You are standing in one area of the building, wirelessly connected, and application performance works great. But as you walk to another area, you notice your radio icon loses a signal strength line or two and things start to lag, or even drop completely.
When this happens, it’s common to initially blame signal coverage and assume that we have stumbled into a dead spot. However, it is entirely possible that another access point is within range of our radio, we are just having problems moving to it. This process is called roaming and there are several reasons why devices can have problems transitioning from one access point to the next one.
Let’s look at the top five causes of Wi-Fi roaming issues:
• Excessive Coverage – Excessive coverage happens when you have too many access points in an area, or the transmit power is higher than necessary for appropriate coverage. Many client devices will not actively look for a new access point until the current signal degrades significantly. Therefore, when there are too many APs, a client device can stay connected to one of them when there is a closer one with a better signal. Client devices can rely on signal strength, signal-to-noise ratio, data rates, or packet retry rates to determine connection quality.
• Poor Signal Coverage – If there are areas of the building with poor coverage (low or no signal overlap), client devices could be completely disconnected from the network while trying to find a new access point to roam to. It is important to have a clear picture of where these problem areas are in the facility.
• Re-Authentication – Wi-Fi devices on a secure network could take longer to roam from one access point to another because of the time it takes to process EAP re-authentication. This can cause performance problems when using latency sensitive applications like voice calls or live video streaming. Total roaming time should be kept to 100ms or less.
• Mismatching Configuration – Mismatching configuration errors can occur in environments without centralized access point controllers or when multiple controllers are used. If access points in an area are not configured with common settings, roaming can fail. To roam, access points need to share the SSID, authentication type, security credentials, and SSID transmission config.
• Hidden SSID’s – When it comes to environments on which Wi-Fi roaming is required, it is best not to use hidden SSID’s. Although there are some use cases where hiding the SSID is necessary, when it comes to roaming, some client devices can have problems when jumping to a new AP with this configuration.
It is critical that network engineers have the tools to test for and troubleshoot these Wi-Fi issues, especially as the demand for quality performance increases. From the ground up, the goal is to design a Wi-Fi network that has thorough coverage, solid channel planning, and takes into consideration user capacity and performance. If all these points are met, client devices should have a clear path to jump from one access point to the next when roaming.
What kinds of tools can help? One test that was designed with these needs in mind is the Roaming Test on the AirCheck G2 or EtherScope nXG. As a network engineer walks the environment, the Roaming Test can pinpoint problems with signal coverage, high roaming times, access point misconfigurations, and hidden SSID’s. These can be quickly identified and resolved to help client devices to roam quickly and efficiently.
