Gsm overview

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Gsm overview

  1. 1. BSNL An Overview ON BSNL SUMMER TRAINING SUBMITTED BY- RAJAN MEENA 08EC071 VII SEM (ECE)
  2. 2. BSNL OBJECTIVESOBJECTIVES  The Cellular Concept  The GSM Access Network  The GSM Core Network
  3. 3. BSNL Communication - Mobile Telephone Exchange Subscriber Line (2W) Inter-Exchange Junction Mobile Switching Centre (MSC) BSC BTS MS
  4. 4. BSNL CELLULAR MOBILE CONCEPTS WHAT IS A CELL ? • A base station (transmitter) having a number of RF channels is called a cell • Each cell covers a a limited number of mobile subscribers within the cell boundaries ( Coverage area) • Typical Cell Radius Aprrox = 30 Km (Start up), 1 KM (Mature)
  5. 5. BSNL Voice Channels Coveragearea Forward path Reversepath Or control channels Lines to BSC MS A RADIO CELL
  6. 6. BSNL Fundamental problems • Radio range, or coverage • No. of channels, or voice circuits • Full, seamless service coverage • Large no. of subscribers in the range of millions
  7. 7. BSNL FERQUENCY SCARCITY PROBLEM Tel Ex.   WIRED NETWORK 100,000  50 Khz = 5 Ghz (NOT POSSIBLE) Hence Individual RF Loop is not extended But a Common group of channels is shared CELLULAR MOBILE CONCEPTS BW for Telephony speech: 3KHz increases to 25 KHz with FM for Radio Trans.
  8. 8. BSNL GSM Specifications Carrier Separation - 200 kHz No. of RF Carriers - 124 Access Method - TDMA/FDMA Modulation Method - GMSK Transmission Rate - 270.833 Kbps Speech Coding - Full rate 13 Kbps Half rate 6.5 Kbps Duplex Distance - 45 MHz
  9. 9. BSNL GSM FDMA (Frequency Division Multiple Access 25 MHz 25 MHz Mobile to Base 0 1 2 890.2 890.4 890.6 (MHz) Base to Mobile 0 1 2 935.2 935.4 935.6 200 kHz 45MHz Channel layout and frequency bands of operation 890 935 960915 200 kHz
  10. 10. BSNL GSM TDMA (Time Division Multiple Access) 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 45 MHz Frequency F2’F1’ (Cell transmit) F2F1 (Cell Rx) Amplitude Typical TDMA/ FDMA frame structure
  11. 11. BSNL FDMA/TDMA Scheme BP1 BP2 BP3 BP4 BP5 BP6 BP7 BP8 BP1 BP2 TIM E 890.0 890.2 890.4 890.6 890.8 891.0 891.2 915.8 FRE Q MHz BURST F R A M E
  12. 12. BSNL LOGICAL CHANNELS • USER INFORMATION( TRAFFIC) • SIGNALLING INFORMATION (CONTROL) GSM RF CHANNELS
  13. 13. BSNL 13 Network Architecture B T S MSC VLR HLR PSTN ISDN Data Networks  Air interface OSS B T S B T S MSC VLR BSCBSC 1 MSC=16 BSC 1 BSC=1024 TRU A Interface A-bis interface
  14. 14. BSNL 14 GSM Network Structure • GSM Service Area: Total area served by the combination of all member countries where a mobile can be served. • MSC Service Area: There can many MSC/VLR in one PLMN area.It is one Mobile Exch. Area. • GMSC: All I/C calls for PLMN N/W will be routed through GMSC. In a GSM/PLMN N/W all mobile terminated calls will be routed to a Gateway MSC. Call connections between PLMNs , or to fixed N/Ws must be routed to a GMSC.The GMSC contains the Inter working functions to make these connections. • Location Area • Cells
  15. 15. BSNL LOCATION AREA : There are several LA in a MSC/VLR combination. A LA is a part of the MSC/VLR service area in which a MS may move freely without updating location information to the MSC/VLR exchange that control the LA. Within a LA a paging message is broadcast in order to find the called mobile subs. LA can be identified by system using the LAI. CELL : A cell is an identity served by one BTS. The MS distinguishes between cells using the BASE STATION IDENTIFICATION CODE(BSIC) that the cell site broadcast over the air. GSM Network Structure
  16. 16. BSNL MSC/VLR MSC/VLR MSC/VLR MSC/VLR II I IIIIV GSM PLMN Service Area
  17. 17. BSNL MSC/VLR LA 1 LA 2 LA 6 LA 3 LA 4 LA 5 GSM MSC Service Area
  18. 18. BSNL MSC/VLR LA 1 LA 2 LA 6 LA 3 LA 4 LA 5 C1 C5 C4 C7 C2 C3 C6 GSM Cells C = Cell
  19. 19. BSNL 19 GSM Relation between areas in GSM Location AreaCell Area served by a BTS Location Area MSC Service Area PLMN Service Area GSM Service Area
