Cellular Network Architecture

1G PERSONAL COMMUNICATION 1G PERSONAL COMMUNICATION SYSTEMS: MOBILITY SYSTEMS: MOBILITY

MANAGEMENTMANAGEMENT

(PART II) (PART II)

Ian F. AkyildizIan F. Akyildiz

Broadband & Wireless Networking LaboratoryBroadband & Wireless Networking Laboratory

School of Electrical and Computer EngineeringSchool of Electrical and Computer Engineering

Georgia Institute of TechnologyGeorgia Institute of Technology

Tel: 404-894-5141; Fax: 404-894-7883 Tel: 404-894-5141; Fax: 404-894-7883

Email: [email protected]: [email protected]

Web: http://www.ece.gatech.edu/research/labs/bwnWeb: http://www.ece.gatech.edu/research/labs/bwn

2IFA’2004

Cellular Network Cellular Network ArchitectureArchitecture

LocationRegister (Database)

Mobile Switching Center

MSC

Backbone Wireline Network

Base Station Controller

Base Station

MobileTerminal

RadioNetwork

Cell

3IFA’2004

Mobility Mobility ManagementManagement

Enables telecomm networks to Enables telecomm networks to – Locate roaming MSs for call deliveryLocate roaming MSs for call delivery– Maintain connections as the MSs move Maintain connections as the MSs move

between different cellsbetween different cells Involves two operationsInvolves two operations

– Location ManagementLocation Management– Handoff ManagementHandoff Management

Involves two types of mobilityInvolves two types of mobility– Terminal mobilityTerminal mobility– Personal mobilityPersonal mobility

4IFA’2004

Types of MobilityTypes of Mobility

TERMINAL MOBILITYTERMINAL MOBILITY (Network should route calls to the MT(Network should route calls to the MT regardless of its point of attachment)regardless of its point of attachment) PERSONAL MOBILITYPERSONAL MOBILITY (Users should access the network (Users should access the network

wherever they are; UPT (Universal Pers. wherever they are; UPT (Universal Pers. Tel #))Tel #))

SERVICE PROVIDER MOBILITYSERVICE PROVIDER MOBILITY (Allow user to roam beyond regional (Allow user to roam beyond regional

networks).networks).

5IFA’2004

Mobility Mobility ManagementManagement

Location ManagementLocation Management Handoff Handoff ManagementManagement

Base StationBase Station

MT A is receiving a call !MT A is receiving a call !How will the networkHow will the networkdeliver the call to A ?deliver the call to A ?

A

6IFA’2004

Location ManagementLocation Management

Call Delivery(Paging)

Location Update(Registration)

7IFA’2004

Cost TradeoffCost Tradeoff

Too Many Location Updates

Too Few Location Updates

Low Paging CostsHigh Update Costs

High Paging CostsLow Update Costs

8IFA’2004

SolutionSolution

Local Areas (GSM) = Registration Areas Local Areas (GSM) = Registration Areas (IS-41)(IS-41)

Registration Area BoundaryRegistration Area Boundary

Center CellCenter Cell

9IFA’2004

Handoff TypesHandoff Types

Intra-CellIntra-Cell Inter-CellInter-Cell

Soft HandoffSoft Handoff Hard HandoffHard Handoff

10IFA’2004

Mobility Management:Mobility Management:Location ManagementLocation Management

Location management enables the system to track the Location management enables the system to track the locations of MTs between consecutive communicationslocations of MTs between consecutive communications

Trade-off between the costs of location update and Trade-off between the costs of location update and paging design optimal location management paging design optimal location management schemes to reduce the overall costschemes to reduce the overall cost

LOCATIONMANAGEMENT

LOCATIONREGISTRATION

(UPDATE)

CALL DELIVERY

AUTHENTICATION

DATABASE UPDATES

DATABASE QUERIES

TERMINAL PAGING

11IFA’2004

Mobility Management:Mobility Management:Handoff ManagementHandoff Management

Handoff management: an MT keeps its connection active Handoff management: an MT keeps its connection active when it moves from one access point to another onewhen it moves from one access point to another one

