Artykuły w czasopismach: „OFDM (Orthogonal Frequency Division Multiplexing)”

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Uppal, Sabhyata, Sanjay Sharma i Hardeep Singh. "Analytical Investigation on Papr Reduction in OFDM Systems Using Golay Codes". Journal of Electrical Engineering 65, nr 5 (1.09.2014): 289–93. http://dx.doi.org/10.2478/jee-2014-0046.

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Abstract Orthogonal frequency division multiplexing (OFDM) is a common technique in multi carrier communications. One of the major issues in developing OFDM is the high peak to average power ratio (PAPR). Golay sequences have been introduced to construct 16-QAM and 256-QAM (quadrature amplitude modulation) code for the orthogonal frequency division multiplexing (OFDM), reducing the peak-to-average power ratio. In this paper we have considered the use of coding to reduce the peakto- average power ratio (PAPR) for orthogonal frequency division multiplexing (OFDM) systems. By using QPSK Golay sequences, 16 and 256 QAM sequences with low PAPR are generated

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Sun, Zeng You, i Fan Ming Zeng. "Optimization and Simulation of OFDM System Based on Orthogonal Wavelet". Applied Mechanics and Materials 548-549 (kwiecień 2014): 1221–26. http://dx.doi.org/10.4028/www.scientific.net/amm.548-549.1221.

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In order to reduce the Orthogonal Frequency division Multiplexing (OFDM) Inter-Carrier Interference (ICI), Put forward a kind of modulation method that based on the orthogonal frequency division multiplexing of orthogonal wavelet, Using orthogonal wavelet instead of discrete Fourier transform, optimize the design for OFDM systems, on the premise of without protection interval to reduce the system interference, using MATLAB to simulate the OFDM system, results show that the optimization of the OFDM can reduce the power of the ICI and Inter-symbol Interference (ISI) and improve the comprehensive anti-jamming of the OFDM system.

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Yang, Xianzhen, Siyuan Yan, Xiao Li i Fu Li. "A Unified Spectrum Formulation for OFDM, FBMC, and F-OFDM". Electronics 9, nr 8 (11.08.2020): 1285. http://dx.doi.org/10.3390/electronics9081285.

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Although orthogonal frequency division multiplexing (OFDM) has been standardized for 5G, filter bank multi-carrier (FBMC) and filtered orthogonal frequency division multiplexing (F-OFDM) remain competitive as candidates for future generations of wireless technologies beyond 5G, due to their reduced spectrum leakage and thus enhanced spectrum efficiency. In this article, we developed a unified spectrum expression for OFDM, FBMC, and F-OFDM, which provides comparative insights into those techniques. A representative sideband quantification is included at the end of this article.

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Koti, Jayasudha, i 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, nr 2 (lipiec 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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Sahrab, Ammar A., i Alaa Doohee Yaseen. "Filtered orthogonal frequency division multiplexing for improved 5G systems". Bulletin of Electrical Engineering and Informatics 10, nr 4 (1.08.2021): 2079–87. http://dx.doi.org/10.11591/eei.v10i4.3119.

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Wireless communications became an integrated part of the human life. Fifth generation (5G) is the modern communication which provides enhanced mobile broadband (eMBB), ultra reliable low latency communications (URLLC), and massive machine type communication (mMTC). Thus, 5G have to provide coverage to multi-numerology devices, therefore, modulation and access schemes are suggested in the literature such as cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) and filtered OFDM (f-OFDM). CP-OFDM suffers from the high out of band emission which limited the multi-numerology applications. In f-OFDM, the out of band emission can be suppressed to an accepted extent such that different numerologies can be coexisting. On the other hand, f-OFDM can be more improved by using a proper filtering approach. In this paper three different filters are suggested based windowed-sinc function; Hanning, Hamming, and Blackman. Simulation results show that the proposed filters are promising for high spectral efficiency and out of band emission rejection. Furthermore, the bit error rate, error vector magnitude, and power spectral density are further improved with respect to CP-OFDM scheme but some trade-off is present. Overall, the suggested windowed-sinc filters are outperforming the traditional CP-OFDM. As a conclusion, the suggested windnowed-sinc filters have no limitations on the modulation order or the number of subcarriers utilized in the system.

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Praveen Kumar Malik i M P Tripathi. "OFDM: A Mathematical Review". Journal on Today's Ideas - Tomorrow's Technologies 5, nr 2 (28.12.2017): 97–111. http://dx.doi.org/10.15415/jotitt.2017.52006.

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Mathematical review of the Orthogonal Frequency Division Multiplexing is demonstrated in terms of Inter symbol interference, Multi carrier modulated system and cyclic prefix. Modeling of the mathematical equation of the Orthogonal Frequency Division Multiplexing, Inverse fast Fourier transform and fast Fourier transform is explained with the suitable example using MATLAB. Bit error rate performance of OFDM is also presented with the help of statistical computation.

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Lowery, Arthur James. "Spectrally efficient optical orthogonal frequency division multiplexing". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, nr 2169 (2.03.2020): 20190180. http://dx.doi.org/10.1098/rsta.2019.0180.

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This paper charts the development of spectrally efficient forms of optical orthogonal frequency division multiplexing (OFDM) that are suited for intensity-modulated direct detection systems, such as wireless optical communications. The journey begins with systems using a DC-bias to ensure that no parts of the signal that modulates the optical source are negative in value, as negative optical intensity is unphysical. As the DC-part of the optical signal carries no information, it is wasteful in energy; thus asymmetrically clipped optical OFDM was developed, removing any negative-going peaks below the mean. Unfortunately, the clipping causes second-order distortion and intermodulation, so some subcarriers appear to be unusable, halving spectral efficiency; this is similar for unipolar and flipped optical OFDM. Thus, a considerable effort has been made to regain spectral efficiency, using layered techniques where the clipping distortion is mostly cancelled at the receiver, from a knowledge of one unpolluted layer, enabling one or more extra ‘layers/paths/depths’ to be received on the previously unusable subcarriers. Importantly, for a given optical power and high-order modulation, layered methods offer the best spectral efficiencies and need the lowest signal-to-noise ratios, especially if diversity combining is used. Thus, they could be important for high-bandwidth optical fibre systems. Efficient methods of generating all layers simultaneously, using fast Fourier transforms with their partial calculations extracted, are discussed, as are experimental demonstrations in both wireless and short-haul communications links. A musical analogy is also provided, which may point to how orchestral and rock music is deciphered in the brain. This article is part of the theme issue ‘Optical wireless communication’.

