LTE Based High Speed Railway Channel Model Research And Simulation

In order to satisfy the requirements of high-speed railroad which is the trend of China railway development, the communication technologies will have to move towards the direction to provide digital, wireless mobile and broadband integrated services. However, the GSM-R communications platform that is currently utilized in China can only support voice services at the data rate of 9.6kbps, which is apparently insufficient for the future demands of high-data-rate railway communication system.LTE is a highly promising system to be applied for the future railway communication due to its huge enhancement on data rate compared with GSM-R. As one of the key technologies of LTE, MIMO can effectively utilize the spatial diversity, which originates from random channel fading and multipath propagation. Therefore MIMO technology can increase the transmission rate and improve the link performance without additional power and bandwidth consumption. Foschini and Gans have pointed out that the channel capacity increases linearly with the number of antenna elements when independent Rayleigh fading channel is assumed. However, this assumption is sometimes over-simplified, because the channel coefficients may not follow Rayleigh distribution and the MIMO sub-channels may be correlated rather than independent. And this correlation will lead to performance degradation to the MIMO channel capacity. Moreover, the MIMO performance also depends on the type of the antenna array, antenna spacing and the angular characteristics of the wireless channel. Therefore, in order to guide the deployment of the next generation railway communication system, it is very important to investigate the performance of different MIMO antenna configurations in terms of channel capacity.As high-speed railway is an emerging technology, wireless communication technology, especially MIMO on high-speed rail environment, has not been studied extensively. Some of the recent works focus on the characteristics of high-speed radio propagation environment. And some other research is based on simplified channel models which can’t accurately describe the complicated radio channel propagation characteristics.In this paper we focus on the influence of MIMO configurations on channel capacity and error rate under high-speed railroad layout. The WINNERⅡchannel model is adopted for the LTE downlink simulate platform and the following capacity and BER (Bit Error Rate) analysis, which follows a geometry based stochastic channel modelling (GBSM) methodology. Different antenna configurations such as antenna number, polarisation, antenna spacing and array orientation are investigated. The results show that the performance of system increases with the element number and antenna spacing. It is also illustrated that dual-polarized antenna array can enhance the capacity due to polarization diversity. Furthermore, a proposed array orientation of the base station (BS) and train-top antennas and spaced antennas on the train are given for the system advantages.