robert morris daniel aguayo, john bicket, sanjit biswas, douglas de couto
DESCRIPTION
MIT Roofnet Performance. Robert Morris Daniel Aguayo, John Bicket, Sanjit Biswas, Douglas De Couto http://pdos.lcs.mit.edu/roofnet. Roofnet node map. 1 kilometer. Typical rooftop view. Roofnet radio links. 1 kilometer. A Roofnet Self-Installation Kit. 50 ft. Cable ($40) - PowerPoint PPT PresentationTRANSCRIPT
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Robert MorrisDaniel Aguayo, John Bicket,
Sanjit Biswas, Douglas De Couto
http://pdos.lcs.mit.edu/roofnet
MIT Roofnet Performance
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Roofnet node map
1 kilometer
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Typical rooftop view
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Roofnet radio links
1 kilometer
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A Roofnet Self-Installation Kit
Computer ($340)533 MHz PC, hard disk, CDROM
802.11b card ($155)Engenius Prism 2.5, 200mW
Software (“free”)Our networking software based on Click
Antenna ($65)8dBi, 20 degree vertical
Miscellaneous ($75)Chimney Mount,Lightning Arrestor, etc.
50 ft. Cable ($40)Low loss (3dB/100ft)
Takes a user about 45 minutes to install on a flat roof
Total: $685
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Roofnet Node Software
802.11 eth
Linux TCP/IP
Click
Linux Kernel
User-space
sshd apachedhcpd
antenna
Living-roomethernet
NAT
srcrr
ETX
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Roofnet link quality distribution
Node Pair
Pack
et
Deliv
ery
Pro
bab
ility
1 megabit/second
11 mbits/sec
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S/N vs loss w/ cable + attenuator
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S/N vs loss for Roofnet links
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Transmit bit-rate choice
Node Pair
Pack
ets
/seco
nd
rece
ived 11 megabits/second
5.5
2
1
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Basic Roofnet performance
Hops NodePairs
ThroughputKilobits/sec
Latency
ms
1 179 2528 12
2 354 784 22
3 354 368 39
4 256 272 44
5 127 216 61
6 43 248 81
7 38 184 72
8 17 168 98
9 6 152 121
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Multi-hop packet loss?
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What is a typical radio range?
Distance (Meters)
Deliv
ery
pro
bab
ility
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Effect of transmit power level
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Would a less-dense mesh work?
Nodes
Connectivity
Throughput
Kilobits/sec
Hop Count
4 17% 16 1.3
9 50% 80 2.2
14 95% 144 3.0
19 100% 224 3.5
24 100% 256 3.5
29 100% 256 3.2
34 100% 320 3.3
• Roofnet is about twice as dense as it needs to be• Higher densities provide higher throughput
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Mesh versus access points
APs or gatewa
ys
AP throughp
ut
AP connectio
ns
Mesh throughp
ut
1 160 25 952
2 688 34 1616
3 864 38 1880
4 1144 40 2096
5 1152 41 2040
6 1608 41 2184
7 1856 41 2296
• 5 APs are required for full connectivity• N mesh gateways give higher throughput than N APs
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Conclusions
• Roofnet provides Internet access to 40+ users• Easy for users to install, self-configuring• Throughput > 200 kilobits/second for most
users• Even 9-hop routes average 150 kilobits/second• Radio range up to 2km, density 10 nodes/km2
• Hard to beat mesh performance w/ access points
• Multi-hop packet loss costs about a factor of two
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How reliant on the “best” nodes? A
vera
ge T
hro
ugh
pu
t (K
B/s
)
Number of Best Nodes Eliminated