Shekar Nethi, Jari Nieminen and Riku Jantti

1. Exploitation of Multi-Channel Communications in Industrial Wireless Sensor Applications: Avoiding Interference and Enabling Coexistence Shekar Nethi, Jari Nieminen and Riku Jantti WCNC 2011 Speaker : Huei-Rung Tsai

2. Outline • Introduction • Goals • G-McMAC Protocol • Simulation Results • Conclusions

3. Outline • Introduction • Goals • G-McMAC Protocol • Simulation Results • Conclusions

4. Introduction • Industrial wireless sensor • Employ Wireless Sensor and Actuator Networks (WSANs) • Low-power sensors collect information about the physical world • Sensors transmit the physical information to actuators wirelessly • In industrial wireless sensor applications • Channel conditions are very likely to vary and harsh • IEEE 802.11 b/g networks may interfere IEEE 802.15.4 sensor networks • Multi channel MAC protocol can improve the network performance

5. Introduction • Rendezvous problem is thorny in Multi-channel environment • Sender and receiver rendezvous • Data transmission channel Where we transmit data? Where we transmit data? Where is R? chN ch2 ch1 S R ch1 ch3 ch3 … … time

6. Introduction • Existing multi-channel MACs can be divided into 4 classes • Dedicated control channel • Common hopping • Parallel rendezvous • Split phase

7. Introduction • Dedicated control channel • Dynamic Channel Assignment (DCA) • Two interfaces • One is fixed on the control transmitted RTS/CTS/RES packets • Other switches between data channel transmitted data/ACK packets • Shortcoming • More cost NAV Control Channel 123 2 2 DATA ACK Control channel Data channel? RTS CTS RES R S time

8. Introduction • Common hopping based • Channel-Hopping Multiple Access (CHMA) • All the nodes obey a common hopping pattern and data transmission will take place on the current channel after a RTS/CTS handshake • Shortcoming • Energy consumption S S S R R R O O O RTS Channel 3 Channel 2 Channel 1 CTS time DATA(S,R)

9. Introduction • Parallel rendezvous • SSCH: Slotted Seeded Channel Hopping for Capacity Improvement in IEEE 802.11 Ad-Hoc Wireless Networks • Shortcoming • Energy consumption f(A.mac)=1,2,0,0,3,1… f(B.mac)=1,0,0,1,2,2…

10. Introduction • Split phase based • Multi-channel MAC (MMAC) • Suitable for WSNs • Nodes can sleep after a contention period if they do not need to transmit or receive Beacon Interval ATIM Window Data Window time

11. Introduction • The problem with these approaches is that predetermined frame structures • Makes the system inflexible • WirelessHART is an industrial standard for wireless automation • Don’t specifically solve the problems • Related to real-time communications • Co-existence of multiple overlapping networks

12. Goals • Design a generic, flexible and robust multi-channel MAC protocol (G-McMAC) • Its enable coexistence of multiple wireless sensor applications • It can dynamically adapt when network topology changed • Achieves low transmission delays and high throughputs

13. Outline • Introduction • Goals • G-McMAC Protocol • Simulation Results • Conclusions

14. G-McMAC Protocol • Network topology 8 8 GW2 GW3 GW1 4 8 2 1 5 3 6

15. G-McMAC Protocol • Channel arrangement CCC ch1 ch2 ... … Beacon Interval Beacon Period (BP) Contention plus Data Period (CDP) chN time

16. G-McMAC Protocol • Beacon Period (BP) • Route establishment • Exchange channel information • Provide time synchronization • Contention plus Data Period (CDP) • Resource negotiations • Data transmissions • Common Control Channel (CCC)

17. G-McMAC Protocol Feedback assisted Beacon Collision Avoidance (FBCA) BP CDP 2 2 GW 3 1 GW 4 3 1 CCC DATA 2→GW 2 2 ch1 DATA 3→1 1 3 ch2 ... … chN time TDMA CSMA : RsACK : Sensing : Beacon : RsREQ

18. G-McMAC Protocol • Feedback assisted Beacon Collision Avoidance (FBCA) • To avoid collisions • To produce optimal sort Expire slot BP CDP BP CDP … … BP 1, 4 GW GW GW Hop0 4 3 1 2 2 3 1 2 3 4 1 4 Hop1 5 6 5 6 5 6 Hop2 time

19. G-McMAC Protocol • Multiple Gatways network priority • Primary networks • Secondary networks SecondaryBP BP CDP BP GW 1 GW2 GW 1 Hop0 GW2 4 3 1 1 2 3 GW2 GW2 7 8 9 Hop1 6 5 5 6 Hop2 time BnAcREQ

20. G-McMAC Protocol • Nodes sense the channel before starting a data transmission • Miss resource reservations when transmission does not matter • Nodes can reserve periodic transmissions simply by setting the Periodic Transmission bit as 1 in RsREQ message

21. Outline • Introduction • Goals • G-McMAC Protocol • Simulation Results • Conclusions

22. Simulation Results • The implementation of G-McMAC is done on ns2 • Environment • Crane (overhead)Control System (CCS) — Primary network • Machine Health Monitoring System (MHMS) • Air Conditioning Unit (ACU) • The goal is to achieve minimum performance degradation for high priority CCS with the added payload in the network

23. Simulation Results • G-McMAC effectively integrates application priority and achieves good performance in case of multiple overlapping WSANs

24. Simulation Results • These results show that G-McMAC is able to avoid interference and enables coexistence of multiple sensor applications

25. Outline • Introduction • Goals • G-McMAC Protocol • Simulation Results • Conclusions

26. Conclusions • G-McMAC protocol achieves high throughput and low packet transmission delays while enabling coexistence of multiple overlapping wireless networks. • In Simulation, showed a comprehensive set of simulation results from a real-world industrial application scenario to confirm that GMcMAC is suitable for industrial wireless sensor applications.

27. Thanks For Your Attention~

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