New hybrid adaptive blind equalization algorithms for QAM signals

Abstract

This paper introduces new hybrid blind equalization algorithms for QAM signals, the first term of which is the constant modulus criterion (CMA) or its extended version (ECMA) and the second are a penalty term that vanishes at constellation points coordinates. Several penalties, based on cosine, gaussian and polynomial 1 -norm fonctions respectively are investigated. Simulations show the effectiveness of these algorithms.

Min‐norm based alphabet‐matching algorithm for adaptive blind equalisation of high‐order QAM signals

“…In , we proposed a new AM function defined from products of ℓ 1 distances between the equaliser outputs and the constellation points. More specifically, it is defined as Although it behaves pretty well, this AM penalty does not perfectly match the desirable symmetry and periodicity properties for an AM in .…”

“…We refer to the algorithm that combines this modified Gaussian AM and the MM term as the MGauss‐MMA, whose cost function is given by where . Penalty that we had introduced in appeared to yield best performance among approaches considered therein. Thus, we will use it for comparisons in simulations.…”

“…In [10], we proposed a new AM function defined from products of`1 distances between the equaliser outputs and the constellation points. More specifically, it is defined as…”

A modified hybrid dual-mode blind equalization algorithm for high-order QAM signals

“…CMA has a good performance to the constant modulus signals, such as PSK signal. But in the QAM system, CMA has the slow convergence rate and large steady-state error after convergence because of QAM's multi-modulus properties [3][4][5][6][7][8]. [12] proposed the dual-mode algorithm.…”

“…To recover the phase rotation, an additional rotator is required at the output of the equalizer, but it increases the complexity of implementation at the receiver in steady-state operation. To overcome the shortcoming, the modified CMA (MCMA), square contour algorithm (SCA), and extended CMA (ECMA) were proposed [6,8,11]. The ECMA algorithm is a particular case of the generalized constant modulus algorithms, which is phase sensitive, so it can modify the phase rotation.…”