Admission control in wireless systems with heterogeneous traffic and overlaid cell structure

This paper proposes and analyzes the performance of admission control policies (ACPs) for wireless cellular networks carrying two classes of service. Each class may have its own bandwidth requirements, call intensity and session duration. In a single tier system, a two-dimensional Markov chain model is used to derive traffic performance measures for each class of service, such as the probability of blocking, the probability of handover failure, and the probability of forced termination. Sharing of resources among services is adopted, in order to prevent trunk inefficiency. An ACP is proposed in a two-tier cellular system, where some ongoing calls are dropped at the lower tier and tentatively reallocated to the upper tier. It is observed that this is an effective technique to manage heterogeneous service requests with sharing of various sets of resources. Each set belongs to a certain coverage tier in a hierarchical coverage architecture. Since upper tiers are typically provided with decreasing amount of resources, lower bandwidth calls are preferably served by upper tiers when traffic congestion occurs at lower tiers