Offset Correction Research Articles

Design and Validation of the Physical Layer Functions of FBMC/OQAM Transceiver With Improved Residual Phase Error Correction

In this paper, we report experimental results on the development and improvement of the physical layer functions of a filter bank multicarrier with off-set quadrature amplitude modulation (FBMC/OQAM) transceiver using a testbed implemented with programmable software-defined radio (SDR). The developed physical layer approach is similar to the IEEE 802.11a standard, and it has been tested for timing synchronization, carrier frequency offset (CFO) correction, channel estimation and equalization. An investigation into the inherent intrinsic imaginary interference in FBMC/OQAM has been carried out, with initial findings indicating the seriousness of the effect of phase noise (PN). The conventional pilot structure used in IEEE 802.11a cannot be directly applied to FBMC/OQAM, thus, a specially designed pilot scheme is proposed to deal with the residual phase error. Three phase noise estimation schemes have been evaluated, namely phase noise compensation (PNC), extended Kalman filter (EKF) and modified blind phase searching (MBPS) methods. To further suppress the residual interference and enhance the phase error correction, an iterative technique is used after the pilot equalization. The performance of the proposed methods has been evaluated experimentally and via simulation for an indoor environment. The results verify the capabilities of the proof-of-concept transceiver and the developed physical layer functions.

In-flight performance analysis and antenna phase center calibration of MEMS GPS receiver on-board TianQin-1 in the nadir-pointing and Sun-pointing modes

The TianQin-1 satellite, which was launched on 20 December 2019 into a Sun-synchronous orbit with an altitude of 628 km, is the first technology demonstration satellite for the TianQin project. A micro-electro-mechanical system (MEMS) global positioning system (GPS) receiver is installed on the satellite for precise orbit determination (POD). In addition to the conventional nadir-pointing mode, a specific Sun-pointing mode was used by the satellite owing to the limitation of system resources. The in-flight performance of the MEMS GPS receiver was assessed. The average numbers of available satellites for dual-frequency navigation in the nadir-pointing and Sun-pointing modes are 7 and 5, respectively. The qualities of the P2 code and carrier phase observations are basically equal for both modes. The average root mean square of the multipath errors for C1 observations in the Sun-pointing mode is 0.29 m, slightly larger than that in the nadir-pointing mode. In the Sun-pointing mode, the body of the TianQin-1 satellite rotates around the Sun-pointing axis, which may provide favourable geometric conditions for the estimation of the antenna phase center offset (PCO) corrections in the X, Y, and Z directions. Its feasibility is demonstrated using the simulated data. The GPS measurements of TianQin-1 are then used to estimate the PCO corrections in all three directions while in the Sun-pointing mode and in the Z direction while in the nadir-pointing mode. Satellite laser ranging validation shows that the orbit accuracy of TianQin-1 is approximately 5.90 cm in the nadir-pointing mode. In the Sun-pointing mode, the three-dimensional position difference of 5-h overlap decreased from 8.87 cm to 8.73 cm when the antenna PCO corrections were used in the POD.

MWA tied-array processing IV: A multi-pixel beamformer for pulsar surveys and ionospheric corrected localisation

AbstractThe Murchison Widefield Array (MWA) is a low-frequency aperture array capable of high-time and frequency resolution astronomy applications such as pulsar studies. The large field-of-view of the MWA (hundreds of square degrees) can also be exploited to attain fast survey speeds for all-sky pulsar search applications, but to maximise sensitivity requires forming thousands of tied-array beams from each voltage-capture observation. The necessity of using calibration solutions that are separated from the target observation both temporally and spatially makes pulsar observations vulnerable to uncorrected, frequency-dependent positional offsets due to the ionosphere. These offsets may be large enough to move the source away from the centre of the tied-array beam, incurring sensitivity drops of${\sim}30{-}50\%$in Phase II extended array configuration. We analyse these offsets in pulsar observations and develop a method for mitigating them, improving both the source position accuracy and the sensitivity. This analysis prompted the development of a multi-pixel beamforming functionality that can generate dozens of tied-array beams simultaneously, which runs a factor of ten times faster compared to the original single-pixel version. This enhancement makes it feasible to observe multiple pulsars within the vast field of view of the MWA and supports the ongoing large-scale pulsar survey efforts with the MWA. We explore the extent to which ionospheric offset correction will be necessary for the MWA Phase III and the low-frequency square kilometre array (SKA-low).

