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1
Sari, Yolen Perdana y Shelvi Eka Tassia. "Estimasi Carrier Ferquency Offset menggunakan Timing Metric pada Sinyal OFDM". Jurnal Informatika Universitas Pamulang 5, n.º 4 (31 de diciembre de 2021): 466. http://dx.doi.org/10.32493/informatika.v5i4.6725.
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OFDM is one of technology that can be utilized in a variety of telecommunication systems that being widely developed today, for application in LAN, WLAN, 3G, 4G, or 5G. One of the problem faced by the OFDM technology that its sensitivity to Carrier Frequency Offset (CFO) and the lack of synchronization in the OFDM signal. This research aims to design the synchronization that estimates Carrier Frequency Offset (CFO) to obtain synchronization of OFDM signal, where the error of the estimated Carrier Frequency Offset can be obtained, minimized and better than previous studies. The CFO estimation method in this research is using the training symbol on the OFDM symbol and utilize the statistical characteristics of the timing metric. This researchs result shows the Mean Square Error (MSE) of estimated Carrier Frequency Offset to Carrier Frequency Offset input, with range MSE 9.43 x 10-3 at 0 dB SNR input and MSE 1.687 x 10-5 at 30 dB SNR input. If Signal to Noise Ratio is greater, then the value of the mean square error (MSE) will be smaller. The position of the timing metric for timing estimation also affects to CFO estimation. CFO estimation accuracy will be maximized when using maximum timing metric.
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Yang, Gang, Hua Xin Yu y Xiao Fei Zhang. "Compressed Sensing Based Blind Carrier Frequency Offset Estimation for OFDM System". Advanced Materials Research 756-759 (septiembre de 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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Yu, Chang Ha, Young Po Lee, Sun Yong Kim, Gyu In Jee y Seok Ho Yoon. "Estimation of OFDM Carrier Frequency Offset Robust to Offset Variation". Applied Mechanics and Materials 284-287 (enero de 2013): 2642–46. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.2642.
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In this paper, we propose a novel carrier frequency offset (CFO) estimation scheme for orthogonal frequency division multiplexing (OFDM) systems. The proposed scheme has much wider estimation range compared with that of the conventional scheme, making it more robust to the fractional FO variation. Numerical results demonstrate that the proposed scheme has better estimation performance than the conventional scheme for wider fractional FO range.
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Su, Ing Jiunn y Chiao Chan Huang. "Robust MVDR Estimation via Polynomial Rooting for MC-CDMA Carrier Frequency Offset". Applied Mechanics and Materials 284-287 (enero de 2013): 2687–93. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.2687.
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In this letter, we present a blind carrier frequency offset (CFO) estimator by exploiting the polynomial rooting technique for multicarrier-code division multiple access (MC-CDMA) systems. Relative high accuracy and low-complexity to the CFO estimation can be achieved by rooting a polynomial. Simulation results are provided for illustrating the effectiveness of the proposed blind polynomial rooting estimator.
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Wang, Yung-Yi, Bo-Rui Chen y Chih-Hsiang Hsu. "Efficient Maximum Likelihood Algorithm for Estimating Carrier Frequency Offset of Generalized Frequency Division Multiplexing Systems". Mathematics 11, n.º 15 (7 de agosto de 2023): 3426. http://dx.doi.org/10.3390/math11153426.
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This study presents a computationally efficient maximum likelihood (ML) algorithm for estimating the carrier frequency offset (CFO) of generalized frequency division multiplexing systems. The proposed algorithm uses repetitive subsymbols and virtual carriers to estimate the fractional and integer CFOs, respectively. Through the use of repetitive subsymbols, this study first calculates the ML estimate of the fractional CFO in the time domain and then, accordingly, compensates for it from the received signal. The integer CFO can then be estimated through a virtual-carrier-mapping process in the frequency domain. In addition to improving performance in terms of estimation accuracy and computational complexity, the proposed non-data-aided algorithm is spectrally efficient relative to traditional algorithms.
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Cheng, Wang, Cao Yushi y Wang Weidong. "Data-Aided Frequency Offset Estimation for CE-OFDM Broadband Satellite Systems". Applied Sciences 9, n.º 11 (5 de junio de 2019): 2310. http://dx.doi.org/10.3390/app9112310.
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In recent years, the constant-envelope orthogonal frequency-division multiplexing (CE-OFDM) has been considered as a candidate waveform in broadband satellite systems as it has a 0-dB peak-to-average power ratio (PAPR). However, the carrier frequency offset (CFO) estimation scheme for CE-OFDM broadband satellite systems directly affects system performance. In this paper, we analyze the network architecture and the propagation environment of CE-OFDM broadband satellite systems, and we propose a data-aided CFO estimation strategy based on the frequency domain pilot symbols. The Cramer–Rao bound (CRB) of our CFO estimator is given by mathematical analysis, and the effect of the number of pilot symbols on the estimation performance is analyzed. The pilot symbol-based CFO estimator is composed of a phase demodulator and a discrete Fourier transform (DFT) module, and it can obtain a large estimation range under a small pilot overhead. The simulation results show that the CE-OFDM broadband satellite systems can achieve a good bit error rate (BER) performance by using the proposed strategy to estimate and compensate the CFO.
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Peng, Gang, Rui Li, Yushu He y Zhiren Han. "Timing and Frequency Synchronization Using CAZAC Sequences for OFDM Systems". Sensors 23, n.º 6 (16 de marzo de 2023): 3168. http://dx.doi.org/10.3390/s23063168.
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Since orthogonal frequency division multiplexing (OFDM) systems are very susceptible to symbol timing offset (STO) and carrier frequency offset (CFO), which cause inter-symbol interference (ISI) and inter-carrier interference (ICI), accurate STO and CFO estimations are very important. In this study, first, a new preamble structure based on the Zadoff–Chu (ZC) sequences was designed. On this basis, we proposed a new timing synchronization algorithm, called the continuous correlation peak detection (CCPD) algorithm, and its improved algorithm: the accumulated correlation peak detection (ACPD) algorithm. Next, the correlation peaks that were obtained during the timing synchronization were used for the frequency offset estimation. For this, the quadratic interpolation algorithm was adopted as the frequency offset estimation algorithm, which was better than the fast Fourier transform (FFT) algorithm. The simulation results showed that when the correct timing probability reached 100%, under the parameters of m = 8 and N = 512, the performance of the CCPD algorithm was 4 dB higher than that of Du’s algorithm, and that of the ACPD algorithm was 7 dB. Under the same parameters, the quadratic interpolation algorithm also had a great performance improvement in both small and large frequency offsets, when compared with the FFT algorithm.
