Effects of filtering on ber performance of an ofdm system
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El documento analiza el rendimiento de la técnica de multiplexión por división de frecuencia ortogonal (OFDM) en un canal de ruido gaussiano aditivo (AWGN) usando filtros de modelado de pulsos, como el coseno elevado y FIR Nyquist. Se presentan resultados de simulación que muestran que el OFDM con filtrado de pulsos mejora significativamente la tasa de error de bits (BER) en comparación con el OFDM simple. La investigación concluye que el uso de un filtro de coseno elevado reduce la interferencia entre símbolos y mejora la eficiencia del ancho de banda.
![IJRET: International Journal of Research in Engineering and Technology
__________________________________________________________________________________________
Volume: 02 Issue: 09 | Sep-2013, Available @
EFFECTS OF FILTERING ON
1
M.Tech.Scholar, 2
Principal, A.C.E.T. College
In upcoming generations, wireless communication system requires a higher standard in order to provide high quality of services
customers. Orthogonal Frequency Division Multiplexing (OFDM) is an
systems which can be implemented easily. In this paper
when a signal is transmitted over an Additive White Gaussian Noise (AWGN) channel
performance of OFDM system with pulse shaping
the overall performance of the system in terms of BER.
SQRT Raised Cosine for analyzingthe Bit Error Rate (
Index Terms: AWGN, ICI, OFDM, Bit E
-----------------------------------------------------------------------
1. INTRODUCTION
High bit error rate(BER) and high bandwidth efficiency
the major desiresfor modern communication sy
the needs for a variety of new and high quality services
developed and delivered to the society [1]. The effect of
multipath delay, spread and fading of signals in the wireless
environment is usually unavoidable [2], [3]. Extreme fading of
the signal amplitude and Inter Symbol Int
introduced during transmission through t
channel and frequency selectivity of the channel appearing at
the receiver side [4], [5] are responsible for a high probability
of errors and reduced overall performance of the system.
Several methods like adaptive equalization and channel coding
have been developed to reduce the above effect. [6], [7]. The
orthogonal Frequency division multiplexing (OFDM) a multi
carrier system can be thought of as a solution and is used in
several applications such as asymmetric digital subscriber
lines (ADSL), a system that makes high bit-rates possible over
twisted-pair copper wires [8], [9], it has also been accepted for
several wireless LAN standards, as well as a number of mobile
multimedia applications [1], [10] and protocols like IEEE
802.11a standard, terrestrial digital video broadcasting (DVB
T) and digital audio broadcasting (DAB) [11]. The purpose of
this paper is to investigate how OFDM performs in an
Additive White Gaussian Noise (AWGN) ch
pulse shaping filter like Raised cosine, FIR Nyquist and
Matched SQRT Raised Cosine. In this channel
one path between transmitter and receiver and
attenuation and noise is considered. In this paper, we define
the simulation methodology of OFDM in section 2 and
simulate the OFDM system using Matlab. The mathematical
model and theoretically simulated constellation diagrams for
various pulse shapes are presented and a procedure for symbol
IJRET: International Journal of Research in Engineering and Technology eISSN: 2319
__________________________________________________________________________________________
2013, Available @ http://www.ijret.org
S OF FILTERING ON BER PERFORMANCE OF AN OFDM
SYSTEM
Navjot Kaur1
, V.K. Banga2
College, Punjab, India, navjosan2011@gmail.com
Abstract
wireless communication system requires a higher standard in order to provide high quality of services
. Orthogonal Frequency Division Multiplexing (OFDM) is an efficient modulation
systems which can be implemented easily. In this paper, an effort has been made to analyze how well an OFDM system
transmitted over an Additive White Gaussian Noise (AWGN) channel using 16 QAM
pulse shaping filters are also evaluated and results reveal that
ce of the system in terms of BER. We use Different pulse shaping filters such as
the Bit Error Rate (BER) performance.
Error Rate.
