Re: 60ms cross continent

[Eric Kuhnke <eric.kuhnke () gmail com>]

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.






On Thu, Jul 9, 2020, 9:01 AM Christopher Munz-Michielin <
christopher () ve7alb ca> wrote:

> > On 09/07/2020 08:00, Mark Tinka wrote:
> > So is there a reason why we are not seeing widespread 1080p TV via
> > satellite? They seem to exist where a broadcaster also supports an IPTV
> > platform.
> >
> > Mark.
> I'd assume it's a question of available bandwidth and availability of
> decoders.  From my observations most HD satellite feeds seem to sit
> between 3 and 5 mbps, a typical Ku band transponder might have a
> bandwidth of around 20-25mbps.  This means you can cram 5-8 HD feeds
> onto a single transponder.  With 4K streams the bandwidth requirements
> double, meaning you can cram a lot less in the same amount of
> transponder space and satellite bandwidth is expensive!
>
> The other issue is on the decoder side.  Right now, the vast majority of
> satellite subscribers receive programming though dedicated decoders (set
> top boxes).  Most of these decoders only have hardware to decode MPEG2
> and H.264 video, while 4K stuff is almost exclusively H.265.   That
> means it's not a simple matter of turning on 4K, you'd have to arrange
> to send new decoders to all your subscribers wanting to receive 4K.
>
> As time moves along, I'm sure we'll start to see more satellite feeds
> available in 4K but like the transition to HD video, it'll be a slow
> process.
>
> Chris