Ultra-low Power Wireless Research Articles

Predictive Maintenance of Induction Motors Using Ultra-Low Power Wireless Sensors and Compressed Recurrent Neural Networks

In real-world applications - to minimize the impact of failures - machinery is often monitored by various sensors. Their role comes down to acquiring data and sending it to a more powerful entity, such as an embedded computer or cloud server. There have been attempts to reduce the computational effort related to data processing in order to use edge computing for predictive maintenance. The aim of this paper is to push the boundaries even further by proposing a novel architecture, in which processing is moved to the sensors themselves thanks to decrease of computational complexity given by the usage of compressed recurrent neural networks. A sensor processes data locally, and then wirelessly sends only a single packet with the probability that the machine is working incorrectly. We show that local processing of the data on ultra-low power wireless sensors gives comparable outcomes in terms of accuracy but much better results in terms of energy consumption that transferring of the raw data. The proposed ultra-low power hardware and firmware architecture makes it possible to use sensors powered by harvested energy while maintaining high confidentiality levels of the failure prediction previously offered by more powerful mains-powered computational platforms.

Analysis of Circuit Noise and Non-Ideal Filtering Impact on Energy Detection Based Ultra-Low-Power Radios Performance

With the coming of age of the Internet of Things, demand on ultra-low power (ULP) radios will continue to boost tremendously. Circuit imperfections, especially in power hungry blocks, i.e., the local oscillators (LO) and band pass filters (BPFs), pose a real challenge for ULP radios designers considering their tight power budget. This brief presents an investigation on the effects of circuit non-idealities on the bit-error rate performance of on-off keying and Gaussian frequency-shift keying energy detection (ED)-based wakeup radios. In particular, this brief analyzes the impact of phase noise and frequency offset in the LO, BPFs bandwidth and roll-off, noise figure on ULP receivers’ performance. This brief contributes to the ongoing research in designing ULP wireless nodes by demonstrating the tradeoffs between these non-idealities and the receiver’s sensitivity level and selectivity and show some design guidelines for ED-based ULP radios.

BATS: Adaptive Ultra Low Power Sensor Network for Animal Tracking.

In this paper, the BATS project is presented, which aims to track the behavior of bats via an ultra-low power wireless sensor network. An overview about the whole project and its parts like sensor node design, tracking grid and software infrastructure is given and the evaluation of the project is shown. The BATS project includes a lightweight sensor node that is attached to bats and combines multiple features. Communication among sensor nodes allows tracking of bat encounters. Flight trajectories of individual tagged bats can be recorded at high spatial and temporal resolution by a ground node grid. To increase the communication range, the BATS project implemented a long-range telemetry system to still receive sensor data outside the standard ground node network. The whole system is designed with the common goal of ultra-low energy consumption while still maintaining optimal measurement results. To this end, the system is designed in a flexible way and is able to adapt its functionality according to the current situation. In this way, it uses the energy available on the sensor node as efficient as possible.

Design of an Ultra-low Power Wireless Temperature Sensor Based on Backscattering Mechanism

In this paper, we propose a passive wireless temperature sensor for long-term and long-range application. A novel architecture of the wireless temperature sensor is proposed based on backscattering mechanism of RFID technology for ultra-low power application. The temperature sensor adopts phase-locked loop-based architecture and can achieve the temperature-digital conversion in frequency domain without any external clock signal. The rectifier employs a gate-boosting scheme to improve the power conversion efficiency. The measurement results show that the proposed wireless temperature sensor obtains a high linearity with a resolution of 0.3 °C/LSB. The measured minimum power dissipation is 2.7 µW, resulting in a maximum operating distance of 34 m under 4 W radiation power.

An experimental study of ultra-low power wireless sensor-based autonomous energy harvesting system

Technological advances for low power consumption and flexible electronics have spurred research on energy harvesting. In this paper, an innovative methodology is proposed to power an ultra-low power wireless sensor node (milliwatt level) autonomously by using a piezoceramic patch which is bonded to a low-frequency vibrating beam. An LTC3588 based energy harvesting module was developed to transfer and collect the energy efficiently. Through a switching interface between the energy harvesting module and the wireless sensor, a 0.33F supercapacitor was charged for 12 h by the harvested vibrational energy to allow the wireless sensor node to join the network and transmit data packets. It was experimentally demonstrated that this applied switching interface could effectively provide on-off control to the power of the wireless sensor node. In order to allow this function, the supercapacitor worked alternatively in the charging mode and the discharging mode. When the supercapacitor stored enough harvested energy, the wireless sensor node initiated the effort to join the wireless network automatically and then sent data packets to the network manager which was connected to a monitoring computer. In addition, wireless sensors which were powered by the energy harvesting system could also send or receive data packets in the network. The developed piezoceramic based energy harvesting method has the potential to be used in structural health monitoring systems by harvesting the ambient mechanical energy.

