International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Analysis of DVB-T system using OWDM with various wavelet
families
Mandeep Kaur, Vikramjeet Singh
Department Of Electronics Engineering
Lovely Professional University, Punjab
Department Of Electronics Engineering
Lovely Professional University, Punjab
ABSTRACT-Orthogonal Frequency Division
channel than a lower bit rate signal. Chang
Multiplexing
of
proposed than an alternative to serial transmission
It is a powerful
i.e. parallel transmission. In parallel transmission,
technique that uses an IFFT at the transmitter to
the bit rates per subcarrier were lower. OFDM is
modulate a high bit error rate signal onto a
underlying technology of the DVB-T standard and
number of carriers. But it faced one problem that
comprises of an IFFT (Inverse Fast Fourier
is inherently inflexible and requires a complex
Transform) at the transmitter and FFT (Fast Fourier
IFFT core. To overcome this problem a new
Transform) at the receiver which performs the
DVB-T system is designed that utilizes the flexible
frequency division multiplex. An alternative is used
nature of Discrete Wavelet Transform by using
the wavelet to separate the sub-band components
OWDM in instead of OFDM. As OWDM has low
like OFDM does. The system is called OWDM.
computational complexity and increased flexibility
The use of filters in the wavelet domain has been
so it utilizes the resources in much better way. In
used for multi carrier resolution analysis of time
OWDM, various mother wavelets can be used to
varying signals. With OWDM, it is possible to
improve the flexibility.
dynamically allocate the number of sub-bands and
Keywords- OFDM, OWDM, DVB-T, Wavelet
bandwidth of each. With all this in mind, this paper
system
used
communication systems.
in
number
OWDM as an alternative to OFDM in DVB-T
modulation, IFFT.
which employs a true time -frequency division
I.
multiplex using wavelet which may provide more
INTRODUCTION
In 1997, the world’s first commercial digital
terrestrial services launched by UK, the next few
years the digital broadcasting has been set up in
many countries.
Digital
Video Broadcasting
Terrestrial standard has been developed in Europe.
It uses Orthogonal Frequency Division Multiplex
and Orthogonal Wavelet Division Multiplex as
modulation scheme. In OFDM, the signal is being
transmitted
at
a
high
data
rate
in
serial
transmission; the signal will be affected by the
ISSN: 2231-5381
flexibility [1]-[3].The objective of this paper is to
identify how the new OWDM system can be
compared with the existing OFDM system so
simulation were first run using OFDM as the RF
modulation front-end. Following this, the OFDM
block was replaced with the OWDM block with
same tests run.
DVB-T Terrestrial Digital Video Broadcasting
(DVB-T) has been subject to technical discussion
for many years and has undoubtedly been shown as
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
a great success in delivering high quality and
single frequency networks (SFN). It employs 6817
standard quality digital television by terrestrial
carriers. Existing DVB-T modes produce a
means. Although originating in Europe, it has been
transport capacity of 5-15 Mbps (1-3 TV Programs)
adopted in many countries around the world. DVB-
suitable for mobile receivers. A simplified block
T is multi carrier system where each carrier
diagram of the European DVB-T standard is shown
modulated digitally. DVB-T standard uses coded
in the figure below. A digital signal processor
Orthogonal
(DSP) performs most of the processes described in
Frequency
Division
Multiplexing
(COFDM) as modulation scheme. In COFDM,
this diagram.
forward error correction is applied to the signal
II.
OWDM
before transmission. Except this property, COFDM
OWDM is a modulation frontend that has been
is same as OFDM. This is to be overcome a errors
proposed as an alternative to OFDM. In DWT -
in the transmission due to lost carriers from channel
OWDM, the modulation and demodulation are
noise,
other
implemented by wavelets rather than by Fourier
propagation effects. The main focus of this project
transform. OWDM using the discrete wavelet
is on OFDM and OWDM, but in real-life
transform is a multiplexing transmission method in
application any practical system will be use
which data being assigned to wavelet sub bands
forward error correction thus would be COFDM.
having different time and frequency resolution.
The DVB-T network operator can choose one of
Wavelet based system establishes a small bit error
the two modes of operation.
rate probability than that of the Fourier transform
frequency
selective
noise
and
based system. Wavelet modulation is modulation
scheme to make use of wavelet transformations
corresponding to the data being transmitted. The
advantage
of
wavelet
transform
than
other
transforms such as Fourier transform is discrete
both in time as well as scale. OWDM allows each
subcarrier to have different coding and different
modulation depending on the channel requirements
so increase in flexibility. The other advantage of
OWDM is increase in resilience to frequency
selective fading by increasing the error correction
on the effected sub bands and decrease in
computational complexity.
III.
Fig.1 Digital Video Broadcasting-Terrestrial
Wavelet
When performing a frequency analysis of a signal,
First is 2K mode which is suitable for single
often, if there is minimal variation in time, Fourier
transmitter operations and small single frequency
transform with appropriate windowing will provide
networks (SFN) with limited transmitter distance. It
accurate information. If however, there are fast
employs 1705 carriers. 8K mode is suitable for
fluctuations in the time domain or the time domain
single transmitter operations and small and large
contains information that is relevant to how the
ISSN: 2231-5381
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
frequency domain information is reacting, a time-
DVB-RCS relies on DVB-Satellite (DVB-S) for the
frequency analysis is necessary. There are several
provision of forward channel. The Digital Signal
mechanisms that can be used to do this but the most
processing (DSP) implemented in the satellite
common
channel adapter block of these standards use
three
are
the
Short-Time
Fourier
Transform (STFT) that works by sweeping a
powerful
window over the time-domain signal and presents a
techniques.
three
dimensional
spectrograph,
the
wavelet
Miele proposed the rapid growth of digital video
broadcasting by terrestrial transmission (DVB-T)
has created the need for getting new measurement
methods as well as getting new test equipment up
and capable of providing reliable and repeatable
results. Some problems are, in fact, experienced in
power measurements conducted through currently
available instruments, especially in those involving
the integration of input signal power spectrum over
a certain frequency interval. Trying to give an
to
the
measurement
and
modulation
CONCLUSION
and comparison has been succeeded of different
Literature Review
L. Angrisani, D. Capriglione, L. Ferrigno and G.
answer
V.
coding
In this paper we have analyze a set of simulation
transform and wavelet packets.
IV.
channel
needs,
power
wavelet filters of OWDM with OFDM. From these
results , it is suggested that the db1 wavelet (the
first wavelet of Daubechies family) is the most
suited for OWDM because of the lower variance to
noise in channel followed by Daubechies family,
while db2 (the second wavelet of Daubechies
family) is the least suited because it has high
variance. The results showed that there were some
OWDM scheme whose variance outperformed that
of OFDM and db1 wavelet achieved the best
performance compared to other wavelet db2 and
OFDM as well.
REFERENCES
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