Distortion correction method of line shape based on harmonic detection

When wavelength modulation spectroscopy is used for gas detection in open space, the second harmonic signal is modified due to the interference of optical noise, uncontrollable environmental noise, etc., resulting in the distortion of the line shape, which affects the measurement accuracy. In this study, the harmonic signal distortion is theoretically analyzed, and a distortion correction method of the line shape is proposed based on harmonic detection. By correcting the zero line offset and line shape distortion, the effect of interference is reduced. Furthermore, a monitoring system based on the harmonic technology is established, and a series of experiments are conducted to validate the efficacy of the proposed method. The experimental results reveal that after background noise elimination and zero line offset correction, the maximum fluctuation of the spectral signal in the non-absorption side of the sidelobe is reduced from 0.093 to 0.055 V on the left side and from −0.111 to −0.032 V on the right side. Furthermore, the standard deviation of the peak height ratio before and after the distortion correction is 0.283 and 0.001, respectively, and the standard deviation of the Euclidean distance is 2.601 and 0.007 pm, respectively. The proposed method is compared with traditional 2f concentration inversion and I2f/I1f methods. The mean values for the three methods are 2.80, 2.80, and 2.83 ppm, respectively. The standard deviation of the proposed method is 0.018 ppm, and the Allan analysis result is 2.65 × 10−8 (1 s). These results verify the accuracy of the proposed method.

A 0.56-mW 63.6-dB SNDR 250-MS/s Two-Step SAR ADC in 8-nm FinFET

This paper presents a two-step SAR ADC that uses coarse and fine comparators with dedicated SAR logics and asynchronous clock generators for each comparator to increase the energy efficiency by optimizing comparators and reduce output loading of the comparators and asynchronous clock generators. The relative offset of the two comparators is calibrated by redundancy based offset detection and input transistor transconductance controlled offset correction method without compromising the power. A constant impedance skewed inverter saves reference current with low short circuit current without additional CDAC settling time and logic. The ADC is fabricated in an 8 nm FinFET process, and achieves 63.6 dB SNDR at 250 MS/s while consuming 0.56 mW, resulting in Walden FoM of 1.81 fJ/conversion step.

Pulsed Blue Laser Diode Thermal Desorption Microplasma Imaging Mass Spectrometry.

An ambient air laser desorption, plasma ionization imaging method is developed and presented using a microsecond pulsed laser diode for desorption and a flexible microtube plasma for ionization of the neutral desorbate. Inherent parameters such as the laser repetition rate and pulse width are optimized to the imaging application. For the desorption substrate, copper spots on a copper-glass sandwich structure are used. This novel design enables imaging without ablating the metal into the mass spectrometer. On this substrate, fixed calibration markers are used to decrease the positioning error in the imaging process, featuring a 3D offset correction within the experiment. The image is both screened spot-by-spot and per line scanning at a constant speed, which allows direct comparison. In spot-by-spot scanning, a novel algorithm is presented to unfold and to reconstruct the imaging data. This approach significantly decreases the time required for the imaging process, which allows imaging even at decreased sampling rates and thus higher mass resolution. After the experiment, the raw data is automatically converted and interpreted by a second algorithm, which allows direct visualization of the image from the data, even on low-intensity signals. Mouse liver microtome cuts have been screened for dehydrated cholesterol, proving good agreement of the unfolded data with the morphology of the tissue. The method optically resolves 30 μm, with 30 μm diameter copper spots and a 10 μm gap. No conventional chemical matrices or vacuum conditions are required.

