Special Topics on Emerging Technologies Standards

The new generation of IPTV

Mahdi Savasari 1091900012 Master of engineering in telecommunications

Faculty of engineering in multimedia university , Cyberjaya , Malaysia msavasari@gmail.com

Abstract The advances in broadband Internet access and scalable video technologies have made it possible for Internet Protocol television (IPTV) to become the next killer application for modern Internet carriers in metropolitan areas. Internet Protocol television (IPTV) is a system through which digital television service is delivered using the architecture and networking methods of the Internet Protocol Suite over a packet-switched network infrastructure, e.g., the Internet and broadband Internet access networks, instead of being delivered through traditional radio frequency broadcast, satellite signal, and cable television (CATV) formats. IPTV services may be classified into three main groups: live television, time-shifted programming, and content (or video) on demand. It is distinguished from general Internet-based or web-based multimedia services by its on-going standardization process (e.g., ETSI) and preferential deployment scenarios in subscriber-based telecommunications networks with high-speed access channels into end-user premises via set-top boxes or other customer-premises equipment. In this article we have a short history of television in then we discuss about new generation of television that is Internet protocol television (IPTV). We will discuss advantages and limitations of IPTV and some challenges in p2p stream, Wimax and compression format of IPTV

Introduction Since the 1950’s, television has been a dominant and pervasive mass media. Over the years, television has transformed itself into a new media. The number of channels has increased from a few free-to-air broadcasts to several hundreds for cable, satellite, and Internet TV networks that transmit more channels to each user. IPTV is the most emerging service these days and its standardization efforts are very active. Globally, IPTV subscribers are about 24 million and expected to grow dramatically. It is very likely to say that IPTV is a just television on the IP. But, ITU-T defines IPTV as multimedia services such as television/video/ audio/text/graphics/data delivered over IP based networks managed to provide the required level of QoS/QoE, security, interactivity and reliability. Actually, scope of IPTV covers researches on IP based networks and managed capabilities as well as multimedia service over IP network. IPTV, as an operator service over broadband networks, has been available for sometime. Figure 1 shows the anticipated increase in traffic over broadband access networks. This increase will largely be driven by IPTV service.

Figure1

In this article we introduce advantages, limitations and technologies behind IPTV. Finally we will discuss about common challenges in over Wimax. We also discuss about the compression method of IPTV

Television is changing Over the last decade, the growth of satellite service, the rise of digital cable, and the birth of HDTV have all left their mark on the television landscape. Now, a new delivery method threatens to shake things up even more powerfully. Internet Protocol Television (IPTV) has arrived, and backed by the deep pockets of the telecommunications industry, it's poised to offer more interactivity and bring a hefty dose of competition to the business of selling TV. IPTV describes a system capable of receiving and displaying a video stream encoded as a series of Internet Protocol packets. If you've ever watched a video clip on your computer, you've used an IPTV system in its broadest sense. As of late 2009, 10 countries had completed the process of turning off analog terrestrial broadcasting. Many other countries had plans to do so or were in the process of a staged conversion. The first country to make a wholesale switch to digital over-the-air (terrestrial) broadcasting was Luxembourg, in 2006, followed by the Netherlands later in 2006 Finland, Sweden, Norway and Switzerland in 2007, and Germany in 2008, and the United States, Denmark, South Africa and Kenya in 2009. In Malaysia, the Malaysian Communications & Multimedia Commission (MCMC) will call for tender bids in the third quarter of 2009 for the UHF 470–742 megahertz spectrum which will pave the way for the country to move into the digital television era. The awarding of the spectrum will see the winner having to build a single digital terrestrial transmission/TV broadcast (DTTB) infrastructure for all broadcasters to ride on to transmit their TV programs. The winner will be announced at the end of 2009 or early 2010 and has to commence digital roll-out soon after the award where the analog switch-off is planned for 2015. Digital television supports many different picture formats defined by the combination of size, aspect ratio (width to height ratio) and interlacing. With terrestrial broadcasting in the USA, the range of formats can be coarsely divided into two categories: HDTV and SDTV. It should be noted that these terms by themselves are not very precise, and many subtle intermediate cases exist. High-definition television (HDTV), one of several different formats that can be transmitted over DTV, uses one of two formats: 1280 × 720 pixels in progressive scan mode (abbreviated 720p) or 1920 × 1080 pixels in interlace mode (1080i). Each of these utilizes a 16:9 aspect ratio. (Some televisions are capable of receiving an HD resolution of 1920 × 1080 at a 60 Hz progressive scan frame rate — known as 1080p60, but this standard is not currently used for transmission.) HDTV cannot be transmitted over current analog channels. Standard definition TV (SDTV), by comparison, may use one of several different formats taking the form of various aspect ratios depending on the technology used in the country of broadcast. For 4:3 aspect-ratio broadcasts, the 640 × 480 format is used in NTSC countries, while 720 × 576 (rescaled to 768 × 576) is used in PAL countries. For 16:9 broadcasts, the 704 × 480 (rescaled to 848 × 480) format is used in NTSC countries, while 720 × 576 (rescaled to 1024 × 576) is used in PAL countries. However, broadcasters may choose to reduce these resolutions to save bandwidth (e.g., many DVB-T channels in the United Kingdom use a horizontal resolution of 544 or 704 pixels per line).

