The technique of joint blind channel estimation and multiple access interference (MAI) suppression for an asynchronous code-division multiple-access (CDMA) system is investigated in this research. To identify and track dispersive time-varying fading channels and to avoid the phase ambiguity that come with the second-order statistic approaches, a sliding-window scheme using the expectation maximization (EM) algorithm is proposed. The complexity of joint channel equalization and symbol detection for all users increases exponentially with system loading and the channel memory. The situation is exacerbated if strong inter-symbol interference (ISI) exists. To reduce the complexity and the number of samples required for channel estimation, a blind multiuser detector is developed. Together with multi-stage interference cancellation using soft outputs provided by this detector, our algorithm can track fading channels with no phase ambiguity even when channel gains attenuate close to zero.

Date Published: 12 November 2002
PDF: 11 pages
Proc. SPIE 4869, Emerging Technologies for Future Generation Wireless Communications, (12 November 2002); doi: 10.1117/12.455461

Published in SPIE Proceedings Vol. 4869:
Emerging Technologies for Future Generation Wireless Communications
Carl R. Nassar, Editor(s)