IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Multi carrier equalization by restoration of redundanc y (merry) for adaptive...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The
performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed
DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated
and less complexity also involved by the simulation of the DST-DMT system.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Wireless communication is one of the most effective areas of technology development of our time.
Wireless communications today covers a very wide array of applications. In this paper, we study the
performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator
(LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh
fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms
others. Result shows that for higher modulation schemes SER performance degrades as well as SER
performance increases for higher no of receiver antennas
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.
IMPROVEMENT OF LTE DOWNLINK SYSTEM PERFORMANCES USING THE LAGRANGE POLYNOMIAL...IJCNCJournal
To achieve a high speed data rate, higher spectral efficiency, improved services and low latency the 3rd
generation partnership project designed LTE standard (Long Term Evolution).the LTE system employs
specific technical as well the technical HARQ, MIMO transmission, OFDM Access or estimation technical.
In this paper we focus our study on downlink LTE channel estimation and specially the interpolation which
is the basis of the estimation of the channel coefficients. Thus, we propose an adaptive method for polynomial interpolation based on Lagrange polynomial. We perform the Downlink LTE system MIMO transmission then compare the obtained results with linear, Sinus Cardinal and polynomial Newton Interpolations. The simulation results show that the Lagrange method outperforms system performance in term of Block Error Rate (BLER) , throughput and EVN(%)vs. Signal to Noise Ratio (SNR).
Multi carrier equalization by restoration of redundanc y (merry) for adaptive...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The
performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed
DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated
and less complexity also involved by the simulation of the DST-DMT system.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Wireless communication is one of the most effective areas of technology development of our time.
Wireless communications today covers a very wide array of applications. In this paper, we study the
performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator
(LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh
fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms
others. Result shows that for higher modulation schemes SER performance degrades as well as SER
performance increases for higher no of receiver antennas
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.
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).
This paper aims, a 3D-Pilot Aided Multi-Input Multi-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) Channel Estimation (CE) for Digital Video Broadcasting -T2 (DVB-T2) for the 5 different proposed block and comb pilot patterns model and performed on different antenna configuration. The effects of multi-transceiver antenna on channel estimation are addressed with different pilot position in frequency, time and the vertical direction of spatial domain framing. This paper first focus on designing of 5-different proposed spatial correlated pilot pattern model with optimization of pilot overhead. Then it demonstrates the performance comparison of Least Square (LS) & Linear Minimum Mean Square Error (LMMSE), two linear channel estimators for 3D-Pilot Aided patterns on different antenna configurations in terms of Bit Error Rate. The simulation results are shown for Rayleigh fading noise channel environments. Also, 3x4 MIMO configuration is recommended as the most suitable configuration in this noise channel environments.
Wireless communication now has been focus to increase data rate and high performance. The
multi carrier on multi-hop communication system using relay's diversity technique which is
supported by a reliable coding is a system that may give high performance.
This research is developing a model of multi carrier CDMA on multi hop communication
system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By
Alamouti research, Space Time Block Code (STBC) for MIMO system can perform high quality
signal at the receiver in the Rayleigh fading channel and the noisy system. In this research,
MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC) with multi
carrier CDMA on multi hop wireless communication system (relay diversity) which is able to
reduce the complexity of the system but the system performance even can be maintained and
improved.
MC CDMA on multi hop wireless communication system with 2 hops is performing much better
than Single Input Single Output (SISO) system (1 hop system). Power needed for 1 hop system to
have the same quality as 2 hops system to reach BER 10-3 is 12 dB. And multi hop system needs
orthogonal symbol to send from relay than original symbol to reach better performance. 12.5
dB power up is needed for multi hop system which sent same symbol as transmitter than relay
system which sent orthogonal symbol.
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.
Intersymbol interference caused by multipath in band limited frequency selective time dispersive channels distorts the transmitted signal, causing bit error at receiver. ISI is the major obstacle to high speed data transmission over wireless channels. Channel estimation is a technique used to combat the intersymbol interference. The objective of this paper is to improve channel estimation accuracy in MIMO-OFDM system by using modified variable step size leaky Least Mean Square (MVSSLLMS) algorithm proposed for MIMO OFDM System. So we are going to analyze Bit Error Rate for different signal to noise ratio, also compare the proposed scheme with standard LMS channel estimation method.
On limits of Wireless Communications in a Fading Environment: a General Param...ijeei-iaes
The reliable services along with high throughput can be achieved by using wireless communication systems. These systems also provides a wide coverage because of their features, no doubt MIMO Communication System [1] is one among them. Features provided by these systems ensure the improved system coverage and increased data transmission rate by considering multiple numbers of transmitter and receiver antennas. In this article, the concept of equalization has been considered and finally the performance of the MIMO Systems in Rician flat fading [5] channel is compared with the Rayleigh flat fading channel. It has also been observed that the performance of these Systems in Rician Flat Fading Channel is the best as compare to the Rayleigh Flat Fading Channel [10]. It has been concluded that the successive interference methods provide better performance as compare to others, but their complexity is high. Simulation results shows that ML provides the better performance in comparison to other equalizers but Sphere decoder provides the best performance.
