摘要
由於大部分運用在IEEE 802.11下的定位系統需要在使用者端另外安裝軟體或是使用特殊的硬體設備才能夠進行定位，而本文中架構在IEEE 802.11的定位系統訴求為使用者端不需要額外安裝軟體在自己的無線網路裝置中，使用者只需利用無線網路裝置連上定位系統的網頁就可以達到定位的目的。
本文使用的定位方式為利用環境中架設的多台snooper輪流監聽定位環境內所有的無線網路頻道，收集有定位需求對象的無線網路定位封包，利用收集到封包中包含的訊號強度資料，比對指定區域內已事先建立的訊號強度分布特徵，再利用定位演算法找出與有定位需求對象發出的封包訊號強度最相近的地點資料。
由於本文中的定位系統是架構在IEEE 802.11下，因此有定位需求的使用者發送無線網路定位封包的行為必須遵從IEEE 802.11中為了避免無線網路封包碰撞且基於CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance)制定的分散式協調功能(Distributed Coordination Function)。而本文中提出一個集中可適性輪盤監聽演算法依據各頻道中無線網路定位封包的傳送情況來彈性的監聽定位環境中多個無線網路頻道且收集各頻道下的無線網路定位封包，以改進原本監聽各頻道一段固定時間的輪盤式監聽演算法，讓架設在環境中的各台snooper可以收到更多來自定位對象的無線網路定位封包，使得位在各頻道中的定位對象有更高的定位成功率並且讓我們的定位系統可以提供更好且有效率的定位服務。

In most localization system under 802.11, users need to install additional software in their wireless devices or use specific devices. But under the localization system architecture in this thesis, users connect the web site of localization system as long as use their wireless devices to locating.
There are several snoopers in the environment to scan all wireless channels and collect the wireless localization packets. The location server compares the signal of collected packets with the RSSI at specific areas and find the nearest site.
We propose a centralized adaptive polling algorithm for IEEE 802.11 localization systems to scan multiple wireless channels to improve polling algorithm and make all users fair.

目錄
摘要...............................................................................................................................I
表目錄..........................................................................................................................III
圖目錄..........................................................................................................................IV
第一章 Introduction簡介...........................................................................................1
1.1 Background背景..........................................................................................1
1.2 Localization System Model定位系統模型.................................................2
第二章 IEEE 802.11 Distributed Coordination Function介紹..................................4
2.1 Carrier Sensing Mechanism..........................................................................4
2.2 Exponential Backoff Procedure....................................................................4
2.3 Retransmission Mechanism..........................................................................8
2.4 Access Mechanism and Backoff Procedure..................................................9
第三章集中可適性輪盤監聽演算法......................................................................12
3.1 問題分析.....................................................................................................12
3.2 變數定義.....................................................................................................13
3.3 定位環境中的頻道數.................................................................................15
3.4 演算法說明.................................................................................................15
第四章 Simulation模擬及結果...............................................................................28
4.1 無線網路頻道環境設定.............................................................................28
4.2 snooper環境設定.......................................................................................31
4.3 模擬結果.....................................................................................................35
第五章結論..............................................................................................................51
第六章參考文獻......................................................................................................52

[1] 黃立恆/林華君,”802.11b/g 無線網路定位系統實作”,碩士論文,國立清華大學
[2] 林士國/林華君,”WLAN 定位系統的一些實驗結果”,碩士論文,國立清華大學
[3] 陳星輯/林華君,”運用輪盤式監聽演算法的IEEE 802.11 多頻道定位系統”,碩士論文,國立清華大學
[4] 林茂群/林華君,“使用快蒐演算法的802.11多頻道無線網路定位系統,碩士論文,國立清華大學
[5] P802.11, IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, ISO/IEC 8802-11:2007(E), June. 2007.
[6] Bianchi, G., Tinnirello, I., “Remarks on IEEE 802.11 DCF Performance Analysis”, Communications Letters, IEEE Volume 9, Issue 8, Aug 2005 Page(s):765 – 767
[7] Matthew S. Gast, “802.11 Wireless Networks: The Definitive Guide, 2nd Edition.“, O’REILLY, 2005
[8] “Centralized Channel Assignment and Routing Algorithms for Multi-Channel Wireless Mesh Networks” from Mobile Computing and Communications Review, Volume 8, Number 2
[9] Chatzimisios, P., Vitsas, V., Boucouvalas, A.C., “Revisit of Fading Channel Characteristics in IEEE 802.11 WLANs: Independent and Burst Transmission Errors”, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on, 11-14 Sept. 2006 Page(s): 1-6