3g mobile core network

Introduction to Mobile Cellular NetworksPart I: 3G Mobile Core Network in a Nutshell

VU 389.168Advanced Wireless Communications 1

14.10.2013

2389.168 Advanced Wireless Communications 1

Outline of this Lecture Cellular Mobile Networks: (14.10.2013 - 18.11.2013 / Svoboda)

PS-Core Network (GSM, UMTS) PS-Core Network (LTE, LTE-A) Link Error Analysis and Prediction Measurement and Analysis in mobile Networks

Video in Error Prone Environments (25.11.2013 - 16.12.2013 / Rupp) Principles of Video Encoding Error Detection and Concealment Cross Layer Error Resilience in Video Streaming End to End Video Quality Estimation

Traffic in Mobile Networks (13.01.2014 - 27.01.2014 / Svoboda) Detection of Anomalies in a Network Traffic Flows Traffic Modeling in High-Delay Environments


What this lecture is about Video and Multimedia Transmissions over Cellular

Networks Cellular networks (GSM, UMTS, LTE, LTE-A) Packet switched data transmission Video and other services Cross layer approaches

How to measure/analyze/optimize such services

What you should already know Cellular network (basics) UDP, TCP, IP, eMail / HTTP / streaming (basics)

HTTP HyperText Transport ProtocolIP Internet ProtocolTCP Transport Control ProtocolUDP User Datagram Protocol


The Problem Today data services generate more traffic than voice

Radio link is expensive and limit resource

Data services consume more bandwidth at less revenue QoS definition is problematic

Looking for ways to offer constant QoS at reduced data-rate/bandwidth needs Measurement and analysis of existing traffic Link layer modeling from IP point of view Cross layer optimization (video streaming, ) Traffic modeling with respect to cellular networks

QoS Quality of Service


Possible Solutions Communication system are split into independent atomic

layers Open Systems Interconnection (OSI) reference model

Data transmission Two consecutive layers: payload Two corresponding layers: payload, signaling

Processing information stays within the layer


Some (more) Motivation Today every layer is optimized to a large extend

e.g.: receivers fight for < 1dB improvement

Idea: use processing information from multiple layers Soften the boundaries between two layers e.g.: variable priority for video streaming and web browsing

Optimization problems get much harder Optimum often hard to prove

X X XTB Transport Block


Outline of today's talk Evolution of mobile cellular networks

3G Network Hierarchy

3G core network Elements

3G protocol Hierarchy

Simple procedures in mobile cellular networks

Journey of a packet through the network


Network Architecture Hierarchical ordering of functional groups Functional structures/groups

Defined by functions / procedures Consist of one or several physical elements

Interfaces (reference points) Points allowing for interconnection between functional structures

IP Internet ProtocolMS Mobile StationUE User Equipment


Network Architecture: Example GSM/GPRS GSM (2G): digital circuit switched network for voice

All services reserve the same fixed bandwidth Charging on time unit basis Data rate: 9.6 kbit/s

GPRS (2.5G): extension for packet switched traffic Packet switched (PS) domain is introduced PS oriented shared data channels at the radio link Data rate: ~114 kbit/s

GSM Global System for Mobile Communication

GPRS General Packet Radio ServiceSIM Subscriber Identity ModuleBTS Base Transceiver StationBSC Base Station ControllerPCU Packet Control UnitMSC Mobile Switching CenterSGSN Serving GPRS Support NodeGGSN Gateway SGSN

10


Network Architecture: Example UMTS/HSPA UMTS (3G):

The UTRAN (UMTS RAN) is added to existing 2.5G networks WCDMA, soft handover, QoS,

Link speed is variable but fixed to certain values. Data rate: 384 kbit/s

HSPA (3.5G): Real packet switched radio bearers (similar to GPRS) No more soft handover Data rate: 7.2 Mbit/s

PS Packet SwitchedUMTS Universal Mobile

Telecommunications SystemHSPA High Speed Packet AccessUSIM Universal SIMNodeB NodeBRNC Radio Network Controller

11


Evolution of (digital) Cellular Networks GSM (2G) GPRS (2.5G)

No changes on the radio interface Large changes in RAN Birth of the PS-Core (!)

GPRS (2.5G) UMTS (3G) Large changes in the RAN

The first network designed for PS traffic

Small changes in the Core

UMTS R99 (3G) HSPA (3.5G) Changes in the radio interface No changes in the Core

RAN Radio Access NetworkPS Packet SwitchedGSM Global System for Mobile

CommunicationGPRS General Packet Radio ServiceUMTS Universal Mobile

Telecommunications SystemHSPA High Speed Packet Access

12


The Complete Picture of a 3G Core Network

2G

3G

13


Summary of (digital) Cellular Networks Main Components of a Cellular Network

User equipment Radio access network Core network

GSM: digital and circuit switched

GPRS: adds the CN PS-domain to GSM

UMTS: pseudo PS radio links, RAN UTRAN

HSPA: PS radio links for UMTS, no soft handover

RAN Radio Access NetworkPS Packet SwitchedGSM Global System for Mobile

CommunicationGPRS General Packet Radio ServiceUMTS Universal Mobile

Telecommunications SystemHSPA High Speed Packet Access

14


The Core Network Elements

15


The Mobile Switching Center (MSC) Routing grid for Circuit Switched (CS) services Main functions:

Interconnect of CS services Mobility Management Localization Signaling

Protocols: PCM30 / PCM30 (not AMR!)

