In this modern era, Orthogonal Frequency Division Multiplexing (OFDM) has been proved to be an explicit promising technique for wired and wireless systems because of its several advantages like high spectral efficiency, robustness against frequency selective fading, relatively simple receiver implementation etc. Besides having a number of advantages OFDM suffers from few disadvantages like high Peak to Average Power Ratio (PAPR), Intercarrier Interference (ICI), Intersymbol Interference (ISI) etc. These detrimental effects, if not compensated properly and timely, can result in system performance degradation. This paper mainly concentrates on reduction of PAPR.A comparisons have been made between various precoding techniques against conventional OFDM.
A Hybrid PAPR Reduction Scheme for OFDM System ijmnct
Orthogonal frequency division multiplexing (OFDM) i
s considered as most efficient technique for future
wireless communication systems due to its higher sp
ectral bandwidth efficiency, robustness to frequenc
y
selective fading channels, etc. However, the succes
sful implementation of the OFDM system necessitates
several difficulties. The biggest disadvantage to w
ork with OFDM system is its high peak-to-average po
wer
ratio PAPR leadsto severe inter carrier interferenc
e, out-of-band radiation, and poor bit error rate
performance due to the nonlinearity of the high pow
er amplifier. In this paper, a novel hybrid techniq
ue is
proposed to reduce PAPR further and comparison has
been done with conventional techniques as well.
Simulated results are presentedconfirm theoretical
results.MATLAB 7.5 is used to simulate the results
for system parametersconsidered.
Performance improvement for papr reduction in lte downlink system with ellipt...IJCNCJournal
This paper is concerned with the performance improvement of PAPR reduction of orthogonal frequency division multiplexing (OFDM) signal using amplitude clipping & filtering based design. Note that OFDM is one of the well adept multi-carrier multiplexing transmission scheme which has been implemented in long term evolution (LTE) downlink. Nonetheless peak to average power ratio (PAPR) is the more rattling problem with OFDM, consequently in this paper a reduction procedure of the PAPR by using amplitude clipping and filtering is proposed. Here we used IIR bandpass elliptic filter after amplitude clipping to
reduce the PAPR. The performance of the system in terms of bit error rate (BER) is also canvased as a new
filter based clipping method. Our results show that the proposed methodology of clipping method with the
IIR elliptic band pass filter significantly reduces the PAPR value.
SLM-PTS BASED PAPR REDUCTION TECHNIQUES IN OFDM SYSTEMHariniChaganti1
Signals, which were initially sent in the analog domain, are being sent more and more in the digital domain these days. For better transmission, even single–carrier waves are being replaced by multi–carriers. Multi-carrier
systems like OFDM are now – a – days being implemented commonly. In the OFDM system,
orthogonally placed subcarriers are used to carry the data from the transmitter end to the receiver end. The presence of a guard band in this system deals with the problem of ISI and noise is minimized by a larger number of sub–carriers. But the large Peak– to –Average Power Ratio of these signal have some undesirable effects on the system. The Peak-to-Average Power Ratio is the ratio between the maximum power and average power of a complex passband signal. It causes many disadvantages like band-in and band-out variation, low signal to quantization noise ratio, low efficiency of power amplifier, etc. Hence, it is necessary to reduce PAPR in OFDM for its efficient use.
In this project, the main objective is to study the basics of an OFDM System and analyze and
simulate various methods such as clipping and filtering, selected mapping, Partial transmit sequence
to reduce the PAPR in the system and compare these techniques with and without PAPR reduction to
obtain an efficient technique so that this system can be used more commonly and effectively.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Hybrid approach to solve the problem of papr in ofdm signal a surveyeSAT Journals
“Orthogonal frequency division multiplexing
method used to achieve the today’s need of wireless communication
3GPP Association for the use of LTE. The
higher data rate, higher bit rate, mitigated delay spread, lower multipath distortion,
OFDM system has few major issues associated with
ratio (PAPR)” associated with the signal.
interleaved OFDM, selective mapping (SLM)
windowing, clipping, filtering, tone rejection(TR), tone injection(TI), compandin
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
PAPR Reduction in OFDM using Active and Non-Active ChannelsIOSR Journals
Abstract : According to the request of advance communication field there should be high data rate in addition to both power efficiency and lower bit error rate. This request of high data rate can be achieved by the multi carrier modulation scheme using the OFDM technique. But the great drawback of the OFDM technique is its high peak to average power ratio (PAPR). High PAPR reduces OFDM signals by driving the analog amplifier to work in the nonlinear region, changing this way the signal and making the amplifier to consume more power. To reduce the PAPR methods exist which adjust or present new signals to battle large signal peaks. The methods which use data carrying channels are called active channel methods and which use redundant channel are called non active channel methods. This work deals with reduction of the PAPR of OFDM signal using both Active and Non Active Channels. Clipping technique has been applied to active channels and Tone reservation has been applied to Non Active Channels. By using both channels we can get considerable reduction in PAPR. Keywords:Orthogonal Frequency Division Multiplexing (OFDM), Peak to Average Power Ratio (PAPR), Power Amplifier (PA).
