Low-power Wake-up Receiver Research Articles

Low-Power Wake-Up Receivers for Resilient Cellular Internet of Things

Smart Cities leverage large networks of wirelessly connected nodes embedded with sensors and/or actuators. Cellular IoT, such as NB-IoT and 5G RedCap, is often preferred for these applications thanks to its long range, extensive coverage, and good quality of service. In these networks, wireless communication dominates power consumption, motivating research on energy-efficient yet resilient and robust wireless systems. Many IoT use cases require low latency but cannot afford high-power radios continuously operating to accomplish this. In these cases, wake-up receivers (WURs) are a promising solution: while the high-power main radio (MR) is turned off/idle, a lightweight WUR is continuously monitoring the RF channel; when it detects a wake-up sequence, the WUR will turn on the MR for subsequent communications. This article provides an overview of WUR hardware design considerations and challenges for 4G and 5G cellular IoT, summarizes the recent 3GPP activities to standardize NB-IoT and 5G wake-up signals, and presents a state-of-the-art WUR chip.

Optimization of MEMS Matching Network for the Sensitivity of GHz Low-Power Wake-Up Receivers

Optimization of MEMS Matching Network for the Sensitivity of GHz Low-Power Wake-Up Receivers

Low Power Wake-Up Receivers for Underwater Acoustic Wireless Sensor Networks

This article reports two low power wake-up receiver (WuRx) circuits (Type A and B) for underwater acoustic wireless sensor networks. The proposed circuits realize the same novel method to extract the wake-up call from the acoustic signals received by a sensor node using different circuit topologies. This is accomplished by comparing the amplitude and the duration of the received pulses to a predefined code. A combination of these two parameters provides a safe and robust decoding system. The values and duration of the predefined code can be adjusted by tuning the biasing voltages in the circuits. The main advantages of the presented designs are modularity and tunability. To verify the operation of the proposed system, an ASIC has been realized. The WuRxs have been characterized in terms of tuning, duty cycle, and power consumption. Both WuRxs can consume less than 0.5. Type A occupies an area of mode = text0.058mm2, has a data rate of mode = text250bit/s, and presents the lowest power consumption reported, consuming 265nW and 61nW in active and sleep modes, respectively.

Toward Zero-Energy Devices: Waveform Design for Low-Power Receivers

The use of a low-power wake-up receiver (WUR) can significantly reduce the device’s energy consumption. To incorporate such WURs into existing communication systems, the waveform design needs to facilitate simple detection yet be compatible with the orthogonal frequency division multiplexing (OFDM) transmission. In this letter, we propose a novel phase design for the wake-up signal (WUS) so that the time-domain distortion of the WUS can be minimized. A majorization-minimization (MM) method is proposed to address the waveform design problem. Simulations show that the proposed scheme can achieve a near-optimal detection performance under different system parameters.

Enhanced Airborne Ultrasound WuRx Using Aluminum Nitride 4-Beam pNUTs Arrays

In this work, we present an implementation of a low-power wake-up receiver (WuRx) that is remotely interrogated by airborne ultrasound. The transduction from ultrasound to electrical signal is performed by arrays of aluminum nitride (AlN) 4-Beam piezoelectric nanoscale ultrasound transducers (pNUTs). Two set of arrays with a center frequency at 45 kHz and 49 kHz are used for two separate validations of the WuRx. The arrays interface with electronics implemented with affordable off-the-shelf (OtS) components for amplification and demodulation of the wake-up signal. The system has a power consumption of <inline-formula> <tex-math notation="LaTeX">$27 ~\mu \text{W}$ </tex-math></inline-formula>, a modulation frequency of 1 kHz, and a minimum detectable pressure between 1.5 Pa and 0.6 Pa depending on the selected device. The individual pNUTs occupy an area of approximately <inline-formula> <tex-math notation="LaTeX">$100 ~\mu \text{m}$ </tex-math></inline-formula> x <inline-formula> <tex-math notation="LaTeX">$100 ~\mu \text{m}$ </tex-math></inline-formula>. A similar electronics architecture as the one presented in this document can be miniaturized to an area comparable to the one of the pNUT if implemented with integrated circuit (IC) technology, pointing to the possibility of integrating ultrasound WuRx into miniaturized, dust-like sensing platforms. [2021-0192]

