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WLAN Access Point Automation Issues: What You Can Do

by Veli-Pekka Ketonen
3 Comments

 

Using Wi-Fi RF automation brings with it a few challenges for those concerned with Wi-Fi performance management. Automation may not always perform as well as expected, especially in dense areas. The automation algorithms developed by WLAN access point vendors might misallocate both channels and power levels, leading to an unstable system and a variety of WLAN performance issues. Here’s how it could happen:

  • To avoid interference, WLAN access points will automatically adjust their power levels downward. The decision is most often based on APs measuring the signal level of their neighboring APs and then keeping that signal level below a predefined limit. But client connectivity and area coverage are not properly considered, therefore, performance issues and a poor client experience are the result. To illustrate this, think about what happens when access points are close to one another or have a direct line of sight, like in a long hallway. The automation plan may adjust AP power levels downward, but in doing so, shrinks the Wi-Fi coverage area such that all the clients in the offices and rooms along the hallway suffer a huge drop in Wi-Fi performance.
  • In addition to power level automation, channel automation has been known to take several APs that are close to one other, and switch them to the same channel. This is a serious issue. Also, access points may find themselves continuously switching channels in an attempt to find a channel without noise. However, in dense networks, there is always noise, so the plan is futile and the situation escalates until you have an unstable system.

Here are some Wi-Fi performance management tips you can do to detect and determine if you are facing these issues:

  • First, take a look at the channel plan at your AP management console. Look at the channel numbers used and superimpose the information over your floor plan or area map. Are all of the allowed channels being used? Are the channels evenly allocated within the area? Are neighboring access points using different channels? It’s also good to check this a few times at different points in the day. If the channels are not allocated properly, the Wi-Fi network will significantly lack capacity and exhibit signs of poor performance.
  • Next, check on the power levels that are being allocated to your wireless access points. Are the levels at the low end of the allowed power control range? With default settings, you may see values down close to 0 dBm or power levels 5-7. Again, it’s best to check a few times throughout the day and especially when there is greater load on the system. Since client terminals usually use power levels around 12-16 dBm, if an access point is using a power level in the range of 0 dBm, then you have a performance problem and the user experience is poor. You’re witnessing an unhealthy and unbalanced radio environment.

With all this said, there are ways to improve the performance of your Wi-Fi network. View my presentation at the WLAN Professionals Summit in Austin, TX. It has quite a few suggestions for Wi-Fi optimization.

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3 Comments

Mark Cowtan

Mark Cowtan

A very important point not mentioned here is that when an AP changes channels it drops all connections. Clients must reconnect on the new channel and that takes a moment. This is a big deal, for anyone using VoIP or multimedia. Most auto-channel algorithms are concerned only with the condition of the spectrum around them, and do not factor in some kind of weighting based on user count or applications in use.

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vponcini

There are some vendors that do take into account both spectrum and user capacity and applications (such as voice or real-time streaming media) before randomly changing channels. This also creates its own set of issues.

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