Design and evaluation of a replicated database for mobile systems

The new generation mobile systems are anticipated to provide mobile users w ith new broadband services such as wireless multimedia, including real-time video and high-speed data. In these systems, the requirement on service tr ansparency placed by the handling of mobility, both personal and terminal, implies a remarkable increase in the complexity of data management. Therefo re, appropriate distributed databases (DDB) must be designed to guarantee s peed in the processing and updating of user information, and a high level o f reliability and performance. In this paper we analyze a minimally replica ted DDB in which different strategies for the redundancy of user data are d iscussed. First, we develop a Petri net based model in order to analyze the consequences on dependability deriving from faults in nodes at different l evels in the DDB structure. Then, we investigate the performance offered by the system through a queueing network model. The measures of interest incl ude reliability, availability, mean time to failure, and mean response time to service access.