Improving Spectral Efficiency for Device-to-Device Data Offloading in Underlay Cellular Networks

Device-to-Device (D2D) communications underlying cellular networks have been becoming a promising technology to improve spectral efficiency in next generation wireless networks. As an emerging paradigm, it decreases latency, increases coverage, and enhances performance of the network in terms of spectral efficiency (SE) of the network. However, the problem of interference imposes a great technical challenge to radio resource allocation in underlay D2D communications. Due to inherent nature of consuming high speed low cost data, D2D enabled cellular devices can switch from licensed cellular network to integrated unlicensed cellular networks by changing underlay D2D mode to unlicensed cellular mode named as global offloading. We study how in global offloading, D2D devices release scare shared resources and reduce interference resulting improvement of SE of the cellular network. We also propose a probabilistic model based on macro-to-femto cell changing probability of D2D devices, and apply the proposed modeling technique on basic Shannon based interference management scheme, optimal resource sharing scheme, and interference-aware graph based scheme to obtain SE of the cellular network. Numerical results confirm that our proposed modeling technique dramatically improves SE of the cellular network with respect to different percentages (e.g., 25%, 50%, and 75%) of resource blocks released by D2D devices during global offloading in all three schemes.