In this paper we propose an iterative parallel decision feedback (P-DF) receivers associated with
parallel interference cancellation (PIC) for multicarrier code division multiple access (MC-CDMA) systems
in a Rayleigh fading channel (cost 207). First the most widely detection techniques, minimum
mean-squared error MMSE, Maximum Likelihood ML and PIC were investigated in order to compare their
performances in terms of Bit Error Rate (BER) with parallel feedback detection P-DFD. A MMSE DF
detector that employs parallel decision-feedback (MMSE-P-DFD) is considered and shows almost the
same BER performance with MMSE and ML, which present a better result than the other techniques. In a
second time, an iterative proposed method based on the multi-stage techniques P-DFD
(parallel DFD with two stages) and PIC was exploited to improve the performance of the system.
This document discusses performance evaluation of channel estimation in TD-SCDMA systems. It begins by describing the Steiner channel estimation algorithm previously used in TD-SCDMA, but notes there are errors due to noise. An improved method is proposed using a standard model with a transfer function. Simulation results show the improved method estimates the channel impulse response more accurately and increases system performance, reducing bit error rate compared to the Steiner algorithm. In conclusion, the adaptive channel estimation implemented at the receiver significantly reduces the bit error rate of the system.
Performance of the MIMO-MC-CDMA System with MMSE EqualizationTamilarasan N
Multipath fading and spectral crowding are the
major challenges in dealing higher data rate in future
broadband wireless communication system. Multi-carrier
Modulation like Multicarrier code division multiple access
(MC-CDMA) can tackle the problem and provide higher data
rate for future wireless communication system. However,
through a frequency selective fading channel, the subcarriers
in MC-CDMA signal have different amplitude levels and phase
shifts which result in loss of the orthogonality among users
and generates Multiple access interference (MAI). To combat
the MAI, various amplitude and phase equalizing techniques
such as Maximum Ratio Combining (MRC), Equal Gain
Combining (EGC), Orthogonal Restoring Combining (ORC),
Threshold Orthogonal Restoring Combining or Minimum
Mean Square Error (MMSE) may be used. Out of these MMSE
offers better performance since the MMSE criterion is applied
independently on each subcarrier. Further improvement in
performance is possible through space–time block coding,
which offers maximum diversity gain and multiplexing gain.
This paper combines MC-CDMA with MMSE equalization
and space–time block coding which proves to be a powerful
physical layer solution in combating delay spread and inter
symbol interference (ISI).
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
The performance of WCDMA system deteriorates in the presence of multipath fading environment.
Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though
conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path
diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses
MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To
overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear,
anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps
of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise,
Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length
MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian
noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake
receiver and MMSE and the simulation results are shown.
BER Performance of Antenna Array-Based Receiver using Multi-user Detection in...ijwmn
1) The document proposes a novel approach to evaluate the average probability of error for a DS-CDMA system using an antenna array receiver. It approximates the angular gain function of the spatial filter as a fixed beamwidth function to partition interferers into in-beam and out-beam groups.
2) It derives an accurate formula for the average bit error rate over Nakagami fading channels. The analysis considers asynchronous transmission and adapts Gaussian approximations to account for noise and multi-user interference after beamforming.
3) Simulation results are provided to validate the research for single antenna systems and show that the proposed model confirms the benefits of adaptive antennas in reducing interference and provides a good approximation of error probability.
11.performance evaluation of maximal ratio receiver combining diversity with ...Alexander Decker
The document evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity technique for an Interleave-Division Multiple Access (IDMA) receiver with single transmit and two receive antennas. Simulation results show that MRRC diversity provides significant improvement to the bit error rate (BER) performance of IDMA. The BER performance of an IDMA system using a prime interleaver is found to be similar to one using a random interleaver, but with reduced bandwidth and memory requirements.
Performance evaluation of maximal ratio receiver combining diversity with pri...Alexander Decker
This document summarizes a research paper that evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity with different interleavers for an Iterative Interleave-Division Multiple Access (IDMA) receiver. The paper finds that using MRRC diversity with one transmit and two receive antennas significantly improves the bit error rate performance of IDMA. It also finds that using a prime interleaver achieves similar performance to a random interleaver but with reduced bandwidth and memory requirements. The document introduces IDMA and describes the system model, interleaving techniques, and MRRC diversity approach that are evaluated through simulation to analyze the bit error rate performance of the IDMA system under different conditions.
Intersymbol interference caused by multipath in band limited frequency selective time dispersive channels distorts the transmitted signal, causing bit error at receiver. ISI is the major obstacle to high speed data transmission over wireless channels. Channel estimation is a technique used to combat the intersymbol interference. The objective of this paper is to improve channel estimation accuracy in MIMO-OFDM system by using modified variable step size leaky Least Mean Square (MVSSLLMS) algorithm proposed for MIMO OFDM System. So we are going to analyze Bit Error Rate for different signal to noise ratio, also compare the proposed scheme with standard LMS channel estimation method.
ICI and PAPR enhancement in MIMO-OFDM system using RNS codingIJECEIAES
The Inter-Carrier-Interference (ICI) is considered a bottleneck in the utilization of Multiple-Input-Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems, due to the sensitivity of the OFDM towards frequency offsets which lead to loss of orthogonality, interference and performance degradation. In this paper Residue Numbers as a coding scheme is impeded in MIMO-OFDM systems, where the ICI levels is measured and evaluated with respect to conventional ICI mitigation techniques implemented in MIMO-OFDM. The Carrier-to-Interference Ratio (CIR), the system Bit-Error-Rate (BER) and the Complementary Cumulative Distribution Function (CCDF) for MIMO-OFDM system with Residue Number System (RNS) coding are analyzed and evaluated. The results had demonstrated a performance of transmission model with and without RNS.
This document discusses performance evaluation of channel estimation in TD-SCDMA systems. It begins by describing the Steiner channel estimation algorithm previously used in TD-SCDMA, but notes there are errors due to noise. An improved method is proposed using a standard model with a transfer function. Simulation results show the improved method estimates the channel impulse response more accurately and increases system performance, reducing bit error rate compared to the Steiner algorithm. In conclusion, the adaptive channel estimation implemented at the receiver significantly reduces the bit error rate of the system.
Performance of the MIMO-MC-CDMA System with MMSE EqualizationTamilarasan N
Multipath fading and spectral crowding are the
major challenges in dealing higher data rate in future
broadband wireless communication system. Multi-carrier
Modulation like Multicarrier code division multiple access
(MC-CDMA) can tackle the problem and provide higher data
rate for future wireless communication system. However,
through a frequency selective fading channel, the subcarriers
in MC-CDMA signal have different amplitude levels and phase
shifts which result in loss of the orthogonality among users
and generates Multiple access interference (MAI). To combat
the MAI, various amplitude and phase equalizing techniques
such as Maximum Ratio Combining (MRC), Equal Gain
Combining (EGC), Orthogonal Restoring Combining (ORC),
Threshold Orthogonal Restoring Combining or Minimum
Mean Square Error (MMSE) may be used. Out of these MMSE
offers better performance since the MMSE criterion is applied
independently on each subcarrier. Further improvement in
performance is possible through space–time block coding,
which offers maximum diversity gain and multiplexing gain.
This paper combines MC-CDMA with MMSE equalization
and space–time block coding which proves to be a powerful
physical layer solution in combating delay spread and inter
symbol interference (ISI).
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
The performance of WCDMA system deteriorates in the presence of multipath fading environment.
Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though
conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path
diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses
MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To
overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear,
anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps
of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise,
Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length
MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian
noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake
receiver and MMSE and the simulation results are shown.
BER Performance of Antenna Array-Based Receiver using Multi-user Detection in...ijwmn
1) The document proposes a novel approach to evaluate the average probability of error for a DS-CDMA system using an antenna array receiver. It approximates the angular gain function of the spatial filter as a fixed beamwidth function to partition interferers into in-beam and out-beam groups.
2) It derives an accurate formula for the average bit error rate over Nakagami fading channels. The analysis considers asynchronous transmission and adapts Gaussian approximations to account for noise and multi-user interference after beamforming.
3) Simulation results are provided to validate the research for single antenna systems and show that the proposed model confirms the benefits of adaptive antennas in reducing interference and provides a good approximation of error probability.
11.performance evaluation of maximal ratio receiver combining diversity with ...Alexander Decker
The document evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity technique for an Interleave-Division Multiple Access (IDMA) receiver with single transmit and two receive antennas. Simulation results show that MRRC diversity provides significant improvement to the bit error rate (BER) performance of IDMA. The BER performance of an IDMA system using a prime interleaver is found to be similar to one using a random interleaver, but with reduced bandwidth and memory requirements.
Performance evaluation of maximal ratio receiver combining diversity with pri...Alexander Decker
This document summarizes a research paper that evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity with different interleavers for an Iterative Interleave-Division Multiple Access (IDMA) receiver. The paper finds that using MRRC diversity with one transmit and two receive antennas significantly improves the bit error rate performance of IDMA. It also finds that using a prime interleaver achieves similar performance to a random interleaver but with reduced bandwidth and memory requirements. The document introduces IDMA and describes the system model, interleaving techniques, and MRRC diversity approach that are evaluated through simulation to analyze the bit error rate performance of the IDMA system under different conditions.
Intersymbol interference caused by multipath in band limited frequency selective time dispersive channels distorts the transmitted signal, causing bit error at receiver. ISI is the major obstacle to high speed data transmission over wireless channels. Channel estimation is a technique used to combat the intersymbol interference. The objective of this paper is to improve channel estimation accuracy in MIMO-OFDM system by using modified variable step size leaky Least Mean Square (MVSSLLMS) algorithm proposed for MIMO OFDM System. So we are going to analyze Bit Error Rate for different signal to noise ratio, also compare the proposed scheme with standard LMS channel estimation method.
ICI and PAPR enhancement in MIMO-OFDM system using RNS codingIJECEIAES
The Inter-Carrier-Interference (ICI) is considered a bottleneck in the utilization of Multiple-Input-Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems, due to the sensitivity of the OFDM towards frequency offsets which lead to loss of orthogonality, interference and performance degradation. In this paper Residue Numbers as a coding scheme is impeded in MIMO-OFDM systems, where the ICI levels is measured and evaluated with respect to conventional ICI mitigation techniques implemented in MIMO-OFDM. The Carrier-to-Interference Ratio (CIR), the system Bit-Error-Rate (BER) and the Complementary Cumulative Distribution Function (CCDF) for MIMO-OFDM system with Residue Number System (RNS) coding are analyzed and evaluated. The results had demonstrated a performance of transmission model with and without RNS.
Multi user performance on mc cdma single relay cooperative system by distribu...IJCNCJournal
Increasing data rate and high performance is the target focus of wireless communication. The multi carrier on multi-hop communication system using relay's diversity technique which is supported by a reliable coding is a system that may give high performance. This research is developing a model of multi user and two scheme of multi carrier CDMA on multi hop communication system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By Alamouti research, Space Time Block Code (STBC) for MIMO system can perform high quality signal at the receiver in the Rayleigh fading channel and the noisy system. In this research, MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC) with multi carrier CDMA on multi hop wireless communication system (relay diversity) which is able to improve the received signal performance.
