Wake-up Receiver Research Articles

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

A Temperature-Robust Envelope Detector Receiving OOK-Modulated Signals for Low-Power Applications

This paper presents a passive Envelope Detector (ED) to be used for reception of OOK-modulated signals, such as in Wake-Up Receivers employed within Wireless Sensor Networks, widely used in the IoT. The main goal is implementing a temperature compensation mechanism in order to keep the passive ED input resistance roughly constant over temperature, making it a constant load for the preceding matching network and ultimately keeping the overall receiving chain sensitivity constant over temperature. The proposed ED was designed using STMicroelectronics 90 nm CMOS technology to receive 1 kbps OOK-modulated packets with a 433 MHz carrier frequency and a 0.6 V supply. The use of a block featuring a Proportional-to-Absolute Temperature (PTAT) current yields a 5 dB reduction in sensitivity temperature variation across the −40 °C to 120 °C range. Moreover, two different implementations were compared, one targeting minimal mismatch and the other one targeting minimal area. The minimal area version appears to be better in terms of estimated overall chain sensitivity at all temperatures despite a higher sensitivity spread.

A Design Pattern for a Single Reliable Addressing Wake-up Receiver Based on Low-Frequency Pattern Matcher

Wake-up receivers (WuRxs) allow wireless sensor nodes to run on battery power while maintaining asynchronous, low-latency communication. This paper focuses on WuRxs based on low-frequency pattern matchers (LFPMs). Many recent studies either investigate physical WuRx implementations or simulate WuRx-based protocols. Our goal is to address the challenges that arise when realizing WuRx-based protocols in hardware. These challenges are, that a packet activates unwanted WuRxs, an unreliable address space, and missing cluster broadcast capabilities. The proposed separation sequences and run-length limited patterns ensure a reliable address space. WuRxs based on LFPMs use a fixed pattern matching. Cluster broadcasts are enabled by the proposed variable Manchester coding. Typically, LFPMs use Manchester coding with an efficiency of only 0.5 bit/symbol. We introduce two non-Manchester coding techniques with higher efficiency: lookup table-based coding with an efficiency of 0.71 and 3S2B coding with an efficiency of 0.67.

Univocal and Reliable Addressing Patterns for Wake-Up Receivers Based on Low-Frequency Pattern Matchers

Univocal and Reliable Addressing Patterns for Wake-Up Receivers Based on Low-Frequency Pattern Matchers

Picowatt-Power Super-Cutoff Analog Building Blocks and 78-pW Battery-Less Wake-Up Receiver for Light-Harvested Near-Always-On Operation

Picowatt-Power Super-Cutoff Analog Building Blocks and 78-pW Battery-Less Wake-Up Receiver for Light-Harvested Near-Always-On Operation

A 55 μ W 2.4 GHz wake-up receiver with offset-based peak detection achieving −90dBm sensitivity for IoT applications

The paper proposes a 2.4 GHz ultra-low power wake-up receiver (WuRX) with offset-based peak detection and mixer-first based radio frequency (RF) front-end for IoT applications. The mixer-first based front-end eliminates RF modules to reduce power consumption. Based on the transparency of the passive mixing switches, a 2-path passive mixer (2-PPM) constructs the high-Q band-pass filter (BPF) at the RF port to improve out-of-band blocker rejection. The offset-based peak detection circuit adaptively extracts the reference voltage for the subsequent comparator according to the real-time signal amplitude of envelope detection, which eliminates the misjudgment of the comparator and improves the accuracy of demodulation. For low power consumption, a ring oscillator is used to generate the local oscillator (LO) signal and the frequency calibration scheme combined with coarse tuning and fine tuning is employed to improve the frequency stability, which completes 10-bit frequency tuning with 2 MHz resolution. Designed in TSMC 28 nm CMOS technology, the mixer-first based front-end achieves a conversion gain of 42 dB and a noise figure of 11.9 dB at 2.4 GHz, an S11 less than −15dB during 2.4–2.5 GHz. The frequency calibration scheme for the ring oscillator completes the 512 MHz dynamic range with a 2 MHz frequency tuning step. The WuRX can achieve −90dBm sensitivity with 55 μ W power consumption at 0.6 V supply voltage and the chip area of 0.19 mm × 0.24 mm.

