In this work, we provide a comprehensive analysis of stability properties and delay gains that wireless multicasting capabilities, as opposed to more traditional unicast transmissions, can provide for content distribution in mobile networks. In particular, we propose a model and characterize the average queue-length (and hence average delay) performance of unicasting and various multicasting strategies for serving a dynamic user population at the wireless edge. First, we show that optimized static randomized multicasting (we call it ‘blind multicasting’) leads to stable-everywhere operation irrespective of the network loading factor (given by the ratio of the demand rate to the service rate) and the content popularity distribution. In contrast, traditional unicasting suffers from unstable operation when the loading factor approaches one, although it outperforms blind multicasting at small loading factor levels. This motivates us to study ‘work-conserving multicast’ policies next that always outperform unicasting while still offering stable-everywhere operation. Then, in the worst-case of uniformly-distributed content popularity, we explicitly characterize the scaling of the average queue-length (and hence delay) under a first-come-first-serve multicast strategy as a function of the database size and the loading factor. Consequently, this work provides the fundamental limits, as well as the guidelines, for the design and performance analysis of efficient multicasting strategies for wireless content distribution.

中文翻译：

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内容分发无线组播的延迟增益分析


在这项工作中，我们对无线组播功能（与更传统的单播传输相反）可以为移动网络中的内容分发提供的稳定性属性和延迟增益进行了全面分析。特别是，我们提出了一个模型，并描述了单播的平均队列长度（以及平均延迟）性能以及为无线边缘的动态用户群体提供服务的各种多播策略。首先，我们表明，优化的静态随机多播（我们称之为“盲多播”）可以实现稳定的无处不在的操作，而与网络负载因子（由需求率与服务率之比给出）和内容流行度分布无关。相比之下，传统单播在负载因子接近 1 时会出现运行不稳定的问题，尽管它在负载因子较小的情况下优于盲组播。这促使我们接下来研究“节省工作的多播”策略，该策略始终优于单播，同时仍提供稳定的无处不在的操作。然后，在内容流行度均匀分布的最坏情况下，我们明确地将先来先服务多播策略下的平均队列长度（以及延迟）的缩放特征描述为数据库大小和负载系数。因此，这项工作为无线内容分发的高效多播策略的设计和性能分析提供了基本限制和指导。