Offset and Gain FPN Calibrated Linear-Logarithmic Image Sensor With Shared Pixel Architecture

This brief presents offset and gain FPN calibrated linear-logarithmic image sensor. Offset FPN originated from threshold voltage variation of the logarithmic conversion transistor is calibrated with Two-step charge transfer operation. Remaining gain FPN is analyzed and its root cause is investigated. The subthreshold slope difference of the logarithmic conversion transistors in the shared pixel architecture is found to be responsible for the increasing FPN in the logarithmic operation region and potentially limiting dynamic range in high illumination region. A simple modeling-based gain FPN correction method in linear-logarithmic APS using shared pixel architecture has been proposed. The prototype sensor is fabricated by using a 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS image sensor process. Thanks to the proposed gain FPN correction together with offset correction using Two-step charge transfer operation, wide dynamic range of more than 120 dB has been achieved while maintaining the total FPN less than 0.29% over the entire dynamic range.

Reducing Aging Impacts in Digital Sensors via Run-Time Calibration

Hazards or intentional perturbations must be identified in safety- and security-critical applications. Digital sensors have been shown to be an appealing approach to detect such abnormalities. However, as any sensor technology, digital sensors are prone to mis-calibration. In particular, even if the digital sensor initial calibration is correct, the rate of false and missed alarms might increase when the sensor is aged. In this paper, we thoroughly study the impact of aging-induced false and missed alarms. Indeed aging relates to the usage time, and a priori model (historical data for environmental variation) for predicting the aging is unrealistic for digital sensors as tracking the usage time with related temperature and voltage variation imposes high overhead. Accordingly, we propose an alternative approach where not one but two sensors are deployed. In practice, one sensor is used to detect environmental deviations, while the second one is used as the reference. In this respect, the second sensor is only operated seldom, mostly to re-calibrate the active sensor when aged. From this dual input (unaged and aged sensor), corrective models are derived. We account for two methods, namely simple but effective offset correction, and adjustment based on machine-learning. We conduct extensive characterizations (both pre-silicon simulations and post-silicon measurements on FPGA) which quantitatively confirm the applicability and high sensitivity of digital sensors.

Comparación de la corrección del offset femoral tras el empleo de un vástago monobloque y un vástago con cuello modular en la artroplastia total de cadera primaria

Introduction and objectiveDual modularity stems were introduced with the theoretical advantage of restoring hip anatomy more precisely through femoral offset and limb length adjustment. Interchangeable necks allow for intraoperative angulation, anteversion and length changes. Our objective is to study whether a better femoral offset correction is achieved with the H MAX-M® prosthesis (Limacorporate, San Daniele, Italy) compared to its monoblock counterpart. Material and methodsA prospective cohort study was conducted by means of consecutive sampling on adult patients undergoing total hip arthroplasty with the diagnosis of coxarthrosis between January 2011 and December 2015. This cohort has two arms, one arm included patients who underwent modular neck arthroplasty and the other included patients who underwent monoblock total hip arthroplasty. Radiographic offset measurement of the operated hip and the contralateral hip was performed, and the difference between both values was calculated. The mean of the measurements obtained for each arm of the cohort were compared with each other. ResultsNo statistically significant differences were observed in the difference in offset between the operated hip and the contralateral hip (P=.323). No statistically significant differences were observed in the correction of the femoral offset, determined as the difference between the operated hip and the contralateral hip (P=.323). Nor were differences observed in the postoperative offset values (P=.097). It should be noted that for both designs, the majority group is the one with restored offset (P=.001).

