Making Sense of a Wireless World
The cadre of companies that are selling an array of wireless phone services make much of the distinction between digital cellular networks and a newer breed of products known as personal communications services, or PCS.
But they certainly don’t have to.
“They both use the same technology, and the systems are built very much the same,†said Mark Lowenstein, vice president of wireless research at Yankee Group, a Boston-based market research firm. “From the perspective of the customer, it’s not really a big deal.â€
Wireless phone calls--be they cellular or PCS--are transmitted by radio signals to antennas that connect to the local phone network. As a caller moves from place to place, the call is relayed from one antenna, or cell site, to another.
The one difference between cellular and PCS is that they operate in different parts of the radio spectrum. Cellular services, including the newer digital varieties, use two regions in the 800- to 900-megahertz range, while PCS operates in the much higher frequencies of 1,850 to 1,990 megahertz. That means that PCS systems must have more antennas, making PCS signals somewhat stronger, but otherwise the two digital services are nearly identical.
“You get your TV reception at different parts of the spectrum--UHF and VHF--but you don’t notice that, either,†said Tim Ayers, a vice president with the Cellular Telecommunications Industry Assn., a Washington-based trade group that represents both cellular and PCS firms.
Both kinds of digital services have clear advantages over analog cellular networks, which customers have been using for nearly 15 years. Digital calls are much tougher for hackers to intercept and decode, voices sound clearer, and the systems can handle more kinds of advanced features like caller ID, call waiting and conference calling.
Digital networks can also carry at least three times as many calls at a time because the calls are transmitted in smaller chunks. Plus, digital phones sport a longer battery life--up to four to five hours of talk time compared with 60 to 90 minutes with an analog phone.
Digital cellular service comes in two varieties: time division multiple access (TDMA) and code division multiple access (CDMA). PCS comes in both of those flavors plus GSM, the standard favored in Europe. Wireless carriers trade barbs over which technology is best, but impartial observers say customers can’t discern any differences in quality.
In any event, manufacturers are expected to eventually devise a phone with enough chips to handle any standard in any frequency.
The one advantage of analog phones is that with a robust network of interconnection agreements, customers can roam almost anywhere in the country without losing service.
Lowenstein expects that advantage to erode within a year as digital cellular and PCS networks become more common and as manufacturers build dual phones that can default to the analog system when they are out of the range of digital transmitters. Digital cellular phones with analog backup are already available, but PCS-analog phones are still a ways away, he said.
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Karen Kaplan can be reached via e-mail at [email protected]
