Now that many personal communications services providers are operating in several cities, most are advertising better call clarity than users received with cellular analog service. But will call clarity remain an issue once cellular carriers begin to aggressively market the same digital features?

If customers are going to be asked to switch to digital, “they are certainly going to look at all the options. When that day comes for the customer, it’s a significant chance [for us] to get the customer,” said Tom Murphy, Sprint Spectrum L.P.’s director of public relations. And call clarity is one option.

Prudential Securities Inc. in New York agrees. It believes PCS providers will have an edge over cellular carriers in terms of migrating customers to digital from existing analog channels, especially in highly dense markets. The firm conducted a call clarity study and concluded that digital systems operating next to analog systems in general performed poorly and appeared to be problematic. Prudential believes voice clarity will become a major issue when PCS pricing becomes more affordable.

But Herschel Shosteck, president and chief executive officer of Herschel Shosteck Associates Ltd., has concluded that analog and digital cellular networks still perform better than PCS networks in every U.S. market.

Shosteck has been measuring the call reception quality of cellular and PCS networks every quarter since December 1995 in major U.S. markets through surveys of carriers, resellers and agent-dealers. Cellular systems outperformed PCS systems in terms of mean opinion scores. PCS scored better than cellular during just one quarter, said Shosteck.

The Prudential survey, highly scrutinized by industry engineers for the methodology used, attempted to simulate real-life phone usage, said the company. Prudential tested in eight markets with five digital cellular and PCS systems. Of the 31 calls made, two wireline calls served as proxies. Sixteen calls were stationary and 13 were mobile. Time Division Multiple Access Interim Standard 136 technology at 1900 MHz was not tested.

Using two wireline calls as control samples and a pay phone as a substitute for a mobile landline call, Prudential recorded messages via each system onto a digital voice messaging system and combined them to create three surveys.

The company sent surveys to 1,000 people. Those who participated rated the calls in terms of distortion, clipping, background noise, tone and in comparison to analog, said Prudential. The survey only sampled the uplink direction of a wireless call, said the company.

Code Division Multiple Access technology at 1900 MHz scored the highest, said Prudential, followed by TDMA IS-136 at 800 MHz. Global System for Mobile communications technology also scored well, said the study. With a few exceptions, CDMA at 800 MHz performed in the bottom half. Nextel Communications Inc.’s integrated Digital Enhanced Network technology consistently performed in the middle.

Michael Elling, senior telecom analyst with Prudential, attributes the lower scores given to digital overlay networks to cell interference. “I think anytime you have any existing spectrum with different radio on it, there’s going to be interference. The hotter the analog system, the more difficult it will be to get a good digital signal,” said Elling. “The performance of the analog systems are different from digital systems, particularly with the handoff issues and cell sector issues. As a result, that’s going to affect the layout of the system.”

The danger, Elling said, will be when PCS carriers gain comparable coverage and begin cutting their prices in half. “To match that, a [cellular carrier] would have to blow up his capacity on a digital platform. Because of the heat of the analog system, the quality (of the digital network) will probably be poorer.”

Interference is a problem, admitted Craig Farrill, vice president of strategic technology for AirTouch Communications Inc., which operates large analog and digital CDMA networks in Los Angeles and San Diego and is part owner of PCS operator PrimeCo Personal Communications L.P. “All wireless systems are based on fixing interference,” he said. “As a result, you have an engineering need to address interference. What you do with it determines the quality of the network. It’s always there.”

“The number of cell sites is related to the number of customers,” said Ron Nelson, senior vice president of engineering for AT&T Wireless Services Inc., which operates TDMA and analog systems. “With fewer cell sites, the potential for interference is less. That doesn’t mean [interference] will degrade the (call) quality in a more heavily loaded network. There’s a greater potential of it. It takes skill and experience of using networks as they grow.”

“There are no inherent problems with digital overlays. You need guard channels between the analog and digital channels and have denser networks (in terms of cell sites). Once those are put in, it should perform well,” said Shosteck. “In the U.S., we tend to shoot from the hip and improvise. We’ve had some digital networks that are not very good.”

The reception quality of PCS networks likely never will outperform cellular networks in the long run, said Shosteck. Cellular operators have had the advantage of building out and perfecting their networks for more than a decade.

PCS networks “cannot perform as well as mature networks,” said Shosteck. “For any network to perform well, the cells have to be closer together … If you look at what has happened to cellular, cell construction doubled in 1994 to 1995. There was another 50 percent increase in 1996. This reflects cellular carriers enhancing the density of networks to fill in dead spots and fill in buildings.”

At any rate, PCS carriers’ ability to distinguish themselves in the marketplace in terms of call quality will come down to savvy marketing techniques and a market-by-market basis.

AT&T Wireless, the largest cellular carrier in the United States, will make that difficult. It has become successful at blurring the line between cellular and PCS by using the brand name Digital PCS in all of its digital cellular and PCS markets. Southwestern Bell Mobile Systems has adopted the same name in its digital and PCS markets as well.


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