The aim of the thesis is to create a radio propagation channel model for communication between unmanned aerial vehicles (UAVs) during emergency scenarios. The propagation channel model is designed at 2.4 GHz based on ray-tracing simulations performed over the Sendai City terrain, Japan and over the sea.During the post-disaster scenario with the loss of communication infrastructure and loss of power, it is essential to provide a means of communication to the people in the affected area. One of the possible solutions is to provide for a relay link from a functioning base station to the affected area using unmanned aerial vehicles. The relay link is established for every 3 km such that each UAV is circling with a radius of about 100 m over a given area. To establish such relay links, characterization of the radio propagation channel is essential in designing the communication systems.The path loss at the desired frequency, effect of various multipath components occurring based on the terrain, small scale fading, the effect of Doppler shift due to the movement of the UAVs and the delay dispersion are characterized. The excess delay and coherence bandwidth are compared to the guard interval and sub-carrier spacing of IEEE 802.11g/n and 802.16 WiMAX standards. The channel modeling is performed for different altitudes of UAV operation (150 m and 500 m) for both horizontal and vertical polarizations of transmitting and receiving fields. The guard interval of 802.16 WiMAX systems is sufficient to prevent inter-symbol interference for all UAV propagation scenarios. Frequency at fading occurs for each Orthogonal Frequency Division Multiplexing (OFDM) sub-carrier and frequency selective fading occurs over the entire channel bandwidth. In case of 802.11g/n systems, the guard interval is not sufficient for all propagation scenarios and at fading for OFDM sub-carriers occurs at UAV altitudes of 150 m for typical cases. The effect of Doppler shift is detrimental for 802.16 OFDM systems.
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