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」 模組名稱： 「LTE-Small Cell 核心網路架構及服務」 單元-A4：核心網路 (EPC) 與 Internet Cloud 的介接與存取 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)

課程單元目標 了解 Data Services in EPS 了解 3GPP Domains and Interfaces 了解 IP Connectivity and Signaling

Data Services in EPS

Evolution of Radio Access Technologies

Growing Mobile Data Traffic Mobile data traffic is growing exponentially, caused by mobile internet offerings and improved user experience with new device types. LTE perspective Long term evolution perspective for 2G and 3G networks based on WCDMA/HSDPA, GSM/EDGE, TD-SCDMA, and CDMA2000 technologies.

Consideration for LTE Definition began: Nov. 2004 3GPP (3rd Generation Partnership Project) began a project to define the Long-Term Evolution (LTE) for Universal Mobile Telecommunications System (UMTS) cellular technology Considerations: Higher performance Backwards compatible Wide applications 第三代合作夥伴計劃（英語：3rd Generation Partnership Project，即3GPP）是一個成立於1998年12月的標準化機構。目前其成員包括歐洲的ETSI、日本的ARIB和TTC、中國的CCSA、韓國的TTA和北美洲的ATIS。

Data Services in EPS EPS is a faster, lower latency mobile broadband solution. Primarily with IP connectivity and data services 1990s (on GPRS) Wireless Access Protocol (WAP) Low successful rates 2000s High Speed Packet Access (HSPA) Indication of high demand for mobile broadband

Global Traffic in Mobile Networks The launch of the first “smartphone” in 2007 – the iPhone – changed everything. Mobile Internet and application-centric ecosystem.

IP Connectivity Smartphones, tablets, and app stores are just the beginning of the changes that mobile broadband will deliver through data services. Essential elements in users’ lives: Roads Electricity Connectivity

Data Services Two aspects– Messaging services Short Messaging Service (SMS) - GSM Multimedia Messaging Service (MMS) Machine-to-Machine communication Industrial and Corporate Uses Big Data Analysis and Management

Subscriptions: Fixed vs. Mobile

Messaging Support with EPC Using an IP-based solution (IMS-based messaging or SMS-over-IP) Messages are sent transparently through the network from a messaging server to the client, and are treated just like any IP packet by the EPC. Using the circuit-switched infrastructure that is normally used to deliver SMS messages over GSM and WCDMA. Noted that LTE is a packet-only radio access

Options for Messaging Services The MME interacts with the MSC Server when the CS infrastructure is used. The MSC Server is normally connected to a messaging center for delivery of SMS messages over control channels in GSM and WCDMA, and via the interaction with MME. Messages are included in NAS signaling messages between MME and the mobile device. This solution supports only SMS text messaging. Other types of messages (e.g., MMS) need to be based on IP.

Machine-to-Machine (M2M) Communication Private cars communicating service needs car’s position (retrieved using GPS) receiving up-to-date traffic data for traffic guidance systems Water or electricity meters remote control and/or remote meter reading Taxi cars validating credit cards

Machine-to-Machine (M2M) Communication (cont’d) Street-side vending machines communicating when goods are out of stock or when enough coins are present Delivery cars fleet management, including optimization of delivery routes and confirming deliveries Ambulances sending life-critical medicine data to the hospital prior to arrival Surveillance cameras home or corporate security

M2M and Data Analysis

3GPP Architecture Domains The Core Network can be divided into multiple domains (Circuit Core, Packet Core, and IMS).

3GPP Domains and Interfaces

3GPP Architecture Domains (cont’d) The subscriber data management domain provides coordinated subscriber information and supports roaming and mobility between and within the different domains.

Domains Circuit Core domain provides support for circuit- switched services over GSM and WCDMA. Packet Core domain provides support for packet- switched services (primarily IP connectivity) over GSM, WCDMA, and HSPA. The IMS domain provides support for multimedia sessions based on SIP (Session Initiation Protocol), and utilizes the IP connectivity provided by the functions in the Packet Core domain.

Logical and Physical Interfaces The physical implementation of a particular interface may not run directly between two nodes. it may be routed via another physical site. Example: X2 interface, connecting two eNodeBs, may physically be routed from eNodeB A together with the S1 interface (which connects an eNodeB to an MME in the core network) to a site in the network with core network equipment. From this site, it would be routed back onto the radio access and finally to eNodeB B.

