Transcript TIPS FOR SUCCESSFUL WIRELESS SENSING

Pete Secor
WIRELESS BASICS
 Industry standards for RF transmission
 IEEE 802.11 WiFi;
 Bluetooth
 IEEE 802.15.4 Low Power Low Data Rate

Platform for ZigBee & Wireless HART & Evergreen Telemetry
 Hierarchy of layers--rule sets—foundation at bottom
 Applications (Smart Energy App passes rate info)
 Network (Customized by ZigBee, Wireless Hart, etc.)
 Data Link (IEEE 802.15.4 defines this layer)
 PHY (Physical, radio, antenna, connector, etc.)
WIRELESS SENSOR NETWORKS
(WSN)
 Key terms: mesh; IEEE 802.15.4; ZigBee; interoperable
 Components
 End node (sleeps), router/repeater, coordinator
 Node contains: radio, antenna, sensing elec.; encl.
 For sensing and/or actuating
 Line powered and/or battery
 Built-in system monitors and reliability features
 Master intelligence
Network Diagram
802.15.4
LOW POWER & LOW DATA RATE
 Battery-based apps
 Short, infrequent transmissions, not time-critical
 xxx bytes per transmission, not x Mb/s.
 Handshaking and error detection—resend if necessary
 Designed to withstand interference, not overpower
 End node battery example—temperature sent 1x/min.
 Lithium button cell 1000 mA-hr battery lasts 5 years.
 This platform selected by ZigBee Alliance
 Ideal building application—wireless thermostats
ISM Frequency Spectrum
 IEEE 802.15.4 specifies these frequency channels:
 0 at 868.3 MHz (Mostly EU only)
 1-10 at about 915 MHz (Mostly N. Amer. Only)
 11-26 near 2.4 GHz. (Available worldwide)

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WiFi on same channels—different wave characteristics
ZigBee Alliance tested WiFi interference
Some transmissions repeated; none lost.
 ZigBee scans for low energy channel at start-up.
 Range at 2.4 GHz 50 to 100 feet per hop, through walls
 Amplified range measured in miles
ZigBee Alliance
 Founded 2002
 HVAC Focus
 Key members:
 Emerson, Itron, Landis & Gyr, Schneider, Aclara
 AEP, Consumer’s Energy, Edison, BC Hydro
 Eaton, Crestron, Distech, Echelon, GE
 Johnson Controls, Siemens, Honeywell
 Atmel, Intel, Sharp, Sony, Samsung, NEC, Oki
 Hundreds of others
ZigBee Alliance
 Industry Liasons
 American Telemedicine; Continua Health Alliance
 BACnet; WiFi; HomePlug Powerline Alliance
 Demand Response and Smart Grid Coalition
 Electric Power Research Institute; NEMA
 European Smart Metering Association
 Society of Automotive Engineers (electric vehicles)
 ANSI; Internet Engineering Task Force
 Continental Automated Buildings Assoc.
 Consumer Electronics Assoc. (RF4CE)
ZIGBEE KILLER APPS
 HVAC monitoring and control
 Thermostats & VAV’s
 Smart Energy
 Term is widely used with different meanings
 One app: Connects electric meter to t-stat & appliances

Utility can control home remotely—temp, pool pump, w. heat
 RF4CE
 Next generation remote control for home
 No line-of-sight issues
 Contemporary display & selection
Your App--What Can Go Wrong?
 Interference--WiFi, oven, cordless phone, other.
 Absorption--Water heater; Human bodies in hallway.
 Move or eliminate a reflective surface
 Change position slightly
 Reflections, phase change add/subtract signal
 Moisture
 Failure of a router/repeater.
 Battery failure
 Range reduction for various reasons
ENSURE WSN SUCCESS
 Experience generally problem-free
 Avoid long range, edge of range operation
 Install extra router/repeaters
 Awareness
 Range issues, number of hops
 Slight position change can help or hurt.
 Battery level—end nodes sleep—coord & routers don’t

Transmission schedule (2 seconds vs. 1 min. vs. 10 min.)
 New emitter or change in environment causes problems

Cycle power, rescan channels for energy, select new channel
SUCCESSFUL WIRELESS SENSING
Questions?
Pete Secor
[email protected]