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ATSC M/H Mobile Broadcast for Portable Services Thomson/Micronas Joint Technology Proposal April 12 2008.

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Presentation on theme: "ATSC M/H Mobile Broadcast for Portable Services Thomson/Micronas Joint Technology Proposal April 12 2008."— Presentation transcript:

1 ATSC M/H Mobile Broadcast for Portable Services Thomson/Micronas Joint Technology Proposal April

2 ATSC M/H Needs and System Overview Rich Citta

3 Broadcaster Requirements True Mobile service Handheld device service Backward compatible Top 5 broadcasters in market Program Full HDTV (14 mbits/s ) New services ( 5 mbits/s ) Bottom 5 broadcasters in market Program SDTV ( 3 mbits/s ) New services (16 mbits/s )

4 Flexibility with Efficiency Allows for Wide Range of Operating Points – Light mobile channels Low rate single channel video Data services – Heavy mobile channels Multi-channel mobile video services High resolution mobile video services – Dynamically changing mobile channels Varying mixes according to changing programming block Maximum Efficiency of Spectrum Used Allows for a wide variety of business models

5 Receiver Market Cell-phone

6 Car TV

7 Smart-phone

8 Lap Top


10 Receiver Markets Cell-phones QVGA Car – TV QVGA-VGA Smart-phones VGA Lap Tops SDTV All ATSC receivers HDTV Multi resolution system needed

11 Receiver Environment





16 Rayleigh Fading Channel

17 Worse cast: Cellphone Cellphone Antenna 10-15dB lost Height 1.5m 5-10dB lost In car speed 3-5dB lost In building 5-30dB lost Pedestrian waking into deep null 10-40dB lost

18 Lower Data Rates Needed R = 1/2 Th. 15dB  7.5 dB R = 1/3 Th.  5.0 dB R = 1/4 Th.  3.5 dB R = 1/6 Th  2.0 dB More improvement needed for worst case environment

19 Diversity Receiver Diversity For cars For laptop computers Time Diversity For Handheld Receivers Transmitter Spatial Diversity S F N Transmitter Frequency Diversity Maximum over lapping coverage M F N Transmitter Frequency & Spatial Diversity For shadowing due to hills

20 Transmitter Spatial Diversity S F N

21 Burst Mode Transmission Allows for power efficient receivers – Power off receiver while waiting for data of interest – Multiple service tiers/power requirements in the same multiplex Seamless MFN operation – Maximizes coverage throughout operating area – Supports current and future SFN and MFN operation Time Mobile Bursts Receiver Off

22 Time Coded Diversity Physical Layer Combiner Delay Buffer 8-10 Seconds!! R = 1/2 Robust time-diverse output  Each Burst independently decodable for deep fades  together they provide maximum threshold performance Redundancy Burst coder Data Block Coding Provides Maximum Diversity Capability

23 Coded Cooperative Transmitter Diversity M F N

24 A Total Diversity Solution

25 Receiver / Transmitter Diversity

26 Channel 51 Sear Tower

27 Channel 52 Sear Tower

28 Channel 53 Hancock Tower

29 Coded Cooperative Transmitter Diversity 2 nd Channel: Frequency Diversity 2 Independently Fading Signals Mitigates Deep Nulls & Fades Improve Quality of Service or Boost Data Rate by more than 2

30 Design Objectives for Mobile System Spectrum is a limited asset with increasing value Efficiency throughout the system Flexibility – Broadcasters have diverse requirements and business models will vary considerably Diversity – Time > 8 sec. To address pedestrian modes – Frequency For overlapping coverage

31 Upper Layer Innovations: SVC and StaggerCasting David Campana

32 Management Layer – Layers (S4-2) Physical Layer – Layers (S4-1) Presentation Layer - Media Formats (S4-3) ATSC M/H Layers Transport-M Streaming DeliveryFile Delivery Application FrameworkCASDRM SignalingAnnouncement VideoCodec(s) &) & Parameters AudioCodec(s) & Parameters Captioning Image Formats

33 Robustness in the Upper Layer Technologies to improve the robustness (coverage and user experience) that are independent of the physical layer S4-3 Presentation Layer – Scalable Video Coding S4-2 Management Layer – StaggerCasting

34 Scalable Video Coding – Motivation QVGA15 Hz SD 30 Hz HD 60 Hz Widescreen SVC Encoder

35 Scalable Video Coding (SVC) “Scalable Video Coding Extensions to H.264 AVC” Adds an enhancement layer to the base H.264 AVC stream Backward compatible with H.264 AVC – SVC base layer is playable by legacy H.264 player Three types of scalability – Spatial (resolution) – most applicable to ATSC M/H – Temporal (time) – Fidelity (SNR)

