The Mesh Potato
The Mesh Potato is an 802.11bg mesh router with a single FXS port (Figure 1). Adjacent Mesh Potatoes automatically form a peer-to-peer network, relaying telephone calls without landlines or cell-phone towers. The Mesh Potato hardware and software is open. The power, Ethernet and FXS ports are robust to developing-world conditions like static, lightning, bad power and accidental abuse. The Mesh Potato comes in a weatherproof box for outdoor mounting and costs about the same as any other Wi-Fi router (less than $100).
An analog phone connects to the Mesh Potato via the FXS port. FXS (Foreign eXchange Station) is a telephone interface that supplies power, dialtone and generates ringing voltage. When you make a phone call, your Mesh Potato talks to the potato down the street, which talks to the next potato, and eventually to the destination. The mesh network can be augmented via backbone links and connected to the rest of the world using VoIP trunks.
This article describes the history of the Mesh Potato Project, including how it was conceived and its development so far. I also discuss the Mesh Potato's design and the technical challenges we have faced.
In June 2008, I attended the Village Telco workshop in Cape Town, South Africa. The Village Telco (and I quote) is an easy-to-use, scalable, standards-based, wireless, local, do-it-yourself telephone company toolkit. Put simply, the idea is that “some guy in a village” can build a local telephone network and make a sustainable business by charging a nominal fee for calls to the PSTN (Public Switched Telephone Network) via VoIP trunks. We were in Cape Town to work out how to build the Village Telco software and hardware.
Steve Song of the Shuttleworth Foundation pulled together a fascinating team of people from the development, VoIP, mesh networking and business communities. The team was small (about ten people) and very hands-on in its outlook and skill sets (Figure 2). The breakfast and dinner conversations were fascinating—funny stories about broken-down hotels in some developing countries and sad stories about the poverty of others.
One of the outcomes was the decision to build a little box called the Mesh Potato. We started out thinking we would use off-the-shelf hardware, like wireless routers and ATAs. Suddenly, it dawned on us that we didn't have to accept non-optimal, off-the-shelf hardware. We had the skills to design and build exactly the hardware we needed for the project. We also chose to make the hardware design open, just like the software.
Since then, we have come a long way. Through a series of development projects funded by the Shuttleworth Foundation, we have designed, debugged and built about 20 Alpha Mesh Potatoes (Figure 3). The first phone calls over Mesh Wi-Fi were made in June 2009, almost exactly one year after the project kicked off. We currently are preparing for a Beta run of Mesh Potatoes, with full production scheduled for early 2010.
We keep hearing how popular mobile (cell) phones are in the developing world. I have seen how well a humble cell-phone works, penetrating to the corners of some really remote areas of the world. So why do we need a Wi-Fi-based system like the Village Telco?
The answer is simple. The call costs for mobile phones are very expensive for many people in the world. In many cases, it's roughly the same cost as a mobile call in a developed country. If you are earning $1/day, a 50-cent mobile call is very expensive (Figure 4).
Although mobile phones have delivered remarkable benefits to developing countries, the mobile oligopolies that have emerged in the process have kept call charges artificially high. Worse, mobile operators tend to function as “walled gardens” in order to entrench their market share. Just compare the price of an e-mail message on the Internet (zero) and via a cell phone (20 cents for a text message), and you get some idea of the problem.
Communities in the developing world need an alternative. Hence the need for the Village Telco—a system that uses commodity Wi-Fi technology and unlicensed spectrum to provide low-cost phone calls.