Journal articles: 'CDMA'

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Kawski, A., B. Kukliński, and P. Bojarski. "Influence Of The Irradiation Time On The Absorption And Emission Spectra Of P-Cyano-N,N-Dialkylanilines In Polar Solvents." Zeitschrift für Naturforschung A 58, no. 7-8 (August 1, 2003): 411–18. http://dx.doi.org/10.1515/zna-2003-7-805.

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The effect of the time of irradiation with the excitation wavelength λexc on the absorption and emission spectra of p-cyano-N,N-dimethylaniline (CDMA), p-cyano-N,N-diethylaniline (CDEA) and N,N- dimethylaniline (DMA) in acetonitrile and in n-hexane, as well as the effect of high temperature is studied. It is found that after sufficiently long irradiation of CDMA and CDEA in acetonitrile the short wavelength SE band intensity strongly increases compared to that of the long wavelength LE band. This phenomenon is caused by the photolysis of CDMA and CDEA in polar solvents. In each case both the irradiation time and the delivery of suitable thermal energy leads to irreversible processes. Investigations of the λexc effect on the location and intensity distribution of emission bands have shown their independence of λexc ranging from 260 nm to 330 nm in the LE band. However, a pronounced effect of λexc on the intensity appears in the SE band. In this spectral region DMA molecules formed due to the photolysis of CDMA absorb strongly. Excitation at λexc = 340 - 360 nm in the dimeric absorption band leads to a new emission band overlapping the LE band, which indicates the presence of luminescing dimers.

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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 (April 6, 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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YU, XIANGBIN, XIAODONG ZHANG, and GUANGGUO BI. "PERFORMANCE ANALYSIS OF MULTICARRIER CDMA SYSTEM BASED ON COMPLEX WAVELET PACKET AND SPACE–TIME BLOCK CODES IN RAYLEIGH FADING CHANNEL." Journal of Circuits, Systems and Computers 15, no. 01 (February 2006): 57–74. http://dx.doi.org/10.1142/s0218126606002939.

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On the basis of analyzing the principle of multicarrier CDMA (MC-CDMA) technique and space–time coding technique, using the optimized complex wavelet packet as multicarrier modulation, a novel MC-CDMA system based on complex wavelet packet and space–time block codes is proposed. The bit error rate (BER) performance of the system is investigated in Rayleigh fading channel, and the corresponding BER expression is derived in detail. The system can overcome the decrease of spectrum efficiency of conventional MC-CDMA due to inserting cyclic prefix (CP). Moreover, the application of space–time coding technique strengthens the capability against fading channel significantly and perfects the system performance. Theoretical analysis shows that the proposed system with 2-transmitter antenna and 2-receiver antenna space–time block codes performs four times better than the single-antenna MC-CDMA system based on complex wavelet packet (CWP-MC-CDMA); the same conclusion is also reached by the simulation results in fading channel. As a result, the performance of the proposed CWP-MC-CDMA system outperforms a conventional MC-CDMA system based on DFT, it is close or superior to that of the conventional MC-CDMA with CP. Especially, the CWP-MC-CDMA system with space–time coding has superior ability to combat spatial fading and multi-access interference, and it slightly outperforms conventional MC-CDMA with CP and space–time coding.

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Hawej, M. "INTERFERENCE MITIGATION BASED ON CARRIER INTERFEROMETRY CODES IN THE DOWNLINK LOW EARTH ORBIT SATELLITE CHANNEL." مجلة الجامعة الأسمرية: العلوم التطبيقية 6, no. 5 (December 31, 2021): 523–35. http://dx.doi.org/10.59743/aujas.v6i5.1509.

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The multi-carrier code division multiple access (MC-CDMA) system employs the Hadamard-Walsh (HW) code in the low earth orbit (LEO) satellite systems. It has been used as spreading code to maintain the multi-access interference (MAI) in the downlink LEO satellite channel. However, due to the non-orthogonality of the HW codes, these interferences are observed at the MC-CDMA satellite receiver. As a result, the LEO satellite system performance is degraded. In this paper, we propose to employ the orthogonal Carrier Interferometry (CI) code with MC-CDMA in the downlink LEO satellite channel. A new system is called CI/MC-CDMA which is used to mitigate the MAI. Moreover, the performance of the CI/MC-CDMA satellite system in terms of bit error rate (BER) is analyzed and simulated. To confirm the analysis, the system is compared to the HW/MC-CDMA system. It has been shown that CI/MC-CDMA satellite system outperforms HW/MC-CDMA

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Zheng, Liang, and Bin Yan. "The Performance Analysis of CDMA Traffic Access Self-Similar Equalization Protocol." Applied Mechanics and Materials 490-491 (January 2014): 1205–8. http://dx.doi.org/10.4028/www.scientific.net/amm.490-491.1205.

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The random access technique has a bigger influence to the performance optimization of CDMA data traffic. A CDMA random access technique based on self-similar model and its performance analysis are put forward in this paper. The simulation results indicate that the access performance of CDMA data traffic based on self-similar model is attenuated by power law, related to such parameters as fractal coefficient H and network load G. The CDMA traffic access self-similar equalization protocol (TASEP) is put forward and it can improve the access performance of CDMA data traffic distinctly.

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Harlen, Sekar, Eva Yovita Dwi Utami, and Andreas Ardian Febrianto. "Bit Error Rate pada Sistem MIMO MC-CDMA dengan Teknik Alamouti-STBC." Techné : Jurnal Ilmiah Elektroteknika 16, no. 02 (October 2, 2017): 99–109. http://dx.doi.org/10.31358/techne.v16i02.163.

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Pada makalah ini dilaporkan hasil penelitian sistem MIMO MC-CDMA dengan teknik Alamouti Space Time Block Code (STBC) menggunakan dua antena pengirim dan dua antena penerima. Kinerja sistem diukur dengan nilai Bit Error Rate (BER). Sistem yang diteliti disimulasikan dengan Matlab, dengan variasi jumlah pengguna, jumlah subpembawa, kecepatan pergerakan pengguna dan frekuensi Doppler. Hasil simulasi menunjukkan BER sistem MIMO MC-CDMA tidak mengalami penurunan yang tajam ketika jumlah pengguna dan frekuensi Doppler meningkat. Sedangkan simulasi dengan peningkatan jumlah subpembawa mampu menurunkan nilai BER sistem. Simulasi juga menunjukkan sistem MIMO-MC-CDMA memiliki kinerja sistem yang lebih baik dibandingkan sistem MC-CDMA yang ditunjukkan dengan nilai BER sistem MIMO MC-CDMA berada pada orde 10-4 dan sistem MC-CDMA pada orde 10-1.

