Journal articles: 'Multi carrier direct sequence code division multiple access'

1

Uddin, Jia, Mohammed Faisal, Md Facihul Azam, and A. F. M. Muzahidur Rahman. "Performance Analysis of Multicarrier Code Division Multiple Access over Rayleigh Fading Channel." Advanced Materials Research 457-458 (January 2012): 985–88. http://dx.doi.org/10.4028/www.scientific.net/amr.457-458.985.

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Recently, multi-carrier transmission schemes have been introduced into Code Division Multiple Access (CDMA) systems to gain advantages for high data rate transmission as well as security. Due to pseudorandom code there is no chance to Inter Symbol Interference (ISI). There are different techniques to mitigate multipath fading. One of the method is to transmit identical narrowband direct-sequence (DS) waveforms in parallel over a number of sub-channels using frequency diversity. Implementation this multi-carrier modulation technique in CDMA system is known as multi-carrier CDMA (MC-CDMA). In Rayleigh fading channel, due to multi-carrier modulation, when one subcarrier goes deep fade another subcarrier may remain safe. Therefore it combats multi-path fading and signal can be received in low bit error rate.

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Zhou, Lin, Qingsheng Zhao, Shukai Chi, Yanlong Li, Lanjun Liu, and Qianxiang Yu. "A fractional Fourier transform–based channel estimation algorithm in single-carrier direct sequence code division multiple access underwater acoustic communication system." International Journal of Distributed Sensor Networks 15, no. 1 (2019): 155014771982600. http://dx.doi.org/10.1177/1550147719826001.

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Due to the complexity and variability of the underwater acoustic channel, the communication signal is affected by multi-path, time delay, and Doppler frequency shift. Based on the advantageous characteristics of fractional Fourier transform on chirp signal processing, a fractional Fourier transform–based algorithm using combined linear frequency–modulated signal is proposed, which can estimate parameters of underwater acoustic channel and has a better performance than the existing methods. To distinguish multi-user in underwater acoustic communication system, a single-carrier direct sequence code division multiple access communication system combined with the fractional Fourier transform–based algorithm is proposed. Thus, a preliminary study on underwater multi-target identification is carried out. The simulation and experimental results show that the fractional Fourier transform–based algorithm is simple and effective, and the energy can be focused at the “best” fractional order, which can directly determine the multi-path number and complete the channel estimation. The proposed single-carrier direct sequence code division multiple access communication system has good performance on bit error rate when we use corresponding spreading code to distinguish multi-user.

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Kattoush, Abbas Hasan, Waleed Ameen Al Jawhar, and Ali T. Shaheen. "A novel Radon-based multi-carrier direct sequence code division multiple access transceiver design and simulation." International Journal of Communication Networks and Distributed Systems 4, no. 4 (2010): 436. http://dx.doi.org/10.1504/ijcnds.2010.033163.

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Sheikh, Javaid A., Shabir A. Parah, and G. Mohiuddin Bhat. "A new multiple input multiple output multi-carrier direct sequence code division multiple access system using T × T spreading with link budget analysis." International Journal of Wireless and Mobile Computing 10, no. 2 (2016): 148. http://dx.doi.org/10.1504/ijwmc.2016.076160.

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Elmissaoui, Taoufik. "Multi-Access Techniques Comparison for Remote Lab System." International Journal of Online and Biomedical Engineering (iJOE) 19, no. 12 (2023): 4–15. http://dx.doi.org/10.3991/ijoe.v19i12.39681.

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Remote lab systems are one of the essential requirements for an increased academic productivity in the modern digital world. These systems support and facilitate effective migration from face-to-face classroom education to online education. Digital technology applications and processes are required to easily build a remote lab system. With the availability of multiple access techniques, users can comfortably share laboratory equipment among themselves. The sharing of resources using the remote lab system is highly required for a smooth deployment and implementation of online education. This paper therefore proposed and tested some techniques that combine Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiplexing (OFDM) in remote lab systems. The tested techniques are Multi-Carrier Direct Sequence CDMA (MC-DS-CDMA), Multi-Tone CDMA (MT-CDMA), Multi-Carrier CDMA (MC-CDMA), and Spread Spectrum Multi-Carrier Multiple Access (SS-MC-MA). The first step proposed in this work had to do with the setting of the comparison criteria. At the second step, the solutions cited previously in the real equipment was tested and the best option that met the criteria was selected for the eLab system since the performance technique varies with the laboratory equipment characteristic. The four techniques that were tested demonstrated high performance in telecommunications and online laboratory systems. The implementation of these techniques will benefit universities in several ways, which include reduction of remote lab cost and optimization of sharing of online resources among users. This will further provide students with conducive learning environment by addressing the challenges of reservation and time slot limit. It is therefore recommended that MC-CDMA should be integrated into remote lab system.

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N. Motade, Sumitra, and Anju V. Kulkarni. "Incremental gradient algorithm for multiuser detection in multi-carrier DS-CDMA system under modulation schemes." International Journal of Engineering & Technology 7, no. 2.6 (2018): 311. http://dx.doi.org/10.14419/ijet.v7i2.6.11270.

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Nowadays, Multicarrier Direct sequence code division multiple access (MC DS-CDMA) systems are used in mobile communication. Performance of these systems are limited by multiple access interference (MAI) created by spread-spectrum users in the channel as well as background channel noise. This paper proposes an incremental gradient descent (IGD) multi-user detection (MUD) for MC DS-CDMA system that can achieve near-optimum performance while the number of users is linear in its implementation complexity. The IGD algorithm make an effort to perform optimum MUD by updating one user's bit decision each iteration in the best way. This algorithm accelerates the gradient algorithm convergence by averaging. When a minimum mean square error (MMSE) MUD is employed to initialize the proposed algorithm, in all cases tested the gradient search converges to a solution with optimum performance. Further, the iterative tests denote that the proposed IGD algorithm provides significant performance for cases where other suboptimum algorithms perform poorly. Simulation compares the proposed IGD algorithm with the conventional detectors.

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Lu, H. Y. "A family of minimum mean square error multiuser detectors for three-domain spread multi-carrier direct sequence-code division multiple access." IET Communications 6, no. 6 (2012): 587. http://dx.doi.org/10.1049/iet-com.2011.0609.

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Kadhim, Nader Abdullah, Ali jawad Alrubaie, and Ameer Al-khaykan. "Two cross coupled and Madgwicks filter for estimation of multichannel dividing systems." Indonesian Journal of Electrical Engineering and Computer Science 27, no. 1 (2022): 262–70. https://doi.org/10.11591/ijeecs.v27.i1.pp262-270.

