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.
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.
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.
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.
CS Based Channel Estimation for OFDM Systems under Long Delay Channels Using ...IJERA Editor
Orthogonal frequency division multiplexing (OFDM) is a technique which are used in the next-generation wireless communication. Channel estimation in the OFDM technique is one of the big challenges, ever since high-resolution channel estimation can significantly improve the equalization at the receiver and consequently enhance the communication performances. Channel computation using superimposed pilot sequences is also a fully new area, idea for using superimposed pilot sequences has been proposed by various authors for different applications. In this paper, we are introduced a high accurate, low complexity compressive sensing (CS) based channel estimation namely Auxiliary information based Subspace Pursuit (ASP) in TFT-OFDM systems. ASP based channel estimation in TFT-OFDM system is based on two steps. First is, by exploiting the signal structure of recently proposed TDM-OFDM scheme, the supporting channel information is obtained. Second is, we propose the supporting information based subspace pursuit (SP) algorithm to use a very small amount of frequency domain pilots embedded in the OFDM block used for the exact channel estimation. Moreover, the obtained auxiliary channel information is adopted to reduce the complexity of the conventional SP algorithm. Simulation results demonstrate a important reduction of the number of pilots relative to least-squares channel estimation and supporting high-order modulations like 256 QAM.
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.
Analysis of Peak to Average Power Ratio Reduction Techniques in Sfbc Ofdm SystemIOSR Journals
Abstract: Orthogonal Frequency Division Multiplexing (OFDM) has become the most popular modulation echnique for high speed data transmission. But the great disadvantage of the OFDM technique is its high Peak to Average Power Ratio (PAPR). In this paper, the Selected Mapping (SLM) technique and Clipping and Differential Scaling is applied to Space Frequency Block Coded (SFBC) OFDM systems to reduce the PAPR with Alamouti coding scheme. In SLM technique, different representations of OFDM symbols are generated by rotation of the original OFDM frame by different phase sequences, and the signal with minimum PAPR is selected and transmitted. To compensate for the effect of the phase rotation at the receiver, it is necessary to transmit the index of the selected phase sequence as side information (SI). Additionally, a suboptimum detection method that does not need SI is introduced at the receiver side. In Clipping and Differential Scaling technique, the amplitude of complex OFDM signal is clipped and then scaled in such a way so that the PAPR is reduced without causing much degradation in bit error rate (BER). The threshold values for clipping and scaling is determined using Monte Carlo Simulations. Simulation results show that the SLM method and Clipping and Scaling method effectively reduce the PAPR. Keywords: Orthogonal frequency division multiplexing (OFDM), peak to average power ratio (PAPR), selected mapping (SLM), space frequency block coded (SFBC), Side information (SI), high power amplifiers (HPA), complementary cumulative density function (CCDF), inter-symbol interference (ISI).
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.
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.
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.
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.
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.
CS Based Channel Estimation for OFDM Systems under Long Delay Channels Using ...IJERA Editor
Orthogonal frequency division multiplexing (OFDM) is a technique which are used in the next-generation wireless communication. Channel estimation in the OFDM technique is one of the big challenges, ever since high-resolution channel estimation can significantly improve the equalization at the receiver and consequently enhance the communication performances. Channel computation using superimposed pilot sequences is also a fully new area, idea for using superimposed pilot sequences has been proposed by various authors for different applications. In this paper, we are introduced a high accurate, low complexity compressive sensing (CS) based channel estimation namely Auxiliary information based Subspace Pursuit (ASP) in TFT-OFDM systems. ASP based channel estimation in TFT-OFDM system is based on two steps. First is, by exploiting the signal structure of recently proposed TDM-OFDM scheme, the supporting channel information is obtained. Second is, we propose the supporting information based subspace pursuit (SP) algorithm to use a very small amount of frequency domain pilots embedded in the OFDM block used for the exact channel estimation. Moreover, the obtained auxiliary channel information is adopted to reduce the complexity of the conventional SP algorithm. Simulation results demonstrate a important reduction of the number of pilots relative to least-squares channel estimation and supporting high-order modulations like 256 QAM.
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.
