A quiet conversation in a noisy room

The explosion of wireless applications in recent years has resulted in concern that the radio frequency (RF) spectrum is not broad enough to support future demands. “Open spectrum” is an emerging technology that could alleviate this concern and fundamentally change the way we think about the airwaves. Open spectrum technology has the potential to revolutionize wireless communications and make it more attractive for your customers to sever the hardwire connection to their wired infrastructure. You need to aware of this technology and its potential value for your customers.

“Open spectrum” is a term used to describe a variety of technologies that allow multiple sets of transmitters and receivers to communicate with each other simultaneously on the same frequency band. This is possible because each receiver is only listening for its transmitter’s signal and ignores signals from other transmitters operating at its frequency. Digital information is sent by the transmitter in packets with addresses similar to the way information is now transmitted on wired networks and the Internet. “Smart” receivers only “hear” the information that is meant for them and ignore all other ambient signals and noise. Kevin Werbach in “Open Spectrum: The New Wireless Paradigm” [werbach.com/docs/new_wireless_paradigm.htm] uses the analogy of two or more people sitting around a table in a crowded room to describe how open spectrum works. Even though the room may be noisy, the people sitting around the table can still communicate because they are concentrating on the speaker to the exclusion of the ambient noise. In addition, if they don’t understand the speaker, they can always ask him or her to repeat what was said until they understand it. This is also similar to open spectrum and other network technologies where the receiver detects transmission errors and the transmitter is asked to resend the information packet until it is error-free.

Open spectrum technology eliminates the need to chop up and allocate the RF spectrum for specific purposes and applications. In theory, with open spectrum technology, signals can coexist in any frequency band and not interfere with one another. The idea of future open and unlicensed airwaves that would allow anyone to set up a transmitter and transmit information just like people are able to establish a web site on the Internet today is an interesting possibility. However, the real value of spread spectrum in the immediate future is providing a means for us to more fully utilize the allocated frequency bands that are already here. For instance, Wi-Fi or IEEE 802.11b wireless data networks operate in the 2.4 GHz band that is also used by cordless telephones and interference sometimes results. In addition, there can only be a limited number of Wi-Fi access points operating within range of one another before interference results. Open spectrum would eliminate this congestion and all devices could operate without restriction.

In a crowded room, the only way you can guarantee that your listener will hear you is to talk louder than the ambient noise. This is the way that current wireless communication systems operate. For the receiver to “hear” the signal, the transmitted signal strength must be greater than the ambient electromagnetic noise. With spread spectrum technology, the signal strength or signal-to-noise ratio is no longer as critical as it is with conventional wireless communications where the receiver is unable to distinguish between the desired signal and other low-level signals and noise at the same frequency. With error detection and the ability to ask the transmitter to resend a garbled signal, open spectrum systems will be able to operate satisfactorily in noisy environments. This means that industrial and other customers that could not use wireless systems in the past due to electromagnetic interference (EMI) caused by production equipment will be able to use open spectrum technology.

Similarly, if signal strength is no longer critical, then transmitters can be operated at lower power. Lower power requirements means smaller transmitter size, lower transmitter cost, and longer battery life. These factors will open the door for even more wireless applications that will benefit your customers’ business.

Open spectrum technology is definitely an area to watch because it could have a significant impact on your business. In the short run, open spectrum technology may allow your customers to cut the cord in noisy or congested environments where either copper or optical fiber cable is required today for reliable communication and control systems. In the future, open spectrum may allow all manner of equipment and appliances to communicate wirelessly with one another without bandwidth restrictions. Electrical contracting firms need to understand this technology and its application so it can help its customers successfully implement it as it becomes commercially available.

This article is the result of an ongoing research project investigating the future of the VDV market that is sponsored by the Electrical Contracting Foundation, Inc. The author would like to thank the Foundation for its continuing support. EC

GLAVINICH is an associate professor in the Department of Civil, Environmental and Architectural Engineering at The University of Kansas and is a frequent instructor for NECA’s Management Education Institute. He can be reached at 785.864.3435 or tglavinich@ku.edu.