Two-tier cellular networks in which small cells are overlaid with macro-cells have attracted considerable attention because these networks are expected to accommodate the rapidly increasing mobile traffic. Enhanced inter-cell interference coordination (eICIC) has also been proposed to further enhance the overall system performance by offloading more macro-cell users to small cells. Even with this approach, it is likely that macro-cell users are effectively offloaded to the small cells in the network because of the following reasons: i) some macro-cell users are offloaded to small cells by simply comparing their received signal strengths, and ii) the almost blank subframe (ABS) in the small cell is strictly assigned to users who experience strong interference from its nearby macro-cells. In this paper, we propose a load balance scheme for improving the downlink network-wide proportional fairness (PF) for two-tier cellular networks using eICIC. In particular, employing a cumulative distribution function-based scheduling scheme that supports sharing ABS across all users in each small cell, the proposed scheme recursively combines i) the user association between the cells and ii) ABS rate adaptation to improve the network PF. Through system-level simulations, we demonstrate that the proposed scheme noticeably improves the network PF compared to the eICIC scheme regardless of the number of macro-cell users offloaded to small cells. Keywords Load balance Enhanced inter-cell interference coordination eICIC Two-tier cellular network Almost blank subframe ABS CDF-based scheduling
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