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The estimates of Rayleigh fading channels are rapidly changing in multi carrier direct sequence code division multiple access (MC-DS-CDMA) multiplexing systems. The most widely accepted answer to this issue is the conventional solution least square (LS) or mean square error estimator (MMSE) using the recursive least squares algorithm (RLS) or the least mean squares (LMS) algorithm. In much of the previous work, only one Kalman filter was used for estimation. In this paper, a Kalman filter is used with a Madgwicks filter together to satisfy the fading problems. However, this requires a priori evaluation of auto regressive (AR) parameters. A standard solution involves the first matching of the auto-completion function of the applying the AR method to Jakes' problem and then tackling it (YWE). Even more the results procedure is limited to crowd constraints and is related to an AR+ process of noise, an approximation considered. In fact, depending on simulation findings, high-AR models outperform conventional models on the basis of spectral estimate and bit error margins (BER). Nevertheless, in order to save costs of computing, the 5-D model of AR is a possibility. The proposed process outperforms edge of art competitors in terms of bit error rate as demonstrated by results.

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Khadam, Nader Abdullah, Ali Jawad Kadhim Jawad Alrubaie, and Osama Qasim Jumah Al-Thahab. "BER estimation for STBC-MC-DS-CDMA-4 antennas system by varied wavelet-carriers features via AWGN-flat channels." Bulletin of Electrical Engineering and Informatics 13, no. 1 (2024): 233–46. http://dx.doi.org/10.11591/eei.v13i1.5371.

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This paper improves the bit error rate (BER) of the modern communication system by taking into account the effect of the wavelet shape and the number of carriers on the performance of the space time block code multi-carrier direct sequence code division multiple access (STBC-MC-DS-CDMA). Here the transmitter is moved with speeds 2 km/hr, 45 km/hr and 100 km/hr via Rayleigh flat fading channel. Here, 2 antennas are employed at the receiver to mitigate the multipath signal influence. The system’s orthogonal frequencies are generated using Haar, Daubechies 4, Symlets 4, Cohen-Daubechies-Feauveau 1.1 with 9.7 and B-spline 3. The number of used carriers is 128, 512, and 1,024. Quadrature phase shift key (QPSK) is used with cyclic prefix 1/16 and a bandwidth of 20 MHz. traditional fast fourier transform (FFT) system is compared to the proposed discrete wavelet packet transform (DWPT) to show the BER enhancements. The space-time block coding (STBC) is used to enhance system cabability in error corection. The proposed system shows significant improvement in BER, so that, it reaches to the same BER when using FFT but with less signal to noise ratio (SNR), which interns reduce the power consumed within the system and the cost.

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Nazrul Islam, A. K. M., and S. P. Majumder. "Effect of Pointing Error on BER Performance of a Multi-wavelength OCDMA FSO System with SIK Dual Detector Receiver." Journal of Optical Communications 40, no. 3 (2019): 247–53. http://dx.doi.org/10.1515/joc-2017-0047.

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Abstract A novel analytical approach is presented to evaluate the bit error rate (BER) performance of a multi-wavelength optical code division multiple access (MW-OCDMA) free space optical (FSO) system using optical domain encoder and sequence inverse keying (SIK) balanced photodetector direct detection receiver taking the effect of pointing errors into considerations. The analysis is carried out to find the expression for the signal, multi-access interference (MAI) and crosstalk at the output of the SIK receiver in presence of pointing error. The BER performance results are evaluated for different values of standard deviation of pointing error, code length, number of simultaneous user and other system parameters. It is found that, MW-OCDMA system offers improved BER performance over single wavelength OCDMA FSO system. However, the performance of an MW-OCDMA system is degraded due to the effect of pointing error between the laser transmitter and optical receiver and the system suffers significant power penalty at a given BER of 10−9. The penalty is found to be 11.0 dB, 24.0 dB and 30 dB for jitter standard deviation of 1.3, 1.8 and 2.5 respectively when code length is 512 and number of user is 8 for number of wavelength 8. Further, the penalty can be greatly reduced by increasing the code length for a given number of user and number of wavelength.

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11

Kadhim, Nader Abdullah, Ali jawad Alrubaie, and Ameer Al-khaykan. "Two cross coupled and Madgwicks filter for estimation of multi-channel dividing systems." Indonesian Journal of Electrical Engineering and Computer Science 27, no. 1 (2022): 262. http://dx.doi.org/10.11591/ijeecs.v27.i1.pp262-270.

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Abstract:

The estimates of Rayleigh fading channels are rapidly changing in multi carrier direct sequence code division multiple access (MC-DS-CDMA) multiplexing systems. The most widely accepted answer to this issue is the conventional solution least square (LS) or mean square error estimator (MMSE) using the recursive least squares algorithm (RLS) or the least mean squares (LMS) algorithm. In much of the previous work, only one Kalman filter was used for estimation. In this paper, a Kalman filter is used with a Madgwicks filter together to satisfy the fading problems. However, this requires a priori evaluation of auto regressive (AR) parameters. A standard solution involves the first matching of the auto-completion function of the applying the AR method to Jakes' problem and then tackling it (YWE). Even more the results procedure is limited to crowd constraints and is related to an AR+ process of noise, an approximation considered. In fact, depending on simulation findings, high-AR models outperform conventional models on the basis of spectral estimate and bit error margins (BER). Nevertheless, in order to save costs of computing, the 5-D model of AR is a possibility. The proposed process outperforms edge of art competitors in terms of bit error rate as demonstrated by results.

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12

Zope, Rajendrakumar Govinda, and Balasaheb Shrirangrao Agarkar. "Channel Estimation for DS-CDMA Rake Receiver using Sparse Recovery Approach." International Journal of Recent Technology and Engineering (IJRTE) 11, no. 1 (2022): 41–46. http://dx.doi.org/10.35940/ijrte.f6841.0511122.

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In the literature of direct-sequence code-division multiple-access (DS-CDMA), for issues related to channel estimation, some exclusive architectures have been proposed, which are characterized by known channel noise statistics and noise observation. But in reality, the channel parameters are frequently assessed utilizing training sequences that lead to difficulty in obtaining the channel noise statistics. Channel estimation quality has been proved to play an important role in the performance of rake receiver. This paper addresses the issues of optimizing DS–CDMA rake receiver channel estimation equipped with an Iterative least square sparse recovery (IL2SR) channel estimator. Moreover, the ambient noises corrupt the signal received and multiple-access interference further aggravates it. Because of this observation noises become hard to acquire. Hence this paper proposes as an iterative least square structure for channel estimation algorithm in rake receiver employed in DS-CDMA communication systems. Further, examination of blind channel estimation problem for rake-based DS-CDMA communication framework having multi-path fading channels with time variation is also attempted. The validity of the proposed techniques has been verified through results obtained from simulation for different channel parameters and spreading codes. Further exploration has been carried out with execution of the IL2SR with Rake receiver in DS-CDMA framework for multi-path fading channels. It is found that better performance is obtained with this framework under various channels with different spreading codes. The proposed system is compared with Kalman based techniques and it was found that DS-CDMA framework under additive white gaussian noise (AWGN)channel with IL2SR receiver reveals better outcomes in terms of bit error rate (BER). Also, there has been improvement in video quality while using the proposed IL2SR receiver with increase in the values of ratio of signal to noise ratio.

