Intersymbol interference caused by multipath in band limited frequency selective time dispersive channels distorts the transmitted signal, causing bit error at receiver. ISI is the major obstacle to high speed data transmission over wireless channels. Channel estimation is a technique used to combat the intersymbol interference. The objective of this paper is to improve channel estimation accuracy in MIMO-OFDM system by using modified variable step size leaky Least Mean Square (MVSSLLMS) algorithm proposed for MIMO OFDM System. So we are going to analyze Bit Error Rate for different signal to noise ratio, also compare the proposed scheme with standard LMS channel estimation method.
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.
Digital signal processing techniques for lti fiber impairment compensationeSAT Journals
Abstract Coherent detection is one of the active research areas for the development of high speed, high spectral efficient optical communication network. Digital signal processing is the important technique for compensating the fiber transmission impairments because of number of advantages such as signal can be amplified, delayed, splitted and manipulated without degrading the signal quality. This paper presents DSP compensation algorithms for linear time invariant (LTI) impairment such as chromatic dispersion (CD) and polarization mode dispersion (PMD) in optical fiber communication. We presented a mathematical framework for compensation of LTI fiber impairments. This paper also focuses the different compensation methods both in time and frequency domain for chromatic dispersion compensation. These DSP techniques confirm that coherent detection with high data rates will become feasible in future for compensating transmission impairments. Keywords: Coherent Detection, Chromatic Dispersion, Polarization Mode Dispersion
BER Performance of Antenna Array-Based Receiver using Multi-user Detection in...ijwmn
Antenna promises to provide significant increases in system capacity and performance in
wireless systems. In this paper, a simplified, near-optimum array receiver is proposed,
which is based on the angular gain of the spatial filter. This detection is then analyzed by
calculating the exact error probability.The proposed model confirms the benefits of adaptive
antennas in reducing the overall interference level (intercell/intracell) and to find an
accurate approximation of the error probability. We extend the method that has been
proposed for propagation over Nakagami-m fading channels, the model shows good
agreements with simulation results.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Signal and image processing on satellite communication using MATLABEmbedded Plus Trichy
Basic Explanations about satellite imaging and signal processing with the help of MATLAB.
Contact us: 23,Nandhi koil Street, Near Nakoda Showroom,Theppakulam,Trichy
Mb.No:9360212155.
Mail:embeddedplusproject@gmail.com,
FB:www.facebook.com/embeddedplusproject
Reduction of PAPR and Efficient detection ordering scheme for MIMO Transmissi...IJERA Editor
The technical challenges for communication engineers is the development of best performance wireless
networks with negligible amount of distortions. We have to consider multipath propagation attenuation and
radio spectrum inefficiency. Now a days, In MIMO (Multi Input Multi Output) systems there is a huge demand
for the networks with the high transmission rates and better quality of service which are having low PAPR ratio.
Instead of OFDMA, filter banks are used in massive MIMO to reduce the complexity. But they are error prone
to noise. This base paper discusses about PAPR reduction in MIMO systems using different precoding based
OFDM systems. Mainly, minimization of multi-antenna systems by controlling the transmission power and
reduction of PAPR using ZC (Zadoff-Chu) matrix transform.
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.
Digital signal processing techniques for lti fiber impairment compensationeSAT Journals
Abstract Coherent detection is one of the active research areas for the development of high speed, high spectral efficient optical communication network. Digital signal processing is the important technique for compensating the fiber transmission impairments because of number of advantages such as signal can be amplified, delayed, splitted and manipulated without degrading the signal quality. This paper presents DSP compensation algorithms for linear time invariant (LTI) impairment such as chromatic dispersion (CD) and polarization mode dispersion (PMD) in optical fiber communication. We presented a mathematical framework for compensation of LTI fiber impairments. This paper also focuses the different compensation methods both in time and frequency domain for chromatic dispersion compensation. These DSP techniques confirm that coherent detection with high data rates will become feasible in future for compensating transmission impairments. Keywords: Coherent Detection, Chromatic Dispersion, Polarization Mode Dispersion
BER Performance of Antenna Array-Based Receiver using Multi-user Detection in...ijwmn
Antenna promises to provide significant increases in system capacity and performance in
wireless systems. In this paper, a simplified, near-optimum array receiver is proposed,
which is based on the angular gain of the spatial filter. This detection is then analyzed by
calculating the exact error probability.The proposed model confirms the benefits of adaptive
antennas in reducing the overall interference level (intercell/intracell) and to find an
accurate approximation of the error probability. We extend the method that has been
proposed for propagation over Nakagami-m fading channels, the model shows good
agreements with simulation results.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Signal and image processing on satellite communication using MATLABEmbedded Plus Trichy
Basic Explanations about satellite imaging and signal processing with the help of MATLAB.
Contact us: 23,Nandhi koil Street, Near Nakoda Showroom,Theppakulam,Trichy
Mb.No:9360212155.
Mail:embeddedplusproject@gmail.com,
FB:www.facebook.com/embeddedplusproject
Reduction of PAPR and Efficient detection ordering scheme for MIMO Transmissi...IJERA Editor
The technical challenges for communication engineers is the development of best performance wireless
networks with negligible amount of distortions. We have to consider multipath propagation attenuation and
radio spectrum inefficiency. Now a days, In MIMO (Multi Input Multi Output) systems there is a huge demand
for the networks with the high transmission rates and better quality of service which are having low PAPR ratio.
Instead of OFDMA, filter banks are used in massive MIMO to reduce the complexity. But they are error prone
to noise. This base paper discusses about PAPR reduction in MIMO systems using different precoding based
OFDM systems. Mainly, minimization of multi-antenna systems by controlling the transmission power and
reduction of PAPR using ZC (Zadoff-Chu) matrix transform.
Multi carrier equalization by restoration of redundanc y (merry) for adaptive...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The
performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed
DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated
and less complexity also involved by the simulation of the DST-DMT system.
