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Journal articles on the topic 'RF impairments'

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Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

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1

Luo, Jian, Wilhelm Keusgen, and 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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2

Morge-Rollet, Louis, Frédéric Le Roy, Denis Le Jeune, Charles Canaff, and Roland Gautier. "RF eigenfingerprints, an Efficient RF Fingerprinting Method in IoT Context." Sensors 22, no. 11 (June 5, 2022): 4291. http://dx.doi.org/10.3390/s22114291.

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In IoT networks, authentication of nodes is primordial and RF fingerprinting is one of the candidates as a non-cryptographic method. RF fingerprinting is a physical-layer security method consisting of authenticated wireless devices using their components’ impairments. In this paper, we propose the RF eigenfingerprints method, inspired by face recognition works called eigenfaces. Our method automatically learns important features using singular value decomposition (SVD), selects important ones using Ljung–Box test, and performs authentication based on a statistical model. We also propose simulation, real-world experiment, and FPGA implementation to highlight the performance of the method. Particularly, we propose a novel RF fingerprinting impairments model for simulation. The end of the paper is dedicated to a discussion about good properties of RF fingerprinting in IoT context, giving our method as an example. Indeed, RF eigenfingerprint has interesting properties such as good scalability, low complexity, and high explainability, making it a good candidate for implementation in IoT context.

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3

Kiayani, Adnan, Lauri Anttila, Yaning Zou, and 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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4

Abushattal, Abdelrahman, Salah Eddine Zegrar, Ayhan Yazgan, and Hüseyin Arslan. "A Comprehensive Experimental Emulation for OTFS Waveform RF-Impairments." Sensors 23, no. 1 (December 21, 2022): 38. http://dx.doi.org/10.3390/s23010038.

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The orthogonal time-frequency space (OTFS) waveform exceeds the challenges that face orthogonal frequency division multiplexing (OFDM) in a high-mobility environment with high time-frequency dispersive channels. Since radio frequency (RF) impairments have a direct impact on waveform behavior, this paper investigates the experimental implementation of RF-impairments that affect OTFS waveform performance and compares them to the OFDM waveform as a benchmark. Firstly, the doubly-dispersive channel effect is analyzed, and then an experimental framework is established for investigating the impact of RF-impairments, including non-linearity, carrier frequency offset (CFO), I/Q imbalances, DC-offset, and phase noise are considered. The experiments were conducted in a real indoor wireless environment using software-defined radio (SDR) at carrier frequencies of 2.4 GHz and 5 GHz based on the Keysight EXG X-Series devices. The comparison of the performances of OFDM and OTFS in the presence of RF-impairments reveals that OTFS significantly outperforms OFDM.

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5

Ryu, Sang-Burm, Joong-Pyo Kim, Jeong-Hwan Yang, Young-Jin Won, and Sang-Kon Lee. "Study of RF Impairments in Wideband Chirp Signal Generator." Journal of Korean Institute of Electromagnetic Engineering and Science 24, no. 12 (December 31, 2013): 1205–14. http://dx.doi.org/10.5515/kjkiees.2013.24.12.1205.

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6

surekha, T. P. "C-Band VSAT Data Communication System and RF Impairments." International Journal of Distributed and Parallel systems 3, no. 3 (May 31, 2012): 339–55. http://dx.doi.org/10.5121/ijdps.2012.3328.

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7

Baudin, P., and F. Belveze. "Impact of RF Impairments on a DS-CDMA Receiver." IEEE Transactions on Communications 52, no. 1 (January 2004): 31–36. http://dx.doi.org/10.1109/tcomm.2003.822159.

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8

Sha, Ziyuan, and Zhaocheng Wang. "Channel Estimation and Equalization for Terahertz Receiver With RF Impairments." IEEE Journal on Selected Areas in Communications 39, no. 6 (June 2021): 1621–35. http://dx.doi.org/10.1109/jsac.2021.3071824.

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9

Boulogeorgos, Alexandros-Apostolos A., Paschalis C. Sofotasios, Bassant Selim, Sami Muhaidat, George K. Karagiannidis, and Mikko Valkama. "Effects of RF Impairments in Communications Over Cascaded Fading Channels." IEEE Transactions on Vehicular Technology 65, no. 11 (November 2016): 8878–94. http://dx.doi.org/10.1109/tvt.2016.2516901.

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10

Sharkasi, Youssif Fawzi, Des McLernon, and Mounir Ghogho. "Spectrum Sensing in the Presence of RF Impairments in Cognitive Radio." International Journal of Interdisciplinary Telecommunications and Networking 4, no. 3 (July 2012): 65–78. http://dx.doi.org/10.4018/jitn.2012070105.

