Patent ID: 9723474
Date: 2017-08-01
CPC Classifications: H04W

Claim:
1. A method of transmitting a discovery signal, the method performed by a user equipment (UE) and comprising: starting, by the UE, a mobility management (MM) back-off timer, when the MM back-off timer is received from a mobility management entity (MME) in a network; checking a priority for detecting at least one different UE, when a discovery of the at least one different UE is required before the MM back-off timer expires; randomly selecting a resource based on a common resource pool included in system information, which is broadcast from a base station, and thereafter transmitting to the at least one different UE a discovery signal including a proximity service code on the randomly selected resource, when the discovery of the at least one different UE has a high priority or is urgent; and waiting until the MM back-off timer expires, and thereafter transmitting to the at least one different UE the discovery signal including the proximity service code on a resource allocated from the base station, when the discovery of the at least one different UE does not have the high priority or is not urgent.