In this paper, channel overhead is reduced by exploiting channel sparsity for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) system. Where, compressive sensing (CS) based dictionary design algorithms has been adopted as a channel estimation technique in high mobile systems with minimal number of pilots, such as high-speed train (HST) systems. A novel framework design of the dictionary-based CS was proposed considering both delay and Doppler effects in order to correctly recover the channel response. The channel under consideration is a 2 by 2 space-time block code (STBC) MIMO channel. Simulation tests according to the international telecommunication union (ITU) channel model demonstrated the suitability of the proposed dictionary for estimating the channel impulse response (CIR) of a liner time varying (LTV) channel with a mobility approaches 675 Km/h related to a Doppler frequency of 1500 Hz and 2.4 GHz carrier frequency. Two CS recovery algorithms were applied; orthogonal matching pursuit (OMP) and basis pursuit (BP), where by about 7 dB gain in signal to noise ratio (SNR) was achieved with mobility of 675 Km/h using OMP as compared to BP at a bit error rate (BER) of with 128 OFDM subcarriers.
Performance evaluation of high mobility OFDM channel estimation techniques IJECEIAES
In wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) has been adopted due to its robustness to multipath fading and high data rate transmissions. At the other hand, the performance of OFDM systems severely degraded due to multi-path fading and Doppler frequency shifts in mobile systems, which causes inter-carrier-interference (ICI). Thus, Estimation of channel parameters is required at the receiver using a pre designed estimator where pilot tones are inserted in each OFDM symbol. In this paper, a random pilot data are generated and inserted in each OFDM symbol at equally spaced locations. The performance test of Least Square (LS) and Linear Minimum Mean Square (LMMSE) estimation methods are proposed with Discrete Fourier Transform (DFT) based on both LS and LMMSE, where different ITU channel models are considered in order to compare their performance for data transmission in high mobile systems with different Doppler frequencies exceeds 200 Hz and minimal number of pilots.
Hybrid Adaptive Channel Estimation Technique in Time and Frequency Domain for...Tamilarasan N
This document summarizes a research paper that proposes a hybrid adaptive channel estimation technique for MIMO-OFDM wireless communication systems. The technique integrates channel estimation in the time domain and frequency domain. It uses column-based time domain estimation initially and switches to row-based frequency domain estimation when channel quality is good and bit error rate is low. It switches back to time domain estimation when channel quality worsens. The goal is to adaptively estimate the channel under different conditions. Experimental results showed the proposed hybrid technique outperformed other methods.
This document proposes a method called simultaneous multi-channel reconstruction for time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) systems. It utilizes the inter-block interference (IBI)-free region within TDS-OFDM symbols to reconstruct multiple sparse multipath channels simultaneously using distributed compressive sensing theory. Specifically, it exploits the temporal correlation of wireless channels and the property that path gains change faster than path delays. It then proposes a parameterized channel estimation method based on simultaneous compressive sampling matching pursuit algorithm to achieve better performance in fast time-varying channels. Simulation results show the proposed scheme improves performance over conventional solutions.
PERFORMANCE OF MIMO MC-CDMA SYSTEM WITH CHANNEL ESTIMATION AND MMSE EQUALIZATIONTamilarasan N
The quality of a wireless link can be described by three basic parameters, namely transmission rate, transmission range
and transmission reliability. With the advent of multiple-input multiple-output (MIMO) assisted Multicarrier code
division multiple access (MC-CDMA) systems, the above-mentioned three parameters may be simultaneously
improved. The MC-CDMA combined with the MIMO technique, has become a core technology for future mobile radio
communication system. However, possible potential gain in spectral efficiency is challenged by the receiver’s ability to
accurately detect the symbol due to inter symbol interference (ISI). Multipath propagation, mobility of transmitter,
receiver and local scattering cause the signal to be spread in frequency, different arrival time and angle, which results in
ISI in the received signal. This will affect overall system performance. The use of MC-CDMA mitigates the problem of
time dispersion. However, still it is necessary to remove the amplitude and phase shift caused by channel. To solve this
problem, a multiple antenna array can be used at the receiver, not only for spectral efficiency or gain enhancement, but
also for interference suppression. This can be done by the, efficient channel estimation with strong equalization. This
paper proposes MIMO MC-CDMA system, Minimum mean square error (MMSE) equalization with pilot based
channel estimation. The simulation result shows improved Bit error rate (BER) performance when the sub carrier (SC)
and antenna configuration were increased
This document summarizes two channel estimation methods for MIMO-OFDM systems: blind channel estimation and QRD-M/Kalman filter based detection. Blind channel estimation works by identifying the channel based on knowledge of the channel and data symbols using noise subspace approach and linear precoding. It has fast convergence, requires few OFDM symbols, and can be used with any number of transmit/receive antennas. QRD-M/Kalman filter based detection uses an adaptive complexity QRD-M algorithm and Kalman filters to track individual channels with lower complexity and good tracking ability. It decomposes the received signal into an upper triangular matrix and uses maximum likelihood detection on individual subcarriers. Both methods are analyzed and their advantages/dis
The document describes experiments conducted using an experimental HSDPA transmission system to measure HSDPA throughput performance. Key findings include:
1) Throughput increased with the maximum number of received codes, with 15 codes achieving up to 17% higher throughput than 10 codes.
2) Field experiments showed throughput was determined by signal to interference ratio and was highest (9.8 Mbps) with 15 codes and line of sight to the base station.
3) Applying transmit/receive diversity at the base station and mobile station further improved throughput by enhancing signal quality.
Estimation of bit error rate in 2×2 and 4×4 multi-input multioutput-orthogon...IJECEIAES
Multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems with multiple input antennas and multiple output antennas in dynamic environments face the challenge of channel estimation. To overcome this challenge and to improve the performance and signal-tonoise ratio, in this paper we used the Kalman filter for the correct estimation of the signal in dynamic environments. To obtain the original signal at the receiver end bit error rate factor plays a major role. If the signal to noise ratio is high and the bit error rate is low then signal strength is high, the signal received at the receiver end is almost similar to the i th transmitted signal. The dynamic tracking characteristic of Kalman filter is used to establish a dynamic space-time codeword and a collection of orthogonal pilot sequences to prevent interference among transmissions in this paper. Using the simulation, the Kalman filter method can be compared to the other channel estimation method presented in this paper that can track timevarying channels rapidly.
Performance evaluation of high mobility OFDM channel estimation techniques IJECEIAES
In wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) has been adopted due to its robustness to multipath fading and high data rate transmissions. At the other hand, the performance of OFDM systems severely degraded due to multi-path fading and Doppler frequency shifts in mobile systems, which causes inter-carrier-interference (ICI). Thus, Estimation of channel parameters is required at the receiver using a pre designed estimator where pilot tones are inserted in each OFDM symbol. In this paper, a random pilot data are generated and inserted in each OFDM symbol at equally spaced locations. The performance test of Least Square (LS) and Linear Minimum Mean Square (LMMSE) estimation methods are proposed with Discrete Fourier Transform (DFT) based on both LS and LMMSE, where different ITU channel models are considered in order to compare their performance for data transmission in high mobile systems with different Doppler frequencies exceeds 200 Hz and minimal number of pilots.
Hybrid Adaptive Channel Estimation Technique in Time and Frequency Domain for...Tamilarasan N
This document summarizes a research paper that proposes a hybrid adaptive channel estimation technique for MIMO-OFDM wireless communication systems. The technique integrates channel estimation in the time domain and frequency domain. It uses column-based time domain estimation initially and switches to row-based frequency domain estimation when channel quality is good and bit error rate is low. It switches back to time domain estimation when channel quality worsens. The goal is to adaptively estimate the channel under different conditions. Experimental results showed the proposed hybrid technique outperformed other methods.
This document proposes a method called simultaneous multi-channel reconstruction for time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) systems. It utilizes the inter-block interference (IBI)-free region within TDS-OFDM symbols to reconstruct multiple sparse multipath channels simultaneously using distributed compressive sensing theory. Specifically, it exploits the temporal correlation of wireless channels and the property that path gains change faster than path delays. It then proposes a parameterized channel estimation method based on simultaneous compressive sampling matching pursuit algorithm to achieve better performance in fast time-varying channels. Simulation results show the proposed scheme improves performance over conventional solutions.
PERFORMANCE OF MIMO MC-CDMA SYSTEM WITH CHANNEL ESTIMATION AND MMSE EQUALIZATIONTamilarasan N
The quality of a wireless link can be described by three basic parameters, namely transmission rate, transmission range
and transmission reliability. With the advent of multiple-input multiple-output (MIMO) assisted Multicarrier code
division multiple access (MC-CDMA) systems, the above-mentioned three parameters may be simultaneously
improved. The MC-CDMA combined with the MIMO technique, has become a core technology for future mobile radio
communication system. However, possible potential gain in spectral efficiency is challenged by the receiver’s ability to
accurately detect the symbol due to inter symbol interference (ISI). Multipath propagation, mobility of transmitter,
receiver and local scattering cause the signal to be spread in frequency, different arrival time and angle, which results in
ISI in the received signal. This will affect overall system performance. The use of MC-CDMA mitigates the problem of
time dispersion. However, still it is necessary to remove the amplitude and phase shift caused by channel. To solve this
problem, a multiple antenna array can be used at the receiver, not only for spectral efficiency or gain enhancement, but
also for interference suppression. This can be done by the, efficient channel estimation with strong equalization. This
paper proposes MIMO MC-CDMA system, Minimum mean square error (MMSE) equalization with pilot based
channel estimation. The simulation result shows improved Bit error rate (BER) performance when the sub carrier (SC)
and antenna configuration were increased
This document summarizes two channel estimation methods for MIMO-OFDM systems: blind channel estimation and QRD-M/Kalman filter based detection. Blind channel estimation works by identifying the channel based on knowledge of the channel and data symbols using noise subspace approach and linear precoding. It has fast convergence, requires few OFDM symbols, and can be used with any number of transmit/receive antennas. QRD-M/Kalman filter based detection uses an adaptive complexity QRD-M algorithm and Kalman filters to track individual channels with lower complexity and good tracking ability. It decomposes the received signal into an upper triangular matrix and uses maximum likelihood detection on individual subcarriers. Both methods are analyzed and their advantages/dis
The document describes experiments conducted using an experimental HSDPA transmission system to measure HSDPA throughput performance. Key findings include:
1) Throughput increased with the maximum number of received codes, with 15 codes achieving up to 17% higher throughput than 10 codes.
2) Field experiments showed throughput was determined by signal to interference ratio and was highest (9.8 Mbps) with 15 codes and line of sight to the base station.
3) Applying transmit/receive diversity at the base station and mobile station further improved throughput by enhancing signal quality.
