A formal approach to modeling and performance analysis of shared channels for real-time services in W-CDMA 3G systems

The third generation of mobile systems will be able to support a plethora of novel and challenging services in an efficient way; multimedia and data applications produce intermittent, variable bit-rate digital flows that can profit of a packet-switched resource allocation technique, whose performance in terms of system capacity, when supporting real-time VBR traffic and adopting a simple call admission control scheme, is illustrated. This non-trivial case study, further complicated by the dependence of W-CDMA capacity on the interference level and QoS requirements, is investigated with the help of a formal approach. Instead of using a simulation environment, a tool for performance evaluation is exploited, where a formal specification of the system is built, verified for proper behavior and analyzed to obtained the steady state probability of the Markov chain equivalent to the specification. The rigorousness of the formal notation and the verifiability of the specification enable one to speed up the modeling phase and give more confidence in the numerical results obtained.