railway operational communication solution gsm-r sgsn9810 product description1.0(20090330)

Product Description

GSM-R SGSN9810 Product Description

Issue V1.0

Date 2009-03-30

HUAWEI TECHNOLOGIES CO., LTD.

Issue V1.0 (2009-03-30) Commercial in Confidence Page 2 of 81

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About This Document

Author

Prepared by Liao Huanran Date 2009-03-30

Reviewed by Date

Approved by Wang Zhoujie Date 2009-03-30

Summary This document provides information for the product function, features, technical indexes, and

structure of the SGSN9810 serving GPRS support node so that you can have a global view of

the SGSN9810.

This document includes:

Chapter Details

1 Overview Describes the position and application of the SGSN9810 in

a network.

2 Product Feature Describes the product features of the SGSN9810.

3 System Structure Describes the hardware, software, and logical structure of

the SGSN9810.

4 Function Describes the product features of the SGSN9810.

5 Operation and

Maintenance

Describes the operation and maintenance of the

SGSN9810.

6 Reliability Describes the hardware and software reliability of the

SGSN9810.

7 Technical Index Describes the technical indexes of the SGSN9810.

8 Installation Describes the fundamental features for the hardware and

software installation of the SGSN9810.


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History

Issue Details Date Author Approved by

V1.0 Creation 2009-03-30 Liao Huanran Wang Zhoujie


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Contents

1 Introduction to the SGSN9810 .................................................................................................... 8

1.1 Structure of a GPRS/UMTS Network .............................................................................................................. 8

1.2 Huawei GPRS/UMTS CN-PS Solution ........................................................................................................... 9

1.2.1 SGSN .................................................................................................................................................... 10

1.2.2 GGSN .................................................................................................................................................... 10

1.2.3 HA ......................................................................................................................................................... 10

1.2.4 CG ......................................................................................................................................................... 11

1.2.5 AAA Server ........................................................................................................................................... 11

1.2.6 DNS Server ........................................................................................................................................... 11

1.2.7 BG ......................................................................................................................................................... 11

1.3 Overview of the SGSN9810 ........................................................................................................................... 12

2 Key Benefits ................................................................................................................................. 15

2.1 Large Capacity and High Integration ............................................................................................................. 15

2.2 High-Speed Hardware Forwarding ................................................................................................................ 15

2.3 Supporting Boards of 750C Series ................................................................................................................. 15

2.4 Standard Protocol Interfaces .......................................................................................................................... 16

2.5 Abundant Physical Interfaces ......................................................................................................................... 17

2.6 Rich Services and Functions .......................................................................................................................... 17

2.7 Accurate Clock System .................................................................................................................................. 18

2.8 Easy Operation and Maintenance ................................................................................................................... 18

2.9 High Reliability .............................................................................................................................................. 19

3 System Structure ......................................................................................................................... 20

3.1 Hardware Configuration ................................................................................................................................. 20

3.1.1 Cabinet Configuration ........................................................................................................................... 20

3.1.2 Switching Subrack ................................................................................................................................ 22

3.1.3 Basic Subrack........................................................................................................................................ 23

3.1.4 Extended Subrack ................................................................................................................................. 25

3.2 Software Structure .......................................................................................................................................... 26

3.3 Logical Structure ............................................................................................................................................ 27

3.3.2 Switching Subsystem ............................................................................................................................ 28

3.3.3 PS Transfer Subsystem.......................................................................................................................... 28

3.3.4 Gb Interface Processing Subsystem ...................................................................................................... 28

3.3.5 Signaling Processing Subsystem ........................................................................................................... 29

3.3.6 Lawful Interception Subsystem............................................................................................................. 29


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3.3.7 Charging Subsystem ............................................................................................................................. 29

3.3.8 Iu Interface Control Plane Processing Subsystem ................................................................................. 29

3.3.9 GTP Control Plane Processing Subsystem ............................................................................................ 29

3.3.10 Operation and Maintenance Subsystem .............................................................................................. 29

3.3.11 Clock Subsystem ................................................................................................................................. 29

4 Services and Functions ............................................................................................................... 30

4.1 Services .......................................................................................................................................................... 30

4.1.1 IP/PPP Bearer Services ......................................................................................................................... 30

4.1.2 Short Message Services ........................................................................................................................ 31

4.1.3 Location Services .................................................................................................................................. 32

4.1.4 CAMEL Phase 3 Services ..................................................................................................................... 33

4.1.5 Lawful Interception ............................................................................................................................... 34

4.2 Functions ........................................................................................................................................................ 35

4.2.1 Mobility Management ........................................................................................................................... 36

4.2.2 Session Management............................................................................................................................. 36

4.2.3 Routing .................................................................................................................................................. 36

4.2.4 IPv6 Support ......................................................................................................................................... 37

4.2.5 IPSec and LLC Encryption ................................................................................................................... 38

4.2.6 Charging ................................................................................................................................................ 38

4.2.7 QoS ....................................................................................................................................................... 39

4.2.8 Iu-FLEX/Gb-FLEX ............................................................................................................................... 40

4.2.9 RAN Sharing in Connected State .......................................................................................................... 41

4.2.10 MVNO ................................................................................................................................................ 42

4.2.11 UESBI-Iu ............................................................................................................................................ 43

4.2.12 Multi-SPs and 2 Mbit/s Signaling Links ............................................................................................. 44

4.2.13 NTP Client Functions .......................................................................................................................... 45

4.2.14 Network-Assisted Cell Change ........................................................................................................... 47

4.2.15 SIGTRAN Support .............................................................................................................................. 47

4.2.16 Gb over IP ........................................................................................................................................... 49

4.2.17 Differential Services ........................................................................................................................... 50

4.2.18 Handover Strategy Control ................................................................................................................. 50

4.2.19 Enhanced MBMS ................................................................................................................................ 51

4.2.20 Network Share .................................................................................................................................... 52

4.2.21 Security Solution ................................................................................................................................. 53

4.2.22 Bidirectional Forwarding Detection (BFD) ........................................................................................ 55

4.2.23 One Tunnel .......................................................................................................................................... 55

4.2.24 SGSN N+1Backup .............................................................................................................................. 56

4.2.25 Multi SIM............................................................................................................................................ 56

5 Operation and Maintenance ..................................................................................................... 58

5.1 O&M System ................................................................................................................................................. 58

5.2 Configuration Management ............................................................................................................................ 59


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5.3 Equipment Management ................................................................................................................................ 59

5.4 Tracing Management ...................................................................................................................................... 59

5.5 Performance Management .............................................................................................................................. 60

5.6 Fault Management .......................................................................................................................................... 60

5.7 Security Management ..................................................................................................................................... 60

5.8 CHR ............................................................................................................................................................... 60

5.9 SSL ................................................................................................................................................................. 61

