Predicting RF coverage in large environments using ray-beam tracing and partitioning tree represented geometry

We present a system for efficient prediction of RF power distribution in site specific environments using a variation of ray tracing, which we calledray-beam tracing. The simulation results were validated against measured data for a number of large environments with good statistical correlation between the two. We represent geometric environments in full 3D which facilitates rooftop deployment along with any other 3D locations. We use broadcast mode of propagation, whose cost increases more slowly with an increase in the number of receiving bins. The scheme works well both for indoor and outdoor environments. Simple ray tracing has a major disadvantage in that adjacent rays from a transmitter diverge greatly after large path lengths due to multiple reflections, such that arbitrarily large geometric entities could fall in between these rays. This results in asampling error problem. The error increases arbitrarily as the incident angle approaches 90°. The problem is addressed by introducing the notion of beams while retaining the simplicity of rays for intersection calculations. A beam is adaptively split into child beams to limit the error. A major challenge for computational efficiency is to quickly determine the closest ray-surface intersection. We achieve this by using partitioning trees which allows representation of arbitrarily oriented polygonal environments. We also use partitioning trees for our full 3D interactive visualization along with interactive placement of transmitters, receiving bins, and querying of power.