Comparison of encoding/detection techniques for the reverse link of an MC-CDMA multiple access scheme

Multicarrier (MC) modulation combined with code division multiple access (CDMA) has gained considerable attention in the last years because of its many advantageous features. However, while downlink design is possible even with M-QAM modulation schemes, a similar solution is much more difficult on the uplink because its asynchronous character complicates the channel identification. Indeed, performance of M-QAM schemes depends strongly on the accuracy of the channel estimation, as well as the adopted equalization techniques. We propose an uplink architecture based on chip-level differential encoding. This choice is motivated by the need to simplify the hardware structure and the channel estimation algorithms as well as to reduce the sensitivity to possible phase noise in the frequency down-conversion circuit. The numerical results of this work are preliminary and they are based on simulations