on the capacity of wireless csma/ca multihop networks
Post on 23-Feb-2016
76 Views
Preview:
DESCRIPTION
TRANSCRIPT
1
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
On the Capacity ofWireless CSMA/CA Multihop NetworksRafael Laufer and Leonard KleinrockBell Labs, UCLAIEEE INFOCOM 2013
2
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Carrier sense multiple access with collision avoidance (CSMA/CA) Before transmitting, the node verifies if the medium is idle via
carrier sensing If idle, sample a random back-off interval and starts counting down Whenever busy, freeze the counter and wait for ongoing
transmission to finish
INTRODUCTIONWireless CSMA/CA Multihop Networks
U2(t)
t
21 3
1
1
3
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Considered unpredictable with unknown throughput limitations Distributed nature of CSMA/CA: nodes should back off from each
other Buffer dynamics of unsaturated sources: time-varying subset of
transmitters Dependence of downstream links on upstream traffic: coupled
queue state• Strong dependence among the state of transmitters
Physical proximity and traffic pattern induce correlation across the network
INTRODUCTIONWireless CSMA/CA Multihop Networks
4
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Understand throughput limits of wireless CSMA/CA multihop networks
• Provide answers to specific questions regarding the network capacity If the rate of f1 increases by 10%, how much can f2 still achieve? If f3 starts, by how much must f1 and f2 slow down to keep the network
stable?• Determine the capacity region of arbitrary wireless networks
INTRODUCTIONGoals
f2
f1
f3
5
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Theory to model the behavior of wireless CSMA/CA multihop networks Handle buffer dynamics of unsaturated traffic sources and multihop
flows Respect interference constraints imposed by the wireless medium
• Characterization of the capacity region of any wireless network No restrictions on node placement: suitable for arbitrary networks Agnostic to the distribution of network parameters: only averages
are relevant Convex only when nodes are within range: nonconvex in general
• Feasibility test
INTRODUCTIONKey Contributions
6
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Single-path routing, with routes and bit rates assumed fixed• Omnidirectional antenna communicating in a single channel• CSMA/CA for medium access control• Network state S composed of links transmitting
Knowledge of the feasible link sets in the network• : fraction of time that all links in S are transmitting
MODEL AND ASSUMPTIONSSystem Model
7
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
THROUGHPUT MODELING
8
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SATURATED SINGLE-HOP FLOWSAll Nodes Within Carrier Sense Range
9
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SATURATED SINGLE-HOP FLOWSAll Nodes Within Carrier Sense RangeU1(t)
t
1
U2(t)
tU3(t)
t
10
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• By definition, the steady-state solution is
• Ratio between and
SATURATED SINGLE-HOP FLOWSAll Nodes Within Carrier Sense Range
11
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• System of linear equations
• Steady-state solution
• Throughput of each flow
SATURATED SINGLE-HOP FLOWSAll Nodes Within Carrier Sense Range
12
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SATURATED SINGLE-HOP FLOWSNot All Nodes Within Carrier Sense Range
2
1
3
13
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SATURATED SINGLE-HOP FLOWSNot All Nodes Within Carrier Sense RangeU1(t)
tU2(t)
tU3(t)
t
14
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Steady-state solution for this case
• General solution
• Throughput of each flow
SATURATED SINGLE-HOP FLOWSNot All Nodes Within Carrier Sense Range
15
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
UNSATURATED SINGLE-HOP FLOWSIdle TimeU1(t)
t1
U2(t)
tU3(t)
t
16
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Steady-state solution
• Source behavior Injecting too little traffic: 0 Injecting too much traffic: 1
UNSATURATED SINGLE-HOP FLOWS
17
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Why the solution is similar to the saturated case?
• Statistically equivalent to a saturated network Average transmission times are the same Average backoff times are larger by 1/
UNSATURATED SINGLE-HOP FLOWS
18
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
UNSATURATED SINGLE-HOP FLOWSPrimal Unsaturated NetworkU1(t)
t1
U2(t)
tU3(t)
t
19
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
UNSATURATED SINGLE-HOP FLOWS Dual Saturated NetworkU1(t)
tU2(t)
tU3(t)
t
1
20
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGION CHARACTERIZATION
21
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Normalized throughput of transmitter i
• Express as a function of
• Find the inverse
• Limit the stability factors to the range
CAPACITY REGIONCharacterization Algorithm
22
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGIONTwo Transmitters Within Carrier Sense Range
23
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGIONTwo Transmitters Within Carrier Sense Range
1
y1
y2
1
1
1
2
2
1
121
2
1
21
1
1
12
22 1
1yy
21
11 1
1yy
01
11
02 12
24
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGIONThree Transmitters Within Carrier Sense Range
25
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGIONThree Transmitters Within Carrier Sense Range
1y1
y21
y31
26
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGIONThree Transmitters Not Within Carrier Sense Range
2
1
3
27
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGIONThree Transmitters Not Within Carrier Sense Range
1
y1
y2
1
1
1
2
2
1
111121
2
1
11121
111
1
11
112
21
22
2
yyyy
21
11 1
1yy
Capacity lost due to the lack of synchronization between
nodes
28
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
CAPACITY REGIONThree Transmitters Not Within Carrier Sense Range
1y1
y21
y31
29
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
FEASIBILITY TEST
30
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Does the network support a given rate vector ?
• Normalized throughput depends only on average values approximates the total transmission time as approximates the total time as
• Plug into the expression and check if
FEASIBILITY TESTFeasibility of Input Rates
31
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SIMULATION RESULTS
32
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SIMULATION SCENARIOMIT Roofnet Network: Single-Hop Flows
33
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SIMULATION RESULTSSingle-Hop Flows (ρ = 1.00)
34
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SIMULATION RESULTSSingle-Hop Flows (ρ = 0.50)
35
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SIMULATION RESULTSSingle-Hop Flows (ρ = 0.25)
36
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
SIMULATION RESULTSSingle-Hop Flows (ρ = 0.01)
37
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
• Capacity of wireless CSMA/CA multihop networks poorly understood
• Theory able to model the network behavior Buffer dynamics of unsaturated sources and multihop flows Wireless CSMA/CA multihop networks are not erratic, but
predictable• System of nonlinear equations characterizes the network capacity Agnostic to the distribution of network parameters, only averages
relevant• Knowledge of the underlying process governing CSMA/CA
networks Opens up new areas of research Routing optimization and network provisioning
CONCLUSIONS
38
COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
On the Capacity ofWireless CSMA/CA Multihop NetworksRafael Laufer and Leonard KleinrockBell Labs, UCLAIEEE INFOCOM 2013
top related