IPTV hit primetime. Main Topic

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2 Main Topic ivideo helps IPTV hit primetime ivideohelps IPTV hit primetime With the development of video services, users want to watch high quality video content through a terminal of their choice, and at a place and time of their convenience. With more broadband networks being built, more operators are providing IPTV services to meet the diversified video and media program requirements, as IPTV supports strong and real interactions between users and media providers. The Huawei video bearer network solution (ivideo) provides ivse (including FCC and RET functions) and irsm to fully guarantee smooth operation of IPTV services. By Chen Haibin 3

3 Huawei Communicate IPTV trends IP television (IPTV) services have grown fast in recent years. According to a Frost & Sullivan report, there were about 40 million IPTV users at the end of 2009, and the number will reach 140 million in At present, the number of IPTV users is growing most rapidly in the United States and Western Europe, while the number of IPTV users in the Asia-Pacific region is expected to grow rapidly in the next few years. Operators provide IPTV services usually because of the following reasons: Competition from other operators; competitive pressures that mobile broadband services bring to fixed broadband services; providing video as a basic service, binding users with multiple services, and increasing user bandwidth to obtain high ARPU; and breaking the boundaries between the TV and the PC to increase the number of broadband users. With the increasing demand for video quality, users are not satisfied with standard-definition (SD) videos. More and more high-definition (HD) videos are being provided by Digital TV, IPTV, Web TV, and mobile TV services and being supported by an increasing number of video sources and video terminals. In America, Verizon IPTV offers 150 HD channels. According to surveys, more than half of the TV terminals around the world support HD services. In addition to HD requirements, users prefer watching programs at a time and place of their convenience. IPTV is not restricted by program schedules; instead, IPTV allows users to enjoy various audio and video programs at any time. Offering an interactive and customized TV-viewing experience, IPTV is gaining popularity. A survey by In-Stat shows that time-shifting, HDTV programs, and video on demand (VOD) are the most popular features among IPTV users. Video basics and challenges to HDTV bearer networks Video basics IPTV performs video compression of received satellite signals, converts the compressed packets to IP packets through IP streaming, and delivers the IP packets through IP networks, thereby fully utilizing the reach and high transmission efficiency of IP networks. The current mainstream video compression standards are MPEG-2 and H.264. MPEG-2 is the dominant standard among digital TV and legacy IPTV, whereas the newly emerging standard H.264 is currently supported by some IPTV vendors. H.264 is more sophisticated than MPEG-2 and its compression efficiency is 1.5 to 2 times the latter s. Thus, more vendors use H.264 video compression, especially for HD videos. Compressed by H.264, SDTV streaming is about 2Mbps, 1080i streaming ranges from 6Mbps to 8Mbps, and 1080p streaming ranges from 12Mbps to 16Mbps. Both MPEG-2 and H.264 use the group of pictures (GoP) structure to compress videos. The GoP comprises I-frames, B-frames, and P-frames. An I-frame, or intra-coded frame, is a baseline frame that contains complete image information. It is the first frame in a GoP. Every GoP has only one I-frame, and cannot be displayed if this I-frame is lost. The I-frame contains the most data traffic and takes up more space than other frames. In addition, the MPEG-TS encapsulation information of a compressed video packet is also very important. If IPTV data is encapsulated within an MPEG-TS packet, the program specific information (PSI), including the program association table (PAT) and program map table (PMT) information, is used to de-multiplex video, audio, and other data in the transport stream (TS). A set top box (STB) starts decoding only after obtaining PSI and an I-frame. Challenges to HDTV bearer networks Videos bring four major challenges to the bearer networks, as they require large bandwidth, low packet loss/corruption ratio, channel change latency of less than a second, and quick fault locating. Large bandwidth requirements. As VOD services (including TSTV services) grow, more bandwidth is consumed on bearer networks. While SDTV requires 2M, HDTV, super HD and ultra HD require 8M, 50M and 200M respectively. Sensitive to packet loss and corruption. Due to high video compression, loss of one packet may cause mosaic or other errors in video images, and thus downgrade the user experience. Different video coding formats have different packet loss ratio (PLR) requirements according to DSL-Forum TR-126. The higher the transport stream bit rate, the smaller the required PLR. HD requires that the PLR should be smaller than 1.0E-07. 4

