Frequency and timing synchronization and channel estimation in preamble based OFDM system

The paper investigates carrier frequency and timing synchronization and channel estimation schemes utilizing a special training structure. The schemes can be used in preamble-based OFDM systems, such as the IEEE 802.11a WLAN system. Several algorithms based on long preamble symbols are presented to work jointly to attain synchronization tasks and channel estimation. Fractional sub-carrier frequency offset (FFO) and initial timing are estimated by correlation metrics in the time domain. Correlation between adjacent subcarriers is proposed to obtain integer sub-carrier frequency offset (IFO) with high reliability. Meanwhile, the initial timing offset is estimated. Then the LS method is used to estimate channel response, accompanied by a search program to find the optimal timing offset.