Block synchronization algorithms for UWB-OFDM systems

Orthogonal Frequency-Division Multiplexing (OFDM) is a modulation known by its high spectral efficiency, high tolerance to multipath delay spread in frequency selective channels, and low cost of implementation. However, OFDM systems are extremely sensitive to synchronizations errors. In this paper, we propose an unbiased block synchronization algorithm that uses the structure of the cyclic prefix, the presence of pilot tones in the OFDM block, and an estimation of the channel time impulse response. This algorithm is able to achieve fast synchronization as required, for instance, on Ultra-Wide Band (UWB) multipath fading channels. To quantify the performance of the block synchronization algorithm, we use the start of frame mean square error. Through numerical simulations, we show that our algorithm outperforms previously published synchronization algorithms.Fil: Maya, Juan Augusto. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Galarza, Cecilia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; Argentin

Blind block synchronization algorithms in cyclic prefix systems

In orthogonal frequency division multiplexing (OFDM) systems, symbol synchronization is a critical step for successful data transmission. While this task is done in most current systems by using training symbols, a few studies have been dedicated to solving the problem blindly, that is, where training symbols are not available. Blind symbol synchronization problem is especially important in many blind channel estimation algorithms in the literature which assume that OFDM symbol synchronization is perfect. In this paper, a broader version of the blind symbol synchronization problem is studied, namely, blind block synchronization in cyclic-prefix (CP) systems. The proposed algorithm for this broader problem covers the blind symbol synchronization problem in OFDM systems. Unlike previously reported algorithms which are based on obtaining sufficient statistics of received samples, the proposed algorithm is capable of identifying the correct block boundaries using much less received data in absence of noise. Simulation results of the proposed algorithm not only verify the declared property but also demonstrate improvement in accuracy of symbol synchronization over previously reported algorithms in presence of noise