1) The document presents research on reducing outage probabilities in MIMO systems operating in fast fading channels using OFDM modulation.
2) Simulation results show that a MIMO-OFDM system provides significant reduction in outage probabilities compared to a conventional MIMO system without OFDM. For example, with a 2x2 antenna configuration and SNR threshold of 5dB, MIMO-OFDM had a 41.38% lower outage probability than MIMO alone.
3) The outage probability is also reduced as the number of antennas increases for a MIMO-OFDM system. For instance, with a transmitted SNR of 10dB, configurations with 2x3, 3x3 and 4x4 antennas had outage probabilities of
Analyses and performance of techniques papr reduction for stbc mimo ofdm syst...ijwmn
An OFDM system is combined with multiple-input mult
iple-output (MIMO) in order to increase the
diversity gain and system capacity over the time va
riant frequency-selective channels. However, a maj
or
drawback of MIMO-OFDM system is that the transmitte
d signals on different antennas might exhibit high
peak-to-average power ratio (PAPR).In this paper, w
e present a PAPR analysis reduction of space-time-
block-coded (STBC) MIMO-OFDM system for 4G wireless
networks. Several techniques have been used to
reduce the PAPR of the (STBC) MIMOOFDM system: clip
ping and filtering, partial transmit sequence
(PTS) and selected mapping (SLM). Simulation result
s show that clipping and filtering provides a bette
r
PAPR reduction than the others methods and only SLM
technique conserve the PAPR reduction in
reception part of signal.
Performance Analysis of MIMO-OFDM System Using QOSTBC Code Structure for M-PSKCSCJournals
MIMO-OFDM system has been currently recognized as one of the most competitive technology for 4G mobile wireless systems. MIMO-OFDM system can compensate for the lacks of MIMO systems and give play to the advantages of OFDM system. In this paper, a general Quasi orthogonal space time block code (QOSTBC) structure is proposed for multiple-input multiple-output–orthogonal frequency-division multiplexing (MIMO-OFDM) systems for 4X4 antenna configuration. The signal detection technology used in this paper for MIMO-OFDM system is Zero-Forcing Equalization (linear detection technique). In this paper the analysis of high level of modulations (i.e. M-PSK for different values of M) on MIMO-OFDM system is presented. Here AWGN and Rayleigh channels have been used for analysis purpose and their effect on BER for high data rates have been presented. The proposed MIMO-OFDM system with QOSTBC using 4X4 antenna configuration has better performance in terms of BER vs SNR than the other systems.
OFDM allows tightly packed carriers to convey information orthogonally and with high bandwidth efficiency
Objectives Description:
Concepts
Basic idea
Introduction to OFDM
Implementation
Advantages and Drawbacks.
FDMA
Comparative performance analysis of different modulation techniques for papr ...IJCNCJournal
One of the most important multi-carrier tran
smission techniques used in the latest wireless com
munication
arena is known as Orthogonal Frequency Division Mul
tiplexing (OFDM). It has several characteristics
such as providing greater immunity to multipath fad
ing & impulse noise, eliminating Inter Symbol
Interference (ISI) & Inter Carrier Interference (IC
I) using a guard interval known as Cyclic Prefix (C
P). A
regular difficulty of OFDM signal is high peak to a
verage power ratio (PAPR) which is defined as the r
atio
of the peak power to the average power of OFDM Sign
al. An improved design of amplitude clipping &
filtering technique of us previously reduced signif
icant amount of PAPR with slightly increase bit err
or rate
(BER) compare to an existing method in case of Quad
rature Phase Shift Keying (QPSK) & Quadrature
Amplitude Modulation (QAM). This paper investigates
a comparative performance analysis of the differen
t
higher order modulation techniques on that design.
Performance Analysis of Massive MIMO Downlink System with Imperfect Channel S...IJRES Journal
We investigate the ergodic sum rate and required transmit power of a single-cell massive
multiple-input multiple-output (MIMO) downlink system. The system considered in this paper is based on two
linear beamforming schemes, that is, maximum ratio transmission (MRT) beamforming and zero-forcing (ZF)
beamforming. What’s more, we use minimum mean square error (MMSE) channel estimation to get imperfect
channel state information (CSI). Compared with the perfect CSI case, both theoretical analysis and simulation
results show that the system performance is different when the imperfect CSI is taken into account.
Analyses and performance of techniques papr reduction for stbc mimo ofdm syst...ijwmn
An OFDM system is combined with multiple-input mult
iple-output (MIMO) in order to increase the
diversity gain and system capacity over the time va
riant frequency-selective channels. However, a maj
or
drawback of MIMO-OFDM system is that the transmitte
d signals on different antennas might exhibit high
peak-to-average power ratio (PAPR).In this paper, w
e present a PAPR analysis reduction of space-time-
block-coded (STBC) MIMO-OFDM system for 4G wireless
networks. Several techniques have been used to
reduce the PAPR of the (STBC) MIMOOFDM system: clip
ping and filtering, partial transmit sequence
(PTS) and selected mapping (SLM). Simulation result
s show that clipping and filtering provides a bette
r
PAPR reduction than the others methods and only SLM
technique conserve the PAPR reduction in
reception part of signal.