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13

Rajendrakumar, Govinda Zope, and Shrirangrao Agarkar Balasaheb. "Channel Estimation for DS-CDMA Rake Receiver using Sparse Recovery Approach." International Journal of Recent Technology and Engineering (IJRTE) 11, no. 1 (2022): 41–46. https://doi.org/10.35940/ijrte.F6841.0511122.

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<strong>Abstract:</strong> In the literature of direct-sequence code-division multiple-access (DS-CDMA), for issues related to channel estimation, some exclusive architectures have been proposed, which are characterized by known channel noise statistics and noise observation. But in reality, the channel parameters are frequently assessed utilizing training sequences that lead to difficulty in obtaining the channel noise statistics. Channel estimation quality has been proved to play an important role in the performance of rake receiver. This paper addresses the issues of optimizing DS–CDMA rake receiver channel estimation equipped with an Iterative least square sparse recovery (IL2SR) channel estimator. Moreover, the ambient noises corrupt the signal received and multiple-access interference further aggravates it. Because of this observation noises become hard to acquire. Hence this paper proposes as an iterative least square structure for channel estimation algorithm in rake receiver employed in DS-CDMA communication systems. Further, examination of blind channel estimation problem for rake-based DS-CDMA communication framework having multi-path fading channels with time variation is also attempted. The validity of the proposed techniques has been verified through results obtained from simulation for different channel parameters and spreading codes. Further exploration has been carried out with execution of the IL2SR with Rake receiver in DS-CDMA framework for multi-path fading channels. It is found that better performance is obtained with this framework under various channels with different spreading codes. The proposed system is compared with Kalman based techniques and it was found that DS-CDMA framework under additive white gaussian noise (AWGN)channel with IL2SR receiver reveals better outcomes in terms of bit error rate (BER). Also, there has been improvement in video quality while using the proposed IL2SR receiver with increase in the values of ratio of signal to noise ratio.

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14

Kim, Taeyoon, Jeffrey G. Andrews, Jaeweon Kim, and Theodore S. Rappaport. "Multi-code Multicarrier CDMA: Performance Analysis." Journal of Communications Software and Systems 2, no. 1 (2017): 12. http://dx.doi.org/10.24138/jcomss.v2i1.301.

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A new multi-code multicarrier code division multiple access (MC-MC-CDMA) system is proposed and analyzed in afrequency selective fading channel. By allowing each user to transmit an M-ary code sequence, the proposed MC-MC-CDMA system can support various data rates as required by next generation standards without increasing the interference which is common in general multicarrier CDMA systems. The bit error rate of the system is analytically derived in frequency selective fading, with Gaussian noise and multiple access interference. The results show that the proposed MC-MC-CDMA system clearly outperforms both single-code multicarrier CDMA (MC-CDMA) and single-carrier multi-code CDMA in a fixed bandwidth allocation.This indicates that MC-MC-CDMA can be considered for next generation cellular systems.

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Zhu, Yun Hang, Qiong Cai, and Xiu Liang Huang. "Research on Key Technologies in Multi-Robotic Spread Spectrum Communication System." Advanced Materials Research 756-759 (September 2013): 2401–5. http://dx.doi.org/10.4028/www.scientific.net/amr.756-759.2401.

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It has become a hot research topic that to improve the coordination performance of multi-robotic system by communication. With rapid development of wireless communication and robot technologies, multi-robotic system based on spread-spectrum technology has become product of combining two technologies. Code Division Multiple Access (CDMA) technology is applied in multi-robotic communication system here. According to the modified m-Walsh sequence got by the way of analyzing the relation characteristic of Walsh-code and m-sequence, the best direct sequence spread spectrum (DSSS) PN code and the improved RAKE receiver scheme are proposed, which satisfied the requirements of real-time performance, reliability and confidentiality in multi-robotic communication system, and have great significance for the research of multi-robotic communication system.

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Nahar, Ali, and Mohammed A. Hussein. "A hybrid of the selected mapping and partial transmit sequence approaches for reducing the high peak average to power ratio based on multi-carrier systems – review." Computer Science and Information Technologies 3, no. 1 (2022): 10–21. http://dx.doi.org/10.11591/csit.v3i1.p10-21.

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The orthogonal frequency division multiplexing (OFDM)-4G and 5G filter technology suffer a drawback that represents the direction of the peak average to power ratio (PAPR) in orthogonal frequency division multiplexing due to the nonlinear nature of the transmitter. There are a lot of traditional and hybrid methods of these traditional methods to reduce the harmful high PAPR value. Newly, several new hybrid methods have been adopted to reduce PAPR but it faces an increasing level of computational complexity in the system. In this paper, two important and effective conventional methods for reducing PAPR are studied, analyzed, and investigated for the hybrid pathway which is the incorporation of selective mapping (SLM) method and partial transport sequencing (PTS) method, which achieve increased efficiency of PAPR reduction while computing the computational complexity of each method. The method depends and balances with computational complexity. The search is based on multi-carrier connections such as multi carrier-code division multiple access (MC-CDMA) and OFDM.

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Ali K. Nahar and Mohammed A. Hussein. "A hybrid of the selected mapping and partial transmit sequence approaches for reducing the high peak average to power ratio based on multi-carrier systems–review." Computer Science and Information Technologies 3, no. 1 (2022): 10–21. http://dx.doi.org/10.11591/csit.v3i1.pp10-21.

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The orthogonal frequency division multiplexing (OFDM)-4G and 5G filter technology suffer a drawback that represents the direction of the peak average to power ratio (PAPR) in orthogonal frequency division multiplexing due to the nonlinear nature of the transmitter. There are a lot of traditional and hybrid methods of these traditional methods to reduce the harmful high PAPR value. Newly, several new hybrid methods have been adopted to reduce PAPR but it faces an increasing level of computational complexity in the system. In this paper, two important and effective conventional methods for reducing PAPR are studied, analyzed, and investigated for the hybrid pathway which is the incorporation of selective mapping (SLM) method and partial transport sequencing (PTS) method, which achieve increased efficiency of PAPR reduction while computing the computational complexity of each method. The method depends and balances with computational complexity. The search is based on multi-carrier connections such as multi carrier-code division multiple access (MC-CDMA) and OFDM.

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Ali, K. Nahar, and A. Hussein Mohammed. "A hybrid of the selected mapping and partial transmit sequence approaches for reducing the high peak average to power ratio based on multi-carrier systems – review." Computer Science and Information Technologies 3, no. 1 (2022): 10–21. https://doi.org/10.11591/csit.v3i1.pp10-21.