IPTV Internet Protocol Television (IPTV) is digital television delivered on your

television (and not PC) through high speed internet (broadband) Connection. In this service, channels are encoded in IP format and delivered to the TV through a set top box. IPTV service also includes video on demand, which is similar to watching video CDs/DVDs using a VCD/DVD player.

Figure2

Figure2 illustrates a typical service architecture, where customers subscribe to IPTV, IP phone, and Internet access. A network device called Digital Subscriber Line Access Multiplexer (DSLAM) aggregates traffic from hundreds to thousands of users and connects to the high-speed IP backbone. For IPTV distribution, the TV head-end streams all the live broadcast TV channels towards DSLAMs through bandwidth-provisioned multicast trees in the backbone. Due to limited access bandwidth at the last mile (i.e., from a DSLAM to the home gateway at the customer ’ s premise), not all TV channels are delivered to customers simultaneously. Internet protocol TV is different from Internet TV given that the user experience is bound to their living rooms and set-top boxes. The quality, though, will be superior since the content is digital (unlike most of the traditional TV content). IPTV, unlike Internet TV, is primarily a TV experience rather than a PC experience and is meant as an alternative to cable and satellite. IPTV converts a television signal into small packets of computer data like any other form of online traffic such as email or a web page. There are three main components of IPTV. First, the TV and content head end, where the TV channels are received and encoded and also other content like videos which are stored. The second component is the delivery network, which is broadband and landline network provided by a telecom operators such as MTNL. The third component is the set top box, which is required at the customer location. The packets are reassembled into programming by software in the set-top box. This box is connected between the operator’s broadband modem and customer’s TV. In table1 we can see some differences between Broadband TV and internet video streaming.

Table1

Triple play IPTV can easily be bundled with broadband Internet service and VoIP services to offer what is popularly known as Triple Play. The commercial bundling of IPTV, VoIP and Internet access is referred to as a Triple Play. This means the service is all set to pose a significant challenge to the established cable and satellite services. In US, Triple Play services are offered by cable television operators as well as by telecommunication operators. Triple Play implies high-speed Internet, television (Video on Demand or regular broadcasts) and telephone service over a single broadband connection. With wireless, it's called Quadruple Play and grouped services (triple and quadruple) are called multi-play.

Figure3

IPTV vs. Internet Television

Now, let us take a look at what makes IPTV and Internet Television different. To differentiate these two models is in general quite challenging. But studying and analyzing the said concepts in depth explains the differences.

IPTV is the representation of a profile of a closed, proprietary TV system. This is somewhat similar to the present day cable service providers. But, unlike IPTV, it is delivered via IP-based secure channels. As a result, it sharply increases the control of content distribution.

Internet Television is an open evolving framework where a huge number of small and medium-sized video producers contribute. Such a service provides highly innovative content, where the contributors are very much comfortable. This is due to the opening of different traditional channels which are either retail and for wide distribution.

