User Scheduling and Beam Alignment in mmWave Networks With a Large Number of Mobile Users
User Scheduling and Beam Alignment in mmWave Networks With a Large Number of Mobile Users
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DOI：
10.1109/twc.2021.3074700
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发表时间：
2021-04
影响因子：
10.4
通讯作者：
Jihyun Lee;E. Ekici
中科院分区：
文献类型：
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作者：
Jihyun Lee;E. Ekici
本文研究了毫米波网络中具有最小波束对准开销的用户调度问题。该问题被描述为约束马尔可夫决策过程(CMDP)，目标是在每个用户的平均速率约束下最小化平均波束对准开销。在对用户速率函数作一定假设的情况下，通过利用CMDP的拉格朗日公式得到的结构结果，我们证明了最优策略应该保持对前一个时隙中调度的用户进行调度，除非波束方向发生突变。利用这一结果，问题的复杂性在用户数的情况下降为多项式。此外，我们还提出了一种启发式确定性算法，它以每个用户较长的传输间隔为代价，以较小的$({1}+\epsilon)$逼近最优解。最后，为了处理由于用户之间的波束冲突而导致速率函数的假设不成立的情况，我们考虑了一个考虑角信道信息的系统模型。提出了一种新的CMDP算法，并提出了一种基于年龄信息的启发式算法。
In this paper, we study an optimal user scheduling with minimum beam alignment overhead in millimeter wave networks. The problem is posed as constrained Markov decision process (CMDP) with the goal of minimizing the average beam alignment overhead subject to the average rate constraint on each user. Under a certain assumption on the rate function of the users, by using a structural result derived from the Lagrangian formulation of the CMDP, we show that the optimal policy should keep scheduling the users that are scheduled in the previous time slot unless an abrupt change in the beam direction occurs. Using this result, the complexity of the problem decreases to polynomial in the number of users. In addition, we provide a heuristic deterministic algorithm that achieves $({1}+\epsilon)$ approximation of the optimal solution, with smaller $\epsilon $ at the cost of longer transmission interval of each user. Lastly, to deal with the case where the assumption on the rate function does not hold due to beam conflicts between the users, we consider a system model that accounts for an angular channel information. A new CMDP is formulated for the problem and a heuristic algorithm based on the age information is proposed.