The Coding And Decoding Technical Research For Floating Nodes Acoustic Positioning

With the increase of the scope and frequency of the human activities in the ocean, and the growing demand for ocean development, underwater target's positioning and tracking technology were received more and more attention of foreign and domestic scholars. Normally, the target's coordinates been measured by the acoustic positioning system are generally relative to a reference object. In order to reconstruct the sound field information of the voice target in the test waters, we should establish a reference coordinate system for this test waters first. Due to the difficulty of laying and adjusting the acoustic array of the existing acoustic positioning system, it is necessary to research a long baseline positioning system which can lay the acoustic array flexibly.First, in the thesis we establish a flexible laying long baseline positioning system model which referenced the GIB buoy of the underwater GPS positioning system floating flexibly in the sea surface, and introduces its independent positioning principle and general structure. The locating nodes and test nodes of the system are floating in the water flexibly where the locating nodes launch a positioning signal once a time interval to detect the relative position of the various nodes timely and master the change of the nodes'position.On this basis, we design an anti-multipath effect positioning signals based on the underwater acoustic channel characteristics and the system parameter requirements. Discuss the various parameters of the positioning signals changed with the positioning range and positioning precision emphasize, and research a series of key technologies such as the choice of coding form, the determination of signal's repeated cycle, the selection of modulation and demodulation mode, the determination of carrier frequency, and get the signal time-delay difference with the sliding relative method based on the sample point, also identify locating node as the same time, namely, complete the system positioning. In this system, the positioning signal coding control module mainly integrated in a CPLD, according to the system positioning range and positioning accuracy, we can modify its coding form, frequency and the repeated cycle of the located beacon signals, and the waveform and frequency of the carrier flexibly to realize the system's expansibility.Finally the overall system is tested in the river. The results show that the positioning system designed in this paper can be located by itself completely, and it can achieve the positioning accuracy within system excogitation, time-delay error is less than 0. 5ms.