I used to play wireless and would get random DCing and lag during certain instances (especially EX primals). I recently got a new router and it was messing up my connection to the point where I would DC for 20-30 seconds at a time and basically could not play. I decided to go wired and hooked my PS3 up with an ethernet cable....BIG difference!
I no longer lag nor DC like I did before (which makes doing Titan EX a breeze)! I highly recommend a wired connection if you're having any kind of connections issues (and on a PS3).