SECURED TEXT MESSAGE TRANSMISSION IN PRE -CHANNEL EQUALIZATION BASED MIMO- OF...IJNSA Journal
In this paper, we made a comprehensive performance evaluative study of a secured MIMO Orthogonal Frequency-Division Multiplexing wireless communication system with implementation of two pre channel equalization techniques such as Pre-Minimum Mean Square Error (Pre-MMSE) and Pre-Zero
Forcing(Pre-ZF) under QPSK and QAM digital modulations. The simulated system deploys three channel coding techniques(1/2-rated Convolutional, CRC and BCH). In the present simulated system, text message transmission has been secured with concatenated implementation of Electronic Codebook (ECB)
and Cipher Feedback(CFB) cryptographic algorithm. It is remarked from simulation results that the MIMO OFDM system outperforms with pre-ZF channel equalization,QAM digital modulation and BCH channel coding schemes under fading channels(AWGN and Raleigh).In Pre-MMSE/pre-ZF channel
equalization scheme, the system shows comparatively worst performance in convolutional channel coding scheme with QAM/QPSK digital modulation. With increase in noise power as compared to signal power, the system is found to have shown performance deterioration
Combining SFBC_OFDM Systems with SVD Assisted Multiuser Transmitter and Multi...IOSR Journals
Abstract: In this work, we exploit the SVD assisted multiuser transmitter (MUT) and multiuser detector (MUD) technique, using downlink (DL) preprocessing transmitter and DL postprocessing receiver matrice .In combination with space frequency block coding (SFBC). And also propose the precoded DL transmission scheme, were the both proposed schemes take advantage of the channel state information (CSI) of all users at the base station (BS), but only of the mobile station (MS)’s own CSI, to decompose the MU MIMO channels into parallel single input single output (SISO), these two proposed schemes are compared to the vertical layered space time (V_BLAST) combined with SFBC (SFBC_VBLAST). Our Simulation results show that the performance of the proposed scheme with DL Zero Forcing (ZF) transmitter for interference canceller outperforms the SFBC_VBLAST and the precoded DL schemes with ZF receiver in frequency selective fading channels. Keywords – Post processing, Preprocessing,, SFBC, SVD, ZF.
Analysis of cyclic prefix length effect on ISI limitation in OFDM system over...IJECEIAES
In this work, the influence of the cyclic prefix on the performance of the OFDM system is studied. We worked out an OFDM transceiver using a 16 QAM modulation scheme, a comparison of the BER for various lengths of the cyclic prefix has been achieved, and the influence of the noise introduced in the channel has been highlighted, for both a Gaussian and Rayleigh noise. The simulation was carried out on MATLAB where the curves of the BER for various lengths of the cyclic prefix are given and compared. We also adopted as a metric the QAM constellation to show the dispersion of the carriers as a consequence of the transmission channel, the mitigation of this effect by the CP is noticeable.
A software framework for dynamic modeling of dc motors at robot jointseSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Synthesis of methyl, benzyl and pseudo halogeno co (iii) complexes of a dioxi...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This paper aims, a 3D-Pilot Aided Multi-Input Multi-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) Channel Estimation (CE) for Digital Video Broadcasting -T2 (DVB-T2) for the 5 different proposed block and comb pilot patterns model and performed on different antenna configuration. The effects of multi-transceiver antenna on channel estimation are addressed with different pilot position in frequency, time and the vertical direction of spatial domain framing. This paper first focus on designing of 5-different proposed spatial correlated pilot pattern model with optimization of pilot overhead. Then it demonstrates the performance comparison of Least Square (LS) & Linear Minimum Mean Square Error (LMMSE), two linear channel estimators for 3D-Pilot Aided patterns on different antenna configurations in terms of Bit Error Rate. The simulation results are shown for Rayleigh fading noise channel environments. Also, 3x4 MIMO configuration is recommended as the most suitable configuration in this noise channel environments.
Wireless communication now has been focus to increase data rate and high performance. The
multi carrier on multi-hop communication system using relay's diversity technique which is
supported by a reliable coding is a system that may give high performance.
This research is developing a model of multi carrier CDMA on multi hop communication
system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By
Alamouti research, Space Time Block Code (STBC) for MIMO system can perform high quality
signal at the receiver in the Rayleigh fading channel and the noisy system. In this research,
MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC) with multi
carrier CDMA on multi hop wireless communication system (relay diversity) which is able to
reduce the complexity of the system but the system performance even can be maintained and
improved.
MC CDMA on multi hop wireless communication system with 2 hops is performing much better
than Single Input Single Output (SISO) system (1 hop system). Power needed for 1 hop system to
have the same quality as 2 hops system to reach BER 10-3 is 12 dB. And multi hop system needs
orthogonal symbol to send from relay than original symbol to reach better performance. 12.5
dB power up is needed for multi hop system which sent same symbol as transmitter than relay
system which sent orthogonal symbol.
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.
Intersymbol interference caused by multipath in band limited frequency selective time dispersive channels distorts the transmitted signal, causing bit error at receiver. ISI is the major obstacle to high speed data transmission over wireless channels. Channel estimation is a technique used to combat the intersymbol interference. The objective of this paper is to improve channel estimation accuracy in MIMO-OFDM system by using modified variable step size leaky Least Mean Square (MVSSLLMS) algorithm proposed for MIMO OFDM System. So we are going to analyze Bit Error Rate for different signal to noise ratio, also compare the proposed scheme with standard LMS channel estimation method.
