Optimal Multi-Antenna Transmission with Per-Group and Joint Power Constraints

In this paper, we determine the optimal transmit strategy that achieves the capacity of a n_t x 1 Multiple-Input Single-Output (MISO) and 2 x n_r Multiple-Input-Multiple-Output (MIMO) channels under: (1) Per-group Power constraints (PGPC), i.e., sum power constraints on groups of antennas, and (2) Joint power constraints, e.g., sum power constraint and per-group power constraints. Sum power constraint over all antennas (SPC) and per-antenna power constraints (PAPC) are special cases of PGPC. The results in this paper generalize some recent results on MISO capacity under: (1) PAPC and (2) joint SPC and PAPC. PGPC and joint power constraints arise naturally in distributed antenna systems, and in systems with some practical implementation constraints.