Call Forwarding: New NIST Procedure Could Speed Cell Phone Testing

As described in a forthcoming paper,* NIST researchers conducted tests in downtown Denver, Colo., to measure precisely the clustering of signal reflections from radio waves bouncing off one or more multi-story buildings multiple times before reaching a distant receiver. The researchers replicated this environment indoors using a “reverberation chamber,” a room with highly reflective surfaces and a big, slowly rotating paddle that automatically alters signal paths.

First, researchers feed a wireless transmitter’s signal into a device called a fading simulator, which is adjusted to re-create the timing and strength of the reflections of an outdoor urban area. The output then is fed into the reverberation chamber, where signal reflections decay exponentially over time, creating a cluster of signals similar to that observed in the field tests.

Industry certification of cell phones currently requires tests of parameters such as total radiated power using the opposite of a reverberation chamber, a room called an anechoic chamber that is lined with materials that absorb radio waves and reflect as little as possible. This testing takes about a day, requiring dozens of measurements of cell phone directional power from multiple angles. By contrast, an equivalent set of tests could be performed in about an hour in a reverberation chamber, according to NIST engineer Kate Remley, a senior author of the new paper. Reverberation chambers also could be used to measure cell phone receiver sensitivity, although currently there would be no time savings for this test, Remley says. Many industry testing practices are established by CTIA-The Wireless Association, the trade group representing the wireless industry.

NIST is studying new applications for reverberation chambers, which have typically been used to measure electronic equipment’s immunity to radio-frequency interference. By adjusting the reflectivity of the chamber through selective use of signal-absorbing material, researchers have found they can “tune” the signal decay time to simulate the conditions found in real-world environments. NIST researchers expect the new method will be useful for test and design of wireless devices such as cell phones, notebook computers equipped with wireless links, as well as new technology such as wireless beacons being developed for the emergency responder community.

The Denver tests were conducted in 2009. NIST researchers measured the power delays between a transmitter and a distant receiver positioned on streets lined with buildings three floors high or taller and a flat, single-layer parking lot. Most buildings were constructed of glass, steel, and concrete.

* H. Fielitz, K.A. Remley, C.L. Holloway, Q. Zhang, Q. Wu and D.W. Matolak. Reverberation-chamber test environment for outdoor urban wireless propagation studies. IEEE Antennas and Wireless Propagation Letters. Forthcoming.

Laura Ost, laura.ost@nist.gov, (303) 497-4880

Media Contact

Laura Ost Newswise Science News

More Information:

http://www.nist.gov

All latest news from the category: Communications Media

Engineering and research-driven innovations in the field of communications are addressed here, in addition to business developments in the field of media-wide communications.

innovations-report offers informative reports and articles related to interactive media, media management, digital television, E-business, online advertising and information and communications technologies.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors