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Mobile cellular-telecommunication-system-revised

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Mobile cellular-telecommunication-system-revised

  1. 1. Mobile CommunicationsAssistant Prof.Dr.Tamer M. BarakatElectronics & Communications Dept.
  2. 2. Course ContentsPART I: Introduction• Conventional mobile system against cellularsystem.• Objectives in design of cellular system.• Basic cellular system.• Operation of cellular systems.• Call supervision.• Modern Wireless Communication Systems:Second Generation (2G - GSM) Cellular Networks.Third Generation (3G - UMTS) Wireless Networks.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 2
  3. 3. Course Contents (Cont…)PART II: GSM Cellular Networks.• GSM parts.• Hanover process.• Digital services:Caller Identification.Short Message Services (SMS).FAX services.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 3
  4. 4. Course Contents (Cont…)PART III: Multiple Access Techniques forWireless Communications.• Introduction to Multiple Access.• FDMA.• TDMA.• Spread Spectrum Multiple Access (SSMA).– Frequency Hopped Multiple Access (FHMA).– Code Division Multiple Access ( CDMA).– Hybrid Spread Spectrum Techniques.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 4
  5. 5. Course Contents (Cont…)– Space Division Multiple Access (SDMA).– Packet Radio.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 5
  6. 6. Course Contents (Cont…)PART IV: Cellular Configuration• Properties of Cellular Geometry.• Capacity of Cellular Systems.• Description of Mobile Transmission Medium.• Co-channel Interference.• Channel Assignment.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 6
  7. 7. References• “Wireless Communications: Principles &Practices – 2nd edition” Theodore S. Rappaport• “Mobile Communications”, Lee.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 7
  8. 8. Lecture #1Mobile Cellular Telecommunication System4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 8
  9. 9. Conventional mobile system againstcellular mobile system• One of many reasons for developing a cellularmobile telephone system is the operationallimitations of conventional mobile telephonesystem:1. Limited service capability.problem of the handoff process.The number of active users is limited to thenumber of channels assigned to a particularfrequency zone.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 9
  10. 10. 2. Poor service performance; the large numberof subscribers created a high blockingprobability during busy hours.3. Inefficient frequency spectrum utilization;In conventional system:𝑀 𝜊 =𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑢𝑠𝑡𝑜𝑚𝑒𝑟𝑠𝑐𝑕𝑎𝑛𝑛𝑒𝑙Where 𝑀 𝜊: the maximum number of customersthat could be served by one channel at the busyhour.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 10
  11. 11. • For example:If given: 𝑀 𝜊 = 53 customers/channelaverage calling time= 1.76 minthe number of channels = 6∴ 𝐴 = 𝑜𝑓𝑓𝑒𝑟𝑒𝑑 𝑙𝑜𝑎𝑑=𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑐𝑎𝑙𝑙𝑖𝑛𝑔 𝑡𝑖𝑚𝑒 × #𝑡𝑜𝑡𝑎𝑙 𝑐𝑢𝑠𝑡𝑜𝑚𝑒𝑟𝑠60 𝑚𝑖𝑛𝐴 =1.76 × 53 × 660= 9.33 𝑒𝑟𝑙𝑎𝑛𝑔∴ from the table we can find the blocking prob. =B =50 %4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 11
  12. 12. Objectives in the design of cellularsystems1. Large subscriber capability.2. Spectrum utilization.3. Compatibility.4. Adoptability to traffic density.5. Quality of service and affordability.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 12
  13. 13. Basic cellular system4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 13MRMTSO MRCell #1voicedata datavoiceCell #2A basic cellular system consists of three parts:I. Mobile units.II. Cell site; it contains a control unit, a radio cabinets, antennas, data terminal andpower planet.III. MTSO; Mobile Telecommunication Switching Office. It is the centralcoordinating element for all cell sites and contains the cellular processor and acellular switch
  14. 14. Operation of cellular systems1) Mobile unit initialization- The user activates the of the mobile unit.- The receiver scan 21 set-up channels from designed 333channels.- It then selects the strongest (the nearest) cell sites. This iscalled self-location scheme.2) Mobile originated call- The user place the called number into an originated registerin the mobile unit which checked that the number is correct.- A request for service is sent on a selected set-up channelobtained from a self-location scheme.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 14