A Hybrid PAPR Reduction Scheme for OFDM System ijmnct
Orthogonal frequency division multiplexing (OFDM) i
s considered as most efficient technique for future
wireless communication systems due to its higher sp
ectral bandwidth efficiency, robustness to frequenc
y
selective fading channels, etc. However, the succes
sful implementation of the OFDM system necessitates
several difficulties. The biggest disadvantage to w
ork with OFDM system is its high peak-to-average po
wer
ratio PAPR leadsto severe inter carrier interferenc
e, out-of-band radiation, and poor bit error rate
performance due to the nonlinearity of the high pow
er amplifier. In this paper, a novel hybrid techniq
ue is
proposed to reduce PAPR further and comparison has
been done with conventional techniques as well.
Simulated results are presentedconfirm theoretical
results.MATLAB 7.5 is used to simulate the results
for system parametersconsidered.
Performance improvement for papr reduction in lte downlink system with ellipt...IJCNCJournal
This paper is concerned with the performance improvement of PAPR reduction of orthogonal frequency division multiplexing (OFDM) signal using amplitude clipping & filtering based design. Note that OFDM is one of the well adept multi-carrier multiplexing transmission scheme which has been implemented in long term evolution (LTE) downlink. Nonetheless peak to average power ratio (PAPR) is the more rattling problem with OFDM, consequently in this paper a reduction procedure of the PAPR by using amplitude clipping and filtering is proposed. Here we used IIR bandpass elliptic filter after amplitude clipping to
reduce the PAPR. The performance of the system in terms of bit error rate (BER) is also canvased as a new
filter based clipping method. Our results show that the proposed methodology of clipping method with the
IIR elliptic band pass filter significantly reduces the PAPR value.
SLM-PTS BASED PAPR REDUCTION TECHNIQUES IN OFDM SYSTEMHariniChaganti1
Signals, which were initially sent in the analog domain, are being sent more and more in the digital domain these days. For better transmission, even single–carrier waves are being replaced by multi–carriers. Multi-carrier
systems like OFDM are now – a – days being implemented commonly. In the OFDM system,
orthogonally placed subcarriers are used to carry the data from the transmitter end to the receiver end. The presence of a guard band in this system deals with the problem of ISI and noise is minimized by a larger number of sub–carriers. But the large Peak– to –Average Power Ratio of these signal have some undesirable effects on the system. The Peak-to-Average Power Ratio is the ratio between the maximum power and average power of a complex passband signal. It causes many disadvantages like band-in and band-out variation, low signal to quantization noise ratio, low efficiency of power amplifier, etc. Hence, it is necessary to reduce PAPR in OFDM for its efficient use.
In this project, the main objective is to study the basics of an OFDM System and analyze and
simulate various methods such as clipping and filtering, selected mapping, Partial transmit sequence
to reduce the PAPR in the system and compare these techniques with and without PAPR reduction to
obtain an efficient technique so that this system can be used more commonly and effectively.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Hybrid approach to solve the problem of papr in ofdm signal a surveyeSAT Journals
“Orthogonal frequency division multiplexing
method used to achieve the today’s need of wireless communication
3GPP Association for the use of LTE. The
higher data rate, higher bit rate, mitigated delay spread, lower multipath distortion,
OFDM system has few major issues associated with
ratio (PAPR)” associated with the signal.
interleaved OFDM, selective mapping (SLM)
windowing, clipping, filtering, tone rejection(TR), tone injection(TI), compandin
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
PAPR Reduction in OFDM using Active and Non-Active ChannelsIOSR Journals
Abstract : According to the request of advance communication field there should be high data rate in addition to both power efficiency and lower bit error rate. This request of high data rate can be achieved by the multi carrier modulation scheme using the OFDM technique. But the great drawback of the OFDM technique is its high peak to average power ratio (PAPR). High PAPR reduces OFDM signals by driving the analog amplifier to work in the nonlinear region, changing this way the signal and making the amplifier to consume more power. To reduce the PAPR methods exist which adjust or present new signals to battle large signal peaks. The methods which use data carrying channels are called active channel methods and which use redundant channel are called non active channel methods. This work deals with reduction of the PAPR of OFDM signal using both Active and Non Active Channels. Clipping technique has been applied to active channels and Tone reservation has been applied to Non Active Channels. By using both channels we can get considerable reduction in PAPR. Keywords:Orthogonal Frequency Division Multiplexing (OFDM), Peak to Average Power Ratio (PAPR), Power Amplifier (PA).
A low complexity partial transmit sequence scheme for better papr reduction i...eSAT Journals
Abstract The main drawback of OFDM system is the high Peak to Average Power Ratio (PAPR) of the transmitted signals. Partial transmit sequence scheme is a promising algorithm to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM). The Partial Transmit Sequence (PTS) consist of several inverse fast Fourier transform (IFFT) operations and complicated calculations to obtain optimum phase sequence which results in increasing the computational complexity of PTS. A phase sequence applied to the PTS Scheme reduces its complexity but at the expense of slight degradation in PAPR reduction. In this paper, for further reduction of PAPR the peak clipping of the OFDM signal is introduced along with the PTS with new phase sequence scheme. Since clipping is one of the simplest techniques of PAPR reduction, it does not increase the complexity of the system much and a better PAPR reduction is obtained with the combined effect of clipping and PTS with New Phase Sequence. But the clipping technique introduce some distortion in the signal, however peak clipping of signal below a particular threshold can maintain the BER in the tolerable range. The clipping threshold selected will be different for different OFDM systems. Index Terms: OFDM, Peak to Average Power Ratio (PAPR), Partial Transmit Sequence (PTS), Clipping.
