1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-06-0xxx-00-0000
Title: Handover flow diagram for abnormal handover case
Date Submitted: December 19, 2006
Presented at IEEE session in London, UK
Authors or Source(s): Junxiang Guo, Yan Peng, Bin Xia
Abstract: This contribution proposes handover flow diagram for abnormal handover case.

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3. Background
In current draft, MN can discover and obtain information of a list of neighbor PoAs, so when handover decision is made MN can have multiple choices of target PoAs, but the current draft does not allow the user to initiate a second handover after an initial handover failed, e.g. when MIH_ Net_HO _Candidate_Query Reponse, or MIH_MN_HO_Candidate _Commit Response is received by MN or serving PoS and they include parameters indicating handover failure, then the handover process will be ceased finally, this does not allow the MN or serving PoS to perform handover to another suitable candidate neighbor PoA. So it does not fully make use of the result of PoA discovery and scanning. Current handover procedure is unefficient and will cause higher handover failure ratio.

4. Proposal
Here we suggest three flow diagrams for two types of handover failure case:
MIH_ Net_HO_Candidate_Query Reponse:
HandoverAck=0: Abort Handover
MIH_MN_HO_Candidate_Commit Response: HandoverStatus=0: Abort Handover

5. Proposal-Handover failure case 1
MIH_ Net_HO_Candidate_Query Reponse:
HandoverAck=0, Abort Handover
For this case MN will initiate another handover process to another suitable target PoA.
The following is the handover flow diagram:

6. Proposal-Handover failure case 1

7. Proposal-Handover failure case 2
MIH_MN_HO_Candidate_Commit Response:
HandoverAck=0, Abort Handover
For this case MN will initiate another handover process to another suitable target PoA
The following is the handover flow diagram:

8. Proposal-Handover failure case 2

9. Proposal-Handover failure case 2
(Continued)

10. Proposal-Handover failure case 2- optimized
MIH_MN_HO_Candidate_Commit Response: HandoverAck=0, Abort Handover
For this case MN will issue MIH_MN_HO_Candidate_Commit to another suitable target PoA, i.e. MN reuses the previous Initiate process result and needs not initiate another handover process again.
The following is the handover flow diagram:

11. Proposal-Handover failure case 2- optimized

12. Proposal-Handover failure case 2- optimized

13. Thank you!