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The Research and Test of Voice Quality in VoIP System

Author: LiMin
Tutor: LiuJinGao
School: East China Normal University
Course: Communication and Information System
Keywords: VoIP Shake Adaptive jitter buffer algorithm Voice Quality
CLC: TN916.2
Type: Master's thesis
Year: 2008
Downloads: 164
Quote: 2
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Abstract


VoIP (Voice over IP) is a new communications technology developed in recent years. It is the result of the fusion of network packet and network business combination of the two mainstream technologies. Rich because of its low cost of communication and support business, so it's in full swing, is encroaching on traditional PSTN phone market. However, VoIP is a real-time voice communication requires a certain amount of network transmission quality assurance. Current Internet service does not meet this requirement, resulting in the current VoIP service unsatisfactory stability and OOS. Which has become its further development of the main obstacles and challenges, but also one of the major problems to be solved by the IP phone. The scientifically reliable measurement and evaluation of the quality of the voice is a crucial prerequisite to improve the VoIP technology. There are many factors affecting the voice quality of VoIP, which is mainly caused by the inherent characteristics of the IP network, including network delay, jitter, packet loss, out-of-order. These transmission impairments will directly affect the voice quality or call between exchanges, thus affecting the entire VoIP communication. Damage parameters are largely dependent on the receiving end of the playback buffer mechanism. Therefore, to improve the voice quality of VoIP, VoIP communications system jitter processing. Jitter buffer neither too long nor too short, so as to ensure a better balance between the packet loss and delay. Most of the communication system using adaptive jitter buffer algorithm to solve this problem. The main work and contributions of this paper are reflected in the following aspects: 1, studied several key factors that affect voice quality in VoIP communications, and analysis of solutions. 2 on VoIP voice quality objective and subjective test methods. And a new method of testing voice quality. In this method, based on the PESQ and E-Model, a combination of the two proposed a nonlinear regression models for different codec. 3, elaborated jitter formation and the impact on voice quality. Focuses on the analysis of seven kinds of adaptive buffer algorithm, and designed on the basis of an improved adaptive jitter buffer algorithm to better adapt to different network environments, and optimize the voice quality purposes. 4, design a simple and effective voice quality test system, test the above algorithms, a comparative analysis of the test results. The results show that, the the new jitter buffering technology has better network adaptability, to a greater extent to reduce packet loss, jitter, out-of-order, showing superior performance.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Communicate > Phone > Telephone lines, telephone network
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