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  • 7/31/2019 IPTV Concepts


    1. IP for IPTV

    The Internet Protocol or IP is a common protocol which provides a datatransmitting mechanism to manage packet flows between devices connected to theInternet. It is also a standard method for formatting data packets over a large

    network such as the Internet. A packet, which is defined as a collection ofinformation, can be sent in a well-defined format over the IP network. In the IPTVsystem, a video signal will be divided into multiple IP packets and then the packetswill be sent across the IP network.

    Internet Protocol is widely used in different networks such as Local Area Networkor LAN, wireless Wi-Fi network and telephony networks.

    In some developed countries, many people are using broadband networksin their homes. Therefore, video service providers do not need to build theirown network and they can use the samenetworks to deliver video services.

    Internet Protocol can easily simplify video services such as programinteraction, video on demand (VOD) and certain advertising.

    Nowadays, the IP networks can be found in every country in the world, thusthe number of users with high speed internet connections is also growingrapidly.

    IP is an excellent network technology for many applications such astransaction of data (for example, email or banking), local area network,sharing files, web surfing and many more.

    1.1 Unicast, multicast and broadcast

    Packet transmission is a process in which a packet of information is transmitted tothe user over the IP network. There are three different transmission processes,namely unicast, multicast and broadcast.

    Unicast transmission: Unicast is a type of transmission in which a single senderand a single receiver communicate with each other over the network. Thus, the

    packet of information is sent from only one sender to only one receiver involvingjust two nodes.In IPTV technology, video on demand is the main example of unicast transmissionwhere the user can stop, pause, play, and replay the video contents. Therefore,with unicast transmission the user can control the data without disturbing otherusers on the Internet.

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    Some other examples of unicast include http, telnet, SSH, SMTP, pop3. With theseapplications, the information can be sent from only one sender to only onereceiver.

    In IPTV, the channel transmission may be sent directly to a specific viewer using

    unicast one to one transmission process. The same television program can bedelivered to several users using unicast channel transmission. In this case, eachuser must be connected directly to the media.

    Multicast transmission: In the multicast transmission the information can be sentfrom a single source to a selected group of destinations. The multicast process iscommonly used to establish communication between a single sender and multiplereceivers. Therefore, a single device sends data packets to a group of devices atthe same time.

    In term of IPTV, each broadcast TV channel should have a single IP multicastgroup in order to send data packets to a selected group of destinations. It meansthat hundreds of viewers will be able to simultaneously watch a single televisionbroadcast. The broadcast packets will be sent to a group of clients and the clientscan enable the broadcast stream route to their network device.

    The use of multicast transmission is much more effective when the same packet ofinformation is sent to many users at the same time. The multicast transmission ismore complicated to implement than unicast transmission as more effort isrequired on the transmission to add and remove users from multicast groups.

    Figure 1 shows the difference between unicast and multicast transmissions. Inunicast transmission, three streams from a single source go to three differentdestinations, but in multicast transmission system, only one stream goes to thegroup of destinations.

    Figure 1. Unicast and multicast transmissions

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    Broadcast Transmission: With broadcast transmission, the packet of information issent from only one sender to all receivers connected to the Internet. Therefore, allthe receivers can get the information packet from the main single source.

    1.2 Signal transmission

    Signals are not transmitting over just one way. Signals can be transmitted overdifferent ways such as cable and satellite to the TV, computer or other displaydevices. If the channels are free, the cable company is oriented to collect signalsfrom all the different stations and goes to the viewers home via cable or network. Ifthe channels are payable, the cable companies scramble and keep the signalsfrom being picked up by the people who do not pay for the service and then go tothe subscribers homes via cable or the Internet. Signal amplifiers will be neededaround the local area to keep the signals strong for the subscribers.

    Today, the cable companies are using satellite dishes Instead of traditionalantennas to collect signals from different stations included in their own servicepackage. Some of the cable stations including ESPN, TBS, and HBO send theirprograms up to a satellite and then back down to the satellite dishes which arecontrolled by the local cable company. With this process, the signal problemscaused by the landscape or by the curve of the earth can be eliminated and theinitial signal arrives to the centre of the cable company.

