Aiming at the threat of anti-aircraft missile faced by helicopter, the mathematical simulation models of helicopter, typical infrared missile and point-source infrared decoy were established. The whole process of jamming missile by helicopter launching decoy was simulated and deduced. According to the simulation experimental data, the impact of time, angle, quantity and interval of launching decoy on jamming effect was analyzed. Finally, the strategy of launching decoy under typical conditions was proposed.
Research on characteristics of atmospheric communication link becomes a subject of current interest, and often mainly
focuses on some fading parameters including the probability of fade, the mean fade number and the mean fade time. The
contribution of false alarm to bit error rate has been considered, however, the temporal characteristic is rarely mentioned.,
To make up the deficiency, parameters integrating the influence of false alarm and fading were defined. On one hand, the
laser communication link were modeled for Gamma-Gamma distribution of irradiance fluctuation subjected to weak
atmospheric turbulence. Accordingly the mathematical expressions of these parameters were deduced. On the other hand,
characteristic of the parameters were obtained by numerical simulation with various channel environment parameters,
such as mean signal-to-noise ratio (SNR), zenith angle and detection threshold. Compared with other researches on fade
characteristic, some different conclusions can be drawn from simulation results. With the same SNR and zenith angle,
there is an optimum value of detection threshold corresponding to the minimum mean error number, which deviates
obviously from that obtained according to the minimum error probability. Either increasing SNR or decreasing zenith
angle can reduce mean error number and the optimum threshold. Different from mean error number, mean error time is
slightly influenced with channel environment parameters and constant at the order of milliseconds.
KEYWORDS: Systems modeling, Free space optics, Mathematical modeling, Telecommunications, Computer simulations, Signal to noise ratio, Free space optical communications, Numerical simulations, Software, Device simulation
Gamma-gamma distribution model was widely used in numerical simulations of the free-space optical communication
system. The simulations are often interrupted by numerical overflow exception due to excessive parameters. Based on
former researches, two modified models are presented using mathematical calculation software and computer program. By means of substitution and recurrence, factors of the original model are transformed into corresponding logarithmic formats, and potential overflow in calculation is eliminated. By numerical verification, the practicability and accuracy of the modified models are proved and the advantages and disadvantages are listed. The proper model should be selected according to practical conditions. The two models are also applicable to other numerical simulations based on gamma gamma distribution such as outrage probability and mean fade time of the free-space optical communication.
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