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