The Simulation Approach For Underwater Broadband Wireless Communications Of Visible Light

With the rapid development of world economy, the pressure of serious shortage of natural resources is increasing. The ocean which is covering 70% of the earth's surface is expected to be future resource for the human being. In recent years, the novel technologies of autonomous underwater vehicle (AUV), underwater wireless sensor networks, in situ observing systems are relied upon underwater wireless communication for real time information exchange. These technologies provide advanced methodology to obtain spatial and temporal ocean information in real-time. As the increased applications of optics and acoustic imaging sensor for underwater monitoring, the traditional acoustic wireless communication suffers low bandwidth limitation and can not meet the needs of mass information transformation of underwater applications. Optical wireless communication, however, has advantages in high-bandwidth, high transmission rate, small delay and good directivity. It provides an alterative means for underwater broadband wireless communication in an acceptable range.This thesis presents the works of a modeling and simulation approach to the performance evaluation of visible light wireless communication for underwater applications and it provides a useful basis and foundation for the design and implementation of underwater broadband wireless optical communication system.The contributions of the work are as following:(1) The basic principles of underwater optical wireless communication system are discussed. According to the optical characteristics of underwater channel, an underwater optical communication link is presented as foundation for simulation model in underwater visible light wireless communication systems, and the structure of three receiving devices, such as pre-amplifier p-i-n Photo-Diode (PIN) photodiode, avalanche photodiode (APD) and photomultiplier tubes (PMT) are discussed.(2) A transmitter model based on light emitting diode (LED) is established, and the simulation model of PIN photodiode receiver modules, avalanche photodiode (APD) module and photomultiplier tubes (PMT) module are described. The digital modulation technique for optical communication is also discussed.(3) The performance with three receiving modules for line of sight underwater communication is evaluated based on on-off Keying (OOK) and pulse position modulation (PPM). The simulation results of non-line-of-sight for underwater optical communication with OOK modulation are presented and the comparison with line of sight underwater optical communication is given.