The transversal and lattice multiple modulus algorithms for blind equalization of QAM signals
R.A. Axford, Larry B. Milstein, J.R. Zeidler · 2002
The most popular algorithm for blind equalization of QAM signals is the constant modulus algorithm (CMA). However, because the CMA cost function is not matched to constellations with signal points on multiple radii, CMA can exhibit excessive misadjustment for QAM signals. This paper develops an alternative to CMA, the multiple modulus algorithm (MMA), which is based on stochastic gradient minimization of a cost function that goes to zero at each radius of the QAM constellation. For the applicable QAM constellations, MMA exhibits significantly reduced misadjustment compared to CMA. A lattice implementation of MMA is also presented.