In an article that will appear in the November issue of Cabling Installation & Maintenance magazine, Carolyn Carter of Fluke Networks explains the significance of interference to WiFi networks and also lists three measures that should be taken against interferers.
Carter, Fluke Networks' portable network tools product manager, initially delivered the information in a presentation made during a Web-based seminar in August. Information from that presentation is being used as the basis for the upcoming article.
"A lot of people don't realize the effects interference has on a wireles network," she said. "802.11 operates in an unlicensed band. That means anyone and any device can run on it. Due to that, there's a lot of interference." The 2.4-GHz band in which 802.11n runs is also the frequency range within which many microwave ovens, cordless phones and Bluetooth devices operate. "Bluetooth may be low-powered by can cause problems if you get enough of these devices in the same area," Carter added.
She recommends users conduct an interference survey before designing a wireless network. During such a survey, users will be able to detect fixed-point interferers such as microwave ovens. Other devices, which cause interference infrequently, may not be designed against initially but users do need the ability to find these types of interferers, she added.
When an interference issue exists, she then explained, it simply must be gotten rid of. One of the following three measures should solve the problem.
- Find the interfering device and remove it.
- If the interfering device cannot be removed, shield around it so it no longer causes interference.
- If you cannot remove or shield the interfering device, reconfigure either the wireless system or the interfering device.
In the presentation and the article, Carter stresses the importance of surveys before and after wireless-network deployment. A post-deployment survey can enable users to detect interference sources that may not have been seen during a pre-deployment survey.
Download the document "20 Myths of WiFi Interference" from Cisco.
