Best practices for roaming and dealing with sticky client issues

A common misunderstanding is that it is the AP that determines whether or not a device will roam but instead it is actually the client device that is the one which decides to roam based on algorithms. Here is an excellent video on this topic: Wi-Fi Roaming Revealed - YouTube

Note, that being said, there are certainly some best practices when it comes to the AP settings which can play a role in when the client will “decide” to roam.

The biggest one and the one I’ll cover here is AP Transmit power. It is common to have an AP’s power turned up but doing so may cause the “sticky client issue”. Because the signal level is (from the client’s perspective) still very strong, it doesn’t think it needs to roam yet.

If a sticky client issue is happening, the first thing to do is turn down power on the AP. A typical power level that I recommend is around 11dBm/17dBm and maintain a 6dB difference between 2.4 and 5GHz. 2.4GHz propagates better so reducing the output power by 6dB makes the coverage for both bands more similar.

I like to also have the 2.4 and 5GHz SSID’s different so there is no chance of “inter-band, inter-AP roaming” happening either.

One may say, “If I turn down power, I will have reduced coverage”. My response to that is for multi-AP deployments where very low power devices such as handheld mobile devices (think iPhones), you should be designing with lower power in mind from the start. The days of 23dBm to 26dBm are over. The only exception I will say is for single AP deployments. In that case, no roaming is happening so there is less of a reason to have power set low.

So if reducing power causes a coverage hole, then you need to have more AP’s. Turning up power is not a solution for a bad design.

One other thing I want to mention is about the “minimum signal strength” tool you commonly see in the AP settings. I don’t recommend using this because what this actually is doing is DEAUTHing the client off the network. This causes a disconnection of the client from the network - which by definition now means that roams will no longer be seamless.

Dan Koz - CWNE#217