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Wang, Haijun, Weihua Jiang, Qing Hu, Jianjun Zhang y Yanqing Jia. "Differential Evolution Algorithm-Aided Time-Varying Carrier Frequency Offset Estimation for OFDM Underwater Acoustic Communication". Journal of Marine Science and Engineering 10, n.º 12 (28 de noviembre de 2022): 1826. http://dx.doi.org/10.3390/jmse10121826.
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Orthogonal frequency division multiplexing (OFDM) is the preferred scheme for high-speed communication in the field of underwater acoustic communication. However, it is very sensitive to the carrier frequency offset (CFO). This study used a time-varying CFO estimation method aided by the differential evolution (DE) algorithm to accurately estimate the CFO of an OFDM system. This method was based on the principle that the received OFDM signal with inter-carrier interference could be considered by a Multi Carrier-code division multiple access (MC-CDMA) system on the receiver side because MC-CDMA is a technology that combines OFDM and code division multiple access (CMDA). Because it is suitable for solving problems where there are dependencies between adjacent variables, the DE algorithm was used to capture the varying CFO values on the adjacent blocks. The spreading code of the MC-CDMA was obtained based on the estimated CFO values, which were elements in the DE solutions. Then the received signal was reconstructed. The Root-Mean-Square Error between the reconstructed and actual received signals was used as the cost function, and the CFO was estimated using the DE algorithm because of its powerful parallel search capability. The simulation results showed that the proposed method had a high estimation accuracy. Compared with other intelligent optimization algorithms such as the genetic algorithm and simulated annealing mutated-genetic algorithm, the time-varying CFO estimation performance of the DE algorithm was better because of its unique ability to solve problems with dependencies between adjacent variables. Specifically, under the condition of a high signal-to-noise ratio, the improvement of estimation accuracy reaches 36.13%, and the Bit Error Rate of demodulation is thus reduced by 75%, compared with the reference algorithms. In addition, the proposed method also has good applicability to modulation methods. For phase-shift keying and quadrature amplitude modulation, in particular, the proposed method not only achieved high-precision time-varying CFO estimation values, but also reduced the demodulation deterioration caused by noise.
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Sastry, K. Seshadri, K. Baburao, A. V. Prabu y 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 de enero de 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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Masmoudi, Ramadhan. "New Iterative Method for Estimation of Carrier Frequency in Multicarrier Systems". Algerian Journal of Renewable Energy and Sustainable Development 01, n.º 01 (15 de junio de 2019): 24–30. http://dx.doi.org/10.46657/ajresd.2019.1.1.3.
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The key problem for OFDM (Orthogonal Frequency Division Multiple) systems is who to Estimate carrier frequency offset (CFO) with reduced complexity and acceptable performance. The CFO must be compensated before DFT (Discrete Fourier Transform) in order to restore data correctly and enhance the system performance. This paper, present a low complexity estimator of CFO with Semi-Blind (SB) criterion based on pilot tones and on virtual subcarriers, and with the aid of subspace based method. However, MUSIC and ESPRIT based semi-blind algorithms require a highly computational complexity. To overcome this drawback, we use Taylor’s series for the first order as developed in [1]. The present methods developed in this paper are very suitable for Multi- Carrier (MC) systems when the CFO are present. Simulation results demonstrated that the semi-blind (SB) approach outperforms the blind-based approach.
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CHITRA, S. y N. KUMARATHARAN. "AN EFFICIENT CFO ESTIMATION AND ICI REDUCTION IN MC-CDMA SYSTEM THROUGH CONJUGATE WEIGHTED MUSIC BASED RPRCC SCHEME". Latin American Applied Research - An international journal 46, n.º 4 (31 de octubre de 2016): 153–59. http://dx.doi.org/10.52292/j.laar.2016.347.
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Multicarrier code division multiple access (MC-CDMA) is one of the most attractive method for future broadband wireless systems and long term evolution (LTE) standard. The performance of MC-CDMA systems is greatly deteriorated by carrier frequency offset (CFO) which is due to oscillator instability and Doppler shifts. CFO leads to loss of orthogonality between the subcarriers and introduces intercarrier interference (ICI). Among the numerous ICI cancellation techniques, the proposed receiver phase rotated conjugate cancellation (RPRCC) offers greater ICI reduction compared to other methods. The distributed nature of networks and concurrent transmission from multiple users in uplink, RPRCC needs multiple frequency offset estimation at the receiver. Multiple signal classification (MUSIC) algorithm is the best suited CFO estimation technique in multiuser environment. However the performance of MUSIC algorithm is inferior for closely spaced CFOs. To achieve precise CFO estimation and greater ICI reduction, RPRCC with conjugate weighted MUSIC based CFO estimation is proposed in this paper. The simulation results depict that the ICI power reduction capability and BER performance of the suggested method outperforms the conventional techniques in both properly and closely spaced CFOs.
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Rahbari, Fahimeh y Hamid Reza Bakhshi. "Timing Synchronization and Frequency Offset Estimation for OFDMA/TDD Mode in Downlink of IEEE 802.16-2004". International Journal of Electronics and Telecommunications 58, n.º 3 (septiembre de 2012): 261–66. http://dx.doi.org/10.2478/v10177-012-0036-0.
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Abstract Timing and frequency synchronization are the important task in receiver. This paper proposes a timing synchronization and carrier frequency offset (CFO) estimation algorithm for orthogonal frequency division multiple access (OFDMA) downlink in IEEE 802.16e standard. This method has high performance and estimates CFO. The proposed scheme utilizes the conjugate symmetry property of preamble structure. Simulations are conducted for AWGN and multipath channels to demonstrate the performance of the proposed timing metric. Our proposed method can achieve reasonable performance at low SNR.
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Jung, Yong-An y Young-Hwan You. "Effective Blind Frequency Offset Estimation Scheme for BST-OFDM Based HDTV Broadcast Systems". Symmetry 10, n.º 9 (3 de septiembre de 2018): 379. http://dx.doi.org/10.3390/sym10090379.
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The integrated services digital broadcasting-terrestrial (ISDB-T) system is designed in order to accommodate high-quality video/audio and multimedia services, using band segmented transmission orthogonal frequency division multiplexing (BST-OFDM) scheme. In the ISDB-T system, the pilot configuration varies depending on whether a segment uses a coherent or differential modulation. Therefore, it is necessary to perform a joint estimation of carrier frequency offset (CFO) and sampling frequency offset (SFO) independent of the segment format in the ISDB-T system. The goal is to complete those synchronization tasks while considering an information-carrying transmission and multiplexing configuration control (TMCC) signal as pilot symbols. It is demonstrated through numerical simulations that the differential BPSK-modulated TMCC information can be efficiently used for a least-squares estimation of CFO and SFO, offering an acceptable performance.