Analysis of Peak to Average Power Ratio Reduction Techniques in Sfbc Ofdm SystemIOSR Journals
Abstract: Orthogonal Frequency Division Multiplexing (OFDM) has become the most popular modulation echnique for high speed data transmission. But the great disadvantage of the OFDM technique is its high Peak to Average Power Ratio (PAPR). In this paper, the Selected Mapping (SLM) technique and Clipping and Differential Scaling is applied to Space Frequency Block Coded (SFBC) OFDM systems to reduce the PAPR with Alamouti coding scheme. In SLM technique, different representations of OFDM symbols are generated by rotation of the original OFDM frame by different phase sequences, and the signal with minimum PAPR is selected and transmitted. To compensate for the effect of the phase rotation at the receiver, it is necessary to transmit the index of the selected phase sequence as side information (SI). Additionally, a suboptimum detection method that does not need SI is introduced at the receiver side. In Clipping and Differential Scaling technique, the amplitude of complex OFDM signal is clipped and then scaled in such a way so that the PAPR is reduced without causing much degradation in bit error rate (BER). The threshold values for clipping and scaling is determined using Monte Carlo Simulations. Simulation results show that the SLM method and Clipping and Scaling method effectively reduce the PAPR. Keywords: Orthogonal frequency division multiplexing (OFDM), peak to average power ratio (PAPR), selected mapping (SLM), space frequency block coded (SFBC), Side information (SI), high power amplifiers (HPA), complementary cumulative density function (CCDF), inter-symbol interference (ISI).
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.
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.
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
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.
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).
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.
Analyses and performance of techniques papr reduction for stbc mimo ofdm syst...ijwmn
An OFDM system is combined with multiple-input mult
iple-output (MIMO) in order to increase the
diversity gain and system capacity over the time va
riant frequency-selective channels. However, a maj
or
drawback of MIMO-OFDM system is that the transmitte
d signals on different antennas might exhibit high
peak-to-average power ratio (PAPR).In this paper, w
e present a PAPR analysis reduction of space-time-
block-coded (STBC) MIMO-OFDM system for 4G wireless
networks. Several techniques have been used to
reduce the PAPR of the (STBC) MIMOOFDM system: clip
ping and filtering, partial transmit sequence
(PTS) and selected mapping (SLM). Simulation result
s show that clipping and filtering provides a bette
r
PAPR reduction than the others methods and only SLM
technique conserve the PAPR reduction in
reception part of signal.
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.
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.
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
A PAPR Reduction for OFDM Signals Based on Self-Adaptive Multipopulation DE a...IJECEIAES
One of major drawbacks of orthogonal frequency division multiplexing (OFDM) systems is the high peak-to-average power ratio (PAPR). A signal with high PAPR leads to nonlinear distortion caused mainly by power amplifiers in wireless transmitters. Partial transmit sequence (PTS) is one of the most attractive methods to reduce the PAPR in OFDM systems. It achieves considerable PAPR reduction without distortion, but it requires an exhaustive search over all the combinations of the given phase factors, which results in a computational complexity that increases exponentially with the number of partitions. For this optimization problem, we propose in this paper a suboptimal PTS method based on the self-adaptive multipopulation differential evolution algorithm (SAMDE). The self adaptation of control parameters and structured population, is able to obtain high quality solutions with low computational cost by evolving each sub-population of individuals over successive generations.
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.
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.
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.
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
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.
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).
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.
Analyses and performance of techniques papr reduction for stbc mimo ofdm syst...ijwmn
An OFDM system is combined with multiple-input mult
iple-output (MIMO) in order to increase the
diversity gain and system capacity over the time va
riant frequency-selective channels. However, a maj
or
drawback of MIMO-OFDM system is that the transmitte
d signals on different antennas might exhibit high
peak-to-average power ratio (PAPR).In this paper, w
e present a PAPR analysis reduction of space-time-
block-coded (STBC) MIMO-OFDM system for 4G wireless
networks. Several techniques have been used to
reduce the PAPR of the (STBC) MIMOOFDM system: clip
ping and filtering, partial transmit sequence
(PTS) and selected mapping (SLM). Simulation result
s show that clipping and filtering provides a bette
r
PAPR reduction than the others methods and only SLM
technique conserve the PAPR reduction in
reception part of signal.
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.
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.
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
A PAPR Reduction for OFDM Signals Based on Self-Adaptive Multipopulation DE a...IJECEIAES
One of major drawbacks of orthogonal frequency division multiplexing (OFDM) systems is the high peak-to-average power ratio (PAPR). A signal with high PAPR leads to nonlinear distortion caused mainly by power amplifiers in wireless transmitters. Partial transmit sequence (PTS) is one of the most attractive methods to reduce the PAPR in OFDM systems. It achieves considerable PAPR reduction without distortion, but it requires an exhaustive search over all the combinations of the given phase factors, which results in a computational complexity that increases exponentially with the number of partitions. For this optimization problem, we propose in this paper a suboptimal PTS method based on the self-adaptive multipopulation differential evolution algorithm (SAMDE). The self adaptation of control parameters and structured population, is able to obtain high quality solutions with low computational cost by evolving each sub-population of individuals over successive generations.
