Method and apparatus for conditional path switching with relay wireless transmit / receive unit

Abstract

Methods, apparatus, and computer-readable storage media for facilitating conditional mobility may perform conditional path switching. In various embodiments, a handover of a WTRU from a current cell to a target cell may involve an intermediate-level relay WTRU, where the handover may occur when a particular condition is satisfied. For example, a remote WTRU may receive path switching configuration information associated with each of a plurality of candidate relay WTRUs. The remote WTRU may select a relay WTRU from the plurality of candidate relay WTRUs based on a condition being satisfied. The path switching configuration information associated with the selected relay WTRU may be applied to the remote WTRU. The remote WTRU may send a message about the plurality of candidate relay WTRUs to a network, and may receive an indication of connection to another relay WTRU.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 442,794, filed February 2, 2023, the entire contents of which are incorporated herein by reference. Background Art

[0003] A typical handover of a wireless transmit / receive unit (WTRU), also known as a user equipment (UE), from one cell to another may be triggered when the radio signal quality is better in a neighboring cell than in the current cell. This may be accomplished, for example, by the WTRU sending a report to the current cell regarding the radio signal quality. Upon receiving the report, the current cell may send a handover command to the WTRU. In another example, the WTRU may monitor the radio signal and, when certain conditions are met, make a decision regarding its own handover. In another example, a first WTRU may configure a second WTRU to measure the signal quality of a neighboring cell and report the results back to the first WTRU. Summary of the Invention

[0004] Disclosed herein are methods and apparatus for implementing conditional mobility. In various embodiments, a handover of a WTRU from a current cell to a target cell may involve an intermediate relay WTRU, wherein the handover may occur when certain conditions are met. The various embodiments discussed herein address how to effectively implement conditional path switching from a direct / indirect link to an indirect link for a remote WTRU. In an exemplary embodiment, a relay WTRU may be configured for path switching of a remote WTRU. A relay WTRU may be configured / prepared to serve one or more remote WTRUs. Upon receiving an indication from the remote WTRU that the remote WTRU has performed a path switch via the relay WTRU, the relay WTRU may apply a configuration associated with the remote WTRU. The configuration may include (re)configuring / establishing a sidelink (SL) (e.g., a radio control link (RLC) channel) between the remote WTRU and the relay WTRU, (re)configuring a backhaul user-to-user (Uu), applying a sidelink relay adaptation protocol (SRAP) configuration to map SL and Uu RLC channels, etc.), or any suitable combination thereof.

[0005] An example process by which a relay WTRU may prepare for a path switch for a remote WTRU may include the relay WTRU receiving a conditional reconfiguration including a remote WTRU identity and a corresponding configuration to be applied on behalf of the remote WTRU. The relay WTRU may receive an indication from the remote WTRU that the remote WTRU has performed a path switch to the relay WTRU. The relay WTRU may apply the configuration associated with the remote WTRU. The relay WTRU may send a radio resource control (RRC) complete message to the network indicating that the relevant configuration has been applied.

[0006] An apparatus configured to perform a process in which a relay WTRU may prepare for a path switch for a remote WTRU may include a processor and a transceiver configured to receive a conditional reconfiguration including a remote WTRU identifier and a corresponding configuration to be applied on behalf of the remote WTRU. The apparatus may also be configured to receive an indication from the remote WTRU that the remote WTRU has performed a path switch to the relay WTRU. The apparatus may also be configured to apply the configuration associated with the remote WTRU. The apparatus may also be configured to send a radio resource control (RRC) complete message to a network indicating that the relevant configuration has been applied.

[0007] An exemplary method for performing conditional mobility may be performed by a relay WTRU. The exemplary method may include receiving reconfiguration information associated with at least one remote WTRU, receiving an indication that a first remote WTRU has performed a path switch to a relay WTRU, in response to receiving the indication that the first remote WTRU has performed a path switch to the relay WTRU, applying corresponding reconfiguration information associated with the first remote WTRU, and providing a message including an indication that the reconfiguration of the first remote WTRU is complete. Applying the corresponding reconfiguration information associated with the first remote WTRU may include establishing a SL communication channel between the relay WTRU and the first remote WTRU. Applying the corresponding reconfiguration information associated with the first remote WTRU may include configuring a backhaul user-to-user (Uu) channel with the first remote WTRU. Applying the corresponding reconfiguration information associated with the first remote WTRU may include configuring a sidelink relay adaptation protocol (SRAP). The indication that the first remote WTRU has performed a path switch to the relay WTRU may include an indication that the first remote WTRU has requested a PC5 connection. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include an indication that the first remote WTRU has requested a PC5 connection reconfiguration. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include a PC5 radio resource control (RRC) message. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include a medium access control-control element (MAC-CE) sent via a sidelink (SL) channel.

[0008] An exemplary WTRU configured to perform conditional mobility may include a processor and a transceiver. The WTRU may be configured to receive reconfiguration information associated with at least one remote WTRU, receive an indication that a first remote WTRU has performed a path switch to a relay WTRU, and in response to receiving the indication that the first remote WTRU has performed a path switch to the relay WTRU, apply corresponding reconfiguration information associated with the first remote WTRU, and provide a message including an indication that the reconfiguration of the first remote WTRU is complete. Applying the corresponding reconfiguration information associated with the first remote WTRU may include establishing a SL communication channel between the relay WTRU and the first remote WTRU. Applying the corresponding reconfiguration information associated with the first remote WTRU may include configuring a backhaul user-to-user (Uu) channel with the first remote WTRU. Applying the corresponding reconfiguration information associated with the first remote WTRU may include configuring an SRAP. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include an indication that the first remote WTRU has requested a PC5 connection. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include an indication that the first remote WTRU has requested a PC5 connection reconfiguration. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include a PC5 radio resource control (RRC) message.The indication that the first remote WTRU has performed a path switch to the relay WTRU may include a MAC-CE sent via the SL channel.

[0009] An exemplary computer-readable storage medium may have executable instructions stored thereon that, when executed by a processor, cause the processor to facilitate conditional mobility. When executing the executable instructions, the processor may be configured to facilitate a relay WTRU receiving reconfiguration information associated with at least one remote WTRU, receiving an indication that a first remote WTRU has performed a path switch to the relay WTRU, and in response to receiving the indication that the first remote WTRU has performed a path switch to the relay WTRU, applying corresponding reconfiguration information associated with the first remote WTRU, and providing a message including an indication that the reconfiguration of the first remote WTRU is complete. Applying the corresponding reconfiguration information associated with the first remote WTRU may include establishing a SL communication channel between the relay WTRU and the first remote WTRU. Applying the corresponding reconfiguration information associated with the first remote WTRU may include configuring a backhaul user-to-user (Uu) channel with the first remote WTRU. Applying the corresponding reconfiguration information associated with the first remote WTRU may include configuring an SRAP. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include an indication that the first remote WTRU has requested a PC5 connection. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include an indication that the first remote WTRU has requested a PC5 connection reconfiguration. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include a PC5 radio resource control (RRC) message. The indication that the first remote WTRU has performed a path switch to the relay WTRU may include a MAC-CE sent via the SL channel.

[0010] An exemplary remote WTRU for facilitating conditional mobility may include a transceiver and a processor. The processor may be configured to receive, via the transceiver, conditional path switching configuration information associated with each of a plurality of candidate relay WTRUs. The processor may be configured to determine, based on the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs, that at least one of the plurality of candidate relay WTRUs satisfies a first condition. The processor may be configured to select, from the at least one of the plurality of candidate relay WTRUs that satisfies the first condition, a first relay WTRU that satisfies a second condition. The processor may be configured to apply the conditional path switching configuration information associated with the first relay WTRU. The processor may be configured to send a message to a network node via the transceiver, wherein the message includes an identifier and sidelink measurements associated with each of the plurality of candidate relay WTRUs that satisfies the first condition. The processor may be configured to receive, from the network node, via the transceiver, an indication to switch to a second relay WTRU from the plurality of candidate relay WTRUs. The processor may be configured to apply the conditional path switching configuration information associated with the second relay WTRU. The processor may be configured to release conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs. The processor may be further configured to maintain the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs for a period of time after applying the conditional path switching configuration information associated with the first relay WTRU and before releasing the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs. The remote WTRU may be directly connected to a network node, such as a next generation Node B (gNB). The remote WTRU may be connected to a network node, such as a gNB, via a source relay WTRU. The first condition may be based on a radio quality of a serving cell, a sidelink radio condition associated with the candidate relay WTRU, a comparison of a sidelink radio condition associated with the source relay WTRU and a sidelink radio condition associated with the candidate relay WTRU, or any suitable combination thereof. The second condition may include determining that the second relay WTRU has a sidelink radio condition above a threshold. The second condition may include determining that the second relay WTRU has the highest quality sidelink radio condition among the plurality of candidate relay WTRUs. The indication from the network node may include a medium access control (MAC) control (CE). The indication from the network node may include a radio resource control (RRC) message. Releasing the conditional path switch configuration information may include releasing the PC5 connection.

[0011] An example method for facilitating conditional mobility may be performed by a remote WTRU. The method may include receiving conditional path switching configuration information associated with each of a plurality of candidate relay WTRUs. The method may include determining, based on the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs, that at least one of the plurality of candidate relay WTRUs satisfies a first condition. The method may include selecting a first relay WTRU that satisfies a second condition from the at least one of the plurality of candidate relay WTRUs that satisfies the first condition. The method may include applying the conditional path switching configuration information associated with the first relay WTRU. The method may include sending a message to a network node via a transceiver, wherein the message includes an identifier and sidelink measurements associated with each of the plurality of candidate relay WTRUs that satisfies the first condition. The method may include receiving an indication from the network node to switch to a second relay WTRU from the plurality of candidate relay WTRUs. The method may include applying the conditional path switching configuration information associated with the second relay WTRU. The method may include releasing the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs. The method may include maintaining the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs for a period of time after applying the conditional path switching configuration information associated with the first relay WTRU and before releasing the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs. The remote WTRU may be directly connected to a network node, such as a gNB. The remote WTRU may be connected to a network node, such as a gNB, via a source relay WTRU. The first condition may be based on a serving cell radio quality, a sidelink radio condition associated with the candidate relay WTRU, a comparison of a sidelink radio condition associated with the source relay WTRU and a sidelink radio condition associated with the candidate relay WTRU, or any suitable combination thereof. The second condition may include determining that the second relay WTRU has a sidelink radio condition that is above a threshold. The second condition may include determining that the second relay WTRU has the highest quality sidelink radio condition among the plurality of candidate relay WTRUs. The indication from the network node may include a medium access control (MAC) control (CE). The indication from the network node may comprise a Radio Resource Control (RRC) message.Releasing the conditional path switch configuration information may comprise releasing the PC5 connection.

[0012] An exemplary computer-readable storage medium may have executable instructions stored thereon that, when executed by a processor, cause the processor to facilitate conditional mobility. When executing the executable instructions, the processor may be configured to receive conditional path switching configuration information associated with each of a plurality of candidate relay WTRUs. When executing the executable instructions, the processor may be configured to determine, based on the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs, that at least one of the plurality of candidate relay WTRUs satisfies a first condition. When executing the executable instructions, the processor may be configured to select a first relay WTRU that satisfies a second condition from the at least one of the plurality of candidate relay WTRUs that satisfies the first condition. When executing the executable instructions, the processor may be configured to apply the conditional path switching configuration information associated with the first relay WTRU. When executing the executable instructions, the processor may be configured to send a message to a network node via the transceiver, wherein the message may include an identifier and sidelink measurements associated with each of the plurality of candidate relay WTRUs that satisfies the first condition. When the executable instructions are executed, the processor may be configured to receive an indication from the network node to switch to a second relay WTRU in the plurality of candidate relay WTRUs. When the executable instructions are executed, the processor may be configured to apply the conditional path switching configuration information associated with the second relay WTRU. When the executable instructions are executed, the processor may be configured to release the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs. When the executable instructions are executed, the processor may be configured to maintain the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs for a period of time after applying the conditional path switching configuration information associated with the first relay WTRU and before releasing the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs. The remote WTRU may be directly connected to a network node, such as a gNB. The remote WTRU may be connected to a network node, such as a gNB, via a source relay WTRU. The first condition may be based on radio quality of a serving cell. The second condition may include determining that the second relay WTRU has a sidelink radio condition that is above a threshold. The second condition may include determining that the second relay WTRU has a sidelink radio condition of the highest quality among the plurality of candidate relay WTRUs. The indication from the network node may include a medium access control (MAC) control (CE). The indication from the network node may include a radio resource control (RRC) message. Releasing the conditional path switch configuration information may include releasing the PC5 connection.

