Downlink Interference Control in Heterogeneous Cellular Networks: Macroscopic and Microscopic Control

In heterogeneous cellular networks that consist of macrocells and small cells, efficient interference management schemes between macrocells and small cells are crucial for overall system performance. To mitigate intercell interference, we propose macroscopic and microscopic interference control schemes. First, as a macroscopic interference control scheme, we propose a dynamic coordinated silencing. This scheme dynamically controls optimal bandwidth silencing between macrocells and small cells. It is carried out from a system quality of service (QoS) perspective on a long-term basis. Second, as a microscopic interference control scheme, we propose a user QoS-based rate splitting. This scheme controls optimal transmit power and rate for the split messages of scheduled users. It works as the complements of the proposed macroscopic control and is carried out on a short-term basis. The performance evaluations with ten small-cell deployment in each macrocell confirm that the proposed macroscopic control offers <inline-formula><tex-math notation="LaTeX">$28\%$</tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$8\%$</tex-math></inline-formula> enhanced cell-average spectral efficiency when it is compared with soft fractional reuse control and static silencing control, respectively, and <inline-formula> <tex-math notation="LaTeX">$55\%$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$23\%$ </tex-math></inline-formula> enhanced cell-edge spectral efficiency when it is compared to partitioning-based control and static silencing control, respectively. Further, it is shown that the proposed microscopic control can additionally enhance cell-edge spectral efficiency by preventing users from being interfered in dead-zone area.