Optimum Power Allocation for Multiuser OFDM with Arbitrary Signal Constellations

This paper formulates the power allocation policy that maximizes the region of mutual informations achievable in multiuser downlink OFDM channels. Arbitrary partitioning of the available tones among users and arbitrary modulation formats, possibly different for every user, are considered. The policy, derived for slowly fading channels tracked by the base station, adopts the form of a multiuser mercury/waterfilling procedure that generalizes the single-user mercury/waterfilling introduced in [1]