About the LTE Application

Long Term Evolution (LTE) is an evolved technology based on 3GPP standards developed to promote an evolved 3GPP packet system accessible from multiple access technologies that supports higher data rates, lower latency, and an all-IP network.

The diagram below shows the LTE core network components and these defined reference points (interfaces):

S1- MMEMME(Mobility Management Entity) — Provides a reference point for the control plane protocol between E-UTRANE-UTRAN(Evolved Universal Terrestrial Radio Access Network) and MME.
S1-U — Provides a reference point between E-UTRAN and Serving GW for the per bearer user plane tunnelling and inter eNodeB path switching during handover.
S3 — Enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state.
S4 — Provides related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW. In addition, if Direct Tunnel is not established, it provides the user plane tunnelling.
S5 — Provides user plane tunneling and tunnel management between Serving GW and PDN GW. It is used for SGW relocation due to UE mobility and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.
S6a/d — Enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME/SGSN and HSS.
Gx — Provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW.
S10 — Provides a reference point between MMEs for MME relocation and MME to MME information transfer.
S11 — Provides a reference point between MME and Serving GW.
S12 — Provides a reference point between UTRANUTRAN(Universal Terrestrial Radio Access Network) and Serving GW for user plane tunneling when Direct Tunnel is established. It is based on the Iu-u/Gn-u reference point using the GTP-U protocol as defined between SGSN and UTRAN or respectively between SGSN and GGSN. Usage of S12 is an operator configuration option.
S13/S13’ — Provides a reference point (EIR Interface) between MME/SGSN and HSS to perform identity check procedure invoked from MME/SGSN, respectively.
SGi — Provides a reference point between the PDN GW and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi for 3GPP accesses.
Rx — Provides a Rx reference point residing between the AF and the PCRF.
LTE-Uu — The radio protocol of E-UTRAN between the UE and the eNodeB.
X2 — Provides buffer and context transfer directly between eNBs without involving the SGW.

3GPP and non-3GPP un-trusted Network

S2a — Provides the user plane with related control and mobility support between trusted non 3GPP IP access and the Gateway.
S2b — Provides the user plane with related control and mobility support between ePDG and the Gateway.
S2c — Provides the user plane with related control and mobility support between UE and the Gateway. This reference point is implemented over trusted and/or untrusted non-3GPP Access and/or 3GPP access.
S5 — Provides user plane tunneling and tunnel management between Serving GW and PDN GW. It is used for SGW relocation due to UE mobility and in case the Serving GW needs to connect to a non collocated PDN GW for the required PDN connectivity.
S6a — Interface is defined between MME and HSS for authentication and authorization.
S6b — The reference point between PDN Gateway and 3GPP AAA server/proxy for mobility related authentication if needed. This reference point may also be used to retrieve and request storage of mobility parameters and static QoS profile for a UE for non-3GPP access in case dynamic PCC is not supported.
Gx — Provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW.
Gxa — Provides transfer of (QoS) policy information from PCRF to the Trusted Non-3GPP accesses.
Gxc — Provides transfer of (QoS) policy information from PCRF to the Serving Gateway
SGi — Reference point between the PDN Gateway and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, for example, for provisioning IMS services. The reference point corresponds to Gi and Wi functionalities and supports any 3GPP and non-3GPP access systems.
SWa — Connects the Untrusted non-3GPP IP Access with the 3GPP AAA Server/Proxy and transports access authentication, authorization and charging-related information in a secure manner.
STa — Connects the Trusted non-3GPP IP Access with the 3GPP AAA Server/Proxy and transports access authentication, authorization, mobility parameters and charging-related information in a secure manner.
SWd — Connects the 3GPP AAA Proxy, possibly via intermediate networks, to the 3GPP AAA Server.
SWm — Reference point is located between 3GPP AAA Server/Proxy and ePDG and is used for AAA signaling (transport of mobility parameters, tunnel authentication and authorization data). This reference point also includes the MAG-AAA interface functionality, IETF Internet-Draft, draft-ietf-dime-pmip6-01 [43] and Mobile IPv6 NAS-AAA interface functionality, RFC 5447 [44].
SWn — Reference point between the Untrusted Non-3GPP IP Access and the ePDG. Traffic on this interface for a UE-initiated tunnel has to be forced towards ePDG. This reference point has the same functionality as Wn which is defined in TS 23.234 [5].
SWu — The reference point between the UE and the ePDG and supports handling of IPSec tunnels. The functionality of SWu includes UE-initiated tunnel establishment, user data packet transmission within the IPSec tunnel and tear down of the tunnel and support for fast update of IPSec tunnels during handover between two untrusted non-3GPP IP accesses.
SWx — The reference point is located between 3GPP AAA Server and HSS and is used for transport of authentication, subscription and PDN connection related data.
ePDG (Evolved Packet Data Gateway) — The ePDG (Evolved Packet Data Gateway) is employed If a non-3GPP un-trusted network is connecting to the 3GPP packet core. This is similar to a VPN concentrator and the mobile network establishes an IPSec tunnel with the ePDG to access an operator’s services. Once the tunnel is in place, the ePDG may implement IP mobility protocols to ensure connectivity is maintained between the mobile network and the service.
Sv — The reference point provides SRVCC (Single Radio Voice Call Continuity) support from 3GPP E-UTRAN/UTRAN (HSPA) to 3GPP UTRAN/GERAN.

The SRVCC indicates the voice call continuity between IMS over PS access and CS access for calls that are anchored in IMS when the UE is capable of transmitting/receiving on only one of the access networks at a given time.

Protocols

S1-MME — NAS, S1-AP, SCTP, S6a, S6d
L3-7 — Data Traffic, IPSec
SGi, S11, S1-U, S13, S13'

Emulators

User Equipment (UE)
ENodeB (E-UTRAN NodeB) (E-UTRAN — Evolved Universal Terrestrial Radio Access Network)
Serving Gateway (SGW)
PDN Gateway (PDN GW)
Network Host (NH)
Security Gateway

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