This document discusses performance analysis of MIMO-OFDM systems using QOSTBC coding for M-PSK modulation. It proposes a QOSTBC code structure for a 4x4 antenna configuration MIMO-OFDM system. It analyzes the performance of the system in AWGN and Rayleigh channels by evaluating BER versus SNR for different M-PSK modulation schemes and antenna configurations. The proposed MIMO-OFDM system with 4x4 QOSTBC coding is shown to have better performance than other systems in terms of lower BER for a given SNR.
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.
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
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.
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
Reduction of Outage Probability in Fast Rayleigh Fading MIMO Channels Using OFDMIJERA Editor
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.
Implementation and Study of Universal Filtered Multi Carrier under Carrier Fr...Editor IJAIEM
Sathiyapriya N.S
PG Student, Dept. of ECE, Periyar Maniammai University Thanjavur, Tamilnadu, India
ABSTRACT
OFDM is a matured technology and applied in various wireless standards. However they are not suitable for Uplink and this
technology is replaced by SC FDMA in 4G standards. Similarly Universal Filtered Multicarrier Communication (UFMC) is
another suitable technology for Multi user Uplink and for applications like cognitive radio. UFMC is a new, non-orthogonal,
waveform designed by Alcatel Lucent Labs which provide a much more efficient way of enabling networks to serve both
broadband users and very narrowband “short data” devices such as any embedded sensor or M2M module. In UFMC the
filtering of waveform is done on a group of subcarriers. In OFDM it is done on the whole subcarriers together. This reduces
the side lobe levels, inters carrier interference (ICI) and requires reduced filter length. Moreover Internet-of-Things where
Machine-Machine communication and applications where very tight response in time requirements are needed, OFDM
miserably fails. We examine impact of carrier frequency offset on the performance of the proposed scheme and compare the
results performance of cyclic prefix based orthogonal frequency division multiplexing(CP-OFDM) system.-
Key words: ICI,CFO,OFDM,UFMC
Comparison of Various Waveform Contenders of 5G Wireless Communication Based ...ijtsrd
This paper presents an extensive and fair comparison among the most promising waveform contenders for the 5G air interface which includes- Filtered OFDM, Filter-bank multi carrier (FBMC), universal filtered multi-carrier (UFMC) has been compared with OFDM in terms of spectral efficiency and bit error rate using mat lab. The disadvantages of OFDM have been addressed and it has shown that (fofdm), (UFMC), (FBMC) could be a more effective solution. FBMC is a method for improving out of band (OOB) characteristics by filtering each subcarrier, it is also expected to improve the Inter-Carrier Interference (ICI) characteristics while UFMC is a method for improving OOB characteristics by filtering each block. Raksha Vishnoi | Saurabh Gaur | Ashish Verma"Comparison of Various Waveform Contenders of 5G Wireless Communication Based on OFDM" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd15637.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/15637/comparison-of-various-waveform-contenders-of-5g-wireless-communication-based-on-ofdm/raksha-vishnoi
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.
Implementation of 8x8 MIMO OFDM systems for higher order modulation using QOS...ijsrd.com
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 8 X 8 antenna configuration. The signal detection technology used in this work for MIMO-OFDM system is Zero-Forcing Equalization (linear detection technique). In this paper, analysis of high level of modulations (i.e. M-QAM and M-PSK for different values of M) on MIMO-OFDM system is presented. In this, AWGN, Rayleigh and Rician channels have been used for analysis purpose and their effect on BER and Spectral Efficiency for high data rates have been presented. The proposed system has better performance than the other systems in terms of SNR improvement of 3-5 dB and spectral efficiency.
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.
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).
PERFORMANCES OF ORTHOGONAL WAVELET DIVISION MULTIPLEX (OWDM) SYSTEM UNDER AWG...IJCNCJournal
Orthogonal Wavelet Division Multiplexing (OWDM) has been considered as an alternative of Orthogonal
Frequency Division Multiplexing (OFDM) in the recent years. OWDM has lower computational complexity
and higher flexibility compared to its OFDM counterpart. The core component of OWDM is wavelet.
Wavelet has been a much investigated and applied topic in digital image processing for a long time.
Recently, it has drawn considerable attention of the researchers working in communication field. In this
work we investigate the performances of OWDM under different channel conditions. We consider three
channel conditions namely Additive White Gaussian Noise (AWGN), Rayleigh, Ricean, and frequency
selective. We consider a number of wavelets namely Haar, Daubechies, Biorthogonal, Reverse
Biorthogonal, Coiflets, and Symlets in OWDM design. For system model we choose Digital Video
Broadcasting-Terrestrial (DVB-T). Originally DVB-T system was designed based on OFDM. In this work
we use OWDM instead. The simulation results show OWDM outperforms OFDM in terms of bit error rate
(BER), noise resiliency, and peak-to-average ration. The results also show that the Haar wavelet based
OWDM outperforms other wavelets based OWDM system under all three considered three channel
conditions.
Ber performance of ofdm with discrete wavelet transform for time dispersive c...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
These slides deal with the basic problem of channel equalization and exposes the issue related to it and shows how it can be balanced by the usage of effective and robust algorithms.
Reduction of Outage Probability in Fast Rayleigh Fading MIMO Channels Using OFDMIJERA Editor
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.
