車用WiFi網路中的碰撞分析｜國立中央大學博碩士論文系統

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研究生：	林正平 Cheng-ping Lin
論文名稱：	車用WiFi網路中的碰撞分析 Analysis of Collision Probability in Vehicular WiFi Networks
指導教授：	孫敏德 Min-Te Sun
口試委員:
學位類別：	碩士 Master
系所名稱：	資訊電機學院 - 資訊工程學系 Department of Computer Science & Information Engineering
畢業學年度：	100
語文別：	英文
論文頁數：	40
中文關鍵詞：	車載網路、WiFi 、ViFi 、碰撞、轉傳
外文關鍵詞：	collision, relay, VANET, ViFi, WiFi
相關次數：	點閱：6 下載：0
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機率性轉傳的技術提昇了車用 WiFi 網路的效能，使得資料能夠在短暫且斷斷續續的通訊品質下順利地送達目的地。然而，過多的轉送卻增加了碰撞的發生，降低網路的傳輸效能。因此，分析車用 WiFi 網路中的碰撞機率，可以使轉送效率最大化，進而增進車用 WiFi 網路的連線品質。

Opportunistic relay improves the performance of transmissions in vehicular WiFi networks, which make data transmitted more effectively in the fleeting and intermittent vehicular networks. However, too many relays may reduce the quality of connections due to the increasing collisions. In this thesis, we analyze the collisions in vehicular WiFi networks and compute the probability of collisions in the network by two different schemes. Besides, we derive the optimal relay probability for an existing relay algorithm to minimize the redundant retransmission with the consideration of collisions.

Introduction 1
Related Work 3
1 Carrier Sense Multiple Access (CSMA) . . . . . . . . . . . . . . . . . . . . 3
1.1 CSMA access mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 CSMA/CA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 IEEE 802.11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Wi-Fi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3 WiFi in Vehicular networks . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1 Cabernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 ViFi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3 Optimal Opportunistic relay in ViFi . . . . . . . . . . . . . . . . . 10
Basic Problem 11
1 Opportunistic Relay Algorithm in ViFi . . . . . . . . . . . . . . . . . . . . 11
2 Optimizing Metrics and Relay Algorithm . . . . . . . . . . . . . . . . . . . 13
2.1 Optimizing Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.1 False Negative Rate . . . . . . . . . . . . . . . . . . . . . 14
2.1.2 False Positive Rate . . . . . . . . . . . . . . . . . . . . . . 14
2.2 Optimization of Relay Algorithm . . . . . . . . . . . . . . . . . . . 16
2.2.1 Simplification . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2.2 Optimization of Relay Algorithm . . . . . . . . . . . . . . 17
Basic Problem with the Consideration of Collisions 19
1 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2 Analysis of the Probability of Collision . . . . . . . . . . . . . . . . . . . . 21
2.1 Analysis of Centralized scheme . . . . . . . . . . . . . . . . . . . . 22
3 Analysis of Distributed scheme . . . . . . . . . . . . . . . . . . . . . . . . 24
3.1 The function p(t; i) . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2 Probability of Collision . . . . . . . . . . . . . . . . . . . . . . . . . 28
4 Performance Metrics and Relay Algorithm
with the Consideration of Collisions . . . . . . . . . . . . . . . . . . . . . . 29
4.1 Optimizing Performance Metrics with the Consideration of Collisions 29
4.2 Optimizing Relay Algorithm with the Consideration of Collisions . 31
Conclusion and Future Work 34

                                

[1] http://en.wikipedia.org/wiki/Carrier sense multiple access
[2] Yaping Zhu, Rui Zhang-Shen, Sampath Rangarajan, Jennifer Rexford, “Cabernet:
connectivity architecture for better network services,” Proceedings of the 2008 ACM
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pp.1-4, Feb 2011.
[8] L. Jiang and J. Walrand, “A Novel Approach to Model and Control the Throughput
of CSMA/CA Wireless Networks,” Technical Report, UC Berkeley, Jan 2009.
[9] Aruna Balasubramanian , Ratul Mahajan , Arun Venkataramani , Brian Neil Levine
, John Zahorjan, ”Interactive wifi connectivity for moving vehicles,” Proceedings of
the ACM SIGCOMM 2008 conference on Data communication, August pp. 17-22,
2008, Seattle, WA, USA.
[10] http://en.wikipedia.org/wiki/Wi-Fi
[11] http://www.webopedia.com/TERM/W/Wi Fi.html
[12] Chunlie Liu, “Optimizing Opportunistic Wi-Fi Relays,” Department of Mathemat-ics and Computer Science, Valdosta State University, USA, unpublished techinical
report.

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