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International Journal of Scientific and Research Publications, Volume 2, Issue 7, July 2012 1
ISSN 2250-3153
Performance Analysis of Digital Audio Broadcasting
System through AWGN and Rayleigh Channels
Mayur Kumar, Anil Kumar#, Santosh Tripathi#, Tripuresh Joshi, Dr. Chandrakant Shukla#
Department of Electronics and Communication Engineering
Sam Higginbottom Institute of Agriculture, Technology and Science, Allahabad, Uttar Pradesh, India -211007
Abstract-This paper presents the performance analysis of
Eureka-147 DAB system. DAB transmission mode-II is
implemented. A frame-based processing is used in this study.
Performance studies for AWGN and Rayleigh channels have
been conducted. For all studies SER has been used as
performance criteria.
Index Terms- Radio, Digital Audio Broadcasting (DAB), Eureka
147, European Telecommunications Standards Institute (ETSI),
Symbol Error Rate (SER), coded Orthogonal Frequency Division
Multiplex (COFDM), and Frequency Response.
I. INTRODUCTION
adio broadcasting is one of the most widespread
electronic mass media comprising of hundreds of
programme providers, thousands of HF transmitters and
billions of radio receivers worldwide. Since the broadcasting
began in the early 1920s, the market was widely covered
by the AM services. Then came the FM and now we live in a
world of digital communication systems and services. Digital
telecommunication has advantages over analog systems such as
storage capacity, reliability, and quality of service,
miniaturization and many more.
R
The new digital radio system, Digital Audio Broadcasting
(DAB) has the capability to replace the existing AM and FM
audio broadcast services in many parts of the World in near
future. This was developed in the 1990s by the Eureka 147 DAB
project. DAB is very well suited for mobile receivers and
provides very high tolerance against multipath reception and
inter symbol interference (ISI). It allows use of single
frequency networks (SFNs) for high frequency efficiency. In
several countries in Europe and overseas, broadcasting
organizations, network providers and receiver manufacturers
are already implementing digital broadcasting services using
the DAB system. Perceptual audio coding (MPEG-2), Coded
Orthogonal Frequency Division Multiplexing (COFDM),
provision for the multiplex of several programmes and data
transmission protocols, are the new concepts of digital radio
broadcasting.
II. RELATED WORK
During its development DAB system has been publicly
demonstrated many times. It has been subject to extensive
computer simulations and field tests in Europe and
elsewhere. It is now in regular service in many European
countries and throughout the world. In 1995, the European DAB
Forum (Euro Dab) was established to pursue the introduction of
DAB services in a concerted manner world-wide and it became
the World DAB Forum in 1997 [1]. As a result of developments
within the Eureka 147 project, the DAB Standard or DAB
Specification in the form of EN 300401 was approved by
the European Telecommunications Standards Institute (ETSI),
which defines the characteristics of the DAB transmission
signal, including audio coding, data services, signal and service
multiplexing, channel coding and modulation [2].
The first digital sound broadcasting systems providing
CD-like audio quality was developed in early 1980s using
Satellite technology. The system employed very low data
compression and was not suitable for mobile reception. It
used frequency in the range 10-12 GHz. Therefore it was not
possible to provide service to large number of listeners. It was
realized terrestrial digital sound broadcasting would do the
job and to develop this new digital solution an international
research project was necessary. So, in 1986 few
organizations from France, Germany, United Kingdom and
The Netherlands signed an agreement to cooperate in the
development of a new standard and with this Eureka-147
project was born [2] [6]. Members of European Broadcasting
Union (EBU), who were the part of work on the satellite
delivery of digital sound broadcasting to mobiles in the
frequency range between 1 and 3 GHz, also joined the Eureka-
147 project. Later International Telecommunications Union
(ITU-R) and the European Telecommunications Standards
Institute (ETSI) started the standardization process.
Following goals were set up for DAB from the beginning with
the sole aim of quality audio for mobile reception:
High quality digital audio services (near CD quality).
Well suited for mobile reception in vehicles, even at higher
speeds.
Efficient frequency spectrum usage
Transmission capacity for ancillary data.
Low transmitting power.
Terrestrial, cable and satellite delivery options.
Easy tuning of receivers.
Large coverage area than current AM and FM systems.
