For those using other APs with a possibly different terminology or abbrevations, the following may be useful:
WMM=WiFi Multimedia aka Wireless Multimedia Extensions (WME)
Short GI=Short Guard Interval
AP isolation=Access Point isolation aka Client isolation
The term performance can be interpreted in many ways and when Stephan says "...we've found for best performance" I think he means the most reliable operation with a GS-911wifi, which of course is and should be the only focus of this thread.
A very simplified technical explanation of the above mentioned features:
WMM prioritizes traffic in different classes and giving precedence to voice and video over other types of traffic. In theory it is useful on an AP with a lot of mixed traffic but it may also limit throughput for a GS-911wifi.
Short GI decreases the time between data characters being sent wirelessly. In an optimal radio environment that could increase throughput but in less than optimal conditions it will instead lead to errors, retransmissions, instability and decreased performance. If you're a RF-engineer you know when you can enable it but for the rest of us it is safer to leave it disabled as Stephan recommends.
AP isolation prevents any traffic between wirelessly connected nodes. This of course very effectively prevents communication between the PC or mobile device running the GS-911 application and the GS-911wifi unit. That is probably not what you want being a reader of this forum.
