I've been battling with this issue for a while on a Samsung Series 5 550PC5 (with the infamous Advanced-N 6235) running Windows 8 64bit. It kept dropping the connection and had trouble reconnecting. I'm in the UK and use BT home hub 3 on Infinity. All other devices, iPhone 4s, Sony Xperia Ray, Nexus 7, Samsung Nc10 etc etc work flawlessly with my WiFi. So it was a huge disappointment that the device which supposedly had an "Advanced" wireless card gave the worst connection!
After trying the many suggestions on this forum and elsewhere it seemed the only thing that fixed it was to disable 802.11n mode. But whilst this stopped it dropping out it also cut my download speed from 60Mb+ to around 20Mb.
So I thought I'd try one more time and came across the suggestion of rolling back to the windows driver instead of the Intel one, so I gave it a go and voila! Everything now works as it should. I've now got 802.11n enabled and the connection is rock solid. Download speeds are back up to normal
If you wish to try this fix but are unsure how I'll try and detail the steps below:
In windows 8 move the cursor to the top right of the screen then select search (magnifying glass)
Click on Settings
Then in the search box type "Device Manager" and then select "Device Manager" from the options that appear on the left.
In the list of devices, look for "Network Adapters" and expand it by clicking on the little white triangle
Double click on "Intel(R) Centrino(R) Advanced-N 6235"
Select the "Driver" tab
Check the Driver provider is Intel and not Microsoft. If the provider is Intel then you can uninstall the drivers back to the default Microsoft ones
If however your driver details look like this
Then you already have the Microsoft driver so STOP!! 
Please note that if you follow the steps below you will lose your Wifi/Internet connection when you uninstall the driver and will have to reconnect once complete, so make sure you have your WiFi password to hand!!!
If your driver is an Intel one make a note of the driver version then click the "Uninstall" button
You will get a popup asking you to confirm. Tick the checkbox to "Delete the driver software for this device" and then click OK.
You should then end up back in the device manager list view.
Find "Intel(R) Centrino(R) Advanced-N 6235" again (if it's not in the list go to the Action menu and select "Scan for hardware changes") and double click the Intel 6235 again.
Go to the driver tab and see if your driver provider has switched to Microsoft. If so you are done 
If not and it is still Intel, you should see that the driver version is now lower than it was. Click on "Uninstall" again and repeat the process until the provider is Microsoft, the version should be 14.8.8.75 as in the screenshot above.
Once finished you can then reconnect to your WiFi.
Good luck!!
PS I also had another issue with this laptop in that web pages were not loading correctly. I had to keep reloading them or clearing out the browser cache. Turned out to be Samsung bloatware that was screwing up the caching. If you have this problem then uninstall "Samsung Support Center".
Laptop now working as it SHOULD have been from the start.