VoLTE data & PS data to UE in same TTI

RAN
1

Hi All,
If UE has VoLTE traffic and PS data transmission at the same time, is it possible to sent both VoLTE data & PS data to UE in same TTI?

2

Scheduling only done in TTI.
Data sent in TBS.
So same user can be scheduled.

3

But how will UE know in 1 TTI, which RB is for VoLTE and which for PS?

4

Different RB allocated as per demand for PS and VoLTE, as modulation scheme and data per RE will be different.

5

DCI for VoLTE & PS is same or not?

6

DCI format will be same for DL and UL but MCS, TBS vary.
VoLTE required min 3 PRB.
But unfortunately Nokia don’t have counters showing PRB consumed by VoLTE users.

7

Huawei has PRB of VoIP.

I never heard that. Is it dynamic scheduling or semi-persistent?

DCI format for VoLTE is same DCI format for PS, in both UL and DL, right?

8

Yes, right.

9

But how UE can know which RB is for VoLTE, which RB is for PS?

10

This is separated at higher layers in UE.

11

By QCI?
RLC layer?

12

At the app layer inside UE.

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13

Yes, correct :+1:

14

For e.g. in same TTI, eNB sent PS data through RB 1-10, VoLTE data through RB 11-15.
How does UE know?

15

UE don’t need to know this.
It is analyzed at higher layers not at MAC or PHY.
In DCI there is only one MCS.
TBS, etc.
UE knows he has to receive data on RBs from 1 to 15.
And that is all.

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16

When TTI bundling is enabled, the modulation scheme must be QPSK but the resource allocation size is no longer limited to three PRBs.
“Modulation order and redundancy version determination” in 3GPP TS 36.213 of Release 10, when TTI bundling is enabled, the modulation scheme must be QPSK and the resource allocation size is restricted to a maximum of three PRBs.
In accordance with 3GPP TS 36.213 CR0463 of Release 12, when TTI bundling is enabled, the modulation scheme must be QPSK but the resource allocation size is no longer limited to three PRBs.
If TTI bundling enabled, in R10, RB <= 3.
In R12, not limit.

17

TDD has a disadvantage as TTI bundling cannot be used in all UL DL configuration.
In VoLTE.

18

I think TTI bundling is just a technique in UL.

19

Yes, due to limitation of UL configuration in TDD.

20

Huawei still has feature TTI bundling for TDD.