Multimedia Services Over Terrestrial Cable Television Networks

Cable Television (TV) networks deliver TV broadcasts from TV stations to cable TV subscriber homes. Digital TV broadcasts using VHF and UHF frequencies between 47 MHz to 862 MHz. Each TV channel occupies 6 MHz bandwidth and modulated using 64/128/256 QAM before combines together with all other channels at the cable TV headend. Coaxial cables are used to deliver the TV RF signals to the subscriber homes. The frequency band below 47 MHz is used to carry return path traffic from the subscribers to the cable TV headend.In order for the cable TV network to delivery high speed data services, a set of cable network communication interface and operation support standards call DOCSIS (Data Over Cable Service Interface Standards) are developed by the cable industry. There are four version of DOCSIS; Versions 1.0, 1.1, 2.0 and 3.0. DOCSIS 1.0 enables cable TV operators to provide internet access up to 36 Mbps downstream over their HFC (Hybrid Fiber Coax) networks. Version 1.1 adds QoS (Quality of Service) capability to enable cable TV networks to deliver voice and streaming services (IP multicast). Version 2.0 enhanced the upstream speed (30 Mbps maximum) using 64 QAM modulation and 6.4 MHz upstream channel bandwidth to accommodate increase in demand of symmetric services (e.g. IP telephony). DOCSIS 3.0 significant increases the downstream speed (to 160 Mbps) and upstream speed (to 120Mbps) by bonding multiple upstream and downstream channels. Version 3.0 also introduces support for IPv6.PacketCable is another cable industry standards developed to provide packet based voice, video and other high speed multimedia service over HFC cable systems. PacketCable is a set of protocols developed to deliver QoS enhanced communications services using packetized data transmission to a consumer’s home over the cable network. PacketCable network architecture support toll quality VOIP (Voice over IP) services and allows connection of a plain analog phone using an Embedded Multimedia Terminal Adapter (EMTA). It supports primary and secondary residential voice line with battery backup capability. PacketCable leverages QoS capability of DOCSIS 1.1/2.0 and will support SIP (Session Initiation Protocol) in version 2.0. While the initial service offerings for PacketCable product line are Packet Voice and Packet Video, the long term objective encompasses a large family of packet based services such as Virtual Private Network (VPN), real time interactive video sessions, multimedia telephony, interactive gaming and media streaming.The two main components in DOCSIS are the Cable Modem (CM) in the subscriber premise and the Cable Modem Termination Systems (CMTS) in the cable operator headend. DOCSIS specifies the physical and MAC layers communications interfaces between CM and CMTS. PacketCable networks use IP as the basis for robust multimedia architecture. PacketCable architecture supports end-to-end functions including signaling for services, media transport at variable QoS levels, security, provisioning of the client device, billing, and other network administration functions. PacketCable VOIP telephone service uses a managed IP network instead of the public internet to carry its voice traffic. PacketCable specifications for Voice over IP (VoIP) describe the basic functions that are typically consolidated onto a single Class 5 central office switch. These functions can be implemented across multiple elements or can be consolidated onto a single element, which leads to a low cost, highly flexible, scalable distributed architecture.With the deployment of DOCSIS and PacketCable network architecture, cable operators can become full service providers of triple play of voice, data and multimedia services. Cable operators can also use their cable network to provide CableHome services such as remote control, management and diagnose of customers’ home network (router, firewall, network address translation, secure software download, etc) and other devices.

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cable TV Network,DOCSIS,PacketCable,QoS,CM,CMTS,VOIP,Multimedia,EMTA,HFC,CableHome,IP Multicast.VPN


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