MAC Enhancements to Support Quality of Service in Wireless Networks Masters Thesis Presentation...

MAC Enhancements to MAC Enhancements to Support Quality of Service in Support Quality of Service in

Wireless NetworksWireless Networks

Masters Thesis PresentationMasters Thesis PresentationS.RajeshS.Rajesh

AU-KBC Research CentreAU-KBC Research Centrehttp://www.au-kbc.orghttp://www.au-kbc.org

http://www.annauniv.eduhttp://www.annauniv.edu

Department of Electronics Engineering, Department of Electronics Engineering, Faculty of Information and Communication Engineering, MIT Campus, Faculty of Information and Communication Engineering, MIT Campus,

Anna University, Chromepet, Chennai, TN 600044 INDIA.Anna University, Chromepet, Chennai, TN 600044 INDIA.

17 Nov, 2005 S.Rajesh, Anna University 2

OutlineOutline• IntroductionIntroduction

– MAC for wireless networksMAC for wireless networks• Ad hoc networksAd hoc networks• Wireless LANWireless LAN

• Problem DefinitionProblem Definition– QoS supportQoS support

• DifferentiatedDifferentiated• IntegratedIntegrated

• MAC EnhancementsMAC Enhancements– In ad hoc networks with directional antennasIn ad hoc networks with directional antennas

• System modelSystem model• ResultsResults

– In WLAN with QoS schedulerIn WLAN with QoS scheduler• System modelSystem model• ResultsResults

• ConclusionConclusion

INTRODUCTIONINTRODUCTION

IntroductionIntroduction

Problem Definition & ContributionProblem Definition & Contribution

MAC Enhancements (Ad hoc / WLAN)MAC Enhancements (Ad hoc / WLAN)

System Model (Ad hoc / WLAN)System Model (Ad hoc / WLAN)

Results (Ad hoc / WLAN)Results (Ad hoc / WLAN)

ConclusionConclusion



• WLAN Standard with QoS EnhancementWLAN Standard with QoS Enhancement– Basics IEEE 802.11Basics IEEE 802.11– QoS enhancements in IEEE 802.11eQoS enhancements in IEEE 802.11e

• HCFHCF– HCF Contention Free Channel Access MechanismHCF Contention Free Channel Access Mechanism– HCF Contention Based Channel Access Mechanism (EDCF)HCF Contention Based Channel Access Mechanism (EDCF)

» (or Enhanced Distributed Coordination Function)(or Enhanced Distributed Coordination Function)

– Scheduling TechniquesScheduling Techniques• Prioritized Scheduling for Differentiated and Integrated Prioritized Scheduling for Differentiated and Integrated

TrafficTraffic– Rate Adaptive SchedulingRate Adaptive Scheduling


WLANWLAN

• Typical ScenariosTypical Scenarios

– Independent BSSIndependent BSS• IBSS (Ad hoc mode)IBSS (Ad hoc mode)• Distributed coordinationDistributed coordination

– Infrastructure BSSInfrastructure BSS• NOT called an IBSSNOT called an IBSS• Central coordinationCentral coordination

Access Point


ESSESS

Access Point

Internet

LAN

WLAN

Backbone

Access Point

BSS BSS

ESS


Basic IEEE 802.11 MACBasic IEEE 802.11 MAC

• CSMA/CA CSMA/CA

• Binary Exponential Back-offBinary Exponential Back-off

• RTS/CTS/Data/ACK handshakeRTS/CTS/Data/ACK handshake

• ModesModes– DCF DCF

• Ad Hoc or infrastructurelessAd Hoc or infrastructureless

– PCFPCF• Infrastructure based Infrastructure based

– Access Point polls the associated stationsAccess Point polls the associated stations


DCFDCF

D S S S D N ST S S

1

2

3

D S S S D BkOff S S time

802.11a parametersS SIFS (Short Inter Frame Space) 16sD DIFS (DCF Inter Frame Space) 34sST Slot Time for each Back-off counter 9 s

