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  • 1. EE 552/452, Spring, 2008 Wireless Communications (and Networks) Zhu Han Department of Electrical and Computer Engineering Class 26 May 6 th , 2008                                                             
  • 2. GSM System Architecture
  • 3. GSM interface
  • 4. GSM Network Structure MSC/VLR HLR/ AUC EIR SC/VM OMC BSC BTS PSTN ISDN PSPDN MS BSS MSS Um Abis BIE A F C H MSC/VLR E
  • 5. 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.
  • 6. 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
  • 7. 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.
  • 8. 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).
  • 9. 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 visitor location register (VLR) address
  • 10. 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
  • 11. 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
  • 12. Overview: Function Layers of GSM-1
  • 13. Protocol Stack Structure of GSM
  • 14. TDMA
    • 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.
    • GSM adopts TDMA/FDMA mode
    • channel width: 200KHz,
    • each channel has 8 timeslots
    User 1 User 2 User 3 Frequency time
  • 15. GSM Timeslot and Frame structure time Frequency BP 15/26ms 200KHz interval
  • 16. GSM Spec
  • 17. Frequency Resource 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 EGSM900 : up: 880~890MHz down: 925~935MHz duplex interval: 45MHz bandwidth: 10MHz , frequency interval: 200KHz GSM1900MHz: up:1850~1910MHz down:1930~1990MHz duplex interval: 80MHz , working bandwidth: 60MHz , frequency interval: 200KHz
  • 18. Frequency Resource 1800MHz 1900MHz 900MHz Single Band Network General Priority High Low For Subscriber For Operator Propagation Characteristic New Operator Which one? Reason
  • 19. Single Band Network 1800MHz 1900MHz 900MHz Single Band Dual Band Triple Band In a sense, the network determines the handsets can be selected. But nowadays, most handsets support dual band.
  • 20. Single Band Network Propagation characteristic Cell coverage radius : The higher the propagation frequency The higher the propagation loss The smaller the cell coverage radius. 900MHz 1800MHz 1900MH z We know
  • 21. Timeslot and Frame structure 1 super high frame = 2048 super frame = 2715648 TDMA frame 1 super frame = 1326 TDMA frame ( 6.12s ) 0 1 25 24 50 49 1 0 1 multiplex frame = 26 TDMA frames ( 120ms ) 1 multiplex frame = 51 TDMA frame 0 1 7 6 5 4 3 2 1 TDMA frame = 8 timeslot ( 120/26 = 4.615ms ) BCCH CCCH SDCH SACCH/TCH FACCH 0 2045 2046 2047 3 2 1 2044 3 2 1 0 49 47 48 50 0 24 25 1
  • 22. GSM Frame
  • 23. Control Channel Frame
  • 24. Time Slot Data Bursts
  • 25. GSM Frame Structure
  • 26. Physical Channel
    • 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.
    0 1 7 6 5 4 3 2 8 9 15 14 13 12 11 10 16 17 23 22 21 20 19 18
  • 27. GSM Speech
  • 28. GSM Speech
  • 29. Channel Type-Summary channel TCH CCH Voice CH Data CH FR Voice Traffic Channel (TCH/FS) HR Traffic Channel (TCH/HS) 4.8Kbit/s HR TCH (TCH/H4.8) 9.6Kbit/s FR TCH(TCH/F9.6) 4.8Kbit/s FR TCH (TCH/F4.8) BCH FCCH (down) SCH (down) BCCH (down) CCCH RACH (up) AGCH (down) PCH (down) DCCH SDCCH FACCH SACCH 14.4Kbit/s FR TCH (TCH/F14.4) Enhanced FR Traffic Channel (TCH/EFR)
  • 30. Channel Type
    • Traffic Channel
      • Transmit voice and data
    • Signaling Channel
      • transmit the signaling and synchronous data between BTS and MS.
    • 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..)
  • 31. 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.
  • 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.
  • 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.
  • 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.
  • 35. 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 .
    • 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.
  • 36. 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.
    • 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
  • 37. Solution -Anti-interference
    • FH technology
    • Dynamic power control (DPC)
    • Discontinuous Transceiving (DTX)
    • Diversity receiving technique
  • 38. 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.
  • 39. 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.
    • TRAU BTS
    • BTS MS
    Speech frame
    • 480 ms
          • comfort noise frame
  • 40. Diversity Reception Technique
    • 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.
  • 41. 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.
  • 42. 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.
  • 43. 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.
  • 44. 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
  • 45. 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
  • 46. Mobile Subscriber Roaming Number (MSRN)
    • The MSRN is temporarily distributed to the subscriber by the VLR according to the request by the HLR when this subscriber is called. The MSRN is released and can be assigned to other subscriber later.
    •    CC + NDC + 00 + M1M2M3 + ABC
    •   CC: country code, 86
    •    NDC: mobile network code, 135—139, 130
    •    M1M2: same as the H2H3 of MSISDN
    •    ABC: 000 -- 999
    • Temporarily Mobile Subscriber Identification Number (TMSI)
      • To insure the IMSI security, the VLR will assign an unique TMSI number for the accessed subscriber. It is used locally only and is a 4-byte TMSI number BCD code.
  • 47. Main Features Of IS-95 (cdmaone)
    • Modulation is performed using DSSS.
    • Employs variable rate coders.
    • Powerful low rate forward error-correcting codes.
    • Fast power control is employed to over come the near-far problem.
    • Soft handoff is employed.
    • Qualcomm code excited linear predictive (QCELP): 13.4 kbps
  • 48. Frequency and Channel Spec
    • Reverse: 824-849MHz, forward: 869-894MHz; PCS version 1800-2000MHz
    • Data rate 9.6kb/s; chip rate 1.2288Mchips/s, spreading factor 128.
    • Power Control:
    • Close-loop/open-loop
    • Rake receiver;
    • Soft handoff
  • 49. Forward CDMA channel
  • 50. Spec
    • Convolution code ½. Repetition circuit depending on speech
    • Block interleaver
    • Long PN sequence:
  • 51. Power Control
    • Open Loop
    • Close Loop
  • 52. Orthogonal Covering and modulation
    • Walsh function: page 574
    • Quadrature modulation
  • 53. Uplink
  • 54. Reverse Link Spec
  • 55. CT2
    • CT2 is a cordless telephony standard that was used in the early nineties to provide short-range proto-mobile phone service in some countries in Europe. It is considered the precursor to the popular DECT system.
  • 56. DECT
    • Digital Enhanced (formerly European) Cordless Telecommunications is an ETSI standard for digital portable phones , commonly used for domestic or corporate purposes. DECT can also be used for wireless data transfers. DECT is recognised by the ITU as
    • fullfilling the IMT-2000
    • requirements and thus
    • qualifies as a 3G system,
    • as a part of the IMT-2000
    • group of technologies,
  • 57. DECT functional concept
    • Portable handset
    • Radio fixed part
    • Cordless controller
    • Network-specific
    • interface unit
    • Supplementary
    • services
  • 58. DEC spec
  • 59. PACS
    • type of wireless telephone network compatible with telephone sets, answering machines, fax machines, and computers. A PACS can be used like a local area network ( LAN ) with voice capability and can be part of a larger network or can be connected into the telephone system.
  • 60. PACS Spec
  • 61. PACS Frame Structure
  • 62. Other issues
    • Pacific Digital Cellular: Japan, similar to IS-54
    • Personal Handyphone System: Japan, like DECT
    • Industrial, Scientific and Medical (ISM) band: Free
    • US PCS:
  • 63. Analog overview
  • 64. Digital Cordless
  • 65. 2G
  • 66. PCS
  • 67. Term Project
    • For presentator
      • Presentation Clearness
      • Timing
      • Preparation for the slides
      • Do you study something
      • Ability to answer questions
    • For audience
      • Bonus on asking good questions
    • 13 minutes + 2 minutes questions
  • 68. Final Comments
    • Final 60% why, why and why. 3 big questions. Control your time.
    • Hope you can get something that can ring a bell to you sometime in the future
    • Evaluation form: I would appreciate if you can fill. It is important for me
      • https://coeneval.boisestate.edu/index.htm
    • If you get A, you can ask me for reference in the future.
    • After graduation, you will all be decent guys. Best wishes to your career. After success, do not forget BSU.

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