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Realisierungskonzepte für drahtlose Sensornetzwerke – Ein Überblick. Stefan von der Mark, Georg Böck. Overview. What are Wireless Sensor Networks? Similarities and differences to RFID Some published approaches PicoRadio/PicoBeacon (Berkeley) WiseNET (CSEM) MUSE and ORBIT (WINLAB) - PowerPoint PPT Presentation
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1Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Realisierungskonzepte für drahtlose Sensornetzwerke – Ein Überblick
Stefan von der Mark, Georg Böck
2Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Overview
• What are Wireless Sensor Networks?• Similarities and differences to RFID• Some published approaches
– PicoRadio/PicoBeacon (Berkeley)– WiseNET (CSEM)– MUSE and ORBIT (WINLAB)
• The AVM eGrain project– Concept– WakeUp– Demonstrator
3Stefan von der Mark
Technische Universität Berlin Microwave Engineering
What are Sensor Networks?
University of Geneva in Switzerland
Smart Dust:
4Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Applications
• Logistics, Locationing– Goods in a warehouse or shopping center– Books in a library
• Environmental monitoring– Indoor: Temperature, humidity, intruders– Outdoor: Pollution, agricultural research
• Structural monitoring– Bridges, skyscrapers, large halls– Ageing, stress from snow, earthquakes
• Military
5Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Properties of Sensor Networks
• Tiny little low cost sensor nodes • Wireless peer to peer communication• Self-sustained operation for prolonged time• Preferably completely integrated (CMOS)• Ad Hoc Networking:
6Stefan von der Mark
Technische Universität Berlin Microwave Engineering
State of the Art
• Existing sensor arrays are usually wired– Classical: Analog wire from each sensor– More modern: Digital bus systems
• Existing wireless sensors usually communicate with dedicated access points
• Sensor communication mostly proprietary,but IEEE standard 802.15.4/ZigBee exists
• New IEEE 1451.4 „plug&play“ standard for– Sensor ID– Type of measurement (Units!)– Calibration data
7Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Sensor Networks vs. RFID
RFID Sensor Networks
Transponder and interrogator All nodes equal
Tags reply only on request of Interrogator
All nodes can initiate transmission
High transmission power available from interrogator
Very low transmission power
Transponder usually powered by incoming RF
Own power source necessary
8Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Similarities
• Low data rates• Only occasional communication• Receivers can be similar• But transmission is completely different
9Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Realisation approaches
• Nothing coming close to the vision has been realized so far
• Different approaches are being pursued:– Big and power hungry, but functional nodes
(for protocol develompment, application research)– Demonstration of particular technologies
(low power circuits, sensing, energy scavenging)– Attempts towards complete low power hardware
(with reduced functionality)– And anything in between
10Stefan von der Mark
Technische Universität Berlin Microwave Engineering
PicoNode I (UC Berkeley)
• „PicoRadio Project“ at Berkeley Wireless Research Center, University of California at Berkeley (UCB)
• Strong ARM CPU• Xilinx FPGA• Proxim RangeLAN
or Bluetooth HW withown protocols
• 24 hr operation out of2 x 1200mAh Li-Ion
• Variety of sensor boards (modular concept)
11Stefan von der Mark
Technische Universität Berlin Microwave Engineering
PicoBeacon (UCB)
• Energy scavenged from light and vibration– 180 W out of 1 cm3 from vibrations
• 1.9 GHz transmission (no receiver)• 10m range• 2.4 x 3.9 cm2
12Stefan von der Mark
Technische Universität Berlin Microwave Engineering
WiseNet (CSEM)
• Swiss Center for Electronics and Microtechnology (CSEM)
• 2 mW RX, 32 mW TX• 433 / 868 MHz ISM• 25 kbps• 25 W for 56 bytes
every 100 seconds• WiseMAC specialized
MAC protocol• External Antenna
13Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Mote (Crossbow Inc.)
• Commercial sensor nodes based on UCB design and TinyOS operating system
14Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Mote (cont.)
