AnalysisoftheStatus Quo of IPTV Technological and Service Development

    目前，随着宽带互联网向家庭用户提供视频点播、电视节目、可视电话、网络游戏、多媒体信息等流媒体类业务的迅猛增长，IPTV业务也随之成为宽带多媒体领域中大家关注的热点。由于开展IPTV业务对承载网的要求有别于普通上网业务，因此，运营商需要针对IPTV业务对既有传输网络尤其是承载接入进行必要的改造，以达到大带宽、高速率、可管理、可控制、具备交互性和安全性的要求。

    Withtherapidgrowth 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.

    一、IPTV技术及标准情况

    I.IPTV Technology and Standard

    IPTV作为一种电信级业务，其亮点应用在于它的交互性和实时性，因此IPTV对服务质量的要求是非常苛刻的。目前参与制订IPTV技术标准的组织或论坛按其研究内容分为三类：第一类是研究并制定物理层、链路层基础协议和编解码标准的组织，它将确保为所有的IPTV实现提供一个统一的基础平台；第二类是研究并制定协议接口开放控制标准的组织；最后一类是推动商用链条形成的组织，并多以产业联盟、工业联盟的形式存在。它将各种基础技术标准、接口协议结合具体应用模式形成设备的研发方向，并制定网络层、业务层、应用层等上层的技术实现规范，最终为系统集成及运营提供业务解决方案。

    Thehighlightedapplicationof 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.

    我国IPTV标准的研究和制订工作是从1995年下半年开始的，由中国通信标准化协会专门成立了IPTV特别工作组，开始启动六项标准的编制：IPTV业务需求、IPTV业务系统总体要求、IPTV业务平台与内容平台接口、IPTV业务平台与机顶盒接口、IPTV的DSLAM设备要求以及IPTV机顶盒设备技术规范。对于运营商来说，最值得一提的是在这首批六个标准中，关于承载接入的《IPTV的DSLAM设备要求》就被纳入其中，可以看出IPTV自身业务平台中和网络承载接入互相形成一个完整的体系，是IPTV业务发展的关键因素之一。

    InChina,researchand formulation of IPTV standards began in the latter half of 1995. China Association of Telecom Standards set Special Working Group on IPTV to start formulation of 6 standards: Technical Standards for IPTV Service Requirements, Overall Requirements of IPTV Service System, Interface between IPTV Service Platform and Content Platform, IPTV DSLAM Equipment Requirement and IPTV STB Device. For operators, it is most worth mentioning that of the first six standards, IPTV DSLAM Equipment Requirements concerning bearer access was included. This shows that the IPTV service platform, together with network bearer access, forming a complete system, is one of key factors for IPTV service development.

    二、IPTV的业务发展分析

    II.Analysisof IPTV Service Development

    在国际上，美国、日本等电信基础设施发达的国家已开始运营IPTV业务，IPTV业务也成为一个极具前景的产业。在国内，中国宽带用户市场强劲的增长为IPTV业务的应用奠定了坚实的基础。TV目前已经被广大用户所普遍认可，而IPTV作为TV的深入应用，同时又在此基础上增加了与用户之间的互动性，可以更好地让用户参与其中。目前看来，IPTV业务从电视应用发展而来同时又融入了通信的元素，与传统电视有所区别，两者又进行了互补，但作为一个新兴的业务，IPTV要吸引用户则需要具有核心竞争力的节目内容，这也是IPTV下一步发展的核心要素之一。

    Internationally,countrieslikethe U.S., European countries and Japan having well-developed telecom infrastructure have begun to operate IPTV service, which becomes a most promising service. In China, the strong growth of the broadband user market lays down a solid foundation for the application of IPTV service. TV has got universal acceptance from users, and IPTV as an in-depth application is added interaction with users, enabling better participation by users. It seems that IPTV service, grown out of TV applications and converged with telecom elements, differs to some extent from traditional TV. They complement each other. But as a newly emerging service, IPTV needs competitive program contents in order to attract users. This is also one of core elements of next development of IPTV.

