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!!