Significant Wave Height Estimation Using Multi-Satellite Observations from GNSS-R

This study proposes a significant wave height (SWH) retrieval method based on multi-satellite observations using Global Navigation Satellite System Reflectometry (GNSS-R). The algorithm obtains the signal-to-noise ratio (SNR) through delay-Doppler maps (DDMs) and introduces an offset correction that combines the differences between the elevation angles of multi-satellites. The correction improves the correlation between SNR and SWH and thus enables the estimation of SWH. The feasibility of the proposed algorithm was verified by experiments and a performance comparison with the traditional estimation method based on SNR. The estimation results of the proposed algorithm, with a mean absolute percentage error of 8.26%, a root mean square error of 0.1671 m, and a maximum error of 0.32 m, better matched the true values than the traditional SNR-based method. The method is intended to improve the retrieval accuracy of SWH based on the GNSS-R technique, and to provide services for sea-state information monitoring and ship navigation.

The importance of residual PVC offset correction for inverse localization of PVC origin using a single dipole

The importance of residual PVC offset correction for inverse localization of PVC origin using a single dipole

A Mathematical Method to Adjust MLC Leaf End Position for Accurate Dose Calculation in Carbon Ion Beam Radiation Therapy Treatment Planning System.

Introduction We present a mathematical method to adjust the leaf end position for dose calculation correction in the carbon ion radiation therapy treatment planning system. Methods and Materials A straggling range algorism of 400 MeV/n carbon ion beam in nine different multileaf collimator (MLC) materials was conducted to calculate the dose 50% point to derive the offset corrections in the carbon ion treatment planning system (ciPlan). The visualized light field edge position in the treatment planning system is denoted as Xtang.p, and MLC position (Xmlc.p) is defined as the source to leaf end midpoint projection on axis for monitor unit calculation. The virtual source position of energy at 400 MeV/n and straggling range in MLC at different field sizes were used to calculate the dose 50% position on axis. On-axis MLC offset (correction) could then be obtained from the position corresponding to 50% of the central axis dose minus the Xmlc.p. Results The exact MLC position in the carbon ion treatment planning system can be used as an offset to do the correction. The offset correction of pure tungsten is the smallest among the others due to its shortest straggling range of carbon ion beam in MLC. The positions of 50% dose of all MLC materials are always located in between Xtang.p and Xmlc.p under the largest field of 12 cm by 12 cm. Conclusions MLC offset should be adjusted carefully at different field sizes in the treatment planning systems especially of its small penumbra characteristic in the carbon ion beam. It is necessary to find out the dose 50% position for adjusting MLC leaf edge on-axis location in the treatment planning system to reduce dose calculation error.

Estimating discharge of the Ganga River from satellite altimeter data

We use the water level data from multiple satellite altimeter missions to estimate discharge at different reaches of varying channel width (130 m to 2 km) of the Ganga River in India. We have established five (Kachla bridge, Kanpur, Shahzadpur, Prayagraj, and Mirzapur) virtual stations in the middle and two (Azmabad and Farakka) in the lower reaches of the Ganga River. For these stations, we acquired the water level from different satellite altimeter mission ERS-2 (1995–2007), ENVISAT (2002–2010), and Jason-2 (2008–2017) from publicly available databases. We applied datum and offset corrections on the altimeter data to make them comparable with the water level measured at the nearest gauge station. At each location, water level from the altimeter and gauge station show a good agreement with root mean square (RMS) error in a range between (22-71cm).We plot the altimeter water level as a function of their corresponding discharge measured at the nearest gauge station to establish a stage-discharge rating curve for each location. We then use these rating curves to estimate monthly discharge of the Ganga River from the altimeter water level. Based on the overall performance analysis of the statistical parameters, i.e; Nash–Sutcliffe efficiency (NSE); 0.86–0.98, RMS-observations Standard deviation Ratio (RSR); 0.15–0.38, Percent Bias (PBIAS); 13–27, and the coefficient of determination (R2); 0.87–0.98, we show that the estimated discharge from altimeter water level accord well with the in-situ discharge measured at the gauge station. According to the Moriasi guideline, our estimate of discharge at all the virtual stations (except Kanpur) can be categorised between “good” to “satisfactory”.

A Four-Channel Low-Noise Readout IC for Air Flow Measurement Using Hot Wire Anemometer in 0.18 μm CMOS Technology.

