The combination of low-power design, energy harvesting and ultra-low-power wake-up radios is paving the way for perpetual operation of Wireless Sensor Networks (WSNs). In this work we present the MagoNode++, a novel WSN platform supporting energy harvesting and radio-triggered wake ups for energy- neutral applications. The MagoNode++ features an energy- harvesting subsystem composed by a light or thermoelectric harvester, a battery manager and a power manager module. It further integrates a state-of-the-art RF Wake-Up Receiver (WUR) that enables low-latency asynchronous communication, virtually eliminating idle listening at the main transceiver. Experimental results show that the MagoNode++ consumes only 2.8uA with the WUR in idle listening and the rest of the platform in sleep state, making it suitable for energy-constrained WSN scenarios and for energy-neutral applications

Chiara Petrioli

Dora Spenza

Luca Benini

Michele Magno

PAOLI, MARIO

English

Paoli, Mario

Spenza, Dora

Petrioli, Chiara

MAGNO, MICHELE

BENINI, LUCA

Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna

Poster Abstract: MagoNode++ - A Wake-Up-Radio-Enabled Wireless Sensor Mote for Energy-Neutral Applications

Archivio della ricerca- Università di Roma La Sapienza

Poster Abstract:MagoNode++: A Wake-Up-Radio-Enabled WirelessSensor Mote for Energy-Neutral ApplicationsMario Paoli*, Dora Spenza, Chiara Petrioli*University of Rome “La Sapienza” and *WSense s.r.l.Email: {paoli, spenza, petrioli}@di.uniroma1.itMichele Magno, Luca BeniniETH Zurich and University of BolognaEmail: {magnom, lbenini}@iis.ee.ethz.chAbstract—The combination of low-power design, energy har-vesting and ultra-low-power wake-up radios is paving the wayfor perpetual operation of Wireless Sensor Networks (WSNs). Inthis work we present the MagoNode++, a novel WSN platformsupporting energy harvesting and radio-triggered wake upsfor energy-neutral applications. The MagoNode++ features anenergy-harvesting subsystem composed by a light or thermoelec-tric harvester, a battery manager and a power manager module.It further integrates a state-of-the-art RF Wake-Up Receiver(WUR) that enables low-latency asynchronous communication,virtually eliminating idle listening at the main transceiver. Ex-perimental results show that the MagoNode++ consumes only2.8𝜇A with the WUR in idle listening and the rest of the platformin sleep state, making it suitable for energy-constrained WSNscenarios and for energy-neutral applications.I. INTRODUCTIONEnergy harvesting, which allows to power embedded de-vices from environmental energy, is presently one of the mostpromising technologies towards the goal of very long-lastingsensing systems [1]. If the harvested energy is efficientlyutilized, nodes of a Wireless Sensor Network (WSN) poweredby renewable energy can achieve long-term uninterruptedoperation. To reach this goal, the system’s energy consumptionshould be dynamically adapted to the availability of the energysource, so as to achieve Energy Neutral Operation (ENO) [2].Informally, a node operates in ENO mode if the energy itconsumes over a given time period is no greater than theenergy harvested during the same time period. Depending onthe considered scenario, achieving ENO may be challenging.For example, indoor energy sources such as ambient lightin illuminated rooms can provide power only in the orderof tens of 𝜇W per cm2. To support energy-neutral operationin such scenarios, the energy consumption of WSN nodesmust be reduced as much as possible. The use of a Wake-UpReceiver (WUR) drastically increases the energy efficiency ofwireless communication by virtually eliminating idle listening,which is one of the main sources of energy waste in WSNs.Motes equipped with a WUR use a dedicated ultra-low powerhardware component to monitor the channel, remaining ina power-saving sleep state until other nodes in the networkdemand their activation.In this work we present the MagoNode++, a novel WSNplatform for energy neutral applications that combines a wake-Fig. 1. A MagoNode++ prototype with energy-harvesting and radio-triggeringcapabilities.up radio, light or thermoelectric harvesters and a batteryand power management module for self-sustainable operationand long-lasting sensing systems. To the best of our knowl-edge, the MagoNode++ is the first WSN platform integratinglight/thermoelectric harvesting, power management and radio-triggering capabilities with a power consumption of less than3𝜇A with the WUR in idle listening.II. MAGONODE++ ARCHITECTUREThe MagoNode++ is built upon the MagoNode [3], a802.15.4 compliant WSN mote operating in the ISM 2.4 GHzband. The MagoNode rev. B features the ATmega256RFR2microcontroller and transceiver bundle and the Texas Instru-ments CC2530 radio front-end, which provides superior radioperformance with low-power consumption. Figure 1 shows theprototype of the MagoNode++, composed by a MagoNode andby the expansion board we have developed to exploit energy-harvesting and wake-up radio capabilities.Fig. 2. Architecture of the MagoNode++.The architecture of the MagoNode++ is depicted in Fig. 2.Energy Harvester and Battery Manager Module Thecore of the energy harvesting