Terminal and method thereof

Abstract

A method performed by a terminal, the method comprising: transmit a signal received from a first node, to a second node, by reflecting or backscattering the signal; and retransmitting, to the second node, the signal a specific number of times.

Description

TERMINAL 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 LTE-Advanced, Next Generation or 5G networks, future generations, and beyond). The present disclosure in particular relates to backscatter (re)transmissions in a communication system including 'Ambient' Internet-of-Tings (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 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, NPL 1 (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 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 F1 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] 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.

[0008] 'Ambient' IoT attempts to address some of the above issues and relies on ultra-low complexity devices with ultra-low power. Such ambient IoT devices (also herein referred to simply as an IoT device for simplicity) may be categorised as follows: - Type A devices: Any ambient IoT device that has no means of energy storage and no independent signal generation / amplification capabilities. Such devices rely on backscatter communications (described below) to communicate with other devices. - Type B devices: Any ambient IoT device that has means of energy storage but no independent signal generation capabilities. Such devices similarly rely on backscatter communications (described below) to communicate with other devices. However, beneficially they can use their stored energy to assist in those backscattering communications. For example, the device can use its stored energy to amplify backscattered signals. - Type C devices: Any ambient IoT device that has means of energy storage and independent signal generation, i.e., the device has active radio frequency (RF) components that can generate signals for transmission. Typically, such type C devices are much reduced capabilities compared to a non-ambient IoT device.

[0009] Typically, type A, B, and C devices each have their own set of power consumption targets, complexity targets, latency targets, data rate targets, and the like.

[0010] For example, the power consumption target for type A devices during transmitting / receiving is typically set to less than or equal to 1 microwatts (μW), or less than or equal to 10 μW, while for type C devices the power consumption target during transmitting / receiving is typically set to a value between 1 milliwatt (mW) and 10 mW. The power consumption target during transmitting / receiving for type B devices is typically set with reference to the power consumption targets of the type A and C devices. For example, typically, the power consumption target during transmitting / receiving for type B devices is either i) much greater than that of type A devices but less than that of type C devices, or ii) greater than or equal to that of type A devices but less than that of type C devices.

[0011] With respect to complexity targets, type A devices typically have a target comparable to that set out in International Radio Frequency Identification (RFID) Standards ISO18000-6C (equivalent to Electronic Product Code (EPC), global Class 1 (C1), Generation 2 (G2) or 'EPC C1G2' for short), while type C devices typically have a complexity target in orders of magnitude lower than the complexity of narrowband-(NB-)IoT. The complexity target for type B devices is typically set with reference to the complexity targets of the type A and C devices. For example, typically the complexity target of type B devices is greater than the complexity target for type A devices but less than the complexity target for type C devices.

[0012] With respect to latency targets, for type A, B, and C devices, typically a one-way end-to-end maximum latency target is set of between 1 second (shorter latency target) to 10 seconds (longer latency target). The data rate targets type A, B, and C devices are typically set at a maximum of no less than 5 kilobits-per-second (kbps), and minimum of no less than 0.1 kbps for both uplink (UL) and downlink (DL) transmission, with a maximum message size target for such transmissions of approximately 1000 bits i.e., it is aimed for ambient IoT devices to receive and transmit a maximum of approximately 1000 bits per message.

[0013] Typically, where such ambient IoT devices are implemented in a communication network (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.

[0014] 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 a base station 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 signal are within the same radio frequency (RF) band. * Topology 2 in which a base station and ambient IoT device communicate with one another via 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 intermediate node and hence faces similar associated challenges. * Topology 3 in which the ambient IoT device: receives data / signalling from the base station directly but transmits data / signalling to the base station indirectly via an assisting node; or transmits data / signalling to the base station directly but receives data / signalling from the base station indirectly via an 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.

[0015] Topology 3 is expected to be particularly important for device type A as it allows the device to remain connected to the network even with a reduced uplink coverage.

[0016] In the case of type A and B devices, as neither have independent signal generation capabilities, any 'transmission' from those devices typically takes the form of a backscattered signal. Backscattered signals are a type of communication that enables devices to transmit data by reflecting or backscattering RF signals from other devices or nodes without actively generating their own RF signals. Instead of emitting their own signals, backscatter devices modulate their impedance or reflectivity in response to an unmodulated carrier signal, and then reflecting that incoming RF signal as a modulated RF signal. This reflected signal carries information, encoded by the modulation, of the impedance or reflectivity of the backscatter device. In the case of type B devices, the device may also amplify the backscattered signal so that the range of the signal is higher than if it were backscattered by a type A device.

[0017] Such backscattered signals (also referred to as 'reflected' signals) are typically transmitted on the same frequency as the unmodulated carrier signal from which it originated, or alternatively, the backscattered signals may undergo additional processing such that the backscattered signals have an offset from the frequency of the unmodulated carrier signal.

[0018] In the context of type A and B devices, where transmission from those devices occurs via backscattering only, it will be appreciated that certain issues and constraints may exist which impact the performance of ambient IoT networks. For example, the backscattering mechanism used by type A and B devices generally assumes that the unmodulated carrier signal, and the reflected signal from the ambient IoT device, are almost simultaneous; this poses scheduling constraints for the different topologies (especially where both the unmodulated carrier signal and the reflected signal are on the same frequency, which may make it difficult for devices to distinguish between signals).

[0019] Different considerations need to be taken into account depending on which node (base station or assisting / intermediate node) transmits the unmodulated carrier and which node (assisting / intermediate node or base station) receives the reflected carrier from the Ambient IoT device.

[0020] For Topology 3, in particular, successful operation may involve tight coordination between the three devices (base station, assisting node and ambient IoT device).

[0021] For example, the following scenarios are possible: * Scenario 1: The base station is responsible for transmission of the unmodulated carrier to the ambient IoT device, and the assisting / intermediate node is responsible for receiving the backscattered signal from the ambient IoT device. This scenario may arise, for example, when the base station needs to fetch a meter record from the ambient IoT device (e.g., a record containing one or more counters employed to register the usage of resources en-masse. It may for example include simple event counters and / or cumulative call second counter). The base station may thus send an unmodulated carrier signal as a stimulus / trigger signal to the ambient IoT device to stimulate reporting of the meter record; and * Scenario 2: The assisting / intermediate node is responsible for transmission of the unmodulated carrier to the ambient IoT device, and the base station is responsible for receiving the backscattered signal from the ambient IoT device. This scenario may arise, for example, when a base station decides to fetch a meter record from the ambient IoT device via an assisting node. For example, the base station may send a request to the assisting node to stimulate / trigger the ambient IoT device to report its meter record to the base station.

[0022] It will be appreciated that other scenarios are also possible. For example: * Scenario 3: The assisting / intermediate node is responsible for both transmission of the unmodulated carrier to the ambient IoT device and for receiving the backscattered signal from ambient IoT device; and * Scenario 4: The base station is responsible for both transmission of the unmodulated carrier to the ambient IoT device and for receiving the backscattered signal from the ambient IoT device.

[0023] It will be appreciated that data retransmission may be required in such scenarios, for example where an initial transmission of the data is not received or is received but is corrupted and cannot be decoded. However, conventional legacy Uu interface-based data (re)transmission techniques, which do not use backscattered based communication, may not be suitable, especially for scenarios 1 and 2.

[0024] For example, in scenario 1, when the receiver of the backscattered signal (i.e., assisting node) cannot decode a transport block (TB) sent using the backscattered signal. The ambient IoT device may need to retransmit the TB, however, the ambient IoT device can only retransmit the TB via modulating an unmodulated carrier signal received from that base station; the ambient IoT device cannot, therefore, retransmit the TB on its own without receiving such an unmodulated carrier signal from the base station.

[0025] Similarly, for scenario 2, when the receiver of the backscattered signal (i.e., base station) cannot decode a TB, the ambient IoT device may need to retransmit the TB. However, the ambient IoT device can only retransmit the TB via modulating an unmodulated carrier signal received from the assisting node; the ambient IoT device cannot, therefore, retransmit the TB on its own without receiving such an unmodulated carrier signal from the assisting node.

[0026] NPL 1: 'NGMN 5G White Paper' V1.0, NGMN Alliance, 2015

[0027] There is, therefore, a need for mechanisms to be developed that address issues surrounding data (re)transmission in ambient IoT.

[0028] The present disclosure aims to provide a terminaland a method that at least partially addresses or contributes to addressing one or more of the above needs.

[0029] According to one aspect, there is provided a method performed by a terminal, the method comprising: transmitting a signal received from a first node, to a second node, by reflecting or backscattering the signal; and retransmitting, to the second node, the signal a specific number of times.

[0030] According to an aspect, there is also provided a terminal comprising: means for transmitting a signal received from a first node, to a second node, by reflecting or backscattering the signal; and means for retransmitting, to the second node, the signal a specific number of times.

[0031] The various functional means described below that are part of the UE may be provided by a memory and one or more processors that execute instructions stored in the memory. Similarly, the various functional means described below that are part of the access network node may be provided by a memory and one or more processors that execute instructions stored in the memory.

[0032] 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 the any of the methods described below. The computer implementable instructions may be provided as a signal or on a tangible computer readable medium.

[0033] According to the aspects described above, it is possible to provide a terminal and a method that at least partially addresses or contributes to addressing one or more of the above needs.

[0034] Examples of apparatus and methods will now be described, by way of example, with reference to the accompanying drawings in which:Fig. 1 illustrates schematically a mobile (cellular or wireless) communication system to which example embodiments of the disclosure may be applied;Fig. 2 illustrates schematically a first connectivity topology that may be used in the communication system of Fig. 1;Fig. 3 illustrates schematically a second connectivity topology that may be used in the communication system of Fig. 1;Fig. 4A illustrates schematically a third connectivity topology that may be used in the communication system of Fig. 1;Fig. 4B illustrates schematically another arrangement of the third connectivity topology of Fig. 4A;Fig. 5A is a simplified sequence diagram illustrating a procedure for transmitting and retransmitting unmodulated carrier signals and backscatter signal transmissions between three devices that may be used in the communication system of Fig. 1;Fig. 5B is a continuation of the simplified sequence diagram shown in Fig. 5A;Fig. 6A is another simplified sequence diagram illustrating a procedure for transmitting and retransmitting unmodulated carrier signals and backscatter signal transmissions between three devices that may be used in the communication system of Fig. 1;Fig. 6B is a continuation of the simplified sequence diagram shown in Fig. 6A;Fig. 7A is another simplified sequence diagram illustrating a procedure for transmitting and retransmitting unmodulated carrier signals and backscatter signal transmissions between three devices that may be used in the communication system of Fig. 1;Fig. 7B is a continuation of the simplified sequence diagram shown in Fig. 7A;Fig. 8 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. 9A is a simplified block schematic illustrating the main components of a respective ambient IoT device that may be used in the communication system of Fig. 1Fig. 9B is a simplified block schematic illustrating the main components of a respective ambient IoT device that may be used in the communication system of Fig. 1Fig. 10 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. 11 is simplified block schematic illustrating the main components of an intermediate or assisting node that may be used in the communication system of Fig. 1.

[0035] Overview 　　An exemplary telecommunication system will now be described in general terms, by way of example only, with reference to Figs. 1 to 4.

[0036] 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.

[0037] In the communication system 1 user equipment (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 or 'gNB' 5-1 operating one or more associated cells 9. 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)).

[0038] 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.

[0039] In the illustrated example, the UEs 3 include at least one 'ambient' IoT device 3-1 (referred to hereafter as an IoT device 3-1 for simplicity) that is capable of performing backscatter communication and a number of other, non-IoT, UEs 3-2, 3-3 (such as smartphones or the like) that communicate in a conventional manner.

[0040] The IoT device 3-1 may, for example, be a Type A, Type B, or Type C device as described in the introduction. As described in more detail later, depending on the connectivity topology employed, the 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 via an 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 5 or a separate node. The intermediate, or assisting, node 5-2 may, for example, be a relay node, an integrated access and backhaul (IAB) node, another UE 3, 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 ambient IoT device 3-1.

[0041] Each 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 each RAN 5 may be configured to support 4G, 5G, 6G and / or later generation, and / or any other 3GPP or non-3GPP communication protocols.

[0042] 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. an F1-C interface) and an appropriated interface (e.g. an F1-U interface) (together forming an F1 interface (or 'reference point')), and with one another via an appropriate interface (e.g. an E1 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.

[0043] The UEs 3 (and possibly the intermediate or assisting node 5-2 if present) are configured for communication with the serving RAN node 5-1 via an appropriate air interface (for example the so-called 'Uu' interface and / or the like). It will be appreciated that the ambient IoT device 3-1 may, alternatively or additionally, be configured for indirect communication with the serving 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 serving 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).

