1. Low-Power Wireless Bus (LWB) SenSys 2012 Federico Ferrari, Marco Zimmerling(ETH), Luca Mottola(SICS), Lothar Thiele (ETH) ("Potential" BEST PAPER/RUNNER UP) NSLab study group 2012/11/05 Presented by: Yu-Ting 1

2. Outline Introduction Protocol Operation Evaluation Discussion 2

3. Comment Part1 Good writing structure Clearly explain how this protocol operates An extended work of Glossy – Take the efficient flooding advantage of Glossy A brand-new and awesome unified solution for WSN communication 3

4. Feature Bootstraps quickly and efficiently, while distributing energy costs evenly In many-to-one scenarios, LWB operates reliably and efficiently under a wide range of traffic loads, and promptly adapts when traffic demands change Supports many-to-many communication without any changes Topology-independent Supports mobile nodes acting as sinks, sources, or both without any changes or performance loss Very good energy consumption! 4

5. Comment Part2 Compare with 7 different protocols – Good to get familiar with important related work Seems to beats all the other state-of-art protocols Clearly describe the scenario and parameters in evaluation – Use fair choices of parameter for the other protocols – With brief explanation of how other protocols operate Multi-Sink is actually not an easy task (few protocols support that) 5

6. Outline Introduction Protocol Operation Evaluation Discussion 6

7. Overview 7

8. Operation Sink acts as host here Inter-packet interval (IPI) = 6s here 8

9. Host Failure Failure of host: complete absence of communication within T hf – Upon detect it, nodes switch to the next channel Hardcode a circular ordered list After not receiving stream request for T hf, host also switch the the next channel 9

10. Scheduler Determining the round period – T min (1s) : > total duration of a round T l – T max (30s) : < time of synchronization failing due to clock skew – d max (60 slots) : number of data slots that the scheduler can map in a single schedule packet (so, # of pkts / round) – When T opt <T min, the network is saturated Allocation data slots to streams – where 10 a s : number of data slots the scheduler allocates to streams during a round r s = T/IPI s

11. Outline Introduction Protocol Operation Evaluation Discussion 11

12. Metrics 12

13. Bootstrapping Fully bootstrapped: when all source nodes delivered at least one packet to the sink LWB, CTP: 18min Fairness in energy consumption: only LWB – Battery depletion may cause a network partition 13

14. Many-to-One Scenario: Light/Heavy/Fluctuating Traffic 14

15. Many-to-Many Scenario 8 sinks 15

16. Topology Changes - External Interference 16

17. Topology Changes - Node Failures 17

18. Mobile Sink 18

19. Mobile Sources(4) and Mobile Sink(1) 19

20. Real-World Trial Many-to-many One-to-many Change traffic demands Change active nodes 5 mobile nodes (B,M 1 ~M 4 ) as both sources and sinks 7 days during working B: trigger high rate stream of all mobile nodes 20

21. Outline Introduction Protocol Operation Evaluation Discussion 21

22. Scalability The more number of streams, the more consumption of memory and computation time – TelosB can support several hundreds of streams (each stream with 15bytes/pkt and 13bytes to store in memory) – [YT] Memory is used to store a burst of received data within 1 round The more number of streams, the more saturated the bandwidth is 22

23. Network Diameter Difficult to determine the network diameter in advance, which affect the length of data (Td) and schedule (Ts) – Current prototype is 7 hops ([YT] it's not short…) When the network spans "several tens" of hops, other approaches may perform better Longer slots (Ts,Td) leads to fewer available slots per round and thus bandwidth – Default setting: support 300 streams with IPI=5s, so double-length slots support at most IPI=10s 23

24. Alternative Scheduling Policies Trade off between latency and energy consumption LWB-low-latency: adapts the round period T such that the next round occurs immediately after the generation of new packets LWB-fixed-period: fixes T = T min LWB is easy to modify this, unlike others! 24

25. Q&A 25