Method for operating the secondary station

Abstract

A method for operating a wireless terminal to communicate in a cellular network, the cellular network having at least a first cell station serving a first cell and at least one relay station served by a second cell station serving a second cell, the method comprising: receiving, by the wireless terminal, a downlink signal sent by the first cell station, the downlink signal carrying downlink control information, the downlink control information including at least an indication of assigned uplink resources to be used by the wireless terminal to transmit a signal to the relay station; generating, by the wireless terminal, uplink information; and transmitting, by the wireless terminal, a signal carrying the uplink information to the relay station on the assigned uplink resources, the uplink information to be forwarded to the second cell station.

Description

[Technical field]

[0001] The present invention relates to the field of wireless communications, in particular to relay architectures in the context of cellular networks, such as UMTS Long Term Evolution (LTE) or LTE-Advanced (both included in 4G), New Radio (NR) (5G) or other cellular or mobile communication networks. [Background technology]

[0002] In a conventional cellular network, a primary station serves multiple secondary stations that are located in the cell served by the primary station. Wireless communication from the primary station to each secondary station occurs on a downlink channel. Conversely, wireless communication from each secondary station to the primary station occurs on an uplink channel. Wireless communication can include data traffic (sometimes called user data) and control information (sometimes called signaling). This control information typically has information to assist the primary and / or secondary stations in exchanging data traffic (e.g., resource allocation / requests, physical transmission parameters, information about the status of the respective stations). Data traffic typically includes useful payloads that are exchanged for the use of end user applications. Data traffic typically consists of IP (Internet Protocol) packets carried in the data plane.

[0003] In the context of cellular networks as standardized by 3GPP, the primary station is called a base station, i.e. a gNodeB (or gNB) in 5G (NR) or an eNodeB (or eNB) in 4G (LTE), or a cell station. The eNB / gNB is part of the Radio Access Network (RAN) and interfaces to the Core Network (CN) functions. In the same context, the secondary station corresponds to a mobile station, i.e. a User Equipment (or UE) in 4G / 5G, which is a wireless client device or there is a specific role played by such a device. The term "node" is further used to represent a UE or a gNB / eNB. "NF" represents the network function of the CN. The direct link between the primary station and the secondary station is called the Uu interface in 4G or 5G networks.

[0004] The secondary stations can be located in different types of wireless terminals, e.g. mobile phones, vehicles (enabled for V2V vehicle-to-vehicle or more general V2X vehicle-to-vehicle / roadway communication), IoT devices (including low power medical sensors for health monitoring, medical (emergency) diagnostic and treatment devices for hospitals or first responders), virtual reality (VR) headsets, or general wireless wearables. These wireless terminals are very different in their behavior or characteristics, e.g. in terms of low power operation, required bandwidth / data rate, maximum acceptable latency, achievable transmit output power, achievable duty cycle when transmitting and / or receiving, or required mobility. The bandwidth available to the devices for uplink (UL) and downlink (DL) data can change dynamically under the control of the base station, based on the data needs and the channel conditions at the time. There is a scheduler in the base station to schedule the UL / DL transmissions of the devices.

[0005] In 3GPP, the role of a relay node has been introduced, as shown in FIG. 1A. This relay node 120 is a wireless communication station 120 with the functionality to relay communications between a base station 100 (e.g. gNB) and a UE 110. This relay functionality serves, for example, to extend the coverage of a cell 10 to an out-of-coverage (OoC) mobile station 110. This relay node 120 can be a mobile station or a different type of device. In the 4G specifications, the Proximity Services (ProSe) functionality is defined in particular in TS 23.303 and TS 24.334 to enable connectivity for cellular user equipment (UE) 110 that is temporarily not in the coverage of a cellular network base station (eNB) 100 serving a cell 10 (among other things). This particular functionality is called ProSe UE-to-network relay, or in short, relay UE. The relay UE 120 relays application and network traffic bidirectionally between the OoC UE 110 and the eNB 100. The local communication between the relay UE 120 and the OoC UE 110 is called device-to-device (D2D) communication or sidelink (also known as PC5) communication in TS 23.303 and TS 24.334. As soon as the relay relationship is established, the OoC-UE 110 is IP connected via the relay UE 120 and acts in the role of "remote UE" 110. This situation means that the remote UE has an indirect network connection (as defined in TS 22.261) to selected functions of the core network, as opposed to a direct network connection to all core network functions, which is the usual case.

[0006] However, while direct communication with a distant gNB requires high energy consumption from the (wireless, typically battery-powered) wearable UE or IoT UE, sidelink operations also include energy-lossy operations, such as sensing the control region to check if a message is addressed to the remote UE. This leads to high energy consumption of the (wireless, typically battery-powered) wearable UE or IoT UE when communicating as a remote UE via such relay UE for sensing. It should be noted that in this application, the term "energy consumption" is used for what may be denoted by the term "power consumption". "Power consumption" is a physical misnomer, since power cannot be consumed. Power is the rate at which energy is "consumed", or more precisely, converted from a first type of energy (e.g., electrochemical energy available by charging a battery) to another type of energy. In the same way, a "power saving mode" is actually a mode in which the power level of the device is set to a value lower than during normal operation, so that energy, not power, is saved in this mode (or, more precisely, not converted as quickly).

[0007] Moreover, besides high energy consumption, the bandwidth available downstream to indirectly connected remote UEs (through relay UEs) is potentially limited, meaning that relay UEs may have insufficient downstream data capacity. For example, one reason for this bottleneck is that the resources allocated for sidelink (SL) communication required by relay UEs to send data to remote UEs are a very limited subset of the full set of available cellular resources. A relay UE may need to serve multiple remote UEs simultaneously, and thus the scarce resources of the relay UE (spectrum, processing time, buffer memory, etc.) may need to be split across multiple devices. Furthermore, other remote UEs have a higher priority to be served by the relay UE. Another issue is the possibility of packet collisions due to overlapping resource allocations (e.g. in mode 2 as defined in TS38.300 and / or TR38.885 Rel.16 and later) when a remote UE goes out of coverage and therefore no resources are scheduled for it to transmit. Summary of the Invention [Problem to be solved by the invention]

[0008] One object of the present invention is to alleviate the above-mentioned problems.

[0009] Another object of the invention is to propose a method for communicating in a network, which allows reduced energy consumption for remote UEs.

[0010] Yet another object of the present invention is to propose a method for secondary stations to communicate in a network that improves latency while keeping energy consumption low.

[0011] Yet another object of the present invention is to propose a secondary station that can flexibly operate according to an optimal network topology so as to optimize energy consumption. [Means for solving the problem]

[0012] Therefore, according to a first aspect of the invention, a wireless terminal as claimed in claim 1 is proposed for communicating in a cellular network, said cellular network comprising at least one first cell station serving a first cell and at least one relay station served by a second cell station serving a second cell, The wireless device a controller operating in a TX limited mode of operation, the controller being adapted to generate uplink information; a receiver configured by the controller to receive, in a TX limited mode of operation, first downlink signals sent directly by a first cell station, said first downlink signals carrying respective first downlink control information, at least one of the respective first downlink control information including at least an indication of a first configuration parameter to be used by the wireless terminal to transmit a signal directly to a relay station, and at least one of the respective first downlink control information including at least a second configuration parameter to be used by the wireless terminal to receive a further downlink signal directly from the first cell station; a transmitter configured by the controller to transmit, in a TX limited mode of operation, a second signal to the relay station using the first configuration parameters, the second signal carrying uplink information to be forwarded to the second cell station; Equipped with The receiver is further adapted to receive a further downlink signal directly from the first cell station using the second configuration parameters.

[0013] Throughout the embodiments of the invention and various aspects and variations thereof, configuration parameters include one or more sets of parameter values ​​related to the configuration of communication. These may be, for example, resources (e.g., resource blocks (e.g., defined in time, frequency, code, and / or spatial channels), spatial beams). These may also be other parameter values ​​such as selected transmission modes, selected modulation schemes, HARQ processes, etc. Furthermore, they may be combinations of resources and other configuration values. Although many examples in the embodiments describe indications of allocated resources, these embodiments are also applicable to other configuration parameters.

[0014] According to a first variant of the first aspect, the controller initiates the TX restricted mode of operation following receipt by the receiver of a TX restricted mode of operation activation signal, the TX restricted mode of operation activation signal being a downlink signal sent directly by the first cell station indicating or triggering TX restricted mode of operation activation.

[0015] In a second variant of the first aspect combined with the first variant, the controller initiates the TX limited mode of operation when a transmit or receive operation meets one or more preconfigured signal strength / signal reception quality thresholds or one or more signal transmission failure thresholds, when the energy level of the wireless terminal falls below a certain threshold, or upon discovery of a relay station.

[0016] In a third variant of the first aspect combined with the first and / or second variants, the transmitter is adapted to transmit an initial signal to the first cell station and / or relay station indicating or triggering TX limited operation mode activation.

[0017] In a fourth variant of the first aspect in combination with one or more of the previous variants of the first aspect, the controller is adapted to alternately operate according to a first operation mode and a second operation mode, the first operation mode being a TX limited operation mode; a receiver adapted to receive, in a second operating mode, second downlink signals sent directly by the first cell station, the second downlink signals carrying respective second downlink control information, at least one of the respective second downlink control information including at least an indication of a third configuration parameter to be used by the wireless terminal to transmit an uplink signal directly to the first cell station, and at least one of the respective second downlink control information including at least an indication of a fourth configuration parameter to be used by the wireless terminal to receive a further downlink signal directly from the first cell station; The controller is adapted to generate uplink information; The transmitter is configured by the controller in the second operating mode to transmit to the first cell station using a third configuration parameter for direct communication to the first cell station, and the receiver is configured by the controller to receive a further downlink signal directly from the first cell station using a fourth configuration parameter.

[0018] According to an alternative and more specific definition of the first aspect, a wireless terminal for communicating in a cellular network is proposed, said cellular network comprising at least one first cell station serving a first cell and at least one relay station served by a second cell station serving a second cell, The wireless device a controller for alternatively operating the wireless terminal according to a first mode of operation (a direct mode of operation) and a second mode of operation (a TX-limited mode of operation); A receiver and a transmitter are provided, The receiver is adapted to receive, in a direct operation mode, first downlink signals sent directly by a first cell station, the first downlink signals carrying respective first downlink control information, at least one of the respective first downlink control information including at least an indication of first assigned uplink resources to be used by the wireless terminal to transmit a first uplink signal directly to the first cell station, and at least one of the respective first downlink control information including at least an indication of a number of first assigned downlink resources to be used by the wireless terminal to receive a further downlink signal directly from the first cell station. and adapted to receive, in a TX limited mode of operation, second downlink signals sent directly by a first cell station, the second downlink signals carrying respective second downlink control information, wherein at least one of the respective second downlink control information includes at least an indication of second resources to be used by the wireless terminal to transmit a second signal directly to the relay station, and wherein at least one of the respective second downlink control information includes at least second assigned downlink resources to be used by the wireless terminal to receive a further downlink signal directly from the first cell station; The controller is adapted to generate uplink information; In a direct operation mode, the transmitter is configured by the controller to transmit to the first cell station on a first assigned uplink resource for direct communication to the first cell station, and the receiver is configured by the controller to receive a further downlink signal directly from the first cell station on the first assigned downlink resource; In a TX limited mode of operation, the transmitter is further configured by the controller to transmit a second signal to the relay station on the second resources, the second signal carrying uplink information to be forwarded to the second cell station, and the receiver is further configured by the controller to receive a further downlink signal directly from the first cell station on the second allocated downlink resources.

[0019] Thus, the wireless terminal of the first aspect and its variants is capable of adapting its operation, for example as required or according to some command from the network. In a first mode of operation, the wireless terminal communicates directly with the first cell station. In a second mode of operation, the wireless terminal still receives messages from the first cell station, but does not transmit replies to the first cell station, but instead transmits to the relay station. This therefore allows lower energy consumption and / or lower transmission power to be used when transmitting in the case where the relay station is closer to the wireless terminal than the first cell station. Furthermore, the resources to be used are, however, still signaled by the first cell station in the downlink in this case. This avoids the wireless terminal having to connect to the relay station and sense whether control data is being sent to the wireless terminal by the relay station (which can be energy consuming and slow) depending on the available downlink bandwidth of the relay station (i.e. the sidelink bandwidth for downstream data) and on the method of resource allocation used for the sidelink transmission. Downlink data is transmitted directly by the first cell station, thus enabling a more reliable lower latency, higher data rate connection than an indirect connection through a relay station. Messages sent to the relay station (or the information that the messages contain) can be forwarded to the network through the cell station that serves the relay station.

[0020] The relay station may be served by a first cell station in a first cell, i.e. the same cell as the wireless terminal (which means that the second cell station is also the first cell station), or possibly by a second cell station in a different cell and thus separate from the first cell station.

[0021] In a variant of the first aspect of the invention, it is proposed that in a TX limited operating mode the transmitter is configured to refrain from transmitting on resources used for direct uplink communication to the first cell station.

[0022] This means that during the TX limited mode of operation, the wireless terminal does not use resources allocated for direct transmission to the first cell station. Thus, for example, no scheduling requests are sent directly to the first cell station, and no information is sent to the first cell station in the control plane. This is done, for example, by simply blocking the use of resources (such as frequency carriers, time slots, and / or codes (e.g., scrambling, channelization, or spreading codes, depending on the system type)) that are typically dedicated to transmission to the first cell station. In another example, transmissions on these resources are disabled by actively limiting the transmission range by blocking transmission powers above a threshold. This threshold is typically lower than the maximum transmission power achievable in the first mode of operation.

[0023] In a first variant of the first aspect of the invention, the receiver is further adapted to receive a third downlink signal sent by the first cell station, said third downlink signal carrying third downlink control information, said third downlink control information including at least an indication of scheduled downlink resources on which user data transmitted by the first cell station should be received, and the controller is adapted to configure the receiver to receive said user data. This variant is also applicable to the variants discussed previously.

[0024] Upon receiving the user data, the wireless terminal decodes the user data. The controller then generates uplink information, which may include an acknowledgement message based on a determination as to whether the user data was successfully decoded, and the acknowledgement message is transmitted by the transmitter to the first cell station using an uplink resource indication, e.g., assigned by a second configuration parameter when the controller is operating in a direct mode of operation, or to the relay station using a first configuration parameter, e.g., a first resource, when the controller is operating in a TX limited mode of operation.

[0025] In a second variant of the first aspect of the present invention, which may be combined with any of the previously discussed variants of the present invention, the wireless terminal includes a buffer memory configured to buffer uplink data to be transmitted, and the uplink information includes a buffer status report indicating an amount of uplink information currently buffered in the buffer memory.

[0026] Thus, a Buffer Status Report (BSR) in the second operating mode is indirectly transmitted to the network via the relay station, which then forwards the BSR to its respective serving cell station. The Buffer Status Report is typically a MAC control element indicating the amount of buffered data waiting for transmission for one or more logical channels or logical channel groups. This allows the network scheduler to grant resources for transmission according to the needs of the wireless terminal. This BSR can be in different formats, for example depending on the size of the resources available for the transmission of the BSR itself or depending on whether the BSR is transmitted via the uplink or the sidelink.

[0027] In an alternative to the second variant, the buffer status report is received by the relay station, which then processes the buffer status report. Such processing may include, for example, generating a new buffer status report that represents the amount of data (or corresponding resource needs) accumulated in the respective buffers of some or all of the wireless terminals for which the relay station serves as a relay.

[0028] In a third variant of the first aspect of the present invention, which may be combined with any of the previously discussed variants of the present invention, the uplink information comprises at least one uplink user data packet, the user data packet being sent directly to the first cell station in the second operating mode, and the user data packet being forwarded by the relay station to the second cell station in the first operating mode.

[0029] As previously explained, this respective serving cell station may be a first cell station if the relay station and the wireless terminal are included in the same cell and served by the same cell station. However, it is also possible that each serving cell station is a different cell station. Furthermore, it is important to note that the relay station may forward the message indirectly to the network through at least one or more further relay stations in some more advanced examples of the present invention. The BSR may include the transmission of user data packets.

[0030] In a fourth variant of the first aspect of the invention, which may be combined with the third variant, the receiver is adapted to receive further downlink control information comprising an indication as to whether the uplink user data packet has been successfully decoded.

[0031] Thus, after transmitting a user data packet (such as application layer information, IP packets, etc.) or a control message (such as BSR) to the relay station, the relay station forwards the user data packet or control message to the network, such as, for example, to a second cell station to which the relay station is connected. As previously explained, the second cell station may actually be the first cell station, for example, if the relay station is in the first cell, or may be a separate station, if the relay station is in a different cell. The second cell station receives and decodes the user data packet or control message or verifies the integrity of the user data packet or control message (e.g., using a cyclic redundancy check (CRC), a message authentication code, or a message integrity code). In an exemplary embodiment, if the message is correctly received and / or if the decoding is successful, the second cell station causes the first cell station to send an acknowledgement to the wireless terminal. This implies sending an instruction to send the acknowledgement over a backhaul channel (e.g., over the X2 interface linking the cell stations or over the core network). Alternatively, the second cell station forwards the received user data packet or control message to the first cell station, which decodes or verifies the integrity of the user data packet or control message and generates an acknowledgement if successful. Since the acknowledgement can be received directly from the first cell station, the wireless terminal does not need to sense the control resource from the relay station to obtain the acknowledgement. Note, however, that the HARQ timer (which triggers a retransmission if it expires without receiving a positive acknowledgement) needs to be adapted to this forwarding architecture. As an example, this HARQ timer is correlated to the number of hops (i.e. including the backhaul link) required to reach the first cell station. Or as another example, no HARQ-based retransmissions are sent by the wireless terminal, instead only PDCP-layer or IP-layer based retransmissions are sent.

[0032] It is also possible that the user data packet or control message is first acknowledged by the relay station, e.g., at the MAC level only to indicate that the first hop of the transmission was successful. Higher layer (e.g., PDCP layer or application layer) acknowledgements are sent directly and separately from the first cell station after the user data packet has been forwarded by the relay station.