MC DS CDMA on multi hop wireless communication system with 2 hops is better performing than MC CDMA on multi user without Multi User Detector. To reach BER 10-3 multi hop system with MC CDMA needs more power 5 dB than MC DS CDMA at 5 users using Alamouti scheme for symbol transmission at the relay.
The document is an abstract for a PhD thesis on cooperative communications over wireless relay channels. It discusses analyzing relay channels from an information-theoretic and communication-theoretic perspective, including single-input single-output and multiple-input multiple-output relay channels. For MIMO relay channels, it focuses on two-hop channels using orthogonal space-time block coding at the relay in Rayleigh fading. It derives approximations for error probability and outage probability for amplify-and-forward relaying, and expressions for ergodic and outage capacity.
This document summarizes the simulation steps for investigating the performance of three multi-carrier code division multiple access (MC-CDMA) techniques: conventional MC-CDMA, orthogonal wavelet packet based MC-CDMA (WP-MC-CDMA), and Huang Hilbert Transformation (HHT) based MC-CDMA. The steps include designing the three systems, simulating them with different modulation techniques under fading channels, and comparing their bit error rate performance. Numerical and simulation results are presented to validate the proposed schemes.
This document summarizes the simulation steps for investigating the performance of three multi-carrier code division multiple access (MC-CDMA) techniques: conventional MC-CDMA, orthogonal wavelet packet based MC-CDMA (WP-MC-CDMA), and Huang Hilbert Transformation (HHT) based MC-CDMA. The steps include designing the three systems, simulating them with different modulation techniques under fading channels, and comparing their bit error rate performance. Numerical and simulation results are presented to validate the proposed schemes.
1) The document compares the performance of coded and uncoded MC-DS-CDMA systems using linear block codes. BCH codes are used as the outer code and convolutional codes are used as the inner code in a concatenated coding scheme.
2) Simulation results show that the coded system significantly outperforms the uncoded system, with a coding gain of around 4dB. Using error correction codes is especially beneficial when the number of users is increased, as it is not as severely impacted by multiple access interference.
3) Performance is better when using a decorrelating detector compared to a maximum ratio combiner. However, the benefit of the decorrelating detector is smaller when there are more users.
This document analyzes the effects of carrier frequency offset (CFO) and fading branch correlation (FBC) on the performance of an asynchronous multi-carrier coded-division multiple-access (MC-CDMA) system. It establishes models for an MC-CDMA system with transmitter and receiver, and examines how CFO and FBC impact the bit error rate (BER) performance. Equations are derived relating CFO and FBC, and simulation results are presented showing which parameter, CFO or FBC, has a greater influence on system performance.
Wireless communication now has been focus to increase data rate and high performance. The
multi carrier on multi-hop communication system using relay's diversity technique which is
supported by a reliable coding is a system that may give high performance.
This research is developing a model of multi carrier CDMA on multi hop communication
system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By
Alamouti research, Space Time Block Code (STBC) for MIMO system can perform high quality
signal at the receiver in the Rayleigh fading channel and the noisy system. In this research,
MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC) with multi
carrier CDMA on multi hop wireless communication system (relay diversity) which is able to
reduce the complexity of the system but the system performance even can be maintained and
improved.
MC CDMA on multi hop wireless communication system with 2 hops is performing much better
than Single Input Single Output (SISO) system (1 hop system). Power needed for 1 hop system to
have the same quality as 2 hops system to reach BER 10-3 is 12 dB. And multi hop system needs
orthogonal symbol to send from relay than original symbol to reach better performance. 12.5
dB power up is needed for multi hop system which sent same symbol as transmitter than relay
system which sent orthogonal symbol.
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.
1. MIMO (multiple-input multiple-output) communication uses multiple antennas at both the transmitter and receiver to improve performance. It can increase data throughput and link range without additional bandwidth or transmit power.
2. MIMO systems can be modeled as a narrowband channel with n transmit antennas and m receive antennas. The channel is represented by a matrix H. MIMO channels can be decomposed into parallel SISO channels through singular value decomposition to simplify processing.
3. The capacity of MIMO channels is determined through water-filling of the eigenvalues of the channel matrix H. MIMO provides diversity gain through techniques like beamforming and exploiting the diversity-multiplexing tradeoff.
NEW BER ANALYSIS OF OFDM SYSTEM OVER NAKAGAMI-n (RICE) FADING CHANNELijcseit
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 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.
VTU 6TH SEM CSE COMPUTER NETWORKS 2 SOLVED PAPERS OF JUNE-2013 JUNE-14 & JUNE...vtunotesbysree
This document contains solved questions from a Computer Networks II exam paper from June 2013 administered by VTU. It includes answers to questions on connection-oriented vs connectionless services, datagram packet switching delays, the Bellman-Ford routing algorithm, FIFO and priority queue scheduling, leaky bucket traffic policing, traffic management at the flow aggregate level, the IPv4 header format, the UDP datagram format, the ICMP protocol, the TCP segment format, the Border Gateway Protocol (BGP), and Network Address Translation (NAT). The document provides detailed explanations and diagrams for each question answer.
COMPARATIVE PERFORMANCE ASSESSMENT OF VBLAST ENCODED 8×8 MIMO MC-CDMA WIRELES...pijans
The bit error rate performance of a V-Blast encoded 8x8 MIMO MC-CDMA wireless communication system
for different signal detection (MMSE and ZF) and digital modulation (BPSK, QPSK, DPSK, and 4QAM)
schemes for grayscale image transmission has been investigated in this paper. The proposed wireless system
employ ½-rated Convolution and cyclic redundancy check (CRC) channel encoding over the AWGN channel
and Walsh Hadamard code as an orthogonal spread code. The present Matlab based simulation study
demonstrates that the V-Blast encoded 8×8 MIMO MC-CDMA wireless system with the employment of 1⁄2-
rated convolution and cyclic redundancy check (CRC) channel encoding strategies shows good performance
utilizing BPSK digital modulation and ZF signal detection scheme in grayscale image transmission
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
A 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.
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
In OFDM-IDMA scheme, intersymbol interference (ISI) is resolved by the OFDM layer and multiple access interference (MAI) is suppressed by the IDMA layer at low cost . However OFDM-IDMA scheme suffers high peakto-average power ratio (PAPR) problem. For removing high PAPR problem a hybrid multiple access scheme SC-FDM-IDMA has been proposed. In this paper, bit error rate (BER) performance comparison of SC-FDM-IDMA scheme, OFDM-IDMA scheme and IDMA scheme have been duly presented. Moreover, the BER performance of various subcarrier mapping methods for SC-FDM-IDMA scheme as well as other results with variation of different parameters have also been demonstrated. Finally simulation result for BER performance improvement has been shown employing BCH code. All the simulation results demonstrate the suitability of SC-FDMIDMA scheme for wireless communication under AWGN channel environment.
A simplified-single-correlator-rake-receiver-for-cdma-communicationsCemal Ardil
This document summarizes a research paper that proposes a simplified single correlator RAKE receiver for CDMA communications. The receiver uses a single correlator and code generator, rather than multiple correlators as in conventional RAKE receivers. It spreads data using modified Walsh-Hadamard codes, which provide better uncorrelation between multipath signals. Simulation results showed the proposed receiver achieves lower bit error rates than conventional RAKE receivers when receiving multiple multipath signals.
MULTIPLE CHOICE QUESTIONS ON COMMUNICATION PROTOCOL ENGINEERINGvtunotesbysree
This document provides information about communication protocol engineering. It begins with an introduction to communication models and their key subsystems. It then discusses network reference models and the OSI model in particular. The document covers topics like communication software, protocols, formal modeling techniques for protocols including finite state machines and Petri nets. It also discusses the phases of protocol engineering like specification, validation, implementation etc. and compares informal vs formal approaches to protocol design and development.
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
Abstract: The performance of WCDMA system deteriorates in the presence of multipath fading environment. Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear, anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise, Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake receiver and MMSE and the simulation results are shown. Keywords – MMSE, MMSE-DFE, rake receiver, WCDMA
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.
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Application of diversity techniques for multi user idma communication systemAlexander Decker
1) The document discusses applying diversity techniques like maximal ratio combining (MRC) to mitigate fading in interleave-division multiple access (IDMA) communication systems.
2) It analyzes both receiver diversity using a 1:2 antenna configuration and transmit diversity using a 2:1 antenna configuration for the MRC approach with IDMA.
3) Simulation results show significant performance improvements when applying MRC diversity to IDMA compared to without diversity, for both random and tree-based interleavers.
Multi user performance on mc cdma single relay cooperative system by distribu...IJCNCJournal
Increasing data rate and high performance is the target focus of wireless communication. The multi carrier on multi-hop communication system using relay's diversity technique which is supported by a reliable coding is a system that may give high performance. This research is developing a model of multi user and two scheme of multi carrier CDMA on multi hop communication system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By Alamouti research, Space Time Block Code (STBC) for MIMO system can perform high quality signal at the receiver in the Rayleigh fading channel and the noisy system. In this research, MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC) with multi carrier CDMA on multi hop wireless communication system (relay diversity) which is able to improve the received signal performance.
MC DS CDMA on multi hop wireless communication system with 2 hops is better performing than MC CDMA on multi user without Multi User Detector. To reach BER 10-3 multi hop system with MC CDMA needs more power 5 dB than MC DS CDMA at 5 users using Alamouti scheme for symbol transmission at the relay.
The document is an abstract for a PhD thesis on cooperative communications over wireless relay channels. It discusses analyzing relay channels from an information-theoretic and communication-theoretic perspective, including single-input single-output and multiple-input multiple-output relay channels. For MIMO relay channels, it focuses on two-hop channels using orthogonal space-time block coding at the relay in Rayleigh fading. It derives approximations for error probability and outage probability for amplify-and-forward relaying, and expressions for ergodic and outage capacity.
This document summarizes the simulation steps for investigating the performance of three multi-carrier code division multiple access (MC-CDMA) techniques: conventional MC-CDMA, orthogonal wavelet packet based MC-CDMA (WP-MC-CDMA), and Huang Hilbert Transformation (HHT) based MC-CDMA. The steps include designing the three systems, simulating them with different modulation techniques under fading channels, and comparing their bit error rate performance. Numerical and simulation results are presented to validate the proposed schemes.
This document summarizes the simulation steps for investigating the performance of three multi-carrier code division multiple access (MC-CDMA) techniques: conventional MC-CDMA, orthogonal wavelet packet based MC-CDMA (WP-MC-CDMA), and Huang Hilbert Transformation (HHT) based MC-CDMA. The steps include designing the three systems, simulating them with different modulation techniques under fading channels, and comparing their bit error rate performance. Numerical and simulation results are presented to validate the proposed schemes.
1) The document compares the performance of coded and uncoded MC-DS-CDMA systems using linear block codes. BCH codes are used as the outer code and convolutional codes are used as the inner code in a concatenated coding scheme.
2) Simulation results show that the coded system significantly outperforms the uncoded system, with a coding gain of around 4dB. Using error correction codes is especially beneficial when the number of users is increased, as it is not as severely impacted by multiple access interference.
