Does UE need to carry out RACH process again after RLF?

Specs & Protocol Testing
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1

Dear Experts.
In LTE after RLF UE need to carry out RACH process again for RRC connection re-establishment?

2

Yes it’s after t310 expiry and need to make sure it’s contention free happening.
If it sync in during t310 then no need for reestablishment.

3

Thanks. But contention free RACH process is during HO only and other than that it will be contention based RACH that is during rrc re-establishment during. Non HO scenario.

4

In Huawei there is switch for unsync ra which behaves as Contention free, this needs to be enabled.
Or else it works as contention based.
For initials access contention based is a must for remaining we have options.
After DRB sync out you can have contention free.
But not during SRB.

5

So in case of contention free RACH after DRB sync out UE uses dedicated preamble or preamble from groupA/B.

6

If enabled.

7

What is the name of the switch?
If this switch is enabled, how the preamble is allocated to the UE after RLF?
I mean in which message?

8

Unsync ra switch.
And ho ra switch.
In cell also switch command.
After Ho ra switch.
Both needs to be ON.

9

Ok. But how preamble is delivered to the UE after RLF?

10

eNodeB instruct UE contention-based / non-contention-based according to these parameters:

  • HoRaSwitch: indicates wheter the random access mode is applied during handovers.

  • UnsyncRaSwitch: indicates wheter the random access mode is applied when UEs are out of synchronization in the uplink.