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Slides of First Day

  1. 1. A THREE DAYS WORKSHOP ON ADVANCE MOBILE TECHNOLOGY (GSM) ICIT GOMAL UNIVERSITY D.I.KHAN Resource Person: ASIF QAYUM MS (Telecom & Networks) Organized By: M.KHALID HAMID
  2. 2. <ul><li>START WITH THE NAME OF ALLAH THE MOST MERCIFULL & MIGHTY </li></ul>
  3. 3. Day 1 (section 1) <ul><li>Cellular Networks </li></ul><ul><li>Cell shape </li></ul><ul><li>Hexagonal Cell </li></ul><ul><li>Cell area </li></ul><ul><li>Frequency spectrum </li></ul><ul><li>Frequency spectrum division </li></ul><ul><li>New standard </li></ul><ul><li>Frequency Re-Use </li></ul><ul><li>Cell cluster </li></ul><ul><li>Any Question </li></ul>
  4. 4. Cellular Networks <ul><li>The essential difference between a cellular and fixed telephony network is that the subscriber’s terminal (the Mobile Station - MS) is not linked by a fixed physical connection to the network </li></ul><ul><ul><li>Connection is a radio based wireless connection </li></ul></ul>
  5. 5. Cell shape <ul><li>Each cell is serviced by a fixed radio transmitter eceiver known as a “base station” (BS) which is commonly located in the centre or corner of a cell </li></ul><ul><li>While often drawn as hexagonal in shape, real cells have no defined shape. The actual area a cell covers depends on many parameters: </li></ul><ul><ul><li>Transmitter power </li></ul></ul><ul><ul><li>Weather </li></ul></ul><ul><ul><li>Antenna directivity </li></ul></ul>
  6. 6. Hexagonal Cell 1 2 3 4 5 6 7 7(Site)X 1(Cell) Re-use Hexagonal cell 2
  7. 7. Cell area <ul><li>The area a cell covers typically varies from a very small region in urban areas to quite large regions (around 35 km radius in GSM) in rural areas </li></ul><ul><li>Cells are often classified as being: </li></ul><ul><ul><li>Microcells </li></ul></ul><ul><ul><li>Macrocells </li></ul></ul><ul><ul><li>Umbrella cells </li></ul></ul><ul><ul><li>Selective (directional) cells </li></ul></ul>
  8. 8. Frequency Spectrum <ul><li>Cellular networks operate within defined frequency bands of the spectrum </li></ul><ul><li>For example, GSM-900 utilises two 25 MHz bands </li></ul><ul><ul><li>890-915 MHz (Uplink - MS to BS) </li></ul></ul><ul><ul><li>935-960 MHz (Downlink - BS to MS) </li></ul></ul><ul><li>These 25 MHz bands are subdivided into 124 carrier frequencies each spaced at approximately 200 kHz (FDMA) </li></ul>
  9. 9. Frequency Spectrum division <ul><li>Not all countries utilise the full 25 MHz and within a country the full GSM band must be subdivided among several network operators </li></ul><ul><li>Additional frequency spectrum is allocated in most countries around 1800 MHz (GSM-1800) </li></ul><ul><li>In US, certain operators implement GSM standard on a frequency band around 1900 MHz (GSM-1900) </li></ul>
  10. 10. New standard 876 880 890 915 921 925 935 960 GSM 900 EGSM – Extra 10MHz, therefore total available ARFCN become 174. RGSM – Extra 15MHz, therefore total available ARFCN become 199. GSM 900   EGSM RGSM RGSM EGSM
  11. 11. Frequency Re-use <ul><li>In a given country with, say, two different GSM networks will each use half the 124 (i.e. 62) GSM-900 carriers </li></ul><ul><li>Clearly, even using TDMA technology this is an extremely small number of carrier frequencies to support a GSM network in a complete country </li></ul><ul><li>All cellular networks address this problem by what is termed “frequency re-use” </li></ul>