5.10 SSH .............................................................................................................................................................. 62

5.11 Online Help .................................................................................................................................................. 63

6 Reliability ..................................................................................................................................... 64

6.1 Hardware Reliability ...................................................................................................................................... 64

6.1.1 Board Hot Backup ................................................................................................................................. 64

6.1.2 ASIC Technology .................................................................................................................................. 64

6.1.3 Quality Components ............................................................................................................................. 64

6.1.4 Load Sharing ......................................................................................................................................... 65

6.1.5 Power Supply Reliability ...................................................................................................................... 65

6.2 Software Reliability ....................................................................................................................................... 65

6.2.1 Reliability Building at Different Phases ................................................................................................ 65

6.2.2 Error Tolerance ..................................................................................................................................... 65

6.3 Charging Reliability ....................................................................................................................................... 66

7 Technical Specifications ............................................................................................................ 67

7.1 Performance Specifications ............................................................................................................................ 67

7.2 Physical Interfaces ......................................................................................................................................... 67

7.3 Clock Indexes ................................................................................................................................................. 68

7.4 Engineering Specifications ............................................................................................................................. 70

7.4.1 Power Consumption .............................................................................................................................. 70

7.4.2 Dimensions and Weight of Cabinets ..................................................................................................... 71

7.4.3 Environment Requirements ................................................................................................................... 71

7.5 Reliability Specifications ............................................................................................................................... 72

8 Installation.................................................................................................................................... 73

A Acronyms and Abbreviations .................................................................................................. 74


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1 Introduction to the SGSN9810 The SGSN9810 is a core device of the packet domain of the GPRS/UMTS core network.

1.1 Structure of a GPRS/UMTS Network

The current wireless technology is evolving from 2G global system for mobile

communications (GSM) to 3G UMTS by way of 2.5G GPRS. Mobile communication

networks now cover large areas, transfer data in high speed, and can access the Internet. These

networks provide a wide range of multimedia services such as voice, data, and video and can

be accessed anytime and anywhere.

Figure 1-1shows the structure of a GPRS/UMTS network.


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Figure 1-1 Structure of a GPRS/UMTS network

Other PLMN

NodeB

RNC

UMTS UTRAN

RANGSM/GPRS BSS

BSC

CN-CS

MGW/MSC

Server

HLR

SGSN

Firewall

BG

DNS Server

SMS-GMSC

SMS-IWMSC

GMSC

Billing

Center

CG

GGSN/

FA

CN-PS

DNS

ServerWAP

Gateway

AAAServer

Firewall

BTSMS

HA

Core

Network

PSTN,

ISDN

Internet,

Intranet,

etc.

SS7

EIR

MS

As shown in Figure 1-1, a GPRS/UMTS network consists of the following parts:

Mobile station (MS): user equipment capable of originating and receiving calls over the

air interface. To handle data services, the MS establishes a logical link with the packet

switched (PS) domain.

Radio access network (RAN): handles all radio related functions.

Core network-circuit switching (CN-CS): provides circuit services and connects to

external circuit switched networks, such as a public switched telephone network (PSTN).

CN-PS: provides packet data services and connects to external public data networks

(PDNs), such as the Internet.

1.2 Huawei GPRS/UMTS CN-PS Solution The Huawei GPRS/UMTS CN-PS consists of the following main network entities:

Serving GPRS support node (SGSN)

Gateway GPRS support node (GGSN) and foreign agent (FA)

Home agent (HA)

Charging gateway (CG)

Authentication, authorization, accounting (AAA) server

Domain name system (DNS) server

Border gateway (BG)


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The CN-PS offers the means for an MS to access an external PDN. It provides packet data

services and charging services, such as prepaid and postpaid services.

1.2.1 SGSN

The SGSN is a functional entity that provides packet data services. It forwards incoming and

outgoing internet protocol (IP) packets to the mobile stations (MSs) within its service area.

The SGSN provides the following functions:

Routing and forwarding of data packets

Encryption and authentication

Session management

Mobility management

Logical link management

Generation and output of call detail records (CDRs)

1.2.2 GGSN

The GGSN is also a functional entity that provides packet data services. It routes and

encapsulates packet data between the GPRS/UMTS network and an external PDN.

The GGSN provides the following functions:

Interface to an external PDN

The GGSN serves as a gateway for an MS to access the external PDN. For the external

network, the GGSN serves as a router for all equipment in the GPRS/UMTS network.

GPRS/UMTS session management

The GGSN sets up a connection between an MS and the external PDN.

Data routing and forwarding

The GGSN receives data from the MS and then forwards the data to the external PDN. It

also receives data from the external PDN and selects a transport channel in the

GPRS/UMTS network based on the destination address to forward the data to the SGSN.

FA functions

To support mobile Internet Protocol (IP) services, the GGSN is embedded with FA

functions. In this case, the GGSN/FA serves as a gateway of the GPRS/UMTS network

and an FA of the network visited by the MS.

Charging for postpaid services

The GGSN generates and outputs CDRs based on the usage of the external network by

the subscribers.

Call control and service switching functions for prepaid services

For prepaid services, the GGSN serves as a service switching point (SSP) that connects a

mobile network and an intelligent network.

1.2.3 HA

The HA is an entity that is used to support mobile IP access. It is an enhanced router that also

maintains the current location information of the MSs.

The HA has the following function:


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Sending broadcast messages to the MSs so that the MSs know if they are on the home

network.

Handling and replying the registration requests from an MS. Generating mobility binding

records (MBRs) between the MS home address and care-of address.

Agency and forwarding: The HA reports the availability of network prefixes for the MS

home address so that the packets for the MS home address can be routed to the home

network. After encapsulating the packets, the HA tunnels them to the GGSN/FA, and

then the GGSN/FA finally forwards the packets to the MS.

1.2.4 CG

The CG is a new device added to the GPRS/UMTS network. It collects, consolidates, and

preprocesses CDRs generated by the SGSN or the GGSN. It provides an interface to the

billing center.

The CDRs are generated by several network entities when a GPRS or UMTS subscriber visits

the Internet. Each entity may generate several CDRs.

The CG is used to reduce the work load of the billing center by consolidating and

preprocessing the CDRs before sending them to the billing center. With the CG in the network,

the SGSN or the GGSN need not provide the charging interface to the billing center.

1.2.5 AAA Server

The AAA server carries out authentication, authorization and accounting according to the

Remote Authentication Dial-In User Service (RADIUS) protocol.

The AAA server is not specific to the GPRS/UMTS system.

1.2.6 DNS Server

There are two types of DNS server in a GPRS/UMTS network.

The first is the DNS between the GGSN and the external PDN. As an ordinary DNS on the

Internet, this DNS resolves the domain name of the external PDN.

