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.
MIMO System Performance Evaluation for High Data Rate Wireless Networks usin...IJMER
Space–time block coding is used for data communication in fading channels by multiple
transmit antennas. Message data is encoded by applying a space–time block code and after the encoding
the data is break into ‘n’ streams of simultaneously transmitted strings through n transmit antennas. The
received signal at the receiver end is the superposition of the n transmitted signals distorted due to noise
.For data recovery maximum likelihood decoding scheme is applied through decoupling of the signals
transmitted from different antennas instead of joint detection. The maximum likelihood decoding scheme
applies the orthogonal structure of the space–time block code (OSTBC) and gives a maximum-likelihood
decoding algorithm based on linear processing at the receiver. In this paper orthogonal space–time
block codes based model is developed using Matlab/Simulink to get the maximum diversity order for a
given number of transmit and receive antennas subject with a simple decoding algorithm.
The simulink block of orthogonal space coding block with space–time block codes is applied with and
without gray coding. The OSTBC codes gives the maximum possible transmission rate for any number of
transmit antennas using any arbitrary real constellation such of M-PSK array. For different complex
constellation of M- PSK space–time block codes are applied that achieve 1/2 and 3/4 of the maximum
possible transmission rate for MIMO transmit antennas using different complex constellations.
Projected Barzilai-Borwein Methods Applied to Distributed Compressive Spectru...Polytechnique Montreal
Cognitive radio allows unlicensed (cognitive) users to use licensed frequency bands by exploiting spectrum sensing techniques to detect whether or not the licensed (primary) users are present. In this paper, we present a compressed sensing applied to spectrum-occupancy detection in wide-band applications. The collected analog signals from each cognitive radio (CR) receiver at a fusion center are transformed to discrete-time signals by using analog-to-information converter (AIC) and then employed to calculate the autocorrelation. For signal reconstruction, we exploit a novel approach to solve the optimization problem consisting of minimizing both a quadratic (l2) error term and an l1-regularization term. In specific, we propose the Basic gradient projection (GP) and projected Barzilai-Borwein (PBB) algorithm to offer a better performance in terms of the mean squared error of the power spectrum density estimate and the detection probability of licensed signal occupancy.
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.
Enhanced Mobile Node Tracking With Received Signal Strength in Wireless Senso...IOSR Journals
Node localization is important parameter in WSN. Node localization is required to report origin of
events which makes it one of the important challenges in WSN. Received signal strength (RSS) is used to
calculate distance between mobile node and reference node. The position of the mobile node is calculated using
multilateration algorithm (MA). Extended Kalman filter (EKF) is utilized to estimate the actual position. In this
paper, the implementation and enhancement of a tracking system based on RSS indicator with the aid of an
Extended Kalman Filter (EKF) is described and an adaptive filter is derived.
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
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, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
MIMO System Performance Evaluation for High Data Rate Wireless Networks usin...IJMER
Space–time block coding is used for data communication in fading channels by multiple
transmit antennas. Message data is encoded by applying a space–time block code and after the encoding
the data is break into ‘n’ streams of simultaneously transmitted strings through n transmit antennas. The
received signal at the receiver end is the superposition of the n transmitted signals distorted due to noise
.For data recovery maximum likelihood decoding scheme is applied through decoupling of the signals
transmitted from different antennas instead of joint detection. The maximum likelihood decoding scheme
applies the orthogonal structure of the space–time block code (OSTBC) and gives a maximum-likelihood
decoding algorithm based on linear processing at the receiver. In this paper orthogonal space–time
block codes based model is developed using Matlab/Simulink to get the maximum diversity order for a
given number of transmit and receive antennas subject with a simple decoding algorithm.
The simulink block of orthogonal space coding block with space–time block codes is applied with and
without gray coding. The OSTBC codes gives the maximum possible transmission rate for any number of
transmit antennas using any arbitrary real constellation such of M-PSK array. For different complex
constellation of M- PSK space–time block codes are applied that achieve 1/2 and 3/4 of the maximum
possible transmission rate for MIMO transmit antennas using different complex constellations.
Projected Barzilai-Borwein Methods Applied to Distributed Compressive Spectru...Polytechnique Montreal
Cognitive radio allows unlicensed (cognitive) users to use licensed frequency bands by exploiting spectrum sensing techniques to detect whether or not the licensed (primary) users are present. In this paper, we present a compressed sensing applied to spectrum-occupancy detection in wide-band applications. The collected analog signals from each cognitive radio (CR) receiver at a fusion center are transformed to discrete-time signals by using analog-to-information converter (AIC) and then employed to calculate the autocorrelation. For signal reconstruction, we exploit a novel approach to solve the optimization problem consisting of minimizing both a quadratic (l2) error term and an l1-regularization term. In specific, we propose the Basic gradient projection (GP) and projected Barzilai-Borwein (PBB) algorithm to offer a better performance in terms of the mean squared error of the power spectrum density estimate and the detection probability of licensed signal occupancy.
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.
Enhanced Mobile Node Tracking With Received Signal Strength in Wireless Senso...IOSR Journals
Node localization is important parameter in WSN. Node localization is required to report origin of
events which makes it one of the important challenges in WSN. Received signal strength (RSS) is used to
calculate distance between mobile node and reference node. The position of the mobile node is calculated using
multilateration algorithm (MA). Extended Kalman filter (EKF) is utilized to estimate the actual position. In this
paper, the implementation and enhancement of a tracking system based on RSS indicator with the aid of an
Extended Kalman Filter (EKF) is described and an adaptive filter is derived.
