Promoting Energy Efficiency and Proportional Fairness in Densely Deployed Backscatter-Aided Networks

Recently, energy-efficient ambient backscatter communication has emerged as a promising technology to build up self-sustainable wireless networks. However, the limited transmission range and rate restrict the communication capability of a single backscatter node. To ensure network coverage and connectivity, the nodes in ambient backscatter-aided wireless networks (AmBWNs) have to be densely deployed. Unfortunately, the fickle and sporadic nature of the energy source and carrier in AmBWNs would lead to unreliable and unstable transmissions. We argue that the network throughput can be significantly improved if we can take full advantages of both stable active transmission and energy-saving backscattering. However, it is challenging to jointly determine nodes' transmission mode to enhance the throughput and energy efficiency. Moreover, the fairness in terms of traffic load at each node of AmBWNs is not thoroughly considered in the existing research. The improper load allocation would hinder the network throughput and even cause network partition if some bottleneck nodes deplete the energy. In this article, a novel metric is defined to measure the aggregate energy efficiency of neighboring nodes, capturing the beneficial interaction of active links and backscatter links. Subsequently, we address the aggregate energy efficiency maximization problem constrained by Gini threshold. The Gini coefficient is used to adjust the load in proportion to the delivery capacity of each node, achieving proportional fairness in the dense AmBWN. The simulation result shows that the well-designed metric can improve the energy efficiency by 11 times and the throughput by 86%.