    Figure 2. Transmitting of TV signals over the satellite

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    1.3 Protocols used for IPTV

    RTP: Real-time Transport Protocol provides packet format for delivering audio andvideo contents over IP networks. The protocol is used for streaming channelscontrolled by Real Time Streaming Protocol (RSTP).

    RTP is commonly used in some streaming media services including telephony andvideo teleconference applications services. Real-time Transport protocol and RTPControl Protocol (RTCP) work together. In this case, RTP delivers the mediastreams like audio and video over IP networks, while RTCP refers to monitortransmission statistics and quality of service (QoS) and helps to synchronizemultiple streams.

    RTSP: Real Time Streaming Protocol or controlling network protocol is used tocontrol streaming media servers. Therefore, RSTP controls the delivery of datawhile RTP streams the channels. This protocol is used to establish and controlmedia sessions from the server to the user. In order to start and stop datatransmission, the media servers issue playand pausecommands to easily controlthe transmission of media files from the server.

    RTSP is used to control unicast and multicast streams.

    Streaming of data in RTSP is one-directional. It means that data streamscan be sent from the server to the user.

    PIM: Protocol-Independent Multicast (PIM) is a set of multicast routing protocolsthat provide data distribution over IP networks such as the Internet, Wide AreaNetwork (WAN) and Local Area Network (LAN). As it is obvious from its name,

    protocol independent, PIM is independent and it uses routing information providedby various routing protocols such as BGP or Border Gateway Protocol. In IPTV,Protocol Independent Multicast (PIM) is commonly used to route IPTV multicaststreams between networks.

    IGMP: The Internet Group Management Protocol (IGMP) is used to managemembership in IP multicast groups. The protocol is widely used in online streamingvideo and gaming.

    In IPTV, the Internet Group Management Protocol is a main part of the multicastspecification over IP network. Therefore, the protocol is used by IPTV in order toconnect to a TV channel and to change from one TV channel to another.

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    2 Compression system

    2.1 Video compressions

    Video signals are always compressing while delivering IPTV services over an IP

    network. Generally, compression means reducing the quantity of bits required forvideo image representations. Therefore, the compressed video reduces therequired bandwidth for transmission of video over cable TV or satellite TV services.

    Video compression is the most efficient method for delivering better quality videoover an IP network. Many local TV broadcasters, cable TV and satellite TVsystems are using the video compression method to allow much more videochannels to be broadcast economically to the users.

    Here are listed some of the main reasons for the use of compression in the IPTVsystem:

    Compressed streams can be delivered over a low rate internet connectionwhile uncompressed streams cannot be delivered over a slow internetconnection.

    Compressed video and audio files take less space on a hard disk or otherstorage devices than uncompressed original files. Therefore, it will allowuser to save more contents in the storage devices.

    2.1.1 Moving Picture Expert Group (MPEG)

    MPEG is a group of experts that developed standards for the video and audiocompressions. The MPEG standard is used for coding video and audio content in acompressed digital format to provide best video and audio services. For example,digital TV, satellite TV, digital cable TV and high definition TV including Blue raydisks, are all using MPEG video compression technology to provide best videoservices. This technology is designed to compress data in order to form small bitsthat can be easily transmitted.The most common video compression systems thathave been developed by the moving picture expert group are MPEG-1, MPEG-2,and MPEG-4.

    MPEG-1 was the first video compression standard developed by the MovingPicture Expert Group in 1990. It is designed to be used in creating video CDs thatis very popular in computer multimedia. MPEG-1 also provides a videocompression method for DVDs where many DVD players can play video CDs aswell.

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    Figure 4 shows the simple process of MPEG-2 system. It shows how signal isdecoded using the MPEG-2 decoding process.

    Figure 4. Decoding process using MPEG-2 system

    MPEG-4 is a more recent video compression standard that was established in2000. MPEG-4 contains new technologies for video compression. Advance videocoding (AVC) or H.264 is the most new and powerful version of MPEG-4 videocompression which enables high definition signals to be encoded at a lowerencoded bit rate (10Mbps). It also provides a better technology for transportinghigh definition video signals. MPEG-4 compression technology can produce higherquality and clear image at lower bandwidth. In addition, it is very easy to implementMPEG-4 encoders and decoders.

