Data transfer schemes for 3G mobile telecommunication systems

In mobile communications, distributed database systems fulfill the requirements of storing, accessing and updating user-related data (service profile, location and charging data, security related parameters, etc.). Second generation systems adopt the home location register (HLR)/visitor location register (VLR) concept, while for third generation (3G) systems, a number of advanced schemes has been proposed. A common issue inherent in all schemes is the transfer of user data from one database node to another whenever the user changes node area. In this paper, we propose a general data transfer scheme, which allows the grouping of database nodes into "domains". The advantage of this scheme is that user data is transferred to a new node, only in case that the user changes domain. The applicability of the proposed scheme for both second and third generation systems is investigated from the functional and performance viewpoints. The performance analysis is based on a simulation model and focuses on the transaction load, the signaling load and the procedure execution delay. The results indicate that the database performance improves as the domain size increases. The limiting factor is the resulting procedure execution delay, due to the increased distance between the actual user location and the node where the user data is stored. Possible enhancements which aim at further performance improvements (e.g., taking into account the user mobility characteristics) are also discussed.