8.3 GPRSmidas1.e-technik.tu-ilmenau.de/~webkn/Webdaten... · 8.3 GPRS GPRS –Session Management •MN registers with GPRS network: GPRS-Attach to SGSN •MN receives Packet Temporary

Data Services in GSM I

• Data transmission standardized with only 9.6 kbit/s

▪ advanced coding allows 14.4 kbit/s

▪ not enough for Internet and multimedia

applications

• HSCSD (High-Speed Circuit Switched Data)

▪ mainly software update

▪ bundling of several time-slots to get higher AIUR

(Air Interface User Rate, e.g., 57.6 kbit/s using 4

slots @ 14.4)

▪ advantage: ready to use, constant quality, simple

▪ disadvantage: channels blocked for voice

transmission

Communication Networks - 8. Public Land Mobile Networks 364

8.3 GPRS

AIUR [kbit/s]

TCH/F4.8 TCH/F9.6 TCH/F14.4

4.8 1

9.6 2 1

14.4 3 1

19.2 4 2

28.8 3 2

38.4 4

43.2 3

57.6 4

8.3 GPRS

Data Services in GSM II

• GPRS (General Packet Radio Service)

▪ packet switching

▪ using free slots only if data packets ready to send (e.g., 50 kbit/s using 4 slots temporarily)

▪ standardization 1998, introduction 2001

▪ advantage: one step towards UMTS, more flexible

▪ disadvantage: more investment needed (new hardware)

• GPRS network elements

▪ GSN (GPRS Support Nodes): GGSN and SGSN

▪ GGSN (Gateway GSN)

❖ interworking unit between GPRS and PDN (Packet Data Network)

▪ SGSN (Serving GSN)

❖ supports the MS (location, billing, security)

▪ GR (GPRS Register)

❖ user addresses


GPRS: Quality of Service


8.3 GPRS

Reliability ClassLost SDU

ProbabilityDuplicate SDU

Probability

Out of Sequence SDU

Probability

Corrupt SDU Probability

1 10-9 10-9 10-9 10-9

2 10-4 10-5 10-5 10-6

3 10-2 10-5 10-5 10-2

DelayClass

SDU size 128 byte SDU size 1024 byte

mean 95 percentile mean 95 percentile

1 < 0.5 s < 1.5 s < 2 s < 7 s

2 < 5 s < 25 s < 15 s < 75 s

3 < 50 s < 250 s < 75 s < 375 s

4 unspecified

Examples for GPRS Device Classes


8.3 GPRS

Class Receiving Slots Sending SlotsMaximum

Number of Slots

1 1 1 2

2 2 1 3

3 2 2 3

5 2 2 4

8 4 1 5

10 4 2 5

12 4 4 5

GPRS User Data Rates in kbit/s


8.3 GPRS

CodingScheme

1 Slot 2 Slots 3 Slots 4 Slots 5 Slots 6 Slots 7 Slots 8 Slots

CS-1 9.05 18.1 27.15 36.2 45.25 54.3 63.35 72.4

CS-2 13.4 26.8 40.2 53.6 67 80.4 93.8 107.2

CS-3 15.6 31.2 46.8 62.4 78 93.6 109.2 124.8

CS-4 21.4 42.8 64.2 85.6 107 128.4 149.8 171.2

GPRS Architecture and Interfaces


8.3 GPRS

MS BSS GGSNSGSN

MSC

Um

EIREIR

HLR/GR

HLR/GR

VLRVLR

PDN

Gb Gn Gi

SGSN

Gn

GPRS Protocol Architecture


8.3 GPRS

Appl.

