spring2005 © university of surrey satcomms b - general - b g evans 1 satellite communications b...

Spring2005 © University of Surrey SatComms B - General - B G Evans 1

Satellite Communications BSpring Semester 2004-5-Satellite Broadcasting-

-Professor Barry G Evans-

EEM.scmB


Contents

1. Analogue TV Satellite Broadcasting

2. Digital Satellite Broadcasting (MPEG/DVB-S)

3. New DVB-S2 standard and IP Delivery

4. DMB


1. Analogue Satellite Broadcasting

• F.M. Theory –S/NW versus C/N

• DTH/Cable head systems

• WARC Broadcasting Plan

• MAC Systems


System model


FDM/FM techniques


FM Transmission Formats

• NB. FDM/FM being replaced . Digital IDR TDM/PSK/FDMA


Characteristics of Frequency

Modulation (FM)


FM Threshold Effect

2

2

31o

mO

mfN

C

N

S

mo f

fm

where

TRADE OFF BETWEEN POWER AND BANDWIDTH

F.M.EQN:


2fkSignal

U

L

U

L

f

f

f

f

o

f

dffNNoise

3

3

2

oLU N

C

ff

f

N

S33

23

or oLU N

C

ff

fB

N

S33

23

note f is the rms deviation. fm peak deviation fPK

oLU

PK

N

C

ff

fBr

N

S33

23

r = pk-rms rationnote that then S is the signal pk

FM Theory

• General


Quality objectives for television

(CCIR Rec. 567-1 & 568)


ITU-R Subjective Quality Service

• Picture Quality Weighted S/N(dB)

5 (excellent) 46.6

4 (good) 42.3

3 (fair) 38.0

2 (poor) 33.6

1 (bad) 29.3

99.9% ITU-R

VIDEO REC. QoS


Base band signals television


BASEBAND SIGNAL (FDM) = 6MHZSIGNAL – 1V pk-pk Test signal

F.M. EQUATION,

33

23

LU ff

fB

N

C

N

S

For T.V. fL << fU fL=0, fU=fm

f = Fr (rms deviation of signal)

3

23

m

r

f

BF

N

C

N

S

CCIR Definition S/No - pk-pk video voltage = S Fpp should be used

Test-Tone for T.V. includes Synch tip.0.7 x pk-pk volts = pk-pk video

2

7.02

22 TTTTPP

FFF

3

2

*2

3*

m

TT

f

FB

N

C

N

S

FM Theory

• Television


Analogue transmission techniques-SCPC/FM transmission of television-


Analogue transmission techniques-pre and de-emphasis

• Noise at the output of a FM demodulator has a parabolic power spectral density: higher frequency components get corrupted by more noise than the lower frequency components.

• PREEMPHASIS increases the amplitude of high frequency components before frequency modulating the carrier.

• DEEMPHASIS removes this ‘distortion’ at the receiver.


Communication techniques


15 KHz TEST-TONE APROACH

For A 1v pk-pk Test Signal with fixed pattern Alternate Black-White lines, which is convenientTest Signal – equivalent deviation 15KHz sinusoid T.T. FTPP

WPf

F

N

CB

N

S

m

TPP3

2

2

3

(WP) is the combined weighting & pre-de-emphasis gain referred to the 15KHz point, which is different from the 0 cross-over value (see slide)

UNIFIED WEIGHTING

Note that a unified weighting defined over satellite. For S/N calc’s the noise is calculatedIs a top baseband of fm=5MHz. Then :

625 Line (WP) = 13.2 dB.525 Line (WP) = 14.8 dB

FM Theory

• Television


Video Weighting Factor

Frequency characteristics of weighting networks for measuring continuous random noise* Improvement by emphasis + weighting factor. (P+O)

The CCIR specifies the identical S/N relating to the continuous random noise, for 525/60 and 625/50 systems. Namely, the S/N should be equal to or better than 53 dB for 99% of time and 45 dB for 99.9% of time (Recommendation 567). This Recommendation was adopted at the CCIR Plenary Assembly in 1978, and the former frequency characteristics of weighting networks which had been separately defined for different TV standards were replaced by a single set of characteristics to give unified S/N objectives.Figure below shows the unified curve as well as the former frequency characteristics of weighting networks.


INTELSAT : 625/50 HzFTPP = 15 MHz. fm’= 6MHz

fm = 5MHz

0

0

2

0

2

5.42

)..(5

1

5

15

2

3

1

2

3

N

CdB

N

Cpw

N

Cpw

ff

F

N

S

mm

TPP

Aim for Fixed Link. S/N=45 dB. C/No=87.5 dB-MHzBW = 15 + 2x6 = 27 MHz

Also ½ TPDR. TV. 15.75 MHz BW. 2 x TV in 36MHzS/N = 29.5 + C/N = 45

C/N = 15.5 dB

ASTRA – DTH.

0

0

2

4.43

)..(5

1

5

5.13

2

3

N

C

N

Cpw

N

S

DTM. S/N=42.3, C/No = 89.8 dB-Hz Bw = 13.5 + 2x6 = 25.5 MHz C/N 15 dBAllows Rain fade to threshold

TV via Satellite

• Example


• Use BW narrower than Carson without excessive distortion

• Inst. Frequency corresponding to PK-DVN is well outside the passband filters when the deviation is close to PK, the carrier is suppressed and a short burst of noise is generated –visible as spots.