Logical and Physical Interfaces An Example:

IP Connectivity and Signaling

Basic IP Connectivity over LTE Access To optimize the handling of the user data traffic itself, through designing a “flat” architecture. To separate the handling of the control signaling (shown as dotted lines) from the user data traffic

Separation of Control Signaling from User Data Traffic Factors: The need to allow independent scaling of control and user plane functions Control data signaling tends to scale with the number of users User data volumes may scale more depending on new services and applications, as well as the capabilities in terms of the device (screen size, supported codecs, etc.).

Separation of Control Signaling from User Data Traffic Factors (continued): Flexibility in terms of network deployment the freedom of locating infrastructure equipment handling user data functions in a more distributed way in the networks allowing for a centralized deployment of the equipment handling the control signaling Minimization of delays in real-time services such as voice or gaming Optimized operational costs (having the functions at separate physical locations in the network)

eNodeBs in the Network In a reasonably sized network scenario, there may be several thousand eNodeBs in the network. Many of these eNodeBs may be interconnected via the X2 interface in order to allow for efficient handovers. All eNodeBs are connected to at least one MME (Mobility Management Entity) over the S1-MME logical interface.

Mobility Management Entity Handling all LTE-related control plane signaling Mobility and security functions for devices and terminals Managing all terminals that are in idle mode Support for Tracking Area management and paging Relying on the existence of subscription-related user data for all users trying to establish IP connectivity over the LTE RAN. For this purpose, the MME is connected to the HSS (the Home Subscriber Server) over the S6a interface.

HSS (Home Subscriber Server) HSS manages user data and related user management logic for users accessing over the LTE RAN Subscription data includes credentials for authentication and access authorization HSS supports mobility management within LTE as well as between LTE and other access networks

Serving GW and PDN GW The user data payload (the IP packets) flowing to and from the mobile devices are handled by two logical nodes: Serving Gateway (Serving GW) PDN Gateway (Packet Data Network GW) The Serving GW and PDN GW are connected over an interface Interface S5 (if the user is not roaming, i.e. the user is attached to the home network) Interface S8 (if the user is roaming, i.e. attached to a visited LTE network)

Serving GW The Serving GW terminates the S1-U user plane interface towards the base stations (eNodeBs) The Serving GW constitutes the anchor point for intra- LTE mobility, as well as (optionally) for mobility between GSM/GPRS, WCDMA/HSPA and LTE. The Serving GW buffers downlink IP packets destined for terminals that happen to be in idle mode. For roaming users, the Serving GW always resides in the visited network, and supports accounting functions for inter-operator charging and billing settlements.

PDN GW The PDN GW is the point of interconnection to external IP networks through the SGi interface. Functionality: IP address allocation, charging, packet filtering, and policy-based control of user-specific IP flows supporting QoS for end-user IP services handles the packet bearer operations supports transport-level QoS (by marking IP packets with appropriate DiffServ code points based on the parameters associated with the corresponding packet bearer)

Split of S-GW and PDN-GW (1/4) S8 interface connecting the Serving GW in the visited network and the PDN GW in the home network.

Split of S-GW and PDN-GW (2/4) When a user wants to connect to more than one external data network at the same time, and not all of these can be served from the same PDN GW. All user data relating to the specific user will then always pass the same Serving GW, but more than one PDN GW.

Split of S-GW and PDN-GW (3/4) When a user moves between two LTE radio base stations that does not belong to the same service area, the Serving GW needs to be changed, while the PDN GW will be retained in order not to break the IP connectivity.

Split of S-GW and PDN-GW (4/4) When an operator’s deployment scenario causes the operator to have their PDN GWs in a central location whereas the Serving GWs are distributed closer to the LTE radio base stations (eNodeBs).

S11 interface Control plane signaling between the MME and the Serving GW One of the key interfaces in the EPC architecture. Establishing IP connectivity for LTE users through connecting Gateways and radio base stations Providing support for mobility when users and their devices move between LTE radio base stations

Advanced Functionality for LTE Access Some more interfaces Some additional advanced features targeting the control of end-user IP flows IP flow: a web browsing session or a TV stream Three new logical nodes: PCRF, the OCS, and the OFCS PCC (Policy and Charging Control) Designed to enable flow-based charging Online credit control Policy control: support for service authorization and QoS management

Advanced Functionality for LTE Access (cont’d) How the data will be charged for or what QoS will be awarded to the service? The PCRF contains policy control decisions and flow-based charging control functionalities. Both the charging and the policy control functions rely on all IP flows being classified (in the PDN GW/ Serving GW) using unique packet filters that operate in real time on the IP data flows.