Method for selecting neighboring UE to perform D2D communication
A disclosure of the present specification provides a method for selecting, by a user equipment (UE) located outside a coverage of a base station, a neighboring UE with which the UE will perform device-to-device (D2D) communication. According to the method, it is possible to quickly find out whether a neighboring UE is located within the coverage of a base station and is capable of operating as a relay, through a DMRS and a detection signal received from the neighboring UE.
1. A method for selecting a neighboring user equipment (UE) to perform a Device to Device (D2D) communication, the method performed by a UE located out of coverage of a base station (BS) and comprising:
receiving a Physical Sidelink Discovery Channel (PSDCH) including a discovery signal and a De-Modulation Reference Signal (DMRS) for demodulating the PSDCH from one or more neighboring UEs, wherein the PDSCH is scrambled by a scrambling sequence;
obtaining a base sequence number of the received a DMRS through a blind detection;
determining whether the one or more neighboring UEs are located in the coverage of the BS based on the obtained base sequence number;
obtaining a scrambling sequence used for scrambling the PSDCH through a blind detection;
obtaining one or more initializing parameters used by the neighboring UE for initializing the obtained scrambling sequence through a blind detection;
determining whether at least one neighboring UE is able to operate as a relay based on the one or more initializing parameters; and
selecting a UE located in the coverage of the BS and able to operate as a relay among the one or more neighboring UEs.
2. The method of claim 1 , wherein the one or more initializing parameters are radio network temporary identifiers (RNTIs).
3. The method of claim 1 , wherein selecting the UE comprises:
selecting at least one UE located in the coverage of the base station among the one or more neighboring UEs; and
selecting a UE operable as a relay among the at least one UE.
4. The method of claim 3 , further comprising:
selecting a resource for transmitting data to the selected UE; and
transmitting a control channel including a scheduling assignment for the selected resource to the selected UE.
5. The method of claim 4 , further comprising:
receiving the control channel including the scheduling assignment from the selected UE.
6. The method of claim 4 , further comprising:
when a resource indicated by the scheduling assignment included in the transmitted control channel and a resource indicated by the scheduling assignment in the received control channel are overlapped, transmitting a silent signal for withdrawing the scheduling assignment included in the transmitted control channel to the selected UE.
7. A user equipment (UE) selecting a neighboring UE that is going to perform a Device to Device (D2D) communication, the UE being located out of coverage of a base station (BS) and comprising:
a transmitting and receiving unit; and
a processor for controlling the transmitting and receiving unit,
wherein the processor is configured to perform:
receiving a Physical Sidelink Discovery Channel (PSDCH) including a discovery signal and a De-Modulation Reference Signal (DMRS) for demodulating the PSDCH from one or more neighboring UEs, wherein the PDSCH is scrambled by a scrambling sequence;
obtaining a base sequence number of the received a DMRS through a blind detection;
determining whether the one or more neighboring UEs are located in the coverage of the BS based on the obtained base sequence number;
obtaining a scrambling sequence used for scrambling the PSDCH through a blind detection;
obtaining one or more initializing parameters used by the neighboring UE for initializing the obtained scrambling sequence through a blind detection;
determining whether at least one neighboring UE is able to operate as a relay based on the one or more initializing parameters; and
selecting a UE located in the coverage of the BS and able to operate as a relay among the one or more neighboring UEs.
8. The UE of claim 7 , wherein the one or more initializing parameters are radio network temporary identifiers (RNTIs).