[0013] An exemplary method performed by a relay WTRU may include receiving conditional reconfiguration information. The conditional reconfiguration information may include an identification of a remote WTRU and remote WTRU configuration information associated with the remote WTRU. The method may include receiving an indication from the remote WTRU that the remote WTRU has performed a path switch to the relay WTRU. The method may also include configuring the relay WTRU using the received remote WTRU configuration information. The method may include sending a radio resource control (RRC) complete message. The RRC complete message may indicate that the relay WTRU has been configured with the remote WTRU configuration information. The remote WTRU configuration information may include sidelink (SL) related configurations. The remote WTRU configuration information may include sidelink relay adaptation protocol (SRAP) configurations. The remote WTRU configuration information may include backhaul user-to-user (Uu) radio control link (RLC) channel configurations. The indication from the remote WTRU may include a PC5 connection establishment request. The indication from the remote WTRU may include a PC5 connection reconfiguration request. The indication from the remote WTRU may include a PC5 RRC message. The indication from the remote WTRU may include a medium access control (MAC) control (CE) sent via the SL. The indication from the remote WTRU may include a Uu RRC message. The method may also include sending the Uu RRC message to a next generation Node B (gNB) via a sidelink channel.

[0014] An exemplary relay WTRU may include a transceiver and a processor. The processor may be configured to receive conditional reconfiguration information via the transceiver, the conditional reconfiguration information including an identification of a remote WTRU and remote WTRU configuration information associated with the remote WTRU. The processor may be configured to receive an indication from the remote WTRU via the transceiver that the remote WTRU has performed a path switch to the relay WTRU. The processor may be configured to configure the relay WTRU using the received remote WTRU configuration information. The processor may be configured to send a radio resource control (RRC) complete message via the transceiver, the RRC complete message indicating that the relay WTRU has been configured with the remote WTRU configuration information. The remote WTRU configuration information may include sidelink (SL) related configurations. The remote WTRU configuration information may include sidelink relay adaptation protocol (SRAP) configurations. The remote WTRU configuration information may include backhaul user-to-user (Uu) radio control link (RLC) channel configurations. The indication from the remote WTRU may include a PC5 connection establishment request. The indication from the remote WTRU may include a PC5 connection reconfiguration request. The indication from the remote WTRU may include a PC5 RRC message. The indication from the remote WTRU may include a medium access control (MAC) control (CE) sent via the SL. The indication from the remote WTRU may include a Uu RRC message. The processor may be further configured to send the Uu RRC message to a next generation Node B (gNB) via a sidelink channel via the transceiver.

[0015] An exemplary computer-readable storage medium may have executable instructions stored thereon that, when executed by a processor, cause the processor to facilitate conditional mobility. When executing the executable instructions, the processor may be configured to receive conditional reconfiguration information, the conditional reconfiguration information including an identification of a remote WTRU and remote WTRU configuration information associated with the remote WTRU. When executing the executable instructions, the processor may be configured to receive an indication from the remote WTRU that the remote WTRU has performed a path switch to the relay WTRU. When executing the executable instructions, the processor may be configured to configure the relay WTRU using the received remote WTRU configuration information. When executing the executable instructions, the processor may be configured to send a radio resource control (RRC) complete message, the RRC complete message indicating that the relay WTRU has been configured with the remote WTRU configuration information. The remote WTRU configuration information may include a sidelink (SL)-related configuration. The remote WTRU configuration information may include a sidelink relay adaptation protocol (SRAP) configuration. The remote WTRU configuration information may include a backhaul user-to-user (Uu) radio control link (RLC) channel configuration. The indication from the remote WTRU may include a PC5 connection establishment request. The indication from the remote WTRU may include a PC5 connection reconfiguration request. The indication from the remote WTRU may include a PC5 RRC message. The indication from the remote WTRU may include a medium access control (MAC) control (CE) sent via the SL. The indication from the remote WTRU may include a Uu RRC message. The processor may be further configured to send the UuRRC message to a next generation Node B (gNB) via a sidelink channel via the transceiver.

[0016] An exemplary method for facilitating conditional mobility may be performed by a remote WTRU. The method may include receiving conditional path switching configuration information associated with a target cell. The conditional path switching configuration information may be received via a relay WTRU. The conditional path switching configuration information may include triggering conditions associated with each of a plurality of candidate relay WTRUs and sidelink (SL) reconfiguration information. The method may also include determining that a triggering condition has been met for a target relay WTRU among a plurality of candidate relay WTRUs associated with the target cell. In addition, the method may include, upon determining that the triggering condition has been met, applying the conditional path switching configuration information associated with the target relay WTRU that may be applied to the remote WTRU, sending a message including an identifier of the remote WTRU via the target relay WTRU, and releasing the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs other than the target relay WTRU. The triggering condition may include a radio condition. The triggering condition may include a measurement threshold associated with one or more relay WTRUs associated with the target cell. The triggering condition may be based on radio quality associated with the target cell. The triggering condition may trigger a measurement report based on radio quality associated with the target cell and neighboring cells. The received conditional path switch configuration information may include radio resource control (RRC) information. The SL reconfiguration information may include the SL path switch configuration. The SL configuration information may include information associated with SL-related operations of the remote WTRU. The message may include an RRCReconfigurationComplete message.

[0017] An exemplary remote WTRU for facilitating conditional mobility may include a transceiver and a processor. The processor may be configured to receive, via the transceiver, conditional path switching configuration information associated with a target cell. The conditional path switching configuration information may be received via a relay WTRU. The conditional path switching configuration information may include triggering conditions associated with each of a plurality of candidate relay WTRUs and sidelink (SL) reconfiguration information. The processor may be configured to determine that the triggering condition has been met for a target relay WTRU among the plurality of candidate relay WTRUs associated with the target cell. The processor may be configured to, upon determining that the triggering condition has been met, apply the conditional path switching configuration information associated with the target relay WTRU, send a message to a network node via the transceiver, wherein the message is sent via the target relay WTRU, and wherein the message includes an identification of the remote WTRU, and release the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs other than the target relay WTRU. The triggering condition may include a radio condition. The trigger condition may include a measurement threshold associated with one or more relay WTRUs associated with the target cell. The trigger condition may be based on a radio quality associated with the target cell. The trigger condition may trigger a measurement report based on the radio quality associated with the target cell and a neighboring cell. The received conditional path switch configuration information may include radio resource control (RRC) information. The SL reconfiguration information may include an SL path switch configuration. The SL configuration information may include information associated with SL-related operations of the remote WTRU. The message may include an RRCReconfigurationComplete message.

[0018] An exemplary computer-readable storage medium may have executable instructions stored thereon that, when executed by a processor, cause the processor to facilitate conditional mobility. When executing the executable instructions, the processor may be configured to receive conditional path switching configuration information associated with a target cell. The conditional path switching configuration information may be received via a relay WTRU. The conditional path switching configuration information may include triggering conditions associated with each of a plurality of candidate relay WTRUs and sidelink (SL) reconfiguration information. When the executable instructions are executed, the processor may be further configured to determine that the triggering condition has been met for a target relay WTRU among the plurality of candidate relay WTRUs associated with the target cell. In addition, when executing the executable instructions, the processor may be further configured to, upon determining that the trigger condition has been met, apply the conditional path switching configuration information associated with the target relay WTRU, send a message including the identity of the remote WTRU via the target relay WTRU, and release the conditional path switching configuration information associated with each of the candidate relay WTRUs other than the target relay WTRU in the plurality of candidate relay WTRUs. The trigger condition may include a radio condition. The trigger condition may include a measurement threshold associated with one or more relay WTRUs, the one or more relay WTRUs being associated with the target cell. The trigger condition may be based on radio quality associated with the target cell. The trigger condition may trigger measurement reporting based on radio quality associated with the target cell and neighboring cells. The received conditional path switching configuration information may include radio resource control (RRC) information. The SL reconfiguration information may include SL path switching configuration. The SL configuration information may include information associated with SL-related operations of the remote WTRU. The message may include an RRCRecofigurationComplete message.

[0019] An exemplary remote WTRU for facilitating conditional mobility may include a transceiver and a processor. The processor may be configured to send information to a network node via the transceiver. The information may indicate that the remote WTRU is connected to a target relay WTRU. The information may indicate multiple candidate relay WTRUs based on a condition set. The information may include measurements associated with each of the multiple candidate relay WTRUs. The processor may be configured to receive an indication from the network node via the transceiver that the remote WTRU is to connect to a selected relay WTRU from the multiple candidate relay WTRUs. The processor may be configured to connect to the selected relay WTRU via the transceiver. The processor may be configured to release PC5 links associated with the multiple candidate relay WTRUs from the multiple candidate relay WTRUs instead of the PC5 link to the selected relay WTRU. The information sent to the network node may be sent via the multiple candidate relay WTRUs. The condition set may include a condition that the candidate relay WTRU is in the same cell as the target relay WTRU. The condition set may include a condition that the candidate relay WTRU has a sidelink (SL) radio condition above a threshold. The SL radio condition above the threshold may include a SL reference signal received power (RSRP). The SL radio condition above the threshold may include a sidelink discovery reference signal received power (SD-RSRP). The processor may be further configured to initiate a PC5 connection with the selected relay WTRU. The processor may be further configured to perform a path switch to the selected relay WTRU using a preconfigured path switch configuration associated with the selected relay WTRU. The processor may be further configured to send a radio resource channel (RRC) completion message via the transceiver when connecting to the selected relay WTRU.

[0020] An exemplary method for facilitating conditional mobility may be performed by a remote WTRU. The method may include sending information to a network node. The information may indicate that the remote WTRU is connected to a target relay WTRU. The information may indicate a plurality of candidate relay WTRUs based on a set of conditions. The information may include measurements associated with each of the plurality of candidate relay WTRUs. The method may include receiving an indication from the network node that the remote WTRU is to connect to a selected relay WTRU from a plurality of candidate relay WTRUs. The method may include connecting to the selected relay WTRU. The method may include releasing PC5 links associated with the plurality of candidate relay WTRUs from the plurality of candidate relay WTRUs instead of the PC5 link to the selected relay WTRU. The information sent to the network node may be sent via a plurality of candidate relay WTRUs. The set of conditions may include a condition that the candidate relay WTRU is in the same cell as the target relay WTRU. The set of conditions may include a condition that the candidate relay WTRU has a sidelink (SL) radio condition above a threshold. The SL radio condition above the threshold may include an SL reference signal received power (RSRP). The SL radio condition above a threshold may include a sidelink discovery reference signal received power (SD-RSRP). The method may include initiating a PC5 connection with the selected relay WTRU. The method may include performing a path switch to the selected relay WTRU using a preconfigured path switch configuration associated with the selected relay WTRU. The method may include sending a radio resource channel (RRC) complete message upon connecting to the selected relay WTRU.

[0021] An exemplary computer-readable storage medium for facilitating conditional mobility may have executable instructions stored thereon that, when executed by a processor, cause the processor to facilitate conditional mobility. When the executable instructions are executed, the processor may be configured to send information to a network node. The information may indicate that a remote WTRU is to connect to a target relay WTRU. The information may indicate multiple candidate relay WTRUs based on a set of conditions. The information may include measurements associated with each of the multiple candidate relay WTRUs. When the executable instructions are executed, the processor may be configured to receive an indication from the network node that the remote WTRU is to connect to a selected relay WTRU from the multiple candidate relay WTRUs. When the executable instructions are executed, the processor may be configured to connect to the selected relay WTRU. When the executable instructions are executed, the processor may be configured to release PC5 links associated with the multiple candidate relay WTRUs from the multiple candidate relay WTRUs instead of the PC5 link to the selected relay WTRU. The information sent to the network node may be sent via the multiple candidate relay WTRUs. The set of conditions may include a condition that the candidate relay WTRUs and the target relay WTRU are in the same cell. The condition set may include a condition that the candidate relay WTRU has a sidelink (SL) radio condition above a threshold. The SL radio condition above the threshold may include an SL reference signal received power (RSRP). The SL radio condition above the threshold may include a sidelink discovery reference signal received power (SD-RSRP). When executing the executable instructions, the processor may be configured to initiate a PC5 connection with the selected relay WTRU. When executing the executable instructions, the processor may be configured to perform a path switch to the selected relay WTRU using a preconfigured path switch configuration associated with the selected relay WTRU. When executing the executable instructions, the processor may be configured to send a radio resource channel (RRC) completion message when connected to the selected relay WTRU. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A more detailed understanding can be obtained from the following detailed description, which is given by way of example in conjunction with the accompanying drawings. As with the detailed description, the figures in these drawings are examples. Therefore, the drawings and detailed description should not be considered limiting, and other equally effective examples are possible and likely. Like reference numerals in the figures represent like elements.

