On the use of chip-level differential encoding for the uplink of MC-CDMA systems

The combination of multicarrier (MC) modulation and code division multiple access (CDMA) is seen as a very promising technique for the development of high capacity wireless communications. However, while downlink design is possible even with coherent detection techniques, a similar solution for the uplink appears to be difficult. In fading channels, the performance of coherent schemes depends strongly on the accuracy of the channel estimation, as well as the adopted equalization techniques. We consider a novel encoding/detection technique involving chip-level differential encoding, which has been suggested in a paper by Cavallini, Giannetti, Luise and Reggianini (see IEEE Trans. on Commun., vol.45, no.4, p.456-63, 1997), although in a different framework. We compare the performance of this scheme with that of symbol-level differential encoding and coherent PSK.