Importance of symbol equity in coded modulation for power line communications

The use of multiple frequency shift keying modulation with permutation codes addresses the problem of permanent narrowband noise disturbance in a power line communications system. In this paper, we extend this coded modulation scheme based on permutation codes to general codes and introduce an additional new parameter that helps to more precisely capture a code´s performance against permanent narrowband noise. As a result, we define a new class of codes, namely, equitable symbol weight codes, which are optimal with respect to this measure. In addition, we demonstrate via simulations that equitable symbol weight codes achieve lower symbol error rates than other codes of the same length and distance over the same alphabet.