Joint power allocation based on link reliability for MIMO systems assisted by relay

A new optimization criterion is proposed to minimize error probability for the proposed joint optimal power allocation (PA) of the MIMO systems enhanced by relay in this paper. It is proved that the cost function obtained is only convex with respect to (w.r.t.) the power parameters of the source or those of the relay separately, but not convex w.r.t. the whole parameters. In order to use convex optimization methods with high efficiency to solve this complicated problem, a tight upper bound of the sum MSE (mean squared error) is derived, and employed to modify the cost function in order to obtain a convex problem. It is verified through simulation results that the proposed PA scheme outperforms the existing one.