Three years of C band signal measurements for overwater, line-of-sight links in the mid-Atlantic coast 1. Fade statistics

摘要

Three years of fade statistics are described for two overwater, line-of-sight propagation links along the mid-Atlantic coast of the United States operating at 4.7 GHz. Single-terminal, joint fade, and fade duration statistics derived from time series of received signal losses due to refractive and diffractive effects are described for combined-year, annual, and monthly cases. In particular, year-to-year and month-to-month variabilities in the statistics and also the efficacy of employing space diversity for the two links to mitigate fade margin requirements are examined. Sustained deep fade (SDF) events due to severe subrefraction during the 3-year period tended to dominate the statistics. Statistics have been culled in terms of contiguous month groupings during which SDF events occurred (November–July) and did not occur (August–October) over the 3-year period. Although the year-to-year variability in the annual fade statistics was relatively small, the year-to-year variability in the monthly statistics was large, especially during the April–July period, which separated the periods during which deep subrefractive fades were maximum and the periods during which they were nonexistent.