Performance modeling of level switching in multitier mobile communication systems

The multitier environment of mobile communication systems is an integration of different mobile systems such as cellular, cordless, and satellite systems for mobile users to communicate with anyone, anywhere, and anytime. An effective and efficient scheme is needed for mobile terminals to dynamically select the most appropriate tier of mobile system for optimizing communication cost and performance. This paper presents a model for studying the effect of level switching in a multitier environment and for the performance evaluation of level switching schemes. This model is based on the continuous-time stochastic process, which is parameterized by a set of state-transition rates and costs derived from the characteristics of the mobile systems and terminals. Several level switching schemes based on different triggering events are proposed and the performance is analyzed using the proposed model. Level switching is found to be an effective way to reduce communication costs. The performance gain increases with the frequency of the switching activities and the level switching costs are insignificant in most cases. By using the model, the most cost-effective switching scheme can be selected to match the characteristics of individual mobile users and mobile systems for optimizing overall system performance.