Performance analysis of a LINK-16/JTIDS compatible waveform transmitted over a channel with pulse-noise interference

Abstract

The Joint Tactical Information Distribution System (JTIDS) is a hybrid frequency-hoped, direct sequence spread spectrum system that utilizes a (31, 15) Reed-Solomon (RS) code and cyclical code-shift keying (CCSK) modulation for the data packets, where each encoded symbol consists of five bits. In this paper, an alternative waveform compatible with the existing JTIDS direct sequence spread spectrum channel waveform is analyzed. The system considered uses the same (31, 15) RS encoding as the original JTIDS but uses 32-ary orthogonal signaling with 32 chip baseband waveforms such as Walsh functions instead of CCSK. Currently, the JTIDS waveform is received noncohe-rently at the chip level, but in this paper the performance of the alternative, JTIDS-compatible waveform is evaluated for coherent as well as for noncoherent demodulation in order to ascertain the performance possible if coherent demodulation were practical. For coherent demodulation, each pair of five-bit symbols at the output of the RS encoder is assumed to undergo serial-to-parallel conversion to two five-bit symbols, which are then independently transmitted on the in-phase and quadrature component of the carrier, with the result that the data rate for coherent demodulation is twice that for noncoherent demodulation. 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.