| DMR is a digital wireless communication standard proposed by the European Telecommunications Standards Institute and formally approved in 2005. It is developed specifically for the users of mobile wireless communications. DMR standard supports voice communication, data transmission and other complementary services. It can improve the spectrum efficiency, increase communication capacity and reduce system cost. The wireless communication services that DMR protocol supplies are not only more clear and reliable,but also more convenient and efficient than the traditional ones.The research of DMR protocol tends to be mature at abroad. However, it has just begun to be studied in recent years in our country because of its late introduction. Since most studies are based on DSP platforms, which are inconvenient for subsequent extension and upgrade. In this paper, we focus on the DMR trunking communication standard, research the baseband key technologies of DMR signal and implement these key technologies on a scalable software-defined radio platform.Firstly, we design the baseband link simulation of DMR signal. DMR adopts 4CPFSK modulation, and belongs to burst communication system. We design DMR baseband link simulation based on the consideration of system complexity and communication performance. Simulation results show that when Eb/N0 is 12 dB, the bit error rate is less than 10-3, which fully meets the needs of DMR voice communication.Secondly, we propose an overall design scheme of the DMR baseband signal processing. According to this scheme, we divide the whole digital signal process into multiple modules and implement the algorithms of each module on FPGA. After that, we verify the correctness of the scheme by functional simulation on this FPGA test platform.Thirdly, we test the functions and performance of the proposed DMR baseband link. By using the chipscope, an on-line debugging tool of FPGA, we capture and analyze the output of each module. According to ours analyzing result, all the modules on the software-defined radio platform have been verified. What’s more, we also hold the point to point communication test in direct mode by adding noises to imitate the real communication environment. During the test, we find that when the Eb/N0 is 14 dB, the bit error rate can be achieved 10-3 level, which meets the voice communication requirement.This paper proposes an implementation method of the baseband key technologies of DMR. It not only provides a reference for the future development of DMR, but also has much value for pre-research. |
