5a tecnologia gprs'edge'umts

8/3/2019 5a Tecnologia Gprs'Edge'Umts

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1 NOKIA CTXX 3220_3.0en.PPT/ 17.09.2001

GPRS Architecture:Interfaces and Protocols


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Requirements of GPRS network

Use existing GSM infrastructure with little modifications to it

GPRS should support one or more packet switchedconnections

referred to as PDP context activations

Support different Quality of Service (QoS) user subscriptions

Compatible with 3G and 4G systems

Support both point-to-point and point-to-multipoint data

connections It should provide secure access to external networks


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GPRS network: Logical networkelements

BTS BSC

SGSN

GGSN Intranet

GGSN Internet

CG

BillingCentre

RouterServer

LAN

Corporate

BG

Inter-PLMNNetwork

LIG

SGSN = Serving GPRS Support NodeGGSN = Gateway GPRS Support NodeNMS = Network Management SystemBG = Border GatewayCG = Charging GatewayFW = FirewallLIG = Lawful Interception Gateway

FW

NMS

DNS

GPRSBackbone

FW

OperatorServices

LAN

GGSN


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What are the functions of SGSN?

The SGSN is the MSC of the GPRS network

At least one SGSN per GPRS network

SGSN has the following functions: Protocol conversion between IP backbone and BSS

protocols Authentication of GPRS users Mobility management of GPRS enabled MS Routing of data to the relevant GGSN Interaction with the NSS (MSC/VLR, HLR, EIR) via SS7

network Collection of charging data records pertaining to GPRS calls Collection of traffic statistics


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What are the functions of GGSN?

GGSN acts as a router to the external network

GGSN has the following functions: Routes mobile-destined packets coming from external

networks to the relevant SGSN Routes packets originating from a mobile to the correct

external network

Interfaces to external IP networks Collects charging data and traffic statistics Allocates dynamic or static IP addresses to mobiles either

by itself or with the help of a DHCP or a RADIUS server


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How is GPRS seen by an externalnetwork?

Host155.222.33.55

Corporate subnetwork131.44.15.xxx

GPRS subnetwork155.222.33.xxx

Host131.44.15.3

Router

Router

LAN

Internet

External point of view, GGSN is a router to an IP network

When the GGSN receives data addressed to a user in themobile network, it first checks if the address is active

If it is, GGSN forwards the data to the SGSN serving themobile

If the address is inactive, the data is discarded


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Firewall

Protects the IP network against external attack (for example,

hackers from the mobile users or from the Internet) Firewall might be configured to reject all packets that are not

part of a GPRS subscriber initiated connection Advantage of dynamic addressing

Can also include NAT or NAPT


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Border Gateway (BG)

Necessary to interconnect operators' GPRS backbone

networks to support roaming Provides a direct tunnel between different operators' GPRS

networks (rather than transferring via the public Internet)

Roaming is not supported in GPRS Release 1


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Charging Gateway (CG)

GPRS charging data records (CDR) are generated by SGSNs

and GGSNs in the network SGSN and GGSN transfer CDR using GTP (GTP Prime)

The Charging Gateway collects all this data together processes it passes it on to the Billing System


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GPRS interfaces

HLR

Air (Um)

Gb

GsGr Gf

Gn

GnInter-PLMN

GPRSbackbone

Gp

Externalpacketnetwork

Gi

SGSN

EIR

BSC

MSC/VLR

SMS-GMSC

Gd

GGSN

BG

Signalling and data

Signalling

GaGa

CG


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Container

SGSN GGSN

The stream of containersforming a tunnel.


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Tunnelling

User packetTunnel ID:IMSI

THE GTP PACKETIP (+TCP/UDP)

Who is the user?

To which GSN?