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Ambrosio, Jefferson Santos, Francisco De Assis Scannavino Junior, and Taufik Abrão. "Seleção de sequências de espalhamento e Desempenho de Sistemas DS/CDMA." Semina: Ciências Exatas e Tecnológicas 37, no. 1 (March 16, 2016): 55. http://dx.doi.org/10.5433/1679-0375.2016v37n1p55.

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Neste trabalho são discutidos conceitos fundamentais relativo à comunicação de múltiplo acesso por divisão de código (CDMA). Especificamente, analisa-se o impacto da seleção de sequências de espalhamento sobre o desempenho e capacidade, em termos de número máximo de usuários suportados, em sistemas CDMA por sequência direta (DS/CDMA), considerando ambientes com ruído branco Gaussiano, carregamento de sistema variável e múltiplas antenas (MISO-CDMA).

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Panday, Sarika, and Saurabh Sardey. "GSM and CDMA Based Communication System." Journal of Communication Engineering and its Innovations 8, no. 2 (August 30, 2022): 21–25. http://dx.doi.org/10.46610/jocei.2022.v08i02.004.

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Cellular mobile services have been around for a while and are continuously developing today. Numerous communication services, including CDMA and GSM, developed alongside these services. The two most significant technical standards for mobile communication are CDMA and GSM. The GSM and CDMA both transform mobile phone data into radio waves. However, these technologies differ in terms of how calls and data transfer occur through a network. One of the primary distinctions between CDMA and GSM is that CDMA doesn't require a SIM card and instead relies on ESNs to link a mobile phone to its network (Electronic Serial Number).

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Mestoui, Jamal, Mohammed El Ghzaoui, Serghini Elaage, Abdelmounim Hmamou, and Jaouad Foshi. "CE-OFDM-CDMA Phase Modulation for 5G System." International Journal of Mathematical, Engineering and Management Sciences 6, no. 4 (July 18, 2021): 1100–1114. http://dx.doi.org/10.33889/ijmems.2021.6.4.065.

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In the present work, we propose a novel modulation scheme for 5G wireless communication system. Our contribution is to combine PM-OFDM (Phase Modulation Orthogonal Frequency Division Multiplexing) and CDMA (Code Division Multiple Access) to exploit their distinctive advantages. On the one hand, PM-OFDM is an effective technique to combat multipath fading effects. On the other hand, CDMA can serve multiple users who are using the same resources of time/frequency. The aim is to make a combination of PM-OFDM and CDMA techniques. In this paper, the OFDM-CDMA scheme and its PAPR (Peak-to-Average Power Ratio) statistics are reviewed. In this paper, the proposed scheme PM-OFDM-CDMA is described and its performances in terms of PAPR, power spectral density, and BER (Bit Error Rate) are analyzed. Moreover, MMSE (Minimum Mean Square Error) equalizer is used to avoid multipath and noise effects simultaneously. The simulation through AWGN (Additive white Gaussian noise) and Rayleigh channels is performed using MATLAB. From the simulation results, we observed that PM-OFDM-CDMA is an efficient technique in terms of energy consumption (PAPR = 0dB). Besides, CE-OFDM-CDMA offers high spectral efficiency with low BER due to its low PAPR. In CE-OFDM-CDMA method, the shape of the spectrum varies according to the value of the modulation index h. The band occupied by the spectrum increases with the value of h. Therefore, CE-OFDM-CDMA could be considered as a suitable technique for 5G applications.

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Kusumawardhani, Eka, Rina Pudji Astuti, Nachwan Mufti Adriansyah, Fitri Imansyah, and Leonardus Sandy Ade Putra. "Performance Analysis of Multiple Input Multiple Output (MIMO) Multi-Carrier Code-Division Multiple Access (MC-CDMA) Combined with Quasi-Orthogonal Space Time Block Coding (QO-STBC) in Rayleigh Fading Channel." POSITRON 12, no. 2 (November 30, 2022): 120. http://dx.doi.org/10.26418/positron.v12i2.46613.

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The need for a communication system with a higher data rate and mobility grows along with information and communication technology development. Combining MC-CDMA with the MIMO system and supporting the system with a good transmit diversity technique is a promising idea to provide the needed communication system, especially in high mobility conditions. MC-CDMA can support ubiquitous communications without affecting the achievable BER and is more capable of high-speed mobility. It integrates the benefit of both OFDM and CDMA. On the other hand, QO-STBC increases the bit rate without using additional bandwidth to transmit diversity in the MIMO system. So, this study proposed a system combining the MIMO MC-CDMA system with QO-STBC. The proposed system is investigated under high mobility conditions to see the system's performance. The simulation results show that our system performs better than the MC-CDMA STBC system and the QOSTBC system but not better than the MC-CDMA multilevel coding scheme. To reach the value of BER 10−3, MC-CDMA multilevel Coding requires less power, around 5 dB, than the proposed system.

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Du, Chuan Bao, Hou De Quan, and Pei Zhang Cui. "Performance Comparison of Carrier Sense Random Packet CDMA and Partitioned Slot Reservation Packet CDMA." Applied Mechanics and Materials 687-691 (November 2014): 2684–88. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.2684.

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The Dual-Channel Network proposed in our previous work can improve the code resource utilization efficiency. Carrier Sense Random Packet (CSRP) CDMA and Partitioned Slot Reservation Packet (PSRP) CDMA were proposed for enhancing the control channel interference resistance of Dual-Channel Networks. In this paper, we investigate CSRP-CDMA and PSRP-CDMA, and derive the performance analytic models by taking into account both intra-cluster MAI and inter-cluster MAI. The models provide the expressions of packet transmission probability and normalized network throughput. Furthermore, the probability of packet successful transmission and the throughput performance are compared between the two protocols. Finally, we analyse the influence on the network performance with spread spectrum gains and network scale. The numerical results show that, normalized network throughput of PSRP-CDMA outperforms CSRP-CDMA by 20% to improving the code resource utilization efficiency of control channel of Dual-Channel Networks.

