I recently ran across an interesting article on the Apple support website that describes the roaming behavior of newer iOS 8 devices. Here's the link: https://support.apple.com/en-us/HT203068
Not every device maker hands that information out, so I really appreciate Apple doing so. This describes the behavior of iPhone 5s and newer, iPad Air, and the retina iPad Mini. It says older devices use the same roaming behavior found in iOS 7, but I have been unable to locate any documentation for that. Has anyone else found roaming documentation for iOS 7?
The key points I see:
- -70 dBm is the threshold before it will scan for a new BSSID.
- They will use 802.11k to streamline the process.
- If the client is actively transmitting or receiving, it looks for an AP with at least an 8dB greater RSSI. If the client is idle, it looks for an AP with at least a 12dB greater RSSI.
There's also a reminder that the iOS AirPort Utility has a scanning feature in it now, which is pretty useful. You can share the data from the scan as a CSV file, so it gives you a way to keep a record of your results, which is also useful.