非线性能量采集的工业物联网非线性信息年龄分析

Analysis of Non-Linear Age of Information in Industrial Internet of Things for Non-Linear Energy Harvesting

针对工业物联网(IIoT)中对信息新鲜性日益增长的需求,提出一种基于非线性能量采集(EH)的IIoT监控系统,配备电池容量大小为B的传感器节点,从无线供电基站(WPS)使用非线性EH技术采集射频(RF)能量进行充电,电池充满后将采集到的数据发送给数据采集节点。此外,针对在复杂场景中需要设置多个非线性信息年龄(AoI)算法所存在系统较为复杂的问题,提出1个普适函数来描述不同的非线性AoI,并通过调节参数来控制函数图像形状。在推导系统非线性AoI封闭表达式的同时引入系统能量效率(EE),以两者的比值Ψ作为系统的性能指标。鉴于问题较为复杂,采用一维搜索方法来寻找最优电池容量。通过系统仿真和数值分析,证明了存在最优的电池容量B使系统Ψ最小化。仿真结果表明,信道衰落参数、状态更新大小、WPS发射功率等参数都会对系统的性能产生影响,在相关系统的优化设计时都需要考虑。当WPS发射功率为0.5 W时,指数型非线性AoI下的Ψ是对数型非线性的2倍,是线性的1.8倍。

To address the growing demand for information freshness in the Industrial Internet of Things(IIoT),this study proposes an IIoT monitoring system based on non-linear Energy Harvesting(EH),which consists of a single sensor and data collection node.The sensor nodes,equipped with rechargeable batteries of size B,harvests Radio Frequency(RF)energy from a Wireless Power Station(WPS)using non-linear EH to charge their batteries.Once the batteries are fully charged,the collected data are transmitted to a data collection node.To avoid the problem of increasing system complexity caused by setting multiple non-linear Age of Information(AoI)algorithms in complex scenes,this study also introduces a universal function to describe the different shapes of the non-linear AoI,where the shape of the functional image is controlled by adjusting the size of the parameter.Simultaneously,the study derives a closed-form expression for the system's non-linear AoI and introduces the concept of Energy Efficiency(EE).The ratio of these two metricsΨserves as the performance indicator for the system.Due to the complexity of the problem,identifying its convexity or concavity is challenging.Therefore,this study also employs a One-Dimensional(1-D)search approach to determine the optimal battery capacity for the system.System simulations and numerical analysis demonstrate the existence of a minimum battery capacity that minimizes the system.The simulation results indicate that system parameters such as the channel fading parameter,sizes of state updates,and the transmission power of WPS all affect the system's performance and must be considered when designing related systems.Notably,Ψunder exponential-shape non-linear AoI is double that under logarithmicshape non-linear AoI and approximately 1.8 times that under linear AoI when the transmission power of WPS is 0.5 W.