Directional beacon based positioning system using RF signals

We present the implementation of a directional beacon based positioning algorithm using radio frequency signals. This algorithm allows each mobile node to compute its position with respect to a set of reference nodes which are equipped with rotational directional antenna. The system implementation is based on the GNU Radio software platform with the Universal Software Radio Peripheral as the hardware component. Even though the technique needs some modification at the reference nodes in the form of a rotational directional antenna, we show that the mobile nodes do not need hardware modifications. We use maximum likelihood based amplitude estimation and least squares based line-of-sight time-delay estimation, to account for the presence of multipath components in the received signal. These techniques enable a more accurate estimation of the bearing of the mobile node with respect to each of the reference nodes. The proposed algorithm does not require any synchronization between the reference nodes and the mobile node. However, the reference nodes are assumed to be synchronized. We demonstrate the ability to obtain mobile node position estimates with sub-meter accuracy.