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 S R Where is R? ch1 ch3 chN time ch2 ch1 …

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 Control channel time RTSCTSRES Control Channel R S 123 2 2 Data channel? DATAACK NA V

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 Channel 3 time Channel 1 Channel 2 RTS CTS O R S O R S O R S 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 ATIM WindowData Window time Beacon Interval

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. Network topology G-McMAC Protocol GW1 1 3 4 2 6 5 GW2GW3 8 8 8

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

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

17. CCC ch1 chN ch2 BPCDP G-McMAC Protocol time... … GWGW 431 2 TDMACSMA Feedback assisted Beacon Collision Avoidance (FBCA) : Beacon : RsACK : Sensing: RsREQ 2 2 GWGW DATA 2→GW 2 31 3 1 DATA 3→1

18. G-McMAC Protocol Feedback assisted Beacon Collision Avoidance (FBCA) To avoid collisions To produce optimal sort Hop0 Hop1 GWGW 431 BPCDPBP GWGW 123 4 time Hop2 5 56 GWGW BPCDP 1, 4 14 6 2 … 2 56 3 Expire slot Expire slot

19. G-McMAC Protocol Multiple Gatways network priority Primary networks Secondary networks Hop0 Hop1 Hop2 GW1GW1 431 GW2GW2 BPCDPBP GW1GW1 123 GW2GW2 6556 GW2GW2 BnAcREQ GW2GW2 78 Secondary BP time 9

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.

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