    Figure 5 shows the simple decoding process of video and audio streams usingMPEG-4 stream decoder.

    Figure 5. MPEG-4 decoding process

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    2.2 MPEG Audio compression

    MPEG also has different audio compressions. There are 3 layers of MPEG audiocalled layer 1, 2 and 3. The most recent audio compressions are Advanced AudioCoding (AAC) along with High Efficiency Advance Audio Coding (HE-AAC) and


    Layer one of the audio compression is the easiest compression system that uses384 input samples while layer 2 uses exactly 1152 input samples for each runningcompression. Layer 1 that uses 384 samples is equivalent to 8 ms of audiomaterial using 48 kHz sampling. Therefore, layer 1 can provide a stable bit rate ata compression ratio of 4:1. This means that 1.4 Mbps compressed audio signalcan be achieved at 384 Kbps stream rate without having loss of quality.

    Layer 2 that uses 1152 is equivalent to 24 ms of audio at 48 kHz sampling. Itallows frequencies to be arranged more properly and provide better compressionof 8:1. It means that audio signal can be achieved at 192 Kbps of stream rate.

    Layer 3 of MPEG audio has the same number of samples as layer 2, but it usesthem more efficiently. Layer 3 uses variable length coding to put more efficientpackage of the compressed audio into the output stream. MPEG audio layer 3 isalso related to the MP3 audio format that is commonly used to store and tocompress audio files in order to transfer and playback on the audio players. Thecompressed MPEG layer 3 files are more popular in downloading music, swappingfiles, and some other portable player systems.

    MPEG-AAC is an advance audio coding system that can be available only withMPEG-2 or MPEG-4 video streams. This system supports a large variety of toolsthat can be used by encoders to create best audio streams. MPEG-AAC supportsup to 48 audio channels.

    3 Multimedia over IP

    Multimedia plays a central role in IPTV as well as networking. Multimediaapplications utilize different media types including graphics, audio, text, animationsand video.

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    3.1 Video conferencing

    Video conferencing also known as video teleconference is a telecommunicationtechnology that transfers audio and video data between two different locations atthe same time. Video conferencing would make an interesting product differentiator

    for an IPTV system. Video conferencing includes the real time streaming of audioand video data over a broadband service and the system is also included within theIPTV set-top box.

    3.2 Video servers

    Video servers carry out two main functions. The first one is called storage functionthat is responsible for keeping files of digital video contents on a hard disk. Thesecond one is called delivery function that is responsible for delivering andtransmitting video contents over an IP network for viewing. Sometimes, videoservers contain different physical hard disk drives and processors for betterreliability and performance. Video servers use RAID (Redundant Array ofInexpensive Disk) technology that store more data for each file. The use of thistechnology can increase the reliability of video servers.

    Ingest servers: they are used to collect contents from different sources such asstudio camera or satellite receiver, videotape, hard disk inside camera, and anyother sources that produce video signal. After collecting these contents, the ingestserver makes them available for use in a variety of applications. When the videohas been ingested, then it can be transmitted to the various devices for furtherprocessing.

    File servers: they are used in the video production process to store video clipstemporarily from a color correction workstation before these clips passed toanother workstation. File servers can also handle manipulated contents into theirfinal forms. They have the ability to store contents and data that are repeatedlyused in the video producing process such as theme songs or music process.

    Production servers: these servers are used to play the final video contents that areready to be played in highly reliable streams. Reliability is a key factor forproduction servers as any failures can cause the broadcaster to go off the air.These servers are using different technologies to obtain redundancy and to providefail-safe operations.

    Archives servers: these servers are used to store a huge amount of contents fromdifferent sources such as live broadcasts, news clips, purchased programming andso on. They are also used for a huge amount of storage at low cost and keepingvideo records of programming.

    Video on demand servers: these servers are responsible for storing contents whichare required by users for viewing. Video on demand servers create as many as

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    possible simultaneous streams and sometimes they create multiple copies of thesame contents. High bandwidth IPTV network or internet connection is used forthis purpose.

