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-A7：LTE-Small Cell 核心網路與網路管理(OAM) 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 IP Connectivity 與 Session Management 了解 Mobility Principles

Data Services in EPS

Introduction to Mobile Network Management (1/3) Requirements toward network management of the mobile backhaul network are increasing due to The vast growth of network capacity The increasing complexity of the mobile network Network Management consists of Element Management System (EMS) Network Management System (NMS) The widest definition of network management is typically called the Operations Support System (OSS). [1] 259

Introduction to Mobile Network Management (2/3) The Operations Support System (OSS) includes all the necessary systems used by the telecommunication service providers to management their networks. Either the Operations and Management (OA&M) interface connects the managed network elements directly to the NMS Or the OA&M interface is provided by the EMS. Network management serves many user groups in the network operator organization, involving Planning Optimization Configuration Monitoring and Trouble Shooting [1] 259

Introduction to Mobile Network Management (3/3) Network management provides a centralized focal point to Collect information about the managed mobile backhaul network, Enable network optimization either manually or automatically. The typical NMS provides the following functionality Fault Management Performance Management Configuration Management Optimization Self-Organizing Network (SON) [1] 259-260

NMS Architecture When looking at the external interfaces, the high-level NMS architecture includes connectivity to Planning and optimization tools and other external systems (such as trouble ticket systems and inventory systems) through northbound interface, EMS through southbound interface

Layered NMS Many operators organize management to have a centralized or a country-level system in addition to regional NMS systems, creating a layered NMS configuration. The centralized NMS provides multiple benefits to Manage border areas between regions due to mobility management Enable a single location to provide 24/7 support instead of multiple ones. Country wide NMS Regional NMS Element management Network elements [1] 260-261

NMS for Mobile LTE and Backhaul Networks The LTE network elements (NEs) includes eNodeBs and S-GW; while the backhaul NEs includes switches and routers. In addition to LTE radio and core functions, the LTE NEs includes transport functions, which shares a common OA&M function with the mobile part. [1] 261-262

Fault Management The purpose of network fault management is to detect faults in the network and make a notification of the fault. Fault notification typically means an alarm event is emitted and sent to the NMS. The alarm contains a standardized set of attributes defined by ITU-T and 3GPP, such as its location, type, severity, cause and time stamp. The NEs and EMS should reduce the amount of alarms by employing fault correlation to combines alarms which are triggered by the same fault. Alarm events can trigger automatic recovery actions and optimization algorithms. [1] 262-263

Performance Management Performance management in EMS/NMS collects network performance indicators emitted by NEs. The amount of collected performance data is reduced with the help of data aggregation, which may apply statistical functions such as averaging and summarizing to raw data. Performance data analysis includes a functionality to perform automatic actions based on predefined thresholds and profiles. Data-forwarding function can automatically send data to an external system such as the centralized NMS. Combined radio and backhaul measurement reporting helps to locate bottlenecks and enhances optimization and planning. [1] 263

Configuration Management Configuration management is a central optimization and planning function to monitor and control NE configurations. The features of configuration management include Maintaining an up-to-date picture of the network Recoding configuration history Configuring network Policy-based configuration management Planning interfaces Network configuration discovery Configuration management of backhaul network [1] 263

Policy-Based Configuration Management Policy-based configuration management introduces a capability to add or change a configuration with templates. Policy templates contains parameters which can be defined and changed. With polices, different parameter setting can be defined for groups of similar elements in the network Grouping criteria can based on location Feature and layer. Policies also enable setting for different services. [1] 265-266

Planning Interfaces In accordance with open policy, the NMS provides a set of well-defined open interfaces for the upper level system. Examples of interfaces typically used are: 3GPP northbound interface XML (Extensible Markup Language) interface CSV (Comma-Separated Values) interface Web service interface, which is based on SOAP (Simple Object Oriented Access Protocol). SOAP is used for exchanging structured data in the form of XML. SOAP protocol uses HTTP or SMTP underneath. Excel interface [1] 266-267

Configuration Management of Backhaul Network (1/2) NMS-based configuration management provides the following benefits and leads to increased service availability as well as reduced OPEX. Cross-domain consistency checking between the radio and the backhaul Auditing leading to less parameter errors Efficient operations due to mass modification possibilities Reducing unnecessary variation in configurations by utilizing policy-based configuration management Quick troubleshooting and combined configuration changes with a radio network [1] 267

