A new work has been proposed in this paper in order to overcome one of the main drawbacks that found in
the Orthogonal Frequency Division Multiplex (OFDM) systems, namely Peak to Average Power Ratio
(PAPR). Furthermore, this work will be compared with a previously published work that uses the neural
network (NN) as a solution to remedy this deficiency.
The proposed work could be considered as a special averaging technique (SAT), which consists of wavelet
transformation in its first stage, a globally statistical adaptive detecting algorithm as a second stage; and
in the third stage it replaces the affected peaks by making use of moving average filter process. In the NN
work, the learning process makes use of a previously published work that is based on three linear coding
techniques.
In order to check the proposed work validity, a MATLAB simulation has been run and has two main
variables to compare with; namely BER and CCDF curves. This is true under the same bandwidth
occupancy and channel characteristics. Two types of tested data have been used; randomly generated data
and a practical data that have been extracted from a funded project entitled by ECEM. From the achieved
simulation results, the work that is based on SAT shows promising results in reducing the PAPR effect
reached up to 80% over the work in the literature and our previously published work. This means that this
work gives an extra reduction up to 15% of our previously published work. However, this achievement will
be under the cost of complexity. This penalty could be optimized by imposing the NN to the SAT work in
order to enhance the wireless systems performance.
Index modulation is one of the promising techniques for future communications systems due to many improvement over the classical orthogonal frequency division multiplexing systems such as single RF chain, increased throughput for the same modulation order, achieved tradeoff between the efficiencies of the power and the spectral, and elimination of inter-channel interference. Many forms of index modulation researches exist where symbols are conveyed in antennas, subcarriers, time slots, and the space-time matrix. Spatial modulation is one member of index modulation family where symbols are conveyed in activating transmit/receive antennas. In this paper, a modification to a standard multiple input single output scheme by integrating spatial modulation using simplified mathematical procedure is achieved. In the transmitter side, data and activation symbols are distributed simultaneously using mathematical module and floor functions. At the receiver, a simplified maximum likelihood detector is used to obtain transmitted pair of symbols. To verify this, MATLAB simulink is used to simulate a downlink system where spatial modulation is applied to a base station. Results for different transmit antenna number and modulation order are obtained in the form of bit error rate versus signal to noise ratio.
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).
Investigating the performance of various channel estimation techniques for mi...ijmnct
This paper simulates and investigates the performance of four widely-used channel estimation techniques for MIMO-OFDM wireless communication systems; namely, super imposed pilot (SIP), comb-type, spacetime block coding (STBC), and space-frequency block coding (SFBC) techniques. The performance is
evaluated through a number of MATLab simulations, where the bit-error rate (BER) and the mean square
error (MSE) are estimated and compared for different levels of signal-to-noise ratio (SNR). The simulation results demonstrate that the comb-type channel estimation and the SIP techniques overwhelmed the performance of the STFC and STBC techniques in terms of both bit-error rate (BER) and mean square error (MSE).
INVESTIGATING THE PERFORMANCE OF VARIOUS CHANNEL ESTIMATION TECHNIQUES FOR MI...ijmnct
This paper simulates and investigates the performance of four widely-used channel estimation techniques for MIMO-OFDM wireless communication systems; namely, super imposed pilot (SIP), comb-type, spacetime block coding (STBC), and space-frequency block coding (SFBC) techniques. The performance is evaluated through a number of MATLab simulations, where the bit-error rate (BER) and the mean square error (MSE) are estimated and compared for different levels of signal-to-noise ratio (SNR). The simulation results demonstrate that the comb-type channel estimation and the SIP techniques overwhelmed the performance of the STFC and STBC techniques in terms of both bit-error rate (BER) and mean square error (MSE).
Index modulation is one of the promising techniques for future communications systems due to many improvement over the classical orthogonal frequency division multiplexing systems such as single RF chain, increased throughput for the same modulation order, achieved tradeoff between the efficiencies of the power and the spectral, and elimination of inter-channel interference. Many forms of index modulation researches exist where symbols are conveyed in antennas, subcarriers, time slots, and the space-time matrix. Spatial modulation is one member of index modulation family where symbols are conveyed in activating transmit/receive antennas. In this paper, a modification to a standard multiple input single output scheme by integrating spatial modulation using simplified mathematical procedure is achieved. In the transmitter side, data and activation symbols are distributed simultaneously using mathematical module and floor functions. At the receiver, a simplified maximum likelihood detector is used to obtain transmitted pair of symbols. To verify this, MATLAB simulink is used to simulate a downlink system where spatial modulation is applied to a base station. Results for different transmit antenna number and modulation order are obtained in the form of bit error rate versus signal to noise ratio.
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).
Investigating the performance of various channel estimation techniques for mi...ijmnct
This paper simulates and investigates the performance of four widely-used channel estimation techniques for MIMO-OFDM wireless communication systems; namely, super imposed pilot (SIP), comb-type, spacetime block coding (STBC), and space-frequency block coding (SFBC) techniques. The performance is
evaluated through a number of MATLab simulations, where the bit-error rate (BER) and the mean square
error (MSE) are estimated and compared for different levels of signal-to-noise ratio (SNR). The simulation results demonstrate that the comb-type channel estimation and the SIP techniques overwhelmed the performance of the STFC and STBC techniques in terms of both bit-error rate (BER) and mean square error (MSE).
INVESTIGATING THE PERFORMANCE OF VARIOUS CHANNEL ESTIMATION TECHNIQUES FOR MI...ijmnct
This paper simulates and investigates the performance of four widely-used channel estimation techniques for MIMO-OFDM wireless communication systems; namely, super imposed pilot (SIP), comb-type, spacetime block coding (STBC), and space-frequency block coding (SFBC) techniques. The performance is evaluated through a number of MATLab simulations, where the bit-error rate (BER) and the mean square error (MSE) are estimated and compared for different levels of signal-to-noise ratio (SNR). The simulation results demonstrate that the comb-type channel estimation and the SIP techniques overwhelmed the performance of the STFC and STBC techniques in terms of both bit-error rate (BER) and mean square error (MSE).
A Review: Significant Research on Time And Frequency Synchronization In MIMO ...IJERA Editor
This paper proposes a fast and dependable procedure for timing and frequency synchronization of multiple-input
multiple- output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Orthogonal frequency
division multiplexing (OFDM) could be a outstanding technique for high info rate remote transmission. The
execution of OFDM framework is exceptionally touchy to transporter repeat Offset (CFO) that presents between
bearer electric resistances (ICI). Multi data multi yield frame work used for increasing various qualities increase
and limit of the framework. During this space repeat synchronization in associate OFDM framework is
contemplated and gave past work OFDM framework.