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
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, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
A novel and efficient mixed-signal compressed sensing for wide-band cognitive...Polytechnique Montreal
In cognitive radio (CR) networks, unlicensed (cognitive) users can exploit the licensed frequency bands by using spectrum sensing techniques to identify spectrum holes. This paper proposes a distributed compressive spectrum sensing scheme, in which the modulated wide-band converter can apply compressed sensing (CS) directly to analog signals at the sub-Nyquist rate and the central fusion receives signals from multiple CRs and exploits the multiple-measurements-vectors (MMV) subspace pursuit (M-SP) algorithm to jointly reconstruct the spectral support of the wide-band signal. This support is then used to detect whether the licensed bands are occupy or not. Finally, extensive simulation results show the advantages of the proposed scheme. Besides, we also compare the performance of M-SP with M-orthogonal matching pursuit (M-OMP) algorithms.
Comparison of Energy Detection Based Spectrum Sensing Methods over Fading Cha...CSCJournals
With the advance of wireless communications, the problem of bandwidth scarcity has become more prominent. Cognitive radio technology has come out as a way to solve this problem by allowing the unlicensed users to use the licensed bands opportunistically. To sense the existence of licensed users, many spectrum sensing techniques have been devised. This paper presents the energy detection based spectrum sensing technique. In the present work, the comparison of ROC curves has been done for various wireless fading channels using squaring and cubing operation. The improvement has gone as high as up to 0.6 times for AWGN channel and 0.4 times for Rayleigh channel as we go from squaring to cubing operation in an energy detector
A novel delay dictionary design for compressive sensing-based time varying ch...TELKOMNIKA JOURNAL
Compressive sensing (CS) is a new attractive technique adopted for Linear Time Varying channel estimation. orthogonal frequency division multiplexing (OFDM) was proposed to be used in 4G and 5G which supports high data rate requirements. Different pilot aided channel estimation techniques were proposed to better track the channel conditions, which consumes bandwidth, thus, considerable data rate reduced. In order to estimate the channel with minimum number of pilots, compressive sensing CS was proposed to efficiently estimate the channel variations. In this paper, a novel delay dictionary-based CS was designed and simulated to estimate the linear time varying (LTV) channel. The proposed dictionary shows the suitability of estimating the channel impulse response (CIR) with low to moderate Doppler frequency shifts with acceptable bit error rate (BER) performance.
The presentation is about Adaptive Beamforming for high data-rate applications. Analog beamforming, which is considered a cost effective solution for consumer devices are investigated. Two adaptive analog beamforming algorithms, i.e., a well-known perturbation-based and dmr-based which overcomes the drawbacks of perturbation-based algorithm are discussed in-detail and their performance comparisons are made with the help of computer simulations. Also variation of single-port structure is considered and it's benefits are exploited with the help of modified analog beamforming algorithms.
Emulation OF 3gpp Scme CHANNEL MODELS USING A Reverberation Chamber MEASUREME...IJERA Editor
The MIMO OTA way forward was approved at the 3GPP RAN4 #62bis meeting in Jeju (Korea) [1], and among
the remaining works to be accomplished it was highlighted that the channel model had to be validated across
methods in order to ensure that a minimal number of artifacts are inserted into the channel model by any given
methodology and that the different methods reproduce, and the DUT experiences, the same radio conditions
regardless of the methodology.The objective of this contribution is to validate the power delay profile (PDP) for
the 3GPP SCME Urban macro (UMA) and Urban micro (UMI) channel models emulated in a mode-stirred
reverberation chamber for the reverberation chamber
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
Area, Delay and Power Comparison of Adder TopologiesVLSICS Design
Adders form an almost obligatory component of every contemporary integrated circuit. The prerequisite of the adder is that it is primarily fast and secondarily efficient in terms of power consumption and chip area. This paper presents the pertinent choice for selecting the adder topology with the tradeoff between delay, power consumption and area. The adder topology used in this work are ripple carry adder, carry lookahead adder, carry skip adder, carry select adder, carry increment adder, carry save adder and carry bypass adder. The module functionality and performance issues like area, power dissipation and propagation delay are analyzed at 0.12µm 6metal layer CMOS technology using microwind tool.
Implementation of Vacate on Demand Algorithm in Various Spectrum Sensing Netw...IJERA Editor
In present days the wireless communications are widely increases because of this reason spectrum utilization can be rapidly increased.For efficient usage of spectrum we can implement the Vacate on demand algorithm in different networks. CR users also need to sense the spectrum and vacate the channel upon the detection of the PU‟s presence to protectPUs from harmful interference. To achieve these fundamental CR functions, CR users usually coordinate with each other by using a common medium for control message exchange ensuring a priority of PUs over CR users. This paper presents the Vacate on Demand (VD) algorithm which enables dynamic spectrum access and ensures to vacate the assigned channel in case of PU activity and move the CR user to some other vacant channel to make spectrum available to PUs as well as to CR users. The basic idea is to use a ranking table of the available channels based on the PU activity detected on each channel. To improve the spectrum efficiency we can implement the Vacate on demand algorithm in MANET Network.
energy lifetime control algorithm for variable target load demands of ad hoc ...INFOGAIN PUBLICATION
The energy and lifetime of Ad hoc wireless sensor-target networks are improved using load control algorithm with different parameters and coverage load in demand, as well as sensor-target configurations. The main goal is to increase the lifetime of sensors by selecting appropriate sensor subsets to satisfy the minimum required value of overall coverage failure probability. The algorithm investigates the different sensor subsets, according to their coverage failure probabilities, and varying intervals of target load demands
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.
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.
A novel and efficient mixed-signal compressed sensing for wide-band cognitive...Polytechnique Montreal
In cognitive radio (CR) networks, unlicensed (cognitive) users can exploit the licensed frequency bands by using spectrum sensing techniques to identify spectrum holes. This paper proposes a distributed compressive spectrum sensing scheme, in which the modulated wide-band converter can apply compressed sensing (CS) directly to analog signals at the sub-Nyquist rate and the central fusion receives signals from multiple CRs and exploits the multiple-measurements-vectors (MMV) subspace pursuit (M-SP) algorithm to jointly reconstruct the spectral support of the wide-band signal. This support is then used to detect whether the licensed bands are occupy or not. Finally, extensive simulation results show the advantages of the proposed scheme. Besides, we also compare the performance of M-SP with M-orthogonal matching pursuit (M-OMP) algorithms.
