Building Your House of Cards

If you've ever built a house of cards, you know that to build a really good one, you need to have a solid base. Those first cards need to support each other securely, and then with a light touch, a steady hand and some good planning, you can build a sprawling skyscraper. The concept also can be applied to wireless carriers and their networks. Each aspect of the network in and of itself is just another jack of spades, but if combined with others, that aspect can become an integral part of a strong structure that is capable of withstanding future layers.

Operators are under a lot of pressure to provide large numbers of minutes at the lowest possible costs, said Mike Malone, Motorola Cellular Infrastructure Group director of product marketing. To help carriers improve efficiency, Motorola introduced the SC4812 CDMA base station, which allows carriers to provision four CDMA carriers in one frame. The base station also offers 6-sector support and an average of 20W of forward power.

Building a Strong Base Although all aspects of a carrier's network are important, if the basic infrastructure isn't solid, then the house will come tumbling down. Change occurs so quickly in this industry, however, that carriers can't afford to think only about the present; they also must keep at least one eye on the future. They must keep the present structure solid in a way that can be integrated easily with future technology as it becomes available -- all without going over budget.

Carriers want to increase coverage and capacity for as little as possible. But they need solutions that allow for simple upgrades.

Part of the answer lies in open architectures and backward compatibility. Vendors are responding to carriers' demands for freedom of choice. Although companies such as Lucent and Motorola emphasize that they are jacks-of-all trades, they, too, are recognizing carriers' demand for choice and are shifting along with the rest of the industry toward an open architecture structure.

Just as there are many ways to skin a cat, there are many ways to improve capacity and coverage, and at Wireless '98, vendors offered a variety of options.

The Bases are Loaded Base-station vendors are offering small, efficient, powerful, aesthetically pleasing and flexible products in an effort to respond to carrier needs. Because competition is driving down the cost for a minute of airtimeMalone said that Motorola also increased the receive sensitivity to match the forward power, which, he said translates to fewer sites. And because an operator would need fewer racks of equipment with the base station, it could use a smaller building, which means finding a site may be a little easier. Locations that might have been out of reach before may be usable with a smaller footprint.

Because real estate is precious, because small is better, and because flexibility is a way of life, Samsung developed the Pico Base Station (PicoBTS). The compact CDMA base station, which features a modular design and requires no field maintenance, provides carriers with macrocell coverage and is suitable for locations where full-size base stations are impractical or too costly to deploy.

The main unit houses fully redundant controllers, a GPS receiver and CDMA channel elements. The radio unit supports diversity receive and 5W of output power. The base station takes less than one hour to install, uses ac power and can be placed in non-traditional areas such as on the sides of buildings, telephone and utility poles, and tunnels and bridges. The PicoBTS also is IS-634-compliant.

Following the open architecture theme, Watkins-Johnson introduced its TDMA (IS-136A)/AMPS wideband, software-definable, dual-mode base station for both mobile and WLL applications. The Base2 MacroCell is scaleable from six to 42 RF carriers and uses open, non-proprietary industry-standard interfaces. It provides an AMPS upgrade path, and enhancements can be added via remote software upgrades. The Base2 is available either as an OEM product or as part of the company's full-system deployment.

Could You Repeat That? Repeaters are coming into their own as a viable part of a wireless network. Vendors have improved their products to position them as a way to increase coverage without the expense of installing a full base station. According to Repeater Technologies, in a repeater-based build-out, you place a base station in a central donor cell and then deploy repeaters in adjacent cells, taking advantage of the base station's signal and capacity. Dave Bolan, Repeater Technologies vice president of marketing and OEM sales, said that this setup offers similar coverage to that of base-station deployment but with several benefits: fewer radio channel units, less backhaul requirement, less switch and base station controller capacity, and lower real estate costs.

Repeater Technologies has signed agreements with ClearNet, Central Wireless Partnership and Wireless Communications Venture (dba Lifecom) to supply its products. The company's OA2900C NR offers 6.3W of output power and features receive diversity that preserves the donor cell capacity, provides 3dB more link budget and maintains the extended battery talk time designed into the PCS network.

A traditional use for repeaters is to cover the hard-to-reach areas. To that end, Allen Telecom has designed the EAC-850 2-channel CDMA repeater to enhance coverage in focused areas such as tunnels, dense urban sites and sports stadiums. The unit also can be used for adding coverage for operators building out over an existing analog system or for in-building coverage systems. Continuing with the smaller-is-better-theme, Allen Telecom's latest repeater is much smaller and weighs less than half as much as its dual-mode repeater.

