Take your PS3 and move it closer to the access point. If you don't have another TV standing there, you'd have to move that one as well. The reason for your bad connection is that the data has to travel too far. A few packages get lost on their way (just like me driving throug the inner city of Vienna :D) and that makes up your bad connection. If you view the details for your connection in the network setting, you should see a fairly low percentage of how good your connection acutally is.
At the time, my PS3 is located about 6 meters away from the access point and I have about 70%. That was enough for that trophy.