Design And Implement Of VoIP Telephone System On Train

The development of Internet increases the progress of other technology. The traditional telephone service based on circuit switch now has been instead by package-based IP net telephone technology, and now the IP telephone technology has been quite mature. VoWLAN is extended and updated to VoIP. The user can be more convenient and more direct with wireless VoIP telephone. User can communicate freely inside WLAN coverage via VoWLAN terminals, which reflect the lower cost of IP network, also make the user got convenience from WLAN.The theory part of this thesis firstly introduce the VoIP develop background and application characteristics, describe the theory of VoIP, and then emphatically discuss the voice coding technology, especially the theory of G723.1 and G729. The protocol of VoIP: H.323 and SIP also is analyzed and meanwhile make contraction. The concept and optimize method of QoS also be introduced. Regarding the VoWLAN, firstly, the relative standards and protocols are given, then the application styles and technology advantage are introduced, lastly, all factors of using VoWLAN to be considered are discussed.The VoWLAN technology has been mature enough, though, it is seldom used in railway coach. Many issues need be considered and solved when integrated. The most important issue is creating the base IP and WLAN networks. This thesis creates a simplified molded train Ethernet network with redundancy function combined with railway coach real situation. The network characteristics: contracture level clear, easy operation and maintenance. To achieve the special situation of railway coach and comply with railway standards, this thesis takes emphasis on system realized solution, and then describes the telephone configuration. At last, also makes further discussion for extension and usage. The railway coach VoIP-VoWLAN telephone system now had passed the system test. The result shows the system complies with relative standards and technical specification, and got the acceptance by final customer.