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Li, Chen Wu, Jian Zhang, Qin Xie i Xiao Hong Zhang. "Carrier Modulation Technology Based on Orthogonal Frequency Division Multiplexing". Advanced Materials Research 774-776 (wrzesień 2013): 1671–76. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.1671.

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This paper first analyzes the transmission characteristics of low-voltage power line channels with the focus on the study of carrier modulation technology regarding the power line communication part, then proposes the orthogonal frequency division multiplexing technology that serves for the digital communication of family network power line communication gateways, analyzes the OFDM system principle, actulizes OFDM modulation and demodulation through discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT), and build the OFDM simulation model. Finally, a specific plan of using power lines as the family network transmission media is proposed.

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Girinath, N. "A Novel Reconfigurable Orthogonal Frequency Division Multiplexing Transceiver". Journal of Computational and Theoretical Nanoscience 16, nr 2 (1.02.2019): 430–35. http://dx.doi.org/10.1166/jctn.2019.7745.

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As the world moves toward 3G/4G there is a need for high data rate and relatively wide bandwidths. OFDM (Orthogonal Frequency Division Multiplexing) a form of multicarrier modulation technique is widely used to achieve high speed efficient data transmission at the rate of several Mbps. It is used in Wi-Fi standards like 802.11a, 802.11n, 802.11ac, broadcast standards like Digital Video Broadcast (DVB) and cellular telecommunications standard LTE. The main advantage of OFDM compared to single carrier modulation is their robustness to channel fading in wireless environment, high baud rates and less inter symbol interference. One major disadvantage is its High PAPR. PTS partial transmit sequences (PTS) and selective mapping are proposed to reduce it. Since FFT is core block of OFDM it must be able to adapt itself to ever changing digital world. A function specific reconfigurable 2k SDF (Single path delay feedback) FFT is proposed. It utilizes less power and can be configured for different FFT sizes ranging from 16-point to 1024-point. The validity and efficiency of the architecture have been verified by simulation in hardware description language VERILOG and targeted on Virtex-6 device. Finally PAPR is estimated by MATLAB simulation.

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Yonis, Aws Zuheer, i Khalid Khalil Mohammed. "Investigation of pattern division multiple access technique in wireless communication networks". Indonesian Journal of Electrical Engineering and Computer Science 26, nr 1 (1.04.2022): 296. http://dx.doi.org/10.11591/ijeecs.v26.i1.pp296-303.

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Recently, <span>pattern division multiple access (PDMA) is a non-orthogonal multiple access system that is now being developed in next-generation telecoms to address the requirement for mass connectivity. The core premise of non-orthogonal multiple access is to simultaneously serve multiple users with varying power levels across the same spectrum resources such as time, frequency, code, as well as space with minimal inter-user interference. A simulation analysis of significant technology enhancements focusing on PDMA aims to describe the benefits of the two plans now being examined by the third-generation partnership project for 5G technologies, namely filtered orthogonal frequency division multiplexing (F-OFDM) and windowed orthogonal frequency division multiplexing (W-OFDM), and to compare them to alternative modulation processes such as 16, 32, and 128 modulations. The research results explained the PDMA is less bit error rate used in multiple access technologies compare with W-OFDM and F-OFDM.</span>

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Sun, Enchang, Kechu Yi, Bin Tian i Dongying Zhang. "Quasi-Orthogonal Time Division Multiplexing and Its Performances in Rayleigh Fading Channels". ISRN Communications and Networking 2012 (27.03.2012): 1–5. http://dx.doi.org/10.5402/2012/295424.

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This paper proposes an efficient transmission scheme, Quasi-Orthogonal Time Division Multiplexing (QOTDM), which employs the shift orthogonal property of the pulse function with raised-cosine spectral shape, and the signal waveforms are quasi-orthogonal in time domain. Comparing to orthogonal frequency division multiplexing (OFDM), QOTDM is less sensitive to carrier frequency offset and power amplifier nonlinearities while keeping a similar spectral efficiency with OFDM due to single-carrier characteristics. QOTDM is a suitable consideration for the downlink transmission such as in satellite communications. An upper bound of sample error probability (SER) is derived to evaluate the performance of QOTDM. Comparisons of QOTDM and OFDM in Rayleigh fading channels show that the proposed QOTDM system is better than that of OFDM system in terms of bit error rate (BER) in high Eb/No regions.

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Solyman, Ahmad AA, Hani Attar, Mohammad R. Khosravi i Baki Koyuncu. "MIMO-OFDM/OCDM low-complexity equalization under a doubly dispersive channel in wireless sensor networks". International Journal of Distributed Sensor Networks 16, nr 6 (czerwiec 2020): 155014772091295. http://dx.doi.org/10.1177/1550147720912950.

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In this article, three novel systems for wireless sensor networks based on Alamouti decoding were investigated and then compared, which are Alamouti space–time block coding multiple-input single-output/multiple-input multiple-output multicarrier modulation (MCM) system, extended orthogonal space–time block coding multiple-input single-output MCM system, and multiple-input multiple-output system. Moreover, the proposed work is applied over multiple-input multiple-output systems rather than the conventional single-antenna orthogonal chirp division multiplexing systems, based on the discrete fractional cosine transform orthogonal chirp division multiplexing system to mitigate the effect of frequency-selective and time-varying channels, using low-complexity equalizers, specifically by ignoring the intercarrier interference coming from faraway subcarriers and using the LSMR iteration algorithm to decrease the equalization complexity, mainly with long orthogonal chirp division multiplexing symbols, such as the TV symbols. The block diagrams for the proposed systems are provided to simplify the theoretical analysis by making it easier to follow. Simulation results confirm that the proposed multiple-input multiple-output and multiple-input single-output orthogonal chirp division multiplexing systems outperform the conventional multiple-input multiple-output and multiple-input single-output orthogonal frequency division multiplexing systems. Finally, the results show that orthogonal chirp division multiplexing exhibited a better channel energy behavior than classical orthogonal frequency division multiplexing, thus improving the system performance and allowing the system to decrease the equalization complexity.

