.g., using an appropriate indication e.g., of a {BLF, M} or {R}) for a Msg1 resource allocation.

[0181] As shown in Figs. 8A and 8B, the Msg3 Extension Pattern mapping table includes a plurality of indices (e.g., 0…N), and each index in the Msg3 Extension Pattern mapping table is mapped to a corresponding 'extension pattern'. Each extension pattern includes a sequence of one or more '1s' and a single '0'. For each extension pattern, 0 indicates a location in frequency corresponding to the frequency domain resources of the indicated Msg1 resource allocation, and a value of 1 indicates a location in frequency corresponding to extended frequency domain resources that are being allocated for use in transmission of Msg3.

[0182] By way of example only, as shown in Figs. 8A and 8B, when Msg3 Resource Allocation Option #2a is to be implemented, an A-IoT device 3-1 may receive, from the A-IoT device reader, a Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) which includes an indication of frequency domain resources that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission.

[0183] That Msg2 may include an extension pattern index, or the like to indicate an extension of Msg3 resources in the frequency domain that should be used by the A-IoT device 3-1 with respect to an indicated Msg1 resource allocation. For example, as shown in resource allocation diagram (a), a plurality of A-IoT devices 3-1 may each be allocated, for transmission of Msg1, a respective set of one or more resources. Each set of one or more resources is identified a respective indication (e.g., of a {BLF, M} or {R}) which may be used to indicate a Msg1 frequency domain resource allocation to the A-IoT device 3-1.

[0184] As shown in resource allocation diagram (b), an extension pattern of resources of [1, 1, 0] (extension pattern index = 4) indicates that two sets of extended resources in the frequency domain should be allocated and used for the Msg3 transmission that are located above the Msg1 resource allocation. Those two sets of extended resources in the frequency domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resources. Accordingly, the set of resources allocated for the Msg3 transmission may be three times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0185] An extension pattern of resources of [1, 0, 1] (extension pattern index = 3) indicates that two sets of extended resources in the frequency domain should be allocated and used for the Msg3 transmission that are located above and below of the Msg1 resources resource allocation. Those two sets of extended resources in the frequency domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be three times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0186] An extension pattern of resources of [0, 1, 1] (extension pattern index = 2) indicates that two sets of extended resources in the frequency domain should be allocated and used for the Msg3 transmission that are located below the Msg1 resource allocation. Those two sets of extended resources in the frequency domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be three times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0187] An extension pattern of resources of [0, 1] (extension pattern index = 1) indicates that one set of extended resources in the frequency domain should be allocated and used for the Msg3 transmission that are located below the Msg1 resource allocation. That set of extended resources in the frequency domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be twice times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0188] An extension pattern of resources of [1, 0] (extension pattern index = 0) indicates that one set of extended resources in the frequency domain should be allocated and used for the Msg3 transmission that are located above the Msg1 resource allocation. That set of extended resources in the frequency domain that should be allocated and used for the Msg3 transmission may each be of the same size as the Msg1 resource allocation. Accordingly, the set of resources allocated for the Msg3 transmission may be twice times the size of the Msg1 resources that are allocated for transmission of Msg1.

[0189] Alternatively, rather than implementing a Msg3 Extension Pattern mapping table as described above, whereby an extension pattern index corresponding to an entry in the Msg3 Extension Pattern mapping table is provided in Msg2, each possible extension pattern may have its own associated indication (e.g., a [1, 1, 0] indication, a [1, 0, 1] indication, etc.) which is provided in Msg2 to indicate to the A-IoT device 3-1 the extension pattern of resources that should be additionally allocated for Msg3 transmissions.

[0190] Alternatively, rather than implementing a Msg3 Extension Pattern mapping table as described above, an 'Extension by Number' indication, or the like, and an 'Extension Direction' indication, or the like may be included in Msg2 to indicate to the A-IoT device 3-1 a number of extended resources that should be additionally allocated for Msg3 transmissions, and the position of those resources with respect to the Msg1 resource allocation.

[0191] For example, the Msg2 transmission may include an Extension by Number indication (e.g., Extension by Number = 1, 2, 3, etc.) and an Extension Direction indication (e.g., Extension Direction = 0 or 1) to indicate a number of extended resources that should be additionally allocated for Msg3 transmissions, and the position of those resources with respect to the Msg1 resource allocation. In this case, an Extension Direction indication = 0 may indicate that the extended resources are to be upwards in frequency of the Msg1 resources to be reused (e.g., as in resource allocation diagram (b)), while an Extension Direction indication = 1 may indicate that the extended resources are to be located downwards in frequency of the Msg1 resource allocation.

[0192] It will be appreciated that in some examples, the number of extended resources to be allocated may be a fixed number. In this case, the Extension by Number indication may be omitted and instead the presence of an Extension Direction indication may implicitly indicate that extended resources for Msg3 are to be allocated.

[0193] It will also be appreciated that in some examples, the position of such extended resources may be fixed (e.g., they may always be located prior to the indicated Msg1 resource allocation). In this case, the Extension Direction indication may be omitted.

[0194] It will be appreciated that this example may be more especially applicable to Type 2b A-IoT devices 3-1 as such A-IoT devices 3-1 can support multiple carrier frequencies for D2R transmissions and thus extending resources in the frequency domain i.e., FDRA, is possible.

[0195] Msg3 Resources Allocated Using Plural Frequency Indices Indications 　　In another example, rather than implementing mapping tables which are (pre)configured or predefined at A-IoT devices 3-1, a plurality of indices each corresponding to a respective Msg1 type resource allocations may be indicated in Msg2.

[0196] Specifically, in this example, an A-IoT device 3-1 may receive, from the A-IoT device reader, a Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) which includes an explicit indication (or indications) of frequency domain resources that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission. For example, each frequency domain resource that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission may, for example, be indicated by a {BLF, M} indication, where BLF represents the backscatter link frequency, and M represent the coding rate, or the baseband waveform multiplied by a square-wave at M times the symbol rate. The frequency resource set for Msg1 (and thus for Msg3 when those Msg1 resources are to be re-used) may alternatively be determined by, for example, an indicated line code repetition number set {R}, or the like.

[0197] For example, an A-IoT device 3-1 may receive a Msg2 transmission from the A-IoT device reader that includes a pair of indices {BLF, M) or multiple pairs of indices {BLF, M} for additional / extended resources to be allocated for Msg3 transmission. Alternatively (or additionally), the Msg2 transmission may include multiple indices {R} for the resource allocation of Msg3.

[0198] It will be appreciated that this example may be more especially applicable to Type 2b A-IoT devices 3-1 as such A-IoT devices 3-1 can support multiple carrier frequencies for D2R transmissions and thus extending resources in the frequency domain i.e., FDRA, is possible.

