Recovery over sidelink
Radio Link Failure (RLF) recovery over Sidelink (SL) is provided. Systems and methods are disclosed herein that avoid triggering of a Radio Resource Control (RRC) re-establishment procedure by a User Equipment (UE) upon an RLF, thereby avoiding unnecessary signaling overhead and connectivity interruption. In some embodiments, the UE (UE1) is in communication with another UE (UE2) over an SL, and UE1 detects an RLF over a radio link. Upon detecting the RLF, UE1 sends a failure message to UE2 via an SL channel identifying the detected RLF. Upon receiving the failure message from UE1, UE2 forwards the message to the network via an available Uu link between UE2 and the network. In some embodiments, before sending the failure message to the network, UE2 performs a random access procedure to a selected cell if no Uu radio link is available and active.
1 . A method performed by a first wireless device for detecting and handling a radio link failure in a cellular communications system wherein the first wireless device is connected to a second wireless device via a sidelink, the method comprising:
detecting a radio link failure of a first radio link between the first wireless device and a radio access network node of the cellular communications system;
sending a failure message to the second wireless device via the sidelink between the first wireless device and the second wireless device to be forwarded to the radio access network node while not initiating a re-establishment procedure with the radio access network node; and
receiving a response message originating from the radio access network node, requesting a Radio Resource Control (RRC) reconfiguration, wherein the response message is received from the second wireless device via the sidelink.
2 . The method of claim 1 wherein the response message is an RRC message that triggers the RRC reconfiguration.
3 . The method of claim 1 wherein the failure message is a FailureInformation message.
4 . The method of claim 1 wherein the failure message is a MCGFailureInformation message or a SCGFailureInformation message.
5 . The method of claim 3 wherein the failure message comprises a wireless device context of the first wireless device.
6 . The method of claim 3 wherein the failure message comprises information that is relevant to the radio link failure.
7 . The method of claim 1 wherein the failure message is an RRC message for handling radio link failure in Carrier Aggregation (CA) Dual Connectivity (DC) or standalone operation with help of the sidelink.
8 . The method of claim 1 wherein the failure message comprises an indication of a failure case that directly or indirectly indicates one or more conditions that caused the radio link failure.
9 . The method of claim 1 wherein the failure message comprises one or more latest measurements related to the first radio link made by the first wireless device.
10 . A method performed by a second wireless device for handling a radio link failure at a first wireless device in a cellular communications system wherein the first device is connected to the second wireless device via a sidelink, the method comprising:
receiving a failure message from the first wireless device via the sidelink between the first wireless device and the second wireless device, the failure message being related to a radio link failure at the first wireless device of a first radio link between the first wireless device and a radio access network node of the cellular communications system, wherein the failure message does not include an initiation of a re-establishment procedure by the first wireless device with the radio access network node; and
forwarding the failure message to the radio access network node in the radio access network of the cellular communications system via a second radio link between the second wireless device and the radio access network node;
receiving a response from the radio access network node requesting; and
sending the response to the first wireless device via the sidelink.
11 . The method of claim 10 further comprising performing a radio access procedure to establish the second radio link between the second wireless device and the radio access network node.
12 . The method of claim 11 wherein the radio access procedure is a random access procedure.
13 . The method of claim 10 wherein the response is a Radio Resource Control (RRC) message that triggers a particular RRC procedure.
14 . The method of claim 10 wherein the failure message is a FailureInformation message.
15 . The method of claim 10 wherein the failure message is a MCGFailureInformation message or a SCGFailureInformation message.
16 . The method of claim 14 wherein the failure message comprises a wireless device context of the first wireless device.
17 . The method of claim 14 wherein the failure message comprises information that is relevant to the radio link failure.
18 . A method performed by a first base station handling radio link failure, the method comprising:
receiving a failure message from a second wireless device, the failure message being indicative of a radio link failure at a first wireless device of a first radio link between the first wireless device and a radio access network node of a cellular communications system, wherein the failure message does not include an initiation of a re-establishment procedure by the first wireless device with the radio access network node; and
sending a response message requesting the first wireless device to perform a Radio Resource Control (RRC) reconfiguration, wherein the response message is sent to the first wireless device via the second wireless device.
19 . A first wireless device for detecting and handling a radio link failure in a cellular communications system wherein the first wireless device is connected to a second wireless device via a sidelink, the first wireless device comprising:
one or more transmitters;
one or more receivers; and
processing circuitry associated with the one or more transmitters and the one or more receivers, the processing circuitry configured to cause the first wireless device to:
detect a radio link failure of a first radio link between the first wireless device and a radio access network node of the cellular communications system;
send a failure message to the second wireless device via the sidelink between the first wireless device and the second wireless device to be forwarded to the radio access network node while not initiating a re-establishment procedure with the radio access network node; and
receive from the radio access network node a response message originating from the radio access network node, requesting a Radio Resource Control (RRC) reconfiguration, wherein the response message is received from the second wireless device via the sidelink.
20 . A second wireless device for handling a radio link failure at a first wireless device in a cellular communications system wherein the first device is connected to the second wireless device via a sidelink, the second wireless device comprising:
one or more transmitters;
one or more receivers; and
processing circuitry associated with the one or more transmitters and the one or more receivers, the processing circuitry configured to cause the second wireless device to:
receive a failure message from the first wireless device via the sidelink between the first wireless device and the second wireless device, the failure message being related to a radio link failure at the first wireless device of a first radio link between the first wireless device and a radio access network node of the cellular communications system, wherein the failure message does not include an initiation of a re-establishment procedure by the first wireless device with the radio access network node; and
forward the failure message to the radio access network node in the radio access network of the cellular communications system via a second radio link between the second wireless device and the radio access network node;
receiving a response from the radio access network node requesting; and
sending the response to the first wireless device via the sidelink.
21 . A first base station for handling radio link failure, the first base station comprising processing circuitry configured to cause the first base station to:
receive a failure message from a second wireless device, the failure message being indicative of a radio link failure at a first wireless device of a first radio link between the first wireless device and a radio access network node of a cellular communications system, wherein the failure message does not include an initiation of a re-establishment procedure by the first wireless device with the radio access network node; and
send a response message requesting the first wireless device to perform a Radio Resource Control (RRC) reconfiguration, wherein the response message is sent to the first wireless device via the second wireless device.