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Mesh Local Synchronization

Mesh Local Synchronization. Authors:. Date: 2007-07-10. Abstract. This presentation proposes a simplified mechanism to achieve localized synchronization in a mesh network. Issues in the current draft. BB issues related with CID 1117, CID 3569, CID 3570, CID 3900

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Mesh Local Synchronization

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  1. Mesh Local Synchronization Authors: Date: 2007-07-10 Zhen Xie, Atheros, et al.

  2. Abstract This presentation proposes a simplified mechanism to achieve localized synchronization in a mesh network. Zhen Xie, Atheros, et al.

  3. Issues in the current draft • BB issues related with CID 1117, CID 3569, CID 3570, CID 3900 • BB concept is not easy to extend to multihop mesh. • BB is too complex in a hidden node environment. • MPs could be outside the range of the BB and the concept of such MPs defer from sending beacon does not work. • Need clarification of how multiple BBs in a mesh coexist and converge. • CID 3567: BB presents two conflicting beacon modes • BB uses infrastructure mode • All other MPs use IBSS mode Zhen Xie, Atheros, et al.

  4. Issues in the current draft Cont. • CID 1578: There is little explanation on connectivity reports. Why they are needed and how they are used? • CID 3565, CID 3889: hidden node problems. What if an MP hears beacons with conflicting TSFs? Zhen Xie, Atheros, et al.

  5. A simplified approach • A synchronization profile can be negotiated and setup based on contribution IEEE 802.11-07/2000r0. • Setup using “Request Synchronization/Response Synchronization” unicast message exchange. • How to setup a profile is out of scope of this proposal. • A mesh network can have multiple synchronization profiles. • Synchronization profile should limit to one hop only. • MPs within the same synchronization profile synchronize with each other by beaconing in IBSS mode. Zhen Xie, Atheros, et al.

  6. Synchronization Profile • Synchronization Profile = { Profile Identifier: a 6-octet random number Mesh Beacon Interval … } • A synchronization profile is uniquely identified by the Profile Id. • An MP not belonging to any profile will have Profile Id of zero (0). Zhen Xie, Atheros, et al.

  7. Mesh Beacon Frames Mesh Beacon Frame for MPs with a sync. profile SUBTYPE MAC HEADER MGMT 00 BEACON1000 ADDR1BA ADDR2TA=SA ADDR3 TimestampTSF Fields/IEs related to Mesh Beacon ADDR3 = Profile Identifier Mesh Beacon Frame for MPs without a sync. profile SUBTYPE MAC HEADER MGMT 00 BEACON1000 ADDR1BA ADDR2TA=SA ADDR300 TimestampTSF Fields/IEs related to Mesh Beacon Zhen Xie, Atheros, et al.

  8. Beacon Generation and Synchronization • MPs with the same profile generate beacon frames according to the procedures described for IBSS operations in base standard 11.1.2.2. • A MP with a sync. profile should update its own TSF time according to the algorithms described for IBSS operations in base standard 11.1.2.4. • A MP with a sync. profile should match a received beacon frame based on Profile Id in Address 3 field with its Profile Id. • MPs with different sync. profiles generate beacon frames independent of each other. • MPs without a sync. profile generate beacon frames independent of other MPs. Zhen Xie, Atheros, et al.

  9. Beacon Generation and Synchronization Cont. • MAP will have to generate two separate beacons, one for Mesh (ADDR3 = Profile Id or 0), one for infrastructure network (ADDR3 = BSSID). • MAP without a sync. profile generates mesh beacon frames independently of other MPs. • A MAP can optionally have a sync. profile if it can maintain Mesh TSF and Infrastructure TSF at the same time. • A MP can optionally have multiple sync. profiles if it can maintain multiple Mesh TSFs at the same time. • How a MP maintains multiple TSFs is out of scope of this proposal. Zhen Xie, Atheros, et al.

  10. Example, Synchronization Profiles MP1 MP5 MP3 MP4 Profile A Profile B MP6 MP2 Non-synchronizing MAP Synchronized Link Non-synchronized Link Zhen Xie, Atheros, et al.

  11. Example, Beacon Generation Profile A Mesh Beacons of Profile A Beacon Interval A Profile B Mesh Beacons of Profile B Beacon Interval B Infrastructure Beacons of MAP Non-synchronizing MAP Mesh Beacons of MAP Infrastructure Beacon Interval Mesh Beacon Interval Infrastructure DTIM Period Zhen Xie, Atheros, et al.

  12. Summary • One or more synchronization profiles will be present in a mesh network. • MPs with synchronization profile generate beacon and synchronize in IBSS mode. • Local Synchronization: one hop only. • Addresses hidden node problems. • A simplified approach: no BB, no MBCA, no connectivity reports. • Backward compatible with many existing WLAN devices. Zhen Xie, Atheros, et al.

  13. Straw Poll • Does TGs wish authors to provide more details of this proposal, including normative text? Zhen Xie, Atheros, et al.

  14. References • doc.: IEEE 802.11-07-2000r0 Zhen Xie, Atheros, et al.

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