Adaptive Channel Equalization using Multilayer Perceptron Neural Networks wit...IOSRJVSP
This research addresses the problem inter-symbol interference (ISI) using equalization techniques for time dispersive channels with additive white Gaussian noise (AWGN). The channel equalizer is modelled as a non-linear Multilayer Perceptron (MLP) structure. The Back Propagation (BP) algorithm is used to optimize the synaptic weights of the equalizer during the training mode. In the typical BP algorithm, the error signal is propagated from the output layer to the input layer while the learning rate parameter is held constant. In this study, the BP algorithm is modified so as to allow for the learning rate to be variable at each iteration and this achieves a faster convergence. The proposed algorithm is used to train the MLP based decision feedback equalizer (DFE) for time dispersive ISI channels. The equalizer is tested for a random input sequence of BPSK signals and its performance analysed in terms of the Bit Error Rates and speed of convergence. Simulation results show that the proposed algorithm improves the Bit Error Rate (BER) and rate of convergence.
Using the Channel State Information (CSI) at the transmitter is fundamental for the precoder
design in Multi-user Multiple Input Single Output (MU-MISO-OFDM) systems. In Frequency
Division Duplex (FDD) systems, CSI can be just available at the transmitter through a limited
feedback channel [1], where we assume that each user quantizes its channel direction with a
finite number of quantization bits. In this paper, we consider a scalar quantization (SQ) scheme
of the Channel Direction Information (CDI). Although vector quantization (VQ) schemes [2],
[3] still outperform this scalar scheme in terms of quantization error and Sum rate, the former
scheme suffers from an exponential search complexity and high storage requirements at the
receiver for high number of feedback bits.
Classical Discrete-Time Fourier TransformBased Channel Estimation for MIMO-OF...IJCSEA Journal
In this document, we look at various time domain channel estimation methods with this constraint of null carriers at spectrumborders.We showin detail howto gauge the importance of the “border effect” depending on the number of null carriers, which may vary from one system to another. Thereby we assess the limit of the technique discussed when the number of null carriers is large. Finally the DFT with the truncated singular value decomposition (SVD) technique is proposed to completely eliminate the impact of the null subcarriers whatever their number. A technique for the determination of the truncation threshold for any MIMO-OFDM system is also proposed.
These slides deal with the basic problem of channel equalization and exposes the issue related to it and shows how it can be balanced by the usage of effective and robust algorithms.
In mmWave massive MIMO systems, the lens antenna array and beam selection by beamspace MIMO are employed to target the number of required RF chains reduced without obvious performance loss. For cost – effective, the number of RF chain is an allowable limitation, however, to obtain the near-optimal capacity efficiently, beam selection must require the exact information of the wide size of beamspace channel. Solution to this problem, in this paper we suggest analyzing whole beamspace based on maximal SINR. More specicfically, it is confirmed that the proposed beam selection algorithms achieve higher power efficiencies than a full system where all beams are employed.
Energy Efficiency of MIMO-OFDM Communication SystemIJERA Editor
With the ever increasing number of subscribers and their seemingly “greedy” demands for high-data-rate services, the next generation networks will have to provide global connectivity to ensure success. So the combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequency division multiplexing (OFDM) is regarded as a promising solution for enhancing the data rates of next-generation wireless communication systems operating in frequency-selective fading environments. Therefore hybrid architecture between terrestrial and satellite networks based on MIMO-OFDM with frequency reuse is employed here. However, this frequency reuse introduces severe co-channel interference (CCI) at the satellite end. To mitigate CCI, we propose an OFDM based adaptive beamformer implemented on-board the satellite with pilot reallocation at the transmitter side. The system performance is simulated by using the software MATLAB, the experimental result shows that the MIMO-OFDM communication system has better performance when compared.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Wireless communication is one of the most effective areas of technology development of our time.
Wireless communications today covers a very wide array of applications. In this paper, we study the
performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator
(LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh
fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms
others. Result shows that for higher modulation schemes SER performance degrades as well as SER
performance increases for higher no of receiver antennas
MIMO Channel Estimation Using the LS and MMSE AlgorithmIOSRJECE
Wireless Communication Technology has developed over the past few yearsfor other objectives.The Multiple InputMultiple Output (MIMO) is one of techniques that is used to enhancethe data rates, in which multiple antennas are employed both the transmitter and receiver. Multiple signals are transmitted from different antennas at the transmitter using the same frequency and separated space. Various channel estimation techniques are employed in order to judge the physical effects of the medium present. In this paper, we analyze and implementvarious estimation techniques for MIMO Systems such as Least Squares (LS), Minimum Mean Square Error (MMSE),these techniques are therefore compared to effectively estimate the channel in MIMO System. The results demonstrate that SNR required to support different values of bit error rate varies depending on different low correlation between the transmitting and the receiving antennas .In addition, it is illustrated that when the number of transmitter and receiver antennas increases, the performance of TBCE schemes significantly improves. The Same behavior isalso observed for MIMO system. Performance of both MMSE and LSestimation are the same for allkinds of modulation at small value of SNR but the more we increase the SNR value the more performance gap goes on increasing.
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
Abstract: The performance of WCDMA system deteriorates in the presence of multipath fading environment. Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear, anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise, Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake receiver and MMSE and the simulation results are shown. Keywords – MMSE, MMSE-DFE, rake receiver, WCDMA
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
The performance of WCDMA system deteriorates in the presence of multipath fading environment.
Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though
conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path
diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses
MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To
overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear,
anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps
of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise,
Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length
MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian
noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake
receiver and MMSE and the simulation results are shown.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Multi carrier equalization by restoration of redundanc y (merry) for adaptive...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The
performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed
DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated
and less complexity also involved by the simulation of the DST-DMT system.
Adaptive Channel Equalization using Multilayer Perceptron Neural Networks wit...IOSRJVSP
This research addresses the problem inter-symbol interference (ISI) using equalization techniques for time dispersive channels with additive white Gaussian noise (AWGN). The channel equalizer is modelled as a non-linear Multilayer Perceptron (MLP) structure. The Back Propagation (BP) algorithm is used to optimize the synaptic weights of the equalizer during the training mode. In the typical BP algorithm, the error signal is propagated from the output layer to the input layer while the learning rate parameter is held constant. In this study, the BP algorithm is modified so as to allow for the learning rate to be variable at each iteration and this achieves a faster convergence. The proposed algorithm is used to train the MLP based decision feedback equalizer (DFE) for time dispersive ISI channels. The equalizer is tested for a random input sequence of BPSK signals and its performance analysed in terms of the Bit Error Rates and speed of convergence. Simulation results show that the proposed algorithm improves the Bit Error Rate (BER) and rate of convergence.
