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With the GateHouse UMTS Non-Access Stratum (UMTS NAS), you will be well underway building your own mobile device protocol stack. Focus on developing your Access Stratum and rely on a proven NAS from GateHouse. Get in touch to learn more The Non Access Stratum is a functional layer running between the UE (User Equipment) and the CN (Core Network). The layer supports traffic and signalling messages between the CN and UE (User Equipment). If you enjoy using our glossary, here are some other useful resources you might like... Get your weekly dose of telecoms terminology delivered straight to your inbox! We promise, no spam - just clear-cut telecoms terms to keep you on top of your game. Our YouTube channel offers over a hundred free videos (and counting!) covering a range of technology topics. Subscribe to our channel to be the first to know when we release new videos: Use this no-obligation free trial to get a taste of what it's like to be an Mpirical student. Included with the trial is an all-access pass to the LearningZone, which contains learning tools and other useful resources to help you make the most of your training.
Author: Frédéric Firmin, 3GPP MCC This article gives an overview of the Non-Access Stratum (NAS) and its protocols EMM and ESM. The Non-Access Stratum is a set of protocols in the Evolved Packet System. The NAS is used to convey non-radio signalling between the User Equipment (UE) and the Mobility Management Entity (MME) for an LTE/E-UTRAN access. NAS From a protocol stack perspective, the NAS is the highest stratum of the control plane, as shown in figure 1. The NAS procedures are grouped in two categories:
EPS Mobility ManagementThe EPS Mobility Management protocol refers to procedures related to mobility over an E-UTRAN access, authentication and security. It is the equivalent in EPS of MM in GSM and GMM in GPRS. 3GPP specifications make distinction between EMM common, specific and connection management procedures: EMM common procedures EMM common procedures refer to various network-initiated mechanisms.
EMM specific procedures EMM specific procedures are UE-initiated. These procedures define attach/detach (to/from the EPC) mechanisms. They also introduce the Tracking Area Update (TAU) mechanism, which update the location of the UE within the network. Tracking Area is the equivalent in EPS of Location Area in GSM and Routing Area in GPRS. In EPS, a UE initiates a Tracking Area Update when it detects that it enters into a new Tracking Area. EMM specific procedures also define periodic Tracking Area Update. EPS also introduces the concept of Tracking Area List (TAL), which allows the provision of lists of Tracking Areas in UEs. A UE does not need to initiate a TAU if it enters a Tracking Area which is included in its TAL. Provisioning different lists to the UEs within the network avoid signalling peaks for instance when all UEs on a train cross a TA border. EMM connection management procedures: (also known as ECM: “EPS Connection Management“) EMM connection management procedures provide several functions to support the connection of the UE to the network (see ESM procedures below):
EPS Session ManagementThe EPS Session Management protocol offers support to the establishment and handling of user data in the NAS. In EPS, two concepts are introduced to define the IP connectivity between a UE and a packet data network (PDN):
As shown in figure 3, a PDN connection is composed of a default EPS bearer and possibly additional ones called "dedicated bearers". A default bearer is created upon establishment of a PDN connection. If a service (e.g. video streaming) requires specific handling in terms of quality of service (QoS), dedicated bearers can be established. Within a PDN connection, all EPS bearers share a same UE IP address and an APN. EPS supports multiple simultaneous PDN connections. For instance, a UE can have a PDN connection to the Internet (with just a default EPS bearer) and one to the operator’s IMS (with additional dedicated bearers, if required by the service). ESM procedures are grouped into two categories:
Further reading:General: The 3GPP website contains all 3GPP specifications. They can be downloaded for free at www.3gpp.org/specifications Descriptions of all 3GPP releases can be found at ftp://ftp.3gpp.org/Information/WORK_PLAN/Description_Releases/ An overview of the EPC can be found at: http://www.3gpp.org/The-Evolved-Packet-Core NAS: 3GPP TS 23.401 defines the architecture of the EPC for an LTE access This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)
This article needs additional citations for verification. (November 2011) This article provides insufficient context for those unfamiliar with the subject. (October 2009) This article may be too technical for most readers to understand. (June 2013) Non-access stratum (NAS) is a functional layer in the NR, LTE, UMTS and GSM wireless telecom protocol stacks between the core network and user equipment.[1]
This layer is used to manage the establishment of communication sessions and for maintaining continuous communications with the user equipment as it moves. The NAS is defined in contrast to the Access Stratum which is responsible for carrying information over the wireless portion of the network.
A further description of NAS is that it is a protocol for messages passed between the User Equipment, also known as mobiles, and Core Nodes (e.g. Mobile Switching Center, Serving GPRS Support Node, or Mobility Management Entity) that is passed transparently through the radio network. Examples of NAS messages include Update or Attach messages, Authentication Messages, Service Requests and so forth. Once the User Equipment (UE) establishes a radio connection, the UE uses the radio connection to communicate with the core nodes to coordinate service. The distinction is that the Access Stratum is for dialogue explicitly between the mobile equipment and the radio network and the NAS is for dialogue between the mobile equipment and core network nodes.
For LTE, the Technical Specification for NAS is 3GPP TS 24.301. For NR, the Technical Specification for NAS is TS 24.501.
The following functions exist in the non-access stratum:
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What is non access stratum
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