1. Telecommunication Systems

2. Mobile phone subscribers worldwide
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Mobile phone subscribers worldwide
approx. 1.7 bn
1600
2009:
>4 bn
2013:
>6 bn!
1400
1200
GSM total
1000
TDMA total
CDMA total
Subscribers [million]
800
PDC total
Analogue total
W-CDMA
600
Total wireless
Prediction (1998)
400
200
1996
1997
1998
1999
2000
2001
2002
2003
2004
year
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

3. Development of mobile telecommunication systems
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Development of mobile telecommunication systems
CT0/1
FDMA
AMPS
CT2
NMT
IMT-FT
DECT
IS-136
TDMA
D-AMPS
EDGE
IMT-SC
IS-136HS
UWC-136
TDMA
GSM
GPRS
PDC
IMT-DS
UTRA FDD / W-CDMA
HSPA
IMT-TC
UTRA TDD / TD-CDMA
CDMA
IMT-TC
TD-SCDMA
IS-95
cdmaOne
IMT-MC
cdma2000 1X EV-DO
cdma2000 1X
1X EV-DV
(3X) 1G 2G
2.5G 3G
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

4. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
GSM: Overview
GSM
formerly: Groupe Spéciale Mobile (founded 1982)
now: Global System for Mobile Communication
Today many providers all over the world use GSM (219 countries in Asia, Africa, Europe, Australia, America)
more than 4.2 billion subscribers in more than 700 networks
more than 75% of all digital mobile phones use GSM
over 29 billion SMS in Germany in 2008, (> 10% of the revenues for many operators) [be aware: these are only rough numbers…]
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

5. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
GSM: Mobile Services
GSM offers
several types of connections
voice connections, data connections, short message service
multi-service options (combination of basic services)
Three service domains
Bearer Services
Tele Services
Supplementary Services
bearer services MS
GSM-PLMN
transit
network
(PSTN, ISDN)
source/
destination
network TE MT TE
R, S Um
(U, S, R)
tele services
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

6. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Bearer Services
Telecommunication services to transfer data between access points
Specification of services up to the terminal interface (OSI layers 1-3)
Different data rates for voice and data (original standard)
data service (circuit switched)
synchronous: 2.4, 4.8 or 9.6 kbit/s
asynchronous: bit/s
data service (packet switched)
asynchronous: bit/s
Today: data rates of approx. 50 kbit/s possible – will be covered later! (even more with new modulation)
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

7. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Tele Services
Telecommunication services that enable voice communication via mobile phones
Offered services
Telephonic-Voice
FAX, SMS, MMS,
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)
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

8. Supplementary services
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Supplementary services
Services in addition to the basic services, cannot be offered stand-alone
May differ between different service providers, countries and protocol versions
Important services
Call forwarding, caller line identification
Call holding, barring calls from specified numbers
Providing information regarding call charges, remaining balance
automatic call-back
conferencing with up to 7 participants
locking of the mobile terminal (incoming or outgoing calls)
...
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

9. Architecture of the GSM system
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Architecture of the GSM system
GSM is a PLMN (Public Land Mobile Network)
several providers setup mobile networks following the GSM standard within each country
components
MS (mobile station)
BS (base station)
MSC (mobile switching center)
LR (location register)
subsystems
RSS (radio subsystem): covers all radio aspects
NSS (network and switching subsystem): call forwarding, handover, switching
OSS (operation subsystem): management of the network
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

10. Ingredients 1: Mobile Phones, PDAs & Co.
The visible but smallest
part of the network!

11. Ingredients 2: Antennas
Still visible – cause many discussions…

12. Ingredients 3: Infrastructure 1
Base Stations
Cabling
Microwave links

13. Ingredients 3: Infrastructure 2
Not „visible“, but comprise the major part of the network (also from an investment point of view…)
Management
Data bases
Switching units
Monitoring

14. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
GSM: overview
OMC, EIR, AUC
fixed network
HLR
GMSC
NSS
with OSS
VLR
MSC
VLR
MSC
BSC
BSC
RSS
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

15. GSM: elements and interfaces
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
GSM: elements and interfaces
radio cell
BSS MS MS Um
radio cell MS
RSS
BTS
BTS
Abis
BSC
BSC A
MSC
MSC
NSS
VLR
VLR
Signaling system no. 7
HLR
ISDN, PSTN
GMSC
PDN
IWF O
OSS
EIR
AUC
OMC
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

16. GSM: system architecture
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
GSM: system architecture
radio subsystem
network and switching subsystem
fixed partner networks MS MS
ISDN PSTN Um
MSC
Abis
BTS
BSC
EIR
BTS
SS7
HLR
VLR
BTS
BSC
ISDN PSTN
BTS A
MSC
BSS
IWF
PSPDN CSPDN
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

