Abstract
In this thesis, we propose a joint time synchronization and carrier frequency offset (CFO) estimation scheme using partial Zadoff-Chu sequences for orthogonal frequency-division multiplexing (OFDM)-based two-way amplify-and-forward (AF) relay systems. In the preamble design, the training signals for the two terminals are not only separated in the frequency domain but also isolated in the time domain so as to limit their mutual interference in both domains. Such a preamble structure allows joint estimation of timing delays and CFOs and, to the best of our knowledge, there is no related joint design in OFDM-based two-way AF relay systems. This joint estimation process could be repeated to improve the overall synchronization performance, where two iterations are often enough to provide satisfactory performance. To reduce the computational complexity and to alleviate the peak-to-average power ratio problem, we also provide some analysis results for appropriately determining the parameter that affects the width of the main lobe of the time-domain training signal. Simulation results demonstrate that the proposed joint scheme has superior timing performance to a previous time synchronization scheme combined with the conventional CFO estimation method for OFDM-based two-way AF relay systems, where both achieve similar CFO estimation performance.