Comparison of Energy Detection Based Spectrum Sensing Methods over Fading Cha...CSCJournals
With the advance of wireless communications, the problem of bandwidth scarcity has become more prominent. Cognitive radio technology has come out as a way to solve this problem by allowing the unlicensed users to use the licensed bands opportunistically. To sense the existence of licensed users, many spectrum sensing techniques have been devised. This paper presents the energy detection based spectrum sensing technique. In the present work, the comparison of ROC curves has been done for various wireless fading channels using squaring and cubing operation. The improvement has gone as high as up to 0.6 times for AWGN channel and 0.4 times for Rayleigh channel as we go from squaring to cubing operation in an energy detector
A novel delay dictionary design for compressive sensing-based time varying ch...TELKOMNIKA JOURNAL
Compressive sensing (CS) is a new attractive technique adopted for Linear Time Varying channel estimation. orthogonal frequency division multiplexing (OFDM) was proposed to be used in 4G and 5G which supports high data rate requirements. Different pilot aided channel estimation techniques were proposed to better track the channel conditions, which consumes bandwidth, thus, considerable data rate reduced. In order to estimate the channel with minimum number of pilots, compressive sensing CS was proposed to efficiently estimate the channel variations. In this paper, a novel delay dictionary-based CS was designed and simulated to estimate the linear time varying (LTV) channel. The proposed dictionary shows the suitability of estimating the channel impulse response (CIR) with low to moderate Doppler frequency shifts with acceptable bit error rate (BER) performance.
The presentation is about Adaptive Beamforming for high data-rate applications. Analog beamforming, which is considered a cost effective solution for consumer devices are investigated. Two adaptive analog beamforming algorithms, i.e., a well-known perturbation-based and dmr-based which overcomes the drawbacks of perturbation-based algorithm are discussed in-detail and their performance comparisons are made with the help of computer simulations. Also variation of single-port structure is considered and it's benefits are exploited with the help of modified analog beamforming algorithms.
Emulation OF 3gpp Scme CHANNEL MODELS USING A Reverberation Chamber MEASUREME...IJERA Editor
The MIMO OTA way forward was approved at the 3GPP RAN4 #62bis meeting in Jeju (Korea) [1], and among
the remaining works to be accomplished it was highlighted that the channel model had to be validated across
methods in order to ensure that a minimal number of artifacts are inserted into the channel model by any given
methodology and that the different methods reproduce, and the DUT experiences, the same radio conditions
regardless of the methodology.The objective of this contribution is to validate the power delay profile (PDP) for
the 3GPP SCME Urban macro (UMA) and Urban micro (UMI) channel models emulated in a mode-stirred
reverberation chamber for the reverberation chamber
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
Area, Delay and Power Comparison of Adder TopologiesVLSICS Design
Adders form an almost obligatory component of every contemporary integrated circuit. The prerequisite of the adder is that it is primarily fast and secondarily efficient in terms of power consumption and chip area. This paper presents the pertinent choice for selecting the adder topology with the tradeoff between delay, power consumption and area. The adder topology used in this work are ripple carry adder, carry lookahead adder, carry skip adder, carry select adder, carry increment adder, carry save adder and carry bypass adder. The module functionality and performance issues like area, power dissipation and propagation delay are analyzed at 0.12µm 6metal layer CMOS technology using microwind tool.
Implementation of Vacate on Demand Algorithm in Various Spectrum Sensing Netw...IJERA Editor
In present days the wireless communications are widely increases because of this reason spectrum utilization can be rapidly increased.For efficient usage of spectrum we can implement the Vacate on demand algorithm in different networks. CR users also need to sense the spectrum and vacate the channel upon the detection of the PU‟s presence to protectPUs from harmful interference. To achieve these fundamental CR functions, CR users usually coordinate with each other by using a common medium for control message exchange ensuring a priority of PUs over CR users. This paper presents the Vacate on Demand (VD) algorithm which enables dynamic spectrum access and ensures to vacate the assigned channel in case of PU activity and move the CR user to some other vacant channel to make spectrum available to PUs as well as to CR users. The basic idea is to use a ranking table of the available channels based on the PU activity detected on each channel. To improve the spectrum efficiency we can implement the Vacate on demand algorithm in MANET Network.
energy lifetime control algorithm for variable target load demands of ad hoc ...INFOGAIN PUBLICATION
The energy and lifetime of Ad hoc wireless sensor-target networks are improved using load control algorithm with different parameters and coverage load in demand, as well as sensor-target configurations. The main goal is to increase the lifetime of sensors by selecting appropriate sensor subsets to satisfy the minimum required value of overall coverage failure probability. The algorithm investigates the different sensor subsets, according to their coverage failure probabilities, and varying intervals of target load demands
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.
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.
Effect of Different Staging Configurations on Seismic Performance of Circular...IJERA Editor
As known from very upsetting experiences adequately designed Elevated water tanks were heavily damaged or
collapsed during earthquakes. Most of the damages observed during the seismic events arise due to causes like
the lack of knowledge regarding the behavior of supporting system, improper selection and design of supporting
system of elevated water tanks. This paper presents the study of seismic performance of the elevated water tanks
for various seismic zones of India with variation in staging heights and different types of staging configurations.
Total 27 combinations were analyzed using Response Spectrum Method (RSM) in finite element based software
SAP2000 by considering two mass idealization systems. Tank responses including base shear, overturning
moment and roof displacement have been observed with the aim of recommendation of best staging
arrangement for different earthquake zones in India.