[0033] According to a second aspect of the invention as defined in claim 12, a cellular communication system is proposed, the cellular communication system comprising: at least one first cell station serving a first cell; at least one relay station served by a second cell station serving a second cell; a wireless terminal served by a first cell station; Equipped with a first cell station comprising a first cell station transmitter for transmitting a first downlink signal carrying first downlink control information directly to a wireless terminal, said first downlink control information including at least an indication of a first configuration parameter to be used by the wireless terminal to transmit a signal to a relay station; a second cell station comprising a second cell station transmitter for transmitting a second downlink signal carrying second downlink control information to the relay station, said second downlink control information including at least an indication of a second configuration parameter to be used by the relay station to receive signals from the wireless terminal; the first and second configuration parameters at least partially overlap; a wireless terminal comprising a wireless terminal controller adapted to generate uplink information; and a wireless terminal transmitter configured by the wireless terminal controller to transmit a message carrying the uplink information to a relay station using a first configuration parameter; The relay station comprises a relay station receiver adapted to receive said message using second configuration parameters.

[0034] Accordingly, according to this second aspect of the present invention, for example, the first and second configuration parameters, which are the first and second resources, or some other parameter values, at least partially overlap. In some variations of this second aspect, the first and second resources correspond to each other. However, in some exemplary embodiments of the present invention, the second resource can actually be a large set of resources, such as a resource pool, to be monitored by the relay station. In this case, the first resource is included in the second pool, that is, one resource element from the resource pool.

[0035] However, in some further variations, the first cell station and the second cell station may use different (e.g., their own) time / clock references, which may be slightly different. This means that the first resource and the second resource are misaligned. In this case, this can result in, for example, the time of the second resource being slightly too short, that is, while they end at time t1, the transmission in the first resource ends at time t2, where t1 < t2. Conversely, the second resource may start slightly too late, that is, while they start at time t3, the transmission in the first resource starts at time t4, where t3 > t4. Due to these examples, the relay station fails to perform part of the transmission. To prevent this problem, some countermeasures are added. As an example, the wireless terminal repeats its transmission message multiple times. Further, when configured like that, the relay station starts receiving slightly before its signaling resource slot to account for the clock difference.

[0036] Alternatively, the first cell station emits a time synchronization signal that can be received by the wireless terminal, while the relay station also emits that time synchronization signal that can be received by the wireless terminal. Accordingly, the wireless terminal can adjust the time offset between the downstream communication (e.g., sent via sidelink) and the upstream communication, and thus can be synchronized with the time reference of the first cell station for reception and the time reference of the relay station for transmission.

[0037] Another solution to this above mentioned problem of different time references is the use of signaled resources that are slightly different (e.g. in length) from the actual resources used, for example if the first cell station and the second cell station use different resource configurations / numerologies.

[0038] In an alternative and more specific definition of the second aspect of the invention, the controller of the wireless terminal is configured to operate alternately according to a first operating mode (direct operating mode) and a second operating mode (TX-limited operating mode), the wireless terminal receiving in the direct operating mode first downlink signals sent directly by a first cell station, said first downlink signals carrying respective first downlink control information, at least one of the respective first downlink control information including at least an indication of first assigned uplink resources to be used by the wireless terminal transmitter to transmit a first uplink signal directly to the first cell station, at least one of the respective first downlink control information including at least an indication of first assigned downlink resources to be used by the wireless terminal receiver to receive a further downlink signal directly from the first cell station, and receiving in the TX-limited operating mode second downlink signals sent directly by the first cell station, said first downlink signals carrying respective first downlink control information. and an adapted wireless terminal receiver for receiving said second downlink signals carrying downlink control information, said respective second downlink signals carrying downlink control information, at least one of said respective second downlink control information including at least an indication of second resources to be used by the wireless terminal transmitter to transmit the second signal directly to the relay station, and at least one of said respective second downlink control information including at least second assigned downlink resources to be used by the wireless terminal receiver to receive further downlink signals directly from the first cell station, said controller being adapted to generate uplink information, and in a direct operation mode, the wireless terminal transmitter being configured by the wireless terminal controller to transmit to the first cell station on the first assigned uplink resources for direct communication to the first cell station, and the wireless terminal receiver being configured by the wireless terminal controller to receive further downlink signals directly from the first cell station on the first assigned downlink resources, In a TX limited mode of operation, the wireless terminal transmitter is further configured by the wireless terminal controller to transmit a second signal to the relay station on the second resource carrying uplink information to be forwarded to the second cell station, and the wireless terminal receiver is further configured by the wireless terminal controller to receive a further downlink signal directly from the first cell station on the second allocated downlink resource.

[0039] According to a second variant of the second aspect of the invention in combination with the first variant, the relay station comprises a relay station transmitter for transmitting a relay message comprising said uplink information to the second cell station.

[0040] According to a third variant of the second aspect of the invention in combination with the first or second variant, the second cell station is adapted to transmit a third downlink signal carrying third downlink control information to the relay station, said third downlink control information including at least an indication of third configuration parameters to be used by the relay station for transmitting a relay message to the second cell station.

[0041] The network therefore has full control and the ability to schedule the resources allocated for transmission from the wireless terminal to the network, and therefore allocates resources for each hop of the transmission, for example to the cell station. This means that the entire path (including multiple hops, if multiple relay stations are used) can be reserved for the transmission by the network scheduler, typically located in the cell station. Depending on the architecture, a second cell station controls all uplink allocations from the relay station to the network.

[0042] As previously described in relation to the first aspect of the invention, the first cell station and the second cell station may be a single cell station.

[0043] According to a fourth variant of the second aspect of the present invention, the first downlink signal and the second downlink signal may be a single downlink signal received at the wireless terminal and the relay station, thus reducing even further the control signaling required for resource allocation for message transmission.

[0044] Similarly to the fourth variant, and possibly in combination with the fourth variant, the second downlink signal and the third downlink signal may also be a single downlink signal received at the relay station, which reduces the allocation signaling even further since a single signal is used for allocation of all upstream paths.

[0045] In a fifth variation of the second aspect combined with any of the variations discussed previously, the relay station comprises a relay station controller for determining whether a message has been correctly received (e.g., by verifying the integrity of the received message) and / or correctly decoded (e.g., by the relay station itself or by a second cell station), and a relay station transmitter configured by said controller to transmit an acknowledgement message to the wireless terminal indicating whether the message has been correctly received and / or decoded.

[0046] In a sixth variant of the second aspect combined with any of the variants previously discussed, the message carrying the uplink information includes at least one uplink user data packet to be forwarded by the relay station to the second cell station.

[0047] In a seventh variant, which can be combined with the sixth variant, the first cell station transmitter is adapted to transmit an acknowledgement message indicating a correct decoding of the message by the second cell station or the first cell station.

[0048] According to a third aspect of the present invention, a relay station as claimed in claim 18 is proposed, the relay station operating in a cellular communication network comprising at least one first cell station and wireless terminals served by the first cell station, the relay station is served by a second cell station serving a second cell; The relay station, a relay station receiver adapted to receive a second downlink signal from a second cell station carrying second downlink control information, the second downlink control information including at least an indication of at least one first configuration parameter for receiving messages from a wireless terminal; and a relay station controller for controlling the relay station receiver to receive said message including uplink information in a first configuration parameter; a relay station transmitter adapted to forward the uplink information in a relay data message to a second cell station; Equipped with.

[0049] It should be noted that the relay data message may include control information and / or user data. Additionally, the relay data message may include uplink information itself (which may also be control information and / or user data) or information that is the result of some processing of the uplink information, including, for example, a combination with other information as described in the following embodiments.

[0050] In a first variant of the third aspect of the present invention, the relay station receiver is adapted to receive a third downlink signal from the second cell station, the third downlink control information carrying third downlink control information, said third downlink control information including at least an indication of allocated uplink resources to be used by the relay station to transmit a relay message to the second cell station.

[0051] In a second variant of the third aspect of the invention combined with the first variant, the relay station controller is adapted to determine whether the message has been correctly received (e.g. by verifying the integrity of the received message) and / or whether it has been correctly decoded (e.g. by the relay station itself or by a second cell station), and the relay station transmitter is configured by said relay station controller to transmit an acknowledgement message to the wireless terminal indicating whether the message has been correctly received and / or decoded.

[0052] According to a fourth aspect of the present invention, there is proposed a first cell station serving a first cell as claimed in claim 19 in a cellular communication system, the cellular communication system comprising: at least one relay station served by a second cell station serving a second cell; a wireless terminal served by a first cell station; Equipped with The first cell station a first cell station transmitter for transmitting a first downlink signal carrying first downlink control information to a wireless terminal, the first downlink control information including at least an indication of a first configuration parameter to be used by the wireless terminal to transmit a message to a relay station; a first cell station controller for configuring a relay station with second downlink control information, the second downlink control information including at least an indication of second configuration parameters to be used by the relay station to receive messages from a wireless terminal, the first and second resources at least partially overlapping; Equipped with.

[0053] In a first variant of the fourth aspect of the present invention, the configuring by the first cell station controller of the relay station includes the first cell station causing the second cell station to transmit a second downlink message to the relay station including the second downlink control information.

[0054] However, it should be noted that, as in other aspects of the invention, the first cell station and the second cell station may be a single cell station, which is the case, for example, when the wireless terminal and the relay station are served by the same cell.

[0055] According to a fifth aspect of the present invention, a method is proposed as claimed in claim 20 for operating a wireless terminal to communicate in a cellular network, the cellular network comprising at least one first cell station serving a first cell and at least one relay station served by a second cell station serving a second cell, The method is: receiving, by the wireless terminal, a downlink signal sent by a first cell station, the downlink signal carrying downlink control information, the downlink control information including at least an indication of a first configuration parameter to be used by the wireless terminal to transmit a message to the relay station; generating uplink information by a wireless terminal; a wireless terminal transmitting a message conveying uplink information to a relay station using a first configuration parameter, the uplink information being to be forwarded to a second cell station; has.

[0056] According to a seventh aspect of the present invention there is proposed a computer program product comprising code means for producing the steps of the method of the sixth aspect of the present invention when executed on a computing device.

[0057] It is pointed out that the above apparatus may be realized based on a discrete hardware circuit arrangement involving an arrangement of discrete hardware components, integrated chips, or chip modules, or based on a signal processing device or chip controlled by a software routine or program stored in a memory, written on a computer readable medium, or downloaded from a network such as the Internet.

[0058] It is to be understood that the wireless terminals, systems, relay stations, cell stations and methods have similar, corresponding and / or identical preferred embodiments, in particular as defined in the dependent claims.

[0059] It is to be understood that preferred embodiments of the invention are also possible in any combination of the dependent claims or embodiments with the respective independent claim.

[0060] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0061] [Figure 1A] 1 is a block diagram illustrating a network in which the present invention may be implemented; [Figure 1B] 1 is a block diagram illustrating a multi-hop network in which the present invention may be implemented. [Figure 2A] This is a block diagram showing the layer model of the user plane based on the relay architecture. [Figure 2B] FIG. 1 is a block diagram illustrating a layer model of a control plane according to a relay architecture. [Diagram 3] FIG. 1 is a block diagram illustrating a network using a multi-hop relay architecture of cell stations. [Figure 4] FIG. 1 is a block diagram illustrating a network according to a first embodiment of the present invention. [Diagram 5]4 is a flowchart showing the operation of the network according to the first embodiment. [Figure 6] 1 is a block diagram illustrating a wireless terminal according to a first embodiment. [Figure 7] FIG. 2 is a block diagram illustrating a relay station according to the first embodiment. [Figure 8] 1 is a block diagram illustrating a cell station according to a first embodiment. [Figure 9] FIG. 4 is a block diagram illustrating a network according to a second embodiment of the present invention. [Figure 10] FIG. 4 is a block diagram illustrating a network according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram illustrating a network according to a fourth embodiment of the present invention. [Figure 12] FIG. 10 is a block diagram illustrating a network according to a fifth embodiment of the present invention. [Figure 13] A block diagram showing a network using dual connectivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] In the following, the embodiments are described in the context of a 3GPP® cellular network, but these embodiments may also be applied to other types of networks. As previously described, cells are served by cellular base stations, referred to in 3GPP® as "eNBs" (4G terminology) and "gNBs" (5G terminology). The eNBs / gNBs are part of the radio access network RAN ​​and interface to the functions of the Core Network (CN). "UE" is "user equipment" and is the standard name in 3GPP® for a wireless client device or a specific role played by such a device. The term "node" is used to represent a UE or a gNB / eNB. "NF" represents the network function of the CN.

[0063] "Indirect network connection" is as defined in TS 22.261. "D2D" is device-to-device communication and "PC5" is an interface for using sidelink communication as defined by V2X (TS 23.287) or ProSe (TS 23.303, TS 23.304, and TS 38.300). "UL" is used for uplink Uu communication as defined in TS 38.300, "DL" is used for downlink Uu communication as defined in TS 38.300, and "Sidelink" or "SL" is used for sidelink communication as defined in TS 38.300.

[0064] In the following description, "upstream" or "uplink" is used for data flows going towards a cell station, e.g., a gNB, while "downstream" or "downlink" is used for data flows from a gNB going towards a UE in the RAN. "User data" is used for any type of user data or application data that is not related to the management or operation of cellular network functions (typically at or above the IP layer). Upstream transmission involves an indirect network connection via one or more relay stations, so that signals / messages are first sent to a relay station, which then forwards the signals / messages to the gNB. Relay stations support UL (Uu interface) and / or SL (PC5 interface). Thus, upstream transmissions occur on UL (Uu interface) and / or SL (PC5 interface), depending on the network configuration and context. In the context of this patent application, unless otherwise specified, the wireless terminal typically uses the term "downlink" for transmissions on the DL (Uu interface) because the wireless terminal is capable of receiving signals / messages directly from a cell station (even when operating in a limited transmission mode to send upstream signals / messages), and typically uses the term "downstream" for indirect communication via a relay station, and therefore transmissions may also occur over the SL (PC5 interface) depending on the network configuration and context.

[0065] In the cellular network in which the present invention is implemented, each cell 10 is served by a base station 100, as mentioned before with reference to FIG. 1A. There are multiple secondary stations near the cell 10 and near the base station 100. At least some of these secondary stations can communicate directly with the base station 100. Furthermore, some of the secondary stations can function as relay stations 120, since they include a function for relaying communication between the base station 100 and another secondary station 110. This relay function serves, for example, to extend the coverage of the cell 10 to an out-of-coverage (OoC) secondary station 110. The relay station 120 can be a mobile station (e.g., a UE) or a different type of device. The cellular network can be, for example, a 4G or 5G network, or some other type of cellular network. Since the 4G and 5G networks include the possibility of relaying by UEs with sidelink capabilities, the relay station 120 and the secondary station 110 in FIG. 1A are, in this example, UEs with sidelink capabilities. Although FIG. 1A is limited to a single-hop architecture, various embodiments of the invention described herein may also be applied to the case of a multi-hop architecture, such as that shown in FIG. 1B.

[0066] Communicating directly with a base station has some drawbacks or may not even be possible for some periods of time. Direct communication with a base station requires high energy consumption and / or high energy peaks to transmit messages with sufficient radio transmission power, which is not acceptable for (wireless, typically battery-powered) wearable UEs or IoT UEs. Sometimes conditions may even worsen (due to interference or further attenuation), making transmission impossible. In practice, a UE (e.g. an IoT device) has limited radio transmission power and therefore can no longer reach a base station (gNB) using the available and / or selected transmission modes when the UE is far away, when it moves out of range, and / or when it is interfered with or has new obstacles on the transmission path. On the other hand, the UE still receives transmissions from the gNB despite the worsened conditions, thanks to e.g. more flexible and robust transmission modes at the gNB, or higher available transmission power.

[0067] Current solutions defined in 3GPP allow a wireless terminal acting as a full or partial OoC remote UE (e.g., intermittently out of coverage or therefore lacking sufficient signal quality for transmissions to a cell station (e.g. gNB) leading to many retries or message losses) to communicate via a relay station acting as a relay UE to send upstream data or receive downstream data. However, all communication with remote UEs is currently performed via a Sidelink (SL) channel and uses the self-scheduling method of resource selection (mode 2) for remote UEs. This self-scheduling has several problems: - Self-scheduling requires the remote UE to extensively "sense" the designated sidelink time / frequency resources to determine when it can transmit to or receive messages from the relay UE. This sensing increases energy consumption. This high energy consumption for (wireless, typically battery-powered) wearable UEs or IoT UEs is unsatisfactory due to the limitations of portable devices and especially for IoT devices. - While self-scheduling restricts the remote UE to use only pre-configured resources, the so-called sidelink resource pool, for sidelink transmissions to relay UEs, in practice there may be further more optimal resources available but which the remote UE is not currently authorized to use. - Furthermore, remote UEs have to compete for (potentially scarce) sidelink resources with other UEs that are out of coverage (e.g. other OoC remote UEs connected to the same relay UE) or with OoC UEs that rely on sidelink communication for their applications, e.g. ProSe D2D or V2X D2D applications. Many users of sidelink spectrum resources combined with a self-scheduling approach (no central orchestration by the gNB for OoC UEs) can increase radio transmission collisions and increase the probability of transmission failures to and from relay UEs. - The potentially limited bandwidth available for downstream data to indirectly connected remote UEs (via relay UEs) may in certain cases result in insufficient downstream data capacity. For example, one reason for this bottleneck is that the resources allocated for sidelink (SL) communication required by a relay UE to send data to a remote UE are a very limited subset of the total set of available cellular resources. b. Another reason is that the relay UE needs to simultaneously serve other remote UEs, and therefore the scarce resources of the relay UE (spectrum, processing time, buffer memory, etc.) need to be split across multiple devices. Other remote UEs have a higher priority to be served by the relay. - Furthermore, if the relay UE needs or wants to apply the DRX feature for power saving, it may happen that the remote UE transmits to the relay UE when the relay UE is in its DRX sleep / inactive state, or the remote UE has to wait until the relay UE is in DRX active state before transmitting, which may increase latency or possibly cause some data loss. - There is a possibility of packet collisions due to overlapping resource allocations (mode 2) when a remote UE is out of coverage and therefore no resources are scheduled for it to transmit.

[0068] A known solution for scheduling SL resources for relay UEs directly connected to a gNB is described in TR37.985 v16.0. The gNB sends a DCI format 3_0 / 3_1 message to the relay UE, which can then transmit in SL on the indicated resources. However, the inventors of the present invention have recognized the following drawbacks to this known solution: ● Since the DCI message is only directed towards the relay UE, the remote UE is not aware of the scheduled resources, and therefore does not know when to prepare to receive in SL from the relay UE. ● This known solution cannot be used to schedule resources for remote UEs for transmission. In fact, in the current specification, scheduling messages are not sent to OoC UEs - including partially OoC UEs such as transmission limited UEs (as will be explained in more detail later). Therefore, the remote UE does not know when / how best to transmit in SL so that the relay UE receives the scheduling message, and the remote UE may perform as bad as self-scheduling.