[0199] Msg3 Resources Allocated Using Frequency Indices Indications and Offsets 　　In this example, as with the previous example, an A-IoT device 3-1 may receive, from the A-IoT device reader, a Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) which includes an explicit indication of frequency domain resources that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission. For example, a frequency domain resource that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission may, for example, be indicated by a {BLF, M} indication or an {R} index. However, rather than providing a number of {BLF, M} indications or {R} indices as in the previous example, the Msg2 transmission may include, as well as a {BLF, M} indication or an {R} index, an indication of an offset associated with {M} or, alternatively an indication of an offset associated with {R} which may be applied to the {BLF, M} indication or {R} index respectively to determine additional frequency resources for use in transmitting Msg3.

[0200] It will be appreciated that this example may be more especially applicable to Type 2b A-IoT devices 3-1 as such A-IoT devices 3-1 can support multiple carrier frequencies for D2R transmissions and thus extending resources in the frequency domain i.e., FDRA, is possible.

[0201] Resource Allocation for Msg3 - Time Domain Resources and Frequency Domain Resource Allocated for Msg3 Indicated 　　As described above, in Msg3 Resource Allocation Option #3 each Msg3 sent by a respective A-IoT device 3-1 may be transmitted over time and frequency resources indicated to that A-IoT device 3-1 in a corresponding Msg2 sent by the A-IoT device reader to that A-IoT device 3-1. For example, in a scenario where the A-IoT system is configured such that each A-IoT device 3-1 sends a respective Msg2 to the A-IoT device reader in response to receiving a Msg1 from that A-IoT device reader (Msg2 Transmission Option #1), the time and frequency resources to be used for each Msg3 transmission performed by each respective A-IoT device 3-1 may be signaled to that A-IoT device 3-1 in a respective Msg2 transmitted by the A-IoT device reader to that A-IoT device 3-1.

[0202] However, as also described above, whilst allocating resources for Msg3 in accordance with Msg3 Resource Allocation Option #3 (i.e., each Msg3 sent by a respective A-IoT device 3-1 is transmitted over the time and frequency resources indicated to that A-IoT device 3-1 in a corresponding Msg2 sent by the A-IoT device reader to that A-IoT device 3-1) high efficiency can be achieved as the resources can be dynamically allocated the need to signal the resource allocations for each Msg3 increases the overall signalling overhead of the A-IoT system.

[0203] In the case where the time and frequency resources for Msg3 are all indicated, the time domain resources for Msg3 may be indicated in accordance with the procedure described above with reference to Fig. 6, while the frequency domain resources for Msg3 may be indicated using frequency indices indications and / or offsets as also described above.

[0204] Enhanced Mechanisms for Msg3 Resource Allocation Using Msg2 Transmitted in Response to a Plurality of Corresponding Msg1s Received from a Respective Plurality of A-IoT Devices 　　In a scenario where the A-IoT system is configured such that the A-IoT device reader sends a single common Msg2 to the A-IoT devices 3-1 (or a group of A-IoT devices 3-1) in response to receiving a Msg1 from each respective one of those A-IoT device 3-1 (i.e., Msg2 Transmission Option #2), the resources to be used for each Msg3 transmission performed by each respective A-IoT device 3-1 may be signaled to A-IoT devices 3-1 in the common Msg2 transmitted by the A-IoT device reader to those A-IoT devices 3-1. However, whilst the signalling of those resources may be signaled to those A-IoT devices 3-1 in the common Msg2, which in turn may reduce signalling overhead, as alluded to previously that common Msg2 may have a large TBS, resulting in greater power consumption and device implementation complexity at the A-IoT devices 3-1.

[0205] There now follows a mechanism for allocating resources for Msg3 in a manner that beneficially facilitates a reduction in the TBS of Msg2, and which may be implemented in the case where Msg2 is transmitted, by the A-IoT device reader, to A-IoT devices 3-1 and that Msg2 is a common Msg2 that is directed toward multiple A-IoT devices 3-1 in response to Msg1 transmissions from those A-IoT devices 3-1.

[0206] As alluded to previously, some A-IoT devices 3-1 in communication with the A-IoT device reader may be grouped in one way or another. For example, A-IoT devices 3-1 may be grouped together based on, for example only, their specific A-IoT device type (e.g., type 1, 2a, 2b), their coverage area, the services they provide, or the like. In this case, as will be appreciated, those A-IoT devices 3-1 that are grouped together may have a number of commonalities, and thus as a consequence the contents of a single (common) Msg2 transmitted by the A-IoT devices reader to a plurality of A-IoT devices 3-1 may be designed to account for the commonalities of grouped A-IoT devices 3-1 to reduce the overall signalling overhead (and thus TBS) of that Msg2.

[0207] Taking those commonalities into account therefore, allocated resources for Msg3, a single (common) Msg2 transmitted by the A-IoT devices reader to a plurality of A-IoT devices 3-1 may include a simplified resource allocation indication to allocate resources for a plurality of Msg3 transmissions, one Msg3 transmission for each respective A-IoT device 3-1 to which the Msg2 was sent.

[0208] That simplified resource allocation indication may, for example, include an indication of one or more specific resources to be used for Msg3 (e.g., Msg1 allocated resources, or other resources), an indication of a resource domain (e.g., time and / or frequency resource domain) in which those indicated resources may be extended, and an indication of an extension rule that is to be applied to extend those indicated resources in the indicated resource domain. It will nevertheless be appreciated that the extension rule need not necessarily be indicated in Msg2, but instead may be, by way of example only, (pre)configured or predefined.

[0209] By way of example only, an A-IoT device 3-1 may receive, from the A-IoT device reader, a single (common) Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) for a plurality of A-IoT devices 3-1 that sent a Msg1 to the A-IoT device reader (at step S506 of Fig. 5). That single (common) Msg2 may include a 2-bit 'mode' indication to indicate whether or not resources indicated in the Msg2 for allocation for multiple Msg3 transmissions (i.e., for each Msg3 transmission to be sent by a respective A-IoT device 3-1 to the A-IoT device reader) should be extended in: a) the time domain ('TDMA only' extension), b) the frequency domain ('FDMA only' extension), or c) the time and frequency domain ('TDMA and FDMA' extension).

[0210] TDMA Only Extension 　　Fig. 9 illustrates an example of a first resource allocation mechanism that may be implemented using a single Msg2 transmitted to a plurality of A-IoT devices 3-1.

[0211] In the case where the Msg2 sent to a plurality of the A-IoT devices 3-1 includes the 2-bit indication, and that 2-bit indication indicates that a resource allocation for Msg3 indicated in the Msg2 should be extended in the time domain ('TDMA only' extension), the Msg2 may include one or more resource allocation indications to indicate one or more resources that are allocated for transmitting Msg3. As shown in Fig. 9, those one or more resources allocated for transmitting Msg3 may be specifically used by a first A-IoT device 3-1 of the plurality of A-IoT devices 3-1 to which the Msg2 is directed. For example, those one or more resources that are allocated for transmitting Msg3 may be specifically used by the A-IoT device 3-1 whose device ID is first listed / indicated in the Msg2.

