The Impact of Combined Equalization on the Performance of MC-CDMA Systems

In this work the performance of a combined equalization for multi-carrier code division multiple access (MC-CDMA) systems is analytically evaluated. Combined equalization consists in performing both pre-equalization at the transmitter and post-equalization at the receiver in order to counteract fading and multi user interference. In this paper we consider partial combining (PC) at the transmitter and threshold orthogonality restoring combining (TORC) at the receiver in the downlink of a MC-CDMA system affected by fading. The analytical framework here proposed allows the derivation of the bit error probability (BEP) and the bit error outage (BEO) and their dependence on the number of subcarriers, the number of active users, the mean signal-to-noise ratio (SNR) averaged over smallscale fading, the partial combining parameter and the threshold of the detector. Moreover, the dependence of the TORC threshold on the other system parameters is derived, providing a thereshold adaptive variation tracking slow processes fluctuations.