wireless comm 1

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A little history and evolutionA little history and evolutionof mobile radioof mobile radioA little history and evolutionA little history and evolutionof mobile radioof mobile radio

1897:1897:Marconi invented wireless conce tMarconi invented wireless conce t

1897:1897:Marconi invented wireless conce tMarconi invented wireless conce t

1960’s & 1970’s:1960’s & 1970’s:

Bell laboratories developed theBell laboratories developed the

1960’s & 1970’s:1960’s & 1970’s:

Bell laboratories developed theBell laboratories developed thecellular conceptcellular concept

1970’s:1970’s:

cellular conceptcellular concept

1970’s:1970’s:

eve opmen o g y re a e, m n a ureeve opmen o g y re a e, m n a uresolid state radio frequency hardwaresolid state radio frequency hardware

eve opmen o g y re a e, m n a ureeve opmen o g y re a e, m n a uresolid state radio frequency hardwaresolid state radio frequency hardware

11

re ess commun ca on era was ornre ess commun ca on era was orn re ess commun ca on era was ornre ess commun ca on era was orn



Cellular phone usersCellular phone users Cellular phone usersCellular phone users

19841984 -- 25,00025,00019941994 -- 16 million16 million19841984 -- 25,00025,00019941994 -- 16 million16 million

19971997 -- 50 million50 million

20002000 -- Number of wireless users =Number of wireless users =

19971997 -- 50 million50 million

20002000 -- Number of wireless users =Number of wireless users =

Number of wired usersNumber of wired users

Number of wired usersNumber of wired users

– – .. – – ..

22



Mobile Radio Systems Used inMobile Radio Systems Used inMobile Radio Systems Used inMobile Radio Systems Used in

Garage door openersGarage door openers Garage door openersGarage door openers

Remote controllers for homeRemote controllers for home

entertainmententertainment

Remote controllers for homeRemote controllers for home

entertainmententertainment Cordless telephonesCordless telephones

HandHand--held walkieheld walkie--talkiestalkies

Cordless telephonesCordless telephones

HandHand--held walkieheld walkie--talkiestalkies

Pagers/beepersPagers/beepers

Cellular telephonesCellular telephones

Pagers/beepersPagers/beepers

Cellular telephonesCellular telephones

33



............ MobileMobile – – Describes a radio terminalDescribes a radio terminal MobileMobile – – Describes a radio terminalDescribes a radio terminal

a ac e o a g spee mo e p a orma ac e o a g spee mo e p a orm(e.g., A cellular phone in a fast moving(e.g., A cellular phone in a fast movinga ac e o a g spee mo e p a orma ac e o a g spee mo e p a orm(e.g., A cellular phone in a fast moving(e.g., A cellular phone in a fast moving..

PortablePortable – – Describes a radio terminal thatDescribes a radio terminal that--

..

PortablePortable – – Describes a radio terminal thatDescribes a radio terminal that--

walking speed (e.g., cordless telephone).walking speed (e.g., cordless telephone).

Subscriber Subscriber – – Mobile or ortable user.Mobile or ortable user.

walking speed (e.g., cordless telephone).walking speed (e.g., cordless telephone).

Subscriber Subscriber – – Mobile or ortable user.Mobile or ortable user.

Base stationsBase stations – – Link mobiles through aLink mobiles through abackbone network.backbone network.

Base stationsBase stations – – Link mobiles through aLink mobiles through abackbone network.backbone network.

44



Transmission SystemsTransmission Systems

Transmission SystemsTransmission Systems

SimplexSimplex – – Communication isCommunication ispossible only in one direction,possible only in one direction,

SimplexSimplex – – Communication isCommunication ispossible only in one direction,possible only in one direction,. ., .. ., .

Half DuplexHalf Duplex – – Two wayTwo way

. ., .. ., .

Half DuplexHalf Duplex – – Two wayTwo way,,same radio channel for bothsame radio channel for bothtransmission and rece tion.transmission and rece tion.

,,same radio channel for bothsame radio channel for bothtransmission and rece tion.transmission and rece tion.User can only transmit or User can only transmit or receive information.receive information.

User can only transmit or User can only transmit or receive information.receive information.

55



......Transmission SystemsTransmission Systems......Transmission SystemsTransmission Systems

Full DuplexFull Duplex – – SimultaneousSimultaneoustwotwo--way radio transmission andway radio transmission and

Full DuplexFull Duplex – – SimultaneousSimultaneoustwotwo--way radio transmission andway radio transmission and

and base station.and base station.and base station.and base station.

separate channels (FDD) or separate channels (FDD) or separate channels (FDD) or separate channels (FDD) or

single radio channel (TDD)single radio channel (TDD) single radio channel (TDD)single radio channel (TDD)

66



Full duplex communicationFull duplex communication Full duplex communicationFull duplex communication

Few hundred metersFew hundred meters

Few hundred metersFew hundred meters

FixedFixedFixedFixed

linklinklinklinkPublicPublicSwitchedSwitched

PublicPublicSwitchedSwitched

(Base(BaseStationStation(Base(Base

StationStation

TelephoneTelephoneNetworkNetwork

TelephoneTelephoneNetworkNetwork cordlesscordlesscordlesscordless

handsethandsethandsethandset

77



Wide Area SystemWide Area System

Wide Area SystemWide Area System

e pag ng con ro cen er e pag ng con ro cen er dispatches pages receiveddispatches pages receivede pag ng con ro cen er e pag ng con ro cen er dispatches pages receiveddispatches pages received

several cities at the same time.several cities at the same time.

several cities at the same time.several cities at the same time.

88



Wide Area Pa in S stemWide Area Pa in S stemWide Area Pa in S stemWide Area Pa in S stemLandline linkLandline linkLandline linkLandline link City 1:City 1:City 1:City 1:

Landline linkLandline linkLandline linkLandline link

terminalterminal

terminalterminal

PSTNPSTNPSTNPSTN

y :y :PagingPaging

y :y :PagingPaging

PagingPaging

controlcontrol

PagingPaging

controlcontrol

City N:City N:City N:City N:

Satellite linkSatellite linkSatellite linkSatellite link terminalterminal terminalterminal

99



communication systemscommunication systemscommunication systemscommunication systems

a subscriber...a subscriber...

a subscriber...a subscriber...

Numeric messagesNumeric messages

AlphaAlpha--numeric messagenumeric message

Numeric messagesNumeric messages

AlphaAlpha--numeric messagenumeric message Voice messageVoice message

News headlinesNews headlines

Voice messageVoice message

News headlinesNews headlines

Stock quotesStock quotes

FaxesFaxes

Stock quotesStock quotes

FaxesFaxes

1010



Coverage AreaCoverage AreaCoverage AreaCoverage Area o mo m

Within individual buildingsWithin individual buildings

o mo m

Within individual buildingsWithin individual buildings

Worldwide coverageWorldwide coverage Worldwide coverageWorldwide coverage

1111



SystemSystem

SystemSystem

Base stationsBase stations(towers)(towers)Base stationsBase stations(towers)(towers)

accessaccessbetweenbetweenaccessaccessbetweenbetweenmobile usersmobile usersand MSC.and MSC.mobile usersmobile usersand MSC.and MSC.

