Iterative decoding and channel estimation of DS/CDMA over slow Rayleigh fading channels

We investigate the application of joint decoding and channel estimation for DS/CDMA transmission over slow Rayleigh fading channels. Some known symbols are inserted in the encoded data stream to enhance the channel estimation process. An iterative algorithm that uses the decoding information, in addition to the information contained in the known symbols, to improve the channel parameters estimate is proposed. A is shown that the optimum scheme has a complexity which grows exponentially with the channel estimation filter length. Hence, we propose some alternative sub-optimum schemes with polynomial complexity. The different techniques that provide a tradeoff between simplicity of implementation and BER performance are compared.