D2D 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. 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. The chapter describes the network architecture, spectrum partitioning and transmission model of a hierarchical HetNet. The first scenario comprised a HetNet without D2D links, and the second scenario considered a hierarchical HetNet with overlay D2D communication. Simulation results show that hierarchical HetNet with D2D communications outperforms the full small‐cell deployment in terms of average user transmission power.