GSM Architecture

GSM Architecture

GSM architecture is basically based on 4 subsystem. These subsystem are -

            1.  Mobile Station (MS)

            2. Base Station Subsystem (BSS)

            3. Network and Switching Subsystem (NSS)

            4. Operation and Support Subsystem (OSS)

GSM Architecture 

1. Mobile Station ( MS):-

MS has two elements: 

1. Mobile equipment (ME).

2. Subscriber Identity Module (SIM).

1. Mobile Equipment (ME)

•  Mobile equipment is a hardware which is purchased by equipment the manufacturer.

2. Subscriber Identity Module (SIM)

• SIM is a detachable smart card.

• SIM carries every user’s personal information like phone book ,security keys, IMSI

   Number etc.

• SIM contains a PIN number as a security mechanism.

• Calls are directed towards SIM card.

2. Base Station Sub system (BSS):-

BSS subsystem comprises BTS & BSC

1. BTS (Base Station):-

• BTS is the physical equipment, which provides radio coverage to a geographical

   area.

• Components include a transmitter, a receiver, and a signaling equipment.

2. BSC (Base Station Controller):-

•  Manages the radio resources for one or more base stations.

•  Interfaces with the Main Switching Center (MSC).

•  Manages radio channel setup, and handovers.

• Controls Radio Frequency power levels in Base Stations.
• 1 BSC can control approximately 100 - 200 BTSs.
• Controls the power management of BTS.
• Help MSC in location updation.

3. Network and switching subsystem (NSS) :-

Heart of NSS is MSC.

Basically NSS is comprises of these two -

1. Mobile Switching Center

2. Network Database

1. Mobile Switching Center (MSC):-

• Call setup

• Interface between mobile Network and other Network (including fixed).

• Manages the location of mobiles means manage location updation.

• Switches calls.

• Manages security features. 

• Controls handover between different Base Station Controllers.

• Resource management.

• Interworks with and manages network databases.

• Collects call billing data and sends to billing system.
• 1 MSC can control 10 - 12 BSCs.
• Operates all the switching function for the mobiles. 

2. Network databases: -

Basically network data base is of 4 type used in GSM .

i. Home Location Register (HLR) -

• It is a permanent database. 

• Contains all the subscriber information for the purposes of call control, and  location
    determination.
• It  contains  every user details information like which service is activate , billing
   information, calls data etc.

ii. Visitor Location Register (VLR) -

• It contains all the information of a visitor in a region.˜
• A temporary storage while the particular subscriber is located in the geographical
    area controlled by the MSC. 
• It is used to reduce the load of HLR.

iii. Authentication Center (AuC) -

• At the time of calling verification of SIM is done by AuC to check whether it is a valid 
    susbcriber or not.
• Protected database that stores the security information for each subscriber.

iv. Equipment Identity Register (EIR) -

• Verification of Mobile Phones is done by this.
• List of all valid mobile equipment on the network.
• keeps the international mobile identity (IMEI) of the terminal type.
• In EIR , It has 3 type of list-

i. White List :-  normal or valid user equipment.
ii. Black List :- theft case or not valid equipment.
iii. Gray List :-  under surveillance.

HLR and VLR together with MSC provides the call routing and roaming

capabilities of GSM.

4. Operation and Support Subsystem (OSS):-

The OSS consists of 

• The Operation and Maintenance Center (OMC) 

• All type of alarm is controlled in OSS

• OSS also controls the Short Message Service Centre (SMSC) for transmission

   of SMS messages.

• OMC is responsible for 

• regular network operation

• subscriber administration
• call billing.

GSM Services

GSM Services

GSM Services are divided into three categories:-

1. Teleservices.

2. Bearer services.

3. Supplementary services.

             1. Teleservices provide:-

• Speech transmission-telephony
• Emergency call.
• Short message service.
• Videotext access.
• Teletext transmission.
• Facsimile transmission.

2. Bearer services :-

                  • Data services 

                  • Speech and data swapping during a call.

                  •  Modem selection.

3. Supplementary services:-

       i.  Call Completion Services like -

                 • Call Waiting (CW).

                 • Call Holding (HOLD).

                 • Completion of Call to Busy Subscriber (CCBS).

       ii. Calling Offering services like -

                 • Call Forwarding Unconditional (CFU).

                 • Call Forwarding Mobile Busy (CFB).

                 • Call Forwarding No Reply (CFNRy).

                 •  Call Forwarding Mobile Not Reachable (CFNRc).

                 •  Mobile Access Hunting (MAH).

     iii. Number Identification services like -

                • Calling Number Identification Presentation (CNIP).

                • Calling Number Identification Restriction (CNIR).

                • Connected Number Identification Presentation (CNOP).

