Erlang capacity for an integrated voice/data DS-CDMA wireless system with variable bit rate sources

This paper presents an approach to study the outage probability of voice calls in an integrated voice/generalized data wireless DS-CDMA network, where both voice and data can be considered as originating from variable bit rate sources. Emphasis is on voice outage probability in anticipation of control strategies for data. Taking into account the imperfections in power control for such CDMA systems, the effect of data transmission variability on the Erlang capacity of voice is analyzed (on the uplink case). All the analysis is reduced to the evaluation of means and variances of the relevant random variables of the model (number of users of a certain service, bit rates, received powers). The results presented on the interplay between the data and the voice calls could be useful in determining control and admission policies for both the services. Illustrative results are given for a CELP speech coder and fax (both real time and store and forward)