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The spectrum detection performance of a matched filter (MF) in the presence of carrier frequency offset (CFO), phase noise (PN) and time offset is analyzed. Detection performance is derived theoretically and confirmed through simulation in the presence of CFO. The results have shown that in the presence of CFO, the MF may be outperformed by an energy detector (ED) over a range of CFO values. The authors propose three spectrum sensing techniques that are robust to CFO. The first technique is called the block-coherent detector (BLCD) with a suboptimal number of blocks (N/2). The second technique is called second-order matched filter-I (SOMF-I), the detection performance of which has been studied both theoretically and confirmed through simulation. The last technique is named the second-order matched filter-II (SOMF-II) and is a modified version of (SOMF-I) but with a superior performance. The presence of PN and time offset and their effect on the detection performance is then examined via simulation. The results have shown that PN has not affected the detection performance of SOMF-I and has only a slight effect on the MF performance. But the time offset has seriously degrades the MF, ED and SOMF-I. Also, the results have shown that the performance of SOMF-I is much less affected by noise uncertainty compared to the ED. Finally, the throughput of SOMF-I has been studied in the presence of CFO and the results have shown that its performance is only marginally degraded compared to the MF.

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11

Deng, Juinn-Horng, Chia-Fang Lee, Meng-Lin Ku, and Jeng-Kuang Hwang. "Self-Calibration of Joint RF Impairments in a Loopback Wideband Transceiver." IEEE Access 8 (2020): 45607–17. http://dx.doi.org/10.1109/access.2020.2976673.

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12

Angrisani, L., and R. Colella. "Detection and evaluation of I/Q impairments in RF digital transmitters." IEE Proceedings - Science, Measurement and Technology 151, no. 1 (January 1, 2004): 39–45. http://dx.doi.org/10.1049/ip-smt:20040005.

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13

Oude Alink, Mark S., Eric A. M. Klumperink, Andre B. J. Kokkeler, Zhiyu Ru, Wei Cheng, and Bram Nauta. "Using Crosscorrelation to Mitigate Analog/RF Impairments for Integrated Spectrum Analyzers." IEEE Transactions on Microwave Theory and Techniques 61, no. 3 (March 2013): 1327–37. http://dx.doi.org/10.1109/tmtt.2012.2235458.

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14

Choi, Jinho. "Downlink Multiuser Beamforming With Compensation of Channel Reciprocity From RF Impairments." IEEE Transactions on Communications 63, no. 6 (June 2015): 2158–69. http://dx.doi.org/10.1109/tcomm.2015.2421904.

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15

Zhang, Xinlin, Michail Matthaiou, Mikael Coldrey, and Emil Bjornson. "Impact of Residual Transmit RF Impairments on Training-Based MIMO Systems." IEEE Transactions on Communications 63, no. 8 (August 2015): 2899–911. http://dx.doi.org/10.1109/tcomm.2015.2432761.

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16

Mohammadian, Amirhossein, and Chintha Tellambura. "Cognitive GFDM Full-Duplex Radios With RF Impairments and ACI Constraints." IEEE Open Journal of the Communications Society 1 (2020): 732–49. http://dx.doi.org/10.1109/ojcoms.2020.2993611.

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17

Badoud, Deborah, Paco Prada, Rosetta Nicastro, Charlotte Germond, Patrick Luyten, Nader Perroud, and Martin Debbané. "Attachment and Reflective Functioning in Women With Borderline Personality Disorder." Journal of Personality Disorders 32, no. 1 (February 2018): 17–30. http://dx.doi.org/10.1521/pedi_2017_31_283.

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Insecure attachment and impairments in reflective functioning (RF) are thought to play a critical role in borderline personality disorder (BPD). In particular, the mentalization-based model argues that insecure attachment indirectly accounts for increased BPD features, notably via disruption of RF capacities. Although the mediation relationship between attachment, RF, and BPD is supported by previous evidence, it remains to be directly tested in adults with BPD. In the current study, a sample of 55 female adult BPD patients and 105 female healthy controls completed a battery of self-report measures to investigate the interplay between attachment, RF capacities, and BPD clinical status. Overall, the results showed that BPD patients pre- dominantly reported insecure attachment, characterized by negative internal working models of the self as unlovable and unimportant to others, and decreased RF abilities. Our findings further indicated that actual RF capacities mediated the relationships between adult insecure attachment and BPD clinical status.

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18

Rehman, Saeed Ur, Shafiq Alam, and Iman T. Ardekani. "An Overview of Radio Frequency Fingerprinting for Low-End Devices." International Journal of Mobile Computing and Multimedia Communications 6, no. 3 (July 2014): 1–21. http://dx.doi.org/10.4018/ijmcmc.2014070101.

