Sum rate maximization of MIMO broadcast channels with coordination of base stations

We consider cooperative downlink transmission in multiuser, multi cell and multiple antenna cellular networks. Recently, it has been shown that multi base coordinated trans mission has significant spectral efficiency gains over that without coordination. The capacity limits can be achieved using a non linear precoding technique known as dirty paper coding, which is still infeasible to implement in practice. This motivates investigation of a simpler linear precoding technique based on generalized zero forcing known as block diagonalization (BD). In this paper, an enhanced form of BD is proposed for multiple input multiple output (MIMO) multi base coordinated network. It involves optimizing the precoding over the entire null space of other users' transmissions. The performance limits of the multiple antenna downlink with multi base coordination are studied using duality of MIMO broadcast channels (BC) and MIMO multiple access channels (MAC) under per antenna power constraint, which has been established recently.