System and Methods for Controlling Out-of-Network D2D Communications

A method for selecting a synchronization master for device-to-device (D2D) communication, the method comprising:

• receiving, by a first user equipment (UE), a discovery signal from a second UE, the discovery signal comprising a synchronization signal indicating whether the second UE is synchronized with a base station and an in-coverage bit/flag indicating whether the second UE is an in-coverage UE or an out-of-coverage UE of the base station;
• and
• participating, by the first UE, in a D2D communication session with the second UE over a predefined uplink carrier as either a timing slave entity or a timing master entity based on the synchronization signal and the in-coverage bit/flag.

A computer program product for installation in a first user equipment (UE), the computer program product comprising a non-transitory computer readable storage medium storing programming, the programming including instructions to:

• receive a discovery signal from a second UE, the discovery signal comprising a synchronization signal indicating whether the second UE is synchronized with a base station and an in-coverage bit/flag indicating whether the second UE is an in-coverage UE or an out-of-coverage UE of the base station;
• and
• participate in a D2D communication session with the second UE over a predefined uplink carrier as either a timing slave entity or a timing master entity based on the synchronization signal and the in-coverage bit/flag.