Method of Handling Device to Device Communication and Related Communication Device

A method of handling device to device communication for a first user equipment (UE) in a wireless communication system, the method comprising:

• establishing a Radio Resource Control (RRC) connection to a network of the wireless communication system;
• performing a proximity-based services (ProSe) communication with a second UE of the wireless communication system;
• and
• changing to a UE-to-network communication mode from a ProSe communication mode when the first UE detects a radio link failure in the ProSe communication.

A method of handling device to device communication for a first user equipment (UE) in a wireless communication system, the method comprising:

• establishing a Radio Resource Control (RRC) connection to a first network of the wireless communication system;
• performing a proximity-based services (ProSe) communication with a second UE of the wireless communication system;
• initiating an RRC connection reestablishment procedure when a connection failure occurs in the RRC connection;
• and
• stopping or releasing the ProSe communication when the connection failure occurs in the RRC connection.

A method of handling device to device communication for a first user equipment (UE) in a wireless communication system, the method comprising:

• establishing a Radio Resource Control (RRC) connection to a network of the wireless communication system;
• performing a proximity-based services (ProSe) communication with a second UE of the wireless communication system;
• and
• suspending the ProSe communication when a connection failure occurs in the RRC connection with the network.