Chelsea boss Jose Mourinho values Belgium playmaker Eden Hazard at £200m after reported interest from Real Madrid.
Alan Pardew is weighing up chasing a big-name summer signing to boost Crystal Palace's profile.
Both men played under former Spurs boss Harry Redknapp at White Hart Lane and will stay at Loftus Road for the rest of the 2013-14 campaign as the Hoops plot an instant return to the Premier League.
Left-back Assou-Ekotto, who is currently on international duty with Cameroon, told the club's official website: "It is fantastic to be linking up with Harry again.
"I enjoyed my best form at Spurs under him and am looking forward to doing my best for QPR.
"I know the way Harry likes his sides to play, and it is a style that suits me which is why I am excited about this opportunity.
"QPR have made a great start and I can't wait to help them build on that during my time here."
Redknapp was equally enthused about bringing 21-year-old midfielder Carroll to the club.
"He's a player I fully expect to go to the very top of the game - he's a future England international," he added.
"I played him at Spurs in Europe and he was fantastic for me. He's got all the attributes to be a top, top player.
"He can pass, he can create, he can score goals - he's a fantastic player and I'm confident he'll flourish here for us."