Low Peak to Average Power Ratio and High Spectral Efficiency Using Selective ...theijes
A low complexity peak to average power ratio (PAPR) reduction scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed. All pass filters technique used PAPR is reduction but small amount of reduction, So use Selective Mapping (SLM) technique reduce PAPR and SNR increases.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Comparative performance analysis of different modulation techniques for papr ...IJCNCJournal
One of the most important multi-carrier tran
smission techniques used in the latest wireless com
munication
arena is known as Orthogonal Frequency Division Mul
tiplexing (OFDM). It has several characteristics
such as providing greater immunity to multipath fad
ing & impulse noise, eliminating Inter Symbol
Interference (ISI) & Inter Carrier Interference (IC
I) using a guard interval known as Cyclic Prefix (C
P). A
regular difficulty of OFDM signal is high peak to a
verage power ratio (PAPR) which is defined as the r
atio
of the peak power to the average power of OFDM Sign
al. An improved design of amplitude clipping &
filtering technique of us previously reduced signif
icant amount of PAPR with slightly increase bit err
or rate
(BER) compare to an existing method in case of Quad
rature Phase Shift Keying (QPSK) & Quadrature
Amplitude Modulation (QAM). This paper investigates
a comparative performance analysis of the differen
t
higher order modulation techniques on that design.
PAPR REDUCTION OF OFDM SIGNAL BY USING COMBINED HADAMARD AND MODIFIED MEU-LAW...IJCNCJournal
Orthogonal frequency division multiplexing (OFDM) is a technique which gives high quality of service (QOS) to the users by mitigating the fading signals as well as high data rates in multimedia services. However, the peak-to-average power ratio (PAPR) is a technical challenge that reduces the efficiency of RF power amplifiers. In this paper, we propose the combined Hadamard transform and modified meu-law companding transform method in order to lessen the effects of the peak-to-average power ratio of the
OFDM signal. Simulation results show that the proposed scheme reduces PAPR compared to other companding techniques as well as the Hadamard transform technique when used on its own.
Performance of Multiple symbol representation with clipping scheme for PAPR r...ijsrd.com
OFDM is one of the multicarrier modulation technique used in various communication systems. The major problem one faces while implementing this system is the high peak to average power .For an efficient OFDM system this PAPR should be low. In this paper a hybrid PAPR (peak to average power ratio) reduction technique for the OFDM (orthogonal frequency division multiplexing) signal which combines a multiple symbol representations method with a signal clipping method is proposed. In multiple symbol representations alternative signaling points are used to represent one symbol and PAPR is further reduced with the clipping scheme. The performance of the hybrid scheme is compared with the partial transmit sequence which is one of the other PAPR reduction scheme. In partial transmit sequence the input data is divided in to disjoint blocks transformed in to time domain sequence and rotated by phase factors. Theoretical analysis and simulation results validate that the proposed scheme has the ability to provide large PAPR reduction, low bit error rate. Performance analysis is also done with the partial transmit sequence scheme.
AN OVERVIEW OF PEAK-TO-AVERAGE POWER RATIO REDUCTION TECHNIQUES FOR OFDM SIGNALSijmnct
OFDM (Orthogonal Frequency Division Multiplexing) has been widely adopted for high data rate wireless
communication systems due to its advantages such as extraordinary spectral efficiency, robustness to
channel fading and better QoS (Quality of Service) performance for multiple users. However, some
challenging issues are still unresolved in OFDM systems. One of the issues is the high PAPR (peak-toaverage
power ratio), which results in nonlinearity in power amplifiers, and causes out of band radiation
and in band distortion. This paper reviews some conventional PAPR reduction techniques and their
modifications to achieve better PAPR performance. Advantages and disadvantages of each technique are
discussed in detail. And comparisons between different techniques are also presented. Finally, this paper
makes a prospect forecast about the direction for further researches in the area of PAPR reduction for
OFDM signals
An Overview : Peak to Average Power Ratio (PAPR) in OFDM system using some ne...Z AL Hashemi
An Overview : Peak to Average Power Ratio (PAPR) in OFDM system using some new PAPR techniques (with matlab code)
By
Zainab Saad Hadi AL-Hashemi
A graduate of University of Baghdad, College of Engineering Electronic & Communications Engineering Department
Peak-to-Average Power Ratio Reduction in NC-OFDM based Cognitive Radio.CSCJournals
This paper presents a novel technique for reducing the peak-to-average power ratio (PAPR) in non-contiguous bands spectrum of Orthogonal Frequency Division Multiplexing (OFDM) based Cognitive Radio (CR). The proposed system exposed to carry the past channel information and the spectrum sensing to utilize the radio spectrum as well as achieving an appropriate PAPR reduction and maintaining end-to-end throughput performance by using a set of approaches in the current CR environment. The simulation results for PAPR reduction has shown that higher constellation modulation schemes are better compared to lower constellation modulation schemes.
Computationally Efficient Algorithm for Reducing PAPR in OFDM using Null Subc...idescitation
A new algorithm is proposed which is used with
existing null-data subcarrier switching method of Peak to
Average Power Ratio (PAPR) reduction in OFDM to lower the
computational complexity. This proposed algorithm is very
simple and achieves significant reduction in computational
overhead without sacrificing PAPR reduction capability of
null-data subcarrier switching method. The proposed
algorithm is compatible with the current commercial systems
and it can be used with other existing algorithms to reduce
the computational overhead further. The proposed algorithm
is very useful in delay sensitive services. The effectiveness of
the proposed algorithm is demonstrated by presenting
simulation results of PAPR and computational time
requirement.
