tv in mobile seminor report

7/30/2019 tv in mobile seminor report

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DVB-H BROADCAST MOBILE

VVCE, Dept E&C Page 1

CHAPTER 1

INTRODUCTION

Digital Video Broadcasting Handheld (DVB-H) enables the delivery of live Broadcast

television to compatible mobile handheld devices. Combined with mobile Broadcasting,

digital broadcasting enables mobile phone users to receive a wide selection of High-

quality TV services over a DVB-H network.

DVB-H technology is a superset of the very successful DVB-T( Digital Video

Broadcasting - Terrestrial ) system for digital terrestrial television, with additional

features to meet the specific requirements of handheld

The DVB-H standard has been approved by the European Telecommunications

Institute (ETSI), and used in mobile TV pilot projects in many countries, including India,

Australia, Finland, Germany, Italy, Malaysia, South Africa, Taiwan, the UK, and the

USA.

It combines traditional television broadcast standards with elements specific to

handheld devices; mobility, smaller screens and antennas, indoor coverage and reliance

on battery power.

DVB-H not only enables mobile users to experience live broadcast TV, it also

complements operators cellular networks, which are available as return channels for

interactive TV services.


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Fig 1. DVB-H Technology for TV broadcast to mobiles devices

The block diagram in Fig 1. Shows TV broadcast using DVB-T for fixed receptions such as

televisions and DVB-H for mobile devices.


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CHAPTER 2

TRANSMITTER AND RECEIVER OF DVB-H

The conceptual structure of a DVB-H receiver is depicted in Fig 2. It includes a DVB-

H demodulator and a DVB-H terminal. The DVB-H demodulator includes a DVB-T

demodulator, a time-slicing module and a MPE-FEC module. The DVB-T demodulator

recovers the MPEG-2 Transport Stream packets from the received DVB-T (EN 300 744 ) RF

signal.

Fig 2. Conceptual Structure of DVB-H Receiver

It offers three transmission modes 8K, 4K and 2K with the corresponding Transmitter

Parameter Signaling (TPS). Note that the 4K mode, the in-depth interleavers and the DVB-H

signaling has been defined while elaborating the DVB-H standard.

The time-slicing module, provided by DVB-H, aims to save receiver power

consumption while enabling to perform smooth and seamless frequency handover. The MPE-

FEC module, provided by DVB-H, offers over the physical layer transmission, a

complementary forward error correction allowing the receiver to cope with particularly

difficult receiving situations.

DVB-H builds on DVB-T and is a system where data (typically digital multimedia

data) is transmitted in IP datagrams. In order to reduce power consumption in small

handheld devices, DVB-H employs a technique called time-slicing, by which 90% of

power is saved.


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An example of using DVB-H for transmission of IP-services is given in Fig 3.

In this example, both traditional MPEG-2 services and time-sliced "DVB-H services" are

carried over the same multiplex. The handheld terminal decodes /uses IP-services only.

Fig 3. Conceptual description of using DVB-H System (sharing MUX with MPEG2 services)


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CHAPTER 3

TECHNICAL CHARECTERISTICS

3.1 Time slicing

Time slicingis a technique used by the DVB-Htechnology for achieving high power-saving effect on terminal devices. It is based on the time-multiplexed transmission of

different services.

DVB-H transmits large pieces of data in bursts, allowing the receiver to be switched

off in inactive periods. The result is power savings of up to 90% - and the same inactive

receiver could be used to monitor neighboring cells for seamless handovers. Each burst may

contain up to two megabits of data (including parity bits). There are 64 parity bits for each191 data bits, protected by Reed-Solomon codes. The front end of the receiver switches on

only for the time interval when the data burst of a selected service is on air. Within this short

period of time a high data rate is received which can be stored in a buffer. This buffer can

either store the downloaded applications or play out live streams. The achievable power

saving depends on the relation of the on/off-time of the bursts as shown in Fig 4. If there are

approximately ten or more bursted services in a DVB-H stream, the rate of the power saving

for the front end could be up to 90%.

Fig 4. Burst Duration Diagram


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In order to drastically reduce power consumption, one would ideally like the receiver

to demodulate and decode only the 2.5% portion of interest, and not the full MPEG-2TS.

With time slicing this is possible, since the MPE sections of a particular ES are sent in high

bit rate bursts instead of with a constant low bit rate. During the time between the bursts inthe off-time no sections of the particular ES are transmitted. This allows the receiver to power

off completely during off-time. The receiver will, however, have to know when to power on

again to receive the next burst against transmission errors.

Fig 4.1. Example of time slicing diagram

Fig 4.1 shows the example for time slicing where each time slot is allotted for different DVB-

H services and different bursts are allotted for different TV programs.


