Extraction of a simplified model for street corner loss in microcells from ray-tracing simulation

摘要

Microcellular propagation follows different laws than the well-known traditional models, and it is strongly affected by the street and building layout. A well-known and evident phenomenon is the street-corner effect, which consists of a sudden decrease of received field strength as soon as a mobile turns into a side street. Predictions based on ray optics, which can be applied to this case, are accurate but time-consuming. Hence, they cannot be used extensively, e.g., to plan a microcellular network in a city. In many cases, a simplified model would be suitable to give account of field strength behaviour in the transition region between line-of-sight (LOS) and non-line-of-sight (NLOS) propagation and could be used as a basis of a complete microcellular field prediction tool. Following this approach, we propose a simple parametrical model for propagation around a corner: the parameter values have been tuned to fit the considered environment. The tuning process can be accomplished by means of either measurements or simulations. In order for the model to be as general as possible, it needs a large amount of reference data: for this reason, we used simulations performed with a validated ray-tracing software tool in a variety of situations. These simulations allow one to derive values of the various parameters as functions of the local topology (e.g., street width, distance from the street corner, etc.). The model thus tuned is compared with measurements, showing a good agreement between estimated and measured path loss. This model is shown to behave satisfactorily when compared with measurements, and it is suitable to characterise the street-corner effect in a variety of cases. Finally, this model, along with a simple model for LOS propagation (double slope, with a breakpoint caused by reflections on the ground and on building walls), is aimed at building a complete, modular prediction tool for the microcellular environment.