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Coherence Time Estimation for Performance Improvement of IEEE 802.11n Link Adaptation
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 Title & Authors
Coherence Time Estimation for Performance Improvement of IEEE 802.11n Link Adaptation
Yeo, Chang-Yeon; Choi, Mun-Hwan; Kim, Byoung-Jin; Choi, Sung-Hyun;
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IEEE 802.11n standard provides a framework for new link adaptation. A station can request that another station provide a Modulation and Coding Scheme (MCS) feedback, to fully exploit channel variations on a link. However, if the time elapsed between MCS feedback request and the data frame transmission using the MCS feedback becomes bigger, the previously received feedback information may be obsolete. In that case, the effectiveness of the feedback-based link adaptation is compromised. If a station can estimate how fast the channel quality to the target station changes, it can improve accuracy of the link adaptation. The contribution of this paper is twofold. First, through a thorough NS-2 simulation, we show how the coherence time affects the performance of the MCS feedback based link adaptation of 802.11n networks. Second, this paper proposes an effective algorithm for coherence time estimation. Using Allan variance information statistic, a station estimates the coherence time of the receiving link. A proposed link adaptation scheme considering the coherence time can provide better performance.
IEEE 802.11n WLAN;Feedback-based;Link adaptation;Coherence time;Online estimation;
 Cited by
IEEE 802.11, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications, IEEE Std. 802.11-2007, Jun. 2007.

IEEE 802.11n, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Enhancements for Higher Throughput, supplement to IEEE Std. 802.11, Oct. 2009.

A. Kamerman and L. Monteban, "WaveLAN-II: a high-performance Wireless LAN for the Unlicensed Band," Bell Labs Technical Journal, vol.2, no.3, pp.118-133, Aug. 1997.

M. Lacage, M. H. Manshaei, and T. Turletti, "IEEE 802.11 Rate Adaptation: A Practical Approach," in Proc. ACM MSWiM'04, Venezia, Italy, Oct. 2004.

J. C. Bicket, "Bit-rate selection in wireless networks," M.S. Thesis, MIT, Feb. 2005.

G. Holland, N. Vaidya, and P. Bahl, "A rate-adaptive MAC protocol for multi-hop wireless networks," in Proc. ACM MobiCom'01, Rome, Italy, Jul. 2001.

B. Sadeghi, V. Kanodia, A. Sabharwal, and E. Knightly, "Opportunistic Media Access for Multirate Ad Hoc Networks," in Proc. ACM MobiCom'02, Atlanta, Georgia, USA, Sep. 2002.

B. Sklar, "Digital Communications: Fundamentals and Applications, 2nd Edition," Prentice Hall, 2001.

J. Camp, and E. Knightly, "Modulation and Rate Adaptation in Urban and Vehicular Environment: Cross-layer Implementation and Experimental Evaluation," in Proc. ACM MobiCom'08, San Francisco, California, USA, Sep. 2008.

J. Kim, S. Kim, S. Choi, and D. Qiao, "CARA: Collision-Aware Rate Adaptation for IEEE 802.11 WLANs," in Proc. IEEE INFOCOM'06, Barcelona, Spain, Apr. 2006.

The Network Simulator - ns-2.