Timely Status Update in Internet of Things Monitoring Systems: An Age-Energy Tradeoff
Timely Status Update in Internet of Things Monitoring Systems: An Age-Energy Tradeoff
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DOI：
10.1109/jiot.2019.2900528
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发表时间：
2019-06-01
影响因子：
10.6
通讯作者：
Vucetic, Branka
中科院分区：
文献类型：
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作者：
Gu, Yifan;Chen, He;Vucetic, Branka
我们考虑物联网(IoT)监控系统，其中IoT设备监控物理过程，并尽可能及时地将随机生成的状态更新传输到其关联的接入点(AP)。状态更新的及时性由最近引入的称为信息年龄(AOI)的度量来表征，该度量被定义为自生成最后成功接收的状态更新以来经过的时间。物联网设备和AP之间的通道被认为是容易出错的，因此状态更新会受到分组丢失的影响。假设AP不向物联网设备提供反馈，我们采用了一种实用的截断自动重传请求(TARQ)方案：物联网设备不断重复发送当前状态更新，直到达到最大允许传输次数或生成新的状态更新。我们描述了所考虑的物联网监控系统固有的年龄-能量权衡。具体地说，最大允许传输次数的较大值降低了平均AOI，代价是在物联网设备处招致更高的平均能耗。基于AOI的演化，我们推导出平均AOI、平均峰值AOI和平均能量消耗的闭合表达式。然后，我们通过优化物联网设备的发射功率和在平均发射功率约束下的最大允许传输次数来最小化平均AOI。仿真结果表明，在相同的平均发射功率约束下，采用的ARQ方案比传统的允许无限次重传的ARQ方案获得了更低的平均AOI。
We consider an Internet of Things (IoT) monitoring system, in which an IoT device monitors a physical process and transmits randomly generated status updates to its associated access point (AP) as timely as possible. The timeliness of the status updates is characterized by a recently introduced metric, termed the age of information (AoI), which is defined as the time elapsed since the generation of the last successfully received status update. The channel between the IoT device and the AP is considered to be error-prone and thus the status updates suffer from packet loss. Assuming that the AP provides no feedback to the IoT device, we adopt a practical truncated automatic repeat request (TARQ) scheme: the IoT device keeps transmitting the current status update repeatedly until the maximum allowable transmission times is reached or a new status update is generated. We characterize the inherent age-energy tradeoff for the considered IoT monitoring system. Specifically, a larger value of the maximum allowable transmission times reduces the average AoI, at the cost of incurring higher average energy consumption at the IoT device. Based on the evolution of AoI, we derive the closed-form expressions of the average AoI, the average peak AoI, and the average energy consumption. We then minimize the average AoI by optimizing the transmit power of the IoT device and the maximum allowable transmission times under an average transmit power constraint. Simulations validate the theoretical analysis and reveal that under the same average transmit power constraint, the adopted TARQ scheme achieves a lower average AoI than the classical ARQ scheme that allows an infinite number of retransmission times.