Journal articles on the topic 'OFDM'
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1
БОЙКО, Юлій, and Ілля ПЯТІН. "СХЕМОТЕХНІЧНІ АСПЕКТИ ЗАБЕЗПЕЧЕННЯ УМОВ СИНХРОНІЗАЦІЇ В СИСТЕМАХ ЗВ’ЯЗКУ З OFDM." MEASURING AND COMPUTING DEVICES IN TECHNOLOGICAL PROCESSES, no. 1 (March 30, 2023): 28–37. http://dx.doi.org/10.31891/2219-9365-2023-73-1-5.
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В запропонованій роботі розглянуто схемотехнічні аспекти забезпечення умов синхронізації в системах зв’язку з OFDM. Наведено дослідження оцінок міжканальних та міжсимвольних завад в системах синхронізації. Описано та алгоритмізовано можливі сценарії оцінки завад в каналах з OFDM за навчальними послідовностями та пілот-сигналами. Наведено експериментальні результати оцінки спотворення OFDM-сигналів в умовах міжканальних завад на основі сигналів типу 16QAM. Здійснено порівняльний аналіз середньоквадратичної оцінки міжканальних завад для трьох методів синхронізації які досліджувались у статті. Розглянуто конструкції OFDМ-сигналів з пілот-сигналами. Досліджено концепції схемотехнічної реалізації систем тактової синхронізації в каналі зв’язку з OFDM. Проілюстровано процес спрацювання системи синхронізації з метою компенсації спотворень на основі сформованої сітки ресурсів в каналі зв’язку з OFDM.
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B., Archana, and T. P. Surekha. "Integrated approach for efficient power consumption and resource allocation in MIMO-OFDMA." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 2 (April 1, 2020): 2069. http://dx.doi.org/10.11591/ijece.v10i2.pp2069-2076.
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The growing interest towards wireless communication advancement with smart devices has provided the desired throughput of wireless communication mechanisms. But, attaining high-speed data packets amenities is the biggest issue in different multimedia applications. Recently, OFDM has come up with the useful features for wireless communication however it faces interference issues at carrier level (intercarrier interferences). To resolve these interference issues in OFDM, various existing mechanisms were utilized cyclic prefix, but it leads to redundancy in transmitted data. Also, the transmission of this redundant data can take some more power and bandwidth. All these limitations factors can be removed from a parallel cancellation mechanism. The integration of parallel cancellation and Convolution Viterbi encoding and decoding in MIMO-OFDMA will be an effective solution to have high data rate which also associations with the benefits of both the architectures of MIMO and OFDMA modulation approaches. This paper deals with this integrated mechanism for efficient resource allocation and power consumption. For performance analysis, MIMO-OFDMA system is analyzed with three different approaches likeMIMO-OFDM system without parallel cancellation (MIMO-OFDMA-WPC), MIMO-OFDMA System with parallel cancellation (MIMO-OFDMA-PC) and proposed IMO-OFDMA system with parallel cancellation and Convolution Viterbi encoding/decoding (pMIMO-OFDMA-PC &CVed) for 4x4 transmitter and receiver. Through performance analysis, it is found that the proposed system achieved better resource allocation (bandwidth) with high data rate by minimized BER rate and achieved least power consumption with least BER.
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Et.al, G. Jagga Rao. "Milli meter Wave MIMO-OFDMA Scheme with MMSE-based VEMF in 6G Wireless Technology." Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, no. 3 (April 10, 2021): 4701–7. http://dx.doi.org/10.17762/turcomat.v12i3.1890.
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Millimetre Wave (MmWave) massive multiple-input multiple-output (MmWave-massive-MIMO) has developed as beneficial for gigabit-per-second data broadcast into 6G digitized wireless technology. The collection of low-rate and energy-efficient (EE) types of machinery, low power consumptions, multi-bit quantized massive MIMO-Orthogonal Frequency Division Multiplexing Access (OFDMA) structure have been planned for the receiver manner. The main concentration effort is the minimization of a state-of-the-art pilot-symbol quantized (PSQ) massive MIMO-OFDMA system (m-MIMO-OFDM-S). Accordingly, in this analysis, by minimizing many advantages of the Variational Estimated Message Fleeting (VEMF) algorithm. A modified low complexity manner VEMF algorithm is invented for the utilization of the ASQ-m-MIMO-OFDM-S structure. Hence, two new modules improve the energy efficiency and spectrum efficiency for wireless smart 6G technology of pilot bits allocation process for MmWave connections of the hybrid MIMO-OFDM receiver structural design. Several technologies such as massive MIMO-OFDMA, 3GPP & 4G& 5G technology, the device to device communication (D2D), GREEN communication have increasingly important consideration in assisting spectrum consumption along with power consumption during simulations. The proposed VEMF algorithm has achieved higher capacity, sum rate, Energy Efficiency (EE), and throughput for the receiver section. Finally, we present a greater number of user's data transmissions MmWave-massive-MIMO-OFDMA system.
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Eneh, T., P. Rapajic, K. Anang, and Bello Lawal. "Adaptive MMSE Multiuser Detection in MIMO OFDM Wireless Communication System." Advanced Materials Research 367 (October 2011): 233–40. http://dx.doi.org/10.4028/www.scientific.net/amr.367.233.
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The combination of MIMO signal processing with OFDM is a solution to achieving high data rates for next generation wireless communication systems operating in frequency selective fading environments. To realize the extension of the MIMO with OFDM, a number of changes are required in the baseband signal processing. The developed adaptive Multiuser Detection in MIMO OFDM(AMUD) scheme performs better compared to non adaptive MIMO OFDM, at low Signal to noise ratio (SNR), it shows good performance in computational complexity, bit error rate (BER) and capacity. Simulation results show that the developed algorithm sum rate capacity is very close to MIMO theoretical upper bound (21.5 bits/s/Hz at signal to noise ratio of 20dB) which strongly indicate it’s applicability to the uplink channel where power transmission at the mobile station is a constraint. The BER performance of the developed scheme shows that, as the number of antenna increases, the 8 x 8 AMUD provides a 2dB gain compared to known non adaptive MIMO OFDMO at low SNR.
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Lopes, Alberto A., José Seguro, Paulo Gomes, Nuno Souto, and Américo Correia. "Interference Coordination for E-MBMS Transmissions in LTE-Advanced." International Journal of Digital Multimedia Broadcasting 2010 (2010): 1–11. http://dx.doi.org/10.1155/2010/689705.
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Interference coordination methods for Evolved-Multimedia Broadcast/Multicast Service (E-MBMS) in Long-Term Evolution Advanced (LTE-A) are presented. In addition, we consider signal space diversity based on Rotation Matrices (RM) known to provide good performance gains over uncorrelated Rayleigh fading channels. OFDM/OFDMA systems can make the use of RM very attractive both for single and multiple antenna transmissions. In this paper, OFDM/OFDMA signals based on LTE parameters are combined with RM, MIMO, Turbo, or LDPC codes. We have considered different types of receivers, namely, we used an MMSE (Minimum Mean Squared Error) equalizer and a Maximum Likelihood Soft Output criterion (MLSO). Frequency, signal, and space diversity gains are evaluated for different spatial channel models (SCM) based on ITU multipath propagation channels. Different adaptive frequency reuse and schedulers are considered to evaluate the E-MBMS spectral efficiency at the cell borders.
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Sergeev, A. M., and N. Sh Blaunstein. "Evolution of multiple-access networks cellular and non-cellular — in historical perspective. Part 1." Information and Control Systems, no. 4 (September 23, 2018): 86–104. http://dx.doi.org/10.31799/1684-8853-2018-4-86-104.
