Wireless communication system, and terminal using said method (as amended)
Provided are a D2D (device-to-device) signal transmitting method implemented by a terminal in a wireless communication system, and a terminal using the method. The method is characterized by the operations of: receiving information showing whether a mode 2 operation is allowed in an exceptional state; determining whether the exceptional state is in effect; and when the exceptional state is determined to be in effect, implementing the mode 2 operation, wherein in the mode 2 operation, the terminal selects a certain resource from a resource pool, and the selected resource is used to transmit the D2D signal.
1. A UE performing device-to-device operation, which includes mode 1 or mode 2 , the UE comprising:
a transceiver; and
a processor, operably coupled to the transceiver, wherein the processor is configured to:
determine whether the UE switches from an out-of-coverage state to an in-coverage state with respect to a frequency to support the D2D operation,
wherein when the UE is located outside the coverage of a network, the UE is in the out-of-coverage state, and
wherein when the UE is located within the coverage of the network, the UE is in the in-coverage state;
determine whether the UE is in a radio resource control (RRC) connected state or an RRC idle state when the UE switches from the out-of-coverage state to the in-coverage state; and
determine whether the UE operates in mode 1 or mode 2 based on the determination of whether the UE is in an RRC connected state or an RRC idle state,
wherein the UE performs a D2D operation using a first resource scheduled by the network when operating in mode 1 ,
wherein the UE selects a second resource by itself and performs the D2D operation using the second resource when operating in mode 2 ,
wherein:
when the UE is in the in-coverage state and in the RRC connected state, the UE operates in mode 1 ;
when the UE is in the in-coverage state and in the RRC idle state, and when the UE receives, from the network, information informing the UE that mode 2 operation is performed in the in-coverage state, the UE operates in mode 2 ; and
when the UE does not receive the information, the UE does not perform the D2D operation.
2. The UE of claim 1 , wherein the processor further determines that the UE switches from the out-of-coverage state to the in-coverage state when a synchronization signal provided by a cell is detected and synchronization with the cell is performed by using the detected synchronization signal.
3. The UE of claim 1 , wherein the processor further determines that the UE switches from the out-of-coverage state to the in-coverage state when the UE acquires required system information provided by the cell.
4. A method for performing device-to-device operation, which includes mode 1 or mode 2 , in a wireless communication system, the method performed by a user equipment (UE) and comprising:
determining whether the UE switches from an out-of-coverage state to an in-coverage state with respect to a frequency to support the D2D operation,
wherein when the UE is located outside the coverage of a network, the UE is in the out-of-coverage state, and
wherein when the UE is located within the coverage of the network, the UE is in the in-coverage state;
determining whether the UE is in a radio resource control (RRC) connected state or an RRC idle state when the UE switches from the out-of-coverage state to the in-coverage state; and
determining whether the UE operates in mode 1 or in mode 2 based on the determination of whether the UE is in an RRC connected state or an RRC idle state,
wherein the UE performs a D2D operation using a first resource scheduled by the network when operating in mode 1 ,
wherein the UE selects a second resource by itself and performs the D2D operation using the second resource when operating in mode 2 ,
wherein:
when the UE is in the in-coverage state and in the RRC connected state, the UE operates in mode 1 ;
when the UE is in the in-coverage state and in the RRC idle state, and when the UE receives, from the network, information informing the UE that mode 2 operation is performed in the in-coverage state, the UE operates in mode 2 ; and
when the UE does not receive the information, the UE does not perform the D2D operation.
5. The method of claim 4 further comprising:
determining to switch from the out-of-coverage state to the in-coverage state when a synchronization signal provided by a cell is detected and synchronization with the cell is performed by using the detected synchronization signal.
6. The method of claim 4 further comprising:
determining to switch from the out-of-coverage state to the in-coverage state when the UE acquires required system information provided by the cell.