Configuration Management of Backhaul Network (2/2) The figure shows a single NMS supporting configuration management (CM) functions for both the LTE radio network and the LTE backhaul. The more the NMS supports CM over various elements, the bigger the benefits achievable in terms of OPEX and quality. [1] 268

IP Connectivity

IP Connectivity Enables Session Management In conjunction with the evolution of the access networks provided with LTE Provides a common packet core with appropriate policy, security, charging, and mobility Provides end-users with ubiquitous access to network services across different access networks Provides session continuity across various access technologies. [1] 267

IP Connectivity (1/8) IPv4 or IPv6 QoS

IP Connectivity (2/8) APN (corresponding PDN) : EPS concerns: user’s subscription profile in the HSS (if not, default) PDN GW EPS concerns: PDN connection layer associated functions such as IP address management, QoS, mobility, charging, security, policy control, etc.

IP Connectivity (3/8) The user IP connection (the PDN connection) is separate from the IP connection between the EPC nodes (the transport layer). Transport network in the EPC provides IP transport: Using different technologies such as MPLS, Ethernet, wireless point-to-point links, etc. Not aware of the PDN connections.

IP Connectivity (4/8) Trusted Non-3GPP Accesses

IP Connectivity (5/8) IP Addresses Can be purely private IP network IPv4 or IPv6 A terminal with a PDN connection in EPS may request an IPv4 address, an IPv6 prefix, or both Two alternative ways ( both methods to coexist in EPC) IPv4 address to the UE during the attach procedure (E-UTRAN) or PDP context activation procedure (GERAN/UTRAN) DHCPv4 Stateless IPv6 address auto configuration (SLAAC)

IP Connectivity (6/8) IP Address Allocation in Other Accesses Trusted Non-3GPP Accesses Untrusted Non-3GPP Accesses

IP Connectivity (7/8) Trusted Non-3GPP Accesses

IP Connectivity (8/8) Untrusted Non-3GPP Accesses

Session Management

Session Management, Bearers, and QoS Aspects (1/13) The basic functions in EPS to manage the user-plane path between the UE and the PDN GW EPS bearer in E-UTRAN and EPS for providing the IP connection for enabling QoS

Session Management, Bearers, and QoS Aspects (2/13) Default bearer associated with a default type of QoS Dedicated bearers Additional EPS bearers activated on demand for example, when an application is started with a specific guaranteed bit rate or prioritized scheduling

Session Management, Bearers, and QoS Aspects (3/13) User-Plane Aspects The UE and the PDN GW (for GTP-based S5/S8) or Serving GW (for PMIP-base S5/S8) use packet filters to map IP traffic onto the different bearers Each EPS bearer is associated with a so-called Traffic Flow Template (TFT)

Session Management, Bearers, and QoS Aspects (4/13) This packet filter information is typically an IP 5-tuple defining the source and destination IP addresses, source and destination port, as well as protocol identifier (e.g. UDP or TCP).

Session Management, Bearers, and QoS Aspects (5/13) The filter information may contain the following attributes: Remote IP Address and Subnet Mask Protocol Number (IPv4)/Next Header (IPv6) Local Address and Mask (introduced in Release 11) Local Port Range Remote Port Range IPSec Security Parameter Index (SPI) Type of Service (TOS) (IPv4)/Traffic Class (IPv6) Flow Label (IPv6).

Session Management, Bearers, and QoS Aspects (6/13) GTP-U header contains: a field that allows the receiving node to identify the bearer the packet belongs to A user-plane packet encapsulated using GTP-U

Session Management, Bearers, and QoS Aspects (7/13)

Session Management, Bearers, and QoS Aspects (8/13)

Session Management, Bearers, and QoS Aspects (9/13) How the UE, PDN connection, EPS bearer, TFT, and packet filters within the TFT relate to each other

Session Management, Bearers, and QoS Aspects (10/13) Control-Plane Aspects To activate, modify, and deactivate bearers, to assign QoS parameters, packet filters, etc., to the bearer. Dedicated bearer network-requested secondary PDP context activation procedure If the default bearer is deactivated the whole PDN connection will be closed.

