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Quality of Service Aware MAC Based on IEEE
802.11 for Multihop Ad-Hoc Networks
S. Sivavakeesar, G. Pavlou
IEEE WCNC 2004
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Outline
INTRODUCTION PREVIOUS WORK AND OUR
MOTIVATION PROPOSED APPROACH EVALUATION THROUGH SIMULATION CONCLUSIONS AND FUTURE WORK
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INTRODUCTION ad hoc network
– real-time application– lack fixed infrastructure– medium access technology– network-level QoS mechanisms cannot work in MANETs
main focus – PCF
• WLAN• AP
combination– random (contention-based) – regulated (contention-free) access
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PREVIOUS WORK AND OUR MOTIVATION(1)
based on IEEE 802.11 main focus – PCF mode
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Time Division Multiple Access (TDMA) Service-differentiation
– no explicit guarantee of service differentiation
Fairness drawbacks of the above
– does not have the capability to provide MAC level QoS
PREVIOUS WORK AND OUR MOTIVATION(2)
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PROPOSED APPROACH (1)
to support both asynchronous and time-sensitive multimedia traffic
to adopt hierarchical
approach
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PROPOSED APPROACH (2)
simultaneous transmission– multiple parallel media (channels) – receiver-based spread-spectrum technology – full duplex radio– medium model
• common medium
• each node has its unique code (medium)
channel management – each node has to maintain constant CP and CFP
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PROPOSED APPROACH (3)
channel management (cont.)– common code
• only pure DCF
• disseminate and acquire routing related information
• to perform dynamic code assignment
– unique code • pure DCF and combined (DCF + PCF) mode
• switches between two mode depending on traffic type
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PROPOSED APPROACH (4)
traffic type– best-effort traffic (low priority)
– time-sensitive multimedia traffic (high priority)• “Association Request” (AReq) frame (to the forwarder)
• Association Response (ARes) frame
• polling-list
• virtual PC (VPC)
• POLLING_TIME_OUT,
three components– admission control
– QoS-mapping
– resource reservation
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PROPOSED APPROACH (5)
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PROPOSED APPROACH (6)
details– superframe
• CFP – high-priority traffic
• CP – AReq, ARes, and best-effort data
– provisioning of network resources• resource reservation in PCF mode
• prioritization in the DCF mode
– prioritization• service-differentiation
• allowing faster access to the medium
• SIFS < PIFS < RIFS < DIFS
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PROPOSED APPROACH (7) details (cont.)
– prioritization (cont.)• fairness• admission control
• Tcp: duration of CP• Tovhd : overhead involved for beacon and CF_END
transmissions• Tv : time to send a voice packet
– the VPC can poll to a maximum of Np number of times (or nodes)
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PROPOSED APPROACH (8)
– QoS-mapping module• calculates the number of times it has to be polled by any
VPC
• AReq frame
• ASSO_PROC_THERESHOLD_TIME_OUT look for another appropriate forwarding node
Exception– cannot rely on PCF-based operation
• depending on relative velocities
– MOBIC model
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PROPOSED APPROACH (9) MOBIC model
– negative value • moving away
– Mx : low value • relatively less mobile
– Mthreshold : higher => rely on common medium
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EVALUATION THROUGH SIMULATION(1)
GloMoSim 500m X 500m 20 nodes 300 seconds of simulation time transmission range of 100m full duplex operation data packet size is 512 bytes
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EVALUATION THROUGH SIMULATION(2)
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EVALUATION THROUGH SIMULATION(3)
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EVALUATION THROUGH SIMULATION(4)
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CONCLUSIONS AND FUTURE WORK
a QoS-aware MAC protocol based on the IEEE 802.11 standard
– To be easily integrated into existing systems
Extension– 802.11e standard – support multiple traffic classes