Using the Channel State Information (CSI) at the transmitter is fundamental for the precoder
design in Multi-user Multiple Input Single Output (MU-MISO-OFDM) systems. In Frequency
Division Duplex (FDD) systems, CSI can be just available at the transmitter through a limited
feedback channel [1], where we assume that each user quantizes its channel direction with a
finite number of quantization bits. In this paper, we consider a scalar quantization (SQ) scheme
of the Channel Direction Information (CDI). Although vector quantization (VQ) schemes [2],
[3] still outperform this scalar scheme in terms of quantization error and Sum rate, the former
scheme suffers from an exponential search complexity and high storage requirements at the
receiver for high number of feedback bits.
Classical Discrete-Time Fourier TransformBased Channel Estimation for MIMO-OF...IJCSEA Journal
In this document, we look at various time domain channel estimation methods with this constraint of null carriers at spectrumborders.We showin detail howto gauge the importance of the “border effect” depending on the number of null carriers, which may vary from one system to another. Thereby we assess the limit of the technique discussed when the number of null carriers is large. Finally the DFT with the truncated singular value decomposition (SVD) technique is proposed to completely eliminate the impact of the null subcarriers whatever their number. A technique for the determination of the truncation threshold for any MIMO-OFDM system is also proposed.
These slides deal with the basic problem of channel equalization and exposes the issue related to it and shows how it can be balanced by the usage of effective and robust algorithms.
In mmWave massive MIMO systems, the lens antenna array and beam selection by beamspace MIMO are employed to target the number of required RF chains reduced without obvious performance loss. For cost – effective, the number of RF chain is an allowable limitation, however, to obtain the near-optimal capacity efficiently, beam selection must require the exact information of the wide size of beamspace channel. Solution to this problem, in this paper we suggest analyzing whole beamspace based on maximal SINR. More specicfically, it is confirmed that the proposed beam selection algorithms achieve higher power efficiencies than a full system where all beams are employed.
Energy Efficiency of MIMO-OFDM Communication SystemIJERA Editor
With the ever increasing number of subscribers and their seemingly “greedy” demands for high-data-rate services, the next generation networks will have to provide global connectivity to ensure success. So the combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequency division multiplexing (OFDM) is regarded as a promising solution for enhancing the data rates of next-generation wireless communication systems operating in frequency-selective fading environments. Therefore hybrid architecture between terrestrial and satellite networks based on MIMO-OFDM with frequency reuse is employed here. However, this frequency reuse introduces severe co-channel interference (CCI) at the satellite end. To mitigate CCI, we propose an OFDM based adaptive beamformer implemented on-board the satellite with pilot reallocation at the transmitter side. The system performance is simulated by using the software MATLAB, the experimental result shows that the MIMO-OFDM communication system has better performance when compared.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Wireless communication is one of the most effective areas of technology development of our time.
Wireless communications today covers a very wide array of applications. In this paper, we study the
performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator
(LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh
fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms
others. Result shows that for higher modulation schemes SER performance degrades as well as SER
performance increases for higher no of receiver antennas
MIMO Channel Estimation Using the LS and MMSE AlgorithmIOSRJECE
Wireless Communication Technology has developed over the past few yearsfor other objectives.The Multiple InputMultiple Output (MIMO) is one of techniques that is used to enhancethe data rates, in which multiple antennas are employed both the transmitter and receiver. Multiple signals are transmitted from different antennas at the transmitter using the same frequency and separated space. Various channel estimation techniques are employed in order to judge the physical effects of the medium present. In this paper, we analyze and implementvarious estimation techniques for MIMO Systems such as Least Squares (LS), Minimum Mean Square Error (MMSE),these techniques are therefore compared to effectively estimate the channel in MIMO System. The results demonstrate that SNR required to support different values of bit error rate varies depending on different low correlation between the transmitting and the receiving antennas .In addition, it is illustrated that when the number of transmitter and receiver antennas increases, the performance of TBCE schemes significantly improves. The Same behavior isalso observed for MIMO system. Performance of both MMSE and LSestimation are the same for allkinds of modulation at small value of SNR but the more we increase the SNR value the more performance gap goes on increasing.
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
Abstract: The performance of WCDMA system deteriorates in the presence of multipath fading environment. Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear, anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise, Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake receiver and MMSE and the simulation results are shown. Keywords – MMSE, MMSE-DFE, rake receiver, WCDMA
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
The performance of WCDMA system deteriorates in the presence of multipath fading environment.
Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though
conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path
diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses
MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To
overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear,
anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps
of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise,
Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length
MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian
noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake
receiver and MMSE and the simulation results are shown.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Capacity Enhancement of MIMO-OFDM System in Rayleigh Fading ChannelIOSR Journals
MIMO-OFDM system in Rayleigh Fading Channel is very popular technique for mobile
communication now a day’s for research. Here we want increase the capacity of MIMO-OFDM of system by
using adaptive modulation, Algebraic Space-Time Codes (ASTC) encoder for MIMO Systems are based on
quaternion algebras .we found that ergodic capacity has some limitation which reduce the system’s
performance to overcome this we use ASTC code . ASTC code are full rank, full rate and non vanishing constant
minimum determinant for increasing spectral efficiency and reducing Peak to Average Power Ratio (PAPR) .
Capacity Enhancement of MIMO-OFDM System in Rayleigh Fading ChannelIOSR Journals
Abstract: MIMO-OFDM system in Rayleigh Fading Channel is very popular technique for mobile communication now a day’s for research. Here we want increase the capacity of MIMO-OFDM of system by using adaptive modulation, Algebraic Space-Time Codes (ASTC) encoder for MIMO Systems are based on quaternion algebras .we found that ergodic capacity has some limitation which reduce the system’s performance to overcome this we use ASTC code . ASTC code are full rank, full rate and non vanishing constant minimum determinant for increasing spectral efficiency and reducing Peak to Average Power Ratio (PAPR) . Keywords— Adaptive modulation ASTC code, Capacity, BER, Ergodic capacity, PAPR, Spectral Efficiency and SNR
IMPROVEMENT OF LTE DOWNLINK SYSTEM PERFORMANCES USING THE LAGRANGE POLYNOMIAL...IJCNCJournal
To achieve a high speed data rate, higher spectral efficiency, improved services and low latency the 3rd
generation partnership project designed LTE standard (Long Term Evolution).the LTE system employs
specific technical as well the technical HARQ, MIMO transmission, OFDM Access or estimation technical.