Air flow measurements provide significant information required for understanding the characteristics of insect movement. This study proposes a four-channel low-noise readout integrated circuit (IC) in order to measure air flow (air velocity), which can be beneficial to insect biomimetic robot systems that have been studied recently. Instrumentation amplifiers (IAs) with low-noise characteristics in readout ICs are essential because the air flow of an insect’s movement, which is electrically converted using a microelectromechanical systems (MEMS) sensor, generally produces a small signal. The fundamental architecture employed in the readout IC is a three op amp IA, and it accomplishes low-noise characteristics by chopping. Moreover, the readout IC has a four-channel input structure and implements an automatic offset calibration loop (AOCL) for input offset correction. The AOCL based on the binary search logic adjusts the output offset by controlling the input voltage bias generated by the R-2R digital-to-analog converter (DAC). The electrically converted air flow signal is amplified using a three op amp IA, which is passed through a low-pass filter (LPF) for ripple rejection that is generated by chopping, and converted to a digital code by a 12-bit successive approximation register (SAR) analog-to-digital converter (ADC). Furthermore, the readout IC contains a low-dropout (LDO) regulator that enables the supply voltage to drive digital circuits, and a serial peripheral interface (SPI) for digital communication. The readout IC is designed with a 0.18 μm CMOS process and the current consumption is 1.886 mA at 3.3 V supply voltage. The IC has an active area of 6.78 mm2 and input-referred noise (IRN) characteristics of 95.4 nV/√Hz at 1 Hz.

Honey authentication in terms of its adulteration with sugar syrups using UV–Vis spectroscopy and one-class classifiers

This work proposes the use of UV–Vis spectroscopy and one-class classifiers to authenticate honey in terms of their individual and simultaneous adulterations with corn syrup, agave syrup, and sugarcane molasses. Then, spectra of aqueous authentic (n = 73) and adulterated (n = 162) honey samples were recorded. Before the construction of OC-PLS and DD-SIMCA models, different pre-processing techniques were used to removed baseline shifts. The best result obtained by DD-SIMCA using offset correction, correctly classifying all the samples in the test set. Therefore, the proposed methodology can be used as a promising tool to authenticate honey and prevent fraudulent labeling, affording security to consumers and providing an alternative to regulatory agencies. Moreover, it avoids laborious sample preparation and additional operational costs, since the analytical information is acquired using a routine instrumental technique, without the need for any sample preparation step, other than dilution of the samples in water alone.

Non-destructive authentication of Gourmet ground roasted coffees using NIR spectroscopy and digital images

The growing demand for excellent-quality coffees allied with their symbolic aestheticization that add value to the products favor the adulteration practices and consequently economic losses. So, this work proposes the suitability of NIR spectroscopy and Digital Images (from CACHAS) coupled with one-class classification methods for the non-destructive authentication of Gourmet ground roasted coffees. For this, Gourmet coffees (n = 44) were discriminated from Traditional (n = 36) and Superior (n = 10) by directly analyzing their powder without any sample preparation. Then, OC-PLS and dd-SIMCA were used to construct the models. dd-SIMCA using offset correction for NIR and RGB histogram for CACHAS achieved the best results, correctly recognizing all the 90 samples in both the training and test sets. Therefore, the proposed methodologies can be useful for both the consumers and regulatory agencies because it confirms the elevated standards of excellence of Brazilian specialty coffees, preventing fraudulent labeling, besides following the Principles of Green Analytical Chemistry.

