Page 1Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Wireless Communication Protocols and Technologies
by Tatiana Madsen & Hans Peter Schwefel
• Mm1 Introduction. Wireless LANs (TKM)
• Mm2 Wireless Personal Area Networks and Bluetooth (TKM)
• Mm3 IP Mobility Support (HPS)
• Mm4 Ad hoc Networks (TKM)
• Mm5 Overview of GSM, GPRS, UMTS (HPS)
www.kom.auc.dk/~tatiana/ www.kom.auc.dk/~hps/
Page 2Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Intro: Cellular systems
• Geographic region subdivided in radio cells
• Base Station provides radio connectivity to Mobile Station within cell
• Handover to neighbouring base station when necessary
• Base Stations connected by some networking infrastructure
Page 3Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Cellular systems: technologies & subscribers
0
200
400
600
800
1000
1200
1996 1997 1998 1999 2000 2001 2002 year
Su
bsc
rib
ers
[mill
ion
] GSM total
TDMA total
CDMA total
PDC total
Analogue total
Total wireless
Prediction (1998)
Page 4Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Content
1. Introduction• Cellular Concepts & Technologies
2. GSM• Network Architecture, Air Interface• Signalling/Call Setup, Mobility Support• Data Services, HSCSD
3. GPRS & UMTS• GPRS: Architecture, Air-Interface, Core-Network Modifications• UMTS domains and architecture
4. IP transport in Packet Switched UMTS/GPRS Networks• PDP contexts, APNs, TFTs• Bearers• ’full’ network architecture
Exercise
Page 5Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GSM: Global System for Mobile Communication
• 2nd Generation of Mobile Telephony Networks• 1982: Groupe Spèciale Mobile (GSM) founded• 1987: First Standards defined• 1991: Global System for Mobile Communication,
Standardisation by ETSI (European Telecommunications Standardisation Institute) - First European Standard
• 1995: Fully in Operation
• Deployed in more than 184 countries in Asia, Africa, Europe, Australia, America)
• more than 747 million subscribers• more than 70% of all digital mobile phones use GSM• over 10 billion SMS per month in Germany, > 360 billion/year
worldwide
History:
Today:
Page 6Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GSM – Architecture
Components:• BTS: Base Transceiver Station• BSC: Base Station Controller• MSC: Mobile Switching Center• HLR/VLR: Home/Visitor Location
Register• AuC: Authentication Center• EIR: Equipment Identity Register• OMC: Operation and
Maintenance Center
Transmission: • Circuit switched transfer• Radio link capacity: 9.6 kb/s
(FDMA/TDMA)• Duration based charging
BSC
BSC
MS
BTS
BTS
BTS
MS
MS
MSC
HLR
VLR
OMC
EIR
AuC
O
Abis AUm
Radio Link
Base StationSubsystem
Network andSwitchung Subsystem
OperationSubsystem
Connection toISDN, PDNPSTN
Radio Subsystem (RSS)
Page 7Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GSM Services ‘Traditional’ voice services
– voice telephonyprimary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz
– emergency numbercommon number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible)
– Multinumberingseveral ISDN phone numbers per user possible
– voice mailbox (implemented in the fixed network supporting the mobile terminals)
– Supplementary services, e.g.: identification, call forwarding, number suppression, conferencing
‘Non-Voice’ Services (examples)• Fax Transmissions• electronic mail (MHS, Message Handling System, implemented in the fixed network)
• Short Message Service (SMS)alphanumeric data transmission to/from the mobile terminal using the signaling channel, thus allowing simultaneous use of basic services and SMS
Page 8Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
possible radio coverage of the cell
idealized shape of the cell
cell
GSM: Radio TechnologyCellular Concept:• segmentation of geographical area into cells
– Cell sizes vary from some 100 m up to 35 km depending on user density, geography, transceiver power etc.