RTS

CTS

DATA

ACK

RTS

CTS

DATA

NAV (RTS from 1)

NAV (RTS from 3)


DCFDCF

• BeaconBeacon» generated by any of the nodes in the IBSSgenerated by any of the nodes in the IBSS

• MPDU transmissionMPDU transmission» If channel is free for a DIFS transmit (RTS,…, Data,...)If channel is free for a DIFS transmit (RTS,…, Data,...)» else else » wait till it becomes free for a DIFSwait till it becomes free for a DIFS

» generate random backoff slot-times in (0-Cwgenerate random backoff slot-times in (0-Cwminmin))

» if channel is free count down one slot timeif channel is free count down one slot time» else freeze and resume countdown else freeze and resume countdown » the channel becomes free for a DIFSthe channel becomes free for a DIFS» on reaching zero transmiton reaching zero transmit» if failed retry from first step (for max retries (7) times)if failed retry from first step (for max retries (7) times)


PCFPCF

BeaconData & CF Poll to 1

CF Poll to 2 &

Ack to 1

Data from 1 &CF

Ack

CF Poll to 3

CF Ack

PC

NAV

M1

NAV

M2

Dead

NAV

M3

NAV

M4,5

IBSS

NAV Time -->

CF End

Contention Free Repetition Interval

Contention periodContention Free Period

Set by Beacon Cleared by CF End

Set by Beacon

Set by Beacon

Cleared by CF End

Cleared by CF End

RTS

CTS

DataAck

SIFS SIFS SIFS PIFS SIFS SIFS DIFS +BK SIFS SIFS SIFS

Set by RTS


PCFPCF

• BeaconBeacon» always generated by the APalways generated by the AP

• TransmissionTransmission» AP transmits Multicast/Broadcast data firstAP transmits Multicast/Broadcast data first» AP transmits data to associated stations one by one and AP transmits data to associated stations one by one and

along with that it polls these stations to send data if any along with that it polls these stations to send data if any in contention free modein contention free mode

» If the station doesn’t respond within PIFS, the AP gets If the station doesn’t respond within PIFS, the AP gets the channel with better chance as PIFS<DIFSthe channel with better chance as PIFS<DIFS

» After CFPmaxduration channel is left for contention After CFPmaxduration channel is left for contention based accessbased access

» Contention Free Period and Contention Period alternateContention Free Period and Contention Period alternate


HCFHCF

BeaconData & CF Poll to 1

CF Poll to 2 &

Ack to 1

Data from 1 &CF

Ack

CF Poll to 3

CF Ack

PC

NAV

M1

NAV

M2

Dead

NAV

M3

NAV

M4,5

IBSS

NAV Time -->

CF End

Contention Free Repetition Interval

Contention periodContention Free Period

Set by Beacon Cleared by CF End

Set by Beacon

Set by Beacon

Cleared by CF End

Cleared by CF End

RTS

CTS

DataAck

SIFS SIFS SIFS PIFS SIFS SIFS AIFS+BK SIFS SIFS SIFS

Set by RTS

Reserved by TXOP Reserved by TXOP

Reserved by TXOP

Reserved by TXOP

Reserved by TXOP

Reserved by TXOP

Reserved by TXOP


EDCF QueuingEDCF Queuing

Mapping toAccess Category

Transmit Queues

Per-queuechannel accessfunctions withinternal collisionresolution


AIFSAIFS

Medium Busy

D1

M1

Rx/Tx

D2

CCADel

M2

Rx/Tx

D2

CCADel

M2

Rx/Tx

D2

CCADel

M2

Rx/Tx

aSIFSTime aSlotTime aSlotTime aSlotTime

DIFS

AIFSD for AIFS=1

aSlotTime aSlotTime aSlotTime

Start monitoring CCAwhen AIFS=1

Decrement backoff andstart transmission if zero

when AIFS=1

Earliest possibletransmission on-air when

AIFS=1

Problem Definition and Problem Definition and ContributionContribution


Problem Definition & ContributionProblem Definition & Contribution






Problem DefinitionProblem Definition

• Link level QoS support inLink level QoS support in– Ad hoc networksAd hoc networks– WLANsWLANs

