i tried this out and it increased my fps by ~10
first go to your main battlefield folder and find a file called 'user.cfg' (its either in program files or program files x86) delete everything in the user.cfg and paste this in:
WorldRender.SpotlightShadowMapResolution 256
WorldRender.SpotlightShadowMapEnable 0
WorldRender.DxDeferredCsPathEnable 0
RenderDevice.TripleBufferingEnable 0
RenderDevice.ForceRenderAheadLimit 1
RenderDevice.Dx11Enable 0
PostProcess.DynamicAOEnable 0
and also google something like 'battlefield 3 boost fps prof_save_body' and if you find the right site or youtube video there should be a file named that and just follow the instructions on where to put that file.
thats pretty much it
---------- Post added at 02:22 PM ---------- Previous post was at 02:20 PM ----------
oh an download 'BF3 Settings Editor'. just google it, its free. you can change your graphic settings option to increase fps, most of them are at the 'Console Commands' tab