– hexagonal shape of cells is idealized (cells overlap, shapes depend on geography)
• use of several carrier frequencies
– avoid same frequency in adjoining cells
• if a mobile user changes cells handover of the connection to the neighbor cell
Page 9Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
1 2 3 124
890 915Uplink Downlink
MHz 935 960
Kanäle:
200 kHz
Frequenzband derMobilstation
Frequenzband derBasisstation
GSM: Air Interface IFrequency Division Multiple Access (FDMA)• Separate up-link (MTBTS) and down-link (BTSMT) traffic
– Two 25MHZ bands
• Distinguish 124 adjacent channels within each band– Each channel 200kHz
Radio Network Planning:• Determine location of BTS• Determine number of TRX per BTS
– Multiple transceivers (TRX) per BTS (e.g. 1,4 ,or 12) simultaneous use of different FDMA channels
• Assign subsets of 124 channels to BTSs
Page 10Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
0 1 2 3 4 5 6 7
4,615 ms
data bits data bitstraining
57 26 57
time slot:
3 tail bits 3 tail bits1 togglebit
1 togglebit
burst 148 bit
time slot 156,25 bit
0,577 ms
GSM: Air Interface IITime Division Multiple
Access (TDMA)• Within each channel: sequence
of TDMA frames• TDMA frames subdivided into
8 time-sots
TDMA Frame
Page 11Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GSM: TDMA hierarchy of frames0 1 2 2045 2046 2047...
hyperframe
0 1 2 48 49 50...
0 1 24 25...
superframe
0 1 24 25...
0 1 2 48 49 50...
0 1 6 7...
multiframe
frame
burst
slot
577 µs
4.615 ms
120 ms
235.4 ms
6.12 s
3 h 28 min 53.76 s
Page 12Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
1 2 3 4 5 6 7 8
higher GSM frame structures
935-960 MHz124 channels (200 kHz)downlink
890-915 MHz124 channels (200 kHz)uplink
frequ
ency
time
GSM TDMA frame
GSM time-slot (normal burst)
4.615 ms
546.5 µs577 µs
tail user data TrainingSguardspace S user data tail
guardspace
3 bits 57 bits 26 bits 57 bits1 1 3
GSM Air Interface: Combination of TDMA & FDMA
Page 13Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Functionalities in Radio Subsystem• BTS comprises radio specific functions• BSC is the switching center for radio channels
Functions BTS BSCManagement of radio channels XFrequency hopping (FH) X XManagement of terrestrial channels XMapping of terrestrial onto radio channels XChannel coding and decoding XRate adaptation XEncryption and decryption X XPaging X XUplink signal measurements XTraffic measurement XAuthentication XLocation registry, location update XHandover management X
Page 14Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Overview: GSM protocol layers for signaling
CM
MM
RR
MM
LAPDm
radio
LAPDm
radio
LAPD
PCM
RR’ BTSM
CM
LAPD
PCM
RR’BTSM
16/64 kbit/s
Um Abis A
SS7
PCM
SS7
PCM
64 kbit/s /2.048 Mbit/s
MS BTS BSC MSC
BSSAP BSSAP
Page 15Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Example: Mobile Terminated Call1. calling a GSM subscriber
2. forwarding call to GMSC
3. signal call setup to HLR
4. 5. request MSRN from VLR
6. forward responsible MSC to GMSC
7. forward call to current MSC
8, 9. get current status of MS
10, 11. paging of MS
12, 13. MS answers
14, 15. security checks
16, 17. set up connection
PSTNcallingstation
GMSC
HLR VLR
BSSBSSBSS
MSC
MS
1 2
3
4
5
6
7
8 9
10
11 12
1316
10 10
11 11 11
14 15
17
Page 16Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Example: Message flow between MS and BTS for Mobile Terminated Call
BTSMS
paging request
channel request
immediate assignment
paging response
authentication request