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Fan, Tong Liang, i Lian Qing Fu. "Channel Estimation for OFDM System with Regularized Total Least-Squares Solution". Key Engineering Materials 467-469 (luty 2011): 1621–26. http://dx.doi.org/10.4028/www.scientific.net/kem.467-469.1621.

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Orthogonal frequency-division multiplexing (OFDM) combines the advantages of high performance and relatively low implementation complexity. However, for reliable coherent detection of the input signal, the OFDM receiver needs accurate channel information. The Doppler shift of fast-fading channels will generate inter-carrier interference (ICI) and, hence, degrade the performance of orthogonal frequency-division multiplexing (OFDM) systems. In this paper, we present regularized total least-squares (RTLS) scheme to eliminate the ICI and noise. A closed-form mathematical expression has been derived to express the channel estimation. It has been shown that the proposed channel estimation and data detect can effectively eliminate the ICI effect.

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Mahender, Kommabatla, Tipparti Anil Kumar i K. S Ramesh. "PAPR Analysis of Fifth Generation Multiple Access Waveforms for Advanced Wireless Communication". International Journal of Engineering & Technology 7, nr 3.34 (1.09.2018): 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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Lian, Jie, Yan Gao, Peng Wu i Dianbin Lian. "Orthogonal Frequency Division Multiplexing Techniques Comparison for Underwater Optical Wireless Communication Systems". Sensors 19, nr 1 (4.01.2019): 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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Wirastuti, N. M. A. E. Dewi, I. G. A. K. Diafari Djuni Hartawan, I. Made Arsa Suyadnya i Duman Care Khrisne. "Carrier Frequency Offset Effects on OFDM System over Rayleigh Fading Channel". Journal of Electrical, Electronics and Informatics 3, nr 2 (9.01.2020): 45. http://dx.doi.org/10.24843/jeei.2019.v03.i02.p03.

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Orthogonal Frequency Division Multiplexing (OFDM) system showed the use of Discrete Fourier Transform (DFT) and Inverse Discrete Fourier Transform (IDFT) to perform the baseband modulation and demodulation. So that, it can increase and improve the efficiency of the modulation and demodulation. Currently, the OFDM is being utilized in the field of broadband wireless communication, which transmit signals orthogonally, that increases speed of information transmission. It also has high proficiency with high bandwidth and provide large data rates and robust against the multipath delay spread. On the other hand, there are some issues faced OFDM system which are high Peak Average Power Ratio (PAPR), and sensitive to Phase Noise (PN) and Carrier Frequency Offset (CFO). This paper presents Orthogonal Frequency Division Multiplexing (OFDM) performance evaluation in the presence of CFO with two different environment scenarios were used: an AWGN channel and a Rayleigh fading channel. The simulation was performed to evaluate the effects of CFO based on Bit Error Rate (BER) vs. Energy Bit per Noise Ratio (Eb/No). The results showed that for BER degradation caused by CFO effects have presented in our simulation for both AWGN and Rayleigh fading channel.

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Soni, G. "Performance Evaluation of OFDM Based Link Using LabVIEW 2012". Information Technologies and Control 14, nr 4 (1.12.2016): 33–38. http://dx.doi.org/10.1515/itc-2017-0015.

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Abstract Background: Orthogonal Frequency Division Multiplexing (OFDM) has emerged as the core technology of the 4th generation mobile communication due to its capacity to combat channel fading also OFDM is highly spectral efficient. Methods/Statistical Analysis: LabVIEW 2012 is used to simulate and evaluate the performance of OFDM link. Bit Error Rate (BER) evaluation of discrete Fourier transform (DFT) based OFDM system is carried out in this work. The simulation based analysis is demonstrated by means of different modulation schemes like QPSK, 16-QAM for OFDM based wireless system. Findings: QPSK needs less SNR as compared to 16-QAM to achieve an acceptable BER Furthermore, the efficiency of OFDM increases with increase of cyclic prefix. In OFDM, ISI and ICI-interference reduced by implying cyclic prefix. Applications/Improvements: The performance analysis of orthogonal frequency division multiplexing is analyzed using LabVIEW 2012 based on performance parameters like cyclic prefix simulated at frequency of 2.4 GHz using FFT size 512, 1024.

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Kumar, Abhishek. "ON VARIOUS TECHNIQUES IN OFDM AND GFDM: A SURVEY". International Journal of Students' Research in Technology & Management 5, nr 4 (26.11.2017): 39–45. http://dx.doi.org/10.18510/ijsrtm.2017.545.

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Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation that divides the available spectrum into a finite number of carriers and applied into a digital transmission system. But it has some drawbacks such as sensitivity in inter-carrier interference, high peak to average power ratio and insufficient cyclic prefix in spectrum. These drawbacks may be reduced by a technique known as Generalized Frequency Division Multiplexing (GFDM). In the present scenario, it is a high speed multi-carrier multiplexing data transfer scheme for the cellular network. This paper deals with a comparison between OFDM and GFDM and focuses on various techniques in OFDM and GFDM.

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Al-Asady, Heba Abdul-Jaleel, Hassan Falah Fakhruldeen i Mustafa Qahtan Alsudani. "Channel estimation of OFDM in C-band communication systems under different distribution conditions". Indonesian Journal of Electrical Engineering and Computer Science 23, nr 3 (1.09.2021): 1778. http://dx.doi.org/10.11591/ijeecs.v23.i3.pp1778-1782.

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<p>Orthogonal frequency division multiplexing (OFDM) is a transmission system that uses multiple orthogonal carriers that are sent out at the same time. OFDM is a technique for mobile and wireless communication that has high-efficient frequency utilization, high data-rate transmission, simple and efficient implementation using the fast Fourier transform (FFT) and the inverse fast Fourier transform (IFFT), and reduces inter symbol interference (ISI) by inserting cyclic prefix (CP). One of the most important approaches in an OFDM system is channel estimation. In this paper, the orthogonal frequency division multiplexing system with the Rayleigh channel module is analyzed for different areas. The proposed approach used large numbers of subcarriers to transmit the signals over 64-QAM modulation with pilot add channel estimation. The accuracy of the OFDM system is shown in the measuring of the relationships of peak power to the noise ratio and bit error rate.</p>

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Kamorudeen Adewale, Rahmon, Ogunti Erastus Olarewaju i Apena Waliu Olalekan. "Characterization of Orthogonal Frequency Division Multiplexing (OFDM) Communication Links". American Journal of Electrical and Electronic Engineering 8, nr 3 (13.08.2020): 91–97. http://dx.doi.org/10.12691/ajeee-8-3-4.

