Key Technologies Of DMR Communicationsystem And Its Application In High-speed Railcommunication

Dedicated wireless communication technology is playing an increasingly important role in modern society.As a widely used technology in the field of dedicated communications,the digitalization of wireless intercom technology is also an inevitable trend.Extensively used in station dispatch and traffic management DMR(Digital Mobile Radio)technology is developed by European Telecommunication Standardization Association and becoming the main protocol used in international digital wireless intercom systems.Starting with the basic protocol of DMR digital wireless communication protocol,the thesis studies the key technologies in the protocol in depth,and the performance of the system is investigated in special scenarios,such as competitive access,high mobile communication and so on.Firstly,the thesis summarizes the research background and current research situation of dedicated wireless communications,with the focus on DMR system at home and abroad.Then,starting with the protocol hierarchy structure,we elaborates the function of each hierarchy and focuses on the key technologies of the system.Secondly,the thesis studies the bit error performance of commonly used channel coding methods in DMR protocol,involving Hamming coding,Golay coding and BPTC(Block Product Turbo Code)coding.The DMR simulation system is constructed here to simulate the BER performance of the above channel coding schemes.Moreover,the theoretical analysis results of BER are derived to verify the performance.Furthermore,we propose to improve the DMR protocol in the case of access competition scenario.DMR system uses color code control to realize the process of channel access.The access channel levels of different users are distinguished by the color code(CC,Color Code)carried by DMR users themselves,and users of different access levels adopt different access strategies.In order to solve the problem of information congestion caused by multi-user communication in DMR system,we consider combining the random competitive access protocol with the color code control protocol of DMR system itself.The introduced random competitive access protocols include pure-ALOHA,slot-ALOHA and np-CSMA protocols.We analyze the relations between terminal traffic and throughput,as well as that between traffic and the number of delay packets through simulation so as to obtain the access performance of different competition protocols introduced in DMR system,on the basis of which,the best solution of multi-user information congestion under different conditions of DMR protocol is provided.Finally,based on the special scene of high-speed train-to-ground communication,the performance of DMR communication system is simulated,and the influence of moving speed on coherent and incoherent reception performance is evaluated.Furthermore,we propose to improve the performance of DMR system by applying multiple antenna technology in the environment of high-speed railway communications.