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Sabhapathy, Umar, and Lenin Anselm Wilson. "Implementation of Underground Water for Wireless Optical Communication System using CDMA." International Innovative Research Journal of Engineering and Technology 6, no. 4 (June 30, 2021): 10–20. http://dx.doi.org/10.32595/iirjet.org/v6i4.2021.147.

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Optical wireless communications is a powerful and cost-effective approach for high-speed wireless links that have been tightly guarded For underwater optical wireless communication, the following three optical code division multiple access (CDMA) techniques have been used. systems are associated, investigated, and presented in this paper, such as AC-biased optical CDMA (ACO-CDMA), symmetrically-SCO-OFDM (clipped optical OFDM), and unipolar CDMA (U-CDMA). Peak power constraints, light source bandwidth tag, there are so many factors to recognize, such turbulence, fading underwater signals, and channel estimation error. Advocate for a bit loading algorithm and a simplified modulation index that determines signal magnitude is being used to minimize the achievable data propagation distance. In this optimization procedure, the signal-to-noise ratio and the clipping distortion triggered by the peak power limitation are balanced (SNR). The SNR and clipping effects of the three compared CDMA techniques are represented in this paper. When the transmitted bit index is greater than the channel bandwidth, ACO-OFDM outperforms SCO- and UCDMA, according to the determined model. U-CDMA, on the other end, has a longer propagation distance but needs less transmitted power.

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Choi, U.-Sung, and Sung-Hyun Yang. "Design and Fabrication of Dielectric Duplexers and Bandpass Filters for CDMA and W-CDMA Dualband Using the Notch and Isolation." Journal of the Korean Institute of Information and Communication Engineering 15, no. 6 (June 30, 2011): 1227–32. http://dx.doi.org/10.6109/jkiice.2011.15.6.1227.

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Ali T. Shaheen. "Design and Simulation of parallel CDMA System Based on 3D-Hadamard Transform." Diyala Journal of Engineering Sciences 6, no. 4 (December 1, 2013): 45–69. http://dx.doi.org/10.24237/djes.2013.06404.

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Future wireless systems aim to provide higher transmission data rates, improved spectral efficiency and greater capacity. In this paper a spectral efficient two dimensional (2-D) parallel code division multiple access (CDMA) system is proposed for generating and transmitting (2-D CDMA) symbols through 2-D Inter-Symbol Interference (ISI) channel to increase the transmission speed. The 3D-Hadamard matrix is used to generate the 2-D spreading codes required to spread the two-dimensional data for each user row wise and column wise. The quadrature amplitude modulation (QAM) is used as a data mapping technique due to the increased spectral efficiency offered. The new structure simulated using MATLAB and a comparison of performance for serial one-dimensional (1-D) CDMA and parallel (2-D) CDMA is made under Additive White Gaussian Noise (AWGN), flat fading and multi-path selective fading channels conditions. It is found that 2-D CDMA has better speed and performance than serial 1-D CDMA.

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OH, TICK HUI, and KIM GEOK TAN. "IMAGE TRANSMISSION THROUGH MC-CDMA CHANNEL: AN IMAGE QUALITY EVALUATION." International Journal of Wavelets, Multiresolution and Information Processing 06, no. 06 (November 2008): 827–50. http://dx.doi.org/10.1142/s0219691308002707.

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The multicarrier code division multiple access (MC-CDMA) system is considered as an advancement in mobile communication system. Seen as the next generation communication technology after the 3G, signals can be easily transmitted and received using the Fast Fourier Transform (FFT) device without increasing the transmitter and receiver complexities. Besides, the MC-CDMA system provides good spectral efficiency. If the number of sub-carriers and the spacing between sub-carriers are chosen properly, it is unlikely that all the sub-carriers will be in deep fade. Thus, it provides frequency diversity. Frequency diversity means that frequencies separated by more than the coherence bandwidth of the channel will be uncorrelated and thus will not experience the same fades. Three types of MC-CDMA systems were proposed — MC-CDMA, multicarrier DS-CDMA and multitone CDMA. In MC-CDMA systems, the transmitter spreads the user data over different sub-carriers using spreading code (Hadamard Walsh code) in frequency domain. The multicarrier DS-CDMA system spreads the S/P converted data streams using spreading code in time domain. This scheme is proposed for uplink communication because this scheme can provide quasi-synchronization. In the MT-CDMA scheme, the S/P converted data stream is spread in time domain so that the spectrum of each sub-carrier prior to spreading operation can satisfy the orthogonality condition with minimum frequency separation. Thus, the spectrum of each sub-carrier no longer satisfies the orthogonality condition. MC-CDMA uses longer spreading code as compared to other schemes and thus accommodates more users. The JPEG2000 still image compression is a new image compression technique which is optimized not only for efficiency, but also for scalability and interoperability in network and mobile environment. This standard can provide superior low bit rate performance and continuous-tone and bi-level compression. Because of the robustness to bit errors, JPEG2000 is widely used in wireless communication channel.

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Arnomo, Ilham. "Authentication Comparison of Telecommunications Technology Using A3, A8, A5 and Rijndael Algorithms." Jurnal INFORM 3, no. 2 (October 3, 2018): 74. http://dx.doi.org/10.25139/inform.v3i2.1031.

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The purpose of the research is to analyze the comparison of technology, network and security aspect between CDMA and GSM (Global System for Car communication). Using a comparative analysis research method between CDMA and GSM technologies that includes comparisons of network, technology, and security aspects. Using references from previous research on cellular telecommunications, the introduction of CDMA and GSM technologies to aspects of technology, networking and security. The results show that the technological aspect, CDMA used advanced spectrum technology that can provide superior sound quality and GSM uses a spectrum division technology that makes communication constant. From the network aspect, CDMA used direct-spreading spectrum (DS-CDMA) and GSM network is divided into three main systems: switching system (SS), base station system (BSS), and operating system and support (OSS). As well as security aspects, the GSM uses A3 and A8 algorithms for authentication and A5 algorithms were used in the process of sending information.But the security system using this algorithm, found weaknesses that allow data tapping or customer identity fraud. While CDMA offers aspects of network security by developing encryption algorithms.For encryption techniques used Rijndael algorithm is safe and very fast. A3 and A8 algorithms can recognize the customer's identity well, and the A5 algorithm can transmit the accuracy of information between MS and BTS.