Image Restitution Using Non-Locally Centralized Sparse Representation ModelIJERA Editor
Sparse representation models uses a linear combination of a few atoms selected from an over-completed
dictionary to code an image patch which have given good results in different image restitution applications. The
reconstruction of the original image is not so accurate using traditional models of sparse representation to solve
degradation problems which are blurring, noisy, and down-sampled. The goal of image restitution is to suppress
the sparse coding noise and to improve the image quality by using the concept of sparse representation. To
obtain a good sparse coding coefficients of the original image we exploit the image non-local self similarity and
then by centralizing the sparse coding coefficients of the observation image to those estimates. This non-locally
centralized sparse representation model outperforms standard sparse representation models in all aspects of
image restitution problems including de-noising, de-blurring, and super-resolution.
Optimization and Improvisation of Production Assembly Line of Two Valve Engin...IJERA Editor
In automobile engineering terminology a multi-valve engine is one where each cylinder has more than two valves. A multivalve engine has better breathing and can operate at higher revolutions per minute (rpm) than a two valve engine, delivering more power. Nowadays Eicher Motor is generating only two valve engines. But the need of the hour is to develop more efficient, four valve engines, which provide better fuel efficiency. Eicher Motor has started working on four valve engines because two valve engines apart from delivering inferior fuel efficiency compared to four valve engines also fall short on the front of emission norms compliance. To keep the transition two valve to four valve economical, it was proposed that instead of having an entirely new set up for assembling the four valve engines, two valve engine assembly line be use after required modification. For this change were made to engine assembly common line (Block), and cylinder head assembly line conveyors, location of cylinder head assembly line, manpower, machine and tools etc. of Eicher Motor as per the requirement of four valve and two valve assembly line and also engine assembly process was changed.
Rule-Based Mamdani-Type Fuzzy Modeling of Perceived Stress, And Cortisol Resp...IJERA Editor
In this paper, Two Mamdani type fuzzy models (four inputs–one output and two inputs–one output) were developed to test the hypothesis that high job demands and low job control (job strain) are associated with elevated free cortisol levels early in the working day and with reduced variability across the day and to evaluate the contribution of anger expression to this pattern. The models were derived from multiple data sources including One hundred five school teachers (41 men and 64 women) classified 12 months earlier as high (N = 48) or low (N = 57) in job strain according to the demand/control model sampled saliva at 2-hour intervals from 8:00 to 8:30 hours to 22:00 to 22:30 hours on a working day. The quality of the model was determined by comparing predicted and actual fuzzy classification and defuzzification of the predicted outputs to get crisp values for correlating estimates with published values. A modified form of the Hamming distance measure is proposed to compare predicted and actual fuzzy classification. An entropy measure is used to describe the ambiguity associated with the predicted fuzzy outputs. The four input model predicted over 70% of the test data within one-half of a fuzzy class of the published data. The two input model predicted over 40% of the test data within one-half of a fuzzy class of the published data. Comparison of the models show that the four input model exhibited less entropy than the two input model.
Natural Dye-Sensitized Solar Cells (NDSSCs) From Opuntia Prickly Pear Dye Usi...IJERA Editor
Natural dye-sensitized solar cells (NDSSCs) have gained considerable attention in the field of solar energy due to their simple fabrication, good efficiency, and low production cost. Natural dyes are environmentally and economically superior to ruthenium-based dyes because they are nontoxic and cheap. However, the conversion efficiency of dye-sensitized solar cells based on natural dyes is low. One way to improve the DSSC performance is to enhance the absorptivity of extracted natural dyes. We investigated the influence of various factors in the extraction process, such as utilization of different extraction approaches, the acidity of extraction solvent, and different compounds of solvents on the optical absorption spectra. It was found that we could considerably enhance the optical absorptivity of dye and consequently the performance of DSSC by choosing a proper mixture of ethanol, methanol and water. In this study, a photo electrode using ZnO doped TiO2 nanoparticles was prepared by sol-gel method. In this paper we investigate the optical absorption, functional group, surface morphology and elementary composition of pure TiO2, ZnO doped TiO2 nanoparticles and opuntia prickly pear dye extract by using UV-Visible, PL-Studies, FT-IR, FE-SEM and EDS analysis. Finally photocurrent-voltaic characterization of nanocrystaline natural dye solar cell using I-V studies. It was found that the levels of short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF) and overall conversion efficiency (η).
Operating Conditions Effects Onenzyme Activity: Case Enzyme ProteaseIJERA Editor
The Proteases an enzyme added to detergents to degrade the protein spots origin.Their action is manifested
through its activity the middle of washing clothes. This activity depends on the operating conditions. In this
article, the effects of temperature and pH of the reaction and the substrate concentration and time of washing
medium on the enzyme activity were studied. There action mechanism has been shown. The activity
measurements were made by absorption spectrometry.
Investigation of the Structural Variation after the Intercalation of Cetylpyr...IJERA Editor
A new hybrid material using vanadium pentoxide xerogel in different concentration of the cationic surfactant cetylpyridinium chloride (V2O5CPC) is investigated. The insertion was accompanied by XRD, FTIR and SEM characterization. These studies revealed the presence of a lamellar structure for the V2O5CPC hybrid material in all concentrations of cetylpyridinium chloride. The intercalation reaction was evidenced on basis of the increase in the d-spacing as well as the displacement of the infrared bands toward lower energy levels. The CPC intercalation occurred by reorganize intermittently forming two domains within the matrix.
