On-board processing of faded satellite communication signals

It is shown that, in a severely faded channel, onboard processing provides essentially no improvement in error probability when both the uplink and downlink are Rayleigh-faded, and when there is no diversity. Dual (or higher-order) diversity not only provides an inherent diversity gain, but also regains a portion of the original on-board processing gain that was lost when the fading occurred. It is concluded that, when either the uplink or the downlink (but not both) undergoes severe fading, on-board processing provides a large processing gain, but only for the link not experiencing the fade.<>