End node to end node communication

Abstract

A mobile device includes means for determining to attempt to create a unicast sidelink communication channel between the mobile device and an identified target user device via a relay user device; and sending a relay request message to at least one user device operable as a relay to the target user device, wherein the relay request message includes at least some information for configuring a sidelink procedure to obtain feedback from the target user device. A mobile device includes means for receiving a relay request message from a source user device, the relay request message including at least some information for configuring a sidelink procedure to obtain feedback from a target user device; and sending a message to the target user device using the configured procedure, wherein the message is configured for the configured procedure in accordance with the received information for configuring the sidelink procedure to obtain feedback from the target user device; and sending a relay response message to the source user device, the relay response message indicating a result of the configured procedure between the mobile device and the target user device.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to terminal node to terminal node communication. Some embodiments relate to terminal node to terminal node communication via a relay that is not a cell base station. BACKGROUND

[0002] Wireless telecommunications networks typically comprise terminal nodes and access nodes such as base stations. Terminal nodes communicate directly with access nodes. Terminal nodes communicate indirectly with each other via one or more access nodes.

[0003] In some cases it can be desirable for terminal nodes to communicate with each other without using intermediate access nodes.

[0004] In 3GPP, terminal nodes (user equipment) are able to communicate directly with another terminal node (terminal device) without using an access node (cell base station) using a sidelink communication channel. SUMMARY

[0005] According to various but not necessarily all embodiments, there is provided a mobile device comprising means for:

[0006] determining to attempt to create a unicast sidelink communication channel between the mobile device and an identified target user equipment via a relay user equipment; and

[0007] sending a relay request message to at least one user equipment operable as a relay to the target user equipment, wherein the relay request message comprises at least some information for configuring a sidelink process to obtain feedback from the target user equipment.

[0008] In some but not necessarily all examples, the sidelink process with feedback is a hybrid automatic repeat request (HARQ) process with feedback enabled.

[0009] In some but not necessarily all examples, the mobile device comprises means for:

[0010] receiving a relay response message indicating a HARQ NACK communication from the target user equipment to the relay user equipment, the HARQ NACK communication being in response to a sidelink message sent from the relay user equipment to the target user equipment using a sidelink HARQ process with feedback enabled.

[0011] In some but not necessarily all examples, the relay request message is broadcast or groupcast.

[0012] In some but not necessarily all examples, the information comprised in the relay request message explicitly or implicitly specifies a sidelink HARQ process with feedback enabled.

[0013] In some, but not necessarily all examples, the information included in the relay request message explicitly specifies that a sidelink HARQ process with feedback enabled is not used.

[0014] In some, but not necessarily all examples, the information included in the relay request message explicitly or implicitly enables the relay user equipment to use a sidelink HARQ process with feedback enabled to transmit a sidelink unicast message having a source identifier that is an identifier of the mobile device and a destination identifier that is an identifier of the target user equipment.

[0015] According to various, but not necessarily all, embodiments there is provided a method comprising:

[0016] determining to attempt to create a unicast sidelink communication channel between the user equipment and an identified target user equipment via a relay user equipment; and

[0017] transmitting a relay request message to at least one mobile device operable as a relay to the target user equipment, wherein the relay request message includes at least some information for configuring a sidelink process to obtain feedback from the target user equipment.

[0018] According to various, but not necessarily all, embodiments there is provided a computer program which when loaded into a processor of a user equipment causes:

[0019] determining to attempt to create a unicast sidelink communication channel between the user equipment and an identified target user equipment via a relay user equipment; and

[0020] transmitting a relay request message to at least one mobile device operable as a relay to the target user equipment, wherein the relay request message includes at least some information for configuring a sidelink process to obtain feedback from the target user equipment.

[0021] According to various, but not necessarily all, embodiments there is provided a mobile device comprising means for:

[0022] receiving a relay request message from a source user equipment, the relay request message including at least some information for configuring a sidelink process to obtain feedback from a target user equipment; and

[0023] transmitting a message to the target user equipment using the configured process, wherein the message is configured for the configured process in dependence on the received information for configuring the sidelink process to obtain feedback from the target user equipment; and

[0024] sending a relay response message to the source user equipment, the relay response message indicating a result of the configured procedure between the mobile device and the target user equipment.

[0025] In some, but not necessarily all examples, the sidelink procedure with feedback is a hybrid automatic repeat request (HARQ) procedure with feedback enabled.

[0026] In some, but not necessarily all examples, the message sent to the target user equipment using the sidelink HARQ procedure with feedback enabled has no transport block, and so will automatically generate a NACK as HARQ feedback from the target user equipment.

[0027] In some, but not necessarily all examples, the mobile device comprises:

[0028] means for receiving a NACK in response to sending the sidelink message to the target user equipment, wherein the sidelink message is configured for a sidelink HARQ procedure with feedback enabled in accordance with the received information for configuring the sidelink HARQ procedure with feedback enabled; and comprising means for sending a relay response message to the source user equipment in response to receiving the NACK.

[0029] In some, but not necessarily all examples, the message is a unicast sidelink message having a source identifier that is an identifier of the source user equipment and a destination identifier that is an identifier of the target user equipment.

[0030] According to various, but not necessarily all, embodiments there is provided a method comprising:

[0031] receiving a relay request message from a source mobile device, the relay request message comprising at least some information for configuring a sidelink procedure to obtain feedback from a target user equipment; and

[0032] sending a message to the target user equipment using the configured procedure, wherein the message is configured for the configured procedure in accordance with the received information for configuring the sidelink procedure to obtain feedback from the target user equipment; and

[0033] sending a relay response message to the source mobile device, the relay response message indicating a result of the configured procedure between the mobile device and the target user equipment.

[0034] According to various, but not necessarily all, embodiments there is provided a computer program which when loaded into a processor of a user equipment causes:

[0035] receiving a relay request message from a source mobile device, the relay request message comprising at least some information for configuring a sidelink procedure to obtain feedback from a target user equipment; and

[0036] sending a message to the target user equipment using the configured procedure, wherein the message is configured for the configured procedure in accordance with the received information for configuring the sidelink procedure to obtain feedback from the target user equipment; and

[0037] sending a relay response message to the source mobile device, the relay response message indicating a result of the configured procedure between the mobile device and the target user equipment.

[0038] According to various but not necessarily all embodiments, examples are provided as claimed in the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0039] Some examples will now be described, by way of example, with reference to the accompanying drawings, in which:

[0040] Figure 1 One example of the subject matter described in this document is illustrated;

[0041] Figure 2 Another example of the subject matter described in this document is illustrated;

[0042] Figure 3A Another example of the subject matter described in this document is illustrated;

[0043] Figure 3B Another example of the subject matter described in this document is illustrated;

[0044] Figure 4 Another example of the subject matter described in this document is illustrated;

[0045] Figure 5 Another example of the subject matter described in this document is illustrated;

[0046] Figure 6 Another example of the subject matter described in this document is illustrated;

[0047] Figure 7 Another example of the subject matter described in this document is illustrated;

[0048] Figure 8 Another example of the subject matter described in this document is illustrated;

[0049] Acronyms

[0050] ACK: acknowledgement positive

[0051] CBR: channel busy ratio

[0052] DTX: discontinuous transmission

[0053] HARQ: hybrid automatic repeat request

[0054] ME: mobile equipment

[0055] NACK: Negative Acknowledgement

[0056] OoC: Out of Coverage

[0057] PSCCH: Physical Sidelink Control Channel

[0058] PSFCH: Physical Sidelink Feedback Channel

[0059] PSSCH: Physical Sidelink Shared Channel

[0060] RSSI: Received Signal Strength Indicator

[0061] RSRP: Reference Signal Received Power

[0062] RSRQ: Reference Signal Received Quality

[0063] R-UE: Relay UE

[0064] Rx UE: Receiver UE

[0065] SCI: Sidelink Control Information

[0066] SL: Sidelink

[0067] TB: Transport Block

[0068] Tx UE: Transmitter UE

[0069] UE: User Equipment DETAILED DESCRIPTION

[0070] Figure 1 An example of a network 100 is shown, which includes a plurality of network nodes, including terminal nodes 110, access nodes 120, and one or more core nodes 129. The terminal nodes 110 and the access nodes 120 communicate with each other. The one or more core nodes 129 communicate with the access nodes 120.

[0071] In this example, the network 100 is a wireless telecommunications network in which at least some of the terminal nodes 110 and the access nodes 120 communicate with each other using the transmission / reception of radio waves.

[0072] In some examples, the one or more core nodes 129 can communicate with each other. In some examples, the one or more access nodes 120 can communicate with each other.

[0073] The network 100 can be a cellular network comprising a plurality of cells 122, each served by an access node 120. In this example, the interface between a terminal node 110 and an access node 120 defining a cell 122 is a wireless interface 124.