[0044] 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 (such as, 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 authorization, user registration, and data network profiles), a Policy Control Function (PCF), an Application Function (AF), and / or the like). It will be appreciated that the nodes or functions may have different names in different systems.

[0045] 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-IoT UEs 3 are each connected to the AMF 10-1 via a non-access stratum (NAS) connection over an appropriate interface (e.g. an N1 reference point (analogous to the S1 reference point in LTE)). It will be appreciated, that N1 communications are routed transparently via the RAN node 5-1.

[0046] One or more UPFs 11 are connected to an external data network (e.g., an IP network such as the internet) 21 via an appropriate interface (e.g. an N6 interface) for communication of the user data.

[0047] The AMF 10-1 performs mobility management related functions, maintains the NAS connection with at least each non-IoT UE 3-2, 3-3 and manages UE registration. The AMF 10-1 is also responsible for managing paging.

[0048] The SMF 10-2 is connected to the AMF 10-1 via an appropriate interface (e.g. an N11 interface). 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-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 SMF10-2 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-IoT UE 3-2, 3-3.

[0049] Each RAN node 5-1 is also configured for transmission of, and at least the non-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.

[0050] 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-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.

[0051] The DL physical signals may include, for example, reference signals (RSs) and synchronization 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 base station 5-1 of the RAN 5. 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).

[0052] Similarly, the at least the non-IoT UEs 3-2, 3-3 are configured for transmission of, and the base station 5-1 of the RAN 5 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.

[0053] Each ambient 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-IoT UEs 3-2, 3-3. It will be appreciated that the specific of functionality with which the ambient IoT device 3-1 is configured is dependent on the type of ambient IoT device 3-1.

[0054] For example, the ambient IoT device 3-1 may be a type A device that has no means of energy storage and no independent signal generation / amplification capabilities. Such type A devices may be, by way of example only, a simple object or 'tag' similar to a passive Radio-frequency identification (RFID) type tag that uses incident electromagnetic fields (from an unmodulated carrier) to automatically transmit a backscattered / reflected signal that is modulated based on information acquired at the device (e.g., a measurement from a sensor and / or an identity of the device stored or hardwired into the device). The ambient IoT device 3-1 in this example, may be powered by energy harvested from the incident electromagnetic radiation or from other sources of energy such as light and / or heat.

[0055] Alternatively, the ambient IoT device 3-1 may be a type B device, which may also be, by way of example only, a simple object or 'tag' similar to a passive RFID tag that uses incident electromagnetic fields (from an unmodulated carrier) to automatically transmit a backscattered / reflected signal that is modulated based on information acquired at the device (e.g., a measurement from a sensor and / or an identity of the device stored or hardwired into the device). In this case, the type B device may also have means of energy storage and / or of amplifying the transmitted backscattered / reflected signal but no independent signal generation capabilities. The ambient IoT device 3-1 in this example, may still be powered by energy harvested from the incident electromagnetic radiation or from other sources of energy such as light and / or heat albeit, in this example, potentially stored at the ambient IoT device 3-1.

[0056] Alternatively, the ambient IoT device 3-1 may be a type C device that has means of energy storage and independent signal generation. In addition to being able to transmit a backscattered / reflected signal that is modulated based on information acquired at the device (e.g., a measurement from a sensor and / or an identity of the device stored or hardwired into the device), such a device may, by way of example only, have at least some (albeit possibly a significantly reduced set) of the capabilities of a non-IoT UE (such as the UEs 3-2, 3-3) to communicate with the RAN node 5-1 (and / or intermediate / assisting node 5-2).

[0057] Connectivity Topologies 　　The ambient 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. 2 to 4.

[0058] Topology 1: RAN node ←→ IoT device: 　　Fig. 2 illustrates schematically a first connectivity topology (topology 1) of a mobile (cellular or wireless) communication system 1.

[0059] As shown in Fig. 2, in topology 1 there is provided the ambient IoT device 3-1 and a RAN node 5-1. As shown, the ambient IoT device 3-1 directly and bidirectionally communicates with the RAN node 5-1. That communication 20 between the RAN node 5-1 and the ambient IoT device 3-1 can include ambient IoT data and / or ambient IoT signalling. The communication 20 between the RAN node 5-1 and the ambient IoT device 3-1 may occur over an appropriate air interface such as the NR Uu air interface, a dedicated interface for ambient IoT, or the like.

[0060] The communication 20 may also comprise a backscatter or reflected signal. For example, the transmission of a signal from the RAN node 5-1 to the ambient IoT device 3-1 may be an unmodulated carrier signal which is, in turn, modulated and backscattered / reflected by the ambient IoT device 3-1 to send a signal back to the RAN node 5-1. Such transmission of an unmodulated carrier signal, 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.

[0061] Nevertheless, although not shown in Fig. 2, topology 1 allows for the possibility that the RAN node (base station) 5-1 transmitting to the ambient IoT device 3-1 is a different RAN node (base station) 5-1 from the RAN node (base station) 5-1 receiving from the ambient IoT device 3-1. For example, there may be provided a first RAN node (base station) 5-1 that transmits to the ambient IoT device 3-1, and a second RAN node (base station) 5-1 that receives from the ambient IoT device 3-1. In this scenario backscattering may be supported even where full duplex operation is not supported at either of the RAN nodes (base stations) 5-1.

[0062] Topology 1 may be deployed for indoor scenarios, with a type A, B, and / or C ambient IoT device 3-1 and the RAN node 5-1 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.

[0063] Alternatively, where the ambient IoT device 3-1 is in an indoor environment but the RAN node 5-1 is located in an outdoor environment, the RAN node 5-1 may be configured to support one or more larger cells (e.g., macro- cells) providing radio coverage to a large area that operate on either licensed frequency division duplex (FDD), licensed time division duplex (TDD), or unlicensed parts of the spectrum. However, in such cases it may be the case that only type C ambient IoT devices 3-1 may be supported.

[0064] Topology 1 may also be deployed for outdoor scenarios with both type C ambient IoT devices 3-1 and the RAN node 5-1 being located in an outdoor environment. In that 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 frequency division duplex (FDD), licensed time division duplex (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 frequency division duplex (FDD), licensed time division duplex (TDD), or unlicensed parts of the spectrum.

[0065] Topology 2: RAN node ←→ Intermediate node ←→ IoT device: 　　Fig. 3 illustrates schematically a second connectivity topology (topology 2) of a mobile (cellular or wireless) communication system 1.

[0066] As shown in Fig. 3, in topology 2, there is provided an ambient IoT device 3-1, a RAN node 5-1 (base station), and an intermediate node 5-2. It will be appreciated that while the intermediate node 5-2 is depicted in Fig. 3 as 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 a RAN node 5-1 and an ambient IoT device 3-1 and that is capable of ambient IoT signalling.

[0067] The ambient IoT device 3-1 in this topology is able to communicate 20-1, 20-2 bidirectionally with the RAN node 5-1 via the intermediate node 5-2 to transfer ambient IoT data and / or signalling between the RAN node 5-1 and the ambient IoT device 3-1.

[0068] The communication 20-1 between the RAN node 5-1 and the intermediate node 5-2 occurs over an 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 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. The communication 20-2 between the intermediate node 5-2 and the ambient IoT device 3-1 also occurs over an appropriate air interface. For example, they may communicate over a Uu or a dedicated interface.

[0069] In a first (downlink) direction (RAN node 5-1 - intermediate node 5-2 - ambient IoT device 3-1) the communication 20-1 may comprise a first signal that is transmitted from the RAN node 5-1 to the intermediate node 5-2. The first signal, once received by the intermediate node 5-2, may trigger transmission of an unmodulated carrier signal to the ambient IoT device 3-1 in communication 20-2 in the downlink direction. The first signal may itself be an unmodulated carrier signal that is then relayed by the intermediate node 5-2 to the ambient IoT device 3-1.

[0070] In a second (uplink) direction (ambient IoT device 3-1 - intermediate node 5-2 - RAN node 5-1) the communication 20-2 may comprise a modulated backscattered signal from the ambient IoT device 3-1 to the intermediate node 5-2 that is transmitted in response to receiving the unmodulated carrier signal from the intermediate node 5-2. This modulated backscattered signal (or at least the information encoded in it), once received by the intermediate node 5-2, may be relayed (transmitted) to the RAN node 5-1 (base station) in communication 20-1 (in the uplink direction). The modulated backscattered signal may be processed before being relayed by the intermediate node 5-2 to the RAN node 5-1. For example, the modulated backscattered signal may be processed by the intermediate 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. Alternatively, the modulated backscattered signal may be processed by the intermediate node 5-2 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.

[0071] 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.

[0072] Topology 2 may be deployed for indoor scenarios with a type A, B, and / or C ambient IoT device 3-1 and RAN node 5-1 both 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.

[0073] Alternatively, where the ambient IoT device 3-1 is in an indoor environment but the RAN node 5-1 is located in an outdoor environment, the RAN node 5-1 may be configured to support one or more larger cells (e.g., macro- cells) providing radio coverage to a large area that operate on either licensed frequency division duplex (FDD), licensed time division duplex (TDD), or unlicensed parts of the spectrum. However, in such cases only type C ambient IoT devices 3-1 may be supported.

[0074] Irrespective of whether the ambient IoT device 3-1 is located in an indoor or an outdoor environment in the deployments described above, the intermediate (or assisting) node 5-2 may be located in an indoor or an outdoor environment.

[0075] Topology 2 may also be deployed for outdoor scenarios with a type A, B or C ambient IoT device 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 frequency division duplex (FDD), licensed time division duplex (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 frequency division duplex (FDD), licensed time division duplex (TDD), or unlicensed parts of the spectrum.

[0076] Topology 3: RAN node ←→ Assisting node ←→ Ambient IoT device ←→ RAN node: 　　Fig. 4A and 4B illustrate schematically a third connectivity topology (topology 3) of a mobile (cellular or wireless) communication system 1.

[0077] As shown in Fig. 4A and 4B, in topology 3, there is provided an ambient IoT device 3-1, a RAN node 5-1, and an assisting node 5-2. It will be appreciated that while the assisting node 5-2 is depicted in Fig. 4A as a type of base station, the assisting node 5-2 may in fact be any one of an IAB node, a Relay UE, 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 ambient IoT device 3-1.

[0078] As shown in Fig. 4A, the ambient IoT device 3-1 may communicate unidirectionally with a RAN node 5-1 in an uplink direction (20-1) and an assisting (intermediate) node 5-2 in a downlink direction (20-2). The communication 20-1 between the RAN node 5-1 and ambient IoT device 3-1, and the communication 20-2 between the assisting node 5-2 and the ambient IoT device 3-1, respectively occur over an appropriate air interface. For example, they may communicate over a Uu or dedicated (sidelink) interface.

[0079] The downlink communication 20-2 from the assisting (intermediate) node 5-2 may comprise an unmodulated carrier signal (which may be triggered by communication 20-3 (e.g., a downlink signal) received by the assisting (intermediate) node 5-2 from the RAN node 5-1). This unmodulated carrier signal may be subsequently modulated and backscattered, as a modulated backscattered signal, from the ambient IoT device 3-1 and received at the RAN node 5-1 as communication 20-1 in the uplink direction.

[0080] The communication 20-3 between the RAN node 5-1 and the assisting node (or intermediate 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 intermediate 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 intermediate 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 20-2 between the assisting node 5-2 and the ambient IoT device 3-1 also occurs over an appropriate air interface. For example, they may communicate over a Uu or a dedicated (sidelink) interface.

[0081] Alternatively, as shown in Fig. 4B, the ambient IoT device 3-1 may communicate unidirectionally with a RAN node 5-1 in a downlink direction (20-1) and an assisting (intermediate) node 5-2 in an uplink direction (20-2). The communication 20-1 between the RAN node 5-1 and the ambient IoT device 3-1, or the communication 20-2 between the assisting node 5-2 and the ambient IoT device 3-1 respectively occurs over an appropriate air interface. For example, they may communicate over a Uu or dedicated (sidelink) interface.

[0082] The downlink communication 20-1 from the RAN node 5-1 may comprise an unmodulated carrier signal. This unmodulated carrier signal may be subsequently modulated and backscattered, as a modulated backscattered signal, from the ambient IoT device 3-1 and received at the assisting (intermediate) node 5-2 as communication 20-2 in the uplink direction. This modulated backscattered signal (or at least the information encoded in it), once received by the assisting node 5-2, may be relayed (transmitted) to the RAN node 5-1 (base station) in communication 20-3 (in the uplink direction). The modulated backscattered signal may be processed before being relayed by the assisting node 5-2 to the RAN node 5-1. For example, the modulated backscattered 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. Alternatively, the modulated backscattered signal may be processed by the assisting node 5-2 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.

