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21-Jun-04Hierarchical Modulation 1 assured communications ™
Hierarchical Modulation for DVB-T
Implementation & ApplicationBernhard Baumgartner
Senior Product Manager
21-Jun-04Hierarchical Modulation 2 assured communications ™
Hierarchical Modulation for DVB-T
• Hierarchical Modulation is nothing new ……it is part of the DVB-T standard 300 744 for several years.
• But– The receiver industry did not always consider it exactly. – Planners seldom check if hierarchical modulation adds
additional value to their DVB-T network application
Target of this presentation is to …explain the theory of hierarchical modulation for DVB …and to provide examples for possible implementations
21-Jun-04Hierarchical Modulation 3 assured communications ™
What is hierarchical Modulation ?
• Hierarchical Modulation allows to transmit two digital data streams via one transmitter
– the LP Stream (Low Priority)• higher bit rate• sensitive (higher C/N needed)
– the HP Stream (High Priority)• lower bit rate• Very robust (less C/N needed)
21-Jun-04Hierarchical Modulation 5 assured communications ™
I
Q
I
Q
I
Q
QPSK 16-QAM 64-QAM
00
0110
110000
1100 0110
1000
QPSK: 4 carrier positions
A QPSK carrier can transport 2 bits
16-QAM: 16 carrier positions
A 16-QAM carrier can transport 4 bits
64-QAM: 64 carrier positions
A 64-QAM carrier can transport 6 bits
Sub Carrier Modulationnon-hierarchical modes
21-Jun-04Hierarchical Modulation 7 assured communications ™
I
Q
Hierarchical ModulationQPSK in 16-QAM
I
QI
Q
High priority bit stream (HP)defines actual quadrant
Low priority bit stream (LP)defines position in actual quadrant
21-Jun-04Hierarchical Modulation 8 assured communications ™
Hierarchical ModulationQPSK in 64-QAM
High priority bit stream (HP)defines actual quadrant
Low priority bit stream (LP)defines position in actual quadrant
I
Q
I
Q
Q
I
21-Jun-04Hierarchical Modulation 10 assured communications ™
αααα- Factor, C/NQPSK in uniform 16-QAM
1
1
1
1 33
3
3
I
Q
αααα = 1:
LP: QPSK, CR 2/3, ���� Req. C/N ~ 11.1 dB���� ~ 7.5 Mbps
HP: QPSK, CR 2/3, ���� Req. C/N ~8.2 dB���� ~ 7.5 Mbps
Required C/N values are for QEF reception after RS decoder !
21-Jun-04Hierarchical Modulation 12 assured communications ™
αααα- Factor, C/NQPSK in non-uniform 16-QAM
Q6
4
6
6 64
4
4
I
αααα = 4:
LP: QPSK, CR 2/3, ���� Req. C/N ~ 19.1 dB���� ~ 7.5 Mbps
HP: QPSK, CR 2/3, ���� Req. C/N ~5.9dB���� ~ 7.5 Mbps
Required C/N values are for QEF reception after RS decoder !
