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Energy-Efficient Device-to-Device Communication in Cellular Networks

Device-to-Device (D2D) communication is expected to satisfy the rapidly increasing capacity, and it can also alleviate the burden of base stations (BSs) by offloading onto direct links in a 5G mobile system, which can support high-speed data rate for local users and provide power-saving services, while enhancing the energy efficiency (EE) of the global network. Therefore, we model the EE of global network underlaid or overlaid D2D direct communications, where the explicit relationships between EE and the offloading strategy radius are signified by quantifying various network parameters (i.e., density of BSs and users, data-rate and system bandwidth, etc). More importantly, we analytically comprehend the EE and user's average transmission power in both D2D modes, that is, underlay and overlay. Furthermore, offloading probability of cellular users and active probability of D2D transmitters are analytically obtained. Simulations are carried out and show that global network EE can be significantly improved by using D2D communication. Moreover, in overlay mode, when the D2D bandwidth is same with underlay mode, users consume less power for transmission, because the inter-tier interference is eliminated at the price of saving gain on the energy and spectrum as the total bandwidth becomes larger.