Wi-Fi for rural communities: from open, to internet, in three acts

The technology known as Wi-Fi is open-everything. It's open standards, open spectrum, open source software, open hardware. Anyone can build a Wi-Fi device — and they do — and the plethora of options means very low cost to buy and deploy a high-speed wireless internet network.

A lot of people are excited about Wi-Fi, the common name for the 802.11 wireless network. The standard sets out the design for radios that use free, open spectrum radio waves to carry internet data. As the standard gained widespread adoption, price competition drove the cost of the radios down from $500 just a few years ago to $100 or less today.

With open technologies there are often unexpected uses. Originally, businesses used Wi-Fi radio in their offices to help roaming laptop users. But the technology sprung an unexpected dividend as enterprising communities used it to bridge the "last mile" between their houses. Now, the last mile is increasingly 5, 10, or 20 miles, driving the creation of community wireless networks.

The radios and equipment are commodity goods that you can purchase off the shelf, just like commodity PCs. They all work the same way, but there are different levels of quality on offer, from Linksys at $100 up to Cisco at $500 or more, like the Dells and IBMs of the computer world. Since they all interoperate on the same channels at the 2.4 GHz frequency, antennas, cables and adapters are also cheap and easy to find, with the total antenna and accessory kit running about $50 to $100.

A typical Wi-Fi network uses a hub-and-spoke design. The hub is a location that is high up, at the top of a building, hill, or tower, where it can be seen visually from many locations. At the hub, the operator of the network installs a sector array of antennas, using antennas from a company like SuperPass (I'm not associated with any of these companies)

http://www.superpass.com/2400-2483M_60.html

For $50 times six you can install a 12dB gain sector array in six different directions, each operating on the same channel. That's coverage in every direction. Then you go down to each location and install customer premises equipment, called CPE even if the users aren't paying customers. The CPE is a weatherproof box that contains the radio, a short cable and a directional antenna with high gain, for example 18dB (available at about $50, a 18dB antenna has a narrow beam with five times sensitivity). The antenna points at the tower to make the link. This is a total gain from both ends of 30dB, which is enough to cover a lot of distance, more than 10 km. You can install higher-gain directionals at both ends to create longer-distance point-to-point links for backhaul (getting the signal to a network point of presence).

Then at each of the locations where you have one of these high-gain directionals picking up the signal from the hub, you can install an omni antenna at say 6dB gain, or another set of sectors, to provide service to people in the neighbourhood and they won't need any external antennas at all most likely within roughly 500m radius.

Of course, with a developing nation, most likely the model is going to be internet cafes, and community computing centres, and schools, so that simply bringing the link into the location is going to be enough. You just run ethernet through the building for the computers there.

Since the whole system is open and standardized, you can build it from the ground up, instead of the sky down, and add nodes as interest and money allows. Each installation will present a marginal cost, but that's not affected by scale. So, you put in the first few nodes for dirt cheap, see how it goes, and then work from there.

There's a learning opportunity as well. The standardization ensures that knowing how to install one system, makes it much easier to install another one even with different equipment. The local people who are involved in the installation can move on to create an internet-provider (ISP) business to further grow the network use.

The wireless network also builds a high-speed network infrastructure. As regional nodes are built, they can be connected over standard internet links from modem lines all the way up to dark fibre. The high-speed infrastructure is light-weight, easy to maintain and upgrade.

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