−52 dBm 수신 감도를 갖는 900 MHz 대역 Wake-Up 수신기 설계

This paper describes the results of manufacturing and measuring low-power wake-up receiver (WuRx) modules operating in the 900 MHz band using the AS3933 amplitude shift keying (ASK) receiver chip. The RF envelope detector has the advantage of low power consumption, but it has the disadvantage of low sensitivity. Therefore, this study designed the WuRx by applying antenna impedance matching circuits, envelope detectors with voltage doubler structure, LC filters in the form of removing ripples, and the 5th-order Chebyshev low-pass filters to increase sensitivity while maintaining low-power conditions. A 3.3 V single supply was applied to the WuRx, and the test result demonstrated −52 dBm sensitivity with 1 % packet error rate (PER) under the current consumption of 619 μA and the data rate of 2.52 kbps.

Low power wake-up receiver based on ultrasound communication for wireless sensor network

Wireless sensor network (WSN) consists of base stations and sensors nodes to monitor physical and environmental conditions. Power consumption is a challenge in WSN due to activities of nodes. High power consumption is required for the main transceiver in WSN to receive communication requests all the time. Hence, a low power wake-up receiver is needed to minimize the power consumption of WSN. In this work, a low power wake-up receiver using ultrasound data communication is designed. Wake-up receiver is used to detect wake-up signal to activate a device in WSN. Functional block modelling of the wake-up receiver is developed in Silterra CMOS 130nm process technology. The performance of the wake-up receiver has been analyzed and achieving low power consumption which is 22.45μW. A prototype to demonstrate a wireless sensor node with wake-up receiver has been developed incorporating both ultrasonic and RF for internal and external communication respectively. We achieve 99.97% of power saving for 10s operation in the experimental setup for the WSN with and without wake-up receiver. Wake-up receiver used in WSN save power and prolong the lifetime of batteries and thus extending the operational lifetime of WSN.

Interference-Free OFDM Embedding of Wake-Up Signals for Low-Power Wake-Up Receivers

The use of ultra-low power wake-up receivers (WuRx) can significantly reduce idle listening energy cost. To tailor a WuRx scheme to orthogonal frequency division multiplexing (OFDM) based systems, such as LTE-MTC or IEEE 802.11, the wake-up signal (WUS) also needs to follow OFDM principles to avoid interfering with other transmissions in the same shared bandwidth. Here, we address this particular issue and propose an approach where the OFDM transmitter is modified to also transmit WUSs designed for non-coherent low-power WuRxs, on a subset of the carriers, thus embedding the WUS correctly and ensuring orthogonality. The approach is evaluated for different system parameters and channel conditions. Its applicability across a wide range of OFDM-based systems is examined.

An 18 nW −47/−40 dBm Sensitivity 3/100 kbps MEMS-Assisted CMOS Wake-Up Receiver

This work demonstrates a low-power wake-up receiver utilizing a MEMS resonant device followed by CMOS demodulator and rectifying trigger circuits. The MEMS device is a Lamb wave piezoelectric-based acoustic resonator utilizing a thin film of lithium niobate (LN) which possess the largest reported electromechanical coupling factors ( ${k} _{t}^{2}$ ). This parameter, in conjunction with the high Q, is of paramount importance in providing for passive voltage amplification and filtering of the input signal. The CMOS demodulator is a 9-stage differential cross-coupled passive rectifier circuit designed with a differential output. It demodulates the signal from the MEMS resonator with the same gain as that could be achieved by a single-ended rectifier, but with half the charging time for double the single-ended bit-rate. The rectifier’s output is AC-coupled and fed to a two-stage differential voltage amplifier. Finally, an active latch rectifier is used to trigger a wake-up signal. The wake-up receiver is tested with an on-off keying modulated signal with carrier frequency around 400 MHz achieving a bit rate up to 100 kbps. This newly proposed system exhibits a sensitivity of −47 dBm at 3 kbps while consuming a total power of 18 nW.

