Center for ICT & Automotive Convergence, Kyungpook National University, Daegu 41566, Republic of Korea.
Graduate School of Electronic and Electrical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea.
Sensors (Basel). 2023 Apr 3;23(7):3713. doi: 10.3390/s23073713.
A reconfigurable intelligent surface (RIS) is a type of metasurface that can dynamically control the reflection and transmission of electromagnetic waves, such as radio waves, by changing its physical properties. Recently, RISs have played an important role in intelligently reshaping wireless propagation environments to improve the received signal gain as well as spectral efficiency performance. In this paper, we consider a millimeter wave (mmWave) vehicle-to-vehicle (V2V) multiple-input multiple-output (MIMO) system in which, an RIS is deployed to aid downlink V2V data transmission. In particular, the line-of-sight path of the mmWave system is affected by blockages, resulting in higher signaling overhead. Thus, the system performance may suffer due to interruptions caused by static or mobile blockers, such as buildings, trees, vehicles, and pedestrians. In this paper, we propose an RIS-assisted hybrid beamforming scheme for blockage-aware mmWave V2V MIMO systems to increase communication service coverage. First, we propose a conjugate gradient and location-based hybrid beamforming (CG-LHB) algorithm to solve the user sub-rate maximization problem. We then propose a double-step iterative algorithm that utilizes an error covariance matrix splitting method to minimize the effect of location error on the passive beamforming. The proposed algorithms perform quite well when the channel uncertainty is smaller than 10%. Finally, the simulation results validate the proposed CG-LHB algorithm in terms of the RIS-assisted equivalent channel for mmWave V2V MIMO communications.
可重构智能表面（RIS）是一种超表面，它可以通过改变其物理特性来动态控制电磁波（如无线电波）的反射和传输。最近，RIS 在智能重塑无线传播环境以提高接收信号增益和频谱效率性能方面发挥了重要作用。在本文中，我们考虑了一种毫米波（mmWave）车对车（V2V）多输入多输出（MIMO）系统，其中部署了一个 RIS 来辅助下行链路 V2V 数据传输。特别是，mmWave 系统的视线路径受到障碍物的影响，导致更高的信令开销。因此，由于建筑物、树木、车辆和行人等静态或移动障碍物的中断，系统性能可能会受到影响。在本文中，我们提出了一种用于感知障碍物的 mmWave V2V MIMO 系统的 RIS 辅助混合波束赋形方案，以增加通信服务覆盖范围。首先，我们提出了一种基于共轭梯度和基于位置的混合波束赋形（CG-LHB）算法来解决用户子速率最大化问题。然后，我们提出了一种两步迭代算法，该算法利用误差协方差矩阵分裂方法来最小化位置误差对无源波束赋形的影响。当信道不确定性小于 10%时，所提出的算法性能非常好。最后，仿真结果验证了所提出的 CG-LHB 算法在 mmWave V2V MIMO 通信中的 RIS 辅助等效信道方面的性能。
