Green Heterogeneous Wireless Networks

Chapter 9D2D Communications in Hierarchical HetNets

The growth in mobile communication systems has led to a tremendous increase in the energy consumed by the mobile networks. Device-to-device (D2D) communications and small-cell networks are considered to be an integral part of the 5G communications due to the low power, low cost and ease of deployment of small-cell BSs (SBSs) and D2D communications. This chapter introduces a three-tier hierarchical HetNet by exploiting D2D communications in traditional HetNets. D2D communications are deployed within the HetNet, where closely located mobile users are engaged in direct communication without routing the traffic through the cellular access network. The proposed configuration mandates reduction of the interference levels in the resultant HetNet by reducing the transmitter–receiver distance and ensuring that the mobile users are transmitting with adaptive power subject to maintaining their desired link quality. The performance of the proposed network configuration is investigated by comparing the spectral and backhaul energy efficiency improvements in the hierarchical HetNet against traditional HetNets. Simulation results show that the proposed deployment achieves a significant reduction in total transmission power compared with the full small-cell deployment. It is shown that the proposed network deployment outperforms the network with full small-cell deployment, and thus it provides a greener alternative to the small-cell deployment. ...