Robust Software Defined COFDM-Modem for Embedded Applications

The presentation will highlight the principles and realization of a high-performance software defined COFDM-modem, designed to make the best use of power lines, sub-sea cables or, simple twisted-pair wires. The modem can also be used in wireless applications. Depending on channel properties, the modem must be configured in terms of positioning the transmission band, its bandwidth, and methods of modulation. The optimization requires signal code construction to produce the maximum effective modem data rate. The optimization yields the structure of the SCC, adapting the bandwidth, the number of active beams and the distribution of QAM-alphabets. An adaptive front-end filter for optimal shortening of the pulse response and a two-stage adaptive equalizer (Kalman) in combination with 4-D Trellis coded modulation achieves a channel capacity just 3.5 dB short of the theoretical limit. The modem automatically adapts all settings during the initial handshake phase which completes within less than one second. The resulting performance is close to the theoretical limit with data rates of up to 11 bits/sec/Hz. The modem can be used in point-to-point or complex point-to-multipoint topologies adapting to new conditions automatically within a fraction of a second. Applications include A/V intercoms, power grid communication, telemetry, smart metering, in-vehicle communication, et cetera. A video transmission across a twisted pair of solid wires will be demonstrated.