1. 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)

2. 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

3. Cellular systems: technologies & subscribers
200
400
600
800
1000
1200
1996
1997
1998
1999
2000
2001
2002
year
Subscribers [million]
GSM total
TDMA total
CDMA total
PDC total
Analogue total
Total wireless
Prediction (1998)

4. Content Introduction GSM GPRS & UMTS
Cellular Concepts & Technologies
GSM
Network Architecture, Air Interface
Signalling/Call Setup, Mobility Support
Data Services, HSCSD
GPRS & UMTS
GPRS: Architecture, Air-Interface, Core-Network Modifications
UMTS domains and architecture
IP transport in Packet Switched UMTS/GPRS Networks
PDP contexts, APNs, TFTs
Bearers
’full’ network architecture
Exercise

5. GSM: Global System for Mobile Communication
History:
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
Today:

6. Base Station Subsystem
GSM – Architecture
BSC MS
BTS
MSC
HLR
VLR
OMC
EIR
AuC O A
bis U m
Radio Link
Base Station Subsystem
Network and
Switchung Subsystem
Operation
Subsystem
Connection to
ISDN, PDN
PSTN
Radio Subsystem (RSS)
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

7. GSM Services ‘Traditional’ voice services
voice telephony primary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz
emergency number common number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible)
Multinumbering several 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

8. GSM: Radio Technology Cellular 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
cell
possible radio coverage of the cell
idealized shape of the cell

9. GSM: Air Interface I Frequency Division Multiple Access (FDMA)
Separate up-link (MTBTS) and down-link (BTSMT) 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

10. GSM: Air Interface II Time Division Multiple Access (TDMA)
TDMA Frame
Time Division Multiple Access (TDMA)
Within each channel: sequence of TDMA frames
TDMA frames subdivided into 8 time-sots

11. GSM: TDMA hierarchy of frames
hyperframe 1 2
...
2045
2046
2047
3 h 28 min s
superframe 1 2
... 48 49 50
6.12 s 1
... 24 25
multiframe 1
... 24 25
120 ms 1 2
... 48 49 50
235.4 ms
frame 1
... 6 7
4.615 ms
slot
burst
577 µs

12. GSM Air Interface: Combination of TDMA & FDMA
MHz
124 channels (200 kHz)
downlink
frequency
MHz
124 channels (200 kHz)
uplink
higher GSM frame structures
time
GSM TDMA frame 1 2 3 4 5 6 7 8
4.615 ms
GSM time-slot (normal burst)
guard
space
guard
space
tail
user data S
Training S
user data
tail
3 bits
57 bits 1
26 bits 1
57 bits 3
546.5 µs
577 µs

13. Functionalities in Radio Subsystem
BTS comprises radio specific functions
BSC is the switching center for radio channels

14. Overview: GSM protocol layers for signalingUm
Abis A MS
BTS
BSC
MSC CM CM MM MM
RR’
BTSM
BSSAP RR
BSSAP
RR’
BTSM
SS7
SS7
LAPDm
LAPDm
LAPD
LAPD
radio
radio
PCM
PCM
PCM
PCM
16/64 kbit/s
64 kbit/s /
2.048 Mbit/s

15. Example: Mobile Terminated Call
calling a GSM subscriber
forwarding call to GMSC
signal call setup to HLR
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 4
HLR
VLR 5 8 9 3 6 14 15
PSTN 7
calling
station
GMSC
MSC 1 2 10 13 10 10 16
BSS
BSS
BSS 11 11 11 11 12 17 MS

16. Example: Message flow between MS and BTS for Mobile Terminated Call
MTC
BTS
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

17. Mobility Support I: Types of handover1 4 3 2 MS MS MS MS
BTS
BTS
BTS
BTS
BSC
BSC
BSC
MSC
MSC

18. Mobility Support II: Handover decision
receive level
BTSold
receive level
BTSold
HO_MARGIN MS MS
BTSold
BTSnew

19. Mobility support III: Handover procedure
MSC MS
BTSold
BSCold
BSCnew
BTSnew
measurement
report
measurement
result
HO decision
HO required
HO request
resource allocation
ch. activation
ch. activation ack
HO request ack
HO command
HO command
HO command
HO access
Link establishment
HO complete
HO complete
clear command
clear command
clear complete
clear complete

20. Mobile Communication & Data Traffic
The future Internet will mainly be accessed by mobile devices
200
400
600
800
1000
1200
1400
1600
1800
1995
2000
2005
2010
Subscriptions worldwide (millions)
Mobile Internet
Subscribers
Mobile
Fixed
Fixed Internet
# Mobile Subscribers higher than wired telephony in 2002
Same crossover predicted for Internet access in the next 5 years

21. 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

22. Content Introduction GSM GPRS & UMTS
Cellular Concepts & Technologies
GSM
Network Architecture, Air Interface
Signalling/Call Setup, Mobility Support
Data Services, HSCSD
GPRS & UMTS
GPRS: Architecture, Air-Interface, Core-Network Modifications
UMTS domains and architecture
IP transport in Packet Switched UMTS/GPRS Networks
PDP contexts, APNs, TFTs
Bearers
’full’ network architecture
Exercise

