| OFDM (Orthogonal Frequency Division Multiplexing) is a multi-carrier data modulation technology. Though the conception of OFDM was brought forward many years ago, it is only in recent years that people recognize it as an excellent way of high speed, bidirectional, wireless data communication. With the development in DSP chip technology, and the import of 64/128/256QAM technology in Fourier Transform/Inversion and High Speed Modem, people are devoting more and more in developing the application of OFDM in mobile communication. It is predicted that OFDM might be the mainstream technology of mobile communication after the third generation.OFDM also has some shortcomings such as being sensitive to symbol synchronization and frequency offset. Firstly, in wireless environment, receiver has no know the time delay between transmitter and itself. In OFDM system, OFDM data is transmitted as one symbol, so in order for correct demodulation, the correct start of symbol should be got from OFDM system to reduce the effect of ISI. Secondly, the high frequency utilization in OFDM is based on the orthogonal properties of sub carriers.If frequency offset is generated , the orthogonal properties among sub carriers will lost, that will cause Inter Carrier Interference (ICI) and high BER of system. So in OFDM system, how to synchronize quickly and accurately is quite important, which affects the performance of whole system. Also symbol synchronization and frequency synchronization algorithms should be proposed and realized in OFDM receiver design.This article achieves physical layer basic emulation of IEEE 802.11a WLAN system with Matlab6.5, and makes basic researches on symbol synchronization and frequency synchronization schemes of IEEE 802.11a WLAN system. New algorithm is also presented and emulated in the article as well. The emulation result shows that the algorithm presented possesses low complexity in implementation as well as high precision. |
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