Photovoltaic Modules Performance Loss Evaluation for Nsukka, South East Niger...IJERA Editor
The Photovoltaic (PV) systems and technology offer excellent reliability when designed with the right implementation tools and based on good technical judgements of components that make up each of the critical sections of solar power system. The PV array is an essential section of a solar power system and it is expected to function to deliver pre – estimated power based on design estimations. There are factors that derail the performance of PV modules; the contributions of these factors are peculiar to specific sites of installation, hence the need to empirically evaluate and characterize installation sites before deployment of PV systems. This paper presents the characterization of Nsukka (South East, Nigeria) environment using decent instrumentation; and consequently highlights the power loss indicators for PV modules in the target site while presenting equally mitigable design.
Performance Evaluation of DSDV and MDSDV Routing Protocol with Varying Node D...IJERA Editor
Mobile Ad Hoc Networks (MANET) is an important and challenging research area. The routing protocol should detect and maintain a good route between source and destination nodes in these dynamic networks. Many routing protocols have been proposed for mobile ad hoc networks, and none can be considered as the best under all conditions. This thesis work consist a systematic comparative evaluation of a new multipath routing protocol for MANETS. The new protocol, called Multipath Destination Sequenced Distance Vector (MDSDV) is based on the well known single path Destination Sequenced Distance Vector (DSDV) is compared with known protocol DSDV. This work containing evaluates the protocols on a range of MANETS with between 50, 75 and 100 nodes, which are static nodes. The protocol comparison metrics are Throughput and Residual Energy.
Trabalho analítico e classificativo, elaborado no ano de 2009, pelos acadêmicos de Administração para obtenção de nota parcial referente ao 1° ano letivo.
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 Group-Blind Multiuser Detectors for Synchronous CDMAidescitation
Blind multiuser detectors are attractive for the
suppression of interference in a CDMA environment. This
paper deals with the performance of group blind multiuser
detector for synchronous CDMA is analyzed. The blind multi
user detectors are Direct Matrix Inversion(DMI),Subspace
and group blind multiuser detector. The performance
analysis is performed by means of the Signal to Interference
Noise Ratio(SINR) and Bit Error Rate(BER). The numerical
results are plotted as variation of SINR Vs SNR, K and M,
SINR with respect to correlation coefficient( ) and BER
Vs Number of samples(M) for three detectors using
MATLAB software. The gain rises in group blind multiuser
detector over the DMI and subspace detectors. The
comparison is carried out for equicorrelated signals for
mathematical simplicity.
In this paper, we analyzed a numerical evaluation of the performance of MIMO radio systems in the LTE network environment. Downlink physical layer of the OFDM-MIMO based radio interface is considered for system model and a theoretical analysis of the bit error rate of the two space-time codes (SFBC 2×1 and FSTD 4×2 codes are adopted by the LTE norm as a function of the signal to noise ratio. Analytical expressions are given for transmission over a Rayleigh channel without spatial correlation which is then compared with Monte-Carlo simulations. Further evaluated channel capacity and simulation results show throughput almost reaches to the capacity limit.
BER Performance of MU-MIMO System using Dirty Paper CodingIJEEE
In this paper Dirty Paper Coding for communication system is implemented. MIMO application that involves devices such as cell phones, pocket PCs require closely spaced antenna, which suffers from mutual coupling among antennas and high spatial correlation for signals. DPC is used for compensating the degradation due to correlation and mutual coupling.
Capsulization of Existing Space Time TechniquesIJEEE
In this paper, we explore the fundamental
concepts behind the emerging field of space-time coding for
wireless communication system. A space–time code (STC)
is a method which employed to increase the reliability of
data transmission in the wireless communication
systems using multiple transmit antennas.
Enhanced Mobile Node Tracking With Received Signal Strength in Wireless Senso...IOSR Journals
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events which makes it one of the important challenges in WSN. Received signal strength (RSS) is used to
calculate distance between mobile node and reference node. The position of the mobile node is calculated using
multilateration algorithm (MA). Extended Kalman filter (EKF) is utilized to estimate the actual position. In this
paper, the implementation and enhancement of a tracking system based on RSS indicator with the aid of an
Extended Kalman Filter (EKF) is described and an adaptive filter is derived.
Keywords - Extended Kalman filter (EKF), mobile node tracking, multilateration algorithm (MA), received
signal strength (RSS), Wireless sensor networks (WSN)
At this present scenario, the demand of the system capacity is very high in wireless network. MIMO
technology is used from the last decade to provide this requirement for wireless network antenna
technology. MIMO channels are mostly used for advanced antenna array technology. But it is most
important to control the error rate with enhanced system capacity in MIMO for present-day progressive
wireless communication. This paper explores the frame error rate with respect to different path gain of
MIMO channel. This work has been done in different fading scenario and produces a comparative analysis
of MIMO on the basis of those fading models in various conditions. Here, it is to be considered that
modulation technique as QPSK to observe these comparative evaluations for different Doppler frequencies.
From the comparative analysis, minimum amount of frame error rate is viewed for Rician distribution at
LOS path Doppler shift of 0 Hz. At last, this work is concluded with a comparative bit error rate study on
the basis of singular parameters at different SNR levels to produce the system performance for uncoded
QPSK modulation.
