Mention some scenarios of when we need RACH procedure?

Question

Need use case scenarios of cut Index and Edge Flag features in Microsoft directx -11 spec, please suggest some pointer.

Answer 1

RACH can be performed in below mentioned scenarios :
1. Initial Access - UE is trying to access the network in RRC idle state.
2. During RRC connection re-establishment procedure .
3. Handover
4. When uplink synchronization is lost (means from a certain duration network has not received anything from UE in uplink.)
5. When UE does not have any PUCCH resources available for SR(Scheduling Request) .
6. When timing advance is needed for positioning purpose in RRC connected state for UE.

Comments

will you explain 5 and 6 scenarios

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Check the following link, should clarify in more detail
http://nitintayal-lte-tutorials.blogspot.in/2013/09/random-access-procedure-rach.html