5.1. IPTV Introduction

Transcription

1 5. Convergence of fixed networks Convergence of TV and Internet (TV over IP) 5.1. IPTV Introduction 5.2. IPTV over DSL 5.3. Video coding standards 5.4. IPTV main building blocks 5.5. QoS issues for multimedia traffic 5.1. IPTV Introduction The rollout of digital networking infrastructure is opening the door for Telcos and operators to offer converged services comprising broadband Internet access and IP based TV and entertainment. TV (or video) over IP is a broad streaming solution that includes several applications, all of which can be implemented on digital broadband networks such as ADSL, VDSL, fiber, LMDS and Wireless LANs. TV over IP is being utilized in the following applications: TV to the living room (instead of cable TV) Time-shifted TV or Personal Video Recorder (PVR) Interactive TV TV to the desktop 1

2 Interactive Television (ITV) Definition Interactive Television is TV with interactive content Combining traditional TV with the interactivity (Internet) Links to Web sites On-line communications Entertainment Home shopping Home banking Video conferencing Video on Demand Distance learning Instant messaging IPTV (Internet Protocol television) IPTV - IPTV (Internet protocol television) is a method of distributing television content over IP that enables a more customized and interactive user experience. Among other things, IPTV could allow people who were separated geographically to watch a movie together, while chatting and exchanging files simultaneously. 2

3 IPTV (Internet Protocol television) Cntd. How does IPTV work? IPTV uses a two-way broadcast signal sent through the provider's backbone network (PSTN) and servers, allowing viewers to select content on demand, time-shift, and take advantage of other interactive TV options. The viewer must have a broadband connection and a set-top box (STB) programmed with software that can handle viewer requests to access to many available media sources IPTV (Internet Protocol television) Cntd. Traditional cable digital TV has the capacity to deliver hundreds of channels simultaneously to each subscriber. IPTV, by contrast, sends only one program at a time. When a viewer changes the channel or selects a program, a new stream of content is transmitted from the provider's server directly to the viewer's set-top box. 3

4 IPTV (Internet Protocol television) Cntd. IPTV primarily uses multicasting with Internet Group Management Protocol (IGMP) version 2 for live television broadcasts and Real Time Streaming Protocol for on-demand programs. Compatible video compression standards include H.264, MPEG-2 and - 4. IPTV has been deployed by telephone companies in Europe but is still in development stages in the U.S. Similar services including video on demand are delivered by cable companies over their proprietary networks using Digital Video Broadcasting, which is not used for IPTV. IP video services market IP video, viewable on TVs, STBs, and PCs, is expected to become a major part of any home s entertainment line-up. According to Multimedia Research Group, Inc. (MRG, Inc.), worldwide IP video services subscriptions are expected to more than quadruple, from under 2 million subscribers in 2004 to over 8 million users in just two years. 4

5 Global IP video subscriber forecast IP video services market (Cntd.) The Telcos face a significant challenge. In an effort to continue to produce revenue-generating services that boost ARPU and retain their market share, Telcos are focusing their efforts on a new video codec, H.264/MPEG-4 Advanced Video Coding (or just H.264/AVC). This new video encoding/decoding scheme enables a compelling solution through IPTV-DVD-quality video services over DSL and the Internet. 5

6 IPTV main protocols - H.264 H.264, also known as MPEG-4 AVC (Advanced Video Coding), is a video compression standard that offers significantly greater compression than its predecessors. The standard is expected to offer up to twice the compression of the current MPEG-4 ASP (Advanced Simple Profile), in addition to improvements in perceptual quality. The H.264 standard can provide DVD-quality video at under 1 Mbps, and is considered promising for full-motion video over wireless, satellite, and ADSL Internet connections. H.264 (Cntd.) The need for an advanced video coding standard that evolves MPEG-2 and H.263 to the next level has been addressed over the last several years through a combined working group of the ITU-T and ISO/IEC organizations, who have previously produced the H.26x and MPEG-x standards, respectively. The new standard has emerged as H.264. It is also called MPEG- 4, Part 10, or MPEG-4 Advanced Video Coding (AVC). H.264/AVC cuts in half the bandwidth required to deliver fullscreen DVD-quality digital video to consumers, and it reduces standard television quality digital transmission bandwidth requirements to 700 kbps both well within the capabilities of a 1.5 Mbps DSL loop. 6