Neural network approach for efficient calculation of the current correction value in the femtoampere range for a new generation of ionizing radiation monitors at CERN

The European Organization for Nuclear Research (CERN) conducts experiments that involve colliding beams of particles either together or into stationary targets. During these interactions, stray radiation may be generated. The ionizing radiation detectors installed at several locations close to the beam lines and targets of these areas allow CERN radiation protection by precisely monitoring radiation levels. Radiation monitoring is one of the main responsibilities of the Radiation Protection Group and a crucial task to indirectly ensure safety at CERN and its surrounding environment.After 30 years of reliable service, the ARea CONtroller (ARCON) system has reached the end of its lifecycle. A new generation of radiation monitors called CROME (Cern RadiatiOn Monitoring Electronics) has been developed at CERN. These monitors incorporate embedded processing capabilities in order to execute various algorithms, such as evaluation of the real electrical current generated by the radiation detectors when they are subject to ionizing fields. This paper presents a case study of a new method for offset correction of a femtoampere current. At this scale, the measured current is sensitive to surrounding environmental factors, such as temperature, vibration. and the permittivity of the air. To guarantee the high precision of calculation and real-time operation, and to overcome the limitations of the field-programmable gate array (FPGA) platform used, a novel method utilizing a neural network approach is proposed. The results obtained with a new model are very satisfactory in terms of both accuracy of prediction and reduced computational complexity. This may encourage further usage of neural networks in safety-critical systems.

Good Outcome Scores and Low Conversion Rate to THA 10 Years After Hip Arthroscopy for the Treatment of Femoroacetabular Impingement.

Arthroscopic treatment of symptomatic femoroacetabular impingement (FAI) has promising short-term to mid-term results. In addition to treating acute pain or impaired function, the goal of hip-preserving surgery is to achieve a lasting improvement of hip function and to prevent the development of osteoarthritis. Long-term results are necessary to evaluate the effectiveness of surgical treatment and to further improve results by identifying factors associated with conversion to THA. (1) How do the Merle d'Aubigné-Postel scores change from before surgery to follow-up of at least 10 years in patients undergoing hip arthroscopy for the treatment of FAI? (2) What is the cumulative 10-year survival rate of hips with the endpoints of conversion to THA or a Merle d'Aubigné-Postel score less than 15? (3) Which factors are associated with conversion to THA? Between 2003 and 2008, we treated 63 patients (65 hips) for symptomatic FAI with hip arthroscopy at our institution. During that period, the indications for using arthroscopy were correction of anterior cam morphology and anterolateral rim trimming with debridement or reattachment of the labrum. We excluded patients who were younger than 16 years and those who had previous trauma or surgery of the hip. Based on that, 60 patients (62 hips) were eligible. A further 17% (10 of 60) of patients were excluded because the treatment was purely symptomatic without treatment of cam- and/or pincer-type morphology. Of the 50 patients (52 hips) included in the study, 2% (1) of patients were lost before the minimum study follow-up of 10 years, leaving 49 patients (51 hips) for analysis. The median (range) follow-up was 11 years (10 to 17). The median age at surgery was 33 years (16 to 63). Ninety percent (45 of 50) of patients were women. Of the 52 hips, 75% (39 of 52) underwent cam resection (femoral offset correction), 8% (4 of 52) underwent acetabular rim trimming, and 17% (9 of 52) had both procedures. Additionally, in 35% (18 of 52) of hips the labrum was debrided, in 31% (16 of 52) it was resected, and in 10% (5 of 52) of hips the labrum was reattached. The primary clinical outcome measurements were conversion to THA and the Merle d'Aubigné-Postel score. Kaplan-Meier survivorship and Cox regression analyses were performed with endpoints being conversion to THA or Merle d'Aubigné-Postel score less than 15 points. The clinical result at 10 years of follow-up was good. The median improvement of the Merle d'Aubigné-Postel score was 3 points (interquartile range 2 to 4), to a median score at last follow-up of 17 points (range 10 to 18). The cumulative 10-year survival rate was 92% (95% CI 85% to 99%) with the endpoints of conversion to THA or Merle d'Aubigné-Postel score less than 15. Factors associated with conversion to THA were each year of advancing age at the time of surgery (hazard ratio 1.1 [95% CI 1.0 to 1.3]; p = 0.01) and preoperative Tönnis Grade 1 compared with Tönnis Grade 0 (no sign of arthritis; HR 17 [95% CI 1.8 to 166]; p = 0.01). In this series, more than 90% of patients retained their native hips and reported good patient-reported outcome scores at least 10 years after arthroscopic treatment of symptomatic FAI. Younger patients fared better in this series, as did hips without signs of osteoarthritis. Future studies with prospective comparisons of treatment groups are needed to determine how best to treat complex impingement morphologies. Level IV, therapeutic study.