• BUT % time when carrier outside passband is small –but excessive O/D will cause deterioration

Satellite TV – Over Deviation

10.9dB310.520logCarson

actual20log

deviation'over'Called

Carson10.5MHzdevnPKuseactuallyINTELSAT

3MHz62

18ΔF

18MHzBWoccupyFMTV625/50

fmΔF2B

P

PC


dB) (13.2 advantage weighting emphasis pre

MHz) (5 videoof baseband top

15kHzat signal sinusoidalby produceddeviation pk -pk

luminance amp. nominal to videomonochrome of amp.pk -pk ratio

13

2

21log10

0

2

2

00

2

00

Q

f

f

r

QN

C

ff

fr

N

S

RbN

C

N

Eb

f

f

N

C

N

C

m

pp

mcmm

pp

mc

dscdata

sc

sc

mcdsc

Data sub-carrier


NB 2 dB better than CCIR-4 (Good) At C/N THRESHOLD = 0 dB gives 3.1 dB margin for propagation

Transponder = +52 dBWDish size TVRO = 60 cm LNB = 1.5 dB noise fig (120K)

UPLINK: Transmit eirp +80 dBW

Pointing loss 0.2 dB

Clear sky abs. Loss 0.5 dB

F.S.L (14.5 GHz) 207.3 dB

Satellite G/T (Land) +7 dB/K

K -228.6 dBW/Hz/K

C/N0 107.6 dB-Hz

DOWNLINK:

Transponder eirp (saturation) 52 dBW

F.S.L (12 GHz) 205.5 dB

Clear Sky absorption (12 GHz) 0.4 dB

TVRO ptg.loss 0.3 dB

TVRO G/T (elev. Sky) 12 dB/K

K -228.6 dBW/Hz/K

C/N0D 86.4 dB-Hz

OVERALL C / (N0D+N0U) 86.4 dB-Hz

C / N(in 26 MHz) 12.2 dB

C / I(adj. Satellites + X path) 28.0 dB

C / (NTH + Nint) 12.1 dB

Deviation (FTPP) 16 MHz

W + P 13.2 dB

S / N 44.2 dB

TVRO Satellite TV


Link Performance -Exercise

– Fixed losses = 0.5dB– Antenna Pt.Loss = 1.4dB– System noise temp. (clear weather) = 22.3dB-K– Rain loss (99.5%) = 0.7dB– Rain temp. = 275k– Desired TV quality S/N = 42.3dB (CCIR Grade 4)– Video bandwidth = 5MHz– Pre-emp . weight gain = 13.2dB– Receiver bandwidth = 27MHz– Video deviation = 13.5 MHz (P-P)

• Calculate the earth-station dish size required to obtain CCIR Grade 4 quality TV reception for 99.5% of the time.

RX DMD

SATELLITE

eirp=+40dBW

TVFREE SPACE LOSS –250.6DB

Diameter? =65%

T=22.3dB-KS/N=42.3dB


TV TRANSMISSION

• ATV link to TVRO from Astra– Calculate the C/No on the uplink. Is this significant?– Calculate the size of dish required to provide CCIR Grade 4 B/N=42.3dB

assuming clear weather(make allowance for absorption, pointing loss, etc.)Video devn 13.5MHz p-p, W+P=13.2dB, fm=5MHz, B=26MHz

– Produce a link budget table for the above– Produce another column in the link budget table to represent the case for

99.5% availability for which a fade of 0.84dB is derived form the CCIR model.

ASTRAeirp =

+52dBW

14.5GHz G/T=+7dB/k

207.3dB

eirp +80dBW

TELEPORT

11.5GHz

C/I=28dB

205.5dB

TVRO =0.6 LNB

1.5dB noise Fig.


Model of a BroadcastingSatellite System


Broadcast Satellites: the WARC Plan Features

• Frequency Band 11.7 to 12.5GHz (Europe & Africa)• 40 channels spaced at 19.18MHz• Orbital positions –generally a 60 spacing• Frequency modulation –deviation 13.5MHz/Volt, i.e.

a bandwidth of about 27MHz• 5 channels for each country• Circular polarisation• Sound –a single channel on a sub-carrier• Video –PAL or SECAM composite


BSS Planning in Europe (1/3)


ITU Region 1 Ku BandFrequency Plan


The MAC/Packet innovation

Time division multiplex components


MAC format optionsB-MAC, D-MAC, D2MAC

• Time Division Multiplex (TDM) at baseband of time compressed TV signal analogue components and digital components (sound/data).

• B-MAC: 4 level encoding of digital components• D-MAC & D2-MAC: duobinary (3 level) encoding of digital

components. Rate divided by 2 with D2-MAC

Chrominance

Luminance

Sound+data

MOD

MOD

TDM RF

TIME COMPRESSION

TIME COMPRESSION

TIME COMPRESSION


MAC format options C-MAC

• Time Division Multiplex (TDM) at radiofrequency of time compressed TV signal analogue components and digital components (sound/data)

Chrominance

Luminance

Sound+data

TDM MOD

MOD

TDMRF

TIME COMPRESSION

TIME COMPRESSION

TIME COMPRESSION


2. Digital Broadcasting

• MPEG Compression Techniques

• MPEG Packets

• DVB-S Transmission


Topics to be covered

• Why compression?• MPEG-2 compression toolbox, including:

– Temporal and spatial redundancy– Discrete Cosine Transform, DCT

• DVB channel adaptation, including:– Forward error correction (FEC) encoding– Modulation and the effects of nonlinearity

• Quality of service and picture impairments• Contribution and distribution


Why is compression necessary?

