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GSM

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81 diapositives · 1.5K Views · Sep 24, 2014

GSM. SEMINAR. ON. TECHNOLOGY. Md. Omar Ali Shamim Ahmed Nasrin Akter Khandakar Menhaz Morshed. Speakers. # What’s a cellular phone?. Now all of these mobile devices are shining in your hands. # Why it calls cellular?. > Uses hexagonal Cells. # If there was no cell

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GSM
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  1. GSM SEMINAR ON TECHNOLOGY

  2. Md. Omar AliShamim Ahmed Nasrin Akter Khandakar Menhaz Morshed Speakers

  3. # What’s a cellular phone? Now all of these mobile devices are shining in your hands.

  4. # Why it calls cellular? > Uses hexagonal Cells

  5. # If there was no cell Limited frequency spectrum for available Mobile Communication Frequency utilization is inefficient Single high power antenna => limited number of users # Why use cells?

  6. # Why use cells? # Benefits of cellular technology • Smaller cells => frequency reuse possible => more number of users • As demand increases (more channels needed) • Number of base stations is increased (by reducing cell size) • Transmitter power is decreased correspondingly to avoid interference (to eliminate adjacent-channel interference)

  7. # Frequency reuse: • Adjacent cells assigned different frequencies to avoid interference or crosstalk. • The same frequency is reused in different areas for different transmissions • In GSM networks a frequency reuse pattern with k = 3, 4, 7, 12 or 21. Here, k= Frequency reuse factor • Each ‘k’ number of cells make a cluster.

  8. # Frequency reuse: >Reuse factor = 4 4 cell Cluster >Reuse factor = 3 3 cell Cluster

  9. # Frequency reuse: >Reuse factor = 7 7 cell Cluster

  10. # Frequency Reuse Problems: • Adjacent-channel interference • Co-channel Interference

  11. # Adjacent-channel interference • Comes from imperfect filters that allow frequency leakage into the band • Serious problem if interferer is nearby, near-far effect • Nearby mobile transmits on a frequency near to that of a weak mobile • Base station receivers need high-Q filters to reject adjacent channel interference.

  12. # Adjacent-channel interference

  13. # Co-channel Interference • One of the primary forms of man-made signal degradation associated with digital radio, co-channel interference occurs when the same carrier frequency reaches the same receiver from two separate transmitters

  14. # Co-channel Interference F1 F1 F1 F1 F1 MS

  15. # Co-channel Interference

  16. # Sectored Cells • To reduce the adjacent channel interference & co-channel interference a cell can divide into 3 or 6 sectors according to the demand.

  17. 1 2 3 2 3 1 2 3 2 3 2 3 • 3 sectors per cell • 3 cells per cluster

  18. 3 3 1 2 4 3 2 4 1 1 1 2 4 3 1 2 4 4 • 3 sectors per cell • 4 cells per cluster

  19. 2 1 1 2 1 2 1 1 1 2 2 2 • 6 sectors per cell • 2 cells per cluster

  20. # Original view of sectors

  21. # Multiplexing & Access Methods Multiplexing Access Method FDM FDMA TDM TDMA CDM CDMA SDM SDMA

  22. # FDM & FDMA F3 Frequency F2 F1 Time

  23. # TDM & TDMA Amplitude T3 T1 T2 Frequency Time

  24. # CDM & CDMA Code3 Code2 Code1 Frequency Code Time

  25. # SDM & SDMA

  26. # Frequency Spectrum Down link 935~960MHz Up link 890~915MHz BTS MS

  27. # Channels • GSM 900 uses 25 MHz frequency spectrum with 124 channels for uplink & downlink. • Each channels have 200 KHz bandwidth. • Each two channels are separated by 1.6 KHz guard band. • Each channel have 8 time slots which allows 8 subscribers to use same frequency by TDMA.

  28. 1 2 3 4 5 6 123 124 1 2 3 4 5 6 7 8 # Channels Channels with 200 KHz bandwidth Time slots 4.615 ms

  29. # Cell Types Cells can be classified into three types according to cell size • Macro cell • Micro cell • Pico cell

  30. # Cell Types

  31. # Antenna Two types of antenna used • Unidirectional antenna • Omni directional antenna

  32. # Unidirectional antenna

  33. # Omni directional antenna Semi omni directional antenna

  34. # Modulation Technique BPSK Two phases represent two binary digits

  35. # Modulation Technique QPSK & OQPSK Each signal element representing more than one bit

  36. # Modulation Technique MSK Just like OQPSK, but the rectangular pulses are replaced by half-sinusoids