                • Connected Number Identification Restriction (CNOR).

    iv. Multiparty Services like -

                • Conference Calling (CONF)

    v. Call Restriction Services like-

               •  Barring All Originated Calls (BAOC).

               •  Barring Outgoing International Calls (BOIC).

               •  BOIC except Home Country (BOIC-exHC).

               • Barring All Incoming Calls (BAIC).

               •  Barring Incoming calls when Roaming (BIC-Roam).

   vi. Charging Services like -

               • Advice of Charge (AoC).

               • Free Phone Service (FPH).

               •  Reverse Charging (REVC).

GSM Frequency Bands

GSM Frequency Bands

• GSM system is a frequency and time division system.
• GSM system frequencies include two bands:-

                      1. At 900 MHZ commonly referred to as GSM 900.
                      2. At 1800 MHz commonly referred as DCS 1800.
                      3. 1900 MHZ is used by Defense.

1.  In GSM 900 system:- 
   • 124 carriers have been defined.
   • Frequencies are assigned in two sub-bands of 25
   • MHz each.
   • The sub-bands are 890-915 MHz and 935-960 MHz.
   • Channel width is 200 KHz.
   • 890-915 MHz is referred as uplink.
   • 935-960 MHz is referred as downlink.

   
   
   NOTE:-  Uplink is the transmission from Mobile to BTS.
                         Downlink is the transmission from BTS to Mobile.
2. In DCS 1800 system:-

• Frequencies are assigned in two sub-bands of 75 MHz each.
• The sub bands are 1710 – 1785 MHz and 1805 – 1880 MHz.
• 1710 – 1785 MHz is referred as uplink.
• 1805 – 1880 MHz is referred as down link.  

NOTE : - 

• Channel width for GSM is 200 KHz. constant.

                              In  900MHz 

uplink frequency                            downlink frequency 

  890 - 915 MHz                                                           935 - 960 MHz

1. Buffer :-  ( 935-915) = 20 MHz

2. Bandwidth :- ( 915- 890) or ( 960- 935) = 25 MHz.

3. Duplexing Space :- ( 935- 890) or ( 960 - 915) = 45 MHz

4. Total Channel :- ( Bandwidth)/( width of a single channel)

                              (25 MHz)/(200 KHz) = 125

5. ARFCN ( Absolute Radio Frequency Channel) :-

                   ( total channel) - 1 = (125) - 1= 124 that means

124 carriers have been defined

                             In  1800MHz 

uplink frequency                            downlink frequency 

  1710 - 1785 MHz                                                           1805 - 1880 MHz

1. Buffer :-  ( 1805 - 1785) = 20 MHz

2. Bandwidth :- ( 1785- 1710) or ( 1880- 1805) = 75 MHz.

3. Duplexing Space :- ( 1805- 1710) or ( 1880 - 1785) = 95 MHz

4. Total Channel :- ( Bandwidth)/( width of a single channel)

                              (75 MHz)/(200 KHz) = 375

5. ARFCN ( Absolute Radio Frequency Channel) :-

                   ( total channel) - 1 = (375) - 1= 374 that means

374 carriers have been defined

                               In  1900MHz 

uplink frequency                            downlink frequency 

  1850 - 1910 MHz                                                           1930 - 1990 MHz

1. Buffer :-   20 MHz

2. Bandwidth :-  60 MHz.

3. Duplexing Space :- 80 MHz

4. Total Channel :- 300

5. ARFCN :- 299

299 carriers have been defined

GSM History

GSM 

(GLOBAL SYSTEM FOR MOBILE COMMUNICATION)

Introduction and History of GSM:-

Before 1980, there was 6 different incompatible analog cellular system standards working in Europe. However with the growth of European Common Market ( ECM) roaming between European countries became necessity and it was too difficult to business person to carry 6 handset and 6 SIM. So in 1982, CEPT(Conference of European Post & Telecommunication ) made a committee named GSM. 

• GSM (Groupe Special Mobile), also known as Global System for Mobile communication.
• Developed by European Telecommunication Standard Institute(ETSI).
• GSM is a set of ETSI standards specifying the infrastructure for a digital cellular service.
• In 1986, task force was formed to resolve roaming problems in 1G analog systems.
• In 1987, a memorandum of understanding (MoU) was signed.
• In 1989, ETSI included GSM in its domain and also name was changed from Groupe Special Mobile to Global System for Mobile communication .
• In 1990, GSM First page specification was published
• In 1991, the specification of the standard was completed and commercial launched.
• In 1992, the first deployment of GSM started  and India adopt GSM.
• By the year 1993, thirty two operators in 22 countries adopted the GSM standard.
• By the year 2001, close to 150 countries had adopted GSM for cellular adaptation.
• GSM specifications define the functions and interface requirements in details but do not address the hardware.
• GSM is an open ended technology i.e. upgradable.