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Introduction:The goal of this review is the analysis of evolution of the current and novel wireless networks, from secondgeneration (2D)tofifth generation(5G),as well as changes in technologies and their corresponding theoretical background andprotocols -from Bluetooth, WLAN, WiFi and WiMAXtoLTE, OFDM/OFDMA, MIMO and LTE/MIMO advanced technologies with new hierarchy of cellular maps design — femto/pico/micro/macro.Methods:We use new theoretical frameworkstodescribe advanced technologies, such as multicarrier diversity technique, OFDM and OFDM novel approach, new aspects ofMIMO description based on multi-beam antennas, design of various cellular maps based on new algorithms of femto/pico/micro/macrocell deployment, and the methodology of a new MIMO/LTE system integration based on multi-beam antennas.Results:We have created a new methodology for multi-carrier diversity description of novel multiple-access networks, forthe usage of OFDM/OFDMA modulation in ordertoovercome inter-user and inter-symbol interference in multiple-access networks, as well as multiplicative noises in multiple-access wireless networks caused by multi-ray phenomena. Finally, wehave suggested howtoovercome the propagation effects occurring in the terrestrial communication channels by using acombination of MIMO and LTE technologies based on multi-beam antennas. For these purposes, we present a new stochasticapproach which takes into account the terrain features, such as buildings' overlay profile, buildings' density around the base station and each user's antennas, andsoforth. These parameters allow ustoestimate the effects of fading as a multiplicativenoise source.Practical relevance:The new methodology of estimating the effects created by multiplicative noise and inter-user and inter-symbol interference in terrestrial wireless networks allows ustopredict a-priory practical aspects of the currentand new multiple-access wireless communication systems, like the potential number of users or the spectral efficiency ofuser channels for various configurations of cell deployment: femto, pico, micro, and macro, as well as the novel MIMO/LTE system configurations for future networks of the 4th and 5th generations.
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Hong, Huandong, and Zhengquan Li. "Hybrid Adaptive Bias OFDM-Based IM/DD Visible Light Communication System." Photonics 8, no. 7 (July 5, 2021): 257. http://dx.doi.org/10.3390/photonics8070257.
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Conventional optical orthogonal frequency division multiplexing (OFDM) schemes, such as adaptively biased optical OFDM (ABO-OFDM) and hybrid asymmetrically clipped optical OFDM (HACO-OFDM), are unable to tap all the resources of the subcarriers and only achieve relatively high power efficiency. In this paper, a hybrid adaptive bias optical OFDM (HABO-OFDM) scheme for visible light communication (VLC) is proposed to improve spectral efficiency and power efficiency. In the proposed HABO-OFDM scheme, different optical OFDM components are combined for transmission at the same time, and the adaptive bias is designed to ensure the non-negativity, as well as obtaining significantly high power efficiency. Meanwhile, the implementation complexity of the HABO-OFDM receiver is notably lower than the conventional superimposed optical OFDM schemes. Simulation results show that the proposed HABO-OFDM scheme outperforms ABO-OFDM and HACO-OFDM in terms of both peak-to-average-power ratio (PAPR) and power efficiency. The PAPR performance of HABO-OFDM is about 3.2 dB lower than that of HACO-OFDM and 1.7 dB lower than that of ABO-OFDM. Moreover, we can see that the Eb(elec)/N0 required for HABO-OFDM to reach the BER target is lower than the other two schemes at the Bit rate/Normalized bandwidth range of 3.5 to 8.75, which means that the power efficiency of HABO-OFDM is higher in this range.
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Chen, Chien Sheng, Yung Chuan Lin, He Nian Shou, and Chi Tien Sun. "Compensation of Phase Noise Effects for IEEE 802.16e OFDMA Systems." Advanced Materials Research 204-210 (February 2011): 1330–35. http://dx.doi.org/10.4028/www.scientific.net/amr.204-210.1330.
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Orthogonal frequency division multiplexing (OFDM) system which provides high spectral efficiency has obvious advantages in robustness against the multipath delay spread and the fading channel. One of the major disadvantages of such a multi-carrier modulated system is the sensitivity of its performance to synchronization error, such as phase noise and frequency offset. Phase noise is caused by the mismatch between the transmitter and the receiver oscillators. Phase noise in an OFDM system can destroy the orthogonality of the subcarriers and cause inter-carrier interference (ICI). Phase noise resulting in common phase error (CPE) and Inter-Carrier Interference is a critical challenge to the implementation of OFDM systems. In this paper, the phase noise effects of the IEEE 802.16e OFDMA systems are compensated. The practical cluster-based method which is used to estimate either the CPE or the ICI coefficients in the fading channel and compensate the effects of phase error is also proposed. Numerical results demonstrate that the proposed algorithm can effectively improve the performance caused by phase noise.
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Gebeyehu, Zelalem Hailu, Philip Kibet Langat, and Ciira Wa Maina. "BER Performance of Stratified ACO-OFDM for Optical Wireless Communications over Multipath Channel." Journal of Computer Networks and Communications 2018 (2018): 1–14. http://dx.doi.org/10.1155/2018/9575281.
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In intensity modulation/direct detection- (IM/DD-) based optical OFDM systems, the requirement of the input signal to be real and positive unipolar imposes a reduction of system performances. Among previously proposed unipolar optical OFDM schemes for optical wireless communications (OWC), asymmetrically clipped optical OFDM (ACO-OFDM) and direct current biased optical OFDM (DCO-OFDM) are the most accepted ones. But those proposed schemes experience either spectral efficiency loss or energy efficiency loss which is a big challenge to realize high speed OWC. To improve the spectral and energy efficiencies, we previously proposed a multistratum-based stratified asymmetrically clipped optical OFDM (STACO-OFDM), and its performance was analyzed for AWGN channel. STACO-OFDM utilizes even subcarriers on the first stratum and odd subcarriers on the rest of strata to transmit multiple ACO-OFDM frames simultaneously. STACO-OFDM provides equal spectral efficiency as DCO-OFDM and better spectral efficiency compared to ACO-OFDM. In this paper, we analyze the BER performance of STACO-OFDM under the effect of multipath fading. The theoretical bit error rate (BER) bound is derived and compared with the simulation results, and good agreement is achieved. Moreover, STACO-OFDM shows better BER performance compared to ACO-OFDM and DCO-OFDM.
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Zhang, Xu, Yu Fang Zhou, Yin Peng Yu, Peng Chao Han, and Xiao Rui Wang. "Comparison and Analysis of DCO-OFDM, ACO-OFDM and ADO-OFDM in IM/DD Systems." Applied Mechanics and Materials 701-702 (December 2014): 1059–62. http://dx.doi.org/10.4028/www.scientific.net/amm.701-702.1059.
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As a promising modulation technology for optical communication, Orthogonal Frequency Division Multiplexing (OFDM) is now increasingly used and a lot of ways of improving the optical efficiency of Intensity Modulated/ Direct Detection (IM/DD) systems have been proposed. And real and non-negative OFDM signals are required in this kind of system. Asymmetrically clipped DC biased Optical OFDM (DCO-OFDM), Asymmetrically Clipped Optical OFDM (ACO-OFDM) and Asymmetrically clipped DC biased Optical OFDM (ADO-OFDM) can satisfy this requirement. In this paper, we analysis the properties and performance orderly of the above three systems and simultaneously compare their performance. The simulation results show that DCO-OFDM is efficient in terms of bandwidth while the ACO-OFDM is efficient in terms of optical power. More importantly, ADO-OFDM is both power-efficient and bandwidth-efficient. At the same time, a developmentally proposal for the future OFDM in IM/DD systems is put forward.
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Nowrin, Itisha, M. Rubaiyat Hossain Mondal, Rashed Islam, and Joarder Kamruzzaman. "A Novel OFDM Format and a Machine Learning Based Dimming Control for LiFi." Electronics 10, no. 17 (August 30, 2021): 2103. http://dx.doi.org/10.3390/electronics10172103.
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This paper proposes a new hybrid orthogonal frequency division multiplexing (OFDM) form termed as DC-biased pulse amplitude modulated optical OFDM (DPO-OFDM) by combining the ideas of the existing DC-biased optical OFDM (DCO-OFDM) and pulse amplitude modulated discrete multitone (PAM-DMT). The analysis indicates that the required DC-bias for DPO-OFDM-based light fidelity (LiFi) depends on the dimming level and the components of the DPO-OFDM. The bit error rate (BER) performance and dimming flexibility of the DPO-OFDM and existing OFDM schemes are evaluated using MATLAB tools. The results show that the proposed DPO-OFDM is power efficient and has a wide dimming range. Furthermore, a switching algorithm is introduced for LiFi, where the individual components of the hybrid OFDM are switched according to a target dimming level. Next, machine learning algorithms are used for the first time to find the appropriate proportions of the hybrid OFDM components. It is shown that polynomial regression of degree 4 can reliably predict the constellation size of the DCO-OFDM component of DPO-OFDM for a given constellation size of PAM-DMT. With the component switching and the machine learning algorithms, DPO-OFDM-based LiFi is power efficient at a wide dimming range.
