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!

[JelleB-2055020]

Hi, were you able to figure this out? I'm in a similar situation where I'm trying to test ETWS and running into some problems as well. Would love to hear if you had any tips for sending out SIB6's!

[JelleB-2055020]

If it is still relevant to you, I seem to have made a breakthrough and am consistently able to transmit warning messages on my gNB. I haven't seen the warning messages arrive on my srsUE, but I'm assuming they haven't implemented handling those messages just like they weren't present in srsRAN.

[JohnWilson614]

Hi there,

Yes, I’ve made some progress on this, and I’d be happy to share some insights:

1. srsUE and SIB6/7/8 Parsing:
If you want to receive SIB6/7/8 messages on srsUE, you’ll need to modify the srsRAN_4G UE code. Currently, srsUE doesn’t have the functionality to parse SIB6/7/8, nor does it trigger the logic to parse these messages. We attempted to implement this, but we found it wasn’t necessary to dive too deep since mobile phones provide a more intuitive experience. If you want to proceed with this, you could try parsing for SIB6/7/8 every time slot to see if the messages are present.

2. Transmitting SIB6 with USRP:
I’ve successfully transmitted SIB6 messages using USRP B210/N310, and devices like the Samsung S24, Motorola X50, and Redmi K60 series were able to receive earthquake warnings. However, the results aren’t consistently reproducible. We suspect this is largely related to the serial_num. Mobile manufacturers likely record this value when processing messages, and updating the serial_num seems to significantly improve success rates (there appears to be a specific range for serial_num that works better).

3. Failed Scenarios:
In cases where the transmission fails, it’s often because the phone receives the SIB6 message but doesn’t trigger the parsing logic. This seems to be related to 5G DCI (Downlink Control Information), which might not be correctly configured or interpreted by the device.
Hope this helps! Let me know if you have any further questions or if you’d like to discuss this in more detail.

[JelleB-2055020]

Hi, thanks for your thoughts. I appreciate that.

Good to know that the UE really has to be modified to support them, I think I can safely assume my messages are being transmitted then given that you also noticed the UE wouldn't parse them.

As for transmission issues, I personally noticed that SIB6 messages weren't being transmitted with the parameters you supplied above because they got 'overruled' by the SIB1 messages. In the srsRAN implementation, they only allow for one SIB message per slot, and the SIB1 message took this slot away from the SIB6 message in my case, leading to it never being transmitted. Altering your configuration above to the one below (increasing the frequency with which the SIB6 gets sent), I saw greater success:

sib: 
    si_window_length: 20
    si_sched_info:
      - si_period: 8
        sib_mapping: 6 

In any case, I really appreciate your thoughts on this and I'll be sure to respond to this thread again if something comes to mind!

[isAlexisUpc]

Hello all,

I am trying to replicate what you did but my OnePlus 12 is not receiving the alert. Have you modified any other file?
Thanks in advance!

[JelleB-2055020]

Hey there, even though I'm not the original poster I thought I could jump in as well. Yes, I am able to receive alerts on a OnePlus 9 device. There's multiple files you need to change. The code shown above in the original post is just one little piece of the puzzle. Depending on how soon you need this information, I could try to find the changes I made to get this working, but that'll be a while before I'm able to do that.

What I can tell you off of memory right now is that you need to find most of the code that handles SIB's and tinker with that to include SIB6. What helped for me as well was increasing the frequency with which the messages were sent (see my post above).

[isAlexisUpc]

Hello @JelleB-2055020 , thanks for your quick response!
Yes, I was debugging and I saw that I had to modify quite a few things.... As soon as you can find the changes you made I would really appreciate your help.
I will keep working with the info you have given :)
Thanks again :)