Research On Synchronization Algorithms Of OFDM System

Orthogonal frequency-division multiplexing is a technology of multi-carrier modulation. OFDM has been widely applied in high data transmission wireless systems, such as digital video broadcast (DVB), digital television (DTV), wireless local area network (WLAN), due to its high frequency utilization efficiency and its robustness to multipath delay spread. OFDM will pay a key role in the forth generation mobile communication OFDM systems are much sensitive to synchronization errors, especially frequency offset. The synchronization errors destroy the orthogonal between sub-carries of system, which leading to interfere between sub-carries and degrade the system performance. So it is important to have a good synchronization algorithm for OFDM system. The paper gives a brief survey of the development of OFDM technology and introduces the advantage of OFDM technology and the key to OFDM system. After presenting the characteristics of the wireless channel, especially super high frequency in detail. At last we bring forward the multipath channel module of super high frequency, which is suit to super high frequency channel of sea. It shows the module of OFDM system of FFT/IFFT, including the main composition of transmitter and receiver. At last we analyze the affect of timing error and frequency offset in OFDM system in theory. The paper studies the synchronization algorithms. At first we present the synchronization algorithms in whole, particularly the synchronization algorithms using training symbol. We provide a timing algorithm which use the training symbol of complementary trait in time domain and symmetry in frequency, after analyzing give the disadvantage and advantage of the classic timing algorithms and the idea of improving algorithms. we estimate the frequency offset, after completing the OFDM system timing. The provided algorithm estimate the fraction frequency offset before FFT and improve the performance of fraction frequency offset estimation. The provided algorithm estimate the integer frequency offset using the symmetry in frequency after FFT, and enlarge the range of frequency offset estimation. At last we design the hardware design of synchronization algorithm, using LPM function of Altera . we present the FPGA design of FFT algorithm .we study complex multiply of twiddle factor in the butterfly module and complete the design of 128-points FFT algorithm based on sequence structure...