• Differentiated Differentiated – Access Category basedAccess Category based

• IntegratedIntegrated– Guaranteed QoSGuaranteed QoS


ContributionContribution

• MAC enhancements to support QoSMAC enhancements to support QoS– In ad hoc networksIn ad hoc networks

• Using directionality of the directional antennaUsing directionality of the directional antenna• Using intermittent immobile nodesUsing intermittent immobile nodes• Using direction aware schedulerUsing direction aware scheduler

– In WLANIn WLAN• Using estimation based Using estimation based

– Scheduler linked withScheduler linked with» Traffic shaping and policing Traffic shaping and policing » Admission ControlAdmission Control

MAC Enhancements in Ad hoc MAC Enhancements in Ad hoc NetworksNetworks


Problem Definition and ContributionProblem Definition and Contribution

MAC Enhancements (Ad hoc Networks)MAC Enhancements (Ad hoc Networks)





• Ad hoc networksAd hoc networks– Structural aspects:Structural aspects:

• topology free, infrastructure topology free, infrastructure independentindependent

– Functional aspects:Functional aspects:• multi-hop, common frequency multi-hop, common frequency

band for all nodes, no central band for all nodes, no central coordinationcoordination

– More overhead / expense on:More overhead / expense on:• routing, MAC, power routing, MAC, power

consumptionconsumption

– due todue to » highly dynamic state and highly dynamic state and

random state transitions, random state transitions, distributed coordinationdistributed coordination

Solution - StructuringSolution - Structuring


Ad hoc Network - ChallengesAd hoc Network - Challenges

Disconnected Clusters

Stray Nodes

Bottle Necks


EnhancementsEnhancements

• UseUse– interspersed stationary nodesinterspersed stationary nodes

• to reduce probability of any region getting void of to reduce probability of any region getting void of even a single node to connect witheven a single node to connect with

– directional antenna in these nodesdirectional antenna in these nodes• to improve range (without power-back-off)to improve range (without power-back-off)• to improve frequency reuse (with power-back-off)to improve frequency reuse (with power-back-off)

– smart directionality schedulersmart directionality scheduler• to help high priority node(s) or traffic to gain accessto help high priority node(s) or traffic to gain access• to prevent starvation of lower priority node(s) or trafficto prevent starvation of lower priority node(s) or traffic


… … contd …contd …

Bottle NecksBottle Necks: Providing more buffers at the strategically placed directional nodes

Stray NodesStray Nodes: High priority far off nodes can be reached with long beam

Disconnected ClustersDisconnected Clusters: Various beam shapes of Directional nodes can form an underlying infrastructure

System Model Ad hoc NetworksSystem Model Ad hoc Networks




System Model (Ad hoc Networks)System Model (Ad hoc Networks)




• Omni-directionalOmni-directional

• Directional AntennaDirectional Antenna– BeamBeam

• singlesingle• multimulti

– PowerPower• same as omni-directionalsame as omni-directional• backed-offbacked-off / / increasedincreased

Antenna PatternsAntenna Patterns


MAC Based on AntennaMAC Based on Antenna

• Omni-directional Omni-directional (e.g.: RTS/CTS/Data/Ack, CSMA/CA as in DCF of IEEE 802.11)(e.g.: RTS/CTS/Data/Ack, CSMA/CA as in DCF of IEEE 802.11)

• DirectionalDirectional– Static directionalityStatic directionality

• based onbased on– node distribution where node density is morenode distribution where node density is more