Advantages of IPTV The quality of digital video and audio is much better compared with the traditional analogue TV. With additional features, it can become interactive. For example, viewers may be able to look up a player’s history while watching a game. They also may be able to schedule a recording of their favorite program

when they are not home. With video on demand, they can browse an online movie catalogue and watch the movies instantly. Because IPTV uses standard networking protocols, it promises lower costs for operators and lower prices for users. Using set-top boxes with broadband internet connections, video can be streamed to households more efficiently than cable. Because each IP television viewer has a unique address, this allows advertising messages to be sent to specific viewers (addressable advertising). The ability to direct advertising messages to specific target audiences (addressable advertising) is more valuable to companies than traditional broadcast advertising and this may result in reduced viewing costs. Another advantage of IPTV is that if the customer has quadruple play (internet, television, telephone, mobile phone service) with the same company, the cell phone can be used to schedule the recording of a program. Excluding cell phone service and having only three services with a company is referred to as triple play. The biggest difference with today’s distribution of television is that you choose which information you want to have everything is not broadcasted as with terrestrial, cable and satellite. Another big difference is that you will be able to have a high capacity two way communication and have the ability to interact with the service provider, for example you request a movie from your TV-guide and the program is delivered to you. Other things that could be provided with IPTV is interactive applications (e.g. video blog) or transactional applications (e.g. TV shopping). Because of the point-to-point connection IPTV offers, every user will be able to view their own individual broadcasts. You will be able to have VoD(Video on Demand) which is your on personal video store where you can decide when you want to see the movie. EPG(Electronic Program Guide) and PVR(Personal Video Recorder), where the EPG will be fully interactive with your own personal needs. You will also be able to use features like pause, fast forward and rewind when you are watching a movie on your TV. It will be possible to have personalized advertising. You will be able to decide yourself, which kind of advertising you would like to see.

IPTV Features • Selection: users are able to select their TV programs with fast channel selection and short channel changing time. • Storage: TV programs are stored in local storage devices so that users can watch them anytime; furthermore, service providers should store at least 100 hours of TV programs and videos. • QoS: QoS must be guaranteed; a standard definition TV and a high definition TV need bandwidth of 1~4 Mb/s and 4~12 Mb/s, respectively. • Low cost: cost to the user must be low; this is the key to success

Limitations of IPTV There are some limitations to IPTV. According to Wikipedia, because IPTV is based on the Internet Protocol, it is sensitive to packet loss and delays if the IPTV connection is not fast enough and it also does not support HDTV at the moment. AT&T is currently experimenting with HDTV and its U-Verse service in the Houston area according to Cable Industry Insider. The networks have to be built so that the End-to-End QoS can be guaranteed, which is not the case with most of the networks today. Set-top boxes are expensive and if you want to watch another channel on a different TV you will have to buy another box.

Technologies behind IPTV The two primary protocols used for IPTV are IGMP version 2 for channel change signaling for live TV and RTSP for Video on Demand. There are of course other protocols, for example to distribute and route multicast groups between routers you can use the PIM-SM protocol. For sending live-TV multicasting is used, this is because it would be impossible to withhold the bandwidth it would require to send with unicast. The providers of IPTV in Sweden are all using MPEG-2 for distributing there media. This means, as you can see below in table2, that SDTV will require for full quality a bit rate of 4-6 Mbps. To watch HDTV other compression algorithms like H.264 are required otherwise it would consume too much bandwidth.

Table2

Compression formats IPTV The first implementations of television over IP by ADSL use (or have used) MPEG-2 for video compression with a bit-rate on the order of 3 Mb/s. This allows, depending on the characteristics of the telephone line, the service provider to offer the TV service up to a distance of about 2500m of the DSLAM. Until the end of 2005, there was practically no other option because of the non-availability of efficient real-time encoders and affordable decoders for more efficient compression formats (H.264, WMV9, etc.). H.264/AVC cuts in half the bandwidth required delivering full screen 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. Using new H.264/AVC delivery platforms and standard PCs or STBs, telcos can offer exciting IP video services—video-on-demand (VOD), local, national, and premium television programming, gaming, music, and, even interactive television—to their home and business customers using their existing copper infrastructure .

