关键词: OFDM, 符号同步, 定时偏移, 共轭对称, 对称相关

Abstract:

This paper studies symbol synchronization methods based on the conjugate-symmetric preamble for OFDM systems in multipath fading channels. We analyze statistic properties of timing metric based on conjugate-symmetric correlation, and show that the compound-conjugate-symmetric structure is formed when two paths are separated by an even number of samples. The timing metric corresponding to the compoundconjugate- symmetric structure may be large under some conditions. We analyze the timing offset when the peak value of timing metric is used to detect the desired timing position, and show that the compound-conjugatesymmetric structure and the first path with small gain may result in backward shift in timing position. A large backward shift can cause inter-symbol and inter-channel interferences, seriously degrading the OFDM system performance. Simulation results confirm the analysis.

Key words: OFDM, , symbol synchronization, , timing offset, , conjugate-symmetric, , symmetric correlation