multi-standard mobile digital televisiontams- · multi-standard mobile digital television norman...

University of Hamburg

MIN Faculty

Department of Informatics

Multi-standard Mobile Digital TV

Multi-standard Mobile Digital Television

Norman Hendrich

University of HamburgMIN Faculty, Dept. of Informatics

Vogt-Kolln-Str. 30, D-22527 [email protected]

13/01/2009

N. Hendrich 1


MIN Faculty


Multi-standard Mobile Digital TV

Outline

I Motivation

I Overview of (mobile) digital TV

I The terrestrial transmission channel

I COFDM

I The transport stream

I Service information and ESG

N. Hendrich 2


MIN Faculty


Introduction Multi-standard Mobile Digital TV

Mobile Digital Television

I ”tele” + ”vision” (Greek ”far” + Latin ”sight”)I the most popular medium

I entertainmentI informationI education

I the most popular electronic deviceI ca. 1.4 billion TV sets worldwideI 800 million fixed phones, 750 million mobile phonesI 277 million PCs

I transition to digital TV during the next 10 years

I mobile reception increasingly important

(data from Wu. et.al. 2006)

N. Hendrich 3


MIN Faculty



Analog TV: History and Timeline

I First experiments around 1900

I BBC experimental broadcasts in 1929

I NTSC broadcasting started 1942

Three main color-TV systems:

I NTSC, 1953, 525 lines, 60 Hz

I SECAM, 1967, 575 lines, 50 Hz

I PAL, 1967, 575 lines, 50Hz

I MUSE, 1986, experimental HDTV system

http://www.tvhistory.tv/ Kuba Komet (1959)

N. Hendrich 4


MIN Faculty



Why go digital?

Technical, economical, and political reasons:

I better use of available spectrum

I due to better modulation and data-compression

I more channels in same bandwidth

I or better quality – including HDTV

I single-frequency networks for flexible network planning

I mobile reception

I data services and interactive TV

I encryption, pay-per-view, premium services

N. Hendrich 5


MIN Faculty



Recent news

12/2008: DVB-T in all of Germany

I reaches 90% of German population

I but different ”bouquets”

I commercial channels only inmetropolitan areas(= where profitable)

I 600 analog transmitters,

I 8700 analog gap-fillers

I replaced by 488 DVB-T transmitters

(ueberallfernsehen.de)

N. Hendrich 6


MIN Faculty



Recent news

11/2008: Mobile 3.0 returns German DVB-H license

I license bought 01/2008

I but no agreement on services/bouquet

I delayed deployment

I no suitable business model

01/2009: analog switch-off in US delayed?

I ”Digital Transition and Public Safety Act” (2005)

I switch-off scheduled for 17/02/2009

I but 40M people waitlist for DTV settop-box

(heise.de, www.mobiledreinull.tv)

N. Hendrich 7


MIN Faculty



Recent news

01/2009: China licenses 3G frequencies

I China Mobile: TD-SCDMA (China)

I China Unicom: WCDMA (European UMTS)

I China Telecom: CDMA-2000 (USA)

I all cities to be covered in 2011

12/2008: DVB-H status in Austria

I 600K customers at provider ”3”

I 90K people watch movies/clips at least once a month

I average watching period: four minutes

I statistics include both streaming (MBMS) and DVB-H

(heise.de)

N. Hendrich 8


MIN Faculty



Broadcast vs. cellular?

"niche" content

broadcasting efficient

program / channel

num

ber

of v

iew

ers

I some content very popular: broadcast efficient

I plus a ”long tail” of niche content: unicast (cellular)

N. Hendrich 9


MIN Faculty


Digital TV Multi-standard Mobile Digital TV

I Motivation



I COFDM



N. Hendrich 10


MIN Faculty



Digital TV: the basic concept

I video source-coding and data-compression (MPEG, H.264)typical data-rates 300 kbps .. 20 Mbps

I add service-information and auxiliary data (e.g. subtitles)

I multiplex into transport format (MPEG TS)

I add error-correction codes (interleaving and FEC: RS, LDPC)