Estimation of bit error rate in 2×2 and 4×4 multi-input multioutput-orthogon...IJECEIAES
Multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems with multiple input antennas and multiple output antennas in dynamic environments face the challenge of channel estimation. To overcome this challenge and to improve the performance and signal-tonoise ratio, in this paper we used the Kalman filter for the correct estimation of the signal in dynamic environments. To obtain the original signal at the receiver end bit error rate factor plays a major role. If the signal to noise ratio is high and the bit error rate is low then signal strength is high, the signal received at the receiver end is almost similar to the i th transmitted signal. The dynamic tracking characteristic of Kalman filter is used to establish a dynamic space-time codeword and a collection of orthogonal pilot sequences to prevent interference among transmissions in this paper. Using the simulation, the Kalman filter method can be compared to the other channel estimation method presented in this paper that can track timevarying channels rapidly.
This document discusses adaptive communication techniques using soft computing methods. It proposes using Ant Colony Optimization (ACO) combined with a Fuzzy Rule Base System (FRBS) for adaptive coding, modulation, and power allocation in an Orthogonal Frequency Division Multiplexing (OFDM) system. It compares the proposed approach to other techniques like Simulated Annealing and FRBS, and to a fixed power scheme. The key contributions of the paper are applying ACO and FRBS together for adaptive parameter selection in OFDM to maximize capacity while meeting power and bit error rate constraints.
The document proposes a new channel estimation algorithm called ICEA-DA for MIMO-OFDM systems. ICEA-DA uses least squares estimation with discrete Fourier transform and integrates it with a differential evolution technique. It is placed at the central part of the MIMO-OFDM system between the transmitter and receiver blocks. The proposed method is evaluated for a 2x4 MIMO system using QPSK modulation. Results show ICEA-DA provides better performance than existing techniques in terms of bit error rate, peak signal-to-noise ratio, channel capacity, and symbol error rate.
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
In this work, high-speed transmission over the long-haul optical channel using orthogonal frequency division multiplexing (OFDM) was investigated. Furthermore, we recommend mixing polarization division multiplexing (PDM) with coherent OFDM (CO-OFDM) and quadrature amplitude modulation (16-QAM) to improve spectral efficiency (SE) while transmitting over a wavelength division multiplexing (WDM) system.
An 800 Gb/s WDM PDM-CO-OFDM-16QAM transmission system with various channel spacing of 100 GHz, 50 GHz, and 25 GHz is examined utilizing the OptiSystem (2021) version 18.0 software package over ten spans of 60 km standard single-mode fiber (SSMF). Different channel spacing WDM systems have been compared in terms of performance and SE. The results reveal that the WDM system with 100 GHz channel spacing has a longer transmission range and needs minimal optical signal to noise ratio (OSNR) at the reception. The 25 GHz channel spacing WDM system exceeds the others in terms of SE. Further, the effect of ultra-low loss and large effective area fiber in lowering span loss and nonlinear effects for
25 GHz channel spacing WDM system is investigated. The findings show that the system performance with the new fiber outperforms the SSMF.
The acceptable bit error rate (BER) for this study is 0.033 (20% concatenated forward error correction (FEC) threshold).
PERFORMANCE EVALUATION OF MC-CDMA SYSTEM OVER RAYLEIGH FADING CHANNELIJCSES Journal
Multi Carrier Code Division Multiple Access (MC-CDMA) is a well known technique for high speed
wireless data transmission .Two advanced technology was included in the MC-CDMA structure, such as
orthogonal frequency division multiplex (OFDM) and the code division multiple access (CDMA),so that it
benefits from the robustness of OFDM against multipath environment and from the capability of multiuser
multiplexing services that is achieved via (CDMA) system. MC-CDMA is a multicarrier spread spectrum
system which is classified as the candidate scheme for future mobile radio systems. In this paper MCCDMA
system, with Rayleigh fading channel and 16QAM array modulation, was simulated to investigate
the effects of different parameters on the system performance, such as processing gain; number of paths;
number of users; interleaving; and coding ratio.MC-CDMA performances can be considerably improved
by proper selection of these parameters. As expected, results show that MC-CDMA has a better performance over CDMA system.
The document proposes a blind channel estimation method for FBMC/OQAM systems based on a modified subspace approach. The key points are:
1) The proposed method utilizes spatial diversity techniques to introduce data redundancy, allowing for blind channel estimation without using a preamble. This improves spectral efficiency compared to conventional preamble-based methods.
2) The accuracy of channel estimation is evaluated using the root mean square error (RMSE) of estimated channel amplitudes.
3) Simulations show the proposed blind estimation method provides better RMSE performance than conventional preamble methods, especially at higher signal-to-noise ratios (SNRs). The validity of the method is verified under different simulation conditions.
This document presents an intelligent link adaptation scheme for OFDM systems that adapts coding, modulation, and power allocation to maximize throughput. It uses a fuzzy rule-based system to select the optimal modulation and coding scheme based on channel state information and quality of service requirements. It then uses a differential evolution algorithm to find the optimal power vector to transmit over OFDM subcarriers while satisfying total power and bit error rate constraints. The proposed scheme is shown through simulations to outperform conventional fixed schemes and adaptive schemes that only optimize a subset of parameters. Product codes and QAM are used as the coding and modulation schemes, respectively.
The document proposes a novel joint carrier frequency offset (CFO) and channel estimation scheme for MIMO-OFDM systems using recursive least squares (RLS) algorithms. It first introduces a joint CFO and channel estimator using two iterative RLS algorithms. It then derives a more precise pilot-aided RLS algorithm to estimate residual CFO errors and enhance channel estimation accuracy. Simulation results show the proposed estimation scheme achieves fast convergence and performance close to theoretical bounds for a wide range of signal-to-noise ratios and an initial CFO up to half the subcarrier spacing.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Peak to Average Power Ratio Reduction in Mc Cdma System by Using Pulse Shapin...IOSR Journals
Abstract: One of the drawback of multicarrier code division multiple access (MC CDMA) is the high peak to
average power ratio (PAPR). In this paper A novel scheme based on pulse shaping described for PAPR
reduction. Here three different pulse shaping filters (Raised cosine, Sinc power pulse and Nyqist pulse) are
described for PAPR reduction in MC CDMA system. The method is based on the proper selection of the pulses
for shaping the different sub carriers of the MC CDMA modulation scheme. It is shown by computer simulation
that the scheme achieves the significant improvement in PAPR reduction in MC CDMA system. Its
implementation complexity is much low in comparison to the previous published methods. Thus pulse shaping
technique can be used not only to shape the spectrum of the transmitted signal but also to reduce its PAPR. In
computer simulation It is observed that by using nyquist pulse near about 6.8 db PAPR is obtained. Which is
considerable PAPR reduction than a PAPR value of Original MC CDMA signal
Keywords: MC CDMA, PAPR, PULSE SHAPING, BPSK
PERFORMANCE COMPARISON DCM VERSUS QPSK FOR HIGH DATA RATES IN THE MBOFDM UWB ...csandit
This document compares the performance of dual carrier modulation (DCM) versus quadrature phase shift keying (QPSK) for high data rates in a multiband orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) system. Simulation results show that using DCM provides better performance than QPSK, with a gain of around 0.7 dB for a bit error rate of 10-3 at 320 Mbps data rates. DCM offers additional diversity and coding gains over QPSK, making it more efficient for high data transmission rates in MBOFDM UWB systems.
Indexed-channel estimation under frequency and time-selective fading channels...IJECEIAES
Index modulation (IM) techniques have been employed in different communication systems to improve bandwidth efficiency by carrying additional information bits. In high-mobility communication systems and under both time-selective and frequency-selective fading channels with Doppler spread, channel variations can be tracked by employing pilot-aided channel estimation with minimum mean-squared error estimation. However, inserting pilot symbols among information symbols reduces the system's spectral efficiency in pilot-aided channel estimation schemes. We propose pilot-aided channel estimation with zero-pilot symbols and an energy detection scheme to tackle this issue. Part of the information bit-stream is conveyed by the indices of zero-pilot symbols leading to an increase in the system's spectral efficiency. We used an energy detector at the receiver to detect the transmitted zero-pilot symbols. This paper examines the impacts of diversity order on the zero-pilot symbol detection error probability and the mean-squared of error estimation. The impacts of pilot symbols number and the zero-pilot symbol number on the mean-squared error of the minimum mean-squared error (MMSE) estimator and the system error performance are also investigated in this paper.
Performance enhancement of audio transmission based on LMMSE methodnooriasukmaningtyas
The research in wireless communication has developed rapidly for the last
decades as a result of raising the demand for efficient data transmission with
more security and accuracy. This paper proposed a system based on the
special multiplexing (SM) technique and linear minimum mean square error
(LMMSE) detection method with the assistance of the hamming code as well
as the interleaving techniques for a better enhanced performance of an audio
transmission. Moreover, the comparison was done between the two systems
for different antenna configurations and with the presence of two types of
modulation: binary phase shift key and quateradure phase shift key. These
systems are employed by Matlab simulation to show significant results in
terms of enhancing the Rayleigh fading channel capacity, bit error rate
(BER) and security as well as in recovering the transmitting audio signals.
Each system has advantages than the others in one performance term respect
to the other terms. The simulation results have provided to prove and discuss
our analysis.
Sparse channel estimation by pilot allocation in MIMO-OFDM systems IRJET Journal
This document summarizes research on sparse channel estimation techniques for MIMO-OFDM systems using compressed sensing theory. It describes how compressed sensing algorithms like Subspace Pursuit (SP) and CoSaMP can provide better channel estimation performance than conventional techniques like least squares estimation. SP and CoSaMP are greedy algorithms that iteratively select columns from the measurement matrix to minimize mean square error. Simulation results showed these compressed sensing algorithms reduce mean square error and bit error rate compared to normal channel estimation.
This document analyzes the performance of adaptive subcarrier allocation in coherent optical OFDM systems. It proposes two allocation schemes: proportional allocation and equal allocation. Proportional allocation aims to maximize data rate while ensuring fairness among users by assigning subcarriers to the user with the highest SNR for that subcarrier, as long as it does not exceed their proportional share. Equal allocation simply divides subcarriers equally among all users. The document models an optical OFDM system transmitting over 1000km of single-mode fiber and investigates how adaptive subcarrier allocation can improve performance compared to static allocation schemes.
Emulation OF 3gpp Scme CHANNEL MODELS USING A Reverberation Chamber MEASUREME...IJERA Editor
1) A test bed was developed to validate 3GPP SCME channel models using a reverberation chamber. Power delay profiles were measured for urban micro and macro channel models and matched well with theoretical profiles.
