The XBox 360 team was able to borrow the Microsoft Research team, in order to create the TrueSkill player ranking system.

It’s a more interesting problem than it seems. The gold standard for player ranking systems over the years has been the chess ranking system (the ELO system), which compares players and the opponents they defeat to rank them against each other. Beating up on newbies doesn’t help your ELO ranking if you’re high up – you have to play other high level players to improve. ELO is used by most 2 player game federations, including Chess and Scrabble.

ELO does have some weaknesses, though, the most fundamental one is that it doesn’t handle games with more than two players gracefully. Microsoft claims to have solved that problem, among other problems related to ranking players. They helpfully provide the formulae – I may have to go back and relearn my high school calculus so I can understand what they’re doing.

Overall, I’ve been impressed at XBox Live’s thinking, even though I tend not to play console games online myself. Microsoft is doing this in order to pair up people for fights that are roughly equal, and in doing so taking on one of the greatest challenges of online FPS gameplay – providing a fair fight.