Eureka 147 consortium alone started choosing the most
appropriate transmission method based on thorough simulation
and field test. Results showed that broadband solutions
performed better than the narrow-band proposal, while the
frequency-hopping solution was considered too demanding
International Journal of Scientific and Research Publications, Volume 2, Issue 7, July 2012 2
ISSN 2250-3153
with respect to network organization. Since the spread-spectrum
was not developed as hardware therefore coded Orthogonal
Frequency Division Multiplex (COFDM) system was chosen
finally.
The next issue was audio coding standard selection for the
Eureka-147 project. By that time the MPEG (Moving Pictures
Expert Group) had already been standardized for data
compression both video and audio coding. The solutions
proposed by the Eureka-147 were sent to the MPEG Audio
group to be evaluated with other several options from other
countries. The performance offered by the methods submitted
by the Eureka consortium was clearly superior so they were
standardized by the MPEG as MPEG Audio Layers I, II and III.
It took a long time until the final decision to which standard
should be used for DAB was taken [4]. Finally, Layer II, also
known as MUSICAM was chosen.
Another important specification for the DAB was the
bandwidth consideration. From a network and service area
planning point of view, one transmitter with the 7 MHz
bandwidth of a TV channel was too much inflexible, but
showed very good performance in a multipath environment [2].
Therefore considerable reduction in transmission bandwidth was
necessary. In Canada experiments with the COFDM system also
revealed that performance degradation begins around 1.3MHz
and lower. Therefore appropriate bandwidth for a DAB channel
was fixed at 1.5MHz.
With this one 7 MHz TV channel can be divided into four
DAB blocks, each carrying ensembles of five to seven programs.
The first DAB standard was achieved in 1993 and then in
1995 the ETSI adopted DAB as the only European standard
for digital radio. The Eureka 147 DAB standard as digital radio
is accepted Worldwide except, USA and Japan.
III. ARCHITECTURE
This section gives an overview of the conceptual architecture
of Digital audio Broadcasting and describes the basic building
blocks. The design decisions draw from several concepts and
approaches. Since COFDM is the heart of Digital Audio
Broadcasting (DAB), to be more presice OFDM, therefore the
basic block diagram of the same is given below.
IV. SIMULATION AND PERFORMANCE EVALUATION
The above system was simulated in MATLAB’s Simulink.
The following are the results obtained from the software
imitating the DAB quite successfully.
Figure 2
shows the real
and imaginary
parts of the
Transmitted signal. This Composite signal is fed to the channel
after the Parallel to serial converter block.
Figure 3 Shows the Real and Imaginary parts of the
Received Composite signal at the output of the OFDM Receiver.
As compared with the input signal the Wave shape, Frequency
and Phase is the same as that of the input signal.
Figure2: Transmitted signal in the simulator.
Figure 3: Received signal in the simulator.
The only difference between the two signals is the
Amplitude level or the power level. The output signal has a lower
power as compared with the input signal.
Figure 1: Basic block diagram of OFDM system
International Journal of Scientific and Research Publications, Volume 2, Issue 7, July 2012 3
ISSN 2250-3153
Figure 4: Spectrum of Transmitted Signal in the simulator.
Figure 4 Shows the Frequency Response of the Transmitted
Composite signal. This can be seen on a spectrum analyzer
places at the output of the parallel to serial converter block in the
simulation
Figure 5: Spectrum of Received signal in the simulator.
Fig 5 shows the Frequency Response of the output signal,
which can be seen at the Spectrum Analyzer placed at the output
of the Decoder in the Receiver. As compared with figure 4.7, the
spectrum is still in good condition. The magnitude has not
decreased so much; it is not much affected by noise, as can be
seen in the frequency axis from -0.6 to +0.6.
There is noise and distortion in the spectrum especially at
higher frequencies outside the bandwidth of 1.5 Mhz, i.e. from
-0.6 to -1 and from +0.6 to +1.
Table 4.1 Parameters of the main Composite signal.
Main Composite Analysis Signal
Secon
d
Total Symbol Error Symbol SER
20 1.683ₑ+004 0 0
40 3.425ₑ+004 0 0
1.00 5.168ₑ+004 18 0.0003
5
1.20 6.928ₑ+004 22 0.0003
2
1.40 8.661ₑ+004 36 0.0004
2
2.00 1.033ₑ+005 44 0.0004
3
2.20 1.197ₑ+005 44 0.0003
7
2.40 1.375ₑ+005 55 0.0004
Table 1 analysis the Main Composite signal, it shows that as
the Total symbol bits increases with the passage of time, the
Error symbols also increase. Initially the Error Symbols are Zero
but at time = 1 minute it starts to increase, and goes up to 55 at
time = 2 minute and 40 second. Also the Symbol Error Rate
(SER) increases with Total symbols transmitted. It is zero
initially but starts to increase at time = 1 minute. It goes upto
0.0004 at time = 2 minute and 40 second.