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Suresh Babu, Sumith Babu, and R. Kumar. "Multigroup Synchronization in 1D-Bernoulli Chaotic Collaborative CDMA." Wireless Communications and Mobile Computing 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/7561757.

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Code-division multiple access (CDMA) has played a remarkable role in the field of wireless communication systems, and its capacity and security requirements are still being addressed. Collaborative multiuser transmission and detection are a contemporary technique used in CDMA systems. The performance of these systems is governed by the proper accommodation of the users and by proper synchronization schemes. The major research concerns in the existing multiuser overloaded CDMA schemes are (i) statistically uncorrelated PN sequences that cause multiple-access interference (MAI) and (ii) the security of the user’s data. In this paper, a novel grouped CDMA scheme, the 1D-Bernoulli chaotic collaborative CDMA (BCC-CDMA), is introduced, in which mutually orthogonal chaotic sequences spread the users’ data within a group. The synchronization of multiple groups in this scheme has been analyzed under MAI limited environments and the results are presented. This increases the user capacity and also provides sufficient security as a result of the correlation properties possessed by the chaotic codes. Multigroup synchronization is achieved using a 1D chaotic pilot sequence generated by the Bernoulli Map. The mathematical model of the proposed system is described and compared with the theoretical model of the synchronization in CDMA, the simulation results of which are presented.

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Hasan, Syed Rizwan-ul, and Shakil Ahmed. "2 Performance Evaluation of Code Division Multiple Access (CDMA) in terms of Power Measurement and Reduction." Sir Syed Research Journal of Engineering & Technology 1, no. 1 (December 20, 2011): 4. http://dx.doi.org/10.33317/ssurj.v1i1.73.

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In this research paper the performance of the CDMA system has been analyzed with respect to PAPR (Peak to Average Power Ratio) measurement and its reduction. Simulation results verify that high peaks degrade the performance of CDMA, application of codes reduced high peaks and PAPR is a good measure for CDMA.

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Hasan, Syed Rizwan-ul, and Shakil Ahmed. "Performance Evaluation of Code Division Multiple Access (CDMA) in terms of Power Measurement and Reduction." Sir Syed University Research Journal of Engineering & Technology 1, no. 1 (December 20, 2011): 4. http://dx.doi.org/10.33317/ssurj.73.

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In this research paper the performance of the CDMA system has been analyzed with respect to PAPR (Peak to Average Power Ratio) measurement and its reduction. Simulation results verify that high peaks degrade the performance of CDMA, application of codes reduced high peaks and PAPR is a good measure for CDMA.

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Sreesudha, P., and G. Rajender. "Performance Enhacement of MIMO-CDMA system using Adaptive Non-Coherent Receiver." International Journal for Research in Applied Science and Engineering Technology 11, no. 9 (September 30, 2023): 649–53. http://dx.doi.org/10.22214/ijraset.2023.55688.

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Abstract: Wireless communication systems are a key means to meet the increasing demands for greater capacity and increased quality-of-service. MIMO systems have the potential to reduce the operational power consumption and enable the use of low complexity schemes for suppressing MU interference (MUI). One of the cellular communication technologies is CDMA. The combine of MIMO and CDMA is most able technique beyond 4G technologies. The DS-CDMA system is widely known for removing the effects of Multiple Access Interference (MAI) which degrades the performance of the system. The addition of interference cancellation which is a sub-optimal procedure of multiuser detector (MUD) in a DS-CDMA-MIMO system can greatly enhance its performance relative to that of conventional CDMA receiver and this can be verified with the help of MATLAB

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Wu, You, Shuang Wang, and You Sai Zhang. "Performance of an Improved MC-CDMA System Based on DT-OCWDM and Quasi-Orthogonal Matrix." Applied Mechanics and Materials 321-324 (June 2013): 2897–901. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.2897.

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In this paper, we propose a new improved MC-CDMA system which combines spreading codes from Quasi-Orthogonal Matrix with Orthogonal Complex Wavelet Division Multiplexing (OCWDM). The system is implemented by complex wavelet filters which are able to lower computational complexity and increase flexibility. Novel spreading codes from Quasi-Orthogonal Matrix can be expanded randomly. It can increase user number hugely in system. Improved MC-CDMA named OCWDM-CDMA has much higher frequency spectrum efficiency and high data rate than conventional MC-CDMA. The system also has better BER performance in Gaussian channel than conventional system for much more users.

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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 (August 31, 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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Yang, Lei, Jian Cheng, Xin Xing Ge, Ning Rui Liang, and Wang Chun Lei. "Multi-User Detection Based on Quasi-Synchronous CDMA Systems." Applied Mechanics and Materials 668-669 (October 2014): 1347–50. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.1347.

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Multi-user detection is one of the key technologies of CDMA systems. Its basic idea is that, all user signals are considered as useful signals. Then, we can use them to eliminate multiple access interference (MAI). This paper presents an improvement of multi-user detection based on QS-CDMA systems. By the improving, computational complexity is lower, and performances approach synchronous CDMA systems.

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Zang, Shaofei, Xinghai Li, Jianwei Ma, Yongyi Yan, Jinfeng Lv, and Yuan Wei. "Discriminative Extreme Learning Machine with Cross-Domain Mean Approximation for Unsupervised Domain Adaptation." Complexity 2022 (October 3, 2022): 1–22. http://dx.doi.org/10.1155/2022/2463746.

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Extreme Learning Machine (ELM) is widely used in various fields because of its fast training and high accuracy. However, it does not primarily work well for Domain Adaptation (DA) in which there are many annotated data from auxiliary domain and few even no annotated data in target domain. In this paper, we propose a new variant of ELM called Discriminative Extreme Learning Machine with Cross-Domain Mean Approximation (DELM-CDMA) for unsupervised domain adaptation. It introduces Cross-Domain Mean Approximation (CDMA) into the hidden layer of ELM to reduce distribution discrepancy between domains for domain bias elimination, which is conducive to train a high accuracy ELM on annotated data from auxiliary domains for target tasks. Linear Discriminative Analysis (LDA) is also adopted to improve the discrimination of learned model and obtain higher accuracy. Moreover, we further provide a Discriminative Kernel Extreme Learning Machine with Cross-Domain Mean Approximation (DKELM-CDMA) as the kernelization extension of DELM-CDMA. Some experiments are performed to investigate the proposed approach, and the result shows that DELM-CDMA and DKELM-CDMA could effectively extend ELM suitable for domain adaptation and outperform ELM and many other domain adaptation approaches.

