The Study Of Timing And Frequency Offset Estimation Algorithms For OFDM Systems

Orthogonal frequency division multiplexing (OFDM), with the advantages of robustness against multipath delay spread, high bandwidth efficiency, and simple hardware implementation, etc., has gained increased interest in the recent years, and is likely to become the key technology for the fourth generation mobile communications system. However, OFDM is sensitive to timing and frequency offset, so how to overcome this limitation is one of the main directions of the research on OFDM.The algorithms for estimating timing and fequency offset are studied in the thesis. They are divided into two categories: data-aided estimator, namely estimator based on the pilot symbols, and non-data-aided estimator, namely blind estimator. The Sch-Cox algorithm based on the pilot symbols is given in the thesis. Estimator based on the pilot symbols has quick acquisition and high precision, but the insertion of the pilot symbols wastes the system resource and reduces the system data transmission efficiency. While blind estimator doesn't need the pilot symbols, avoids the waste of the system resource, and saves the bandwidth. So blind estimator is studied deeply in the thesis. A joint estimator using the cyclic prefix and a frequency offset estimator using the virtual carriers are given. Their system models and particular algorithm descriptions are given, and their simulations and performance analyses are done. In the end the performance of the algorithms are compared and a summary is given.