Session Management, Bearers, and QoS Aspects (11/13) Bearers in PMIP- and GTP-Based Deployments GTP designed to support all functionality required to handle the bearer signaling the user plane transport, PMIP designed by IETF to only handle functions for mobility and forwarding of the user plane.

Session Management, Bearers, and QoS Aspects (12/13) When PMIP-based S5/S8 is used: Packet filters are needed to map the downlink traffic onto the appropriate bearer

Session Management, Bearers, and QoS Aspects (13/13)

Session Management for EPS and GERAN/UTRAN Accesses (1/3) The SGSN provides the mapping between PDP context and EPS bearer procedures, and maintains a one-to-one mapping between PDP contexts and EPS bearers. By using PDP context procedures between UE and SGSN, the UE can use similar ways to connect when the 2G/3G access connects to EPC. By using the EPS bearer in the EPC also for 2G/3G access, it is easier for the PDN GW to handle mobility between E-UTRAN and 2G/3G.

Session Management for EPS and GERAN/UTRAN Accesses (2/3)

Session Management for EPS and GERAN/UTRAN Accesses (3/3) SGSN using S4 maps “the UE-initiated PDP context procedures over GERAN/UTRAN” into “corresponding EPS bearer procedures towards the Serving GW” For example, when the UE is using GERAN/UTRAN and has requested activation of a secondary PDP context, the PDNGW must activate a new EPS bearer corresponding to the PDP context

Subscriber Identifiers and Corresponding Legacy Identities (1/3) Permanent Subscriber Identifiers Structure of IMSI

Subscriber Identifiers and Corresponding Legacy Identities (2/3) Temporary Subscriber Identifiers stored in an MME (or SGSN in the 2G/3G case) The GUTI (Globally Unique Temporary ID) is a worldwide unique identity that points to a specific subscriber context in a specific MME. The S-TMSI is unique within a particular area of a single network.

Subscriber Identifiers and Corresponding Legacy Identities (3/3)

Relation to Subscription Identifiers in 2G/3G

Mobility Principles

Mobility Principles EPS The functionality of mobility management complete realization of multi-access convergence: a packet core network that supports full mobility management access network discovery and selection for any type of access network. The functionality of mobility management the network can “reach” the user a user can initiate communication towards other users or services ongoing sessions can be maintained as the user moves

Mobility within 3GPP Family of Accesses Cellular Idle-Mode Mobility Management Not be practical to keep track of a UE in idle mode every time it moves between different cells. Not practical to search for the UE in the whole network for every terminating event (incoming call) Cells are grouped together into “registration areas”

Cellular Idle-Mode Mobility Management (1/7)

Cellular Idle-Mode Mobility Management (2/7) Base stations broadcast registration area information. UE compares the broadcasted registration area information with its own information

Cellular Idle-Mode Mobility Management (3/7) In EPS the registration areas are called Tracking Areas (TAs). As long as the UE moves within its list of allocated TAs, it does not have to perform a tracking area update. Periodic updates are used to clear resources in the network for UEs that are out of coverage or have been turned off.

Cellular Idle-Mode Mobility Management (4/7) In GSM/WCDMA there are two registration area concepts: the PS domain (Routing Areas, RAs) the CS domain (Location Areas, LAs). The Routing Areas are a subset of the Location Areas and can only contain cells from the same LA.

Cellular Idle-Mode Mobility Management (5/7) A summary of the idle mobility procedure in EPS: A TA consists of a set of cells The registration area in EPS is a list of one or more TAs The UE performs TA Update when moving outside its TA list The UE also performs TA Update when the periodic TA Update timer expires. An outline of the Tracking Area Update procedure is shown in the figure of next slide.

Cellular Idle-Mode Mobility Management (6/7)

Cellular Idle-Mode Mobility Management (7/7) Paging is used to search for Idle UEs and establish a signaling connection.

References M. Olsson, Shabnam Sultana, Stefan Rommer, Lars Frid, and C. Mulligan, “EPC and 4G Packet Networks,” Second Edition: Driving the Mobile Broadband Revolution, Elsevier, 2013