EEM.scmB
Satellite Communications B
Spring Semester 2004-5
-Satellite Broadcasting-Professor Barry G Evans-
Spring2005 © University of Surrey
SatComms B - General - B G Evans
1
Contents
1. Analogue TV Satellite Broadcasting
2. Digital Satellite Broadcasting (MPEG/DVB-S)
3. New DVB-S2 standard and IP Delivery
4. DMB
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1. Analogue Satellite
Broadcasting
•
•
•
•
F.M. Theory –S/NW versus C/N
DTH/Cable head systems
WARC Broadcasting Plan
MAC Systems
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System model
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FDM/FM techniques
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FM Transmission Formats
• NB. FDM/FM being replaced . Digital IDR
TDM/PSK/FDMA
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Characteristics of Frequency
Modulation (FM)
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FM Threshold Effect
TRADE OFF BETWEEN POWER AND BANDWIDTH
F.M.EQN:
S
C 1 3 2

mo
N NO fm 2
where
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mo 
f
fm
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FM Theory
Signal  kf 2
• General
Noise 
fU
N
o
f 2 df
fL
fU
 f3
  
 3  fL
S
3f 
C
  3
N  f U  f L3  N o
2
or
S
3Bf  C
 3
N
f U  f L3 N o
2


note f is the rms deviation.
fm peak deviation fPK
S 3Br f PK  C

N
 fU3  f L3  N o
2
r = pk-rms ration
note that then S is the signal pk
Spring2005 © University of Surrey
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Quality objectives for television
(CCIR Rec. 567-1 & 568)
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ITU-R Subjective Quality Service
• Picture Quality
5 (excellent)
4 (good)
3 (fair)
2 (poor)
1 (bad)
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Weighted S/N(dB)
46.6 99.9% ITU-R
42.3
VIDEO REC. QoS
38.0
33.6
29.3
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Base band signals television
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FM Theory
• Television
BASEBAND SIGNAL (FDM) = 6MHZ
SIGNAL – 1V pk-pk Test signal
F.M. EQUATION,
S
C 3B f 

N
N  f U3  f L3 
2
For T.V. fL << fU
fL=0, fU=fm
f = Fr (rms deviation of signal)
S
C 3BFr


N
N f m3
2
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
 FPP  0.7FTT 
2
2
S
C 3B FTT


*
*
N
N 2
f m3
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FTT2

2
2
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Analogue transmission techniques
-SCPC/FM transmission of television-
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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.
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Communication techniques
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FM Theory
• Television
15 KHz TEST-TONE APROACH
For A 1v pk-pk Test Signal with fixed pattern Alternate BlackWhite lines, which is convenient
Test Signal – equivalent deviation 15KHz sinusoid T.T. FTPP
S 3B C FTPP
WP 
 
N
2 N f m3
2
(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 calculated
Is a top baseband of fm=5MHz. Then :
625 Line (WP) = 13.2 dB.
525 Line (WP) = 14.8 dB
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Video Weighting Factor
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.
Frequency characteristics of weighting networks for measuring continuous random noise
* Improvement by emphasis + weighting factor. (P+O)
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TV via Satellite
• Example
ASTRA – DTH.
INTELSAT : 625/50 Hz
FTPP = 15 MHz. fm’= 6MHz
fm = 5MHz
S
3  FTPP


N
2
fm





2
1
fm
 pw
S
N
C
N0
2
3  15   1 
C


   .( pw).
2  5  5
N0
C
 42.5dB 
N0
2
3  13.5   1 
C
 
   .( pw).
2  5  5
N0
C
 43.4 
N0
DTM. S/N=42.3, C/No = 89.8 dB-H
Bw = 13.5 + 2x6 = 25.5 MHz
C/N  15 dB
Allows Rain fade to threshold
Aim for Fixed Link. S/N=45 dB.
C/No=87.5 dB-MHz
BW = 15 + 2x6 = 27 MHz
Also ½ TPDR. TV. 15.75 MHz BW. 2 x TV in 36MHz
S/N = 29.5 + C/N = 45
C/N = 15.5 dB
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Satellite TV – Over Deviation
• Use BW narrower than Carson without excessive distortion
BC  2ΔFP  fm 
625/50 TV  FM occupy BW  18MHz
18
ΔFP 
 6  3MHz
2
INTELSAT actually use PK devn  10.5MHz  Carson
Called ' over deviation'
 20log actual
 20log 10.5  10.9dB
Carson
3