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Shi, Yun Qiu, Chuan Sheng Wu, Shi Cheng Zhao, and Fang Hui Liu. "The Research of CDMA SMS Send-Receive Based on Embedded S3C2410A." Applied Mechanics and Materials 602-605 (August 2014): 2565–68. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.2565.

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With the popularity and mature of CDMA technology, in addition to inherit the CDMA covering a wide range, small influence by the environment, security, real-time characteristics, SMS has the advantages of low cost、convenience which make the utilization rate more and more high. SMS has great potential application in the field of industrial automation. Experimental study on the S3C2410A embedded control system to send and receive message in English or Chinese by Siemens company TC35i module in CDMA, using the embedded technology and CDMA low cost and mobility , unattended advantage , show broad prospects in the field of environment of mobile operation and distributed remote data acquisition, monitoring system.

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Saragih, Hoga, and Djoko Soetarno. "Slotted ALOHA CDMA By Dual Model Path Gains." CCIT Journal 3, no. 1 (September 7, 2009): 55–67. http://dx.doi.org/10.33050/ccit.v3i1.301.

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Throughput Slotted ALOHA CDMA by dual model path gain Nakagami/Nakagami fading channel by capture effect is analyzed. The approach of fading effect to BER is calculated by path gain. Path gain for desired signal and interference signal is unequal. Therefore, at this research BER used on S-ALOHA CDMA is BER with two different model path gains at Nakagami/Nakagami fading channel with capture effect. Result of calculation indicates that throughput of slotted ALOHA CDMA are getting better with increase level of parameter fading signal and long code. Others throughput slotted ALOHA CDMA also better progressively with the decrease of capture ratio and simultaneous user.

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Jabbari, B. "Wideband CDMA." IEEE Communications Magazine 36, no. 9 (September 1998): 46. http://dx.doi.org/10.1109/mcom.1998.714614.

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Salehi, J. A., and Eung Gi Paek. "Holographic CDMA." IEEE Transactions on Communications 43, no. 9 (1995): 2434–38. http://dx.doi.org/10.1109/26.412717.

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RIM, M. "Gated-CDMA: Frequency-Domain Equalization for CDMA Systems." IEICE Transactions on Communications E88-B, no. 2 (February 1, 2005): 811–14. http://dx.doi.org/10.1093/ietcom/e88-b.2.811.

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Prasad, Ramjee, and Tero Ojanpera. "An overview of CDMA evolution toward wideband CDMA." IEEE Communications Surveys & Tutorials 1, no. 1 (1998): 2–29. http://dx.doi.org/10.1109/comst.1998.5340404.

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Petrosky, Eric E., Alan J. Michaels, and Joseph M. Ernst. "A Low Power IoT Medium Access Control for Receiver-Assigned CDMA." International Journal of Interdisciplinary Telecommunications and Networking 11, no. 2 (April 2019): 24–41. http://dx.doi.org/10.4018/ijitn.2019040103.

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Low power, low cost, and security-conscious wireless sensor networks are becoming increasingly pervasive in the internet of things (IoT). In these networks, receiver-assigned code division multiple access (RA-CDMA) offers benefits over existing multiple access techniques. RA-CDMA networks are asynchronous, robust against multipath interference, and offer resilience against collision. A lightweight medium access control (MAC) protocol is needed to facilitate communication in RA-CDMA networks between low power sensor nodes and access points. This article provides an overview of RA-CDMA and proposes elements of a new MAC protocol that could improve performance of certain wireless sensor networks. Key features of the proposed MAC design are introduced and compared to those of existing protocols, highlighting its simple and lightweight design. Through its compatibility with RA-CDMA, the MAC design eliminates significant overhead and complexity while meeting requirements for low power networks, which enables the implementation of dense IoT sensor networks.

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Ravikumar, C. V., Kalapraveen Bagadi, K. Rushendrababu, Asadi Srinivasulu, and Satish Kumar. "Optimizing Nonlinear Distortion and Interference in MC-CDMA Receivers Employing Deep Neural Networks." Mobile Information Systems 2023 (August 21, 2023): 1–13. http://dx.doi.org/10.1155/2023/6430987.

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Systems that employ multicarrier code division multiple access, commonly known as MC-CDMA, produce outstanding results in terms of both the performance of the system as a whole and the efficiency with which it uses the spectrum. However, multiple access strategies are susceptible to interference despite their high spectrum efficiency. This work aims to reduce multiple access interference (MAI) by developing an MC-CDMA receiver. When MC-CDMA deteriorates nonlinearly, standard receivers, namely, zero forcing (ZF), maximal ratio combining (MRC), minimum mean square error (MMSE), and equal gain combining (EGC), are unable to cancel MAI. Neural network (NN) receivers are a better option due to their nonlinear nature. Based on the simulation results, the suggested deep neural network- (DNN-)based schemes outperform the current baselines in terms of error handling and usability. This research explores the viability and effectiveness of a DNN-based receiver designed for MC-CDMA with nonlinearity degradations. The focus of this research is on MC-CDMA.

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Wang, Yong, Xin Ge, Yu Bin Xu, and Lin Ma. "A Novel Degradation Scheme Based on User Satisfaction in CDMA Systems." Applied Mechanics and Materials 198-199 (September 2012): 1678–83. http://dx.doi.org/10.4028/www.scientific.net/amm.198-199.1678.

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Within the past few years, a great deal of attention has been drawn towards the CDMA system. The state of a CDMA system has two cases: saturation and instauration. After the system is saturated, no more users are allowed to access to CDMA systems with traditional method. In order to enhance the maximum number of users and the all users’ satisfaction while guaranteeing users’ quality of service (QoS) –SINR (signal-to-interference–plus-noise) requirement, this paper presents a degradation scheme based on user satisfaction in CDMA systems. Simulation results show that the proposed scheme can be allowed more users to access to and increase the total users’ satisfaction, leading to higher system capacity and resource utilization.

