無線區域網路中基於OFDM的頻域競爭機制，在每次競爭回合中允許多人獲勝

An OFDM-Based Frequency Domain Contention Mechanism in Wireless LANs with Multiple Winners for Each Contention Cycle

張寬宏(Kuan-Hong Chang)

指導教授 ： 黃育銘

國立暨南國際大學/科技學院/資訊工程學系/碩士(2020年)

https://doi.org/10.6837/ncnu202000272

摘要

在無線區域網路媒體存取控制（MAC）層中之退避機制（Backoff），我們觀察到頻域通道競爭機制（FD-Backoff）[6]在競爭回合結束後，往往只有一個傳送端屬於競爭成功，其他傳送端所挑選的子載波即便沒有發生競爭碰撞，卻因為不是最小子載波而被排除在外，需要等待下一回合競爭，因此，本文提出兩個改良型的頻域競爭機制，兩個方案都降低了競爭回合的系統碰撞及個人碰撞機率，其中第二個方案在每次競爭回合中允許多人獲勝，模擬實驗中我們以[6]作比較，觀察傳統單人獲勝的頻域競爭機制與多人獲勝情況下的效能表現。此外，對於所提出之第二種通道競爭機制，也做了完整的數學分析以驗證其正確性。

關鍵字

無線網路隨機存取 ； 頻域退避演算法 ； 正交分頻多工

並列摘要

In the wireless local area network, for the frequency domain Backoff mechanism of the media access control (MAC) layer, we observe that most of the channel contention mechanisms, only one transmitter will win the permission of the data channel transmission at the end of each contention round. Even if the contention collision did not occur for the other larger subcarrier selected by only one transmitter, the system did not send data packet after the end of the contention period due to the selected subcarrier is not the smallest.
In this thesis, we proposed two enhanced FD-Backoff schemes for IEEE 802.11 WLANs. The second scheme allows multiple people to win in each competition cycle. Both of these schemes reduce the system and individual contention collision probabilities which are directly related to the network throughput and the packet delay time. We compared the proposed schemes with FD-Backoff [6]. Simulated results show that our proposed schemes had lower packet delay time and higher throughput gain. In addition, a complete mathematical analysis has also been done to verify the correctness of the second proposed channel contention mechanism.

並列關鍵字

Wireless random access ； Frequency-domain backoff ； OFDM

參考文獻

[1]G. Bianchi, “Performance analysis of the IEEE 802.11 distributed coordination function,” IEEE Journal on Selected Areas in Communications, vol. 18, pp. 535–547, March 2000.

[2]IEEE Standard for Telecommunications and Information Exchange Between Systems - LAN/MAN Specific Requirements - Part 11: Wireless Medium Access Control (MAC) and physical layer (PHY) specifications: High Speed Physical Layer in the 5 GHz band," in IEEE Std 802.11a-1999 , vol., no., pp.1-102, 30 Dec. 1999.

[3]H.Al-Mefleh, O.Al-Kofahi, “Frequency-domain contention and polling MAC protocols in IEEE 802.11 wireless networks: A survey,” Comput. Commun., 129 (2018), pp. 1-18.

[4]S. Sen, R. R. Choudhury, and S. Nelakuditi, “Listen (on the frequency domain) before you talk,” in Proc. of the 9th ACM SIGCOMM Workshop on Hot Topics in Networks, 2010, pp. 1-6.

[5]S. Sen, R. R. Choudhury and S. Nelakuditi, "No time to countdown: Migrating backoff to the frequency domain", Proc. 13th Annu. Int. Conf. Mobile Comput. Netw., pp. 241-252, 2011