An Efficient Performance of Mimo - Ofdm Based Cognitieve Radio System for Arr...IOSR Journals
Abstract: The wireless channel is central within this context, thus estimating the channel is the key to make CR operational, taking in consideration that the transmission-reception technology is available. In this thesis, we design a MIMO system using OFDM modulation technology to transmit and receive two signals over the mobile wireless channel. First formulate the pilot design as a new optimization problem. We use MIMO concept to enhance system capacity and robustness of the wireless transmission. In Multi-Input Multi-Output (MIMO) based cognitive radio (CR) systems, with the increasing demand for data rate and reliability in Wireless communicationsand devices, several issues become very important like bandwidth efficiency, quality of service and radio coverage. In this new scheme, adaptive arrays are group-selected in the spatial domain. Simulation shows that the proposed system can get significant performance improvements over the conventional array based OFDM systems over frequency-selective multipath fading channels with cognitive radio (CR) system. Keywords: Cognitive radios, MIMO, OFDM, and Joint transmit and receive group selected arrays.
In recent past the influence of Radar has played a significant part in various fields. Radar sensing is one of
the prime application by which velocity and distance of a moving target can be found out. A joint RadCom
system to serve both radar sensing and wireless communication is proposed which ensures better
performance in terms of spectral efficiency, extended detection range and cost effectiveness. Such systems
demand for a common waveform which is designed in this work that perfectly matches to the system
requirements. OFDM multi carrier technique is chosen to generate a common waveform. Applicability of
multiple antenna technique for direction of arrival estimation is also considered. MIMO-OFDM technique
has gained much interest in the field of communication which improves the signal to noise ratio and lowers
the bit error rate. On the other hand the usage of MIMO reflects in the form of interference between
signals. In order to overcome this effect beamforming technique is used. In addition to theoretical
explanations we have also simulated and discussed the results for the proposed RadCom system using
MATLAB simulation tool.
COMPARING VARIOUS CHANNEL ESTIMATION TECHNIQUES FOR OFDM SYSTEMS USING MATLABijwmn
This paper compares the performance of various channel estimation techniques for OFDM systems over quasi-static channels using MATLab. It compares the performance of five channel estimation techniques, these are: decision directed (DD), linear interpolation, second-order interpolation, discrete Fourier transform (DFT) interpolation, minimum mean square error (MMSE) interpolation. The performance is evaluated in terms of two widely-used performance measures, namely, bit-error rate (BER) and the mean square error (MSE) for different levels of signal-to-noise ratio (SNR). The OFDM model is explained and implemented using MATLab to run different simulations. The simulation results demonstrate that the DD channel estimation provides the lowest BER and MSE as compared to interpolation techniques, at the cost of extra processing delay and comparatively sensitive to channel variations between OFDM symbols. Also, the MMSE interpolation outperforms all other interpolation techniques.
Performance analysis for Adaptive Subcarriers Allocation in Coherent Optical ...iosrjce
The constraint to satisfy the need of increased bandwidth requirement for high speed applications
with higher performance has been a motivation to work on Optical Orthogonal Frequency division multiplexing
(OOFDM) technique with coherent detection. We implement the coherent optical OFDM (CO-OOFDM)
technique and investigate the effect of the number of sub-carriers on performance over single mode fiber (SMF)
links. To explore improvement in performance adaptive subcarriers has been selected by assigning subcarriers
to user according to the conditions of channel. An adaptive subcarrier allocation has been investigated and
performance comparison for proportional and equal allocation has been carried over.
Interoperator Dynamic Spectrum Sharing (Analysis, Costs and Implications)CSCJournals
This paper addresses Dynamic Spectrum Sharing (DSS) between two wireless operators. The Universal Mobile Telecommunication System (UMTS) network is used as a case study. The proposed protocol is evaluated under the uniform and non-uniform traffic conditions. The underlying principles of the algorithm can be deployed in the UMTS extension Band (2500MHz-2690MHz) which is yet to be allocated or the re-farmed GSM spectrum (900MHz/1800MHz). The simulation results for the proposed protocol shows that significant spectrum sharing gains can be obtained. However such spectrum efficiency gain need to be carefully balanced with the complexity in terms of latency (delays) and additional overhead it brings to the network. The results show that significant spectrum sharing gain of 4.0 % and 2.0 % can be obtained under uniform and non-uniform traffic conditions
CL-SA-OFDM: cross-layer and smart antenna based OFDM system performance enha...IJECEIAES
The growing usage of wireless services is lacking in providing high-speed data communication in recent times. Hence, many of the modulation techniques are evolved to attain these communication needs. The recent researches have widely considered OFDM technology as the prominent modulation mechanism to fulfill the futuristic needs of wireless communication. The OFDM can bring effective usage of resources, bandwidth, and system performance enhancement in collaboration with the smart antenna and resource allocation mechanism (adaptive). However, the usage of adaptive beamforming with the OFDM leads to complication in the design of medium access layer and which causes a problem in adaptive resource allocation mechanism (ARAM). Hence, the proposed manuscript intends to design an OFDM system by considering different switched beam smart antenna (SBSA) along with the cross-layer adaptive resource allocation (CLARA) and hybrid adaptive array (HAA). In this, various smart antenna mechanism are considered to analyze the quality of service (QoS) and complexity reduction in the OFDM system. In this paper, various SA schemes are used as per the quality of service (QoS) requirement of the different users. The performance analysis is conducted by considering data traffic reduction, bit-rate reduction, and average delay.
Channel Estimation Techniques in MIMO-OFDM LTE SystemsCauses and Effects of C...IJERA Editor
There is an increasing demand for high data transmission rates with the evolution of the very large scale integration (VLSI) technology. The multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems are used to fulfill these requirements because of their unique properties such as high spectral efficiency, high data rate and resistance towards multipath propagation. MIMO-OFDM systems are finding their applications in the modern wireless communication systems like IEEE 802.11n, 4G and LTE. They also offer reliable communication with the increased coverage area. The bottleneck to the MIMO-OFDM systems is the estimation of the channel state information (CSI). This can be estimated with the help of any one of the Training Based, Semiblind and Blind Channel estimation algorithms. This paper presents various channel estimation algorithms, optimization techniques and their effective utilization in MIMO-OFDM for modern wireless LTE systems.