Analysis of Space Time Codes Using Modulation TechniquesIOSR Journals
Abstract: In this Paper, Analysis of channel codes for improving the data rate and reliability of communication over fading channels using multiple transmit antennas has been considered. The codes, namely ’Space Time Codes’ render full diversity and amend coding gain. Performance criteria for designing such codes, under this assumption that the fading is slow and nonselective frequency, is also analysed. Under this research, Study of Frame Error Rate(FER) and outage capacity is compared for different no. Of transmit and receive antennas as well as for different modulation techniques. According to theoretical results FER decreases with increasing SNR and No. Of receiving antennas. Numerical and practical result shows that FER decreases with increasing SNR and no. Of receiving antennas. Keywords: Space time Block Codes ,Space time trellis Codes,Frame Error Rate(FER),Outage capacity,Pairwise Error Probability
Performance of Wideband Mobile Channel with Perfect Synchronism BPSK vs QPSK ...Editor Jacotech
Direct-sequence code-division multiple access (DS-CDMA) is
currently the subject of much research as it is a promising
multiple access capability for third and fourth generations
mobile communication systems. The synchronous DS-CDMA
system is well known for eliminating the effects of multiple
access interference (MAI) which limits the capacity and
degrades the BER performance of the system. In this paper,
we investigate the bit error rate (BER) performance of a
synchronous DS-CDMA system over a wideband mobile
radio channel. The BER performance is affected by the
difference in path length ΔL and the number of arriving
signals N. Furthermore, the effect of these parameters is
examined on the synchronous DS-CDMA system for different
users’ number as well as different processing gain Gp. In this
environment and under the above conditions the performances
of the BPSK (Binary Phase Shift Keying) and the QPSK
(Quadrature Phase Shift Keying) modulations are compared.
The promising simulation results showed the possibility of
applying this system to the wideband mobile radio channel.
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.
Improved performance of scs based spectrum sensing in cognitive radio using d...eSAT Journals
Abstract
Tremendous growth in current wireless networks raises the demand of more frequency spectrum, over the finite availability of spectrum resource. Although, the research has specifies that the available primary users (i.e. licensed user) has not occupying the channel all the time. The most effective technology known as Cognitive radio giving promises for a solution of under utilization of available frequency spectrum in wireless communication. In cognitive radio network two types of wireless user can be define as primary user and secondary user. Primary users have highest priority to utilize the available band of frequency and secondary user can utilize these services only when the channel is vacant by primary user and there will be no any interference. The optimization of this may be implemented by a smart technique such as cognitive radio, which is fully automated intelligent wireless sensor tool having capability to sense, learn & adjust relevant operating parameters dynamically in radio atmosphere. This can be happen if we prefer the appropriate window technique to evaluate system parameter for sensing the availability of vacant band. We show that by comparing the different windows techniques, cognitive radios not only provide better spectrum opportunity but also provide the chance to huge number of wireless users.
Keywords: Primary user, Secondary user, Spectrum Sensing and Window technique etc.
Multiuser Detection with Decision-feedback Detectors and PIC in MC-CDMA SystemTELKOMNIKA JOURNAL
In this paper we propose an iterative parallel decision feedback (P-DF) receivers associated with
parallel interference cancellation (PIC) for multicarrier code division multiple access (MC-CDMA) systems
in a Rayleigh fading channel (cost 207). First the most widely detection techniques, minimum
mean-squared error MMSE, Maximum Likelihood ML and PIC were investigated in order to compare their
performances in terms of Bit Error Rate (BER) with parallel feedback detection P-DFD. A MMSE DF
detector that employs parallel decision-feedback (MMSE-P-DFD) is considered and shows almost the
same BER performance with MMSE and ML, which present a better result than the other techniques. In a
second time, an iterative proposed method based on the multi-stage techniques P-DFD
(parallel DFD with two stages) and PIC was exploited to improve the performance of the system.
Performance Analysis of Ultra Wideband Receivers for High Data Rate Wireless ...graphhoc
For high data rate ultra wideband communication system, performance comparison of Rake, MMSE and Rake-MMSE receivers is attempted in this paper. Further a detail study on Rake-MMSE time domain equalizers is carried out taking into account all the important parameters such as the effect of the number of Rake fingers and equalizer taps on the error rate performance. This receiver combats inter-symbol interference by taking advantages of both the Rake and equalizer structure. The bit error rate performances are investigated using MATLAB simulation on IEEE 802.15.3a defined UWB channel models. Simulation results show that the bit error rate probability of Rake-MMSE receiver is much better than Rake receiver and MMSE equalizer. Study on non-line of sight indoor channel models illustrates that bit error rate performance of Rake-MMSE (both LE and DFE) improves for CM3 model with smaller spread compared to CM4 channel model. It is indicated that for a MMSE equalizer operating at low to medium SNR values, the number of Rake fingers is the dominant factor to improve system performance, while at high SNR values the number of equalizer taps plays a more significant role in reducing the error rate.
In this paper, three beamforming design are considered for multi user MIMO system. First, transmit
beamformers are fixed and the receive (RX) beamformers are calculated. Transmit beamformer (TX-BF)is
projectedas a null space of appropriate channels. It reduces the interference for each user. Then the receiver
beamformer is determined which maximize the SNR. This beamforming design provides less computation time.
The second case is joint TX and RX beamformer for SNR maximization. In this transmitter and receiver
beamformer are calculated using extended alternating optimization (EAO) algorithm. The third one is joint
transmitter and receiver beamforming for SNR and SINR maximization using EAO algorithm. This algorithm
provides better error performance and sum rate performance. All the design cases are simulated by using
standard multipath channel model. Our simulation results illustrate that compared to the least square design and
zero forcing design, the joint TX and RX beamforming design using EAO algorithm provides faster
beamforming and improved error performance and sum rate.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
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LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
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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.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
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Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
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GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
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The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
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A tale of scale & speed: How the US Navy is enabling software delivery from l...sonjaschweigert1
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In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
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H44093641
1. Tarak Bahroun et al Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 4( Version 9), April 2014, pp. 36-41
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Adaptive Space-Time Processing For Multiuser Detection in
Multipath CDMA Systems
Khairy Elbarbary*
, Tarak Bahroun **
* Prof. Dr of Electrical Engineering. Suez Canal University
** Ph. D. student in the EW. Dpt, MTC, Cairo, Egypt www.tar2001b@yahoo.com.
Abstract
Wireless communications poses some unique challenges including multipath fading and co-channel
interference. Diversity techniques, among which space diversity, are overwhelmingly used in wireless
communication systems to enhance capacity, coverage and quality. We have considered sample-by-sample
adaptive space-time multiuser detectors for multipath CDMA channels with multiple receive antennas. Fully
exploiting diversities through space-time processing and multiuser detection offers substantial improvement in
the performance of CDMA systems.
