Propagation modeling of an L-shaped structure: What happened when its width shrank

Ray tracing method has conventionally played an important role in radio propagation modeling, which outputs an estimation of signal strength given certain input parameters. Being a time-honored method, ray tracing is expected to continue to play an important role in next generation propagation modeling. In this paper, we place our focus on a narrow L-shaped structure which oftentimes at first glance appeared simple, yet presents technical complexity that even commercial propagation tool might fail to yield accurate prediction results. The L-shaped structure under scrutiny has a very narrow width, which found its applications in a wide variety of scenarios, ranging from mining and tunnel activities, to speleology and spelunking exploration, and others. Our findings suggest that contrary to what is commonly perceived, in the non-line-of-sight (NLoS) section of the L-shaped structure, reflection turned out to be a very complex propagation mechanism when the width of the structure is very narrow. Instead, diffraction, which in many instances is ignored due to its mathematical complication, emerged as one alternative propagation mechanism that should be explored.