Block Diagonalization for Multi-User MIMO
with Other-Cell Interference


S. Shim, J.-S. Kwak, R. W. Heath, Jr., and J. G. Andrews


IEEE Transaction on Wireless Communications, vol. 7, no. 7, pp. 2671-2681, July 2008.


Block diagonalization is one approach for linear precoding in the multiple-input multiple-output broadcast channel that sends multiple interference free data streams to different users in the same cell. Unfortunately, block diagonalization neglects out of cell interference, which limits the performance of users at the edge of the cell. This paper presents an OCI-aware enhancement to block diagonalization that uses a whitening filter for interference suppression at the receiver and a novel precoder using the interference-plus-noise covariance matrix for each user at the transmitter. For complex Gaussian matrix channels, the asymptotic sum rate of the proposed system is analyzed under a large antenna assumption for isotropic inputs and compared to conventional block diagonalization. The capacity loss due to OCI is quantified in terms of results from single-user MIMO capacity. Several numerical examples compare achievable sum rates, the proposed asymptotic rates, and the capacity loss, in low and high interference regimes.