Inspiron 7520 occasional lag spikes ('request timed out' in CMD)

Hello, I hope anyone doesn't mind helping me!

So I recently got my laptop, an Inspiron 7520 SE, and I am happy with it apart from this strange wireless problem.

I first noticed it in online games; every now and then (about once every minute or two) the game would lag for a few seconds. At first I thought it was a problem with the game, but I noticed it happening in every online application. 

I tested this by opening the command line and pinging my router, and saw that I would often receive a 'request timed out' message, and nothing I do seems to fix this.

However, when I use a USB wireless adapter, I don't have this problem. My other devices connected to the router also are unaffected, which makes me think the fault lies with the inbuilt wireless adapter itself.

My laptop uses the Centrino 2230 adapter, and I've tried resetting my system, updating drivers, but the problem remains.

Would anyone know the cause of the problem, and how to fix it? Any help would be appreciated, thanks!