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GSM Fundamental

GSM Fundamental

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GSM Fundamental

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  1. GSM Fundamental By Uke Kurniawan Usman Uke Kurniawan Usman - 2005

  2. Agenda • Network Architecture • Functional Layer of GSM • Air Interface • System Capacity • Anti Interference Technology • Network Planning • Numbering arrangement Uke Kurniawan Usman - 2005

  3. GSM Network Structure OMC MSC/VLR BSC E BIE PSTN ISDN PSPDN A Abis MSC/VLR BTS BSS C H F Um HLR/ AUC EIR SC/VM MS MSS Uke Kurniawan Usman - 2005

  4. Mobile Station ( MS ) Equipment used by mobile service subscribers for access to services. Mobile Equipment Subscriber Identity Module (SIM) • Mobile stations are not fixed to one subscriber. A subscriber is identified with the SIM card. Uke Kurniawan Usman - 2005

  5. GSM Network Entity Base Transceiver Station ( BTS ) Base Transceiver Station (BTS) Wireless transmission Wireless diversity Wireless channel encryption Conversion between wired and wireless signals Frequency Hopping • BaseBand Unit: • voice and data speed adapting and channel coding • RF Unit: • modulating/demodulating, transmitter and receiver • Common Control Unit: • BTS operation and maintenance Uke Kurniawan Usman - 2005

  6. GSM Network Entity Base Station Controller ( BSC ) Managing Wireless network-BSS Monitoring BTS Controls: Wireless link distribution between MS and BTS Communication connection and disconnection MS location, handover and paging Voice encoding, transecoding (TC), rate, adaptation, The operation and maintenance functions of BSS. Uke Kurniawan Usman - 2005

  7. GSM Network Entity Mobile Service Switching Center ( MSC ) • holds all the switching functions • manages the necessary radio resources, • updating the location registration • carrying out the inter-BSC and inter-MSC tender • Inter-working with other networks (IWF). Uke Kurniawan Usman - 2005

  8. GSM Network Entity Home Location Register ( HLR ) Manages the mobile subscribers database • subscriber information • part of the mobile location information • 3 identities essential the International Mobile subscriber Identity the Mobile station ISDN Number • the VLR address Uke Kurniawan Usman - 2005

  9. GSM Network Entity Visitor Location Register ( VLR ) • dynamically stores subscriber information needed to handle incoming/outgoing calls • Mobile Station Roaming Number • When a roaming mobile enters an MSC area. This MSC warns the associated VLR of this situation; the mobile enters a registration procedure through which it is assigned a mobile subscriber roaming number (MSRN) • Temporary Mobile Subscriber Identity, if applicable • The location area in which the mobile has been • registered • Data related to supplementary service parameters Uke Kurniawan Usman - 2005

  10. GSM Network Entity AUC/EIR Authentication Center(s) (AUC) Providing the authentication key used for authorizing the subscriber access to the associated GSM PLMN. Equipment Identity Register(s) (EIR) Handling Mobile Station Equipment Identity Uke Kurniawan Usman - 2005

  11. Agenda • Network Architecture • Functional Layer of GSM • Air Interface • System Capacity • Anti Interference Technology • Network Planning • Numbering arrangement Uke Kurniawan Usman - 2005

  12. Overview: Function Layers of GSM-1 Uke Kurniawan Usman - 2005

  13. Protocol Stack Structure of GSM Uke Kurniawan Usman - 2005

  14. Agenda • Network Architecture • Functional Layer of GSM • Air Interface • System Capacity • Anti Interference Technology • Network Planning • Numbering arrangement Uke Kurniawan Usman - 2005

  15. TDMA time Concept: channel is composed of a series of timeslots of periodicity. Different signal energies are distributed into different timeslots. The adjacent channel interference is restricted by connection choosing from time to time. So the useful signal is passed only in the specified timeslot. User 3 User 2 User 1 Frequency GSM adopts TDMA/FDMA mode channel width: 200KHz each channel has 8 timeslots Uke Kurniawan Usman - 2005

