Relevant bibliographies by topics / Direct-Sequence Code Division Multiple Access (DS-CDMA)

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers

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

Author: Grafiati
Published: 4 June 2021
Last updated: 7 September 2023

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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 (May 28, 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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Argüello, Francisco, Manuel Bugallo, and Juan López. "Blind Multiuser Receivers for Chaos Based Communications." International Journal of Bifurcation and Chaos 13, no. 08 (August 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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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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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 (October 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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Bilal Abdalla, Khalid Hamid. "Simulation Performance of CDMA/QA in Mobile Channel." FES Journal of Engineering Sciences 5, no. 1 (October 6, 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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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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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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Litvinenko, A., and E. Bekeris. "Statistical Analysis of Multiple Access Interference in Chaotic Spreading Sequence Based DS-CDMA Systems." Electronics ETF 21, no. 1 (July 14, 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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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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Dissertations / Theses on the topic "Direct-Sequence Code Division Multiple Access (DS-CDMA)"

1

Kim, Kyungseok. "Efficient signal enhancement schemes for adaptive antenna arrays in DS-CDMA systems." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843053/.

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Adaptive antenna array technology will undoubtedly form a vital part of third generation cellular systems owing to not only confining the radiated energy associated with a mobile to a small volume on the downlink but also reducing the interference due to cochannel users on the uplink. The objective of this thesis is to develop signal enhancement schemes for adaptive antenna arrays for the purpose of enhancing the quality and capacity of direct sequence code division multiple access (DS-CDMA) systems. Firstly, The signal enhancement scheme using a real symmetric array covariance matrix (RSACM) method was proposed. This proposed scheme is composed of a unitary and persymmetric transformation methods. A real symmetric array covariance matrix has the same Toeplitz-plus-Hankel matrix structure that is produced by almost total noiseless data sequence. The second proposed signal enhancement scheme consists of the rotation of signal subspace (RSS) and Toeplitz matrix approximation (TMA) methods. This proposed scheme improved the system performance by reducing the interference- plus-noise effect from the complex array covariance matrix of the pre-correlation received signal vector. The third proposed signal enhancement scheme is a modified linear signal estimator (MLSE) which involves the rank N approximation by reducing total noise eigenvalues (RANE) and TMA methods. The aim of this proposed scheme is to improve the system performance by effectively reducing the interference-plus-noise effect from the post-correlation received signal. Secondly, the computational complexity and the performance for all proposed signal enhancement schemes in this thesis are investigated and compared. The signal enhancement scheme using the RSS+TMA and MLSE methods was also proposed for a multi-rate and multicell DS-CDMA systems. The relative other-cell interference factor was analysed for a multicell condition. Finally, the performance of all proposed signal enhancement schemes is shown to be much better than that of no signal enhancement method under a single cell, multicell, single rate, and multirate conditions.
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2

Kocakanat, Murat. "A direct sequence - code division multiple access/binary phase shift keying (DS-CDMA/BPSK) modem design." Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8270.

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Bian, Yan Qing. "Advanced multi-user direct-sequence code division multiple access (DS-CDMA) detection techniques for cellular communications." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398603.

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4

Aue, Volker. "Optimum linear single user detection in direct-sequence spread-spectrum multiple access systems." Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/43609.

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After Qualcomm's proposal of the IS-95 standard, code-division multiple access (CDMA) gained popularity as an alternative multiple-access scheme in cellular and personal communication systems (PCS). Besides the advantage of allowing asynchronous operation of the users, CDMA direct-sequence spread spectrum (DS-SS) offers resistance to frequency selective fading and graceful degradation of the performance as the number of users increases.

Orthogonality of the signals in time-division multiple access and frequency-division multiple access is inherent from the nature of the multiple access scheme. In a CDMA system, orthogonality of the signals is not guaranteed in general. Consequently, the performance of conventional correlation receivers suffers.

