In DS-CDMA (Direct Sequence-Code Division Multiple Access) mobile systems, soft handoff is recognized as reducing interference and increasing reverse link capacity, whereas from the radio channel resource viewpoint, soft handoff can make the system performance deteriorate significantly. This paper focuses on using the channel resources of soft handoff in a limited field environment for evaluating the performance of DS-CDMA mobile systems. Our traffic model is based on the mobile traffic environment with region overlap among multiple cells. The soft handoff rates are estimated by the mobility of mobiles, and simulation results show good agreement with the traffic model. The channel holding time distribution of the soft handoff traffic model, which does not have a closed-form solution, is derived by a numerical integration method. Computer simulations show promising results based on the non-closed-form application. We analyze the performance of DS-CDMA mobile systems with the proposed traffic model to see the effect of the soft handoff region on blocking probability. From the result, when the soft handoff region is extended with the given channels, both the handoff rate and the mean channel holding time are increased and these make the blocking probability increase a great deal. To maintain the required blocking probability as before, additional channel resources should be supplied according to the extended region. It is our belief that the proposed traffic model and the performance analysis presented in this paper are practically acceptable.

In this paper, we propose a simple and accurate method to derive the dwell time distribution of a mobile in a cell by a numerical integration approach. In practical applications, only a few traffic models have a known closed-form solution, most of the models can not be solved in closed form. Therefore a simulation or approximating method has to be used to solve the problems. To validate the accuracy of the proposed method, we apply it to a typical hard handoff traffic model with known closed-form solution and the goodness-of-fit is measured. We also apply this method to a soft handoff traffic model, which does not have a closed-form solution. Computer simulations show promising results based on the non-closed-form application.