Channel coding and power control for DS-CDMA multimedia wireless communications

Abstract

This paper studies a packetized direct sequence code division multiple access (DS-CDMA) wireless network for providing multimedia services to mobile users. In particular, we focus on channel coding and optimal power control for reverse link transmission using Hadamard-Walsh (H-W) orthogonal sequences for noncoherent demodulation. Because of various multimedia traffic types with different quality of service (QoS) requirements, the concept of perfect power control for voice only DS-CDMA networks cannot be directly applied to the multimedia wireless network. Under the circumstances, we give a new definition to the optimal power control and discuss how to achieve it together with error control techniques in order to maximize the frequency bandwidth efficiency and to guarantee various QoS requirements. Numerical results are presented to evaluate (i) the optimal signal to interference ratio of the received signals at base stations with various transmission accuracy requirements and (ii) the system radio frequency spectrum efficiency versus BER requirement under the assumption of the optimal power control. It is shown that the spectral efficiency (and hence the system capacity) can be significantly increased when using the optimal power control and convolutional coding with ARQ protocol for delay insensitive traffic.