Sub-optimum receivers which use knowledge of the interfering signals have been investigated by other researchers. These receivers attempt to cancel the multi-user interference by despreading the interfering users. Hence, these receivers require knowledge about all the spreading codes, amplitude levels, and signal timing, and are, in general, computationally intensive.

In this thesis, a technique is presented for which a high degree of interference rejection can be obtained without the necessity of despreading each user. It is shown that exploiting spectral correlation can help mitigate the effects of the multiple-access interference. If code-on-pulse DS-SS modulation is used, a cyclic form of the Wiener filter provides substantial improvements in performance in terms of bit error rate and user capacity. Furthermore, it is shown, that a special error-criterion should be used to adapt the weights of the filter.

The computational complexity of the receiver is equivalent to that of conventional equalizers.


Master of Science
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Wang, Beibei. "Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems." Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173119961.

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Carey, Daniel Jeffrey. "Statistical modelling and reduction of multiple access interference power in wideband DS-CDMA and MC-CDMA communications systems." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16342/1/Daniel_Carey_Thesis.pdf.

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With code division multiple access (CDMA) systems being the prominent multiple access scheme for the air interface for 3G cellular systems, most standardisation bodies have based their terrestrial cellular systems on DS-CDMA (W-CDMA, UMTS, cdma2000). With 4G systems fast approaching, bringing with them improved services and quality of service standards, there is growing interest in further investigating and developing more efficient multiple access techniques such as multicarrier CDMA (MC-CDMA) systems. MC-CDMA combines multicarrier modulation (MCM), namely OFDM, with CDMA profiting from the benefits of both multiplexing techniques; as such, MC-CDMA is emerging as a possible candidate for the air interface multiple access scheme for 4G cellular systems. Multiple access interference (MAI) is a limiting factor of CDMA systems in terms of system capacity as orthogonally designed spreading sequences lose their orthogonality in the presence of timing misalignments amongst mobile subscribers in a cell; such is the case over the uplink channel. Ensuring orthogonal code properties minimises the MAI over synchronous environments, however, it is when the users are allowed to transmit asynchronously, as is the case over the uplink channel, that MAI inflicts significant performance degradation. In CDMA systems, all subscribers are active on the same frequency band simultaneously and signal separation is facilitated upon reception via the properties of the assigned spreading codes. Under asynchronous conditions the code properties alone do not provide the necessary separation and an additive MAI term remains in the detection process. In addition to the separation abilities of the spreading codes, a further method of deciphering the desired subscriber signal from the interfering subscriber signals is sought. In this thesis we propose a statistical model for both the probability density function (pdf) of the total MAI power and the corresponding bit-error rate (BER) observed during asynchronous CDMA transmission. The modelling offers the full statistic the MAI power and resulting BER, not just the first and second order statistics. In addition to statistically quantifying the MAI power, the thesis also proposes a technique for the successful reduction of MAI caused by asynchronous transmission. This interference reduction technique is derived from an ambiguity domain analysis of the asynchronous CDMA detection problem and its application to both the DS-CDMA and MC-CDMA multiplexing techniques is presented and the results show significant MAI reduction, and thus an improved the BER. A methodology for the approximation of the total MAI power pdf and the resulting BER pdf is proposed for the asynchronous DS-CDMA and MC-CDMA techniques. This methodology is derived for the use of Walsh-Hadamard (WH) and Gold spreading sequences, however, it is applicable to any given set of deterministic spreading sequences. The total MAI power pdfs of both systems are statistically modelled as being Nakagamim distributed and the corresponding BER modelling is derived from the Nakagami-m formulation offering the full statistic of both the incurred MAI power and the achievable BER. The proposed pdf acquisition methodology and statistical models can be used as analysis tools to assess the relative performances of the DS-CDMA and MC-CDMA techniques for a variety of communications environments. Here the asynchronous uplink channel is considered in the absence of fading and the results show a clear distinction between the BER performances of the MC-CDMA and DS-CDMA systems, for which the MC-CDMA system offers a superior performance for the purely asynchronous channel considered. The results suggest a higher resistance to MAI in the MC-CDMA technique in comparison to the DS-CDMA system for the considered transmission scenario. Following ambiguity function analysis of the asynchronous CDMA detection problem, the concept of dual-frequency switching is introduced to the existing DS-CDMA and MC-CDMA techniques giving rise to the proposed dual-frequency DS-CDMA (DF/DSCDMA) and dual-frequency MC-CDMA (DF/MC-CDMA) schemes. Periodically switching the carrier frequency between dual frequency bands at consecutive symbol boundaries facilitates partial CDMA signal separation upon asynchronous reception. Such switching of the carrier frequency induces a separation in frequency between offset interference signals and the reference signal; this is equivalent to shifting the energy concentration of the interference signals away form the ambiguity domain origin (representing the decision variable of the matched filter). Further MAI reduction is demonstrated through careful design of the dual carrier frequencies. The newly proposed DF systems clearly outperform the standard DS-CDMA and MC-CDMA systems when adopting equivalent spreading factors. The DF/DS-CDMA technique in particular achieves the most MAI reduction and in doing so, surpasses all other considered techniques to offer the best BER performance for the purely asynchronous channel considered. In terms of bandwidth usage, the DF/DS-CDMA band width is 1.5 times that of the DF/MC-CDMA system and from the BER results presented, one may argue that DF/MC-CDMA offers the better BER given the bandwidth usage. The multicarrier systems presented, MC-CDMA and DF/MC-CDMA, offer attractive BER performances for the bandwidth used and it is concluded that MC-CDMA is a genuine candidate for the uplink air interface multiple access scheme for future mobile cellular technologies.
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7