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Li, Baolong, Jianfeng Shi, and Simeng Feng. "Reconstructed Hybrid Optical OFDM-NOMA for Multiuser VLC Systems." Photonics 9, no. 11 (November 13, 2022): 857. http://dx.doi.org/10.3390/photonics9110857.
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Non-orthogonal multiple access (NOMA) is deemed to be a prospective multiple access technology of the next generation. However, in visible light communication (VLC), when advanced hybrid optical orthogonal frequency division multiplexing (O-OFDM), such as hybrid asymmetrically clipped O-OFDM (HACO-OFDM), is combined with NOMA, error propagation is induced, which degrades the system performance. Therefore, a novel reconstructed hybrid O-OFDM-NOMA (RHO-OFDM-NOMA) scheme is conceived in this paper. In order to eliminate the error propagation, the users in RHO-OFDM-NOMA opt for the ACO-OFDM or clipping-free O-OFDM signals according to their channel qualities, which are subsequently superimposed on pulse-amplitude-modulated discrete multitone (PAM-DMT) to yield the spectrum-efficient hybrid O-OFDM signal. Furthermore, a reconstruction process is designed to ensure the non-negativity. Compared with HACO-OFDM, the proposed RHO-OFDM can retain the error propagation in NOMA-VLC, whilst maintaining the superiorities of high spectral and power efficiency. It is demonstrated by simulation results that RHO-OFDM-NOMA can support a notably higher data rate than the NOMA schemes using conventional O-OFDM.
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Guo, Jianzhong, Jinpeng Xiao, Jing Chen, Xin Shan, Dejin Kong, Yan Wu, and Yong Ai. "Performance Analysis of LDPC-Coded OFDM in Underwater Wireless Optical Communications." Photonics 10, no. 3 (March 20, 2023): 330. http://dx.doi.org/10.3390/photonics10030330.
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The performance of Low-Density Parity-Check (LDPC)-coded Orthogonal Frequency Division Multiplexing (OFDM) is investigated over turbulence channels in underwater wireless optical communications (UWOC). The relation between the bit error ratio (BER) and parameters such as the scintillation coefficient, signal-to-noise ratio (SNR), length of LDPC code, and order of OFDM is quantified by simulation. Results show that while the OFDM with subcarrier quadrature amplitude modulation (QAM-OFDM) has slightly better anti-turbulence performance than the OFDM with subcarrier phase shift keying modulation (PSK-OFDM), the LDPC-coded QAM-OFDM has a much better performance than the QAM-OFDM and the LDPC-coded PSK-OFDM, and, at SNR = 12, it decreases the BER by four orders of magnitude compared to the 16QAM-OFDM system when the scintillation coefficient σξ2 = 0.05.
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Sergeev, A. M., and N. Sh Blaunstein. "Evolution of multiple-access networks - cellular and non-cellular - in historical perspective. Part 3." Information and Control Systems, no. 6 (December 18, 2018): 82–94. http://dx.doi.org/10.31799/1684-8853-2018-6-82-94.
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Introduction:The goal of this issue is the analysis of evolution of the current and novel wireless networks, from second generation (2D) to fifth generation (5G), as well as changes in technologies and their corresponding theoretical background and protocols — from Bluetooth, WLAN, WiFi and WiMAX to LTE, OFDM/OFDMA, MIMO and LTE/MIMO advanced technologies with new hierarchy of cellular maps design — femto/plco/mlcro/macro.Methods:We use new theoretical frameworks for description of the advanced technologies, such as multicarrier diversity technique, OFDM and OFDM novel approach, MIMO aspects description based on multi-beam antennas approach, various cellular maps design based on a new algorithms offemto/pico/micro/macrocell deployment, and a new methodology of a new MIMO/LTEsystem integration based on multi-beam antennas.Results:We have created a new methodology of multi-carrier diversity description for novel multiple-access networks, of usage of OFDM/OFDMA modulation to obey inter-user and inter-symbol interference in multiple-access networks, of how to obey the multiplicative noises occurring in the multiple-access wireless networks, caused by multi-ray phenomena, and finally, of how to overcome propagation effects occurring in the terrestrial communication links by use combination of MIMO and LTE technologies based on multi-beam antennas. For these purposes we present new stochastic approach that accounts for the terrain features, such as buildings' overlay profile, buildings' density around the base station and each user antennas, and so forth. These parameters allow us to estimate for each situation occurs at the built-up terrain area the effects of fading, as a source of multiplicative noise.Practical relevance:New methodology of how to estimate effects of multiplicative noise, inter-user and inter-symbol interference, occurring in the terrestrial wireless networks, allows us to predict a-priory practical aspects of the current and new multiple-access wireless communication networks, such as: the users' capacity and user's links spectral efficiency for various configurations of cells deployment — femto, pico, micro, and macro, as well as the novel MIMO/LTEsystem configuration for future networks of 4thand 5thgeneration deployment.
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Sergeev, A. M., and N. Sh Blaunstein. "Evolution of multiple-access networks — cellular and non-cellular — in historical perspective. Part 4." Information and Control Systems, no. 1 (February 19, 2019): 65–75. http://dx.doi.org/10.31799/1684-8853-2019-1-65-75.
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Introduction:The goal of this issue is the analysis of evolution of the current and novel wireless networks, from second generation (2G) to fifth generation (5G), as well as changes in technologies and their corresponding theoretical background and protocols — from Bluetooth, WLAN, WiFi and WiMAX to LTE, OFDM/OFDMA, MIMO and LTE/MIMO advanced technologies with new hierarchy of cellular maps design — femto/pico/micro/macro.Methods:We use new theoretical frameworks for description of the advanced technologies, such as multicarrier diversity technique, OFDM and OFDM novel approach, MIMO aspects description based on multi-beam antennas approach, various cellular maps design based on a new algorithms of femto/pico/micro/macrocell deployment, and a new methodology of a new MIMO/LTE system integration based on multi-beam antennas.Results:We have created a new methodology of multi-carrier diversity description for novel multiple-access networks, of usage of OFDM/OFDMA modulation to obey inter-user and inter-symbol interference in multiple-access networks, of how to obey the multiplicative noises occurring in the multiple-access wireless networks, caused by multi-ray phenomena, and finally, of how to overcome propagation effects occurring in the terrestrial communication links by use combination of MIMO and LTE technologies based on multi-beam antennas. For these purposes we present new stochastic approach that accounts for the terrain features, such as buildings’ overlay profile, buildings’ density around the base station and each user antennas, and so forth. These parameters allow us to estimate for each situation occurs at the built-up terrain area the effects of fading, as a source of multiplicative noise.Practical relevance:New methodology of how to estimate effects of multiplicative noise, inter-user and inter-symbol interference, occurring in the terrestrial wireless networks, allows us to predict a-priory practical aspects of the current and new multiple-access wireless communication networks, such as: the users’ capacity and user’s links spectral efficiency for various configurations of cells deployment — femto, pico, micro, and macro, as well as the novel MIMO/LTE system configuration for future networks of 4th and 5th generation deployment.
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Uryvsky, Leonid, and Serhii Osypchuk. "OFDM Signal Research with Varied Subcarriers Number." Transport and Telecommunication Journal 17, no. 3 (September 1, 2016): 192–201. http://dx.doi.org/10.1515/ttj-2016-0017.
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AbstractThe orthogonal frequency division multiplexing (OFDM) aggregate signal energy characteristics are studied based on the OFDM signal simulation model. The information reliability of OFDM signal is explored for different sets of OFDM subcarrier numbers and varied multiposition keying types (MPK) on OFDM subcarriers. The conditions for optimal gain factor for OFDM signal are described analytically based on the simulation modeling results. The effect and value from using an optimal gain factor for OFDM signal is shown in this paper.
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Shrestha, Sunil Kumar. "Computational Complexity Comparison between DC-biased Optical OFDM and Asymmetrically Clipped Optical OFDM in Visible Light Communication." Journal of Science and Engineering 10 (December 31, 2023): 13–17. http://dx.doi.org/10.3126/jsce.v10i1.61013.
