An experimental adaptively equalized modem for data transmission over the switched telephone network

The relative merits of the zero-forcing, mean-square error and quantized-feedback algorithms are compared for data transmission over the switched telephone network, bearing in mind the nature of the transmission impairments met in this medium. The design and performance of an experimental 4-level vestigial-sideband amplitude-modulated modem operating at a data signalling rate of 4800 bit/s with a hybrid 37-tap equalizer using the mean-square error algorithm for 6 leading taps and quantized feedback for 30 trailing taps is discussed.