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The orthogonal frequency division multiplexing (OFDM)-4G and 5G filter technology suffer a drawback that represents the direction of the peak average to power ratio (PAPR) in orthogonal frequency division multiplexing due to the nonlinear nature of the transmitter. There are a lot of traditional and hybrid methods of these traditional methods to reduce the harmful high PAPR value. Newly, several new hybrid methods have been adopted to reduce PAPR but it faces an increasing level of computational complexity in the system. In this paper, two important and effective conventional methods for reducing PAPR are studied, analyzed, and investigated for the hybrid pathway which is the incorporation of selective mapping (SLM) method and partial transport sequencing (PTS) method, which achieve increased efficiency of PAPR reduction while computing the computational complexity of each method. The method depends and balances with computational complexity. The search is based on multi-carrier connections such as multi carrier-code division multiple access (MCCDMA) and OFDM.

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Liu, Xiao Zhi, Da Wei Feng, and Tian Shuang Zhang. "Multi-User Detection of DS-CDMA Based on Improved-FastICA." Applied Mechanics and Materials 128-129 (October 2011): 633–36. http://dx.doi.org/10.4028/www.scientific.net/amm.128-129.633.

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Multi-user detection (MUD) is used to control multiple access interference (MAI) and promote system performance and capacity, which is one of the key technology for CDMA system. Independent component analysis (ICA) aims to recover a set of unknown mutually independent source signals from theirs observed mixtures without knowledge of the mixing coefficients. FastICA, one of the ICA methods, has been successfully applied in various fields. But the classical FastICA does not converge quickly. In multi-user detection of direct sequence code division multiple access (DS-CDMA) system, we proposes an Improved-FastICA algorithm to reduce multiple access interference (MAI). The improved-FastICA algorithm uses a new Fifth-order Newton iterative method to estimate the negentropy. The experimental results show that the improved algorithm has the advantages of smaller bit error rate than traditional algorithm. The Improved-FastICA is more suitable for applications in DS-CDMA system.

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Prayoga, Kadek Agus Mahabojana Dwi, Ni Made Ary Esta Dewi Wirastuti, and I. Gst A. Komang Diafari Djuni Hartawan. "Analisis Unjuk Kerja Convolutional Code pada Sistem MIMO MC-DSSS Melalui Kanal Rayleigh Fading." Majalah Ilmiah Teknologi Elektro 16, no. 2 (2017): 66. http://dx.doi.org/10.24843/mite.2017.v16i02p11.

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Kombinasi antara sistem MIMO (multiple input multiple output), OFDM (orthogonal frequency division multiplexing), dan spread spectrum serta adanya teknik pengkodean kanal mampu mengurangi efek fading dan error yang terjadi. Penelitian ini bertujuan untuk mengetahui perbandingan performansi dari sistem MIMO MC-DSSS (multi carrier-direct sequence spread spectrum) Uncoded atau tanpa pengkodean kanal dan MIMO MC-DSSS Convolutional Code atau dengan pengkodean kanal Convolutional yang melalui kanal Rayleigh Fading, ditinjau dari nilai dan grafik BER (bit error rate) berbanding Eb/No (energy per bit to noise power spectral density ratio). Penelitian ini menggunakan metode simulasi dengan menggunakan program Matlab R2015a. Hasil dari simulasi didapat unjuk kerja sistem MIMO MC-DSSS dengan Convolutional Code memiliki hasil yang lebih baik dari MIMO MC-DSSS. Pada kanal transmisi Rayleigh Fading untuk mencapi nilai BER sebesar 10-3 pada sistem MIMO MC-DSSS dengan Convolutional Code dibutuhkan Eb/No sebesar -7 dB. Sedangkan pada sistem MIMO MC-DSSS dibutuhkan Eb/No sebesar -3 dB.[turnitin 20%, 7-11-2016]

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Cheng, Hao, Na Yu, and Jun Liu. "Improved Natural Gradient Algorithms for Multi-Channel Signal Separation." Applied Mechanics and Materials 651-653 (September 2014): 2326–30. http://dx.doi.org/10.4028/www.scientific.net/amm.651-653.2326.

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In this paper, an Multi-channel blind separation of Direct Sequence Code Division Multiple Access (DS-CDMA) has been introduced. Most of which we assume statistically stationary sources as well as instantaneous mixtures of signals using blind source separation (BSS) algorithms. In practicality, the CDMA sources received are convolute mixing. A more complex blind separation algorithm is required to achieve better source separation. Based on the minimizing the average squared cross-output-channel-correlation, the proposed scheme obtains the better source separation. Simulation results show that the proposed optimal scheme not only achieves superior bit error rate (BER) performance to those of the existing ones, but also provides a guaranteed-convergent solution under different channel conditions.

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Islam, A. K. M. Nazrul, and Satya Prasad Majumder. "Bit Error Rate Performance in CDMA Free Space Optical Links with SIK Receiver under Fog Conditions." MIST INTERNATIONAL JOURNAL OF SCIENCE AND TECHNOLOGY 11 (December 28, 2023): 81–86. http://dx.doi.org/10.47981/j.mijst.11(02)2023.409(81-86).

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This article presents a novel analytical method for evaluating fog's impact on Bit Error Rate (BER) in an Optical Code Division Multiple Access (OCDMA) Free Space Optical (FSO) connection. The investigation employs an optical encoder and direct detection receiver employing a balanced photo detector with Sequence Inverse Keying (SIK) to explore fog effects. By scrutinizing multi-access interference (MAI) current and signal current values at the SIK receiver's output under varied fog conditions, we deduce BER expressions for diverse scenarios. These encompass different fog thickness levels, code lengths, simultaneous users, and system parameters. The results reveal substantial OCDMA degradation due to fog thickness and users. Also, the system incurs a marked power penalty at a specific BER, especially with higher fog and user density. However, we identify a potential solution: increasing code length, effectively mitigating fog-induced performance decline.

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Sirithummachak, P., and C. Benjangkaprasert. "Adaptive Equalizer for DS-CDMA Multi-User Communication System Using Sign-Algorithm Based on Laguerre Filter Structure." Applied Mechanics and Materials 548-549 (April 2014): 1231–34. http://dx.doi.org/10.4028/www.scientific.net/amm.548-549.1231.

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This paper proposes a sign-algorithm based on adaptive Laguerre filter structure for improving the performance of the direct sequence-code division multiple access (DS-CDMA) communication system. The proposed adaptive equalizer employs a combination of sign and least mean square (LMS) algorithms to minimizing the effect of inter-symbol interference (ISI) that arises due to multipath propagation, and the computational complexity of equalizer. The performance of proposed equalizer was compared with traditional equalizers such as LMS and RLS algorithms in terms of varying path. The function detail and performance results of the proposed equalizer are described by computer simulations in terms of the bit error rate (BER).

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Öztürk, E. "Performance analysis of asynchronous direct sequence code division multiple access for general chip waveforms over multi-path Rayleigh fading channels." IET Communications 1, no. 4 (2007): 570. http://dx.doi.org/10.1049/iet-com:20060272.

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Wang, Feng, and Xuan De Ji. "A Joint Chip Equalization Adaptive Rake Receiver for DS-CDMA UWB Systems over ISI Channels." Advanced Materials Research 505 (April 2012): 274–81. http://dx.doi.org/10.4028/www.scientific.net/amr.505.274.

