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MOBILE TV

MOBILE TV. -Narendranath Kanukolanu. Topics. Introduction DVB-T DVB-H Issues and Solutions Conclusion References. Introduction. Convergence of digital media and communication give users possibility to consume most digital content also in mobile environment

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MOBILE TV

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  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 @ C/N=25dB • 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/N=19.2 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: < 50 km/h • 2k QPSK: > 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. MobileTV On-line video services Video to-go 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. Timesliced: • Service 1 • Service 2 • Service 3 • Not timesliced: • Service 4 1 2 3 1 2 3 1 2 3 1 2 4 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. Good picture and sound quality Service availability Value for money Simplicity of use Right selection of channels What the Consumer expect? . Single Device to carry (phone) Multimedia Device

  19. DVB-H SERVICES OPTIONAL: DVB-T SERVICES DVB-H System overview 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. 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) DVB-H features/pros

  24. DVB-T ETS 300 744 8k, 2k Time Slicing MPE FEC DVB-T RF in IP-out , 4k, TPS DVB-H CODEC 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. ISSUE1:Battery Power • TIME SLICING is the mechanism DVB-H uses to transmit data in periodic bursts with significant and higher instantaneous bit rates • Using TDMsignificant 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 DVB-T SERVICE 4 TV 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. ISSUE2:Continuous 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 rburstand the time between two bursts of the same service (cycle time) is called t, the burst duration tburstthat may be calculated from the other values using… tburst = ravg/ rburst* t

  36. Contd.. • As the offtime toff is the difference between the cycle time and the burst time, • toff = 1- ravg/ rburst* t

  37. Continuous Transmission TIME SLICING TECHNIQUE 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. ISSUE3:Loss 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 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 IP FEEDING STREAM TO CELL 1 SIGNAL OF CELL 1 1 2 3 4 5 6 DVB-H TIME SLICE 7 8 9 1 0 1 1 1 2 IP FEEDING STREAM TO CELL 2 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 2 3 4 5 6 7 8 9 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 beingtsetup

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