• Hi guys.
    As you all know, some wireless vendors out there implement autochannel function on their products. The autochannel function detects its own surroundings and select the best quality channel for the wireless client.
    So do you guys think that the AP should only scan for the best channel at start-up time or it should also make changes whenever its surroundings is full of APs conflicting its own channel?
    Hope someone can post your opinions.

  • Raul:

    We use a lot of APs, and before I deploy a unit I know what channel I would prefer to have it come up on, based on my records from the site survey AND based on my records of what channels are in use from past deployments.

    But when I first turn on the AP, I allow it to auto-select, simply as a means of convenience while I go through the configuration. Then I check to see what channel it came up on verses what channel I had previously decided, as a comparison. If there is a difference, then I want to know why.. (maybe some unknown interference has come up since the time of the site survey?, etc)

    Also, if you are deploying a lot of APs, you really need to keep track of what channels they are all on, as a matter of good spectrum planning.

    But, I could be wrong...


  • In my opinion, scanning only at startup time is useless. The RF environment will almost certainly change before the AP reboots (unless it's a cruddy AP and it reboots all the time). I want the AP to detect changes in the RF environment and respond to them.

    I have found the built-in auto-channel sensing algorithms in many access points to be woefully inadequate. In one network that I saw in mid-2005, made up of Cisco 1400 bridges and Cisco 1200 APs, the devices had configured themselves on consecutive channels--1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11! Needless to say, network performance STUNK! I don't know if Cisco's auto-channel algorithm has improved since then, but I avoid it like the plague to this day.

    On the other hand, my experience is that centralized technologies, like WLAN switches, like Cisco's "lightweight" architecture with the WCU, and like NetGear's AutoCell, do a pretty good job. When I'm working with a client that is using Cisco and the job has a large number of APs or the job has a high density of APs relatively close together, I always strongly recommend that they use a lightweight architecture so that the WCU can automatically manage power output and channel allocation. After a certain point, the network is too large and complex to handle this by yourself.

  • I'm not sold on autochannel technology yet. I liken it to the early days of plug and pray. I've had the same experience as JB, so I would rather base my decisions on a site survey.

    I also agree centralized switches do seem to be improving in this area though.

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