2) The reverberation chamber was able to control delay spread by adding absorbing materials, allowing different channel models to be emulated. Measurements showed Rayleigh fading was maintained with losses.
3) Convolution of signals with 3GPP channel model taps allowed emulation of multi-cluster channels. Measurements found emulated profiles matched theoretical profiles specified in 3GPP standards.
Iaetsd stbc-ofdm downlink baseband receiver for mobile wmanIaetsd Iaetsd
This document discusses a proposed space time block code-orthogonal frequency division multiplexing (STBC-OFDM) downlink baseband receiver for mobile wireless metropolitan area networks (WMANs). The proposed receiver applies STBC-OFDM techniques using two transmit antennas and one receive antenna to provide robust performance in outdoor mobile environments. It includes a simple and robust synchronizer and an accurate but affordable channel estimator to overcome challenges of multipath fading channels. Simulation results show the receiver can achieve a coded bit error rate of less than 10-6 for 16QAM modulation under vehicle speeds of 120 km/hr while supporting up to 27.32 Mb/s of uncoded data transmission. The receiver designed in a 90-nm CMOS
Orthogonal Frequency Division Multiplexing (OFDM) is of great interest for the development of
the fifth-generation technology. It is the cornerstone of Multiple-input multiple-output (MIMO) systems.
Even though inter carrier interference (ICI) and inter symbol interference (ISI) have been processed for
the fourth-generation standards, they still present a huge problem for the fifth-generation standards. This
paper explores the tradeoff between the length of the cyclic prefix and the performances of the OFDM
system. It also studies the effect of carrier frequency offset (CFO) on OFDM systems. A blind frequency
offset estimator that uses the correlations between the remodulated sequence in the receiver side and
the conventional received symbol is presented and a closed form solution is derived. The proposed
estimator is derived under short interval when the correlation is high, so it has low computational
complexity. Lin and Beek’s estimators are used for comparison. Simulations demonstrate the effectiveness
of the proposed estimator under Rayleigh fading channel.
This report discusses the planning Associate in
nursing the implementation of an OFDM system
in several information module schemes like MQPSK,
M-QAM. First, a short introduction is
provided by explaining the background and the
specification of the project. Then the report deals
with the system model, every block of the OFDM
system is represented (IFFT, FFT, Cyclic prefix,
modulation / reception, Channel estimation, bit
error rate). System design is analyzed. The
transmission techniques, further because the
system parameters for transmission and reception
are explained well. Finally, the results are
provided.
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.
Amazon products reviews classification based on machine learning, deep learni...TELKOMNIKA JOURNAL
In recent times, the trend of online shopping through e-commerce stores and websites has grown to a huge extent. Whenever a product is purchased on an e-commerce platform, people leave their reviews about the product. These reviews are very helpful for the store owners and the product’s manufacturers for the betterment of their work process as well as product quality. An automated system is proposed in this work that operates on two datasets D1 and D2 obtained from Amazon. After certain preprocessing steps, N-gram and word embedding-based features are extracted using term frequency-inverse document frequency (TF-IDF), bag of words (BoW) and global vectors (GloVe), and Word2vec, respectively. Four machine learning (ML) models support vector machines (SVM), logistic regression (RF), logistic regression (LR), multinomial Naïve Bayes (MNB), two deep learning (DL) models convolutional neural network (CNN), long-short term memory (LSTM), and standalone bidirectional encoder representations (BERT) are used to classify reviews as either positive or negative. The results obtained by the standard ML, DL models and BERT are evaluated using certain performance evaluation measures. BERT turns out to be the best-performing model in the case of D1 with an accuracy of 90% on features derived by word embedding models while the CNN provides the best accuracy of 97% upon word embedding features in the case of D2. The proposed model shows better overall performance on D2 as compared to D1.
Design, simulation, and analysis of microstrip patch antenna for wireless app...TELKOMNIKA JOURNAL
In this study, a microstrip patch antenna that works at 3.6 GHz was built and tested to see how well it works. In this work, Rogers RT/Duroid 5880 has been used as the substrate material, with a dielectric permittivity of 2.2 and a thickness of 0.3451 mm; it serves as the base for the examined antenna. The computer simulation technology (CST) studio suite is utilized to show the recommended antenna design. The goal of this study was to get a more extensive transmission capacity, a lower voltage standing wave ratio (VSWR), and a lower return loss, but the main goal was to get a higher gain, directivity, and efficiency. After simulation, the return loss, gain, directivity, bandwidth, and efficiency of the supplied antenna are found to be -17.626 dB, 9.671 dBi, 9.924 dBi, 0.2 GHz, and 97.45%, respectively. Besides, the recreation uncovered that the transfer speed side-lobe level at phi was much better than those of the earlier works, at -28.8 dB, respectively. Thus, it makes a solid contender for remote innovation and more robust communication.
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Similar to Compressive sensing-based channel estimation for high mobile systems with delay Doppler effects
This document discusses adaptive communication techniques using soft computing methods. It proposes using Ant Colony Optimization (ACO) combined with a Fuzzy Rule Base System (FRBS) for adaptive coding, modulation, and power allocation in an Orthogonal Frequency Division Multiplexing (OFDM) system. It compares the proposed approach to other techniques like Simulated Annealing and FRBS, and to a fixed power scheme. The key contributions of the paper are applying ACO and FRBS together for adaptive parameter selection in OFDM to maximize capacity while meeting power and bit error rate constraints.
The document proposes a new channel estimation algorithm called ICEA-DA for MIMO-OFDM systems. ICEA-DA uses least squares estimation with discrete Fourier transform and integrates it with a differential evolution technique. It is placed at the central part of the MIMO-OFDM system between the transmitter and receiver blocks. The proposed method is evaluated for a 2x4 MIMO system using QPSK modulation. Results show ICEA-DA provides better performance than existing techniques in terms of bit error rate, peak signal-to-noise ratio, channel capacity, and symbol error rate.
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
In this work, high-speed transmission over the long-haul optical channel using orthogonal frequency division multiplexing (OFDM) was investigated. Furthermore, we recommend mixing polarization division multiplexing (PDM) with coherent OFDM (CO-OFDM) and quadrature amplitude modulation (16-QAM) to improve spectral efficiency (SE) while transmitting over a wavelength division multiplexing (WDM) system.
An 800 Gb/s WDM PDM-CO-OFDM-16QAM transmission system with various channel spacing of 100 GHz, 50 GHz, and 25 GHz is examined utilizing the OptiSystem (2021) version 18.0 software package over ten spans of 60 km standard single-mode fiber (SSMF). Different channel spacing WDM systems have been compared in terms of performance and SE. The results reveal that the WDM system with 100 GHz channel spacing has a longer transmission range and needs minimal optical signal to noise ratio (OSNR) at the reception. The 25 GHz channel spacing WDM system exceeds the others in terms of SE. Further, the effect of ultra-low loss and large effective area fiber in lowering span loss and nonlinear effects for
25 GHz channel spacing WDM system is investigated. The findings show that the system performance with the new fiber outperforms the SSMF.
The acceptable bit error rate (BER) for this study is 0.033 (20% concatenated forward error correction (FEC) threshold).
PERFORMANCE EVALUATION OF MC-CDMA SYSTEM OVER RAYLEIGH FADING CHANNELIJCSES Journal
Multi Carrier Code Division Multiple Access (MC-CDMA) is a well known technique for high speed
wireless data transmission .Two advanced technology was included in the MC-CDMA structure, such as
orthogonal frequency division multiplex (OFDM) and the code division multiple access (CDMA),so that it
benefits from the robustness of OFDM against multipath environment and from the capability of multiuser
multiplexing services that is achieved via (CDMA) system. MC-CDMA is a multicarrier spread spectrum
system which is classified as the candidate scheme for future mobile radio systems. In this paper MCCDMA
system, with Rayleigh fading channel and 16QAM array modulation, was simulated to investigate
the effects of different parameters on the system performance, such as processing gain; number of paths;
number of users; interleaving; and coding ratio.MC-CDMA performances can be considerably improved
by proper selection of these parameters. As expected, results show that MC-CDMA has a better performance over CDMA system.
The document proposes a blind channel estimation method for FBMC/OQAM systems based on a modified subspace approach. The key points are:
1) The proposed method utilizes spatial diversity techniques to introduce data redundancy, allowing for blind channel estimation without using a preamble. This improves spectral efficiency compared to conventional preamble-based methods.
2) The accuracy of channel estimation is evaluated using the root mean square error (RMSE) of estimated channel amplitudes.
3) Simulations show the proposed blind estimation method provides better RMSE performance than conventional preamble methods, especially at higher signal-to-noise ratios (SNRs). The validity of the method is verified under different simulation conditions.
This document presents an intelligent link adaptation scheme for OFDM systems that adapts coding, modulation, and power allocation to maximize throughput. It uses a fuzzy rule-based system to select the optimal modulation and coding scheme based on channel state information and quality of service requirements. It then uses a differential evolution algorithm to find the optimal power vector to transmit over OFDM subcarriers while satisfying total power and bit error rate constraints. The proposed scheme is shown through simulations to outperform conventional fixed schemes and adaptive schemes that only optimize a subset of parameters. Product codes and QAM are used as the coding and modulation schemes, respectively.
The document proposes a novel joint carrier frequency offset (CFO) and channel estimation scheme for MIMO-OFDM systems using recursive least squares (RLS) algorithms. It first introduces a joint CFO and channel estimator using two iterative RLS algorithms. It then derives a more precise pilot-aided RLS algorithm to estimate residual CFO errors and enhance channel estimation accuracy. Simulation results show the proposed estimation scheme achieves fast convergence and performance close to theoretical bounds for a wide range of signal-to-noise ratios and an initial CFO up to half the subcarrier spacing.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Peak to Average Power Ratio Reduction in Mc Cdma System by Using Pulse Shapin...IOSR Journals
Abstract: One of the drawback of multicarrier code division multiple access (MC CDMA) is the high peak to
average power ratio (PAPR). In this paper A novel scheme based on pulse shaping described for PAPR
reduction. Here three different pulse shaping filters (Raised cosine, Sinc power pulse and Nyqist pulse) are
described for PAPR reduction in MC CDMA system. The method is based on the proper selection of the pulses
for shaping the different sub carriers of the MC CDMA modulation scheme. It is shown by computer simulation
that the scheme achieves the significant improvement in PAPR reduction in MC CDMA system. Its
implementation complexity is much low in comparison to the previous published methods. Thus pulse shaping
technique can be used not only to shape the spectrum of the transmitted signal but also to reduce its PAPR. In
computer simulation It is observed that by using nyquist pulse near about 6.8 db PAPR is obtained. Which is
considerable PAPR reduction than a PAPR value of Original MC CDMA signal
Keywords: MC CDMA, PAPR, PULSE SHAPING, BPSK
PERFORMANCE COMPARISON DCM VERSUS QPSK FOR HIGH DATA RATES IN THE MBOFDM UWB ...csandit
This document compares the performance of dual carrier modulation (DCM) versus quadrature phase shift keying (QPSK) for high data rates in a multiband orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) system. Simulation results show that using DCM provides better performance than QPSK, with a gain of around 0.7 dB for a bit error rate of 10-3 at 320 Mbps data rates. DCM offers additional diversity and coding gains over QPSK, making it more efficient for high data transmission rates in MBOFDM UWB systems.
