The Research On The Realization & QoS Of VoIP Over HFC

Voice-over-IP (VoIP) is a new communication technology to transfer audio data through IP packet-based network, gradually developing from 1970's. Hybrid Fiber Coaxial (HFC) plants are an one-way transport medium for Community Antenna Television (CATV). With VoIP and data services rapidly extending, HFC plants operators are quickly recognizing the need to upgrade their network infrastructures for two-way services. Since wideband HFC plants can support multiple services on two ways after upgrade, HFC plants operators in some area begin offering data services. Offering VoIP services on Softswitch platform is a cost-effective way for operators to take advantage of the HFC plants, grow revenue and move quickly into new markets.At the first beginning of the dissertation, the developments and advantages of VoIP over HFC is presented. The key technologies of access layer, transport layer, control layer and application layer are also studied.Then, the dissertation discusses three essential problems of VoIP over HFC in detail. The first problem is how to cooperate with existing public telecom networks. Three models are recommended which are Local Convergence, CPN+IP and CPN+PSTN, and then these models are compared with one another. The second problem is residential audio access. There are four models expounded which are Group Access, SOHO Access, Intelligent Terminal Access and IP Telephone Booth Access. Each model has their own characteristics and fit different subscriber. The last problem, but not unimportant, is how to reduce the noises and distortion in the upstream channel of HFC plants. There are many kinds of sources that bring noises or distortion in the upstream channel of HFC plants. Different noise or distortion should be reduced in different ways that are analyzed in the dissertation, too. After resolving the former three problems, the dissertation brings forward a realization scheme of VoIP over HFC on the base of the factual market environment of Changsha city.Finally, test contents and test method are both given for VoIP over HFC system.VoIP over HFC provide an end-to-end IP telephone scheme, which is active to accelerate the merging of TV network, telephony network and computer network. In one word, VoIP over HFC has a bright feature.