Performance Analysis of MIMO-OFDM System Using QOSTBC Code Structure for M-PSKCSCJournals
MIMO-OFDM system has been currently recognized as one of the most competitive technology for 4G mobile wireless systems. MIMO-OFDM system can compensate for the lacks of MIMO systems and give play to the advantages of OFDM system. In this paper, a general Quasi orthogonal space time block code (QOSTBC) structure is proposed for multiple-input multiple-output–orthogonal frequency-division multiplexing (MIMO-OFDM) systems for 4X4 antenna configuration. The signal detection technology used in this paper for MIMO-OFDM system is Zero-Forcing Equalization (linear detection technique). In this paper the analysis of high level of modulations (i.e. M-PSK for different values of M) on MIMO-OFDM system is presented. Here AWGN and Rayleigh channels have been used for analysis purpose and their effect on BER for high data rates have been presented. The proposed MIMO-OFDM system with QOSTBC using 4X4 antenna configuration has better performance in terms of BER vs SNR than the other systems.
OFDM allows tightly packed carriers to convey information orthogonally and with high bandwidth efficiency
Objectives Description:
Concepts
Basic idea
Introduction to OFDM
Implementation
Advantages and Drawbacks.
FDMA
Comparative performance analysis of different modulation techniques for papr ...IJCNCJournal
One of the most important multi-carrier tran
smission techniques used in the latest wireless com
munication
arena is known as Orthogonal Frequency Division Mul
tiplexing (OFDM). It has several characteristics
such as providing greater immunity to multipath fad
ing & impulse noise, eliminating Inter Symbol
Interference (ISI) & Inter Carrier Interference (IC
I) using a guard interval known as Cyclic Prefix (C
P). A
regular difficulty of OFDM signal is high peak to a
verage power ratio (PAPR) which is defined as the r
atio
of the peak power to the average power of OFDM Sign
al. An improved design of amplitude clipping &
filtering technique of us previously reduced signif
icant amount of PAPR with slightly increase bit err
or rate
(BER) compare to an existing method in case of Quad
rature Phase Shift Keying (QPSK) & Quadrature
Amplitude Modulation (QAM). This paper investigates
a comparative performance analysis of the differen
t
higher order modulation techniques on that design.
Performance Analysis of Massive MIMO Downlink System with Imperfect Channel S...IJRES Journal
We investigate the ergodic sum rate and required transmit power of a single-cell massive
multiple-input multiple-output (MIMO) downlink system. The system considered in this paper is based on two
linear beamforming schemes, that is, maximum ratio transmission (MRT) beamforming and zero-forcing (ZF)
beamforming. What’s more, we use minimum mean square error (MMSE) channel estimation to get imperfect
channel state information (CSI). Compared with the perfect CSI case, both theoretical analysis and simulation
results show that the system performance is different when the imperfect CSI is taken into account.
OFDM: Modulation Technique for Wireless CommunicationAM Publications
Orthogonal Frequency Division Multiplexing (OFDM) has become the modulation technique for many wireless
communication standards. In a wireless system, a signal transmitted into channel bounces off from various surfaces resulting
in multiple delayed versions of the transmitted signal arriving at the receiver. The multiple signals are received due to the
reflections from large objects, diffraction of electromagnetic waves around objects .This causes the received signal to be
distorted. OFDM provides tolerance to such frequency selective channels and provides high data rates. In this paper we propose to analyze the theory of OFDM, simulate the OFDM transceiver using MATLAB and perform BER analysis.
Deterministic MIMO Channel Capacity
• CSI is Known to the Transmitter Side
• CSI is Not Available at the Transmitter Side
Channel Capacity of Random MIMO Channels
Spatial multiplexing ofdmoqam systems with time reversal techniqueijwmn
Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation (OFDM/OQAM) is a multicarrier modulation scheme that can be considered as an alternative to the conventional Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) for transmission over multipath fading channels. In this paper, we investigate the combination of the OFDM/OQAM with Multiple Input Multiple Output (MIMO) system with Time Reversal (TR) technique.
TR can be viewed as a precoding scheme which can be combined with OFDM/OQAM and easily carried out in a MIMO context using spatial data multiplexing.
We present the simulation results of the performance of OFDM/OQAM system in SISO case compared with the conventional CP-OFDM system and the performance of the combination MIMO-OFDM/OQAM with TR compared to MIMO-CP-OFDM. The performance is derived by computing the Bit Error Rate (BER) as a function of the transmit signal-to-noise ratio (SNR).
Performance and Analysis of OFDM Signal Using Matlab SimulinkIJMER
Multi-carrier modulation is an attractive technique for fourth generation .OFDM is based on
multicarrier modulation technique. In OFDM system the bit stream is divided into many different sub
channels. An efficient and distortionless scheme for peak power reduction in OFDM is proposed. In this
paper, a set of mapping where the actual transmit signal is selected. From this set of signal reduced
PAPR. Simulation results are shown. The lowest PAPR is compared with conventional work. It is also
compared BER to SNR and best result is achieved.
Hybrid approach to solve the problem of papr in ofdm signal a surveyeSAT Journals
“Orthogonal frequency division multiplexing
method used to achieve the today’s need of wireless communication
3GPP Association for the use of LTE. The
higher data rate, higher bit rate, mitigated delay spread, lower multipath distortion,
OFDM system has few major issues associated with
ratio (PAPR)” associated with the signal.
interleaved OFDM, selective mapping (SLM)
windowing, clipping, filtering, tone rejection(TR), tone injection(TI), compandin
MIMO radar is introduced in presentation ,its advantage .future scope,research area.
