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Transcript of 1G PERSONAL COMMUNICATION SYSTEMS: MOBILITY MANAGEMENT (PART II) Ian F. Akyildiz Broadband &...
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
Location RegistrationLocation Registration
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
Location RegistrationLocation Registration
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
HANDOFF REGIONHANDOFF REGION
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
HANDOFF REGIONHANDOFF REGION
* 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
Handoff Handoff ManagementManagement
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 Handoff ManagementManagement
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
Handoff Decision Handoff Decision Time AlgorithmsTime Algorithms
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
Handoff Decision Handoff Decision Time AlgorithmsTime Algorithms
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
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
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
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
56IFA’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
57IFA’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
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
Show the handoff times for:
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?