A Power Processing Circuit for Indoor Wi-Fi Energy Harvesting for Ultra-Low Power Wireless Sensors

This article proposes a complete power processing circuit for an indoor 2.45 GHz Wi-Fi energy harvesting system. The proposed power processing circuit works by using power harvested from indoor Wi-Fi transmitters. The overall system of this work is simplified as an equivalent circuit and analyzed mathematically. A two-port network is analyzed in formulating the relevant equations of the equivalent circuit. The importance of matching the impedance of a harvesting antenna to the rectifier circuit is highlighted by using simulation analysis, and it is shown that the impedance matching for both components has satisfied the conditions for a high sensitivity circuit and radio frequency-to-direct current (RF-to-DC) power conversion. Actual experiments showed that the proposed power processing circuit could operate with an incident power as low as −50 dBm. It has been found that the proposed harvesting system stored 0.11 J in a 200 mF supercapacitor as the storage device in 20 hours of the experimentation periods. Moreover, actual results for the overall energy harvesting system is compared with previous research, and it has been found that the proposed system has advantages over the listed works.

Theoretical Analysis of Magneto-Inductive THz Wireless Communications and Power Transfer With Multi-Layer Graphene Nano-Coils

Graphene with significant potentials in diverse areas of physical and biological sciences is proposed as a solution to complementary problems of semiconductor and biomedical industries, i.e., the on-chip (OC) interconnect bottleneck and in-body (IB) wireless communications/power transfer (PT), respectively. Emerging nanoscale solutions with radio frequency, optical, ultrasonic, or molecular channels in OC and IB media have various challenges including achievable footprints and frequency, energy consumption, medium dependent features, and interference. In this paper, major challenges are addressed with magneto-inductive (MI) transceivers by combining the advantages of THz operation frequency, unique features of intercalated multi-layer graphene (MLG) coils and range extension with MI waveguides. Our design promises scalable and high performance solutions for the OC interconnect bottleneck while providing biocompatible and universal solutions for challenging IB medium. The proposed solution is theoretically analyzed and numerically compared with the copper-based alternatives, and the practical challenges are discussed. Simulation results achieve high capacity (several Tbit/s) and ultra-low power (500 zJ/bit) wireless communications while providing high (hundreds of kWs) and efficient (109 W/mm2) wireless PT at several millimeters. In addition, unique properties of MLG such as lightweight structure, biocompatibility, current carrying capacity, and planar manufacturability make the solution more promising for challenging environments.

A novel power efficient asynchronous time difference of arrival indoor localization system using CC1101 radio transceivers

ABSTRACTThis paper presents a novel 434MHz asynchronous time difference of arrival (A‐TDOA) Indoor Localization System (ILS) using three CC1101 ultra low power radio transceivers from Texas Instruments as asynchronous measuring receivers for time difference of arrival estimation. The three deployed TDOA measuring units are not required to be precisely synchronized in contrast to conventional TDOA localization systems where stringent time synchronization is required between measuring units. Time synchronization is achieved by using a reference transmitter to record the time offset in two TDOA measurements. Actual TDOA measurements are obtained by compensating the time difference measurements for real transmitter using time offsets caused by asynchronous receivers. The implemented system demodulates the obtained time difference pulses to mitigate the clock jitter effect and provides voltage levels corresponding to time differences which are mapped to distance differences. The performance of implemented ILS is evaluated using two sets of real time indoor measurements to estimate the position of mobile transmit node in two dimensional space. The positioning accuracy of implemented system is better than 1.8m along with telemetry data reception capability and low DC power consumption. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:550–555, 2017

Reliable Next-Generation Cortical Interfaces for Chronic Brain–Machine Interfaces and Neuroscience

This review focuses on recent directions stemming from work by the authors and collaborators in the emerging field of neurotechnology. Neurotechnology has the potential to provide a greater understanding of the structure and function of the complex neural circuits in the brain, as well as impacting the field of brain–machine interfaces (BMI). We envision ultralow-power wireless neural interface systems that are life-lasting, fully integrated, and that supports bidirectional data flow with high bandwidth. Moreover, we believe in the importance of building neural interface technology that is truly tetherless, has a very small recording footprint, and little to no mechanical coupling between the sensor and the external world. We believe these developments will impact both neuroscience and neurology, revealing fundamental insight about how the nervous system functions in health and disease.

