Why is my iPhone's YouTube service over Wifi so slow?

It goes so slow! I can't watch a video without it stoppin a couple hundred times. The load bar doesn't loa fast enough with the video. I have a cisco router, and even when my phone has 2-3 bars, it STILL WON'T LOAD fast enough. I have the iPhone 4th generation, can someone tell me what's wrong or how to make the wifi faster?