    目前，IPTV在我国已经经过了试点、总结、创新三个阶段，由于相关运营牌照都集中在广电总局下属的集团和企业，电信运营商还很难涉足，因此目前主要是由广电自主开展运营。综合来看，在上海、哈尔滨、河南等地的应用情况主要局限在酒店、高档社区，但仍然是高投入低产出，因此不少相关企业对国内发展IPTV仍缺乏信心，导致产业投入不足，这也在一定程度上影响了产业链条各个环节发展的力度。在IPTV普及率不高的情况下，由于其核心技术主要掌握在飞利浦和德州仪器两家企业手中，因此其产品的价格一直居高不下，这也在一定程度上制约了IPTV产业的发展。在IPTV的产业链上，表面上看其核心部分是内容及应用推广，但实质是要进行资源合作和价值整合，因为要克服内容上的政策和版权等问题，要克服机顶盒等设备专利问题，需要电信和广电合作开展，多方携手共同推动才能在短时间扭转产业发展不利的态势。

    InChina,IPTVhas gone through three stages of experiment, summing up and innovation. As relevant operation licenses are concentrated in groups and enterprises under the State Administration of Radio, Film and Television, telecom operators are hard to set foot there, so IPTV is now still operated independently by the Radio and Television sector. Generally, applications in places like Shanghai, Harbin and Henan are mainly limited in hotels and high-end communities, but high input and low output remains. Therefore, quite a few enterprises concerned still lack confidence in developing IPTV, resulting in insufficient industrial input. This also affects, to a certain extent, the development intensity of the links in the industrial chain. With lower penetration rate of IPTV, core technologies mainly held in the hands of Philips and Texas Instruments, the price of the products remains high, which also restricts the development of IPTV industry to a certain extent. In the IPTV industrial chain, its core superficially is content and application promotion, but essentially is to conduct resource cooperation and value integration. This is because to overcome content-related policy and copyright issues and to overcome patent issues concerning STB (Set Top Box) and other devices, cooperation between telecom and radio & television sectors is required. Only by joining hands to push forward can we put an end to the unfavorable development trend.

    三、IPTV业务对承载接入的要求

    III.Requirement of IPTV Service for Bearer Access

    目前，基于IPTV可提供流媒体服务、通信服务、游戏服务和信息服务四类服务，其核心业务是流媒体服务中的单播和组播，所采用的编解码标准是MPEG-4和H.264。其中，MPEG-4标准通过分级编码技术来适应承载网络的要求，其码率从5Kbit/s～2Mbit/s可变以保证流媒体通信的灵活性；H.264标准在技术上采用了面向IP包的编码机制，可以支持网络中视频流媒体传输，并且在编解码压缩技术上取得了突破，其码率仅在1Mbit/s左右，是MPEG-4标准的一半。因此，一套标清的节目源在考虑IP封装开销及信令占用等情况下，其业务流下行速率可达2Mbit/s左右。如果传送高清的节目源，则可达6～8Mbit/s的下行速率。在组播的情况下还需要网络设备具备更大的复制转发带宽。

    Presentlyfourcategoriesof 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.

    可以看出，IPTV技术标准对承载层面提出了不同于普通以太网传输的要求：在管理上针对用户和节目的网络带宽管理、VLAN功能管理、精细播放权限控制、频道切换时间控制和组播业务安全等新的功能要求；在传输上IPTV业务的流媒体特性决定了用户需要长时间占用网络带宽，而且要实时保证网络的QoS。

    Itcanbeseen 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.

    在我国，IPTV业务是主要面向家庭用户的，目前IPTV业务承载接入网部署有三种方式可供选择：PON方式、LAN方式和DSL方式，这三种方式的选择要结合具体技术应用和网络改造的投入一起考虑。在PON方式中的技术性能和安全性能相对较好，但设备及铺设成本较高，目前不易大规模推广，但从长远来看，以PON为代表的光网络技术仍是最具有发展潜力的；LAN方式中对于楼内综合布线是个不能回避的问题，此外，LAN设备还必须具备支持IGMPSnooping的以太接入网交换机并进行组播权限控制功能升级；DSL方式已成为大多数用户的普遍选择，并随着ADSL2/2+技术的成熟、设备价格下降使ADSL2/2+成为宽带接入“最后一公里”的主流发展趋势。xDSL技术作为充分利用现有双绞线资源进行数据传输的接入技术，经过多年的应用发展已形成了两代产品。第一代ADSL产品是基于ITU-TG.992.1技术标准发展形成的，其用户目标速率下行6.144Mbit/s，上行800kbit/s。随着IP宽带业务的发展，尤其是IPTV类流媒体业务发展的需要，要求DSLAM设备不再仅局限于ATM层接入复用功能的实现，而要具备更强大的IP业务分发和控制能力。因此，基于纯IP高转发能力的第二代ADSL2产品应运而生，其标准是基于ITU-TG.992.3规范，用户目标速率下行可达8Mbit/s，上行1Mbit/s，而且在IP层的受控组播、QoS和安全控制能力上都得到质的飞跃。随后，又出现了基于G.992.5技术标准的增强型第二代ADSL2+产品，其用户目标速率可达到下行24Mbit/s，上行1Mbit/s，这大大突破了原有第一代、第二代产品的传输速率。同时，还出现了基于G.993.1技术标准的VDSL产品和基于G.993.2技术标准的VDSL2产品，其速率分别可达下行50Mbit/s、上行 15Mbit/s和上下行100Mbit/s。