[0212] The Msg2 includes one or more rules of extension ('extension rules') that may be applied by the A-IoT devices 3-1 to extend the one or more resources indicated in the Msg2 that are allocated for transmitting Msg3. For example, Msg2 may include an indication that the one or more resources indicated in the Msg2 allocated for transmitting Msg3 should be repeated automatically over and over, with a time gap (TGap) in between each repetition. As shown in Fig. 9, those one or more resources that are allocated may be repeated over and over in time with a time gap (TGap) in between, and each subsequent repeat of those resource may be used by a subsequent one of the plurality of A-IoT devices 3-1 to which the Msg2 is directed. For example, each subsequent repeat of those resources may be used by the A-IoT device 3-1 whose device ID is next listed / indicated in the Msg2.

[0213] It will nevertheless be appreciated that the one or more extension rules need not necessarily be indicated in Msg2, but instead may be, by way of example only, (pre)configured or predefined.

[0214] FDMA Only Extension 　　Fig. 10 illustrates an example of a second resource allocation mechanism that may be implemented using a single Msg2 transmitted to a plurality of A-IoT devices 3-1.

[0215] In the case where the Msg2 sent to a plurality of the A-IoT devices 3-1 includes the 2-bit indication, and that 2-bit indication indicates that a resource allocation for Msg3 indicated in the Msg2 should be extended in the frequency domain ('FDMA only' extension), the Msg2 may include one or more resource allocation indications to indicate one or more resources allocated for transmitting Msg3. As shown in Fig. 10, those one or more resources that are allocated for transmitting Msg3 may be specifically used by a first A-IoT device 3-1 of the plurality of A-IoT devices 3-1 to which the Msg2 is directed. For example, those one or more resources that are allocated for transmitting Msg3 may be specifically used by the A-IoT device 3-1 whose device ID is first listed / indicated in the Msg2.

[0216] The Msg2 includes one or more rules of extension ('extension rules') that may be applied by the A-IoT devices 3-1 to extend the one or more resources indicated in the Msg2 that are allocated for transmitting Msg3. For example, Msg2 may include an indication that the one or more resources indicated in the Msg2 allocated for transmitting Msg3 should be repeated automatically over and over in a default direction (e.g., upward, or downward) in the frequency domain. As shown in Fig. 9, those one or more resources allocated may be repeated over and over in increasing / decreasing sections of the frequency domain, and each subsequent repeat of those resource may be used by a subsequent one of the plurality of A-IoT devices 3-1 to which the Msg2 is directed. For example, each subsequent repeat of those resources may be used by the A-IoT device 3-1 whose device ID is next listed / indicated in the Msg2.

[0217] Alternatively, as also shown in Fig. 10, those one or more resources that are allocated for transmitting Msg3 by a first A-IoT device 3-1 of plurality of A-IoT devices 3-1 may be repeated in multiples of {R} and each repeat of those resource may be used by a subsequent one of the plurality of A-IoT devices 3-1 to which the Msg2 transmission by the A-IoT device reader is directed. For example, each subsequent repeat of those resources may be used by the A-IoT device 3-1 whose device ID is next listed / indicated in the Msg2.

[0218] It will nevertheless be appreciated that the one or more extension rules need not necessarily be indicated in Msg2, but instead may be, by way of example only, (pre)configured or predefined.

[0219] TDMA and FDMA Extension 　　Fig. 11 illustrates an example of a third resource extension mechanism that may be implemented using a single Msg2 transmitted to a plurality of A-IoT devices 3-1.

[0220] In the case where the Msg2 sent to a plurality of the A-IoT devices 3-1 includes the 2-bit indication, and that 2-bit indication indicates that a resource allocation for Msg3 indicated in the Msg2 should be extended in the time domain and the frequency domain ('TDMA and FDMA' extension), the Msg2 may include one or more resource allocation indications to indicate one or more resources allocated for transmitting Msg3. As shown in Fig. 11, those one or more resources allocated for transmitting Msg3 may be specifically used by a first A-IoT device 3-1 of the plurality of A-IoT devices 3-1 to which the Msg2 is directed. For example, those one or more resources that are allocated for transmitting Msg3 may be specifically used by the A-IoT device 3-1 whose device ID is first listed / indicated in the Msg2.

[0221] The Msg2 includes one or more rules of extension ('extension rules') that may be applied by the A-IoT devices 3-1 to extend the one or more resources indicated in the Msg2 that are allocated for transmitting Msg3. For example, Msg2 may include an index corresponding to an entry in a Msg3 Extension Pattern mapping table implemented by the A-IoT device reader and (pre)configured or predefined at A-IoT devices 3-1.

[0222] As shown in Fig. 11, the Msg3 Extension Pattern mapping table includes a plurality of indices (e.g., 0…N), and each index in the Msg3 Extension Pattern mapping table is mapped to a corresponding 'extension pattern'. Each extension pattern includes a sequence of one or more '1s' and '0s'. For each extension pattern, 0 indicates a location in a time-frequency domain grid where an extended resource is not allocated, and a value of 1 indicates a location in the time-frequency domain grid where an extended resource is allocated. A bold and underlined 1 indicates a location in the time frequency domain grid where the resources explicitly indicated in the Msg2 are located.

[0223] By way of example only, as shown in Fig. 11, when Msg3 Resource Allocation Option #3 is to be implemented, an A-IoT device 3-1 may receive, from the A-IoT device reader, a Msg2 transmission (e.g., Msg2 sent at step S508 of Fig. 5) which includes an indication of time-frequency domain resources that should be used by the A-IoT device 3-1 for transmission of a subsequent Msg3 transmission.

[0224] That Msg2 may include an extension pattern index, or the like to indicate an extension of Msg3 resources in the time and frequency domain that should be used by the A-IoT device 3-1 with respect to an indicated resource allocation in the Msg2. As shown, for example, an extension pattern of resources: (extension pattern index = 1) indicates that two sets of extended resources as arranged in Fig. 11 should be allocated and used for the Msg3 transmission, and those allocated resource may be used by the A-IoT device 3-1 in order of the IDs of those A-IoT devices 3-1 listed / indicated in the Msg2, with the extended resources in the frequency domain being used first and the extended resources in the time domain being used second (or vice versa).

