Modern wireless communication systems support high speed multimedia services. These services require
high data rates with acceptable error rates. Orthogonal Frequency Division Multiplexing (OFDM) is a
capable candidate to solve this problem. In this paper, a new expression for the BER of OFDM system has
been derived over Nakagami–n (Rice) fading channels using characteristics function (CHF) approach. The
exact probability density function of first order of Nakagami-n (Rice) random vector is used to derive the
expression for the error rates of OFDM system. The BER derivation of Rician fading channel is slightly
more complex compared to the Nakagami–m distribution because the PDF of the Rician RV contains an
explicit term of a modified Bessel function of first kind. Earlier, this problem was solved by replacing the
Bessel function with its infinite series and exponential integral representation. Here we propose an integral
expression to remove the complexity of the expression.
This document describes modeling mobile radio channels in MATLAB. It introduces concepts for modeling flat fading channels using user-defined m-files. Typical small-scale fading channel models like uncorrelated Rician and Rayleigh fading with Doppler shift are derived. MATLAB code is provided to generate uncorrelated and correlated fading samples. The code also approximates cumulative distribution functions and compares them to analytical distributions. Finally, a Monte Carlo simulation example of digital modulation over a Rician fading channel is presented.
Lantiq/Intel Contributions to G.fast at Scientific ConferencesLantiq
This document summarizes research on achievable data rates for hybrid copper/fiber networks using G.fast technology. It finds that linear precoding methods like zero-forcing perform well for shorter copper line lengths, while nonlinear methods have advantages for longer lines. The work analyzes performance losses from implementation limitations and proposes optimizing the transmit spectrum to improve achievable rates by incorporating these limitations into the optimization process. Rate-reach curves are generated based on a statistical channel model and constraints from the G.fast standard.
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.
MODIFIED LLL ALGORITHM WITH SHIFTED START COLUMN FOR COMPLEXITY REDUCTIONijwmn
Multiple-input multiple-output (MIMO) systems are playing an important role in the recent wireless
communication. The complexity of the different systems models challenge different researches to get a good
complexity to performance balance. Lattices Reduction Techniques and Lenstra-Lenstra-Lovàsz (LLL)
algorithm bring more resources to investigate and can contribute to the complexity reduction purposes.
In this paper, we are looking to modify the LLL algorithm to reduce the computation operations by
exploiting the structure of the upper triangular matrix without “big” performance degradation. Basically,
the first columns of the upper triangular matrix contain many zeroes, so the algorithm will perform several
operations with very limited income. We are presenting a performance and complexity study and our
proposal show that we can gain in term of complexity while the performance results remains almost the
same.
Design and Implementation of Efficient Analysis and Synthesis QMF Bank for Mu...TELKOMNIKA JOURNAL
The present section deals with a new type of technique for designing an efficient two channel Quadrature Mirror Filter Bank with constant phase in frequency. For achieving the Perfect Reconstruction Condition in Filter bank, an attempt has been made to design the low pass prototype filter with its impulse response and frequency response in three regions namely pass band, stop band and transition band region. With the error in terms of Reconstruction and the attenuation in the stop band as seen in the prototype filter response, one can evaluate the performance of the introduced filter with the help of filter coefficients generated in the design examples that affects the quality of filter bank design under the constraints of Near Perfect Reconstruction Conditions.
IRJET- High Speed Multi-Rate Approach based Adaptive Filter using Multiplier-...IRJET Journal
This document presents a high-speed multi-rate approach for an adaptive filter using a multiplier-less technique. The proposed approach uses decimator and interpolator structures in VHDL to design a narrow band filter. Each structure is simulated using an FPGA and compared to existing structures. The resulting structure is more hardware efficient and uses fewer logic slices than existing structures. Key aspects of multi-rate signal processing and the proposed narrow band filter design using decimation and interpolation are discussed. Simulation results show the proposed approach reduces hardware complexity and resource usage compared to direct-form implementation of the filter.
On Channel Estimation of OFDM-BPSK and -QPSK over Nakagami-m Fading ChannelsCSCJournals
This paper evaluates the performance of OFDM - BPSK & -QPSK based system with and without channel estimation over Nakagami-m fading channels. Nakagami-m variants are generated by decomposition of Nakagami random variable into orthogonal random variables with Gaussian distribution envelopes. Performance of OFDM system in Nakagami channel has been reported here. The results yield the optimum value of m based on BER and SNR. Using this optimum value of m, Channel estimation over flat fading has been reported here. It has been depicted clearly from simulated graphs that channel estimation has further reduced the BER. However, threshold value of m has played a vital role during channel estimation.
Orthogonal Frequency Division Multiplexing (OFDM) is of great interest for the development of
the fifth-generation technology. It is the cornerstone of Multiple-input multiple-output (MIMO) systems.
Even though inter carrier interference (ICI) and inter symbol interference (ISI) have been processed for
the fourth-generation standards, they still present a huge problem for the fifth-generation standards. This
paper explores the tradeoff between the length of the cyclic prefix and the performances of the OFDM
system. It also studies the effect of carrier frequency offset (CFO) on OFDM systems. A blind frequency
offset estimator that uses the correlations between the remodulated sequence in the receiver side and
the conventional received symbol is presented and a closed form solution is derived. The proposed
estimator is derived under short interval when the correlation is high, so it has low computational
complexity. Lin and Beek’s estimators are used for comparison. Simulations demonstrate the effectiveness
of the proposed estimator under Rayleigh fading channel.
This document describes modeling mobile radio channels in MATLAB. It introduces concepts for modeling flat fading channels using user-defined m-files. Typical small-scale fading channel models like uncorrelated Rician and Rayleigh fading with Doppler shift are derived. MATLAB code is provided to generate uncorrelated and correlated fading samples. The code also approximates cumulative distribution functions and compares them to analytical distributions. Finally, a Monte Carlo simulation example of digital modulation over a Rician fading channel is presented.