[0023] Figure 1A is an exemplary system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented.

[0024] Figure 1B is a diagram showing that according to an embodiment, Figure 1AAn exemplary system diagram of an exemplary wireless transmit / receive unit (WTRU) for use within a communication system is shown.

[0025] Figure 1C is a diagram showing that according to an embodiment, Figure 1A An exemplary system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within a communication system is shown in FIG.

[0026] Figure 1D is a diagram showing that according to an embodiment, Figure 1A An exemplary system diagram of another exemplary RAN and another exemplary CN for use within the illustrated communication system.

[0027] Figure 2 An exemplary user plane protocol stack for Layer 2 (L2) WTRU-to-network relay is described.

[0028] Figure 3 An exemplary control plane protocol stack for L2 WTRU-to-network relay is described.

[0029] Figure 4 An exemplary discovery message protocol stack for L2 WTRU to network relay is described.

[0030] Figure 5 An exemplary procedure for L2 User-to-Network (U2N) handover to a direct User-to-User (Uu) cell is described.

[0031] Figure 6 An example procedure for switching a L2 U2N remote WTRU to an indirect path via a L2 U2N relay WTRU in Radio Resource Control Connected (RRC_Connected) mode is described.

[0032] Figure 7 An example of utilizing direct to indirect handover between gNBs (next generation Node Bs) is described.

[0033] Figure 8 Exemplary conditional switching configuration and execution are described.

[0034] Figure 9 Exemplary conditional switching scenarios are described.

[0035] Exemplary Network for Implementing Embodiments of the Invention

[0036] Figure 1Ais a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources, including wireless bandwidth. For example, the communication system 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero-tailing unique word DFT spread OFDM (ZT-UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0037] like Figure 1A As shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, the Internet 110, and other networks 112. However, it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Any of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to transmit and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or MiFi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), consumer electronic devices, devices operating on a commercial and / or industrial wireless network, etc. Any of the wireless transmit / receive units 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0038] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly connect to at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be base transceiver stations (BTSs), NodeBs, eNodeBs, Home NodeBs, Home eNodeBs, gNBs, NRNodeBs, site controllers, access points (APs), wireless routers, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0039] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage to a specific geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, one for each sector of the cell. In one embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may use multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0040] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0041] More specifically, as described above, the communication system 100 may be a multiple-access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0042] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0043] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0044] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement both LTE radio access and NR radio access, for example, using dual connectivity (DC) principles. Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions to / from multiple types of base stations, such as eNBs and gNBs.

[0045] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement wireless technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA 2000, CDMA 2000 1X, CDMA 2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), etc.

[0046] Figure 1A The base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business place, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. Figure 1A As shown, base station 114b may have a direct connection to the Internet 110. Thus, base station 114b may not need to access the Internet 110 via CN 106 / 115.

[0047] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. Data may have varying quality of service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions (e.g., user authentication). Although in Figure 1AAlthough not shown, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0048] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) from the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may use the same RAT as the RAN 104 / 113 or a different RAT.

[0049] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers to communicate with different wireless networks via different wireless links). Figure 1A The WTRU 102c shown may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0050] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power supply 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0051] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0052] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It should be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0053] Although the transmit / receive element 122 is Figure 1B Although depicted as a single element in the embodiment, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0054] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As described above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0055] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. Furthermore, the processor 118 may access information from and store data in any suitable type of memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0056] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0057] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or as an alternative to the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more neighboring base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with the embodiments.

[0058] The processor 118 may also be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripheral device 138 may include one or more sensors, which may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0059] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all of the signals (e.g., signals associated with particular subframes for uplink (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and / or substantially eliminate self-interference through hardware (e.g., a choke) or through signal processing by a processor (e.g., a separate processor (not shown) or the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., signals associated with particular subframes for uplink (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0060] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0061] The RAN 104 may include eNode-Bs 160a, 160b, and 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, and 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, and 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0062] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. Figure 1C As shown in FIG, eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0063] Figure 1C The CN 106 shown in FIG may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements is depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0064] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may also provide a control plane function for facilitating switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0065] The SGW 164 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-eNode B handovers, triggering paging when downlink data is available for the WTRUs 102a, 102B, 102c, managing and storing the context of the WTRUs 102a, 102B, 102c, and the like.

[0066] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0067] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0068] Although the WTRU Figures 1A-1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may utilize a wired communication interface with a communication network (eg, temporarily or permanently).

[0069] In a representative embodiment, the other network 112 may be a WLAN.

[0070] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic entering and / or leaving the BSS. Traffic originating from outside the BSS and destined for a STA may arrive through the AP and be delivered to the STA. Traffic originating from a STA destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Traffic between STAs within a BSS may be sent through the AP, for example, where a source STA may send traffic to the AP, and the AP may deliver the traffic to the destination STA. Traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. This peer-to-peer traffic may be sent between a source and destination STA (e.g., directly between the source and destination STAs) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an independent BSS (IBSS) mode cannot have an AP, and STAs (eg, all STAs) within or using the IBSS can communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

[0071] When using 802.11ac infrastructure operation mode or a similar operation mode, the AP can send beacons on a fixed channel (such as a primary channel). The primary channel can be a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel can be the operating channel of the BSS and can be used by STAs to establish a connection with the AP. In certain representative embodiments, such as in an 802.11 system, carrier sense multiple access with collision avoidance (CSMA / CA) can be implemented. For CSMA / CA, STAs (e.g., each STA) including the AP can sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a specific STA, the specific STA can back off. One STA (e.g., only one station) can transmit at any given time in a given BSS.

[0072] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, by combining a primary 20 MHz channel with adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0073] Very high throughput (VHT) STAs can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz and / or 80MHz channels can be formed by combining consecutive 20MHz channels. A 160MHz channel can be formed by combining 8 consecutive 20MHz channels, or by combining two discontinuous 80MHz channels, which can be referred to as an 80+80 configuration. For the 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be subjected to inverse fast Fourier transform (IFFT) processing and time domain processing respectively. The streams can be mapped onto two 80MHz channels, and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the operation of the above-mentioned 80+80 configuration can be reversed, and the combined data can be sent to the media access control (MAC).

[0074] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. The channel operating bandwidth and carrier frequency are reduced in 802.11af and 802.11ah relative to the channel operating bandwidth and carrier frequency used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communications, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, for example, limited capabilities including support for certain and / or limited bandwidths (e.g., only support). MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0075] WLAN systems that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah) include a channel that can be designated as a primary channel. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by the STA that supports the smallest bandwidth operating mode among all STAs operating in the BSS. In the example of 802.11ah, for a STA that supports (e.g., only supports) 1 MHz mode (e.g., an MTC-type device), the primary channel can be 1 MHz wide, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings can depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which only supports 1 MHz operating mode) transmitting to the AP, the entire available frequency band can be considered busy, even if most of the frequency band remains idle and available.

[0076] In the United States, the available frequency band for 802.11ah is from 902 MHz to 928 MHz. In South Korea, the available frequency band is from 917.5 MHz to 923.5 MHz. In Japan, the available frequency band is from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah ranges from 6 MHz to 26 MHz, depending on the country code.

[0077] Figure 1D1 is a system diagram illustrating the RAN 113 and the CN 115 according to an embodiment. As described above, the RAN 113 may employ NR wireless technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0078] The RAN 113 may include gNBs 180a, 180b, and 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. Each of the gNBs 180a, 180b, and 180c includes one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, and 180c may implement MIMO technology. For example, the gNBs 180a and 180b may utilize beamforming to transmit and / or receive signals to and from the gNBs 180a, 180b, and 180c. Thus, the gNB 180a may, for example, use multiple antennas to transmit and / or receive wireless signals to and from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, and 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In one embodiment, the gNBs 180a, 180b, and 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0079] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of varying or scalable lengths (e.g., containing a varying number of OFDM symbols and / or an absolute time duration of varying length).

[0080] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without also accessing other RANs (e.g., the eNode-Bs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNBs 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may serve as mobility anchors for the WTRUs 102a, 102b, 102c, while the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput to serve the WTRUs 102a, 102b, 102c.

[0081] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to a user plane function (UPF) 184a, 184b, routing of control plane information to an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c can communicate with each other via the Xn interface.

[0082] Figure 1DThe CN 115 shown in FIG may include at least one AMF 182 a, 182 b, at least one UPF 184 a, 184 b, at least one session management function (SMF) 183 a, 183 b, and may include a data network (DN) 185 a, 185 b. Although each of the aforementioned elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0083] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, managing registration areas, terminating NAS signaling, mobility management, and the like. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of service being used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine-type communication (MTC) access, and the like. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro and / or non-3GPP (3rd Generation Partnership Project) access technologies, such as WiFi.

[0084] The SMFs 183a and 183b can connect to the AMFs 182a and 182b in the CN 115 via the N11 interface. The SMFs 183a and 183b can also connect to the UPFs 184a and 184b in the CN 115 via the N4 interface. The SMFs 183a and 183b can select and control the UPFs 184a and 184b and configure traffic routing through the UPFs 184a and 184b. The SMFs 183a and 183b can perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications. The PDU session type can be IP-based, non-IP-based, Ethernet-based, and so on.

[0085] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0086] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. Furthermore, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b through the UPFs 184a, 184b via the N3 interface to the UPFs 184a, 184b and the N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0087] Given that Figures 1A-1D and Figures 1A-1D

[0015] As described herein, one or more or all of the functionality described herein with respect to one or more of the following may be performed by one or more emulated devices (not shown): the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MMEs 162, SGWs 164, PGWs 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other devices described herein. An emulated device may be one or more devices configured to emulate one or more or all of the functionality described herein. For example, an emulated device may be used to test other devices and / or simulate network and / or WTRU functionality.

[0088] The simulation device can be designed to implement one or more tests of other devices in a laboratory environment and / or an operator network environment. For example, one or more simulation devices can perform one or more or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more simulation devices can perform one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device can be directly coupled to another device for testing purposes and / or can use over-the-air wireless communication to perform testing.

[0089] One or more emulation devices can perform one or more functions (including all functions) without being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation device can be used in a test scenario in a test lab and / or a wired and / or wireless communication network that is not deployed (e.g., testing) to enable testing of one or more components. The one or more emulation devices can be test devices. The emulation device can transmit and / or receive data using direct RF coupling and / or wireless communication via RF circuitry (e.g., which can include one or more antennas).

[0090] This document describes mechanisms for conditional handover and conditional path switching. In various example scenarios, a relay WTRU may be used in conjunction with a network. An exemplary WTRU-to-network relay architecture is described below.

[0091] Figure 2 and Figure 3 Exemplary protocol stacks for the user plane and control plane, respectively, of a Layer 2 (L2) UE-to-Network (U2N) relay architecture are shown. Figure 2 An exemplary user plane protocol stack for Layer 2 (L2) WTRU to network relay is described. And Figure 3 An exemplary control plane protocol stack for L2 WTRU to network relay is depicted. The SRAP (Sidelink Relay Adaptation Protocol) sublayer ( Figure 2 202 of them, Figure 3 302) can be placed in the radio control link (RLC) sublayer ( Figure 2 204 of them, Figure 3 Uu SDP (Service Data Adaptation Protocol) Figure 2 206 of them, Figure 3 306), PDCP (Packet Data Convergence Protocol) Figure 2 208 of them, Figure 3308) and RRC (Radio Resource Control) can be in L2 U2N remote WTRU ( Figure 2 214 of them, Figure 3 314 in) and appropriate network nodes (e.g. gNB (next generation Node B) ( Figure 2 216 of them, Figure 3 316)) terminated between, and SRAP, RLC, MAC (Media Access Control) ( Figure 2 210 of them, Figure 3 310) and PHY (physical layer) ( Figure 2 212 of them, Figure 3 312) may terminate in each hop (e.g., the link between the L2 U2N remote WTRU and the L2 U2N relay WTRU, and the link between the L2 U2N relay WTRU and the network node gNB).