A low complexity partial transmit sequence scheme for better papr reduction i...eSAT Journals
Abstract The main drawback of OFDM system is the high Peak to Average Power Ratio (PAPR) of the transmitted signals. Partial transmit sequence scheme is a promising algorithm to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM). The Partial Transmit Sequence (PTS) consist of several inverse fast Fourier transform (IFFT) operations and complicated calculations to obtain optimum phase sequence which results in increasing the computational complexity of PTS. A phase sequence applied to the PTS Scheme reduces its complexity but at the expense of slight degradation in PAPR reduction. In this paper, for further reduction of PAPR the peak clipping of the OFDM signal is introduced along with the PTS with new phase sequence scheme. Since clipping is one of the simplest techniques of PAPR reduction, it does not increase the complexity of the system much and a better PAPR reduction is obtained with the combined effect of clipping and PTS with New Phase Sequence. But the clipping technique introduce some distortion in the signal, however peak clipping of signal below a particular threshold can maintain the BER in the tolerable range. The clipping threshold selected will be different for different OFDM systems. Index Terms: OFDM, Peak to Average Power Ratio (PAPR), Partial Transmit Sequence (PTS), Clipping.
Low Peak to Average Power Ratio and High Spectral Efficiency Using Selective ...theijes
A low complexity peak to average power ratio (PAPR) reduction scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed. All pass filters technique used PAPR is reduction but small amount of reduction, So use Selective Mapping (SLM) technique reduce PAPR and SNR increases.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Comparative performance analysis of different modulation techniques for papr ...IJCNCJournal
One of the most important multi-carrier tran
smission techniques used in the latest wireless com
munication
arena is known as Orthogonal Frequency Division Mul
tiplexing (OFDM). It has several characteristics
such as providing greater immunity to multipath fad
ing & impulse noise, eliminating Inter Symbol
Interference (ISI) & Inter Carrier Interference (IC
I) using a guard interval known as Cyclic Prefix (C
P). A
regular difficulty of OFDM signal is high peak to a
verage power ratio (PAPR) which is defined as the r
atio
of the peak power to the average power of OFDM Sign
al. An improved design of amplitude clipping &
filtering technique of us previously reduced signif
icant amount of PAPR with slightly increase bit err
or rate
(BER) compare to an existing method in case of Quad
rature Phase Shift Keying (QPSK) & Quadrature
Amplitude Modulation (QAM). This paper investigates
a comparative performance analysis of the differen
t
higher order modulation techniques on that design.
PAPR REDUCTION OF OFDM SIGNAL BY USING COMBINED HADAMARD AND MODIFIED MEU-LAW...IJCNCJournal
Orthogonal frequency division multiplexing (OFDM) is a technique which gives high quality of service (QOS) to the users by mitigating the fading signals as well as high data rates in multimedia services. However, the peak-to-average power ratio (PAPR) is a technical challenge that reduces the efficiency of RF power amplifiers. In this paper, we propose the combined Hadamard transform and modified meu-law companding transform method in order to lessen the effects of the peak-to-average power ratio of the
OFDM signal. Simulation results show that the proposed scheme reduces PAPR compared to other companding techniques as well as the Hadamard transform technique when used on its own.
Performance of Multiple symbol representation with clipping scheme for PAPR r...ijsrd.com
OFDM is one of the multicarrier modulation technique used in various communication systems. The major problem one faces while implementing this system is the high peak to average power .For an efficient OFDM system this PAPR should be low. In this paper a hybrid PAPR (peak to average power ratio) reduction technique for the OFDM (orthogonal frequency division multiplexing) signal which combines a multiple symbol representations method with a signal clipping method is proposed. In multiple symbol representations alternative signaling points are used to represent one symbol and PAPR is further reduced with the clipping scheme. The performance of the hybrid scheme is compared with the partial transmit sequence which is one of the other PAPR reduction scheme. In partial transmit sequence the input data is divided in to disjoint blocks transformed in to time domain sequence and rotated by phase factors. Theoretical analysis and simulation results validate that the proposed scheme has the ability to provide large PAPR reduction, low bit error rate. Performance analysis is also done with the partial transmit sequence scheme.
AN OVERVIEW OF PEAK-TO-AVERAGE POWER RATIO REDUCTION TECHNIQUES FOR OFDM SIGNALSijmnct
OFDM (Orthogonal Frequency Division Multiplexing) has been widely adopted for high data rate wireless
communication systems due to its advantages such as extraordinary spectral efficiency, robustness to
channel fading and better QoS (Quality of Service) performance for multiple users. However, some
challenging issues are still unresolved in OFDM systems. One of the issues is the high PAPR (peak-toaverage
power ratio), which results in nonlinearity in power amplifiers, and causes out of band radiation
and in band distortion. This paper reviews some conventional PAPR reduction techniques and their
modifications to achieve better PAPR performance. Advantages and disadvantages of each technique are
discussed in detail. And comparisons between different techniques are also presented. Finally, this paper
makes a prospect forecast about the direction for further researches in the area of PAPR reduction for
OFDM signals
An Overview : Peak to Average Power Ratio (PAPR) in OFDM system using some ne...Z AL Hashemi
An Overview : Peak to Average Power Ratio (PAPR) in OFDM system using some new PAPR techniques (with matlab code)
By
Zainab Saad Hadi AL-Hashemi
A graduate of University of Baghdad, College of Engineering Electronic & Communications Engineering Department
Peak-to-Average Power Ratio Reduction in NC-OFDM based Cognitive Radio.CSCJournals
This paper presents a novel technique for reducing the peak-to-average power ratio (PAPR) in non-contiguous bands spectrum of Orthogonal Frequency Division Multiplexing (OFDM) based Cognitive Radio (CR). The proposed system exposed to carry the past channel information and the spectrum sensing to utilize the radio spectrum as well as achieving an appropriate PAPR reduction and maintaining end-to-end throughput performance by using a set of approaches in the current CR environment. The simulation results for PAPR reduction has shown that higher constellation modulation schemes are better compared to lower constellation modulation schemes.