Telecom Circles in India

Telecom Circles in India

Before some time in India, total telecom circle is 22 but now a days they increases to 23 and these 23 circles are further  divided in 4 group on the basis on revenue.

Telecom Circles in India

1. Metro circle	2. A Circle	3. B Circle	4. C Circle
Chennai	Andhra Pradesh	Haryana	Assam
Delhi	Gujarat	Kerala	Bihar
Kolkata	Karnataka	Madhya Pradesh	Himachal Pradesh
Mumbai	Maharashtra	Punjab	Jammu & Kashmir
	Tamil Nadu	Rajasthan	Northeast
		Uttar Pradesh (East) Uttar Pradesh (West) West Bengal	Orissa

All Generation

1 G ( First Generation )

Started in 1980.

 Features of 1 G:-

• Analog in nature
• Only FM ( Frequency Multiplexing), FDMA ( Frequency Division Multiple Access),       FDD ( Frequency Division  Duplexing ).
• Only work on Frequency
• Voice only ( no Data Transfer and no SMS )
• Limited Regional Scope
• No international roaming
• All the Technologies where incompatible with each other.
• Example  of 1 G -- 

                    AMPS ( US),
                    TACS ( UK), ETACS ( UK),
                    NMPT- 450 ( Europe), NMPT- 900 ( Europe),
                    Radicomm-2000 ( France) , 
                    NETZ  (Germany ) 

 Disadvantages of  1 G:-

• Low capacity
• No security
• Costly services
• Large handsets
• High power consumption
• Poor hands off / hand over
• Poor voice quality
• Inefficient spectrum utilization

2 G ( Second Generation) 

2nd generation Digital Cellular System Standard 

• NOTE:- In India, we started from here . India adopt 2 G ( GSM ) as  in 1992
• GSM used GMSK ( Gaussian Minimum Shift Keying ) Modulation
  

Features of 2 G:-

•  All the Technologies were  Digital in nature.
• Support voice + data
• Concept of SMS and Fax was introduce
• All the 2 G Technologies were compatible with fixed Digital Line Network like ISDN, Internet, PLMN.
• It provide international roaming
• Better voice quality
• Low power consumption
• It is classified in 2 sub-categories - TDMA & CDMA

             TDMA example - GSM, PDC ( Japan), IS-136

             CDMA example - IS-95

Advantages of 2 G:-  

• Advantage of Digital over Analog like easy to multiplex, easy to Encrypt, more data security, less expensive compare to 1 G, more reliable.
• Digital signal can be transmitted  over long distance without distortion.
• Better spectrum utilization
• Smaller handsets
• Low power consumption

Disadvantages of 2 G:-

• Low speed Data transmission 
• GSM speed ( 9.6 Kbps to 14.4 Kbps)
• No support for packet data transfer
• Semi global roaming
• Lots of Network equipment / elements
• Long call setup time
• Expensive services as compared to 2.5 G.

2.5  G

 started in late 1990's

    These are 2 G system that have incorporated Packet Switching and Circuit Switching.

Features  of  2.5 G:-

• High data rate 
• Global Roaming
• Internet, Radio, Email, other multimedia services introduced.
• Example - Data rate of GPRS - 115Kbps  & HSCSD - 57.6 Kbps
• It allows existing 2 G network equipment to be modified by new base station addons.
• Subscriber  unit ( mobile) was  also upgraded at software level to support high data rate .
• It can support high speed application like Emails, Multimedia services, web browsering etc.

 2.5 G is sub divided in two parts :- 1. HSCSD & 2. GPRS

HSCSD 

( HIGH SPEED CIRCUIT SWITCH DATA)

• It is a part of 2.5 G.
• GSM  gives a data rate of 9.6 Kbps to 14.4 Kbps by using 1 Time Slot but HSCSD give 4 Time Slot per user. Hence Data Rate increases to 4* 14.4 Kbps  = 57.6 Kbps.
• Minimum network change required.

Disadvantage of HSCSD:-

• Based on Circuit Switching which inefficient for Packet Data Transfer.

GPRS

( GENERAL PACKET RADIO SERVICES)

Features of GPRS:-

• Totally based on Packet switching.
• Non - voice
• Value added
• High speed
• Packet swtching
• Data rate is 115 Kbps
• GPRS reserve radio resource only when there is data to be transferred or received . Thus Providing efficient resource utilization.
• It allows sending & receiving small burst of data like Email as well as large files over PLMN( Public Landline Mobile Network).

Advantages of GPRS:-

• High data rate ( 3 to 8 times higher speed than GSM).
• Instant connection to internet and service access any time any where.

