Backhaul Overhead Traffic Reduction in Dense MmWave Heterogeneous Networks Towards 5G Cellular Systems

High dense heterogeneous networks (HetNets) are considered as one of the most promising solutions paving the way towards fifth generation (5G) cellular network. Conventionally, in the LTE HetNets, legacy microwave macro cell (MC), such as LTE eNB, with wide coverage is densely overlaid with a large number of small cells (SCs), such as micros, picos and femtos to support extra high capacity. In addition to network densification, millimetre wave (mmWave)-based HetNet with SCs utilizes the huge bandwidth available in this band has got the attention of both academia and industry to support the required 5G multi-gigabit data rates. However, the dense deployment of SCs combined with mmWave propagation limitations induces several challenging issues in HetNets realization such as heavy backhaul traffic and signalling overhead on the core network (CN). This paper addresses the challenges of dense HetNets and analyse its associated massive backhaul traffic. Moreover, the energy efficiency of backhaul networks is evaluated and compared with the legacy and the mmWave-based HetNet architectures. Furthermore, in this paper, a cluster-based central HetNet architecture is introduced to mitigate the backhaul traffic due to the heavy signalling in mmWave-based 5G HetNets. Numerical comparisons assess the superiority of the mmWave-based HetNet energy efficiency than the legacy LTE HetNets. Also, simulations show that the proposed mmWave HetNet architecture can effectively decrease the signalling load and backhaul traffic towards CN.