In this paper we focus our study on downlink LTE channel estimation and specially the interpolation which
is the basis of the estimation of the channel coefficients. Thus, we propose an adaptive method for polynomial interpolation based on Lagrange polynomial. We perform the Downlink LTE system MIMO transmission then compare the obtained results with linear, Sinus Cardinal and polynomial Newton Interpolations. The simulation results show that the Lagrange method outperforms system performance in term of Block Error Rate (BLER) , throughput and EVN(%)vs. Signal to Noise Ratio (SNR).
Multi-carrier Equalization by Restoration of RedundancY (MERRY) for Adaptive ...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated and less complexity also involved by the simulation of the DST-DMT system.
Performance analysis of adaptive filter channel estimated MIMO OFDM communica...IJECEIAES
Advanced Communication Systems are wideband systems to support multiple applications such as audio, video and data so and so forth. These systems require high spectral efficiency and data rates. In addition, they should provide multipath fading and inter-symbol interference (ISI) free transmission. Multiple input multiple output orthogonal frequency division multiplexing (MIMO OFDM) meets these requirements Hence, MIMOOFDM is the most preferable technique for long term evaluation advanced (LTEA). The primary objective of this paper is to control bit error rate (BER) by proper channel coding, pilot carriers, adaptive filter channel estimation schemes and space time coding (STC). A combination of any of these schemes results in better BER performance over individual schemes. System performance is analyzed for various digital modulation schemes. In this paper, adaptive filter channel estimated MIMO OFDM system is proposed by integrating channel coding, adaptive filter channel estimation, digital modulation and space time coding. From the simulation results, channel estimated 2×2 MIMO OFDM system shows superior performance over individual schemes.
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.
ICI and PAPR enhancement in MIMO-OFDM system using RNS codingIJECEIAES
The Inter-Carrier-Interference (ICI) is considered a bottleneck in the utilization of Multiple-Input-Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems, due to the sensitivity of the OFDM towards frequency offsets which lead to loss of orthogonality, interference and performance degradation. In this paper Residue Numbers as a coding scheme is impeded in MIMO-OFDM systems, where the ICI levels is measured and evaluated with respect to conventional ICI mitigation techniques implemented in MIMO-OFDM. The Carrier-to-Interference Ratio (CIR), the system Bit-Error-Rate (BER) and the Complementary Cumulative Distribution Function (CCDF) for MIMO-OFDM system with Residue Number System (RNS) coding are analyzed and evaluated. The results had demonstrated a performance of transmission model with and without RNS.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Abstract : Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this paper, we study the performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator (LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms others. Result shows that for higher modulation schemes SER performance degrades as well as SER performance increases for higher no of receiver antennas. Keywords - Multi Input Multi Output, Zero-forcing receiver, Linear Least Square Estimation, V-BLAST.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Abstract : Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this paper, we study the performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator (LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms others. Result shows that for higher modulation schemes SER performance degrades as well as SER performance increases for higher no of receiver antennas. Keywords - Multi Input Multi Output, Zero-forcing receiver, Linear Least Square Estimation, V-BLAST.
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.
CHANNEL ESTIMATION AND MULTIUSER DETECTION IN ASYNCHRONOUS SATELLITE COMMUNIC...ijwmn
In this paper, we propose a new method of channel estimation for asynchronous additive white Gaussian noise channels in satellite communications. This method is based on signals correlation and multiuser interference cancellation which adopts a successive structure. Propagation delays and signals amplitudes are jointly estimated in order to be used for data detection at the receiver. As, a multiuser detector, a single stage successive interference cancellation (SIC) architecture is analyzed and integrated to the channel estimation technique and the whole system is evaluated. The satellite access method adopted is the direct sequence code division multiple access (DS CDMA) one. To evaluate the channel estimation and the detection technique, we have simulated a satellite uplink with an asynchronous multiuser access.
PERFORMANCE ANALYSIS OF CLIPPED STBC CODED MIMO OFDM SYSTEMIAEME Publication
A combination of Multiple-Input Multiple-Output Spatial Division Multiplexing technology and Orthogonal Frequency Division Multiplexing technique, namely MIMO-OFDM systems, been well-known as a potential technology to provide high speed data transmission and spectrum efficiency to attain throughput of 1 Gbit/sec and beyond improves link reliability for modern wireless communications. The rising development of Internet related contents and demand of multimedia services leads to increasing curiosity to high speed communications. It has been shown that by using MIMO system, it is possible to increase that capacity considerably.
Designing Financial Information System Using Structured System Analysis and D...ijcnac
In the following research, the financial information system for the studied company
which had various sub-systems of accounting, payment, storage, properties, salary and
wages systems were analyzed properties system is developed as one of the sub-systems
subsequent to sub-systems problems identification. In both stages of analysis and
designing, Structured System Analysis and Design Method methodology, which has a
Top-Down approach, is used. Based on the studied methodology in analysis stage, system
requirements including needs (determined through studying present system problems)
and obligations (determined by the designer and according to experiences obtained from
similar systems) were identified and considering such requirements, the proper
information system concept model was designed. Some suggestions are represented for
organizations use and information systems development fans, in the final part to the
article.
EFFICIENT IMAGE COMPRESSION USING LAPLACIAN PYRAMIDAL FILTERS FOR EDGE IMAGESijcnac
This project presents a new image compression technique for the coding of retinal and
fingerprint images. Retinal images are used to detect diseases like diabetes or
hypertension. Fingerprint images are used for the security purpose. In this work, the
contourlet transform of the retinal and fingerprint image is taken first. The coefficients of
the contourlet transform are quantized using adaptive multistage vector quantization
scheme. The number of code vectors in the adaptive vector quantization scheme depends
on the dynamic range of the input image.