[0074] The access nodes 120 are cellular radio transceivers. The terminal nodes 110 are cellular radio transceivers.

[0075] In the illustrated example, the cellular network 100 is a Third Generation Partnership Project (3GPP) network in which the terminal nodes 110 are user equipment (UE) and the access nodes 120 are base stations.

[0076] In the particular example illustrated, the network 100 is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN includes E-UTRA NodeBs (eNBs) 120 that provide E-UTRA user plane and control plane (RRC) protocol terminations toward the UEs 110. The eNBs 120 are interconnected with each other through the X2 interface 126. The eNBs are also connected by the S1 interface 128 to the Mobility Management Entity (MME) 129.

[0077] In another example, the network 100 is a Next Generation (or New Radio, NR) Radio Access Network (NG-RAN). The NG-RAN includes gNodeBs (gNBs) 120 that provide user plane and control plane (RRC) protocol terminations toward the UEs 110. The gNBs 120 are interconnected with each other through the X2 / Xn interface 126. The gNBs are also connected by the N2 interface 128 to the Access and Mobility Management Function (AMF).

[0078] 3GPP TS 38.300 provides an overall description of NR-based sidelink (SL) communication between proximate user equipment for both in-coverage (IC) operation and out-of-coverage (OoC) operation.

[0079] Sidelink (SL) communication is based on a source user equipment (Tx UE) transmitting a sidelink message directly to a target user equipment (Rx UE) through a SL between the Tx UE and the Rx UE.

[0080] The target UE (Rx UE) monitors one or more (pre-)configured resource pools to receive the transmitted SL message. For example, the SL message can be unicast, groupcast, or broadcast.

[0081] The SL message includes a source ID (SRC ID) identifying the source UE (Tx UE) and a destination ID (DST ID) identifying the target UE (Rx UE) in SL control information. They are partly included in the SL control information (SCI) sent by the source UE (Tx UE) to schedule the SL transmission of a transport block (TB) and partly in the header of the MAC PDU within the TB.

[0082] SL messages may also include the following in the SL control information (SCI): HARQ process number, new data indicator, redundant version, and HARQ feedback enable / disable indicator.

[0083] SL messages with HARQ feedback include a HARQ feedback enable indicator.

[0084] The target UE (Rx UE) monitors (multiple) (pre)configured resource pools and filters based on DSTID in order to receive SCI and TB.

[0085] Sidechain HARQ with feedback uses the Physical Sidechain Feedback Channel (PSFCH) and can operate in one of two options. In one option, the PSFCH uses resources dedicated to a single PSFCH transmission UE to transmit ACK or NACK. In the other option, the PSFCH transmits NACK on resources that can be shared by multiple PSFCH transmission UEs, or no PSFCH signal is transmitted on resources that can be shared by multiple PSFCH transmission UEs.

[0086] The NACK only option and the ACK / NACK option can be used for multicast SL messages from source UE 110 (Tx UE) to a group of target UEs (Rx UE). The ACK / NACK option can be used for unicast SL between source UE 110 (Tx UE) and target UE 110 (Rx UE).

[0087] Figure 2 An example is shown in which a unicast sidelink communication channel 19 is created between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via a relay UE 110 (R-UE).

[0088] The relay UE 110 (R-UE) is configured to probe the target UE 110 (Rx UE) to determine whether the relay UE (R-UE) can reach the target UE 110 (Rx UE) in order to form a communication channel 19.

[0089] In box 12, the source UE 110 (Tx UE) determines whether to attempt to establish a unicast sidelink communication channel 19 between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via the relay UE 110 (R-UE). The target UE 110 (Rx UE) is a known identified UE.

[0090] If it is determined to attempt to create a unicast sidelink communication channel 19 between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via a relay UE 110 (R-UE), the source UE 110 (Tx UE) sends a relay request message 11.

[0091] For example, the source UE 110 (Tx UE) can determine to attempt to create an indirect unicast sidelink communication channel 19 with the target UE 110 (Rx UE) via a relay UE (R-UE) 110 when the source UE 110 (Tx UE) needs to communicate with the target UE 110 (Rx UE) and either no direct sidelink communication channel 19 exists or existing direct or indirect sidelink communication channels are insufficient.

[0092] In some examples, the indirect unicast sidelink communication channel 19 via the relay UE 110 (R-UE) is the only communication channel 19 between the source UE (Tx UE) 110 and the target UE 110 (Rx UE). In other examples, the indirect unicast sidelink communication channel 19 via the relay UE 110 (R-UE) is one of multiple parallel communication channels (not shown) between the source UE 110 (Tx UE) and the target UE 110 (Rx UE).

[0093] The relay request message 11 is sent to at least one relay UE 110 (R-UE) in the vicinity of the source UE (Tx UE). The relay UE 110 (R-UE) has the capability to operate as a relay to the target UE 110 (Rx UE). The identity of the relay UE 110 (R-UE) and the capability to operate as a relay to the target UE 110 (Rx UE) are either known or unknown to the source UE 110 (Tx UE).

[0094] The relay request message 11 includes at least some information used to configure a sidelink procedure to obtain feedback from the target user equipment.

[0095] The configured sidelink procedure to obtain feedback can be used to test communication between the relay UE 110 (R-UE) and the target UE 110 (Rx UE), and in particular to test an onward relay sidelink between the relay UE 110 (R-UE) and the target UE 110 (Rx UE).

[0096] In at least some examples, the sidelink procedure to obtain feedback is a sidelink transmission procedure with feedback control, as described below.

[0097] An example of a procedure for obtaining feedback is a procedure that comprises transmitting a request 13 at a relay UE 110 (R-UE) and receiving an answer 15 from a target UE 110 (Rx UE), and receiving a request 13 at a target UE 110 (Rx UE) and transmitting an answer 15 to a relay UE 110 (R-UE). The request 13 can be, for example, a unicast, groupcast or broadcast SL message. The answer 15 can be, for example, a unicast, groupcast or broadcast SL message.

[0098] In case there is or has been a direct SL communication between the source UE 110 (Tx UE) and the target UE 110 (Rx UE), the sidelink procedure for obtaining feedback can be:

[0099] i) a SL HARQ procedure, e.g. a SL HARQ procedure with feedback enabled; or

[0100] ii) a SL measurement procedure.

[0101] For example (i), the relay request message 11 comprises at least some information for configuring a SL HARQ procedure, e.g. a SL HARQ procedure with feedback enabled, wherein the relay UE 110 (R-UE) sends a request (SL message 13) and the target UE 110 (Rx UE) sends an answer (HARQ response 15).

[0102] For example (ii), the relay request message 11 comprises at least some information for configuring a SL measurement procedure, wherein the relay UE 110 (R-UE) sends a SL measurement request 13 and the target UE 110 (Rx UE) sends a SL measurement report as answer 15;

[0103] Option i) operates at the physical (PHY) layer (layer 1), while option (ii) operates at layer 2.

[0104] In case there is or has been no direct SL communication between the source UE 110 (Tx UE) and the target UE 110 (Rx UE), the sidelink procedure for obtaining feedback can be a SL establishment procedure.

[0105] For this example, the relay request message 11 is a sidelink message 13 comprising at least some information for configuring a SL establishment procedure, wherein the relay UE 110 (R-UE) sends a unicast SL establishment request 13 to the target UE 110 (Rx UE) and receives a SL unicast establishment response 15 from the target UE 110 (Rx UE) as answer. The unicast SL establishment request can be sent using, for example, HARQ with blind repetitions and without feedback.

[0106] Overall, the sidelink procedure for obtaining feedback from the target UE 110 (Rx UE) can thus comprise signaling 13, 15 at layer 1 or higher. Thus, the sidelink procedure for obtaining feedback from the target UE 110 (Rx UE) can comprise HARQ with or without feedback. In case HARQ with feedback is used, the HARQ procedure with feedback enabled is the sidelink procedure for obtaining feedback, and the acknowledgement 15 from the target UE 110 (Rx UE) is HARQ feedback. In case HARQ without feedback is used, the sidelink procedure for obtaining feedback is not a HARQ procedure, but a higher layer (above L1) procedure based on a sidelink interface, and the acknowledgement 15 from the target UE 110 (Rx UE) is a SL message at the higher layer of the higher layer procedure for the sidelink.

[0107] In at least some examples, the relay request message 11 comprises at least an identifier of the source UE 110 (Tx UE) and an identifier of the target UE 110 (Rx UE).

[0108] For example, the relay request message 11 can be a sidelink message with a source identifier (e.g., SRC ID) as an identifier of the source UE 110 (Tx UE), the relay request message 11 comprising an identifier of the target UE 110 (Rx UE).

[0109] In at least some examples, the relay request message 11 is broadcast or groupcast.

