Space time coded data transmission via inductive effect between adjacent power lines

Space time coded data is transmitted via electricity mains by sending data encoded with some redundancy ("time diversity") from one modem down one conducting line which interacts inductively with adjacent conducting lines to provide further replication of itself ("space diversity"). The effects of induction on parallel conductors will cause all receiving modems to receive some of the signal, necessitating an identifier (eg. header) of the intended recipient to form part of the signal. A handshake procedure employing test signals is used to establish the nonlinearity of the frequency response and time domain response of the link, and appropriate coding and selected combinations of frequency channels and time slots involving different conducting lines are chosen to optimise communication (fig 3), thus providing diversity in an analogous manner to mobile telephone communication via multiple antennas. A filter is used to minimise "mains hum", ie. signals at electricity supply ...

Communications system