jtd wrote:
Throughput deteriorates as the mesh size increases. U have increased
latency and reduced per user bandwidth. These are things which are
being addressed. Latency is the issue for voip over 802.11.
This is a suggestion. If rural or long distance coverage with good
latency and bandwidth is the final goal and cabling is too expensive,
then a combination of wireless radio (APs) as well as wireless optical
technologies could be tried out. The long link in lieu of the cable can
be established using laser tx/rx units mounted high on relaying towers
so that
maximum LOS distance can be achieved. The last mile connectivity can be
provided by the APs.
Optical trancievers will provide almost similar high bandwidth as the
optic fibre cables and can be mounted on independent towers that are
solar powered during the day and rechargable batt. during the night. A
thin long laser beam should be adequete enough to reach a few kms. In
order to overcome the wind sway of the tower tops, the optical sensors
can be mounted at the focus of parabolic reflectors that are sized as
per the maximum deviation of the beam due to the sway. A more
sophisticated approach could be to use (if available and not expensive)
the military type sensors used in laser guided weapons systems to be
able to track moving beams. The entire assembly can be mounted in a
sealed all weather box and a water pump positioned to automatically
spray water at an off peak hour can be used to clean the optical system
everyday, thus eliminating the need for a human touch every day for
every tower. Water can be made available once a month from a tanker or
from an underground tube well.
The protocol used could be such that a minor interruption caused by bird
flights does not disconnect the link, it only pauses till signal is back.
At the final destination, a cluster of towers could optically connect
with the final tower and this cluster will mount the APs to give full
area coverage. In all this process, no cables are used.
I don't know if this idea may work but an experiment can be carried out
in laser based optical connectivity between two tall buildings in Mumbai.
Regards,
Rony.
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