A Fractionally Spaced Blind Equalizer Based on Linear Programming

In this paper, we formulate the blind fractionally spaced equalization (FSE) problem as one that minimizes a piecewise linear convex function subject to some linear constraints on the equalizer parameters. We show that this formulation achieves both the interference removal and the carrier phase recovery when the input signal possesses a certain quadrature amplitude modulation (QAM) type symmetry. A fast linear programming implementation is presented to solve the convex minimization problem. Computer simulation results indicate the new linear programming-based FSE is able to accurately equalize channels that are known to be not equalizable by $T$-spaced (or baud rate) blind equalizers and yields superior performance to other blind FSE methods.