My Dell Inspiron 5520 with an Intel Centrino Wireless-N 2230 will NOT connect to a Cisco Linksys E900, E1200, or E1500 router at N speed above 54 Mbps when Wireless Multimedia (WMM) is disabled in the router QOS settings. However, my daughter's lower end Dell Inspiron 5040N with a Dell Wireless WLAN 1502 always connects at N speeds above 54 Mbps with WMM disabled.
The 2230 immediately connects as it should at nearly 150 Mbps on single 20 MHz channel or 300 Mbps on bonded 40 MHz channel as soon as I enable WMM in the router QOS settings. This happens on the three different Cisco Linksys routers mentioned above that I have tried thinking it was a problem with the router.
This clearly indicates a problem with the Intel Centrino 2230 with WMM disabled since the Dell Wireless WLAN 1502 consistently connects at N speeds with WMM disabled or enabled.
I have to disable WMM because there is apparently a compatibility issue with WMM QOS and Comcast Xfinity Internet service because the issue happens with Cisco, Netgear, Belkin, and other routers. With WMM enabled, my Internet download speed is less than .5 Mbps while my upload speed is unaffected around 3 Mbps. My LAN download speed, however, is what it should be at around 150 Mbps on single 20 MHz channel or 300 Mbps on bonded 40 MHz channel. As soon as I disable WMM on the router, my Internet download speeds are what they should be around 25 Mbps.
Google "Comcast slow download" for more info on the Comcast WMM compatibility issue. Here are a few articles that I found.
Thank you for your post, sorry to hear that you are experiencing speed problems with our wireless adapter. Note that because our wireless adapters are certified with IEEE and the WiFi alliance the adapter needs to comply with the specifications stating that WMM is required to be enabled for speeds higher than 54mbps.
See the link below that describes this a bit better: