Yazar "Mohammed, Ahmed Hossam" seçeneğine göre listele

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    Fm channel model development and its emulator
    (Institute of Electrical and Electronics Engineers Inc., 2018) Mohammed, Ahmed Hossam; Özdemir, Mehmet Kemal
    With the widespread availability of Internet, voice only broadcast in the FM Band will soon be abandoned as Internet Radio can provide the same content with no boundaries. The available band can then be exploited for bi-directional wireless services. However, before we can realize this transformation, it is crucial to lay down the channel characteristics of the FM Band to better anticipate its affect on new wireless services. As a starting point, in this study we develop a FM Band channel model for dense Hilly Terrain Regions (HTRs) by the concept of directional channel modelling. The proposed model is verified by exploiting existing channel measurements for the bands near the FM Band and simulations via ray tracing by Wireless Insite tool. Finally, a hardware implementation, capable of emulating the different wireless channel clusters for the FM Band, is introduced. The analysis, simulations, and measurements through the emulator show that the FM Band channel model proposed can indeed represent a typical FM Band channel. Thus, the performance of future wireless systems in the FM Band can be better assessed.
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    Rf circuit implementation of a real-time frequency spread emulator
    (IEEE-Institute of Electrical and Electronics Engineers Inc, 2018) Karabacak, Murat; Mohammed, Ahmed Hossam; Özdemir, Mehmet Kemal; Arslan, Hüseyin
    Despite their reliability, on-site measurements are time-consuming and costly actions for the evaluation of new devices. Channel emulators are widely utilized measurement instruments to generate desired environmental channel effects in laboratory environments. Within these instruments, baseband emulators are expensive, and reverberation chambers provide limited control of the channel. However, radio-frequency (RF) circuit implementation of channel emulators provides an affordable and easy tool to test performances of new systems and methods under different channel effects. In this paper, a new RF domain Doppler emulator, which is compact and easy to control, is presented for measuring signal characteristics under frequency dispersive channel conditions. The circuit has been implemented using variable attenuators, switches, and power splitters to emulate the Doppler spread of air-ground channels, and the performance is evaluated through measurements. It is observed that the emulator indeed generates the desired Doppler model close enough to replicate environmental channels for mobile applications in laboratory environments.