  20. 20. BSNL 20 GSM Functions of Mobile Station • Voice and data transmission • Frequency and time synchronization • Monitoring of power and signal quality of the surrounding cells • Provision of location updates even during inactive state • Equalization of multi path distortions
  21. 21. BSNL 21 GSM Mobile Station • Portable, vehicle mounted, hand held • MS identified by unique IMEI(International Mobile Equipment Identity) • Shell display at least last ten received, dialled and missed calls • Minimum talk time of 1hr 30 min. and standby time of 80 hrs • 160 characters long SMS
  22. 22. BSNL 22 GSM Mobile Identification Numbers IMEI MSISDN IMSI
  23. 23. BSNL 23 GSM IMSI • International mobile subscriber’s Identity • The IMSI is an unique identity which is used internationally and used within the network to identify the mobile subscribers. • The IMSI is stored on the subscriber identity module (SIM), the HLR, VLR and AC database.
  24. 24. BSNL 24 RSSRSS n BTS n BTS BSC BSC BSC MSC/VLR RADIO SUB SYSTEM (RSS)
  25. 25. BSNL 25 GSM FUNCTION OF BTS -I • Encodes, encrypts, multiplexes, modulates and feeds the RF signals to the antenna • Transcoding and rate adaption Functionality • Time and frequency synchronisation signals transmission. • 11 power classes from .01 watts to 320 watts
  26. 26. BSNL 26 GSM FUNCTION OF BTS -II • Frequency hopping • Random access detection • Uplink radio channel measurements • BTS mainly consists of a set of transceivers (TRX).
  27. 27. BSNL 27 GSM FUNCTIONS OF BSC-I • It is connected to BTS and offloads MSC • Radio resource management • Inter-cell handover • Reallocation of frequencies • Power control
  28. 28. BSNL 28 GSM FUNCTIONS OF BSC-II • Time delay measurement of the received signals from MS with respect to BTS clock. • Performs traffic concentration to reduce the number of lines from BSC to MSC.
  29. 29. BSNL 30 GSM MSC-BSS Configurations BTS BTS BTS A-bis BSC BSS Configuration -6 Multi - cell site = multi--BTS site Many single cell sites BSS MSC BTS A A A Single - cell site Configuration -1 Multi - cell site (sector Cells Configuration -5 MSC: Mobile Switching Centre BSS: Base Station System BSC: Base Station Controller BTS: Base Transceiver Station A-bis BTS BTS BTS
  30. 30. BSNL 31 GSM MSC ( MOBILE SWITCHING CENTRE) Manages communication between GSM & other network Call setup functions, basic switching are done MSC takes into account the RR allocation in addition to normal exchange functions MSC does gateway function while its customers roams to other network by using HLR /VLR
  31. 31. BSNL 32 GSM MSC Functions - I Paging, specifically call handling Location updation Handover management Billing for all subscribers based in its area Reallocation of frequencies to BTSs in its area to meet heavy demands
  32. 32. BSNL 33 GSM MSC Functions - II  Echo canceller operation control  Signaling interface to databases like HLR, VLR.  Gateway to SMS between SMS centers and subscribers
  33. 33. BSNL 34 GSM VISITOR LOCATION REGISTER (VLR)-I It controls those mobiles roaming in its area. VLR reduces the number of queries to HLR One VLR may be incharge of one or more LA. VLR is updated by HLR on entry of MS its area. IMSI detach and attach operation
  34. 34. BSNL 35 GSM Home Location Register(HLR)-I • Reference store for subscriber’s parameters, numbers, authentication & Encryption values. • Current subscriber status and associated VLR. • Both VLR and HLR can be implemented in the same equipment in an MSC. • One PLMN may contain one or several HLR.
  35. 35. BSNL 36 GSM Home Location Register(HLR)-II Data stored is changed only by man-machine. Category of MS ( whether pay phone or not ) Roaming restriction ( allowed or not ). Supplementary services like call forwarding Permanent data in HLR
  36. 36. BSNL 37 Temporary data in HLR The data changes from call to call & is dynamic VLR address, MSC address. Messages waiting data used for SMS GSM Home Location Register(HLR)-II
  37. 37. BSNL

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