BOULDER, Colo.-Engineers have completed a month-long test of the Global System for Mobile communications standard at 1.8 GHz as part of an assessment for the U.S. wireless industry entering the personal communications services market.
Field tests took place at U S West Inc.’s Boulder Industry Test Bed facility in cooperation with the Joint Technical Committee. This is the first formal test for the JTC, a spin-off group of the Telecommunications Industry Association and Committee T1.
“Each technology has been invited to use this facility to verify system characteristics. But we have not elected to do competitive evaluations at this time,” said JTC Co-chairman Charles Cook.
Test results will be released in late January. The GSM system, based on Time Division Multiple Access digital technology, is an offspring of the European DCS-1800 standard. It is a “high tier” system using a high-powered base system and a minimal number of cell sites.
“Low tier” systems being developed use more low-power cell sites and can handle a larger volume of calls.
Two manufacturers, Motorola Inc. and Northern Telecom Inc., participated in the jointly designed program. The plan called for the companies to provide full coverage for Boulder, a city of 80,000 resting at the foot of the Rocky Mountains.
Northern Telecom set up two base stations, one downtown and another atop nearby Green Mountain. The Northern Telecom base site controller and switch were located in Richardson, Texas, just outside of Dallas.
Motorola’s combined base station-base site controller unit was located in suburban Boulder, hooked up to the Northern Telecom switch in Richardson.
“GSM offers an open interface, so Motorola (base stations) can talk to the Northern switch,” said Ken Riordan, engineering manager of Motorola’s Cellular Infrastructure Group. The open interface offers the interoperability requested by industry operators, something not always available in current cellular systems, Riordan said.
“This will appeal to operators who want that (interoperability) for a competitive environment. Our system can even tie into cable,” said Myles Naughton, Motorola’s lead engineer for PCS.
Five other PCS standards are emerging for U.S. systems:
Interim Standard 95 based on Qualcomm Inc.’s Code Division Multiple Access technology.
The PACS system, a hybrid of the Wide Area Communications System and the Japanese Personal Handyphone System.
A hybrid TDMA-CDMA system created and supported by Omnipoint Corp.
A TDMA-based system supported by AT&T Corp., L.M. Ericsson and Hughes.
A broadband CDMA system supported by InterDigital Communications Corp. and Oki America Inc.
U S West Technologies spokesman Ty Larson said the Boulder test explores three operational issues-coverage, functionality and interference.
“For coverage, we turned on one base station at a time. For functionality, we examined how it did handoffs and placed calls. To test for interference, we used the Walnut (suburban Boulder) site as the normal site, then turned on Green Mountain at the same frequency, then checked to see if it met the specs,” Larson said.
A few glitches were found in the system, but overall the results have been satisfactory, he said. Results from each field test will be published by JTC.
“Our mission is to help U.S. industry move along with the development process, to look at performance under the same conditions-in a common environment-so others can make a valid comparison,” Larson said.