[0225] Enhanced Mechanisms for Indicating Timing Relations between Msg2 and Msg3 　　In all of the mechanisms and procedures described above with respect to Msg2 Transmission Option #1 (i.e., Msg2 transmitted in response to a corresponding Msg1 received from an A-IoT device 3-1), it will be appreciated that, as a Msg2 is transmitted by the A-IoT device reader to each respective A-IoT device 3-1 that sends a Msg1 to the A-IoT device 3-1, and that following those Msg2 transmissions, each A-IoT device 3-1 sends a Msg3 to the A-IoT device reader, the timing relations between the transmission of the Msg2s by the A-IoT device reader and the subsequent reception of the Msg3s may be configured in a number of ways.

[0226] In one example, as shown in Figs. 12A and 12B, each A-IoT device 3-1 may transmit its Msg3 after a last Msg2 transmission by the A-IoT device reader (Timing Relation Option #1). Alternatively, as shown in Figs. 13A and 13B, each A-IoT device 3-1 may transmit its Msg3 after its corresponding Msg2 transmission (Timing Relation Option #2).

[0227] For example, as shown in Fig. 12A, which corresponds to a scenario where transmission of Msg2 is in accordance with Msg2 Transmission Option #1 (i.e., the A-IoT device reader, in response to Msg1s received from one or more A-IoT devices, may send a corresponding A-IoT Msg2 to each respective A-IoT device 3-1 that sent an Msg1 to the A-IoT device reader), each A-IoT device 3-1 may transmit its Msg3 after a last Msg2 transmission by the A-IoT devices reader such that Msg3 transmissions do not begin until after the last Msg2 transmission.

[0228] Similarly, as shown in Fig. 12B, which corresponds to a scenario where transmission of Msg2 is in accordance with Msg2 Transmission Option #2 (i.e., the A-IoT device reader, in response to the Msg1s received from one or more A-IoT devices 3-1, may send a single (common) Msg2 to a group of A-IoT devices 3-1 that sent an Msg1 to the A-IoT device reader), each A-IoT device 3-1 may transmit its Msg3 after a last Msg2 transmission by the A-IoT devices reader such that Msg3 transmissions do not begin until after the last Msg2 transmission.

[0229] Alternatively, as shown in Fig. 13A, which corresponds to a scenario where transmission of Msg2 is in accordance with Msg2 Transmission Option #1 (i.e., the A-IoT device reader, in response to Msg1s received from one or more A-IoT devices 3-1, may send a corresponding A-IoT Msg2 to each respective A-IoT device 3-1 that sent an Msg1 to the A-IoT device reader), each A-IoT device 3-1 may transmit its Msg3 after its corresponding Msg2 transmission.

[0230] Similarly, as shown in Fig. 13B, which corresponds to a scenario where transmission of Msg2 is in accordance with Msg2 Transmission Option #2 (i.e., the A-IoT device reader, in response to the Msg1s received from one or more A-IoT devices 3-1, may send a single (common) Msg2 to a group of A-IoT devices 3-1 that sent an Msg1 to the A-IoT device reader), each A-IoT device 3-1 may transmit its Msg3 after its corresponding Msg2 transmission for the group of A-IoT devices 3-1.

[0231] However, as will be appreciated in the case where each A-IoT device 3-1 may transmit its Msg3 after a last Msg2 transmission by the A-IoT device reader (Timing Relation Option #1), an appropriate indication may need to be implemented to inform the A-IoT devices 3-1 that the last Msg2 transmission by the A-IoT device reader has occurred.

[0232] For example, a one-bit indication may be included in each Msg2 transmitted by the A-IoT device reader to indicate whether that Msg2 transmission by the A-IoT device reader is the last Msg2 transmission. In this case, the first Msg2 by the A-IoT device reader may include an appropriate indication of a timing relationship between that first Msg2 transmission and its corresponding (i.e., the first) Msg3 transmission. Alternatively, the timing relationship between that first Msg2 transmission and its corresponding (i.e., the first) Msg3 transmission may be preconfigured / predefined such that no indication is required in the first Msg2 transmission.

[0233] Once the first Msg2 is received, the A-IoT devices 3-1 may then continue to monitor for subsequent Msg2 transmissions until they receive a Msg2 that includes the one-bit indication indicating that that Msg2 is the last Msg2 to be transmitted by the A-IoT device reader.

[0234] Having received a Msg2 that includes the one-bit indication indicating that that Msg2 is the last Msg2 to be transmitted by the A-IoT device reader, the A-IoT devices 3-1 may then take the received time of that last Msg2 as a reference point, and apply to that reference point, the timing relationship between the first Msg2 transmission and its corresponding (i.e., the first) Msg3 transmission indicated in the first Msg2 to determine a final start time of the first Msg3.

[0235] For example, as shown in Fig. 14A, which corresponds to a scenario where transmission of Msg2 is in accordance with Msg2 Transmission Option #1 (i.e., the A-IoT device reader, in response to Msg1s received from one or more A-IoT devices 3-1, may send a corresponding A-IoT Msg2 to each respective A-IoT device 3-1 that sent an Msg1 to the A-IoT device reader), the first Msg2 transmitted by the A-IoT device reader may include an appropriate indication of a timing relationship between that first Msg2 transmission and its corresponding (i.e., the first) Msg3 transmission (see arrow shown in Fig. 14A), and the last Msg2 may include an one-bit indication that indicates that it is the last Msg2 transmission.

[0236] Similarly, as shown in Fig. 14B, which corresponds to a scenario where transmission of Msg2 is in accordance with Msg2 Transmission Option #2 (i.e., the A-IoT device reader, in response to the Msg1s received from one or more A-IoT devices 3-1, may send a single (common) Msg2 to a group of A-IoT devices 3-1 that sent an Msg1 to the A-IoT device reader), the first Msg2 transmitted by the A-IoT device reader may include an appropriate indication of a timing relationship between that first Msg2 transmission and its corresponding (i.e., the first) Msg3 transmission (see arrow shown in Fig. 14B), and the last Msg2 may include an one-bit indication that indicates that it is the last Msg2 transmission.

[0237] Devices in the Communication System User Equipment 　　Fig. 15 is a simplified block schematic illustrating the main components of a UE 3-2; 3-3 for implementation in the communication system 1. It will be appreciated that the UE 3-2; 3-3 may be configured to operate as an intermediate / assisting node 5-2 (i.e., and A-IoT device reader) in the communication system 1.

[0238] As shown, the UE 3-2; 3-3 has a transceiver circuit 31 that is operable to transmit signals to and to receive signals from a RAN node (base station) 5-1 via one or more antenna 33 (e.g., comprising one or more antenna elements). The UE 3 has a controller 37 to control the operation of the UE 3. The controller 37 is associated with a memory 39 and is coupled to the transceiver circuit 31. Although not necessarily required for its operation, the UE 3-2; 3-3 might, of course, have all the usual functionality of a conventional UE 3-2; 3-3 (e.g., a user interface 35, such as a touch screen / keypad / microphone / speaker and / or the like for, allowing direct control by and interaction with a user) and this may be provided by any one or any combination of hardware, software, and firmware, as appropriate. Software may be pre-installed in the memory 39 and / or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example.

