Buffer-aided device-to-device communication: opportunities and challenges

To meet the increasing demands for popular content downloading services in next-generation cellular networks, device-to-device (D2D) communication was proposed to enable user equipments (UEs) to communicate directly over the D2D links in addition to traditional cellular operation by base stations (BSs), which is capable of utilizing the available cellular network´s resource more efficiently to enhance content downloading performance. Although buffer-aided protocols may provide significant throughput gains in wireless networks, the opportunities and challenges of buffer-aided D2D communications are not yet fully understood. Differing from most existing works that focus on investigating buffering policy, we analyze the fundamental impact of the constrained buffers on the D2D communication underlaying cellular system by an optimization framework. Our study quantitatively reveals the positive correlation between the buffer sizes of BSs and UEs and the overall system performance, as well as further revealing the opportunities created by buffer-aided D2D communications for bandwidth conservation. In addition, we discuss practical challenges inherent in buffer-limited D2D communication underlaying next generation cellular networks, including increased transmission delay and optimal bandwidth allocation.