Implementation and Study of Universal Filtered Multi Carrier under Carrier Fr...Editor IJAIEM
Sathiyapriya N.S
PG Student, Dept. of ECE, Periyar Maniammai University Thanjavur, Tamilnadu, India
ABSTRACT
OFDM is a matured technology and applied in various wireless standards. However they are not suitable for Uplink and this
technology is replaced by SC FDMA in 4G standards. Similarly Universal Filtered Multicarrier Communication (UFMC) is
another suitable technology for Multi user Uplink and for applications like cognitive radio. UFMC is a new, non-orthogonal,
waveform designed by Alcatel Lucent Labs which provide a much more efficient way of enabling networks to serve both
broadband users and very narrowband “short data” devices such as any embedded sensor or M2M module. In UFMC the
filtering of waveform is done on a group of subcarriers. In OFDM it is done on the whole subcarriers together. This reduces
the side lobe levels, inters carrier interference (ICI) and requires reduced filter length. Moreover Internet-of-Things where
Machine-Machine communication and applications where very tight response in time requirements are needed, OFDM
miserably fails. We examine impact of carrier frequency offset on the performance of the proposed scheme and compare the
results performance of cyclic prefix based orthogonal frequency division multiplexing(CP-OFDM) system.-
Key words: ICI,CFO,OFDM,UFMC
Comparison of Various Waveform Contenders of 5G Wireless Communication Based ...ijtsrd
This paper presents an extensive and fair comparison among the most promising waveform contenders for the 5G air interface which includes- Filtered OFDM, Filter-bank multi carrier (FBMC), universal filtered multi-carrier (UFMC) has been compared with OFDM in terms of spectral efficiency and bit error rate using mat lab. The disadvantages of OFDM have been addressed and it has shown that (fofdm), (UFMC), (FBMC) could be a more effective solution. FBMC is a method for improving out of band (OOB) characteristics by filtering each subcarrier, it is also expected to improve the Inter-Carrier Interference (ICI) characteristics while UFMC is a method for improving OOB characteristics by filtering each block. Raksha Vishnoi | Saurabh Gaur | Ashish Verma"Comparison of Various Waveform Contenders of 5G Wireless Communication Based on OFDM" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd15637.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/15637/comparison-of-various-waveform-contenders-of-5g-wireless-communication-based-on-ofdm/raksha-vishnoi
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.
Implementation of 8x8 MIMO OFDM systems for higher order modulation using QOS...ijsrd.com
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 8 X 8 antenna configuration. The signal detection technology used in this work for MIMO-OFDM system is Zero-Forcing Equalization (linear detection technique). In this paper, analysis of high level of modulations (i.e. M-QAM and M-PSK for different values of M) on MIMO-OFDM system is presented. In this, AWGN, Rayleigh and Rician channels have been used for analysis purpose and their effect on BER and Spectral Efficiency for high data rates have been presented. The proposed system has better performance than the other systems in terms of SNR improvement of 3-5 dB and spectral efficiency.
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.
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).
PERFORMANCES OF ORTHOGONAL WAVELET DIVISION MULTIPLEX (OWDM) SYSTEM UNDER AWG...IJCNCJournal
Orthogonal Wavelet Division Multiplexing (OWDM) has been considered as an alternative of Orthogonal
Frequency Division Multiplexing (OFDM) in the recent years. OWDM has lower computational complexity
and higher flexibility compared to its OFDM counterpart. The core component of OWDM is wavelet.
Wavelet has been a much investigated and applied topic in digital image processing for a long time.
Recently, it has drawn considerable attention of the researchers working in communication field. In this
work we investigate the performances of OWDM under different channel conditions. We consider three
channel conditions namely Additive White Gaussian Noise (AWGN), Rayleigh, Ricean, and frequency
selective. We consider a number of wavelets namely Haar, Daubechies, Biorthogonal, Reverse
Biorthogonal, Coiflets, and Symlets in OWDM design. For system model we choose Digital Video
Broadcasting-Terrestrial (DVB-T). Originally DVB-T system was designed based on OFDM. In this work
we use OWDM instead. The simulation results show OWDM outperforms OFDM in terms of bit error rate
(BER), noise resiliency, and peak-to-average ration. The results also show that the Haar wavelet based
OWDM outperforms other wavelets based OWDM system under all three considered three channel
conditions.
Ber performance of ofdm with discrete wavelet transform for time dispersive c...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
These slides deal with the basic problem of channel equalization and exposes the issue related to it and shows how it can be balanced by the usage of effective and robust algorithms.
the presentation consists of a brief description about ADAPTIVE LINEAR EQUALIZER , its classification and the associated attributes of ZERO FORCING EQUALIZER and MMSE EQUALIZER
Multiuser MIMO-OFDM simulation framework in MatlabPavel Loskot
Simulation framework for multiuser MIMO-OFDM over multipath fading channels. Also created a C-like pre-processor in Matlab to add flexibility in configuring the simulation prior its run.
This MATLAB section of source code covers MATLAB based projects.
Download free source code viz. FIR,IIR,scrambler,interleaver,FFT,convolution,correlation,interpolation,decimation,CRC,impairments,data type conversions and more.
RS encoder,convolutional encoder,viterbi decoder,OFDM,OFDMA,MIMO is also covered.WiMAX,WLAN,LTE source codes are also provided.
In a communications system, the channel is affected by an additive white Gaussian noise (AWGN)
and a fading due to a distance between a transmitter and a receiver. Especially, there are many kinds of
channel fadings. Depending on the moving speeds of transmitters or receivers, a fading type can be a slow
fading or a fast fading (i.e., the product of 0.1 and coherence time than smaller or larger than the symbol
period of signal are corresponding to fast and slow fadings). Moreover, a channel can be referred as a
selective fading or a flat fading corresponding to the product of 0.1 and coherence bandwidth than smaller
or larger than the bandwidth of signal. These above effects can suffer received signals at a destination.
Hence the performance of received signals in term of bit-error-rate (BER) is much degraded.
In order to overcome these issues, communications systems would be carefully designed. In detail,
application systems operating over the AWGN channels would use coding schemes to combat an additive
white noise. However, if environment is affected by fading, coding techniques only solve a fast fading.
It implies that, coding schemes degrade received signals when they go through slow fading channels. In
this case, an interleaving technique would be added to a communications system. In order to overcome
the fading channels, besides, using an interleaver as above, we can exploit the diversity of multi-path. It
implies that the effects of fading can be combated by transmitting the original signals over multiple paths
(experiencing independent fading) and then combining all received signals at the receiver. There are many
kinds of diversities to mitigate this issue, such as diversity in time, frequency, and space. Correspondingly,
a lot of state-of-art methods are given, viz. diversity receiving and transmitting, OFDM, space-time block
codes, MIMO, Cooperation and etc.