[0239] The controller 37 is configured to control overall operation of the UE 3-2; 3-3 by, in this example, program instructions or software instructions stored within memory 39. As shown, these software instructions include, among other things, an operating system 41, and a communication control module 43.

[0240] The communication control module 43 is operable to control the communication between the UE 3-2; 3-3 and its serving RAN node or RAN nodes 5-1 (and other communication devices connected to the RAN node 5-1, such as further UEs and / or core network nodes). The communication control module 43 is configured for the overall handling of uplink communication via associated uplink channels (e.g., via a physical uplink control channel (PUCCH), random access channel (RACH), and / or a physical uplink shared channel (PUSCH)) including both dynamic and semi-static signalling (e.g., SRS). The communication control module 43 is also configured for the overall handling of receipt of downlink communication via associated downlink channels (e.g., of DCI via a physical downlink control channel (PDCCH) and / or a physical downlink shared channel (PDSCH)) including both dynamic and semi-persistent scheduling (e.g., SPS). The communication control module 43 is responsible, for example: for determining where to monitor for downlink control information; for determining the resources to be used by the UE 3 for transmission / reception of UL / DL communication (including interleaved resources and resources subject to frequency hopping); for managing frequency hopping at the UE side; for determining how slots / symbols are configured (e.g., for UL, DL or full duplex communication, or the like); for determining which bandwidth parts are configured for the UE 3-2; 3-3; for determining how uplink transmissions should be encoded and the like.

[0241] Where the UE 3-2, 3-3 is configured to operate as an intermediate / assisting node 5-2 (i.e., as an A-IoT device reader) the communication control module 43 may be operable to control the communication between the IoT device 3-1 and the UE 3-2, 3-3, for example, via the associated physical channels (e.g., via a physical D2R channel (PDRCH), random access channel (RACH), and / or a physical R2D channel (PRDCH)).

[0242] It will be appreciated that the communication control module 43 may include a number of sub-modules ('layers' or 'entities') to support specific functionalities. For example, the UE 3-2, 3-3 may include sub-modules corresponding to the layers of a conventional protocol stack (PHY, MAC, RRC, RLC, PDCP etc.). Moreover, where the UE 3-2, 3-3 is configured to operate as an intermediate / assisting node 5-2, communication control module 43 may include sub-modules corresponding to the layers of a dedicated ambient IoT device protocol stack for controlling functions associated with those layers.

[0243] The communication control module 43 is configured, in particular, to control the UE's communication, where applicable, in accordance with any of the methods described herein.

[0244] Ambient IoT device 　　Fig. 16 is a simplified block schematic illustrating the main components of an example of a UE comprising an ambient IoT device 3-1 for possible implementation in the communication system 1.

[0245] As shown, the ambient IoT device 3-1 (also referred to simply as an IoT device 3-1) has a transceiver circuit 331 that is operable to transmit signals to and to receive signals from a RAN node 5-1 (and / or an assisting node 5-2, and / or an intermediate node 5-2) via one or more antenna 333 (e.g., comprising one or more antenna elements).

[0246] The transceiver circuit 331 may comprise energy harvesting circuitry 331-1 that is configured to harvest and / or collect energy from an ambient energy source such as an incoming signal and / or other ambient sources of energy (e.g., of light, vibrations, or heat). That collected energy may then be provided to other modules of IoT device 3-1 to provide a stable power supply to those modules. The energy harvesting circuitry 331-1 may include, by way of example only, inductive and / or capacitive architectures to harvest energy from incoming signals.

[0247] It will however be appreciated that the energy harvesting circuitry 331-1 may alternatively not form part of the transceiver circuit 331, but instead is its own module. For example, this may be the case when the energy to be harvested does not originate from signals transmitted to the IoT device 3-1. By way of example only, the IoT device 3-1 may harvest energy from solar cells such as dye-sensitised solar cells (DSSCs).

[0248] The transceiver circuit 331 also has modulation circuitry 331-2 which modulates an incoming unmodulated carrier signal to the IoT device 3-1 to produce the modulated backscatter signal to be reflected from the IoT device 3-1 for receipt by another device. For example, the modulation circuitry 331-2 may be configured modulate an incoming RF signal to the IoT device 3-1 by altering the impedance or reflectivity of the IoT device 3-1 in response to receiving that incoming RF signal. The modulation circuitry 331-2 may be configured to modulate the incoming signal to encode data provided from one or more data sources 332. Typically, for example, the IoT device 3-1 may comprise a data source 332 in the form of a sensor (e.g., an optical, temperature, position sensor or the like) for providing measurement data or a sensor alert, may comprise a data source 332 in the form of a stored or hardwired parameter such as a device or device type identifier, and / or may comprise one or more other sources of data.

[0249] In this example, the transceiver circuit 331 may also have a signal amplifier 331-3 (which may utilise energy harvested by the energy harvesting circuitry 331-1) for amplifying any modulated backscattered signal to be reflected by the IoT device 3-1 for receipt at another device.

[0250] In this example, the IoT device 3-1 also has a controller 337 to control the overall operation of the IoT device 3-1. The controller 337 is associated with a memory 339 and is coupled to the transceiver circuit 331. Although not necessarily required for its operation, the IoT device 3-1 might, of course, have all the usual functionality of a more conventional UE (e.g., a user interface 335, such as a touch screen / keypad / microphone / speaker and / or the like for, allowing direct control by and interaction with a user) and this may be provided by any one or any combination of hardware, software, and firmware, as appropriate. Software may be pre-installed in the memory 339 and / or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example.

[0251] The controller 337 includes processing circuitry 338 configured to control overall operation of the IoT device 3-1 by, in this example, program instructions or software instructions stored within memory 339. As shown, these software instructions include, among other things, an operating system 341, and a communication control module 343.

[0252] The communication control module 343 is operable to control the communication between the IoT device 3-1, the RAN node 5-1, and / or the assisting node 5-2. The communication control module 343 may, for example, be configured for the overall handling of communication via associated physical channels (e.g., via a physical D2R channel (PDRCH), random access channel (RACH), and / or a physical R2D channel (PRDCH)).

[0253] It will be appreciated that the communication control module 343 may include a number of sub-modules ('layers' or 'entities') to support specific functionalities. For example, the communication control module 343 may include sub-modules corresponding to the layers of a dedicated ambient IoT device protocol stack for controlling functions associated with those layers.

[0254] The communication control module 343 is configured, in particular, to control the IoT device's communication, where applicable, in accordance with any of the methods described herein.

[0255] RAN node 　　Fig. 17 is a simplified block schematic illustrating the main components of a RAN node 5-1 (e.g., a base station / IoT device reader) for implementation in the communication system 1. It will be appreciated that the RAN node 5-1 may be configured to operate as an A-IoT device reader in the communication system 1.