The second is the DNS on the GPRS/UMTS CN. The main functions of the DNS server

include the following:

Resolves the GGSN IP address from the access point name (APN) to set up a connection

between the GGSN and the MS when the MS accesses the external PDN.

Resolves the SGSN IP address from the old routing area code during the inter-SGSN

routing area update.

Resolves the SGSN IP address from the new radio network controller (RNC) identity (ID)

during RNC relocation.

The DNS server is not specific to the GPRS/UMTS system.

1.2.7 BG

The BG is a router. In addition to security functions, it provides a routing function between

the SGSN and the GGSN in different PLMNs.

The BG is not specific to the GPRS/UMTS system.


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The FA and the HA are mandatory for mobile IP access. If the mobile IP access function is not required,

the FA and the HA are not required.

1.3 Overview of the SGSN9810 The SGSN9810 can be used in a GPRS and a UMTS network. It supports up to 3 million

subscribers attached to the network at the same time.

Figure 1-2 shows the SGSN9810 appearance.

Figure 1-2 SGSN9810 appearance

The SGSN9810 provides a wide range of services, functions, protocol interfaces, and physical

interfaces. Built on the mature platform of Huawei products, it is reliable and easy to operate.


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The main functions of the SGSN9810 are listed as follows:

IP bearer services

Mobility management

Security management

Session management

Charging

Quality of service (QoS) and flow management

Static and dynamic routing

Simple network management protocol (SNMP) support

Optional functions include:

Point-to-Point Protocol(PPP) bearer services

Short message service (SMS)

Customized applications for mobile network enhanced logic (CAMEL) 3 intelligent

services

Location service (LCS)

Internet protocol security extensions (IPSec) function

Lawful interception

2 Mbit/s signaling link

Multiple signaling points

Network time protocol (NTP)

Multiple HPLMNs

Iu-FLEX

Mobile virtual network operator (MVNO)

Network assisted cell change (NACC)

IP multimedia subsystem (IMS) bearing

IPv6

RAN sharing in connected mode

UESBI-Iu

Enhanced data rates for GSM evolution (EDGE)

High speed downlink packet access (HSDPA)

Differential service

Handover strategy control

Gb over IP

Signaling transport (SIGTRAN) support

SGSN N+1 backup

One Tunnel

Multi-SIM

APN error correction

The following features are added in the SGSN9810 V800R009 version:

Supporting boards of 750C series

Enhanced multimedia broadcast and multicast service (MBMS)


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Network share in the gateway core network (GWCN)

Security solution

Security Socket Layer (SSL)

Bidirectional forwarding detection (BFD)


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2 Key Benefits The SGSN9810 is a competitive SGSN product offered by Huawei. It has multiple features

and functions.

2.1 Large Capacity and High Integration

If the boards of 750B series are used, the SGSN9810 can support a maximum of 2 million

2.5G and 3G attached subscribes concurrently. A fully configured SGSN9810 system requires

five cabinets for a 2.5G network or three cabinets for a 3G network.

If the boards of 750C series are used, the SGSN9810 can support a maximum of 3 million

2.5G and 3G attached subscribes concurrently. Only two cabinets are required for

configuration of 2 million 2.5G or 3G subscribers, whereas three cabinets are required for

configuration of 3 million subscribers.

2.2 High-Speed Hardware Forwarding

The user plane data of the SGSN9810 is forwarded using hardware. This improves the

processing efficiency and integration of the system.

The hardware supports the traffic at the rate of 900 Mbit/s in a 2.5G system or the traffic at

the rate of 10 Gbit/s in a 3G system.

2.3 Supporting Boards of 750C Series

The SGSN9810 supports the boards of 750C series and thus the system performance and

specification are greatly improved. As a result, the SGSN can meet the present and future

performance requirements.

Table 2-1 lists the hardware comparison between the 750C series and the 750B series.


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Table 2-1 Hardware comparison

Hardware 750C 750B

CPU

750GX(clock frequency

1GHz)

750(clock frequency

500MHz)

Memory 1GB 512MB

FLASH 32M 16M

The maximum number of subscribers supported by the SGSN increases to 3 million. The

number of cabinets for 2 million 2.5G subscribers decreases from five to two and that for 3G

subscribers decreases from three to two.

2.4 Standard Protocol Interfaces

The SGSN9810 supports a variety of 3rd Generation Partnership Project (3GPP) protocol

interfaces to connect to the equipment from different vendors. This makes network

deployment easy for operators.

Figure 2-1 shows the protocol interfaces supported by the SGSN9810.

Figure 2-1 Protocol interfaces supported by the SGSN9810

Gf

Gi

GnIu

Gc

Gp

Gs

MSC/VLR

TE MT UTRAN TEPDN

Gr

HLR

Other PLMN

SGSN

GGSN

Gd

SM- SCSMS-GMSC

SMS-IWMSC

GGSN

EIRSGSN

GnCGF

GaGa

Billing

System

Gb

TE MT BSS

CAMEL GSM-

SCF

Ge

GLMC

Lg


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2.5 Abundant Physical Interfaces

The SGSN9810 provides the following physical interfaces to adapt different networks:

Gn, Gp, Ga, Iu-CS, and Iu-PS interfaces: STM-1, STM-4, 10 Mbit/s, 100 Mbit/s, and

1,000 Mbit/s Ethernet interfaces

Gb, Gd, Ge, Gf, Gr, Gs, and Lg interfaces: E1, T1, STM-1, STM-4, 10 Mbit/s, 100

Mbit/s, and 1,000 Mbit/s Ethernet interfaces

The 1,000 Mbit/s Ethernet interfaces support both optical ports and electrical ports.

2.6 Rich Services and Functions

The SGSN9810 provides a wide range of services and functions. The basic functions include:

IP bearer services

Mobility management

Security management

Session management

Charging

Quality of service (QoS) and flow management

Static and dynamic routing

Simple network management protocol (SNMP) support

Optional functions include:

Point-to-Point Protocol(PPP) bearer services

Short message service (SMS)

Customized applications for mobile network enhanced logic (CAMEL) 3 intelligent

services

Location service (LCS)

Internet protocol security extensions (IPSec) function

Lawful interception

2 Mbit/s signaling link

Multiple signaling points

Network time protocol (NTP)

Multiple HPLMNs

Iu-FLEX

Mobile virtual network operator (MVNO)


IP multimedia subsystem (IMS) bearing

IPv6

RAN sharing in connected mode

UESBI-Iu

Enhanced data rates for GSM evolution (EDGE)

High speed downlink packet access (HSDPA)


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Differential service


Gb over IP

Signaling transport (SIGTRAN) support

Supporting boards of 750C series

Enhanced multimedia broadcast and multicast service (MBMS)

Network share in the gateway core network (GWCN)

Security solution

Security Socket Layer (SSL)

Bidirectional forwarding detection (BFD)

2.7 Accurate Clock System A clock synchronization system is required when the SGSN9810 uses the E1/T1 interface and

the STM-1 or STM-4 optical interface to interconnect with other devices. The clock system of

the SGSN9810, using the advanced digital phase-locked loop and reliable software

phase-locked technology, has the following features:

It provides stratrum-2 (A and B types) and stratum-3 clocks.

