Open loop channel estimation and tracking in DS-CDMA system with selective fading

In this paper we study the performance of a simple and easy-to-implement open loop channel estimation and tracking strategy applicable to a DS-CDMA system. The scheme makes use of tentative channel estimates which are available whenever a CDMA signal is despread as part of the detection process for either multiuser decorrelator or MAI canceller based receivers. The algorithm employs a windowing approach to track and update the channel estimate. It takes advantage of the averaging effects of PN sequences in CDMA to improve channel estimates despite severe MAI or high co-channel interference levels. The estimated channel parameters are used to study the performance of a typical DS-CDMA receiver which uses a multistage interference cancellation scheme. The numerical results show that apart from the estimator being unbiased, it has a low mean estimation error. The performance degradation of a multi-user multistage interference cancellation scheme employing the channel estimator is shown to be small.