Parameter Estimation and Detection of DS-CDMA Signals subject to Multipath Propagation
Stefan Parkvall, Erik G. Ström · 1995
In this paper we consider the problem of estimating the propagation delays and relative amplitudes of the transmitted signals as well as detecting the data bits in an asynchronous direct-sequence code division multiple access (DS-CDMA) system operating over a fading channel. A subspace based estimator is proposed for estimating the propagation delays. The path gains and data bits are estimated with minimum mean squared error techniques. Special attention is paid to the near-far problem. 1 Introduction One major problem in a DS-CDMA system is the near-far problem [2] which occurs when different users have dissimilar powers and their code sequences are not perfectly orthogonal. The standard receiver, the matched filter receiver, is known to fail in a near-far environment. Therefore, several near-far resistant receivers have been previously proposed, e.g., [1, 8, 9]. These receivers all assume that the propagation delays of all users are known. The This work was supported in part by t...