A symbol-by-symbol multiuser detector with joint amplitude and delay estimation

A multiuser detector is developed for code-division multiple access applications, in which the delays and amplitudes of the incoming waveforms are estimated recursively. The overall algorithm is an approximation to the symbol-by-symbol detector of K. Abend and B. Fritchman (1970), in which the likelihoods are computed using extended Kalman filter (EKF) innovations. The EKF provides, in addition to the likelihoods, joint estimates of the signal delays and amplitudes. The resulting algorithm is quite complex, due to the large number of possible composite symbols corresponding to the multiple users. However, it is shown that the likelihood computation and EKF updates can be expressed in terms of a set of cross-correlation functions, which need only be computed for a subset of the possible symbols. Thus, the algorithm may be practical for certain narrowband applications using programmable DSP device implementations