[0110] At optional block 14, the relay UE 110 (R-UE) determines whether to send a message 13 to the target UE 110 (Rx UE).

[0111] For example, the decision can be based on a comparison of one or more quality metrics of the received relay request message 11 with one or more threshold conditions. Examples of quality metrics include RSSI, RSRP, RSRQ. For example, the decision can be based on a measurement of a power level of the received relay request message 11 and a comparison of the measured power level with a decision threshold. For example, if the link between the relay UE 110 (R-UE) and the source UE 110 (Tx UE) is bad or unreliable, no message 13 is sent to the target UE 110 (Rx UE).

[0112] The relay UE 110 (R-UE) sends the message 13 to the target UE 110 (Rx UE) using a sidelink procedure for obtaining feedback from the target UE 110 (Rx UE).

[0113] In at least some examples, message 13 is a unicast sidelink message 13 having a source identifier that is an identifier of the source UE 110 (Tx UE) (rather than a relay UE 110 (R-UE)) and a destination identifier that is an identifier of the target UE 110 (Rx UE). The sidelink message 13 spoofs the identifier of the source UE 110 (Tx UE) as its source.

[0114] The target UE 110 (Rx UE) receives message 13, performs a portion of the sidelink procedure for obtaining feedback at block 18, and sends a response message 15 in reply.

[0115] The relay UE 110 (R-UE) receives response message 15 in reply to sending message 13 to the target UE 110 (Rx UE).

[0116] The relay UE 110 (R-UE) sends a relay response message 17 to the source UE 110 (Tx UE) in reply to receiving the response message, the relay response message 17 indicating an outcome of the sidelink procedure for obtaining feedback.

[0117] In at least some examples, the relay response message 17 is configured to identify or enable identification of the relay UE 110 (R-UE). In at least some examples, the relay response message 17 is additionally configured to identify or enable identification of the target UE 110 (Rx UE).

[0118] If the relay response message 17 is a unicast SL message, the message can include an identifier of the relay UE 110 (R-UE) as a source identifier (e.g., SRC ID) and an identifier of the source UE 110 (Tx UE) as a destination identifier (e.g., DST ID). In some examples, an information element of the message includes an identifier of the target UE 110 (Rx UE).

[0119] If the relay response message 17 is a unicast SL message, the relay UE 110 (R-UE) can spoof its identity, and the message can include an identifier of the target UE 110 (Rx UE) as a source identifier (e.g., SRC ID) and an identifier of the source UE 110 (Tx UE) as a destination identifier (e.g., DST ID). An information element of the message includes an identifier of the relay UE (R-UE).

[0120] If the relay response message 17 is a broadcast or groupcast SL message, the information elements of the message can include an identifier of the relay UE (R-UE) and an identifier of the source UE 110 (Tx UE). In some examples, the information elements can include an identifier of the target UE 110 (Rx UE).

[0121] In at least some examples, the relay response message 17 is configured to convey the capabilities of the relay UE 110 (R-UE) and / or to convey measurements of the relay UE (R-UE) or details of a sidelink procedure configured by the relay request message 11 to enable the relay UE 110 (R-UE) to acquire feedback from the target UE 110 (Rx UE).

[0122] For example, the relay response message 17 can be a pre-defined protocol data unit (PDU) of a sidelink radio resource control (SL RRC) protocol or generally a pre-defined protocol data unit (PDU) of a sidelink control protocol. Thus, it is expected that at least a unique ID of the PDU and one or more information elements (IEs) included in such a PDU exist. The IEs can include, for example, an identifier of the target UE 110 (Rx UE), capabilities of the relay UE 110 (R-UE) sending the PDU, a report of the outcome of the HARQ procedure (e.g., a number of NACKs received from the target UE and / or a measurement of the received NACKs), etc.

[0123] After sending the relay request, the Tx UE can start a timer to wait for one or more relay response messages 17 from one or more relay UEs 110 (R-UEs). The relay request message 11 and the relay response message 17 are expected to be messages of the same SL control protocol. The relay response message 17 should implicitly or explicitly identify the corresponding relay request message 11 (e.g., with an ID of the source UE (Tx UE) and / or a sequence number of the relay request).

[0124] In some, but not necessarily all, examples, sending the relay response message 17 to the source UE 110 (Tx UE) is conditional. For example, at optional block 20, the relay UE 110 (R-UE) determines whether to send the relay response message 17 to the source UE 110 (Tx UE).

[0125] For example, the decision can be based on a comparison of one or more quality metrics of the received response message 15 to one or more threshold conditions. Examples of quality metrics include RSSI, RSRP, RSRQ. For example, the decision can be based on a measurement of a power level of the received response message 15 and a comparison of the measured power level to a decision threshold. For example, if the link between the relay UE 110 (R-UE) and the target UE 110 (Rx UE) is poor or unreliable, no relay response message 17 is sent to the source UE 110 (Tx UE).

[0126] The source UE 110 (Tx UE) receives a relay response message 17 from the relay UE 110 (R-UE) indicating successful communication 13, 15 between the relay UE 110 (R-UE) and the target UE 110 (Rx UE).

[0127] At block 22, the source UE 110 (Tx UE) determines whether to establish a communication channel 19.

[0128] For example, the decision can be based on a comparison of one or more quality metrics of the received relay response message 17 to one or more threshold conditions. Examples of quality metrics include RSSI, RSRP, RSRQ. For example, the decision can be based on a measurement of a power level of the received relay response message 17 and a comparison of the measured power level to a decision threshold. For example, if the link between the relay UE 110 (R-UE) and the source UE 110 (Tx UE) is poor or unreliable, no sidelink communication channel 19 is sent to the target UE 110 (Rx UE).

[0129] In other examples, the decision is additionally or alternatively based on measurements made at blocks 14 and / or 18 and / or 20 and included in the received relay response message 17.

[0130] In the case of multiple alternative relay UEs 110 (R-UEs) available to form the communication channel 19, at block 22, the source UE 110 (Tx UE) can select a relay UE 110 (R-UE) for use in the sidelink communication channel 19.

[0131] Finally, a unicast sidelink communication channel 19 is created between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via the relay UE 110 (R-UE).

[0132] From the foregoing, it will be appreciated that the source UE 110 (Tx UE) comprises means for:

[0133] determining to attempt to create a unicast sidelink communication channel 19 between the mobile device 110 and the identified target UE 110 (Rx UE) via a relay UE 110 (R-UE); and

[0134] sending a relay request message 11 to at least one user device 110 operable as a relay to a target UE 110 (Rx UE), wherein the relay request message 11 includes at least some information for configuring a sidelink procedure to obtain feedback from the target user device.

[0135] A mobile equipment (ME) for use by a source UE 110 (Tx UE) includes means for:

[0136] determining to attempt to create a unicast sidelink communication channel 19 between the mobile device 110 and the identified target UE 110 (Rx UE) via a relay UE 110 (R-UE); and

[0137] sending a relay request message 11 to at least one user device 110 operable as a relay to a target UE 110 (Rx UE), wherein the relay request message 11 includes at least some information for configuring a sidelink procedure to obtain feedback from the target user device.

[0138] The ME / UE also includes means for receiving a relay response message 17 from the relay UE 110 (R-UE) indicating communications 13, 15 between the relay UE 110 (R-UE) and the target UE 110 (Rx UE) that occurred during a sidelink procedure configured to obtain feedback from the target UE 110 (Rx UE).

[0139] In at least some examples, the relay request message 11 includes at least some information for configuring a feedback-enabled sidelink HARQ procedure between the relay UE 110 (R-UE) and the target UE 110 (Rx UE). The relay UE 110 (R-UE) sends a sidelink message 13 to the target UE 110 (Rx UE) using the feedback-enabled sidelink HARQ procedure 16. The target UE 110 (Rx UE) receives the sidelink message 13, performs a portion of the HARQ procedure with feedback at block 18, and sends a HARQ response message 15 in reply, which in some examples is a NACK.

[0140] The configured feedback-enabled HARQ process can be used to test communication between the relay UE 110 (R-UE) and the target UE 110 (Rx UE), in particular to test a forward relay sidelink between the relay UE 110 (R-UE) and the target UE 110 (Rx UE).

[0141] In at least some examples, the information included in the relay request message 11 explicitly or implicitly enables the relay UE 110 (R-UE) to transmit a unicast sidelink message 13 using the feedback-enabled sidelink HARQ process 16 with a source identifier (e.g., SRC ID) that is an identifier of the source UE 110 (Tx UE) and a destination identifier (e.g., DST ID) that is an identifier of the target UE 110 (Rx UE).

[0142] The information included in the relay request message 11 can explicitly or implicitly specify the feedback-enabled sidelink HARQ process.