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Meylani, Linda, Nur Andini, and Iswahyudi Hidayat. "Performance of Coded Modulation in Multicarrier CDMA System." Indonesian Journal of Electrical Engineering and Computer Science 1, no. 3 (March 1, 2016): 583. http://dx.doi.org/10.11591/ijeecs.v1.i3.pp583-589.

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Coded modulation scheme introduce robust and reliable system. It combine coding and modulation in one system. This paper show performance of coded modulation with coding rate 2/3, using 8PSK and convolutional coding that implemented in MC CDMA system. MC CDMA is one of multicarrier system that combine OFDM and CDMA so its offer reliable system in frequency selective fading. Decoding process for coded modulation is done by using log likelihood ratio for least significant bit (define the subset) and the entire bits (member of subset). Simulation result shown that coded modulation in MC CDMA system have a good performance in flat fading and frequency selective fading.

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Xiao, Zhe Yun. "Interworking of LTE with CDMA EVDO." Applied Mechanics and Materials 462-463 (November 2013): 712–15. http://dx.doi.org/10.4028/www.scientific.net/amm.462-463.712.

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G, Narayana Gowda. "Chaotic Code Division Multiple Access." INTERANTIONAL JOURNAL OF SCIENTIFIC RESEARCH IN ENGINEERING AND MANAGEMENT 08, no. 04 (April 2, 2024): 1–5. http://dx.doi.org/10.55041/ijsrem29967.

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Chaotic signals are gaining importance in the field of communication these days. The chaotic Pseudo Noise sequences give a uniform spread over the entire frequency bandwidth. The sequences produce good performance as Pseudo random patterns when used in Code Division Multiple Access (CDMA) systems. This paper introduces to the field of chaotic signals and demonstrates how it is used in CDMA systems Key Words: Chaotic signals, DS CDMA, Nonlinear systems, PN sequences.

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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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Bendelhoum, Mohammed Soﬁane, Ali Djebbari, Ismail Boukli-Hacene, and Abdelmalik Taleb-Ahmed. "An Improved Downlink MC-CDMA System for Eﬃcient Image Transmission." Journal of Telecommunications and Information Technology 4 (December 20, 2017): 5–16. http://dx.doi.org/10.26636/jtit.2017.110917.

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Image compression is an essential stage of the data archiving and transmitting process, as it reduces the number of bits and the time required to complete the transmission. In this article, a study of image transmission over the Multi-Carrier Code Division Multiple Access (MC-CDMA) downlink system is presented. The solution proposed relies on source coding combined with channel coding. The Discrete Wavelet Transform (DWT) method is used in conjunction with the SPIHT coder to compress the image, then the data generated is transmitted with the MC-CDMA technique over a noisy channel. The results show that image transmissions performed over MC-CDMA using the SPIHT model are better than the traditional approach like MC-CDMA in the AWGN channel.

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Alsowaidi, Naif, Tawfig Eltaif, and Mohd Ridzuan Mokhtar. "Hybrid optical CDMA and DWDM system implemented under the influence of Non-linear effects." Indonesian Journal of Electrical Engineering and Computer Science 15, no. 3 (September 1, 2019): 1485. http://dx.doi.org/10.11591/ijeecs.v15.i3.pp1485-1490.

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A hybrid optical CDMA-DWDM system accommodating 12 optical CDMA users carried by 5 DWDM wavelengths at a data rate of 60Gb/s/wavelength with channel spacing of 0.4nm is implemented under the effect of four-wave mixing (FWM). It was found that the FWM effect could be minimized by the use of CDMA technology, where the energy of each bit is spread over the optical sequence code. Over a distance of 105.075km, significant performance of all optical CDMA users in terms of the BER is achieved. The results reveal that the inter-symbol interference (ISI) can be mitigated when the interval of optical signature sequence code is squeezed into 25% of the bit duration.

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Geetanjli. "Study of Power Control in CDMA System on the basis of optimization Technique." International Journal of Advanced Research in Computer Science and Software Engineering 7, no. 8 (August 30, 2017): 126. http://dx.doi.org/10.23956/ijarcsse.v7i8.38.

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The power control in CDMA systems, grant numerous users to share resources of the system uniformly between each other, leading to expand capacity. With convenient power control, capacity of CDMA system is immense in contrast of frequency division multiple access (FDMA) and time division multiple access (TDMA). If power control is not achieved numerous problems such as the near-far effect will start to monopolize and consequently will reduce the capacity of the CDMA system. However, when the power control in CDMA systems is implemented, it allows numerous users to share resources of the system uniformly between themselves, leading to increased capacity For power control in CDMA system optimization algorithms i.e. genetic algorithm & particle swarm algorithm can be used which regulate a convenient power vector. These power vector or power levels are dogged at the base station and announce to mobile units to alter their transmitting power in accordance to these levels. The performances of the algorithms are inspected through both analysis and computer simulations, and compared with well-known algorithms from the literature.

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POURZAKI, ABBAS, KHALIL MAFINEJAD, and SAYYED HOSAIN KESHMIRI. "A NEW METHOD FOR CDMA SIGNAL MODELING IN NONLINEAR SYSTEMS." Journal of Circuits, Systems and Computers 15, no. 06 (December 2006): 833–48. http://dx.doi.org/10.1142/s0218126606003374.

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When a CDMA signal is passed through an RF transmitter, nonlinear elements cause spectral regrowth which result in reduction of spectral efficiency. CDMA signal has a pseudo noise nature; hence its mathematical treatment is too complex to analysis. In this paper, first it will be shown how to simplify the complex mathematics of CDMA signal. Then, a deterministic signal replaces the CDMA signal and the system response to both of them is calculated. In this paper, for the first time, ACPR is explicitly calculated for both the CDMA and deterministic signals. ACPR is calculated in terms of the nonlinear system coefficients and input power, and therefore, can be used in design objectives. In addition, it will be shown that if input power of the deterministic signal is multiplied by [Formula: see text] (i.e., correction factor), ACPR error of these kinds of signals in -55 dBc is less than 2.2% for the system nonlinearity orders up to 13. This correction factor is obtained by both theoretical and simulation methods.

