Slow wireless internet on ps3!

Hello,
Im always having problems with my internet on ps3 it works good on computer but on ps3 it gets slow (wirelessly) and when i get in a game all it says is 'setting up game...' for a while so i need to turn off my controller which lets me in but i just want to connect normally and easily and fast. (Game-call of duty 4).

Thnaks please help! =[