Carey, Daniel Jeffrey. "Statistical modelling and reduction of multiple access interference power in wideband DS-CDMA and MC-CDMA communications systems." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16342/.

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With code division multiple access (CDMA) systems being the prominent multiple access scheme for the air interface for 3G cellular systems, most standardisation bodies have based their terrestrial cellular systems on DS-CDMA (W-CDMA, UMTS, cdma2000). With 4G systems fast approaching, bringing with them improved services and quality of service standards, there is growing interest in further investigating and developing more efficient multiple access techniques such as multicarrier CDMA (MC-CDMA) systems. MC-CDMA combines multicarrier modulation (MCM), namely OFDM, with CDMA profiting from the benefits of both multiplexing techniques; as such, MC-CDMA is emerging as a possible candidate for the air interface multiple access scheme for 4G cellular systems. Multiple access interference (MAI) is a limiting factor of CDMA systems in terms of system capacity as orthogonally designed spreading sequences lose their orthogonality in the presence of timing misalignments amongst mobile subscribers in a cell; such is the case over the uplink channel. Ensuring orthogonal code properties minimises the MAI over synchronous environments, however, it is when the users are allowed to transmit asynchronously, as is the case over the uplink channel, that MAI inflicts significant performance degradation. In CDMA systems, all subscribers are active on the same frequency band simultaneously and signal separation is facilitated upon reception via the properties of the assigned spreading codes. Under asynchronous conditions the code properties alone do not provide the necessary separation and an additive MAI term remains in the detection process. In addition to the separation abilities of the spreading codes, a further method of deciphering the desired subscriber signal from the interfering subscriber signals is sought. In this thesis we propose a statistical model for both the probability density function (pdf) of the total MAI power and the corresponding bit-error rate (BER) observed during asynchronous CDMA transmission. The modelling offers the full statistic the MAI power and resulting BER, not just the first and second order statistics. In addition to statistically quantifying the MAI power, the thesis also proposes a technique for the successful reduction of MAI caused by asynchronous transmission. This interference reduction technique is derived from an ambiguity domain analysis of the asynchronous CDMA detection problem and its application to both the DS-CDMA and MC-CDMA multiplexing techniques is presented and the results show significant MAI reduction, and thus an improved the BER. A methodology for the approximation of the total MAI power pdf and the resulting BER pdf is proposed for the asynchronous DS-CDMA and MC-CDMA techniques. This methodology is derived for the use of Walsh-Hadamard (WH) and Gold spreading sequences, however, it is applicable to any given set of deterministic spreading sequences. The total MAI power pdfs of both systems are statistically modelled as being Nakagamim distributed and the corresponding BER modelling is derived from the Nakagami-m formulation offering the full statistic of both the incurred MAI power and the achievable BER. The proposed pdf acquisition methodology and statistical models can be used as analysis tools to assess the relative performances of the DS-CDMA and MC-CDMA techniques for a variety of communications environments. Here the asynchronous uplink channel is considered in the absence of fading and the results show a clear distinction between the BER performances of the MC-CDMA and DS-CDMA systems, for which the MC-CDMA system offers a superior performance for the purely asynchronous channel