7 H.264 (Cntd.) The enhanced compression and perceptual quality of H.264 are obtained by: Motion estimation, which minimizes temporal redundancies Intra estimation, which minimizes spatial redundancies Transformation of motion estimation and intra estimation into the frequency domain Entropy coding, which assigns a smaller number of bits to frequently encountered symbols and a larger number of bits to infrequently encountered symbols. IPTV main protocols - IGMP The Internet Group Management Protocol (IGMP) is the Internet protocol, part of the Network Layer. IGMP is formally described in the Internet Engineering Task Force (IETF) Request for Comments (RFC) IGMP provides a way for an Internet computer to report its multicast group membership to adjacent routers. Multicasting allows one computer on the Internet to send content to multiple other computers that have identified themselves as interested in receiving the originating computer's content. Multicasting applications: updating the address books of mobile computer users in the field sending out company newsletters to a distribution list "broadcasting" high-bandwidth programs of streaming video to an audience 7

8 5.2. IPTV over DSL Using new H.264/AVC delivery platforms and standard PCs or STBs, Telcos can offer exciting IP video services - Video-on- Demand (VOD), television programming, gaming, music, and, even interactive television - to their home and business customers using their existing copper infrastructure. With DSL technology, the Telcos hold a significant advantage by delivering IPTV to more of the masses than cable operators. While cable and satellite Internet access is encroaching on the Telcos long-held dominance, DSL is still the leading broadband technology that users subscribe to around the world. Global DSL connections forecast According to the DSL Forum ( 55 million Internet users worldwide use DSL in September of 2003; 25 million new subscribers alone were added from September 2002 to September The growth trend is expected to continue, with subscriptions reaching nearly 100 million users worldwide by H.264/AVC reduces the barriers to entry for Telcos, who can offer more services than cable operators. 8

9 Global DSL connections forecast Delivering video services over DSL Similar to MPEG-2, H.264/AVC requires encoding and decoding technology to prepare the video signal for transmission and then read it at the customer s receiver (STB and TV set, or PC). In fact, H.264/AVC can use transport technologies compatible with MPEG-2, simplifying an upgrade from MPEG-2 to H.264/AVC to help protect the investments in MPEG-2 some companies have already made, while enabling transport over TCP/IP and wireless. This also allows service providers to deliver content to devices for which MPEG-2 cannot be used, such as PDA and digital cell phones. 9

10 Delivering video services over DSL (Cntd.) The H.264/AVC encoder system in the main office turns the raw video signals received from content providers into H.264/AVC video streams. The streams can be captured and stored on a video server at the head-end, or sent to a video server at a regional or central office (CO), for video-on-demand services. The video data can also be sent as live programming over the network. Standard networking and switching equipment routes the video stream, encapsulating the stream in standard network transport protocols, such as ATM. Delivering video services over DSL (Cntd.) A special part of H.264/AVC, called the Network Abstraction Layer (NAL), enables encapsulation of the stream for transmission over the Telco s DSL Internet access services network. When the video data reaches the customer s site, it is routed to the client through a DSL modem and the customer s local network (wired or wireless). An STB client decodes the stream for display on a TV set, while a PC client decodes the data using a plug-in for the client s video player (Real Player*, Windows* Media Player*, etc.). 10

11 Delivering video services over DSL (Cntd.) Switch TV over IP using ADSL ADSL can support last-mile bandwidths between 512 Kbps and 6 Mbps. The actual bandwidth available depends on the distance between the end-point and the ADSL DSLAM. Depending on the last mile bandwidth available, users can receive 2 channels of video. In this case, two IP STBs will reside at the end point (one STB for each channel). Streaming Server 11

12 TV over IP using VDSL VDSL configuration rests on fiber connectivity over the backbone at bit rates of 155 Mbps and up. Transmission from the last mile network node to the end point is at bit rates of between 10 and 40 Mbps. The high bandwidths supported by VDSL enable consumers to receive multiple channels for playback on multiple TV sets. With VDSL, the backbone infrastructure is based on fiber to the curb/basement while the last mile solution uses VDSL over the telephone copper line. Streaming Server TV over IP using FTTH (Fibre to the Home) FTTH configuration rests on fibre connectivity from the head-end to the end-point. In this configuration video is transmitted over a fibre backbone at more than 155 Mbps. Last mile configuration consists of a 100BaseT network. Such wide bandwidths allow users to receive multiple channels, which are played back by IP/STB. Streaming Server 12

13 5.3. Video coding standards H.264 Features H.264 compresses video more efficiently, cutting transmission costs over satellite or terrestrial links. Density of services over existing DSL loops is high: two standard-quality video streams can be transmitted over a single 1.5 Mbps loop. Customers can watch (and Telcos can bill for) two video-on-demand streams at the same time. H.264 Features More content can be transmitted on longer loops - to more customers. Where MPEG-2 could only reach customers in a 9,000 sq. ft service area per CO, H.264/AVC video streams can reach customers in a 16,000 sq. ft service area per CO. H.264/AVC is also part of the upcoming 3GPPv6 specifications. With the use of joint technologies, UDP or TCP/IP and H.264, there is a common ground for greater interaction between the home and mobile devices. 13

