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

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Presentation on theme: "Cellular Mobile Communications-I An Introduction Dr. Nasir D. Gohar Dr. Nasir D. Gohar."— Presentation transcript:

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

2 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 billion subscribers shared between China and India alone, the world's two biggest mobile markets

3 Cellular Mobile Communications-I An Introduction  Several Types of Mobile Radio Systems  Garage Door Controller [<100 MHz]  Remote Controllers [TV/VCR/DISH][Infra-Red: THz]  Cordless Telephone [<100 MHz]  Hand-Held Radio [Walki-Talki] [VHF-UHF: 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]

4 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]

5 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

6 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

7 Cellular Mobile Communications-I An Introduction

8  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

9 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

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

11 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 = users  Scenario 4:  M = 100 cells, N = 1  system capacity n = users

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

13 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

14 Cellular Mobile Communications-I An Introduction  Call Setup Procedure (Cont’d)

15 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  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.

16 Cellular Mobile Communications-I An Introduction  Comparison of Common Wireless Communication Systems

17 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

18 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

19 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]

20 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 ] 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 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.

21 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.

22 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 : 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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