D2D辅助NB-IoT系统的传输设备数优化算法

针对窄带物联网(narrowband internet of things,NB-IoT)中,处于蜂窝边缘覆盖薄弱区域的用户设备(user e-quipment,UE)到基站的直接链路质量可能并不满足数据传输的服务质量(quality of service,QoS)要求,提出一种设备到设备(device-to-device,D2D)通信辅助NB-IoT UE数据上传的方案.该方案采用D2D通信作为NB-IoT系统的路由扩展.当候选中继UEs工作在D2D通信模式以节省能量时,边缘UEs根据它们的中继时间表选择一组D2D中继设备,用于上行链路数据的传输.此外,对于NB-IoT系统传输设备数不足的问题,进一步提出基于动态规划的优化算法,实现了最佳的单位能量提供的传输设备数(transmission device number provides by unit energy,NUE).仿真结果表明,与直接传输、单中继和多中继等其他算法相比,所提的maxNUE算法在不同的UE/中继发射功率和中继占空比下均获得了最大的NUE.

Transmission device number optimization algorithm for D2D-assisted NB-IoT system

Considering the fact that the direct link quality between the user equipment (UE) and the base station in the cellular edge coverage of narrowband internet of things (NB-IoT) does not meet the quality of service (QoS) requirements of the data transmission, we propose a device-to-device (D2D) communication assisted data uploading scheme. The scheme adopts D2D communication as the route extension of the NB-IoT system. When the candidate relay UEs work in the D2D communication mode to save energy, they are selected for assisting NB-IoT UEs to transmit uplink data according to their relay schedules. Moreover, this paper further proposes an optimization algorithm based on dynamic programming to achieve the best transmission device number provides by unit energy (NUE) for the insufficient transmission equipment in NB-IoT system. Simulation results show that compared with direct transmission, single-relay and multi-relay algorithm, the proposed maxNUE algorithm achieves the largest NUE under different UE/relay transmit power and relay duty cycle.