23. 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)

24. GPRS - Architecture Components: Transmission: Radio link:
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

25. GPRS: Channel Coding and Multiplexing
.....
Time Slot (MS-> BTS) 1 2 3 8
9,05 kbit/s
9,05 kbit/s
9,05 kbit/s
9,05 kbit/s
Coding Scheme 1
.....
Selection of Coding depending on quality of radio connection
13,4 kbit/s
13,4 kbit/s
13,4 kbit/s
Coding Scheme 2
.....
15,6 kbit/s
15,6 kbit/s
15,6 kbit/s
Coding Scheme 3
.....
‚optimal‘ radio quality: no interference, etc.
21,4 kbit/s
21,4 kbit/s
21,4 kbit/s
Coding Scheme 4
.....
Erhöhte Datenrate bei GPRS durch neue „Coding Schemes“ und Kanalbündelung :
„Coding Schemes“
Abhängig von der Qualität der Funkschnittstelle können unterschiedliche „Coding Schemes“ verwendet werden.
So hat z.B. das „Coding Scheme 4“ keine „Forward Error Correction“ (FEC) mehr und erlaubt die Übertragung von 21,4kbit/s auf einem physikalischen Kanal (TS). CS-4 kann aber nur bei einer sehr guten Qualität der Funkverbindung eingesetzt werden. (MS sehr nah an der BTS in der unmittelbaren Umgebung)
Bündelung mehrerer physikalischer Kanäle: In einer Zelle, die GPRS unterstützt, können ein oder mehrere physikalische Kanäle (Time Slots) für die Übertragung von GPRS-Daten allokiert werden.
Theoretisch, wenn alle 8 physikalischen Kanäle zur Datenübertragung mit CS-4 genutzt werden, ist auf der Luftschnittstelle eine „Peak“-Datenrate von bis zu 171,2 kbit/s möglich.
Um die zur Verfügung stehenden Funkfrequenzen + Ressourcen optimal für Sprach + GPRS-Datenverkehr zu nutzen gibt es folgendes Konzept:
Overall transmission rate
,2 kbit/s

26. Examples for GPRS device classes
Receiving slots
Sending slots
Maximum number of slots 1 2 3 5 4 8 10 12

27. 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

28. GPRS architecture and interfacesMS
BSS
GGSN
SGSN
MSC Um
EIR
HLR/ GR
VLR
PDN Gb Gn Gi

29. GPRS Core Network Functions

30. GPRS: Protocol Stack RLC: Radio Link Control LLC: Logical Link Control
Acknowledged mode (reliable) or unacked
LLC: Logical Link Control
BSSGRP: BSS GPRS Protocol
SNDCP: Sub-Network Dependent Convergence Protocol
GTP: GPRS Tunneling Protocol
Mobility Support

31. Data Units in GPRS

32. Authentication/Ciphering
GPRS: Obtaining IP Connectivity
SGSN
HLR
GPRS attach
Authentication of MS
Establishment/Initialization of security functions
PDP Context Setup
Obtain IP address
Connect to ‚external‘ network
[see later]
BSS Um Gb Gr
Attach Request
(NSAPI,TI,PDP Type)
Authentication/Ciphering
Authentication/Ciphering
Insert Subscriber Data
(NSAPI,TI,PDP Type)
Insert Subscriber Data Ack
(NSAPI,TI,PDP Type)
Attach Accept
(NSAPI,TI,PDP Type)
Attach Complete
(NSAPI,TI,PDP Type)

33. Enhanced Data rates for the GSM Evolution (EDGE)
....
Time Slot (MS-> BTS) 1 2 8
Transmission Rate
New Modulation Scheme
48 kbit/s
48 kbit/s
48 kbit/s
8 PSK
....
kbit/s
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
Enhanced Data Rates for the GSM Evolution (EDGE)
Mit EDGE (ab Release ‚99) soll durch Änderung des Modulationsverfahrens
8 PSK (Phase Shift Keying) statt 21,4 kbit/s GMSK (Gausschen Minimum Shift Keying; ist quasi eine Art Frequenzmodulation) pro physikalischem Kanal 48 kbit/s realisiert werden.
Wieder durch die Bündelung von bis zu 8 Kanälen sind so theoretisch Übertragungsraten bis zu 384 kbit/s möglich.
Ein Nachteil:
Die Erweiterung des Modulationsverfahrens auf 8PSK zusätzlich zu GSMK erfordert die Erweiterung der BTS-Hardware: Einsatz einer neuen Coding Unit (CU).
Da die im SGSN un GGSN benutzten Protokolle (später dazu mehr) keine direkten Einfluß auf die Datenübertragungsrate haben, [wieviel „Bits“ per IP-Protokoll transportiert werden berührt den SGSN nicht] hat die Benutzung des Features EDGE nur einen geringen Einfluß auf die notwendigen Protokollerweiterungen im SGSN und GGSN.
Mit EDGE sind Anforderungen an die 3. Mobilfunkgenaration erfüllbar.
(Die Änderung des Modulationsverfahrens auf der Luftschnittstelle erfolgt jeweils burstweise. Pro „burst“ jeweils ein Modulationsverfahren GSMK oder 8PSK.)
Welche Datendienste „typischerweise“ mit GPRS bzw. EDGE möglich sind, auf der nächsten Folie
Literatur: Detailed Operational Specification LM Functional Specification Level 2 P30309-A0295-A H1
Marketing-Präsentationen:

