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Improving the Performances of Distributed Coordinated Scheduling in IEEE 802.16 Mesh Networks

Improving the Performances of Distributed Coordinated Scheduling in IEEE 802.16 Mesh Networks. Published: TVT July 2008 Authors: Shie-Yuan Wang, Chih-Che Lin, Han-Wei Chu, Teng-Wei Hsu, and Ku-Han Fang. Outline. Introduction Proposed algorithms Simulation Conclusion. Introduction.

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Improving the Performances of Distributed Coordinated Scheduling in IEEE 802.16 Mesh Networks

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  1. Improving the Performances of Distributed Coordinated Scheduling in IEEE 802.16 Mesh Networks Published: TVT July 2008 Authors: Shie-Yuan Wang, Chih-Che Lin, Han-Wei Chu, Teng-Wei Hsu, and Ku-Han Fang

  2. Outline • Introduction • Proposed algorithms • Simulation • Conclusion

  3. Introduction • Standard defined • The problem of Holdoff time • Goals

  4. The defined of Holdoff time in IEEE 802.16 standard

  5. Scheduling type • IEEE 802.16 • PMP • Mesh • Centralized • Distributed • Coordinated • uncoordinated

  6. Frame structure of the IEEE 802.16 mesh mode

  7. Node’s transmission cycle

  8. Holdoff time • After a node wins a transmission opportunity, the IEEE 802.16 standard requires it to refrain from contending for another transmission opportunity in a certain number of consecutive transmission opportunities, which is called the holdoff time. 4

  9. Who wins the transmission opportunity • Each node listens to the MSH-DSCH messages advertised by its neighboring nodes. • Based on the scheduling information carried in the MSH-DSCH messages, each node knows the transmission interval of each of its neighboring nodes. • Each node knows for which transmission opportunities its neighboring nodes may contend. • Each node uses the same pseudo-random election algorithm to resolve contention of transmission opportunities.

  10. The problem of Holdoff time • When the holdoff time is set too large, network nodes will suffer from long delays in transmitting control message and thus cannot fully utilize the link bandwidth. • When the holdoff time is set too small, the number of nodes competing for a transmission opportunity will be large.

  11. Goals • Do not decrease the success rate of network initialization • Increase the efficiency of MAC-layer scheduling • Fairly share resource

  12. Proposed algorithms

  13. observation

  14. SRNI • NCSUCCESS: the number of cases in which the network succeeds in initialization • NCtotal: the number of total cases

  15. ATOUN • txnum(j): the number of transmission opportunities won by node j • total(j): the number of total transmission opportunities since node j has attached itself to the network • m: the number of nodes in a network case

  16. ATHPT • tij: the time required to establish the ith data schedule of node j • n: the number of node j’s data schedules • m: the number of nodes in a network case

  17. IICMT (1) • NumTxOppwin(i): the number of transmission opportunities that node i wins in the period • NumTxOpptotal: the total number of transmission opportunities that are available in the period • |nbr(i)|: the number of nodes in node i’s two-hop neighborhood

  18. IICMT (2) • m: the number of nodes in a network case

  19. Two-Phase Holdoff Time-Setting Scheme • Assume that, for each node, the network operator has given it the total number of nodes in its two-hop neighborhood • Initialization phase • After being powered on, each node initially stays in the network initialization phase. • Each node change to data transmission phase when its two-hop neighborhood have successfully initialized and attached them selves to the network • Set holdoff time to a large value • Data transmission phase • Set holdoff time to a small value

  20. Static approach

  21. Dynamic approach

  22. Simulation • NCTUns

  23. Chain network topology

  24. Grid network topology

  25. Random network topology

  26. Conclusion • In an IEEE 802.16 mesh network, the holdoff time value setting design is very important • The proposed algorithm guarantees the success of network initialization and improves MAC-layer scheduling performances

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