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Pabbati, Omkar y Rutvij Joshi. "Performance Analysis of ML-based Low Complex CFO Estimation for MIMO-OFDMA Uplink Systems". ECTI Transactions on Electrical Engineering, Electronics, and Communications 20, n.º 3 (15 de octubre de 2022): 307–14. http://dx.doi.org/10.37936/ecti-eec.2022203.246952.
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Carrier frequency offset (CFO) estimation in multiuser multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system is investigated in this study. MIMO-OFDM is very sensitive to CFOs due to oscillator frequency mismatch and/or Doppler shift. Inaccurate CFO estimation results in intercarrier interference (ICI) through the loss of orthogonality among subcarriers. In this paper, the performance of the ML and APFE algorithm is analyzed for CFO estimation. ML becomes extremely complex due to the multidimensional exhaustive search issue, which is the basic concern in ML estimation. However, making use of the iterative low complex APFE method, here this multidimensional search is replaced with a sequence of mono-dimensional searches. This results in an estimation algorithm of reasonable complexity which is suitable for practical applications. In addition, ML accuracy is compared with the Cramer-Rao bound (CRB).
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N., Rashmi y Mrinal Sarvagya. "Self-improved grey wolf optimization for estimating carrier frequency offset in SCM-OFDM systems". International Journal of Pervasive Computing and Communications 16, n.º 1 (2 de enero de 2020): 53–73. http://dx.doi.org/10.1108/ijpcc-03-2019-0020.
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Purpose The purpose of this paper is to demonstrate a proficiency for accomplishing optimal CFO and keep down the error among the received and transmitted signal. Orthogonal frequency-division multiplexing (OFDM) is considered as an attractive modulation scheme that could be adopted in wireless communication systems owing to its reliability in opposition to multipath interruptions under different subchannels. Carrier frequency offset (CFO) establishes inter-carrier interference that devastates the orthogonality between the subcarriers and fluctuates the preferred signal and minimizes the effectual signal-to-noise ratio (SNR). This results in corrupted system performance. For sustaining the subcarriers’ orthogonality, timing errors and CFOs have to be approximated and sufficiently compensated for. Single carrier modulation (SCM) is a major feature for efficient OFDM system. Design/methodology/approach This paper introduces a novel superposition coded modulation-orthogonal frequency-division multiplexing (SCM-OFDM) system with optimal CFO estimation using advanced optimization algorithm. The effectiveness of SCM-OFDM is validated by correlating the transmitted and received signal. Hence, the primary objective of the current research work is to reduce the error among the transmitted and received signal. The received signal involves CFO, which has to be tuned properly to get the signal as closest as possible with transmitted signal. The optimization or tuning of CFO is done by improved grey wolf optimization (GWO) called GWO with self-adaptiveness (GWO-SA). Further, it carries the performance comparison of proposed model with state-of-the-art models with the analysis on bit error rate (BER) and mean square error (MSE), thus validating the system’s performance. Findings From the analysis, BER of the proposed and conventional schemes for CFO at 0.25 was determined, where the adopted scheme at 10th SNR was 99.6 per cent better than maximum likelihood, 99.6 per cent better than least mean square (LMS), 99.3 per cent better than particle swarm optimization (PSO), 75 per cent better than genetic algorithm (GA) and 25 per cent better than GWO algorithms. Moreover, MSE at 1st SNR, the proposed GWO-SA scheme, is 4.62 per cent better than LMS, 60.1 per cent better than PSO, 37.82 better than GA and 67.85 per cent better than GWO algorithms. Hence, it is confirmed that the performance of SCM-OFDM system with GWO-SA-based CFO estimation outperformed the state-of-the-art techniques. Originality/value This paper presents a technique for attaining optimal CFO and to minimize the error among the received and transmitted signal. This is the first work that uses GWO-SA for attaining optimal CFO.
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Qu, Fengzhong, Zhengchao Li, Minhao Zhang, Xingbin Tu y Yan Wei. "A Carrier-Based Gardner Timing Synchronization Algorithm for BPSK Signal in Maritime Communication". Journal of Marine Science and Engineering 11, n.º 4 (13 de abril de 2023): 829. http://dx.doi.org/10.3390/jmse11040829.
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Wireless communication at sea is an essential way to establish a smart ocean. In the communication system, however, signals are affected by the carrier frequency offset (CFO), which results from the Doppler effect and crystal frequency offset. The offset deteriorates the demodulation performance of the communication system. The conventional Gardner bit-synchronization algorithm performs timing synchronization on the baseband, but it fails to solve the problem of carrier frequency offset. In this paper, a carrier-based timing-synchronization Gardner algorithm was proposed. The algorithm performed error detection in the carrier signal to estimate the synchronization error in real time and the time-domain expansion in the passband signal. Based on the estimated expansion factor, the algorithm located the sampling points of the ideal signal and re-interpolated all the sampling points on the passband to recover the passband signal without Doppler. This algorithm can solve both the frequency shift and time-domain expansion caused by the Doppler effect without further CFO estimation and compensation, thus reducing the overall computational complexity of the system. The simulations showed that the proposed algorithm greatly improves the ability of the communication system to combat Doppler compared to the conventional Gardner algorithm. The algorithm is primarily designed for binary phase-shift keying (BPSK)-modulated signals under the additive white Gaussian noise (AWGN) channel and can be applied to various maritime communication scenarios.
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Wang, Zhenyi, Shengyun Wei, Li Zou, Feifan Liao, Weimin Lang y Yuanzhuo Li. "Deep-Learning-Based Carrier Frequency Offset Estimation and Its Cross-Evaluation in Multiple-Channel Models". Information 14, n.º 2 (6 de febrero de 2023): 98. http://dx.doi.org/10.3390/info14020098.
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The most widely used Wi-Fi wireless communication system, which is based on OFDM, is currently developing quickly. The receiver must, however, accurately estimate the carrier frequency offset between the transmitter and the receiver due to the characteristics of the OFDM system that make it sensitive to carrier frequency offset. The autocorrelation of training symbols is typically used by the conventional algorithm to estimate the carrier frequency offset. Although this method is simple to use and low in complexity, it has poor estimation performance at low signal-to-noise ratios, which has a significant negative impact on the performance of the wireless communication system. Meanwhile, the design of the communication physical layer using deep-learning-based (DL-based) methods is receiving more and more attention but is rarely used in carrier frequency offset estimation. In this paper, we propose a DL-based carrier frequency offset (CFO) model architecture for 802.11n standard OFDM systems. With regard to multipath channel models with varied degrees of multipath fadding, the estimation error of the proposed model is 70.54% lower on average than that of the conventional method under 802.11n standard channel models, and the DL-based method can outperform the estimation range of conventional methods. Besides, the model trained in one channel environment and tested in another was cross-evaluated to determine which models could be used for deployment in the real world. The cross-evaluation demonstrates that the DL-based model can perform well over a large class of channels without extra training when trained under the worst-case (most severe) multipath channel model.