  12. 12. Frequency Re-use <ul><li>Frequency re-use means that the same set of carrier frequencies being used in one cell can be re-used in the network in a different cell </li></ul><ul><li>However, the cells re-using the same carriers must not be adjacent as they would interfere with one another </li></ul><ul><li>In practice, these cell must be distant from one another </li></ul><ul><ul><li>Typical “re-use distance” is 2.5 to 3 times the cell “radius” </li></ul></ul>
  13. 13. Frequency Reuse How can we reuse frequency? 1 3 2 1 3 2 1 3 2 1 3 2 1 3 2
  14. 14. Cell Clusters <ul><li>Cells in a cellular network are generally “grouped” together into cell clusters </li></ul><ul><li>Cellular networks are generally designed as a repeated cluster pattern </li></ul><ul><li>The number of cells in a cluster (typically 4,7, 12 or 21) is a trade-off between the traffic capacity in the cluster and its interference with the adjacent cluster of cells (where the same frequencies will be re-used) </li></ul>
  15. 15. Cluster Larger cluster size Longer distance between interferers k=4 k=7 k=9 k=12 k=3 Less interference BUT Reduced capacity Cluster of 3,4,7,9 & 12 1 3 4 2 1 3 4 2 1 3 4 2 1 3 4 2 1 3 4 2 1 5 4 3 6 7 2 1 5 4 3 6 7 2 1 5 4 3 6 7 2 1 5 4 3 6 7 2 1 5 4 3 6 7 2 8 9 1 5 4 3 6 7 2 8 9 1 5 4 3 6 7 2 8 9 1 5 4 3 6 7 2 8 9 1 5 4 3 6 7 2 8 9 10 11 12 1 5 4 3 6 7 2 8 9 10 11 12 1 5 4 3 6 7 2 8 9 10 11 12 1 3 2 1 3 2 1 3 2 1 3 2 1 3 2
  16. 16. <ul><ul><ul><ul><ul><li>ANY QUESTION </li></ul></ul></ul></ul></ul>
  17. 17. DAY1 (SECTION 2) <ul><li>GSM Cellular Standard </li></ul><ul><li>Justification for GSM </li></ul><ul><li>Meeting these Criteria </li></ul><ul><li>GSM Network Architecture </li></ul><ul><li>Mobile Station (MS) </li></ul><ul><li>Base station subsystem (BSS) </li></ul><ul><li>Network Subsystem (NSS) </li></ul><ul><li>HLR & VLR </li></ul><ul><li>AuC & EIR </li></ul><ul><li>Other Network function </li></ul><ul><li>GSM Air Interface </li></ul>
  18. 18. GSM Cellular Standard <ul><li>All GSM networks and equipment conform to a defined GSM standard issued by ETSI (European Telecommunications Standard Institute) </li></ul><ul><li>GSM is a second generation or digital cellular technology </li></ul><ul><ul><li>All transmissions (signalling as well as traffic - speech) between MS and BS is by digital modulation of frequency carrier </li></ul></ul><ul><li>Currently, the most widely used of several second generation digital cellular telephony standards </li></ul>
  19. 19. Justification for GSM <ul><li>GSM development started in the early 1980s to replace first generation (analogue) cellular technology </li></ul><ul><li>The proposed system had to meet certain criteria </li></ul><ul><ul><li>Good subjective speech quality </li></ul></ul><ul><ul><li>Low terminal and network equipment costs </li></ul></ul><ul><ul><li>Support of international roaming </li></ul></ul><ul><ul><li>Efficient use of available spectrum </li></ul></ul>
  20. 20. Meeting these Criteria <ul><li>GSM has been very successful in meeting all of these criteria </li></ul><ul><ul><li>Widely used in well over 100 countries </li></ul></ul><ul><ul><li>Equipment costs are low </li></ul></ul><ul><ul><li>Voice, data and new services available </li></ul></ul><ul><li>However, </li></ul><ul><ul><li>Still not a single “global” standard </li></ul></ul><ul><ul><li>MS to BS bearer rates are still very slow for non-voice services </li></ul></ul><ul><li>Third generation “global” standard UMTS </li></ul>