A review paper on the papr analysis of orthogonal frequency division multiple...ijmnct
OFDM (Orthogonal Frequency Division Multiplexing) has been raised a new modulation technique. Due
to its advantages in multipath fading channel e.g. robust against ISI, ICI and some other advantages like
best QoS for multiple users, efficient usage of bandwidth it is suggested to be the modulation technique for
next generation 4G networks e.g. LTE. But along with all its advantages there are some disadvantages also
e.g. High PAPR (Peak to Average Power Ratio) at the transmitter end and BER (Bit Error Rate) at the
receiving end. Since OFDM is only used in the downlink of 4G networks. To reduce the problems of OFDM
some techniques e.g. SLM, PTS, Clipping, Coding, & Pre-coding etc are suggested but none of them is
reduce the PAPR and BER to an acceptable value. This Paper will discuss some techniques of PAPR &
BER reduction, and their advantages and disadvantages in detail.
Signal Strength Evaluation of a 3G Network in Owerri Metropolis Using Path Lo...Onyebuchi nosiri
Abstract: In this work, the path loss and the received signal strength of a 3G network at 2.1GHz was evaluated to determine its performance within the Owerri metropolis. Various measuring equipment such as Transmission Evaluation and Monitoring System (TEMS 11), Global positioning system (BU353 GPS) and laptop were deployed for the drive test within the selected urban and sub-urban regions. From the data collected, Owerri sub-urban region showed poor received signal power level compared to the Owerri urban region. The path loss exponents computed for the Owerri urban and sub-urban regions are 3.24 and 4.34 respectively, the mean square error was evaluated as 1.96 and 1.68. The result obtained showed deviations between the compared existing models (Hata and Cost 231) and the proposed models. However, the slope of the Hata plot was relatively close in comparison to the proposed model than that of Cost 231; hence, the proposed model was best suited for the environment followed by the Hata model.
Peak detection using wavelet transformIJCNCJournal
A new work based-wavelet transform is designed to overcome one of the main drawbacks that found in the
present new technologies. Orthogonal Frequency Division Multiplexing (OFDM)is proposed in the
literature to enhance the multimedia resolution. However, the high peak power (PAPR) values will obstruct
such achievements. Therefore, a new proposition is found in this work, making use of the wavelet
transforms methods, and it is divided into three main stages; de-noising stage, thresholding stage and then
the replacement stage.
In order to check the system stages validity; a mathematical model has been built and its checked after
using a MATLAB simulation. A simulated bit error rate (BER) achievement will be compared with our
previously published work, where an enhancement from 8×10-1 to be 5×10-1 is achieved. Moreover, these
results will be compared to the work found in the literature, where we have accomplished around 27%
PAPR extra reduction.
As a result, the BER performance has been improved for the same bandwidth occupancy. Moreover and
due to the de-noise stage, the verification rate has been improved to reach 81%. This is in addition to the
noise immunity enhancement.
A SEMI BLIND CHANNEL ESTIMATION METHOD BASED ON HYBRID NEURAL NETWORKS FOR UP...ijwmn
The paper describes how to improve channel estimation in Single Carrier Frequency Division Multiple
Access (SC-FDMA) system, using a Hybrid Artificial Neural Networks (HANN). The 3rd Generation
Partnership Project (3GPP) standards for uplink Long Term Evolution Advanced (LTE-A) uses pilot based
channel estimation technique. This kind of channel estimation method suffers from a considerable loss
ofbitrate due to pilot insertion; all data frame sent contains reference signal. The HANN converts data
aided channel estimator to semi blind channel estimator. To increase convergence speed, HANN uses some
channel propagation Fuzzy Rules to initialize Neural Network parameters before learning instead of a
random initialization, so its learning phase ismore rapidly compared to classic ANN.HANN allows more
bandwidth efficient and less complexity. Simulation results show that HANN has better computational
efficiency than the Minimum Mean Square Error (MMSE) estimator and has faster convergence than
classic Neural Networks estimators.
A Review: Significant Research on Time And Frequency Synchronization In MIMO ...IJERA Editor
This paper proposes a fast and dependable procedure for timing and frequency synchronization of multiple-input
multiple- output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Orthogonal frequency
division multiplexing (OFDM) could be a outstanding technique for high info rate remote transmission. The
execution of OFDM framework is exceptionally touchy to transporter repeat Offset (CFO) that presents between
bearer electric resistances (ICI). Multi data multi yield frame work used for increasing various qualities increase
and limit of the framework. During this space repeat synchronization in associate OFDM framework is
contemplated and gave past work OFDM framework.
An Efficient Performance of Mimo - Ofdm Based Cognitieve Radio System for Arr...IOSR Journals
Abstract: The wireless channel is central within this context, thus estimating the channel is the key to make CR operational, taking in consideration that the transmission-reception technology is available. In this thesis, we design a MIMO system using OFDM modulation technology to transmit and receive two signals over the mobile wireless channel. First formulate the pilot design as a new optimization problem. We use MIMO concept to enhance system capacity and robustness of the wireless transmission. In Multi-Input Multi-Output (MIMO) based cognitive radio (CR) systems, with the increasing demand for data rate and reliability in Wireless communicationsand devices, several issues become very important like bandwidth efficiency, quality of service and radio coverage. In this new scheme, adaptive arrays are group-selected in the spatial domain. Simulation shows that the proposed system can get significant performance improvements over the conventional array based OFDM systems over frequency-selective multipath fading channels with cognitive radio (CR) system. Keywords: Cognitive radios, MIMO, OFDM, and Joint transmit and receive group selected arrays.
In recent past the influence of Radar has played a significant part in various fields. Radar sensing is one of
the prime application by which velocity and distance of a moving target can be found out. A joint RadCom
system to serve both radar sensing and wireless communication is proposed which ensures better
performance in terms of spectral efficiency, extended detection range and cost effectiveness. Such systems
demand for a common waveform which is designed in this work that perfectly matches to the system
requirements. OFDM multi carrier technique is chosen to generate a common waveform. Applicability of
multiple antenna technique for direction of arrival estimation is also considered. MIMO-OFDM technique
has gained much interest in the field of communication which improves the signal to noise ratio and lowers
the bit error rate. On the other hand the usage of MIMO reflects in the form of interference between
signals. In order to overcome this effect beamforming technique is used. In addition to theoretical
explanations we have also simulated and discussed the results for the proposed RadCom system using
MATLAB simulation tool.
COMPARING VARIOUS CHANNEL ESTIMATION TECHNIQUES FOR OFDM SYSTEMS USING MATLABijwmn
This paper compares the performance of various channel estimation techniques for OFDM systems over quasi-static channels using MATLab. It compares the performance of five channel estimation techniques, these are: decision directed (DD), linear interpolation, second-order interpolation, discrete Fourier transform (DFT) interpolation, minimum mean square error (MMSE) interpolation. The performance is evaluated in terms of two widely-used performance measures, namely, bit-error rate (BER) and the mean square error (MSE) for different levels of signal-to-noise ratio (SNR). The OFDM model is explained and implemented using MATLab to run different simulations. The simulation results demonstrate that the DD channel estimation provides the lowest BER and MSE as compared to interpolation techniques, at the cost of extra processing delay and comparatively sensitive to channel variations between OFDM symbols. Also, the MMSE interpolation outperforms all other interpolation techniques.