• 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
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Data sub-carrier
2


C 
C 



f
sc


  
  10 log 1 
 
 2  f sc  
 N 0  dsc  N 0  mc


 Eb 
C 
2

  
 
 N 0  data  N 0  dsc Rb
S
 
 N  mc
2
f p  p  1  C 
2


 Q
 3r 
 f m  f m  N 0  mc
r  ratio pk - pk amp. of monochrome video to nominal amp. luminance
f p  p  pk - pk deviation produced by sinusoidal signal at 15kHz
f m  top baseband of video (5 MHz)
Q  pre emphasis  weighting advantage (13.2 dB)
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TVRO Satellite TV
Transponder = +52 dBW
Dish size TVRO = 60 cm
LNB = 1.5 dB noise fig (120K)
Transmit eirp
Pointing loss
Clear sky abs. Loss
F.S.L (14.5 GHz)
Satellite G/T (Land)
K
+80 dBW
0.2 dB
0.5 dB
207.3 dB
+7 dB/K
-228.6 dBW/Hz/K
UPLINK:
C/N0
DOWNLINK
:
107.6 dB-Hz
Transponder eirp (saturation)
F.S.L (12 GHz)
Clear Sky absorption (12 GHz)
TVRO ptg.loss
TVRO G/T (elev. Sky)
K
C/N0D
52 dBW
205.5 dB
0.4 dB
0.3 dB
12 dB/K
-228.6 dBW/Hz/K
86.4 dB-Hz
OVERALL
C / (N0D+N0U)
C / N(in 26 MHz)
C / I(adj. Satellites + X path)
86.4 dB-Hz
12.2 dB
28.0 dB
C / (NTH + Nint)
12.1 dB
Deviation (FTPP)
W+P
16 MHz
13.2 dB
S/N
44.2 dB
NB 2 dB better than CCIR-4 (Good)
At C/N THRESHOLD = 0 dB gives 3.1 dB margin for propagation
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Link Performance -Exercise
SATELLITE
eirp=+40dBW
TV
FREE SPACE LOSS –250.6DB
Diameter?  =65%
T=22.3dB-K
–
–
–
–
–
–
–
–
–
–
•
RX
DMD
S/N=42.3dB
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.
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TV TRANSMISSION
ASTRA
eirp = +52dBW
11.5GHz
14.5G
Hz
C/I=28dB
G/T=+7dB/k
205.5dB
207.3dB
eirp
+80dBW
 =0.6
TELEPORT
• ATV link to TVRO from Astra
TVRO
LNB
1.5dB noise Fig.
– 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.
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Model of a Broadcasting
Satellite System
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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
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BSS Planning in Europe (1/3)
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BSS Planning in Europe (2/3)
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BSS Planning in Europe (3/3)
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ITU Region 1 Ku Band
Frequency Plan
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The MAC/Packet innovation
Time division multiplex components
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MAC format options
B-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
TIME
COMPRESSION
Luminance
TIME
COMPRESSION
Sound+data
TIME
COMPRESSION
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TDM
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MOD
RF
MOD
33
MAC format options C-MAC
• Time Division Multiplex (TDM) at
radiofrequency of time compressed TV signal
analogue components and digital
components (sound/data)
Chrominance
TIME
COMPRESSION
TDM
Luminance
Sound+data
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TIME
COMPRESSION
TIME
COMPRESSION
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MOD
RF
TDM
MOD
34
2. Digital Broadcasting
• MPEG Compression Techniques
• MPEG Packets
• DVB-S Transmission
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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
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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 2736MHz bandwidth, cost roughly £2-3m/year, and
can carry 30-40Mbit/s OR one FM TV channel.
• Transponder cost/channel is much lower for MPEG2 compression than FM-TV.
• Digital format allows many more applications.
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Elements of a digital satellite
broadcasting system
STUDIO
Camera
MPEG-2
Encoder
Tape
Multiplexer
Modulator
Film
File server
Contribution
MPEG-2
Encoder
Electronic Programme
Guide (EPG)
Subscriber
Management System
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Conditional Access
System
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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)
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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.
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Temporal redundancy
Predicted frames
Intraframes
• Use motion estimation to predict the next frame.
• Use DCT to encode the difference between predicted
and actual.
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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.
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Spatial redundancy
176
176
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176
171
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171
171
185
185
185
185
185
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185
185
203
203
203
203
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203
206
206
206
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203
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203
203
203
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193
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Pixel values for
a block taken from
a typical picture
Increasing horizontal frequency
Increasing
vertical
frequency
Values after
DCT processing
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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
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Spatial redundancy
DCT values after quantisation and scaling:
Increasing horizontal frequency