[0069] The proposed embodiment of the present invention overcomes these shortcomings by defining a scheduling and data transmission method such that both relay and remote UEs are informed about the resources to use for communication, e.g. in situations where the remote UE has limited connectivity.

[0070] By limited connectivity, it should be understood that this may be due to external conditions and design / operational choices of the remote UE. For example, the remote UE may encounter limited connectivity due to its location (e.g., at the edge of a cell, or inside a building) where direct uplink transmission to the base station becomes too expensive in terms of energy or power, or due to its capacity (low remaining battery charge, low power device such as energy harvesting terminal), or leads to many retries or message loss due to poor signal quality. In another example, the remote UE is used in a location where transmission levels are not allowed to exceed a threshold (hospital, laboratory where radiation levels must remain within a given range). These limitations correspond to TX-limited wireless terminals that are not capable (or preferably not) of transmitting directly to a cell station.

[0071] Such an asymmetric situation of inability to send a reply may arise due to inherent TX limitations at the wireless terminal (or remote UE) - such as one or more of the following examples: 1. The maximum allowable peak current drain from a wireless terminal battery due to, for example, a small battery form factor such as a coin cell or due to the inherent battery chemistry. 2. Maximum allowed transmit power of a wireless terminal radio, for example by using low cost / low power / compact form factor radio modules. 3. Limited duty cycle available for high power transmissions, for example when the high power Tx mode is powered via a battery with limited output current or by an (ultra)capacitor charged through energy harvesting. 4. Suboptimal antenna design, e.g., limited number of antennas or low effective radiated Tx power due to the small form factor of the wireless terminal. While a cell station compensates for this limitation by increasing its transmit power and / or increasing signal repetition or other means, the wireless terminal cannot compensate due to one or more of limitations 1, 2, 3, or 8. 5. Sub-optimal device placement that obstructs wireless terminal transmissions, e.g., embedded UE or M2M modules placed in basements, deep indoors, etc. The cell station compensates for this limitation by increasing its transmit power and / or increasing signal repetition or other means, but the wireless terminal cannot compensate because of one or more of limits 1, 2, 3, or 8, or because the location (e.g., human body) limits transmit power due to regulations. 6. Inability to perform (effective) Tx beam steering towards the cell station, e.g. due to a small number of antennas or limited capacity for signal processing at the wireless terminal. The cell station compensates for this limitation by increasing its transmission power and / or increasing signal repetition or other means, but the wireless terminal cannot compensate due to one or more of limitations 1, 2, 3, or 8. 7. In general, the "asymmetric" nature of the cell station transmitter and the wireless terminal transmitter. 8. Limited support in the UE for coverage extension modes, such as increasing the number of repetitions of sending messages to a cell station. 9. The transmit and receive frequencies are different (e.g. FDD) or the modulation for the transmit / receive signals is different, resulting in different transmit vs receive link budgets. 10. The wireless terminal has limited energy for transmission (e.g., remaining battery power is low or the energy harvesting capacitor is not yet fully charged) but still has an urgent / important message to be sent (e.g., an emergency SMS).

[0072] Thus, as explained above, one object of the present invention in the case of a TX-limited wireless terminal is to solve the above problem for the specific case where the wireless terminal is capable of receiving a transmission from a cell station (i.e. a channel on the DL) but is not capable of physically transmitting a reply (i.e. over the UL), or is capable in principle of transmitting a reply but does not do so in order to save energy usage or for other reasons (e.g. possible local usage rules).

[0073] Conversely, limited connectivity also includes Rx-limited stations that are capable of transmitting directly to a cell station but cannot receive directly from it, which may be due to poor receiver sensitivity or local interference (e.g., coexistence with a Wi-Fi network near the wireless terminal).

[0074] The “asymmetric” aspect mentioned in point 7 above is about the difference between the cell station transmitter and the wireless terminal transmitter, which in some circumstances can make it more likely that the cell station can transmit to the wireless terminal than vice versa, due to: 1. High power (dBm) available for transmission at a cell station versus low power at a wireless terminal 2. Different frequency bands are used for transmission and reception, resulting in a higher link budget for the downlink than for the uplink 3. Wall-powered cell stations versus battery-powered (or energy-harvested) wireless devices.

[0075] In view of these cases, it is recognized by the inventors that the above list of limitations will become relatively common cases in the future as 5G is increasingly adopted for wearable, low power, and IoT devices.

[0076] Other work in 3GPP, discussed in TR23.733 and TR36.746, includes consideration of architecture enhancements to allow wireless terminals, such as IoT devices (in the role of remote UEs), to operate at very low power, for example by connecting to a wider network using relay stations acting as relay UEs. Relay UEs can be reached using very low power transmissions, since they are physically very close. These discussions lead to several new relay architectures, including Layer 2 (L2) relay architectures. Layer 2 of the OSI model corresponds to the data link layer or radio layer 2 in 3GPP (RLC, MAC, PDCP), while Layer 3 of the OSI model corresponds to the network layer (Internet Protocol layer). This L2 relay architecture, unlike ProSe 4G relay, which operates at the application layer (L3, roughly the Internet Protocol IP layer), is intended to provide end-to-end IP and PDCP packet transmission to and from wireless terminals, as shown in Figure 2A for the user plane stack. Similarly, as can be seen in Figure 2B for the control plane stack, an L2 relay for the control plane data is proposed.

[0077] Such an architecture allows a wireless terminal acting as a remote UE to be directly visible as a registered entity in the core network. This brings several advantages for applications like monitoring or billing, and for improved control by cell stations via the wireless terminal. Furthermore, the wireless terminal has access to all the functions of the core network as if it were directly connected. It should be noted that alternative relaying architectures exist and are very similar to the 4G case, such as the proposal for Layer 3 (L3) relaying in ProSe 5G (user plane only) in TR 23.752. Furthermore, other types of relaying devices have been or are being discussed (see, for example, TR 22.859), such as using a UE as a gateway UE (e.g. mobile phone or residential gateway) to relay traffic of personal IoT devices (e.g. wearables, in-home devices) to the 5G network.

[0078] Additionally, 3GPP is further working on new features discussed in TR38.874 for Integrated Access and Backhaul (IAB) to enable relaying between cell stations. The purpose of IAB is to make it easier to expand the coverage area of ​​5G radio access networks through the deployment of additional intermediate wirelessly connected cell stations or small cells. The main difference with UE-based relaying (such as sidelink) is that in IAB the devices are very sophisticated devices with many resources, while in UE-based relays the wireless terminals can be very low-power resource-limited devices with very few resources to dedicate to act as relay stations. Furthermore, in IAB the cell stations are typically owned and operated by the same network infrastructure provider, while in the case of UE-based relays the relay stations acting as relay UEs will typically be owned by many different individuals with different subscriptions for each mobile network operator. Furthermore, in the case of relay UEs, the mobile network operator wants full authorization control over which UEs can act as relay UEs and which remote and relay UEs are allowed access to the mobile network, whereas in IAB this is seamlessly integrated in the core network. The mobile network operator also wants full control over the resources / frequencies that relay UEs can use for sidelink communication with remote UEs, whereas in IAB the intermediate nodes have more autonomy in scheduling resources for downlink devices. Note that in some cases (e.g. 3GPP also discusses the use of in-vehicle IAB nodes (see, e.g. TR22.839)), some of these characteristics and procedures (e.g. ownership, authorization, resource allocation) are more similar to relay UEs than to base stations.

[0079] As shown in Figure 3, this architecture uses a mechanism similar to ProSe repeaters, where an IAB node can relay traffic for other IAB nodes towards an IAB donor. Communication between IAB nodes uses the 5G defined interface "F1", as defined in TS38.473, between a base station central unit (CU) and its linked distributed unit (DU), typically used for distributed cell stations. For registration and some control information, the IAB node further includes a mobile terminal / UE component.

[0080] However, these improvements cannot solve all the previously mentioned problems related to sidelink scheduling on the one hand, and direct communication with unreliable base stations, which requires high energy consumption on the other hand.

[0081] Thus, according to a first embodiment of the invention, a cellular network is proposed as shown in Fig. 4, with a cell station 400, for example a gNB 400 serving a cell 40. A number of secondary stations are included in this cell. A first type of secondary station 410 is a secondary station that encounters (or requests) a restricted connection. In this embodiment, this restricted connection corresponds to a transmission restriction as previously explained, in the sense that direct transmission to the cell station is prevented (or blocked). This first type of secondary station is a wireless terminal, for example a remote UE 410. Secondary stations of a second type, also in this example in the first cell, act as relay stations 420, i.e. have sufficient capacity and suitable functionality to act as relays between the cell station and other secondary stations. These relay stations 420 are between the cell station 400 and the first type of secondary station, i.e. the wireless terminal 410, or possibly the second type of secondary station (i.e. the relay station 420) in case of a multi-hop system (not shown in Fig. 4). This relay station 420 acts as a relay UE 420 only for the upstream flow. This first embodiment allows an upstream data flow 411 and a downlink data flow 401 (including both e.g. data traffic and control information, sent e.g. over the respective channels). According to this embodiment, the direct radio link 401 (DL) from the cell station 400 to the wireless terminal 410 and the relay station 420 is used to schedule resources to the wireless terminal and the relay station and to publish the downlink data. The indirect link 411 between the wireless terminal 410 and the cell station 400 through the relay station 420 can be used for the upstream data. Another downlink direct link 402 between the cell station 400 and the relay station 420 is used to schedule the upstream resources (e.g. sidelink resources) to be used between the wireless terminal 410 and the relay station 420 on the one hand, and the uplink resources to be used between the relay station 420 and the cell station 400 on the other hand. Additionally, relay station 420 uses its own uplink connection 403 for transmission to cell station 400 .In Fig. 4, this uplink connection 403 is direct to the cell station 400. However, in the case of a multi-hop relay system, this uplink connection 403 is indirect. Note that in various embodiments below, upstream link 411 is logically included in uplink connection 403 (allowing for more flexibility in connections). Alternatively, the operation of the various embodiments below can be adapted to keep link 411 and link 403 as separate logical (or possibly physical) links.

[0082] Thus, it is proposed that a cellular wireless communication system includes at least one cell station 400, at least one secondary station 420 acting as a relay station 420 (e.g. a relay UE), and at least one wireless terminal 410 (e.g. acting as a remote UE). In this embodiment, the cell station 400 is capable of transmitting one or more communication resource reservation messages via the downlink direct links 401 and 402 to indicate at least one of the following: - downlink resources, also referred to as "DL resources", for future downlink data transmissions from the cell station 400 directly to the wireless terminal 410; - upstream resources, also called "Us resources", for future upstream data transmissions from the wireless terminal 410 via the SL and / or UL, and - Upstream resources for reception by the relay station, also referred to as "Us-Rx resources", at the secondary station 420 functioning as a relay station 420, for receiving upstream data transmissions from the wireless terminal 410, typically via SL and / or UL.

[0083] The uplink and upstream resources may be the same or based on the same resource pool, or may be based on separate resource pools. The uplink and upstream resources may not be distinguishable by the wireless terminal 410 or the relay station 420 (this is the case, for example, when the uplink resources are shared with a relay station to enable the relay station 420 to act on behalf of a cell station (as depicted later). However, the uplink and upstream resources are typically distinguishable and thus the cell station can indicate which type the cell station is, for example, by using a different DCI format or a different RRC message. Optionally (as applied to any other embodiment), the first cell station schedules both direct uplink resources (e.g. for communication over the Uu interface) and upstream resources (e.g. for communication over the sidelink, e.g. to a relay station) for the wireless terminal 410 and / or sends information about both uplink and upstream resources in the first message to the wireless terminal and / or sends configuration information about conditions or thresholds for which circumstances the uplink resources should be used and the upstream resources should be used. A wireless terminal receiving both sets of resources sends copies of that message / signal in both uplink and upstream resources or selects which resources to use based on configuration information received from the cell station about the conditions or thresholds to apply or based on pre-configured conditions or thresholds (e.g. stored in the USIM). These conditions / thresholds are the same as or overlap with the conditions / thresholds based on which the wireless terminal decides that it will or should operate in the TX restricted mode.If the wireless terminal determines to operate in the TX restricted mode, the wireless terminal will communicate with the relay station using upstream resources instead of using uplink resources, and will adjust its transmit power depending on whether uplink or upstream resources are used and / or whether the wireless terminal is configured by the cell station with uplink or upstream resources. The cell station configures the wireless terminal (e.g., through control signals / messages, e.g., as part of SIB, RRC, or DCI signals / messages, or as part of UE policy information) with information about transmit power limits (e.g., minimum or maximum) and / or recommended transmit powers to use for different (types of) resources (e.g., uplink via Uu, or upstream via sidelink), for different destinations (e.g., identified via a given identifier if a particular relay station is to be used), and for different modes / situations / coverage levels / signal quality thresholds in which the device (e.g., a wireless terminal operating in the TX restricted mode) will operate. The wireless terminal uses this configuration information to determine which transmit power to use.

[0084] It should be noted that this architecture is part of a special operating mode, and a different architecture is typically used, such as a conventional architecture having a direct duplex link between the wireless terminal and the cell station. As will be described in more detail later, an operating condition or some other event triggers the network, the cell station, the relay station, and / or the wireless terminal to operate in this special operating mode (i.e., TX limited mode).

[0085] In any event, according to this architecture, a mechanism is included for operating a secondary station, e.g., a wireless terminal 410, e.g., a remote UE, in communication with a cell station 400 in a cellular network. This first cell station 400 serves a first cell 40. Additionally, in this cell, at least one other secondary station 420 is operable as a relay station 420. As depicted in FIG. 5, the mechanism includes the following steps: S51: The first cell station 400 sends a first message to the wireless terminal 410 carrying first downlink control information including an indication of allocated upstream resources. S52: The first cell station 400 sends at least one second message carrying second downlink control information to the relay station 420. This second downlink control information is carried by one or more messages and includes information about upstream allocated resources on which the wireless terminal intends to transmit the message to the relay station 420. The second downlink control information further includes a message for allocating resources to be used by the relay station 420 when forwarding the message. S53: The first message is detected by the wireless terminal 410, which decodes the message to obtain an indication of allocated upstream resources available for use by the wireless terminal 410 to transmit an upstream signal to the relay station 420. S54: The wireless terminal 410 generates uplink information to be included in the message (i.e. information (e.g. user data) to be transmitted directly to the gNB over the Uu interface in normal bidirectional communication mode) and uses the allocated upstream resources to transmit an upstream signal carrying the message to the relay station 420. Note that the uplink information is intended to be forwarded to the cell station 400. For this purpose, the uplink information is appended / pre-pended / updated / multiplexed with information about the relay station (e.g. L2 identifier or other identifier of the relay station) as part of the upstream message. S55: The relay station 420 receives a message from the wireless terminal 410 on the upstream resources allocated by the cell station 400. S56: The relay station 420 optionally processes the message, if necessary, and forwards the uplink information (or upstream signal / message) to the cell station 400.

[0086] In this embodiment, only one cell station 400 is included, but this mechanism can be adapted to cases where more than one cell station needs to operate. As will be detailed in further embodiments, this is the case, for example, when the relay station is not served by the cell station 400 but by another station, for example if the relay station is in a different cell. As will be detailed later, the first cell station 400 takes care of sending a message containing a resource allocation (e.g. Us resources and / or Ds resources) to the wireless terminal 410, while the different station transmits resource allocations, e.g. UL resources and Us-Rx resources (respectively for the UL and coming from the wireless terminal via SL), for the relay station 420.

[0087] Note that the message sent in step S51 and the message sent in step S52 are merged (e.g., tied together or encoded together in a single message using a common identifier for both the relay station 420 and the wireless terminal 410). Alternatively, as described above, these messages allocating resources for the wireless terminal 410 to transmit and for the relay station to receive are sent via two separate messages that are decoded by both UEs. These messages could be sent by the first cell station 400, or in the case of two cell stations, by either cell station, or each message could be sent by one of the cell stations.

[0088] Additionally, the first cell station 400 directly signals the scheduled downlink transmission to the wireless terminal. In an example, this signaling occurs in the same frame as the downlink transmission. Thus, the wireless terminal 410 can receive downlink data on DL resources signaled by the first cell station and transmit upstream data on the assigned Us resources. This upstream data includes, for example, at least one of user data that is to flow to or beyond the core network or feedback data, such as, for example, an acknowledgement (ACK / NACK), describing the status of whether the wireless terminal 410 correctly received downlink data previously sent directly to the wireless terminal 410 by the first cell station 400.

[0089] Optionally, the relay station 420 sends acknowledgement data (e.g., HARQ signal) to the wireless terminal 410 as soon as the upstream signal of step S54 is received. This acknowledgement data thus indicates correct / incorrect reception of this data signal. For this purpose, the first cell station 400 includes HARQ process information (e.g., HARQ process ID, timing / resource information), for example, in the second downlink control information of step S52. In an example, the relay station 420 can act on behalf of the first cell station to send HARQ feedback information back to the wireless terminal 410. The first cell station further provides (e.g. as part of the second downlink control information) some security certificates or information about the type, format, encoding, scrambling or content of the signal or message to enable the relay station 420 to verify the integrity of the message or to (partially) decode the message / signal, and further provides instruction / policy information under which conditions the relay station 420 is allowed to send acknowledgement data to the wireless terminal (410) (e.g. if the CRC or message integrity code / message authentication code is verified as correct). The relay station 420 uses the information received from the first cell station to perform some processing on the upstream signal / message received from the wireless terminal 410, and sends the acknowledgement data to the wireless terminal 410 if the result of this processing satisfies one or more conditions. Alternatively, the relay station 420 may first forward the received upstream signal / message (or the uplink information added to a different message after processing) to the first cell station, which may then send a signal / message to the relay station 420 upon successful reception / decoding / integrity verification of the forwarded upstream signal / message (or a different message containing the uplink information) (instead of sending the authorization data directly to the wireless terminal 410), and thus the relay station 420 may then send the authorization data to the wireless terminal 410.

