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					Cellular Mobile Communications-I
An Introduction
Dr. Nasir D. Gohar
Cellular Mobile Communications-I
An Introduction

 Cell Phone Growth in Pakistan & Worldwide
    According to a Media Report (Goliath, May 25, 2005), Cell
    Phones in Pakistan to Touch 15M mark in December 2005
    Another Media Report (Middle East Times, June 20, 2006)
    Predicts the number of Cell Phones will rise from 2.2 Billion to 3
    Billion worldwide by the end of Year 2008
    According to MOBILEDIA (Jan 20, 2006)
       U.S. offers more room for growth than Russia, and Japan offers greater
        future growth than South Africa
        The number of mobile subscribers worldwide reached over 2 billion by the
        end of 2005, and is predicted to rise to 3.96 billion by 2011
        The Asia Pacific Region will account for 50% of the total number of
        subscribers worldwide by the end of this decade with a staggering 1.067
        billion subscribers shared between China and India alone, the world's two
        biggest mobile markets
Cellular Mobile Communications-I
An Introduction

Several Types of Mobile Radio Systems
    Garage Door Controller [<100 MHz]
    Remote Controllers [TV/VCR/DISH][Infra-Red: 1-100 THz]
    Cordless Telephone [<100 MHz]
    Hand-Held Radio [Walki-Talki] [VHF-UHF:40-480 MHz]
    Pagers/Beepers [< 1 GHz]
    Cellular Mobile Telephone[<2 GHz]
Classification
    Simplex System:             Communication is possible in only one direction : Garage Door
      Controller, Remote Controllers [TV/VCR/DISH] Pagers/Beepers

    Semi-Duplex System:              Communication is possible in two directions but one talks
      and other listens at any time[Push to Talk System]: Walki-Talki
    Duplex System: Communication is possible in both directions at any time: Cellular
      Telephone [FDD or TDD]
Cellular Mobile Communications-I
An Introduction


Paging System:                      For Transmission of Brief Numeric/Alpha-
  numeric/Voice Messages [Pages] to Subscriber
        To Notify/Alert the User
        Simplex Service
        Modern Paging Systems Can Send News Head-Lines, Stock Info, or Fax
        Application Dependent System Range [2 Km to World-wide]


                                                        City 1

                                   Land Line Link   Paging Terminal



                    PSTN
                                                        City 2
                                   Land Line Link
                  PAGING CONTROL
                                                    Paging Terminal
                      CENTRE




                                                    City N


                                                    Paging Terminal
Cellular Mobile Communications-I
An Introduction


Cordless Telephone System: To Connect a Fixed
  Base Station to a Portable Cordless Handset
    Early Systems (1980s) have very limited range of few tens of
     meters [within a House Premises]
    Modern Systems [PACS, DECT, PHS, PCS] can provide a limited
     range & mobility within Urban Centers

                                               Cordless Handset


                                  Fixed Base
                  PSTN
                                    Station
Cellular Mobile Communications-I
An Introduction

 Limitations of Simple Mobile Radio Systems
 The Cellular Approach
    Divides the Entire Service Area into Several Small Cells
    Reuse the Frequency
 Basic Components of a Cellular Telephone System
    Cellular Mobile Phone: A light-weight hand-held set which is an
     outcome of the marriage of Graham Bell’s Plain Old Telephone
     Technology [1876] and Marconi’s Radio Technology [1894] [although a
     very late delivery but very cute]
    Base Station: A Low Power Transmitter, other Radio Equipment
     [Transceivers] plus a small Tower
    Mobile Switching Center [MSC] /Mobile Telephone
     Switching Office[MTSO]
        An Interface between Base Stations and the PSTN
        Controls all the Base Stations in the Region and Processes User ID and
         other Call Parameters
        A typical MSC can handle up to 100,000 Mobiles, and 5000 Simultaneous
         Calls
        Handles Handoff Requests, Call Initiation Requests, and all Billing & System
         Maintenance Functions
Cellular Mobile Communications-I
An Introduction
Cellular Mobile Communications-I
An Introduction

 The Cellular Concept

    RF spectrum is a valuable and scarce commodity
    RF signals attenuate over distance
    Cellular network divides coverage area into cells, each
     served by its own base station transceiver and antenna
    Low (er) power transmitters used by BSs; transmission
     range determines cell boundary
    RF spectrum divided into distinct groups of channels
    Adjacent cells are (usually) assigned different channel
     groups to avoid interference
    Cells separated by a sufficiently large distance to avoid
     mutual interference can be assigned the same channel group 
      frequency reuse among co-channel cells
Cellular Mobile Communications-I
An Introduction