MIMO radars represent a new generation of radars. In contrast to the traditional phased-array radar in which the transmit elements can transmit only the scaled versions of same signal, a MIMO radar allows the transmitters to transmit multiple signals. This waveform diversity offers enhanced flexibility in transmit beampattern synthesis which is an important area of MIMO radar signal processing
A Novel Solitude Conserving Location Monitoring Approach for Wireless Sensor ...IJERA Editor
Observing individual locations with a capable untrusted server impose secrecy threats to the monitored individuals. In this paper we propose “A Novel Solitude Conserving Location Monitoring approach for Wireless Sensor networks”. We design two approaches to study nondescript locations in-network approaches, namely quality-aware and resource-aware approaches, that aims to enable the system to give high end quality location monitoring services for end users, while conserving personal location privacy. Both approaches are worked based on k-anonymity solitude (i.e.,an object is indistinguishable among k objects), to enable highly trusted sensor nodes to provide the collective location data of monitored objects for our system. Each collective location is in a form of a observed area X along with the number of monitored objects reside in X. The resource-aware approach objective to optimize the computational and communication value, while quality-aware approach aims to increase the reliability of the collective location data by reducing their observing areas. We use spatial histogram methodology to estimates the distribution of observing objects based on the gathered collective location data. We evaluated these two approaches through simulated experiments. The simulation results shows that these approaches gives high quality location observing services for end users and assure the location secrecy of the monitored objects.
OFDM: Modulation Technique for Wireless CommunicationAM Publications
Orthogonal Frequency Division Multiplexing (OFDM) has become the modulation technique for many wireless
communication standards. In a wireless system, a signal transmitted into channel bounces off from various surfaces resulting
in multiple delayed versions of the transmitted signal arriving at the receiver. The multiple signals are received due to the
reflections from large objects, diffraction of electromagnetic waves around objects .This causes the received signal to be
distorted. OFDM provides tolerance to such frequency selective channels and provides high data rates. In this paper we propose to analyze the theory of OFDM, simulate the OFDM transceiver using MATLAB and perform BER analysis.
Deterministic MIMO Channel Capacity
• CSI is Known to the Transmitter Side
• CSI is Not Available at the Transmitter Side
Channel Capacity of Random MIMO Channels
Spatial multiplexing ofdmoqam systems with time reversal techniqueijwmn
Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation (OFDM/OQAM) is a multicarrier modulation scheme that can be considered as an alternative to the conventional Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) for transmission over multipath fading channels. In this paper, we investigate the combination of the OFDM/OQAM with Multiple Input Multiple Output (MIMO) system with Time Reversal (TR) technique.
TR can be viewed as a precoding scheme which can be combined with OFDM/OQAM and easily carried out in a MIMO context using spatial data multiplexing.
We present the simulation results of the performance of OFDM/OQAM system in SISO case compared with the conventional CP-OFDM system and the performance of the combination MIMO-OFDM/OQAM with TR compared to MIMO-CP-OFDM. The performance is derived by computing the Bit Error Rate (BER) as a function of the transmit signal-to-noise ratio (SNR).
Performance and Analysis of OFDM Signal Using Matlab SimulinkIJMER
Multi-carrier modulation is an attractive technique for fourth generation .OFDM is based on
multicarrier modulation technique. In OFDM system the bit stream is divided into many different sub
channels. An efficient and distortionless scheme for peak power reduction in OFDM is proposed. In this
paper, a set of mapping where the actual transmit signal is selected. From this set of signal reduced
PAPR. Simulation results are shown. The lowest PAPR is compared with conventional work. It is also
compared BER to SNR and best result is achieved.
Hybrid approach to solve the problem of papr in ofdm signal a surveyeSAT Journals
“Orthogonal frequency division multiplexing
method used to achieve the today’s need of wireless communication
3GPP Association for the use of LTE. The
higher data rate, higher bit rate, mitigated delay spread, lower multipath distortion,
OFDM system has few major issues associated with
ratio (PAPR)” associated with the signal.
interleaved OFDM, selective mapping (SLM)
windowing, clipping, filtering, tone rejection(TR), tone injection(TI), compandin
MIMO radar is introduced in presentation ,its advantage .future scope,research area.
MIMO radars represent a new generation of radars. In contrast to the traditional phased-array radar in which the transmit elements can transmit only the scaled versions of same signal, a MIMO radar allows the transmitters to transmit multiple signals. This waveform diversity offers enhanced flexibility in transmit beampattern synthesis which is an important area of MIMO radar signal processing
A Novel Solitude Conserving Location Monitoring Approach for Wireless Sensor ...IJERA Editor
Observing individual locations with a capable untrusted server impose secrecy threats to the monitored individuals. In this paper we propose “A Novel Solitude Conserving Location Monitoring approach for Wireless Sensor networks”. We design two approaches to study nondescript locations in-network approaches, namely quality-aware and resource-aware approaches, that aims to enable the system to give high end quality location monitoring services for end users, while conserving personal location privacy. Both approaches are worked based on k-anonymity solitude (i.e.,an object is indistinguishable among k objects), to enable highly trusted sensor nodes to provide the collective location data of monitored objects for our system. Each collective location is in a form of a observed area X along with the number of monitored objects reside in X. The resource-aware approach objective to optimize the computational and communication value, while quality-aware approach aims to increase the reliability of the collective location data by reducing their observing areas. We use spatial histogram methodology to estimates the distribution of observing objects based on the gathered collective location data. We evaluated these two approaches through simulated experiments. The simulation results shows that these approaches gives high quality location observing services for end users and assure the location secrecy of the monitored objects.
