Indoor channel measurements and capacity evaluation with directional antennas

Recently UWB beamforming attracts significant research attention to obtain spatial gain in the form of antenna array. It is commonly believed that directional antenna based communication could improve the system performance. In order to further make clear the relationship between system performance and the antenna radiation pattern, UWB indoor channels extracted from practical measurements with omnidirectional antenna are combined with circular horn antenna to evaluate the channel capacity. In the line of sight (LOS) environments, the channel capacity increases with the antenna beamwidth decreasing and is always larger than that of omnidirectional antenna. However in the non-line of sight (NLOS) environments, the capacity is not always better with directional antenna. And the change consistency between the capacity and the antenna beamwidth disappears. This reminds us that when antenna beamforming is used to obtain array gain, the beamwidth should be carefully designed to obtain optimal performance, especially in the NLOS environments.