• ITU-R BT.601-5 specifies 27Msamples/s at 8bits/sample = 216Mbits/s.

• MPEG-2 can deliver consumer quality video at ~1Mbits/s to 6Mbits/s.

• Typical broadcast satellite transponders have 27-36MHz bandwidth, cost roughly £2-3m/year, and can carry 30-40Mbit/s OR one FM TV channel.

• Transponder cost/channel is much lower for MPEG-2 compression than FM-TV.

• Digital format allows many more applications.


Elements of a digital satellite broadcasting system

STUDIOCamera

Tape

Film

File server

Contribution

Electronic Programme Guide (EPG)

MPEG-2 Encoder

Subscriber Management System

Conditional Access System

MultiplexerModulator

MPEG-2 Encoder


MPEG-2 Video Compression

Toolbox for bit-rate reduction includes:– Removal of temporal redundancy: inter-frame compression

– Removal of spatial redundancy (DCT): intra-frame compression

– Quantisation of DCT coefficients

– Variable length coding (VLC)


Temporal redundancy

Three classes of video frame:

• I-frames, make no reference to other frames• P-frames, predicted from earlier I- or P-frames• B-frames, predicted from both past and future frames

Only P- and B-frames use temporal redundancy.


Temporal redundancy

• Use motion estimation to predict the next frame.• Use DCT to encode the difference between predicted

and actual.

Intraframes

Predicted frames


Spatial redundancy

• Operates on blocks of 8x8 pixels.• Discrete Cosine Transform (DCT) converts spatial

elements to frequency domain (lossless).• Scaling related to human vision’s perceptual

sensitivity.• Quantisation controlled by feedback from rate

buffer.


Spatial redundancy

Pixel values fora block taken froma typical picture

Increasing horizontal frequency

Values afterDCT processing

Increasing vertical

frequency

176 176 176 176 176 176 176 176

171 171 171 171 171 171 171 171

185 185 185 185 185 185 185 185

203 203 203 203 203 203 203 203

206 206 206 206 206 206 206 206

203 203 203 203 203 203 203 203

193 193 193 193 193 193 193 193

178 178 178 178 178 178 178 178

1106 12 -22 12 4 6 2 0

145 -15 -16 10 3 7 1 0

98 -4 -20 4 5 1 1 -1

52 -15 -8 1 -1 2 -2 0

18 -10 -1 -1 -1 1 -2 0

9 -4 -3 -2 1 -1 0 0

-4 2 -4 1 -3 2 1 0

-13 1 0 0 -1 1 1 2


Spatial redundancy

Increasing horizontal frequency

Increasing vertical

frequency

DCT values after quantisation and scaling:

138 1 -1 0 0 0 0 0

8 -1 -1 0 0 0 0 0

5 0 0 0 0 0 0 0

2 -1 0 0 0 0 0 0

1 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0


Spatial redundancy

• Conversion to serial data by zig-zag scanning:

• Run length coding removes long strings of zeros.• Variable length coding replaces common values with shorter symbols (c.f. Morse code).

138 1 -1 0 0 0 0 0

8 -1 -1 0 0 0 0 0

5 0 0 0 0 0 0 0

2 -1 0 0 0 0 0 0

1 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0


Control of quantisation

Bufferoccupancy

Quantisation threshold

Fixed rateVariable rate

From DCTprocess

Data ratecontrol

Quantisation of DCT coefficients

Variable length coding

Buffer store


MPEG audio

• Uses a psychoacoustic algorithm based on the characteristics of the human hearing system.

• Divides the audio spectrum into sub-bands.• The model determines the just-noticeable level of

noise for each sub-band, and adjusts quantisation.

• Loud sounds reduce the ability to hear quiet sounds at other frequencies, so the quiet sounds may not need to be transmitted.


MPEG system layer

Elementary Stream: a stream of information that forms part of a programme, eg sound.

Programme Stream: a set of elementary streams having a common time base, that form a programme. A programme typically comprises video, associated sound channels, and data.

Transport Stream: a combination of one or more programme streams with one or more independent time bases, formed into a single stream. The transport stream is formed into packets of 188 bytes.


MPEG system layer

Video encoder

Audio encoder

Data encoder

Other programmes

Other data

Elementarystreams Programme

streams

Transportstream


Broadcast transmission - enter the DVB!

• MPEG defines the Transport Stream but not how to carry it.• DVB defines framing structure, channel coding and

modulation for satellite (DVB-S) in EN 300 421.• DVB is a European project, but DVB-S has been adopted

around the world.


Channel adaptation

Channel Adaptation: the processes involved in taking a Transport Stream and converting it to a form suitable for transmission on the satellite.

Energydispersal

Outer FECencoder

Interleaver

Inner FEC encoder

Baseband shaping

QPSK Modulation

To RF channel

Transportstream


Energy dispersal

• Energy dispersal: intended to ensure that patterns in the data stream do not cause power spectral density peaks.

