Real-time Clock Research Articles

Maintaining real-time precise point positioning during outages of the corrections broadcast by BDS-3 global short-message communication

Real-time precise point positioning (RTPPP) is a popular technique for precision applications, which is based on real-time service (RTS) products. However, one serious problem for RTPPP users is the potential communication break for a period from a few minutes to an hour. A significant decline in positioning accuracy may occur since the receiving of the RTS corrections is discontinuous. In this study, the real-time orbit and clock corrections are converted into the equivalent range corrections and broadcast by BeiDou global navigation satellite system (BDS-3) global short-message communication (GSMC). We focus on maintaining global navigation satellite systems (GNSS) RTPPP during outages of the range corrections. Three prediction methods are presented, including “linear function”, “mean value” and “last value” methods. The predicted corrections will be carried out with only at most 5 latest epochs of the registered corrections. The “last value” method shows the optimal prediction performance and the prediction errors of Galileo are minimal compared to GPS and BDS. Both simulated and vehicle kinematic experiments are conducted to evaluate the performance of RTPPP with the predicted corrections. The results show that the three proposed predicted corrections can maintain centimeter-to decimeter-level accuracy in both static and kinematic mode during outages of the BDS-3 GSMC that may be from a few minutes to an hour. Using the last registered equivalent range correction value is the most recommended choice to maintain multi-GNSS RTPPP.

Design of High Precision Temperature Sensor with Current Gain Compensation Technology for On-Chip Application

The integration of on-chip temperature sensors within various systems, industrial Internet of Things (IoT), and wireless sensor networks is greatly facilitated by their small size, cost-effectiveness, and capability to provide direct digital output. However, the diverse application scenarios pose challenges in designing these sensors. On one hand, real-time clock calibration demands high-precision temperature sensors, while on-chip heat management emphasizes compactness and low-voltage operation. Additionally, streamlining the calibration cost for mass production holds significant practical value. Addressing these challenges, this study systematically investigates on-chip complementary metal-oxide-semiconductor (CMOS) temperature sensors based on distinct signal domains processed by temperature readout circuits. Specifically, the research commences by analyzing the issues of several degeneracy points in the front-end circuit of a bipolar junction transistor (BJT) temperature sensor with current gain compensation technology. To address the intricate design challenges in advanced technologies and calibration complexities in industrial applications, dynamic component matching, current gain compensation, and chopper stabilization are harnessed. A novel dynamic current gain canceling technique for temperature readout is introduced, enhancing temperature measurement accuracy without incurring additional power consumption or area overhead. Ultimately, an all-digital CMOS temperature sensor is realized using the SMIC 55 nm CMOS process. Occupying a mere 0.29 mm2 of core area, the design operates efficiently across a wide supply voltage range of 1.2 V to 3.6 V. Covering a temperature spectrum from −40 °C to 125 °C, the sensor demonstrates a calibration error of just ±0.7 °C. This achievement is attributed to the incorporation of the proposed dynamic current gain compensation technique.

Design and Build Automatic Catfish Feeding System Biofloc

Catfish is one of the results of freshwater cultivation that is popular with the community and has economic value. The high public interest in catfish, is one of the factors cultivators increase production yields. Feeding and treatment of catfish pond water still uses human resources. This reduces the efficiency of the farmer and allows for negligence in providing feed and water treatment if the farmer has a large number of ponds or more than one. In this study, it is proposed to control and monitor feeding and water treatment with a biofloc system automatically and regularly, with the catfish biofloc system also obtaining natural food when the feeding schedule is raining. It takes a wireless sensor network system as a control system, fc-37 sensor, Total Dissolved Solids (TDS), Loadcell, Real Time Clock (RTC). All of these sensors will be integrated with the Arduino Uno which will then send data from each sensor to the Raspberry Pi with the nRF24l01 communication module. The results of this study are monitoring the appearance of the web server processed by the Raspberry Pi which shows feed availability, pond conditions and turbidity levels. From the experimental results, it is found that the planned system can work well and as desired.

