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Liz Cray
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Old Pages/Byzantium/Byzantium_Sprint_2.md
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Old Pages/Byzantium/Byzantium_Sprint_2.md
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Summary: Build at least one long-haul link to bridge two meshes.
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Planning meeting: Thu Mar 3 2011 after the bike maintenance class (done)
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Planning meeting \#2: Wed Mar 16 2011 after the elements of computing
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class (doneish)
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**Sprint Date: Fri-Sun March 25-27**
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[Inventory](Byzantium_Sprint_2_Inventory "wikilink")
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### Schedule
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FRI: 8:00pm Pizza, sprint 1 recap, and prep (mostly ripping thing apart
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and some assembly) SAT:
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- Noon Brunch and final assembly followed by bench tests and midrange
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tests depending on speed of success
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- Dinner Time: Dinner outside the space. This must occur outside the
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space.
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- 9:00pmish? Discussion and general planning for Sunday optionally
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followed by more testing/making
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SUN:
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- Noon Brunch prep for long distance tests followed by long distance
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tests
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- Dinner Time: Dinner outside the space. This must occur outside the
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space.
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- 9:00pmish? Discussion and planning for the next sprint
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### Stuff to bring (proposed)
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- FMRS/GMRS radios that you wouldn't mind hacking.
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- Childrens' walkie-talkies. [User:Drwho](User:Drwho "wikilink") knows
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where to buy cheap pairs of them locally.
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- Webcams *that are known to work with Linux*. That's closer to black
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magick than computer science, so do your homework first (or on your
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smartphone while at the store). The feature to look for is called
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[UVC](http://en.wikipedia.org/wiki/USB_video_device_class) though
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webcam boxes still might not mention it.
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- Laser pointers (the more exotic the colors the better). Buy them when
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you find them. When you go looking for them you can never find them.
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- Really bright LEDs
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- Photocells, photoresistors, photodetectors.
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- Microcontrollers. They may come in handy for modulating/demodulating
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signals.
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- Hackable wireless access points. Here are some
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[examples](http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=BESTMATCH&Description=dd+wrt)
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that might work.
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- old headphones/headsets/stereo audio cables and phone cords for
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cutting up and making into modem to radio connectors
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### Radio
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- radio shack/hardware store high bandwidth unlicensed spectrum
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- Hacked FRS/GMRS radios
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- [Text messages over
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walkie-talkies.](http://takethingsapart.blogspot.com/2010/07/note-before-constructing-device-such-as.html)
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- [Forum post with some
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ideas.](http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270645507)
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- Pros:
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- cheap
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- longish range (35mi allegedly)
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- Cons:
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- Need an automated PTT switch or two radios per node
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- Develop improvised antennae to improve signal quality, distance
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covered.
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- anything + aluminium foil = bouncy bouncy for radio waves
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The FCC has designated a number of channels in the 27 MHz band that can
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be used for signaling and radio control. They are unnumbered and
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in-between CB channels 1-13
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([source](http://forum.servomagazine.com/viewtopic.php?f=1&t=2736))
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### Optical
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- Modified Ronja-like
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- with lasers
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- with balloon targets
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- with lasers and balloon targets
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- with lasers and self-adhesive mirrored decals.
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- All Electronics Magazine had a couple of articles on building
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lasercomm devices on the cheap. Somebody remind the Doctor to go
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through his magazine collection.
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- [How to make a simple laser
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communicator.](http://www.make-digital.com/make/vol16/?pg=69#pg69) (I
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do have this issue. Have bought parts to build a pair of transceivers.
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--The Doctor)
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- [Handbook of Optical Through-the-Air
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Communications](http://www.imagineeringezine.com/files/air-bk2.html)
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is a good read on the basics of an LED-based hardware setup, though
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he's aiming at voice comms. (Elliot)
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### Inspiration
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- [Ronja](Ronja "wikilink")
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### Homework
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- read up on [Ronja](http://ronja.twibright.com/)
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- read up on FMRS/GMRS
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- read up on and talk to the HacDC Spaceblimp team about soundcard
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modems: like [this](http://www.baycom.org/~tom/ham/soundmodem/) (also
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available via apt [like so](Notes_on_Soundmodem "wikilink"))
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- [Howto](http://www.linux-ax25.org/wiki/Soundmodem)(go here last it's
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a bit short on soundmodem specific info)
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- [Notes on Soundmodem](Notes_on_Soundmodem "wikilink")
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- [Soundmodem in the
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field.](http://www.qbjnet.com/packet.html#soundmodem)
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- Read up on [AX.25](AX.25 "wikilink").
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### Goals (proposed)
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- Optimize for hackability. Could your average geek build a few of these
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using junk around zir house and deploy them in an emergency situation?
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- not a chance
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- Determine the optimum speed in bits per second for a mesh-to-mesh
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link.
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- very crazy slow (we didn't bother measuring it was so slow)
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- Measure the bandwidth of a point-to-point long haul connection at a
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particular distance.
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- again to slow to bother
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- Determine the maximum practical distance for a long haul connection
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between two meshes in an urban environment.
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- didn't get that far
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- Mathematically describe the way to maximize throughput with a minimum
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number of nodes.
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- didn't get that far
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- Run an ssh session over whatever link is established.
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- done
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- Interact with a web page over whatever link is established.
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- connection was too unstable to get this far
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- Develop methods to minimize latency.
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- tweak the source and transmitter volume A LOT until the it's perfect
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- Determine the efficiency of the mesh routing protocol we settle on.
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- didn't get this far
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- How many active nodes per mesh can be reasonably supported before
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connectivity breaks down?
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- to be determined
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### Apps running on Windbringer (laptop/node) to prove functionality
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- [status.net v0.9.6](http://status.net/open-source)
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- [Mediawiki](http://www.mediawiki.org/wiki/MediaWiki)
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### Lessons Learned
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- "how hard can it be" ... oops :(
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- very. soundmodem is finicky and creates unstable connections 20%
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packet loss at best 80-90% avg.
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- Don't forget network latency of 35,500ms over a distance of eight
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feet.
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- "What could possibly go wrong?" ... oops :(
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- everything
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- [There are no experimental failures. There is only more
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data.](http://drwho.virtadpt.net/archive/2011/04/14/project-byzantium-development-sprint-2)
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Let's see how much of [Project FabFi](http://fabfi.fablab.af/) we can
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make use of!
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