Power allocation in cooperative MIMO systems under individual power constraints

Power allocation (PA) plays an important role in capacity improvement for cooperative multiple-input multiple-output (Co-MIMO) systems. Many contributions consider a total power constraint (TPC) on the sum of transmit power from all nodes in addressing PA problem. However, in practical implementations, each transmit node is equipped with its own power amplifier and is limited by individual power constraint (IPC). Hence these PA methods under TPC are not realizable in practical systems. Meanwhile, the PA problem under IPC is essential, but it has not been studied. This paper extends the traditional non-cooperative water-filling PA algorithm to IPC-based Co-MIMO systems. Moreover, the PA matrix is derived based on the compound channel matrix from all the cooperative nodes to the user. Therefore, the cooperative gain of the IPC-based Co-MIMO systems is fully exploited, and further the maximal instantaneous capacity is achieved. Numerical simulations validate that, under the same IPC conditions, the proposed PA scheme considerably outperforms the non-cooperative water-filling PA and uniform PA design in terms of ergodic capacity.