17. System architecture: radio subsystem
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
System architecture: radio subsystem
radio subsystem
network and switching subsystem
Components
MS (Mobile Station)
BSS (Base Station Subsystem): consisting of
BTS (Base Transceiver Station): sender and receiver
BSC (Base Station Controller): controlling several transceivers
Interfaces
Um : radio interface
Abis : standardized, open interface with 16 kbit/s user channels
A: standardized, open interface with 64 kbit/s user channels MS MS Um
Abis
BTS
BSC
MSC
BTS A
BTS
MSC
BSC
BTS
BSS
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

18. System architecture: network and switching subsystem
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
System architecture: network and switching subsystem
network subsystem
fixed partner networks
Components
MSC (Mobile Services Switching Center):
IWF (Interworking Functions)
ISDN (Integrated Services Digital Network)
PSTN (Public Switched Telephone Network)
PSPDN (Packet Switched Public Data Net.)
CSPDN (Circuit Switched Public Data Net.)
Databases
HLR (Home Location Register)
VLR (Visitor Location Register)
EIR (Equipment Identity Register)
ISDN PSTN
MSC
EIR
SS7
HLR
VLR
ISDN PSTN
MSC
IWF
PSPDN CSPDN
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

19. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Radio subsystem
The Radio Subsystem (RSS) comprises the cellular mobile network up to the switching centers
Components
Base Station Subsystem (BSS):
Base Transceiver Station (BTS): radio components including sender, receiver, antenna - if directed antennas are used one BTS can cover several cells
Base Station Controller (BSC): switching between BTSs, controlling BTSs, managing of network resources, mapping of radio channels (Um) onto terrestrial channels (A interface)
BSS = BSC + sum(BTS) + interconnection
Mobile Stations (MS)
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

20. Universität Karlsruhe Institut für Telematik
GSM: cellular network
Mobilkommunikation
SS 1998
segmentation of the area into cells
cell
possible radio coverage of the cell
idealized shape of the cell
use of several carrier frequencies
not the same frequency in adjoining 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)
if a mobile user changes cells handover of the connection to the neighbor cell
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

21. GSM frequency bands (examples)
Type
Channels
Uplink [MHz]
Downlink [MHz]
GSM 850
GSM 900
classical
extended
0-124,
124 channels
+49 channels
GSM 1800
GSM 1900
GSM-R
exclusive
, 0-124
69 channels
Additionally: GSM 400 (also named GSM 450 or GSM 480 at / or / MHz)
Please note: frequency ranges may vary depending on the country!
Channels at the lower/upper edge of a frequency band are typically not used

22. Example coverage of GSM networks (www.gsmworld.com)
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Example coverage of GSM networks (
T-Mobile (GSM-900/1800) Germany
O2 (GSM-1800) Germany
AT&T (GSM-850/1900) USA
Vodacom (GSM-900) South Africa
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

23. Base Transceiver Station and Base Station Controller
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Base Transceiver Station and Base Station Controller
Tasks of a BSS are distributed over BSC and BTS
BTS comprises radio specific functions
BSC is the switching center for radio channels
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

24. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Mobile station
Terminal for the use of GSM services
A mobile station (MS) comprises several functional groups
MT (Mobile Terminal):
offers common functions used by all services the MS offers
corresponds to the network termination (NT) of an ISDN access
end-point of the radio interface (Um)
TA (Terminal Adapter):
terminal adaptation, hides radio specific characteristics
TE (Terminal Equipment):
peripheral device of the MS, offers services to a user
does not contain GSM specific functions
SIM (Subscriber Identity Module):
personalization of the mobile terminal, stores user parameters R S Um TE TA MT
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

25. Network and switching subsystem
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Network and switching subsystem
NSS is the main component of the public mobile network GSM
switching, mobility management, interconnection to other networks, system control
Components
Mobile Services Switching Center (MSC) controls all connections via a separated network to/from a mobile terminal within the domain of the MSC - several BSC can belong to a MSC
Databases (important: scalability, high capacity, low delay)
Home Location Register (HLR) central master database containing user data, permanent and semi-permanent data of all subscribers assigned to the HLR (one provider can have several HLRs)
Visitor Location Register (VLR) local database for a subset of user data, including data about all user currently in the domain of the VLR
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

26. Mobile Services Switching Center
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Mobile Services Switching Center
The MSC (mobile services switching center) plays a central role in GSM
switching functions
additional functions for mobility support
management of network resources
interworking functions via Gateway MSC (GMSC)
integration of several databases
Functions of a MSC
specific functions for paging and call forwarding
termination of SS7 (signaling system no. 7)
mobility specific signaling
location registration and forwarding of location information
provision of new services (fax, data calls)
support of short message service (SMS)
generation and forwarding of accounting and billing information
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

27. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Operation subsystem
The OSS (Operation Subsystem) enables centralized operation, management, and maintenance of all GSM subsystems
Components
Authentication Center (AUC)
generates user specific authentication parameters on request of a VLR
authentication parameters used for authentication of mobile terminals and encryption of user data on the air interface within the GSM system
Equipment Identity Register (EIR)
registers GSM mobile stations and user rights
stolen or malfunctioning mobile stations can be locked and sometimes even localized
Operation and Maintenance Center (OMC)
different control capabilities for the radio subsystem and the network subsystem
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

28. List of mobile network operators

29. Localization and calling
Automatic, worldwide localization of users
Roaming
- Changing VLRs with uninterrupted availability of all services
GSM – one device, over 190 countries

30. To locate an MS and to address the MS, we need
Mobile station international ISDN number(MSISDN)
(e.g )
Country code 91 , national destination code (address of the network provider), subscriber number
International mobile subscriber identity (IMSI)
- internal unique identification of a subscriber
- Mobile country code, mobile network code, mobile subscriber identification number
Temporary mobile subscriber identity (TMSI)
- 4 byte number selected by VLR
Mobile station roaming number (MSRN)
VLR generates this address on request from the MSC and the address is stored in HLR
Visitor country code, Visitor national destination code, identification of current MSC with subscriber number

31. Difference between IMSI and MSISDN
IMSI is used to identify a subscriber by the operator.
MSISDN is the number which is used for dialing.
When you call your friend/a mobile, you call the MSISDN number of the mobile, not the IMSI.
For Eg: Consider 2 subscriber's A & B.
IMSI (A) :
IMSI (B) :
MSISDN (A) :
MSISDN (B) :
When A would like to call B, A dials the MSISDN number of B, i.e, And same is true for vice-versa.
Whereas IMSI is used to identify and authenticate the subscriber with the network

32. Mobile Terminated Call
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Mobile Terminated Call
1: 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 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
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

33. Mobile Originated Call
Universität Karlsruhe
Institut für Telematik
Mobile Originated Call
Mobilkommunikation
SS 1998
1, 2: connection request
3, 4: security check
5-8: check resources (free circuit)
9-10: set up call
VLR 3 4
PSTN 6 5
GMSC
MSC 7 8 2 9 1 MS
BSS 10
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

34. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
MTC/MOC
BTS MS
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
service request
MTC
MOC
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

35. Handover Reasons for a handover MS moves out of the range of a BTS
MSC and BSC may decide that the traffic in one cell is too high and shift some MS to other cells

36. Handover process Important one in any cellular network
Must be completed efficiently and without inconvenience to the user
Different networks use different types of
handover techniques

37. Two main types of handover
Hard handover─ GSM systems
Soft handover ─ CDMA systems

38. Hard Handover
Existing radio link must be dropped for a small period of time
Then taken over by another base station
A call in progress redirected not only from a base station to another base station but also from its current transmit–receive frequency pair to another frequency pair
An ongoing call can not exchange data or voice for this duration

39. Hard Handover Break in call transmission
Handover takes place in a few ms (at best in 60 ms)
Interruption is hardly discernible by the user
Handover to another cell is required when the signal strength is low and error rate is high.
GSM systems perform hard handovers

40. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
4 types of handover 1 2 3 4 MS MS MS MS
BTS
BTS
BTS
BTS
BSC
BSC
BSC
Intra-cell handover
Inter-cell, Intra-BSC handover
Inter-BSC, Intra-MSC handover
Inter MSC handover
MSC
MSC
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

41. Intra-cell Handover
Due to interference at certain frequencies, the signal quality poor
The BSC can handover the call to another frequency of the cell in such cases

42. Inter-cell, Intra-BSC Handover
When an MS moves to a neighbouring cell and suffers poor signal quality, the BSC can handover the call to a different BTS channel of the same BSC

43. Inter-BSC, Intra MSC Handover
Handover for load balancing when the traffic from the cells and BTSs high
The BSCs connect to an MSC
A call, which is ongoing in a cell through a BTS, may be handed over to another BSC connected to the same MSC
Since the BSCs connect to the MSC interfaces by PCM, the handover is over a wired line

44. Inter-MSC Handover
Handover also takes place for load balancing when the traffic from the cells and BSCs high
An ongoing call, which is being handled by a cell, may be handed over to another MSC
Since the two MSCs are interfaced through PCM the handover performed over a wired line

45. Soft handover
Mobile station at the boundary of two adjacent cells─ does not suffer call drops due to handover in the boundary region
Soft handover does not require breaking of the radio link for cell-to-cell transfer of a call.
A mobile device can be simultaneously connected to several base stations

46. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Handover decision
receive level
BTSold
receive level
BTSold
HO_MARGIN MS MS
BTSold
BTSnew
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

47. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Handover procedure MS
BTSold
BSCold
MSC
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
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