3) Performance is better when using a decorrelating detector compared to a maximum ratio combiner. However, the benefit of the decorrelating detector is smaller when there are more users.
This document analyzes the effects of carrier frequency offset (CFO) and fading branch correlation (FBC) on the performance of an asynchronous multi-carrier coded-division multiple-access (MC-CDMA) system. It establishes models for an MC-CDMA system with transmitter and receiver, and examines how CFO and FBC impact the bit error rate (BER) performance. Equations are derived relating CFO and FBC, and simulation results are presented showing which parameter, CFO or FBC, has a greater influence on system performance.
Wireless communication now has been focus to increase data rate and high performance. The
multi carrier on multi-hop communication system using relay's diversity technique which is
supported by a reliable coding is a system that may give high performance.
This research is developing a model of multi carrier CDMA on multi hop communication
system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By
Alamouti research, Space Time Block Code (STBC) for MIMO system can perform high quality
signal at the receiver in the Rayleigh fading channel and the noisy system. In this research,
MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC) with multi
carrier CDMA on multi hop wireless communication system (relay diversity) which is able to
reduce the complexity of the system but the system performance even can be maintained and
improved.
MC CDMA on multi hop wireless communication system with 2 hops is performing much better
than Single Input Single Output (SISO) system (1 hop system). Power needed for 1 hop system to
have the same quality as 2 hops system to reach BER 10-3 is 12 dB. And multi hop system needs
orthogonal symbol to send from relay than original symbol to reach better performance. 12.5
dB power up is needed for multi hop system which sent same symbol as transmitter than relay
system which sent orthogonal symbol.
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.
1. MIMO (multiple-input multiple-output) communication uses multiple antennas at both the transmitter and receiver to improve performance. It can increase data throughput and link range without additional bandwidth or transmit power.
2. MIMO systems can be modeled as a narrowband channel with n transmit antennas and m receive antennas. The channel is represented by a matrix H. MIMO channels can be decomposed into parallel SISO channels through singular value decomposition to simplify processing.
3. The capacity of MIMO channels is determined through water-filling of the eigenvalues of the channel matrix H. MIMO provides diversity gain through techniques like beamforming and exploiting the diversity-multiplexing tradeoff.
NEW BER ANALYSIS OF OFDM SYSTEM OVER NAKAGAMI-n (RICE) FADING CHANNELijcseit
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 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.
VTU 6TH SEM CSE COMPUTER NETWORKS 2 SOLVED PAPERS OF JUNE-2013 JUNE-14 & JUNE...vtunotesbysree
This document contains solved questions from a Computer Networks II exam paper from June 2013 administered by VTU. It includes answers to questions on connection-oriented vs connectionless services, datagram packet switching delays, the Bellman-Ford routing algorithm, FIFO and priority queue scheduling, leaky bucket traffic policing, traffic management at the flow aggregate level, the IPv4 header format, the UDP datagram format, the ICMP protocol, the TCP segment format, the Border Gateway Protocol (BGP), and Network Address Translation (NAT). The document provides detailed explanations and diagrams for each question answer.
COMPARATIVE PERFORMANCE ASSESSMENT OF VBLAST ENCODED 8×8 MIMO MC-CDMA WIRELES...pijans
The bit error rate performance of a V-Blast encoded 8x8 MIMO MC-CDMA wireless communication system
for different signal detection (MMSE and ZF) and digital modulation (BPSK, QPSK, DPSK, and 4QAM)
schemes for grayscale image transmission has been investigated in this paper. The proposed wireless system
employ ½-rated Convolution and cyclic redundancy check (CRC) channel encoding over the AWGN channel
and Walsh Hadamard code as an orthogonal spread code. The present Matlab based simulation study
demonstrates that the V-Blast encoded 8×8 MIMO MC-CDMA wireless system with the employment of 1⁄2-
rated convolution and cyclic redundancy check (CRC) channel encoding strategies shows good performance
utilizing BPSK digital modulation and ZF signal detection scheme in grayscale image transmission
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
A 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.
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
In OFDM-IDMA scheme, intersymbol interference (ISI) is resolved by the OFDM layer and multiple access interference (MAI) is suppressed by the IDMA layer at low cost . However OFDM-IDMA scheme suffers high peakto-average power ratio (PAPR) problem. For removing high PAPR problem a hybrid multiple access scheme SC-FDM-IDMA has been proposed. In this paper, bit error rate (BER) performance comparison of SC-FDM-IDMA scheme, OFDM-IDMA scheme and IDMA scheme have been duly presented. Moreover, the BER performance of various subcarrier mapping methods for SC-FDM-IDMA scheme as well as other results with variation of different parameters have also been demonstrated. Finally simulation result for BER performance improvement has been shown employing BCH code. All the simulation results demonstrate the suitability of SC-FDMIDMA scheme for wireless communication under AWGN channel environment.
A simplified-single-correlator-rake-receiver-for-cdma-communicationsCemal Ardil
This document summarizes a research paper that proposes a simplified single correlator RAKE receiver for CDMA communications. The receiver uses a single correlator and code generator, rather than multiple correlators as in conventional RAKE receivers. It spreads data using modified Walsh-Hadamard codes, which provide better uncorrelation between multipath signals. Simulation results showed the proposed receiver achieves lower bit error rates than conventional RAKE receivers when receiving multiple multipath signals.
MULTIPLE CHOICE QUESTIONS ON COMMUNICATION PROTOCOL ENGINEERINGvtunotesbysree
This document provides information about communication protocol engineering. It begins with an introduction to communication models and their key subsystems. It then discusses network reference models and the OSI model in particular. The document covers topics like communication software, protocols, formal modeling techniques for protocols including finite state machines and Petri nets. It also discusses the phases of protocol engineering like specification, validation, implementation etc. and compares informal vs formal approaches to protocol design and development.
Channel Equalization of WCDMA Downlink System Using Finite Length MMSE-DFEIOSR Journals
Abstract: The performance of WCDMA system deteriorates in the presence of multipath fading environment. Fading destroys the orthogonality and is responsible for multiple access interference (MAI). Though conventional rake receiver provides reasonable performance in the WCDMA downlink system due to path diversity, but it does not restores the orthogonality. Linear equalizer restores orthogonality and suppresses MAI, but it is not efficient, since its performance depends on the spectral characteristics of the channel. To overcome this, Minimum Mean Square Error- Decision Feedback Equalizer (MMSE-DFE) with a linear, anticausal feedforward filter, causal feedback filter and simple detector is proposed in this paper. The filter taps of finite length DFE is derived using the cholesky factorization theory, capable of suppressing noise, Intersymbol Interference (ISI) and MAI. This paper describes the WCDMA downlink system using finite length MMSE-DFE and takes into consideration the effects of interference which includes additive white gaussian noise, multipath fading, ISI and MAI. Furthermore, the performance is compared with conventional rake receiver and MMSE and the simulation results are shown. Keywords – MMSE, MMSE-DFE, rake receiver, WCDMA
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Application of diversity techniques for multi user idma communication systemAlexander Decker
1) The document discusses applying diversity techniques like maximal ratio combining (MRC) to mitigate fading in interleave-division multiple access (IDMA) communication systems.
2) It analyzes both receiver diversity using a 1:2 antenna configuration and transmit diversity using a 2:1 antenna configuration for the MRC approach with IDMA.
3) Simulation results show significant performance improvements when applying MRC diversity to IDMA compared to without diversity, for both random and tree-based interleavers.
CHANNEL ESTIMATION AND MULTIUSER DETECTION IN ASYNCHRONOUS SATELLITE COMMUNIC...ijwmn
In this paper, we propose a new method of channel estimation for asynchronous additive white Gaussian noise channels in satellite communications. This method is based on signals correlation and multiuser interference cancellation which adopts a successive structure. Propagation delays and signals amplitudes are jointly estimated in order to be used for data detection at the receiver. As, a multiuser detector, a single stage successive interference cancellation (SIC) architecture is analyzed and integrated to the channel estimation technique and the whole system is evaluated. The satellite access method adopted is the direct sequence code division multiple access (DS CDMA) one. To evaluate the channel estimation and the detection technique, we have simulated a satellite uplink with an asynchronous multiuser access.
Using the Channel State Information (CSI) at the transmitter is fundamental for the precoder
design in Multi-user Multiple Input Single Output (MU-MISO-OFDM) systems. In Frequency
Division Duplex (FDD) systems, CSI can be just available at the transmitter through a limited
feedback channel [1], where we assume that each user quantizes its channel direction with a
finite number of quantization bits. In this paper, we consider a scalar quantization (SQ) scheme
of the Channel Direction Information (CDI). Although vector quantization (VQ) schemes [2],
[3] still outperform this scalar scheme in terms of quantization error and Sum rate, the former
scheme suffers from an exponential search complexity and high storage requirements at the
receiver for high number of feedback bits.
Combining SFBC_OFDM Systems with SVD Assisted Multiuser Transmitter and Multi...IOSR Journals
Abstract: In this work, we exploit the SVD assisted multiuser transmitter (MUT) and multiuser detector (MUD) technique, using downlink (DL) preprocessing transmitter and DL postprocessing receiver matrice .In combination with space frequency block coding (SFBC). And also propose the precoded DL transmission scheme, were the both proposed schemes take advantage of the channel state information (CSI) of all users at the base station (BS), but only of the mobile station (MS)’s own CSI, to decompose the MU MIMO channels into parallel single input single output (SISO), these two proposed schemes are compared to the vertical layered space time (V_BLAST) combined with SFBC (SFBC_VBLAST). Our Simulation results show that the performance of the proposed scheme with DL Zero Forcing (ZF) transmitter for interference canceller outperforms the SFBC_VBLAST and the precoded DL schemes with ZF receiver in frequency selective fading channels. Keywords – Post processing, Preprocessing,, SFBC, SVD, ZF.
Performance of Wideband Mobile Channel with Perfect Synchronism BPSK vs QPSK ...Editor Jacotech
Direct-sequence code-division multiple access (DS-CDMA) is
currently the subject of much research as it is a promising
multiple access capability for third and fourth generations
mobile communication systems. The synchronous DS-CDMA
system is well known for eliminating the effects of multiple
access interference (MAI) which limits the capacity and
degrades the BER performance of the system. In this paper,
we investigate the bit error rate (BER) performance of a
synchronous DS-CDMA system over a wideband mobile
radio channel. The BER performance is affected by the
difference in path length ΔL and the number of arriving
signals N. Furthermore, the effect of these parameters is
examined on the synchronous DS-CDMA system for different
users’ number as well as different processing gain Gp. In this
environment and under the above conditions the performances
of the BPSK (Binary Phase Shift Keying) and the QPSK
(Quadrature Phase Shift Keying) modulations are compared.
The promising simulation results showed the possibility of
applying this system to the wideband mobile radio channel.
