PERFORMANCE RELIABILITY OF DS-CDMA MOBILE COMMUNICATION SYSTEM
K.M. Shaheen, Someshwar C. Gupta · International Journal of Reliability Quality and Safety Engineering · 1996
Applications of DS-CDMA in mobile communication systems, in forward link and reverse link, imply certain precautions against near–far effect (NFE), multi-access (co-channel) interference (MAI/CCI), and multipath fading. In this paper, two multi-user detection schemes are proposed to enhance the reliability of DS-CDMA system against NFE and MAI for both reverse link and forward link applications. The first scheme, reverse link multistage CCI cancellation (RLCCI) scheme, is derived for a single path channel model and is based on minimization of estimation error between the received signal and its projections on spreading sequences subspace. The second scheme, forward link CCI (FLCCI) cancellation scheme is based on keeping a simple yet robust decoder at the mobile station (MS), reducing the negative impact of CCI, and enhancing CCI positive contributions. FLCCI minimizes the negative impact of CCI by adjusting the magnitudes of vulnerable spreading codes to compensate in advance for CCI losses. Block diagrams, mathematical models, performance analysis and reliability of both cancellation schemes against NFE, MAI, and external noise are discussed in details. The improvements in BER and overall performance are evaluated using Monte Carlo simulation for both schemes.