considered. The results suggest a higher resistance to MAI in the MC-CDMA technique in comparison to the DS-CDMA system for the considered transmission scenario. Following ambiguity function analysis of the asynchronous CDMA detection problem, the concept of dual-frequency switching is introduced to the existing DS-CDMA and MC-CDMA techniques giving rise to the proposed dual-frequency DS-CDMA (DF/DSCDMA) and dual-frequency MC-CDMA (DF/MC-CDMA) schemes. Periodically switching the carrier frequency between dual frequency bands at consecutive symbol boundaries facilitates partial CDMA signal separation upon asynchronous reception. Such switching of the carrier frequency induces a separation in frequency between offset interference signals and the reference signal; this is equivalent to shifting the energy concentration of the interference signals away form the ambiguity domain origin (representing the decision variable of the matched filter). Further MAI reduction is demonstrated through careful design of the dual carrier frequencies. The newly proposed DF systems clearly outperform the standard DS-CDMA and MC-CDMA systems when adopting equivalent spreading factors. The DF/DS-CDMA technique in particular achieves the most MAI reduction and in doing so, surpasses all other considered techniques to offer the best BER performance for the purely asynchronous channel considered. In terms of bandwidth usage, the DF/DS-CDMA band width is 1.5 times that of the DF/MC-CDMA system and from the BER results presented, one may argue that DF/MC-CDMA offers the better BER given the bandwidth usage. The multicarrier systems presented, MC-CDMA and DF/MC-CDMA, offer attractive BER performances for the bandwidth used and it is concluded that MC-CDMA is a genuine candidate for the uplink air interface multiple access scheme for future mobile cellular technologies.
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Mangalvedhe, Nitin R. "Development and Analysis of Adaptive Interference Rejection Techniques for Direct Sequence Code Division Multiple Access Systems." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28399.

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The inadequacy of conventional CDMA receivers in a multiple access interference-limited mobile radio environment has spurred research on advanced receiver technologies. This research investigates the use of adaptive receivers for single user demodulation to overcome some of the deficiencies of a conventional receiver and, hence, enhance the system capacity. Several new adaptive techniques are proposed. The new techniques and some existing schemes are analyzed. The limitation of existing blind algorithms in multipath channels is analyzed and a new blind algorithm is proposed that overcomes this limitation. The optimal receiver structure for multi-rate spread spectrum systems is derived and the performance of this receiver in various propagation channels is investigated. The application of coherent and differentially coherent implementations of the adaptive receiver in the presence of carrier frequency offsets is analyzed. The performance of several new adaptive receiver structures for frequency offset compensation is also studied in this research. Analysis of the minimum mean-squared error receiver is carried out to provide a better understanding of the dependence of its performance on channel parameters and to explain the near-far resilience of the receiver. Complex differentially coherent versions of the sign algorithm and the signed regressor algorithm, algorithms that have a much lower computational complexity than the least-means square algorithm, are proposed and applied for CDMA interference rejection.
Ph. D.
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9

Alsharekh, Mohammed Fahad. "Transform domian/cyclic code shift keying system on an urban multipath channel." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1177003745.

