Homemade VoIP Network Over Wi-Fi Routers

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."

In a somewhat similar vein

[fuzzyfuzzyfungus]

David Rowe [rowetel.com] 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.

Re:Why not cellular?

[William Robinson]

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.

Re:Why not cellular?

[Steauengeglase]

Why not? Easy, you could give your kids an old PDA or hacked Skype phone or something for use around the neighborhood without having to pay an extra phone bill.

Re:Tried something similar... didn't work well

[klapaucjusz]

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 [wikipedia.org] 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 [wikipedia.org]. Unfortunately, current hardware doesn't do 802.11e in ad-hoc mode.

Re:mountains and wireless

[klapaucjusz]

mountains will severely block radio waves from any part of the spectrum...

The way I read the article, he's using carefully positioned directional antennas to get line-of-sight links.

Check the site of this wifi coop, full of specs

[Pirulo]

We at Santa Fe, NM, don't have high speed internet everywhere,
the option was this coop [lcwireless.net] formed by advanced users.

The results on the shared T4, (yes, as in tee-four), are amazing and it's the fastest and most inexpensive, -at $30/month- internet access in town.

You just need to provide your own hardware,