A study on service data transfer procedure using SCF and SDF

There has been a rapid increase in the use of mobile telecommunication systems, such as GSM, PDC and PCS, so many people are now using mobile terminal based services. In Japan, the Personal Handy Phone System (PHS) service, which offers a cheaper personal communication service, started in July 1995. Moreover, FPLMTS is being considered as the next generation architecture. As these mobile services become widely used, it will be necessary for a user belonging to one network to be served independently of his location. Therefore, it is important to achieve roaming from one network to another. There are two ways to achieve roaming: one is the HLR (home location register)-based procedure and the other is the VLR (visited location register)-based procedure. In the VLR-based procedure, the visited network can use the data copied from a roaming user´s home network, i.e., the VLR. The article discusses VLR-based procedures for roaming and shows which procedure should be applied. Moreover, some message flows are proposed that use the X.500 series recommendation. All of these procedures use the SDF (service data function)-SDF interactions, and it is the agreement between networks that decides the treatment of the copied data