Performance of Interference Rejection Combining Receiver to Suppress Inter-Cell Interference in LTE-Advanced Downlink

The interference rejection combining (IRC) receiver, which can suppress inter-cell interference, is effective in improving the cell-edge user throughput. The IRC receiver is typically based on the minimum mean square error (MMSE) criteria, which requires highly accurate channel estimation and covariance matrix estimation that includes the inter-cell interference. This paper investigates the gain from the IRC receiver in terms of the downlink user throughput performance in a multi-cell environment. In the evaluation, to assess the actual gain, the inter-cell interference signals including reference signals from the surrounding 56 cells are generated in the same way as the desired signals, and the channel propagation from all of the cells is explicitly taken into account considering pathloss, shadowing, and multipath fading. The results of simulations that assume the inter-site distance of 500 m, the spatial correlation at the transmitter and the receiver of 0.5, and the numbers of transmitter and receiver antennas of 2 and 2, respectively, show that the IRC receiver improves the cell-edge user throughput (defined as the 5% value in the cumulative distribution function) by approximately 15% compared to the simplified MMSE receiver that approximates the inter-cell interference as AWGN, at the cost of a drop in the average user throughput due to less accurate channel and covariance matrices. Furthermore, we consider dynamic switching between the IRC receiver and the simplified MMSE receiver according to the number of streams and modulation and coding scheme levels. The results show that with dynamic switching, both the cell-edge throughput and average user throughput are improved to the same level as that for the IRC receiver and the simplified MMSE receiver, respectively. Therefore, the best performance can be achieved by employing the dynamic switching in all throughput regions.