A 2.4 GHz Interferer-Resilient Wake-Up Receiver Using A Dual-IF Multi-Stage N-Path Architecture

A 2.4 GHz interferer-resilient wake-up receiver for ultra-low power wireless sensor nodes uses an uncertain-IF dual-conversion topology, combining a distributed multi-stage N-path filtering technique with an unlocked low-Q resonator-referred local oscillator. This structure provides narrow-band selectivity and strong immunity against interferers, while avoiding expensive external resonant components such as BAW resonators or crystals. The 65 nm CMOS receiver prototype provides a sensitivity of −97 dBm and a carrier-to-interferer ratio better than −27 dB at 5 MHz offset, for a data rate of 10 kb/s at a 10−3 bit error rate, while consuming 99 $\mu \text{W}$ from a 0.5 V voltage supply under continuous operation.

Enerji verimli ve düşük maliyetli sensör ağlarının ISM bandı FSK alıcı vericiyle tasarlanması

Safe wireless link and long battery life are indispensable feature for a portable and outdoor used device with build-in sensors. For this purpose, duty cycling, ultra-low power electronics design, dynamic power management, wireless network architecture and medium access control concepts in the design are explained in detailed. In this work, an ultra-low power wireless sensor network is designed with 4cmx4cm size and light weight nodes sending once every three minutes 115.2 kbps 5 byte package that have up to 131.25 year battery life time in theory with 3V (2x1.5V) 1000mAh battery. 868 and 915 MHz programmable 115.2 kbps ISM band FSK RF transceiver with a low power wake-up scheme is utilized for low cost unlicensed-used wireless sensor networks designed with Back Inverted F Antennas with 100m communication range for outdoor applications and 25m for indoor applications. Sensor node requires 0.5 uA, 2.5 mA, 0.8 uA, 14.6 mA and 25mA during sleep, measurement, sniff, receive and transmit mode respectively @ 868 MHz with 3V battery. The sensors has temperature compensation feature with -40-85 °C working range.

Wireless actuation of micromechanical resonators.

The wireless transfer of power is of fundamental and technical interest, with applications ranging from the remote operation of consumer electronics and implanted biomedical devices and sensors to the actuation of devices for which hard-wired power sources are neither desirable nor practical. In particular, biomedical devices that are implanted in the body or brain require small-footprint power receiving elements for wireless charging, which can be accomplished by micromechanical resonators. Moreover, for fundamental experiments, the ultralow-power wireless operation of micromechanical resonators in the microwave range can enable the performance of low-temperature studies of mechanical systems in the quantum regime, where the heat carried by the electrical wires in standard actuation techniques is detrimental to maintaining the resonator in a quantum state. Here we demonstrate the successful actuation of micron-sized silicon-based piezoelectric resonators with resonance frequencies ranging from 36 to 120 MHz at power levels of nanowatts and distances of ~3 feet, including comprehensive polarization, distance and power dependence measurements. Our unprecedented demonstration of the wireless actuation of micromechanical resonators via electric-field coupling down to nanowatt levels may enable a multitude of applications that require the wireless control of sensors and actuators based on micromechanical resonators, which was inaccessible until now.

A Fully Integrated Bluetooth Low-Energy Transmitter in 28 nm CMOS With 36% System Efficiency at 3 dBm

We propose a new transmitter architecture for ultra-low power radios in which the most energy-hungry RF circuits operate at a supply just above a threshold voltage of CMOS transistors. An all-digital PLL employs a digitally controlled oscillator with switching current sources to reduce supply voltage and power without sacrificing its startup margin. It also reduces 1/f noise and supply pushing, thus allowing the ADPLL, after settling, to reduce its sampling rate or shut it off entirely during a direct DCO data modulation. The switching power amplifier integrates its matching network while operating in class-E/F2 to maximally enhance its efficiency at low voltage. The transmitter is realized in 28 nm digital CMOS and satisfies all metal density and other manufacturing rules. It consumes 3.6 mW/5.5 mW while delivering 0 dBm/3 dBm RF power in Bluetooth Low-Energy mode.