[0092] For L2 U2N relay, the SRAP sublayer on the PC5 hop may be used for bearer mapping purposes. The SRAP sublayer may not be present on the PC5 hop to relay L2 U2N remote UE messages on the BCCH and PCCH. For L2 U2N remote UE messages on SRB0, the SRAP header is not present on the PC5 hop, but is present on the Uu hop for both DL and UL.

[0093] Relay discovery may be used in WTRU to NW (network) relaying for the remote WTRU to perform relay selection (when in RRC_IDLE / RRC_INACTIVE) and also for the remote WTRU to send measurements of potential relays to the network (for remote WTRU in RRC_CONNECTED) for the network to make potential path switching decisions.

[0094] Model A and Model B discovery models can support U2N relay discovery. Figure 4 An exemplary protocol stack that may be used for discovery is shown. The U2N remote WTRU 402 may perform relay discovery message transmission and, when in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED, may monitor the sidelink for relay discovery messages. The network may broadcast or configure, via dedicated RRC signaling, a Uu RSRP (reference signal received power) threshold that may be used by the U2N remote WTRU 402 to determine whether it may transmit a relay discovery message to the U2N relay WTRU(s) 404.

[0095] The U2N relay WTRU 404 may perform relay discovery message transmission and may monitor the sidelink for relay discovery messages when in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED. The network may broadcast or configure, via dedicated RRC signaling, a maximum Uu RSRP threshold, a minimum Uu RSRP threshold, or both, which the U2N relay WTRU 404 uses to determine whether it can transmit a relay discovery message to the U2N remote WTRU 402.

[0096] The network may use broadcast or dedicated signaling to provide relay discovery configuration for relay discovery. Additionally, the U2N remote WTRU 402 and the U2N relay WTRU 404 may use pre-configuration for relay discovery.

[0097] Regarding WTRU to Network Relay Mobility, when the L2 U2N Remote WTRU and the L2 U2N Relay WTRU belong to the same network node (e.g., gNB), the service continuity procedures may be applicable for mobility use cases of path switching from indirect path to direct path and from direct path to indirect path. Other use cases (e.g., indirect to indirect, direct to indirect, and indirect to direct for different network nodes (e.g., gNB)) may be supported.

[0098] Regarding service continuity when switching from indirect path to direct path for L2U2N relay, Figure 5 In the case where the L2U2N remote WTRU switches to a direct path as described in

[0066] , the following procedure may be used. Figure 5 An exemplary procedure for handing over an L2U2N remote WTRU 502 to a direct Uu cell is described. In step 1, a Uu measurement configuration and measurement report signaling procedure may be performed to evaluate relay link measurements and Uu link measurements. When the configured measurement reporting criteria are met, the measurement results from the L2U2N remote WTRU 502 may be reported. The sidelink relay measurement report may include the source L2 ID (identifier) ​​of the L2 U2N relay WTRU 504, the serving cell ID (e.g., NCGI (NR Cell Global Identity) / NCI (NR Cell Identity), sidelink measurement quantity results, or any appropriate combination thereof. The sidelink measurement quantity may include the SL-RSRP of the serving L2 U2N relay WTRU, and if SL-RSRP is not available, SD-RSRP (Sidelink Discovery Reference Signal Received Power) may be used.

[0099] In step 2, the network node (e.g., gNB 506) may decide to switch the L2 U2N remote WTRU to the direct Uu path. In step 3, the network node (e.g., gNB 506) may send an RRCReconfiguration message to the L2 U2N remote WTRU. After receiving the RRCReconfiguration message with the path switch configuration, the L2 U2N remote WTRU 502 may stop UP and CP transmission via the L2 U2N relay WTRU 504. In step 4, the L2 U2N remote WTRU 502 may synchronize with the network node (e.g., gNB 506) and may perform random access. In step 5, the WTRU 502 (e.g., the L2 U2N remote WTRU in the previous step) may send an RRCReconfigurationComplete message to the gNB 506 via the direct path using the configuration provided in the RRCReconfiguration message. From this step onwards, the WTRU 502 (e.g., the L2 U2N remote WTRU in the previous step) may use an RRC connection via a direct path to a network node (e.g., the gNB 506).

[0100] In step 6, the network node (e.g., gNB 506) may send an RRCReconfiguration message to the L2 U2N relay WTRU 504 to reconfigure the connection between the L2 U2N relay WTRU 504 and the network node (e.g., gNB 506). The RRCReconfiguration message may be sent to the L2 U2N relay WTRU 504 at any time after step 3 based on the network node (e.g., gNB 506) implementation (e.g., to release the Uu and PC5 relay RLC channels configured for relaying, and the bearer mapping configuration associated with the L2 U2N remote UE).

[0101] In step 7, the AS (Access Stratum) layer of the L2 U2N relay WTRU 504 or L2 U2N remote WTRU 502 may release the PC5-RRC connection and may instruct upper layers to release the PC5 unicast link after receiving an RRCReconfiguration message from the network node (e.g., gNB 506). The timing of performing the link release may be determined by the WTRU implementation. In step 8, the data path may be switched from an indirect path to a direct path between the WTRU 502 (e.g., the previous L2 U2N remote WTRU) and the network node (e.g., gNB 506). If configured by the network node (e.g., gNB 506), PDCP re-establishment or PDCP (Packet Data Convergence Protocol) data resumption in the uplink may be performed by the WTRU 502 (e.g., the previous L2 U2N remote WTRU) for lossless delivery during the path switch. Step 8 may be performed at any time after step 4. Step 8 may be independent of steps 6 and 7.

[0102] When switching from a direct path to an indirect path, the network node (e.g., gNB 506) may select a L2U2N relay WTRU in any RRC state (e.g., RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED) as the target L2 U2N relay WTRU for direct-to-indirect path handover.

[0103] For service continuity of the L2 U2N remote WTRU, in case the L2 U2N remote WTRU switches to an indirect path via the L2 U2N relay WTRU in RRC_CONNECTED, the following may be used: Figure 6 The following process is described in

[15] . In step 1, after the L2 U2N remote WTRU 602 measures / discovers the L2 U2N relay WTRU(s) 604, it may report one or more candidate L2 U2N relay WTRU(s) 604 and Uu measurements. The L2 U2N remote WTRU 602 may filter suitable L2 U2N relay WTRUs 604 based on relay selection criteria before reporting. The L2 U2N remote WTRU 602 may report the L2 U2N relay WTRU 604 candidate(s) that meet higher layer criteria. The report may include the L2 U2N relay WTRU 604 ID, the serving cell ID of the L2 U2N relay WTRU 604, sidelink measurement quantity information, or any suitable combination thereof. SD-RSRP may be used as the sidelink measurement quantity.

[0104] In step 2, the network node (e.g., gNB 606) may decide to handover the L2 U2N remote WTRU 602 to the target L2 U2N relay WTRU 604. The network node (e.g., gNB 606) may then send an RRCReconfiguration message to the target L2 U2N relay WTRU 604. The RRCReconfiguration message may include the local ID and L2 ID of the L2 U2N remote WTRU 602, Uu and PC5 relay RLC (Radio Link Control) channel configurations for relaying, bearer mapping configuration, or any suitable combination thereof. In step 3, the network node (e.g., gNB 606) may send an RRCReconfiguration message to the L2 U2N remote WTRU. The RRCReconfiguration message may include the L2 U2N relay WTRU ID, the local ID of the remote WTRU 602, the PC5 relay RLC channel configuration for relaying traffic, and the associated end-to-end radio bearer(s), or any suitable combination thereof. The L2 U2N remote WTRU may stop UP and CP transmission over the direct path after receiving an RRCReconfiguration message from a network node (e.g., gNB 606).

[0105] In step 4, the L2 U2N remote WTRU 602 may establish a PC5 RRC connection with the target L2 U2N relay WTRU 604. In step 5, the L2 U2N remote WTRU 602 may complete the path switching procedure by sending an RRCReconfigurationComplete message to the network node (e.g., gNB 606) via the L2 U2N relay WTRU 604. In step 6, the data path may be switched from a direct path to an indirect path between the L2 U2N remote WTRU 602 and the network node (e.g., gNB 606).

[0106] In the case that the L2 U2N relay WTRU 604 selected for direct-to-indirect path handover is in RRC_IDLE or RRC_INACTIVE, upon receiving the path switch command, the L2 U2N remote WTRU 602 may establish a PC5 link with the L2 U2N relay WTRU 604 and may send an RRCReconfigurationComplete message via the L2 U2N relay WTRU 604, which may trigger the L2 U2N relay WTRU 604 to enter the RRC_CONNECTED state. The procedure for switching the L2 U2N remote WTRU 602 to an indirect path may also be applied to the use case where the L2 U2N relay WTRU 604 selected for direct-to-indirect path switching is in RRC_IDLE or RRC_INACTIVE, except that after the L2 U2N relay WTRU 604 enters the RRC_CONNECTED state, an RRCReconfiguration message may be sent from the network node (e.g., gNB 606) to the L2 U2N relay WTRU 604, which occurs between steps 4 and 5.

[0107] The U2N relay described herein is applicable to indirect-to-indirect handover for intra-network node use cases (e.g., intra-gNB use cases), as well as handover options (direct-to-indirect, indirect-to-direct, indirect-to-indirect) for inter-network node use cases (e.g., inter-gNB use cases). In the description herein, the terms "network node," "gNB X," and "gNB Y" are used interchangeably. The mechanisms for enhancing service continuity for a single-hop Layer 2 WTRU to a network relay may be applied to the following scenarios [RAN2, RAN3]: inter-gNB indirect-direct path handover (e.g., “remote WTRU <-> relay WTRU A <-> gNB X” to “remote WTRU <-> gNB Y”), inter-gNB direct-indirect path handover (e.g., “remote WTRU <-> gNB X” to “remote WTRU <-> relay WTRU A <-> gNB Y”), intra-gNB indirect-indirect path handover (e.g., “remote WTRU <-> relay WTRU A <-> gNB X” to “remote WTRU <-> relay WTRU B <-> gNB X”), and inter-gNB indirect-indirect path handover (e.g., “remote WTRU <-> relay WTRU A <-> gNBX” to “remote WTRU <-> relay WTRU B <-> gNB Y”).

[0108] Figure 7 Example extensions for direct to indirect handover for the inter-gNB use case are described. Figure 7 An example of utilizing inter-gNB direct to indirect handover is described. Figure 7As shown, the difference in the intra-gNB use case is that the reconfiguration of the target relay WTRU 704 for the remote WTRU 702 can be done directly from the target gNB.

[0109] In various exemplary embodiments regarding direct / indirect to indirect path handover, the source or target network node / cell may determine the target relay WTRU. Factors to consider may include that the remote WTRU is unaware of the backhaul Uu link quality of the candidate relay WTRU when performing measurements, and therefore the measurement configuration from the source to the remote WTRU that triggers the HO (handover) decision of the source gNB may be based on the link from the remote WTRU to the source (Uu or SL) and the target relay. In other words, a HO may be triggered to a target relay WTRU that has excellent conditions for the remote WTRU, but may have a poor backhaul Uu link to the target network node / cell.

[0110] Two exemplary options for performing an inter-gNB path handover from direct / indirect to indirect may include (1) the source gNB may select a target relay WTRU, and (2) the source gNB may send a list of candidate relay WTRUs to the target gNB, and the target gNB may select the final target relay among these (e.g., taking into account the indicated backhaul Uu link quality of the relay WTRU).

[0111] Figure 8 An example process for conditional handover (CHO) configuration and execution is depicted. CHO and conditional PSCell addition / change (CPA / CPC, or collectively referred to as CPAC) can reduce the likelihood of radio link failure (RLF) and handover failure (HOF). Conventional LTE / NR handovers may typically be triggered by measurement reports, even if nothing prevents the network from sending a HO command to the WTRU and even if no measurement report is received. For example, the WTRU may be configured with an A3 event that triggers a measurement report to be sent when the radio signal level / quality (RSRP, RSRQ, etc.) of a neighboring cell becomes better than the primary serving cell (PCell) or also better than the primary and secondary serving cells (PSCells) in the case of dual connectivity (DC). The WTRU may monitor the serving cell and the neighboring cells and may send measurement reports when conditions are met. Upon receiving such a report, the network (current serving node / cell) may prepare a HO command (e.g., an RRC reconfiguration message with reconfigurationWithSync) and may send it to the WTRU, which may execute the HO command so that the WTRU connects to the target cell.

