Seeking Guidance on ETWS Testing with SIB6 Implementation

[JohnWilson614]

Hello ,

I’ve been experimenting with ETWS testing by creating a SIB6 in the srsRAN project, attempting to verify if COTS UE can properly receive ETWS messages. I broadcasted SIB6 similarly to how SIB2 is broadcasted, with the following configuration:

cell_cfg:
  dl_arfcn: 157100
  band: 28                             
  channel_bandwidth_MHz: 10         
  common_scs: 15                      
  plmn: "00101"                       
  tac: 7
  pci: 1
  sib: 
    si_window_length: 20
    si_sched_info:
      - si_period: 128
        sib_mapping: 6 

Interestingly, my Samsung S24 successfully received an earthquake warning once with this setup. However, I haven’t been able to reproduce this success consistently. The warning appeared only once and hasn’t been received again in subsequent tests.

A few additional details about my setup:

1. The core network I’m using is Open5GS, which currently doesn’t seem to support ETWS functionality. As a result, I attempted to broadcast SIB6 directly from the gNB side.
2. I also considered using DCI format 1_0 with CRC scrambled by P-RNTI to indicate Short Messages, but this approach hasn’t been successful so far.
3. Below is the code snippet I used to implement SIB6 broadcasting in srsRAN:

//  apps/units/flexible_du/du_high/du_high_config_translators.cpp
static sib6_info create_sib6_info()
{
  sib6_info sib6;
  sib6.msg_id       = "0001000100000001";
  sib6.serial_num   = "010001100101000";
  sib6.warning_type = "30";
  return sib6;
}

I would greatly appreciate any insights or suggestions from the community regarding:

1. Potential reasons for the inconsistent ETWS reception.
2. Best practices for SIB6 configuration in ETWS testing, especially when broadcasting directly from the gNB.
3. Any known issues or limitations with COTS UE compatibility for ETWS.
4. Are there any references or examples for implementing ETWS in srsRAN or similar environments?

Thank you in advance for your expertise and assistance!