MOBILE TV

1
MOBILE TV

• -Narendranath Kanukolanu

2
Topics

• Introduction
• DVB-T
• DVB-H
• Issues and Solutions
• Conclusion
• References

3
Introduction

• Convergence of digital media and communication
  give users possibility to consume most digital
  content also in mobile environment
• The emerging DVB-H standard aims to provide
  digital TV reception in mobile devices
• Earlier known as DVB-X
• DVB-H is being standardized by and ad hoc group
  of the DVB organization
• Expected to be standardized in the first quarter
  of 2004
• DVB-H combines traditional television broadcast
  standards with elements specific to handheld
  devices mobility, smaller screens and antennas,
  indoor coverage and reliance on battery power 

4
DVB-T

• DVB-T stands for Digital Video Broadcasting -
  Terrestrial and it is the DVB European consortium
  standard for the broadcast transmission of
  digital terrestrial television.
• This system transmits an MPEG-2 family digital
  audio/video stream, using OFDM modulation with
  concatenated channel coding

5
DVB-T

• One-to-many broadband wireless data transport
• Video, audio, data and importantly IP packets
• Scalable cell size up to 100km (DVB-H cell size
  is smaller)
• Huge capacity 54 channels each 5-32Mbit/s
• Shut down of analog TV will free up huge
  frequency capacity for DVB-T usage

DVB-T Digital Video Broadcasting - Terrestrial
6
DVB-T

• Developed for MPEG-2 stream distribution, but can
  basically carry any data
• Flexible, has many modes, 4.98-31.67 Mbit/s _at_
  C/N25dB
• COFDM multi-carrier modulation with 2k and 8k
  modes
• One DVB channel is 8MHz
• 1705 sub carriers (spacing 4464 Hz) - 2k mode
• 6817 sub carriers (spacing 1116 Hz) - 8k mode
• Carrier modulation QPSK, 16 QAM or 64 QAM
• Error correction convolution code and
  Salomon-Reed
• Basic mode in Finland
• 64 QAM, code rate 2/3, guard interval 1/8
• Gives 22.12 Mbits/s capacity when C/N19.2 dB and
  8 MHz channel

COFDM Coded Orthogonal Frequency Division
MultiplexingC/N Carrier to Noise ratio
7
Mobile reception of DVB-T

• DVB-T includes hierarchical modes where two
  transport streams can be sent simultaneously
• Low capacity, high capacity
• DVB-T can also be used for broadcast to mobile
  devices, but a suitable mode have to be selected
• 8k 64 QAM lt 50 km/h
• 2k QPSK gt 400 km/h tolerable
• A separate network for DVB-H is desired
• Optimization of speed, coverage and capacity

8
World Standards

• DAB and E-DMB-in Europe and China
• DVB-H- USA/Europe and any where there is digital
  TV spectrum
• HD Radio-USA
• Media FLO (Qualcomm)-USA
• T-DMB-Korea and Possibly Europe and China
• ISDB-T- Japan

9
Comparison Charts
10
Motivation for creating DVB-H

• Why not use UMTS?
• Not scalable for mass content delivery
• For delivery of mass media content, broadcast
  networks should be preferred over point-to-point
  cellular networks
• Why not use DVB-T?
• Was designed for rooftop reception
• Need for an efficient power saving mechanism
• Inadequate impulse noise protection
• Why not use DAB?
• Designed for devices with similar power
  constraints but too narrow spectrum is assigned
  for data transmission

DAB Digital Audio Broadcasting
11
What Is Mobile TV

• Mobile TV DVB-H
• Mobile Broadcast
• A Small digital TV, set top box receiver
• Watch and record TV programs, interact with
  programs and other viewers
• Other Rich Media experiences
• On-line video services
• Access on-line services to rent or buy TV shows,
  videos, and movies download them to mobile
  device
• Video to-go
• Store videos to mobile format and manage them
  with Nokia PC Suite
• Transfer and syncronize recorded, downloaded or
  ripped videos from PC/Mac or home media devices

