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Cellular Traffic Offloading onto Network-Assisted Device-to-Device Connections
While operators have finally started to deploy fourth generation broadband technology, many believe it will still be insufficient to meet the anticipated demand in mobile traffic over the coming years. Generally, the natural way to cope with traffic acceleration is to reduce cell size, and this can be done in many ways. The most obvious method is via picocells, but this requires additional CAPEX and OPEX investment to install and manage these new base stations. Another approach, which avoids this additional CAPEX/OPEX, involves offloading cellular traffic onto direct D2D connections whenever the users involved are in proximity. Given that most client devices are capable of establishing concurrent cellular and WiFi connections today, we expect the majority of immediate gains from this approach to come from the use of the unlicensed bands. However, despite its huge commercial success, WiFi-based direct connectivity may suffer from stringent session continuity limitations, excessive user contention, and cumbersome manual setup/security procedures. In this article, we detail our vision of integrating managed D2D communications into current cellular technology to overcome the limitations of WiFi. We also quantify the estimated network performance gains from offloading cellular traffic onto D2D connections. Our analysis is based on an advanced system-level simulation toolkit that captures the relevant details of the network environment, and a detailed characterization of dynamic D2D communications based on stochastic geometry. We conclude that D2D communications provide a significant boost to network capacity as well as user energy efficiency and quality of service perception.