Outdoor coverage & capacity estimation in small cells with a 3D ray tracing model

A computationally efficient ray tracing model is developed and implemented for three-dimensional (3D) coverage analysis and predictions, as well as for MIMO capacity estimation within small urban cells of cellular mobile networks, where the radio base station (RBS) antenna height can be below the average roof-top level. Field strength calculations involve reflected, diffracted, doubly-reflected and reflected-diffracted rays, as well as higher order terms, in addition to a direct field in free space, appropriately attenuated through buildings in shadowed regions. The field transfer functions obtained from field and EMF calculations can be employed to assess improvement in diversity gain and capacity improvement in systems employing MIMO spatial multiplexing, particularly in low coverage areas. The 3D propagation geometry is modelled by a triangular mesh derived from the transformation and processing of high resolution digital LIDAR data. The computations are validated with comparisons against mobile measurements at 2.4GHz along different routes within selected site topographies.