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Optical wireless systems are constrained to send real and positive values to the optical transmitter as only intensity of a signal is used to carry information. Therefore, conventional OFDM cannot be directly applied in optical systems. To combat multipath distortion, several modified OFDM systems have been studied, such as DC-biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM). In order to transmit real signal in optical environments, there is a Hermitian symmetric constraint with Discrete Fourier transform (DFT). This paper compares transceiver complexity of ACO-OFDM with that of DCO-OFDM which is used in Visible Light Communication (VLC), and it is found that for the same number of subcarriers, computational complexity is higher in ACO-OFDM.
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Lian, Jie, Yan Gao, Peng Wu, and Dianbin Lian. "Orthogonal Frequency Division Multiplexing Techniques Comparison for Underwater Optical Wireless Communication Systems." Sensors 19, no. 1 (January 4, 2019): 160. http://dx.doi.org/10.3390/s19010160.
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Optical wireless communication is an energy-efficient and cost-effective solution for high-speed and highly-secure wireless connections. In this paper, we compare, discuss, and analyze three popular optical orthogonal frequency division multiplexing (OFDM) techniques, such as DC-biased optical OFDM (DCO-OFDM), asymmetrically-clipped optical OFDM (ACO-OFDM), and unipolar OFDM (U-OFDM), for underwater optical wireless communication systems. The peak power constraint, bandwidth limit of the light source, turbulence fading underwater channel, and the channel estimation error are taken into account. To maximize the achievable data propagation distance, we propose to optimize the modulation index that controls the signal magnitude, and a bitloading algorithm is applied. This optimization process trades off the clipping distortion caused by the peak power constraint and the signal to noise ratio (SNR). The SNR and clipping effects of the three compared OFDM techniques are modeled in this paper. From the numerical results, DCO-OFDM outperforms ACO- and U-OFDM when the transmitted bit rate is high compared to the channel bandwidth. Otherwise, U-OFDM can provide a longer propagation distance or requires less transmitted power.
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Dawood, Sameer A., F. Malek, M. S. Anuar, and Suha Q. Hadi. "Discrete Multiwavelet Critical-Sampling Transform-Based OFDM System over Rayleigh Fading Channels." Mathematical Problems in Engineering 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/676217.
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Discrete multiwavelet critical-sampling transform (DMWCST) has been proposed instead of fast Fourier transform (FFT) in the realization of the orthogonal frequency division multiplexing (OFDM) system. The proposed structure further reduces the level of interference and improves the bandwidth efficiency through the elimination of the cyclic prefix due to the good orthogonality and time-frequency localization properties of the multiwavelet transform. The proposed system was simulated using MATLAB to allow various parameters of the system to be varied and tested. The performance of DMWCST-based OFDM (DMWCST-OFDM) was compared with that of the discrete wavelet transform-based OFDM (DWT-OFDM) and the traditional FFT-based OFDM (FFT-OFDM) over flat fading and frequency-selective fading channels. Results obtained indicate that the performance of the proposed DMWCST-OFDM system achieves significant improvement compared to those of DWT-OFDM and FFT-OFDM systems. DMWCST improves the performance of the OFDM system by a factor of 1.5–2.5 dB and 13–15.5 dB compared with the DWT and FFT, respectively. Therefore the proposed system offers higher data rate in wireless mobile communications.
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Hagras, Esam A. A., Sameh F. Desouky, Saad Aldosary, Haitham Khaled, and Tarek M. Hassan. "Time Reduction for SLM OFDM PAPR Based on Adaptive Genetic Algorithm in 5G IoT Networks." Sensors 23, no. 23 (November 21, 2023): 9310. http://dx.doi.org/10.3390/s23239310.
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In this paper, a new peak average power and time reduction (PAPTR) based on the adaptive genetic algorithm (AGA) strategy is used in order to improve both the time reduction and PAPR value reduction for the SLM OFDM and the conventional genetic algorithm (GA) SLM-OFDM. The simulation results demonstrate that the recommended AGA technique reduces PAPR by about 3.87 dB in comparison to SLM-OFDM. Comparing the suggested AGA SLM-OFDM to the traditional GA SLM-OFDM using the same settings, a significant learning time reduction of roughly 95.56% is achieved. The PAPR of the proposed AGA SLM-OFDM is enhanced by around 3.87 dB in comparison to traditional OFDM. Also, the PAPR of the proposed AGA SLM-OFDM is roughly 0.12 dB worse than that of the conventional GA SLM-OFDM.
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Wei, Min, Hong Wen Yang, and Da Cheng Yang. "Comparison of Shannon Capacity between OFDM and DFT-S OFDM." Applied Mechanics and Materials 513-517 (February 2014): 3639–43. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.3639.
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DFT-S OFDM, short for DFT Spread OFDM, is employed in LTE uplink to reduce the Peak-To-Average Power Ratio (PAPR) introduced by multicarrier transmission. In this paper, we compare the maximum achievable data rate, i.e. the Shannon capacity, of DFT-S-OFDM and OFDM under Rayleigh and with clipping. Our results indicate that, in terms of Shannon Capcity, OFDM outperforms DFT-S-OFDM with ZF or MMSE.
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Mahender, Kommabatla, Tipparti Anil Kumar, and K. S Ramesh. "PAPR Analysis of Fifth Generation Multiple Access Waveforms for Advanced Wireless Communication." International Journal of Engineering & Technology 7, no. 3.34 (September 1, 2018): 487. http://dx.doi.org/10.14419/ijet.v7i3.34.19364.
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This paper describes the aspects of multiple access for emerging (5G) Wireless Communication Systems. Orthogonal Frequency Division Multiplexing (OFDM) is best suited for fourth generation (4G) but it suffers from the problem of high Peak to Average Power Ratio (PAPR) & Side band leakage. Single carrier frequency division multiple access (SC-FDMA) has worked like an alternative to OFDMA only in the uplink process and PAPR was reduced. OFDM based 4G network is not capable of supporting diverse applications and these applications can be implemented by 5G. High traffic requirements of 5G can be evaluated by using multiple access schemes, namely filter-bank multi-carrier (FBMC), universal-filtered multi-carrier (UFMC), generalized frequency-division multiplexing (GFDM). Comparison of PAPR reduction is done based on Complementary Cumulative Distribution Function (CCDF), for various multiple access 5G waveforms.
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Zuo, Jiajun, Ruijuan Yang, Shaohua Luo, and Xiaobai Li. "Training Sequence Design of TDS-OFDM Signal in Joint Radar and Communication System." Mathematical Problems in Engineering 2019 (July 30, 2019): 1–10. http://dx.doi.org/10.1155/2019/3914314.
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In the joint radar and communication system, using orthogonal frequency division multiplexing (OFDM) signals, cyclic prefix (CP) and pilots lead to the problem of high peak at the sidelobe (PSL) level in autocorrelation function (ACF), which deteriorates the radar detection performance seriously. To solve this problem, first, a new RadCom signal based on time-domain synchronization OFDM (TDS-OFDM) was proposed. TDS-OFDM adopts training sequence (TS) for guard interval, as well as synchronization and channel estimation, so that CP and pilots can be avoided. And then, ambiguity function (AF) of TDS-OFDM RadCom signal was analyzed. Finally, TS are optimized to suppress PSL of TDS-OFDM signal and maintain the autocorrelation properties of TS simultaneously. The results show that the autocorrelation performance of designed TDS-OFDM RadCom signal is much better than that of CP-OFDM RadCom signal. Considering the importance of radar target detection, TDS-OFDM is more appropriate than CP-OFDM for the RadCom system.
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Ding, Wei, Tao Xu, Min Song, and Wei Gu. "Parallel Channel Equalizer for Mobile OFDM Baseband Receivers." Applied Mechanics and Materials 333-335 (July 2013): 640–45. http://dx.doi.org/10.4028/www.scientific.net/amm.333-335.640.
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Mobile OFDM refers to OFDM systems with fast moving transceivers, contrastive to traditional OFDM systems whose transceivers are stationary or with a low velocity. An efficient implementation of the channel equalization for mobile OFDM is presented in this paper. Based on the particular OFDM subcarrier allocations, the channel equalizer is split into separated sub-equalizers, enabling a concurrent implementation. This parallel equalizer is implemented on an FPGA platform. The experimental results show that without an efficient design, mobile OFDM leads to an unacceptable hardware cost. The proposed parallel equalizer for mobile OFDM can compensate for time-varying channels, in which a traditional OFDM receiver fails to operate, although the paid price is that the hardware resource is reasonably increased.