Indexed-channel estimation under frequency and time-selective fading channels...IJECEIAES
Index modulation (IM) techniques have been employed in different communication systems to improve bandwidth efficiency by carrying additional information bits. In high-mobility communication systems and under both time-selective and frequency-selective fading channels with Doppler spread, channel variations can be tracked by employing pilot-aided channel estimation with minimum mean-squared error estimation. However, inserting pilot symbols among information symbols reduces the system's spectral efficiency in pilot-aided channel estimation schemes. We propose pilot-aided channel estimation with zero-pilot symbols and an energy detection scheme to tackle this issue. Part of the information bit-stream is conveyed by the indices of zero-pilot symbols leading to an increase in the system's spectral efficiency. We used an energy detector at the receiver to detect the transmitted zero-pilot symbols. This paper examines the impacts of diversity order on the zero-pilot symbol detection error probability and the mean-squared of error estimation. The impacts of pilot symbols number and the zero-pilot symbol number on the mean-squared error of the minimum mean-squared error (MMSE) estimator and the system error performance are also investigated in this paper.
Performance enhancement of audio transmission based on LMMSE methodnooriasukmaningtyas
The research in wireless communication has developed rapidly for the last
decades as a result of raising the demand for efficient data transmission with
more security and accuracy. This paper proposed a system based on the
special multiplexing (SM) technique and linear minimum mean square error
(LMMSE) detection method with the assistance of the hamming code as well
as the interleaving techniques for a better enhanced performance of an audio
transmission. Moreover, the comparison was done between the two systems
for different antenna configurations and with the presence of two types of
modulation: binary phase shift key and quateradure phase shift key. These
systems are employed by Matlab simulation to show significant results in
terms of enhancing the Rayleigh fading channel capacity, bit error rate
(BER) and security as well as in recovering the transmitting audio signals.
Each system has advantages than the others in one performance term respect
to the other terms. The simulation results have provided to prove and discuss
our analysis.
Sparse channel estimation by pilot allocation in MIMO-OFDM systems IRJET Journal
This document summarizes research on sparse channel estimation techniques for MIMO-OFDM systems using compressed sensing theory. It describes how compressed sensing algorithms like Subspace Pursuit (SP) and CoSaMP can provide better channel estimation performance than conventional techniques like least squares estimation. SP and CoSaMP are greedy algorithms that iteratively select columns from the measurement matrix to minimize mean square error. Simulation results showed these compressed sensing algorithms reduce mean square error and bit error rate compared to normal channel estimation.
This document analyzes the performance of adaptive subcarrier allocation in coherent optical OFDM systems. It proposes two allocation schemes: proportional allocation and equal allocation. Proportional allocation aims to maximize data rate while ensuring fairness among users by assigning subcarriers to the user with the highest SNR for that subcarrier, as long as it does not exceed their proportional share. Equal allocation simply divides subcarriers equally among all users. The document models an optical OFDM system transmitting over 1000km of single-mode fiber and investigates how adaptive subcarrier allocation can improve performance compared to static allocation schemes.
Emulation OF 3gpp Scme CHANNEL MODELS USING A Reverberation Chamber MEASUREME...IJERA Editor
1) A test bed was developed to validate 3GPP SCME channel models using a reverberation chamber. Power delay profiles were measured for urban micro and macro channel models and matched well with theoretical profiles.
2) The reverberation chamber was able to control delay spread by adding absorbing materials, allowing different channel models to be emulated. Measurements showed Rayleigh fading was maintained with losses.
3) Convolution of signals with 3GPP channel model taps allowed emulation of multi-cluster channels. Measurements found emulated profiles matched theoretical profiles specified in 3GPP standards.
Iaetsd stbc-ofdm downlink baseband receiver for mobile wmanIaetsd Iaetsd
This document discusses a proposed space time block code-orthogonal frequency division multiplexing (STBC-OFDM) downlink baseband receiver for mobile wireless metropolitan area networks (WMANs). The proposed receiver applies STBC-OFDM techniques using two transmit antennas and one receive antenna to provide robust performance in outdoor mobile environments. It includes a simple and robust synchronizer and an accurate but affordable channel estimator to overcome challenges of multipath fading channels. Simulation results show the receiver can achieve a coded bit error rate of less than 10-6 for 16QAM modulation under vehicle speeds of 120 km/hr while supporting up to 27.32 Mb/s of uncoded data transmission. The receiver designed in a 90-nm CMOS
Orthogonal Frequency Division Multiplexing (OFDM) is of great interest for the development of
the fifth-generation technology. It is the cornerstone of Multiple-input multiple-output (MIMO) systems.
Even though inter carrier interference (ICI) and inter symbol interference (ISI) have been processed for
the fourth-generation standards, they still present a huge problem for the fifth-generation standards. This
paper explores the tradeoff between the length of the cyclic prefix and the performances of the OFDM
system. It also studies the effect of carrier frequency offset (CFO) on OFDM systems. A blind frequency
offset estimator that uses the correlations between the remodulated sequence in the receiver side and
the conventional received symbol is presented and a closed form solution is derived. The proposed
estimator is derived under short interval when the correlation is high, so it has low computational
complexity. Lin and Beek’s estimators are used for comparison. Simulations demonstrate the effectiveness
of the proposed estimator under Rayleigh fading channel.
This report discusses the planning Associate in
nursing the implementation of an OFDM system
in several information module schemes like MQPSK,
M-QAM. First, a short introduction is
provided by explaining the background and the
specification of the project. Then the report deals
with the system model, every block of the OFDM
system is represented (IFFT, FFT, Cyclic prefix,
modulation / reception, Channel estimation, bit
error rate). System design is analyzed. The
transmission techniques, further because the
system parameters for transmission and reception
are explained well. Finally, the results are
provided.
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.
Similar to Compressive sensing-based channel estimation for high mobile systems with delay Doppler effects (20)
Amazon products reviews classification based on machine learning, deep learni...TELKOMNIKA JOURNAL
In recent times, the trend of online shopping through e-commerce stores and websites has grown to a huge extent. Whenever a product is purchased on an e-commerce platform, people leave their reviews about the product. These reviews are very helpful for the store owners and the product’s manufacturers for the betterment of their work process as well as product quality. An automated system is proposed in this work that operates on two datasets D1 and D2 obtained from Amazon. After certain preprocessing steps, N-gram and word embedding-based features are extracted using term frequency-inverse document frequency (TF-IDF), bag of words (BoW) and global vectors (GloVe), and Word2vec, respectively. Four machine learning (ML) models support vector machines (SVM), logistic regression (RF), logistic regression (LR), multinomial Naïve Bayes (MNB), two deep learning (DL) models convolutional neural network (CNN), long-short term memory (LSTM), and standalone bidirectional encoder representations (BERT) are used to classify reviews as either positive or negative. The results obtained by the standard ML, DL models and BERT are evaluated using certain performance evaluation measures. BERT turns out to be the best-performing model in the case of D1 with an accuracy of 90% on features derived by word embedding models while the CNN provides the best accuracy of 97% upon word embedding features in the case of D2. The proposed model shows better overall performance on D2 as compared to D1.
Design, simulation, and analysis of microstrip patch antenna for wireless app...TELKOMNIKA JOURNAL
In this study, a microstrip patch antenna that works at 3.6 GHz was built and tested to see how well it works. In this work, Rogers RT/Duroid 5880 has been used as the substrate material, with a dielectric permittivity of 2.2 and a thickness of 0.3451 mm; it serves as the base for the examined antenna. The computer simulation technology (CST) studio suite is utilized to show the recommended antenna design. The goal of this study was to get a more extensive transmission capacity, a lower voltage standing wave ratio (VSWR), and a lower return loss, but the main goal was to get a higher gain, directivity, and efficiency. After simulation, the return loss, gain, directivity, bandwidth, and efficiency of the supplied antenna are found to be -17.626 dB, 9.671 dBi, 9.924 dBi, 0.2 GHz, and 97.45%, respectively. Besides, the recreation uncovered that the transfer speed side-lobe level at phi was much better than those of the earlier works, at -28.8 dB, respectively. Thus, it makes a solid contender for remote innovation and more robust communication.
Design and simulation an optimal enhanced PI controller for congestion avoida...TELKOMNIKA JOURNAL
This document describes using a snake optimization algorithm to tune the gains of an enhanced proportional-integral controller for congestion avoidance in a TCP/AQM system. The controller aims to maintain a stable and desired queue size without noise or transmission problems. A linearized model of the TCP/AQM system is presented. An enhanced PI controller combining nonlinear gain and original PI gains is proposed. The snake optimization algorithm is then used to tune the parameters of the enhanced PI controller to achieve optimal system performance and response. Simulation results are discussed showing the proposed controller provides a stable and robust behavior for congestion control.
Improving the detection of intrusion in vehicular ad-hoc networks with modifi...TELKOMNIKA JOURNAL
Vehicular ad-hoc networks (VANETs) are wireless-equipped vehicles that form networks along the road. The security of this network has been a major challenge. The identity-based cryptosystem (IBC) previously used to secure the networks suffers from membership authentication security features. This paper focuses on improving the detection of intruders in VANETs with a modified identity-based cryptosystem (MIBC). The MIBC is developed using a non-singular elliptic curve with Lagrange interpolation. The public key of vehicles and roadside units on the network are derived from number plates and location identification numbers, respectively. Pseudo-identities are used to mask the real identity of users to preserve their privacy. The membership authentication mechanism ensures that only valid and authenticated members of the network are allowed to join the network. The performance of the MIBC is evaluated using intrusion detection ratio (IDR) and computation time (CT) and then validated with the existing IBC. The result obtained shows that the MIBC recorded an IDR of 99.3% against 94.3% obtained for the existing identity-based cryptosystem (EIBC) for 140 unregistered vehicles attempting to intrude on the network. The MIBC shows lower CT values of 1.17 ms against 1.70 ms for EIBC. The MIBC can be used to improve the security of VANETs.
