| Orthogonal frequency-division multiplexing (OFDM) is a promising technology for its high spectral efficiency and robustness to selective fading and narrow band interference. As multiple inputs multiple outputs (MIMO) technology can be adopted to increase system capacity, data rate, and make the transmission more reliable, it has become a key technology in wireless communications now. OFDM and MIMO are widely believed to be the candidate technologies for next generation wireless communications (Beyond 3G or 4G) systems. A MIMO-OFDM system is a seamless merger of MIMO and OFDM, which can potentially provide larger coverage range, more reliable transmission, higher data rate and spectrum efficiency. However OFDM and MIMO-OFDM systems are very sensitive to time and frequency synchronization errors, especially the frequency synchronization errors. Accurate frequency synchronization is the precondition of the OFDM systems. Based on the key technology research in B3G-TDD systems, carrier frequency synchronization in SISO-OFDM systems and MIMO-OFDM systems are researched in this dissertation.At first, this dissertation has analyzed the model of wireless channel, reviewed the basic theory of OFDM technology and the structure of OFDM system. The influence of CFO is also summarized. In OFDM system, each sub-carrier is identified by orthogonal character. So, accurate frequency synchronization is very important to OFDM systems. This dissertation focuses on carrier synchronization in SISO-OFDM system and MIMO-OFDM system.The algorithm of carrier synchronization in SISO-OFDM system is... |
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