Fading statistics of transhorizon microwave signals over a troposcatter path in northern India

An experimentel microwave troposcatter communication link established between the Indian Institute of Technology, Delhi, and the Central Electronics Engineering Research Institute, Pilani, is described. The link, which spans a distance of 158 km over an East-West path in the arid zones of Northern India, operates in the frequency range 4.4 to 5.0 GHz. The fading nature of the signal received over a spread of a few months is analysed with the help of a computerised data-acquisition system. Space diversity signals are analysed in terms of their cross-correlation, rate of fading, fade depth, probability distribution function, and spectral density. The median levels ond cross-correlation for morning hours are found to be generally higher than those for afternoon hours. Scatter diagrams are plotted to depict the statistical connection between median level and fade depth, between median level and fade rate, and between fade rate and fade depth. The connection between median level and surface refractivity is examined. Also examined is the variation of median level at sunrise, which shows a gradually diminishing trend.