– need for bridging or relayingneed for bridging or relaying

– Dynamic directionalityDynamic directionality• based onbased on

– (source, destination) pairs(source, destination) pairs

– Traffic Traffic

» Traffic intensity for uniform trafficTraffic intensity for uniform traffic

» Traffic categoryTraffic category


State diagram of enhanced MACState diagram of enhanced MAC


Results inResults in

• Improved connectivityImproved connectivity

• Improved QoSImproved QoS


Connectivity Improvement with Connectivity Improvement with Stationary NodesStationary Nodes

• ProbabilityProbability– that two mobile nodes that two mobile nodes

contact at single hopcontact at single hop– that a mobile and a that a mobile and a

immobile node contact immobile node contact at single hopat single hop

• Improvement factor in Improvement factor in contact probabilitycontact probability


Connectivity Improvement with Connectivity Improvement with Directional NodesDirectional Nodes

• Coverage radiusCoverage radius– RRomniomni = 100m = 100m

– RRdirectionaldirectional = 500m = 500m

– RRnetworknetwork = 1000m = 1000m

• Single hop Single hop probability withprobability with– Omni-directional nodesOmni-directional nodes

10010022//1000100022 = 1/100 = 1/100– Directional nodesDirectional nodes

50050022//1000100022 = 1/4 = 1/4

• Improvement factorImprovement factor 5522 or (R or (Romniomni/R/Rdirectionaldirectional))22


Traffic Intensity CalculationTraffic Intensity Calculation


Traffic Based Direction Traffic Based Direction Scheduling for Better QoSScheduling for Better QoS

p is the priority weight of the corresponding traffic class


ScenarioScenario

• All mobile caseAll mobile case

• With intermittent mobile nodesWith intermittent mobile nodes– without directional antennaswithout directional antennas– with directional antennaswith directional antennas

• with smart traffic-intensity based schedulingwith smart traffic-intensity based scheduling• with smart traffic-category based schedulingwith smart traffic-category based scheduling


Simulation ParametersSimulation Parameters

• Network DiameterNetwork Diameter• Antenna PatternAntenna Pattern

– Omni-directional: radiusOmni-directional: radius– DirectionalDirectional

• beam width (lower limit)beam width (lower limit)• range (upper limit)range (upper limit)

• Access MethodAccess Method

• Routing TechniqueRouting Technique

2000m2000m

100m100m

22/6.25 for reaching/6.25 for reaching

250m with same power250m with same power

802.11 MAC802.11 MACCSMA/CACSMA/CA

RTS/CTS/Data/ACKRTS/CTS/Data/ACK

Shortest PathShortest Path


……Contd...Contd...Simulation ParametersSimulation Parameters

Best E ffo rtA C = 0

E xp on en tia l

N on Q oSTra ffic

Video P robeA C = 1

P are to w ith cu to ff(1 .7 , 1 8 6 4 b its , 1 2 0 0 0 b its )

VideoA C = 2

P are to w ith cu to ff(1 .1 , 6 5 2 b its , 1 2 0 0 0 b its )

AudioA C = 3C B R

3 2 & 6 4 K b p s

Q oSTra ffic

T raffic T ypeA ccess C ateg ory

Non Preemptive scheduling FCFS

Scheduler

More Delay sensitiveLess Delay sensitive

Preemptive scheduling

ResultsResults



MAC Enhancements (Ad hoc / WLAN) MAC Enhancements (Ad hoc / WLAN)


Results (Ad hoc Networks)Results (Ad hoc Networks)



Throughput PerformanceThroughput Performance


Delay PerformanceDelay Performance

MAC Enhancements in WLANsMAC Enhancements in WLANs



MAC Enhancements (WLANS)MAC Enhancements (WLANS)





Solution StructuringSolution Structuring

• To design a common scheduler To design a common scheduler – that can handle boththat can handle both

• (a) Contention free traffic and(a) Contention free traffic and• (b) Contention based traffic(b) Contention based traffic

– oror• (1) Traffic with resource reservation and(1) Traffic with resource reservation and• (2) Traffic without resource reservation(2) Traffic without resource reservation