Computationally Efficient Algorithm for Reducing PAPR in OFDM using Null Subc...idescitation
A new algorithm is proposed which is used with
existing null-data subcarrier switching method of Peak to
Average Power Ratio (PAPR) reduction in OFDM to lower the
computational complexity. This proposed algorithm is very
simple and achieves significant reduction in computational
overhead without sacrificing PAPR reduction capability of
null-data subcarrier switching method. The proposed
algorithm is compatible with the current commercial systems
and it can be used with other existing algorithms to reduce
the computational overhead further. The proposed algorithm
is very useful in delay sensitive services. The effectiveness of
the proposed algorithm is demonstrated by presenting
simulation results of PAPR and computational time
requirement.
A Modified Design Of Acf Operation For Reducing Papr Of Ofdm Signaljosephjonse
Next generation wireless communication technology long term evolution (LTE) has implemented orthogonal frequency division multiplexing (OFDM) technique as a strong candidate for radio access systems. It has several attributes such as providing robustness to multipath fading & impulse noise, eliminating intersymbol interference (ISI), inter carrier interference (ICI) & the need for equalizers. The major challenging issue of OFDM technique is the high peak to average power ratio (PAPR) which is defined as the ratio of the peak power to the average power of the OFDM signal. A trade-off is necessary for reducing PAPR with increasing bit error rate (BER), computational complexity or data rate loss etc. In this paper, a moderately modified design of amplitude clipping & filtering operation (ACF) is proposed and implemented which shows the significant improvement in case of PAPR reduction for both quadrature phase shift keying (QPSK) & quadrature amplitude modulation (QAM) while increasing slight BER match up to to an existing method.
A modified design of acf operation for reducing papr of ofdm signalijngnjournal
Next generation wireless communication technology long term evolution (LTE) has implemented
orthogonal frequency division multiplexing (OFDM) technique as a strong candidate for radio access
systems. It has several attributes such as providing robustness to multipath fading & impulse noise,
eliminating intersymbol interference (ISI), inter carrier interference (ICI) & the need for equalizers. The
major challenging issue of OFDM technique is the high peak to average power ratio (PAPR) which is
defined as the ratio of the peak power to the average power of the OFDM signal. A trade-off is
necessary for reducing PAPR with increasing bit error rate (BER), computational complexity or data rate
loss etc. In this paper, a moderately modified design of amplitude clipping & filtering operation (ACF) is
proposed and implemented which shows the significant improvement in case of PAPR reduction for both
quadrature phase shift keying (QPSK) & quadrature amplitude modulation (QAM) while increasing slight
BER match up to to an existing method.
Bessel Companding Transform for reducing PAPR, OBI and BER in OFDM SystemsIOSR Journals
Abstract : Orthogonal Frequency division multiplexing (OFDM) is a very popular technique in wireless communications which provides excellent robustness to channel fading and immune to interference. OFDM is one of a popular modulation technique for transmitting large amounts of digital data over radio carriers. One of the major problems that had been observed in this is the Peak-To Average power Ratio (PAPR). PAPR is a distortion that had occurred due to large number of sub carriers that are used in OFDM for modulating the digital data. Many techniques were available to reduce the PAPR in OFDM systems, among them the companding technique can be used to enhance the OFDM transmission performance by decreasing the PAPR effectively and hence BER. Here we proposed “Bessel Companding Algorithm” to reduce this significant drawback in OFDM Systems. Keywords : Orthogonal Frequency Division Multiplexing (OFDM), peak to average power ratio (PAPR), bit error rate (BER), Out Band Interference (OBI), Additive White Gaussian Noise (AWGN), Bessel Companding Algorithm, Quadrature Amplitude Modulation (QAM) and Multi Carrier Modulation (MCM).
Performance Evaluation of PAPR Reduction with SER and BER by Modified Clippin...ijcsse
This paper work focuses on performance analysis of PAPR reduction of orthogonal frequency division multiplexing (OFDM) using amplitude clipping & filtering based design. Now a days one of the most proficient multi-carrier transmission techniques widely used today is orthogonal frequency division multiplexing (OFDM) which has been implemented by the next generation wireless communication technology: Long Term Evolution (LTE). Extra robustness to multipath fading and impulse noise is provided OFDM. It eliminates inter symbol interference (ISI) & inter carrier interference (ICI) with certain procedure. Therefore peak to average power ratio (PAPR) is the basic problem with OFDM. However in this paper we proposed a reduction procedure of the PAPR by using clipping and filtering. Here we use a composed high pass , low pass & Chevyshev band pass filter II after amplitude clipping to reduce the PAPR. The performance of the system in terms of bit error rate (BER) and symbol error rate (SER) is also investigated as a new filter based clipping method is proposed. Our proposed clipping method with and composed high pass the Chevyshev bandpass filter II in PAPR performance of the system with a little compromise of BER & SER showing the significant improvement in Quadrature Amplitude Modulation (QAM).
