Interleaver performance for FSK transmission on the acoustic fading channel

The performance advantages provided by the use of a symbol interleaver in a frequency shift keying (FSK) autonomous underwater vehicle (AUV) data communications link are demonstrated. The communication system is a digital FSK data link. It is well known that a Rayleigh fading medium introduces significant bit-error-rate (BER) degradations with respect to the additive noise channel due to the correlated nature of the induced errors. To reduce error correlation, symbol (chip) repeat and interleaver processing functions are introduced. By distributing transmitted chips in a predictable fashion. a time diversity is introduced from which the original can be efficiently reconstructed. The implementation of interleavers at various end-to-end delay to channel correlation time ratios is investigated. Residual correlations introduce degradations which are evaluated at various bit rates to characterize the data link BER performance for range of signal-to-noise ratios. It is demonstrated that interleavers provide an efficient method of improving AUV data link BER performance