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There is serious inter-symbol interference (ISI) when ultra-wideband (UWB) wireless communication systems work at high data speed since there is much larger channel delay spread. The serious ISI becomes a major factor that affects the performance of UWB systems. In this paper, suppression ISI is developed for direct sequence spread-code division multiple access (DS-CDMA) UWB systems with a high data speed, and a joint chip equalization adaptive Rake (JCE-Rake) receiver is proposed. The proposed JCE-Rake receiver spreads the number of traditional Rake receiver taps to collect multi-path component and equalize the inter-chip interference simultaneously. Then the soft output of JCE-Rake receiver is despreaded with the user's spreading code. Finally the decision is made to recover the transmitted symbol. The simulation results verify that ISI is suppressed effectively and the system performance is improved evidently.

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Jorge, Aguilar-Torrentera, Ramón Rodríguez-Cruz Jesús, Patricia Puente-Ramírez Norma, and Rodríguez-Morales Gustavo. "Spectral-amplitude encoding CDMA system based on high-speed electronic encoder/ decoder structures." Revista Facultad de Ingeniería –redin-, no. 78 (March 19, 2016): 99–104. https://doi.org/10.17533/udea.redin.n78a13.

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A new method for high-speed Code Division Multiple Access (CDMA) systems that lies on the analogue performance of distributed-based transversal filters is proposed. The method allows spectral-amplitude encoding CDMA system implementations leading to an improvement of orthogonality among users over temporal encoding direct-sequence systems. The maximal degrees of flexibility in the design of transversal filters are considered to generate waveforms that exhibit large temporal variation over the filter span time in accordance with an encoded waveform. Applications of our method to high-speed CDMA are discussed towards the end of the paper.

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Abdel Hadi Fadhel, Ahmed. "Novel Space Time Spreading Scheme." University of Thi-Qar Journal for Engineering Sciences 2, no. 3 (2011): 35–43. http://dx.doi.org/10.31663/utjes.v2i3.150.

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In this paper two spreading schemes and their detection methods were proposed and compared. The comparison depends on the performance of each scheme in Rayleigh flat fading channel. Space Time Spreading (STS) codes are used with Layered Space Time Codes(LST), with Vertical Bell Laboratories Space Time codes (V-BLAST) in particular. Also,Direct Sequence Code Division Multiple Access system (DS-CDMA) was used as a multi-user criterion. As a result of this spreading, a simple decoding algorithm was used. The simulation shows that STS-LST-DS-CDMA system with 3TX-3RX (3 transmitting antennas-3 receiving antennas) using all paths between transmitter and receiver was better than LST-DS-CDMA system by about 4dB in SNR at BER of 10-4. More detailed results are shown in Table 1. Also, the proposed scheme (may be partially) solves the problem of the code reuse.

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Samsami Khodadad, Farid, and Ghosheh Abed Hodtani. "Blind joint estimation of channel order and the number of active users in direct sequence code‐division multiple‐access multi‐path channels." IET Signal Processing 8, no. 2 (2014): 158–66. http://dx.doi.org/10.1049/iet-spr.2012.0296.

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Hassan, MD Zoheb, Tanveer Ahmed Bhuiyan, S. M. Shahrear Tanzil, and S. P. Majumder. "Turbo-Coded MC-CDMA Communication Link over Strong Turbulence Fading Limited FSO Channel with Receiver Space Diversity." ISRN Communications and Networking 2011 (August 22, 2011): 1–14. http://dx.doi.org/10.5402/2011/701670.

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This paper demonstrates an analytical approach on the bit error rate (BER) performance evaluation of a multi- carrier code division multiple access (MC-CDMA) communication link operating over terrestrial free space optical (FSO) channel considering effect of atmospheric turbulence The turbulence induced intensity fading is statistically modeled by Gamma-Gamma PDF (probability density function). Bit error rate performance improvement is proposed using photo detector spatial diversity with Equal Gain Combining (EGC) and Turbo Coding. Analysis is carried out with different bandwidth efficient phase shift keying (PSK) based sub-carrier intensity modulation (SIM) with direct detection. Numerical simulation results of proposed analytical model indicate that, sub-carrier intensity modulation scheme; number of receiver photo detectors, turbo coding parameter and link length should be optimally engineered for ensuring system reliability. It can be inferred from the simulation that, a reliable communication link ( BER) can be established over a link length of 4 Km in strong turbulence fading condition using an array of 4 PIN photo detectors, 8-ary PSK based sub-carrier intensity modulation scheme and appropriate turbo coding parameter with an average 10.2 dB CINR (Carrier to Interference and Noise Ratio) requirement per photo detector. Besides, more than 130 dB average CINR gain is also confirmed from BPSK modulated, un-coded SISO (single input-single output) system for maintaining targeted BER () in presence of strong turbulence fading.

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She, Feng, Hsiao Hwa Chen, and Hongyang Li. "Joint Angular and Time Diversity of Multi-Antenna CDMA Systems in Wireless Fading Channels." International Journal of Wireless Networks and Broadband Technologies 1, no. 1 (2011): 1–14. http://dx.doi.org/10.4018/ijwnbt.2011010101.

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In this paper, a multi-antenna based receiver structure for direct sequence code division multiple access (DS/CDMA) system is proposed. The proposed scheme exploits the excellent time resolution of a CDMA RAKE receiver and uses an antenna array beamforming structure to resolve multipath returns in both angular and time domains. A much higher diversity gain than that based only on the time domain diversity can be achieved. This work suggests a new space-time diversity paradigm, namely angular-time diversity, which differs from traditional Alamouti-type space-time coded schemes. The impairments caused by multipath and multiuser interference are analyzed. The performance of the proposed receiver in multipath fading channel is explicitly evaluated. An expression for uncoded system bit error probability is derived. Simulation results show the performance improvement in terms of BER due to the use of multi-antenna in the receiver, and the results illustrate that the multi-antenna based receiver works effectively in resolving multipaths in both angular and time domains to achieve performance improvement due to angular and time diversity gain provided by the multi-antenna system.

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Zhang, Jiang, Hang Zhang, and Zhifu Cui. "Dual-antenna-based blind joint hostile jamming cancellation and multi-user detection for uplink of asynchronous direct-sequence code-division multiple access systems." IET Communications 7, no. 10 (2013): 911–21. http://dx.doi.org/10.1049/iet-com.2013.0036.

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Kochanska, Iwona, Roman Salamon, Jan H. Schmidt, and Aleksander M. Schmidt. "Study of the Performance of DSSS UAC System Depending on the System Bandwidth and the Spreading Sequence." Sensors 21, no. 7 (2021): 2484. http://dx.doi.org/10.3390/s21072484.