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RF fingerprinting is proposed as a means of providing an additional layer of security for wireless devices. A masquerading or impersonation attacks can be prevented by establishing the identity of wireless transmitter using unique transmitter RF fingerprint. Unique RF fingerprints are attributable to the analog components (digital-to-analog converters, band-pass filters, frequency mixers and power amplifiers) present in the RF front ends of transmitters. Most of the previous researches have reported promising results with an accuracy of up to 99% using high-end receivers (e.g. Giga-sampling rate oscilloscopes, spectrum and vector signal analysers) to validate the proposed techniques. However, practical implementation of RF fingerprinting would require validation with low-end (low-cost) devices that also suffers from impairments due to the presence of analog components in the front end of its receiver. This articles provides the analysis and implementation of RF fingerprinting using low-cost receivers and challenges associated with it.

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19

Ayesha, Areeba, MuhibUr Rahman, Amir Haider, and Shabbir Majeed Chaudhry. "On Self-Interference Cancellation and Non-Idealities Suppression in Full-Duplex Radio Transceivers." Mathematics 9, no. 12 (June 20, 2021): 1434. http://dx.doi.org/10.3390/math9121434.

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One of the major impediments in the design and operation of a full-duplex radio transceiver is the presence of self-interference (SI), that is, the transceiver’s transmitted signal, 60–100 dB stronger than the desired signal of interest. To reduce the SI signal below the receiver’s sensitivity before coupling it to the receiver, radio frequency (RF)/analog domain cancellation is carried out. Even after SI cancellation to the required level in the analog domain, the residual SI signal still exits and lowers the transceiver’s performance. For residual SI cancellation, a digital domain cancellation is carried out. RF impairments are the major obstacle in the residual SI cancellation path in the digital domain. Linearization of RF impairments such as IQ mixer imbalance in the transmitter and receiver chain, non-linear PA with memory, and non-linear LNA are also carried out. Performance evaluation of the proposed techniques is carried out based on SINR, the power of different SI signal components, PSD, output to input relationship, SNR vs. BER, spectrum analyzer, constellation diagram, and link budget analysis. The proposed techniques provide attractive RF/analog SI cancellation of up to 80–90 dB, digital residual SI cancellation of up to 35 to 40 dB, total SI cancellation of up to 110 to 130 dB, and an SINR improvement of up to 50 dB.

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20

Vanwoerden, Salome, Francesca Penner, Caroline Pearson, Johanna Bick, Hanako Yoshida, and Carla Sharp. "Testing the Link Between Mothers’ General Reflective Function Capacity and Adolescent Borderline Personality Features: Perceived Parenting Behaviors as a Potential Mechanism." Journal of Personality Disorders 35, Supplement B (June 2021): 56–73. http://dx.doi.org/10.1521/pedi_2021_35_505.

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Impairments in mothers’ reflective function (RF), the ability to imagine the mental states of the self and others, underlies maladaptive parenting strategies, which have been associated with borderline personality disorder (BPD). The current study evaluated the association between mother's RF and adolescents’ BPD and the mediating role of a range of parenting behaviors. Five hundred and thirty-one inpatient adolescents and their mothers participated in the current study. A multimethod assessment of BPD was used alongside mothers’ self-reported quality of RF. Children completed three questionnaires about maternal parenting behaviors. There was no direct relation between mother's RF capacity and adolescents’ BPD. However, mothers’ adaptive certainty about mental states related to less severe BPD in adolescents, specifically through decreases in inconsistent punishment. Mothers’ RF capacity predicted various parenting behaviors, which was associated with adolescents’ BPD severity. Implications of findings for early intervention and prevention are discussed.

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21

Inserra, Daniele, and Andrea M. Tonello. "Characterization of Hardware Impairments in Multiple Antenna Systems for DoA Estimation." Journal of Electrical and Computer Engineering 2011 (2011): 1–10. http://dx.doi.org/10.1155/2011/908234.

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We consider the effects introduced by hardware impairments on the estimation of the direction of arrival (DoA) deploying a multiple antenna radio system. We derive a system model from experimental measurements of a state-of-the-art hardware test bed based on an RF direct-conversion architecture. The system model includes DC offsets, carrier frequency and phase offsets, and the phase noise. Then, we propose a simple digital compensation algorithm of the impairments for bidimensional DoA estimation (azimuth and elevation) with a 3D orthogonal linear array. The robustness of the algorithm in terms of minimum-mean-squared error as a function of the hardware impairments is evaluated and compared with that achieved using the root-MUSIC algorithm.

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22

Maletic, Nebojsa, Jesus Gutierrez, and Eckhard Grass. "On the Impact of Residual Transceiver Impairments in mmWave RF Beamforming Systems." IEEE Communications Letters 24, no. 11 (November 2020): 2459–63. http://dx.doi.org/10.1109/lcomm.2020.3013171.

