Indoor Ray Tracing evaluation of enhanced High Frequency communications using Directional Antennas at the Basestation and Space Diversity at the Terminal

This paper analyses field strength coverage predictions for high frequency indoor communications at 17 GHz using directional antennas at the basestation and 2 branch spaced antenna diversity at the terminal. Detailed propagation information is generated for a typical two-dimensional indoor environment using a ray-tracing propagation tool developed at the University of Bath. As a performance benchmark, initial field strength predictions are generated for omni-directional basestation and terminal antennas. Downlink performance is enhanced by the use of 2 branch spaced antenna diversity at the terminal. Factors such as antenna spacing and the choice of diversity combining algorithm are considered. At the basestation, a novel 3 branch phased array beam pattern diversity system is compared with an ideal six branch sectorised antenna. For each configuration, detailed propagation studies are performed to determine the relative (compared to omni-directional antennas) coverage improvement over the entire environment. Results indicate that the use of spaced diversity at the terminal can improve the expected coverage by as much as 10.7dB. Beam pattern and sector switching arrangements at the basestation result in a 7.2-10.4dB improvement. The most impressive gains were observed using directional antennas at the basestation and spaced antenna diversity at the terminal. Gains of 17.2dB and 19.4dB were observed for 3 (beam pattern) and 6 (sectorised) branch systems respectively at the basestation.