Performance analysis of a JTIDS/link-16-type waveform transmitted over slow, flat Nakagami fading channels in the presence of narrowband interference

摘要

Link-16 is a tactical data link currently employed by the United States Navy, the Joint Services, and forces of North Atlantic Treaty Organization. It provides presumably secure and jam-resistant tactical information for land, sea, and air platforms. The communication terminal of Link-16 is called Joint Tactical Information Distribution System (JTIDS) and features Reed-Solomon (RS) coding, symbol interleaving, cyclic code-shift keying (CCSK) for M-ary symbol modulation, minimum-shift keying for chip modulation, and combined frequency-hopping and direct sequence spread spectrum for transmission security. In this dissertation, we investigate the performance of a JTIDS/Link-16-type waveform in both additive white Gaussian noise (AWGN) and narrowband interference when the signal is transmitted over a slow, flat Nakagami fading channel. In general, the results show that barrage noise interference has the most effect in degrading JTIDS's performance when signal-to-interference ratio (SIR) is small, whereas pulsed-noise interference for a smaller fraction of time that the interference is on causes the greatest degradation when SIR is large, whether the channel is fading or not. In addition, two modified JTIDS/Link-16-compatible systems are proposed and evaluated. The first system uses errors-and-erasures decoding (EED) in place of errorsonly RS decoding, and the second system employs a new 32-chip CCSK sequence instead of the 32-chip CCSK sequence chosen for JTIDS. For the first modified system, the results show that EED outperforms errors-only RS decoding in all cases, whether channel is fading or not. With EED, the most significant improvement is found when both the fraction of time the interference is on is small and the signal-to-AWGN ratio is large. For the second modified system, the new 32-chip CCSK sequence, obtained from a search algorithm, allows for seven instead of six chip errors in the received sequence without making a symbol error, but the results show that the probability of symbol error obtained with the new CCSK sequence is only slightly better than that obtained with the sequence chosen for JTIDS.