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23

Balti, Elyes, Mohsen Guizani, Bechir Hamdaoui, and Bassem Khalfi. "Aggregate Hardware Impairments Over Mixed RF/FSO Relaying Systems With Outdated CSI." IEEE Transactions on Communications 66, no. 3 (March 2018): 1110–23. http://dx.doi.org/10.1109/tcomm.2017.2776261.

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24

Solanki, Sourabh, Vibhum Singh, and Prabhat Kumar Upadhyay. "RF Energy Harvesting in Hybrid Two-Way Relaying Systems With Hardware Impairments." IEEE Transactions on Vehicular Technology 68, no. 12 (December 2019): 11792–805. http://dx.doi.org/10.1109/tvt.2019.2944248.

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25

Do, Nhu Tri, Daniel Benevides da Costa, and Beongku An. "Performance analysis of multirelay RF energy harvesting cooperative networks with hardware impairments." IET Communications 10, no. 18 (December 15, 2016): 2551–58. http://dx.doi.org/10.1049/iet-com.2016.0392.

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26

Al-Dhahir, Naofal, Anand Dabak, Marc Moonen, Ali H. Sayed, and Zoran Zvonar. "Introduction to the Issue on DSP Techiques for RF/Analog Circuit Impairments." IEEE Journal of Selected Topics in Signal Processing 3, no. 3 (June 2009): 345–47. http://dx.doi.org/10.1109/jstsp.2009.2020417.

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27

Tuan, Van Phu, and Hyung Yun Kong. "Impact of residual transmit RF impairments on energy harvesting relay selection systems." International Journal of Electronics 104, no. 6 (November 30, 2016): 928–41. http://dx.doi.org/10.1080/00207217.2016.1253788.

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28

Singal, Anuj, and Deepak Kedia. "Performance Analysis of Antenna Selection Techniques in MIMO-OFDM System with Hardware Impairments: Energy Efficiency perspective." International Journal of Electrical and Computer Engineering (IJECE) 8, no. 4 (August 1, 2018): 2272. http://dx.doi.org/10.11591/ijece.v8i4.pp2272-2279.

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<p>In this paper we propose a new MIMO-OFDM model in which we consider various antenna selection techniques like Bulk selection and Per-subcarrier selection etc. with hardware impairments such as non-linearties of amplifiers, quantization noise, phase noise and I-Q imbalance etc. As we know that the transceiver hardware impairments limit the channel capacity and the energy efficiency of MIMO-OFDM system, so we can not neglect the fundamental impacts of these hardware impairments {Kappa (0.05 0.1)} on the energy efficiency in the high SNR domain. Therefore we analyze the Energy Efficiency of Bulk and Per-subcarrier antenna selection techniques with or without hardware impairments. It has been observed that the energy efficiency decreases as the value of these hardware impairments increases. As we compared the Bulk antenna selection with the Per-subcarrier antenna selection scheme, the Per-subcarrier antenna selection requires more number of RF (radio frequency) chains and transmits power in comparison to the Bulk selection. Due to this, the Bulk antenna selection technique is more energy efficient than Per-subcarrier antenna selection.</p>

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29

Shatti, Ahmed Hussein, and Ehab Abdul Razzaq Hussein. "Massive multiple-input multiple-output channel estimation under hardware and channel impairments." Bulletin of Electrical Engineering and Informatics 12, no. 1 (February 1, 2023): 215–23. http://dx.doi.org/10.11591/eei.v12i1.4025.

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Hardware problems are the most detrimental issues to channel estimates in wireless communication systems. Because of the enormous number of antennas at the base station (BS) in cellular massive multiple-input multiple-output (MIMO) systems and because one radio frequency (RF) chain per antenna is required, hardware impairments in such systems will be quite severe. Many research publications have used a quality-cost tradeoff to adjust for RF unit hardware issues. In this study, we have taken a different approach by reducing the error floor caused by impairments in the predicted channels. Here are two steps to remedy the problem. In phase 1, a single active user channel in a single cell was calculated statistically rather than parametrically. In phase 2, a convex optimization approach was used to regularize the estimated channel in phase 1 to reduce error and provide a robust channel estimate. The results of our proposed procedure are measured by the normalized minimum mean squared error (NMSE) versus a range from the effective signal-to-noise ratio, and it shows a significant reduction (nearly one order of magnitude) in the error floor as compared with the conventional one, especially at high signal-to-noise ratio (SNR) in the range of (20 dB-30 dB). Simulation results were extracted in MATLAB R2020a.