On limits of Wireless Communications in a Fading Environment: a General Param...ijeei-iaes
The reliable services along with high throughput can be achieved by using wireless communication systems. These systems also provides a wide coverage because of their features, no doubt MIMO Communication System [1] is one among them. Features provided by these systems ensure the improved system coverage and increased data transmission rate by considering multiple numbers of transmitter and receiver antennas. In this article, the concept of equalization has been considered and finally the performance of the MIMO Systems in Rician flat fading [5] channel is compared with the Rayleigh flat fading channel. It has also been observed that the performance of these Systems in Rician Flat Fading Channel is the best as compare to the Rayleigh Flat Fading Channel [10]. It has been concluded that the successive interference methods provide better performance as compare to others, but their complexity is high. Simulation results shows that ML provides the better performance in comparison to other equalizers but Sphere decoder provides the best performance.
SECURED TEXT MESSAGE TRANSMISSION IN PRE -CHANNEL EQUALIZATION BASED MIMO- OF...IJNSA Journal
In this paper, we made a comprehensive performance evaluative study of a secured MIMO Orthogonal Frequency-Division Multiplexing wireless communication system with implementation of two pre channel equalization techniques such as Pre-Minimum Mean Square Error (Pre-MMSE) and Pre-Zero
Forcing(Pre-ZF) under QPSK and QAM digital modulations. The simulated system deploys three channel coding techniques(1/2-rated Convolutional, CRC and BCH). In the present simulated system, text message transmission has been secured with concatenated implementation of Electronic Codebook (ECB)
and Cipher Feedback(CFB) cryptographic algorithm. It is remarked from simulation results that the MIMO OFDM system outperforms with pre-ZF channel equalization,QAM digital modulation and BCH channel coding schemes under fading channels(AWGN and Raleigh).In Pre-MMSE/pre-ZF channel
equalization scheme, the system shows comparatively worst performance in convolutional channel coding scheme with QAM/QPSK digital modulation. With increase in noise power as compared to signal power, the system is found to have shown performance deterioration
Combining SFBC_OFDM Systems with SVD Assisted Multiuser Transmitter and Multi...IOSR Journals
Abstract: In this work, we exploit the SVD assisted multiuser transmitter (MUT) and multiuser detector (MUD) technique, using downlink (DL) preprocessing transmitter and DL postprocessing receiver matrice .In combination with space frequency block coding (SFBC). And also propose the precoded DL transmission scheme, were the both proposed schemes take advantage of the channel state information (CSI) of all users at the base station (BS), but only of the mobile station (MS)’s own CSI, to decompose the MU MIMO channels into parallel single input single output (SISO), these two proposed schemes are compared to the vertical layered space time (V_BLAST) combined with SFBC (SFBC_VBLAST). Our Simulation results show that the performance of the proposed scheme with DL Zero Forcing (ZF) transmitter for interference canceller outperforms the SFBC_VBLAST and the precoded DL schemes with ZF receiver in frequency selective fading channels. Keywords – Post processing, Preprocessing,, SFBC, SVD, ZF.
Analysis of cyclic prefix length effect on ISI limitation in OFDM system over...IJECEIAES
In this work, the influence of the cyclic prefix on the performance of the OFDM system is studied. We worked out an OFDM transceiver using a 16 QAM modulation scheme, a comparison of the BER for various lengths of the cyclic prefix has been achieved, and the influence of the noise introduced in the channel has been highlighted, for both a Gaussian and Rayleigh noise. The simulation was carried out on MATLAB where the curves of the BER for various lengths of the cyclic prefix are given and compared. We also adopted as a metric the QAM constellation to show the dispersion of the carriers as a consequence of the transmission channel, the mitigation of this effect by the CP is noticeable.
A software framework for dynamic modeling of dc motors at robot jointseSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Synthesis of methyl, benzyl and pseudo halogeno co (iii) complexes of a dioxi...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Advanced control systems in two wheeler and finding the collision site of the...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Structure, microstructure and dielectric study of (ba0.6 sr0.4)(zr0.6ti0.4)o3...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Performance analysis of al fec raptor code over 3 gpp embms networkeSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
The effect of rotor disc clearance on the lift performance of contra rotating...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
In this paper, Space Time Block Code (STBC), Spatial Multiplexing (SM) and hybrid model with OFDM
are designed for Rayleigh fading channel. Combination of SM and STBC forms hybrid MIMO model. The
performances of the above mentioned models with different modulations such as Quadrature Phase Shift
Keying (QPSK) and Quadrature Amplitude Modulation (QAM) with multiple antennas are measured with
respect to BER. In this paper, it is shown that Hybrid MIMO provides low BER. Thus, in wireless
communication, hybrid model improves the data rate and link reliability.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Iterative qr decompostion channel estimation for mimo ofdm systems eSAT Journals
Abstract Channel estimation algorithms have a key role in signal detection in MIMO-OFDM systems. In this system, the number of channel components which need to be estimated is much more than conventional SISO wireless systems. Consequently, the computational process of channel estimation is highly intensive. In addition, the high performance channel estimation algorithms mostly suffer from high computational complexity. In the other words, the system undergoes intensive computations if high performance efficiency is desired. However, there is an alternative solution to achieve both high performance efficiency and relatively low level of computational complexity. In this solution, high efficient channel estimation is firstly designed, and then it is simplified using alternative mathematical expressions. In this paper, Iterative channel estimation based on QR decomposition for MIMO-OFDM systems is proposed. From simulation results, the iterative QRD channel estimation algorithm can provide better mean-square-error and bit error rate performance than conventional methods. Index Terms: MIMO, OFDM, QRD,Least squre Channel estimation
BER Analysis of OFDM Systems with Varying Frequency Offset Factor over AWGN a...rahulmonikasharma
The progressively escalating demand for tremendously high rate data transmission over wireless mediums needsresourcefulconcord of electromagnetic resources considering restrictions like power incorporation, spectrum proficiency, robustness in disparity to multipath propagation and implementation complication. Orthogonal frequency division multiplexing (OFDM) is a favorable approach for upcoming generation wireless communication systems. However its susceptibility to the frequency offset triggered by frequency difference between local oscillator of transmitter and receiver or due to Doppler shift results to Inter Carrier Interference. This delinquent of ICI results inworsening performance of the wireless systems as bit error rate increaseswith increase in value of frequency offset. In this paper simulation results aredemonstratedfor analyzing the effect of varying frequency offset factor on system’s error rate performance.