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Farhan, Ikhlas Mahmoud, Dhafer R. Zaghar, and Hadeel Nasrat Abdullah. "Enhancement of code division multiple access system performance using raptor codes." Indonesian Journal of Electrical Engineering and Computer Science 26, no. 3 (June 1, 2022): 1460. http://dx.doi.org/10.11591/ijeecs.v26.i3.pp1460-1468.

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Some kinds of communication systems work in very low signal-to-noise (LSNR) environments. For these systems to function reliably, specific techniques and methodologies have to be used to mitigate the degrading effects of the channel. The channel coding method is the key element in most LSNR communication systems, but emphasizing the code division multiple access (CDMA) is a new transmission technique in these channels. To enhance the CDMA scheme's system capacity and reach unprecedented ranges of LSNR values in wireless sensor network. This paper suggests combining CDMA with certain types of channel coding algorithms, such as the raptor codes. The raptor channel encoding technique has improved the CDMA system's performance when using binary phase-shift keying (BPSK) modulation in additive white gaussian noise (AWGN) channels. It has achieved a low bit error rate in range of 10-7 at Eb/No value of (-3) dB and about 10-6 at shannon's limit. The Raptor-coded CDMA scheme works well for channel signal to noise ration (SNR) values of greater than -9 dB, showing an improvement of about 7 dB compared with turbo/convolutional channel coding methods used with the CDMA system bit error rate (BER) and throughput. On the other hand, it has been shown that the convolutional encoder presents the weakest performance compared to both the turbo and raptor codes.

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Xie, Jiahao, Chao Zhang, Zebang Shen, Weijie Liu, and Hui Qian. "CDMA: A Practical Cross-Device Federated Learning Algorithm for General Minimax Problems." Proceedings of the AAAI Conference on Artificial Intelligence 37, no. 9 (June 26, 2023): 10481–89. http://dx.doi.org/10.1609/aaai.v37i9.26246.

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Minimax problems arise in a wide range of important applications including robust adversarial learning and Generative Adversarial Network (GAN) training. Recently, algorithms for minimax problems in the Federated Learning (FL) paradigm have received considerable interest. Existing federated algorithms for general minimax problems require the full aggregation (i.e., aggregation of local model information from all clients) in each training round. Thus, they are inapplicable to an important setting of FL known as the cross-device setting, which involves numerous unreliable mobile/IoT devices. In this paper, we develop the first practical algorithm named CDMA for general minimax problems in the cross-device FL setting. CDMA is based on a Start-Immediately-With-Enough-Responses mechanism, in which the server first signals a subset of clients to perform local computation and then starts to aggregate the local results reported by clients once it receives responses from enough clients in each round. With this mechanism, CDMA is resilient to the low client availability. In addition, CDMA is incorporated with a lightweight global correction in the local update steps of clients, which mitigates the impact of slow network connections. We establish theoretical guarantees of CDMA under different choices of hyperparameters and conduct experiments on AUC maximization, robust adversarial network training, and GAN training tasks. Theoretical and experimental results demonstrate the efficiency of CDMA.

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Kawski, A., G. Piszczek, and B. Kukliński. "Can Twisted Internal Charge-Transfer(TICT)State be Formed in Rigid Polymers?" Zeitschrift für Naturforschung A 50, no. 10 (October 1, 1995): 949–52. http://dx.doi.org/10.1515/zna-1995-1007.

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Abstract Absorption, emission and emission anisotropy spectra of 4-cyano-N,N-dimethylaniline (CDMA) and 4-cyano-2,6,N,N-tetramethylaniline (CTMA) were investigated in polyvinyl alcohol) (PVA) films. It was found that the CDMA and CTMA molecules in PVA films at room temperature display phosphorescence, the emission band of which overlaps with the longwave fluorescence band a. The low value of the emission anisotropy shows that in the rigid PVA matrix there are microscopic defects in the form of empty spaces in which a certain fraction of the CDMA or CTMA molecules can attain twisted intramolecular charge-transfer states (TICT) due to rotational relaxation. The emission anisotropies in the shortwave, b, and longwave, a, fluorescence bands of CDMA in propylene glycol were found to be distinctly different, this indicating that the directions of the transition moments are not parallel.

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Kawski, A., P. Bojarski, and B. Kukliński. "Emission Anisotropy of p-Cyano-N,N-Dialkylanilines in Poly(vinyl alcohol) Film." Zeitschrift für Naturforschung A 58, no. 4 (April 1, 2003): 194–96. http://dx.doi.org/10.1515/zna-2003-0402.

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The emission anisotropy spectra, r, (λ ) of p-cyano-dimethylaniline (CDMA) and p-cyano-diethylaniline (CDEA) in PVA films are temperature dependent. At 296 K a characteristic dependence of r, (λ ) on the absorption (A), short emission (SE) and long emission (LE) band, responsible for the total emission of fluorescence and phosphorescence is observed. On temperature enhancement to 355 K and next to 380 K the phosphorescence is eliminated. In the case studied the emission anisotropy is positive for the fluorescence bands SE and LE and it attains approximately 0.2, confirming thus that the transition moments’ directions are in these bands parallel.

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GAVRISHEV, A. A., and D. L. OSIPOV. "ON THE APPLICATION OF CDMA TECHNOLOGY TO HIDDEN CONTROL OF A GROUP OF ROBOTIC COMPLEXES VIA A COMMON RADIO CHANNEL." Fundamental and Applied Problems of Engineering and Technology 6 (2020): 62–69. http://dx.doi.org/10.33979/2073-7408-2020-344-6-62-69.

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The paper assesses the possibility of using CDMA technology in the interests of centralized hidden control of a group of robotic complexes. For this purpose, the CDMA technology was simulated in the ScicosLab software package and the data obtained was studied using BDS statistics. As a result of research, it was found that when using PN generators with a long register length, sufficient signal stealth is not provided. And the use of PN generators with a shorter register length is impractical because of their predictability, which allows interception, substitution or jamming of the signal. When using CDMA technology for centralized control of a group of robotic complexes via a radio channel using a control server, alternative solutions should be sought instead of PN generators. In the authors' opinion, chaotic signals can become a promising approach that provides hidden control in the conditions of using CDMA technology.