    In China,IPTVservice is mainly oriented to home subscribers. Presently, IPTV service bearer access network deployment has three options: PON, LAN and DSL. The three options should be considered in light of specific technological applications and network transformation input. In PON, technological performance and security performance are relatively good, but cost of equipment and installation is higher, it is not easy to apply it in a big way. But from a long-term point of view, optical network technology represented by PON has the greatest development potential; in LAN, in-building integrated wiring is an unavoidable problem. In addition, LAN equipment must have Ethernet access network exchange that supports IGMPSnooping and conduct multicast authority control functional upgrading; DSL has become a popular choice for most users, and, with the maturity of ADSL2/2+ technology and the drop of equipment price, ADSL2/2+ becomes the main development trend of broadband access “last mile”. xDSL as an access technology to fully exploit existing twisted-pair resource for data transmission has formed two generations of product after years of application and development. The first-generation ADSL product is developed based on ITU-T G.992.1 technical standard. Its targeted user rate is 6.144Mbit/s downlink, and 800kbit/s uplink. With the development t of IP broadband service, especially IPTV streaming media service development needs, DSLAM devices are required no longer limited to the realization of ATM layer access multiplexing function, but to have even stronger IP traffic distribution and control ability. The second-generation ADSL2 product based on pure IP high forward capability thus emerged. Its standard is based on ITU-T G.992.3, targeted user rate can reach 8Mbit/s downlink, and 1Mbit/s uplink, and it sees qualitative leap in IP layer controlled multicast, QoS and security control ability. Later, the enhanced second-generation ADSL2+ product based on G.992.5 took place. Its targeted user rate can reach 24Mbit/s downlink and 1Mbit/s uplink, much higher than the transmission rate of the first two generations. At the same time, there appeared VDSL product based G.993.1 and VDSL2 product based on G.993.2, whose rates can reach 50Mbit/s downlink and 15Mbit/s uplink, and 100Mbit/s uplink and downlink, respectively.

    四、展望

    IV.Prospect

    就宽带的建设和改造而言，自2003年起中国电信、中国铁通等运营商就开始大规模推广ADSL的宽带应用，目前已从第一代发展到第二代，传输带宽从原来的1Mbit/s上升到24Mbit/s，足够开展IPTV的相关业务，而宽带的直接应用与感受就是视频的播放，但由于核心内容的缺乏及受政策和版权的影响，宽带应用目前仍停留在视频聊天、在线游戏等初级业务上，而直播电视、视频点播等业务并未普及开来。随着运营商企业转型的实施，其重要的特征就是向下一代网络演进发展，业务也将从单一窄带语音向综合多媒体转变，其中宽带业务是运营商发展的重点，因此IPTV业务也必将成为宽带发展中的主流。

    As for the construction and upgrading of broadband, fixed network operators China Telecom and China Tietong began in 2003 to promote ADSL broadband applications in a big way, which has now developed from the first generation to the second generation, with transmission bandwidth rising from 1Mbit/s to 24Mbit/s. This is high enough to develop IPTV related services. And direct application and experience of broadband is video play. But due to lack of core contents and affected by policy and copyright, broadband application remains at the level of video chatting, online game and other primary services, and services like direct-broadcast TV and VOD are not popular. With the implementation of enterprise transformation, whose important characteristic is to evolve towards NGN, and services are to turn from unitary narrowband voice to integrated services, of which broadband service is the chief base for the development, therefore, IPTV service will become a mainstream in the broadband development.（火王编辑）