Research On Channel Estimation And Its Application In High Speed Underwater Acoustic Communication

With the development of ocean exploitation strategy and the needs for militaryoperations on the sea, the needs for information transmission are greatly increased with thehelp of underwater acoustic (UWA) communication. But in UWA communication system,the acoustic wave is the only efficient method for long distance transmission, because of theabsorption to the signal especially the high frequency signal in the sea, where there havedifferent kinds of non uniform medium. What’s worse, because of the higher complexity inthe underwater acoustic channel, the UWA communication is far behind the terrestrialwireless communication. The purpose of the UWA communication system lies independablely transmitting the signal form the source to the end through ocean acousticchannel at high speed. Orthogonal Frequency Division Multiplexing (OFDM) can takes fulladvantage of the limited bandwidth in UWA channel and effectively against inter-symbolinterference which caused by multi-paths transmission. Meanwhile, it also can combineswith Many Input Many Output (MIMO) technology, to further improve the system’sinformation transmission rate which has a promising future in UWA communication. Whilelonger the transmission range, worse the underwater with multi-paths and Doppler offset,which needs to take practical methods to improve the system. Channel estimation is one ofthe key technologies in communication transmission field. They directly affect theperformance of the communication system. In this paper, we studied the channel estimationtechnology in underwater acoustic OFDM system and underwater acoustic MIMO-OFDMsystem, and then we designed a three dimensional underwater acoustic data communicationnetwork.We analyzed the marine water channel’s transmission characteristics and its impact tothe acoustic communication. And then we established the underwater acoustic channelmodel.We deeply analyzed the basic principles of OFDM system and the key technology,which has a technical superiority in high-speed UWA communication. Next we mainlystudied the channel estimation technology in underwater acoustic OFDM communicationbased on pilot. And then we analyzed and compared the performance of several algorithmsbased on block pilot, including algorithms of LS (Least-square), MMSE (Minimum MeanSquare Error) and LMMSE (Linear Minimum Mean Square Error), so as to know the advantages and disadvantages among them. We can draw some useful conclusions throughthe simulation and theoretical analysis.We completely analyzed the basic principles of MIMO system and the key technologyin order to lead to the UWA MIMO-OFDM communication system. Then we mainlydiscussed and studied the channel estimation technology in MIMO-OFDM based on thestudying discussed in OFDM system. We explored the designing of the orthogonality ofpilot and contrasted the diversity between the two systems on channel estimation based onpilot. The simulation results show that the predominance in MIMO-OFDM systemWe did a depth study on the workflow, network building and serial communication ofthe Z-Stack based on ZigBee technology. According to the feature of UWA channel, weestablished a remote monitoring platform about the three dimensional underwater acousticdata communication network, including the building of the hardware system and the controlsoftware, which based on the wireless sensor networks on land and underwater acousticcommunication networks.