CoMP in Heterogeneous Networks: Linear Transceiver Design Using the Minimum Weighted Arithmetic-MSE Criterion

Coordinated multipoint transmission (CoMP) is considered for a heterogeneous network (HetNet) where different kinds of base stations (BS) are located. We focus on linear transceiver design with the goal of maximizing the weighted sum-rate in the downlink of a multiple-input multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) system, where each subchannel is allocated to a single user (termed as single-user MIMOOFDMA). We address this in the context of minimizing the weighted arithmetic mean of the mean-square-errors (MSEs), i.e., weighted arithmetic-MSE minimization. The problem is shown to be non-convex for a given rank constraint on the number of streams at a subchannel. Therefore, the solutions to the rank-constrained problem are suboptimal in general. We show that iterative approaches provide more efficient suboptimal solutions compared to the rank-relaxed approach, especially in a heterogeneous network where highly imbalanced base stations are located.