Performance improvements of integrated voice and data transmission in DS-CDMA

We propose two schemes which improve the performance of integrated voice and data transmission in DS-CDMA systems. One is an interference canceller combined with two packet detectors. The first packet detector sounds a propagation channel, estimates delayed paths of data packets with the use of periodically inserted pilot symbols in each packet, and then demodulates data packets temporarily by RAKE combining. These estimated delayed paths are incorporated into the interference canceller so as to enhance the cancelling capability and to improve the voice signal quality. Then, by separating voice signals from a received signal, data packets can be more reliably detected by the second packet detector. The other is a power control scheme for data packets which avoids the degradation of the voice signal quality. In this scheme, data packets are transmitted with smaller power when the number of active voice users gets larger. The performance improvements are confirmed at the cost of slight increase of transmission delay of data packets by computer simulations