Integrated power control with concatenated coding for DS-CDMA systems

In this paper, highly reliable data transmission using concatenated Reed-Solomon (RS)/convolutional coding for a Direct-Sequence Code Division Multiple Access system is studied. The study is based on the analysis of the tradeoff between coding and spreading, and on the compromise between RS outer code and convolutional inner code under the constraint of a fixed bandwidth expansion for each service class. Some insightful observations about the mechanism of the concatenated coding scheme and their explanations are presented. Numerical results show that a best outer/inner code rate pair exists. By applying this best code rate pair over a slow Rayleigh fading channel, depending on the system load and the constraint length of the inner code, a gain of 2dB to more than 9dB in received power reduction for each user can be achieved, compared to the conventionally used code rate pair (outer/inner code rate = 0.8/0.5).