[0090] It should be noted that the upstream signal in step S54 sent on the assigned Us resource is incidentally received directly by the first cell station 400 (e.g., if the channel conditions improve momentarily). Thus, the data sent in step S54 can in fact be transmitted directly to the cell station 400, and the link to the relay station 420 can serve as a backup in case the direct transmission power level is insufficient. This is particularly relevant for the case where the wireless terminal 410 is at the edge of the Tx connection to the cell station 400, and its transmission may be correctly received by the first cell station 400. In that case, the cell station 400 can directly process the upstream signal / message containing the uplink information. The cell station 400 informs the relay station 420 (e.g., through a second control signal) that the upstream signal (e.g., identified by its upstream resource, message identifier, or other part of the message) has already been correctly received directly by the first cell station 400. The relay station 420 may then discard the message, avoid sending the message to the cell station 400 , or avoid sending the grant data to the wireless terminal 410 .

[0091] As mentioned in step S56, the relay station 420 can relay the uplink data received from the wireless terminal 410 upstream towards its upstream cell station via one or more hops. For each hop, there is a HARQ feedback. The uplink data is then finally received by the first cell station 400. In the case where the data includes upstream user data, the receiving cell station directly sends feedback data, e.g., an ACK / NACK, back to the wireless terminal 410 in a future downlink (DL) transmission using the new Ds resource indicating whether the user data was successfully received. In the case where the user data was not correctly received, the feedback data, e.g., a NACK, indicates to the wireless terminal 410 that at least a portion of the previously transmitted data is missing. The cell station 400 then directly schedules a retransmission of the data by the wireless terminal 410. This can be done by allocating future Us resources. The retransmission is then possibly relayed through the relay station 420.

[0092] In a particular variation of this embodiment, the cell station instructs the wireless terminal in the TX-Restricted state (e.g. via a SIB / RRC message sent as part of the first or second downlink signal) to operate with a sidelink mode 2 resource allocation, and at the same time, the wireless terminal in the TX-Restricted state uses the sidelink mode 2 resource allocation instead of the scheduled upstream or uplink resources. In accordance with what has been mentioned previously, the wireless terminal limits or reduces its transmit power when using these Mode 2 resources in the TX-Restricted state.

[0093] According to a first embodiment and now with reference to FIG. 6, a wireless terminal acting as a wireless terminal 410 typically comprises an antenna 61 or an antenna array (e.g. in the case of a MIMO compatible wireless terminal). This antenna 61 is coupled to a communication unit 62 comprising a receiver 621 and a transmitter 622. The communication unit 62 is compatible with a 3GPP® standard such as UMTS, LTE or NR and operates accordingly depending on the current connection. In an embodiment, a controller 63 such as a microprocessor for controlling the communication unit and its receiver 621 and transmitter 622 is included. It is noted that the controller 63 is dedicated to the communication unit 62 and possibly included therein. The controller 63 further operates other systems and is not only dedicated to the communication unit 62. Typically, some or all of the processes involved are operated by software stored in the memory 64 of the wireless terminal 410. However, it is also possible that the entire invention is included in hardware within the components. It is noted that the wireless terminal includes functionality for operating according to a relay architecture such as a sidelink defined in a 3GPP® network.

[0094] In an embodiment, the controller 63 causes the communication unit to operate in a TX restricted mode (i.e., a mode in which the wireless terminal is unable (or undesirable) to transmit directly to the cell station and in which the wireless terminal reduces its transmit power but can still receive downlink signals from the cell station). This can be implemented according to an architecture as described with reference to FIG. 4 or in any of the further embodiments detailed further herein. The controller 63 is capable of configuring the receiver and transmitter of the communication unit and is capable of generating uplink data (e.g., user data, acknowledgement data, buffer status information). Depending on currently encountered conditions or based on a specific trigger message, the controller 63 switches to the TX restricted mode of operation.

[0095] In the TX restricted mode, the receiver is adapted to receive first downlink signals conveying respective first downlink control information (used herein as a generic term for any control / configuration related information not necessarily limited to DCI related content / messages) sent directly by the first cell station, one of the respective first downlink control information including configuration parameters (such as a first resource indication, a transmission mode indication, or an operating mode indication, or one or more other parameters related to communication (reception or transmission)) to be used by the wireless terminal to transmit a second signal (i.e. an upstream signal / message) to the relay station, and at least one of the respective first downlink control information including at least a second assigned downlink resource to be used by the wireless terminal to receive a further downlink signal directly from the first cell station. The configuration parameters are, for example, resources, frequencies, time / wake schedules, information about which modulation or signal encoding or scrambling or transmission power should be used for the upstream signal / message, information about which particular type of upstream signal / message should be used (such as sidelink discovery message), and / or L1 / L2 source or target identity information (or other identity information such as User Information ID, PRUK ID, SUCI, SUPI, GUTI, or RNTI) to use in the upstream signal / message (e.g. relay station identity), or a set of particular security credentials to be used for the upstream signal / message. The receiver is further adapted to receive a further downlink signal directly from the first cell station on the second allocated downlink resources. Optionally, the resource reservation message and the data transmission occur within the same radio frame.

[0096] In the TX limited mode, the transmitter is adapted to transmit a second signal (i.e., an upstream signal / message (e.g. as in step S54 above)) carrying uplink information to the relay station on the first resources and / or to use the received configuration parameters to generate an upstream signal / message having desired characteristics (e.g., having a particular transmit power, frequency, modulation format, coding scheme, protection mechanism based on battery level), which uplink information will be forwarded to the second cell station (e.g. by forwarding the received upstream signal / message and / or by sending a different message including the uplink information).

[0097] As an option in this embodiment (and also applicable to other embodiments), the controller initiates TX restricted mode operation after the receiver receives a downlink signal sent directly by the first cell station (e.g., after the first cell station determines through measurements that the wireless terminal's uplink signal is of insufficient quality) indicating or including a trigger to activate the TX restricted mode. As mentioned before, this triggers a reduction in the transmit power or various resources to be used (e.g., upstream resources directed towards the relay station, rather than uplink resources for direct Uu communication with the first cell station). For this purpose, the cell station transmits, as a downlink signal or as a specific downlink signal for this purpose (e.g. with a specific waveform or frequency), a separate TX Restricted Mode Switch message or TX Restricted Mode information element, for example as part of a SIB or RRC message or wake-up signal (i.e. a specific signal received by the wake-up receiver to wake up the main radio communication module, similar to a WUS as specified in e.g. 3GPP TS36.300 and TS36.213 or similar to IEEE 802.11ba, and thus the trigger to switch to the TX Restricted Mode is indicated by the specific timing / resource / identity used or through the wake-up signal payload). Such a message / information element / signal includes the identity of the wireless terminal (e.g. L2 identity, SUCI / SUPI / GUTI or RNTI) or the identity of the group of devices to which the wireless terminal belongs (e.g. L2 group identity), so that the wireless terminals are able to determine that the message / information element / signal applies to the respective wireless terminal.The above mentioned messages / information elements / signals need to be encrypted (e.g. using a pre-shared key or a public key received from the first cell station (signed by the core network or a certificate authority) or using a previously used key (e.g. based on a Kamf or Kausf or ProSe Remote User Key (PRUK))) or a key derived from this key) to prevent a malicious device being able to use such messages to force the wireless terminal to switch to TX-restricted communication.

[0098] As another option (for this and other embodiments), the controller initiates TX restricted mode operation if the transmission or reception operation satisfies one or more (pre-)configured conditions (e.g. configured by the cell station through SIB / RRC messages or through UE policy information (e.g. from PCF) or pre-configured in the USIM) or (pre-configured) signal strength / signal reception quality thresholds or signal transmission failure thresholds, or if the energy level of the wireless terminal falls below a certain threshold. This decision may be based, for example, on any one or more of the following methods: a) A measurement of a signal metric of a signal received directly by the wireless terminal from a first station of the cell, of a signal received at the wireless terminal from a relay station, or of a signal received by the wireless terminal from another cell station. For example, an event such that the RSRP of a downlink transmission from a cell station falls below a certain threshold indicates to the wireless station that the wireless terminal is approaching the edge of the coverage area where it can transmit directly to the cell station. The wireless station needs to perform the measurement at a certain time interval or apply some historical offset to ensure that the situation is stable and to avoid ping-pong effects. The threshold to be applied is (pre-)configured by the cell station through configuration information sent to the wireless terminal (e.g. as part of the SIB) that contains the conditions / policies (e.g. RSRP thresholds) that the wireless terminal should apply to decide to use the TX restricted mode. b) Detection of a failed or near-failed transmission, such as no acknowledgement of a message sent to the first cell station, e.g. a retry counter reported directly from the wireless terminal to the cell station or vice versa, or a retry counter reported to the wireless terminal via a relay station, the threshold to be applied for which is (pre-)configured by the cell station through configuration information (e.g. as part of the SIB) sent to the wireless terminal, which contains the conditions / policies (e.g. maximum number of failed uplink transmissions) that the wireless terminal should apply to decide to use the TX restricted mode. c) Possible coverage extension modes requested by the wireless terminal or enabled by the network. d) The remaining battery charge or type of battery / power source used by the wireless terminal, and / or whether the Tx power level of the wireless terminal is above / below a particular threshold.

[0099] Additionally or alternatively, the controller initiates TX restricted mode operation when a relay station is discovered, such that a discovery message received from the relay station indicates support for TX restricted operation or indicates a field (e.g., a Boolean information element) that, when included or having a particular value, should trigger the wireless terminal to switch to the TX restricted mode.

[0100] As yet another option (of this and other embodiments), the transmitter is adapted to transmit an initial signal indicating or including a trigger for activating the TX restricted mode either directly to the first cell station (i.e. via the Uu interface) or to the relay station (i.e. via an indirect message to be forwarded by the relay station to the first cell station, e.g. using the ProSe relaying procedure). In the case of the Uu interface, this is a one-off high power "hello" message transmission sent directly to the first cell station, e.g. via the assigned UL resources or as a new or existing RACH message (e.g. with a new / additional information element indicating a request for the TX restricted mode) sent on non-scheduled resources during a random access procedure (see TS38.300), assuming that the wireless terminal has enough Tx power headroom and enough energy still remaining to send the "hello" message transmission. In this way, the wireless station can inform the cell station that the wireless terminal is there and that it needs the relay station to send a reply (at a sustainable lower power transmission level). As soon as the cell station receives such a message, the cell station determines, e.g., based on location information, measurement data, or discovery information further included as part of such initial signal (e.g., a “hello” message), which relay station the wireless terminal should use (if the wireless terminal is not already using it) and schedules upstream resources for the wireless terminal accordingly, which the cell station then transmits to the wireless terminal in one of the first downlink signals previously mentioned.

[0101] As yet another option, when the wireless terminal stops using the TX-restricted communication mode, the relay station optionally continues to listen to upstream signals from pre-authorized wireless terminals that are present in the pre-established security context. This is useful, for example, to detect devices that at this time can only use TX-restricted communication (and therefore are not capable of reaching the cell station directly), devices that have entered the vicinity of the relay station, as well as devices that need to communicate. For this purpose, the pre-authorized wireless terminal needs to use a unique identity or certificate in its discovery, "relay join request", or other upstream signal / message (e.g. PC5 signaling message). In order for the relay station to be able to verify that the wireless terminal is pre-authorized, the relay station is configured with corresponding information or remembers corresponding information from a previous communication with the wireless terminal (e.g. using the same or derived PC5 session key). Alternatively, the relay station forwards the incoming upstream signal to the cell station to which the relay station is connected and / or to the core network for further processing and to further check whether the wireless terminal is pre-authorized or not.

[0102] In the case of TX restricted mode, since the wireless terminal sends uplink information to the relay station instead of directly towards the cell station, the wireless terminal deploys two sets of antennas (e.g., antennas for receiving DL signals from the cell station coming from one direction and antennas for transmitting upstream signals to the relay station in the other direction) or a single set of antennas that switches intermittently between a mode for receiving DL signals from the cell station and a mode for transmitting upstream signals to the relay station. For this purpose, the wireless terminal is configured by the cell station with (estimated) location information (e.g., geographic or relative coordinates, or distance / direction from a reference point) and / or directional information (e.g., angle between DL signals coming from the cell station and upstream signals going out to the relay station, launch angle of DL signals or upstream signals relative to a reference line or magnetic north). This enables the wireless terminal to configure the antennas accordingly and receive / send signals from / in the correct direction (e.g., by changing the beamforming characteristics of the transmitted signals). This allows beamforming in the direction of the relay station (which may be a different beam or have a different synchronization signal block (SSB) index) than the beam directed to the first cell station). The wireless terminal is further configured by the cell station with information about the timing of mode switching (e.g., based on a regular interval or with respect to resources scheduled for downlink and upstream communication). This is useful in the case of switching the antenna between a mode for receiving DL signals from the cell station and a mode for transmitting upstream signals to the relay station. Alternatively, the wireless terminal deploys one or more omni-directional antennas, in which case the location / angle is not necessary and is ignored. However, in the case of a single omni-directional antenna, mode switching is applied and the wireless terminal is appropriately configured with information about the timing of mode switching.

[0103] In other words, optionally, the receiver and transmitter each operate different sets of antennas, and the controller instructs the transmitter to perform beamforming towards the relay station, for example, based on the relay station's location and / or angle information (e.g., the angle between the beam used for the downlink signal from the cell station as received by the wireless terminal and the beam used for the upstream signal directed towards the relay station), such location or angle information being received from the first cell station and / or the relay station.

[0104] In an embodiment, the controller 63 alternately operates the communication units according to a network having a conventional architecture and a network having a specialized architecture as described with reference to FIG. 4 or in any of the further embodiments detailed below. Depending on the currently encountered conditions or based on a specific trigger message, the controller 63 switches from conventional operation (e.g. direct bidirectional operation with the cell station acting as a scheduler) to asymmetric operation (i.e. TX-limited operation mode). In this case, the controller 63 can configure the receiver to receive and decode a resource reservation message indicating an incoming downlink message (e.g. paging message) from the cell station and to receive a downlink data transmission from the cell station on the scheduled radio resources. Optionally, the resource reservation message and the data transmission occur within the same radio frame.

[0105] Furthermore, the controller 63 is adapted to request radio resources for data transmission by causing the transmitter 622 to send a message to the at least one relay station 420 .

[0106] Additionally, as described in connection with the flowchart of FIG. 5, the reservation message coding, content, and / or timing can indicate to the wireless terminal 410, optionally in a single message, the Ds resources for downlink data reception and the allocated Us resources for transmission.

[0107] The transmitter 622 can be configured to send data destined for the cell station to the relay station via the reserved upstream resources, including, for example, feedback data, such as an ACK / NACK, indicating whether the wireless terminal 410 successfully received a data transmission from the cell station, new user data destined for the network or an edge server located at the first cell station, or other control messages, such as Buffer Status Report (BSR) data indicating the status of one or more of the transmission buffers of the wireless terminal 410.

[0108] As shown in FIG. 7, a relay station 420 operable as a relay UE typically comprises an antenna 71 or an antenna array (e.g. in the case of a MIMO compatible wireless terminal). This antenna 71 is coupled to a communication unit 72 comprising a receiver 721 and a transmitter 722. The communication unit 72 is compatible with a 3GPP standard such as UMTS, LTE or NR in these exemplary embodiments and operates accordingly depending on the current connection. In an embodiment, a controller 73 such as a microprocessor is included for controlling the communication unit 72 and its receiver 721 and transmitter 722. It should be noted that the controller 73 is dedicated to the communication unit 72 and possibly included therein. The controller 73 also operates other systems and is not only dedicated to the communication unit 72. Typically, some or all of the processes involved are operated by software stored in the memory 74 of the relay station 420. However, it is also possible that the entire invention is included in hardware in a component. It should be noted that the relay station includes functionality to operate as a relay UE in a 3GPP network in accordance with relay operations such as sidelink transmission and reception.

[0109] In this embodiment, the relay station is directly or indirectly connected to a network, e.g., a core network (CN), via a cell station, e.g., a RAN base station. The receiver 721 is configured by the controller 73 to receive and decode an upstream assignment sent by the cell station and indicating resources to be used for an incoming upstream transmission from the wireless terminal 410. This scheduling assignment includes reservation coding, content, frequency information, and / or timing information that indicates, implicitly or explicitly (e.g., with an identifier), the resource reservation to be used by the wireless terminal 410 directly connected to the relay station via an air link. Optionally, an identifier (e.g., L1 or L2 identifier) ​​of the wireless terminal 410 is included in the scheduling assignment to indicate the wireless terminal 410. The controller 73 is adapted to configure the receiver to subsequently receive data from the wireless terminal 410 on the scheduled resources, as mentioned in step S55.

[0110] The controller 73 is adapted to control the receiver 721 and the transmitter 722 to relay upstream data from the wireless terminal 410 to the cell station 400 according to a relay operation. This forward transmission may be directly or indirectly through an upstream parent node.

[0111] Additionally, the relay station is adapted to, in response to receiving data from the wireless terminal 410, send feedback data (e.g., ACK / NACK) to the wireless terminal 410 indicating whether the data was correctly received or not.

[0112] As shown in FIG. 8, the cell station 400 comprises an antenna 81 or an antenna array (e.g. in the case of a MIMO compatible cell station). This antenna is coupled to a communication unit 82 comprising a receiver 821 and a transmitter 822. The communication unit 82 is in these exemplary embodiments compatible with a 3GPP standard such as UMTS, LTE or NR and operates accordingly depending on the current connection. In the embodiment, a controller 83 such as a microprocessor is included for controlling the communication unit 82 and its receiver 821 and transmitter 822. It should be noted that the controller 83 is dedicated to the communication unit 82 and possibly included therein. The controller 83 also operates other systems and is not only dedicated to the communication unit 82. Typically, some or all of the processes involved are operated by software stored in the memory 84 of the cell station 400. However, it is also possible that the entire invention is included in hardware within the components. Furthermore, the cell station 400 comprises a scheduler 85 coupled to the controller 83 which takes care of allocating the shared resources of the cell to the multiple secondary stations. An interface 86 is included for managing communications with a core network, the interface 86 being further adapted to manage communications with other cell stations over a different interface (e.g., X2) using a backhaul channel.

[0113] 5, the controller 83 of the cell station 400 is adapted to configure the transmitter 822 to transmit downlink data to the wireless terminal 410. The controller is operable without receiving (at least not directly) any transmission, e.g. feedback, from said wireless terminal 410. Furthermore, the receiver 821 is adapted to receive and process feedback data, received directly or indirectly, i.e. via the relay station 420, from the wireless terminal 410 indicating whether a previous DL transmission to the wireless terminal 410 was received correctly or not.