Noise Analysis of a 434-MHz Wakeup Receiver Analog Frontend Core With $-$93-dBm Input Sensitivity and 65-pJ/Bit Efficiency Based on a Switched Injection-Triggered Oscillator With Surface Acoustic Wave Resonator

Noise Analysis of a 434-MHz Wakeup Receiver Analog Frontend Core With $-$93-dBm Input Sensitivity and 65-pJ/Bit Efficiency Based on a Switched Injection-Triggered Oscillator With Surface Acoustic Wave Resonator

A–102-dBm Sensitivity Multichannel Heterodyne Wake-Up Receiver With Integrated ADPLL

A–102-dBm Sensitivity Multichannel Heterodyne Wake-Up Receiver With Integrated ADPLL

Fog-Based Bootstrapping and Failure Repair Protocols for Wake-Up Receiver (WuRx)-Based Wireless Sensor Networks

Fog-Based Bootstrapping and Failure Repair Protocols for Wake-Up Receiver (WuRx)-Based Wireless Sensor Networks

Super-Regenerative Receiver Wake-Up Radio Solution for 5G New Radio Communications

Wake-up radio is a promising solution to reduce the energy wasted by mobile devices during an idle state. In this paper, we propose a new wake-up radio solution for 5G mobile devices based on a super-regenerative receiver characterized by its low cost and low power consumption and investigate how to build on the orthogonal frequency-division multiplexing (OFDM) modulation capability at the base station to generate optimal wake-up signals. After presenting the relevant features and limitations of super-regenerative receivers operating in different 5G New Radio (NR) frequency bands, we evaluate how the numerology, the number of resource blocks, and the quadrature amplitude modulation (QAM) scheme used affect the sensitivity of the super-regenerative wake-up receiver. The results show that a 256-QAM modulation scheme, together with the highest numerology values, achieves optimal receiver sensitivity with a minimal number of resource blocks, yielding higher duty cycle pulses that also facilitate symbol synchronization tasks.

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.

A 19-μW Blocker-Tolerant Wake-Up Receiver With −90–dBm Energy-Enhanced Sensitivity

A 915-MHz energy-enhanced wake-up receiver (EE WuRx) is proposed for wireless energy-harvesting (WEH) systems based on a modified legacy device. With the presented frequency-hopping two-tone modulation (FH TTM), the receiver converts the in-band harvesting energy (HE) from the legacy device into the data power with reduced constraint to the HE frequency. Fabricated in a 65-nm CMOS process, the proposed wake-up receiver (WuRx) achieves a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 90-dBm EE sensitivity when receiving a continue-wave (CW) energy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 25 dBm and gives a sensitivity improvement of 26.4 dB compared with the case without HE, while consuming 19 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W at a 5-kb/s data rate. Upon the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 90-dBm EE sensitivity, the WuRx performs 46.5-and 22-dB tolerances to a 100-kb/s amplitude-modulated (AM) blocker and an 8-MS/s quadrature-AM blocker, respectively.

An Improved Wake-Up Receiver Based on the Optimization of Low-Frequency Pattern Matchers.

Wake-up receivers are gaining importance in power-aware wireless sensor networks, as they significantly reduce power consumption during RF reception, enabling asynchronous communication with low latency. However, the performance of wake-up receivers still lags behind that of off-the-shelf RF transceivers. There is a growing demand for higher sensitivity, enhanced reliability, and lower latency while maintaining the lowest power consumption. In this article, our goal is to advance the performance of wake-up receivers based on off-the-shelf components and low-frequency pattern matchers. Through a systematic investigation, we proposed multiple improvements aimed at enhancing wake-up receiver performance and reliability. We introduced an improved passive envelope detector and realized a wake-up receiver for the 868 MHz band, which achieves a power consumption of 5.71 μW and latency of 9.02 ms. Our proposed wake-up receiver is capable of detecting signals down to an average power level of -61.6 dBm. These achievements represent significant advancements compared to the existing state of research on wake-up receivers based on low-frequency pattern matchers. Recent articles have not been able to attain such improved values in signal detection, power consumption, and latency.