Real-time validation of downstream 50G/25G and 50G/100G flexible rate PON based on Miller encoding, NRZ, and PAM4 modulation

Experimental demonstration is given of a real-time flexible downstream 50 Gb/s passive optical network (PON) mixed with 25 Gb/s or 100 Gb/s signals. 25 Gb/s transmission is enabled by using 25 Gb/s Miller encoding. For back-to-back a lower sensitivity for 25 Gb/s Miller of ∼2.2dB is found relative to 50 Gb/s non-return-to-zero (NRZ). An extended reach of 40 km and up to ∼5dB optical power budget improvement after worst-case 20 km standard single-mode fiber over 50 Gb/s NRZ was shown for 25 Gb/s Miller. It was also shown that optical network units (ONUs) that have 9 dB additional optical received power because they experience a lower optical loss can receive 100 Gb/s four-level pulse amplitude modulation (PAM4) instead of NRZ in a flexible rate PON, which will double the bit-rate to these ONUs. 50 Gb/s NRZ transmission under mixed modulation (50% NRZ and 50% Miller or 50% PAM4) can operate with very low penalty. A power penalty of <0.4dB was found for 50 Gb/s NRZ after worst-case total dispersion (as specified in ITU-T G.9804) when mixed with 25 Gb/s Miller or 100 Gb/s PAM4. For back-to-back there was a smaller penalty of <0.2dB for 50 Gb/s NRZ under mixed modulation. The 25 Gb/s Miller signal spectrum is similar to 50 Gb/s NRZ and 100 Gb/s PAM4, which enables good performance of the real-time clock and data recovery with an integrated adaptive feed-forward-equalizer based equalizer under mixed signal modulation. The increased optical power budget enabled by the 25 Gb/s Miller encoding effectively improves power margins of the high-speed PON and will enable reliable transmission for ONUs deployed with out-of-spec (higher) loss and/or (larger) fiber reach. The additional margin provided by 25 Gb/s Miller encoding will also enable a safe-mode for ONUs that experience out-of-spec scenarios because of faults in the PON fiber network.

LEO Satellite Clock Modeling and Its Benefits for LEO Kinematic POD

High-accuracy Low Earth Orbit (LEO) satellite clock and orbital products are preconditions to realize LEO augmentation for high-accuracy GNSS-based positioning on the ground. There is a high correlation between the orbit and clock parameters in the kinematic Precise Orbit Determination (POD) process. While future LEO satellites are planned to be equipped with better clocks, the benefits of modeling high-stability LEO satellite clocks are not yet thoroughly investigated, particularly when mid- to long-term systematic effects induced by the complex LEO relativistic effects and the external environment remain in the clocks. Through clock modeling, this study attempts to reduce not only the short-term noise of radial kinematic orbits, but also mis-modeled effects caused by, e.g., real-time GNSS orbital and clock errors. To explore the benefits of clock modeling, the clocks need to be first detrended by the mid- to long-term systematic effects. While over-detrending limits the orbital improvements, weak detrending would also hamper strong clock modeling and easily lead to performance degradations. A balance between the strengths of the detrending and the model thus needs to be investigated for different clock types. In this study, the Piece-Wise Linear (PWL) model of different time lengths and a 2.5-state filter with different strengths (h values) are tested using real data from GRACE FO-1 with an Ultra-Stable Oscillator (USO) on board. Using the CNES real-time GPS products, it was found that when detrending the clocks with a smoothing window of 300 to 500 s, one could generally expect an improvement larger than 10% in the estimation of radial orbits when applying a PWL model with a length from 300 to 1200 s. Improvements of this size can also be expected when using the 2.5-state model with h−1 (for Flicker Frequency Noise) from 10−28 to 10−30.