Conceptual model of internet banking adoption with perceived risk and trust f...TELKOMNIKA JOURNAL
Understanding the primary factors of internet banking (IB) acceptance is critical for both banks and users; nevertheless, our knowledge of the role of users’ perceived risk and trust in IB adoption is limited. As a result, we develop a conceptual model by incorporating perceived risk and trust into the technology acceptance model (TAM) theory toward the IB. The proper research emphasized that the most essential component in explaining IB adoption behavior is behavioral intention to use IB adoption. TAM is helpful for figuring out how elements that affect IB adoption are connected to one another. According to previous literature on IB and the use of such technology in Iraq, one has to choose a theoretical foundation that may justify the acceptance of IB from the customer’s perspective. The conceptual model was therefore constructed using the TAM as a foundation. Furthermore, perceived risk and trust were added to the TAM dimensions as external factors. The key objective of this work was to extend the TAM to construct a conceptual model for IB adoption and to get sufficient theoretical support from the existing literature for the essential elements and their relationships in order to unearth new insights about factors responsible for IB adoption.
Efficient combined fuzzy logic and LMS algorithm for smart antennaTELKOMNIKA JOURNAL
The smart antennas are broadly used in wireless communication. The least mean square (LMS) algorithm is a procedure that is concerned in controlling the smart antenna pattern to accommodate specified requirements such as steering the beam toward the desired signal, in addition to placing the deep nulls in the direction of unwanted signals. The conventional LMS (C-LMS) has some drawbacks like slow convergence speed besides high steady state fluctuation error. To overcome these shortcomings, the present paper adopts an adaptive fuzzy control step size least mean square (FC-LMS) algorithm to adjust its step size. Computer simulation outcomes illustrate that the given model has fast convergence rate as well as low mean square error steady state.
Design and implementation of a LoRa-based system for warning of forest fireTELKOMNIKA JOURNAL
This paper presents the design and implementation of a forest fire monitoring and warning system based on long range (LoRa) technology, a novel ultra-low power consumption and long-range wireless communication technology for remote sensing applications. The proposed system includes a wireless sensor network that records environmental parameters such as temperature, humidity, wind speed, and carbon dioxide (CO2) concentration in the air, as well as taking infrared photos.The data collected at each sensor node will be transmitted to the gateway via LoRa wireless transmission. Data will be collected, processed, and uploaded to a cloud database at the gateway. An Android smartphone application that allows anyone to easily view the recorded data has been developed. When a fire is detected, the system will sound a siren and send a warning message to the responsible personnel, instructing them to take appropriate action. Experiments in Tram Chim Park, Vietnam, have been conducted to verify and evaluate the operation of the system.
Wavelet-based sensing technique in cognitive radio networkTELKOMNIKA JOURNAL
Cognitive radio is a smart radio that can change its transmitter parameter based on interaction with the environment in which it operates. The demand for frequency spectrum is growing due to a big data issue as many Internet of Things (IoT) devices are in the network. Based on previous research, most frequency spectrum was used, but some spectrums were not used, called spectrum hole. Energy detection is one of the spectrum sensing methods that has been frequently used since it is easy to use and does not require license users to have any prior signal understanding. But this technique is incapable of detecting at low signal-to-noise ratio (SNR) levels. Therefore, the wavelet-based sensing is proposed to overcome this issue and detect spectrum holes. The main objective of this work is to evaluate the performance of wavelet-based sensing and compare it with the energy detection technique. The findings show that the percentage of detection in wavelet-based sensing is 83% higher than energy detection performance. This result indicates that the wavelet-based sensing has higher precision in detection and the interference towards primary user can be decreased.
A novel compact dual-band bandstop filter with enhanced rejection bandsTELKOMNIKA JOURNAL
In this paper, we present the design of a new wide dual-band bandstop filter (DBBSF) using nonuniform transmission lines. The method used to design this filter is to replace conventional uniform transmission lines with nonuniform lines governed by a truncated Fourier series. Based on how impedances are profiled in the proposed DBBSF structure, the fractional bandwidths of the two 10 dB-down rejection bands are widened to 39.72% and 52.63%, respectively, and the physical size has been reduced compared to that of the filter with the uniform transmission lines. The results of the electromagnetic (EM) simulation support the obtained analytical response and show an improved frequency behavior.
Deep learning approach to DDoS attack with imbalanced data at the application...TELKOMNIKA JOURNAL
A distributed denial of service (DDoS) attack is where one or more computers attack or target a server computer, by flooding internet traffic to the server. As a result, the server cannot be accessed by legitimate users. A result of this attack causes enormous losses for a company because it can reduce the level of user trust, and reduce the company’s reputation to lose customers due to downtime. One of the services at the application layer that can be accessed by users is a web-based lightweight directory access protocol (LDAP) service that can provide safe and easy services to access directory applications. We used a deep learning approach to detect DDoS attacks on the CICDDoS 2019 dataset on a complex computer network at the application layer to get fast and accurate results for dealing with unbalanced data. Based on the results obtained, it is observed that DDoS attack detection using a deep learning approach on imbalanced data performs better when implemented using synthetic minority oversampling technique (SMOTE) method for binary classes. On the other hand, the proposed deep learning approach performs better for detecting DDoS attacks in multiclass when implemented using the adaptive synthetic (ADASYN) method.
The appearance of uncertainties and disturbances often effects the characteristics of either linear or nonlinear systems. Plus, the stabilization process may be deteriorated thus incurring a catastrophic effect to the system performance. As such, this manuscript addresses the concept of matching condition for the systems that are suffering from miss-match uncertainties and exogeneous disturbances. The perturbation towards the system at hand is assumed to be known and unbounded. To reach this outcome, uncertainties and their classifications are reviewed thoroughly. The structural matching condition is proposed and tabulated in the proposition 1. Two types of mathematical expressions are presented to distinguish the system with matched uncertainty and the system with miss-matched uncertainty. Lastly, two-dimensional numerical expressions are provided to practice the proposed proposition. The outcome shows that matching condition has the ability to change the system to a design-friendly model for asymptotic stabilization.
Implementation of FinFET technology based low power 4×4 Wallace tree multipli...TELKOMNIKA JOURNAL
Many systems, including digital signal processors, finite impulse response (FIR) filters, application-specific integrated circuits, and microprocessors, use multipliers. The demand for low power multipliers is gradually rising day by day in the current technological trend. In this study, we describe a 4×4 Wallace multiplier based on a carry select adder (CSA) that uses less power and has a better power delay product than existing multipliers. HSPICE tool at 16 nm technology is used to simulate the results. In comparison to the traditional CSA-based multiplier, which has a power consumption of 1.7 µW and power delay product (PDP) of 57.3 fJ, the results demonstrate that the Wallace multiplier design employing CSA with first zero finding logic (FZF) logic has the lowest power consumption of 1.4 µW and PDP of 27.5 fJ.
Evaluation of the weighted-overlap add model with massive MIMO in a 5G systemTELKOMNIKA JOURNAL
The flaw in 5G orthogonal frequency division multiplexing (OFDM) becomes apparent in high-speed situations. Because the doppler effect causes frequency shifts, the orthogonality of OFDM subcarriers is broken, lowering both their bit error rate (BER) and throughput output. As part of this research, we use a novel design that combines massive multiple input multiple output (MIMO) and weighted overlap and add (WOLA) to improve the performance of 5G systems. To determine which design is superior, throughput and BER are calculated for both the proposed design and OFDM. The results of the improved system show a massive improvement in performance ver the conventional system and significant improvements with massive MIMO, including the best throughput and BER. When compared to conventional systems, the improved system has a throughput that is around 22% higher and the best performance in terms of BER, but it still has around 25% less error than OFDM.
Reflector antenna design in different frequencies using frequency selective s...TELKOMNIKA JOURNAL
In this study, it is aimed to obtain two different asymmetric radiation patterns obtained from antennas in the shape of the cross-section of a parabolic reflector (fan blade type antennas) and antennas with cosecant-square radiation characteristics at two different frequencies from a single antenna. For this purpose, firstly, a fan blade type antenna design will be made, and then the reflective surface of this antenna will be completed to the shape of the reflective surface of the antenna with the cosecant-square radiation characteristic with the frequency selective surface designed to provide the characteristics suitable for the purpose. The frequency selective surface designed and it provides the perfect transmission as possible at 4 GHz operating frequency, while it will act as a band-quenching filter for electromagnetic waves at 5 GHz operating frequency and will be a reflective surface. Thanks to this frequency selective surface to be used as a reflective surface in the antenna, a fan blade type radiation characteristic at 4 GHz operating frequency will be obtained, while a cosecant-square radiation characteristic at 5 GHz operating frequency will be obtained.
Reagentless iron detection in water based on unclad fiber optical sensorTELKOMNIKA JOURNAL
A simple and low-cost fiber based optical sensor for iron detection is demonstrated in this paper. The sensor head consist of an unclad optical fiber with the unclad length of 1 cm and it has a straight structure. Results obtained shows a linear relationship between the output light intensity and iron concentration, illustrating the functionality of this iron optical sensor. Based on the experimental results, the sensitivity and linearity are achieved at 0.0328/ppm and 0.9824 respectively at the wavelength of 690 nm. With the same wavelength, other performance parameters are also studied. Resolution and limit of detection (LOD) are found to be 0.3049 ppm and 0.0755 ppm correspondingly. This iron sensor is advantageous in that it does not require any reagent for detection, enabling it to be simpler and cost-effective in the implementation of the iron sensing.
Impact of CuS counter electrode calcination temperature on quantum dot sensit...TELKOMNIKA JOURNAL
In place of the commercial Pt electrode used in quantum sensitized solar cells, the low-cost CuS cathode is created using electrophoresis. High resolution scanning electron microscopy and X-ray diffraction were used to analyze the structure and morphology of structural cubic samples with diameters ranging from 40 nm to 200 nm. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 °C, 120 °C, 150 °C, and 180 °C under vacuum. The fluorine doped tin oxide (FTO)/CuS cathode electrode reached a maximum efficiency of 3.89% when it was calcined at 120 °C. Compared to other temperature combinations, CuS nanoparticles crystallize at 120 °C, which lowers resistance while increasing electron lifetime.
In place of the commercial Pt electrode used in quantum sensitized solar cells, the low-cost CuS cathode is created using electrophoresis. High resolution scanning electron microscopy and X-ray diffraction were used to analyze the structure and morphology of structural cubic samples with diameters ranging from 40 nm to 200 nm. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 °C, 120 °C, 150 °C, and 180 °C under vacuum. The fluorine doped tin oxide (FTO)/CuS cathode electrode reached a maximum efficiency of 3.89% when it was calcined at 120 °C. Compared to other temperature combinations, CuS nanoparticles crystallize at 120 °C, which lowers resistance while increasing electron lifetime.
