The identification module 620 may be adapted to identify a UE involved in the VoLTE call that is in LTE coverage provided by LTE network(s). For example, the identification module 620 may comprises a header analyzer to analyze header fields comprised in the request to determine whether the originating UE or terminating UE is in LTE coverage.

The control module 630 may be adapted to send one or more dummy messages through the communication interface 610 to the identified UE. The control module 630 sends the dummy messages after the VoLTE call enters into ringing phase, and stops sending when the VoLTE call is answered or is cancelled. An interval between successive dummy messages is set to be shorter than a first time period set for determining whether to release radio resource for supporting the VoLTE call in LTE coverage.

In an embodiment, the apparatus may comprise a ringing timer, e.g. a No-Reply timer. The ringing timer is set to expire when a VoLTE call is not answered in a second time period. The control module 630 may be adapted to stop sending dummy message when the ringing timer expires.

It would be understood that all of processes according to the present invention, such as processes illustrated above with reference to FIGS. 4, 5a, 5b, may be implemented in connect with the apparatus 600.