14 H.264/AVC enables reaching greater distances over DSL with more content H.264/MPEG-4 AVC: The IPTV enabling technology standard The following table summarizes the development of different H.26x/MPEG standards and their intended applications. 14

15 Video coding standards (Cntd.) MPEG-2 (hardware technology) has been the industry-standard digital video broadcast codec for many years for high bit rate applications. MPEG-2 requires 2 Mbps of bandwidth, which is available over coaxial lines and satellite lines, to deliver broadcast-quality, jitter-free, digital video. MPEG-4 Simple Profile (SP) and Advanced Simple Profile (ASP) were developed for streaming video over Internet connections. MPEG-4 offers a software method to compress and decompress video over a network that provides only a best-possible connection with a wide range of data rates. The result is not what viewers have come to expect from their televisions, but enough to offer interesting services and enhance the richness of the Internet experience. Video coding standards (Cntd.) H.264/MPEG-4 AVC addresses the needs for greater compression, leading to lower data rates, while maintaining broadcast quality for video-on-demand (VOD) and high-definition television (HDTV) needs. H.264 meets the needs of both broadcast and the Internet by cutting the MPEG-2 bit rates in about half for digital video transmission-without a loss in video quality. This advance has followed the evolution of video compression science toward higher quality and lower bandwidth, and it opens new doors for service providers operating over the local copper loop infrastructure. Using H.264/MPEG-4 AVC and new H.264-enabling technology platforms for encoding, transport, and decoding, Telcos and ISPs can boost their average revenue per user (ARPU) with exciting and compelling new video-on-demand, HDTV distribution, and interactive TV services. The age of IPTV over DSL has arrived. 15

16 Codecs Kbit/ sec Audio CD Alcatel Propr. Codec M-JPEG MPEG2 MPEG G.711 G.726 G.728 MP3 MP3Pro, AAC G.729 G voice HiFi audio TV qual video Source: Alcatel Video compression of 1024x768 pixel, 24-bit color image 16

17 H.264/AVC benefits bandwidth demand, storage requirement, and download times 5.4. IPTV main building blocks Streaming Server Streaming server resides at the head- end. It can encode and stream live streams in real-time and pre-encoded streams that are stored on the video server. Streaming server transmits the streams to the switch or router which transfers them over the backbone to the central/remote offices, and from there to the end user location. 17

18 IPTV main building blocks (Cntd.) Video Server Video servers fulfill several purposes. For store and forward transmissions, video servers store digitally encoded content and stream it through level III devices via operators networking infrastructure. Video servers receive newly encoded digital content that is uploaded from the streaming server. Video servers also enable time shifted TV applications. Viewers at home can then watch any program at a time convenient to them. IPTV main building blocks (Cntd.) Level III Device A switch or router that supports multicast transmission. The router or switch resides at the head-end, interfacing with the network. Another router or switch receives data at the central office and transmits either to DSLAMS located there, or into end-user network. 18

19 IPTV main building blocks (Cntd.) DSLAM The DSLAM (Digital Subscriber Line Access Multiplexer) resides at the central office, connecting xdsl subscribers to the backbone and subsequently to the head-end. When distributing TV over IP, the DSLAM should support multicast transmission. If it doesn t, the switch or router at the central office has to replicate each channel for each request. This can cause congestion at the DSLAM input level. If the DSLAM supports multicast, it receives one stream for each channel and replicates the stream for each end point. IPTV main building blocks (Cntd.) CPE (Customer Premises Equipment) The equipment located at the end-point that receives the TV/IP stream. Usually the term CPE refers to the DSL modem. The DSL modem receives the stream from the DSLAM or Level III device and transfers it directly to the PC for display on the desktop or to the IP STB. 19

20 IPTV main building blocks (Cntd.) Set-top Box (STB) Gateway between TV set/pc-tv and NT (PSTN line, satellite or cable) Signal processing receiving, decoding/decompressing STB also accepts commands from the user and transmits these commands back to the network, often through a back channel Functions - TV signal receiver, modem, game console, Web browser, capabilities, video-conferencing, cable telephony Set-top Box (STB) Cntd. Components - Electronic Program Guide (EPG), CD ROM, DVD player etc. Many STBs are able to communicate in real time with devices such as camcorders, DVDs, CD players and music keyboards Hardware Data network interface Decoder Buffer Synchronization hardware 20