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.
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.
A Comparison between Natural and Synthetic Food Flavoring Extracts Using Infr...IOSR Journals
Food is the basic necessity of life. One works hard and earns to satisfy our hunger .But at the end of the day, many of us are not sure of what we eat. We may be eating a dangerous flavors and dyes. Often, we invite diseases rather than good health. The purpose of this article is to detect the presence of food adulterants in some common foods and to create awareness about the artificial tests and dyes. A study of the IR spectra and the optical activitiy of two natural and artificial most common used flavor and colors (Vanilla and Strawberry) were detected. IR spectra of synthetic Vanilla were dominated by specific peaks that attributed to corresponding synthetic pigments (specific spectral band of stretching C=0 ester of aldehydic and ketonic groups in synthetic flavor at1744.87cm-1 with a weak shoulder at1700 cm-1 .And stretching CO of sucrose at (990.49 and 923,70) cm-1.The synthetic Strawberry characterized with specific spectral bands of (C=O stretching at 1634.96 cm-1 in ester and CO stretching of sucrose at 925 cm-1), while these functional groups disappeared in natural. Vanilla and Strawberry extracts. The natural Flavoring extracts posse's levorotatory property; they are optically active, while the synthetic extracts not rotates the plane of polarization of the light which passes through the material, they are said to be; not active optically. The obtained results indicated that, Infrared spectrum and Optical activity could be adapted to detect adulterants added products, and to differentiate between natural and artificial food flavoring extracts.
Comparative Study of End Moments Regarding Application of Rotation Contributi...IOSR Journals
Abstract: Analysis of portal frames involves lot of complications and tedious calculations by conventional
methods. To carry out such analysis is a time consuming task. The rotation contribution method i.e. Kani’s
Method & Moment Distribution Method for analysis of portal frames can be handy in approximate and quick
analysis so as to get the detailed estimates ready. In this work, these two methods have been applied only for
vertical loading conditions. This paper presents the analysis of portal frame, considering mainly the case of
single bay portal frame, which is the most common in practice. The Kani’s method is self correcting, that is, the
error, if any, in a cycle is corrected automatically in the subsequent cycles. The checking is easier as only the
last cycle is required to be checked. The convergence is generally fast. It leads to the solutions in just a few
cycles of iterations.
Physiological, Biochemical and Modern Biotechnological Approach to Improvemen...IOSR Journals
Rauwolfia serpentina also known as Sarpagandha (Apocynaceae) is an integral part of Ayurvedic medical system in India for over centuries for the treatment of various ailments. The leaves and roots ofRauwolfiaserpentina contain alkaloids which are secondary metabolites. Major alkaloids identified are Reserpine, Rauwolfine, Serpentine, Sarpagine, Ajmaline, Yohimbine and Ajmalicine.The present paper is an overview of the studies concerning with physiological, biochemical and modern biotechnological approach to improvement of Rauwolfiaserpentina.
Field Programmable Gate Array for Data Processing in Medical SystemsIOSR Journals
Abstract: Two- dimensional &Three–dimensional (3-D) image segmentation is on of the most demanding tasks in image processing. It has been proven that only the 14-neighborship of a rhombic dodecahedron can satisfy the aforementioned requirements. The 3-D-GSC process is executed in the following three phases ,coding phases,linking phases,splitting phases. An FPGA-based digital signal processing board optimized for applications needing large memory with high bandwidth has been developed and successfully used for the parallelization of a modern image segmentation algorithm for medical and industrial real-time applications.The Use of this 128-bit coprocessor board is not limited to image segmentation.We propose the perfectly parallelizable 3-D Gray-Value Structure Code (3-D-GSC) for image segmentation on a new FPGA custom machine. This 128-Bit FPGA coprocessing board features an up-to-date Virtex-II Pro architecture, two large independent DDR-SDRAM channels, two fast independent ZBT-SRAM channels, and PCI-X bus and CameraLink interfaces. Key words: Field Programmable Gate Array, Segme-ntation, Vogel bruch, Gray-valve structure code ,Homogeneous, Linking phase, Coding phase, Splitting phase, SDRAM.
