Recent Advances in Underlay Heterogeneous Networks: Interference Control, Resource Allocation, and Self-Organization

By deploying additional low power nodes (LPNs) within the coverage area of traditional high power nodes (HPNs) and bringing them closer to users, underlay heterogeneous networks (HetNets) can significantly boost the overall spectral efficiency (SE) and energy efficiency (EE) through a full spatial resource reuse. Considering that the severe intra-tier interference among dense LPNs and inter-tier interference between LPNs and HPNs are challenging the successful rollout and commercial operations of underlay HetNets, a great emphasis is given towards advanced techniques that take interference control, radio resource allocation, and self-organization into account to enhance both SE and EE in this paper. The interference control techniques presented in this paper are classified as the spatial interference coordination at the transmitter and the interference cancelation at the receiver. For the radio resource allocation, the multi-dimensional optimization, cross-layer optimization, and cooperative radio resource management are comprehensively summarized. The self-configuration, self-optimization, and selfhealing techniques for the self-organized underlay HetNets are surveyed. Furthermore, this paper outlines the potential open issues for underlay HetNets to improve SE and EE when combining with energy harvesting and cloud computing.