Four types of handoffs: Four types of handoffs: Network Controlled HandoffNetwork Controlled Handoff (NCHO), (NCHO), Mobile Controlled HandoffMobile Controlled Handoff (MCHO), (MCHO), Network Assisted Network Assisted HandoffHandoff (NAHO), and (NAHO), and Mobile Assisted HandoffMobile Assisted Handoff (MAHO) (MAHO)

HANDOFFMANAGEMENT

NEW CONNECTION GENERATION

USER MOVEMENT

NETWORK CONDITIONS

RESOURCE ALLOCATION

CONNECTION ROUTING

DATA FLOW CONTROL

INITIATION

BUFFERING/SEQUENCING

MULTICAST

12IFA’2004

Location Location ManagementManagement

BACKBONE TELEPHONE NETWORK

(HLR)

Mobile Switching Center

Visitor Location Register

Mobile Terminal(MT)

MSC

VLR

Local Signaling Long Distance Signaling

(MSC)

(VLR)

Home Location Register

13IFA’2004

Location RegistrationLocation Registration

MT enters a new LA, and transmits location update to new BS

BS forwards update to MSC, which queries VLR

Does the MT have an existing record?

New LA is under same VLR. VLR updates the LA ID # for the MT.

Yes No

VLR determines address of HLR, and sends location registration message

HLR authenticates and registers MT by updating the VLR ID # for the MT. Then, HLR cancels former VLR.

14IFA’2004


BS keeps broadcasting Location Area (LA) BS keeps broadcasting Location Area (LA) ID#. ID#.

MT listens to broadcast and will perform a MT listens to broadcast and will perform a location update when:location update when:– Powering upPowering up– Crossing LA boundariesCrossing LA boundaries– After a defined period of timeAfter a defined period of time

15IFA’2004


16IFA’2004

Call DeliveryCall Delivery

Incoming call for roaming MT reaches an MSC

The calling MSC determines the address of the MT’s HLR, and sends a location request message to the HLR.

The HLR sends a route request message to the VLR, which forwards the message to its MSC

The MSC gives the MT a Temporary Local Directory Number, and forwards the TLDN back to the HLR

The HLR forwards this message to the calling MSC, which sets up a route to the MT at its current MSC.

Finally, the current MSC tells all of the BSs in the MT’s LA to send a polling signal to page the MT. When the MT responds, the call is connected.

17IFA’2004

Call DeliveryCall Delivery

18IFA’2004

How is a Cell Phone Call made?How is a Cell Phone Call made?

When a mobile originates a call, a call initiation request is When a mobile originates a call, a call initiation request is sent on the control channel to BS.sent on the control channel to BS.

With this request the mobile transmits its tel number (MIN;With this request the mobile transmits its tel number (MIN; Mobile ID Number), electronic serial number (ESN) and tel Mobile ID Number), electronic serial number (ESN) and tel

number of the called party.number of the called party. Base station receives this data and sends it to the MSC.Base station receives this data and sends it to the MSC. MSC validates the request make connection to the called MSC validates the request make connection to the called

party through the PSTN and instructs base station and party through the PSTN and instructs base station and mobile to use an idle forward and reverse voice channel to mobile to use an idle forward and reverse voice channel to allow conversation to begin.allow conversation to begin.

(in AMPS -> 10-60 voice channels; one control channel in (in AMPS -> 10-60 voice channels; one control channel in each cell base station).each cell base station).