-----------------------------------------------------------------------***--------------------------------------------------------------------
andwidth efficiency are
modern communication systems to satisfy
f new and high quality services
developed and delivered to the society [1]. The effect of
multipath delay, spread and fading of signals in the wireless
environment is usually unavoidable [2], [3]. Extreme fading of
the signal amplitude and Inter Symbol Interference (ISI)
transmission through the conventional
frequency selectivity of the channel appearing at
the receiver side [4], [5] are responsible for a high probability
of errors and reduced overall performance of the system.
Several methods like adaptive equalization and channel coding
have been developed to reduce the above effect. [6], [7]. The
orthogonal Frequency division multiplexing (OFDM) a multi
carrier system can be thought of as a solution and is used in
lications such as asymmetric digital subscriber
rates possible over
pair copper wires [8], [9], it has also been accepted for
several wireless LAN standards, as well as a number of mobile
ations [1], [10] and protocols like IEEE
802.11a standard, terrestrial digital video broadcasting (DVB-
T) and digital audio broadcasting (DAB) [11]. The purpose of
this paper is to investigate how OFDM performs in an
e (AWGN) channel for different
Raised cosine, FIR Nyquist and
. In this channel there is only
receiver and a constant
attenuation and noise is considered. In this paper, we define
the simulation methodology of OFDM in section 2 and
simulate the OFDM system using Matlab. The mathematical
model and theoretically simulated constellation diagrams for
shapes are presented and a procedure for symbol
error rate is derived and finally a
for various pulse shaping filter
presented.
2. SYSTEM MODEL
Figure 1(a) and 1(b) show
communication system with various
this communication system
binary information. The high speed serial data stream is split
up into a set of low speed sub streams and modulated onto the
orthogonal carriers through Inverse Fast Fourier
(IFFT) [2].
Figure-1(a): Transmitter of
eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
117
BER PERFORMANCE OF AN OFDM
navjosan2011@gmail.com, vijaykumar.banga@gmail.com
wireless communication system requires a higher standard in order to provide high quality of services to
modulation technique of forthcoming wireless
made to analyze how well an OFDM system can perform
using 16 QAM modulation techniques. The
filters are also evaluated and results reveal that the pulse shaped OFDM improve
such asRaised cosine, FIR Nyquist and
--------------------------------------------------------------------
r rate is derived and finally a BER simulation of OFDM
ulse shaping filters at different SNR value is
Figure 1(a) and 1(b) show the structure of a typicalOFDM
communication system with various pulse shaping filters. In
system, QAMconstellation is used to map
binary information. The high speed serial data stream is split
up into a set of low speed sub streams and modulated onto the
arriers through Inverse Fast Fourier transform
Transmitter of a pulse shaped OFDM system](https://image.slidesharecdn.com/effectsoffilteringonberperformanceofanofdmsystem-140805014116-phpapp01/85/Effects-of-filtering-on-ber-performance-of-an-ofdm-system-1-320.jpg)
![IJRET: International Journal of Research in Engineering and Technology
__________________________________________________________________________________________
Volume: 02 Issue: 09 | Sep-2013, Available @
Figure-1(b): Receiver of a pulse shaped OFDM System
OFDM with pulse-shaping filter can be representedas:
s t e ∑ D p t e ...
Where j=√ 1 , Number of subcarrier is N, Carrier frequency
of OFDM system isf , Subcarrier frequency of kth subcarrier
is, f and here k = 0, 1… N – 1, and p t is time limited pulse
shaping filter. Transmitted symbol is Dk which is assumed to
have zero mean and normalized average symbol energy. Also
we consider that all data symbols are uncorrelated [9, 10] i.e.