Lantiq/Intel Contributions to G.fast at Scientific ConferencesLantiq
This document summarizes research on achievable data rates for hybrid copper/fiber networks using G.fast technology. It finds that linear precoding methods like zero-forcing perform well for shorter copper line lengths, while nonlinear methods have advantages for longer lines. The work analyzes performance losses from implementation limitations and proposes optimizing the transmit spectrum to improve achievable rates by incorporating these limitations into the optimization process. Rate-reach curves are generated based on a statistical channel model and constraints from the G.fast standard.
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.
MODIFIED LLL ALGORITHM WITH SHIFTED START COLUMN FOR COMPLEXITY REDUCTIONijwmn
Multiple-input multiple-output (MIMO) systems are playing an important role in the recent wireless
communication. The complexity of the different systems models challenge different researches to get a good
complexity to performance balance. Lattices Reduction Techniques and Lenstra-Lenstra-Lovàsz (LLL)
algorithm bring more resources to investigate and can contribute to the complexity reduction purposes.
In this paper, we are looking to modify the LLL algorithm to reduce the computation operations by
exploiting the structure of the upper triangular matrix without “big” performance degradation. Basically,
the first columns of the upper triangular matrix contain many zeroes, so the algorithm will perform several
operations with very limited income. We are presenting a performance and complexity study and our
proposal show that we can gain in term of complexity while the performance results remains almost the
same.
Design and Implementation of Efficient Analysis and Synthesis QMF Bank for Mu...TELKOMNIKA JOURNAL
The present section deals with a new type of technique for designing an efficient two channel Quadrature Mirror Filter Bank with constant phase in frequency. For achieving the Perfect Reconstruction Condition in Filter bank, an attempt has been made to design the low pass prototype filter with its impulse response and frequency response in three regions namely pass band, stop band and transition band region. With the error in terms of Reconstruction and the attenuation in the stop band as seen in the prototype filter response, one can evaluate the performance of the introduced filter with the help of filter coefficients generated in the design examples that affects the quality of filter bank design under the constraints of Near Perfect Reconstruction Conditions.
IRJET- High Speed Multi-Rate Approach based Adaptive Filter using Multiplier-...IRJET Journal
This document presents a high-speed multi-rate approach for an adaptive filter using a multiplier-less technique. The proposed approach uses decimator and interpolator structures in VHDL to design a narrow band filter. Each structure is simulated using an FPGA and compared to existing structures. The resulting structure is more hardware efficient and uses fewer logic slices than existing structures. Key aspects of multi-rate signal processing and the proposed narrow band filter design using decimation and interpolation are discussed. Simulation results show the proposed approach reduces hardware complexity and resource usage compared to direct-form implementation of the filter.
On Channel Estimation of OFDM-BPSK and -QPSK over Nakagami-m Fading ChannelsCSCJournals
This paper evaluates the performance of OFDM - BPSK & -QPSK based system with and without channel estimation over Nakagami-m fading channels. Nakagami-m variants are generated by decomposition of Nakagami random variable into orthogonal random variables with Gaussian distribution envelopes. Performance of OFDM system in Nakagami channel has been reported here. The results yield the optimum value of m based on BER and SNR. Using this optimum value of m, Channel estimation over flat fading has been reported here. It has been depicted clearly from simulated graphs that channel estimation has further reduced the BER. However, threshold value of m has played a vital role during channel estimation.
Orthogonal Frequency Division Multiplexing (OFDM) is of great interest for the development of
the fifth-generation technology. It is the cornerstone of Multiple-input multiple-output (MIMO) systems.
Even though inter carrier interference (ICI) and inter symbol interference (ISI) have been processed for
the fourth-generation standards, they still present a huge problem for the fifth-generation standards. This
paper explores the tradeoff between the length of the cyclic prefix and the performances of the OFDM
system. It also studies the effect of carrier frequency offset (CFO) on OFDM systems. A blind frequency
offset estimator that uses the correlations between the remodulated sequence in the receiver side and
the conventional received symbol is presented and a closed form solution is derived. The proposed
estimator is derived under short interval when the correlation is high, so it has low computational
complexity. Lin and Beek’s estimators are used for comparison. Simulations demonstrate the effectiveness
of the proposed estimator under Rayleigh fading channel.
A SEMI BLIND CHANNEL ESTIMATION METHOD BASED ON HYBRID NEURAL NETWORKS FOR UP...ijwmn
The paper describes how to improve channel estimation in Single Carrier Frequency Division Multiple
Access (SC-FDMA) system, using a Hybrid Artificial Neural Networks (HANN). The 3rd Generation
Partnership Project (3GPP) standards for uplink Long Term Evolution Advanced (LTE-A) uses pilot based
channel estimation technique. This kind of channel estimation method suffers from a considerable loss
ofbitrate due to pilot insertion; all data frame sent contains reference signal. The HANN converts data
aided channel estimator to semi blind channel estimator. To increase convergence speed, HANN uses some
channel propagation Fuzzy Rules to initialize Neural Network parameters before learning instead of a
random initialization, so its learning phase ismore rapidly compared to classic ANN.HANN allows more
bandwidth efficient and less complexity. Simulation results show that HANN has better computational
efficiency than the Minimum Mean Square Error (MMSE) estimator and has faster convergence than
classic Neural Networks estimators.
COMPARING VARIOUS CHANNEL ESTIMATION TECHNIQUES FOR OFDM SYSTEMS USING MATLABijwmn
This document compares the performance of five channel estimation techniques for OFDM systems over quasi-static channels using MATLAB simulations. The techniques evaluated are: decision directed (DD), linear interpolation, second-order interpolation, discrete Fourier transform (DFT) interpolation, and minimum mean square error (MMSE) interpolation. Simulation results show that DD channel estimation provides the lowest bit-error rate and mean square error, but has extra processing delay and is sensitive to channel variations. MMSE interpolation outperforms the other interpolation techniques.
This document describes a method for maximizing the total throughput of a two-way relay network using orthogonal frequency-division multiplexing (OFDM). The method jointly optimizes subcarrier pairing and relay selection by formulating the problem as a maximum weighted bipartite matching problem, which can be solved in polynomial time. Simulation results show that the proposed method increases total throughput compared to benchmark methods, especially as the number of relays increases. The throughput is evaluated for different numbers of subcarriers and relays to analyze the system's performance under various conditions.