19IFA’2004

Research Areas in Research Areas in Location Location ManagementManagement

Database ArchitecturesDatabase ArchitecturesPaging TechniquesPaging TechniquesMulti-network location Multi-network location

managementmanagementLocation Area DesignLocation Area Design

20IFA’2004

Database Database ArchitecturesArchitectures

CentralizedCentralized– Increase database hierarchyIncrease database hierarchy– Cache user locations at switching pointsCache user locations at switching points– Replicate user profiles at more than one Replicate user profiles at more than one

databasedatabase– Use pointers to follow a path of VLRs to Use pointers to follow a path of VLRs to

the MT’s current locationthe MT’s current location DistributedDistributed

– Database TreesDatabase Trees– PartitioningPartitioning

21IFA’2004

Paging TechniquesPaging Techniques

Blanket pagingBlanket paging– Paging the MS in all cells belonging to an LA Paging the MS in all cells belonging to an LA

simultaneously. simultaneously. Advantage: The delay of the response to paging is kept Advantage: The delay of the response to paging is kept

at a minimum.at a minimum.Disadvantage: Paging has to be done in several cells.Disadvantage: Paging has to be done in several cells.

Closest-cells firstClosest-cells first– The cell where the MS was last seen is paged The cell where the MS was last seen is paged

first followed by subsequent equidistant ring first followed by subsequent equidistant ring of cells.of cells.

– Several rings may be polled simultaneously in Several rings may be polled simultaneously in a paging cycle to keep delay low.a paging cycle to keep delay low.

Sequential pagingSequential paging– Subsequent pages are performed in most likely Subsequent pages are performed in most likely

locations based on past history and distance.locations based on past history and distance.

22IFA’2004

PagingPaging

(MSC)

VLR

23IFA’2004

Location Area Location Area DesignDesign

TradeoffTradeoff– Location Updates versus Terminal Location Updates versus Terminal

PagingPagingGoal: Improvements to tradeoffGoal: Improvements to tradeoffGeographicalGeographicalFixed versus DynamicFixed versus DynamicUser-based versus Global User-based versus Global

definitiondefinitionNetwork-specificNetwork-specific

24IFA’2004

Dynamic Location Update Dynamic Location Update

SchemesSchemes

Movement-basedMovement-based– The MT performs an update each time it The MT performs an update each time it

crosses a certain crosses a certain movement thresholdmovement threshold, , where one movement is made by crossing a where one movement is made by crossing a cell boundary.cell boundary.

Distance-basedDistance-based– The MT performs an update when its The MT performs an update when its

distance from the cell where it performed distance from the cell where it performed its last update surpasses a certain its last update surpasses a certain distance distance thresholdthreshold. .

Time-basedTime-based– The MT performs an update at a constant The MT performs an update at a constant

time thresholdtime threshold, deltaT., deltaT.

25IFA’2004

ExampleExample

A MT is moving through the A MT is moving through the cellular network (R= km) as cellular network (R= km) as shown in the figure at a rate of shown in the figure at a rate of 30km/hour. 30km/hour.

Label the cell ID’s where the MT Label the cell ID’s where the MT will perform its updates for:will perform its updates for:– Movement-based (T=3)Movement-based (T=3)– Distance-based (T=6km)Distance-based (T=6km)– Time-based (30 minutes)Time-based (30 minutes)

3

26IFA’2004

Example FigureExample Figure

A MT is moving A MT is moving through the cellular through the cellular network network (R= km) at a rate of (R= km) at a rate of 30km/hour.30km/hour.

Where will updates be Where will updates be performed for:performed for:– Movement-based (T=3)Movement-based (T=3)

– Distance-based (T=6km)Distance-based (T=6km)

– Time-based (30 minutes)Time-based (30 minutes)

A

D

C

B

H

G

FL

KP

NS

R

QM

J

IE O

3

27IFA’2004

Answer-Movement-Answer-Movement-

basedbased

A

D

C

B

H

G

FL

KP

NS

R

QM

J

IE O

T = 3, 2 h = 3Update at S and G

28IFA’2004

Answer-Distance-Answer-Distance-basedbased

A

D

C

B

H

G

FL

KP

NS

R

QM

J

IE O

Update at O, and near the M/G border

T=6km

T = 6, 2 h = 3

29IFA’2004

Answer-Time-basedAnswer-Time-based

A

D

C

B

H

G

FL

KP

NS

R

QM

J

IE O

Update only at M

3h*2

15km.30km/hour*0.5hoursevery update 1

-- minutes 30

30IFA’2004

Group ProblemGroup Problem

Design a location update and Design a location update and paging scheme. paging scheme. – Provide a diagram with Provide a diagram with

numbered steps.numbered steps.– Explain how your scheme Explain how your scheme

reduces the signaling reduces the signaling overhead.overhead.