  15. 15. Operation of cellular systems Cont.- The cell site, which is directional antenna, selectsthe best directive antenna for the voice channel touse.- At the same time the cell site sends the request toMTSO via a high-speed data link.- The MTSO selects an appropriate voice channelfor the cell and then the cell site acts on it throughthe best directive antenna to link the mobile unit.- The MTSO also connects the wire-line partythrough the telephone company.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 15
  16. 16. Operation of cellular systems Cont.3) Network originated call- A land-line party dials a mobile unit number.The telephone company office recognizes that the numberis mobile and forwards the call to the MTSO.- The MTSO sends a paging message to certain cell sitesbased on the mobile unit number and the searchalgorithm.- Each cell site transmits the page on its own set-upchannel.- The mobile unit recognizes its own identification on aset-up channel and responds to the cell site.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 16
  17. 17. Operation of cellular systems Cont.4) Call termination.5) Handoff procedure.- when the mobile unit moves out of coverage area of aparticular cell site, the reception becomes weak.- The present cell site request a handoff.- The system switches the call to a new frequencychannel in a new cell site without either interrupting thecall or altering the user.- The call continuous as long as the user is talking.- The user does not notice the handoff procedures.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 17
  18. 18. Call supervision• On the voice channel, one of the three tones is used forsupervision.• These tones are centered at 6 KHz and calledSupervisory Audio Tones (SAT).• The SAT is added to the voice transmission by a landstation.• The three frequencies used are:5970, 6000, and 6030 Hz.• The other tones is known as Signaling Tone (ST).• ST is transmitted at 10 KHz and it is used to indicatethe mobile user on-hook and off-hook conditions4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 18
  19. 19. End of Lecture #14/10/2011 Assistant Prof.Dr.Tamer M. Barakat 19
  20. 20. Lecture #2GSM4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 20
  21. 21. GSM PartsA GSM network comprised of several major portions:• A mobile radio part.• Subscriber information part.• A radio network.• A switching system.• A network intelligence (primarily data base).• Mobile phone which called Mobile Station (MS).• An electronic card which called Subscriber IdentityModule (SIM).• Mobile stations communicate with nearest radio powercalled Base Station Subsystem (BSS).4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 21
  22. 22.  Base Station Subsystem (BSS)- The radio part of the GSM network equipmentare contained within the BSS.- It is consists of two main parts:a) The base Transceiver Station (BTS).b) The Base Station Controller (BSC).4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 22
  23. 23.  Base Station Subsystem (BSS) Cont….a) Base Transceiver Station (BTS):the BTS consists of transmitters, receivers,antenna, power supply and test circuit.b) Base Station Controller (BSC):The BSC comprises:1. A control computer ( typically a microprocessorcontrol processing unit with memory).2. Data communication facilities.3. Multiplexing and de-multiplexing equipment.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 23
  24. 24.  Base Station Subsystem (BSS) Cont….• The basic function of BSC:1) It can control the radio power levels of the varioustransceiver in the BTS.2) It can autonomously control the mobile stations radiotransmitter power level as well.3) The BSC passes certain type of control messagesbetween the BTS and the mobile Switching Center.4) The BSC handles certain types of control messages itselfunder appropriate conditions.Note: A single BSC can control several BTS radio equipmenttransmitters. The BSC can be located in a base station or at anotherremote site.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 24
  25. 25.  Network and Switching Subsystem (SS)4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 25BTSBSCOMC MSCVLRHLREIRMSBSSBasic parts of GSM network
  26. 26.  Network and Switching Subsystem (SS)Cont….The switching system includes the following functional unit:i. Mobile Services Switching Centre (MSC).ii. Visitor Location Register (VLR).iii. Home Location Register (HLR).iv. Authentication Centre (AUC).v. Equipment Identity Register (EIR).Note:- Operations and Maintenance Centre (OMC); is connected toall equipment in the switching system and to the BSC. Thepurpose of OMC is to offer the customer cost-effectivesupport for centralized, regional, and local operational andmaintenance activities that are required for a GSM network.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 26
