In this paper, we propose a new call admission control (CAC) scheme for voice calls in mobile communication networks. Rejection of a hand-off call is more undesirable than that a new call, for a hand-off call loss couses a severer mental pain. By quantifying their respective pains, we consider them as different costs. The key point of our CAC is restricting new calls in order to minimize the total expected costs per unit time over the long time term. An optimal policy is derived from a semi-Markov decision process in which the interval between two consecutive decision epochs is exponentially distributed. Based on this potimal policy, we calculate the steady probability with respect to the number of estabished voice connections on the uplink. Thereafter, we evaluate the blocking and forced termination probabilities for voice traffic. Furthermore, we present an analytic model for the integranted voice and data traffic on the downlink. The state of this model stands for the number of voice calls in OFF state and data packets in the system at the beginning of every frame on condition that the number of voice connections is fixed. After the steady state probability for this model is calculated, we examine the effect of CAC on the throughput and waiting time of data packets at low, middle and high voice load conditions. We find that the forced termination probability is improved by our CAC scheme at the sacrifice of the blocking probability and channel utilization for voice calls. Basides our CAC is effective for data traffic at middle and high voice load condition.
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