Blind Equalization using Coordinate Mapping for 4-PAM and 16-QAM Signals

It is well known that the famous Constant modulus algorithm (CMA) presents a large steady-state Mean square error (MSE) for nonconstant modulus signals. In this paper a coordinate mapping approach for a 4-PAM nonconstant modulus signal is described which can change the signal to an Offset QPSK (OQPSK) constant modulus signal. And a new algorithm based on this approach is proposed which is also suitable for a 16-QAM signal. For the 4-PAM and 16-QAM nonconstant modulus signals the proposed algorithm can achieve a zero steady-state MSE in a noiseless environment but CMA cannot. Theoretical analysis and simulations results demonstrate the high performance of the proposed algorithm.