    Live streaming servers: these servers are designed to take live streams and then

    generate multiple copies of the streams for transmission over an internetconnection. Live streaming servers do not need storage for this process, butinstead they need to have a huge amount of processing capacity to generate IPpackets for the individual recipient of the stream. Live streaming servers also needhigh bandwidth internet connection in order to transmit all of the streams createdby them, to the IP network.

    4 Characteristics of the IPTV system

    4.1 Video on Demand (VOD)

    Video on demand (VOD) is an IPTV technology that allows user to watch and tolisten to TV programs on a TV or computer screen. With VOD, the user can selecta favorite program or a movie to begin immediately. This technology streams thecontents using a set-top box, computer or other devices in real time and downloadsTV programs that can be watched and viewed later. A VOD system consists of aset-top box along with a standard TV receiver. Finally, the service can be deliveredover the Internet to home TV using an IPTV set-top box and to portable or laptopcomputers, new mobile phone sets and advanced digital media devices. In order toprovide best services for the consumers, IPTV providers need to ensure that theirsystems can support video on demand even now or in the near future. Video ondemand performs the following tasks:

    Like any other video server, video on demand stores the video contents andhas the ability to deliver multiple copies of a single content.

    It performs network interface function that is also similar to other videoservers. But in this case, the video on demand server needs to support ahuge number of simultaneous streams.

    It supports user interaction that gives the opportunity to the viewer to pause,replay and fast forward video contents. It also supports catalog and ordering which means that video on demand

    provides support for the systems which enable user to display the list ofavailable contents.

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    True video on demand: True VOD is the special type of video on demand, whereeach user can receive an individual video stream which is under their control.Therefore, viewers have a free choice to start, stop, pause, replay, and forward thevideo contents. In this case, viewers typically pay a fee for each title viewed bythem. They can pay fees either from their prepaid account or it might be a monthly


    Near Video on demand: This type of video on demand is similar to true VOD, but inthis case the viewers do not have any control over the individual video stream.Stagger casting is one common type of near video on demand, in which multiplecopies of a program are played at short time intervals (approximately 5 minutes).

    Free video on demand: Free video on demand is a variation of VOD where viewersdo not need to pay if they want to view video. In most VOD systems, this content isbounded to long form advertisements, guides and other low cost content.

    Subscription Video on demand: Subscription VOD has the same deliverytechnology and viewer control as VOD that gives users unlimited access to aselection of programs for their fixed monthly payments. In this VOD service, theusers have control over a video stream where they can start, stop, pause, rewindand fast forward video contents.

    Personal Video Recorders: A Personal Video Recorder (PVR) is an electronicsdevice that compresses and records incoming video programming in a digitalformat to the hard disk located either in the set top box (STB) or it might be a USBflash drive, secure digital (SD) memory card or other local or networked massstorage devices. With PVR, users will be able to set PVRs to record specificprograms at specific times and control play back contents including pause, rewindand fast-forward capabilities.

    Figure 6. Simple IPTV video on demand

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    4.2 Triple Play

    Triple Play means the delivery of voice, data and video over a single accesssubscription. An IPTV broadband network can handle all three (voice, data, andvideo) services. The common applications for this procedure are Telephony,

    Television and high-speed internet services.

    The telephony option offers call services such as call forwarding, caller ID, callwaiting, call screening, selective call blocking and call conferencing. The networkoperators are interested in carrying out all these services using the same accesstechnology called Internet Protocol (IP), where IP is playing as a host for all thecommunications and signaling. The medium for the transmission of these servicesmight be fiber optic cable, conventional cable or satellite transmitter. Figure 7shows delivery of triple play services over the network.

    Figure 7. Delivery of Triple play services

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    4.3 IPTV Set-Top Box (STB)

    A set-top box (STB) is an IPTV device that is commonly used to receive anddecode digital television broadcast and to turn the signal into content which is thendisplayed on a television screen or other display devices. In order to view and

    watch programs on the television screen or other display devices, the STB must beconnected to the usable device using an Internet connection.

    Professional set-top box: Professional set-top-boxes referred to as IntegratedReceiver Decoders or IRD are the professional method of the broadcasting videoand audio contents to the television or other display devices. They are designed towork the best as they are technically superior.

