introduction to cellular mobile communications

Cellular Mobile Cellular Mobile Communications-ICommunications-IAn IntroductionAn Introduction

Dr. Nasir D. Dr. Nasir D. GoharGohar


Cell Phone Growth in Pakistan & WorldwideCell Phone Growth in Pakistan & Worldwide According to a Media Report (Goliath, May 25, 2005), According to a Media Report (Goliath, May 25, 2005),

Cell Phones in Pakistan to Touch 15M mark in December Cell Phones in Pakistan to Touch 15M mark in December 20052005

Another Media Report (Middle East Times, June 20, Another Media Report (Middle East Times, June 20, 2006) Predicts the number of Cell Phones will rise from 2006) Predicts the number of Cell Phones will rise from 2.2 Billion to 3 Billion worldwide by the end of Year 20082.2 Billion to 3 Billion worldwide by the end of Year 2008

According to MOBILEDIA (Jan 20, 2006)According to MOBILEDIA (Jan 20, 2006) U.S. offers more room for growth than Russia, and Japan offers U.S. offers more room for growth than Russia, and Japan offers

greater future growth than South Africagreater future growth than South Africa The number of mobile subscribers worldwide reached over 2 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 billion by the end of 2005, and is predicted to rise to 3.96 billion by 20112011

The Asia Pacific Region will account for 50% of the total number of The Asia Pacific Region will account for 50% of the total number of subscribers worldwide by the end of this decade with a staggering subscribers worldwide by the end of this decade with a staggering 1.067 billion subscribers shared between China and India alone, 1.067 billion subscribers shared between China and India alone,

the world's two biggest mobile marketsthe world's two biggest mobile markets


Several Types of Mobile Radio SystemsSeveral Types of Mobile Radio Systems Garage Door Controller [<100 MHz]Garage Door Controller [<100 MHz] Remote Controllers [TV/VCR/DISH][Infra-Red: 1-100 THz]Remote Controllers [TV/VCR/DISH][Infra-Red: 1-100 THz] Cordless Telephone [<100 MHz]Cordless Telephone [<100 MHz] Hand-Held Radio [Walki-Talki] [VHF-UHF:40-480 MHz]Hand-Held Radio [Walki-Talki] [VHF-UHF:40-480 MHz] Pagers/Beepers [< 1 GHz]Pagers/Beepers [< 1 GHz] Cellular Mobile Telephone[<2 GHz]Cellular Mobile Telephone[<2 GHz]

ClassificationClassification Simplex System:Simplex System: Communication is possible in only one direction :Communication is possible in only one direction :

Garage Door Controller, Remote Controllers [TV/VCR/DISH] Pagers/BeepersGarage Door Controller, Remote Controllers [TV/VCR/DISH] Pagers/Beepers

Semi-Duplex System:Semi-Duplex System: Communication is possible in two directions but Communication is possible in two directions but one talks and other listens at any time[Push to Talk System]: Walki-Talkione talks and other listens at any time[Push to Talk System]: Walki-Talki

Duplex SystemDuplex System:: Communication is possible in both directions at any time: Communication is possible in both directions at any time: Cellular Telephone [FDD or TDD]Cellular Telephone [FDD or TDD]


Paging System:Paging System: For Transmission of For Transmission of Brief Numeric/Alpha-Brief Numeric/Alpha-numeric/Voice Messages [Pages] to Subscribernumeric/Voice Messages [Pages] to Subscriber

To Notify/Alert the UserTo Notify/Alert the User Simplex ServiceSimplex Service Modern Paging Systems Can Send News Head-Lines, Stock Info, or FaxModern Paging Systems Can Send News Head-Lines, Stock Info, or Fax Application Dependent System Range [2 Km to World-wide] Application Dependent System Range [2 Km to World-wide]

PAGING CONTROL CENTRE

Paging Terminal

PSTN

Land Line Link

Land Line LinkPaging Terminal

Paging Terminal

City 1

City 2

City N


Cordless Telephone System:Cordless Telephone System: To Connect a To Connect a Fixed Base Station to a Portable Cordless HandsetFixed Base Station to a Portable Cordless Handset Early Systems (1980s) have very limited range of few Early Systems (1980s) have very limited range of few

tens of meters [within a House Premises]tens of meters [within a House Premises] Modern Systems Modern Systems [PACS, DECT, PHS, PCS][PACS, DECT, PHS, PCS] can provide a can provide a

limited range & mobility within Urban Centerslimited range & mobility within Urban Centers

PSTNFixed Base

Station

Cordless Handset


Limitations of Simple Mobile Radio SystemsLimitations of Simple Mobile Radio SystemsThe Cellular ApproachThe Cellular Approach

Divides the Entire Service Area into Several Small Cells Divides the Entire Service Area into Several Small Cells Reuse the FrequencyReuse the Frequency

Basic Components of a Cellular Telephone SystemBasic Components of a Cellular Telephone System Cellular Mobile PhoneCellular Mobile Phone:: A light-weight hand-held set A light-weight hand-held set

which is an outcome of the marriage of Graham Bell’s Plain Old which is an outcome of the marriage of Graham Bell’s Plain Old Telephone Technology [1876] and Marconi’s Radio Technology Telephone Technology [1876] and Marconi’s Radio Technology [1894] [although a very late delivery but very cute][1894] [although a very late delivery but very cute]