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Suyoto, Suyoto, Agus Subekti, Arief Suryadi Satyawan, Nasrullah Armi, Chaeriah Bin Ali Wael, and Galih Nugraha Nurkahfi. "Impact of carrier frequency offset and in-phase and quadrature imbalance on the performance of wireless precoded orthogonal frequency division multiplexing." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 5 (October 1, 2022): 5153. http://dx.doi.org/10.11591/ijece.v12i5.pp5153-5163.
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<p>Precoding in orthogonal frequency division multiplexing (OFDM) system proved to reduce the peak-to-average power ratio (PAPR), so that it improves BER. However, from the existing literature, the effect of carrier frequency offset (CFO), in-phase and quadrature (IQ) imbalance on precoded wireless OFDM systems has not been carried out. Therefore, this study evaluated the precoded OFDM (P-OFDM) system performance by considering the impact of CFO and IQ imbalance. P-OFDM performance evaluation is expressed in signal-to-interference noise ratio (SINR) and bit error rates (BER). The communication channels used are the additive white Gaussian noise (AWGN) channel and the frequency-selective Rayleigh fading (FSRF) channel, while the channel equalization process is considered perfect. The results of the analysis and simulation show that P-OFDM is greater affected by the presence of CFO and IQ imbalance than conventional OFDM system. In AWGN channel, P-OFDM experiences different SINR for each subcarrier. This is different from conventional OFDM system, where all SINRs are the same for all subcarriers. In the FSRF channel, both the POFDM system and the OFDM system experience different SINR for each subcarrier, where the SINRs fluctuation in the P-OFDM system is much larger than in the OFDM system.</p>
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Wang, Yong, and Yan Ling Jing. "Research on Timing Synchronization Method for DC-Biased Optical OFDM Communication System." Applied Mechanics and Materials 441 (December 2013): 911–14. http://dx.doi.org/10.4028/www.scientific.net/amm.441.911.
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The timing synchronization methods for dc-biased optical OFDM system are different from wireless OFDM system because dc-biased optical OFDM system use intensity modulation/direct detection. Existing synchronization methods cant be used directly in dc-biased optical OFDM system. Therefore, the new timing synchronization method for dc-biased optical OFDM system is presented. The simulation results show that this timing synchronization method increasingly improves the estimated accuracy of dc-biased optical OFDM system.
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Koti, Jayasudha, and Braj Kishore Mishra. "BER Performance Comparison of DCO-OFDM and Convolutional Coded DCO-OFDM in IM/DD Systems." International Journal of Electronics, Communications, and Measurement Engineering 8, no. 2 (July 2019): 26–39. http://dx.doi.org/10.4018/ijecme.2019070102.
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Optical wireless communication (OWC) is an alternative technology to meet the demands of the exponentially-growing high data rate applications run by broadband users. The implementation of single carrier modulation techniques in OWC is an age old technology, but for the last few years research is focused towards the multicarrier modulation techniques in OWC. In OWC, information is carried using intensity modulation and retrieved using direct detection. To perform intensity modulation, the baseband signal should be a unipolar signal. To obtain a unipolar signal, various techniques such as DC-biased orthogonal frequency division multiplexing (DCO-OFDM), Asymmetrically clipped orthogonal frequency division multiplexing (ACO-OFDM), Flip orthogonal frequency division multiplexing (Flip-OFDM) and Unipolar orthogonal frequency division multiplexing (U-OFDM) techniques are reported in the literature. Though the DCO-OFDM is spectrally efficient compared to other techniques it requires more power to achieve the targeted BER. In this article, a convolutional Coded DCO-OFDM (CDCO-OFDM) has been introduced by applying channel coding. A convolutional encoder and a hard-decision Viterbi decoder are considered in CDCO-OFDM. It has been observed that CDCO-OFDM requires less transmitted power than DCO-OFDM to attain the targeted BER. The performance of DCO-OFDM and CDCO-OFDM is evaluated for 4, 16, 64 QAM- 7dB and 13dB bias, in the presence of the additive white Gaussian noise (AWGN) channel. It is observed that CDCO requires less power to transmit than DCO-OFDM for the BER 10-4.
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Zhou, Xiao, Chengyou Wang, and Ruiguang Tang. "Channel Estimation Based on IOTA Filter in OFDM/OQPSK and OFDM/OQAM Systems." Applied Sciences 9, no. 7 (April 7, 2019): 1454. http://dx.doi.org/10.3390/app9071454.
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In this paper, we present a study of bit error rate (BER) for orthogonal frequency division multiplexing/offset quadrature phase shift keying (OFDM/OQPSK) and OFDM/offset quadrature amplitude modulation (OQAM) systems with an isotropic orthogonal transfer algorithm (IOTA) filter. The novel noise suppression method based on an IOTA filter is proposed to reduce the error of channel estimation caused by additive white Gaussian noise (AWGN). The OFDM/OQPSK and OFDM/OQAM systems do not insert the guard interval (GI) and pilots in the signal frames, thus they possess transmission efficiency. An analysis was carried out for convolutional coded OFDM/OQPSK and OFDM/OQAM systems in Rayleigh fading channels with generator polynomials and constraint lengths. Compared with conventional OFDM/QPSK and OFDM/QAM systems with the insertion of comb-type pilots, the proposed IOTA filter-based channel estimation method can provide significant energy per bit to time-varying noise power spectral density ratio gains over time and frequency-selective propagation Rayleigh fading channels in OFDM/OQPSK and OFDM/OQAM systems.
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Shi, Chong-Yue, Hui Li, You-Ling zhou, Ping Wang, Qian Li, Liu-Xun Xue, and Jie Xu. "Research on LDPC in an OFDM System." Journal of Physics: Conference Series 2078, no. 1 (November 1, 2021): 012075. http://dx.doi.org/10.1088/1742-6596/2078/1/012075.
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Abstract In this paper, LDPC codes and OFDM technologies are studied, and combines LDPC and OFDM to simulate and verify the performance. The encoding of LDPC and logarithmic domain BP decoding algorithm and the principle of OFDM are introduced. Through MATLAB, the simulation of OFDM-LDPC system in different channel, different code length, different iteration times, LDPC and OFDM-LDPC in the same conditions are compared. Through simulation analysis, we can know that the performance of OFDM-LDPC system will improve with the increase of the code length. When the SNR is small, the number of iterations has little effect on the performance of OFDM-LDPC system. When the SNR is large, the performance of the system will be improved with the increase of the number of iterations. The performance of OFDM-LDPC codes is better than that of LDPC codes. The performance of OFDM-LDPC code is better than LDPC code in multipath Rayleigh fading channel.
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Mohammed, Abdulwahid, Hassan Mostafa, and Abdelhady Abdelazim Ammar. "An effective technique for increasing capacity and improving bandwidth in 5G narrow-band internet of things." International Journal of Electrical and Computer Engineering (IJECE) 13, no. 5 (October 1, 2023): 5232. http://dx.doi.org/10.11591/ijece.v13i5.pp5232-5242.
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<p>In recent years, the wireless spectrum has become increasingly scarce as demand for wireless services has grown, requiring imaginative approaches to increase capacity within a limited spectral resource. This article proposes a new method that combines modified symbol time compression with orthogonal frequency division multiplexing (MSTC-OFDM), to enhance capacity for the narrow-band internet of things (NB-IoT) system. The suggested method, MSTC-OFDM, is based on the modified symbol time compression (MSTC) technique. The MSTC is a compressed waveform technique that increases capacity by compressing the occupied symbol time without losing bit error rate (BER) performance or data throughput. A comparative analysis is provided between the traditional orthogonal frequency division multiplexing (OFDM) system and the MSTC-OFDM method. The simulation results show that the MSTC-OFDM scheme drastically decreases the symbol time (ST) by 75% compared to a standard OFDM system. As a result, the MSTC-OFDM system offers four times the bit rate of a typical OFDM system using the same bandwidth and modulation but with a little increase in complexity. Moreover, compared to an OFDM system with 16 quadrature amplitude modulation (16QAM-OFDM), the MSTC-OFDM system reduces the signal-to-noise ratio (SNR) by 3.9 dB to transmit the same amount of data.</p>
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Zhang, Peidong. "System optimization for index modulated OFDM." Highlights in Science, Engineering and Technology 53 (June 30, 2023): 88–97. http://dx.doi.org/10.54097/hset.v53i.9686.