H.264/AVC Benefits • Doubles compression efficiency, lowering bit rates to half of the MPEG-2 requirements for high-quality video and decreasing necessary storage capacity • Allows more content to be transmitted over existing infrastructures using its lower bit rates. • Lowers transmission costs by sending the same information in half the time. • Lowers deployment costs with new H.264/AVC technology platforms built on standards-based, non-proprietary processing hardware. • Incorporates a Network Adaptation Layer that offers flexibility through transportability over packet and bit stream networks, allowing easy upgrades to existing MPEG-2-based delivery solutions. • Maintains a high level of viewer experience in packet and wireless bit stream networks through error resilience. • Uses a common set of technologies between mobile and IPTV • Uses multiple reference frame

Figure 4

MGS coding-based IPTV stream H.264 MGS coding scheme supports the flexible adaptation of video quality under bandwidth fluctuation by using a hierarchical layer structure. In the following, every IPTV channel stream is assumed to be encoded in two streams, i.e. BL (Base Layer) and EL (Enhancement Layer) stream. BL stream includes the information required for displaying the minimum quality video, and EL stream allows some loss of quality refinement packets but it cannot be used alone. When some parts of EL stream are available together with BL stream, subscribers are able to watch better quality video by combining both of them. In the proposed system, H.264 MGS coding scheme is applied to each GOP (Group of Pictures). BL stream is encoded at a fixed bit-rate and transmitted by using the sparsest modulation scheme and the lowest coding rate at the PHY layer to provide IPTV service of minimum quality to as many subscribers as possible. Actually, the BL stream rate is one of the main parameters. On the other hand, some parts of EL stream are transmitted from the BS according to the selected MCS (modulation and coding scheme) as shown in figure 5

Figure 5

P2P IPTV With the success of P2P file sharing, new emerging P2P applications arise on the Internet for streaming content like voice (VoIP) or live video (IPTV). Nowadays, there are lots of works measuring P2P file sharing or P2P telephony systems, but there is still no comprehensive study about P2P IPTV, whereas it should be massively used in the future. A significant problem in providing IPTV services is its high deployment and maintenance cost. In addition, the capacity of the video servers can quickly become a bottleneck. One solution to alleviate the load on servers is to use peer-to-peer (P2P) systems. While early P2P systems were mostly used for file downloading, recently there have been several efforts on using the peer-to-peer approach to support live streaming and VOD streaming

Figure6

In P2P IPTV, end-hosts are responsible to duplicate flows to each other. End-hosts are not entities dedicated to stay in the networks all time: they can join or leave the network whenever they want and are prone to suffer failures. P2P IPTV systems have to deal with the arrivals and departures of peers (churn of peer). It is a challenging issue because live video has to respect playback instant to get smooth playback quality. A high churn of peers will involve additional delays or jitter variations for packet delivery, which will decrease overall video quality. In this section, we show the video peers lifetime to point out the churn of peers. Since our nodes have only a local view of all the peers in the network, the video peer lifetime is the duration between the first time and the last time our controlled nodes exchange video traffic with another peer.

IPTV over WiMAX Worldwide Interoperability for Microwave Access (WiMAX) offers a wireless solution in the access networks that can support IPTV services. WiMAX is capable of very high data rates, longer reach, and operates in non-line of sight (NLOS) modes in licensed and license exempt frequencies. Bandwidth is scalable and managed. Contents are encrypted for secured transmission and mobility is supported at vehicular speeds. Installation and maintenance costs of WiMAX systems are at a fraction of the costs of wired access networks. Taking advantage of these features, IPTV services can be designed, delivered, and managed cost effectively without compromising the video and audio quality.

Figure 7

Internet Protocol Television (IPTV) has been becoming popular as it promises to deliver the content to users whenever they want. The next step is to deliver this content wherever the users are. Traditional wire-based access networks can deliver the contents only to the fixed points. Hence, a new technology that can deliver the content to mobile users is needed. WiMAX network is very useful for media broadcasting applications, which is implemented by leveraging on the successful features of popular technologies such as DVB-H (Digital Video Broadcast-Handheld), MediaFLO (Media Forward Link Only), and 3GPP (the Third Generation Partnership Project) EUTRA (Enhanced UMTS Terrestrial Radio Access). Although Wi-MAX network provides high data rates in wireless environment, it is still poor compared to wired networks such as Ethernet, DOCSIS (Data Over Cable Service Interface Specifications), and fiber network. It is still a challenging problem to provide mobile IPTV service of high quality over wireless network. Furthermore, it is expected that much higher bandwidth will be required at BS (Base Station) sooner or later to support various multimedia services over mobile wireless environments. Thus, mobile IPTV systems must be designed to effectively manage the resource usage of IPTV channel streams over WiMAX network.

