[Ronja] Multiple receivers and transmitters

[Gregory Maxwell]

On Sat, Sep 20, 2008 at 1:09 PM, J.D. Bakker <jdb at lartmaker.nl> wrote:
>>I have been thinking how to divide multiple heads between receivers
>>and transmitters optimally, i. e. if we want to build N heads, how
>>to get the maximum range.
>
> Given N transmitters and M receivers, it might be better (but more
> complicated) to apply MIMO techniques.


In radio the problem that MMIO solves is multipath: Between your TX
and RX  there are obstructions which alter the signal, they shift
phase in a frequency dependent manner, and creates nulls and peaks.
MMIO uses spatially separated antenna which get different views of the
multi-path environment.  You can then define a collection of filters
which take advantage of the multipath to form separate channels and
gain capacity.

For a fairly slowly amplitude modulated optical path like RONJA I
would not expect there to be significant multipath. I do not believe
MMIO would help.  But MMIO systems typically use efficient modulation
systems  which would probably help ronja very much, but supporting
them would be very costly.

Karel where does the noise come from in the receive head are we
talking about optical background noise which would increase with
increased collection area or is it primarily noise from the
photodetector and amplifier?   If it is primary electronic noise,
creating a larger passive collector may allow you to increase receiver
area without seeing much of a nosie increase.

So long as your transmitter area is strictly smaller than the
reciever's field of view, however, you would always be as well or
better off to increase the transmitter area.  though perhaps you may
wish to make the receiver more selective (for example, by placing it
at the back of a long black tube).