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    Title: IEEE 802.11r無線區域網路預先註冊換手機制之研究
    Other Titles: A pre-registered handoff scheme in IEEE 802.11r wireless local area networks
    Authors: 楊慧玉;Yang, Huei-yu
    Contributors: 淡江大學電機工程學系碩士班
    李維聰;Lee, Wei-tsong
    Keywords: 快速換手;IEEE 802.11r;Fast Handoff
    Date: 2009
    Issue Date: 2010-01-11 07:18:35 (UTC+8)
    Abstract: 隨著IEEE 802.11(WiFi)的大量建置,使用WiFi 上網的使用者逐年增加,使用者使用網路的情況也由固定式網路,改變為使用手持式系統運用無線網路來擷取資訊。其中,最受人注目的就是即時影像服務與VoIP。對於即時服務的應用程式而言,最重要的就是網路延遲率,IEEE 802.11家族,為了能夠支援在高速的移動率下,仍然能夠提供無縫式換手,訂定了IEEE 802.11r protocol,IEEE 802.11r 定義了新的金鑰架構,利用事先註冊金鑰的方式,將註冊程序提前到re-association 之前,讓換手時間大幅降低,同時,為了避免金鑰因為預先註冊而有被盜用的危險,IEEE 802.11r 使用了IEEE 802.11i 對於金鑰有更嚴格的產生方式,用來作安全的金鑰交換。
    由於IEEE 802.11r 中預設所有基地台都會有身份認證的金鑰,雖然因此降低了換手的時間,但無形中也增加了在網路上的認證資訊,在本論文中,提出基於IEEE 802.11r 的架構下,對數個基地台做預先註冊的程序避免因為安全認證資訊增加了網路的負擔。論文中,先將基地台分為四個區域(前、後、左、右)。接著,利用移動使用者在速度越快的情況下越不易改變移動方向的特性來縮減考慮預先註冊的基地台範圍。
    最後,再預估使用者前方的基地台所服務的使用者數目,選擇使用者較少的基地台作為預先註冊的基地台。藉此平衡基地台的服務負荷量,避免大量使用者同時與同一個基地台請求連線服務。經過了本論文的改善後,IEEE 802.11r 不但能夠兼顧快速換手的需求,還能避免過多的認證資訊交換造成網路的負擔,並且能夠平衡基地台的服務負荷量。
    Recently, with the more extensive deployment of Wireless Local Area Networks (WLAN) and the growing population of mobile users, more users accustomed getting information by way of wireless network. For real-time service, real-time video and VOIP attract many attentions and the delay time which the mobile user executes handoff is the most important issue for the service. In order to provide high speed and low delay service, IEEE 802.11r defines new key architecture which executes register a part of procedure before re-association procedure to reduce handoff time. Moreover in order to prevent the information security, IEEE 802.11r keeps using IEEE 802.11i which defines strict key generation to execute secure key exchange.
    Due to IEEE 802.11r will expect that all Access Point (AP) has exchanged secure keys. In this way it will reduce handoff delay time but will cause the authenticated information increment. In this paper which based on IEEE 802.11r, executes pre-register procedure with several specific AP in order to reduce exchanged secure keys. First, separates APs into for regions (besides user’s front, behind, left or right) using RSSI variation. Second, uses user’s feature that moves high speed, changes direction hardly, when user moves faster, the region (besides user’s front) changes concentration. Finally, predicts AP service number of persons, and choices AP that services fewest people. And it will avoid users register with unique AP at the same time; balance the AP service overhead. Through above three suggestions, IEEE 802.11r will execute fast handoff, avoid a lot of authenticated messages exchange over the air and balance the APs service overhead.
    Appears in Collections:[電機工程學系暨研究所] 學位論文

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