Review of WiMAX network WiMAX network is an emerging standard for wireless access technology that provides high data rates and QoS over a wide area. Now, a brief introduction to the physical and MAC layers of the Wi- MAX network follows.

Physical layer WiMAX network supports several transmission modes at the physical layer, i.e. SC (Single Carrier) mode, OFDM (Orthogonal Frequency Division Multiplex) mode, and OFDMA (Orthogonal Frequency Division Multiple Access) mode. In

the OFDM system, FEC coding is applied to the transmitted data stream for error resilience (i.e. more robust FEC coding provides stronger error protection). RS concatenated with CC (Convolutional Code) coding is mandatory for all WiMAX network implementations. The standard optionally supports CTC and LDPC (Low-Density Parity Check) codes. Then a resulting data stream is divided into multiple parallel low rate data streams. Each low rate data stream is mapped to an individual data subcarrier and modulated using some sort of PSK (Phase Shift Keying) or QAM(Quadrature Amplitude Modulation) such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM, and 64QAM. In fact, modulation is the process of translating a data stream into a form suitable for transmission on the physical medium, and its performance is measured by the ability to preserve the accuracy of the encoded data. Subcarriers are distributed into several groups, which are called sub-channels. Sub-channels may be configured by using contiguous subcarriers or pseudo-randomly distributed subcarriers over the frequency spectrum. Sub-channels formed by using pseudo-randomly distributed subcarriers provide improved frequency diversity and are particularly useful for mobile applications. Representative combinations of modulation and coding rate of the WiMAX network is given in Table 3.

Table3

MAC layer In general, MAC, sub-layer of Data Link layer, supports addressing and channel access control mechanisms for network nodes or terminals to communicate within a network. MAC of the WiMAX network is operated in a centrally controlled manner, i.e. the resource allocation is dynamically managed by BS. Fig. 1 represents the OFDMA frame structure in TDD (Time Division Duplex) implementation. The medium is divided into continuous MAC frames in time and sub-channels. Each MAC frame is configured by DL (DownLink) and UP (UpLink) sub-frames. At the beginning of each MAC frame, the BS transmits DL Map and UL Map into the DL subframe. These maps provide resource allocation and other control information for DL and UL sub-frames, respectively. In each frame, TTG (Tx/Rx Transmission Gap) and RTG (Rx/Tx Transmission Gap) are inserted between

the DL and UL sub-frames, which are time gaps between transmission and reception. The minimum resource allocation unit is called a slot, which is configured by one sub-channel over one, two, or three OFDM symbols depending on the subcarrier permutation scheme. A burst is a contiguous series of slots assigned to a given subscriber and different MCS (Modulation and Coding Scheme) can be applied to it. Transmission rate on the slot is dependent on associated MCS and a tradeoff exists between link robustness and throughput. In other words, the BER (Bit Error Rate) performance which suffers from fading and shadowing in wireless channels is improved at the cost of bandwidth efficiency, as modulation becomes sparserand coding rate lower. In contrast, denser modulation and higher coding rate provide higher data rates on the slot and increase sensibility against wireless channel error.

Conclusion Television has long been a dominant and pervasive mass media and its

viewing behavior has many important implications on the video distribution networks and systems. With the increasing popularity of Internet services, multimedia consumption patterns could change significantly over the coming years. However, the average time spent on watching television remains significant despite the uptake of broadband services. In fact, we expect TV to remain a crucial mass media in the future as it integrates many innovations in the Internet and as well as in the mobile space. With WiMAX offering high data rates to both mobile and fixed users, and the desire of users to watch real-time TV or VoD services make the implementation of IPTV over WiMAX an exciting killer application. Realization of IPTV will enable users to have VoD services as well as to subscribe whichever channel of their choice giving them the great deal of flexibility. IPTV is a technology that is now causing widespread disruption across the whole telecoms market place. Many of the world’s major telecommunications providers are exploring IPTV as a new opportunity from their existing markets and they are treating it as a defensive measure against many conventional cable television services entering into the market. Previously known as phone companies, the telcos now want to turn a “triple play” of voice, data and video through the IPTV. Finally “IPTV is an emerging technology that would evolve into a completely interactive experience in the future”.

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