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Wireless power transfer up to the 5W power level has become a recent trend for mobile phones, which can be classified into two types: inductive type and resonant type. Inductive type usually has higher efficiency but requires short distance and precise alignment between the transmitter and receiver. From the viewpoint of convenience, resonant type has much better freedom from distance and alignment...
Cognitive radio networks can be designed to manage the radio spectrum more efficiently by utilizing the spectrum holes in primary user's licensed frequency bands. The currently available unlicensed spectrum is reaching its limit and various demands for applications and data rates in wireless communications requires additional spectrum which imposes limits on spectrum access. These requirements demand...
Wireless devices can communicate between each other without existing infrastructure in mobile Ad-hoc network. Ad hoc networks can be used under difficult conditions, where it is difficult to construct infrastructures, such as shadowing areas, disaster areas, war area, and so on. In order to support to considerable and various wireless services, more spectrum resources are needed. However, efficient...
In this paper, we propose a efficient primary user detection method in cognitive radio (CR). We adopt a delay diversity receiver for solving problems of the conventional spectrum detector utilizing multiple antennas, which are the increase in hardware complexity and cost. From simulation results, it is demonstrated that the primary user detector with delay diversity receiver has almost half complexity...
According to dramatic increase of wireless communication demand, more spectrum resources are needed to support considerable and various wireless services. However, limited spectrum resources are regulatory assigned to licensed user and no interference needs to occur from unlicensed user to licensed user. In this paper, we propose efficient decision rule in order to get better chance to detect the...
Cognitive radio (CR), which is proposed as a technology that utilizes the frequency resources effectively, has studied to relive scarcity of the frequency resources. CR provides opportunistically under-utilize licensed frequency to the secondary user. Spectrum sensing is the most important technology to detect primary user. However, in the wireless channels, according to the effect of fading and shadowing...
Geospatial research interests in emergency responses in micro-scale environments have been increased after 9/11. The application requires to define optimal paths in emergency situation, to support evacuees and rescuers. The optimal path defined in this study is used to guide rescuers. So, the path is from entrances to the disaster site (room), not from rooms to entrances in the building. In this study,...
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