We analytically decide whether the broadcast transmission scheme or the unicast transmission scheme achieves the optimal age of information (AoI) performance of a multiuser system where a base station (BS) generates and transmits status updates to multiple user equipments (UEs). In the broadcast transmission scheme, the status update for all UEs is jointly encoded into a packet for transmission, while in the unicast transmission scheme, the status update for each UE is encoded individually and transmitted by following the round robin policy. For both transmission schemes, we examine three packet management strategies, namely the non-preemption strategy, the preemption in buffer strategy, and the preemption in serving strategy. We first derive new closed-form expressions for the average AoI achieved by two transmission schemes with three packet management strategies. Based on them, we compare the AoI performance of two transmission schemes in two systems, namely, the remote control system and the dynamic system. Aided by simulation results, we verify our analysis and investigate the impact of system parameters on the average AoI. For example, the unicast transmission scheme is more appropriate for the system with a large number UEs. Otherwise, the broadcast transmission scheme is more appropriate.

翻译：我们通过分析决定在多用户系统中，基站生成并向多个用户设备传输状态更新时，广播传输方案还是单播传输方案能实现最优的信息时效性性能。在广播传输方案中，所有用户设备的状态更新被联合编码到一个数据包中进行传输；而在单播传输方案中，每个用户设备的状态更新被单独编码，并按照轮询策略依次传输。针对这两种传输方案，我们研究了三种数据包管理策略，即非抢占策略、缓冲区抢占策略和服务中抢占策略。我们首先推导了两种传输方案结合三种数据包管理策略下平均信息时效性的新闭合表达式。基于这些表达式，我们比较了两种传输方案在远程控制系统和动态系统两个系统中的信息时效性性能。借助仿真结果，我们验证了分析的正确性，并探讨了系统参数对平均信息时效性的影响。例如，当系统中用户设备数量庞大时，单播传输方案更为合适；否则，广播传输方案更为合适。