MMobileobile SSwitchingwitchingCCenter enter

MMobileobile SSwitchingwitchingCCenter enter PSTNPSTNPSTNPSTN

1212



----

RVCRVCRVCRVC

FCCFCCFCCFCC

RCCRCCRCCRCC

FForwardorward VVoiceoice CChannelhannel

FForwardorward VVoiceoice CChannelhannel

everseeverse o ceo ce anneanneFForwardorward CControlontrol CChannelhannel

everseeverse o ceo ce anneanneFForwardorward CControlontrol CChannelhannel

1313



Provides wireless connectionProvides wireless connection Provides wireless connectionProvides wireless connection

o e or any user oca ono e or any user oca onwithin the radio range of the system.within the radio range of the system.

o e or any user oca ono e or any user oca onwithin the radio range of the system.within the radio range of the system.

by limiting the coverage of eachby limiting the coverage of each

by limiting the coverage of eachby limiting the coverage of each

geographical area called ageographical area called a cell cell , and, andgeographical area called ageographical area called a cell cell , and, and

another base station located someanother base station located somedistance awadistance awa – – Fre uenc reuse.Fre uenc reuse.another base station located someanother base station located somedistance awadistance awa – – Fre uenc reuse.Fre uenc reuse.

1414



............ Switching system, calledSwitching system, called Switching system, calledSwitching system, called

handoff handoff , enables call to proceed, enables call to proceeduninterrupted when theuninterrupted when thehandoff handoff , enables call to proceed, enables call to proceeduninterrupted when theuninterrupted when the..

Typical MSC handlesTypical MSC handles

..

Typical MSC handlesTypical MSC handles,,5,000 simultaneous conversations5,000 simultaneous conversations

,,5,000 simultaneous conversations5,000 simultaneous conversations

....

1515



Telephone Call MadeTelephone Call MadeTelephone Call MadeTelephone Call Made

To To Mobile User...Mobile User...To To Mobile User...Mobile User...

1616



ncomingncomingTelephoneTelephone

ncomingncomingTelephoneTelephone

Base StationsBase StationsBase StationsBase Stations

Mobile XMobile X

Mobile XMobile X ,,,,epepepep

3, 73, 73, 73, 7

SwitchingSwitching

Center Center 4444

PSTNPSTNPSTNPSTNMobile XMobile XMobile XMobile X

1717



Telephone Call Placed to a Mobile User Telephone Call Placed to a Mobile User Telephone Call Placed to a Mobile User Telephone Call Placed to a Mobile User

Step 1Step 1 – – The incoming telephone call toThe incoming telephone call toMobile X is received at the MSC.Mobile X is received at the MSC.Step 1Step 1 – – The incoming telephone call toThe incoming telephone call toMobile X is received at the MSC.Mobile X is received at the MSC.

Step 2Step 2 – – The MSC dispatches the requestThe MSC dispatches the request

to all base stations in the cellular system.to all base stations in the cellular system.

Step 2Step 2 – – The MSC dispatches the requestThe MSC dispatches the request

to all base stations in the cellular system.to all base stations in the cellular system. tep 3tep 3 – – e ase stations roa caste ase stations roa cast

thethe Mobile Identification Number Mobile Identification Number (MIN),(MIN),tep 3tep 3 – – e ase stations roa caste ase stations roa castthethe Mobile Identification Number Mobile Identification Number (MIN),(MIN),

,,message over the FCC throughout themessage over the FCC throughout thecellular s stem.cellular s stem.

,,message over the FCC throughout themessage over the FCC throughout thecellular s stem.cellular s stem.

1818



............Step 4Step 4 – – The mobile receives the pagingThe mobile receives the pagingStep 4Step 4 – – The mobile receives the pagingThe mobile receives the paging

message sen y e ase s a onmessage sen y e ase s a onmonitors and responds by identifyingmonitors and responds by identifyingmessage sen y e ase s a onmessage sen y e ase s a onmonitors and responds by identifyingmonitors and responds by identifying

(RCC)(RCC)..

– –

(RCC)(RCC)..

– –acknowledgement sent by the mobileacknowledgement sent by the mobileand informs the MSC of the handshake.and informs the MSC of the handshake.

acknowledgement sent by the mobileacknowledgement sent by the mobileand informs the MSC of the handshake.and informs the MSC of the handshake.

Step 6Step 6 – – The MSC instructs the base stationThe MSC instructs the base stationto move the call to an available voiceto move the call to an available voice

Step 6Step 6 – – The MSC instructs the base stationThe MSC instructs the base stationto move the call to an available voiceto move the call to an available voice

1919

c anne w n e ce .c anne w n e ce .c anne w n e ce .c anne w n e ce .



MobileMobileSwitchingSwitching 3333

en er en er 2222

Call PlacedCall PlacedCall PlacedCall Placed1111

2121



............Step 1Step 1 – – When a mobile originates a call,When a mobile originates a call,Step 1Step 1 – – When a mobile originates a call,When a mobile originates a call,

sen s e ase s a on s e ep onesen s e ase s a on s e ep onenumber (MIN),number (MIN), electronic serial number electronic serial number

sen s e ase s a on s e ep onesen s e ase s a on s e ep onenumber (MIN),number (MIN), electronic serial number electronic serial number

,,party. It also transmits aparty. It also transmits a station class station class

mark mark SCM which indicates what theSCM which indicates what the

,,party. It also transmits aparty. It also transmits a station class station class

mark mark SCM which indicates what theSCM which indicates what themaximum power level is for themaximum power level is for theparticular user.particular user.maximum power level is for themaximum power level is for theparticular user.particular user.

Step 2Step 2 – – The cell base station receivesThe cell base station receivesthe data and sends it to the MSC.the data and sends it to the MSC.

Step 2Step 2 – – The cell base station receivesThe cell base station receivesthe data and sends it to the MSC.the data and sends it to the MSC.

2222



............Step 3Step 3 – – The MSC validates the request,The MSC validates the request,Step 3Step 3 – – The MSC validates the request,The MSC validates the request,

through the PSTN and validates thethrough the PSTN and validates thethrough the PSTN and validates thethrough the PSTN and validates the

to an unused forward and reverseto an unused forward and reverse

channel pair to allow the conversationchannel pair to allow the conversation

to an unused forward and reverseto an unused forward and reverse

channel pair to allow the conversationchannel pair to allow the conversationto begin.to begin.to begin.to begin.

2323



All cellular systems provideAll cellular systems provide All cellular systems provideAll cellular systems providea serv ce ca ea serv ce ca e roam n roam n ..This allows subscribers to operateThis allows subscribers to operatea serv ce ca ea serv ce ca e roam n roam n ..This allows subscribers to operateThis allows subscribers to operate

from which service is subscribed.from which service is subscribed.

from which service is subscribed.from which service is subscribed.

geographic area that is differentgeographic area that is differentfrom its home service area, it isfrom its home service area, it isgeographic area that is differentgeographic area that is differentfrom its home service area, it isfrom its home service area, it is

registered as aregistered as a roamer roamer in the newin the newservice area.service area.registered as aregistered as a roamer roamer in the newin the newservice area.service area.