48. New generation (3G) networks
Ensure mobility by handover not only among the BTSs, BSCs, or MSCs but also among the in-between LANs
Ensures seamless (uninterrupted) connectivity to the user

49. GSM networks various security features
A wireless radio based network system quite sensitive to the unauthorized use of resources
Designed to protect subscriber privacy
Secured network against misuse of resources by unregistered users
Controlled access to the network by Mobile station
Required to use a PIN before it can access the network through Um interface

50. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
Security in GSM
Security services
access control/authentication
user  SIM (Subscriber Identity Module): secret PIN (personal identification number)
SIM  network: challenge response method
confidentiality
voice and signaling encrypted on the wireless link (after successful authentication)
anonymity
temporary identity TMSI (Temporary Mobile Subscriber Identity)
newly assigned at each new location update (LUP)
encrypted transmission
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

51. Security Algorithms 3 algorithms specified in GSM
A3 for authentication (“secret”, open interface)
A5 for encryption (standardized)
A8 for key generation (“secret”, open interface)

52. Authentication Algorithm
The AuC first authenticates the subscriber Mobile station and only then does the MSC provide the switching service to another terminal TE, which is also authenticated in case it is a Mobile station.
Use a random number sent by the AuC during the connection set up
An authentication key which is already saved in the SIM
Authentication algorithm used differs for different mobile service providers

53. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
GSM - authentication
SIM
mobile network
RAND Ki
RAND
RAND Ki
128 bit
128 bit
128 bit
128 bit AC A3 A3
SIM
SRES* 32 bit
SRES bit
SRES* =? SRES
SRES
MSC
SRES
32 bit
Ki: individual subscriber authentication key SRES: signed response
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

54. Encryption
The BTS and the Mobile station perform ciphering before call initiation or before connecting for receiving a call
The Mobile station uses a cipher (encryption key) for encryption
Only encrypted voice and data traffic and control channel data transmit to the BTS

55. GSM - key generation and encryption
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
GSM - key generation and encryption
mobile network (BTS)
MS with SIM
RAND Ki
RAND
RAND Ki AC
SIM
128 bit
128 bit
128 bit
128 bit A8 A8
cipher
key Kc
64 bit Kc
64 bit
data
encrypted data
SRES
data
BSS MS A5 A5
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

56. Radio Interface Um Radio interface SDMA – Each cell (BTS)
Assigns an MS to a BTS
Media access combines TDMA with FDMA

57. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
GSM - 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
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

58. Logical channel Traffic Channel – Transmit user data
Traffic Channel(TCH)
Control Channel (CCH)
Dedicated Control Channel (DCCCH)
Full rate TCH (TCH/F)
22.8 Kbit/s
Half rate TCH
(TCH/H)
11.4 Kbit/s
Common Control Channel (CCCH)
Broadcast Control Channel
(BCCH)
Access Grant Channel (AGCH)
Paging Channel(PCH)
Slow Associated DCCCH (SACCH)
Frequency Correction
Channel (FCCH)
Synchronization Channel (SCH)
Random Access Channel (RACH)
Traffic Channel – Transmit user data
Control channel – control Medium access, Allocation of traffic channel and mobility management
DCCCH – Bidirectional channel
Standalone Dedicated Control channel (SDCCH)
Fast Associated DCCCH (FACCH)

59. GSM hierarchy of frames
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
GSM 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
TTTTTTTTTTTTSTTTTTTTTTTTTx
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

60. GSM protocol layers for signaling
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
GSM protocol layers for signaling Um
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
LAPD – Link access procedure for the D channel
RR – Radio resource Management
MM – Mobility management
CC – Call management
BTSM – BTS management
BSSAP – BSS Application Part
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

61. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
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 )
advantage: ready to use, constant quality, simple
disadvantage: channels blocked for voice transmission
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

62. Universität Karlsruhe Institut für Telematik
Mobilkommunikation
SS 1998
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
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

63. Examples for GPRS device classes
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Examples for GPRS device classes
Class
Receiving slots
Sending slots
Maximum number of slots 1 2 3 5 4 8 10 12
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

64. GPRS user data rates in kbit/s
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
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
18.1
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
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

65. GPRS architecture and interfaces
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
GPRS architecture and interfaces MS
BSS
GGSN
SGSN
MSC Um
EIR
HLR/ GR
VLR
PDN Gb Gn Gi
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

66. GPRS protocol architecture
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
GPRS protocol architecture MS
BSS
SGSN
GGSN Um Gb Gn Gi
apps.
IP/X.25
IP/X.25
SNDCP
SNDCP
GTP
GTP
LLC
LLC
UDP/TCP
UDP/TCP
RLC
RLC
BSSGP
BSSGP IP IP
MAC
MAC FR FR
L1/L2
L1/L2
radio
radio
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller