The Study On Technology And Interworking Of Videotelephone In 3G Network

The current standard of the 3G networks use different air interface technologies, which brings the magnitude of differences in the way of implementation of the videotelephone in 3G network. Although these internal system can communicate with each videotelephone, interworking remains a critical interconnection technical problems because of the absence of standards. Hereby, the technology and interoperability of 3G videotelephone are researched from both theoretical and practical points of view in this paper. A novel gateway structure is designed based on the detailed investigations of the videotelephone interworking theory. The interworking tests are implemented by a simulated gateway using the open-source Asterisk system. The work in this paper provides a possible way of achieving interworking of videotelephone, and thus has the strong practical and engineering significances.In theoretical aspects, The technical characteristics of videotelephone service are analyzed under the various standards of 3G networks, including the 3G-324M-based technology in WCDMA/ TD-SCDMA system in the CS domain and the SIP-based technology in cdma2000 systems in the PS domain. An ISUP-based approach of video interconnect gateway between 3G-324M and SIP is designed including the logical structure and function module, address and data conversion mapping, message structure and code mapping, signaling processes and state machine. The technical feasibility to realize the videotelephone exchange in CS and PS domains is discussed. In practical aspects, the Asterisk system is used to simulate the VIG for testing the videotelephone interworking in various standard protocols. Based on the analysis of the function modules and calling flow of Asterisk system, the libh324m videotelephone interworking module is compiled and debugged in the Ubuntu operating system. After that, three experiments are performed in the lab environment to verify our design, which are the interconnections between the SIP videotelehone terminal in LAN, between SIP terminal and WiFi mobile terminal in WLAN, and between the UMG8900 and the interface of Asterisk hardware in WCDMA. Besides, the interoperability between 3G-324M and SIP terminal in actual 3G network environment is tested. These experiment results show that the designed VIG structure and the method using Asterisk to simulate the VIG have significant reference value for achieving interworking videotelephone under different standards.