Why text messages are limited to 160 characters

Credit: Lori Shepler / Los Angeles Times

Alone in a room in his home in Bonn, Germany,Friedhelm Hillebrand sat at his typewriter, tapping out random sentences and questions on a sheet of paper.

As he went along, Hillebrand counted the number of letters, numbers, punctuation marks and spaces on the page. Each blurb ran on for a line or two and nearly always clocked in under 160 characters.

That became Hillebrand's magic number -- and set the standard for one of today's most popular forms of digital communication: text messaging.

"This is perfectly sufficient," he recalled thinking during that epiphany of 1985, when he was 45 years old. "Perfectly sufficient."

The communications researcher and a dozen others had been laying out the plans to standardize a technology that would allow cellphones to transmit and display text messages.  Because of tight bandwidth constraints of the wireless networks at the time -- which were mostly used for car phones -- each message would have to be as short as possible.

Before his typewriter experiment, Hillebrand had an argument with a friend about whether 160 characters provided enough space to communicate most thoughts. "My friend said this was impossible for the mass market," Hillebrand said. "I was more optimistic."

His optimism was clearly on the mark. Text messaging has become the prevalent form of mobile communication worldwide. Americans are sending more text messages than making calls on their cellphones, according to a Nielsen Mobile report released last year.

U.S. mobile users sent an average of 357 texts per month in the second quarter of 2008 versus an average of 204 calls, the report said.

Texting has been a boon for telecoms. Giants Verizon Wireless and AT&T each charge 20 to 25 cents a message, or $20 for unlimited texts. Verizon has 86 million subscribers, while AT&T's wireless service has 78.2 million.

And Twitter, the fastest growing online social network, which is being adopted practically en masse by politicians, celebrities ...

... and news outlets, has its very DNA in text messaging. To avoid the need for splitting cellular text messages into multiple parts, the creators of Twitter capped the length of a tweet at 140 characters, keeping the extra 20 for the user's unique address. 

Back in 1985, of course, the guys who invented Twitter were probably still playing with Matchbox cars.

Credit: Friedhelm Hillebrand

Hillebrand found new confidence after his rather unscientific investigations. As chairman of the nonvoice services committee within the Global System for Mobile Communications (GSM), a group that sets standards for the majority of the global mobile market, he pushed forward the group's plans in 1986. All cellular carriers and mobile phones, they decreed, must support the short messaging service (SMS).

Looking for a data pipeline that would fit these micro messages, Hillebrand came up with the idea to harness a secondary radio channel that already existed on mobile networks.

This smaller data lane had been used only to alert a cellphone about reception strength and to supply it with bits of information regarding incoming calls. Voice communication itself had taken place via a separate signal.

"We were looking to a cheap implementation," Hillebrand said on the phone from Bonn."Most of the time, nothing happens on this control link. So, it was free capacity on the system."

Initially, Hillebrand's team could fit only 128 characters into that space, but that didn't seem like nearly enough. With a little tweaking and a decision to cut down the set of possible letters, numbers and symbols that the system could represent, they squeezed out room for another 32 characters.

Still, his committee wondered, would the 160-character maximum be enough space to prove a useful form of communication? Having zero market research, they based their initial assumptions on two "convincing arguments," Hillebrand said.

For one, they found that postcards often contained fewer than 150 characters. Second, they analyzed a set of messages sent through Telex, a then-prevalent telegraphy network for business professionals. Despite not having a technical limitation, Hillebrand said, Telex transmissions were usually about the same length as postcards. 

Just look at your average e-mail today, he noted. Many can be summed up in the subject line, and the rest often contains just a line or two of text asking for a favor or updating about a particular project.

But length wasn't SMS's only limitation. "The input was cumbersome," Hillebrand said. With multiple letters being assigned to each number button on the keypad, finding a single correct letter could take three or four taps. Typing out a sentence or two was a painstaking task.

A GSM document outlining the definition of SMS. Credit: Friedhelm Hillebrand.

Later, software such as T9, which predicts words based on the first few letters typed by the user, QWERTY keyboards such as the BlackBerry's and touchscreen keyboards including the iPhone's made the process more palatable.

But even with these inconveniences, text messaging took off. Fast. Hillebrand never imagined how quickly and universally the technology would be adopted. What was originally devised as a portable paging system for craftsmen using their cars as a mobile office is now the preferred form of on-the-go communication for cellphone users of all ages.

"Nobody had foreseen how fast and quickly the young people would use this," Hillebrand said. He's still fascinated by stories of young couples breaking up via text message. 

When he tells the story of his 160-character breakthrough, Hillebrand says, people assume he's rich. But he's not. There are no text message royalties. He doesn't receive a couple of pennies each time someone sends a text, like songwriters do for radio airplay. Though "that would be nice," Hillebrand said. Now Hillebrand lives in Bonn, managing Hillebrand & Partners, a technology patent consulting firm. He has written a book about the creation of GSM, a $255 hardcover tome.

Following an early retirement that didn't take, Hillebrand is pondering his next project. Multimedia messaging could benefit from regulation, he said. With so many different cellphones taking photos, videos and audio in a variety of formats, you can never be sure whether your friend's phone will be able to display it. But he's hoping to make a respectable salary for the work this time.

-- Mark Milian

Source: http://latimesblogs.latimes.com/technology/2009/05/invented-text-messaging.html

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