Architecture of Ultra Low Power Micro Energy Harvester Using RF Signal for Health Care Monitoring System: A Review

This research presents architecture of Ultra Low Power (ULP) Micro Energy Harvester (MEH) using Radio Frequency (RF) signal as an input. RF has many advantages compared to other ambient sources because it is not affected by changes of weather or time, does not require heat or wind exposure and it can be moved randomly within the bound of the transmission source. When RF is used as the sole input, the designer needs to consider impedance matching as the most important element so that the antenna can transfer maximum power. The existing energy harvesters apply conjugate matching network as the current solution. However, this method causes some difficulties since the solution requires consideration of both voltage boosting and conjugate matching network simultaneously. To solve this problem, we propose ULP Radio Frequency Micro Energy Harvester (RFMEH) that will utilize a control loop as voltage boosting adjuster and network tuner to achieve maximum power transfer and minimum power reflection. The proposed architecture will also improve the RF-DC conversion efficiency and the sensitivity of the system. This is achieved using an efficient rectification scheme to convert RF to DC, DC-DC boost converter to increase the dc output voltage, adaptive control circuit to adjust the switching timing of boost converter, voltage limiter and regulator to produce the best output voltage. The proposed ULP RFMEH architecture will be designed and simulated using PSPICE software, Verilog coding using Mentor Graphics and functional verification using FPGA board (FPGA) before being implemented in CMOS 0.13 µm process technology. The proposed architecture will deliver approximately 2.45 V of output voltage from low input power level (-20 dBm) with an efficiency of more than 60%. This design will minimize the power consumption as compared to previous achievements and it can be applied in supplying power for health care monitoring systems or micro biomedical applications.

Unifying energy harvesting, sensing, and communication for ultra-low power structure health monitoring

A new ultra-low power (ULP) wireless sensor network (WSN) is proposed to monitor the vibration properties of critical structures such as buildings, bridges, and the wings and bodies of aircrafts. The new scheme integrates energy harvesting, data sensing, and wireless communication into a unified process, and it is fundamentally different from all the existing WSNs. In the new WSN, self-powered sensors are employed to harvest vibration energy and measure vibration intensity simultaneously, by utilizing the fact that the harvested energy accumulated through time is proportional to the vibration amplitude and frequency. Once the harvested energy reaches a threshold, it is released as an impulse with a wireless transmitter. An estimate of the structure vibration intensity can then be obtained by measuring the number of binary impulses in a unit time. Such an approach does not require complicated analog-to-digital conversion or signal processing, and it can achieve an ULP performance unrivaled by existing technologies. Optimum and sub-optimum impulse density estimation algorithms are proposed to take advantage of the spatial correlation among signals from the sensors. Analytical and simulation results demonstrate that the proposed scheme can efficiently operate at a low signal-to-noise ratio (SNR).

A 0.33 nJ/bit IEEE802.15.6/Proprietary MICS/ISM Wireless Transceiver With Scalable Data Rate for Medical Implantable Applications.

This paper presents an ultra-low power wireless transceiver specialized for but not limited to medical implantable applications. It operates at the 402-405-MHz medical implant communication service band, and also supports the 420-450-MHz industrial, scientific, and medical band. Being IEEE 802.15.6 standard compliant with additional proprietary modes, this highly configurable transceiver achieves date rates from 11kb/s to 4.5 Mb/s, which covers the requirements of conventional implantable applications. The phase-locked loop-based transmitter architecture is adopted to support various modulation schemes with limited power budget. The zero-IF receiver has programmable gain and bandwidth to accommodate different operation modes. Fabricated in 40-nm CMOS technology with 1-V supply, this transceiver only consumes 1.78 mW for transmission and 1.49 mW for reception. The ultra-low power consumption together with the 15.6-compliant performance in term of modulation accuracy, sensitivity, and interference robustness make this transceiver competent for various implantable applications.

