Research On Synchronization For OFDM System

The next-generation wireless personal communication systems are expected to provide ubiquitous, high-quality, and high-rate mobile multimedia transmission. However, to achieve this objective various technical challenges must be overcome. For example, the deployment of broadband wireless access systems would require a transmission technique which can mitigate the detrimental effects of the inter-symbol interference (ISI) caused by the multi-path fading channels. In recent years, there has been a lot of interest in applying orthogonal frequency division multiplexing (OFDM) in wireless systems because of its various advantages in less-ing the severe effects of ISI. However, the OFDM system is vulnerable to synchronization errors. How to effectively do the synchronization at the OFDM receiver are the important issues which need to be addressed in OFDM systems. According the problems mentioned above, the dissertation focuses on the synchronization for OFDM systems.In chapter 2, we expound the principle of synchronization for OFDM systems, and present some synchronization schemes, especially on the frequency synchronization. Because of the narrow bandwidth between sub-channels of OFDM systems, the whole performance of communication systems is sensitive to the frequency offset, so frequency synchronization is more important. In chapter 3, combining the MIMO technique, we present some current research on synchronization for MIMO-OFDM systems, and illustrate several classical methods. In chapter 4, we propose a novel synchronization algorithm for the LTE-TDD systems. This algorithm takes the advantage of the TDD timeslot, and processes the pilot sub-carriers after FFT transforms. Simulation results shows that this method can get better synchronization performance in the condition of low SNR and multi-path fading channels.Finally, in chapter 5, we summarized and concluded the whole dissertation. Further research issues and possible research directions were pointed out.