> Motivation

> System Evaluation

> System Architecture

RTD 2010X-Sense

Felix Sutton, Bernhard Buchli, Jan BeutelComputer Engineering and Networks Laboratory, ETH Zurich, Switzerland Technische Informatik und Kommunikationsnetze

Computer Engineering and Networks Laboratory

An Ultra-Low Power Wireless Multi-Sensor Interface

> Proposed Solution

REFERENCES: [1] G. U. Gamm, M. Sippel, M. Kostic, L. M. Reindl, "Low-power sensor node with addressable wake-up on-demand capability", International Journal of Sensor Networks, Vol. 11, No. 1, January 2012.

Practical limitations of multiplexed wired sensors: - Inherent fragility of sensor cabling - Restricted sensor placement - Cumbersome installation Damage by wildlife

Rock fall damage

Moisture damage

Cumbersome installation

Wireless Sensor Network

Microcontroller(PIC24F32KA302)

Voltage Regulator

Battery

Sensor Non-Volatile Memory

Power Management

Configuration Interface

Wake-up Radio

Data Radio(TI CC110L)

Antenna Switch

Microcontroller(PIC24F32KA302)

Measurement Request

DataInterface

Data Radio(TI CC115L)

Wake-up Channel

Data Channel

Cluster Node

Cluster-head

GainEnvelope DetectorCorrelator

Serial Data Interface

Real-Time Clock

Control Logic

AS3930 Wake-up ReceiverOOK Demodulator

Z0

Wake-up Radio (Gamm, et al. [1])

Key Features: - Ultra-low power wake-up radio on 434MHz ISM band - Cluster time-synchronization using wake-up radio - Collision-free data transmission using TDMA policy - Periodic sensor sampling and FRAM data storage - Power gating of all microcontroller peripherals - User configurable RTC and measurement period

Cluster node prototype Cluster-head prototype

Data Radio

Antenna Switch

Wake-up Radio

ConfigurationInterface

FRAMVoltage Regulator

Data Radio

Microcontroller

Measurement Request

Data Interface

Microcontroller

Activity Component Duration [s] Power [mW]

MeasuringMicrocontroller

0.04562.4399

Memory 0.1811Wake-up Radio 0.0032

Communicating

Microcontroller

0.3020

2.5092Data Radio 22.1637Memory 0.0195

Wake-up Radio 0.0032

SleepingMicrocontroller

10799.65240.0236

Wake-up Radio 0.0032

LDO Regulator 10800 0.0510Total 0.0785mW

Performance Summary: - Total average power dissipation of 78.5μW - Estimated > 3 years on 1Ah coin cell battery - Communication range up to 14 meters LOS

Summary of power analysis measured at 2.5V(assuming 1 hour measurement interval with a data request every 3 hours).

0 5 10 15 20 25 30 35

10−2

10−1

100

101

102

Time [s]

Pow

er [m

W]

Microcontroller

Data Radio

Non−volatile Memory

Wake−up Radio

Communication(22mW avg., 300ms)

Measurements(2.4mW avg., 45ms)

Microcontroller Sleep: 23μW avg.

Wake-up Radio Active: 3.2μW avg.

Impedance matching analysis

400 405 410 415 420 425 430 435 440 445 450−30

−25

−20

−15

−10

−5

0

Frequency [MHz]

Ret

urn

Loss

[dB

]

PIN = 0 dBm

PIN = −10 dBm

PIN = −20 dBm

PIN = −30 dBm

Wake-up receiver return loss

Hierarchical sensing network provides: - Wireless connectivity for flexible sensor placement - Autonomous operation mitigating fragile sensor cabling - Sensor abstraction for aggregation of sensor data

Cluster-head

Cluster Nodes

readSensor(...)Asynchronous Wake-up Request

Synchronous Data Response