Capacity with Probabilistic Delay Constraint for Voice Traffic in a Rayleigh Channel

The capacity with probabilistic delay constraint C_{D t ,epsiv} expresses the maximum source rate that may be supported in a wireless system with a probability epsiv of exceeding certain delay bound D^t. In a previous paper by the authors (see Proc. IEEE GLOBECOM, November 2007), C_{D t ,epsiv} was calculated for a Rayleigh channel carrying a constant rate flow. In this work, the potential of the effective bandwidth theory is shown by evaluating this constrained capacity for a variable rate source modeled as an ON-OFF process. Cross relations among ON-OFF process parameters, fading channel statistics, QoS constraints and maximum allowable mean source rate are displayed by the obtained closed-form expressions. C_{D t ,epsiv} is measured in different scenarios to exhibit to which extent higher time-correlation of the channel response or longer ON-OFF periods are harmful to the delay behaviour, getting a lower value of the capacity C_{D t ,epsiv}.