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TSMP Time Synchronized Mesh Protocol Seminar in Distributed Computing, FS 2010, ETH Zrich Joo Moreno TSMP: Time Synchronized Mesh Protocol Overview Definition Background Protocol Details Results Conclusions Seminar in Distributed

  1. TSMP Time Synchronized Mesh Protocol Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  2. TSMP: Time Synchronized Mesh Protocol Overview Definition Background Protocol Details Results Conclusions Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  3. TSMP: Time Synchronized Mesh Protocol What is it? Also... scalable, flexible, The TSMP is a low-maintenance, medium access and self-organizing, networking self-healing, wow! protocol that provides reliable, low power and secure communication in a managed wireless mesh network! Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  4. TSMP: Time Synchronized Mesh Protocol Background Check control industrial warning monitoring automation alarm Presented on DSN 2008 , Orlando, Florida, USA Kristofer S. J. Pister, Lance Doherty Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  5. TSMP: Time Synchronized Mesh Protocol Management Yup, managed network. TSMP relies on the existence of a centralized controller to coordinate the communication schedule of the network. This guy is called the manager. Real deployments show that scalability and robustness are no big issues. But the limit is somewhere. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  6. TSMP: Time Synchronized Mesh Protocol Wireless Challenges what?! Interference Blocked paths Node loss I said... "can you hear me?!" Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  7. TSMP: Time Synchronized Mesh Protocol TSMP is all about... Application Presentation Session Network Media Access Physical Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  8. TSMP: Time Synchronized Mesh Protocol MA C Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  9. TSMP: Time Synchronized Mesh Protocol Packet format PHY MAC NET APP MAC Payload FCS Preamble Header Header MIC MIC 80 bytes In the 802.15.4 wireless standard, packet size is 127 bytes, of which 47 bytes are reserved by TSMP, leaving 80 bytes as payload. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  10. TSMP: Time Synchronized Mesh Protocol Packet format PHY MAC NET APP MAC Payload FCS Preamble Header Header MIC MIC The NET header contains information on End-to-End addressing and routing. The MAC header contains information about Per-hop addressing and timing. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  11. TSMP: Time Synchronized Mesh Protocol Packet format PHY MAC NET APP MAC Payload FCS Preamble Header Header MIC MIC TSMP first constructs a Message Integrity Code of both the application layer payload and a nonce that resides in the Network Header. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  12. TSMP: Time Synchronized Mesh Protocol Packet format PHY MAC NET APP MAC Payload FCS Preamble Header Header MIC MIC Then, the MAC Message Integrity Code is build from both headers, the payload and the previous MIC. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  13. TSMP: Time Synchronized Mesh Protocol Nice packet! TSM P Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  14. TSMP: Time Synchronized Mesh Protocol 1. TDMA Time Division Multiple Access Reduces interference from other TSMP nodes by scheduling communication in precise instances of time. Frame Unallocated slot Allocated slot Time Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  15. TSMP: Time Synchronized Mesh Protocol 1. TDMA Time Division Multiple Access Also, it may reduce energy consumption and increase credibility of QoS promises. sync! Frame Unallocated slot Allocated slot Time Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  16. TSMP: Time Synchronized Mesh Protocol Synchronization Rule #1: Do it well Sync Energy VS. frequency consumption Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  17. TSMP: Time Synchronized Mesh Protocol Synchronization Rule #2: Do it fast Time spent Time gained VS. sync'ing by sync'ing Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  18. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization TSM ACK P oh hai there! Time sync information is shared by piggybacking it with every ACK packet! Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  19. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization A node expects a packet at instant t. Establish T g seconds as the worst-case clock skew between any two nodes. Guard time → 2T g Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  20. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization Given a guard time T g , how often ( T sync ) need two nodes to synchronize? Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  21. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization r 1 r 2 ε ← r 2 - r 1 Once synced at t 0 , synced again at t, with synch error δ. Worst difference in shared time is Δt max = ε ( t - t 0 ) + δ . Δt max < T g ( t - t 0 ) max = T sync < ( T g - δ ) / ε !!! Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  22. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization r 1 r 2 T sync < ( T g - δ ) / ε For example, define a guard time of ±1ms , 50μs of synch error and ±10ppm of rate difference between two nodes... ... they need to be synchronized every 48s ! Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  23. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization What if they're not? brb... Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  24. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization mine is a Rolex! Time is propagated from a single time-master... Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  25. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization cool, I have a Swatch ... through a loop-free graph of participating nodes, creating a parent-child like hierarchy. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  26. TSMP: Time Synchronized Mesh Protocol TSMP Synchronization What if they're not? Parents can broadcast beacon packets. Children can send keepalive packets. Ultimately how often your nodes will sync depends on the type of network installed: periodic data-gathering, alert-based, et al. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  27. TSMP: Time Synchronized Mesh Protocol 2. FHSS Frequency-hopping Spread Spectrum Reduces interference probability by spreading the signal over several channels, using different frequencies. Channel meeny eeny offset Time Frame Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  28. TSMP: Time Synchronized Mesh Protocol 2. FHSS Frequency-hopping Spread Spectrum Also, it increases bandwidth in the order of the number of channels! miny Channel meeny eeny offset Time moe Frame Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  29. TSMP: Time Synchronized Mesh Protocol TSMP Channel Hopping Channel = Lookup[(ASN + Offset) % #Channels ] Lookup is a randomly sorted loop-up-table with values ranging from 0 to #Channels -1. ASN stands for the Absolute Slot Number since the beginning of the network. Communication happens in links which are characterized by their offsets (more on links later). Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  30. TSMP: Time Synchronized Mesh Protocol Bandwidth Using the 802.15.4 wireless, with 16 channels, 60 time slots per second and 80 bytes of payload, theoretically we get 16 * 60 * 80 = 76.8 KB/second of application level bandwidth. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  31. TSMP: Time Synchronized Mesh Protocol Network Maintenance But, do remember that TSMP reserves time slots for network configuration, neighbor discovery and join requests listening. This will come in handy in a sec... Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  32. TSMP: Time Synchronized Mesh Protocol 3. DSSS Direct-sequence Spread Spectrum Reduces interference probability by spreading the signal over more bandwidth. Original signal Resulting signal Frequency Bandwidth Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  33. TSMP: Time Synchronized Mesh Protocol 3. DSSS Direct-sequence Spread Spectrum O riginal signal Resulting signal Chipping sequence Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  34. TSMP: Time Synchronized Mesh Protocol 3. DSSS Direct-sequence Spread Spectrum Received signal Decoded signal Chipping sequence Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

  35. TSMP: Time Synchronized Mesh Protocol Extra: Link-Layer ACKs One more thing... ACKs are generated on the Link layer! PHY MAC NET APP MAC Payload FCS Preamble Header Header MIC MIC After FCS and MAC MIC verification, a positive or negative ACK is sent back accordingly. Seminar in Distributed Computing, FS 2010, ETH Zürich João Moreno

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