Performance Analysis of Iterative CDMA Receivers with Channel Estimation in Flat Fading Channels

In this work we analyze the evolution of the multiuser-efficiency for the uplink of a coded iterative CDMA receiver with channel estimation in flat Rayleigh fading channels with block fading characteristic. The receiver processing parts are: Multiuser detector implemented as PIC-LMMSE, a bank of single user MAP decoders, and a channel estimator unit which makes use of fed back soft bit values in the estimation process. We derive the expression for the mean channel estimation vector and its error variance vector as a function of the block length, the number of pilot symbols, the decoder output distribution, the system load, and the SNR. Further, we derive and illustrate a fixed-point equation expressing the multiuser-efficiency as a function of the imperfect channel state information and the fed back decoder information.