IPTV Technolog Feasible Research And Implementation Of Tianjin Netcom

With the rapid growth of streaming media services such as VOD, TV programs, videophone, web games and multimedia information broadband Internet provides to home subscribers, IPTV service becomes a hotspot in the broadband multimedia field. As the requirement of IPTV service for the bearer network differs from ordinary go-online service, operators need to make necessary transformation of the existing transmission networks, especially bearer access to meet the requirements for large bandwidth, high rate, manageability, controllability, interaction and security.The high lighted application of IPTV as a carrier-grade service lies in its being interactive and real-time. Therefore, the requirement of IPTV for service quality is extremely exacting. Organizations or forums presently involved in formulating IPTV technical standard are classified into three categories by their research content: the first category is an organization to study and formulate physical layer, link layer basic protocols and coding-decoding standards. It will ensure provision of a unified basic platform for all IPTV realizations. The second category is an organization that studies and formulates protocol interface open control standards. And the last category is the organization to promote the formation of a commercial chain, mostly being in the form of industrial alliance. It forms equipment R&D orientation with basic technical standards, interface protocols combined with specific application modes, and formulates technical realization standards for network layer, service layer, application layer and other upper layers, and ultimately provides service solutions for system integration and operators.Presently four categories of IPTV-based service can be provided: streaming media service, telecom service, games service and information service, with the core service being unicast and multicast of the streaming media service, coding/decoding standard adopted being MPEG-4 and H.264. Of the standards, MPEG-4 uses hierarchical coding technology to adapt to bearer network requirement. Its code rate varies from5Kbit/s-2Mbit/s to ensure the flexibility of streaming media communications. H.264 technologically adopts IP packet-oriented coding mechanism, can support video streaming media transmission in the network, and makes a breakthrough in coding-decoding compression technology. Its code rate is around 1Mbit/s, half of MPEG-4. Therefore, considering IP encapsulation overhead and signaling occupation, the downlink rate of the traffic flow of a set of standard-definition program sources can reach about 2Mbit/s. If high-definition program sources are transmitted, downlink rate of 6-8Mbit/s can be reached. In the case of multicast, greater reproducing forward bandwidth is required of network equipment.It can be seen that IPTV technical standard sets requirements different from ordinary Ethernet transmission on the bearer layer: In management, subscriber and program-oriented network bandwidth management, VLAN functional management, fine cast authority control, channel switch time control and multicast service security and other new functional requirements; in transmission, the streaming media characteristic of IPTV service determines subscribers' need for long occupation of network bandwidth, and the need for real-time assurance of QoS.