Scenarios for Admission Control Failure in RRC phase

Hi 5G SA Working Experts.

Can anyone list done Scenarios for Admission Control Failure in RRC phase?

I.e. network send RRC reject in response to RRC request

Few can be:

  1. MAX number RRC users reached on cell
  2. PUCCH limitation for CQI reporting

Need to add more, let’s have complete list.

You can add:

  • Transport network limitation
  • Baseband processing

Please tell how Transport network limitation lead to admission control failure.

And Baseband processing means some limitations in hardware? Is it correct?

As we don’t have sub unit concept in baseband like 3G days, even such failure reason not seen in 4G as well.

But I remember for 3G users have certain consumption from baseband as well in term of subunit.

For 5G only limiting factors seen number of users which depends on bandwidth, hardware type etc.

If your S1 limitation is just 1 Gbpsec and you have 6 cells of 4G and 3cells of 5G at some point new connections will nto be accepted due to TNL limitation.
Huawei has counter for this.

Baseband is board limitations, max numbers of RRc users is license limitation not hardware limitation.

Yes, but linked with bandwidth and system module type used, i.e. FPGA used.

Add one more thing:

  • Number of nGBR DRBs per cell and per CU/DU

For Huawei, suggestion is to open huawei counter list, go to RRC reject group counters.

There are list of reject cause, that mean resource involved in admission control.

TNL mean eRAB setup failure when MME give eNB one IP address of user-plane CN to setup transport path for data. But eNB fail to setup, ping to sgw IP address.

Baseband hardware also limit RRC user - some board support 3.600 users, some other support 7.200 or 14.400 user.

User number often limited by license because operator purchase license much less than hardware capacity.

I m looking for a similar thing in Ericsson for 4G to figure out the limitation in the transmission site.

Till now unable to find something accurate and meaningful.