Introduction to Cellular Mobile Communications

e u ar Mo Cellular Mobilee Communications-I Dr. Nasir D. Gohar

Cellular Mobile Communications-I An Introduction

Cell Cell Phone Growth in Pakistan & Worldwide \ue000 Phone Growth in Pakistan & Worldwide According to ato Media Report (Goliath, May 25, 2005), \ue000 According a Media Report (Goliath, May 25,

2005), Cell Phones in Pakistan to Touch 15M mark in December 2005 Another Media Report (Middle East East Times, June 20, \ue000 Another Media Report (Middle 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(Jan 20, 2006) \ue000 According to MOBILEDIA 20, 2006)

U.S. offers more room growth Russia, Japanand offers \ue000 U.S. offers morefor room for than growth thanand Russia, Japan offers greater future growth than South Africa The number of mobile subscribers worldwide reached reached over 2 over 2 \ue000 The number of mobile subscribers worldwide billion by the end of 2005, and is predicted to rise to 3.96 billion by 2011

The Asia RegionRegion will account for 50% for of the total of numbe \ue000 The Pacific Asia Pacific will account 50% of number the total 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


Several Types Mobile Radio Radio Systems \ue000 Several Tyof pes of Mobile Systems Garage DoorDoor Controller [<100 MHz]MHz] \ue000 Garage Controller [<100

Remote Controllers [TV/VCR/DISH][Infra-Red: 1-100 THz]THz] \ue000 Remote Controllers [TV/VCR/DISH][Infra-Red: 1-100 Cordless Telephone [<100 MHz]MHz] \ue000 Cordless Telephone [<100

Hand-Held Radio [Walki-Talki] [VHF-UHF:40-480 MHz] \ue000 Hand-Held Radio [Walki-Talki] [VHF-UHF:40-480 MHz] Pagers/Beepers [< \ue000 Pagers/Beepers

1[< GHz] 1 GHz] Cellular Mobile Telephone[<2 GHz]GHz] \ue000 Cellular Mobile Telephone[<2

Classification \ue000 Classification

Communication is is possible possible in in only only one Simplex System: Communication one direction direction :: \ue000 Simplex System: Garage Door Controller, Remote Controllers [TV/VCR/DISH] Pagers/Beepers

Communicationis ispossible possible in in two two directions directions but but Semi-Duplex System: Communication \ue000 Semi-Duplex System: one talks and other listens at any time[Push to Talk System]: Walki-Talki

Duplex System Communicationisispossible possiblein inboth bothdirections directionsat atany anytime: time: :: Communication \ue000 Duplex System Cellular Telephone [FDD or TDD]


Paging System: System: Paging

ForTransmission Transmissionof of Brief Brief Numeric/AlphaNumeric/AlphaFor

numeric/Voice Messages [Pages] to Subscriber

ToNotify/Alert Notify/Alert the the User To User Simplex Service Service Simplex ModernPaging Paging Systems Systems Can Head-Lines, Stock Info, or Fax Modern CanSend SendNews News Head-Lines, Stock Info, or Fax ApplicationDependent Dependent System to World-wide] Application System Range Range[2[2Km Km to World-wide]

City 1 Land Line Link

PSTN

PAGING CONTROL CENTRE

Paging Terminal

City 2 Land Line Link

Paging Terminal

City N Paging Terminal


ToConnect Connectaa CordlessTelephone Telephone System: System: To Cordless

Fixed Base Station to a Portable Cordless Handset

Early Systems Systems (1980s) limited range of few Early (1980s) have havevery very limited range of few tens of meters [within a House Premises] ModernSystems Systems [P PHS, PCS] PCS] can [PA ACS, CS, DECT, DECT, PHS, canprovide provideaa Modern limited range & mobility within Urban Centers Cordless Handset

PSTN

Fixed Base Station


Limitationsof of Simple Limitations Simple Mobile Mobile Radio RadioSystems Systems The Cellular Cellular Approach Approach The

Divides the the Entire Several Small Cells Divides Entire Service Service Area Areainto into Several Small Cells Reuse the the FFrrequency Reuse equency

Basic Components Components of System Basic of aaCellular CellularTelephone Telephone System CellularMobile Mobile Phone Phone : : AA light-weight light-weight hand-held hand-held set set Cellular