Simulation and Experimental Studies on Composite BeamsIJERA Editor
A composite beam a one dimensional structure or a rod all of them are sectional dimensions in which width and height are much smaller in comparison to the structure. In structural applications longer beams are more frequently used. In this work a composite beam is manufactured with glass and epoxy combination. And stress analysis is carried out using derived analytical expressions. This research work carried out will enable to determine the beam strength due to bending loads. The importance of fiber reinforcement in the manufacturing of the beam is studied in terms of bending strength of the beam. Mat lab codes are generated to implement analytical equations of the composite beam. The analytical results are validated by performing experiments on composite beams. In this investigation, two different composite beams have been tested and compared the experimental results with the analytical results.
Extensive Reviews of OSPF and EIGRP Routing Protocols based on Route Summariz...IJERA Editor
The increasing demand of computer networks is growing rapidly day by day. The growing need to distribute applications across multiple networks with high capacity and high-performance intermediate switching nodes and networks. This research primarily focuses on route redistribution and route summarization of different intra-domain routing protocols such as EIGRP and OSPF. Routing Protocols that use facilitate to exchange routing information between routers. Reasons such as multiple departments managed by multiple network Administrators, company mergers. In any case, having a multiple routing protocol and different autonomous system in networks then without route redistribution we cannot advertise route from source to destination. Of course Network complexity will increase with the size of routing table of routers then route summarization is necessity, to reduce traffic and complexity of network.
MHD convection flow of viscous incompressible fluid over a stretched vertical...IJERA Editor
The effect of thermal radiation, viscous dissipation and hall current of the MHD convection flow of the viscous incompressible fluid over a stretched vertical flat plate has been discussed by using regular perturbation and homotophy perturbation technique with similarity solutions. The influence of various physical parameters on velocity, cross flow velocity and temperature of fluid has been obtained numerically and through graphs.
Power Quality Improvement at Distribution Level for Grid Connected Renewable ...IJERA Editor
The non-linear load current harmonics may result in voltage harmonics and can create a serious PQ problem in
the power system network. Active power filters (APF) are extensively used to compensate the load current
harmonics and load unbalance at distribution level. This results in an additional hardware cost. However, in this
project it has incorporated the features of APF in the conventional inverter interfacing renewable with the grid,
without any additional hardware cost. Here, the main idea is the maximum utilization of inverter rating which is
most of the time underutilized due to intermittent nature of RES. The grid-interfacing inverter can effectively be
utilized to perform the four important functions they are to transfer active power harvested from the renewable
resources (wind, solar, etc.), load reactive power demand support, current harmonics compensation at PCC and
current unbalance and neutral current compensation in case of 3-phase 4-wire system. Moreover, with adequate
control of grid-interfacing inverter, all the four objectives can be accomplished either individually or
simultaneously. The PQ constraints at the PCC can therefore be strictly maintained within the utility standards
without additional hardware cost.
With such a control, the combination of grid-interfacing inverter and the 3-phase 4-wire linear/non-linear
unbalanced load at point of common coupling appears as balanced linear load to the grid. This new control
concept is demonstrated with extensive MATLAB/Simulink simulation studies
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
Performance evaluation on the basis of bit error rate for different order of ...ijmnct
Today, we have required to accommodate a large number of users under a single base station. This can be
possible only if we have some flexibility over the spectrum. Previously we have lots of multiplexing methods
to accommodate large number of signals in time and frequency domain. But now we have required to
accommodate a large number of users in the same bandwidth, without any fading over the received signal.
So, orthogonality can be maintained over the frequency response. This technology is now more popular in
the mobile communication domain, called Orthogonal Frequency Division Multiplexing (OFDM). Actually
user data can be converted into the parallel form and then they are modulated using digital modulation
techniques. Finally, they have followed by OFDM Modulator and cyclic prefix can be inserted into the
OFDM symbols. Here, I have worked on the measurement of Bit error rate for different modulation
techniques in OFDM technology. It has been considered that subchannel size is not constant. According to
that I have concluded the overall idea regarding the performance under OFDM technology.
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).
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
HYBRID LS-LMMSE CHANNEL ESTIMATION Technique for LTE Downlink Systemsijngnjournal
In this paper, we propose to improve the performance of the channel estimation for LTE Downlink systems under the effect of the channel length. As LTE Downlink system is a MIMO-OFDMA based system, a cyclic prefix (CP) is inserted at the beginning of each transmitted OFDM symbol in order to mitigate both intercarrier interference (ICI) and inter-symbol interference (ISI). The inserted CP is usually equal to or longer than the channel length. However, the cyclic prefix can be shorter because of some unforeseen channel behaviour. Previous works have shown that in the case where the cyclic prefix is equal to or longer than the channel length, LMMSE performs better than LSE but at the cost of computational complexity .In the other case, LMMSE performs also better than LS only for low SNR values. However, LS shows better performance for LTE Downlink systems for high SNR values. Therefore, we propose a hybrid LS-LMMSE channel estimation technique robust to the channel length effect. MATLAB Monte –Carlo simulations areused to evaluate the performance of the proposed estimator in terms of Mean Square Error (MSE) and Bit Error Rate (BER) for 2x2 LTE Downlink systems.