In summary, the main scope of this report is modeling a communications system. First, I create a
basic communications system, where it includes the modulation/demodulation using a QPSK modulation,
a channel type is an AWGN channel. Secondly, a coder/decoder scheme is added to a transmitter/receiver to
improve received signals. Thirdly, the fading channel is considered when a receiver/transmitter is moving.
It means that the slow fading is mentioned. The performance is shown to prove that the received signal
2
is degraded whether a coding scheme is used or not. Finally, an interleaver/deinterleaver is used to solve
this problem.
Besides, the performance in terms of BER is used to verify a validity of these above techniques in a
communications system.
Massive MIMO (also known as “Large-Scale Antenna Systems”, “Very Large MIMO”, “Hyper MIMO”, “Full-Dimension MIMO” and “ARGOS”) makes a clean break with current practice through the use of a large excess of service-antennas over active terminals and time division duplex operation. Extra antennas help by focusing energy into ever-smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include the extensive use of inexpensive low-power components, reduced latency, simplification of the media access control (MAC) layer, and robustness to intentional jamming. The anticipated throughput depend on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly-joined terminals, the exploitation of extra degrees of freedom provided by the excess of service-antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios.
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.
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 analysis of DWT based OFDM over FFT based OFDM and implementing o...VLSICS Design
Growth in technology has led to unprecedented demand for high speed architectures for complex signal processing applications. In 4G wireless communication systems, bandwidth is a precious commodity, and service providers are continuously met with the challenge of accommodating more users with in a limited allocated bandwidth. To increase data rate of wireless medium with higher performance, OFDM (orthogonal frequency division multiplexing) is used. Recently DWT (Discrete wavelet transforms) is adopted in place of FFT (Fast Fourier transform) for frequency translation. Modulation schemes such as 16-QAM, 32-QAM, 64-QAM and 128-QAM (Quadrature amplitude modulation) have been used in the developed OFDM system for both DWT and FFT based model. In this paper we propose a DWT-IDWT based OFDM transmitter and receiver that achieve better performance in terms SNR and BER for AWGN channel. It proves all the wavelet families better over the IFFT-FFT implementation. The OFDM model is developed using Simulink, various test cases have been considered to verify its performance. The DWTOFDM using Lifting Scheme architecture is implemented on FPGA optimizing hardware, speed & cost. The wavelet filter used for this is Daubechies (9, 7) with N=2. The RTL code is written in Verilog-HDL and simulated in Modelsim. The design is then synthesized in Xilinx and implemented on Virtex5 FPGA board and the results were validated using ChipScope.
Performance analysis of DWT based OFDM over FFT based OFDM and implementing o...VLSICS Design
Growth in technology has led to unprecedented demand for high speed architectures for complex signal processing applications. In 4G wireless communication systems, bandwidth is a precious commodity, and service providers are continuously met with the challenge of accommodating more users with in a limited allocated bandwidth. To increase data rate of wireless medium with higher performance, OFDM (orthogonal frequency division multiplexing) is used. Recently DWT (Discrete wavelet transforms) is adopted in place of FFT (Fast Fourier transform) for frequency translation. Modulation schemes such as 16-QAM, 32-QAM, 64-QAM and 128-QAM (Quadrature amplitude modulation) have been used in the developed OFDM system for both DWT and FFT based model. In this paper we propose a DWT-IDWT based OFDM transmitter and receiver that achieve better performance in terms SNR and BER for AWGN channel. It proves all the wavelet families better over the IFFT-FFT implementation. The OFDM model is developed using Simulink, various test cases have been considered to verify its performance. The DWTOFDM using Lifting Scheme architecture is implemented on FPGA optimizing hardware, speed & cost. The wavelet filter used for this is Daubechies (9, 7) with N=2. The RTL code is written in Verilog-HDL and simulated in Modelsim. The design is then synthesized in Xilinx and implemented on Virtex5 FPGA board and the results were validated using ChipScope.
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.
Index modulation is one of the promising techniques for future communications systems due to many improvement over the classical orthogonal frequency division multiplexing systems such as single RF chain, increased throughput for the same modulation order, achieved tradeoff between the efficiencies of the power and the spectral, and elimination of inter-channel interference. Many forms of index modulation researches exist where symbols are conveyed in antennas, subcarriers, time slots, and the space-time matrix. Spatial modulation is one member of index modulation family where symbols are conveyed in activating transmit/receive antennas. In this paper, a modification to a standard multiple input single output scheme by integrating spatial modulation using simplified mathematical procedure is achieved. In the transmitter side, data and activation symbols are distributed simultaneously using mathematical module and floor functions. At the receiver, a simplified maximum likelihood detector is used to obtain transmitted pair of symbols. To verify this, MATLAB simulink is used to simulate a downlink system where spatial modulation is applied to a base station. Results for different transmit antenna number and modulation order are obtained in the form of bit error rate versus signal to noise ratio.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of 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.
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.
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.
A Potent MIMO–OFDM System Designed for Optimum BER and its Performance Anal...inventionjournals
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Performance Analysis of MIMO-OFDM System Using QOSTBC Code Structure for M-PSK
1. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 19
Performance Analysis of MIMO-OFDM System Using QOSTBC
Code Structure for M-PSK
Lavish Kansal lavish.s690@gmail.com
Electronics and Communication Engineering
Department Thapar University
Patiala (147004), INDIA
Ankush Kansal akansal@thapar.edu
Electronics and Communication Engineering
Department Thapar University
Patiala (147004), INDIA
Kulbir Singh ksingh@thapar.edu
Electronics and Communication Engineering
Department Thapar University
Patiala (147004), INDIA
Abstract
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.
