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Multirate Anypath Routing in Wireless Mesh Networks Rafael Laufer †, Henri Dubois-Ferrière ‡,...
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Transcript of Multirate Anypath Routing in Wireless Mesh Networks Rafael Laufer †, Henri Dubois-Ferrière ‡,...
Multirate Anypath Routing in Wireless Mesh Networks
Rafael Laufer†, Henri Dubois-Ferrière‡, Leonard Kleinrock†
Acknowledgments to Martin Vetterli and Deborah Estrin
†Computer Science Department
University of California at Los Angeles
‡Riverbed Technology, Inc.
Lausanne, Switzerland
Loss and Instability
M. Lukac, Measuring Wireless Link Quality, 2007
Wireless Networks
Different properties for the wireless medium Lossy and unstable links Limited transmission range Collisions and hidden terminals Intra- and inter-flow interference Broadcast nature
Same routing paradigm for wireless networks? Can the broadcast medium work in our favor?
Anycast Forwarding
Packet sent to multiple nodes simultaneously High chance of at least one node receiving it Node with the shortest distance forwards it on Coordination with overhearing and suppression
Anypath Routing
Every node forwards the packet to a set of nodes A set of paths from the source to the destination This set of paths is called an anypath
Our Contributions
Potential issues with single-rate anypath routing New routing paradigm for wireless networks
Anypath routing with multiple bit rates
Rate diversity imposes new challenges Introduction of a routing metric for multirate Routing algorithm for a single and multiple rates
Not exponential Same complexity as Dijkstra’s and optimal
Indoor 18-node 802.11b testbed measurements
Single-Rate Anypath Routing
Under-utilization of available bandwidth resources Some hyperlinks perform well at higher rates Others may only work at low rates
Transmission Rate
De
live
ry p
rob
abi
lity
Optimal operation point
Single-Rate Anypath Routing
Network disconnection at high rates Higher rates have a shorter transmission range Significant decrease in network density Lossier links and eventually disconnection Connectivity guaranteed only at low rates!
Multirate Anypath Routing
Every node forwards the packet to a set of nodes A transmission rate for each forwarding set A set of paths with potentially different rates We call this a multirate anypath
Challenges
Loss ratios usually increase with rate Higher rate is not always beneficial
Shorter radio range for higher rates Different connectivity and density for each rate Higher rates
Less spatial diversity and more hops between nodes Lower rates
More spatial diversity and less hops between nodes How to choose both the forwarding set and rate?
Shortest multirate anypath problem
Multirate Anypath Cost
What is the cost of a multirate anypath? Composed of two different components
Hyperlink cost Remaining cost
diJ DJ
diJ
DJ
i
J
(r)
(r)
(r) (r)
Expected transmission time (ETT) Average time used to transmit a packet Assuming a link with delivery probability Transmission rate and packet size
Expected anypath transmission time (EATT) Tradeoff between bit rate and delivery probability
Routing Metric
Remaining Cost
Weighted average of the distances of nodes in J
If D1 ... Dn, node j is the relay with probability
Weight wj(r) defined as
with
The Single-Rate Case
Link-state routing protocol Shortest Anypath First algorithm Running time of O(V log V + E)
0
.4 .6
.4
.6
.3
.3
.5
.8
.2
.7.8 .9
.7
.6
.9
.5
.7
.5
.3
.2
.2
.9
.4
.7
0
4040
60
60
404060
6084
60
78
6090
757590
87
82
78
82
73738685
89
85
89s
d
0
The Single-Rate Case
