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Introduction There are two broad ways to achieve less energy consumption There are two broad ways to achieve less energy consumption –Topology control by making the topology sparser, the ambient interference is reduced –Power control
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Adaptive Power Control Adaptive Power Control Algorithm for Ad Hoc Networks Algorithm for Ad Hoc Networks with Short and Long Term with Short and Long Term Packet CorrelationsPacket Correlations
Jun Zhang, Zuyuan Fang, and Brahim BensaouJun Zhang, Zuyuan Fang, and Brahim BensaouDept. of Computer Science, The Hong Kong UnivDept. of Computer Science, The Hong Kong University of Science and Technologyersity of Science and TechnologyIEEE Conference on Local Computer Networks (LIEEE Conference on Local Computer Networks (LCN), 2005CN), 2005
OutlineOutline IntroductionIntroduction Adaptive Power Control Based Adaptive Power Control Based
Packet Delivery CurvePacket Delivery Curve Correlative Adaptive Power Correlative Adaptive Power
Control (CAPC)Control (CAPC) Performance evaluationPerformance evaluation ConclusionConclusion
IntroductionIntroduction There are two broad ways to There are two broad ways to
achieve less energy consumptionachieve less energy consumption– Topology control Topology control
by making the topology sparser, the by making the topology sparser, the ambient interference is reducedambient interference is reduced
– Power controlPower control
Basic Concept of Basic Concept of Power Control Power Control ProtocolsProtocols To adjust the transmission power To adjust the transmission power
(TP) level to the suitable level (TP) level to the suitable level according to the network according to the network conditioncondition
Major Differences of Major Differences of Power Control Power Control ProtocolsProtocols The major difference between The major difference between
most power control algorithms most power control algorithms lies inlies in
1.1. How to adapt the power to the How to adapt the power to the network statusnetwork status
2.2. What metric to use to reflect the What metric to use to reflect the network statusnetwork status
3.3. How to track such statusHow to track such status
Packet Delivery Curve Packet Delivery Curve ExampleExample
# of transmitted packets
# of packets received
successfully
Feasible and Infeasible Feasible and Infeasible Packet CurvesPacket Curves
L: the longest streakof packet losses
M: packet deliverycurve count limit
Packet Delivery Curves Packet Delivery Curves (C2)(C2) Case 1 : curve drops below Case 1 : curve drops below
SS = = pp * ( * ( TT – – LL ), it means either ), it means either– Avg. packet loss ratio is much higher Avg. packet loss ratio is much higher
than than pp– The longest streak of frame losses is The longest streak of frame losses is
much longer than much longer than LL Infeasible power level, should Infeasible power level, should
increase power and reset the curveincrease power and reset the curve
Packet Delivery Curves (C1)Packet Delivery Curves (C1) Case 2: curve is always above Case 2: curve is always above SS = =
pp * ( * ( TT – – LL ), but is below ), but is below SS = = pp * * T, T, when when TT = = MM– Current avg. packet loss ratio is Current avg. packet loss ratio is
higher than higher than pp– Longest streak of loses is less than Longest streak of loses is less than LL
Infeasible power level, should Infeasible power level, should increase power and reset the curveincrease power and reset the curve
Packet Delivery Curves (C0)Packet Delivery Curves (C0) Case 3: curve is always above Case 3: curve is always above SS = =
pp * * TT , exactly at , exactly at SS = = pp * * TT when when TT = = MM
Feasible power levelFeasible power level
SummarySummary The adaptive transmission power The adaptive transmission power
control control – Reduces the TP while guaranteeing Reduces the TP while guaranteeing
a similar throughput as when max a similar throughput as when max power is usedpower is used
– Response quickly (C2)Response quickly (C2)– Not to sensitive to long streaks of Not to sensitive to long streaks of
losses (C0)losses (C0)
Relations between the Relations between the TP of RTS-CST-DATA-TP of RTS-CST-DATA-ACKACK When packet When packet xx is transmitted at a high is transmitted at a high
TP (α), the successor packet TP (α), the successor packet yy can be can be transmitted at a relative lower TP (β)transmitted at a relative lower TP (β)
(x, y) are in the set(x, y) are in the set– (RTS, CTS)(RTS, CTS)– (CTS, DATA)(CTS, DATA)– (DATA, ACK)(DATA, ACK)
The larger α, the smaller β and vice The larger α, the smaller β and vice versaversa
Relations between the TP Relations between the TP of RTS-CST-DATA-ACKof RTS-CST-DATA-ACK RTS frame may be discarded RTS frame may be discarded
when the receiver is not idlewhen the receiver is not idle– The NAV of the receiver is not zeroThe NAV of the receiver is not zero
Increasing TP under this scenario Increasing TP under this scenario is not suitableis not suitable
Correlative Adaptive Correlative Adaptive Power Control (CAPC)Power Control (CAPC) Each station maintains 2 curves Each station maintains 2 curves
for a neighborfor a neighbor– RTSRTS– DATADATA
Finite State MachineFinite State Machine M: parameter measurement stateM: parameter measurement state
– Measure Measure pp and and LL R: RTS/CTS TP-lower bound stateR: RTS/CTS TP-lower bound state
– Do not allow to decrease RTS TPDo not allow to decrease RTS TP D: DATA/ACK TP-lower bound D: DATA/ACK TP-lower bound
statestate– Do not allow to decrease DATA TPDo not allow to decrease DATA TP
Algorithm DescriptionAlgorithm Description
Simulation ScenarioSimulation Scenario TCP congestion TCP congestion
window is 32window is 32 Packet size is 512 BPacket size is 512 B CBR for each UDP is CBR for each UDP is
400 packets/s400 packets/s Max TP is 250 MMax TP is 250 M R1, R2 are 400, R1, R2 are 400,
40004000 M is 25M is 25
End-to-end End-to-end ThroughputThroughput
Throughput/Energy Throughput/Energy Consumption RatioConsumption Ratio
Fairness IndexFairness Index
End-to-end End-to-end Throughput with CBR Throughput with CBR TrafficTraffic
Throughput/Energy Throughput/Energy Consumption Ratio with Consumption Ratio with CBR TrafficCBR Traffic
Fairness Index with Fairness Index with CBR TrafficCBR Traffic
ConclusionConclusion This paper proposed a CAPC This paper proposed a CAPC
algorithmalgorithm– Relies on packet delivery curveRelies on packet delivery curve
CAPC tries to achieve the same CAPC tries to achieve the same throughput as IEEE 802.11 DCF throughput as IEEE 802.11 DCF but uses lowest TP as possiblebut uses lowest TP as possible
Thank you!!Thank you!!