21 Set-top Box (STB) - Cntd Types of STB (1) Broadcast TV Set-top Boxes - (Thin Boxes) More elementary level set-top box with no return channel (back-end). Some memory, interface ports and some processing power. (2) Enhanced TV Set-top Boxes - (Smart TV set-top box, Thick Boxes) These have a return channel, usually through a phone line. Video on Demand, Near Video on Demand, e-commerce, Internet browsing, communications and chat. (3) Advanced Set-top Boxes - (Advanced digital Set-top boxes, Smart TV Set-top box, Thick Boxes) Like a PC -processors, memory and optional large hard-drives. (4) All-in-one Set-top Boxes - (Integrated set top box, Super Box) A fully integrated set-top box. Features could include everything from highspeed Internet access to digital video recording to games and capacity QoS issues for different types of traffic Voice traffic is smooth, benign, drop-sensitive, and delay-sensitive, and is typically UDP-based. Bandwidth per call depends on the particular codes adopted, sampling rate, and Layer 2 media employed. Voice quality is directly affected by all three QoS quality factors (loss, delay, and delay variation). Data traffic is much more varied. It can be smooth or bursty, benign or greedy, or drop- and delay-insensitive, and involves Transmission Control Protocol (TCP) for send/receive acknowledgment and retransmit. Traffic patterns vary by application, and data classes must support several different priorities or application categories. Video traffic is bursty, bandwidth-greedy, drop-sensitive, and delaysensitive. IP-based videoconferencing has some of the same sensitivities as voice traffic. 21

22 QoS issues for different types of traffic (Cntd.) Data traffic is typically handled with multiple classes, where each class can be defined and given the appropriate support based on the priority requirement of the application that is generating the traffic. In general, enterprises should restrict themselves to about five main traffic classes, such as: Mission-critical and real-time - Transactional and interactive applications with high business priority; in some cases, real-time traffic such as voice over IP (VoIP) can be subdivided into a separate class Transactional/interactive - Client-server applications, messaging applications (typically foreground activities that directly affect employee productivity) Bulk - Large file transfers, , network backups, database synchronization and replication, and video content distribution (background activities that do not directly affect employee productivity and are generally time-insensitive) Best-effort - Default class for all unassigned traffic; typically at least 25 percent of bandwidth is reserved for best-effort traffic Scavenger (optional) Peer-to-peer media sharing applications, gaming traffic, and entertainment traffic QoS issues for different types of traffic (Cntd.) QoS requirements for video applications There are two main types of video applications interactive video (such as videoconferencing) and streaming video (such as IP/TV content, which may be either unicast or multicast). Provisioning for interactive video traffic: # Packet loss should be no more than 1 percent. # One-way latency should be no more than 150 ms. # Jitter should be no more than 30 ms. # The minimum priority bandwidth guarantee is the size of the video conferencing session plus 20 percent. (For example, a 384 kbps video conferencing session requires 460 kbps of guaranteed priority bandwidth.) 22

23 QoS issues for different types of traffic (Cntd.) Streaming video applications have more tolerant QoS requirements, as they are delay insensitive and are largely jitter insensitive (due to application buffering). However, streaming video may contain valuable content, such as e-learning applications or multicast company meetings, and therefore may require service guarantees through QoS. Provisioning for streaming video traffic: # Loss should be no more than 2 percent. # Latency should be no more than 4-5 seconds (depending on video application's buffering capabilities). # There are no significant jitter requirements. # Guaranteed bandwidth requirements depend on the encoding format and rate of the video stream. QoS issues for different types of traffic (Cntd.) Streaming video is typically unidirectional and, therefore, remote branch routers may not require provisioning for streaming video traffic on the customer edge (CE) in the direction of branch to campus. Non-important streaming video applications (either unicast or multicast), such as entertainment video, content may be provisioned in the Scavenger traffic class and assigned a minimal bandwidth percentage. 23

24 Scavenger Class The Scavenger class is intended to provide deferential services, or less-than Best-Effort services, to certain applications. Applications assigned to this class have little or no contribution to the organizational objectives of the enterprise and are typically entertainmentoriented. These include: Peer-to-peer media-sharing applications (KaZaa, Morpheus, Groekster, Napster, imesh, etc.) Gaming applications (Doom, Quake, Unreal Tournament, etc.), and any entertainment video applications. Assigning a minimal bandwidth queue to Scavenger traffic forces it to be squelched to virtually nothing during periods of congestion, but allows it to be available if bandwidth is not being used for business purposes, such as might occur during off-peak hours. Bandwidth consumption of video over IP traffic in the face of competing web surfing traffic. No traffic shaping is present. 24

25 Additional network latency added by congestion With QoS From Packet Shaper (guaranteed bandwidth of 820k for video traffic) 25