Performance comparison of two clipping based filtering methods for papr reduc...ijmnct
The growth of wireless communication technologies has been producing the intense demand for high-speed,
efficient, reliable voice & data communication. As a result, third generation partnership project (3GPP)
has implemented next generation wireless communication technology long term evolution (LTE) which is
designed to increase the capacity and speed of existing mobile telephone & data networks. LTE has
adopted a multicarrier transmission technique known as orthogonal frequency division multiplexing
(OFDM). OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for
very wide carriers. One major generic problem of OFDM technique is high peak to average power ratio
(PAPR) which is defined as the ratio of the peak power to the average power of the OFDM signal. A
trade-off is necessary for reducing PAPR with increasing bit error rate (BER), computational complexity or
data rate loss etc. In this paper, two clipping based filtering methods have been implemented & also
analyzed their modulation effects on reducing PAPR.
Impact of Clipping and Filtering on Peak to Average Power Ratio of OFDM Systemijsrd.com
Orthogonal Frequency Division Multiplexing (OFDM) is an emerging field of research in the field of 4G broadband wireless communications due to its robustness against multipath fading and relatively simple implementation. Peak to Average Power Ratio (PAPR) is the limiting factor for an OFDM system as it consists of large number of independent subcarriers as a result of which the amplitude of such a signal can have high peak values which degrades the system performance. Such a signal when amplified by a Power Amplifier without processing results spectral regrowth and intermodulation among subcarrier. Hence this non linearity destroys the orthogonally of the OFDM signal and introduces out-of-band radiation and in band distortions causing significant performance degradation. The clipping and filtering method is analysed which is an efficient and simple method to reduce the PAPR. We have shown the effects of clipping and filtering on the performance of OFDM, including the power spectral density, the crest factor, and the bit-error rate.
Peak to Average Power Ratio Performance of a 16-QAM/OFDM System with Partial ...IOSR Journals
Abstract : Orthogonal Frequency Division Multiplexing is a spectral efficient transmission format. But it suffers from the problem of high Peak to Average Power Ratio. This high Peak to Average Power Ratio leads the power amplifier into saturation and results in non-linear distortion at the output of power amplifier. Different peak to average power ratio reduction techniques are available in literature. This paper computes the performance of partial transmit scheme, which is one of the important peak to average power ratio reduction technique Keywords: Orthogonal Frequency Division Multiplexing, Partial Transmit Sequence, Peak to Average Power Ratio, Power Amplifier, Scrambling Techniques.
PAPR Reduction in OFDM using New Hybrid Techniquesijtsrd
With the advancement in age and its growing demands, there has been fast production in the field of communication system. Signals, which were sent at the beginning in the analog form, are being sent more and more in the digital form now in these days. For improved transmission, even single carrier waves are being recouped by multi carriers' waves. Multi carrier systems like CDMA and OFDM are now a days being implemented commonly. In the OFDM system, orthogonally placed subcarriers are used to send the data from the transmitter end to the receiver end. Presence of guard band in this communication system deals with the ISI issues and noise is mitigated by larger number of sub carriers. But the large PAPR Peak to Average Power Ratio of these signals have some unsuitable effects on the communication system. In this research work we have focused on the OFDM System and have implemented various techniques to reduce the PAPR in the OFDM system so that this system can be used more commonly and energetically. Vikas kumar | Preeti Sondhi "PAPR Reduction in OFDM using New Hybrid Techniques" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27820.pdf Paper URL: https://www.ijtsrd.com/engineering/other/27820/papr-reduction-in-ofdm-using-new-hybrid-techniques/vikas-kumar
Peak to Average Power Ratio (PAPR) Reduction in OFDM-OQAM Signalspaperpublications3
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Comparative Analysis of PAPR Reduction Techniques in OFDM Using Precoding Tec...IJSRD
In this modern era, Orthogonal Frequency Division Multiplexing (OFDM) has been proved to be an explicit promising technique for wired and wireless systems because of its several advantages like high spectral efficiency, robustness against frequency selective fading, relatively simple receiver implementation etc. Besides having a number of advantages OFDM suffers from few disadvantages like high Peak to Average Power Ratio (PAPR), Intercarrier Interference (ICI), Intersymbol Interference (ISI) etc. These detrimental effects, if not compensated properly and timely, can result in system performance degradation. This paper mainly concentrates on reduction of PAPR.A comparisons have been made between various precoding techniques against conventional OFDM.
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Comparative Analysis of PAPR Reduction Techniques in OFDM Using Precoding Techniques
1. IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 10, 2015 | ISSN (online): 2321-0613
All rights reserved by www.ijsrd.com 1041
Comparative Analysis of PAPR Reduction Techniques in OFDM using
Precoding Techniques
Jaya Misra1 Rakesh Mandal2
1
Research scholar 2
Assistant Professor
1,2
SSGI, Bhilai
Abstract— In this modern era, Orthogonal Frequency
Division Multiplexing (OFDM) has been proved to be an
explicit promising technique for wired and wireless systems
because of its several advantages like high spectral
efficiency, robustness against frequency selective fading,
relatively simple receiver implementation etc. Besides
having a number of advantages OFDM suffers from few
disadvantages like high Peak to Average Power Ratio
(PAPR), Intercarrier Interference (ICI), Intersymbol
Interference (ISI) etc. These detrimental effects, if not
compensated properly and timely, can result in system
performance degradation. This paper mainly concentrates on
reduction of PAPR.A comparisons have been made between
various precoding techniques against conventional OFDM.
