Investigation on interference rejection combining receiver in heterogeneous networks for LTE-Advanced downlink

In Long-Term Evolution (LTE)-Advanced, heterogeneous networks where low power nodes such as picocells are overlaid onto macrocells were extensively investigated to improve further the system throughput per unit area. In heterogeneous networks, to achieve an offloading gain from macrocells to picocells, cell range expansion (CRE) is applied. Additionally, inter-cell interference coordination (ICIC) is applied to reduce the severe inter-cell interference transmitted from the macrocells to the sets of user equipment (UEs) connected to the picocells. In such cases, since the interference statistics are completely different from traditional well-planned macrocell deployments according to the parameters specified for CRE and ICIC, it is important to investigate using the interference rejection combining (IRC) receiver because it effectively improves the cell-edge user throughput by suppressing interference from the surrounding cells. To clarify the improvement in user throughput due to the IRC receiver, this paper investigates the interference statistics and evaluates the user throughput performance of the IRC receiver in heterogeneous networks employing CRE and ICIC. Simulation results show that the throughput gain from the IRC receiver becomes small due to a reduction in the severe inter-cell interference from ICIC. However, we clarify that a cell-edge user throughput gain from the IRC receiver exceeding 10% is achieved compared to the conventional minimum mean square error (MMSE) receiver in a heterogeneous network with four picocells within each macrocell. Furthermore, we show that the same parameters specified for CRE and ICIC can be set regardless of the IRC or conventional MMSE receiver.