The need for TVE is increasing as a result of so many factors: technological advancement,
globalization process, knowledge economy, changes in modes of production in the work place, growing
economic openness and competitiveness. TVE is very vital to the sustenance of technological development of
every nation in the present 21st century. For Nigeria to become developed greater emphasis must be placed on
technology education in order to improve on its quality for sustainable national development. This paper
discussed extensively on quality assuranceon TVE for sustainable national development in the 21st century. The
paper highlights on the concept of TVE and discusses on the status of TVE in Nigeria. Issues on sustainable
development and rationale for enhancing the quality of TVE in Nigeria in the 21st century were explained.
Conclusions were drawn and recommendations made amongst which are that: Government should introduce
sustainable financing scheme for TVE and increase the percentage of total expenditure on education to TVE and
also grant financial aids to trainees who are interested in pursuing TVE programs at whatever level and also
the involvement of major Nigerian stakeholders in the provision of workshop tools, equipment and other
infrastructural facilities for TVE graduates skills acquisition for sustainable national development.
Unified V- Model Approach of Re-Engineering to reinforce Web Application Deve...IOSR Journals
Abstract: The diverse and dynamic nature of elements and techniques used to develop Web Application, due to
the lack of testing technique and effective programming principles which are used for implementing
basic software engineering principles, and undisciplined development processes insure by the high pressure
of a very short time to satisfy market request to develop Web application. This paper represent approaches of
reengineering in web that how reengineering process can be carried out to evolution activities in legacy
system as well we propose the V-model for re-engineering process. This paper presents the need of the
technologies and approaches for building new web-services from existing web-applications. In this
paper we present the processing of V-model for Reengineering in web application which is the extension of Vmodel
used in software domain. In our approach V-model incorporates with the methodology
throughout the phases of web development process to re-engineer the web system.
Keywords:Re-engineering, reverse engineering, forward engineering, V-model, application migration.
Pollution Due To Noise from Selected PlacesIOSR Journals
Noise pollution degrades environment and also causes health hazard to human beings. In urban areas major sources of noise pollution are traffic and construction activities. Available guide lines for noise pollution have been reviewed in the paper. Measurement of noise levels at selected locations reported in the paper, for example, railway stations, use of machinery at construction sites, etc., was made and compared with the guide line values. It has been observed that the noise level at all locations exceeds the value prescribed by the competent authorities. At the pedestrian locations the noise level is 60 dB to 110 dB. At the railway crossing the noise level is 45 dB to 110 dB. The above inference shows that the noise pollution is paramount at all sources. Due to the various adverse impacts of noise on humans and environment, noise should be controlled. The conclusion drawn from this study is that the technique or the combination of techniques to be employed for noise control depends upon the extent of the noise reduction required, nature of the equipment used and the economy aspects of the available techniques
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.
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.
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.
Design Ofdm System And Remove Nonlinear Distortion In OFDM Signal At Transmit...Rupesh Sharma
although OFDM seems to be a solution to keep up with
the demand of increasing data rates, it has some drawbacks.
Sensitivity to high PAPR is the most significant of these
drawbacks. The main objective of this paper was to investigate
and document the effects of PAPR on the performance of OFDM
based digital communications under different channel conditions.
A step-by-step approach was adopted in order to achieve the
objective of this paper. The first step is to provide a basic
background on the principles of OFDM. The reasons for the
PAPR and a theoretical analysis of these effects on OFDM
systems are documented. The OFDM system has a high peak-toaverage
power ratio (PAPR) that can cause unwanted saturation
in the power amplifiers, leading to in-band distortion and out-ofband
radiation. To be able to observe the system behavior, the
simulation results for different channel models are presented in
graphical form. Next, the simulation results obtained in this work
are compared to the simulation results reported in related studies
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).
Hardware Implementation of OFDM system to reduce PAPR using Selective Level M...IOSR Journals
Abstract : OFDM is a modulation as well as multiplexing technique which is widely used in various high speed mobile and wireless communication systems because of its capacity of ensuring high level robustness against interference. In this paper the design and implementation of OFDM system along with SLM implementation to reduce PAPR[6]is illustrated and a detailed simulation of the OFDM system with 16-QAM. OFDM transceiver is implemented using FPGA Spartan6 kit. The hardware results show a detailed study of RTL schematics and Test Bench. In this paper, the software simulation results show 2dB reduction in the peaks. Keywords - Field Programmable Gate Array, Matlab Simulink, Orthogonal Frequency Division Multiplexing , Peak-to-Average Power Ratio, Selective level Mapping and Xilinx
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.
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.
