1. Mobile Network

2. What is GSM ?
Global System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation

3. Tele-services Bearer or Data Services Supplementary services
GSM Services
Tele-services
Bearer or Data Services
Supplementary services

4. Tele Services
• Telecommunication services that enable voice communication
via mobile phones
• Offered services
- Mobile telephony
- Emergency calling

5. Bearer Services Unified Messaging Services(UMS)
Include various data services for information transfer between GSM and other networks like PSTN, ISDN etc at rates from 300 to 9600 bps
Short Message Service (SMS)
up to 160 character alphanumeric data transmission to/from the mobile terminal
Unified Messaging Services(UMS)
Group 3 fax
Voice mailbox
Electronic mail

6. Supplementary Services
Call related services :
Call Waiting- Notification of an incoming call while on the handset
Call Hold- Put a caller on hold to take another call
Call Barring- All calls, outgoing calls, or incoming calls
Call Forwarding- Calls can be sent to various numbers defined by the user
Multi Party Call Conferencing - Link multiple calls together
CLIP – Caller line identification presentation
CLIR – Caller line identification restriction
CUG – Closed user group

7. GSM System Architecture
PSTN
ISDN
PDN
BSC MS
BTS
MSC
GMSC
BTS
BSC
VLR MS
EIR
BTS
AUC MS
HLR

8. GSM System Architecture-I
Mobile Station (MS)
Mobile Equipment (ME)
Subscriber Identity Module (SIM)
Base Station Subsystem (BSS)
Base Transceiver Station (BTS)
Base Station Controller (BSC)
Network Switching Subsystem(NSS)
Mobile Switching Center (MSC)
Home Location Register (HLR)
Visitor Location Register (VLR)
Authentication Center (AUC)
Equipment Identity Register (EIR)

9. System Architecture Mobile Station (MS)
In 2G it is known as MS.
In 3G systems, It is referred as User Equipment (UE).
The Mobile Station is made up of two entities:
Mobile Equipment (ME)
Subscriber Identity Module (SIM)

10. System Architecture- Mobil Station (MS)
In GSM, the Mobile Station consists of four main components:
Mobile Terminal (MT)- offers common functions that are used by all the service the Mobile Station offers. It is equivalent to the network termination of an ISDN access and is also the end-point of the radio interface.
Terminal Equipment (TE) - is a peripheral device of the Mobile Station and offers services to the user. It does not contain any functions specific to GSM.
Terminal Adapter (TA) - hides radio-specific characteristics.
Subscriber Identity Module (SIM) - is a personalization of the Mobile Station and stores user specific parameters (such as mobile number, contacts etc).

11. System Architecture Mobile Station (MS) -Mobile Equipment
Portable,vehicle mounted, hand held device
Uniquely identified by an IMEI (International Mobile Equipment Identity)
IMEI can be displayed on most phones by dialing the code *# 06 #.
It is not stored in SIM. It is stored in the phone
If a mobile handset is lost or stolen, CEIR (Central Equipment Identity Register) can be contacted.
CERI will blacklist the device in all currently operating switches.
This makes the lost or stolen handset unusable.
Blacklisting stolen mobile handsets is seen as a deterrent to crime.
It is possible, however, to change an IMEI with special tools.
Certain mobile networks that do not automatically blacklist handsets registered with the CEIR.
Approximately 10% of IMEI's in use today are not unique or have been reprogrammed (hacked).

12. Format of IMEI Mainly two types
15 Digits or 17 Digits
The IMEI (14 decimal digits plus a check digit) or IMEISV (16 digits)
The structure of the IMEI/SV are specified in 3GPP TS
The model and origin comprise the initial 8-digit portion of the IMEI/SV, known as the Type Allocation Code (TAC).
Format of the IMEI is AA-BBBBBB-CCCCCC-D
AA: Reporting Body Identifier, indicating the GSMA-approved group that allocated the model TAC.
BBBBBB: The remainder of the TAC (Type Approval Code)
CCCCCC: Serial sequence of the model
D: Luhn check digit of the entire number (or zero)
EE: Software Version Number (SVN)

13. Example: Format of IMEI
What is the meaning of it.
so it was issued by the BABT (British Approvals Board for Telecommunications) and has the allocation number 2099.
The Reporting Body Identifier is allocated by the Global Decimal Administrator;
FAC (Finally Assembly Code): 00 so it was numbered during the transition phase from the old format to the new format
SNR: uniquely identifying a unit of this model CD: 1 so it is a GSM Phase 2 or higher

14. Mobile Equipment Identifier
There are two administrators:
the Global Decimal Administrator (GDA) for IMEIs
Global Hexadecimal Administrator (GHA).

15. CDMA Format Manufacturer code Serial number CD R X Z C
An MEID is 56 bits long (14 hex digits). It consists of three fields, including an 8-bit regional code (RR), a 24-bit manufacturer code, and a 24-bit manufacturer-assigned serial number. The check digit (CD) is not considered part of the MEID.
As of August 2006, the TIA acts as the Global Hexadecimal Administrator (GHA) to assign MEID, and the GSM Association acts as the Global Decimal Administrator

16. Luhn algorithm The check digit is validated in three steps:
Starting from the right, double a digit every two digits (e.g., 7 → 14).
Sum the digits (e.g., 14 → 1 + 4).
Check if the sum is divisible by 10.
Conversely, one can calculate the IMEI by choosing the check digit that would give a sum divisible by 10. For the example IMEI ?,

17. Luhn algorithm
IMEI 4 9 1 5 2 3 7  ?
Double every other 18 8 14
Sum digits
4 + (1 + 8) (1 + 4)  ? = 52 + ?
To make the sum divisible by 10, we set ? = 8, so the IMEI is

18. CEIR Classification of Handsets
Color
Meaning
White
Valid Mobile Station
Grey
Mobile Station to be tracked
Black
Barred Mobile Station

19. System Architecture Mobile Station (MS) - Mobile Equipment
Voice and data transmission
Monitoring power and signal quality of surrounding cells for optimum handover
Power level : 0.8W – 20 W
160 character long SMS.

20. What is an IMSI?
The IMSI (International Mobile Subscriber Identity) is a unique 15-digit code used to identify an individual user on a GSM network.
The IMSI consists of three components:
Mobile Country Code (MCC)
Mobile Network Code (MNC)
Mobile Subscriber Identity Number (MSIN)
The IMSI is stored in the Subscriber Identity Module (SIM).

21. System Architecture Mobile Station (MS) contd.
Subscriber Identity Module (SIM)
Smart card contains the International Mobile Subscriber Identity (IMSI)
Allows user to send and receive calls and receive other subscribed services
Encoded network identification details
- Key Ki,Kc and A3,A5 and A8 algorithms
Protected by a password or PIN
Can be moved from phone to phone – contains key information to activate the phone

22. New Trends In random order Mega-trends of Mobile Industry are:
The threat and possibilities of the Discount Mobile Service Providers,
Falling profit margins on basic mobile services (voice, SMS) as a result of competition,
The use of outsourcing - to minimize OPEX,
Controlled investment in infrastructure - to reduce CAPEX,
The use of micro-segmentation (Mobile operators will use sub-brands and producers of mobile terminals will introduce a wide range of different terminal models),
Higher marketing expenses – partly because of the use of micro-segmentation,
Stock Rotation Risk – the result of the terminal producers larger product portfolio,
New business models in the mobile value chain – the existing business models are an impediment on economic growth,
A more complex value chain – a growing number of different players seek the place in the mobile value chain,
Mobile penetration vs. SIM-penetration – there is an important difference.

23. Issues Environmental Related
About 1.2 billion mobile handsets were sold worldwide. To put that into context, it means that, on average, more than 3 million new handsets were sold every day last year.
How to reduce power consumption
How to use solar power
How to reduce CO2 emission.
How to take care of large number of chargers lying with subscribers.
It should be done through regulation
It should be done through Innovation
Or combination of both
Reduction of Hazardous Substances (RoHS) directive
Waste Electrical and Electronic Equipment (WEEE) Directive

24. Statistics SN Manufacturer Year 2008 2007 2006 2005 1 Nokia
468.3 (39.93%)
436.38
(38.98%)
(34.97)
265.0 (32.70%) 2
Samsung
196.5 (16.76%)
(14.39%)
118.0 (11.86)
103.0 (12.70%) 3 LG
101.1 (8.62%)
80.50 (7.19%)
66.4 (6.67)
55.0 (6.80%) 4
Motorola
100.1 (8.54%)
(14.20%)
217.4 (21.85)
146.0 (18.00%) 5
Sony Ericsson
96.6 (8.24%)
103.4 (9.24)
74.5 (7.49)
51.0 (6.30%)
Others
210.1 (17.92%)
(16.0%)
171.8 (17.16)
191.0 (23.50%)
Total
(100%)
(100%)
996.1 (100%)
811.0 (100%)

25. Indian Statistics SN Manufacturer September 5, 2005 June 17, 2008 1
Nokia
59.0%
65.2% 2
Sony Ericsson
12.8% 3
Samsung
13.0%
6.2 % 4
L&G
6.2% 5
Motorola
7.0%
5.0%

26. System Architecture Base Station Subsystem (BSS)
Base Station Subsystem is composed of two parts that communicate across the standardized Abis interface allowing operation between components made by different suppliers
Base Transceiver Station (BTS)
Base Station Controller (BSC)

27. BSS interfaces
Um: The air interface between the mobile station (MS) and the BTS.
Abis: The interface between the BTS and BSC.
A: The interface between the BSC and MSC.
Ater: The interface between the BSC and transcoder.
Gb: Connects the BSS to the SGSN in the GPRS core network

28. System Architecture Base Station Subsystem (BSS)
Base Transceiver Station (BTS):
Encodes,encrypts,multiplexes,modulates and feeds the RF signals to the antenna.
Frequency hopping
Communicates with Mobile station and BSC
Consists of Transceivers (TRX) units

29. System Architecture Base Station Subsystem (BSS)
Base Station Controller (BSC)
Manages Radio resources for BTS
Assigns Frequency and time slots for all MS’s in its area
Handles call set up
Transcoding and rate adaptation functionality
Handover for each MS
Radio Power control
It communicates with MSC and BTS

30. System Architecture Network Switching Subsystem(NSS)
Mobile Switching Center (MSC)
Heart of the network
Manages communication between GSM and other networks
Call setup function and basic switching
Call routing
Billing information and collection
Mobility management
- Registration
- Location Updating
- Inter BSS and inter MSC call handoff
MSC does gateway function while its customer roams to other network by using HLR/VLR.

