Abstract-The invariance of wave equations in lossless media allows the Time Reversal (TR) technique to spatio-temporally refocus back-propagated signals in a given ultrawideband imaging scenario. However, the existence of dispersion and loss in the propagation medium breaks this invariance and the resultant TR focusing exhibits frequency and propagation duration dependent degradation. We propose an algorithm based on the continuous wavelet transform that tackles this degradation to improve focusing resolution under such conditions. The developed algorithm has been successfully applied to the scenario for localization of lung cancer.
Abstract-In microwave imaging applications, propagating signals undergo additional attenuation in dispersive and lossy media when compared to non-dispersive and lossless media. In this paper, we introduce a threshold approach and Short-Time Fourier transform (STFT) based inverse filters to compensate for such additional attenuation in time reversal (TR) based imaging algorithms. The method introduced here is utilized to reduce the unwanted noise amplification in the received signals during the compensation stage. Additionally, optimum settings for window type and length in the STFT method are obtained through a scanning operation in the propagation medium. Different window types and lengths are studied to achieve best focusing resolution in TR applications. While utilizing large number of windows with short spatial lengths provides improved TR focusing performance, it also increases the overall cost and complexity of the imaging system. The threshold method introduced here achieves improved TR focusing performance without increasing the cost by utilizing a lower number of inverse filters.
The internet is considered to be the most advanced technology today and a gateway to modern communication and the sharing of information, products, services, and technology. Nowadays, users want to be able to access anywhere and anytime several services and applications, which is increasing data traffic and triggering a mobile data explosion. Iraq has major problems in increasing the growth and use of the internet and changing the standard method of communication. This is a big challenge, however, since there are several variables that characterize this phase of transformation. In this paper, the problems, vision, and solutions are presented in details. This study aims to clarify the factors of internet use in Iraq by the use of an acceptable approach and by suggesting new solutions for all the presented problems. This work also, clarify the expected traffic and the mechanism to transform the traffic between local ISP’s networks (AS) internet exchange points.
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