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Banerjee, Purnima. "Transmission of Data over Orthogonal Frequency Division Multiplexing (OFDM)". International Journal of P2P Network Trends and Technology 13 (25.11.2014): 11–15. http://dx.doi.org/10.14445/22492593/ijptt-v13p403.

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Yadav, Sarita, Ashish Nema i Jitendra Mishra. "Space Time Trellis Code Frequency Index Modulation with Neuro-LS Channel Estimation in OFDM". SMART MOVES JOURNAL IJOSCIENCE 5, nr 9 (14.09.2019): 7. http://dx.doi.org/10.24113/ijoscience.v5i9.226.

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In wireless communication, orthogonal frequency division multiplexing (OFDM) plays a major role because of its high transmission rate. In space-time shift keying (STSK), the information is conveyed by both the spatial and time dimensions, which can be used to strike a trade-off between the diversity and multiplexing gains. On the other hand, orthogonal frequency division multiplexing (OFDM) relying on index modulation (IM) conveys information not only by the conventional signal constellations as in classical OFDM, but also by the indices of the subcarriers. In this paper compressed sensing(CS) is studied in order to increase throughput and bit-error performance by transmitting extra information bits in each subcarrier block as well as to decrease the complexity of the detector. In this paper, soft trellis decoding algorithm is implemented with channel estimation using Neuro-LS technique. The result analysis shows the better performance of trellis decoder with respect to BER and Neuro-LS channel estimation with respect to BER.

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Vimala, P., i G. Yamuna. "Pilot Design for Sparse Channel Estimation in Orthogonal Frequency Division Multiplexing Systems". Journal of Telecommunications and Information Technology 2 (29.06.2018): 60–68. http://dx.doi.org/10.26636/jtit.2018.113817.

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Orthogonal Frequency Division Multiplexing (OFDM) is a well-known technique used in modern wide band wireless communication systems. Coherent OFDM systems achieve its advantages over a multipath fading channel, if channel impulse response is estimated precisely at the receiver. Pilot-aided channel estimation in wide band OFDM systems adopts the recently explored compressive sensing technique to decrease the transmission overhead of pilot subcarriers, since it exploits the inherent sparsity of the wireless fading channel. The accuracy of compressive sensing techniques in sparse channel estimation is based on the location of pilots among OFDM subcarriers. A suﬃcient condition for the optimal pilot selection from Sylow subgroups is derived. A Sylow subgroup does not exist for most practical OFDM systems. Therefore, a deterministic pilot search algorithm is described to select pilot locations based on minimizing coherence, along with minimum variance. Simulation results reveal the eﬀectiveness of the proposed algorithm in terms of bit error rate, compared to the existing solutions.

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Васюта, К. С., У. Р. Збежховська, В. В. Слободянюк, В. С. Загривий i В. І. Чистов. "Метод прихованої передачі інформації в системах з Orthogonal frequency division multiplexing (OFDM) модуляцією". Наука і техніка Повітряних Сил Збройних Сил України, nr 2(43), (11.05.2021): 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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Guo, Kai, Yun Jia Zhang, Dan Luo i Zhuo Liu. "High Capacity and Power Efficient PON Combining ACO-OFDM and WDM Technologies". Advanced Materials Research 909 (marzec 2014): 260–64. http://dx.doi.org/10.4028/www.scientific.net/amr.909.260.

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An upstream transmission scheme of asymmetric clipping optical orthogonal frequency division multiplexing (ACO-OFDM) based WDMA-PON is proposed. Performance of 10Gbit/s/ONU upstream ACO-OFDM signal is analyzed. The scheme is high capacity and power efficient.

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Gunawan, Wahyu-Hendra, Yang Liu, Chi-Wai Chow, Yun-Han Chang i Chien-Hung Yeh. "High Speed Visible Light Communication Using Digital Power Domain Multiplexing of Orthogonal Frequency Division Multiplexed (OFDM) Signals". Photonics 8, nr 11 (8.11.2021): 500. http://dx.doi.org/10.3390/photonics8110500.

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In order to increase transmission capacity, multiplexing schemes in different physical dimensions, including time, frequency, modulation quadrature, polarization, and space, can be employed. In this work, we propose and demonstrate a red color laser-diode (LD) based visible-light-communication (VLC) system using two kinds of digital domain multiplexing schemes, orthogonal-frequency-division-multiplexing (OFDM) and power-domain division-multiplexing (PowDM). The two digital domain multiplexed data can achieve data rates of 1.66 Gbit/s and 6.41 Gbit/s, respectively, providing a total data rate of 8.07 Gbit/s, fulfilling the pre-forward error correction (pre-FEC) bit-error-rate (BER) limit. The measured signal-to-noise ratios (SNRs) are 10.96 dB and 14.45 dB, respectively. Here, similar to OFDM, the PowDM can enhance the total system capacity by allowing acceptable signal spectra overlapping among different power division signals to maximize the bandwidth utilization. An experiment to verify and evaluate the proposed work is performed. The modulation and demodulation of OFDM and PowDM are discussed. The optimum power levels of the individual signals in the PowDM signal are also analyzed.

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Bai, Yiqi, i Pierre-Jean Bouvet. "Orthogonal Chirp Division Multiplexing for Underwater Acoustic Communication". Sensors 18, nr 11 (7.11.2018): 3815. http://dx.doi.org/10.3390/s18113815.

