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Wireless Telecommunication System

Wireless Telecommunication System. Contd.. AMPS: Advanced Mobile Phone System DECT: Digital Enhanced Cordless Telephone NMT : Nordic Mobile Telephone PDC : Personnal Digital Cellular IMT : International Mobile Telecommunication GPRS: General Packet Radio Service

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Wireless Telecommunication System

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  1. Wireless Telecommunication System

  2. Contd.. • AMPS: Advanced Mobile Phone System • DECT: Digital Enhanced Cordless Telephone • NMT : Nordic Mobile Telephone • PDC : Personnal Digital Cellular • IMT : International Mobile Telecommunication • GPRS: General Packet Radio Service • EDGE: Enhanced Data Rates for GSM Evolution • UMTS: Universal Mobile Telecommunication System • EVDO: Evolution Data Optimized • EVDV: Evolution Data and Voice • UTRA: UMTS Terrestrial Radio Access

  3. GSM • Groupe Speciale Mobile -1982 • Global System for Mobile Communication ->Goal: Roam and Provide Voice Services (But not offering high world wide data rates that 3G/UMTS are promising) 890 -915 MHZ for Uplinks 935 -965 MHZ for Downlinks

  4. Performance Characteristics of GSM

  5. DisAdvantagesin GSM

  6. GSM : MOBILE SERVICE

  7. BEARER SERVICE • Transparent transmission of data between the interfaces to the network (TE-TE) • Within MS,MT(Mobile Termination-TDMA,FDMA,Coding etc) • Increasing Transmission Quality-Forward Error Correction(FEC) • PLMN –Public Land Mobile Network • ISDN -Integrated Service Digital Network • PSDN –Public SwitcedDigital Network

  8. Contd..

  9. TELE SERVICES • Mobile Telephony • Emergency Number • Multinumbering • SMS –160 Characters • EMS –760 Characters • MMS –(GIF,JPG,WBMP) • Group 3 Fax

  10. Supplementary Services • User Identification • Call Redirection or Forwarding • Closed User Groups(Multi Party Communication)

  11. GSM :Architecture

  12. GSM Architecture

  13. Radio Sub System

  14. Radio SubSystem

  15. Mobile Station • SIM (Stores User Specific Data) • IMEI • PIN • IMSI

  16. Network & Switching SubSystem

  17. NSS • Msc –High Performance Digital ISDN Switches • GMsc–Gateway Msc-Fixed • SS7-Standard SIGNALLING SYSTEM -> Connection Setup, Release & HO

  18. HLR • STATIC • IMSI • CALL FORWARDING,ROAMING • Dynamic Information (Location Area (LA)) • MSRN --Mobile SubsciberRoaming Number • MSLeave <- Update

  19. VLR • Dynamic Database • Associated with each Msc • MS􀃅CurrentLocation Area • Copies from HLR

  20. Operation Subsystem • OMC -Traffic Moinitoring -Status Report of N/W Entities -Accounting&Billing,Security MGT • AUC -User Identity and Data Transmission • EIR -DB for IMEI,Black list,WhiteList,Gray List -Synchronization not done

  21. GSM

  22. Radio Interface • Um interface-Multiplexing,Media Access • FDD –Separate UP&DOWN Links • 1-124 Channels each 200 Khz • 32 Channels for organization Data • Remaining for Customer Use -90 channels • 248 Channels –additionaly seperated by GSM TDMA Frame • Each 200Khz carrier is divided into frames

  23. Contd.. • Duration of each frame is 4.615 ms • 8 GSM Time Slots ( 577 μs) • Data –BURSTS(NORMAL BURST) • Each Burst is 546.5 μs long & remaining is 30.5 μs(GuardSpace) • Whole Data is 156.25 bit with 577 μs

  24. GSM-TDMA/FDMA

  25. GSM :FDMA/TDMA • Tail-> Enhance the Receiver Performance • Training Sequence-> Select Strongest Signal(mpp) • Flag S -> Data Field contains user data or Network Data

  26. Other Bursts • Frequency Correction Burst MS to correct local oscillator to avoid interferences in neighbor channel • Synchronization Burst synchronization burst (BTS-MS) • Access Burst Initial Connection Setup (BTS-MS) • Dummy Burst if no data is available for slot

  27. GSM: Logical Channels • Traffic Channels (TCH) (i) Full Rate (ii) Half Rate • Control Channels ->Control Medium Access ->Allocation of Traffic Channels ->Mobility Management

