We have a number of users on the local network, most of whom are on MacBook Pro laptops, who have been having an issue in which their WIFI drops periodically and must be manually reselected after which a few minutes later, it drops again. It happened intermittently, and more in certain parts of the office than others. I did some research and found lots of postings of people having issues with their MacBook Pro laptops and lots of 'possible' solutions to the issue, not of which really helped. Ideas like resetting the NVRAM and creating new 'Locations' with only one SSID. Nothing helped in our case so I started to do my own research.
Our WIFI Setup is as follows:
Cisco 981w router with integrated Dual Band, Dual Radio WAP
2 SSIDs, each broadcasting on both 2.4GHZ and 5GHZ
Most clients authenticating with WPS2/Personal/AES
I made some interesting observations. First, the MacBooks seemed to all be connecting to 2.4 GHZ, even though it is really congested and the 5GHZ band is wide open. The client itself is pretty dumb and has no way that I could find to tell it which frequency to favor. It automagically figures it out based on signal strength. Interestingly, the places in the office with the biggest issues are where the signal is the weakest. There is also not a way to tell it to use a, b, g, or n, it's pretty much all or nothing.
So the first thing I did, which is sort of the only thing I did, was to change the WAP in the router so that the 2nd SSID was only broadcasting on 5GHZ which forced users who connected to that SSID to use 5GHZ. This would prevent the MacBook from trying to jump between them if it thought that it had a stronger signal bands (with the same SSID) if it thought that it had a better signal. Problem solved. Damn that was easy.
Next step is to change my 2 SSID (guest, and corp) to 4 SSIDs (guest2, guest5, corp2, corp5). I suspect that with some additional troubleshooting I could figure out why specifically was causing problems when the same SSID is on 2.4GHZ and 5GHZ, but this solves my problem in this environment and I have other things to do. Hope this helps.