摘 要
隨著海洋開發(fā)大戰(zhàn)略的實施以及海上軍事行動的實際需要，利用水下聲信道進行信息傳輸?shù)男枨蟠蟠笤黾印Ｓ捎诤Ｋ蟹蔷鶆蚪橘|的吸收作用特別是對高頻信號，使得水聲通信中只能以聲波作為唯一有效的載體信號，再加上水聲信道較無線電信道更強的復雜性，導致了水聲通信遠遠落后于陸地無線通信。水聲通信的目的在于高速、可靠地將信源信息經過水聲信道傳輸?shù)叫潘?。正交頻分復用(OFDM)技術能夠充分的利用水聲信道的有限帶寬，有效地抵抗多徑傳輸所帶來的碼間串擾。同時它還可以與多輸入多輸出(MIMO)技術相結合，在保證原有性能指標的同時，進一步提高系統(tǒng)的信息傳輸速率，在水聲通信中具有廣闊的發(fā)展前景。但隨著傳輸距離的增加，信道條件惡化，多徑、多普勒頻移影響加劇，需要采取有效手段進一步改善系統(tǒng)的性能。信道估計是其中的關鍵技術，直接影響水聲通信傳輸系統(tǒng)的性能。本文以信道估計為出發(fā)點，研究了水聲OFDM系統(tǒng)和水聲MIMO-OFDM系統(tǒng)中的基于導頻的信道估計算法，并結合水聲通信特點設計一套立體式的水聲數(shù)據(jù)傳輸通信網(wǎng)絡。
本文對海洋水聲信道的主要物理傳輸特性及其對水聲通信的影響進行比較深入的分析，并在此基礎上建立了水聲信道模型。
對OFDM技術的基本原理以及關鍵技術進行深入分析，并由此得出其在水聲高速通信中的技術優(yōu)越性。在深刻理解OFDM技術的基礎上，著重研究了水聲OFDM系統(tǒng)中基于導頻的信道估計技術的相關問題。結合塊狀導頻的插入形式，對導頻處的LS算法、MMSE算法和LMMSE算法進行了分析比較，通過理論及仿真分析得出了一些有用的結論。
對MIMO技術的基本原理以及關鍵技術進行了全面的分析，由此引出水聲MIMO-OFDM通信系統(tǒng)。在上一章基礎上，研究了水聲MIMO-OFDM系統(tǒng)中基于導頻的信道估計技術。探討了信道估計中導頻正交性的設計以及OFDM系統(tǒng)和MIMO-OFDM系統(tǒng)間導頻信道估計的差異性。通過理論和仿真分析，驗證了 MIMO-OFDM系統(tǒng)較OFDM系統(tǒng)有更好的性能表現(xiàn)。
對基于ZigBee技術的協(xié)議棧的工作流程、無線網(wǎng)絡的建立、串口通信等進行了較深入的研究。結合水聲通信信道特點，同時針對水聲高速通信的應用需求，在陸上無線傳感器網(wǎng)絡和水聲通信網(wǎng)絡的基礎上，建立了一套立體式的水聲數(shù)據(jù)傳輸通信網(wǎng)絡遠程監(jiān)控平臺，其中包括硬件系統(tǒng)的設計和控制軟件的設計。

關鍵詞 水聲通信；正交頻分復用；多輸入多輸出；導頻；信道估計


Abstract
With the development of ocean exploitation strategy and the needs for military operations on the sea, the needs for information transmission are greatly increased with the help of underwater acoustic (UWA) communication. But in UWA communication system, the acoustic wave is the only efficient method for long distance transmission, because of the absorption to the signal especially the high frequency signal in the sea, where there have different kinds of non uniform medium. What’s worse, because of the higher complexity in the underwater acoustic channel, the UWA communication is far behind the terrestrial wireless communication. The purpose of the UWA communication system lies in dependablely transmitting the signal form the source to the end through ocean acoustic channel at high speed. Orthogonal Frequency Division Multiplexing (OFDM) can takes full advantage of the limited bandwidth in UWA channel and effectively against inter-symbol interference which caused by multi-paths transmission. Meanwhile, it also can combines with Many Input Many Output (MIMO) technology, to further improve the system's information transmission rate which has a promising future in UWA communication. While longer 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 of the key technologies in communication transmission field. They directly affect the performance of the communication system. In this paper, we studied the channel estimation technology in underwater acoustic OFDM system and underwater acoustic MIMO-OFDM system, and then we designed a three dimensional underwater acoustic data communication network.
We analyzed the marine water channel’s transmission characteristics and its impact to the acoustic communication. And then we established the underwater acoustic channel model.
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 mainly studied the channel estimation technology in underwater acoustic OFDM communication based on pilot. And then we analyzed and compared the performance of several algorithms based on block pilot, including algorithms of LS (Least-square), MMSE (Minimum Mean Square Error) and LMMSE (Linear Minimum Mean Square Error), so as to know the advantages and disadvantages among them. We can draw some useful conclusions through the simulation and theoretical analysis.
We completely analyzed the basic principles of MIMO system and the key technology in order to lead to the UWA MIMO-OFDM communication system. Then we mainly discussed and studied the channel estimation technology in MIMO-OFDM based on the studying discussed in OFDM system. We explored the designing of the orthogonality of pilot and contrasted the diversity between the two systems on channel estimation based on pilot. The simulation results show that the predominance in MIMO-OFDM system
We did a de..