A New Frontier in Ultralow Power Wireless Links: Network-on-Chip and Chip-to-Chip Interconnects

This paper explores the general framework and prospects for on-chip and off-chip wireless interconnects implemented for high-performance computing (HPC) systems in the context of micro power wireless design. HPC interconnects demand very high (≥ 10 Gb/s) transmission rates using ultraefficient (~ 1 pJ/bit) transceivers over extremely short (≤ 100 cm) ranges. In an attempt to design such wireless interconnects, first a model for the wireless communication channel properties is developed. The use of CMOS-based energyefficient on-off keying (OOK) transceiver architectures operating in the 60-90 GHz bands is considered as a practical solution. In order to address strict performance requirements of wireless HPC interconnects, and taking advantage of the recent developments in device scaling, compact low-power and innovative circuits based on novel double-gate MOSFETs (DG-MOSFETs) are proposed in the implementation of the architecture. The performance of a compact low-noise amplifier (LNA) design using common source (CS) inductive degeneration with 32 nm DGMOSFETs is investigated by quantitative analysis and simulation. The proposed inductor-less two-stage cascode cascade LNA is optimized for 90 GHz operation and has the advantage of gain switching over its CMOS counterpart without the use of additional switching transistors, which makes it remarkably power efficient and faster. As further examples of efficient and compact DG-MOSFET circuits for OOK transceiver design, a three-stage CS 5 dB tunable power amplifier operating up to 90 GHz, and a novel 90 GHz voltage controlled oscillator are also presented. This is followed by the proposal of an array of four monopole antennas studied using full-wave EM solver.

A Sub-GHz Multi-ISM-Band ZigBee Receiver Using Function-Reuse and Gain-Boosted N-Path Techniques for IoT Applications

Internet of Things (IoT) represents a competitive and large market for short-range ultra-low-power (ULP) wireless connectivity [1, 2]. According to [3], by 2020 the IoT market will be close to hundreds of billion dollars (annually ~16 billions). To bring down the hardware cost of such massive inter-connections, sub-GHz ULP wireless products compliant with the existing wireless standard such as the IEEE 802.15.4c/d (ZigBee) will be of great demand, especially for those that can cover all regional ISM bands [e.g., China (433 MHz), Europe (860 MHz), North America (915 MHz) and Japan (960 MHz)]. Together with the obvious goals of small chip area, minimum external components and ultra-low-voltage (ULV) supply (for possible energy harvesting), the design of such a receiver poses significant challenges.

Adaptive synchronization in multi-hop TSCH networks

Time Slotted Channel Hopping (TSCH) enables highly reliable and ultra-low power wireless networking, and is at the heart of multiple industrial standards. It has become the de facto standard for industrial low-power wireless solutions, and a true enabler for the Industrial Internet of Things. In a TSCH network, all nodes remain tightly synchronized by periodically communicating with one another to compensate for clock drift. The synchronization algorithm used in a network determines how often the nodes need to re-synchronize, which greatly influences their energy consumption.This article presents an adaptive synchronization technique which allows a node to learn and predict how its clock is drifting relative to its neighbors’, and coordinates the instants at which the nodes re-synchronize. This technique increases synchronization accuracy, while reducing synchronization communication overhead, thereby extending the battery lifetime of the network.Through simulation, we show how adaptive synchronization allows the nodes in a 3-hop deep network to maintain synchronization within 76μs of one another, while sending an average of only 18.9 re-synchronization packets per hour, a 83% reduction compared to a network not using adaptive synchronization. Through experimentation on a range of hardware platforms, we show how adaptive synchronization is needed for interoperability.

An ultralow power wireless intraocular pressure monitoring system

This paper describes an ultralow power wireless intraocular pressure (IOP) monitoring system that is dedicated to sensing and transferring intraocular pressure of glaucoma patients. Our system is comprised of a capacitive pressure sensor, an application-specific integrated circuit, which is designed on the SMIC 180 nm process, and a dipole antenna. The system is wirelessly powered and demonstrates a power consumption of 7.56 μW at 1.24 V during continuous monitoring, a significant reduction in active power dissipation compared to existing work. The input RF sensitivity is −13 dBm. A significant reduction in input RF sensitivity results from the reduction of mismatch time of the ASK modulation caused by FM0 encoding. The system exhibits an average error of ± 1.5 mmHg in measured pressure. Finally, a complete IOP system is demonstrated in the real biological environment, showing a successful reading of the pressure of an eye.