Performance analysis of a multicarrier CDMA system in frequency selective rayleigh fading channel

Abstract

In this thesis, we analyzed the performance of the multicarrier CDMA system in frequency selective Rayleigh fading channel and proposed a new multicarrier system. It has been shown that when the bandwidth is fixed, the number of carriers does not affect the system performance. It is also shown that when the processing gain is fixed, the system has the best performance if the carrier number becomes equal to the number of resolvable paths. This new proposed multicarrier system makes the channel frequency nonselective and has the advantage over the single carrier system especially when the SNR is low in spite of using narrower bandwidth. The diversity technique outperforms the proposed system only with diverisity order of 2. However, the implementation of rake receiver has many difficulties, and as an alternative this system is of some value. When the bit stream is convolutionally coded by the rate which is the inverse of the number of resolvable paths and each coded bit is modulated on the carriers of the same number of resolvable paths, the pefromance becomes better than the single carrier coded system if the processing gain equals to that of one coded bit of single carrier system.