The Design And Implementation Of Underwater Sensor Networks On The Physical Layer

The basic idea of wireless sensor networks originated in the 20th century,70s, the study focused primarily on national defense projects. In the past few decades, wireless sensor technology has made rapid development. Wireless sensor network applications currently expanded to many other areas from the military field, marine monitoring is one of them. In recent years, people have more and more make wireless sensor technology use in marine monitoring, through underwater sensor technology to monitor the waves, currents, tide, sea surface temperature and salinity such a number of elements of the marine hydrology has been widely used.Currently, underwater sensor networks research has focused on acoustic communication based on sensor network technology nodes. However, there are still underwater communication questions, such as narrow bandwidth, low-rate, delay jitter, etc, and simulation software is difficult to construct model for time-varying and air-change underwater acoustic channel. Those made a higher demand on the design of underwater acoustic communication. Underwater sensor networks for the development of the current situation, this paper introduces the self-designed program to complete the underlying physical layer modulation data, send and receive.This design of underwater sensor network physical layer structure includes four parts:MAC layer and physical layer interface module design, signal processing module design, power amplifier module design and the acoustic transducer module design. MAC layer and physical layer interface module makes a proprietary design of the circuit by extending the pin as a signal line handshake protocol to complete the serial communication and parallel communication with the signal processing module. Modem technology is an important component of underwater communication, which plays a vital role in underwater acoustic communication network. Modem module implements two functions, receiving the digital signal which is to be sent from the network protocol module, After DDS (direct digital frequency synthesis) and digital-analog converter, it modulates analog signals which is suitable for underwater transmission. The received analog signal demodulates the original digital signal transmitting network protocol module after the analog-digital conversion and DFT (Fourier transform). Power amplifier module is achieved to underwater acoustic signal emission and amplification, it contains the following two parts:one is to send acoustic signals to the modulator signal amplification to drive ultrasonic signal emitted by the water. Second, let the weak signal received amplify to the appropriate range, output to the level A/D converter. Besides, we need according to the received acoustic signal size, generate the appropriate A/D conversion trigger signal. Acoustic transducer module is mainly used to complete acoustic and electric acoustic signal conversion, methods of work adopted is the transceiver mode.In this paper, the design of underwater autonomous sensor network physical layer structure solves the reliability of data transmission, underwater sensor nodes size, costs and energy consumption. Presented a unique node architecture and communication protocol interfaces between modules. The deployment is reliable, practical through experimental verification of the program. For underwater sensor nodes of the similar design of physical layer provides a reference.