A Comparative Analysis of the Performance of VoIP Traffic with Different Type...ijcnac
The key QoS parameters for VoIP are delay, jitter and loss. In the Internet, VoIP requires
the underlying packet switched network to minimize the impact of these parameters. A
major contributing factor in this regard is traffic engineering carried out by scheduling
algorithms. This paper studies the behavior of different types of scheduling algorithms on
the delay, jitter and loss QoS parameters. The performance evaluation involves
identifying the scheduling algorithms which are most suitable for VoIP communications.
The result from the analysis also shows the impact of the QoS parameters on VoIP over
the Internet.
Coverage of WCDMA Network Using Different Modulation Techniques with Soft and...ijcnac
The wideband code division multiple access (WCDMA) based 3G cellular mobile
wireless networks are expected to provide a diverse range of multimedia services to
mobile users with guaranteed quality of service (QoS). To serve diverse quality of service
requirements of these networks it necessitates new radio resource management strategies
for effective utilization of network resources with coding schemes. In this paper coverage
area for voice traffic and with different modulation techniques, coding schemes and
decision decoder are discussed. These discussions are to improve the coverage area in
the mobile communication system. This paper is mainly focuses on coverage area of
WCDMA system using link budget calculation with different modulation, coding schemes
and decision decoder. Simulation results demonstrate coverage extension for voice
service with different modulation,coding scheme, soft and hard decision decoder using
appropriate Bit error rate (BER) to maintain QoS of the voice.
The Escalating Nigeria National Security Challenge: Smart Objects and Interne...ijcnac
Since October 1st 2011, when Nigeria Federal Govenrment marked Nigerian�s 51st National Indepedence celebration at Eagles Square Abuja that witnessed the first bomb blast in the country, there have been a catalogue of avalanche of security challenges throughout the country ranging from bomb blasts, suicide bombings, terrorist attacks, kidnapping for ransoms, ritual killings, political assassinations and political brigande, crude oil bunkering and pipeline vandalism, armed robbery but to mention a few. The Federal and State governments have made much effort through the engagement of the law enforcement agencies and security forces such as Police, Joint Military Task Force (JTF), State Security Service (SSS), Nigeria Security and Civil Defnce Corps (NSCDC) but their combined effort have not yielded much positive result towards arresting these security menace.This paper attempts to proffer a security solution framework using newly emerging security technological solutions known as �smart objects� and �internet-of-things�, combining the cooperative efforts of security technologies such as Wireless Sensor and Actuator Networks(WSANs), Global Positioning System (GPS), IP surveillance using specialized cameras and Close Circuit Television Cameras (CCTV) and fusing their cooperative outputs into the Internet using novelty telecommunication networks such as Wi-Fi, 3G, ZigBee, Internet Protocol (IP) to aid security agents to track, trace, apprehend and prosecute the culprits who perpetuate these security challenges.Since October 1st 2011, when Nigeria Federal Govenrment marked Nigerian�s 51st National Indepedence celebration at Eagles Square Abuja that witnessed the first bomb blast in the country, there have been a catalogue of avalanche of security challenges throughout the country ranging from bomb blasts, suicide bombings, terrorist attacks, kidnapping for ransoms, ritual killings, political assassinations and political brigande, crude oil bunkering and pipeline vandalism, armed robbery but to mention a few. The Federal and State governments have made much effort through the engagement of the law enforcement agencies and security forces such as Police, Joint Military Task Force (JTF), State Security Service (SSS), Nigeria Security and Civil Defnce Corps (NSCDC) but their combined effort have not yielded much positive result towards arresting these security menace.This paper attempts to proffer a security solution framework using newly emerging security technological solutions known as �smart objects� and �internet-of-things�, combining the cooperative efforts of security technologies such as Wireless Sensor and Actuator Networks(WSANs), Global Positioning System (GPS), IP surveillance using specialized cameras and Close Circuit Television Cameras (CCTV) and fusing their cooperative outputs into the Internet using novelty telecommunication networks such as Wi-Fi, 3G, ZigBee, Internet Protocol (IP) to aid security agents to track, trace, apprehend and pr
Performance Analysis and Simulation of OLSR Routing Protocol in MANET ijcnac
Mobile ad hoc network is a collection of wireless nodes that are communicate other
nodes (router) without using access point, infrastructure . Mobile ad-hoc network is an
autonomous system that means no need for depaentd other nodes it have own capability
to handle and controlling all funcitionlity, to sending and receiving all information form
one device to other device. MANET has power full feature that controlling itself by
dynamic nature, multihop,low power and configuration of the system. In this paper we
analyzing, simulation and implements the TC messages and HELLO Message by MPR of
OLSR routing performance checked at 200 nodes on Qualnet 5.0.2 simulator. In Qualnet
simulator to simulate and implement the performance of OLSR routing protocols takes
various performance metrics like hello message sent (HMS) , hello message received
(HMR), TC message generated (TCMG), TC message replied (TCMR), TC messages
received on Constant Bit Rate (CBR) using random waypoint model. In this paper check
the performance OLSR routing protocol gives effective performance for lage networks.
BookyScholia: A Methodology for the Investigation of Expert Systemsijcnac
Mathematicians agree that encrypted modalities are an interesting new topic in the field
of software engineering, and systems engineers concur. In our research, we proved the
deployment of consistent hashing, which embodies the intuitive principles of algorithms.
Our focus in our research is not on whether the World Wide Web and SMPs are largely
incompatible, but rather on presenting an analysis of interrupts (BookyScholia).
Experiences with such solution and active networks disconfirm that access points and
cache coherence can synchronize to realize this mission. W woulde show that
performance in BookyScholia is not an obstacle. The characteristics of BookyScholia, in
relation to those of more seminal systems, are famously more natural. Finally,we would
focus our efforts on validating that the UNIVAC computer can be made probabilistic,
cooperative, and scalable.
A Joint Encryption/Watermarking Algorithm for Secure Image Transferijcnac
This paper presents a method combining encryption and watermarking for secure images transfer. The proposed solution gives access to the outcomes of the image integrity and of its origins as its attachment to one user even if the image is stored encrypted. This method is based on the combination of encryption algorithms public-private keys and secret keys, and watermarking. The algorithm for image encryption uses a secret key. We encrypt the secret key with an asymmetric algorithm. This encrypted secret key is then inserted into the encrypted image using watermark algorithm.