[0143] In at least some examples, the information included in the relay request message 11 explicitly specifies that no transport block is used for the feedback-enabled sidelink HARQ process between the relay UE 110 (R-UE) and the target UE 110 (Rx UE).

[0144] In at least some examples, the relay request message 11 includes at least an identifier of the source UE 110 (Tx UE) and an identifier of the target UE 110 (Rx UE).

[0145] The relay UE 110 (R-UE) transmits a sidelink message 13 to the target UE 110 (Rx UE) using the feedback-enabled sidelink HARQ process 16.

[0146] The sidelink message 13 is configured for the feedback-enabled sidelink HARQ process 16 according to the information received in the relay request message 11 for configuring the feedback-enabled sidelink HARQ process 16.

[0147] In at least some examples, the sidelink message 13 is a unicast sidelink message 13 with a source identifier that is an identifier of the source UE 110 (Tx UE) (rather than the relay UE 110 (R-UE)) and a destination identifier that is an identifier of the target UE 110 (Rx UE). The sidelink message 13 falsely identifies the source UE 110 (Tx UE) as its source.

[0148] In at least some examples, the sidelink message 13 sent to the target UE 110 (Rx UE) using the feedback-enabled sidelink HARQ procedure 16 has no transport block and will therefore automatically generate a NACK as HARQ feedback from the target UE 110 (Rx UE).

[0149] The target UE 110 (Rx UE) receives the sidelink message 13, performs part of the HARQ procedure with feedback at block 18, and sends a HARQ response message 15, which in some examples is a NACK, in reply.

[0150] The relay UE 110 (R-UE) receives the HARQ response message 15 in response to sending the sidelink message 13 to the target UE 110 (Rx UE).

[0151] In response to receiving the HARQ response message, the relay UE 110 (R-UE) sends a relay response message 17 to the source UE 110 (Tx UE) indicating the outcome of the sidelink HARQ procedure.

[0152] In some, but not necessarily all, examples, sending the relay response message 17 to the source UE 110 (Tx UE) is conditional. For example, at optional block 20, the relay UE 110 (R-UE) determines whether to send the relay response message 17 to the source UE 110 (Tx UE).

[0153] For example, the decision can be based on a comparison of one or more quality metrics of the received HARQ response message 15 to one or more threshold conditions. Examples of quality metrics include RSSI, RSRP, RSRQ. For example, the decision can be based on a measurement of a power level of the received HARQ response message 15 and a comparison of the measured power level to a decision threshold. For example, if the link between the relay UE 110 (R-UE) and the target UE 110 (Rx UE) is poor or unreliable, no relay response message 17 is sent to the source UE 110 (Tx UE).

[0154] From the foregoing, it will be appreciated that the source UE 110 (Tx UE) can comprise means for:

[0155] determining to attempt to create a unicast sidelink communication channel 19 between the mobile device 110 and an identified target UE 110 (Rx UE) via a relay UE 110 (R-UE); and

[0156] A relay request message 11 is transmitted to at least one user equipment 110 operable as a relay to a target UE 110 (Rx UE), where the relay request message 11 includes at least some information for configuring a sidelink hybrid automatic repeat request (HARQ) process 16 with feedback enabled.

[0157] A mobile equipment (ME) used by the source UE 110 (Tx UE) can include components for:

[0158] determining to attempt to create a unicast sidelink communication channel 19 between the mobile equipment 110 and an identified target UE 110 (Rx UE) via a relay UE 110 (R-UE); and

[0159] A relay request message 11 is transmitted to at least one user equipment 110 operable as a relay to a target UE 110 (Rx UE), where the relay request message 11 includes at least some information for configuring a sidelink hybrid automatic repeat request (HARQ) process 16 with feedback enabled.

[0160] The ME / UE also includes components for receiving a relay response message 17 from the relay UE 110 (R-UE) indicating a communication 13, 15 between the relay UE 110 (R-UE) and the target UE 110 (Rx UE) that occurred during the sidelink hybrid automatic repeat request (HARQ) process 16 with feedback enabled.

[0161] In some examples, the relay response message 17 can indicate a HARQ NACK communication 15 from the target UE 110 (Rx UE) to the relay UE 110 (R-UE) that was a response to a sidelink message 13 transmitted from the relay UE 110 (R-UE) to the target UE 110 (Rx UE) using the sidelink HARQ process 16 with feedback enabled.

[0162] The relay request message 11 can be a sidelink message with a source identifier that is an identifier of the mobile equipment 110, the relay request message 11 including an identifier of the target UE 110 (Rx UE). The relay request message 11 can be broadcast or groupcast.

[0163] The information included in the relay request message 11 explicitly or implicitly enables the relay UE 110 (R-UE) to transmit a unicast sidelink message 13 using the sidelink HARQ process 16 with feedback enabled, the unicast sidelink message 13 having a source identifier that is an identifier of the mobile equipment 110 and a destination identifier that is an identifier of the target UE 110 (Rx UE).

[0164] It will also be appreciated from the foregoing that the relay UE 110 (R-UE) comprises means for:

[0165] receiving a relay request message 11 from a source UE 110 (Tx UE) comprising at least some information for configuring a sidelink procedure (e.g. a sidelink hybrid automatic repeat request (HARQ) procedure 16 with feedback enabled) to obtain feedback from a target user equipment; and

[0166] transmitting a message (e.g. a sidelink message 13) to the target UE 110 (Rx UE) using the configured procedure (e.g. a sidelink HARQ procedure 16 with feedback enabled), wherein the message (e.g. the sidelink message 13) is configured for the configured procedure (e.g. the sidelink HARQ procedure 16 with feedback enabled) in accordance with the received information for configuring a sidelink procedure to obtain feedback from a target user equipment (e.g. configuring a sidelink HARQ procedure 16 with feedback enabled); and

[0167] transmitting a relay response message 17 to the source UE 110 (Tx) indicating a result of the configured procedure (e.g. a sidelink HARQ procedure) between the relay UE 110 (R-UE) and the target UE 110 (Rx UE).

[0168] A mobile equipment (ME) for use by a relay UE 110 (R-UE) comprises means for:

[0169] receiving a relay request message 11 from a source UE 110 (Tx UE) comprising at least some information for configuring a sidelink procedure (e.g. a sidelink hybrid automatic repeat request (HARQ) procedure 16 with feedback enabled) to obtain feedback from a target user equipment; and transmitting a message (e.g. a sidelink message 13) to the target UE 110 (Rx UE) using the configured procedure (e.g. a sidelink HARQ procedure 16 with feedback enabled), wherein the message (e.g. the sidelink message 13) is configured for the configured procedure (e.g. the sidelink HARQ procedure 16 with feedback enabled) in accordance with the received information for configuring a sidelink procedure to obtain feedback from a target user equipment (e.g. configuring a sidelink HARQ procedure 16 with feedback enabled); and

[0170] transmitting a relay response message 17 to the source UE 110 (Tx UE) indicating a result of the configured procedure (e.g. a sidelink HARQ procedure) between the mobile equipment 110 and the target UE 110 (Rx UE).

[0171] Message 13 can be a unicast sidelink message 13 having a source identifier as an identifier of the source UE 110 (Tx UE) and a destination identifier as an identifier of the target UE 110 (Rx UE).

[0172] In some examples, the sidelink message 13 sent to the target UE 110 (Rx UE) using the feedback-enabled sidelink HARQ procedure 16 has no transport block and will therefore automatically generate a NACK as HARQ feedback from the target UE 110 (Rx UE).

[0173] The UE / ME can also include means for receiving a NACK 15 in response to sending the sidelink message 13 to the target UE 110 (Rx UE), where the sidelink message 13 is configured for the feedback-enabled sidelink HARQ procedure 16 according to the received information for configuring the feedback-enabled sidelink HARQ procedure 16; and means for sending a relay response message 17 to the source UE 110 (Tx UE) in response to receiving the NACK.

[0174] Figure 3A It is shown Figure 2 It is shown how the example is extended to include multiple candidate relay UEs 110 (R-UE1, R-UE2, R-UE3, R-UE4).

[0175] There are multiple candidate relay UEs 110 (R-UEs) in proximity to the source UE 110 (Tx UE), which can be a serving relay UE 110 (R-UE) in the sidelink communication channel 19. Each candidate relay UE (R-UE) is configured to probe the target UE (Rx UE) to find out whether the relay UE (R-UE) can reach the target UE (Rx UE) in order to form a communication channel 19.

[0176] In at least some examples, the probing uses SL HARQ so that the probing is treated by the target UE 110 (Rx UE) as a regular SL procedure initiated from the source UE 110 (Tx UE) for backwards compatibility.

