A multi-pass strategy for channel estimation and data detection in long-code uplink CDMA systems

In this paper the problem of joint data detection and channel estimation for the uplink of a CDMA system employing aperiodic spreading codes is considered. Assuming that each transmitted data-frame contains a short preamble of known bits, the detection strategy that is proposed here relies on an iterative exchange of information between the data detector and the channel estimator. This strategy, which is termed "multi-pass," is shown to be capable of alleviating, at the price of some attendant increased computational complexity increase, the performance degradation induced by the lack of prior knowledge on the channel state and on the users\´ timing offsets. Extensive computer simulations confirm that the proposed strategy achieves excellent results.