Key words: OFDM, PAPR, ICI, ISI
I. INTRODUCTION
OFDM is basically a combination of both modulation and
multiplexing. Multiplexing generally refers to independent
signals, those produced by different sources. But in OFDM
the question of multiplexing is applied to independent
signals and these independent signals are a sub-set of the
one main signal. In OFDM the signal itself is first split into
independent channels, modulated by data and then re-
multiplexed to create the OFDM carrier. OFDM is a special
kind of Frequency Division Multiplexing (FDM). To
understand the difference between normal FDM and OFDM,
let us take an example of water tap and a shower. A general
FDM can be considered as water flow coming out of a water
Faucet whereas OFDM is analogous to a shower. In a faucet
all water comes out like a big stream while in shower the
water comes out in combination of little streams.
Orthogonal Frequency Division Multiplexing
(OFDM) is a multicarrier transmission scheme has now
became the technology for next generation wireless and
wired digital communication systems because of its high
speed data rates, high spectral efficiency, high quality
service and robustness against narrow band interference and
frequency selective fading[1]. Despite of several
advantages, the OFDM systems also have some major
problems like high Peak to Average Power Ratio (PAPR) of
transmitted signal, Synchronization (timing and frequency)
at the receiver, Inter carrier interference etc.
This paper mainly deals with high peak to average
power ratio reduction techniques. Due to the high Peak to
average Power Ratio, the quiescent point of the amplifier
used in the transmitter section is forced to enter into the
saturation region (non-linear region) resulting in reduction
in the efficiency of the HPA. Once the amplifier enters its
saturation region ,the amplification process no longer
remains linear , moreover the orthogonality between the
subcarriers gets lost which leads to Intercarrier
Interference(ICI).One way to solve this problem is to force
the amplifier to work in its linear range or to increase the
dynamic range of the amplifier. Unfortunately, these
solutions are not power efficient and cost efficient. Power
efficiency is very much necessary in wireless
communication as it saves power, provides adequate area
coverage etc. Thus inspite of modifying the amplifier
characteristic we prefer to reduce peak power swing with
respect to the mean power.
II. PEAK TO AVERAGE POWER RATIO (PAPR)
Large envelope fluctuations or High PAPR is another major
limitation of an OFDM system. An OFDM signal consists of
a large number of independently modulated subcarriers,
which when added up coherently, yields a very high
amplitude as compared to the average amplitude, resulting
in a large peak to average power ratio (PAPR).
The PAPR of the continuous time baseband OFDM
transmitted signal x(t) is the ratio of maximum
instantaneous power and the average power. By definition,
Where, E{.}denotes expectation operator and
E{|x(t)|^2}is average power of x(t) and T is an original
symbol period.
Since, multiple subcarriers are added in this
technique to form the transmitted signal therefore OFDM
suffers from high Peak to Average Power Ratio (PAPR)
value of the transmitted signal.
Peak-to-average power ratio (PAPR) is directly
proportional to the number of subcarriers used for OFDM
systems. In other words Any OFDM system with large
number of subcarriers will have a large PAPR as these
subcarriers add up coherently which results in high peaks.
III. EFFECT OF HIGH PAPR
In the transmitter section, linear power amplifiers are being
used so that the quiescent point (Q-point) remains in the
linear or active region. But due to high peak to average
power ratio, the Q-point starts moving towards the
saturation region and hence the clipping of signal takes
place which in turn gives rise to in-band and out-of- band
distortion. For faithful amplification ,the Q-point must lie in
the linear region and to keep the Q-point in the active
region, the linear range of the power amplifier have to be
increased i.e needs to be operated with huge back-off, which
reduces its efficiency and increases the cost factor[2]. If the
composite time OFDM signal is amplified by a power
amplifier having nonlinear transfer function, the
performance of an OFDM System get degrades .Hence, a
trade off always lies between non-linearity and efficiency.
The high PAPR also results in the increased complexity
(number of bits) of DAC and ADC used in the transmitter
and receiver section respectively such that large peaks can
be represented with good precision. Thus it becomes a prime
2. Comparative Analysis of PAPR Reduction Techniques in OFDM using Precoding Techniques
(IJSRD/Vol. 3/Issue 10/2015/239)
All rights reserved by www.ijsrd.com 1042
concern for a telecommunication engineer to develop an
efficient algorithm for PAPR reduction.
So, the major impact of a high PAPR is:
1) Increased complexity in the analog to digital and
digital to analog converters.
2) Reduction in the efficiency of radio frequency (RF)
power amplifiers.
It has been observed that the effects of nonlinearity
depends upon the type of modulation used in OFDM
systems, because different modulation schemes give rise to
different amplitude and phase of signal, which is ultimately
related the peak to average power ratio (PAPR). [3]
Fig. 1: Input- Output characteristic of an HPA.
A linear amplifier shows non linear distortion in
their outputs when its input is much larger than its nominal
value. Figure shows the input-output characteristics of high
power amplifier (HPA) in terms of the input power and the
output power. As illustrated in Figure , the input power
must be backed off so as to operate in the linear region
describing the nonlinear region by Input Back-Off (IBO) or
Output Back-Off (OBO).[4]
IV. DISTRIBUTION OF PAPR
The Cumulative Distribution Function (CDF) is one of the
most regularly used parameters to measure the efficiency of
any PAPR technique. Normally, the Complementary
Cumulative Distribution Function (CCDF) is used instead of
CDF which helps us to measure the probability that the
PAPR of a certain data block exceeds the given threshold.