The stratum-2 and stratum-3 clocks can be flexibly configured through terminals.

It provides multiple input reference signals, which include 2.048 MHz and 2.048 Mbit/s.

It provides powerful software functions, including display, alarm, O&M functions. The

operators can conveniently control the phase-locked method and the source reference of

the clock through the maintenance console.

It has powerful phase-locked capability and adapts to all kinds of clock transmission. In

case that the clock reference has fault, the clock synchronization system of the

SGSN9810 can work in free running mode and keep synchronization.

2.8 Easy Operation and Maintenance The operation and maintenance (O&M) system of the SGSN9810 has the following features:

Flexible O&M methods

The O&M system can be flexibly built according to the network structure and customer

requirements. Multiple maintenance interfaces are supported, including the interfaces to

the local maintenance terminal (LMT), the Huawei centralized network management

system iManager M2000, and the Simple Network Management Protocol (SNMP) based

on the network management system. Through the Common Object Request Broker

Architecture (CORBA) interface provided by the iManager M2000, more network

management requirements can be fulfilled.

Friendly user interfaces

The SGSN9810 provides O&M interfaces that combines the merits of both man-machine

language (MML) and graphic user interface (GUI).

Powerful signaling tracing


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The SGSN9810 provides functions to trace the messages of designated subscribers and

the signals on the protocol interfaces such as the Iu, Gb, Gs, and Gr. The SGSN9810 also

provides message explanation and filtering.

Software patching in function level

Through online software patching, software errors can be solved without interrupting

services. The SGSN9810 also supports remote patching and version fallback.

2.9 High Reliability

The SGSN9810 is highly reliable because of the following features:

Backup of important data

The SGSN9810 automatically backs up important data, such as the configuration data,

performance data, and operation logs.

Operation security management

Different management privileges are assigned to different users. During the user login,

the SGSN9810 checks the user identity. After the user login, the SGSN9810 maintains

the complete operation to ensure system security.

CG redirection and bill buffering

When the active CG or the link to the active CG fails, the SGSN9810 sends the bills to

the standby CG. If the standby CG is also faulty, the SGSN9810 stores the bills in its

buffer.

Hardware redundancy design

All critical boards are configured in the 1+1 backup or N+1 redundancy to ensure the

high reliability of the system.

Fault Avoidance

The SGSN9810 provides protection mechanisms to avoid the following system faults:

System power off

Maloperation on system power switch

Lightning surge on the system power

High voltage and low voltage

Short circuit of power supply

Lightning surge on E1/T1 links

Current surge and high voltage on the power supply and interfaces

System overload control

In the case of center processing unit (CPU) overload or resource congestion, the

SGSN9810 adjusts the traffic smoothly to avoid system down.

Board locking and system shutdown

This function ensures that a service can slowly exit from a board or the system if

required without interrupting other services.


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3 System Structure The system structure of the SGSN9810 includes hardware structure, software structure, and

logical structure.

3.1 Hardware Configuration

The SGSN9810 hardware consists of the cabinet, subrack, and board.

Cabinet

The SGSN9810 uses Huawei's N68-22 cabinet. This cabinet is a standard 19-inch one

and is in compliance with the IEC297. The SGSN9810 requires 1~6 cabinets.

Subrack

The SGSN9810 uses the standard 19-inch subrack, which is also called the PSM subrack.

A maximum of four PSM subracks can be configured in each cabinet. Each PSM subrack

contains 21 slots. Boards are inserted in front and rear of the backplane.

According to the board configuration, the PSM subrack is classified into three types,

namely, switching subrack, basic subrack and extension subrack.

Board

According to the position, the boards of the SGSN9810 are classified into the front card,

back card, and pinch board. The number of boards depends on the capacity of the

system.

3.1.1 Cabinet Configuration

Figure 3-1 shows an example of the cabinet configuration of the SGSN9810.


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Figure 3-1 Hardware configuration of the SGSN9810

PSM Subrack

Air Deflector

Air Deflector

Air Deflector

Dummy Panel

Power Distribution Box

PSM Subrack

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3.1.2 Switching Subrack

The switching subrack refers to the PSM subrack that is configured with the UFCU boards.

Only one switching subrack is required.

The fundamental function of the switching subrack is to forward data among the PSM

subracks.

Figure 3-2 shows the boards in the switching subrack.

Figure 3-2 Boards in the switching subrack

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In Figure 3-2, the boards in the upper half of the subrack are inserted from the rear, and the boards in the

lower half are inserted from the front.

Table 3-1 briefs the functions of the boards in the switching subrack.

Table 3-1 Functions of the boards in the switching subrack

Board Function

Subrack control unit (URCU) Bus mediation

Board configuration

Maintains boards

Controls the PSM subrack

PSM back interface unit (UBIU) Provides optical ports, network ports, and serial ports

for the URCU.


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Board Function

Auxiliary control unit (UACU) Works with the URCU board to control the two

buses in the PSM subrack.

Controls hot swap of the service processing boards

in the PSM subrack.

Controls the switchover of URCU boards.

PSM alarm unit (UALU) Monitors the power module of the PSM subrack.

Monitors back board status.

Monitors subrack temperature.

PSM power module (UPWR) Provides power supply for the PSM subrack.

Frame connect unit (UFCU) Forwards service subrack data.

Packet interface unit (UPIU) Receives and forwards Asynchronous Transfer Mode

(ATM) data and Ethernet link data.

GTP forwarding unit (UGFU) Forwards GPRS Tunneling Protocol (GTP) data.

Charging detail record unit

(UCDR)

Collects, encodes, and sends CDRs, and stores CDRs

in the buffer.

Back storage unit (UBSU) Provides external interfaces and a hard disk for the

UCDR.

GTP processing unit (UGTP) Forwards GPRS tunneling protocol for control plane

(GTP-C) signaling messages and implements the

charging function of GPRS tunneling protocol for

user plane(GTP-U) data

For NTP, DNS client and IPSec functions

3.1.3 Basic Subrack

The basic subrack refers to the PSM subrack that is configured with the UOMU boards. Only

one basic subrack is required.

The fundamental function of the basic subrack is to provide operation and maintenance to the

system, including operator management, configuration management, alarm management,

tracing management, and performance measurement.

Figure 3-3 to Figure 3-4 show the boards in the basic subrack for 2.5G network and 3G

network.


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Figure 3-3 Boards in the basic subrack (2.5G network)

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Figure 3-4 Boards in the basic subrack

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Table 3-2 briefs the functions of the boards in the basic subrack.