Automation and Control of a Multi-feedstock Biodiesel Production Plant

The increasing need to develop renewable sources of energy to complement the energy generated via fossil fuel necessitates this study. This study demonstrates the process control and automation of a biodiesel processing plant. The developed biodiesel processing plant has a total output capacity of 200 litres per day with nine compartments divided into three major sections. The first section (pre-processing section) has the oil storage, pre-treatment, methanol and mixing tanks. The second section (main processing section) comprises of the reactor. The last section (post-processing section) comprises of the water, wash and separating tanks as well as the glycerol and biodiesel storages. The control and automation was achieved with the following components; three 3 kW variable speed electric motor, four 2.5 kW pumps, three 300 kW electric heater that are thermostatically controlled. Other materials used for the control and automation include: real time clock, Atmega328 microcontroller, LM6009 and LM 2596 modules, Liquid Crystal Display (LCD), switches, relay, LED, three temperature probes, 220 V AC alarm, four flow switches, 220 V timer relay, 220 V and 60 A contactor. Sensors are incorporated to measure the temperature, pressure, and flow level in the main reactor and the measured variables compared with the threshold values pre-set on the micro controller for control actions. The results obtained indicated that the performance of the plant was enhanced with the capacity to independently execute control actions during the biodiesel production. Thus, this study adds to the practical knowledge of system's control and automation for biodiesel production.

BDS/GPS/Galileo Precise Point Positioning Performance Analysis of Android Smartphones Based on Real-Time Stream Data

Smartphones with the Android operating system can acquire Global Navigation Satellite System (GNSS) raw pseudorange and carrier phase observations, which can provide a new way for the general public to obtain precise position information. However, only postprocessing precise orbit and clock offset products in some older smart devices are applied in current studies. The performances of precise point positioning (PPP) with the smartphone using real-time products and newly smartphones are still unrevealed, which is more valuable for real-time applications. This study investigates the observation data quality and multi-GNSS real-time PPP performance using recent smartphones. Firstly, the observed carrier-to-noise density ratio (C/N0), number of satellites and position dilution of precision (PDOP) of GNSS observations are evaluated. The results demonstrate that the C/N0 received by Huawei Mate40 is better than that of the Huawei P40 for GPS, BDS, QZSS and Galileo systems, while the GLONASS is poorer, and the PDOP of the Huawei P40 is slightly better than that of Mate40. Additionally, a comprehensive analysis of real-time precise orbit and clock offset products performance is conducted. The experiment result expresses that the orbit and clock offset performance of GPS and Galileo is better than that of BDS-3 and GLONASS, and BDS-2 is the worst. Finally, single- and dual-frequency multi-GNSS combined PPP experiments using observations received from smartphones and real-time products are conducted; the results indicate that the real-time static PPP using a smartphone can achieve decimeter-level positioning accuracy, and kinematic PPP can achieve meter-level positioning accuracy after convergence.

Improved short-term stability for real-time GNSS satellite clock estimation with clock model

Improved short-term stability for real-time GNSS satellite clock estimation with clock model

IoT-Based Smart Medicine Dispenser

Abstract: Correct on-time medication is very important to recover from the health problem. This paper aims to develop a smart medicine dispenser system. Taking medicines for elderly, deaf, and blind people is difficult without any attendant around. The designed system helps to remind them to take their medicines and delivers the medicine according to the prescription. The system has three medicine delivery parts one for the morning, one for the afternoon, and one for the night. The pills are put in the boxes according to the prescription and delivered automatically based on the input from a real-time clock (RTC) at appropriate timings. The system uses a microcontroller to control various operations. It senses the inputsignal from RTC and gives a control signal to the servo motor to actuate dispensing the box containing pills. The provision is made to give an alarm to the patient through voice message andLCD displays to remind the patient to take medicine. A mobile app is developed using the Cayenne mobile app developer so that the caretaker will get a live notification at his or her workplace. This ensures the caretaker that the patient has takenthe medicine. The system has the facility to store medicine for seven days. The scheduling and modification can be done through the mobile app according to the prescription. The prototype has been developed and tested. The system is workingsatisfactorily

