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OLPC Mesh Networking Tester Explains How It Works
An anonymous reader writes "James Cameron is an engineer working on the OLPC project, specifically testing the wireless network capabilities of the OLPC XO laptop. Cameron lives in a small town called Tooraweenah in a remote region of the Australian outback. There is little noise in the spectrum in the area, so it's perfect for testing the wireless networking capabilities of the XO as it mirrors the kind of rural, spacious environment the XO is intended to be deployed in. Cameron breaks down exactly how the OLPC XO's mesh networking works, including the cheap US$35 solar powered mesh nodes that can be mounted on top of a tree to further the network's reach. Testing in the Australian outback, Cameron discovered that the range of the XO could go up to 1.6km 'quite easily' at 1.5m above ground. 'Assuming a range of 1.6km holds true, (the mathematical formula for area of a circle) Pi R squared tells us one well placed mesh node will cover up to eight square kilometers.' The article also includes numerous pictures of the mesh nodes and testing of the XO."
In a wireless mesh network, 99.9% of which are implemented using half-duplex transceivers, once past your immediately adjacent nodes, for each additional hop away you halve the bandwidth and double the latency. No way around that, and in a large area mesh (think muni wifi here) you must re-insert an additional backbone feed about every 4 to 8 hops into the mesh either by landline or by point-to-point wireless bridges, else performance across the mesh gets abysmally poor, very quickly.
Dense meshes just don't work very well, they implode upon themselves. Very sparse meshes, such as used in the battlefield by our military, of perhaps in remote areas like the Aussie Outback as mentioned in the FA, are ideal applications of a wireless mesh network, but all the folks who think they can make a successful commercial venture with a wireless mesh in a dense urban or suburban environment are in for a rude awakening if they drink too much of the Koolaid hype that many of the consumer-grade hardware vendors are trying to push.