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What is the difference between Forward handover, Incoming successful handover ?

+7 votes
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As handover is having different types so what is the difference and relation between Successful handover , forward handover and incoming successful handover .... Is forward handover decisions behave same as successful handover

posted Nov 19, 2013 by Sachidananda Sahu

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1 Answer

+3 votes
 
Best answer

Actually handover required only at the cell edges since UE experiences lower RSRP value for source and better for target eNodeB. Based of couple of scenarios handover types are defined.
1. Backward handover.
2. RLF handover
3. NAS Recovery
4. Forward handover.

  1. Backward handover is normal handover, in which source eNodeB start handover and target eNodeB allocated required resources for handover. In normal call flow of handover, handover command message is prepared by target eNodeB and send by source eNodeB to UE.

  2. When UE is not able to decode Handover command due to poor channel conditions. RLF happen and UE latch on target as part of RRC Connection -Restablishment .

  3. Due to extremely poor channel condition, eNodeB could not decode measurement report which is sent by UE. In that situation, even eNodeB doesn't aware that UE is experiencing poor channel condition and after some time UE lost the connection with source eNodeB and send Re-establishment . Since target eNodeB is not prepared (it means target eNodeB doesn't have valid Ue context) , eNodeB will send RRC re- establishment reject to UE. Then UE initiates attach procedure at target eNodeB.

  4. UE sends measure report to source eNodeB. target has been prepared with resource and immediately UE lost the radio and latch on target eNodeB via Re-establishment. Since target eNodeB has been already prepared the context then target eNodeB will accept Re-establishment.

answer Nov 19, 2013 by Vimal Kumar Mishra
Ok thanks for the overall description,
But in case of Backward handover UE Context release has to be sent by New ENB to Old,Like that in Forward  handover whether we should send that ???

Whether Forward handover is always successful handover like backward handover ???
commented Nov 20, 2013 by Sachidananda Sahu
Vimal can u reply for this context ???
commented Nov 20, 2013 by Sachidananda Sahu
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