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

The interference rejection combining (IRC) receiver is effective in improving the cell-edge user throughput because it suppresses inter-cell interference. The IRC receiver is typically based on the minimum mean square error (MMSE) criteria, which requires channel estimation and covariance matrix estimation including the inter-cell interference with high accuracy. The paper investigates the gain from the IRC receiver taking into account the estimation of the interference signal, i.e., the covariance matrix, in terms of the downlink user throughput performance in a multi-cell environment. For the estimation of the covariance matrix, two estimation schemes are considered one based on data signals and the other based on the demodulation reference signal (DM-RS). In the evaluation, to assess the actual gains of the two schemes, the inter-cell interference signals from the surrounding 56 cells are actually generated in the same way as the desired signals including reference signals, and the channel propagation from all of the cells is explicitly taken into account considering pathloss, shadowing, and multipath fading. The simulation results when the inter-site distance is 500 m and the numbers of transmitter and receiver antennas are 2 and 2, respectively, show that the IRC receiver employing the covariance matrix comprising the interference and noise component estimation improves the cell-edge user throughput (defined as the 5% value in the cumulative distribution function) by approximately 22% compared to the simplified MMSE receiver that approximates the inter-cell interference as AWGN, while the IRC receiver employing the full covariance matrix estimation degrades the average user throughput due to less accurate channel and covariance matrices.