2424



………… Periodically, the MSC issuesPeriodically, the MSC issues Periodically, the MSC issuesPeriodically, the MSC issues

a g o a comman over eaca g o a comman over eacFCC in the system, asking for FCC in the system, asking for a g o a comman over eaca g o a comman over eacFCC in the system, asking for FCC in the system, asking for

unregistered to report their MIN andunregistered to report their MIN and

ESN over the RCC for billin ur oses.ESN over the RCC for billin ur oses.

unregistered to report their MIN andunregistered to report their MIN and

ESN over the RCC for billin ur oses.ESN over the RCC for billin ur oses. If a particular mobile user has roamingIf a particular mobile user has roaming

authorization for billing purposes, MSCauthorization for billing purposes, MSC If a particular mobile user has roamingIf a particular mobile user has roaming

authorization for billing purposes, MSCauthorization for billing purposes, MSC

registers the subscriber as a validregisters the subscriber as a validroamer.roamer.registers the subscriber as a validregisters the subscriber as a validroamer.roamer.

2525



US Cellular Radio ServiceUS Cellular Radio ServiceUS Cellular Radio ServiceUS Cellular Radio Service

ChannelChannel Center FrequencyCenter FrequencyNumber Number (MHZ)(MHZ)ChannelChannel Center FrequencyCenter FrequencyNumber Number (MHZ)(MHZ)

11 ≤ NN ≤ 799799 .03 N + 825.03 N + 825

≤ ≤ – –

11 ≤ NN ≤ 799799 .03 N + 825.03 N + 825

≤ ≤ – –≤ ≤ ..

11 ≤ NN ≤ 799799 .03 N + 870.03 N + 870

≤ ≤ ..

11 ≤ NN ≤ 799799 .03 N + 870.03 N + 870

≤ ≤ .. – – ++Channels 800Channels 800--989 are unused.989 are unused.

≤ ≤ .. – – ++Channels 800Channels 800--989 are unused.989 are unused.

2626



Personal Communications:Personal Communications:


A Comparison of A Comparison of --


Mobile StationMobile Station......

Mobile StationMobile Station......

2727



FunctionFunction--alityality

Carrier Carrier frequencyfrequency

HardwareHardwarecostcost

ComCom--plexityplexity

infrainfra--

structurestructure

CoverageCoveragerangerange

ServiceService

Gara eGara e

ransrans--

mitter mitter infrainfra--redredlowlowlowlowlowlowlowlow

remoteremotecontrolcontrol

Pa inPa in

--mitter mitter

MHzMHzlowlowlowlowlowlowlowlowdoor door

opener opener

transtrans--<100<100lowlowmoderatemoderatelowlowlowlowCordlessCordless

rece ver rece ver < z< zowowowowggggsystemsystem

transtrans--ceiver ceiver <1 GHz<1 GHzmoderatemoderatehighhighhighhighhighhigh

Cellular Cellular phonephone

2828







Base StationBase Station......

Base StationBase Station......

2929



FunctionFunction--alityality

Carrier Carrier frequencyfrequency

HardwareHardwarecostcost

ComCom--plexityplexity

infrainfra--

structurestructure

CoverageCoveragerangerangeServiceService

Gara eGara e

infrainfra--redredlowlowlowlowlowlowlowlow

remoteremotecontrolcontrol

receiver receiver

Pa inPa in

receiver receiver MHzMHzlowlowlowlowlowlowlowlowdoor door opener opener

--

transtrans--<100<100moderatemoderatelowlowlowlowlowlowCordlessCordless

< z< zggggggggsystemsystem mitter mitter

transtrans--ceiver ceiver <1 GHz<1 GHzhighhighhighhighhighhighhighhigh

Cellular Cellular phonephone

3030



– –System Design FundamentalsSystem Design Fundamentals

– –System Design FundamentalsSystem Design Fundamentals

The cellular concept was a major The cellular concept was a major breakthrough in solving the problembreakthrough in solving the problem

The cellular concept was a major The cellular concept was a major breakthrough in solving the problembreakthrough in solving the problemoo spec ra conges on spec ra conges on anan user user capacity capacity ..

oo spec ra conges on spec ra conges on anan user user capacity capacity ..

transmitter transmitter (large cell)(large cell) with manywith many

transmitter transmitter (large cell)(large cell) with manywith many

each providing coverage to only aeach providing coverage to only asmall portion of the service area.small portion of the service area.

each providing coverage to only aeach providing coverage to only asmall portion of the service area.small portion of the service area.

3131



Each cellular base station isEach cellular base station isEach cellular base station isEach cellular base station isa oca e a group o ra oa oca e a group o ra ochannels.channels.a oca e a group o ra oa oca e a group o ra ochannels.channels.

assigned channel groups whichassigned channel groups which

contain different channels thancontain different channels than

assigned channel groups whichassigned channel groups which

contain different channels thancontain different channels thanneighboring cells.neighboring cells.neighboring cells.neighboring cells.

3232



Cells with the same letter, useCells with the same letter, useCells with the same letter, useCells with the same letter, use

BB

e same se o requenc es.e same se o requenc es.

A cellA cell cluster cluster is outlinedis outlined

e same se o requenc es.e same se o requenc es.

A cellA cell cluster cluster is outlinedis outlinedAA

CCGG

FF DD

in bold, and replicated over in bold, and replicated over

the coverage area.the coverage area.

in bold, and replicated over in bold, and replicated over

the coverage area.the coverage area.GG

BB CCAA

GGCC

In this example, theIn this example, thecluster size,cluster size, N N , is equal to 7;, is equal to 7;

In this example, theIn this example, thecluster size,cluster size, N N , is equal to 7;, is equal to 7;

FFEE

EEDD

an e requency reuse ac or s ,an e requency reuse ac or s ,since each cell contains 1/7 of the totalsince each cell contains 1/7 of the totalan e requency reuse ac or s ,an e requency reuse ac or s ,since each cell contains 1/7 of the totalsince each cell contains 1/7 of the total

3333

....



Factors:Factors:

Equal areaEqual area

No overlap between cellsNo overlap between cells

Equal areaEqual area

No overlap between cellsNo overlap between cells

Choices:

SS

A1A1 AA22 AA33

3434



A3 > A1A3 > A1

A3 > A1A3 > A1

>>

Here, A3 provides maximumHere, A3 provides maximum

>>

Here, A3 provides maximumHere, A3 provides maximumcoverage area or a g ven va ue o .coverage area or a g ven va ue o .

Actual cellular footprint is determinedActual cellular footprint is determined

coverage area or a g ven va ue o .coverage area or a g ven va ue o .

Actual cellular footprint is determinedActual cellular footprint is determined

antenna.antenna.

antenna.antenna.

,,fewest number of cells covers a givenfewest number of cells covers a given

eo ra hic re ion.eo ra hic re ion.

,,fewest number of cells covers a givenfewest number of cells covers a given

eo ra hic re ion.eo ra hic re ion.

3535



Let a cellular system have total of Let a cellular system have total of Let a cellular system have total of Let a cellular system have total of

up ex c anne s or use.up ex c anne s or use.

If S channels are divided into N cellsIf S channels are divided into N cells

up ex c anne s or use.up ex c anne s or use.

