The Research On The Multiple Access Technology And The Underwater Acoustic Network

Along with the great progress of information technology, the stereo information network which covers the ground, sky, outer space, and ocean has already formed and served for the communication, traffic, resource investigation, national defense all over the world. As the limitation of the transition of the radio wave under the sea, the construction of the information network is in blank stage, the research and use of the underwater acoustic communication is just for the point to point situation. Trough the wireless buoy, the underwater acoustic network can switch-in the existing information network; as a result, the information network can cover the whole world. Along with the exploiture of the ocean resource all over the world, the developed countries start to do the research of the UWN (Underwater Acoustic Network).The research on the underwater communication technology in China initial started in the late 80's, which now have not got the experiment achievements yet. As a result, the study of the UWN becomes the hotspot in the world. The main difficulty of the UWN includes: the long time-delay of the ocean acoustic channel, the limited usable frequency band, heavy time-varying influence, power consumption limit, and network security. Aiming at the research of the multi-access technology for the UWN, this article composes the system of the UWN using the OFDM and CDMA technology with the suitable transmitting method and protocol.This paper does some research on the correlation of the m and the Gold sequence with matlab, at the same time it completes the simulation under the situation that multiple users using the same channel and analyses its error rate. It also completes the simulation of the MACAW protocol using the Simulink. It completes the transmission of the data depending on the MC-CDMA technology using the matlab between the nodes in the UWN; it also shows the results of the simulation. It also implements the system in the DSP and put on trial in the pool. The situation under the acoustic channel is the same as that simulation. The MC-CDMA system materializes the better performance. The increase of the child-carrier number N will reduce the system error code rate greatly, but it will bring the increase of the system complicacy and reduce the average throughput by contraries. As a result, the child-carrier number N should be chosen in view of the reliability and efficiency of the system.