On 10/Jul/20 10:50, Eric Kuhnke wrote:
With common Ku band TVRO (receive only) dishes and decoders, one of the constraints for moving to higher bitrates is the physical sizes of the customer dish and economics.
For a good example go to a very densely populated developing nation environment. Saddar, central Rawalpindi, Pakistan would be one such place. Get up on a tall roof and look at the numerous low cost Ku dish and LNB setups on other roofs.
Achievable bps/Hz and modulation type, code rates, and type of FEC are very limited when the antenna has to be so small. Usually something like qpsk 3/4. In order to have something like a 4k stream and not require end users to replace their 75-100cm size dishes with something much bigger, you'd need to use a lot more MHz on the geostationary satellite's transponder. Greatly increasing monthly transponder fees for the tv broadcaster. Any sort of modulation like 8PSK or a 16QAM is probably not achievable as long as the end user consumer antennas remain so small.
For people who are accustomed to a terrestrial microwave link budget and path loss, Geostationary will seem weird. For SCPC two way data links you can spend a lot of money and construct 3.8-4.5m size earth stations, definitely a construction project with a capital P, but the laws of physics will dictate your link sees only 4 bps/Hz or less. Even with the very best modems on the market now.
Ultimately advances in codecs may help this somewhat. 4k AV1 at fairly low bitrates is remarkably not terrible. H.266 was just standardized. It'll take a long time for full hardware decode to show up in ultra low cost satellite TV boxes.
When the leading satellite TV provider in Africa first started delivering service via satellite back in 1997, it was on C-Band, with the smallest dish needing to be 2.4m. When they moved to Ku-Band around 2010, every home now has 90cm dishes. While they do say 60cm dishes are viable, you won't be able to pick up any HD service with those. Mark.