New blind equalization techniques based on constant modulus algorithm

Abstract

New blind equalization techniques based on the constant modulus algorithm (CMA) are investigated. Since CMA is phase-blind, an output constellation has a phase error at convergence. The modified constant modulus algorithm (MCMA) that accomplishes blind equalization and carrier phase recovery simultaneously is proposed. Then, the performance of the MCMA is enhanced by incorporating a decision-directed (DD) algorithm. The resultant scheme, dual-mode MCMA, achieves the faster convergence speed and smaller residual ISI. A blind decision feedback equalizer (DFE) using MCMA is also presented, which leads to superior performance compared to ones without the feedback path over the channel with in-band spectral nulls. Simulation results confirm the effectiveness of the proposed techniques on various channels and signals.