Robust multiuser OFDM power line communications over medium voltage networks

Modern smart grid and smart metering concepts are based on reliable digital communications. Due to the enormous expansion of the power line grid in the last century, the limited availability of conventional systems (e. g. ADSL) as well as the economic risks connected to wireless solutions, power line communications (PLC) constitutes a promising solution. However, reliable data transmission over the so-called „horrible“ PLC channel is a modern challenge. In contrast to earlier publications concerning digital communications over the Medium Voltage Network (MVN), a complete, functional system is presented. The selected transmission technique is OFDM, as it offers excellent possibilities for increasing the system's adaptivity and robustness. The proposed combination of OFDM with novel adaptive signal processing methods for frame synchronisation, phase based signal to noise (plus interference) ratio estimation and dynamic adaptation of the transmission parameters constitutes a new contribution to the effort of overcoming the MVN time-frequency selectivity, very high signal attenuation, (self-) interference, impulsive noise, etc. Within the scope of an industry project funded by a major European utility, the proposed system was implemented in the form of a proprietary DSP based OFDM modem for IP communications over the MVN. The increased system's robustness was proved within a 4-month pilot project with 10 prototypes.