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Tri Dharma Prawira, I. Gd, I. G. A. K. Diafari Djuni Hartawan, and N. Pramaita. "ANALISIS KINERJA KOMBINASI SISTEM CODE DIVISION MULTIPLE ACCESS MULTIPLE INPUT MULTIPLE OUTPUT DENGAN KODE PENEBAR WALSH PADA KANAL RAYLEIGH FADING." Jurnal SPEKTRUM 5, no. 2 (December 19, 2018): 285. http://dx.doi.org/10.24843/spektrum.2018.v05.i02.p36.

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The increasing human population are same to the need for telecommunications. Code Division Multiple Access (CDMA) is one of the most widely used telecommunications technologies. But with the increasing number of users, this technology is no longer able to meet the needs of users. With the required capacity requirements, the CDMA system and Multiple Input Multiple Output (MIMO) technology are merged.To find out the performance of a combined CDMA MIMO system, the system was tested by increasing the number of users and Signal to Noise Ratio (SNR) where the spreading code used was the Walsh code and the channel used was Rayleigh Fading modeling. The reference value used as material for consideration are the value of Bit Error Rate (BER).The method used in testing the CDMA MIMO system is the increase number of users, starting with a single user up to 16 users and SNR values from -15 dB to a maximum of 15 dB.Where all users will be combined with the CDMA technique then it will be sent using MIMO technology. The system will be tested using a simulation of the MatLab R2012a software.The results of the simulation show the performance of the CDMA MIMO system when using SNR that is increasing high, the BER will be lower or better used for communication. Whereas for simulations using a user that increases it results in a BER value that is almost the same because of the nature of the orthogonal Walsh code so that each user does not experience interference with other users.

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Salim, Rose Mini Agoes, and Shahnaz Safitri. "CAREER DECISION-MAKING ATTRIBUTION AND SELF EFFICACY: THE MODERATING ROLE OF EMOTIONAL INTELLIGENCE." Jurnal Psikologi 19, no. 1 (April 15, 2020): 1–14. http://dx.doi.org/10.14710/jp.19.1.1-14.

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It is known that gifted high-school students tend to have difficulty in choosing career due to their wide-range interests and capabilities. In order to successfully making an appropriate career choice, having a high level of career decision making self-efficacy (CDMSE) is an important precondition. CDMSE is the belief in one’s ability to successfully complete the task necessary to make career-related decisions. Of several factors known to be affecting CDMSE, previous study has shown that career decision-making attribution (CDMA) could affect students CDMSE. However, the CDMA effect on CDMSE in gifted student is seemed to be related to personal trait of students, namely emotional intelligence (EI). Therefore, this study aims to examine the moderating role of EI on the impact of gifted high-school student CDMA on CDMSE. Subjects in this study were gifted high school students (N = 165; 52.12% males; M-age = 16.20 years old) in Jakarta. The measurement tools used are CDMSE Scale Short-Form, Assessment of Attribution for Career Decision Making, and Trait Emotional Intelligence Questionnaire Short-Form (TEIQue-SF) adapted into Indonesian language. The data were analyzed using simple regression analysis with Hayes PROCESS model. It was found that there is a direct effect of CDMA on CDMSE with (F (1,163) = 10.6661, p = .0033 < .001), in which CDMA serves as a predictor of CDMSE. We also found that EI can serve as a predictor of CDMSE (F (1,163) = 10.6661, p = .0007<.001. However, EI did not moderate the CDMA-CDMSE relation. Discussion, limitations, and suggestions for further research are listed.

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Mrabet, Hichem. "A Performance Analysis of a Hybrid OCDMA-PON Configuration Based on IM/DD Fast-OFDM Technique for Access Network." Applied Sciences 10, no. 21 (October 30, 2020): 7690. http://dx.doi.org/10.3390/app10217690.

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The purpose of this article is to propose a new configuration based on OCDMA and Fast-OFDM techniques for access network applications. A hybrid intensity modulation with direct detection, fast orthogonal frequency-division multiplexing–code division multiplexing access (IM/DD Fast-OFDM-CDMA) system is analytically and numerically evaluated for an amplifier-free access network. Therefore, system performance is analytically investigated in terms of bit error rate/Q-factor as a function of simultaneous users, fiber length and launched optical power. Firstly, the proposed analytical model includes the overlapping effect among OFDM subcarriers, the peak-to-average power ratio (PAPR), and multiple access interference (MAI). Secondly, a simulation setup is performed, allowing four simultaneous users operating at 40 Gb/s in a passive optical network (PON) context. Furthermore, a power budget analysis is made between IM/DD Fast-OFDM-CDMA, all-optical IM/DD OFDM-CDMA (IM/DD AO-OFDM-CDMA) and OCDMA wavelength division multiplexing (OCDMA-WDM) configurations. It is shown that at 40 Gb/s and by using 2D-hybrid coding (2D-HC), the maximum achievable transmission-reach of IM/DD Fast-OFDM-CDMA is 142 km, which is 34 km and 60 km higher than those provided by the IM/DD AO-OFDM-OCDMA and OCDMA-WDM PON configurations, respectively.

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Fateh, Rachid, Anouar Darif, and Said Safi. "Performance Evaluation of MC-CDMA Systems with Single User Detection Technique using Kernel and Linear Adaptive Method." Journal of Telecommunictions and Information Technology 4, no. 2021 (December 30, 2021): 1–11. http://dx.doi.org/10.26636/jtit.2021.151621.

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Among all the techniques combining multi-carrier modulation and spread spectrum, the multi-carrier code division multiple access (MC-CDMA) system is by far the most widely studied. In this paper, we present the performance of the MC-CDMA system associated with key single-user detection techniques. We are interested in problems related to identification and equalization of mobile radio channels, using the kernel method in Hilbert space with a reproducing kernel, and a linear adaptive algorithm, for MC-CDMA systems. In this context, we tested the efficiency of these algorithms, considering practical frequency selective fading channels, called broadband radio access network (BRAN), standardized for MC-CDMA systems. As far as the equalization problem encountered after channel identification is concerned, we use the orthogonality restoration combination (ORC) and the minimum mean square error (MMSE) equalizer techniques to correct the distortion of the channel. Simulation results demonstrate that the kernel algorithm is efficient for practical channels.

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Journal articles on the topic 'CDMA'

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