Choosing a Cell Phone Standard

In the jargon-laden world of high technology, few things have become more confusing than sorting out the differences among competing digital cellular phone technologies.

At least four major digital phone transmission standards are in use in the United States. They carry such bewildering acronyms as CDMA, GSM, IDEN and TDMA, and the battle among them is quickly accelerating, as incumbent carriers and new rivals race to build their new digital wireless networks.

Consumers wouldn’t have to worry too much about the standard--as opposed to the features and overall value offered by a carrier--except that the choice of standard has a great deal to do with whether and where a phone will work outside of the home service area.

Until recently, mobile phones came in one flavor: analog cellular. These phones use a technology similar to FM radio, called advanced mobile phone standard, to transmit conversations.

But in recent years, cellular carriers have begun switching from analog to digital to increase capacity and improve service, and a new set of networks that uses a different portion of the radio spectrum is being deployed as PCS (for personal communicatons services).

Before you shop around for the smartest service plan, handiest features and lowest prices in a digital cellular, consider where and how you plan to use your wireless service.

Global jet-setters will probably want to at least consider cellular phones that use the global system for mobile communications, or GSM, standard. That digital transmission technology has become the dominant standard in much of the world--the exceptions are Japan, the United States and South America--with about 55 million customers in 109 nations. The technology converts voices into digital signals and transmits them within assigned slots on the airwaves.

In the U.S., 10 GSM systems are providing service to about 800,000 subscribers in 30 states, including California. Pacific Bell Mobile Services is offering GSM-based PCS in Los Angeles County and much of the rest of Southern California.

The company does not have so-called roaming agreements with any international carriers, so you can’t yet use a PacBell GSM phone overseas without first establishing an account with an overseas carrier. But a spokesman for Pacific Bell Mobile said the company expects to have the agreements with carriers in 10 foreign countries by the end of the year.

Domestically, GSM coverage is expected to be spotty for the next few years, in part because Pocket Communications, the second-largest PCS licensee in the U.S. that is using the technology, has filed for bankruptcy protection because it cannot afford to pay for the licenses it won at Federal Communications Commission auction. Pocket won licenses in such major markets as Chicago, Detroit, Dallas-Fort Worth, St. Louis, New Orleans, Omaha, Las Vegas, Honolulu and Little Rock, Ark.

“With GSM you can roam outside the United States and use your phone in [many] countries, but within the U.S. you may have more difficulty” when traveling until the GSM network is built out, said Jane Zweig, senior vice president at Herschel Shosteck Associates, a Wheaton, Md., wireless consulting firm.

A second mobile phone transmission technology called code division multiple access, or CDMA, is quickly becoming the dominant digital wireless standard in North America, claiming about 900,000 subscribers. Commercial CDMA service is also offered in South Korea and Hong Kong, and CDMA has been purchased, or selected for testing by wireless carriers, in Argentina, Brazil, Chile, China, Germany, Israel, Peru, the Philippines and Thailand.

Many incumbent carriers have been converting their analog systems to the standard, which was developed by San Diego-based Qualcomm and has far outpaced the original digital standard chosen by the cellular industry, time-division multiple access, or TDMA.

Skeptics long argued that CDMA--based on a military communications technology that splits a digital information stream into many pieces, sends them along different radio frequencies and then reassembles them--would not work on big systems in major cities. But the skeptics have been proved wrong.

In Southern California, CDMA service is available in most of Los Angeles County and in San Diego, as well as in Las Vegas, from AirTouch Communications and Sprint PCS. GTE Wireless is rolling out CDMA service in San Francisco this year. Carriers would not disclose their CDMA subscriber numbers in these markets.

Industry experts predict CDMA will ultimately handle the majority of the nation’s digital wireless phone traffic, with GSM a close second.

The remaining two digital transmission standards have been championed largely by just two carriers. AT&T; Wireless, the nation’s largest wireless carrier, has stuck with TDMA, and Nextel is building the Integrated Digital Enhanced Network, or IDEN.

Both systems are available in major markets nationwide, but Nextel is targeting its system mostly at business users, offering a number of unique features.

Nextel lets users roam nationwide for no additional charge, and, unlike most competitors, who use less precise pricing, its connect charges are rounded to the nearest second after the first minute. Nextel also lets users circumvent the public phone network entirely and communicate, walkie-talkie fashion, with as many as 30 people, at rates that are as much as one-third less than regular cellular phone rates.

Meanwhile, AT&T; is going after the mass market. Like many of its digital rivals, AT&T; digital phones offer paging and support text messaging technologies such as electronic mail.

One last caveat: Be vigilant in examining claims about coverage areas, especially if you intend to use your phone outside of major cities.

Mobile phone “coverage doesn’t just mean being able to leave the state; coverage can differ in a community from your work to your home,” said Amy Daminakes, an AirTouch spokeswoman. “Consumers should check coverage maps and have clear [ideas] of what to expect. I . . . think that in the past, some carriers shot themselves in the foot by promising something and not delivering.”