Stable Beamforming With Low Overhead for C/U-Plane Decoupled HSR Wireless Networks
Stable Beamforming With Low Overhead for C/U-Plane Decoupled HSR Wireless Networks
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DOI：
10.1109/tvt.2018.2810245
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发表时间：
2018-07
影响因子：
6.8
通讯作者：
Li Yan;X. Fang;Yuguang Fang
中科院分区：
文献类型：
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作者：
Li Yan;X. Fang;Yuguang Fang
毫米波 (mmWave) 定向通信已成为实现低延迟多千兆数据速率目标的重要 5G 技术，这也适用于高速铁路 (HSR) 无线网络。然而，HSR场景中的高移动性导致频繁的波束重新对准，从而导致高反馈开销，降低了传输可靠性和效率。在毫米波波束成形系统中，除了发射器（TX）和接收器（RX）之外，还配备了天线阵列，这相当于为链路自适应引入了新的自由度。基于这一观察，提出了一种低开销的稳定波束成形方案，包括长期 TX 波束成形和短期 RX 波束成形。在长期发射波束成形中，在满足基本接收灵敏度的前提下，发射机被设计为使用尽可能宽的波束，以延长每个波束的服务时间。在短期RX波束成形中，在TX波束内，RX根据当前信道状态信息自主调整RX波束，而不是频繁地将其反馈给TX，从而减少反馈开销并加速链路自适应。通过该方案，接收信噪比保持在较高且稳定的水平。为了满足高铁中严格的传输可靠性要求，采用控制/用户平面解耦架构来减轻毫米波定向波束固有的盲目性。理论和数值结果表明，所提出的方案可以显着减少反馈开销并保证所需的性能。
Millimeter wave (mmWave) directional communications have become a vital 5G technique to achieve the goal of multiple gigabit data rate with low latency, which also hold true for high-speed railway (HSR) wireless networks. However, the high mobility in HSR scenarios causes frequent beam realignments and consequently high feedback overheads, degrading the transmission reliability, and efficiency. In mmWave beamforming systems, besides transmitters (TXs) and receivers (RXs) are also equipped with antenna arrays, which equivalently introduces a new degree of freedom for link adaptation. Based on this observation, a stable beamforming scheme with low overhead, consisting of both long-term TX beamforming and short-term RX beamforming, is proposed. In the long-term TX beamforming, under the premise of satisfying the basic receiver sensitivity, TXs are devised to use as wide beams as possible to extend the serving time of each beam. In the short-term RX beamforming, within a TX beam, RXs autonomously adjust RX beams according to the current channel state information instead of frequently feeding it back to TXs, thereby reducing feedback overheads and accelerating link adaptation. Through this scheme, the received signal to noise ratio is kept at a high and stable level. To meet the strict transmission reliability requirements in HSRs, the control/user-plane decoupled architecture is applied to mitigate the inherent blindness of mmWave directional beams. Theoretical and numerical results show that the proposed scheme can significantly reduce feedback overheads and guarantee the desired performance.