Multiple-access interference suppression for OFDM systems based on Doppler shifts
June Namgoong, T.F. Wong, J.S. Lehnert · 2003
We consider multiuser communications in an additive white Gaussian noise (AWGN) channel in the presence of significant Doppler shifts. It is well-known that the time asynchrony between users in a direct-sequence (DS) code-division multiple-access (CDMA) system allows for interference suppression. Similarly, the different Doppler shifts of received signals from a multiuser channel can be exploited in the frequency domain to achieve interference suppression. We show that this can be achieved with multicarrier CDMA (MC-CDMA). The relationship between the interference suppression capability and the Doppler shifts is studied in terms of signal-to-interference ratio (SIR).