Power-Controlled Multicarrier and Multiuser Detection Techniques in Wireless CDMA Systems

Abstract

This paper describes power-controlled multi carrier and multiuser detection techniques for Code Division Multiple Access (CDMA) systems. In conventional CDMA systems, a RAKE receiver is employed to overcome wireless channel effect due to frequency selective characteristics of wireless CDMA systems. Alternatively, multi carrier technique can also be used to overcome the effect of frequency selective channel. Conventional CDMA systems also employ single-user detection scheemes, in that interference between users, called the multiple access interference (MAI), is considered as interference which contributes to the statistics of detection variables affecting the quality of detection. Now, multiuser detection method is proposed to mitigate the inter user interference in CDMA systems. In multiuser detections, the MAI component can be eliminated or cancelled by the use of all user’s spreading code in the system to be available to each user. Another technique that is commonly employed in CDMA system is power control, to mitigate the effects of near-far and fading channel fluctuations. In this study, the basic concept of multi carrier and multiuser detection technique is described in a simple model and the performance for various number of users is simulated and evaluated. The performance of power-controlled multi-carrier and multiuser detection technique is then evaluated and compared with that of the singleuser detection to show a significant improvement.