Research On The Transmission Techniques Of Modernistic Wireless Digital Communication

With the plentifulness of the Internet resources and the development of the 3G mobile communication network, customer request correspond by communication contents to continuously increase and this needs make the system capacity, transmittable velocity, communication quality and the safety of wireless communication become hot point in the study field of wireless wideband transmission today. Based on the communication engineering applications, this thesis study the intelligent transmission technology and the performance of the spread spectrum modulated sequence. In this thesis, some own conclusions have been concluded and testified using communication simulink under the possibility of the applied environment.In chapter one, the transmission characteristics for the wireless channel and the performance parameters of the spread spectrum modulated sequence are analyzed. At the same time, the research background and significance are introduced. Finally, the main contents of the research are pointed out. In later several chapters, efficient and dependable transmission technology is studied in detail with theories analysis and computer simulink.Chapter 2 is detailed to introduce the realization principle of the adaptive multilevel modulation and its deciding threshold of choosing modulated method aggregate under the single channel, and discussed some main parameters that have great impact to modulation performance. Based on the existent theory and the engineering application, the thesis study the good performance by combined the adaptive modulation technology and the multilevel modulation technology on the simulink model. Experiment results show that this combination bring on the high data transmittable efficiency and the well transmission quality. This chapter is a base of next chapter.Chapter 3 studied the results that come from the combination of the multi-carrier transmission technology and the adaptive multilevel modulation technology in detail, and bringed up to apply the technology to wireless channel transmission. The feasibility and advantage been testified by computer simulink. Multi-carrier adaptive multilevel modulation technology maybe regards as a kind of transform combination by n single-carrier adaptive multilevel modulation technology approximatively. Multi-carrier transmission can improve performance of the attenuation consumedly but single-carrier transmission can't. Based on the communication engineering application, several practical problems been discussed after introducing multi-carrier adaptivemultilevel modulation principle. In thesis, alterable channel model been designed and realized dynamic choosing modulated method aggregate to subchannel, and theoretic analysis and computer simulink keep consistent.In chapter 4, the spread spectrum modulation sequence performance is discussed on the base of the multiple address selected ability and secret communication. This chapter is a base of next chapter. Mathematics theory and pseudo stochastic code theory for spread spectrum modulation sequence are introduced, and simulink experiment and analysis about correlation performance of the most common use spectrum modulation sequence are processed, these experiment contact to performance parameters of the spread spectrum sequence. The correlation performance and address quantity are compared between m sequence and Gold sequence.Chapter 5 is detailed to discuss the produced principle, correlation function and application of Gold code. From several aspects, the chapter studied the balanced Gold code in-depenth. The balanced Gold code is well performance spread spectrum modulation sequence. Simulink and analysis about balanced Gold code from correlation and power spectrum density curve are processed. At the same time, simulink experiment of BER performance on the base of theory analysis using designed spread spectrum system model.In chapter 6, the summary of this thesis is made and review all works. The questions still in this subject are discussed, and the further development and researc...