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This paper introduces the system optimization scheme of OFDM-IM, an emerging modulation technology that combines OFDM technology and modulation index technology to improve spectral efficiency and system reliability while ensuring high-speed transmission. However, as a new technology, OFDM still has shortcomings. This paper investigates three system optimization schemes for OFDM-IM: he deep learning-based OFDM-IM optimization scheme, MIMO-OFDM-IM, and LDPC coding-assisted subcarrier index protection scheme. It is found that these three optimization schemes are indeed helpful for optimizing the performance of OFDM-IM through system simulation experiments. The IM-OFDM system optimization based on deep learning is very helpful for IM-OFDM in terms of channel estimation, signal detection, and modulation classification. MIMO-OFDM-IM can increase channel capacity and signal transmission reliability. By protecting the subcarrier index, LDPC codes can effectively reduce the subcarrier error rate and improve the reliability and performance of IM-OFDM systems. Due to their different technical characteristics, the three optimization schemes have different advantages. They also have their application scenarios in which they excel. However, considering these technologies are relatively new, there are still certain drawbacks to these three technologies. Researchers need to continue to study them in-depth and gradually overcome them.
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Tomar, Pragate. "Bit Error Rate (BER) Analysis of Conventional OFDM (DFT - OFDM) And Wavelet Based OFDM (DWT – OFDM)." International Journal on Recent and Innovation Trends in Computing and Communication 3, no. 1 (2015): 423–26. http://dx.doi.org/10.17762/ijritcc2321-8169.150184.
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Abbas, Sulaiman M., Mohammed Nadhim Abbas, and Saifuldeen A. Mohammed. "SLANTLET TRANSFORM-BASED OFDM SCHEME." Journal of Engineering 12, no. 03 (September 1, 2006): 1638–47. http://dx.doi.org/10.31026/j.eng.2006.03.04.
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Wireless digital communication is rapidly expanding resulting in a demand for systems that are reliable and have a high spectral efficiency. To fulfill these demands OFDM technology has drawn a lot of attention. In this paper a new technique is proposed to improve the performance of OFDM. The new technique is use the slantlet transform (SLT) instead Fast Fourier transform (FFT) in order to reduce the level of interference. This also will remove the need for Guard interval (GI) in the case of the FFT-OFDM and therefore improve the bandwidth efficiency of the OFDM. The SLT-OFDM is also better than wavelet packet (WP)-OFDM in the selective channel because the slantlet filter bank is less frequency selective than the traditional DWT filter bank, due to the shorter length of the filters and SLT algorithm is faster than WP algorithm. The main results obtained indicate that the performance of SLT-OFDM is better on average by 18dB in comparison with that of FFT-OFDM flat fading channels. For frequency selective fading channel the SLT-OFDM performs is better than the FFT-OFDM on the lower SNR region, while the situation will reverse with increase SNR values.
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Furqan, Haji M., Jehad M. Hamamreh, and Huseyin Arslan. "Adaptive OFDM-IM for Enhancing Physical Layer Security and Spectral Efficiency of Future Wireless Networks." Wireless Communications and Mobile Computing 2018 (August 15, 2018): 1–16. http://dx.doi.org/10.1155/2018/3178303.
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In this paper, we propose algorithms for enhancing physical layer security and spectral efficiency of Orthogonal Frequency Division Multiplexing (OFDM) with Index Modulation (IM) systems. Particularly, different activation ratios and/or Constellation Modulation orders are selected adaptively for each subblock based on the channel quality of the legitimate receiver. More specifically, three approaches named as (1) OFDM with Adaptive Index Modulation and Fixed Constellation Modulation (OFDM-AIM-FCM), (2) OFDM with Adaptive Index Modulation and Adaptive Constellation Modulation (OFDM-AIM-ACM), and (3) OFDM with Variable Index Modulation and Variable Constellation Modulation (OFDM-VIM-VCM) are proposed for enhancing physical layer security and spectral efficiency. Simulation results are presented to investigate the effectiveness of the proposed algorithms.
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Zhang, Xue Yi, and Shuang Le Zhao. "Simulation and Study for the Optical OFDM Communication." Applied Mechanics and Materials 530-531 (February 2014): 729–33. http://dx.doi.org/10.4028/www.scientific.net/amm.530-531.729.
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This paper gives a theoretical basis principle and structure of OFDM. The O-OFDM has three parts including transmitter, receiver and fiber. The main and key component is IFFT and FFT block. And then a basic direct detection optical-OFDM system (DO-OFDM) is designed and simulated by the software Optisystem. The performance of the system is viewed by the visualizer of the software compared to the RZ, OFDM and QAM modulation system. The result shows that the OFDM system is better than conventional serial modulation schemes like RZ, QAM.
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Raj, Ajay Amrit. "Adaptive Neuro-Fuzzy Inference System-based Nonlinear Equalizer for CO-OFDM Systems." Computer Journal 63, no. 2 (November 18, 2019): 169–78. http://dx.doi.org/10.1093/comjnl/bxz072.
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Abstract The principle of orthogonal frequency-division multiplexing (OFDM) is to transmit the data through a large number of multiple orthogonal subcarriers. The coherent optical OFDM (CO-OFDM) is OFDM data that are being modulated to light frequency and being detected in coherent manner. CO-OFDM brings to optical communications the combination of two powerful techniques, coherent optical detection and OFDM. One of the primary challenges in the CO-OFDM system is to remove optical fiber nonlinear effects. This makes nonlinearity compensation a critical task of the CO-OFDM system. So a nonlinear equalizer (NLE) based on adaptive neuro-fuzzy inference system (ANFIS) is presented for CO-OFDM systems to mitigate nonlinearities on long-haul optical communications with high bit rate and bit error rate (BER)of the system. Various performance metrics were analyzed for the proposed ANFIS–NLE, and it is compared with existing techniques such as support vector machine and artificial neural network. From the experimental results, our proposed approach gives better performance in terms of BER and Q-factor on comparing with existing methods.
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Leftah, Hussein. "Efficient Optical OFDM System Resilience to Indoor Wireless Multipath Channels." Iraqi Journal for Electrical and Electronic Engineering 20, no. 1 (November 5, 2023): 78–83. http://dx.doi.org/10.37917/ijeee.20.1.8.
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This article presents a developed intensity modulation/direct detection (IM/DD) optical orthogonal frequency division multiplexing (O-OFDM). More precisely, the presented C-O-OFDM is based on the C-transform as a unitary orthogonal transform instead of the state-of-the-art discrete Fourier transform (DFT). Due to the properties of the real C-transform, Hermitian symmetry (HS) is not required to produce real OFDM samples. Therefore, the proposed scheme supports twice the input symbols compared to conventional DFT-based OFDM system. Real data mapping and DC bias technology is considered to evaluate the performance of the presented scheme over optical wireless multipath. The simulation results shows that the proposed C-O-OFDM is more resilience to multipath phenomena than the competitive DFT-O-OFDM and DHT-O-OFDM schemes for similar bit rate. The proposed scheme achieves about 22 dB signal-to-noise ratio (SNR) gain in comparison with the DFT-O-OFDM and about 2.5 dB SNR gain in comparison with the DHT-O-OFDM scheme.
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Prayoga, Kadek Agus Mahabojana Dwi, NMAE Dewi Wirastuti, and Nyoman Pramaita. "Analisis Unjuk Kerja Improved Sinc Power Pulse pada Sistem OFDM Melalui Kanal Frequency Selective Fading." Majalah Ilmiah Teknologi Elektro 18, no. 3 (September 4, 2019): 323. http://dx.doi.org/10.24843/mite.2019.v18i03.p04.
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Kombinasi antara sistem OFDM (orthogonal frequency division multiplexing) dan Pulse Shaping mampu mengurangi Inter Carrier Interference (ICI) dan error yang terjadi. Penelitian ini bertujuan untuk mengetahui perbandingan performansi dari sistem OFDM tanpa pulse shaping dan OFDM dengan pulse shaping Improved Sinc Power (ISP) pulse yang melalui kanal Frequency Selective Fading, ditinjau dari BER (bit error rate) berbanding Eb/No (energy per bit to noise power spectral density ratio). Penelitian ini menggunakan metode simulasi dengan menggunakan program Matlab R2018a. Hasil dari simulasi didapat unjuk kerja sistem OFDM dengan pulse shaping ISP pulsememiliki hasil yang lebih baik dari OFDM tanpa pulse shaping. Pada kanal transmisi Frequency Selective Fading untuk mencapi nilai BER sebesar 10-1 sistem OFDM dengan pulse shaping ISP pulse dibutuhkan Eb/No sebesar 2 dB. Sedangkan pada sistem OFDM tanpa pulse shaping dibutuhkan Eb/No sebesar 10 dB.
