Abstract
Dense and heterogeneous networks (HetNets) are being deployed to provide better coverage and throughput, thus improving the quality of experience at mobile users. Besides the important implications for energy consumption, the trend towards densification calls for more and more wireless links to forward a massive backhaul traffic into the core network. It is critically important to take into account the presence of a wireless backhaul for the energy-efficient design of HetNets. In this paper, we provide a general framework to analyze the energy efficiency of a two-tier MIMO heterogeneous network with wireless backhaul under spatial multiplexing and dynamic time division duplex. We find that a two-tier HetNet with wireless backhaul can be significantly more energy efficient than a one-tier cellular network. However, this requires the backhaul bandwidth to be carefully allocated according to the network load conditions.