• Achieved by exclusive-or with PRBS.


Outer FEC encoding

• Reed-Solomon (204,188) encoding adds 16 bytes to each MPEG packet.

188 bytes

16 bytes RS 16 bytes RS

204 bytes

188 bytes

204 bytes


Interleaver

Interleaver: breaks up bursts of errors, so that the performance of the Reed-Solomon error corrector in the receiver is enhanced.

Achieved by changing the sequence of transmission of bytes, then performing the inverse function in the receiver.


Inner FEC encoder

• Provides a second layer of forward error correction.• Target BER in receiver after error correction is 10-11,

corresponding to roughly one uncorrected error per hour.

• Target BER can be achieved with channel BER<10-2.• Choice of code rates of 1/2, 2/3, 3/4, 5/6, 7/8 allows

trading of bandwidth and error performance.


Modem performance

DVB specifies modem performance in IF loop to achieve quasi error-free performance:

Note: Eb/N0 = 10log(C/N0) - 10log(bit rate). The bitrate referred to in this table is the useful bit rate beforeRS encoding.

Inner code rate Eb/No (dB)1/2 4.52/3 5.03/4 5.55/6 6.07/8 6.4


Modulation

• Modulation cannot be AM because the satellite TWTA must operate at saturation to deliver maximum power.

• Modulation must therefore be some form of phase shift keying (PSK).

• Requirement for the smallest possible receiving antennas means that the modulation must be rugged, i.e. able to be demodulated at low C/N.

• Must be spectrally efficient (bits/Hz) to maximise transponder payload.


Modulation

• BPSK has largest inter-symbol distance.• QPSK has half BPSK’s symbol rate, so half the bandwidth.

Inter-symbol distance is down 3dB relative to BPSK, but so is received noise power!

I

Q

0

1

I

Q

0,0

1,1 0,1

1,0

BPSK constellation QPSK constellation


Baseband shaping

Amplitude Nyquist bandwidth

Slow roll-off Medium roll-off Fast roll-off


Modulation performance

Typical receiver performance in a linear channel:

Measured

Theoretical

Note: in this casethe bit rate usedto calculate Eb/N0

from C/N0 is thechannel rate.


Effects of nonlinearity

• Modem performance is not significantly affected by TWTA nonlinearity, even at saturation, for a single carrier.

• Note the effect of nonlinearity on the spectrum (next slide). It can have significant impact on the design of the uplink earth station, in order to meet adjacent channel interference (ACI) criteria.


Effect of TWTA on spectrum

Spectrum of 11Mbits/s (gross rate) QPSK signal after passingthrough a wideband TWTA at saturation.


Example payload calculation

Q. 30MHz of bandwidth is available. If the inner code rate is 3/4, what is the bit-rate available to the MPEG stream?

A. The relationship between bandwidth at -20dB relative to mid-band and the symbol rate is

BW = 1.28 x symbol rate.

Therefore, symbol rate = 30 / 1.28 = 23.4Msym/s

QPSK has two bits per symbol, so the gross bit rate is 23.4 x 2 = 46.8Mbits/s.


Example payload calculation

The rate after the inner layer of error correction is

46.8 x 3/4 = 35.1Mbits/s.

The rate after the outer (RS) layer of error correction is

35.1 x 188/204 = 32.3Mbit/s.

(Inner code) (Outer code)

MPEG stream todecoder

Fromdemodulator

46.8Mbits/s 35.1Mbits/s 32.3Mbits/s

Convolutionaldecoding (3/4)

RS (204,188) decoding


Quality of service

• The two concatenated error correcting codes give an abrupt failure as C/N degrades.

• Above the failure point, picture quality is the same as that leaving the studio.

PictureQuality

C/N

FM

DigitalFM threshold

Digital threshold


Picture impairments

• Impairments are different from PAL (eg cross-colour).

• Dependent on bit rate.• Dependent on picture content.• Rule of thumb: <2Mbits/s for talking heads at VHS

quality, 6Mbits/s for high quality action sports.• Impairments are mainly due to detail being omitted,

and in severe cases can lead to blocks becoming visible.

• Broadcaster can trade picture quality with number of services.


Contribution and Distribution

• Broadcaster to broadcaster connections:– Programme exchange– Feeds to cable head-ends (primary distribution)– Digital Satellite News Gathering (DSNG)

• DVB-DSNG (EN 301 210):– Specifies QPSK, same as DVB-S– Adds 8PSK and 16QAM


Links to IP deliveryover MPEG/DVB-S & DVB-S-RCS

• Having a digital transport packet, PES, it is possible to load IP packets into these and thus deliver. IP over MPEG/DVB-S

• As well as the forward channel MPEG/DVB-S a return channel –RCS –return channel via satellite- has been standardised –DVB-S-RCS.

