Integrated error control and power control for DS-CDMA multimedia wireless communications

The paper studies a packetised direct sequence code division multiple access (DS-CDMA) wireless network for providing multimedia services to mobile users. A strategy for integrating transmission error control with power control is presented and evaluated for the reverse link transmission where orthogonal signalling and noncoherent demodulation are necessary. For delay insensitive traffic requiring a very low bit error rate (BER), convolutional coding and an automatic retransmission request (ARQ) protocol are used to guarantee the transmission accuracy. By using the modified Viterbi decoder for decoding error detection, power control based on the received E_b /I_o (the ratio of signal energy per bit to interference-and-noise density) is employed to minimise the total received power at the base station, resulting in a maximal frequency spectrum efficiency. Numerical results are presented to evaluate the optimal received E_b/I_o value, the system radio frequency spectrum efficiency, and the optimal packet length, given the required BER and the traffic type. It is shown that the spectrum efficiency can be significantly increased by using an ARQ protocol with integrated optimal power control and convolutional coding for delay insensitive traffic