Angle Diversity Performance on Different Radio Links

The paper describes propagation experiments and the performance of angle-diversity reception on two different test links. One of the test links exhibited a good path clearance with a pronounced height difference between transmitter and receiver terminals, whereas the second link ran parallel to the earth's surface with smaller path clearance given by the radius of the first Fresnel zone. The results for both test links showed that the dispersive nature of the fading is caused mainly by ground reflections or ray bending at ground-based layers. Outage calculations were performed for 16 QAM and 64 QAM digital radio systems with different parameters using the measured propagation channel responses. The results show that propagation impairments can be reduced strongly by angle-diversity reception as compared with single reception for both links. With additional adaptive equalization, outage can be avoided on both links if the flat-fade margin is large enough.