This letter studies the information freshness in an industrial Internet of Things (IIoT) network, measured by Age of Information (AoI). We consider a scenario where a sink node collects information update packets from different sensors and then uploads the collected packets to an edge server. This scenario has two main requirements: high information freshness (low AoI) and high reliability (low packet error rate, PER). Since update packets are usually short in practice, previous works usually packed and encoded multiple short packets from different sensors into a long packet to improve PER performances. However, while such a joint coding approach improves reliability, it generally leads to longer delay and hence possibly higher AoI. This letter investigates the AoI performance tradeoff by examining the number of packets to be jointly encoded. We consider two AoI metrics, average AoI and bounded AoI. In particular, bounded AoI is the threshold below which the instantaneous AoI falls for a given percentage of the time. Our theoretical analysis and numerical results show that there exist optimal numbers of jointly coded packets that minimize the average AoI and the bounded AoI. Specifically, a smaller number of packets is usually sufficient to achieve both high information freshness and high reliability.

中文翻译：

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工业物联网中联合分组编码的信息时代

这封信研究了以信息时代 (AoI) 衡量的工业物联网 (IIoT) 网络中的信息新鲜度。我们考虑一个场景，其中一个汇聚节点从不同的传感器收集信息更新数据包，然后将收集到的数据包上传到边缘服务器。该场景有两个主要要求：高信息新鲜度（低 AoI）和高可靠性（低误包率，PER）。由于更新数据包在实践中通常很短，因此以前的工作通常将来自不同传感器的多个短数据包打包并编码为一个长数据包以提高 PER 性能。然而，虽然这种联合编码方法提高了可靠性，但它通常会导致更长的延迟，因此可能会导致更高的 AoI。这封信通过检查要联合编码的数据包数量来研究 AoI 性能权衡。我们考虑两个 AoI 指标，平均 AoI 和有界 AoI。特别是，有界 AoI 是在给定时间百分比内瞬时 AoI 低于该阈值的阈值。我们的理论分析和数值结果表明，存在最小化平均 AoI 和有界 AoI 的联合编码数据包的最佳数量。具体而言，较少数量的数据包通常足以实现高信息新鲜度和高可靠性。