[0083] Similarly, to Fig. 4A, in Fig. 4B the communication 20-3 between the RAN node 5-1 and the assisting node (or intermediate 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 intermediate 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 intermediate 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 20-2 between the assisting node 5-2 and the ambient IoT device 3-1 also occurs over an appropriate air interface. For example, they may communicate over a Uu or a dedicated (sidelink) interface. In either scenario, such backscattering may be supported even if the RAN node 5-1 and / or the assisting node 5-2 do not support full duplex operation.

[0084] Where topology 3 is used, appropriate coordination between the three devices (e.g., the RAN node 5-1, the assisting node 5-2, and the ambient IoT device 3-1) is provided taking into account the fact that the reception of the unmodulated carrier signal and the transmission of the reflected signal, by the ambient IoT device 3-1, may be assumed to be (almost) simultaneous.

[0085] For example, where topology 3 is used in a manner in which the communication 20-2 comprises a modulated backscattered signal sent from the ambient IoT device 3-1 and received at the assisting node 5-2, based on an unmodulated carrier signal that was initially received by the ambient IoT device 3-1 from the RAN node 5-1 (as shown in Fig. 4B), then the different devices may be mutually configured for coordinating transmissions in at least one of a number of different ways. For example: - The RAN node 5-1 may determine the scheduling requirements of the unmodulated carrier signal, as well as the radio resources to be used for any backscattered transmissions; - The RAN node 5-1 may determine the radio resources to be used for the unmodulated carrier signal and indicate those resources to the assisting node 5-2. The assisting node 5-2 may then subsequently determine the scheduling requirements of the backscattered transmissions; or - The assisting node 5-2 may determine the radio resources to be used for the backscattered transmissions and indicate those resources to the RAN node 5-1. The base station 5-2 may then subsequently determine the radio resources to be used for unmodulated carrier signal.

[0086] Moreover, where topology 3 is used in a manner in which the communication 20-1 comprises a modulated backscattered signal sent from the ambient IoT device 3-1 to the RAN node 5-1, based on an unmodulated carrier signal that was initially received by the ambient IoT device 3-1 from the assisting (intermediate) node 5-2 (as shown in Fig. 4A), the different devices are mutually configured for coordinating transmissions in at least one of a number of different ways. For example: - The RAN node 5-1 may determine the scheduling requirements of the unmodulated carrier signal, as well as the radio resources to be used for any backscattered transmissions; - The RAN node 5-1 may determine the radio resources to be used for any backscattered transmissions and indicate those resources to the assisting node 5-2. The assisting node 5-2 may then subsequently determine the scheduling requirements of the unmodulated carrier signal; or - The assisting node 5-2 may determine the radio resources to be used for the unmodulated carrier signal and indicate those resources to the RAN node 5-1. The RAN node 5-1 may then subsequently determine the radio resources to be used for backscattered transmissions.

[0087] Beneficially, the RAN node 5-1, assisting node 5-2, and ambient IoT device 3-1 are mutually configured for implementing one or more feedback and data (re)transmission procedures that take into account the fact that backscattered signals from the ambient IoT devices 3-1 may sometimes need to be retransmitted, e.g., when they are not correctly received and / or decoded by the device configured to receive such backscattered signals. Specifically, then the different devices are mutually configured for transmitting and receiving an appropriate feedback message (e.g., an ACK / NACK signal or the like) to indicate whether data (e.g., in the form of a transport block (TB)) encoded in a backscattered signal was correctly received and decoded, and to trigger retransmission of such data in the event of unsuccessful reception / decoding.

[0088] For example, when an ambient IoT device 3-1 encodes data (e.g., a TB) in a backscattered signal reflected to another device, the data (e.g., the TB) encoded in that signal may be stored at the ambient IoT device 3-1 (e.g., in a data buffer, data register, or similar) for possible future retransmission. The ambient IoT device 3-1 can then either retransmit previously (re)transmitted data in response to a negative feedback message (e.g., a NACK signal) from the RAN node 5-1, or assisting node 5-2, that indicates that the data has not been successfully received or decoded. Similarly, the ambient IoT device 3-1 can transmit new data in response to a positive feedback message (e.g., an ACK signal) from the RAN node 5-1, or assisting node 5-2, that indicates that the data has been successfully received or decoded.

[0089] It will be appreciated that whilst the procedures will be described in the context of topology 3, similar procedures could be implemented for topologies 1 and / or 2.

[0090] For example, as described in more detail later, where topology 3 is used in a manner in which the communication 20-2 comprises a modulated backscattered signal sent from the ambient IoT device 3-1 and received at the assisting node 5-2, based on an unmodulated carrier signal that was initially received by the ambient IoT device 3-1 from the RAN node 5-1 (as shown in Fig. 4B) then, depending on the type of assisting node 5-2: the RAN node 5-1 may send an appropriate feedback message (e.g., ACK / NACK signal) to the ambient IoT device 3-1 indirectly via the assisting node 5-2; the RAN node 5-1 may send an appropriate feedback message (e.g., ACK / NACK signal) to the ambient IoT device 3-1 directly; or the assisting node 5-2 may, of its own volition, initiate the sending of an appropriate feedback message (e.g., ACK / NACK signal) to the ambient IoT device 3-1.

[0091] Specifically, if the assisting node 5-2 is of a type that simply forwards the backscattered signal (rather than first attempting to demodulate the received signal and only forwarding the received data if it has been successfully received), then upon an unsuccessful attempt to decode / receive the data at the RAN node 5-1, the RAN node 5-1 may indicate this, via an appropriate negative feedback message (e.g., a NACK signal) sent to the ambient IoT device 3-1 (possibly indirectly via the assisting node 5-2), to trigger a corresponding retransmission procedure in which the ambient IoT device 3-1 retransmits the same data as it previously transmitted (rather than new data), when the RAN node 5-1 next (re)sends an unmodulated carrier signal.

[0092] If the assisting node 5-2 is of a type that attempts to demodulate the received backscattered signal for subsequent forwarding of the data to the RAN node 5-1, then upon an unsuccessful attempt to demodulate the received signal, the assisting node 5-2 may indicate this, via an appropriate negative feedback message (e.g., a NACK signal), sent to either (or both) of the IoT device 3-1 and the RAN node 5-1 to trigger a retransmission procedure in which the ambient IoT device 3-1 retransmits the same data as it previously transmitted (rather than new data), when the RAN node 5-1 next (re)sends an unmodulated carrier signal.

[0093] Moreover, as described in more detail later, where topology 3 is used in a manner in which the communication 20-1 comprises a modulated backscattered signal sent from the ambient IoT device 3-1 to the RAN node 5-1, based on an unmodulated carrier signal that was initially received by the ambient IoT device 3-1 from the assisting (intermediate) node 5-2 (as shown in Fig. 4A), then, depending on the type of assisting node 5-2: the RAN node 5-1 may send an appropriate feedback message (e.g., ACK / NACK signal) to the ambient IoT device 3-1 indirectly via the assisting node 5-2, and may separately trigger the assisting node 5-2 to (re)send an unmodulated carrier signal; or the RAN node 5-1 may send a request to the assisting node 5-2 to (re)send an unmodulated carrier signal including, when the data has not been received successfully, an indication that the request is due to an unsuccessful data transmission, and receipt of the request may trigger the assisting node 5-2 both to send an appropriate feedback message (e.g., ACK / NACK signal) to the ambient IoT device 3-1, and (re)send an unmodulated carrier signal.

[0094] Specifically, if the assisting node 5-2 is of a type that simply forwards signals (rather than first demodulating those signals), then upon an unsuccessful attempt to decode / receive the data encoded in the backscattered signal as received directly at the RAN node 5-1, the RAN node 5-1 may indicate this, via an appropriate negative feedback message (e.g., a NACK signal) sent to the ambient IoT device 3-1, indirectly via the assisting node 5-2. Receipt of this negative feedback message (e.g., a NACK signal) then triggers a corresponding retransmission procedure in which the ambient IoT device 3-1 retransmits the same data as it previously transmitted (rather than new data), when the assisting node 5-2 next (re)sends an unmodulated carrier signal. The RAN node 5-1 may then separately send a request to the assisting node 5-2 to (re)send the unmodulated carrier signal and thus trigger the retransmission.

[0095] If the assisting node 5-2 is of a type that attempts to demodulate signals for subsequent forwarding, then upon an unsuccessful attempt to decode / receive the data encoded in the backscattered signal as received directly at the RAN node 5-1, the RAN node 5-1 may indicate this to the assisting node 5-2, by requesting the assisting node 5-2 to (re)send an unmodulated carrier signal, and including an indication that the request is due to an unsuccessful data transmission in the request. The assisting node 5-2 then sends an appropriate negative feedback message (e.g., NACK signal) to the ambient IoT device 3-1. Receipt of this negative feedback message (e.g., a NACK signal) then triggers a corresponding retransmission procedure in which the ambient IoT device 3-1 retransmits the same data as it previously transmitted (rather than new data), when the assisting node 5-2 next (re)sends an unmodulated carrier signal. Then, after sending the negative feedback message, the assisting node 5-2 (re)sends the unmodulated carrier signal and thus triggers the retransmission.

[0096] It will be appreciated that the various different feedback and data (re)transmission methods described are not mutually exclusive and all or a subset of the feedback and (re)transmission methods may be implemented in the same communication system. For example, the various devices involved in the ambient IoT type communication may be configured to use different feedback and (re)transmission methods in different scenarios as appropriate.

[0097] It can be seen that, by triggering the ambient IoT device 3-1 to retransmit its most recently transmitted data (e.g., a TB most recently generated, transmitted, and stored in its data buffer / register), in response to an unmodulated carrier signal, until a positive feedback message has been received (and / or while negative feedback messages continue to be received) by the ambient IoT device 3-1 indicating that the data has been correctly received and decoded, ambient IoT operation is improved.

[0098] Each of the (re)transmission scenarios outlined above will now be discussed in more detail with reference to Figs. 5 to 7.

[0099] Data (Re)transmissions for Backscattered Signal 　　(Re)transmission of an unmodulated carrier signal - Base station responsibility 　　As mentioned above, in topology 3 the RAN node 5-1 may be responsible for the (re)transmission of the unmodulated carrier signal to the ambient IoT device 3-1, and the assisting node 5-2 may be responsible for (re)receiving the modulated backscattered signal from the ambient IoT device 3-1.

[0100] An example of one way in which feedback and data (re)transmission may be implemented in this scenario will now be described in more detail, by way of example only, with reference to Figs. 5A and 5B.

[0101] Figs. 5A and 5B depict a simplified sequence diagram illustrating a procedure for (re)transmitting data encoded in a backscattered signal (e.g., a transport block (TB)) from an ambient IoT device 3-1 to an assisting node 5-2 (for forwarding to a RAN node 5-1) that may be used in the communication system 1 of Fig. 1.

[0102] This feedback and data (re)transmission procedure may be particularly (but not exclusively) applicable to scenarios where the ambient IoT device 3-1 is a type B, or a type C device as described above. This retransmitting procedure is also particularly (but not exclusively) applicable to scenarios where the assisting node 5-2 is 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).

[0103] It will be appreciated that where the assisting node 5-2 is 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 L2 relay device), the assisting node 5-2 may be, for example, a relay UE or a relay node. Where the assisting node 5-2 is a relay UE, the assisting node 5-2 and the IoT device 3-1 may communicate with each other over a device-to-device (D2D) communication link, also referred to as a sidelink e.g., the assisting node 5-2 and the IoT device 3-1 may communicate with each other over a PC5 interface. Alternatively, where the assisting node 5-2 is a relay node the assisting node 5-2 and the IoT device 3-1 may communicate with each other over another interface (e.g., a Uu interface or the like).

[0104] As shown in Fig. 5A, there is provided a RAN node 5-1, an assisting node 5-2, and an ambient IoT device 3-1 that are deployed using topology 3, e.g., as described with reference to Fig. 4B in which the RAN node 5-1 is responsible for transmission of the unmodulated carrier signal. Specifically, as shown in Fig. 4B, the ambient IoT device 3-1 can receive an unmodulated carrier signal from the RAN node 5-1 and modulate and transmit (reflect) a backscattered signal based on the unmodulated carrier signal, which is received at the assisting node 5-2. This modulated backscattered signal (or at least the information encoded in it), once received by the assisting node 5-2, may be relayed (transmitted) to the RAN node 5-1.

[0105] Upon reception of the modulated backscattered signal, it may be processed (e.g., decoded / demodulated) before being relayed by the assisting node 5-2 to the RAN node 5-1. For example, the modulated backscattered signal may be processed (e.g., decoded / demodulated) by the assisting node 5-2 to extract the data (e.g., a TB) encoded in the modulated backscattered signal, and to encapsulate the extracted data into an appropriate message format (e.g., in accordance with a corresponding application protocol) for communication with the RAN node 5-1. However, when an attempt to process (e.g., decode / demodulate) a modulated backscattered signal results in an error, then a retransmission of the modulated backscattered signal may be triggered as described in more detail below.

