1 WP2.4 System performance employing Handoff techniques to overcome platform movement CAPANINA...
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Transcript of 1 WP2.4 System performance employing Handoff techniques to overcome platform movement CAPANINA...
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WP2.4 System performance employing Handoff
techniques to overcome platform movement
CAPANINA Virtual Meeting – July 2005
Konstantinos KatzisUniversity of York
Department of Electronics
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Overview
Intra HAP HandoffWhy Handoff?Footprints and Cells Mobility Models
Six Degrees of FreedomRandom Walk and Reflection
Cell Overlap
Immediate Handoff SimulationDesign Parameters Model ImplementationImmediate Handoff ResultsDiscussion of Results
Improved Handoff ScenarioRandom Acceptance Factor (RAF)Forced Blocked Limit (FBL)
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Why Handoff?
Intra HAP Handoff is required to cope with:Station Keeping
HAP movements contribute on call-dropping.Intra HAP Handoff can reduce call-dropping.
User MovementsMoving “targets” such as trains travelling from cell-to-cell. To ensure continuity in service we need to perform Handoffs.
Traffic Control ManagementIntra HAP handoff can be used to redirect users connected to a highly populated cell to nearby cells in order to minimise blocking levels and ensure fairness in the system.
We will be looking at Station Keeping
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Footprints and Cells
Footprint “Moving”
Cell (Service Area)“Fixed”
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Footprint
Cell (Service Area)1
Cell Boundaries are based on the closest boresight centre
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Mobility Models
Drift - x Drift - y Drift - z
Roll YawPitchx
y
z
6 Degrees of Freedom
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Mobility Model
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Assuming a 20km/h rotation
eg:Rotation Effect
90 Degrees Rotation
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Mobility Models
Random WalkHAP moves at any direction at a predefined speed. HAP position is maintain within the cylindrical boundaries defined in HeliNet.
ReflectionHAP moves from current location to new location at a preddefined speed. The direction and the distance appart of the new location is randomly selected. HAP position is maintain within the cylindrical boundaries defined in HeliNet.
Start
End
Start
End
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Cell Overlap
Cell OverlapCells on the ground overlap each other.Overlapping occurs because of the way the power decreases away from the boresight of the antenna.
Areas Formed Areas are formed on a circular footprint due to
the overlapping with other cell Overlap is maintained between three cells
Channel Allocation
Cell overlap improve use of channel allocation
Users in area B and C can be assigned channels from two or three Base stations respectively.
Intra-cell handoff performance can improve utilising cell overlap
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Immediate Handoff Simulation
Simulation Parameters19 Cells of 3.15km radiusUniformly randomly distributed users within a radius of 9kmUsers sent messages on the uplink to identify the most appropriate beams based on received power signal, CIR levels or Traffic conditionsHandoff is centrally managed at the HAP802.16 TDMA/TDM structure is assumed to be used to allow users to connect to more than one cell simultaneously. All HAP movements are restricted within the HeliNet based model.HAP does not employ any antenna steering mechanismCPE employ antenna steering mechanism
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Immediate Handoff Simulation
X-axis drift ResultsHandoff and Dropping probability performance
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Immediate Handoff Simulation
X-axis drift ResultsHandoff and Dropping probability wrt distance from centre
Speed fixed at : 100km/h
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Immediate Handoff Simulation
X-axis drift ResultsBlocking Probability
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Immediate Handoff Simulation
Reflection, Rotation and Random Walk ResultsHandoff and Dropping probability performance
No Overlap
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Immediate Handoff Simulation
Reflection, Rotation and Random Walk ResultsHandoff and Dropping probability wrt distance from centre
No OverlapSpeed fixed at : 100km/h
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Immediate Handoff Simulation
Reflection, Rotation and Random Walk ResultsHandoff and Dropping probability performance
With Overlap
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Immediate Handoff Simulation
Reflection, Rotation and Random Walk ResultsHandoff and Dropping probability wrt distance from centre
With Overlap
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Immediate Handoff Simulation
Discussion of ResultsUsers at the edge of the cell experience increased number of handoffs. They therefore have an increased probability of being dropped.
Cell Overlap improved QoS by reducing blocking and dropping probability
Dropping probabiltiy in the case of no overlap seems to increase and levels up whereas for the case of overlap it is constantly increasing.
Blocking probability decreases at high speed in the case of no overlap due to the increased number of dropped users
Random Walk causes less Handoffs than other movements tried with the most extreme being the reflection
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Improved Handoff Scenario
Random Acceptance Factor (RAF)Use cell overlap effectivelyEnsure uniform QoS in terms of blocking probability and bits per connection independently from the position of the userThere is a connection between the dropping and blocking probability that needs to be investigated
Forced Blocked Limit (FBL)Connection Admission Control (CAC) based on channel availability in a given cell radius of that of the new user. This will indirectly reserve channels for handing off users.The blocking is expected to increase but in a uniform manner while the dropping should become minimal.