Freshness of status update packets is essential for enabling services where a destination needs the most recent measurements of various sensors. In this paper, we study the information freshness of single-server multi-source queueing models under a first-come first-served (FCFS) serving policy. In the considered model, each source independently generates status update packets according to a Poisson process. The information freshness of the status updates of each source is evaluated by the average age of information (AoI). We derive an exact expression for the average AoI for the case with exponentially distributed service time, i.e., for a multi-source M/M/1 queueing model. Moreover, we derive three approximate expressions for the average AoI for a multi-source M/G/1 queueing model having a general service time distribution. Simulation results are provided to validate the derived exact average AoI expression, to assess the tightness of the proposed approximations, and to demonstrate the AoI behavior for different system parameters.

中文翻译：

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多源排队模型中的信息时代

在目的地需要对各种传感器进行最新测量的情况下，状态更新数据包的新鲜度对于启用服务至关重要。在本文中，我们研究了先来先服务（FCFS）服务策略下单服务器多源排队模型的信息新鲜度。在所考虑的模型中，每个源根据泊松过程独立生成状态更新包。每个源的状态更新的信息新鲜度通过信息的平均年龄（AoI）来评估。对于服务时间呈指数分布的情况，即多源 M/M/1 排队模型，我们推导出平均 AoI 的精确表达式。此外，我们推导出了平均 AoI 的三个近似表达式，用于具有一般服务时间分布的多源 M/G/1 排队模型。