authentication response
ciphering command
ciphering complete
setup
call confirmed
assignment command
assignment complete
alerting
connect
connect acknowledge
data/speech exchange
MTC
Page 17Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Mobility Support I: Types of handover
MSC MSC
BSC BSCBSC
BTS BTS BTSBTS
MS MS MS MS
1
23
4
Page 18Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Mobility Support II: Handover decision
receive levelBTSold
receive levelBTSold
MS MS
HO_MARGIN
BTSold BTSnew
Page 19Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Mobility support III: Handover procedure
HO access
BTSold BSCnew
measurementresult
BSCold
Link establishment
MSC
MSmeasurementreport
HO decision
HO required
BTSnew
HO request
resource allocation
ch. activation
ch. activation ackHO request ackHO commandHO commandHO command
HO completeHO completeclear commandclear command
clear complete clear complete
Page 20Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
0
200
400
600
800
1000
1200
1400
1600
1800
1995 2000 2005 2010
Subscriptions worldwide (millions)
Mobile InternetSubscribers
MobileSubscribers
Mobile
Fixed
Mobile Internet
Fixed Internet
• The future Internet will mainly be accessed by mobile devices
Mobile Communication & Data Traffic
Page 21Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Data services in GSM• 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 each)
– advantage: ready to use, constant quality, simple– disadvantage: channels blocked for voice transmission
AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F14.44.8 19.6 2 1
14.4 3 119.2 4 228.8 3 238.4 443.2 357.6 4
Page 22Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Content
1. Introduction• Cellular Concepts & Technologies
2. GSM• Network Architecture, Air Interface• Signalling/Call Setup, Mobility Support• Data Services, HSCSD
3. GPRS & UMTS• GPRS: Architecture, Air-Interface, Core-Network Modifications• UMTS domains and architecture
4. IP transport in Packet Switched UMTS/GPRS Networks• PDP contexts, APNs, TFTs• Bearers• ’full’ network architecture
Exercise
Page 23Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GPRS: General Packet Radio Service
• Packet Switched Extension of GSM• 1996: new standard developed by ETSI• Components integrated in GSM architecture• Improvements:
– Packet-switched transmission– Higher transmission rates on radio link (multiple
time-slots)– Volume based charging ‚Always ON‘ mode
possible• Operation started in 2001 (Germany)
Page 24Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GPRS - Architecture
PDN
Other
PLMN
GSM GPRS
BTS
CCU
MSC
BSC
PCU
HLR GR
GGSN
Components
A Abis Gb Gp
Gs
Gn
G Gr
Gi
UmBSS
SGSN
MS
Components:• CCU: Channel Coding Unit
• PCU: Packet Control Unit
• SGSN: Serving GPRS Support Node
• GGSN: Gateway GPRS Support Node
• GR: GPRS Register
Transmission: • Packet Based Transmission• Radio link:
– Radio transmission identical to GSM– Different coding schemes (CS1-4)– Use of Multiple Time Slots
• Volume Based Charging
Page 25Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GPRS: Channel Coding and Multiplexing
9,05 kbit/s
.....
Time Slot (MS-> BTS)
Coding Scheme 1
72.4.......171,2 kbit/s
9,05 kbit/s
13,4 kbit/s
9,05 kbit/s
1 2 8
13,4 kbit/s 13,4 kbit/s
15,6 kbit/s 15,6 kbit/s 15,6 kbit/s
.....
.....
21,4 kbit/s .....21,4 kbit/s 21,4 kbit/s
9,05 kbit/s
3
Coding Scheme 2
Coding Scheme 3
Coding Scheme 4
.....
‚optimal‘ radio quality: no interference, etc.