If S channels are divided into N cellsIf S channels are divided into N cells(in a cluster) into unique and disjoint(in a cluster) into unique and disjointchannel groups which each has thechannel groups which each has the(in a cluster) into unique and disjoint(in a cluster) into unique and disjointchannel groups which each has thechannel groups which each has the

,,of available radio channels is:of available radio channels is:

,,of available radio channels is:of available radio channels is:

Where K is the number of channels / cell.Where K is the number of channels / cell. Where K is the number of channels / cell.Where K is the number of channels / cell.

3636



…………If a cluster is replicated M timesIf a cluster is replicated M timesIf a cluster is replicated M timesIf a cluster is replicated M timeswithin the system, the totalwithin the system, the totalnumber of duplex channels, C,number of duplex channels, C,within the system, the totalwithin the system, the totalnumber of duplex channels, C,number of duplex channels, C,

,,,,

= = .= = .

Cluster size N = 4, 7 or 12Cluster size N = 4, 7 or 12

= = .= = .

Cluster size N = 4, 7 or 12Cluster size N = 4, 7 or 12

3737



In order to connect without gapsIn order to connect without gapsIn order to connect without gapsIn order to connect without gapsbetween adjacent cells (tobetween adjacent cells (to tessellate tessellate ))

== 22 ++ 22

between adjacent cells (tobetween adjacent cells (to tessellate tessellate ))

== 22 ++ 22

Where i and j are nonWhere i and j are non--negative integersnegative integers

Where i and j are nonWhere i and j are non--negative integersnegative integersExample i = 2, j = 1Example i = 2, j = 1

22 22

Example i = 2, j = 1Example i = 2, j = 1

22 22

3838



CoCo--channel Neighbor of channel Neighbor of CoCo--channel Neighbor of channel Neighbor of

Move i cells along any chainMove i cells along any chain Move i cells along any chainMove i cells along any chainor exagon.or exagon.

Then turn 60 degreesThen turn 60 degrees

or exagon.or exagon.

Then turn 60 degreesThen turn 60 degreesmove j cells.move j cells.

move j cells.move j cells.

3939



----Cells in a Cellular SystemCells in a Cellular System Cells in a Cellular SystemCells in a Cellular System

example,example,N = 19N = 19example,example,N = 19N = 19

AA AA

(( i.e.,i.e.,

i = 3,i = 3,

(( i.e.,i.e.,

i = 3,i = 3,AA j = 2 j = 2 )) j = 2 j = 2 ))AA

ap e romap e rom[Oet83] © [Oet83] © ap e romap e rom[Oet83] © [Oet83] © AA

4040

....



If a particular FDD cellular If a particular FDD cellular If a particular FDD cellular If a particular FDD cellular e ep one sys em as a o ae ep one sys em as a o a

bandwidth of 33 MHz,bandwidth of 33 MHz,

e ep one sys em as a o ae ep one sys em as a o a

bandwidth of 33 MHz,bandwidth of 33 MHz,

two 25 KHz simplex channels totwo 25 KHz simplex channels totwo 25 KHz simplex channels totwo 25 KHz simplex channels to

control channels...control channels...

com ute the number of com ute the number of

control channels...control channels...

com ute the number of com ute the number of

channels per cell if channels per cell if N = 4, 7, 12.N = 4, 7, 12.channels per cell if channels per cell if N = 4, 7, 12.N = 4, 7, 12.

4141



Total bandwidth = 33 MHzTotal bandwidth = 33 MHzTotal bandwidth = 33 MHzTotal bandwidth = 33 MHz

Channel bandwidth = 25 KHz x 2 = 50 KHzChannel bandwidth = 25 KHz x 2 = 50 KHz

Total avail. channels = 33 MHz / 50 KHz = 660Total avail. channels = 33 MHz / 50 KHz = 660

Channel bandwidth = 25 KHz x 2 = 50 KHzChannel bandwidth = 25 KHz x 2 = 50 KHz

Total avail. channels = 33 MHz / 50 KHz = 660Total avail. channels = 33 MHz / 50 KHz = 660

N = 4N = 4 Channel per cell = 660 / 4 =Channel per cell = 660 / 4 =

165 channels165 channels

N = 4N = 4 Channel per cell = 660 / 4 =Channel per cell = 660 / 4 =

165 channels165 channelsN = 7N = 7 Channel per cell = 660 / 7 =Channel per cell = 660 / 7 =N = 7N = 7 Channel per cell = 660 / 7 =Channel per cell = 660 / 7 =

N = 12N = 12 Channel per cell = 660 / 12 =Channel per cell = 660 / 12 =N = 12N = 12 Channel per cell = 660 / 12 =Channel per cell = 660 / 12 =

4242



Fixed Channel AssignmentsFixed Channel Assignments

Fixed Channel AssignmentsFixed Channel Assignments

ac ce s a oca e a preac ce s a oca e a pre-- e erm nee erm ne

set of voice channels.set of voice channels.

ac ce s a oca e a preac ce s a oca e a pre-- e erm nee erm ne

set of voice channels.set of voice channels. ,,

the call is blocked, and the subscriber the call is blocked, and the subscriber ,,

the call is blocked, and the subscriber the call is blocked, and the subscriber

Variation includes a borrowing strategy:Variation includes a borrowing strategy:a cell is allowed to borrow channels from aa cell is allowed to borrow channels from a

Variation includes a borrowing strategy:Variation includes a borrowing strategy:a cell is allowed to borrow channels from aa cell is allowed to borrow channels from a

neighboring cell if all its own channels areneighboring cell if all its own channels areoccupied. This is supervised by the MSC.occupied. This is supervised by the MSC.neighboring cell if all its own channels areneighboring cell if all its own channels areoccupied. This is supervised by the MSC.occupied. This is supervised by the MSC.

4343



Dynamic Channel AssignmentsDynamic Channel Assignments

Dynamic Channel AssignmentsDynamic Channel Assignments

o ce c anne s are no a oca e oo ce c anne s are no a oca e o

different cells permanently.different cells permanently.

o ce c anne s are no a oca e oo ce c anne s are no a oca e o

different cells permanently.different cells permanently. ,,

serving base station requests a channelserving base station requests a channel ,,

serving base station requests a channelserving base station requests a channel

The switch then allocates a channel toThe switch then allocates a channel tothe re uested call based on a decisionthe re uested call based on a decision

The switch then allocates a channel toThe switch then allocates a channel tothe re uested call based on a decisionthe re uested call based on a decision

algorithm taking into account differentalgorithm taking into account differentfactorsfactors -- frequency refrequency re--use of candidateuse of candidatealgorithm taking into account differentalgorithm taking into account differentfactorsfactors -- frequency refrequency re--use of candidateuse of candidate

4444

c anne , cos ac ors.c anne , cos ac ors.c anne , cos ac ors.c anne , cos ac ors.



......Dynamic Channel AssignmentsDynamic Channel Assignments......Dynamic Channel AssignmentsDynamic Channel Assignments

Dynamic channel assignment isDynamic channel assignment ismore complex (real time), butmore complex (real time), butDynamic channel assignment isDynamic channel assignment ismore complex (real time), butmore complex (real time), but

....

