Synchronization Technologies for OFDM on the System of Satellite Communication

Satellite communications is an important component of the the world's communication networks and has become an indispensable means of communication in modern society. Wireless communication technology Based on orthogonal frequency division multiplexing (OFDM) is in rapid development. OFDM can provide high-capacity information transmission and Solve the issue of wireless Channel performance variation when the channel of high-speed data transmission in the mobile terminal, which greatly improve the quality of transmission channel. OFDM technology has the character of anti-multipath fading, high spectral efficiency, and so on, which is suitable for satellite communications with high-speed transmission in the wireless environment. In order to achieve a real sense of the OFDM system, synchronization is a critical issue.

At first, the current satellite communications and the development of OFDM technology are introduced in this paper, which is the research background of the subject. Some problems in the satellite communications and the necessary of OFDM technology applied for satellite communications are discussed.Second, the importance of the satellite communication channel in the analysis and designing of communication systems is discussed. The characteristics of satellite channels and the propagation characteristics described in detail. The probability density function of the satellite channels as well as the satellite channel model is analyzed.OFDM system and its synchronization technology are studied, the basic principles of OFDM are introduced and OFDM system model is given. The OFDM synchronization and synchronization technology are focused on the basis of analysis the factors of Synchronization in a variety of non-ideal. Various synchronization methods and improved synchronization algorithm of satellite communications based OFDM are analyzed on the basis of channel model and the corresponding results of computer simulation are given.At last, low-orbit satellite communication system is introduced, and the mode of satellite channels in the theoretical analysis is further simplified. On the analysis of low-orbit satellites, the effects of low signal to noise ratio and Doppler frequency shift Focus on considered. Synchronization of carrier frequency under the low signal to noise ratio of low-orbit satellites is analyzed in this paper, including the degradation of the capture performance under low signal to noise ratio and the design of loop carrier.
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