Angle and space diversity comparisons in different mobile radio environments

The angle diversity performances of two types of high-gain multibeam antennas-24 vertically polarized 15 degrees beams and 12 vertically polarized 30 degrees beams-were tested and compared to the space-diversity performances of traditional sector antenna configurations. The antennas were tested at 850 MHz in dense urban and rural cellular mobile radio environments. A vehicle equipped with a mobile transmitter was driven in the coverage area, while the received signal strength (RSS) was recorded on multiple receiver channels attached to multibeam and sector antennas at the base site. The RSS data recorded included fast (Rayleigh) fading and was averaged into local means based on the mobile's position/speed. The fast fading was extracted from the recorded RSS and the fading distributions of the two multibeam antennas tested were studied in two distinctly different mobile environments. Fading cumulative distributions for the angular diverse antennas were compared to those of spatially diverse antennas. Diversity gain was calculated and compared to traditional space diversity in these mobile environments. Results in urban environments indicated that angular diversity performance was comparable to space diversity (similar to-8 dB improvement). Rural tests typically suggested that both space diversity and angular diversity provided little or no (<2 dB) fading reduction. A description of the experiment, data reduction and analyses, and calculation of diversity gain are presented. The motivation for this experiment is the application of fixed multiple beam antennas (FMBA) in cellular radio and digital personal communication systems.