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Digital Video Broadcasting An Overview

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Presentation on theme: "Digital Video Broadcasting An Overview"— Presentation transcript:

1 Digital Video Broadcasting An Overview
Prof. Dr. Mehmet Şafak Hacettepe University Dept. of Electrical and Electronics Engineering 06800 Beytepe, Ankara, Turkey

2 Digital TV How come a man can be so sensitive as to distinguish between resolutions 1024 x 678 and 1365 x 768, but can not see the difference between 15 totally different woman shoes ? I could see the difference if they were on the TV 14 July 2006 DVB - An Overview

3 Outline Vision Data Broadcasting Integrated Receiver Decoders (IRD)
Transmission on Cable, Satellite and Terrestrially Interaction Channels The Multimedia Home Platform (MHP) DVB-Handheld Hybrid Networks Prospects for Future Developments 14 July 2006 DVB - An Overview

4 Vision Initially, DVB concentrated on broadcasting of audio and video services. In later phases, DVB addressed areas which lie outside of the classical broadcast world. Vision defined in 2000: DVB’s vision is to build a content environment that combines the stability and interoperability of the world of broadcast with the vigor, innovation, and multiplicity of services of the world of the Internet 14 July 2006 DVB - An Overview

5 Data Broadcasting

6 Data Broadcasting A 4:2:2 picture requires a raw transmission rate of 13.5 Msamples/s x 16 bits/sample =216 Mbps. The 216 Mbps just to transmit one digital TV channel is very high, so the need for compression is obvious. Using compression techniques, the data rates on the order of 3.2 Mbps per TV channel are currently used. 14 July 2006 DVB - An Overview

7 Data Broadcasting nn 14 July 2006 DVB - An Overview
Ken McCann, HDTV in Europe:Theory and Practice, DVB-Scene, 18, 2006 14 July 2006 DVB - An Overview

8 Data Broadcasting For real-time HDTV encoders, the rate of improvement in practice has been significantly less than for SDTV: smaller number of channels per multiplex means that the introduction of statistical multiplexing techniques did not yield as much of a benefit for HDTV as it did for SDTV. Today’s real-time HDTV encoders for H.264/AVC or VC-1 do not yet fully exercise all of the additional tools in the new algorithms, such as variable block sizes Within a year, 8-10 Mbps is expected to be sufficient for the transmission of HDTV signals. Ken McCann, HDTV in Europe:Theory and Practice, DVB-Scene, 18, 2006 14 July 2006 DVB - An Overview

9 Components inside the DVB data container
Data Broadcasting Components inside the DVB data container U. Reimers, DVB-the family of international standards for DVB, Proc. IEEE, vol.94, no.1, pp , Jan. 2006 14 July 2006 DVB - An Overview

10 Data Broadcasting The output of the MPEG-2 multiplexer (transport stream) consists of 188-byte packets, where different video, audio and data channels are multiplexed. Depending on the usable data rate of the broadcast channel, the size of the container varies. The program specific information (PSI) provides a list of packet ID (PID) values of the corresponding program numbers. The service information (SI) contains the modulation parameters, translates program numbers into service names and electronic program guide. 14 July 2006 DVB - An Overview

11 Data Broadcasting Data services can be
program related (e.g., teletext), or independent of any other service in the multiplex (e.g., software download, MHP applications, information services). DVB data broadcasting offers fast Internet access via satellites. Users may be connected to the Internet via standard modems and in addition install a satellite receiver card into their PCs for broadband downstream. 14 July 2006 DVB - An Overview

12 Integrated Receiver Decoders (IRD)

13 Integrated Receiver Decoders (IRD)
SDTV or HDTV Baseline IRD or IRD with digital interface whether or not they are intended for use with a digital bitstream storage device such as a digital VCR Video coding formats: MPEG-2 video or MPEG-4 AVC (H.264) Audio coding formats: Dolby AC-3, DTS and MPEG-4 AVC (H.264) 14 July 2006 DVB - An Overview

