Capacity calculation in DS-CDMA systems supporting multi-class services

In this paper, we calculate the capacity of DS-CDMA systems supporting multi-class services with different transmission rates and bit error rates. Two techniques, a single-code scheme using a variable processing gain and a multi-code scheme, are considered to provide multi-rate services. The capacity is expressed by an inequality to which the number of accepted calls of each class should conform. The inequality is the necessary and sufficient condition satisfying the requirement of the bit energy-to-interference power spectral density ratio. The optimal received power is derived to cause the least interference to other signals while maintaining the acceptable bit energy-to-interference power spectral density ratio. Finally, capacity is also derived in a dynamic multiple cell environment.