A 220-$\mu$ W −83-dBm 5.8-GHz Third-Harmonic Passive Mixer-First LP-WUR for IEEE 802.11ba

A 40-nm CMOS IEEE 802.11ba low-power wake-up receiver (LP-WUR) is presented. It receives 802.11ba messages generated by an 802.11 orthogonal frequency-division multiplexing (OFDM) transmitter operating at 5.8 GHz. The power consumption of the RF front-end is minimized by removing active RF gain stages and using a third harmonic passive mixer with a ring-based local oscillator (LO) operating at one-third of the RF frequency. The noise figure is 14 dB, taking advantage of a 1:3 transformer that provides passive voltage gain in front of the high switch loss mixer-first RF front-end, and matching across 5.5-5.8 GHz with <; -12 dB S11. The receiver achieves a sensitivity of -83-dBm and -20-dB adjacent channel signal-tointerference ratio (SIR) while consuming 220 μW at a bit error rate (BER) of 10-3 and data rate of 62.5 kb/s, which shows the best sensitivity-power tradeoff among >3-GHz receivers.

Resonant Microelectromechanical Receiver

This paper reports a practical demonstration of a proposed resonant microelectromechanical receiver for low power wake-up receiver (WuRx) applications. The proposed system is made of three main components: a piezoelectric based acoustic resonator, an electrostatically-driven MEMS resonant demodulator, and a CMOS baseband trigger circuit. The filtering, amplification, and demodulation of the incoming signal are performed through the piezoelectric resonator and the resonant demodulator, ensuring zero power consumption for both the radio frequency (RF) and mixing stages. The only power consumption occurs at baseband by operating the CMOS circuit in deep subthreshold. This system utilizes a lithium niobate piezoelectric resonator possessing a figure of merit of around 650 and achieving voltage gain of 28 dB. A resonant demodulator fabricated in the Epi-Seal MEMS process is utilized to attain a conversion efficiency of 13.8 nA/V2. In the trigger circuit, an amplifier with transimpedance $>200~\text{M} {\Omega }$ is utilized to sense the output current from the demodulator. An intermediate buffer and a multiple stage passive latch rectifier are utilized to generate the wake-up signal through a Schmitt trigger. The demonstrated system achieves −40.2 dBm sensitivity for a 44 kHz amplitude-modulated 50 MHz RF signal while consuming 38.75 nW. This architecture is a promising step toward a WuRx capable of achieving higher interference rejection, high sensitivity, and nW range power consumption at a high data rate. [2018-0261]

2.4\xa0GHz wake-up receiver with suppressed substrate noise coupling

The switching noise generated in digital circuits propagates through conductive silicon substrate to analog circuits in a mixed-signal CMOS LSI. Substrate noise coupling may degrade the performance of the analog circuits, and may result in a fault operation of the mixed-signal LSI in the worst-case. In this paper, the substrate noise coupling between the clock recovery circuit and the input port of the envelop detector in a low-power wake-up receiver (WuRx) was investigated experimentally. The propagation path of the substrate noise coupling was clarified by comparing the experimental results with the circuit simulations on the basis of an equivalent circuit model. The design of the WuRx was modified on the basis of the findings to suppress the substrate noise coupling. The fabricated WuRx successfully operated a 100-kbps PWM signal with a carrier frequency of 2.4 GHz, and the effectiveness of the noise coupling suppression recipe was confirmed.