    Figure 8. IPTV Set-Top-Box

    4.4 Digital Subscriber Line (DSL)

    Digital Subscriber Line or DSL is a high-speed Internet service that competes withcable Internet to provide high-speed internet access to the local customers. Thereare several options of Internet access such as dial up, cable, DSL, satellite, fiberoptic, mesh wireless or point distribution wireless. DSL operates over a standardtelephone connection like dial-up connection, but it is faster than dial-up, becauseDSL does not tie up the phone line. DSL Internet access is delivered across thetelephone network using a DSL modem, which connects to the telephone wall jackand computer. Now, many IPTV service providers deliver their IPTV services usingthe DSL network. The main components of the DSL network are central office(CO), remote terminals (RT), feeder plant and Digital Subscriber Line AccessMultiplexer (DSLAM). A DSL modem must be installed to receive signals from the

    DSLAM and convert them into the appropriate form for the display devices such asa PC or a TV set.

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    Figure 9. Configuration of the DSL network

    4.5 Digital Subscriber Line Access Multiplexer (DSLAM)

    A Digital Subscriber Line Access Multiplexer or DSLAM is a network device thatconnects multiple DSL connections using multiplexing technique to make faster

    connections to the internet. It is one of the key delivery elements in IP videotransport that receives signals from multiple customer DSL connections and putsthem on a high-speed backbone line. At the Telephone Company or TELCO, theDSLAM device collects the data from its modem ports and combines their data andvoice traffic into one complex composite "signal" using multiplexing method.Depending on the type of product and setup, a DSLAM connects the DSL linesover its Asynchronous Transfer Mode (ATM), Internet Protocol and frame relay.DSLAM enables a telephone company to offer the fastest DSL phone line serviceswith the fastest backbone network technology called ATM to the business partneror home users.

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    Figure 10. ADSLAM operation

    4.6 Quality of Service (QoS)

    Quality of Service or QoS is a combination of networking technology andnetworking technique. IPTV system requires a high level of QoS to provide best

    IPTV services to the customers. There are two main categories of the QoS, audioquality and video quality.

    Audio quality: Audio quality is the quality of the audio output that enables thesystem to recreate the main characteristics of the original audio signal. It can beaffected by several factors such as audio compression, transmission system andbandwidth limits. The recent audio compression technology helps audio files toremain in small size and deliver high quality audio signal. A poor transmission ofaudio signal is caused by packet loss or packet corruption. Packet loss happenswhen the network fails to deliver packets to the destination within a specific time.

    Packet loss can cause network congestion or equipment failures. The impressionof packet loss on the audio system is to temporarily mute the audio signal. Packetlosses are rare since the systems normally resend data packets that are failed toreach within a specific time. Packet corruption is the modification of data packetswhile transmitting over the network. It can happen due to a weak quality of thecommunication line. Therefore, if corrupted data is used, it will create differentaudio sound than expected.

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    Video Quality: Video quality is a quality of video output that enables the videotransmission system to recreate the main characteristics of the original videosignals. Similar to the audio quality, the same factors affect video quality such asvideo codec or video compression, transmission system and limit of bandwidth.

    Some of the distortions such as blurriness and edge noise will affect analog videosystems. Some factors such as tiling, block error, smearing, jerkiness, edgebusyness and object retention will impair the digital video transmission system.Tiling means changing of the digital video image into square tiles that are locatedas unoriginal positions on the screen. Block error is a type of error in digital TVtransmission system that does not represent error signals while compressingimages. Jerkiness means skipping of the video image frames. Object retention isresponsible for keeping of the frame portion when the image has changed.

    4.7 Mobile IPTV

    This is a new easy and comfortable technology that uses mobile devices to receiveand transmit multimedia traffic including video and audio contents, data andgraphic services, and more IP-based functions using wired and wireless IPnetworks.

    With this technology, the users will be able to enjoy various IPTV services over IPnetwork everywhere.

    Mobile IPTV is available on a limited level and very limited services. The newMobile IPTV technology uses 3G of the mobile data network for running IPTVservices on the mobile phone. Since IPTV is an advanced technology, it allowsusers to play previously recorded programs for fresh viewing.

    The other benefits of this technology include switching the channels where userscan switch various channels just like they switch them on their TV Set top box.