[0177] The source UE 110 (Tx UE) transmits (by broadcast or groupcast) a relay request message 11 to a plurality of relay UEs 110 (R-UEi). The relay request message 11 includes at least some information used to configure a sidelink process to obtain feedback from a target user equipment. In at least some examples, the relay request message 11 includes at least an identifier of the source UE 110 (Tx UE) and an identifier of the target UE 110 (Rx UE). For example, the relay request message 11 can be a sidelink message with a source identifier (e.g., SRC ID) that is an identifier of the source UE 110 (Tx UE), the relay request message 11 including an identifier of the target UE 110 (Rx UE). In this example, the information included in the relay request message 11 configures a sidelink hybrid automatic repeat request (HARQ) for which feedback is enabled. In some examples, this information explicitly specifies that no transport block is used for the sidelink HARQ process for which feedback is enabled.

[0178] In response to receiving the relay request message 11, one or more relay UEs 110 (R-UE4) can determine not to transmit a sidelink message 13 to the target UE 110 (Rx UE).

[0179] In response to receiving the relay request message 11, one or more relay UEs 110 (R-UE1, R-UE2, R-UE3) can determine to transmit a sidelink message 13 to the target UE 110 (Rx UE).

[0180] The sidelink message 13 is configured for a sidelink HARQ process for which feedback is enabled according to the information received in the relay request message 11 used to configure the sidelink HARQ process for which feedback is enabled.

[0181] The sidelink message 13 is transmitted by different relay UEs 110 (R-UE1, R-UE2, and R-UE3) using the same SCI, and the same resources configured by the source UE 110 (Tx UE), for each scheduled HARQ transmission of the common HARQ process, so that for each scheduled HARQ transmission from the source UE 110 (Tx UE), it appears to the target UE 110 (Rx UE) as the same SCI.

[0182] In at least some examples, the source UE 110 (Tx UE) and / or the serving network can control the involved relay UEs 110 (R-UEs) such that all involved relay UEs 110 (R-UEs) transmit the same SCI to the target UE 110 (Rx UE) using the same resources for the common feedback-enabled HARQ process. Thus, the content of this same SCI including the HARQ configuration can be determined (e.g. on the fly) by the source UE 110 (Tx UE) and provided to the involved relay UEs 110 (R-UEs) and / or determined (e.g. in advance) by the serving network and provided to the involved relay UEs 110 (R-UEs).

[0183] In some examples, the source UE 110 (Tx UE) is configured to control the relay UEs 110 (R-UEi) such that e.g. a minimum number of HARQ (re-)transmissions will be transmitted and / or which relay UEs (R-UEj) transmit which HARQ (re-)transmissions. All relay UEs 110 (R-UEi) can monitor for the HARQ response message 15 (e.g. NACK) for each HARQ (re-)transmission.

[0184] In at least some examples, the sidelink message 13 is a unicast sidelink message 13 having a source identifier that is an identifier of the source UE 110 (Tx UE) (rather than a relay UE 110 (R-UEi)) and a destination identifier that is an identifier of the target UE 110 (Rx UE). The sidelink message 13 falsely identifies the source UE 110 (Tx UE) as its source.

[0185] In at least some examples, the sidelink message 13 transmitted to the target UE 110 (Rx UE) using the feedback-enabled sidelink HARQ process 16 has no transport block, so a NACK will automatically be generated as HARQ feedback from the target UE 110 (Rx UE).

[0186] The target UE 110 (Rx UE) receives the sidelink message 13 and transmits a HARQ response message 15 in response, which in some examples is a NACK.

[0187] The relay UEs 110 (R-UEs) receive the HARQ response message 15 in response to transmitting the sidelink message 13 to the target UE 110 (Rx UE).

[0188] For example, a NACK is transmitted back when the target UE 110 (Rx UE) receives the SCI but not the transport block. All relay UEs 110 (R-UEi) can monitor for the HARQ response message 15 (e.g. NACK) regardless of whether they were involved in transmitting the sidelink message 13.

[0189] If the HARQ response message 15 (e.g., NACK) is not received, the SCI of the sidelink message 13 can be updated to increment the HARQ transmission # (i+1) of the common HARQ process, which is then retransmitted. This retransmission can be configured by the source UE 110 (Tx UE) with the information included in the relay request message to configure the HARQ process for which feedback is enabled.

[0190] In response to receiving the HARQ response message 15, the relay UEs 110 (R-UEs) can send a relay response message 17 to the source UE 110 (Tx UE) indicating the outcome of the sidelink HARQ process.

[0191] In some, but not necessarily all, examples, sending the relay response message 17 to the source UE 110 (Tx UE) is conditional. For example, one or more relay UEs 110 (e.g., R-UE3) can determine not to send the relay response message 17 to the source UE 110 (Tx UE), and one or more relay UEs 110 (e.g., R-UE1, R-UE2) can determine to send the relay response message 17 to the source UE 110 (Tx UE).

[0192] The relay UEs 110 (R-UEi) can determine whether to send the relay response message 17 based on one or more HARQ response messages 15 (e.g., NACK) received from the target UE 110 (Rx UE) during the configured common HARQ process. For example, sending the relay response message 17 can be based on a number of HARQ response messages 15 (e.g., NACK) received from the target UE 110 (Rx UE) and / or a power measurement (e.g., RSRP) of one or more HARQ response messages 15 (e.g., NACK) being above a threshold, which can be configured, for example, by the source UE 110 (Tx UE).

[0193] The source UE 110 (Tx UE) receives the relay response messages 17 from the multiple relay UEs 110 (R-UE1, R-UE2) indicating successful communication 13, 15 between the respective relay UEs 110 (R-UE 1, R-UE 2) and the target UE 110 (Rx UE).

[0194] The source UE 110 (Tx UE) selects a relay UE 110 (e.g., R-UE1) to use as a serving relay UE in the sidelink communication channel 19. Finally, as Figure 3BA unicast sidelink communication channel 19 is created between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via the selected relay UE 110 (e.g., R-UE1) as shown.

[0195] In some examples, SL-based UE-to-UE relaying can be used to provide or enhance service continuity, power efficiency, or QoS for an ongoing unicast SL between the source UE 110 (Tx UE) and the target UE 110 (Rx UE).

[0196] For example, SL-based UE-to-UE relaying can be used as a primary option for possible recovery from SL radio link failure, especially for OoC operation. SL-based UE-to-UE relaying can be used as an alternative to direct SL to proactively avoid SL radio link failure or to reduce the transmission power of the source UE 110 (Tx UE) and thus reduce power consumption. In addition to direct SL, SL-based UE-to-UE relaying can be used as an auxiliary connection to provide or enhance QoS for the unicast SL between the source UE 110 (Tx UE) and the target UE 110 (Rx UE), which is required for high-reliability communication over SL, for example.

[0197] Figure 4 SL-based UE-to-UE relaying as previously described in Figure 2 , Figure 3A and Figure 3B is shown. In this example, the SL-based UE-to-UE relaying for an ongoing unicast SL between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via a relay UE 110 (R-UE) is not visible to the target UE 110 (Rx UE) in terms of supporting backward compatibility.

[0198] In this example, the source UE 110 (Tx UE) is configured to coordinate and control the relay UE 110 (R-UEi) to probe the target UE 110 (Rx UE) via the use of a common feedback-enabled HARQ process without scheduling a transport block.

[0199] This control can be done by the source UE 110 (Tx UE) for on-the-fly control, and / or by the serving network for semi-static control, and / or by SIM-based pre-configuration for out-of-coverage operation.

[0200] At block 30, the source UE 110 (Tx UE) transmits data to the target UE 110 (Rx UE) using a unicast sidelink communication channel. In this example, the source UE 110 (Tx UE) is capable of supporting SL-based UE-to-UE relaying, while the target UE 110 (Rx UE) is not necessarily capable of supporting SL-based UE-to-UE relaying.

[0201] At block 12, the source UE 110 (Tx UE) determines to establish an SL-based UE-to-UE relay, e.g., due to one of the use cases described above. The source UE 110 (Tx UE) determines whether to attempt to create a unicast sidelink communication channel 19 between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via a relay UE 110 (R-UE).

[0202] If it is determined to attempt to create a unicast sidelink communication channel 19 between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via a relay UE 110 (R-UE), the source UE 110 (Tx UE) sends a relay request message 11.

[0203] The source UE 110 (Tx UE) sends (by broadcast or groupcast) the relay request message 11 to one or more relay UEs 110 (R-UEi) that are known or unknown to the source UE 110 (Tx UE). The relay request message 11 includes at least some information to configure a sidelink hybrid automatic repeat request (HARQ) process with feedback enabled. In this example, the relay request message 11 is a sidelink message with a source identifier (e.g., SRC ID) that is an identifier of the source UE 110 (Tx UE). The relay request message 11 includes an identifier of the target UE 110 (Rx UE). In at least some examples, the information included in the relay request message 11 explicitly specifies that no transport block is for a sidelink HARQ process with feedback enabled.