14 Integrated Receiver Decoders (IRD)
Reception of DVB services delivered over IP-based networks DVB-TXT replaces Teletext which is transported during the period of the vertical blanking interval (VBI) of analog television. DVB developed a generic means for the delivery of all VBI data, e.g., to enable the control of video recorders, the signaling of wide screen programs. 14 July 2006 DVB - An Overview

15 Integrated Receiver Decoders (IRD)
As part of DVB signals, it is possible to provide a translation of original soundtrack in the form of subtitles add graphic elements to the transmitted images, e.g., station logos. TV-Anytime information in DVB transport streams help personal digital recorders (PDR) to search, select and acquire the content, the viewer wishes to record. 14 July 2006 DVB - An Overview

16 Transmission on Cable, Satellite and Terrestrially

17 Transmission Block diagram of the DVB-T encoder
(Blue blocks are used in DVB-C and DVB-S as well) U. Reimers, Digital Video Broadcasting, IEEE Comm. Mag., pp , June 1998 14 July 2006 DVB - An Overview

18 Transmission DVB-S DVB-S2 Published in 1993 Modulation: QPSK and BPSK
Convolutional codes concatenated with RS codes DVB-S2 Published in 2003 Modulation: QPSK, 8-PSK (broadcast applications), APSK and 32-APSK (professional applications) Backward-compatibity with existing DVB-S receivers Reasonable receiver complexity Interactivity (i.e., Internet access) Professional services, such as digital satellite news gathering 14 July 2006 DVB - An Overview

19 Transmission DVB-S2 Best transmission performance Maximum flexibility
LDPC codes concatenated with BCH codes Variable and adaptive coding and modulation (recovers rain margin) Approximately 30 % capacity increase compared to DVB-S Maximum flexibility framing structure variable and adaptive coding and modulation can operate in any existing satellite transponder accommodates any input stream format (188-byte MPEG-2 transport streams (packets), continuous bit streams, IP, ATM) 14 July 2006 DVB - An Overview

20 Performance of LDPC codes over AWGN channel (N=64800)
Transmission M.Eröz, F-W. Sun and L-N. Lee, An innovative LDPC code design with near-Shannon-Limit Performanve and Simple Implementation, IEEE Trans. Comms., vol.54, no.1, pp.13-17, January 2006 Performance of LDPC codes over AWGN channel (N=64800) 14 July 2006 DVB - An Overview

21 Transmission M. Eröz et al., An innovative LDPC code design with near-Shannon-limit performance and simple implementation, IEEE Trans. Communications, vol.54, no.1, pp.13-17, January 2006. M.Eröz, F-W. Sun and L-N. Lee, An innovative LDPC code design with near-Shannon-Limit Performanve and Simple Implementation, IEEE Trans. Comms., vol.54, no.1, pp.13-17, January 2006 Comparison of DVB-S2 (LDPC+ BCH) codes to DVB-S (convolutional+ RS) and channel capacity 14 July 2006 DVB - An Overview

22 Transmission For each code rate, a parity-check matrix is specified by listing adjacent check nodes for the first bit node in a group of M=360. Irregular LDPC codes are used, where degrees of bit nodes are varying. DVB-S2 offers more than 30% capacity improvement DVB-S2 is, on average, about only dB away from Shannon limits. 14 July 2006 DVB - An Overview

23 Transmission DVB-C DVB-H Published in 1994
Modulation: M-QAM with M=16, 32, 64,128 or 256. Only RS coding is used (no convolutional coding). DVB-H Published in November 2004 Enables the reception of digital TV signals by handheld devices Additional FEC, in-depth interleaving and time slicing 14 July 2006 DVB - An Overview

