How do you check a swap file?
Drivers are good, and it's a wireless connection. Too far away to do wired.
ok with Wifi and windows Vista/7/8 check in device manager that the power saving features of your wifi adapter is unticked.
To check your swapfile on vista onwards :-
Right click Computer in start menu
On system window click "advanced system properties"
Click Settings under performance
Choose automatic setting and windows should look after it for you. (AFAIK this is the default option for Windows)
I have mine fixed at 2048Mb due to having 8Gb ram. Without any swapfile assigned Ive found some games which use texture streaming (bf3 does), gets a touch laggy at times without a swapfile even with 8Gb ram and 3Gb on my 660ti.
I ended up removing wireless for my gaming rig and bought the powerline adapters and connected cat5, this improved my ping over what wifi n (300mbps) would return, while better its not as good as having a length of cat5 direct from router to PC, but this was my only options.
Also try and pop your PC in the DMZ of your router (if that's how your net is presented) or tell your router to give highest priority to either your PC or BF3 (depending on how your router sets up QoS)