Sun Haixin

Performance comparison of time synchronization algorithms for OFDM underwater communication system

This paper is about time synchronization algorithms for Orthogonal Frequency Division Multiplexing (OFDM) system based on the features of underwater acoustic (UWA) channel. The three time synchronization algorithms are analyzed at the first place. Then on the basis of computer simulation, the performance of the three algorithms are compared and tested in the actual lab pool. Latter experimental results shows LFM chirp signals as synchronization symbol are more suitable for OFDM underwater communication system.

A New Accurate Symbol Synchronization Scheme for underwater acoustic communication systems

In underwater acoustic communication systems, symbol synchronization accuracy is affected gravely by Doppler effect. So it is very important to structure a new accurate symbol synchronization scheme. Accurate symbol synchronization and Doppler effect value can be gained by designing a new frame structure using LFM (linear frequency modulation signals).

The research of the cooperative OFDM system

The main idea to the OFDM is to divide the channel into many orthogonal sub channels in the frequency, which use parallel transmission sub-carriers to modulate. So that, the signal bandwidth is less than the channel coherence bandwidth, which can effectively eliminate ISI. Cooperative diversity is widely used in wireless communication. By taking the advantage of cooperative communication, we try to combine Cooperative diversity with OFDM. In this paper, key technologies of OFDM system, two types of cooperative protocols to realize cooperative diversity in OFDM systems, and two kinds of combining methods, are proposed. Simulations on two types of cooperative protocols to realize cooperative diversity, on two kinds of combining methods are performed. In addition, we simulated the performance of the cooperative diversity OFDM system with relay nodes located in different locations.

Notice of Retraction A research of signal combining technologies in cooperative diversity of OFDM communication system

Cooperative diversity is widely used in wireless communication. Because of its own unique advantages, we try to combine Cooperative diversity with OFDM. Key technologies of OFDM, three methods of channel estimation, two types of cooperation, and two combining methods in OFDM system are presented in this paper. Simulations of OFDM cooperative diversity system with two combining methods are performed. The performances of OFDM cooperative diversity system under three methods of channel estimation are simulated and analyzed respectively.