IP/X.25

LLC

GTP

MAC

Radio

MAC

RadioFR

RLC BSSGP

IP/X.25

FR

Um Gb Gn

L1/L2 L1/L2

MS BSS SGSN GGSN

UDP/TCP

Gi

SNDCP

RLC BSSGP IP IP

LLC UDP/TCP

SNDCP GTP

8.3 GPRS

GPRS – Session Management

• MN registers with GPRS network:

▪ GPRS-Attach to SGSN

• MN receives Packet Temporary Mobile Subscriber Identity P-TMSI

• Then, MN gets a Packet Data Protocol Address (PDP-Address), e.g. an IP-Address

• Finally, the PDP context is created in MN, SGSN, GGSN:

▪ PDP-Type (e.g. IPv4)

▪ PDP-Address of MN (e.g. 129.187.222.10)

▪ Desired Quality of Service (QoS Class)

▪ GGSN address that serves as gateway to the external network


GPRS – PDP Context Activation


8.3 GPRS

MNMN SGSNSGSN GGSNGGSN

Security FunctionsSecurity Functions

8.3 GPRS

GPRS – Location Management

• Main task: retrieving the current location of a mobile subscriber

• Periodical Location Update messages to SGSN→ special state model:


IDLEIDLE

READYREADY

STANDBYSTANDBY

GPRSAttach

GPRSDetach

Ready Timer expiredor Force to Standby

Packetdelivery

Standby Timerexpired

GPRS – Intra-SGSN Routing Area Update


8.3 GPRS


MNMN BSSBSS SGSNSGSN

GPRS – Inter-SGSN Routing Area Update


8.3 GPRS


MNMN BSSBSSNewSGSNNewSGSN

OldSGSNOld

SGSNGGSNGGSN HLRHLR

MSC/VLR

MSC/VLR

GPRS – Data Flow and Segmenting


8.3 GPRS

HeaderHeader

HeaderHeader

Header Information

SegmentSegment SegmentSegment

SegmentSegment FCSFCS

SegmentSegment SegmentSegment

SegmentSegment BCSBCS

...

...

IP-Packet

SNDCP-Layer

LLC Frame LLC-Layer

RLC/MAC-Block

RLC/MAC-Layer

Internet


GPRS – Routing and Address Translation (I)

SGSN

SGSN

GGSNBSC

IP Packet(IP Source,IP Destination)

1.) Address translationaccording to PDP-context:IP-Destination →TID+SGSN-Address

1.) Address translationaccording to PDP-context:IP-Destination →TID+SGSN-Address

GTP (SGSN-Address,TID, IP Packet)

2.) Address translationaccording to PDP-context:TID → TLLI + NSAPI (+CI)

2.) Address translationaccording to PDP-context:TID → TLLI + NSAPI (+CI)

SNDCP (TLLI,NSAPI, IP Packet)

IP Packet


GPRS – Routing and Address Translation (II)

SGSN

SGSN

GGSNBSC

IP Packet(IP Source,IP Destination)

1.) Address translationaccording to PDP-context:IP Source → TLLI + NSAPI

1.) Address translationaccording to PDP-context:IP Source → TLLI + NSAPI

SNDCP (TLLI,NSAPI, IP Packet)

2.) Address translationaccording to PDP-context: TLLI + NSAPI → TID + GGSN

2.) Address translationaccording to PDP-context: TLLI + NSAPI → TID + GGSN

GTP (GGSN-Address,TID, IP Packet)

IP PacketInternet

GPRS – Air Interface

• GSM-based FDMA/TDMA-combination with 8 time slots per TDMA frame

• More flexible channel assignment scheme for GPRS:

▪ Multi-slot operations

▪ Separate assignment of uplink and downlink for asymmetric traffic

• Available channels dynamically assigned to both kinds of traffic (“Capacity on Demand”)

• Multiplexing several users over one physical GPRS channel

• GPRS „steals“ TCH capacity not used by CS traffic (https://www.slideshare.net/Pfedya/gprs-40919387):


8.3 GPRS

0

2

4

6

8

10

12

14

03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00

Number of CS Channels in Use(in Cell)

0

2

4

6

8

10

12

14

Number of CS channels in use

GPRS – Logical Channels


8.3 GPRS

Group Channel Function Direction

Traffic Channels Packet DataTraffic Channel

PDTCH Packet Data Traffic MS BSS

Signaling Channels Packet BroadcastControl Channel

PBCCH Packet Broadcast Control MS BSS

Packet Common

Control Channel

(PCCCH)

