Bringing Safety and Security to Battery-less

Smart ClothesShilin Zhu Apr 2017

Questions To Be Answered

• Is the current user the secure owner of smart cloth?

• Is the user having safe interaction with the environment and other people?

Three Technical Questions• How to sense the security and safety?

• Wireless, Computer Vision, Electrical, Pressure …

• How to actively react to danger by clothes?

• Display, Physical, Communication …

• How to make the cloth battery-less?

• Energy Harvesting: RF, Solar, Temperature, Motion, …

Is the current user the secure owner of smart cloth?Distributed

Capacitance / Impedance

Across Body

Motion and Deformation

Tracking

Sound Pattern Recognition

Infrared Emission

Is the user having safe interaction with the environment and people?

Smart Pocket with Capacitance

Monitoring and Light Sensing

Pre-Collision System

Body and External Pressure

Monitoring

Outdoor Traffic Safety

Radiation Absorption (Asymmetric)

Disabilities Guide and Track

Appearance Adaptation

(For Soldiers) Weather Forecasting

Space Suit

How is such smart clothes made of?

Smart Conductive Textile

Stretchable and Washable Electronics, Sensors and Display

Communication Unit with

Computing Unit

Safety Reaction Components

Attachments

Tactile Motion

Display Report

Pressure

Power Supply (Passive or Active)

What kind of designs do we need?

Distributed On-Body Capacitance, Shadows

and Vital Signs Computing and Action

Classification

360 Degree Environmental

Learning and Strategy

Reliable Cloth-Mobile and Cloth-Attachment

Communication (e.g., cloth-watch)

Overcome Frequent Interference on Clothes (environment or human)

Signal Injection and Extraction on Clothes

Sensor Distribution Based on Cloth

Dynamics (stretchable, rigid, …)

Customized In-Cloth Smart TagStretchable and Washable Tag

Capacitance Sensing (Similar as LiveTag)

Antenna for BackScatter (Unique Frequency Point)

OR Active Transceiver

3D Printed Inside Cloth with Conductive Textile

Deformation Dependent Response Combined with

Phased ArrayCloth Dependent

Response

Active Sensor Panel

(e.g., PD, Sonar)

Energy Harvesting

Module

Safety Reaction Module (e.g., LED,

Stretchable Display)

Must do Both Active and Passive Ways

Smart Tag Reader

(Frequency Sweeping)

In-Cloth Simple Controller

with Energy Harvesting

Controller

Computing

Passive for the Body Active for the Environment

Tag Returns Body Information

Tag Returns Environment Information

Both Wireless (WiFi, mmWave, Visible Light) and Wired

Controller

WiredConductive

Fabrics

Wireless Reader Channel

Body

Wireless Environment

Channel

Visible Light WirelessChannel

Wireless Attachment Channel

On-Body and On-Cloth Safety and Security Network

Controller

Like a On-Body SDN

Highly Connected

Light-Weight Tags/Controller

Tag Works Both Like an Integrated Sensor and a Router

Safe?

Safe?

Safe?

Safe?

Safe?

Safe?

Safe?

Safe?

Safe?

Safe?

Secure?

NFC BackScatterMIMO Patch

Antenna

NFC Coil

Time Multiplexingand PipeliningBackScatter

NFC Power

Capacitance SensingTag

No Longer Neededfor Passive Sensing

MicrophonePocket

LED

Energy Storage

Magnetic ConductorSensing

UltrasonicSensor?

More on Pipelining

!!!!A1! !!!!A2! !!!!A3! !!!!A4!

!!!!B1! !!!!B2! !!!!B3! !!!!B4!

!!!!C1! !!!!C2! !!!!C3! !!!!C4!

Powered' Unpowered'

1'''''''''''''''''''0''''''''''''''''''0'0'''''''''''''''''''1''''''''''''''''''0'0'''''''''''''''''''0''''''''''''''''''1'

Pipeline'Design'

Master/Slave'D'flip9flop,'controlling'module'selec>on'

Security and Safety Oriented Data Analysis

• Capacitance Tag: Body and Motion Monitoring

• Microphone: Human Talk, Car Engine

• MIMO Patch Antenna: Obstacle Detection

• Magnetic Coil: Conductors

Secure? Safe?

Power• Cloth itself is Battery-less (Harvested from NFC since

others are too unreliable)

• Energy Storage System is used for Maintaining Power Supply (Overcome NFC Coupling Dynamics when Smartphone is in the Pocket)

• Time Slot and Pipelining: Power and Latency Reduction

• We Simplify the Circuits used for Data Receiving (e.g., avoid using Micro-controllers) , mW Level (NFC provides W Level)

Two ModesActive Mode:

It works like a Smartphone-Powered Radar and Metal Detector - Safety

Whether NFC has the ability to power the entire active system is a question.

