Optimal Status Updating with a Finite-Battery Energy Harvesting Source
Optimal Status Updating with a Finite-Battery Energy Harvesting Source
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DOI：
10.1109/jcn.2019.000033
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发表时间：
2019-06-01
影响因子：
3.6
通讯作者：
Mutlu, Volkan
中科院分区：
文献类型：
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作者：
Bacinoglu, Baran Tan;Sun, Yin;Mutlu, Volkan
我们考虑一个配备有限电池的能量收集源，它需要向远程目的地及时发送状态更新。状态更新的及时性通过信息年龄（AoI）的一个非递减惩罚函数来衡量。问题是要找到一种生成更新的策略，使其在所有在线策略中实现尽可能低的时间平均预期年龄惩罚。我们证明这个问题的一个最优解是一个单调阈值策略，它满足：（i）只有当年龄高于一个阈值时才发送每个新的更新；（ii）该阈值是瞬时电池电量水平的一个非递增函数。令\(\tau(B)\)表示对应于满电池电量水平\(B\)的最优阈值，\(p(.)\)表示年龄惩罚函数，那么我们可以证明\(p(\tau(B))\)等于最优目标值，即最小可实现的时间平均预期年龄惩罚。这些结构特性被用于开发一种算法来计算最优阈值。我们的数值分析表明，在电池容量较小时，增加电池容量对平均年龄的改善最大；具体来说，当电池存储的能量从一次传输所需的能量增加到两次传输所需的能量时，年龄的总可能减少量的一半以上得以实现。这鼓励进一步研究具有小电池存储的传感器的状态更新策略。
We consider an energy harvesting source equipped with a finite battery, which needs to send timely status updates to a remote destination. The timeliness of status updates is measured by a non-decreasing penalty function of the age of information (AoI). The problem is to find a policy for generating updates that achieves the lowest possible time-average expected age penalty among all online policies. We prove that one optimal solution of this problem is a monotone threshold policy, which satisfies (i) each new update is sent out only when the age is higher than a threshold and (ii) the threshold is a non-increasing function of the instantaneous battery level. Let tau(B) denote the optimal threshold corresponding to the full battery level B, and p(.) denote the age-penalty function, then we can show that p(tau(B)) is equal to the optimum objective value, i.e., the minimum achievable time-average expected age penalty. These structural properties are used to develop an algorithm to compute the optimal thresholds. Our numerical analysis indicates that the improvement in average age with added battery capacity is largest at small battery sizes; specifically, more than half the total possible reduction in age is attained when battery storage increases from one transmission's worth of energy to two. This encourages further study of status update policies for sensors with small battery storage.