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The objective of this study is to investigate a novel Underwater Acoustic Communication (UWAC) system based on a modulated chirp signal termed as Orthogonal Chirp Division Multiplexing (OCDM). Originating from the Fresnel transform, OCDM uses chirp signals to exploit the multipath diversity of the channel, achieving a good robustness against frequency fading, especially in the underloaded scenario where only a subset of the available waveforms is modulated. The implementation of the OCDM system for the UWAC scenario is described, and the performance results over an experimental water tank and realistic replayed underwater channel are compared against the traditional Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme.

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Shakhtarin, B. I., V. V. Chudnikov i R. M. Dyabirov. "Methods of Frequency Synchronization of OFDM Signals in an Underwater Acoustic Channel". Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, nr 4 (127) (sierpień 2019): 62–70. http://dx.doi.org/10.18698/0236-3933-2019-4-62-70.

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Application of signals with orthogonal frequency division multiplexing in underwater communication systems allows efficient use of the information transfer channel bandwidth and thereby increase the carrying capacity of the system. Among the main distinguishing features of the underwater channel there are the relatively low speed of sound propagation in water, multiple reflections from the water surface and the bottom of the reservoir and the Doppler effect, which leads to compression / stretching of the signal in time. The model of the underwater acoustic channel was developed on the assumption that the signal at the receiver input is a superposition of the signals which are copies of the transmitted signal, but passed through different paths from the transmitter. Each signal has its own amplitude, time delay and degree of compression / stretching in time. For correct demodulation of the orthogonal frequency division of the channel-signal, the receiver must first perform time and frequency synchronization. Time synchronization is performed to determine the beginning of the packet and the symbols’ boundaries, and frequency synchronization is necessary for matching the receiver and transmitter sampling frequency to eliminate interchannel interference.For frequency synchronization in a hydroacoustic channel of orthogonal frequency division type, either the preambles invariant to Doppler effect or pilot components of the channel of the orthogonal frequency division type are used. The method based on the synchronization preamble and on a bank of matched filters uses a non-invariant to the Doppler effect preamble at the beginning of the packet. Each filter is matched with a preamble having compression / stretching in time. The autocorrelation method assumes that two identical symbols are included in the transmitted data block for signals with orthogonal frequency division multiplexing, which are used to estimate the scale of signal stretching / compression. The conclusions on the advantages of using orthogonal frequency division multiplexing in an underwater acoustic channel are given.

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29

Li, Tong Qiang, i Li Gang Xu. "Study and Simulation Analysis of OFDM System Based on Simulink". Advanced Materials Research 706-708 (czerwiec 2013): 1967–70. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.1967.

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Orthogonal Frequency Division Multiplexing(OFDM) is going to become the most important technique in the future communication system. The paper presents the principle of OFDM,establishes a simulation model of OFDM communication system based on simulink.By utilizing the system,we briefly analyse the simulation results and conclude the the performance characteristics of OFDM system.

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30

Tang, Tao, Yulong Mao i Guangmin Hu. "A Fair Power Allocation Approach to OFDM-Based NOMA with Consideration of Clipping". Electronics 9, nr 10 (21.10.2020): 1743. http://dx.doi.org/10.3390/electronics9101743.

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Orthogonal frequency division multiplexing-based non-orthogonal multiple access (OFDM-NOMA) is a competitive solution to achieve a capacity gain over orthogonal frequency division multiplexing-based orthogonal multiple access (OFDM-OMA). However, a major drawback of OFDM-based systems is the high peak-to-average power ratio (PAPR). Clipping is widely used for PAPR reduction, but it will degrade the capacity performance. Motivated by this fact, a fair user signal power allocation approach to OFDM-NOMA with clipping is proposed, where the power allocation factor is selected from a fair region. This approach fulfills the demand that OFDM-NOMA capacity can always outperform OFDM-OMA capacity for each paired user, regardless of the user pairing criteria, making it applicable for implementation using any scheduling paradigms. Therefore, the proposed approach can also be viewed as a solution to address fairness for the cell edge user in OFDM-NOMA systems. Both the theoretical and numerical results indicate that, although the capacity performance of OFDM-NOMA and OFDM-OMA is decreased and restrained at a high signal-to-noise ratio (SNR) by clipping, applying the proposed approach on OFDM-NOMA can still meet the aforementioned demand. Besides, it is shown that both the lower and upper bounds of the fair region are increased with a decreasing of clipping ratio.

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31

Choi, Jae-Woong, i Eui-Rim Jeong. "Multi-output Convolutional Neural Network Based Distance and Velocity Estimation Technique for Orthogonal Frequency Division Multiplexing Radar Systems". Webology 19, nr 1 (20.01.2022): 4555–70. http://dx.doi.org/10.14704/web/v19i1/web19302.

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The objective of this work is to propose a new method of estimating velocity and distance based on multi-output convolutional neural network (CNN) for orthogonal frequency division multiplexing (OFDM) radars. The two-dimensional (2D) periodogram is extracted from the received reflected waveforms through radar signal processing of received OFDM symbols. Conventionally, constant false alarm rate (CFAR) algorithm is used to estimate distance and velocity of targets. In contrast, this paper proposes a novel deep-learning based approach for the estimation of the targets in OFDM radar systems. The proposed multi-output CNN-based target detector estimates the distance and velocity of the target simultaneously. The proposed technique is verified through computer simulation. The results show that the proposed multi-output CNN-based method demonstrates more accurate distance and speed estimates than the conventional CFAR. Specifically, the distance and speed estimates of the proposed method are 9.8 and 12.3 times accurate, respectively, than those of the conventional CFAR.

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32

Wang, Chunyan. "Beyond 3G Techniques of Orthogonal Frequency Division Multiplexing and Performance Analysis via Simulation". International Journal of Advanced Pervasive and Ubiquitous Computing 3, nr 3 (lipiec 2011): 1–13. http://dx.doi.org/10.4018/japuc.2011070101.

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As one of the techniques beyond 3G, because of the effective performance of high spectrum utilization and anti-fading for frequency selecting and adopted multi-carrier modulation technique that meets the requirement of the explosive traffic capacity, Orthogonal Frequency Division Multiplexing (OFDM) has carried great weight in wireless communications. This paper expounds OFDM technical characteristics and performs computer simulation on the OFDM system based on Inverse Fast Fourier Transform (IFFT) by means MATLAB. During the course of simulation, comparison between OFDM and traditional single-carrier technology is performed. The simulation results have great significance for research and applications in the field.