Passive Mode:

It works like a Large Backscatter Device - Safety

Environment must emit some signals that can be passively received.

This is still energy harvesting, the smartphone is powering the entire system.

I do not know if the system drains the phone’s battery slow or quick.

If quick, then it is worse than directly embedding a battery (Smartphone needs to do better things like phone calls).

Why Not Camera for now?• Cannot be further made stretchable for now

• Need high resolution to do image recognition

• More Power Consuming

• Sending a 8MP image back through NFC is impossible for safety applications, need to add a video streaming unit

• Won’t work during the night which is very important for safety applications

Long-Wave Magnetic Field Sensing

Environment Conductive Objects

(Object can be Passive)

Other Non-Conductive Objects

(Object must be Active)

Magnetic MIMO Beamforming: MagMIMO (MobiCom 2014, 1MHz)

and MultiSpot (MobiCom 2015, 1MHz)

Existing Magnetic MIMO is Used For Wireless Charging,Not Sensing

We also Need to Measure the Relative Motion (Tracking) to Do Classification

They are Focusing on Circuits, Not Mag Field Formula

Magnetic Beamforming

Hbeam = ai ⋅ejθi ⋅ xi{ }

i=1

n

∑Hcoil ∝ Icoil

Frequency

• Rubee Uses 131 KHz

• Disney Research Uses 360 KHz - 50 m, Single Coil

• MagMIMO and MultiSpot Uses 1 MHz (Wireless Charging)

Why Long Wave Magnetic Signals?

Behind the Obstacle Especially Steel

(RF may get blocked)Ultra Low Power

Reasonable For IoT

Safety Issues Are Always Hidden

Magnetic Field is Safer than Electrical Field

SuitableFor IoTSafetyApps e.g., Powder

MultiPath-Free

Object - Object & Human-Human & Human-Object

3 ModesActive

Half-Active

Half-Passive

Do We Need Magnetic Channel Estimation?

M1

M2

α1x

α 2x

Real(α1)Real(α 2 )

= Img(α1)Img(α 2 )

= M1

M 2

M1/M2 determined by pre-computation/pre-training,based on object classification?

How M1/M2 changes with receivers at same location/angle?

2 Coils:

M1

M 2

= Z1' − Z1

Z2' − Z2

Zi' =Vi / Ii

Simple Sim (Single Coil & a Metal)

Smart Pocket• RF Solution: In-Pocket Antenna Connected to the

Cloth Antenna (Use WiFi?)

• Magnetic Solution: In-Pocket Magnetic Coil

• 2 Functions:

• Classification: User’s Own Hand OR Stranger’s Hand

• Track Things (Either Conductive Or Non-Conductive) In the Pocket

Challenges• Passive Ways are Limited to Conductor, Otherwise Need an Active Mag Tag

Powered by Battery or Energy Harvesting Attached to the Object

• Range, Antenna Size and Shape Dynamics, Magnetic Core

• Poor Directionality Unless MIMO

• Bandwidth is Limited

• Separate Multiple Signals (Multiplexing?)

• Magnetic Signal Modulation (Specific Time-Varying Magnetic Field)

• Receiver Side is Totally Unknown, Making Mutual Inductance Computation Very Hard (Assume multiple M when Calculation? Beam Scanning Algo?)

• Unpredicted Environment Impact

Magnetic Signal Ad-Hoc Sensing

Tranceiver

Passive Conductor

Active Mag Tag

Max Sensing Range

Active Mag Tag & Router

Active Mag Tag & Router

Pocket

Max Safety Range

Power• Battery (can last for 5-25 years?)

• Energy Harvesting (Indoor: WiFi, NFC, Magnetic; Outdoor: Solar, NFC, Magnetic

• Battery Fabrication: Flexible Printed Battery may be Used since RuBee does not Require Much Power

One-Time Recharging for Several Years?

Antenna• Self Magnetic Loop Antenna

• Without Steel Magnetic Core? Should be Easy to Be Printed

• Make Attached Conductor as Antenna (e.g., Human Body, Steel, …)

• How to Sense the Direction of Magnetic Source? And Distance?

Range

• Limited: Maximum 20 meters (in air, maybe), Otherwise We need Higher Power?

• Could we Use Multiple Objects to Do Ad-Hoc Magnetic Transmission (e.g., Act as Routers as well)?

Thanks