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34-591: SAE is the evolution of the GPRS Core Network , but with a simplified architecture; an all-IP Network (AIPN); support for higher throughput and lower latency radio access networks (RANs); and support for, and mobility between, multiple heterogeneous access networks, including E-UTRA ( LTE and LTE Advanced air interface), and 3GPP legacy systems (for example GERAN or UTRAN , air interfaces of GPRS and UMTS respectively), but also non-3GPP systems (for example Wi-Fi , WiMAX or CDMA2000 ). The SAE has

68-470: A "ready-to-use" IP connectivity and an "always-on" experience by linking between mobility management and session management procedures during the UE attach procedure. Complete NAS transactions consist of specific sequences of elementary procedures with EPS Mobility Management (EMM) and EPS Session Management (ESM) protocols. The EPS (Evolved Packet System) Mobility Management (EMM) protocol provides procedures for

102-468: A default EPS bearer context. The EPS session management messages for the default EPS bearer context activation are transmitted in an information element in the EPS mobility management messages. The UE and network complete the combined default EPS bearer context activation procedure and the attach procedure before the dedicated EPS bearer context activation procedure is completed. The success of the attach procedure

136-659: A flat, all-IP architecture with separation of control plane and user plane traffic. The main component of the SAE architecture is the Evolved Packet Core ( EPC ), also known as SAE Core . The EPC will serve as the equivalent of GPRS networks (via the Mobility Management Entity , Serving Gateway and PDN Gateway subcomponents). The subcomponents of the EPC are: The MME is the key control-node for

170-562: A mobile wants to use GPRS, it must first attach and then activate a PDP context . This allocates a PDP context data structure in the SGSN that the subscriber is currently visiting and the GGSN serving the subscriber's access point. The data recorded includes Within the GPRS core network standards, there are a number of interfaces and reference points (logical points of connection that probably share

204-465: Is activated when the UE requests a connection to a PDN. The first default EPS bearer context, is activated during the EPS attach procedure. Additionally, the network can activate one or several dedicated EPS bearer contexts in parallel. Generally, ESM procedures can be performed only if an EMM context has been established between the UE and the MME, and the secure exchange of NAS messages has been initiated by

238-463: Is based on pre-Rel-4 Home Location Register (HLR) and Authentication Center (AuC). The ANDSF provides information to the UE about connectivity to 3GPP and non-3GPP access networks (such as Wi-Fi). The purpose of the ANDSF is to assist the UE to discover the access networks in their vicinity and to provide rules (policies) to prioritize and manage connections to these networks. The main function of

272-533: Is dependent on the success of the default EPS bearer context activation procedure. If the attach procedure fails, then the ESM session management procedures also fails. The EPS Session Management (ESM) protocol provides procedures for the handling of EPS bearer contexts. Together with the bearer control provided by the Access Stratum , it provides the control of user plane bearers. The transmission of ESM messages

306-441: Is suspended during EMM procedures except for the attach procedure. EPS Bearer: Each EPS bearer context represents an EPS bearer between the UE and a PDN. EPS bearer contexts can remain activated even if the radio and S1 bearers constituting the corresponding EPS bearers between UE and MME are temporarily released. An EPS bearer context can be either a default bearer context or a dedicated bearer context. A default EPS bearer context

340-685: Is the central part of the general packet radio service (GPRS) which allows 2G , 3G and WCDMA mobile networks to transmit Internet Protocol (IP) packets to external networks such as the Internet . The GPRS system is an integrated part of the GSM network switching subsystem . The network provides mobility management , session management and transport for IP packet services in GSM and WCDMA networks. The core network also provides support for other functions such as billing and lawful interception . It

374-520: Is the protocol which allows end users of a GSM or WCDMA network to move from place to place while continuing to connect to the Internet as if from one location at the Gateway GPRS support node (GGSN) . It does this by carrying the subscriber's data from the subscriber's current serving GPRS support node (SGSN) to the GGSN which is handling the subscriber's session. Three forms of GTP are used by