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30

Bouhlel, Nizar, Majed Saad, and Faouzi Bader. "Sub-Terahertz Wireless System Using Dual-Polarized Generalized Spatial Modulation With RF Impairments." IEEE Journal on Selected Areas in Communications 39, no. 6 (June 2021): 1636–50. http://dx.doi.org/10.1109/jsac.2021.3071828.

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31

Mohammadian, Amirhossein, and Chintha Tellambura. "RF Impairments in Wireless Transceivers: Phase Noise, CFO, and IQ Imbalance – A Survey." IEEE Access 9 (2021): 111718–91. http://dx.doi.org/10.1109/access.2021.3101845.

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32

Boulogeorgos, Alexandros-Apostolos A., and George K. Karagiannidis. "Energy Detection in Full-Duplex Systems With Residual RF Impairments Over Fading Channels." IEEE Wireless Communications Letters 7, no. 2 (April 2018): 246–49. http://dx.doi.org/10.1109/lwc.2017.2769651.

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33

Safatly, Lise, Mario Bkassiny, Mohammed Al-Husseini, and Ali El-Hajj. "Cognitive Radio Transceivers: RF, Spectrum Sensing, and Learning Algorithms Review." International Journal of Antennas and Propagation 2014 (2014): 1–21. http://dx.doi.org/10.1155/2014/548473.

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A cognitive transceiver is required to opportunistically use vacant spectrum resources licensed to primary users. Thus, it relies on a complete adaptive behavior composed of: reconfigurable radio frequency (RF) parts, enhanced spectrum sensing algorithms, and sophisticated machine learning techniques. In this paper, we present a review of the recent advances in CR transceivers hardware design and algorithms. For the RF part, three types of antennas are presented: UWB antennas, frequency-reconfigurable/tunable antennas, and UWB antennas with reconfigurable band notches. The main challenges faced by the design of the other RF blocks are also discussed. Sophisticated spectrum sensing algorithms that overcome main sensing challenges such as model uncertainty, hardware impairments, and wideband sensing are highlighted. The cognitive engine features are discussed. Moreover, we study unsupervised classification algorithms and a reinforcement learning (RL) algorithm that has been proposed to perform decision-making in CR networks.

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34

Marino, Perfecto, Fernando Machado, Fernando P. Fontan, and Santiago Otero. "Hybrid Distributed Instrumentation Network for Integrating Meteorological Sensors Applied to Modeling RF Propagation Impairments." IEEE Transactions on Instrumentation and Measurement 57, no. 7 (July 2008): 1410–21. http://dx.doi.org/10.1109/tim.2008.915451.

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35

Xu, Tongyang, Hedaia Ghannam, and Izzat Darwazeh. "Practical Evaluations of SEFDM: Timing Offset and Multipath Impairments." Infocommunications journal, no. 4 (2018): 2–9. http://dx.doi.org/10.36244/icj.2018.4.1.

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The non-orthogonal signal waveform spectrally efficient frequency division multiplexing (SEFDM) improves spectral efficiency at the cost of self-created inter carrier interference (ICI). As the orthogonal property, similar to orthogonal frequency division multiplexing (OFDM), no longer exists, the robustness of SEFDM in realistic wireless environments might be weakened. This work aims to evaluate the sensitivity of SEFDM to practical channel distortions using a professional experiment testbed. First, timing offset is studied in a bypass channel to locate the imperfection of the testbed and its impact on SEFDM signals. Then, the joint effect of a multipath frequency selective channel and additive white Gaussian noise (AWGN) is investigated in the testbed. Through practical experiments, we demonstrate the performance of SEFDM in realistic radio frequency (RF) environments and verify two compensation methods for SEFDM. Our results show first frequency-domain compensation works well in frequency non-selective channel conditions while time-domain compensation method is suitable for frequency selective channel conditions. This work paves the way for the application of SEFDM in different channel scenarios.

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36

Song, Jia, Shuaishuai Chu, Xin Fang, Fangxia Xu, Peng Zhang, Xin Zhao, Zhengliang Ma, Tianjiao Xia, and Xiaoping Gu. "Time-restricted feeding alters isoflurane-induced memory deficits." Translational Neuroscience 11, no. 1 (September 21, 2020): 341–55. http://dx.doi.org/10.1515/tnsci-2020-0130.