12
DVB-H Introduction

• Convergence of digital media and communication
  give users possibility to consume most digital
  content also in mobile environment
• The emerging DVB-H standard aims to provide
  digital TV reception in mobile devices
• Earlier known as DVB-X
• DVB-H is being standardized by and ad hoc group
  of the DVB organization
• Standardized in the first quarter of 2004

13
DVB-H

• The DVB-H system is largely compatible to the
  DVB-T standard, which means that the modulator
  and RF circuits can be reused with only slight
  additions. It is possible to have both DVB-T
  services and DVB-H services broadcast by a single
  transmitter

14
Contd..

• DVB-H combines traditional television broadcast
  standards with elements specific to handheld
  devices mobility, smaller screens and antennas,
  indoor coverage and reliance on battery power are
  the challenges
• Re-uses basically the well-known DVB-T
  transmission parameters
• Inheriting the DVB-T flexibility performance,
• Offering additional delivery methods to extend
  the traditional tradeoff bit rate capacity
  ruggedness cell size to a new dimension the
  nomad city.

15
DVB-H system elements

• Time slicing for power saving
• Time between the bursts gives the power saving
  (off time)
• MPE-FEC for performance
• 4k mode was chosen to provide mobility in medium
  SFNs
• Extended TPS bits for efficient signaling

MPE Multiprotocoll encapsulationFEC Forward
Error CorrectionSFN Single Frequency Network
16
Drivers for Mobile TV

• TV application missing from Mobile Phone
• TV is bigger application than telephone globally
• Daily amount of time spent on multimedia is more
• Digital convergence happening in Mobile Handsets

17
Mobile reception of DVB-T

• DVB-T includes hierarchical modes where two
  transport streams can be sent simultaneously
• Low capacity, high capacity
• A separate network for DVB-H is desired
• Optimization of speed, coverage and capacity

18
What the Consumer expect?

• .

Single Device to carry (phone)
Multimedia Device
19
DVB-H System overview

• .

DVB-H SERVICES
OPTIONAL DVB-T SERVICES
ERROR PROTECTION (MPE-FEC)
IP EN- CAPSULATION
TIME SLICING
TRANSPORT STREAM MULTIPLEXER
DVB-T CODER/MODULATOR
4k-MODE
SIGNALLING
20
When will it be used?
21
System Architecture For Collaboration Between
Mobile and Broadcast Operators
22
Network Design Flexibility Signaling

• Different datacast network operator and cellular
  network operator
• Digital broadcast infrastructure
• More transmission sites than normal broadcast
  networks required, but less than normal cellular
  phone networks existing masts can be reused
• Cellular networks used for payment and
  administrative data
• Cellular network and broadcast network can share
  same core network

Mobile Operator
ISP
UTMS Base station
Core
DVB-T Broadcasters
DVB-H transmitter
IP Backbone
Mux
DVB-H Broadcasters
Broadcast operator
23
DVB-H features/pros

• Cost efficient delivery of broadcast content to a
  large audience
• Low time to market and complexity
• Flexible transport stream sharing between DVB-T
  and DVB-H possible
• Based on DVB-T with minimal changes
• Only IP based services possible
• Reduced power saving when total bit rate for
  DVB-H services is very low (no big bursts
  possible)

24
DVB-T and DVB-H coexistence
25
IP Datacast (IPDC)

• IP data casting is a service where digital
  content formats, software applications,
  programming interfaces and multimedia services
  are combined through IP (Internet Protocol) with
  digital broadcasting. All content delivered as
  IP packets
• Connectivity layer convergence
• DVB-H combined with IP data casting enables
  distribution of many kinds of digital content
• TV broadcast, music, games etc.

26
Power consumption and handover

• IP encapsulation allows sending the data in
  bursts to the mobile station and this saves
  energy (battery power)
• Power consumption and handover
• 2 Mbit buffer
• Handover possible during off time (services can
  be used even if the terminal has moved during off
  time)

27
Mobile Terminal

• FE Front End, contains radio receiver and
  demultiplexer

FE
CPU
Media decoder
Display
WLAN
Cellular Link
28
ISSUES

• Battery Power
• Loss Free Handover for IP Data Cast
• Continuous Transmission

29
ISSUE1Battery Power

• TIME SLICING is the mechanism DVB-H uses to
  transmit data in periodic bursts with significant
  and higher instantaneous bit rates
• Using TDM significant power savings can be
  achieved
• TDM (Time Division Multiplexing) is the
  technology used in Time Slicing.
• TDM combines data streams by assigning each
  stream a different time slice in a set .
• TDM repeatedly transmits a fixed sequence of
  time slices over a single transmission channel.