4 Main Topic ivideo helps IPTV hit primetime Channel change latency. Analog TV does not use compression technologies; images are immediately displayed on the terminal when they are received. The channel change time is usually less than a second. In the case of IPTV, the terminal device will not start decoding until it obtains the key information such as PAT, PMT, and an I-frame. As a result, the channel change latency is unstable, and the quality of user experience cannot be ensured. If without any special measure, the latency could reach 5 seconds, and it will seriously impact the user experience. C o m p l i c a t e d o p e r a t i o n a n d maintenance. Video operation and maintenance involves O&M of IPTV, metropolitan area network (MAN), and access network. When an IPTV service has problems, the fault must be effectively and quickly located and cleared to guarantee the user experience. HDTV bearer network solution Huawei provides an innovative video solution called ivideo, which comprises i V S E a n d i R S M, t o a d d ress t h e challenges to the video bearer network. The integrated Value-added Service Enhancement (ivse) solution uses built-in video cards of network devices to implement low-cost fast channel change (FCC) and application layer retransmission (RET) and ensure highquality video experience. The in-line Real Stream Monitoring (irsm) solution delivers low-cost and effective video operation and maintenance. The N2510 monitors the quality of video streaming on the lastmile network. The U2520 monitors the video streaming quality of the MAN. The Media Quality Monitor Center (MQMC) monitors the video streaming quality at the IPTV headend and STBs. The MQMC cooperates with the U2520 and N2510 to deliver a unified end-to-end video operation and maintenance solution. Solving large bandwidth requirements Huawei has adopted two approaches to cut down bandwidth usage. One is to deploy multicast points as close to users as possible and leverage multicast technology. The other is to deploy content delivery networks (CDNs) for VOD and TSTV unicast services, where the content is delivered as close to users as possible and storage used to save bandwidth. ivse uses built-in video cache cards to expand CDNs to the user side, thus resulting in savings in both cost and bandwidth, and an improved user experience. Video cache cards can be deployed in different positions to achieve optimum balance between card-deployment cost and bandwidth saving. Huawei provides flexible video cache card deployment solutions that are suitable for various scenarios and applications, with support from Huawei s series of routers and OLT. Reducing packet loss/ corruption ratio: RET Videos are very sensitive to packet l o s s a n d c o r r u p t i o n. Fo r I P T V, there are various end-to-end quality factors that may cause serious packet loss or corruption, like aging and interference of last mile copper cables, family networking, and MAN congestion. Huawei has the automatic r e t r a n s m i s s i o n r e q u e s t ( R E T ) mechanism at the application layer to help reduce the packet loss/corruption ratio and remove the video mosaic. The mechanism reveals whether a stream loses any packet via the continuity of sequence number (SN) value in the RTP header, as the SN value increases by one when one more IP packet is added to the same stream. Specifically, Huawei ivse caches every video stream for one or two seconds on the video cache card. The STB receives, caches, and checks the video packets. Upon detecting packet loss, the STB sends a packet retransmission request through RTCP (based on RFC 4585) to the ivse card. Upon receiving this request, the ivse card finds the packet according to the requested SN value, and retransmits the packet to the STB. The STB inserts this packet into the proper position in the cache and sends the packet to the decoder, thus fixing the video stream. The RET mechanism supports single-card multi-level deployment. If packet loss occurs between two video cards, a lower-level video card can serve as an RET client and request the upper-level video card to retransmit the lost packets. If the IPTV system supports the RET function, the video card considers the IPTV system as the RET server and sends a retransmission request to the IPTV system. In this case, the upper-level video card can instruct, through multicast, the STBs not to send retransmission requests. This prevents a large number of retransmission requests from being sent to the video card. Upon receiving the retransmitted packet, the video card can multicast this packet to the STBs. As required by the RET mechanism, video packets should be encapsulated within RTP, and