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AbstractFood consumption during the rest phase promotes circadian desynchrony, which is corrected with harmful physiological and mental disorders. Previously, we found that circadian desynchrony was involved in isoflurane-induced cognitive impairment. Here, we scheduled food access to modulate daily rhythm to examine its impact on isoflurane-induced cognitive impairments. Mice were randomly transferred to restricted feeding (RF) time groups: Control group (Zeitgeber time (ZT) 0–ZT24, ad libitum feeding), Day-Feeding group (ZT0–ZT12, misaligned feeding), and Night-Feeding group (ZT12–ZT24, aligned feeding). Then, some of them were subjected to 5 h of 1.3% isoflurane anaesthesia from ZT14 to ZT19 and were divided into the Control + Anes group, the Day-Feeding + Anes group, and the Night-Feeding + Anes group. Mini-Mitter was used to monitor the daily rhythm. Fear conditioning system was conducted to assess cognition of mice. We observed that the Night-Feeding group adapted to RF gradually, whereas the Day-Feeding group exhibited a disturbed daily rhythm. The Night-Feeding + Anes group exhibited a partially enhanced daily rhythm, whereas the Day-Feeding + Anes group exhibited sustained phase advances and diurnality score increase 7 days after isoflurane anaesthesia. Notably, in tests of hippocampus-dependent contextual memory, the Night-Feeding + Anes group demonstrated decreased deficits; the Day-Feeding + Anes group showed prolonged post-anaesthetic deficits 14 days after isoflurane anaesthesia. However, amygdala-dependent cued-fear conditioning post-anaesthesia was not altered by the RF schedule. In conclusion, we demonstrated that misaligned feeding disturbed the daily rhythm and led to persistent post-anaesthetic cognitive dysfunction. Aligned feeding enhanced the daily rhythm partially and improved post-anaesthetic cognitive dysfunction.

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37

Mohammadzadeh, Nazanin, Na Zhang, William G. Branton, Ouafa Zghidi-Abouzid, Eric A. Cohen, Benjamin B. Gelman, Jerome Estaquier, Linglong Kong, and Christopher Power. "The HIV Restriction Factor Profile in the Brain Is Associated with the Clinical Status and Viral Quantities." Viruses 15, no. 2 (January 23, 2023): 316. http://dx.doi.org/10.3390/v15020316.

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HIV-encoded DNA, RNA and proteins persist in the brain despite effective antiretroviral therapy (ART), with undetectable plasma and cerebrospinal fluid viral RNA levels, often in association with neurocognitive impairments. Although the determinants of HIV persistence have garnered attention, the expression and regulation of antiretroviral host restriction factors (RFs) in the brain for HIV and SIV remain unknown. We investigated the transcriptomic profile of antiretroviral RF genes by RNA-sequencing with confirmation by qRT-PCR in the cerebral cortex of people who are uninfected (HIV[−]), those who are HIV-infected without pre-mortem brain disease (HIV[+]), those who are HIV-infected with neurocognitive disorders (HIV[+]/HAND) and those with neurocognitive disorders with encephalitis (HIV[+]/HIVE). We observed significant increases in RF expression in the brains of HIV[+]/HIVE in association with the brain viral load. Machine learning techniques identified MAN1B1 as a key gene that distinguished the HIV[+] group from the HIV[+] groups with HAND. Analyses of SIV-associated RFs in brains from SIV-infected Chinese rhesus macaques with different ART regimens revealed diminished RF expression among ART-exposed SIV-infected animals, although ART interruption resulted in an induced expression of several RF genes including OAS3, RNASEL, MX2 and MAN1B1. Thus, the brain displays a distinct expression profile of RFs that is associated with the neurological status as well as the brain viral burden. Moreover, ART interruption can influence the brain’s RF profile, which might contribute to disease outcomes.

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Hafner, Stephan, Andre Durr, Christian Waldschmidt, and Reiner Thoma. "Mitigation of RF Impairments of a 160-GHz MMIC FMCW Radar Using Model-Based Estimation." IEEE Transactions on Microwave Theory and Techniques 68, no. 3 (March 2020): 1065–73. http://dx.doi.org/10.1109/tmtt.2019.2950204.

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Ermolova, Natalia Y., Yaning Zou, Mikko Valkama, and Olav Tirkkonen. "Error-Rate Analysis of OFDM Radio Link Over Mobile Rayleigh Channel Under Multiple RF Impairments." IEEE Transactions on Vehicular Technology 63, no. 2 (February 2014): 930–36. http://dx.doi.org/10.1109/tvt.2013.2279013.

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Anttila, Lauri, Peter Händel, Olli Mylläri, and Mikko Valkama. "Recursive learning-based joint digital predistorter for power amplifier and I/Q modulator impairments." International Journal of Microwave and Wireless Technologies 2, no. 2 (April 2010): 173–82. http://dx.doi.org/10.1017/s1759078710000280.