[0114] Furthermore, the scheduler is adapted to schedule resources to enable the special asymmetric operation described in Fig. 5. This includes scheduling of downlink data for direct downlink transmission from the cell station 400 to the wireless terminal 410. This further includes allocation of upstream resources between the wireless terminal 410 and the relay station 420. Corresponding resources (for receiving upstream signals / uplink information from the wireless terminal 410) are further signaled to the relay station to direct incoming upstream transmissions from the wireless terminal. Finally, in this particular example where the relay station is in a cell served by the cell station, the scheduler can further schedule resources to be used by the relay station for forwarding incoming upstream data.

[0115] The scheduling operation is based at least in part on information regarding the buffer status of various stations in the network, including relay station 420 and possibly wireless terminal 410. The BSR may be received directly or indirectly from wireless terminal 410.

[0116] Similar to the wireless terminal 410 and relay station 420, the controller 83 can switch for a given station between a "normal" mode of operation (direct bidirectional connection), a "relay" mode (indirect bidirectional connection (all communication upstream and downstream goes through one or more relay stations)) and / or a "TX-limited" mode (indirect connection with direct DL data transfer and scheduling). The connection mode is selected depending on the given UE capabilities, i.e., if the UE supports these modes.

[0117] As a result of this embodiment, a wireless terminal acting as a remote UE is able to reduce the number of times that the wireless terminal needs to “sense” the sidelink channel in order to self-schedule resources on which to transmit – in many cases the wireless terminal can simply wait for the cell station (gNB) scheduling decision about Us resources and send on these Us resources, thus reducing the energy consumption of the wireless terminal.

[0118] Furthermore, the cell station or gNB can use knowledge / data / measurement reports of many UEs and even more communication resources / channels / bands knowledge / data / measurement reports to more optimally schedule communication resources. Thus, the cell station or gNB has the ability to better evaluate the load per relay station and make smarter decisions on scheduling and / or switching of possible UEs to this asymmetric mode of operation.

[0119] It should be noted that in some situations self-scheduling by the wireless terminal is still necessary, e.g. when a cell station has not allocated any resources to the wireless terminal and the latter needs to indirectly indicate to the network that it has data waiting for transmission, e.g. by transmitting a BSR and / or by transmitting user data (e.g. urgent user data, such as for emergency services) to a relay station.

[0120] Furthermore, in the “TX Limited” mode, the downlink data capacity is as high as in the “Relay” mode, since data can be sent directly from the cell station to the wireless terminal acting as a remote UE without requiring an indirect path through the relay station, as is typically the case with relayed data. As a result, data from the cell station to the wireless terminal does not “burden” the available sidelink (SL) resources between the relay station and that wireless terminal. In one implementation where the network or relay station defines how the sidelink resources are shared between upstream and downstream data, it is possible, for example, to reduce the sharing of downstream sidelink resources in favor of upstream sidelink resources. This makes more sidelink resources available for other types of sidelink communication (e.g., D2D, V2X, ProSe, relaying).

[0121] It is also advantageous for the relay station not to have to sense all potential SL channels on which a wireless terminal acting as a remote UE may transmit at all times. Instead, the relay station listens specifically on a scheduled channel, i.e. resource Us-Rx, to receive wireless terminal transmissions. As a result, the relay station can use more advanced "energy saving" modes, as in 3GPP (e.g. DRX energy saving mode), that do not require "always on" listening to sidelink resources on which a wireless terminal may potentially send data to the relay station.

[0122] Some further details regarding resource scheduling as envisioned in 5G are provided below: Resource scheduling in 5G consists of a complex interplay of multiple scheduling mechanisms and protocols working in conjunction with each other.

[0123] The main method of scheduling in 5G is dynamic, meaning that resources are allocated according to demand based on available data and channel conditions. There is also semi-persistent scheduling (SPS), which is a pre-configured schedule that can be quickly activated / deactivated by the gNB based on current demand. Finally, there is a persistent schedule that can be activated once and remains active until explicitly cleared by a specific specified event. The intention is that dynamic scheduling decisions will always be added in addition to persistent / semi-persistent scheduling decisions to handle special occurrences such as data rate fluctuations or data retransmissions. A complex ensemble of reporting structures is defined in 3GPP for reporting measurements to the gNB along with control mechanisms for the gNB to enable / disable / request reporting on the fly in order for the scheduler to learn channel conditions.

[0124] The protocols used to implement the scheduling mechanisms vary. ● RRC, see also Fig. 2B. This can run end-to-end between gNB and UE in UL and DL, potentially via one or multiple relay hops over SL when using the new L2 relay architecture. RRC is mainly used for non-time critical static or semi-static schedule information. In other words, configuration of the schedule. ConfiguredGrantConfig is the information element for uplink scheduling. ● MAC Control Elements (CEs) - These are short elements (aka Information Elements or IEs) inserted between existing UL / DL / SL transmissions over the MAC layer, used to efficiently signal a specific event or configuration in UL, DL or SL. One specific case is the Buffer Status Report (BSR) MAC CE used by the UE to signal its current data buffer status towards the gNB / scheduler. The MAC CE is the main mechanism for the UE to indicate that it has data pending that requires UL scheduling. When the UE has some data available for transmission in its buffers, and a UL grant for resources, the UE will add information about one or more of its buffers using some of this resources for one or more corresponding logical channel groups. But when there is no UL grant for resources, another mechanism to request resources is the Scheduling Request (SR) in the UCI. Another MAC CE is used by the gNB to control the UE's behavior in performing the measurements and DRX mentioned above. ● Downlink Control Information (DCI) - a short message sent in the downlink in the low bit rate control channel (PDCCH) with a special blindly detectable modulation / coding. This is at the PHY L1 layer and does not use the MAC L2 header structure. Various DCI formats are defined with different information content. Resources for dynamic scheduling are indicated in the DCI, DL data transmissions usually follow the DCI message within 1 ms, but can be scheduled up to 4 ms ahead. For UL, scheduling is usually done for the next slot, 1-2 ms ahead, but can be up to 8 ms ahead. For scheduling of sidelink resources DCI format 3_0 and format 3_1 are defined in TS 38.212. These are only the SL resources that should be used by the UE itself that has been scheduled for transmission, not the SL resources used by remote UEs to transmit to relaying UEs.

[0125] It should be noted that in this document the term downlink control information is used generically for any control / configuration related information and is not necessarily limited to DCI related content / messages, but may also be sent as part of e.g. a System Information Block (SIB), RRC or MAC CE message. ● Uplink Control Information (UCI) - a short sequence of bytes sent on the uplink in the PUCCH using one of several different formats. The UCI contains a Scheduling Request (SR) bit and is used by the UE when there are no UL resources to transmit a BSR MAC CE. In response to the SR, the gNB scheduler will allocate UL resources for the UE in the future.

[0126] Of the above, only the RRC protocol messages can be carried end-to-end between the remote UE and the gNB in ​​case of the L2 relay architecture (see Figure 3). All other mechanisms need to work either directly between the gNB and the UE in direct radio contact at L1 / L2 or, if defined, between the relay UE and its downstream remote UE.

[0127] The above overview of resource scheduling is applicable to UEs directly connected to a gNB. If single or multi-hop relays are introduced into the network, these solutions are not sufficient as they mainly operate on the direct link between the gNB and the UE. There are various solutions already known or discussed in the 3GPP RAN working group on how such scheduling can work in the single-hop relay situation. For example: ● An OoC remote UE can self-schedule its transmissions on the SL based on its own channel measurements and random access process, this is called “resource allocation mode 2” in TR37.985. ● The gNB can schedule resources for all directly connected relay UEs as defined in TR37.985 “Resource Allocation Mode 1” for transmission to remote UEs. However, there is no mechanism for the gNB to schedule for reverse traffic back to the relay UEs. ● The gNB schedules all resources for all directly and indirectly connected UEs (Note: the details of such method are not yet defined by 3GPP). ● One lead UE of a group can tailor resource allocation to its group members and possibly function when some group members are out of coverage but still within range of the lead group member UE.

[0128] It is important to note that one issue recently mentioned in the 3GPP® RAN#86 meeting discussions on the scope of Release 17 is that self-scheduling for the Sidelink (SL) as currently defined for V2X communications is not considered energy efficient and therefore not suitable for small battery-powered devices such as mobile phones or IoT devices. The primary V2X use case for this communication has so far been V2V (vehicle-to-vehicle) communications, where energy consumption is not a major issue.

[0129] In a variation of the previous embodiment, the wireless terminal can be connected as a remote UE. In this role, the wireless terminal can detect that it is capable of receiving one or more cell station signals. Upon determining this, the wireless terminal sends a message to its relay station (e.g., relay UE) indicating the cell station signals (and / or the identity of the cell stations) that the wireless terminal is capable of receiving. The message includes an indication of the energy, power level, and signal quality that aids in the decision to switch to an asymmetric mode of operation. The relay station then further sends or relays this information to its own upstream cell station. Optionally, this information is further disseminated within the RAN to enable the RAN to configure at least one cell station (preferably corresponding to the one first detected by the wireless terminal) for direct data transmission and / or resource reservation as described in the previous embodiment or as detailed in further embodiments.

[0130] Furthermore, when a wireless terminal is connected as a remote UE and in a TX-restricted state, the cell station may be configured to monitor and detect a change from the TX-restricted state to a normal state that allows two-way communication with the wireless terminal. This can be done, for example, by the cell station detecting a transmission from the wireless terminal to the relay station on the assigned Us resources. Other suitable methods (monitoring RSSI, signal quality monitoring based on a reference signal, or others) may be used. In response, the cell station informs the wireless terminal to trigger a switch from TX-restricted operation to normal operation.

[0131] When the wireless terminal is connected in a TX-limited state as a remote UE, the wireless terminal similarly detects a change from the TX-limited state to a state outside gNB coverage, where communication with the gNB is no longer possible. This can be monitored by detecting that no gNB transmissions are received any more, such as synchronization signals or periodically broadcasted system information (SIBs). Alternatively, conventional monitoring of some part of the received power or quality (similar to measurements performed for handover) is used in this context. In response, the wireless terminal switches from TX-limited operation to normal relay operation like a remote UE. The wireless terminal further informs the cell station gNB of this new situation (via an indirect message forwarded by the relay UE).

[0132] In an embodiment, let us choose the case where the wireless terminal 410 is connected as a remote UE and in a transmission restricted state. When the relay station 420 detects that the wireless terminal 410 goes out of coverage of the cell station 400 and thus relay communication between the cell station and the relay station is no longer possible, the relay station 420 stops its relaying operation for the wireless terminal 410 and informs the wireless terminal 410 via a sidelink message. The wireless terminal 410 then starts a discovery process to look for a new relay station to use. Meanwhile, the wireless terminal 410 further checks whether it is possible to re-enter normal operation with direct bidirectional operation with the cell station. For the relay station 420 to detect that the wireless terminal 410 goes out of coverage, the wireless terminal 410 can detect that no gNB transmissions are received any more, e.g., periodically broadcasted system information (SIB). In another example, the relay station can use one of the measurement events, such as detecting that the RSRP / RSRQ from the cell station is lower than a threshold. These events are a sign that the relay station is moving out of the cell or that its connection quality is deteriorating. Another possibility could be that the relay station announces a substantial change in location, for example based on GPS coordinates.

[0133] In a further embodiment, a cell station (denoted gNBx) sends out a specific "discovery" type signal instructing all wireless terminals acting as remote UEs and / or in a transmission restricted state, that they should respond to the signal if they are capable of receiving it. After receiving such a signal, such wireless terminals operating in a fully relaying operation can respond by sending a discovery request or response (e.g. using a ProSe / sidelink discovery message) to their own relay station 420 or to another nearby relay station 420. The relay station 420 then forwards the discovery response via the RAN to their own cell station gNB1 that generated the "discovery" signal, to the core network CN, and / or to the cell station gNBx, for example if this is part of its active set (the base station with which the relay station 420 is currently in contact). After receiving the discovery response, one entity in the RAN (e.g. gNBx) configures the direct transmission of data / resource reservation to the possible wireless terminals as described in the embodiments of the present invention (e.g. to enable asymmetric operation modes).

[0134] In these various examples, the cell station gNBx may determine that a possible wireless terminal is in a TX restricted state and / or the network (e.g., NG-RAN) may determine that a possible wireless terminal is in a TX restricted state and then instruct one or more cell stations to use TX restricted operation by the possible wireless terminal. This determination may be based on any one or more of the following methods: a) Measurements of signal metrics of signals received directly by the cell station from the considered wireless terminal, signals from the wireless terminal received at a relay station, signals from relay stations near the wireless terminal, signals from relay stations serving the wireless terminal, or signals from the wireless terminal received by another cell station. For example, an event such as the RSRP of an uplink transmission from the wireless terminal dropping below a certain threshold indicates to the cell station that the wireless terminal is approaching the edge of its coverage area where it can transmit directly to the cell station. The cell station needs to make measurements over a certain time interval or apply some history offset to ensure that the situation is stable and to avoid ping-pong effects. b) Detection of a failed or near-failed transmission, e.g., no acknowledgement of a message sent to the wireless terminal, a retry counter reported directly from the wireless terminal to the cell station, or a retry counter reported from the wireless terminal to the cell station via a relay station, or a subsequent Tx power level of the wireless terminal reported directly to the cell station that exceeds a certain threshold. c) The coverage extension mode may be requested by the wireless terminal or enabled by the network. d) Historical or analytical data indicates that the wireless terminal is experiencing uplink problems. e) capability information (e.g. representing TX limited capabilities and / or status) and / or status information of a possible wireless terminal (e.g. a device belonging to a particular group of TX limited devices) received from a possible wireless terminal (e.g. via an RRC, MAC CE or initial RACH message or registration / attach message), from an application function, or from a Unified Data Management (UDM) network function (e.g. part of subscription information) or received through a Network Exposure Function (NEF), including knowledge about device model, number of antennas, UE category, whether RF backscatter communication is supported, etc. f) The remaining battery charge or type of battery / power source used by the wireless terminal. This further includes information on whether the device has no battery and / or is only getting energy from energy harvesting. This information is reported, for example, while the wireless terminal still has a bidirectional link with the cell station or through an initial RACH message or a registration / attach message.

[0135] In a further variant of the previous embodiment, as soon as the cell station determines, for example based on one of the mechanisms discussed above, that the considered wireless terminal is in a TX-restricted state, the cell station possibly sends a message to a relay station (preferably the relay station communicating with the considered wireless terminal) indicating the identity of the wireless terminal and indicating that the wireless terminal should use a TX-restricted communication mode. The indicated identity of the considered wireless terminal is used in future resource scheduling messages from the cell station, so that the relay station can infer from the resource scheduling message that the wireless terminal is going to transmit upstream data to the relay station. It is also possible that the relay station is informed about incoming uplink messages on some of the uplink / upstream resources. As an example, the identity is the RNTI (Radio Network Temporary Identifier) ​​of the wireless terminal. The relay station uses this RNTI in addition to its own RNTI to monitor PDCCH messages to receive DCI from the cell station for the wireless terminal, and to use the DCI so that it can receive upstream information from the wireless terminal using the assigned uplink / upstream resources.

[0136] Alternatively, the cell station signals a set of Us-Rx resources (e.g., a resource pool) to be monitored by the relay station (instead of specific resources for a single transmission). The actual resources allocated to the wireless terminal are simply one or more resource blocks from the set of Us-Rx resources signaled by the cell station to the relay station. As in the above example, the identity of one or more wireless terminals expected to transmit is optionally signaled. The set of Us-Rx resources is further signaled as a semi-persistent schedule, a time / wake schedule, or as specific frequencies to monitor.

[0137] In a further variant of the invention, the wireless terminal is capable of connecting to the relay station using the 3GPP 5G ProSe relay discovery and selection procedure.

[0138] In yet another variation of the previous embodiment, the wireless terminal can report any location change indirectly (via the relay station) to the cell station in a location change status report. If there is little or no location change, the cell station can maintain the same operating mode (e.g., full relay operation or TX limited mode, or direct two-way mode) towards the wireless terminal. If there is a significant location change, the cell station can adapt its transmission settings towards the wireless terminal and / or let a different cell station take over its role as the direct cell station. Another possibility is for the cell station to configure the wireless terminal to initiate some measurements or to perform some measurements to detect if another cell station is more suitable or if another operating mode is more suitable for the current conditions. The measurements performed at the wireless terminal can be similar to those performed for cell station handover mechanisms.

[0139] In yet another variation of the previous embodiment, the cell station can configure and activate a discontinuous reception (DRX) mode in the wireless terminal by direct message, and the wireless terminal can then transmit to its relay station during its "wake" times. The DRX mode allows the terminal to reduce its energy consumption by intermittently switching off its communication unit and being active during certain periodic wake periods. Since the cell station is aware of the period of the DRX burst pattern, it can adapt resource scheduling accordingly. Similarly, the cell station can activate DRX in the relay station and then schedule resources for transmissions from the wireless terminal to that relay station only during the wake periods of both the wireless terminal and the relay station.

[0140] It should be noted that all previously described embodiments may be combined with each other. Moreover, unless expressly indicated otherwise, these variations are equally applicable to other embodiments of the invention.

[0141] According to a second embodiment of the invention, the operation of the system will now be described with reference to Fig. 9. In this system, a wireless terminal 910 is in the coverage, i.e. cell 90, of a cell station 900. A relay station 920, further connected to the cell station 900, can act as a relay between the wireless terminal 910 and the cell station 900. During normal operation, the wireless terminal can receive data and control signaling directly from the cell station 900 and transmit data and control information back to the cell station on a direct link. If the wireless terminal 910 is completely disconnected from the cell station 900, e.g. when it is not able to correctly receive signals originating from the cell station 900, the wireless terminal 910 can enter into a full relaying operation thanks to the relay station 920. In this operation mode, all upstream and downstream connections go through the relay station 920. However, as described in the previous embodiments, the wireless terminal 910 can further operate in a TX-limited operation when in a TX-limited state.