[0256] As shown, the RAN node 5-1 has a transceiver circuit 51 for transmitting signals to and for receiving signals from the communication devices (such as UEs 3-2; 3-3, IoT devices 3-1, and possibly assisting or intermediate devices 5-2) via one or more antenna 53 (e.g., a single or multi-panel antenna array / massive antenna), and a core network interface 55 for transmitting signals to and for receiving signals from network nodes in the core network 7. Although not shown, the RAN node 5-1 may also be coupled to other RAN node 5-1 via an appropriate interface (e.g., the so-called 'X2' interface in LTE or the 'Xn' interface in NR). The RAN node 5-1 has a controller 57 to control the operation of the RAN node 5-1. The controller 57 is associated with a memory 59. Software may be pre-installed in the memory 59 and / or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example. The controller 57 is configured to control the overall operation of the RAN node 5-1 by, in this example, program instructions or software instructions stored within memory 59.

[0257] As shown, these software instructions include, among other things, an operating system 61, and a communication control module 63.

[0258] The communication control module 63 is operable to control the communication between the RAN node 5-1 and UEs 3 and other network entities (e.g., core network nodes) that communicate with the RAN node 5-1. The communication control module 63 is configured for the overall control of the reception and decoding of uplink communication, via associated uplink channels (e.g., via a physical uplink control channel (PUCCH), a random-access channel (RACH), and / or a physical uplink shared channel (PUSCH)) including both dynamic and semi-static signalling (e.g., SRS), and modulated backscattered communication in accordance with ambient IoT (where applicable). The communication control module 63 is also configured for the overall control of the transmission of downlink communication including downlink communication via associated downlink channels (e.g., via a physical downlink control channel (PDCCH) and / or a physical downlink shared channel (PDSCH)) including both dynamic and semi-persistent scheduling (e.g., SPS), and downlink communication of an unmodulated carrier signal in accordance with ambient IoT (where applicable). The communication control module 63 is responsible, for example: for determining where to configure the UE 3 to monitor for downlink control information (e.g., the location of search spaces, CORESETs, and associated PDCCH candidates to monitor); for determining the resources to be scheduled for UE transmission / reception of UL / DL communication (including interleaved resources and resources subject to frequency hopping); for managing frequency hopping at the base station side; for configuring slots / symbols appropriately (e.g., for UL, DL or full duplex communication, or the like); for configuring bandwidth parts for the UE 3; for providing related configuration signalling to a UE 3; and the like.

[0259] Where the RAN node 5-1 is configured to operate as an A-IoT device reader the communication control module 63 is operable to control the communication between the IoT device 3-1 and the RAN node 5-1, for example, via the associated physical channels (e.g., via a physical D2R channel (PDRCH), random access channel (RACH), and / or a physical R2D channel (PRDCH)) including both dynamic and semi-static signalling.

[0260] It will be appreciated that the communication control module 63 may include a number of sub-modules ('layers' or 'entities') to support specific functionalities. By way of example only the communication control module 63 may include sub-modules corresponding to the layers of a conventional protocol stack (PHY, MAC, RRC, RLC, PDCP etc.). Moreover, where the RAN node 5-1 is configured to operate as an A-IoT device reader, the communication control module 63 may include, sub-modules corresponding to the layers of a dedicated ambient IoT device protocol stack for controlling functions associated with those layers.

[0261] The communication control module 63 is configured in particular, to control the base station's communication, in accordance with any of the methods described herein.

[0262] Assisting (or intermediate) node 　　Fig. 18 is a simplified block schematic illustrating the main components of an example of an assisting (or intermediate) node 5-2 for possible implementation in the communication system 1.

[0263] As shown, the assisting node 5-2 may comprise a UE 3 (such as, or similar to, UE 3-2; 3-3), an IAB node, a repeater, or the like, which is capable of ambient IoT operation. In this scenario, the assisting node 5-2 has a transceiver circuit 151 that is operable to transmit signals to and to receive signals from a UE 3 (such as an ambient IoT device) via one or more antenna 153 (e.g., comprising one or more antenna elements), and a RAN interface 155 for transmitting signals to and for receiving signals from the RAN node 5-1 (which may also be over the air via the antenna 153, or via a different antenna).

[0264] The assisting node 5-2 has a controller 157 to control the operation of the assisting node 5-2. The controller 157 is associated with a memory 159 and is coupled to the transceiver circuit 151. Although not necessarily required for its operation, the assisting node 5-2 might, of course, have other functionality (e.g., a user interface, such as a touch screen / keypad / microphone / speaker and / or the like for, allowing direct control by and interaction with a user) and this may be provided by any one or any combination of hardware, software, and firmware, as appropriate. Software may be pre-installed in the memory 159 and / or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example.

[0265] The controller 157 is configured to control overall operation of the UE 3 by, in this example, program instructions or software instructions stored within memory 159. As shown, these software instructions include, among other things, an operating system 161, and a communication control module 163.

[0266] The communication control module 163 is operable to control the communication between the assisting node 5-2, the RAN node 5-1, and any IoT devices (including the ambient IoT device 3-1). The communication control module 163 is configured, in particular, for the overall handling of communication with the RAN node 5-1. For example, where the intermediate / assisting node 5-2 is a UE 3 (or at least operates like a UE 3 in its communication with the RAN node 5-1) this uplink communication may be via associated uplink channels (e.g., via a physical uplink control channel (PUCCH), random access channel (RACH), and / or a physical uplink shared channel (PUSCH)) including both dynamic and semi-static signalling (e.g., SRS). The communication control module 163 is also configured for the overall handling of receipt of downlink communication from the RAN node 5-1. For example, where the intermediate / assisting node 5-2 is a UE 3 (or at least operates like a UE 3 in its communication with the RAN node 5-1) this downlink communication may be via associated downlink channels (e.g., of DCI via a physical downlink control channel (PDCCH) and / or a physical downlink shared channel (PDSCH)) including both dynamic and semi-persistent scheduling (e.g., SPS). It will, nevertheless, be appreciated that where the assisting node 5-2 is a device other than a UE 3 (e.g., an IAB or dedicated relay) then the communication control module 163 will be configured to communicate with the RAN node 5-1 using an appropriate corresponding signalling protocol for doing so.

[0267] The communication control module 163 is also responsible for appropriate ambient IoT related communication including, for example, reception of modulated backscattered communication from an ambient IoT device (where applicable) and / or downlink communication of an unmodulated carrier signal in accordance with ambient IoT (where applicable).

