To address the high mobility impacts and the ultra-reliable and low-latency communication (URLLC) requirements in autonomous driving scenarios, rate-splitting multiple access (RSMA) combined with short-packet communication (SPC) emerges as a promising solution.Autonomous vehicles rely on real-time information exchange to ensure safety and coordination, making information freshness essential.By jointly capturing transmission delays and packet errors, age of information (AoI) serves as a comprehensive metric for freshness.In this paper, we investigate short-packet rate splitting to enhance information freshness measured by the AoI.By splitting the unicast messages into common and private parts, encoding all common parts together with the multicast message into a common stream, and encoding each private part into a private stream, RSMA effectively manages interference and enables achieving lower AoI.By considering critical factors such as transmit power, vehicle velocity, blocklength, and the number of transmit antennas, we derive closed-form expressions for the average AoI (AAoI) of the common stream under partial decoding and the overall AAoI under complete decoding.To enhance the AAoI performance, we propose the multi-start two-step successive convex approximation (SCA) algorithm.This algorithm first optimizes the power allocation and subsequently optimizes the rate splitting under the quality of service (QoS) trade-off constraint.Simulation results demonstrate that our short-packet rate-splitting scheme significantly improves the AAoI performance while ensuring system fairness and enabling ultra-low AAoI through the common stream, meeting the requirements of autonomous driving applications.Moreover, the trade-off between the common and overall performance is revealed, indicating that the overall performance can be further enhanced while maintaining the advantages of the common stream.

翻译：为应对自主驾驶场景中的高移动性影响及超可靠低延迟通信（URLLC）需求，速率分割多址接入（RSMA）结合短包通信（SPC）成为有前景的解决方案。自主车辆依赖实时信息交换确保安全与协调，因此信息新鲜度至关重要。通过联合捕获传输延迟与数据包错误，信息年龄（AoI）成为衡量新鲜度的综合指标。本文研究基于短包速率分割方法，以提升由AoI表征的信息新鲜度。通过将单播消息分割为公共部分与私有部分，将全部公共部分与多播消息联合编码为公共流，并将各私有部分编码为私有流，RSMA有效管理干扰并实现更低的AoI。考虑发射功率、车辆速度、块长度与发射天线数量等关键因素，我们推导了部分译码下公共流平均AoI（AAoI）及完全译码下整体AAoI的闭合表达式。为优化AAoI性能，提出多起点两步连续凸近似（SCA）算法：首先优化功率分配，随后在服务质量（QoS）权衡约束下优化速率分割。仿真结果表明，所提短包速率分割方案在保证系统公平性的同时显著提升AAoI性能，并通过公共流实现超低AAoI，满足自主驾驶应用需求。此外，揭示了公共性能与整体性能之间的权衡关系，表明在维持公共流优势的前提下可进一步优化整体性能。