[0204] At block 14, the relay UE 110 (R-UE) determines whether to participate in probing the target UE 110 (Rx UE) using the configured common HARQ process and the allocated resources configured by the relay request message 11.

[0205] In response to receiving the relay request message 11, one or more relay UEs 110 (R-UE4) can determine not to send a sidelink message 13 to the target UE 110 (Rx UE).

[0206] In response to receiving the relay request message 11, one or more relay UEs 110 (R-UE1, R-UE2, R-UE3) can determine to send a sidelink message 13 to the target UE 110 (Rx UE).

[0207] In this example, the sidelink message 13 sent to the target UE 110 (Rx UE) using the feedback-enabled sidelink HARQ procedure has no transport block, so a NACK will automatically be generated as the HARQ response message 15 from the target UE 110 (Rx UE).

[0208] The relay UEs 110 (R-UEs) are configured by the relay request message 11 to use the common feedback-enabled SL HARQ procedure, but without transmitting the actual transport block (TB) to probe the target UE 110 (Rx UE). The common HARQ procedure with feedback without TB causes the target UE 110 (Rx UE) to keep sending NACK as long as they receive a HARQ (re)transmission, e.g., the sidelink message 13 sent by the relay UE 110 (R-UE). The HARQ (re)transmission includes the sidelink control information (SCI), but not the transport block (TB) scheduled in the SCI.

[0209] In this example, the sidelink message 13 is a unicast sidelink message 13 with a source identifier that is the identifier of the source UE 110 (Tx UE) (instead of the relay UE 110 (R-UEi)) and a destination identifier that is the identifier of the target UE 110 (Rx UE). The sidelink message 13 falsely takes the identifier of the source UE 110 (Tx UE) as its source. This provides backward compatibility with legacy target UEs 110 (Rx UE).

[0210] For each HARQ (re)transmission of the configured common HARQ procedure, more than one relay UE 110 (R-UE) can send the same SCI in the sidelink message 13 using the same allocated resources.

[0211] Based on monitoring for a NACK from the target UE 110 (Rx UE) for each transmission HARQ (re)transmission during the common HARQ procedure, the individual relay UEs 110 (R-UE) are able to determine whether the target UE 110 (Rx UE) can be reached correctly and thus whether to respond to the relay request message 11 of the source UE 110 (Tx UE).

[0212] It should be noted that a relay UE 110 (R-UE) can receive a NACK and act upon that NACK that is a response to a sidelink message 13 sent by a different relay UE 110 (R-UE).

[0213] In case no NACK 15 is received from the target UE 110 (Rx UE) during the common HARQ process (denoting HARQ DTX), the target UE 110 (Rx UE) is considered unreachable to the corresponding relay UE 110 (R-UEi) and the corresponding relay UE 110 (R-UEi) can not need to send a relay response message 17 to the source UE 110 (Tx UE).

[0214] At block 20, the relay UE 110 (R-UE) determines whether to send a relay response message 17. The decision can be based on the NACK(s) 15 received from the target UE 110 (Rx UE).

[0215] In some, but not necessarily all examples, as mentioned before, sending a relay response message 17 to the source UE 110 (Tx UE) is conditional.

[0216] In response to receiving the HARQ response message 15, the relay UE 110 (R-UE) can send a relay response message 17 to the source UE 110 (Tx UE), the relay response message 17 indicating the outcome of the sidelink HARQ process. In this example, the relay response message 17 is a unicast sidelink message. The ID of the involved target UE 110 (Rx UE) is used as the source ID (SRC ID) of the relay response message 15, and the ID of the source UE 110 (Tx UE) is used as the destination ID (DST ID) of the relay response message 15.

[0217] At block 22, the source UE 110 (Tx UE) determines whether to establish a communication channel 19. The source UE 110 (Tx UE) selects at least one relay UE 110 (R-UE) that has sent a relay response message 17 as a serving relay UE for the SL communication channel 19. Thus, based on the received relay response messages 17, the source UE 110 (Tx UE) can select one or more most suitable relay UEs 110 (R-UE) for the current needs of the source UE 110 (Tx UE).

[0218] At block 32, a SL connection is established with the selected relay UE 110 to establish a relay connection to the source UE 110 (Rx UE). The source UE 110 (Tx UE) can initiate the actual relay connection setup to the selected individual relay UE 110 (R-UE). For example, the source UE 110 (Tx UE) can send a UE-to-UE relay connection setup request message to the selected relay UE 110 (R-UE). The message can provide the selected relay UE 110 (R-UE) with further configurations related to the SL communication between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) and the SL communication between the source UE 110 (Tx UE) and the selected relay UE 110 (R-UE). The selected relay UE 110 (R-UE) can respond to the source UE 110 (Tx UE) with a UE-to-UE relay connection setup complete message. The source UE 110 (Tx UE) can then start using the established UE-to-UE relay connection (channel 19) for actual SL data transmission to and / or from the target UE 110 (Rx UE).

[0219] The unicast sidelink communication channel 19 for data transmission is thereby created and used between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via the selected relay UE 110.

[0220] In one embodiment, the configuration of the common HARQ process with feedback (e.g., without TB) can be partly provided to the source UE 110 (Tx UE) and the relay UE 110 (R-UE) by the serving network using dedicated or common signaling or as a SIM-based pre-configuration as a semi-static configuration.

[0221] The configuration of the common HARQ process with feedback can include, for example, HARQ process ID, maximum number of HARQ transmissions, transmission power, content of SCI to be sent to the target UE 110 (Rx UE) (as for a regular HARQ transmission scheduling a TB), etc.

[0222] The rules for the relay UE 110 (R-UE) to transmit HARQ transmissions 13 and to monitor for NACKs 15 from the target UE 110 (Rx UE) can be included in the common HARQ process configuration.

[0223] In one example, the rules can cause the involved relay UE 110 (R-UE) to transmit at least k HARQ (re)transmissions 13 and to monitor for at least i HARQ NACKs 15 during the configured common HARQ process, where k and i are below the maximum number of HARQ (re)transmissions.

[0224] In another example, the rules can be such that the involved relay UE 110 (R-UE) keeps transmitting HARQ (re)transmissions 13 and monitors for HARQ NACKs 15 until the HARQ NACK(s) 15 are correctly received or the configured common HARQ procedure reaches the maximum number of HARQ transmissions 13.

[0225] In one embodiment, the configuration of the feedback-enabled common HARQ procedure (e.g. without TB) can be determined by the source UE 110 (Tx UE) on the fly and provided to the relay UE 110 (R-UE) with the relay request message 11. In this case, the configurations can be adapted to the allocated resources to be used by the relay UE 110 (R-UE) for transmitting the HARQ (re)transmissions 13 and / or for the proximity awareness (such as pre-discovered relay UEs 110 (R-UE) and / or measured proximity SL traffic load or CBR) as determined by the source UE 110 (Tx UE).

[0226] The configurations and allocated resources can be such that the same SCI is used for the HARQ (re)transmissions 13 on the same resources from different relay UEs 110 (R-UE).

[0227] If the source UE 110 (Tx UE) does not provide any configurations or allocated resources for the common feedback-enabled HARQ procedure, the relay UEs 110 (R-UE) would need to coordinate the transmission of the SCI to the target UE 110 (Rx UE) among them. This is not practical.

[0228] In one embodiment, the involved relay UEs 110 (R-UE) are configured to send a relay response message 17 to the source UE 110 (Tx UE) when the involved relay UEs 110 (R-UE) correctly receive the NACK(s) 15 from the target UE 110 (Rx UE) during the common HARQ procedure, e.g. at least m NACKs 15 are received (m = 1 is sufficient, but more than one NACK can be used for reassurance purposes, especially when the common HARQ procedure is configured to have a fixed number of HARQ (re)transmissions to be sent by the R-UE) and / or a NACK 15 with a received signal strength above a preconfigured threshold level is received. Otherwise, the involved relay UEs 110 (R-UE) can stop participating and not send a relay response message 17.

[0229] In one embodiment, the relay response message 17 can indicate the number of received NACKs 15 and / or the received signal strength of the most recently received NACK 15.

[0230] In one embodiment, the source UE 110 (Tx UE) can select more than one relay UE 110 (R-UE) from the relay UEs 110 (R-UEs) from which it receives relay response messages 17 to establish a relay connection to the target UE 110 (Rx UE). There can be multiple parallel unicast SL communication channels 19 between the source UE 110 (Tx UE) and the target UE 110 (Rx UE), each with a different relay UE 110 (R-UE).

[0231] It should be noted that the proposed approach using feedback-enabled common HARQ procedure (e.g., without TB) to enable the relay UE 110 (R-UE) to probe the target UE 110 (Rx UE) for SL-based UE-to-EU relay setup can generally be applied, regardless of whether the relay needs to be invisible / translucent to the target UE 110 (Rx UE).