Although superconducting filters have not taken the industry by storm thus far, vendors are continuing to offer more advanced superconducting products, and carriers are starting to look at those products as an option for improving coverage, particularly to fill in coverage gaps in less densely populated areas such as along a heavily traveled highway.

Illinois Superconductor designed its PCS PowerMaster duplexer, which is a transmit filter, a receive preselect filter and a receive low-noise amplifier (LNA) in one package, to handle as much as 30W of continuous power. Ted Laves, president & CEO, said that superconductors, up until now, could handle only a few milliwatts of power, which is why the first implementations were on the uplink side.

"Nobody thought you could do that kind of power handling on the downlink or transmit side because you obviously had the issue of power overrunning the superconducting and causing unwanted signals, technically called inter-modulation distortion," he said.

The company also introduced the SpectrumMaster Ultra, which has 24 poles and is about "10,000 times better than a conventional filter," Laves said. The third product the company introduced was the RangeMaster Omega, which is a combination filter and LNA that is especially suited for rural areas. The TowerMaster packages a RangeMaster Omega into a strong outdoor case that can be mounted on the top of a tower. The fifth product the company introduced was a plug-and-play product that fits in a cabinet that can be wheeled in and hooked up in the amount of time it takes to hook up a VCR.

Bell Atlantic Mobile has purchased five RangeMaster receive filter systems, which have been installed in the carrier's Southeast region to enhance cell-site coverage and portable subscriber performance in rural and mid-size market locations. The sale follows three months of testing.

Superconducting Core Technologies debuted its ambient temperature (AT) products for cellular and GSM networks. The AT products were created for customers whose networks incorporate dual-duplexed cell-site antennas and for those that need low-cost coverage enhancement, said President Steve Nurnberg.

The company's SC-200 receiver front end system is a tower-mounted unit that incorporates superconducting filters and a cooled LNA. The company's existing Reach receiver front-end system will support up to six receive antennas for a 3-sectored, dual-diversity antenna platform, with one low-profile, tower-mounted module.

In an effort to satisfy those operators needing smaller products, Conductus has added to its ClearSite product family with a compact, 3-sector filter receiver front-end. Two carriers are conducting trials involving base stations enhanced with the ClearSite receiver front-end subsystem. The unnamed Midwest carrier is looking to enhance its base-station footprint after it completes a roll-out of TDMA service during the first half of 1998. The Southeast carrier is testing whether Conductus' technology will enhance base-station coverage for low-power handsets. The local geography varies from rolling hills to mountainous terrain, leading to coverage gaps or poor coverage areas.

Get Smart Another way for carriers to improve capacity is through smart- antenna technology. Metawave's SpotLight 2000 is a dual-mode spectrum-management system for CDMA, AMPS and N-AMPS networks. The system uses smart- antenna technology to improve the capacity of both CDMA and analog networks. The system is aimed at solving the problems faced by carriers in managing capacity in a mixed AMPS/CDMA network. Operators can reconfig-ure their systems as their networks evolve, protecting their analog investment while making room for CDMA service.

SpotLight 2000 replaces con-ventional antennas with a multibeam antenna array. The antenna's radiation pattern is controlled by SpotLight's spectrum-management hardware that connects to the wireless base station. When configured for dual-mode operation, the system allows operators to optimize analog and CDMA networks separately while using a single antenna. Robert Shuman, vice president of product management, said that the product allows carriers to accommodate increased subscriber demand without the costs, delays and zoning hurdles that come with adding new cell sites.

Carriers are focusing on solving current coverage and capacity issues while positioning themselves to take advantage of future technology, and vendors are doing their best to get the carriers what they need. The solutions are out there. It's just a matter of how you stack the cards.

Sometimes big things come in little packages, and improvements aren't always detectable from the outside. Lucent's Microelectronics Group demonstrated its next-generation digital signal processor (DSP) in Atlanta. The chip can process at least three times the number of phone calls as DSPs currently in use, which translates to more powerful and efficient base stations. The chip, which was introduced last September, can process six GSM or CDMA phone calls at once, up from a current maximum of two, and reduces the electronics cost, size and power consumption of base stations by at least 50%.