Selection of Codingdepending on qualityof radio connection
Overall transmission rate
Page 26Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Examples for GPRS device classes
Class Receiving slots Sending slots Maximum 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
Page 27Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GPRS user data rates in kbit/s
Coding scheme
1 slot 2 slots 3 slots 4 slots 5 slots 6 slots 7 slots 8 slots
CS-1 9.05 18.2 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
Page 28Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GPRS architecture and interfaces
MS BSS GGSNSGSN
MSC
Um
EIR
HLR/GR
VLR
PDN
Gb Gn Gi
SGSN
Gn
Page 29Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Packet Handling
MobilityManagement
SessionManagement
InterceptionHandling
ConfigurationManagement
SMS HandlingProtocols
&Interfaces
PerformanceManagement
Fault & MaintenanceManagement
AccountingResource
Management
Handover Controland
SGSN ChangeHandling
Functions in SGSN and GGSN
Functions in SGSN
GPRS Core Network Functions
Page 30Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GPRS: Protocol Stack
• RLC: Radio Link Control– Acknowledged mode (reliable) or unacked
• LLC: Logical Link Control– Acknowledged mode (reliable) or unacked
• BSSGRP: BSS GPRS Protocol
• SNDCP: Sub-Network Dependent Convergence Protocol
• GTP: GPRS Tunneling Protocol– Mobility Support
Page 31Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Data Units in GPRS
Page 32Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
BSS
SGSN
Um GbGr
Insert Subscriber Data Ack(NSAPI,TI,PDP Type)
Insert Subscriber Data(NSAPI,TI,PDP Type)
Attach Request(NSAPI,TI,PDP Type)
Attach Accept(NSAPI,TI,PDP Type)
Attach Complete(NSAPI,TI,PDP Type)
HLR
Authentication/Ciphering Authentication/Ciphering
GPRS: Obtaining IP Connectivity
• GPRS attach– Authentication of
MS– Establishment/
Initialization of security functions
• PDP Context Setup– Obtain IP
address– Connect to
‚external‘ network[see later]
Page 33Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Enhanced Data rates for the GSM Evolution (EDGE)
Time Slot (MS-> BTS) Transmission Rate
48.......384 kbit/s
1 2 8
48 kbit/s ....48 kbit/s 48 kbit/s8 PSK
....
New Modulation Scheme
• Advantages– Increased Data Rate– No Modificatíons in Core Network (SGSN/GGSN) required
• Disadvantages– New Modulationscheme(8 PSK), not compatible to GSMK– HW Changes in the BTS required
Page 34Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
3rd Generation Systems: IMT-2000• Proposals for IMT-2000 (International Mobile Telecommunications)
– UWC-136, cdma2000, WP-CDMA– UMTS (Universal Mobile Telecommunications System) from ETSI
• Frequencies
IMT-2000
1850 1900 1950 2000 2050 2100 2150 2200 MHz
MSS
ITU allocation(WRC 1992) IMT-2000
MSS
Europe
China
Japan
NorthAmerica
UTRAFDD
UTRAFDD
TDD
TDD
MSS
MSS
DECT
GSM1800
1850 1900 1950 2000 2050 2100 2150 2200 MHz
IMT-2000MSS
IMT-2000MSS
GSM1800
cdma2000W-CDMA
MSS
MSS
MSS
MSS
cdma2000W-CDMA
PHS
PCS rsv.
Page 35Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Universal Mobile Telecommunication System (UMTS)
• Currently standardized by 3rd Generation Partnership Project (3GPP), see http://www.3GPP.org[North America: 3GPP2]
• So far, four releases: R’99, R4, R5, R6
Modifications:• New methods & protocols on radio link increased access bandwidth• Coexistence of two domains in the core network
– Packets Switched (PS)– Circuit Switched (CS)
• New Services• IP Service Infrastructure: IP Based Multimedia Subsystems (IMS) (R5)
Page 36Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
UMTS Domains
BSC
BTS
BTS
BSS (RAN/GERAN)
RNC
Node B
Node B
UTRAN
ME
SIM
USIM
MS
SGSN
PS Domain
GGSN
CS MGW
CS
Domain HSS/AuC
RNC
MSC-Serv./VLR Abis
SIM-ME
Iu bis Cu
Um
Uu
Iu Cs Gb
A
Iu PS
C
D
Iur
Gn
Gr Gc
Gs
CS MGW MSC-Serv./VLR
CS MGW
GMSC-Serv.
