Getting the signal out Radio vendors broadcast quality, extension messages >BY JASON MEYERS, Wireless Networks Editor

While switching and software vendors at Wireless '97 showcased interoperable services that would entice customers to use wireless networks, radio equipment manufacturers were convincing carriers that they could provide the strength and clarity to make it all come together.

The biggest equipment providers focused primarily on the quality question, and solutions introduced at the show ran the gamut of digital platforms. Northern Telecom, Lucent Technologies, Ericsson and Hughes Network Systems introduced new enhanced full-rate speech vocoders for IS-136 time division multiple access (TDMA) networks, all of which use the algebraic code excited linear predictive (ACELP) coding algorithm specified in the IS-136 standard. The challenge for TDMA developers is to surmount the technology's past flops and false starts and help it regain promise.

"While TDMA has not gotten the best rap for quality, we believe our networks are above the norm," said Matthew Desch, president of Nortel Wireless Networks. The vendor's solution, which it demonstrated at Wireless '97, uses enhanced coding algorithms to improve audio quality and resistance to channel interference. The vocoder supports TDMA, AMPS and cellular digital packet data on a per-call basis.

Lucent also conducted a live demonstration of its new vocoder that incorporates an ACELP algorithm, using a link to the AT&T Wireless Services network currently under construction in Chicago.

Ericsson showcased other TDMA enhancements in addition to demonstrating its IS-136 ACELP vocoder. The company introduced a combining technique that reduces interference on the uplink between the mobile and the base station antennas, as well as an adaptive channel allocation solution that allows base stations to identify potential interference and retune automatically to improve voice quality.

"What you're seeing is continuous refinements that add more value," said Bo Piekarski, vice president of Ericsson's U.S. GSM business unit.

Motorola's Cellular Infrastructure Group concentrated its voice quality improvement efforts on code division multiple access (CDMA), demonstrating its 8 kb/s enhanced variable rate vocoder, which the company says is the first public demonstration of its kind. The system is capable of providing more than 100% additional capacity than 13 kb/s CDMA vocoders using the same number of cell sites, according to Motorola.

For many Wireless '97 exhibitors, the newly competitive wireless crowd proved to be an attentive audience for demonstrations of equipment that can help push radio signals farther, facilitating the tiered combination of outdoor and in-building coverage so crucial to boosting network usage. Ericsson and Texas Instruments announced the completion of a trial of TI's 1250 W active antenna in conjunction with Ericsson's radio base station in Powertel's GSM network in Auburn, Ala. Originally a Pan-European digital wireless standard, some U.S. carriers are now adopting GSM. The high-powered "boomer" antenna is ideal for covering large expanses or city edges, said Piekarski, but sometimes terrain makes high power obsolete.

"Whether its 500 W, 5000 W or 50,000 kW, into a mountain is into a mountain," he said.

For spot coverage, Ericsson introduced a 250 W active antenna for 1900 MHz GSM markets that can help carriers refine coverage gradually, thereby deferring capital investments. "As the system grows, you keep putting on more panels," said Piekarski. "The idea is that it's directional, so you have to be cognizant of how you place it.

Ericsson also introduced new additions to its RBS family of radio base stations-a macrocell, a microcell and a picocell unit-that can help carriers structure their radio design in a more organized, layered manner as opposed to simply putting up sites.

"Before it was, 'Build, build, build,'" said Stuart Rosenfield, marketing manager for Ericsson's D-AMPS/AMPS business unit. "Now it's, 'What and who are we building it for?'"

Other vendors also looked toward signal extension. Ortel introduced several additions to its MirrorCell family of wireless repeaters, including a two-channel CDMA repeater called the MirrorCell Select CDR1902. The vendor also introduced an element manager software package and announced a contract to provide channel-selective repeaters to Microcell Connexions in Canada.

In addition to booth displays, Ortel's equipment was put to the test inside San Francisco's Moscone Center, where Cellular One has deployed 16 MirrorCell repeaters. At the show, Ortel found heightened interest among carriers in ensuring extension technology is included in the post-launch phases of their buildouts. "They're only now realizing how much they need this," said Hal Zarem, business manager for wireless communications at Ortel.

ADC Wireless Systems found a similarly receptive crowd. The company highlighted its range of microcell equipment, including the T-1 CityCell it recently introduced for AMPS cellular systems as an addition to its CityWide family of microcell and antenna devices. At the show, the company also introduced CityPower, a new line of cellular power amplifiers resulting from ADC's acquisition of Pacific Amplifier.

"We're finding that carriers want more power than the equipment gives them-especially microcells," said Joe Roissier, director of marketing at ADC Wireless. "Carriers still seem to be addicted to power," (see sidebar on page 32).

Allen Telecom Group joined the RF extension crowd by introducing several new repeaters and microcells, including the EAC-800 digital repeater family for CDMA and TDMA systems, a 2 W channel-selective CDMA PCS repeater, an IS-136 software option for high-power analog repeaters and NanoLite, a fiber optic microcell system.

Metawave used the Wireless '97 venue to highlight its SpotLight multibeam antenna platform and to announce that it has successfully completed a trial with 360° Communications at two cell sites in Tallahassee, Fla. The trial showed an improvement in carrier-to-interference ratio of 6 to 10 dB over a three-sector system. The vendor also announced that it had formed Metawave Network Services, a division that will offer engineering and project management services for wireless systems implementation.

While all those vendors and more have been developing solutions to meet carrier needs for RF coverage, a small company called Innovation is trying to help wireless operators make sense of it all by piecing it together for them. The systems integrator announced its Intelligent Integrated Communications Systems approach, which encompasses several base station, power and antenna products and delivers them ready-to-use to network operators.

"We're not a technology developer, we're a technology enabler," said John Diefendorf, president of Innovation. "Very often we're redesigning and re-racking a lot of existing equipment to provide more capacity in a smaller footprint.

The goal for wireless network operators is to drive up revenue by putting more customers on the network and giving them more reasons to eat up airtime. In order to achieve that, solutions like the ones demonstrated at Wireless '97 must be firmly in place and logically connected to existing wireless systems to ensure that radio signals are extended into the places where people live and work.