On Achievable Sum Rate for Vector Gaussian Interference Channels

We develop a procedure to compute a lower bound of the sum capacity for the vector Gaussian interference channel (IFC). The obtained lower bound is shown to be tight for the very strong interference case and the procedure can be used to construct an inner bound for the vector Gaussian IFC. Alternatively, orthogonal transmission via frequency division multiplexing is considered and we establish the concavity of the sum rate as a function of the bandwidth allocation factor for the vector channel case. Numerical examples indicate that the achievable sum rate via the superposition code compares favorably with orthogonal transmission. This improvement holds for all interference power levels, a sharp contrast to that of the scalar counterpart