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Introduction Estimate the carrier sensing and Predict interference Before: Symmetric CS relation This paper: Asymmetric CS relation Based on a mesh network testbeds Two links
Citation preview
RSS-based Carrier Sensing and Interference Estimation in 802.11 Wireless Networks
Jeongkeun Lee*, Sung-Ju Lee+, Wonho Kim*, Daehyung Jo*, Taekyoung Kwon* and Yanghee Choi*
IEEE SECON 2007
Outline
Introduction Carrier sense and Interference relation RSS based prediction Evaluation Conclusion
Introduction
Estimate the carrier sensing and Predict interference Before:
Symmetric CS relation This paper:
Asymmetric CS relation
Based on 802.11a mesh network testbeds Two links
Carrier sensing and Interference relation
In 802.11a systems Energy-detection carrier sensing threshold
20dB (6 Mbps) CS range Communication range≦
RSS: receiver signal strength
Carrier sensing and Interference relation
C1 : Y (L2 can be sensed by L1)F1: Y (L1 suffers interference form L2)
Two Link Topologies
Mutual CS
No interference (INT)Mutually hidden INT
Mutual INT
One-way hidden INT
Normalized link throughput/goodput UDP packets: 1000bytes PHY rate: 6Mbps Broadcast/unicast transmission period: 30s TX throughput (traffic rate) RX goodput (traffic rate successfully delivere
d)
RSS based prediction
RSS Measurement Methodology Carrier Sensing and TX Throughput Predict
ion Interference and RX Goodput Prediction
RSS Measurement Methodology
Broadcast hello messages 6 Mbps High power and normal power
HP = NP + Y dB
Carrier Sensing and TX Throughput Prediction
RSSlow
RSShigh
Carrier Sensing and TX Throughput Prediction
S1
R1
S2
R2
r1= S1 estimates by the RSS of hellos form S2
TX1 =1- C*TXdef,1^ ^
Interference and RX Goodput Prediction
SIR at R1 : sir1 = r11 –r21 (dB)SIR : signal-to-interference-ratio
Evaluation
Testbed in HP labs(HPL) 11 nodes 200 hello packet for each node 9hrs
Evaluation
Conclusion
RSS based prediction Physical layer capture Hidden interference
In experiments O(n) measurement overhead
Future work Different chipsets Many interferers
Thank for your listening
Occurrence Frequency
10-node testbed in HP labs(HPL) 11-node testbed in Seoul National Uni
versity (SNU)
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