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Table 3-2 Functions of the boards in the basic subrack

Board Function

Clock unit (UCKI) Provides operation clock for the SGSN9810

Packet service signal

processing unit (USPU)

For application layer protocols such as Session Management

(SM), Mobility Management (MM), and Customized

Applications for Mobile network Enhanced Logic (CAMEL)

Processes Signaling System No.7 (SS7) L3 messages

Gb interface unit (UGBI) For Gb interface protocols

Iu_PS control processing

unit (UICP)

For Iu-PS control plane protocols

Packet service O&M unit

(UOMU)

For the operation and maintenance functions of the

SGSN9810

PSM flashdisk storage unit

(UFSU)

Provides external interfaces and a hard disk for the UOMU

E1 processing interface

unit (UEPI)

Provides external E1 interfaces for the Packet Service Signal

Processing Unit (USPU) or Gb Interface Unit (UGBI)

T1 processing interface

unit (UTPI)

Provides external T1 interfaces for the USPU or UGBI

LAN switch card (ULAN) Serves as a local area network (LAN) switch to provide a

connection between the UOMU and URCU

SIGTRAN process unit

(USIG)

For the MTP3 User Adaptation Layer (M3UA) and Stream

Control Transmission Protocol (SCTP) of the SIGTRAN

Lawful interception

processing unit (ULIP)

Provides the following interfaces for lawful interception:

The interfaces for receiving interception requests

The interfaces for collecting and transmitting interception

messages

Lawful Interception

Enhanced Processing

Unit(ULEP)

For Lawful Interception Enhanced Processing Unit

3.1.4 Extended Subrack

The extended subracks process services. An extended subrack can be configured to process

2.5G services, 3G services, or both.

Figure 3-5 shows the boards in a extended subrack for both 2.5G and 3G services. For the

description of these boards, see Table 3-2.


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Figure 3-5 Boards in the extended subrack (2.5/3G)

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3.2 Software Structure

The SGSN9810 is a distributed system where functions are distributed in and implemented by

different boards. Each board has its own software that consists of a platform module and

function-specific modules.

Figure 3-6 shows the structure of the SGSN9810 software.


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Figure 3-6 Structure of the SGSN9810 software

Platform management sub-system (OS and DOPRA)

O&M sub-system

Device management

sub-system

Database

management sub-

systemUGFU UFCU

USPU UCDR

ULIP UGTP

UICP

Service feature plane

Data forwarding plane System management plane

Data service plane

UGBI

The data service plane consists of a platform management subsystem, that is, the operating

system (OS) and the Distributed Object-oriented Programmable Real-time Architecture

(DOPRA). This plane is the basis of other software modules.

The system management plane manages the whole SGSN9810 system. It consists of

three subsystems:

O&M

Device management

Database management

The system management plane and the data service plane are the basic modules in each

board software.

The data forwarding plane consists of the UGFU and UFCU. It carries out the switching,

routing, and forwarding of ATM and IP packets.

The service plane processes services. It consists of the USPU, UCDR, ULIP, UGBI,

UGTP, and UICP.

3.3 Logical Structure The SGSN9810 has twelve logical functional subsystems, as shown in Figure 3-7.


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Figure 3-7 Logical structure of the SGSN9810

Switching

subsystem

PS transfer

subsystem

Gb interface

processing

subsystem

Signaling

processing

subsystem

Clock subsystem

Operation and

maintenance

subsystem

Iu interface

control

plane

processing

subsystem

GTP

control

plane

processing

subsystem

Lawful

interception

subsystem

Charging

subsystem

GGSN

NTP

DNS

RNC

BITS

ATM

IP HLR

E1/T1

LMT

M2000

IP

PCU

This section briefs the functions of these subsystems and the hardware that implements the

functions.

3.3.2 Switching Subsystem

Function: Packets switching and interconnection between subracks

Hardware: URCU, UPIU, and UFCU

3.3.3 PS Transfer Subsystem

Function: routing and forwarding of GTP user data; Gn/Gp external interfaces

Hardware: UGFU and UPIU

3.3.4 Gb Interface Processing Subsystem

Function: implementing L1, Network Service (NS) and Base Station Subsystem GPRS

Protocol (BSSGP) layer protocols of the Gb interface

Hardware: UGBI and E1 processing interface unit (UEPI) or T1 processing interface unit

(UTPI)

The UEPI or UTPI is not required when the Gb over IP function is enabled.


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3.3.5 Signaling Processing Subsystem

Function: implementing L1, L2, and L3 of the Message Transfer Part (MTP), SIGTRAN,

Signaling Connection and Control Part (SCCP), Mobile Application Part (MAP), MM, SM,

CAMEL, and Location Service (LCS) protocols.

Hardware: USPU, SIGTRAN process unit (USIG), and UEPI/UTPI

3.3.6 Lawful Interception Subsystem

Function: X1-1/X2/X3 interfaces, collection and transmission of lawful interception data

Hardware: ULIP and ULEP

3.3.7 Charging Subsystem

Function: collection, storage, coding, and transmission or CDR data

Hardware: UCDR

3.3.8 Iu Interface Control Plane Processing Subsystem

Function: implementing the control plane Signaling ATM Adaptation Layer (SAAL), MTP3B,

SCCP, and Radio Access Network Application Part (RANAP) protocols of the Iu interface

Hardware: UICP

3.3.9 GTP Control Plane Processing Subsystem

Function: implementing the GTP-C protocol and IPSec encryption of GTP-C signaling

messages

Hardware: UGTP

3.3.10 Operation and Maintenance Subsystem

Function: external O&M interfaces, system O&M, configuration management, performance

management, alarm management, and operation logs

Hardware: UOMU and Flash Storage Unit (UFSU)

3.3.11 Clock Subsystem

Function: providing stratum-2 or stratum-3 clock (secondary clock) for the system

Hardware: clock unit (UCKI)


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4 Services and Functions The SGSN9810 offers abundant services and functions, and meets the requirements of

multiple networks and operations.

4.1 Services

The SGSN9810 provides a full range of services to meet the demands of various subscribers.

This section introduces the following services:

IP/PPP bearer services

Short message services (SMS)

Location services

CAMEL Phase 3 services

Lawful interception

4.1.1 IP/PPP Bearer Services

The GPRS/UMTS network supports protocols such as the IPv4, IPv6, and Point-to-Point

Protocol (PPP).

The IP/PPP packets can travel transparently on the GPRS/UMTS network. Subscribers can

use various IP and PPP applications, such as web browsing, File Transfer Protocol (FTP), and

Virtual Private Network (VPN), through the GPRS/UMTS network.

Figure 4-1 shows the structure of the protocol stacks that provide IP and PPP bearer services

in a 3G network.