Performance comparison of two clipping based filtering methods for papr reduc...ijmnct
The growth of wireless communication technologies has been producing the intense demand for high-speed,
efficient, reliable voice & data communication. As a result, third generation partnership project (3GPP)
has implemented next generation wireless communication technology long term evolution (LTE) which is
designed to increase the capacity and speed of existing mobile telephone & data networks. LTE has
adopted a multicarrier transmission technique known as orthogonal frequency division multiplexing
(OFDM). OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for
very wide carriers. One major generic problem of OFDM technique is high peak to average power ratio
(PAPR) which is defined as the ratio of the peak power to the average power of the OFDM signal. A
trade-off is necessary for reducing PAPR with increasing bit error rate (BER), computational complexity or
data rate loss etc. In this paper, two clipping based filtering methods have been implemented & also
analyzed their modulation effects on reducing PAPR.
The International Journal of Engineering and Science (The IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
Ofdm-cpm Ber Performance and FOBP Under IEEE802.16 ScenarioCSCJournals
The application of Orthogonal frequency domain modulation-Continuous Phase Modulation (OFDM-CPM) in multipath Stanford University Interim (SUI) channels is presented in this paper. OFDM-CPM is proposed for IEEE 802.16 standards as an alternative technique of orthogonal frequency division multiplexing (OFDM) in physical layer. It is shown that, in addition to 0dB Peak to Average Power Ratio (PAPR) and power efficiency, un-coded OFDM-CPM exploits the frequency diversity of multipath channel. Taking into account the Input Power Back off (IBO), OFDM-CPM is shown to outperform OFDM at high bit energy-to-noise density ratios (Eb/N0). However, at low Signal to Noise Ratio (SNR), the OFDM-CPM phase demodulator receiver suffers from a threshold effect. In addition, this paper compares the spectral fractional out of band power of OFDM-CPM for different modulation indices.
A Hybrid PAPR Reduction Scheme for OFDM System ijmnct
Orthogonal frequency division multiplexing (OFDM) i
s considered as most efficient technique for future
wireless communication systems due to its higher sp
ectral bandwidth efficiency, robustness to frequenc
y
selective fading channels, etc. However, the succes
sful implementation of the OFDM system necessitates
several difficulties. The biggest disadvantage to w
ork with OFDM system is its high peak-to-average po
wer
ratio PAPR leadsto severe inter carrier interferenc
e, out-of-band radiation, and poor bit error rate
performance due to the nonlinearity of the high pow
er amplifier. In this paper, a novel hybrid techniq
ue is
proposed to reduce PAPR further and comparison has
been done with conventional techniques as well.
Simulated results are presentedconfirm theoretical
results.MATLAB 7.5 is used to simulate the results
for system parametersconsidered.
BER Performance of OFDM-QAM over AWGN and RICAIN Channels Using Error Correct...IJERA Editor
In this paper, the performance of OFDM - QAM system by using error correcting codes (Convolutional, Reed Solomon and Interleaving) schemes that are used to encode the data stream in wireless communications using AWGN and RICIAN channels has been reported here. OFDM is presented for wireless communications we curing basic OFDM and affined modulations, as well as techniques to improve the performance of OFDM for wireless communications. Various simulations are performed to detect the best BER performance of each of the QAM system; OFDM-QAM and OFDM-QAM with Error Correction and to use the best outcomes to model the OFDM-QAM, Their effect of improving the total BER can be noticed due to the benefits of OFDM-QAM with correcting codes.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Reduction of Outage Probability in Fast Rayleigh Fading MIMO Channels Using OFDM
1. Robert O. Abolade Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 9( Version 5), September 2014, pp.06-12
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Reduction of Outage Probability in Fast Rayleigh Fading MIMO Channels Using OFDM
Robert O. Abolade*, Olumide O. Ajayi**
(Department of Electronic and Electrical Engineering, Ladoke Akintola University of Technology, PMB 4000, Ogbomoso, Nigeria. ABSTRACT Multiple-input multiple-output (MIMO) techniques are used in wireless communications for achieving high spectral efficiency; however, a fast fading spatial channel can increase the outage probability of a MIMO system if not taken care of. This paper investigates the use of orthogonal frequency division multiplexing (OFDM) modulation technique for a MIMO system operating in fast Rayleigh fading channels with the aim of eliminating outage probabilities in the MIMO systems. Simulation results show that the MIMO-OFDM system gives significant reduction in outage probabilities compared to the conventional MIMO system.
