Realization Of The Maritime Mobile Communications System Based On The Ad Hoc Network

Wireless Mobile Ad Hoc Network(Ad Hoc),a temporary system of a group of wireless transceiver mobile terminals,is set up on specific occasions to constitute arbitrary network topology through wireless communication,and has the possibility to realize the VHF(Very high frequency) over-horizon transmission.VHF communication system,one of the important components of ship detection and safety communications system,has been an indispensable communication method of the water search and rescue,navigation management in coastal and inland water transport for short distance. In order to ensure the communication command in salvage of the emergency smoothly, VHF based on Ad Hoc Network would play an important role.According to the needs of the marine VHF communication and the spectrum of the current modulation, anti-interference ability and other factors,we selected the Gaussian filtered Minimum Shift Keying(GMSK) and three-level FSK(3FSK) modulation and demodulation to research.In this thesis,we introduce the currently research and development of the Ad Hoc network and maritime VHF communication,the specific requirements of the project,the reason for choosing the GMSK and 3FSK as digital modulation methods,the relevant theory and the researches of GMSK and the implementations of GMSK modem.Then with the derivation of its power spectrum,the basic theory of 3FSK based on the fourth category of response system is specific analyzed.According to the system's requirements,the hardware platform of GMSK modem that used CMX909B is designed and its design of each part and analysis are given.Meanwhile,the softwares of modulator and demodulator are designed,the function of the baseband is tested and analyzed.Then with the detail derivation and analysis of 3FSK modulation and demodulation implementations in ADF7021 chip,the relevant interface and parameters of FC-222 wireless digital radio are introduced,as well as the design of modem system based on FC-222 and each part of the interface circuit.Lastly,related software to FC-222 is designed and implemented,including the choice of radio channels,CRC check of the data and the time-delay measurement in air. After experimental testing,the Ad hoc routing protocol and the MAC(Media Access Control) protocol are achieved,and through the VHF radio,the automatic building of network nodes and the completion of the multi-hop data packet transmission are achieved by the network topology that we made,and achieved the ultimate purpose of the study.