24 Transmission DVB-T, published in 1997, uses OFDM transmissions
OFDM has 2K (subcarriers), 4K and 8K versions OFDM allows single-frequency network (SFN) operation Modulation: QPSK, 16-QAM or 64-QAM. Hierarchical modulation: High and low priority streams are modulated onto a single DVB-T stream for SDTV and HDTV Reception by roof-top antenna, portable and mobile reception DVB-T is adopted in large parts of the world with built-in front-ends set-top-boxes PCI cards and USB boxes for desk-top PCs PCMCIA modules for lap-top PCs DVB-T reception in cars in driving speeds 14 July 2006 DVB - An Overview

25 SFN Range vs Mobility Trade-off
OFDM with 2K: widest subcarrier spacing, hence least susceptible against Doppler shifts (suitable for high-mobility applications) shortest symbol duration, hence provides the minimum range for SFN. OFDM with 8K: narrowest subcarrier spacing, hence most susceptible against Doppler shifts (suitable for low-mobility applications) longest symbol duration, hence provides the maximum range for SFN. OFDM with 4K provides a trade-off between 2K and 8K 14 July 2006 DVB - An Overview

26 Hierarchical Modulation
Two separate data streams modulated onto a single DVB-T stream, high-priority (HP) (low data rate) stream is embedded within a low-priority (LP) (high data rate) stream Receivers with good reception conditions can receive both streams Only HP streams are received in bad channel conditions, e.g., mobile and portable reception 14 July 2006 DVB - An Overview

27 Hierarchical Modulation
An example of a constellation diagram for hierarchical modulation HP bit stream (QPSK) LP bit stream (64-QAM) 14 July 2006 DVB - An Overview

28 Hierarchical Modulation
Broadcasters can target two different types of DVB-T receiver with two completely different (LP or HP) services LP stream is of higher bit rate, but lower robustness than the HP one; hence, a trade-off between service bit-rate versus signal robustness A broadcast could choose to deliver HDTV in the LP stream. 14 July 2006 DVB - An Overview

29 Choice of parameters for non-hierarchical DVB-T transmission
U. Ladebusch and C.A. Liss, Terrestrial DVB, Proc. IEEE, vol.94, no.1, pp , Jan 2006 14 July 2006 DVB - An Overview

30 Transmission ETSI EN V1.5.1 ( ), Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital terrestrial television Useful bit rate (Mbit/s) for all combinations of guard interval, constellation and code rate for non-hierarchical systems for 8 MHz channels (irrespective of the transmission modes) 14 July 2006 DVB - An Overview

31 Transmission For the hierarchical schemes the useful bit rates can be obtained from the table as follows: HP stream: figures from QPSK columns; LP stream, 16-QAM: figures from QPSK columns; LP stream, 64-QAM: figures from 16-QAM columns. ETSI EN V1.5.1 ( ), Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital terrestrial television 14 July 2006 DVB - An Overview

32 Transmission Minimum C/N ratio in the transmission channel required for quasi-error-free (QEF) reception for DVB-T QEF reception: BER <10-11 at the output of the RS decoder 14 July 2006 DVB - An Overview

33 Interaction Channels

34 Interaction Channels The data belonging to a certain interactive service is transmitted in the broadcast channel The interaction channel enables the user to respond in some way (for instance via the standard remote control ) to the interactive service. The service provider or network operator listens and reacts to that response. 14 July 2006 DVB - An Overview

35 Generic system reference model used by DVB for interactive services
Interaction Channels Generic system reference model used by DVB for interactive services U. Reimers, DVB-the family of international standards for DVB, Proc. IEEE, vol.94, no.1, pp , Jan. 2006 14 July 2006 DVB - An Overview

36 Interaction Channels The user’s response may take the form of some simple commands, like voting in a game show, purchasing goods advertised in a shopping program. Interactive services may take the form of full Internet access at the receiver. 14 July 2006 DVB - An Overview

