A User Equipment, UE, comprising: a transmitting and receiving unit (305, 307) configured to: send, to a network device having a Proximity-based Services, ProSe, function, a discovery request containing: a ProSe Application ID, a command set to indicate to announce, and the UE's International Mobile Subscriber Identity, IMSI, and receive, from the network device having the ProSe function, a discovery response as a response to the discovery request, the discovery response containing: a first ProSe Application Code corresponding to the ProSe Application ID, and a first timer value associated with the first ProSe Application Code; and a control unit configured to start a timer with the first timer value, based on the reception of the first ProSe Application Code associated with the first timer value in the discovery response, wherein the transmitting and receiving unit (305, 307) is further configured to send the first ProSe Application Code until the timer with the first timer value expires, in a procedure to update the first ProSe Application Code, the transmitting and receiving unit (305, 307) is further configured to receive, from the network device having the ProSe function, an update request message containing: the UE's IMSI, a second ProSe Application Code for the ProSe Application ID, and a second timer value for the second ProSe Application Code, the control unit is further configured to replace the first ProSe Application Code with the second ProSe Application Code and start the timer with the second timer value, in a case of receiving the update request message, wherein the update request message initiates the procedure to update the first ProSe Application Code, and the second ProSe Application Code is different from the first ProSe Application Code. a transmitting and receiving unit (305, 307) configured to: send, to a network device having a Proximity-based Services, ProSe, function, a discovery request containing: a ProSe Application ID, a command set to indicate to announce, and the UE's International Mobile Subscriber Identity, IMSI, and receive, from the network device having the ProSe function, a discovery response as a response to the discovery request, the discovery response containing: a first ProSe Application Code corresponding to the ProSe Application ID, and a first timer value associated with the first ProSe Application Code; and send, to a network device having a Proximity-based Services, ProSe, function, a discovery request containing: a ProSe Application ID, a command set to indicate to announce, and the UE's International Mobile Subscriber Identity, IMSI, and a ProSe Application ID, a command set to indicate to announce, and the UE's International Mobile Subscriber Identity, IMSI, and receive, from the network device having the ProSe function, a discovery response as a response to the discovery request, the discovery response containing: a first ProSe Application Code corresponding to the ProSe Application ID, and a first timer value associated with the first ProSe Application Code; and a first ProSe Application Code corresponding to the ProSe Application ID, and a first timer value associated with the first ProSe Application Code; and a control unit configured to start a timer with the first timer value, based on the reception of the first ProSe Application Code associated with the first timer value in the discovery response, wherein the transmitting and receiving unit (305, 307) is further configured to send the first ProSe Application Code until the timer with the first timer value expires, in a procedure to update the first ProSe Application Code, the transmitting and receiving unit (305, 307) is further configured to receive, from the network device having the ProSe function, an update request message containing: the UE's IMSI, a second ProSe Application Code for the ProSe Application ID, and a second timer value for the second ProSe Application Code, the UE's IMSI, a second ProSe Application Code for the ProSe Application ID, and a second timer value for the second ProSe Application Code, the control unit is further configured to replace the first ProSe Application Code with the second ProSe Application Code and start the timer with the second timer value, in a case of receiving the update request message, wherein the update request message initiates the procedure to update the first ProSe Application Code, and the second ProSe Application Code is different from the first ProSe Application Code.