A first communication device for handling device to device, D2D, communication in a wireless communication system, the first communication device comprises: a communication interfacing unit; and a display unit; and a processor, electrically connected with the communication interfacing unit and the display unit, wherein the processor is configured to perform operations of: activating the D2D communication to transmit/receive a D2D signal with a second communication device (104, 204); controlling the display unit to display a user interface; controlling the display unit to display a first icon on the user interface, wherein the first icon indicates a first strength of a first signal of a radio access technology, RAT, received by the communication interfacing unit; and controlling the display unit to display, together with the first icon, a second icon on the user interface corresponding to a second strength of a second signal of the RAT received by the communication interfacing unit of the first communication device, wherein the first signal is transmitted by an evolved node B, eNB, and the second signal is a device to device, D2D, signal transmitted by the second communication device, wherein under a condition that the second signal of the RAT is not received for a predetermined time threshold, controlling the display unit of the first communication device to display a third icon indicating that there is no service of communication relevant to the second signal. a communication interfacing unit; and a display unit; and a processor, electrically connected with the communication interfacing unit and the display unit, wherein the processor is configured to perform operations of: activating the D2D communication to transmit/receive a D2D signal with a second communication device (104, 204); controlling the display unit to display a user interface; controlling the display unit to display a first icon on the user interface, wherein the first icon indicates a first strength of a first signal of a radio access technology, RAT, received by the communication interfacing unit; and controlling the display unit to display, together with the first icon, a second icon on the user interface corresponding to a second strength of a second signal of the RAT received by the communication interfacing unit of the first communication device, wherein the first signal is transmitted by an evolved node B, eNB, and the second signal is a device to device, D2D, signal transmitted by the second communication device, wherein under a condition that the second signal of the RAT is not received for a predetermined time threshold, controlling the display unit of the first communication device to display a third icon indicating that there is no service of communication relevant to the second signal. activating the D2D communication to transmit/receive a D2D signal with a second communication device (104, 204); controlling the display unit to display a user interface; controlling the display unit to display a first icon on the user interface, wherein the first icon indicates a first strength of a first signal of a radio access technology, RAT, received by the communication interfacing unit; and controlling the display unit to display, together with the first icon, a second icon on the user interface corresponding to a second strength of a second signal of the RAT received by the communication interfacing unit of the first communication device, wherein the first signal is transmitted by an evolved node B, eNB, and the second signal is a device to device, D2D, signal transmitted by the second communication device, wherein under a condition that the second signal of the RAT is not received for a predetermined time threshold, controlling the display unit of the first communication device to display a third icon indicating that there is no service of communication relevant to the second signal.