Ultra-low Power Wake-up Receiver Research Articles

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.

A Wake-Up Receiver With a Multi-Stage Self-Mixer and With Enhanced Sensitivity When Using an Interferer as Local Oscillator

An ultra-low power wake-up receiver with an energy-detection passive-RF architecture uses a multi-stage self-mixer that has a better conversion gain than the conventional envelope detector. The self-mixer, co-designed with the RF matching network, optimizes the sensitivity and minimizes the power consumption of the receiver. A wake-up receiver prototype in 0.13- $\mu \text{m}$ CMOS operates at 550 MHz, consumes 220 nW from 0.5 V, and achieves a sensitivity of −56.4 dBm at a 400-kb/s chip rate using an 11-bit wake-up code. When a large interferer is present, the receiver operates in an interferer-enhanced mode, leveraging the interferer as a local oscillator to improve the sensitivity; in the presence of a −43.5-dBm interferer, a −63.6-dBm sensitivity is achieved while consuming 1.1 $\mu \text{W}$ .

Analysis and Design of a Multi-Mode Wake-Up Receiver Based on Direct Envelope Detection in Wireless Sensor Networks

In this paper, a multi-mode ultra-low power wake-up receiver based on direct envelope detection in HF/UHF band is analyzed and presented. Narrow-band LC matching network with passive voltage gain, active common source envelope detector with high conversion gain and baseband modules with signal amplification are clarified, separately. In order to balance the power consumption and sensitivity, multi-mode with power detection (PD), signal detection (SD), and high sensitivity signal detection (HSSD) are adopted. The PD mode is used to monitor the incident radio power, while in SD/HSSD modes, the wake-up sequences of 100/10 kb/s are detected with different power consumption and sensitivity. The presented wake-up receiver prototype is fabricated in a 95-nm CMOS process with an area of 0.6*0.3 mm2. Measurement results show that the wake-up receiver achieves a sensitivity of −45/−42 dBm, −43/−40 dBm and −58/−55 dBm while dissipating 120 nW, 600 nW, and 1 $\mu \text{W}$ in PD mode, SD mode, and HSSD mode, respectively, while working in the HF/UHF band, separately.

Leveraging Energy Harvesting and Wake-Up Receivers for Long-Term Wireless Sensor Networks.

Wireless sensor nodes are traditionally powered by individual batteries, and a significant effort has been devoted to maximizing the lifetime of these devices. However, as the batteries can only store a finite amount of energy, the network is still doomed to die, and changing the batteries is not always possible. A promising solution is to enable each node to harvest energy directly in its environment, using individual energy harvesters. Moreover, novel ultra-low power wake-up receivers, which allow continuous listening of the channel with negligible power consumption, are emerging. These devices enable asynchronous communication, further reducing the power consumption related to communication, which is typically one the most energy-consuming tasks in wireless sensor networks. Energy harvesting and wake-up receivers can be combined to significantly increase the energy efficiency of sensor networks. In this paper, we propose an energy manager for energy harvesting wireless sensor nodes and an asynchronous medium access control protocol, which exploits ultra-low power wake-up receivers. The two components are designed to work together and especially to fit the stringent constraints of wireless sensor nodes. The proposed approach has been implemented on a real hardware platform and tested in the field. Experimental results demonstrate the benefits of the proposed approach in terms of energy efficiency, power consumption and throughput, which can be up to more than two-times higher compared to traditional schemes.

802.11g/n Compliant Fully Integrated Wake-Up Receiver With −72-dBm Sensitivity in 14-nm FinFET CMOS

This paper presents an 802.11g/n compliant wake-up radio solution that consists of an innovative on–off keying (OOK) emulating orthogonal frequency division multiplexing (OFDM) modulation scheme, and a fully integrated, highly scaled, ultra-low power wake-up receiver design in 14-nm FinFET CMOS technology requiring only a 32-kHz real-time clock reference. The receiver achieves −72-dBm sensitivity and +20 dBr adjacent channel interference (ACI) rejection at 10−3 bit error rate (BER) while consuming $95~\mu \text{W}$ . This receiver can be utilized along with any legacy Wi-Fi transmitter without changing any hardware.

A 0.3-V 1- $\mu \text{W}$ Super-Regenerative Ultrasound Wake-Up Receiver With Power Scalability

This brief presents an ultralow-power wake-up receiver using ultrasound for Internet of Things applications. To achieve both high sensitivity and low power consumption, we propose a Colpitts-oscillator-based super-regenerative receiver (COSR). Owing to the simple architecture of the proposed COSR, a lowest supply voltage operation of 0.3 V and a smallest area are achieved. Furthermore, the power consumption of the proposed wake-up receiver is scalable and is determined by the input signal sensitivity and data rate, which are configurable by the user. In a field test, the proposed wake-up receiver consumes $1~\mu \text{W}$ , which is smaller by 77% than that of a conventional ultrasound wake-up receiver at a comparable communication distance and data rate.

Exploiting Concurrent Wake-Up Transmissions Using Beat Frequencies.

Wake-up receivers are the natural choice for wireless sensor networks because of their ultra-low power consumption and their ability to provide communications on demand. A downside of ultra-low power wake-up receivers is their low sensitivity caused by the passive demodulation of the carrier signal. In this article, we present a novel communication scheme by exploiting purposefully-interfering out-of-tune signals of two or more wireless sensor nodes, which produce the wake-up signal as the beat frequency of superposed carriers. Additionally, we introduce a communication algorithm and a flooding protocol based on this approach. Our experiments show that our approach increases the received signal strength up to 3 dB, improving communication robustness and reliability. Furthermore, we demonstrate the feasibility of our newly-developed protocols by means of an outdoor experiment and an indoor setup consisting of several nodes. The flooding algorithm achieves almost a 100% wake-up rate in less than 20 ms.

