The Use of Ray Tracing Models to Predict MIMO Performance in Urban Environments

Abstract

The ray tracing approximation was used to compute propagation channel characteristics in an urban setting and results were used to predict multiple input multiple output (MIMO) performance at 1.5 GHz. The computation used mobile radio parameters and provided the maximum theoretical MIMO capacity gain. Receiver positions were moved relative to a fixed transmitter within the urban area and MIMO performance was evaluated as a function of receiver position. A 2times2 MIMO system was used for simplicity and three propagation related parameters were varied to assess the behavior and capability of this method: MIMO antenna spacing, ground and building electric properties. Spatial averaging of the ray tracing solutions was required to obtain consistent results. The averaging was necessary due to the narrow bandwidth solutions associated with this technique, where results were sensitive to small changes in relative transmitter/receiver positions and computational parameters. Upon appropriate averaging, the ray tracing solutions yielded MIMO capacities that depended on antenna spacing and surface electrical properties in a consistent manner. For example, MIMO gains improved with increased antenna separation. Behavior such as key-holing, where RF energy propagates in an urban corridor, was observed. In those cases, MIMO gains were low