[0112] CHO differs from conventional handover in that multiple handover targets may be prepared (compared to only one target in the conventional case), and the WTRU may not perform CHO immediately as in the case of conventional handover. Instead, the WTRU may be configured with a trigger condition comprising a set of radio conditions, and when / if the trigger condition is met, the WTRU may perform a handover to one of the targets.

[0113] The CHO command may be sent when the radio conditions towards the current serving cell are still favorable, thereby reducing two points of failure in traditional handovers, such as the risk of failure to send measurement reports (e.g., if the link quality to the current serving cell has fallen below an acceptable level when the measurement report is triggered in a normal handover) and the risk of failure to receive the handover command (e.g., if the link quality to the current serving cell has fallen below an acceptable level after the WTRU has sent the measurement report but before it has received the HO command).

[0114] The trigger conditions for CHO may trigger measurement reports based on the radio quality of the serving cell and neighboring cells. For example, a WTRU may be configured with CHO that has a trigger condition of class A3 and an associated HO command (802). The WTRU 804 may monitor the current cell and the serving cell (806), and when the A3 trigger condition is met, the WTRU 804 will execute the associated HO command (808) and switch its connection to the target cell (810) instead of sending a measurement report.

[0115] CHO may help prevent unnecessary re-establishment in the event of a radio link failure (RLF). For example, assume that a WTRU is configured with multiple CHO targets, and the WTRU experiences RLF before the triggering conditions for any of the targets are met. Conventional operation would result in an RRC re-establishment procedure that would cause a considerable interruption time for the WTRU's bearers. However, in the case of CHO, if after detecting an RLF the WTRU ends up with a cell that has CHO associated with it (e.g., a target cell is already prepared for it), the WTRU may directly execute the HO command associated with that target cell, rather than continuing with the full re-establishment procedure.

[0116] In the DC scenario, CPC and CPA may be considered as extensions of CHO.A WTRU may be configured with trigger conditions for a PSCell change or addition, and when the trigger conditions are met, the WTRU may execute the associated PSCell change command or PSCell add command.

[0117] In sidelink (SL) operation, the WTRU may configure the associated peer WTRU to perform NR sidelink measurements according to the NR sidelink measurement configuration for unicast via the RRC RecongulationSidelink message and report on the corresponding PC5-RRC connection. The WTRU may derive NR sidelink measurement results by measuring one or more DMRS (demodulation reference signals) associated with each PC5-RRC connection configured by the associated peer WTRU. For the NR sidelink measurement results, the WTRU may apply layer 3 filtering before using the measurement result evaluation reporting criteria and measurement reporting. In an exemplary embodiment, the NR sidelink RSRP may be configured as a trigger quantity and a reporting quantity.

[0118] The following terminology is used herein with respect to measurement events for the NR sidelink. Event S1 refers to the service becoming better than a threshold, and event S2 refers to the service becoming worse than a threshold. Measurements (reports) based on S1 and S2 can be used by the WTRU receiving the reports to adjust the power level when transmitting data. NR sidelink transmissions can have the following two resource allocation modes. Mode 1 refers to sidelink resources being scheduled by the gNB, while Mode 2 refers to the WTRU autonomously selecting sidelink resources from a (pre-)configured sidelink resource pool(s) based on a channel sensing mechanism. For WTRUs within coverage, the WTRU can be configured to operate in Mode 1 or Mode 2, and for WTRUs outside coverage, Mode 2 can be employed. To enhance the QoS (Quality of Service) of the NR sidelink transmission, congestion control (e.g., Mode 2) can be used to prevent the transmitting WTRU from occupying too many resources in the sidelink transmission. For this purpose, two metrics are described herein. Channel Busy Rate (CBR) refers to the portion of subchannels whose RSSI (Received Signal Strength Indicator) exceeds a preconfigured value for a specific duration. Channel occupancy ratio (CR) refers to when considering a specific time slot n, CR is (X+Y)M, where X is the number of subchannels occupied by the transmitting WTRU in [na, n-1], Y is the number of authorized subchannels in [n, n+b], and M is the total number of subchannels in [na, n+b].

[0119] For congestion control, CR limit An upper limit on the CR indicated may be imposed on the transmitting WTRU, where CR limit is a function of the CBR (constant bit rate) and the priority of the sidelink transmission. In an exemplary embodiment, the amount of resources occupied by the transmitting WTRU may not exceed the CR limit .

[0120] This CBR report may also be used by the gNB to determine the resource pool to allocate for sidelink communication (e.g., if the WTRU participating in the sidelink communication reports a high CBR, then increase the resource pool, if the reported CBR is low, then decrease the resource pool, etc.).

[0121] In addition to peer WTRUs participating in sidelink operations configuring each other for measurements (either periodic or S1 / S2 events), for coverage operations (e.g., when the remote WTRU is within the coverage of the gNB), the gNB may configure the remote WTRU with CBR measurements, which may be periodic or event-triggered. The following two measurement events may be configured for CBR measurement reporting: Event C1 (CBR of NR sidelink communication becomes better than an absolute threshold) and Event C2 (CBR of NR sidelink communication becomes worse than an absolute threshold).

[0122] In CHO in Uu, the WTRU may perform a HO to a pre-configured target cell when some conditions associated with the quality of the source and target cells are met. This avoids having the WTRU send measurement reports to the network for the network to make a HO decision, as the measurement reports or the HO command itself may be degraded / lost, leading to RLF before the HO is performed.

[0123] Due to the possibility of direct / indirect to indirect CHO, more than one WTRU may be involved in the final handover (e.g., a remote WTRU and a target relay WTRU), unlike traditional CHO, which only involves one WTRU. Since there may be several target relay WTRUs served by a given target cell, configuring different events for each possible target relay WTRU may exceed the capabilities of a WTRU configured for multiple CHOs. Whether the final decision on the target relay is made by the source gNB or the target gNB can also affect how CHO operates in SL relay scenarios.

[0124] Various embodiments discussed herein address how to efficiently implement conditional path switching from a direct / indirect link to an indirect link for a remote WTRU. In an exemplary embodiment, the remote WTRU may perform a conditional path switching in which the remote WTRU connects to the target cell via one of the relay WTRUs under the target cell when the radio conditions between the remote WTRU and one of the relay WTRUs meet a path switching trigger condition (e.g., above an absolute threshold, better than the serving link by a certain threshold, etc.). Upon completing the connection, the remote WTRU may send an RRC reconfiguration complete message including the remote WTRU's identity.

[0125] In another exemplary embodiment, the target relay WTRU selection may be made by the target gNB after an initial conditional path switch performed by the remote WTRU. After performing a path switch via a specific relay WTRU, the remote WTRU maintains the other conditional path switch configurations (e.g., for a specific configuration time) and sends the SL measurements of the other candidate relay WTRUs to the target gNB (e.g., in an RRC reconfiguration complete message). If the remote WTRU receives an indication from the target gNB (e.g., MAC CE, RRC) with the identity of one of the candidate relays, it performs a path switch to the indicated relay WTRU.

[0126] In another exemplary embodiment, a relay WTRU may prepare for a path switch for a remote WTRU. A relay WTRU may be configured / prepared to serve one or more remote WTRUs. Upon receiving an indication from the remote WTRU that the remote WTRU has performed a path switch via the relay WTRU, the relay WTRU may apply configurations associated with the remote WTRU (e.g., (re)configure / setup a SL (e.g., RLC channel) between the remote WTRU and the relay WTRU, (re)configure backhaul Uu, apply SRAP configuration to map SL and Uu RLC channels, etc.).

[0127] In another exemplary embodiment, redundancy may be used to handle failure cases such as a congested target relay WTRU or a bad backhaul to the target gNB. The remote WTRU, when performing a path switch to the target relay WTRU, may send an indication of the path switch to the network via multiple candidate relay WTRUs (e.g., other relay WTRUs serving the same cell as the target relay WTRU), and the remote WTRU may receive from the network a confirmation of the path switch to the target relay WTRU or an indication to switch to one of the other candidate relay WTRUs.

[0128] Figure 9 Describes an exemplary conditional switching scenario. Figure 9 To describe different embodiments of CHO operation in direct / indirect to indirect path switching. Figure 9As shown, a remote WTRU 902 is being served in a source cell 904 (either directly to a network node or via a source relay WTRU such as SL relay 908), and there are two candidate target cells (target cell 906—also shown as target cell x, and target cell 910—also shown as target cell y), with two relay WTRUs (relay WTRU 912—also shown as relay WTRU B, relay WTRU 914—also shown as relay WTRU B) under target cell 906 and three relay WTRUs (relay WTRU 916—also shown as relay WTRU C, relay WTRU 918—also shown as relay WTRU D, and relay WTRU 920—also shown as relay WTRU 920E) under target cell 910. There are several possible handovers or path switches that the WTRU 902 may perform. For example, any suitable combination of the following handovers may be performed: [Case 1] WTRU HO directly to the target cell 906; [Case 2] WTRU HO directly to the target cell 910; [Case 3] WTRU HO via the relay WTRU 912 of the target cell 906; [Case 4] WTRU HO via the relay WTRU 914 of the target cell 906; [Case 5] WTRU HO via the relay WTRU 916 of the target cell 910; [Case 6] WTRU HO via the relay WTRU 918 of the target cell 910; and [Case 7] WTRU HO via the relay WTRU 920 of the target cell 910. Combinations of cases are also possible for multipath (e.g., Case 1+3, where the WTRU ends up being simultaneously connected to the target cell 906 directly and to the target cell 906 via the relay WTRU 912).

[0129] As described herein, the terms PC5 and SL are used interchangeably. The terms reconfiguration and configuration are used interchangeably. The terms reconfiguration complete message, RRC complete message, path switch complete message, and complete message are used interchangeably. The terms path switch and path switch are used interchangeably. The terms candidate relay and target relay are used interchangeably. Although the focus is on the L2 U2N relay use case, the solution is equally applicable to any appropriate layer (e.g., Layer 3 (L3)), network, etc. Unless otherwise specified, the WTRU in the following discussion refers to the remote WTRU. Unless otherwise specified, the term "source" refers to the source gNB / network node / cell. Unless otherwise specified, the term target refers to the target gNB / network node / cell. The terms conditional handover (CHO), conditional mobility, and conditional path switch (CPS) are used interchangeably. In the following description, unless otherwise specified, the phrase "measurements of a certain relay" is intended to describe SL measurements between a remote WTRU and a relay WTRU.

[0130] This paper considers conditional mobility. However, some aspects also apply to traditional measurement-based mobility (for example, the new measurement events proposed in this paper can be used to send measurement reports to the source gNB instead of triggering conditional path switching).

[0131] In the following description, the conditional path switch configuration at the remote WTRU may be any information element (IE) in the RRC reconfiguration message related to the operation of the remote WTRU via the SL relay. This includes, but is not limited to, dedicated configuration of the PC5 link, including information such as PC5 PHY / MAC configuration, RLC channels, bearers, measurements, DRX, etc. (e.g., as indicated in the SL-ConfigDedicatedNR IE), SRAP configuration (e.g., as indicated in the SL-L2RelayUEConfig IE), serving cell information, etc., and the identity of the target relay WTRU (e.g., included in the sl-PathSwitchConfig IE).

[0132] In an example process, a relay WTRU (e.g., relay WTRU 908, relay WTRU 912, relay WTRU 914, relay WTRU 916, relay WTRU 918, relay WTRU 920) may prepare for a path switch for a remote WTRU (e.g., remote WTRU 902). The relay WTRU may receive conditional reconfiguration information that includes a remote WTRU identity (or set of identities) and remote WTRU configuration information associated with (corresponding to) the remote WTRU (or set of remote WTRUs). The corresponding configuration may be applied on behalf of the associated remote WTRU (e.g., SL-related configuration, SRAP configuration, backhaul UuRLC channel configuration, etc.). A relay WTRU (e.g., relay WTRU 908, relay WTRU 912, relay WTRU 914, relay WTRU 916, relay WTRU 918, relay WTRU 920) may receive an indication from a remote WTRU that the remote WTRU has performed a path switch to the relay WTRU. The indication from the remote WTRU may include a PC5 connection establishment request, a PC5 connection reconfiguration request, a new PC5 RRC message, a new MAC CE sent via the SL, a Uu RRC message (e.g., a reconfiguration complete message) to be forwarded to the gNB (e.g., via a pre-configured SL RLC channel), or any suitable combination thereof. The relay WTRU may apply the (re)configuration associated with the associated remote WTRU. That is, the relay WTRU may be configured with the remote WTRU configuration information. The relay WTRU may send an RRC complete message to the network indicating that the associated relay WTRU has been configured with the remote WTRU configuration / reconfiguration information (that the configuration / reconfiguration has been applied).

