Optimum and suboptimum channel estimation for the uplink of CDMA mobile radio systems with joint detection

Abstract In the present paper, channel estimation in the uplink of CDMA mobile radio systems with burst transmission applying joint detection is considered. The different radio channels are estimated at the receiver using known midamble codes. Either maximum‐likelihood, i.e. optimum, or suboptimum channel estimation can be realized at the receiver. Several methods for constructing code sets for the simultaneously active users are proposed. It is shown that the structure of the channel estimator for a multi‐user synchronous CDMA mobile radio system is the same as for a single‐user system when the mid amble codes of the users are segments derived from a single basic code. Furthermore, it is shown that the channel estimator can be implemented as a correlator when the midamble codes are constructed from a periodic basic code. Finally, the effect of noisy channel estimation, i.e. the presence of channel estimation errors, on the detected data is examined.