White Paper N°6 - Sep. 2009
DVB-SH and DVB-T2,
why these two new standards?
Two new standards, DVB-SH and DVB-T2, have appeared over the past three years causing some confusion with
respect to their fields of application. DVB-SH was designed for Mobile TV reception over a large area via a hybrid
satellite/terrestrial network while DVB T2 is an evolution of DVB-T dedicated to increase spectral efficiency to carry more
data (e.g. HDTV).
The objective of this paper is to simulate the performance of each standard for different operational modes and channels
and therefore conclude which application is better suited for each standard.
DVB-SH
The DVB-SH specification was developed during 2006 by an ad-hoc group of the DVB Technical Module and it became
an ETSI European Standard in July 2007. The key feature of DVB-SH (Satellite services to Handhelds) is that users in
large regions or countries can be reached by just one satellite. Wherever a line of sight between terminal and satellite
does not exist, terrestrial gap fillers will be able to provide the missing coverage.
The DVB-SH specification has been designed for frequencies below 3 GHz. A typical range in which it will be used is the
S Band, which offers more available frequencies compared to the UHF band.
High power
satellite
Interactivity
Multicast TV
channels
Service
delivery
platform
Terrestrial
Transmitters
DVB-T2
DVB-T2 is a new standard for Terrestrial
Broadcasting, approved in June 2008 by the DVB
Steering Board.
Following a technical study mission and the
preparation of commercial requirements, the DVB
Project concluded that a new standard should be
able to provide increased capacity and ruggedness in
the terrestrial transmission environment, primarily
(but not exclusively) for HDTV broadcasting to
fixed and portable receivers.
Terrestrial
Transmitters
Multicast TV
channels
Service
delivery
platform
© Copyright DiBcom - MK0909WP6
© Copyright DiBcom - MK0701DP_US
1
DVB-SH and DVB-T2,
Comparison Synthesis
The following table summarizes the main parameters and technical difference between the two standards.
DVB-SH
Modulation
COFDM:
Frequency Carrier
S-Band, UHF, L-Band
QPSK - 16QAM
Frequency Bandwidth 1.7MHz (1k mode), 5MHz to 8MHz
Interleavers
Channel
coding
DVB-T2
COFDM:
QPSK to 256 QAM
UHF, L-band
1.7, 5, 6, 7, and 8MHz
(10 MHz for professional application)
[BW=5MHz] 4 interleavers (Bit/Cell/Time/Freq)
[BW=5MHz]
[BW=5MHz] Max interleaving depth:100 ms [8MHz]
(72 ms for BBC mode )
• MPE-iFEC (Interleaved FEC) on the
Mac layer corrects long duration errors
on the MPE section level spanning several
consecutive time slice bursts (up to 25s)
• Class 1: 320ms in QPSK
160ms in 16QAM
• Class 2: 10 seconds
Very long interleaver is mandatory for
satellite reception (masks effect)
Interleaving depth too short for good
satellite reception
Turbo – Code (+MPE-iFEC)
LDPC (~ DVB-S2)
+BCH for residual floor errors
Code Rate: 1/2, 3/5, 2/3, 3/4, 4/5, 5/6
Code Rate: 1/5, 2/9, 1/4, 2/7,
1/3, 2/5, 1/2, 2/3
Code rates below 1/2 are suitable for
tough environments (Mobile TV)
The minimum code rate (1/2) is not low
enough for Mobile applications.
FFT size
1k, 2k, 4k, 8k
Guard Interval
1/32
C/N ranges
(Gaussian mode)
-3 dB (QPSK 1/5) to 7 dB (16 QAM 1/2)
-6 dB to 4 dB in Diversity mode
Low C/N designed for Mobile TV
1 dB (QPSK) to 22 dB (256 QAM)
Patterns
1 pilot pattern (idem DVB-T)
8 pilots patterns : PP1 to PP8
PP1: idem DVB-T (-8% bit rate penalty)
PP8: less pilots (-1% bit rate penalty)
1/16
1/8
1k, 2k, 4k, 8k, 16k, 32k
16k and 32k OK for fix applications only
1/4
1/128 1/32 1/16 19/256 1/8 19/128 1/4
Designed mostly for fixed reception at
high bit rate (HD)
Smaller pilot ratio (as PP8) has been
defined to increase capacity.