[0268] It will be appreciated that the communication control module 163 may include a number of sub-modules ('layers' or 'entities') to support specific functionalities. By way of example only the communication control module 163 may include sub-modules corresponding to the layers of a conventional protocol stack (PHY, MAC, RRC, RLC, PDCP etc.). Moreover, the communication control module 163 may include, sub-modules corresponding to the layers of a dedicated ambient IoT device protocol stack for controlling functions associated with those layers.

[0269] The communication control module 163 is configured, in particular, to control the assisting node's communication, in accordance with any of the methods described herein.

[0270] Modifications and Alternatives 　　Detailed examples been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above examples whilst still benefiting from the enhancements embodied therein.

[0271] It will be appreciated that description of features of and actions performed by a RAN node (or a RAN operating as an A-IoT device reader), apply equally to distributed type RAN nodes as to non-distributed type RAN nodes.

[0272] It will also be appreciated that whilst information elements having specific names may have been described, differently named information elements but having a similar purpose may be used.

[0273] In the above description the UE, A-IoT device, intermediate / assisting node, and the RAN node are described for ease of understanding as having a number of discrete functional components or modules. Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the disclosed enhancements, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities.

[0274] In the above examples, a number of software modules were described. As those skilled in the art will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied to the UE or base station as a signal over a computer network, or on a recording medium. Further, the functionality performed by part, or all, of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of the UE or the base station in order to update their functionalities.

[0275] Each controller may comprise any suitable form of processing circuitry including (but not limited to), for example: one or more hardware implemented computer processors; microprocessors; central processing units (CPUs); arithmetic logic units (ALUs); input / output (IO) circuits; internal memories / caches (program and / or data); processing registers; communication buses (e.g. control, data and / or address buses); direct memory access (DMA) functions; hardware or software implemented counters, pointers and / or timers; and / or the like. Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0276] The User Equipment (or "UE," "mobile station," "mobile device" or "wireless device") in the present disclosure is an entity connected to a network via a wireless interface.

[0277] It should be noted that the present disclosure is not limited to a dedicated communication device and can be applied to any device having a communication function as explained in the following paragraphs.

[0278] The terms "User Equipment" or "UE" (as the term is used by 3GPP), "mobile station", "mobile device", and "wireless device" are generally intended to be synonymous with one another, and include standalone mobile stations, such as terminals, cell phones, smart phones, tablets, cellular IoT devices, IoT devices, and machinery. It will be appreciated that the terms "mobile station" and "mobile device" also encompass devices that remain stationary for an extended period of time.

[0279] A UE may, for example, be an item of equipment for production or manufacture and / or an item of energy related machinery (for example equipment or machinery such as: boilers; engines; turbines; solar panels; wind turbines; hydroelectric generators; thermal power generators; nuclear electricity generators; batteries; nuclear systems and / or associated equipment; heavy electrical machinery; pumps including vacuum pumps; compressors; fans; blowers; oil hydraulic equipment; pneumatic equipment; metal working machinery; manipulators; robots and / or their application systems; tools; moulds or dies; rolls; conveying equipment; elevating equipment; materials handling equipment; textile machinery; sewing machines; printing and / or related machinery; paper converting machinery; chemical machinery; mining and / or construction machinery and / or related equipment; machinery and / or implements for agriculture, forestry and / or fisheries; safety and / or environment preservation equipment; tractors; precision bearings; chains; gears; power transmission equipment; lubricating equipment; valves; pipe fittings; and / or application systems for any of the previously mentioned equipment or machinery etc.).

[0280] A UE may, for example, be an item of transport equipment (for example transport equipment such as: rolling stocks; motor vehicles; motorcycles; bicycles; trains; buses; carts; rickshaws; ships and other watercraft; aircraft; rockets; satellites; drones; balloons etc.).

[0281] A UE may, for example, be an item of information and communication equipment (for example information and communication equipment such as: electronic computer and related equipment; communication and related equipment; electronic components etc.).

[0282] A UE may, for example, be a refrigerating machine, a refrigerating machine applied product, an item of trade and / or service industry equipment, a vending machine, an automatic service machine, an office machine or equipment, a consumer electronic and electronic appliance (for example a consumer electronic appliance such as: audio equipment; video equipment; a loud speaker; a radio; a television; a microwave oven; a rice cooker; a coffee machine; a dishwasher; a washing machine; a dryer; an electronic fan or related appliance; a cleaner etc.).

[0283] A UE may, for example, be an electrical application system or equipment (for example an electrical application system or equipment such as: an x-ray system; a particle accelerator; radio isotope equipment; sonic equipment; electromagnetic application equipment; electronic power application equipment etc.).

[0284] A UE may, for example, be an electronic lamp, a luminaire, a measuring instrument, an analyser, a tester, or a surveying or sensing instrument (for example a surveying or sensing instrument such as: a smoke alarm; a human alarm sensor; a motion sensor; a wireless tag etc.), a watch or clock, a laboratory instrument, optical apparatus, medical equipment and / or system, a weapon, an item of cutlery, a hand tool, or the like.

[0285] A UE may, for example, be a wireless-equipped personal digital assistant or related equipment (such as a wireless card or module designed for attachment to or for insertion into another electronic device (for example a personal computer, electrical measuring machine)).

[0286] A UE may be a device or a part of a system that provides applications, services, and solutions described below, as to "internet of things (IoT)," using a variety of wired and / or wireless communication technologies.

[0287] Internet of Things devices (or "things") may be equipped with appropriate electronics, software, sensors, network connectivity, and / or the like, which enable these devices to collect and exchange data with each other and with other communication devices. IoT devices may comprise automated equipment that follow software instructions stored in an internal memory. IoT devices may operate without requiring human supervision or interaction. IoT devices might also remain stationary and / or inactive for an extended period of time. IoT devices may be implemented as a part of a (generally) stationary apparatus. IoT devices may also be embedded in non-stationary apparatus (e.g., vehicles) or attached to animals or persons to be monitored / tracked.

[0288] It will be appreciated that IoT technology can be implemented on any communication devices that can connect to a communication system for sending / receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

[0289] It will be appreciated that IoT devices are sometimes also referred to as Machine-Type Communication (MTC) devices or Machine-to-Machine (M2M) communication devices. It will be appreciated that a UE may support one or more IoT or MTC applications. Some examples of MTC applications are listed in the following table. This list is not exhaustive and is intended to be indicative of some examples of machine-type communication applications.

[0290] Further, the above-described UE categories are merely examples of applications of the technical ideas and exemplary examples described in the present document. Needless to say, these technical ideas and examples are not limited to the above-described UE and various modifications can be made thereto.

[0291] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0292] While the present disclosure has been particularly shown and described with reference to example embodiments thereof, the present disclosure is not limited to these example embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the claims. And each embodiment can be appropriately combined with at least one of embodiments.

[0293] The whole or part of the example embodiments disclosed above can be described as, but not limited to, the following supplementary notes.

