Getting WISE to building wireless networks

To a new PCS operator with no customers and a world of debt, the only formula for competition might be to pick up the phone and start selling to anyone and everyone. Building a network and some kind of customer base are by far the top short-term concerns.

However, there should be a method to the madness. Building a wireless communications network is not a slap-dash, random act. It requires a high level of exactness. This is most true of campus or in-building networks, as well as wireless local loops where the quality of wireless service is expected to be almost as good as or equal to that of wireline.

Traditionally, cellular companies have not been very involved in establishing fixed wireless deployments for campus, in-building or wireless local loop environments. The few corporations that required such wireless networks most often used wireless PBXs instead.

Cellular companies, like their wireline counterparts, mostly ignored a market that seemed interested in private enterprise solutions.

This is no longer the case. Both traditional network operators and new PCS entrants have recognized the lucrative potential for extending their public networks to operate and manage campus, in-building and wireless local loop networks. These networks are expected to be key battlegrounds as wireless competition increases in the next few years.

Planning WISEly With so much pressure on planners and engineers to develop effective and efficient networks, the technical staff at Lucent Technologies has written a new software system called Wireless System Engineering (WISE).

WISE uses computational geometric algorithms and optimization measurements as parameters to determine the best single locations for base stations or the most efficient multiple base station configurations, says Jonathan Ling, a member of the technical staff at Lucent's wireless communications research department. These determinations are based on elements of the environment surrounding potential base station locations, including wall location, composition and thickness, as well as natural elements.

In addition, signal strength can be a function of multipath propagation dispersion and attenuation, and the software can produce results accordingly. The system also takes into consideration users' preferred locations for base stations, says Ling.

And planners and engineers can use graphical interfaces to quickly respond to questions about how network coverage characteristics would change if new base stations were added to the network, or if existing base stations were relocated, he says.

"You have to do a lot of 'what if' scenarios when you are building a wireless network. This software does that for you," adds Steve Cosmas, technical manager in charge of developing RF engineering tools at Lucent's wireless communications department.

Lucent demonstrated the WISE software system for attendees of the International Telecommunication Union's Americas Telecom exposition this past June in Rio de Janeiro, Brazil. Although the system has been used only by Lucent Technologies, the company plans to eventually make it available to network planners and engineers outside the company, says Ling.

Merging Models WISE draws its analysis of network environments from five major components. The propagation model predicts the results of signal strength at a given point in the network. The model produces a mean of the strength from multipath network components reaching a particular spot, says Ling. It also accounts for the effects of polarization, diffraction, angle of incidence and other constants.

Another component is the physical database of the building, campus or other outdoor locations in which networks are being planned. Environmental drawings or floor plans are digitized and fed into the system through computer-aided design. The system also uses a three-dimensional ray-tracing process that traces "useful" transmission paths-the ones with the least amount of reflection or other interference-from a base station to a handset, says Cosmas. This algorithm is more exact than other ray-tracing methods that focus on any paths that might work.

The base station optimization algorithm compiles parameters for transmitter frequency, signal-to-noise ratios and power to determine base station placement based on minimum requirements for signal consistency.

The final component, the graphical user interface, displays the environment at issue, offering elevation and perspective views that can be alternated. A color scale represents signal strength changes, and various parameters can be entered or adjusted through pull-down menus or dialogue boxes. Base stations can be repositioned and compared on-screen with previous positions, says Ling.

"Without all this output in a graphic way, there would be a lot of time involved," adds Cosmas.

Efficiency Counts There may be more simple-minded ways to approach building wireless networks. Less mathematical forms of estimation based on cell site power could get the job done, at least until users start complaining about dropped calls in certain areas where handoffs just do not seem to be happening.

Also, a network operator could simply load a specific area with an obviously heavy number of cell sites. This may provide some sense of security with network reliability, but given the inherent cost of such a proposition and ongoing fears about the electromagnetic effects of wireless transmissions, this may not be the best idea.

Engineering tools such as WISE, which draw on the industry knowledge of propagation, material or natural facts and mathematical models, can probably provide a quicker, non-complicated and cost-efficient way to build tomorrow's networks, especially as they extend into complex environments that require special attention.

Many people think of wireless local loop deployments as something of a foreign concept-literally. Indeed, wireless local loop networks are the most efficient way to bring many developing countries into the communications age, but they may also have merit in the U.S.

Many wireless local loop infrastructure vendors, having won network contracts overseas, are also beginning to target the U.S., particularly the U.S. PCS market.

"We see it as an important market, but one that will take some time to develop fully," says Paul Mueller, president and chief executive officer of Phoenix Wireless Group.

Some PCS providers, especially smaller ones in somewhat rural areas or those focusing on specific market niches, will deploy wireless local loops and low-tier technologies such as PACS (see story on page 24) to efficiently reach their customers.

Perhaps surprisingly, the existing U.S. wireline local exchange market, once thought to be a dead end for wireless local loop vendors, may eventually create new wireless local loop deployment opportunities. For wireline providers, wireless local loops can offer cost-effective extension of last-mile access to rural customers at far less cost to both the carrier and the customer.

It also could provide quicker local access in some dense and complicated urban environments, on campuses or inside buildings.

Most wireline local exchange carriers have probably flirted with wireless local loop strategies over the last few years, but few have discussed them. Earlier this summer, however, at "The Wireless Local Loop," sponsored by ICM Conferences, Southwestern Bell revealed some details of its recent wireless local loop trial in St. Louis.

The small ongoing trial set up wireless local loop access for 15 households on a grid of about two square miles, says Sherry Ramsey, associate director of strategic business development at SBC Communications. Cell sites consisted of 40- to 45-ft. antennas that offered limited mobility of 1000 to 1300 ft. The trial used PACS technology.

Among other things, the test gauges service quality and voice quality as compared with wireline, traffic capacity, enhanced service introduction and data transmission. Voice quality was determined to be equivalent to wireline, says Ramsey, and new digital service features were adequately supported by the network.

The company so far has graded wireless local loop as a "viable business opportunity," but Southwestern Bell plans to continue studying wireless local loop deployment, says Ramsey.