Adaptive Multi-Carrier CDMA (MC-CDMA) Structure for Downlink PCS
Conventional multi-user Code Division Multiple Access (CDMA) suffers from the well-known near-far problem. Both the conventional decorrelator and an adaptive separator termed Bootstrap algorithm were used to mitigate this problem and obtain near-far resistant receivers. Nevertheless, those approaches still require the knowledge of which users are active and their respective powers. Eliminating this requirement is advantageous for downlink communication as we are only interested in one desired user. Furthermore, in a multipath environment the use of the RAKE receiver adds to the complexity. A transmission method called Multi-Carrier CDMA (MC-CDMA) uses multiple narrowband subcarriers and as a result the channel is flat-fading at each sub carrier. However, due to frequency selective fading the fading at adjacent subcarriers will be correlated. We propose a downlink MC-CDMA communication system which has a special structure and requires less complex hardware at the receiver. The performance of this system is analyzed and simulation results are obtained for the AWGN channel and the Rayleigh fading channel with and without correlation between the subcarriers.
KeywordsCode Division Multiple Access Rayleigh Fading Channel Multiuser Detector Rake Receiver Code Division Multiple Access System
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