Dmr Terminal Symbol Synchronization Technology

According to the survey of the global trunking communication technology and market by the well-known international consulting firm IMS, it is an important period for trunking communication system’s transition from analog to digital between2008and2013. As the latest digital trunking communication standard proposed, the DMR (Digital Mobile Radio) is getting more attention, and the number of companies which support the standard is also increasing.In the DMR communication system, because of the factors such as the delay of the channel and time offset between sender and receiver, the receiver could not sample and judge the symbols in the right sample and judge moment ever, resulting in some certain distortion between the recovery signal and the signals from the sender. In order to solve the above problems, the receiver must manage to obtain accurate sampling judgment moment in order to recover the signal that closer to the original signal. Therefore, the fast and accurate timing and synchronization is critical for the DMR transmission system.Firstly, according to the requirements of the DMR burst communication, this study uses the feedforward symbol synchronization structure in the all-digital receiver. Digital filter and square time recovery algorithm is used in the structure to work out the symbol delay value of the output signal of matching filter in this structure, then considered the optimal sampling interpolation points with the symbol delay value, the interpolation points and use the code matched filter interpolation filter, this thesis uses linear interpolation in the interpolation filter.Secondly, according to the design of DMR symbol synchronization algorithm, this thesis proposes the division and design functional modules of the symbol synchronization system, which can be divided into three sub-modules, they are symbol timing offset estimation module, interpolation control module and interpolation filter module, with the design of each sub-module including the module function interface and software processes. On this basis, this thesis gives Verilog functional simulation of sub-modules of the symbol synchronization system.Finally, test the performance of the communication between two DMR mobile terminals, which work on the half-duplex and direct mode, while the test contents include the wireless half-duplex test without symbol synchronization module, base-band half-duplex test and wireless half-duplex test with symbol synchronization module.In brief, this thesis designed and realized the symbol synchronization algorithm on the FPGA platform. It also meets the requirements of the DMR burst communication, so it has some construction value and practical significance.