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April 2015
May 2015

2015-04-23 »

Mesh power!

What we mainly learn from this diagram is a) my path to the bathroom is a long, circuitous one, and b) the 'circo' program from graphviz is pretty fun, and c) the hallway is some kind of communication nexus. 

On a system that started off with ~80 Mbps of TCP throughput (which is about right for a 2x2 radio at 20 MHz... too bad it's a 3x3 radio though), using the mesh I was able to still sustain 14 Mbps from a distance of about 114 AnandSteps.  That's about a 6x decline, or about 3 hops at 50% signal power.

By my rough calculation, that means a 4x4 radio @ 80 MHz should be able to do 14 Mbps * 2 * 4 = 112 Mbps at that distance, which comes out to about 5 TVs (and absolutely no bandwidth leftover for a safety margin or actually using wifi for Internet traffic).

On the other hand, 114 AnandSteps in linear distance is, hmm, maybe 250 feet, which would be a 62,500 sq.ft. one-story house.  Which is maybe unreasonably large.  (It would also need more than 8 mesh nodes to properly cover the whole area, but in theory could still connect any two points in about 3 hops.)

With only two hops (more reasonable for a reasonably-sized home), speeds were around 35 Mbps, so the 4x4 @ 80 equivalent would be about 280 Mbps, which seems to leave plenty of room for TVs and Internet.

Disclaimer: these estimates are extremely rough.

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