I have a Dell N7110 with an Intel Centrino N-1030 Wireless Adapter. And an unbranded router provided by my ISP. For the past 6 months since I got my Dell, I've been able to connect to the wireless without issue, and get somewhere between 60 and 80Mbps. As of about a week ago, my speed suddenly dropped to 20Mbps. I can confirm the router is just fine, I've got two other laptops on the wi-fi, and they both get around 60Mbps.
I updated the drivers for my N-1030, and made sure the advanced settings were configured correctly. It appears that the problem is that I'm no longer able to connect using 802.11n, and am instead defaulting to 802.11g. In an effort to fix the issue, I configured the router to only use 802.11n, upon doing so, my Dell was no longer able to connect to the wi-fi. It was able to see the network, it starts to connect, and then disconnects. When I switch the router mode back to 802.11b/g/n, it connects just fine, but with severely limited speed.
I'm considering doing a system wipe and clean install, but would love to have this issue fixed without such drastic measures. I read a post somewhere saying that for 802.11n to work correctly the security settings should be WPA2 Personal, with AES instead of TKIP, so I changed the settings on my router, and still no luck. Does anyone have any idea what the issue may be?
After reading on some Dell forums about an issue with the N-1030 card, and how some users found disabling bluetooth fixed the issue, I gave that a shot, it didn't work. I disabled everything relating to bluetooth in device manager, and still no change.
I understand you are having problems with the speed connection and I will make my best to help you.
There is some information I would like to know first so I can provide accurate information. Can you please let me know what the driver version you have installed is? How far is the computer from the Router?