Keywords: MIMO, OFDM, QOSTBC, M-PSK
1. INTRODUCTION
As the demand for high-data rate multimedia grows, several approaches such as increasing
modulation order or employing multiple antennas at both transmitter and receiver have been
studied to enhance the spectral efficiency. [1][2] In today’s communication systems Orthogonal
Frequency Division Multiplexing (OFDM) is a widespread modulation technique. Its benefits are
high spectral efficiency, robustness against inter-symbol interference, ease of implementation
using the fast Fourier transform (FFT) and simple equalization techniques. Recently, there have
been a lot of interests in combining the OFDM systems with the multiple-input multiple-output
(MIMO) technique. These systems are known as MIMO OFDM systems.
Spatially multiplexed MIMO is known to boost the throughput, on the other hand, when much
higher throughputs are aimed at, the multipath character of the environment causes the MIMO
channel to be frequency-selective. OFDM can transform such a frequency-selective MIMO
channel into a set of parallel frequency-flat MIMO channels and also increase the frequency
2. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 20
efficiency. Therefore, MIMO-OFM technology has been researched as the infrastructure for next
generation wireless networks. [3]
Therefore, MIMO-OFDM, produced by employing multiple transmit and receive antennas in an
OFDM system has becoming a practical alternative to single carrier and Single Input Single
Output (SISO) transmission.[4] However, channel estimation becomes computationally more
complex compared to the SISO systems due to the increased number of channels to be
estimated. This complexity problem is further compounded when the channel from the ith transmit
antenna to the mth receive antenna is frequency-selective. Using OFDM, information symbols are
transmitted over several parallel independent sub-carriers using the computationally efficient
IFFT/FFT modulation/demodulation vectors. [5]-[8]
These MIMO wireless systems, combined with OFDM, have allowed for the easy transmission of
symbols in time, space and frequency. In order to extract diversity from the channel, different
coding schemes have been developed. The seminal example is the Alamouti Space Time Block
(STB) code [9] which could extract spatial and temporal diversity. Many other codes have also
been proposed [10]–[12] which have been able to achieve some or all of the available diversity in
the channel at various transmission rates.
In open-loop schemes, there are generally two approaches to implement MIMO systems. One is
to increase the spatial transmit diversity (STD) by means of space-time coding and space-
frequency coding. Another is to raise the channel capacity by employing spatial division
multiplexing (SDM) that simultaneously transmits independent data symbols through multiple
transmit antennas. STD mitigates impairments of channel fading and noise, whereas SDM
increases the spectral efficiency. [13][14]
In section 2, general theory of OFDM and the necessary condition for orthogonality is discussed.
In section 2.1, the signal model of OFDM system with SISO configuration is discussed in detail
with the help of block diagram. In section 2.2, M-PSK (M-Phase Shift Keying) modulation
technique is discussed in detail. In section 2.3, different channels used for analyses purpose are
discussed namely AWGN and Rayleigh channel. In section 3, general theory about the MIMO
system is presented. In section 4, MIMO-OFDM system with QOSTBC is discussed. In section
4.1, general theory about QOSTBC and the proposed QOSTBC code structure for 8x8 antenna
configuration is presented. In section 4.2, idea about the linear detection technique i.e. Zero
Forcing equalization for MIMO-OFDM system is presented. Finally in section 5, the simulated
results based on the performance of MIMO-OFDM system in AWGN and Rayleigh channels have
been shown in the form of plots of BER vs SNR for M-PSK modulation and for different antenna
configurations.
2. ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (OFDM)
OFDM is a multi-carrier modulation technique where data symbols modulate a sub-carrier which
is taken from orthogonally separated sub-carriers with a separation of ‘fk’ within each sub-carrier.
Here, the spectra of sub-carrier is overlapping; but the sub-carrier signals are mutually
orthogonal, which is utilizing the bandwidth very efficiently. To maintain the orthogonality, the
minimum separation between the sub-carriers should be ‘fk’ to avoid ICI (Inter Carrier
Interference).
By choosing the sub-carrier spacing properly in relation to the channel coherence bandwidth,
OFDM can be used to convert a frequency selective channel into a parallel collection of
frequency flat sub-channels. Techniques that are appropriate for flat fading channels can then be
applied in a straight forward fashion .
3. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 21
2.1 OFDM Signal Model
Figure.1 shows the block diagram of a OFDM system with SISO configuration. Denote Xl ( l =
0,1,2,....,N −1) as the modulated symbols on the lth transmitting subcarrier of OFDM symbol at
transmitter, which are assumed independent, zero-mean random variables, with average power
.
The complex baseband OFDM signal at output of the IFFT can be written as:
xn = l (1)
where N is the total number of subcarriers and the OFDM symbol duration is T seconds.
FIGURE 1: Block Diagram of OFDM system
At the receiver, the received OFDM signal is mixed with local oscillator signal, with the frequency
offset deviated from Δf the carrier frequency of the received signal owing to frequency estimation
error or Doppler velocity, the received signal is given by:
n = (xn hn) + zn (2)
where hn, , and zn represent the channel impulse response, the corresponding frequency
offset of received signal at the sampling instants: Δf T is the frequency offset to subcarrier
frequency spacing ratio, and the AWGN respectively, while denotes the circular convolution.
Channel
Coding
Inter
leaving
Modulation S
/
P
I
F
F
T
P
/
S
Cyclic
Prefix
CHANNEL
Remove
Cyclic
Prefix
S
/
P
F
F
T
P
/
S
Demodulation De-Inter
leaving
Channel
Decoding
Source
Data
Receive
Data
4. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 22
Assuming that a cyclic prefix is employed; the receiver have a perfect time synchronization. Note
that a discrete Fourier transform (DFT) of the convolution of two signals in time domain is
equivalent to the multiplication of the corresponding signals in the frequency domain.
