Research And Realization Of Digital Interphone Test Based On PDT Protocol

PDT protocol is the standard of digital trunking communication system proposed by our own country. It is mainly used in police wireless communication and national network construction. PDT is compatible with DMR protocol, which is proposed by European Telecommunication Standard Institute. While digital walkie-talkie products have been designed and produced by domestic manufactures, no company in China develops the test equipment for PDT digital signal. Thus, the main aim of our project is to study the signal test of PDT digital walkie-talkie, including modulation error, symbol offset, amplitude error and the bit error rate test. In order to complete the test of each segment in PDT, we need produce the baseband test signal in the standard of PDT protocol. This paper mainly completes the generation and analysis of the digital signal.This article is mainly based on the data link layer of the whole project. The whole process of sending and receiving message is based on software implementation to complete the formation of test sequence, channel coding and decoding, modulation and demodulation and the analysis of error rate. Firstly, this paper introduces the current situation of trunking standards and walkie-talkie test technology to describe the significance of the project. Then this paper gives three layers architecture of PDT protocol, covering the frame and signaling structure, synchronization and timing sequence, call flows and the principle of 4FSK modulation, which are used in the signal test.The main parts of this paper are the algorithms of channel coding and channel decoding during the data transmission, which are the core algorithms of software implementation. The channel coding can protect signal from interference and improve the quality of communication. There are mainly three key tasks: The first task is to study the BPTC code, which is the most widely used code in PDT protocol, and the decoding order for some possible situations which may not be correctly decoded. The second task is to describe the error pattern polynomial of the quadratic residue code for the EMB check. In this part, the solution analysis and formula explanations are given and the decoding algorithm is improved to meet the demand of QR decoding. The third task is to analyze different decoding methods of Golay which is used to protect the data type. The decoding algorithm which measures the weight of syndrome is chose to be used in theproject. This part mainly analyzes various decoding performance, the complexity of the algorithm and the consumption of resources and select the proper decoding algorithm. Meanwhile, these chapters give detailed decoding procedures and realization process of the software.Finally, this paper builds the software architecture of the data link layer in PDT to implement the test of channel coding and decoding and the simulation of bit error rate. Then analysis of channel coding in the performance of error correction and communication is given through the signal test of BPTC, QR and Golay coding and decoding. Thus, the result of this paper can provide theory support for hardware realization and actual point to point communication performance test.