[0142] In this particular case, the wireless terminal 910 can generate upstream user data that is sent via the relay station 920. The data is then optionally acknowledged by the cell station 900 via direct transmission. The detailed operation is performed as described below. ● As a first step S90 (not shown), optionally the wireless terminal 910 indicates to the relay station 920 that it has pending data to be transmitted. This can be done for example through a Buffer Status Report (BSR) type message or a Scheduling Request type message followed by a BSR, for example using sidelink resources preconfigured for this purpose. This step is optional, especially if the cell station already has Us resources scheduled for the wireless terminal 910 (for use for reception of incoming upstream data) and corresponding resources Us-Rx for the relay station 920 for use in the near future, for example based on a BSR or SR+BSR previously received by the cell station. After the wireless terminal 910 has sent this indication to the relay station 920, for example a Buffer Status Report type message, the relay station 920 indicates to the cell station that the wireless terminal needs resources. This can be done simply by forwarding the corresponding BSR or by some other signaling. The wireless terminal sends additional information to the relay station to be further sent to the cell station 900, such as, for example, a measurement report or other message indicating that the wireless terminal 910 is now a TX-limited station, i.e., it can receive data directly from the cell station 900, but cannot successfully send data to the cell station 900. The wireless terminal further sends a request to transition to TX-limited operation (e.g., due to limited remaining battery capacity or other events as mentioned in the previous example). Additionally, some user data, with SR / BSR and previously mentioned messages inserted, is sent to the relay station 920. Upon receiving information via the relay station that the wireless terminal 910 needs resources or operates / supports the TX-limited mode, the cell station 900 schedules upstream resources for the wireless terminal 910 and further schedules corresponding resources for the relay station 920 for receiving upstream signals from the wireless terminal 910 and sending the scheduled resources as part of the first or second downlink signal.Alternatively, even if the wireless terminal 910 is TX restricted, the wireless terminal 910 may send a specific signal (e.g., a narrowband pulse, or a scheduling request, or a signal at a specific frequency and / or a lower frequency than the wireless terminal uses for normal operation, or a signal sent temporarily at a higher transmit power than the device can sustain for a longer period of time) that is received by the cell station 900 (or other nearby cell station) indicating that the wireless terminal needs resources or operates / supports a TX restricted mode. If such a signal is received by the cell station 900, the cell station 900 will schedule upstream resources for the wireless terminal 910 and will further schedule corresponding resources for the relay station 920 for receiving the upstream signal from the wireless terminal 910 and for sending the scheduled resources as part of the first or second downlink signal. ● In step S91, the cell station 900 (gNB1) transmits one single control message including the allocation of resources or a set of control messages indicating a set of resources, frequencies, and / or time / wake schedule related information. The control message includes an identifier of the wireless terminal 910 or an identifier common to the combination "wireless terminal 910-relay station 920". The message indicates a corresponding indication of the allocation of Us resources or specific frequencies for use by the wireless terminal for performing future data transmissions, and / or resources (for use by the relay station) corresponding to the Us resources and indicating incoming upstream data from the wireless terminal 910. In an example, the indication about the assigned Us resources and the assigned Us-Rx resources for incoming upstream are expressed in a single field or in a single byte array of the control message. As another example of an indication on the assigned Us resources, the control message from the cell station 900 (gNB1) includes a flag or parameter to instruct the wireless terminal 910 to use (a subset of) sidelink resources already configured in the wireless terminal 910. The control message further includes additional information on how the upstream signals should be transmitted by the wireless terminal 910 (e.g., which modulation or signal encoding or scrambling or transmit power should be used, which specific type of signal / message (e.g., sidelink discovery message) should be used / generated), and / or which L1 / L2 source or target identity information (or other identity information such as User Information ID, PRUK ID, SUCI, SUPI, GUTI, or RNTI) should be used in the message (e.g., relay station identity) or which specific security credentials should be used for the message. The wireless terminal 910 uses this information to generate the respective upstream signals to be received by the relay station 920.Similarly, relay station 920 receives corresponding information from cell station 900 and uses this information to receive the particular upstream signal from wireless terminal 910 .

[0143] It should be noted that the wireless terminal 910 and relay station 920 are pre-configured to monitor the control region for the corresponding DCI type and based on the identifier. As mentioned before, the identifier can be a newly defined "remote-UE-RNTI" associated with the wireless terminal 910 or an identifier created for the "wireless terminal 910-relay station 920" concatenation. This therefore allows the cell station to schedule resources for different wireless terminals for each relay station. This mitigates the risk of the relay station completely losing the upstream connection of the wireless terminal if the relay station moves away, since a spare relay station can be easily used by assigning resources with different RNTIs. When monitoring the control region, each of the wireless terminal 910 and relay station then blindly decodes the set of PDCCH candidates based on the RNTI to detect whether a valid DCI is included.

[0144] Thus, in step S91, both the wireless terminal 910 and the relay station 920 receive and decode the PDCCH message from the cell station 900 with a CRC scrambled with this new RNTI type. As a result, this causes the relay station 920 to attempt to "descramble" the PDCCH message with both its own identity (typically its C-RNTI) and the new RNTI to determine what and who the message is intended for. If the PDCCH decoding is successful, the corresponding DCI allows for the following configuration: a wireless terminal 910 transmitter for preparing and transmitting a data transmission using the allocated Us resources; and - A relay station 920 receiver (Rx) for listening to data transmissions using the same Us resource. ● In step S92, the wireless terminal 910 transmits data in the scheduled resources and the relay station 920 listens to the transmitted data in the same / corresponding resources. Typically, the cell station 900 cannot correctly receive the transmitted data due to transmission restrictions for wireless terminals, as indicated previously. ● In step S93, the relay station 920 relays the received data from the wireless terminal upstream towards the cell station 900. It should be noted that this relay may be directly or indirectly connected via multiple hops. For simplicity, only a direct relay is shown in Fig. 9. The relay station 920 uses the uplink resources allocated in a separate PDCCH message concomitant to the resources allocated in step S91, the CRC now being scrambled with the RNTI of the relay station 920. It is also possible that semi-persistent scheduling resources are allocated to the relay station to enable it to forward data transmissions from all its sidelink connected terminals. Yet another possibility is that the message sent in step S91 contains a further allocation of resources to be used by the relay station for forwarding. This further resource allocation needs to be signaled before the normal allocation in order to enable the relay station to process the incoming upstream and prepare the data packets to be forwarded. ● In step S94, the cell station 900 optionally sends feedback data directly to the wireless terminal 910, for example to acknowledge (ACK / NACK) the reception of upstream data from the relay station 920. This may be HARQ acknowledgement data, PDCP feedback data using PDCP control PDU (or higher layer, e.g. IP, or other), PDCP status report PDU type, including FMC and bitmap data as specified by TS 38.323. Furthermore, the cell station 900 may also (or alternatively) transmit this feedback data via a relay station (thus indirectly) to the wireless terminal. However, it is assumed that direct transmission is more efficient. The feedback data is optionally combined with further downlink data to the wireless terminal, for efficiency, in the same transport block.

[0145] It should be noted that each transmission hop of the indirect network connection includes a corresponding MAC HARQ process, for example, such that each hop is acknowledged at the MAC level.

[0146] The third embodiment depicted in FIG. 10 corresponds to the second embodiment, except that the relay station 1020 is currently served by a cell station 1001 (in cell 10b) different from the cell station 1000 serving the wireless terminal 1010 (in cell 10a). Thus, this particular case where the wireless terminal 1010 generates upstream user data that is authorized by the cell station 1001 will now be described. As described, there are two cell stations: the cell station 1001 used by the relay station 1020, and the cell station 1000, which is a cell station that can transmit directly to the wireless terminal 1010. Thus, the cell station 1000 can transmit an upstream resource allocation to the wireless terminal 1010, and the cell station 1001 can transmit a corresponding upstream resource allocation to the relay station 1020. ● As a preliminary step not shown, the wireless terminal 1010 initiates / trigger resource reservation if necessary, as was done in step S90 of the previous embodiment. ● In step S100, the two cell stations 1000 and 1001 coordinate in time their upcoming transmissions: Us resources to use for transmission for the wireless terminal 1010 and Us-Rx resources to listen for the relay station 1020. In this case, the Us resources are identical to the Us-Rx resources or significantly overlap with the Us-Rx resources (i.e., the Us resources are included in the signaled Us-Rx resources, which can be signaled, for example, via semi-persistent scheduling (SPS), dynamic scheduling, or as a pool of resources). ● In steps S101 and S102, the cell stations 1000 and 1001 each transmit a communication resource reservation message indicating radio Us and Us-Rx resources, respectively, for use by one or more of the wireless terminals 1010 for future data transmissions and by the relay station 1020 for data reception. Note that the Us-Rx resources are previously signaled, e.g. as part of a pool of resources or a relay configuration information element indicating SPS allocation. In this case, this can be done before step S100. This is not specific to this embodiment and is further applicable to other described embodiments. Both the wireless terminal 1010 and the relay station 1020 receive the reservation via their respective cell stations and decode the PDCCH message by detecting or descrambling the message with an identifier. This identifier is the "remote UE-RNTI" mentioned in the previous embodiment for both. Alternatively, this is the "remote UE-RNTI" to be used by the relay station to descramble the PDCCH candidates, and the normal RNTI to be used by the wireless terminal to descramble the PDCCH candidates. The relay station then configures its receiver to listen for data transmissions using the Us-Rx resources (Rx).Alternatively or additionally, the cell stations 1000 and 1001 may exchange information with each other and / or transmit a set of control messages to the wireless terminal 1010 indicating a set of resources, frequencies, and / or time / wake schedule related information, or including additional information about how the upstream signals should be transmitted by the wireless terminal 1010 (e.g., what modulation or signal encoding or scrambling or transmit power should be used, what particular type of signal / message (e.g., sidelink discovery message) should be used / generated), and / or what L1 / L2 source or target identity information (or other identity information, such as User Information ID, PRUK ID, SUCI, SUPI, GUTI, or RNTI) should be used in the message (e.g., the identity of the relay station), or what particular security credentials should be used for the message. The wireless terminal 1010 uses this information to generate the respective upstream signals to be received by the relay station 1020. Similarly, relay station 1020 receives corresponding information from cell station 1000 or 1001 and uses this information to receive the particular upstream signal from wireless terminal 1010 . ● In step S103, the wireless terminal 1010 transmits upstream information in scheduled Us resources, and the relay station 1020 receives the upstream information in Us-Rx resources.

[0147] Typically, the cell station 1000 is unable to properly receive the transmitted data due to transmission limitations for wireless terminals as previously indicated, and the cell station 1001 may be out of range for the wireless terminal and / or the wireless terminal 1010 does not have an active connection to the cell station 1001 to transmit directly to the cell station 1001. ● In step S104, the relay station 1020 relays upstream received upstream information, e.g. user data, from the wireless terminal 1010 towards its cell station 1001. The cell station 1001 optionally informs the cell station 1000 about which feedback data should be sent back from the cell station 1000 to the wireless terminal 1010.

[0148] It should be noted that this relaying can be direct or indirect via multiple hops. For simplicity, only direct relaying is shown in Fig. 10. The relay station 1020 uses the uplink resources allocated in step S101 in a separate PDCCH message, this time with the CRC scrambled with the RNTI of the relay station 1020. It is also possible that semi-persistent scheduling resources are allocated to the relay station, possibly even before step S100, to allow the relay station to forward data transmissions from all its sidelink connected terminals. Yet another possibility, as mentioned in the previous embodiment, is that the message sent in step S101 includes a further allocation of resources to be used by the relay station 1020 for forwarding. This further resource allocation needs to be signaled before the normal allocation, so that the relay station 1020 can process the incoming upstream and prepare the data packets to be forwarded. • In step S105, the cell station 1000 optionally sends feedback to the wireless terminal, for example an acknowledgement indicating whether the data was correctly received, as in the previous embodiment. o These may be HARQ or PDCP level acknowledgements as detailed in the previous embodiments, or higher layer (e.g. IP), or other. The feedback data in steps 104 and 105 are marked as optional since they may be sent further to the wireless terminal 1010 via the relay station 1020 rather than the cell station 1000, depending on the decision of the scheduler in the cell station 1001.

[0149] The fourth embodiment depicted in Figure 11 corresponds to the second embodiment, except that it represents the case where a wireless terminal receives downlink user data from a core network. As in the second embodiment, only one cell station 1100 serving the cell 11 is considered. ● In step S111, the cell station 1100 transmits, for example on the PDCCH, a communication resource reservation message including or indicating / encoding an identifier of the wireless terminal 1110. This resource reservation message indicates Us resources on which the wireless terminal 1110 can transmit in the sidelink (SL) and Us-Rx resources on which the relay station 1120 can receive in the SL. The cell station 1100 further transmits a resource reservation indicating Ds resources on which the wireless terminal shall receive downlink data. It should be noted that the Ds resource allocation and the Us resource allocation may be combined in a single message or in separate messages. o In step S111a, the cell station 1100 transmits downlink data in the assigned Ds resources and the wireless terminal 1110 receives and decodes the user data in the Ds resources. The Us resources are scheduled some time after the Ds resources so that the wireless terminal 1110 has an opportunity to send feedback data in the assigned Us resources. As discussed in connection with the second embodiment, the Us and Us-Rx resources may be allocated in the same message or in different messages. As mentioned, in the third embodiment, the Us and Us-Rx resources are identical or substantially overlapping. In the case where a single message allocates both the Us and Us-Rx resources, the single message is a PDCCH message whose CRC is scrambled with an identifier selected as discussed in connection with the second embodiment, with the newly defined "remote-UE-RNTI". ● In step S112, the wireless terminal 1110 transmits feedback data, e.g. an acknowledgement (ACK) or non-acknowledgement (NACK) message, to the relay station 1120 via the side link (SL), indicating whether the DL data from the cell station 1100 was received correctly (ACK), incorrectly (NACK) or possibly partially incorrectly (e.g. NACK'), respectively. Typically, the cell station 1100 is not able to receive the transmitted data correctly due to transmission restrictions for the wireless terminal 1110, as previously indicated. The relay station 1120 receives the feedback data transmission from the wireless terminal 1110 in the Us-Rx resources. It should be noted that the feedback data may further include regular upstream data or a MAC control element such as a BSR, as in the two previous embodiments for upstream user data. ● In step S113, the relay station 1120 forwards the information to the cell station 1100 directly or indirectly (eg via a further relay UE). ● In the case where the feedback data indicates a NACK, or alternatively where the feedback data was not received in time, the cell station 1100, in step S114, optionally retransmits, fully or partially (in the case of a NACK'), the relevant DL data block within the new resource DL' allocation sent to the wireless terminal 1110.

[0150] The fifth embodiment of the invention depicted in Figure 12 corresponds to the fourth embodiment, except that the relay station 1220 is currently served by a cell station 1201 in a different cell 12b than the cell station 1200 (in cell 12a) serving the wireless terminal 1210. This therefore represents the case where the wireless terminal 1210 receives downlink user data from a core network having two cell stations serving it. ● In step S120, the cell station 1201 coordinates with other cell stations 1200 for downlink user data for the wireless terminal 1210 and for resource reservation for the next steps as in the third embodiment. Thus, the coordination ensures that the Us resources and the Us-Rx resources are equal or at least overlap significantly. ● In step S121, the cell station 1201 transmits a communication resource reservation message to the wireless terminal 1210 indicating the Us-Rx resources that the relay station needs to receive on the sidelink (SL) for one of its remote UEs. The details of this transmission are similar to, for example, the third and fourth embodiments. The relay station 1220 schedules reception on the Us-Rx resources. Optionally, as described in relation to the previous embodiments, step S121 is performed earlier, for example before step S120. That is, the cell station 1201 has selected a resource pool for the relay station 1220 to monitor the sidelink. The cell station 1201 can therefore signal this to the other cell stations 1200 in step S120 as part of the coordination. The cell station 1200 can then select an available resource in this resource pool.

[0151] Note that in addition to the resource pool, the relay station 1220 should listen for periodic resource reservations. This periodic resource reservation is first configured in the relay station 1220 in step S121. Then, after this, the two cell stations 1200 and 1201 cooperate in step S120 when the periodic reservation resources are still available for use. The cell station 1201 can, for example, send one or more resource proposals to the other cell station 1200. The cell station 1201 can store this information, for example, in a table listing which of the resource opportunities are still free. Then, in step S122, the cell station 1200 can transmit one specific resource reservation to the wireless terminal 1210.

[0152] A variant using a resource pool can work similarly to the periodic resource reservation described above. The cell station 1201 keeps a table of all the resources in the pool and which resources are already in use. The coordination step S120 thus involves the cell station 1201 choosing from the table a free resource and sending this information to the other cell stations 1200.

[0153] Alternatively, cooperation simply involves cell station 1201 telling other cell stations 1200 "pick any resource you prefer from this pool X", and thus the responsibility of choosing the resource is left to cell station 1200. If cell station 1200 is an exclusive user of the resource pool, no collisions can be expected. However, this is prone to resource collisions and / or interference if multiple cell stations are all using the same resource pool and independently choose resources from the resource pool without cooperation. To prevent this, cell station 1200 can, for example, collect measurements itself and from many UEs on resource usage / interference levels in order to choose resources correctly. ● In step S122, the other cell station 1200 sends a similar message indicating Us resources to the wireless terminal 1210. The cell station 1200 further sends a resource reservation to the wireless terminal indicating Ds resources for receiving downlink (DL) data, either in the same or a different message. o In step S122a, the cell station 1200 then transmits user data in the designated Ds resources which are received and decoded by the wireless terminal. Note that the Us resource allocation may be signaled before, after or during the transmission of the DL user data.

[0154] Furthermore, steps S121 and S122 may be performed in parallel. ● In step S123, the wireless terminal 1210 transmits feedback data, e.g. an acknowledgement (ACK) or a non-acknowledgement (NACK) message, to the relay station 1220 using Us resources, indicating whether the data from the cell station 1200 was received correctly (ACK), incorrectly (NACK) or partially incorrectly (NACK′), respectively. This feedback is received by the relay station 1220. ● In step S124, the relay station 1220 forwards the feedback information to the cell station 1201 directly or indirectly (eg via a relay UE - not shown). Optionally, in step S125, the cell station 1201 forwards all or part of the feedback data to the other cell station 1200. ● In the case where the feedback data indicates NACK / NACK', or alternatively if the feedback data was not received within time, the cell station 1200 is set up to retransmit the non-existent / corrupted data to the wireless terminal 1210 in a new resource reserved DL' in the next step S126.

