GSM introduction

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GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard set developed by the European Telecommunications Standards Institute (ETSI) to describe protocols for second generation (2G) digital cellular networks used by mobile phones. It became the de facto global standard for mobile communications with over 80% market share.

GSM introduction

  1. 1. By : Amit Kumar Sinha Date:23-02-2010 8/5/2013 1
  2. 2. History……Yaaaaawn  When the acronym GSM was used for the first time in 1982, it stood for Groupe Spéciale Mobile, a committee under the umbrella of Conférence Européenne des Postes et Télécommunications (CEPT), the European standardization organization.  The task of GSM was to define a new standard for mobile communications in the 900 MHz range. It was decided to use digital technology. In the course of time, CEPT evolved into a new organization, the European Telecommunications Standard Institute (ETSI).  The first GSM network was launched in 1991 by Radiolinja in Finlandwith joint technical infrastructure maintenance from Ericsson. 8/5/2013 2
  3. 3. GSM Present…… 8/5/2013 3 2,449,937309,907,068118,688,849 3,450,410,548 255,630,141133,286,097825,044 1,480,766 9,5930 500,000,000 1,000,000,000 1,500,000,000 2,000,000,000 2,500,000,000 3,000,000,000 3,500,000,000 cdmaOne CDMA2K 1X EVDO GSM WCDMA WCDMA HSPA TD- SCDMA TDMA Analog Connections by Bearer Technology 0 500,000,000 1,000,000,000 1,500,000,000 2,000,000,000 2,500,000,000 A frica A m erica s A sia P acificE uro pe:E aste rnE uro pe:W estern M iddle E ast U S A /C ana da Series1
  4. 4. GSM Architecture: Interface Types 8/5/2013 4
  5. 5. GSM Air Interface  Bursts  Each carrier frequency used in GSM is divided into 8 independent timeslots and into each of these timeslots a burst is placed. The diagram shows the general format of a GSM burst. The receiver can only receive the burst and decode it if it is received within the timeslot designated for it. The timing, therefore, must be extremely accurate, however, the structure does allow for a small margin of error by incorporating a ‘guard period’ as shown in the diagram. To be precise, the timeslot is 0.577ms long, whereas the burst is slightly shorter at 0.546ms. Eight bursts occupy one TDMA frame.  The ‘‘flag-bits” are set when the frame has been ‘stolen’ by FACCH (the Fast Associated Control Channel).  The ‘‘training sequence” is used by the receiver’s equaliser as it estimates the transfer characteristic of the physical path between the base-station and the mobile. 8/5/2013 5
  6. 6. GSM Air Interface 8/5/2013 6
  7. 7. GSM Burst Types 8/5/2013 7
  8. 8. GSM Control Channels 8/5/2013 8 SHOLAY Thakur JaiVeeru Gabbar Basanti Sambha Jailor Mausi Ramlal
  9. 9. GSM Signaling Model 8/5/2013 9
  10. 10. MO Call Establishment 8/5/2013 10
  11. 11. MT Call Establishment 8/5/2013 11
  12. 12. Location Update 8/5/2013 12
  13. 13. Authentication in GSM 8/5/2013 13
  14. 14. Erlang B  One Erlang is a measure of one traffic channel permanently occupied at busy hour.  For example busy hour (if measured for hourly basis) in Bangalore occurs twice in 24 hrs. Generally between 10 am to 11 am and 8 pm to 9pm.  Then if I say 0.25 Erl corresponds to 1 resource occupied for 25 % of time(i.e. 15 minutes in our case) 8/5/2013 14
  15. 15. How is Erlang calculated??? 8/5/2013 15 25 mE 10 mE 5 mE
  16. 16. TCH Calculation 8/5/2013 16  Max. traffic/subscriber at busy hour = 25 mE  No. of subscriber = 1700  Then planned traffic in cell including the 1700 subscriber=42.5 Erlang  No. of necessary resources with a blocking rate of 2% obtained from Erlang B table = 53 resources  TCH channels = 53 for 42.5 Erlang
  17. 17. SDCCH Calculation 8/5/2013 17  Now for SDCCH calculation,  If TCH = 42.5 Erlang then SDCCH = 28% of TCH (i.e. 42.5)= 11.9 Erlang  So the no. of SDCCH resources at 0.1% blocking rate = 24 (from table)  No. of SDCCH = 24/8 = 3 SDCCH TS
  18. 18. TRX Calculation 8/5/2013 18  No. of CCCH required = 1 per cell  Therefore we can conclude now  That , total no. of TS required = 53 + 3 + 1 = 57  Total of TRX= 57 / 8 = 8 (rounding to upper limit)
  19. 19. Site Dimensioning 8/5/2013 19 42.5 Erlang giving us 8 TDMA or TRXs Cell 1 Cell 2 Cell 3
  20. 20. References 8/5/2013 20  GSM Networks: Protocols, Terminology and Implementation – by Gunnar Heine  www.etsi.org
  21. 21. Those who are sleeping, its time to wake up and clap and for those who aren’t BIG THANK YOU 8/5/2013 21

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