1. Localized Scheduling for End-to-End Delay
Constrained Low Power Lossy Networks with 6TiSCH
SPEAKER: CHEN-YU HO ADVISOR: DR. HO-TING WU DATE: 2017/12/15 1

2. Outline Introduction Related Work Problem Statement
Distributed Stratum Scheduling
Experimental Results
Conclusion
Reference 2

3. Introduction
The IoT expects to exploit IEEE e-TSCH, designed for wireless industrial sensor networks.
Since many applications may require low end-to- end delay (e.g. alarms) 3

4. IEEE e -TSCH
IEEE e has proposed the TSCH mode for industrial wireless sensor networks.
When a node is neither receiver nor transmitter, it turns its radio off. 4

5. IEEE e -TSCH (cont’d.)
To improve the reliability, TSCH proposes to implement channel hopping. 5

6. IEEE e -TSCH (cont’d.) 6

7. 6TiSCH
The 6TiSCH IETF working group designs the protocols to operate IPv6 (6LoWPAN) over a reservation based MAC layer (IEEE TSCH). 7

8. 6TiSCH (cont’d.) 8

9. Traffic Aware Scheduling Algorithm
To assign the resource for each packet is currently a very challenging objective. 9

10. Problem Statement

11. Large end-to-end Delay with a Random Distributed Scheduling
Here the average end-to-end delay we may obtain with a random scheduling algorithm.
B->A
Z -> Y
W->N

12. OutCell_Delay Assume the first hop has selected the timeslot 0.
A packet has to be enqueued until the next outgoing cell

13. Hop_Delay
A packet needs possibly several retransmissions if the link is unreliable. Precisely, it needs on average ETX transmissions

14. E2E_Delay
Assume a packet may be generated at anytime, the end-to-end delay for a packet along the route p.

15. E2E_Delay (cont’d.)
Slotframe of 1001 slots.
Packet every 15 seconds.

16. Distributed Stratum Scheduling
Guarantee a maximum end-to-end delay equal to the slotframe duration.
Divide the network in stratums.
Assigning a time-frequency block (a band) to each stratum.

17. Sizing the number of stratums and their width
Nodes are uniformly distributed in a given area, and all the nodes generate the same amount of traffic.
It closest to the border router have more traffic to forward

18. What is the block?

19. Frequency re-use Fix the number of blocks to be equal to dmax.
A node in the stratum k will use the block k mod (dmax),

20. Experimental Results
To evaluate thoroughly the behavior of our solution, we used the FIT/IOT-LAB testbed ( lab.info/, cortex-m3 nodes).

21. Parameters For The Experiments

22. End-to-end Delay Random strategy may reach almost 4.5 s.
Delay is on average 15ms * (SFlength / 2) * depth
Stratum strategy may reach almost 1.5 s.

23. Scalability

24. Traffic Scalability

25. Energy Savings

26. Conclusion
Studied in depth the end-to-end delay provided by a TSCH MAC layer.
This strategy is much more efficient than a random distributed scheduling to upper bound the delay.

27. Reference
Hosni, F. Theoleyre, and N. Hamdi, “Localized scheduling for end-to-end delay constrained Low Power Lossy networks with 6TiSCH,” 2016 IEEE Symposium on Computers and Communication (ISCC), 2016.