Robust early-late gate system for symbol timing recovery in MIMO-OFDM systems

This paper presents a robust timing recovery scheme for orthogonal space-time block coding (OSTBC) multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with constant modulus constellation. In the proposed system, the symbol timing is achieved either by minimizing the power difference between adjacent subcarriers in one STC block or between subcarriers with similar indices in consecutive STC blocks. The proposed technique is totally blind because it does not require any prior information about the channel state or the transmitted data. The early-late gate (ELG) configuration is utilized to realize the proposed timing recovery scheme efficiently. Monte Carlo simulations are used to assess the performance of the two realizations of the proposed system over fading channels with different frequency-selectivity conditions. Simulation results demonstrated the superiority of the proposed technique to provide accurate symbol timing even in severe frequency-selective fading channels which remarkably outperforms other timing metrics.