Compensation Systems and Performance Comparison of the Very High Doppler Frequency

Recently, vehicular communication is very important to provide the broadband data transmission even at the very high speed mobility. The most serious problem is the big Doppler frequency so that the communication system will be degraded due to the big carrier frequency offset (CFO) effect. The low earth orbit (LEO) satellite communication system is typical to show the serious problem since the LEO satellite system moves very fast to keep the orbit altitude. The Doppler effect results in the big carrier frequency offset (CFO) effect, and it can cause the performance degradation in the satellite communication system. So, in this paper, the suppression systems of this very high Doppler frequency are studied and their communication performances are compared. In this paper, 2 kind of Doppler compensation methods are studied: pilot method and phase locked loop (PLL) method. As simulation results show, when the SNR is approximately 5 dB or less, the pilot method provides better performance, compared with the PLL method. However, it sacrifices the data rate because of the insertion of pilot. When the SNR is approximately 6 dB or more, it can be confirmed that the PLL method outperforms than the pilot method, which is almost same to the theoretical performances. However, PLL method does not show good performance in the low SNR range.