Performance of Multiple symbol representation with clipping scheme for PAPR r...ijsrd.com
OFDM is one of the multicarrier modulation technique used in various communication systems. The major problem one faces while implementing this system is the high peak to average power .For an efficient OFDM system this PAPR should be low. In this paper a hybrid PAPR (peak to average power ratio) reduction technique for the OFDM (orthogonal frequency division multiplexing) signal which combines a multiple symbol representations method with a signal clipping method is proposed. In multiple symbol representations alternative signaling points are used to represent one symbol and PAPR is further reduced with the clipping scheme. The performance of the hybrid scheme is compared with the partial transmit sequence which is one of the other PAPR reduction scheme. In partial transmit sequence the input data is divided in to disjoint blocks transformed in to time domain sequence and rotated by phase factors. Theoretical analysis and simulation results validate that the proposed scheme has the ability to provide large PAPR reduction, low bit error rate. Performance analysis is also done with the partial transmit sequence scheme.
This document summarizes a research paper that investigates reducing peak-to-average power ratio (PAPR) in an MC-CDMA system using partial transmit sequence (PTS) technique with a suboptimal combination algorithm. The paper simulates a downlink MC-CDMA system with BPSK and QPSK modulation under varying system parameters like number of users and phase sequences. Results show the complementary cumulative distribution function (CCDF) of PAPR for the original and PTS-processed signals. Using PTS with 4, 8, or 16 phase sequences provides 1dB, 2dB, and 4.2dB of PAPR reduction respectively compared to the original signal for a 8-user BPSK modulated MC-CD
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.
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
New Technique Combining the Tone Reservation Method with Clipping Technique t...IJECEIAES
Nonlinear distortions and impairments appear in multicarrier signal with high fluctu- ations when amplified by a Radio Frequency Power Amplifier (RF PA). This article is a contribution to improving the Tone Reservation (TR) method dedicated to reducing fluctuations in the Orthogonal Frequency Division Multiplexing (OFDM) modulation. This method exploits the null sub-carriers in communications standards in order to generate a correction signal used to reduce the Peak-to-Average Power Ratio (PAPR) with nevertheless limited performances due to the reduced number of these sub-carriers. For this purpose, our contribution is to combine the TR method with the Clipping (CL) method to improve the PAPR reduction without significantly impacting the quality of transmissions. We also show the gain provided by this strategy compared to the use of classical methods. Experiments using a simulated example on a complete WiMax 802:16e transmitter have been made in order to investigate the PAPR reduction performances on presence of the non-linear Power Amplifier model based on gain compression response and phase distortion.
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.
Narrowband Spectrum Sensing for Different Fading Channels for Cognitive Radio...IJMERJOURNAL
Abstract: Nowadays the demand of applications of wireless communication has increased rapidly which causes the scarcity of radio spectrum. To empower future wireless communication services, the radio spectrum management is a very important factor. Cognitiveradio is a promising technology which provides an innovative way to improve utilization efficiency of available electromagnetic spectrum by sensing spectrum and shares it without harmful interference to other users. Narrowband spectrum sensing is the technique where the bandwidth of active primary transmitter in the vicinity of cognitive radio is less than the coherence bandwidth of channel. Fading is one of the greatest impairment of narrowband spectrum sensing. It is deflection of the attenuation. It influences a signal over certain propagation media.A communication channel that experiences fading isknown as fading channel. The effects of fading can be reduced by several fading models. In this paper, performanceanalysis of several realistic fading models on narrowband channel using energy detection method is employed. Finally, performance comparison of various fading models is guaranteed through simulation.
This document simulates and analyzes the Nakagami fading channel using MATLAB. It begins by introducing multipath fading channel models including Rayleigh, Ricean, and Nakagami distributions. It then uses MATLAB to simulate the complex envelope, level crossing rates, and average fade durations of the Nakagami fading channel under various conditions by varying the Nakagami m parameter. The simulations demonstrate how diversity techniques like maximal ratio combining can mitigate fading effects. Increasing the diversity order or Nakagami m parameter results in lower level crossing rates and shorter average fade durations, improving signal quality.
This document proposes using a Markov chain model and bipartite graphing to efficiently schedule spectrum in cognitive radio networks. It models the cognitive radio network as a k-connected bipartite graph and uses a Markov chain to represent the state transitions of channels between idle and busy. It then applies the Banker's algorithm to the modeled cognitive radio network to allocate spectrum to users while avoiding deadlock. The proposed approach indicates it could improve spectrum scheduling and allocation performance in cognitive radio networks.
Capsulization of Existing Space Time TechniquesIJEEE
1) The document discusses space-time coding techniques used in wireless communication systems to improve reliability of data transmission using multiple transmit antennas.
2) It describes space-time block codes (STBC) such as Alamouti codes and orthogonal designs which transmit redundant copies of data across antennas without loss of data rate.
3) It also discusses space-time trellis codes (STTC) which provide coding gain but have higher complexity than STBCs.
This document discusses using Gamma tone Frequency Cepstral Coefficients (GFCC) and K-means clustering to identify singers based on their voice. It begins by explaining that MFCC is not accurate in noisy environments, while GFCC performs well in both clean and noisy audio. The process involves extracting GFCC features from the audio, using K-means clustering to group similar voices into clusters, and dynamic time warping for authentication. Feature extraction with GFCC involves preprocessing, framing, windowing, computing the discrete Fourier transform, applying a gamma tone filter bank, logarithmic compression, and discrete cosine transformation to generate feature vectors. K-means clustering is then used to group the feature vectors from similar voices into clusters to identify
Emulation OF 3gpp Scme CHANNEL MODELS USING A Reverberation Chamber MEASUREME...IJERA Editor
1) A test bed was developed to validate 3GPP SCME channel models using a reverberation chamber. Power delay profiles were measured for urban micro and macro channel models and matched well with theoretical profiles.
2) The reverberation chamber was able to control delay spread by adding absorbing materials, allowing different channel models to be emulated. Measurements showed Rayleigh fading was maintained with losses.
3) Convolution of signals with 3GPP channel model taps allowed emulation of multi-cluster channels. Measurements found emulated profiles matched theoretical profiles specified in 3GPP standards.