4545



Handoff Handoff -- when a mobile moves intowhen a mobile moves intoHandoff Handoff -- when a mobile moves intowhen a mobile moves intoa eren ce w e a conversa ona eren ce w e a conversa on

is in progress, the MSC automaticallyis in progress, the MSC automatically

a eren ce w e a conversa ona eren ce w e a conversa on

is in progress, the MSC automaticallyis in progress, the MSC automatically

belonging to the new base stationbelonging to the new base station

belonging to the new base stationbelonging to the new base station

cellular radio systemcellular radio system

Handoffs must be erformedHandoffs must be erformed

cellular radio systemcellular radio system

Handoffs must be erformedHandoffs must be erformed

successfully, as infrequently assuccessfully, as infrequently aspossible and not visible to users.possible and not visible to users.successfully, as infrequently assuccessfully, as infrequently aspossible and not visible to users.possible and not visible to users.

4646



A Handoff ScenarioA Handoff ScenarioA Handoff ScenarioA Handoff Scenario

at Cell Boundary...at Cell Boundary...at Cell Boundary...at Cell Boundary...

4747



a Im ro er Handoff Situationa Im ro er Handoff Situation

l e v e l

l e v e l Level at point ALevel at point A

i g n

a l

i g n

a l Handoff thresholdHandoff threshold

Minimum acce tableMinimum acce table PPnn

i

v e d

i

v e d signal to maintain the callsignal to maintain the call

PPmm

R e c

R e c

(call is terminated)(call is terminated)

AA BB PPnn – – PPmm = ∆= ∆

4848

BS1BS1 BS2BS2



……Cell BoundaryCell Boundary……Cell BoundaryCell Boundary

PPnn – – PP

mm= ∆= ∆

∆ should be optimal value∆ should be optimal value

PPnn – – PP

mm= ∆= ∆

∆ should be optimal value∆ should be optimal value

∆ too large:∆ too large:

too man handoffstoo man handoffs

∆ too large:∆ too large:

too man handoffstoo man handoffs∆ too small:∆ too small:∆ too small:∆ too small:

4949



bb PPro er Handoff Situationro er Handoff Situation

l e v e l

l e v e l

Level at point BLevel at point B

i g n

a l

i g n

a l

i v e d

i v e d Level at whichLevel at which

handoff is madehandoff is made

R e c

R e c

memeAA BB

5050

BS1BS1 BS2BS2



Time over which a call mayTime over which a call may Time over which a call mayTime over which a call may

e ma n a ne w n a ce ,e ma n a ne w n a ce ,

without handwithout hand--off.off.

e ma n a ne w n a ce ,e ma n a ne w n a ce ,

without handwithout hand--off.off.

monitors the signal strength of all itsmonitors the signal strength of all its

monitors the signal strength of all itsmonitors the signal strength of all its

the relative location of each mobilethe relative location of each mobileuser with respect to the base stationuser with respect to the base stationthe relative location of each mobilethe relative location of each mobileuser with respect to the base stationuser with respect to the base station

tower.tower.tower.tower.

5151



………… Mobile assisted handMobile assisted hand--off (MAHO)off (MAHO) --

Mobile assisted handMobile assisted hand--off (MAHO)off (MAHO) --

very mo e s a on measures every mo e s a on measures e

received power from surroundingreceived power from surrounding

very mo e s a on measures every mo e s a on measures e

received power from surroundingreceived power from surrounding

reports the results of thesereports the results of these

measurements to the servin basemeasurements to the servin base

reports the results of thesereports the results of these

measurements to the servin basemeasurements to the servin basestationstation -- Faster handFaster hand--off rate.off rate.

Inter Inter--system handoff system handoff --

stationstation -- Faster handFaster hand--off rate.off rate.

Inter Inter--system handoff system handoff --

One cellular system to a differentOne cellular system to a differentcellular system.cellular system.One cellular system to a differentOne cellular system to a differentcellular system.cellular system.

5252



System CapacitySystem Capacity

System CapacitySystem Capacity

Major limiting factor inMajor limiting factor inperformance of cellular radioperformance of cellular radioMajor limiting factor inMajor limiting factor inperformance of cellular radioperformance of cellular radio

--

CoCo--channel interferencechannel interference

--

CoCo--channel interferencechannel interference

acen c anneacen c anneinterferenceinterference

acen c anneacen c anneinterferenceinterference

5353



----Cells that use the same setCells that use the same setCells that use the same setCells that use the same seto requenc es are ca eo requenc es are ca e

co co- -channel cells channel cells ..

o requenc es are ca eo requenc es are ca e

co co- -channel cells channel cells ..n er erence e weenn er erence e ween

the cells is calledthe cells is calledn er erence e weenn er erence e ween

the cells is calledthe cells is called

....

5454



----Signal to interference ratioSignal to interference ratioSignal to interference ratioSignal to interference ratio

receiver is given by:receiver is given by:

receiver is given by:receiver is given by:

S/S/ II = S= SIIR = S /(R = S /( IIii))S/S/ II = S= SIIR = S /(R = S /( IIii))=

iioo∑

S = si nal ower from desi nated baseS = si nal ower from desi nated baseS = si nal ower from desi nated baseS = si nal ower from desi nated base

stationstation

stationstation

5555



--for a Cluster Size of N = 7for a Cluster Size of N = 7

--for a Cluster Size of N = 7for a Cluster Size of N = 7

When the mobile is at theWhen the mobile is at the

cell boundary (point A),cell boundary (point A),

When the mobile is at theWhen the mobile is at the

cell boundary (point A),cell boundary (point A),

coco--channel interference onchannel interference oncoco--channel interference onchannel interference on

The marked distances between theThe marked distances between themobile and different comobile and different co--channel cellschannel cellsThe marked distances between theThe marked distances between themobile and different comobile and different co--channel cellschannel cells

are based on approximations madeare based on approximations madefor easy analysis.for easy analysis.are based on approximations madeare based on approximations madefor easy analysis.for easy analysis.

5656



CoCo--ChannelChannelCoCo--ChannelChannel

Cluster SizeCluster SizeCluster SizeCluster Size AAAA DD++RRo =o =o =o =

IIii = Interference= InterferenceIIii = Interference= Interference --

DD++RR

power causedpower causedby the ithby the ithpower causedpower causedby the ithby the ith AAAA DD--RR

DD

coco--channel cellchannel cell

coco--channel cellchannel cell

AA

5757



For any given antennaFor any given antennaFor any given antennaFor any given antenna

at a distance d is given by:at a distance d is given by:

at a distance d is given by:at a distance d is given by:

PPoo ddPPr r

PP = P= P d / dd / d --nn ; n is ath loss ex onent; n is ath loss ex onent

5858



............