Link-state routing protocol Shortest Anypath First algorithm Running time of O(V log V + E)
.2 .1
.1
.5
.2
.1
.2
.4
.1
.2.2 .4
.2
.3
.6
.1
.3
.4
.3
.1
.2
.2
.2
.2
0
20
90
87
80
6960
62
6538
30
24
sd
0
The Multirate Case
Shortest Multirate Anypath First algorithm A distance estimate for each rate Running time of O(V log V + ER)
(.4,.2) (.6,.1)
(.4,.1)
(.6,.5)
(.3,.2)
(.3,.1)
(.5,.2
)
(.8,.4)
(.2,.1)
(.7,.2) (.8,.2
) (.9,.4)(.7,.2)
(.6,.3)
(.9,.6)
(.5,.1)
(.5, .4)
(.3,.3)
(.2,.1)
(.2,.2)(.9,.2)
(.4,.2
)
(.7,.2)
0
(.7, .3)
4040
60
60
2030
30
20292424448444
30
3870
43
5090
60
3870
43
38
43
5365
62
53
4343
58
73
7358
435753
53
56
5764
53
57
53
11357
65
70
66
69
6565
706868
Di(r)
sd
Shortest Multirate Anypath First
Why does it work? Three properties assuming D1 D2 ... Dn
Property 1 Shortest forwarding set is of the form J = {1, 2,..., j}
D1
D2
D3
Shortest Anypath First
Why does it work? Still assuming D1 D2 ... Dn
Property 2 Nodes are settled in order {1, 2,...,n} Forwarding sets tested in order {1}, {1, 2},..., {1, 2,..., j}
{1}{1,2}{1,2,3}
D1
D2
D3
DiDi’Di’’
Shortest Multirate Anypath First
Why does it work? Still assuming D1 D2 ... Dn
Property 3 Distance using {1} higher than distance using {1,2},
which is higher than using {1,2,3}, until {1, 2,..., j}
Di Di’ Di’’
{1}{1,2}{1,2,3}
D1
D2
D3
Shortest Multirate Anypath First
Putting it all together Three properties assuming D1 D2 ... Dn
Shortest forwarding set is of the form J = {1, 2,..., j} Forwarding sets tested in order {1}, {1, 2},..., {1, 2,..., j} Distance using {1} higher than distance using {1,2},
which is higher than using {1,2,3}, until {1, 2,..., j}
All properties and optimality proven in the paper
802.11b Indoor Testbed
802.11b Indoor Testbed
Stargate microserver Intel 400-MHz Xscale PXA255 processor 64 MB of SDRAM Linux OS
SMC EliteConnect SMC2532W-B PCMCIA IEEE 802.11b Prism2 chipset and HostAP driver Maximum transmission power of 200 mW Proprietary power control algorithm
802.11b Indoor Testbed
Wireless mesh network 3-dB omni-directional rubber duck antenna 30-dB SA3-XX attenuator Weaker signal during both transmission and reception Larger distance emulated
Network diameter At 11 Mbps, up to 8 hops with 3.1 hops on average At 1 Mbps, up to 3 hops with 1.5 hops on average
802.11b Indoor Testbed
Software Click modular router MORE software package Modified HostAP driver Raw 802.11 frames
Measure the delivery probability of each link 1500-byte frames Transmitted at 1, 2, 5.5 and 11 Mbps
Distribution of Delivery Probabilities
Evaluation Metric
Multirate anypath routing Always lower cost than single-rate anypath
Gain of multirate over single-rate anypath Ratio between single-rate and multirate distances How many times is multirate anypath better?
GDi
Di’=
Gain of Multirate Anypath Routing
Transmission Rate Distribution
Conclusions
Opportunistic routing paradigm for multiple rates Range and delivery probability change with rate Shortest multirate anypath problem Introduction of the EATT routing metric Shortest Multirate Anypath First algorithm Measurements from an indoor 802.11b testbed
Single rate may lead to network disconnection Multirate outperforms 11-Mbps anypath routing by 80%
on average and up to 6.4x with full connectivity Distribution of bit rates not concentrated at any rate
Multirate Anypath Routing in Wireless Mesh Networks
Rafael Laufer†, Henri Dubois-Ferrière‡, Leonard Kleinrock†
Acknowledgments to Martin Vetterli and Deborah Estrin
†Computer Science Department
University of California at Los Angeles
‡Riverbed Technology, Inc.
Lausanne, Switzerland