• Though not necessary, (1) is handled using (a) and (2) using (b).Though not necessary, (1) is handled using (a) and (2) using (b).• Exceptionally some bursts are allowed for (1) in (b) also called CFB or Exceptionally some bursts are allowed for (1) in (b) also called CFB or

Contention Free BurstsContention Free Bursts


System - Block DiagramSystem - Block Diagram

InputQueue

Twin TokenBucket

RED Queue AccessCategories (4)AC=0,1,2,3

Traffic Streams(variablenumber)

HCF

EDCFFIFO per AC

TSScheduler

Chan

nel

Rate,size control

Drop RateControl

Admissioncontrol

EDCFParameters

Packet PathControl Information Path


Traffic FlowTraffic Flow

• Traffic ClassificationTraffic Classification– Traffic corresponding to declared Traffic Traffic corresponding to declared Traffic

Streams (TSs) Streams (TSs) • Shaped and Policed using Twin Token BucketShaped and Policed using Twin Token Bucket• Sent as per TS scheduler in HCFSent as per TS scheduler in HCF

– Traffic not associated with Traffic Streams (TSs)Traffic not associated with Traffic Streams (TSs)• RED queue mechanism usedRED queue mechanism used• Sent as per EDCF budget declared by HC in HCFSent as per EDCF budget declared by HC in HCF


Twin Token BucketTwin Token Bucketr2 tokens/s

Overflow

Droppedpackets

TokenAddition

Peak-ratelimited

s2

r1 tokens/s

Overflow

Droppedpackets

TokenAddition

Receivedtraffic

s1

Shapedtraffic

Bucket 1 Bucket 2Token filling rate (Constant) r1 = Peak Data Rate r2 = Mean Data RateBucket Size s1 = 1 token (mimic leaky bucket) s2 = Maximum Burst Size tokensToken extraction rate - At most Peak Data RateMajor purpose Rate limiting Burst size limiting

• TrafficTraffic– ShapingShaping– PolicingPolicing


Scheduling Based on Packet Scheduling Based on Packet Error InformationError Information

• Scheduler schedules and admits Traffic Scheduler schedules and admits Traffic Streams based on effective bandwidthStreams based on effective bandwidth– Effective Mean Data Rate (EMDR)Effective Mean Data Rate (EMDR)

– control factor control factor n n is varied based on observed packet errorsis varied based on observed packet errors

EMDR (Mbps)

54--------

27---------

n

-infinity +infinity0


• EMDR estimate = 54/(1+eEMDR estimate = 54/(1+e--nn))n n = = n-1 n-1 + x+ x

• where, where, » x= 1 if successful, -1 if unsuccessful x= 1 if successful, -1 if unsuccessful

• In implementation In implementation n n ranging to infinity can not be realized, ranging to infinity can not be realized,

nn should itself adapt based on channel condition should itself adapt based on channel condition

• So, So, n n is is – upper limited to +/- 127upper limited to +/- 127

– replaced by replaced by ’ which is a function of deviation in ’ which is a function of deviation in n n


• Aggregate the mean and peak data rate Aggregate the mean and peak data rate requirements mentioned through TSPEC for requirements mentioned through TSPEC for each admitted TSeach admitted TS

• Set rate of token filling in second bucket in Set rate of token filling in second bucket in Twin Token bucket , Twin Token bucket , rr22 to to

max(Estimated EMDR, algebraic sum of mean data rates of admitted TSs)max(Estimated EMDR, algebraic sum of mean data rates of admitted TSs)


Admission PolicyAdmission Policy

• Admit Traffic Streams until aggregate mean Admit Traffic Streams until aggregate mean data rate of existing traffic streams does not data rate of existing traffic streams does not exceed EMDR, exceed EMDR, – (reject otherwise).(reject otherwise).

