| UV communication is a kind of wireless optical scatter communication using "solar-blind"characteristics, has a good security, strong anti-jamming ability, non-line-of-sight and other advantages, and is very suitable for secure communication, but is still far from practical application now. This thesis carries out preliminary theoretical and experimental research on some basic problems of UV communication by means of theoretical derivation, simulation and prototype testing, and does a thorough and meticulous work on the atmospheric transmission theory, channel propagation characteristics, modulation technology and experimental prototype developed etc.On the basis of a detailed discussion of the UV atmospheric propagation theory, UV non-line-of-sight single scattering and multiple scattering channel models are analyzed and simulated, and then an improved multiple scattering model based on Monte Carlo methods is proposed. The receiving terminal of currently model detects the photon according to the size of the coplanar scattering angle, we replace it with the range of the spatial distance, so the condition of the detection is extended from the coplanar to the space, which is more in line with the actual situation that transmission of the vast majority photons in space are non-coplanar. At the same time, the amount of computation and accuracy in the process of establishing the model are optimized. By using the multiple scattering model, we study the pulse response characteristics of the ultraviolet communication channel, obtain the integrate channel response results,and reveal the impact of the transmission distance, the transmitter and receiver geometry configuration parameters on the pulse delay, pulse broadening and path loss.A scattering contrast channel model based on Monte Carlo method is created, through the simulation experiments, the single scattering approximation condition that Van de Hulst proposed in UV communication field is verified. The contribution ratio of the single, secondary and multiple scattering on the reception of energy are in-depth studied, which provides the basis for channel modeling using how many times of scattering; meanwhile the survival rate of photon effect on the path loss is relatively small.In the Poisson and Gauss noise models, we systematically analyze the tradeoff among the transmission distance, power, rate and bit error rate (or packet error rate) in the OOK, PPM, DPPM and DPIM modulation with UV transmission channel model, derive in the required transmit power formula of the four kinds of modulation under a given packet error rate, and compare the power efficiency of the different modulation technology, bandwidth efficiency, implementation complexity, and the impact on the system performance by using of the different modulation order. The performances of the communication link are obtained according to the different modulation.The general scheme of NLOS UV communication prototype system is put forward. Based on the STM32core processing board that we independently research and develope, we design and optimize the communication protocol of the UV communication test-bed and software architecture, propose an adaptive energy threshold algorithm. The key technologies of UV communication test-bed are systematically researched, and the architecture of the NLOS UV communication system is constructed, each component of the transceiver terminal and the methed of implementation are builded. Finally successfully develope two communication test-beds differently based on the light source of UV LED and low-pressure mercury lamp, the short-distance communication rate is up to lOkbps. These lay a foundation for the further development of ultraviolet communication theory analysis, test and practical application, and provide a good platform. |
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