A progressive learning for structural tolerance online sequential extreme lea...TELKOMNIKA JOURNAL
This article discusses the progressive learning for structural tolerance online sequential extreme learning machine (PSTOS-ELM). PSTOS-ELM can save robust accuracy while updating the new data and the new class data on the online training situation. The robustness accuracy arises from using the householder block exact QR decomposition recursive least squares (HBQRD-RLS) of the PSTOS-ELM. This method is suitable for applications that have data streaming and often have new class data. Our experiment compares the PSTOS-ELM accuracy and accuracy robustness while data is updating with the batch-extreme learning machine (ELM) and structural tolerance online sequential extreme learning machine (STOS-ELM) that both must retrain the data in a new class data case. The experimental results show that PSTOS-ELM has accuracy and robustness comparable to ELM and STOS-ELM while also can update new class data immediately.
Electroencephalography-based brain-computer interface using neural networksTELKOMNIKA JOURNAL
This study aimed to develop a brain-computer interface that can control an electric wheelchair using electroencephalography (EEG) signals. First, we used the Mind Wave Mobile 2 device to capture raw EEG signals from the surface of the scalp. The signals were transformed into the frequency domain using fast Fourier transform (FFT) and filtered to monitor changes in attention and relaxation. Next, we performed time and frequency domain analyses to identify features for five eye gestures: opened, closed, blink per second, double blink, and lookup. The base state was the opened-eyes gesture, and we compared the features of the remaining four action gestures to the base state to identify potential gestures. We then built a multilayer neural network to classify these features into five signals that control the wheelchair’s movement. Finally, we designed an experimental wheelchair system to test the effectiveness of the proposed approach. The results demonstrate that the EEG classification was highly accurate and computationally efficient. Moreover, the average performance of the brain-controlled wheelchair system was over 75% across different individuals, which suggests the feasibility of this approach.
Adaptive segmentation algorithm based on level set model in medical imagingTELKOMNIKA JOURNAL
For image segmentation, level set models are frequently employed. It offer best solution to overcome the main limitations of deformable parametric models. However, the challenge when applying those models in medical images stills deal with removing blurs in image edges which directly affects the edge indicator function, leads to not adaptively segmenting images and causes a wrong analysis of pathologies wich prevents to conclude a correct diagnosis. To overcome such issues, an effective process is suggested by simultaneously modelling and solving systems’ two-dimensional partial differential equations (PDE). The first PDE equation allows restoration using Euler’s equation similar to an anisotropic smoothing based on a regularized Perona and Malik filter that eliminates noise while preserving edge information in accordance with detected contours in the second equation that segments the image based on the first equation solutions. This approach allows developing a new algorithm which overcome the studied model drawbacks. Results of the proposed method give clear segments that can be applied to any application. Experiments on many medical images in particular blurry images with high information losses, demonstrate that the developed approach produces superior segmentation results in terms of quantity and quality compared to other models already presented in previeous works.
Automatic channel selection using shuffled frog leaping algorithm for EEG bas...TELKOMNIKA JOURNAL
Drug addiction is a complex neurobiological disorder that necessitates comprehensive treatment of both the body and mind. It is categorized as a brain disorder due to its impact on the brain. Various methods such as electroencephalography (EEG), functional magnetic resonance imaging (FMRI), and magnetoencephalography (MEG) can capture brain activities and structures. EEG signals provide valuable insights into neurological disorders, including drug addiction. Accurate classification of drug addiction from EEG signals relies on appropriate features and channel selection. Choosing the right EEG channels is essential to reduce computational costs and mitigate the risk of overfitting associated with using all available channels. To address the challenge of optimal channel selection in addiction detection from EEG signals, this work employs the shuffled frog leaping algorithm (SFLA). SFLA facilitates the selection of appropriate channels, leading to improved accuracy. Wavelet features extracted from the selected input channel signals are then analyzed using various machine learning classifiers to detect addiction. Experimental results indicate that after selecting features from the appropriate channels, classification accuracy significantly increased across all classifiers. Particularly, the multi-layer perceptron (MLP) classifier combined with SFLA demonstrated a remarkable accuracy improvement of 15.78% while reducing time complexity.
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
UNLOCKING HEALTHCARE 4.0: NAVIGATING CRITICAL SUCCESS FACTORS FOR EFFECTIVE I...amsjournal
The Fourth Industrial Revolution is transforming industries, including healthcare, by integrating digital,
physical, and biological technologies. This study examines the integration of 4.0 technologies into
healthcare, identifying success factors and challenges through interviews with 70 stakeholders from 33
countries. Healthcare is evolving significantly, with varied objectives across nations aiming to improve
population health. The study explores stakeholders' perceptions on critical success factors, identifying
challenges such as insufficiently trained personnel, organizational silos, and structural barriers to data
exchange. Facilitators for integration include cost reduction initiatives and interoperability policies.
Technologies like IoT, Big Data, AI, Machine Learning, and robotics enhance diagnostics, treatment
precision, and real-time monitoring, reducing errors and optimizing resource utilization. Automation
improves employee satisfaction and patient care, while Blockchain and telemedicine drive cost reductions.
Successful integration requires skilled professionals and supportive policies, promising efficient resource
use, lower error rates, and accelerated processes, leading to optimized global healthcare outcomes.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
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Compressive sensing-based channel estimation for high mobile systems with delay Doppler effects
1. TELKOMNIKA Telecommunication Computing Electronics and Control
Vol. 20, No. 6, December 2022, pp. 1206~1213
ISSN: 1693-6930, DOI: 10.12928/TELKOMNIKA.v20i6.24233 1206
Journal homepage: http://telkomnika.uad.ac.id
Compressive sensing-based channel estimation for high mobile
systems with delay Doppler effects
Khalifa A. Salim1
, Bayan Mahdi Sabbar2
, Maryam K. Abboud3
1
Department of Information and Communication Engineering, Al-Khwarizmy College of Engineering, Baghdad University,
Baghdad, Iraq
2
Department of Computer Network Engineering, College of Information Engineering, Al-Nahrain University, Baghdad, Iraq
3
Department of Computer Engineering, Al-Farabi College University, Baghdad, Iraq
Article Info ABSTRACT
Article history:
Received May 01, 2021
Revised Jul 20, 2022
Accepted Aug 01, 2022
In this paper, channel overhead is reduced by exploiting channel sparsity for
multiple input multiple output-orthogonal frequency division multiplexing
(MIMO-OFDM) system. Where, compressive sensing (CS) based dictionary
design algorithms has been adopted as a channel estimation technique in
high mobile systems with minimal number of pilots, such as high-speed train
(HST) systems. A novel framework design of the dictionary-based CS was
proposed considering both delay and Doppler effects in order to correctly
recover the channel response. The channel under consideration is a 2 by 2
space-time block code (STBC) MIMO channel. Simulation tests according
to the international telecommunication union (ITU) channel model
demonstrated the suitability of the proposed dictionary for estimating the
channel impulse response (CIR) of a liner time varying (LTV) channel with
a mobility approaches 675 Km/h related to a Doppler frequency of 1500 Hz
and 2.4 GHz carrier frequency. Two CS recovery algorithms were applied;
orthogonal matching pursuit (OMP) and basis pursuit (BP), where by about
7 dB gain in signal to noise ratio (SNR) was achieved with mobility of 675
Km/h using OMP as compared to BP at a bit error rate (BER) of 10−3
with
128 OFDM subcarriers.
Keywords:
CS
Delay-Doppler
HST systems
LTV
MIMO-OFDM
Sparse channel estimation
STBC
This is an open access article under the CC BY-SA license.
Corresponding Author:
Khalifa A. Salim
Department of Information and Communication Engineering, Al-Khwarizmy College of Engineering
Baghdad University, Baghdad, Iraq
Email: khalifaabboud@yahoo.com
1. INTRODUCTION
In wireless communications, there is an increased demand for high data rate transmissions with
effective spectrum utilization [1], [2]. Multiple input multiple output orthogonal frequency division
multiplexing (MIMO-OFDM) has been considered in communication systems to fulfil these requirements [3], [4].
At the other hand, the accurate estimation of channel impulse response (CIR) is crucial in order to remove the
effect of the channel at the receiver end. However, there are many estimation algorithms applied to estimate
liner time varying (LTV) channel response. They are almost fail to track the channels with high Doppler
environments such as high-speed train (HST) systems [5].
After the first introduction of compressive sensing (CS) in 2006 [6], it found its way into wireless
communication channel estimation purpose known as compressive estimation [7]–[11]. However, CIR of the
wireless channel is determined by a small number of strong paths, therefore, the wireless channel is sparse in
nature. At the other hand, the working principle of CS is to recover a sparse signal with limited number of
measurements; hence, compressive sensing can be used to recover the required CIR [12], [13]. Since the idea
2. TELKOMNIKA Telecommun Comput El Control
Compressive sensing-based channel estimation for high mobile systems with … (Khalifa A. Salim)
1207
behind spares wireless channels and signal sparsity appears, many publications in the field of compressive
sensing and signal processing community were introduced. A doubly selective channel estimation technique
using CS was introduced in [14], [15]. The proposed methodology exploits the most effecting parameters;
delay and Doppler, where the pilot’s number used for estimation is reduced by about half of the total number
of pilots required for least square (LS) method.
An advanced compressive estimation method was introduced in [16] for doubly dispersive channel
estimation within a multicarrier OFDM system, where simulations using geometry based channel simulators
outperforms the classical CS methods in terms of complexity. A recursive tracking of doubly selective channel
based sequential delay-Doppler sparsity was exploited by [17] to improve estimation performance. The technique
suggests the use of a modified version of orthogonal matching pursuit (OMP), where it demonstrates a substantial
performance gain over conventional CS estimation in terms of computational complexity.
Ren et al. [18], CS approach was adopted for channel estimation in high mobility OFDM systems,
where it used to utilize the inherent channel sparsity of the time-selectivity channel caused by high mobility
in order to recover the CIR. A pilot pattern design within the OFDM symbol was considered with 120 pilots
out of 512 subcarriers at a speed of 600 Km/h with a carrier frequency of 2.5 GHz. In [19], a single input
multiple output single input multiple output orthogonal frequency division multiplexing (SIMO-OFDM) typical
HST system was investigated to eliminate the inter carrier interference (ICI) of time variant channels, where CS
is adopted with position based interference detection to recover the CIR by designing a pilot pattern. Out of 512
subcarriers, 40 pilots are used to recover the CIR correctly with 500 Km/h vehicle speed and carrier frequency
of 2.35 GHz.
