Two-Level Fractional Guard Channels for Priority Access in Cellular Systems

A two-level fractional guard channels (TLFGC) scheme to efficiently provide priority access for handoff calls over new calls in cellular systems is proposed. The switching between the levels is controlled by a dropped call. The first level has a small number of guard channels like the fixed guard channel (FGC) scheme, while the second level has a larger number of guard channels and a smaller number of fractional guard channels. An analytical formulation of the steady state probabilities, new call blocking probability, handoff call blocking probability, system utilization, probabilities in each level and the equivalent number of guard channels is presented. Numerical results show that the performance of TLFGC is almost the same as a fixed guard channels (FGC) scheme under light load. However, the advantage of the TLFGC scheme is demonstrated under heavy load where the handoff call blocking probability is much better than that of a FGC scheme, giving more priority and protection to handoff calls over new calls