[0133] A remote WTRU may perform a conditional path switching operation. For example, a remote WTRU currently being served by a direct Uu link to a source cell may be configured with a measurement event that is used to trigger a conditional path switching of an indirect link to a target cell, wherein the conditions of the event are considered satisfied if the source Uu radio link quality (e.g., RSRP, RSRQ, etc.) is below a first threshold and / or there is at least one candidate relay WTRU to the target cell having an SL radio condition above a second threshold.

[0134] for Figure 9, the WTRU 902 may be configured with two conditional events regarding the indirect target links to the two target cells 906 and 910. That is, one event is configured to handle use cases 3 and 4 (WTRU HO to the target cell 906 via relay WTRU 912 or relay WTRU 914), and the other event is configured to handle use cases 5, 6, and 7 (WTRU HO to the target cell 910 via relay WTRU 916, relay WTRU 918, or relay WTRU 920). A remote WTRU currently being indirectly served by a source cell via an SL relay WTRU may be configured with a measurement event that is used to trigger a conditional path switch for the indirect link to the target cell, wherein the conditions of the event are considered met if the source SL radio link quality is below a first threshold and / or there is at least one candidate relay WTRU to the target cell having an SL radio condition above a second threshold.

[0135] In another embodiment, a remote WTRU that is currently being indirectly served by a source cell via an SL relay WTRU may be configured with a measurement event that is used to trigger a conditional path switch to an indirect link to a target cell, wherein the condition of the event is considered to be met if there is at least one candidate relay WTRU to the target cell having an SL radio condition that is greater than a certain threshold than the source SL radio link quality.

[0136] In the above embodiments, the SL radio quality / condition may be based on SL-RSRP (if available), or based on SD-RSRP (otherwise). In another exemplary embodiment, different thresholds may be associated with SL-RSRP measurements compared to SD-RSRP measurements. In another exemplary embodiment, the source and target relay measurements are based on the same type of measurement (e.g., SL-RSRP for both the target and the source or SD-RSRP for both the target and the source), and in another exemplary embodiment, the source and target relay measurements may be based on different types of measurements (e.g., SL-RSRP for the source and SD-RSRP for the target, SD-RSRP for the source and SL-RSRP for the target). In another embodiment, the threshold used by all relay WTRUs under the same target cell is the same. In another exemplary embodiment, the threshold used for all relay WTRUs (regardless of whether they are under the same target cell) is the same. In another embodiment, the threshold used for relay WTRUs may be different even under the same target cell. In another exemplary embodiment, in addition to the SL radio conditions of the source / target relay WTRU, the CBR / CR conditions on the SL path to the source / relay WTRU may also be considered (e.g., CBR / CR thresholds that may prioritize or degrade a target or source relay WTRU, CBR / CR thresholds that may disqualify a candidate relay from consideration, etc.). In another exemplary embodiment, the remote WTRU may monitor the trigger conditions of all relay WTRUs it detects under the target cell. In another exemplary embodiment, the remote WTRU may monitor the trigger conditions only for relay WTRUs indicated by the network (e.g., explicitly indicated in a conditional path switching configuration, etc.). This may be a list of L2 relay WTRU IDs. In another exemplary embodiment, the remote WTRU may be configured (e.g., explicitly within a conditional path switching configuration, etc.) with an allowed list of candidate relay WTRUs for conditional path switching (e.g., for a given target cell). This may be a list of L2 relay WTRU IDs. In another exemplary embodiment, the remote WTRU may be configured (e.g., explicitly in a conditional path switching configuration) with a blocking list of relay WTRUs that should not be considered for conditional path switching (e.g., for a given target cell). This may be a list of L2 relay WTRU IDs.

[0137] Various embodiments may involve RRC reconfiguration. In another exemplary embodiment, the remote WTRU may be configured with one or more RRC reconfigurations (or information elements IE for RRC reconfiguration) to be applied for each conditional event of path switching, the one or more RRC reconfigurations (or information elements IE for RRC reconfiguration) being applied when the triggering condition of the relevant event is met. In another exemplary embodiment, the remote WTRU may be configured with a conditional RRC reconfiguration message (e.g., containing IEs such as SL-ConfigDedicatedNR, SL-L2RemoteUEConfig, SL-SRAP-Config, reconfigurationWithSync containing sl-PathSwitchConfig, etc.) that is associated with each candidate relay WTRU, even with relay WTRUs serving the same cell. For example, for Figure 9 For the scenario depicted in , where there are 2 candidate relays serving cell 906 and 3 candidate relays serving the same cell 910 , the measurement and event configuration can be depicted as follows.

[0138] Conditional path switching configuration 1 may include the target cell 906, a measurement event in which one of the target relay WTRUs has an SL radio condition greater than threshold 1, reconfiguration 1 via the target relay WTRU 912, and reconfiguration 2 via the target relay STRU 914. Conditional path switching configuration 2 may include the target cell 910, a measurement event in which one of the target relay WTRUs has an SL radio condition greater than threshold 3 and Uu less than threshold 4, reconfiguration 1 via the target relay WTRU 916, reconfiguration 2 via the target relay WTRU 918, and reconfiguration 3 via the target relay STRU 920. Threshold 3 and Threshold 1 may be the same or different. Threshold 2 and Threshold 4 may be the same or different.

[0139] In another exemplary embodiment, there may be a common conditional RRC reconfiguration message common to multiple target relays (e.g., containing IEs such as SL-ConfigDedicatedNR, SL-L2RemoteUEConfig, SL-SRAP-Config, etc.), while there may be a dedicated conditional RRC reconfiguration message associated with each target relay WTRU (e.g., containing IEs such as reconfigurationWithSync containing sl-PathSwitchConfig, etc.). For example, for Figure 9For the scenario described in

[15] , the measurement and event configurations may be as follows. Conditional path switching configuration 1 may include the target cell 906, a measurement event where one of the target relays has an SL radio condition above threshold 1, a common RRC reconfiguration, dedicated reconfiguration 1 via relay WTRU 912, and dedicated reconfiguration 2 via relay WTRU 914. Conditional path switching configuration 2 may include the target cell 910, a measurement event where one of the target relays has an SL radio condition above threshold 3 and a serving Uu below threshold 4, a common RRC reconfiguration, dedicated reconfiguration 1 via relay WTRU 916, dedicated reconfiguration 2 via relay WTRU 918, and dedicated reconfiguration 3 via relay WTRU 920.

[0140] In another exemplary embodiment, a common RRC reconfiguration may be associated with a target relay WTRU serving a different target cell. Figure 9 For the scenario described in

[15] , the measurement and event configurations may be as follows. A common conditional path switch configuration may include a common reconfiguration. Conditional path switch configuration 1 may include a target cell 906, a measurement event where one of the target relays has an SL radio condition above threshold 1 and a serving Uu below threshold 2, dedicated reconfiguration 1 via relay WTRU 912, and dedicated reconfiguration 2 via relay WTRU 914. Conditional path switch configuration 2 may include a target cell 910, a measurement event where one of the target relays has an SL radio condition above threshold 3 and a serving Uu below threshold 4, dedicated reconfiguration 1 via relay WTRU 916, dedicated reconfiguration 2 via relay WTRU 918, and dedicated reconfiguration 3 via relay WTRU 920.

[0141] In other example embodiments, a common configuration may be shared by a subset of the conditional path switching configurations, rather than by all or only those conditional path switching configurations belonging to a given cell.

[0142] In other exemplary embodiments, there may be only a common configuration for a given target cell or even for relays serving different cells (i.e., no dedicated configuration for a given target relay), and the WTRU may implicitly determine or learn dedicated information (e.g., such as the relay WTRU identity, which may be included in an IE such as sl-pathswitchConfig), for example, from a relay discovery message or the like.

[0143] Various exemplary embodiments may involve performing a conditional path switch when a trigger condition is met. In one exemplary embodiment, when one of the candidate relay WTRUs meets the trigger condition for the conditional path switch configuration, the remote WTRU may perform common and / or dedicated RRC configuration associated with the triggered conditional event and the specific target relay that meets the condition.

[0144] In another exemplary embodiment, if the trigger condition is satisfied by more than one relay WTRU, the remote WTRU may be configured to randomly select one of the relays based on the SL radio condition (e.g., the radio condition with the highest quality such as the highest SL / SD-RSRP), based on the CBR / CR condition (e.g., the one with the lowest CBR / CR), the relay with which the remote WTRU has established PC5, or any appropriate combination thereof.

[0145] In another exemplary embodiment, the remote WTRU may instruct upper layers to establish a PC5 link to the selected target relay WTRU (if PC5 has not already been established). In another exemplary embodiment, the remote WTRU sends an RRCReConfigurationComplete message to the target gNB via the selected target relay WTRU. In another exemplary embodiment, the remote WTRU may include its identity (e.g., L2 remote WTRU ID) in the RRCReconCompoutionComplete message. In another exemplary embodiment, after completing the path switch to the selected target relay WTRU, the remote WTRU may release all other conditional path switch configurations (e.g., measurement events, associated public and dedicated RRC configurations, etc.). In another exemplary embodiment, after completing the path switch to the selected target relay WTRU, the remote WTRU may release a subset of the conditional path switch configurations (e.g., measurement events, associated public and dedicated RRC configurations, etc.). For example, the conditional path switch reconfiguration associated with the target cell may be released, while other reconfigurations may be retained.

[0146] In an exemplary process, in which a remote WTRU (e.g., remote WTRU 902) is configured for conditional path switching, the remote WTRU may receive conditional path switching configuration information for a target cell (e.g., target cell 906, target cell 910) (associated therewith). The conditional path switching information may be received via a relay WTRU. The conditional path switching configuration information may include one or more triggering conditions, or conditions (e.g., at least one relay WTRU under the target cell reaches an absolute or relative threshold), and may include corresponding RRC reconfiguration (e.g., SL path switching reconfiguration information and other configurations related to SL and remote WTRU operation). The triggering condition(s) and SL reconfiguration information may be associated with more than one (multiple) candidate relay WTRUs (e.g., relay WTRU 908, relay WTRU 912, relay WTRU 914, relay WTRU 916, relay WTRU 918, relay WTRU 920). The remote WTRU (e.g., remote WTRU 902) may monitor the triggering conditions of one or more relay WTRUs under the target cell. Upon determining that one of the relay WTRUs satisfies (has satisfied) the trigger condition, the remote WTRU may apply the RRC reconfiguration information associated with the selected target relay WTRU. The remote WTRU may send an RRCReconfigurationComplete message to a network node (e.g., a gNB) via the selected target relay WTRU, where the message may include an identity of the remote WTRU. The remote WTRU may release the conditional path switching configuration associated with other relay WTRUs (e.g., other relay WTRUs in a plurality of relay WTRUs).

[0147] Target relay WTRU selection may be performed by the target network node (e.g., gNB) after an initial conditional path switch is performed by the remote WTRU. In some cases, a path switch decision based solely on SL conditions may not be sufficient because the conditions of the backhaul Uu path from the candidate relay WTRUs to the target gNB are not known. For example, the remote WTRU may end up performing a path switch to a relay WTRU (e.g., based on receiving a path switch configuration from the source gNB, based on satisfying a trigger condition of a conditional path switch configuration, etc.) that has very good SL conditions but does not have the best backhaul Uu compared to other candidate relay WTRUs. An embodiment of a mechanism is described herein whereby the target gNB may change the relay selected by the WTRU immediately after a path switch (e.g., after considering the backhaul Uu conditions of the relay to which the WTRU has changed its path and the other candidate relay WTRUs).

