Yopi
ah, sorry i misread that as 6.3.1.8.... Client match does tend to handle iOS devices a little better than the older bandsteering, you can test in your lab and see.
If you have high or medium density of APs, then you can try the following which is trying to achieve two things:
1. when in the usual range of the AP, the 5GHz signal is always strongest by a decent margin
2. tx power between APs is more even - this will help with sticky clients and roaming (not related to your issue specifically, but it will help)
> create two new ARM profiles, call one of them arm-g and one arm-a
> ensure the max tx power for the 11g arm profile is less than the min tx power for 11a arm profile, preferably by 3dB at least
> enure the difference between min and max tx power is not more than 6dB
Example:
11g min-tx-power 12 , max-tx-power 18
11a min-tx-power 21 , max-tx-power 127
** Warning ** these are just example values and need to be fine tuned a bit depending on the environment, if there are clients that are on the coverage edge and you go and reduce 2.4ghz max tx power, then this will cause them issues.
*edit* this also assumes you have a device population that is predominantly 5ghz capable
regards
-jeff