The Power Controlled Mac Protocol With Relay Station in AdHoc Wireless Networks

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A Spatial Backoff Algorithm Using the Joint
Control of Carrier Sense Threshold
and Transmission Rate
Authors X Yang, and N Vaidya Source IEEE SECON
2007
Reporter Han-Chiuan Luo Apr. 14th, 2008
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Outline

• Introduction
• Dynamic Spatial Backoff Algorithm
• Performance
• Related Works
• Future Works

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Introduction

• In 802.11 multi-hop ad hoc network
• Aim at improving throughput by Spatial Backoff
• Contending Region
• Smaller
• Three tunable factors
• Power
• Carrier Sense Threshold
• Transmission Rate
• 802.11a 54, 36, 18, 9 Mbps

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Spatial Backoff
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Contending Region(one active successful sending)
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A Smaller Contending Region

• More concurrent transmissions ()
• Reduce the collision probability ()
• Decrease transmission rate (-)
• Reduce the rate-independent MAC overhead ()
• Overhead TR/(PlTR)
• Smaller R ? Smaller Overhead

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CS Threshold ?Contending Region-
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Power- ?Contending Region-
But violate connectivity
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802.11a Rate ? SINR
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Carrier Sense Threshold and Transmission Rate
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Carrier Sense Threshold and Transmission Rate
(con.)
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Carrier Sense Threshold and Transmission Rate
(con.)
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Carrier Sense Threshold and Transmission Rate
(end.)

• CSi RXth/SINRi
• At rate Ratei using CSi fails ?
• no more benefit in reducing the CS threshold

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Dynamic Spatial Backoff Algorithm
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Performance
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Performance (con.)
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Performance (con.)
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Performance (con.)
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Related Works

• Temporal contention resolution
• Dynamically adjusts the CS threshold
• Adapt transmission rate
• Transmission power CS threshold

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Future Works

• Power rate
• Power rate CS threshold

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Thanks!