Performance analysis for Adaptive Subcarriers Allocation in Coherent Optical ...iosrjce
The constraint to satisfy the need of increased bandwidth requirement for high speed applications
with higher performance has been a motivation to work on Optical Orthogonal Frequency division multiplexing
(OOFDM) technique with coherent detection. We implement the coherent optical OFDM (CO-OOFDM)
technique and investigate the effect of the number of sub-carriers on performance over single mode fiber (SMF)
links. To explore improvement in performance adaptive subcarriers has been selected by assigning subcarriers
to user according to the conditions of channel. An adaptive subcarrier allocation has been investigated and
performance comparison for proportional and equal allocation has been carried over.
Interoperator Dynamic Spectrum Sharing (Analysis, Costs and Implications)CSCJournals
This paper addresses Dynamic Spectrum Sharing (DSS) between two wireless operators. The Universal Mobile Telecommunication System (UMTS) network is used as a case study. The proposed protocol is evaluated under the uniform and non-uniform traffic conditions. The underlying principles of the algorithm can be deployed in the UMTS extension Band (2500MHz-2690MHz) which is yet to be allocated or the re-farmed GSM spectrum (900MHz/1800MHz). The simulation results for the proposed protocol shows that significant spectrum sharing gains can be obtained. However such spectrum efficiency gain need to be carefully balanced with the complexity in terms of latency (delays) and additional overhead it brings to the network. The results show that significant spectrum sharing gain of 4.0 % and 2.0 % can be obtained under uniform and non-uniform traffic conditions
CL-SA-OFDM: cross-layer and smart antenna based OFDM system performance enha...IJECEIAES
The growing usage of wireless services is lacking in providing high-speed data communication in recent times. Hence, many of the modulation techniques are evolved to attain these communication needs. The recent researches have widely considered OFDM technology as the prominent modulation mechanism to fulfill the futuristic needs of wireless communication. The OFDM can bring effective usage of resources, bandwidth, and system performance enhancement in collaboration with the smart antenna and resource allocation mechanism (adaptive). However, the usage of adaptive beamforming with the OFDM leads to complication in the design of medium access layer and which causes a problem in adaptive resource allocation mechanism (ARAM). Hence, the proposed manuscript intends to design an OFDM system by considering different switched beam smart antenna (SBSA) along with the cross-layer adaptive resource allocation (CLARA) and hybrid adaptive array (HAA). In this, various smart antenna mechanism are considered to analyze the quality of service (QoS) and complexity reduction in the OFDM system. In this paper, various SA schemes are used as per the quality of service (QoS) requirement of the different users. The performance analysis is conducted by considering data traffic reduction, bit-rate reduction, and average delay.
Channel Estimation Techniques in MIMO-OFDM LTE SystemsCauses and Effects of C...IJERA Editor
There is an increasing demand for high data transmission rates with the evolution of the very large scale integration (VLSI) technology. The multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems are used to fulfill these requirements because of their unique properties such as high spectral efficiency, high data rate and resistance towards multipath propagation. MIMO-OFDM systems are finding their applications in the modern wireless communication systems like IEEE 802.11n, 4G and LTE. They also offer reliable communication with the increased coverage area. The bottleneck to the MIMO-OFDM systems is the estimation of the channel state information (CSI). This can be estimated with the help of any one of the Training Based, Semiblind and Blind Channel estimation algorithms. This paper presents various channel estimation algorithms, optimization techniques and their effective utilization in MIMO-OFDM for modern wireless LTE systems.
A review paper on the papr analysis of orthogonal frequency division multiple...ijmnct
OFDM (Orthogonal Frequency Division Multiplexing) has been raised a new modulation technique. Due
to its advantages in multipath fading channel e.g. robust against ISI, ICI and some other advantages like
best QoS for multiple users, efficient usage of bandwidth it is suggested to be the modulation technique for
next generation 4G networks e.g. LTE. But along with all its advantages there are some disadvantages also
e.g. High PAPR (Peak to Average Power Ratio) at the transmitter end and BER (Bit Error Rate) at the
receiving end. Since OFDM is only used in the downlink of 4G networks. To reduce the problems of OFDM
some techniques e.g. SLM, PTS, Clipping, Coding, & Pre-coding etc are suggested but none of them is
reduce the PAPR and BER to an acceptable value. This Paper will discuss some techniques of PAPR &
BER reduction, and their advantages and disadvantages in detail.
Signal Strength Evaluation of a 3G Network in Owerri Metropolis Using Path Lo...Onyebuchi nosiri
Abstract: In this work, the path loss and the received signal strength of a 3G network at 2.1GHz was evaluated to determine its performance within the Owerri metropolis. Various measuring equipment such as Transmission Evaluation and Monitoring System (TEMS 11), Global positioning system (BU353 GPS) and laptop were deployed for the drive test within the selected urban and sub-urban regions. From the data collected, Owerri sub-urban region showed poor received signal power level compared to the Owerri urban region. The path loss exponents computed for the Owerri urban and sub-urban regions are 3.24 and 4.34 respectively, the mean square error was evaluated as 1.96 and 1.68. The result obtained showed deviations between the compared existing models (Hata and Cost 231) and the proposed models. However, the slope of the Hata plot was relatively close in comparison to the proposed model than that of Cost 231; hence, the proposed model was best suited for the environment followed by the Hata model.
Peak detection using wavelet transformIJCNCJournal
A new work based-wavelet transform is designed to overcome one of the main drawbacks that found in the
present new technologies. Orthogonal Frequency Division Multiplexing (OFDM)is proposed in the
literature to enhance the multimedia resolution. However, the high peak power (PAPR) values will obstruct
such achievements. Therefore, a new proposition is found in this work, making use of the wavelet
transforms methods, and it is divided into three main stages; de-noising stage, thresholding stage and then
the replacement stage.
In order to check the system stages validity; a mathematical model has been built and its checked after
using a MATLAB simulation. A simulated bit error rate (BER) achievement will be compared with our
previously published work, where an enhancement from 8×10-1 to be 5×10-1 is achieved. Moreover, these
results will be compared to the work found in the literature, where we have accomplished around 27%
PAPR extra reduction.
As a result, the BER performance has been improved for the same bandwidth occupancy. Moreover and
due to the de-noise stage, the verification rate has been improved to reach 81%. This is in addition to the
noise immunity enhancement.