Study of Polarization Mode Dispersion in the Optical Digital Connection to Hi...ijcnac
Polarization Mode Dispersion (PMD) is a factor which limits the bit rate of the optical transmissions. The PMD is such an effect which is time broadening due to the dependence of the group velocity to the signal polarization. The deformation effects of the impulses become considerable from 40 Gb/s. This paper, we reviews the degrade PMD effect in the telecommunications optical connections to high bit rate, due to the evolution of quality factor (Q) according to the fiber length, bit rate and PMD coefficient , well as the impact PMD on the degree of polarization and electrical power, we discuss also the representation of the polarization state and PMD vector on the Poincare sphere.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
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Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
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State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
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Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
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Performance Comparison of Modified Variable Step Size Leaky LMS Algorithm for Channel Estimation in Noisy Environment
1. International journal of Computer Networking and Communication (IJCNAC)Vol. 1, No. 1 (August 2013) 13
www.arpublication.org
Performance Comparison of Modified Variable
Step Size Leaky LMS Algorithm for Channel
Estimation in Noisy Environment
Dinesh B.Bhoyar1*
, C.G.Dethe2
, M.M.Mushrif3
1
Department of E&T Yeshwantrao Chavan College of Engineering, Nagpur, India
1
dinesh_bhoyar@rediffmail.com
2
Priyadarshini Institute of Engineering & Technology,Nagpur,India
2
cgdethe@rediffmail.com
3
Department of E&T Yeshwantrao Chavan College of Engineering, Nagpur, India
3
milindmushrif@yahoo.com
Abstract
Intersymbol interference caused by multipath in band limited frequency selective time dispersive
channels distorts the transmitted signal, causing bit error at receiver. ISI is the major obstacle to
high speed data transmission over wireless channels. Channel estimation is a technique used to
combat the intersymbol interference. The objective of this paper is to improve channel estimation
accuracy in MIMO-OFDM system by using modified variable step size leaky Least Mean Square
(MVSSLLMS) algorithm proposed for MIMO OFDM System. So we are going to analyze Bit Error
Rate for different signal to noise ratio, also compare the proposed scheme with standard LMS
channel estimation method
Keywords: MIMO,OFDM,MVSSLLMS,ISI
1. INTRODUCTION
Future wireless systems will require high data rate capable technologies. MIMO-OFDM [1]
[9][10][11]is the best choice for high data rate transmission. Orthogonal frequency division
multiplexing (OFDM)[8] is a widely used modulation and multiplexing technology, which has
become the basis of many telecommunications standards including wireless local area networks
(LANs), digital terrestrial television (DTT) and digital radio broadcasting. The OFDM divides the
available spectrum into a number of overlapping and orthogonal narrowband sub channels. The
carriers are made orthogonal to each other by appropriately choosing the frequency spacing
between them. The orthogonality will ensure the subcarrier separation at the receiver. It gives
better spectral efficiency. It has the advantage of spreading out a frequency selective fade over
many symbols. This effectively randomizes burst errors caused by fading or impulse interference.
Because of dividing an entire signal bandwidth into many narrow sub bands, the frequency
response over individual sub bands is relatively flat. Multiple Input Multiple Output (MIMO)
technology transmit different data streams on different transmit antennas simultaneously. An
appropriate processing architecture handles these parallel streams of data. The data rate and the
Signal-to-Noise Ratio (SNR) performance can be increased.
2. 14
www.arpublication.org
Over the year, various computational techniques have been adopted for channel estimation in
wireless communication. Least square (LS)[9], Least mean square (LMS),normalized NLMS[15],
variable step size LMS(VSS-LMS)[5,16,17] Recursive least square (RLS), Kalman filter,
orthogonal Frequency response filtering are some of the well known techniques employed for the
purpose of channel estimation[14]more accurately and efficiently. At the same time soft
computing approaches such as fuzzy logic, neural network, genetic algorithm and simulated
annealing [6] have also been used for channel estimation. However such computing approaches
suffer from poor convergence rate and computational complexity is more.
The problem of filter design for estimating the desired signal based on another signal
formulated from the deterministic point of view .Channel estimation is usually refers to
estimation of the frequency response of the path between the transmitter and receiver, also this is
used to optimize performance and maximize the transmission rate [12]. The channel estimation in
MIMO-OFDM system is more complicated in comparison with SISO system due to simultaneous
transmission of signal from different antennas that cause co-channel interference [13].
In this paper, Modified variable step size leaky Least Mean Square Leaky Least Mean Square
(MVSSLLMS) adaptive channel estimator is described for MIMO OFDM systems. These
channel estimation methods uses adaptive estimator which are able to update parameters of the
estimator continuously, so that knowledge of channel and noise statistics are required [3].
This can be done in a digital communication system by periodically transmitting a training
sequence that is known to the receiver. The approaches based on modified variable step size leaky
Least Mean Square LMS technique that is computationally efficient and robust with respect to the
dynamic variation in the system also the computational complexity of the proposed technique is
less as compare to the VLLMS and RLS.MVSSLLMS gives better performance in the noisy
environment.The remainder of the paper is organized as follows. Section 2 represents the system
model of MIMO-OFDM system. Section 3 presents the proposed algorithm and formulation of
the equations. Section 4 discusses the comparative simulation results of the proposed algorithm
with the existing ones. Section 5 concludes the paper.
