Coarse symbol timing recovery and carrier frequency offset tracking for MIMO DVB-T OFDM systems

This thesis presents a novel and accurate combination of non-data-aided synchronization techniques based on a correlation algorithm for Maximum Likelihood (ML) coarse symbol timing and Carrier Frequency Offset (CFO) tracking estimation of Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) outdoor systems constructed by DVB-T subsystems. The embedded continual pilot tones modulated according to a known Pseudo Random Binary Sequence (PRBS) in the DVB-T OFDM physical layer are utilized to perform the coarse timing recovery of the OFDM symbol with low system complexity. Another inherent part of DVB-T OFDM symbols, i.e. Cyclic Prefix (CP) is used for the maximum likelihood carrier frequency offset estimation at the receivers of the MIMO OFDM system. From the thorough simulation analysis, it is shown that the proposed coarse timing method has excellent robustness in symbol timing recovery even with very low Signal to Noise Ratio (SNR) for continuous transmission mode, e.g. DVB-T. It is also suitable for burst transmission mode systems, e.g. Wireless Local Area Network (WLAN) based on IEEE 802.11a. The performance of the proposed carrier frequency offset tracking estimator is close to the Cramer-Rao lower bound and increases for increasing Root Mean Square (RMS) delay spreads of Rayleigh multipath propagations as well as number of receive antennas, and also shows sensitivity to timing errors induced by the previous coarse timing estimator, which all agree well with the theoretical results.