Frequency-time MMSE equalizer for BER enhancement of MC-CDMA systems over mulipath fading channel
Résumé
This paper examines the performance of a multicarrier CDMA system over multipath fading channel. Due to the dispersive nature of the mobile communications channels, Multi-Carrier Code Division Multiple Access (MC-CDMA) signals will be affected by Inter Channel Interference (ICI), Inter Symbol Interference (ISI) and Multiple Access Interference (MAI), due to the loss of subcarrier orthogonality. To solve the ISI problem, a cyclic extension was introduced to the transmitted symbols, known as guard time, but its introduction results into loss of spectral efficiency. In this context, we consider the use of a Frequency-Time minimum mean square error Equalizer (FTE) to compensate for the corresponding loss in performance, and compare the resulting MC-CDMA systems with the use of guard time. The effect of system parameters such as output Signal-to Noise Ratio (SNR), number of sub-carriers, delay spread, is investigated by simulation, from which we show that MC-CDMA/FTE provides better performance than guard time technique.