[0106] Prior to the procedure shown in Fig. 5A, the RAN node 5-1, or the assisting node 5-2 may allocate radio resources for the transmission of the unmodulated carrier signal. It will be appreciated that in the scenario depicted in Fig. 5, when such radio resources are determined by the assisting node 5-2, the assisting node 5-2 may first be triggered by the RAN node 5-1 to determine such radio resources, which are in turn signalled to the RAN node 5-1.

[0107] Similarly, prior to the procedure shown in Fig, 5A, the RAN node 5-1, or the assisting node 5-2 may allocate radio resources for the transmission of appropriate feedback messages for the assisting node 5-2 to feedback to the ambient IoT device 3-1 and / or the RAN node 5-1, whether there is successful reception or unsuccessful reception (e.g., successful, or unsuccessful decoding) of a backscattered signal (e.g., a backscattered TB) that is backscattered from the ambient IoT device 3-1 to the assisting node 5-2. The allocation of the radio resources for the transmission of appropriate feedback messages may occur in response to the RAN node 5-1 deciding to send the ambient IoT device 3-1 an unmodulated carrier signal. For example, having determined radio resources for the transmission of an unmodulated carrier signal (or having triggered the assisting node to determine such radio resources), the RAN node 5-1 may determine (or trigger the assisting node 5-2 to determine) radio resources for the transmission of the appropriate feedback messages.

[0108] It will be appreciated that an appropriate feedback message may include, by way of example only, hybrid automatic repeat request (HARQ) acknowledgement (ACK) / negative acknowledgement (NACK) message, such as when the (re)transmission of backscattered signals are seen as HARQ-based (re)transmission at layer 1 (L1) e.g., the physical layer. Alternatively, an appropriate feedback message may include, by way of example only, an automatic repeat request (ARQ) acknowledgement ACK / NACK message, such as when the (re)transmission of backscattered signals are seen as ARQ-based (re)transmission at layer 2 (L2) e.g., the data link layer. It will be appreciated however that the feedback messages described above are by way of example only and that as further advancements are made in ambient IoT devices 3-1and backscattered signalling, other appropriate feedback messages and types of data (re)transmission may be implemented.

[0109] For simplification only, further description of the feedback messages will refer to HARQ ACKs / NACKs, although it will be appreciated that other types of feedback messages could be implemented instead as described above.

[0110] It will be appreciated that the radio resources for the feedback messages are determined by the RAN node 5-1, the RAN node 5-1 may determine such radio resources independently, e.g., of its own volition. Alternatively, the RAN node 5-1 may be triggered by another device to determine radio resources for the feedback messages, for example it may be triggered by the assisting node 5-2 which sends a request to the RAN node 5-1 for the allocation of radio resources for the appropriate feedback messages.

[0111] As shown in Fig. 5A, at step S502, the RAN node 5-1 transmits an unmodulated carrier signal to the ambient IoT device 3-1 using radio resources for the unmodulated carrier signal which may have been determined by the RAN node 5-1, or the assisting node 5-2 at some earlier step (described above).

[0112] Upon reception of that unmodulated carrier signal, the ambient IoT device 3-1 (simultaneously or near-simultaneously) generates, at step S504, a TB (e.g., a block of data) to be sent to the assisting node 5-2, and modulates its impedance or reflectivity in response to the unmodulated carrier signal to encode the TB in a modulated signal sent (reflected / backscattered) to the assisting node 5-2 at step S506.

[0113] When the ambient IoT device 3-1 reflects the signal simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for the backscattered transmission and the symbol used for the associated unmodulated carrier may be the same. Whereas when the ambient IoT device 3-1 reflects the signal near-simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for backscattered transmission and the symbol used for the associated unmodulated carrier may be within a threshold time gap.

[0114] Additionally, (not shown) the ambient IoT device 3-1 may store the generated TB (e.g., a copy of the generated TB) in a data buffer / register at the ambient IoT device 3-1 for possible future retransmission by the ambient IoT device 3-1.

[0115] At step S508, the assisting node 5-2, upon receiving the TB sent at S506, attempts to decode the received TB. For example, the assisting node 5-2 may attempt to decode the received TB for resending in a suitable message for L2 signalling to the RAN node 5-1 e.g., as part of a transmission on the physical uplink control channel (PUCCH), or the like. If the TB is not decoded successfully during the attempted decoding of the received TB at step S508 (e.g., the assisting node 5-2 detects a decoding error for the TB) then the procedure continues at box A) 'Decoding error for TB' shown in Fig. 5A.

[0116] Having not successfully decoded the TB at step S508, the assisting node 5-2 transmits to the RAN node 5-1, at step S510a a first negative feedback message. The first negative feedback message may be any appropriate message that indicates to the RAN node 5-1 that the TB has not been received successfully (e.g., that a decoding error for the TB has been detected by the assisting node 5-2). For example, the first negative feedback message may comprise at least one of: an indication of an unsuccessful TB transmission, and / or a request for an additional unmodulated carrier signal transmission. For example, the indication of an unsuccessful TB transmission may be in the form of a HARQ NACK message sent by the assisting node 5-2 to the RAN node 5-1 using dedicated radio resources for HARQ ACK / NACK signalling determined by the RAN node 5-1 or the assisting node 5-2 as described above. Additionally, or alternatively, the assisting node 5-2 may send a request message to the RAN node 5-1 to request the (re)transmission of an unmodulated carrier signal to the ambient IoT device 3-1 to stimulate / trigger a retransmission of the TB previously generated by the ambient IoT device 3-1 at step S504.

[0117] At step S512a, which may or may not be simultaneous with step S510a, the assisting node 5-2 sends a suitable second negative feedback message to the ambient IoT device 3-1 indicating to the ambient IoT device 3-1 that the received TB was not successfully received (e.g., because of a decoding error for the TB). The second negative feedback message may be any appropriate message that can indicate unsuccessful reception e.g., a HARQ NACK message. The second negative feedback message may be sent on radio resources determined by the assisting node 5-2 or the RAN node 5-1 as described above.

[0118] Upon receipt of the second negative feedback message from the assisting node 5-2, the ambient IoT device 3-1 may at, step S514a, fetch, from its data buffer / register, the previous TB that it generated at step S504.

[0119] At step S516a, in response to the RAN node 5-1 receiving the first negative feedback message at step S510, the RAN node 5-1 transmits an unmodulated carrier signal, to the ambient IoT device 3-1. That unmodulated carrier signal may be different, or the same as the unmodulated carrier signal set at step S502.

[0120] In response to the unmodulated carrier signal being sent to the ambient IoT device 3-1 at step S516a, the ambient IoT device 3-1 is triggered to (re)transmit the TB it fetched from its data buffer / register at step S514a i.e., the ambient IoT device 3-1 is triggered to retransmit the TB it initially transmitted to the assisting node 5-2 at step S506.

[0121] It will be appreciated that while the above describes the previous TB being fetched from the data buffer / register of the ambient IoT device 3-1 in response to the ambient IoT device 3-1 receiving the second negative feedback message from the assisting node 5-2 at step S512a, the ambient IoT device 3-1 may fetch the previous TB from its buffer / register in response to receipt of the unmodulated carrier signal sent at step S516a. In this scenario, the second negative feedback message sent to the ambient IoT device 3-1 at step S512a may indicate (and / or trigger) the ambient IoT device 3-1 to consider the next unmodulated carrier signal that it receives as a trigger for retransmitting the TB stored in its data buffer. For example, the ambient IoT device 3-1 may be configured to retransmit the TB stored in its data buffer in response to receiving an unmodulated carrier signal, if the ambient IoT device 3-1 has also received a feedback message from the assisting node 5-2 indicating that the previous TB has not been successfully received and / or decoded e.g., if the ambient IoT device 3-1 has received a HARQ NACK message from the assisting node 5-2. The ambient IoT device 3-1 may continue to retransmit the TB stored in its data buffer each time it receives an unmodulated carrier signal from the RAN node 5-1, until the ambient IoT device 3-1 receives from the assisting node 5-2, a feedback message indicating that the previous TB has been successfully received and / or decoded e.g., if the ambient IoT device 3-1 has received a HARQ ACK message from the assisting node 5-2.

[0122] Beneficially, by triggering the ambient IoT device 3-1 to retransmit its most recently transmitted TB (i.e., the TB most recently generated, transmitted, and stored in its data buffer / register), in response to an unmodulated carrier signal, until a positive feedback message is received by the ambient IoT device 3-1 indicating that the TB has been correctly received, ambient IoT operation is improved.

[0123] Alternatively, if during the attempted decoding of the received TB at step S508, the assisting node 5-2 successfully decodes the TB then the procedure continues at box B) 'Successful decoding for TB' shown in Fig. 5B.

[0124] Having successfully decoded the TB at step S508, the assisting node 5-2 transmits to the RAN node 5-1, at step S510b a first positive feedback message. The first positive feedback message may be any appropriate message that indicates to the RAN node 5-1 that the TB has been successfully decoded by the assisting node 5-2. For example, the first feedback positive message may comprise an indication of a successful TB transmission. For example, the indication of a successful TB transmission may be in the form of a HARQ ACK message sent by the assisting node 5-2 to the RAN node 5-1 using dedicated radio resources for HARQ ACK / NACK signalling determined previously by the RAN node 5-1 or the assisting node 5-2 as described above.

[0125] At step S512b, which may or may not be simultaneous with step S510b, the assisting node 5-2 sends a suitable second positive feedback message to the ambient IoT device 3-1 indicating to the ambient IoT device 3-1 that the received TB was decoded properly. For example, the second positive feedback message may be any appropriate message that can indicate the TB was received / decoded successfully e.g., a HARQ ACK message. The second positive feedback message may be sent on radio resources determined by the assisting node 5-2 or the RAN node 5-1 as described above.

[0126] At step S516b, after receiving the first positive feedback message at step S510b, the RAN node 5-1 may transmit an unmodulated carrier signal to the ambient IoT device 3-1 using radio resources for the unmodulated carrier signal which may have been determined by the RAN node 5-1, or the assisting node 5-2 at some earlier step (described above).

[0127] Upon reception of that unmodulated carrier signal, the ambient IoT device 3-1 (simultaneously or near-simultaneously) generates, at step S520, a TB (e.g., a block of data) to be sent to the assisting node 5-2, and modulates its impedance or reflectivity in response to the unmodulated carrier signal to encode the TB in a modulated signal sent (reflected / backscattered) to the assisting node 5-2 at step S522.

[0128] When the ambient IoT device 3-1 reflects the signal simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for the backscattered transmission and the symbol used for the associated unmodulated carrier may be the same. Whereas when the ambient IoT device 3-1 reflects the signal near-simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for backscattered transmission and the symbol used for the associated unmodulated carrier may be within a threshold time gap.

[0129] Additionally, (not shown) the ambient IoT device 3-1 may store the generated TB in a data buffer / register at the ambient IoT device 3-1. For example, in response to the ambient IoT device 3-1 receiving from the assisting node 5-2, the second positive feedback message indicating to the ambient IoT device 3-1 that the received TB was decoded properly at step S512b, then the ambient IoT device 3-1 may replace the data stored in its data buffer / register with the new generated TB. Alternatively, where the data buffer / register is capable of storing multiple sets of data at any one time, the ambient IoT device 3-1 may store the new generated TB in the data buffer / register along with other previously generated TBs. In that case, previously generated TBs may only be replaced if at the point of storing a new TB the data buffer / register is full. It will be appreciated that where multiple TBs are stored in the data buffer / register, those TBs may be stored using an indication of their age (e.g., a timestamp) and / or may be stored in a last in first out (LIFO) sequential data structure.

[0130] After transmission of the new TB at step S522, the procedure may revert to step S508, where the assisting node 5-2 attempts to decode the new TB. Based on the success, or lack of, the decoding of that new TB, the process proceeds to Box 'B' or Box 'A' respectively as discussed above.

[0131] Alternatively, rather than the assisting node 5-2 transmitting the first and second negative / positive feedback messages at S510a, b and S512a, b respectively, the RAN node 5-1 may be (pre)configured to perform a fixed number of unmodulated carrier signal (re)transmissions. For example, the unmodulated carrier signal may always be retransmitted for a fixed number of instances by the RAN node 5-1, and the ambient IoT device 3-1 will always blindly retransmit a TB for the same fixed number regardless of the reception status of the TB at assisting node 5-2.

[0132] Beneficially, whilst this alternative involves potentially unnecessary repetitive signalling, by (pre)configuring the communication system 1 such that the RAN node 5-1 performs a fixed number of unmodulated carrier signal (re)transmissions as described above, the need for a first and a second negative / positive feedback message (e.g., a first and second HARQ ACK or NACK message) is not required. That in turn reduces the amount of signalling resources that need to be scheduled by the RAN node 5-1 and / or the assisting node 5-2 and simplifies the signalling procedure overall.

