Influence of imperfect channel estimation on the global performances of a turbo coded UMTS/TDD system

In this paper, the loss in performances due to imperfect channel estimation, caused by the presence of noise is presented. Channel estimation in UMTS/TDD is done using the training sequences or "midambles", positioned at the middle of the slot. The estimated channel parameters are necessary to operate match filtering at the head of the baseband part of the receiver. The results obtained for the Vehicular B profile and the indoor A channel defined by the UMTS standard is presented. System performances are estimated in terms of the BER (bit error rate) obtained after turbo-decoding iterations.