Performance Analysis of PAPR Reduction in MIMO-OFDMIJARBEST JOURNAL
Authors: Jayaraman.G1, VeeraKumar K2, Selvakani.S3
Abstract— In communication system, it is aimed to provide highest possible
transmission rate at the lowest possible power and with the least possible noise. MIMOOFDM
has been chosen for high data rate communications and widely deployed in many
wireless communication standards. The major drawback in OFDM signal transmission is
high PAPR. In previous, use clipping technique to tackle this problem. In this paper, use
EM-GAMP algorithm to reduce PAPR in considerable amount.
IRJET- Survey Paper on Paper Reduction for MIMO-OFDM Systems using PTS SchemeIRJET Journal
This document summarizes research on techniques to reduce peak-to-average power ratio (PAPR) in MIMO-OFDM systems. It discusses how PAPR significantly affects OFDM and can cause nonlinearity in high power amplifiers. The paper focuses on using partial transmit sequence techniques to reduce PAPR. It reviews related work applying techniques like iterative clipping and filtering, partial transmit sequences, and adaptive selected mapping to reduce PAPR. The document also discusses system models for MIMO-OFDM and analyzing PAPR reduction performance.
This report discusses the planning Associate in
nursing the implementation of an OFDM system
in several information module schemes like MQPSK,
M-QAM. First, a short introduction is
provided by explaining the background and the
specification of the project. Then the report deals
with the system model, every block of the OFDM
system is represented (IFFT, FFT, Cyclic prefix,
modulation / reception, Channel estimation, bit
error rate). System design is analyzed. The
transmission techniques, further because the
system parameters for transmission and reception
are explained well. Finally, the results are
provided.
The document compares the performance of a Root Raised Cosine matched filter implemented using hybrid-logarithmic arithmetic versus standard binary and floating point arithmetic. Simulations showed that the hybrid logarithmic structure offered superior performance to fixed point solutions while having significantly reduced complexity compared to floating point equivalents. The use of hybrid logarithmic arithmetic also has the potential to reduce power consumption, latency, and hardware complexity for mobile applications.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Multi-carrier Equalization by Restoration of RedundancY (MERRY) for Adaptive ...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated and less complexity also involved by the simulation of the DST-DMT system.
A SEMI BLIND CHANNEL ESTIMATION METHOD BASED ON HYBRID NEURAL NETWORKS FOR UP...ijwmn
The paper describes how to improve channel estimation in Single Carrier Frequency Division Multiple
Access (SC-FDMA) system, using a Hybrid Artificial Neural Networks (HANN). The 3rd Generation
Partnership Project (3GPP) standards for uplink Long Term Evolution Advanced (LTE-A) uses pilot based
channel estimation technique. This kind of channel estimation method suffers from a considerable loss
ofbitrate due to pilot insertion; all data frame sent contains reference signal. The HANN converts data
aided channel estimator to semi blind channel estimator. To increase convergence speed, HANN uses some
channel propagation Fuzzy Rules to initialize Neural Network parameters before learning instead of a
random initialization, so its learning phase ismore rapidly compared to classic ANN.HANN allows more
bandwidth efficient and less complexity. Simulation results show that HANN has better computational
efficiency than the Minimum Mean Square Error (MMSE) estimator and has faster convergence than
classic Neural Networks estimators.
COMPARING VARIOUS CHANNEL ESTIMATION TECHNIQUES FOR OFDM SYSTEMS USING MATLABijwmn
This document compares the performance of five channel estimation techniques for OFDM systems over quasi-static channels using MATLAB simulations. The techniques evaluated are: decision directed (DD), linear interpolation, second-order interpolation, discrete Fourier transform (DFT) interpolation, and minimum mean square error (MMSE) interpolation. Simulation results show that DD channel estimation provides the lowest bit-error rate and mean square error, but has extra processing delay and is sensitive to channel variations. MMSE interpolation outperforms the other interpolation techniques.
This document describes a method for maximizing the total throughput of a two-way relay network using orthogonal frequency-division multiplexing (OFDM). The method jointly optimizes subcarrier pairing and relay selection by formulating the problem as a maximum weighted bipartite matching problem, which can be solved in polynomial time. Simulation results show that the proposed method increases total throughput compared to benchmark methods, especially as the number of relays increases. The throughput is evaluated for different numbers of subcarriers and relays to analyze the system's performance under various conditions.
Performance of Multiple symbol representation with clipping scheme for PAPR r...ijsrd.com
OFDM is one of the multicarrier modulation technique used in various communication systems. The major problem one faces while implementing this system is the high peak to average power .For an efficient OFDM system this PAPR should be low. In this paper a hybrid PAPR (peak to average power ratio) reduction technique for the OFDM (orthogonal frequency division multiplexing) signal which combines a multiple symbol representations method with a signal clipping method is proposed. In multiple symbol representations alternative signaling points are used to represent one symbol and PAPR is further reduced with the clipping scheme. The performance of the hybrid scheme is compared with the partial transmit sequence which is one of the other PAPR reduction scheme. In partial transmit sequence the input data is divided in to disjoint blocks transformed in to time domain sequence and rotated by phase factors. Theoretical analysis and simulation results validate that the proposed scheme has the ability to provide large PAPR reduction, low bit error rate. Performance analysis is also done with the partial transmit sequence scheme.
This document summarizes a research paper that investigates reducing peak-to-average power ratio (PAPR) in an MC-CDMA system using partial transmit sequence (PTS) technique with a suboptimal combination algorithm. The paper simulates a downlink MC-CDMA system with BPSK and QPSK modulation under varying system parameters like number of users and phase sequences. Results show the complementary cumulative distribution function (CCDF) of PAPR for the original and PTS-processed signals. Using PTS with 4, 8, or 16 phase sequences provides 1dB, 2dB, and 4.2dB of PAPR reduction respectively compared to the original signal for a 8-user BPSK modulated MC-CD
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.
