My Wifi experience is steadily growing. I have now been involved in a couple of long distance links with directional antennas and several mesh networks. Some patterns are emerging:
- Long distance Wifi is an inherently unreliable medium. It’s no where near as reliable a DSL, or mobile phones, or a TV antenna installation that “just works” for years. Expect a lot of work to set up a reliable link, and ongoing work by skilled people to maintain the links.
- Each node takes a surprisingly large amount of hard work to set up – on that Sunday we invested around 4 man days, and the link is not complete yet. In Dili our first mesh link took over a week to set up due to interference problems. However even in Timor Leste I can buy a sim-card and have reliable telephony (and 3G Internet) in 60 seconds.
- There is also work to maintain Wifi links, they periodically go down for one reason or another. Once you set them up you are not finished. There is a dubious plus side to this – it means a job for life for the people running the networks!
- One reason Wifi links are hard in the need for Line of Sight (LOS). Do not underestimate this requirement. It means pain. Wifi works fine indoor for a few 10′s of meters. Outdoors, once you get past 100m or so, you need Line of Sight. If a tree or other obstacle get between you and the other node your link won’t work. This sounds easy, but in practice if you have a 25m tree, you need a 25m tower. This is very tough from a mechanical point of view – it means big, complex towers, lots of work, and physical safety issues. Even on my house we needed a 12m height, just to clear some of the local obstacles you get in a 1st world neighbourhood. This means a big, guyed, mast, and man-days of effort for installation. These photos show what was required for our first node in Dili (although it got easier after that):
- Another big issue is interference from other 2.4 GHz activity, in particular the hidden node problem. This has been my biggest problem in the Dili and Kilkenny meshes. In practice it means small packets tend to get through, but large ones do not. In an extreme case for one link in Dili we needed to resort to Ethernet cable as a Wifi link simply wouldn’t work. Directional antennas can help this problem, but mesh routing need omnis by definition. In practice, the mesh networks I have seen have a mixture of omni and directional links.
Mesh nodes in the Village Telco are designed to be set up by people with modest Wifi skills in remote, developing world locations, where technical help (like an Air Stream team), 1st world hardware and Wifi equipment shops are not available. If you need one more D-shackle, a Nanostation 2, or a new grid antenna that’s too bad, expensive, and months of delay while it gets shipped in.
Village Telco end users are going to depend on these networks for telephone calls. In some cases it might be their only telecommunications. End users have high expectations for telephone network up-time – much higher than for Internet. People running these networks (the Village Telco Entrepreneur) will be investing their life savings and expecting to generate an income.
So a key challenge of the Village Telco is to take an inherently unreliable, hard to set up, hard to maintain technology (long range Wifi), and make it simple and reliable in a 3rd world environment when installed and maintained by local people.
I am gathering data on this challenge as the Dili Village Telco grows. Over the next few months we will get experience with up time and scale up to 100 nodes. I am hoping that mesh networks will offer reliability advantages over point-point, statically routed Wifi links, and that installation gets smoother with experience and a denser mesh. The up time of the 10 node pilot network to date has been good. Despite the set-up hassles, the Timorese guys are hungry for more Potatoes. The magic of free local calls makes the set-up effort worth it. I’ll post more on this (and an update of the Dili Village Telco) soon.
Last week I was chatting with Alipio, one of my friends in Timor Leste. He has experience in mesh networks and Ubuntu Linux, and was a great help with the Dili Village Telco Workshop last April. Alipio is excited about the possibilities of the Mesh Potato and Village Telco. If it can be shown to work, he wants to promote the system to the Timorese government. However he is wary – foreigners are always dropping out the sky with magic technology that breaks 2 days after they leave. I asked him what he needs to see:
- The Timor Leste government wants to see sustainable, durable, renewable, up to date technology.
- It needs to be locally owned and operated, not driven by 1st world people.
- It needs to work reliably for 6-12 months before he would consider promoting it to his government.
- It needs to work.