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Ardebilipour, Mehrdad. "Acquisition techniques for mobile CDMA systems." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843192/.

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The initial code Acquisition Techniques of Direct Sequence Spread Spectrum Systems for two categories of serial and parallel search strategies is investigated. A simple and economic scheme for coarse code acquisition of Reverse Link for UMTS (FDD-WCDMA) application is presented. The emphasis is on the performance of a new scheme (using a Surface Acoustic Wave Matched Filter) as a term of probability of false detection (pf) in code division multiple access (CDMA) systems. Knowledge of initial code uncertainty phases help to reduce the overhead of preamble on the access channel and a very simple scheme for acquisition to be determined. In the reverse link this uncertainty is due to the cell radius only. Acquisition time required for a simple serial search scheme may therefore be unacceptably large. On the other hand, for parallel acquisition using parallel branches in accordance with the chip uncertainty time region leads to a lot of hardware complexity. Initially, the effect of multiple access interference and spreading sequence length are determined for models applicable to the reverse link of a mobile communications system. Then the acquisition performance is derived using a model of a cellular mobile communication channel, which includes the effects of multiple access interference, adjacent cell interference, frequency selective Rician channel, shadowing, power control error, and vehicle speed. It is shown that the most significant factors in determining the acquisition performance are the acquisition observation interval, the number of users, and the specular to diffuse power ratio. Numerical results based on analysis of acquisition performance in mobile channel show that the proposed acquisition scheme is efficient, robust, fast and suitable for real time low cost implementation.
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Books on the topic "Direct-Sequence Code Division Multiple Access (DS-CDMA)"

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Gao, Li. Adaptive direct sequence code division multiple access (DS-CDMA) systems based on sequence optimization. 2002.

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A Direct Sequence - Code Division Multiple Access/Binary Phase Shift Keying (DS-CDMA/BPSK) Modem Design. Storming Media, 1997.

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A Direct-Sequence-Code Division Multiple Access/Differential Phase-Shift Keying (DS-CDMA/DPSK) Modem Design. Storming Media, 1997.

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Book chapters on the topic "Direct-Sequence Code Division Multiple Access (DS-CDMA)"

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"Direct-Sequence Code-Division Multiple Access (DS-CDMA)." In Digital Communication over Fading Channels, 735–56. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2005. http://dx.doi.org/10.1002/0471715220.ch12.

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"Initial Synchronization in Single and Multi-Carrier Direct-Sequence Code Division Multiple-Access Systems." In Single- and Multi-Carrier DS-CDMA, 749–856. Chichester, UK: John Wiley & Sons, Ltd, 2004. http://dx.doi.org/10.1002/0470863110.ch21.

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Drakshayini M N and Manjunath R. Kounte. "Smart DS-CDMA Receiver Based on Feed Forward Neural Network." In Advances in Parallel Computing Algorithms, Tools and Paradigms. IOS Press, 2022. http://dx.doi.org/10.3233/apc220004.

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Direct Sequence Code Division Multiple Access (DS-CDMA) is a schemewhere several users transmit their data simultaneously over a common wireless communication channel,by spreading each data by distinct codes. At the receiver, the individual data are detected by appropriate decoding. In this paper, a new smart receiver is proposed for detecting DS-CDMA signals based on a multi-layer Feed Forward Neural Network (FFNN). The proposed receiver detects the transmitted data when the received signal is distorted due to channel noise, near-far effect and Rayleigh fading. The channel state information is indirectly captured during the training of the FFNN and hence the conventional channel state estimation using pilot signal or training sequences is eliminated. Experimental results show that the performance of the proposed receiver in terms of detection accuracy is superior to similar competitive demodulators.
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Kashayp, Katyayani, Kandarpa Kumar Sarma, and Manash Pratim Sarma. "Design of Logistic Map-Based Spreading Sequence Generation for Use in Wireless Communication." In Next Generation Wireless Network Security and Privacy, 81–121. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-8687-8.ch003.

