On the two-user MISO interference channel with single user decoding and partial CSIT

This paper studies the Rayleigh fading two-user multiple-input single-output interference channel with single user decoding and limited channel state information (CSI) feedback. Two contributions are presented. First, the achievable rate-region with partial CSI at the transmitters due to channel quantization errors is analyzed. We derive an analytically tractable inner bound on that region, which provides insights into the problem. It is shown that, similarly to the case of perfect transmitter CSI, beamforming is optimal for achieving every boundary point of the inner bound. The second contribution is a novel CSI feedback scheme that reduces the cross-link CSI feedback overhead, and enhances throughput for any rate-limited feedback scheme. Such feedback reduction is crucial when control channels for sharing information between transmitters and unintended receivers are rate limited. The proposed scheme takes feedback into account already at the channel estimation stage. While maintaining a high array gain in the direct channel towards the intended user, the scheme induces an effective low-dimensional cross-link channel, which can be quantized more accurately than the full-dimensional channel, leading to enhanced performance.