Mobile Terminated Calls

Mobiillee-Terminated (Network-Originated) Call

The above example illustrates the following steps in establishing a Mobile Terminated (MT)
(Network Originated) call:
(1) The incoming call is passed from the fixed network to the gateway MSC (GMSC).
(2) Using the MSISDN of the calling MS, the GMSC interrogates the HLR to determine the
IMSI number of the called party.
(3) The HLR checks for the existence of the called number and identifies the VLR to which it
is currently affiliated. It then requests the mobile station roaming number (MSRN) from the
identified VLR.
(4) Upon receipt, the HLR transmits the MSRN back to the GMSC.
(5) When the GMSC receives a valid MSRN, it switches the call through to the appropriate
MSC.
(6) The VLR is queried for the location range and reachability status of the mobile subscriber.
(7) If the MS is marked reachable, a radio call is enabled at the MSC.

(8) This generates a paging request to from the MSC to all BSSs in the MS’s last recorded
Location Area.
(9) The mobile subscriber telephone responds to the paging request from its current cell, the
link is extended to the MS and authentication information is passed from the MS to the MSC .
(10) All necessary security procedures are executed.
(11) If security procedures are successful, the VLR indicates to the MSC that the call can be
completed.
(12) The MSC then extends the call from the GMSC to the MS.