An Ultra-Wideband (UWB) Ad Hoc Sensor Network for Real-time Indoor Localization of Emergency Responders

A localization system is a network of nodes, which is used by an unknown-location node to determine its physical location. The Global Navigation Satellite System, GNSS (HofmannWellenhof, 2008) is an example of a widely used outdoor localization system. However, outdoor localization systems perform poorly in indoor environments due to strong signal attenuation and reflection by building materials, and no line-of-sight propagation. Thus, Indoor Localization Systems (ILSs) are needed to provide similar localization inside buildings. ILSs have many potential applications in the commercial, military and public safety sectors. This chapter focuses on the public safety application. The considered ILS is used to track emergency responders, e.g. fire-fighters and policemen, who carry out search and rescue missions in the disaster zone such as building fires and collapsed tunnels. Such an ILS was first crystallized in the EUROPCOM (Emergency Ultra wideband RadiO for Positioning and COMmunications) project (Harmer, 2008; Harmer et al., 2008). The EUROPCOM system is an ad hoc sensor network which comprises a small number of base or reference nodes deployed outside surrounding a building, and the rest of the nodes are unknown-location nodes which are worn and deployed by emergency responders entering the hostile building. The unknown-location node is self-localized by collectively determining its position relative to base nodes. Additionally, the unknown-location node is also allowed to determine its position relative to neighboring unknown-location nodes. This greatly enhances the accuracy and robustness of the ILS. It is fully autonomous and can be rapidly deployed with little human intervention. Ultra-WideBand (UWB) is the radio transmission technology used by the EUROPCOM system. A UWB signal is defined to be one that possesses an absolute bandwidth of at least 500 MHz or a fractional bandwidth larger than 20% of the center frequency. Currently, several UWB technologies exist, namely direct sequence UWB, impulse radio UWB, Multi-