21-Jun-04Hierarchical Modulation 15 assured communications ™
Distance in km
Fie
ld s
tren
gth 64 QAM
Code rate 7/8~ 30 Mbit /s
16 QAM Code rate 3/4
~ 15 Mbit/s
QPSK Code rate 1/2
~ 5 Mbit/s
The area covered by a DVB-T transmitter is strongly depending on the selected parameters for the COFDM signal
Coverrage Area of DVB-T
Transmitters
noise floor
C/N
C/N
C/N
21-Jun-04Hierarchical Modulation 16 assured communications ™
Possible applications for hierarchical modulation
• transmit services to portable and fixed receivers at the same time
• increase net bit rate of the broadcast channel
• transmit services to stationary and mobile receivers at the same time
• transmit HDTV and SDTV at the same time with different coverage areas
21-Jun-04Hierarchical Modulation 17 assured communications ™
Stationary vs Portable receivers
Non-Hierarchical
Non-hierarchical:64 QAM, GI 1/8, FEC 2/3Bit rate: 22.12 MbpsC/N (Gaussian): 16.5 dB
HP
HP:QPSK, GI 1/8, FEC 1/2Bit rate: 5.53 MbpsC/N (Gaussian): 8.9 dB
LP
LP:16-QAM, GI 1/8, FEC 2/3Bit rate: 14.75 MbpsC/N (Gaussian): 16.9 dB
21-Jun-04Hierarchical Modulation 18 assured communications ™
Increased useful bit rate
Non-Hierarchical
Non-hierarchical:64 QAM, GI 1/8, FEC 2/3Bit rate: 22.12 MbpsC/N (Gaussian): 16.5 dB
HP:QPSK, GI 1/8, FEC 3/4Bit rate: 8.29 MbpsC/N (Gaussian): 13.7 dB
HP
LP:16-QAM, GI 1/8, FEC 3/4Bit rate: 16.59 MbpsC/N (Gaussian): 18.6 dB
LP
+2.76 Mbps
21-Jun-04Hierarchical Modulation 19 assured communications ™
Mobile & Stationary reception
RF1Non-
Hierarchical
Non-hierarchical RF1:64 QAM, GI 1/8, FEC 2/3 = 22.12 MbpsNon-hierarchical RF2:QPSK, GI 1/8, FEC 2/3 = 7.37 Mbps
RF 2Non-
Hierarchical
HP - RF1:QPSK, GI 1/8, FEC 1/2 = 5.53 MbpsLP - RF1:16-QAM, GI 1/8, FEC 3/4 = 16.59Mbps
RF 1HP
RF1LP
21-Jun-04Hierarchical Modulation 20 assured communications ™
Simulcast HDTV & SDTV
HP(SDTV)
HP:QPSK, GI 1/16, FEC 3/4Bit rate: 5.53 MbpsC/N (Gaussian): 10.8 dB
LP(HDTV)
LP:16-QAM, GI 1/16, FEC 3/4Bit rate: 17.56 MbpsC/N (Gaussian): 21 dB
Non-hierarchical:64 QAM, GI 1/8, FEC 2/3Bit rate: 22.12 MbpsC/N (Gaussian): 16.5 dB
Non-Hierarchical
(HDTV)
21-Jun-04Hierarchical Modulation 25 assured communications ™
Hierarchical Modulation in SFN Operation
Only Requirement:• Correct maximum network delay entered in SFN adapter
TransportStream
MultiplexerLP
TransportStream
MultiplexerLP
ModulatorAmplifier
ModulatorAmplifier
ModulatorAmplifier
Audio/VideoEncoder
Telecom Network(Microwave, Fibre optics)Audio/Video
Encoder
Audio/VideoEncoder
Audio/VideoEncoder
Telecom Network(Microwave, Fibre optics)
SFNAdapter
TransportStream
MultiplexerHP
TransportStream
MultiplexerHP
21-Jun-04Hierarchical Modulation 26 assured communications ™
� 1U rackable frame� Input redundancy management� Automatic bit rate adaptation process� Mandatory and optional MIP management� NIT update feature� Embedded SNMP agent� Internal PRBS generators for test purpose
Time Stamp generation
for Hierarchical M
odulation
integrated as
a standard feature !
Synchrony – SFN Adapter
21-Jun-04Hierarchical Modulation 27 assured communications ™
Hierarchical Modulation
Is available as a standard
option for all Harris DVB-T
Transmitters
Atlas - DTV660 Product Line
Air Liquid
21-Jun-04Hierarchical Modulation 28 assured communications ™
Summary
• Hierarchical modulation allows the – Transmission of two independent ASI data streams with different
characteristic via one transmitter– Transmission to stationary and mobile receivers on
the same channel.– Broadcasting of SDTV and HDTV on the same channel
• The required technology is now available as a standard transmitter option
Hierarchical Modulation adds a lot of advantages and flexibility …
... to make Hierarchical Modulation a long term success DVB-T equipment manufacturers and broadcasters have to work together !
21-Jun-04Hierarchical Modulation 29 assured communications ™
Herzlichen Dank für Ihre Aufmerksamkeit!