31. System Architecture Network Switching Subsystem
Home Location Registers (HLR)
- permanent database about mobile subscribers in a large service area(generally one per GSM network operator)
database contains IMSI,MSISDN,prepaid/postpaid,roaming restrictions,supplementary services.
Visitor Location Registers (VLR)
Temporary database which updates whenever new MS enters its area, by HLR database
Controls those mobiles roaming in its area
Reduces number of queries to HLR
Database contains IMSI,TMSI,MSISDN,MSRN,Location Area,authentication key

32. System Architecture Network Switching Subsystem
Authentication Center (AUC)
Protects against intruders in air interface
Maintains authentication keys and algorithms and provides security triplets ( RAND,SRES,Kc)
Generally associated with HLR
Equipment Identity Register (EIR)
- Database that is used to track handsets using the IMEI (International Mobile Equipment Identity)
Made up of three sub-classes: The White List, The Black List and the Gray List
Only one EIR per PLMN

33. GSM Specifications-1 RF Spectrum GSM 900
Mobile to BTS (uplink): Mhz
BTS to Mobile(downlink): Mhz
Bandwidth : 2* 25 Mhz
GSM 1800
Mobile to BTS (uplink): Mhz
BTS to Mobile(downlink) Mhz
Bandwidth : 2* 75 Mhz

34. GSM Specification-II
Carrier Separation : 200 Khz
Duplex Distance : 45 Mhz
No. of RF carriers : 124
Access Method : TDMA/FDMA
Modulation Method : GMSK
Modulation data rate : Kbps

35. GSM Operation Radio Interface Demodulation Speech decoding
Channel decoding
De-interleaving
Burst Formatting
De-ciphering
Demodulation
Modulation
Ciphering
Interleaving
Channel Coding
Speech coding
Radio Interface
Speech
13 Kbps
22.8 Kbps
33.6 Kbps
Kbps

36. Call Routing
Call Originating from MS
Call termination to MS

37. Outgoing Call MS sends dialled number to BSS
BSS sends dialled number to MSC
3,4 MSC checks VLR if MS is allowed the requested service.If so,MSC asks BSS to allocate resources for call.
MSC routes the call to GMSC
GMSC routes the call to local exchange of called user
7, 8,
9,10 Answer back(ring back) tone is routed from called user to MS via GMSC,MSC,BSS

38. Incoming Call Calling a GSM subscribers Forwarding call to GSMC
Signal Setup to HLR
5. Request MSRN from VLR
Forward responsible MSC to GMSC
Forward Call to current MSC
9. Get current status of MS
11. Paging of MS
13. MS answers
15. Security checks
17. Set up connection

39. Handovers Between 1 and 2 – Inter BTS / Intra BSC Between 1 and 3 –
Inter BSC/ Intra MSC
Between 1 and 4 –
Inter MSC

40. Security in GSM
On air interface, GSM uses encryption and TMSI instead of IMSI.
SIM is provided 4-8 digit PIN to validate the ownership of SIM
3 algorithms are specified :
- A3 algorithm for authentication
- A5 algorithm for encryption
- A8 algorithm for key generation

41. Authentication in GSM

42. Key generation and Encryption

43. Characteristics of GSM Standard
Fully digital system using 900,1800 MHz frequency band.
TDMA over radio carriers(200 KHz carrier spacing.
8 full rate or 16 half rate TDMA channels per carrier.
User/terminal authentication for fraud control.
Encryption of speech and data transmission over the radio path.
Full international roaming capability.
Low speed data services (upto 9.6 Kb/s).
Compatibility with ISDN.
Support of Short Message Service (SMS).

44. Advantages of GSM over Analog system
Capacity increases
Reduced RF transmission power and longer battery life.
International roaming capability.
Better security against fraud (through terminal validation and user authentication).
Encryption capability for information security and privacy.
Compatibility with ISDN,leading to wider range of services

45. GSM Applications Mobile telephony GSM-R Telemetry System
- Fleet management
- Automatic meter reading
- Toll Collection
- Remote control and fault reporting of DG sets
Value Added Services

46. Future Of GSM 2nd Generation GSM -9.6 Kbps (data rate)
2.5 Generation ( Future of GSM)
HSCSD (High Speed ckt Switched data)
Data rate : 76.8 Kbps (9.6 x 8 kbps)
GPRS (General Packet Radio service)
Data rate: Kbps
EDGE (Enhanced data rate for GSM Evolution)
Data rate: Kbps (max)
3 Generation
WCDMA(Wide band CDMA)
Data rate : – 2.0 Mbps

47. Questions ?