Radio E-mail in West Africa: The Complete Version

"Deep inside the warm green interior of Guinea, centered in the frontal lobe of West Africa, field personnel in the widely scattered village-towns of Dabola, Kissidougou and Nzerekore now enjoy access to regular internet e-mail, directly from their desktops. Here we have bridged the digital divide, and there isn't a telephone line or satellite dish in sight. Instead we are moving the mail over distances of hundreds of miles--over jungled mountains and high palmy savannahs--through wavelengths of high-frequency (HF) radio. Our project is called Radio E-mail, and here is its story...

The International Rescue Committee (IRC) has one of their largest operations in Guinea, providing services and support to a population of up to 200,000 refugees quartered in many camps established throughout the country...Traveling outside the capital city of Conakry, one immediately finds that Guinea has little infrastructure, especially in the way of electrical grid and telecommunication systems...So IRC field offices must provide their own infrastructure: diesel generators for electricity and high-frequency (HF), two-way radio sets to communicate with other offices and mobile units, up to hundreds of miles apart.

Expecting this isolation and general lack of connectivity, I was quite astonished when we arrived in Kissi. Here I found the radio operator using his equipment to make a binary file transfer from his desktop PC to another field office, wirelessly!

This capability surprised and intrigued me. On top of the operator's radio set, connected to the serial port of his PC, sat a dingy black box simply labeled 9002 HF Data Modem. I noticed the operator used a proprietary, MS-DOS program to make his file transfers, but I immediately began wondering: if this device is truly some kind of modem, moving binary data over the ether of radio, why couldn't we set it up with Linux and network with PPP connections as well?

After a little research and testing, I soon confirmed this equipment could indeed form the basis of a wide area network, providing full access to internet e-mail via the Conakry office for all personnel in each of the three field offices. Moreover, since IRC owned most of the equipment already--and since we would be using Linux and other freely available, open-source software--the system could be implemented at negligible cost, with no increase in operating expenses. For the price of some network cards and category 5 cable, we could connect our bush offices to the rest of the world. I developed a design and specification for the system, and the project we call Radio E-mail has been continuously operational since January 2002...

HF radio...waves roll out across the landscape, reflecting off the ionosphere to follow the curvature of the earth. This gives HF signals a range in the hundreds of miles. From Conakry to Nzerekore--IRC Guinea's most distant field office--HF easily covers a straight-line distance of over 375 miles (600 kilometers.)...

...Now for the bad news: where HF wins the wireless game in range, it loses its pants in data capacity. If 802.11b is considered broadband, think of HF as slim-to-none-band...

And wait, it gets worse. Two-way radio is the classic half-duplex medium of communication; that is, you are either transmitting--push to talk--or receiving, not both at the same time...

Given these capabilities and limitations of HF, our design strategy for the project uses radio modems in a topology among field offices.."

The article proceeds to explore this design strategy in detail.

Click here for the full article online.