• Variety of different nodes• MICA2 or 802.15.4/ZigBee protocols • 315/433/868/916 MHz options (MICA)
or 2.4 GHz (ZigBee)• 1 yr operation out of
AAA batteries
15Stefan von der Mark
Technische Universität Berlin Microwave Engineering
MUSE (WINLAB)
• Wireless Information Network Laboratory, Rutgers University, New Jersey
• Commercial embedded computers and WLAN transceiver
• Target is completeintegration
16Stefan von der Mark
Technische Universität Berlin Microwave Engineering
ORBIT (WINLAB)
• 400 nodes• Pure software testbed• No development of sensor hardware
17Stefan von der Mark
Technische Universität Berlin Microwave Engineering
The AVM eGrain Project
• AVM – „Autarke Verteilte Mikrosysteme“• 3 year BMBF project with these partners:
AVMMWT - ANT - TKN
BMBF grant No. 16SV1658
18Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Concept
• Development of completely autarkic ultra low power pico cell network
• Nodes are self organizing, no master/slave principle
• Highly integrated, node size ~1 cm3
• RF frequency 24 GHz• Development of low power system
architecture• Development of ultra low power RF
components
19Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Wakeup Strategies
Periodic Wakeup Wakeup Receiver
No extra components
Network synchronization necessary
Waste of power through unnecessary wakeups
Delay in communications
Immediate response
No reference clock
Standby power consumption
Nodes need to be in a sleep mode most of the time, but how and when to activate them?
20Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Block Diagram of the Wakeup Circuit
21Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Detector Principle
• Zero bias Schottky Diodes• FET size increases from first to third stage
22Stefan von der Mark
Technische Universität Berlin Microwave Engineering
0.5 1.0 1.50.0 2.0
20
40
60
0
80
U [V]
I [m
A]
Diode-like behavior of an NMOS Transistor:
„MOS Diode“
U
I
23Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Alternative Principle
• MOS rectifier• CMOS compatible, no BiCMOS necessary• But: less sensitivity, more standby power
Load
Vout
24Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Wake-Up Address Decoder
• Main requirement: low power consumption• Block diagram:
Detector
PWM-signal
serial Input
Shift registersAdress
correlator
A1-A8
Discriminators&
Logic
serialdata (0/1)
clock
reset
Adress preset
A1-
A8
Wakeupparallel
data
datavalid
25Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Prototype of Address Decoder
• CMOS-technology• Low complexity: ca. 470 transistors• No oscillator• Low data rate:
e.g. 50 kb/s
Address preset
RF Input
PWM signal
Wakeup-Output
Bias
Vcc: + 3V
26Stefan von der Mark
Technische Universität Berlin Microwave Engineering
RF Frontend Overview
• Frontend characteristics– Frequency: 24.125 GHz– Range: ca. 1 m– Transmit power: ca. 1 mW
• Flip-Chip-Assemblyand integrated Antenna
• IC-Technology: GaAs-HBT-MMICs (FBH)• TU Berlin (MWT, ANT), FBH
27Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Heterodyne Concept
• Standard approach• Upconversion and downconversion mixers• Good channel selectivity• Oscillator needed for Tx and Rx
LNA
BandFilter Mixer
VCO
Demodulator
PARF FilterIF Filter Mixer
VCO
28Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Zero IF Concept
• No oscillator needed in the receiver • Power consumption determined by LNA• Low complexity, low power consumption
Data
BatteryOscillator
LNA Detector LF-Amplifier
Discriminator
Data
Band filter
29Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Baseband demonstrator
• Concept
• Real data transmission at 24 GHz• Patch antenna realised on multilayer PCB• Minimum component count
RS232 12V
3V
TX Demonstrator
12V
3V
RX Demonstrator
RS232
2 2
30Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Transmitter
– On-Off-Keying (OOK) modulation– No power consumption in standby mode– No power consumption for „0“ bits
Data
BatteryOscillator
Antenna
31Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Receiver