Keywords- Fast fading, outage probability, MIMO, OFDM, SNR, transmission rate, channel capacity
I. Introduction
The rising demands for mobile wireless systems that are capable of providing very high data rates for multimedia applications with seamless quality of service (QoS) delivery have lead to the development of more robust technologies such as the multiple- input multiple-output (MIMO) communication systems. MIMO technology has been in existence for over a decade [1], [2]. A MIMO communication system exploits spatial diversity by utilizing multiple antennas at the transmitting and receiving ends of the system, which considerably increase the link capacity and reliability compared to the single-input single- output (SISO) communication systems [3]. The advancement in very large scale integration (VLSI) technology has made the implementation of MIMO antenna configuration possible in mobile devices, and MIMO has found applications in a number of standards such as UMTS, WLAN and WiMAX [4]. However, in highly-mobile scenarios, the MIMO channels experience rapid variations [5]; a phenomenon referred to as fast fading that could increase the probability of signal outages and results in performance degradation of the MIMO system. A mobile wireless channel exhibits fast fading if the channel symbol period is greater than the coherence time of the channel or if the Doppler spread increases relative to the bandwidth of the transmitted signal [6], [7]; this can lead to outage of the signal or a complete loss of the signal. Outage probability is the probability that the received SNR falls below a specified threshold value [8]. In a MIMO system, it is the probability that the average capacity of the system is below a specified rate. In other words, a system outage occurs when the
instantaneous error probability cannot be made arbitrarily small with the information rate [9]. In wireless system designs, the typical outage probability target is 5% [8]. Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technique capable of mitigating ISI, and has been shown to be very effective for high-rate data transfer through dispersive channels [10], [11]. OFDM breaks a high- rate single carrier into parallel low-rate subcarriers [12], [13]. The subcarriers are given the minimum frequency separation required to maintain orthogonality between them in order to prevent intercarrier interference (ICI) [13]. OFDM modulation has found application in a number of digital wireless communication systems such as DAB, DVB and 3GPP LTE [14], [15]. A conventional MIMO system operating in a fast fading environment would require complex channel equalizers to be able to mitigate deep fades that may cause system outages; and the complexity of the required equalizers increases with the number of antennas of the MIMO system. Intensive researches are on going on the enhancement of MIMO systems as well as the suitability of MIMO-OFDM for providing very high QoS of broadband wireless communications [5], [16], [4], [12]; however, most of these investigations are based on bit error rate (BER) and spectral efficiency evaluations of the MIMO- OFDM. This work therefore shows how OFDM could be used to reduce outage probabilities of the MIMO system in fast fading environments.
RESEARCH ARTICLE OPEN ACCESS
2. Robert O. Abolade Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 9( Version 5), September 2014, pp.06-12
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II. MIMO-OFDM System Model
The MIMO scheme considered in this study is
the spatial multiplexing which offers very high
spectral efficiency. A MIMO-OFDM system model
of 2x2 ( R N x T N ) antenna configuration is shown in
Fig. 1. The system consists of T N transmit and R N
receive antennas, and assuming no channel state
information at the transmitter (CSIT). The
information bits to be transmitted are first
demultiplexed into T N data streams; each bit stream
is then mapped onto M-QAM constellation where M
is the constellation size. The serial M-QAM stream at
each transmitter branch is
Fig. 1: 2x2 MIMO-OFDM System Model
converted into K parallel streams and IFFT is applied
to form time-domain signals. The parallel time-domain
signals are converted back into a serial signal
and a cyclic prefix (CP) is appended to form the
OFDM signal. After filtering, each transmitter sends
an OFDM signal over a fast Rayleigh fading MIMO
channel; this implies non line of sight (NLoS)
between the transmitter and the receiver. At the
receiving end, the process is reversed to recover the
information bits. The length of the CP is assumed to
be longer than the channel delay spread to mitigate
the fading effect. After the FFT demodulation, the
received OFDM signal of the k-th subcarrier at the i-th
receive antenna can be expressed as:
NT
j
k
i
k
j
k
i j
k
i y t H t s t z t
1
, ( ) ( ) ( ) ( ) ,
R i 1,2,..., N
(1)
where ( ) , H t k
i j is the channel coefficient between the
j-th transmitter and the i-th receiver, s (t) k
j is the
transmitted data symbol on k-th subcarrier, z (t) k
i is
the additive white Gaussian noise (AWGN) at i-th
receive antenna and t is the time instant. The MIMO
channel matrix corresponding to the k-th subcarrier
of an OFDM symbol is given by:
( ) ( ) ( )
( ) ( ) ( )
( ) ( ) ( )
ˆ ( )
,1 ,2 ,
2,1 2,2 2,
1,1 1,2 1,
H t H t H t
H t H t H t
H t H t H t
H t
k
N N
k
N
k
N
k
N
k k
k
N
k k
k
R R R T
T
T
(2)
The MIMO-OFDM channel coefficient is given as:
1
2 / ( ) ( )
L
l
j f tk T
l
H k t h t e m
,
k 0,1,...,K 1
(3)
where h (t) l is the Rayleigh fading coefficient for the
l -th path modelled as an independent zero mean
random Gaussian process, L is the number of
resolvable multipath components, T is the OFDM
symbol period, m f is the maximum Doppler
frequency shift caused by the relative motion
between the transmitter and the receiver. m f is a
function of the speed of the mobile station and the
carrier frequency [7].