Performance evaluation on the basis of bit error rate for different order of ...ijmnct
Today, we have required to accommodate a large number of users under a single base station. This can be
possible only if we have some flexibility over the spectrum. Previously we have lots of multiplexing methods
to accommodate large number of signals in time and frequency domain. But now we have required to
accommodate a large number of users in the same bandwidth, without any fading over the received signal.
So, orthogonality can be maintained over the frequency response. This technology is now more popular in
the mobile communication domain, called Orthogonal Frequency Division Multiplexing (OFDM). Actually
user data can be converted into the parallel form and then they are modulated using digital modulation
techniques. Finally, they have followed by OFDM Modulator and cyclic prefix can be inserted into the
OFDM symbols. Here, I have worked on the measurement of Bit error rate for different modulation
techniques in OFDM technology. It has been considered that subchannel size is not constant. According to
that I have concluded the overall idea regarding the performance under OFDM technology.
Investigation and Analysis of SNR Estimation in OFDM systemIOSR Journals
Estimation of signal to noise ratio (SNR) of received signal and to transmit the signal effectively for
the modern communication system. The performance of existing non-data-aided (NDA) SNR estimation methods
are substantially degraded for high level modulation scheme such as M-ary amplitude and phase shift keying
(APSK) or quadrature amplitude modulation (QAM).In this paper SNR estimation proposed method which uses
zero point auto-correlation of received signal per block and auto/cross- correlation of decision feedback signal
in orthogonal frequency division multiplexing (OFDM) system. Proposed method can be studied into two types;
Type 1 can estimate SNR by zero point auto-correlation of decision feedback signal based on the second
moment property. Type 2 uses both zero point auto-correlation and cross-correlation based on the fourth
moment property. In block-by-block reception of OFDM system, these two SNR estimation methods can be
possible for the practical implementation due to correlation based the estimation method and they show more
stable estimation performance than the earlier SNR estimation methods.
Performance analysis of papr reduction techniques in multicarrier modulation ...eSAT Journals
Abstract Orthogonal FrequencyDivisionMultiplexing (OFDM) is one of the many multicarrier modulation techniques which provide high spectral efficiency, less vulnerability to echoes,low implementation complexity and resilience to non – linear distortion. It is used in communication systems due to its various advantages. However, while this system is implemented problem of high peak – to – average power ratio(PAPR) is encountered. The reason behind this drawback is the existence of manyindependent subcarriers, due towhichthesignal amplitudecanhavehighpeakvalues as compared to average of whole system. The high PAPR in multicarrier transmission systems causes power degradation and spectrum spreading.Interleaving, Tone Reservation, Peak Reduction Carrier,Block Coding, Active Constellation Extension, Envelope ScalingareamongmanyPAPRreductionschemesthathavebeenproposedas a remedy to thisproblem. In this paper, performances of Amplitude Clipping and Filtering, Selected Level Mapping (SLM), and PartialTransmitSequence (PTS) techniques of PAPR reduction in OFDM systems by parameter variations are analyzed, based on Complementary Cumulative Distribution Function. An attempt has been made to simulate clipping and filtering technique with iterations and the simulation shows that PAPR problem is reduced as number of iterations increases. The attempts have also been made to simulate SLM technique and PTS technique by varying number of phase sequences, number of sub-blocks in SLM, PTS respectively and simulation results shows that by increasing the number of phase sequences, sub-blocks, PAPR can be reduced significantly.The mathematical equations are incorporated here to compute the maximum expected PAPR from an OFDM signal which shows when there is phase alignment of all sub carriers and sub carriers are equally modulated, then signal peak value hits the maximum. Besides these computer simulations, a comparative study of these three techniques is done.
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.
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.
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 analysis of papr reduction techniques in multicarrier modulation ...eSAT Publishing House
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.
Performance and Analysis of OFDM Signal Using Matlab SimulinkIJMER
Multi-carrier modulation is an attractive technique for fourth generation .OFDM is based on
multicarrier modulation technique. In OFDM system the bit stream is divided into many different sub
channels. An efficient and distortionless scheme for peak power reduction in OFDM is proposed. In this
paper, a set of mapping where the actual transmit signal is selected. From this set of signal reduced
PAPR. Simulation results are shown. The lowest PAPR is compared with conventional work. It is also
compared BER to SNR and best result is achieved.
