In the early 2000s, wireless local area networking became a mainstream technology known as Wi-Fi. Computing devices such as laptops and notebooks began to support the IEEE 802.11b standard, which has a top data rate of 11 Mb/s and operates in the 2.4 GHz frequency band.
After 802.11b came 802.11g, which is five times faster, and then 802.11n, which boasts data rates that rival those of wired networking options. Today, Wi-Fi is found not just in computing devices but also in medical devices such as imaging systems, patient monitoring systems, and infusion pumps.
The vast majority of Wi-Fi client devices operate in the 2.4 GHz band. Only three nonoverlapping channels are available in the band, so every Wi-Fi client and infrastructure device, such as an access point (AP), must operate on one of three channels. When two Wi-Fi clients or APs on the same channel are in relatively close proximity, the transmissions of one act as interference or noise to the other.
The 2.4 GHz band also is the home of microwave ovens, baby monitors, some cordless phones, and Bluetooth. A Wi-Fi client transmits on one channel, but other wireless devices can cause interference across the entire band. In many hospitals, the 2.4 GHz band is nearly saturated with wireless traffic. As Wi-Fi continues to grow in popularity ensuring reliable connectivity in the 2.4 GHz band will become more and more challenging.
Fortunately, there is another frequency band for Wi-Fi: the 5-GHz band. This band offers many more Wi-Fi channels (23 in North America). Because few devices operate at 5 GHz, the band is relatively uncluttered. A Wi-Fi deployment in the 5-GHz band, however, is different than a deployment in the 2.4-GHz band.
"Exploiting the 5-GHz Band for Medical Devices", which was originally posted at Medical Electronics Design, looks some of the differences between the 2.4-GHz and the 5-GHz band, including issues of multipath, range, attenuation, and mobility; it also includes recommendations for setup in a hospital environment.
About the author
Chris Bolinger is vice president of engineering at Summit Data Communications (Akron, Ohio).
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