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33

Putri, Widya Catur Kristanti. "Software-Based Analysis of Multi User Orthogonal Frequency Division Multiplexing (OFDM)". Jurnal Jartel: Jurnal Jaringan Telekomunikasi 3, nr 2 (7.11.2016): 1–6. http://dx.doi.org/10.33795/jartel.v3i2.185.

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The application of OFDM technology is still not fully implemented in the Telecommunication Study Program at State Polytechnic of Malang. This is because the application of this technology is applied to hardware. However, this can be overcome by simulating the OFDM technology through software. From the application of the system into the program by entering the predetermined parameters, the BER value can be compared to the predetermined parameters. Bit error that appears in the application of the OFDM Multi user system for bit error in BPSK Modulation with AWGN and Rayleigh Fading channels appears bit error respectively with an average of 9 bits and 14 bits at 11 dB SNR. Whereas in the QPSK modulation with AWGN and Rayleigh Fading channels, each bit error appears with an average of 13 bits and 18 bits on the SNR of 14 dB. Furthermore, in the calculation of bandwidth efficiency in the frequency allocation of 20 MHz for BPSK modulation, three values ??of bandwidth efficiency are obtained, among others, 1 bps / Hz in theory for practical, namely the code rate ½ is 0.3 bps / Hz and the code rate ¾ is 0.45 bps / Hz. While the QPSK modulation also obtained three values ??of bandwidth efficiency, namely, 2 bps / Hz in theory for practical, namely the code rate ½ is 0.6 bps / Hz and the code rate ¾ is 0.9 bps / Hz.

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34

Nguyen, Viet-Hung, Minh-Tuan Nguyen i Yong-Hwa Kim. "Deep neural network for orthogonal frequency division multiplexing systems without cyclic prefix transmission". MATEC Web of Conferences 189 (2018): 04016. http://dx.doi.org/10.1051/matecconf/201818904016.

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Orthogonal frequency division multiplexing (OFDM) is widely used in wired or wireless transmission systems. In the structure of OFDM, a cycle prefix (CP) has been exploited to avoid the effects of inter-symbol interference (ISI) and inter-carrier interference (ICI). This paper proposes a new approach to transmit the signals without CP transmission. Using the deep neural network, the proposed OFDM system transmits data without the CP. Simulation results show that the proposed scheme can estimate the CP at the receiver and overcome the effect of ISI.

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35

Abdourahamane, Ali. "ADVANTAGES OF OPTICAL ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING IN COMMUNICATIONS SYSTEMS". EUREKA: Physics and Engineering 2 (31.03.2016): 27–33. http://dx.doi.org/10.21303/2461-4262.2016.00058.

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The role of the optical transmitter is to generate the optical signal, impose the information bearing signal, and launch the modulated signal into the optical fiber. The semiconductor light sources are commonly used in state-of-the-art optical communication systems. Optical communication systems has become one of the important systems after the advent of telephone, internet, radio networks in the second half of the 20th century. The development of optical communication was caused primarily by the rapidly rising demand for Internet connectivity. Orthogonal frequency-division multiplexing (OFDM) belongs to a wide class of multicarrier modulation. Orthogonal frequency-division multiplexing has succeeded in a wide range of applications in the wireless communication domain from video/audio digital broadcasting to wireless local area networks (LANs). Although their very low loss compared to that of the wireless counterpart, optical systems still need renovation for spans commonly less than150 Km. In this paper advantages of optical orthogonal frequency division multiplexing in communications systems will explained.

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36

Sastry, K. Seshadri, K. Baburao, A. V. Prabu i G. Naveen Kumar. "Comparison of SPS and FA methods for Blind Carrier Frequency Offset Estimation in OFDM systems". International Journal of Mathematical Models and Methods in Applied Sciences 16 (10.01.2022): 7–11. http://dx.doi.org/10.46300/9101.2022.16.2.

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In orthogonal frequency-division multiplexing (OFDM) systems, synchronization issues are of great importance since synchronization errors might destroy the orthogonality among all subcarriers and, therefore, introduce intercarrier interference (ICI) and intersymbol interference (ISI). Several schemes of frequency offset estimation in OFDM systems have been investigated. This paper compares performance and computational complexity of Smoothing Power Spectrum (SPS) and Frequency Analysis (FA) methods for blind carrier frequency offset (CFO) estimation in OFDM systems.

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37

Rashid Ahmed, Saadaldeen, Ahmed S.Abdullah i Nayif Mohammed Hammash. "Universal Filtered Multicarrier (UFMC) vs. Orthogonal Frequency Division Multiplexing (OFDM)". Journal of Physics: Conference Series 1530 (maj 2020): 012092. http://dx.doi.org/10.1088/1742-6596/1530/1/012092.

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38

Astuti, Dian Widi. "Analisa Simulasi Performansi Penggunaan Orthogonal Frequency Division Multiplexing Pada Sistem Digital Video Broadcasting-Terrestrial". Jurnal Telekomunikasi dan Komputer 3, nr 1 (27.02.2017): 65. http://dx.doi.org/10.22441/incomtech.v3i1.1114.

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Orthogonal Frequency Division Multiplexing (OFDM) merupakan suatu teknik transmisi yang menggunakan beberapa buah frekuensi pembawa (multicarrier) dalam satu saluran dimana setiap frekuensi pembawa tersebut saling orthogonal (tegak lurus). OFDM banyak dipakai untuk sistem komunikasi wireless mengingat kemampuan dari OFDM mengatasi multipath fading yang menyebabkan terjadinya intersymbol interference (ISI). Dampak dari ISI tersebut adalah penerima tidak dapat membaca sandi informasi dengan benar sehingga mengurangi performasi sistem komunikasi digital. Cara OFDM mengatasi ISI adalah dengan menggandakan simbol dan menambah simbol secara periodik yang digunakan sebagai guard interval. Penambahan dari guard band yang terlalu lebar bisa mengurangi throughput data yang dikirimkan. Fading juga menyebabkan amplitudo dan phasa berfluktuatif sehingga cara untuk mengatasinya adalah estimasi kanal (Channel Estimation) dengan menyisipkan simbol pilot pada pengiriman frame OFDM sehingga penerima dapat memperkirakan karakteristik kanal dan dapat mengembalikan data yang terkirim. CE terdiri atas comb-type pilot channel estimation dan block-type pilot channel estimation. DVB-T sebagai penyiaran televisi digital terestrial juga memakai OFDM dengan skema modulasi OFDM tambahan yaitu berupa pilot simbol atau yang lebih dikenal dengan estimasi kanal (Channel Estimation). Mengingat jumlah subcarrier dari DVB-T cukup besar jika dibandingkan dengan aplikasi lain yang menggunakan OFDM maka perlu dilakukan sebuah penelitian tentang analisa performasi penggunaan OFDM untuk sistem DVB-T terhadap perubahan guard interval, modulasi dan penggunaan kanal pada estimasi kanal tersebut.