  21. 21. Air Internet PSTN BTS BTS BTS BTS BTS BTS BTS BTS BTS BTS BTS BTS BSC BSC BSC BSC BSC MSC IWF GSM Network Architecture <ul><ul><ul><li>PPP session termination (learn wireless-specific info. while </li></ul></ul></ul><ul><ul><ul><li>establishing PPP session. Security and policy are linked. </li></ul></ul></ul><ul><ul><ul><li>QoS management </li></ul></ul></ul><ul><ul><ul><li>wireless-TCP </li></ul></ul></ul><ul><ul><ul><li>Personalization of Content Services depending on the device </li></ul></ul></ul><ul><ul><ul><li>PUSH and PULL services for Wireless advertisements </li></ul></ul></ul><ul><ul><ul><li>Wireless-Specific Policy Gateway </li></ul></ul></ul><ul><ul><ul><li>Wireless-VPNs </li></ul></ul></ul>
  22. 22. GSM Network Components AUC ME SIM OMC HLR MSC/VLR BTS BSC PSTN MS NSS BSS EIR
  23. 23. Mobile Station—MS <ul><li>ME = Mobile Equipment </li></ul>MS=ME+SIM SIM = Subscriber Identity Module
  24. 24. Subscriber Identity Module – SIM <ul><li>International Mobile Subscriber Identity (IMSI) </li></ul><ul><li>Temporary Mobile Subscriber Identity (TMSI) </li></ul><ul><li>Authentication Key (Ki) </li></ul><ul><li>Algorithms A3,A5,A8 </li></ul>GSM
  25. 25. Base Station Subsystem – BSS <ul><li>The Base Station Controller – BSC </li></ul><ul><li>The Base Transceiver Station – BTS </li></ul><ul><li>TRAU </li></ul>BTS BSC TRAU BSS MSC
  26. 26. BTS <ul><li>The BTS provide the physical connection of an MS to the Network inform of Air interface “U m </li></ul><ul><li>On the other side towards NSS ,the BTS is connected to the BSC via the Air interface “Abis” </li></ul><ul><li>Size of BTS = Today the size is comparable to a mailbox </li></ul>
  27. 27. BTS Block Diagram
  28. 28. Base Station Controller (BSC) <ul><li>BSC forms the center of BSS </li></ul><ul><li>BSC connect to many BTSs over Abis interface </li></ul><ul><li>Technically BSC is a small digital exchange with mobile-specific extension </li></ul>
  29. 29. Architecture of BSC
  30. 30. Switch Matrix <ul><li>Its function is to switch the incoming traffic channels (A-interface from MSC) to the correct Abis-interface channels </li></ul><ul><li>It take care of the relay functionality </li></ul><ul><li>It is also used as the internal control buss </li></ul>
  31. 31. Terminal Control Elements (TCE) Abis- interface <ul><li>The connection to the BTSs is establish via the TCEs </li></ul><ul><li>The connection is establish independently from BSC central Unit </li></ul><ul><li>The number of TCE depends on the number of BTSs connected with BSC </li></ul>
  32. 32. A-interface Terminal Control Elements <ul><li>The connection of a BSC to the MSC is establish via the A-TCEs </li></ul><ul><li>Remember that every BSC is connected to only one MSC </li></ul><ul><li>So large number of A-TCEs is needed to support the A-interface becoz all the payload and signaling data of the entire BSC have to be conveyed over this interface </li></ul>
  33. 33. Data Base (DB) <ul><li>The BSC database contain the maintenance status of the whole BSS </li></ul><ul><li>It contain the complete BTS operations software for all attached BTSs </li></ul>
  34. 34. Central Module (CM) <ul><li>The main task of CM is the Handover decision </li></ul><ul><li>It decide when a Handover should take place </li></ul><ul><li>For both intra BTS and intra BSC Handover decision BSC do not required the permission of MSC </li></ul><ul><li>Only for external Handover BSC needs to involve of MSC </li></ul><ul><li>Power control is also the main task of CM </li></ul>
