Application of forward-error correction to a Rayleigh fading h.f. communication channel

The performance is assessed of a Rayleigh fading h.f. communication channel which transmits binary data using a selection of forward-error correction systems. The criteria adopted are the probabilities of no character error, and not more than one character error in a message containing a specified number of characters, each character consisting of five information bits. The basic standards for comparison are taken to be the start/stop telegraphy mode of transmission and the synchronous transmission of pure information. The error-correction systems studied are tor, autospec and BCH(31, 21), all employing block coding. Where interleaving is applicable the improvement obtained is assessed. The advantages of employing space diversity are also assessed. The case of a constant signal is included for completeness. It is assumed that the probability of an element error is related to channel signal/noise by an exponential modem curve. The calculations are part probabilistic, part simulation. Errors and efficiency of the method are discussed.