E [D D∗
] =
1, k m
0, k $ m
%... (2.2)
where m=0, 1,......, N-1
Where D∗
is the complex conjugate of Dk .To ensure the
orthogonality of subcarrier, it is very important to satisfied the
below equation for OFDM system [9, 10]. The subcarrier
frequency is
f
k
T'
… 2.3
wherek 0, 1, . . . . . . . . . , N
f f
k m
T'
… 2.4
where k m 0,1, … … . , N 1
For maintaining orthogonality between subcarriers, the
minimum required subcarrier frequency spacing is 1/
received signal at the receiver can be represented as:
r t s t ⊗ h t 2 w t ... (2.5
IJRET: International Journal of Research in Engineering and Technology eISSN: 2319
__________________________________________________________________________________________
2013, Available @ http://www.ijret.org
OFDM System
representedas:
... (2.1)
, Number of subcarrier is N, Carrier frequency
, Subcarrier frequency of kth subcarrier
is time limited pulse
shaping filter. Transmitted symbol is Dk which is assumed to
have zero mean and normalized average symbol energy. Also
we consider that all data symbols are uncorrelated [9, 10] i.e.
% (2.2)
is the complex conjugate of Dk .To ensure the
orthogonality of subcarrier, it is very important to satisfied the
below equation for OFDM system [9, 10]. The subcarrier
1
For maintaining orthogonality between subcarriers, the
minimum required subcarrier frequency spacing is 1/T'. The
received signal at the receiver can be represented as:
(2.5)
In above equation convolution is denoted by
channel impulse response and
noise is represented by w (t) which process with zero mean
and variance NO / 2 per dimension.
3. PULSE SHAPING FILTER
Each carrier in the OFDM spectrum is represented by main
lobe with a number of side lobes having lower amplitudes.
Since peak power is associated with main lobe and ICI power
is associated with side lobes, so the motive of pulse shaping
filter is to increase the width of mai
amplitude of side lobes [9]. Pulse shaping technique is used to
transmit data within a limited
the Inter Symbol Interference(
most commonly used pulse shaping
introduced. These pulse shaping filters are
Nyquist and Square Root Raised Cosine
various shaping pulses is:
a) Raised Cosine Pulse
P45 f sinc
Where ‘α’ is roll-off factor
frequency & time respectively
b) Square Root Raised Cosine Pulse
P':: f sinc
;
<=>
'?@
A
Figure-2: Magnitude Response of
eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
118
In above equation convolution is denoted by ⊗, h (t) is the
channel impulse response and the additive white Gaussian
noise is represented by w (t) which process with zero mean
and variance NO / 2 per dimension.
FILTER
OFDM spectrum is represented by main
lobe with a number of side lobes having lower amplitudes.
Since peak power is associated with main lobe and ICI power
is associated with side lobes, so the motive of pulse shaping
is to increase the width of main lobe and/or reduce the
[9]. Pulse shaping technique is used to
transmit data within a limited bandwidthwhich further reduces
the Inter Symbol Interference(ISI) [11]. In this section some
most commonly used pulse shaping filters have been
pulse shaping filters are Raised Cosine,FIR
Nyquist and Square Root Raised Cosine Filter. ICI power for
ft
B' C
C D .....(3.1)
off factor 0 E α E 1 and f, t are called
frequency & time respectively.
Square Root Raised Cosine Pulse
ft
FG
√
cos 1 2 a 2
'?@ G
J=
;
A
<=>
;
K
D .....(3.2)
Magnitude Response of various filters](https://image.slidesharecdn.com/effectsoffilteringonberperformanceofanofdmsystem-140805014116-phpapp01/85/Effects-of-filtering-on-ber-performance-of-an-ofdm-system-2-320.jpg)
![IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 02 Issue: 09 | Sep-2013, Available @ http://www.ijret.org 119
4. SIMULATION RESULTS
Simulation results have been prepared to demonstrate the
performance enhancement of shaping an OFDM system using
various pulse shaping filters which have been mentioned in
section 3.
