Wi-Fi frequency selection concept for effective coverage in collapsed structures

Currently, there is a growing tendency of research on leveraging Wi-Fi signals as sensors for various IoT applications. We observe that most studies deal with the behavior of wireless signals for regular structures in indoor environments. But there is a lack of investigation on Wi-Fi signals behavior for a complex structure like collapsed buildings. This study investigates the possible Wi-Fi signal penetration for collapsed structures. We consider two objectives of this study. Firstly, there is a need to figure out the most common collapsed environments and then to select the best frequency selection concept from available license-free ISM bands to have better coverage. We achieve the first goal through a field survey of an earthquake hit area followed by a debris model constituent of brick and concrete materials. To address the second objective, we have employed two methods for selection of the best frequency. Firstly, we use theoretical bijective soft set approach to select the best available concept and then a modified path loss termed as PL-Collapsed has been introduced to estimate the losses encountered to the wireless signal under debris while providing the best possible coverage with available ISM bands for Wi-Fi. We then compare signal coverage for Wi-Fi bands with each other to finally select the possibly best frequency. Simulation results show that newly introduced Wi-Fi Halow operating at sub 1GHz has relatively better coverage which is also cross-verified by the theoretical bijective soft-set approach. This study triggers the application of wireless signals under collapsed structures where there is a need to rescue the lives. Furthermore, this also prompts new dimensions in IoTs hence emphasizing more ubiquitous systems. (C) 2019 Elsevier B.V. All rights reserved.