SAGE algorithms for multipath detection and parameter estimation in asynchronous CDMA systems

Algorithms to estimate blindly the parameters and input sequences for a multiuser asynchronous code division multiple access (CDMA) system are proposed. The communication system is modeled as a frequency selective fading channel with multipath propagation, where the number of active propagation channels is unknown and highly time varying. Estimates of input sequences and unknown parameters are jointly computed via the SAGE algorithm. The SAGE algorithm provides a unified approach in combining jointly multiuser detection and parameter estimation in an optimal way. Depending on the realizations of the SAGE algorithm, well-known state and parameter estimation schemes of various complexities are optimally combined.