Similar to OFDM PAPR Reduction by Shifting Two Null Subcarriers among Two Data Subcarriers (20)
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
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Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
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Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
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OFDM PAPR Reduction by Shifting Two Null Subcarriers among Two Data Subcarriers
1. IOSR Journal of Electronics and Communication Engineering (IOSR-JECE)
e-ISSN: 2278-2834,p- ISSN: 2278-8735.Volume 10, Issue 1, Ver. III (Jan - Feb. 2015), PP 87-90
www.iosrjournals.org
DOI: 10.9790/2834-10138790 www.iosrjournals.org 87 | Page
OFDM PAPR Reduction by Shifting Two Null Subcarriers
among Two Data Subcarriers
Rupesh L. Patil1
, S. K. Sudhansu2
1
P. G. Dept., MBES College of Engineering, Ambajogai, India, 431 517
2
P. G. Dept., MBES College of Engineering, Ambajogai, India, 431 517
Abstract: Orthogonal frequency division multiplexing (OFDM) is an attractive modulation technique for
transmitting large amount of digital data over radio waves. High PAPR of the transmit signal is major
drawback of OFDM. Proposed method promises PAPR reduction by shifting and switching null subcarrier with
data subcarrier. When it is compared with existing reduction techniques (Such as Shifting Null Subcarrier
among Data Subcarrier, Interleaving Technique, PTS, SLM, Tone rejection etc), the proposed method is
compatible with current commercial system. The MATLAB simulations show a PAPR reduction of around 1.4dB
using the proposed method than the existing methods also BER performance of proposed method is much better
than that of existing methods.
Keywords: Orthogonal frequency division multiplexing, peak-to-average power ratio, intersymbol interference,
null subcarriers.
I. Introduction
Orthogonal frequency division multiplexing (OFDM) is a special case of multi carrier transmission,
where a single data stream is transmitted over a number of lower rate subcarriers [8][9]. In single carrier system,
if signal gets faded or interfered, then entire link gets failed, where as in a multicarrier system, only a small
percentage of the subcarriers will be affected. It is very easy and efficient in dealing with multipath fading and
robust again narrow band interference [14]. It has been widely adopted in many international standards; out of
these standards we used IEEE 802.11a for proposed method.
High PAPR is one of the most serious problems in OFDM system [8][9]. To transmit signals with high
PAPR, it requires power amplifiers with very high power scope. These kinds of amplifiers are very expensive
and have low efficiency-cost factor. This gives rise to non-linear distortion which changes the superposition of
the signal spectrum [3] resulting in performance degradation.
The PAPR issue and its drawbacks are discussed in many papers. Such as PAPR reduction in OFDM
by shifting null and data subcarriers is suggested as, “OFDM PAPR Reduction by Shifting Null Subcarriers
Among Data Subcarriers,” by Bo Wang, Pin-Han Ho, and Chih-Hao Lin [1]. “PAPR Reduction of OFDM
Signals Using Partial Transmit Sequence: An Optimal Approach Using Sphere Decoding,” by Ali Alavi and
Chintha Tellambura [2]. “Peak-to-Average power ratio Reduction using OFDM Null subcarriers,” by
Wang,Bo[10]. “Dynamic null-data subcarrier switching for OFDM PAPR reduction with low computational
overhead,” by S. Ahmed and M. Kawai[11]. “An overview: peak-to-average power ratio reduction techniques
for OFDM signals,” by T. Jiang and Y. Wu [7] et.al which explain the new PAPR reduction techniques, which
reduces the PAPR of OFDM system with many other advantages.
In classical parallel data system, the total signal frequency band is divided in to non overlapping
frequency subchannels. Each subchannel is modulated with separate symbol and then these subchannels are
frequency multiplexed. It results it avoids spectral overlap to eliminate Interchannel Interference (ICI) [9].
However it leads inefficient use of available spectrum. Orthogonal word indicates that there is a precise
mathematical relationship between frequencies of the carrier system. These orthogonal signals follows: Each
subcarrier has exactly an integer number of cycles in FFT interval and number of cycles between adjacent
subcarriers differs by exactly one. For integer number of cycles, all smoothing windows yields the same peak
amplitude reading and have excellent amplitude accuracy side lobes do not appear because spectrum of the
smoothing window approaches zero at Δf intervals (distance between subcarriers in frequency domain) on either
side of the main lobe. At transmitter IFFT acts as specialized multiplexer also it takes complex numbers
representing the modulated subcarriers.