    Further, with the pause option, the user can pause the TV program that can bewatched later by the viewer.

    Therefore, this technology gives a better quality of service by adjusting the videobroadcast depending on the network connectivity.

    The user does not need to buy an expensive mobile phone in order to use thistechnology, so a normal colored screen phone with fair display resolution andmobile data connectivity will be fine. The user needs to install Java applications onthe mobile phone to properly use this technology service. Many new mobilephones support Java applications. Mobile IPTV services are provided by theMobile operator, thus the application, service, channel packages and tariffs will beset by them.

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    4.8 IPTV Testing

    In order to test an IPTV operation, the measurements of the system, device orservice that provide television services through a data network must be performed

    to validate its successful operation. The IPTV testing mechanism can becomplicated as there are many interrelated processes where all these process canreduce the quality of the media services that are used to control the media flow.

    Since the IPTV system is differ from a broadcast television system, IPTV isdesigned to use transmission systems that provide different levels of performance.

    4.8.1 IPTV Testing over DSL

    Figure 11 shows how to deliver Internet protocol TV (IPTV) using DSL. Nowadays,this is a better technology that gives many new business opportunities to theservice providers. The voice, video and data services, commonly called triple-playservices can be easily integrated by ADSL2 and VDSL2 over a single telephoneline. With all these technological improvement it is now more practical to providesimultaneously multiple standard (SDTV) and high-definition television (HDTV)channels to the appropriate users.

    Figure 11.Typical IPTV over DSL network

    4.9 IPTV network construction

    Construction of IPTV networks can serve people over an IP network. IPTV candelivers hundreds of TV channels to the subscribers using an internet connection.The IPTV financial system is determined two main factors. The first factor is thecalculation of the total number of homes or total number of residence which are

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    connected to the IP network and the network connection is available for anycustomer who wants to become a subscriber. The second factor is the calculationof the total number of subscribers who have made subscription for the IPTVservices to get IPTV videos to their display devices. There are some facilitiesconstructed for the large IPTV delivery system to deliver video services across a

    large expanse of area.

    4.9.1 Super Head End (SHE)

    Super Head End (SHE) provides services to the large number of customers byprocessing the video contents that are commonly available to all subscribers.Therefore, a Super Head End (SHE) is used to collect the contents from differentprograms suppliers and convert them into the appropriate form and then deliverthem over an IP network.

    Generally, super head end (SHE) describes the following four functions:

    1. Content aggregation: contents must be collected from different programmingsuppliers.

    2. Conversion: the incoming contents should be converted into the appropriateform in order to deliver over an IPTV system.

    3. Transport: the compressed video signals must be transported to the videoservice office (VSO) over IP network.

    4. Formatting: the video contents must be formatted and then they can betransmitted to the viewers. The contents can be also delivered as a datafiles over an IP network.

    4.9.2 Video Serving Office (VSO)

    Video serving office is located in every required area to provide video delivery andvideo processing services for a single city or geographical area. Each videoserving office obtains contents from a super head end and local programmingsources. So, VSO is used for real time distribution of these contents to each centraloffice in the area. Video serving office provides additional services such ascustomer billing and other related services. The following functions are included inthe video serving office (VSO):

    Localization: This is one of the most functions of the video serving office thatprocesses specific contents to the local area. Similar to the super head end (SHE),the arriving local contents must be converted to the IPTV delivery format.

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    Compression: The video content processors convert different video signals that arecompressed at one bit, into the different bit rate. These processors can also takevideo signals that are compressed using the MPEG compression system such asMPEG-2 and convert them into the different compression standards.

    Creation of stream: Video serving office can create IPTV streams containing thepackets that are sent to the central office. VSO can create one stream for eachactive viewer using simple remote equipment. Only one stream will need to begenerated for each broadcast channel using sophisticated remote equipment. Inthis case, when multiple users are watching the same TV channel, the remoteequipment is responsible for creating as many as needed copies of the samechannel to send one to every active user.

    Storage: The video serving office (VSO) and video on demand (VOD) functions arecombined with each other. This means that they are used to create one way(unicast) streams that are delivered to the subscribers while viewing video ondemand contents. In this case, each viewer will be able to pause, replay and fastforward the video streams.