PERFORMANCE EVALUATION OF MC-CDMA SYSTEM OVER RAYLEIGH FADING CHANNELIJCSES Journal
Multi Carrier Code Division Multiple Access (MC-CDMA) is a well known technique for high speed
wireless data transmission .Two advanced technology was included in the MC-CDMA structure, such as
orthogonal frequency division multiplex (OFDM) and the code division multiple access (CDMA),so that it
benefits from the robustness of OFDM against multipath environment and from the capability of multiuser
multiplexing services that is achieved via (CDMA) system. MC-CDMA is a multicarrier spread spectrum
system which is classified as the candidate scheme for future mobile radio systems. In this paper MCCDMA
system, with Rayleigh fading channel and 16QAM array modulation, was simulated to investigate
the effects of different parameters on the system performance, such as processing gain; number of paths;
number of users; interleaving; and coding ratio.MC-CDMA performances can be considerably improved
by proper selection of these parameters. As expected, results show that MC-CDMA has a better performance over CDMA system.
Computationally Efficient Multi-Antenna Techniques for Multi-User Two-Way Wire...IJECEIAES
In this work, we are interested in implementing, developing and evaluating multi-antenna techniques used for multi-user two-way wireless relay networks that provide a good tradeoff between the computational complexity and performance in terms of symbol error rate and achievable data rate. In particular, a variety of newly multi-antenna techniques is proposed and studied. Some techniques based on orthogonal projection enjoy low computational complexity. However, the performance penalty associated with them is high. Other techniques based on maximum likelihood strategy enjoy high performance, however, they suffer from very high computational complexity. The Other techniques based on randomization strategy provide a good trade-off between the computational complexity and performance where they enjoy low computational complexity with almost the same performance as compared to the techniques based on maximum likelihood strategy.
A blind channel shortening for multiuser, multicarrier CDMA system over multi...TELKOMNIKA JOURNAL
In this paper we derive the Multicarrier Equalization by Restoration of Redundancy (MERRY) algorithm: A blind, adaptive channel shortening algorithm for updating a Time-domain Equalizer (TEQ) in a system employing MultiCarrier Code Division Multiple Access (MC-CDMA) modulation. We show that the MERRY algorithm applied to the MC-CDMA system converges considerably more rapidly than in the Orthogonal Frequency Division Multiplexing (OFDM) system [1]. Simulations results are provided to demonstrate the performance of the algorithm.
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.
This document summarizes a research paper on developing a reconfigurable hardware architecture for implementing maximum likelihood (ML) decoding algorithms in MIMO systems. It begins by introducing MIMO techniques for improving wireless communication throughput. It then describes various MIMO receiver algorithms and chooses ML for its best performance. The document outlines the ML decoding algorithm and presents a Simulink model. It discusses implementing the MIMO decoder as a modular, reconfigurable architecture on an FPGA and shows placement results on a Xilinx Virtex 4 chip. The work aims to provide flexible hardware for MIMO signal processing applications.
MIMO Channel Estimation Using the LS and MMSE AlgorithmIOSRJECE
Wireless Communication Technology has developed over the past few yearsfor other objectives.The Multiple InputMultiple Output (MIMO) is one of techniques that is used to enhancethe data rates, in which multiple antennas are employed both the transmitter and receiver. Multiple signals are transmitted from different antennas at the transmitter using the same frequency and separated space. Various channel estimation techniques are employed in order to judge the physical effects of the medium present. In this paper, we analyze and implementvarious estimation techniques for MIMO Systems such as Least Squares (LS), Minimum Mean Square Error (MMSE),these techniques are therefore compared to effectively estimate the channel in MIMO System. The results demonstrate that SNR required to support different values of bit error rate varies depending on different low correlation between the transmitting and the receiving antennas .In addition, it is illustrated that when the number of transmitter and receiver antennas increases, the performance of TBCE schemes significantly improves. The Same behavior isalso observed for MIMO system. Performance of both MMSE and LSestimation are the same for allkinds of modulation at small value of SNR but the more we increase the SNR value the more performance gap goes on increasing.
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.
Low Complexity Multi-User MIMO Detection for Uplink SCMA System Using Expecta...TELKOMNIKA JOURNAL
Sparse code multiple access (SCMA), which combines the advantages of low density signature
(LDS) and code-division multiple access (CDMA), is regarded as one of the promising modulation technique
candidate for the next generation of wireless systems. Conventionally, the message passing algorithm (MPA)
is used for data detector at the receiver side. However, the MPA-SCMA cannot be implemented in the next
generation wireless systems, because of its unacceptable complexity cost. Specifically, the complexity of
MPA-SCMA grows exponentially with the number of antennas. Considering the use of high dimensional
systems in the next generation of wireless systems, such as massive multi-user MIMO systems, the conventional
MPA-SCMA is prohibitive. In this paper, we propose a low complexity detector algorithm named the
expectation propagation algorithm (EPA) for SCMA. Mainly, the EPA-SCMA solves the complexity problem
of MPA-SCMA and enables the implementation of SCMA in massive MU-MIMO systems. For instance, the
EPA-SCMA also enables the implemantation of SCMA in the next generation wireless systems. We further
show that the EPA can achieve the optimal detection performance as the numbers of transmit and receive
antennas grow. We also demonstrate that a rotation design in SCMA codebook is unnecessary, which is
quite rather different from the general assumption.
This document discusses techniques for improving multiuser detection in DS-CDMA systems using successive interference cancellation. It begins with an introduction to the multiple access interference problem in CDMA systems and how multiuser detection can help address this issue. It then provides the system model for a CDMA uplink and describes the matched filter receiver structure. Next, it discusses multiuser detection algorithms and focuses on successive interference cancellation as a suboptimal but lower complexity method. The document describes the successive interference cancellation algorithm and introduces the groupwise successive interference cancellation technique, which provides cancellation in groups to handle multirate users. It provides a block diagram of the groupwise successive interference cancellation receiver and discusses how it works to sequentially detect and cancel the strongest user signals
Discrete-wavelet-transform recursive inverse algorithm using second-order est...TELKOMNIKA JOURNAL
The recursive-least-squares (RLS) algorithm was introduced as an alternative to LMS algorithm with enhanced performance. Computational complexity and instability in updating the autocolleltion matrix are some of the drawbacks of the RLS algorithm that were among the reasons for the intrduction of the second-order recursive inverse (RI) adaptive algorithm. The 2nd order RI adaptive algorithm suffered from low convergence rate in certain scenarios that required a relatively small initial step-size. In this paper, we propose a newsecond-order RI algorithm that projects the input signal to a new domain namely discrete-wavelet-transform (DWT) as pre step before performing the algorithm. This transformation overcomes the low convergence rate of the second-order RI algorithm by reducing the self-correlation of the input signal in the mentioned scenatios. Expeirments are conducted using the noise cancellation setting. The performance of the proposed algorithm is compared to those of the RI, original second-order RI and RLS algorithms in different Gaussian and impulsive noise environments. Simulations demonstrate the superiority of the proposed algorithm in terms of convergence rate comparedto those algorithms.
Peak to Average Power Ratio Reduction in Mc Cdma System by Using Pulse Shapin...IOSR Journals
Abstract: One of the drawback of multicarrier code division multiple access (MC CDMA) is the high peak to
average power ratio (PAPR). In this paper A novel scheme based on pulse shaping described for PAPR
reduction. Here three different pulse shaping filters (Raised cosine, Sinc power pulse and Nyqist pulse) are
described for PAPR reduction in MC CDMA system. The method is based on the proper selection of the pulses
for shaping the different sub carriers of the MC CDMA modulation scheme. It is shown by computer simulation
that the scheme achieves the significant improvement in PAPR reduction in MC CDMA system. Its
implementation complexity is much low in comparison to the previous published methods. Thus pulse shaping
technique can be used not only to shape the spectrum of the transmitted signal but also to reduce its PAPR. In
computer simulation It is observed that by using nyquist pulse near about 6.8 db PAPR is obtained. Which is
considerable PAPR reduction than a PAPR value of Original MC CDMA signal
Keywords: MC CDMA, PAPR, PULSE SHAPING, BPSK
PERFORMANCE OF MIMO MC-CDMA SYSTEM WITH CHANNEL ESTIMATION AND MMSE EQUALIZATIONTamilarasan N
The quality of a wireless link can be described by three basic parameters, namely transmission rate, transmission range
and transmission reliability. With the advent of multiple-input multiple-output (MIMO) assisted Multicarrier code
division multiple access (MC-CDMA) systems, the above-mentioned three parameters may be simultaneously
improved. The MC-CDMA combined with the MIMO technique, has become a core technology for future mobile radio
communication system. However, possible potential gain in spectral efficiency is challenged by the receiver’s ability to
accurately detect the symbol due to inter symbol interference (ISI). Multipath propagation, mobility of transmitter,
receiver and local scattering cause the signal to be spread in frequency, different arrival time and angle, which results in
ISI in the received signal. This will affect overall system performance. The use of MC-CDMA mitigates the problem of
time dispersion. However, still it is necessary to remove the amplitude and phase shift caused by channel. To solve this
problem, a multiple antenna array can be used at the receiver, not only for spectral efficiency or gain enhancement, but
also for interference suppression. This can be done by the, efficient channel estimation with strong equalization. This
paper proposes MIMO MC-CDMA system, Minimum mean square error (MMSE) equalization with pilot based
channel estimation. The simulation result shows improved Bit error rate (BER) performance when the sub carrier (SC)
and antenna configuration were increased
Performance evaluation of high mobility OFDM channel estimation techniques IJECEIAES
In wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) has been adopted due to its robustness to multipath fading and high data rate transmissions. At the other hand, the performance of OFDM systems severely degraded due to multi-path fading and Doppler frequency shifts in mobile systems, which causes inter-carrier-interference (ICI). Thus, Estimation of channel parameters is required at the receiver using a pre designed estimator where pilot tones are inserted in each OFDM symbol. In this paper, a random pilot data are generated and inserted in each OFDM symbol at equally spaced locations. The performance test of Least Square (LS) and Linear Minimum Mean Square (LMMSE) estimation methods are proposed with Discrete Fourier Transform (DFT) based on both LS and LMMSE, where different ITU channel models are considered in order to compare their performance for data transmission in high mobile systems with different Doppler frequencies exceeds 200 Hz and minimal number of pilots.
Similar to Multiuser Detection with Decision-feedback Detectors and PIC in MC-CDMA System (20)
Amazon products reviews classification based on machine learning, deep learni...TELKOMNIKA JOURNAL
In recent times, the trend of online shopping through e-commerce stores and websites has grown to a huge extent. Whenever a product is purchased on an e-commerce platform, people leave their reviews about the product. These reviews are very helpful for the store owners and the product’s manufacturers for the betterment of their work process as well as product quality. An automated system is proposed in this work that operates on two datasets D1 and D2 obtained from Amazon. After certain preprocessing steps, N-gram and word embedding-based features are extracted using term frequency-inverse document frequency (TF-IDF), bag of words (BoW) and global vectors (GloVe), and Word2vec, respectively. Four machine learning (ML) models support vector machines (SVM), logistic regression (RF), logistic regression (LR), multinomial Naïve Bayes (MNB), two deep learning (DL) models convolutional neural network (CNN), long-short term memory (LSTM), and standalone bidirectional encoder representations (BERT) are used to classify reviews as either positive or negative. The results obtained by the standard ML, DL models and BERT are evaluated using certain performance evaluation measures. BERT turns out to be the best-performing model in the case of D1 with an accuracy of 90% on features derived by word embedding models while the CNN provides the best accuracy of 97% upon word embedding features in the case of D2. The proposed model shows better overall performance on D2 as compared to D1.