Kata Kunci — OFDM, Pulse Shaping, ICI, ISP pulse, Frequency Selective Fading.
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Jihad, Noor J., and Sinan M. Abdul Satar. "BER performance study for optical OFDM of optical camera communication." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 5 (October 1, 2021): 4263. http://dx.doi.org/10.11591/ijece.v11i5.pp4263-4271.
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In this article, different forms of optical orthogonal frequency division multiplexing (OFDM) were observed which were suitable for optical camera communication (OCC) systems. This research aims to establish the bit error rate (BER) versus signal-to-noise ratio (SNR) of the OCC system. This research will focus on OCC systems and the design that produces the noise of the clipping but will gain SNR as a whole if an optimum clipping factor is chosen. The BER versus SNR analysis was investigated for the different clipping factors 0.7, 1.4, and 2.6. The BER performance of the asymmetrically clipped optical OFDM (ACO-OFDM) was also compared with the direct current optical OFDM (DCO-OFDM) to show the suitable effectiveness of the proposed approach. ACO-OFDM was considered to be better due to lower bit loading, but DCO-OFDM was efficient for higher SNR values. This was because the DC bias used was inefficient in terms of optical capacity, while ACO-OFDM used only half of the subcarriers to transmit the information. Moreover, ACO-OFDM two-dimensional half-subcarriers of mapping rule would introduce the clipping noise to its unused 2D subcarriers, although further data can be provided by the 2D DCO-OFDM mapping rule.
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Васюта, К. С., У. Р. Збежховська, В. В. Слободянюк, В. С. Загривий, and В. І. Чистов. "Метод прихованої передачі інформації в системах з Orthogonal frequency division multiplexing (OFDM) модуляцією." Наука і техніка Повітряних Сил Збройних Сил України, no. 2(43), (May 11, 2021): 132–39. http://dx.doi.org/10.30748/nitps.2021.43.18.
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У статті проаналізовано можливості використання сигналів з Orthogonal frequency division multiplexing (OFDM) модуляцією для організації скритного радіозв’язку в системах спеціального призначення. Побудовано та проаналізовано “образ” сигналу з OFDM модуляцією в псевдофазовому просторі. Візуальний аналіз “образу” показав, що його структура є близькою до структури регулярних процесів. Дана оцінка скритності функціонування систем з OFDM модуляцією за допомогою непараметричної Brock Dechert Scheinkman (BDS) статистики. Запропоновано метод підвищення скритності сигналів з OFDM модуляцією за допомогою використання поліномів Чебишева. Проведено порівняльний аналіз Independent аnd Identically Distributed (IID) скритності хаотичних та гармонічних OFDM сигналів. Отримані результати показують, що запропонований метод формування OFDM сигналів дозволяє забезпечити вищий рівень IID скритності.
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Suyoto, Suyoto, Agus Subekti, Arief Suryadi Satyawan, Vita Awalia Mardiana, Nasrullah Armi, and Dayat Kurniawan. "Performance analysis of OFDM-IM scheme under STO and CFO." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 4 (August 1, 2021): 3293. http://dx.doi.org/10.11591/ijece.v11i4.pp3293-3299.
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In this letter, performance analysis of orthogonal frequency division multiplexing with index modulation (OFDM-IM) is presented in term of bit error rate (BERs). The analysis considers its performance under two impairments, symbol time offset (STO) and carrier frequency offset (CFO) in frequency-selective fading channel. As orthogonal multicarrier system, OFDM-IM is subject to both inter-symbol interference (ISI) and inter-carrier interference (ICI) in a frequency-selective fading channel. OFDM-IM is a new multicarrier communication system, where the active subcarriers indices are used to carry additional bits of information. In general, in the previous existing works, OFDM-IM are evaluated only for near-ideal communication scenarios by only incorporating the CFO factor. In this work, the OFDM-IM performance is investigated and compared with conventional OFDM in the presence of two impairments, STO and CFO. Simulation results show that OFDM-IM outperforms the conventional OFDM with the presence of STO and CFO, especially at high SNR areas.
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Sarker, Sohag, Laila Arzuman Ara, Tahsin Alam, and Tarun Debnath. "Design and Analysis of MIMO F-OFDM Systems for 5G and Beyond Wireless Communications." International Journal of Recent Technology and Engineering (IJRTE) 10, no. 2 (July 30, 2021): 203–10. http://dx.doi.org/10.35940/ijrte.b6274.0710221.
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F-OFDM (Filtered-OFDM) is a flexible waveform that has been considered suitable for 5G and beyond systems for its improved spectrum utilization, moderates PAPR, low OOB emission, multiple asynchronous sub-band transmission, and high robustness to frequency selectivity. It can attain a desirable balance between frequency and time localizations for narrow bandwidths. It is also MIMO friendly. In this paper, a comprehensive design and analysis have been made to evaluate the performance of MIMO (4×4) CP-OFDM and F-OFDM systems for message bits transmission using several digital modulation techniques (16-QAM, 16-PSK, 16-DPSK, 64-QAM, 64-PSK, and 64-DPSK), RA channel coding, different windowed (Hanning, Hamming, Blackman, Blackman-Harris, RRC) sinc FIR filters for length N = 513, and MMSE signal detection technique. From MATLAB based simulation results, it is observed that F-OFDM reduces spectrum leakage thus enhances spectrum efficiency than conventional CP-OFDM. F-OFDM based system offers lower BER (Bit Error Rate) performance than CP-OFDM based system.
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Zhang, Zhen Yu, Feng Chun Tian, Fan Xin Zeng, Li Jia Ge, and Gui Xin Xuan. "Symbol Timing Sequence Structure for OFDM-CDMA Communication System under Low SNR." Applied Mechanics and Materials 713-715 (January 2015): 1188–92. http://dx.doi.org/10.4028/www.scientific.net/amm.713-715.1188.
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Symbol synchronization offset of orthogonal frequency division multiplexing (OFDM) communication system will cause the rotation of data constellation at receiver even if such offset falls in the range of the appended cyclic prefix. When OFDM modulation is combined with spread spectrum technique, e.g., OFDM code division multiple access (OFDM-CDMA), the problem becomes more serious since OFDM-CDMA communication system generally works under very low signal-to-noise ratio. This paper focuses on symbol timing synchronization of OFDM-CDMA communication system and proposes an effective sequence structure on the basis of circular conjugate-symmetric properties of discrete Fourier transform. The proposed frequency-domain sequence not only can generate real time-domain signal to reduce calculation complexity, but also can resist peak-to-average power ratio of OFDM modulation by exploiting suitable computer search algorithm. The simulation results show a sharp cross-correlation peak can be obtained, which is quite helpful for accurate symbol timing synchronization of OFDM-CDMA communication system.
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Prayitno, R. A., N. M. A. E. D. Wirastuti, and I. G. A. K. D. D. Hartawan. "ANALISIS UNJUK KERJA ZERO FORCING EQUALIZER PADA SISTEM OFDM MIMO." Jurnal SPEKTRUM 5, no. 1 (June 25, 2018): 68. http://dx.doi.org/10.24843/spektrum.2018.v05.i01.p10.
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Wireless network is one of the most important things in the development of telecommunication. However, the existing wireless technology has not been able to efficiently create a very high data rate because it was very sensitive to fading. Therefore, Orthogonal Frequency Division Multiplexing (OFDM) technology combined with MIMO (Multiple Input Multiple Output) transceiver system was used to gain more diversity and bandwidth efficiency. The propagation performed on the OFDM MIMO system was multipath propagation. To reduce Intersymbol Interference (ISI) was used Zero Forcing (ZF) equalizer which works by combining channel response and equalizer response itself to eliminate ISI. This study aims to determine the effect of Zero Forcing Equalizer on OFDM MIMO system using rayleigh fading channel and compared the result with OFDM MIMO STBC system. The research method used was simulation using MatLab R2015a. The simulation results showed that the performance of OFDM MIMO ZF system was worse than OFDM MIMO STBC system i.e BER vs EbNo simulation, eye diagram simulation, and constellation diagram simulation. The OFDM MIMO ZF system was required an Eb / No value more than 25 dB to achieve BER 10-4 while the OFDM MIMO STBC system only required an Eb / No value of 10.5 dB to achieve BER 10-4. The eye pattern generated by the OFDM MIMO ZF system was more closed and the dispersion of constellation signals away from the ideal point while OFDM MIMO STBC system displayed a more open eye pattern and the dispersion of its constellation signal closer to the ideal point. It indicated more ISI occurs in the OFDM MIMO ZF system than that in OFDM MIMO STBC system.