Not applicable for Mobile TV due to poor
channel estimation performance.
2
Extended Bandwidth
No
7.77 MHz instead of 7.6 MHz at “8MHz”
for large FFT only (8k, 16k, 32k)
Additional sub carriers together with wider
Baseband Filter.
Allows more bitrate
Physical Layer Pipe
(PLP)
No
A service or group of services that share the
same code rate and modulation.
Diversity
SIMO
MISO, SIMO, MIMO (under study)
Rotated
Constellations
No
Significant improvement in robustness
(5 dB for Code Rate = 5/6), particularly in
the case of challenging terrestrial channels
(echoes, SFN,…)
Future Extension
Frame (FEF)
No
Reserved for either Next Generation
Handheld (NGH) standard or future versions
of DVB-T2 which might include Full Rate
MIMO.
Bit rate Max
17.2 Mbit/s
(NQAM=4, CR=2/3, GI=1/32, BW=8)
50.6 Mbit /s in 32k mode
(NQAM=8, CR=5/6, GI=1/128, PP7, BW=8)
Bit rate used
For Mobile TV applications: ~5 Mbit/s
Ex: BBC1: 35.9 Mbit/s
BBC2: 40 Mbit/s
DVB-SH and DVB-T2,
Simulations and Analysis
DiBcom has performed extensive simulations and lab measurements to estimate the performance of DVB-T2 and
DVB‑SH for different parameters and under different channel propagation models in order to assess the expected
spectral efficiency that can be obtained in the field (for DVB-SH, we have used the lab tests performance found within
the framework of the Celtic project B21C).
For fixed reception, it is commonly accepted that the Ricean channel (F1) is the best model, whereas for mobile
reception, the TU6 Rayleigh model has often been used to compare standards and receivers.
The figures below show the spectral efficiency versus the required C/N in mobile environment and fixed reception
applications. These figures show that:
• In Fig. 1, DVB-SH is better for Mobile TV in the area of very low C/N range, with a very good tolerance to signal
loss thanks to the very long interleaver required for satellite reception. The spectral efficiency of DVB-SH clearly shows
that it is dedicated for low bitrate mobile receivers and makes it totally not adequate for HDTV signals.
• In Fig. 2, DVB-T2 is better for high bit rate when the signal is strong and not distorted by the channel (high C/N).
It is highly probable that DVB-T2 will be used at these high bit rates for which a mobile reception is totally impossible.
Fig. 1: Capacity Performance in Mobile Environment (TU6 profile)
B
DV
Shannon limit
2
Bit/s/Hz
Satellite
Demodulation
Zone
DV
H
B-
16
-T
VB
M
QA
16
D
DV
1
-T2
VB
D
H
VB-
SK
QP
DVB
K
QPS
DV
0
5
10
Shannon limit
DVB-SH 2k GI=1/4
DVB-T2 2k GI=1/4 PP1
DVB-H 2k GI=1/4 Mfec=7/8
DVB-T 2k GI=1/4
P
HQ
B-S
0
K
PS
-T Q
D
SK
-5
M
QA
M
QA
16
SH
B-
AM
16Q
-T2
15
20
25
(C/N) dB TU6@10Hz
The Fig. 1 also shows that DVB-SH performs better than DVB-H in a Mobile environment. The C/N improvement is about
4-5 dB when considering the same spectral efficiency. This result confirms some recent simulations and tests which
have shown that a DVB-SH Mobile TV network is about 30 to 40% more cost-effective than a DVB-H one when used in
terrestrial mode.
