Robust transmission method in KHz-band PLC
This paper describes a robust transmission method for KHz-band PLC. The method is robust for heavy interference from electric appliances. Interference is not always stochastic in nature, as it is an artificial event. Thus, any transmission method based on Shannon's theory will not always yield reliable results. The robust transmission method proposed in this paper is to detect the correct symbol when the interference generated by many electric appliances fades out. However, interference-free zones cannot be determined within drastically time-variant interference envelopes, and they cannot be detected directly from the shape of the received signal. Interference-free zones can only be identified if an adaptive receiver outputs the true symbol. In order to solve this dilemma, we introduce a blind equalizer with rapid convergence. In addition, we employ a code that has symbol-position information built into the symbol sequence of the data frame. Through the combination of these two methods, we can maintain connections even when fading-out intervals are very short, by exploiting speed-reductions in the information rate. Implementing this method on a FPGA, we demonstrate that robustness can be realized even under the most problematic case of real KHz-band PLC networks. Application of this technique is vital for building dependable systems to control for electric appliances.