GSN IP-address

E.g. a TCP/IP packetcarrying e-mail


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Tunnelling

GGSN

GTP

IP IP

IPbackbone data using private IP addresses

SGSNMS

IP

GTPTunnel

user data using 'public' IP addresses


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BTS BSC

SGSN

GGSN Internet

GPRSBackboneIP Network

FW

L1

L2

IP

GTP

USERPAYLOAD TCP/UDP

L1

L2

IP

APP

UDP

Gn G i

Backbone Internet

Gn Gi

BTS BSCSGSN

GPRS Tunnelling Protocol (GTP)

GTP tunnel between SGSN and GGSN Carrying signalling and user traffic

Hiding backbone from Internet and theMSs Mobility management Tunnel Identifier TID= IMSI + NSAPI


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GGSN functionalities

GPRSBackboneLayers 1 & 2 Network layer

BTS BSC

SGSN

GGSN Internet

GPRSCore

Network

SS7

HLRMSC/

VLR

TCP/UDP

IP

APP

L1

L2 PublicData NetworkLayers 1 & 2

Tunnelledpayload Network layer

Transport layer

Transport layer

GPRS tunnel

Application Layer

Server

L1

L2

IP

GTP

USERPAYLOAD

UDP


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Key points

The Gateway GPRS Support Node (GGSN):

acts as the interface between the GPRS network andexternal networks collects charging data and traffic statistics can allocate IP addresses for users routes packets coming from external networks towards the

correct SGSN and vice versa

Serving GPRS Support Node (SGSN): converts protocols used in the IP backbone to protocols

used in the BSS and the MS takes care of authentication and mobility management routes data to the relevant GGSN when connection to an

external network is required collects charging data and traffic statistics


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19 NOKIA CTXX 3220_3.0en.PPT/ 17.09.2001

Key points

The most important open interfaces in the GPRS network are:

Gb - SGSN to BSS Gn - between GSNs (GTP) Gr - between SGSN and HLR (MAP) Gs - SGSN to MSC (BSSAP+) Gi - GGSN to external data networks Gf - SGSN and the EIR (MAP) Gd - SGSN and the GMSC (SMSC) Gp - between GSNs of different PLMNs

The user packets are transported encapsulated using theGPRS Tunnelling Protocol (GTP) over the GPRS backbone.The backbone is an IP network.


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GPRS Tunnelling Protocol principle


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What sort of procedures are needed?

MS switches on for the first time.

MS indicates that it is switched on and ready (GPRS attach). MS indicates that it is switched off (GPRS detach).

MS indicates that it wants to transmit data (PDP contextactivation).

MS indicates stop data transmission (PDP contextdeactivation).

MS moves from one part to another of a service area(Cell update and RA update procedure).

MS may roam into another networks service area (Roaming). etc.


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Subscriber information information


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Type of info What info Where

Identity IMSI

TMSI

IP address

SIM, HLR, VLR, SGSN

SGSN, MS

MS, SGSN, GGSN

Location VLR address

Location area

Serving SGSN

Routing area

HLR

SGSN, VLR

HLR, VLR

SGSN

Services Basic services, supplementaryservices, circuit switched bearerservices, GPRS serviceinformation

Basic services, supplementaryservices, CS bearer services

GPRS service information

HLR

VLR

SGSN

Authentication data Ki, algorithms

Triplets

SIM, AC

VLR, SGSN

Subscriber information, informationelements, and location

Wh t i ti ?


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What is a routing area?

RA-2

RA-1

RA-3

R ti


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Routing area

SGSN-1

BSC-1

RA-1 RA-3

SGSN-2

BSC-2

RA-2

LA-1LA-3


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MS states

RA-1

VLR-1

HLR

SGSN-1BSC

LA-1

MS Idl


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MS Idle

RA-1

VLR-1

HLR

SGSN-1BSC

IMSI 244...VLRSGSN

IMSILAI

SGSN ?

IMSI ?RA ?Cell ?

LA-1


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MS Standby


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MS Standby

RA-1

VLR-1

HLR

SGSN-1BSC

IMSI 244...VLR VLR-1SGSN SGSN-1

IMSI 244...LAI LA-1

SGSN SGSN-1

IMSI 244...RAI RA-1Cell ?????

