Investigation of Wireless Channel Asymmetry in Indoor Environments

Asymmetry is unquestionably an important characteristic of the wireless propagation channel, which needs to be accurately modeled for wireless and mobile communications, 5G networks, and associated applications such as indoor/outdoor localization. This paper reports on the potential causes of propagation asymmetry. Practical channel measurements at Khalifa University premises proved that wireless channels are asymmetric in realistic scenarios. Some important conclusions and recommendation are also summarized.Comment: Accepted in IEEE International Symposium on Antennas and Propagation (APS17), San Diego, California, 9-14 Jul. 2017. arXiv admin note: substantial text overlap with arXiv:1704.0687

Exploring Symmetry in Wireless Propagation Channels

Wireless communications literature is very rich with empirical studies and measurement campaigns that study the nature of the wireless propagation channel. However, despite their undoubted usefulness, many of these studies have omitted a fundamental yet key feature of the physical signal propagation, that is, wireless propagation asymmetry. This feature does not agree with the electromagnetic reciprocity theorem, and the many research papers that adopt wireless channel symmetry, and hence rendering their modeling, unexpectedly, inaccurate. Besides, asymmetry is unquestionably an important characteristic of wireless channels, which needs to be accurately characterized for vehicular/mobile communications, 5G networks, and associated applications such as indoor/outdoor localization. This paper presents a modest and a preliminary study that reports potential causes of propagation asymmetry. Measurements conducted on Khalifa University campus in UAE show that wireless channels are symmetric in the absence of symmetry impairments. Therefore, care should be taken when considering some practical wireless propagation scenarios. Key conclusions and recommendation are summarized. We believe that this study will be inspiring for the academic community and will trigger further investigations within wireless propagation assumptions.Comment: Accepted in IEEE European Conference on Networks and Communications (EuCNC17), Oulu, Finland,12-15 Jun. 201

Waypoint Planning for Autonomous Aerial Inspection of Large-Scale Solar Farms

Solar energy is seen as a sustainable and nondepletable source of energy supply. Worldwide, large-scale solar power infrastructure is being installed every day. Such structures can suffer from many faults and defects that degrade their energy output during their operational life. Detecting such faults and defects requires regular inspection over physically large and distributed solar infrastructure. On-site manual human inspection tends to be impractical, risky and costly. As such, replacing humans with autonomous robotic aerial inspection systems has great potential. In this work, we propose an unmanned aerial vehicle (UAV) waypoint generation system that is specifically designed for aerial inspection of solar infrastructure. Our system takes into consideration the physical structure and the dynamic nature of sun-tracking solar modules and generates waypoints with the right camera viewing pose and drone orientation. Statistical methods are used to generate a randomly selected set of modules as a representation of the entire solar farm. The set is guaranteed to satisfy a user-defined confidence level and margin of error requirements. A path is generated to visit selected modules in an optimal way by deploying the traveling-salesman shortest path algorithm, allowing the vehicle to maximize battery use. Illustrative flights and preliminary inspection results are presented and discussed.This research was supported by the Australian Renewable Energy Agency (ARENA), through Grant G00853 “A robotic vision system for rapid inspection and evaluation of solar plant infrastructure”