Both time domain preambles and frequency domain pilots are adopted in [20] to recover the
selective channel response. First, the training in time domain is exploited. Seconed, pilot locations are
optimized using genetic algorithm, where it employed to build the structured CS and estimating the channel
at 240 Km/h with different number of transmit antennas.
A performance analysis of OMP based CS for channel estimation in mobile OFDM systems was
proposed in [21]. The tests shows that the bit error rate (BER) performance degraded as the mobility
increased. By using 90 pilots out of 512 subcarriers over a small-scale fading channel, the maximum speed
provided was 140 Km/h at a BER performance of 7.8×10-4
and signal to noise power ratio (SNR) of 20 dB,
where both assumed bandwidth and carrier frequency are 2.8 MHz and 5.8 MHz respectively.
A performance comparison of LS, basis pursuit (BP) and OMP based channel estimation was
introduced by [22]. The tests consider a single input single output orthogonal frequency division multiplexing
(SISO-OFDM) system with 128 OFDM subcarriers transmitted over a 3 tap Rayleigh channel. The tests do
not consider a Doppler shift. With 25 pilots out of 128 subcarriers, the BER performance of BP algorithm
outperforms both OMP and LS algorithms, where, the BER performance of LS, OMP, and BP are 0.0435,
0.0130, and 0.0022 at 30 dB respectively.
Abboud and Sabbar [23], a BER performance comparision of LS and BP algorithms was introduced
with a dictionary design based channel delay variation for CS estimation. The tests show that the designed
dictionary-based CS is suitable to recover the channel information with low to moderate Doppler effects.
The main contributions of this paper are:
− A novel CS dictionary is designed based LTV channels’ delay and Doppler effects analysis to estimate
its coefficients.
− The suggested dictionary desgin is adopted to recover the CIR with different conditions of subcarrier
length or Doppler shifts, which approves its applicability to estimate the CIR for high mobility systems.
Where, the CIR is estimated with a mobility exceeds 675 Km/h at a BER approaching 10-4
.
− The spectral efficiency is improved by about 25%, while the estimation performance is improved by
either increasing the Doppler shift and/or the OFDM subcarriers with a fixed ratio of pilot number.
− By adopting the designed dictionary-based CS, the BER performance of BP and OMP is improved,
where the required SNR to obtain an acceptable error rate is reduced.
The rest of this paper is organized as: the proposed system model with required LTV channel
analysis is presented in section 2 with CS methodology of the proposed dictionary. In section 3, simulation
tests and assessment of results are proposed. Finally, in section 4, the final concluding remarks with
suggestions of future work are proposed.
2. SYSTEM MODEL AND CS BASED LTV CHANNEL ESTIMATION METHODOLOGY
The MIMO-OFDM system of Figure 1 is considered with a stream of bits 𝑋[𝑘], (data 𝑑[𝑘] and
pilots 𝑝[𝑘]) are mapped using binary phase shift keying (BPSK) mapper and space-time block code (STBC)
encoded using 2 by 2 Alamouti STBC encoder. To simplify analysis, the system is modeled as a 2 by 2 MIMO
channel. Where, the transmitter has 𝑁𝑡 parallel transmission paths. For each path, the frequency domain
STBC encoded OFDM block 𝑋[𝑘]of 𝑁 subcarriers is transformed into a time domain block 𝑥[𝑛] by applying
3. ISSN: 1693-6930
TELKOMNIKA Telecommun Comput El Control, Vol. 20, No. 6, December 2022: 1206-1213
1208
inverse fast fourier transform (IFFT) process, which followed by cyclic prefix (CP) insertion of length 𝐿𝑐𝑝 in
order to prevent adjacent interference.
Figure 1. MIMO-OFDM system model
After 𝑐𝑝 insertion, the resultant OFDM blocks will be transmitted through multiple antenna system a
cross a LTV MIMO channel which is modeled by both 𝐿 paths of delay and Doppler effects 𝜏𝑖 and 𝑓𝑑
respectively with attenuation 𝑎𝑖.
ℎ(𝑡) = ∑ 𝑎𝑖 𝑒−𝑗2𝜋𝑓𝑐𝜏𝑖
𝐿−1
𝑖=0 𝑒𝑗2𝜋𝑓𝑑𝑡
(1)
At the receiver side, the tow effecting parameters (𝜏𝑖 and 𝑓𝑑) of the LTV channel of (1) should be
taken into consideration in order to recover time variant coefficients of the LTV channel. By applying CS
technique to estimate the CIR using the classical linear measurement model 𝑦 = 𝜙𝑥 = 𝜙𝜓𝜃, where; 𝑦 is a
measurement vector of size 𝑁 × 1, 𝜓 is of size 𝑀 × 𝑀, and 𝜃 represents 𝑘-sparse vector of 𝑀 × 1 to be predicted
using the functional measurement matrix 𝜙𝜓. The sensing matrix 𝜙 is of size 𝑁 × 𝑀 should be designed carfuly.
therefore, each noting of 𝑦 vector represents the tumbling of vector 𝑥 on a sensing matrix 𝜙 row [24].
In order to estimate the channel vector ℎ𝑀𝑟,𝑁𝑡 ∈ 𝐶𝑁×1
from 𝑦𝑀𝑟 received measurements, a CS
problem should be formulated, where 𝑦𝑀𝑟 is expressed.
𝑦𝑀𝑟 = 𝐴ℎ𝑀𝑟,𝑁𝑡 + 𝑤𝑀𝑟,𝑁𝑡 (2)
Where: 𝑤𝑀𝑟,𝑁𝑡 is the additive white gaussian noise (AWGN) noise of 𝑁𝑡ℎ
transmit antenna and 𝑀𝑡ℎ
receive
antenna of zero mean and fixed variance 𝑁(0, 𝜎𝑛
2
), and 𝐴 represents the designed sensing matrix. Referring to (1),
CS dictionary atoms are designed considering both delay and Doppler channel profiles. The equispaced pilot
subcarriers 𝑝[𝑘] are inserted within the data subcarriers 𝑑[𝑘] of the OFDM symbol, and the time domain
channel matrix can be represented with both delay 𝐶ℓ and Doppler 𝐹𝑗.
ℎ(𝑡) = ∑ ∑ 𝑎𝑖
𝑁−1
ℓ=𝑗=0 𝐶ℓ
𝐿−1
𝑖=0 𝐹𝑗 (3)
The delay profiles 𝐶ℓ of (3) is represented in (4) with 𝑁 × 𝑁 circulant matrix of the 𝑖𝑡ℎ
path delay,
and its atoms represented with a taped delay profile ∆𝑡 of (5) along the OFDM symbol.
𝐶ℓ = [
𝑒−𝑗2𝜋∆𝑡,1
⋯ 𝑒−𝑗2𝜋∆𝑡,𝑁
⋮ ⋱ ⋮
𝑒−𝑗2𝜋∆𝑡,2
⋯ 𝑒−𝑗2𝜋∆𝑡,1
] (4)
∆𝑡 = [0, 𝑖 ×
𝛼
𝑁
, 𝛼] , 𝑤ℎ𝑒𝑟𝑒 𝑖 = 1, 2, 3, … , 𝑁 (5)
Where, 𝛼 represents the minimum spacing between channel taps, which equals to (𝐺𝑖 × 𝑇𝑠 −
𝐺𝑖×𝑇𝑠
𝑁
), and 𝐺𝑖
represents the guard interval, which assumed to be the cyclic prefix length applied to each OFDM symbol in
order to overcome the ICI problem, and 𝑇𝑠 represents the OFDM sampling time.
4. TELKOMNIKA Telecommun Comput El Control
Compressive sensing-based channel estimation for high mobile systems with … (Khalifa A. Salim)
1209
At the other hand, the Doppler profile 𝐹𝑗 of (3) is represented in (6) with a diagonal matrix of the 𝑗𝑡ℎ
Doppler shifts. The Doppler shift 𝑓𝑑 is assumed to be normalized across OFDM symbols which calculated
using (7).
𝐹𝑗 = [
𝑒𝑗2𝜋𝑓𝑑𝑛𝑜𝑟𝑚 ⋯ 0
⋮ 𝑒𝑗2𝜋(𝑁−1)𝑓𝑑𝑛𝑜𝑟𝑚 ⋮
0 ⋯ 𝑒𝑗2𝜋𝑁𝑓𝑑𝑛𝑜𝑟𝑚
] (6)
𝑓𝑑𝑛𝑜𝑟𝑚 =
𝑓𝑑
𝐵𝑁
, 𝐵𝑁 =
𝐵.𝑊
𝑁
(7)
Where 𝐵𝑁 represents the subcarrier spacing between OFDM symbols.
At the receiver side, the symbols after reception are passed to 𝑁 point fast fourier transform (FFT)
process and retransformed to frequency domain. Mathematically, the Fourier transform of a circulant matrix
results a diagonal matrix and vice versa [25]. Hence, the frequency domain channel matrix can be expressed.
𝐻(𝑓) = ∑ ∑ 𝑎𝑖
𝑁−1
𝐿=𝐽=0 𝐶𝐿
𝐿−1
𝑖=0 𝐹𝐽 (8)
From the above analysis, the dictionary 𝐷𝑁×𝑁 is represented by atoms related to both channel delay and
Doppler, where each OFDM subcarrier experience all delay and Doppler effects.
𝐷𝑁×𝑁 = [
𝑒𝑗2𝜋𝑓𝑑𝑛𝑜𝑟𝑚 ⋯ 𝑒𝑗2𝜋𝑁𝑓𝑑𝑛𝑜𝑟𝑚
⋮ ⋱ ⋮
𝑒𝑗2𝜋2𝑓𝑑𝑛𝑜𝑟𝑚 ⋯ 𝑒𝑗2𝜋𝑓𝑑𝑛𝑜𝑟𝑚
] × [
𝑒−𝑗2𝜋∆𝑡(1)
⋯ 0
⋮ ⋱ ⋮
0 ⋯ 𝑒−𝑗2𝜋∆𝑡(𝑁)
] (9)
However, 𝑁𝑝 rows are chosen from 𝐷 matrix which related to pilot locations in order to construct
the sensing matrix 𝐴. The selected rows are multiplied by the pilot data of 𝑁𝑝 × 𝑁 matrix using dot product
multiplication. Where, 𝑁𝑝 represents the number of training pilots, 𝑃𝑗 represents the pilot symbol which used
for estimation assuming equally likely symbols, and 𝑗 = 1,2,3, … . , 𝑁𝑝.
