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Bin Cao, Gang Feng, Yun LiUniversity of Electronic Science and Technology of ChinaChongqing University of Post and Telecommunications

IEEE Globecom 2011Relay Selection for Cooperative MAC Considering Retransmission Overhead1OutlineIntroductionGoalsProblem DescriptionCooperative MAC MechanismRelay Selection in Cooperative MACSimulationConclusion

IntroductionThe cooperative communication approach effective uses of spatial diversity in wireless ad hoc networksImproved throughput Delay performance

ACBIntroductionPrevious papers have not taken into account MAC overhead caused by retransmission due to impaired wireless channel

MAC overhead is incurred by Failure of contending Transmission error

4Related WorkCoopMAC I

Its performance deteriorates under fading conditions due to lower direct path or relay path reliability5GoalsWe address the issue of Relay Selection MAC overhead is taken into accountA good tradeoff between transmission delay and error probabilityAchieve a better performance gain

6Problem Description

The Bit Error Rate of direct mode and cooperation mode

Frame Loss ProbabilityFrame Transmission Time The throughput for direct and cooperative communications

SNR7Cooperative MAC MechanismSDRC-RTSC-CTSSIFSRTRSIFSSIFSACKDATASIFSDATASIFSRelay Selection in Cooperative MACFTT in direct communication mode

FTT in cooperative communication mode

9Relay Selection in Cooperative MACFrame Loss Probability for direct communications

Frame Error Ratio Bit Error Rate 10Relay Selection in Cooperative MACFrame Loss Probability for cooperative communications

11SimulationSimulation parameters

ParametersValueSimulatorNS-2MAC header272bitsPHY header192bitstc-rts , tc-cts / trtr / tack352s , 304stSLOT , tDIFS10s , 50sCWmin 31sr / rd 9dBRsr / Rrd2MbpsRsd1MbpsContending nodes 10data frame length 1000 bytesSimulation

13Simulation

14ConclusionOur proposed cooperative MAC Can select the most suitable node as a relay Alleviates the retransmission probability Enhances the cooperation opportunity.15