7 Network Functions

Roaming denotes the ability of an MS to make use of networks from different operators. Therefore, information about the MS has to be transferred from the HLR to the corresponding VLR independent of MSC borders. For reachability reasons besides the MSISDN and IMSI also the Mobile Station Roaming Number (MSRN) is given as a temporary address and information for routing between operators. Roaming only is possible between networks of operators who have signed roaming agreements. The MS has to be able to transmit in the frequency range of the new system.