Fig. 2: Capacity Performance in Fixed Reception (RICE profile)
256QAM 5/6
6
High Definition
Demodulation
Zone
5
BBC2
BBC1
Bit/s/Hz
4
3
SH
DVB-
QPSK 1/5 0
-5
DV
T2
0
B-T
Shannon limit
DVB-SH 8k GI=1/32
DVB-T2 32k GI=1/128 PP7
DVB-T 8k GI=1/32
QPSK 1/2
5
64QAM 7/8
DV
16QAM 2/3
QPSK 1/2
1
256QAM 3/5
France
64QAM 3/4
B-
Shannon limit
2
256QAM 2/3
10
15
20
25
(C/N) dB RICE
3
CONCLUSION on Commercial
Applications of DVB-SH and DVB-T2
DVB-SH
Most decisions in the DVB-SH design were directed by the requirement to maximize Mobile TV satellite Reception and
correction of errors due to long interruptions (shading by building, bridge, trees,…).
• Two modulation schemes, SHA and SHB are normalized:
The SHA mode uses COFDM both on the satellite and terrestrial links and requires satellite transponders to be operated
in a linear mode. The SHB mode uses a single carrier / Time Division Multiplex (TDM) on the satellite link but the OFDM
signal is maintained on the terrestrial link. This SHB version targets satellite transponders operated in full saturation
• Two types of convolutional interleaver have been defined on the SHA physical layer:
- Class1 receiver is able to cope with rather short interruptions using a convolutional interleaver with a typical depth
of 160ms in 16 QAM and 320 ms in QPSK (for BW=5 MHz). A longer interleaver can be obtained by using MPE-iFEC
(Interleaved FEC) on the Mac layer in order to support reception in situations of long duration erasure on the MPE
section level spanning several consecutive time slice bursts (up to 25 seconds).
- Class2 receiver is able to handle long interruptions but it requires an external memory with a size of 256 Mbit for
a correction depth of about 10s.
• The Channel Coding in SHA uses a completely new scheme based on Turbo-codes with a minimum value of code rate
as low as 1/5 dimensioned for difficult transmission environments.
Our lab and field measurements have shown that the commercial requirements have been met by the
DVB‑SH standard, offering the highest spectral efficiency at low C/N and strong robustness even in case of
long signal interruption.
DVB-T2
The DVB-T2 commercial requirements included:
• T2 should provide a minimum of 30% capacity increase over DVB-T. [256QAM, less dense pilot patterns, minimum
GI ratio = 1/128, extended bandwidth, TFS]
• T2 should provide for improved single-frequency-network (SFN) performance compared with DVB-T. [Rotated
constellation, long GI in 16k or 32k FFT]
• T2 transmissions must be able to use existing domestic receive antenna installations and must be able to re-use
existing transmitter infrastructure. [Not possible to use full rate MIMO]
• T2 should have a mechanism for providing service-specific robustness; i.e it should be possible to give different
levels of robustness to some services compared to others. [Multiple PLPs]
• T2 should provide for bandwidth and frequency flexibility. [1.7 MHz to 8MHz, up to 10 MHz for professional usage]
Simulations have shown that these commercial requirements have been met by the DVB-T2 standard,
offering the highest spectral efficiency at high C/N and without taking into account the problem of signal
interruption.
Conclusion:
While there has been some confusion between
the objectives of DVB-T2 and DVB-SH during the
development of these standards, this paper clearly
shows that each of these standards is dedicated to
completely different applications and cannot be used
for purposes other than the ones each standard was
originally intended for. As the requirements for a
next generation handheld (NGH) are constituted, the
question remains whether it will be possible to find
a way to mix the requirements of both mobile and
fixed environments in order to enable a combination
of both applications over the same spectrum.
As these simulations have shown, the requirements
are so different for both applications that it is not an
easy task, and DiBcom will be glad to offer its expertise
in another future white paper when the time comes!
www.dibcom.com
DiBcom provides a chip for DVB-SH reception,
the DIB29098-SH. It embeds a dual Tuner + two
Demodulators offering a MRC diversity reception,
improving drastically the performance in term of
sensitivity and speed.
The DiBcom Octopus platform is based on a
programmable Vector Signal Processing engine.
It provides a family of powerful flexible and universal
mobile TV receiver chip on which the DVB-T2 standard
can be supported.
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