CEPT
ECC
Electronic Communications Committee
TG6(13)045
Task Group 6
ECC TG6 – M2
Lisbon, 03 - 05 December 2013
Date issued:
28 November 2013
Source:
MEDIA BROADCAST GmbH
Case study on a comparison between eMBMS and DVB-T2 on a high
tower high power network
Subject:
Password protection required? (Y/N)
N
Summary:
The document summarizes a case study on eMBMS and DVB-T2 implemented on a high power
high tower network topology, with the aim to compare results with general findings in other
documents.
All LTE eMBMS calculations were based on what is currently standardised and carried out for
one of the Federal states in Germany (Northrhein-Westfalia). All coverage predictions were
performed for fixed and for portable outdoor reception, for different levels of location probability
and with the goal to cover 95% or more of the population in Northrhein-Westfalia.
In contrast to another study provided to the first meeting of TG6, coverage predictions for eMBMS
always showed a much lower population and area coverage than for DVB-T2, even for a C/N as
low as 0 dB. A potential reason for these discrepancies is discussed.
Proposal:
TG6 to consider this document
Background:
ECC-TG6 should provide technical studies on the evolution of broadcasting and mobile networks
and services as well as other services and applications.
In this context, broadcasting should encompass foreseen developments in video resolution,
coding, modulation/systems, receiving modes and coverage requirements. This includes aspects
as network topologies and new technologies such as eMBMS and Tower-Overlay. In addition, the
concept of convergence/cooperation of both types of services/networks should be addressed.
Case study on a comparison between eMBMS and DVB-T2 on a
high tower high power network
1
Introduction
The aim of this document is to discuss the impact of OFDM parameters like Guard Interval
(GI, for DVB-T/T2) or Cyclic Prefix (CP, for eMBMS) on coverage probability if the signals are
provided via a high-power/high-tower (HPHT) network topology.
A planning tool has been used which allows e.g. coverage predictions for OFDM-based radio
systems, for all kind of parameter settings. All coverage predictions were performed using a
wave propagation model developed within Deutsche Telekom1, based on Deygout (see e.g.
ITU-R P.526) and millions of measurements in order to verify/improve the model. Predictions
were further based on topographic and clutter data as well as on information on land usage
classes. For statistical analysis, information on population and population density was used.
2
Simulation framework
The network under consideration consists of existing 20 sites, providing DVB-T coverage for
public broadcasting TV services throughout the Federal State of Northrhein-Westfalia in five
different SFN’s. The ERP values were kept constant, i.e. as in use for DVB-T. The coverage
was simulated for both, LTE eMBMS and DVB-T2. For the purpose of these simulations, a
single SFN on channel 35 has been created.
The ERP ranges from 3 kW (two transmitters providing local coverage) to 50 kW, antenna
heights from 62 m to 313 m. In most cases real antenna diagrams were used.
Parameter
Modulation
C/N [dB]
Value
Remark
64-QAM 2/3
16.6 / 14.8
Noise Figure [dB]
7 dB
Standard deviation
6 dB
Guard Interval [s]
448 (1/4)
portable / fixed reception
field strength
FFT-mode: 16 kFFT
Table 1: DVB-T2 parameters which have been used in simulations
For DVB-T2, a 16 kFFT 64-QAM 2/3 has been used which is amongst those modes which
are under consideration for DVB-T2 in Germany. This mode has a theoretical C/N which is
similar to the one of the current DVB-T mode and is a tradeoff between high data rate,
enough robustness for mobile or portable reception and network costs. A guard interval (GI)
of 448 s (corresponding to 1/4) has been chosen to cover the entire area. It is noted that
this would result in a certain loss of data rate compared to the currently used GI of 224 s.
LTE eMBMS has been simulated by adopting the corresponding time parameters (e.g. FFT
size, symbol length and a cyclic prefix of 33 s). With respect to ERP, the same values have
been used as for DVB-T2 simulations, i.e. values which are currently in use for DVB-T. The
SINR value has been reduced to 0 dB. No additional delays have been applied.
3
Coverage Predictions and Results
It is assumed that all signals follow a log-normal distribution, i.e. useful as well as interfering
signals. The summation of different signals is of particular significance in a single frequency
1
Kuhlmann-Eibert-model, see also [1]
network (SFN) where it is necessary to sum up all wanted signals and all interfering signals
as well as to take account of the minimum field strength required to overcome noise. More
explanation e.g. on summation of log-normally distributed signals can be found in [2] and [3].
Coverage prediction maps are provided in the Annex for fixed reception and for portable
outdoor reception. The typical patterns of self-interferences are clearly visible in the case of
eMBMS (fixed reception and portable outdoor reception).
The results of statistical analysis are provided in Table 2.
Fixed
eMBMS
C/N (dB)
Portable outdoor
DVB-T2
eMBMS
DVB-T2
0
14.8
0
16.6
Population coverage
66.9 %
99.6 %
45,1 %
94.9 %
Area coverage
63.2 %
98.8 %
43,1 %
89.3 %
Table 2 Results for fixed and for portable outdoor reception, 95% cov. probability or better
The following can be observed:


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For a high power/high tower network topology and due to the larger GI, a DVB-T2
system provides a much better coverage.
Due to the short CP of 33s and the overall symbol length, an LTE eMBMS network
based on exactly the same network layout provides a much lower coverage, even for
a C/N which is lower by more than 16dB.
Conclusions
We fully agree with the conclusion in TG6(13)012 that eMBMS as it is currently standardised
is not suitable for a high-power/high-tower network. However, our results show that the effect
is dramatically worse, i.e. that LTE eMBMS with the current configuration cannot provide a
similar coverage as DVB-T2 when using the same HPHT network topology.
One of the potential reasons for differences with respect to results provided in TG6(13)008 is
that our calculations are based on a proper statistical summation of all signals involved and
taking into time domain/delays, not on C/I results.
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References
[1]
Eibert, T.F.; Kuhlmann, P.: Notes on Semiempirical Terrestrial Wave Propagation
Modelling for Macrocellular Environments – Comparisons with Measurements; IEEE
Trans on Ant. and Prop., Vol.51, No.9, Sept. 2003
[2]
Beeke, K.: “Spectrum Planning - Analysis of methods for the summation of Lognormal distributions”, in EBU Technical Review; October 2007
[3]
EBU: “TERRESTRIAL DIGITAL TELEVISION PLANNING AND IMPLEMENTATION
CONSIDERATIONS”, section 3 of BPN 005, Spring 2001; available at
http://www.itu.int/ITU-D/pdf/3888-21.3-en.pdf
[4]
Brugger, R.; Hemingway, D.: “OFDM receivers – impact on coverage of inter-symbol
interference and FFT window positioning”,; EBU Technical Review; July 2003
Annex1
Figure A1: Coverage prediction map for fixed reception, for DVB-T2 (left) and LTE eMBMS (right)
Legend:
white – coverage probability better than 99%; green - coverage probability better than 95%
yellow - coverage probability better than 90%; orange - coverage probability better than 50%; red - coverage probability less than 50%
Figure A2: Coverage prediction map for portable outdoor reception, for DVB-T2 (left) and LTE eMBMS (right)
Legend:
white – coverage probability better than 99%; green - coverage probability better than 95%
yellow - coverage probability better than 90%; orange - coverage probability better than 50%; red - coverage probability less than 50%
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