[0133] Alternatively, after the assisting node 5-2 transmits a (negative) feedback message at S510a, the assisting node 5-2 may not send a (negative) feedback message to the ambient IoT device 3-1 at S512a. The RAN node 5-1 may be (pre)configured to perform unmodulated carrier signal (re)transmissions following the receipt of a negative feedback message at S510a to the ambient IoT device 3-1. The RAN node 5-1 may be configured, in response to receiving the negative feedback message at S510a, to alter its transmission properties / behaviours such that a retransmission of the unmodulated carrier signal at step S516a can be distinguished / differentiated from the initial unmodulated carrier signal transmission at step S502. For example, the RAN node 5-1 may adjust its transmission properties such that the retransmitted unmodulated carrier signal S516a has e.g., a different power level, a different resource based transmission, a different wave form, a different time-space, and the like from that used for the initial unmodulated carrier signal transmission at S502.

[0134] Following the receipt of the unmodulated signal from the RAN node 5-1, the ambient IoT device 3-1 is able to use the above differences to distinguish between the initial unmodulated carrier signal and the retransmitted unmodulated carrier signal. If the unmodulated signal is a retransmission, the ambient IoT device 3-1 fetches the previous TB from its data buffer / register, and then generates the backscattered transmission accordingly with the previous TB for retransmission. If the unmodulated signal is an initial transmission, the ambient IoT device 3-1 generates a new TB (or fetches it from its data buffer / register, other data source, or the like if the TB has already been generated), and then generates the backscattered transmission accordingly with this new TB for an initial transmission.

[0135] Beneficially, whilst this alternative requires the RAN node 5-1 to alter its unmodulated signal transmission to stimulate a retransmission, the feedback response message from the assisting node 5-2 to the ambient IoT device 3-1 is not needed. That in turn reduces the amount of signalling resources that need to be scheduled by the RAN node 5-1 and / or the assisting node 5-2 and simplifies the signalling procedure overall.

[0136] In another alternative, rather than the assisting node 5-2 transmitting the first negative or positive feedback message to the RAN node 5-1 at S510a,b, the ambient IoT device 3-1 may be (pre)configured to perform a fixed number of backscattered retransmissions to the assisting node 5-2. For example, the unmodulated carrier signal may always be retransmitted for a fixed number of instances by the RAN node 5-1, and the ambient IoT device 3-1 device will retransmit a TB for up to a maximum of the same fixed number of times as long as a positive feedback message has not been received by the ambient IoT device 3-1 from the assisting node 5-2 indicating that the TB previously sent to the assisting node 5-2 was successfully received / decoded (e.g., similar to the second feedback message sent at S512b in Fig. 5B). It will nevertheless be appreciated that, conceivably, the ambient IoT device 3-1 device could retransmit a TB for up to a maximum of the fixed number of times as long as a negative feedback message is received in respect of that TB before an unmodulated carrier signal is received.

[0137] It can be seen, therefore, that in this scenario, although the assisting node 5-2 does not have to transmit the first message at S510a, b to the RAN node 5-1, the sending of at least a positive feedback messages to the ambient IoT device 3-1 corresponding to the second feedback messages sent at S512b in Fig. 5A is nevertheless supported (i.e., transmission of a feedback message over Uu interface is not required, but transmission of a feedback message over the sidelink is supported).

[0138] Once a positive feedback message is received by the ambient IoT device 3-1 from the assisting node 5-2 indicating that the TB previously sent to the assisting node 5-2 was successfully received and decoded, the ambient IoT device 3-1 will not retransmit a previous TB, but rather will generate and transmit a new TB in response to receiving the next unmodulated carrier signal from the RAN node 5-1 as long as there is data to be transmitted.

[0139] Beneficially, by (pre)configuring the communication system 1 such that the ambient IoT device 3-1 performs a fixed number of backscattered retransmissions as described above until positive feedback is received (and / or negative feedback is no longer received) this alternative reduces potentially unnecessary repetitive signalling compared to the above alternative albeit at the expense of some additional complexity arising from the need for positive (and / or negative) feedback messages (e.g., a HARQ ACK (and / or NACK) messages) to be sent to the ambient IoT device 3-1 by the assisting node 5-2.

[0140] (Re)transmission of an unmodulated carrier signal - Assisting node responsibility 　　As mentioned above, in topology 3 the assisting node 5-2 may be responsible for the (re)transmission of the unmodulated carrier signal to the ambient IoT device 3-1, and the RAN node 5-1 may be responsible for (re)receiving the modulated backscattered signal from the ambient IoT device 3-1.

[0141] An example of two different possible ways in which feedback and data (re)transmission may be implemented will now be described in more detail, by way of example only, with reference to Figs. 6 and 7.

[0142] Figs. 6A and 6B depict a simplified sequence diagram illustrating a procedure for (re)transmitting data encoded in a backscattered signal (e.g., a TB) from an ambient IoT device 3-1 to a RAN node 5-1 that may be used in the communication system 1 of Fig. 1.

[0143] This feedback and data (re)transmission procedure may be particularly (but not exclusively) applicable to scenarios where the ambient IoT device 3-1 is a type B, or a type C device as described above. This retransmitting procedure is particularly (but not exclusively) applicable to scenarios where the assisting node 5-2 is a layer-1 (L1) repeater device or a network-controlled repeater (NCR) node. In this scenario, the assisting node 5-2 does not demodulate any L1 signals that it receives.

[0144] As shown in Fig. 6A, there is provided a RAN node 5-1, an assisting node 5-2, and an ambient IoT device 3-1 that are deployed using topology 3, e.g., as described with reference to Fig. 4A in which the assisting node 5-2 is responsible for transmission of the unmodulated carrier signal. Specifically, as shown in Fig. 4A, the ambient IoT device 3-1 is able to receive an unmodulated carrier signal from the assisting node 5-2 and modulate and transmit (reflect) a backscattered signal based on the unmodulated carrier signal which is received at the RAN node 5-1.

[0145] Upon reception of the modulated backscattered signal, it may be processed (e.g., decoded / demodulated). For example, the modulated backscattered signal may be processed (e.g., decoded / demodulated) by the RAN node 5-1 to extract information encoded in the modulated backscattered signal. However, if the modulated backscattered signal is processed (e.g., decoded / demodulated) by the RAN node 5-1 and the decoding results in an error, then a retransmission of the modulated backscattered signal may be triggered in one of several different ways.

[0146] Prior to the procedure shown in Fig. 6A, the RAN node 5-1, or the assisting node 5-2 may allocate radio resources for the transmission of the unmodulated carrier signal. It will be appreciated that when such radio resources are determined by the RAN node 5-1, the RAN node 5-1 may first be triggered by the assisting node 5-2 to determine such radio resources, which are in turn signalled to the assisting node 5-2.

[0147] Similarly, prior to the procedure shown in Fig, 6A, the RAN node 5-1, or the assisting node 5-2 may allocate radio resources for the transmission of appropriate feedback messages for the RAN node 5-1 to feedback if there is successful reception and / or unsuccessful reception (e.g., successful and / or unsuccessful decoding) of a TB backscattered from the ambient IoT device 3-1 to the RAN node 5-1. The allocation of the radio resources for the transmission of appropriate feedback messages may occur in response to the RAN node 5-1 deciding to request an assisting node 5-2 to send the ambient IoT device 3-1 an unmodulated carrier signal. For example, having triggered the assisting node 5-2 to determine such radio resources, the RAN node 5-1 may determine (or trigger the assisting node 5-2 to determine) radio resources for the transmission of the appropriate feedback messages.

[0148] It will be appreciated that an appropriate feedback message may include, by way of example only, hybrid automatic repeat request (HARQ) acknowledgement (ACK) / negative acknowledgement (NACK) message, such as when the (re)transmission of backscattered signals are seen as HARQ-based (re)transmission at layer 1 (L1) e.g., the physical layer. Alternatively, an appropriate feedback message may include, by way of example only, an automatic repeat request (ARQ) acknowledgement ACK / NACK message, such as when the (re)transmission of backscattered signals are seen as ARQ-based (re)transmission at layer 2 (L2) e.g., the data link layer. It will be appreciated however that the feedback messages described above are by way of example only and that as further advancements are made in IoT devices and backscattered signalling, other appropriate feedback messages and types of data (re)transmission may be implemented.

[0149] For simplification only, further description of appropriate feedback messages will refer to HARQ ACKs / NACKs, although it will be appreciated that other types of feedback messages could be implemented instead as described above.

[0150] It will be appreciated that the radio resources for the feedback messages are determined by the RAN node 5-1, the RAN node 5-1 may determine such radio resources independently, e.g., of its own volition. Alternatively, the RAN node 5-1 may be triggered by another device to determine radio resources for the feedback messages, for example it may be triggered by the assisting node 5-2 which sends a request to the RAN node 5-1 for the allocation of radio resources for the appropriate feedback messages.

[0151] At step S602, the RAN node 5-1 sends an appropriate request message to the assisting node 5-2 to request that the assisting node 5-2 transmit an unmodulated carrier signal to the ambient IoT device 3-1.

[0152] At step S604, in response to the request to send an unmodulated carrier signal transmitted to assisting node 5-2, the assisting node 5-2 transmits an unmodulated carrier signal to the ambient IoT device 3-1 (e.g., using radio resources for the unmodulated carrier signal which may have been determined by the RAN node 5-1, or the assisting node 5-2 at some earlier step (described above)).

[0153] Upon reception of that unmodulated carrier signal, the ambient IoT device 3-1 (simultaneously or near-simultaneously) generates, at step S606, a TB (e.g., a block of data) to be sent to the RAN node 5-1, and modulates its impedance or reflectivity in response to the unmodulated carrier signal to encode the TB in a modulated signal sent (reflected / backscattered) to the RAN node 5-1.

[0154] When the ambient IoT device 3-1 reflects the signal simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for the backscattered transmission and the symbol used for the associated unmodulated carrier may be the same. Whereas when the ambient IoT device 3-1 reflects the signal near-simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for backscattered transmission and the symbol used for the associated unmodulated carrier may be within a threshold time gap.

[0155] Additionally, (not shown) the ambient IoT device 3-1 may store the generated TB (e.g., a copy of the generated TB) in a data buffer / register at the ambient IoT device 3-1 for possible future retransmission by the ambient IoT device 3-1.

[0156] At step S610, the RAN node 5-1, upon receiving the TB sent at S608, attempts to decode the received TB. If the TB is not decoded successfully during the attempted decoding of the received TB at step S608, by the RAN node 5-1 (e.g., the RAN node 5-1 detects a decoding error for the TB) then the procedure continues at box A) 'Decoding error for TB' shown in Fig. 6A.

[0157] Having not successfully decoded the TB at step S610, the RAN node 5-1 transmits to the ambient IoT device 3-1, at step S612a, a first negative feedback message. The first negative feedback message may be any appropriate message that indicates to the ambient IoT device 3-1 that the TB has not been received successfully (e.g., that a decoding error for the TB has been detected by the RAN node 5-1). For example, the first negative feedback message may comprise an indication of an unsuccessful TB transmission, and / or that a decoding error for the TB was detected by the RAN node 5-1. For example, the first negative feedback message may be in the form of a HARQ NACK message sent by the RAN node 5-1 to the ambient IoT device 3-1 (which may be via the assisting node 5-2) using dedicated radio resources for HARQ ACK / NACK signalling determined by the assisting node 5-2 or the RAN node 5-1 as described above. Additionally, or alternatively, the RAN node 5-1 may send a request message to the assisting node 5-2 to request the (re)transmission of an unmodulated carrier signal to the ambient IoT device 3-1 to stimulate / trigger a retransmission of the TB previously generated by the ambient IoT device 3-1.

[0158] As shown in Fig. 6A and briefly described above, the first negative feedback message sent at S612a may be sent indirectly from the RAN node 5-1 to the ambient IoT device 3-1. For example, the first negative feedback message may be sent to the ambient IoT device 3-1 via the assisting node 5-2. In this example, the first negative feedback message is transparent to the assisting node 5-2 (hence no attempt is made to demodulate it) and the assisting node 5-2 merely forwards the first negative feedback message on to the ambient IoT device 3-1 when it is received from the RAN node 5-1. It will be appreciated that where the assisting node 5-2 is of a type that demodulates incoming signals the assisting node 5-2 may first demodulate the first negative feedback message before sending the first negative feedback message (or a corresponding negative feedback message using a different application protocol) on to the ambient IoT device 3-1.

