Doppler Dispersion Estimation In High-Speed Railway Mobile Communications

The fast development of high-speed railway imposes higher requirements on railway mobile communication systems. Ensuring reliability of real-time train control information and providing efficient broadband wireless access for passengers have been hot research areas. Long Time Evolution (LTE) has drawn extensive attention in high-speed railway mobile communication, because it supports high-speed data rates, high efficiency on spectral resources and high mobility. However, high-mobility also brings new challenges to Orthogonal Frequency-Division Multiplexing (OFDM)-based LTE systems. Doppler dispersion caused by high mobility of train destructs orthogonality between subcarriers of OFDM systems, produces intercarrier inference (ICI), and affects communication quality of LTE systems. Therefore researching and resolving interference problems caused by Doppler dispersion has important scientific significance and application value in high-speed mobile scenarios.This paper is based on deeply understanding the impact of Doppler effects on mobile communications systems and study of estimation methods of Doppler shift and Doppler dispersion. It is focused on Doppler effects on high-speed railway mobile communications and Doppler dispersion estimation for high-speed railway environments. The article first outlines characteristics of fading channels, analyses Doppler effects on high-speed railway mobile communications and establishes the physical model. A channel model for high-speed railway is built according to the LTE standard. Secondly, Doppler dispersion estimation methods in mobile communication system is introduced, and their application scopes. Doppler dispersion estimation algorithms based on LTE is studied. The maximum Doppler shift estimation method through Doppler power spectrum is simulated by computer simulation. The algorithm performance is checked under Rayleigh and Rice channels. The algorithm is improved for power azimuth spectrum (PAS) corresponding to different shapes of Doppler power spectrum.