Increasing
vertical
frequency
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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
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Spatial redundancy
• Conversion to serial data by zig-zag scanning:
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
• Run length coding removes long strings of zeros.
• Variable length coding replaces common values
with shorter symbols (c.f. Morse code).
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Control of quantisation
Quantisation threshold
From DCT
process
Quantisation of
DCT coefficients
Data rate
control
Variable
length coding
Buffer
occupancy
Buffer
store
Variable rate
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Fixed rate
46
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.
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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.
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MPEG system layer
Elementary
Programme
streams
streams
Video encoder
Transport
stream
Audio encoder
Data encoder
Other programmes
Other data
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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.
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Channel adaptation
Channel Adaptation: the processes involved in taking a
Transport Stream and converting it to a form suitable for
transmission on the satellite.
Transport
stream
Energy
dispersal
Outer FEC
encoder
Inner FEC
encoder
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Interleaver
Baseband
shaping
SatComms B - General - B G Evans
QPSK
Modulation
To RF channel
51
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.
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Outer FEC encoding
• Reed-Solomon (204,188) encoding adds 16 bytes to each
MPEG packet.
204 bytes
204 bytes
188 bytes
188 bytes
16 bytes RS
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16 bytes RS
53
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.
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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.
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Modem performance
DVB specifies modem performance in IF loop to achieve quasi
error-free performance:
Inner code rate
1/2
2/3
3/4
5/6
7/8
Eb/No (dB)
4.5
5.0
5.5
6.0
6.4
Note: Eb/N0 = 10log(C/N0) - 10log(bit rate). The bit
rate referred to in this table is the useful bit rate before
RS encoding.
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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.
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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!
Q
Q
0
1,0
I
I
1
1,1
BPSK constellation
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0,0
0,1
QPSK constellation
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58
Baseband shaping
Amplitude
Slow roll-off
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Nyquist
bandwidth
Medium roll-off
SatComms B - General - B G Evans
Fast roll-off
59
Modulation performance
Typical receiver performance in a linear channel:
Note: in this case
the bit rate used
to calculate Eb/N0
from C/N0 is the
channel rate.
Measured
Theoretical
Spring2005 © University of Surrey
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60
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.
Spring2005 © University of Surrey
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61
Effect of TWTA on spectrum
Spectrum of
11Mbits/s
(gross rate)
QPSK signal
after passing
through a
wideband
TWTA at
saturation.
Spring2005 © University of Surrey
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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.
Spring2005 © University of Surrey
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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.
46.8Mbits/s
From
demodulator
35.1Mbits/s
Convolutional
decoding (3/4)
(Inner code)
Spring2005 © University of Surrey
32.3Mbits/s
RS (204,188)
decoding
MPEG stream to
decoder
(Outer code)
SatComms B - General - B G Evans
64
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.
FM
Picture
Quality
Digital
FM threshold
Digital threshold
C/N
Spring2005 © University of Surrey
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Picture impairments
• Impairments are different from PAL (eg crosscolour).
• 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.
Spring2005 © University of Surrey
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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
Spring2005 © University of Surrey
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Links to IP delivery
over 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-SRCS.
• These topics will be covered in an associated
lecture (Dr Haitham Cruickshank)
Spring2005 © University of Surrey
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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
Spring2005 © University of Surrey
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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 0.54.5 bits/unit bandwidth
– C/N from –216dB
• Backward compatibility with DVB-S
• Opens up range of new services and reduced
costs
Spring2005 © University of Surrey
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70
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
Spring2005 © University of Surrey
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Modulation schemes DVB-S2
Q
I=MSB
Q
Q=LSB
100
110
10
000
00