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Figure 4-1 IP/PPP bearer protocols (3G)

3G-SGSNUTRANMSIu-PS Gn Gi

3G-GGSNUu

L1

RLC

PDCP

MAC

Application

E.g.,

IP,PPP

L1

RLC

PDCP

MAC

L1

UDP/IP

GTP-U

L2

Relay Relay

L1

UDP/IP

L2

GTP-U

E.g.,

IP,PPP

L1

UDP/IP

GTP-U

L2

L1

UDP/IP

GTP-U

L2

Figure 4-2 shows the structure of the protocol stacks that provide IP and PPP bearer services

in a 2.5 network.

Figure 4-2 IP/PPP bearer protocols (2.5G)

L2

Application

IP

SNDCP

LLC

RLC

MAC

GSM RF

LLC

BSSGP

L1bis L1

IP

L2

L1

IP

GTP-U

IP

Um Gb GnMS BSS SGSN GGSN

NetworkService

UDPUDP

MAC

GSM RF L1bis

NetworkService

RLC BSSGP

Relay

Relay

SNDCP GTP-U

Gi

4.1.2 Short Message Services

Short message services (SMS) include normal SMS and enhanced SMS.

Normal SMS allows for the messages that contain up to 160 bytes (including control

bytes).

Enhanced SMS allows for formats in a message in addition to texts. These formats may

include objects such as animations and images. A short message can contain more than

one object.

SMS consists of two types of basic service:

mobile terminated short message (SM-MT)


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SM-MT is the capability that enables the GSM/UMTS system to deliver the short

messages submitted by the short message center (SMC) to the specified MS. At the same

time, result (success or failure) of the message delivery is provided. In the case of

delivery failure, a repeat strategy is implemented.

mobile originated short message (SM-MO)

SM-MO is the capability that enables the GSM/UMTS system, with the help of the SMC,

to forward the short messages submitted by an MS to the short message entity (SME). At

the same time, result (success or failure) of the message submission is provided.

Figure 4-3 shows the basic network structure of the SMS.

Figure 4-3 Basic network structure of the SMS

No.7

MSC

SGSN

RNC

BSC/PCU

NodeB

BTS

SMC

The GPRS-attached MSs or the GPRS-attached but international mobile subscriber identity

(IMSI) -unattached MSs submit and receive short messages through the PS domain.

The GPRS-attached and IMSI-attached MSs submit and receive short messages through either

the PS domain or the circuit switching (CS) domain. If the messages are submitted through

the CS domain, the SGSN can be used for paging.

4.1.3 Location Services

The LCS enables the GPRS/UMTS network to locate an MS in the network and provide the

geographic location of the MS after data conversion and calculation.

The location data can be applied internally or externally.

For internal purposes, it can be used by the operator to fulfill certain requirements such

as location-based charging.

For external purposes, it can be used by the network to provide various location-based

services such as on-demand services, customized messages, and customized services.

Figure 4-4 shows the network of the LCS.


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Figure 4-4 Network of the LCS

GMLC

2G-

MSC

3G-

SGSN

2G-

SGSN

MSC

server

gsmSCF

LgGb

A

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Lc

Le

Iu

HSS

Iu

Iu

Lg

Um

Uu

LgLh

External LCSClient

Iu

LIF-MLP

OSA APIProprietary

OSA SCS

Proprietary

UE

GERAN

UTRAN

The LCS network includes the following major entities:

LCS client

The LCS client originates location requests. Corresponding to the application of LCS,

the LCS client includes the internal LCS client and the external LCS client.

GMLC

The Gateway mobile location center (GMLC) provides an path for the LCS client to

access the public land mobile network (PLMN).

After receiving the location request from the LCS client, the GMLC requests routing

data from the home location register (HLR) or the home subscriber server (HSS).

At the same time, the GMLC forwards the request to the visited mobile switching center

(VMSC), SGSN, or MSC server after authentication.

The location result is also forwarded through the GMLC.

MSC, MSC server, and SGSN

These entities connect to the GMLC through the Lg interface. They receive, process, and

respond to the location request.

4.1.4 CAMEL Phase 3 Services

The CAMEL enables operators to provide subscribers special services such as the prepaid

service.

Figure 4-5 shows how the SGSN supports CAMEL Phase 3 services in a GPRS/UMTS

network.


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Figure 4-5 SGSN support to CAMEL Phase 3 services

MS

Visiting NetworkInterrogating Network

Home Network

CAP

Home/Interrogating/Visiting Network

MAP

HLR gsmSCF

SGSN

gprsSSF

As shown in the figure, the SGSN integrates the GPRS service switching function (gprsSSF)

and provide CAMEL Phase 3 services under the control of the GSM service control function

(gsmSCF).

4.1.5 Lawful Interception

The lawful interception is a capability of the mobile network to provide the content of

communication (CC) of MSs and intercept related information (IRI) to a law enforcement

agency (LEA).

Figure 4-6 shows the procedure of lawful interception.

Figure 4-6 Procedure of lawful interception

Network node

ADMF

DF2

DF3

X1-1

X2

X3

LEA

Intercept request

IRI

CC

Intercept reques

The procedure for lawful interception is as follows:

1. The LEA sends an intercept request to the administration function (ADMF) entity.


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2. The ADMF forwards the request to the network node.

3. The network node starts intercepting the CC of the target subscriber.

4. The network node forwards the IRI and CC of the target subscriber to the LEA through the delivery function (DF).

As shown in Figure 4-6, the logical entities relating to the interception in a mobile network

include the network nodes (SGSN and GGSN), ADMF, and DF.

The ADMF controls the interception while the DF collects and forwards the IRI and the CC.

Relevant interfaces include the X1-1 interface, X2 interface, and X3 interface.

X1-1 interface is between the ADMF and the network node.

It transfers interception-related management messages from the ADMF to the network

node.

X2 interface is between the DF2 and the network node.

It transfers the IRI.

X3 interface is between the DF3 and the network node.

It transfers the CC.

4.2 Functions The SGSN9810 provides powerful functions to meet the requirements of network operators.

This section introduces the following functions:

Mobility management

Session management

Routing

IPv6 support

IPSec and logical link control (LLC) encryption

Charging

QoS

Iu-FLEX/Gb-FLEX

RAN sharing in connected state

MVNO

UESBI-Iu

Multi-SPs and 2 Mbit/s signaling link

NTP client functions


SIGTRAN support

Gb over IP

Differential services



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4.2.1 Mobility Management

The MM function is used to control an MS access to the GPRS/UMTS network and trace the

location of the MS, such as the routing area (RA) and SGSN information of the MS.

The MM function is fulfilled mainly by attach, detach, and route updating procedures. It

ensures that the location of the MS is updated while the MS is moving, such as the updating

of the current SGSN information in the HLR.

4.2.2 Session Management

The SM carries out Packet Data Protocol (PDP) context management.