  16. GSM Timeslot and Frame structure Frequency 200KHz time BP 15/26ms interval Uke Kurniawan Usman - 2005

  17. Frequency Resource EGSM900 : up: 880~890MHz down: 925~935MHz duplex interval: 45MHz bandwidth: 10MHz, frequency interval: 200KHz GSM900 : up: 890~915MHz down: 935~960MHz duplex interval: 45MHz bandwidth: 25MHz, frequency interval: 200KHz GSM1800 : up: 1710-1785MHz down: 1805-1880MHz duplex interval: 95MHz, working bandwidth: 75MHz, frequency interval: 200KHz GSM1900MHz: up:1850~1910MHz down:1930~1990MHz duplex interval: 80MHz, working bandwidth: 60MHz, frequency interval: 200KHz Uke Kurniawan Usman - 2005

  18. Which one? Reason Frequency Resource General Priority Single Band Network 900MHz High 1800MHz Low 1900MHz New Operator Propagation Characteristic For Operator For Subscriber Uke Kurniawan Usman - 2005

  19. Frequency Resource Single Band Network Single Band 900MHz 1800MHz Dual Band 1900MHz Triple Band In a sense, the network determines the handsets can be selected. But nowadays, most handsets support dual band. Uke Kurniawan Usman - 2005

  20. Frequency Resource Single Band Network Cell coverage radius : We know Propagation characteristic The higher the propagation frequency The higher the propagation loss The smaller the cell coverage radius. 900MHz 1800MHz 1900MHz Uke Kurniawan Usman - 2005

  21. 0 1 2 3 2044 2045 2046 2047 0 1 2 3 47 48 49 50 0 1 24 25 Timeslot and Frame structure 1 super high frame = 2048 super frame = 2715648 TDMA frame BCCH CCCH 1 super frame = 1326 TDMA frame(6.12s) SACCH/TCH SDCH FACCH 1 multiplex frame = 26 TDMA frames(120ms) 1 multiplex frame = 51 TDMA frame 0 1 24 25 0 1 49 50 1 TDMA frame = 8 timeslot(120/26 = 4.615ms) 0 1 2 3 4 5 6 7 Uke Kurniawan Usman - 2005

  22. Physical Channel 0 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 18 19 20 21 22 23 17 • The physical channel adopts FDMA and TDMA techs. • On the time domain, a specified channel occupies the same timeslots in each TDMA frame, so it can be identified by the timeslot number and frame number. Uke Kurniawan Usman - 2005

  23. Channel Type-Summary 14.4Kbit/s FR TCH (TCH/F14.4) 9.6Kbit/s FR TCH(TCH/F9.6) Data CH 4.8Kbit/s FR TCH (TCH/F4.8) TCH 4.8Kbit/s HR TCH (TCH/H4.8) FR Voice Traffic Channel (TCH/FS) Voice CH Enhanced FR Traffic Channel (TCH/EFR) HR Traffic Channel (TCH/HS) FCCH (down) channel SCH (down) BCH BCCH (down) RACH (up) CCH AGCH (down) CCCH PCH (down) SDCCH DCCH FACCH SACCH Uke Kurniawan Usman - 2005

  24. Channel Type Traffic Channel Transmit voice and data Signaling Channel transmit the signaling and synchronous data between BTS and MS. Uke Kurniawan Usman - 2005

  25. ChannelType BCH : Frequency Correction CHannel(FCCH) -- for MS error correction Synchronous Channel(SCH) -- for MS frame synchronization and BTS recognization Broadcasting Control CHannel(BCCH) -- broadcasting information(cell selection information, etc..) Uke Kurniawan Usman - 2005

  26. Channel Type DCCH Self-help Dedicated Control Channel(SDCCH) for channel distribution information transmission Slow Associated Control Channel (SACCH) combined with one traffic channel or SDCCH, to transmit some specific information of user information Fast Associated Control Channel (FACCH) combined with one traffic channel, taking the same signal as SDCCH. It occupies the service channel to transmit signaling information. Uke Kurniawan Usman - 2005

