New technologies for sensing and communication act as enablers for cooperative driving applications. Sensors are able to detect objects in the surrounding environment and information such as their current location is exchanged among vehicles. In order to cope with the vehicles' mobility, such information is required to be as fresh as possible for proper operation of cooperative driving applications. The age of information (AoI) has been proposed as a metric for evaluating freshness of information; recently also within the context of intelligent transportation systems (ITS). We investigate mechanisms to reduce the AoI of data transported in form of beacon messages while controlling their emission rate. We aim to balance packet collision probability and beacon frequency using the average peak age of information (PAoI) as a metric. This metric, however, only accounts for the generation time of the data but not for application-specific aspects, such as the location of the transmitting vehicle. We thus propose a new way of interpreting the AoI by considering information context; thereby incorporating vehicles' locations. As an example, we characterize such importance using the orientation and the distance of the involved vehicles. In particular, we introduce a weighting coefficient used in combination with the PAoI to evaluate the information freshness; emphasizing on information from more important neighbors. We further design the beaconing approach in a way to meet a given AoI requirement, thus, saving resources on the wireless channel while keeping the AoI minimal. We illustrate the effectiveness of our approach in Manhattan-like urban scenarios; reaching pre-specified targets for the AoI of beacon messages.

翻译：传感与通信新技术为协同驾驶应用提供了实现基础。传感器能够探测周围环境中的物体，车辆之间可交换诸如当前位置等感知信息。为应对车辆移动性，此类信息需保持高度时效性以确保协同驾驶应用正常运行。信息年龄（AoI）已被提出作为评估信息新鲜度的指标，近年来其在智能交通系统（ITS）领域亦得到应用。本文研究在控制信标消息发送频率的同时，降低其承载数据信息年龄的机制。我们以平均峰值信息年龄（PAoI）为度量标准，旨在平衡数据包碰撞概率与信标发送频率。然而该指标仅考虑数据生成时间，未纳入发送车辆位置等应用特定因素。为此我们提出考虑信息上下文的信息年龄新解读方式，将车辆位置信息融入其中。以典型场景为例，通过车辆间的方向角与距离表征信息重要性。具体而言，引入与PAoI协同使用的权重系数来评估信息新鲜度，重点突出来自重要邻域车辆的信息价值。进一步设计满足给定信息年龄要求的信标发送策略，在最小化信息年龄的同时节省无线信道资源。通过在曼哈顿式城市交通场景中的仿真验证，所提方法能实现信标消息信息年龄的预设目标。