31IFA’2004

HandoffHandoff

The transfer of a mobile terminal’s active connection(s) from one channel to another.

Hard handoffs vs. soft handoffs– Hard handoff: break old connection, then form

new connection. – Soft handoff: Connect to several BSs

simultaneously.In CDMA, handoff does not change the physical

channel, it just changes the BS that handles the channel.

32IFA’2004

SIGNAL STRENGTHSIGNAL STRENGTH

Cellular systems depend on the radio Cellular systems depend on the radio signals received by an MS throughout signals received by an MS throughout the cell and on the contours of signal the cell and on the contours of signal strength emanating from the BSs of strength emanating from the BSs of two adjacent cells i and j.two adjacent cells i and j.

33IFA’2004

Select cell i on left of boundary

Select cell j on right of boundary

Ideal Boundary

Cell i

Cell j

-60-

70-80-

90-100

-60-70

-80-90

-100

Signal strength (in dB)

Signal StrengthSignal Strength

34IFA’2004

Signal strength contours indicating actual cell tiling. This happens because of terrain, presence of obstacles and signal attenuation in the atmosphere.

-100

-90-80

-70

-60

-60-70

-80

-90

-100

Signal Strength

(in dB)

Cell i

Cell j

Signal Strength (2)Signal Strength (2)

35IFA’2004

SIGNAL STRENGTHSIGNAL STRENGTH

Signal strength goes down as a mobile Signal strength goes down as a mobile terminal moves away from the BS.terminal moves away from the BS.

As the mobile terminal moves away As the mobile terminal moves away from the BS of the cell, the signal from the BS of the cell, the signal strength weakens and the so-called strength weakens and the so-called HANDOFF occurs.HANDOFF occurs.

This implies a radio connection to This implies a radio connection to another adjacent cell.another adjacent cell.

36IFA’2004

BSi

Signal strength due

to BSj

E

X1

Signal strength due

to BSi

BSj

X3

X4

X2

X5 Xth

MS

Pmin

Pi(x) Pj(x)

Pz(x) (for z=1,2) denote the power received at MS from BS z.

By looking at the variation of signal strength from either base station it is possible to decide on the optimum area where handoff can take place.

Handoff RegionHandoff Region

37IFA’2004

HANDOFF REGIONHANDOFF REGION

At XAt X11 the received signal from BS the received signal from BSj j is close to is close to 0 and the signal strength at the mobile 0 and the signal strength at the mobile terminal could be primarily attributed to BSterminal could be primarily attributed to BSii..

Similarly, at distance XSimilarly, at distance X2 2 the signal from BSthe signal from BSii is is negligible.negligible.

To receive and interpret signals correctly at To receive and interpret signals correctly at mobile, the received signal must be at a mobile, the received signal must be at a minimum power level Pminimum power level Pminmin (X (X33 and X and X44), i.e., ), i.e., between Xbetween X33 and X and X44 the mobile terminal can the mobile terminal can be served either by BSbe served either by BSii or BS or BSjj..

38IFA’2004


The area between XThe area between X33 and X and X4 4 is called is called HANDOFF AREA or HANDOFF REGION..

Where to perform HANDOFF depends Where to perform HANDOFF depends on many factors.on many factors.

* Do handoff at X* Do handoff at X55 where two BSs where two BSs have equal signal strength.have equal signal strength.

HARD HANDOFF!!!!!HARD HANDOFF!!!!!