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A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and transmission rate. In such propagation conditions, the Direct-Sequence Spread Spectrum (DSSS) method is one of the solutions that make reliable data transmission possible. In systems with one-to-one communication, it ensures communication with a satisfactory Bit Error Rate (BER). Additionally, it makes it possible to implement the Code-Division Multiple Access (CDMA) protocol in underwater acoustic networks. This paper presents the results of simulation and experimental communication tests on a DSSS-based UAC system using three types of spreading sequence, namely m-sequences, Kasami codes and Gold codes, and occupying different bandwidths from 1 kHz to 8 kHz around a carrier frequency equal to 30 kHz. The UAC channel was simulated by impulse responses calculated by the virtual sources method and the UAC chanel models available in the Watermark simulator. The experimental tests were conducted in a model pool. Based on the obtained results, a transmission rate was estimated, which is possible to achieve in strong multipath propagation conditions, assuming reliability expressed as BER less than 0.001.

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Ravindrababu, J., Dasi Swathi, J. V. Ravi Teja, J. V. Ravi Chandra, N. Pranavi Sri, and Shaik Arshiya. "Analysis of Multiuser Detectors and Performance improvement in DS-CDMA system using Multistage Multiuser Detection Techniques." WSEAS TRANSACTIONS ON ELECTRONICS 15 (January 23, 2024): 1–10. http://dx.doi.org/10.37394/232017.2024.15.1.

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The Direct Sequence Code Division Multiple Access (DS-CDMA) system faces several disruptions, this is most crucial of which is the Multi Access Interference (MAI) caused by its users. The efficiency of the system gradually declines as every quantity rises, and the MAI rises, especially in faded environments. This work proposes a multiple-phase multiuser identification approach called Differencing Partial Parallel Interference Cancellation (DPPIC), which improves the overall efficiency. The methods known as Differencing Parallel Interference Cancellation (DPIC) and Partial Parallel Interference Cancellation (PPIC) are combined in this methodology. Current solutions for Parallel Interference Cancellation (PIC) and PPIC have enhanced overall effectiveness; however, this has come at the expense of increasing the complexity of computation. As the variety of consecutive stages grows, the MAI falls. Using the DPIC approach may reduce the computational burden without improving system functionality. The use of the Partial Differencing Parallel Interference Cancellation (PDPIC) technique can enhance system performance while lowering the level of complexity. According to the simulation findings, Bit Error Rate (BER) vs normalized signal strength (i.e., Eb / N0) performs more effectively for the suggested DPPIC approach than for PIC, the PPIC, and PDPIC.

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Zhang, Yang, Qiang Ni, and Hsiao Hwa Chen. "A new partial transmit sequence scheme using genetic algorithm for peak-to-average power ratio reduction in a multi-carrier code division multiple access wireless system." International Journal of Autonomous and Adaptive Communications Systems 2, no. 1 (2009): 40. http://dx.doi.org/10.1504/ijaacs.2009.024282.

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Khan, Mr Wasim, Mrs Nilofar Khan, and Sanmati Jain. "BER performance analysis of Subtractive interference cancellation (SIC) Using Rayleigh channel in DS-CDMA Receiver system." INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY 13, no. 6 (2014): 4603–14. http://dx.doi.org/10.24297/ijct.v13i6.2523.

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In this paper, we present and analyze the performance of a parallel interference cancellation (PIC) scheme for multicarrier (MC) direct-sequence code-division multiple-access (DS-CDMA) systems. In order to mitigate the multi-path interference (MPI) in the DS CDMA system. At each cancellation stage in the proposed PIC scheme, on each subcarrier, a weighted sum of the soft outputs of the other users in the current stage is cancelled from the soft output of the desired user to form the input to the next stage. At the last stage, the interference cancelled outputs from all the subcarriers are maximal ratio combined (MRC) to form the decision statistic. Parallel interference elimination is first proposed in this paper the multi-path interference are evaluated by tentative decision and known user information. Then the performance over Rayleigh fading channel are analyzed and compared to Matched filter, Decorelator, successive interference cancellation (SIC) and conventional parallel interference cancellation (PIC). It is shown that PIC performance can be improved greatly by using this method with simple structure and easy implementation.

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Umamaheswari, R., M. Ramya Princess, and P. Nirmal Kumar. "Improved Whale Optimized MLP Neural Network-Based Learning Mechanism for Multiuser Detection in MIMO Communication System." Journal of Circuits, Systems and Computers 29, no. 15 (2020): 2050239. http://dx.doi.org/10.1142/s0218126620502394.

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Direct-Sequence Code Division Multiple Access (DS-CDMA) is a digital method to spread spectrum modulation for digital signal transmission. We propose to detect signal in DS-CDMA communication using the learning mechanism. Initially, the user signals are spread using the respective pseudo-noise (PN) code where the input signal is multiplied with the code which is then modulated using the quadrature phase shift keying (QPSK) modulator. The modulated signal is then transmitted in a 3G/4G channel considering all types of fading. The transmitted signal is received by the antenna array which is performed by demodulation. We propose to adaptively assign the weights by employing Improved Whale Optimized Multi-Layer Perceptron Neural Network (IWMLP-NN)-based learning mechanism. To design IWMLP-NN, Improved Whale Optimization Algorithm is combined with multilayer perceptron neural network. This is used instead of the normal Multiple Signal Classification (MUSIC) and least mean squares (LMS)/root-mean-square (RMS) algorithms used in beam-forming networks. After assigning weight through IWMLP-NN-based learning mechanism, we de-spread to get the original user data. We have compared our proposed technique with the normal techniques with the help of plots of Bit Error Rate (BER) versus Signal-to-Noise Ratio (SNR). We use both the AWGN channel and fading channel for analysis. Experimental results prove that our proposed method achieves better BER performance results even with deep fading.

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Rajendrakumar, Govinda Zope, and Ningappa Kyatanavar Devendra. "Pseudo Convex Framework using Sparse Channel Estimation for Multipath Fading Channels in DS-CDMA Systems." International Journal of Engineering and Advanced Technology (IJEAT) 9, no. 5 (2020): 104–11. https://doi.org/10.35940/ijeat.D9066.069520.

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Direct-Sequence Code-Division Multiple-Access (DS-CDMA) with rake receiver for multiuser system sets up a new dimension in mobile communication system. We propose a pseudo convex framework using an optimum sparse channel estimation technique for DS-CDMA mobile communication systems. Further, the blind channel estimation problem will be examined for rake-based DS-CDMA communication framework with time variant multi-path fading channels This receiver accomplishes an effective assessment of channel according to a maximum convexity criterion, by means of the sparse technique. This estimation method requires a convenient representation of the discrete multipath fading channel based on the sparse theory. In this paper, we have defined a specialized interior-point method for solving large-scale ℓ1- problem in multiuser detection. Our method can be generalized to handle a variety of extensions such as various channel conditions. A new solution to DS-CDMA based sparse channel estimation is presented in this paper that assures a global optimal solution. Also, it is proven that the said solution can be used as an apparent program that shall enable solutions utilizing interior point techniques involving polynomial time complexity. Through simulation the rationality of the techniques proposed in this paper has been highlighted by results obtained for various modulation schemes and channel parameters. The execution of a pseudo convex framework using sparse channel estimation technique with rake receiver in DS-CDMA framework for multipath fading channels is explored. The overall performance is evaluated in terms of bit error rate (BER) for a range of values of signal to noise ratio (SNR). This framework gives better performance under various modulation schemes using pseudo noise (PN) spreading code. Furthermore, performance of the proposed system is compared with different detectors.

