LoRa-Based Mobile Localization System

The node location has been regarded as one of the most important pieces of information to many novel applications of Internet of Things (IoT) in recent years. Typically, IoT nodes are always resource-constrained in terms of battery capacity, manufacturing cost, and computing ability. Thus, costly and energy-hungry localization techniques fall short for those applications. In this chapter, we present iLoc, a low-cost, low-power, and wide-area mobile localization system for IoT applications. iLoc is built on the emerging LoRa technologies and overcomes most disadvantages of the local localization techniques. Central to iLoc is a mobile anchor comprised of a simplified gateway and a commercial smartphone. To locate an IoT target node, the mobile anchor moves in a scheduled way, during which the gateway receives its locations from the smartphone and measures the time of flight (ToF) from the target node as well. The measurements are jointly optimized via fusing the RSSI and ToF in the ranging. Meanwhile, the inertial measurement unit, the GPS receiver, and the magnetometer are also fused in the anchor location estimation. We further design an iterative localization algorithm by judiciously deciding the locations of the anchor in an optimized way that not only minimizes the localization error bound but also reduces the system power consumption. We prototype the gateway and IoT node that cost less than 10 and 5 dollars, respectively. The extensive experiments demonstrate that iLoc achieves a mean localization error of 1.19 m and the power consumption is less than 1.06 mAh in an open outdoor environment.