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System Architecture Evolution
System Architecture Evolution (SAE) is the core network architecture of mobile communications protocol group 3GPP's LTE wireless communication standard.
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 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 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 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 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 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 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 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).
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System Architecture Evolution
System Architecture Evolution (SAE) is the core network architecture of mobile communications protocol group 3GPP's LTE wireless communication standard.
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 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 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 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 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 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 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 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).