An Ultralow-Power Wake-Up Receiver Based on Direct Active RF Detection

An ultralow-power direct active RF detection wake-up receiver (WuRx) is presented. In order to reduce the power consumption and system complexity, a differential RF envelope detector is implemented in a complementary current-reuse architecture. The detector sensitivity is enhanced through an embedded matching network with signal passive amplification. A prototype receiver is fabricated in 0.18- $\mu \text{m}$ CMOS technology with a core size of 0.46 mm2. At the operating frequency of 2.4 GHz, the receiver achieves a −50 dBm sensitivity [10−3 bit error rate (BER)] at a data rate of 200 kbps while consuming $4.5~\mu \text{W}$ from a 0.8 V supply voltage. The WuRx is capable of achieving a 10−3 BER for 200 kb/s data rate with a signal to interference ratio greater than −30 dB at ±10 MHz offset.

Comparing Analog Front-Ends for Duty-Cycled Wake-Up Receivers in Wireless Sensor Networks

Using ultralow-power wake-up receivers (WRxs) can reduce idle listening energy cost in wireless sensor networks with low traffic intensity. This has led to many WRx analog front-end (AFE) designs presented in literature, with a large variety of trade-offs between the sensitivity, the data rate, and the power consumption. Energy consumed during wake-up in a network depends on many parameters and without a unified energy analysis, we cannot compare performance of different AFEs. We present an analysis of duty-cycled WRx schemes which provides a simple tool for such a comparison based on the energy consumed in an entire single-hop network during a wake-up. The simplicity is largely due to the fact that all network and communication parameter settings can be condensed into a single scenario constant. This tool allows us to both compare AFEs for specific scenarios and draw more general conclusions about AFE performance across all scenarios.

Design, Implementation, and Performance Evaluation of a Flexible Low-Latency Nanowatt Wake-Up Radio Receiver

Wireless sensor networks (WSNs) have received significant attention in recent years and have found a wide range of applications, including structural and environmental monitoring, mobile health, home automation, Internet of Things, and others. As these systems are generally battery operated, major research efforts focus on reducing power consumption, especially for communication, as the radio transceiver is one of the most power-hungry components of a WSN. Moreover, with the advent of energy-neutral systems, the emphasis has shifted toward research in microwatt (or even nanowatt) communication protocols or systems. A significant number of wake-up radio receiver (WUR) architectures have been proposed to reduce the communication power of WSN nodes. In this work, we present an optimized ultra-low power (nanowatt) wake-up receiver for use in WSNs, designed with low-cost off-the-shelf components. The wake-up receiver achieves power consumption of 152 nW (with -32 dBm sensitivity), sensitivity up to -55 dBm (with maximum power of 1,2 μW), latency from 8 μs, tunable frequency, and short commands communication. In addition, a low power solution, which includes addressing capability directly in the wake-up receiver, is proposed. Experimental results and simulations demonstrate low power consumption, functionality, and benefits of the design optimization compared with other solutions, as well as the benefits of addressing false positive (FP) outcomes reduction.

Performance Analysis and Energy Optimization of Wake-Up Receiver Schemes for Wireless Low-Power Applications

The use of duty-cycled ultralow-power wake-up receivers (WRxs) can significantly extend a node lifetime in low-power sensor network applications. In the WRx design, both the low-power operation of the WRx and the wake-up beacon (WB) detection performance are of importance. We present a system-level analysis of a duty-cycled WRx design, including an analog front end, a digital baseband, the WB structure, and the resulting WB detection and false-alarm probabilities. We select a low-power WRx design with about two orders of magnitude lower power consumption than the main receiver. The associated cost is an increase in the raw bit error rate (BER), as compared with the main receiver, at the same received power level. To compensate, we use a WB structure that employs spreading. The WB structure leads us to an architecture for the digital baseband with high address-space scalability. We calculate closed-form expressions for detection and false-alarm probabilities. Using these, we analyze the impact of design parameters. The analytical framework is exemplified by the minimization of the WB transmit energy. For this particular optimization, we also show that the obtained results are valid for all transmission schemes with an exponential relationship between the signal-to-noise ratio and the BER, e.g., the binary orthogonal schemes with noncoherent detection used in many low-power applications.

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.

A 37.5 /spl mu/W Body Channel Communication Wake-Up Receiver With Injection-Locking Ring Oscillator for Wireless Body Area Network

An ultra-low power wake-up receiver for body channel communication (BCC) is implemented in 130 nm CMOS process. The proposed wake-up receiver uses the injection-locking ring oscillator (ILRO) to replace the RF amplifier with low power consumption. Through the ILRO, the frequency modulated input signal is amplified to the full swing rectangular signal directly demodulated by the following low power PLL-based FSK demodulator. In addition, the energy-efficient BCC link mitigates the sensitivity and selectivity requirements for the receiver, which significantly reduces the power consumption. Furthermore, the auto frequency calibrator (AFC) is adopted to compensate the free running frequency of the ring oscillator which is caused by temperature variation and leakage current. The AFC reuses the PLL-based demodulator to periodically set the free running frequency to the desired frequency without any area overhead. As a result, the proposed wake-up receiver achieves a sensitivity of -62.7 dBm at a data rate of 200 kbps while consuming only 37.5 μW from the 0.7 V supply.