39IFA’2004


* Avoid “Ping-Pong Effect”, if the * Avoid “Ping-Pong Effect”, if the mobile moves back and forth between mobile moves back and forth between BSBSii and BS and BSjj

* * SOLUTIONSOLUTION SOFT HANDOFF!!!!: SOFT HANDOFF!!!!:

Continue to maintain both links with Continue to maintain both links with BSBSii and BS and BSjj until the signal strength until the signal strength from BSfrom BSjj exceeds that of B exceeds that of Bi i by some by some pre-specified threshold value E as pre-specified threshold value E as shown by point X in Figure.shown by point X in Figure.

40IFA’2004

Handoff ControlHandoff Control

NCHO (Network-Controlled Handoff) NCHO (Network-Controlled Handoff) – All close-by BSs monitor signal strength from the mobile All close-by BSs monitor signal strength from the mobile

terminal. terminal. – MSC collects data from BSs, decides best candidate BS for MSC collects data from BSs, decides best candidate BS for

the mobile terminal, and initiates the MS’s handoff (CT-2, the mobile terminal, and initiates the MS’s handoff (CT-2, AMPS).AMPS).

– Results in heavy signaling load, handoff delay of many Results in heavy signaling load, handoff delay of many seconds.seconds.

MAHO (Mobile-Assisted Handoff) MAHO (Mobile-Assisted Handoff) – MT monitors signal strength from nearby BSs and reports MT monitors signal strength from nearby BSs and reports

the measurements back to the BS/MSC (twice per second).the measurements back to the BS/MSC (twice per second).– MSC decides best candidate BS and initiates the handoff MSC decides best candidate BS and initiates the handoff

(GSM)(GSM) MCHO (Mobile-Controlled Handoff) MCHO (Mobile-Controlled Handoff)

– MT monitors signal strength from nearby BSs, decides MT monitors signal strength from nearby BSs, decides best candidate BS, and initiates handoff (DECT)best candidate BS, and initiates handoff (DECT)

41IFA’2004

Handoff Handoff ManagementManagement

(Detection &Decision)

Channel Assignment

Radio LinkTransfer

42IFA’2004


Initiation (Detection/Decision)Initiation (Detection/Decision)– The user, the network, or changing channel The user, the network, or changing channel

conditions detect the need for handoff.conditions detect the need for handoff. New connection generation (Channel New connection generation (Channel

Assignment)Assignment)– The network must find new resources for The network must find new resources for

the handoff call the handoff call – The network must also perform any needed The network must also perform any needed

routing operations.routing operations. Data flow control (Radio Link Transfer)Data flow control (Radio Link Transfer)

– Delivery of the data from the old path to the Delivery of the data from the old path to the new path is maintained according to new path is maintained according to agreed-upon service guarantees.agreed-upon service guarantees.

43IFA’2004

Handoff InitiationHandoff Initiation

A balance of user movement A balance of user movement versus network conditionsversus network conditions

Goals:Goals:– Keep user connectedKeep user connected– Minimize network signalingMinimize network signaling– Minimize “ping-pong” handoffsMinimize “ping-pong” handoffs

44IFA’2004

Handoff Initiation—Handoff Initiation—What criteria should cause What criteria should cause handoff?handoff?

1rP2rP

45IFA’2004


Handoff in cellular telephony: Handoff in cellular telephony: – Transfer of a voice call from one BS Transfer of a voice call from one BS

to anotherto another Handoff in WLANs:Handoff in WLANs:

– Transfer of a connection from one Transfer of a connection from one AP (Access Point) to anotherAP (Access Point) to another

Handoff in hybrid networks:Handoff in hybrid networks:– From a BS to another, from an AP to From a BS to another, from an AP to

another, from a BS to an AP, or vice another, from a BS to an AP, or vice versaversa

46IFA’2004

Handoff Decision Handoff Decision Time AlgorithmsTime Algorithms

Traditional algorithms employ thresholdsTraditional algorithms employ thresholds Channel measurements:Channel measurements:

– Received Signal Strength (RSS)Received Signal Strength (RSS)Measures the co-channel interference power and Measures the co-channel interference power and

noisenoise– Alternatively to RSS or in conjunction:Alternatively to RSS or in conjunction:

Path lossPath lossCarrier-to-interference ratio (CIR)Carrier-to-interference ratio (CIR)Signal-to-interference ratio (SIR)Signal-to-interference ratio (SIR)BERBERBlock error rate (BLER)Block error rate (BLER)Symbol error rate (SER)Symbol error rate (SER)Etc.Etc.

47IFA’2004


Goals:Goals:– Keep user connectedKeep user connected– Minimize network signalingMinimize network signaling– Minimize “ping-pong” handoffsMinimize “ping-pong” handoffs

In order to avoid the ping-pong In order to avoid the ping-pong effect, additional parameters are effect, additional parameters are used such as hysteresis margin, used such as hysteresis margin, dwell timers, and averaging windows.dwell timers, and averaging windows.

48IFA’2004


Received Signal Strength (RSS)Received Signal Strength (RSS): The BS whose signal is : The BS whose signal is received with the largest strength is selected.received with the largest strength is selected.

RSS + ThresholdRSS + Threshold: If the RSS of a new BS exceeds that of the : If the RSS of a new BS exceeds that of the current one and the signal strength of the current BS is current one and the signal strength of the current BS is below a threshold.below a threshold.

RSS + HysteresisRSS + Hysteresis: If the RSS of a new BS is greater than : If the RSS of a new BS is greater than that of the old BS by a hysteresis margin.that of the old BS by a hysteresis margin.

RSS + Hysteresis + ThresholdRSS + Hysteresis + Threshold: If the received signal : If the received signal strength of a new BS exceeds that of the current one by a strength of a new BS exceeds that of the current one by a hysteresis margin and the signal strength of the current BS hysteresis margin and the signal strength of the current BS is below a threshold.is below a threshold.

Algorithms + Dwell TimerAlgorithms + Dwell Timer: A timer is started at the instant : A timer is started at the instant when the condition in the algorithm is true. The handoff is when the condition in the algorithm is true. The handoff is performed is the condition continues to be true until the performed is the condition continues to be true until the timer expires.timer expires.

49IFA’2004

Traditional Handoff Traditional Handoff AlgorithmsAlgorithms

What kind of handoff isHappening in A, B, C, D?

50IFA’2004

Sample RSS seen by MS Sample RSS seen by MS traveling in a straight line traveling in a straight line between thembetween them

51IFA’2004

Performance of Handoff Performance of Handoff AlgorithmsAlgorithms

Performance measures (related to voice Performance measures (related to voice connections):connections):– Call blocking probabilityCall blocking probability– Handoff blocking probabilityHandoff blocking probability– Delay between handoff request and Delay between handoff request and

executionexecution– Call dropping probabilityCall dropping probability

Objective: Minimize unnecessary handoffsObjective: Minimize unnecessary handoffs Overlooked issues:Overlooked issues:

– Throughput maximizationThroughput maximization– Maintaining QoS guarantees during and Maintaining QoS guarantees during and

after handoffafter handoff

52IFA’2004

Generic Handoff Generic Handoff Management Management ProcessProcess

(1) Decision to handoff is made (network-controlled, mobile-assisted or controlled)(2) MT registers with visiting database via a handoff announcement(3) New visiting database communicates with home database for authentication

and subscriber profile(4) Home database responds with authentication. Both databases are updated.(5) Home database communicates with old visiting database to clear registration information

for the MT(6) The old visiting database flushes or redirect packets to the new visiting database and removes

the MT form its list.

