WirelessHART: Applying Wireless Technology
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WirelessHART: Applying Wireless Technology in Real-Time Industrial Process Control Jianping Song, Song Han, Al Mok University of Texas at Austin Deji Chen, Mike Lucas, Mark Nixon Emerson Process Management Wally Pratt HART Communication Foundation. Outline. Background

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Outline

WirelessHART: Applying Wireless Technology in Real-Time Industrial Process ControlJianping Song, Song Han, Al MokUniversity of Texas at AustinDeji Chen, Mike Lucas, Mark NixonEmerson Process ManagementWally PrattHART Communication Foundation


Outline

Outline

  • Background

  • Introduction to WirelessHART

  • Development Challenges and Solutions

  • WirelessHART Demonstration

  • Summary


Future wireless plant

Future Wireless Plant


Wirelesshart history

WirelessHART: History

  • HART (Highway Addressable Remote Transducer)

    • Bi-directional industrial field communication protocol

    • Used to communicate between field devices and host systems

    • The global installed base of HART-enabled devices is more than 20 million

  • WirelessHART

    • Wireless extension of HART

    • Released in 09/2007


Wirelesshart designed for wireless plant solutions

WirelessHART: Designed for Wireless Plant Solutions

  • Real-Time

    • TDMA technology

    • Centralized Network Management

  • Reliability

    • Channel Hopping and Channel Blacklisting

    • Mesh Networking

  • Security

    • Data Integrity on MAC layer

    • Data Confidentiality on the Network layer


Alternative wireless standards not suitable for process control

Alternative Wireless Standards: Not Suitable for Process Control

  • Zigbee

    • No Channel Hopping or Channel Blacklisting

    • Problem with persistent noises

  • Bluetooth

    • Only supports star type network topology

    • Not scalable for large industrial control systems

  • Wi-Fi

    • No Channel Hopping

    • Power Consumption

  • ISA SP100

    • Not available yet


Outline1

Outline

  • Background

  • Introduction to WirelessHART

  • Development Challenges and Solutions

  • WirelessHART Demonstration

  • Summary


Wirelesshart architecture

WirelessHART Architecture


Wirelesshart architecture1

WirelessHART Architecture

  • Physical Layer (IEEE 802.15.4)

  • Data Link Layer

  • Network Layer and Transport Layer

  • Security

  • Network Manager


Data link layer

Data Link Layer


Timer module

Timer Module

  • Time is sliced into time slots (starting from 0)

  • Time intervals in a time slot

  • Clock synchronization is critical


Links and superframes

Links and Superframes

  • Link: activity in a time slot

    • Neighbor

    • Send/Receive

    • Communication channel

  • Superframe: a group of links

    • Defined by network manager

    • Repeat itself infinitely

    • A device can support several superframes


Data link layer state machine

Data Link Layer State Machine

  • Each run of the state machine

    • Call the link scheduler to determine the next slot to be serviced

    • On receiving the ”time slot start” event, increment the ASN (Absolute Slot Number) by 1

    • When it is time to service the given time slot derived in step 1), execute the associated transaction (SEND/RECV)


Wirelesshart architecture2

WirelessHART Architecture

  • Physical Layer (IEEE 802.15.4)

  • Data Link Layer

  • Network Layer and Transport Layer

  • Security

  • Network Manager


Security

Security

  • Data Link Layer

    • Hop-to-hop data integrity

    • CCM* (Counter with CBC-MAC) mode with AES-128 to generate the MIC

  • Network Layer

    • Public keys: used to generate MICs on MAC layer by joining devices

    • Network keys: used by existing devices in the network to generate MAC MIC’s

    • Join keys: used during the joining process to authenticate the joining device

    • Session keys: unique for each end-to-end connection between two network devices


Network keying model

Network Keying Model


Wirelesshart architecture3

WirelessHART Architecture

  • Physical Layer (IEEE 802.15.4)

  • Data Link Layer

  • Network Layer and Transport Layer

  • Security

  • Network Manager


Functions of network manager

Functions of Network Manager

  • Support devices joining/leaving the network

  • Create routes

  • Schedule communications

  • Adapt the schedule upon network changes


Outline2

Outline

  • Background

  • Introduction to WirelessHART

  • Development Challenges and Solutions

  • WirelessHART Demonstration

  • Summary


Hardware platform

Hardware Platform

  • MC1321x Evaluation Kit by Freescale

    • One 1321x-NCB board, two 1321x-SRB boards

    • 40 MHz 8-bit HCS08 MCU

    • 2.4 GHz 802.15.4 Transceiver

    • Programmable 60 KB Flash and 4KB RAM

    • Multiple 16-bit timers

    • 4 LEDs for demonstrations and monitoring

  • A simple IEEE 802.15.4 Physical Layer Library


Challenge 1 timer design

Challenge 1: Timer Design

  • Challenge

    • Stringent timing requirements – a 10ms time slot further sliced into several time intervals

    • Some tasks are time consuming and may exceed allocated time

  • Solution

    • Use a separate hardware timer for WirelessHART

    • The caller informs the timer module current slot type

    • The timer generates required timer events accordingly


Challenge 1 timer design1

Challenge 1: Timer Design


Challenge 2 time synchronization

Challenge 2: Time Synchronization

  • Challenge

    • Synchronize the nodes in a network

    • A new node should derive current time during the joining process

  • Solution

    • A node records the time when the first bit of a frame arrives

    • The receiver calculates the clock drift TsError

    • The receiver includes the drift in the time adjustment field of the corresponding ACK frame

    • When a node receives an ACK from its time source, it will adjust its clock


Challenge 3 speed up security calculations

Challenge 3: Speed Up Security Calculations

  • Challenge

    • The receiver must run CCM* on the received frame and the corresponding ACK frame within TsTxAckDelay (1ms)

    • The lower power HCS08 MCU can not meet the requirement

  • Solution

    • Upon request, Freescale is developing a new chipset with hardware encryption accelerator

    • We propose to execute CCM* as soon as every 16 bytes are received


A wirelesshart demonstration

A WirelessHART demonstration

  • One gateway and two devices: Device 1 and Device 2

    • The gateway and Device 2 exchange values through Device 1 and show the received values on the LEDs

    • All frames are captured by a sniffer

  • Time slot configuration


A wirelesshart demonstration1

A WirelessHART Demonstration

  • A device can synchronize to its time source within 3 time slots

  • A data frame is always ACKed in the same time slot

  • Device 1 acts as a router for the Gateway and Device 2


Summary

Summary

  • Conclusions

    • Introduction of the WirelessHART architecture

    • Discussion of the challenges and solutions

    • Demonstration of a prototype WirelessHART network

  • Future Works

    • Full-featured WirelessHART prototype

    • Network Manager

    • Co-existence with ZigBee and Bluetooth


Thank you

Thank you!

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