  37. # Modulation Technique GMSK Using FSK modulation

  38. On the next session Shamim Ahmed will with you

  39. NSS BSS E PSTN PSTN Abis D C A B H BSC MS MSC GMSC BTS VLR SS7 HLR AuC GSM 2G Architecture BSS — Base Station System BTS — Base Transceiver Station BSC — Base Station Controller MS — Mobile Station NSS — Network Sub-System MSC — Mobile-service Switching Controller VLR — Visitor Location Register HLR — Home Location Register AuC — Authentication Server GMSC — Gateway MSC GSM — Global System for Mobile communication

  40. GSMSub-Systems • Radio Sub System (RSS) • RSS = MS + BSS • BSS = BTS+ BSC • Network Sub System (NSS) • NSS = MSC+ HLR + VLR + GMSC • Operation Sub System • OSS = EIR + AuC

  41. GSM network layer #Radio resource management (RR) sublayer • Establishment, maintenance, and termination of radio channel connections #Mobility management (MM) sublayer • Registration, authentication, and location tracking #Call control (CC) sublayer • Establishment, maintenance, and termination of circuit-switched calls

  42. NSS BSS E PSTN PSTN Abis Gb Gn Gc Gr Gi B D A C H BSC MS MSC GMSC BTS VLR Gs SS7 2G+ MS (voice & data) HLR AuC PSDN IP SGSN GGSN 2.5G Architectural Detail 2G MS (voice only) BSS — Base Station System BTS — Base Transceiver Station BSC — Base Station Controller NSS — Network Sub-System MSC — Mobile-service Switching Controller VLR — Visitor Location Register HLR — Home Location Register AuC — Authentication Server GMSC — Gateway MSC SGSN — Serving GPRS Support Node GGSN — Gateway GPRS Support Node GPRS — General Packet Radio Service

  43. H Abis Iub Gn Gc Gr Gi B D C IuCS RNS ATM IuPS RNC Node B 3G UE (voice & data) 3G rel99 Architecture (UMTS) —3G Radios 2G MS (voice only) CN BSS E PSTN PSTN A BSC MSC GMSC Gb BTS VLR Gs SS7 2G+ MS (voice & data) HLR AuC PSDN IP SGSN GGSN BSS — Base Station System BTS — Base Transceiver Station BSC — Base Station Controller RNS — Radio Network System RNC — Radio Network Controller CN — Core Network MSC — Mobile-service Switching Controller VLR — Visitor Location Register HLR — Home Location Register AuC — Authentication Server GMSC — Gateway MSC SGSN — Serving GPRS Support Node GGSN — Gateway GPRS Support Node UMTS — Universal Mobile Telecommunication System

  44. 2G MS (voice only) CN CS-MGW Nb BSS CS-MGW A PSTN Nc PSTN Abis Iub Gn Gc Gr Gi B H D C Mc Mc BSC MSC Server GMSC server Gb BTS VLR Gs SS7 2G+ MS (voice & data) IuCS RNS IP/ATM HLR AuC ATM IuPS PSDN RNC SGSN GGSN Node B 3G UE (voice & data) BSS — Base Station System BTS — Base Transceiver Station BSC — Base Station Controller RNS — Radio Network System RNC — Radio Network Controller CN — Core Network MSC — Mobile-service Switching Controller VLR — Visitor Location Register HLR — Home Location Register AuC — Authentication Server GMSC — Gateway MSC SGSN — Serving GPRS Support Node GGSN — Gateway GPRS Support Node 3G rel4 Architecture (UMTS) —Soft Switching

  45. GSM Speech Coding 104 kbps 13 kbps Low-pass filter A/D RPE-LTP speech encoder Channel encoder Analog speech 8000 samples/s, 13 bits/sample

  46. MS Hands off

  47. GSM Call Routing For Incoming Call 1. MSISDN LA2 ISDN 4. MSRN BSC MS GMSC/IWF BTS 2. MSISDN MSC 3. MSRN 7. TMSI 7. TMSI EIR BSC AUC HLR VLR BTS LA1 7. TMSI 5. MSRN BTS 6. TMSI MS 8. TMSI

  48. Signalingover SS7 Where is the subscriber? MAP/ IS41 (over TCAP) ISUP 2 4 3 Provide Roaming 5 Routing Info 1 6 IAM IAM 514 581 ... PSTN-to-Mobile Call PLMN PLMN PSTN (Visitor) (Home) (SCP) HLR SCP (STP) VMSC GMSC MS BSS (SSP) (SSP) (STP) (SSP) VLR

  49. Mobile-Terminated Short Message Example (MTSM)

  50. Mobile-Originated Short Message Example (MOSM)