BonnSens: A Mesh-based Command and Control Sensing System for Public Safety Scenarios

Abstract

In public safety scenarios, different kind of sensor information, e.g. GPS, vital, and environmental data, needs to be transported from mobile units over a wireless network to a centralized command point in order to increase situational awareness. Hence, for command and control robust communication networks are required. These networks must be reliable even when all infrastructure has been destroyed. Wireless multi-hop networks meet the requirements of spontaneous deployment, independence of any kind of existing infrastructure, and robustness in the sense of self-organization and self-healing by their very definition. However, concerning public safety requirements, real-world testbeds and deployments lack significant aspects: No spontaneous deployment, no or at least no mobility typical for public safety, and no typical applications and traffic. Due to these characteristics, developing algorithms and protocols for these scenarios as well as deploying public safety networks is a huge challenge. To overcome this challenge, we developed BonnSens a prototype based on commercial off the-shelf (COTS) hardware. The prototype comprises typical public safety applications and is spontaneously deployable. Furthermore, this prototype enabled us to perform on-site evaluations with real public safety end-users in disaster area maneuvers.The BonnSens architecture consists of a distributed sensor and collector application for the transmission of sensor data over a wireless multi-hop network based on IEEE 802.11. The sensing application supports the gathering of sensor information via modular extensible plugins, whereas the gathered data is processed and visualized subsequently by the collector on the server side. The BonnSens framework consists of two hardware components: (1) portable, lightweight sensing nodes and (2) fullyequipped collector nodes. For the sensing nodes, we have implemented a client sensing application for Android OS and use IEEE 802.11 capable smartphones with their integrated sensors. For the collector nodes, standard COTS laptops can be used. All nodes (lightweight and fully-equipped) are routers at the same time. However, to have a more robust network and to safe energy at the lightweight nodes, we add a mesh backbone with optional UMTS connection consisting of COTS mesh routers. We chose the reactive mesh-based On-Demand Multicast Routing Protocol (ODMRP) [2] for routing as it showed promising results in public safety specific simulative performance evaluations. Since the quality of wireless links in real deployments turned out to be extremely variable, unpredictable, and asymmetric, we take these characteristics into account by using a routing metric estimating the link quality based on the hello messages received in our implementation.To provide a common framework for the transport of sensor data and for basic functionality such as registering at a receiver, timestamping of sensor data, and synchronization of all nodes, we specified the Sensor Data Transmission and Management Protocol (STMP) [1], impleme...