Future railway is expected to accommodate both train operation services and passenger broadband services. The millimeter wave (mmWave) communication is a promising technology in providing multi-gigabit data rates to onboard users. However, mmWave communications suffer from severe propagation attenuation and vulnerability to blockage, which can be very challenging in high-speed railway (HSR) scenarios. In this paper, we investigate efficient hybrid beamforming (HBF) design for train-to-ground communications. First, we develop a two-stage HBF algorithm in blockage-free scenarios. In the first stage, the minimum mean square error method is adopted for optimal hybrid beamformer design with low complexity and fast convergence; in the second stage, the orthogonal matching pursuit method is utilized to approximately recover the analog and digital beamformers. Second, in blocked scenarios, we design an anti-blockage scheme by adaptively invoking the proposed HBF algorithm, which can efficiently deal with random blockages. Extensive simulation results are presented to show the sum rate performance of the proposed algorithms under various configurations, including transmission power, velocity of the train, blockage probability, etc. It is demonstrated that the proposed anti-blockage algorithm can improve the effective rate by 20% in severely-blocked scenarios while maintaining low outage probability.

中文翻译：

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用于高速铁路通信的具有抗阻塞设计的高效混合波束成形

未来铁路预计将同时容纳列车运营服务和客运宽带服务。毫米波 (mmWave) 通信是一种向机载用户提供数千兆位数据速率的有前途的技术。然而，毫米波通信受到严重的传播衰减和阻塞的影响，这在高速铁路 (HSR) 场景中可能非常具有挑战性。在本文中，我们研究了用于列车对地通信的高效混合波束成形 (HBF) 设计。首先，我们在无阻塞场景中开发了一个两阶段 HBF 算法。第一阶段采用最小均方误差法优化混合波束形成器设计，复杂度低，收敛快；在第二阶段，正交匹配追踪方法用于近似恢复模拟和数字波束形成器。其次，在阻塞场景中，我们通过自适应调用所提出的 HBF 算法设计了一种抗阻塞方案，该算法可以有效地处理随机阻塞。大量的仿真结果展示了所提出算法在各种配置下的总速率性能，包括传输功率、列车速度、阻塞概率等。证明所提出的抗阻塞算法可以将有效速率提高 20 % 在严重阻塞的情况下，同时保持低中断概率。