• These topics will be covered in an associated lecture (Dr Haitham Cruickshank)


DVB-DSNG Standard 1992

• Upgrading DVB-S to satellite news gathering at contribution qualities

• 8PSK/16QAM with standard conv codes –spectrum eff. 3.2 bits/symbol

• Allow smaller dish SNG to operate at higher C/N’s


3. New Standard DVB-S2 – 2003

• Achieves 35-40% increase in throughput for same bandwidth

• Greater than 20 combinations of modulation and coding schemes offer– Spectrum efficiency 0.54.5 bits/unit bandwidth– C/N from –216dB

• Backward compatibility with DVB-S

• Opens up range of new services and reduced costs


New Standard DVB-S2 – 2003

• Layered modulation– QPSK, 8 PSK, 16 APSK, 32 APSK

• Low density parity check (LDPC)– Codes rates 1/4,1/3, ½, 3/5, 2/3, ¾, 4/5, 5/6, 8/9,

9/10

• Concatenated scheme– Inner LDPC– Outer BCH


Modulation schemes DVB-S2

The four possible DVB-S2 constellations before physical layer scrambling

00

I

Q

10

11 01

Q=LSB I=MSB

000

I

Q

011

111

001

101

010

110

100

text

1100

1101 1111

1110

0000

0100

0101

0001

1001 1011

0011

0111

0110

0010

1010 1000

I

Q

LSB

MSB

R1

R2

text

10001

10011 10111

10101

00000

10000

10010

00010

00011 00111

00110

10110

10100

00100

00101 00001

I

Q

R1

R2

R3

11000

01000

11001

01001 01101

11101

01100

11100

11110

01110

11111

01111 01011

11011

01010

11010



• QPSK/8 APSK broadcast applications

• 16/32 APSK professional applications requiring higher C/N– Need pre-distortion in uplink to overcome non-

linear.– Schemes better in non-linear channel cf. 16/32

QAM

• Roll-off factors - =0.35, 0.25, 0.2



Functional block diagram of the DVB-S2 system

BBFRAME PLFRAME

FEC ENCODING MODULATION PL FRAMING

BCH outer LDPC inner

PL Signalling Pilot symbols

BB Filter &

Quadrature Modulation

QPSK, 8PSK,

16APSK, 32APSK constel-lations

1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6,

8/9, 9/10

=0,35, 0,25, 0,20

to the RF

satellite channel

MAPPING

SCRAM

BLER

Dummy FRAME

LP stream for BC modes

MODE & STREAM ADAPTATION

STREAM ADAPTER

BB Signalling

Merger Slicer

Input interface & adaptation tools

#1

Single Input Stream

Multiple Input Streams

DATA

ACM COMMAND

CRC-8 Encoder

Input interface & adaptation tools

#n



• LDPC inner codes –simple block code (Gallager)

• BCH outer coding removes the error floor (no interleavers)

• FEC coded blocks (FEC frames) length 64800 or 16200 bits


Framing Structure:the system train

Pictorial representation of the physical layer framing structure

FEC FRAME H FEC FRAME H FEC FRAME H

PL FRAME

8PSK 5/6 QPSK 2/3 16APSK 3/4

Useful data

FEC redundancy

Type of channel coding and modulation adopted in the wagon



• Physical level: robust synch. and signalling– Physical train: sequences of periodic wagons (PL

frames)– Within PL frame. M/C is homogeneous– With variable C/M –(VCM) –M/C changes in

adjustment wagons



• PL frame =– Payload (64.800bits) – LDPC/BCH FEC

+ PL header (90 symbols) synch/sig. Mod. & coding type FEC rate, frame length, pilots, etc.

• PL header –uses fixed /2 BPSK –7/64 block coded

• Base band level– Configures Rx according to application– Single or multiple input streams, generic or transport

stream– CCM (const. M/C)– ACM (adaptive M/C)


DVB-S2 Performance

• Required C/N versus spectrum efficiency, obtained by computer simulations on the AWGN channel (idea demodulation) (C/N refers to average power)

• Operates C/N’s –2.4dB with QPSK/1/4 to 16dB with 32APSK/9/10 (for PER of 10-7)

• Note: 20-35% capacity increase over DVB-S

Spectrum efficiency versus required C/N on AWGN channel

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

-3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

C/N [dB] in R s

Ru

[bit

/s]

pe

r u

nit

Sy

mb

ol

Ra

te

QPSK

8PSK

16APSK

32APSK

DVB-S

Dotted lines= modulation constrained Shannon limit

DVB-DSNG


DVB-S2 Range of C and M

Examples of useful bit rates Ru versus LDPC code rate per unit symbol rate Rs


Comparison DVB-S and S2 (CCM)

Example comparison between DVB-S and DVB-S2 for TV broadcasting Satellite EIRP (dBW) 51 53.7 System DVB-S DVB-S2 DVB-S DVB-S2 Modulation & coding QPSK 2/3 QPSK 3/4 QPSK 7/8 8PSK 2/3 Symbol-rate (Mbaud) 27.5 (=0.35) 30.9 (=0.20) 27.5 (=0.35) 29.7 (=0.25) C/N (in 27.5 MHz) (dB) 5.1 5.1 7.8 7.8 Useful bit-rate (Mbit/s) 33.8 46 (gain=36%) 44.4 58.8 (gain=32%) Number of SDTV programmes

7 MPEG-2 15 AVC

10 MPEG-2 21 AVC

10 MPEG-2 20 AVC

13 MPEG-2 26 AVC


New standard DVB-S2 – 2003

• Standard optimised for range of satellite transponder characteristics and satellite channels

• Variable coding and modulation allows change on frame to frame basis

• Allows MPEG2, MPEG4, IP and ATM input streams

• Adaptive M&C can be operated between forward/return (RCS) to secure 4-8dB added advantages


Using ACM for IP Unicast (1)

Block diagram of a DVB-S2 ACM link

• Rx means C/N+I and reports to G.W.• GW adapts M and C on frame basis• Ka-band needs ACM to compensate fades 0.5dB/s –leads to

around 1dB accuracy corrections.