Medicine Dispenser Using RFID

Abstract: A medicine dispenser powered by a Atmel ATmega2560 controller was proposed in this article as a way to help people take their medications on schedule and in the recommended dosages given by their physicians. Only two out of fifty people use this innovative assistance due to its high cost, lack of information on the subject, and accessibility. It has been discovered that people are more concerned about their physique than their well-being, with many older people needing at least two assistive items per family by the year 2050. This device plan helps patients avoid this problem by reminding them to take their prescriptions on time and within the recommended window. It provides updates for patients, which is helpful for people who are aware of when to take their dosage and is particularly helpful for those who forget to do so. One of this device's key advantages is the ease of use and affordability of the framework. The device uses an Arduino MEGA, LCD display, Real-Time Clock (RTC) module, and RFID to inform patients and remind them to take their medications at the recommended time. This concise and useful framework can be of great use to older patients and those who are economically disadvantaged. Families with older citizens may find this medicine dispenser helpful as their responsibilities are reduced by reminders to take prescription medications as directed. The framework has also been connected to an online database to track the patient's medical history when needed.

RANCANG BANGUN ALAT UJI PERKOLASI TANAH BERBASIS ARDUINO

Water absorption testing through soil percolation test is mostly handled manually. During the testing process, it still requires many people to supervise it, and the reading error rate is still high. Therefore, a measuring instrument that works automatically is needed that can more specifically read the rate of water absorption into the soil accurately. In this final project, the tool is made using Arduino Mega, HC-SR04 ultrasonic sensor, 128x64 LCD, buzzer, NEO6MV2 GPS Module, RTC (Real Time Clock), push button, and Lithium-Ion Battery. The result of this final project is a soil permeability measuring instrument that can accurately measure the rate of water infiltration. Based on the results of design, testing and analysis of the design results, a soil permeability measuring instrument is obtained that can properly measure the rate of water infiltration

An Implantable Bio-Signal Sensor SoC with Low-Standby-Power 8K-Bit SRAM for Continuous Long-Term Monitoring

Individualized treatment of chronic diseases opens up great opportunities for implantable biosensor systems capable of tracking vital signals over long periods of time. To this end, low-power techniques in standby mode and the efficient utilization of storage space will be important issues for the implementation of such rechargeable implants with a built-in memory. This paper presents key circuit techniques, including a leakage-current-based clock generator that eliminates the need for an internal reference clock source, a low-standby-power 8Kbit SRAM with negative wordline and dynamic supply voltage scaling, and an adaptive sensing scheme to improve storage space utilization. When implemented with commercial 180 nm CMOS technology for the circuit simulation, approximately 70% (100 nW) of power dissipation was reduced from internal clock source, about 70% of power consumed by 8Kbit SRAM was saved, and the storage space utilization was improved by about 42.8%. In the end, the proposed implantable biosensor SoC consumes about 82.5 nW of standby power, saving about 42% from the previous approach and can last for 2.5 days using a 5 uAh thin-film battery (CYMBET® 1.7 × 2.2 mm2).

Second-Dimension Temperature Programming System for Comprehensive Two-Dimensional Gas Chromatography. Part 2: Technical Improvements and Compatibility with Flow Modulation and Time-of-Flight Mass Spectrometry

The second-dimension (2D) temperature programming system (2DTPS) for comprehensive two-dimensional gas chromatography (GC × GC) described in Part 1 was updated and tested with the time-of-flight mass spectrometer (TOFMS) and flow modulator. Addition of a real-time clock and remote port allowed the 2DTPS to be a truly standalone system to be used with any GC × GC instrument. GC × GC reproducibility with the 2DTPS was tested with thermal and flow modulation, coupled with the TOFMS and/or FID to demonstrate compatibility with all typical GC × GC setups. An improvement in the match factor, reverse match factor, and signal-to-noise ratio was found when performing 2D temperature programming. Within-day and day-to-day reproducibility of the 2DTPS for the 1D retention time (≤0.04 and ≤0.05%), 2D retention time (≤0.36 and ≤0.52%), and peak area (≤2.47 and ≤3.37%) were acceptable, while providing flexibility in 2D optimization and improved peak capacity.