2. SYSTEM MODEL
2.1 MIMO-OFDM System
S
/
P
M-ary
Mappi
ng
Pilot
Insert
Pilot
Insert
I
F
A
dd
C
Remove
CP
FFT
Channel
Estimati
on
Remove
CP
FFT
S
/
P
P
/
S
P
/
S
S
/
P
S
/
P
P
/
S
M-ary
De-
Mapp
ing
Output
Data
Binary Data
I
F
Ad
d
CP
Figure 1 Block Diagram of MIMO-OFDM System
3. International journal of Computer Networking and Communication (IJCNAC)Vol. 1, No. 1 (August 2013) 15
www.arpublication.org
In this paper, we considered MIMO-OFDM system with two transmitting antennas and two
receiving antennas. The total number of subcarriers is N. MIMO-OFDM transmitter has parallel
transmitter paths which are very similar to the single antenna OFDM system. Each branch
performing serial to parallel conversion, pilot insertion, N-point IFFT, cyclic extension and up-
converted to RF before the final data transmission. The channel encoder and the digital
modulation can also be done in some spatial modulation system. At the receiver, the cyclic prefix
is removed and N-point FFT is performed per received branch. Next, the transmitted symbol per
TX antenna is combined and outputted for the subsequent operations like digital demodulation
and decoding. Finally all the input binary data are recovered with certain BER [1].Fig.1 shows the
MIMO system. The technique develop in this paper can be directly applied to any MIMO-OFDM
system. The data block is {b[n,k]:k=0,1--------}transmitted into two different signals, {ti[n,k]:
k=0,1,.......K-1 and i=1,2} at the transmit diversity processor,[2] where, K, k, and i are the number
of sub-channels of the OFDM systems, sub-channel index, and antenna index, respectively. This
OFDM signal is modulated by using the ti[n,k] where i=1,2. At the receiver, the discrete Fourier
transform (DFT or FFT) of the received signal at each receive antenna is the superposition of two
distorted transmitted signals. The received signal at the jth receive antenna can be expressed as
[ , ] [ , ] [ , ] [ , ]j ij i j
i
r n k n k x n k n n kw= +∑ (1)
Where, the channel frequency response [ , ]ij
W n k at th
k the tone of the th
n OFDM block,
corresponding to the th
i transmit and th
j receive antenna. [ , ]jn n k denotes the additive complex
Gaussian noise on the th
j receive antenna and is assumed to be zero mean with variance 2
nσ .
The noise is uncorrelated for different n’s, k’s or j’s [7].
Above equation can be expressed in matrix form as,
[ ]
1
[ ] [ ] [ ]
n
n
ij
i
n n n
j j jr w x n
=
= +∑ (2)
[ ]
[ [ , 0], [ ,1],....., [ , 1]]
n T
j j j j
r r n r n r n N= − (3)
[ ]
[ [ , 0], [ ,1],....., [ , 1]]
n T
j j j j
t t n t n t n N= − (4)
2.2 Adaptive Channel Estimator
Fig.2 shows, the discrete time model of adaptive linear[2] channel estimation using LMS –
like algorithms. The baseband equivalent channel impulse response is modeled as a transversal
filter with M weights given in the vector
W(n) =[w0(n),w1(n)………wN-1]T
(5)
Where the subscript n indicate the time index.
We assume that the intersymbol interference is due solely to the propagation medium,
which is modeled as an AWGN channel with discrete multipath intensity profile and delays
spaced by the symbol duration.
4. 16
www.arpublication.org
So the channel tap weights wi (n)=0,1...,.M-1 are modelled as mutually uncorrelated complex
Gaussian process with zero mean and variance and identical Doppler spectrum shape given in
multipath intensity profile is the input vector composed of statistically independent and
equiprobable complex modulation symbol with zero mean and variance σ2.
Let d (n) be the desired response of the adaptive filter
d(n) = xT
(n)w(n) +n(n) (6)
Where, x(n)=[x(n),x(n-1),...........x(n-M+1]T
is the input vector composed of statistically independent and equiprobable complex
modulation symbol with zero mean and variance σ2
.
The adaptive filter output is
y(n) = w(n) xT
(n) (7)
n(n) is the system noise that is independent of x(n)
We express the estimation error as
e(n) = d(n) – y(n) (8)
There are various algorithms are available for minimizing the weight w (n).The updating of
µ(n) is required to use the autocorrelation of the error rather than the square of the error value.
A. LMS
In the LMS, the updatation is in such a way that the instantiation cost function
Jn = (e)2
(9)
The weight is updated by the steepest decent rule.
W(n+1) = w(n) -µ∂Jn/∂w(n) (10)
The final weight will be
Unknown
System
AWGN
Adaptive
Filter
+
+
X(n)
d(n)
e(n)
--
+
Y(n)
Fig. 2 Block Diagram of Generalised Channel Estimtor
5. International journal of Computer Networking and Communication (IJCNAC)Vol. 1, No. 1 (August 2013) 17
www.arpublication.org
W(n+1) = w(n) -µe(n)x(n) (11)
B. RLS
The RLS channel estimation algorithm requires all the past samples of the input and the
desired output is available at each iteration. The updating equation is
k = λ-1p.u/(1 + λ-1p x(n)' p x(n)) (12)
w = w + k *conj(e(n)) (13)
p = λ-1p - λ-1 p k x(n) (14)
C. VLLLMS
In VSLLMS[18]adaptive channel estimator the cost function Jn is the square of the estimated
error.
Jn = (e)2
+ γ(n) + x(n) W(n) WT
(n) (15)
Where γ(n) is the variable leakage factor which is defined as
γ (n+1) = γ (n) - 2µ(n) ρ e(n) xT
(n)w(n-1) (16)
Constant ρ and whose value is greater than 1
The equation of the adaptive step size is
µ(n+1) = λµ(n) + γ(n) p2
(n) (17)
the autocorrelation of e(n) is
p(n) = βp(n-1) + (1-β)e(n)e(n-1) (18)
where, 0<β<1
and finally weight is updated as
w(n+1) = (1-2µ(n)γ(n)) w(n) + 2µ(n)x(n) (19)
D. Derivation of the proposed modified LLMS algorithm
The error signal at time n is given by
e(n) = d(n) - y(n) (20)
Where d(n) is the desired signal
The output of the linear filter is given by
y(n) = wT
(n)x(n) (21)
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Where x(n) is the input to the filter which is
x(n) =[x(n) x(n-1) x(n-2)……. x(n-L+2) x(n-L-1)]T
and w (n) is the filter gain
w(n) = [w(0) w(1) w(2)….. ……..w(n-L+2) w(L-1)]T
In adaptive filtering, the Wiener solution is found through an iterative procedure,
W(n+1) = w(n) + ∆w(n) (22)
where ∆w(n) is an incrementing vector.
