WirelessHART, Technology and Deployment( ETSI Nov. 09 )Jean-Luc Griessmann, HART Communication Foundation Europe
IntroductionWireless devices are everywhere!
• We use wireless devices in everyday life.� Devices are simple and often
work out of the box� We sometimes accept poor
service (battery life – signal loss)• Industry has special • Industry has special
requirements� Reliable, Secure, Simple� Based upon standards� We can not just send process
data over a radio link433MHz
433/915MHz
315/413MHz
315/426MHz
433/868MHz
315/915MHz
2.4 GHz
WirelessHART, Designed for Process Applications
• Reduce installation costs� Cable – connections – cable
trays…• Process monitoring / Control
� Hard to reach / expensive to install locations
� Full access to multivariable devices
� Control where appropriate• Asset Management
� Condition monitoring� Configuration database� Plug in upgrade adapter
What is HART ? Communication over wire
4 cyclical variables
3.5psi
Device set up
Calibration
Diagnostic and maintenance status
4-20mA Process
Building on HART for evolving to WirelessHART
• HART is the industry standard Instrument communications protocol� Main use is for commissioning� Less than 10% of instruments have
remote access HART 5
HART 6
HART 7Time/Cond. ReportingPV Trending
SecurityMesh & Star
All PV With StatusLong Tags
Process MonitoringDiagnostics
Configuration• HART is evolving
� Adding features• Wireless is the next step
� Simple – Secure – Reliable� For wireless power is important
• Standardization� now IEC/PAS 62591 Ed. 1
ConfigurationRemote Access
4-20mA Loop
Wireless
The wireless resource…
Find a Frequency band which •Does not need a license•Is available world wide
300GHz
30GHz
3GHz
30MHz
3MHz
300MHz
Wireless Spectrum
• Use an open wireless band� Industrial Scientific Medical
(ISM)• No site license required• Need to work alongside other
433MHz
315/413MHz
315/426MHz
433/868MHz
315/915MHz
2.4 GHz
users (ZigBee – Bluetooth, WiFi…)
• Choose an ISM band with global coverage�2.4GHz� IEE 802.15.4 – 2006 250kbps�Channel hopping on per packet
basis
433MHz433/915MHz
Coexisting with other networks
• Need to coexist with other users of the ISM band�Good worker gets the
message through �Good neighbour works with
CH-12.405GHz
CH-152.475GHz
802.15.4 Radio
WirelessH
AR
T
�Good neighbour works with alongside networks
• Asses a channel before you use it
• Hop to other channels• Reduce power to limit
signal range
802.15.4 Radio
Other N
etwork
802.11W
iFi
CH-12.412GHz
Co-Existence
• Channel hop to avoid busy channels (15 channels)
• Asses channels before you use them
• Black list channels which • Black list channels which have heavy use
• Transmit for a short period of time (good neighbour)
• Vary transmit power (security benefit too)
Built into WirelessHART
Co-Existence
Testing with other ISM users•Wifi 802.11b/g•Video•Phone•Phone•Others
WirelessHARTMaintained 99.999%data reliability in a 20 Instrument mesh
Video, Phone & WiFi
Main requirements (User Input)
• Make it Reliable�Manage power�Process plants change�Need redundant paths
• Make it Secure• Make it Secure�Secure the data�Authenticate data and
devices
• Make it Simple�As simple as 4-20mA
WirelessHART Reliable
• MESH network� Multiple pathways� Adapts to plant conditions
• Gateway� Multiple access points� Security and Network manager
Host Connection (High Speed fieldbus)
Gateway
� Security and Network manager• Co existence
� Work within the ISM band� Channel assessment � Black listing
99.999% end to end reliability
WirelessHART Secure
• Always enabled ( keys, encryption AES 128 )
• Data level� Instrument authentication� Message authentication� Data Encryption� Data Encryption
• Network level� Monitor join attempts� Rotate encryption keys� Defeat replay attacks
• Short time synchronized messages (<4 msec)
Can you break the code in real time?
