Monday, October 12, 2009

NAS: Non-Access Stratum

This post is to give short description of NAS protocols, procedures and functions.
NAS is a layer for communication between Ue and Core Network (CN). This communication is transparent for underlaying Access Stratum.
NAS protocols:
  • GMM - GPRS Mobility Management
  • MM - Mobility Management
  • SM - Session Management
  • CC - Call Control
  • SS - Supplementary Services
  • SMS - Short Message Services
SM, SMS, SS and CC form a group of protocols called Connection Management.

Figure - Inter protocols communication MS side [3GPP 24.007]

SM - its functions is to activate, deactivate or modify PDP contexts which are sessions for PS traffic in UMTS/GPRS networks

Figure 1 - Simplified PDP context activation procedure

Figure 2 - Inter protocol communication for PDP context activation - MS side

CC - its functions is to establish, maintain and finally release CS calls in UMTS/GPRS/GSM networks

Figure 3- Simplified CS call proceeding

Figure 4 - Inter protocol communication for CS call setup


  1. Hey there!

    Interesting blog. I will add this blog to my blog roll. It would be nice discussing with you.

    Thanks, Santosh

  2. Hi Santosh,

    Thanks for Your opinion. I really appreciate.

    It would be really nice discussing with you since I would like to start LTE posts really soon.

    Thanks, Regards

  3. Any good books on this ? Handset side and not network side.

  4. Can anybudy tell me, What is NAS Procedure??

  5. Hi, is the non access stratum same as Iu in GSM/UTRAN?

    1. Hi. In general NAS procedures are quite similar for Iu and A/Gb interfaces. There are procedures dedicated for Iu interface - for instance GMM Service Request.

    2. This comment has been removed by the author.

  6. Hi...would you help me how NAS in UE communicate with NAS in core network even though there is no NAS in RNC.

  7. In UMTS there are dedicated RRC and RANAP messages to carry NAS signalling from UE to CN (and the other way around). RNC acts as relay node in this case and just takes NAS message from RRC and puts it into RANAP message.

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