A heterogeneous RSSI-based localization system for indoor and outdoor sports activities

Localization and tracking of players is crucial for monitoring both indoor and outdoor sports activities. The effects of the environment pose a major challenge for an accurate position estimation. In this paper, we present a novel solution based on the received signal strength indication (RSSI) feature provided by off-the-shelf wireless networks. Trilateration is used for estimating the position of targets with a RSSI to distance mapping function based on the path-loss shadowing propagation model. Key to our system is the real-time collection of RSSI measurements for which we designed and implemented a new, channel-hopping, TDMA-based protocol, which coordinates frame transmissions among nodes. A further innovative aspect of our solution is that the nodes are heterogeneous, using Waspmote and IRIS nodes as well as XBee modules. The latter enables a signicant boost in the transmit power, which in turn improves the resolution of the RSSI to distance estimates. Additionally, we address the challenges of fast deployment and testing by using a semi-automatic calibration mechanism for adjusting the distances estimated from RSSI measurements. Our experiments, conducted both indoors and outdoors, show that sub-meter accuracy can be achieved by combing a high transmit power, multiple channels, together with multiple antennas.