3.3 Turbo-Coded ARQ Schemes for DS-CDMA Data Networks over Fading and Shadowing Channels

In this paper modified ARQ (automaticrepeat-request) techniques based on turbo coding are investigated for asynchronous DS-CDMA (directsequence code-division multiple-access) data networks under shadowing and frequency selective fading channel conditions. The throughput, delay, and energy efficiency performance of standard ARQ, metric combining, and RCPT (rate compatible punctured turbo) coded ARQ schemes are compared via simulations. The RCPT/ARQ schemes are shown to outperform the other two schemes in terms of both throughput and energy efficiency at the cost of larger delay and complexity. Maximum network throughput is investigated for different ARQ schemes under energy constraints.