37 Interaction Channels DVB broadcast channels can deliver information at typical rates of 20 Mbps per channel for terrestrial broadcast networks, 38 Mbps per channel for broadcast networks via satellite and cable. Capacity of interaction channel may range from a few kbps to up to 10 Mbps in cable networks. 14 July 2006 DVB - An Overview

38 Interaction Channels Return Channel Terrestrial (RCT):
Multiple access: OFDMA Coding: Turbo or RS+ convolutional Several kbps per TV viewer in cells with 65 km radius Can handle large peaks in traffic Use any gaps or under-utilised spectrum Serve portable and mobile devices Can operate in 6, 7 and 8 MHz channels Transmit power < 0.5 W rms Time interleaving against impulsive interference 14 July 2006 DVB - An Overview

39 Interaction Channels V. Paxal, DVB with return channel via satellite, DVB-RCS200, Simplified diagram of a network architecture for DVB return channel satellite systems (RCS) 14 July 2006 DVB - An Overview

40 The Multimedia Home Platform (MHP)

41 The Multimedia Home Platform
The MHP specification defines an interface between a digital TV and the network to be connected to in order to support interactive services. It provides features and functions required for the Enhanced Broadcast, Interactive Broadcast, Internet Access. The right to use the MHP logo is only granted to those MHP implementations that pass some tests, defined by ETSI. 14 July 2006 DVB - An Overview

42 The Multimedia Home Platform
MHP offers true multimedia services to TV users. MHP provides a technical solution for the user terminal enabling the reception and presentation of applications in an environment that is independent of specific equipment vendors, application authors, broadcast service providers. 14 July 2006 DVB - An Overview

43 The Multimedia Home Platform
Some examples: Electronic program guides for the channels/services provided by a broadcaster Information services (superteletex, news tickers, stock tickers) Enhancements to TV content (sporting and voting applications and local play-along games) E-commerce, e-government and other applications relying upon secure transactions Educational applications 14 July 2006 DVB - An Overview

44 DVB over IP-based Networks

45 DVB over IP-based Networks
A typical IPTV service involves the delivery of broadcast television, radio and similar on-demand services over IP networks, hence, a bi-directional IP communication. An open IP infrastructure is used to reach the customers that can not be reached via classical broadcast networks. Thus, the geographical reach of DVB services can be extended using broad-band IP networks. 14 July 2006 DVB - An Overview

46 DVB over IP-based Networks
Basic IPTV architecture 14 July 2006 DVB - An Overview

47 DVB over IP-based Networks
The work on IPTV can be divided into three areas: Set-top boxes and personal video recorders (PVR), Home networking, Additions to the Multimedia Home Platforms (MHP). A specification has been developed that describes the transport of MPEG-2 based DVB services over IP-based networks. Creation of a wireless home network segment is soon expected. 14 July 2006 DVB - An Overview

48 DVB-Handheld

49 DVB-Handheld The system takes into account the specific properties of typical DVB-H terminals: Battery-powered User mobility Handover between cells Mobile multipath channels (antenna diversity) High levels of man-made noise Indoor and outdoor operation Flexibility to operate in various transmission bands and channel bandwidths (to operate in various parts of the world) 14 July 2006 DVB - An Overview

50 DVB-Handheld DVB-H requires some additional features in the link layer of the existing DVB-T standard; Existing receivers for DVB-T are not disturbed by DVB-H signals The additional elements in the link layer: Time slicing to reduce the average power in the receiver front-end significantly (significant power savings in the receiver) to enable smooth and wireless handover when the users leave one service area as they enter a new cell 14 July 2006 DVB - An Overview

51 DVB-Handheld The capacity of one DVB-T channel is split between three TV programs and an additional eight DVB-H services Slice duration: 625 ms Bit rate: 3.2 Mbps (=2 Mb/625 ms) Average bir rate: 0.4 Mbps(=3.2/8) 625 ms U. Reimers, DVB-the family of international standards for DVB, Proc. IEEE, vol.94, no.1, pp , Jan. 2006 14 July 2006 DVB - An Overview

