Adaptive Blind Equalization Algorithms for Indoor Wireless Communication Channels



Lin He, Moeness G. Amin, Charles Reed, Jr. and Robert Malkemes



A modified constant modulus algorithm (MCMA) algorithm for adaptive channel equalization for QAM signals is proposed. The proposed algorithm minimizes an error cost function that includes both amplitude and phase of the equalizer output. In addition to the amplitude-dependent term that is provided by the conventional constant modulus algorithm (CMA), the cost function includes a signal constellation matched error (CME) term. This term can be designed using finite or infinite order polynomials and should satisfy a set of desirable properties. The MCMA is compared with the CMA for blind equalizations. The performance is evaluated for indoor wireless channels using both transient and steady-state behaviors of the mean square error (MSE). While the CMA is successful in achieving good performance, it is shown that MCMA is superior and more robust in low SNR environments. Simulation results demonstrate that using MCMA improves adaptive channel equalizations by increasing convergence rate and decreasing the steady-state mean square error.