  35. 35. TRAU <ul><li>The task of TRAU is to compress or decompress speech </li></ul><ul><li>It compress speech from 64kbps to 16kbps </li></ul><ul><li>Typically it is located between the BSC and MSC but it can be placed between BTS and BSC </li></ul>
  36. 36. Possible installation site of TRAU <ul><li>The speech compression is intended mainly to save resources over the Air-interface </li></ul><ul><li>It is also suitable to save line cost </li></ul><ul><li>So to get the most benefit from the compression,the TRAU would be install at the site of the MSC. </li></ul><ul><li>The GSM specification also allow the installation of TRAU b/w the BTS & BSC </li></ul>
  37. 38. The Network Switching System Mobile Switching Center – MSC Home Location Register – HLR Visitor Location Register – VLR Equipment Identity Register – EIR Authentication Center – AUC Inter-Working Function – IWF Echo Cancellor – EC AUC HLR MSC/VLR PSTN NSS EIR OMC BSS EC IWF
  38. 39. NSS Hierarchy
  39. 40. NSS Architecture
  40. 41. Mobile Service Switching Center – MSC <ul><li>Call Processing </li></ul><ul><li>Operations and Maintenance Support </li></ul><ul><li>Inter-network & Inter-working </li></ul><ul><li>Billing </li></ul>
  41. 42. Home Location Register – HLR <ul><li>Subscriber ID (IMSI and MSISDN) </li></ul><ul><li>Current subscriber VLR (current location) </li></ul><ul><li>Supplementary service information </li></ul><ul><li>Subscriber status (registered/deregistered) </li></ul><ul><li>Authentication key and AuC functionality </li></ul>
  42. 43. Visitor Location Register – VLR <ul><li>Mobile Status(IMSI detached/ attached) </li></ul><ul><li>Location Area Identity(LAI) </li></ul><ul><li>Temporary Mobile Subscriber Identity(TMSI) </li></ul><ul><li>Mobile Station Roaming Number(MSRN) </li></ul>
  43. 44. Equipment Identity Register – EIR IMEI Is Checked against White List IMEI Is Checked against Black/Grey List If NOT found, checked against Grey/Black List
  44. 45. Authentication A3 =? A3 RAND RAND Ki Ki MS Network Um interface Accept / reject? SRES SRES Ki = authentication key RAND = random number SRES = Signal Response
  45. 46. <ul><ul><ul><ul><li> </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Any Question </li></ul></ul></ul></ul>
  46. 47. Short Break <ul><ul><ul><ul><ul><li> 15 minutes </li></ul></ul></ul></ul></ul>
  47. 48. Day1 (section 3) <ul><li>GSM Channels </li></ul><ul><li>GSM Burst </li></ul>
  48. 49. Physical and Logical Channels The physical channel is the medium over which the information is carried The logical channels consist of the information carried over the physical channel 0 0 1 2 3 4 5 6 7 TDMA FRAME Timeslot The information carried in one time slot is called a “burst”
  49. 50. Traffic Channel TCH Traffic Channels Speech TCH/FS Data TCH/HS TCH/9.6 TCH/2.4 TCH/4.8 Normal Burst TCH Traffic Channel TCH/FS Full rate Speech Channel TCH/HS Half rate Speech Channel TCH/9.6 Data Channel 9.6kb/s TCH/4.8 Data Channel 4.8kb/s TCH/2.4 Data Channel 2.4Kb/s
  50. 51. Control Channel Broadcast Control Channel – BCCH Common Control Channel – CCCH Dedicated Control Channel – DCCH Associated Control Channel – ACCH FCCH SCH CCH Control Channels DCCH SDCCH BCCH BCCH Synch. CH. ACCH SACCH FACCH CCCH RACH CBCH PCH/AGCH
  51. 52. GSM Multiframe TDMA Frames 0 1 0 1 2 4 3 21 22 23 25 24 26 – Frame Multiframe (120ms) 0 1 1 0 TRAFFIC CHANNELS 2 3 4 5 6 7 2 3 5 7 6 4
  52. 53. GSM Multiframe TDMA Frames 0 1 0 1 2 4 3 46 47 48 50 49 51 – Frame Multiframes (235.3ms) 0 1 1 0 CONTROL CHANNELS 2 3 4 5 6 7 2 3 5 7 6 4