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39

Zhang, Tianhong, Limei Xu, Kaiyu Qin i Xiao Yan. "Research on a Unified Framework Based on Linear Frequency Modulation and Orthogonal Frequency-Division Multiplexing". Journal of Computer Networks and Communications 2019 (24.09.2019): 1–7. http://dx.doi.org/10.1155/2019/6587562.

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This paper proposes a unified system framework based on linear frequency modulation (LFM) and orthogonal frequency-division multiplexing (OFDM) as a solution for resource sharing, especially sharing space and hardware. The proposed OFDM-LFM framework can not only transmit data flow by OFDM but also make it possible to extract features from the signal by LFM. Further, the signal features are used to construct a pseudospectrum related to the target speed and distance, thereby estimating the speed and distance of the target. Unified means using signal features to estimate target speed and distance while ensuring data transmission including communication and remote control data information. Besides the traditional data transmission mode, the ability of estimating target speed and distance is an additional benefit. The proposed unified framework makes control of transmission easier and saves more hardware resources. The simulation results show that the proposed LFM-OFDM framework can not only transmit data information including communication and remote control data information, but also estimate the speed and distance of the target by its signal features.

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40

Al-Rawi, M. "Performance analysis of OFDMA and SC-FDMA". International Review of Applied Sciences and Engineering 8, nr 2 (grudzień 2017): 113–16. http://dx.doi.org/10.1556/1848.2017.8.2.2.

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The main challenge in any high-speed digital communication system is how to maximize the data rate with minimizing the bit error rate. Several techniques have been developed to achieve this point. Some of these techniques are orthogonal frequency division multiplexing (OFDM), single-carrier frequency domain equalization (SC-FDE), orthogonal frequency division multiple access (OFDMA), and single-carrier frequency division multiple access (SC-FDMA). These four techniques are described briefly in this paper. Also, the paper measures the performances of OFDMA and SC-FDMA systems over international telecommunication union (ITU) vehicular-A channel using minimum mean square error (MMSE) equalization. Simulation results show that the performances with interleaved mapping outperform that with localized mapping. Also, the performances with quadrature phase shift keying (QPSK) are better than that with 16-ary quadrature amplitude modulation (16QAM). In addition, the performance of SC-FDMA is better than that of OFDMA, when QPSK is used, but the latter is little bit better than that of SC-FDMA when 16QAM is used.

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41

Wang, Fanggang, i Xiaodong Wang. "Coherent Optical DFT-Spread OFDM". Advances in Optical Technologies 2011 (31.03.2011): 1–4. http://dx.doi.org/10.1155/2011/689289.

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We consider application of the discrete Fourier transform-spread orthogonal frequency-division multiplexing (DFT-spread OFDM) technique to high-speed fiber optic communications. The DFT-spread OFDM is a form of single-carrier technique that possesses almost all advantages of the multicarrier OFDM technique (such as high spectral efficiency, flexible bandwidth allocation, low sampling rate, and low-complexity equalization). In particular, we consider the optical DFT-spread OFDM system with polarization division multiplexing (PDM) that employs a tone-by-tone linear minimum mean square error (MMSE) equalizer. We show that such a system offers a much lower peak-to-average power ratio (PAPR) performance as well as better bit error rate (BER) performance compared with the optical OFDM system that employs amplitude clipping.

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42

Uryvsky, Leonid, i Serhii Osypchuk. "OFDM Signal Research with Varied Subcarriers Number". Transport and Telecommunication Journal 17, nr 3 (1.09.2016): 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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Raza, W., X. Ma, A. Ali, A. Ali, A. Raza i S. Shaikh. "Performance Analysis of Selective Mapping in Underwater Acoustic Orthogonal Frequency Division Multiplexing Communication System". Engineering, Technology & Applied Science Research 11, nr 1 (6.02.2021): 6696–702. http://dx.doi.org/10.48084/etasr.3941.

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Under-Water Acoustic (UWA) communication networks are commonly formed by associating various independent UWA vehicles and transceivers connected to the bottom of the sea with battery-operated power modems. Orthogonal Frequency Division Multiplexing (OFDM) is one of the most vital innovations for UWA communications, having improved data rates and the ability to transform fading channels into flat fading. Moreover, OFDM is more robust on Inter-Symbol and Inter-Carrier Interferences (ISI and ICI respectively). However, OFDM technology suffers from a high Peak to Average Power Ratio (PAPR), resulting in nonlinear distortions and higher Bit Error Rates (BERs). Saving power of battery deployed modems is an important necessity for sustainable underwater communications. This paper studies PAPR in UWA OFDM communications, employing Selective Mapping (SLM) as a tool to mitigate PAPR. The proposed SLM with the oversampling factor method proves to be less complex and more efficient. Simulation results indicate that SLM is a promising PAPR reduction method for UWA OFDM communications reducing BER.

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44

Pallavi, C. H., i G. Sreenivasulu. "A High Speed Underwater Wireless Communication Through a Novel Hybrid Opto-Acoustic Modem Using MIMO-OFDM". Instrumentation Mesure Métrologie 20, nr 5 (31.10.2021): 279–87. http://dx.doi.org/10.18280/i2m.200505.

