Binary Error Rates in Fading FDM-FM Communications

This paper discusses the transmission of binary data over a fading frequency-division multiplexed FM (FDM-FM)radio system. The important results are convenient design formulas for binary error rate in terms of the symbol duration, the IF bandwidth, the per channel rms frequency deviation, the average received carrier-to-noise ratio, and the particular types of binary detection and diversity combining techniques used. By using accepted telephone talker statistics and the CCIF recommendations with regard to data channel loading in a combined voice-data system binary error rate is further related to FM deviation ratio, and the pre-emphasis time constant etc., which are of more specific interest to system design. An important corollary of the analysis is that in a fading environment FDM-FM offers relatively inefficient means for data transmission. In particular it is shown that an FDM-FM data system does not perform as well as does the equivalent FDM-SSB system by an amount in the order of 10 db.