Table-1: BER of OFDM communication system under
various filters with varying SNR
0-dB
SNR
04-dB
SNR
08-dB
SNR
12-dB
SNR
Simple
OFDM 0.2956 0.2129 0.1011 0.0209
RC-
OFDM 0.2845 0.2045 0.0887 0.0184
FIR-
Nyquist
OFDM
0.2875 0.2041 0.0967 0.0196
SRRC-
OFDM 0.0764 0.0110 0.0001 0
Some outcomes have been derived on thebasis of Bit Error
Rate (BER) and Impulse Response. In this experimental test
what we come to know is, matched square root raised cosine
pulse shaped OFDM has outperformed.
Figure-3: BER of OFDM with or without Pulse Shaping Filter
Figure-4: Impulse Response of OFDM with different Pulse
Shaping Filter
CONCLUSIONS
In this work, simulation results have been presented to
demonstrate that pulse shaped OFDM significantly enhances
the performance of communication system as compared to
simple OFDM. It can be concluded that if pulse shaping filter
has the spectrum with higher width of main lobe and smaller
amplitude of side lobes, then pulse shaping filter will lead less
ICI and better bandwidth efficiency.
In this paper, we have studied and analyzed the family of
pulse shaping filters. We have evaluated the performance of
these pulse shaping filters with OFDM in terms of BER with
varying SNR values for 16-QAM modulation under AWGN
channel. From this BER analysis it can be concluded that
performance of pulse shaped OFDM is better as compared to
simple OFDM. Simulation results reveal that pulse shaped
OFDMwith Square Root Raised Cosine filterdesign method
has less BER as compared to others so it can be a better option
in contrast to other pulse shaping filter.
REFERENCES
[1]. S. D. Assimonis et. al., “OptimizedBetter than Raised-
Cosine Pulse for Reduced ICI in OFDM Systems”, 17th
International Conference on Telecommunications,
2010.
[2]. M.Palaivelan, S. Anand and S. P. Venkatesan, “PAPR
and ICI Reduction in OFDM Systems using Modified
Raised Cosine Power Pulse Shape”, European Journal
of Scientific Research, ISSN: 1450-216, Vol.72, No.4,
pp. 618-627, 2012.
[3]. Srabani Mohapatra and Susmita Das,“A New Approach
for Performance Improvement of OFDM System Using
Pulse Shaping”, NIT Rourkela, 2009.](https://image.slidesharecdn.com/effectsoffilteringonberperformanceofanofdmsystem-140805014116-phpapp01/85/Effects-of-filtering-on-ber-performance-of-an-ofdm-system-3-320.jpg)
![IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 02 Issue: 09 | Sep-2013, Available @ http://www.ijret.org 120
[4]. S. Aenagandula, A. Kumar, Srinivas K. and M. Nanda,
“ Inter Carrier Interference and Signal to Interference
Ratio of various Pulse Shaping Filters used in OFDM
System with Carrier Frequency Offset”, IJESS
(International Journal of Electronics Signals and
Systems), ISSN: 2231-5969, Vol-1, Iss-3, 2012.
[5]. Ali T. Shaheen, “Design and Simulation of Hartley
based Multi Orthogonal Band OFDM”, International
Journal of Computer Applications,Volume 68, Issue 15,
pp. 10-16, April 2013.
[6]. J. Armstrong, “Analysis of new and existing methods of
reducing inter-carrier interference due to carrier
frequency offset in OFDM,” IEEE Transactions on
Communications, Vol. 47, No. 3, pp. 365-369, March
1999.
[7]. H.M. Mourad, “Reducing ICI in OFDM systems using
a proposed pulse shape”, Wireless Person.
Communications, vol. 40, pp: 41–48, 2006.
[8]. Volkan Kumbasar et al,“ICI reduction in OFDM
systems by using improved sinc power pulse”, Digital
Signal ProcessingAcademic Press, Inc. Orlando, FL,
USA, vol. 17, issue 6, pp. 997–1006, November 2007.
[9]. Srabani Mohapatra and Susmita Das, “Performance
Enhancement of OFDM System with ICI Reduction
Technique”, In Proceedings of the World Congress on
Engineering, Vol. 1, July 2009.