PAPR reduction techniques classified on Distortion based technique in which the time domain signals
are directly suppressed for which the power signal exceeds a certain threshold level. (e.g. Clipping Technique,
PTS etc.) [2]. and Redundancy based technique in which number of candidate signals are generated and then
selects the one candidate signal which will have lowest PAPR for transmission (e.g. Null Switching Method,
SLM, etc.)[1][10]. In proposed method, null subcarrier which is used as guard band to avoid aliasing effect also
2. OFDM PAPR Reduction by Shifting Two Null Subcarriers among Two Data Subcarriers
DOI: 10.9790/2834-10138790 www.iosrjournals.org 88 | Page
it is known as unused carriers with zero transmit energy. In IEEE 802.11a, 6 null subcarriers at low frequency
end and 5 null subcarriers at high frequency end [12].
II. Proposed Method
Consider OFDM transmission splits the high rate data stream into S sub streams of the lower data rate
i.e. parallel system divide the available bandwidth into S non overlapping subchannels with ascending
frequencies set {fs, s = 1, 2,..., S}. the total S subcarriers are the combination of data subcarriers(D) and null
subcarriers(N), where for N ascending frequency set {fn,n=1,2,..., N} and for D ascending frequency set {fd,d =
1, 2,…., S − N}.
Moreover, fn ≠fd, ∀n,d. Assigned to the data subcarriers at {fd, 1 ≤ d ≤ S − N} are, respectively, the M-ary data
symbols {.xd, d = 1, · · · , L − N}, taken from a quadrature amplitude modulation (QAM) constellation.
Null Switching Method
Before Switching
Null Subcarrier Data Subcarrier
After Switching
Proposed Null Switching Method
Before Switching
Null Subcarrier Data Subcarrier
After Switching
Fig. 1. Comparison between Null Switching method[1] and Proposed Null Switching method
Null Subcarrier Among Data Subcarrier
Before Shifting
Null Subcarrier Data Subcarrier
After Shifting
Proposed Null Subcarrier Among Data Subcarrier
Before Shifting
Null Subcarrier Data Subcarrier
After Switching
Fig. 2. Shifting Null Subcarrier Among Data Subcarrier[1] and Proposed Shifting Null Subcarrier
Among Data Subcarrier
From Fig. 1 and 2, without changing the values of total subcarrier, data subcarrier and null subcarrier,
we need to shifts P elements to generate number of candidates and then selects one candidate which will have
lowest PAPR for transmission. For finding shifting possibilities we can derive using
3. OFDM PAPR Reduction by Shifting Two Null Subcarriers among Two Data Subcarriers
DOI: 10.9790/2834-10138790 www.iosrjournals.org 89 | Page
= (1)
The designing of null subcarrier in standard is at low frequency end is one more than that at high frequency end
when shifting element is even and vice versa. Proposed method requires low CSI, for maintaining the
synchronization between transmitter and receiver which helps to recover data subcarrier as in its original form
i.e. sequencing back to original format which were changed due to various shifting to get one of the candidate
which having lowest PAPR. Here two proposed methods are derived from existing reduction techniques which
shown in figure.
III. Simulations
The standard IEEE 802.11a ensures appropriate candidate which has minimum PAPR after shifting of
null subcarrier. An 802.11a OFDM carrier signal (burst type) is the sum of one or more OFDM symbols each
comprised of 52 orthogonal subcarriers with baseband data on each subcarrier being independently modulated
using Quadrature amplitude modulation (QAM). This composite baseband signal is used to modulate a main RF
carrier.
To begin the OFDM signal creation process, the input bit stream is encoded with convolution coding
and interleaving. Each data stream is divided into group of 4 bits because here we are using 16-QAM and then
converts into complex numbers representing the mapped constellation point. 52 bins of the IFFT
block are loaded. Out of these 48 bins contains constellation points which are mapped into frequency offset
indexes ranging from -26 to +26, skipping the 4 pilot and zero bins. There are 4 pilot subcarrier inserted into
frequency offset index location -21,-7, +7 and +21. The zero bin is the Null or DC subcarrier (contains 0 value
i.e. 0+0j) and is not used. When the IFFT block is completely loaded, the IFFT computed, giving a set of
complex time domain samples representing the combined OFDM subcarrier waveform. In between each OFDM
symbols preamble is used for synchronization and concatenated together, in this way OFDM burst is
transmitted.
Fig. 3. The PAPR’s CCDF @ [1], Switching by 3 & 2 Null subcarrier, Null switching and .
