Operating states for D2D discovery

A device capable of device-to-device (D2D) communication in a wireless communication network in accordance with a Long Term Evolution (LTE) standard, the device comprising:

• at least one antenna configured to transmit and receive signals;
• and
• at least one processor configured to control the device to:
• receive, from the network via a base station in association with a registration process, an assignment of a D2D identifier for identification of the device during D2D communication both when the device is in-coverage of the base station and when the device is out-of-coverage of the base station;
• enter a radio resource control-idle (RRC-Idle) state or a radio resource control-connected (RRC-Connected) state;
• transmit, while operating in the RRC-Idle state or the RRC-Connected state, a D2D discovery signal, in accordance with the D2D identifier for identification of the device, for receipt by one or more second devices in the network;
• receive, in the RRC-Idle state or the RRC-Connected state, at least one D2D discovery signal from at least one of the one or more second devices in the network;
• and
• transmit a D2D signal that includes the D2D identifier to the one or more second devices in the network, wherein the device transitions between states at an occurrence of a frame boundary or a subframe boundary.

A system for device-to-device (D2D) communication in a wireless communication network in accordance with a Long Term Evolution (LTE) standard, the system comprising:

• a first D2D device;
• and
• one or more second D2D devices,
• wherein the first D2D device is configured to:
• receive, from the network via a base station in association with a registration process, an assignment of a D2D identifier for identification of the first D2D device during D2D communication both when the first D2D device is in-coverage of the base station and when the first D2D device is out-of-coverage of the base station;
• enter a radio resource control-idle (RRC-Idle) state or a radio resource control-connected (RRC-Connected) state;
• transmit, while operating in the RRC-Idle state or the RRC-Connected state, a D2D discovery signal, in accordance with the D2D identifier for identification of the first device, for receipt by the one or more second D2D devices;
• receive, while operating in the RRC-Idle state or the RRC-Connected state, at least one D2D discovery signal from the at least one of the one or more second D2D devices;
• and
• transmit a D2D signal that includes the D2D identifier to the one or more second devices in the network, wherein the first D2D device transitions between states at an occurrence of a frame boundary or a subframe boundary.