[srsran-users] New functionality implementation

[Patrycja Palus (TME)]

•• PROTECTED 関係者外秘

Hello,

I hope you are doing well.
Currently, together with SDR,  I use SRSran 4G project (eNB and EPC) for testing purposes. Recently I wanted to test attachment reject procedures, but I discovered that this functionality is not implemented, although I found attach reject messages (LIBLTE_MME_ATTACH_REJECT_MSG_STRUCT). So far, I'm interested in specific attachment reject reason, which is cause #12 (tracking area not allowed).  I have idea how it could be implemented, but before I start, I would be grateful for the feedback of my idea:


Functional requirements:​

  *
Function must be enabled from terminal with following command:​
srsepc mme.attach_rej_cause12 = {True, False}

Non-functional requirements:​

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​When epc.mme.attach_rej_cause12 = False, network always returns Attach Reject message with emm_cause=12​

​Implementation idea

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epc.conf file must be updated in section [mme] by adding attach_rej_cause12 and setting it to False by default.​
  *
SRSran doesn’t handle attach reject procedure although reject message is implemented. nas.h and nas.cc shall be updated with procedure send_attach_reject containing message LIBLTE_MME_ATTACH_REJECT_MSG_STRUCT.

The function I want to implement is simple: if srsepc is started with parameter mme.attach_rej_cause12=True, any user, who will try to attach will be rejected with cause #12. At this point I don't want to implement the whole algorithm making decision that user has to be rejected as I'm interested in seeing UE's behaviour in case of receiving this specific error.

I'd like to ask if these requirements are enough to start implementation or I missed something important? I ask also for understanding since I'm not a professional C++ developer, so I may miss some basic procedures 🙂

Br,
Patrycja

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