Satellite Terminal

Info SOURCE(s)

ACM DVB-S2 MODULATOR

ACM Gateway

Return channel

High bit-rate forward-link

C/N+I signalling

UP-LINK STATION

C/N+I measurement

ACM command: Modulation & coding selection

User bit-rate control



Example of IP services using a DVB-S2 ACM link

Satellite Terminal

Info Provider

AC

M R

ou

ter

Internet

ACM DVB-S2 SYSTEM

AC

M ro

utin

g

man

ager

ACM Satellite Gateway

Interaction channel

GW Server

Router Return channel

High bit-rate forward-link

C/N+I signalling

Buffers per: Protection level user service level level M1

BUF

Info Request

Info Response

Info Response

BUF BUF

ACM Command

Info Response



• ACM routing manager –separates the IP pkts/user per required protection and per service level and can prioritise per service.

• Single streams –ACM router and DVB-S2 mod independent and can implement any routing policy.

• Multiple streams –ACM is active and selects and prioritises packets as well as delaying for prioritisation.


New standard DVB-S2 – 2003

• Delivery HDTV and IP services• Combining DVB-S2 – MPEG4, ACM schemes get

25 video channels in 33MHz transponder• DVB-S2 and ACM with multispot Ka-band satellites

and DVB-RCS– reduce IP delivery costs by factor 10– Compatible cable/fibre costs

• DVB-S2 has backward compatibility but will take time to replace large number of home decoders


DMB – Digital Multimedia Broadcasting

• DMB and multicasting to mobile terminals is a major new market.

• Forecasts for MB market in 2008– 90 million users worldwide – 80 B € revenue

• Satellite can play major role (SDMB,MBSAT) but terrestrial options. (DAB, DVB-H).


DMB: convergenceof different worlds

Live TV

Driven

DMBDMB

Web-accessDriven

Gaming

Driven

Tecnhology

Driven

BROADCASTINGBROADCASTING

PC

WO

RL

DP

C W

OR

LDIN

TE

RN

ET

INT

ER

NE

T

MOBILE TELECOMsMOBILE TELECOMs


DMB services: real-time vs non real-time

• RT: real-time broadcast/multicast to mobile terminal– Live TV

– Live music

– Information (news, traffic)

– Advertising

– Webcams

– Multiplayer gaming

– Emergency messages

• NRT: non-real time, content stored on terminal and consumed later– Video on-demand

– Music on-demand

– Webcasting

– Web-browsing

– Personalised content

– Video games


Content for Mobile TV

• Existing TV content cannot be directly transported to mobile terminals

• “Mobile TV is not TV on the mobile”

• Content adaptation strategies are necessary– Small screens

– Detail-driven source coding

– Content trasducers

• New content produced for mobile TV– Short sequences (1 to 15 mins typical)

• NAVSHP (Networked Audio Visual Systems and Home Platforms)– New media technology platform for EC IST FP7

– Thomson, Alcatel, ST, Siemens, Nokia, Philips, Intel

– New Media Council: next meeting Dec 2-3, 2004.


DMB systems

• Classification is difficult, due to large overlap• Criteria

– Coverage: terrestrial/satellite

– Terminals: handset/vehicular

– Target service: audio/video/multimedia

– World region of operation

– Integration with cellular networks

– In operation/planned

– Standard/proprietary air interface

• Examples– Digital Audio Broadcasting (e.g. DAB, XM radio, Sirius)

– Digital Video Broadcasting (e.g. DVB-T, DVB-H)

– MBSAT

– IMT2000 (e.g., UMTS-MBMS, S-DMB)

– …


DAB

• Standardized by ETSI in 1995

• Replacement for analog AM and FM

• MPEG2 audio layer II

• Enhanced data services

• N x 24 ms Frames, DQPSK, OFDM

• 1/4 - rate Conv. Code, Interleaving, Puncturing

• 4-Modes of Operation

• Deployed in >35 Cntrs. Around the world


DARS systems: XM radio

• DARS = Digital Audio Radio Service • XM Satellite Radio (CONUS)

– started in 2001

– A $1,5 billions program targeting vehicular market

– 100 Thematic radio channels, FM+ quality

– $10/month subscription

– Receivers price starting today from $120

– XM exceeded 1 million customers end of October 2003

– Constellation• 2 GEO satellites• Terrestrial repeaters (~1500)

– Air interface• QPSK TDM• S-Band


DARS systems: Sirius

• Sirius (CONUS)– Started 2002– 120 Thematic radio

channels, FM+ quality– $12.25/month subscription– 400K users end of June

2004– Member of ASMS-TF– Constellation:

• 3 HEO sat • Terrestrial

repeaters (~ 90)

– Air interface:• Direct link: QPSK TDM• Terrestrial repeater link:

