Abstract:

Aiming at the throughput of high-speed railway Multiple Input Multiple Output (MIMO) system has not been fully improved, an adaptive beam transmission scheme based on antenna grouping was proposed. Firstly, the train position information was predicted by the Base Station (BS), and the beamforming technology was introduced into high-speed railway environment to establish a high-speed Massive MIMO three-dimensional model. Secondly, it was verified that in BS antenna grouping situation, the throughput of a sub-beam and its corresponding number of transmit antennas satisfied nonlinear relationship and the number change of sub-beam antennas did not affect the throughput of other beams. Finally, based on the above, an adaptive beamforming scheme based on antenna grouping was used to adjust the number of beams required and the number of transmit antennas required by the sub-beams when the train runed at different locations to ensure optimal system throughput at all the locations. The computer simulation results show that compared with the traditional single-beam, dual-beam and eight-beam schemes, the proposed scheme achieves 87.9%, 62.3%, and 50.6% improvement respectively in system throughput when the distance between the train and the BS is less than 125 m, achieves a similar system throughput of single beamforming when the distance is more than 125 m. The experimental results show that the proposed scheme has best system throughput whether the train is far away from or close to the BS, and is better adapted to high-speed railway environment.

Key words: throughput, high-speed railway, beamforming, massive MIMO (Multiple Input Multiple Output), multi-beam

摘要：

针对高铁大规模多输入多输出（MIMO）系统的吞吐量未被充分提升的问题，提出一种基于天线分组的自适应波束传输方案。首先利用基站（BS）预知的列车位置信息，并将波束赋形技术引入高速场景，建立高铁大规模MIMO的三维模型；其次验证BS天线分组情况下，子波束的吞吐量与其对应的发射天线数满足非线性关系，且子波束天线数变化并未对其他波束的吞吐量产生影响。基于此，以天线分组的自适应波束赋形方案对列车运行至不同位置的波束数和子波束所需的发射天线数进行调整，保证不同位置的最优系统吞吐量。计算机仿真表明，该方案与传统的单波束、双波束、八波束相比，在列车距基站125 m范围内分别实现了系统吞吐量87.9%、62.3%、50.6%的提升，在125 m之外与单波束赋形的系统吞吐量相近。实验结果表明，所提方案无论列车距BS较近或较远时，系统吞吐量均处于最佳水平，更好地适应高速铁路环境。

关键词: 吞吐量, 高速铁路, 波束赋形, 大规模多输入多输出, 多波束