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Häring, L. y A. Czylwik. "Synchronization in MIMO OFDM systems". Advances in Radio Science 2 (27 de mayo de 2005): 147–53. http://dx.doi.org/10.5194/ars-2-147-2004.
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Abstract. In this paper, an overview of carrier frequency offset (CFO) estimation algorithms for Orthogonal Frequency Division Multiplexing (OFDM) systems is presented. It is well-known that multicarrier systems suffer from their high sensitivity to mismatches of transmitter and receiver oscillator frequencies. The performance degrades since the CFO destroys the orthogonality of the subcarriers. Hence, extensive research has been done on the estimation and correction of the CFO in Single-Input Single-Output (SISO) systems. Mainly, the proposed algorithms can be categorized into data-aided and blind techniques. Several estimation techniques have been extended to the Single-Input Multiple- Output (SIMO) case where multiple receive antennas can be utilized to gain diversity. However, less attention has been paid on synchronization in the attractive Multiple-Input Multiple-Output (MIMO) case which is topic of tremendous interest in current research. The present paper concentrates on aspects of this new scenario. Starting with algorithms for SISO and SIMO, this contribution reviews briefly proposed carrier frequency synchronization techniques which could be implemented in forthcoming MIMO systems.
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Liu, Yun, Fei Ji, Hua Yu, Dehuan Wan, Fangjiong Chen y Ling Yang. "Robust Preamble-Based Timing Synchronization for OFDM Systems". Journal of Computer Networks and Communications 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/9319272.
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This study presents a novel preamble-based timing offset estimation method for orthogonal frequency division multiplexing (OFDM) systems. The proposed method is robust, immune to the carrier frequency offset (CFO), and independent of the structure of the preamble. The performance of the new method is demonstrated in terms of mean square error (MSE) obtained by simulation in multipath fading channels. The results indicate that the new method significantly improves timing performance in comparison with existing methods.
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Abshir, Abdul Gani, M. M. Abdullahi y Md Abdus Samad. "A Comparative Study of Carrier Frequency Offset (CFO) Estimation Techniques for OFDM Systems". IOSR Journal of Electronics and Communication Engineering 9, n.º 4 (2014): 01–06. http://dx.doi.org/10.9790/2834-09440106.
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Shao, Gang, Wen-qin Wu, Lei Yin, Chen-yang Ding y Xiao-yuan Zhang. "Spatial-Frequency Estimation for OFDM System with Coprime Array". Wireless Communications and Mobile Computing 2021 (27 de mayo de 2021): 1–9. http://dx.doi.org/10.1155/2021/9998342.
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Orthogonal frequency division multiplexing (OFDM) is the key technique of the communication system. In this paper, coprime array is designed in OFDM system to obtain joint direction of arrival (DOA) and carrier frequency offset (CFO) estimates. The proposed system can achieve beamforming and adaptive signal processing, reduce the multipath fading, and attain angle diversity. Meanwhile, coprime array has the advantages of extended array aperture, increased degrees of freedom, and reduced mutual coupling effect, which is adaptable in OFDM system. Moreover, this paper proposes a low-complexity parameter algorithm with superior performance, which first exploits propagator method (PM) as the initialization and then parallel factor (PARAFAC) method is employed for the accurate DOA and CFO estimation. Simulation results verify the effectiveness of the OFDM coprime array system and the proposed low-complexity multiparameter algorithm.
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Chang, Qing Wen, Xiao Hong Shen y Juan Chang. "Research on the Doppler Shift Mitigation Scheme for OFDM Underwater Acoustic Communication". Applied Mechanics and Materials 135-136 (octubre de 2011): 820–25. http://dx.doi.org/10.4028/www.scientific.net/amm.135-136.820.
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Doppler shift decreases the estimation accuracy of carrier frequency and may result in divergent estimation. It thus degrades the performance of orthogonal frequency division multiplexing (OFDM) underwater acoustic (UWA) communication system. In this paper, the two-step Doppler shift mitigation scheme[4] was adopted to mitigate the Doppler effect. The innovation lied in the second step in which an enhanced carrier frequency offset (CFO) two-time estimation approach on basis of the pilot was proposed to improve the Doppler shift mitigation scheme. In addition, the new Doppler shift mitigation scheme with the proposed approach was implemented in the OFDM communication system under the simulated multipath-spread channel environment. The experiment results show that the new scheme is able to improve the performance of OFDM UWA communication significantly.
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GONZÁLEZ-BAYÓN, JAVIER, ANGEL FERNÁNDEZ-HERRERO y CARLOS CARRERAS. "EVALUATION OF RAPID PROTOTYPING SOLUTIONS FOR A 802.16D FREQUENCY OFFSET ESTIMATION SCHEME". Journal of Circuits, Systems and Computers 21, n.º 07 (noviembre de 2012): 1250056. http://dx.doi.org/10.1142/s0218126612500569.
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Synchronization of the carrier frequency offset (CFO) is a critical task in orthogonal frequency division multiplexing systems. Imperfect estimation of the CFO causes inter-carrier interference (ICI) that severely degrades the performance of the communications system. Although this is a well studied subject at the algorithmic level, more research is needed when considering implementations in real hardware. Translation of an algorithmic specification to a hardware language is a time consuming task for the designer. This task is more difficult when the target technology offers limited resources, as in the case of field programmable gate arrays (FPGAs). Some rapid prototyping tools, as System Generator from Xilinx or Synplify DSP from Synopsys Synplicity, are available for the designer to facilitate this task. However, their performance has not been evaluated in the literature. Therefore, the goal of this paper is to present an illustrating example of an implementation methodology using these tools and to evaluate their performance when considering a real design. In particular, several FPGA implementations of a frequency synchronization scheme for the 802.16d (fixed WiMAX) standard using these rapid prototyping tools are studied and evaluated. The results from the different solutions are analyzed and compared to draw conclusions about their advantages and drawbacks.
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Luo, Jian, Wilhelm Keusgen y Andreas Kortke. "Efficient Joint Estimation and Compensation of CFO, Tx/Rx Frequency-Selective I/Q Imbalance, and the MIMO Radio Channel in OFDM Systems". Journal of Electrical and Computer Engineering 2013 (2013): 1–20. http://dx.doi.org/10.1155/2013/679032.