Demultiplexer
M-QAM
Mapper
M-QAM
Mapper
Serial to Parellel
IFFT
S[0]
S[1]
S[K-1]
Serial to Parellel
IFFT
S[0]
S[1]
S[K-1]
Parellel to Serial
& Append CP
Fast
Rayleigh
fading
MIMO
channel
Remove CP &
Serial to Parellel
Remove CP &
Serial to Parellel
FFT
FFT
One-tap frequency
domain Equalizer
One-tap frequency
domain Equalizer
Parellel to Serial
& Append CP
Parellel to Serial Parellel to Serial
M-QAM
Demapper
Data detection
M-QAM
Demapper Transmit
data
Receive
data
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III. Outage Probabilities
3.1 Outage Probability in terms of Instantaneous
SNR
Outage probability is the probability that the received
SNR falls below a specified threshold value and can
be expressed as:
( ) Pr( ) out t t P (5)
where is the received or instantaneous SNR and
t is the specified SNR threshold which is the
minimum required received SNR. Outage probability
requires the knowledge of the probability density
function (pdf) of the received SNR ( ), which is
given by:
t
P p d out
0
( ) (6)
where ( ) p is the pdf of . Assuming a Rayleigh
distribution, equation (6) can be approximated as:
exp
1
0
t
out P (7)
where is the average SNR. An outage occurs in a
MIMO system when every branch is in outage;
hence, the MIMO system outage probability is the
product of the outage probabilities of all the branches
which can be expressed as:
Ns t
i i
i
i
out P
1 0
exp
1
(8)
where i and i are the received SNR and average
SNR of the i-th branch, respectively,
and min( , ) s R T N N N .
3.2 Outage Probability in terms of Instantaneous
Capacity
A MIMO system could also be said to be in outage if
the instantaneous capacity or spectral efficiency is
less than the required transmission rate; and can be
expressed as:
P R C H R out ( ) Pr ( ) (9)
where C(H) is the instantaneous capacity of the
MIMO channel and R is the required transmission
rate in bit/sec/Hertz or bps/Hz. R is related to the
spatial multiplexing gain as:
0 R mlog (10)
where m is the spatial multiplexing gain and 0 is
the transmitted SNR.
The instantaneous capacity of the k-th subcarrier
of the OFDM over the MIMO channel,
assuming R T N N , can be expressed as:
0
( ) ( )*
2
( ) log det ˆ ˆ k k
k N C H I H H
R
(11)
where * denotes the complex conjugate transpose and
NR I is R R N N identity matrix. Thus, the total
capacity of the MIMO-OFDM system is the sum of
the instantaneous capacity of all the subcarriers,
which is given by:
1
0
( ) ( )
K
k
k C H C H (12)
The flow chart for calculating an outage probability
in a received signal is shown in Fig. 2.
Start
Set parameters; count = 0,
threshold t or R
Get received signal sample
Is
?
t
C(H) R
count = count + 1
Is
Total no. of
samples reached
?
Calculate or C(H)
Pout = count / Total no. of samples
Output the Outage
probability Pout
Stop
NO
YES
NO
YES
Fig. 2 Flow chart for calculating outage probability
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ISSN : 2248-9622, Vol. 4, Issue 9( Version 5), September 2014, pp.06-12
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IV. Results and Discussion
The outage probability performance of the
MIMO-OFDM system was analyzed through
computer simulations in terms of both instantaneous
SNR and capacity for 2x2, 3x3 and 4x4 antenna
configurations. The information bits are modulated
using 16-QAM and subsequently mapped to 256
subcarriers of a 256-point FFT OFDM based on
IEEE802.16e standard. The CP is taken as ¼ of the
OFDM symbol length. The mobile speed was set to
be 120 km/h and a carrier frequency of 2.5 GHz. The
Rayleigh fading channel model was used and all
simulations carried out in MATLAB software
environment. The performance of the MIMO-OFDM
is compared with the conventional MIMO in which
OFDM is not utilized.
The outage probability performances versus
transmitted SNR for the MIMO-OFDM and MIMO
with 2x2 antenna configuration when the SNR
threshold ( t ) is set to 5dB is presented in Fig. 3. At
transmitted SNR of 10 dB, the outage probability of
the MIMO-OFDM and MIMO are 0.1064 and 0.1815
respectively; this shows that the MIMO-OFDM has
41.38% reduced outage probability compared to
MIMO. For all values of the transmitted SNR, the
MIMO-OFDM gives lower outages compared to
MIMO. Fig. 4 shows the effect of antenna
configuration on the outage probability performance
of the MIMO-OFDM system when t is set to 5 dB.
Also, at transmitted SNR of 10 dB, the 2x3, 3x3 and
4x4 MIMO-OFDM configurations give 0.1064,
0.0722 and 0.0501 respectively. This result reveals
that the system outage reduces by an average of 31%
with increasing number of antennas.
