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

The centralized WLAN structure VoIP voice quality evaluation system

Author YanYiZuo
Tutor SunWeiChi
School Fudan University
Course Software Engineering
Keywords Centralized WLAN VoIP Packet loss Delay Shake E-Model
CLC TN916.2
Type Master's thesis
Year 2010
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With the rapid development of WLAN and VoIP technology , Voice over IP over WLAN transmission has gradually become a hot topic , VoWLAN concept came into being . However, due to the instability of the wireless medium , the VoWLAN voice quality can not reach the level of the conventional telephone . Based on the the centralized WLAN structure of voice quality assessment methods can provide an objective basis to improve the quality of VoWLAN voice . In this paper, the characteristics of the centralized WLAN for the main factors affecting the quality of VoIP voice study voice quality evaluation method proposed improved E -Model design VoWLAN voice quality evaluation system based on the model . Specifically, the paper first studies the key technologies in WLAN and VoIP detailed centralized WLAN architecture and H.323 protocol . Then VoIP centralized WLAN introduces the the VoWLAN basic concepts , it analyzed the problems and solve these problems , the the IEEE802.11 protocol and centralized WLAN structure support of VoIP technology , including IEEE802 .11 e and - CAPWAP the QoS achieve , radio resource management techniques and subnets seamless roaming . Second , the analysis of the affect VoWLAN voice quality , packet loss , delay , jitter and wireless signal strength of these key factors , the proposed VoWLAN QoS metrics , and voice quality evaluation method . Focus on the E-Model, and improved representatives jitter parameters . On this basis , the design based on the improvement of the E-Model VoWLAN voice quality evaluation system . The system captures the RTP / RTCP data stream carrying VoWLAN NIC UDP packet to analyze and calculate the delay and packet loss parameters based on inside information , combined with Hurst coefficient encoder jitter buffer size parameters , improved E-Model calculated MOS scores reflect the voice quality . Finally , based on the centralized WLAN architecture design simulation experiment , experiment using NISTNet software to simulate real network environment , packet loss , delay and jitter . VoWLAN voice quality evaluation in the experiment , while the use of the present system and PESQ evaluation method , after contrast, the present system and mature PESQ Evaluation on the same voice of the MOS score is quite proved the effectiveness of the VoWLAN voice quality of the system evaluation .

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