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How many times UE can send rach when ue try to sync at target enb during HO

+3 votes
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Suppose UE have mobility parameters for intra LTE HO . UE try to sync with target eNB to confirm HO completion. So UE performs rach with target eNB. Suppose rach is not getting successful then how many time UE will perform rach at target eNB .

posted Dec 22, 2015 by Veer Pal Singh Yadav

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1 Answer

+2 votes

Hi,
If Both ENBs are in sync over the GPS or any other resources then UE will successfully perform rach to the target cell using dedicated preamble received in mobility control info.
But question is maximum how many times UE will do rach to the target cell nothing but how many times UE will do preamble transmission, it depends on the IE preambleTransMax present in RACH-ConfigCommon as a part of MobilityControlInfo.
So UE initially will try with preambleInitialReceivedTargetPower if it fails to receive RAR(MSG2) then UE will try again with power = preambleInitialReceivedTargetPower + delta_preamble + (preamble_trans_counter - 1) * PowerRampingStep.
where,
delta_preamble based on preamble format (0 for 0 preamble format)and
0 < preamble_trans_counter <= preambleTransMax
These all parameters will be present in RACH-ConfigCommon in SIB2 and mobilitycontrolinfo

answer Mar 20, 2016 by Ashish Barapatre
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