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Robust digital receiver for frequency redundant digital communications over power lines

Low voltage electrical power distribution networks represent an attractive medium for digital communications. A modified frequency hopping spread spectrum modulation scheme has been reported as an efficient method to overcome high interference level and time-variant and frequency-selective attenuation on power lines. In spread spectrum systems, the cost-effective solution of synchronisation problem is of decisive importance. Fluctuations of power line frequency, asymmetrical loading, on three-phase networks and propagation delay along the cable, limit the data rate and seriously degrade performance of the systems which use zero crossings of the mains voltage as a synchronisation reference. In this paper we propose a digital receiver that derives timing information from the received signal, and therefore, is not sensitive to the mentioned effects, The receiver design is based on sliding DFT calculation. To overcome time-variant attenuation, an adaptive algorithm is used.