  27. 27.  Network and Switching Subsystem(SS) Cont….• Mobile Services Switching Centre: (MSC):- A number of BSC are served by a MSC which controlscalls to and from other telephony and datacommunication system such as PSTN, ISDN, PLMN orPublic Data Network.- It is consists of switching Centre and power supplies.- The switches allow connection between each basestation and PSTN. Basically, these switches use anElectronic Switching System (ESS) which uses processcalled Time Slot Interchange (TSI) to connect incomingand outgoing digital lines together through the use oftemporary memory locations.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 27
  28. 28.  Network and Switching Subsystem (SS)Cont….• home location register (HLR)It contains subscriber information such assupplementary services and authenticationparameters.• authentication center (AUC)- It is connected to the HLR.- Its function is to provide the HLR with theauthentication parameter and ciphering keys.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 28
  29. 29.  Network and Switching Subsystem(SS) Cont….• visitor location register (VLR)- It is a database containing information about allthe MSs currently located in the MSC area.- If the MS wants to make a call, the VLR will haveall the information needed about call set upwithout having to interrogate the HLR each time.- The VLR can be seen as distributed HLR.- The VLR will also contain more exact informationabout the location of MS in MSC area.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 29
  30. 30.  Network and Switching Subsystem (SS)Cont….• equipment identity register (EIR)—The EIR is a database that containsinformation about the identity of mobileequipment that prevents calls from stolen,unauthorized, or defective mobile stations. TheAUC and EIR are implemented as stand-alonenodes or as a combined AUC/EIR node.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 30
  31. 31.  Mobile Station- The term mobile station is taken to meanequipment necessary to access the GSMPLMN.- It consists of:a) Mobile equipment. It being the actual phonewhich identified by its identity number IMEI(International Mobile Equipment Identity).b) SIM card. It being a card with information a boutthe subscription.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 31
  32. 32.  Mobile Station Cont…• Different types of MS:a) Vehicle mounted station.b) Portable station.c) Hand-held station.• Mobile station classes4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 32CLASS TYPE MAX OUTPUT POWER1 ---------------------------- ----------------------------2 Vehicle mounted 8 WATT3 Portable 5 WATT4 Handheld 2 WATT5 Handheld 0.8 WATT
  33. 33.  Handover (Hand off) Process• It is a means to continue a call even when amobile station crosses the border of one cell intoanother.• In a cellular network, one cell has a setneighboring cells. The system has to determinewhich cell the mobile station should be passed.• The difference in the procedure can bedetermined from the different names; thehandoff comes from the analog system whereasthe handover was introduced by GSM.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 33
  34. 34.  Handover (Hand off) Process Cont…• In analog system, the MS is the passive participant inthe handoff process. All measurements and work aredone in the base station and the network.• In GSM system, the MS continuously monitor theneighboring cells perceived power levels:i. The base station gives the mobile a list of basestations channels on which to perform powermeasurements.ii. The MS performs continuous measurements on thequality and the power level of the serving cell andoff the power levels of the adjacent cells.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 34
  35. 35.  Handover (Hand off) Process Cont…iii. The measurement results are put into ameasurement report, which are periodically sentback to the BS.iv. The BS itself may also be performing measurementson the quality and power of the link to the MS.v. If these measurements indicate the necessary for ahandover, as appropriate BS for a handover isalready known.vi. The GSM system distinguishes different types ofhandover depending on what type of cell border theMS is crossing.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 35
  36. 36.  Handover (Hand off) Process Cont…vii. If a handover has to be performed within thearea of a BSC, it can be controlled by BSCwithout consulting the MSC. This handover iscalled a simple handover between BTSs.viii.If instead, a MS is crossing the border of a BSC(rather than a BTS), then, the MSC has tocontrol the procedure in order to ensure thesmooth transition of the conversation. Thistype is called a handover between two MSCs.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 36
