I have Xfinity for a internet provider and it is fine when it's just me playing and no one else is on the internet. But, when someone else with a computer for example gets on the internet also my internet begins the lag on my PS3. Is it possible that I can have a separate IP address from the other people in my house? If so, someone please provide instructions and thanks.
You already have a different IP address from the computer. Each host has to have a different address on the LAN. All hosts on the LAN share the same public Internet address, but that isn't why your online gaming performance is reduced. It is because the PS3 and the PC are competing for bandwidth. Data transfers made by the PC are delaying your gaming packets. As long as both are using the same broadband connection, that will continue to be a problem. Changing the modem configuration won't fix the problem. You just can't play online with good performance while someone else is using a PC on the same Internet connection. You either have to get a separate Internet connection for yourself, or you have to play when no one else is doing anything significant on the network.