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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".