We propose a new call admission control (CAC) scheme for voice calls in cellular mobile communication networks. It is assumed thatthe rejection of a hand-off call is less desirable than that of a new call,for a hand-off call loss would cause a severe mental pain to a user. We consider the pains of rejecting new and hand-off calls as differentcosts. The key idea of our CAC is to restrict the admission of new calls in order to minimize the total expected costs per unit time over thelong term. An optimal policy is derived from a semi-Markov decision process in which the intervals between successive decision epochs areexponentially distributed. Based on this optimal policy, we calculate the steady state probability for the number of established voice connections in a cell. We then evaluate the probability of blocking new calls and the probability of forced termination of hand-odd calls. In the numerical experiments, it is found that the forced termination probability of hand-off calls is reduced significantly by our CAC scheme at the slight expense of the blocking probability of new calls and the channel utilization.
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