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
New Technique Combining the Tone Reservation Method with Clipping Technique t...IJECEIAES
Nonlinear distortions and impairments appear in multicarrier signal with high fluctu- ations when amplified by a Radio Frequency Power Amplifier (RF PA). This article is a contribution to improving the Tone Reservation (TR) method dedicated to reducing fluctuations in the Orthogonal Frequency Division Multiplexing (OFDM) modulation. This method exploits the null sub-carriers in communications standards in order to generate a correction signal used to reduce the Peak-to-Average Power Ratio (PAPR) with nevertheless limited performances due to the reduced number of these sub-carriers. For this purpose, our contribution is to combine the TR method with the Clipping (CL) method to improve the PAPR reduction without significantly impacting the quality of transmissions. We also show the gain provided by this strategy compared to the use of classical methods. Experiments using a simulated example on a complete WiMax 802:16e transmitter have been made in order to investigate the PAPR reduction performances on presence of the non-linear Power Amplifier model based on gain compression response and phase distortion.
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.
Narrowband Spectrum Sensing for Different Fading Channels for Cognitive Radio...IJMERJOURNAL
Abstract: Nowadays the demand of applications of wireless communication has increased rapidly which causes the scarcity of radio spectrum. To empower future wireless communication services, the radio spectrum management is a very important factor. Cognitiveradio is a promising technology which provides an innovative way to improve utilization efficiency of available electromagnetic spectrum by sensing spectrum and shares it without harmful interference to other users. Narrowband spectrum sensing is the technique where the bandwidth of active primary transmitter in the vicinity of cognitive radio is less than the coherence bandwidth of channel. Fading is one of the greatest impairment of narrowband spectrum sensing. It is deflection of the attenuation. It influences a signal over certain propagation media.A communication channel that experiences fading isknown as fading channel. The effects of fading can be reduced by several fading models. In this paper, performanceanalysis of several realistic fading models on narrowband channel using energy detection method is employed. Finally, performance comparison of various fading models is guaranteed through simulation.
This document simulates and analyzes the Nakagami fading channel using MATLAB. It begins by introducing multipath fading channel models including Rayleigh, Ricean, and Nakagami distributions. It then uses MATLAB to simulate the complex envelope, level crossing rates, and average fade durations of the Nakagami fading channel under various conditions by varying the Nakagami m parameter. The simulations demonstrate how diversity techniques like maximal ratio combining can mitigate fading effects. Increasing the diversity order or Nakagami m parameter results in lower level crossing rates and shorter average fade durations, improving signal quality.
This document proposes using a Markov chain model and bipartite graphing to efficiently schedule spectrum in cognitive radio networks. It models the cognitive radio network as a k-connected bipartite graph and uses a Markov chain to represent the state transitions of channels between idle and busy. It then applies the Banker's algorithm to the modeled cognitive radio network to allocate spectrum to users while avoiding deadlock. The proposed approach indicates it could improve spectrum scheduling and allocation performance in cognitive radio networks.
Capsulization of Existing Space Time TechniquesIJEEE
1) The document discusses space-time coding techniques used in wireless communication systems to improve reliability of data transmission using multiple transmit antennas.
2) It describes space-time block codes (STBC) such as Alamouti codes and orthogonal designs which transmit redundant copies of data across antennas without loss of data rate.
3) It also discusses space-time trellis codes (STTC) which provide coding gain but have higher complexity than STBCs.
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This document describes a simulator designed to analyze bit error rates using orthogonal frequency division multiplexing (OFDM) under different modulation schemes and channel conditions. The simulator was implemented in MATLAB and allows users to choose modulation types, channel types (AWGN, Rayleigh, Rician), and other parameters. It then generates plots of bit error rate versus signal-to-noise ratio for performance analysis. Screenshots of the user interface are provided along with sample output plots and discussion of the simulator design and capabilities.
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.
EFFICIENCY ENHANCEMENT BASED ON ALLOCATING BIZARRE PEAKSijwmn
A new work has been proposed in this paper in order to overcome one of the main drawbacks that found in
the Orthogonal Frequency Division Multiplex (OFDM) systems, namely Peak to Average Power Ratio
(PAPR). Furthermore, this work will be compared with a previously published work that uses the neural
network (NN) as a solution to remedy this deficiency.
The proposed work could be considered as a special averaging technique (SAT), which consists of wavelet
transformation in its first stage, a globally statistical adaptive detecting algorithm as a second stage; and
in the third stage it replaces the affected peaks by making use of moving average filter process. In the NN
work, the learning process makes use of a previously published work that is based on three linear coding
techniques.
In order to check the proposed work validity, a MATLAB simulation has been run and has two main
variables to compare with; namely BER and CCDF curves. This is true under the same bandwidth
occupancy and channel characteristics. Two types of tested data have been used; randomly generated data
and a practical data that have been extracted from a funded project entitled by ECEM. From the achieved
simulation results, the work that is based on SAT shows promising results in reducing the PAPR effect
reached up to 80% over the work in the literature and our previously published work. This means that this
work gives an extra reduction up to 15% of our previously published work. However, this achievement will
be under the cost of complexity. This penalty could be optimized by imposing the NN to the SAT work in
order to enhance the wireless systems performance.
EFFICIENCY ENHANCEMENT BASED ON ALLOCATING BIZARRE PEAKSijwmn
A new work has been proposed in this paper in order to overcome one of the main drawbacks that found in
the Orthogonal Frequency Division Multiplex (OFDM) systems, namely Peak to Average Power Ratio
(PAPR). Furthermore, this work will be compared with a previously published work that uses the neural
network (NN) as a solution to remedy this deficiency.
The proposed work could be considered as a special averaging technique (SAT), which consists of wavelet
transformation in its first stage, a globally statistical adaptive detecting algorithm as a second stage; and
in the third stage it replaces the affected peaks by making use of moving average filter process. In the NN
work, the learning process makes use of a previously published work that is based on three linear coding
techniques.
