Blind turbo multipath channel estimation of PAM signals exploiting multilevel codes

We present a blind turbo equalizer for pulse amplitude modulation (PAM) signals that exploits the statistics that a multilevel code imposes on the transmitted signal. The receiver here is an adaptation of previous work presented in A.F. Santos, et al, (2008), where a BPSK signal is encoded by a binary code and blindly recovered in a turbo way. The main concept is to exploit the constraints imposed by the parity check equations of the code at the transmitted sequence for estimating the channel. Here multilevel codes are used for imposing the necessary constraints on a PAM signal for blind channel estimation. The performance of the proposed system is encouraging. It shows that our blind channel estimator gets close to the same BER of the turbo equalizer with perfect channel knowledge.