IMS Domain
(Release 5)
Mb/Gi
Cx
Mc
Nb
Nb
G/E/Nc
Nc
Mc
User Equipment Domain
Access Network Domain
Core Network Domain
Infrastructure Domain
Page 37Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
User Equipment
Domain
User Equipment
DomainAccess
Network
Domain
Access
Network
Domain
Core
Network
Domain
Core
Network
Domain
Service and Application
Domain
Service and Application
Domain
Charging/ Lawful Interception/ OAMCharging/ Lawful Interception/ OAM
Other
Networks (IP/ ISDN)
Other
Networks (IP/ ISDN)
• Radio Access Network– Node B (Base station)– Radio Network Controller (RNC)
• Mobile Core Network– Serving GPRS Support Node (SGSN)– Gateway GPRS Support Node (GGSN)– Mobile Switching Center (MSC)– Home/Visited Location Register (HLR/VLR)– Routers/Switches, DNS Server, DHCP Server,
Radius Server, NTP Server, Firewalls/VPN Gateways
• Application/Services• IP-Based Multimedia Subsystem (IMS)
– [see 9th Semester]• Operation, Administration & Maintenance (OAM)• Charging Network • [Legal Interception]
UMTS Network Domains
Page 38Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
UMTS Radio Access Network (UTRAN): architecture
• CDMA (Code Division Multiple Access) on Radio Link
• transmission rate theoretically up to 2Mbit/s (realistic up to 300kb/s)
Page 39Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Content
1. Introduction• Cellular Concepts & Technologies
2. GSM• Network Architecture, Air Interface• Signalling/Call Setup, Mobility Support• Data Services, HSCSD
3. GPRS & UMTS• GPRS: Architecture, Air-Interface, Core-Network Modifications• UMTS domains and architecture
4. IP transport in Packet Switched UMTS/GPRS Networks• PDP contexts, APNs, TFTs• Bearers• ’full’ network architecture
Exercise
Page 40Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Transport of IP packets
ApplicationServer
GGSNTerminal SGSNUTRAN
GTP-UGTP-U
User IP (v4 or v6)
Radio Bearer
IP tackets are tunnelled through the UMTS/GPRS network (GTP – GPRS tunneling protocol)
L1
RLC
PDCP
MAC
IPv4 or v6
Application
L1
RLC
PDCP
MAC
ATM
UDP/IPv4 or v6
GTP‑U
AAL5
Relay
L1
UDP/IPv4 or v6
L2
GTP‑U
IPv4 or v6
Iu-PSUu Gn Gi
ATM
UDP/IPv4 or v6
GTP‑U
AAL5
L1
UDP/IPv4 or v6
GTP‑U
L2
Relay
L1
L2
IPv4 or v6
[Source: 3GPP]
Page 41Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
IP Transport: Concepts• PDP contexts (Packet Data Protocol) activation
• done by UE before data transmission• specification of APN and traffic parameters• GGSN delivers IP address to UE• set-up of bearers and mobility contexts in SGSN and GGSN• activation of multiple PDP contexts possible
•Access Point Names (APN)• APNs identify external networks (logical Gi interfaces of GGSN)• At PDP context activation, the SGSN performs a DNS query to find out the GGSN(s) serving the APN requested by the terminal.• The DNS response contains a list of GGSN addresses from which the SGSN selects one address in a round-robin fashion (for this APN).
•Traffic Flow Templates (TFTs)• set of packet filters (source address, subnet mask, destination port range, source port range, SPI, TOS (IPv4), Traffic Class (v6), Flow Label (v6)• used by GGSN to assign IP packets from external networks to proper PDP context
• GPRS tunneling protocol (GTP) •For every UE, one GTP-C tunnel is established for signalling and a number of GTP-U tunnels, one per PDP context (i.e. session), are established for user traffic.
