[srslte-users] PLMN-Id decoding and encoding

[nauga+srsran at mailbox.org]

Hi,

currently I'm having some problems to understand the decoding of PLMN-Id 
from SIB1. PLMN contains MCC and MNC. According to Standard ETSI TS 129 
171 V14.0.0 under “7.4.27 PLMN Identity” the encoding of PLMN-Id is more 
or less swapping digits in Hexbyte and adding f, if MNC has only 2 
digits. This is clear for me.

Unclear for me is what Wireshark is displaying in its Hexbyte window, 
using a srsue .pcap file or function srsran_vec_fprint_byte() in 
pdsch_ue.c. For Germany and Provider Vodafone the PLMN-Id is: MCC=262, 
MNC=02. This is displayed in the tree view of the SIB1 package and 
should be right according to wikipedia. The encoded PLMN-Id in my 
understanding according to Standard would be something like: 62f220. But 
Wireshark is displaying 49 88 05. This difference happens also with 
other providers and other countries, e.g. 49 88 07 for MCC=262, MNC=03.

So Wireshark is displaying the right decoded PLMN-Id, but in my 
understanding different Hexbyte as to the standard.
Is someone to able to explain me these “false” Hexbytes?

Many thanks in advance.

Regards,
Dom