The Design And Implementation Of Telephone Gateway Interface In Digital Trunking System

In recent years, digital trunking communication system has come to the sight of people and attracted more attention for its significant advantages, and the tendence that digital trunking communication system will take the place of analogue truking communication system is inevitable in the private mobile communication field. In order to communicate with other systems, there must exist various gateway interfaces in digital trunking communication system. In this thesis, the wireline telephone gateway interface will be researched for the interconnection between digital trunking communication system and wireline telephone systems (such as PABX, PSTN etc.).The thesis begins with the theory, the operation process and principles of the telephone gateway in digital trunking communication system is analysed. Then, the structure of telephone gateway interface and trunk interface are introduced and their functions in telephone gateway are analysed by which a telephone gateway scheme is designed. Meanwhile, the telephone gateway in TETRA system is introduced. In further research, the principle of TETRA speech coding algorithm– Algebraic Codebook Excitation Linear Prediction (ACELP) is introduced and analysed in detail, which is a advanced Codebook Excitation Linear Prediction (CELP). ACELP algorithm replaces the excitation signals with algebraic codebook and uses some technique such as minimizing the mean square error(MSE) and the analysis-synthesis method to obtain characteristic parameters of speech. It can reduce the bit rate greatly and achieve reconstruction speech with high level quality.Based on system analysis, a scheme of telephone gateway interface is presented using TETRA system as an example to divide the interface into two parts: interface signal processing and speech signal processing by different functions whose hardware structures are designed by using MCU and TMS320VC5410 as cores respectively. It is helpful for simplifying system structure and improving system performance. Finaly, the hareware implementation and flow graphs of software design are given.The debugging of the telephone gateway interface which is designed in the...