E-DEFINITIONS WITH MARK TAMMINGA
Cell Phone Systems: Multigenerational Crumbs
When the Europeans first set foot on the New World, they saw land, limitless land. They thought it was boundless and that’s how they treated it. Well, much the same thing happened with the electromagnetic spectrum.
No one knew the spectrum even existed until Heinrich Hertz proved, in 1888, that electric waves could move through the air. But by World War I, hobbyists were using bedsprings and Quaker Oats boxes to build radio equipment, nattering away at each other on any old frequency they chose. What had seemed limitless rapidly became a congested space of incoherent babble. The Great War and the emergence of the first broadcast radio stations in the early ‘20s brought home the pressing need to sort out what had become a nasty mess.
So in 1927, the U.S. government decided to impose some order on the spectrum hubbub. The Federal Radio Commission, precursor to the FCC, doled out licenses to blocks of frequency, giving them to commercial and military interests. It added wiggle room to each side of the blocks to make allowances for the crude transmitters of the time and insisted that the blocks be used for a single purpose. No buying, selling or subdividing of your block. Add television and new military uses to the mix, and spectrum shortage became the way of things.
When a new demand for spectrum came along—like that caused by the two-way radios we’ve come to know as cell phones—things got complicated. The theory behind a working cell phone system was fully formed by 1947. Recognizing that bandwidth was scarce, but also that transmitters had limited range, engineers at Bell Labs cooked up a way to reuse the same set of frequencies by dividing broader areas into cells. They even theorized about ways to hand off a call from one cell to another without it getting dropped.
Keen on this new idea, AT&T requested, in late 1947, that frequency be freed up so that a commercial cell phone system could be developed. The FCC, ever miserly about bandwidth, decided it would only free up enough spectrum to carry 23 simultaneous calls per service area. Not much there to build a business on. Of course, even had the FCC been more generous, the equipment needed to run your mobile phone—essentially a fully functioning radio station—would have taken up the backseat of your Packard sedan.
Over the next 30 years, we learned much about using the radio spectrum more effectively and, handily enough, everything electronic got smaller. A lot smaller. In 1978, after much bickering, the FCC gave authority to test the Advanced Mobile Phone System. But regulators were too busy busting up the Bell System monopoly to distract themselves with radical new phone technologies. Broader commercial service would have to wait until 1983, first in Chicago and then in Washington, D.C.
At the time of the early market tests, engineers estimated that no more than 1 million people would subscribe to cell service by 2000. The initial commercial markets, however, proved to be terrific money-spinners and cell phone service based on the AMPS model took off, blasting past the million-subscriber mark by 1987. This led, naturally, to apocalyptic predictions of system saturation. The analog AMPS standard used up a certain portion of the available spectrum with each call made. Make more calls, use up more spectrum. The simple arithmetic warned planners that they were headed for a wall.
Digital Cellular: TDMA, GSM and CDMA
The FCC was in no mood to help. Moving frequency around for the benefit of phone people was a huge bother, particularly because it usually meant knocking heads with radio and television interests and, oh, the military. The FCC did drop this crumb: It permitted phone companies to experiment with alternative ways to transmit voice and data wirelessly using the same frequencies they already had. That meant going digital. Converting voice into a stream of 1s and 0s opened up all kinds of possibilities. But the big payoff came in using digital technology and its inherent speed to sneak several calls onto one frequency.
The first off the mark was Time Division Multiple Access. TDMA initially squeezed three calls into the same frequency used by one AMPS call by splitting up the time devoted to each call and then rotating among them hundreds of times a second. TDMA has been modestly successful in the United States, but its most aggressive use is in the Global System for Mobile Communications standard used throughout Europe, Asia and Africa. GSM uses TDMA techniques to cram eight calls onto the same frequency and has twice as many subscribers as all other systems combined.
A more recent alternative, introduced in 1995 by Qualcomm, is Code Division Multiple Access, which smears phone calls across the allocated spectrum range and then reassembles them in your phone. The CDMA standard is complicated stuff, but also the clear winner in terms of capacity and future growth potential.
And, of course, none of these approaches is compatible with any of the others, and all four approaches (that includes AMPS, which is still very much alive) remain in use in North America. Oh, and the digital standards operate at two different sets of frequencies—the 800 MHz band and the newer 1900 MHz band (the so-called PCS band). To cope with the mess, phone designers have built dual and tri-mode phones, which try to get beyond the incompatibility problem by incorporating two or three phone technologies in one handset. This puts a heavy load on those of us who are trying to figure out what to buy.
The rescue is supposed to be in the form of third-generation wireless services. Europeans, the Japanese and the Koreans will be the first to benefit—but eventually phone service with 10 times the capacity of today’s phones will be offered even in the fractious U.S. market.
Mark Tamminga (firstname.lastname@example.org) practices law and fiddles with software at Gowling Lafleur Henderson LLP in Toronto.