Reconfigurable Adaptive Channel Sensing

This paper proposes an energy-efficient detection scheme, referred to as AdaSense, that is particularly suitable in the sparse regime when events to be detected happen rarely. To minimize energy consumption, AdaSense exploits the dependency between the receiver noise figure (i.e., the receiver added noise) and the receiver power consumption; less noisy channel observations typically imply higher power consumption. AdaSense is duty-cycled and begins each cycle with a few channel observations in a low-power-low-reliability mode. Based on these observations, it makes a first tentative decision on whether or not a message is present. If no message is declared, AdaSense waits till the beginning of the next cycle and starts afresh. If a message is tentatively declared, AdaSense enters a confirmation second phase, takes more samples, but now in a high-power-high-reliability mode. If these observations confirm the tentative decision, AdaSense stops, else AdaSense waits till the beginning of the next cycle and starts afresh in the low-power-low-reliability mode. Compared to prominent detection schemes such as the clear channel assessment algorithm of the Berkeley Media Access Control (BMAC) protocol, AdaSense provides relative energy gains that grow unbounded in the small probability of false-alarm regime, as communication gets sparser. In the non-asymptotic regime, energy gains are 30% to 75% for communication scenarios typically found in the context of wake-up receivers.

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.

An Innovative Clustering Hierarchical Protocol for Data Collection from Remote Wireless Sensor Networks Based Internet of Things Applications

Recently, unmanned aerial vehicles (UAVs) have emerged as a viable solution for data collection from remote Internet of Things (IoT) applications. However, the successful implementation in this regard necessitates the development of a reliable and energy-efficient routing protocol. This paper proposes a reliable and an energy-efficient UAV-assisted clustering hierarchical (EEUCH) protocol designed for remote wireless sensor networks (WSNs) based IoT applications. The proposed EEUCH routing protocol facilitates UAVs to collect data from ground sensor nodes (SNs) that are equipped with wake-up radios (WuRs) and deployed remotely from the base station (BS) in the field of interest (FoI). During each round of the EEUCH protocol, the UAVs arrive at the predefined hovering positions at the FoI, perform clear channel assignment, and broadcast wake-up calls (WuCs) to the SNs. Upon receiving the WuCs by the SNs’ wake-up receivers, the SNs perform carrier sense multiple access/collision avoidance before sending joining requests to ensure reliability and cluster-memberships with the particular UAV whose WuC is received. The cluster-member SNs turn on their main radios (MRs) for data packet transmission. The UAV assigns time division multiple access (TDMA) slots to each of its cluster-member SNs whose joining request is received. Each SN must send the data packets in its assigned TDMA slot. When data packets are successfully received by the UAV, it sends acknowledgments to the SNs, after which the SNs turn off their MRs, completing a single round of the protocol. The proposed EEUCH routing protocol with WuR eliminates the issue of cluster overlapping, improves the overall performance, and increases network stability time by a factor of 8.7. It also improves energy efficiency by a factor of 12.55, resulting in a longer network lifespan compared to Low Energy Adaptive Clustering Hierarchy (LEACH) protocol. Moreover, EEUCH collects 5.05 times more data from the FoI than LEACH. These results are based on simulations in which the EEUCH protocol outperformed the existing six benchmark routing protocols proposed for homogeneous, two-tier, and three-tier heterogeneous WSNs.

A −124-dBm Sensitivity Interference-Resilient Direct-Conversion Duty-Cycled Wake-Up Receiver Achieving 0.114 mW at 1.966-s Wake-Up Latency

This article presents an interference-resilient high-sensitivity binary frequency-shift keying (BFSK) multi-channel wake-up receiver (WuRX) supporting 900-MHz bands for low-power wide-area network (LPWAN) applications. The proposed WuRX uses a direct-conversion architecture, a frequency-to-energy demodulator, and a 4096-bit correlator Direct conversion using a 50%-to-25% duty-cycle conversion mixer and two-stage ring voltage-controlled oscillator (VCO) minimizes the power consumption. The frequency-to-energy demodulator offers a process-voltage-temperature (PVT) variation-tolerant symbol recovery based on an image rejection <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$</tex-math> </inline-formula> -path filter (IRNF), a poly-phase filter (PPF), and a quadrature envelope detector (ED). The 4096-bit correlator provides a digital processing gain of about 17 dB, improving both the sensitivity and the selectivity. To reduce the power consumption further, the proposed WuRX supports an asynchronous duty-cycling operation based on repetition of the wake-up code. Implemented in the 55-nm complementary metal–oxide–semiconductor (CMOS), the proposed WuRX achieves sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 124 dBm in the always-on mode while dissipating 781 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W. For the duty-cycling mode with wake-up codes repeated 15 times, the proposed WuRX exhibits the same sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 124 dBm with reduced power consumption of 114 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W and extended wake-up latency of 1.966 s. The proposed WuRX shows robust interference resilience with a signal-to-interference ratio (SIR) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 76 dB at a 20-MHz offset against a continuous wave (CW). The CMOS radio module, including the proposed WuRX, showed packet-error rates (PERs) of 0% and 5.7% in the 4.8-and 9.8-km ground-to-ground wireless communication tests, respectively.

