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Module 2

LTE Architecture

Agenda

Network Architecture Evolution Identify the major Nodes Network Elements Key functionalities

Architecture Evolution

Many of the targets implied that a flat architecture would need to be developed. Flat architecture with less involved nodes reduces latencies and improves performance. Development towards this direction had already started in Release 7 where the Direct Tunnel concept allows User Plane (UP) to bypass the Serving GPRS support node (SGSN), and the placement of Radio network controller(RNC) functions to High speed packet access(HSPA) NodeB was made possible

LTE Interfaces

LTE Interfaces:•S1-MME :- Reference point for the control plane protocol between E-UTRAN and MME.•S1-U:- Reference point between E-UTRAN and Serving GW for the per bearer user plane tunneling and inter eNodeB path switching during handover.•S3:- It enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state.•S4:- It 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 tunneling.•S5:- It provides user plane tunneling and tunnel management between Serving GW and PDN GW. It is used for Serving GW 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:- It enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS.•S7:- It provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW.•S8:- Inter-PLMN reference point providing user and control plane between the Serving GW in the VPLMN and the PDN GW in the HPLMN. S8 is the inter PLMN variant of S5.•S9:- It provides transfer of (QoS) policy and charging control information between the Home PCRF and the Visited PCRF in order to support local breakout function.•S10:- Reference point between MMEs for MME relocation and MME to MME information transfer.•S11:- Reference point between MME and Serving GW.•S12:- Reference point between UTRAN 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:- It enables UE identity check procedure between MME and EIR.•SGi:- It is the 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:- The Rx reference point resides between the AF (Application Function) and the PCRF in the TS 23.203.•SBc:- Reference point between CBC (Cell Broadcast Center) and MME for warning message delivery and control functions.

Interfaces

EPS Network Architecture

eNodeB and UE

MME

• It is a pure signaling entity inside the Evolved Packet Core(EPC)• SAE uses tracking areas to track the position of idle UEs. The basic principle is identical to 2G/3G Location Area or Routing Area. • MME handles attaches and detaches to the SAE system, as well as tracking area updates. • Therefore it possesses an interface towards the HSS (home subscriber server) which stores the subscription relevant information and the currently assigned MME in its permanent data base.• A second functionality of the MME is the signaling coordination to setup transport bearers (SAE bearers) through the EPC for a UE.•It generates and allocates temporary ids like TMSIs (Temporary Mobile subscriber Identity) for UEs.• It has got Visitor Location Register(VLR)-like functionality

S-GW

•The serving gateway is a network element that manages the user data path (SAE bearers) within EPC. • It therefore connects towards eNodeB and receives uplink packet data and transmits downlink packet data on it. • Thus the serving gateway is some kind of distribution and packet data anchoring function within EPC.• It relays the packet data within EPC via interface to or from the PDN gateway.• A serving gateway is controlled by one or more MMEs.• At a given time, the UE is connected to the EPC via a single Serving-GW.PMPI- Proxy Mobile IPv6 is a network-based mobility management protocol. It is a protocol for building a common and access technology independent of mobile core networks, accommodating various access technologies like 3GPP

P-GW

•The PDN gateway (or P-GW or PDN-GW) provides the connection between EPC and a number of external data networks.• It is comparable to Gateway GPRS Support Node(GGSN) in 2G/3G networks.• A major functionality provided by a PDN gateway is the QoS coordination between the external PDN and EPC.• Therefore the PDN gateway has to be connected to a PCRF (Policy & Charging Rule Function). • If a UE is connected simultaneously to several PDNs this may involved connections to more than one PDN-GW

PCRF

•The PCRF major functionality is the Quality of Service (QoS) coordination between the external PDN and EPC.• Therefore the PCRF is connected to the external Data network (PDN).• This function can be used to check and modify the QoS associated with a SAE bearer setup from SAE or to request the setup of a SAE bearer from the PDN. •This QoS management resembles the policy and charging control framework introduced for IMS with UMTS release 6.

HSS

Home Subscriber Server(HSS) • The HSS is already introduced by UMTS release 5.• With LTE/EPS the HSS will get additionally data per subscriber for mobility and service handling. •The HSS can be accessed by the MME

“Thank you”