简要介绍了水声通信网的研究现状以及常用的组网方式,比较了几种可实际应用的数据链路层协议,在此基础上提出了一种适用于区域性海洋观测的混合型网络协议,进行了仿真研究。该协议通过记录网络中数据包的发送频率来动态地调整所使用的MAC(Media Access Control)协议,当频率较高时选择查询方式的MAC协议,减少数据包的冲突;当频率较低时选择MACAW(Media Access with Collision Avoidance for Wireless),避免查询信号带来的额外开销。仿真结果表明,对于区域性海洋观测,这种包产生速率低,但可能出现短时间通信量大的应用情况,该协议可以有效地降低每bit的能耗,适用于长时间海洋观测。
针对广泛应用于水声通信网的MACAW(medium access with collision auoidance for wireless)协议在多跳通信延时严重的问题,在传统握手协议的基础上,提出了节点预约的方法.该方法通过多跳转发的握手信号CTS预约处于通信链路上的下级节点,并通过复用上级节点的握手信号CTS(clear to send)及数据信号DATA,形成一种流水线式的传输协议.仿真结果表明:在多跳网络通信中,该协议与传统的MACAW相比,在能耗变化较小的情况下,时延性能有较大幅度的提高,适用于移动节点通信、灾难预警、战时侦测等需要快速反应的水声通信应用场景.
For the first time in the world, underwater acoustic transmission of images, human voice, data and texts between vehicle under 7000 m depth and surface ship was accomplished by underwater acoustic communication system of manned deep submersible Jiaolong＇. In this paper, signal processing in underwater acoustic communication system for manned deep submersible ＂Jiaolong＂ is introduced. （1） Four communication methods are integrated to meet different needs： 1） coherent underwater acoustic communication, with a variable transmission rate from 5 kbps to 15 kbps, to transmit images. 2） Non-coherent underwater acoustic com- munication, with a transmission rate 300 bps, to transmit texts, instructions, and sensor data. 3） Spread spectrum underwater acoustic communication, with a transmission rate 16 bps, to transmit instructions. 4） Underwater voice communication, using single sideband modulation to transmit hmnan voice. （2） Signal processing method in coherent communication mainly consists of concatenation of decision feedback equalizer and Turbo decoder, and wavelet based image compression with fixed length coding. In the equalizer, Doppler compensation, multi- channel combining and equalizer coefficients updating are all using fast self-optimized adaptive algorithm. （3） A linear hydrophone array is lowered from the mother ship to certain depth, and spatial diversity combining technology is adopted. （4） Diving trials of ＂Jiaolong＂ were carried out in Pacific Ocean. The communication range can cover nearly all ocean depth. One optical/acoustic image can be transmitted in 7 or 14 seconds.