I

010
I
001
11
011
01
101
111
Q
Q
1010
1000
LSB
R1
1100
11001
00101
R3
MSB
0000
R2
1110
01001
01100
0010
0110
01101
11101
11100
0100
11110
00000
00100
10100
00001
01000
R2
10101
R1
10000
10001
11000
I
text
0111
1111
I
text
1101
10110
0101
10111
10010
10011
01110
00010
00110
0011
11010
0001
00111
11111
1011
1001
01111
00011
01011
01010
11011
The four possible DVB-S2 constellations before physical layer scrambling
Spring2005 © University of Surrey
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Modulation schemes DVB-S2
• QPSK/8 APSK broadcast applications
• 16/32 APSK professional applications
requiring higher C/N
– Need pre-distortion in uplink to overcome nonlinear.
– Schemes better in non-linear channel cf. 16/32
QAM
• Roll-off factors - =0.35, 0.25, 0.2
Spring2005 © University of Surrey
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Modulation schemes DVB-S2
Single Input Stream
DATA
ACM
COMMAND
1/4, 1/3, 2/5,
1/2, 3/5, 2/3,
3/4, 4/5, 5/6,
8/9, 9/10
BB
Signalling
Input interface &
adaptation tools
#1
Merger
Slicer
Input
interface &
CRC-8
adaptation
Encodertools
#n
Multiple Input Streams
STREAM
ADAPTER
BCH outer
LDPC inner
PL Signalling
Pilot symbols
QPSK,
8PSK,
16APSK,
32APSK
constellations
MODE & STREAM
FEC ENCODING MAPPING
ADAPTATION
BBFRAME
LP stream for
BC modes
SCRAM
BLER
=0,35,
0,25,
0,20
BB Filter
&
Quadrature
Modulation
Dummy
FRAME
PL FRAMING
MODULATION
PLFRAME
to
the RF
satellite
channel
Functional block diagram of the DVB-S2 system
Spring2005 © University of Surrey
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Modulation schemes DVB-S2
• 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
Spring2005 © University of Surrey
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Framing Structure:
the system train
FEC
redundancy
Useful
data
Type of channel
coding and modulation
adopted in the wagon
PL FRAME
H
FEC FRAME
8PSK 5/6
H
FEC FRAME
QPSK 2/3
H
FEC FRAME
16APSK 3/4
Pictorial representation of the physical layer framing structure
Spring2005 © University of Surrey
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Framing Structure:
the system train
• 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
Spring2005 © University of Surrey
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Framing Structure:
the system train
• 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)
Spring2005 © University of Surrey
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DVB-S2 Performance
Spectrum efficiency versus required C/N on AWGN channel
4,5
32APSK
Ru [bit/s] per unit Symbol Rate
4,0
Dotted lines= modulation constrained Shannon limit
16APSK
3,5
3,0
2,5
8PSK
DVB-DSNG
2,0
QPSK
1,5
DVB-S
1,0
0,5
0,0
-3
•
•
•
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
C/N [dB] in Rs
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
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DVB-S2 Range of C and M
1/3
1/4
2/5
2/3
3/5
1/2
8/9
3/4 4/5 5/6 9/10
4,5
4,0
32APSK
3,5
3,0
16APSK
RU
2,5
2,0
8PSK
1,5
QPSK
1,0
0,5
0,0
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
LDPC code rate
Examples of useful bit rates Ru versus LDPC code rate per unit symbol rate
Rs
Spring2005 © University of Surrey
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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 7 MPEG-2
10 MPEG-2
10 MPEG-2
13 MPEG-2
programmes
15 AVC
21 AVC
20 AVC
26 AVC
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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
Spring2005 © University of Surrey
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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.
Spring2005 © University of Surrey
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Using ACM for IP Unicast (2)
Example of IP services using a DVB-S2 ACM link
Spring2005 © University of Surrey
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Using ACM for IP Unicast (3)
• 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.
Spring2005 © University of Surrey
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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
Spring2005 © University of Surrey
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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).
Spring2005 © University of Surrey
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DMB: convergence
of different worlds
BROADCASTING
Web-access
Driven
DMB
Gaming
Driven
PC WORLD
INTERNET
Live TV
Driven
Tecnhology
Driven
MOBILE TELECOMs
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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
Spring2005 © University of Surrey
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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.
Spring2005 © University of Surrey
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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)
…
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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)
…
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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
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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
Spring2005 © University of Surrey
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DARS systems: Sirius
•
Sirius (CONUS)
–
–
–
–
–
–
Started 2002
120 Thematic radio
channels, FM+ quality
$12.25/month subscription
400K users end of June