Design, simulation, and analysis of microstrip patch antenna for wireless app...TELKOMNIKA JOURNAL
In this study, a microstrip patch antenna that works at 3.6 GHz was built and tested to see how well it works. In this work, Rogers RT/Duroid 5880 has been used as the substrate material, with a dielectric permittivity of 2.2 and a thickness of 0.3451 mm; it serves as the base for the examined antenna. The computer simulation technology (CST) studio suite is utilized to show the recommended antenna design. The goal of this study was to get a more extensive transmission capacity, a lower voltage standing wave ratio (VSWR), and a lower return loss, but the main goal was to get a higher gain, directivity, and efficiency. After simulation, the return loss, gain, directivity, bandwidth, and efficiency of the supplied antenna are found to be -17.626 dB, 9.671 dBi, 9.924 dBi, 0.2 GHz, and 97.45%, respectively. Besides, the recreation uncovered that the transfer speed side-lobe level at phi was much better than those of the earlier works, at -28.8 dB, respectively. Thus, it makes a solid contender for remote innovation and more robust communication.
Design and simulation an optimal enhanced PI controller for congestion avoida...TELKOMNIKA JOURNAL
This document describes using a snake optimization algorithm to tune the gains of an enhanced proportional-integral controller for congestion avoidance in a TCP/AQM system. The controller aims to maintain a stable and desired queue size without noise or transmission problems. A linearized model of the TCP/AQM system is presented. An enhanced PI controller combining nonlinear gain and original PI gains is proposed. The snake optimization algorithm is then used to tune the parameters of the enhanced PI controller to achieve optimal system performance and response. Simulation results are discussed showing the proposed controller provides a stable and robust behavior for congestion control.
Improving the detection of intrusion in vehicular ad-hoc networks with modifi...TELKOMNIKA JOURNAL
Vehicular ad-hoc networks (VANETs) are wireless-equipped vehicles that form networks along the road. The security of this network has been a major challenge. The identity-based cryptosystem (IBC) previously used to secure the networks suffers from membership authentication security features. This paper focuses on improving the detection of intruders in VANETs with a modified identity-based cryptosystem (MIBC). The MIBC is developed using a non-singular elliptic curve with Lagrange interpolation. The public key of vehicles and roadside units on the network are derived from number plates and location identification numbers, respectively. Pseudo-identities are used to mask the real identity of users to preserve their privacy. The membership authentication mechanism ensures that only valid and authenticated members of the network are allowed to join the network. The performance of the MIBC is evaluated using intrusion detection ratio (IDR) and computation time (CT) and then validated with the existing IBC. The result obtained shows that the MIBC recorded an IDR of 99.3% against 94.3% obtained for the existing identity-based cryptosystem (EIBC) for 140 unregistered vehicles attempting to intrude on the network. The MIBC shows lower CT values of 1.17 ms against 1.70 ms for EIBC. The MIBC can be used to improve the security of VANETs.
Conceptual model of internet banking adoption with perceived risk and trust f...TELKOMNIKA JOURNAL
Understanding the primary factors of internet banking (IB) acceptance is critical for both banks and users; nevertheless, our knowledge of the role of users’ perceived risk and trust in IB adoption is limited. As a result, we develop a conceptual model by incorporating perceived risk and trust into the technology acceptance model (TAM) theory toward the IB. The proper research emphasized that the most essential component in explaining IB adoption behavior is behavioral intention to use IB adoption. TAM is helpful for figuring out how elements that affect IB adoption are connected to one another. According to previous literature on IB and the use of such technology in Iraq, one has to choose a theoretical foundation that may justify the acceptance of IB from the customer’s perspective. The conceptual model was therefore constructed using the TAM as a foundation. Furthermore, perceived risk and trust were added to the TAM dimensions as external factors. The key objective of this work was to extend the TAM to construct a conceptual model for IB adoption and to get sufficient theoretical support from the existing literature for the essential elements and their relationships in order to unearth new insights about factors responsible for IB adoption.
Efficient combined fuzzy logic and LMS algorithm for smart antennaTELKOMNIKA JOURNAL
The smart antennas are broadly used in wireless communication. The least mean square (LMS) algorithm is a procedure that is concerned in controlling the smart antenna pattern to accommodate specified requirements such as steering the beam toward the desired signal, in addition to placing the deep nulls in the direction of unwanted signals. The conventional LMS (C-LMS) has some drawbacks like slow convergence speed besides high steady state fluctuation error. To overcome these shortcomings, the present paper adopts an adaptive fuzzy control step size least mean square (FC-LMS) algorithm to adjust its step size. Computer simulation outcomes illustrate that the given model has fast convergence rate as well as low mean square error steady state.
Design and implementation of a LoRa-based system for warning of forest fireTELKOMNIKA JOURNAL
This paper presents the design and implementation of a forest fire monitoring and warning system based on long range (LoRa) technology, a novel ultra-low power consumption and long-range wireless communication technology for remote sensing applications. The proposed system includes a wireless sensor network that records environmental parameters such as temperature, humidity, wind speed, and carbon dioxide (CO2) concentration in the air, as well as taking infrared photos.The data collected at each sensor node will be transmitted to the gateway via LoRa wireless transmission. Data will be collected, processed, and uploaded to a cloud database at the gateway. An Android smartphone application that allows anyone to easily view the recorded data has been developed. When a fire is detected, the system will sound a siren and send a warning message to the responsible personnel, instructing them to take appropriate action. Experiments in Tram Chim Park, Vietnam, have been conducted to verify and evaluate the operation of the system.
Wavelet-based sensing technique in cognitive radio networkTELKOMNIKA JOURNAL
Cognitive radio is a smart radio that can change its transmitter parameter based on interaction with the environment in which it operates. The demand for frequency spectrum is growing due to a big data issue as many Internet of Things (IoT) devices are in the network. Based on previous research, most frequency spectrum was used, but some spectrums were not used, called spectrum hole. Energy detection is one of the spectrum sensing methods that has been frequently used since it is easy to use and does not require license users to have any prior signal understanding. But this technique is incapable of detecting at low signal-to-noise ratio (SNR) levels. Therefore, the wavelet-based sensing is proposed to overcome this issue and detect spectrum holes. The main objective of this work is to evaluate the performance of wavelet-based sensing and compare it with the energy detection technique. The findings show that the percentage of detection in wavelet-based sensing is 83% higher than energy detection performance. This result indicates that the wavelet-based sensing has higher precision in detection and the interference towards primary user can be decreased.
A novel compact dual-band bandstop filter with enhanced rejection bandsTELKOMNIKA JOURNAL
In this paper, we present the design of a new wide dual-band bandstop filter (DBBSF) using nonuniform transmission lines. The method used to design this filter is to replace conventional uniform transmission lines with nonuniform lines governed by a truncated Fourier series. Based on how impedances are profiled in the proposed DBBSF structure, the fractional bandwidths of the two 10 dB-down rejection bands are widened to 39.72% and 52.63%, respectively, and the physical size has been reduced compared to that of the filter with the uniform transmission lines. The results of the electromagnetic (EM) simulation support the obtained analytical response and show an improved frequency behavior.
Deep learning approach to DDoS attack with imbalanced data at the application...TELKOMNIKA JOURNAL
A distributed denial of service (DDoS) attack is where one or more computers attack or target a server computer, by flooding internet traffic to the server. As a result, the server cannot be accessed by legitimate users. A result of this attack causes enormous losses for a company because it can reduce the level of user trust, and reduce the company’s reputation to lose customers due to downtime. One of the services at the application layer that can be accessed by users is a web-based lightweight directory access protocol (LDAP) service that can provide safe and easy services to access directory applications. We used a deep learning approach to detect DDoS attacks on the CICDDoS 2019 dataset on a complex computer network at the application layer to get fast and accurate results for dealing with unbalanced data. Based on the results obtained, it is observed that DDoS attack detection using a deep learning approach on imbalanced data performs better when implemented using synthetic minority oversampling technique (SMOTE) method for binary classes. On the other hand, the proposed deep learning approach performs better for detecting DDoS attacks in multiclass when implemented using the adaptive synthetic (ADASYN) method.
The appearance of uncertainties and disturbances often effects the characteristics of either linear or nonlinear systems. Plus, the stabilization process may be deteriorated thus incurring a catastrophic effect to the system performance. As such, this manuscript addresses the concept of matching condition for the systems that are suffering from miss-match uncertainties and exogeneous disturbances. The perturbation towards the system at hand is assumed to be known and unbounded. To reach this outcome, uncertainties and their classifications are reviewed thoroughly. The structural matching condition is proposed and tabulated in the proposition 1. Two types of mathematical expressions are presented to distinguish the system with matched uncertainty and the system with miss-matched uncertainty. Lastly, two-dimensional numerical expressions are provided to practice the proposed proposition. The outcome shows that matching condition has the ability to change the system to a design-friendly model for asymptotic stabilization.
Implementation of FinFET technology based low power 4×4 Wallace tree multipli...TELKOMNIKA JOURNAL
Many systems, including digital signal processors, finite impulse response (FIR) filters, application-specific integrated circuits, and microprocessors, use multipliers. The demand for low power multipliers is gradually rising day by day in the current technological trend. In this study, we describe a 4×4 Wallace multiplier based on a carry select adder (CSA) that uses less power and has a better power delay product than existing multipliers. HSPICE tool at 16 nm technology is used to simulate the results. In comparison to the traditional CSA-based multiplier, which has a power consumption of 1.7 µW and power delay product (PDP) of 57.3 fJ, the results demonstrate that the Wallace multiplier design employing CSA with first zero finding logic (FZF) logic has the lowest power consumption of 1.4 µW and PDP of 27.5 fJ.
Evaluation of the weighted-overlap add model with massive MIMO in a 5G systemTELKOMNIKA JOURNAL
The flaw in 5G orthogonal frequency division multiplexing (OFDM) becomes apparent in high-speed situations. Because the doppler effect causes frequency shifts, the orthogonality of OFDM subcarriers is broken, lowering both their bit error rate (BER) and throughput output. As part of this research, we use a novel design that combines massive multiple input multiple output (MIMO) and weighted overlap and add (WOLA) to improve the performance of 5G systems. To determine which design is superior, throughput and BER are calculated for both the proposed design and OFDM. The results of the improved system show a massive improvement in performance ver the conventional system and significant improvements with massive MIMO, including the best throughput and BER. When compared to conventional systems, the improved system has a throughput that is around 22% higher and the best performance in terms of BER, but it still has around 25% less error than OFDM.
