Does RRC_conn_setup contains any grant for the UE to send RRC_conn_setup_complete?

Specs & Protocol Testing
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1

Hi Experts, one question.
Does RRC_conn_setup contains any grant for the UE to send RRC_conn_setup_complete or eNB indicate in PDCCH explicitly?

2

Generally grants comes into picture from lower layer point of you i.e, physical layer so any uplink or downlink data grants will be received via pdcch.
To send RRC connection complete UE should get uplink grants from eNodeB.
Via pdcch.

3

Rrc connection setup contain scheduling request config IE.

4

Thanks @vinod_081. That was my question.
So PDCCH will carry grant to send Msg5?

5

UE need to send SR request to access ul grants.

image
image639Ă—625 76.2 KB

Similarly BSR field is part of RRC connection setup.

1 Like
6

Normally UE sends SR but some implementations include prescheduling features to speed up call setup

7

If you’re talking in terms of Msg 4 and Msg 5. RRC connection setup is also called MSG4 which includes CRI ( Contention resolution identity) which contains Msg3 itself.
Before this eNB send DCI-0 which asks UE to send data in UL, using that DCI0 info UE will send Msg5 which is setup complete message.

8

I just checked the message contents and yes eNB sends SR info.

9

UE sends SR request but only when UE is in connected state.

10

What I meant is Scheduling Request Config.

11

At that time you won’t be talking in terms MSG1,2,3,4,5 Since these no. are MAC layer representation’s.

12

OK.

This are the contents of RRC conn setup:

image

13

Can you send the link of image, something weird here which needs to be figured out.
You might have read RAR header, is it?

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As per picture in step 2, eNB sending Timing advanced command.
Since it talked about prach that means its 11 bit TA which comes inside RAR header.
If yes, then RAR header itself contains 20 bit UL-Grant for UE.
So, if eNB already sending UL grant Info to UE packed inside RAR message over pdsch then why would UE send SR request?

16

Correct me if I am wrong, since new to LTE.
That 20Bit UL -grant which eNB sent to UE is for sending RRC_Conn_request msg, right?

17

Yes, that’s right.

18

So, similary when UE wants to sends RRC_conn_setup_complete does eNB sends UL grant in RRC_conn_setup?
And in RRC_Conn_setup message content i saw SR IE.
So i think UE will send SR to get grant.
This is my assumption.

19
  1. The MSG 4 does not contain any grant for MSG 5 (RRC Connecion Set UP Complete)
  2. The UE sends SR to ask for UL Grant to send MSG 5. The eNB sends DCI Format 0 (on PDCCH) to indicate UL Grant on PDSCH.
20

Yes, PUCCH UCI SR sent by UE to get UL grant from eNB.