 An Example of Frequency Reuse

                           Suppose we have spectrum
                            for 100 voice channels
                           Scenario 1: a high power
                            base station covering entire
                            area – system capacity = 100
                            channels
                           Scenario 2: divide spectrum
                            into 4 groups of 25 channels
                            each; cells (1, 7), (2, 4), (3,
                            5), 6 are assigned distinct
                            channel groups – system
                            capacity = 175 channels
Cellular Mobile Communications-I
An Introduction

Frequency Reuse Factor




   Frequency Reuse Factor N = No. of Distinct Channel Groups = Maximum Cluster Size
Cellular Mobile Communications-I
An Introduction

Frequency Reuse Example-2
  Suppose W = 25 MHz and B = 25 KHz/voice channel
  W/B = 1000 voice channels can be supported over the spectrum
  Scenario 1: a high power base station covering entire area (M = N = 1)
    system capacity n = 1000 users
  Scenario 2:
       Coverage area divided into M = 20 cells with reuse factor N = 4
       Each cluster accommodate 1000 active users
       5 clusters in coverage area  system capacity n = 5000 users
  Scenario 3:
       M = 100 cells, N = 4  system capacity n = 25000 users
  Scenario 4:
       M = 100 cells, N = 1  system capacity n = 100000 users
Cellular Mobile Communications-I
An Introduction

 Common Air Interface (CAI)
 Common Air Interface: A Standard
 that defines Communication between a
 Base Station and Mobile
       Specifies Four Channels [Voice
       Channels and Control / Setup
       Channels]                       Reverse Channel
          FVC: Forward Voice Channel
          RVC: Reverse Voice Channel
          FCC: Forward Control Channel                  Forward Channel
          RCC: Reverse Control Channel
Cellular Mobile Communications-I
An Introduction

 Call Setup Procedure
  Cellular Phone Codes: Special Codes are associated with each Cell
  Phone to identify the phone, its owner, and service provider:
       Electronic Serial Number(ESN) -A Unique 32-bit Code
       Mobile Identification Number(MIN): A Subscriber’s Telephone Number
        Station Class mark (SCM): Indicates the Max Tx Power for the User
  When a Cellular Phone is turned on and Initiates a Call:[see
  next slide]
       Monitors the Control Channels and gets hold on to the strongest one
       Makes a Call Initiation Request[Dials the Called part Number, MIN , ESN and SCM
       automatically transmitted]
       Validation Procedure at MSC & Voice-Frequency pair Allocation
       Base Station Pages the Information for the Mobile
       MSC Connects the Mobile with the Called Party[Another Mobile/Landline Phone]
       Call is Established and Communication Starts
Cellular Mobile Communications-I
An Introduction

 Call Setup Procedure (Cont’d)
                                                                                 4. Locates the
                                                       3. Receives a Call
                                                                                  Called Party,                                  7. Connects the
                                                     Initiation Request from
                                                                                Allocates a VFPs                                  Called Party[on
      MSC                                               Base Station, and
                                                                                and Instructs the                               PSTN]/Mobile to the
                                                     Verifies that User has a
                                                                                Base Stations via                                     Mobile
                                                      Valid MIN & ESN pair
                                                                                      FCC
                                                                                                    5. Pages for the Called
                                                                                                     Mobile, the Mobiles are
                  FCC                                                                               instructed to move to the
                                                                                                         Allocated VFPs
                                                                                                           respectively
                           2. Receives a Call
   Base Station          Initiation Request, with
                  RCC
                          MIN, ESN, SCM and
                           Called Part Number

                  FVC
                                                                                                                                                      8. Begins Voice
                                                                                                                                                       Transmission

                  RVC
                                                                                                                                                      8. Begins Voice
                                                                                                                                                        Reception
                                                                                                      6. Receives [Called
                                                                                                    Mobile] the Page and
                                                                                                    Matches the MIN, the
                  FCC
                                                                                                     Mobiles get ready to
                                                                                                    move to the respective
                                                                                                      Allocated VFPs

     Mobile             1. Makes a Call Initiation
                  RCC    Request, with MIN and
                          Called Part Number

                  FVC
                                                                                                                                                      8. Begins Voice
                                                                                                                                                        Reception

                  RVC
                                                                                                                                                      8. Begins Voice
                                                                                                                                                       Transmission
                                                    TIME
Cellular Mobile Communications-I
An Introduction

 Handoff and Roaming
 Handoff
      When a Mobile is on the edge of a Cell
          RSL of the Mobile in that Cell gets bellow a set Level
          Base Station of the Cell originates a Handoff request
          MSC gets RSL Info from all the Candidate Cells
          MSC asks the Originating Cell and the Strongest
          Candidate Cell to Coordinate                              MSC
          In Case the Handoff is Successful, the Mobile is asked
          to switch to another VFP
          All this happens in a matter of seconds and you hear a
          little CLICK sound
 Roaming
      When SID of the Control Channel and that
        programmed in the Mobile does not match:
          The Mobile is in another Service Provider’s Area
          MSC of the Cell contacts the MSC of the Mobile’s
          Home System
          After Verification, if the Mobile is Allowed, the new
          MSC is ready to Serve.
 Cellular Mobile Communications-I
 An Introduction