An Alternative to IEEE 802.11ba: Wake-Up Radio With Legacy IEEE 802.11 Transmitters

Current standardization process for Wake-up Radio (WuR) within the IEEE 802.11 Working Group, known as the IEEE 802.11ba, has brought interest to the IEEE 802.11-related technologies for the implementation of WuR systems. This paper proposes a new WuR system, where the Wake-up Transmitter (WuTx) is based on the legacy IEEE 802.11 Orthogonal Frequency Division Modulation (OFDM) Physical Layer (PHY) specification. Using the IEEE 802.11, OFDM PHY makes it possible for an IEEE 802.11a/g/n/ac transmitter to operate as WuTx for this WuR system. The WuTx generates a Wake-up Signal (WuS) coded with an amplitude-based digital modulation, achieving a bit rate of 250 kbps. This modulation, which we call Peak-Flat modulation, can be received using low-power receivers. A simulated proof of concept of the WuTx based on the IEEE 802.11g is presented and evaluated using MATLAB WLAN Toolbox. A method to generate the Peak-Flat modulated WuS from an IEEE 802.11a/g standard-compliant transmitter, using only software-level access, is explained. In addition, two possible low-power Wake-up Receiver (WuRx) architectures capable of decoding the presented modulation are proposed. The design of those receivers is generic enough to be used as a reference to compare the performance of the Peak-Flat Modulation with the other state-of-the-art approaches. The evaluation results conclude that the Peak-Flat modulation has similar performance compared to the other IEEE 802.11 WuR solutions on the reference receivers. Moreover, this solution provides a notorious advantage: legacy OFDM-based IEEE 802.11 transmitters can generate the Peak-Flat modulated WuS.

Energy-Efficient Data Collection Method for Sensor Networks by Integrating Asymmetric Communication and Wake-Up Radio

In large-scale wireless sensor networks (WSNs), nodes close to sink nodes consume energy more quickly than other nodes due to packet forwarding. A mobile sink is a good solution to this issue, although it causes two new problems to nodes: (i) overhead of updating routing information; and (ii) increased operating time due to aperiodic query. To solve these problems, this paper proposes an energy-efficient data collection method, Sink-based Centralized transmission Scheduling (SC-Sched), by integrating asymmetric communication and wake-up radio. Specifically, each node is equipped with a low-power wake-up receiver. The sink node determines transmission scheduling, and transmits a wake-up message using a large transmission power, directly activating a pair of nodes simultaneously which will communicate with a normal transmission power. This paper further investigates how to deal with frame loss caused by fading and how to mitigate the impact of the wake-up latency of communication modules. Simulation evaluations confirm that using multiple channels effectively reduces data collection time and SC-Sched works well with a mobile sink. Compared with the conventional duty-cycling method, SC-Sched greatly reduces total energy consumption and improves the network lifetime by 7.47 times in a WSN with 4 data collection points and 300 sensor nodes.

A Low-Power OFDM-Based Wake-Up Mechanism for IoE Applications

This brief presents a wake-up mechanism for orthogonal frequency division multiplexing (OFDM) modulation-based systems by coding a low data-rate wake-up signal in transmitter without extra circuitry overhead. It is achieved by controlling data pattern for each OFDM subcarrier in one symbol of frame to produce an equivalent amplitude-modulated (AM) signal as a wake-up query without contaminating protocol integrity. A low-power wake-up receiver is used to demodulate this signal and interpret the wake-up query. A system using proposed wake-up mechanism has been built based on IEEE 802.11ah standard. Measurement results demonstrate that an AM-type wake-up signal with a data-rate of 31.25 Kb/s is generated through the proposed method. Moreover, an envelope detector with −35-dBm sensitivity at 900 MHz has been implemented in 0.13- ${\mu }\text{m}$ CMOS technology for wake-up signal detection and consumes 120-nW power.

Implementation of envelope detection based Wake-Up Receiver for IEEE 802.15.4 WPAN from off-the-shelf components

Abstract. Power consumption in wireless networks is crucial. In most scenarios the transmission time is short compared to the idle listening time for data transmission, the most power is consumed by the receiver. In low latency systems there is a need for low power wake-up receivers (WuRx) that reduce the power consumption when the node is idle, but keep it responsive. This work presents a WuRx designed out of commercial components to investigate the needs of a WuRx when it is embedded in a Wireless Personal Area Network (WPAN) system in a real environment setup including WLAN and LTE communication and considering interferer rejection. The calculation necessary for the attenuation of those interferers is explained in detail. Furthermore, a system design is presented that fulfills the requirements for this environment and is build from off-the-shelf components.

