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Low-Power Wireless Bus (LWB)

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. Outline. Introduction Protocol Operation Evaluation Discussion.

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Low-Power Wireless Bus (LWB)

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  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

  2. Outline • Introduction • Protocol Operation • Evaluation • Discussion

  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

  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!

  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)

  6. Outline • Introduction • Protocol Operation • Evaluation • Discussion

  7. Overview

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

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

  10. Scheduler • Determining the round period • Tmin (1s): > total duration of a round Tl • Tmax (30s): < time of synchronization failing due to clock skew • dmax(60 slots): number of data slots that the scheduler can map in a single schedule packet (so, # of pkts/ round) • When Topt <Tmin, the network is saturated • Allocation data slots to streams • where as: number of data slots the scheduler allocates to streams during a round rs = T/IPIs

  11. Outline • Introduction • Protocol Operation • Evaluation • Discussion

  12. Metrics • Metrics • Data yield: • Radio duty cycle • Protocols • Testbeds

  13. Bootstrapping • Fully bootstrapped: when all source nodes delivered at least one packet to the sink • LWB, CTP: < 2min; Dozer: >18min • Fairness in energy consumption: only LWB • Battery depletion may cause a network partition

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

  15. Many-to-Many Scenario • 8 sinks

  16. Topology Changes - External Interference

  17. Topology Changes - Node Failures

  18. Mobile Sink

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

  20. Real-World Trial • Many-to-many • One-to-many • Change traffic demands • Change active nodes • 5 mobile nodes (B,M1~M4) as both sources and sinks • 7 days during working • B: trigger high rate stream of all mobile nodes

  21. Outline • Introduction • Protocol Operation • Evaluation • Discussion

  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

  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

  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 = Tmin • LWB is easy to modify this,unlike others!

  25. Q&A

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