Binary Data Transmission by FM over a Real Channel

This paper undertakes to refine and extend the state of knowledge concerning performance of FM systems for binary data transmission over real-life channels. The particular aim is application to facilities such as exist in the telephone plant. Efficient use of the available channels constrains the bandwidth allowed for a given signaling speed. The luxury of a bandwidth sufficient to permit frequency transitions without amplitude variations and without dependence of present waveform on past signal history would in general imply an unjustifiably low information rate for the frequency range occupied. We therefore concentrate our attention on the band-limited channel with its inherent distortion of the FM data wave. We assume a linear time-invariant transmission medium specified by its amplitude- and phase-vs-frequency functions and the statistics of its additive noise sources. The limiting noise environment in the telephone plant is typically nongaussian and not well defined even in a 2387