I encode and modulate for transmission channel:satellite, cable, terrestrial, mobile, . . .optimize parameters for the channel (COFDM, QAM)

I receiver applies steps in reverse order:demodulate, FEC-decode, demultiplex, decode, play video

N. Hendrich 11


MIN Faculty



Digital TV: receiver

(Frontier Silicon)

N. Hendrich 12


MIN Faculty



Digital TV: timeline

I 1987: ATSC ”petition” for HDTV

I 1993: DVB founded

I DVB-S 1993, DVB-C 1994

I 1995: ATSC digital HDTV

I 1997: ISDB digital HDTV

I 2000: DVB-T

I 2004: DVB-H

I 2006: DTMB

I 2008: DVB-T2, DVB-SH

I ...

LG KB770 (2008) BBC OFDM modulator (1996)

N. Hendrich 13


MIN Faculty



Digital TV: Competing standards

I ATSC (USA), IDSB (Japan), DVB (Europe)

I DAB/T-DMB (Europe/Korea)

I MediaFLO (Qualcomm)

I DTMB, DMMB, . . . (China)

I variants for satellite, cable, terrestrial, mobile/handheld

I overall similar architectures and algorithms

I but different / incompatible parameters

I most systems based on MPEG-2 transport stream

I newer systems use IP (over TS)

N. Hendrich 14


MIN Faculty



Digital TV: systems

DVB-T DVB-H DAB T-DMB DTMB

spectrum VHF/UHF UHF VHF/L VHF VHF/UHFbandwidth (Mhz) 6/7/8 6/7/8 1.53 1.53 6/8modulation QAM QAM QPSK QPSK QAMOFDM carriers 2K 8K 2K 4K 8K 1536 1536 3780guard-interval 1/8 1/8 1/4 1/4 ?FEC RS RS - RS LPDCTS-rate (Mbps) 3..30 11 1.15 1.15 5..30

mobile no yes yes yes no

codec MPEG2 MPEG4 DAB MPEG4 MPEG2SI/ESG MPEG2 MPEG2 DAB DAB MPEG2IP downloads yes yes no yes yes

VHF: 170–230MHz, UHF 470–862MHz, L-band 1.452–1.492GHz

N. Hendrich 15


MIN Faculty



Mobile digital TV: the challenges

Mobility:

I usually, low-gain antenna(s) instead of rooftop

I quickly changing receiver conditions

I multipath reception, interference

I need inter-cell and inter-network handover

Handheld:

I small devices, small antenna

I battery weight and lifetime are critical

I low-power operation

I small screen: low-bitrate video sufficent?

N. Hendrich 16


MIN Faculty



Mobile digital TV: world map

(Frontier-Silicon data, end of 2006)

N. Hendrich 17


MIN Faculty



Mobile digital TV: DVB-H

”DVB for handheld and mobile”

I fully IP-based

I time-slicing for power-saving

I 4K-OFDM mode (option)

I MPE-FEC improved error-correction (option)

I in-depth interleaving (option)

I 11Mbps: 20..30 channels at about 300..500 kbps

I compatible with DVB-T transmitters

I embed DVB-H service within DVB-T network

I return-channel via GSM/UMTS (option)

N. Hendrich 18


MIN Faculty



DVB-H: Services and time-slicing

N. Hendrich 19


MIN Faculty



Mobile digital TV: business models?

I four traditional TV business modelsI free-to-air model, financed via taxes (German ”GEZ”)I commercial free-to-air, financed via advertisingI subscription pay-TVI on-demand pay-TV

I quite difficult for mobile, becauseI small screen, low video qualityI short watching times (e.g., while commuting)I users unwilling to pay for that

I role of telcom/mobile operators?

N. Hendrich 20


MIN Faculty



Mobile digital TV: Use-casesAssumes the integrated network / multi-standard network

I Service discovery - multiple-network ESG/EPG

I (free to air) TV

I (pay per view) TV

I VOD/file download

I Broadcast service with auxiliary data and interaction

I Broadcast service for roaming mobile terminal

I Seamless handover between networks

I Multiple-network services

I . . .