-n -niioo∑

--nn,, ii

ii = 11

∑

io = total number of first layer interfacing cells

If the mobile is at the center of the cell D = D

io = total number of first layer interfacing cells

If the mobile is at the center of the cell D = D

-

-

-

-

-

-

iioo

∑= = o= = oii = 11∑

5959



√

√==√ == -- --

reuse ratioreuse ratio

==√ == -- --

reuse ratioreuse ratio

S /S / II = [= [√((3N) ]3N) ] nn / i/ ioo

S /S / II = [= [√((3N) ]3N) ] nn / i/ ioo

6060



-- – – when mobile is at cellwhen mobile is at cell

-- – – when mobile is at cellwhen mobile is at cell

. =. =. =. =

~~ --

[ 2(D[ 2(D--R)R)--44+2(D+R)+2(D+R)--44+ 2D+ 2D--44]]~~ --

[ 2(D[ 2(D--R)R)--44+2(D+R)+2(D+R)--44+ 2D+ 2D--44]]

6161



Interference resulting fromInterference resulting from Interference resulting fromInterference resulting from

frequency to the desired signal.frequency to the desired signal.

frequency to the desired signal.frequency to the desired signal. ue o mper ec rece ver ers a a owue o mper ec rece ver ers a a ow

nearby frequencies to leak into pass band.nearby frequencies to leak into pass band.

ue o mper ec rece ver ers a a owue o mper ec rece ver ers a a ownearby frequencies to leak into pass band.nearby frequencies to leak into pass band.

an e m n m ze y care u er ng anan e m n m ze y care u er ng anassignments; and, by keeping frequencyassignments; and, by keeping frequency

an e m n m ze y care u er ng anan e m n m ze y care u er ng anassignments; and, by keeping frequencyassignments; and, by keeping frequency

as large as possible, the adjacent channelas large as possible, the adjacent channelinterference ma be reduced considerabl .interference ma be reduced considerabl .

as large as possible, the adjacent channelas large as possible, the adjacent channelinterference ma be reduced considerabl .interference ma be reduced considerabl .

6262



Cellular radio system relies on trunking toCellular radio system relies on trunking to Cellular radio system relies on trunking toCellular radio system relies on trunking to

accommo a e a arge num er o users naccommo a e a arge num er o users n

a limited radio spectruma limited radio spectrum -- How a largeHow a large

accommo a e a arge num er o users naccommo a e a arge num er o users n

a limited radio spectruma limited radio spectrum -- How a largeHow a large

limited number of services.limited number of services.

--

limited number of services.limited number of services.

--channel on a per channel on a per--call basis; and uponcall basis; and upontermination of the call, the previouslytermination of the call, the previouslychannel on a per channel on a per--call basis; and uponcall basis; and upontermination of the call, the previouslytermination of the call, the previously

occupied channel is immediately returnedoccupied channel is immediately returnedto the pool of available channelsto the pool of available channels

occupied channel is immediately returnedoccupied channel is immediately returnedto the pool of available channelsto the pool of available channels

6363

n a e y an s ma ema c an, r ang.n a e y an s ma ema c an, r ang. n a e y an s ma ema c an, r ang.n a e y an s ma ema c an, r ang.



Measure of ability of the user toMeasure of ability of the user toMeasure of ability of the user toMeasure of ability of the user toaccess a run e sys em ur ng eaccess a run e sys em ur ng e

busiest hour during a week, month or year.busiest hour during a week, month or year.

access a run e sys em ur ng eaccess a run e sys em ur ng e

busiest hour during a week, month or year.busiest hour during a week, month or year.

ExampleExample: 4: 4 -- 6 pm on Thursday or Friday6 pm on Thursday or Fridayevening.evening.ExampleExample: 4: 4 -- 6 pm on Thursday or Friday6 pm on Thursday or Fridayevening.evening.

Traffic intensity (ATraffic intensity (Aμ Erlang) of each user is:Erlang) of each user is:AAμ == λ HHTraffic intensity (ATraffic intensity (Aμ Erlang) of each user is:Erlang) of each user is:AAμ == λ HHμ

λ -- Average number of call requests per unitAverage number of call requests per unit

μ

λ -- Average number of call requests per unitAverage number of call requests per unit

6464

HH -- duration of a callduration of a call

HH -- duration of a callduration of a call



For system entering U users,For system entering U users,For system entering U users,For system entering U users,

e o a o ere ra c n ens ye o a o ere ra c n ens y

A is given as:A is given as:

e o a o ere ra c n ens ye o a o ere ra c n ens y

A is given as:A is given as:

A = U AA = U Aμ ErlangsErlangs

A = U AA = U Aμ ErlangsErlangs

,,average intensity per channel is:average intensity per channel is:

,,average intensity per channel is:average intensity per channel is:

cc == μ cc == μ

6565



No queuing for call requestsNo queuing for call requests

No queuing for call requestsNo queuing for call requests

If no channels are available, theIf no channels are available, theIf no channels are available, theIf no channels are available, thereques ng user s oc e w oureques ng user s oc e w ouaccess and is free to try again later.access and is free to try again later.reques ng user s oc e w oureques ng user s oc e w ouaccess and is free to try again later.access and is free to try again later.

6666



Assuming a finite number ofAssuming a finite number of Assuming a finite number ofAssuming a finite number of

ava a e c anne s , an us ngava a e c anne s , an us ng

queuing theory, we obtain:queuing theory, we obtain:

ava a e c anne s , an us ngava a e c anne s , an us ng

queuing theory, we obtain:queuing theory, we obtain:GOS = Probability (call is blocked)GOS = Probability (call is blocked)GOS = Probability (call is blocked)GOS = Probability (call is blocked)

== [A[Acc / C! ]/ [/ C! ]/ [ ∑ AAkk / k!]/ k!]== [A[Acc / C! ]/ [/ C! ]/ [ ∑ AAkk / k!]/ k!]

k=0k=0k=0k=0

6767



AMPS cellular is designedAMPS cellular is designed AMPS cellular is designedAMPS cellular is designed

or = .or = .

This is called Erlang B formulaThis is called Erlang B formula

or = .or = .

This is called Erlang B formulaThis is called Erlang B formula(Appendix A)(Appendix A) -- Figure 3.6 (2.6 in 1Figure 3.6 (2.6 in 1stst edition)edition)in book.in book.(Appendix A)(Appendix A) -- Figure 3.6 (2.6 in 1Figure 3.6 (2.6 in 1stst edition)edition)in book.in book.

6868



Queue is provided to hold calls which are blocked.Queue is provided to hold calls which are blocked. Queue is provided to hold calls which are blocked.Queue is provided to hold calls which are blocked.

,,

request may be delayed until a channel becomesrequest may be delayed until a channel becomesavailableavailable

,,

request may be delayed until a channel becomesrequest may be delayed until a channel becomesavailableavailable

Prob [Delay > 0 ] = AProb [Delay > 0 ] = Acc / [ A/ [ A cc + C!+ C! Prob [Delay > 0 ] = AProb [Delay > 0 ] = Acc / [ A/ [ A cc + C!+ C!

CC--11

( 1( 1 – – A / C )]A / C )] [[ ∑ AAkk / k!]/ k!]

CC--11

( 1( 1 – – A / C )]A / C )] [[ ∑ AAkk / k!]/ k!]