[0148] In an exemplary embodiment, the remote WTRU may start a timer (with a configured value) after sending the path switch complete message. The WTRU may keep / maintain some or all conditional path switch configurations until the timer expires (e.g., all conditional path switch configurations associated with the relay WTRU in the same target cell as the relay to which the WTRU has switched its path). When the timer expires, the configuration may be released if not released earlier due to some of the solutions described below.

[0149] In another exemplary embodiment, maintaining / maintaining the conditional path switch configuration may require performing measurements and monitoring conditions associated with the path switch configuration. In another exemplary embodiment, maintaining / maintaining the conditional path switch configuration may mean simply maintaining the stored configuration (e.g., the WTRU will not monitor the triggering conditions for the path switch configuration). In another exemplary embodiment, the remote WTRU may send the measurement values ​​(e.g., SL / SD-RSRP) of the selected target relay WTRU and / or the identities and measurement values ​​of other candidate relay WTRUs to the network (e.g., in a reconfiguration complete message, immediately after the reconfiguration complete message, or in a separate message multiplexed with the reconfiguration complete message, etc.). In another exemplary embodiment, the other indicated candidate relay WTRUs may be relay WTRUs serving the same cell as the selected target relay WTRU. In another exemplary embodiment, the other indicated candidate relay WTRUs may be relay WTRUs serving any cell that belongs to the same gNB as the cell of the selected target relay WTRU. In another exemplary embodiment, the other indicated relay WTRU may be a relay WTRU that serves a cell belonging to a different gNB than the cell gNB of the selected target relay WTRU. In another exemplary embodiment, only candidate relay WTRUs that meet certain SL radio conditions are indicated by the remote WTRU (e.g., SL radio is above a configured threshold). In another exemplary embodiment, only candidate relay WTRUs that meet certain SL congestion / load conditions are indicated by the remote WTRU (e.g., CBR / CR is below a configured threshold). In another exemplary embodiment, after completing the path switch and having sent a reconfiguration complete message to the target gNB, the remote WTRU may receive an indication from the target gNB to switch the path to another relay WTRU (e.g., one of the other candidate relay WTRUs that it had previously indicated). In another exemplary embodiment, the indication may include an identification of the relay WTRU (e.g., L2 relay WTRU ID) to which the remote WTRU should switch the path. In another exemplary embodiment, the indication may be received in a MAC CE (control unit). In another exemplary embodiment, the indication may be received in an RRC reconfiguration message (eg, possibly including additional / incremental reconfiguration related to SL / relay operations).

[0150] In another exemplary embodiment, the indication may be received via the target relay WTRU (e.g., the relay WTRU to which the WTRU has switched the path), wherein the reconfiguration complete message was originally sent to the target gNB via this target relay WTRU. In another exemplary embodiment, the indication may be received via a different target relay WTRU selected by the target gNB. For example, a PC5 connection establishment request or reconfiguration message may be received from the new target relay WTRU with an implicit or explicit indication that the path is to be switched to the relay WTRU. In another exemplary embodiment, the remote WTRU may apply the path switch to the indicated new target relay WTRU without checking any additional conditions (e.g., trigger conditions associated with the relay WTRU indicated in the saved conditional path switch reconfiguration). In another exemplary embodiment, the remote WTRU may apply the path switch to the indicated new target relay WTRU only if the trigger conditions associated with the relay WTRU indicated in the saved conditional path switch reconfiguration are met. In another exemplary embodiment, after switching the path to the relay WTRU indicated in the received indication, the remote WTRU may release some or all of the saved conditional path switching configurations (if any) (even if the timer associated with maintaining the configuration is still running).

[0151] In an exemplary process, a target relay WTRU selection may be made by a target network node (e.g., a gNB) after an initial conditional path switch is performed by a remote WTRU, and the remote WTRU may perform a path switch to the target relay WTRU (e.g., based on satisfying a trigger condition of a conditional path switch configuration). A remote WTRU (e.g., remote WTRU 902) may receive conditional path switch configuration information associated with multiple relay WTRUs, and the remote WTRU may maintain the conditional path switch configuration for a specific configuration duration. Satisfaction of the trigger condition may include determining that a subset of the multiple relay WTRUs satisfies a first condition, and selecting a relay WTRU from the subset that satisfies a second condition. The remote WTRU may apply the conditional path switch configuration information associated with the selected relay WTRU. The remote WTRU may send identities and SL measurement results of multiple candidate relay WTRUs to the network (e.g., in a reconfiguration complete message) that meet certain conditions (e.g., all detected relay WTRUs in the same cell as the selected target relay WTRU, those relay WTRUs with SL radio conditions above a certain threshold, etc.). Upon receiving an indication from the network to switch to one of the indicated candidate relay WTRUs (e.g., in a MAC CE, RRC reconfiguration, etc.), the remote WTRU may change the path to the indicated relay WTRU by applying the RRC reconfiguration associated with the indicated relay WTRU. The remote WTRU may release other conditional path switching configurations.

[0152] In an exemplary embodiment, the relay WTRU may be prepared and / or configured for path switching of the remote WTRU. In the embodiments described herein, the conditional configuration prepared at the relay WTRU on behalf of the remote WTRU may be any information element (IE) in the RRC reconfiguration message that is related to the operation of the remote WTRU via the associated relay WTRU. This may include any appropriate combination of the following. Dedicated configuration for the PC5 link, including information such as PC5 PHY / MAC configuration, RLC channels, bearers, measurements, DRX, etc. (e.g., indicated in the SL-ConfigDedicatedNR IE). Backhaul Uu RLC channel for relaying remote WTRU data (e.g., in the uu-RelayRLC-ChannelToAddModList-r17 IE in the cell group configuration portion of the RRC reconfiguration, etc.). SRAP configuration, serving cell information, etc. (e.g., indicated in the SL-L2RelayUEConfig IE), which is used, for example, to map the remote WTRU's identity between PC5 and backhaul Uu RLC channels, etc. (e.g., included in the SL-L2RelayUEConfig IE).

[0153] In an exemplary embodiment, a relay WTRU may apply conditional RRC reconfiguration(s) on behalf of a remote WTRU. In an exemplary embodiment, a relay WTRU may be configured with an RRC (re)configuration (or an information element IE of RRC reconfiguration) to be applied on behalf of a remote WTRU, wherein the reconfiguration is applied when the relay WTRU receives an indication from the remote WTRU that the remote WTRU has performed a path switch to the relay WTRU.

[0154] In another exemplary embodiment, the indication received from the remote WTRU may be a PC5 connection establishment request. In another exemplary embodiment, the indication received from the remote WTRU may be a PC5 connection modification / reconfiguration request. In another exemplary embodiment, the indication received from the remote WTRU may be a new PC5 RRC message. In another exemplary embodiment, the indication received from the remote WTRU may be a MAC CE sent via PC5. In another exemplary embodiment, the indication received from the remote WTRU may be a Uu RRC message to be forwarded to the gNB (e.g., an RRC Reconfiguration Complete message from the remote WTRU, which is received via a pre-configured SL RLC channel). In another exemplary embodiment, the relay WTRU may be configured with a set of RRC (re)configurations, where each configuration is associated with a specific remote WTRU (e.g., the L2 ID of the remote WTRU). The relay WTRU may apply the reconfiguration associated with that remote WTRU. In another exemplary embodiment, the RRC (re)configuration for configuring the relay WTRU in association with a specific remote WTRU may include configuration regarding the PC5 link between the remote WTRU and the relay WTRU (e.g., information for establishing the PC5 link, information for reconfiguring the PC5 link if the PC5 link already exists, information regarding the PC5 RLC channel, and other configurations). In another exemplary embodiment, the RRC (re)configuration for configuring the relay WTRU in association with a specific remote WTRU may include configuration regarding the backhaul Uu link between the remote WTRU and the relay WTRU (e.g., information for establishing the backhaul Uu link if the relay WTRU is in an INACTIVE / IDLE state, information for reconfiguring the backhaul Uu link if the relay WTRU is in a CONNECTED state, backhaul Uu RLC channel configuration, and the like). In another exemplary embodiment, the RRC (re)configuration for configuring the relay WTRU in association with a specific remote WTRU may include configuration linking the PC5 link with the backhaul Uu link (e.g., SRAP configuration, which may be used, for example, for mapping between backhaul and SL RLC channels, and the like). In another example embodiment, the relay WTRU may be configured with a separate RRC (re)configuration associated with each remote WTRU (ie, a dedicated configuration to be applied on behalf of each remote WTRU).In another exemplary embodiment, the relay WTRU may be configured with a common RRC (re)configuration that is applicable to all remote WTRUs or a subset of remote WTRUs (e.g., a common configuration for establishing a backhaul link if the relay WTRU is in IDLE / INACTIVE state, a common configuration for establishing a reference / basic Uu RLC channel to be used commonly by multiple remote WTRUs, for example, where data for multiple remote WTRUs may end up being multiplexed, etc.).

[0155] Combinations of the above are possible, where there is a common RRC (re)configuration that applies to all remote WTRUs, and a dedicated RRC (re)configuration for each remote WTRU. For example, the configuration at the relay WTRU can be categorized as follows: Common reconfiguration (for remote WTRUs 1 and 2); Common reconfiguration (for remote WTRUs 3 and 4); Dedicated reconfiguration for WTRU 1; Dedicated reconfiguration for WTRU 2; Dedicated reconfiguration for WTRU 3; Dedicated reconfiguration for WTRU 4.

[0156] Some examples of how these configurations may be applied are described. Upon receiving a path switch indication from a remote WTRU, the relay WTRU may apply the common configuration associated with that WTRU and subsequently apply the dedicated configuration associated with that WTRU. Upon receiving a first indication of a path switch from one of the remote WTRUs with a shared configuration, the relay WTRU may apply the common reconfiguration associated with that relay WTRU and subsequently apply the dedicated configuration associated with that remote WTRU. Thereafter, when the relay WTRU receives a path switch indication from another remote WTRU in the same group, the relay WTRU may apply the dedicated reconfiguration associated with that remote WTRU.

[0157] In another exemplary embodiment, according to any of the above solutions, the relay WTRU may send an RRC Complete message after performing configuration associated with the remote WTRU. In another exemplary embodiment, the relay WTRU may forward the Uu RRC Complete message received from the remote WTRU in a separate message. In another exemplary embodiment, the relay WTRU may forward the UuRRC Complete message received from the remote WTRU in its own RRC Complete message (e.g., embedded in a transparent container). In another exemplary embodiment, the relay WTRU may include an identification of the associated remote WTRU in the complete message.

[0158] In an exemplary embodiment, a relay WTRU may conditionally apply a reconfiguration associated with a remote WTRU. In an exemplary embodiment, the relay WTRU may be configured with some conditions / thresholds, and if these conditions are not met when a path switch indication is received from the remote WTRU, the relay WTRU may reject the path switch performed by the relay WTRU by performing an appropriate combination of the following operations: disabling the application of the reconfiguration(s) associated with the remote WTRU, disabling the establishment of the backhaul Uu link (e.g., if the relay WTRU is in IDLE / INACTIVE state), sending an indication to the remote WTRU (e.g., indicating that the backhaul Uu is no longer suitable for path switching via the relay WTRU), rejecting a PC5 connection establishment or modification request from the remote WTRU, or triggering a PC5 connection release procedure to the remote WTRU, etc.

[0159] According to the above solution, the conditions / thresholds with which the relay WTRU is configured to reject / accept path switching from the remote may be any appropriate combination of: a radio quality threshold of the backhaul Uu link (e.g., Uu RSRP / RSRQ is above a certain threshold), a load threshold (e.g., the number of remote WTRUs being served by the relay WTRU is below a certain threshold, the data / buffer level to be transmitted by the relay WTRU to the gNB or remote WTRU is below a certain threshold, the remaining UL / DL buffer level at the relay WTRU is above a certain threshold, etc.), or a CBR / CR threshold (e.g., the CBR on the SL between the relay WTRU and the remote WTRU is below a certain threshold).

[0160] In another exemplary embodiment, the signal level and / or load level and / or CBR thresholds may be different for each remote WTRU. In another exemplary embodiment, the signal level and / or load level and / or CBR thresholds may be common for all remote WTRUs. In another exemplary embodiment, the signal level and / or load level and / or CBR thresholds may be common for a subset of remote WTRUs, while some remote WTRUs may have thresholds specific to them. In another embodiment, the signal level and / or load level and / or CBR thresholds may depend on the number of associated remote WTRUs. For example, the more remote WTRUs to the same target cell being served by a relay WTRU, the signal level threshold may be increased. For example, the radio level threshold may be set to x1, and when a first remote WTRU switches to the relay WTRU's path, the backhaul Uu link quality is compared to this threshold. When a second remote WTRU switches to the relay WTRU's path, the backhaul link quality is compared to an updated threshold (e.g., f*1, where f is configured as a scaling factor for each additional WTRU).

