Ensuring Line-of-Sight Condition for Accurate Positioning and Sensing Over RF/OWC Networks

Accurate positioning and precise sensing are essential features for the widespread adoption of beyond 5G (6G) applications, including augmented reality, digital twinning, and industrial automation. However, most popular positioning and sensing techniques, which are based on angle-of-arrival/departure and time(-difference)-of-arrival measurements, assume Line-of-Sight (LoS) propagation and are prone to systematic errors when this condition is not met. To enhance the accuracy of these systems when using proximity, triangulation, or multilateration principles, this paper proposes to deploy reference nodes ensuring LoS conditions to one, two, or three reference nodes depending on the used approach and regardless of the position of the target object in the service area. For this, the indoor service area of the radio/optical wireless network is modeled as a graph, where nodes represent polygons that partition the floor plan. This graph is then divided into the minimum number of cliques, which determine the optimal number and the placement of reference nodes required to guarantee LoS coverage in the whole service area. To meet additional accuracy and sensing requirements, the proposed algorithms include two configurable parameters: a minimum distance and a minimum angle between reference nodes. The resulting framework enables efficient reference node deployment, supporting robust, reliable, and accurate indoor positioning and sensing for next-generation wireless applications.