PCM/FM performance enhancement using Reed Solomon channel coding

This paper presents analytical and detailed computer simulation results of the performance enhancement of pulse code modulation/frequency modulation (PCM/FM) links using Reed Solomon (RS) channel coding. PCM/FM is a commonly deployed technique for a wide variety of telemetry and other links. Nevertheless, the required SNR to provide acceptable bit error rate (BER) can be considerable. Thus, it is desired to provide channel coding to reduce the SNR requirement. The simulation of PCM/FM with and without RS coding requires the application of a variety of signal processing techniques discussed in the paper. RS channel coding is considered in this paper and is often used as a forward-error-correction strategy for digital links. In communication links, random and burst errors can result from a variety of interferences. This results in high symbol rate errors, some of which can be corrected by a RS code. RS codes are powerful burst-error correcting codes. An analytical model is developed for this paper, and detailed simulations are performed for PCM/FM with and without RS coding. The FM demodulator for small SNR input creates click noise, while for very large signals Gaussian type noise is anticipated. The implications of these types of noise and how it relates to BER are discussed in the paper. Detailed BER versus SNR curves are produced from both analysis and simulation. The results of the analysis and the simulation indicate that coding can substantially enhance link closure.