Studying For Voice Gateway Based On New HFC Networks

Along with incessant improving of internet and increasing demand for"Convergence of Three Networks"of people in the comprehensive information age of twenty one century, video, voice and data services are unified for one network platform. The thesis introduces New HFC Networks shall be the best choice of broadband integrated service net. This network can overcome the serious effect of funnel noise existing in old one. New HFC Networkss can provide integrated services including digital TV, IP phone and data transmitting. New HFC Networkss voice gateway which researched in the paper depends on this network is a component of the New HFC Networks IP phone system.Firstly the sense of this research is narrated in the paper. New HFC Networks has plenitudinous bandwidth. In this network voice data need not to be compressed and New IP phone has many advantages like more simple structure, lower cost and better timbre. However, due to the New HFC Networks IP phone uses the uncompressed voice data that can not to communicate with common IP phone comes from Internet, the code conversion is needed. The primary functions of New HFC Networks voice gateway is voice code protocol conversion in the boundary of different network and insure voice communicate rightly. Therefore, it is significant to research and design the New HFC Networks voice gateway for New HFC Networks IP phone servers.Based on the characteristics of New HFC Networks IP phone in this paper, function requirements of New HFC Networks voice gateway are analyzed. The primary function of the voice gateway is converting code of the grouping voice which acrossed it. But grouping voice is mixed with other data, the voice gateway must separate the voice which is mixed in data stream by some filter mechanism. So, function partition about voice filter module, voice processing module and Ethernet interface module were compartmentalized in the paper. The overall scheme of New HFC Net work voice gateway is designed and discussed two possible disposing instances of the voice gateway.The pivotal technologies of New HFC Networks voice gateway are studied and analyzed in the paper. In the audio compressing part, the audio code standard and souce code and the bit range order of G.711, G.729 and G.723.1 are analyzed. For ensuring the transport of real-time services of audio data, UDP and RTP/RTCP that used for real-time data transport are introduced and analyzed. In the audio data filtering part, an arithmetic and program used for separating voice and data is schemed out based on characters of the bit range order of different audio code and IP encapsulation of each different transport protocols. Generally, grouping voice is encapsulated in a fixed length, the voice gateway could filtrate most data that the grouping length is not up to the mark. Voice and the a few data which has the equal length mixed together after that. Voice gateway must identify the transport protocls of grouping voice to rightly separate the voice which need to be processed. In the last of this paper, testing environment of pivotal programs is introduced; program flow and outcomes of environment test are showed also. It is proved by the outcomes of test that: the software which is designed for voice gateway could accomplish its work reliably in simulated environment and fit the requirements of design.