LTE Initial Attach with Call flow and messages

Here comes the big one: The LTE Initial Attach 
messages messages everywhere...




LTE initial Attach









Message Box in Blue Color: NAS messages
Message Box in Red Color: P-GW and PCRF interaction

Looks like the image is not clear enough. The solution is to click on the image and then zoom in. thought of mentioning the workaround :-)

The call flow is self explanatory. This procedure also gives the default bearer setup during the Initial Attach procedure. Bearers will be covered in a separate post.

14 comments:

  1. Can't read it.
    Picture is not clear.
    Thanks.

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    Replies
    1. I have mentioned the workaround. Click and Zoom in

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  2. Excellent knowledge sharing...a goog introduction to LTE.

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  3. Excellent callflow diag to get a birds-eye view of the basics!

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  4. Hello Arjit,

    Good work! Very usefull to undestand overall LTE callflow.

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  5. Really it's very clear and easy to understand.

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  6. Really it's very clear and easy to understand.

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  7. Hi Arijit,
    Just wondering how S1-Setup can start before RRC Connection Request and I hope it is not Mobile Terminated type scenario.

    Seems some kinda message alignment issue.

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    1. S1-Setup has nothing to do with RRCconnReq. S1-Setup is the link between eNB and MME.
      It is MO-Signalling as the Title suggests -Initial Attach-.

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  8. Hi Arjit,

    Could you please describe NAS....

    Regards,
    Sangit Kumar

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    1. Hello Sangit, this is a very open ended query.

      See, for couple of scenarios; there is need for EPC to talk to the UE directly. But in between the UE and EPC, eNB exists. Hence, for directly talking to each other NAS is used. eNB doesn't care for these kind of messages and simple acts as a relay agent.
      Hope this is what you were looking for!

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  9. Excellent way of presenting .. Good for begineers in this domain .. can u suggest me some books for learning LTE ? Easy language book

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