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3.2 MPE-FEC (Forward Error Correction for Multi Protocol Encapsulated

data)

The objective of the MPE-FEC is to improve the C/N- and Doppler performance in

mobile channels and to improve the tolerance to impulse interference.

This is accomplished through the introduction of an additional level of error correction

at the MPE layer. By adding parity information calculated from the datagrams and sending

this parity data in separate MPE-FEC sections, error-free datagrams can be output after

MPE-FEC decoding despite a very bad reception condition.

This MPE-FEC scheme should allow high-speed single antenna DVB-T reception using

8K/16-QAM or even 8K/64-QAM signals. In addition MPE-FEC provides good immunity to

impulse interference.

When time slicing and MPE-FEC are used together, one Time Slice burst carries exactly

one MPE-FEC frame. The first part of the burst is the MPE sections carrying the IP

datagrams belonging to the MPE-FEC frame. Immediately following the last MPE section is

the first MPE-FEC section carrying the parity bytes. All sections contain a table boundary

flag; this is set high in the last MPE section to indicate this is the last MPE section of the

MPE-FEC frame. If all the MPE sections within the burst have been received correctly the

receiver can then neglect the MPE-FEC sections and go to sleep until the next burst. All

sections contain a frame boundary flag, this is set high in the last MPE-FEC section to

indicate that this is the last MPE-FEC section and hence the end of the MPE-FEC frame.


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3.2.1 Forward error correction

Forward error correction (FEC) or channel codingis a technique used forcontrolling

errors in data transmission over unreliable or noisy communication channels. The central idea

is the sender encodes their message in a redundant way by using an error-correcting code

(ECC). The American mathematician Richard Hammingpioneered this field in the 1940s and

invented the first error-correcting code in 1950: the code. For the forward error correction

using RS Code, there are 64 parity bits for each 191 data bits, protected by Reed-Solomon

codes.

The redundancy allows the receiver to detect a limited number of errors that may

occur anywhere in the message, and often to correct these errors without retransmission. FEC

gives the receiver the ability to correct errors without needing a reverse channel to request

retransmission of data, but at the cost of a fixed, higher forward channel bandwidth. FEC is

therefore applied in situations where retransmissions are costly or impossible, such as one-

way communication links and when transmitting to multiple receivers in multicast. FEC

information is usually added to mass storage devices to enable recovery of corrupted data,

and is widely used in modems.
http://en.wikipedia.org/wiki/Error_controlhttp://en.wikipedia.org/wiki/Error_controlhttp://en.wikipedia.org/wiki/Data_transmissionhttp://en.wikipedia.org/wiki/Redundancy_%28information_theory%29http://en.wikipedia.org/wiki/Richard_Hamminghttp://en.wikipedia.org/wiki/Reverse_channelhttp://en.wikipedia.org/wiki/Multicasthttp://en.wikipedia.org/wiki/Mass_storagehttp://en.wikipedia.org/wiki/Modemhttp://en.wikipedia.org/wiki/Modemhttp://en.wikipedia.org/wiki/Mass_storagehttp://en.wikipedia.org/wiki/Multicasthttp://en.wikipedia.org/wiki/Reverse_channelhttp://en.wikipedia.org/wiki/Richard_Hamminghttp://en.wikipedia.org/wiki/Redundancy_%28information_theory%29http://en.wikipedia.org/wiki/Data_transmissionhttp://en.wikipedia.org/wiki/Error_controlhttp://en.wikipedia.org/wiki/Error_control


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3.2.2 Multi Protocol Encapsulation (MPE):

Multiprotocol Encapsulation, or MPE for short, is a Data link layer protocol defined

by DVB which has been published as part of ETSI. It provides means to carry packet orientedprotocols (like for instance IP) on top of MPEG transport stream (TS).The Fig 5. shows the

encapsulation of data from IP datagram to TS packets.

Fig 5. Multi protocol encapsulation


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CHAPTER 4

DVB-H SIGNALING:

The objective of the DVB-H signaling is to provide a robust and easy-to-access

signaling to the DVB-H receivers, thus enhancing and speeding up service discovery.

TPS is a very robust signaling channel allowing TPS-lock in a demodulator with very

low C/N-values. TPS provides also a faster way to access signaling than demodulating and

decoding the Service Information (SI) or the MPE-section header.

4.1 Frequencies:

DVB-H is designed to work in the following bands:

1. VHF-III (170-230 MHz, or a portion of it)2. UHF-IV/V (470-862 MHz, or a portion of it)3. L (1.452-1.492 GHz)


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CHAPTER 5

4K MODE AND IN-DEPTH INTERLEAVERS

The objective of the 4K mode is to improve network planning flexibility by trading

off mobility and SFN size. To further improve robustness of the DVB-T 2K and 4K modes in

a mobile environment and impulse noise reception conditions, an in-depth symbol interleaver

is also standardized.

