The Journal of Korean Institute of Communications and Information Sciences (한국통신학회논문지)

The Korean Institute of Commucations and Information Sciences (한국통신학회)
권호 표지

Realization of an IEEE 802.11g VoWLAN Terminal with Support of Adaptable Power Save and QoS During a Call

통화 중 적응적 Power Save와 QoS 지원이 가능한 IEEE B02.11g VoWLAN 단말기 구현

  • Published : 2006.10.31
Download PDF
⟨ Previous Next ⟩

Abstract

There is a serious problem in an 802.11g VoWLAN (Voice over Wireless LAN) terminal that talk time is less than 30% compared with an 802.11b terminal. It is almost impossible to achieve talk time level of the 802.11b MAC transmission method because IEEE 802.11g uses OFDM modulation, which is a kind of multi-carrier method and OFDM transmission speed is 54 Mbps faster than normal modulation. In this paper, a new concept of a Holdover time as a power saving method during a call with 802.11g terminal is suggested for the first time. Increase in the number of engaged terminals as a result of holdover time causes to QoS problem because of the increase in the number of back-off and then contention window. In this paper, to solve the QoS problem, a new approach is suggested such that when in down lint the sequence number of 802.11 G.711 is analyzed in the MAC of the terminal and then the Hold over time depending on loss rate is changed. Also, consumption of an electric current of 802.11b/g and MAC parameter's performance due to busy traffic caused by increase in the number of terminal are analyzed and then real data using VQT and Airopeek are analyzed.

IEEE802.11g VoWLAN (Voice over Wireless LAN) 단말기는 802.11b 전용 단말기에 비해 통화시간이 30 % 이상 감소하는 문제점이 있어 통화시간이 문제로 대두되고 있다. 일반적으로, 802.11g에서는 멀티캐리어 방식인 OFDM (Orthogonal Frequency Division Multiplexing) 변조방식을 사용하여 54 Mbps속도로 전송하기 때문에 기존의 802.11b MAC (Medium Access Control) 전송방식과 비교하여 통화시간을 만족시키는 것이 어렵다. 본 논문에서는 802.11g 규격을 적용한 단말기에서 통화중 Power Save 방법으로 Holdover Time을 처음으로 제안하므로 통화시간을 만족시킨다. 다만, 통화 단말기 수 증가에 따른 네트워크 혼잡으로 경합 창 (contention window)이 많이 발생하여, Back-off 수 증가로 인한 통화품질(QoS)의 문제가 발생하지만, QoS 해결 방안으로 다운 링크 시 802.11 G.711 Sequence Number를 단말기 MAC 단에서 분석하여 손실율에 따른 Holdover Time을 가변 하는 방법을 제안하므로 이 문제를 해결한다. 802.11b/g 소비전류 분석과 통화 단말기 증가에 따른 네트워크 혼잡에 의한 MAC 파라미터 성능을 분석하며, VQT장비와AiroPeek를 이용하여 실제적인 데이터를 분석한다.

Keywords

References

  1. IEEE Std. 802-11-1999, Part 11: Wireless Medium Access Control (MAC) and Physical Layer (PRY) specifications, IEEE 802.11 Std, 1999
  2. X. P. Costa, D. C. Mur, and T. Sashihara, 'Analysis of the integration of IEEE 802.11e capabilities in battery limited mobile devices,' IEEE Wireless Communications, vol. 12, no. 6, pp. 26-32, Dec. 2005 https://doi.org/10.1109/MWC.2005.1561942
  3. IEEE Std. 802-11e-Supplement to Part 11: Wireless Medium Access Control (MAC) and Physical Layer (PHY) specifications; Medium Access Control (MAC) Enhancement for Quality of Service (QoS), IEEE 802.11e/D8.0, February 2004
  4. T. Mo and C. W. Bostian, 'A throughput optimization and transmitter power saving algorithm for IEEE 802.11b links,' Proc. IEEE Wireless Communications and Networking Conf., vol. 1, pp. 57-62, March 2005
  5. IEEE Std 802. 11b-Supplement to Part 11: Wireless Medium Access Control (MAC) and Physical Layer (PHY) specifications; Highspeed Physical Layer Extension in the Sept. 1999, 2.4 GHz Band, IEEE 802.11b Std, 1999
  6. F. Anjum, M. Elaoud, D. Famolari, A. Ghosh, R. Vaidyanathan, A. Dutta, P. Agrawal, T. Kodama, and Y. Katsube, 'Yoice Performance in WLAN Networks-An Experimental Study,' Proc. IEEE Global Telecomm.Conf., pp. 3504-3508, Dec. 2003
  7. G. H. Hwang and D. H. Cho, 'Voice capacity in IEEE 802.11 wireless LANs,' Electron. Lett., vol. 40, no. 18, pp. 1137-1138, Sept. 2004 https://doi.org/10.1049/el:20045603
  8. X. Wang, T. D. Todd, D. Zhao, and Y. Kezys, 'Power saving gateways for real-time voice handset support in IEEE 802.11 wireless LANs,' Proc. IEEE Int. Conf. Communications, vol. 1, pp. 164-169, June 2004
  9. P. Wang, H. Jiang, and W. Zhuang, 'IEEE 802.11e enhancement for voice service,' IEEE Wireless Communications, vol. 13, no. 1, pp. 30-35, Feb. 2006 https://doi.org/10.1109/MWC.2006.1593522
  10. M. Narbutt and M. Davis, 'An assessment of the audio codec performance in voice over WLAN (YoWLAN) systems,'Proc. 2nd Int. Conf. Mobile and Ubiquitous Systems: Networking and Services, pp. 461-467, July 2005