Cinamin: A Perpetual and Nearly Invisible BLE Beacon Bradford Campbell, Joshua Adkins, and Prabal Dutta Electrical Engineering and Computer Science Department University of Michigan Ann Arbor, MI 48109

{bradjc,adkinsjd,prabal}@umich.edu Abstract Bluetooth Low Energy beacons have immense potential to provide rich contextual information to smartphone applications and people by bridging the physical and digital worlds. Beacons perform the simple operation of periodically chirping URLs, locations, and other pointers, however, today’s beacons use relatively large and battery powered implementations. To truly make these beacons pervasive, they will need to be smaller, self-powered, and, ideally, invisible. To facilitate this, we propose the Cinamin beacon design that exploits the powerful but simple primitive of periodic packet broadcast to replace the volume-defining battery with an energy-harvesting power supply and achieve a beacon in under 100 mm3 . This design, however, raises new issues relevant to energy-harvesting and challenges with pursuing miniaturization.

1

Introduction

Bluetooth Low Energy (BLE) beacons enable a host of applications that blend physical and digital spaces. By embedding wireless communication that interoperates with smartphones, smart watches, and other wearable technology, beacons such as iBeacon [2] and Eddystone [1] allow people to connect seamlessly with their surroundings. Existing beacon hardware designs support these applications but are limited in two ways: 1) they rely on batteries, which have a fixed lifetime and will need to be replaced after a year or two, and 2) are noticeably large on account of including the volume of a battery. Common beacons run on a CR2032 battery and therefore are at least 1 cm3 in volume. MEMS-scale beacons are not yet commercially available. Given the immense application space that leverages beacon-provided context information, can we build a better beacon that is small enough to be placed anywhere unnoticed, does not have a lifetime limitation, and can be built today with COTS parts?

International Conference on Embedded Wireless Systems and Networks (EWSN) 2016 15–17 February, Graz, Austria © 2016 Copyright is held by the authors. Permission is granted for indexing in the ACM Digital Library ISBN: 978-0-9949886-0-7

Figure 1: Cinamin BLE beacon model on a CR2032 coin cell battery. The radio, crystal, antenna, energy buffer, antenna, PCB, power supply, and solar panel all fit in a 5 mm x 5 mm x 3.4 mm cube.

To accomplish this, we propose replacing the batterybased power supply with an energy-harvesting design based on indoor solar. BLE beacons are well suited for energyharvesting as they provide utility while requiring little device complexity: the device must only transmit the same packet periodically. Harvesting can potentially remove the lifetime constraint as the beacon can harvest whenever the lights are on (which is typically correlated with when people are around), and can drive down the form factor as a sufficient solar cell and buffer capacitor are smaller than a typical coin cell. One potential design is shown sitting on a CR2032 battery in Figure 1 and occupies 85 mm3 . To understand the feasibility of this design point, we explore what energy budget a 5 mm x 5 mm solar panel may provide in an indoor setting, what the state-of-the-art BLE radios require in terms of startup, advertising, and sleep energy, and what low-power ICs exist for controlling the power supply in this energy-harvesting context. We analyze the two modes of operation for this energy-harvesting beacon: cold-booting before each transmission or maintaining lowpower sleep, and note that startup energy costs often outweigh keeping the radio in sleep mode. We find that the components needed for this application are mostly available today, with size being the largest hurdle. Both indoor photovoltaics and energy-harvesting ICs need better options for miniaturization efforts. Scaling BLE beacons down to fit unnoticed inside of light fixtures will significantly lower the bar for making immersive experiences possible, pervasive, and seamless.

331

Packet Interval (s)

1000

IC AKM AP4400A Analog ADM8642 Linear LTC1540 TI BQ25504

DA14581 Cold Boot DA14581 Sleep DA14581 Ideal IcyTRX-65 Cold Boot IcyTRX-65 Sleep IcyTRX-65 Ideal

100 10

IQ 20 nA 92 nA 300 nA 330 nA

Voltage Divider Required No Yes Yes No

Size (mm2 ) 14.7 1.5 9.0 9.0

Internal Power Gate No No No No

Table 1: Comparison of potential harvesting solutions.

1 0.1 0

5

10 15 Harvested Power (uW)

20

Figure 2: Beacon performance at different harvesting levels.

2

Design Tradeoffs

Three major components define the operation of the energy-harvesting BLE beacon: the harvesting source, the BLE radio, and the power supply.

2.1

Indoor Solar Harvesting

To estimate the amount of energy that can be harvested from indoor solar, we examine existing studies of indoor irradiance and indoor photovoltaic efficiencies. Yerva et. al [5] found that sensors placed indoors can expect an irradiance of about 100 uW/cm2 , and assuming an efficiency of 10% [4], a 5 mm square solar panel could harvest 2.5 µW. To improve this, the beacon may be placed closer to the light, and De Rossi et. al [4] found that for an amorphous silicon cell in 500 lux of florescent light could harvest 17.1 uW/cm2 . If placed very close to the light, or inside of the fixture, the beacon would likely be able to harvest more.