In order to check the proposed work validity, a MATLAB simulation has been run and has two main
variables to compare with; namely BER and CCDF curves. This is true under the same bandwidth
occupancy and channel characteristics. Two types of tested data have been used; randomly generated data
and a practical data that have been extracted from a funded project entitled by ECEM. From the achieved
simulation results, the work that is based on SAT shows promising results in reducing the PAPR effect
reached up to 80% over the work in the literature and our previously published work. This means that this
work gives an extra reduction up to 15% of our previously published work. However, this achievement will
be under the cost of complexity. This penalty could be optimized by imposing the NN to the SAT work in
order to enhance the wireless systems performance. Orthogonal Frequency Division Multiplexing
Iaetsd adaptive modulation in mimo ofdm system for4 gIaetsd Iaetsd
This paper proposes applying hybrid adaptation techniques in MIMO OFDM systems to improve spectral efficiency and reduce transmit power. It first analyzes the bit error rate of M-QAM modulation in OFDM systems with different numbers of subcarriers. Channel estimation is performed using MMSE, which estimates the channel with less error than LS. Feedback from channel estimation is then used with hybrid adaptation techniques. Simulation results show MMSE has lower MSE and symbol errors than LS estimation.
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NEW BER ANALYSIS OF OFDM SYSTEM OVER NAKAGAMI-n (RICE) FADING CHANNEL
1. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
DOI : 10.5121/ijcseit.2011.1302 12
NEW BER ANALYSIS OF OFDM SYSTEM OVER
NAKAGAMI-n (RICE) FADING CHANNEL
1
Mukesh Kumar Mishra, 2
Neetu Sood
1,2
Department of Electronics & Communication Engineering
mukesh8620@gmail.com
3
Ajay K Sharma
3
Department of Computer Science Engineering
National Institute of Technology Jalandhar, India
ABSTRACT
Modern wireless communication systems support high speed multimedia services. These services require
high data rates with acceptable error rates. Orthogonal Frequency Division Multiplexing (OFDM) is a
capable candidate to solve this problem. In this paper, a new expression for the BER of OFDM system has
been derived over Nakagami–n (Rice) fading channels using characteristics function (CHF) approach. The
exact probability density function of first order of Nakagami-n (Rice) random vector is used to derive the
expression for the error rates of OFDM system. The BER derivation of Rician fading channel is slightly
more complex compared to the Nakagami–m distribution because the PDF of the Rician RV contains an
explicit term of a modified Bessel function of first kind. Earlier, this problem was solved by replacing the
Bessel function with its infinite series and exponential integral representation. Here we propose an integral
expression to remove the complexity of the expression.
KEYWORD
Error Rate Analysis, Fading Channel, Orthogonal Frequency Division Multiplexing (OFDM),Nakagami-n
(Rice) distribution.
1. INTRODUCTION
Today the demand of wireless communication is increasing exponentially and next generation of
wireless broadband multimedia communication system will require high-speed, high-quality
digital mobile portable reception and transmission. A receiver has to cope with a signal that is
often weaker than desirable and that contains many echoes. Simple digital systems do not work
well in the multipath environment. When solving this problem, first question is how to put this
large bit stream on wireless channel with sufficient Quality of services (QoS) guaranties, i.e.
which modulation can compromise all contradicting requirements in the best way. Using different
equalization techniques at the receiver side could be the solution, but there are many practical
difficulties to implement this equalization in real-time at several Mbps with compact, low-cost
hardware. A capable candidate that eliminates a need for the complex equalizers at receiver side
is the OFDM, a multiple carrier modulation technique so that it has been employed in many
wireless standards [1].
In an ideal radio channel, the received signal would consist of only a single direct path signal,
which would be a perfect reconstruction of the transmitted signal [2]. However, in a real channel,
the signal is modified during transmission in the channel. The received signal consists of a
combination of attenuated, reflected, refracted, and diffracted replicas of the transmitted signal
[24]. Understanding of these effects on the signal is important because the performance of a radio
2. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
13
system is dependent on the radio channel characteristics. The rapid fluctuations of the
instantaneous received power due to multipath effects are usually described with Rayleigh, Rician,
Nakagami-m or Nakagami-q model [3, 4]. Among them Nakagami-n (Rice) and Nakagami-q
(Hoyt) fading channels, has not yet received as much attention as the Rayleigh and Nakagami-m
fading channels, mainly due to the complex form of their PDF, despite the fact that these models
exhibit an excellent fit to experimental fading channel measurements for land, mobile, terrestrial,
and satellite telecommunications[5,6]. In [5] by using an alternative moments-based approach
performance analysis of equal-gain combining (EGC) receivers over independent, not necessarily
identically distributed Rice and Hoyt-fading channels has been derived. Moreover, using Padé
rational approximation to the moment-generating function of the output SNR, the average symbol
error probability and the outage probability are evaluated. In [6] complexity of the PDF has been
solved by replacing the Bessel function with its infinite series representation and [7] used
exponential integral representation for Bessel function. Further [20] the combination of OFDM
and diversity has been becoming popular in wireless communications.
In digital communication system the bit error rate has been very extensively used as a
performance measurement. This measurement is one of the prime considerations in determining
signal quality and quantifies the reliability of the entire radio system. It is the one that is most
revealing about the nature of the system behavior and the one most often illustrated in documents
containing system performance evaluations; thus, it is of primary interest to have a method for its
evaluation that reduces the degree of difficulty as much as possible[4,8]. Generally researchers
perform the averaging using the probability density function method or the moment generating
function (MGF). The third technique is CHF approach which is more efficient to evaluate the
system performance and overcomes all the limitations of the MGF method [9].
So our motivation behind this paper is to study the performance of OFDM system over
Nakagami-n (Rice) fading channel using CHF method to remove the complexity of the system,
and within a single common framework, developed a general method for calculating the average
error rates of single channel and multiple channel reception.
The main objective of paper is to derive the analytical expression for error rates of OFDM
systems over Nakagami-n (Rice) fading channel. To accomplish this, in first step we have derived
the PDF of Nakagami-n (Rice) random phase vector in an integral form by using CHF method.
Further this PDF is used to calculate the error rate performance of OFDM system over frequency
selective Nakagami-n fading channels. The error rate derivation of Nakagami-n (Rice) fading
channel is slightly more complex compared to the Nakagami–m fading case because the PDF of
the Rician RVs contains an explicit term of a modified Bessel function of first kind. To remove
this complexity we are using an integral expression, to express CHF in a closed form expression,
which has resulted into less complexity and easy numerical computation of the expression. Here
the average error rate is expressed in terms of exponential and imaginary error function. Finally it
is observed through numerical results, that error rate performance of an OFDM signal over multi
propagation Nakagami-n channels does not improve with increasing Nakagami-n fading
parameter n.