Figure 6: Total symbol Vs Error Symbol (Main composite
Signal)
The graph shown in Figure 4.8 is a relationship between
Total Symbols sent from Transmitter to Receiver and the Error
symbols encountered at the receiver. The Total symbols are taken
on Y – axis, and the values starts from 104 Symbols to 106.
Error symbols are taken on X –axis. The value varies
from 0 to 60 symbols. The error symbol is 0 when the Total
Symbol varies from 104 up to 104.3. Then it increases up to 60
when the Total Symbols vary from 104.3 to 105.05. Therefore
the Error Symbols occur between 104.3 to 105.05.
International Journal of Scientific and Research Publications, Volume 2, Issue 7, July 2012 4
ISSN 2250-3153
Figure 4.9 SER Vs Total symbol (Main Composite signal)
Figure 4.9 shows how Symbol Error Rate (SER) changes with
respect to the Total symbols sent. On X – Axis Total Symbol are
taken from 104 to 106, but the SER varies only from 104.08 to
105.05.
On Y – Axis SER is taken. SER is 0 until when the Total
symbol is at 104.25. Then it rises up to 4.3x10-4, which is in line
with ETSI (EN 300 401).
Table 4.2 Parameters of the Encoded signal.
Encoded Signal Analysis
Secon
d
Total Symbol Error Symbol SER
20 2.295ₑ+004 29 0.00126
4
40 4.671ₑ+00
4
86 0.00184
1
1.00 7.047ₑ+00
4
131 0.00185
9
1.20 9.447ₑ+00
4
177 0.00187
4
1.40 1.181ₑ+00
5
220 0.00186
3
2.00 1.409ₑ+00
5
247 0.00175
3
2.20 1.632ₑ+00
5
294 0.00180
1
2.40 1.875ₑ+00
5
347 0.00185
1
Table 4.2 shows the analysis of the encoded signal. With
the passage of time the Total Symbols increases. The Error
symbols also increases from 29 to 347. The Symbol Error Rate
(SER) also increases with respect to the increase in the Total
symbol.
Figure 4.10 Total Symbol Vs Error Symbol in Encoded Signal.
On Y – axis Total Symbol has been taken from 104 to 106. On
X – axis Error Symbol is taken from 0 to 350. The Error symbol
varies between Total Symbol 104.12 to 105.09. The Error Symbol
increases from 30 onwards and becomes constant at 350.
Thus Coding helps to make the Error symbol stable. The Error
symbol does not increases after 350, but remains constant.
On X – Axis Total Symbol are taken from 0.2x105 to 2x105.
On Y – Axis SER is taken. The SER increases from 1.26 to 1.84.
Then it remains somewhat constant in the range of 1.75 to 1.88.
Thus coding helps to stabilize the SER.
Figure 4.11 SER Vs Total Symbol in the Encoded Signal.
V. Conclusion
We presented the simulated model of DAB based on OFDM
system, communicating in AWGN and Rayleigh channel. The
performance analysis of the system shows that degradation in
limited only to a certain part of the spectrum and also encoding
and decoding at the Transmitter and receiver respectively lowers
International Journal of Scientific and Research Publications, Volume 2, Issue 7, July 2012 5
ISSN 2250-3153
the degradation. This work used the previous work of [25] as
reference.
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AUTHORS
Mayur Kumar;
PG-Student; SHIATS-DU, Allahabad, Uttar Pradesh,
India-211007
e-mail – 01mayurkumar@gmail.com
Anil Kumar#;
Assistant Professor; SHIATS-DU, Allahabad, Uttar
Pradesh, India-211007
Santosh Tripathi#;
Assistant Professor; SHIATS-DU, Allahabad, Uttar
Pradesh, India-211007
Tripuresh Joshi;
PG- Student; SHIATS-DU, Allahabad, Uttar
Pradesh, India-211007
e-mail – coolcog@gmail.com.
Dr. Chandrakant Shukla#;
Professor; SHIATS-DU, Allahabad, Uttar Pradesh,
India-211007