2.2

Beacon Operation

Because of its simple execution mode (send a BLE advertisement), the beacon can either stay off and cold boot before each transmission or transition to sleep mode when not active. The relation between incoming harvested energy and beacon period can be described as: (PHARV EST − PLEAK − PSLEEP ) · t period = ESTARTUP + EADV (1) when the incoming power minus losses and the power to keep the radio in sleep over the period between transmissions must equal the energy needed to start the radio and transmit a packet. In cold boot mode, PSLEEP will be zero, and in sleep mode ESTARTUP will be zero. PLEAK is the power lost due to leakage and the power supply overhead. Figure 2 shows the beacon interval time versus harvested power for two BLE radios, the Dialog DA14581 and the CSEM IcyTRX-65, that represent the lowest power radios available. Startup and advertising energy and sleep power numbers were obtained from [3] and relevant data sheets. For each radio there are curves for the two modes, plus an “ideal” case where both startup and sleep costs are zero. Marked with vertical lines are harvesting estimations from Section 2.1 and one at 9 µW that would likely be possible very near a light with a well matched solar panel at the 5 mm x 5 mm form factor. At low harvesting levels (below 5.5 µW) it is better to cold boot the DA14581 before each transmission than try to keep the radio in sleep mode (which would likely be infeasible).

332

The lower power IcyTRX-65 radio displays less of a gap, but has a crossover point at 4.3 µW. Therefore, when targeting the extreme low end of harvesting and miniaturization, paying the startup energy cost before each packet allows for a higher advertising rate than maintaining sleep mode.

3

Challenges Three main challenges exist for building this node today.

3.1

Energy-Harvesting Power Supplies

The beacon requires a power supply to buffer energy in a storage capacitor and monitor voltage to indicate when there is sufficient energy available to successfully transmit. Table 1 highlights four ICs that can be used for this type of power supply. To facilitate cold booting, the supply must be able to enable VCC to the radio and disconnect the radio to allow for recharging. Also, any quiescent current of the harvester or voltage monitor (PLEAK ) reduces the input power. While we found no ICs that perfectly matched our goals, and none that included a power gate for enabling cold booting, the AKM AP4400A provides the best set of features, albeit in a rather large package and without configurable voltage thresholds. To better support these types of energyharvesting applications, better ICs are needed that continue to minimize quiescent current while including configurable high and low voltage detection and internal power switches.

3.2

Indoor Photovoltaics

Current COTS solar panels provide little flexibility for small, indoor systems. The estimates in this work are linearly scaled figures from measurements taken with larger panels (at least 12x larger) as smaller panels largely do not exist. The ones that do include significant packaging overhead. Today, beacon size is often dictated and guided by the available solar panel sizes. More panel sizes and mounting options are required to facilitate this frontier of beacons.

3.3

Transmission Range

A small node necessitates a small antenna with little RF keepout room. The beacon must be able to transmit at least short distance (1-3 m), but limited range may be advantageous to prevent congestion and user confusion. Prototyping the beacon is required to evaluate this fully.

4

References

[1] Eddystone. https://github.com/google/eddystone. [2] iBeacon. https://developer.apple.com/ibeacon/. [3] J. Bernegger and M. Meli. Comparing the energy requirements of current bluetooth smart solutions. Technical report, 2014. [4] F. De Rossi, T. Pontecorvo, and T. M. Brown. Characterization of photovoltaic devices for indoor light harvesting and customization of flexible dye solar cells to deliver superior efficiency under artificial lighting. Applied Energy, 156(C):413–422, 2015. [5] L. Yerva, B. Campbell, A. Bansal, T. Schmid, and P. Dutta. Grafting energy-harvesting leaves onto the sensornet tree. IPSN ’12, 2012.

Cinamin: A Perpetual and Nearly Invisible BLE Beacon - EWSN

Figure 1: Cinamin BLE beacon model on a CR2032 coin cell battery. The radio, crystal, antenna, energy buffer, antenna,. PCB, power supply, and solar panel all ...

2MB Sizes 3 Downloads 185 Views

Recommend Documents

Cheap Nordic Nrf51822 Bluetooth 4.0 Beacon Ble Holyiot Ibeacon ...
Cheap Nordic Nrf51822 Bluetooth 4.0 Beacon Ble Holyi ... ximity Marketing Free Shipping & Wholesale Price.pdf. Cheap Nordic Nrf51822 Bluetooth 4.0 Beacon ...

Towards a Secure Key Generation and Storage Framework ... - EWSN
International Conference on Embedded Wireless ..... ported on this technology. Most of .... tional Conference on Advanced Video and Signal-Based Surveillance.