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MIMO OFDM is a very promising technique for future wireless communication systems. By applying direct conversion architecture, low-cost, low-power, small size, and flexible implementation of MIMO OFDM systems can be realized. However, the performance of direct conversion architecture-based MIMO OFDM systems can be seriously affected by RF impairments incling carrier frequency offset (CFO) and I/Q-imbalance. While OFDM is sensitive to CFO, direct conversion architecture is sensitive to I/Q imbalance. Such RF impairments aggravate as the carrier frequency becomes higher for example, beyond 60 GHz. To achieve the desired high performance of MIMO OFDM, such RF impairments have to be compensated for. In this paper, the joint compensation of CFO, transmitter and receiver frequency-selective I/Q imbalance, and the MIMO radio channel is investigated. Two preamble-based schemes are proposed for impairment parameter estimation. The proposed preambles are constructed both in time and frequency domains and require much less overhead than the state-of-the-art designs. Furthermore, much lower computational complexity is allowed, enabling efficient implementation. The advantages and effectiveness of both proposed schemes are compared and verified by numerical simulations and complexity analysis.
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Jiang, Yufei, Zhu Xu, Enggee Lim y Huang Yi. "Orthogonal sequences based multi-CFO estimation and semi-blind ICA based equalization for multiuser comp systems". Computer Science and Information Systems 9, n.º 4 (2012): 1385–406. http://dx.doi.org/10.2298/csis120303051j.
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We propose a low-complexity carrier frequency offset (CFO) estimation approach and an independent component analysis (ICA) based semi-blind equalization structure for the orthogonal frequency division multiplexing (OFDM) based multiuser coordinated multi-point (CoMP) systems. A group of orthogonal sequences are employed to enable separation and simultaneous estimation of multiple CFOs at base stations, dividing a complex multi-dimensional search into series of low-complexity mono-dimensional searches. Then, a small number of pilot symbols attached to the source data, are used to resolve the ambiguity problem in the ICA equalized signals. It has a low complexity, as the permutation and quadrature ambiguity can be eliminated simultaneously, rather than sequentially by the previous precoding aided method. Simulation results show that the proposed semi-blind equalization structure has a bit error rate (BER) performance close to the ideal cases of the zero forcing (ZF) and minimum mean square error (MMSE) based equalization with perfect channel state information (CSI) and no CFO, and also significantly outperforms the constant amplitude zero autocorrelation (CAZAC) sequences based CFO estimation method.
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Mihaljević, Ante, Adriana Lipovac, Vlatko Lipovac y Jasmin Musovic. "Practical BER-Based Estimation of Residual OFDM CFO by Reducing Noise Margin". Wireless Communications and Mobile Computing 2020 (26 de septiembre de 2020): 1–5. http://dx.doi.org/10.1155/2020/8881436.
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The main OFDM drawbacks are Carrier Frequency Offset (CFO) and large Peak-to-Average Power Ratio (PAPR), which both degrade the Bit Error Rate (BER). Specifically, we consider here clipping or any other PAPR reduction method sufficient to prevent the nonlinear high-power amplifier from generating errors. Moreover, in small cells, the signal-to-noise ratio is large, while the small time dispersion allows the OFDM symbol cyclic prefix to prevent intersymbol interference. This retains the CFO to solely determine the BER and vice versa, enabling indirect estimation of CFO-induced phase distortion by simple BER testing. However, a particular problem is measuring very low BER values (generated by alike residual CFO), which could last a long time in order to acquire statistically enough errors. The test time can be drastically reduced if the noise margin is reduced in a controllable way, by adding the interfering signal to each subcarrier at the receiver. This approach is shown to enable efficient and accurate short-term BER (and so CFO phase error) testing.
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Kiayani, Adnan, Lauri Anttila, Yaning Zou y Mikko Valkama. "Advanced Receiver Design for Mitigating Multiple RF Impairments in OFDM Systems: Algorithms and RF Measurements". Journal of Electrical and Computer Engineering 2012 (2012): 1–16. http://dx.doi.org/10.1155/2012/730537.
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Direct-conversion architecture-based orthogonal frequency division multiplexing (OFDM) systems are troubled by impairments such as in-phase and quadrature-phase (I/Q) imbalance and carrier frequency offset (CFO). These impairments are unavoidable in any practical implementation and severely degrade the obtainable link performance. In this contribution, we study the joint impact of frequency-selective I/Q imbalance at both transmitter and receiver together with channel distortions and CFO error. Two estimation and compensation structures based on different pilot patterns are proposed for coping with such impairments. The first structure is based on preamble pilot pattern while the second one assumes a sparse pilot pattern. The proposed estimation/compensation structures are able to separate the individual impairments, which are then compensated in the reverse order of their appearance at the receiver. We present time-domain estimation and compensation algorithms for receiver I/Q imbalance and CFO and propose low-complexity algorithms for the compensation of channel distortions and transmitter IQ imbalance. The performance of the compensation algorithms is investigated with computer simulations as well as with practical radio frequency (RF) measurements. The performance results indicate that the proposed techniques provide close to the ideal performance both in simulations and measurements.
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Abdul Majed, Mahmood Mohmmmed saeed y Buthaina Mosa Omran. "Pilot Based Channel Estimation and Synchronization in OFDM System". Journal of Engineering 26, n.º 6 (1 de junio de 2020): 50–59. http://dx.doi.org/10.31026/j.eng.2020.06.04.
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Channel estimation and synchronization are considered the most challenging issues in Orthogonal Frequency Division Multiplexing (OFDM) system. OFDM is highly affected by synchronization errors that cause reduction in subcarriers orthogonality, leading to significant performance degradation. The synchronization errors cause two issues: Symbol Time Offset (STO), which produces inter symbol interference (ISI) and Carrier Frequency Offset (CFO), which results in inter carrier interference (ICI). The aim of the research is to simulate Comb type pilot based channel estimation for OFDM system showing the effect of pilot numbers on the channel estimation performance and propose a modified estimation method for STO with less number of pilot to mitigate ISI effect. Channel estimation is simulated for different pilot number with 16QAM modulation in Ped-A Rayleigh channel. The STO effect assumed less than the cyclic prefix length to minimize ISI and maintain the orthogonality between subcarriers. The simulation results show that the high number of pilots are needed to achieve good channel estimation in case no synchronization used while similar results are achieved with smaller number of pilots if the propose modification on the synchronization method are used aligned with the channel estimation. The proposed system is evaluated in terms of BER and SNR.
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Lipovac, Adriana, Vlatko Lipovac y Pamela Njemčević. "Suppressing the OFDM CFO-Caused Constellation Symbol Phase Deviation by PAPR Reduction". Wireless Communications and Mobile Computing 2018 (1 de agosto de 2018): 1–8. http://dx.doi.org/10.1155/2018/3497694.