Reflector antenna design in different frequencies using frequency selective s...TELKOMNIKA JOURNAL
In this study, it is aimed to obtain two different asymmetric radiation patterns obtained from antennas in the shape of the cross-section of a parabolic reflector (fan blade type antennas) and antennas with cosecant-square radiation characteristics at two different frequencies from a single antenna. For this purpose, firstly, a fan blade type antenna design will be made, and then the reflective surface of this antenna will be completed to the shape of the reflective surface of the antenna with the cosecant-square radiation characteristic with the frequency selective surface designed to provide the characteristics suitable for the purpose. The frequency selective surface designed and it provides the perfect transmission as possible at 4 GHz operating frequency, while it will act as a band-quenching filter for electromagnetic waves at 5 GHz operating frequency and will be a reflective surface. Thanks to this frequency selective surface to be used as a reflective surface in the antenna, a fan blade type radiation characteristic at 4 GHz operating frequency will be obtained, while a cosecant-square radiation characteristic at 5 GHz operating frequency will be obtained.
Reagentless iron detection in water based on unclad fiber optical sensorTELKOMNIKA JOURNAL
A simple and low-cost fiber based optical sensor for iron detection is demonstrated in this paper. The sensor head consist of an unclad optical fiber with the unclad length of 1 cm and it has a straight structure. Results obtained shows a linear relationship between the output light intensity and iron concentration, illustrating the functionality of this iron optical sensor. Based on the experimental results, the sensitivity and linearity are achieved at 0.0328/ppm and 0.9824 respectively at the wavelength of 690 nm. With the same wavelength, other performance parameters are also studied. Resolution and limit of detection (LOD) are found to be 0.3049 ppm and 0.0755 ppm correspondingly. This iron sensor is advantageous in that it does not require any reagent for detection, enabling it to be simpler and cost-effective in the implementation of the iron sensing.
Impact of CuS counter electrode calcination temperature on quantum dot sensit...TELKOMNIKA JOURNAL
In place of the commercial Pt electrode used in quantum sensitized solar cells, the low-cost CuS cathode is created using electrophoresis. High resolution scanning electron microscopy and X-ray diffraction were used to analyze the structure and morphology of structural cubic samples with diameters ranging from 40 nm to 200 nm. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 °C, 120 °C, 150 °C, and 180 °C under vacuum. The fluorine doped tin oxide (FTO)/CuS cathode electrode reached a maximum efficiency of 3.89% when it was calcined at 120 °C. Compared to other temperature combinations, CuS nanoparticles crystallize at 120 °C, which lowers resistance while increasing electron lifetime.
In place of the commercial Pt electrode used in quantum sensitized solar cells, the low-cost CuS cathode is created using electrophoresis. High resolution scanning electron microscopy and X-ray diffraction were used to analyze the structure and morphology of structural cubic samples with diameters ranging from 40 nm to 200 nm. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 °C, 120 °C, 150 °C, and 180 °C under vacuum. The fluorine doped tin oxide (FTO)/CuS cathode electrode reached a maximum efficiency of 3.89% when it was calcined at 120 °C. Compared to other temperature combinations, CuS nanoparticles crystallize at 120 °C, which lowers resistance while increasing electron lifetime.
A progressive learning for structural tolerance online sequential extreme lea...TELKOMNIKA JOURNAL
This article discusses the progressive learning for structural tolerance online sequential extreme learning machine (PSTOS-ELM). PSTOS-ELM can save robust accuracy while updating the new data and the new class data on the online training situation. The robustness accuracy arises from using the householder block exact QR decomposition recursive least squares (HBQRD-RLS) of the PSTOS-ELM. This method is suitable for applications that have data streaming and often have new class data. Our experiment compares the PSTOS-ELM accuracy and accuracy robustness while data is updating with the batch-extreme learning machine (ELM) and structural tolerance online sequential extreme learning machine (STOS-ELM) that both must retrain the data in a new class data case. The experimental results show that PSTOS-ELM has accuracy and robustness comparable to ELM and STOS-ELM while also can update new class data immediately.
Electroencephalography-based brain-computer interface using neural networksTELKOMNIKA JOURNAL
This study aimed to develop a brain-computer interface that can control an electric wheelchair using electroencephalography (EEG) signals. First, we used the Mind Wave Mobile 2 device to capture raw EEG signals from the surface of the scalp. The signals were transformed into the frequency domain using fast Fourier transform (FFT) and filtered to monitor changes in attention and relaxation. Next, we performed time and frequency domain analyses to identify features for five eye gestures: opened, closed, blink per second, double blink, and lookup. The base state was the opened-eyes gesture, and we compared the features of the remaining four action gestures to the base state to identify potential gestures. We then built a multilayer neural network to classify these features into five signals that control the wheelchair’s movement. Finally, we designed an experimental wheelchair system to test the effectiveness of the proposed approach. The results demonstrate that the EEG classification was highly accurate and computationally efficient. Moreover, the average performance of the brain-controlled wheelchair system was over 75% across different individuals, which suggests the feasibility of this approach.
Adaptive segmentation algorithm based on level set model in medical imagingTELKOMNIKA JOURNAL
For image segmentation, level set models are frequently employed. It offer best solution to overcome the main limitations of deformable parametric models. However, the challenge when applying those models in medical images stills deal with removing blurs in image edges which directly affects the edge indicator function, leads to not adaptively segmenting images and causes a wrong analysis of pathologies wich prevents to conclude a correct diagnosis. To overcome such issues, an effective process is suggested by simultaneously modelling and solving systems’ two-dimensional partial differential equations (PDE). The first PDE equation allows restoration using Euler’s equation similar to an anisotropic smoothing based on a regularized Perona and Malik filter that eliminates noise while preserving edge information in accordance with detected contours in the second equation that segments the image based on the first equation solutions. This approach allows developing a new algorithm which overcome the studied model drawbacks. Results of the proposed method give clear segments that can be applied to any application. Experiments on many medical images in particular blurry images with high information losses, demonstrate that the developed approach produces superior segmentation results in terms of quantity and quality compared to other models already presented in previeous works.
Automatic channel selection using shuffled frog leaping algorithm for EEG bas...TELKOMNIKA JOURNAL
Drug addiction is a complex neurobiological disorder that necessitates comprehensive treatment of both the body and mind. It is categorized as a brain disorder due to its impact on the brain. Various methods such as electroencephalography (EEG), functional magnetic resonance imaging (FMRI), and magnetoencephalography (MEG) can capture brain activities and structures. EEG signals provide valuable insights into neurological disorders, including drug addiction. Accurate classification of drug addiction from EEG signals relies on appropriate features and channel selection. Choosing the right EEG channels is essential to reduce computational costs and mitigate the risk of overfitting associated with using all available channels. To address the challenge of optimal channel selection in addiction detection from EEG signals, this work employs the shuffled frog leaping algorithm (SFLA). SFLA facilitates the selection of appropriate channels, leading to improved accuracy. Wavelet features extracted from the selected input channel signals are then analyzed using various machine learning classifiers to detect addiction. Experimental results indicate that after selecting features from the appropriate channels, classification accuracy significantly increased across all classifiers. Particularly, the multi-layer perceptron (MLP) classifier combined with SFLA demonstrated a remarkable accuracy improvement of 15.78% while reducing time complexity.
Software Engineering and Project Management - Software Testing + Agile Method...Prakhyath Rai
Software Testing: A Strategic Approach to Software Testing, Strategic Issues, Test Strategies for Conventional Software, Test Strategies for Object -Oriented Software, Validation Testing, System Testing, The Art of Debugging.
Agile Methodology: Before Agile – Waterfall, Agile Development.
Prediction of Electrical Energy Efficiency Using Information on Consumer's Ac...PriyankaKilaniya
Energy efficiency has been important since the latter part of the last century. The main object of this survey is to determine the energy efficiency knowledge among consumers. Two separate districts in Bangladesh are selected to conduct the survey on households and showrooms about the energy and seller also. The survey uses the data to find some regression equations from which it is easy to predict energy efficiency knowledge. The data is analyzed and calculated based on five important criteria. The initial target was to find some factors that help predict a person's energy efficiency knowledge. From the survey, it is found that the energy efficiency awareness among the people of our country is very low. Relationships between household energy use behaviors are estimated using a unique dataset of about 40 households and 20 showrooms in Bangladesh's Chapainawabganj and Bagerhat districts. Knowledge of energy consumption and energy efficiency technology options is found to be associated with household use of energy conservation practices. Household characteristics also influence household energy use behavior. Younger household cohorts are more likely to adopt energy-efficient technologies and energy conservation practices and place primary importance on energy saving for environmental reasons. Education also influences attitudes toward energy conservation in Bangladesh. Low-education households indicate they primarily save electricity for the environment while high-education households indicate they are motivated by environmental concerns.
Applications of artificial Intelligence in Mechanical Engineering.pdfAtif Razi
Historically, mechanical engineering has relied heavily on human expertise and empirical methods to solve complex problems. With the introduction of computer-aided design (CAD) and finite element analysis (FEA), the field took its first steps towards digitization. These tools allowed engineers to simulate and analyze mechanical systems with greater accuracy and efficiency. However, the sheer volume of data generated by modern engineering systems and the increasing complexity of these systems have necessitated more advanced analytical tools, paving the way for AI.
AI offers the capability to process vast amounts of data, identify patterns, and make predictions with a level of speed and accuracy unattainable by traditional methods. This has profound implications for mechanical engineering, enabling more efficient design processes, predictive maintenance strategies, and optimized manufacturing operations. AI-driven tools can learn from historical data, adapt to new information, and continuously improve their performance, making them invaluable in tackling the multifaceted challenges of modern mechanical engineering.
Height and depth gauge linear metrology.pdfq30122000
Height gauges may also be used to measure the height of an object by using the underside of the scriber as the datum. The datum may be permanently fixed or the height gauge may have provision to adjust the scale, this is done by sliding the scale vertically along the body of the height gauge by turning a fine feed screw at the top of the gauge; then with the scriber set to the same level as the base, the scale can be matched to it. This adjustment allows different scribers or probes to be used, as well as adjusting for any errors in a damaged or resharpened probe.
Use PyCharm for remote debugging of WSL on a Windo cf5c162d672e4e58b4dde5d797...shadow0702a
This document serves as a comprehensive step-by-step guide on how to effectively use PyCharm for remote debugging of the Windows Subsystem for Linux (WSL) on a local Windows machine. It meticulously outlines several critical steps in the process, starting with the crucial task of enabling permissions, followed by the installation and configuration of WSL.
The guide then proceeds to explain how to set up the SSH service within the WSL environment, an integral part of the process. Alongside this, it also provides detailed instructions on how to modify the inbound rules of the Windows firewall to facilitate the process, ensuring that there are no connectivity issues that could potentially hinder the debugging process.
The document further emphasizes on the importance of checking the connection between the Windows and WSL environments, providing instructions on how to ensure that the connection is optimal and ready for remote debugging.
It also offers an in-depth guide on how to configure the WSL interpreter and files within the PyCharm environment. This is essential for ensuring that the debugging process is set up correctly and that the program can be run effectively within the WSL terminal.
Additionally, the document provides guidance on how to set up breakpoints for debugging, a fundamental aspect of the debugging process which allows the developer to stop the execution of their code at certain points and inspect their program at those stages.
Finally, the document concludes by providing a link to a reference blog. This blog offers additional information and guidance on configuring the remote Python interpreter in PyCharm, providing the reader with a well-rounded understanding of the process.
