A method and apparatus are described for performing a Proximity-based Service (ProSe) by a ProSe-enabled user equipment (UE) in a cellular communication system. A connection is established with a network via a public safety band. A scheduling request (SR) signal is transmitted to the network via the public safety band. A first resource allocation is received from the network. The ProSe is performed using the first resource allocation. If a condition including a lack of channel resources is not satisfied, the SR signal carries a first identifier used for requesting resource of the public safety band. If the condition including the lack of channel resources is satisfied, the SR signal carries a second identifier used for requesting resource of a non-public safety band.