  53. 54. Timeslots and TDMA Frames Higher Capacity Cell Broadcast Traffic Dedicated Traffic 0 0 1 2 3 4 5 6 7 0 0 1 2 3 4 5 6 7 Low Capacity Cell Combined Traffic 0 0 1 2 3 4 5 6 7
  54. 55. GSM Burst <ul><li>The timeslots are termed burst periods because the GSM transmitter must transmit its data in a short “burst” within the time slot </li></ul><ul><li>Random Access burst (RACH): Used in MS initial access </li></ul><ul><li>Frequency correction burst (FCH): Used in frequency synchronization between MS and BTS </li></ul><ul><li>Synchronous burst (SCH): Used in timing synchronization between MS and BTS </li></ul>
  55. 56. BURST Frame Format Guard interval 8bit 41 synchronous bits 36 encrypted bits 3bit 68.25bit Tail bit Tail bit Guard interval Data <ul><li>Random Access burst (RACH): Used in MS initial access </li></ul>3bit 142bit 3bit 8.25bit Tail bit Tail bit Data <ul><li>Frequency correction burst (FCH): Used in frequency synchronization between MS and BTS </li></ul>3bit 39 encrypted bits 39 encrypted bits 3bit 8.25bit Tail bit Tail bit Guard interval Data Data 64 synchronous bits <ul><li>Synchronous burst (SCH): Used in timing synchronization between MS and BTS </li></ul>
  56. 57. Burst Mapping on physical channel Burst (148 bits) Guard Interval (8.25 bits) 577µs (156.25 bits) 0 7 TDMA frame = 4.615 ms 0 f s 7 0 s 7
  57. 58. <ul><ul><li> Any Question </li></ul></ul>
  58. 59. Day 1 (Section 4) <ul><li>GSM Modulation </li></ul><ul><li>Battery Life </li></ul><ul><li>IMSI </li></ul><ul><li>TMSI </li></ul><ul><li>IMEI </li></ul>
  59. 60. Modulation Techniques Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM) Phase modulation can be implemented easily for digital signals, this is the method which is Used for the GSM air interfaces. Phase Modulation is known as Phase Shift Keying when applied to Digital signals.
  60. 61. Gaussian Minimum Shift Keying (GMSK ) 1 0 0 1 1 Gaussian Digital Filter GMSK Modulator Gaussian Minimum Shift Keying (GMSK)
  61. 62. Battery Life <ul><li>Power Control </li></ul>Voice Activity Detection – VAD Discontinuous Transmission – DTX Discontinuous Reception – DRX
  62. 63. IMSI MCC : Mobile Country Code , It consists of 3 digits . For example: The MCC of China is &quot;460&quot; 。 MNC : Mobile Network Code , It consists of 2 digits . For example: The MNC of China Telecom is &quot;00&quot; 。 MSIN : Mobile Subscriber Identification Number. H1H2H3 S ABCDEF For example: 666-9777001 NMSI : National Mobile Subscriber Identification , MNC and MSIN form it together. For Example of IMSI : 460-00-666-9777001 Not more than 15 digits 3 digits 2 digits IMSI MCC MNC MSIN NMSI
  63. 64. TMSI <ul><li>The TMSI is assigned only after successful subscriber authentication. </li></ul><ul><li>The VLR controls the allocation of new TMSI numbers and notifies them to the HLR. </li></ul><ul><li>TMSI is used to ensure that the identity of the mobile subscriber on the air interface is kept secret. </li></ul><ul><li>The TMSI consists of 4 bytes( 8 HEX numbers) and determined by the telecom operator. </li></ul>TMSI: Temporary Mobile Subscriber Identification)
  64. 65. IMEI (15 digits) TAC : Type approval code. It is administered by the type approval center. FAC : Final assembly code.It is administered by the manufacturer. SNR : Serial number.It is issued by the manufacturer of the MS. SP : Not used. IMEI: International Mobile Station Equipment Identification TAC FAC SNR SP IMEI
  65. 66. <ul><li>THANKS </li></ul><ul><li>END OF THE DAY </li></ul>

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