1. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 1 MDA Issues Date: 2008-07-15 Authors:

2. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 2 Not All 1-Hop Neighbors are Peer MP MP DTIM Beacon Interval Issues

3. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 3 Issue: Not All 1-Hop Neighbors are Peer MPs The number of one-hop neighbors that can become peer MPs is restricted by the MP’s capacity. –So some one-hop neighbors may reach each other through multi-hop paths of peer MPs (See MP1 to MP9 below). MDAOP Advertisement Request & MDAOP Advertisements action frames are not permitted to be transmitted among 1-hop neighbors which are not peer MPs. –The reason is the rule that an MP shall not transmit data/management frames other than the ones used for discovery and peer link management until the peer link has been established. Peer MPs MP2 MP3 MP1 MP4 MP5 MP6 MP7 MP8 MP9 1-hop neighbors Maximum number of peer MPs is 3.

4. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 4 Solution to Not All 1-Hop Neighbors are Peer MPs MDAOP Advertisement Request/MDAOP Advertisements action frames are defined as multi-hop action frames. When 1-hop neighbors can not become peer MPs, they use multi-hop MDAOP Advertisement Request/MDAOP Advertisements action frames to exchange TX-RX time report and interfering time report. –Shorter responding time than beacon-based information exchange. –Encrypted transmission of MDAOP Advertisement transmission. Peer MPs MP2 MP3 MP1 MP4 MP5 MP6 MP7 MP8 MP9 1-hop neighbors Maximum number of peer MPs is 3. MDAOP Advertisement frame path

5. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 5 Not All 1-Hop Neighbors are Peer MP MP DTIM Beacon Interval Issues

6. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 6 MP DTIM Beacon Interval Issue If neighbor MPs have different DTIM beacon interval, –A MP can not use the current MDAOP Advertisements element to forward its neighbor’s TX-RX time/interference time report without suffering collisions. –This also makes selection of MDAOP TXOP complicated: A MP can not reference its Neighbor MP’s MDAOP TXOP as a fixed offset with respect to its own MDAOP TXOP, because the MDAOP TXOP “slide” with respect to each other. There are two methods to solve the problem: –Method 1: an 11s mesh network has a unique DTIM beacon interval. But 11s currently does not define how to determine this value. –Method 2: in an 11s mesh network, each MP can have a different DTIM beacon interval, but MDA would use a common DTIM Beacon Interval. TDBTT Service Interval TDIM Beacon Interval Offset TDBTT Service Interval TDIM Beacon Interval Offset TDBTT Service Interval Duration Service Interval TDIM Beacon Interval TDBTT TDIM Beacon Interval Service Interval

7. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 7 Method 1: Unique Mesh Network DTIM Beacon Interval Determination The initiator MP selects the DTIM beacon interval for the mesh network. When a MP joins a mesh network, it accepts the DTIM beacon interval broadcasted in the beacon/probe response frame. When a mesh network (say mesh network A) selects to merge with another mesh network (say mesh network B), mesh network A shall use mesh network B’s DTIM beacon interval. –To maintain peer link relationship between MPs in mesh network A after the merging, mesh channel switch announcement element should include MP DTIM beacon interval of mesh network B. –If two mesh networks have different DTIM beacon intervals, MPs in mesh network A shall tear down its MDAOP TXOPs.

8. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 8 Method 2: Virtual Mesh DTIM Beacon Interval Each MP in a mesh network may use different beacon intervals. A common (mesh network virtual) DTIM beacon interval is used to select service interval, offset, duration of the reserved TXOP. Example of the mesh network virtual DTIM beacon interval includes: –The default DTIM beacon interval, –The DTIM beacon interval of mesh network initiator. Virtual DTIM beacon target transmission time and DTIM beacon interval are carried in MDA Advertisement element.

9. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 9 Method 2: Virtual Mesh DTIM Beacon Interval (Cont’d) The difference between the mesh network virtual TBTT, mesh network virtual TDBTT and MP’s TBTT, MP’s TDBTT should also be included in the “TX-RX times report” and “Interfering times report”. When a reserved service interval covers its own TBTT, the MP may extend the reserved service interval to compensate the beacon transmit time. When a reserved service interval covers its neighbor MP’s TBTT, the MP may cease its MDA transmission. When a mesh network (say mesh network A) selects to merge with another mesh network (say mesh network B), mesh network A shall use mesh network B’s virtual mesh DTIM beacon interval. –To maintain peer link relationship between MPs in mesh network A after the merging, mesh channel switch announcement element should include virtual mesh DTIM beacon interval of mesh network B. –If two mesh networks have different virtual DTIM beacon intervals, MPs in mesh network A shall tear down its MDAOP TXOPs.

10. doc.: IEEE 802.11-08/0635r2 Submission July 2008 L. Chu Etc.Slide 10 Straw Poll Do you think the problems in 11-08/635 should be solved based on the methods or the updated methods in 11-08/635? –YesNoDo not know