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Nazrul Islam, A. K. M., and S. P. Majumder. "Effect of Pointing Error on the BER Performance of an Optical CDMA FSO Link with SIK Receiver." Journal of Optical Communications 38, no. 4 (2017). http://dx.doi.org/10.1515/joc-2015-0078.

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AbstractAn analytical approach is presented for an optical code division multiple access (OCDMA) system over free space optical (FSO) channel considering the effect of pointing error between the transmitter and the receiver. Analysis is carried out with an optical sequence inverse keying (SIK) correlator receiver with intensity modulation and direct detection (IM/DD) to find the bit error rate (BER) with pointing error. The results are evaluated numerically in terms of signal-to-noise plus multi-access interference (MAI) ratio, BER and power penalty due to pointing error. It is noticed that the OCDMA FSO system is highly affected by pointing error with significant power penalty at a BER of 10

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Jouini, Abdelhafid, Abdelmadjid Maali, Mustapha Benssalah, Ammar Mesloub, Genevieve Baudoin, and Mhamed Hamadouche. "A robust auto‐adaptive approach for serial acquisition of generalized multi‐carrier spread spectrum in multipath fading mobile channels." International Journal of Communication Systems 34, no. 1 (2020). http://dx.doi.org/10.1002/dac.4659.

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SummaryIn this paper, a new robust auto‐adaptive approach for pseudo‐noise (PN) code acquisition is proposed. It is applied to the generalized multi‐carrier direct‐sequence code‐division multiple‐access (MC DS‐CDMA) systems communicating over frequency‐selective multipath Rayleigh fading channels. This new approach is based on the constant false alarm rate (CFAR) detection algorithm, referred here as automatic selection partial sum ordered statistics (ASPSOS)‐CFAR. The proposed approach does not require any prior information about the background environment and uses maximum likelihood estimation (MLE) method to detect the interfering signals group in the ranked cells for the full reference window. Once this group is identified and censored, the remaining smaller ranked cells are combined to form an estimate of the background noise level to compute the adaptive threshold. Through simulations, the performance of the proposed detector is analyzed and compared with traditional CFAR detectors based on fixed or automatic censoring algorithms. The obtained results show that the proposed detector eliminates the drawbacks of the previously related detectors and offers a robust detection performance to enhance the acquisition process in heterogeneous background environments.

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Nader, Abdullah Khadim, Jawad Kadhim Jawad Alrubaie Ali, and Qasim Jumah Al-Thahab Osama. "BER estimation for STBC-MC-DS-CDMA-4 antennas system by varied wavelet-carriers features via AWGN-flat channels." Bulletin of Electrical Engineering and Informatics (BEEI) 13, no. 1 (2024). https://doi.org/10.11591/eei.v13i1.5371.

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This paper improves the bit error rate (BER) of the modern communication system by taking into account the effect of the wavelet shape and the number of carriers on the performance of the space time block code multi-carrier direct sequence code division multiple access (STBC-MC-DS-CDMA). Here the transmitter is moved with speeds 2 km/hr, 45 km/hr and 100 km/hr via Rayleigh flat fading channel. Here, 2 antennas are employed at the receiver to mitigate the multipath signal influence. The system’s orthogonal frequencies are generated using Haar, Daubechies 4, Symlets 4, Cohen-Daubechies-Feauveau 1.1 with 9.7 and B-spline 3. The number of used carriers is 128, 512, and 1,024. Quadrature phase shift key (QPSK) is used with cyclic prefix 1/16 and a bandwidth of 20 MHz. traditional fast fourier transform (FFT) system is compared to the proposed discrete wavelet packet transform (DWPT) to show the BER enhancements. The space-time block coding (STBC) is used to enhance system cabability in error corection. The proposed system shows significant improvement in BER, so that, it reaches to the same BER when using FFT but with less signal to noise ratio (SNR), which interns reduce the power consumed within the system and the cost.

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Nahid, Ardalani, Khoogar Ahmadreza, and Roohi H. "A Comparison of Adaline and MLP Neural Network based Predictors in SIR Estimation in Mobile DS/CDMA Systems." September 21, 2007. https://doi.org/10.5281/zenodo.1061585.

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In this paper we compare the response of linear and nonlinear neural network-based prediction schemes in prediction of received Signal-to-Interference Power Ratio (SIR) in Direct Sequence Code Division Multiple Access (DS/CDMA) systems. The nonlinear predictor is Multilayer Perceptron MLP and the linear predictor is an Adaptive Linear (Adaline) predictor. We solve the problem of complexity by using the Minimum Mean Squared Error (MMSE) principle to select the optimal predictors. The optimized Adaline predictor is compared to optimized MLP by employing noisy Rayleigh fading signals with 1.8 GHZ carrier frequency in an urban environment. The results show that the Adaline predictor can estimates SIR with the same error as MLP when the user has the velocity of 5 km/h and 60 km/h but by increasing the velocity up-to 120 km/h the mean squared error of MLP is two times more than Adaline predictor. This makes the Adaline predictor (with lower complexity) more suitable than MLP for closed-loop power control where efficient and accurate identification of the time-varying inverse dynamics of the multi path fading channel is required.

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Chourasiya, Keerti. "PERFORMANCE OF MU-MC-DS-CDMA SYSTEM IN RAYLEIGH FADING CHANNEL." INTERANTIONAL JOURNAL OF SCIENTIFIC RESEARCH IN ENGINEERING AND MANAGEMENT 07, no. 01 (2023). http://dx.doi.org/10.55041/ijsrem17416.

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The Multi user Multi Carrier Direct sequencing Code Division Multiple Access (MU-MC-DS-CDMA) strategy was developed in response to rising demand for system capacity, higher data rates, and multimedia services. It's essentially a combination of CDMA and OFDM schemes. As a result, MC-CDMA takes the advantages of both CDMA and OFDM technologies. CDMA improves bandwidth consumption performance, whereas OFDM helps to minimize Inter Symbol Interference (ISI) and multipath fading. This dissertation suggests a method for evaluating the performance of multi user MC-DS-CDMA system. BER and PAPR are used to evaluate the results. The Bit Error Rate (BER) output of the proposed method is then examined using MATLAB for various modulation techniques. By using Walsh-Hadamard (W-H) code is used because it eliminates Multiple Access Interference (MAI). In terms of BER, it can be shown that BPSK performs better than QPSK. Key Words: AWGN, BER, ISI, MC-CDMA, Rayleigh Fading Channel, SNR, QPSK, MAI

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43

"Analysis of sliding window decorrelation in DS-CDMA mobile radio." Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences 447, no. 1930 (1994): 313–40. http://dx.doi.org/10.1098/rspa.1994.0143.