52 DVB-Handheld Additional forward error correction (FEC) gives an improvement in carrier-to-noise (C/N) performance Doppler performance in mobile channels tolerance to impulsive interference e.g., ignition noise in cars. In view of the restricted data rates and small displays of handheld terminals, it is suggested to exchange MPEG-2 video by H.264/AVC. 14 July 2006 DVB - An Overview

53 DVB-Handheld The extensions to the physical layer of DVB-T:
Bits in transmitter parameter signaling (TPS) are upgraded to indicate the presence of DVB-H service A new 4K OFDM mode adopted for trading off mobility and single-frequency network (SFN) size All modulation formats (QPSK, 16QAM and 64QAM) with nonhierarchical or hierarchical modes can be used A new way of using the symbol interleaver of DVB-T has been defined (to provide tolerance against impulsive noise) The addition to DVB-T physical layer of a 5-MHz channel bandwidth to be used in non-broadcast bands. 14 July 2006 DVB - An Overview

54 DVB-Handheld DVB-H is intended to use the same broadcasting spectrum, which DVB-T is currently using. DVB-H services can be introduced in a dedicated DVB-H network now it is possible to select 4K mode or in-depth interleavers by sharing an existing DVB-T multiplex between DVB-H and DVB-T services by using the high-priority part of the DVB-T hierarchical modulation 14 July 2006 DVB - An Overview

55 DVB-Handheld Possible applications for DVB-H:
IP datacasting service to handheld terminals like mobile phones Broadcast services for the mobile phone users frequency allocation for simultaneous operation? DVB-H is very spectrum-efficient when compared with the traditional TV services: One 8-MHz channel can deliver video streaming services to the small screen terminals 10 times more than SDTV with MPEG-2 20 times more than HDTV with AVC 14 July 2006 DVB - An Overview

56 Hybrid Networks

57 Hybrid Networks Hybrid networks exploit the benefits of both DVB and mobile communications to enhance services provided to the consumer: Broadcast networks typically involve wide area and high throughput at the expense of high Tx powers. Mobile communications offer low-power transmitters covering smaller areas (cells) Network cost per user is higher than for a broadcast network 14 July 2006 DVB - An Overview

58 Hybrid Networks Hybrid Networks www.dvb.org 14 July 2006
DVB - An Overview

59 Hybrid Networks The IP datacast, used by DVB for a system under development, integrates DVB-H in a hybrid network structure consisting of a mobile communications network such as GPRS or UMTS, and an additional DVB-H downstream. In the process of being standardized A paid service Possibility of handover 14 July 2006 DVB - An Overview

60 Hybrid Networks Architecture of the IP datacast system
U. Reimers, DVB-the family of international standards for DVB, Proc. IEEE, vol.94, no.1, pp , Jan. 2006 14 July 2006 DVB - An Overview

61 Prospects for Future Developments

62 Future Developments Mobile communications, digital broadcasting and Internet are converging. Current achievements of DVB: Broadcast delivery to fixed, portable and mobilr terminals Interactivity-capability in receivers Data broadcasting over IP-based networks Multimedia home platform (MHP) to run software applications on all sorts of terminal devices. To understand a person’s current location, availability, and preferred method of communication at that moment e.g., a mobile phone or a DVB-H terminal. 14 July 2006 DVB - An Overview

63 Future Developments The focus is now moving to the content itself:
The ubiquitous access to media content requires content management, and copy protection measures Portable content formats To deliver or update the content over fixed and mobile IP networks (for portable video players) TV anytime/anywhere 14 July 2006 DVB - An Overview

64 References Special issue of Proc. IEEE on global digital television, vol.94, number 1, January 2006. DVB-T: ETSI EN V1.5.1 ( ) DVB-S2: Draft ETSI EN V1.1.1 ( ) DVB-S: EN V1.1.2 ( ) 14 July 2006 DVB - An Overview

65 Thanks


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