Sending Data 160 Characters at a Time

Earl Oliver at at the University of Waterloo, Ontario, Canada, has an unusual phone bill. Unlimited texting plan or no, most of us would take a few years to send 80,000 messages. Oliver did it in just a few months. Rather than being victim to an unusual obsession, though, Oliver is attempting to bring better communications to rural parts of the developing world – by developing a protocol to send data packed into series of SMS messages.

In rural areas of India, Africa and China, use of SMS has skyrocketed in recent years, as cellphone towers have brought the first reliable telecommunications to previously unconnected areas. “SMS is ubiquitous, reliable and mostly low cost,” says Oliver, while data services are expensive and patchy.

Oliver’s huge messaging spree was visited on Canadian carrier Rogers, and included tests to probe what happens when you send huge batches of messages, and a data transfer system he built informed by the results. Oliver had to make his system resilient to the fact that his bulk sending tests showed that around 3 percent of messages arrived out of order, thanks to the variable delay between messages.

The question is what kind of data rate can you achieve this way? Oliver managed to get up to a blistering 20 bytes per second when sending using a custom app written for a BlackBerry smartphone. It takes about 250 messages to send 32 kilobytes of data.

Oliver isn’t intending this to be used to bring youtube videos to rural areas, though. Instead it provides a way to bring connectivity to community kiosk computers designed to give a whole village to access information like crop prices. Usually connected via very unreliable dial up connections, being able to use the cellphone network instead might improve reliability. Rather than being used for accessing information on demand, the kiosk would have to use text messages to download it prior to use, for example once a day. Oliver and colleagues have already built SMS data transfer into a software platform they designed for kiosks, called VLink.

Oliver presented details of his idea at the MobiSys conference in San Francisco last week, where one attendee questioned whether the roll out of cellphone data networks would make the idea shortlived. Romit Roy Choudhury of Duke University, also in attendance, suggested otherwise. “3G is being rolled out to metropolitan areas now, but it will take much longer to arrive in rural areas,” he said.

Oliver was also asked if he had made enemies of his cellphone provider. “About ninety five per cent of traffic to my website comes from telcos,” he admitted, “but in theory sending in bulk shouldn’t degrade the experience of others.”