[10]. Nadieh M. Moghaddam and Mohammad Mohebbi, “ICI
Reduction Methods in OFDM Systems", Recent
Advance in Wireless Communication and Networks,
Prof. Jia-Chin Lin (Ed.), ISBN: 978-953-307-274-6,
August 23, 2011.
[11]. P. Tan, N.C. Beaulieu, “Reduced ICI in OFDM systems
using the better than raised-cosine pulse”, IEEE
Commun. Lett. volume 8 issue 3, pp. 135–137, 2004.
[12]. Mahua Pal, “Algorithm for sharpening Raised Cosine
Pulse shaping Digital Filter and Analysis of
Performance Of QAM system when subjected to
Sharpened Raised Cosine Filter”, International Journal
of Scientific and Research (IJSAR) Publications,
Volume 2, Issue 1, ISSN 2250-3153, January 2012.](https://image.slidesharecdn.com/effectsoffilteringonberperformanceofanofdmsystem-140805014116-phpapp01/85/Effects-of-filtering-on-ber-performance-of-an-ofdm-system-4-320.jpg)
Effects of filtering on ber performance of an ofdm system
- 1. IJRET: International Journal of Research in Engineering and Technology __________________________________________________________________________________________ Volume: 02 Issue: 09 | Sep-2013, Available @ EFFECTS OF FILTERING ON 1 M.Tech.Scholar, 2 Principal, A.C.E.T. College In upcoming generations, wireless communication system requires a higher standard in order to provide high quality of services customers. Orthogonal Frequency Division Multiplexing (OFDM) is an systems which can be implemented easily. In this paper when a signal is transmitted over an Additive White Gaussian Noise (AWGN) channel performance of OFDM system with pulse shaping the overall performance of the system in terms of BER. SQRT Raised Cosine for analyzingthe Bit Error Rate ( Index Terms: AWGN, ICI, OFDM, Bit E ----------------------------------------------------------------------- 1. INTRODUCTION High bit error rate(BER) and high bandwidth efficiency the major desiresfor modern communication sy the needs for a variety of new and high quality services developed and delivered to the society [1]. The effect of multipath delay, spread and fading of signals in the wireless environment is usually unavoidable [2], [3]. Extreme fading of the signal amplitude and Inter Symbol Int introduced during transmission through t channel and frequency selectivity of the channel appearing at the receiver side [4], [5] are responsible for a high probability of errors and reduced overall performance of the system. Several methods like adaptive equalization and channel coding have been developed to reduce the above effect. [6], [7]. The orthogonal Frequency division multiplexing (OFDM) a multi carrier system can be thought of as a solution and is used in several applications such as asymmetric digital subscriber lines (ADSL), a system that makes high bit-rates possible over twisted-pair copper wires [8], [9], it has also been accepted for several wireless LAN standards, as well as a number of mobile multimedia applications [1], [10] and protocols like IEEE 802.11a standard, terrestrial digital video broadcasting (DVB T) and digital audio broadcasting (DAB) [11]. The purpose of this paper is to investigate how OFDM performs in an Additive White Gaussian Noise (AWGN) ch pulse shaping filter like Raised cosine, FIR Nyquist and Matched SQRT Raised Cosine. In this channel one path between transmitter and receiver and attenuation and noise is considered. In this paper, we define the simulation methodology of OFDM in section 2 and simulate the OFDM system using Matlab. The mathematical model and theoretically simulated constellation diagrams for various pulse shapes are presented and a procedure for symbol IJRET: International Journal of Research in Engineering and Technology eISSN: 2319 __________________________________________________________________________________________ 2013, Available @ http://www.ijret.org S OF FILTERING ON BER PERFORMANCE OF AN OFDM SYSTEM Navjot Kaur1 , V.K. Banga2 College, Punjab, India, navjosan2011@gmail.com Abstract wireless communication system requires a higher standard in order to provide high quality of services . Orthogonal Frequency