M-ary frequency mapping techniques for power-line communications

M.Ing. (Electrical and Electronic Engineering)Power line communications have been in use since the early 1900‟s. The early use of this technology was mostly found within utility companies where it was used for intra telephonic service over the electrical distribution network. This technology has evolved remarkably to include not only low voltage medium and high voltage electric network but it has also extended to home automation and network. Literature on power line communications has pointed out major hindrances such as cable characteristics, impedance variations and noise signals from various sources. Most importantly, noisy characteristics of power line channels make it difficult to transmit information data in an effective and reliable way. More often data transmitted through power line channels is corrupted by three main types of noise, the background noise, the impulse noise and the permanent frequency disturbances. Consequently, researchers have focused on the optimum use of power line channel through combining channel coding and modulation schemes. In this study, we have, through simulations and practical experimentations, investigated the performance of a new mapping technique called “frequency mapping” over power line channel. The study material began with reviews of channel coding, modulation and permutation codes schemes. Further we presented through computer simulation, the inherent benefit of using permutation codes obtained through construction technique. Secondly, we detailed the use of Hadamard transform to produce frequency sequences. In reality, sign changes, drawn from observing Hadamard matrix and Walsh functions, were conceptualised as frequencies from which frequency sequences were produced. This technique termed “frequency mapping” showed effectiveness against narrow band noise in simulation environment. The study closed with an experimental verification of this new technique through custom designed communication system on a real power line channel where we observed a net BER performance gain when frequency sequences are ordered through Hadamard transform