The rest of the paper organized as follows. The section 2 deals with the OFDM system model. In
section 3 multipath fading channels is explained. In section 4 we derive an integral expression for
the PDF of Nakagami-n (Rice) random phase vectors. In section 5 the error rate expressions for
OFDM system has been derived. The section 6 discusses about the numerical results and finally
section 7 concludes the work.
3. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
14
2. OFDM SYSTEM MODEL
Let an OFDM system with N sub-carriers and X (k) is the kth
OFDM data block to be transmitted
with narrowband N subcarriers. These data are used to modulate N orthogonal sub carriers. Then
IDFT is used to modulate the input signal. After modulation signal can be represented as [10]:
( ) 1...1,0,
2
exp1)(
1
0
−=
= ∑
−
=
Nn
N
knj
kX
N
nx
N
k
π
(1)
Cyclic prefix is inserted after IDFT modulation, which is removed before demodulation at the
OFDM receiver. The received signal after removal of cyclic prefix can be demodulated using
DFT. Output of DFT can be represented as [19]:
( ) ( ) ( ) k
N
n
WkHkXNnkjnrkR +=−= ∑
−
=
1
0
)2exp()( π , k=0, 1….N-1 (2)
Where Wk is additive complex Gaussian noise with zero mean and unit variance and H (k) is
frequency domain channel impulse response.
3. MULTIPATH FADING CHANNEL MODEL
Due to multipath phenomenon many reflected signals arrive at receiver side with different times.
The reason behind these delayed signals is reflection, diffraction, scattering etc. from the hills,
buildings, trees, vehicles. To understand this whole effect on the signal, we express the multipath
channel with its impulse response. The channel impulse response of a multipath fading channel is
modeled as a finite impulse response filter with taps hl (n).We can express channel impulse
response as [11]:
( ) 1,...1,0,)2exp()(
1
0
−=−= ∑
−
=
MkNnkjnhkH
M
n
ll π
(3)
Where n identify each path number, M is the number of paths.
4. PDF OF NAKAGAMI RV & BER PERFORMANCE ANALYSIS
In this section, an integral expression for the first order PDF is evaluated based on CHF approach.
Assume an auxiliary function Z=R cos (θ ), where R is the fading amplitude and θ is the random
phase distributed uniformly over [0, 2π ]. The Nakagami-n (Rice) distribution is given by [12]:
( ) 0,
)1(
2
)1(2
0
)1( 2
≥
Ω
+
Ω
+
=
Ω
+−−
r
KK
rIre
K
rf
rKK
(4)
The standard derivation for the CHF, as derived in [13, 17, 21]
( ) ( )drrJrfnX η0
0
∫
∞
=Ψ
(5)
Using the eq. (4), eq. (5) can be written as:
4. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
15
( )drrJ
KK
rIere
K
rK
K
nX η0
0
0
)1(
)1(
2
)1(2
2
∫
∞
Ω
+−
−
Ω
+
Ω
+
=Ψ
(6)
To simplify the eq. (6) we use integral identity [14, eq. 6.633.4] and eq. (6) can be expressed as:
( )
( )
+
Ω
+
Ω−
=Ψ
)1(14
exp 0
2
n
nn
n
n
nX
K
K
J
K
ηηη
(7)
Because channel tap coefficients are independent so CHF can be written as [11]:
( )
( )
( )ηηηη Ψ≅
+
Ω
+
Ω−
=Ψ ∏
−1
0 0
2
)1(14
exp
M
n
nn
n
n
nX
K
K
J
K
(8)
To obtain the PDF for X the inverse FT is used to get the equation as given in [13, 15]:
( ) ( ) ηη
π
η
dexf xj
X Ψ= ∫
∞
∞−
−
2
1
(9)
After some simplification eq. (9) can be written as [13]:
( ) ( ) ( ) ηηη
π
dxxfX Ψ= ∫
∞
0
cos
1
(10)
Using eq. (7) the integral PDF is given by
( ) ( )
( )
ηηηη
π
d
K
K
J
K
xxf
n
nn
n
n
X
+
Ω
+
Ω−
= ∫
∞
)1(14
expcos
1
0
2
0
(11)
Equation (11) is integral expression for PDF ,which is furher used to derive the BER expression
for OFDM system.
5. BER PERFORMANCE ANALYSIS
The conditional BER of a particular modulation is given by Q (Sr), where
dtexQ
x
t
∫
∞
−
=
2
2
2
1
)(
π
Using the alternative representation of above equation as given in [16].
φ
π
π
φ
deSxQ
xS
∫
−
=
2
0
)(sin2 2
22
1
)(
(12)
Where S is a factor related to signal to noise ratio (SNR), as given in [8] 02 NgES b= , where
g=1 for coherent binary phase shift keying (BPSK). The parameter x is the fading amplitude.