LA-1


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GPRS Attach

PDU transmission

GPRS Detach GPRS Attach

PDU reception

GPRS Detachor

Cancel Location

MM State Model of MS MM State Model of SGSN

IDLE

READY

STANDBY

IDLE

READY

STANDBY

STANDBY timer expiryor

Cancel Location

READY timer expiry

or

Force to STANDBY

READY timer expiry

or

Force to STANDBY

or

Abnormal RLC condition

STANDBY timer

expiry

GPRS attach (0)


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GPRS attach (0)

RA-1

HLR

SGSN-1

BSC

LA-1

GPRS attach (1) (First time in PLMN)


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GPRS attach (1) (First time in PLMN)

RA-1

HLR

SGSN-1

BSC

LA-1

1

2a 2b

(1) MS Requests GPRS attach.(2a) The SGSN requests subscriber identity.

(2b) The MS sends its IMSI.

GPRS attach (2) authentication


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GPRS attach (2) authentication

(3a) SGSN requests tripletsfrom AC. (First time in

PLMN).

(3b) The AC generates thetriplets (RAND, SRES, Kc)and hands them to theSGSN.

(3c) SGSN sends anauthentication request tothe MS (along with RAND).

(3f) The SIM calculatesSRES and sends it to

SGSN.(3g) SGSN verifies

(SRES=SRES).

RA-1

HLR/AC

SGSN-1

BSC

LA-1

3f

3a

3b

3c

GPRS attach (3) IMEI check


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GPRS attach (3) IMEI check

RA-1

EIR

SGSN-1

BSC

LA-1

4a

4b

4c

4d(4a) SGSN asks for MSIMEI.

(4b) MS sends the IMEI.

(4c) SGSN sends a CheckIMEI message to the EIR.

(4d) EIR replies with aCheck IMEI ack that willinclude the list type wherethe IMEI was found(unknown, white, grey, orblack).

GPRS attach (4)


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GPRS attach (4)

RA-1

HLR

SGSN-1

BSC

LA-1

5a

5b

5c

5d

6a

6b

(5a) SGSN sends Updatelocation message to HLR with

subscriber IMSI.(5b) HLR responds by giving

subscriber data to the SGSN.

(5c) SGSN acknowledges that ithas received the subscriber

data ok.(5d) HLR ends the transaction

with an Update Location ack.

(6a) SGSN accepts the GPRSattach and sends MS a newP-TMSI.

(6b) MS acknowledges that ithas received the new P-TMSI.

What happens after a GPRS attach?


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What happens after a GPRS attach?

After GPRS attach, SGSN starts tracking location of the MS

MS can send and receive SMS, but no other data To transfer other data it first has to activate a PDP context

When the subscriber wants to end a connection to the GPRSnetwork, the GPRS detach is used

GPRS detach changes state of MS to Idle and mobilitymanagement context in SGSN (and in the MS) is removed

MS normally initiates GPRS detach, but it can also be initiatedby the network if mobile reachable timer expires

What is session management?


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What is session management?

Procedures that handle the GPRS MS connection to theexternal data networks are called Session Management (SM).

What types of SM procedures exist?

PDP Context Activation

PDP Context Deactivation

PDP Context Modification: modifying a PDP context

What kinds of IP addresses can be used during a SM?

Static IP address (permanent MS IP address)

Dynamic IP address allocated by GGSN, DHCP, or RADIUSserver

HPLMN Dynamic IP Address

VPLMN Dynamic IP Address

Steps during PDP context activation


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Steps during PDP context activation

Receive request from subscriber

Check MS subscription data (static/dynamic, APN, etc.) Authenticate subscriber

Check if IP address has to be allocated and by whom

Convert APN name to GGSN IP Address using DNS

Contact GGSN and check if it is prepared to accept MS

Await GGSN confirmation

Get ready for charging!!!

PDP context activation - 0


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PDP context activation 0

BTS BSC

SGSN

GGSN

Intranet

GPRSCore

Network

DNS

Internet

AccessPoint


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PDP context activation: Step B


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PDP context activation: Step B

BTS BSC

SGSN

GGSN

GPRSCore

Network

DNS

(1) SGSN gets the GGSN IP addressfrom DNS, which maps APN to theGGSN IP address.

(2) SGSN sends 'Create PDP ContextRequest to GGSN

PDP type (e.g. IP) PDP address (if empty dynamicadd.) Access point name Proposed TID QoS & other options

Intranet

Internet

1.

