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Homemade VoIP Network Over Wi-Fi Routers

Posted by timothy on from the warms-the-cochleas-of-the-heart dept.

AnInkle writes "A blogger on The Tech Report details his research and testing of wireless voice communication options for remote mountainous villages in rural undeveloped areas. The home-built project involves open-source software, low-cost wireless routers, solar power, mesh networking, unlicensed radio frequencies and VoIP technology. Although his research began several months ago, he has concluded the first stage of testing and is preparing to move near one of the sites where he hopes to eventually install the final functional network. Anyone with experience or ideas on the subject is invited to offer input and advice."

13 of 71 comments (clear)

  1. Urban Networks... by PC+and+Sony+Fanboy · · Score: 3, Insightful

    Wouldn't this be great! You could use your networking skills to setup a private, free telephone system. And, if it was encrypted, no one could snoop in on it... and if it was in an urban environment... Hmmm....

    1. Re:Urban Networks... by William+Robinson · · Score: 4, Funny

      And, if it was encrypted, no one could snoop in on it

      Hold your horses, Osama, it's not perfect yet :)

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      hilarious
    2. Re:Urban Networks... by Opportunist · · Score: 4, Interesting

      Zero chance. I'd even deem it unlikely that the original project survives for long. Telcos are missing out revenue when you communicate for free, the feds owe them one for the wiretapping thing, so I expect a law soon against this. Because of ... because of ... national security or whatever fits.

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      We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
    3. Re:Urban Networks... by jamesh · · Score: 3, Interesting

      There are (still?) cell phones with DECT (household grade cordless phone technology) built in. I always thought this would be a much better alternative to a cell phone with wifi built in to accomplish VoIP. DECT is pretty lightweight, so do VoIP to the DECT base station, then DECT to the phone. When you are in range of the DECT base station (eg at your house) you'd make calls via that instead of the more expensive cell network.

      Not sure why this never took off... could have something to do with the less money that the cell providers would make.

    4. Re:Urban Networks... by jimthehorsegod · · Score: 3, Interesting

      BT tried something not a million miles from this in the UK. Went by the name of BT Fusion and the principle was that the compatible handsets used Bluetooth to communicate with a base station (which was also a DSL Router) and thus your mobile/cell phone used that to route calls when in range. AFAIK the base station used normal PSTN lines to route the calls out, but that's just a technicality - it could have been doing whatever at that point, it would be transparent to the end user

  2. Why not cellular? by ostiguy · · Score: 3, Insightful

    Read this yesterday, still don't get it. Can omni directional wifi ever compete with a cell tower's coverage range? Cellular has the advantage of insanely cheap commoditized phones.

    Seems a bit like trying to use bluetooth to connect two buildings in a campus together - nominally cheap hardware, but probably cannot be coerced into doing what you seek.

    1. Re:Why not cellular? by Anonymous Coward · · Score: 3, Insightful

      Insanely cheap commoditized phones subsidized by an insanely marked up cell phone plan. The point of this exercise is to provide the infrastructure where private business currently doesn't feel there would be return on investment. Think OLPC for VoIP.

    2. Re:Why not cellular? by Timberwolf0122 · · Score: 5, Interesting

      I think the main drive according to the article is the 802.11x frequencies tend to be de-regulated and free to use, cell networks have ongoing fees to use that portion of the spectrum. Also wireless routers have very low power requirements and can be run via hippy fuel (aka solar) instead of some poor bugger having to run the mother of all extension cords up a mountain.

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      In the not too distant future, next Sunday A.D.
    3. Re:Why not cellular? by William+Robinson · · Score: 4, Informative
      FTFA,

      Technology alone is not sufficient. For any project like this to work for more than a couple of years, it must have a sustainable business model. (In the long run, at least as much money needs to come in as is going out.) Village Phone, which builds on traditional cell phone technology, has been very successful in bringing communications to rural Africa. Their model, in summary, involves an entrepreneur from the village purchasing a cell phone, roof antenna, and charger with the help of a microloan. They are then able to sell minutes to villagers for a profit. The cell phone antenna must be within about 35 km of a cell phone tower and have line of sight, thus making the technological aspect of this model unworkable in many rural or mountainous regions.The business model, however, could potentially be used just as successfully with other technologies, including WiFi paired with VoIP.

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      hilarious
  3. In a somewhat similar vein by fuzzyfuzzyfungus · · Score: 4, Informative

    David Rowe has been quite busy working on cool, low-cost telcomm stuff. His site also has links and comments and so forth from others interested in the subject, including people doing actual, in the field, deployments in fairly poor and hostile(to the tech) environments.

  4. Tried something similar... didn't work well by cciRRus · · Score: 5, Interesting

    I experimented with 5 units of WRT54G wireless routers running Freifunk firmware and I tried saturating the link with several G.729 VoIP calls. The system doesn't scale well. Over 3 hops, the number of calls greatly reduces as there is just too much random delay. In order for voice communication to be worthwhile, the latency cannot be more than 200ms although there are good forward error correction schemes and huge buffers.

    Latency is a real problem especially when you are doing it over several hops. The "lag" isn't consistent. It will hit you at random interval, and that can be extremely irritating. This may be due to the use of CSMA/CA and RTS/CTS (depending on configuration). I haven't found a way to improve it though...

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    w00t
    1. Re:Tried something similar... didn't work well by klapaucjusz · · Score: 3, Informative

      Over 3 hops, the number of calls greatly reduces as there is just too much random delay.

      Yes, there are a number of issues with building multihop mesh networks over wifi.

      If you're using omni-directional antennas, the most serious issue is that the multiple hops interfere with each other. Ideally, you'd have multi-radio nodes that use different frequencies, and a routing protocol that attempts to maximise path diversity, but the multiple radios increase total cost, and building a routing protocol that takes diversity into account is not completely trivial.

      This issue doesn't happen with directional antennas, which is what the author of the article appears to be using.

      The second issue is that 802.11 performs reemissions, which cause timing jitter when there is interference. The solution is to modify the link layer to send VoIP packets with lower reliability, which is supported in 802.11e. Unfortunately, current hardware doesn't do 802.11e in ad-hoc mode.

  5. i know someone by extirpater · · Score: 4, Funny

    Anyone with experience or ideas on the subject is invited to offer input and advice. http://img368.imageshack.us/img368/5753/macgyver2rs.png