教育部補助「行動寬頻尖端技術跨校教學聯盟第二期計畫 -- 行動寬頻網路與應用 -- 小細胞基站聯盟中心」 EPC核心網路系統設計 課程單元 02：行動寬頻網路與 Small Cell 架構 計畫主持人：許蒼嶺 (國立中山大學 電機工程學系) 授課教師：萬欽德 (國立高雄第一科技大學 電腦與通訊工程系)

Introduction to Small Cell

Why Small Cell? Coverage Voice Quality VoLTE EVS codec Throughput

Source: Ericsson Mobility Report

Source: Ericsson Mobility Report

Source: Ericsson Mobility Report

Source: Ericsson Mobility Report

Small Cell As more subscribers use mobile broadband services from their smartphones and tablets, the demand for bandwidth and coverage is increasing. MSPs (Mobile Service Providers) are updating their networks to LTE networks and adding small cells as part of a heterogeneous network (HetNet) architecture. Small cells are wireless infrastructure equipment that operates in licensed bands within cellular networks.

HetNet (Heterogeneous Network)

Pros Because of their size and low power requirements, small cells are simplerand can be deployed more quickly than macro cells. As mobile network operators (MNOs) build out LTE networks, the need for additional coverage and capacity in specific locations is driving them to deploy small cell networks. Cheaper Doesn’t require special phones High quality Open or restricted access

Cons Significantly increase the signaling load on the core network Hard to management and scheduling More Interference Security

Use Cases There are three types of small cells with varying capacity, coverage, power requirements. A metrocell provide increased capacity in urban hotspots or coverage in a rural location.

LTE EPC Architecture

Circuit Switched Core The Radio Network Controller (or RNC) is a governing element in the UMTS radio access network and is responsible for controlling the NodeBs that are connected to it. Mobile switching center (MSC):This is essentially the same as that within GSM, and it manages the circuit switched calls under way. Gateway MSC (GMSC):GMSC has all the standard functionality of a MSC (Mobile Switching Centre) but provides interconnectivity between other licensed operators. PSTN (public switched telephone network) : It is the world's collection of interconnected voice-oriented public telephone networks.

Packet Switched Core Serving GPRS Support Node (SGSN):The SGSN provides a number of functions within the UMTS network architecture. Mobility management: When a UE attaches to the Packet Switched domain of the UMTS Core Network, the SGSN generates MM information based on the mobile's current location. Session management: The SGSN manages the data sessions providing the required quality of service and also managing what are termed the PDP (Packet data Protocol) contexts, i.e. the pipes over which the data is sent. Interaction with other areas of the network: The SGSN is able to manage its elements within the network only by communicating with other areas of the network, e.g. MSC and other circuit switched areas. Billing: The SGSN is also responsible billing. It achieves this by monitoring the flow of user data across the GPRS network. CDRs (Call Detail Records) are generated by the SGSN before being transferred to the charging entities (Charging Gateway Function, CGF).

Packet Switched Core (cont’d) Gateway GPRS Support Node (GGSN): Like the SGSN, this entity was also first introduced into the GPRS network. The Gateway GPRS Support Node (GGSN) is the central element within the UMTS packet switched network. It handles inter-working between the UMTS packet switched network and external packet switched networks, and can be considered as a very sophisticated router. In operation, when the GGSN receives data addressed to a specific user, it checks if the user is active and then forwards the data to the SGSN serving the particular UE. Packet Data Serving Node (PDSN): It provides access to the Internet, intranets and applications servers for mobile stations utilizing a cdma2000 Radio Access Network (RAN).

LTE System Core Structure

LTE and SAE Long Term Evolution (LTE) refers to the Evolved UMTS Radio Access Network (E-UTRAN) System Architecture Evolution (SAE) refers to the Evolved Packet Core (EPC) LTE uses a flat architecture No BSC (in 2G networks) No RNC (in 3G networks)

LTE and SAE (cont’d)

Small Cell Architecture (NSYSU)

System Architecture Evolution

2G Network Architecture

2G and 3G Network Architecture

2G, 3G and 4G Network Architecture

Simplified View of the SAE Architecture

What is EPC? All-IP mobile core network From 3GPP Release: (Radio access): LTE  E-UTRAN (eNodeB) (Core network): SAE  EPC Evolved Packet System = E-UTRAN + EPC E-UTRAN EPC

Evolved Packet Core (EPC) New, all-IP mobile core network introduced with LTE End-to-end IP (All-IP) Clear delineation of control plane and data plane Simplified architecture: flat-IP architecture with a single core A multi-access core network based on the Internet Protocol (IP) EPC enables operators to deploy and operate one common packet core network for 3GPP radio access (LTE, 3G, and 2G) non-3GPP radio access (HRPD, WLAN, and WiMAX) fixed access (Ethernet, DSL, cable, and fiber).

All-IP Core, New Network Elements

Flat IP: Less Hierarchy, Lower Latency

EPC Elements Mobility Management Entity (MME) Serving Gateway Control-plane element, responsible for high volume mobility management and connection management (up to thousands of eNodeBs) Serving Gateway Serving a large number of eNodeBs, focus on scalability and security Packet Data Network (PDN) Gateway IP management (“IP anchor”), connection to external data networks focus on highly scalable data connectivity and QoS enforcement Policy and Charging Rules Function (PCRF) Network-wide control of flows: detection, gating, QoS and flow- based charging, authorizes network-wide use of QoS resources (manages millions of service data flows)

LTE + EPC Elements & Interface

Control Plane (CP) Control plane gets new mobile-specific attributes Mobility across networks (and operator domains) Distributed mobility management Massive increase in scalability Dynamic policy management

User Plane (UP) User plane has many common attributes with fixed broadband Broadband capacity QoS for multi-service delivery Per-user and per-application policies Highly available network elements