  37. 37.  Cellular Digital Services1. Caller Identification4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 37MSCMS1. Dial mobiletelephone2. Decode digitsfrom phonecompanyBS3. Send dialed digitmessage4. Lockup name from memory+ display number5. Customer decides ifnecessary to answercall.Telephone Line
  38. 38.  Cellular Digital Services Cont…2. Short Message Services (SMS):The SMS can be divided into three generalcategories:i. Point to Point.ii. Point to Multi-point.iii. Broadcast.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 38
  39. 39.  Cellular Digital Services Cont…i. Point to Point Messaging:4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 39MSCMS1. send message2. Store MessageBS3. Locate MobileTelephone5. AcknowledgeMessageTelephone LineMessageCentre4. Deliver Message6. Display Message
  40. 40. End of Lecture #24/10/2011 Assistant Prof.Dr.Tamer M. Barakat 40
  41. 41. Celluler Configuration• The coverage planning depend on:1. Power planning (the adjustement of cellspower)2. Frequency planning ( the assignment offrequency to cells)3. Traffic planning.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 41
  42. 42. Celluler Configuration Cont…• Properties of cellular geometry:- The main purpose of cells in a portable radio telephonesystem is to define an area in which either specific channelsor the specific cell sites will be used.- The proper positioning of cell site equipment and properselection of equipment to service each cell made isnecessary to realize the advantage of the designed cellpattern.- To achive this end, a geometry patterned structure is usedrather than irregular strucure.- The use of irregular cell structure lead to an inefficient useof spectrum due to an inability to reuse frequenciesbecause of co-channel interference.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 42
  43. 43. Celluler Configuration Cont…• To assure complete area coverage with nodead spots, a series of regular polygons havebeen adopted by Advanced Mobile PhoneService (AMPS).• The defualt cell structure is the hexagonalshape which has the maximum area coverage.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 43R RR𝐴 𝑠𝑞 = 2𝑅260°𝐴ℎ𝑒𝑥 = 6 × 1 2 𝑅 × 𝑅𝑐𝑜𝑠 30=2.6𝑅2𝐴 𝑡𝑟𝑖 = 1.3𝑅2
  44. 44. Cellular Geometry• The distance 𝐷 between two cells:𝐷 = 𝑣2 − 𝑣12 + 𝑢2 − 𝑢12 − 2 𝑢2 − 𝑢1 𝑣2 − 𝑣1 𝑐𝑜𝑠120°∴ 𝐷2= 𝑣2 − 𝑣12+ 𝑢2 − 𝑢12+ 𝑣2 − 𝑣1 𝑢2 − 𝑢14/10/2011 Assistant Prof.Dr.Tamer M. Barakat 44V, ju, 𝑖x𝜽 = 𝟔𝟎°
  45. 45. Cellular Geometry Cont…• Let 𝑢1, 𝑣1 = 0, 0 the origin• Let 𝑢2, 𝑣2 = 𝑖, 𝑗 the shiftingparameters• Hence, 𝐷2= 𝑖2+ 𝑗2+ 𝑖𝑗• Thus, the center-to-center distance of theadjacent hexagon is 2𝑅𝑐𝑜𝑠30 = 3 R• ∴ 𝑫 𝟐= 𝟑𝑹 𝟐𝒊 𝟐+ 𝒋 𝟐+ 𝒊𝒋 GeneralForm4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 45
  46. 46. Determination of number of cells percluster4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 46
  47. 47. Determination of number of cells percluster Cont…• ∵The distance between two co-cells𝐷 = 3 𝑅 𝑖2 + 𝑗2 + 𝑖𝑗 radius of large hexagon∴ the area of hexagon is proportional to the square of theradius∴ the area enclosed in large hexagon is𝐴 = 𝐾𝐷2 = K 3𝑅2 𝑖2 + 𝑗2 + 𝑖𝑗From symmetry, large hexagon encloses𝑁 + 1 3 𝑁 × 6 = 3𝑁 cellsWhere:- N: No. of cells /cluster for 1 𝑠𝑡 cluster.-1 3 𝑁: No. of cells associated with other six clusters4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 47
  48. 48. Determination of number of cells percluster Cont…• The area enclosed in the small hexagon:𝐴 𝑠𝑚𝑎𝑙𝑙 = 𝐾𝑅2∴𝐴𝑙𝑎𝑟𝑔𝑒𝐴 𝑠𝑚𝑎𝑙𝑙=𝐷2𝑅2= 3 𝑖2+ 𝑗2+ 𝑖𝑗∴ 𝑁 = 𝑖2+ 𝑗2+ 𝑖𝑗Where 𝑁: the frequency re-use pattern;No. of cells /cluster; orcell re-use factor∴ 𝑫 = 𝑹 𝟑𝑵 𝒒 =𝑫𝑹= 𝟑𝑵Where: 𝒒: co-channel re-use ratio4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 48
  49. 49. Co-channel interference ratio• As 𝑁 no. of cluster/area system capacity•• But 𝑁 𝐷 𝑞 i.e. co-channel interference• So we must select the value of 𝑁 to optimize both systemcapacity and co-channel interference.• ∴𝑰𝑺=𝟏𝟎 𝒍𝒐𝒈 𝟏𝟎 𝟔𝑫 − 𝑹𝑹−𝒏= 𝟏𝟎 𝒍𝒐𝒈 𝟏𝟎 𝟔 𝟑𝑵 − 𝟏−𝒏Where: 𝑅: cell radius𝐷: distance to the co-located channel𝑛: propagation decay; 2 ≤ 𝑛 ≤ 44/10/2011 Assistant Prof.Dr.Tamer M. Barakat 49
  50. 50. Description of mobile transmissionmedium• Free space loss- According to poynting theorem, the power fluxdensity is given by:∅ =𝐸 × 𝐻∗2But, ∅ =𝑃𝑡4𝜋𝑑2Where, 𝑃𝑡: power tranmitted𝑑: distance between isotropic transmitingand receiving antennas.4/10/2011 Assistant Prof.Dr.Tamer M. Barakat 50

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