𝐴𝑁𝑝×𝑁 = 𝐷𝑁𝑝×𝑁 . [
𝑒−𝑗𝜋 𝑃1,1 ⋯ 𝑒−𝑗𝜋 𝑃1,𝑁
⋮ ⋱ ⋮
𝑒
−𝑗𝜋 𝑃𝑁𝑝,1
⋯ 𝑒
−𝑗𝜋 𝑃𝑁𝑝,𝑁
]
𝑁𝑝×𝑁
(10)
In order to prevent ICI and save bandwidth, an optimal number of pilot subcarriers should be assumed
for estimation. The classical channel estimation methods can only be employed under the assumption that
𝑁𝑝 ≥ 𝐿𝑐𝑝 [7], while, by adopt CS technique to estimate channel coefficients, an functional channel estimation
can be acquired with a littel number of pilots using a smart construction of sensing matrix. A primary target is
to recover the k-sparse channel coeffecints while utilizing bandwidth using a limited number of pilots with
almost no performance degradation such that 𝑁𝑝 ≤ 𝐿𝑐𝑝.
Once the channel significant taps estimated, the reminder CIR is constructed at all channel taps using:
𝐻
̂ = 𝐷 × 𝜃 (11)
When estimating the CIR 𝐻
̂(𝑀𝑟, 𝑁𝑡) at each channel path, the multiple received signal copies 𝑌𝑗[𝑘] are
combined by STBC combiner system with the estimated CIR. It is important to mention that maximum
likelihood (ML) detection is used in order to estimate the transmitted symbols. After signal combining which
resulting with a single data stream 𝑌[𝑘], the frequency domain signal is passed to the detection process in
order to recover the original data.
3. SIMULATIONS AND RESULTS
The 2×2 STBC MIMO-OFDM system of Figure 1 was simulated and performance test was carried
over international telecommunication union (A-ITU) time varying channel of Table1 in the form of BER
versus SNR. In simulations, SNR is defined by the corresponding
𝐸𝑏
𝑁0
in dB. Two CS algorithms; BP and
OMP, was evaluated with different Doppler frequencies in order to compare their performances with
conventional LS. The OFDM system parameters considered in simulations are shown in Table 2. For the
purpose of evaluating the effectiveness of the suggested dictionary in recovering CIR with limited number of
pilots, 16 pilots are considered in simulations out of different subcarriers.
5. ISSN: 1693-6930
TELKOMNIKA Telecommun Comput El Control, Vol. 20, No. 6, December 2022: 1206-1213
1210
In the proposed simulations, Figure 2(a) and Figure 2(b) are presented to evaluate the design success
of the suggested dictionary in recovering the CIR with a variations of Doppler shifts considering 64
subcarriers. Using BP based CS channel estimation, the BER performance approaches 10-6
as compared to
7×10-6
using LS method at 40 dB with 𝑓𝑑𝑚𝑎𝑥 = 0 Hz. In order to evaluate the dictionary applicability to
recover the CIR in the existence of high Doppler effects. When Doppler frequency increased above 0 Hz,
the BER performance degraded and LS method could not track channel variations. Regarding the performance
tests of OMP and BP in moderate Doppler effects, the performance of OMP algorithm outperforms BP tests at
low SNR values, where for 𝑓𝑑𝑚𝑎𝑥 = 500 Hz. Regarding Figure 3(a) and Figure 3(b) tests considering the same
parameter simulations, OMP outperforms BP performance by about 9 dB at a BER of 10-3
, and by about 5 dB
when 𝑓𝑑𝑚𝑎𝑥 increased to 1000 Hz and 1500 Hz at the same error rate respectively. This improvement can be
explained by the relation of (7), where, as the Doppler shifts increased, the normalized Doppler value 𝑓𝑑𝑛𝑜𝑟𝑚
is increased, and the sensitivity of the proposed dictionary for the real Doppler values increased, which
enhance the estimation performance. After proving the success of the work of the proposed dictionary with
different Doppler values, Figure 4 and Figure 5 are presented to evaluate the applicability of the suggested
dictionary to retrieve the CIR with various OFDM subcarriers. And since the main target of this work is to
estimate channel parameters with high Doppler shifts and minimal number of pilots, both tests consider 16
pilots and a Doppler shift of 1000 Hz, and 1500 Hz.
Table 1. Vehicular A-ITU channel model [26]
Taps no. Relative delay (ns) Average power (dB)
1 0 0
2 310 -1.5
3 710 -9.0
4 1090 -10.0
5 1730 -15.0
6 2510 -20.0
Table 2. Simulation parameters
Parameter Value
Modulation BPSK
Sampling time 𝑇𝑠 sec. 10-6
Bandwidth 𝐵. 𝑊 Hz 20×10-6
OFDM subcarriers 𝑁 64, 128, 256
Number of pilots 𝑁𝑝 16
Cyclic prefix length 𝐿𝑐𝑝 = 𝐺𝑖 16, 32, 64
Transmit and receive antennas 𝑁𝑡, 𝑀𝑟 2, 2
Carrier frequency 𝑓𝑐 Hz 2.4×109
Maximum Doppler shift 𝑓𝑑𝑚𝑎𝑥 Hz 0 − 1500
Mobile velocity 𝑣 Km/h (𝑓𝑑 × 𝑐) 𝑓𝑐
⁄
Speed of light 𝑐 m/sec. 3×108
(a) (b)
Figure 2. BER Performance of different estimation methods for MIMO-OFDM system with 𝑁𝑝 = 16,
𝑁 = 64, zero and 500 Hz: (a) 𝑓𝑑𝑚𝑎𝑥 = 0 𝐻𝑧 and (b) 𝑓𝑑𝑚𝑎𝑥 = 500 Hz
6. TELKOMNIKA Telecommun Comput El Control
Compressive sensing-based channel estimation for high mobile systems with … (Khalifa A. Salim)
1211
(a) (b)
Figure 3. BER Performance different estimation methods for MIMO-OFDM system with 𝑁𝑝 = 16, 𝑁 = 64,
zero and high 𝑓𝑑𝑚𝑎𝑥: (a) 𝑓𝑑𝑚𝑎𝑥 = 1000 Hz and (b) 𝑓𝑑𝑚𝑎𝑥 = 1500 Hz
Figure 4(a) and Figure 4(b) consider 128 subcarrieres, which showed the BER performance of LS, BP,
and OMP with respect to 1000 Hz and 1500 Hz Doppler frequencies. The tests show that as 𝑁 increased from
64 subcarrier to 128 subcarrier, the BER performance of BP and OMP is improved by about 6 dB and 9 dB
respectively at 𝑓𝑑𝑚𝑎𝑥 = 1000 𝐻𝑧 and by about 6 dB and 8 dB at 𝑓𝑑𝑚𝑎𝑥 = 1500 𝐻𝑧 for the same error rate
respectively with 128 subcarriers. Considering 256 subcarriers tests of Figure 5(a) and Figure 5(b), the test
results show that by increasing the subcarrier number to 256 subcarriers, the BER performance of both BP and
OMP is improved to be almost identical at low SNR values, where they need only 0 dB to obtain a BER of 10-3
.
The reason behind the performance improvement when the subcarrier number increased is also related to (7).
Where, as OFDM subcarrier number increased, the spacing between OFDM subcarriers decreased, which
effects the Doppler distribution. With a higher normalized Doppler frequency 𝑓𝑑𝑛𝑜𝑟𝑚, the proposed
dictionary becom more sensitive to the real Doppler values, which enhance the estimation performance.
As a final assessment of results, either by increasing of OFDM subcarriers from 64 to 256 or
Doppler shifts up to 1500 Hz, the BER performance is improved, where the sensitivity of the proposed
dictionary for real Doppler values is increased. At the other hand, bandwidth efficiency is improved by using
a minimum number of pilots which adopted for estimation. This indicates the suitability of the proposed
dictionary in recovering the CIR at high mobility conditions while saving bandwidth by using a minimum
number of pilots.
(a) (b)
Figure 4. BER Performance different estimation methods for MIMO-OFDM system with 𝑁𝑝 = 16, N = 128,
and high 𝑓𝑑𝑚𝑎𝑥: (a) 𝑓𝑑𝑚𝑎𝑥 = 1000 Hz and (b) 𝑓𝑑𝑚𝑎𝑥 = 1500 Hz
7. ISSN: 1693-6930
TELKOMNIKA Telecommun Comput El Control, Vol. 20, No. 6, December 2022: 1206-1213
1212
(a) (b)
Figure 5. BER Performance different estimation methods for MIMO-OFDM system with 𝑁𝑝 = 16, 𝑁 = 256,
and high 𝑓𝑑𝑚𝑎𝑥: (a) 𝑓𝑑𝑚𝑎𝑥 = 1000 Hz and (b) 𝑓𝑑𝑚𝑎𝑥 = 1500 Hz
4. CONCLUSIONS AND FUTURE WORK
In the proposed work, a noval frame work design of CS dictionary is introduced in order to recover the
channel response. The design considers both delay and doppler effects of LTV channel. As a result of applying CS
based the proposed dictionary to estimate CIR, the response was recovered correctly for MIMO-OFDM systems
with only 16 pilots out of 64, 128, and 256 subcarrirs even when the mobile system moves with high-speed
approaches 675 Km/h such as in HST systems. This result indicates that the analysis of the delay and Doppler
effects on the doubly selective channel with the proposed dictionary design is working probably. At the other
hand, the combination of MIMO-OFDM system improves channel capacity as well as BER using STBC.
Hence, by applying MIMO-OFDM combination jointly with the proposed CS dictionary, bandwidth
efficiency can be increased and CIR can be successfully recovered even for deep faded time variant channels.
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BIOGRAPHIES OF AUTHORS
Khalifa A. Salim received his B.S, M.S and phd degrees all in electrical Engineering
from University of Technology Bagdad Iraq in 1980, 1983, 2005 respectively. He joined scientific
research center from 1985 to 2006 and lecturer in the College of Engineering Information and
Communication Department, University of Baghdad in 2007. He became Assistant Prof. in 2014.
His current research interest in wireless communication, communication security and digital signal
processing for communication systems. He can be contacted at email: khalifaabboud@yahoo.com.
Bayan Mahdi Sabbar Phd. in 1987 in signal processing from Loughborough
University of Technology, UK 1987. Head of Computer Network Eng. Department, College of
information engineering, Al-Nahrain University, Baghdad. He can be contacted at email:
bayan.mahdi@nahrainuniv.edu.iq.
Maryam K. Abboud received her B.S. in Information and Communication Engineering
from Al-Khwarizmy college of Engineering, Baghdad University, Baghdad, Iraq in 2012, the M.S
and PhD in Information and Communication Engineering from College of Information Engineering,
Al-Nahrain University, Baghdad, Iraq in 2016 and 2020 respectively. Her research interest include;
signal processing, wireless communication, communication security, network and channel coding.
She can be contacted at email: maryamkhalifa@alfarabiuc.edu.iq.