Page 42Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
GGSN
IP Transport: PDP Context & APNs
Terminal SGSNGGSN
PDP Context X 2 (APN X, IP address X, QoS 2)
PDP Context X 1 (APN X, IP address X, QoS 1)
ISP X
ISP Z
ISP Y
PDP Context Z (APN Z, IP address Z, QoS)
PDP Context Y (APN Y, IP address Y, QoS)
AP
N Y
AP
N Z
AP
N X
Same PDP (IP) address and APN
PDP Context selectionbased on TFT (downstream)
[Source: 3GPP]
Page 43Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
UMTS Data Transport: Bearer Hierarchy
TE MT UTRAN/GERAN
CN IuEDGENODE
CNGateway
TE/AS
End-to-End Service(IP Bearer Service)
TE/MT LocalBearer Service
UMTS BearerService
External BearerService
UMTS Bearer Service
Radio Access BearerService
CN BearerService
BackboneBearer Service
Iu BearerService
Radio BearerService
PhysicalRadio
Service
PhysicalBearer Service
Air Interface
3G GGSN3G SGSNRAN
User Equipment
Page 44Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
The ’full picture’ of the UMTS packet switched domain
GGSN SGSN
DHCP
RADIUS
IMS Domain
HSS
HLR/AuC
RNC
Node B
Node B
Network Services
SS7, Gr
SS7, Gc
GRX Network
DNS Gn-SEC
DNS Gn-PRI
Gn Network
DNS Ext
BG
Gi Network
DMZ
DNS Ext
HTTP proxy
DNS NS
DNS IMS
P-CSCF
I/S-CSCF
MNO1̀s Backbone
AS Network
Messages
FTP
Video
DNS AS
Corp. Network
VPN -GWY
AS
BG
IDS
IDS
MNO1̀s Network
BG
1 2 3 4 5 6 7 8 9 * 0 # UE1
BG
Internet AS
MNO3
UE3
MNO2
UE2
IMS
Roaming Support: • UE attaches with SGSN in visited network• PDP context is set-up to GGSN in home network (via Gp interface, GRX network)
Page 45Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Message Flow: PDP Context Setup
…
…
Page 46Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Summary
1. Introduction• Cellular Concepts & Technologies
2. GSM• Network Architecture, Air Interface• Signalling/Call Setup, Mobility Support• Data Services, HSCSD
3. GPRS & UMTS• GPRS: Architecture, Air-Interface, Core-Network Modifications• UMTS domains and architecture
4. IP transport in Packet Switched UMTS/GPRS Networks• PDP contexts, APNs, TFTs• Bearers• ’full’ network architecture
Exercise
Page 47Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Acknowledgements/References
• Lecture notes: Mobile Communciations, Jochen Schiller, www.jochenschiller.de• Marco Hoffmann, Master Thesis, ‘Simulation of a flow-control algorithm between two nodes of
the GPRS network’, TU Munich and Siemens AG, 2001.• Tutorial: IP Technology in 3rd Generation mobile networks, Siemens AG (J. Kross, L. Smith, H.
Schwefel)• Various 3GPP Presentations. www.3gpp.org• J. Schiller: ’Mobile Communications’. Addison-Wesley, 2000.• GPRS books:
– T. Halonen, J. Romero, J. Melero: ‘GSM, GRPS, EDGE Performance: Evolution towards 3G/UMTS’, Wiley, 2003
Page 48Hans Peter Schwefel
Wireless Networks I, Lecture 5, Spring 04
Exercises:1. Data Rates: A user wants to do an FTP download of a 8MB Power-Point Presentation.
Compute the duration of this download for the following access technologies• GSM data service• HSCSD, 4 timeslots• GPRS, 4 timeslots (downlink)• EDGE, 8 timeslots• Wired ISDN access (64kbit/s)Give at least two reasons why the actual download times are likely to be longer than the ones
just computed.Charging: The operator charges in GSM 15cent/min, in GPRS 0.1cent/kB. Compare the
costs of the GSM and GPRS download in the FTP case as well as for a Web-session with duration of 1hour and overall data volume of 150kB.
2. IP transport in GPRS networks: a mobile user has set-up a PDP context to an ISP which has assigned him the IP address 10.10.123.45 (private). The user now iniates a web access to the CNN server. Describe the path of the IP packet through the mobile operator’s network, showing the header structure of the packet (detailling the IP source and destination address).