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ATSC M/H Mobile Broadcast for Portable Services

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Presentation on theme: "ATSC M/H Mobile Broadcast for Portable Services"— Presentation transcript:

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

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

9 ATSC HDTV

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

12 Receiver Environment

13 Receiver Environment

14 Receiver Environment

15 Receiver Environment

16 Rayleigh Fading Channel

17 Worse cast: Cellphone Cellphone Antenna dB lost Height 1.5m dB lost In car speed dB lost In building dB 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 Time 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 Mobile Bursts Time Receiver Off

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

23 Coded Cooperative Transmitter Diversity
M F N

24 A Total Diversity Solution

25 Receiver / Transmitter Diversity

26 Channel Sear Tower

27 Channel Sear Tower

28 Channel Hancock Tower

29 Coded Cooperative Transmitter Diversity
2nd 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)
ATSC M/H Layers Management Layer – Layers (S4-2) Transport - M Streaming Delivery File Delivery Application Framework CAS DRM Signaling Announcement Video Codec(s ) & Parameters Audio Captioning Image Formats Presentation Layer - Media Formats (S4-3) Physical Layer – Layers (S4-1)

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 SVC Encoder HD 60 Hz Widescreen

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

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

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
Lost packets Stagger c d e f i j k l “c” = “C” A B C D G H I J Base time Recovered A B C D e f G H I J

44 StaggerCast –Block Diagram
Broadcast Terminal Stagger = original Delay Source (RTP stream) output (RTP stream) 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
d e f r s t u v w Stagger Base A B C D P Q R S T U time Stagger stream protects from this point forward Terminal immediately plays new channel. Playback is not yet protected by stagger stream.

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

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 bytes 207 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 bytes 207 bytes R = 2/3 TS R S Encoder Trellis Interleaver SCBC

56 Rate 1/2 Byte Code (N=2, K=1) byte code (GF(256) code) Example:
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) Example:
The Generator matrix is Example:

58 Byte Code Design Optimization
+3 +1 -1 -3 Z2 Z1 1 1 1 0 0 1 0 0 4PAM Z1 Z2 +3 +1 -1 -3 Z2 Z1 1 1 1 0 0 1 0 0 4PAM 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 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

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

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

61 Concatenation of RS and SCBC code
12 MH packets 187 bytes 14 parity packets SCBC Encoder RS Encoder 20 bytes RS Parity Byte RS Parity byte 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

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

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 13th 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 ½ Byte code 12/26 Encoder 12 Parity packets 26 packets Stream A 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 C i t y A B Time Network A CH 3 5 Network N Network C CH 6 13

68 Backup Slides

69 12/26 SCBC Code decoder: Iterative decoder

70 12/52 SCBC Code decoder: Iterative decoder

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

72 Convolutional Byte Inter leaver
After convolution interleaver, 52 TS packets appear as following: 0 Packet 1 2 51 Packet 207 bytes

73 Convolutional Byte Inter leaver
Byte 104 Byte 156 52 53 Byte Byte 26 Byte 206 Byte 51

74 Convolutional Interleaver byte locations with a contiguous codeword

75 Convolutional Byte Inter leaver
For 12/26 or 12/52 SCBC code, gray regions contains complete 12/26 SCBC coded codeword Byte 26 51 104 156 52 53

76 ATSC Trellis coded Modulation (TCM)


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