MIMO Channel Estimation Using the LS and MMSE AlgorithmIOSRJECE
Wireless Communication Technology has developed over the past few yearsfor other objectives.The Multiple InputMultiple Output (MIMO) is one of techniques that is used to enhancethe data rates, in which multiple antennas are employed both the transmitter and receiver. Multiple signals are transmitted from different antennas at the transmitter using the same frequency and separated space. Various channel estimation techniques are employed in order to judge the physical effects of the medium present. In this paper, we analyze and implementvarious estimation techniques for MIMO Systems such as Least Squares (LS), Minimum Mean Square Error (MMSE),these techniques are therefore compared to effectively estimate the channel in MIMO System. The results demonstrate that SNR required to support different values of bit error rate varies depending on different low correlation between the transmitting and the receiving antennas .In addition, it is illustrated that when the number of transmitter and receiver antennas increases, the performance of TBCE schemes significantly improves. The Same behavior isalso observed for MIMO system. Performance of both MMSE and LSestimation are the same for allkinds of modulation at small value of SNR but the more we increase the SNR value the more performance gap goes on increasing.
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.
A JOINT TIMING OFFSET AND CHANNEL ESTIMATION USING FRACTIONAL FOURIER TRANSFO...IJCNCJournal
This paper deals with symbol timing offset and channel estimation in OFDM (orthogonal frequency
division multiplexing) system in fast varying channel. Symbol timing offset (STO) estimation is a major task
in OFDM. Most of existing methods for estimating STO used cyclic prefix or training sequences. In this
paper, we consider a new system for STO estimation using constant amplitude zero autocorrelation
(CAZAC) sequences as pilot sequences in conjunction with fractional Fourier transform (FRFT). After STO
estimation is done, timing compensation is made. Thereafter, channel is estimated to well recover the
original transmitted signal. This method gives good results in terms of MSE in comparison with other
known techniques, it estimated well the channel and it is important for fast varying channel. MATLAB
Monte-Carlo simulations are used to evaluate the performance of the proposed estimator.
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
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.
Classical Discrete-Time Fourier TransformBased Channel Estimation for MIMO-OF...IJCSEA Journal
In this document, we look at various time domain channel estimation methods with this constraint of null carriers at spectrumborders.We showin detail howto gauge the importance of the “border effect” depending on the number of null carriers, which may vary from one system to another. Thereby we assess the limit of the technique discussed when the number of null carriers is large. Finally the DFT with the truncated singular value decomposition (SVD) technique is proposed to completely eliminate the impact of the null subcarriers whatever their number. A technique for the determination of the truncation threshold for any MIMO-OFDM system is also proposed.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Similar to Adaptive transmit diversity selection (atds) based on stbc and sfbc fir 2 x1 mimo ofdm systems (20)
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
Online aptitude test management system project report.pdfKamal Acharya
The purpose of on-line aptitude test system is to take online test in an efficient manner and no time wasting for checking the paper. The main objective of on-line aptitude test system is to efficiently evaluate the candidate thoroughly through a fully automated system that not only saves lot of time but also gives fast results. For students they give papers according to their convenience and time and there is no need of using extra thing like paper, pen etc. This can be used in educational institutions as well as in corporate world. Can be used anywhere any time as it is a web based application (user Location doesn’t matter). No restriction that examiner has to be present when the candidate takes the test.
Every time when lecturers/professors need to conduct examinations they have to sit down think about the questions and then create a whole new set of questions for each and every exam. In some cases the professor may want to give an open book online exam that is the student can take the exam any time anywhere, but the student might have to answer the questions in a limited time period. The professor may want to change the sequence of questions for every student. The problem that a student has is whenever a date for the exam is declared the student has to take it and there is no way he can take it at some other time. This project will create an interface for the examiner to create and store questions in a repository. It will also create an interface for the student to take examinations at his convenience and the questions and/or exams may be timed. Thereby creating an application which can be used by examiners and examinee’s simultaneously.