N. Hendrich 21


MIN Faculty



Mobile digital TV: a typical handsetNokia N96 (2008)

UMTS

WLAN

BluetoothGPS

DVB-T

DVB-HDTMB

FM Radio

DAB

T-DMB

GSM

DMMB

MediaFLOWiMAX

4G LTE

GPRS, EDGEHSPA

N. Hendrich 22


MIN Faculty


The terrestrial transmission channel Multi-standard Mobile Digital TV

I Motivation



I COFDM



N. Hendrich 23


MIN Faculty



Digital TV: three transmission channels

I cable low interference, high bandwidth

I satellite long-distance, line-of-sight, very low power

I terrestrial multipath, echoes, interference

I completely different environments

I therefore, different coding and modulation

I DVB-C, DVB-S, DVB-T, DVB-H, DVB-S2, DVB-T2, . . .

I mobile reception from satellite ”within reach” now

I e.g., DVB-SH, Stimi/DMMB

N. Hendrich 24


MIN Faculty



The electromagnetic spectrum

N. Hendrich 25


MIN Faculty



The terrestrial frequency bands

I VHF: 30..300 MHz, ”meter band”, ideal for short-rangeterrestrial

I UHF: 500..900 MHz (..3 GHz), ”decimeter band”

I L-Band: 1..1.4 GHz

(wikipedia)

N. Hendrich 26


MIN Faculty



The terrestrial transmission channel

Rural scenario:

I high-power transmitter on ”TV tower”

I usually, big rooftop antenna

I signal power decreases with distance

I frequency dependency, atmospheric effects

I gaussian-noise

I small-band interference

I burst-noise (e.g. motors)

I multipath-reception and echoes

N. Hendrich 27


MIN Faculty



Urban scenario and mobile reception

Much more difficult for handheld:

I antenna very small, low gain

I antenna very low, usually no line-of-sight

I even worse indoors

I strong multipath-effects: interference, long echoes

Even worse for mobile:

I channel conditions change quickly,typically O(wavelength)

I Doppler-effect

N. Hendrich 28


MIN Faculty



Interference and fading

t / [µs]

f / [Hz]

sign

al p

ower

/ [d

B]

A(t)

B(t)

A(t)

+ B

(t)

I constructive interference

I desctructive interference

Typical multipath frequency response:

I superposition of many signals

I ”fading” of some frequencies

I very irregular on small scales

I need ”channel estimation”

I required very quickly for mobile

N. Hendrich 29


MIN Faculty



Rayleigh fading: example

Channel attenuation (dB) vs. carrier frequency (MHz) and time (ms). wireless.per.nl/reference/chaptr03/

N. Hendrich 30


MIN Faculty



Channel modelling

t / [µs]

t / [µs]

A(t

)A

(t)

Rural scenario

Urban scenario

I signal power and attenuation

I frequency response

I gaussian noise

I ASNR / PSNR ratios (average/peak)

I propagation delay

I multipath delay

I . . .

I active research area

N. Hendrich 31


MIN Faculty


COFDM Multi-standard Mobile Digital TV

I Motivation



I COFDM



N. Hendrich 32


MIN Faculty



Coded Orthogonal Frequency-Division Multiplex

I very efficient modulation scheme

I based on very many but narrow carriers

I carrier frequencies matched to symbol duration

I to reduce inter-carrier interference

I first proposed in 1960s

I but impractical without digital signal processing

I only popular since low-cost DSPs available

I used in WLAN (802.x) and WiMAX

I used in DAB, T-DMB, DVB-T, DVB-H, DTMB

I will be used for UMTS-LTE, 4G

N. Hendrich 33


MIN Faculty



COFDM: the name

0f

1f

nff¢§

0f

I divide total bandwidth into many small carriers(frequency-division)

I select carrier frequencies to minimize interference(orthogonal)

I transmit symbols in parallel on each carrier(multiplex)

I use error-correction codes against noise and interference(coded)

N. Hendrich 34


MIN Faculty



COFDM: one symbol per carrier

I each carrier modulated with one symbol

I e.g. QPSK, QAM-16, QAM-64

I symbol duration ∆t

I Fourier spectrum is sin(f)/(f)