[0232] The feedback-enabled HARQ procedure provides a controllable fast and efficient procedure to check the communication between the relay UE 110 (R-UE) and the target UE 110 (Rx UE) with little impact on the existing standards. However, more optimization can be made in case of allowing visibility. For example, the SCI sent by the relay UE 110 (R-UE) to the target UE 110 (Rx UE) for probing can have a new format.

[0233] In the above example, a unicast sidelink communication channel 19 is created between the source UE 110 (Tx UE) and the target UE 110 (Rx UE) via a single relay UE 110 (R-UE). This is achieved in a way that has minimal impact on the existing 3GPP specifications, no new physical layer channel / signal is needed, but rather the existing sidelink HARQ with feedback is re-used in a way that not only creates backward compatibility (transparent to the target UE 110) but also creates a fast, robust, and efficient procedure.

[0234] However, the example is not necessarily limited to using a configured common feedback-enabled HARQ procedure to allow one or more relay UEs (R-UEs) to probe the target UE (Rx UE). Generally, a sidelink communication procedure with feedback control can be used. The use of a sidelink communication procedure with feedback control, including a feedback-enabled HARQ procedure, is configured and controlled by the source UE (Tx UE) and / or the serving network and / or based on SIM-based pre-configuration (e.g., for out-of-coverage operation).

[0235] In at least some of the foregoing examples, the relay request message 11 can additionally include one or more of the following: quality of service (QoS) requirements for the intended data or SL QoS flow; a reason for attempting to establish a communication channel 19 with relay at block 12 (e.g., radio link failure recovery, reliability, or power saving); an indication (implicit or explicit) of whether the requested relay must be a 2-hop relay (implicit for preconfigured reasons such as radio link failure over SL or dual connectivity (DC), or for reconfigured QoS requirements); and an indication of whether the relay is for one-way or two-way U-plane data.

[0236] In at least some of the foregoing examples, the relay response message 17 can additionally include one or more of the following: UE capabilities of the responding relay UE 110 (R-UE); limitations / preferences of the responding relay UE 110 (R-UE) in serving the relay request.

[0237] Figure 5 An example of a method 200 is shown. For example, the method can be performed by a source UE 110 (Tx UE) to create a unicast sidelink communication channel 19 between the source UE 110 (Tx UE) and a target UE 110 (Rx UE) via a relay UE 110 (R-UE).

[0238] At block 202, the method 200 includes determining to attempt to create a unicast sidelink communication channel 19 between a source UE 110 (Tx UE) and an identified target UE 110 (Rx UE) via a relay UE 110 (R-UE).

[0239] At block 204, the method 200 includes sending a relay request message 11 to at least one relay user equipment 110 (R-UE). The relay UE 110 is a mobile device 110 that is operable as a relay to the target UE 110 (Rx UE). The relay request message 11 includes at least some information for configuring a sidelink hybrid automatic repeat request (HARQ) process 16 with feedback enabled.

[0240] At block 206, the method 200 can include receiving a relay response message 17 from the relay UE 110 (R-UE) indicating a communication 13, 15 between the relay UE 110 (R-UE) and the target UE 110 (Rx UE).

[0241] At block 206, the method 200 can include creating a unicast sidelink communication channel 19 between the user equipment 110 and the identified target UE 110 (Rx UE) via the relay UE 110 (R-UE) based on the received relay response message.

[0242] Figure 6 An example of a method 210 is shown. For example, the method can be performed by a relay UE 110 (R-UE) to create a unicast sidelink communication channel 19 between a source UE 110 (Tx UE) and a target UE 110 (Rx UE) via the relay UE 110 (R-UE).

[0243] At block 212, the method 210 includes receiving a relay request message 11 from the source UE 110 (Tx UE). The relay request message 11 includes at least some information to configure a feedback-enabled sidelink hybrid automatic repeat request (HARQ) process 16.

[0244] At block 214, the method 210 includes transmitting a sidelink message 13 to the target UE 110 (Rx UE) using the feedback-enabled sidelink HARQ process 16. The sidelink message 13 is configured for the feedback-enabled sidelink HARQ process in accordance with the received information to configure the feedback-enabled sidelink HARQ process 16.

[0245] At block 216, the method 210 includes determining a result of the sidelink HARQ process between the mobile device 110 and the target UE 110 (Rx UE).

[0246] At block 218, the method 210 includes transmitting a relay response message 17 to the source UE 110 (Tx UE) indicating the determined result of the sidelink HARQ process between the mobile device 110 and the target UE 110 (Rx UE).

[0247] Figure 7 An example of a controller 400 suitable for use in a mobile device 110 is shown. The controller 400 can be configured to enable the mobile device 110 to operate as a source UE (Tx UE) and / or a relay UE (R-UE) and / or a target UE (Rx UE).

[0248] Implementations of the controller 400 can be as controller circuitry. The controller 400 can be implemented in hardware alone, have certain aspects in software including firmware alone, or can be a combination of hardware and software (including firmware).

[0249] As Figure 7 shown, the controller 400 can be implemented using instructions that enable the functionality of the hardware, for example, using executable instructions of a computer program 406 in a general purpose or special purpose processor 402 that can be stored on a computer readable storage medium (disk, memory etc.) to be executed by such a processor 402.

[0250] The processor 402 is configured to read from and write to the memory 404. The processor 402 can also comprise an output interface and an input interface, via which the processor 402 outputs data and / or commands, which are input to the processor 402 via the input interface.

[0251] The memory 404 stores a computer program 406 comprising computer program instructions (computer program code) which, when loaded into the processor 402, controls the operation of the apparatus 110. The computer program instructions of the computer program 406 provide the logic and routines Figures 2 to 6 enabling the apparatus to perform the methods illustrated. The processor 402 is able to load and execute the computer program 406 by reading the memory 404.

[0252] The apparatus 110 can therefore comprise:

[0253] at least one processor 402; and

[0254] at least one memory 404 including computer program code

[0255] The at least one memory 404 and the computer program code are configured, with the at least one processor 402, to cause the apparatus 110 at least to perform:

[0256] determining to attempt to create a unicast sidelink communication channel between a user equipment and an identified target user equipment via a relay user equipment; and

[0257] sending a relay request message to at least one mobile device operable as a relay to the target user equipment, wherein the relay request message comprises at least some information for configuring a sidelink procedure to obtain feedback from the target user equipment.

[0258] The apparatus 110 can therefore comprise:

[0259] at least one processor 402; and

[0260] at least one memory 404 including computer program code

[0261] The at least one memory 404 and the computer program code are configured, with the at least one processor 402, to cause the apparatus 110 at least to perform:

[0262] receiving a relay request message from a source mobile device, the relay request message comprising at least some information for configuring a sidelink procedure to obtain feedback from a target user equipment; and

[0263] sending a message to the target user equipment using the configured procedure, wherein the message is configured for the configured procedure in accordance with the received information for configuring the sidelink procedure to obtain feedback from the target user equipment; and

[0264] sending a relay response message to the source mobile device, the relay response message indicating a result of the configured procedure between the mobile device and the target user equipment.

[0265] As Figure 8 indicated, the computer program 406 can arrive at the apparatus 110 via any suitable delivery mechanism 408. The delivery mechanism 408 can be, for example, a machine-readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a compact disc read-only memory (CD-ROM) or digital versatile disc (DVD), or a solid state memory, an article of manufacture that comprises or embodies the computer program 406. The delivery mechanism can be a signal configured to reliably transfer the computer program 406. The apparatus 110 can propagate or transmit the computer program 406 as a computer data signal.

[0266] The computer program instructions can cause the apparatus 110 to perform at least or be used for performing the following:

[0267] determining to attempt to create a unicast sidelink communication channel between the user equipment and the identified target user equipment via the relay user equipment; and

[0268] sending a relay request message to at least one mobile device operable as a relay to the target user equipment, wherein the relay request message comprises at least some information for configuring a sidelink procedure to obtain feedback from the target user equipment.

[0269] The computer program instructions can cause the apparatus 110 to perform at least or be used for performing the following:

[0270] receiving a relay request message from a source mobile device, the relay request message comprising at least some information for configuring a sidelink procedure to obtain feedback from a target user equipment; and

[0271] sending a sidelink message to the target user equipment using a feedback-enabled sidelink HARQ procedure, wherein the sidelink message is configured for the feedback-enabled sidelink HARQ procedure in accordance with the received information for configuring the feedback-enabled sidelink HARQ procedure; and

[0272] sending a relay response message to the source mobile device, the relay response message indicating a result of the sidelink HARQ procedure between the mobile device and the target user equipment.