  28. Control Channels • Broadcast Control Channel (BCCH) ->BTS signals all information to MS Synchronization in time(Cell) –SCH Frequency Correction (Cell) -FCH • Common Control Channel (CCCH) 􀃆Connection Setup(MS-BTS) Paging Channel(PCH)-BTS-Pages-MS Random Access Channel(RAC)-MS-BTS • Dedicated Control Channel (DCCH) -> Bidirectional MS uses Stand-Alone Dedicated Control Channel(SDCCH) with low data rate for signaling; if (Ms using TCH not estabilished –BTS) TCH & SDCCH is associated with SLOW ASSOCIATED DEDICATED CONTROL CHANNEL(SACCH)

  29. GSM:HIERARCHY OF FRAMES

  30. GSM PROTOCOL LAYERS FOR SIGNALING

  31. GSM PROTOCOL LAYERS FOR SIGNALING • Layer –I (Radio Specific Function) Creation of Bursts; Multiplexing of Bursts in TDMA Frame Synchronization Detection of Idle Channel Measurement of Channel Quality Synchronization (Correction –Individual path delay)

  32. Contd.. • BTS –MS (RTT is short for near and .25ms for 35kms) • VAD(Voice Activity Detection) Scheme for voice transmission • During Period of Silence; COMFORT NOISE to fake a connection

  33. Signaling Between two Entities-Layer 2 • LAPD (Link Access Procedure for D-Channel) -> Reliable Data Transfer over connections -> Flow control,Segmentation&Reassembly of Data -> ACK for Data Transfer

  34. Layer –3Sub Layers • RR-Radio Resource Management(RR) (Part of BTS Supported by BTSM) Setup,Maintenance & Release of Radio Channels • MM-Mobility Management (MM) Registration,Authentication,Identification, Location Updating,TMSI(IMSI)

  35. LAYER -3 Contd… • CALL MANAGEMENT (CM) (i) Call Control (ii) SMS –SDCCH /SACCH (iii) Supplementary Services

  36. MSC • PULSE CODE MODULATION • SS7 (BSC-MSC)->Transfer all MGT info between MSC(HLR,VLR,AUC,EIR,OMC) • BSSAP: An MSC can also control a BSS (via) BSS Application Part.

  37. Localization and Calling • GSM System-Automatic Worldwide Localization of users • Periodic Location Updates • ROAMING *Changing VLR’s with uninterrupted Availability of all services *One Provider / Two providers in a Country/Two providers in a two different countries

  38. Locating an MS • Mobile Station International ISDN Number(MSISDN) CC + National Destination Code + Sub. Number(eg.+49 179 1234567) • IMSI- Internal unique identification of a subscriber • TMSI- current VLR- valid temporarily- LA- VLR changes periodically. • Mobile Station Roaming Number (MSRN) -Hides the identity and location of the user -VLR-Generates on request from MSC –HLR -VCC –VNDC –SN -MSRN helps HLR to find user for an incoming call

  39. Mobile Terminated

  40. Visitor Location Register (VLR) • Suppose your mobile is registered in Mumbai and you are currently in Delhi • What happens when your friend in Mumbai calls you?

  41. Mobile Originated Call

  42. Visitor Location Register (VLR) • 2. What happens when you call to a friend (a)In the home network ? (Mumbai) (b)In the visitor network ? (Delhi) (c)Both are from Mumbai and currently in Delhi

  43. HANDOVER • Should not cause a Cut-off.(CALLDROP) • Maximum Duration is 60 ms • Basic Reason 1. Quality of the Radio Link 2. Load Balancing(MSC,BSC to decide –Traffic in an Cell –High) • Error Rates and Signal Levels

  44. Four Types of HandOver • Intra-Cell Handover --Within a cell • Inter-Cell, Intra-Bsc Handover --Cell to another cell –Bsc • Inter-Bsc,Intra-Msc Handover --Bsc to Bsc ->Msc • Inter Msc Handover --Msc to Msc

  45. Types of Handover

  46. Signal Flow-Inter-BSC,Intra-MSC

  47. SECURITY • Security to AUC and SIM • A3 –Authentication • A5 –Encryption • A8 –Generation of Cipher Key

  48. Authentication • Any Service –GSM • Authentication is based on Individual Authentication Key IMSI A3 • Challenge-Response Method Generating a Random Number

  49. Authentication

  50. Key Generation and Encryption

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