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Analysis of multipath fading observations in British Columbia, Canada Lee, Edwin Kam-lun


Analysis of the data measured in twelve selected microwave links in the Province of British Columbia, Canada, between July '79 to October '82 has been carried out. These links are representative of about 90% of the microwave links distributed in three of the five main topographic-climatic regions of the Province. The observations are given in terms of worst-month multipath fading probability as a function of fade depth, the number of fading events, the average fade duration, and the variation of monthly fading time over the measurement period. The diurnal fading characteristics of several paths are also shown. The analysis involves: (1) comparisons of certain parameters derived from the observations with those given in the literature and generalized in the CCIR formula which describes multipath fading probability, (2) finding of the exponent values in the expressions concerning the number of fading events and the average fade duration, and (3) finding of the yearly to worst month fading ratio. It is found that the Morita parameters, of the CCIR formula, are most appropriate for application to microwave links in British Columbia. The exponent values in the expressions concerning the number of fading events and the average fade duration are a₁=0.67 and a₂=0.33, respectively. The yearly to worst month fading ratio can be assumed to be 2.0 for most links. Moreover, the observations show that the most active multipath fading months are July to October. The peak of the diurnal multipath fading for links over, and perhaps along, a water body is around afternoon and at sunset. For plateau links, the fadings occur mostly around sunrise and for most mountain links, no general pattern can be observed. Furthermore, different types of multipath fading mechanisms specific to various topographic-climatic regions are investigated. The dominant multipath mechanisms for coastal region are sea breeze, offshore streaming, and advection of nocturnally-cooled air. For plateau region, the dominant mechanism is radiation inversion and for mountain region, multipath fading is most likely caused by trapped radiation fog in the valleys with clear air above.

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