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408-515: The Home Subscriber Server ). The Non Access Stratum (NAS) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to UEs. It checks the authorization of the UE to camp on the service provider's Public Land Mobile Network (PLMN) and enforces UE roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles

442-589: The UTRAN through the Iu interface. A SGSN is responsible for the delivery of data packets from and to the mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN stores location information (e.g., current cell, current VLR ) and user profiles (e.g., IMSI , address(es) used in

476-444: The protocol data units (PDUs) to the SGSN that services a particular mobile station (MS). The GGSN converts the GPRS packets coming from the SGSN into the appropriate packet data protocol (PDP) format (e.g., IP or X.25) and sends them out on the corresponding packet data network. In the other direction, PDP addresses of incoming data packets are converted to the GSM address of the destination user. The readdressed packets are sent to

510-633: The ECM-IDLE, ECM CONNECTED and EMM-DEREGISTERED states. The MME protocol stack consists of: MME supports the S1 interface with eNodeB. The integrated S1 MME interface stack consists of IP , SCTP , S1AP. MME supports S11 interface with Serving Gateway. The integrated S11 interface stack consists of IP , UDP , eGTP-C . The SGW consists of SGW supports S11 interface with MME and S5/S8 interface with PGW. The integrated control plane stack for these interfaces consists of IP , UDP , eGTP-C . SGW supports

544-621: The GGSN functionality moves to SAE gateway (with SGSN functionality working in MME ). The Serving GPRS Support Node (SGSN) is the node that is serving the MS / UE . The SGSN supports GPRS and/or UMTS . The SGSN keeps track of the location of an individual MS / UE and performs security functions and access control. The SGSN is connected to the GERAN base station system through the Gb or Iu interface and/or to

578-547: The GPRS core network. A GSN is a network node that supports the use of GPRS in the GSM core network. All GSNs should have a Gn interface and support the GPRS tunneling protocol. There are two key variants of the GSN, namely gateway GPRS support node and serving GPRS support node. The gateway GPRS support node (GGSN) is one of two components of the GPRS PS domain. The GGSN together with the SGSN handle packet transmissions between

612-411: The GPRS network and external packet-switched networks , such as the Internet or an X.25 network. From an external network's point of view, the GGSN is a router to a "sub-network", because the GGSN ‘hides’ the GPRS infrastructure from the external network. When the GGSN receives data addressed to a specific user, it checks if the user is active. If it is, the GGSN forwards the data to the SGSN serving

646-447: The IP address of the GGSN which should serve the access point. At this point a PDP context can be activated. The packet data protocol (PDP; e.g., IP, X.25, FrameRelay) context is a data structure present on both the serving GPRS support node (SGSN) and the gateway GPRS support node (GGSN) which contains the subscriber's session information when the subscriber has an active session. When

680-716: The IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception. The Packet Data Network Gateway (PDN Gateway, also PGW) provides connectivity from the User Equipment (UE) to external packet data networks (PDNs) by being its point of exit and entry of traffic. A piece of User Equipment may have simultaneous connectivity with more than one Packet Data Network Gateway for accessing multiple packet data networks. The PDN Gateway performs policy enforcement, packet filtering for each user, charging support, lawful interception and packet screening. Another key role of

714-542: The LTE access-network. It is responsible for idle mode User Equipment (UE) paging and tagging procedure including retransmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the Serving Gateway for a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN) node relocation. It is responsible for authenticating the user (by interacting with

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748-590: The MME by use of the EMM procedures. Once the UE is successfully attached, the UE can request the MME to set up connections to additional PDNs. For each additional connection, the MME activates a separate default EPS bearer context. A default EPS bearer context remains activated throughout the lifetime of the connection to the PDN. Types of ESM procedures: ESM involves different types of procedures such as: The MME maintains EMM context and EPS bearer context information for UEs in

