Adaptive modulation based MC-CDMA systems for 4G wireless consumer applications

Adaptive modulation based MC-CDMA systems can play a vital role in future generation consumer communication electronics. Adaptive modulation, combined with MC-CDMA based transmission technology, is a promising way to increase the data rate that can be reliably transmitted over the wireless radio channels. For 4G wireless networks, which demand very high data rate up to 100 Mbits/s with the constraints limiting higher data rate being severe ISI due to multipath and limited spectrum, such kind of adaptive modulation based multi-carrier systems applied to a wide-area environment, can achieve very large average user throughputs. In this paper, adaptive modulation based M-ary PSK, M-ary QAM, M-ary CPM, M-ary MHPM and GMSK systems applied to a turbo coded MC-CDMA system in a Rayleigh fast fading channel environment have been investigated and the BER performance of all these digital modulation techniques have been compared. Results of the comparative study indicate that the continuous phase modulation schemes like CPM, MHPM, and GMSK gives better performance as compared to PSK and QAM schemes. At most of the time, the MHPM systems outperforms both GMSK and CPM. The PSK and QAM based systems perform well till the number of users are around 10. As a whole, the adaptive MHPM system is found to give the optimum performance among the considered digital modulation schemes for the MC-CDMA system in a 4G environment.