• Bandwidth not used for TS is allocated Bandwidth not used for TS is allocated through EDCF budget for Contention based through EDCF budget for Contention based accessaccess


Scheduling Based on Rate Scheduling Based on Rate Adaptation InformationAdaptation Information

• Typically multiple rates are allowedTypically multiple rates are allowed– 54, 48, 36, 24, 18,12, 9, 6 Mbps54, 48, 36, 24, 18,12, 9, 6 Mbps

• Rate adaptation is done based RSSI or other Rate adaptation is done based RSSI or other techniquestechniques

• n n = = n-1 n-1 + x’+ x’

– where, x’ = x*(54*106)/rwhere, x’ = x*(54*106)/r• where, where,

» x= 1 if successful, -1 if unsuccessfulx= 1 if successful, -1 if unsuccessful

• andand» r is the rate of transmission of previous packet r is the rate of transmission of previous packet


……Contd...Contd...Simulation ParametersSimulation Parameters

Best E ffo rtA C = 0

E xp on en tia l

N on Q oSTra ffic

Video P robeA C = 1

P are to w ith cu to ff(1 .7 , 1 8 6 4 b its , 1 2 0 0 0 b its )

VideoA C = 2

P are to w ith cu to ff(1 .1 , 6 5 2 b its , 1 2 0 0 0 b its )

AudioA C = 3C B R

3 2 & 6 4 K b p s

Q oSTra ffic

T raffic T ypeA ccess C ateg ory

Non Preemptive scheduling FCFS

Scheduler

More Delay sensitiveLess Delay sensitive

Preemptive scheduling

ResultsResults





Results (WLAN)Results (WLAN)



Goodput of EDCFGoodput of EDCF


Traffic Streams Supported for Different Peak Data Rate Traffic Streams Supported for Different Peak Data Rate Deviation on Ideal ChannelDeviation on Ideal Channel


Traffic Streams supported and EDCF Throughput for a Traffic Streams supported and EDCF Throughput for a network when scheduler in HCF handles TXOPs of both network when scheduler in HCF handles TXOPs of both

contention free and contention based categoriescontention free and contention based categories

CONCLUSIONCONCLUSION









• In ad hoc networksIn ad hoc networks– Directional MAC - simple & robust technique to improveDirectional MAC - simple & robust technique to improve– Connectivity / CapacityConnectivity / Capacity– QoS performanceQoS performance

• In WLANs In WLANs – a scheduler with knowledge of a scheduler with knowledge of

• packet error information performs goodpacket error information performs good• rate adaptation mechanism provided by the management layer rate adaptation mechanism provided by the management layer

could help in better performance could help in better performance » particularly in poor channel conditionsparticularly in poor channel conditions


Node Interactions with a Node Interactions with a Directional NodeDirectional Node

• Directional nodeDirectional node• Omni-directional nodesOmni-directional nodes

– reached by the reached by the directional nodedirectional node

– not reached by the not reached by the directional nodes butdirectional nodes but

• exposedexposed• not exposed andnot exposed and

– forming independent forming independent local network(s)local network(s)

– astrayastray


Service Provider NetworkService Provider Network

• Building support Building support infrastructure infrastructure

• Combination ofCombination of– Stationary nodesStationary nodes

• omni-directional omni-directional (support in dense areas (support in dense areas with less or no mobility)with less or no mobility)

• directionaldirectional– static (relays on static (relays on

highways)highways)

– dynamic (in areas dynamic (in areas with highly random with highly random mobility)mobility)


ReferencesReferences[1] M. Grossglauser and D. Tse, ``Mobility increases the capacity of ad-[1] M. Grossglauser and D. Tse, ``Mobility increases the capacity of ad-

hoc wireless networks,” hoc wireless networks,” Proc. INFOCOMProc. INFOCOM, pp. 1360-1369, April 2001., pp. 1360-1369, April 2001.

[2] M. Sanchez, T. Giles and J. Zander, ``CSMA/CA with Beam Forming [2] M. Sanchez, T. Giles and J. Zander, ``CSMA/CA with Beam Forming Antennas in Multi-hop Packet Radio,” Antennas in Multi-hop Packet Radio,” Proc. Swedish Workshop on Proc. Swedish Workshop on Wireless Ad hoc NetworksWireless Ad hoc Networks, March 2001., March 2001.

