Emergency Response and Post-Disaster Recovery Using Smartphone-Based Applications

Introduction

The number of natural disasters, such as Tsunami, earthquake, flooding, bushfire, etc. and the destruction of lives and properties is increasing globally. The international disaster database suggests that in 2018, 315 natural disasters occurred across the world that resulted in 11,804 deaths while affecting a total of 68 million people and causing economic damage of US$131.7 billion (Natural disaster 2018, 2019). During the recent bushfire incident in Australia (2019-20), around 17 million hectares have burned, which is more than the size of South Korea and 33 people lost their lives including nine firefighters (Richards, Brew, & Smith, 2020). Approximately, 3000 homes have also been destroyed (Richards, Brew, & Smith, 2020). During a natural disaster, people often get trapped into damaged properties and need to be rescued within the first 72 hours, which is known as the golden relief time (Mezghani, Kortoc, Mitton, & Francesco, 2019). However, the destruction of electric lines and cellular networks during such natural disasters make it difficult to establish communication with the affected people, locate their positions, and rescue them (Lu, Cao, & La Porta, 2017; Mezghani, Kortoc, Mitton, & Francesco, 2019; Sciullo, Trotta, & Di Felice, 2020). The rescue workers need to know the exact position of the affected people, their current conditions, and the severity of the damage before making a well-informed rescue decision and conducting a rescue operation. On the other hand, emergency information diffusion is also important in these scenarios to inform the affected people about the upcoming warnings or provide them with rescue instructions. The destruction of powerline hampers the traditional medium of communication, such as TV and radios. The destruction of cellular towers can also impact the availability of the cellular network, which ultimately makes it difficult to broadcast information through mobile messaging or phone calls. The availability also suffers due to high demand during a disaster. In these scenarios, making contact between rescue workers and the survivors become challenging and crucial.

The advent of smart mobile devices equipped with short-range communication technologies, such as Wi-Fi and Bluetooth, has opened new possibilities to address the above-mentioned issues. Smart mobile devices, such as smartphones, tablets, and PDAs have become extremely popular among users worldwide. The number of smartphone users around the world is currently 3.5 billion, which is approximately 45% of the world’s population and it is expected that by 2021, the number of smartphone users will reach 3.8 billion (O'Dea, 2020). A similar trend is also observed for other smart mobile device usages. The short-range communication capability of these devices allows them to form a peer-to-peer type ad-hoc network among co-located devices to exchange messages, images, videos, and/or location information. The maximum distance for this type of communication between two devices can be 10m ~200m based on the underlying technology. In this case, Bluetooth offers a shorter range and consumes less energy while Wi-Fi does the opposite. However, it is possible to extend this range using multi-hop communication. Figure 1 shows the use of multi-hop communication in forming an ad-hoc network to share messages or contents including pictures, videos, or texts. In this case, the application installed in a source node (i.e., smart device user) is trying to send a message (can contain text, videos, or images) to a receiver node. Although an end-to-end communication path is shown in the figure for ease of presentation, such a persistent communication path is usually not available in an ad-hoc network due to node movement and intermitted connectivity. Therefore, the actual message delivery happens through multiple message-forwarding events that may occur at different timesteps rather than instantly. In such a network, a few devices play the role of a forwarder node who keeps carrying the message until they reach the destination or another suitable forwarder. This kind of message forwarding technique is called store-carry-and-forward message forwarding. Further details about this are discussed later in the routing module section. This type of communication is also referred to as opportunistic communication, and the path used for this communication is termed as an opportunistic communication path as demonstrated in Figure 1.