Method and device for selecting relay in wireless communication system
An embodiment of the present invention relates to a method of selecting, by a first UE, a relay in a proximity service (ProSe) in a wireless communication system, the method including the steps of transmitting a UE-to-Network Relay discovery message; selecting a second UE as the UE-to-Network Relay; setting a connection for direct communication with the second UE; and transmitting a registration request message to a group communication service application server (GCS AS) through the second UE, wherein when the UE-to-Network Relay discovery message includes UE-to-UE Relay related request information, the UE-to-UE Relay related information is received from the second UE and the second UE is selected as the UE-to-UE Relay based on the UE-to-UE relay related information.
1. A method of selecting, by a first user equipment (UE), a relay in a proximity service (ProSe) in a wireless communication system, the method comprising:
transmitting a UE-to-Network Relay discovery message;
selecting a second UE as a UE-to-Network Relay;
establishing a connection for direct communication with the second UE; and
transmitting a registration request message to a group communication service application server (GCS AS) through the second UE,
wherein when the UE-to-Network Relay discovery message includes UE-to-UE Relay related request information, UE-to-UE Relay related information is received from the second UE and the second UE is selected as a UE-to-UE Relay based on the UE-to-UE relay related information, and
wherein when the registration request message includes the UE-to-UE Relay related request information, the UE-to-UE Relay related information is received from the GCS AS, and the second UE is selected as the UE-to-UE Relay on the basis of the UE-to-UE Relay related information.
2. The method according to claim 1 , wherein the first UE is located outside coverage.
3. The method according to claim 1 , wherein the UE-to-UE Relay related information includes one or more of information indicating that the UE-to-UE Relay shall be selected, information indicating that communication will be performed through the UE-to-UE Relay, information indicating information required to select/determine the UE-to-UE Relay is requested, information on a UE which becomes a target for communication through the UE-to-UE Relay, and information on a group which becomes a target for communication through the UE-to-UE Relay.
4. The method according to claim 1 , wherein the UE-to-UE Relay related information received from the second UE includes one or more of information on a UE to which the second UE currently provides a UE-to-Network Relay, information on a UE having a proximity relation with the second UE, information on a group to which the second UE may provide a UE-to-UE Relay function, and information indicating that the second UE may be selected as the UE-to-UE Relay.
5. The method according to claim 1 , wherein the UE-to-UE Relay related information received from the GCS AS includes one or more of information on a UE that receives evolved packet core (EPC) connectivity through the same UE-to-Network Relay as the first UE, information on a UE which camps on the same cell as that of the UE-to-Network Relay which serves the first UE, information on a UE which camps on a neighboring cell of the cell camped on by the UE-to-Network Relay which serves the first UE, and information on a UE having a proximity relation with the second UE.
6. The method according to claim 1 , wherein, if the UE-to-Network Relay discovery message includes UE-to-UE Relay related request information, the UE-to-UE Relay related information is included in a UE-to-Network Relay discovery response.
7. The method according to claim 1 , wherein, if the registration request message includes UE-to-UE Relay related request information, the UE-to-UE Relay related information is included in a registration response message.
8. The method according to claim 1 , further comprising:
receiving a registration response message in response to a response to the registration request message; and
establishing the connection with the second UE determined based on the UE-to-UE Relay related information.
9. The method according to claim 1 , wherein the UE-to-Network Relay discovery message is one of an announcement message or a solicitation message.
10. The method according to claim 1 , wherein the UE-to-Network Relay discovery message is a PC5-D message.
11. A proximity service (ProSe) user equipment (UE) for selecting a relay in a wireless communication system, the ProSe UE comprising:
a transceiver; and
a processor,
wherein the processor transmits a UE-to-Network Relay discovery message, selects a second UE as a UE-to-Network Relay, establishes a connection for direct communication with the second UE, and transmits a registration request message to a group communication service application server (GCS AS) through the second UE,
wherein when the UE-to-Network Relay discovery message includes UE-to-UE Relay related request information, UE-to-UE Relay related information is received from the second UE and the second UE is selected as a UE-to-UE Relay based on the UE-to-UE relay related information, and
wherein when the registration request message includes the UE-to-UE Relay related request information, the UE-to-UE Relay related information is received from the GCS AS, and the second UE is selected as the UE-to-UE Relay on the basis of the UE-to-UE Relay related information.