The Research And Simulation Of Demodulation And Synchronization Algorithm In The System Of Digital Mobile Radio

DMR (Digital Mobile Radio) is the latest digital mobile communication system which the ETSI (European Telecommunications Standards Institute) is developing. As the new communication system, DMR is engaging more and more concentrations from communication organizations and device providers. The 4FSK recommended by DMR system is the continuous phase frequency shift keying (CPFSK), which has very good spectral properties because of its phase continuity. With the rapid growth of the needs of spectrum, CPFSK is gradually attracting people's attention. It has better spectral properties than PSK and FSK signal due to its smooth phase shift, and makes out-band power of CPFSK less than PSK and FSK signals. In addition, constant envelope of CPFSK signal is easy to be enlarged, which is critical attention in mobile communications in the land.In this paper, differential demodulation and synchronization algorithms of 4FSK are studied in DMR system. Firstly, the principle of Time Division Multiplexing technology that is adopted by DMR is studied, and synchronization problems required in TDM system are analyzed. Secondly, the demodulation algorithms of 4FSK signal are studied. And the coherent demodulation used commonly is compared with differential demodulation in this article. Thirdly, for differential demodulation,two kinds of timing algorithm and improvements in application are proposed, joint synchronization algorithm and statistical algorithm. Finally, the programs of the symbol synchronization and frame synchronization are imitated by Matlab. The results of the simulation prove the reliability and accuracy of the differential demodulation and synchronization algorithms.The differential demodulation and synchronization algorithms are adopted successfully for 4CPFSK in this issue. Statistical algorithm has advantages in computational speed and design so that the symbol synchronization could be achieved fast. The joint synchronization algorithm could consider the symbol synchronization and frame synchronization together, and it is able to determine the symbol synchronization very accurately while achieving a frame synchronization, which improves performance of the system.