subsystem is an energy-harvesting integrated circuit designed for low-power appli-cation, the BQ25570 by Texas Instruments. The BQ25570efficiently converts and stores energy generated from vari-ous sources, including photovoltaic panels and thermoelectricgenerators, using a dynamic MPPT algorithm. The harvestedenergy is accumulated in a storage device, such as superca-pacitors or Li-Ion, Li-Polymer, NiCd or NiMH batteries. TheBQ25570 is equipped with a nano-power buck converter tosupply the load with a regulated voltage.Power Management Module To support energy-neutral op-eration, a WSN platform should provide fine-grained estima-tions of energy harvesting and consumption. To calculate theenergy budget in a reliable and low-power way, we equippedthe MagoNode++ with a fuel gauge (the ST STC3115) thatestimates the battery state of charge (SOC) based on its voltageand on the current flowing from and to the battery. For fine-grained estimations of the harvested energy, a high-accuracylow-power light sensor (the Rohm BH1750FVI) allows tocorrelate data about the energy gathered from the solar panelwith luminance variations. As for energy consumption, theamount of energy needed to perform a given task can beestimated by either using the fuel gauge or by referring toa look-up table reporting the power consumption of commonoperations (computed offline and stored in the mote’s memoryat programming time).Wake-up Receiver and Wake-up Transmitter Use ofa wake-up radio increases the energy efficiency of wirelesscommunication by eliminating idle listening on the mainradio transceiver. The wake-up module of the MagoNode++ iscomposed by a ultra-low-power wake-up receiver (WUR) andby a wake-up transmitter (WTX) to send awakening requests.The wake-up system uses on-off keying modulation and it isoptimized to work at 868MHz. The WUR module featureshigh sensitivity (up to -55dBm), short wake-up latency, nano-ampere current consumption (560nA at 3V) and selectiveaddressing capability [4]. 0 5 10 15 20 25 30 35WTX [TX]WUR [RX]MagoNode [TX]MagoNode [RX]Light Sensor [ON]Fuel Gauge [ON]Current consumption [mA]Active states [mA]31.10.046527.714.50.16 0.051 0 1 2 3 4 5 6WTX [SLEEP]WUR [IDLE]MagoNode [SLEEP]Light Sensor [SLEEP]Fuel Gauge [SLEEP]MagoNode++ [LPM](total current)PWmote+WUR+WTX [5](total current)Current consumption [uA]LPM state [uA]0.90.51.10.212.85.5Fig. 3. Current consumption of the components of the MagoNode++ in activeand sleep states.III. EXPERIMENTAL RESULTSWe experimentally determine the current consumption ofthe MagoNode++ in different operational states by performingmeasurements using a digital multimeter. Results for a supplyof 3V are reported in Figure 3. The first histogram depicts thecurrent consumption of the system in typical active states: datatransmission and reception using the main transceiver, wake-up message transmission and reception, light sensor samplingand SOC estimation. The second histogram shows the cur-rent consumption of the MagoNode++ in its lowest powerconsumption state, denoted as Low Power Mode (LPM), anddetails the current drained by each individual module in thisstate. Results show that the MagoNode++ consumes only2.8𝜇A in LPM with its WUR module in listening mode,outperforming existing prototypes such as [5] (PWmote V1MSP430+CC2420, WUR and WTX CC1100) with a reductionof almost 50% in energy consumption.Overall, the low power consumption, energy-harvestingand radio-triggering capabilities of the MagoNode++ make itsuitable to challenging application scenarios that requires highenergy efficiency and self-sustainable operations.Acknowledgments This work was partly supported bythe MIUR Cluster Smart Communities Tech, by the projectSMARTOUR founded by MIUR and by the project Harvesting-Aware Communication Protocols in the Self-Powered Internetof Things founded by University of Rome “La Sapienza”.REFERENCES[1] S. Basagni, M. Y. Naderi, C. Petrioli, and D. Spenza. Wireless SensorNetworks with Energy Harvesting. In Mobile Ad Hoc Networking: TheCutting Edge Directions, chapter 20, pages 701–736. Mar 2013.[2] A. Kansal, J. Hsu, S. Zahedi, and M. B. Srivastava. Power Managementin Energy Harvesting Sensor Networks. ACM Transactions on EmbeddedComputing Systems, 6(4), 2007.[3] M. Paoli, A. Lo Russo, U. M. Colesanti, and A. Vitaletti. MagoNode:Advantages of RF front-ends in wireless sensor networks. In Real-WorldWireless Sensor Networks, volume 281 of Lecture Notes in ElectricalEngineering, pages 125–137. 2014.[4] D. Spenza, M. Magno, S. Basagni, L. Benini, M. Paoli, and C. Petrioli.Beyond duty cycling: Wake-up radio with selective awakenings for long-lived wireless sensing systems. In Proceedings of IEEE INFOCOM 2015,pages 522–530, April 2015.[5] T. N. Le, M. Magno, A. Pegatoquet, O. Berder, O. Sentieys, andE. Popovici. Ultra low power asynchronous MAC protocol using wake-up radio for energy neutral WSN. In Proceedings of ACM ENSSys 2013,pages 10:1–10:6, 2013.View publication stats

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Poster Abstract: MagoNode++ - A Wake-Up-Radio-Enabled Wireless Sensor Mote for Energy-Neutral Applications

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