with step 6 if the msc server and the target msc to which the local ue is to be handover are the same one steps 6 8 and 9 in fig4 6 will be omitted that is receiving means 701 will trigger calculation means 703 to calculate the first time duration p 1 as soon as it receives the ps to cs req message from the source mme specifically calculation means 703 informs transmitting means 702 to transmit a request message of non session handover request to the scc as in ims such as the invite message in step 10 of fig4 6 different from the invite message in step 10 of fig2 this invite message does not contain sdp information of mgw the calculation means 703 records the time when it transmits the invite message as t 4 because fails to obtain sdp information of mgw the scc as cannot initiate a session handover procedure at the remote end ue side after receiving the invite message the scc as transmits a 200 ok reply message to the msc server after interacting with the remote end ue the msc server receives this message via the receiving means 701 the receiving means 701 informs this event to the calculation means 703 and records the time when it receives the 200 ok message as t 5 the calculation means 703 calculates p 1 based on time t 4 and t 5 e g calculating p 1 as a certain proportion of the time duration between time t 4 and t 5 wherein the proportion can be set in according to experiences and network conditions such as 50 or 45 then calculation means 703 notifies the.