[3] O. Somarriba, ``Multihop Packet Radio Systems in Rough Terrain", [3] O. Somarriba, ``Multihop Packet Radio Systems in Rough Terrain", Licentiate Thesis, Radio Communication Systems, Department of S3, Licentiate Thesis, Radio Communication Systems, Department of S3, Royal Institute of Technology, SwedenRoyal Institute of Technology, Sweden, Oct. 1995., Oct. 1995.

[4] L. E. Miler, ``Multihop Connectivity of Arbitrary Networks", [4] L. E. Miler, ``Multihop Connectivity of Arbitrary Networks", Multihop Multihop ConnectivityConnectivity, NIST, March 2001., NIST, March 2001.

[5] `ÌEEE 802.11b, Part 11: Wireless LAN MAC and PHY Specification: [5] `ÌEEE 802.11b, Part 11: Wireless LAN MAC and PHY Specification: High-Speed Physical Layer Extension in the 2.4GHz Band", 1999.High-Speed Physical Layer Extension in the 2.4GHz Band", 1999.

[6] `ÌEEE 802.11e, Part 11: Wireless LAN MAC and PHY Specification: [6] `ÌEEE 802.11e, Part 11: Wireless LAN MAC and PHY Specification: MAC Enhancements for QoS”, D3.3, Oct 2002.MAC Enhancements for QoS”, D3.3, Oct 2002.


ReferencesReferences

[1] "IEEE 802.11, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification on 2.4GHz band," 1999.

[2] "IEEE 802.11a, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specificatio, on 5GHz band," 1999.

[3] Draft Supplement 4.1 "IEEE 802.11e, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification: Medium Access Control (MAC) enhancements for Quality of Service (QoS)", Feb 2003.

[4] Andrew Moore, Simon Crosby, "Experimental results from a practical implementation of a Measurement Based CAC algorithm," BTL Final Report, May 1998.

[5] Sunghyun Choi, Javier del Prado, Sai Shankar N, and Stefan Mangold, "IEEE 802.11e Contention-Based Channel Access (EDCF) Performance Evaluation" in Proc. IEEE ICC 2003, Anchorage, Alaska, USA, May 2003.

[6] “An architecture for Differentiated services”, IETF RFC 2475, 1998.

[7] J. Wroclawski, "The use of RSVP with IETF integrated services," RFC 2210, Sept. 1997.

[8] IEEE Std 802.1Q-1998, IEEE Standards for Local and Metropolitan Area Networks: Virtual Bridged Local Area Networks.

[9] IETF RFC 2215, 2215 General Characterization Parameters for Integrated Service Network Elements. S.Shenker, J.Wroclawski. September 1997.

[10] S. Floyd and V. Jacobson, “Random early detection gateways for congestion avoidance”, IEEE/ACM Transactions on Networking, 1(4):397-413, August 1993.

[11] Javier del Prado and Sunghyun Choi, "Link Adaptation Strategy for IEEE 802.11 WLAN via Received Signal Strength Measurement," in Proc. IEEE ICC 2003, Anchorage, Alaska, USA, May 2003.

Thank YouThank You

S.Rajesh, S.Rajesh,

AU-KBC Research Centre,AU-KBC Research Centre,Department of Electronics Engineering, Faculty of Information and Communication Department of Electronics Engineering, Faculty of Information and Communication

Engineering, MIT Campus, Anna University, Chromepet, Chennai, TN 600044 INDIA.Engineering, MIT Campus, Anna University, Chromepet, Chennai, TN 600044 INDIA.

http://www.au-kbc.orghttp://www.au-kbc.org

http://www.annauniv.eduhttp://www.annauniv.edu

MAC Enhancements to Support Quality of Service in Wireless Networks Masters Thesis Presentation...

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