Network-Assisted Device-to-Device Connectivity: Contemporary Vision and Open Challenges

Embracing the contemporary wireless landscape, global research is rapidly advancing on the 5G topics. Whereas Europe is definitely on the forefront of 5G research with Horizon 2020 and other visible initiatives, the unconventional deviceto- device (D2D) component of the emerging 5G ecosystem is not nearly well-understood. Furthermore, many promising D2Dcentric research attempts still remain disjoint and contradictory, lacking a harmonizing and unifying perspective. Correspondingly, with this position paper, we target to comprehensively review the background of network-assisted proximal communication, as well as consistently outline the most promising directions for further necessary research in this area. The envisioned challenges include the choice of attractive D2D-centric application scenarios, progress in device-centric system architectures, appropriate D2D mechanisms and corresponding performance evaluation methods, as well as opportunities to efficiently leverage the benefits of proximal connectivity for network operators and end users. We hope that the proposed roadmap will become of value not only to investigators interested in D2D communication per se, but also to the much broader 5G research community. Our group is confident that the lines of work indicated in this paper have the potential to eventually demystify the ultimate benefits of D2D, develop its native support in forthcoming 5G architectures by 2020, as well as unveil the promises that it holds for traffic offloading and new proximity-aware services.