Zhang Xiao-min

Design of sensor nodes in underwater sensor networks

Since the mid of 1990s, terrestrial wireless sensor network is developing quickly. However, constrained by certain characteristics of underwater acoustic channel such as limited available bandwidth and large propagation delays, which means development of underwater sensor networks, the extension of the concept of terrestrial wireless sensor network in ocean application, lags behind that of terrestrial wireless sensor network. Besides, due to the fact that the underwater instruments are usually battery-powered, and the power consumption of single node is directly relevant to the life of entire network, the design of low power architecture of nodes and energy-efficient MAC protocol are the highlight in recent research. This paper proposed a design of underwater acoustic network node with low power consumption. By using the ‘Sleep/Wake’ operation mode, the average power dissipation of the node is reduced. And then based on software radio concept, the node project can achieve a better extent of application flexibility. A complete prototype has been tested in a anechoic pond, and the result shows the prototype has features of compact structure, reliable performance and low power consumption. Since the network node is the core section of underwater sensor networks, this design provides good platform for the research and verification of MAC layer of practical underwater sensor network.

Design and realizatiom of receiver based on eastimation of acoustic target signal intensity

With the development of modern noise reduction technology, the noise levels of the surface ship and underwater submarine are lower, making the target signal weaker and weaker. When knowing target distance and sonar system parameters, in order to acquire target signal noise level, and not lose the effective information of target signals, this paper introduces a method of estimating target signal intensity of sound source. Its characteristic is adopting diode detection and level ascension circuit. After the processing of MCU (MSP430F5438), target signal intensity is got. The designed receiver has advantages of simple structure, reliable performance, good realtime performance and low power-consumption. Test results of the entire prototype system in anechoic tank show that the maximum error of received source level is not more than 1 dB when the emission source level is between 100dB and 180dB. The designed receiver can meet the designing requirements of modern underwater receiver.

A new architecture design of remote access system for underwater acoustic sensor networks

In this paper, a new architecture design of remote access system for underwater acoustic sensor networks is proposed. This design of architecture contains a band-pass filter characterized by ultra low power consumption and high-sensitivity, which is appropriate for signal inception under low Signal to Noise Ratio. The security of the system is enhanced by means of Direct Sequence Spread Spectrum that can prevent unauthorized users from using the networks. In order to further reduce power consumption of the system, ‘sleep-wake’ mode is applied. Test of the entire prototype system in anechoic tank shows that the system has steady performance, and achieves good performances of low power, long distance transmission and security. The system can not only realize long-distance access of underwater acoustic sensor networks but also offer an approach for sensor networks safely and reliably.

Design for underwater platform's attitude data acquisition system based on software radio technology

That the underwater platform rocks constantly in the water will lead to serious bias in the long-range detection to a target. Therefore it is necessary to track and predict the attitude of the swaying platform accurately. This paper introduced an attitude data acquisition system which uses the principle of software radio technology, and can operate steadily for a long time based on a low power electronic compass. Meanwhile, the function that controls the sampling model in the dynamic condition has been verified correctly with the prototype of data acquisition system.