The PDP context is a group of messages related to the PDP. The network elements, such as

the MS, SGSN, and GGSN, send and manage the PDP data based on the PDP context.

Session management includes PDP context activation, modification, and deactivation.

Before the MS transmits data, it must activate the PDP context. During the data transfer, the

PDP context can be modified based on the requirement of the QoS. After data transfer, the

PDP context must be deactivated to release network resources.

4.2.3 Routing

The SGSN9810 supports various routing protocols to ensure the flexible networking using the

Gn/Gp interface.

Static Routing

Static routes are manually configured by the administrator. Users can configure static routes

to set up a connected network.

In a simple network, static routes can be used to ensure the stable operation of the router. Well

configured static routes can improve the performance of the network and ensure the

bandwidth for critical applications.

When the network is faulty, the static route cannot adjust itself and requires reconfiguration.

OSPF

The open shortest path first (OSPF) is an interior gateway protocol (IGP) developed by the

internet engineering task force (IETF). The OSPF is implemented based on link status.

The OSPF has the following features:

Large scope

The OSPF can be used for the networks of various sizes and support up to hundreds of

routers.

Fast convergence

After the network topology is changed, an update message is sent at once to synchronize

the data in the autonomous system.

Loop free

The OSPF uses the shortest path algorithm to determine a route based on the link status.

The algorithm ensures that the route is loop free.

Area division


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The network of the autonomous system can be divided into several areas so that the

network is easy to manage. The route information transferred between the areas is

abstracted, so the required bandwidth is further reduced.

Equivalent route

Multiple equivalent routes to the same destination are supported.

Hierarchical routes

Routes are classified into four categories. They are (from high to low priority) intra-area

routes, inter-area routes, class-1 external routes, and class-2 external routes.

RIP II

The routing information protocol (RIP) is a simple IGP that is used in small networks.

The RIP is widely used in networks thanks to the following features:

Easy to implement

Little protocol overhead which makes almost no impact on the network performance

Easy to configure and maintain compared with the OSPF and intermediate

system-to-intermediate system (IS-IS) intra-domain routing information exchange

protocol

4.2.4 IPv6 Support

The rapid development of Internet services requires more and more IP addresses, which are

beyond the capability of the IPv4 protocol. As a result, the IPv6 is developed to address this

problem.

Compared with the IPv4, the IPv6 boasts of the following advantages:

Extended IP addresses

IP addresses are extended from 32 bits in the IPv4 to 128 bits in the IPv6, indicating that

the address resources are abundant. This address structure also improves routing

efficiency.

Simplified packet header format

The packet header is simplified to minimize the processing by routers; thus it improves

routing efficiency.

Enhanced support for extension and option capability

The IPv6 satisfies additional requirements without affecting the routing of normal

packets or special packets.

Flow identity

The flow identity is used to improve the processing of packet flows, especially real-time

applications.

Identity verification and security

Enhanced identity verification and security measures make IPv6 especially suitable for

sensitive commercial information.

The data plane and the signaling plane of the SGSN9810 Gn/Gp interface supports both IPv4

and IPv6 addresses.

Operators can choose one of the following four operational modes:

Supporting only IPv6 addresses


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Preferring IPv6 addresses

Supporting only IPv4 addresses

Preferring IPv4 addresses

4.2.5 IPSec and LLC Encryption

To ensure the security of data transfer, the SGSN9810 supports IPSec encryption for the

signaling massages on the Gn/Gp interface and data encryption for the Gb interface messages.

IPSec

The SGSN9810 encrypts the Gn/Gp signaling messages by using the IP Security (IPSec)

protocols.

The IPSec is a series of protocols developed by the IETF to ensure the security of the data that

is transmitted on the Internet.

Through encryption and data source verification on the IP layer, the privacy and integrity of

data packets can be guaranteed when the packets are transferred on the Internet.

LLC Encryption

In a 2.5G system, the encryption on the Logical Link Control (LLC) layer between the MS

and SGSN is the traditional stream encryption using the GPRS-A5 algorithm.

The data to be encrypted includes the information field and the authentication field carried by

LLC frames.

4.2.6 Charging

Figure 4-7 shows the GPRS/UMTS charging network.

The SGSN and GGSN collect the charging information relating to radio network resource

usage and CN resource usage by each MS. Then they generate CDRs and send them to the

CG through the Ga interface.

Figure 4-7 GPRS/UMTS charging network

GGSN

CG Billing Centre

SGSN

Internet

BSC/PCU

RNC

BTS

NodeB

Gn

GaGa


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The SGSN9810 can generate the following seven CDRs:

SGSN generated - CDR(S-CDR): records the information related to certain PDP contexts

in the SGSN

Mobility management generated - CDR(M-CDR): records the mobility-related

information

SGSN delivered short message mobile originated - CDR(S-SMO-CDR): records the

information related to SM-MO services

SGSN delivered short message mobile terminated - CDR(S-SMT-CDR): records the

information related to SM-MT services

Mobile terminated LCS CDR(LCS-MT-CDR): records the information related to

mobile-terminated location services

Mobile originated LCS CDR(LCS-MO-CDR): records the information related to

mobile-originated location services

Network induced LCS CDR(LCS-NI-CDR): records the information related to

network-initiated location services

4.2.7 QoS

The 3GPP R5 specifications define four classes of QoS, as described in Table 4-1.

Table 4-1 UMTS QoS classes

Traffic Class Conversational Class

Streaming Class

Interactive Class

Background Class

Characteristics Preserve time

relation between

entities of the

stream

Conversational

pattern (high

quality, low delay)

Preserve time

relation

between

entities of the

stream

Request

response

pattern

Destination

does not expect

the data within

a certain time.

Example of the

application

Voice Video Web

browsing

Download or

sending

e-mails

The SGSN9810 support the four QoS classes by using the following mechanisms:

Access control

When the subscriber activates the PDP context, the SGSN negotiates the QoS with the

MS.

If the negotiation fails, the SGSN denies the MS access.

QoS queue management

The data packets are assigned to QoS queues based on the QoS class. The SGSN

dispatch the queues using the class-based weighted fair queuing (CBWFQ) algorithm to

decide the order of transmission.


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In case of congestion, the SGSN decides the discard criteria of packets by using the

weighted random early detection (WRED) algorithm. This ensures the transmission

reliability of the high-priority data.

Differentiated Services (DiffServ)

DiffServ is an IP QoS model that is used in a backbone network to meet various service

requirements.

In the DiffServ system, the network node determines the per-hop behavior (PHB)

according to the differentiated services code point (DSCP) in the IP header.

The SGSN supports the following PHBs: expedited forwarding (EF), assured forwarding

(AF), and best-effort (BE). It also supports the three discard priorities of the AF.

QoS mapping

QoS mapping converts the QoS attributes of different bearer protocols.

