Energy-efficient heterogeneous networks for green communications by inter-layer interference coordination

Hierarchical layering of cells with macrocells coexisting with low-power small cells has been investigated as a promising technique to enhance coverage extension and reduce power consumption, which has emerged as a candidate for green communications. Due to the challenging interference scenarios, Cell Range Extension (CRE) and enhanced inter-cell interference coordination (eICIC) are the key technologies that make HetNets a reality. However, when macrocells and low-power nodes (LPNs) share the same spectrum, the total network throughput could actually decrease due to CRE if the inter-layer interference can´t be effectively managed. In this paper, we propose an inter-layer interference coordination scheme on the downlink side for a co-channel macro-pico HetNet that carries out CRE technique. The idea of the proposed method is to coordinate frequency and power resource allocation among macrocells and picocells with a set of rules, which can lead to interference mitigation and power reduction. Then a utility function combining interference and throughput is calculated to find the optimal transmission power of each macro base station (MBS) in some special bands by using Differential Evolution (DE) theory. Finally, simulation results show that the proposed method can not only promote the system throughput and energy efficiency greatly but also keep better link quality in the system.