Academic literature on the topic 'Direct-Sequence Code Division Multiple Access (DS-CDMA)'

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Journal articles on the topic "Direct-Sequence Code Division Multiple Access (DS-CDMA)"

1

Mandalapu, Harinath, and B. Murali Krishna. "FPGA implementation of DS-CDMA Transmitter and Receiver." International Journal of Reconfigurable and Embedded Systems (IJRES) 6, no. 3 (2018): 179. http://dx.doi.org/10.11591/ijres.v6.i3.pp179-185.

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Direct sequence spread Spectrum (DSSS) is also known as direct sequence code division multiplexing. In direct sequence spread spectrum the stream of information to be transmitted is divided into small pieces each of which is allocated across to a frequency channel across the spectrum. Data signal at the point of transmission is collaborated with a higher data-rate bit sequence (also called chipping code) that divides the data according to a spreading ratio. A redundant chipping code helps the signal resist interference and also enables the original data to be recovered if data bits are damaged during the transmitting. In this project direct sequence spread spectrum principle based code division multiple access (CDMA) transmitter and receiver is implemented on SPARTAN 3E FPGA. The Xilinx synthesis technology (XST) of Xilinx ISE tool used for synthesis of transmitter and receiver on FPGA Spartan 3E.
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2

Argüello, Francisco, Manuel Bugallo, and Juan López. "Blind Multiuser Receivers for Chaos Based Communications." International Journal of Bifurcation and Chaos 13, no. 08 (2003): 2353–59. http://dx.doi.org/10.1142/s0218127403008028.

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Recently, there has been a good deal of interest in the use of chaotic signals for direct sequence code division multiple access (DS-CDMA) communication systems. The capacity of DS-CDMA systems is interference-limited, and can therefore be increased by techniques that suppress interference. This letter is devoted to the evaluation of the impact of blind multiuser detection techniques on chaos based DS-CDMA systems. Blind receivers can suppress multiple access interference and do not require knowledge of the code sequences and propagation channels of the interference. We demonstrate that, for chaotic sequence-based communications, blind multiuser receivers significantly improve the BER with respect to single-user receivers, and that their use is practically essential with a high number of users.
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3

Alami Hassani, Aicha, Mohcine Zouak, and Mostafa Mrabti. "Contribution to Synchronization and Tracking Modelisation in a CDMA Receiver." Journal of Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/936495.

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We propose and analyze a noncoherent receiver with PN code tracking for direct sequence code division multiple access (DS-CDMA) communication systems. We employ the delay-lock loop (DLL) architectures for the tracking stage. The choice of DLL parameters is studied with special focus on DS-CDMA communication systems and orthogonality conditions. We described the modeling and simulation of the NCO using hardware description language VHDL. Details of the VHDL implementation are shown.
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4

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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5

Men, Wei, Liang Zhang, Jing-wei Yin, Xiao Han, and Hong-yu Yin. "Blind beamforming-based strong interference suppression in underwater acoustic direct-sequence code-division multiple-access systems." Journal of the Acoustical Society of America 152, no. 4 (2022): 2128–39. http://dx.doi.org/10.1121/10.0014598.

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In an underwater acoustic direct-sequence code-division multiple-access (DS-CDMA) system, the performance of the conventional receiver is severely limited by the strong multiple-access interferences, which is due to the near-far effect. In this paper, a time-frequency-time with eigendecomposition-based blind beamformer (TFT-EBB) method is proposed for a distant user to suppress strong interference from a nearby user in DS-CDMA underwater acoustic communications. When the interference level is moderately higher than that of the desired signal, the TFT-EBB method can estimate the composite steering vector of all multipath components of the weak desired user signal via the eigendecomposition of the array covariance matrix at each frequency bin. Then the proposed energy detection-based RAKE receiver is cascaded to achieve multipath diversity, in which it requires less prior information compared with the conventional RAKE receiver. The proposed method is evaluated by using both simulated and field experimental data, which verifies its effectiveness.
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6

Bilal Abdalla, Khalid Hamid. "Simulation Performance of CDMA/QA in Mobile Channel." FES Journal of Engineering Sciences 5, no. 1 (2011): 14. http://dx.doi.org/10.52981/fjes.v5i1.32.

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The aim of this work is to study, analyze and evaluate software the link performance of mobile communication system under the impairment of the multiple access schemes, down-link thermal noise and the multipath fading in the mobile channel. For this purpose, modeling and simulation has been used to study the effects of nonlinearities in mobile channel using spread spectrum for Direct Sequence Code Division Multiple Access, with Quadrature Amplitude Modulation (DS-CDMA/QAM).
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7

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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8

Hassani, A., Y. Garrouani, F. Mrabti, and F. Abdi. "Acquisition Time and Probabilities of Detection and False Alarm in Direct Sequence Code Division Multiple Access Systems." Jordan Journal of Electrical Engineering 9, no. 1 (2023): 60. http://dx.doi.org/10.5455/jjee.204-1668454435.

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Multiple access interference (MAI) is one of the most important issues to consider in the design, implementation and operation of 5G systems using code division multiple access (CDMA) technique based on spread spectrum that offers a more flexible solution, compared to other techniques. Especially, it permits a much higher user bit rate, due to the bandwidth allocated to the emitted signal; thus, allowing very attractive multimedia services. In this paper, we develop the expressions of the detection probability, false alarm probability and the average acquisition time - in a direct sequence CDMA (DS-CDMA) transmission system - using a serial search and taking into consideration MAI. The evolution of these parameters according to the signal- to-noise ratio (SNR) and the decision threshold leads to study performances of the system in terms of detection and average acquisition time. The obtained results reveal that the acquisition time decreases when the SNR increases. Additionally, it is found that the probability of detection increases when the threshold decreases, and increasing SNR it reaches a constant value for an SNR/chip around 0 dB for all thresholds.
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9

Litvinenko, A., and E. Bekeris. "Statistical Analysis of Multiple Access Interference in Chaotic Spreading Sequence Based DS-CDMA Systems." Electronics ETF 21, no. 1 (2017): 34. http://dx.doi.org/10.7251/els1721034l.

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This paper presents a statistical analysis of multiple access interference (MAI) in Direct Sequence Code Division Multiple Access (DS-CDMA) communication systems based on different types of chaotic spreading sequences. The probability distribution of the interference in a system with K users causing the MAI is studied using MATLAB simulation. For chaotic spreading sequence generation six different 1-D chaotic maps are used: modified Bernoulli, modified Tent, Gauss, Sine-Circle, Cubic and Pinchers map. A brief statistical analysis of the cross-correlation properties of the chaotic sequences generated by the aforementioned maps is also presented.
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10

Varzakas, Panagiotis. "Capacity Estimation for a DS-CDMA System in Nakagami-m Fading." WSEAS TRANSACTIONS ON COMMUNICATIONS 21 (March 3, 2022): 31–33. http://dx.doi.org/10.37394/23204.2022.21.6.

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Ιn this paper, a novel closed-form expression of the Shannon average channel capacity per user for direct- sequence code-division multiple access (DS-CDMA) systems, operating in Nakagami-m fading, with optimum RAKE reception, is obtained. Numerical results are also presented to illustrate the proposed mathematical analysis and to point out the effect of the fading severity on the user’s average channel capacity.
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