Gullmerkemedlemmene ble hedret.pdf
stiftelsesmøtet i Oslo 21. november 1981. Det skulle vise seg å bli en stor lykke for den. organiserte biljardsporten i Norge. I de neste 23 årene påtok han seg betydelig ansvar og. arbeidsoppgaver innenfor en rekke områder, og han behersket dis

Finding Perpetual Beta.pdf
fundamental changes in networked society,. business, and education. Harold Jarche. R E F L E C T I O N S. ON THE NETWORK ERA. finding perpetual beta.

Demo: Ball and Plate Wireless Control - EWSN
now targeting control applications in many domains such as industries ... monitoring systems. Despite ... antee, at the application level, the state of the system.

IoT Meets Robotics - EWSN
emerging applications mixing robotics with the Internet of. Things. Keywords. IoT, Robotics, Cloud Computing. 1 Introduction. The recent years have seen wide interest and innovation in the field of Internet of Things (IoT), triggered by techno- logic

Towards a Secure, Resilient, and Distributed Infrastructure for ... - EWSN
Runs on. Inspired by IEC 61131. Offers Values as Datapoints. Hardware. View. Software. View. Cyclic. Task. Component. Component. Composition. Component.

Estimation and Inference with a (Nearly) Singular ...
Sun and Edward Vytlacil for helpful comments. This paper is developed from ..... that ensures the reparameterization function h(·) in Procedure 3.1 below is nonrandom and does not depend on the true DGP. ...... many distinct but related contexts inc

The Beacon Cover Competition 2016 - Beacon Hill School
Everything else is up to you. Will you choose a theme? Will you choose a way of showing what Beacon Hill represents to you? Remember to make it colourful and eye-catching to be able to encourage people to want to read more! Your entry needs to be ret

Estimation and Inference with a (Nearly) Singular ...
are both binary (e.g., Evans and Schwab, 1995; Goldman et al., 2001; Lochner and Moretti,. 2004; Altonji et al., 2005; Rhine et al., 2006) and instruments are ...

Perpetual Preservation System
name indicates the macro elements are needed in much larger quantities by ... are and accordingly we dose the micronutrients separately and usually in much ...

the Beacon
Internet, this book will give you the motivation to find the tools to educate your kids and to set .... It seems to be the way of things that Home is never fully appreciated until it has been .... the summit of Cummings Hill (4 miles to go). Plunge d

The Beacon Cover Competition 2016 - Beacon Hill School
Everything else is up to you. Will you choose a theme? Will you choose a way of showing what Beacon Hill represents to you? Remember to make it colourful ...

Supplementary Appendix to: Perpetual Learning and Apparent Long ...
Apr 13, 2017 - Perpetual Learning and Apparent Long Memory. Guillaume Chevillon. ESSEC Business School & CREST .... T large enough, f (2π. T n) > 0. Also for n ≤ T, n−δTδ+1 → ∞ as n → ∞. Therefore, there exist (n0 ..... where ⌊x⌋ i

Grove-BLE (dual model) v1.0.sch - GitHub
2015/1/29 16:32:21 E:\Work\BLE (dual model)\Grove-BLE (dual model) v1.0\Grove-BLE (dual model) v1.0\Grove-BLE (dual model) v1.0 sch_pcb\Grove-BLE ...

Perpetual Learning and Apparent Long Memory
Apr 14, 2017 - of the literature has focused on persistence at business cycle frequencies, .... defined as the solution to the minimization problem: ... The above learning algorithms can be all expressed as linear functions of past values of ..... On

Channel Exploration/Exploitation Based on a Thompson ... - EWSN
Systems and Networks (EWSN) 2016 ... operating system one with a learning algorithm and one as ... We programmed two Telosb nodes; one as an oracle.

Perpetual Whelping Chart.pdf
Perpetual Whelping Chart.pdf. Perpetual Whelping Chart.pdf. Open. Extract. Open with. Sign In. Main menu. Displaying Perpetual Whelping Chart.pdf.

Bahana Beacon -
The Bakrie Group may sell ANTV to raise cash .... Following the Constitutional Court decision to allow SOE banks to write off past bad debts, ...... ICB Bumiputera.

Perpetual Whelping Chart[1].pdf
There was a problem previewing this document. Retrying... Download. Connect more apps... Try one of the apps below to open or edit this item. Perpetual ...

FlightCheck 7.75 Mac (Perpetual License)
typography, design, publishing, prepress, printing- generally on software and technology. ... Adobe Acrobat DC and Reader compatibility Official Apple ... Unique ...

CESEL: Securing a Mote for 20 Years - EWSN
of modern system-on-a-chip (SoC) designs provides ample space for hardware ..... In Parallel and Distributed Processing Symposium, 2003. Proceedings.