Performance analysis of a Link-16 compatible waveform using errors-and-erasures decoding when corrupted by pulse-noise interference

Abstract

The Link-16 is the tactical data link utilized by the Joint Tactical Information Distribution System (JTIDS). The JTIDS system is important due to its wide use by U.S. armed forces, NATO, and other allied militaries. Link-16 is a hybrid frequency-hopped/direct sequence spread spectrum system that utilizes minimum-shift keying (MSK) to modulate the chips, cyclical code-shift keying (CCSK) to modulate the 32-chip symbols, and a (31, 15) Reed Solomon (RS) code with hard decision decoding (HDD) for forward error correction (FEC). This paper analyzes an alternative waveform compatible with the existing Link- 16 which uses orthogonal modulation such as Walsh codes vice CCSK and errors-and-erasures decoding (EED) vice hard decision decoding. Both of these modifications are suggested for enhanced bit error rate (BER) performance. Orthogonal modula­tion for Link-16 with HDD has been explored before [1][2]. [2] shows that the proposed alternative waveform outperforms the Link-16 waveform slightly when HDD is used. This paper reveals potential further improvement through the use of EED. Currently, the Link-16 waveform is received noncoherently at the chip level, but in this paper the performance of the alternative Link-16-compatible waveform is evaluated for coherent as well as for noncoherent demodulation in order to ascertain the perform­ance possible if coherent demodulation becomes practical. The performance of the alternative waveform for the relatively benign case where additive white Gaussian noise is the only noise present as well as when pulse-noise interference is present is investigated for both coherent and noncoherent demodulation.