Wideband Characterization of Equatorial Ionospheric Fading Using MUOS Signals

Six hundred hours of data from a receiver located at the Cape Verde Atmospheric Observatory at 15°N (dip latitude), has been used to explore the fading correlation of 300–360 MHz trans-ionospheric signals from the MUOS satellite. Using these data, we have highlighted that the inter-frequency correlation varies with the fading frequency; components at frequencies close to the Fresnel frequency tend to be well correlated over bandwidths between 15 MHz and greater than 20 MHz, but those at higher fading frequencies are only well correlated over bandwidths between 0.1 and 5 MHz at a correlation threshold of 0.7. When considered over all fading frequencies, flat fading is far more common than frequency selective fading, such that when the frequency separation is 5 MHz and when S₄ lies between 0.7 and 0.8, the ratio is ∼16:1, when the separation is 10 MHz the ratio is ∼9:1 and when the separation is 15 MHz it is ∼7:1. Together, the results in this paper suggest that flat fading is the dominant fading mechanism for satellite communication systems, with bandwidths up to 15 MHz, operating in the high VHF and low UHF bands in the equatorial region. At still higher operating bandwidths we expect frequency selective fading to become dominant as the differentially delayed multipath components, occurring via Fresnel scale irregularities, cause destructive and constructive interference.