2004
Member of ASMS-TF
Remote
Constellation:
•
•
–
3 HEO sat
Terrestrial
repeaters (~ 90)
•
•
TDM
Ground
Repeaters
TDM
OFDM
TDM
Uplink Site
Mobile
Receiver
OFDM TDM
12.5 MHz
National
Broadcast
Studio
Air interface:
•
•
VSAT
Satellite
SIRIUS
Satellite
Direct link: QPSK TDM
Terrestrial repeater link:
QPSK COFDM
Coding: RS+Conv
Sat diversity
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MBSAT
•
MBSAT (Japan and Korea)
–
–
–
–
–
–
–
–
–
•
System Cost ~800 M$
–
•
•
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
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
Spring2005 © University of Surrey
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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
Spring2005 © University of Surrey
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DVB-H System overview (1)
•
Objectives
–
•
Constraints
–
–
•
Broadcast transmission to mobile handheld terminals of datagrams (IP or other datagrams)
pertaining to multimedia services, file downloading services, etc
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
Spring2005 © University of Surrey
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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
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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
Spring2005 © University of Surrey
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DVB-T/H: functional block
diagram
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DVB-T/H: MPEG-2
MPEG-2 transport multiplex packet:
188 byte: 1 synch word + payload
Sync
1 byte
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MPEG-2 transport MUX data 187 bytes
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DVB-T/H: RS outer coding
RS (204, 188, t=8)
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DVB-T/H: outer interleaving
Convolutional interleaving (Forney approach)
INTERLEAVING DEPTH = 12 BYTES
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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
Spring2005 © University of Surrey
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Mobile TV: the DVB-T/H technology
MPEG-2 over DVBIP over DVB-H
T
24 Mbps
5 to 10 Mbps
Source
Nokia
2003
128-400
3 Mbps
4-6 TV programs for large screen
>
kbps
50-80 video streams for small screen
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
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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
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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
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The SDMB architecture: a
satellite overlay network for 3G
and beyond 3G network
High power
Geo-stationary
satellite
3G handset
Example of umbrella
cells coverage
over Europe
Satellite distribution link
in IMT2000 mobile satellite
band
3G Air
interface
Interactive link in IMT2000
mobile terrestrial band
Hub based
on 3G equipment
Content
providers
3G Mobile Network
3G Base
station
Spring2005 © University of Surrey
Content
Network
MBMS Broadcast/Multicast
Service Centre
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S-DMB: key design principles
•
•
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
1900 1920
1980 2010 2025
Return link: PPDR, safety
2110
2170 2200 MHz
Satellite IMT2000 FDD European allocation
Terrestrial IMT2000 FDD European allocation
Terrestrial IMT2000 TDD European allocation
PUSH
SELEC
T
2G/3G HANDSET with
extended frequency agility
in Satellite IMT2000 band
Spring2005 © University of Surrey
STORE
REPLA
Y
SatComms B - General - B G Evans
Terrestrial
repeaters
integrated in 3G
base stations for
dense urban area
coverage
512 Mbytes
Memory card
with integrated DRM
110
High power GEO satellite to
accommodate 3G handheld terminal RF
characteristics
Ka band
RX Antenna
Ø < 1.2 m
Ka band
TX Antenna
Ø < 1.5 m
IMT2000 Satellite band
TX/RX Antenna
Ø  12 m
Mirror or subreflector
Example of 1° Beams
• Satellite & Payload characteristics • Satellite flexibility
–
–
–
–
–
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°
Spring2005 © University of Surrey
– Coverage (beam selection and
beam size)
– Power sharing among active
beams
– Transparent architecture towards
3GPP air interface (e.g. W-CDMA
& Beyond 3G waveform)
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111
Terrestrial repeater
Low
Noise
Block
RF
filter
O&M
controller
Rx antenna dish
 20-30 cm
Ka band
Power
Amplifier
* RF cable to Node B antenna
(Signal is 3GPP TS 25.106 compliant
in IMT2000 satellite band)
Cellular
Modem
Rx Antenna
Frequency conversion
terrestrial repeater
Block architecture
Site sharing with
2G/3G base station site
* cost effective
* environment friendly:
Tx antenna
Repeater
Tx antenna
On the rooftop
- Antenna sharing with
NodeB possible.
- RF power ~ 10 W
Typical installation in tri-sectorised site
Spring2005 © University of Surrey
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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
1900 1920
1980 2010 2025
2110
2170 2200 MHz
• Reliable transport protocol (File FEC, Interleaving, Carrousel)
• Dual operation mode: SDMB reception while attached to UMTS
or GSM network
• SDMB Service management
Spring2005 © University of Surrey
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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
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