RF Channel Performance Prediction
6.1 Advanced RF Propagation Models
Propagation models have evolved over the years as wireless deployments and the density increased, but not enough to be used for 4G deployments. The complexity of the wireless markets requires a new breed of propagation models that will provide precise and consistent results at a pixel basis. These models not only have to work across multiple quality terrain databases, from low, canopy resolutions to high, building-level resolutions but also must be able to simultaneously predict signal levels outdoors and indoors. This new breed of RF propagation models addresses many of the weak points in empirical and physical models. These new models can be considered as hybrids and their main characteristics are described in the following sections.
6.1.1 Terrain Databases
Terrain databases are defined by topography and morphology layers. Topography represents the terrain altitude, whereas morphology, or clutter, represents anything that is above ground (e.g. vegetation, trees, and buildings). These databases store raster data defined by pixels of a certain resolution.
Terrain databases resolution is expressed in arc seconds or meters and defines the size of the smaller pixel (rectangle) that carries information. Arc seconds representation uses variable size pixels, which get narrower at higher latitudes, and are well suited to represent a spherical surface. Meter representation uses square pixels, but has a limited ...