Keywords: Code Division Multiple Access (CDMA), Adaptive MMSE ST MUD.
I. INTRODUCTION
The presence of both multiple-access interference (MAI) and intersymbol interference (ISI) constitutes
a major impediment to reliable high-data-rate CDMA communications in multipath channels. These phenomena
present challenges as well as opportunities for receiver designers; through multiuser detection (MUD) [1] and
space time (ST) processing [2] , the inherent code, spatial, temporal and spectral diversities of multipath multi-
antenna CDMA channels can be exploited to achieve substantial gain.
Advanced signal processing typically improves system performance at the cost of computational
complexity. It is well known that the optimal maximum likelihood (ML) multiuser detector has prohibitive
computational requirements for most current applications. A variety of linear and nonlinear multiuser detectors
have been proposed to ease this computational burden while maintaining satisfactory performance. However, in
asynchronous multipath CDMA channels with receive antenna arrays and large data frame lengths, direct
implementation of these suboptimal techniques still proves to be very complex.
Techniques for efficient space-time multiuser detection includes sample-by-sample adaptive methods,
which require knowledge only of the signal and (possibly) channel of a desired user. Sample-by sample adaptive
methods are suitable for mobile end processing, which entails decentralized data detection, and for base station
processing due to the time varying nature of wireless communications. We may think of the sample-by-sample
adaptive method discussed here as being most suitable for application at the base station, where it is more
practical to install an antenna array. However, most of the described blind techniques are readily applied to the
mobile user end when multiple antennas can be applied at mobile terminals.
This paper is organized as follows. In Section II a space-time multiuser signal model is presented.
while sample by-sample adaptive methods are dealt with in Section III. Computer simulation examples are
given in Section IV. and Section V provides the Conclusions.
II. SPACE-TIME SIGNAL Model
Consider a direct-sequence CDMA communication system with K users employing normalized
spreading waveforms 1, , KS S given by:
1
0
1
,0 ,1
N
K k c
j
s t c j t jT t T k K
N
(1)
where, N is the processing gain, ; 0 1kc j j N is a signature sequence of ±1’s assigned to the
kth
user, and . is a normalized chip waveform of duration cT T N with T the symbol interval. User
1k for k K transmits a frame of M independent equiprobable BPSK symbols
RESEARCH ARTICLEOPEN ACCESS
2. Tarak Bahroun et al Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 4( Version 9), April 2014, pp. 36-41
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1, 1 , 0 1kb i i M ; and the symbol sequences from different users are assumed to be
mutually independent. The transmitted baseband signal due to the kth
user is thus given by:
1
0
,
M
k k k k
i
x t A b i S t iT
1 ,k K (2)
Where kA is the amplitude associated with user kth
transmission. The transmitted signal of each user passes
through a multipath channel before it is received by a uniform linear antenna array (ULA) of P elements with
inter-element spacing d . Then the single-input multiple-output (SIMO) vector impulse response between the kth
user and the receive array can be modeled as:
1
L
k kl kl kl
l
t g t
h a (3)
where L is the maximum number of resolvable paths between each user and the receive array (for simplicity we
assume L is the same for each user), klg and kl are respectively the complex gain and delay of the lth
path of
the kth
user, and
,1
2 sin /
,2
2 1 sin /
,
1
kl
kl
kl
j d
kl
kl
j d P
kl P
a
a e
a e
a
(4)
is the ULA response corresponding to the signal of the lth
path of the kth
user with direction of arrival (DOA)
kl and carrier wavelength . t denotes the Dirac delta function. The received signal at the antenna
array is the superposition of the channel distorted signals from the K users together with additive Gaussian
noise, which is assumed to be spatially and temporally white. This leads to the vector received signal model
1
K
k k
k
t x t t t
r h n (5)
where denotes convolution and
2
is the spectral height of the ambient Gaussian noise at each antenna
element.
A sufficient statistic for demodulating the multiuser symbols from the space-time signal (5) is given by
[3]:
1 1 10 , , 0 , 1 , , 1 , , 1
T
k kY y y y y M y M (6)
Where the elements ky i are defined as follows:
1
kl
L
H
k kl kl k kl
l
Z i
y i g t S t iT dt
a r
1 ,k K 0 1i M (7)
To produce this sufficient statistic, the received signal vector tr is first match-filtered for each path of each
user to form the vector observables, klZ i , after which beams are formed on each path of each user via the
3. Tarak Bahroun et al Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 4( Version 9), April 2014, pp. 36-41
www.ijera.com 38 | P a g e
dot products with the array responses kla , and then all the paths of each user are combined with a RAKE
receiver. This process produces one observation for each symbol of each user. Since the system is in general
asynchronous and the users are not orthogonal, we need to collect the statistic for all users over the entire data
frame. The observable ky i corresponds to the output of a conventional space-time matched filter, matched
to the ith
symbol of user k. Therefore, a general space-time multiuser receiver is a space-time matched filter
bank, followed by a decision algorithm as shown in Figure 1. In the following, we will present, a new ST MUD
receiver structure will also be introduced, in which chip-level observables are exploited.
The sufficient statistic (6) can be written as (see [1]).
