Abstract:

At the receiver of an orthogonal frequency division multiplexing (OFDM) system, the wrong estimation for the start point of fast Fourier transform (FFT) windows can lead to a frame offset of OFDM symbols, which can bring severe inter symbol interference (ISI) and inter carrier interference (ICI) for an OFDM system and decrease the OFDM modulation performance. Firstly, an OFDM system model with frame synchronization is built up. Then the influence of frame offset on the OFDM system is deduced theoretically. Consequently, an improved frame synchronization algorithm based on pseudonoise (PN) sequence preamble is developed by utilizing the relative good correlation characteristics of PN sequence. Three kinds of classical frame synchronization algorithms based on cyclic prefix (CP) are alse introduced. A group of simulation experiments are performed to compare and analyze the classical and improved algorithms. The simulation results indicate that the frame offset estimation results of the PN preamble based algorithm is much more accurate, stable and resourcesaving than the classical algorithms, even though under poor channel conditions, such as lower signal-to-noise ratio (SNR) or larger carrier frequency offset (CFO).