Wired connection problems

Hello,
when i 1st had my ps3 i was usin a wireless connection. i was gettin a very poor connection on all my games even though my router was in the next room. i bought a cable which plugs into the back of my router and in the back of my ps3 (wired connection obviously) and it isnt any better, in fact its a lot worse. im at my wits end now because its really affectin my gameplay. also i get signed out of ps network everytime my house phone rings (if that helps). any advise anyone could give would be really helpful.