M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks Oliver Harms 1,2 , Olaf Landsiedel 1,2 1 Kiel University, Germany 2 Chalmers University of Technology, Sweden International Conference on Distributed Computing in Sensor Systems (DCOSS) 2020
Industrial Internet of Things (IIoT) • Requirements: High reliability • Low latency • Guaranteed • performance • Central Scheduling M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 2
Contributions • M ASTER : centralized router and scheduler • Targets IEEE 802.15.4 and TSCH MAC • Provides easy extendibility • Sliding Windows: transmission strategy • Enables flexible, stable, and reliable communication • Extensive testbed evaluation • Long-term stable schedule (24 hours) M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 3
Outline 1. Motivation 2. Background a. Time-Slotted Channel Hopping (TSCH) b. Central Scheduling 3. M ASTER a. Design b. Transmission strategies: Sliding Windows 4. Evaluation 5. Conclusion M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 4
Time-Slotted Channel Hopping (TSCH) • TDMA • Control information • FDMA (up to 16 channels) • Recurring Slotframes M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 5
Central Scheduling C-TSCH: A Centralized Scheduler for TSCH 6
Outline 1. Motivation 2. Background a. Time-Slotted Channel Hopping (TSCH) b. Central Scheduling 3. M ASTER a. Design b. Transmission strategies: Sliding Windows 4. Evaluation 5. Conclusion M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 7
M ASTER M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 8
M ASTER Overview • Central Scheduler • Routing Layer M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 9
M ASTER building blocks Transmission Routing Scheduling Strategy M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 10
Routing • Dijkstra’s shortest path algorithm • Metric: ETX, ETX 2 , or ETX 3 M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 11
Transmission Strategies • No retransmissions • Slot-based retransmissions • Flow-based retransmissions • Sliding Windows M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 12
Traditional approaches • No retransmissions A B C D • Slot-based retransmissions 1 2 3 1 2 3 4 5 6 A TX A TX TX B RX TX B RX RX TX TX TX RX TX TX RX RX C C D RX D RX RX M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 13
Sliding Windows • Flow-based retransmissions A B C D • Slot role: RX, TX, shared (RXTX) • Number transmissions 1 2 3 4 5 6 • Fixed A TX TX TX TX • 𝐹𝑈𝑌 -based B RX RXTX RXTX RXTX TX • 𝑜 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 𝑜 ∗ ∑ 𝐹𝑈𝑌 !"#$ RX RXTX RXTX RXTX TX C D RX RX RX RX M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 14
Sliding Windows in action 1 2 3 4 5 6 A B C D A TX B RX TX RX TX C D RX M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 15
Sliding Windows in action 1 2 3 4 5 6 A B C D A TX TX TX B RX RX RX TX RX RX RX TX TX C D RX RX RX RX M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 16
Scheduling • R-LPF (Reverse Longest Path First) • Best-effort • Non deadline-based M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 17
Outline 1. Motivation 2. Background a. Time-Slotted Channel Hopping (TSCH) b. Central Scheduling 3. Master a. Design b. Transmission strategies: Sliding Windows 4. Evaluation 5. Conclusion M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 18
Evaluation Setup • Testbed at Kiel University • 500 m 2 • 20 nodes • Platform: Zolertia Firefly • Evaluation configuration • 6 flows, 2-4 hops • 2 hours • 1 packet per second • 64 bytes payload + headers M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 19
M ASTER ’s Transmission Strategies • Baseline • Slot-based • 1 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 2 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 1 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 2 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 3 ∗ ∑ 𝐹𝑈𝑌 !"#$ M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 20
M ASTER ’s Transmission Strategies • Baseline • Slot-based • 1 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 2 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 1 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 2 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 3 ∗ ∑ 𝐹𝑈𝑌 !"#$ M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 21
M ASTER vs. Orchestra • 3 ∗ ∑ 𝐹𝑈𝑌 !"#$ at night • 3 ∗ ∑ 𝐹𝑈𝑌 !"#$ during daytime • Orchestra at night • Orchestra during daytime M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 22
M ASTER ’s Long-Term Stability • 1 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 2 ∗ ∑ 𝐹𝑈𝑌 !"#$ • 3 ∗ ∑ 𝐹𝑈𝑌 !"#$ M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 23
Conclusion • M ASTER : centralized router and scheduler for TSCH • Sliding Windows: flexible and stable transmission strategy • Implementation available at https://github.com/ds-kiel/master-scheduler • Long-term stable schedules • Outperforms Orchestra latency wise M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 24
Thank you for your attention https://github.com/ds-kiel/master-scheduler oha@informatik.uni-kiel.de M ASTER : Long-Term Stable Routing and Scheduling in Low-Power Wireless Networks – Oliver Harms 25
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