53IFA’2004

ProblemProblemTime(s)Time(s) 00 2.52.5 55 7.57.5 1010 12.512.5 1515 17.517.5 2020

BS1BS1 -47-47 -57-57 -52-52 -55-55 -60-60 -62-62 -60-60 -65-65 -66-66

BS2BS2 -59-59 -56-56 -55-55 -54-54 -52-52 -51-51 -49-49 --60.560.5

-52-52

BS3BS3 -70-70 -72-72 -75-75 -70-70 -58-58 -50-50 --60.560.5

-62-62 -75-75

BS4BS4 -72-72 -71-71 -65-65 -60-60 -55-55 -53-53 -50-50 -49-49 -56-56

Show the handoff times for:

a) RSSb) RSS + threshold of -60 dBmc) RSS + hysteresis of 10 dBd) RSS + hysteresis of 5 dB + threshold of -55 dBm

54IFA’2004

ProblemProblem Time(s)Time(s) 00 2.52.5 55 7.57.5 1010 12.512.5 1515 17.517.5 2020

BS1BS1 -47-47 -57-57 -52-52 -55-55 -60-60 -62-62 -60-60 -65-65 -66-66

BS2BS2 -59-59 -56-56 -55-55 -54-54 -52-52 -51-51 -49-49 --60.560.5

-52-52

BS3BS3 -70-70 -72-72 -75-75 -70-70 -58-58 -50-50 --60.560.5

-62-62 -75-75

BS4BS4 -72-72 -71-71 -65-65 -60-60 -55-55 -53-53 -50-50 -49-49 -56-56



55IFA’2004

ProblemProblem Time(s)Time(s) 00 2.52.5 55 7.57.5 1010 12.512.5 1515 17.517.5 2020

BS1BS1 -47-47 -57-57 -52-52 -55-55 -60-60 -62-62 -60-60 -65-65 -66-66

BS2BS2 -59-59 -56-56 -55-55 -54-54 -52-52 -51-51 -49-49 --60.560.5

-52-52

BS3BS3 -70-70 -72-72 -75-75 -70-70 -58-58 -50-50 --60.560.5

-62-62 -75-75

BS4BS4 -72-72 -71-71 -65-65 -60-60 -55-55 -53-53 -50-50 -49-49 -56-56



56IFA’2004


BS1BS1 -47-47 -57-57 -52-52 -55-55 -60-60 -62-62 -60-60 -65-65 -66-66

BS2BS2 -59-59 -56-56 -55-55 -54-54 -52-52 -51-51 -49-49 --60.560.5

-52-52

BS3BS3 -70-70 -72-72 -75-75 -70-70 -58-58 -50-50 --60.560.5

-62-62 -75-75

BS4BS4 -72-72 -71-71 -65-65 -60-60 -55-55 -53-53 -50-50 -49-49 -56-56



57IFA’2004


BS1BS1 -47-47 -57-57 -52-52 -55-55 -60-60 -62-62 -60-60 -65-65 -66-66

BS2BS2 -59-59 -56-56 -55-55 -54-54 -52-52 -51-51 -49-49 --60.560.5

-52-52

BS3BS3 -70-70 -72-72 -75-75 -70-70 -58-58 -50-50 --60.560.5

-62-62 -75-75

BS4BS4 -72-72 -71-71 -65-65 -60-60 -55-55 -53-53 -50-50 -49-49 -56-56



58IFA’2004

Problem: SolutionProblem: Solution

59IFA’2004

ExerciseExercise

Time(s)Time(s) 00 2.52.5 55 7.57.5 1010

BS1BS1 -50-50 -58-58 -60-60 -65-65 -62-62

BS2BS2 -55-55 -53-53 -57-57 -65-65 -54-54

BS3BS3 -72-72 -70-70 -55-55 -70-70 -60-60

BS4BS4 -78-78 -75-75 -68-68 -60-60 -57-57


a) RSS BS1-BS?-BS?-BS?-BS?b) RSS + threshold of -60 dBm

BS1-BS?-BS?-BS?-BS?c) RSS + hysteresis of 5 dB

BS1-BS?-BS?-BS?-BS?

Documents

Cellular Network Architecture