– Zero IF– No mixer => no LO necessary (power saving!)– LF amplifier has very low current consumption
(ca. 100 µA)– Total battery current < 15 mA– Dielectric Resonator as BPF
LNA Detector LF-Amplifier
Discriminator
Data
Band filter
32Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Detector• Detector
– Diode type HSCH-3486 (Agilent)– Single stage detector – Other topologies are less efficient (bridge, cascade)
– PTX = 0 dBm, Pathloss (1m@24 GHz) = 76 dB=> PRX = –76 dBm, Gain LNA = 13 dB=> Pin, Detector = –63 dBm => Uout = 3 µV
-70 -60 -50 -40 -30-80 -20
1E-7
1E-6
1E-5
1E-4
1E-3
1E-8
1E-2
P_in
HB
.V_out_
e[::,0]
Matching
33Stefan von der Mark
Technische Universität Berlin Microwave Engineering
LNA• Measured LNA performance
– 14 mA DC @ 2 V– 13.3 dB gain @ 24.8 GHz– Bandwidth 4.2 GHz– NF 5.8 dB
(simulated) DC
IN
OUT
Bias Bias
Chipsize 1.1x1.3 mm
34Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Assembly
• Aperture coupled patch antenna
• Industry standard multilayer PCB
• RF Chip Flip-Chip mounted
• LF electronics in SMD• Housing soldered
• => only standard assembly technologies
Battery
RF ChipGroundplane
Patch-AntennaApertureFeedlineTeflon
Multilayer- PCB
1cm
LF Components
FR4
Solder
35Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Patch Antenna Principle
• Whole module size is antenna base
• Great beam collimation – Directivity 19.6 dB– Gain 8.5 dB (theo. Max. 9 dB)
• Coax feed
36Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Aperture coupled feed
• Greater bandwidth than for coaxial feed
• Lower directivity of15.6 dB
• Gain 7.8 dB• Fabrication much easier
than coax feed
37Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Photo
• 1 cm3
• 2 button cellbatteries
• 24 GHz• 2400 bps
38Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Future Work
• CMOS LNA to further reduce power consumption of the receiver (7 mA @ 1.2 V)
• Integration of detector with LNA– BiCMOS with schottky diodes– Pure CMOS with MOS rectifier
• Complete integration as SoC
39Stefan von der Mark
Technische Universität Berlin Microwave Engineering
Summary
• Today the vision is still far from reality• But many efforts and progress are made in
– Hardware design (digital and RF)– Integration and miniaturization– Energy scavenging and storage– Software design
• Some day the vision will become reality!
40Stefan von der Mark
Technische Universität Berlin Microwave Engineering
ReferencesT. T. Hsieh Using sensor networks for highway and traffic applications IEEE Potentials, vol. 23, no. 2,
pp. 13 – 16, Apr-May 2004
Christian C.Enz, Amre El-Hoiydi, Jean-Dominique Decotignie, Vincent Peiris WiseNET: An Ultralow-Power Wireless Sensor Network Solution IEEE Computer, August 2004, p. 62-70
Shad Roundy, Brian P. Otis, Yuen-Hui Chee, Jan M. Rabaey, Paul Wright A 1.9GHz RF Transmit Beacon using Environmentally Scavenged Energy IEEE Int.Symposium on Low Power Elec. and Devices 2003
Stefan von der Mark, Meik Huber, Mathias Wittwer, Wolfgang Heinrich, and Georg Boeck System Architecture for Low Power 24 GHz Front-End Frequenz -Zeitschrift für Telekommunikation, Special Issue Autarkic Distributed Microsystems in Sensor Networks, 3-4/2004, p. 70-73
M. Huber, S.v.d. Mark, N. Angwafo and G. Boeck Ultra low power Wakeup Circuits for Pico Cell Networks, A conceptional View Technical Report of the 1st European Workshop on Wireless Sensor Networks (EWSN), Jan 2004
Stefan von der Mark, Roy Kamp, Meik Huber and Georg Boeck Three Stage Wakeup Scheme for Sensor Networks IEEE/SBMO International Microwave and Optoelectronics Conference IMOC 2005; Brasilia, Brazil, July 25-28
http://tcs.unige.ch/doku.php/web/wirelesssensornetworks University of Geneva in Switzerland
http://bwrc.eecs.berkeley.edu BWRC at UCB: PicoRadio, PicoNode, PicoBeacon
http://www.csem.ch CSEM: WiseNet
http://www.xbow.com Crossbow: Mote
http://www.winlab.rutgers.edu WINLAB: Muse, Orbit
http://www-mwt.ee.tu-berlin.de Technische Universität Berlin Microwave Engineering: AVM