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The well-known major drawbacks of the Orthogonal Frequency-Division Multiplexing (OFDM), namely, the transmitter versus receiver Carrier Frequency Offset (CFO), and the Peak-to-Average Power Ratio (PAPR) of the transmitted OFDM signal, may degrade the error performance, by causing Intercarrier Interference (ICI), as well as in-band distortion and adjacent channel interference, respectively. Moreover, in spite of the utmost care given to CFO estimation and compensation in OFDM wireless systems, such as wireless local networks or the mobile radio systems of the fourth generation, e.g., the Long-Term Evolution (LTE), still some residual CFO remains. With this regard, though so far the CFO and the PAPR have been treated independently, in this paper, we develop an Error Vector Magnitude (EVM) based analytical model for the CFO-induced constellation symbol phase distortion, which essentially reveals that the maximal CFO-caused squared phase deviation is linear with the instantaneous (per-OFDM-symbol) PAPR. This implies that any PAPR reduction technique, such as simple clipping or coding, indirectly suppresses the CFO-induced phase deviation, too. The analytically achieved results and conclusions are tested and successfully verified by conducted Monte Carlo simulations.
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Lipovac, Adriana, Vlatko Lipovac y Borivoj Modlic. "Efficient Estimation of CFO-Affected OFDM BER Floor in Small Cells with Resource-Limited IoT End-Points". Sensors 20, n.º 13 (4 de julio de 2020): 3747. http://dx.doi.org/10.3390/s20133747.
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Contemporary wireless networks dramatically enhance data rates and latency to become a key enabler of massive communication among various low-cost devices of limited computational power, standardized by the Long-Term Evolution (LTE) downscaled derivations LTE-M or narrowband Internet of Things (NB IoT), in particular. Specifically, assessment of the physical-layer transmission performance is important for higher-layer protocols determining the extent of the potential error recovery escalation upwards the protocol stack. Thereby, it is needed that the end-points of low processing capacity most efficiently estimate the residual bit error rate (BER) solely determined by the main orthogonal frequency-division multiplexing (OFDM) impairment–carrier frequency offset (CFO), specifically in small cells, where the signal-to-noise ratio is large enough, as well as the OFDM symbol cyclic prefix, preventing inter-symbol interference. However, in contrast to earlier analytical models with computationally demanding estimation of BER from the phase deviation caused by CFO, in this paper, after identifying the optimal sample instant in a power delay profile, we abstract the CFO by equivalent time dispersion (i.e., by additional spreading of the power delay profile that would produce the same BER degradation as the CFO). The proposed BER estimation is verified by means of the industry-standard LTE software simulator.
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Chen, Chien-Sheng, Chyuan-Der Lu, Ho-Nien Shou y Le-Wei Lin. "Baseband Transceiver Design of a High Definition Radio FM System Using Joint Theoretical Analysis and FPGA Implementation". International Journal of Antennas and Propagation 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/580479.
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Advances in wireless communications have enabled various technologies for wireless digital communication. In the field of digital radio broadcasting, several specifications have been proposed, such as Eureka-147 and digital radio mondiale (DRM). These systems require a new spectrum assignment, which incurs heavy cost due to the depletion of the available spectrum. Therefore, the in-band on-channel (IBOC) system has been developed to work in the same band with the conventional analog radio and to provide digital broadcasting services. This paper discusses the function and algorithm of the high definition (HD) radio frequency modulation (FM) digital radio broadcasting system. Content includes data format allocation, constellation mapping, orthogonal frequency division multiplexing (OFDM) modulation of the transmitter, timing synchronization, OFDM demodulation, integer and fraction carrier frequency (integer carrier frequency offset (ICFO) and fractional CFO (FCFO)) estimation, and channel estimation of the receiver. When we implement this system to the field programmable gate array (FPGA) based on a hardware platform, both theoretical and practical aspects have been considered to accommodate the available hardware resources.
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Younis, Sedik, A. Al-Dweik, Bayan Sharif y C. C. Tsimenidis. "Architectural Exploration of Blind CFO Estimation in OFDM Systems for Prototyping on a Reconfigurable Platform". Kurdistan Journal of Applied Research 2, n.º 3 (27 de agosto de 2017): 147–51. http://dx.doi.org/10.24017/science.2017.3.4.
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This paper presents two architectures for prototyping an advanced carrier frequency offset (CFO) estimation technique for OFDM systems on field programmable gate array (FPGA). The parallel stream architecture (PSA) exploits the FPGA parallelism while the multiplexed stream architecture (MSA) employs multiplexing for more efficient hardware implementation. The dual-mode of operation for the proposed architectures has been proposed to achieve optimum performance depending on channel conditions. The proposed architectures with different implementation alternatives have been simulated and verified for FPGA implementation using the Xilinx’s DSP design flow. The estimation accuracy and the resource utilization for the proposed architectures have been evaluated. The prototyping results showed that MSA allows for more resource efficient implementation, where a single FFT core can be shared between parallel streams compared with PSA.
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Ngoc, Nguyen Dinh y Kien Truong. "Phase Impairment Estimation for mmWave MIMO Systems with Low Resolutions ADC and Imperfect CSI". EAI Endorsed Transactions on Industrial Networks and Intelligent Systems 9, n.º 4 (28 de octubre de 2022): e3. http://dx.doi.org/10.4108/eetinis.v9i4.2467.
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Multiple-Input Multiple-Output systems operating at millimeter wave band (mmWave MIMO) are a promising technology next generations of mobile networks. In practice, the non-ideal hardware is a challenge for commercially viable mmWave MIMO transceivers and come from non-linearities of the amplifier, phase noise, quantization errors, mutual coupling between antenna ports, and In-phase/Quadrature (I/Q) imbalance. As a result, the received signals are affected by non-ideal transceiver hardware components, thus reduce the performance of such systems, especially phase impairment caused by phase noise and carrier frequency offset (CFO). In this paper, we consider a mmWave MIMO system model that takes into account many practical hardware impairments and imperfect channel state information (CSI). Our main contributions are a problem formulation of phase impairments with imperfect CSI and a low-complexity estimation method to solve the problem. Numerical results are provided to evaluate the performance of the proposed algorithm.
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Aboltins, Arturs y Nikolajs Tihomorskis. "Software-Defined Radio Implementation and Performance Evaluation of Frequency-Modulated Antipodal Chaos Shift Keying Communication System". Electronics 12, n.º 5 (4 de marzo de 2023): 1240. http://dx.doi.org/10.3390/electronics12051240.