[0155] In a particular variant of the previous embodiment, applicable to both single gNB or dual gNB cases, the relay station, when in range of a cell station transmitting user data directly to the wireless terminal, can send back to the transmitting cell station - on behalf of the wireless terminal - a PHY level ACK / NACK such as HARQ feedback data. This variant is based on the assumption that the relay station and the wireless terminal are relatively close, e.g. in the same area and under roughly the same radio conditions, so that the relay station feedback has some value to indicate how well the wireless terminal received the data transmission from the transmitting cell station. The benefit here is that the transmitting cell station can directly receive feedback at PHY level about whether the data was received correctly, without waiting for the above PHY layer feedback information (such as PDCP feedback, or feedback information via the IP layer), which in some cases takes a long time to arrive and be generated, incurring latency for DL ​​data.

[0156] The relay station transmits PHY feedback (e.g., HARQ feedback information) autonomously or after receiving a signal from the wireless terminal indicating its own PHY feedback. The HARQ feedback is preferably sent to the transmitting cell station within the HARQ feedback time interval (flexible in 5G, but typically 4 ms as in LTE). To achieve this, the relay station receives (from the cell station or from the wireless terminal) an RNTI value or other identity information that the cell station uses to send resource reservation messages or downlink messages to the wireless terminal. This allows the relay station to decode the PDCCH resource reservation message and become aware when a transmission to the wireless terminal is to occur, after which the relay station can decide to send a PHY level ACK / NACK, such as HARQ feedback, back to the cell station instead of the wireless terminal. The relay station further receives information from the cell station or from the wireless terminal that is TX limited, and / or determines the connection quality between the wireless terminal and the cell station using recently received measurement data from the wireless terminal. This can serve as a trigger for the relay station to decide on behalf of the wireless terminal when to send ACK / NACK feedback and when not to send it. Alternatively, the relay station is further aware that HARQ feedback is sent between a wireless terminal and a cell station, and replicates the HARQ feedback if the relay station knows the TX limited status of the wireless terminal (and thus knows that the HARQ feedback will be unlikely to arrive at the cell station). To this end, the relay station receives HARQ process information from the wireless terminal or from the cell station to act on behalf of the wireless terminal to ensure that the same HARQ process number and the same subframe are used. In yet another alternative, the wireless terminal can send a signal with information indicating the HARQ feedback information to the relay station (e.g., using a sidelink) before the HARQ feedback time interval occurs, and the relay station can then transmit the HARQ feedback information to the cell station during the scheduled feedback time interval.

[0157] For a wireless terminal, this means that upon receiving a PDCCH indicating a scheduled DL transmission, the wireless terminal forwards some or all of the received DCI, such as the HARQ process number, subframe number, etc., to the relay station in order to enable the relay station to provide feedback on behalf of the wireless terminal.

[0158] Similarly, in another variation of the previously discussed embodiment, if the wireless terminal transmits user data directly to the cell station (e.g., using uplink resources U allocated for the wireless terminal, but also decodable by the relay station), the relay station can send PHY level ACK / NACKs such as HARQ feedback to the wireless terminal on behalf of the cell station. For this purpose, the wireless terminal receives HARQ process information (e.g., HARQ process ID, timing / resource information) from the cell station to act on behalf of the cell station, to ensure that the same HARQ process number and the same subframe are used. The first or second cell station may further provide (e.g., through an RRC message) some security certificate or information about the type, format, encoding, scrambling or content of the signal or message to enable the relay station to verify the integrity of the message or to (partially) decode the message / signal, and further provide instruction / policy information under which the relay station is allowed to send acknowledgement data to the wireless terminal (e.g., if the CRC or message integrity code / message authentication code is verified as correct). It should be noted that such policy information may further be configured on the device by the core network (e.g., through a Policy Control Function (PCF)). The relay station uses the information received from the first or second cell station to perform some processing on the uplink / upstream signal / message received from the wireless terminal, and sends grant data to the wireless terminal if the result of this processing satisfies one or more conditions.Alternatively, the relay station may first forward the received uplink / upstream signal / message to the second cell station to which it is connected (which in turn forwards it to the first cell station), and then the second cell station (or the first cell station indirectly through the second cell station) upon successful reception / decoding / integrity verification of the forwarded uplink / upstream signal / message, may send the signal / message to the relay station (instead of sending the acknowledgement data directly to the wireless terminal), which in turn may then send the acknowledgement data to the wireless terminal.

[0159] The guiding assumption for the above solution for sending acknowledgements is that the relay station and the remote UE are relatively close together and the relay station has a higher incoming signal quality than the wireless terminal's signal, while the cell receives only a very weak signal directly from the wireless terminal. This has the benefit that in the typical case where the cell station can receive uplink transmissions directly from the wireless terminal, the cell station can respond directly to the feedback information itself, but in the extraordinary situation where the cell station cannot receive uplink transmissions due to TX limitations, the relay station can receive uplink data on behalf of the cell station. Furthermore, the relay station can respond on behalf of the cell station with feedback (e.g., ACK / NACK, or HARQ) information. The relay station will further take care that the uplink data is further relayed to its cell station so that the uplink data is not lost.

[0160] To accomplish that task, various techniques can be used by the relay station to avoid collisions with potential feedback information sent by the cell station. The relay station may, for example, detect that a wireless terminal has made a direct uplink transmission but that the cell station has not responded with PHY feedback information within the expected time frame. The relay station may then send this information to the wireless terminal on behalf of the cell station. The relay station receives an instruction from the cell station to start sending feedback information on behalf of the wireless terminal, the instruction being triggered, for example, by a measurement at the cell station indicating that the wireless terminal signal is becoming too weak. ● The relay station uses a random backoff period to send feedback data and the cell station does the same. The feedback responses from the relay station and the cell station will then be separated in time with a certain probability, and if one party notices that the other party has already responded, then there is no need for the other party to respond any more.

[0161] The overall solution has the benefit that wireless terminals (e.g., resource-constrained, low-power IoT devices) do not need to retransmit uplink data to the cell station or relay station that was lost by the cell station. Reducing the need for retransmissions saves energy.

[0162] In an alternative embodiment, multiple cell stations within the area send DL transmissions to the wireless terminal. This results in duplication of the data sent, thus improving transmission robustness and also creating diversity in radio conditions. This therefore improves the probability of correct data reception by the wireless terminal. This duplication reduces the probability of incomplete DL data transmission at the wireless terminal, since a TX-limited wireless terminal cannot directly send PHY-level ACK / NACK back to one or more of the cell stations. Furthermore, the multiple cell stations can further send resource reservation messages to the wireless terminal indicating resources Us' / Us'', each with a specific spectrum allocation that the wireless terminal can choose from and use to send upstream data, if necessary, and can send corresponding resource reservations to nearby relay stations to receive upstream data from the wireless terminal.

[0163] In an alternative embodiment, a cell station capable of reaching the wireless terminal sends relay selection or reselection information to the wireless terminal. This information can be encoded in a system information block (SIB) or an RRC message or a downlink control information (DCI) or other type of message, and includes, for example, the L2 identity of nearby relay stations and other information (e.g., information about the timing / frequency / resources when nearby relay stations transmit discovery messages (e.g., ProSe / sidelink discovery messages) or listen for incoming discovery or "relay join request" messages). The wireless terminal can use this information to select or reselect the best relay station to use. The wireless terminal can further select multiple relay stations as parents, for example, if suggested by the cell station information.

[0164] Such relay selection is particularly useful when the cell station was previously in contact with the wireless terminal (bidirectional) but has just detected that a TX limited situation applies, i.e., the wireless terminal's signal has become so weak that it cannot be received any more. This could be because the wireless terminal has reduced its transmission power due to lack of energy or to improve battery life, or because more power is required for another task and the total power budget is limited, or because the wireless terminal has moved out of range. The cell station can then send relay selection information to the wireless terminal in only one direction to help the wireless terminal quickly acquire the relay station.

[0165] Relay reselection is used when a wireless terminal is already using a relay but should select a better relay parent.

[0166] Additionally, the cell station can schedule resources for the relay station to listen for potential discovery messages or "relay join requests" or other upstream messages (e.g. PC5 signaling messages) from a wireless terminal, the messages indicating that the wireless terminal is looking for a repeater. For this purpose, the cell station further provides the relay station with information about the identity (e.g. L2 identity) that the wireless terminal should use in its discovery messages or "relay join requests" or upstream messages. These scheduled resources are chosen within the same range / pool as the resources communicated to the wireless terminal via the above mentioned SIB / RRC. This allows the relay station to more easily and reliably pick up the "relay join requests", discovery messages and / or upstream messages of the wireless terminal. For example, this could be that the relay station has temporarily disabled its relaying functionality to save energy, and after receiving a message indicating the scheduled resources, the relay station decides to make its relaying functionality available again to receive potential relay discovery requests from the wireless terminal and subsequently potentially serve as a repeater for this terminal.

[0167] Optionally, the cell station may send messages to the relay station requesting it to send out SL discovery messages. These messages have the purpose of being detected by the wireless terminal and therefore can be used during the relay selection process to choose the best relay station (e.g. in terms of signal quality). The messages sent by the cell station act as a trigger for the relay station to enable its relay function in case the relay station was (temporarily) disabled when the message was received.

[0168] Moreover, to trigger the sending of relay (re)selection information by the cell station, the cell station optionally requests a one-time high power "hello" message transmission from the wireless terminal to the cell station to inform the cell station that the wireless terminal is there and needs the relay to send a reply (at a sustainable lower power level). The cell station can broadcast relay selection information that is received by the wireless terminal as soon as it knows that the wireless terminal is somewhere. After relay selection / connection, asymmetric operation according to an embodiment of the invention can begin. This embodiment can only work if the wireless terminal has enough Tx power headroom and enough energy reserve to send a "hello" message transmission.

[0169] In an alternative embodiment, the wireless terminal switches intentionally to the TX restricted mode in order to conserve energy and / or to prepare for the imminent situation of going out of Tx coverage for the cell station. The cell station in this case has already sent relay selection information to the wireless terminal (e.g. before the wireless terminal switches to the TX restricted mode) as detailed in the previous embodiment, after which the wireless terminal can select and set up a relay connection. As soon as the relay connection is active, the wireless terminal reduces its Tx power and no longer transmits directly to the cell station but only to its relay. - The wireless terminal decides this autonomously and signals the cell station that the wireless terminal will perform this procedure. ● Or the cell station signals to the wireless terminal that it needs to perform this procedure (in this case the relay selection information may already be included). This is useful if the cell station, using its advanced RAN measurements and analysis, determines that the wireless terminal is at risk of going out of coverage and there are no other suitable cell stations to handover to. For this purpose the cell station transmits the relay selection information or a specific signal for switching to the TX restricted mode, which therefore includes the identity of the wireless terminal or the group of wireless terminals to which the wireless terminal belongs. The wireless terminal switches to the TX restricted mode upon receiving the relay selection information from the cell station or upon receiving the specific signal for switching to the TX restricted mode from the cell station, for example if the identity of the wireless terminal matches the identity of the wireless terminal or the group of wireless terminals to which the wireless terminal belongs.

[0170] It is important to note that various embodiments of the present invention can be combined with LTE / NR Dual Connectivity (DC), which means connecting to multiple gNBs / cells simultaneously. In both 4G and 5G standards, the concept of "Dual Connectivity" (DC) is defined. It is a solution to connect a wireless terminal, such as a UE, to two cell stations (here gNBs) simultaneously. In simple terms, one of the cell stations is the "master" and the other is the "secondary". In this document, this is referred to as the Master Cell Group (MCG) and Secondary Cell Group (SCG) since a single cell station is actually a group of cell stations due to the Carrier Aggregation (CA) feature.

[0171] This solution has several different variants specified for different use cases, for example: ● LTE-NR dual connectivity - allows a UE to connect to, for example, a master LTE eNB while using an additional NR gNB as a secondary cell to obtain spare throughput for the downlink. ● NR-NR Dual Connectivity (NR-DC) - Allows a UE to be connected to, for example, two NR gNBs, using a master gNB for control plane traffic and UL on a lower frequency, while using a secondary gNB for user plane DL traffic on a higher frequency, for example mmWave. This increases DL data rates while providing the UE's UL with a stable connection to the CN and long-range, low-power Tx operation.

[0172] As can be seen in Fig. 13, CUE1 and CUE2 are relay UEs and TUE is a wireless terminal acting as a remote UE. In this case, downlink data (resource reservation request, user data, or feedback data) sent by the cell station to the wireless terminal is sent by multiple gNBs.

[0173] In one refinement of the various embodiments, the cell station may employ near real-time beam steering (e.g., directed to a wireless terminal), where feedback is sent by the wireless terminal in the form of statistics / measurement reports via an indirect (relayed) path back to the cell station. The feedback is used by the cell station to adapt the beam steering in a closed loop. This is expected to be beneficial only in cases where the wireless terminal is stationary / not moving or moving very slowly, since feedback information sent via a relayed path will be slower than sending feedback information directly.

[0174] In another embodiment, a low-power wireless terminal, such as an NB-IoT or machine-to-machine module (e.g. LTE-M or UE cat.0), receives a (one-way) message directly from a cell station, including configuration information inviting the low-power wireless terminal to connect via a repeater instead of the cell station. This is useful in cases where the low-power wireless terminal has recently lost its connection to that cell station, at least "lost" in the uplink direction. Assuming that the downlink connection is still operational (the low-power wireless terminal is able to receive), the low-power wireless terminal is still able to receive this configuration message.

[0175] The message may further include information about the CE mode / repetition rate change of the wireless terminal. The message may further include a security key (e.g., stored in an encrypted container message) for directly connecting the wireless terminal to a relay station in its vicinity in a secure manner.

[0176] After the low power wireless terminal selects a repeater from the configuration information, any one of the previously described embodiments is used for further communication via the repeater, i.e., upstream, and for the direct downlink from the cell station.

[0177] In the example embodiments previously discussed, the wireless terminal can use the concept of RF backscatter communication, also known as ambient backscatter (sometimes combined with an energy harvester device). Such backscatter communication methods are useful for ultra-low power devices, which typically do not necessarily operate in the complete absence of an internal energy source during the period when backscatter communication is used. There are several cases (=device classes) possible, all within the scope of the present embodiments. 1. The device has an internal energy source that the device can use for normal 3GPP® communications, but has the ability to switch to backscatter communications for a time when desired to limit the energy consumption from that internal energy source to a very low level, or to avoid using energy from that internal source entirely by using some form of energy harvesting, such as RF energy harvesting or vibration energy harvesting. 2. The device has no internal energy source, the only source of energy available is energy harvesting, for example via RF waves. 3. The device has no internal energy source, but besides energy harvesting, e.g. from RF waves or vibration energy, there are also other intermittent external energy sources, such as solar or wind energy. During the time when the mentioned external energy sources do not provide enough energy, the device can fall back to energy harvesting, e.g. from RF waves or vibration energy.

[0178] The cell station can provide a strong RF signal directly to the wireless terminal that delivers data to the wireless terminal and provides energy to the wireless terminal's RF harvester. The cell station determines at some point that the wireless terminal is TX-limited and capable of using backscatter communications (e.g., using one of the previously indicated methods, such as capability or status information received from the wireless terminal, identity information (e.g., device belonging to a particular group of TX-limited devices and / or backscatter devices), or information received from the UDM or via the NEF), and therefore the cell station instructs the relay station and / or the wireless terminal to initiate or switch to backscatter communications, for example, by one or more of the following: 1. Providing enhanced configuration for discovery message monitoring in RRC signaling (e.g. SIB19 extended or dedicated). 2. Sending normal configuration messages to the wireless terminal while it is still connected to a cell station directly or indirectly as a remote UE, without using backscatter communications, e.g., using RRC for configuration messages. Note that this only works if the wireless terminal is capable of being in a non-backscatter communications mode. 3. Sending a configuration message to the relay station to instruct the relay station to begin listening for backscatter communications from the wireless terminal, and, in some cases, to instruct the relay station to transmit sufficient RF energy to be harvested by an RF energy harvester in the wireless terminal. 4. Sending / broadcasting a signal (e.g., a SIB or a wake-up signal) to the wireless terminal that includes an indication of using the backscatter communication mode (e.g., by setting the backscatter communication mode bit) and / or the identity of the wireless terminal (e.g., an L2 identity, SUCI / SUPI / GUTI, or RNTI) or the identity of a group of devices to which the wireless terminal belongs (e.g., an L2 group identity). 5. Sending / broadcasting configuration information to the wireless terminal (e.g., as part of the SIB) including conditions / policies that the wireless terminal should apply in order to decide to use backscatter communication (e.g., RSRP thresholds or maximum number of failed uplink transmissions).

[0179] The above mentioned messages need to be encrypted (e.g., using a pre-shared key, or a public key received from the first cell station (signed by the core network or a certificate authority), or using a previously used key, or a key derived from a previously used key (e.g., based on a Kamf or Kausf or ProSe Remote User Key (PRUK))) to prevent a malicious device from using such a message to force the wireless terminal to switch to backscatter communications. The above mentioned messages may further include additional information as to which (type of) signal the cell station will use to enable backscatter communication by the wireless terminal and / or how the backscatter signal should be transmitted by the wireless terminal (e.g., information on how to adapt / process the signal received from the cell station to the backscatter signal, such as which modulation or signal encoding or scrambling or transmission power to use, which signal processing algorithm to apply (e.g. as indicated by an algorithm identifier), which time delay to apply, which frequency modification to apply, which multiplexing method to apply, which particular type of signal / message to be used by the cell station or which particular type of upstream signal / message the wireless terminal is expected to transmit for use (e.g. sidelink discovery message), which L1 / L2 source or target identity information (or other identity information such as User Information ID, PRUK ID, SUCI, SUPI, GUTI, or RNTI) to be used in the upstream signal / message (e.g. the identity of the relay station), or which particular security credentials to be used for the message).