[0159] At step S614a, which may or may not be simultaneous with step S612a, the RAN node 5-1 transmits to the assisting node 5-2, a request for an unmodulated carrier signal (re)transmission. The request may include a suitable second negative feedback message indicating to the assisting node 5-2 that the received TB has not been successfully received (e.g., because of a decoding error for the TB). It will nevertheless be appreciated that the second negative feedback message may comprise an indication of an unsuccessful TB transmission that is sent separately to the request (or instead of the request - i.e., the indication itself could function as an implicit request). The indication of an unsuccessful TB transmission may, for example, be in the form of a HARQ NACK message sent by the RAN node 5-1 to the assisting node 5-2 using dedicated radio resources for HARQ ACK / NACK signalling determined previously by the RAN node 5-1 or the assisting node 5-2 as described above.

[0160] At step S616a, in response to the assisting node 5-2 receiving the request at step S614a, the assisting node 5-2 transmits an unmodulated carrier signal, to the ambient IoT device 3-1. That unmodulated carrier signal may be different, or the same as the unmodulated carrier signal set at step S604.

[0161] Upon receipt of the unmodulated carrier signal (or possibly earlier, following receipt of first feedback message from the RAN node 5-1), the ambient IoT device 3-1 may, at step S618a, fetch, from its data buffer / register, the previous TB that it generated at step S606, and which was stored at the data buffer / register as described above.

[0162] The ambient IoT device 3-1 is thus triggered to transmit the TB it fetched from its data buffer / register at step S620a i.e., the ambient IoT device 3-1 is triggered to retransmit the TB it initially transmitted to the assisting node 5-2 at step S608.

[0163] It will be appreciated that the first negative feedback message sent to the ambient IoT device 3-1 at step S612a may indicate (and / or trigger) the ambient IoT device 3-1 to consider the next unmodulated carrier signal that it receives as a trigger for (re)transmitting the TB stored in its data buffer / register. Moreover, the ambient IoT device 3-1 may be configured to retransmit a TB stored in its data buffer / register in response to receiving an unmodulated carrier signal, if the ambient IoT device 3-1 has not received a positive feedback message from the assisting node 5-2 indicating that the previous TB was successfully received and / or decoded e.g., the ambient IoT device 3-1 receives a HARQ ACK message from the assisting node 5-2. The ambient IoT device 3-1 may continue to retransmit the TB stored in its data buffer / register each time it receives an unmodulated carrier signal from the RAN node 5-1, until the ambient IoT device 3-1 receives from the assisting node, a positive feedback message indicating that the previous TB has been successfully received and / or decoded.

[0164] Beneficially, by triggering the ambient IoT device 3-1 to retransmit its most recently transmitted TB (i.e., the TB most recently generated, transmitted, and stored in its data buffer / register), in response to an unmodulated carrier signal, until a positive feedback message is received by the ambient IoT device 3-1 indicating that the TB has been correctly received ambient IoT operation is improved.

[0165] Alternatively, if during the attempted decoding of the received TB at step S610, the assisting node 5-2 successfully decodes the TB then the procedure continues at box B) 'Successful decoding for TB' shown in Fig. 6B.

[0166] Having successfully decoded the TB at step S610, the RAN node 5-1 transmits to the assisting node 5-2, at step S612b a first positive feedback message. The first positive feedback message may be any appropriate message that indicates to the assisting node 5-2 that the TB has been successfully decoded by the RAN node 5-1. For example, the first positive feedback message may comprise an indication of a successful TB transmission. For example, the indication of a successful TB transmission may be in the form of a HARQ ACK message sent by the RAN node 5-1 to assisting node 5-2 using dedicated radio resources for HARQ ACK / NACK signalling determined previously by the RAN node 5-1 or the assisting node 5-2 as described above.

[0167] Optionally, at step S614b, which may or may not be simultaneous with step S612b, the RAN node 5-1 may also send a suitable second positive feedback message to the assisting node 5-2 indicating successful receipt of the TB. For example, the second positive feedback message may be any appropriate message that can indicate the TB was decoded successfully e.g., a HARQ ACK message. The second positive feedback message may be sent on radio resources determined by the assisting node 5-2 or the RAN node 5-1 as described above.

[0168] When transmission of new data by the ambient IoT device 3-1 is required, the RAN node 5-1 sends at step S622 an appropriate request to the assisting node 5-2 to request that the assisting node 5-2 transmits an unmodulated carrier signal to the ambient IoT device 3-1.

[0169] At step S624, in response to the request sent at S622, the assisting node 5-2 transmits an unmodulated carrier signal to the ambient IoT device 3-1 (e.g., using radio resources for the unmodulated carrier signal which may have been determined by the RAN node 5-1, or the assisting node 5-2 at some earlier step (described above)).

[0170] Upon reception of that unmodulated carrier signal, the ambient IoT device 3-1 (simultaneously or near-simultaneously) generates, at step S626, a new TB (e.g., a block of data) to be sent to the RAN node 5-1, and modulates its impedance or reflectivity in response to the unmodulated carrier signal to encode the new TB in a modulated signal sent (reflected / backscattered) to RAN node 5-1 at step S628.

[0171] When the ambient IoT device 3-1 reflects the signal simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for the backscattered transmission and the symbol used for the associated unmodulated carrier may be the same. Whereas when the ambient IoT device 3-1 reflects the signal near-simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for backscattered transmission and the symbol used for the associated unmodulated carrier may be within a threshold time gap.

[0172] After transmission of the new TB at step S628, the process reverts to step S610, where the RAN node 5-1 attempts to decode the new TB. Based on the success, or lack of, the decoding of that new TB, the process proceeds to Box 'B' or Box 'A' respectively as discussed above.

[0173] Alternatively, the RAN node 5-1 may not send a feedback message to the ambient IoT device 3-1 at S612a (in Fig. 6A), or S612b (in Fig. 6B). Following the receipt of the feedback information from the RAN node 5-1, the assisting node 5-2 may be (pre)configured to perform unmodulated carrier signal (re)transmissions following the receipt of a negative feedback message e.g. at S614a (in Fig. 6A) from the RAN node 5-1. The assisting node 5-2 may be configured, in response to receiving the negative feedback message at S614a, to alter its transmission properties / behaviours such that a retransmission of the unmodulated carrier signal at step S616a can be distinguished / differentiated from the initial unmodulated carrier signal transmission at step S602. For example, the assisting node may adjust its transmission properties such that the retransmitted unmodulated carrier signal S616a has e.g., a different power level, a different resource based transmission, a different wave form, a different time-space, and the like from that used for the initial unmodulated carrier signal transmission at S602.

[0174] Following the receipt of the unmodulated signal from the assisting node 5-2, the ambient IoT device 3-1 is able to use the above differences to distinguish between the initial unmodulated carrier signal and the retransmitted unmodulated carrier signal. If the unmodulated signal is a retransmission, the ambient IoT device 3-1 fetches the previous TB from its data buffer / register, and then generates the backscattered transmission accordingly with the previous TB for retransmission. If the unmodulated signal is an initial transmission, the ambient IoT device 3-1 generates a new TB (or fetches it from its data buffer / register, other data source, or the like if the TB has already been generated), and then generates the backscattered transmission accordingly with this new TB for an initial transmission.

[0175] Beneficially, whilst this alternative requires the assisting node 5-2 to alter its unmodulated signal transmission to stimulate a retransmission, the feedback response message from the RAN node 5-1 to the ambient IoT device 3-1 is not needed. That in turn reduces the amount of signalling resources that need to be scheduled by the RAN node 5-1 and / or the assisting node 5-2 and simplifies the signalling procedure overall.

[0176] Figs. 7A and 7B depict a simplified sequence diagram illustrating another procedure for (re)transmitting data encoded in a backscattered (e.g., TB) from an ambient IoT device 3-1 to a RAN node 5-1 that may be used in the communication system of Fig. 1.

[0177] This (re)transmitting procedure may be particularly (but not exclusively) applicable to scenarios where the ambient IoT device 3-1 is a type B, or a type C device as described above. This retransmitting procedure is particularly (but not exclusively) applicable to scenarios where the assisting node 5-2 is a L2 relay node. In this scenario, the assisting node 5-2 is of a type that demodulates any L1 signals that it receives.

[0178] It will be appreciated that where the assisting node 5-2 is 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 L2 relay device), the assisting node 5-2 may be, for example, a relay UE or a relay node. Where the assisting node 5-2 is a relay UE, the assisting node and the ambient IoT device 3-1 may communicate with each other over a device-to-device (D2D) communication link, also referred to as a sidelink e.g., the assisting node and the ambient IoT device 3-1 may communicate with each other over a PC5 interface. Alternatively, where the assisting node 5-2 is a relay node the assisting node and the ambient IoT device 3-1 may communicate with each other over another interface (e.g., a Uu interface or the like).

[0179] As shown in Fig. 7A, there is provided a RAN node 5-1, an assisting node 5-2, and an ambient IoT device 3-1 that are deployed using topology 3, e.g., as described with reference to Fig. 4A in which the assisting node 5-2 is responsible for transmission of the unmodulated carrier signal. Specifically, as shown in Fig. 4A, the ambient IoT device 3-1 is able to receive an unmodulated carrier signal from the assisting node 5-2 and modulate and transmit (reflect) a backscattered signal based on the unmodulated carrier signal which is received at the RAN node 5-1.

[0180] Upon reception of the modulated backscattered signal, it may be processed (e.g., decoded / demodulated) For example, the modulated backscattered signal may be processed (e.g., decoded / demodulated) by the RAN node 5-1 to extract information encoded in the modulated backscattered signal. However, if the modulated backscattered signal is processed (e.g., decoded / demodulated) by the RAN node 5-1 and the decoding results in an error, then a retransmission of the modulated backscattered signal may be triggered in one of several different ways.

[0181] Prior to the procedure shown in Fig. 7A, the RAN node 5-1, or the assisting node 5-2 may allocate radio resources for the transmission of the unmodulated carrier signal. It will be appreciated that when such radio resources are determined by the RAN node 5-1, the RAN node 5-1 may first be triggered by the assisting node 5-2 to determine such radio resources, which are in turn signalled to the assisting node 5-2.

[0182] Similarly, prior to the procedure shown in Fig, 7A, the RAN node 5-1, or the assisting node 5-2 may (not shown) allocate radio resources for the transmission of appropriate feedback messages for the RAN node 5-1 to feedback if there is successful reception and / or unsuccessful reception (e.g., successful and / or unsuccessful decoding) of a TB backscattered from the ambient IoT device 3-1. The allocation of the radio resources for the transmission of appropriate feedback messages may occur in response to the RAN node 5-1 deciding to request an assisting node 5-2 to send the ambient IoT device 3-1 an unmodulated carrier signal. For example, having triggered the assisting node to determine such radio resources, the RAN node 5-1 may determine (or trigger the assisting node 5-2 to determine) radio resources for the transmission of the appropriate feedback messages.

[0183] It will be appreciated that an appropriate feedback message may include, by way of example only, hybrid automatic repeat request (HARQ) acknowledgement (ACK) / negative acknowledgement (NACK) message, such as when the (re)transmission of backscattered signals are seen as HARQ-based (re)transmission at layer 1 (L1) e.g., the physical layer. Alternatively, an appropriate feedback message may include, by way of example only, an automatic repeat request (ARQ) acknowledgement ACK / NACK message, such as when the (re)transmission of backscattered signals are seen as ARQ-based (re)transmission at layer 2 (L2) e.g., the data link layer. It will be appreciated however that the feedback messages described above are by way of example only and that as further advancements are made in IoT devices and backscattered signalling, other appropriate feedback messages and types of data (re)transmission may be implemented.

[0184] For simplification only, further description of appropriate feedback messages will refer to HARQ ACKs / NACKs, although it will be appreciated that other types of feedback messages could be implemented instead as described above.

[0185] It will be appreciated that the radio resources for the feedback messages may be determined by the RAN node 5-1 (and the assisting node 5-2). The RAN node 5-1 may determine such radio resources independently, e.g., of its own volition. Alternatively, the RAN node 5-1 may be triggered by another device to determine radio resources for the feedback messages, for example it may be triggered by the assisting node 5-2 which sends a request to the RAN node 5-1 for the allocation of radio resources for the appropriate feedback messages. Similarly, the assisting node 5-2 may determine such radio resources independently, e.g., of its own volition. Alternatively, the assisting node 5-2 may be triggered by another device to determine radio resources for the feedback messages, for example it may be triggered by the RAN node 5-1 which sends a request to the assisting node 5-2 for the allocation of radio resources for the appropriate feedback messages.

[0186] At step S702, the RAN node 5-1 sends an appropriate request message to the assisting node 5-2 to request that the assisting node 5-2 transmit an unmodulated carrier signal to the ambient IoT device 3-1.

[0187] At step S704, in response to the request to send an unmodulated carrier signal transmitted to assisting node 5-2 by the RAN node 5-1, the assisting node 5-2 transmits an unmodulated carrier signal to the ambient IoT device 3-1 (e.g., using radio resources for the unmodulated carrier signal which may have been determined by the RAN node 5-1, or the assisting node 5-2 at some earlier step (described above)).