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This paper is devoted to software-defined radio (SDR) implementation of frequency modulated antipodal chaos shift keying (FM-ACSK) transceiver and presents results of prototype testing in real conditions. This novel and perspective class of spread-spectrum communication systems employs chaotic synchronization for the acquisition and tracking of the analog chaotic spreading code and does not need resource-demanding cross-correlation. The main motivation of the given work is to assess the performance of FM-ACSK in real conditions and demonstrate that chaotic synchronization can be considered an efficient spread-spectrum demodulation method. The work focuses on the real-time implementation aspects of the modulation-demodulation algorithms, forward error correction (FEC) and symbol timing synchronization approach in MATLAB Simulink. The performance of the presented prototype is assessed via extensive testing, which includes measurement of bit error ratio (BER) in single-user and multi-user scenarios, estimation of carrier frequency offset (CFO) impact and image transmission over-the-air between two independent sites and comparison with classical frequency hopping spread spectrum (FHSS). The paper shows that the presented class of the spread spectrum communication systems demonstrates good performance in low signal-to-noise ratio (SNR) conditions and in terms of BER significantly outperforms the classic spread-spectrum modulation schemes which employ correlation-based detection.
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Zhou, De Fu y Yong Feng Wang. "A Fast and High Efficiency Carrier Offset Estimator for OFDM". Applied Mechanics and Materials 513-517 (febrero de 2014): 3928–33. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.3928.
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In this paper, a fast and high-efficiency carrier frequency offsets (CFO) estimation algorithm is proposed. This new algorithm exploits the intrinsic structure information of OFDM signals and the unimodality of the cost function for CFO estimation. It reduces the computational complexity by using the golden section method in searching for the extremum of the cost function. The performance of the proposed algorithm is investigated with numerical simulations. The results show that the new algorithm has much lower complexity than Turelis MUSIC-like approach while achieves same performance in both additive white Gaussian noise (AWGN) and multipath fading channels.
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Mohan, K. Jagan, K. Suresh y J. Durga Rao. "Carrier Frequency Offset Estimation Algorithm in the Presence of I/Q Imbalance in OFDM Systems". International Journal of Instrumentation Control and Automation, octubre de 2011, 148–53. http://dx.doi.org/10.47893/ijica.2011.1027.
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In this paper, we analyzed the feasibility of using a virtual carrier based carrier frequency offset estimation algorithm in the presence of I/Q imbalance in OFDM systems. Based on the analysis of the signal model with both receiver CFO and I/Q imbalance impairment we conclude that it is feasible to extending the virtual carrier based CFO estimation algorithm to the I/Q imbalance scenario. The CFO estimation performance is evaluated through computer simulation. Impact of parameters on the estimation performance is investigated and it is consistent with our analysis. After CFO correction, a blind based I/Q imbalance estimation and compensation algorithm is applied. The final detection performance demonstrates that the virtual carrier based CFO estimation performance is good enough for subsequent I/Q imbalance estimation and compensation.
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Cheng, Nan‐Hung, Chien‐Chung Chen, Yi‐Fan Wang y Yung‐Fang Chen. "Adaptive Carrier Frequency Offset Estimation in Interference Environments for OFDMA Uplink Systems". IEEJ Transactions on Electrical and Electronic Engineering, 21 de agosto de 2023. http://dx.doi.org/10.1002/tee.23894.
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In orthogonal frequency division multiple access (OFDMA) systems, carrier frequency offsets (CFOs) influence the different users. In this paper, we proposed a CFO estimation algorithm with strong interference resistant capability for OFDMA systems. The first part of the proposed algorithm processes the received signals so as to deal with the CFO estimation problem. And the second part of the proposed algorithm is to use the proposed adaptive process to obtain the updated CFO estimation and track the parameters' time‐variations. Simulations demonstrate the effectiveness of this method and show that its performance is to the Cramer‐Rao Bounds (CRB). © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.
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Cheng, Qi y Mosin Russell. "Hybrid Cramer-Rao Bound on Carrier and Sampling Frequency Offset Estimation for OFDM Systems in Rayleigh Fading Channels". Wireless Personal Communications, 29 de septiembre de 2022. http://dx.doi.org/10.1007/s11277-022-09978-3.
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AbstractFor the carrier frequency offset (CFO) and sampling (clock) frequency offset (SFO) estimation, the hybrid Cramer-Rao bound (HCRB) is developed when the CFO, SFO, information-bearing symbols are deterministic and channel coefficients are random. Both noise and channel coefficients are complex Gaussian. The HCRB is a lower bound on the mean squared estimation error for any unbiased estimator of a parameter. For the HCRB to be applicable, it is necessary for deterministic parameters to be identifiable (uniquely determined). Some necessary identifiability conditions of some deterministic parameters are found and presented. The HCRB is dependent on the initial time instant. The HCRB is used to assess the performances of some existing methods via simulation. Our results demonstrate that even the best performance is still around 10 dB higher than the HCRB. Further effort is needed to develop more accurate methods.
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Cheng, Nan-Hung, Kai-Chieh Huang, Yung-Fang Chen y Shu-Ming Tseng. "Maximum likelihood-based adaptive iteration algorithm design for joint CFO and channel estimation in MIMO-OFDM systems". EURASIP Journal on Advances in Signal Processing 2021, n.º 1 (13 de enero de 2021). http://dx.doi.org/10.1186/s13634-020-00711-5.
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AbstractIn this paper, we present a joint time-variant carrier frequency offset (CFO) and frequency-selective channel response estimation scheme for multiple input-multiple output-orthogonal frequency-division multiplexing (MIMO-OFDM) systems for mobile users. The signal model of the MIMO-OFDM system is introduced, and the joint estimator is derived according to the maximum likelihood criterion. The proposed algorithm can be separated into three major parts. In the first part of the proposed algorithm, an initial CFO is estimated using derotation, and the result is used to apply a frequency-domain equalizer. In the second part, an iterative method is employed to locate the fine frequency peak for better CFO estimation. An adaptive process is used in the third part of the proposed algorithm to obtain the updated CFO estimation and track parameter time variations, including the time-varying CFOs and time-varying channels. The computational complexity of the proposed algorithm is considerably lower than that of the maximum likelihood-based grid search method. In a simulation, the mean squared error performance of the proposed algorithm was close to the Cramer-Rao lower bound. The simulation results indicate that the proposed novel joint estimation algorithm provides a bit error rate performance close to that in the perfect channel estimation condition. The results also suggest that the proposed method has reliable tracking performance in Jakes’ channel models.
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Lien, Pham Hong y Nguyen Duy Lai. "An Algorithm Combining Synchronization and Channel Estimation for OFDM Systems". Journal of Research and Development on Information and Communication Technology, 28 de octubre de 2009. http://dx.doi.org/10.32913/mic-ict-research.v3.n6.280.
