Mobile-Traffic-Aware Offloading for Energy- and Spectral-Efficient Large-Scale D2D-Enabled Cellular Networks

This paper investigates how to enhance the energy and spectral efficiency (ESE) performance of large-scale cellular networks by offloading mobile traffic with the aid of device-to-device (D2D) communication. By appropriately exploiting the D2D-based mobile-traffic offloading mechanism, the users' behaviors and the specific network operating conditions, we develop an ESE evaluation framework for large-scale D2D-enabled cellular networks. This framework enables us to characterize the explicit relationship between the network's ESE and the offloading parameters as well as to quantify the influence of the users' behavior. Explicitly, we quantify the effects of the mobile-traffic intensity, the users' quality of service requirements as well as the base station density and other cellular system parameters on the achievable ESE. Tractable closed-form ESE-expressions are derived for a pair of spectrum sharing schemes, namely, D2D overlay and underlay in-band modes. Furthermore, we apply the analytical results to derive an optimal D2D-enabled mobile-traffic offloading scheme for the D2D overlay cellular networks to maximize the network's ESE under a specific maximal cellular user outage and D2D transmitter power constraint. The numerical and simulation results are provided to verify our modeling accuracy and to demonstrate the impact of the system parameters on the achievable ESE.