Age of information (AoI), a notion that measures the information freshness, is an essential performance measure for time-critical applications in Internet of Things (IoT). With the surge of computing resources at the IoT devices, it is possible to preprocess the information packets that contain the status update before sending them to the destination so as to alleviate the transmission burden. However, the additional time and energy expenditure induced by computing also make the optimal updating a non-trivial problem. In this paper, we consider a time-critical IoT system, where the IoT device is capable of preprocessing the status update before the transmission. Particularly, we aim to jointly design the preprocessing and transmission so that the weighted sum of the average AoI of the destination and the energy consumption of the IoT device is minimized. Due to the heterogeneity in transmission and computation capacities, the durations of distinct actions of the IoT device are non-uniform. Therefore, we formulate the status updating problem as an infinite horizon average cost semi-Markov decision process (SMDP) and then transform it into a discrete-time Markov decision process. We demonstrate that the optimal policy is of threshold type with respect to the AoI. Equipped with this, a structure-aware relative policy iteration algorithm is proposed to obtain the optimal policy of the SMDP. Our analysis shows that preprocessing is more beneficial in regimes of high AoIs, given it can reduce the time required for updates. We further prove the switching structure of the optimal policy in a special scenario, where the status updates are transmitted over a reliable channel, and derive the optimal threshold. Finally, simulation results demonstrate the efficacy of preprocessing and show that the proposed policy outperforms two baseline policies.
翻译:信息时代(AoI)是衡量信息新鲜度的一种概念,它是一个时间紧迫的IoT系统,它能够预处理传输前的状态更新。特别是,我们的目标是联合设计预处理和传输渠道,以便将目的地平均AoI和IoT设备能源消耗的加权总和最小化。由于传输和计算能力的差异,IoT设备不同行动的时间长度不统一。因此,我们把状况更新问题描述为最佳地平线平均成本半马尔科夫决策程序(SMDP),然后将其转换为离地平时政策升级。我们用最优政策格式展示了最佳政策格式。我们用最优政策格式展示了最优政策格式,我们用最优政策格式展示了最优政策格式,我们用最优政策格式展示了最优政策格式的A。我们用最优政策格式展示了最优政策格式显示最佳政策格式的A。