Division Multiplexing (OFDM) is an efficient modulation systems which can be implemented easily. In this paper, an effort has been made to analyze how well an OFDM system transmitted over an Additive White Gaussian Noise (AWGN) channel using 16 QAM pulse shaping filters are also evaluated and results reveal that ce of the system in terms of BER. We use Different pulse shaping filters such as the Bit Error Rate (BER) performance. Error Rate. -----------------------------------------------------------------------***-------------------------------------------------------------------- andwidth efficiency are modern communication systems to satisfy f new and high quality services developed and delivered to the society [1]. The effect of multipath delay, spread and fading of signals in the wireless environment is usually unavoidable [2], [3]. Extreme fading of the signal amplitude and Inter Symbol Interference (ISI) transmission through the conventional frequency selectivity of the channel appearing at the receiver side [4], [5] are responsible for a high probability of errors and reduced overall performance of the system. Several methods like adaptive equalization and channel coding have been developed to reduce the above effect. [6], [7]. The orthogonal Frequency division multiplexing (OFDM) a multi carrier system can be thought of as a solution and is used in lications such as asymmetric digital subscriber rates possible over pair copper wires [8], [9], it has also been accepted for several wireless LAN standards, as well as a number of mobile ations [1], [10] and protocols like IEEE 802.11a standard, terrestrial digital video broadcasting (DVB- T) and digital audio broadcasting (DAB) [11]. The purpose of this paper is to investigate how OFDM performs in an e (AWGN) channel for different Raised cosine, FIR Nyquist and . In this channel there is only receiver and a constant attenuation and noise is considered. In this paper, we define the simulation methodology of OFDM in section 2 and simulate the OFDM system using Matlab. The mathematical model and theoretically simulated constellation diagrams for shapes are presented and a procedure for symbol error rate is derived and finally a for various pulse shaping filter presented. 2. SYSTEM MODEL Figure 1(a) and 1(b) show communication system with various this communication system binary information. The high speed serial data stream is split up into a set of low speed sub streams and modulated onto the orthogonal carriers through Inverse Fast Fourier (IFFT) [2]. Figure-1(a): Transmitter of eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ 117 BER PERFORMANCE OF AN OFDM navjosan2011@gmail.com, vijaykumar.banga@gmail.com wireless communication system requires a higher standard in order to provide high quality of services to modulation technique of forthcoming wireless made to analyze how well an OFDM system can perform using 16 QAM modulation techniques. The filters are also evaluated and results reveal that the pulse shaped OFDM improve such asRaised cosine, FIR Nyquist and -------------------------------------------------------------------- r rate is derived and finally a BER simulation of OFDM ulse shaping filters at different SNR value is Figure 1(a) and 1(b) show the structure of a typicalOFDM communication system with various pulse shaping filters. In system, QAMconstellation is used to map binary information. The high speed serial data stream is split up into a set of low speed sub streams and modulated onto the arriers through Inverse Fast Fourier transform Transmitter of a pulse shaped OFDM system