==

Prob [Delay > t sec ] = Prob [Delay > 0 ] xProb [Delay > t sec ] = Prob [Delay > 0 ] x – – --

==

Prob [Delay > t sec ] = Prob [Delay > 0 ] xProb [Delay > t sec ] = Prob [Delay > 0 ] x – – --

6969



Average Delay D for all calls in aAverage Delay D for all calls in a Average Delay D for all calls in aAverage Delay D for all calls in a

queue sys em s g ven y:queue sys em s g ven y:queue sys em s g ven y:queue sys em s g ven y:

= ro e ay > /= ro e ay > / -- = ro e ay > /= ro e ay > / --

This is called Erlang C formulaThis is called Erlang C formula --Figure 3.7 (Figure 2.7 in 1Figure 3.7 (Figure 2.7 in 1stst Edition)Edition)

This is called Erlang C formulaThis is called Erlang C formula --Figure 3.7 (Figure 2.7 in 1Figure 3.7 (Figure 2.7 in 1stst Edition)Edition)

7070



A hexagonal cell in a 4A hexagonal cell in a 4--cell system hascell system has A hexagonal cell in a 4A hexagonal cell in a 4--cell system hascell system hasa ra us o . m; an a o a oa ra us o . m; an a o a o

channels are used within the entire system.channels are used within the entire system.

a ra us o . m; an a o a oa ra us o . m; an a o a o

channels are used within the entire system.channels are used within the entire system. . ,. ,λ = 1 call per hour, compute the= 1 call per hour, compute the

. ,. ,λ = 1 call per hour, compute the= 1 call per hour, compute the

has a 5% probability of a delayed call.has a 5% probability of a delayed call.

a. How man users er s uare kma. How man users er s uare km

has a 5% probability of a delayed call.has a 5% probability of a delayed call.

a. How man users er s uare kma. How man users er s uare km

will the system support?will the system support?b. What is the Prob Dela > 10s ?b. What is the Prob Dela > 10s ?

will the system support?will the system support?b. What is the Prob Dela > 10s ?b. What is the Prob Dela > 10s ?

7171



Cell radius = R = 1.387 kmCell radius = R = 1.387 km Cell radius = R = 1.387 kmCell radius = R = 1.387 km

Area covered per cell =Area covered per cell =2.598 1.3872.598 1.387 22 = 5 s km= 5 s km

Area covered per cell =Area covered per cell =2.598 1.3872.598 1.387 22 = 5 s km= 5 s km

Number of cells per cluster = 4Number of cells per cluster = 4

Number of cells per cluster = 4Number of cells per cluster = 4

o a num er o c anne s per ce =o a num er o c anne s per ce =60 / 4 = 15 channels60 / 4 = 15 channels

o a num er o c anne s per ce =o a num er o c anne s per ce =60 / 4 = 15 channels60 / 4 = 15 channels

7272



............a.a. From Erlang C chart, GOS = 0.05, C = 15,From Erlang C chart, GOS = 0.05, C = 15,a.a. From Erlang C chart, GOS = 0.05, C = 15,From Erlang C chart, GOS = 0.05, C = 15,

Traffic intensity A = 9.0 ETraffic intensity A = 9.0 E Traffic intensity A = 9.0 ETraffic intensity A = 9.0 E

Number of usersNumber of users Number of usersNumber of users

= 9.0 / 0.029 = 310 users= 9.0 / 0.029 = 310 users

= 9.0 / 0.029 = 310 users= 9.0 / 0.029 = 310 users

Number of users per sq. km =Number of users per sq. km = Number of users per sq. km =Number of users per sq. km =

7373

. .. .. .. .



............b.b. Prob Dela > 10s = Pr Dela > 0 eProb Dela > 10s = Pr Dela > 0 e – –(C(C--A) tA) t / H / Hb.b. Prob Dela > 10s = Pr Dela > 0 eProb Dela > 10s = Pr Dela > 0 e – –(C(C--A) tA) t / H / H

= 0.05 x e= 0.05 x e – –(15(15--9) 10 / H9) 10 / H

= 0.05 x e= 0.05 x e – –(15(15--9) 10 / H9) 10 / H

HH = A= Aμ / / λ = 0.029 hr = 0.029 hr

= .029 x 60 x 60 seconds= .029 x 60 x 60 seconds

HH = A= Aμ / / λ = 0.029 hr = 0.029 hr

= .029 x 60 x 60 seconds= .029 x 60 x 60 seconds

= 104.4 seconds= 104.4 seconds

– – --

= 104.4 seconds= 104.4 seconds

– – --ro e ay s = . ero e ay s = . e ..

= 0.0281= 0.0281

ro e ay s = . ero e ay s = . e ..

= 0.0281= 0.0281

7474

= 2.81%= 2.81%= 2.81%= 2.81%



Cellular SystemsCellular Systems Cellular SystemsCellular Systems

As demand for wireless servicesAs demand for wireless services

increases, the number of channelsincreases, the number of channels

As demand for wireless servicesAs demand for wireless services

increases, the number of channelsincreases, the number of channelsass gne o a ce s no enoug oass gne o a ce s no enoug osupport the required number of users.support the required number of users.ass gne o a ce s no enoug oass gne o a ce s no enoug osupport the required number of users.support the required number of users.

Solution is to increase channels per Solution is to increase channels per unit coverage area.unit coverage area.

Solution is to increase channels per Solution is to increase channels per unit coverage area.unit coverage area.

7575



Subdivides a congested cell intoSubdivides a congested cell into Subdivides a congested cell intoSubdivides a congested cell into

sma er ce s, eac w s ownsma er ce s, eac w s own

base station.base station.

sma er ce s, eac w s ownsma er ce s, eac w s own

base station.base station. ncreases e capac y o a ce u ar ncreases e capac y o a ce u ar

system.system. ncreases e capac y o a ce u ar ncreases e capac y o a ce u ar

system.system.

7676



Achieves capacity improvement byAchieves capacity improvement by Achieves capacity improvement byAchieves capacity improvement by..

Cell radius R is unchanged but theCell radius R is unchanged but the--

..

Cell radius R is unchanged but theCell radius R is unchanged but the-- ..

Capacity improvement is achieved byCapacity improvement is achieved by

reducin the number of cells in a cluster reducin the number of cells in a cluster

..

Capacity improvement is achieved byCapacity improvement is achieved by

reducin the number of cells in a cluster reducin the number of cells in a cluster and this increases frequency reuse.and this increases frequency reuse.

Replacing a single omniReplacing a single omni--directional antennadirectional antenna

and this increases frequency reuse.and this increases frequency reuse.

Replacing a single omniReplacing a single omni--directional antennadirectional antenna

at base station with several directionalat base station with several directionalantennas, each radiating within a specifiedantennas, each radiating within a specifiedat base station with several directionalat base station with several directionalantennas, each radiating within a specifiedantennas, each radiating within a specified

7777....



Large control base station is replacedLarge control base station is replaced Large control base station is replacedLarge control base station is replaced

on the edge of the cell.on the edge of the cell.

on the edge of the cell.on the edge of the cell.

and the base station simply switchesand the base station simply switches

the channel to a different zone site andthe channel to a different zone site and

and the base station simply switchesand the base station simply switches

the channel to a different zone site andthe channel to a different zone site andthe mobile moves from zone to zone.the mobile moves from zone to zone.

Since a iven channel is active onl inSince a iven channel is active onl in

the mobile moves from zone to zone.the mobile moves from zone to zone.