I carriers orthogonal if∆f = 1/∆t

N. Hendrich 35


MIN Faculty



COFDM: example signal

(Reimers: Digitale Fernsehtechnik)

N. Hendrich 36


MIN Faculty



COFDM: block diagramuse FFT/iFFT instead of thousands of carriers

N. Hendrich 37


MIN Faculty



COFDM: channel estimation

thousands of sub-carriers:

I each sub-channel is very narrow

I channel response C (ω) nearly flat for each channel

I compensation is easy (multiplcation by constant)

I transmit known ”pilot” symbols for training

I on all or on selected carriers

I trade-off between overhead and robustness

I quick channel estimation becomes possible

N. Hendrich 38


MIN Faculty



DVB-T: carriers and pilots

N. Hendrich 39


MIN Faculty



COFDM: inter-symbol interference

multipath reception over different paths

I symbols received at different times

I symbols overlap and cannot be decoded correctly

N. Hendrich 40


MIN Faculty



COFDM: guard interval

I introduce a ”guard interval” between symbols

I interval duration must cover longest expected echo

I c = 3 · 108m/s, e.g. 100µs for 30km

N. Hendrich 41


MIN Faculty



COFDM: cyclic prefix

I fill guard-interval with part of the next symbol

I use auto-correlation for precise synchronization

I note: DTMB uses pseudo-noise sequence instead of CP

N. Hendrich 42


MIN Faculty



COFDM: synchronization

N. Hendrich 43


MIN Faculty



DVB-T: modes

I Example: 8MHz, 8K-mode, 64-QAM, guard 1/4, rate 3/4:6048 payload carriers, 6-bits/symbol,symbol duration (896+224)µs, RS(188,204) code:= 6048 · 6 bits

(896µs+224µs) · 34 · 188

204 = 22.39 Mbps.

N. Hendrich 44


MIN Faculty



DVB-T: data-rates

N. Hendrich 45


MIN Faculty



COFDM: single-frequency networks

I multiple transmitters with the same frequency?I severe multipath effects, strong fadingI impossible for single-carrier systemsI adjacent network cells must use different frequenciesI wasted bandwidth, difficult network planning

With COFDM:

I fading affects only a few subcarriers

I reception possible if FEC strong enough

I adapt guard-interval to SFN cell size

I possible to use repeaters and gap-fillers

I transmitters must be synchronized (e.g. via GPS)

N. Hendrich 46


MIN Faculty



COFDM: network planning

"gap filler" SFN radius

2

32

3

2 3

11

1 1

1

11

1

1

1

1

1

1

1

3

3

2

2

2 2

23

3

332

2

3

14

I typical frequency allocation in MFN/SFN networks

I max. SFN radius depends on selected guard-intervalN. Hendrich 47


MIN Faculty



The terrestrial transmission channel: summary

I rural vs. urban environments

I no direct line-of-sight

I multipath reception

I attenuation and interference

I plus Doppler-effect when mobile

I COFDM modulation

I guard-interval avoids inter-symbol interference

I FEC used to recover weak subchannels

I efficient calculation via FFT/IFFT

N. Hendrich 48


MIN Faculty


Multi-standard receivers Multi-standard Mobile Digital TV

Multi-standard receivers

I current (mobile) DTV systems based on COFDM

I but very different FFT and FEC parameters

I multi-band single-chip tuners already exist (RF frontend)

Baseband-processor design options:

I SoC style, use optimized IP-blocks (e.g. FFT, RS, LDPC)

I programmable DSPs (”software defined radio”)

I combinations of the above

I how many / which radios to use in parallel?

N. Hendrich 49


MIN Faculty



Chip area: example

(Ramacher 2007)

N. Hendrich 50


MIN Faculty



SDR example: Infineon ”MuSIC 1”

(Ramacher 2007)

N. Hendrich 51


MIN Faculty



Terminal middleware overview

CodingScalable

DataA/VESG

Adaptation LayerAdaptation Layer

DTMBDVB-H(802.11)WiFi

Broadcast Transport Convergence Sublayer

Co

ord

inat

ion

Mobile Convergence Sublayer

Multimedia Framework

Mobile CommunicationBroadcast Multimedia Framework

Converged Interactive Services / User-Interface

(3G)(2G)

Adaptation Layer

T-DMBGSM UMTS

N. Hendrich 52


MIN Faculty


The MPEG-2 transport stream Multi-standard Mobile Digital TV

I Motivation



I COFDM



N. Hendrich 53


MIN Faculty



MPEG-2 transport layer

How to encode A/V data for streaming transmission?