    Local ads: Local ads are very important sources for the IPTV operators. They canbe inserted into both national and local programming. Advertisement servers areresponsible for storing advertisements that are received from super head end(SHE) or other sources.

    Interactivity: This is the main function for IPTV compared to satellite TV. Withinteractivity operation, commands are collected from individual set-top boxes to beprocessed at the video serving office. Selection, purchase and viewer control of thevideo contents are the main functions of the interactivity.

    STB authorization: This function is very important to the financial purpose for theIPTV providers. The VSO system will confirm each authorized set-top box before itcan get video contents for viewing. Two main functions can be taken during theencryption and scrambling process. Firstly, the IPTV operators must ensure thatonly paying customers are able to view contents. Secondly, they also must ensurethat viewing contents are protected from retransmission and unauthorizedduplication.

    Fiber delivery: For this VSO function, the fiber optic network which containsnumerous gigabit Ethernet lines can be used in order to provide connectionbetween video serving office and central office or remote terminal locations.

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    4.9.3 Central Office (CO) and Remote Terminal (RT)

    Some IPTV networks are using existing physical infrastructure of the telephonecompany, such as buildings. CO and RT are two locations where the central officeincludes call switching equipment and the remote terminal includes systems that

    connect subscriber lines including digital or fiber optic links to the neighboringcentral office. In both locations, the IPTV equipment can be installed to deliverIPTV services over digital subscriber lines (DSL).

    The installed equipment can perform several tasks including the following:

    DSLAM function: There is one or maybe several digital subscriber line accessmultiplexer (DSLAM) units inside each central office (CO) or remote terminal (RT).The DSLAM is used to connect incoming video traffics from the video serving officeto the DSL lines sending out to each subscriber. The IP address of each incomingpacket must be examined by the DSLAM and then it can be delivered to the DLSline connected to the subscriber device with that IP address.

    Multicasting technology: This technology is based on internet group managementprotocol (IGMP). Multicasting which is supported by some of the recent DSLAM isused to broadcast IPTV videos. In this case, the DSLAM has the ability to take onestream from the video serving office (VSO) and make multiple simultaneousstreams of the single channel to multiple viewers at the same time. The videoserving office must provide individual video stream for individual users in the regionif they do not wish to use multicasting technology.

    Connectivity: DSLAM is also used to connect existing telephony system in thecentral office or remote terminal. In this function, the DSL splitter allows DSLequipment and the existing telephone equipment to share a single pair of copperwires that connects to each subscribers home.

    Combining services: Different IPTV services such as IPTV video and data servicescan share high speed bandwidth provided by a DSL line to the customer premises.The data traffic can be separated by the DSALAM within the central office and canbe connected to an IP data router for future processing. The appropriatelyconfigured services such as voice over IP (VOIP) could also be separated by theDSLAM.

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    4.9.4 Customer premises

    This is the most difficult environment for the IPTV operators. Some of therequirements such as power, physical location and a network wiring system areneeded for the IPTV devices to be connected to the set-top boxes located in the

    customer homes. Different technology could be used for this purpose includingcoax, twisted pair and as well as wireless connection. The following technologiesare employed here:

    DSL modem: A stand-alone or integrated into a home gateway DSL modem mustbe configured in the house to get digital signals from the DSL connection andconvert data into the usable forms for the other user devices.

    DSL filter: This filter is responsible for preventing standard telephones fromreceiving signals that are processed by the DSL modem.

    Home gateway: This gateway can be installed by some service providers toestablish communications to multiple set-top boxes. It is also used to managehome network and convert between different types of cabling and the high speedDSL lines.

    Set-top box (STB): The set-top box supports many functions in IPTV technology. Itis used to decode digital video signals, provide graphics for the display screen,supports channel selection by the viewer and performs many other tasks. The set-top box must be suitable for each television set, otherwise the IPTV system mightnot work.

    Figure 12. IPTV system architecture

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    4.9.5 Typical software capabilities

    Software provides several key functions for the IPTV system. To watch IPTVvideos on display devices, software is needed to perform this task. Some of thesoftware functions available in the IPTV system are described as follows.