The additional 4K transmission mode is a scaled set of the parameters defined for the

2K and 8K transmission modes. It aims to offer an additional trade-off between Single

Frequency Network (SFN) cell size and mobile reception performance, providing an

additional degree of flexibility for network planning.

Terms of the trade-off can be expressed as follows:

1. The DVB-T 8K mode can be used both for single transmitter operation and for small,medium and large SFNs.It provides a Doppler tolerance allowing high speed

reception.

2. The DVB-T 4K mode can be used both for single transmitter operation and for smalland medium SFNs. It provides a Doppler tolerance allowing very high speed

reception.3. The DVB-T 2K mode is suitable for single transmitter operation and for small SFNs

with limited transmitter distances. It provides a Doppler tolerance allowing extremely

high speed reception.

For 2K and 4K modes the in-depth interleavers increase the flexibility of the symbol

interleaving, by decoupling the choice of the inner interleaver from the transmission mode

used. This flexibility allows a 2K or 4K signal to take benefit of the memory of the 8K

symbol interleaver to effectively quadruple (for 2K) or double (for 4K) the symbol

interleaver depth to improve reception in fading channels. This provides also an extra level of

protection against short noise impulses caused by, e.g. ignition interference and interference

from various electrical appliances.


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CHAPTER 6

ADVANTAGES OF DVB-H

It provides the best user experience in the mobile environment, with an energy-saving

handset that is only on 10-25% of the time, program guide, and soft loss-free handover and in

building coverage.

It offers an excellent-quality picture and audio quality when desired. Time-slicing

technology (meaning the DVB-H receiver is in sleep mode mostly and wakes up to receive

the data) saves up to 90% of power compared to non-time sliced technologies. Efficient use

of bandwidth enables up to 55 mobile channels plus scalability.

Another use of DVB-H is in mobile devices such as portable video recorders (PVRs).

These are effectively portable set top boxes. Most consist for example of a hard disk, DVD

reader,CPU, computer memory, 6 inch LCD screen and with the ability to download and

record digital TV broadcasts, MP3 music, films, photos ; play it all back as and when

required whilst on the move.

DVB-H is having an ability to receive 15Mbit/s in an 8MHz channel and in a wide area

single frequency network (SFN) at high speed. These requirements were drawn up after much

debate and with an eye on emerging convergence devices providing video services and otherbroadcast data services to 2.5G and 3G handheld devices.


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CHAPTER 7

FUTURE ENHANCEMENT

1. Using LPDC (Low-density parity-check) at receiver rather than RS Coding since RScoding takes a long time for coding and decoding.

2. Use of OFDM modulation techniques.7.1. Case study

A recent pilot mobile TV project1 revealed the popularity of mobile TV services and

the key issues for participants to use mobile TV services:

1. Easy, intuitive services.2. Good technical functionality and reliability.3. Content suitable for short-period viewing.

DVB-H

Fig 6. Worldwide forecast of Mobile TV users by technology

From the Fig 6. DVB-H technology is predicted to be the globally preferred technology for

the broadcast mobile TV.


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CHAPTER 8

CONCLUSION

Mobile TV is one of the fastest growing and expanding businesses in the technology

industry. Easily portable devices such as smart phones and tablet computers have helped push

the mobile on-demand TV business sky high. Advertising for devices capable of using mobile

television is expected to reach 1.4 billion by 2015. As of 2010, some 17.6 million people in

the United States were actively using TV on their mobile. This number is expected to climb

to 52 million viewers within four years. ESPN changed the sports landscape by being the first

sports network to offer sports games to stream live online for mobile television viewers.

These companies and many more are quickly helping to expand the use of TV on portable

electronics. With the rise of mobile media, carriers have been scrambling to keep up with

consumer demands. AT&T, Metro PCS, and Verizon are all working to create LTE networks

which will have the ability to increase available data usage and speed up connection times to

work with mobile TV users.


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CHAPTER 9

REFERENCES

[1] ETSI EN 300 744: "Digital Video Broadcasting (DVB); Framing structure, channel

coding and modulation for digital terrestrial television". (DVB-T).

[2] ETSI EN 300 468: "Digital Video Broadcasting (DVB); Specification for Service

Information (SI) in DVB systems". (DVB-SI).

[3] ETSI EN 301 192: "Digital Video Broadcasting (DVB); DVB specification for data

broadcasting". (DVB-DATA).

[4] ETSI TS 101 191: "Digital Video Broadcasting (DVB); DVB mega-frame for Single

Frequency Network (SFN) synchronization".[5] ISO/IEC 7498-1: "Information technology - Open Systems Interconnection - Basic

Reference Model: The Basic Model".

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