Erlang Capacity Analysis of CDMA Systems Supporting Voice and Delay-Tolerant Data Services Under the Delay Constraint

In this paper, we analyze the Erlang capacity of a code-division multiple-access system supporting voice and delay-tolerant data services. The novelty here is to consider the characteristic of delay-tolerant traffic in terms of a delay confidence. The delay confidence is defined as the probability that a new data call is accepted within the maximum tolerable delay without being blocked. In this case, the Erlang capacity is confined not only by the required blocking probability of voice call but also by the required delay confidence of data call. For the performance analysis, we develop a 2-D Markov model, which is based on the First-Come- First-Serve service discipline, and further present a numerical procedure to analyze the Erlang capacity. According to the procedure, we can make a balance between the Erlang capacities with respect to the blocking probability of voice call and with respect to the delay confidence of data call, in order to accommodate extra Erlang capacity. We demonstrate the balancing by properly selecting the size of the designated queue for data traffic.