Then the output of the FFT in frequency domain signal on the kth receiving subcarrier becomes:
k = lHlYl - k + Zk , k=0,….,N-1
= XkHkU0 + HlYl - k + Zk (3)
The first term of (3) is a desired transmitted data symbol Xk. The second term represents the ICI
from the undesired data symbols on other subcarriers in OFDM symbol. Hk is the channel
frequency response and Zk denotes the frequency domain of zn. The term Yl - k is the coefficient of
FFT (IFFT), is given by:
Yl - k = (4)
when the channel is flat, Yl - k can be considered as a complex weighting function of the
transmitted data symbols in frequency domain. [15]
2.2 Different Modulations Techniques Used in OFDM System
Modulation is the process of mapping the digital information to analog form so it can be
transmitted over the channel. Consequently every digital communication system has a modulator
that performs this task. Closely related to modulation is the inverse process, called demodulation,
done by the receiver to recover the transmitted digital information. [16]
Modulation of a signal changes binary bits into an analog waveform. Modulation can be done by
changing the amplitude, phase, and frequency of a sinusoidal carrier. There are several digital
modulation techniques used for data transmission. The nature of OFDM only allows the signal to
modulate in amplitude and phase.
There can be coherent or non-coherent modulation techniques. Unlike non-coherent modulation,
coherent modulation uses a reference phase between the transmitter and the receiver which
brings accurate demodulation together with receiver complexity. [17]
2.2.1 Phase Shift Keying
Phase-shift keying (M-PSK) for which the signal set is:
Si(t)= *(cos (2π*fc + 2 )) (5)
i=1,2,…..M & 0 < t < Ts
where Es the signal energy per symbol Ts is the symbol duration, and fc is the carrier frequency.
This phase of the carrier takes on one of the M possible values, namely
θi = 2(i-1)π/M where i=1,2,…,M
An example of signal-space diagram for 8-PSK is shown in figure 2
5. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 23
FIGURE 2 : Signal-space diagram for 8-PSK
2.3 CHANNELS
Wireless transmission uses air or space for its transmission medium. The radio propagation is not
as smooth as in wire transmission since the received signal is not only coming directly from the
transmitter, but the combination of reflected, diffracted, and scattered copies of the transmitted
signal.
Reflection occurs when the signal hits a surface where partial energy is reflected and the
remaining is transmitted into the surface. Reflection coefficient, the coefficient that determines the
ratio of reflection and transmission, depends on the material properties.
Diffraction occurs when the signal is obstructed by a sharp object which derives secondary
waves. Scattering occurs when the signal impinges upon rough surfaces, or small objects.
Received signal is sometimes stronger than the reflected and diffracted signal since scattering
spreads out the energy in all directions and consequently provides additional energy for the
receiver which can receive more than one copies of the signal in multiple paths with different
phases and powers. Reflection, diffraction and scattering in combination give birth to multipath
fading. [18]
2.3.1 AWGN Channel
Additive white Gaussian noise (AWGN) channel is a universal channel model for analyzing
modulation schemes. In this model, the channel does nothing but add a white Gaussian noise to
the signal passing through it. This implies that the channel’s amplitude frequency response is flat
(thus with unlimited or infinite bandwidth) and phase frequency response is linear for all
frequencies so that modulated signals pass through it without any amplitude loss and phase
distortion of frequency components. Fading does not exist. The only distortion is introduced by
the AWGN. AWGN channel is a theoretical channel used for analysis purpose only.
The received signal is simplified to:
r(t) = s(t) + n(t) (6)
where n(t) is the additive white Gaussian noise. [18]
2.3.2 Rayleigh Fading Channel
Constructive and destructive nature of multipath components in flat fading channels can be
approximated by Rayleigh distribution if there is no line of sight which means when there is no
direct path between transmitter and receiver. The received signal can be simplified to:
6. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 24
r(t) = s(t)*h(t) + n(t) (7)
where h(t) is the random channel matrix having Rayleigh distribution and n(t) is the additive
white Gaussian noise. The Rayleigh distribution is basically the magnitude of the sum of two
equal independent orthogonal Gaussian random variables and the probability density function
(pdf) given by:
p(r) = 0 (8)
where σ2
is the time-average power of the received signal. [19][20]
3. MULTI INPUT MULTI OUTPUT (MIMO) SYSTEMS
Multi-antenna systems can be classified into three main categories. Multiple antennas at the
transmitter side are usually applicable for beam forming purposes. Transmitter or receiver side
multiple antennas for realizing different (frequency, space) diversity schemes. The third class
includes systems with multiple transmitter and receiver antennas realizing spatial multiplexing
(often referred as MIMO by itself).
In radio communications MIMO means multiple antennas both on transmitter and receiver side of
a specific radio link. In case of spatial multiplexing different data symbols are transmitted on the
radio link by different antennas on the same frequency within the same time interval. Multipath
propagation is assumed in order to ensure the correct operation of spatial multiplexing, since
MIMO is performing better in terms of channel capacity in a rich scatter multipath environment
than in case of environment with LOS (line of sight). This fact was spectacularly shown in [21].
MIMO transmission can be characterized by the time variant channel matrix:
H( ) = (9)
where the general element, hnt,nr (τ, t) represents the complex time-variant channel transfer
function at the path between the nt-th transmitter antenna and the nr-th receiver antenna. NT and
NR represent the number of transmitter and receiver antennas respectively.
Derived from Shannon’s law, for the capacity of MIMO channel the following expression was
proven in [21] and [22]:
C = (det (I + H Rss HH)) (10)
where H denotes the channel matrix and HH its transpose conjugate, I represents the identity
matrix and Rss the covariance matrix of the transmitted signal s.
7. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 25
Transmitting antennas MIMO-channels Receiving antennas
Tx 1 Rx 1
Tx 2 Rx 2
Tx M Rx N
FIGURE 3: Block Diagram of a generic MIMO system with M transmitters and N receivers
4. MIMO-OFDM WITH QUASSI ORTHOGONAL SPACE TIME BLOCK
CODING (QOSTBC)
MIMO-OFDM systems with orthogonal space–time block coding (O-STBC) [12] are particularly
attractive due to the fact that they require a relatively simple linear decoding scheme while still
providing full diversity gain . Unfortunately, they suffer from a lower code rate when a complex
signal constellation and the complexity that more than two transmit antennas are used. To
overcome the disadvantages of O-STBC, quasi-orthogonal space–time block coding (QO-STBC)
was proposed in the literature [23]-[24] and the existing works have shown that QO-STBC offers
a higher data rate and partial diversity gain.
To design a QO-STBC with full diversity gain, an improved QO-STBC through constellation
rotation was proposed in [25] and [26].Maximum-likelihood (ML) decoding in QO-STBC works
with pairs of transmitted symbols, leading to an increase in decoding complexity with modulation
level M2. This subsequently increases transmission delay when a high-level modulation scheme
or multiple antennas are employed. Sung et al. [27] proposed a method to improve the QO-STBC
performance with iterative decoding, which of course achieves higher reliability but increases
decoding complexity. In [28]–[32], some new decoding methods were proposed to reduce the
computational complexity.
4.1 Quassi Orthogonal Space Time Block Codes
Consider a system with eight transmit antennas (i.e. M = 4) and 4 receive antennas (i.e. N=4). In
what follows, assume that perfect channel state information (CSI) is available at the receiver but
unavailable at the transmitter. Also assume that the channel is quasi-static, i.e. the channel
coefficients are constant within one block of code transmission and independently realized from
block to block. Let A12 and A34 be Alamouti code as in [9]
A12 = and A34 =
Here the subscript 12 and 34 are used to represent the indeterminate s1, s2, s3 and s4 in the
transmission matrix. Now consider the space time block code for M and N equals to 4 according
the method given in [24], the matrix for 4X4 antenna configuration can also be constructed as
follows :
B = = (11)
Note that it has been proven in [33] maximum diversity of the order of 4*N for a rate one code is
impossible in this case. Now, suppose Vi, i = 1 ,2…..4 as the ith column of Q, it is easy to see that
8. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 26
(12)
Where = is the inner product of vectors Vi and Vj . Therefore, the subspace
created by V1 and V4 is orthogonal to the subspace created by V2 and V3 , and similar is true for
other columns as given by equation(11).
4.2 Signal Detection of Mimo-ofdm System
Signal detection of MIMO-OFDM system can be carried out by various sub-carrier channel signal
detection. Although the whole channel is a frequency-selective fading, but various sub-carriers
channel divided can be regarded as flat fading, so the flat fading MIMO signal detection algorithm
for MIMO-OFDM system can be directly into the detection of all sub-channels, and signal
detection algorithm of the corresponding MIMO-OFDM system can be obtained. Similarly, the
other optimization algorithms used in flat fading MIMO signal detection can also be leaded into
the MIMO-OFDM system. MIMO-OFDM detection methods consist of linear and nonlinear
detection test.
4.2.1 Zero Forcing Algorithm [34]
Zero Forcing algorithm is regard the signal of each transmitting antenna output as the desired
signal, and regard the remaining part as a disturbance, so the mutual interference between the
various transmitting antennas can be completely neglected. The specific algorithm is as follows:
For k = 0, 1, 2,………….,K-1, so that,
R(k) = [R1(k),R2(k),…….……..,RN(k)]T (13)
S(k) = [S1(k),S2(k),…………….,SM(k)]T (14)
N(k) = [N1(k),N2(k),……...……,NN(k)]T (15)
H(k) = (16)
Here R(k), S(k), N(k) respectively express output signal, the input signal and noise vector of the k
sub-channels in MIMO-OFDM system, for M transmitting antennas and N receiving antennas,
H(k) expresses channel matrix of the k sub-channels, mathematical expression of sub-channel in
the MIMO-OFDM system is as follows:
9. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 27
R(k) = H(k)S(k) + N(k) (17)
S1(k) R1(k) (k)
S2(k) R2(k) (k)
SM(k) RN(k) (k)
FIGURE 4: Baseband block diagram of k subcarrier channel in MIMO-OFDM system
There is a linear relationship between input signal S(k) and output signal R(k), that is similar to
the flat fading channel for each subcarrier channel in MIMO-OFDM system. Its equivalent block
diagram is shown in Figure 4. Therefore, signal detection can be transformed into K sub-channels
in their signal detection to complete in MIMO-OFDM system and each sub-channel detection of
the above can be used flat fading MIMO channel to achieve the detection algorithm.
Zero-forcing (ZF) detection algorithm for MIMO detection algorithm is the most simple and basic
algorithms, and the basic idea of zero forcing algorithm is get rid of MIMO-channel interference by
multiplying received signal and the inverse matrix of channel matrix. Zero-Forcing solution of
MIMO-OFDM system is as follows:
SZF = H-1 R = S + H-1 N (18)
In which H-1 is the channel matrix for the generalized inverse matrix, the type is obtained for hard-
decision demodulation after that to be the source signal estimates:
ZF = E(SZF) (19)
5. SIMULATION RESULTS DISCUSSIONS
The system discussed above has been designed and results are shown in the form of SNR vs
BER plot for different modulations and different channels. Here different antenna configurations
such as 1x1, 2x2 are used to show the advantage in term of SNR of using 4X4 antenna
configuration over the other configurations. The analyses have been done for three channels
AWGN and Rayleigh channel.
Sub-
carrier
channel
H(k)
Sub-
channel
detection
Channel
Estimation
10. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 28
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 32-PSK in AWGN channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 5: (a)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 64-PSK in AWGN channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 5: (b)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 128-PSK in AWGN channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 5: (c)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 256-PSK in AWGN channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 5: (d)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 512-PSK in AWGN channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 5: (e)
Figure 5 (a)-(e): SNR vs BER plots for PSK
over AWGN channel for MIMO-OFDM system
employing different antenna configurations (a)
32-PSK (b) 64-PSK (c) 128-PSK (d) 256-PSK
(e) 512-PSK.
