LTE-M在地铁隧道中的非稳态MIMO信道的几何建模

Geometrical modeling of non-stationary LTE-M MIMO channel in subway tunnel

轨道交通中基于通信的列车控制(communication based train control, CBTC)系统采用多输入多输出(multiple-input multiple-output, MIMO)信道的LTE-M(long term evolution-metro)技术以确保可靠的车地通信,因此需要研究地铁隧道环境下MIMO信道的统计特性.针对隧道内2×2 MIMO信道在列车移动特别是列车经过基站的过程中呈现的非稳态特性,建立了隧道环境下基于几何的单反射(geometrically based single bounce,GBSB)时变MIMO信道模型.推导了复信道增益以及时变统计特性,包括信道时变自相关函数(autocorrelation function, ACF)、信道时变功率谱密度(power spectral density, PSD)、信道时变互相关函数(cross correlation function, CCF)等.分析了列车运行速度、天线间距等参数对信道相关性的影响.结果表明,信道时变自相关性随列车运行速度增加而降低.当天线间隔增大,信道互相关性呈现波动性下降.仿真结果与实测结果相一致,验证了所提出模型的有效性.

For reliable train-ground communications in urban rail transit,LTE-M(long term evolution-metro)technology based on multiple-input multiple-output(MIMO)channel will be used in the communication based train control(CBTC)system.It is thus necessary to study statistical properties of MIMO channel in a subway tunnel.A geometrically based single bounce(GBSB)time-varying model is proposed to take into account non-stationary characteristics in a2×2MIMO channel when train moves,especially passing through a base station in the tunnel.A complex channel gain function is developed from this model.Time-varying statistical properties including autocorrelation function(ACF),power spectral density(PSD)and cross correlation function(CCF)of the channelare studied.Effects of parameters such as train speed and antenna spacing on the channelcorrelation are analyzed.The results show that the time-varying ACF of the channeldecreases with the increasing train speed.The channel cross correlation decreases with afluctuating period when the antenna spacing increases.Simulation results are consistentwith measured results,showing effectiveness of the model.