Re: 60ms cross continent

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

The most noteworthy thing I'm seeing in C band these days, is many
customers formerly 100% reliant upon it shifting their traffic to newly
built submarine fiber routes.

On Mon, Jul 6, 2020, 11:51 PM Denys Fedoryshchenko <
nuclearcat () nuclearcat com> wrote:

> On 2020-07-07 08:32, Eric Kuhnke wrote:
> > "no clouds" is overstating the effect somewhat. I've operated a number
> > of mission critical Ku band based systems that met four nines of
> > overall link uptime. The operational effect of a cloud that isn't an
> > active downpour of rain is negligible. Continual overcast of clouds is
> > not much of a problem at all, it's active rain rate in mm/hour and its
> > statistical likelihood, climate parameters of the location.
> >
> > Yes, during rain fade events, current generation VSAT modems will drop
> > all the way down to BPSK 1/2 code rate to maintain a link, with
> > corresponding effect on real world throughput in kbps each direction,
> > but entirely dropping a link is rare.
> BPSK 1/2 is quite extreme. In my case it was 32APSK 8/9 at 36Mhz
> transponder
> (yes it was quite large antenna), ~140Mbit, so switching to 1/2 BPSK
> will make it
> ~16Mbit/s, which is pretty useless for telco purposes.
> For corporate, end-users, with QoS - it can be ok, but still depends on
> climatic zone.
> Remember, it is not downlink only issue, but uplink too. And depends on
> antenna elevation angle
> as well.
> Even for end-user it is not fun to have 1/10 of capacity, most likely
> means unable to do
> video conferencing anymore, for few days, just because it is few rainy
> days.
> And as Ku is often covering specific regions, often it means rainy days
> for most transponder customers.
> This is why in zones closer to equator, with their long-term monsoon,
> C-Band was only option,
> no idea about now.