[0294] (Supplementary Note 1) 　　A method performed by a first device, the method including: 　　receiving a first message from a first reader, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　transmitting, to the first reader, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

[0295] (Supplementary Note 2) 　　The method of supplementary note 1, further including: 　　initiating a Random Access procedure; and 　　transmitting a Random ID to the first reader, wherein the first message is a response message for the Random ID.

[0296] (Supplementary Note 3) 　　The method of supplementary note 1 or 2, wherein a first length allocated to the second message is defined in units of chips.

[0297] (Supplementary Note 4) 　　The method of any one of supplementary notes 1-3, wherein the first message is received in a Medium Access Control, MAC, Control Element, CE.

[0298] (Supplementary Note 5) 　　The method of any one of supplementary notes 1-4, wherein the first time interval includes a minimum time period between the first timing and when the first device is able to send the second message.

[0299] (Supplementary Note 6) 　　The method of any one of supplementary notes 1-4, wherein the first time interval includes a predefined time period between the first timing and when the first device is able to send the second message.

[0300] (Supplementary Note 7) 　　The method of any one of supplementary notes 1-6, wherein the first message includes first information indicating a first index which identifies the first starting time and the first length.

[0301] (Supplementary Note 8) 　　The method of supplementary note 7, wherein the first index is associated with the first starting time and the first length in a predefined table.

[0302] (Supplementary Note 9) 　　The method of any one of supplementary notes 1-8, wherein the first message is for multiple devices.

[0303] (Supplementary Note 10) 　　The method of any one of supplementary notes 1-9, further including: 　　selecting a resource occasion for transmitting the Random ID.

[0304] (Supplementary Note 11) 　　The method of any one of supplementary notes 1-10, wherein the first message further includes second information indicating a first offset of a third value of a frequency resource for the second message, with respect to a reference value.

[0305] (Supplementary Note 12) 　　The method of supplementary note 11, wherein the first message includes multiple values of first offsets with respect to the reference value.

[0306] (Supplementary Note 13) 　　The method of supplementary note 11 or 12, further including: 　　determining a time offset corresponding to the first starting time, based on the third value.

[0307] (Supplementary Note 14) 　　The method of any one of supplementary notes 1-13, wherein the first message includes third information indicating a frequency for backscattering.

[0308] (Supplementary Note 15) 　　The method of supplementary note 14, wherein the first message includes multiple values of frequencies for backscattering.

[0309] (Supplementary Note 16) 　　A first device including: 　　means for receiving a first message from a first reader, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　means for transmitting, to the first reader, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

[0310] (Supplementary Note 17) 　　A method performed by a first reader, the method including: 　　transmitting a first message to a first device, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　receiving, from the first device, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

[0311] (Supplementary Note 18) 　　A first reader including: 　　means for transmitting a first message to a first device, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　means for receiving, from the first device, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

[0312] This application is based upon and claims the benefit of priority from United Kingdom applications No. 2501784.9, filed on February 6, 2025, the disclosure of which is incorporated herein in its entirety by reference.

[0313] 1 COMMUNICATION SYSTEM 3 UE 31 TRANSCEIVER CIRCUIT 33 ANTENNA 35 USER INTERFACE 37 CONTROLLER 39 MEMORY 41 OPERATING SYSTEM 43 COMMUNICATIONS CONTROL MODULE 331 TRANSCEIVER CIRCUIT 331-1 ENERGY HARVESTING CIRCUITRY 331-2 MODULATION CIRCUITRY 331-3 SIGNAL AMPLIFIER 332 DATA SOURCE 333 ANTENNA 335 USER INTERFACE 337 CONTROLLER 338 PROCESSING CIRCUITRY 339 MEMORY 341 OPERATING SYSTEM 343 COMMUNICATIONS CONTROL MODULE 345 DATA BUFFER 5 RAN NODE 51 TRANSCEIVER CIRCUIT 53 ANTENNA 55 CORE NETWORK INTERFACE 57 CONTROLLER 59 MEMORY 61 OPERATING SYSTEM 63 COMMUNICATIONS CONTROL MODULE 151 TRANSCEIVER CIRCUIT 153 ANTENNA 155 RAN NETWORK INTERFACE 157 CONTROLLER 159 MEMORY 161 OPERATING SYSTEM 163 COMMUNICATIONS CONTROL MODULE 6 SEPARATE COMMUNICATION NODE 7 CORE NETWORK 10 CPF 10-1 AMF 10-2 SMF 11 UPF 40 EXTERNAL DATA NETWORK

Claims

1. A method performed by a first device, the method comprising: 　　receiving a first message from a first reader, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　transmitting, to the first reader, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

2. The method of claim 1, further comprising: 　　initiating a Random Access procedure; and 　　transmitting a Random ID to the first reader, wherein the first message is a response message for the Random ID.

3. The method of claim 1 or 2, wherein a first length allocated to the second message is defined in units of chips.

4. The method of any one of claims 1-3, wherein the first message is received in a Medium Access Control, MAC, Control Element, CE.

5. The method of any one of claims 1-4, wherein the first time interval comprises a minimum time period between the first timing and when the first device is able to send the second message.

6. The method of any one of claims 1-4, wherein the first time interval comprises a predefined time period between the first timing and when the first device is able to send the second message.

7. The method of any one of claims 1-6, wherein the first message comprises first information indicating a first index which identifies the first starting time and the first length.

8. The method of claim 7, wherein the first index is associated with the first starting time and the first length in a predefined table.

9. The method of any one of claims 1-8, wherein the first message is for multiple devices.

10. The method of any one of claims 1-9, further comprising: 　　selecting a resource occasion for transmitting the Random ID.

11. The method of any one of claims 1-10, wherein the first message further comprises second information indicating a first offset of a third value of a frequency resource for the second message, with respect to a reference value.

12. The method of claim 11, wherein the first message comprises multiple values of first offsets with respect to the reference value.

13. The method of claim 11 or 12, further comprising: 　　determining a time offset corresponding to the first starting time, based on the third value.

14. The method of any one of claims 1-13, wherein the first message comprises third information indicating a frequency for backscattering.

15. The method of claim 14, wherein the first message comprises multiple values of frequencies for backscattering.

16. A first device comprising: 　　means for receiving a first message from a first reader, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　means for transmitting, to the first reader, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

17. A method performed by a first reader, the method comprising: 　　transmitting a first message to a first device, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　receiving, from the first device, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

18. A first reader comprising: 　　means for transmitting a first message to a first device, wherein the first reader is connected to the first device via an Ambient Internet of Things, A-IoT, radio interface; and 　　means for receiving, from the first device, a second message in a Physical device-to-reader channel, PDRCH, wherein, 　　a first starting time of the second message is offset by a first time interval from a first timing of reception of the first message, 　　the first time interval is the based on a sum of a first value and a second value, and 　　the first value is determined based on table.

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