On the adaptability of OFDM-CDMA forward link with time-frequency spreading in multi-path fading channels

Abstract

OFDM-CDMA (orthogonal frequency division multiplexing, code division multiple access) with joint time and frequency spreading has a great potential to achieve very high spectrum efficiency by exploiting both the temporal and spectral characteristics of the multi-path fading channels. A full realization of this potential however is contingent on the system's ability to adapt to the changing operating environments. In this paper, we explore this adaptability for the forward link of such a system by adapting the receiver detector, spreading pattern, spreading format and spreading code to the channel and traffic conditions. Numerical results show that significant performance improvement can be achieved as compared to the non-adaptive counterparts.