Direction of arrival of radio signals inside and outside buildings

In the design of UHF radio systems for mobile and personal communications the characteristics of the RF channel present problems. Scattering, diffraction, refraction and reflection by the structure of buildings leads to multipath propagation. This in turn leads to distortion of the signals transmitted over the radio channel. It is therefore of interest to investigate the sources of the multipath propagation. The paper reports measurements made at 870 MHz inside the Department of Electronic and Electrical Engineering building and around the campus at the University of Leeds. The measurement system uses a synthetic aperture phased array antenna to measure directions of arrival in azimuth and elevation. The directions an deduced using normal beamforming methods and the high resolution MUSIC method. The measurements show the effects of reflection, diffraction, and guiding of signals by the structure of the building. Signals are guided by corridors within the building and the direction of arrival of signals transmitted from one floor to another may be by way of the corridors and stairwells rather than by penetration through the floor. Outside the building reflections from the walls of buildings play a large part in the transmission of the signals. The result is that the major components of signal received at a particular point may come from a direction very different to the direction of the geometrical line from transmitter to receiver. The use of high resolution signal processing makes the identification of the individual multipath components much clearer as is shown