Friday 27 June 2014

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.

2Subscriber 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.˜
• 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).



    Thursday 26 June 2014

    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.