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Spread spectrum modulation (SSM) finds important place in wireless communication primarily due to its application in Code Division Multiple Access (CDMA) and its effectiveness in channels fill with noise like signals. One of the critical issues in such modulation is the generation of spreading sequence. This chapter presents a design of chaotic spreading sequence for application in a Direct Sequence Spread Spectrum (DS SS) system configured for a faded wireless channel. Enhancing the security of data transmission is a prime issue which can better be addressed with a chaotic sequence. Generation and application of chaotic sequence is done and a comparison with Gold sequence is presented which clearly indicates achieving better performance with simplicity of design. Again a multiplierless logistic map sequence is generated for lower power requirements than the existing one. The primary blocks of the system are implemented using Verilog and the performances noted. Experimental results show that the proposed system is an efficient sequence generator suitable for wideband systems demonstrating lower BER levels, computational time and power requirements compared to traditional LFSR based approaches.
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Zouine, Younes, and Zhour Madini. "Direct Sequence-Optical Code-Division Multiple Access (DS-OCDMA): Receiver Structures for Performance Improvement." In Multiplexing. IntechOpen, 2019. http://dx.doi.org/10.5772/intechopen.85860.

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Abdullah, M. K. A., S. A. Aljunid, M. D. A. Samad, S. B. A. Anas, and R. K. Z. Sahbudin. "Unified KS-Code." In Encyclopedia of Multimedia Technology and Networking, Second Edition, 1473–79. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-014-1.ch198.

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Many codes have been proposed for optical CDMA system as discussed in Svetislav, Mari, Zoran, Kosti, and Titlebaum (1993), Salehi (1989), Liu and Tsao (2002), Maric, Moreno, and Corrada (1996), Wei and Ghafouri-Shiraz (2002), and Prucnal, Santoro, and Ting (1986). Optical code division multiple access (OCDMA) has been recognized as one of the most important technologies for supporting many users in shared media simultaneous, and in some cases can increase the transmission capacity of an optical fiber. OCDMA is an exciting developments in short haul optical networking because it can support both wide and narrow bandwidth applications on the same network, it connects large number of asynchronous users with low latency and jitter, and permits quality of service guarantees to be managed at the physical layer, offers robust signal security and has simplified network topologies. However, for improperly designed codes, the maximum number of simultaneous users and the performance of the system can be seriously limited by the multiple access interference (MAI) or crosstalk from other users. Another issue in OCDMA is how the coding is implemented. The beginning idea of OCDMA was restricted in time domain, in which the encoding/decoding could not been fully utilized in optical domain. Therefore a new coding in OCDMA has been introduced based on spectral encoding (Kavehrad & Zaccarin, 1995; Pearce & Aazhang, 1994; Smith, Blaikie, & Taylor, 1998; Wei & Ghafouri-Shiraz, 2002). The system, called Optical Spectrum CDMA, or OS-CDMA, has the advantage of using inexpensive optical sources, and simple direct detection receivers. In this article with an emphasis on the Spectral Amplitude Coding scheme, a new code known as Khazani-Syed (KS) code is introduced.
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Conference papers on the topic "Direct-Sequence Code Division Multiple Access (DS-CDMA)"

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Vethanayagam, N., and R. I. MacDonald. "Demonstration of a Novel Optical Code Division Multiplex system at 800 MChips/s." In Photonic Switching. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/phs.1991.we5.

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Direct sequence Code Division Multiple Access (CDMA) provides a method of exploiting the wide bandwidth offered by optical fibres without the added complexity of wideband electronics. Each data bit is encoded with a code sequence (of N chips) which represents the destination address of each data bit. The correct selection of orthogonal codes allows the data bit destined for a given receiver to be extracted in the presence of noise (i.e., interference from other users in the system). Due to the uni-polar nature of light, coding schemes used in conventional CDMA cannot be applied directly to optical CDMA. Coding schemes have been proposed for optical CDMA [1] [2] but they have a number of limitations which include high bandwidth expansion factors and significant cross-talk levels. These problems can be overcome by employing complementary correlation detection which generates bi-polar electrical signals from received uni-polar optical ones [3]. Correctly selected codes (Alberta codes) are truly orthogonal for complementary correlation detection.
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Geslin, S. "The impact of imperfect power control on direct-sequence code division multiple access in optical transmission." In IEE Colloquium on CDMA Techniques and Applications for Third Generation Mobile Systems. IEE, 1997. http://dx.doi.org/10.1049/ic:19970715.

