Variable-rate adaptive channel coding for CDMA - Reverse link

In this paper, we introduce an adaptive coding scheme for a direct-sequence code division multiple access (DS-CDMA) system. The system uses noncoherent M-ary orthogonal modulation with a RAKE receiver and power control. We considered both a fast fading channel and a combined fast fading, shadowing, and power control channel. To evaluate the performance of the system, we derived analytical bounds and conducted simulations. We found significant improvements in the average throughput and the bit error rate (BER) performance using the adaptive coding scheme. The amount of improvement drops as the number of diversity branches increases. More importantly, we found that the adaptive coding scheme is relatively robust to shadowing, while fixed-rate codes are ineffective in the shadowing environment. The adaptive coding scheme is also robust to mobile speed, feedback delay, and finite interleaving depth.