Since a iven channel is active onl inSince a iven channel is active onl in

a particular zone in which mobile isa particular zone in which mobile istraveling, base station radiation istraveling, base station radiation isa particular zone in which mobile isa particular zone in which mobile istraveling, base station radiation istraveling, base station radiation is

7878oca ze an n er erence s re uce .oca ze an n er erence s re uce .oca ze an n er erence s re uce .oca ze an n er erence s re uce .



............ The channels are distributed inThe channels are distributed in The channels are distributed inThe channels are distributed in

me an space y a zones areme an space y a zones are

reused in coreused in co--channel cells.channel cells.

me an space y a zones areme an space y a zones are

reused in coreused in co--channel cells.channel cells.

Advantage is that while the cellAdvantage is that while the cell Advantage is that while the cellAdvantage is that while the cell

radius, coradius, co--channel interference ischannel interference isreduced due to zone transmittersreduced due to zone transmittersradius, coradius, co--channel interference ischannel interference isreduced due to zone transmittersreduced due to zone transmitters

on edge of the cell.on edge of the cell.on edge of the cell.on edge of the cell.

7979

r r

r r



fiber optic linkfiber optic link e l e c t

e l e c t

e l e c t

e l e c t

o n

e

o n

e

o n

e

o n

e BaseBasestationstation

Tx/RxTx/Rx Tx/RxTx/Rx

Cell ConceptCell ConceptCell ConceptCell Concept

[Lee91b] © IEEE)[Lee91b] © IEEE)

[Lee91b] © IEEE)[Lee91b] © IEEE)Tx/RxTx/Rx

8080



The US AMPS system isThe US AMPS system isThe US AMPS system isThe US AMPS system isallocated 50 MHz of spectrum inallocated 50 MHz of spectrum in

the 800 MHz range and providesthe 800 MHz range and provides

allocated 50 MHz of spectrum inallocated 50 MHz of spectrum in

the 800 MHz range and providesthe 800 MHz range and provides..

channels are control channels.channels are control channels...

channels are control channels.channels are control channels.

exactly 45 MHz greater than theexactly 45 MHz greater than thereverse channel fre uenc .reverse channel fre uenc .

exactly 45 MHz greater than theexactly 45 MHz greater than thereverse channel fre uenc .reverse channel fre uenc .

8181



…………a.a. Is the AMPS system simplex,Is the AMPS system simplex,a.a. Is the AMPS system simplex,Is the AMPS system simplex,

aa -- up ex or up exup ex or up ex

What is the bandwidth for eachWhat is the bandwidth for each

aa -- up ex or up exup ex or up ex

What is the bandwidth for eachWhat is the bandwidth for each,,distributed between the basedistributed between the base

station and the subscriber?station and the subscriber?

,,distributed between the basedistributed between the base

station and the subscriber?station and the subscriber?

8282



............b.b. Assume a base stationAssume a base stationb.b. Assume a base stationAssume a base station

ransm s con ro n orma onransm s con ro n orma on

on channel 352 operating aton channel 352 operating at

ransm s con ro n orma onransm s con ro n orma on

on channel 352 operating aton channel 352 operating at. .. .What is the transmissionWhat is the transmission

fre uenc of a subscriber fre uenc of a subscriber

. .. .What is the transmissionWhat is the transmission

fre uenc of a subscriber fre uenc of a subscriber unit transmitting onunit transmitting onchannel 352?channel 352?unit transmitting onunit transmitting onchannel 352?channel 352?

8383



............c.c. The A side and B side cellular The A side and B side cellular c.c. The A side and B side cellular The A side and B side cellular

carr ers even y sp ecarr ers even y sp e

channels.channels.

carr ers even y sp ecarr ers even y sp e

channels.channels.

channels and number of channels and number of

control channels for eachcontrol channels for each

channels and number of channels and number of

control channels for eachcontrol channels for eachcarrier?carrier?carrier?carrier?

8484



............d.d. For an ideal hexagonal cellular For an ideal hexagonal cellular d.d. For an ideal hexagonal cellular For an ideal hexagonal cellular

ayou w c as en ca ceayou w c as en ca ce

sites, what is the distancesites, what is the distance

ayou w c as en ca ceayou w c as en ca ce

sites, what is the distancesites, what is the distance

nearest conearest co--channel cells:channel cells:nearest conearest co--channel cells:channel cells:

For 4 cell reFor 4 cell re--use?use?

For 4 cell reFor 4 cell re--use?use?

8585



....AMPS system is duplex.AMPS system is duplex.AMPS system is duplex.AMPS system is duplex.

Total bandwidth = 50 MHzTotal bandwidth = 50 MHzTotal number of channels = 832Total number of channels = 832Total bandwidth = 50 MHzTotal bandwidth = 50 MHzTotal number of channels = 832Total number of channels = 832Bandwidth for each channelBandwidth for each channel= 50 MHz / 832 = 60 KHz= 50 MHz / 832 = 60 KHzBandwidth for each channelBandwidth for each channel= 50 MHz / 832 = 60 KHz= 50 MHz / 832 = 60 KHz

60 KHz is split into two 30 KHz channels60 KHz is split into two 30 KHz channels(forward and reverse channels).(forward and reverse channels).60 KHz is split into two 30 KHz channels60 KHz is split into two 30 KHz channels(forward and reverse channels).(forward and reverse channels).

The forward channel isThe forward channel is45 MHz > reverse channel.45 MHz > reverse channel.The forward channel isThe forward channel is45 MHz > reverse channel.45 MHz > reverse channel.

8686



....For FFor Ffwfw = 880.560 MHz= 880.560 MHzFor FFor Ffwfw = 880.560 MHz= 880.560 MHz

FFrevrev = F= Ffwfw – – 45 MHz45 MHzFFrevrev = F= Ffwfw – – 45 MHz45 MHz....

8787



....Total number of channels = 832 = NTotal number of channels = 832 = NTotal number of channels = 832 = NTotal number of channels = 832 = N

Total number of control channels NTotal number of control channels Nconcon = 42= 42Total number of control channels NTotal number of control channels Nconcon = 42= 42o a num er o vo ce c anne so a num er o vo ce c anne s vovo ==

832832 – – 42 = 79042 = 790o a num er o vo ce c anne so a num er o vo ce c anne s vovo ==

832832 – – 42 = 79042 = 790

Number of voice channels for each carrier =Number of voice channels for each carrier =790 / 2 = 395 channels790 / 2 = 395 channelsNumber of voice channels for each carrier =Number of voice channels for each carrier =790 / 2 = 395 channels790 / 2 = 395 channels

Number of control channels for each carrier =Number of control channels for each carrier =42 / 2 = 21 channels42 / 2 = 21 channelsNumber of control channels for each carrier =Number of control channels for each carrier =42 / 2 = 21 channels42 / 2 = 21 channels

8888



....N = 7N = 7N = 7N = 7

Q = D / R = = = 4.58Q = D / R = = = 4.58

==

Q = D / R = = = 4.58Q = D / R = = = 4.58

==

3 N 21

.. ..

==Q = = 3.46Q = = 3.46

==Q = = 3.46Q = = 3.4612

= .= .= .= .

8989

wireless comm 1

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