Examination System is very useful for Teachers/Professors. As in the teaching profession, you are responsible for writing question papers. In the conventional method, you write the question paper on paper, keep question papers separate from answers and all this information you have to keep in a locker to avoid unauthorized access. Using the Examination System you can create a question paper and everything will be written to a single exam file in encrypted format. You can set the General and Administrator password to avoid unauthorized access to your question paper. Every time you start the examination, the program shuffles all the questions and selects them randomly from the database, which reduces the chances of memorizing the questions.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
Water billing management system project report.pdfKamal Acharya
Our project entitled “Water Billing Management System” aims is to generate Water bill with all the charges and penalty. Manual system that is employed is extremely laborious and quite inadequate. It only makes the process more difficult and hard.
The aim of our project is to develop a system that is meant to partially computerize the work performed in the Water Board like generating monthly Water bill, record of consuming unit of water, store record of the customer and previous unpaid record.
We used HTML/PHP as front end and MYSQL as back end for developing our project. HTML is primarily a visual design environment. We can create a android application by designing the form and that make up the user interface. Adding android application code to the form and the objects such as buttons and text boxes on them and adding any required support code in additional modular.
MySQL is free open source database that facilitates the effective management of the databases by connecting them to the software. It is a stable ,reliable and the powerful solution with the advanced features and advantages which are as follows: Data Security.MySQL is free open source database that facilitates the effective management of the databases by connecting them to the software.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
Adaptive transmit diversity selection (atds) based on stbc and sfbc fir 2 x1 mimo ofdm systems
1. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Special Issue: 07 | May-2014, Available @ http://www.ijret.org 56
ADAPTIVE TRANSMIT DIVERSITY SELECTION (ATDS) BASED ON
STBC AND SFBC FIR 2X1 MIMO OFDM SYSTEMS
K. Vinod Babu1
, G. Ramachandra Reddy2
, Bala Krishna Nallagatla3
, Bibin Baby John4
, Suraj Gawande5
Abstract
In this paper, a new adaptive transmit diversity selection (ATDS) scheme is proposed for future wireless communication system to
provide high spectral efficiency (SE) and good quality of service (QOS) .The ATDS scheme selects the space time block code (STBC)
orthogonal frequency division multiplexing (OFDM) scheme for flat fading channel and it selects space frequency block code (SFBC)
OFDM scheme for frequency selective fading channel. The proposed scheme provides low average bit error rate (BER) and high
average SE by using the benefits of STBC-OFDM for flat fading channel and SFBC-OFDM for frequency selective fading channel.
The obtained simulation results validate this statement.
Keywords- ATDS, Channel Index (CI), STBC-OFDM, SFBC-OFDM
---------------------------------------------------------------------***---------------------------------------------------------------------
I. INTRODUCTION
The growing need for high rate spectrally efficient transmission
has always forced researchers to come up with better
transmission schemes. The flat fading and frequency selective
fading caused by multipath effect is one major concern issue for
future wireless communication systems. While flat fading
causes signal deterioration and can be easily compensated, the
Inter Symbol Interference (ISI) caused by frequency selective
fading requires the need of complex equalizers at receiver side
[1,2]. Multicarrier systems like OFDM can completely mitigate
the effect of ISI using Cyclic Prefix (CP). This simple one tap
equalization has made OFDM the favorite scheme for many 4G
standards. It is used for various applications such as Digital
Video Broadcasting (DVB), Digital Audio Broadcasting (DAB)
and Asymmetric Digital Subscriber Line (ADSL) services. It
can also be used for LTE, Wi-MAX based 4G systems [3].
Multi Input Multi Output (MIMO) systems were originally
developed for flat fading channels. It offers spatial multiplexing
as well as diversity gains which provides higher data rate and
improved reliability respectively. In order to use the same
concept in frequency selective channels, OFDM was used along
with MIMO to convert the frequency selective channel to a
number of flat fading channels. Transmit diversity and receive
diversity are the two different diversities implemented in
MIMO-OFDM systems [4, 5]. Transmit diversity is attractive
for downlink purposes as more number of transmitting antennas
can be used in the Base Station (BS). Transmit Diversity needs
accurate channel information at the transmitter side it is not
practically possible. STBC and Space Time Trellis Codes
(STTC) are other transmit diversity schemes which work
without the channel information at the transmitter side. In
STTC, with the increase in number of states the complexity
increases exponentially [3].
But both STTC and STBC are ideal only for flat fading
channels. The major drawback of applying STBC for frequency
selective fading channel is that fading destroys the
orthogonality of STBC matrix. So it is preferred only for indoor
environment and low data rate applications. MIMO equalizers
are used with STBC systems for frequency selective fading
channels. This again increases the complexity of the system.
Hence a frequency diversity scheme, SFBC is employed for
MIMO-OFDM to overcome frequency selective fading [3, 6].
In this paper, an adaptive transmit diversity selection scheme
(ATDS) that uses the best of space diversity (MIMO), time
diversity (STBC), frequency diversity (SFBC) and OFDM is
proposed. Alamouti codes are used with STBC and SFBC to
increase diversity gain [2, 5]. The ATDS estimate the channel
condition at the receiver and determines whether it is flat fading
or frequency selective fading. The channel fading index (CI=0
for flat fading and CI=1 for frequency selective fading) is fed
back to the transmitter. This helps in reducing the amount of
feedback data and thus providing with better spectral efficiency.
The transmitter then uses time diversity scheme for flat fading
and frequency diversity scheme for frequency fading channels.
