| With the development of modern science and technology, especially thedevelopment of communication technology, and with the people’s exploration ofmarine activities deeply, underwater acoustic communication technology also gotpeople’s attention. So far, below the surface, because of the special nature ofcommunication technologies and applications channel, underwater communicationtechnology has far-reaching significance. Underwater acoustic communication isflexible, convenient, economical, and there is no cable winding. It can completenavigation, positioning, exchange of information, communications and liaison andtransmission of information security required, and is the primary means of achievingintegrated information perception and information exchange underwater. In themilitary, in order to ensure the concealment of information interoperability betweeneach unit Underwater Warfare Systems, underwater acoustic communication is one ofthe most widely used communication applications.CDMA technology is the core of3G communication, the application of CDMAtechnology is already quite mature on the ground, while the CDMA technology usedin the underwater communications is not as mature as on the ground. The study ofunderwater communication modulation/demodulation system is based on CDMA.Spread spectrum communication technology is built on the basis of informationtheory, is one of the most advanced radio communication technologies in today’sinformation society. Since the spread spectrum communication has a stronganti-jamming, anti-interception, anti-multipath capability, multi-site capability,confidentiality and measurement accuracy, etc. It not only plays an important role inmilitary communications, but also be applied in the civilian communications widely.This design of the system is based on the study of the DS system.This paper introduces the background and significance of underwater acousticcommunications, development status of underwater acoustic communication at home and abroad. Domestic underwater acoustic communication development started late,so it has great technical improvement, is a good use of the opportunity for researchersin the country. Then this paper introduced CDMA technology and its characteristics,and elaborated CDMA technology’s good benefits.Next, the paper introduces the relevant theory and technology for underwateracoustic communication modulation/demodulation system based on CDMAtechnology. Article focuses on the direct sequence spread spectrum technology used inthe system, introduced the principle of the structure of several pseudo-randomsequence and features, and stated the carrier modulation technique.The paperanalyzes several synchronization scheme. It has an important impact for overallsystem in selecting the synchronization scheme. Next article describes the hardwaredesign of the system, and introduced several chips used in the system, then introducesthe software platform used in the system. The software platform of this design isAltera’s Quartus II11.0, the VHDL is used to achieve the modulation/demodulationsystem, and with Cyclone III family’s EP3C10E144C8N as the main chip, thenachieving a systematic design simulation, synthesis, verification and so on.The important work of this paper is the algorithm of the system. Firstly itintroduced the design of communication module, followed by the design of thetransmitter unit and a receiver unit. Each module was introduced separately, and thesimulation results are listed in Figure each module, to verify its correctness. Finally,the article summarizes the design of the system and makes a prospect in the furtherresearch on the system. |
