Research On Synchronization Technology For OFDM Underwater Acoustic Communication System

The underwater acoustic(UWA) channel is a doubly-selective fading channel. It varies in time, space and frequency, and has multipath effect and Doppler effect. The main obstacles of realizing reliable high-speed underwater acoustic communication are multipath fading,time-varying, background noise, narrow band and so forth. Due to the high spectrum efficiency, strongly anti-channel multipath effect, OFDM(Orthogonal Frequency Division Multiplexing) is becoming an outstanding solution in reliable high-speed underwater acoustic communication. However, the OFDM system is highly sensitive to time and frequency offsets,which will worsen its BER performance. As we known, the synchronization is one of key technologies to OFDM system so that it is significant to research the synchronization of OFDM UWA communication system. On this context, this paper is mainly researching OFDM synchronization algorithms. The aim is to propose a new synchronization algorithm for OFDM UWA communication system.The main work and achievements are summarized as follows:1, This paper will introduce the characteristics of UWA channel, the basic principles of OFDM system, OFDM UWA communication system model and its differences with terrestrial radio communication system. Then this paper will discuss the design parameter of OFDM UWA communication system. Moreover, The effect of OFDM synchronization offsets will be analyzed.2, This paper will analyze three kinds of traditional OFDM timing synchronization algorithm, two kinds of OFDM carrier frequency synchronization algorithm and one timing and frequency joint synchronization scheme. The timing synchronization algorithm by using Chirp signal will be analyzed later. Moreover, a new synchronization algorithm will be proposed for OFDM UWA communication system. All these synchronization algorithms will be simulated in Rayleigh fading channel and these algorithms’ performance will also be analyzed. This paper will also analyze and simulate signal detection method by using Chirp signal.3, UWA channel is a sparse time-varying multipath fading channel whose taps often form clusters. The strongest path is not often the first path, which is needed to find by timingsynchronization. Hence, this paper will research and analyze some typical models of UWA channel. The algorithms which is discussed above will be simulated in these UWA channels.Finally, this paper will analyze the differences between the proposed algorithm and other algorithms in these UWA channels. The proposed algorithm can be traced back to the first path so that it will reduce timing error.