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Fang, Hui. "A Novel Approach for PAPR Reduction of NC-OFDM System." Applied Mechanics and Materials 519-520 (February 2014): 1021–26. http://dx.doi.org/10.4028/www.scientific.net/amm.519-520.1021.
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Although Non-continuous OFDM (NC-OFDM) has the unique advantage of eliminating interference to authorized user in cognitive radio context, it also confronts a difficulty of reducing peak to average power ratio (PAPR) like other OFDM techniques. In this paper, carrier interferometry is proposed to apply in NC-OFDM system in order to reduce its PAPR using the construction feature of CI code itself. The coding principle of CI code is analyzed at first. Then NC-OFDM base-band system based on carrier interferometry (CI/NC-OFDM) is modeled. Theoretical analysis and matlab simulation results indicate that CI code can bring 3 dB lower PAPR reference with the same probability of exceeding some PAPR reference, compared with traditional NC-OFDM system. This method is effective and feasible and gets better BER performance as well.
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Murthy, K. Chidananda. "Performance evaluation of chaotic spreading codes in massive MIMO OFDM system." Indian Journal of Science and Technology 13, no. 42 (November 14, 2020): 4374–85. http://dx.doi.org/10.17485/ijst/v13i42.2027.
Full textAbstract:
Background/Objectives: Wireless communication systems are growing towards the implementation of 5G communication systems to satisfy the demand of services in future. OFDMA has some shortcoming like one or more subcarriers of OFDM are completely affected due to the characteristic of the transmission channel. Spreading scheme has been introduced to combat the aforementioned issue. Furthermore, communication channels are affected by multipath fading which changes the amplitude of the received signal. This fading severely affects the communication systems. Therefore, it is essential to develop a more robust technique for higher data transmission and larger throughput. The main objective of this study is to design a massive MIMOOFDM system for secure transmission of data. Chaos based sequence is used to spread the data before transmission which will solve intercell interference and improve the security of data. Methods: This study presents a chaos based massive MIMO-OFDM communication system. The proposed chaos based massive MIMO-OFDM system is implemented and its efficacy is evaluated by computing bit error rate. The effectiveness of the proposed system is investigated by varying the parameters including modulation methods such as PSK and QAM, number of users 10, 20 and 30 and spreading factor of 5, 10 and 15. Findings: Results clearly proved that the proposed system provides exceptional performance with 16QAM modulation scheme, 10 users at high spreading factor value of 15. Novelty: The uniqueness of the proposed system is with enhanced performance and usage of novel modulation scheme by varying the spreading factor value, when compared to its peers. Keywords: Communication system; spreading code; chaotic code; massive MIMO-OFDM; bit error rate
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Badawi, Waleed K., Marwa G. El-Hossary, and Moustafa H. Aly. "Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation." Symmetry 13, no. 2 (February 5, 2021): 270. http://dx.doi.org/10.3390/sym13020270.
Full textAbstract:
Both light emitting diode (LED) characteristics for illumination and communication simultaneously have made visible light communication-orthogonal frequency division multiplexing (VLC-OFDM) a strong competitive to radio frequency (RF). In this juncture, to improve signal to noise ratio (SNR) and coverage contour, the wavelet-OFDM is suggested for indoor VLC systems. In this paper, a wavelet VLC-OFDM is proposed for imaging multiple-input multiple-output (MIMO) systems. The proposed wavelet-OFDM is exploited for a hybrid space-frequency domain pre-equalization technique instead of the traditional fast Fourier transform (FFT)-OFDM technique. The Meyer filter is selected and employed in the proposed technique. A comparable achievement is elaborated for several numbers of channels to achieve the enhanced performance in terms of bit rate and coverage contour. In addition, a useful comparison is executed between our wavelet VLC-OFDM and the traditional FFT-OFDM for a hybrid space-frequency domain pre-equalization technique. The simulation results emphasize the superiority point of wavelet VLC-OFDM MIMO system by improving the coverage contour by ~20% over the traditional OFDM at a 10−3 bit error rate (BER) target. Hence, the proposed technique can be potentially executed in indoor VLC-MIMO systems.
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Purnita, Krishna Saha, and M. Rubaiyat Hossain Mondal. "Machine learning for DCO-OFDM based LiFi." PLOS ONE 16, no. 11 (November 23, 2021): e0259955. http://dx.doi.org/10.1371/journal.pone.0259955.
Full textAbstract:
Light fidelity (LiFi) uses different forms of orthogonal frequency division multiplexing (OFDM), including DC biased optical OFDM (DCO-OFDM). In DCO-OFDM, the use of a large DC bias causes optical power inefficiency, while a small bias leads to higher clipping noise. Hence, finding an appropriate DC bias level for DCO-OFDM is important. This paper applies machine learning (ML) algorithms to find optimum DC-bias value for DCO-OFDM based LiFi systems. For this, a dataset is generated for DCO-OFDM using MATLAB tool. Next, ML algorithms are applied using Python programming language. ML is used to find the important attributes of DCO-OFDM that influence the optimum DC bias. It is shown here that the optimum DC bias is a function of several factors including, the minimum, the standard deviation, and the maximum value of the bipolar OFDM signal, and the constellation size. Next, linear and polynomial regression algorithms are successfully applied to predict the optimum DC bias value. Results show that polynomial regression of order 2 can predict the optimum DC bias value with a coefficient of determination of 96.77% which confirms the effectiveness of the prediction.
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Mukhtar, Shaika, and Gh Rasool Begh. "Performance Analysis of Filtered OFDM Based Downlink and Uplink NOMA System over Nakagami-m Fading Channel." Journal of Telecommunications and Information Technology 2 (March 30, 2021): 11–23. http://dx.doi.org/10.26636/jtit.2021.148020.
Full textAbstract:
Efficient consumption of available resources and fulfillment of increasing demands are the two main challenges which are addressed by exploring advanced multiple access schemes along with efficient modulation techniques. To this end, non-orthogonal multiple access (NOMA) is discussed as a promising scheme for future 5G traffic. NOMA enables the users to share same resource block, permitting certain level of interference. In this paper, we propose filtered OFDM (F-OFDM) as a transmission waveform for NOMA systems, as it offers all the advantages of OFDM with the additional provision of sub-band filtering to satisfy the diverse services of the users. We examine F-OFDM in both downlink and uplink NOMA systems. Error-related performances of both downlink and uplink F-OFDM NOMA systems are analyzed and compared with conventional OFDM NOMA system over Nakagami-m fading channel. The results show that the error performance of F-OFDM NOMA is better than that of OFDM NOMA. An improvement of about 2 dB and 1 dB in bit error rate is achieved in downlink and uplink F-OFDM NOMA, respectively. Monte Carlo simulations are conducted for different values of fading parameter m, supporting the obtained analytical results
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Bauch, Gerhard. "Aspects of Delay Diversity in OFDM." African Journal of Information & Communication Technology 2, no. 1 (February 28, 2006): 12. http://dx.doi.org/10.5130/ajict.v2i1.3.
Full textAbstract:
We consider several aspects of delay diversity in coded OFDM. The cyclic properties of the FFT allow to do delay diversity in a cyclic manner without exceeding the guard interval. We investigate the impact of different cyclic delays in terms of achievable diversity level, information theory and BER performance. Furthermore, we propose an interleaving and user assignment strategy which allows multiple users to exploit the full spatial diversity in an OFDMA system with appropriately chosen cyclic delays. Finally, we introduce a scheme with low delay and low reference symbol overhead for differential modulation in frequency direction which can be detected non-coherently and is able to cope with the increased frequency-selectivity which is caused by the cyclic delays.