SNR vs BER plots for M-PSK over AWGN channel for MIMO-OFDM system employing different antenna
configurations are presented in Figure 5. Here the graph depicts that in MIMO-OFDM system as we goes
on increasing the no. of Transmitters and Recievers the BER keeps on decreasing due to space diversity
and the proposed system provide better BER performance as compared to the other antenna
configurations.
11. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 29
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 32-PSK in RAYLEIGH channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 6: (a)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 64-PSK in RAYLEIGH channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 6: (b)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 128-PSK in RAYLEIGH channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 6
(c)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 256-PSK in RAYLEIGH channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 6: (d)
0 10 20 30 40 50 60 70 80 90
10
-3
10
-2
10
-1
10
0
signal to noise ratio
biterrorrate
SNR vs BER plot for MIMO-OFDM FOR 512-PSK in RAYLEIGH channel
1 TX x 1 RX
2 TX x 2 RX
4 TX x 4 RX
FIGURE 6: (e)
Figure 6 (a)-(e): SNR vs BER plots for PSK
over Rayleigh channel for MIMO-OFDM system
employing different antenna configurations (a)
32-PSK (b) 64-PSK (c) 128-PSK (d) 256-PSK
(e) 512-PSK.
In Figure 6 SNR vs BER plots for M-PSK over Rayleigh channel for MIMO-OFDM system employing
different antenna configurations are presented. It can be concluded from the graphs that in MIMO-
OFDM system as we goes on increasing the no. of Transmitters and Recievers the BER keeps on
decreasing due to space diversity and the proposed system provide better BER performance as
compared to the other antenna configurations. But here BER is greater than the AWGN channel.
12. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 30
Table 1 shows the improvement in terms of decibels shown by proposed system employing QOSTBC
code structure for 4X4 antenna configuration over the system employing QOSTBC code structure for 2X2
antenna configuration for different modulation schemes over different environments (channels).
Different
Modulations
For AWGN
Channel
For Rayleigh
Channel
32-PSK 3.22 dB 3.85 dB
64-PSK 5.02 dB 3.42 dB
128-PSK 4.75 dB 3.88 dB
256-PSK 6.5 dB 4.98 dB
512-PSK 3.42 dB 3.05 dB
TABLE 1: Table showing the improvement in terms of dB, by using the proposed QOSTBC code
structure (for 4X4 antenna configuration) for different Modulations and for different Channels.
7. CONCLUSION
In this paper, an idea about the performance of the MIMO-OFDM systems at higher modulation levels
and for different antenna configurations is presented. MIMO-OFDM system can be implemented using
higher order modulations to achieve large data capacity. But there is a problem of BER (bit error rate)
which increases as the order of the modulation increases. The solution to this problem is to increase the
value of the SNR so, that the effect of the distortions introduced by the channel will also goes on
decreasing, as a result of this, the BER will also decreases at higher values of the SNR for high order
modulations.
The motive of using high order antenna configuration (4X4) is to increase the space diversity, which will
automatically lower the BER at given SNR as compared to lower order Antenna configuration (1x1, 2x2).
By doing so, higher data capacity at any given SNR can be achieved. The proposed MIMO-OFDM system
with 4X4 antenna configuration provides better performance in terms of SNR as compared to the MIMO-
OFDM system with 2X2 antenna configuration at a BER of 10
-2
.
8. REFERENCE
[1] H. Jiang and P. A. Wilford, "A hierarchical modulation for upgrading digital broadcasting systems",
IEEE Transaction on Broadcasting, vol. 51, pp. 222-229, June 2005.
[2] P. W. Wolniansky, G. J. Foschini, G. D. Golden and R. A. Valenzuela, "V-BLAST: an architecture for
realizing very high data rates over the rich- scattering wireless channel," In Proceeding of
International symposium on Signals, Systems and Electronics, October 1998, pp. 259-300.
[3] M. Jiang and L. Hanzo, “Multiuser MIMO-OFDM for next generation wireless systems,” In Proceedings
of IEEE, vol. 95, pp.1430-1469, July 2007.
[4] C. C. Tu and B. Champagne, “Subspace Blind MIMO-OFDM Channel Estimation with Short Averaging
Periods: Performance Analysis,” In Proceeding of IEEE Conference on Wireless Communications
and Networking, (Las Vegas, NV) April 2008, pp. 24–29.
[5] A. Tarighat and A. H. Sayed, “MIMO OFDM receivers for systems with IQ imbalances”, IEEE
Transactions on Signal Processing, vol. 53, pp. 3583–3596, September 2005.
[6] P. Rabiei, W. Namgoong and N. Al-Dhahir, “Frequency domain joint channel and phase noise
estimation in OFDM WLAN systems,” In Proceeding of Asilomar Conference on Signals, Systems
and Computers, (Pacific Grove, CA)October 2008, pp. 928–932.
[7] A. Tarighat, R. Bagheri and A. H. Sayed, “Compensation schemes and performance analysis of IQ
imbalances in OFDM receivers,” IEEE Transactions on Signal Processing, vol. 53, pp. 3257–3268,
August 2005.
13. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 31
[8] S. Wu and Y. Bar-Ness, “OFDM systems in the presence of phase noise: Consequences and
solutions,” IEEE Transactions on Communications, vol. 52, pp. 1988–1996, November 2004.
[9] S. Alamouti, “A simple transmit diversity technique for wireless communications,” IEEE Journal on
Selected Areas Communication., vol. 16, pp. 1451–1458, October 1998.
[10] H. El Gamal and A. R. Hammons, “On the design of algebraic space time codes for MIMO block-
fading channels,” IEEE Transaction on Information Theory, vol. 49, pp. 151–163, 2003.