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For efficient underwater opto/acoustic communication, this research proposes the use of MIMO in conjunction with OFDM. OFDM (Orthogonal Frequency-Division Multiplexing) and MIMO (Multiple Input Multiple Output) systems may be widely used in wireless networks to provide high data transfer rates, resistance to multipath fading, and an increase in the channel's Spatial Multiplexing and Spatial Diversity Gain. Transmission speed can be increased by altering bandwidth or spectral efficiency (or both) in wireless data transmission systems. Systems that use Multi-Input Multi-Output (MIMO) technologies have the potential to improve spectral efficiency by employing several transmitters and receivers in tandem. To maximize spectrum efficiency and minimize inter-symbol interference, Orthogonal Frequency Division Multiplexing (OFDM) divides signals into a number of narrow band channels (ISI). In other words, combining the benefits of MIMO with OFDM will boost spectral efficiency while also increasing the link's dependability and spectral gain. MIMO and OFDM approaches are integrated in this research to increase opto-acoustic modem performance. MATLAB Simulink tool was used to design and simulate the proposed hybrid opto-acoustic modem with MIMO-OFDM for optical and acoustic (EM) signal transmission and reception. The simulation results verify the viability of the proposed method, and the measured bit-error rate (BER) for acoustic (EM) signal is 0.4958 and optical signal is 0.5101. The overall bandwidth of the system is from -150 MHz to +150 MHz.

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45

Xie, Feng, Feng Liu i Xiao Hui Ye. "Radar Orthogonal Frequency Division Multiplexing Waveforms Agility Processing with Compressive Sensing". Applied Mechanics and Materials 416-417 (wrzesień 2013): 1181–86. http://dx.doi.org/10.4028/www.scientific.net/amm.416-417.1181.

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CS is a very new method that is being evaluated for many applications, in which signals are sparse in some basis/dictionary, e.g. the radar range profile. In this article, we have formulated the range processing with CS and introduced fair comparisons between matched filter and CS with chirps and OFDM signals. Two relevant features have been inspected: waveform bandwidth and measurement matrix.

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46

Dai, Tianfang. "APR Reduction Technique based on OFDM Pilot Filter Bank Limiting for Satellite Mobile Communications". MATEC Web of Conferences 246 (2018): 03002. http://dx.doi.org/10.1051/matecconf/201824603002.

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Combined with OFDM (Orthogonal Frequency Division Multiplexing), satellite mobile communications will effectively achieve on-demand communication in areas with an ultra-low density of users. With OFDM multiple access optimization, the bandwidth utilization efficiency can be increased by 5 to 10 times. However, satellites are power-constrained systems, so higher PAPR requires greater power backoff, resulting in a decline in satellite transmission capacity. To use OFDM technology in satellites, there are problems such as reduced transmission capacity resulted from high PAPR, complication of lowering PAPR, and difficulty in hardware implementation. In order to deal with the problem of high bit error rate and hardware implementation difficulties in PAPR reduction technique of non-orthogonal frequency division multiplexing, this paper proposes a limiting PAPR reduction technique with OFDM pilot filter banks for satellite mobile communications. Firstly, the applicability of OFDM in satellite mobile communications is analyzed, and the influence of high PAPR on satellite power utilization and the influence of frequency shift sensitivity on inter-satellite communication interference are obtained. Then design the PAPR reduction technique based on the pilot filter bank. By setting the tunable filter bank to the pilot, the sideband power suppression in the OFDM frequency domain is realized, and the PAPR of the OFDM signal is reduced. Finally, the experimental results show that the PAPR performance is improved by 3dB without reducing the bit error rate.

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Ding, Y. H., R. J. Tian, K. Xue, Y. Tian, X. C. Wang, Y. M. Shi i X. Ma. "The Diversity Gains of Amplify-and-Forward Relay System with Frequency Selective Channels". Applied Mechanics and Materials 644-650 (wrzesień 2014): 4297–302. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.4297.

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The diversity gains of amplify-and-forward (AF) relay system with frequency selective channels are discussed. The orthogonal frequency division multiplexing (OFDM) is applied to overcome the inter-symbol interference. The diversity gains are presented for single and multiple relay systems with detailed derivations.

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48

Yang, Gang, Hua Xin Yu i Xiao Fei Zhang. "Compressed Sensing Based Blind Carrier Frequency Offset Estimation for OFDM System". Advanced Materials Research 756-759 (wrzesień 2013): 1894–97. http://dx.doi.org/10.4028/www.scientific.net/amr.756-759.1894.

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In this paper, we address the problem of carrier frequency offset (CFO) estimation for Orthogonal Frequency Division Multiplexing (OFDM) systems. This paper links CFO estimation problem in OFDM systems to the compressed sensing model. Exploiting this link, it derives a compressed sensing-based CFO estimation algorithm. The proposed algorithm has better CFO estimation performance than ESPRIT method with lower signal-to-noise ratio (SNR). Simulation results illustrate performance of this algorithm.

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49

Palle Jagadeeswara Rao and Dr. A S Srinivasa Rao. "PAPR Reduction of OFDM System with Biorthoganoal Wavelet Transforms". International Journal for Modern Trends in Science and Technology, nr 02 (12.02.2021): 17–22. http://dx.doi.org/10.46501/ijmtst0702004.

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Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input and Multiple Output (MIMO) are two main techniques employed in 4th Generation Long Term Evolution (LTE). In OFDM multiple carriers are used and it provides higher level of spectral efficiency as compared to Frequency Division Multiplexing (FDM). In OFDM because of loss of orthogonality between the subcarriers there is intercarrier interference (ICI) and intersymbol interference (ISI) and to overcome this problem use of cyclic prefixing (CP) is required, which uses 20% of available bandwidth. Wavelet based OFDM provides good orthogonality and with its use Bit Error Rate (BER) is improved. Wavelet based system does not require cyclic prefix, so spectrum efficiency is increased. It is proposed to use wavelet transform including biorthoganoal wavelet transform with OFDM systems. This approach will reduce PAPR in the OFDM system effectively. We will design this model with different modulation Techniques like QPSK and QAM and compare the BER results.

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Nahar, Ali, i Mohammed A. Hussein. "A hybrid of the selected mapping and partial transmit sequence approaches for reducing the high peak average to power ratio based on multi-carrier systems – review". Computer Science and Information Technologies 3, nr 1 (1.03.2022): 10–21. http://dx.doi.org/10.11591/csit.v3i1.p10-21.

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

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