Interfaces: IuCS / SS7(E)

16


The Serving GPRS Support Node Counter part to the MSC in the Packet Switched (PS)

domain Main functions:

Security / authentication Mobility Management (MM): cell update, etc. Handling of data sessions (routing) Caching user subscriber data

Protocols: GTP / GTP (not terminated in SGSN!)

Interfaces: IuPS / Gn RNC

SGSN GGSNIu-ps Gn

HLR

Gr

SGSN

Gn

17


The Gateway GPRS Supporting Node (GGSN) The Gatekeeper to the outer Territories GGSN hides the GPRS infrastructure Main functions:

Handling of the PDP Context Building a bridge to the external networks eg. Internet Converting the IP packets to GTP protocol Billing, QoS,

Protocols: GTP / IP

Interfaces: Gn (GTP) / Gi (IP)

SGSN GGSNGn INTERNETGi

18


The Home Location Register (HLR) Database holding static user information

Telephone number (MSISDN = CC + NDC + SN) Subscriber number (IMSI = MCC + MNC + MSIN) Security issues AUC (key) QoS parameters Available services (voice, packet....) Position information: Visitor Location Register (VLR)

Protocols: IP

Interfaces: Gr, C

Gr

C

MSISDN = MS - ISDNCC Country CodeNDC National Dest. CodeSN Subscriber Number

IMSI Int. Mobile Subscriber IdMCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Id Number

19


Summary of Core Network Elements Core Network Elements

CS: MSC, G-MSC PS: SGSN, GGSN OM: HLR, VLR, EIR,

MSC / SGSN interconnect RAN to the CN G-MSC / GGSN interconnect CN with other networks HLR holds all static user information VLR local copy of HLR in SGSN Further Management units:

EIR, OMC,

CS Circuit SwitchedPS Packet SwitchedOM Operation and MaintenanceMSC Mobile Switching CenterG-MSC Gateway MSCSGSN Serving GPRS Supporting NodeGGSN Gateway GPRS Supporting NodeHLR Home Location RegisterVLR Visiting Location Register

20


The Protocols

21


The Protocol Hierarchy

22


The Control Plane

SDH

23


The User Plane

ATM/UDP

GTP-U

MAC

RLC

PDCP

UDP/ATMATM UDP/ATM

GTP-U GTP-U GTP-U

IP

Iu - UP Iu - UP

SDH

24


The GPRS Mobility Management (GMM) GPRS version of the MM protocol (MM still needed) Managing the mobility of the terminals

Present location Connections management services User identity confidentiality User states:

Idle: the subscriber is not attached Standby: the subscriber is attached Ready: the subscriber is active

25


The RAN Application Part (RANAP) Handles the signaling between UTRAN and PS-CN (Iu)

Booking ATM lines, Changing Setup, .

Includes all control information for UTRAN 3 Classes of elementary procedures:

General control services Notification services Dedicated control services

Some functions: Iu Release (1) Overload Control (2) RAB Assignment (3)

RAB Radio Access Bearer

26


The Signaling Connection Control Part (SCCP) Task:

Abstraction between UMTS and transport system (ATM, IP) Transport System is hidden.

Supports connection -less and oriented extension to MTP Address translation Full OSI layer 3 compatibility Below SS7 protocol

27


The GPRS Tunneling Protocol (GTP v0) For the connection between RNC, SGSN, GGSN Payload is attached to GTP headers (8Bytes) Used for signaling and data Fields:

Version: GTP v0 or v1 Protocol Type: GTP, GTP (GTP protocol is used to transfer charging data to the

Charging Gateway Function) Flags: Extension, Sequence, N-PDU Message Type: What is this GTP message about Length: length of payload Tunnel Endpoint Identifier: Start/End point of the GTP tunnel (user, APN)

28


The GTP -U / -C GTP-C(ontrol)

GPRS mobility management between GSNs Logically attached to the GTP-U tunnel physically separated Functions:

Create/Update/Change PDP Context Echo Request/Response RAN Information

GTP-U(ser) Hides mobility from IP layer Supports reordering of T-PDUs TEID is always unique Functions:

Data Transmission Tunnel Setup/Release/Error Echo Request/Response

TEID Tunnel Endpoint IDentifier

29


Summary of Core Network Protocols Protocol hierarchy

Non-access / Access Stratum Radio / Transport Network Layer

Core network protocols: GMM: location, user mobility, RANAP: signaling between UTRAN and CN SCCP: abstraction between UMTS layers and transport layer GTP-U: transport of user data payload GTP-C: managing of corresponding GTP-U (always in pairs)

Every user has a least one GTP tunnel (pair) active SGSN records the states of these protocols for every user

CS Circuit SwitchedPS Packet Switched

30


Let's start the Journey . . .