[0273] The computer program instructions can be included in a computer program, non-transitory computer-readable medium, computer program product, machine-readable medium. In some, but not necessarily all, examples, the computer program instructions can be distributed over more than one computer program.

[0274] Although the memory 404 is shown as a single component / circuitry, it can be implemented as one or more separate components / circuitry, or all of which can be integrated / removable, and / or can be provided permanent / semi-permanent / dynamic / cached storage.

[0275] Although the processor 402 is shown as a single component / circuitry, it can be implemented as one or more separate components / circuitry, or all of which can be integrated / removable. The processor 402 can be a single-core or multi-core processor.

[0276] References to “computer-readable storage medium”, “computer program product”, “tangibly embodied computer program” etc., or a “controller”, “computer”, “processor” etc. should be understood to encompass not only computers having different architectures such as single / multi-processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a field-programmable gate array (FPGA), or programmable logic.

[0277] As used in this application, the term “circuitry” can refer to one or more or all of the following:

[0278] (a) hardware-only circuitry implementations (such as implementations in only analog and / or digital circuitry) and

[0279] (b) combinations of hardware circuits and software, such as (as applicable):

[0280] (i) combinations of analog and / or digital hardware circuit(s) with software / firmware and

[0281] (ii) any portions of hardware processor(s) with software (including digital signal processors); software and memory that work together to cause an apparatus, such as device 100 (e.g., a mobile phone or server), to perform various functions and

[0282] (c) hardware circuitry and / or (d) a processor, such as a microprocessor or a portion thereof, which requires software (e.g., firmware) for operation, but need not necessarily have software or firmware present.

[0283] The definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation that includes one or more processors and / or a processor and memory coupled to the one or more processors and / or separate software and / or firmware instruction sets (and unique configurations of hardware back ends of the processors) that are executed by then one or more processors. For example, if applicable, the circuitry includes a baseband integrated circuit or portions thereof for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0284] Figures 2 to 6 The illustrated blocks can represent steps in a method and / or code segments in a computer program 406. The specific order of the blocks illustrated is not to be construed as requiring or implying any order of the blocks, and the order and arrangement of the blocks can change. Additionally, some of the blocks can be optional.

[0285] Where a structural feature is described, it can be replaced by a component that functions to perform the structural feature, whether that function or those functions are explicitly described or implied.

[0286] The above examples apply the application as a component that implements the following functions:

[0287] Automotive systems; telecommunication systems; electronic systems, including consumer electronics; distributed computing systems; media systems for generating or rendering media content, including audio, video and audiovisual content and mixed, mediated, virtual and / or augmented reality; personal systems, including personal health systems or personal fitness systems; navigation systems; user interfaces, also known as human-machine interfaces; networks, including cellular, non-cellular and optical networks; self-organizing networks; the Internet; the Internet of Things; virtualized networks; and related software and services.

[0288] The term “comprise” as used in this document has an inclusive, rather than an exclusive, meaning. That is, any reference to X comprising Y indicates that X can comprise only one Y or can comprise more than one Y. If it is intended to use “comprise” in an exclusive sense, it will be explicitly stated as, for example, “comprising only one,” or “consisting of.”

[0289] In this specification, reference to various examples means that particular features, structures, or characteristics described in connection with the example are included in at least that example. The appearance of the phrases in text in no way limits the scope of such features, structures, or characteristics to the particular example being described. The description is not an exhaustive list of examples. The description serves merely as an example of what is included in the scope of the various examples. The description serves merely as an example of what is included in the scope of the various examples. The description is not an exhaustive list of examples.

[0290] Although examples have been described in the preceding paragraphs with reference to a variety of examples, it should be understood that modifications can be made to the examples given without departing from the scope of the claims.

[0291] Features described in the preceding description can be used in combinations other than the combinations explicitly described above.

[0292] Although functions have been described with reference to certain features, those functions can be performed by other features whether described or not.

[0293] Although features have been described with reference to certain examples, those features can also be present in other examples whether described or not.

[0294] The terms “a” or “the” as used herein have an inclusive rather than an exclusive meaning. That is, any reference to X including a Y or the Y indicates that X can include only one Y or can include more than one Y unless the context clearly indicates otherwise. If it is intended to use “a” or “the” with an exclusive meaning, then it will be explicitly stated in the context. In some cases, “at least one” or “one or more” can be used to emphasize an inclusive meaning, but the absence of these terms is not to be taken as a deduction of any exclusive meaning.

[0295] The presence of a feature (or combination of features) in a claim has the meaning attributed to that feature (or combination of features) in the specification and the meaning of that feature (or combination of features) should be understood in the context of this specification. Equivalent features include, for example, features that are variants and achieve substantially the same outcome in substantially the same way. Equivalent features include, for example, features that perform substantially the same function in substantially the same way to achieve substantially the same results.

[0296] In this specification, reference to various examples uses the term "comprise" or variations such as "comprises" or "comprising". This is taken to mean an inclusion of not only the stated features, but also equivalents or alternatives of those features. In other words, it is to be understood that the features so described are not to be interpreted exclusivel

[0297] While endeavoring in the foregoing specification to draw attention to those features of the application believed to be of particular importance it should be understood that the applicant claims protection for any patentable feature or combination of features disclosed or suggested herein, whether or not it is specifically emphasized.

Claims

1. A mobile device comprising components for: Determine whether to attempt to create a unicast sidelink communication channel between the mobile device and the identified target user device via a relay user device; Sending a relay request message to at least one user equipment, said at least one user equipment operable to relay to said target user equipment, said relay request message including at least some information for configuring a sidechain process to obtain feedback from said target user equipment; and Receive a relay response message, the relay response message indicating HARQ NACK communication from the target user equipment to the relay user equipment, the HARQ NACK communication being a response to a sidechain message sent from the relay user equipment to the target user equipment using the sidechain HARQ procedure with feedback enabled; The sidechain process with feedback is a Hybrid Automatic Repeat Request (HARQ) process with feedback enabled. The information included in the relay request message explicitly specifies that there is no transport block for feedback of the enabled sidechain HARQ process.

2. The mobile device according to claim 1, wherein the relay request message is a broadcast or multicast.

3. The mobile device of claim 1, wherein the information included in the relay request message explicitly or implicitly specifies the sidechain HARQ process in which feedback is enabled.

4. The mobile device of claim 1, wherein the information included in the relay request message explicitly or implicitly enables the relay user equipment to use the sidechain HARQ procedure with feedback enabled to send a sidechain unicast message having a source identifier and a destination identifier, the source identifier being an identifier of the mobile device and the destination identifier being an identifier of the target user equipment.

5. A mobile device comprising components for: Receive a relay request message from the source user equipment, the relay request message including at least some information, the at least some information being used to configure the sidechain process to obtain feedback from the target user equipment; The configured process is used to send a message to the target user equipment, wherein the message is configured for the configured process based on the received information used to configure the sidechain process to obtain feedback from the target user equipment; as well as A relay response message is sent to the source user equipment, the relay response message indicating the result of the configured process between the mobile device and the target user equipment; The sidechain process with feedback is a Hybrid Automatic Repeat Request (HARQ) process with feedback enabled. The message sent to the target user equipment by the sidechain HARQ procedure where feedback is enabled has no transport block, and therefore a NACK will be automatically generated as HARQ feedback from the target user equipment, and wherein the mobile device includes: A component for receiving a NACK in response to sending the sidechain message to the target user equipment, wherein the sidechain message is configured to provide feedback on the enabled sidechain HARQ process based on the received information for configuring feedback on the enabled sidechain HARQ process. as well as A component for sending a relay response message to the source user equipment in response to receiving the NACK.

6. The mobile device according to claim 5, wherein the message is a unicast sidechain message having a source identifier and a destination identifier, wherein the source identifier is an identifier of the source user device and the destination identifier is an identifier of the target user device.

7. A method for communication, comprising: Receive a relay request message from the source mobile device, the relay request message including at least some information used to configure the sidechain process to obtain feedback from the target user device; The configured process is used to send a message to the target user equipment, wherein the message is configured for the configured process based on the received information used to configure the sidechain process to obtain feedback from the target user equipment; as well as Send a relay response message to the source mobile device, the relay response message indicating the result of the configured process between the mobile device and the target user device; The sidechain process with feedback is a Hybrid Automatic Repeat Request (HARQ) process with feedback enabled. The method further includes: In the case where the message sent to the target user equipment by the sidechain HARQ procedure with feedback enabled has no transport block, and therefore a NACK will be automatically generated as HARQ feedback from the target user equipment; Receive NACK in response to sending the sidechain message to the target user equipment, wherein the sidechain message is configured to provide feedback on the enabled sidechain HARQ process based on the received information for configuring feedback on the enabled sidechain HARQ process; as well as In response to receiving the NACK, a relay response message is sent to the source mobile device.

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