30
TIME SLICING TECHNIQUE
SERVICE 1
SERVICE 1
SERVICE 1
SERVICE 2
DVB-H
SERVICE 3
SERVICE 4 TV
DVB-T
SERVICE 4
DVB-H Time Slices
REGULAR DVB-T MULTIPLEX
always on-not used data is skipped
SLEEP
MODE
31
Contd

• Time slicing enables a receiver to stay active
  only a fraction of time while receiving bursts of
  a requested service saving battery power.
• When the receiver is tuned to receive one of the
  programs it has to receive the other unwanted
  programs at the same time consuming a lot of
  battery.
• The High bit rate signals are buffered in the
  time slicing memory of the DVB-H capable
  receiver.

32
Contd

• The DVB-H receiver will receive its intended high
  bit rate service in one time slice and make the
  front end sleep during the other slices,
• The High end Bit rate service received will be
  buffered in the receiver memory and played out
  continuously to provide the desired QoS.

33
Time Slicing Contd
1536kbps_DVBH
1536 kbps
1536 kbps
Content Provider
1536kbps_DVBH
1536 kbps
DVB-H TOWER
Ethernet Switch
1536 kbps
1536kbps_DVBH
1536kbps_DVBH
34
ISSUE2Continuous Transmission

• A DVB-H receiver is expected to usually be a
  single antenna terminal.
• As the DVB-H cell becomes smaller up to several
  kilometers radius, handover between different
  cells will happen.
• When the receiver works in time slicing mode, it
  can measure the signal SNR value In the off burst
  time and eventually perform soft handover.
• Thus the time slicing mode makes seamless soft
  handover possible for single antenna DVB-H
  reception.

35
Calculation

• If a service has an average bite rate of ravg is
  transmitted in bursts with the bit rate rburst
  and the time between two bursts of the same
  service (cycle time) is called t, the burst
  duration tburst that may be calculated from the
  other values using
• tburst ravg/ rburst t

36
Contd..

• As the off time toff is the difference between
  the cycle time and the burst time,
• toff 1- ravg/ rburst t

37
TIME SLICING TECHNIQUE

• Continuous Transmission

Capacity
SERVICE 1
SERVICE 2
SERVICE 3
SERVICE 4
Time
38
Continuous Transmission

• .

384kbps_DVBH
384 kbps
384 kbps
Content Provider
384kbps_DVBH
384 kbps
DVB-H TOWER
Ethernet Switch
384 kbps
384kbps_DVBH
384kbps_DVBH
39
Contd

• Each receiver will receive an effective bit rate
  of 384 Kbps and the the other 1152 Kbps of
  unwanted traffic. Thus each receiver will receive
  1536 Kbps in total of which three quarters is
  unwanted traffic.

40
ISSUE3Loss Free Handover for IP Data Cast

• Mobility is the most important feature of
  handheld devices and uninterrupted service has to
  be provided when there is movement.
• A technology called Phase shifting is proposed
  for Loss free handover.

41
Contd

• The main challenge in today's field of
  communication is to offer high data rates while
  having a error-prone communication channel and
  only a small battery power budget Additionally,
  seamless mobility is a strong demand.
• An Algorithm for synchronizing adjacent cells in
  order to ensure seamless handovers is proposed.
• Time slicing is also important for handover.

42
Handover in Broadcast Systems

• The Technique used is PHASE SHIFTING.
• Different from cellular Telecommunication systems
  as no return channel exists.
• Emphasis on how the signals of neighboring DVB-H
  cells may be synchronized and under which
  conditions seamless handover themselves may
  actually be one.