Research on high‐precision synchronous output technology of multi‐reference source weighted synthesis in power system

AbstractThe massive perception data based on efficient analysis and intelligent decision have put forward higher requirements for high‐precision time synchronisation with the construction and development of smart power grid. However, multi‐reference source time‐frequency synchronisation of power system only selects the best method after comparison, which cannot make the most efficient use of the existing resources. It also cannot meet the need for high‐precision time synchronisation of future power system. The existing multi‐reference source synthesis algorithms cannot take into account both long‐term stability and high‐precision synchronous output. This article presents a multi‐reference source weighted improved noise model and the high‐precision output method. The multi‐reference source error after classification is eliminated by leading into classification vector and classification coefficient. The synthesised frequency offset or the time precision of output can be optimised as the objective function by weighted classification algorithm and genetic algorithm. A simulation example based on the synthesis of two satellite system clock sources and three local caesium reference sources shows that the peak value of long‐term output accuracy is controlled within 10 ns after classification weighted synthesis and optimisation, which is better than that of any single reference source.

Development Board Implementation and Chip Design of IEEE 1588 Clock Synchronization System Applied to Computer Networking

With the vigorous development of industrial automation and the Internet of things, the transmission of data is more dependent on immediacy, so network devices have higher and higher requirements for time synchronization accuracy. The clock source of common network devices is provided by the transistor oscillator in the server, but the oscillator will change with factors such as aging and temperature, and it cannot be guaranteed that the oscillator in the server will work at the same frequency. Time synchronization can be achieved by technologies such as IRIG-B, NTP, or IEEE 1588 (PTP), but the hardware cost of building IRIG-B is high, and NTP has the lowest cost, but it can only provide time accuracy from milliseconds to microseconds. PTP can provide sub-microsecond or even nanosecond time precision. It is a system of time synchronization mechanisms through Ethernet transmission. In this article, we first propose a time synchronization system using the development board and PDP protocol. On the Xilinx Zynq-7000 SOC platform of Petalinux, we implement the hardware solution of Linux PTP. The hardware time stamp is 20 ns. To improve the accuracy, the congenital frequency error between the oscillators must be considered. Therefore, a PTP auxiliary time stamp with dynamic frequency compensation is proposed and designed into a chip. Experimental results show that at 45 nm (TN40G) it can operate at 370 MHz and achieve 2.7 ns resolution, which can be applied to more demands.

Design and Implementation of Precision Phase Measurement Module Base on Digital Dual Mixer Time Difference

Precise phase difference measurement is critical for distributed time synchronization systems. Aiming at the problem of how to realize the sub-nanosecond phase difference measurement of the time signal, the digital dual mixer time difference (DDMTD) measurement technology is used to measure the fine transmission delay and the two digital clock phase difference. Given the problem that it is difficult to generate a common clock source with fine frequency changes inside the FPGA chip, the Si5338 chip is used to generate 4 differential clocks, and the communication with the FPGA is completed through the I2C protocol, and the differential signal is converted into a single-ended clock source inside the FPGA as two The common standard frequency of clock signals with the same frequency and different phases, realize the amplification of the phase difference measurement range, making the measurement accuracy reach sub-nanosecond level.

External Measurement System for Aircraft Structural Parts Based on Digital Image Correlation in Signal-limited Spaces

An experimental study was performed on the application of the digital image correlation (DIC) technique to characterize aircraft components for which accurate time information is required. This study builds an aircraft external measurement system based on Stereo DIC. This system obtains real-time satellite time information from a GPS clock source and transmits it to a trigger unit. A camera acquires this information and displays it on the image. This solves the problem that some closed laboratories can use only computer time and cannot obtain accurate satellite time when using camera measurements. Moreover, we verify the reliability and accuracy of this approach, finding an average angular accuracy of better than 0.02 degrees and a relative error of less than 1%. Using the binocular Stereo DIC system, the accuracy of the measurements is clarified for specific conditions. Furthermore, we use this system to measure simulated aircraft landing gear, which moves at an angular velocity of 52.4 °/ s over a distance of 5 m with a wide field of view of 16.8°. The satellite time information acquired by the camera and the time information of the captured time targets are highly stable. The system’s reliability is demonstrated for use in practical engineering, contributing to the engineering application of Stereo DIC for external aircraft measurements.

