Lucent Researchers Announce Faster And More Accurate Method To Predict Wireless Signal Strengths

The latest enhancements to the Wireless System Engineering (WiSE) software package are being presented here today through Thursday (May 19-21) at the 48th Annual Vehicular Technology Conference, sponsored by the Institute of Electrical and Electronics Engineers.

The current version of WiSE, for instance, is 10 to 1,000 times faster than previous versions, said researcher Reinaldo Valenzuela of Bell Labs, which is Lucent's research and development arm.

For more than a year, Lucent has been using the WiSE package when installing its indoor DEFINITY® Wireless Business System at retail stores, hospitals, offices and warehouses. The DEFINITY® system allows employees to talk with each other on handheld phones while walking throughout buildings.

WiSE, which is not for sale as an individual product, is vastly different from the two other methods to place base stations. A trial-and-error approach involves placing base stations throughout the building until the desired results are achieved. This approach wastes not only time, but also potentially money because too many base stations may be used.

Another traditional method uses statistical modeling. This approach is not precise because it includes only average parameters - for instance, assuming all walls are concrete and five inches thick - instead of accounting for specific features. In one scenario, the statistical approach showed that one hotel floor needed nine base stations, but WiSE predictions indicated only three were necessary.

"The statistical models don't take advantage of a building's layout and construction," said Steven Fortune, a Bell Labs computer scientist. WiSE, meanwhile, tracks signal paths through buildings, incorporating precise information about wall material and thickness (dry wall vs. brick, for example), room layout, and signal strength.

In fact, WiSE is especially helpful for potential DEFINITY® customers who are planning new stores and want operating wireless systems when the stores first open. That's because WiSE can use blueprint information to determine optimal placements for base stations.

"WiSE has been extremely helpful because it gives us a competitive edge," said Sue Klein, an engineer who works on the DEFINITY® Wireless Business System at Lucent's Business Communications Systems unit. Currently, Lucent is ranked No. 1 in the United States for wireless business handsets, according to the independent analyst firm Phillips InfoTech.

Before Lucent developed the three-dimensional, ray-tracing technique used in WiSE, other researchers had thought the approach was not realistic because it would require an impractical amount of computer time. The trick, Fortune said, is separating a building's layout into a series of triangular grids. So as the signal moves from region to region, WiSE is concerned with only one grid at a time, whereas other ray-tracing methods include information about every wall in the building.

When the Bell Labs researchers compared WiSE test results in three Bell Labs buildings in New Jersey with actual readings, their results were off by not more than six decibels in 90 percent of the locations, compared with 15 decibels using statistical methods.

WiSE, which operates on a desktop personal computer and can compute results within seconds, also is applicable to outdoor wireless networks. For instance, when Bell Labs researchers tested WiSE to determine outdoor signal strength in sections of Munich, Germany and Rosslyn, Va., the results closely matched actual measurements. The trick, Valenzuela said, was predicting how signals diffracted around building corners.

As more detailed maps and environmental information become available, Lucent's use of WiSE for wireless networks will increase significantly. Currently, because of the lack of such information, WiSE is used in only 5 to 10 percent of outdoor cases, said Steve Cosmas, an electrical engineer at Lucent's Wireless Networks Group.

Other Bell Labs researchers making presentations at the conference include Margaret Wright, Samuel Morgan, Dmitry Chizhik, Jonathan Ling, and Chokri Trabelsi.

WiSE is one of 12 Bell Labs research and development projects featured on the Bell Labs web site at http://www.bell-labs.com/innovate98/wireless/wiseindex.html

Lucent Technologies, headquartered in Murray Hill, N.J., designs, builds and delivers a wide range of public and private networks, communications systems and software, data networking systems, business telephone systems and microelectronic components. For more information on Lucent Technologies, visit the company's web site at http://www.lucent.com.