Traffic offloading problem in two-tier HetNets with D2D support for emergency communications

In emergency situations such as catastrophes, the cellular infrastructure can be partially or totally damaged. For rescue teams to transmit and receive on-sight reports using live video and high quality images, the provisioning of seamless coverage with high data rates is inevitable. As cellular networks continue to evolve into more heterogeneous structures regarding the size of deployed cells, the implementation of traffic offloading strategies is essential to achieve high data rates and more power saving. In regard to network modeling, stochastic geometry has been considered in the literature as an efficient approach for modeling the locations of base stations (BSs). Moreover, stochastic geometry provides tractable mathematical expressions for key network parameters such as coverage probability and average data rate. In heterogeneous networks (HetNets), density and power of BSs in a given tier influence the volume of traffic offloaded to other tiers. However, these two parameters are generally constrained together in practical scenarios. In other words, given a BS density, the power per BS must be adjusted to satisfy the inter-tier traffic flow to maximized system throughput. Furthermore, in D2D networks the fraction of spectrum allocated to D2D links also affects the net achieved throughput. In this paper, we formulate the problem of jointly optimizing the power of small BSs (SBSs), SBS density, and the fraction of spectrum allocated for D2D communications in order to maximize system throughput for critical conditions such as rescue missions.