Comparison of Underwater Laser Communication System with Underwater Acoustic Sensor Network

In this paper approach for the underwater sensor network based on the blue-green laser has been proposed. We describe the application of the underwater sensor network in the undersea exploration, and discuss the difficulties in the traditional underwater sensor network. A basic of prototype of underwater laser sensor network has been advanced, which include the architecture of laser network and protocol stack for underwater laser sensor network. Based on the advantages in the underwater laser communication, the underwater laser sensor network has great potential perspective in the undersea exploration. Key-Words: Underwater sensor network, blue-green laser, laser communication Introduction Under water communication has become the need of modern communication worldwide. Submarine to submarine, ship to submarine and satellite to submarine communication has emerged as one of the most challenging and necessary technologies in the present network centric warfare scenario. Radio frequency (RF) and acoustical techniques of underwater communication suffer from various drawbacks such as extremely low data transmission rates (few bps), smaller range, and multi-path reflections and so on. Laser based communication using blue-green lasers is a potential technique for high bandwidth underwater wireless communication because of its high data transfer rate, reasonably large range, small size, low power consumption, immunity to interference and jamming and covertness of transmission. In this paper, we described the various advantageous factors of underwater communication system using blue green laser with practical results over underwater acoustic network. Underwater communication system using blue green laser may be used for transmitting any type of file (Video, Audio, PPT, DOC, PDF and EXE) from one platform to the other. Underwater Acoustic Sensor Network: In traditional, the acoustic communication has been developed for the underwater network since World War II. With the exploitation in the sea, more and more underwater acoustic network projects have been carried out. For example, the Georgia Institute of Technology, Massachusetts Institute of Technology, University of Princeton and many other universities already developed some underwater acoustic sensor networks. However, the underwater acoustic signal is influenced by path loss, noise, multi-path, Doppler spread and high variable propagation Author Vikrant is currently pursuing his P.hD in E.C.E. from Singhania University, Rajasthan, India. Ph. +919315159900, [email protected] Co-Author Anjesh Kumar is working at Laser Science & Technology Centre, Delhi, India. [email protected] Co-Author Dr.R.S.Jha is the Supervisor of Vikrant at Singhania University, Rajasthan, India delay. And the direction of underwater acoustic communication also affect the acoustic link, which means that the different propagation direction has different propagation characteristics, especially with respect to the time dispersion, multi-path spread and delay variance. Hence, the underwater acoustic channel is a temporal and spatial variable system, which makes the available bandwidth limited and dramatically dependent on both range and frequency. Hereafter some disadvantage factors have been listed that influence acoustic communications in order to state the challenges posed by the underwater channel for underwater sensor networks. High delay: The signal propagation speed in the underwater acoustic channel is about 1.5×103 m/sec, which is five orders of magnitude lower than the radio propagation speed (3×108 m/sec). The large propagation delay seriously reduces the throughput of the system considerably, and also determines the unstable in the underwater control network system. Limited bandwidth: The acoustic band underwater is very little due to absorption, so most acoustic communication system operates below 30 KHz. As a result, the bandwidth of underwater acoustic channels operating over several kilometres is about several tens of kbps, while short range system over several tens of meters can reach hundreds of kbps. High bit error rate: Because of path loss, multi-path fading, Doppler spread, and noise (from man and ambient) in the underwater acoustic channel, there is a large bit error rate in the underwater acoustic channel, which is on the order of 10-2-10-5 High energy consumption: The power consumed in the underwater acoustic communication is more than in the terrestrial radio communication, because more power is consumed in the complex signal processing at receivers to compensate for the impairments of the channel. Affected by the above factors, the current underwater acoustic sensor network just provides the limited communication for International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 2 ISSN 2229-5518