PRACH Packet Random Access MS → BSS

PAGCH Packet Access Grant MS BSS

PPCH Packet Paging MS BSS

PNCH Packet Notification MS BSS

Packet DedicatedControl Channels

PACCH Packet Associated Control MS BSS

PTCCH Packet Timing Advance Control MS BSS

Interworking with IP Networks


8.3 GPRS

DNS DHCP

GPRS internalIP Network

Fire-wall

Intra-PLMNGPRS Backbone

InternetRou-ter

Gn Gn

Gi

SGSN GGSN

8.4 WAP

WAP - Wireless Application Protocol

• Goals

▪ Internet contents and enhanced services available for mobile end devices like cell phones or PDAs

▪ Independent standards for wireless networks

▪ Open standards: everybody may submit proposals for standardization

▪ Applications should be scalable and future-proof

• Platforms

▪ Many platforms must be supported:

❖ E.g. GSM (900, 1800, 1900), CDMA IS-95, TDMA IS-136, IMT-2000, UMTS, W-CDMA

• Forum

▪ WAP Forum, founded by (among others) Ericsson, Motorola, Nokia, Unwired Planet

▪ see http://www.wapforum.org


http://www.wapforum.org/

WAP – Standardization

• Browser

▪ „Micro-Browser”, comparable to familiar Internet browser

• Scripting Language

▪ Comparable to Java-Script, adapted to mobile enviroment

• WTA/WTAI

▪ Wireless Telephony Application (Interface): Access to telephone functionality

• Contents Formats

▪ Business cards (vCard)

▪ Calendar entries (vCalender)

• Protocol Stack

▪ Transport, Security and Session Layer

• Working Groups

▪ WAP Architecture Working Group

▪ WAP Wireless Protocol Working Group

▪ WAP Wireless Security Working Group

▪ WAP Wireless Application Working Group


8.4 WAP

WAP 1.x – Layers and Protocols


8.4 WAP

WAE includes e.g. WML (Wireless Markup Language), WML Script, WTAI

Bearer Services (GSM, Cellular Digital Packet Data, ...)

Security Layer (WTLS)

Session Layer (WSP)

Application Layer (WAE)

Transport Layer (WDP)TCP/IP,UDP/IP,

Phys. Media

SSL/TLS

HTML, Java

HTTP

Internet WAP

Transaction Layer (WTP)

Additional servicesand protocols

WCMP

A-SAP

S-SAP

TR-SAP

SEC-SAP

T-SAP

WAP – Network Elements


8.4 WAP

Mobile NetworkMobile NetworkFixed NetworkFixed Network

WAPProxyWAPProxy

WTAServerWTA

Server

Filter/WAPProxy

Filter/WAPProxyWeb

ServerWeb

Server

FilterFilter

TelephoneNetwork

Internet

Binary WML: Binary data format for clients

Binary WML

Binary WML

Binary WML

HTML

HTML

HTML WML

WMLHTML

Wireless Application Environment: Logical Model


8.4 WAP

Original ServerOriginal Server

webserver

otherservers

GatewayGateway ClientClient

otherWAE

user agents

WMLuser agent

WTAuser agent

Coder&

Decoder

codedrequest

request

coded reply

reply

pushcontents

codedpushcontents

Wireless Telephony Application: Logical Architecture


8.4 WAP

AdditionalServer

ClientClient

Repository

WTA-User-Agent

WTA-GatewayWTA-Gateway

Coder&

Decoder

Other TelephoneNetworks

WTA-ServerWTA-Server

WTA & WMLServer

WML-Scripts

WML-Stack

WTA-Services

MobileNetwork

ExternalServer

Secure ProviderNetwork

Device Spec.Functions

Fire-wall

Example Voice Box


8.4 WAP

Service Indication

WTA-User-Agent WTA-Server Mobile Network Voice Box

Create Content

Presentation; User Selection

Connection Setup

Accept Call

Voice connection

Indicate new voice message

Request to deliver voice message

Connection establishment

Call acceptance Call acceptance

WTA-Gateway

Push URL

Indication; User Selection

WSP GetHTTP Get

Reply with ContentWMLBinary WML

WSP GetHTTP Get

Reply with Card for CallWMLBinary WML

Waiting for Call

Connection establishment

Possible Protocol Stacks for WAP 1.x


8.4 WAP

WAE

WSP

WTP

UDP

IP(GPRS, ...)