A SEMI BLIND CHANNEL ESTIMATION METHOD BASED ON HYBRID NEURAL NETWORKS FOR UP...ijwmn
The paper describes how to improve channel estimation in Single Carrier Frequency Division Multiple
Access (SC-FDMA) system, using a Hybrid Artificial Neural Networks (HANN). The 3rd Generation
Partnership Project (3GPP) standards for uplink Long Term Evolution Advanced (LTE-A) uses pilot based
channel estimation technique. This kind of channel estimation method suffers from a considerable loss
ofbitrate due to pilot insertion; all data frame sent contains reference signal. The HANN converts data
aided channel estimator to semi blind channel estimator. To increase convergence speed, HANN uses some
channel propagation Fuzzy Rules to initialize Neural Network parameters before learning instead of a
random initialization, so its learning phase ismore rapidly compared to classic ANN.HANN allows more
bandwidth efficient and less complexity. Simulation results show that HANN has better computational
efficiency than the Minimum Mean Square Error (MMSE) estimator and has faster convergence than
classic Neural Networks estimators.
Reducing the Peak to Average Power Ratio of Mimo-Ofdm SystemsIJCNCJournal
In this paper, we proposed a particle swarm optimization (PSO) based partial transmit sequence (PTS)
technique in order to achieve the lowest Peak-to-Average Power Ratio(PAPR) in Multiple Input Multiple
Output- Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems. Our approach consist of
applying the PSO based PTS on each antenna of the system in order to find the optimal phase factors,
which is a straightforward method to get the minimum PAPR in such a system. The simulation results
demonstrate that the PSO based PTS algorithm when applied to MIMO-OFDM systems with a wide range
of phase factors, tends to give a high performance. In addition, there is no need to increase the number of
particles of the PSO algorithm to enhance the performance of the system. As a result of this, the complexity
of finding the minimum PAPR is kept at a reasonable level.
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.
Pwm technique to overcome the effect ofIJCNCJournal
Many current communication systems suffer from performance degradation due to the high sensitivity to
high power peaks especially in the nonlinear devices. The author introduces a new concept based on the
Pulse Width Modulation (PWM), namely MIMO-OFDM system based PWM (MO-PWM) to overcome this
deficiency. Here, the peak-to-average power ratio (PAPR) problem in Orthogonal Frequency Division
Multiplexing (OFDM) technique is used as a criterion to check the validity of the proposed work.
Moreover, the proposed system work has been implemented over Field Programmable Gate Array (FPGA),
which is designed to characterize both of the complexity and the speed issues.
The systems performance based MO-PWM and validity have been checked based on a numerical analysis
and a conducted simulation. The simulation results show that the MO-PWM can clearly reduce the PAPR
values nevertheless the used OFDM systems’ specifications, and gives a promising results over some
techniques found in the literature, such as clipping, SLM and PTS under same bandwidth occupancy and
system’s specifications.
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 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.
IMPROVEMENT OF LTE DOWNLINK SYSTEM PERFORMANCES USING THE LAGRANGE POLYNOMIAL...IJCNCJournal
To achieve a high speed data rate, higher spectral efficiency, improved services and low latency the 3rd
generation partnership project designed LTE standard (Long Term Evolution).the LTE system employs
specific technical as well the technical HARQ, MIMO transmission, OFDM Access or estimation technical.
In this paper we focus our study on downlink LTE channel estimation and specially the interpolation which
is the basis of the estimation of the channel coefficients. Thus, we propose an adaptive method for polynomial interpolation based on Lagrange polynomial. We perform the Downlink LTE system MIMO transmission then compare the obtained results with linear, Sinus Cardinal and polynomial Newton Interpolations. The simulation results show that the Lagrange method outperforms system performance in term of Block Error Rate (BLER) , throughput and EVN(%)vs. Signal to Noise Ratio (SNR).
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.
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.
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.
Dynamic bandwidth allocation scheme in lr pon with performance modelling and ...IJCNCJournal
We consider models of telecommunication systems that incorporate probability, dense real-time and data.
We present a new formal abstraction method for computing minimum and maximum reachability
probabilities for such models. Our approach uses strictly local formal abstract steps to reduce both the size
of abstract specifications generated and the complexity of operations needed, in comparison to previous
approaches of this kind. A selection of large case studies are implemented the techniques and evaluate,
which include some infinite-state probabilistic real time models, demonstrating improvements over existing
tools in several cases. The capacity of metro and access networks are extended the reach and split ratio of
the conventional Long - Reach Passive Optical Networks (LR-PONs). The efficient solutions of LR-PONs
are appeared in feeder distances around 100km and high split ratios up to 1000-way . Among many
existing approaches, one of the most effective options to improve network performance in LR-PONs are the
multi-thread based dynamic bandwidth allocation (DBA) scheme where several bandwidth allocation
processes are performed in parallel is considered. Without proper intercommunication between the
overlapped threads, multi-thread DBA may lose efficiency and even perform worse than the conventional
single thread algorithm. Real Time Probabilistic Systems are used to evaluate a typical PON systems
performance. This approach is more convenient, flexible, and lower cost than the former simulation method,
which do not need develop special hardware and software tools. Moreover, how changes in performance
depend on changes in the particular modes can be easily analysis by supplying ranges for parameter values.
The proposed algorithm with traditional DBA is compared, and shows its advantage on average packet
delay. The key parameters of the algorithm are analysed and optimized, such as initiating and tuning
multiple threads, inter -thread scheduling, and fairness among users. The algorithms advantage in
numerical results are decreased the average packet delay and improve network throughput under varying
offered loads.
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.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
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
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
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• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
EFFICIENCY ENHANCEMENT BASED ON ALLOCATING BIZARRE PEAKS
1. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
DOI: 10.5121/ijwmn.2016.8407 107
EFFICIENCY ENHANCEMENT BASED ON
ALLOCATING BIZARRE PEAKS
Q. J. Hamarsheh1
, O. R. Daoud2*
, M. M. Ali1
and A. A. Damati3
1
Department of Computer Engineering,
2
Department of Communications and Electronics Engineering,
3
Department of Electrical Engineering,
Philadelphia University, Amman, Jordan
ABSTRACT
A new work has been proposed in this paper in order to overcome one of the main drawbacks that found in
the Orthogonal Frequency Division Multiplex (OFDM) systems, namely Peak to Average Power Ratio
(PAPR). Furthermore, this work will be compared with a previously published work that uses the neural
network (NN) as a solution to remedy this deficiency.