Series Editorial: Mobile Communications and Networks

We are excited to have an unusually large number of articles in this issue of Mobile Communications and Networks series. These articles explore further evolutions of communications and some potentials for 6G, including delivery of high-precision clock sources, next generation connectivity for Railways, integration of terrestrial and non-terrestrial networks, integration of artificial intelligence (AI) into open Radio Access Network (O-RAN), investigation of MIMO channel quantization and channel error models towards 6G, the potential of near-field beam focusing for 6G, enabling rural connectivity by recycling TV towers with massive MIMO, integration of satellite communication systems into 5G networks, efficient decoders for short block length codes for ultra-reliability low-latency communications (URLLC), and the potential benefits of virtualized distributed unit (vDU) standardization in softwarized RAN.

Development of Non-Intrusive Low-Power Digital Water Meter Reading System Based On Wireless Mesh Network and Internet of Things

The application of WMN and IoT technology to the metering infrastructure is proven to provide convenience in data collection, access to information, and management of metering devices. Unfortunately, the use of this technology is still minimal in developing countries like Indonesia. In this study, the development of a digital meter reading system that focuses on low-power non-intrusive reading devices and the application of WMS in the water meter reading system is carried out. This system consists of a series of meter reader sensors that are connected mesh to a gateway where meter data can be monitored in real-time and remotely. This sensor circuit is an integrated circuit added to the existing mechanical water meter which allows recording the volume of water consumption digitally. This circuit consists of an optical sensor, real-time clock (RTC), microcontroller, Lora Transmitter, and power supply. The use of solar cells to supply energy for meter reading devices is another interesting aspect of the development of this system. A gateway is a circuit built to bridge the transmission of meter data from a radio-based sensor network to the internet. The result of this research is the establishment of a meter reading system capable of accurately reading water consumption, low power where the meter data is easily accessible using a device connected to the internet. This system has been evaluated for every part of development such as reading water consumption, power consumption, and also communication in the mesh network. The contribution of this research is that it can be used as a reference for developing a digital meter system that is more effective, has low power, and has easy access to meter data

A Real-Time Linear Prediction Algorithm for Detecting Abnormal BDS-2/BDS-3 Satellite Clock Offsets

Due to space environment interference, imperfect data processing model, and the performance of atomic clocks, real-time satellite clock products often contain outliers or irregular biases. We propose a real-time linear moving short-term prediction algorithm to predict clock offsets and detect abnormalities. The proposed algorithm mainly includes phase/frequency anomaly detection and real-time prediction part. Both the phase and frequency domains are used to detect abnormal clock offsets with previous epochs for building the clock prediction model accurately. The real-time moving prediction module utilizes the high short-term prediction performance to check the clock abnormality. The performance of the algorithm is then evaluated for all satellites with real-time estimated satellite clock offsets. To verify the feasibility and effectiveness of the proposed linear moving model and algorithm, the results of the grey model GM(1,1) and the ARIMA model are also compared. The experimental results indicated that the algorithm can detect clock outliers, frequency modulation, and phase jumps, and the linear model has a better clock performance improvement. After the abnormalities are removed with the proposed algorithm, the average STD accuracy of the real-time clock offsets for all satellites is improved by 15.5%, compared to an improvement of 11.4% by the GM(1,1) model and 11.5% by the ARIMA model. The PPP results demonstrate that the proposed clock prediction algorithm improves the positioning accuracy by 8.1%, 13.3%, and 16.9% in the east, north, and up components, respectively.