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Kwong, Wing C., Jian-Guo Zhang, and Guu-Chang Yang. "Optical code-division multiple-access coding architecture with 2n prime-sequence codes." In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cthi3.

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Recent study1 shows that the performance of an optical code-division multipleaccess (CDMA) network cannot be evaluated by only considering the correlation properties of the selected optical pseudo-orthogonal codes.2,3 The coding architecture (i.e., the structures of the optical encoders and decoders) is another important factor to consider, since it affects the power budget and feasibility of the system. As a result, "tunable prime" and "modified 2 n " coding architectures, respectively, for the prime-sequence and 2 n codes have been proposed to improve the power-efficiency.1,4 Recently, "2 n primesequence" codes, a collection of symmetric binary sequences with weight 2 n , have been introduced and pose the pseudo-orthogonal and algebraic properties of the original prime-sequence codes.5 To effectively utilize these codes, a novel coding architecture, which consists of a "modified" tunable prime encoder and a 2 n decoder, is proposed to substantially reduce the power loss, cost, and complexity of the systems using optical CDMA.
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Prucnal, Paul R., and Mario Santoro. "Local area network with optical spread spectrum processing." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.wj25.

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Asynchronous multiplexing schemes are most applicable when the traffic on the network is characterized by relatively long idle periods between the transmitted packets of data. An asynchronous system that provides random access makes the most efficient use of the channel. However, when the intensity of the traffic increases (i.e., the channel is being accessed by many users at the same time), collisions between packets become unavoidable and the throughput of the channel is greatly degraded. To alleviate this problem, spread spectrum multiplexing techniques, commonly known as code division multiple access (CDMA), can be applied. Application of CDMA requires a channel with a large bandwidth, such as an optical channel. Processing the received coded data requires a correlator. If high data rates are used, because of the bandwidth expansion of CDMA, a fast correlator must be implemented. Although for conventional systems this correlation requires sophisticated electronics, optical correlators could handle this fast processing with less complexity. Therefore, the CDMA scheme proposed here was implemented by optically correlating the incoming coded data. One set of codes that show promise for our application are prime sequences obtained from a Galois field GF(P) where P is a prime number and N = P**2. An experiment is described employing a P = 5 code sequence on a 100-Mbps fiber-optic link using 32 chips per bit. This optical CDMA system can potentially allow many more chips per bit, and therefore more users, than conventional systems.
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Nakamura, Moriya, and Ken-ichi Kitayama. "Error-free Transmission in Optical Space-CDMA for 2-D Parallel Data Links." In Optics in Computing. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/oc.1997.othd.9.

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Code division multiple access (CDMA) is an asynchronous, random access protocol. In conventional time-domain CDMAs, each data bit is encoded into a waveform which corresponds to a signature code sequence [1], [2]. We have proposed and experimentally demonstrated a space-CDMA for parallel transmission aiming at the applications to future high-throughput 2-D parallel data links connecting massively parallel processors of a number of data bits regularly aligned on two-dimensional (2-D) grids, so-called bit-planes [3], [4].
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Iversen, Kay, Jens Mueckenheim, and Dirk Junghanns. "Performance evaluation of optical code division multiple access (CDMA) using polarization shift keying direct dectection (PolSK-DD) to improve bipolar capacity." In Advanced Networks and Services, edited by Robert A. Cryan, P. Nalinaj Fernando, Pierpaolo Ghiggino, and John M. Senior. SPIE, 1995. http://dx.doi.org/10.1117/12.201277.

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