782-551: The Packet Data Network Gateway is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA 1X and EvDO ). The Home Subscriber Server is a central database that contains user-related and subscription-related information. The functions of the HSS include mobility management, call and session establishment support, user authentication and access authorization. The HSS

816-587: The S1-U interface with eNodeB and S5/S8 data plane interface with PGW. The integrated data plane stack for these interfaces consists of IP , UDP , eGTP-U . Main interfaces supported by the P-GW are: The EPC is a packet-only core network. It does not have a circuit-switched domain, which is traditionally used for phone calls and SMS . 3GPP specified two solutions for voice: 3GPP specified three solutions for SMS: CSFB and SMS over SGs are seen as interim solutions,

850-451: The UE and the session management procedures to establish and maintain IP connectivity between the UE and a PDN GW. They define the rules for a mapping between parameters during inter-system mobility with 3G networks or non-3GPP access networks. They also provide the NAS security by integrity protection and ciphering of NAS signaling messages. EPS (Evolved Packet System) provides the subscriber with

884-511: The control of mobility when the User Equipment (UE) uses the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN). It also provides control of security for the NAS protocols. EMM involves different types of procedures such as: The UE and the network execute the attach procedure, the default EPS bearer context activation procedure in parallel. During the EPS attach procedure the network activates

918-403: The ePDG is to secure the data transmission with a UE connected to the EPC over untrusted non-3GPP access, e.g. Wi-Fi calling ( VoWiFi ). For this purpose, the ePDG acts as a termination node of IPsec tunnels established with the UE. The Non-Access Stratum (NAS) protocols form the highest stratum of the control plane between the user equipment (UE) and MME. NAS protocols support the mobility of

952-516: The long term being IMS . The UE can connect to the EPC using several access technologies. These access technologies are composed of: It is up to the network operator to decide whether a non-3GPP access technology is trusted or untrusted. It is worth noting that these trusted/untrusted categories do not apply to 3GPP accesses. The 3GPP delivers standards in parallel releases, which compose consistent sets of specifications and features. 03056876920 GPRS Core Network The GPRS core network

986-524: The mobile user, but if the mobile user is inactive, the data is discarded. In the other direction, mobile-originated packets are routed to the right network by the GGSN. The GGSN is the anchor point that enables the mobility of the user terminal in the GPRS/ UMTS networks. In essence, it carries out the role in GPRS equivalent to the home agent in Mobile IP . It maintains routing necessary to tunnel

1020-458: The mobility anchor for the user plane during inter- eNodeB handovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and Packet Data Network Gateway). For idle state User Equipment, the Serving Gateway terminates the downlink data path and triggers paging when downlink data arrives for the User Equipment. It manages and stores UE contexts, e.g. parameters of

1054-448: The packet data network) of all GPRS users registered with it. Enhanced Data Rates for GSM Evolution (EDGE) specific SGSN functions and characteristics are: An access point is: When a GPRS mobile phone sets up a PDP context, the access point is selected. At this point an Access Point Name (APN) is determined This access point is then used in a DNS query to a private DNS network. This process (called APN resolution) finally gives

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1088-467: The responsible SGSN. For this purpose, the GGSN stores the current SGSN address of the user and his or her profile in its location register. The GGSN is responsible for IP address assignment and is the default router for the connected user equipment (UE). The GGSN also performs authentication and charging functions. Other functions include subscriber screening, IP pool management and address mapping , QoS and PDP context enforcement. With LTE scenario

1122-557: The security key management. Lawful interception of signaling is also supported by the MME. The MME also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME from the SGSN . The MME also terminates the S6a interface towards the HSS for roaming UEs. The Serving Gateway routes and forwards user data packets, while also acting as

1156-466: Was also proposed, at one stage, to support packet radio services in the US D-AMPS TDMA system, however, in practice, all of these networks have been converted to GSM so this option has become irrelevant. PRS module is an open standards driven system. The standardization body is the 3GPP . GPRS Tunnelling Protocol is the defining IP -based protocol of the GPRS core network. Primarily it

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