Quality-of-Service
Routing in Ad-Hoc Network Using OLSR
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Ying Ge1, Thomas Kunz2,
Louise Lamont1 |
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1 Communications Research
Center |
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2 Carleton University |
Difficulties in QoS
Routing
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Link state metrics should be available
and manageable |
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Link quality changes quickly and
continuously due to node movement and surrounding changes |
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Computational cost and protocol
overhead affect the performance of the QoS routing protocol |
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Protocol performance evaluation is
complex |
Proactive QoS Routing
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Advantages |
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suitable for the unpredictable nature
of Ad-Hoc networks |
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suitable for the requirement of quick
reaction to QoS demands |
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makes call admission control possible |
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avoids the waste of network resources |
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Disadvantages |
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introduces additional protocol overhead |
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trade-off between the QoS performance
and traditional protocol performance |
Description of OLSR
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Selects MPR to cover 2-hop neighbors |
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Exchanges neighbor/MPR information in
Hello message |
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Generates and relays TC message to
broadcast topology information |
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Reduces control overhead by limiting
MPR set |
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In the graph, B selects C as MPR |
QoS Versions of OLSR
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OLSR protocol does not guarantee to
find the best bandwidth route |
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Three heuristics are proposed to
enhance OLSR in bandwidth aspect |
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The heuristics select good bandwidth
neighbor as MPR |
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Based on evaluation in static network
scenarios, heuristic … is chosen |
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In the previous network topology, B
selects A,F as MPRs |
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Simulations in OPNET
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Implement heuristic in OPNET |
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Define different bandwidth updating
threshold to compare the performance (20% OLSR, 40% OLSR, 80% OLSR) |
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Revise Wireless LAN model to compute
idle time, which reflects link available bandwidth |
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Piggyback idle time info in Hello and
TC messages |
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Computing best bandwidth routes based
on available topology |
Simulation Results I –
Basic Performance
Simulation Result II –
QoS Performance
Analysis of Results (Cost
Introduced by the QoS Versions of OLSR)
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More MPRs are selected; more TC
messages are generated and relayed |
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The additional control messages
increase the Wireless LAN network load |
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The overlap of 2-hop neighbors covered
by MPRs causes TC collision |
Analysis of Results –
(Achievement Gained by the QoS Versions of OLSR )
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Outperforms the original OLSR protocol
in bandwidth aspect |
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In a dense network, the 40% OLSR finds
the best bandwidth route |
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In a sparse network, the 20% OLSR finds
the best bandwidth route |
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There is a trade-off, so must select
routing algorithms based on the request of the data application |
Thank You!