CCDF provides an indication of the probability of
the OFDM signal’s envelope exceeding a specified PAPR
threshold within the OFDM symbol and is given by
CCDF [PAPR (xn(t)] = prob [PAPR (xn(t) > δ]
where PAPR (xn(t)) is the PAPR of the nth OFDM
symbol and δ is some threshold value.
V. PAPR REDUCTION METHODS
Various techniques have been proposed in the literature for
PAPR reduction, each having its own advantages and
disadvantages. Among them, some are Clipping and
Filtering, Partial Transmit Sequence (PTS), Selected
Mapping (SLM), Precoding, Tone Injection (TI),Tone
Reservation(TR) ,Companding ,Coding Methods or Hybrid
Techniques etc [5].
In this paper , we presented a comparative analysis
among various precoding techniques such as Walsh
Hadamard Transform (WHT),Discrete Fourier Transform
(DFT) and Discrete Hartley Transform(DHT) and on the
basis of computer simulation using MATLAB concluded
that precoding techniques can reduce PAPR as compared to
the conventional OFDM system.
VI. CONVENTIONAL OFDM SYSTEM
Fig. 2: Block diagram of conventional OFDM transmitter
section.
Fig 2 shows the basic block diagram of an conventional
OFDM system. ,Here the Mapper transforms the input bit
stream into constellation corresponding to various
modulation techniques .Here we have performed our
simulations considering two modulation techniques: M-
QPSK and M-QAM.The baseband modulated symbols are
then passed through a serial to parallel converter ,which
generates a complex vector of size N. .The complex vector
of size N can be written as X = [X0,X1,X2,…….,XN-1]T.
This X is then passed through the IFFT block. The IFFT
block converts the frequency domain baseband spectrum
into its time domain equivalent. After the IFFT operation,
the data are transformed and multiplexed to x (n) given by
[6].
VII. MODEL FOR PRECODED OFDM SYSTEM
Fig. 3: Block diagram of precoded OFDM transmitter
section.
Figure 3 shows a precoded OFDM system. In Precoding
method, the modulated data is first multiplied with shaping
matrix or precoding matrix before the formation of OFDM
symbol (before IFFT) . Different methods like pulse shaping
function, discrete cosine transformation (DCT) matrix,
Hadamard matrix, Zadoff-chu sequence etc. are used to
generate precoding matrix. After that these precoded data
are transmitted through IFFT to generate OFDM symbols.
Each element of precoding matrix should be carefully
designed, so that it can reduce the PAPR.In this model a
precoding matrix P of dimension N×N has been
implemented before the IFFT to reduce the PAPR.
Now the modulated OFDM vector signal with N
the subcarriers can be expressed as follows.
Xn = IFFT { P Xn}
VIII. DISCRETE FOURIER TRANSFORM (DFT) PRECODING
For generating the precoding matrix using DFT function, the
size of DFT precoder is kept same as IFFT size. The DFT of
a sequence of length N can be defined as:
And IDFT for the above can be written as
And
3. Comparative Analysis of PAPR Reduction Techniques in OFDM using Precoding Techniques
(IJSRD/Vol. 3/Issue 10/2015/239)
All rights reserved by www.ijsrd.com 1043
Here the ‘m’ and ‘ n’ are integers from 0 to N-1
and the precoding matrix is of size N x N given by
IX. THE DISCRETE HARTLEY TRANSFORM (DHT) PRECODING
The DHT is also a linear transformation of data. In DHT,
real numbers[ xo,x1,…..,xN-1] are transformed into N real
numbers . According to [4], the N-point DHT can be defined
as follows:
Where,
cas Ɵ=cosƟ +sin Ɵ and k=0 ,1,…..N-1
X. DISCRETE WALSH HADAMARD TRANSFORM (WHT)
PRECODING
This is the simplest and linear transformation. WHT does
not increase the complexity of the system. Walsh functions
are the basis for Walsh transform. Walsh functions are
orthogonal and have only +1 and -1 values [5] . In general,
the Walsh transform can be generated by the Hadamard
matrix as follows:
For k=1,2,3….. and H_1=1 for k=0
Here in this case the H matrix of eq. becomes
precoding matrix.
XI. SIMULATION RESULS
In this section we have compared the various precoding
techniques mentioned in the above section with 16-QAM for
subcarriers N=64 and found that Discrete Fourier Transform
outperforms the other conventional precoding techniques.
A. PAPR Reduction Results With 16-QAM Modulation
Fig. 4: PAPR reduction results for 16-QAM.
S. No. PAPR Reduction Technique PAPR (dB)
1 Conventional OFDM 9.7211
2 DWT Precoding 8.9343
3 DHT Precoding 8.5462
4 DFT Precoding 7.5067
Table 1: Obtained PAPR values for conventional OFDM
and various precoding techniques for 16-QAM and number
of subcarriers=64.
XII. CONCLUSION
Here, we analyzed performance of various precoding
techniques. The precoding technique is quite simple to
implement and has no boundations on the system parameters
like modulation order, number of subcarriers etc. The
Discrete Fourier Transform gives a better PAPR reduction
performance than other other precoded techniques.
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