[0180] The wireless terminal decides to use backscatter communications using one or more of the above messages (e.g., to receive an incoming DL signal from a cell station and process the signal such that the wireless terminal can construct an upstream signal containing data / control information that the wireless terminal wants to transmit upstream to the cell station via the relay station (e.g., through multiplexing, signal manipulation)) and configures its receiver and transmitter and signal processing accordingly. Since the backscatter signal is not reflected directly towards the cell station, the wireless terminal deploys two sets of antennas (e.g., one antenna for receiving the DL signal from the cell station coming from one direction and one antenna for transmitting the upstream signal to the relay station in the other direction), or a single set of antennas that intermittently switches between a mode for receiving the DL signal from the cell station and a mode for transmitting the upstream signal to the relay station. For this purpose, the wireless terminal is configured by the cell station with (estimated) location information (e.g., geographic or relative coordinates, or distance / direction from a reference point) and / or direction information (e.g., angle between DL signal coming from the cell station and upstream signal going out to the relay station, launch angle of DL signal or upstream signal relative to a reference line or magnetic north) of the cell station, wireless terminal, and / or relay station. This enables the wireless terminal to configure the antenna accordingly and receive / send signals from / in the correct direction (e.g., by changing the beamforming characteristics of the transmitted signal). The wireless terminal is further configured by the cell station with information about the timing of mode switching (e.g., based on regular intervals or with respect to resources scheduled for downlink and upstream communication). This is useful in the case where the antenna is switched between a mode for receiving DL signals from the cell station and a mode for transmitting upstream signals to the relay station. Alternatively, the wireless terminal deploys one or more omni-directional antennas, in which case the location / angle is not necessary and is ignored.However, in the case of a single omni-directional antenna, mode switching is applied and the wireless terminal is configured with information about the timing of mode switching accordingly.

[0181] A cell station assigns identifiers in the security context of the cell station's PLMN to identify nearby wireless terminals and relay stations capable of supporting backscatter communications. A cell station can select backscatter communications-capable relay stations, for example, by: ● Proximity discovery data received by the cell station either directly from the wireless terminal (in the case where this wireless terminal is not yet TX-limited but will soon need to switch to TX-limited mode), or from the wireless terminal via the relay station (in the case where the wireless terminal is already acting as a remote UE for the relay station before switching to backscatter communication), or directly from the relay station (e.g. reporting that the relay station has detected a wireless terminal in the vicinity that can use backscatter communication), or from other cell stations. - Historical discovery data describing the wireless terminal and its prioritized list of past relay stations. ● User selected relay stations. • Detection of dedicated backscatter communication capable relay stations (symbiotic nodes) in the vicinity of the wireless terminal that can be selected by the wireless terminal as relay stations to be used. - Based on capability information from a connected relay station or a UE capable of becoming a relay station, or capability information provided through an application function, NEF, or information from the UDM.

[0182] The cell station configures relay stations in the vicinity of the wireless terminal by transmitting backscatter communication control information (BCI), for example in SIB18 or otherwise, to define PHY / MAC properties for: • System information corresponding to backscatter communications (e.g. modulation format, coding scheme, frequencies, schedules, etc. used). ● Backscatter communication channel allocation and its corresponding SL-channel mapping. A multi-UE backscatter communication connection, in which backscatter signals from a wireless terminal can be received by multiple relay stations in the vicinity, which can then be forwarded to a cell station and aggregated. • Congestion mitigation techniques configured to prevent multiple wireless terminals from simultaneously transmitting backscatter signals so as to avoid interference.

[0183] In the backscatter communication mode, the energy required for the wireless terminal to reflect or modulate a signal towards the relay station is typically derived from the RF signal of the cell station. Information about the generated power or received signal strength / bandwidth / frequency / density available at the wireless terminal (remote UE) is used to select device specific scheduling, modulation format, transmit power, coding scheme, protection mechanisms and connection termination indications. For example: - The wireless terminal autonomously determines such a set of parameters based on the available energy while already operating on RF powered energy. ● The wireless terminal, while still in the non-backscatter communication mode, measures the incoming RF power and / or other signal characteristics and first reports this to the cell station (directly or indirectly via its relay station), which then suggests parameters to be used and communicates this to the wireless terminal. Then, when the wireless terminal begins to use the RF backscatter communication mode, the wireless terminal will use the specified parameters for transmission. ● The cell station provides configuration information to the wireless terminal (e.g., via SIB or RRC) about sets of parameters to use for different levels of available RF generated energy and / or different RF signal strengths / bandwidths / frequencies / densities and / or different RF signal types, and the wireless terminal uses this configuration information to select a set of parameters to use for the upstream signal to the relay station. These parameters may be different for each cell or synchronization signal block (SSB).

[0184] Upon successful completion of backscatter communication during a period, the participating devices are returned to their normal state, for example: - Return to TX limited operation with no backscatter communication as specified in this invention. ● Revert to operating as a wireless terminal directly connected to a cell station, without using relay stations. Using both a direct cell station connection and one or more relay connections, or just one or more relay connections, etc.

[0185] When the wireless terminal stops using RF backscatter communication, the relay station optionally continues to listen for backscatter signals / requests from pre-authorized wireless terminals present within the pre-established security context. This is useful, for example, to detect devices that can only use RF backscatter communication at this time and that have entered the vicinity of the relay station and need to communicate. For this purpose, the pre-authorized wireless terminal needs to use a unique identity or certificate in its discovery, "relay join request", or other upstream signal / message (e.g. PC5 signaling message). To allow the relay station to verify that the wireless terminal is pre-authorized, the relay station is configured with corresponding information or remembers corresponding information from a previous communication with the wireless terminal (e.g. using the same or derived PC5 session key). Alternatively, the relay station forwards the incoming RF backscatter communication to the cell station to which the relay station is connected and / or to the core network for further processing and to further check whether the wireless terminal is pre-authorized or not.

[0186] In other words, to enable RF backscatter communications, the wireless terminal is configured for communicating in a cellular network, the cellular network further comprising at least one first cell station serving a first cell and at least one relay station served by a second cell station serving a second cell; The wireless device a controller adapted to generate uplink information, the controller operating in a backscatter communication mode and capable of configuring a receiver and a transmitter; a receiver adapted to receive, in a backscatter communication mode, first downlink signals sent directly by a first cell station, the first downlink signals carrying respective first downlink control information, at least one of the respective first downlink control information including at least an indication of a first resource and / or configuration parameter (e.g. a specific modulation) to be used by the wireless terminal to transmit a second signal directly to the relay station, and at least one of the respective first downlink control information including at least a second assigned downlink resource to be used by the wireless terminal to receive a further downlink signal directly from the first cell station; and a transmitter adapted to transmit, in a backscatter communication mode, a second signal to the relay station on the first resource carrying uplink information to be forwarded to the second cell station, the receiver being further adapted to receive directly from the first cell station a further downlink signal on the second allocated downlink resource. Optionally, the controller initiates the backscatter communication mode operation after the receiver receives a downlink signal sent directly by the first cell station indicating or including a trigger for activating the backscatter communication mode. As another option, the controller initiates the backscatter communication mode operation when the transmission or reception operation meets one or more (pre)configured signal strength / signal reception quality thresholds or signal transmission failure thresholds, or when the energy level of the wireless terminal falls below a certain threshold, or when a relay station is discovered. As yet another option, the transmitter is adapted to transmit, directly to the first cell station or to the relay station, an initial signal indicating or including a trigger for activating the backscatter communication mode.

[0187] The controller is further adapted to derive energy from the incoming downlink signal and / or perform signal processing on the incoming downlink signal from the first cell station, such that the controller processes the incoming signal to generate an output signal that includes or has uplink information multiplexed therein, such that the output signal (i.e., an upstream signal / message to be received by the relay station) carries the uplink information.

[0188] As a further option, the receiver and transmitter each operate a different set of antennas, and the controller instructs the transmitter to perform beamforming towards the relay station, for example, based on the relay station's location and / or angle information (e.g., the angle between the beam used for the downlink signal from the cell station as received by the wireless terminal and the beam used for the upstream signal directed towards the relay station), such location or angle information being received from the first cell station and / or the relay station.

[0189] As a further option, the controller is capable of alternately operating according to the backscatter communication mode and a second operating mode and configuring the receiver and the transmitter to operate in the selected mode, the receiver being adapted to receive, in the second operating mode, second downlink signals sent directly by the first cell station, the second downlink signals carrying respective second downlink control information, at least one of the respective second downlink control information including at least an indication of third allocated uplink resources to be used by the wireless terminal to transmit the first uplink signal directly to the first cell station, and at least one of the respective second downlink control information including at least an indication of third allocated uplink resources to be used by the wireless terminal to transmit the first uplink signal directly to the first cell station. includes at least an indication of a fourth allocated downlink resource to be used by the wireless terminal to receive a further downlink signal directly from the first cell station, the transmitter is adapted, in the second mode of operation, to transmit to the first cell station on the third allocated uplink resource for direct communication to the first cell station, and the receiver is configured by the controller to receive the further downlink signal directly from the first cell station on the fourth allocated downlink resource, such that the signal transmitted on the uplink to the first cell station is a reflected backscattered signal, and the reflected backscattered signal is processed to carry uplink information generated by the controller.

[0190] As mentioned throughout this description, embodiments and variants of the present invention relate to the context of the 3GPP 5G standard. They are applicable in: ● Medical applications / connected healthcare involving multiple wireless (4G / 5G) connected sensor nodes or actuator nodes. ● Medical applications / connected healthcare devices with small form factor, for example the HealthDot patch that has a built-in detector and should be placed on the skin. ● General IoT applications involving sensor or actuator nodes, be they wireless, mobile or fixed. ○ For example, smart cities, logistics, agriculture, etc. o In general, any IoT application where the UE needs to be low power, cheap, or have a small form factor. ● Emergency services, public services, & critical communications applications. ● Typical V2X system. • Specifically V2P systems, where a person (P) carries a wireless terminal with limited battery capacity and / or limited transmission power. ● Improved coverage for 5G cellular networks using higher frequency (e.g. mmWave) RF communications. ● Any other application area of ​​4G / 5G communications where relay stations are used.

[0191] It should be noted that the above described embodiments are not limited to out-of-coverage devices. They can be beneficial for any wireless terminal, even when operating within the coverage of a cell. Indeed, as previously explained, a wireless terminal has the ability to reduce the amount of power required for operation, since for example using an indirect link allows for a communication that consumes less energy, while at the same time using a direct link avoids the monitoring / detection costs of sidelink resources.

[0192] Moreover, it will be understood by those skilled in the art that the terms used in this specification, in general, and in the appended claims in particular, are generally intended to be "open" terms, e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "comprising" should be interpreted as "comprising but not limited to," etc. If recitation of a particular number of introduced claims is intended, such intent will be explicitly recited in the claims, and it will be further understood by those skilled in the art that in the absence of such recitation, no such intent exists. For example, as an aid to understanding, the following appended claims include the use of the introductory phrases "at least one" and "one or more" to introduce the recitation of the claims. However, the use of such phrases should not be taken to mean that introducing a claim recitation with the indefinite article "a" or "an" implies that any particular claim that includes such an introduced claim recitation is limited to implementations that include only one such recitation, even when the same claim includes the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an"; for example, "a" and / or "an" should be interpreted to mean "at least one" or "one or more," and the same applies to the use of definite articles used to introduce claim recitations. Furthermore, in instances where a convention similar to "at least one of A, B, and C, etc." is used, such construction is generally intended to mean that one of ordinary skill in the art would understand the convention; for example, "a system having at least one of A, B, and C" includes, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together.In instances where a convention similar to "at least one of A, B, or C, etc." is used, such construction is generally intended to mean that one of ordinary skill in the art would understand the convention, e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc. It will be further understood by those of ordinary skill in the art that any disjunction and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0193] The apparatus are each executed by means of the program code of a computer program and / or as dedicated hardware of an associated device. The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

Claims

1. A wireless terminal for communicating in a cellular network, wherein the cellular network has at least one first cell station serving a first cell and at least one relay station served by a second cell station serving a second cell, wherein the wireless terminal is a controller operating in a TX restriction operation mode, the controller generating uplink information, is a receiver configured by the controller to receive, in the TX restriction operation mode, a first downlink signal directly sent by the first cell station, the first downlink signal carrying respective first downlink control information, wherein at least one of the respective first downlink control information includes at least an indication of a first configuration parameter to be used by the wireless terminal to directly transmit a signal to the relay station, and at least one of the respective first downlink control information includes at least a second configuration parameter to be used by the wireless terminal to directly receive a further downlink signal from the first cell station, is a transmitter configured by the controller to transmit, in the TX restriction operation mode, a second signal carrying the uplink information to be transferred to the second cell station to the relay station using the first configuration parameter and the receiver further directly receives the further downlink signal from the first cell station using the second configuration parameter, a wireless terminal.

2. The wireless terminal according to claim 1, wherein the controller starts the TX restriction operation mode after the receiver receives the TX restriction operation mode activation signal, which is a downlink signal directly sent by the first cell station indicating or triggering the activation of the TX restriction operation mode.

3. The wireless terminal according to claim 1 or 2, wherein the controller starts the TX restriction operation mode when one or more preconfigured signal strength / signal reception quality thresholds or one or more signal transmission failure thresholds are met by the transmission or reception operation, when the energy level of the wireless terminal falls below a specific threshold, or when the relay station is discovered.

4. The wireless terminal according to claim 1, 2 or 3, wherein the transmitter transmits an initial signal instructing or triggering activation of the TX restriction operation mode to the first cell station and / or the relay station.

5. The controller operates alternately according to a first operation mode and a second operation mode which are the TX restriction operation mode, The receiver is adapted to receive, in the second operation mode, a second downlink signal directly sent by the first cell station and carrying respective second downlink control information, at least one of the respective second downlink control information including at least an indication of a third configuration parameter to be used by the wireless terminal to directly transmit an uplink signal to the first cell station, and at least one of the respective second downlink control information including at least an indication of a fourth configuration parameter to be used by the wireless terminal to directly receive a further downlink signal from the first cell station, The controller generates uplink information, The transmitter is configured by the controller to transmit, in the second operation mode, to the first cell station using the third configuration parameter for direct communication with the first cell station, and the receiver is configured by the controller to directly receive the further downlink signal from the first cell station using the fourth configuration parameter. The wireless terminal according to claim 1, 2, 3 or 4.

6. The receiver further receives a third downlink signal sent by the first cell station and carrying third downlink control information, the third downlink control information including at least an indication of a downlink resource scheduled to receive user data transmitted by the first cell station, and the controller configures the receiver to receive the user data. The wireless terminal according to claim 5.

7. The uplink information includes approval data based on a determination as to whether the user data has been successfully decoded, and when the controller is operating in the second operating mode, the third configuration parameter is used to send the approval data to the first cell station, or when the controller is operating in the first operating mode, the first configuration parameter is used to send the approval data to the relay station, and the approval data is transmitted by the transmitter. The wireless terminal according to claim 6.

8. The uplink information includes at least one uplink user data packet, the user data packet is directly sent to the first cell station in the second operating mode, and the user data packet is transferred by the relay station to the second cell station in the first operating mode. The wireless terminal according to claim 5, 6 or 7.

9. The receiver of the wireless terminal according to claim 8 receives further downlink control information including an indication as to whether the uplink user data packet has been successfully decoded.

10. The wireless terminal according to any one of claims 1 to 9, wherein the first cell station and the second cell station are a single cell station.

11. The wireless terminal according to any one of claims 1 to 9, wherein the transmitter uses backscatter communication.

12. At least one first cell station serving a first cell, At least one relay station served by a second cell station serving a second cell, A wireless terminal served by the first cell station A cellular communication system comprising: The first cell station includes a first cell station transmitter for directly transmitting a first downlink signal carrying first downlink control information to the wireless terminal, and the first downlink control information includes at least an indication of a first configuration parameter to be used by the wireless terminal to transmit a signal to the relay station. The second cell station includes a second cell station transmitter for transmitting a second downlink signal that carries second downlink control information to the relay station, the second downlink control information including at least an indication of second configuration parameters to be used by the relay station to receive the signal from the wireless terminal, the first and second configuration parameters at least partially overlapping, The wireless terminal includes a wireless terminal controller that generates uplink information, and a wireless terminal transmitter configured by the wireless terminal controller to transmit a message that carries the uplink information to the relay station using the first configuration parameters, The relay station includes a relay station receiver that receives the message using the second configuration parameters, A cellular communication system.

13. The cellular communication system according to claim 12, wherein the relay station includes a relay station transmitter for transmitting a relay message including the uplink information to the second cell station.

14. The cellular communication system according to claim 13, wherein the second cell station transmits a third downlink signal that carries third downlink control information to the relay station, the third downlink control information including at least an indication of third configuration parameters to be used by the relay station to transmit the relay message to the second cell station.

15. The cellular communication system according to claim 14, wherein the first downlink signal and the second downlink signal are a single downlink signal received by the wireless terminal and the relay station.

16. The cellular communication system according to claim 14 or 15, wherein the second downlink signal and the third downlink signal are a single downlink signal received by the relay station.

17. The cellular communication system according to any one of claims 12 to 16, wherein the message that carries the uplink information includes at least one uplink user data packet to be forwarded by the relay station to the second cell station.

18. A relay station operating in a cellular communication network comprising at least one first cell station serving a first cell and a wireless terminal served by the first cell station, wherein the relay station is served by a second cell station serving a second cell, wherein the relay station, a relay station receiver that receives from the second cell station a second downlink signal carrying second downlink control information, the second downlink control information including at least an indication of at least one first configuration parameter for receiving a message from the wireless terminal, a relay station controller for controlling the receiver of the relay station to receive the message including uplink information in the first configuration parameter, and a relay station transmitter for transferring the uplink information in the relay data message to the second cell station A relay station comprising: **Claim 19** A first cell station serving a first cell in a cellular communication system comprising a wireless terminal served by a first cell station and at least one relay station served by a second cell station serving a second cell, wherein the first cell station, a first cell station transmitter for transmitting to the wireless terminal a first downlink signal carrying first downlink control information, the first downlink control information including at least an indication of at least one first configuration parameter to be used by the wireless terminal for transmitting a message to the relay station, a first cell station controller for configuring the relay station with second downlink control information, the second downlink control information including at least an indication of at least one second configuration parameter to be used by the relay station for receiving the message from the wireless terminal, and the first and second resources at least partially overlapping, A first cell station comprising: **Claim 20** A method for operating a wireless terminal to communicate in a cellular network comprising at least one first cell station serving a first cell and at least one relay station served by a second cell station serving a second cell, the method comprising: The step of the wireless terminal receiving a downlink signal sent by the first cell station, the downlink signal carrying downlink control information, wherein the downlink control information includes at least an indication of a first configuration parameter to be used by the wireless terminal to transmit a message to the relay station; The step of the wireless terminal generating uplink information; The step of the wireless terminal transmitting the message carrying the uplink information to the relay station using the first configuration parameter, wherein the uplink information will be transferred to the second cell station; A method comprising the above steps.

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