- 2. IJRET: International Journal of Research in Engineering and Technology __________________________________________________________________________________________ Volume: 02 Issue: 09 | Sep-2013, Available @ Figure-1(b): Receiver of a pulse shaped OFDM System OFDM with pulse-shaping filter can be representedas: s t e ∑ D p t e ... Where j=√ 1 , Number of subcarrier is N, Carrier frequency of OFDM system isf , Subcarrier frequency of kth subcarrier is, f and here k = 0, 1… N – 1, and p t is time limited pulse shaping filter. Transmitted symbol is Dk which is assumed to have zero mean and normalized average symbol energy. Also we consider that all data symbols are uncorrelated [9, 10] i.e. E [D D∗ ] = 1, k m 0, k $ m %... (2.2) where m=0, 1,......, N-1 Where D∗ is the complex conjugate of Dk .To ensure the orthogonality of subcarrier, it is very important to satisfied the below equation for OFDM system [9, 10]. The subcarrier frequency is f k T' … 2.3 wherek 0, 1, . . . . . . . . . , N f f k m T' … 2.4 where k m 0,1, … … . , N 1 For maintaining orthogonality between subcarriers, the minimum required subcarrier frequency spacing is 1/ received signal at the receiver can be represented as: r t s t ⊗ h t 2 w t ... (2.5 IJRET: International Journal of Research in Engineering and Technology eISSN: 2319 __________________________________________________________________________________________ 2013, Available @ http://www.ijret.org OFDM System representedas: ... (2.1) , Number of subcarrier is N, Carrier frequency , Subcarrier frequency of kth subcarrier is time limited pulse shaping filter. Transmitted symbol is Dk which is assumed to have zero mean and normalized average symbol energy. Also we consider that all data symbols are uncorrelated [9, 10] i.e. % (2.2) is the complex conjugate of Dk .To ensure the orthogonality of subcarrier, it is very important to satisfied the below equation for OFDM system [9, 10]. The subcarrier 1 For maintaining orthogonality between subcarriers, the minimum required subcarrier frequency spacing is 1/T'. The received signal at the receiver can be represented as: (2.5) In above equation convolution is denoted by channel impulse response and noise is represented by w (t) which process with zero mean and variance NO / 2 per dimension. 3. PULSE SHAPING FILTER Each carrier in the OFDM spectrum is represented by main lobe with a number of side lobes having lower amplitudes. Since peak power is associated with main lobe and ICI power is associated with side lobes, so the motive of pulse shaping filter is to increase the width of mai amplitude of side lobes [9]. Pulse shaping technique is used to transmit data within a limited the Inter Symbol Interference( most commonly used pulse shaping introduced. These pulse shaping filters are Nyquist and Square Root Raised Cosine various shaping pulses is: a) Raised Cosine Pulse P45 f sinc Where ‘α’ is roll-off factor frequency & time respectively b) Square Root Raised Cosine Pulse P':: f sinc ; <=> '?@ A Figure-2: Magnitude Response of eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ 118 In above equation convolution is denoted by ⊗, h (t) is the channel impulse response and the additive white Gaussian noise is represented by w (t) which process with zero mean and variance NO / 2 per dimension. FILTER OFDM spectrum is represented by main lobe with a number of side lobes having lower amplitudes. Since peak power is associated with main lobe and ICI power is associated with side lobes, so the motive of pulse shaping is to increase the width of main lobe and/or reduce the [9]. Pulse shaping technique is used to transmit data within a limited bandwidthwhich further reduces the Inter Symbol Interference(ISI) [11]. In this section some most commonly used pulse shaping filters have been pulse shaping filters are Raised Cosine,FIR Nyquist and Square Root Raised Cosine Filter. ICI power for ft B' C C D .....(3.1) off factor 0 E α E 1 and f, t are called frequency & time respectively. Square Root Raised Cosine Pulse ft FG √ cos 1 2 a 2 '?@ G J= ; A <=> ; K D .....(3.2) Magnitude Response of various filters