The rest of the paper is organized as followed. A brief
explanation of STBC is given in section II. SFBC OFDM is
discussed in section III. The proposed ATDS is explained in
section IV. Section V contains simulation results and Section
VI concludes the paper.
2. STBC OFDM
Space Time Block Code (STBC) is an efficient way to provide
time diversity. The use of STBC along with MIMO OFDM
offer simultaneous time and space diversity. The use of
Alamouti code ensures orthogonality of the STBC matrix. A
communication system with 2 transmitter antenna and 1
2. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Special Issue: 07 | May-2014, Available @ http://www.ijret.org 57
receiver antenna is considered and hence STBC 2X1 block is
considered [5].
The two OFDM symbols x1(n) and x2(n) are transmitted in two
different time periods and through two different antennas,
thereby providing both time and space diversity. For efficient
implementation of STBC with 2x1 systems, the channel should
be Quasi Static (QS) for two OFDM symbol periods [4]. The
signal received at the receiver during the first and second
symbol durations can be written as
Ts 1,1 1,2 Ts
1 2y (n) h x (n) h x (n) w (n) (1)
2Ts 1,1 * 1,2 * 2Ts
2 1y (n) h x (n) h x (n) w (n) (2)
Where n=0, 1, 2,…., L-1.
Stacking (1) and conjugate of (2) in matrix form, we get
Ts 1,1 1,2 Ts
1
2Ts * 1,2* 1,1* 2Ts *
2
x (n)y (n) h h w (n)
x (n)y (n) h h w (n)
(3)
Let the weight matrix S be given as
1,1 1,2
1,2* 1,1*
2 22 1,1 1,2
h h1
S
h h h
where h h h
(4)
The detection of the transmitted OFDM symbols at the receiver
can be done by the following procedure. Now multiplying (3)
with SH
on both sides,
1
2
11
22
h 0y (n) x (n) w (n)
0 h x (n)y (n) w (n)
(5)
Where
1,1 1,2
Ts 2Ts
1
1,2 1,1
Ts 2Ts
2
h * h
y (n) y (n) y (n)
h h
h * h
y (n) y (n) y (n)
h h
1
1,1 1,2
Ts 2Ts *h * h
w (n) w (n) w (n)
h h
2
1,2 1,1
Ts 2Ts *h * h
w (n) w (n) w (n)
h h
(6)
From (5)
111
222
y (n) h x (n) w (n)
y (n) h x (n) w (n)
(7)
The transmitted two OFDM symbols can be detected from (7)
with a simple Zero Forcing (ZF) equalization as
1
1
2
2
y (n)
x (n)
h
y (n)
x (n)
h
(8)
In STBC with 2 Transmitting antennas and 1 receiving antenna,
two OFDM symbols are transmitted in two OFDM symbol
periods. It is a Rate 1 system [5]. The STBC system is suitable
only for operation in flat fading channels. For frequency
selective channels, we go for SFBC system.
3. SFBC OFDM
Space Frequency Block Codes (SFBC) can be considered as the
counterpart of STBC which when used with MIMO system
provide frequency diversity together with space diversity. As in
the case with STBC, we use Alamouti codes for the purpose of
orthogonality and consider the same communication system
with 2 transmitter antenna and 1 receiver antenna that make use
of 2X1 SFBC matrix which is given as[4,5]
Fig 1: STBC 2X1 system using Alamouti Codes
3. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Special Issue: 07 | May-2014, Available @ http://www.ijret.org 58
I I
* *
I I
X [2m] X [2m 1]
D
X [2m 1] X [2m]
(9)
Where
L
m 0,1... 1
2
In (9), XI denote the M-QAM modulated symbols for the lth
OFDM symbol and is given as
T
I I I I IX [X [0],X [1],X [2].....X [L 1]] (10)
The symbols coded in the first and second column of the matrix
(9) are transmitted through first and second transmitting
antennas respectively. The outputs obtained from each column
is given for separate IFFT blocks and two different OFDM
symbols are generated for the same set of L modulated symbols
which is given by,
j2 mnL 1
1,1 1,1 L
I I
m 0
j2 mnL 1
1,2 1,2 L
I I
m 0
1
x n X m e
L
1
x n X m e
L
where n 0,1.......L 1
(11)
In i,j
Ix n , the superscript i, j represents receiving and
transmitting antenna indexes respectively. The signal received
at the receiving antenna is given as
1 1,1 1,1 1,2 1,2 1
I I I Iy [n] x n h [n] x n h [n] w [n] (12)
where 1
Iw [n] is Additive White Gaussian Noise (AWGN).
1,1
h [n]and
1,2
h [n]are the fading channels corresponding to
first and second transmitting antennas respectively. After L
point FFT in the receiver,
1 1,1 1,1 1,2 1,2 1
I I I IY [m] X m H [m] X m H [m] W [m] (13)
Where m=0,1,…,L-1
The decoding of SFBC coded symbols in first two subcarriers is
explained below. The same procedure is carried out to detect
the symbols available in the rest of the subcarriers.
1 1,1 1,1 1,2 1,2 1
I I I I
1 1,1 1,1 1,2 1,2 1
I I I I
Y [0] X 0 H [0] X 0 H [0] W [0]
Y [1] X 1 H [1] X 1 H [1] W [1]
(14)
As in the case with STBC, the quasi static condition must be
satisfied for SFBC also. Hence the channels for two
neighboring subcarriers are assumed to be constant [4].