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

MobileSwitching Switching Center Center [MSC] Mobile [MSC] /Mobile /Mobile Telephone Telephone Switching Office[MTSO]

An Interface Interface between thethe PSTN An between Base BaseStations Stationsand and PSTN Controlsall all the Base thethe Region and and Processes User User ID Controls BaseStations Stationsin in Region Processes ID and other Call Parameters typical MSC to to 100,000 Mobiles, and 5000 AA typical MSC can can handle handleupup 100,000 Mobiles, and 5000 Simultaneous Calls Handles Handoff Handoff Requests, Call all all Billing & & Handles Call Initiation InitiationRequests, Requests,and and Billing System Maintenance Functions



The The Cellular Cellular Concept Concept RF spectrum spectrum is a scarce commodity is valuable a valuable and and scarce commodity RF RF signals signals attenuate RF attenuate over overdistance distance Cellularnetwork network divides divides coverage , each cells , each Cellular coverage area areainto into cells served by its own base station transceiver and antenna Low (er) (er) power BSs; transmission Low power transmitters transmitters used usedbyby BSs; transmission range determines cell boundary RF spectrum spectrum divided channels RF divided into intodistinct distinctgroups groupsof of channels Adjacent cells cells are channel Adjacent are (usually) (usually)assigned assigneddifferent different channel groups to avoid interference Cells separated separated by distance to avoid Cells by aasufficiently sufficientlylarge large distance to avoid ⇒ group same group mutual interference can be assigned thechannel ⇒ same channel frequency reuseamong co-channel among co-channelcells cells


An Reuse An Example ExampleofofFrequency 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


FrequencyReuse Reuse Factor Factor Frequency

Frequency Reuse Factor

N

= No. of Distinct Channel Groups = Maximum Cluster


FrequencyReuse Reuse Example-2 Example-2 Frequency 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

M

= 100 cells,

N

= 1 ⇒ system capacity

n

= 100000 users

Scenario 4:


Common Air Air Interface Interface(CAI) (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 RCC: Reverse Control Channel

Forward Channel


Call Setup Setup Procedure Procedure Cellular Phone Codes: Special

Codes are associated with each Ce

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

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


Call Setup Setup Procedure Procedure (Cont’d) (Cont’d) 3. Receives a Call

Called Party, Initiation Request from Allocates a VFPs Base Station, and and Instructs the Verifies that User has a Base Stations via Valid MIN & ESN pair FCC

MSC

RCC

7. Connects the

Called Party[on PSTN]/Mobile to the Mobile 5. Pages for the Called

Mobile, the Mobiles are instructed to move to the Allocated VFPs respectively

FCC

Base Station

4. Locates the

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

FVC

8. Begins Voice

RVC

8. Begins Voice

Transmission Reception

6. Receives [Called

Mobile] the Page and Matches the MIN, the Mobiles get ready to move to the respective Allocated VFPs

FCC

Mobile RCC

1. Makes a Call Initiation

Request, with MIN and Called Part Number

FVC

8. Begins Voice

RVC

8. Begins Voice

Reception

Transmission


Handoff and and Roaming 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.

MSC


Comparisonof of Common Wireless Comparison Wireless Communication Communication Systems Comparison of Mobile Communication Systems - Mobile/Base Station System

Coverage Range

Required InfraStructure

Complexity

Hardware Cost

Carrier Frequency

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

Cellular Phone

High

High

Tx = Transmitter

Rx = Receiver

Moderate/Low Low/Moderate High

Moderate/High

Functionality

<100 MHz

Transceiver

<1 GHz

Transceiver


CellularMobile MobileAccess Access Technologies Cellular 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


CellularMobile MobileAccess Access Technologies Cellular 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


CellularMobile MobileAccess Access Technologies Cellular 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]


CellularSystem System vs. Personal Cellular Personal Communication 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 infrastructure

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 IS54/IS-136]

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


Dual Band/Dual Band/Dual Mode Mode Cellular Dual Cellular Phones Phones Dual Band Phone:

Supports both bands 800 MHz

Dual Mode Phone:

Supports both FDMA and TDMA

and 1900 MHz Access

Technologies

Dual Band/Dual Mode Phone: Bands and Both Access Technologies

Tri-Mode Phone:

Supports both

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.


Trendsinin Cellular Cellular radio radio and Trends and Personal 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

Introduction to Cellular Mobile Communications

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