Nokia LTE2026 Information and Past Experiences

4G LTE
1

Hello, Nokia Gurus.

I`ve performed a trial with LTE2026: RRC Signaling Robustness - Downlink and got some good, but unexpected results. Your inputs and previous experiences are welcome!

The feature itself states that it can increase the SRB1 reliability by offering some configurable link adaptation offsets, which, in practical terms will increase or reduce the PDCCH aggregation level for SRB1. DL SRB1 traffic is about 0.1% of total DL traffic, as reference in this NW.

Based on NIB, this feature should keep at minimum the impact legacy Link Adaptation algorithms for PDCCH or PDSCH.

What I`m seeing and it is expected:

  1. reduction on SRB1 BLER (2 p.p.)
  2. increase on the average PDCCH aggregation level (2.5%).

What I`m seeing and it is NOT expected, especially in the magnitude of the change (remember, SRB1 traffic is 0.1).
A) reduction on the PDCCH control area size (9%).
b) reduction on the amount of samples with PDCCH using 3 symbols, the maximum (24%)

Sounds like in practice, the feature is impacting PDCCH link adaptation more than initially stated on NIB.

All feedback is appreciated, thanks!

2

PDCCH CFI MODE 5 (on 3 symbols) reduced, check how the number of CCE utilization, has it increased? This increase in SRB could be to more resource utilization to strengthen weak RL in bad RF or RL in high UL interference

3

Hi, Tammam.

Yes, there is increase on AGG Level, PRB Utilization for SRB but in a marginal value, as expected since the feature should work only for SRB1.

What is strange and unexpected is the overall impact in PDCCH control area, even with SRB1 being 0.1% of the total DL traffic.

4

Hi Marcengo,

We did the trial 3 years ago and didn’t get results we expected.

We tried with 2 different values:
Cqi Offset =-2 --> there was no impact on KPIs
Cqi Offset =-4 --> a little improvements of E-RAB Setup Success Ratio for about 0.1% and Mean E-Rab stp time for about 1ms

BR

5

Hi, Spale!

Very odd, right? I couldn’t see the gains claimed in NIB as well, only E-RAB SSR as you mentioned, but in a small value, almost neglectable.

Here, we trialed -2, -5 and -8, the results are related to -8.