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The sliding window decorrelating algorithm (SLWA) has been proposed in Wijayasuriya et al . (1992 b, c ) as an alternative to dynamic power control in mobile direct sequence code division multiple access (DS-CDMA) systems. The architecture is readily extended to incorporate RAKE diversity combining techniques, thereby overcoming the aggravated near—far problem (NFP) found in multipath fading environments. In this paper we derive a mathematical model for a multi-user DS-CDMA system incorporating a sliding window (finite sequence length) decorrelator. The main contributions of the analysis are the investigation of performance under the practical limitation of incomplete RAKE combining, characterization of the interference variance in a finite sequence length asynchronous configuration, and the incorporation of vehicle motion. Decorrelation in a mobile radio channel is discussed and results derived from a simulation model presented, in addition to numerical examples from the analytical model.

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Ehab, F. Badran, and Gu Guoxiang. "Optimal Channel Equalization for MIMO Time-Varying Channels." International Journal of Electrical, Electronic and Communication Sciences 1.0, no. 11 (2008). https://doi.org/10.5281/zenodo.1330755.

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We consider optimal channel equalization for MIMO (multi-input/multi-output) time-varying channels in the sense of MMSE (minimum mean-squared-error), where the observation noise can be non-stationary. We show that all ZF (zero-forcing) receivers can be parameterized in an affine form which eliminates completely the ISI (inter-symbol-interference), and optimal channel equalizers can be designed through minimization of the MSE (mean-squarederror) between the detected signals and the transmitted signals, among all ZF receivers. We demonstrate that the optimal channel equalizer is a modified Kalman filter, and show that under the AWGN (additive white Gaussian noise) assumption, the proposed optimal channel equalizer minimizes the BER (bit error rate) among all possible ZF receivers. Our results are applicable to optimal channel equalization for DWMT (discrete wavelet multitone), multirate transmultiplexers, OFDM (orthogonal frequency division multiplexing), and DS (direct sequence) CDMA (code division multiple access) wireless data communication systems. A design algorithm for optimal channel equalization is developed, and several simulation examples are worked out to illustrate the proposed design algorithm.

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"Implementation of Knowba Filtering Method for Intereference Rejection in NBDSSS." International Journal of Engineering and Advanced Technology 9, no. 2 (2019): 2368–71. http://dx.doi.org/10.35940/ijeat.a2245.129219.

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Spread spectrum communication is a communication method that deliberately makes the bandwidth of the transmitted waveform larger than would be required to transmit the data over the channel.One of the most encouraging multiplexing techniques for present and forthcoming telecommunications services, such as private communications, ad-hoc wireless communications, third-generation cellular telephony and sensor networks, is the CDMA(code division multiple access) implemented with direct-sequence (DS) signaling. DS-CDMA's benefits include superior operation in multi-path settings, flexibility in channel allocation, enhanced capacity in fading settings, and the capability to share bandwidth with narrowband communication technologies without deteriorating the efficiency of either system. In our work,we are proposing a new know-ba strategy to dismissing interference where originally monitoring signal environment with high precision is called from the library and subsequently based on data that is appropriate for dismissing interference. Various interference scenarios are simulated using computer simulations to show the efficiency of the method.

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Zeeshan, Muhammad, and Shoab Ahmed Khan. "A Robust Carrier Frequency Offset Estimation Algorithm in Burst Mode Multicarrier CDMA based Ad Hoc Networks." International Journal of Communication Networks and Information Security (IJCNIS) 4, no. 3 (2022). http://dx.doi.org/10.17762/ijcnis.v4i3.221.

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The future wireless communication systems demand very high data rates, anti-jamming ability and multiuser support. People want large amount of data to be continuously accessible in their personal devices. Direct Sequence (DS) spread spectrum based techniques such as Code Division Multiple Access (CDMA) fulfil these requirements but, at the same time, suffer from the Intersymbol Interference (ISI). Multicarrier CDMA (MC-CDMA) is an emerging technology to be used in mobile devices operating in an ad hoc setting due to its immunity towards ISI and having all the advantages of spread spectrum communication. One of the major problems with MC-CDMA is the high sensitivity towards carrier frequency offsets caused due to the inherent inaccuracy of crystal oscillators. This carrier frequency offset destroys the orthogonality of the subcarriers resulting in Intercarrier Interference (ICI). In this paper, we propose a computationally efficient algorithm based on Fast Fourier Transform (FFT) and biquadratic Lagrange interpolation. The FFT is based on the use of overlapping windows for each frame of the data instead of non-overlapping windows. This gives a coarse estimate of the frequency offset which is refined by the successive application of Lagrange quadratic interpolation to the samples in the vicinity of FFT peak. The proposed algorithm has been applied to the multiuser ad hoc network and simulated in Stanford University Interim (SUI) channels. It has been shown by simulations that the proposed algorithm provides better performance of almost 1~2 dB as compared to the well-known algorithms.

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"Pseudo Convex Framework using Sparse Channel Estimation for Multipath Fading Channels in DS-CDMA Systems." International Journal of Engineering and Advanced Technology 9, no. 5 (2020): 104–11. http://dx.doi.org/10.35940/ijeat.d9066.069520.

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A Direct-Sequence Code-Division Multiple-Access (DS-CDMA) with rake receiver for multiuser system sets up a new dimension in mobile communication system. We propose a pseudo convex framework using an optimum sparse channel estimation technique for DS-CDMA mobile communication systems. Further, the blind channel estimation problem will be examined for rake-based DS-CDMA communication framework with time variant multi-path fading channels This receiver accomplishes an effective assessment of channel according to a maximum convexity criterion, by means of the sparse technique. This estimation method requires a convenient representation of the discrete multipath fading channel based on the sparse theory. In this paper, we have defined a specialized interior-point method for solving large-scale ℓ1 - problem in multiuser detection. Our method can be generalized to handle a variety of extensions such as various channel conditions. A new solution to DS-CDMA based sparse channel estimation is presented in this paper that assures a global optimal solution. Also, it is proven that the said solution can be used as an apparent program that shall enable solutions utilizing interior point techniques involving polynomial time complexity. Through simulation the rationality of the techniques proposed in this paper has been highlighted by results obtained for various modulation schemes and channel parameters. The execution of a pseudo convex framework using sparse channel estimation technique with rake receiver in DS-CDMA framework for multipath fading channels is explored. The overall performance is evaluated in terms of bit error rate (BER) for a range of values of signal to noise ratio (SNR). This framework gives better performance under various modulation schemes using pseudo noise (PN) spreading code. Furthermore, performance of the proposed system is compared with different detectors.

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Journal articles on the topic 'Multi carrier direct sequence code division multiple access'

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