An improved channel estimation with turbo codes over fading channel for DS-CDMA

The application of regression algorithm in channel estimation (CE) with turbo codes over slow fading channel for DS-CDMA is presented in this paper. None of the classical methods like wiener filter, simple average (SA) and linear interpolation (LI) algorithms, utilizes channel coherent property sufficiently. Therefore, a low complexity improved method using low order robust regression algorithm for QPSK and 16QAM modulation is proposed. After initial channel estimation with classical methods, channel gains estimated are filtered by linear or conic regression algorithm within a given regression length. In this improved method, the length and order of regression algorithm are two key parameters, which affect the system performance significantly and the optimal values of which depend on the speed of mobile station. It is demonstrated by computer simulations that this improved method can track fading channel accurately and outperforms over classical methods substantially by selecting appropriate parameters of regression algorithm under a certain channel environment.