MIMO Capacity with Per-Antenna Power Constraint

In this paper, we consider the single-user MIMO channel with per-antenna power constraint. We formulate the capacity optimization problem with per-antenna constraint in the SDP framework and analyze its optimality conditions. We establish in closed-form the optimal input covariance matrix as a function of the dual variable. We then propose a simple algorithm to find this optimal input covariance and the capacity. Results show that the capacity with per-antenna power can be significantly different from those with sum power or with independent multiple access constraint.