i would try getting closer to the router that helps me or make sure a wall isn't in the way of the signal that could also be the problem. you may also want to ask your internet provider about your upload download speed if possible see if you can upgrade to higher speeds.
I've been having that same exact problem today, it all started after the PSN was down yesterday. I thought it was my provider so I did a speed test on laptop and its running perfectly, then speed test on ps3 and got extremely slow results so its not the provider. Cant be anything with my setting considering i havent touch any of them it was running perfectly fine all last week all up to the psn outage, so i believe its on the psn side.