Direct and turbo multi-user spatio-temporal channel estimation schemes for CDMA FDD UMTS uplink

Many multi-user receivers have been developed to mitigate the effects of both multipath and interference in CDMA radiocommunication networks. However, despite of these works, very few papers have been devoted to the implementation of these receivers and, more precisely, to the channel estimation problem in both the multi-user and FDD UMTS context. Assuming specular propagation channels and a multi-sensor receiver, the purpose of this paper is to present direct and turbo multi-user schemes for the joint estimation of the impulse response of the propagation channels between each user and each sensor for the FDD UMTS uplink. The quality of the latter are then evaluated through the bit error rate (BER) computation at the output of two receivers (2D-RAKE and decorrelator receiver) adapted to the FDD UMTS uplink.