The proposed work could be considered as a special averaging technique (SAT), which consists of wavelet
transformation in its first stage, a globally statistical adaptive detecting algorithm as a second stage; and
in the third stage it replaces the affected peaks by making use of moving average filter process. In the NN
work, the learning process makes use of a previously published work that is based on three linear coding
techniques.
In order to check the proposed work validity, a MATLAB simulation has been run and has two main
variables to compare with; namely BER and CCDF curves. This is true under the same bandwidth
occupancy and channel characteristics. Two types of tested data have been used; randomly generated data
and a practical data that have been extracted from a funded project entitled by ECEM. From the achieved
simulation results, the work that is based on SAT shows promising results in reducing the PAPR effect
reached up to 80% over the work in the literature and our previously published work. This means that this
work gives an extra reduction up to 15% of our previously published work. However, this achievement will
be under the cost of complexity. This penalty could be optimized by imposing the NN to the SAT work in
order to enhance the wireless systems performance.
KEYWORDS
Orthogonal Frequency Division Multiplexing, Neural Network, Linear Codes, Wavelet, Moving Average
Filter.
1. INTRODUCTION
Orthogonal Frequency Division Multiplexing (OFDM) is considered as one of the main topics
that is taken into consideration in order to enhance the wireless systems reliability during the last
decades. This is in order to achieve a promising data rates either for the downlinks or the uplinks
physical transmissions, especially after the rapid growth in using the mobile phone applications
[1, 2]. Along the last decades, the researchers got from the benefits of OFDM technology and are
adopted widely in the recent wireless communications technologies; especially in the wide band
2. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
108
systems and standards, where the Mobile data traffic expected to increase by 11 times by 2018 [3,
4]. However, the Peak-to-Average Power ratio problem is considered as one of the major
drawbacks that limits the efficiency of OFDM technology. The sensitivity to the nonlinear
behavior especially with none constant envelops plays a vital role in affecting the powerfulness of
using OFDM. Thus a spectral regrowth in adjacent channels and deformation of the signal
constellation could happen. Accordingly and in order to minimize the PAPR values, many
solutions were found in the literature. This will prevent the limitations in using the nonlinear
devices without back-off levels, especially the power amplifiers and mixers; such as multiple
signal representations, neural networks, neuro-fuzzy, selective mapping, partial transmit
sequence, coding, clipping, filtering and travelling wave tube amplifiers[1,5-12].
Furthermore and to enhance the OFDM systems robustness, Multiple-Input Multiple-Output
(MIMO) technology has been proposed to be combined with the OFDM techniques. MIMO
technology also has a number of powerful advantages including the ability to increase the system
capacity and improving the communication reliability via the diversity gain. The capacity of
MIMO channels scale linearly with respect to the minimum available transmitter and receiver
antennas [11, 13].
In this work, we are motivated to compare a new proposition based on a special averaging
technique with the previously published work based on NN in [2]. In [2], the NN were imposed
and trained based on our previously attained results in [11-13], this is in order to attain the goal of
maximum amplification [14]. The NN will intelligently choose the best combination that reduces
the PAPR ratio values in the transmitted OFDM signal. As a result of imposing the NN, slight
enhancement has been attained at the 10 dB threshold for the BER; since it has been reduced to
be 2.5×10-2
from 1.1×10-2
[2]. Furthermore, the MIMO technology has been imposed in order to
enhance the system’s capacity by introducing the use of Vertical Bell Laboratories Layered
Space-Time (V-BLAST) techniques [15].
The special averaging technique will be divided into three main stages and it will make use of the
test data has been collected from a funded work by the European Union (SRTD-II) and
Philadelphia University; entitled by Energy Consumption Efficiency Management-Phase I
(ECEM). Therefore, the wireless systems based MIMO-OFDM performance will be checked
based on the bit error rate (BER) that is based on the Chernoff Union Bound and the
complementary cumulative distribution function (CCDF) curves. These three stage will consist of
a pre-processing stage (check the noise removal effect and to enhance the input signal
characteristics), detecting the odd peaks stage (derivatives theorem, magnitude sign selection,
template matching process, adaptive thresholding process), and the post processing stage (moving
averaging filter).
The rest of paper is organized as follows; the introduced structure of the wireless system based on
MIMO-OFDM models is defined in Section 2, the numerical and simulation results are presented
in Section 3, while the last section summarizes the conclusion.
2. MIMO-OFDM SYSTEM DESCRIPTION
In order to fulfill the requirements of this work, the MIMO-OFDM system’s parts will cover the
followings; 2/3 turbo encoder, 64 QAM, and a V-BLAST MIMO encoder. V-BLAST is used for
increasing the overall throughput expressed in terms of bits/symbol, while applying the IFFT to
generate the OFDM symbols [2, 15]. As a consequence for the coherent addition after the IFFT, a
3. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
109
huge peak value may appear [1-12].
In this work, a comparison between two main proposed work will accomplished; consequently
the work based on NN and will be described in subsection A, the proposed work that is based on
a special averaging technique will be covered in subsection B.
In this configuration, the transmitted OFDM signal consists of a sum of 64 QAM modulated
subcarriers and is shown in [1] as:
T
t
t
t
e
d
t
s s
s
N
N
i
t
t
T
i
f
j
N
i
s
s
s
c
s
+
≤
≤
= ∑ −
=
−
+
−
+
,
)
( 2
2
)
)(
5
.
0
2
(
2
π
(1)
Here, di can be considered as a complex input symbol resulted from the modulation stage, the
carrier frequency of the i-th subcarrier is depicted in fc, the OFDM symbol duration is defined as
T and the starting time of one OFDM symbol is t=ts.
2.1. NN-Based Proposed Work
Figure 1 shows the main parts of the MIMO-OFDM transmitter stages with the addition the NN
part [2].
Figure 1. AN MIMO-OFDM-Based NN Transmitter
It shows that the NN part has been imposed after the IFFT stage. This is due to that the same
phase addition will increase the probability of PAPR appearance [1, 2]. A high peak power equals
to N times the average power occasionally appears as a result of this addition process. Thus, the
PAPR definition can be written as:
=
avg
peak
P
P
10
10log
PAPR (2)
where, Ppeak is the maximum power of an OFDM symbol, and Pavg is the average power.
4. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
110
From [11], a conclusion has been drawn that the PAPR will decrease if the average power of the
OFDM symbol is decreased. This mathematical derivation was the basis of our previously
published work to combat the effect of the PAPR drawback on the MIMO-OFDM systems.
Imposing the NN can improve MIMO-OFDM systems performance; as it is the simplest way of
linearization for RFPA. This is due to the NN ability of simultaneous BW linearization [16].
