raindrop: a multi-rate multi-channel wireless lan tianbo kuang qian wu carey williamson department...
Post on 19-Dec-2015
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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
Outline
• Problem Statement and Motivation
• Multi-Rate Multi-Channel (MRMC) protocol
• Simulation Evaluation of MRMC
• Summary and Conclusions
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 Lucent’s WaveLAN-II)
• This is both a good thing and a bad thing...
AP
MH MH
MHMH
1 Mbps
11Mbps11Mbps
1 Mbps
when sharing the same physical channel
Performance Anomaly of IEEE 802.11b [Heusse et al. 2003]
• An ns-2 network simulation experiment showing the problem
35 m
< 8 m
start at time = 0 s
start at time = 150 s
Node 0
Node 1
Node 2 Node 3
Server
100 Mbps
APRange = 45m
Throughput of Node 0 versus time (before vs after)
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
1 Mbps
2 Mbps
5.5 Mbps
11 Mbps
RainDrop: A Multi-Rate Multi-Channel WLAN
AP
Notes: 4x antenna “cost” (?)+77% capacity
Multi-Rate Multi-Channel (MRMC) MAC protocol
• Channel association algorithm
1. Beacon (channel, transmission rate, SNR threshold)
2. Get SNR3. Channel association frame
4. Channel association grant
SNRavg = αlpha * SNRavg + (1- αlpha) * SNRnew
APMH
Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of αlpha on throughput
• stationary scenario:
5, 15, 25, 35m
AP
MH
Server
100 Mbps
Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of αlpha on throughput
• stationary scenario:
5, 15, 25, 35m
AP
MH
Server
100 Mbps
mobile scenario:
< 45m
100 Mbps
Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of αlpha on throughput
• stationary scenario:
5, 15, 25, 35m
AP
MH
Server
100 Mbps
mobile scenario:
< 45m
100 Mbps
Simulation Evaluation of the MRMC protocol (ns-2)
Experiment 1. Effect of αlpha on throughput
• stationary scenario:
5, 15, 25, 35m
AP
MH
Server
100 Mbps
mobile scenario:
< 45m
100 Mbps
Experimental Factors
• Experiment 1: Effect of alpha
Stationary Mobile
Distance to AP 5m, 15m, 25m, 35m < 45m
Mobile Speed 0 m/s 0.5m/s, 1m/s, 2m/s, 3m/s, 4m/s
αlpha 0, 0.1,…0.9, 0.92, 0.94,…0.98
Wireless Channel Model: Rayleigh fading, Jakes’ method
Simulation Results: Effect of αlpha on Throughput
stationary mobile
SNRavg = αlpha * SNRavg + (1- αlpha) * SNRnew
Simulation Evaluation of the MRMC Protocol (ns-2)
Expt 2. MRMC performance in a stationary scenario
(comparison to results for previous problem scenario)
Simulation Evaluation of the MRMC Protocol (ns-2)
AP
Server
100 Mbps
Node 1
Node N
< 45m
< 45m
Experiment 3. Static scenario with N mobile hosts
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
Simulation Results
Total Throughput Per-Node Throughput
Simulation Evaluation of the MRMC Protocol (ns-2)
AP
Server
100 Mbps
< 45m
< 45m
Node 1
Node 20
Experiment 4. Mobile scenario with 20 hosts
Simulation Evaluation of the MRMC Protocol (ns-2)
AP
Server
100 Mbps
< 45m
< 45m
Node 1
Node 20
Experiment 4. Mobile scenario with 20 hosts
Simulation Evaluation of the MRMC Protocol (ns-2)
AP
Server
100 Mbps
< 45m
< 45m
Node 1 Node 20
Experiment 4. Mobile scenario with 20 hosts
Simulation Evaluation of the MRMC Protocol (ns-2)
AP
Server
100 Mbps
< 45m
< 45m
Node 1
Node 20
Experiment 4. Mobile scenario with 20 hosts
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)
Simulation Results
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
Future Work: Multiple APs