36 SVC – Encoder structure SD Source Video Spatial Scaling AVC Encoding AVC-Like Encoding Packetizer Inter-layer prediction Bitstream CIF AVC Layer SD SVC layer CIF source

37 Extended Spatial Scalability This example shows the use of SVC for Upscaling to higher resolution Cropping (narrow to widescreen adaptation) Base Layer Enhancement Layer

38 Additional Use Cases SVC elegantly supports several interesting use cases which are difficult or impractical using traditional video compression

39 Fast Channel Change Encoder selects different GOP length for the base and enhancement layers – Short GOP in base layer for fast channel change – Long GOP in enhancement layer for bit rate efficiency

40 SVC Value Proposition to ATSC M/H Standard Evolution – Standard can evolve to higher resolution and quality without obsoleting current generation AVC only devices. Graceful Degradation of Video Quality – If enhancement layer is lost, SVC decoder can decode base layer and upsample to conceal loss. Efficient Simulcast – SVC is 10-30% more efficient than H.264 AVC simulcast at the exact same resolutions and encoder video quality settings.

41 StaggerCast - Motivation Mobile channels require significant time diversity for good performance Other methods of adding time diversity (interleaving, long block codes) add unacceptable delay to channel change for the user.

42 StaggerCast Redundant stream sent in advance of the original stream Adds significant time diversity (seconds) Introduces no channel change delay Operates at application level (ie. RTP in ATSC M/H)

43 StaggerCast - Illustration cdefijkl ABCDGHIJ Lost packets “c” = “C” time ABCDGHIJef Stagger Base Recovered

44 output (RTP stream) Source (RTP stream) TerminalBroadcast Stagger = original StaggerCast –Block Diagram Delay Stream Combiner Delay Base = Delayed original

45 StaggerCast – Channel Change StaggerCast does not add to channel change delay. On channel change: – The receiver plays back base stream immediately – The receiver buffers the stagger stream. After stagger buffer is filled: – The receiver can use the stagger stream to protect against loss.

46 Channel Change Illustration cdefrstuvw ABCDPQRSTU Stagger stream protects from this point forward Channel change Terminal immediately plays new channel. Playback is not yet protected by stagger stream. time Base Stagger

47 StaggerCast Summary Adds time diversity at application level Doesn’t impact channel change Optional tool for both receiver and broadcaster

48 StaggerCast with SVC StaggerCast and SVC benefit from each other SVC improvement over AVC is more dramatic when base layer is protected more strongly Minimized StaggerCast overhead by protecting only the critical elements of the stream – SVC base layer only – Audio

49 SVC and StaggerCast Demo Video: – 384x224 (widescreen) – 24 fps – IDR every 24 frames Channel: – ATSC M/H approximation – 1 second burst losses – 10% packet loss

50 SVC and StaggerCast Demo - Video AVC SVC and StaggerCast

51 PHY Architecture Wen Gao

52 Outline of Thomson/Micronas PHY Layer Overview of PHY proposal Important Features of PHY proposal – No modification of the ATSC transmitter since all encoding is done at the transport level Serial concatenated block code (SCBC) – Flexible training data without trellis reset – Low latency symbols – Burst transmission – Transmitter diversity

53 ATSC MH Transmitter Proposal Modulation Pilot Insertion Sync Insertion 12-1 Trellis Encoder Byte Interleaver Reed Solomon Encoder Data Randomizer ATSC A53 (legacy) Legacy MPEG TS Source Preamble Packets Insertion Virtual TS Header Modifier Packet Deinterleaver GF(256) SCBC Packetization and Interleaver ATSC M/H Mobile Data Source MUX Common Timing

54 Legacy ATSC Encoding – RS code Defined on a Galois Field GF(256) – (K=187, N=207) Non-binary Linear systematic block code – Adding two code words produces a code word – Multiplying a code word by a field element produces a code word 187 bytes207 bytes R = 2/3 TS R S encoder Trellis Encoder Interleaver

55 ATSC MH Encoding – SCBC code New non-binary linear Systematic block code – Serial concatenation of simple byte codes with byte interleaver – Byte Codes defined on same Galois Field as RS code – Achieve excellent performance with short block length 26 bytes, 52 bytes All encoding done at Transport level. Hence no modification of the transmitter – Ensure fully backward compatible 187 bytes207 bytes R = 2/3 TS R S Encoder Trellis Encoder Interleaver SCBC Encoder 187 bytes

56 Rate 1/2 Byte Code (N=2, K=1) byte code (GF(256) code) – The information byte is m – Generator matrix is: G = (1, 2) – The codeword is C = mG – Note that all the operations are done in GF(256) field Example: m=(12), C= (12) (1, 2) = (12,24) m=(154), C= (154)(1,2) = (154, 41)