Power is everything
• High data rate = reduced battery life
• Battery development will help
• Can use energy
WirelessHART Gateway
Note:Radio time • Can use energy
scavenging• Build features into the
specification to extend battery life
Radio time can depend upon location in the mesh
Location in the Mesh and Power
Power:• Power options include
� Battery� External power� Energy scavenging
• The radio burns significant battery power
Parentsrouting 50% life
WirelessHART Gateway
• The radio burns significant battery power
• Parents have to route data from children
• Children can have routing feature switched off.
• Radio is on for� Routing� Synchronising� Advertising
ChildrenNo routing 100% life
Parents & Childrensome routing 70% life
routing 50% life
~10 years
When to transmit in WirelessHART
• WirelessHART instruments are time synchronised�Time distribution�Time slots�Time slots
• Allows different reporting rates within one mesh
• Synchronise for channel hopping
• Access and timing is handled automatically
TDMA Time Division Multiple Access
• Time Slot�1 Slot/Channel = 1
Transaction (10msec)�Dedicated slot (PV update)�Shared slot (alarm/events)
• Time SynchronizationSlots
Cycle nCycle n-1 Cycle n+1
STXACK
Destination Listensfor Start of Message
Transmission Starts
Destination ACK Starts
Source Now Listening
Transaction
• Time Synchronization�When a Slot Begins�Common time�What Frequency To use
• Time synchronisation and time slots are handled automatically
• Slot - A fixed time interval that may be used for communication between neighbors.
• Superframe - A collection of slots repeating at a constant rate. Each slot may have several links associated with it.
• Link - The full communication specification between adjacent nodes in the network. i.e., the communication parameters necessary to move a packet one hop.
Superframe
Cycle nCycle n-1 Cycle n+1
TDMA SlotTDMA Slot--based Communicationbased Communication
Slot Timing Transmitting
Start SlotAssessment
Switch to Transmit
Wait forack
Receiveack
ListenCCA
Message3 to 4 msec
Switch to receive
10 msec - 1 time slot - 1 channel
1 slot can transmit up to 8 PV’s plus statusPacket = 133 bytes250kbit/s
Using WirelessHARTApplications
• Process monitoring/Control� Hard to reach locations� Better insight into process� Ad-hoc measurements� multivariable devices
• Equipment Monitoring� Bearing temperatures� Vibration� Vibration� Corrosion� Oil pressure� Air flow
• Asset Management� Maintenance
• Calibration• Record valve signatures• Radar echo
� Diagnostics• Valve position feedback• Device health (status)
PlanningSite Assessment
• Detailed site survey not required
• Line of Site� Clear line of sight to the
device with no obstructions• Low Density
� Open areas where you can see from one device to
Unobstructed 150m
Moderate Density75m
Highly Dense 30m
Clear Line of Site 225m
see from one device to multiple other devices
• Medium Density� Can drive a truck through the
process area• High Density
� Can not see from one device to the next
� Significant metal and structural material
Planning, DeploymentBest Practice
• Each field device has at least 3 neighbors� The 3rd neighbor will act as a
backup if one of the two primary paths is obstructed or unavailableunavailable
• Devices (antenna) mounted >0.5m from any solid surface and off the ground
• Gateway� Should have 5 neighbors� 20% of field devices connect
directly to the gateway
Planning, DeploymentDevice location
• Locate instruments� Use repeater for devices out
of range� ½ power beam 45deg about
horizontal
• Locate gateway • Locate gateway � plant segmentation� Network capacity� Area classification
Conclusion
• Hart is the ideal basis for a wireless instrument network� Industry standard�30,000,000 installed devices
• WirelessHART ticks the • WirelessHART ticks the boxes�Reliable – Secure - Simple
• Backing of major vendors• Int. Standard
� IEC/PAS 62591