I need common bitstream format

I combine multiple A/V streams into one single signal

I receivers switched on/off at unknown times

I receivers need to synchronize quickly

Most current systems use MPEG-2:

I ISO/IEC 13818-1 (”Systems” 1993)

I (Packetized) Elementary Stream specification

I Transport Stream specification

I Service information

N. Hendrich 54


MIN Faculty



MPEG-2 stream hierarchy

N. Hendrich 55


MIN Faculty



MPEG-2 PES (packetized elementary stream)

I variable length packets

I packet headers identified by reserved bit-patterns,namely start-code plus 8-bit opcode0000 0000 0000 0000 0000 1AAAA AAAA

I packet-length matches codec requirements,e.g. one complete video frame

I multiplex of the different video, audio, metadata streams

I designed for reliable media

I e.g. Video-DVD

N. Hendrich 56


MIN Faculty



MPEG-2 PES: video stream format

I-macroblock

"group of pictures"

"picture layer"

"slice layer"

"video sequence layer"

seq. end codeseq. end codeGOPGOP

r-l code r-l code r-l codediff. DC coeff EOB

(if D-picture)end-of-mbblock 5block 1block 0macroblock header

macroblockmacroblockmacroblockslice header

slicesliceslicepicture header

seq. header GOPsequence header

GOP header picturepicturepicture

N. Hendrich 57


MIN Faculty



MPEG-2 TS (transport-stream) and SI/PSI

I fixed packet size of 188 bytesI packet header includes PID (stream identifier)I each audio and video stream has its own PIDI 13-bit PID allows up to 8K streamsI system-information packets multiplexed in the stream

I PAT: program association table (PID=0)I lists one PMT index (0x20..0x1FFE) for each ”program”

I PMT: program map tableI lists all A/V streams corresponding to the program

I several other pre-defined tables

N. Hendrich 58


MIN Faculty



MPEG-2 transport-stream multiplex

N. Hendrich 59


MIN Faculty



MPEG-2 transport-stream example

N. Hendrich 60


MIN Faculty


Service information Multi-standard Mobile Digital TV

I Motivation



I COFDM



N. Hendrich 61


MIN Faculty



Service information and ESG

I broadcast based on multiplexed transport stream

I multiple programs with their A/V data and metadata

I need data-structures to find the requested content

I ”service information” for parsing the stream

I SI: ”service information”

I PSI: ”program specific information”

I EPG: ”electronic program guide”

I ESG: ”electronic service guide”

N. Hendrich 62


MIN Faculty



Service information

I most current systems based on MPEG-2

I ATSC, IDSB-T, DVB-C/-S/-T

I also, the Chinese cable-TV and DTMB

I overall very similar, standard set of SI tables

I plus a few system-specific tables

I embedded into the MPEG transport stream

I but DVB-H more complex because of IP-encapsulation

N. Hendrich 63


MIN Faculty



MPEG-2: SI/PSI/ESG tables

N. Hendrich 64


MIN Faculty



MPEG-2: PAT (Program Association Table)

I PID = 0x00

I repeat very 25ms..500ms

I usually fits into one TS packet

I table-ID 0x00

I one entry for every ”program”

I which lists the PID for the program PMT

I one extra entry: program number 0 lists the PIDof the NIT (network information table)

N. Hendrich 65


MIN Faculty



MPEG-2: PMT (Program Map Table)

I PID in range 0x20..0x1FFE

I one PID for each program in the TS multiplex

I repeat every 500 ms

I table-ID 0x02

I one entry for every audio- and video stream of the program

I stream type (0x01: MPEG-1 video, 0x02: MPEG-2 video,0x03: MPEG-1 audio, 0x04: MPEG-2 audio,0x05 private sections, . . . )