57 Rate 2/3 Byte code (N=3, K=2) byte code (GF(256) code) – The Generator matrix is Example:

58 Byte Code Design Optimization Use 4 PAM as an example – Un-equal noise protection of bit Z1 and Z2 Byte codes are optimized – One bit will appear in both noise-prone bit position and reliable bit position in general Z1Z1 Z2Z Z 2 Z PAM Use 4 PAM as an example – Un-equal noise protection of bit Z1 and Z2 Byte codes are optimized – One bit will appear in both noise-prone bit position and reliable bit position in general – Overall bit error rate is reduced Z1Z1 Z2Z Z 2 Z PAM

59 Rate 12/26 SCBC Code Serial Concatenation of two 2/3 byte codes and byte interleaver Encoding is done across packets 12 TS packets 187 bytes 12 TS packets 14 parity packets 187 bytes 12/26 SCBC Byte Encoder R=2/3 Byte Puncture R=27/26 Byte Encoder R=2/3 18 Byte Interleaver 12 Bytes18 Bytes 27 Bytes26 Bytes

60 Rate 12/52 SCBC Code Serial Concatenation of ½ byte code and 12/26 SCBC code with byte inter-leaver 1st 12 Bytes 2nd 12 Bytes Byte Encoder R=1/2 24 Byte Interleaver 12 Bytes 2nd 26 Bytes Byte Encoder R=2/3 Byte Puncture R=27/26 Byte Encoder R=2/3 18 Byte Interleaver 1st 26 Bytes Byte Encoder R=2/3 Byte Puncture R=27/26 Byte Encoder R=2/3 18 Byte Interleaver

61 Concatenation of RS and SCBC code Due to the concatenation, the parity bytes are also SCBC encoded – For MH data, the legacy RS code will still be useful, rather than simply for backward compatibility 12 MH packets 187 bytes 12 MH packets 14 parity packets 187 bytes SCBC Encoder 12 MH packets 14 parity packets 187 bytes RS Encoder 20 bytes RS Parity Byte RS Parity byte

62 ATSC MH Receiver Soft symbols from Trellis decoder are fed back to equalizer Iterative decoding process Trellis decoder SCBC decoder Interleaver R S decoder Equalizer DeInterleaver Interleaver

63 The 12/26 Rate: AWGN Threshold 7.0 dB at 9-th iteration

64 The 12/52 Rate: AWGN Threshold 3.5 dB at 13 th iteration

65 Summary of SCBC code Variety of code rates for trade-off between robustness and data rate – 12/26,12/52,17/26,24/208, etc Ensure backward compatibility with no modifications of the transmitters SCBC codes achieve significant coding gain – TOV threshold CNR 14.9 dB  3.5 dB

66 Code Cooperative Diversity SCBC code allows code cooperative diversity Example: 12/52 SCBC encoding forms two streams – Stream A and B are decodable separately (7 dB CNR threshold) – Joint decoding of stream A and B can achieve lower CNR threshold (3.5dB) Variety of diversity can be formed using stream A and B – Sent with relative delay  code and time diversity – Sent from two transmitters using different channels  code and freq diversity 12 MH packets 187 bytes 12 MH packets 187 bytes ½ Byte code 12/26 Encoder 12 Parity packets 12/26 Encoder 26 packets Stream A Stream B

67 System Synchronization in MFN Approach – Broadcast stations are synchronized (e.g. using GPS) – Burst time slots are coordinated Value – Enables soft handoff with network affiliates broadcasting same program – Enables a mobile receiver to obtain program guide from all local mobile stations without interrupting the current mobile program Network N Network C CH6 13 C i t y A C i t y B Time Network A CH3 5 Network A

68 Backup Slides

69 12/26 SCBC Code decoder: Iterative decoder

70 12/52 SCBC Code decoder: Iterative decoder

71 ATSC MH data frame Note: 1 block contains 26 TS packets

72 Convolutional Byte Inter leaver 0 Packet Packet 207 bytes After convolution interleaver, 52 TS packets appear as following:

73 Convolutional Byte Inter leaver Byte 0 Byte 26 Byte 51 Byte 104 Byte Byte 206

74 Convolutional Interleaver byte locations with a contiguous codeword

75 Convolutional Byte Inter leaver Byte 0 Byt e 26 Byte 51 Byte 104 Byte 156 Byte 51 Byt e For 12/26 or 12/52 SCBC code, gray regions contains complete 12/26 SCBC coded codeword

76 ATSC Trellis coded Modulation (TCM)

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