Quality of Service Aware MAC Based on IEEE

802.11 for Multihop Ad-Hoc Networks

S. Sivavakeesar, G. Pavlou

IEEE WCNC 2004

Outline

INTRODUCTION PREVIOUS WORK AND OUR

MOTIVATION PROPOSED APPROACH EVALUATION THROUGH SIMULATION CONCLUSIONS AND FUTURE WORK

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

PREVIOUS WORK AND OUR MOTIVATION(1)

based on IEEE 802.11 main focus – PCF mode

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)

PROPOSED APPROACH (1)

to support both asynchronous and time-sensitive multimedia traffic

to adopt hierarchical

approach

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

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

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

PROPOSED APPROACH (5)

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

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)

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

PROPOSED APPROACH (9) MOBIC model

– negative value • moving away

– Mx : low value • relatively less mobile

– Mthreshold : higher => rely on common medium

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

EVALUATION THROUGH SIMULATION(2)

EVALUATION THROUGH SIMULATION(3)

EVALUATION THROUGH SIMULATION(4)

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