[srslte-users] Trying to display the information in the Master Information Block

[Nehemiah Chan]

Hi everyone,

I am currently an intern and am tasked to demonstrate a paging sniffer for
broadcast messages.

I appreciate all the help here so far in the srsLTE mailing list, I have
done some reading in the codes. I am not proficient in understanding in
C/C++ codes. Appreciate all the help I can get here.

Goal:
1. First, which is able to display the broadcast messages when the UE is
connected to the network (I believe between the connection of the UE and
enb, do correct if I am mistaken).
2. Utilize a paging sniffer to capture broadcast messages (following the
research paper down below).

http://www.softwareradiosystems.com/pipermail/srslte-users/2016-February/000154.html
I have also referred to this issue however, I looked at line 499, where I
am supposed to find the code where it shows the message has been decoded.
For my case, at line 499, it shows the sampling frequency. For my case, the
pdsch_ue.c file is under srslte/lib/examples.

Progression: I have done the setup for srsue by configuring the USIM to the
4G network.

I am tasked with research based on a research paper:
http://homepage.divms.uiowa.edu/~comarhaider/publications/LTE-torpedo-NDSS19.pdf
where it stays at Page 10:

For capturing broadcast messages we set upa sniffer using a Universal
Software-defined Radio Peripheral device, i.e., USRP B210 [16] (costs
$1300) connected to an Intel Core i7 machine running Ubuntu 16.04 as the
hardware component and srsLTE [17], an open source LTE protocol stack
implementation. We modified the srsLTE’s pdsch_ue application to enable the
sniffer to periodically (∼10minutes)switch its decoding mode between the
master_info_block and paging channels. Thus the sniffer periodically
synchronizes the network time/frame similar to
commercial-off-the-shelf(COTS) UEs and reliably computes the SFN value for
a received paging message. We also use the sniffer to capture and decode the
sys_info_block_1andsys_info_block_2messages and learn the parameters
relevant for computing the victim UE’s paging occasion (e.g., T and nB)

I have been focusing on the pdsch_ue.c file for a while. By looking at line
732 from the pdsch_ue file, at the switch case function, about the
broadcast channel payload, I tried to find the link if I can implement the
code for decoding mode between MIB and paging channels( I can't seem to
find it.) I also looked at the rf.h/rf_utils.h files which were included in
the pdsch_ue.c file.

Any approach to this matter would be appreciated with steps given. I had
tried to reach out for the main researcher for this research paper that I
have been working on(but there's no response which is expected). I have
been stuck for quite a while. Do bear with me as my understanding in C/C++
is very basic.


Thanks in advance.

Best Regards,
Nehemiah
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