31


Processed Steps Now we will use the basics. GPRS attach PDP context activation Mobile Station starts to send data (IP Packets)

32


Svoboda

Activating a PDP Context

33


Protocol Mapping

Image Size = 2000 Bytes

Data1 (1472)

0 1500

TCP IP

201472 20

Data2

0 1500

TCP IP

20528 20

Original

IP Layer USER

UTRAN

GTP Layer + UDP, IP CoreGTP

8

UDP IP

8 20

GTP

8

UDP IP

8 20

ATM Layer48 5 48 5 48 5 5 48 5 48 548

34


Sending the Packet: UTRAN-SGSN

35


Sending the Packet: SGSN-GGSN

PAYLOAD (1500)

TCP Header (20)

IP Header (20)

GTP Header (8)

SGSN GGSNGn

PAYLOAD (1500)

TCP Header (20)

IP Header (20)

PAYLOAD (1500)

TCP Header (20)

IP Header (20)

GTP Header (8)

UDP (8)

IP (20)

ATM (5)

PDH (var)

36


Sending the Packet: Outer Regions

INTERNET

PAYLOAD (1500)

TCP Header (20)

IP Header (20)

Ethernet

PAYLOAD (1500)

TCP Header (20)

IP Header (20)

Ethernet

GGSN

Where is the bird?

37


Summary of this lecture Network hierarchy Core network elements Protocol hierarchy How a data (IP) transmission over mobile cellular networks

works Important things/abbreviations

Subscriber: IMSI, TIMSI, GTP Elements: RNC, SGSN, GGSN, NodeB Interfaces: Gi, Gn, IuCS, IuPS Procedures: PDP, GMM

Next stop: UTRAN

Thank you for your attention

[email protected]

39


Where to look?

[1] RANAP on Iu: 3gpp 25.413; 23.108 (E Interface)

[2] Iu User Plane: 3gpp 25.415

[3] GTP: 3gpp 29.060

[4] Core Network Basics: 3gpp 23.002

[5] www.umtslink.at

[6] http://www.techfest.com/networking/

[7] http://www.manualy.sk/protocols2/pbook/gprs.htm#GTP

[8] http://www.manualy.sk/protocols2/pbook/umts.htm

[9] http://www.tkn.tu-berlin.de/curricula/ws0405/vl-umts/

40


Abbreviations (1)AAL2 ATM Adaptation Layer type 2ALCAP Access Link Control Application PartAPN Access Point NameAS Access StratumASN.1 Abstract Syntax Notation OneATM Asynchronous Transfer ModeBSC Base Station ControllerBTS Base Transceiver StationCC Call ControlCN Core NetworkCRNC Controlling RNCCS Circuit SwitchedDCH Dedicated ChannelDL DownlinkDRNC Drift RNCDRNS Drift RNSDSCH Downlink Shared ChannelEP Elementary ProcedureGERAN GSM/EDGE Radio Access NetworkGGSN Gateway GPRS Supporting NodeG-MSC Gateway Mobile Switching CenterGMM/SM GPRS Mobility Management / Session ManagementGPRS General Packet Radio SystemGSM Global System for Mobile communicationsGTP GPRS Tunneling ProtocolGWCN GateWay Core NetworkHLR Home Location RegisterIE Information ElementIMEI International Mobile Equipment IdentityIMSI International Mobile Subscriber Identity

IPv4 Internet Protocol (version 4)IPv6 Internet Protocol (version 6)MAC Media Access ControlMBMS Multimedia Broadcast Multicast ServiceMM Mobility ManagementMOCN Multi Operator Core NetworkMSC Mobile services Switching CentreMTP Message Transfer PartNACC Network Assisted Cell ChangeNAS Non Access StratumNRT Non-Real TimeN-PDU Network Protocol Data UnitP-TMSI Packet TMSIPCM Puls Code ModulationPCU Packet Control UnitPDCP Packet Data Convergence ProtocolPDP Packet Data ProtocolPDU Protocol Data Unit PLMN Public Land Mobile NetworkPS Packet SwitchedPSTN Public Switched Telephone NetworkQoS Quality of ServiceRAB Radio Access BearerRANAP Radio Access Network Application PartRLC Radio Link ControlRNC Radio Network ControllerRNS Radio Network SubsystemRRC Radio Resource ControlRT Real Time

3g mobile core network

Documents