fixeria submitted this change.
library/GSM_Types: fix encoding of BcdMccMnc (3 octets)
In [1] I copied the hexstring concatenation statement for the 3-digit
MNC from the original function f_enc_BcdMccMnc(), which was renamed
to f_enc_BcdMccMnc_int(). Unfortunately, this statement (originally
introduced in commit [2]) is incorrect.
In our implementation a pair of MCC and MNC is encoded as follows:
| MCC digit 1 | MCC digit 2 | octet 1
| MNC digit 3 | MCC digit 3 | octet 2
| MNC digit 1 | MNC digit 2 | octet 3
Additionally, in the case of a 2-digit MNC, the original variant
of f_enc_BcdMccMnc() (before [1]) would swap MCC and MCC in the
2nd octet, generating even more unpredictable results.
According to 3GPP TS 24.008, Figure 10.5.13, the correct coding is:
| MCC digit 2 | MCC digit 1 | octet 1
| MNC digit 3 | MCC digit 3 | octet 2
| MNC digit 2 | MNC digit 1 | octet 3
So far the only user of this API is the PCU_Tests module. Looking
at the PCAPs of testcases invoking this function, Wireshark indeed
shows weird MCC/MNC values (expected 262/42):
Routing area identification: 23-43-423-2
Mobile Country Code (MCC): Unknown (23)
Mobile Network Code (MNC): Unknown (43)
Location Area Code (LAC): 0x01a7 (423)
Routing Area Code (RAC): 0x02 (2)
Change-Id: Ifa3083fdd6307b56baa1ef3ac85a3e7a2efab728
Related: [1] 7a92d5fbc008ba7c3085fe1b524424a32da3a49f
Fixes: [2] 0637ba072820a370ed539ab0e23f8ded8bce6d16
---
M library/GSM_Types.ttcn
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/library/GSM_Types.ttcn b/library/GSM_Types.ttcn
index 07da576..134edbd 100644
--- a/library/GSM_Types.ttcn
+++ b/library/GSM_Types.ttcn
@@ -440,7 +440,11 @@
if (lengthof(mnc) == 2) {
mnc := mnc[0] & mnc[1] & 'F'H;
}
- return mcc[0] & mcc[1] & mnc[2] & mcc[2] & mnc[0] & mnc[1];
+ /* 3GPP TS 24.008, Figure 10.5.13
+ * | MCC digit 2 | MCC digit 1 | octet 1
+ * | MNC digit 3 | MCC digit 3 | octet 2
+ * | MNC digit 2 | MNC digit 1 | octet 3 */
+ return mcc[1] & mcc[0] & mnc[2] & mcc[2] & mnc[1] & mnc[0];
}
/* Compute BcdMccMnc from integer values */
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