1 WP2.4 System performance employing Handoff techniques to overcome platform movement CAPANINA Virtual Meeting – July 2005 Konstantinos Katzis University of York Department of Electronics

2 Overview Intra HAP Handoff Why Handoff? Footprints and Cells Mobility Models Six Degrees of Freedom Random Walk and Reflection Cell Overlap Immediate Handoff Simulation Design Parameters Model Implementation Immediate Handoff Results Discussion of Results Improved Handoff Scenario Random Acceptance Factor (RAF) Forced Blocked Limit (FBL)

3 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 Movements Moving “targets” such as trains travelling from cell-to-cell. To ensure continuity in service we need to perform Handoffs. Traffic Control Management Intra 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

4 Footprints and Cells Footprint “Moving” Cell (Service Area) “Fixed” Footprint Cell (Service Area) 1 Cell Boundaries are based on the closest boresight centre

5 Mobility Models Drift - x Drift - y Drift - z Roll YawPitch x y z 6 Degrees of Freedom

6 Mobility Model Assuming a 20km/h rotation eg:Rotation Effect 90 Degrees Rotation

7 Mobility Models Random Walk HAP moves at any direction at a predefined speed. HAP position is maintain within the cylindrical boundaries defined in HeliNet. Reflection HAP 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

8 Cell Overlap Cells 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

9 Immediate Handoff Simulation Simulation Parameters 19 Cells of 3.15km radius Uniformly randomly distributed users within a radius of 9km Users sent messages on the uplink to identify the most appropriate beams based on received power signal, CIR levels or Traffic conditions Handoff is centrally managed at the HAP 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 mechanism CPE employ antenna steering mechanism

10 Immediate Handoff Simulation X-axis drift Results Handoff and Dropping probability performance

11 Immediate Handoff Simulation X-axis drift Results Handoff and Dropping probability wrt distance from centre Speed fixed at : 100km/h

12 Immediate Handoff Simulation X-axis drift Results Blocking Probability

13 Immediate Handoff Simulation Reflection, Rotation and Random Walk Results Handoff and Dropping probability performance No Overlap

14 Immediate Handoff Simulation Reflection, Rotation and Random Walk Results Handoff and Dropping probability wrt distance from centre No Overlap Speed fixed at : 100km/h

15 Immediate Handoff Simulation Reflection, Rotation and Random Walk Results Handoff and Dropping probability performance With Overlap

16 Immediate Handoff Simulation Reflection, Rotation and Random Walk Results Handoff and Dropping probability wrt distance from centre With Overlap

17 Immediate Handoff Simulation Discussion of Results Users 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

18 Improved Handoff Scenario Random Acceptance Factor (RAF) Use cell overlap effectively Ensure uniform QoS in terms of blocking probability and bits per connection independently from the position of the user There 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.

19 Questions? Konstantinos Katzis

20 Document Properties