Outline

1. 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

2. Outline • Background • Introduction to WirelessHART • Development Challenges and Solutions • WirelessHART Demonstration • Summary

3. Future Wireless Plant

4. 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

5. 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

6. 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

7. Outline • Background • Introduction to WirelessHART • Development Challenges and Solutions • WirelessHART Demonstration • Summary

8. WirelessHART Architecture

9. WirelessHART Architecture • Physical Layer (IEEE 802.15.4) • Data Link Layer • Network Layer and Transport Layer • Security • Network Manager

10. Data Link Layer

11. Timer Module • Time is sliced into time slots (starting from 0) • Time intervals in a time slot • Clock synchronization is critical

12. 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

13. 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)

14. WirelessHART Architecture • Physical Layer (IEEE 802.15.4) • Data Link Layer • Network Layer and Transport Layer • Security • Network Manager

15. 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

16. Network Keying Model

17. WirelessHART Architecture • Physical Layer (IEEE 802.15.4) • Data Link Layer • Network Layer and Transport Layer • Security • Network Manager

18. Functions of Network Manager • Support devices joining/leaving the network • Create routes • Schedule communications • Adapt the schedule upon network changes

19. Outline • Background • Introduction to WirelessHART • Development Challenges and Solutions • WirelessHART Demonstration • Summary

20. 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

21. 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

22. Challenge 1: Timer Design

23. 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

24. 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

25. 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

26. 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

27. 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

28. Thank you! Comments?