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Wireless Training


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Wireless Training

  1. 1. 1 WIRELESS COMMUNICATION SYSTEMS From 1st Generation to 3rd Generation Rohit Joshi,
  2. 2. Contents 2  Type of wireless services.  Basics of wireless communication.  Cellular Concepts.  Generations of wireless communication.  Introduction to GSM.  GSM Radio Interface.  Introduction to GPRS.  GPRS Channel Structure
  3. 3. Contents cont.. 3  Introduction to UMTS  UTRAN Channel structure.  Comparison between 2G,2G+ and 3G
  4. 4. Type of wireless services 4  Outdoor Mobile Communication. – E.g. cellular telephony, WLL etc.  Outdoor Fixed Communication – E.g. Television broadcast .  Indoor ( Wireless LAN) – E.g. IEEE 802.11  Satellite Mobile – E.g. Thuraya, Inmarset etc.
  5. 5. Basics of wireless commn 5  Access  Some Basic Technologies Terminology – TDMA – Bandwidth – FDMA – Channel – CDMA – Protocol
  6. 6. Some Basic Terminology 6  Bandwidth  A signal is normally compose of a range of frequencies. This range of frequency occupied by the signal is termed as its BandWidth.  Channel  In communication, the term channel refers to the communication path between the two devices. It can refer to a physical medium or to a set of properties which distinguishes one channel from other.  Protocol  A set of rules that govern the operation of functional units to achieve communication
  7. 7. Access Technologies 7  TDMA  CDMA  Time Division Multiple Access  Code Division Multiple Access  FDMA  Frequency Division Multiple Access F F F r r r e e e q q q u u u e e e n n n c c c y y y Time Time Time TDMA FDMA CDMA
  8. 8. Cellular Concepts 8  Why Cells?  What shape and why?  How to allocate frequencies?  What is cell capacity?  How it is calculated?
  9. 9. Cellular Concepts Contd.. 9  Why Cells ?  Each Call Require Pair of RF Channel.  Need to server big community networks.  Radio spectrum available is limited.  Reuse of frequencies required.  What shape and why?  Cells in cellular system is drawn as hexagons.  Actual cell takes different shapes.  Bigger cell for low subscriber density.  Smaller cell for high subscriber density.  On highways cells are optimized to cover length.
  10. 10. Cellular Concepts Contd.. 10  How to allocate frequencies?  Split number of channels into groups  Assigns Frequency in each group to a cell.  Group cells into cluster containing all frequencies. g2 Each cluster size N satisfy g7 g3 g2 g1 g7 g3 N = I2 + ij + j2 g6 g4 g1  Repeat cluster across area to g5 g6 g4 be covered. g2 g5 g7 g3  g1 NFAP/contents.htm g6 g4 g5
  11. 11. Cellular Concepts Contd.. 11  What is cell capacity?  The cell capacity: Equal to the number of available voice channels per cell.  The cell Erlang capacity: Equal to the traffic carrying capacity of a cell (in Erlangs) for a specified call blocking probability.  How it is calculated?  The Erlang capacity can be calculated using the famous Erlang-B formula. B( p , m) = pm / ( m!  mk=0 ( pk / k! ) ) B( p , m) -> Call blocking probability. m -> Total number of channels p = µ ->  is the call arrival rate and  is the mean call duration.
  12. 12. Generations of wireless commn 12 1G 2G 2G+ 3G AMPS GSM900 GSM Europe TACS DCS1800 - HSCD - UMTS W-CDMA NMT 450 PCS1900 - GPRS US NMT900 IS 95 CDMA - EDGE - CDMA 2000 NADC/PDC IS-95 CDMA - HSD 80s 90s 200? 
  13. 13. Generations of wireless commn contd. 13  1st Generation  First Generation, analog cellular system were based on FDMA technology, to provide basic mobile telephony. It used narrow band, 30KHz channels, each carrying one telephone ckt. The number of calls in a sector were limited to the amount of carriers that can be assigned to the given spectrum.  2nd Generation  Using digital techniques, Second Generation digital wireless systems offer increased voice capacity, increased security, low bit rate data and regional roaming.  2.5 Generation  Here air interface was like 2G only but the upper layer protocols were optimized for packet switched service so that higher data rate can be achieved.
  14. 14. Generations of wireless commn contd. 14  Third Generation  Today’s 2G networks are primarily voice centric. By contrast, 3G systems will be primarily data and applications centric, combining high-speed mobile access with packet-based Internet Protocol (IP). Data rates as high as 2 Megabits per second will be possible in 3G (indoors)2, enabling high-speed data and mobile multimedia services that include voice, video, low and high-bit-rate data, internet access, location-based services, and access to information and services, anytime, anywhere.
  15. 15. Introduction to GSM 15  Architecture of GSM system. BTS - Base Transreceiver Station GMSC - Gateway MSC HLR - Home Location Register SMS Gateway/IWF MS - Mobile Station C MSC - Mobile Switching Center E SME SM-SC OMC - Operation and Maintenance HLR/GR Center MSC/VLR PSTN -Public Switch Telephone N. VLR - Visitor Location Register R Um BSS EIR
  16. 16. Introduction to GSM Contd.. 16  Mobile Station consist of  Mobile Equipment  Identified with International Mobile Equipment Identifier-IMEI  Subscriber Identity Module -SIM  Identified with International Mobile Subscriber Identifier –IMSI  Authentication and Ciphering Key generation algorithm.  Subscriber information  Access control class  Additional GSM services  Forbidden PLMN
  17. 17. Introduction to GSM Contd.. 17  Base Station Subsystem consist of  BTS  The Base Transceiver Station houses the radio tranceivers that define a cell and handles the radio-link protocols with the Mobile Station. The base station is under direction of a base station controller.  BSC  BSC does the Radio Resource Management.  BSC is responsible for Speech coding and rate adaptation.  BSC handles radio-channel setup, frequency hopping, and handovers  BSC can manage tens of BTSs.
  18. 18. Introduction to GSM Contd.. 18  Network Sub System consist of  MSC Mobile Switching Center:  the main function is to setting-up of calls  MSC controls a few BSCs  HLR:  stores subscribers’ info e.g. IMSI and current location etc.  AuC:  does the mgmt. of security data for the authentication of subscriber  VLR: (Visitor’s Location Register)  is in charge of temporarily storing subscription  GMSC:  the MT call is first routed to a Gateway MSC. The GMSC are in charge of fetching the location information and of routing the call towards the MSC.
  19. 19. GSM Security 19  RAND + Subscriber Key (Ki) + A3 = SRES  RAND + Subscriber Key (Ki) + A8 = Ciphering Key (Kc)  Kc + Frame Number + A5 = 114 bits to be XOR with 114 of the burst.  A3 and A8 are implemented in SIM and HLR/AuC
  20. 20. GSM Identities 20 MSISDN RAI Mobile Subscriber International Routing Area Identity ISDN Number (20 digits Max) IMSI PLMN International Mobile Subscriber Public Land Mobile Network Identity (15 digits) MCC IMEI Mobile Country Code International Mobile Equipment Identity (15 digits) MNC TMSI/PTMSI Mobile Network Code Temporary Mobile Subscriber ARFCN Identity (4 octets) Packet Temporary Mobile Absolute Radio Frequency Subscriber Identity Number LAI Location Area Identity
  21. 21. GSM Bands 21 P-GSM - Primary GSM GSM1800/DCS1800 Frequency 890-915MHz(Uplink) Frequency 1710-1785MHz(Uplink) 935-960MHz(Downlink) 1805-1880MHz(Downlink) ARFCN 1-124 ARFCN 512-885 E-GSM - Extended GSM GSM1900/PCS1900 Frequency 880-915MHz(Uplink) Frequency 1850-1910MHz(Uplink) 925-960MHz(Downlink) 1930-1990MHz(Downlink) ARFCN 975-1023 ARFCN 512-810
  22. 22. GSM Radio Interface 22
  23. 23. GSM Radio Interface 23 Logical Channels Broadcast Channels Traffic Channels Control Channels BCCH/EBCCH Common Control Dedicated Control FCCH RACH SDCCH SCH AGCH SACCH NCH PCH FACCH
  24. 24. GSM Radio Interface. 24 +4 dB - 6 dB +1.0 dB -1.0 dB - 6 dB  Channel structure.  Broadcast Control Channel (BCCH) 147 “Useful” bits - 30 dB 542.8 µ secs - 30 dB  Stand-alone Dedicated Control Channel (SDCCH) - 70 dB - 70 dB 10 µs 8 µs 10 µs 3 57 bits 1 26 bits 1 57 bits 3 10 µs 8 µs 10 µs  Common Control Channel (CCCH) 148 “Active” Bits 546.42 µsec  Random Access Channel (RACH)  Paging Channel (PCH)  Access Grant Channel (AGCH) F F Down Link  Traffic Channel (TCH) 0 1  Slow Associated Channel (SACCH)  Fast Associated Channel (FACCH)
  25. 25. GSM Radio Interface cont.. 25  Speech Coding  20 msec sample  260 bits per sample  Channel coding and modulation  Class Ia 50 bits - most sensitive to bit errors.  Class Ib 132 bits - moderately sensitive to bit errors.  Class II 78 bits - least sensitive to bit errors  1/2 rate convolution coding gives 456 bits  456 bits are divided into 8 blocks of 57 bits.  Blocks from two 20 msec sample are interleaved.
  26. 26. GSM Protocol Architecture 26 MS BSS MSC CM Radio Interface A - Interface CM MM MM BSSAP RR BSSAP RR SCCP SCCP LAPDm LAPDm MTP MTP TDMA/FDMA TDMA/FDMA
  27. 27. Location Update 27 MS BTS BSC MSC/VLR RACH CHANNEL REQ. IMMEDIATE ASSIGNMENT SABM (Location update Request) UA (Location update Request) Complete layer 3 info Authentication Request Authentication Request Authentication Response Authentication Response Cipher Mode Command Cipher Mode Command Cipher Mode Complete Cipher Mode Complete Location Update Accept Location Update Accept TMSI Reallocation Complete TMSI Reallocation Complete Clear Command Channel Released Clear Complete
  28. 28. MS MT Call BTS BSC Paging Paging 28 RACH CHANNEL REQ. IMMEDIATE ASSIGNMENT SABM ( Paging Response) UA ( Paging Response ) Complete layer 3 info Authentication Request Authentication Request Authentication Response Authentication Response Cipher Mode Command Cipher Mode Command Cipher Mode Complete Cipher Mode Complete SETUP SETUP Call Confirmed Call Confirmed Assignment Command Assignment Request Assignment Complete Assignment Complete Alerting Alerting Connect Connect Connect Acknowledge Connect Acknowledge
  29. 29. Introduction to GPRS 29  Architecture of GPRS system. SM E SM -S C TE SM S Pac k et Gatew ay/IW F D ata E C N etw ork HLR/ GR M SC/ VLR D Gd Gi TE Gs Gr Gc A EI R Gf PCU BSS Gb SGSN Gn GGSN m U Gn Other PLMN S GS N GGS N Ot her SGSN - Serving GPRS Support Node SGS N B order GGSN - Gateway GPRS Support Node Gatew ay BG Ga Gp TE - Terminal Equipment. R Inter-P LMN Charging N etw ork Gateway Ac c ounting C enter
  30. 30. GPRS Channel Structure 30  Multi slot operation.  Asymmetric channel allocation.  Need based (dynamic) allocation. Group Channel Function Direction Packet data traffic channel PDTCH Data traffic MS BSS Packet broadcast control channel control PBCCH Broadcast MS BSS Packet common control channel (PCCCH) PRACH Random access MS BSS PAGCH Access grant MS BSS PPCH Paging MS BSS PNCH Notification MS BSS Packet dedicated control channels PACCH Associated control MS BSS PTCCH Timing advance control MS BSS
  31. 31. GPRS Transmission Plane 31 Application IP / X.25 IP / X.25 Relay SNDCP SNDCP GTP-U GTP-U LLC LLC UDP / UDP / Relay TCP TCP RLC RLC BSSGP BSSGP IP IP MAC MAC Network Network L2 L2 Service Service GSM RF GSM RF L1bis L1bis L1 L1 Um Gb Gn Gi MS BSS SGSN GGSN
  32. 32. GPRS Signaling Plane 32 GMM/SM GMM/SM LLC LLC Relay RLC RLC BSSGP BSSGP MAC MAC Network Network Service Service GSM RF GSM RF L1bis L1bis Um Gb MS BSS 2G-SGS N
  35. 35. Introduction to UMTS 35  Architecture of UMTS system.
  36. 36. Introduction to UMTS cont.. 36  Architecture of UMTS system.
  37. 37. UMTS Channel Structure 37  Two level hierarchy.  Logical -> Transport -> Physical  Radio frames.  10 ms  15 Slots  Each Slot 2560 chips.
  38. 38. UMTS Channel Structure cont.. 38
  39. 39. UMTS Channel Structure cont.. 39
  40. 40. Comparison between 2G, 2G+ and 3G 40 Feature 2G 2G+ 3G Core Network MSC/VLR, GMSC, MSC/VLR, GMSC, 3G MSC/VLR (with added HLR/AuC/EIR SGSN,GGSN, HLR/AuC/EIR, interworking and transcoding), CGF GMSC, HLR/AuC/EIR, 3G- MM, CM, BSSAP, SCCP, SGSN, GGSN, CGF ISUP,TCAP, MAP, MTP 3, GMM/SM/SMS, MM, CM, MTP 2, MTP 1 GTP, SNDCP,NS, FR, GMM/SM,MM,CM,BSSAP, LLC,BSSGP, BSSAP, RANAP,GTP,SCCP, MTP3B, TDM transport BSSAP+,SCCP, TCAP, MAP, M3UA, SCTP, Q.2630.1 ISUP,MTP 3, MTP 2, MTP 1 (NNI), TCAP, MAP, ISUP, MTP 3, MTP 2, MTP 1, TDM, Frame Relay transport Q.2140, SSCOP ATM, IP transport Radio Access BTS, BSC, MS BTS, BSC, MS Node B, RNC, MS FDMA, TDMA, CDMA TDMA, CDMA, EDGE W-CDMA, CDMA2000, IWC- 136 MM, CM, RR, LAPDm, MAC, RLC, LAPD, BSSAP, SCCP, GMM/SM/SMS,LLC, SNDCP, GMM/SM, MAC, RLC, MTP 3, MTP 2, MTP 1 BSSGP, NS,FR,RR,BSSAP, PDCP,RRC,Q.2630.1(UNI+N SCCP, MTP 3,MTP 2, MTP 1 NI),NBAP, RNSAP,RANAP, SCCP, MTP3B, M3UA, SCTP, GTP-U, Q.2140, Q.2130, SSCOP,CIP Handsets Voice only terminals New type of terminal New type of terminal Multiple modes Dual mode TDMA and CDMA Voice, data and video terminals Voice and data terminals WAP, multimedia mgmt WAP, no multimedia support
  41. 41. Comparison between 2G, 2G+ and 3G cont... 41 Databases HLR, VLR, EIR, AuC HLR, VLR, EIR, AuC Enhanced HLR, VLR, EIR,AuC Data Rates Up to 9.6 Kbps Up to 57.6 Kbps (HSCSD) Up to 2Mbps Up to 115Kbps (GPRS) Up to 384 Kbps (EDGE) Applications Advanced voice, Short SMS, Internet Internet, multimedia Message Service (SMS) Roaming Restricted, not global Restricted, not global global Compatibility Not compatible to 3G Not compatible to 3G Compatible to 2G, 2G+ and Bluetooth
  42. 42. 42 Backup
  43. 43. Co-Channel Reuse Factor 43  For hexagonal Cells the reuse Factor is D/R = (3N) ^ 0.5  N can be 3,4 or 7
  44. 44. Worst Case Co-Channel interference 44  C/I = 6.3 db With N=3  C/I = 9.2 db With N=4 D  C/I = 14.3 db With D+R D-R N=7  Desired is 12db in fwd D+R D-R ch and 9 db rev ch D
  45. 45. Worst Case Co-Channel interference 45  C/I = 15 db With N=3  C/I = 17.1 db With D+0.7R N=4 D+0.7R D  C/I = 21.1 db With N=7 D D-0.7R D-0.7R
  46. 46. Different Picture 46 SGSN HLR BTS MAP-C Gs MAP-D BTS BSC MSC/VLR GMSC MAP-E BTS MSC/VLR Um Abis A-Int.
  47. 47. What is PLMN Selection? 47 The Mobile Station upon Switch-On will attempt to find its Home PLMN. The Mobile Station will scan through frequencies looking for Home PLMN. Scanning frequencies will be based on list’s available in the SIM.  BCCH List  Preferred PLMN List  Forbidden PLMN List  BA Range Modes of PLMN Selection: Manual Mode All PLMN’s found by the Mobile Station after switching on are presented to the Subscriber. The subscriber can select the PLMN and the Mobile station will attempt to access that PLMN. Automatic Mode A search is conducted for the Preferred PLMN (generally is the home PLMN network) and the Mobile station automatically accesses the home PLMN.
  48. 48. What is Cell Selection? 48 Cell Selection is the process used by the Mobile Station to ‘Camp On’ to the best cell available when a MS is Switched ON. Steps Involved: • The Mobile Station reads the SI on the cell of the chosen PLMN, measures RLA ,reads the Neighbor cell list(BA List) and C1 criteria. • The Mobile Station reads the SI on the cells of the BA List, measures RLA and C1 criteria for each cell. • The Mobile Station compares the calculated the C1 of all the cells and ‘Camps On’ to the cell with largest C1 value. Note: C1 = RLA – RXLEV_ACCESS_MIN – max(MS_TXPWR_MAX_CCH – MSPC, 0)
  49. 49. What is Cell Re-Selection? 49 When camped on a cell, the mobile shall regularly search for a better cell according to the cell reselection criteria. If a better cell is found, that cell is selected. This process is identified as the 'C2’ or ‘C32’ in the GSM system. C2 Cell Criteria is a Phase 2 refinement to the C1 criterion. It adds an offset margin in db to C1 which can make a Particular cell appear more attractive or less attractive as a selection candidate. Note: C2 =( C1 + CELL_RESELECT_OFFSET) - (TEMP_OFFSET for PENALTY_TIME)
  50. 50. What is Location Update? 50 Location Update is the process of informing the Network about the Location of the MS (Mobile Subscriber) Types of Location Updates:  IMSI Attach  Normal Location Update  Periodic Location Update
  51. 51. What is Handover? 51 Definition: • The Handover process allows to change the serving cell without loosing the call in progress. The reasons for performing handover : • Distance (or propagation delay)between MS and BTS is too big • Receive signal quality (RXQUAL)becomes too bad • Receive signal level (RXLEV)becomes too bad • Path loss for the MS to other cell is better • Duration that MS stays in a cell Types of Handover: • Intra Cell Handover • Inter Cell Handover • Intra BSC Handover • Inter BSC Handover
  52. 52. VLR MSC BSC BTS MS Channel Request (RACH) Channel Required Channel Activation Radio Channel Activation Ack Access Part Immediate Assign Cmd Immediate Assignment(AGCH) Locaion Update Request Location Locaion Update Request Locaion Update Request Establish Indication UA (SDCCH) Update Process Access Request CC Request Identity Request Identity Request Identity Request (SDCCH) Identity Response (SDCCH) Identity Response (SDCCH) Identification, Identity Response Authenticate Authentication Authenticate Request Authentication Request (SDCCH) Authentication Response (SDCCH) Authenticate Response Authentication Response Set Ciphering Mode Cipher Mode Command Encryption Command Ciphering Mode Command (SDCCH) Cipher Mode Complete (SDCCH) Ciphering Cipher Mode Complete Access Request Accpeted Encryption Loc Update Accepted (NEW TMSI/IMSI) Location Update Accepted TMSI Reallcation Complete TMSI Reallcation Complete Clear Command Channel Release (SDCCH) Deactivate SACCH DISC (FACCH) UA (FACCH) Release Indication RF Channel Release RF Channel Release Ack Clear Complete RLSD (SCCP Released RLC (SCCP Released Ack) RR Message CC Message BSSMAP BTSM Message Message 52 MM Message L3 Message