- 3. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 02 Issue: 09 | Sep-2013, Available @ http://www.ijret.org 119 4. SIMULATION RESULTS Simulation results have been prepared to demonstrate the performance enhancement of shaping an OFDM system using various pulse shaping filters which have been mentioned in section 3. Table-1: BER of OFDM communication system under various filters with varying SNR 0-dB SNR 04-dB SNR 08-dB SNR 12-dB SNR Simple OFDM 0.2956 0.2129 0.1011 0.0209 RC- OFDM 0.2845 0.2045 0.0887 0.0184 FIR- Nyquist OFDM 0.2875 0.2041 0.0967 0.0196 SRRC- OFDM 0.0764 0.0110 0.0001 0 Some outcomes have been derived on thebasis of Bit Error Rate (BER) and Impulse Response. In this experimental test what we come to know is, matched square root raised cosine pulse shaped OFDM has outperformed. Figure-3: BER of OFDM with or without Pulse Shaping Filter Figure-4: Impulse Response of OFDM with different Pulse Shaping Filter CONCLUSIONS In this work, simulation results have been presented to demonstrate that pulse shaped OFDM significantly enhances the performance of communication system as compared to simple OFDM. It can be concluded that if pulse shaping filter has the spectrum with higher width of main lobe and smaller amplitude of side lobes, then pulse shaping filter will lead less ICI and better bandwidth efficiency. In this paper, we have studied and analyzed the family of pulse shaping filters. We have evaluated the performance of these pulse shaping filters with OFDM in terms of BER with varying SNR values for 16-QAM modulation under AWGN channel. From this BER analysis it can be concluded that performance of pulse shaped OFDM is better as compared to simple OFDM. Simulation results reveal that pulse shaped OFDMwith Square Root Raised Cosine filterdesign method has less BER as compared to others so it can be a better option in contrast to other pulse shaping filter. REFERENCES [1]. S. D. Assimonis et. al., “OptimizedBetter than Raised- Cosine Pulse for Reduced ICI in OFDM Systems”, 17th International Conference on Telecommunications, 2010. [2]. M.Palaivelan, S. Anand and S. P. Venkatesan, “PAPR and ICI Reduction in OFDM Systems using Modified Raised Cosine Power Pulse Shape”, European Journal of Scientific Research, ISSN: 1450-216, Vol.72, No.4, pp. 618-627, 2012. [3]. Srabani Mohapatra and Susmita Das,“A New Approach for Performance Improvement of OFDM System Using Pulse Shaping”, NIT Rourkela, 2009.
- 4. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 02 Issue: 09 | Sep-2013, Available @ http://www.ijret.org 120 [4]. S. Aenagandula, A. Kumar, Srinivas K. and M. Nanda, “ Inter Carrier Interference and Signal to Interference Ratio of various Pulse Shaping Filters used in OFDM System with Carrier Frequency Offset”, IJESS (International Journal of Electronics Signals and Systems), ISSN: 2231-5969, Vol-1, Iss-3, 2012. [5]. Ali T. Shaheen, “Design and Simulation of Hartley based Multi Orthogonal Band OFDM”, International Journal of Computer Applications,Volume 68, Issue 15, pp. 10-16, April 2013. [6]. J. Armstrong, “Analysis of new and existing methods of reducing inter-carrier interference due to carrier frequency offset in OFDM,” IEEE Transactions on Communications, Vol. 47, No. 3, pp. 365-369, March 1999. [7]. H.M. Mourad, “Reducing ICI in OFDM systems using a proposed pulse shape”, Wireless Person. Communications, vol. 40, pp: 41–48, 2006. [8]. Volkan Kumbasar et al,“ICI reduction in OFDM systems by using improved sinc power pulse”, Digital Signal ProcessingAcademic Press, Inc. Orlando, FL, USA, vol. 17, issue 6, pp. 997–1006, November 2007. [9]. Srabani Mohapatra and Susmita Das, “Performance Enhancement of OFDM System with ICI Reduction Technique”, In Proceedings of the World Congress on Engineering, Vol. 1, July 2009. [10]. Nadieh M. Moghaddam and Mohammad Mohebbi, “ICI Reduction Methods in OFDM Systems", Recent Advance in Wireless Communication and Networks, Prof. Jia-Chin Lin (Ed.), ISBN: 978-953-307-274-6, August 23, 2011. [11]. P. Tan, N.C. Beaulieu, “Reduced ICI in OFDM systems using the better than raised-cosine pulse”, IEEE Commun. Lett. volume 8 issue 3, pp. 135–137, 2004. [12]. Mahua Pal, “Algorithm for sharpening Raised Cosine Pulse shaping Digital Filter and Analysis of Performance Of QAM system when subjected to Sharpened Raised Cosine Filter”, International Journal of Scientific and Research (IJSAR) Publications, Volume 2, Issue 1, ISSN 2250-3153, January 2012.