Y HAb v (8)
Where H is a KM KM matrix capturing the cross-correlations between different symbols and different
users, A is the KM KM diagonal matrix whose k +iK diagonal elements are equal to Ak
1 1 10 , , 0 , 1 , , 1 , , 1
T
K Kb b b b M b M b and 0,Nv H (i.e., v is Gaussian
with zero mean and covariance matrix H). An optimal ML space time multiuser detector will maximize the
following log-likelihood function [1]
2Re T T
y b b A b AHAb (9)
Figure 1: A conventional space-time multiuser receiver structure
III. ADAPTIVE MMSE ST MUD
Figure 2 depicts the structure of a decentralized adaptive space-time multiuser detector of interest in
detecting the ith
symbol of kth
user. Each antenna element is equipped with a chip matched filter followed by a
chip-interval-spaced adaptive finite-impulse-response (FIR) filter. The outputs of all FIR filters are summed and
sampled at the symbol rate to form a soft decision output, which serves two purposes: to form an estimate for
the desired bit through a decision device, and to form an error signal for adjustment of adaptive filter
coefficients.
Collect the weights of the FIR filter banks at the pth
antenna element into an N-vector
,0 ,1 , 1, , ,
T
k k k k
P P P P Nw w w
w and then collect such vectors from all antenna elements into a
PN -vector 1 2, , ,
TT T Tk k k
k P
W w w w . kW is thus applied to the signal vector
k
r to make
4. Tarak Bahroun et al Int. Journal of Engineering Research and Applications www.ijera.com
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a decision about kb . A useful performance metric for the receiver of Figure 2 is the output signal-to-noise ratio
(SINR), which can be estimated as:
, (10)
with mean square error defined as:
10
1
10log k
k
k
MSE
SINR
MSE
W
W
2H k
k k kMSE E b W W r 1
H H H
k k k k k k k W h h W W R W (11)
Where
k k H
k ER r r is the autocorrelation matrix of the signal vector
k
r and
k
k kE bh r
is the crosscorrelation vector between
k
r and the desired bit kb . An optimum choice for kW is that which
minimizes the mean square error kMSE W .This choice, known as the MMSE detector, is given by the
Wiener-Hopf solution
1opt
k k k
W R h (12)
For this theoretical optimum solution, the achieved minimum value of the mean square error is given by:
2H kopt opt
k k k kMMSE MSE E b
W W r 1
1 1
H Hopt opt
k k k k k k
W R W h R h (13)
Figure 2: Structure of an adaptive MMSE space-time multiuser detector
A number of algorithms are available to seek the solution (12) adaptively, from the simple least-mean-
squares (LMS) algorithm to various fast yet complex recursive-least squares (RLS) methods. The properties and
behavior of these algorithms are well known and documented [4]. Here we adopt the LMS algorithm as a simple
tool to obtain MMSE FIR filter banks. This choice is illustrated as follows. The soft decision ouput is given by:
kH
k ky i i i W r (14)
from which a bit estimate is formed as:
ˆ sgn Rek kb i y i (15)
5. Tarak Bahroun et al Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 4( Version 9), April 2014, pp. 36-41
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where “Re” indicates the real part. An error signal is then formed as:
k k ki b i y i (16)
and the filter coefficients are updated as:
1
k
k k ki i i i
W W r (17)
Where is the step size of the adaptive algorithm. Note that after the training period, the receiver is switched
to decision-directed mode and the error signal is formed as:
ˆ
k k ki b i y i (18)
IV. COMPUTER SIMULATIONS.
The performance of the above described adaptive space-time multiuser detectors is examined through
computer simulations. We assume a K = 16-user CDMA system with spreading gain N = 16, which is heavily
loaded with severe near-far problem. Each user travels through L = 3 paths before it reaches a ULA with P = 3
elements and half-wavelength spacing. The maximum delay spread is set to be 4T. The complex gains and
delays of the multipath and the directions of arrival are randomly generated and kept fixed for all the
simulations. We assume 1 KA A for simplicity, but the received signal powers of different users are
unequal due to the effects of multipath. The number of symbols per frame is M = 250. The step size of the LMS
algorithm is fixed to be 0.001 .
Figure 3 shows the learning curve for the decentralized adaptive MMSE ST MUD. The user of interest
is user 1. The theoretical MMSE is also plotted in the figure (as the dashed line) for comparison. Figure 4
compares the steady-state bit error rate (BER) of the adaptive MMSE ST MUD with that of the batch iterative
MMSE ST MUD. The error is counted and averaged for consecutive 400 data frames after an initial 4 data
frames (1000 iterations) of adaptation. These results show that this adaptive ST MUD structure approaches the
optimum MMSE ST MUD, while using only knowledge of the timing and training sequence of the desired user.
This simple adaptive structure effectively combines the function of beamforming, RAKE combining and
multiuser detection.
V. CONCLUSIONS
The adaptive space-time multiuser receivers combine the functions of adaptive beamforming, RAKE
combining and multiuser detection with no side information needed other than the timing and training sequences
of the desired user. The ST MUD performance these results show that this adaptive ST MUD structure
approaches the optimum MMSE ST MUD, while using only knowledge of the timing and training sequence of
the desired user.
REFERENCES
[1] S. Verdú, Multiuser Detection, Cambridge, UK: Cambridge University Press, 1998.
[2] J. Paulraj and C. B. Papadias, “Space-time processing for wireless communications,” IEEE Signal
Processing Mag., pp. 49-82, Nov. 1997.
[3] X. Wang and H. V. Poor, “Space-time multiuser detection in multipath CDMA channels,” IEEE Trans.
Signal Processing, vol. 47, no. 9, pp. 2356-2374, Sept. 1999.
[4] S. Haykin, Adaptive Filter Theory, third edition, Englewood Cliffs, NJ: Prentice- Hall, 1996.
6. Tarak Bahroun et al Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 4( Version 9), April 2014, pp. 36-41
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Figure 3. Convergence of the decentralized adaptive MMSE space-time multiuser detector
Figure 4. Bit error rate of the decentralized adaptive MMSE space-time multiuser detector in the steady state