RainDrop: A Multi-Rate Multi-Channel Wireless LAN

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RainDrop A Multi-Rate Multi-Channel Wireless
LAN
Tianbo Kuang Qian Wu Carey Williamson
Department of Computer Science University of
Calgary
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Outline

• Problem Statement and Motivation
• Multi-Rate Multi-Channel (MRMC) protocol
• Simulation Evaluation of MRMC
• Summary and Conclusions

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Problem Statement

• The IEEE 802.11b WLAN supports automatic rate
  selection
• Each station dynamically chooses its
  transmission rate of either 1, 2, 5.5, or 11
  Mbps, depending on channel conditions (e.g.,
  rate selection algorithm in Lucents WaveLAN-II)
• This is both a good thing and a bad thing...

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Performance Anomaly of IEEE 802.11b Heusse et
al. 2003

• An ns-2 network simulation experiment showing
  the problem

Node 0
Server
start at time 150 s
start at time 0 s
Node 1
100 Mbps
AP
Node 2
Node 3
Range 45m
lt 8 m
35 m
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Throughput of Node 0 versus time (before vs after)
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Our Solution Multi-Rate Multi-Channel (MRMC)
WLAN

• Use multiple physical channels (3 or 4)
  simultaneously at AP, each with a different
  transmission rate (static or dynamic)

1 Mbps
2 Mbps
5.5 Mbps
11 Mbps
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RainDrop A Multi-Rate Multi-Channel WLAN
Notes 4x antenna cost (?) 77 capacity
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Multi-Rate Multi-Channel (MRMC) MAC protocol

• Channel association algorithm

1. Beacon (channel, transmission rate, SNR
threshold)
2. Get SNR
3. Channel association frame
MH
AP
4. Channel association grant
SNRavg alpha SNRavg (1- alpha) SNRnew
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Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of alpha on throughput
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Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of alpha on throughput
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Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of alpha on throughput
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Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of alpha on throughput
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Experimental Factors

• Experiment 1 Effect of alpha

Stationary Mobile
Distance to AP 5m, 15m, 25m, 35m lt 45m
Mobile Speed 0 m/s 0.5m/s, 1m/s, 2m/s, 3m/s, 4m/s
alpha 0, 0.1,0.9, 0.92, 0.94,0.98 0, 0.1,0.9, 0.92, 0.94,0.98
Wireless Channel Model Rayleigh fading, Jakes
method
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Simulation Results Effect of alpha on Throughput
SNRavg alpha SNRavg (1- alpha) SNRnew
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Simulation Evaluation of the MRMC Protocol (ns-2)
Expt 2. MRMC performance in a stationary
scenario (comparison to results for previous
problem scenario)
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Simulation Evaluation of the MRMC Protocol (ns-2)
Experiment 3. Static scenario with N mobile hosts
Server
Node N
AP
lt 45m
100 Mbps
lt 45m
Node 1
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Experimental Factors and Performance Metrics

• Factors

• Number of nodes N 2, 4, 6,50
• MAC layer protocols MRMC, WaveLAN-II

• Metrics

• Total throughput of nodes (99 confidence
  intervals)
• Mean throughput for each node

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Simulation Results
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Simulation Evaluation of the MRMC Protocol (ns-2)
Experiment 4. Mobile scenario with 20 hosts
Server
AP
lt 45m
100 Mbps
lt 45m
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Simulation Evaluation of the MRMC Protocol (ns-2)
Experiment 4. Mobile scenario with 20 hosts
Server
AP
lt 45m
100 Mbps
lt 45m
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Simulation Evaluation of the MRMC Protocol (ns-2)
Experiment 4. Mobile scenario with 20 hosts
Server
AP
lt 45m
100 Mbps
lt 45m
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Simulation Evaluation of the MRMC Protocol (ns-2)
Experiment 4. Mobile scenario with 20 hosts
Server
AP
lt 45m
100 Mbps
lt 45m
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Experimental Factors and Performance Metrics

• Factors

• Mean moving speed 0.5 m/s, 1 m/s, 2 m/s, 3 m/s,
  4 m/s
• MAC layer protocols MRMC, WaveLAN-II

• Metrics

• Total throughput of nodes (99 confidence
  intervals)

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Simulation Results
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Conclusions

• The proposed MRMC protocol is promising
• Performance is not very sensitive to value of
  alpha
• With 4 channels and 4 rates, the MRMC protocol
  offers a 450 throughput advantage over the
  WaveLAN-II IEEE 802.11b MAC protocol
• Super-linear throughput improvement (450)
  from 77 increase in channel capacity (4x cost?)
• Primary benefit isolating low-rate/high-rate
  users

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Future Work Multiple APs
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Questions?