Base StationBase Station:: A Low Power Transmitter, other Radio A Low Power Transmitter, other Radio Equipment [Transceivers] plus a small TowerEquipment [Transceivers] plus a small Tower

Mobile Switching Center [MSC] /Mobile Telephone Mobile Switching Center [MSC] /Mobile Telephone Switching Office[MTSO]Switching Office[MTSO] An Interface between Base Stations and the PSTNAn Interface between Base Stations and the PSTN Controls all the Base Stations in the Region and Processes User ID Controls all the Base Stations in the Region and Processes User ID

and other Call Parametersand other Call Parameters A typical MSC can handle up to 100,000 Mobiles, and 5000 A typical MSC can handle up to 100,000 Mobiles, and 5000

Simultaneous Calls Simultaneous Calls Handles Handoff Requests, Call Initiation Requests, and all Billing & Handles Handoff Requests, Call Initiation Requests, and all Billing &

System Maintenance FunctionsSystem Maintenance Functions


The Cellular ConceptThe Cellular Concept

RF spectrumRF spectrum is a valuable and scarce commodity is a valuable and scarce commodityRF signals attenuate over distanceRF signals attenuate over distanceCellular network divides coverage area into cellsCellular network divides coverage area into cells, each , each

served by its own base station transceiver and antennaserved by its own base station transceiver and antennaLow (er) power transmitters used by BSs; transmission Low (er) power transmitters used by BSs; transmission

range determines cell boundaryrange determines cell boundaryRF spectrum divided into distinct groups of channelsRF spectrum divided into distinct groups of channelsAdjacent cells are (usually) assigned different channel Adjacent cells are (usually) assigned different channel

groups to avoid interferencegroups to avoid interferenceCells separated by a sufficiently large distance to avoid Cells separated by a sufficiently large distance to avoid

mutual interference can be assigned themutual interference can be assigned the same channel group same channel group frequency reuse frequency reuse among co-channel cellsamong co-channel cells


An Example of Frequency ReuseAn 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


Frequency Reuse FactorFrequency Reuse Factor

Frequency Reuse Factor N = No. of Distinct Channel Groups = Maximum Cluster Size


Frequency Reuse Example-2Frequency Reuse Example-2 Suppose Suppose WW = 25 MHz and = 25 MHz and BB = 25 KHz/voice channel = 25 KHz/voice channel W/BW/B = 1000 voice channels can be supported over the spectrum = 1000 voice channels can be supported over the spectrum Scenario 1:Scenario 1: a high power base station covering entire area ( a high power base station covering entire area (M M = = N N = =

1) 1) system capacity system capacity nn = 1000 users = 1000 users Scenario 2:Scenario 2:

Coverage area divided into Coverage area divided into MM = 20 cells with reuse factor = 20 cells with reuse factor NN = 4 = 4 Each cluster accommodate 1000 active usersEach cluster accommodate 1000 active users 5 clusters in coverage area 5 clusters in coverage area system capacity system capacity nn = 5000 users = 5000 users

Scenario 3:Scenario 3: MM = 100 cells, = 100 cells, NN = 4 = 4 system capacity system capacity nn = 25000 users = 25000 users

Scenario 4:Scenario 4: MM = 100 cells, = 100 cells, NN = 1 = 1 system capacity system capacity nn = 100000 users = 100000 users


Common Air Interface (CAI)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 ChannelRVC: Reverse Voice ChannelFCC: Forward Control ChannelRCC: Reverse Control Channel


Call Setup ProcedureCall 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 oneMakes 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 MobileMSC Connects the Mobile with the Called Party[Another Mobile/Landline Phone]Call is Established and Communication Starts


Call Setup Procedure (Cont’d)Call Setup Procedure (Cont’d)

MSC

3. Receives a Call Initiation Request from

Base Station, and Verifies that User has a Valid MIN & ESN pair

4. Locates the Called Party,

Allocates a VFPs and Instructs the Base Stations via

FCC

7. Connects the Called Party[on

PSTN]/Mobile to the Mobile

FCC

5. Pages for the Called Mobile, the Mobiles are

instructed to move to the Allocated VFPs

respectively

RCC

2. Receives a Call Initiation Request, with MIN, ESN, SCM and Called Part Number

FVC 8. Begins Voice Transmission

RVC 8. Begins Voice Reception

FCC

6. Receives [Called Mobile] the Page and Matches the MIN, the Mobiles get ready to

move to the respective Allocated VFPs

RCC1. Makes a Call Initiation Request, with MIN and

Called Part Number

FVC8. Begins Voice

Reception

RVC8. Begins Voice

Transmission

Base Station

Mobile

TIME


Handoff and RoamingHandoff and RoamingHandoff

When a Mobile is on the edge of a CellRSL of the Mobile in that Cell gets bellow a set LevelBase Station of the Cell originates a Handoff requestMSC gets RSL Info from all the Candidate CellsMSC asks the Originating Cell and the Strongest Candidate Cell to CoordinateIn Case the Handoff is Successful, the Mobile is asked to switch to another VFPAll this happens in a matter of seconds and you hear a little CLICK sound

RoamingWhen SID of the Control Channel and that

programmed in the Mobile does not match:

The Mobile is in another Service Provider’s AreaMSC of the Cell contacts the MSC of the Mobile’s Home SystemAfter Verification, if the Mobile is Allowed, the new MSC is ready to Serve.

