Low Dimensional Channel Feedback Scheme for Interferenc Mitigation in Cellular Networks

Channel state information is a crucial ingredient in Cooperative Multi-Point (CoMP) communication schemes in cellular networks. It required that the interfering Base Station (BS) knows the interference channel to out-of-cell user equipment (UE); a challenging task due to the large feedback overhead in case there is no channel reciprocity. We focus in this work on the downlink; to obtain channel state information, the channel is estimated by the UE, quantized, fed back to the interfering BS. Due to channel quantization errors, the interference to the UE cannot be completely eliminated; hence, out-of-cell UEs are affected by residual interference. 

We study the Rayleigh fading two-user MISO interference channel with single user decoding and limited channel state information. In this work a low dimensional channel state feedback scheme was proposed. The scheme reduces the overhead by restricting the signal transmitted by the interfering BS to a low dimensional signal space. The projection yields an equivalent channel that can be quantized with a small number of bits compared to the original channel, while achieving a considerable interference reduction at the interfered UE. We study the effect of the proposed scheme on the channel quantization error, the residual interference as a function of the number of feedback bits, and the new achievable rate region. 

* This research was carried out towards the M.Sc. Degree in Electrical Engineering at Bar-Ilan University, under the supervision of Dr. Yair Noam.