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Realisierungskonzepte für drahtlose Sensornetzwerke – Ein Überblick

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Presentation on theme: "Realisierungskonzepte für drahtlose Sensornetzwerke – Ein Überblick"— Presentation transcript:

1 Realisierungskonzepte für drahtlose Sensornetzwerke – Ein Überblick
Stefan von der Mark, Georg Böck

2 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

3 What are Sensor Networks?
Smart Dust: University of Geneva in Switzerland

4 Applications Logistics, Locationing Environmental monitoring
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

5 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: Only some sensors communicate with base stations Data is routed through the sensors

6 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 /ZigBee exists New IEEE „plug&play“ standard for Sensor ID Type of measurement (Units!) Calibration data

7 Sensor Networks vs. RFID
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

8 Similarities Low data rates Only occasional communication
Receivers can be similar But transmission is completely different

9 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 Kleine Auswahl, bei Weitem nicht vollständig

10 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 with own protocols 24 hr operation out of 2 x 1200mAh Li-Ion Variety of sensor boards (modular concept) January 2002

11 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 Agilent Film Bulk Acoustic Resonator (FBAR) for 1.9 GHz Oscillator

12 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

13 Mote (Crossbow Inc.) Commercial sensor nodes based on UCB design and TinyOS operating system

14 Mote (cont.) Variety of different nodes
MICA2 or /ZigBee protocols 315/433/868/916 MHz options (MICA) or 2.4 GHz (ZigBee) 1 yr operation out of AAA batteries

15 MUSE (WINLAB) Wireless Information Network Laboratory, Rutgers University, New Jersey Commercial embedded computers and WLAN transceiver Target is complete integration

16 ORBIT (WINLAB) 400 nodes Pure software testbed
No development of sensor hardware

17 The AVM eGrain Project AVM – „Autarke Verteilte Mikrosysteme“
3 year BMBF project with these partners: MWT - ANT - TKN AVM BMBF grant No. 16SV1658

18 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

19 Wakeup Strategies Nodes need to be in a sleep mode most of the time, but how and when to activate them? 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

20 Block Diagram of the Wakeup Circuit

21 Detector Principle Zero bias Schottky Diodes
FET size increases from first to third stage

22 „MOS Diode“ Diode-like behavior of an NMOS Transistor:

23 Alternative Principle
MOS rectifier CMOS compatible, no BiCMOS necessary But: less sensitivity, more standby power

24 Wake-Up Address Decoder
Main requirement: low power consumption Block diagram: Detector PWM-signal serial Input Shift registers Adress correlator A1-A8 Discriminators & Logic serial data (0/1) clock reset Adress preset Wakeup parallel data valid

25 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

26 RF Frontend Overview Frontend characteristics
Frequency: GHz Range: ca. 1 m Transmit power: ca. 1 mW Flip-Chip-Assembly and integrated Antenna IC-Technology: GaAs-HBT-MMICs (FBH) TU Berlin (MWT, ANT), FBH

27 Heterodyne Concept Standard approach
Upconversion and downconversion mixers Good channel selectivity Oscillator needed for Tx and Rx

28 Zero IF Concept No oscillator needed in the receiver
Power consumption determined by LNA Low complexity, low power consumption

29 Baseband demonstrator
Concept Real data transmission at 24 GHz Patch antenna realised on multilayer PCB Minimum component count

30 Transmitter On-Off-Keying (OOK) modulation
No power consumption in standby mode No power consumption for „0“ bits

31 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

32 Detector Detector Diode type HSCH-3486 (Agilent) Single stage detector
Other topologies are less efficient (bridge, cascade) PTX = 0 dBm, Pathloss GHz) = 76 dB => PRX = –76 dBm, Gain LNA = 13 dB => Pin, Detector = –63 dBm => Uout = 3 µV Matching

33 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) Chipsize 1.1x1.3 mm

34 Assembly Aperture coupled patch antenna
Industry standard multilayer PCB RF Chip Flip-Chip mounted LF electronics in SMD Housing soldered => only standard assembly technologies

35 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

36 Aperture coupled feed Greater bandwidth than for coaxial feed
Lower directivity of 15.6 dB Gain 7.8 dB Fabrication much easier than coax feed

37 Photo 1 cm3 2 button cell batteries 24 GHz 2400 bps

38 Future Work CMOS LNA to further reduce power consumption of the receiver (7 1.2 V) Integration of detector with LNA BiCMOS with schottky diodes Pure CMOS with MOS rectifier Complete integration as SoC

39 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!

40 References T. 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 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 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 University of Geneva in Switzerland BWRC at UCB: PicoRadio, PicoNode, PicoBeacon CSEM: WiseNet Crossbow: Mote WINLAB: Muse, Orbit Technische Universität Berlin Microwave Engineering: AVM

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