Home security is of paramount importance in today's world, where we rely more on technology, home
security is crucial. Using technology to make homes safer and easier to control from anywhere is
important. Home security is important for the occupant’s safety. In this paper, we came up with a low cost,
AI based model home security system. The system has a user-friendly interface, allowing users to start
model training and face detection with simple keyboard commands. Our goal is to introduce an innovative
home security system using facial recognition technology. Unlike traditional systems, this system trains
and saves images of friends and family members. The system scans this folder to recognize familiar faces
and provides real-time monitoring. If an unfamiliar face is detected, it promptly sends an email alert,
ensuring a proactive response to potential security threats.
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associated with iterative successive parallel arbitrated decision feedback detectors is
considered in DS-CDMA systems [17]. In order to refine the symbol estimates, multistage and
iterative DF schemes are combined based on the successive interference cancellation S-DFD
and parallel interference cancellation P-DFD [18].
In this work, multiuser detection in MC CDMA system for an uplink scenario was
performed using the combinations of minimum mean squared error MMSE detectors with
non-linear detectors such as, decision feedback detection DFD and parallel interference
cancellation (PIC). In order to improve the performance of the MC-CDMA system in Rayleigh
fading channel different processing are suggest, first we adopt in the analyze usually detections
techniques MMSE, the maximum likelihood (ML), PIC, P-DFD and MMSE-P-DF detector. The
results in terms of performance show that MMSE and ML present better performance than the
other method detection. In the second time we propose an iterative method established on the
multi-stage techniques MMSE-PIC, P-DFD-PIC to evaluate the system.
This paper is organized as follows: In section 2 we first review the MC-CDMA data
model and formulate the problem of interest. In section 3 we examine the multiuser
decision-feedback receiver, where we develop mathematical concepts of MMSE decision
feedback detector and the parallel feedback detector P-DFD. Section 4 is devoted to
the iterative technique and the proposed model. Section 5 presents and discusses of the
simulation results, then a comparison of recently studies is made. Finally, section 6 contains
conclusions.
2. MC-CDMA System Model
We consider a synchronous MC-CDMA in uplink system with binary phase shift keying
(BPSK) modulation in a Rayleigh fading channel as shown in Figure 1.
Figure 1. MC-CDMA system model
First, user bits bk are multiplied by a spreading code Skn and then inverse fast Fourier
transform (IFFT) is performed. The number of sub-carriers and all users has the same
spreading factor. Finally, the signal is transmitted through a Rayleigh fading channel. At the
receiver, after the fast Fourier transform (FFT) operation, received vector r(t) is expressed
as [19]:
𝑟(𝑡) = ∑ ∑ 𝐴 𝑘 𝑏 𝑘 𝑆 𝑘𝑛ℎ 𝑘𝑛 𝑒 𝑗𝑤 𝑛 𝑡
+ 𝑛(𝑡), 𝑡 ∈ [0, 𝑇𝑠]𝑁
𝑛=1
𝐾
𝑘=1 (1)
where bk is the input bit of the kth user, bk € {1, −1}, Ak is the received amplitude of the kth user,
Ts is the symbol interval and wn=2πn/Ts. Skn denotes the nth component of the kth user’s
spreading code, the spreading code length is the same size of the IFFT length N. The Rayleigh
fading channel is denoted by hkn complex coefficients and assumed frequency-flat fading for
each subcarrier of all users.
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hkn(t) = CKe−jφknδ(t − tk) (2)
𝐶 𝑘𝑛 is amplitude of kth user that Rayleigh distribution, 𝜑 𝑘𝑛is the phase in the range
[0,2𝜋] and 𝑡 𝑘 is the delay in range[0,T] and the additive white Gaussian noise (AWGN) is
denoted n(t). Matrix form can be written (1):
rn = ∑ AkbkSknhkn + ηn
K
k=1 (3)
where ηn a complex Gaussian random variable with zero mean and variance 2σ2/Ts.
Matrix notation can be shown in (3) such as [19]:
𝑟 = 𝐶𝐴𝑏 + 𝑛 (4)
[
𝑟1
𝑟2
⋮
𝑟𝑁
] = [
𝑠11ℎ11 𝑠21ℎ21 ⋯ 𝑠 𝐾1ℎ 𝐾1
𝑠12ℎ12 𝑠22ℎ22 ⋯ 𝑠 𝐾2ℎ 𝐾2
⋮ ⋮ ⋱ ⋮
𝑠1𝑁ℎ1𝑁 𝑠2𝑁ℎ2𝑁 ⋯ 𝑠 𝐾𝑁ℎ 𝐾𝑁
] [
𝐴1 0 ⋯ 0
0 𝐴2 ⋯ 0
⋮ ⋮ ⋱ ⋮
0 0 ⋯ 𝐴 𝐾
] [
𝑏1
𝑏2
⋮
𝑏 𝐾
] + [
𝑛1
𝑛2
⋮
𝑛 𝐾
] (5)
where
C = [
𝑠11ℎ11 𝑠21ℎ21 ⋯ 𝑠 𝐾1ℎ 𝐾1
𝑠12ℎ12 𝑠22ℎ22 ⋯ 𝑠 𝐾2ℎ 𝐾2
⋮ ⋮ ⋱ ⋮
𝑠1𝑁ℎ1𝑁 𝑠2𝑁ℎ2𝑁 ⋯ 𝑠 𝐾𝑁ℎ 𝐾𝑁
] (6)
In (4), A is the amplitude matrix which consist of amplitude values of each user, b is
the original message matrix that consist of bits of each user’s message and n is noise matrix.
3. Multiuser Decision-Feedback Receiver
3.1. MMSE Decision Feedback Detector
In this part the design of synchronous MMSE decision feedback detector is described.
The input to the hard decision device corresponding to the ith symbol is for:
𝑧(𝑖) = 𝑊 𝐻
𝑟(𝑖) − 𝐹 𝐻
𝑏̂(𝑖) (7)
where the input 𝑧(𝑖) = [𝑧1(𝑖) … … 𝑧 𝑘(𝑖)] 𝑇
, 𝑊(𝑖) = [𝑤1(𝑖) … … 𝑤 𝑘(𝑖)] is the M×k feedforward matrix,
𝑏̂(𝑖) = [𝑏̂1(𝑖) … … 𝑏̂ 𝑘(𝑖)]
𝑇
is the k×1 vector of estimated symbols, which are fed back through
the k×k feedback matrix 𝐹(𝑖) = [𝑓1(𝑖) … … 𝑓𝑘(𝑖)]. The block diagram of MMSE decision feedback
receiver is shown in Figure 2.
Figure 2. Block diagram of MMSE decision feedback receiver [17]
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Multiuser Detection with Decision-feedback Detectors and PIC... (Leila Sahraoui)
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Specifically, the DF receiver design is equivalent to determining for user k a feedforward
filter 𝑤 𝑘(𝑖) with M elements and a feedback one fk(i) with k elements that provide an estimate of
the desired symbol
𝑧 𝑘(𝑖) = 𝑤 𝑘
𝐻
(𝑖)𝑟(𝑖) − fk
H
(𝑖)𝑏̂(𝑖), 𝑘 = 1,2, … , 𝐾 (8)
where 𝑏̂(𝑖) = 𝑠𝑔𝑛[𝑅(𝑊 𝐻
𝑟(𝑖))] is the vector with initial decisions provided by the linear section,
wk and fk are optimized by the MMSE criterion. The final detected symbol is
𝑏̂
𝑘
𝑓
(𝑖) = 𝑠𝑔𝑛(𝑅[𝑧 𝑘(𝑖)]) = 𝑠𝑔𝑛(𝑅[𝑤 𝑘
𝐻
(𝑖)𝑟(𝑖) − 𝑓𝑘
𝐻
(𝑖)𝑏̂(𝑖)]) (9)
where the operator (.) H denotes Hermitian transpose, R(.) selects the real part and sgn(.) is
the signum function. To describe the optimal MMSE filters we will initially assume perfect
feedback, that is 𝑏̂ = 𝑏,
𝑒 𝐷𝐹𝐷 = 𝑏(𝑖) − 𝑧 𝑘(𝒊) (10)
The error at DFD output. The error covariance matrix is then:
𝜖 𝐷𝐹𝐷 = 𝐸[𝑒 𝐷𝐹𝐷 𝑒 𝐷𝐹𝐷
𝐻
] (11)
Then will consider a more general framework. Consider the following cost function: the MSE for
user k is:
𝐽 𝑀𝑆𝐸 = [𝜖 𝐷𝐹𝐷] 𝑘 = 𝐸 [|𝑏 𝑘(𝑖) − 𝑤 𝑘
𝐻
𝑟(𝑖) + 𝑓𝑘
𝐻
𝑏̂(𝑖) |
2
] (12)
Similarly, to Figure 2, the users are divide into two sets:
𝐷 = {𝑗: 𝑏𝑗
̂ 𝑖𝑠 𝑓𝑒𝑑 𝑏𝑎𝑐𝑘} (13)
𝑈 = {𝑗: 𝑗 ∉𝐷} (14)
where the two sets D and U correspond to detected and undetected users, respectively. Let us
also define the matrices of effective spreading sequences= [𝑃1 … . . 𝑃𝐾], 𝑃𝐷 = [𝑃1 … . . 𝑃𝐷], 𝑃𝑈 =
[𝑃1 … . . 𝑃𝑈]. The minimization of the cost function in (12) with respect to the filters wk and fk
yields:
𝑤 𝑘 = 𝑅 𝑈
−1
𝑃𝑘 (15)
𝑓𝑘 = 𝑃𝐷
𝐻
𝑤 𝑘 (16)
where the associated covariance matrices are 𝑅 = [𝑟(𝑖)𝑟𝐻(𝑖)] = 𝑃𝑃 𝐻
+ σ2
I
𝑅 𝑈 = 𝑃𝑈 𝑃𝐻 + 𝜎2
𝐼 = 𝑅 − 𝑃𝐷 𝑃𝐷
𝐻
(17)
The associated MMSE for the DF receiver with assuming perfect feedback is given by:
𝐽 𝑀𝑀𝑆𝐸 = 𝜎𝑏
2
− 𝑝 𝑘
𝐻
𝑅 𝑈
−1
𝑝 𝑘 (18)
3.2. The Parallel Feedback P-DFD:
In order to design P-DFD receivers and satisfy their constraints, the designer must
obtain the vector with initial decisions 𝑏̂(𝑖) = 𝑠𝑛𝑔[𝑅(𝑊 𝐻(𝑖)𝑟(𝑖)] and then resort to the following
cancellation approach. The non-zero part of the filter fk corresponds to the number of used
feedback connections and to the users to be cancelled.
In the P-DF, the feedback connections used and their associated number of non-zero
filter coefficients in fk are equal to K−1 for all users and the matrix F(i) has zeros on the main
diagonal to avoid cancelling the desired symbols. The parallel feedback interference
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cancellation (P-DF) receiver can offer uniform performance over the users but it suffers from
error propagation (14). For the P-DF in a single cell, we have:
𝐷 = {1, … , 𝑘 − 1 𝑘 + 1, … , 𝐾}, 𝑈 = {𝑘} (19)
𝑤 𝑘 = 𝑅 𝑈
−1
𝑝 𝑘 =
𝑝 𝑘
A 𝑘
2+𝜎2 (20)
The MMSE associated with the P-DF system is obtained by substituting 𝑅 𝑈 = 𝑅 − 𝑃𝐷 𝑃𝐻 D
into (15), which yields:
𝐽 𝑀𝑀𝑆𝐸 = 𝜎𝑏
2
− 𝑝 𝑘
𝐻
(𝑝 𝑘 𝑝 𝑘
𝐻
+ 𝜎2
𝐼)−1
𝑝 𝑘 =
𝜎2
𝐴 𝑘
2+𝜎2 (21)
Now let us consider a more general framework, where the feedback is not perfect.
