Cost-Effective MAB Approaches for Reconfigurable Intelligent Surface Aided Millimeter Wave Relaying
Cost-Effective MAB Approaches for Reconfigurable Intelligent Surface Aided Millimeter Wave Relaying
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DOI：
10.1109/access.2022.3195303
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发表时间：
2022-01-01
期刊：
影响因子：
3.9
通讯作者：
Fouda, Mostafa M.
中科院分区：
文献类型：
--
作者：
Mohamed, Ehab Mahmoud;Hashima, Sherief;Fouda, Mostafa M.
最近，可重构智能表面（RIS）中继被建议作为扩展毫米波（mmWave）覆盖范围的一项天才技术。然而，找出最佳RIS中继以最大化可实现的数据速率是太耗时的过程，这是由于调整毫米波基站（BS）和探测RIS中继两者的天线相移（PS）所需的波束成形训练（BT）过程。因此，找出具有最小BT时间成本的最佳RIS中继似乎具有挑战性。在本文中，一个具有成本效益的在线学习方法，提出了通过多臂强盗（MAB）假设来解决这个问题。在这种情况下，两个MAB计划的时间成本效率，MAB-CE 1，和MAB-CE 2，提出。在MAB-CE 1中，选择RIS中继的BT时间成本被包括在MAB算法的开发项中。然而，在MAB-CE 2中，利用预期RIS的可实现频谱效率的置信下限和置信上限（LCB，UCB）值来支持由最小BT时间成本表征的RIS中继的选择。数值分析表明，所提出的具有成本效益的MAB计划RIS毫米波中继在BT时间成本和可实现的吞吐量方面优于其他基准。
Recently, reconfigurable intelligent surface (RIS) relaying is suggested as a talented technology for extending the millimeter wave (mmWave) coverage. However, finding out the best RIS relay to maximize the achievable data rate is a too time-consuming process due to the beamforming training (BT) procedure needed for adjusting the antenna phase shifts (PSs) of both the mmWave base station (BS) and the probed RIS relay. Thus, finding out the best RIS relay with the minimum BT time cost seems challenging. In this paper, a cost-effective online learning approach is proposed by means of the multi-armed bandit (MAB) hypothesis to address this problem. In this context, two MAB schemes with time-cost efficiency, MAB-CE1, and MAB-CE2, are proposed. In MAB-CE1, the BT time cost of selecting the RIS relay is included in the exploitation term of the MAB algorithm. However, in MAB-CE2, lower and upper confidence bounds (LCB, UCB) values of the expected RISs' achievable spectral efficiencies are utilized to support the selection of the RIS relay characterized by the minimum BT time cost. Numerical analysis shows the superior performance of the proposed cost-effective MAB schemes for RIS mmWave relaying over other benchmarks in terms of BT time cost and the achievable throughput.