Three-Site Diversity at Ka-Band Satellite Links in Norway: Gain, Fade Duration and the Impact of Switching Schemes

Analysis of two years of measurements from a three-site satellite beacon diversity experiment in Norway is presented. The operating frequency was 19.68 GHz, elevation angles were between 21.7° and 22°, and site separations 23, 29.7 and 50.1 km. Due to spatial decorrelation of rain, simultaneous attenuation at all sites occurs much less frequently than at a single site. All three two-site diversity combinations and a threesite diversity combination were investigated. Measured values for diversity gain at 0.01% exceedance level were 8.8, 10.7 and 12.1 dB for the two-site pairs and 12.5 dB for three-sites, given a single site attenuation level between 13 and 16 dB. Comparison of the measured data showed excellent agreement with current ITU-R model. Fade duration statistics for single-site and for the combinations are analyzed and it is shown that the statistics for the diversity combinations can be modelled using a double-lognormal function as is the case for single-site statistics. Analysis of the effects of a non-perfect switch-over scheme showed that using moderate switch-over threshold levels and time delays, the number of switch-overs can be significantly reduced while most of the diversity gain and reduction in number of fades is retained.