The minimization of the cost function in (8) with respect to wk and fk leads to the following filter
expressions:
𝑤 𝑘 = 𝑅−1(𝑝 𝑘 + 𝐵𝑓𝑘) (22)
𝑓𝑘 = (𝐸[𝑏̂ 𝑏̂ 𝐻
])−1
𝐵 𝐻
𝑤 𝑘 ≈ 𝐵 𝐻
𝑤 𝑘 (23)
where
𝑃𝐾 = 𝐸[𝐵 𝑘
∗
(𝑖)𝑟(𝑖)] = 𝑆 𝑘𝑛ℎ 𝑘𝑛 (effective spreading sequences)
𝑅 = 𝐸[𝑟(𝑖)𝑟ℎ
(𝑖)], The receiver input covariance matrix
𝐵 = 𝐸[𝑟(𝑖)𝑏̂ 𝐻
(𝑖)],et 𝐸[𝑏̂ 𝑏̂ 𝐻
] ≈ I
for small error rates. The associated MMSE for DF receivers subject to 𝐸[𝑏̂ 𝑏̂ 𝐻
] ≈ I and
imperfect feedback is approximately given by
𝐽 𝑀𝑀𝑆𝐸 ≈ 𝜎𝑏
2
− 𝑝 𝑘
𝐻
𝑅−1
𝑝 𝑘 − 𝑝 𝑘
𝐻
𝑅−1
𝐵𝑓𝑘 (21)
Note: The MMSE associated with DF receivers that are subject to imperfect feedback
depends on the matrix 𝐵 = 𝐸[𝑟𝑏̂ 𝐻
] and the feedback filter fk or set of filters F.
4. Iterative Section
In this section, we present iterative Decision Feedback DFD based on parallel feedback
with hard decisions, defined by the recursion:
𝑥(𝑚+1)
(𝑖) = 𝐹 𝐻
𝑟(𝑖) − 𝐵 𝐻
𝑏̂(𝑚)
(𝑖)} (22)
where F and B are the P-DFD filters, and 𝑏̂(𝑚)
is the vector of tentative decisions from
the preceding iteration. For the uncoded P-DFD with hard decisions and binary signaling, have:
𝑏̂(1)
(𝑖) = 𝑠𝑛𝑔{𝐹 𝐻
𝑟(𝑖)} (23)
𝑏̂(𝑚)
(𝑖) = 𝑠𝑛𝑔{𝑥 𝑚(𝑖)} m>1 (24)
where the number of stages m depends on the application. More stages can be added and the
order of the users is reversed from stage to stage.
4.1. P-DFD-PIC Receiver
The detection of the MAI is calculated for each user and subtracts from the outputs of
the adapted filter. it is applied for all users in a bit period even the uncorrected bits are also
considered correct, so the BER performance of a PIC of one stage is not better. We can
improve the performance of the PIC receiver with a multi-stage structure but the system will
become more complex.
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In the PIC, the output of the filter bank (matched filter) is taken as input of
the corresponding stage, the BER performance of the PIC is degraded when the number of
active user’s increases, errors increase in the input of the PIC, so BER performance of the PIC
degrades. In the proposed receiver P-DFD-PIC is an iterative method with P-DFD (with two
stage) and PIC is considered. P-DFD decision device is used between the output of
the matched filter and the PIC input. In this case, PIC uses more correct bits than the output of
the matched filter.
5. Results and Discussion
In this part: the performances of the multiuser MUD detection techniques are exposed
for an uplink MC-CDMA system, in Rayleigh fading channel (cost 207 channel). For uplink
mobile channel with BPSK modulation scheme and Walsh Hadarmad orthogonal codes of
processing gain of 16 is used. The binary source data rate of 512 kbit/s are considered. With
serial to parallel conversion factor of 4,8 and processing gain of 16, Number of actives user is
8,16 and 32, plus an appropriate CP.
Figures 3, 4 ,5 below on the left show the BER value versus SNR for MMSE, ML,
parallel DFD (non-iterative) and multiuser bound(MUB) compared with an estimation of
the channel using an adaptive Least Square filter (LS), this form of estimation with adaptive filter
is generally adopted in multi-pilot MIMO-OFDM systems [14].
The results of performances show perfectly that the ML and MMSE techniques offer
better results compared to the two other techniques SL and the P-DFD which gives a less
efficient result. In Figures 3, 4, 5 below on the right, we represent combination of the two
techniques MMSE and P-DFD (MMSE-P-DFD) receivers which makes the performances similar
to those of the ML and MMSE techniques, which stays even better with the SNR less than
10 dB for k=8. The MMSE detector offers the best performance. For this reason,
the performance of this technique is presented in the results which will follow for comparison.
Figure 3. Performance comparison of different receivers for synchronous MC-CDMA
(BER versus SNR, k=8)
In order to exploit interference cancelation an iterative section is investigated with a
comparative study between two methods which are the PIC and the P-DFD (with two additional
iterations). Figures 6, 7, 8 below on the left, Show a comparison of the BER performance of the
linear MMSE, PIC, the three stages PIC (3 PIC), and iterative P-DFD (with two additional
iterations). The 3PIC and the P-DFD always give the best performance compared to the other
0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR/dB
BER
LS
P-DFD
MMSE
ML
MUB
0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR/dB
BER
LS
MMSE
ML
MMSE-P-DFD
MUB
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techniques and the result of these receivers follows the MMSE performance. With the evolution
of the number of users (8, 16 and 32), there is a degradation of performance for all techniques
but the 3PIC, P-DFD and MMSE always remain the methods that give the most correct
performances.
Figure 4. Performance comparison of different receivers for synchronous MC-CDMA
(BER versus SNR, k=16)
Figure 5. Performance comparison of different receivers for synchronous MC-CDMA
(BER versus SNR, k=32)
In Figures 6, 7, 8 below on the right, the curves show the combinations of
the MMSE-P-DFD and P-DFD-PIC techniques, compared with the PIC and 3 PIC. The
performance variations in the iterative combination of the proposed method P-DFD-PIC gives
performances results superior to other techniques but still close to the MMSE-P-DFD
combination, and hence a significant improvement over all other exposed receivers. Increasing
the number of users causes a degradation in the performance results, however the combination
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MMSE-PIC always gives the best results, for k=32 we observe a superposition of graphs, the
receiver P-DFD-PIC is almost the same with MMSE-P-DFD.
Figure 6. Performance comparison of different receivers for synchronous MC-CDMA
(BER versus SNR, k=8)
Figure 7. Performance comparison of different receivers for synchronous MC-CDMA
(BER versus SNR, k=16)
Figure 8. Performance comparison of different receivers for synchronous MC-CDMA
(BER versus SNR, k=32)
5.1. Comparison of results
In the same concept of multistage detection, in [20] they employed multi -level detection
with the PIC multi-user detection’s performance comparison, which uses the maximum ratio
combining (MRC), de-correlation (DEC) and minimum mean square error (MMSE) in first-level
detection. The result exhibit that the detection which uses MMSE have the best performance
than the others detection. When the previous level detection is not effective the performance of
the following levels will be seriously affected.
0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR/dB
BER
PIC
MMSE
P-DFD
3PIC
0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR/dB
BER
PIC
MMSE-P-DFD
P-DFD-PIC
3PIC
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In addition, in [12] a PIC with neural network receiver are investigated for AWGN and
Rayleigh fading asynchronous channels in MC-CDMA system. it shows that multi-stage
detection improves performances of system specifically when the PIC is established in the last
stage with neural network receiver.
Considering the use of high dimensional systems in the next generation of wireless
systems, such as massive multi-user MIMO systems where cdma is one modulation technique
candidate for the next generation of wireless systems, used to improve complexity detectors
algorithm [21]. Moreover, a multiple of recent studies advised the minimum mean-square error
(MMSE) and different combining schemes with parallel interference cancellation (PIC), decision
feedback detectors (DFD), frequency domain equalization (FDE) and zero forcing (ZF) on
the performance of MC-CDMA system among different scenario (MC-CDMA cellular systems,
uplink of MC-CDMA systems, and multicarrier complementary-coded MC CC-CDMA).
The performance of the proposed OFDM-CDMA joint detectors with orthogonal and
non-orthogonal spreading sequences are investigated in mobile radio channels in [22].
Simulation examples are given to demonstrate the effectiveness of the proposed detectors zero
forcing (ZF) and minimum mean square error (MMSE) detectors with decision feedback (DF)
structures. The channel sorting method offers approximately 2 dB gain for the decision feedback
detectors (DFD) and reduces the impairing effect of error propagation. The bit error rate (BER)
performance of orthogonal codes is better than that of non-orthogonal ones in time varying
channels.
In [23], the aim to enhance the performance of downlink MC CC-CDMA system by
mitigating MAI in frequency-selective Nakagami-m fading channels. A comparison among
different combining schemes is suggested to show the impact of PIC with minimum mean
square error combining (MMSEC) and maximal ratio combining (MRC) on the performance of
MC CC-CDMA system. The simulation results show that the combination of general combining
schemes with PIC provides an efficient solution to suppress MAI in downlink MC CC-CDMA
system than conventional MC-CDMA systems using Walsh codes under frequency-selective
channels.
In [24] the paper proposed a new algorithm to improve Modified Minimum Mean Square
Error Frequency Domain Equalization (Modified MMSE-FDE) performance in mitigating
multiuser interference (MUI) in single cell MC-CDMA uplink system. In order to get signal
processing more efficient, in Carrier Frequency Offset Estimation-Minimum Mean Square Error
Frequency Domain Equalization (CFO Estimation-MMSE FEQ). Takes only the real trace of
equalization coefficient matrix makes better performance of Estimation-MMSE FEQ in
MC-CDMA with CFO, than MC-CDMA with Modified MMSE-FDE.
6. Conclusion
Our first contribution focused on the study of the multiuser MMSE, ML and P-DFD
(Parallel decision-feedback detector) based on structures of synchronous MC-CDMA system
receivers were applied on an uplink scenario in the Rayleigh fading channel. The results are
compared with an estimation of channel using an adaptive Least Square filter (LS) and an
association of two methods MMSE and P-DFD which gives better performance in large loaded
system compared with MMSE and ML.
Another so-called iterative receiver technique based on the multistage techniques PIC
and P-DFD (parallel DFD with two additional iterations) was proposed in the second section.
The results of exploiting the possibility of combining the two techniques (P-DFD and PIC) allow
us to conclude that the combination of methods contributes to improve the performance of the
system which remain stable with the evolution of the number of users (8, 16 and 32) and even
better than MMSE-P-DFD in the first part.
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