Look Before You Leap
There are two basic schemes for packing as many digital calls as possible into the available bandwidth. The Time Division Multiple Access protocol, an early format championed by AT&T, has evolved into the Global System for Mobile Communications, now a near-universal standard in Europe and Japan. Code Division Multiple Access arose as the main alternative, adopted by Sprint and GTE, and by the end of the decade it reduced noise better than the time division method and packed more data into a single channel.
The leading 3G standards approved by the International Telecommunication Union are based on the code division protocol. But to implement them, telecom companies must license expensive new spectrum and overhaul cell-tower and handset technology. After initial blind enthusiasm, few U.S. carriers now seem in a hurry to make massive investments. Tom Crook, director of technology research for Sprint PCS, speaks for many when he says, “I don’t see us doing 3G anytime soon.”
Technical assessment groups like Adventis in Boston also say that, on a real street corner, 3G data rates won’t come close to the maximums industry proponents quote, which are based on pristine lab conditions. In a recent compilation of technical and investment studies examining eight proposed broadband technologies, Adventis concluded that only three could realistically achieve average data speeds faster than a desktop modem’s. And those three would roughly double the speed, far shy of the quadrupling needed for real broadband performance.
Ken Hyers, an industry analyst with Cahners In-Stat Group, says that the daunting expense and dubious technical results of 3G are causing U.S. carriers to “take a wait-and-see attitude. They’re saying, Let’s see how much bandwidth our customers are really going to use.’” If all they want are simple Web services such as online restaurant directories, the answer may be, not much.
Rather than taking the true broadband leap, Sprint PCS and others have decided to test the waters using 2.5G technology, which uses the same spectrum as current 2G networks and requires only a relatively minor hardware upgrade. Although 2.5G can’t achieve true broadband data rates, it does offer one huge advance: it’s “always on”-instantly available, 24 hours a day. You won’t have to dial in and wait 30 seconds while your mobile device connects to the Internet. Instant access changes your relationship to the Internet profoundly. Studies show that people in homes with instant access through hard-wired systems such as digital subscriber lines and cable modems use the Internet three times as much as people who must dial in each time. When you’re mobile, any delay is even more discouraging and may stop you from accessing the Net altogether.
So who really needs 3G, then? Some of the canniest telecoms have begun to blur the distinction by defining their 2.5G technology as 3G. Anil Kripalani, a senior vice president at Qualcomm, says, “We know how to push the envelope.” Like other U.S. proponents, he sees no need for carriers to jump to the real 3G. Thus the world’s telecom disparity could continue, with America leaning toward 2.5G, Japan intent on 3G, and Europe and the rest of Asia vacillating in between.
Yet even if the 3G dream touted so boldly within the industry fades away, it won’t have been in vain, since it is what has motivated carriers to move to 2.5G standards. Engineers are devising intriguing cell-tower transceivers and handset antennas to help ensure that wireless users get the maximum bandwidth and strongest signals available, regardless of how many Gs they’re pulling. Yet incompatible transmission protocols still pose a problem. Each cellular device uses a microprocessor-radio chip that supports only one protocol. A phone using a code division protocol requires a different chip than a phone using a time division protocol, and different 3G phones from AT&T and GTE, say, would use different chips even if they were both based on a code division protocol.
One technology, known as software-defined radio chips, could provide a solution, according to Benny Bing, a leading wireless authority at the Georgia Institute of Technology Broadband Institute. Still in prototype, software-radio chips can switch among protocols, filtering techniques and detection schemes. At any moment, a mobile device with software radio inside could switch seamlessly among American, European and Japanese telecom standards, as well as competing transmission protocols (see “The Universal Cell Phone,” TR April 2001).