Has anyone spent time tuning a WiNG5 environment (in my case RFS and AP650s) to achieve HT data rates on disparate devices? I have a mixture of Windows laptops (some 11n, some not) and "i" devices (again some 11n and some not) and it seems that recommended settings for the Windows laptops conflict with the "i" devices. One laptop, which has an Intel Wireless-N 1030 adapter in it (2.4GHz 802.11n), requires WMM to be enabled in the infrastructure for it to achieve 300Mbps data rates. Conversely, enabling WMM seems to bring the 11n "i" devices back to 54Mbps). I am keen to find a happy medium for this environment, where all devices get the best connection rates possible. I have an old Moto document, on configuring Intel adapters for 802.11n, which seems to work, but I really want to get the 802.11n "i" devices (MACbook Air for one) working at high rates as well. Having individual WLANs is an option but not ideal for a commercial environment. Any ideas will be much appreciated. Thanks, Damian
Tuning A WiNG5 Environment For 802.11n Performance// Expert user has replied. |
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Hi, Damian. Every time HT (802.11n) network hears a non-HT (legacy) frame (even if it's a beacon from neighbouring AP) it drops into HT Protection mode, essentially throttling down, doing protection frames, etc. In fact, every device will get it's own best rate (be it .11n or .11g/a/b), but you also get lots of protection overhead. The only way to overcome it (as per standard) is to have spearate WLANs: some Pure HT (Greenfield, with a/b/g rates disabled) and some pure/mixed HT/legacy. Provided this setup does not create excessive interference - you'll be fine. Apple is known for all kinds of issues in their Wi-Fi stack, and IOS/MacBook devices typically cannot sustain high rates anyway (I mean, yes, you can download into /dev/null at 123mbps, but what's the point?), so it's fine to throttle them down. Did you look into the proble and association request frames issued by the MBA to see if it ever requests higher rates? If not - it's definitely client-side issue. At am a bit surprised at the "enabling WMM" statement, as WMM is enabled by default on WING5, did change any settings? Disabling WMM may be not a good idea, as you lose advanced power management (U-APSD and it's HT counterpart) as well. In the end, keep in mind, that it's not the device, but the application that's important. We discuss this and many other topics (but not the bugs :)) in "Design & Deploy WLAN Solution" course WEL2307, which you may be interested in. P.S. Interested to see the "old Moto doc" you mentioned.