1,1 1,1
1,2 1,2
H [0] H [1]
H [0] H [1]
(15)
Substituting (15) in (14)
1 1,1 1,2 1
I I I IY [0] X 0 H [0] X 1 H [0] W [0] (16)
* *1 1,1 1,2 1
I I I IY [1] X 1 H [0] X 0 H [0] W [1] (17)
Stacking (16) and conjugate form of (17) in matrix form as
1 11,1 1,2
II I
1 11,2 1,1
II I
X 0Y [0] W [0]H [0] H [0]
X 1Y [1] W [1]H [0] H [0]
(18)
Let the weight matrix S be given as
1,1 1,2
1,2 1,1
2 22 1,1 1,2
H [0] H [0]
H(0) H(0)
S
H [0] H [0]
H(0) H(0)
where H(0) H [0] H [0]
(19)
Multiplying both sides of (18) with SH
,
II I
II I
Y [0] H[0] X [0] W [0]
Y [1] H[0] X [1] W [1]
(20)
Where
1,1 * 1,2
1 1
I I I
1,2 1,1
1 1
I I I
H [0] H [0]
Y [0] Y [0] Y [1]
H(0) H(0)
H [0] H [0]
Y [1] Y [0] Y [1]
H(0) H(0)
1,1 * 1,2
1 1
I I I
1,2 1,1
1 1
I I I
H [0] H [0]
W [0] W [0] W [1]
H(0) H(0)
H [0] H [0]
W [1] W [0] W [1]
H(0) H(0)
(21)
A simple zero forcing equalizer can be used to detect the
transmitted coded OFDM symbols from (20)
I
Y[0]
X [0]
H[0]
4. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Special Issue: 07 | May-2014, Available @ http://www.ijret.org 59
I
Y[1]
X [1]
H[0]
(22)
4. ADAPTIVE TRANSMIT DIVERSITY
SELECTION
The Adaptive transmit Diversity Selection (ATDS) adaptively
selects a diversity scheme based on the current channel
condition. The receiver estimates the channel and determines
whether it is flat fading or frequency fading. Based on this
information, the diversity scheme determination is done at the
receiver and the channel index (CI=0 for flat fading and CI=1
for frequency fading) is fed back to the transmitter side.
The ATDS block at the transmitter assigns the diversity scheme
using the received channel index (CI). For CI=0, the ATDS
assigns Path 0 that provide time and space diversity using
Alamouti STBC coding. The OFDM signals at the output of the
IFFT block undergoes STBC encoding (see section II) and is
transmitted through two transmitting antennas to obtain spatial
diversity. On the other hand, for CI=1, Path 1 is assigned which
give frequency diversity. The M-QAM modulated symbols are
SFBC encoded (section III) and then produce two separate
OFDM symbols that are transmitted through two transmitted
antennas just like Path 1 in order to achieve spatial diversity.
At the receiver side decoding is done in the same way based on
CI. The Diversity Determination block chooses the path in the
receiver side. Path 0 provides STBC decoding
Table 1: The Proposed ATDS Algorithm
Whereas Path 1 provides SFBC decoding. Unlike the
conventional diversity techniques which could follow both time
or frequency diversity, the ATDS adaptively selects the
diversity scheme and hence uses the full benefits time,
frequency and spatial diversity techniques and thus improves
the overall system performance.
Fig 2: ATDS block diagram
5. SIMULATION RESULTS
To test the performance of proposed ATDS scheme we take the
following parameters. The number of Subcarriers in one OFDM
symbol is 64 and Bandwidth (B) is assumed to be 5 MHz,
number of transmitting antennas (NT) are 2 and number of
receiving antenna (NR) is 1, the code rate (RC)is one and the
target BER is 10-4
. The performance of the proposed scheme is
evaluated for 100 channels and the average BER and SE results
are compared with the conventional system. The fading process
is assumed to be stationary and the channel is assumed to be
static during one OFDM block length.
The instantaneous BER of mth
subcarrier in Ith
OFDM symbol
with M-QAM is given as
2 21,1 1,2S
I b(m)
1.6
BER (m) 0.2exp ( H [m] H [m] )
2(2 1)
(23)
where , S S 0E N and ES is the symbol energy at the
transmitter and N0/2 is the variance of Additive White
Gaussian Noise (AWGN), b(m) is the number of bits loaded on
the mth
subcarrier and 1,1 1,2
H [m],H [m] are the mth
sub channel
amplitudes of transmitter antennas to the receiver antenna[4].
5. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Special Issue: 07 | May-2014, Available @ http://www.ijret.org 60
L 1
m 0
1
BER BER(m)
L
(24)
Where L represents the total number of subcarriers in one
OFDM symbol[3, 4].
The Average SE of the Ith
OFDM symbol is given as
L 1
I I
m 0u g
1
SE b(m)(1 BER (m))
B(T T )
(25)
Where uT is the useful symbol duration and gT is the guard
interval [4,5].
Fig 3 Average BER comparison of proposed scheme and
conventional STBC-OFDM over frequency selective fading
channel.
Fig 4 Average Spectral Efficiency comparison of Proposed
Scheme and Conventional STBC-OFDM over frequency
selective fading channel.