[0161] In an exemplary embodiment, when the remote WTRU switches to another path, the relay WTRU may release the configuration associated with the remote WTRU. In an exemplary embodiment, the relay WTRU may receive an indication from the remote WTRU it is currently serving, where the indication indicates that the remote WTRU is no longer using the relay WTRU (e.g., the remote WTRU has changed to another relayed path, the remote WTRU has changed to a direct path, the remote WTRU has switched to another cell / gNB, etc.). The indication may be an implicit indication (e.g., the remote WTRU releases the PC5 link) or an explicit indication (e.g., a (new) PC5 RRC message, a (new) MAC CE, etc.). In another exemplary embodiment, the relay WTRU may release all configurations and contexts / resources associated with the remote WTRU (e.g., SL-related, Uu-related) upon receiving such an indication.

[0162] In an exemplary process using redundancy, a remote WTRU may perform a path switch to a target relay WTRU (e.g., based on receiving a path switch command from the network, performing a conditional path switch when a conditional path switch trigger condition is met, etc.). A remote WTRU (e.g., remote WTRU 902) may send information about the path switch to the network. The information may be sent via the target relay WTRU. The information may indicate that the remote WTRU is connected to the target WTRU. The information may indicate one or more candidate relay WTRUs based on a set of conditions (e.g., all detected relay WTRUs in the same cell as the target relay WTRU, those relay WTRUs with SL radio conditions above a certain threshold, etc.). The information may include measurements of the SL between the remote WTRU and the candidate relay WTRUs. If a PC5 link has not yet been established to the relevant (one or more) candidate relay WTRUs, the remote WTRU may trigger a PC5 connection establishment. The remote WTRU may receive an indication from the network confirming the path switch or a request to change the path to one of the candidate relay WTRUs. If the indication is a path change request, the remote WTRU may perform a path switch to the indicated relay WTRU (e.g., using a pre-configured path switch configuration for the indicated relay). The remote WTRU may release the PC5 link to all other relay WTRUs except the one indicated / confirmed by the network.

[0163] In an exemplary embodiment, redundancy may be implemented to handle the use case where the target relay WTRU has a poor backhaul to the target gNB. Upon deciding to perform a path switch to the target relay WTRU (e.g., based on receiving a path switch command from the network, performing a conditional path switch when a conditional path switch trigger condition is met, etc.), the remote WTRU may send an indication of the path switch to the network (e.g., an RRC complete message) via the target relay WTRU and one or more candidate relay WTRUs. In another exemplary embodiment, the remote WTRU includes its identity (e.g., L2 ID, etc.) in the indication. In another exemplary embodiment, the candidate relay WTRUs selected for sending the indication are all detected relay WTRUs serving the same cell / gNB as the target relay WTRU. The candidate relay WTRUs selected for sending the indication may be relay WTRUs with which the remote WTRU has a SL radio quality (e.g., SL-RSRP, SD-RSRP, etc.) above a certain configured threshold. The candidate relay WTRUs selected for sending the indication may be relay WTRUs that meet certain SL congestion / load conditions (e.g., CBR / CR below a configured threshold). The remote WTRU may include the SL radio quality to the target and associated candidate relay WTRUs (and the identity of the candidate relay WTRUs) in the indication of the path switch. If no PC5 has been established, the remote WTRU may establish a PC5 connection to the candidate relay WTRU. If a PC5 connection has been established, the remote WTRU may reconfigure / modify the PC5 connection to the candidate relay WTRU. The remote WTRU may receive an indication from the network confirming / accepting the path switch performed by the remote WTRU and may release the PC5 connection towards other candidate relay WTRUs and / or the (conditional) path switch configuration associated with these candidate relay WTRUs, if any. The remote WTRU may receive an indication from the network that the path switch performed by the remote WTRU is not accepted and an indication of a new target relay WTRU to be used by the remote WTRU (e.g., one of the candidate relay WTRUs), and the remote WTRU may perform the path switch to the indicated relay WTRU and release the PC5 connections to the other relay WTRUs (e.g., the other candidate relay WTRUs and the original target relay WTRU selected by the remote WTRU, etc.) and / or the (conditional) path switch configurations associated with these relay WTRUs (if any). The remote WTRU may wait for a confirmation or change indication from the network only for a specific configured duration after sending the path switch complete message. If no confirmation or change indication message is received before the timer expires, the remote WTRU may consider the path switch to be accepted.If no confirmation or change indication message is received upon expiration of the timer, the remote WTRU may consider the path switch rejected (and may release the PC5 connection to the associated relay WTRU, eg, reverting to the source configuration before the path switch).

[0164] Although features and elements are provided above in specific combinations, it will be understood by those skilled in the art that each feature or element can be used alone or in any combination with other features and elements. The present disclosure should not be limited in terms of the specific embodiments described in this application, which are intended to illustrate various aspects. Without departing from the spirit and scope of the present invention, many modifications and variations can be made, which will be apparent to those skilled in the art. Unless expressly stated otherwise, the elements, actions or instructions used in the description of this application should not be interpreted as being critical or necessary to the present invention. Based on the foregoing description, in addition to those enumerated herein, functionally equivalent methods, devices and products within the scope of this disclosure will be apparent to those skilled in the art. These modifications and variations are intended to fall within the scope of the appended claims.

[0165] In addition, the method provided herein can be implemented in a computer program, software or firmware incorporated into a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection) and computer-readable storage media (which exclude transient signals). Examples of computer-readable storage media different from signals include, but are not limited to, read-only memories (ROMs), random access memories (RAMs), registers, cache memories, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROMs and digital versatile disks (DVDs). A processor associated with the software can be used to implement a radio frequency transceiver used in a WTRU, UE, terminal, base station, RNC, or any host computer.

[0166] In an illustrative embodiment, any operations, processes, etc. described herein may be implemented as computer-readable instructions stored on a computer-readable storage medium. The computer-readable instructions may be executed by a processor of a mobile unit, a network element, and / or any other computing device.

Claims

1. A long-range wireless transmit / receive unit (WTRU), comprising: transceiver; as well as The processor is configured to: receiving, via the transceiver, conditional path switching configuration information associated with each of a plurality of candidate relay WTRUs; determining, based on the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs, that at least one of the plurality of candidate relay WTRUs satisfies a first condition; selecting a first relay WTRU that satisfies a second condition from the at least one of the plurality of candidate relay WTRUs that satisfies the first condition; applying the conditional path switching configuration information associated with the first relay WTRU; sending, via the transceiver, a message to a network node, wherein the message includes an identity and sidelink measurements associated with each of the plurality of candidate relay WTRUs that satisfies the first condition; receiving, via the transceiver, from the network node an indication to switch to a second relay WTRU of the plurality of candidate relay WTRUs; applying the conditional path switching configuration information associated with the second relay WTRU; as well as The conditional path switching configuration information associated with each candidate relay WTRU of the plurality of candidate relay WTRUs is released.

2. The remote WTRU of claim 1 , wherein the processor is further configured to maintain the conditional path switching configuration information associated with each of the multiple candidate relay WTRUs for a period of time after applying the conditional path switching configuration information associated with the first relay WTRU and before releasing the conditional path switching configuration information associated with each of the multiple candidate relay WTRUs.

3. The remote WTRU of claim 1 , wherein the remote WTRU is one of: Connect directly to a network node; or The WTRU is connected to the network node via a source relay.

4. The remote WTRU of claim 3, wherein the first condition is based on at least one of: Radio quality of the serving cell; sidelink radio conditions associated with the candidate relay WTRU; or A comparison of sidelink radio conditions associated with the source relay WTRU and sidelink radio conditions associated with the candidate relay WTRUs.

5. The remote WTRU of claim 1 , wherein the second condition comprises determining that the second relay WTRU has the highest quality sidelink radio condition among the plurality of candidate relay WTRUs.

6. The remote WTRU of claim 1, wherein the indication from the network node comprises a medium access control (MAC) control (CE).

7. The remote WTRU of claim 1 , wherein the indication from the network node comprises a radio resource control (RRC) message.

8. The remote WTRU of claim 1 , wherein releasing the conditional path switching configuration information comprises releasing a PC5 connection.

9. A method performed by a remote wireless transmit / receive unit (WTRU), the method comprising: receiving conditional path switching configuration information associated with each of a plurality of candidate relay WTRUs; determining, based on the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs, that at least one of the plurality of candidate relay WTRUs satisfies a first condition; selecting a first relay WTRU that satisfies a second condition from the at least one of the plurality of candidate relay WTRUs that satisfies the first condition; applying the conditional path switching configuration information associated with the first relay WTRU; sending a message to a network node, wherein the message includes an identity and sidelink measurements associated with each of the plurality of candidate relay WTRUs that satisfies the first condition; receiving an indication from the network node to switch to a second relay WTRU from the plurality of candidate relay WTRUs; applying the conditional path switching configuration information associated with the second relay WTRU; as well as The conditional path switching configuration information associated with each candidate relay WTRU of the plurality of candidate relay WTRUs is released.

10. The method according to claim 9 also includes maintaining the conditional path switching configuration information associated with each of the multiple candidate relay WTRUs for a period of time after applying the conditional path switching configuration information associated with the first relay WTRU and before releasing the conditional path switching configuration information associated with each of the multiple candidate relay WTRUs.

11. The method of claim 9, wherein the remote WTRU is one of: Connect directly to a network node; or The WTRU is connected to the network node via a source relay.

12. The method of claim 11, wherein the first condition is based on at least one of: Radio quality of the serving cell; sidelink radio conditions associated with the candidate relay WTRU; or A comparison of sidelink radio conditions associated with the source relay WTRU and sidelink radio conditions associated with the candidate relay WTRUs.

13. The method of claim 9, wherein the second condition comprises determining that the second relay WTRU has the highest quality sidelink radio condition among the plurality of candidate relay WTRUs.

14. The method of claim 9, wherein the indication from the network node comprises a medium access control (MAC) control (CE).

15. The method of claim 9, wherein the indication from the network node comprises a radio resource control (RRC) message.

16. The method according to claim 9, wherein releasing the conditional path switching configuration information comprises releasing a PC5 connection.

17. At least one computer-readable storage medium having program instructions stored thereon, the program instructions, when executed by a processor, causing the processor to: receiving conditional path switching configuration information associated with each of a plurality of candidate relay WTRUs; determining, based on the conditional path switching configuration information associated with each of the plurality of candidate relay WTRUs, that at least one of the plurality of candidate relay WTRUs satisfies a first condition; selecting a first relay WTRU that satisfies a second condition from the at least one of the plurality of candidate relay WTRUs that satisfies the first condition; applying the conditional path switching configuration information associated with the first relay WTRU; sending a message to a network node, wherein the message includes an identity and sidelink measurements associated with each of the plurality of candidate relay WTRUs that satisfies the first condition; receiving an indication from the network node to switch to a second relay WTRU from the plurality of candidate relay WTRUs; connecting to the second relay WTRU using the conditional path switching configuration information associated with the second relay WTRU; as well as The conditional path switching configuration information associated with each candidate relay WTRU of the plurality of candidate relay WTRUs is released.

18. According to at least one computer-readable storage medium according to claim 17, the executable instructions are also used to configure the at least one processor to maintain the conditional path switching configuration information associated with each of the multiple candidate relay WTRUs for a period of time after applying the conditional path switching configuration information associated with the first relay WTRU and before releasing the conditional path switching configuration information associated with each of the multiple candidate relay WTRUs.

19. The at least one computer-readable storage medium of claim 17, wherein the first condition is based on at least one of: Radio quality of the serving cell; sidelink radio conditions associated with the candidate relay WTRU; or A comparison of sidelink radio conditions associated with the source relay WTRU and sidelink radio conditions associated with the candidate relay WTRUs.

20. The at least one computer-readable storage medium of claim 17, wherein the second condition comprises determining that the second relay WTRU has the highest quality sidelink radio condition among the plurality of candidate relay WTRUs.

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