Fig. 3 shows the PAPR values of various reduction techniques, here proposed null switching method
i.e. 2-null switching (≈ 7.8dB) is better than Null switching method i.e. 1-null switching (≈ 8.5dB) based on
same computational complexity also graph shows proposed shifting null subcarrier among data subcarrier
method i.e. (≈ 6.7dB) is better than shifting null subcarrier among data subcarrier method i.e. (≈
9.2dB) [1]. Comparing all methods, Shifting Null Subcarrier among Data Subcarrier Method is better than other
methods. Figure 4 shows that the BER performance of proposed null subcarrier among data subcarrier method
(≈ 14.8dB) is close to that of Shifting at (≈15.3dB) [1]. But when comparing both with proposed null
4. OFDM PAPR Reduction by Shifting Two Null Subcarriers among Two Data Subcarriers
DOI: 10.9790/2834-10138790 www.iosrjournals.org 90 | Page
switching i.e. 2-null switching (>15.3dB) is not better one. As we have seen in Fig. 3 PAPR performance of
proposed Null switching method i.e. 2-null switching is better than Null switching method i.e. 1-null switching
and shifting null subcarrier among data subcarrier method i.e. [1]. But in case of BER performance is
not good as shown in Fig. 4.
Fig. 4. BER against SNR at with [1], Switching by 3 & 2 Null subcarrier and .
IV. Conclusion
The simulation results have demonstrated the effectiveness of the approach for a 16 QAM modulation
scheme and had been evaluated in terms of BER versus SNR. The results clearly show the effectiveness of our
proposed algorithm, as well as ability to achieve large reduction in PAPR by keeping constant performance of
BER.
References
[1] Bo Wang, Pin-Han Ho, and Chih-Hao Lin“OFDM PAPR Reduction by Shifting Null Subcarriers Among Data Subcarriers”, IEEE
Communication Letters, Vol. 16, No.9, Sept 2012.
[2] Ali Alavi, Chintha Tellambura, Senior Member, IEEE, and Ivan Fair “PAPR Reduction of OFDM Signals Using Partial Transmit
Sequence: An Optimal Approach Using Sphere Decoding”, IEEE Communications Letters, Vol. 9, No. 11, November 2005.
[3] Haijian ZHANG, Didier LE RUYET, Michel TERRE “Spectral Efficiency Analysis in OFDM and OFDM/OQAM based Cognitive
Radio Networks” Electronics and Communications Laboratory, CNAM Paris, France.
[4] S. H. Han and J. H. Lee, “An overview of peak-to-average power ratio reduction techniques for multicarrier transmission,” IEEE
Wireless Commun., pp. 56–65, Apr. 2005.
[5] Aida Zaier and Ridha Bouallegue “Blind channel estimation enhancement for MIMO- OFDM systems under high mobility
conditions”, International Journal of Wireless & Mobile Networks (IJWMN) Vol. 4, No. 1, February 2012 DOI :
10.5121/ijwmn.2012.4115 207.
[6] Umar Faruq “Peak-To–Average Power Ratio Reduction of OFDM Signals” IOSR Journal of Electronics and Communication
Engineering (IOSR-JECE) ISSN: 2278-2834, ISBN: 2278-8735. Volume 3, Issue 2 (Sep-Oct. 2012).
[7] T. Jiang and Y. Wu, “An overview: peak-to-average power ratio reduction techniques for OFDM signals” IEEE Trans. Broadcast.,
vol. 54, no. 2, pp. 257–268, June 2008.
[8] The Basic Principles of OFDM, CCU Wireless Access Tech. Lab.
[9] Ho Chin Keong “Overview on OFDM Design” Communication Systems & Signal Processing Centre for Wireless Communications
National University of Singapore November 9, 2001.
[10] Wang, Bo “Peak-to-Average power ratio Reduction using OFDM Null subcarriers ” The Hongkong Polytechnic University
Department of Electronics and Information Engineering January 2011.
[11] S. Ahmed and M. Kawai “Dynamic null-data subcarrier switching for OFDM PAPR reduction with low computational overhead”
Electronics Letters 26th April 2012 Vol. 48 No. 9.
[12] Szymon Grabski, Krzysztof Szczypiorski “Steganography in OFDM Symbols of Fast IEEE 802.11n Networks”, Institute of
Telecommunications Warsaw University of Technology Warsaw, Poland 2013, IEEE Security and Privacy Workshop.
[13] Dr.Ali Muqaibel, Review of Digital Communication Fundamentals V2.0, Digital Communication II.
[14] Hlaing Minn, Member, IEEE, Vijay K. Bhargava, Fellow, IEEE, and Khaled Ben Letaief, Fellow, IEEE “A Robust Timing and
Frequency Synchronization for OFDM Systems”. IEEE Transactions on Wireless Communications, Vol. 2, No. 4, July 2003.