    Electronic Program Guide (EPG): Generally, this is an on-screen menu that letsviewers to know which content is available on which channel or channels. Thechannels can be broadcast channels available for all users at the same time or bevideo on demand (VOD) content available for individual viewers. The IPTV networkproviders provide the program guide, but in some cases it can be purchased froman external supplier. There are two types of EPG, scrolling program guide (SPG)and interactive program guide (IPG). In the scrolling program guide, the content onevery available channel is displayed in channel number order on a grid that slowlyscrolls up the TV screen. However, in the interactive program guide, the channelsand contents can be displayed on a TV screen where the viewers can use remotecontrol to scroll up or down in the grid to view different available channels and tosee detailed information about the current programs and they can also scroll to theright to see next programs.

    Conditional Access System: The control access system (CA) controls theavailability of programs to viewers. Therefore, CA controls which program isavailable for which user. For example, only the subscribed user to the premiummovie channel is allowed to access and view that channel. It is fairly simple way toimplement an IPTV system because the IPTV system needs to ensure thatunauthorized viewers cannot receive the IPTV content.

    Digital Rights Management System: The digital rights management system (DRM)is designed to control viewer action after the content is delivered. Therefore, DRMis used to protect property rights of the content owner after he/she received thecontent. This system provides some encryption forms and scrambling, thus thecontents will not be viewable without the allocated key. In addition to the contentscrambling, the system does not allow unauthorized copies or recordings of thecontents to be made.

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    4.10 IPTV Advantages and disadvantages

    There are several advantages of the IPTV technology over current digital oroverthe air broadcast TV signals; here are a few of them.

    Integration: Integration is one of the IPTV advantages as many companies offerseveral services in one integrated package. IPTV is one example of an integratedpackage with normal broadband Internet connection and Voice over InternetProtocol (VoIP). All these services can be delivered directly to the consumer.Therefore, the costs for the system can be reduced and the consumer only has todeal with one provider instead of more, making it more convenient.

    Switched IP Technology: Cable TV broadcasters and Satellite TV broadcastersgenerally send all television signals at the same time and then the viewer chooseswhich signal to show on his/her television set. Therefore, lots of unnecessarybandwidth is used in this process.

    IPTV commonly uses switched IP technology because the entire process is moreefficient with this technology. In this case, all the TV data is held in a centrallocation and only the chosen channel by the consumer at home is piped in. Sincethe bandwidth is no longer a big issue, this technology provides the ability to addmuch data and much bandwidth in order to deliver services of a better quality.

    Interactivity: Compared to cable, satellite or broadcast TV systems, it is very easyto perform interactivity with the IPTV system. Because the IPTV system delivers itsservices over the Internet directly to the consumer homes, it is very easy to movedata from the TV company to the consumer home and from the consumer homeback to the TV company. There are several ways of best interaction between theconsumer and a TV company using television. With interactive TV, the viewers canbuy or order products directly from their TV screen. Viewers can also request moreinformation on a program that they wish to view on a TV screen.

    Home Network: A television that is connected to the Internet, allows users to playstored media files such as digital photos, videos or music. Today, many computermonitors contain TV tuners, so viewers can also watch TV programs on theircomputer monitors. Therefore, if the computer has such a TV tuner, it means thereis an additional TV set at home.

    Video on Demand (VOD): IPTV system uses Video on Demand (VOD) which is aninteractive and famous technology in the IPTV system. It allows users toconveniently request TV programs from the television. For example, users caneasily turn on their TV set, scroll up or down through a menu and request theprogramming that they wish to view on a TV screen.

    Better Compression: IPTV provides a better video and audio compression as wellas creating best quality images and several programming options such as

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    interactivity, integrity, networking and so on. Compared to the current digital TVstandard, the IPTV system uses an advanced compression standard to providehigh quality TV images for the consumers.

    Since the advantages of IPTV are much greater, there are some disadvantages

    that we should be aware of. Packet loss and system delay are some of thesedisadvantages. Like other types of data, the IPTV system uses IP technology tosend and receive information. Considering this fact, if the Internet connection is notfast enough, the IPTV system may not work properly and will face to packet lossand system delay during the transmission process.

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