Study Of OFDM Timing And Frequency Synchronization

Orthogonal frequency division multiplexing (OFDM) has evolved over the years to become one of the most important techniques in mobile communications. Its ability to suppress Intersymbol Interference (ISI) and frequency selective fading as a result of multipath fading in the radio channel has made it a very strong candidate for future communication standards. Recently, the combination of OFDM with Multiple Input Multiple Output known simply as MIMO-OFDM has been deployed in many 4th generation mobile standards in order to combat fading and increase the data rate.In this thesis, MATLAB software was used to investigate the performance of OFDM without and with timing synchronization. Initially, the performance of OFDM in Additive White Gaussian Channel was simulated and compared to the theoretical value. It was found to be in conformity though with small deviations. The performance of different PSK modulation schemes was also compared and the results show that BPSK has a better performance at the same SNR. For the timing synchronization, a simple solution in the form of the cyclic prefix was presented and simulations were carried out to analyze its performance. It was found out as far as the maximum channel delay is less than the cyclic prefix, the effect of timing synchronization errors i.e. ISI is drastically reduced. Similarly, the role of the IEEE.802.11a short preamble in combating carrier frequency offset was simulated and the results were given as well. It was shown that the short preambles are capable of estimating the carrier frequency offset.