  A game theoretic approach is used to derive the optimal decentralized power
allocation (PA) in fast fading multiple access channels where the transmitters
and receiver are equipped with multiple antennas. The players (the mobile
terminals) are free to choose their PA in order to maximize their individual
transmission rates (in particular they can ignore some specified centralized
policies). A simple coordination mechanism between users is introduced. The
nature and influence of this mechanism is studied in detail. The coordination
signal indicates to the users the order in which the receiver applies
successive interference cancellation and the frequency at which this order is
used. Two different games are investigated: the users can either adapt their
temporal PA to their decoding rank at the receiver or optimize their spatial PA
between their transmit antennas. For both games a thorough analysis of the
existence, uniqueness and sum-rate efficiency of the network Nash equilibrium
is conducted. Analytical and simulation results are provided to assess the gap
between the decentralized network performance and its equivalent virtual
multiple input multiple output system, which is shown to be zero in some cases
and relatively small in general.