-5 0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR [dB]
Outage probability Pr( <
t
)
MIMO
MIMO-OFDM
Fig. 3: Outage probability in terms of instantaneous
SNR for 2x2 antenna configuration
-5 0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR [dB]
Outage probability Pr( <
t
)
2x2 MIMO-OFDM
3x3 MIMO-OFDM
4x4 MIMO-OFDM
Fig. 4: Outage probability in term of instantaneous
SNR for different antenna configurations
The outage probability performance in terms of
instantaneous capacity was also investigated for
comparison between MIMO-OFDM and MIMO. The
threshold transmission rate (R) is varied from 0 to 12
bps/Hz, and the transmitted SNR at 12 dB. Fig. 5
shows the outage probabilities of both MIMO-OFDM
and MIMO in terms of instantaneous capacity for 2x2
antenna configuration; taking R of 6 bps/Hz, the
outage probability for MIMO-OFDM and MIMO are
0.4468 and 0.5826 respectively. This reveals that
MIMO-OFDM gives 0.1358 lower outages compared
to MIMO. Also from the result, the largest possible R
such that the outage probability is less than 0.1 (or
10%) for MIMO-OFDM is 3.4 bps/Hz while for
MIMO is 2.6 bps/Hz. This reveals that MIMO-OFDM
gives higher transmission rate than MIMO for
the same transmitted SNR. The MIMO-OFDM
system is able to achieve this because in a fast fading
environment, some of the subcarriers in a
transmission branch may experience deep fading and
thus low instantaneous capacities but the other
subcarriers may not be in deep fade and thus
experience high instantaneous capacity; thereby
giving a high total instantaneous capacity. However,
for the conventional MIMO, with a single carrier, an
entire transmission branch could experience deep
fade which results in lower total instantaneous
capacity for the system.
Fig. 6 shows the outage probabilities of both
MIMO-OFDM and MIMO in terms of instantaneous
capacity for 3x3 antenna configuration; taking R of 6
bps/Hz, the outage probability for MIMO-OFDM and
MIMO are 0.296 and 0.3966 respectively. This
reveals that MIMO-OFDM gives 0.1006 lower
outages compared to MIMO. Also, the largest
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possible R such that the outage probability is less
than 0.1 (or 10%) for MIMO-OFDM is 4.2 bps/Hz
while for MIMO is 3.2 bps/Hz. This also reveals that
MIMO-OFDM gives higher transmission rate than
MIMO for the same transmitted SNR. For the 4x4
antenna configuration, the outage probabilities of
both MIMO-OFDM and MIMO in terms of
instantaneous capacity are presented in Fig. 7. From
the results, taking R of 6 bps/Hz, the outage
probability for MIMO-OFDM and MIMO are 0.2088
and 0.3284 respectively. This reveals that MIMO-OFDM
gives 0.1196 lower outages compared to
MIMO. The largest possible R such that the outage
probability is less than 0.1 (or 10%) for MIMO-OFDM
is 5.0 bps/Hz while for MIMO is 3.8 bps/Hz.
This also reveals that MIMO-OFDM gives higher
transmission rate than MIMO for the same
transmitted SNR.
The effect of antenna configuration on the outage
probability performance of the MIMO-OFDM system
in terms of instantaneous capacity is presented in Fig.
8. At transmitted SNR of 12 dB and R of 6 bps/Hz,
the 2x3, 3x3 and 4x4 MIMO-OFDM configurations
give 0.4468, 0.296 and 0.2088 respectively. This
result reveals that the system outage reduces by an
average of 32% with increasing number of antennas.
This also confirms the outage probability result
obtained in terms of instantaneous SNR. The results
show that outage probability in terms of
instantaneous capacity increases with increasing
transmission rate.
0 2 4 6 8 10 12
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Threshold Rate[bps/Hz]
Outage Probability Pr[C(H)<R]
MIMO
MIMO-OFDM
Fig. 5: Outage probability in terms of instantaneous
capacity for 2x2 antenna configuration
0 2 4 6 8 10 12
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Threshold Rate[bps/Hz]
Outage Probability Pr[C(H)<R]
MIMO
MIMO-OFDM
Fig. 6: Outage probability in terms of instantaneous
capacity for 3x3 antenna configuration
0 2 4 6 8 10 12
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Threshold Rate[bps/Hz]
Outage Probability Pr[C(H)<R]
MIMO
MIMO-OFDM
Fig. 7: Outage probability in terms of instantaneous
capacity for 4x4 antenna configuration
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0 2 4 6 8 10 12
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Threshold Rate[bps/Hz]
Outage Probability Pr[C(H)<R]
2x2 MIMO-OFDM
3x3 MIMO-OFDM
4x4 MIMO-OFDM
Fig. 8: Outage probability in terms of instantaneous
capacity for different antenna configurations
V. CONCLUSION
In this paper, the performance of OFDM for the
reduction of outage probability in a MIMO system
has been investigated. The outage probability was
evaluated in terms of instantaneous SNR and
instantaneous capacity. The simulation results
obtained showed that the MIMO-OFDM system
gives relatively lower outage probabilities compared
to the conventional MIMO for all target SNRs and
transmission rates.
The combination of OFDM and the MIMO
system could help to eliminate the use of complex
equalizers; this is because OFDM is capable of
converting a fast fading channel into slow fading
subchannels that can be easily handled by simple
channel equalization. This also implies that the
MIMO system may not require perfect CSIT. This
paper has been able to show that OFDM could help
to reduce the probability of signal outage in a MIMO
system.
In this study, coding and interleaving were not
utilized for the system so further investigations could
consider incorporating coding and interleaving into
the system with a view to improving the outage
probability performance of the system. The use of
adaptive modulation and power allocation in the
system could also be investigated for very highly
mobile scenarios of up to 300 km/h. The results of
this paper can serve as a useful reference for
researchers and designers of MIMO-OFDM system.
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