Radio E-mail in West Africa: The Complete Version
Editors' Note: The following is the complete version of the article by the same title that appears in the November 2002 issue of Linux Journal.
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 Republic of Guinea is a cashew-shaped nation with Atlantic view property, 10 degrees north of the equator in west West Africa. It is a beautiful and resource-rich nation, with an total land area about the size of Oregon. As far as African countries go, Guinea is a calm pocket of peace and stability, and it generally doesn't attract a lot of attention from beyond its own borders.
But Guinea has quietly played a heroic role in the theater of world events in recent years. It provides a safe and welcome refuge for as many as half a million people displaced by brutal wars and civil upheavals in the neighboring countries of Sierra Leone and Liberia.
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. I became involved with IRC when my wife accepted the position of Country Director for the program in the summer of 2001. Soon we were traveling on an inspection tour of the camps, making the long road-trip to visit the program's three field offices up-country. Our first destination was a distant and dusty village, delightfully named Kissidougou—frequently called Kissi in the local vernacular.
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—to say nothing of Starbucks and broadband access to the internet. 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.
If you have been making the move to wireless lately, most likely you are working with the microwave, high bandwidth frequencies of 802.11b. If so, you know that on a clear day you maybe can get a line-of-sight connection out 10 miles or so. That surely won't do for the vast distances and wild terrain we need to cover in rural Africa.
HF radio is another animal. Its longer 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.) The road that sometimes connects these two points is, of course, much longer—a gut-slamming, spine-jamming, two-day punishment for the damned.
So the great advantage of HF is it can go the distance, leaping the obstacles in its path with aplomb. 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. The radio modems we are using here are speced at an anorexic 2400 baud!
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. This, plus the robust error-checking protocols implemented by the modem hardware itself, means the actual link experience is more on the order of 300 baud. Does anyone remember 300 baud? Unless you measure your patience with radio-carbon, your dreams of remote login sessions will be dashed and splattered. As for on-line browsing, chat, video-conferencing and the like, well, best to not even think about it.
Yet for classic store-and-forward applications like text-based e-mail, the bandwidth limitation of HF radio is workable. We simply need to pay close attention to our configuration and try to optimize as much as possible. With HF radio, every packet is precious.
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