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As more GPS receivers are used in navigation systems to obtain precise position information, concerns about GPS jamming vulnerability are growing. The most effective way to overcome this jamming weakness is to use an array antenna that consists of many antenna elements and RF channels. However, an array antenna causes two side effects: a nulling pattern and a time delay error in positioning performance. We analyze the effects on the positioning accuracy of a GPS receiver equipped with a precise time-delay-compensated array antenna to overcome jamming situations. We present an analysis of the theoretical gain pattern of a 4-array antenna and experimental verification of GPS signal attenuation by obtaining a satellite's CN0 value in the near jamming direction. We show the results of the time delay measurement in the array antenna system using two independent methods and present a new baseband linear interpolation algorithm that is evaluated as having a 0.95 ns RMS error after compensating for the invariant RF time delays. Finally, using the realistic gain pattern and time-delay-compensation results, we assess the position error of the GPS receiver and show the possibility of attaining a precise navigation system in jamming environments. [ABSTRACT FROM AUTHOR]

We study the dynamics of cyclic competing mobile five species on spatially extended systems originated from asymmetric initial populations and investigate the basins for the three possible asymptotic states, coexistence of all species, existences of only two independent species, and the extinction. Through extensive numerical simulations, we find a prosperous dependence on initial conditions for species biodiversity. In particular, for fixed given equal densities of two relevant species, we find that only five basins for the existence of two independent species exist and they are spirally entangled for high mobility. A basin of coexistence is outbreaking when the mobility parameter is decreased through a critical value and surrounded by the other five basins. For fixed given equal densities of two independent species, however, we find that basin structures are not spirally entangled. Further, final states of two independent species are totally different. For all possible considerations, the extinction state is not witnessed which is verified by the survival probability. To provide the validity of basin structures from lattice simulations, we analyze the system in mean-field manners. Consequently, results on macroscopic levels are matched to direct lattice simulations for high mobility regimes. These findings provide a good insight into the fundamental issue of the biodiversity among many species than previous cases. [ABSTRACT FROM AUTHOR]

This study investigated the anti-spoofing capability of a Commercial-Off-The-Shelf (COTS) Global Positioning System (GPS) receiver and proposes a spoofing detection method with minimum user complexity. A spoofing test environment with a GPS simulator was developed to test a conventional GPS receiver with an in-line radio frequency (RF) signal. The tests on a geodetic-grade receiver revealed a vulnerability in the COTS GPS receiver against spoofing attacks. Receiver Autonomous Integrity Monitoring (RAIM) was not capable of handling a spoofing attack sufficiently, but could manage a low-level attack. Thus, a spoofing detection method based on the simulation results is proposed as a feasibility check. [ABSTRACT FROM AUTHOR]

We study the spatial rock-paper-scissors game with adaptive mutation which may describe imitation behaviors of two competing species. We introduce an adaptive mutation where one of the species may tend to mutate the other by implementing a fundamental mutation mechanism with respect to local fitness of two competing species by comparing payoffs of its origin with the updated one when it mutates to the other. By means of Monte Carlo simulations, we show that species coexistence can be promoted by the intensification of adaptive mutation at certain high mobility regimes which lead the extinction traditionally, even if extremely high mobility results in the extinction as well. In addition, by measuring the extinction probability for extensive scales of spatial domains, we also found that the critical mobility to lead extinction is shifted according to the rate of adaptive mutation. Ultimately, our findings may indicate that adaptive mutation can be a significant role to maintain coexistence for moderately strong individuals' mobilities. [ABSTRACT FROM AUTHOR]