It includes the mapping between the 3GPP QoS and DSCP, between the DSCP and the

ATM QoS, and between the R97/98 and the R99 QoS attributes.

CAR and Remarking

If the actual data packet stream requires the QoS higher than the requested one, the

SGSN handles the packets based on the committed access rate (CAR) and discard the

extra packets.

SGSN can also carry out a Remarking process to lower the QoS of the data packet.

4.2.8 Iu-FLEX/Gb-FLEX

The Iu-FLEX/Gb-FLEX function allows one RAN or base station subsystem (BSS) to

connect to several CN nodes in the same domain.

The Iu-FLEX/Gb-FLEX function introduces the concept of pool areas. Similar to an MSC or

SGSN service area, a pool area contains one or more RAN/BSS service areas, but it is served

by multiple CN nodes (MSC or SGSN) at the same time. See Figure 4-8 for details.


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Figure 4-8 Example of pool area configuration

Area 1

RANnode

Area 5

RANnode

Area 6

RANnode

Area 7

RANnode

Area 8

RANnode

Area 2

RANnode

Area 3

RANnode

Area 4

RANnode

PS pool-area 2

PS pool-area 1

CS pool-area 2

CS pool-

area 1

MSC 3MSC 2

MSC 1

MSC 6MSC 5

MSC 4

SGSN 6

SGSN 2

SGSN 1

SGSN 5SGSN 4

SGSN 3

MSC 7

The Iu-FLEX/Gb-FLEX function expands the service areas of each CN node and reduces the

effort required for the inter-node update, handover, relocation, and HLR update.

This function also improves system availability. If one CN node in the pool area is faulty,

other nodes can provide services.

4.2.9 RAN Sharing in Connected State

Figure 4-9 shows the scenario of RAN sharing in connected state. In this scenario, the

networks of operator A and operator B together cover a large area in which an overlap area

exists. The RANs of operator A and operator B are connected through the CNs, so the user

equipment (UE) of operator B can operate in the network of operator A. In the overlap area,

the UE of operator B must access the RAN of operator B rather than the network of operator

A.


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Figure 4-9 RAN sharing between operators

Core Network A Core Network B

Radio Access Network

BRadio Access Network

A

To solve the problem mentioned above, the R5 protocol introduces the concept of shared

network area (SNA). An SNA corresponds to one or more location areas (Las) that control the

UE access.

The SNA is configured in the CN. The CN provides an SNA ID list that contains the SNAs

that the UE can access.

If the location area (LA) is in the SNA that the UE can access, the RAN allows the UE to

access the network. Otherwise, it denies the UE.

4.2.10 MVNO

A mobile virtual network operator (MVNO) uses the resources authorized by a mobile

network operator (MNO) to provide services and maintain the authorized resources.

The MVNO function enables more operators to invest on and share the network to lower the

investment risk and maximize resource usage.

The network resources authorized by the MNO can be the RAN, part of the CN, or the whole

CN. Figure 4-10 shows the example of partial CN sharing. In the example, the MNO shares

its SGSN with the MVNO, and the MVNO owns the GGSN, CG, and other network

equipment.


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Figure 4-10 MVNO network

GGSN

CG Billing Centre

SGSN

Internet

BSC/PCU

RNC

BTS

NodeB

GGSNCG

MVNO

MNO

4.2.11 UESBI-Iu

The UEs may have potential standard or manufacture defects. The RAN needs UE-specific

behavior information (UESBI) regarding 3GPP features to help the lower layer process the

local 3GPP features.

The UESBI corresponds to the following two sets of information:

UESBI-Uu: The messages are sent by the UE to the RAN through the messages defined

by the Radio Resource Control (RCC) protocol.

UESBI-Iu: The message is obtained by the CN from the International Mobile Station

Equipment Identity and Software Version number (IMEISV) of the UE. The CN then

sends the messages to the RAN through the Iu interface.

Figure 4-11 shows the network structure of the UESBI-Iu.


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Figure 4-11 Network structure of the UESBIIu

IMEISVUE

SGSNSRNCNodeB

1Attach and IMEISVinterrogation

IMEISVStorage

2

UESBI

3

MSC

When the UE accesses the VLR or SGSN, the IMEISV from the UE is saved in the VLR or

SGSN. When an Iu connection (such as CS voice session and PS data transfer) is set up later,

the IMEISV is read from the MM context of the VLR or SGSN to obtain the UESBI. The

UESBI is then sent to the serving RNC (SRNC).

4.2.12 Multi-SPs and 2 Mbit/s Signaling Links

Ever increasing equipment capacity boosts the signaling flow between signaling points. The

16 signaling links specified by the protocol are far from enough to fulfill actual networking

requirements.

To solve this problem, the SGSN9810 provides the multiple signaling points (multi-SPs)

function and 2 Mbit/s signaling links.

Multi-SPs Function

The SGSN9810 entity can be divided virtually into several logical signaling points. Thus the

restriction of 16 signaling links between two signaling points is broken.

As shown in Figure 4-12, from the aspect of other signaling points, the SGSN9810 contains

multiple signaling points, and there are 16 links for each signaling point.


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Figure 4-12 Multiple signaling points supported by the SGSN9810

SP SP

Single SP

Multi SPs

Link

Link Set

LinkLink Set

LinkLink Set

SP

SP2

SP1

2 Mbit/s Signaling Links

A 2 Mbit/s signaling link binds multiple timeslots into an E1/T1 link to increase the

throughput of a link.

4.2.13 NTP Client Functions

The network time protocol (NTP) is a TCP/IP protocol that is used to issue accurate time in

the entire IP network. Its transmission is based on the UDP. The RFC1305 specifies the

algorithm used by the NTP to ensure the accuracy of clock synchronization. Theoretically, the

accuracy can be 1 ns.

Figure 4-13 shows the synchronous networking mode of the NTP. The NTP time

synchronization can be realized provided that the network from the device or the lower server

to the upper server is available. The time accuracy offered by the NTP synchronous

networking mode is of ms. This can be applied in alarm, log, and performance measurement.


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Figure 4-13 NTP synchronous networking mode

NTP Server

NTP Server NTP Server

NTP Server NTP Server

NTP Server

NTP ClientNTP Client

Class 0

Class 1

Class 2

The NTP services can be classified into three types when the NTP synchronous networking

mode is used.

NTP server of the highest layer: It refers to the NTP server of stratum 0, which offers

time synchronization service to the lower layer.

NTP server of the intermediate layer: Stratum 1 and stratum 2 obtain time from the time

server of upper layer, and offer time synchronization to the lower layer.

NTP client: It only obtains time. Time synchronization service is not offered.

When the SGSN9810 is configured as the NTP client, it obtains time from the NTP server of

upper layer and synchronizes time. Figure 4-14 shows the networ

railway operational communication solution gsm-r sgsn9810 product description1.0(20090330)

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