I PID of the stream packets

N. Hendrich 66


MIN Faculty



MPEG-2: NIT (Network Information Table)

I PID = 0x10, table-ID = 0x40/0x41

I repeated every 25 ms..10 s

I one entry for each ”network”

I for each network, one entry for each transport-stream

I describes the physical parameters of the channel

I e.g. frequency, modulation, error-correction

I receiver can quickly switch channels

I faster ”zapping” :-)

I also used in DVB-H to support cell-handover

N. Hendrich 67


MIN Faculty



MPEG-2: SDT (Service Description Table)

I PID = 0x11, table-ID = 0x42/0x46

I also BAT (Bouquet Association Table)

I repeated every 25 ms..2 s

I user-readable description of each program

I in the transport stream (bouquet)

I including channel name (”ARD”, ”Arte”, ”CNN”, . . . , ”ZDF”)

I references to the EIT (event information table)

I references to the RST (running status table)

I . . .

N. Hendrich 68


MIN Faculty



DVB-H: Protocol stack

(ETSI 102 472)

N. Hendrich 69


MIN Faculty



DVB-H: INT (IP/MAC Notification Table)

I in DVB-H, all data delivered via IPI A/V streams transmitted via RTPI services identified via IP address and port-numbers

I INT table lists IP/MAC addresses for all servicesI bootstrap ESG at ”well-known” IP addressI points to additional ESGs, which point to servicesI one SDP file (session description protocol)

to describe each A/V service

I extra complication due to time-slicingI all in all, pretty complex. . .

(ETSI 102 472 RFC 3550 RFC 2327)N. Hendrich 70


MIN Faculty



DVB-H: Service access

N. Hendrich 71


MIN Faculty



DVB-H: Example SDP file

N. Hendrich 72


MIN Faculty



DVB-H: ESG

(full specs: ETSI TS 102 471)N. Hendrich 73


MIN Faculty



TV-Anytime

I TV-Anytime forum founded 1999 (successor of DAVIC)

I association of 60 organizations (e.g. BBC, Disney, EBU, Nokia, Philips, . . . )

I ”targeting specifications to enable audio-visual and otherservices on mass-marked digital storage in comsumer platforms”

I first spec published in 2003 ”Broadcast and On-line Services:Search, select, and rightful use of content on personal storagesystems” (”TV-Anytime”) (ETSI TS 102 822-1)

I CRID: content reference identifier

I content classification based on MPEG-7

I details: www.tv-anytime.org/

N. Hendrich 74


MIN Faculty



TV-Anytime: Program Information table

BBC http://backstage.bbc.co.uk/feeds/tvradio/

N. Hendrich 75


MIN Faculty



TV-Anytime: Program Location table


N. Hendrich 76


MIN Faculty



TV-Anytime: Content Referencing table


N. Hendrich 77


MIN Faculty



Multi-standard service information

I standard SI/PSI tables of home network

I including NIT data for inter-cell handover

I enhanced NIT:I include transmission parameters for other networksI allows fast inter-network handoverI bypass the slow frequency-scan (network-search)

I enhanced ESG:I include ESG information for other networksI including content-categoriesI seamless inter-network handover when matching content

N. Hendrich 78


MIN Faculty


Summary Multi-standard Mobile Digital TV

Summary



I COFDM



N. Hendrich 79


MIN Faculty



Discussion

Thanks for your attention!Any questions?

N. Hendrich 80


MIN Faculty



References

Ulrich Reimers, Digitale Fernsehtechnik, Springer, 1995

Walter Fischer, Digitale Fernsehtechnik in Theorie und Praxis,Springer, 2006

Chinese National Standard DB 20600-2006, Framing Structure,Channel Coding and Modulation for Digital Television TerrestrialBroadcasting System, 2006

ISO/IEC 13818-1, Generic coding of moving pictures andassociated audio information: Systems (MPEG2], 1985

Proceedings of the IEEE, Global Digital Television, Vol.94-1, 2006

Wikipedia

N. Hendrich 81

multi-standard mobile digital televisiontams- · multi-standard mobile digital television norman...

Documents