In this dissertation, the probability of symbol error for a JTIDS/Link-16-type waveform with errors-only RS decoding in both AWGN and narrowband interference when the signal is transmitted over a slow, flat Nakagami fading channel was investigated. To improve the performance in terms of probability of symbol error, two modified systems were also proposed and evaluated. The first system uses EED in place of errors-only RS decoding, while the second system employs a new 32-chip CCSK sequence instead of the 32-chip CCSK sequence chosen for JTIDS. Several novel contributions and major findings that result from the analysis of this dissertation are summarized below.
To the best of the author’s knowledge, the performance analysis and simulation of CCSK shown in Chapter IV is a novel contribution of this dissertation. Even though [11] was the first to publish an analysis of CCSK performance, the analysis is unsound due to the overly optimistic assumption that the cross-correlation values of CCSK symbols are statistically independent. In Chapter IV, the cross-correlation properties of CCSK are first formulated, and then an analytic upper bound on the probability of symbol error of CCSK in AWGN is derived for the 32-chip CCSK sequence chosen for JTIDS. The analytic upper bound is shown to be a tight upper bound by comparing the analytic results with two different Monte Carlo simulations. Based on two totally different approaches, the two Monte Carlo simulations yield a virtually identical result, which in turn is very close to the analytic result.
In Chapter V, the performance analysis of a JTIDS/Link-16 type waveform for both the single- and the double-pulse structure with errors-only RS decoding in both AWGN and narrow-band interference when the signal is transmitted over a slow, flat Nakagami fading channel is another novel contribution of this dissertation. Several major findings can be summarized. First, the double-pulse structure outperforms the single- pulse structure in most cases except when both PNI is present with smallρ1 (such as
0.1
performance for the double-pulse structure tends to be poorer than that of the single-pulse structure since the double-pulse structure is more likely to have at least one pulse jammed. Second, for both the single- and the double-pulse structure in both AWGN and narrowband interference (without fading), the value of ρ1 that maximizes the probability of symbol error decreases as Eb' N increases; that is, barrage noise interference (I ρ1= ) 1
has the most effect in degrading performance when Eb' N is relatively small, while PNI I
with smaller ρ1 (such as ρ1=0.1) causes the greatest degradation when Eb' N is I
relatively large. This is consistent with our intuition that, for strong signals, the jammer power must be large during a symbol in order to make symbol error likely. Third, when a JTIDS/Link-16-type waveform transmitted over a slow, flat Nakagami fading channel in the presence of both AWGN and PNI, the probability of symbol error for the single-pulse structure increases as m decreases for a fixed value of ρ1 and Eb' N . This is consistent 0
with our intuition that the single-pulse structure is less robust and therefore suffers more as fading worsens. Lastly, when the signal is transmitted over a slow, flat Nakagami fading channel and subjected to both AWGN and PNI when PSI is assumed, the double- pulse structure with PSI outperforms the single-pulse structure by a greater margin for smaller m when Eb' N is fixed. Perfect side information (PSI) is not realistic but gives 0
us a benchmark against which to measure receivers that have imperfect or no side information.
In Section A of Chapter VI, the performance analysis of a JTIDS/Link-16 type waveform for both the single- and the double-pulse structure with EED in both AWGN and narrow-band interference when the signal is transmitted over a slow, flat Nakagami fading channel is another novel contribution of this dissertation. Two major findings are summarized. First, EED outperforms errors-only RS decoding in all cases, whether the channel is fading or not and whether the narrowband interference is present or not.
Second, when ρ1 is small and Eb' N is large, with EED, the performance of a 0
JTIDS/Link-16 type waveform is significantly improved (more than 5 dB is observed for the single-pulse structure) as compared to errors-only RS decoding, whether the channel is fading or not.
In Section B of Chapter VI, the probability of symbol error for CCSK in AWGN was investigated based on a new 32-chip CCSK sequence obtained from a search algorithm. This new 32-chip CCSK sequence has a smaller maximum off-peak cross- correlation value (H =0 instead of H = ) and allows for seven chip errors instead of 4
six chip errors in the received sequence without making a symbol error. This new CCSK sequence is the fourth novel contribution of this dissertation. The results show that the probability of symbol error obtained for the new 32-chip CCSK sequence is only slightly smaller than that obtained with the 32-chip CCSK sequence chosen for JTIDS. There is an appreciable improvement in performance for an extremely small probability of symbol error P , but for S PS ≈0.01 as required for JTIDS, the difference is negligible.