34. 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
1850
1900
1950
2000
2050
2100
2150
2200
MHz
ITU allocation
(WRC 1992)
IMT-2000
MSS 
IMT-2000
MSS 
GSM
1800 DE CT T D
UTRA
FDD 
MSS  T D
UTRA
FDD 
MSS 
Europe
GSM
1800
IMT-2000
MSS 
IMT-2000
MSS 
China
PHS
cdma2000
W-CDMA
MSS 
cdma2000
W-CDMA
MSS 
Japan
PCS
MSS 
rsv.
MSS 
North
America
1850
1900
1950
2000
2050
2100
2150
2200
MHz

35. Universal Mobile Telecommunication System (UMTS)
Currently standardized by 3rd Generation Partnership Project (3GPP), see [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)

36. UMTS Domains

37. UMTS Network Domains Radio Access Network Mobile Core 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]

38. 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)

39. Content Introduction GSM GPRS & UMTS
Cellular Concepts & Technologies
GSM
Network Architecture, Air Interface
Signalling/Call Setup, Mobility Support
Data Services, HSCSD
GPRS & UMTS
GPRS: Architecture, Air-Interface, Core-Network Modifications
UMTS domains and architecture
IP transport in Packet Switched UMTS/GPRS Networks
PDP contexts, APNs, TFTs
Bearers
’full’ network architecture
Exercise

40. Transport of IP packets
IP tackets are tunnelled through the UMTS/GPRS network (GTP – GPRS tunneling protocol)
Application
Server
GGSN
Terminal
SGSN
UTRAN
GTP-U
User IP (v4 or v6)
Radio Bearer
Application IP
v4 or v6 IP
v4 or v6 IP
v4 or v6
Relay
Relay
PDCP
PDCP
GTP‑U
GTP‑U
GTP‑U
GTP‑U
RLC
RLC
UDP/IP
v4 or v6
UDP/IP
v4 or v6
UDP/IP
v4 or v6
UDP/IP
v4 or v6
MAC
MAC
AAL5
AAL5 L2 L2 L2
[Source: 3GPP] L1 L1
ATM
ATM L1 L1 L1 Uu
Iu-PS Gn Gi

41. 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.

42. IP Transport: PDP Context & APNs
PDP Context X1 (APN X, IP address X, QoS1)
PDP Context X2 (APN X, IP address X, QoS2)
IP Transport: PDP Context & APNs
ISP X
PDP Context Y (APN Y, IP address Y, QoS)
Terminal
PDP Context Z (APN Z, IP address Z, QoS)
Same PDP (IP) address and APN
GGSN
SGSN
ISP Y
APN X
PDP Context selection based on TFT (downstream)
GGSN
APN Y
ISP Z
APN Z
[Source: 3GPP]

43. UMTS Data Transport: Bearer Hierarchy
Air Interface TE MT
UTRAN/ CN Iu CN
TE/AS
GERAN
EDGE
Gateway
NODE
End-to-End Service (IP Bearer Service)
TE/MT Local
UMTS Bearer Service
UMTS Bearer
External Bearer
Bearer Service
Service
Service
Radio Access Bearer
CN Bearer
Service
Service
Radio Bearer
Iu Bearer
Backbone
Service
Service
Bearer Service
Physical
Physical
Radio
Bearer Service
Service
RAN
3G SGSN
3G GGSN
User Equipment

44. The ’full picture’ of the UMTS packet switched domain
Roaming Support:
UE attaches with SGSN in visited network
PDP context is set-up to GGSN in home network (via Gp interface, GRX network)

45. Message Flow: PDP Context Setup… …

46. Summary Introduction GSM GPRS & UMTS
Cellular Concepts & Technologies
GSM
Network Architecture, Air Interface
Signalling/Call Setup, Mobility Support
Data Services, HSCSD
GPRS & UMTS
GPRS: Architecture, Air-Interface, Core-Network Modifications
UMTS domains and architecture
IP transport in Packet Switched UMTS/GPRS Networks
PDP contexts, APNs, TFTs
Bearers
’full’ network architecture
Exercise

47. Acknowledgements/References
Lecture notes: Mobile Communciations, Jochen Schiller,
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.
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

48. Exercises:
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.
IP transport in GPRS networks: a mobile user has set-up a PDP context to an ISP which has assigned him the IP address (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).