Call admissibility for multirate traffic in wireless ATM networks

For multirate wireless ATM traffic, the first part of the call admission process is to determine whether to admit calls as long as bandwidth is available or to deny admission to a call of a particular class even if there is enough bandwidth available, in the hope of admitting calls of some other class later. A second part of the process is to determine if the quality of service requested by the call can be met. A scenario in which the first part is particularly important a's when the blocking probability requirements for different classes is different. In this paper, we consider four policies to determine the circumstances under which calls of different types are admissible. For each of these policies, we show how to compute the blocking probabilities. For three of these policies, the blocking probabilities can be found by using results from product form networks. For the fourth, we provide an approximation which works extremely well in practice. We also formulate a non-linear programming problem which attempts to determine the parameters of the admissibility policies in such a way to maximize the call arrival rates while keeping the blocking probabilities under specified bounds. We provide an, algorithm for solving the non-linear programming problem and use this as a basis for comparing the policies. We show that under some circumstances, it is possible to improve the system throughput by as much as 35% by a suitable use of the admissibility policies. This improvement in throughput is particularly important in wireless ATM networks, supporting high rate multimedia traffic because of the inherent limitations in bandwidth availability.