More on angle diversity for digital radio links

Propagation experiments and the performance of angle-diversity reception, on two different test links are described. The first test link (equipped additionally with space-diversity antennas) exhibited a good path clearance with a pronounced height difference between transmitter and receiver terminals, whereas the second test link ran parallel to the earth´s surface with path clearance for the first Fresnel ellipsoid only. The results for both test links show that the dispersive nature of the fading is mainly caused by ground reflections or ray bending at ground-based layers. Angle diversity reduces the occurrence of in-band amplitude dispersions to the same extent as space diversity, but is not as effective in reducing flat-fade conditions. Outage calculations were performed for 16-QAM and 64-QAM digital radio systems with different parameters using the measured propagation responses. The results prove that propagation impairments can be reduced strongly by angle-diversity reception as compared with single reception for both links