Intelligent controllers are generally self-organizing or adaptive and are naturally able to cope with
the significant changes in the plant and its environment. As processes increase in complexity,
they become less amenable to direct mathematical modeling based on physical laws, since they
may be, distributed, stochastic, nonlinear and time-varying.
Research into intelligent systems integrates concepts and methodologies from a range of
disciplines including neurophysiology, artificial intelligence, optimization and
approximationtheory, control theory and mathematics. This integration of research fields has led
to an emergent discipline, frequently referred to as connectionism or neuron science that
inherently incorporates distributed processing concepts organized in an intelligent manner.
Connectionist or neurons systems, unlike conventional techniques and self-programming, appear
to be stochastic or fuzzy, heuristic and associative. An approximation to the desired mapping is
constructed in intelligent or learning systems [17].
ANNs or simply NNs go by many names such as connectionist models, parallel distributed
processing models, and neuromorphic systems, whatever the name, all these models attempt to
achieve good performance via dense interconnection of simple computational elements.
Computational elements or nodes used in neural net models are nonlinear and typically analog.
The simplest node sums N weighted inputs and passes the results through a nonlinear function [2,
17, 18]. From this work, very promising results have been extracted as shown in Figure 2. The
structure of the used NN can be found in Table 1 as:
Table 1. NN structure
Functions Description
Network Type FFB-P
Number of layers 3
Number of Neurons 512, 30, 512
Activation Function Bipolar-Sigmoid
Training Function Error B-P
Performance Function &
number of epochs
10-3
and(24873, 16470)
5. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
111
Figure 2. BER vs. SNR curves for the NN based work [2]
As mentioned previously, the previous achieved result in combatting the PAPR [11-13] has been
used in the learning process of the NN part. This is in to model the MIMO-OFDM system based
on multipath fading channels. The achieved results are depicted in Table 2 [2].
Table 2. Back-propagation based Powell-Beale conjugate gradient
Learning
Parameter
MSE Number of trained OFDM
symbols
0.1 6.254×10-5
100
0.01 8.157×10-5
100
Based on the results in [2], it can be concluded that the NN work has a slight improvement over
the previously achieved results in [11-13]. From the complexity point of view, this enhancement
comes in addition to the simplicity of the system structure, i.e. the NN simplifies the complexity
of the work in addition to boost the performance enhancement by combatting the PAPR
intelligently. In addition to the CCDF results, Figure 2 depicts a slight modification in the
system’s performance from the BER point of view; at 10 dB threshold as an example the BER has
been reduced from 49×10-2
to 12×10-3
. Furthermore, at 16dB threshold this enhancement has been
considered and valuable since it reduces the BER from 15×10-2
to 15×10-7
.
2.2. Spatial Averaging Technique-Based Proposed Work
As described in [17], Figure 3 is clearly shows the stages of the proposed work.It is based on the
adaptive convolutional approach and divided into three main stages. The procedure of these
stages is as follows:
- After reading the affected OFDM signal by PAPR, the pre-processing stage is started with
experiences the effect of some wavelet families and their effect on clean the signal from the
6. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
112
attached noise, such as the Biorthogonal, Daubechis, Symmlet, Coiflet and Haar wavelets.
Here, three main factors have been taking into consideration in order to check the noise
removal effect and to enhance the input signal characteristics, namely mean square error
(MSE), signal to noise ratio (SNR) and the peak SNR (PSNR).The results from the first stage
can be shown in Figure 3. It shows the results of the checked performance based on the three
factors between the wavelet-based noise reduction approach and the noiseless OFDM
Signals.
- The process of detecting the odd peaks (having the high PAPR) is covered in the second stage
and starts with
o Linking the idea of local maxima with the derivatives theorem and looking for the
increasing-decreasing pair in the differences.
o Convert the derived signal into a modified signal based on magnitude sign selection,
where the sign indicates the trend of increasing, decreasing or remaining no change.
o Allocating the peaks based on a template matching process making use of the discrete
convolution idea. Thus, the [-1,1] pattern is used as sliding kernel window and
convolved with signed data. In the output result of this process, the value of 2 appears
only if the pattern matches exactly and its corresponding peak value.
o The final step in this stage is to threshold the founded peaks by making use of a
globally statistical adaptive thresholding process. Adaptively, the threshold will be
determined with respect to descriptive statistics (maximum, mean and standard
deviation values and constant adaptive parameter k). it is clearly found in (3) as:
Thresh = (m + avgabs + avgdev ) / k (3)
Here, m stands for the OFDM signal maximum value, avgabs is the mean of the
absolute OFDM values, avgdev is the standard deviation, and a predefined constant k
that is used in order to control the thresholding process adaptively. Thus, a
thresholding limit will be varied according to the systems’ limitations.
Figure 3. The flowchart of the proposed algorithm
7. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
Figure 4.performance assessment methods and the wavelet
- The final stage deals with the post processing of the thresholded founded peaks making use of
averaging filters (AF) such as the simple
averaging filter is used in order to deal with the peak values with special treatment found in
(4). These peaks will be replaced with a certain value that is extracted based on its surrounded
values. The modified affected OFDM sample will be represented as:
= ( +
Where
is the modified OFDM sample,
is the affected OFDM sample.
Figure 5 depicts the results of the proposed procedure for detecting the large peaks and
thresholding them below a predefined threshold.
Figure 5. OFDM peaks detection using adaptive convolution
International Journal of Wireless Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
assessment methods and the wavelet-based noise reduction approach.
The final stage deals with the post processing of the thresholded founded peaks making use of
averaging filters (AF) such as the simple-AF, exponential-AF and Weighted-AF. The moving
raging filter is used in order to deal with the peak values with special treatment found in
(4). These peaks will be replaced with a certain value that is extracted based on its surrounded
values. The modified affected OFDM sample will be represented as:
+ )/3
is the modified OFDM sample, … !##$ is the number of OFDM sample,
is the affected OFDM sample.
Figure 5 depicts the results of the proposed procedure for detecting the large peaks and
thresholding them below a predefined threshold.
OFDM peaks detection using adaptive convolution-based approach
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based noise reduction approach.
The final stage deals with the post processing of the thresholded founded peaks making use of
AF. The moving
raging filter is used in order to deal with the peak values with special treatment found in
(4). These peaks will be replaced with a certain value that is extracted based on its surrounded
(4)
is the number of OFDM sample,
Figure 5 depicts the results of the proposed procedure for detecting the large peaks and
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In this Figure, the red stars defining the peaks above certain threshold. These peaks are clearly
treated in the modified OFDM signal part by making use of equation (4).