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The main implementation impairments degrading the performance of direct-conversion radio transmitters are in-phase/quadrature (I/Q) mismatch, local oscillator (LO) leakage, and power amplifier (PA) nonlinear distortion. In this article, we propose a recursive least-squares-based learning algorithm for joint digital predistortion (PD) of frequency-dependent PA and I/Q modulator impairments. The predistorter is composed of a parallel connection of two parallel Hammerstein (PH) predistorters and an LO leakage compensator, yielding a predistorter which as a whole is fully linear in the parameters. In the parameter estimation stage, proper feedback signal from the transmitter radio frequency (RF) stage back to the digital parts is deployed, combined with the indirect learning architecture and recursive least-squares training. The proposed structure is one of the first techniques to explicitly consider the joint estimation and mitigation of frequency-dependent PA and I/Q modulator impairments. Extensive simulation and measurement analysis is carried out to verify the operation and efficiency of the proposed PD technique. In general, the obtained results demonstrate linearization and I/Q modulator calibration performance clearly exceeding the performance of current state-of-the-art reference techniques.

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Xu, Liangyuan, Xintong Lu, Shi Jin, Feifei Gao, and Yongxu Zhu. "On the Uplink Achievable Rate of Massive MIMO System with Low-Resolution ADC and RF Impairments." IEEE Communications Letters 23, no. 3 (March 2019): 502–5. http://dx.doi.org/10.1109/lcomm.2019.2895823.

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Solanki, Sourabh, Prabhat K. Upadhyay, Daniel Benevides da Costa, Petros S. Bithas, Athanasios G. Kanatas, and Ugo Silva Dias. "Joint Impact of RF Hardware Impairments and Channel Estimation Errors in Spectrum Sharing Multiple-Relay Networks." IEEE Transactions on Communications 66, no. 9 (September 2018): 3809–24. http://dx.doi.org/10.1109/tcomm.2018.2832623.

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Gomes, Rodolfo, Akram Hammoudeh, Rafael F. S. Caldeirinha, Zaid Al-Daher, Telmo Fernandes, and Joao Reis. "Towards 5G: Performance evaluation of 60 GHz UWB OFDM communications under both channel and RF impairments." Physical Communication 25 (December 2017): 527–38. http://dx.doi.org/10.1016/j.phycom.2017.10.011.

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Kiayani, Adnan, Lauri Anttila, Yaning Zou, and Mikko Valkama. "Channel Estimation and Equalization in Multiuser Uplink OFDMA and SC-FDMA Systems Under Transmitter RF Impairments." IEEE Transactions on Vehicular Technology 65, no. 1 (January 2016): 82–99. http://dx.doi.org/10.1109/tvt.2015.2397277.

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Chitra, S., S. Ramesh, Beulah Jackson, and S. Mohanraj. "Performance enhancement of generalized frequency division multiplexing with RF impairments compensation for efficient 5G wireless access." AEU - International Journal of Electronics and Communications 127 (December 2020): 153467. http://dx.doi.org/10.1016/j.aeue.2020.153467.

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Le, Thi Anh, and Hyung Yun Kong. "Performance analysis of downlink NOMA–EH relaying network in the presence of residual transmit RF hardware impairments." Wireless Networks 26, no. 2 (October 11, 2018): 1045–55. http://dx.doi.org/10.1007/s11276-018-1851-8.

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Wood, A. C., F. Rijsdijk, K. A. Johnson, P. Andreou, B. Albrecht, A. Arias-Vasquez, J. K. Buitelaar, et al. "The relationship between ADHD and key cognitive phenotypes is not mediated by shared familial effects with IQ." Psychological Medicine 41, no. 4 (June 4, 2010): 861–71. http://dx.doi.org/10.1017/s003329171000108x.

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BackgroundTwin and sibling studies have identified specific cognitive phenotypes that may mediate the association between genes and the clinical symptoms of attention deficit hyperactivity disorder (ADHD). ADHD is also associated with lower IQ scores. We aimed to investigate whether the familial association between measures of cognitive performance and the clinical diagnosis of ADHD is mediated through shared familial influences with IQ.MethodMultivariate familial models were run on data from 1265 individuals aged 6–18 years, comprising 920 participants from ADHD sibling pairs and 345 control participants. Cognitive assessments included a four-choice reaction time (RT) task, a go/no-go task, a choice–delay task and an IQ assessment. The analyses focused on the cognitive variables of mean RT (MRT), RT variability (RTV), commission errors (CE), omission errors (OE) and choice impulsivity (CI).ResultsSignificant familial association (rF) was confirmed between cognitive performance and both ADHD (rF=0.41–0.71) and IQ (rF=−0.25 to −0.49). The association between ADHD and cognitive performance was largely independent (80–87%) of any contribution from etiological factors shared with IQ. The exception was for CI, where 49% of the overlap could be accounted for by the familial variance underlying IQ.ConclusionsThe aetiological factors underlying lower IQ in ADHD seem to be distinct from those between ADHD and RT/error measures. This suggests that lower IQ does not account for the key cognitive impairments observed in ADHD. The results have implications for molecular genetic studies designed to identify genes involved in ADHD.

