RE: Enter the Party Pooper3 Feb 2022 10:39
"I also wonder if the carrier capacity between a large rural cell is comparable with a satellite. A bit like comparing a B road with the M25. Must be a profit curve moving from urban wifi to rural cell v satellite. Interesting now I am thinking about it"
My experience was in line of sight terrestrial links at 10Ghz, 13Ghz, 23Ghz, and 50Ghz. 10 and 13Ghz had good rain fade characteristics, 23Ghz not so good, and 50Ghz was only used for short range communication up to a couple of miles. The customer facing radios were low power, around 20dbm (100mw), with higher power 10/13 Ghz backhaul radio using travelling wave tubes to amplify to over a Watt, ensuring reliable transmission for higher bandwidths in bad weather. The required gain is achieved using amplifiers and directional antenna's (Dish's)
The technology has moved on a lot, by the look of things, with mobile cells using phased array antenna's (MIMO) and 5G Massive MIMO, to service many users giving the best compromise gain in multiple directions on different channels. Also to cram data into the available bandwidths, they use a technique called QAM, which uses phase changes to modulate the carrier wave; The higher the QAM rate, the higher the bandwidth, with more power and better conditions required to transmit and recieve reliably.
I think the idea with Starlink is to have multiple satellites, with the customer dish selecting the best line of site signal available to particular satellites, but if it's hammering down, the rain fade attenuation will severly attenuate the signal in all directions, even overhead. The problems get worse as you move up the mm Wave band, so the lower the frequency, the less the atmospheric problems. The Earth station uplink/downlinks will have much higher bandwidth requirements than customer terminals, as they will carry the aggregated data, with much higher powers and big dishes. I suppose time will tell how LEO's perform in bad weather, and what sort of reputation they'll get. In arid climates, like Africa, with clear sky's, rain fade probably wouldn't be a big issue, but the UK's a different matter lol.