STBs should support retransmission. Since most legacy IPTV systems output video streams without RTP encapsulation, the IPTV systems need to be upgraded or installed with an independent RTP encapsulation device to meet the RET requirement. For STBs to support RET, Huawei provides two solutions. One is to load SDK software to the STBs simply by binding the API interfaces. Currently, all the STBs Huawei offers for IPTV systems are integrated with this function. The other one is to cooperate with a third-party company. For example, in the case of UAE-based operator Etisalat, STBs from four vendors already exist on the telco s network. To introduce a new IPTV system and deliver FCC and RET functions, Etisalat employed a thirdparty company named Soft@home to integrate the IPTV system and FCC 5

5 Huawei Communicate and RET functions with the existing STBs. Solving channel change requirements: FCC The channel change time is greatly affected by the waiting time of PSI (including PAT and PMT) and I-frame. Based on the standard RTCP protocol, the FCC mechanism works by decreasing the waiting time for PSI and I-frame and thus cutting the channel change time to within a second. When transmitting IPTV video streams, the network device uses the built-in video card to cache the video stream of each channel for a certain time interval. The cached information includes two or three GoPs and PSI. When the user changes the channel, the STB sends a unicast channel change request based on extended RTCP to the video card. The video card then sends the cached PSI of the new channel to the STB. This effectively reduces the PSI waiting time. Then the video card unicasts the content of the new channel (starting with the I-frame) to the STB. The STB immediately decodes the content. The entire channel change time is therefore less than a second. The unicast streams are sent out at a faster speed than the normal multicast speed, to keep pace with the subsequent multicast streams. When the video card decides that the unicast streams are keeping pace with the normal multicast streams, it sends RTCP signaling to instruct the STB to join the multicast group of the new channel. Meanwhile, the video card slows down the sending speed of the unicast streams by half of the normal speed and stops sending unicast streams. The unicast streams and the multicast streams connect to each other, even as the user is oblivious of this process. Huawei ivse uses a special method to decide when to stop sending unicast streams, and when to connect the unicast streams to the multicast streams without packet loss. When the STB receives multicast packets, the STB sends the SN value of the first multicast packet to the video card. Then the video card stops sending unicast packets after sending out the packet with the SN value. This method ensures that the unicast packets connect to the multicast packets without packet loss. FCC consumes large network bandwidth, especially when many users change channels simultaneously. Fast unicast also has higher requirements for last mile bandwidth. For example, some vendors require that the last mile bandwidth must be 1.3 times the normal bandwidth. This is a huge challenge to the access network bandwidth resources. If the operator provides 8Mbps HD video bandwidth and 10Mbps access bandwidth, FCC cannot be deployed. To address the bandwidth challenge, Huawei uses OLT, the CX600, and the NE series routers to provide video cards for FCC. Operators can deploy the video cards at suitable positions as needed. In addition, Huawei provides an intelligent method to discard unimportant video packets during FCC to save bandwidth without affecting user experience. With this method, the last mile network bandwidth can be just 1.1 times the normal bandwidth, and MAN bandwidth is cut by 30%. Like RET, FCC requires that video streams be encapsulated within RTP, and the STBs support the FCC process. Huawei provides SDK software for upgrading of STBs. And the IPTV systems and STBs offered by Huawei can cooperate with ivse to support FCC. Huawei also promotes the FCC standard process in the IETF. A draft in this regard has already been published. When an FCC standard is published, STB vendors only need to comply with this standard to support FCC. In addition, to implement FCC and RET, STBs must know the IP address of every video card that corresponds to each channel. When ivse cooperates with Huawei IPTV systems, STBs obtain the IP addresses of ivse cards through the IPTV system configuration. When ivse cooperates with other IPTV systems, STBs contact the ivse center provided by Huawei to obtain the IP addresses of video cards for delivering FCC/RET. The ivse center is preconfigured with channel information and the IP addresses of the corresponding channel cards. Solving operation and maintenance requirements: irsm IPTV operation and maintenance is very complicated, When a problem occurs, it is hard to locate the fault. Moreover, a small error on the network or head-end can have serious impact on user experience. To avoid such situation, operators must quickly locate and clear the fault to ensure high-quality user experience. Huawei provides irsm to quickly detect and locate faults. The irsm uses the built-in software monitoring module to deliver low-cost and effective video operation and maintenance, uses Mean 6