QPSK COFDM• Coding: RS+Conv• Sat diversity

TDM OFDM

TDM

GroundRepeaters

SIRIUSSatellite

VSATSatellite

NationalBroadcast

Studio

RemoteUplink Site

MobileReceiver

TDM OFDM TDM

12.5 MHz


MBSAT

• MBSAT (Japan and Korea)– opening 2004

– 1 GEO sat, 12 m antenna

– Gap fillers

– 25 MHz band at 2,6 GHz, 7 Mb/s capacity

– Vehicular and pedestrian usage

– 10 TV and 50 Radio broadcast programs

– Target 20 Million customers in 2010

– 400 to 600 $ receivers

– 3 to 20$/month subscription

• System Cost ~800 M$– Tens of thousands of terrestrial repeaters

• Partnership: Toshiba, NTV, NTT, SKT, Toyota, Mitsubishi, Samsung,...

• Strong involvement of SKT in Korea to market the MBSAT system

– Targeting video over cellphone with Samsung products


DVB standards: DVB-T/H

• DVB-T has been standardized in 1997

and now deployed worldwide

• DVB-T adopts QAM-OFDM

• DVB-H is the evolution of

DVB-T for broadcasting to

mobile handsets

– Targeting 2005 commercial

product availability

• Regulatory allocation for

DVB-H Network is a big

concern

– Will require tremendous

lobbying effort to grant

VHF/UHF before 2010


DVB-H System overview (1)

• Objectives– Broadcast transmission to mobile handheld terminals of datagrams (IP or other datagrams)

pertaining to multimedia services, file downloading services, etc

• Constraints– Limited power supply (small terminals)

– Varying transmission conditions (mobile terminals)

• Systems specification– DVB-H = DVB-T +

• 4K OFDM mode• Enhanced interleaving for native DVB-T 2K and 4K modes• Time slicing• Enhanced signalling• Packet coding: MPE-FEC• 5MHz bandwidth

– Reference documents• EN 300 744: Framing structure, channel coding and modulation for digital terrestrial television (DVB-T),

Appendix G and H specific for DVB-H• EN 301 192: Link Layer• EN 300 468: Service Information• TS 101 191: Single Frequency Network


DVB-T/H System overview (2)

• 4 bandwidth modes: 5, 6, 7, and 8 MHz• 3 OFDM modes: 2K, 4K, 8K• 3 modulation formats:

– 4-QAM

– 16-QAM

– 64-QAM

• Hierarchical and non-hierarchical transmission– Non-hierarchical: constant error protection

– Hierarchical: higher protection for basic information, lower protection for additional information

• Bit-wise and symbol-wise interleaving• Concatenated channel coding

– Inner code: convolutional code with 4 coding rates: 1/2, 3/4, 5/6, and 7/8

– Outer code: RS code


DVB-T/H network layout

• 4 kinds of frequency networks can be deployed

– Large area SFN (Single Frequency Network) :

• Many high power repeaters with large transmitter space large delays large guard time required

Challenging transmitter synchronization

– Regional SFN:

• Few high power repeaters with large transmitter space Large delays large guard time required

Simpler transmitter synchronization

– MFN (Multi Frequency Network) with dense SFN around each MFN

transmitter:

• Medium power SFM transmitter with medium transmitter spacing

– SFN gap fillers

• Low power SFN transmitter with small spacing to fill gaps in coverage Small delays small guard time required


DVB-T/H: functional block diagram


DVB-T/H: MPEG-2

MPEG-2 transport multiplex packet:188 byte: 1 synch word + payload

MPEG-2 transport multiplex packet:188 byte: 1 synch word + payload

Sync1 byte

MPEG-2 transport MUX data 187 bytes


DVB-T/H: RS outer coding

RS (204, 188, t=8)RS (204, 188, t=8)


DVB-T/H: outer interleaving

Convolutional interleaving (Forney approach)

INTERLEAVING DEPTH = 12 BYTES


DVB-T/H: inner convolutional coding

Convolutional codes: •Mother code rate 1/2, 64 states

•G1= 171oct, G2=133oct

•Punctured codes at rates•2/3•3/4•5/6•7/8

•This is the same code used by DVB-S

Convolutional codes: •Mother code rate 1/2, 64 states

•G1= 171oct, G2=133oct

•Punctured codes at rates•2/3•3/4•5/6•7/8

•This is the same code used by DVB-S


Mobile TV: the DVB-T/H technology

3 Mbps

MPEG-2 over

DVB-T 24 Mbps

IP over

DVB-H 5 to 10 Mbps

128-400

kbps

50-80 video streams for small screen4-6 TV programs for large

screen

Source Nokia 2003

> Mobile terrestrial broadcast (DVB-H) is an “add-on” to the standard terrestrial broadcast (DVB-T)

• Reuse of high power DVB-T transmitter + deployment of dedicated on-channel and frequency conversion repeaters

• Additional FEC protection and introduction of Time Division Multiplexing• New service delivery “IP based” for flexible aggregation of services• Trials in Helsinki (Q3/04), Berlin (Q4/04), commercial limited opening in 2006

(Finland)• Operation scenario 1, 2 or 3


Mobile Broadcasting will happen• Mobile broadcasting is becoming a fact in different parts of the world

using terrestrial or satellite infrastructure– Satellite: MBSAT for Japan and Korea (just launched), US with XM Radio – Terrestrial: T-DAB and DVB-T deployed/selected in significant parts of the world with

mobility as target for home and vehicular usage(?). DVB-H/T-DMB initiative are natural complement for handsets.

