ROOM
13
Special Report
Using geostationary satellites to provide truly
global internet access is problematic due to
both technical and physical challenges. Latency
is significant and there would be no coverage
in polar regions. At 36,000 km altitude, it takes
the information about 200 milliseconds to be
transmitted from the user to the server, which can
accumulate to almost 500 milliseconds of delay
between the request and the response.
This issue is a physical limitation and cannot
be solved technologically and so both companies
have decided to use low Earth orbit (LEO)
satellites, which offer much lower latency and
stronger signals.
However, they move fast with respect to the
ground and one specific satellite is only be visible
to an observer for a limited time before it sets over
the horizon. To provide continuous coverage, a
constellation of satellites is needed, the number
varying depending on the system design.
Launching such a large constellation is
expensive and raises additional issues such
as interference, controlling the constellation,
avoiding debris and avoiding becoming debris, as
well as maintaining the constellation and replacing
or replenishing satellites.
In November 2016, SpaceX requested approval
from the US government for a constellation of
4425 satellites to orbit in LEO between 1,150 and
1,325 km. OneWeb plans to use a constellation
of 648 LEO satellites, of which the first 10 are
planned for launch in late 2017.
Technique comparison
Balloons are an affordable option. They can
cover a wide area at a lower cost than drones
and be made available with a shorter lead-time
than satellites. Balloons can be deployed in a
variety of locations, although they do require
fortuitous wind conditions to fly over a desired
area. Less infrastructure would be required than
for drones, without the need for airports and
maintenance facilities. Wind can be a limiting
factor in the way that balloons fly at certain
latitudes. Google is forging ahead with its own
balloon concept called Project Loon, which
would use fleet control algorithms to fly across
some countries and latitudes.
Drones have high bandwidth capacity, are also
highly maintainable and offer the possibility for
upgrade. Perhaps one of the greatest potential
uses of drone technology is for post-disaster
internet, where they can be launched quickly and
then directed to fly over affected areas at short
notice. The biggest drawback is the low altitude
giving restricted coverage area, and it is the most
Facebook’s Aguila solar
powered aircraft.
Facebook
