Accurate Clock Discipline For Long-Term Synchronization Intervals

Martínez, Borja; Vilajosana, Xavier; Dujovne, Diego

doi:10.1109/jsen.2017.2662323

Cited by 8 publications

(4 citation statements)

References 14 publications

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“…Borja et al [13] propose another synchronization approach for long-term synchronization interval. Instead of simply recalculating the drift when temperature change exceeds a threshold, it maintains a reference drift table at different temperatures.…”

Section: Related Workmentioning

confidence: 99%

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Surviving the Hair Dryer: Continuous Calibration of a Crystal-Free Mote-on-Chip

Chang¹,

Watteyne

Wheeler

et al. 2022

IEEE Internet Things J.

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The single chip micro-mote (SCµM) is a 2×3 mm 2 single-chip crystal-free mote-on-chip. SCµM implements the IEEE802.15.4 and BLE standards and can communicate with offthe-shelf radios compliant to those standards. SCµM exclusively uses on-chip oscillators, including a 2.4 GHz LC oscillator to synthesize the communication frequency, and a 2 MHz RC oscillator to clock the chip rate. The challenge is that the LC oscillator drifts at 2,100 ppm over a temperature range of 45 • C, far from the 40 ppm maximum drift mandated by the IEEE802.15.4 standard. While one-shot calibration is possible, any temperature change causes IEEE802.15.4 communication to fail. This paper describes a continuous calibration approach for SCµM to adapt the tuning of its oscillators as the temperature changes. Experimental results show that it allows SCµM to keep communicating with an IEEE802.15.4 radio even under the extreme condition of using a hair dryer to heat up the chip at 3 • C/min. Under these conditions, the drift of the LC oscillator stays within the ±40 ppm limit over 94% of the time. Similarly, the drift of the 2 MHz RC oscillator stays within ±1,000 ppm limit 99.98% of the time.

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Section: Related Workmentioning

confidence: 99%

“…The major difference between SCµM and the work presented in [12], [13] and [11] is that they are dealing with a crystal-based clock, rather than RC or LC oscillators. Typically, the synchronization approaches presented in these articles rely on sending a packet to obtain the time offset and calculates the drift based on the offset.…”

Section: Related Workmentioning

confidence: 99%

Surviving the Hair Dryer: Continuous Calibration of a Crystal-Free Mote-on-Chip

Chang¹,

Watteyne

Wheeler

et al. 2022

IEEE Internet Things J.

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show abstract

“…In [19,20], the random-access channel (RACH) for narrow band IoT uses the frequency hopping scheme as the wireless access protocol and thus the suppression of MAI and the estimation of CFO through RACH are considered. In [21], the frequency synchronization scheme based on global positioning system for LPWA is considered. The unique word for estimating CFO is considered [22].…”

Section: Related Workmentioning

confidence: 99%

ID Insertion and Data Tracking with Frequency Offset for Physical Wireless Parameter Conversion Sensor Networks

Takyu

Shirai

Ohta

et al. 2019

Sensors

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As the applications of the internet of things are becoming widely diversified, wireless sensor networks require real-time data reception, accommodation of access from several sensors, and low power consumption. In physical wireless parameter conversion sensor networks (PhyC-SN), all the sensors use frequency shift keying as the modulation scheme and then access the channel to the fusion center, simultaneously. As a result, the fusion center can recognize the statistical tendency of all the sensing results at a time from the frequency spectrum of the received signal. However, the information source, i.e., the sensor, cannot be specified from the received signal because no ID-indicating sensor is inserted to the signal. The data-tracking technique for tracing the time continuity of the sensing results is available for decomposing the sequence of the sensing results per sensor but the error tracking, which is a wrong recognition between the sensing results and the sensor, occurs owing to the similarity of the sensing results. This paper proposes the sensing result separation technique using a fractional carrier frequency offset (CFO) for PhyC-SN. In the proposed scheme, the particular fractional CFO is assigned to each user and it is useful for the ID specifying sensor. The fractional CFO causes inter-carrier interference (ICI). The ICI cancellation of the narrowband wireless communications is proposed. The two types of data-tracking techniques are proposed and are selectively used by the fusion center. Since the proposed data-tracking technique is multi-dimensional, high accuracy of data tracking is achieved even under the similar tendency of the sensing results. Based on computer simulation, we elucidate the advantage of the proposed sensing results separation.

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“…There have also been other approaches developed for crystal-based architectures. Martinez et al apply quadratic least-squares to a periodically updated table of frequency drift measurements to build a drift-temperature model with a maximum drift of 10 ms over 24 h (close to 0.1 ppm) [8]. Lee et al present a compensation circuit to program a 23-bit frequency divider based on measurements between −40 °C and 60 °C to achieve less than 1 ppm of frequency variation [9].…”

Section: Introductionmentioning

confidence: 99%

A Temperature-Compensated BLE Beacon and 802.15.4-to-BLE Translator on a Crystal-Free Mote

Yuan

Maksimovic

Wheeler

et al. 2022

2021 51st European Microwave Conference (EuMC)

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Crystal-free radios have the potential to revolutionize the IoT: due to their single-chip nature, they are both very cheap (no external components required) and very small (the size of a grain of rice). The Single-Chip Micro Mote (SCµM) is a 2×3×0.3 mm 3 crystal-free chip that can communicate with off-the-shelf transceivers over Bluetooth Low Energy (BLE) or IEEE 802.15.4. Setting its communication frequency is challenging because the crystal-free chip can rely only on internal oscillating circuits, which are very susceptible to temperature. Without compensation, a SCµM chip can no longer communicate with an off-the-shelf BLE receiver if the temperature changes by more than 1.25 °C. This paper introduces a two-step temperature compensation method, allowing SCµM to successfully send BLE frames over a 20 °C temperature range. After performing initial calibration during optical bootloading, we use an open-loop linear model to estimate the ambient temperature and continuously tune the mote's local oscillator (LO) frequency as the temperature changes. We show how the mote can use the intermediate frequency of 802.15.4 frames it receives from nearby off-the-shelf transceivers as a frequency reference to adjust its LO frequency. This compensation method enables SCµM to operate as a tiny BLE beacon, a BLE temperature sensor (for retail or medical applications), or a 802.15.4-to-BLE translation device.

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Accurate Clock Discipline For Long-Term Synchronization Intervals

Cited by 8 publications

References 14 publications

Surviving the Hair Dryer: Continuous Calibration of a Crystal-Free Mote-on-Chip

Surviving the Hair Dryer: Continuous Calibration of a Crystal-Free Mote-on-Chip

ID Insertion and Data Tracking with Frequency Offset for Physical Wireless Parameter Conversion Sensor Networks

A Temperature-Compensated BLE Beacon and 802.15.4-to-BLE Translator on a Crystal-Free Mote

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