Passive Wake-up Radio Research Articles

BEE-DRONES: Ultra low-power monitoring systems based on unmanned aerial vehicles and wake-up radio ground sensors

Nowadays, Unmanned Aerial Vehicles (UAVs) represent a significant aid on scenarios where fixed, ground infrastructures are temporarily or permanently not available; this is the case of large-scale applications of the Internet of Things (IoTs), e.g. smart city and agriculture 3.0, where the UAVs can be employed as mobile data mules and gather the data from Wireless Ground Sensors (WGSs). UAV-aided wireless sensor networks (WSNs) introduce considerable advantages both in terms of performance and costs since they avoid the need of error-prone multi-hop communications, and also the installation of static gateways; at the same time, they pose formidable research challenges for their implementation, like the synchronization issue between the UAV and the WGS and the path planning, which should take into account the extremely limited flight autonomy of the UAVs. In this paper, we address both the issues above by proposing BEE-DRONES, a novel framework for large-scale, ultra low-power UAV-aided WSNs. In order to mitigate the synchronization problem, we investigate the utilization of passive Wake-up Radio (WR) technology on the WGSs, and of wireless power transfer from the UAVs: by harvesting the energy from the UAV hovering over it, the WGS is activated only for the short time required to transfer the data toward the mobile sink, while it experiences zero-consumption in sleep mode. We investigate the performance of passive WR-based WGS through real measurements, under different WGS-UAV distances and antenna orientations. Then, based on such results, we formulate the joint WGS scheduling and UAV path planning problem, where the goal is to determine the optimal trajectory of the UAVs activating the WR-based WGSs while taking into account the Value of the Sensing (VoS) as well as the total lifetime of the WSN. The original problem is transformed into a multi-commodity flow problem, and both centralized and distributed heuristics over the multi-graph are proposed. Finally, we evaluate the proposed algorithms through extensive OMNeT++ simulations; the results demonstrate the gain of BEE-DRONES in terms of extended lifetime compared to traditional, non WR-based solutions (e.g. duty-cycle), and in terms of reduced data-correlation compared to non VoS-aware path planning solutions.

Advances and Opportunities in Passive Wake-Up Radios with Wireless Energy Harvesting for the Internet of Things Applications.

Wake-up radio is a promising approach to mitigate the problem of idle listening, which incurs additional power consumption for the Internet of Things (IoT) wireless transmission. Radio frequency (RF) energy harvesting technique allows the wake-up radio to remain in a deep sleep and only become active after receiving an external RF signal to ‘wake-up’ the radio, thus eliminating necessary hardware and signal processing to perform idle listening, resulting in higher energy efficiency. This review paper focuses on cross-layer; physical and media access control (PHY and MAC) approaches on passive wake-up radio based on the previous works from the literature. First, an explanation of the circuit design and system architecture of the passive wake-up radios is presented. Afterward, the previous works on RF energy harvesting techniques and the existing passive wake-up radio hardware architectures available in the literature are surveyed and classified. An evaluation of the various MAC protocols utilized for the novel passive wake-up radio technologies is presented. Finally, the paper highlights the potential research opportunities and practical challenges related to the practical implementation of wake-up technology for future IoT applications.

Viability Bounds of M2M Communication Using Energy-Harvesting and Passive Wake-Up Radio

Techniques for wireless energy harvesting (WEH) are being emerged as a fascinating set of solutions to extend the lifetime of energy-constrained wireless networks. They are commonly regarded as a key functional technique for almost perpetual communications. With the WEH technology, wireless devices are able to harvest energy from, e.g., different light sources or RF signals broadcast by ambient/dedicated wireless transmitters to support their operation and communications capabilities. The WEH technology will have increasingly wider range of use in upcoming applications for, e.g., wireless sensor networks, machine-to-machine (M2M) communications, and the Internet of Things (IoT). In this paper, the usability and fundamental limits of solar cell or photovoltaic harvesting-based M2M communication systems are studied and presented. The derived theoretical bounds are in essence based on the Shannon capacity theorem, combined with selected propagation loss models, assumed additional link nonidealities, as well as the given energy harvesting and storage capabilities. Fundamental performance limits and available capacity of the communicating link are derived and analyzed, together with extensive numerical results evaluated in different practical scenarios, including realistic implementation losses and the state-of-the-art printed supercapacitor performances. In particular, low-power sensor-type communication applications using passive wake-up radio (WuR)-assisted operation are addressed in this paper. The results show the benefits of using passive WuR, especially when the number of nodes is small. Moreover, the presented analysis principles and results establish clear feasibility regions and performance bounds for WEH-based low rate M2M communications in the future IoT networks.

REACH 2 -Mote

A wireless sensor network that employs passive radio wake-up of the sensor nodes can reduce the energy cost for unnecessary idle listening and communication overhead, extending the network lifetime. A passive wake-up radio is powered by the electromagnetic waves transmitted by a wake-up transmitter rather than a battery on the sensor node. However, this method of powering the wake-up radio results in a short wake-up range, which limits the performance of a passive wake-up radio sensor network. In this article, we describe our design of a passive wake-up radio sensor node—REACH 2 -Mote—using a high-efficiency, energy-harvesting module and a very low power wake-up circuit to achieve an extended wake-up range. We implemented REACH 2 -Mote in hardware and performed field tests to characterize its performance. The experimental results show that REACH 2 -Mote can achieve a wake-up range of 44 feet. We also modeled REACH 2 -Mote and evaluated its performance through simulations, comparing its performance to that of another passive wake-up radio approach, an active wake-up radio approach, and a conventional duty cycling approach. The simulation results show that REACH 2 -Mote can significantly extend the network lifetime while achieving high packet delivery rate and low latency.

Passive wake-up radios: From devices to applications

Energy efficiency is one of the most important criteria in the design of a wireless sensor network. Sensor nodes are usually battery-powered and thus have very limited lifetime. In this paper, we introduce a novel passive wake-up radio device named WISP-Mote that uses a passive RFID tag as a wake-up receiver for a traditional sensor node. We characterize the WISP-Mote with field tests in different operating environments and present the wake-up probabilities based on the distance between the wake-up transmitter and receiver. We then perform simulations to compare the performance of a network with WISP-Motes and with duty-cycling of the sensor nodes, using the wake-up probabilities measured in our field tests. Additionally, potential applications that can benefit from WISP-Motes are discussed, and the advantages of using WISP-Motes are identified by simulation results based on these application scenarios. Results show that the wake-up radio sensor networks have great potential over duty-cycling approaches for energy efficiency, while providing similar latency and packet delivery performances.