spring2005 © university of surrey satcomms b - general - b g evans 1 satellite communications b...
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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
Spring2005 © University of Surrey SatComms B - General - B G Evans 2
Contents
1. Analogue TV Satellite Broadcasting
2. Digital Satellite Broadcasting (MPEG/DVB-S)
3. New DVB-S2 standard and IP Delivery
4. DMB
Spring2005 © University of Surrey SatComms B - General - B G Evans 3
1. Analogue Satellite Broadcasting
• F.M. Theory –S/NW versus C/N
• DTH/Cable head systems
• WARC Broadcasting Plan
• MAC Systems
Spring2005 © University of Surrey SatComms B - General - B G Evans 4
System model
Spring2005 © University of Surrey SatComms B - General - B G Evans 5
FDM/FM techniques
Spring2005 © University of Surrey SatComms B - General - B G Evans 6
FM Transmission Formats
• NB. FDM/FM being replaced . Digital IDR TDM/PSK/FDMA
Spring2005 © University of Surrey SatComms B - General - B G Evans 7
Characteristics of Frequency
Modulation (FM)
Spring2005 © University of Surrey SatComms B - General - B G Evans 8
FM Threshold Effect
2
2
31o
mO
mfN
C
N
S
mo f
fm
where
TRADE OFF BETWEEN POWER AND BANDWIDTH
F.M.EQN:
Spring2005 © University of Surrey SatComms B - General - B G Evans 9
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 10
Quality objectives for television
(CCIR Rec. 567-1 & 568)
Spring2005 © University of Surrey SatComms B - General - B G Evans 11
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 12
Base band signals television
Spring2005 © University of Surrey SatComms B - General - B G Evans 13
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 14
Analogue transmission techniques-SCPC/FM transmission of television-
Spring2005 © University of Surrey SatComms B - General - B G Evans 15
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 16
Communication techniques
Spring2005 © University of Surrey SatComms B - General - B G Evans 17
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 18
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 19
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 20
• 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
Spring2005 © University of Surrey SatComms B - General - B G Evans 21
Spring2005 © University of Surrey SatComms B - General - B G Evans 22
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 23
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 24
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 25
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 26
Model of a BroadcastingSatellite System
Spring2005 © University of Surrey SatComms B - General - B G Evans 27
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 28
BSS Planning in Europe (1/3)
Spring2005 © University of Surrey SatComms B - General - B G Evans 29
BSS Planning in Europe (2/3)
Spring2005 © University of Surrey SatComms B - General - B G Evans 30
BSS Planning in Europe (3/3)
Spring2005 © University of Surrey SatComms B - General - B G Evans 31
ITU Region 1 Ku BandFrequency Plan
Spring2005 © University of Surrey SatComms B - General - B G Evans 32
The MAC/Packet innovation
Time division multiplex components
Spring2005 © University of Surrey SatComms B - General - B G Evans 33
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 34
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 35
2. Digital Broadcasting
• MPEG Compression Techniques
• MPEG Packets
• DVB-S Transmission
Spring2005 © University of Surrey SatComms B - General - B G Evans 36
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 37
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 38
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 39
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)
Spring2005 © University of Surrey SatComms B - General - B G Evans 40
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 41
Temporal redundancy
• Use motion estimation to predict the next frame.• Use DCT to encode the difference between predicted
and actual.
Intraframes
Predicted frames
Spring2005 © University of Surrey SatComms B - General - B G Evans 42
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 43
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 44
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 45
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 46
Control of quantisation
Bufferoccupancy
Quantisation threshold
Fixed rateVariable rate
From DCTprocess
Data ratecontrol
Quantisation of DCT coefficients
Variable length coding
Buffer store
Spring2005 © University of Surrey SatComms B - General - B G Evans 47
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 48
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 49
MPEG system layer
Video encoder
Audio encoder
Data encoder
Other programmes
Other data
Elementarystreams Programme
streams
Transportstream
Spring2005 © University of Surrey SatComms B - General - B G Evans 50
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 51
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 52
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 53
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 54
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 55
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 56
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 57
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 58
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 59
Baseband shaping
Amplitude Nyquist bandwidth
Slow roll-off Medium roll-off Fast roll-off
Spring2005 © University of Surrey SatComms B - General - B G Evans 60
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 61
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 SatComms B - General - B G Evans 62
Effect of TWTA on spectrum
Spectrum of 11Mbits/s (gross rate) QPSK signal after passingthrough a wideband TWTA at saturation.
Spring2005 © University of Surrey SatComms B - General - B G Evans 63
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 SatComms B - General - B G Evans 64
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 65
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 66
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.
Spring2005 © University of Surrey SatComms B - General - B G Evans 67
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 SatComms B - General - B G Evans 68
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)
Spring2005 © University of Surrey SatComms B - General - B G Evans 69
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 SatComms B - General - B G Evans 70
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 71
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 SatComms B - General - B G Evans 72
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 73
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 non-
linear.– Schemes better in non-linear channel cf. 16/32
QAM
• Roll-off factors - =0.35, 0.25, 0.2
Spring2005 © University of Surrey SatComms B - General - B G Evans 74
Modulation schemes DVB-S2
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 75
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 SatComms B - General - B G Evans 76
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 77
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 SatComms B - General - B G Evans 78
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 SatComms B - General - B G Evans 79
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 80
DVB-S2 Range of C and M
Examples of useful bit rates Ru versus LDPC code rate per unit symbol rate Rs
Spring2005 © University of Surrey SatComms B - General - B G Evans 81
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 82
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 SatComms B - General - B G Evans 83
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 84
Using ACM for IP Unicast (2)
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 85
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 SatComms B - General - B G Evans 86
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 SatComms B - General - B G Evans 87
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 SatComms B - General - B G Evans 88
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 89
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 SatComms B - General - B G Evans 90
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 SatComms B - General - B G Evans 91
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)
– …
Spring2005 © University of Surrey SatComms B - General - B G Evans 92
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)
– …
Spring2005 © University of Surrey SatComms B - General - B G Evans 93
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 94
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 SatComms B - General - B G Evans 95
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 96
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 97
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 SatComms B - General - B G Evans 98
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 99
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 100
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 SatComms B - General - B G Evans 101
DVB-T/H: functional block diagram
Spring2005 © University of Surrey SatComms B - General - B G Evans 102
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 103
DVB-T/H: RS outer coding
RS (204, 188, t=8)RS (204, 188, t=8)
Spring2005 © University of Surrey SatComms B - General - B G Evans 104
DVB-T/H: outer interleaving
Convolutional interleaving (Forney approach)
INTERLEAVING DEPTH = 12 BYTES
Spring2005 © University of Surrey SatComms B - General - B G Evans 105
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 106
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 107
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 108
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 109
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 110
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 111
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)
Spring2005 © University of Surrey SatComms B - General - B G Evans 112
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 113
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
Spring2005 © University of Surrey SatComms B - General - B G Evans 114
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