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Xiaodong Wang, Jun Yin and Dharma P. Agrawal University of Cincinnati, Cincinnati, Ohio.

Effects of Contention Window and Packet Size on the Energy Efficiency of Wireless Local Area Network. Xiaodong Wang, Jun Yin and Dharma P. Agrawal University of Cincinnati, Cincinnati, Ohio. IEEE WCNC 2005. Outlines. Introduction Analysis methods Packet transmission probability

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Xiaodong Wang, Jun Yin and Dharma P. Agrawal University of Cincinnati, Cincinnati, Ohio.

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  1. Effects of Contention Window and Packet Size on the Energy Efficiency of Wireless Local Area Network Xiaodong Wang, Jun Yin and Dharma P. Agrawal University of Cincinnati, Cincinnati, Ohio. IEEE WCNC 2005

  2. Outlines • Introduction • Analysis methods • Packet transmission probability • Energy efficiency analysis • Packet error probability • Simulations • Conclusions

  3. Introduction • Technology in battery capacity hasn’t a big advance in recent years • Energy efficiency is one of the most important challenging problems in wireless communications

  4. Introduction (cont.) • 802.11 standard specifies a power saving mode (PSM) • Synchronized • This paper concentrate on 802.11 DCF protocol

  5. Introduction (cont.) • In 802.11 DCF, energy could be consumed by • Idle listening • Transmission / Receiving • Packet size • Collision • Exponential backoff procedure (CW)

  6. Goal • Optimize energy efficiency by the analytical model • Optimal contention window • Optimal packet size

  7. Packet transmission probability • The probability to send a packet successfully after itimes of unsuccessful transmission is Pi where pu indicates the unsuccessful probability

  8. Packet transmission probability • With maximum backoff stage m and retry count m ’ whenm’≦m whenm’＞m

  9. Packet transmission probability • τis the average probability of each node to send a packet if the medium is idle • Collision probability p • Transmission error probability

  10. Packet transmission probability • Probabilities of • transmission in one of the other (n-1) node • contends successfully of any other (n-1) node • transmits successfully of any other (n-1) node

  11. Energy efficiency analysis • Average number of unsuccessful transmission Collision Error

  12. Energy efficiency analysis • Time of success / collision • Total energy consumption of a successful transmission Backoff Freeze Collision Error Success

  13. Energy efficiency analysis • Time of backoff period

  14. Energy efficiency analysis • Average number of transmission overhead can be expressed by we could get E_FR

  15. Energy efficiency analysis • E_SU can simply expressed by • Finally, we get η

  16. Simulations • System parameters

  17. Energy efficiency of DCF under ideal and non-ideal environment n=20 CWmin=32 PKT = 1000B

  18. Effects of CWminon the energy efficiency of DCF n=20 PKT = 1000B

  19. Effects of packet size on the energy efficiency of DCF with RTS/CTS n=20

  20. Comparison of optimal packet size and optimal CWmin

  21. Conclusions • This paper present the analysis of the energy efficiency in 802.11 DCF • Compare the impact of CW and Packet size • Packet size can effect the energy efficiency under error-prone channel

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