High Rate CV-QKD Secured Mobile WDM Fronthaul for Dense 5G Radio Networks

A coherent transmission methodology for a continuous-variable quantum key distribution (CV-QKD) system based on quantum-heterodyne measurement through a coherent intradyne receiver is experimentally demonstrated in the framework of 5G mobile fronthaul links. Continuous optical carrier synchronization is obtained through training information, which is multiplexing to the quantum signal as pilot tone in both, frequency and polarization. Spectral tailoring by means of optical carrier suppression and single-sideband modulation is adopted to simultaneously mitigate crosstalk into the quantum channel and self-interference for the pilot tone, thus allowing for a high signal-to-noise ratio for this training signal. Frequency offset correction and optical phase estimation for the free-running local oscillator of the receiver is accurately performed and guarantees low-noise quantum signal reception at high symbol rates of 250 MHz and 500 MHz with additional Nyquist pulse shaping. A low excess noise in the order of 0.1% to 0.5% of shot-noise units is obtained for fiber-based transmission over a fronthaul link reach of 13.2 km. Moreover, co-existence with 11 carrier-grade classical signals is experimentally investigated. Joint signal transmission in the C-band of both, quantum signal and classical signals, is successfully demonstrated. Secure-key rates of 18 and 10 Mb/s are obtained under strict security assumptions, where Eve has control of the receiver noise, for a dark and a lit fiber link, respectively. Moreover, rates of 85 and 72 Mb/s are resulting for a trusted receiver scenario. These secure-key rates are well addressing the requirements for time-shared CV-QKD system in densified 5G radio access networks with cloud-based processing.

Seasonal marine carbon system processes in an Arctic coastal landfast sea ice environment observed with an innovative underwater sensor platform

Studying carbon dioxide in the ocean helps to understand how the ocean will be impacted by climate change and respond to increasing fossil fuel emissions. The marine carbonate system is not well characterized in the Arctic, where challenging logistics and extreme conditions limit observations of atmospheric CO2 flux and ocean acidification. Here, we present a high-resolution marine carbon system data set covering the complete cycle of sea-ice growth and melt in an Arctic estuary (Nunavut, Canada). This data set was collected through three consecutive yearlong deployments of sensors for pH and partial pressure of CO2 in seawater (pCO2sw) on a cabled underwater observatory. The sensors were remarkably stable compared to discrete samples: While corrections for offsets were required in some instances, we did not observe significant drift over the deployment periods. Our observations revealed a strong seasonality in this marine carbon system. Prior to sea-ice formation, air–sea gas exchange and respiration were the dominant processes, leading to increasing pCO2sw and reduced aragonite saturation state (ΩAr). During sea-ice growth, water column respiration and brine rejection (possibly enriched in dissolved inorganic carbon, relative to alkalinity, due to ikaite precipitation in sea ice) drove pCO2sw to supersaturation and lowered ΩAr to &amp;lt; 1. Shortly after polar sunrise, the ecosystem became net autotrophic, returning pCO2sw to undersaturation. The biological community responsible for this early switch to autotrophy (well before ice algae or phytoplankton blooms) requires further investigation. After sea-ice melt initiated, an under-ice phytoplankton bloom strongly reduced aqueous carbon (chlorophyll-a max of 2.4 µg L–1), returning ΩAr to &amp;gt; 1 after 4.5 months of undersaturation. Based on simple extrapolations of anthropogenic carbon inventories, we suspect that this seasonal undersaturation would not have occurred naturally. At ice breakup, the sensor platform recorded low pCO2sw (230 µatm), suggesting a strong CO2 sink during the open water season.