Pre-season training begins on Thursday and so the midfield trio, along with defenders John Anderson and Greg Strong, will join up with the rest of the Tigers squad for the first time.
Assistant manager Gary Barnett said: "Ian is an experienced campaigner and has played a lot of games for Cambridge over the past few years.
"He will be a key figure and hopefully he'll settle in straight away as the midfield area will be vital for us this season.
"The holding role is where Ian will probably play, but as well as being a good defensive midfielder he also has a good range of passing and has that awareness which tells him when and when not to part with the ball."
Meanwhile Barnett added: "We believe that the players we've brought in are excellent signings for the club and it's a bonus that they'll be there on the first day of pre-season.
"Of course, we are still looking at a couple more players and although they may miss the start it won't be a major problem."