[0188] Upon reception of that unmodulated carrier signal, the ambient IoT device 3-1 (simultaneously or near-simultaneously) generates, at step S706, a TB (e.g., a block of data) to be sent to the RAN node 5-1 and modulates its impedance or reflectivity in response to the unmodulated carrier signal to encode the TB in a modulated signal sent (reflected / backscattered) to the RAN node 5-1.

[0189] When the ambient IoT device 3-1 reflects the signal simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for the backscattered transmission and the symbol used for the associated unmodulated carrier may be the same. Whereas when the ambient IoT device 3-1 reflects the signal near-simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for backscattered transmission and the symbol used for the associated unmodulated carrier may be within a threshold time gap.

[0190] Additionally, (not shown) the ambient IoT device 3-1 may store the generated TB (e.g., a copy of the generated TB) in a data buffer / register at the ambient IoT device 3-1 for possible future retransmission by the ambient IoT device 3-1.

[0191] At step S710, the RAN node 5-1, upon receiving the TB sent at S708, attempts to decode the received TB. If the TB is not decoded successfully during the attempted decoding of the received TB at step S708, by the RAN node 5-1 (e.g., the RAN node 5-1 detects a decoding error for the TB) then the procedure continues at box A) 'Decoding error for TB' shown in Fig. 7A.

[0192] Having detected a decoding error for the TB at step S710, the RAN node 5-1 transmits to the assisting node 5-2, at step S712a a request for an unmodulated carrier signal (re)transmission. The request may include a suitable first negative feedback message indicating to the assisting node 5-2 that the received TB has not been successfully received (e.g., because of a decoding error for the TB). It will nevertheless be appreciated that the first negative feedback message may comprise an indication of an unsuccessful TB transmission that is sent separately to the request (or instead of the request - i.e., the indication itself could function as an implicit request). The first negative feedback message may, for example, be in the form of a HARQ NACK message sent by the RAN node 5-1 to the assisting node 5-2 using dedicated radio resources for HARQ ACK / NACK signalling determined previously by the RAN node 5-1 or the assisting node 5-2 as described above.

[0193] At step S714a, in response to receiving the first negative feedback message (e.g., included in the request sent at S712a), the assisting node 5-2 sends a suitable second negative feedback message indicating to the ambient IoT device 3-1 that the TB was not successfully received by the RAN node 5-1 (e.g., a decoding error for the TB was detected by the RAN node 5-1). The second negative feedback message may be any appropriate message that can indicate the occurrence of such unsuccessful reception of the TB. The second negative feedback message may, for example, take the form of a HARQ NACK message or the like. The second negative feedback message may be sent on radio resources determined by the assisting node 5-2 or the RAN node 5-1 as described above.

[0194] Similarly, at step S715a, in response to the assisting node 5-2 receiving the request sent at S712a, the assisting node 5-2 transmits an unmodulated carrier signal, to the ambient IoT device 3-1. That unmodulated carrier signal may be different, or the same as the unmodulated carrier signal set at step S704.

[0195] It will be appreciated that the second negative feedback message sent at step S714a, and the unmodulated carrier signal sent at step S715a, may be sent simultaneously (or near simultaneously), for example using different respective resources.

[0196] Upon receipt of the unmodulated carrier signal sent at S715a, and / or the second negative feedback message sent at S714a, the ambient IoT device 3-1 may at, step S716a, fetch, from its data buffer / register, the previous TB that it generated at step S706, and which was stored at the data buffer / register as described above. The ambient IoT device 3-1 is thus triggered to transmit the TB it fetched from its data buffer / register at step S718a i.e., the ambient IoT device 3-1 is triggered to retransmit the TB it initially transmitted to the assisting node 5-2 at step S708. Beneficially, by triggering the ambient IoT device 3-1 to retransmit its most recently transmitted TB (i.e., the TB most recently generated, transmitted, and stored in its data buffer / register), in response to an unmodulated carrier signal, until a positive feedback message is received by the ambient IoT device 3-1 ambient IoT operation is improved.

[0197] Alternatively, if during the attempted decoding of the received TB at step S710, the assisting node 5-2 successfully decodes the TB then the procedure continues at box B) 'Successful decoding for TB' shown in Fig. 7B.

[0198] Having successfully decoded the TB at step S710, the RAN node 5-1 transmits to the assisting node 5-2, at step S712b a first positive feedback message. The first positive feedback message may be any appropriate message that indicates to the assisting node 5-2 that the TB has been successfully decoded by the RAN node 5-1. For example, the first positive feedback message may comprise an indication of a successful TB transmission. For example, the indication of a successful TB transmission may be in the form of a HARQ ACK message sent by the RAN node 5-1 to assisting node 5-2 using dedicated radio resources for HARQ ACK / NACK signalling determined previously by the RAN node 5-1 or the assisting node 5-2 as described above.

[0199] At step S714b, which may or may not be simultaneous with step S712b, the assisting node 5-2 sends a suitable second positive feedback message to the ambient IoT device 3-1 indicating to the ambient IoT device 3-1 that the received TB was received successfully. For example, the second positive feedback message may be any appropriate message that can indicate the TB was decoded successfully e.g., a HARQ ACK message. The second positive feedback message may be sent on radio resources determined by the assisting node 5-2 or the RAN node 5-1 as described above.

[0200] When transmission of new data by the ambient IoT device 3-1 is required, the RAN node 5-1 sends at step S730 an appropriate request to the assisting node 5-2 to request that the assisting node 5-2 transmits an unmodulated carrier signal to the ambient IoT device 3-1.

[0201] At step S732, in response to the request sent at S730, the assisting node 5-2 transmits an unmodulated carrier signal to the ambient IoT device 3-1 (e.g., using radio resources for the unmodulated carrier signal which may have been determined by the RAN node 5-1, or the assisting node 5-2 at some earlier step (described above)).

[0202] Upon reception of that unmodulated carrier signal, the ambient IoT device 3-1 (simultaneously or near-simultaneously), generates, at step S734, a new TB (e.g., a block of data) to be sent to the RAN node 5-1, and modulates its impedance or reflectivity in response to the unmodulated carrier signal to encode the new TB in a modulated signal sent (reflected / backscattered) to RAN node 5-1 at step S736.When the ambient IoT device 3-1 reflects the signal simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for the backscattered transmission and the symbol used for the associated unmodulated carrier may be the same. Whereas when the ambient IoT device 3-1 reflects the signal near-simultaneously to the reception of the unmodulated carrier signal by the ambient IoT device 3-1, the symbol used for backscattered transmission and the symbol used for the associated unmodulated carrier may be within a threshold time gap.

[0203] After transmission of the new TB at step S736, the process reverts to step S710, where the RAN node 5-1 attempts to decode the new TB. Based on the success, or lack of, the decoding of that new TB, the process proceeds to Box 'B' or Box 'A' respectively as discussed above.

[0204] Alternatively, rather than the RAN node 5-1 and the assisting node 5-2 transmitting the feedback messages at S712a,b and S714a,b respectively, the assisting node 5-2 may be (pre)configured to perform a fixed number of unmodulated carrier signal (re)transmissions. For example, the RAN node 5-1 may request that the unmodulated carrier signal is (re)transmitted for a fixed number of instances by the assisting node 5-2, and the ambient IoT device 3-1 may always blindly retransmit a TB for the same fixed number regardless of the reception status of the TB at RAN node 5-1.

[0205] Beneficially, whilst this alternative involves potentially unnecessary repetitive signalling, by (pre)configuring the communication system 1 such that the assisting node 5-2 performs a fixed number of unmodulated carrier signal (re)transmissions as described above, the need for a first and a second positive / negative feedback message (e.g., a first and second HARQ ACK or NACK message) is not required. That in turn reduces the amount of signalling resources that need to be scheduled by the RAN node 5-1 and / or the assisting node 5-2 and simplifies the signalling procedure overall.

[0206] Alternatively, the RAN node 5-1 may not send a feedback message to the ambient IoT device 3-1 at S714a (in Fig. 7A), or S714b (in Fig. 7B). Following the receipt of the feedback information from the RAN node 5-1, the assisting node 5-2 may be (pre)configured to perform unmodulated carrier signal (re)transmissions following the receipt of a negative feedback message e.g. at S712a (in Fig. 7A) from the RAN node 5-1. The assisting node 5-2 may be configured, in response to receiving the negative feedback message at S712a, to alter its transmission properties / behaviours such that a retransmission of the unmodulated carrier signal at step S715a can be distinguished / differentiated from the initial unmodulated carrier signal transmission at step S702. For example, the assisting node may adjust its transmission properties such that the retransmitted unmodulated carrier signal S715a has e.g., a different power level, a different resource based transmission, a different wave form, a different time-space, and the like from that used for the initial unmodulated carrier signal transmission at S702.

[0207] Following the receipt of the unmodulated signal from the assisting node 5-2, the ambient IoT device 3-1 is able to use the above differences to distinguish between the initial unmodulated carrier signal and the retransmitted unmodulated carrier signal. If the unmodulated signal is a retransmission, the ambient IoT device 3-1 fetches the previous TB from its data buffer / register, and then generates the backscattered transmission accordingly with the previous TB for retransmission. If the unmodulated signal is an initial transmission, the ambient IoT device 3-1 generates a new TB (or fetches it from its data buffer / register, other data source, or the like if the TB has already been generated), and then generates the backscattered transmission accordingly with this new TB for an initial transmission.

[0208] Beneficially, whilst this alternative requires the assisting node 5-2 to alter its unmodulated signal transmission to stimulate a retransmission, the feedback response message from the assisting node 5-2 to the ambient IoT device 3-1 is not needed. That in turn reduces the amount of signalling resources that need to be scheduled by the RAN node 5-1 and / or the assisting node 5-2 and simplifies the signalling procedure overall.

[0209] Components of the Communication System 　　User Equipment 　　Fig. 8 is a simplified block schematic illustrating the main components of a UE 3-2; 3-3 for implementation in the system of Fig. 1.

[0210] 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 base station 5 via one or more antenna 33 (e.g., comprising one or more antenna elements). The UE 3-2; 3-3 has a controller 37 to control the operation of the UE 3-2; 3-3. 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.

[0211] 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.

[0212] 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 communications 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 communications 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 3-2; 3-3 for transmission / reception of UL / DL communications (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.

[0213] 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 communication control module 43 may include a PHY sub-module, a MAC sub-module, an RLC sub-module, a PDCP sub-module, an RRC sub-module, etc.

[0214] The communication control module 43 is configured, in particular, to control the UE's communications, where applicable, in accordance with any of the methods described herein.

[0215] Ambient IoT device 　　Fig. 9A is a simplified block schematic illustrating the main components of another example of a UE comprising an ambient IoT device 3-1 for possible implementation in the system of Fig. 1.

[0216] As shown, the ambient IoT device 3-1 (also referred to simply as an IoT device 3-1) has a transceiver circuit 231 that is operable to transmit signals to and to receive signals from a RAN node 5-1 (and / or an assisting node 5-2) via one or more antenna 233 (e.g., comprising one or more antenna elements).

[0217] The transceiver circuit 231 has energy harvesting circuitry 231-1 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 231-1 may include, by way of example only, inductive and / or capacitive architectures to harvest energy from incoming signals.

[0218] It will however be appreciated that the energy harvesting circuitry 231-1 may alternatively not form part of the transceiver circuit 231, 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).

[0219] The transceiver circuit 231 also has modulation circuitry 231-2 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 231-2 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 231-2 may be configured to modulate the incoming signal to encode data provided from one or more data sources 232. Typically, for example, the IoT device 3-1 may comprise a data source 232 in the form of a sensor (e.g., an optical, temperature, position sensor or the like) for providing measurement data or a sensor alert, or it may comprise a data source 232 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.

[0220] A data buffer 234 is provided for storing data from the data source 232. By way of example only, where the data source 232 is a sensor (e.g., an optical, temperature, position sensor or the like), the data buffer 234 may store measurement data from the one or more sensors. The data buffer may be configured to store the last set of data (e.g., a TB) generated by the data source 232, or alternatively it may be configured to store multiple sets of data (e.g., TBs) generated by the data source. For example, the data buffer may store a specific number of sets of data (e.g., TBs) generated by the data sources that are overwritten incrementally as new sets of data are generated. The number (amount) of sets of data (e.g., TBs) to be stored by the data buffer may be preconfigured. The data buffer 234 is also configured to provide data to the transceiver circuit 231 to allow transmission by the IoT device 3-1 when triggered to do so.

[0221] In this example, the transceiver circuit 231 may also have a signal amplifier 231-3 (which may use energy harvested by the energy harvesting circuitry 231-1) for amplifying any modulated backscattered signal to be reflected by the IoT device 3-1 for receipt at another device.