  27. Structure of 51-frame Control CH Uke Kurniawan Usman - 2005

  28. Channel Combination Type Several logic channels combine together in some way to form some specific types of channel to transmit user data or signaling information. They are called combined channels. One combined channel can be mapped to a physical channel. There are the following combined channels: a TCH/F + FACCH/F + SACCH/TF b TCH/H(0,1) + FACCH/H(0,1) + SACCH/TH(0,1) c TCH/H(0,0) + FACCH/H(0,1) + SACCH/TH(0,1) + TCH/H(1,1) d FCCH + SCH + BCCH + CCCH e FCCH + SCH + BCCH + CCCH + SDCCH/4(0...3) + SACCH/C4(0...3) f BCCH + CCCH g SDCCH/8(0 ..7) + SACCH/C8(0 .. 7) CCCH = PCH + RACH + AGCH Uke Kurniawan Usman - 2005

  29. Channel Assignment inside cells • Small capacity cell with only 1 TRX TN0: FCCH+SCH+CCCH+BCCH+SDCCH/4(0,_,3)+SACCH/C4(0,_,3); TN1-7: TCH/F+FACCH/F+SACCH/TF • The medium-size cell with 4 TRXs 1TN0 group: FCCH+SCH+BCCH+CCCH; 2 SDCCH/8(0,_,7)+SACCH/C8(0,_,7); 29 TCH/F+FACCH/F+SACCH/TF Uke Kurniawan Usman - 2005

  30. Channel Assignment inside cells • Large-size cell with 12 TRXs 1 TN0 group: FCCH+SCH+BCCH+CCCH; 1 TN2 group, 1 TN4 group and 1 TN6 group: BCCH+CCCH; 5 SDCCH/8(0,_,7)+SACCH/C8(0,_,7); 87 TCH/F+FACCH/F+SACCH/TF Uke Kurniawan Usman - 2005

  31. Agenda • Network Architecture • Functional Layer of GSM • Air Interface • System Capacity • Anti Interference Technology • Network Planning • Numbering arrangement Uke Kurniawan Usman - 2005

  32. Cell Mode Layout Omni-directional cell Adopt omni-directional antenna, the overall directional propagation characteristic is the same. Directional cell In general, cell with multi-sector is in common use. Every directional cell adopts directional antenna. Uke Kurniawan Usman - 2005

  33. BTS Mode • Capacity • When the traffic is very low, and no possibility for quick increment, Omni-directional cell is used in common. Otherwise, we suggest to adopt the sector cell. • Note: TRX-transceiver,each TRX handles 1 frequency. • Coverage Area • Sector cell is often used to enlarge the cell coverage radius because of the higher antenna gain. • For special coverage ,such as road coverage, two-sector cell is adopted firstly. Uke Kurniawan Usman - 2005

  34. System capacity Erlang : the traffic intensity of a totally occupied channel (i.e. the call hour of a unit hour or the call minute of a unit minute). For example, the traffic of a channel occupied for 30 minutes in an hour is 0.5 Erlang) GOS: defined as the probability of call blocking or the probability when the call delay time is longer than a given queuing time. Uke Kurniawan Usman - 2005

  35. Agenda • Network Architecture • Functional Layer of GSM • Air Interface • System Capacity • Anti Interference Technology • Network Planning • Numbering arrangement Uke Kurniawan Usman - 2005

  36. Reasons for Interference The transmission path is very complex, ranging from the simple line-of-sight transmission to encountering such terrain as buildings, hills and trees. Wireless channels are extremely unpredictable. Abrupt drop, or fading, of signal strength in the land mobile wireless channel is quite common. The fading feature of the mobile channel depends on the radio wave propagation environment. Uke Kurniawan Usman - 2005

  37. Reasons for interference • Environmental factors: • Terrain (mountains, hills, plains, water bodies, etc.); • The quantity, heights, distribution and materials of buildings; • The vegetation of the region; • Weather conditions; • Natural and artificial electromagnetic noises; • Frequency; • How MS is moved. Uke Kurniawan Usman - 2005