A Micro-Acoustic Enhanced Low-Impedance Antenna System for IoT Wake-Up Receivers

In this work, we propose a passive radio frequency (RF) front-end tailored for wake-up receivers (WuRx) to be deployed in cellular IoT devices and wearables networks, featuring a low radiation resistance antenna and a high-Q matching network implemented with microacoustic resonators integrated to obtain a systematic higher node’s sensitivity at no cost in terms of power consumption. We show how these components can be co-designed to obtain high passive voltage gain, hardwarelevel blocker immunity, and increased resilience to integration parasitics, relaxing link budget for low-power IoT nodes. We report experimental validation of a PCB antenna with 2 dBi gain measured on an 11Ω input resistance at resonance, and an in-house fabricated Micro-Electro-Mechanical System (MEMS) thin-film aluminum nitride bulk acoustic resonator with a quality factor Q = 550 and a piezoelectric coupling coefficient k2 t =7%, hybridly integrated with a commercial off-the-shelf low-power WuRx circuit to benchmark the proposed RF front-end design at 850MHz. We demonstrate a passive voltage gain of 12 dB due to the MEMS resonator, and an additional 11 dB due to the proposed antenna design (for a total of an unprecedented 23 dB passive gain in this frequency range) leading to an over the air.61dBm minimum detectable input power and 23 dB blocker rejection.

Modeling of Packet Error Rate Distribution Based on Received Signal Strength Indications in OMNeT++ for Wake-Up Receivers.

Wireless sensor network (WSN) with energy-saving capabilities have drawn considerable attention in recent years, as they are the key for long-term monitoring and embedded applications. To improve the power efficiency of wireless sensor nodes, a wake-up technology was introduced in the research community. Such a device reduces the system's energy consumption without affecting the latency. Thereby, the introduction of wake-up receiver (WuRx)-based technology has grown in several sectors. The use of WuRx in a real environment without consideration of physical environmental conditions, such as the reflection, refraction, and diffraction caused by different materials, that affect the reliability of the whole network. Indeed, the simulation of different protocols and scenarios under such circumstances is a success key for a reliable WSN. Simulating different scenarios is required to evaluate the proposed architecture before its deployment in a real-world environment. The contribution of this study emerges in the modeling of different link quality metrics, both hardware and software metrics that will be integrated into an objective modular network testbed in C++ (OMNeT++) discrete event simulator afterward are discussed, with the received signal strength indicator (RSSI) for the hardware metric case and the packet error rate (PER) for the software metric study case using WuRx based on a wake-up matcher and SPIRIT1 transceiver. The different behaviors of the two chips are modeled using machine learning (ML) regression to define parameters such as sensitivity and transition interval for the PER for both radio modules. The generated module was able to detect the variation in the PER distribution as a response in the real experiment output by implementing different analytical functions in the simulator.

Wake-Up Receiver for Underwater Acoustic Communication Using in Shallow Water.

A data frame transmitted over the underwater acoustic channel usually begins with a preamble. Therefore, underwater communication systems have a dedicated receiver that constantly listens to the preamble signals. A receiver that is to work effectively in shallow waters must have solutions that effectively reduce the impact of the permanently occurring multipath propagation. The article presents a solution based on complementary broadband signals. Initial tests were carried out using the Watermark simulator to determine its reliability in such a difficult propagation environment. The results of experimental tests carried out in a model pool are also included. Details of the implementation of the wake-up receiver are presented.