Time and Frequency Synchronization in OFDM System

Orthogonal frequency division multiplexing (OFDM) is one of the multicarrier modulation techniques, which transmits data in very high rate and efficiently mitigates the effects of multipath distortions as well as loss in bandwidth efficiency. However, OFDM systems are very sensitive towards synchronization error. Synchronization of an OFDM signal is required to find the symbol timing and carrier frequency offset (CFO). Before demodulation of subcarriers, either from explicit training data or using cyclic prefix of the OFDM signal we can get synchronization at receiver. After demodulation of the OFDM subcarriers, information about the synchronization can be obtained from training symbols embedded into the regular data symbol pattern. The estimation of synchronization error can be performed depending on the type of the training data. In this paper, it is focused on preamble based training data following IEEE802.11a preamble structure of the WLAN system and cyclic prefix based training data. According to the preamble structure of IEEE 802.11a Wireless Local Area Network (WLAN) standard, the problem of synchronization is solved. The OFDM system is modelled by using LTE standards as it is more popular in 4G mobile communications. And the synchronization is being tested in simulation by using preamble structure of IEEE 802.11a in preamble based synchronization and by using cyclic prefix in cyclic prefix based synchronization.