43
Contd..

• The network's infrastructure has no feedback
  about who is using the services and possibly
  moving from one cell to another. All the
  information for performing handovers has to be
  deployed to the terminals which will perform the
  handovers on their own.
• The term cell in this context is used for a
  subsystem that may consist of one or more several
  transmitters sending entirely identical content
  on the same frequency.
• A Cell Handover in this context is the change of
  frequency and data stream in order to receive the
  same service continued within another cell.

44
Example Scenario
45
Phase Shifting Algorithm

• When a terminal changes from one DVB-H cell to
  another, ideally it should be able to seamlessly
  continue receiving the current service in the new
  cell without any packet loss, assuming that the
  service is available in both cells.
• The Phase shifting should be big enough so that
  there is no overlapping between the time slices
  of the adjacent cell and the necessary
  synchronization time for the terminal to change
  from one signal to another.

46
Algorithm
IP PACKET

• .

4
1 3
1 2
1 1
1 0
5
6
7
8
9
1 4
1 5
1 6
IP FEEDING STREAM TO CELL 1
1
2
3
4
5
6
7
1 2
1 1
1 0
9
8
SIGNAL OF CELL 1
DVB-H TIME SLICE
4
1 3
1 2
1 1
1 0
5
6
7
8
9
1 4
1 5
1 6
IP FEEDING STREAM TO CELL 2
4
5
6
7
8
9
1
2
3
SIGNAL OF CELL 2
PHASE SHIFT
47
Contd..

• There is an overlapping of IP packets between two
  consecutive time slices of two different cells.
  This ensures, even with significant tolerance
  towards IP feeding stream delays, seamless
  loss-free handovers.
• More than two cells have common borders, so more
  than two different phase shifts are needed.

48
4 -Coloring Graph Problem

• The various phase shifts that are necessary for n
  adjacent cells can be interpreted mathematically
  as colors in a graph coloring problem, never
  allowing twice the same color in adjacent nodes.
• With four different phase shifts loss-free
  handover between any two cells will be possible,
  no matter how the shape of the cells might be.
  (Ideally Hexagonal)

49
Quantitative Analysis

• tburst ravg/ rburst t (1)
• toff 1- ravg/ rburst t (2)
• From Equation 1 and 2

50
Contd..

• To simplify the equation the sum of tsync and
  tsafety is defined as being tsetup

51
Contd..

• From Eq 1,2,4

52
Contd..

• The result is that the ratio between the average
  data rate of a service and the whole data rate
  that can be used for a service supporting soft
  handover must be smaller than 25reduced by the
  ratio of the setup time and t.
• At is also dependent of ravg as the memory of the
  terminal mbuf is limited.
• For the consumption of a service, only half of
  the terminal buffer size mbuf can be used, as the
  other half is needed to monitor the same service
  of an adjacent cell, at least in handover status.

53
Contd..
54
Conclusion

• Traditional broadcasting is undergoing a process
  of change as a consequence of the move towards an
  all-digital broadcasting environment. New
  technology, such as DVB-H, streaming technology
  and personal video recorders (PVRs) can
  complement traditional broadcasting.

55
References

• Loss-free handover for IP datacast over DVB-H
  networksMay, G. Consumer Electronics, 2005.
  (ISCE 2005). Proceedings of the Ninth
  International Symposium on 14-16 June 2005
• Performance analysis of time slicing in
  DVB-HYang, X.D. Song, Y.H. Owens, T.J.
  Cosmas, J. Itagaki, T. Mobile Future, 2004 and
  the Symposium on Trends in Communications. Sympo
  TIC '04. Joint IST Workshop on 24-26 Oct. 2004
• Digital Video Broadcast - Handheld (DVB-H)-A
  Mobile Last-Mile Tactical Broadcast
  SolutionBennett, B. Hemmings, P. Holt, C.
  Military Communications Conference, 2005. MILCOM
  2005. IEEE 17-20 Oct. 2005

56

• DVB-H digital TV for handhelds? Jukka
  Henriksson, Nokia
• Content Distribution Using Wireless Broadcast and
  Multicast Communication Networks. Janne Aaltonen,
  Thesis for Degree of Doctor, Tampere University
  of Technology
• DVB lthttp//www.dvb.org/index.php?id20gt