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Full Version: Li-Fi - an asymmetric back haul solution
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Problem defined:
Next gen wifi systems will have 4x4 and 8x8 antennas in a phased array MIMO arrangement. Such systems are able to project highly focused directional beams. These systems significantly increase the power and signal strength at the receiver, but do not symmetrically improve antenna gain for return signals.

Similarly, a high powered, amplified wifi signal through a directional antenna may be received at a site fifteen miles away, but reception of the signal from the site cannot similarly be amplified as easily as power can be boosted in transmission.

Solution proposed:
We propose, Asymmetric routes, for situations where messages can be received by a node, but where the node cannot directly communicate back. In an asymmetric route, confirmation messages are relayed over the network by a route, enabling full utilization of asymmetric connectivity over one way communication channels.

Situations where this will become increasingly relevant

* Rural SONET arrangements with amplified Wifi over directional antennas
* Urban connectivity between highly directional and non-directional antennas broadcasting at the same power levels
* Concrete penetration in 802.11af systems

Remarkable aspects of Li-Fi solution:
* Non-line of sight LiFi propagation can transmit over 200 Mb/s but its highly asymmetrical
* RONJA type Li-Fi systems have theoretical capacity limits over 10 Gb/s line-of-sight and there is cost/setup advantage for asymmetrical connectivity

Utilizing asymmetric connectivity and routes allowing only one way direct data transmission between nodes has several advances, especially for rural developments and reducing cost of integrating high capacity of next-gen technologies.

More info on Li-Fi here:
http://theinstitute.ieee.org/members/pro...arald-haas
https://purelifi.com/purelifi-has-two-vi...s-of-2017/
This comes out to about $100 and $25 USD:

Material for one Ronja 10M Metropolis device costs 2000CZK and building the device takes 70 hours.

Electronic parts for one Ronja 10M Metropolis device costs about 490CZK in Czech Republic. For Ronja Tetrapolis it is about 750CZK.

In Switzerland, where parts are more expensive than equivalent calcualted from CZK, Metropolis parts cost 71CHF and Tetrapolis 118CHF.
Li-Fi technology is very interesting!!!
If theres enough interest I'd be willing to orchestrate a group buy for the PCB boards, or if a more trusted member of the community were willing.

PCB's: http://ronja.twibright.com/transmitter/pcb.php

Cool DIY article:
https://hackaday.com/2016/03/10/gigabit-...h-the-air/

It seems like a viable solution if this could actually be developed to transfer larger sums of data, but it's a starting point to play around with. I wonder if these could be tuned to be run in tandem. Would anyone be able to speak to this? at under $200 a set, 100mbps would cost us under 2k at this point.