WDP

non IP(SMS, ...)

WTLS

WAE user agentWAP Standard

Not part of WAP

WTP

UDP

IP(GPRS, ...)

WDP

non IP(SMS, ...)

WTLS

UDP

IP(GPRS, ...)

WDP

non IP(SMS, ...)

WTLS

Transaction-basedApplications

Datagram-basedApplications

typical WAP Application based on complete protocol stack

Simple data transfer with or without security mechanisms

8.4 WAP

WAP 2.0 (July 2001)

• New▪ XHTML

▪ TCP with „Wireless Profile“

▪ HTTP

• Innovative Applications▪ Color graphics

▪ Animation

▪ Download of big files

▪ Location-based services

▪ Synchronization with PIMs

▪ Pop-up/context-sensitive menus

• Goal▪ Integration of WWW, Internet, WAP, i-mode


WAP 2.0 Architecture


8.4 WAP

ServiceLocalization

SecurityServices

Ap

plic

atio

nFr

amew

ork

Pro

toco

l Fra

me

wo

rk

External Services

EFI

External Services

EFI

Provisio-ning

Provisio-ning

NavigationDiscoveryNavigationDiscovery

ServiceLookupServiceLookup

Crypto-LibrariesCrypto-Libraries

Authenti-cation

Authenti-cation

Identifica-tion

Identifica-tion

PKIPKI

SecureTransport

SecureTransport

SecureBearersSecureBearers

Sess

ion

Sess

ion

Tran

sfer

Tran

sfer

Tran

spo

rtTr

ansp

ort

Bea

rer

Bea

rer

Multimedia Messaging (Email)

Multimedia Messaging (Email)

WAE/WTA User Agent (WML, XHTML)

WAE/WTA User Agent (WML, XHTML)

ContentFormatsContentFormats

PushPush

IPv4IPv4

IPv6IPv6

CSDCSD

SMSSMS

USSDUSSD

FLEXFLEX

GUTSGUTS

MPAKMPAK

......

......

Datagrams(WDP, UDP)Datagrams(WDP, UDP)

Connections(TCP with

wireless profile)

Connections(TCP with

wireless profile)

Hypermedia Transfer

(WTP+WSP, HTTP)

Hypermedia Transfer

(WTP+WSP, HTTP)

Strea-mingStrea-ming

MMSMessa-

ges

MMSMessa-

ges

Push OTAPush OTA

Capability NegotiationCapability

Negotiation

Synchronization Synchronization

CookiesCookies

WAP 2.0 Protocol Stacks


8.4 WAP

TrägerWDPWTLSWTPWSPWAE

WAP Device

TrägerWDPWTLSWTPWSP

IPTCPTLS

HTTP

IPTCPTLS

HTTP

WAEWeb ServerWAP Gateway

WAP 1.x Server/Gateway/Client

IPTCP‘TLS

HTTPWAE

WAP Device

IPTCP‘

IPTCP

IPTCPTLS

HTTPWAE

Web ServerWAP Proxy

WAP Proxy with TLS-Tunneling

IPTCP‘HTTPWAE

WAP Device

IPTCP‘

IPTCP

IPTCP

WAEWeb ServerWAP Proxy

WAP HTTP Proxy with adapted TCP

HTTP HTTP HTTP

IPTCP‘HTTPWAE

WAP Device

IP IP IPTCP

WAEWeb-Server

IP Router

WAP direct access

HTTP

8.3 GPRSmidas1.e-technik.tu-ilmenau.de/~webkn/Webdaten... · 8.3 GPRS GPRS –Session Management •MN registers with GPRS network: GPRS-Attach to SGSN •MN receives Packet Temporary

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