Instructions
Use your PlayStation 3's wired connection instead of its wireless connection while playing "Call of Duty 4: Modern Warfare" online. A wired connection will naturally have a faster data-transfer speed than one of a wireless variety. Use an Ethernet cable to plug your PlayStation 3 directly into your modem or router to get the fastest possible ping during online gameplay.
Stop any downloads that you are currently transferring via your PlayStation 3. If you've purchased a game from the PlayStation Store or have downloaded a file or video from the Internet, for example, this will eat up bandwidth that could be going to "Call of Duty 4." Select "Network" from the menu and "Download Management." Stop or pause any downloads before continuing to play the game.
Download any "Call of Duty 4: Modern Warfare" updates that you are prompted to install before you start the game. Every time you start a game on your PlayStation 3, the console automatically checks for updated versions of the software. If updates are available, press "X" to download and install them. These updates can improve the performance of "Call of Duty 4" and increase your ping during online server games.