The instaneous cosy function defined as,
Jn = e2
(n) (23)
w(n+1) = w(n) - µ∇ (e2
(n)) (24)
∇ is the gradient operator, ∇ = [∂/∂w0 ∂/∂w1 ∂/∂w2 ....... ∂/∂wN-1]T
∂e2
(n)/∂wi = 2e(n) ∂ e(n)/∂wi
= -2e(n)x(n)
So Equ. (21) becomes
w(n+1) = w(n) + 2e(n)x(n) (25)
The cost function of the modified leaky LMS algorithm is defined by the following equation
Jn = e2
(n) + γwT
(n)w(n) (26)
Where 0 ≤ γ < 1 so as to avoid parameter drifting and γwT
(n) w(n) is a regularization
component
Selecting a constant γ may lead to over/under parameterization of this regularization
component. One
way to avoid this use variable γ.
Jn = e2
(n) + γ(n)wT
(n)w(n) (27)
Then the equation of weight updatation becomes
W(n+1) = e2
(n) - µ∂Jn/∂w(n) (28)
Where µ > 0 is a step size parameter to be chosen by the designer. Choosing a constant µ puts
some weights on the correlation term throughout the estimation process that may suffer the
convergence of the algorithm.
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This feature may be incorporated using a variable step size updatation scheme for µ that
yield a faster convergence.
W(n+1) = e2
(n) - µ(n) ∂Jn / ∂w(n) (29)
Where µ(n) is a variable step size parameter and may be updated as
µ(n+1) = γ µ(n) + γ(n) e2
(n) (30)
In leaky LMS we are considering non stationary noise field, low SNR.Updating of µ(n) is
required to use the autocorrelation of the error rather than the square of the error value to take
care of the effect of the external disturbances in the step size u
So equ.(11) modified as
µ(n+1) = λ µ(n) + γ(n) P2
(n) (31)
where P(n) is the autocorrelation of e(n) and can be computed for an ergodic process by using
a time average of it.
P(n+1) = β P(n) + (1- β e(n) e(n-1) (32)
Where 0 < β < 1 is a forgotten parameter to be chosen by the designer. Choosing a constant β
puts some weights on the convergence of the algorithm. and gives larger BER.To overcome this
we use variable β(n) ,
β(n+1) = β(n) – logβ(n) / M (33)
equ.(13) modified as
P(n+1) = β(n)P(n) + (1- β(n)e(n)e(n-1) (34)
Now we are ready to obtain the final update equation
for w(n) and Now update the λ(n) and γ(n).
γ(n+1) = γ(n) – 4µ(n))ρ e(n) xT
(n)w(n-1) (35)
where ρ>1And finally weight is updated as
W(n+1) = (1-2µ(n) λ(n))w(n) + 2µ(n)e(n)x(n) (36)
3. FLOW CHART
This flow chart fig 3 contents the total process step by step done in Modified Least Mean
Square (MLMS) Algorithm for Channel Estimation in MIMO-OFDM System.
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4. SIMULATION RESULT
In this section we consider 2x2 MIMO-OFDM system. Simulate Modified variable step size leaky least
mean square (MLLMS) algorithm for different SNR and iterations. Also compare the result with the
standard LMS and RLS algorithm. For implementing the proposed MLLMS algorithm, first requires setting
the parameter µ, α and w and the initial values for µ, α, ρ and w. In the present work, we chosen µ, α, ρ,
w=0 .BPSK signal with Gaussian noise is used to study the performance of the algorithms in presence of
noise. Seven different cases of noises with signal-to-noise ratio (SNR) of 1 to 20 dB and iterations of 5 to
10000 are considered for the study shown in table 2 and 3. The corresponding results are shown in fig.4 and
fig.5.It can be observed that the BER reduces as the SNR increases from 1 to 20 dB .In MLLMS the
forgetting factor β is adaptive in nature and whose value is adapt as per equation 33.by using the
logarithmic we can overcome the problem of parameter drifting in the LMS algorithm.
Start
Initialize all Parameter & value
Set reference Phase value
Mapping of Binary Data
TX carried all Process to Tx the Data
Add Noise to Channel
Rx Receive the Data
Update the Step Size, Leakage Factor and Weight Vector
Is final iteration
reached?
Update Weight vector
Stop
Yes
No
Fig. 3 Flow Chart
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Iteration LMS VLLMS MLLMS
5 0.00032 0.00016 0.000079
10 0.00016 0.00008 0.000039
15 0.000106 0.000053 0.000026
20 0.00008 0.00004 0.000020
25 0.000062 0.000023 0.000018
50 0.000075 0.00002 0.000010
100 0.000046 0.000028 0.000012
200 0.000047 0.00002 0.000010
500 0.000045 0.000024 0.000010
1000 0.000045 0.000028 0.000018
2000 0.000052 0.00002 0.000014
5000 0.000046 0.00002 0.000010
10000 0.00004 0.000026 0.000011
Table 1 BER Comparison of algorithm for SNR=10
5. CONCLUSION
A MLLMS algorithm has been used to estimate the channel in pilot aided MIMO-OFDM system. The
BER performance of channel estimation was improved because the received data were subtracted from the
desired signals. It has been shown using several simulations and experimental studies that this algorithm is
superior to LMS,VLLMS and RLS for channel estimation. Although the proposed algorithm is slightly
computationally complex compare to LMS. It has been observed that it is faster in convergence, more
accurate and consistent with respect to several irregularities that are encountered in channel estimation
schemes. Based on these observations use of MLMS is suggested for channel estimation in high data rate
wireless communication.
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Fig. 4 BER Comparison of LMS,VLLMS and MLLMS for SNR=10
Figure 5 BER Comparison of MLLMS and RLS for SNR=20
6. FUTURE WORK
We will extend the work to compare with other algorithm by using other modulation techniques with
different fading channels such as Rayleigh, recian. And furthermore reduces Symbol Error Rate or Bit
Error Rate.
BER Comparison of LMS,VLLMS and MLLMS for SNR=10
BER Comparison of MLLMS and RLS for SNR=20
We will extend the work to compare with other algorithm by using other modulation techniques with
different fading channels such as Rayleigh, recian. And furthermore reduces Symbol Error Rate or Bit
We will extend the work to compare with other algorithm by using other modulation techniques with
different fading channels such as Rayleigh, recian. And furthermore reduces Symbol Error Rate or Bit