  38. Interference • Co-Channel Interference • Conception: • the interference among the signals of co- channel cells is called co-channel interference. • Result from : • Frequency reuse • Reduction method: • co-channel cells must physically be spaced at a minimum interval to ensure adequate isolation of transmissions.  Uke Kurniawan Usman - 2005

  39. Interference • Adjacent Channel Interference • Conception: • The signal interference from the frequency adjacent to that of the signal used is called adjacent channel interference. • Reduction method: • accurate filtering and channel allocation (maximizing channel intervals of the cell). Interval of frequency reuse inter-cell interference, such as C/I, C/A Uke Kurniawan Usman - 2005

  40. Solution -Anti-interference • FH technology • Dynamic power control (DPC) • Discontinuous Transceiving (DTX) • Diversity receiving technique Uke Kurniawan Usman - 2005

  41. Frequency Hopping Technique Reason: • counteract Rayleigh Fading • scatter interference among multiple calls Types: • Base band frequency hopping keeps the transmission and receiving frequency of each carrier unit unchanged, but merely sends FU transmission data to different carrier units at different FN moments. • radio frequency hopping controls the frequency synthesizer of each transceiver, making it hop according to different schemes in different time slots. Uke Kurniawan Usman - 2005

  42. TRAU BTS • BTS MS • 480 ms • comfort noise frame Speech frame Discontinuous Speech Transmission (DTX) • Two aims can be achieved by adopting DTX mode: • lower the total interference electric level in the air • save transmitter power. Uke Kurniawan Usman - 2005

  43. Diversity Reception Technology • The multi-path propagation of radio signals causes • magnitude fading and delay time. • Space Diversity (antenna diversity) • Polarization Diversity • orthogonal polarization diversity. • horizontal polarization and vertical polarization. • Frequency Diversity • The working principle of this technology is that such fading won’t take place on the frequency outside the coherence bandwidth of the channel. Uke Kurniawan Usman - 2005

  44. Agenda • Network Architecture • Functional Layer of GSM • Air Interface • System Capacity • Anti Interference Technology • Network Planning • Numbering arrangement Uke Kurniawan Usman - 2005

  45. Frequency Reuse “4 ´ 3” reuse mode: one group includes 3 sectors /site ,12 frequency which are distributed to 4 sites. Every site owns 3 frequency. Uke Kurniawan Usman - 2005

  46. Frequency Reuse “3 ´ 3” reuse mode: one group includes 3 sectors /site ,9 frequency which are distributed to 3 sites. Every site owns 3 frequency. Uke Kurniawan Usman - 2005

  47. Agenda • Network Architecture • Functional Layer of GSM • Air Interface • System Capacity • Anti Interference Technology • Network Planning • Numbering arrangement Uke Kurniawan Usman - 2005

  48. Numbering Arrangement International Mobile Subscriber Identification number (IMSI) • It identifies a unique international universal number of a mobile subscriber, which consists of MCC+MNC+MSIN. • 1) MCC: country code, 460 • 2)MNC: network code, 00 or 01 • 3)MSIN: subscriber identification, H1H2H3H4 9XXXXXX, • H1H2H3H4: subscriber registering place • H1H2: assigned by the P&T Administrative Bureau (operator )to different provinces, to each province • H3H4: assigned by each province/city • the IMSI of user will be written into the SIM card by specific device and software and be stored into the HLR with other user information. Uke Kurniawan Usman - 2005

  49. Numbering Arrangement Mobile Subscriber ISDN Number(MSISDN) • It is the subscriber number commonly used. China uses the TDMA independent numbering plan: • CC+NDC+ H1H2H3H4 +ABC • CC: country code, 86 • NDC: network code, 135—139, 130 • H1H2H3H4: HLR identification code ABCD: mobile subscriber number inside each HLR Uke Kurniawan Usman - 2005

  50. Numbering Arrangement International Mobile Equipment Identification code (IMEI) • It will uniquely identify a mobile station. It is a decimal number of 15 digits. Its structure is: • TAC+FAC+SNR+SP • TAC=model ratification code, 6 digits • FAC=factory assembling code, 2 digits • SNR=sequence code, 6 digits • SP=reserved, 1 digit Uke Kurniawan Usman - 2005