 Comparison of Common Wireless Communication
  Systems

       Comparison of Mobile Communication Systems - Mobile/Base Station

                                     Required
                       Coverage                                  Hardware         Carrier
      System                           Infra-    Complexity                                  Functionality
                        Range                                      Cost         Frequency
                                     Structure
 Tv Remote Control        Low          Low           Low            Low          Infra-Red       Tx/Rx

Garage Door Contol        Low          Low           Low            Low          <100 Mhz        Tx/Rx

   Paging System          High         High        Low/High       Low/High        <1GHz          Rx/Tx

  Cordless Phone          Low          Low       Moderate/Low   Low/Moderate     <100 MHz     Transceiver

   Cellular Phone         High         High          High       Moderate/High     <1 GHz      Transceiver


Tx = Transmitter     Rx = Receiver
Cellular Mobile Communications-I
An Introduction

 Cellular Mobile Access Technologies
 FDMA        Assigns each Call a Separate Frequency
      Works like Radio Stations
      Mainly Analogue Technology-used by AMPS, NAMPS, E-TACS, NMT-450, JTACS
      Not an Efficient Method for Digital Transmission




                                                        849 MHz



                                                        869 MHz
Cellular Mobile Communications-I
An Introduction

 Cellular Mobile Access Technologies
 TDMA        Assigns each Call a
 certain Time-Slot on a Designated
 Frequency

      Each Mobile/User gets one-third of
      a total Channel Time-Slot[6.7 ms]
      Courtesy of Compression
      Techniques: Speech Data in Digital
      Form takes considerably less time
      Optimal Frequency Usage: System
      Capacity improves by three times
      Operates both in 800 MHz[IS-54]
      and 1900 MHz[IS-136]
      Digital Access Technology use by
      GSM, USDC, IDEN, PDC and PCS
Cellular Mobile Communications-I
An Introduction

 Cellular Mobile Access Technologies
  CDMA         Assigns a Unique Code to
  each Call and Spreads it over the entire
  bandwidth available
        A form of Spread Spectrum
       Technology
       Speech Data is sent in small pieces
       over number of Discrete Frequencies
       available at any time in a specified range
        Receiver uses the same unique Code
       to Recover the Speech Data
       GPS used for Exact Time Stamp
       Can handle 8-10 Calls in the same
       Channel Space as one Analogue Channel
       An Access Technology for 3G Mobile
       Systems[IMT-2000]
       Supports both Bands [800 MHz and
       1900 MHz]
Cellular Mobile Communications-I
An Introduction

 Cellular System vs. Personal Communication
  System/Network (PCS/PCN)
 Personal Communication Services [PCS] is a system, very similar
  to Cellular Phone Service with great emphasis on personal
  services (such as Paging, Caller ID, and E-mail] and mobility
 Originated in UK, to improve its competitiveness in the field
 PCS has smaller Cell size, therefore, requires more infra-structure
 PCS works in 1.85-1.99 GHz band
 PCS uses TDMA Technology but with 200 KHz Channel Bandwidth
  with eight time-slots[as compared to 30 KHz and 3 time-slots used
  by Digital Cellular Phone System IS-54/IS-136]
 GSM and Cellular Digital Packet Data[CDPD] also use PCS Tech.
Cellular Mobile Communications-I
An Introduction

 Dual Band/Dual Mode Cellular Phones

   Dual Band Phone:           Supports both bands 800 MHz and
      1900 MHz
   Dual Mode Phone:           Supports both FDMA and TDMA Access
       Technologies
   Dual Band/Dual Mode Phone: Supports both Bands
      and Both Access Technologies

   Tri-Mode Phone: It can Support FDMA/TDMA/CDMA all
      Access Tech. A popular version of Tri-Mode Cellular Phone is the
      one which supports GSM [800 MHz as well as 1900 MHz (USA
      version)] as well as FDMA.
Cellular Mobile Communications-I
An Introduction

 Trends in Cellular radio and Personal
  Communications
   PCS/PCN: PCS calls for more personalized services whereas
    PCN refers to Wireless Networking Concept-any person,
    anywhere, anytime can make a call using PC. PCS and PCN
    terms are sometime used interchangeably
   IEEE 802.11: A standard for computer communications using
    wireless links[inside building].
   ETSI’s 20 Mbps HIPER LAN: Standard for indoor Wireless
    Networks
   IMT-2000 [International Mobile Telephone-2000
    Standard]: A 3G universal, multi-function, globally compatible
    Digital Mobile Radio Standard is in making
   Satellite-based Cellular Phone Systems
   A very good Chance for Developing Nations to Improve
    their Communication Networks

				
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posted:10/27/2011
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