OPTIMIZATION OF SYMBOL DISTANCE METRIC IN DIRECTIONAL MODULATION SYSTEMS

Abstract

This paper investigates a directional modulation (DM) method that distorts the received symbol constellations along a set of undesired directions while maintaining an undistorted constellation in the direction of intended communications. The problem is formulated in terms of minimization of the symbol distance metrics along the undesired directions. An algorithm assigns a symbol pair to each undesired direction for symbol distance minimization. Constraints for good reception in the desired direction are also included. The method involves iterations between a quadratic minimization problem and an unbalanced transportation problem. Numerical results are presented to show the bit error rate (BER) benefits of the proposed method.