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Roberto Attias, Duke Lee, Anju Puri, Starvros Tripakis, Raja Sengupta, Pravin Varaiya

A Token-Ring Medium-Access-Control Protocol with Quality of Service Guarantees for Wireless Ad-hoc Networks. Roberto Attias, Duke Lee, Anju Puri, Starvros Tripakis, Raja Sengupta, Pravin Varaiya PATH research report, 2000. Motivation.

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Roberto Attias, Duke Lee, Anju Puri, Starvros Tripakis, Raja Sengupta, Pravin Varaiya

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  1. A Token-Ring Medium-Access-Control Protocol with Quality of Service Guarantees for Wireless Ad-hoc Networks Roberto Attias, Duke Lee, Anju Puri, Starvros Tripakis, Raja Sengupta, Pravin Varaiya PATH research report, 2000.

  2. Motivation Current (2000) wireless MAC protocols (IEEE 802.11 and Hyperlan) provide no QoS guarantees that are required by V2V applications like fairness, medium-access time.

  3. Overall design MAC Component Unique ring address One token in the ring Joining and leaving stations Reconstituting a ring in case of failure

  4. Normal operations Normal operation a node has a direct connection with it’s previous and next station in normal operation. Leaving operation When B leaves, it informs A and A will inform C

  5. Normal operations Joining operation G sends invitation A checks it connectivity to G and E A responds

  6. Abnormal operations Station moves out of range Implicit acknowledgements are used in token transmission No tokens Timer Multiple tokens Mechanism deletes all, except the highest priority token Priority is based on sequence number and ring address

  7. Abnormal operations Malformed rings A thinks the token is lost A generates a new token and transmits it to B B does not accept the token A finally understands he is out of the ring

  8. Detailed operations… The paper provides details about the FSMs, timers, packets, proof of stability, etc. … left out of this presentation

  9. Generalized protocol Simple protocols assumes a connection between previous and next station Suboptimal The generalized protocol assumes just one connection (with either the previous or next station)

  10. Implications of generalized protocol A Join invitation contains the route to the next station Implicit acknowledgement includes also transmission of routing nodes Source is informed when forwarding of the token failed at an intermediate node

  11. Wireless Token Ring Protocol Duke Lee

  12. Outline Describes the Wireless Token Ring Protocol Describes an implementation in Linux on top of CSMA/CA The performance of the implementation Covered by this presentation

  13. Performance Medium-access latency Independent of the number of transmissions Increases linearly with the number of nodes in the ring Fairness The bandwidth is almost equally divided Cause: the token-holding timer

  14. Performance Responsiveness (system of 2 nodes) Measured by token rotation time 2 ms during no transmission 18 ms during an FTP session Within delay boundaries… but no results for many nodes Scalability Token rotation time increases linearly Token rotation time variance increases linearly

  15. Comparison with IEEE802.11 The achieved bandwidth of WTRP is compared with IEEE802.11 (three nodes in the ring) WTRP achieves better performance at more simultaneous transmissions

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