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Mokhtari, Zahra, Maryam Sabbaghian, and Rui Dinis. "A Survey on Massive MIMO Systems in Presence of Channel and Hardware Impairments." Sensors 19, no. 1 (January 4, 2019): 164. http://dx.doi.org/10.3390/s19010164.

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Massive multiple input multiple output (MIMO) technology is one of the promising technologies for fifth generation (5G) cellular communications. In this technology, each cell has a base station (BS) with a large number of antennas, allowing the simultaneous use of the same resources (e.g., frequency and/or time slots) by multiple users of a cell. Therefore, massive MIMO systems can bring very high spectral and power efficiencies. However, this technology faces some important issues that need to be addressed. One of these issues is the performance degradation due to hardware impairments, since low-cost RF chains need to be employed. Another issue is the channel estimation and channel aging effects, especially in fast mobility environments. In this paper we will perform a comprehensive study on these two issues considering two of the most promising candidate waveforms for massive MIMO systems: Orthogonal frequency division multiplexing (OFDM) and single-carrier frequency domain processing (SC-FDP). The studies and the results show that hardware impairments and inaccurate channel knowledge can degrade the performance of massive MIMO systems extensively. However, using suitable low complex estimation and compensation techniques and also selecting a suitable waveform can reduce these effects.

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Nair, Deepukumar M., K. M. Nair, Ken Souders, Michael Smith, Mark McCombs, James Parisi, Tim Mobley, and Bradley Thrasher. "Investigation of Silver Migration Impacts on Microwave Systems Fabricated on LTCC Substrate Under High-Power RF Excitation and High Temperature and Humidity Conditions." International Symposium on Microelectronics 2010, no. 1 (January 1, 2010): 000242–47. http://dx.doi.org/10.4071/isom-2010-tp3-paper1.

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The demand for cost effective LTCC systems has led to increasing use of silver based thick film conductors for inner layers of RF modules. There exists some level of concern about the reliability of silver as a conducting material for electronic circuit packaging. This arises from the tendency of silver to migrate under the influence of electric fields when subjected to certain favorable environment conditions. However, previous research has shown that if silver is used in a properly designed LTCC system on inner layers, the LTCC dielectric forms a hermetic seal around the circuit pattern, which leads to a highly reliable circuit and a low cost solution. This paper describes the results of an investigation to characterize and quantify the impact of silver migration on real-life microwave systems fabricated with DuPont GreenTape™ 951 LTCC material system with silver metallization. A buried multilayer filter was chosen from an actual production design in a high-reliability application, and was tested at 15W of continuous RF power at 1.5 GHz under 85°C/85% temperature and relative humidity. The chosen test conditions were meant to simulate actual operating conditions encountered by the circuit in real-world, high reliability applications. The focus of this work is to collect useful operational information under environmental stresses encountered in typical applications. To this effect, unlike previously reported work [1 ], [2 ], [3 ] by proponents of silver, the work described in this paper is not forcing silver to migrate, but rather tries to evaluate the performance of an actual application circuit fabricated with silver under high-reliability test conditions and high power, high frequency RF excitation. Material characterization data as well as RF performance data – in terms of S parameters and power delivered – indicates no evidence of detrimental effects or performance impairments due to silver migration or other mechanisms.

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Vlachos, Evangelos, John Thompson, Aryan Kaushik, and Christos Masouros. "Radio-frequency chain selection for energy and spectral efficiency maximization in hybrid beamforming under hardware imperfections." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2244 (December 2020): 20200451. http://dx.doi.org/10.1098/rspa.2020.0451.

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The next-generation wireless communications require reduced energy consumption, increased data rates and better signal coverage. The millimetre-wave frequency spectrum above 30 GHz can help fulfil the performance requirements of the next-generation mobile broadband systems. Multiple-input multiple-output technology can provide performance gains to help mitigate the increased path loss experienced at millimetre-wave frequencies compared with microwave bands. Emerging hybrid beamforming architectures can reduce the energy consumption and hardware complexity with the use of fewer radio-frequency (RF) chains. Energy efficiency is identified as a key fifth-generation metric and will have a major impact on the hybrid beamforming system design. In terms of transceiver power consumption, deactivating parts of the beamformer structure to reduce power typically leads to significant loss of spectral efficiency. Our aim is to achieve the highest energy efficiency for the millimetre-wave communications system while mitigating the resulting loss in spectral efficiency. To achieve this, we propose an optimal selection framework which activates specific RF chains that amplify the digitally beamformed signals with the analogue beamforming network. Practical precoding is considered by including the effects of user interference, noise and hardware impairments in the system modelling.

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