– 3G Cellular: Reserved for unicast, potentially multicast with limited throughput but no real broadcast services could be offered

• Broadcast services on Handset will be a mix of Live TV and on demand video

– Open service platform is key in the success of those services, with a seamless delivery between broadcast and unicast/multicast services

• Mobile Operators have to assess cooperation/competition issues between broadcast technologies and mobile network

– Clear role distribution between Broadcaster and Mobile operators is key in the success of Mobile broadcast services


The convergence challenge• Mobile operator and content editors/Broadcaster to find

agreement on a long list of issues– Resources sharing

– Access to customer

– billing policy

– Sharing revenues

– Subsidizing of bi-mode terminal

– Portal content policy

– Service exclusivity

– Mobile right issues

– Infrastructure deployment and O&M, ...

• Political/regulatory issues to shape the agreement framework

• Several Mode of Operation can be envisaged


The SDMB architecture: a satellite overlay network for 3G

and beyond 3G network

3G Mobile Network

3G Basestation

Content provide

rs

Hub basedon 3G

equipment

ContentNetwork

High powerGeo-stationary

satellite

3G handset

Interactive link in IMT2000 mobile terrestrial band

MBMS Broadcast/Multicast

Service Centre

Example of umbrella cells coverageover Europe

Satellite distribution link in IMT2000 mobile

satellite band3G Air interface


2G/3G HANDSET with extended

frequency agility in Satellite IMT2000

band

512 Mbytes Memory card

with integrated DRM

Terrestrial repeaters integrated in 3G base stations for dense urban area coverage

STORE

REPLAY

PUSH

SELECT

S-DMB: key design principles

Satellite IMT2000 FDD European allocationTerrestrial IMT2000 FDD European allocationTerrestrial IMT2000 TDD European allocation

1900 1980 2010 21702200 MHz1920 21102025

• Hybrid satellite/terrestrial architecture: Global coverage for Outdoor & Indoor usage• Low cost impact on 3G handheld terminal

– Satellite frequencies are adjacent to IMT2000 terrestrial ones– Satellite waveform compliant to 3GPP UTRA FDD WCDMA standard– High reception margin, hence no form factor impact

• Concurrent evolution with 3GPP architecture

Return link: PPDR, safety


High power GEO satellite to

accommodate 3G handheld terminal RF characteristics

• Satellite & Payload characteristics– 15 years Lifetime– Launch mass: up to 5900 Kg– P/L DC power consumption: 12 kW– Up to 6 beams per satellite– EIRP (EOC): up to 76 dBW/beam over 1°

IMT2000 Satellite bandTX/RX Antenna

Ø 12 m

Ka bandTX AntennaØ < 1.5 m

Ka bandRX AntennaØ < 1.2 m

Mirror or subreflectorExample of 1° Beams

• Satellite flexibility– Coverage (beam selection and

beam size)– Power sharing among active

beams– Transparent architecture towards

3GPP air interface (e.g. W-CDMA & Beyond 3G waveform)


Terrestrial repeater

Rx antenna dish 20-30 cm

Ka band

RF filter

Power Amplifier

* RF cable to Node B antenna(Signal is 3GPP TS 25.106 compliantin IMT2000 satellite band)

Low Noise Block

CellularMode

m

Frequency conversion

terrestrial repeaterBlock architecture

O&M controlle

r

Rx Antenna

Tx antenna

Tx antenna

Repeater

On the rooftop

Typical installation in tri-sectorised site

Site sharing with2G/3G base station site* cost effective* environment friendly:

- Antenna sharing with NodeB possible.- RF power ~ 10 W


S-DMB enabling features in 3G user equipment

• 3GPP & OMA features– HW: Local memory storage

– SW• MBMS (including Power saving management)• Streaming service and related codecs• Digital Right Management• Mobile broadcast services (service discovery, service

protection, electronic service guide, etc...)

• SDMB specific– HW: Radio frequency agility extension to IMT2000 satellite

band

– SW• Reliable transport protocol (File FEC, Interleaving, Carrousel)• Dual operation mode: SDMB reception while attached to UMTS

or GSM network• SDMB Service management

1900 1980 2010 21702200 MHz1920 21102025


Conclusion

• S-DMB is designed as an open infrastructure providing efficient content delivery services to 3G mobile operators, to meet the Mobile Video challenge

• Viable positioning compared to DVB-H in the following situations:– Coverage at low cost focusing on Mobile video business model rather than TV– Regulations or competitive environment blocking the Broadcasters/Mobile

operators co-operation

– Technological competition between DVB-H and UMTS

• MAESTRO is the cornerstone to demonstrate the SDMB value proposition toward mobile industry

• Need to implement appropriate regulatory framework for 3G satellite systems in Europe

• Paving the way for appropriate regulation in other part of the world

spring2005 © university of surrey satcomms b - general - b g evans 1 satellite communications b...

Documents

b g evans

scmb slide

qos slide

diversity slide

dmb slide

world slide

professor barry g evans

system model slide