Abstract
In recent years, there has been a worldwide boom in mountain climbing because the activity has become easier due to the higher functionality and lighter weight of mountaineering equipment. Along with this boom, mountain distress accidents have also increased. In the event of a disaster, effective communication with search and rescue victims is important. Mobile communication in the mountains, however, is limited because radio waves from the base station may be blocked due to topographic features, vegetation in the surrounding environment, etc. Therefore, a mobile ad hoc network (MANET) could be a useful means of communication. Recently, unmanned aerial vehicles (UAVs, e.g., drones and balloons) have become smaller and more sophisticated, with the result that UAVs could now be available as relay devices for MANETs. However, the effectiveness of MANETs in combination with UAVs in mountainous areas has not yet been clarified and no construction method has yet been established. Furthermore, in the case of mountain communication simulations, elevation differences of several thousand meters on mountain trails and radio wave propagation losses peculiar to mountains must be considered, as these conditions differ from those of common MANET simulations. Therefore, in this study, we simulated 3-dimensional MANET with UAVs using the Hotaka mountain range as an example case. Our radio wave propagation model includes the 2-ray ground reflection model, the double knife-edge diffraction loss model, and the standard model of vegetation attenuation. We simulated communication between a climber and a basecamp or hut on the mountain by MANET relayed by drones and a balloon in four scenarios, finding that the UAV expands the communicable area substantially in the mountains. We also examined the influence of rainfall and snow on mountain MANET communication.
Highlights
There has been a worldwide boom in mountain climbing, because it has become easier for people to engage in this activity due to the higher functionality and lighter weight of mountaineering equipment
We first constructed a radio wave propagation model for a mountainous area by combining the 2-ray ground reflection model, the double knife-edge diffraction loss, and the standard model of vegetation attenuation. 3-D mobile ad hoc network (MANET) simulations were performed for a case in the Hotaka mountain range
The simulation results of MANET communication using unmanned aerial vehicles (UAVs) as relay devices in 4 scenarios showed that UAV expands the communication area in the mountain substantially
Summary
There has been a worldwide boom in mountain climbing, because it has become easier for people to engage in this activity due to the higher functionality and lighter weight of mountaineering equipment. If it were always possible to use MANET to secure communications to mountain trails and all huts like as the mountaineering base, these could be used for quick contact in the case of an emergency. We focused on MANET with only climbers' mobile terminals and showed the effect of the number of climbers on radio wave propagation loss, packet delivery ratio (PDR), throughput, and energy consumption by simulation. At Abuta in Hokkaido, an experiment was conducted to search for terminals embedded in snow in the mountains by flying wireless relay stations in the air [9] From such examples, we theoretically analyzed that in cases of mountain distress, UAVs could be used for rescue by relaying messages to other terminals and mountain huts, using the UAV as an aerial radio relay station. We examined the influence of rainfall and snow on the mountain MANET communication
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