In the frequency selective fading channel multiple versions of
the faded transmitted signal delayed in time are received and it
induces inter symbol interference (ISI). A four tap channel is
considered for the analysis.
In Figure 3, the average BER values of the proposed scheme
and conventional STBC-OFDM system over frequency
selective fading channel are calculated with equation (24) by
varying the SNR values from 0 to 40dB. For the proposed
scheme (SFBC-OFDM) the average BER value at 0dB SNR is
3
10
but this BER value is achieved at 7dB SNR in case of
conventional STBC-OFDM, i.e., the proposed scheme gains
7dB over frequency selective fading channel.
Figure 4 shows the spectral efficiency comparison of proposed
scheme and conventional scheme over frequency selective
fading channel. The SE values are calculated by equation (25).
For the proposed scheme (SFBC-OFDM) the average SE value
at 12dB SNR is 4bits/Hz but in case of conventional STBC-
OFDM the value is 2bits/Hz. So the SFBC-OFDM over
frequency selective fading channel provides high SE compared
to the STBC-OFDM.
In flat fading channel the spectral characteristics of the
transmitted signal are maintained at the receiver but the strength
of the received signal varies with time due to fluctuations in the
gain of the channel caused by multipath and for analysis of this
a single tap channel is considered.
In Figure 5 the average BER values of the proposed scheme and
conventional SFBC-OFDM system over flat fading channel are
calculated with equation (24) by varying the SNR. For the
proposed scheme the average BER value at 0dB SNR is
3
0.07 10
but this same BER value is achieved at 14dB SNR
in case of SFBC-OFDM, which implies that the proposed
scheme gains 14dB over flat fading channel.
Figure 6 shows the spectral efficiency comparison of proposed
scheme and conventional scheme over flat fading channel.
0 5 10 15 20 25 30 35 40
10
-4
10
-3
10
-2
10
-1
SNR(dB)
AverageBER
Proposed System (SFBC-OFDM)
Conventional System (STBC-OFDM)
0 5 10 15 20 25 30 35 40
0
2
4
6
8
10
12
14
SNR(dB)
AverageSpectralEfficieny(b/s/Hz)
Proposed System (SFBC-OFDM)
Conventional System (STBC-OFDM)
6. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Special Issue: 07 | May-2014, Available @ http://www.ijret.org 61
Fig 5 Average BER comparison of proposed scheme and
conventional SFBC-OFDM over flat fading channel
Fig 6 Average Spectral Efficiency comparison of Proposed
Scheme and Conventional SFBC-OFDM over flat fading
channel.
The SE values are calculated by equation (25). For the proposed
scheme (STBC-OFDM) the average SE value at 12dB SNR is
2bits/Hz but in case of conventional SFBC-OFDM the value is
1bits/Hz. So the STBC-OFDM over flat fading channel
provides high SE compared to the SFBC-OFDM. From the
results, it can be seen that the proposed ATDS scheme greatly
improves the performance of a system by selecting the
transmission scheme based on the present channel condition.
6. CONCLUSIONS
An adaptive transmit diversity selection (ATDS) scheme is
proposed in this paper. The proposed scheme greatly improves
the performance of a system in terms of Spectral Efficiency(SE)
and quality by using the benefits of STBC-OFDM for flat
fading channel and SFBC-OFDM for frequency selective
fading channel as compared to a conventional system where
either STBC-OFDM or SFBC-OFDM are used for both flat
fading and frequency selective fading channels. Simulation
results shows that in flat fading channel the proposed scheme
(using STBC-OFDM) gains 14dB SNR compared to SFBC-
OFDM system for getting
3
0.07 10
BER and SE is 2bits/Hz
rather than 1bits/Hz for conventional system at 12dB SNR. In
frequency selective fading channel the proposed scheme gains
7dB SNR compared to STBC-OFDM for getting
3
10
BER and
SE is 4bits/Hz rather than 2bits/Hz for STBC-OFDM at 12dB
SNR.
REFERENCES
[1] Theodore S Rappaport, 2002, Wireless Communications
Principles and Practice, Pearson Education Inc, India.
[2] Ramjee Prasad, 2004, OFDM for Wireless
Communication Systems, Artech House, Inc. Boston,
London.
[3] Yong Soo Cho, Jaekwon Kim, Won Young Yang and
Chung G. Kang, MIMO-OFDM Wireless
Communications with Matlab, John Wiley & Sons Pvt.
Ltd, Asia, 2010.
[4] Mohammad Torabi, “Antenna selection for MIMO-
OFDM systems,” Signal Processing, vol. 88, 2008, pp.
2431-2441.
[5] S.M. Alamouti, “A simple transmit diversity technique
for wireless communications,” IEEE Journal on Selected
Areas in Communication, vol. 16, no. 8, 1998, pp. 1451-
14558.
[6] Mohammad Torabi, “Adaptive modulation for space-
frequency block coded OFDM systems,” International
Journal of Electronics and Communications, vol. 62, no.
7, 2008, pp. 521-533.
0 5 10 15 20 25 30 35 40
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
SNR(dB)
AverageBER
Conventional System (SFBC-OFDM)
Proposed System (STBC-OFDM)
0 5 10 15 20 25 30 35 40
0
2
4
6
8
10
12
SNR(dB)
AverageSpectralEfficieny(b/s/Hz)
Conventional System (SFBC-OFDM)
Proposed System (STBC-OFDM)