3. SIMULATION RESULTS AND DISCUSSION
Comparison between the previously published work that is based on the NN and the new work
based on a special averaging technique has been made. In order to accomplish this target, a
MATLAB-based simulation has been performed to imitate both of block diagram in Figure 1 and
the flowchart of Figure 3. The results of this simulation will compare the OFDM performance
based on the different two proposed techniques keeping in mind the two main factors; BER and
CCDF. This is in addition to taking into consideration identical channel conditions with the
theoretical representation. Furthermore, real signals will be extracted from the funded project by
both of European Union under the SRTD-II and Philadelphia University. This is in addition to the
theoretically initiated data. The system parameters were chosen to cover the following:
- 512 subcarrier
- 64-QAM modulation technique
- 2/3 inner coding rate
- 1/4 Guard interval duration
- V-BLAST MIMO coding technique
This is in addition to keep in mind the NN structure settings that shown previously in Table 1 and
Table 2, which they were extracted experimentally in previous work [2].
Figures 6 and 7 show the simulation results based on CCDF curves and the BER ones,
respectively. These results cover the comparison between the different two works. Furthermore
and in order to check its performance, Table 3 shows a comparison that has been made with
previously published work. From the achieved results, the OFDM system QoS has been checked
and verified from both of two different kinds of data.
Table 3. The Simulation results of the proposed technique compared to the literature work for a 64-QAM modulation
technique.
Input
Data
CCDF (2%)
Additional
Reduction over
literature (%)
Conventional
PAPR
(dB)
Proposed
Work
(dB)
Clipping
SLM
PTS
Theoretical 20 8.3 75 53.3 20
ECEM 22 8 69 54 21
It is clearly shown that there is a huge improvement achieved from the proposed work; at a
probability of 2% the PAPR has been reduced to around 8 dB instead of 20 dB. Moreover and
comparing to the work in the literature, the attained improvement falls in the range of 20% to
9. International Journal of Wireless Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
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75% more enhancements over the three of them. The best values were over the clipping technique
and the worst were over the PTS technique.
Figure 6 shows the CCDF comparison between the NN based work and the special averaging
technique based work. These curves contain the thresholds that the probability of the PAPR will
not exceed. The limitation for such simulation as mentioned earlier.
Figure 6. PAPR combating proposed work comparison
Figure 6 shows that a very promising results especially after exceeding the 12 dB threshold. It is
clearly shown that before 12 dB there is an enhancement; however it cannot reflect the imposed
work weight; as an example at 8 dB the probability comes between 1.5×10-2
to around 6×10-2
. At
16 dB threshold, the probability of using the SAT gives exceeds the 10-7
, while the NN based
work does not exceed the probability of 7×10-6
and the Linear coding one has the probability
1.8×10-5
.
Figure 7. BER curves comparison
Figure 7, shows that nevertheless the SAT work gives a better enhancement in the CCDF curves,
the NN gives better BER curves. This is due to that the NN is adaptive and compatible with the
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systems behavior changings. Here, the BER at 16 dB as an example is enhanced from 5.3 ×10-2
to
1.5 ×10-2
and fall between enhancement ratios from 18.5% to 72%.
3. CONCLUSIONS
In this paper, a new work has been proposed based a special averaging technique. In order to
validate its efficiency, it has been compared to a previously published work that is based on
neural networks, where the learning process of the proposed NN has been accomplished based on
the previously extracted data from our previous published work.
From the achieved results, the OFDM system QoS has been checked and verified from both of
two different kinds of data. It is clearly shown that there is a huge improvement achieved from
the proposed work; at a probability of 2% the PAPR has been reduced to around 8 dB instead of
20 dB. Moreover and comparing to the work in the literature, the attained improvement falls in
the range of 20% to 75% more enhancements over the three of them. The best values were over
the clipping technique and the worst were over the PTS technique. Furthermore, at At 16 dB
threshold, the probability of using the SAT gives exceeds the 10-7
, while the NN based work does
not exceed the probability of 7×10-6
and the Linear coding one has the probability 1.8×10-5
. From
the other side, the NN gives better BER curves. This is due to that the NN is adaptive and
compatible with the systems behavior changings. Here, the BER at 16 dB as an example is
enhanced from 5.3 ×10-2
to 1.5 ×10-2
and fall between enhancement ratios from 18.5% to 72%.
As a conclusion from the previous results, the proposed work have proved their reliability in
overcoming the effect of PAPR. This is in addition to that the use of NN reduces the added
complexity at the receiver side since there is no need to send a control data that has been sent in
the previously published work.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the financial support from the SRTD-II projects under the
umbrella of the European Union support and from the Philadelphia University to build the project
entitled “Energy Consumption Efficiency Management (ECEM)”, which is managed by the
Higher Council for Science Technology.
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Authors
Qadri J. Hamarsheh has received the master degree of Computer Machines,
Systems and Networks from the department of Computer Engineering, Lviv
Polytechnic Institute in 1991. He obtained his Ph.D degree from Lviv National
University “LvivskaPolytechnica”, Ukraina in 2001. Currently he is working as
assistant professor of Computer Engineering, Philadelphia University-Jordan. He
is in teaching since 2001. His areas of interest include Digital Signal Processing
(DSP), Digital Image, Speech Processing, Object-Oriented Technology and
Programming Languages, Internet Technology and Wireless Programming.
Omar R. Daoud has achieved the PhD in the field of Communication and
Electronics Engineering at DMU/ UK 2006. He joined Philadelphia University in
2007 as Assistant Professor. His current work is about achieving the Quality of
Service for the 4th Generation of the Wireless and Mobile Communication
Systems by combining the advantages of the OFDM and the multiple antenna
technology. He is the Assistant Dean in the Faculty of Engineering in addition to
the Head of Communications and Electronics engineering department. Moreover, and in March 2012 he
has promoted to the associate professor rank.
12. International Journal of Wireless Mobile Networks (IJWMN) Vol. 8, No. 4, August 2016
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Mohammed M. Ali, received the BSc, MSc and PhD degrees in computer and
control engineering from the university of Technology, Iraq in 1981, 1993, and 1998
respectively. He is currently an assistant professor in the department of computer
engineering at Philadelphia University, Jordan. His research interest includes fuzzy
logic, neural networks, image processing, and computer interfacing. He has 16
published papers related to real-time computer control applications.
Ahlam A. Damati has achieved the MSc in the field of Electrical Engineering/
Communications from The University of Jordan/ Jordan 2002. She had worked as a
lecturer in different universities since 2003; UJ and GJU, while she joined
Philadelphia University in 2014 as a lecturer in the Electrical Engineering
department. Her research interests are in achieving the Quality of Service for the
wireless new technologies based on a variety of digital signal processing techniques.