Design and evaluation of a system of direct connections D2D with LTE cellular assistance

Due to the growing popularity of mobile user applications, cellular network operators are increasingly interested in offloading their scarce licensed spectrum resources. To this aim, using unlicensed-band radio technologies is attractive owing to its reduced costs. This work designs a system of direct D2D (device-to-device) connections to offload mobile traffic that is served by LTE (long-term evolution) cellular networks. In particular, a network assistance protocol over LTE architecture is proposed for D2D connections, and its system-level performance is evaluated to quantify the resulting traffic-steering efficiency. In addition, practical operation of D2D communication in a test LTE network is described, which allows making substantiated conclusions about the actual feasibility of the proposed solution in real-life conditions.