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OFDM (Orthogonal Frequency Division Multiplexing) is more and more popular in applications of digital communications because of the effective spectrum and less impacts of multipath fading. However, beside these advantages, OFDM signals are destroyed easily by errors such as CFO (Carrier Frequency Offset), SFO (Sampling Clock Frequency Offset). Thus, it’s necessaryto have robustly offset algorithms to overcome these disadvantages. Studies about OFDM we just examined channel estimation with assumptions that synchronization is perfect, and vice versa. However, they have a close relationship, channel estimation can be restricted if synchronization is bad, and vice versa. This paper presents an algorithm combining synchronization and channel estimation in OFDM systems. The algorithm is compared with other proposed algorithms by simulation. The simulation result of the algorithm combining synchronization and channel estimation is close to that of ideal conditions: perfect channel estimation and synchronization.
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Manasseh, Emmanuel, Shuichi Ohno y Toru Yamamoto. "Preamble design for estimation and compensation of channel distortion parameters in OFDM systems". APSIPA Transactions on Signal and Information Processing 3 (2014). http://dx.doi.org/10.1017/atsip.2014.2.
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In this paper, preamble design for estimation and compensation of channel distortion parameters (or channel impairments) in orthogonal frequency-division multiplexing (OFDM) transmission over peak-limited channels is studied. Specifically, the designed preamble considers the estimation of frequency selective channels, carrier frequency offset (CFO), in-phase/quadrature-phase (I/Q) imbalance together with the minimization of peak-to-average power ratio (PAPR) of the transmitted signals. In the proposed design, we employ adaptive Markov chain Monte Carlo (AMCMC) techniques to select preamble sequence that minimizes the channel estimate mean-squared error while suppressing the effect of the I/Q mismatch. AMCMC algorithm is also deployed to select phase information to the designed preamble in order to minimize the PAPR of the oversampled preamble signals in time domain. To estimate CFO, maximum likelihood-based scheme that utilizes two successive OFDM preambles is employed, and the CFO is estimated by considering phase rotation between two consecutive received OFDM preambles. Numerical simulations are provided to verify the efficacy of the proposed design.
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"Development of Software Defined Radio Algorithm using Mimo OFDM for Short Range Communication". VOLUME-8 ISSUE-10, AUGUST 2019, REGULAR ISSUE 8, n.º 10 (10 de agosto de 2019): 3994–4003. http://dx.doi.org/10.35940/ijitee.j1047.0881019.
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In the recent past, the software defined radio (SDR) using Multiple-Input-Multiple-Output Orthogonal Frequency Division Multiplex (OFDM) is implemented to improve the data rate and channel estimation with high spectrum and maximum throughput for short range communication. The short range of communication is established to communicate the data between different nodes placed in the appropriate position using localization technique using SDR MIMO OFDM. The 256-M Array Quadrature Amplitude Modulation (256 M-Ary Quartrature Amplitude Modulation) is applied to SDR MIMO OFDM to reduce Modulation Error Rate (MER) for efficient transmission of data through SDR. The high data rate is achieved by applying the beam-forming equalization technique by applying beam-forming between transmitter and receiver of SDR. The Zero-forcing-beam-forming (ZFBF) equalizer is used in frequency domain to correlate transmitter and receiver to improve the spectrum efficiency better. The synchronization error is reduced in the transceiver of SDR by reducing Carrier Frequency Offset (CFO) mismatch and Sampling Time Offset (STO). The simulation results have proved that the proposed algorithm have better performance in data rate improvement with elimination of CFO mismatch problem to improve the spectrum efficiency and higher range of channel estimation.
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Sharma, Srishti y Pradeep Kumar Krishnamurthy. "Reduced sampling rate Kalman filters for carrier phase and frequency offset tracking in 200 Gbps 16 QAM coherent communication system". Scientific Reports 11, n.º 1 (21 de enero de 2021). http://dx.doi.org/10.1038/s41598-020-80822-z.
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AbstractWe propose 1 state and 2 state multi-step Kalman filters (MKFs) to estimate and compensate CFO, LPN and NLPN in long-haul coherent fiber-optic communication systems. The proposed filters generate state estimates once every m symbols and therefore operate at a reduced sampling rate compared to conventional KFs that perform symbol by symbol processing. No computations are performed to obtain phase estimates of the intermediate $$m-1$$ m - 1 samples; instead, the present and previous estimates are averaged and used to derotate the intermediate $$m-1$$ m - 1 samples which are then demodulated to recover the transmitted symbols. This reduces the computational load on the receiver DSP. Further, in order to improve estimation accuracy, we adaptively vary the process noise covariance Q. Simulation results of 200 Gbps PDM 16 QAM system over 12 spans shows that the proposed 1 state MKF can reduce the sampling rate requirement by a factor of $$m = 20$$ m = 20 with Q-factor degradation of 1.32 dB compared to single-step KF at linewidth of 100 kHz. The 2 state MKF tracks PN and CFO with a maximum step size of $$m=10$$ m = 10 for a CFO of 100 MHz at linewidth of 100 kHz. We also study the dynamic performance of the proposed algorithms by applying step change to CFO. The 2 state MKF with adaptive Q is able to track a step change of 400 MHz of CFO with $$m = 1$$ m = 1 and 3 with high estimation accuracy but slower convergence time compared to the non-adaptive 2 state MKF. Finally, we study the computational requirements of the proposed MKFs and show that they offer significant reduction in computations compared to single-step KF thus making the proposed filters suitable for hardware implementation.
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Goel, Ashish. "Performance analysis of ICI self-cancellation schemes in OFDM systems". Journal of Optical Communications, 14 de abril de 2023. http://dx.doi.org/10.1515/joc-2023-0062.
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Abstract Orthogonal frequency division multiplexing (OFDM) is a promising technique in modern high data rate wireless communication system. However, the serious problem in OFDM system is the inter-carrier-interference (ICI) that is produced by the carrier frequency offset (CFO). CFO destroys the orthogonal properties among the sub-carriers and introduces ICI. ICI is a major impairment in OFDM system as it can degrade the bit error rate (BER) performance of the system. In this paper we have proposed an optimal ICI self-cancellation scheme that can maximize the carrier-to-interference-ratio (CIR) of the system. This scheme is based on optimizing the data allocation and combining parameters where, for estimated CFO, the optimized values of these parameters are calculated using Nelder Mead simplex algorithm. An approach to calculate the sub-optimized values of data allocation and combining parameters is also proposed, where the knowledge of CFO estimation can be avoided. In this paper, we have carried out the complete performance analysis of ICI self-cancellation schemes. We have also derived the mathematical expressions for ICI coefficients and presented a comparative analysis of standard OFDM system with different ICI cancellation schemes. The mathematical expressions for CIR and BER performance are further derived. To confirm the validity of the results Monte Carlo simulations using Matlab are also performed. We have also done the comparison of peak-to-average power ratio (PAPR) of conventional ICI self-cancellation scheme and proposed scheme.