Admission control and adaptive CDMA for integrated voice and data systems

We propose a new direct-sequence code division multiple access (DS-CDMA) strategy for combining voice and variable-rate data. Our admission control policy uses a reservation policy for voice calls and different variable-rate schemes for data to maximize throughput on the residual bandwidth unused by voice. The data schemes we consider include variable bit rate (VBR), multicode (MC), and variable constellation size (VCS). We determine the voice call blocking probability and the data throughput for each of the variable-rate schemes. We find that VBR outperforms MC and VCS in terms of data throughput. We also calculate the improvement to system performance obtained by exploiting voice activity detection.