Non-Uniform Codebook Configurations for High-Speed Rail Communications

Improved coverage, high data rates and Quality of Service (QoS) constitute important features of 5G networks. The spectrum limitations, currently faced in 4G, will be resolved by adopting millimeter-Wave (mmWave) frequencies technologies, which will also result in high throughput. High mobility scenarios will pose additional challenges in 5G communications, due to the rapid change in the environment, i.e. channel coefficients and Doppler effect. In this paper, we introduce our research on the achievable throughput, coverage and Signal-to-Noise-Ratio (SNR), considering a High-Speed Train (HST) in a simulated rail scenario in the UK. The paper's premises are that the line-of-sight (LOS) rays dominate the mmWave links and the sectors with the highest antenna gains are the ones around the LOS ray direction. With the proposed non-Uniform configurations, we aim to find the sectors which cover the LOS ray in fewer search steps. This reduces the BF setup time significantly and saves power while at the same time keeping throughput stable. Link performance evaluation of the proposed scheme is provided, and the number search steps are then compared to standard search algorithms.