We are deploying an 802.11n wireless network in a manufacturing floor environment. What methods can be used to prevent wireless interference during mobile device testing (Wi-Fi or Bluetooth)?
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There are several ways to prevent wireless interference during mobile device testing. All Wi-Fi devices share radio bands with each other and with Bluetooth devices. Devices that are operating correctly avoid “stepping” on each other by listening first to avoid transmitting when others are using a channel. However, sometimes devices cannot hear each other -- for example, clients A and B that are in-range of the same Access Point (AP) yet facing in opposite directions.
Older clients also may not be able to hear or correctly interpret transmissions from newer clients unless protection mechanisms or mixed mode operation is used. Finally, as you point out, new products going through mobile device testing sometimes behave in unexpected ways, making it desirable to insulate new devices until they have been tested for compatibility.
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Short of physical isolation, the best way to prevent wireless interference is to test new devices on different channels, ideally in a different frequency band. For example, if your manufacturing network operates on 5 GHz channels, conduct new mobile device testing using channels in the 2.4 GHz band. Alternatively, test new devices in a currently unused portion of the same band; this is more feasible at 5 GHz, given the small number of non-overlapping channels at 2.4 GHz.
Unfortunately this wireless interference prevention technique cannot be used for Bluetooth since those devices use the 2.4 GHz band in a different way than 802.11n devices. However, Bluetooth is a much shorter range technology and may be easier to physically separate from your production network.
Finally, no matter how you choose to insulate your production network during new mobile device testing, visibility will be essential. Invest in a spectrum analyzer that lets you see how new devices are using your airspace and impacting existing devices. If nothing else, spectrum analysis can help you rule out suspected RF interference when might otherwise cause a lot of angst and wasted diagnostic effort.
This was first published in July 2012