Influence of Duty-Cycled Wake-Up Receiver Characteristics on Energy Consumption in Single-Hop Networks

In sensor network applications with low traffic intensity, idle channel listening is one of the main sources of energy waste. The use of a dedicated low-power wake-up receiver (WRx), which utilizes duty-cycled channel listening, can significantly reduce the idle listening energy cost. Extreme low-power design typically leads to performance losses, indirectly increasing energy costs. Striking the right balance is, therefore, very important when introducing WRxs. We present a system analysis and heuristic parameter optimization for an existing duty-cycled WRx medium access control scheme. First, we introduce a framework for analysis of energy consumption and delay of an entire single-hop network where we include WRx characteristics. The WRx characteristics are condensed into two parameters: reduction in power consumption and associated loss of performance, compared with the main receiver. The analysis framework is used to find optimal wake-up beacon and protocol parameters for different WRx characteristics to minimize the total network energy consumption per data packet. The importance of the optimization is that it provides information on if, and how much, we can save in terms of energy by introducing a WRx with a certain characteristic. We also present accurate approximations of both optimal energy savings and resulting delays.

T-ROME: A simple and energy efficient tree routing protocol for low-power wake-up receivers

Wireless sensor networks are deployed in many monitoring applications but still suffer from short lifetimes originating from limited energy sources and storages. Due to their low-power consumption and their on-demand communication ability, wake-up receivers represent an energy efficient and simple enhancement to wireless sensor nodes and wireless sensor network protocols. In this context, wake-up receivers have the ability to increase the network lifetime. In this article, we present T-ROME, a simple and energy efficient cross-layer routing protocol for wireless sensor nodes containing wake-up receivers. The protocol makes use of the different transmission ranges of wake-up and main radios in order to save energy by skipping nodes during data transfer. With respect to energy consumption and latency, T-ROME outperforms existing protocols in many scenarios. Here, we describe and analyze the cross layer multi-hop protocol by means of a Markov chain model that we verify using a laboratory test setup.

Improving Practical Sensitivity of Energy Optimized Wake-Up Receivers: Proof of Concept in 65-nm CMOS

We present a high performance low-power digital base-band architecture, specially designed for an energy optimized duty-cycled wake-up receiver scheme. Based on a careful wake-up beacon design, a structured wake-up beacon detection technique leads to an architecture that compensates for the implementation loss of a low-power wake-up receiver front-end at low energy and area costs. Design parameters are selected by energy optimization and the architecture is easily scalable to support various network sizes. Fabricated in 65nm CMOS, the digital base-band consumes 0.9uW (V_DD=0.37V) in sub-threshold operation at 250kbps, with appropriate 97% wake-up beacon detection and 0.04% false alarm probabilities. The circuit is fully functional at a minimum V_DD of 0.23V at f_max=5kHz and 0.018uW power consumption. Based on these results we show that our digital base-band can be used as a companion to compensate for front-end implementation losses resulting from the limited wake-up receiver power budget at a negligible cost. This implies an improvement of the practical sensitivity of the wake-up receiver, compared to what is traditionally reported.

Design of Low Power Wake-up Receiver for Wireless Sensor Network

Wireless Sensor Networks find various applications in different fields. Sensor nodes are small, low-cost and lowpowered communication devices. Hence designing a network with low power consumption is a critical issue in WSN. Different schemes are projected for achieving low power communication under short network range. To reduce the use of power and retaining a good lifetime, ultra-low power wakeup receiver is introduced. Energy dissipation is reduced here by maximizing data transceivers sleep time. In this paper, design and simulation of a wake-up receiver is carried out at 90nm and 45nm technology. Results are found to be satisfactory.