Bring your own device (BYOD) policies create a lack of device control, mobility issues, neighbouring network interference and guest authentication requirements. Lately, with cellular speeds increasing, users frustrated with the wireless network can simply connect corporate applications online without going through the corporate network.
Users’ attraction to cellular data is bad for organisations because cellular devices can damage network performance for Wi-Fi devices. Some devices have a Wi-Fi radio that remains very active when the device isn’t connected to a Wi-Fi network, even if the user is happily accessing cellular data. And, if that isn’t frustrating enough, the behaviour varies. Some devices may be polite, so to speak, when not actively using Wi-Fi. Other devices may be chatty when not connected via Wi-Fi.
This means that Wi-Fi-enabled devices can still degrade performance when not connected via Wi-Fi.
Amit Rao, director – APAC channels, NETSCOUT, said, “The problem, as so often is the case, is Wi-Fi bandwidth. Wi-Fi devices and access points (APs) share a channel. Only one device can transmit over the channel at any given moment, otherwise a collision is likely.
“Channel sharing works fine for Wi-Fi, most of the time. When one device or AP begins transmitting, other devices and APs go quiet. Then, once data has been transmitted, all devices and APs go through a process called ‘arbitration’ to determine who sends next. The winner of arbitration sends data, thus starting the whole process over.”
Wi-Fi arbitration keeps data flowing across the channel while keeping collisions to a minimum. And it usually works well. The problem with Wi-Fi bandwidth is that it can fluctuate. Wi-Fi devices use a protocol called dynamic rate switching (DRS), which lets devices switch between different data rates as needed.
Amit Rao said, “DRS is a good thing for Wi-Fi because different devices may need different data rates. When channel conditions worsen, low-rate Wi-Fi traffic can remain successful even as high rate traffic fails. Whether distance, walls, mobility, interference or something else is causing unstable channel conditions, low data rates can allow a Wi-Fi connection to remain usable.”
The end result of DRS is that devices on the same channel may be using different rates. Once different rates are used, Wi-Fi bandwidth starts to change. The entire channel loses data capacity because the low-rate traffic takes up more channel time when facilitating the same amount of data.
Fewer data frames can traverse the channel when each data frame takes up more time. The end result is that the whole network gets slower. This all circles back to unconnected Wi-Fi devices in a very real way.
The problem is that many Wi-Fi devices keep active Wi-Fi radios so that users have a seamless experience when moving from a cellular-only area to an area where Wi-Fi is present. The process of looking for Wi-Fi, even while connected via the cell network, is what causes devices to remain active on the Wi-Fi channel when unconnected to the Wi-Fi network. Devices looking for Wi-Fi can lead to big problems.
Amit Rao said, “There is some good news in all of this: Wi-Fi devices have become less rude. Three or four years ago, Wi-Fi devices were extremely chatty when unconnected. While it is good that Wi-Fi devices are typically less chatty than they once were, unconnected Wi-Fi devices can still be a problem. Certain Wi-Fi devices can get chatty enough to cause Wi-Fi performance and stability issues, especially in areas with dense concentrations of people.
“In some ways, the problem is even trickier because there is less certainty. Wi-Fi professionals used to know if they needed all these Wi-Fi devices connected, or we need to get users to turn their Wi-Fi radios off. Now we need to find out whether the unconnected devices are too chatty, because they might be a problem or they might not.
“To address the problem, and provide more certainty, organisations should look at employing a Wi-Fi network analyser. Analysing unconnected device chattiness is an inexact science but the right analyser will give organisations a reasonable scope of the problem of unconnected devices getting chatty.”