[0222] Although not necessarily required for its operation, the IoT device 3-1 might, of course, have additional functionality (e.g., a user interface, a touch screen / keypad / microphone / speaker and / or the like for, allowing direct control by and interaction with a user).

[0223] Fig. 9B is a simplified block schematic illustrating the main components of another example of a UE comprising an ambient IoT device 3-1 for possible implementation in the system of Fig. 1.

[0224] 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) via one or more antenna 333 (e.g., comprising one or more antenna elements).

[0225] The transceiver circuit 331 has 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.

[0226] 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).

[0227] 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.

[0228] In this example, the transceiver circuit 331 may also have a signal amplifier 331-3 (which may use 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.

[0229] 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.

[0230] The controller 337 is 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.

[0231] The controller 337 also comprises any suitable form of processing circuitry 338 to process, for examples, signals received and transmitted by the IoT device 3-1. For example, the processing circuitry 338 may be configured to process (H)ARQ ACK / NACK messages received from other devices and respond according to those (H)ARQ ACK / NACK messages. The processing circuitry 338 may include (but is 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.

[0232] The communication control module 343 is operable to control the communication between the IoT device 3-1, a RAN node 5-1, and / or an assisting node 5-2. The communication control module 343 may, for example, be configured for the overall handling of uplink communications 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 343 may also be configured for the overall handling of receipt of downlink communications 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).

[0233] A data buffer 345 provided as part of the memory 339 (although it could be provided separately) and is configured to store data from the data source 332. By way of example only, where the data source 332 is a sensor (e.g., an optical, temperature, position sensor or the like), the data buffer 245 may store measurement data from the one or more sensors. The storage of data from the data source 332 in the data buffer 345 is controlled by the controller 337. The data buffer may be configured to store the last set of data (e.g., TB) generated by the data source 332, or alternatively it may be configured to store multiple sets of data (e.g., TBs) generated by the data source. For example, the data buffer may store a specific number of sets of data (e.g., TBs) generated by the data sources that are overwritten incrementally as new sets of data are generated. The number (amount) of sets of data (e.g., TBs) to be stored by the data buffer may be preconfigured at the controller 337. Alternatively, the number (amount) of sets of data (e.g., TBs) to be stored by the data buffer may be adjustable by the controller 337. The controller 337 is also configured to allow data from the data buffer 345 to be transmitted by the IoT device 3-1 when triggered to do so. It will be appreciated that the communication control module 343 may include a number of sub-modules ('layers' or 'entities') to support specific functionalities.

[0234] The communication control module 343 is configured, in particular, to control the IoT device's communications, where applicable, in accordance with any of the methods described herein.

[0235] RAN node 　　Fig. 10 is a simplified block schematic illustrating the main components of a RAN node 5-1 (e.g., a base station) for implementation in the system of Fig. 1.

[0236] 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, ambient 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 base stations 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.

[0237] As shown, these software instructions include, among other things, an operating system 61, and a communication control module 63.

[0238] 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 communications, 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 communications 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 communications (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.

[0239] It will be appreciated that the communication control module 63 may include a number of sub-modules ('layers' or 'entities') to support specific functionalities. For example, the communication control module 63 may include, for communicating with a UE 3, a PHY sub-module, a MAC sub-module, an RLC sub-module, a PDCP sub-module, an RRC sub-module, etc. Moreover, the communication control module 63 may include, for communicating with a core network entity such as an AMF 10-1 (or similar node such as an MME), an NG / S1 application protocol (NG / S1-AP) sub-module, a stream control transmission protocol (SCTP) sub-module, an IP sub-module, a layer 1 (L1) sub-module, a layer 2 (L2) sub-module, etc (or corresponding sub-modules for communicating with a core network function).

[0240] The communication control module 63 is configured in particular, to control the base station's communications, in accordance with any of the methods described herein.

[0241] Assisting (or intermediate) node 　　Fig. 11 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 system of Fig. 1.

[0242] As shown, the assisting node 5-2 may comprise a UE (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).

[0243] 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.

[0244] 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.

[0245] 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 communications control module 163 is configured, in particular, for the overall handling of uplink communications to the RAN node 5-1. For example, where the assisting node 5-2 is a UE (or at least operates like a UE 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 communications from the RAN node 5-1. For example, where the assisting node 5-2 is a UE (or at least operates like a UE 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 (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.

[0246] The communication control module 163 is also responsible for appropriate ambient IoT related communications 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).

[0247] It will be appreciated that the communication control module 163 may include a number of sub-modules ('layers' or 'entities') to support specific functionalities. For example, the communication control module 163 may include a PHY sub-module, a MAC sub-module, an RLC sub-module, a PDCP sub-module, an RRC sub-module, etc.

[0248] The communication control module 163 is configured, in particular, to control the assisting node's communications, in accordance with any of the methods described herein.

[0249] Modifications and Alternatives 　　Detailed example embodiments 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. And, each example embodiment can be appropriately combined with at least one of example embodiments.

[0250] For example, it will be appreciated that whilst the described signalling procedures related to topology 3 in which a different node transmits the unmodulated carrier than receives the backscattered transmission, the principles described herein may be applied to scenarios in which the same node transmits the unmodulated carrier an receives the backscattered transmission (e.g., using connectivity topology 1 or 2 described above).

[0251] It will be appreciated that description of features of and actions performed by a RAN node (base station), apply equally to distributed type base stations as to non-distributed type base stations.

[0252] It will also be appreciated that whilst information elements having specific names have been described differently named information elements but having a similar purpose may be used.

[0253] In the above description the UE and the base station 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.

[0254] 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.

[0255] 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.

[0256] 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.

[0257] 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.

[0258] 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.

[0259] 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.).

[0260] 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.).

[0261] 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.).

[0262] 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.).

[0263] 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.).

[0264] 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.

[0265] 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)).

[0266] 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.

[0267] 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.

[0268] It will be appreciated that IoT technology can be implemented on any communication devices that can connect to a communications network for sending / receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

[0269] 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.

[0270] 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.

[0271] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0272] Furhter, each of the drawings or figures is merely an example to illustrate one or more example embodiments. Each figure may not be associated with only one particular example embodiment, but may be associated with one or more other example embodiments. As those of ordinary skill in the art will understand, various features or steps described with reference to any one of the figures can be combined with features or steps illustrated in one or more other figures, for example, to produce example embodiments that are not explicitly illustrated or described. Not all of the features or steps illustrated in any one of the figures to describe an example embodiment are necessarily essential, and some features or steps may be omitted. The order of the steps described in any of the figures may be changed as appropriate.

[0273] Furhter, the whole or part of the example embodiments disclosed above can be described as, but not limited to, the following supplementary notes. 　　(Supplementary Note 1) 　　A method performed by a terminal, the method comprising: 　　transmitting a signal received from a first node, to a second node, by reflecting or backscattering the signal; and 　　retransmitting, to the second node, the signal a specific number of times. 　　(Supplementary Note 2) 　　The method according to supplementary note 1, wherein 　　the retransmitting is performed regardless of a reception status of the signal at the second node. 　　(Supplementary Note 3) 　　The method according to supplementary note 1, wherein 　　the retransmitting is performed upon receiving, from the second node directly or via the first node, information indicating negative acknowledgment regarding the signal. 　　(Supplementary Note 4) 　　The method according to supplementary note 1, wherein 　　the retransmitting is performed unless receiving, from the second node directly or via the first node, information indicating acknowledgment regarding the signal. 　　(Supplementary Note 5) 　　The method according to supplementary note 4, further comprising: 　　receiving, from the second node directly or via the first node, information indicating acknowledgment regarding the signal; and 　　determining whether to generate transmission for a received signal based on whether there is no other data available. 　　(Supplementary Note 6) 　　The method according to supplementary note 5, wherein 　　in a case where new data transmission for the received signal is generated, the number of times for the retransmitting is recounted by the first node. 　　(Supplementary Note 7) 　　The method according to any one of supplementary notes 1 to 6, wherein 　　the specific number of times is: 　　　　a fixed number of times, or 　　　　a number of times configured by the first node or the second node. 　　(Supplementary Note 8) 　　The method according to any one of supplementary notes 1 to 7, wherein 　　the signal is an unmodulated signal. 　　(Supplementary Note 9) 　　The method according to any one of supplementary notes 1 to 8, wherein 　　the first node is an access network node, and the second node is an assisting node which is connected with the first node via an Uu interface and is connected with the terminal via a sidelink, or 　　the second node is an access network node, and the first node is an assisting node which is connected with the first node via an Uu interface and is connected with the terminal via a sidelink. 　　(Supplementary Note 10) 　　A terminal comprising: 　　means for transmitting a signal received from a first node, to a second node, by reflecting or backscattering the signal; and 　　means for retransmitting, to the second node, the signal a specific number of times.

[0274] Furhter, Some or all of elements specified in Supplementary Notes 2 to 9 dependent on Supplementary Note 1 may also be dependent on Supplementary Note 10 in dependency similar to that of Supplementary Notes 2 to 9 on Supplementary Note 1. Some or all of elements specified in any of Supplementary Notes may be applied to various types of hardware, software, and recording means for recording software, systems, and methods.

[0275] This application is based upon and claims the benefit of priority from Great Britain Patent Application No. 2317668.8, filed on November 17, 2023, the disclosure of which is incorporated herein in its entirety by reference.

[0276] 1　　COMMUNICATION SYSTEM 3 (3-1, 3-2, 3-3)　　USER EQUIPMENT (UE) 5-1　　RADIO ACCESS NETWORK (RAN) NODE 5-2　　NODE 7　　CORE NETWORK 9　　CELL 10　　CONTROL PLANE FUNCTION (CPF) 10-1　　ACCESS AND MOBILITY MANAGEMENT FUNCTION (AMF) 10-2　　SESSION MANAGEMENT FUNCTION (SMF) 10-N　　OTHER FUNCTIONS 11　　USER PLANE FUNCTION (UPF) 20, 20-1, 20-2, 20-3　　COMMUNICATION 21　　EXTERNAL DATA NETWORK 31　　TRANSCEIVER CIRCUIT 33　　ANTENNA 35　　USER INTERFACE 37　　CONTROLLER 39　　MEMORY 41　　OPERATING SYSTEM 43　　COMMUNICATION CONTROL MODULE 51　　TRANSCEIVER CIRCUIT 53　　ANTENNA 55　　CORE NETWORK INTERFACE 57　　CONTROLLER 59　　MEMORY 61　　OPERATING SYSTEM 63　　COMMUNICATION CONTROL MODULE 151　　TRANSCEIVER CIRCUIT 153　　ANTENNA 155　　RAN INTERFACE 157　　CONTROLLER 159　　MEMORY 161　　OPERATING SYSTEM 163　　COMMUNICATION CONTROL MODULE 231　　TRANSCEIVER CIRCUIT 231-1　　ENERGY HARVESTING CIRCUITRY 231-2　　MODULATION CIRCUITRY 231-3　　SIGNAL AMPLIFIER 232　　DATA SOURCE 233　　ANTENNA 234　　DATA BUFFER 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　　COMMUNICATION CONTROL MODULE 345　　DATA BUFFER

Claims

1. A method performed by a terminal, the method comprising: 　　transmitting a signal received from a first node, to a second node, by reflecting or backscattering the signal; and 　　retransmitting, to the second node, the signal a specific number of times.

2. The method according to claim 1, wherein 　　the retransmitting is performed regardless of a reception status of the signal at the second node.

3. The method according to claim 1, wherein 　　the retransmitting is performed upon receiving, from the second node directly or via the first node, information indicating negative acknowledgment regarding the signal.

4. The method according to claim 1, wherein 　　the retransmitting is performed unless receiving, from the second node directly or via the first node, information indicating acknowledgment regarding the signal.

5. The method according to claim 4, further comprising: 　　receiving, from the second node directly or via the first node, information indicating acknowledgment regarding the signal; and 　　determining whether to generate transmission for a received signal based on whether there is no other data available.

6. The method according to claim 5, wherein 　　in a case where new data transmission for the received signal is generated, the number of times for the retransmitting is recounted by the first node.

7. The method according to any one of claims 1 to 6, wherein 　　the specific number of times is: 　　　　a fixed number of times, or 　　　　a number of times configured by the first node or the second node.

8. The method according to any one of claims 1 to 7, wherein 　　the signal is an unmodulated signal.

9. The method according to any one of claims 1 to 8, wherein 　　the first node is an access network node, and the second node is an assisting node which is connected with the first node via an Uu interface and is connected with the terminal via a sidelink, or 　　the second node is an access network node, and the first node is an assisting node which is connected with the first node via an Uu interface and is connected with the terminal via a sidelink.

10. A terminal comprising: 　　means for transmitting a signal received from a first node, to a second node, by reflecting or backscattering the signal; and 　　means for retransmitting, to the second node, the signal a specific number of times.

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