[Photo] on the IPTV access network solutions, research and application-IPTV, acc
Summary outlines the implications of IPTV development driving force, IPTV access network business requirements and current status of the access network of networks, from the network scheme, authentication, multicast, QoS assurance programs and four aspects, proposed IPTV access network design.
1, IPTV video services to develop a good choice
1.1 IPTV meaning IPTV (Internet protocoltelevision) refers to the use of broadband network infrastructure, computer (PC) or "ordinary TV + Internet set-top box (TV + IPSTB)" as the main terminal, to provide users with live television, video-on-demand video content-based applications of new technologies [1].
1.2 driving force for the development of IPTV
With the Internet to advance the era of broadband, Internet technology and application of more and more consumers into the domestic life, entertainment and work. Good prospects for broadband Internet applications and guide the global telecommunications industry to increase the content of Internet application development, training and market forward, and IPTV to the liberation of the traditional broadcast TV time limits on people, so that television can be personalized and truly interactive.
The domestic fixed-line operators, the development of IPTV business must have a variety of internal and external driving forces:
1) continued decline in traditional telecom services increased, the value-added video class business seeking new ways of sustainable development into its a good choice;
2) only relies on Internet business, because of its scarcity, poor earnings, may wish to make full use of their own superiority cut into the existing broadband network, which provides for the development of IPTV business the original driving force;
3) the development from the perspective of the evolution of NGN, IPTV is the future of a typical business has great prospects for industrial development [2];
4) As part of the foreign fixed-line operators to carry out the bullish trend of IPTV business development, domestic and foreign equipment providers, content providers invested considerable human, financial, industrial environment has begun to take shape, enhanced solid IPTV network operator involved in confidence and determination.
IPTV is one of the most important features of broadband interactive real-time, so that it is different from traditional cable television, but also different from the currently emerging conventional digital TV. IPTV enables users no time limit, can always choose the form of diversification, ease of operation and personalized interactive multimedia services, and can take various effective broadband access, such as xDSL, LAN, FTTH / FTTP (Fiber to the home / fiber to the resident), WiMAX and other high-speed access technologies, in order to maximize user-friendly personalized broadband applications.
2, IPTV service on the existing access network challenges
2.1 IPTV service requirements on the network
IPTV business is to provide users with high-quality digital audio and video services, the effect of the image has higher requirements, the need to control the quality of the image. The rate determines the video signal image and the quality of IPTV, the higher the rate, the higher the image quality grade accordingly, a corresponding demand for broadband increases.
IPTV business, high-definition (HD: high definition) or SD (SD: standarddefinition) the quality of uncompressed digital video to be in dozens of Mbit / s transmission rate can, in order to reduce the transmission bandwidth and storage requirements, Video must be sent in compressed form. Video compression technology, IPTV services selected determines the bandwidth requirements of users. The two mainstream industry's current technology MPEG4 and H.264. MPEG4 encoding format of the program to provide quality SD programs generally require the customer opened 3Mbit / s over broadband, and almost no possibility of improvement; and H.264 format, the program code corresponding quality programs generally require the customer opened 1.5Mbit / s over bandwidth can be at the same time, with the H.264 encoding technology, the future is expected to develop in the 1Mbit / s to provide the following standard definition DVD quality image.
Analysis of the above two codes, IPTV users to receive video stream data, generally at least 1.5Mbit / s of bandwidth requirements, coupled with the agreement of 10% -20% of the package overhead, signaling control channel flow and the appropriate IP fluctuation margin, the proposed plan for each IPTV users 2Mbit / s over the bandwidth.
IPTV platform bearer network should first ensure the availability of IPTV services, which ensure the authentication of users through the use of business anytime, anywhere; secondly, to ensure that operational response time of the user within a tolerable range, so that users do not too long because the connection is established to give up using business; again, to ensure that the visual effects business, especially audio and video business clarity and fluency. These requirements reflect the level of the bearer network, namely, bandwidth, network delay, jitter, packet loss and reliability. Enough bandwidth to provide the basic conditions for good quality of service, delay, jitter, packet loss three network parameters are the most basic network-layer QoS indicators; In addition, the reliability of the network but also to provide an effective, in the link or node failure occurs circumstances, to promptly detect and take appropriate measures to ensure uninterrupted business or rapid restart.
2.2 existing IP network, inadequate
Existing broadband access network is basically for the WWW, E-mail, FTP and other traditional Internet business design, and although it provides Web-based video (such as online TV and video communication), etc, but the distance truly commercial-scale operations there are still a large gap between performance in the following areas:
1) structure is unreasonable, insufficient bandwidth.
Over existing broadband networks with centralized plug-BRAS (Broadband Remote Access Server), a single BRAS first million users processing thousands of business flow, throughput is limited, while access layer DSLAM (digital subscriber line access multiplexer) / LANswitch are multi-level aggregation, bandwidth convergence than the big, the actual average bandwidth per user only 100kbit / s around with trillion required for IPTV business than the premium required for IPTV bandwidth, a far cry.
2) can not support Quanchengquanwang multicast.
For historical reasons, the existing metro / access network routers, L3/L2switch, DSLAM multicast capability uneven, not Quanchengquanwang support multicast [3]. Although the unicast can be adopted to provide live TV services, video servers, network equipment, overwhelmed, network expansion can not keep up the user develop quickly lead to network congestion, quality of service decline.
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