We study content caching in a wireless network in which the users are connected through a base station that is equipped with a finite-capacity cache. We assume a fixed set of contents whose popularity varies with time. Users' requests for the content depend on their instantaneous popularity levels. Proactively caching contents at the base station incurs a cost but not having requested contents at the base station also incurs a cost. We propose to proactively cache contents at the base station so as to minimize content missing and caching costs. We formulate the problem as a discounted cost Markov decision problem that is a restless multi-armed bandit problem. We provide conditions under which the problem is indexable and also propose a novel approach to maneuver a few parameters to render the problem indexable. We demonstrate the efficacy of the Whittle index policy via numerical evaluation.

翻译：我们研究了无线网络中的内容缓存问题，用户通过配备有限容量缓存的基础站相连。假设存在一组固定内容，其流行度随时间变化。用户对内容的请求取决于其即时流行度水平。主动在基础站缓存内容会产生成本，但基础站未缓存请求内容同样会产生成本。我们提出主动在基础站缓存内容，以最小化内容缺失成本与缓存成本之和。将该问题建模为具有折扣成本的马尔可夫决策问题，其本质属于不安分多臂赌臂问题。我们给出了问题可索引化的条件，并提出了一种通过调控若干参数实现问题可索引化的新方法。通过数值评估验证了Whittle索引策略的有效性。