Averaging the CEP over derived PDF the error rate denoted by P(S) can be expressed as [11]:
5. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
16
dxxfSxQSP X )()()(
0
∫
∞
=
(13)
( ) dxdxd
xS
SP
Ψ×
−= ∫∫
∞
ηηη
π
φ
φπ
π
)(cos
1
)(sin2
exp
1
)(
0
2/
0
2
22
(14)
With an exchange of order of integration eq. (14) can be given as:
φ
φ
ηηη
π
π
ddx
xS
xdSP
−Ψ= ∫ ∫∫
∞∞
)(sin2
exp)cos()(
1
)( 2
222/
0 00
2
(15)
Using the identity[14,eq. 3.896.4],eq.(15) can be written as:
−Ψ= ∫∫
∞
φ
φηφπ
ηη
π
π
d
SS
dSP 2
222/
0
2
2
0
2
2
)(sin
exp
)(sin2
)(
1
)(
(16)
After integration and some simplification eq.(16) can be expressed as :
( )
η
η
η
ηη
π
η
d
S
erfi
e
K
K
J
K
SP S
M
n
nn
n
n
+
Ω
+
Ω−
=
−∞
−
∫∏
2
)1(14
exp
2
1
)(
2
2
2
0
1
0 0
2
(17)
Where erfi is imaginary error function, eq. (17) can be used for numerical computation of BER
for OFDM signals transmitted over Nakagami-n (Rice) channels. Further eq. (17) is used to
express the BER expression for the single tap and two tap multipath channels. For single tap BER
expression can be given as:
( )
η
η
η
ηη
π
η
d
S
erfi
e
K
K
J
K
SP S
+
Ω
+
Ω−
=
−∞
∫
2
)1(14
exp
2
1
)(
2
2
2
0
00
0
2
0
0
0
(18)
In the similar way for the two tap multipath channel we have expression as:
( ) ( )
η
η
η
η
η
η
η
π
η
d
S
erfi
e
K
K
J
KK
K
J
K
SP S
+
Ω
+
Ω−
+
Ω
+
Ω−
=
−∞
∫
2
)1(14
exp
)1(14
exp
2
1
)(
2
2
2
1
11
0
1
2
1
0
00
0
0
2
0
0
(1
9)
When we have condition 0Ω = 1Ω =Ω and 0K = 1K = K , eq. (19) can be expressed as
6. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
17
( )
η
η
η
ηη
π
η
d
S
erfi
e
K
K
J
K
SP S
+
Ω
+
Ω−
=
−∞
∫
2
)1(12
exp
2
1
)(
2
2
2
2
0
2
0
(20)
Above derived eq. (18) and (20) is used for numerical evaluation of OFDM-BPSK and OFDM-
BFSK system.
6. RESULTS & DISCUSSIONS
In this section the BER performance of an OFDM-BPSK system over Nakagami-n (Rice) fading
channels are analytically evaluated. Fig.1 illustrates the average BER performance versus the
SNR in a BPSK modulated OFDM system for single tap channel. It is well known, that at n=0
Nakagami-n fading corresponds to Rayleigh fading. So, results for the same have been achieved
through numerical evaluation. Further when value of n is increased, the BER starts reducing at
different values of n.We have further analyzed OFDM-BFSK system as shown in Fig.2.
Results obtained from numerical evaluation for OFDM-BFSK system is similar in nature to that
of OFDM-BPSK system. BER starts decreasing with increasing value of n. Fig.3 shows the error
rate curves for a two-tap OFDM BPSK system over frequency-selective Nakagami-n channel
with n0=n1=n and 0= 1= =1.
Fig.1 BER Vs SNR for OFDM-BPSK system with single tap
Fig.2 BER Vs SNR for OFDM-BFSK system with single tap
7. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
18
Fig.3 BER Vs SNR for OFDM-BPSK system with two tap
If fading parameter n increases, slopes of the error rate performance increases. But further, if we
increase n, no reduction in BER has been reported rather it starts increasing. So this put a limit to
increase the value of n beyond the certain value. This interesting fact is expected because
according to [4, 6, 12] we can approximate the Rician distribution by a Nakagami-m distribution
that means if for the Nakagami-m (Two Tap) case error rate performance degrades with
increasing values of m as reported in [11, 16, 19] then same nature of the BER performance
should be shown by the Nakagami-n (Rice) fading distribution, and same results, we are achieved
in our numerical analysis. Here the threshold value for Nakagami-n is achieved to be 1.4 through
analytical results.
We have further analyzed OFDM-BFSK system as shown in Fig.4. Results obtained from
numerical evaluation for OFDM-BFSK system is similar in nature to that of OFDM-BPSK
system. BER starts decreasing with increasing value of n.
Fig.4 BER Vs SNR for OFDM-BFSK system with two tap
7. CONCLUSION
In this paper, Nakagami-n (Rice) PDF has been derived in an integral form using CHF approach
and further utilized for evaluating the average error rate expression for OFDM system over
Nakagami-n (Rice) fading channel with the fading severity index n. The derived PDF remove the
8. International Journal of Computer Science, Engineering and Information Technology (IJCSEIT),Vol.1, No.3, Aug 2011
19
complexity of the SER expression efficiently. The evaluated analytical error rate expression over
Nakagami-n (Rice) fading is useful where model propagation path consisting of one strong direct
LOS component and many random weaker components. Further as per the previous papers, we
can approximate the Nakagami-m fading channels with the Nakagami-n (Rice) channel, i.e. the
nature of the error rate performance should be same. This fact is proved by our numerical result.
Finally it has been concluded that, depending on the number of channel taps, larger Nakagami-n
(Rice) fading parameters do not necessarily give smaller error rates.
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Authors
Mukesh Kumar Mishra received the B.E. degree in Electronics and Tele-
communication from Pt.Ravishankar Shukla University , India 2008.Currently, he is
pursuing his M.Tech in National Institute of Technology , Jalandhar, India. His
current research includes the analytical performance analysis of OFDM based
wireless communication system.
Neetu Sood received the B.Tech. degree (with Honour) in Electronics and
Communication from Sant Longowal Institute of Engineering and Technology, India
2000. In year Jan. 2002, she completed her M.Eng.Degree (With Honour) in
Electronics and Communication from Thapar University, Patiala, India.Currently, she
is working as Assistant Professor at Dr. B R Ambedkar National Institute of
Technology, Jalanadhar and working towards her PhD degree. Her current research
includes the simulation of wireless systems based on OFDM and simulation of fading
channels.
Ajay K Sharma received his BE in Electronics and Electrical Communication
Engineering from Punjab University Chandigarh, India in 1986, MS in Electronics
and Control from Birla Institute of Technology (BITS), Pilani in the year 1994 and
PhD in Electronics Communication and Computer Engineering in the year 1999. He
has joined National Institute of Technology (Erstwhile Regional Engineering
College) Jalandhar as Assistant Professor in the Department of Electronics and
Communication Engineering in the year 1996. From November 2001, he has worked
as Professor in the same department and presently he working as Professor in
Computer Science & Engineering in the same institute. His major areas of interest
are broadband optical communication systems, dispersion compensation, fiber
nonlinearities, optical soliton transmission, WDM systems and networks, Radio-over-Fiber (RoF) and
wireless communication and networks. He has published 202 research papers in the International/National
Journals/Conferences and 12 books.