M S C


Comparison of Common Wireless Communication Comparison of Common Wireless Communication SystemsSystems

SystemCoverage

Range

Required Infra-

StructureComplexity

Hardware Cost

Carrier Frequency

Functionality

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

Comparison of Mobile Communication Systems - Mobile/Base Station


Cellular Mobile Access TechnologiesCellular Mobile Access TechnologiesFDMA Assigns each Call a Separate Frequency

Works like Radio StationsMainly Analogue Technology-used by AMPS, NAMPS, E-TACS, NMT-450, JTACSNot an Efficient Method for Digital Transmission

849 MHz

869 MHz


Cellular Mobile Access TechnologiesCellular 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 timeOptimal Frequency Usage: System Capacity improves by three timesOperates both in 800 MHz[IS-54] and 1900 MHz[IS-136]Digital Access Technology use by GSM, USDC, IDEN, PDC and PCS


Cellular Mobile Access TechnologiesCellular Mobile Access TechnologiesCDMA Assigns a Unique Code to each Call and Spreads it over the entire bandwidth available

A form of Spread Spectrum TechnologySpeech 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 DataGPS used for Exact Time StampCan handle 8-10 Calls in the same Channel Space as one Analogue ChannelAn Access Technology for 3G Mobile Systems[IMT-2000]Supports both Bands [800 MHz and 1900 MHz]


Cellular System vs. Personal Communication Cellular System vs. Personal Communication System/Network (PCS/PCN)System/Network (PCS/PCN)

Personal Communication Services [Personal Communication Services [PCSPCS] is a system, very ] is a system, very similar to Cellular Phone Service with great emphasis on similar to Cellular Phone Service with great emphasis on personal servicespersonal services (such as Paging, Caller ID, and E-mail] (such as Paging, Caller ID, and E-mail] and and mobilitymobility

Originated in UK, Originated in UK, to improve its competitiveness in the to improve its competitiveness in the fieldfield

PCS PCS has smaller Cell size, therefore, requires more infra-has smaller Cell size, therefore, requires more infra-structurestructure

PCS works in 1.85-1.99 GHz bandPCS works in 1.85-1.99 GHz band PCS uses TDMA Technology but with 200 KHz Channel PCS uses TDMA Technology but with 200 KHz Channel

Bandwidth with eight time-slots[as compared to 30 KHz Bandwidth with eight time-slots[as compared to 30 KHz and 3 time-slots used by Digital Cellular Phone System IS-and 3 time-slots used by Digital Cellular Phone System IS-54/IS-136]54/IS-136]

GSM and Cellular Digital Packet Data[CDPD] also use PCS GSM and Cellular Digital Packet Data[CDPD] also use PCS Tech.Tech.


Dual Band/Dual Mode Cellular PhonesDual Band/Dual Mode Cellular Phones

Dual Band PhoneDual Band Phone:: Supports both bands 800 MHz Supports both bands 800 MHz and 1900 MHzand 1900 MHz

Dual Mode Phone:Dual Mode Phone: Supports both FDMA and TDMA Supports both FDMA and TDMA Access Access TechnologiesTechnologies

Dual Band/Dual Mode PhoneDual Band/Dual Mode Phone:: Supports both Supports both Bands and Both Access TechnologiesBands and Both Access Technologies

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


Trends in Cellular radio and Personal Trends in Cellular radio and Personal CommunicationsCommunications

PCS/PCN:PCS/PCN: PCS calls for more personalized services PCS calls for more personalized services whereas PCN refers to Wireless Networking Concept-any whereas PCN refers to Wireless Networking Concept-any person, anywhere, anytime can make a call using PC. person, anywhere, anytime can make a call using PC. PCS and PCN terms are sometime used interchangeablyPCS and PCN terms are sometime used interchangeably

IEEE 802.11IEEE 802.11:: A standard for computer communications A standard for computer communications using wireless links[inside building].using wireless links[inside building].

ETSI’s 20 Mbps HIPER LAN:ETSI’s 20 Mbps HIPER LAN: Standard for indoor Standard for indoor Wireless Networks Wireless Networks

IMT-2000 [International Mobile Telephone-2000IMT-2000 [International Mobile Telephone-2000 StandardStandard]:]: A 3G universal, multi-function, globally A 3G universal, multi-function, globally compatible Digital Mobile Radio Standard is in makingcompatible Digital Mobile Radio Standard is in making

Satellite-based Cellular Phone SystemsSatellite-based Cellular Phone Systems A very good A very good ChanceChance for Developing Nationsfor Developing Nations to to

Improve their Communication NetworksImprove their Communication Networks

introduction to cellular mobile communications

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