Joint Carrier Frequency And Timing Synchronization In OFDM System

In recent years, great interest was focused on OFDM just because its inherent technical advantages in combating multi-path fading and its high resource utilization, and it is considered as the core technical of the next generation mobile communication. But frequency offset will destroy the orthogonal character of sub-channels and very small carrier frequency offset may induce large demodulation errors in the receiver, so it is more sensitive to the carrier frequency offset than sing-carrier systems, besides, the change of symbol timing may increase the sensitivity to time-delay. Therefore carrier synchronization and symbol timing synchronization are the emphasis and focus. There are three kinds of synchronal modes in OFDM system: symbol timing synchronization, carrier synchronization, sampling-bell synchronization. This paper chiefly studies joint symbol timing and carrier frequency synchronization. Here firstly introduces the basic principle of OFDM technique and the characteristics of wireless fading channel and so on, then analyses the influence of timing error and carrier frequency offset on the system performance. It is followed that two typical synchronization algorithms are analyzed and modified .based on the analysis of the current (ML) method which is using cycle prefix, two new methods are proposed in AWGN channel and multi-path channel. Moreover, aiming at the problem of imprecise timing synchronization in Schmidl' algorithm which is using pilot symbol, a new synchronization scheme is proposed. These algorithms are simulated and confirmed in computer.