Disadvantages of GPRS:-

• Much low speed in reality
• No support for MTC ( Mobile Terminated Call)
• Sub- optimal ( GMSK) modulation was used ( GMSK - Gaussian Minimum Shift Keying ) Modulation)
• High transit delay ( Propagation delay )
• No store and forward technique is used.

2.75 G( EDGE)

Enhance Data Rate for GSM Evolution

• EDGE was introduced.
• High data rate 384 Kbps
• In it 8 PSK modulation scheme is used
• Multiple coding schemes are used ( MSC-1  to MSC-9). 

3 G WCDMA/ UMTS

(WIDE BAND CODE DIVISION MULTIPLE ACCESS /

UNIVERSAL MOBILE TELECOM SERVICES)

• 3G is merger of- 

(Telecom Services) + (Data communication services) + (Multimedia Services)

•  It’s a Next Generation Technology that support greater Band Width & better service   capability

Features of 3G:-

• Data rate up to 2Mbps
• Better spectrum utilization
• Mechanism to support Bandwidth on demand & variable bit rate services
• Support for services with different QoS ( Quality of Services) requirement
• Support for Real Time and Non Real Time Data Transfer
• BER (Bit Error Rate) is less than 10^-6.
•  Simultaneously co-existing with 2G network
• Intra System Hand Over
• High Spectrum Efficiency

3.5 G (HSDPA / HSUPA)       
(HIGH SPEED DOWN-LINK PACKET ACCESS /

HIGH SPEED UP-LINK PACKET ACCESS)

HSDPA	HSUPA
HIGH SPEED DOWN-LINK  PACKET ACCESS	HIGH SPEED UP-LINK PACKET ACCESS
DATA RATE UP TO    10 to 14 Mbps	DATA RATE UP TO   5 Mbps

    

•   Higher  Modulation Schemes are used like 16 QAM ( Quadrature Amplitude Modulation)

3.75G (HSPA+)

(HIGH SPEED PACKET ACCESS ADVANCE)

• Data rate up to 50 Mbps
• High speed achieve through MIMO (Multi Input Multi Output )  ( This is an Antenna solution).

3.9 G              

(LTE / SAE)             

         (LONG TERM EVOLUTION /                   

  SYSTEM ARCHITECTURE EVOLUTION)            

Disadvantage of 3 G:-

• Low data rate for high speed application like multimedia , video etc.
• Very costly services
• High transit delay i.e. latency greater than 100 ms
• Now a days consumer wants high speed ( up to 100 Mbps) at a low cost
• Today it is desired to migrate from circuit switched voice to packet data infrastructure, so as to reduce the cost of maintaing  two different network
• Not optimized  for real time application & IP based multimedia services.

4 G ( LTE ADVANCE)

                (LONG TERM EVOLUTION ADVANCE)  

• 4 G is also a merger of -

(Telecom Services) 

• Its is based on  OFDMA ( Orthogonal Frequency division Multiplexing Access) modulation.
• High speed data 
• Parallel send and receive data ( this is a feature of OFDM and all other technologies based on serially send and receive of data )
• It use multiple antenna technique
• Packet oriented network design based on IP ( Internet Protocol ) / VoIP( Voice over Internet Protocol)

Features of 4G:-

• High data rate ( Downlink data rate is greater than 100 Mbps and Uplink data rate is greater than 50 Mbps)
• Low latency ( less than 50 ms)
• Better spectrum utilization
• Low cost
• Inter-working  with other 3G System i.e. Backward Compatible
• Less network nodes so less complex network  and less expensive
• Reduced cost per bit ( to send a bit from A to B is reduced)
• Advance services and better user experiences. 

Graph of 4 G Technologies:-

1.  3GPP --> UMTS --> HSDPA/ HSUPA --> LTE

2. 3GPP2 --> CDMA- 2000 --> EV-DO --> XUMB

3.  WiMax --> 802.16 (fixed) --> 802.16e

4. WLAN --> 802.11 --> 802.11 b/g --> 802.11n

Note :- All bold are 4 G technologies.

All Generation Handsets

Varies Releases

1. R99 - Release 99  - in it  data rate is 2 Mbps & but practical value is 384 Kbps
2. R4 - Release 4 - separate Circuit Switch & Packet Switch domain & introduction to IP ( Internet Protocol) ( IPv4 & IPv6)
3. R 5- introduction to HSDPA & Multimedia subsystem completed
4. R6 - introduction to HSUPA & data rate increases & Multimedia broadcast multicast services ( MBMS) introduced
5. R7 - HSPA+ was introduced , High modulation schemes were introduced & MIMO concept was introduced
6. R8 - LTE Released  & Home-eNodeB concept was introduced
7. R10 - LTE Advance was introduce.