In this article, we study the problem of user association, i.e., determining which base station (BS) a user should associate with, in a dense millimeter wave (mmWave) network. In our system model, in each time slot, a user arrives with some probability in a region with a relatively small geographical area served by a dense mmWave network. Our goal is to devise an association policy under which, in each time slot in which a user arrives, it is assigned to exactly one BS so as to minimize the weighted average amount of time that users spend in the system. The above problem is a restless multi-armed bandit problem and is provably hard to solve. We prove that the problem is Whittle indexable, and based on this result, propose an association policy under which an arriving user is associated with the BS having the smallest Whittle index. Using simulations, we show that our proposed policy outperforms several user association policies proposed in prior work.

中文翻译：

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密集毫米波网络中的用户关联就像不安分的强盗


在本文中，我们研究了密集毫米波（mmWave）网络中的用户关联问题，即确定用户应该与哪个基站（BS）关联。在我们的系统模型中，在每个时隙中，用户都有一定概率到达由密集毫米波网络服务的地理区域相对较小的区域。我们的目标是设计一种关联策略，在该策略下，在用户到达的每个时隙中，将其恰好分配到一个基站，以最小化用户在系统中花费的加权平均时间。上述问题是一个不安定的多臂老虎机问题，并且被证明很难解决。我们证明该问题是Whittle可索引的，并基于此结果提出一种关联策略，在该策略下到达的用户与具有最小Whittle索引的BS关联。通过模拟，我们表明我们提出的策略优于先前工作中提出的几种用户关联策略。