A new architecture

Upgrading analog networks to digital and finding an economical means to fill in nationwide footprints are primary concerns for wireless carriers today. Repeater and antenna manufacturers at Wireless '99 demonstrated a wide array of creative solutions to these problems.

Metawave is targeting analog operators that are upgrading to digital with a new version of its SpotLight 2000 smart antenna system, which is compatible with Motorola SC2450 base stations and analog base stations such as the Motorola HDII.

"It's a primary capacity solution for customer networks that are overstressed," said Lowell Anderson, director of SpotLight products for Metawave.

When used in code division multiple access networks with a 12-beam antenna system, the solution can dynamically change the size of individual beams. "A typical site has lumpy traffic distribution around the site that causes the noise floor to rise and limits capacity across the network," said Anderson. By reducing the size of crowded beams, operators can increase capacity by up to 40%, he said.

To simplify the process of configuring the SpotLight 2000, Metawave offers Beam Controller software. "It allows you to model in an RF environment what the cell site is going to look like as you pull beams in and adjust the sector size," Anderson said.

The Beam Controller software also can help overcome pilot pollution, which occurs when a mobile phone can see more than two or three pilot channels. To support soft handoff, a phone needs to be able to process two pilot channels, but if the phone is looking at more than two or three, efficiency can get degraded, said Anderson. That situation typically occurs across a body of water. With Beam Controller, operators can scale a cell back to decrease power over water.

Another smart antenna manufacturer, Arraycom, is working with several wireless system manufacturers to build its technology into their products. Arraycom's adaptive array processing incorporates multiple antenna elements on a base station and uses microprocessors to selectively distribute energy, said Martin Cooper, Arraycom chairman.

"We aim at a subscriber and when [he] talks, we listen to that subscriber and not any others," said Cooper. That capability enables multiple phones to use the same channel at the same time, increasing system capacity.

Arraycom's technology has enabled a personal handy-phone system operator in Japan to triple capacity on what had been an overloaded network, Cooper said, adding, "Everything we do is in the software. In one year, we'll triple capacity again. [Operators] can have a software-oriented base station that keeps getting better without buying new hardware."

US West Wireless hopes to solve a different type of deployment problem by using a new macrocell from Qualcomm dubbed QCell. The QCell offering, which U S West will deploy first in Salt Lake City, provides macrocell functionality in a unit the size of a microcell.

Because QCell is so compact, it can be pole-mounted. "QCell enables operators to sidestep zoning requirements," said Phil Hester, director of product marketing for Qualcomm wireless systems. "It can be added to existing towers and is excellent for rooftops. It's designed to be installed on a wall."

"We don't need to have ground space, and that's really important for a wireless operator," said Wayne Leuck, vice president of wireless engineering technology for U S West Wireless. "QCell provides an excellent platform for our next generation of rollouts."

Qualcomm reduced the size of the macrocell by supporting eight channels on a single chip and by reducing the size of the power amplifiers, said Irwin Jacobs, Qualcomm chairman and CEO. "We've also gotten the reliability of each component to the point where we can get rid of some redundancy," he said.

A new role for repeaters As wireless operators look to fill in nationwide footprints and keep costs down, repeaters are beginning to play a larger role in network architecture.

Repeater Technologies, which in September 1998 turned up its first hybrid base station and repeater network in St. Cloud, Minn., now has six networks up and running, said Ken Kenitzer, Repeater president and CEO. "We've targeted large and small companies wherever they need coverage but capacity is not an issue," he said. "If carriers want to be ubiquitous, they have to cover these areas."

In St. Cloud, Repeater's carrier customer Lifecom had been considering installing 24 base stations for a total system cost of $16 million, but instead was able to use six base stations and 24 repeaters for a cost of $6 million, said Kenitzer. The net result is that Lifecom can sell service for less than 6 cents a minute.

Repeater Technologies' RepeaterNet network management software, which provides advance notice of trouble conditions, has been key to gaining carrier confidence, Kenitzer said. "Repeaters in the past were thought of as a patch or hole fill. When your livelihood depends on a piece of equipment, you want to feel close to it. With [RepeaterNet], carriers feel confident because they know where their equipment is at all times."

A new GSM repeater from Ortel uses frequency translation to tackle several installation problems. The device converts signals from a base station to a different frequency for transmission, then reconverts it, said Douglas H. Morais, president of Ortel's wireless group.

"It allows [wireless carriers] to operate the repeater with minimum separation between the antenna that looks at the base station and the one that looks at the user," said Morais. That's important because it can sometimes be difficult to obtain appropriate real estate to support the higher level of antenna separation that would otherwise be needed for proper isolation, he added.

Operators can also use the new Ortel repeater for installations where they must put the repeater far from the base station. Frequency translation enables the device to operate at high gain to support this type of application, Morais said. The new device also can be used with an omni-directional antenna.

Ortel also introduced a CDMA repeater that operates at 800 MHz.

Allen Telecom's new line of Interference Cancellation Equipment repeaters requires less isolation than conventional offerings, said Todd Johnson, Allen's market segment manager. The product, originally developed in Germany, will be available initially in a GSM version, but other versions are planned. The ICE repeaters have an interference canceller that enables wireless operators to run at higher gain or to build a lower-cost repeater site, Johnson said.

Allen also is offering an upgrade kit to add IS-136 capability for its line of EAC2000 analog repeaters. By supporting operation in analog and digital modes, a wireless carrier can preserve its investment in its original infrastructure, said Johnson.

NEC America is working with carrier's carrier Pathnet on a novel idea for a repeater-based network.

When microwave operators using the 1900 MHz range were forced to move to a different spectrum to make way for PCS, Pathnet saw an opportunity: It would work with the displaced operators to build a new 10,000-mile network at 6 GHz. In the process, it would build in extra capacity, which it would wholesale to other operators, sharing revenues with its construction partners.

Pathnet has chosen NEC America to provide high-capacity transmission equipment for its network, which initially will operate at OC-3 (155.5 Mb/s) but can be upgraded to support 14 times that bandwidth.

"It's easy to add capacity. You just add plug-in modules," said Becky Holland, manager of sales and marketing for the public networks group at NEC America's communications systems division. Users can put up to seven modules in two bays of equipment and, with an additional polarized echo cancellation feature, they can transmit on the horizontal or vertical of the same frequency pair, effectively doubling total capacity, said Holland.

One of the reasons Pathnet chose NEC was because the compact size of NEC's offering enabled it to be installed in existing shelters, she said.