Choosing Channels in an increasingly crowded 2.4ghz spectrum

With the proliferation of do everything hubs and wifi extenders it’s becoming increasingly difficult to make sure that everything keeps working that wants a chunk of the 2.4ghz band. It is quite possible now to have several wifi channels in use and a ZigBee device like the Phillips Hue bridge and then some xbee radios and then add another hub like the new quirky devices or something and to start having significant problems keeping everything working.

Some things to keep in mind:

  • ZWave runs in the 900mhz band, so thats not a problem, though if you have several overlapping ZWave networks you may have to look at that too.
  • Wifi and ZigBee (and xBee which is ZigBee too) channel numbers are not the same thing. Wifi channel 11 is not the same as ZigBee channel 11 so you need to check the overlaps.
  • Each wifi channel is not actually totally separate. You actually have to move up or down 5 channels before you get to one that wont overlap the other. So there are basically 3 fully separate wifi channels available in any given place if you want them to not to have to share bandwidth with others. 1, 6 and 11.
  • If you dont have any legacy devices and the range is enough you may be able to turn off 2.4ghz support on your wifi router completely and just use the 5ghz channels. Much less to bump into there and leaves things totally free for other devices in the 2.4ghz range.
  • Unless you live underneath dozens of wifi networks you really should pick a channel and manually set it. Also for your ZigBee and xBee devices rather than let them automatically choose it. Things can work perfectly for years only to fail suddenly and without warning as one device decides to change over to the same channel as another.
  • There is a great graphic of the overlaying channel frequencies at Fosiao.com use that to choose what to put where.
  • This page at Digikey Has far more than anyone would want to know about the topic including details on these and other low power radio communications systems including blue tooth and blue tooth low energy making it easier to select those channels too.

As of build 878 you can create a unit on your Phillips Hue bridge interface with an address of “zigbeeaddress” which will be set to the current running channel of it’s network. This is a read only unit, changes must be made from inside the Hue configuration utility or web page, but it will let you know what it’s doing and if it changed on you.

tech_notes/channels.txt · Last modified: 2015/01/28 09:38 by James Sentman
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