Dynamic relay access for D2D-aided low-latency and high-reliability communications

Device-to-device (D2D) communications allow direct connections among devices to lower transmission latency and network loads of the existing cellular mobile networks. To fully exploit the benefits of D2D communications, relay access is one of the critical challenges upon employing the optimal cooperative relay user equipments (UEs) for data forwarding. The existed relay access approaches usually neglect the inherent motivation that whether the relay is reluctant to forward the information of other UEs based on its status, such as limited battery, service cost and social ties. In this paper, we jointly investigate both the transmission delay and the reliability performance for designing a relay access scheme combined with the impacts of the physical layer and the social layer. Meanwhile, considering the user mobility and status, a dynamic relay access model is constructed with the utility function of the weighted average of latency and social trust level under the long-term constraints. To solve this problem, Lyapunov framework is proposed for converting it into a renewal-reward system towards infinite time horizon, and numerical results show the benefits of the proposed scheme compared with other schemes under dynamic scenarios, as it can lower the latency while guaranteeing the reliability of relay access.