Cross-Tier Cooperation for Optimal Resource Utilization in Ultra-Dense Heterogeneous Networks

Ultra-dense network is a promising technology for 5G cellular networks, and its approach is to densify the network to enhance system throughput via universal frequency reuse. Traditionally, macro cells and small cells usually operate on separate dedicated channels in the ultra-dense environment. This dedicated channel approach leads to resource underutilization because base stations may not be able to fully utilize their radio resource with fixed partitioning when the traffic load in the network is fluctuating. In this paper, we study this underutilization problem in ultra-dense heterogeneous networks, and propose two adaptive channel partitioning schemes to enhance the system throughput: D
²
CP and D
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CP-C. Both schemes require the coordination between macrocell and small cells, and D
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CP-C takes advantage of cross-tier cooperation to further enhance the system throughput. We analyze the proposed schemes based on stochastic geometry, and evaluate the performance via simulations. The simulation results show that D
²
CP and D
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CP-C outperform fixed channel partitioning by 33.37% and 76.01%, respectively, demonstrating that base station coordination and cross-tier cooperation can achieve better radio resource utilization in ultra-dense heterogeneous networks.