ADAPTIVE FILTERS IN MULTIUSER (MU) CDMA DETECTION

The primary purpose of this work is to provide a perspective on adapti ve code-division multiple-access (CDMA) MU receivers that have been pr oposed for future digital wireless systems. Adaptive receivers can pot entially adapt to unknown and time-varying environmental parameters su ch as the number of users, their received powers, spreading codes and time-delays. Two adaptive receiver architectures are primarily conside red - one in which the sampled received signal is filtered, and can be used in both the uplink (i.e., at the base station) and downlink (i.e ., at the mobile handset), and another in which the spreading codes of users are filtered (assuming knowledge of users' codes and its timing at the receiver) for use in the uplink. Relevant issues such as train ing-based and blind implementations of the adaptive receiver are discu ssed, as well as (transient) convergence rates and estimation noise in steady-state.