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Robust Rate Adaptation for 802 11 Wireless Networks Starsky H Y Wong1 Hao Yang2 Songwu Lu1 and Vaduvur Bharghavan3 Dept of Computer Science UCLA 4732 Boelter Hall Los Angeles CA 90025 1 IBM T J Watson Research 19 Skyline Drive Hawthorne NY 10532 2 Meru Networks 1309 South Mary Avenue Sunnyvale CA 94087 3 hywong1 slu cs ucla edu1 haoyang us ibm com2 bharghav merunetworks com3 ABSTRACT Rate adaptation is a mechanism unspecified by the 802 11 standards yet critical to the system performance by exploiting the multi rate capability at the physical layer In this paper we conduct a systematic and experimental study on rate adaptation over 802 11 wireless networks Our main contributions are two fold First we critique five design guidelines adopted by most existing algorithms Our study reveals that these seemingly correct guidelines can be misleading in practice thus incur significant performance penalty in certain scenarios The fundamental challenge is that rate adaptation must accurately estimate the channel condition despite the presence of various dynamics caused by fading mobility and hidden terminals Second we design and implement a new Robust Rate Adaptation Algorithm RRAA that addresses the above challenge RRAA uses short term loss ratio to opportunistically guide its rate change decisions and an adaptive RTS filter to prevent collision losses from triggering rate decrease Our extensive experiments have shown that RRAA outperforms three well known rate adaptation solutions ARF AARF and SampleRate in all tested scenarios with throughput improvement up to 143 Categories and Subject Descriptors C 2 1 ComputerCommunication Networks Network Architecture and Design Wireless communication General Terms Design Experimentation Performance Keywords Rate Adaptation 802 11 1 INTRODUCTION Rate adaptation is a link layer mechanism critical to the system performance in IEEE 802 11 based wireless networks yet left unspecified by the 802 11 standards The current 802 11 specifications

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