6 Main Topic ivideo Helping IPTV hit primetime ivideo helps IPTV hit primetime Opinion Score-V (MOS-V) and Real Media Rate (RMR) detection to quickly detect faults, and uses media delivery index (MDI)/RTP detection to quickly locate faults. All monitoring information is delivered to the U2520 and is displayed on the U2520 to facilitate IPTV operation and maintenance. Fault detection MOS-V and RMR are deployed at the egress of video stream to detect the quality of video streams output from the IPTV head-end. MOS-V determines the quality of the video streams and shows the output quality of the head-end, but cannot determine whether the output rate is proper. If the output IPTV video streams are of good quality but the burst rate exceeds the upper limit of the bearer network, the output video streams are also determined as unqualified. The RMR detection shows the rate changes of every video stream in real time, and helps detecting whether a rate burst occurs in the output IPTV code streams, and whether the burst rate exceeds the threshold predefined according to the network bandwidth and lining capacity. Fault location The media delivery index (MDI) is an algorithm that uses the MPEG-TS encapsulation information to measure the transmission quality of IPTV video streams over IP networks, and it applies to all IPTV video streams that are encapsulated within MPEG- TS packets. It comprises two parameters: the media loss rate (MLR) and delay factor (DF). MLR indicates the rate at which packets of the tested video streams are discarded during transmission and thus the ideal MLR during the transmission of IP video streams is 0. DF indicates the delay and jitter of the tested video streams in the unit of millisecond. When the time of video contents contained in the buffer of network devices and decoders is equal to or greater than the DF value of tested video streams, the video display quality does not decline. The MDI can easily and quickly obtain the packet-loss ratio and latencies of every video stream based on the SN value in RTP header information. The Timestamp field of the RTP packet can be compared with the local time to show the unidirectional latency of the arriving packet (depending on the network time synchronization). End-to-end service quality monitoring Huawei video bearer network solution can also closely work with Huawei IPTV system monitoring solution. The media quality monitor center (MQMC) monitors the video quality of the IPTV head-end and STBs, the U2520 monitors the video quality of each network node, and the N2510 monitors the video quality of the last mile network. The N2510, U2520, and MQMC can communicate with one another, and the MQMC shows the end-to-end video quality. The end-to-end service quality monitoring (SQM) solution has the following advantages: Real end-to-end: The network device uses a built-in SQM module to monitor the network layer quality. The video server and STB use builtin probes to monitor the service layer quality. Thus, the real end-to-end service quality monitoring from the IPTV head-end to the end users is implemented. Unified management platform: The MQMC seamlessly connects to the U2520, and functions as a unified management platform for network layer monitoring and service layer monitoring. This management platform delivers precise and unified monitoring indices to facilitate user management and fault locating. Reduced TCO: The built-in probes in the headend and the STB provide the most precise and real IPTV quality monitoring indices. The built-in SQM module in a network device saves space and network interfaces, and reduces the maintenance cost. The built-in SQM module reduces CAPEX and OPEX in aspects of deployment, maintenance, and operation. Huawei s ivse + irsm solution provides FCC, RET, and end-to-end SQM functions, serves as a full-dimensional integrated video solution for service providers, reduces their CAPEX and OPEX, and ensures the high-quality video experience. This solution has been utilized in constructions of more than 100 backbone networks and 600 MANs, and is deployed by the world s leading operators, including China Telecom, China Mobile, China Unicom, France Telecom, Deutsche Telekom, British Telecom, Telefonica, SingTel, and Etisalat. Editor: Zhu Wenli [email protected] Thanks for your reading, the electronic version and subscription information are available at Questions and suggestions may be directed to the editor concerned. 7