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In this paper, we have considered the uplink cross-tier interference in multi-macrocell heterogeneous networksystem, where each macrocell consists of a number of small cells. Cross-tier interference between macrocell user equipments (MUEs) and small cells base stations (SBSs) exists in both intra-macrocell and inter-macrocell due to high transmit power of MUEs. The MUE-to-SBS interference from both local and adjacent macrocells is dealt with interference alignment (IA) with the aid of a central processing node, and co-tier interference caused by small cell user equipments (SUEs) and MUEs is dealt with minimum mean square error method. To reduce the channel state information (CSI) bits transmitted through inter-cell backhaul with limited capacity required by IA, the idea of MUE-to-SBS interfering pair selection (IPS) is employed before IA. The effects of different IPS schemes on the performance of the system …