[11] W. Su, Z. Safar and K. J. R. Liu, “Towards maximum achievable diversity in space, time, and
frequency: performance analysis and code design,” IEEE Transaction on Wireless Communication,
vol. 4, pp. 1847–1857, 2005.
[12] V. Tarokh, N. Seshadri and A. R. Calderbank, “Space–time codes for high data rate wireless
communication: Performance criterion and code construction,” IEEE Transaction on Information
Theory, vol. 44, pp. 744–765, March 1998.
[13] R. Y. Mesleh, H. Haas, S. Sinanovic, C. W. Ahn and S. Yun, "Spatial modulation”, IEEE Transaction
on Vehicular Technology, vol. 57, pp. 2228-2241, July 2008.
[14] J. Jeganathan, A. Ghrayeb, and L. Szczecinski, "Spatial modulation: Optimal detection and
performance analysis," IEEE Communication Letters, vol. 12, pp. 545-547, August 2008.
[15] A. Yiwleak and C. Pirak, “Intercarrier Interference Cancellation Using Complex Conjugate
Technique for Alamouti-Coded MIMO-OFDM Systems” In Proceeding of International conference on
Electrical Engineering/Electronics Computer Telecommunications and Information Technology,
(Chaing Mai) 2010, pp-1168-1172.
[16] P. S. Mundra , T. L. Singal and R. Kapur, “The Choice of A Digital Modulation ,Schemes in A
Mobile Radio System”, In proceedings of IEEE Vehicular Technology Conference, ( Secaucus,
NJ)1993, pp 1-4.
[17] W.A.C. Fernando, R.M.A.P. Rajatheva and K. M. Ahmed, “Performance of Coded OFDM with Higher
Modulation Schemes”, In proceedings of International Conference on Communication Technology,
Vol. 2, (Beijing)1998, pp 1-5.
[18] J. J. V. de Beek, O. Edfors, M. Sandell, S.K. Wilson and P.O. Borjesson, “On channel estimation in
OFDM systems” , In proceedings of 45th
IEEE Vehicular Technology Conference, Vol. 2, (Chicago,
IL)1995, pp 815-819.
[19] S. Kaiser, “On the performance of different detection techniques for OFDM-CDMA in fading
channels”, In proceedings of IEEE Global Telecommunication Conference, Vol. 3, 1995, pp 2059-
2063.
[20] H.B. Voelcker , “Phase-shift keying in fading channels” , In IEEE Proceeding on Electronics and
Communication Engineering, Vol. 107, 1960, pp 31-38.
[21] A. van Zelst and T. C. W. Schenk, “Implementation of a MIMO OFDM-Based Wireless LAN System,”
IEEE Transaction on Signal Processing, Vol. 52, pp 483-494, February 2004.
[22] D. S. Shiu, G. J. Foschini, M. J. Gans, and J. M. Kahn, “Fading correlation and its effect on the
capacity of multi element antenna systems”, IEEE Transactions on Communications, vol. 48, pp.
502–513, 2000.
[23] C. B. Papadias and G. J. Foschini, “A space–time coding approach for systems employing four
transmit antennas,” In Proceeding of IEEE International Conference on Acoustics, Speech and
Signal Processing, vol. 4, (Salt Lake City, UT)2001, pp. 2481–2484.
14. Lavish Kansal, Ankush Kansal & Kulbir Singh
Signal Processing: An International Journal (SPIJ), Volume (5) : Issue (2) : 2011 32
[24] H. Jafarkhani, “A quasi-orthogonal space–time block code,” IEEE Transaction on Communication,
vol. 49, pp. 1–4, January 2001.
[25] W. Su and X. G. Xia, “Signal constellations for quasi-orthogonal space–time block codes with full
diversity”, IEEE Transaction on Information Theory, vol. 50, pp. 2331–2347, October 2004.
[26] N. Sharma and C. B. Papadias, “Improved quasi-orthogonal codes through constellation rotation”
IEEE Transaction on Communication, vol. 51, pp. 332–335, March 2003.
[27] C. K. Sung, J. Kim, and I. Lee, “Quasi-orthogonal STBC with iterative decoding in bit interleaved
coded modulation,” In Proceeding of IEEE conference on Vehicular Technology, vol. 2, September
2004, pp. 1323–1327.
[28] J. Kim and I. Lee, “Space–time coded OFDM systems with four transmit antennas,” In Proceeding of
IEEE conference on Vehicular Technology, vol. 2, September 2004, pp. 2434–2438.
[29] C. Yuen, Y. Wu, and S. Sun, “Comparative study of open-loop transmit diversity schemes for four
transmit antennas in coded OFDM systems,” In Proceeding of IEEE conference on Vehicular
Technology, (Baltimore, MD) September 2004, pp. 482–485.
[30] C. Yuen, Y. L. Guan, and T. T. Tjhung, “Quasi-orthogonal STBC with minimum decoding complexity”
IEEE Transaction on Wireless Communication, vol. 4, pp. 2089–2094, September 2005.
[31] M. T. Le, V. Su Pham, L. Mai, and G. Yoon, “Low-complexity maximum likelihood decoder for four-
transmit-antenna quasi-orthogonal space–time block code,” IEEE Transaction on Communication,
vol. 53, pp. 1817–1821, November 2005.
[32] L. He and H. Ge, “Fast maximum likelihood decoding of quasi-orthogonal codes” In Proceeding of
Asilomar Conference Signals, Systems, Computer, vol. 1, Nov. 2003, pp. 1022–1026.
[33] V. Tarokh, H. Jafarkhani, and A. R. Calderbank, “Space-time block codes from orthogonal designs”
IEEE Transactions on Information Theory, vol. 45, pp. 1456–1467, July 1999.
[34] X. Zhang, Y. Su and G. Tao, “Signal Detection Technology Research of MIMO-OFDM System” In
Proceeding of International Congress on Image and Signal Processing, Vol.7, Issue 11, (Yantai)
2010, pp 3031-3034.