Research On APSK Modulation And Channel Estimation For OFDM Communication Systems

With land mobile/wireless communication system integration is the inevitable developing trend of future mobile satellite communication systems, the fusion of the two is one of the way to realize the personal communications(i.e., achieve 5 w).At present, the mainstream technology of the wireless communication transmission is OFDM technology, in view of this, this paper designs a mobile satellite communication system based on OFDM, the system working in S-band. This paper firstly introduces the basic principle of OFDM. Secondly, the modulation method for satellite communication system is studied, and then the design for channel estimation and equalization algorithm. Finally it builds the satellite communication system simulation platform. This article’s main research content is as follows:1. This paper introduces the OFDM system model, the working principle of each module and function, analyzes three key technologies such as the peak to average power ratio(PAPR), synchronization technology and the channel estimation techniques.2. In the nonlinear satellite channel, amplitude’s nonlinear phase distortion is how to influence the signal modulation way such as QAM, PSK, APSK, through contrasting the SNR and BER performance. The conclusion is that APSK has better BER performance in nonlinear satellite channel. Two APSK constellation structure is designed, and the modulation and demodulation algorithm is studied.3. According to the system research of the channel model, the paper designs the channel estimation and equalization algorithm suitable for the system, and the algorithm is based on pilot channel estimation. This paper improves the algorithm based on the LS algorithm. The improved algorithm can not only improve the BER performance of 3d B, but also can, to a certain extent, correct symbol timing offset and residual frequency offset.4. The system overall scheme is designed, including the design of the OFDM frame structure and form, transceiver design and simulation of channel. And the simulationresult is analyzed in the BIR(Bit Rate), spectral efficiency and BER(Bit Error Rate).