2.

AccessPoint

PDP context activation: Step C


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p

BTS BSC

SGSN

GGSN

GPRSCore

Network

User authenticated OK (non-transparent case)

User dynamic IP address allocated by RADIUSserver, or DHCP server, or GGSN internal pool

(1) GGSN sends 'Create PDP Context Response'back to SGSN with IP address, TID confirm, andcharging ID.

(2) SGSN sends 'Activate PDP Context Accept' to theMS.

SGSN is now ready to route user traffic between MSand GGSN.

Intranet

Internet

1.

2.

PDP context information


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Mobile Station SGSN GGSN

PDP Type PDP Type PDP Type

PDP Address PDP Address PDP Address

NSAPI IMSI IMSI

APN NSAPI NSAPI

APN APN

GGSN Address SGSN Address

Charging ID Charging ID

What is transparent access to Internet?


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GGSN

InternetEdge

Router Service

GPRSBackbone

DNS

Operator's ISP Network

AP1

GGSNAP2

NAT

VAS

BTS BSC

SGSN

p

GGSN has no active role in user authentication

Subscriber IP address static or GGSN allocated fromoperator's ISP

Operator ISP gives Internet access and value-added services(e-mail, web, etc.)

What is non-transparent access?


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GGSN

Intranet

Service

GPRSBackbone

VPN

Infra servers- RADIUS

(SecurID)- DNS

InternetEdgeRouter

VPN

DNS

BTS BSC

SGSN

Service

p GGSN provides user authentication towards RADIUS server

Subscriber IP address allocated from intranet address space

Connection to the intranet router via a dedicated link or a VPN

Non-transparent access to intranet


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BTS BSC

SGSN

GGSN

Router

Service

GPRSBackbone

o t a spa e t access to t a et

AP

Intranet Internet

Infra servers- RADIUS- DNS

Connection from GGSN to intranetrouter is built using dedicated linee.g. Serial link.


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49 NOKIA CTXX 3220_3.0en.PPT/ 17.09.2001

GPRS Evolution from 2G to 3G

Evolution steps


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2.5G

2G

First generation (1G) mobilecommunication


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HLR - Home Location Register

VLR - Visitor Location RegisterAuC - Authentication Centre

communication

Second generation (2G) mobile system


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2G network architecture

MS Mobile StationBTS Base Transceiver StationBSC Base Station ControllerBSS Base Station Subsystem

GSM


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HSCSD


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GPRS


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55 NOKIA CTXX 3220_3.0en.PPT/ 17.09.2001

The GSM/GPRS network architecture

GPRS vs. HSCSD


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EDGE


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High data rates

Uses 8-PSK modulation scheme Bandwidth efficient

More bits per unit spectrum (greater speed)

EDGE can be used with HSCSD

ECSD (Enhanced Circuit Switched Data) = EDGE +HSCSD

EDGE can be used with GPRS EGPRS (Enhanced GPRS) = EDGE + GPRS

3G requirements


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The system should be fully specified (like GSM)

The specifications should be valid worldwide Must bring clear added value

Must be backward compatible with GSM and ISDN(at least for a short term)

Should support multimedia systems Radio access should be generic

Services to the end-users must be independent of access

3GPP


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59 NOKIA CTXX 3220_3.0en.PPT/ 17.09.2001

3GPP specifies standards for 3G systems

Incorporates the following ITU-T International Telecommunications Union -

Telecomms ETSI European Telecommunications Standards Institute ARIB Association of radio Industries and Business ANSI American National Standards Institute

3GPP documents www.3gpp.org

Standards are based on UTRA interface


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UMTS


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61 NOKIA CTXX 3220_3.0en.PPT/ 17.09.2001

3G-SGSN

GGSN

BackboneIPGi.IP

Firewall

Corporateintranet

Gp

SS7Network

PacketnetworkPSTN

Network

RNCBSUmR/S

Iub

Iur ATM

Inter

PLMNbackbone

(IP)

Internet

MSC/VLR

GMSC

SCPHLR

Iu

GnGn

Iu

Iu

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