| Wireless optical communication is a different communication mode with optical fibre communication, using atmosphere as transmission medium. It has two communication modes, including line-of-sight and non-line-of-sight communication. Solar blind non-line-of-sight communication ultraviolet (UV) communication is a new kind of wireless optical communication, which can provide non-line-of-sight links by exploiting atmospheric scattering of light. Solar blind ultraviolet communication can be used for a variety of close anti-jamming communications environment, due to its excellent performances of safety, anti-interference and non-line-of-sight. In recent years, UV communication has been concerned by the military power and is a front field of the wireless communication.The thorough studies for UV communication had not been carried out and only modulation, UV atmosphere characteristic path loss model and so on are studied at present. The serious inter-symbol interference and multiplexing fading, narrow bandwidth and high bit-error-rate (BER) are markedly characteristics for UV communication. In order to improve communication performance, characteristics of UV channel, channel equalization, signal detection and multip input multip output (MIMO) are studied for the UV communication. The paper contains theoretical research and prototype design. Base on the theoretical research, the digital base band system of UV communication is designed and realized. The research conclusions are got for the first time. The main results are summarized as follows:Characteristics of UV channel are studied in this paper. Path loss model has mainly been studied at present, and the analytic expression of the channel impulse response is derived at first in this paper. The relationships between channel length, inter-symbol interference and BER and bit rate and system geometry configuration are got. The results indicate that the channel bandwidth mainly rest on the attenuation coefficient and channel capability is affected by the communication range and attenuation coefficient. The derivation results will give important guidances on the designs of the wireless ultraviolet communication system.The equalizer fot the UV communication is investigated for the first time, reducing the inter-symbol interference. The some base problemes of the equalizer design are analyzed for the UV communication, and then LMS class and CMA equalizeres are studied. The convergence rate is very slow for LMS equalizer on UV channel, BER are nearly not affected by equalizer tap numbers and step size has an optimal value. The relations between parameters of two variable step size LMS algorithms and BER are studied at the same time. It is proved UV channel is a minimum phase system and blind equalizer can be used. BER is not sensitive to variation of step size and tap number for CMA blind equalizer and LMS equalizer has better performance than CMA blind equalizer.For acquiring the best equalization performance, we had studied a maximum likelihood sequence estimation (MLSE) and maximum a posteriori (MAP) equalizer for the UV communication, which have the same properties and little different capabilities. The MLSE equalizer has little better performance than the MAP equalizer, and the MAP equalizer has lower design complexities. At the same time, the MAP equalizer is suitable with iteration-decoding system and can be used with turbo channel coding. The results indicate performance of equalizer is nearly not affected by the attenuation coefficient and channel bandwidth for the short range communication, but is sensitive to variation of attenuation coefficient for the long range communication with the same receiver signal-noise-rate(SNR).The performance of equalizer is also sensitive to variation of channel length and bit rate. The BER can vary greatly with the variation of channel length and bit rate and can be reduced significantly when the adaptive power control is used. It is discovered that the noise observed has great effect on the equalizer and modulation schemes have not. At last, the optimal lengths of the training sequence and frame are derived.Adaptive signal detectors are designed in wireless optical communication based on atmosphere turbulence and Gauss noise. In this paper, we present several adaptive methods to detect the signals in the Poisson and Gauss regime, when the light fluctuations exit in ultraviolet and infrared communication, and an adaptive method to select the different simple turbulence model based on the scintillation index in different turbulence conditions, which can simplify engineering design. It is proved that the methods can significatively improve system performance. MIMO techniques and space-time coding are investigated for the UVcommunication, in order to reduce fading and increase channel capability. The results indicate that space-time block code and repetition code can provide full diversity, but repetition code outperforms orthogonal space-time block codes. The findings indicate also that the BER of equal gain combining receiver is very similar with that of the optimal receiver, so receive aperture with a large optical collecting area can have nearly the same performance with receive aperture with several smaller optical collecting area. The ultraviolet communication system has large receive aperture, so a receiver aperture is only needed. To improve the error rate performance and the channel capacity, a new hybrid space-time coding approach is proposed by combining V-BLAST and repetition code. The results indicate that the new code combining V-BLAST and repetition code has better performance than V-BLAST and even outperforms the code combining V-BLAST and orthogonal space-time block code (OSTBC). The system has low BER and design can be simple. The findings indicate also that multiple antenna diversity gain is decided by number of the receive antenna and repetition code provide code gain for the hybrid code system on the channel of the ultraviolet communication. Code gain obviously increases with increment of number of transfer antenna used by repetition code and system bandwidth increases with number of transfer antenna used by V-BLAST. The hybrid code provides a method for video and high rate transmission in ultraviolet communication.A new adaptive bit synchronizer based on DDS is brought forward. The synchronizer has adaptive characteristic, so the modified quantities of phase can be self adjustment based on difference of the phase. It has also programmable characteristic, so frequency resolution, trace step size and phase accuracy can be set previously for the need. The analysis results show that the bit synchronizer has high phase accuracy, wide acquisition range, short latch-down time and good adaptation and timing-jitter performance. It can be implemented easily based on FPGA.Original viewpoint or innovative theoretical research is need in doctor paper, and ecumenic project implement is not nearly treated. So design viewpoint, top design or key modules design are only described in this paper. The digital base band system of physical layer is designed and implemented based on FPGA, including many kinds of filteres, AGC, adaptive signal detector, adaptive decision-feedback and fraction-interval equalizer, RS(255,239) channel coding and decoding, clock and frame synchronization and so on.
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