Design And Simulation Of Maritime Mobile Communication Baseband System

The thesis conducts research on the wireless baseband trasmisssion technologies for matitime fishery vessels communications using UHF radio waves. The complexity of the electromagnetic wave propagation over the sea and the characteristics of the communication between fishing boats are important factors to design maritime wireless trasmission system. With the application of the Fast Fourier Transform and the development of the digital processor, SC-FDMA can be applied to the design of maritime wireless transmission system, because of its high spectrum utilization, low PAPR, anti-multipath fading performance, bandwidth allocation flexibility, frequency-domain equalization and so on. This thesis consists of three parts:the modeling of the electromagnetic wave propagate over the sea, the BER performance of the SC-FDMA system and the PAPR performance of the SC-FDMA system:First of all, the propagation characteristics of electromagnetic waves over the sea depends on three factors of the electromagnetic wave frequency, the roughness of the sea surface and the grazing angle. The Roughness factor judgment, Rayleigh judgment, coherent reflection coefficient method and specular and diffuse reflection coefficients method are used to analyze the reflection characteristics of electromagnetic waves over the sea. From the results it is concluded that the sea surface can be assumed smooth mirror surface when the sea state is seven and the grazing angle is from0to1.3degrees or the sea state is six and the grazing angle is from0to2.5degrees. According to whether the multipath components of received signal can be discrete separated, this thesis establishes discrete multipath fading channel model in the area of the first Fresnel zone and diffusion multipath fading channel model in the area of the effective scattering area respectively.Secondly, this thesis analyzes the basic principle of the SC-FDMA system, the architecture of the SC-FDMA system, subcarrier mapping schemes and the baseband signal representation in different subcarrier mapping schemes. The design of the SC-FDMA system parameters fully take into account the signaling overhead of the system, the anti-fading performance, the communication coverage, the performance of anti-frequency offset, spectrum utilization, the scheduling overhead of the system and transmission delay of the SC-FDMA system. This thesis focus on the analysis and simulation of the BER performance of three kinds of subcarrier mapping schemes under AWGN channel, discrete and diffusion multipath fading channels.The BER performance is influenced by the subcarrier mapping the starting position. It is concluded that the interleaved subcarrier mapping scheme exhibits the best performance among the three mapping schemes, followed by the localized scheme, and the worst is the distributed subcarrier mapping scheme.Thirdly, considering that PAPR is the important elements to measure the communication coverage, receiver sensitivity, and transmit power efficiency of mobile communication systems, the conclusion that the SC-FDMA system has lower PAPR comparing with OFDMA is obtained by analyzing the structure of baseband signal and complementary cumulative distribution function. This thesis analyzes and simulates the PAPR performance of the SC-FDMA system under three subcarrier mapping schemes. From the simulation results, the interleaved subcarrier mapping scheme exhibits the best PAPR performance and the worst is the distributed subcarrier mapping scheme. The PAPR performance of the SC-FDMA system is influenced by the pulse shaping of the SC-FDMA system, the number of subcarriers of the SC-FDMA system and the roll coefficient factors of the pulse shaping filter.