IEEE 802.11s MDA在多通道環境下動態分配競爭區間比例之研究

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研究生：	黃品翰 Pin-han Huang
論文名稱：	IEEE 802.11s MDA在多通道環境下動態分配競爭區間比例之研究 Study on IEEE 802.11s MDA Reservation Mechanism for Dynamically Allocate Contention Period Ratio in Multi-channel Wireless Mesh Network
指導教授：	黎碧煌 Bih-hwang Lee
口試委員:	吳傳嘉 Chwan-chia Wu 鍾添曜 Tein-yaw Chung 楊英魁 Ying-kuei Yang
學位類別：	碩士 Master
系所名稱：	電資學院 - 電機工程系 Department of Electrical Engineering
論文出版年：	2011
畢業學年度：	99
語文別：	中文
論文頁數：	64
中文關鍵詞：	802.11s 、MDA 、多通道、無線網狀區域網路
外文關鍵詞：	MDA, multi-channel, wireless mesh LAN, 802.11s
相關次數：	點閱：260 下載：2
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無線網狀區域網路是由一些支援網狀服務(Mesh service)的節點所組成的通訊網路。在IEEE802.11s草案中，除了導入網狀網路架構外，亦加入以預約為基礎的存取機制，稱為MDA(Mesh deterministic access)。MDA能讓節點以較少的競爭與碰撞來進行媒體存取，但只能工作於單通道環境，造成網路流量無法提升。
而在之前的研究中，有人提出讓MDA可以運行在多通道環境下的機制，稱之為MMDA(Multi-channel MDA)。MMDA相較與原本的MDA確實有效提升系統的效能。本論文便是延伸之前的研究，針對MMDA不足的地方提出改良。
MMDA當負載高的情況下，各通道之間的傳輸區間(Data Transmission Period)都已經被預約飽和，並且MDAOP釋放的機率不高，此時競爭區間(Contention Period)就會形成浪費。於是為了提高系統效能，本論文提出當傳輸區間已經被預約接近飽和時，動態調整競爭區間。使得在Mesh DTIM interval中，傳輸區間的長度變長，以便節點可以預約到更多的MDAOP。並且根據節點預約MDAOP的情況，來改變節點的後退時間(Backoff Time)，讓MDAOP較少的節點可以提高預約到MDAOP的機率，以提高效能以及公平性。

A wireless mesh LAN is a communications network made up of radio nodes that support Mesh service. In IEEE 802.11s draft, not only the Mesh network topology be introduced, but also a new reservation based MAC access scheme, MDA, be introduced. Nodes that support MDA can access wireless medium with lower collision probability. But MDA can just work in the single channel environment and so the capacity of network is limited.
In a previous study, it was suggested so that MDA can operate on multi-channel environment. Compared with the MDA, MMDA does effectively enhance the system performance. This paper is an extension of previous research for improves MMDA deficiencies.
However, when the network load is high, the available duration in Data Transmission Period have been almost reserved. At this time Contention Period will be a waste. So in order to increase system capacity, We propose a scheme, which can dynamically adjust Contention Period when Data Transmission Period became saturated. Therefore, node can use the increased Data Transmission Period to reserve more MDAOPs. In addition our scheme also adapts backoff time according to MP’s own MDAOP number. This is allows MP which has less MDAOPs to increase the reserving MDAOPs probability, and improves the system performance and fairness.

中文摘要	iv
英文摘要	v
誌謝	vi
目次	vii
圖目次	x
表目次	xiii
第一章 緒論	1
1簡介	1
2研究動機與目的	2
3章節概要	3
第二章 IEEE 802.11s標準概述	4
1 IEEE 802.11S標準簡介	4
1.1網路拓樸	4
1.2 MAC訊框結構	7
2 MDA預約機制概述	8
2.1 MDA運作機制	9
2.2 MDAOP建立流程	9
2.3預約訊框格式	11
3相關研究	13
3.1 NMST	14
3.2四向交握機制	17
第三章 動態多通道預約機制介紹	19
1問題描述	19
2研究方法	21
2.1動態變更競爭區間比例機制	21
2.2縮短競爭區間比例範例	30
2.4 後退時間變更機制	31
2.5 後退時間變更範例	33
第四章 系統模擬與結果	34
1模擬環境與參數	34
2效能評估項目	37
2.1平均節點產能(average throughput)	37
2.2平均等待時間(average waiting time)	37
2.3封包丟棄率(packet drop ratio)	38
2.4 公平性(fairness index)	38
2.5 系統節點碰撞率(collision ratio)	39
3一般模擬環境之系統效能分析與比較	40
3.1一般模擬環境之平均節點產能分析與比較	41
3.2一般模擬環境之平均等待時間分析與比較	42
3.3一般模擬環境之系統封包丟棄率分析與比較	43
3.4一般模擬環境之系統公平性分析與比較	44
3.5一般模擬環境之系統節點碰撞率分析與比較	48
3.6一般模擬環境之各種類型節點之產能分佈分析	49
3.7不同負載情況下各種類型節點數量變化分析與比較	51
4 熱點模擬環境之系統效能分析與比較	52
4.1 熱點模擬環境之平均節點產能分析與比較	53
4.2 熱點模擬環境之平均等待時間分析與比較	54
4.3 熱點模擬環境之系統封包丟棄率分析與比較	55
4.4 熱點模擬環境之系統公平性分析與比較	56
4.5 熱點模擬環境之系統節點碰撞率分析與比較	60
4.6 熱點環境下各種類型節點之數目分佈分析	61
第五章 結論	62
參考文獻	63

                                

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