發(fā)布時(shí)間：2018-05-07 01:16

  本文選題：WiFi + IEEE��； 參考：《西安理工大學(xué)》2017年碩士論文

【摘要】：自20世紀(jì)9如年代以來,無線局域網(wǎng)(Wireless Local Area Networks,WLAN) 因具有無線通信技術(shù)和計(jì)算機(jī)網(wǎng)絡(luò)的覆蓋范圍廣、布線靈活、傳輸速率快等諸多優(yōu)點(diǎn)得到了快速的發(fā)展和應(yīng)用。在無線局域網(wǎng)標(biāo)準(zhǔn)中,IEEE 802.11系列標(biāo)準(zhǔn)因簡單規(guī)范、兼容性好和眾多廠商支持等優(yōu)勢已然成為事實(shí)上近距離無線通信技術(shù)的通用標(biāo)準(zhǔn),盡管WLAN能夠?yàn)橐苿?dòng)應(yīng)用提供足夠的帶寬,然而由于無線接入點(diǎn)(Access Point, AP)發(fā)射功率受限,其服務(wù)覆蓋的范圍也就受限,用戶越來越不滿族于在固定AP的服務(wù)區(qū)域內(nèi)上網(wǎng),這使得移動(dòng)終端(Mobile Node,MN)在移動(dòng)過程中需要在不同AP之間頻繁切換換。而IEEE 802.11“先斷后連”的思想極大地限制了MN的切換性能,由此帶來的切換延時(shí)嚴(yán)重影響了通信的服務(wù)質(zhì)量和實(shí)時(shí)性應(yīng)用程序的用戶體驗(yàn)。因此,如何減少介質(zhì)訪問控制(Media Access Control ,MAC )層的切換延時(shí),改善網(wǎng)絡(luò)中MN的漫游切換性能,已經(jīng)成為IEEE 802.11移動(dòng)切換管理研究中一項(xiàng)亟待解決的關(guān)鍵技術(shù)。針對上述問題,本文作了如下3點(diǎn)研究:(1)從理論上分析了傳統(tǒng)IEEE 802.11無線網(wǎng)絡(luò)MAC層的切換機(jī)制和各階段延時(shí),分析出掃描階段是造成切換延時(shí)的重要因素,井對該階段算法采取了改進(jìn)措施。(2)基信道優(yōu)先級和掩碼機(jī)制,本文設(shè)計(jì)了減少信道描數(shù)算法;在此基礎(chǔ)上,改進(jìn)的選擇性鄰居圖緩存算法運(yùn)用鄰居圖原理,將移動(dòng)終端MN掃描和接入的AP相關(guān)信息上傳給服務(wù)器,版務(wù)器根據(jù)接收信號強(qiáng)度,用戶負(fù)載和歷史接入數(shù)據(jù)對鄰居AP進(jìn)行優(yōu)化排序。然后把AP列表信息緩存到本地,等待客戶端移動(dòng)切換。(3)最后在搭建的共享WiFi系統(tǒng)環(huán)境中,使用網(wǎng)絡(luò)協(xié)議分析軟件WireShark對移動(dòng)終端MN在多AP間的MAC層水平切換性能進(jìn)行分析。經(jīng)實(shí)驗(yàn)測試,與傳統(tǒng)的全信道掃描算法對比可知,改進(jìn)的切換算法在該環(huán)境下可有效減少整體切換的延遲,從而滿足實(shí)時(shí)性業(yè)務(wù)的服務(wù)質(zhì)量要求。
[Abstract]:Since the 9th century, WLAN Wireless Local Area Networks (WLAN) has been rapidly developed and applied because of its wide coverage of wireless communication technology and computer network, flexible wiring, fast transmission rate, and so on. In the WLAN standards, the IEEE 802.11 series standards have become the common standard of the close-range wireless communication technology because of the advantages of simple specification, good compatibility and support from many manufacturers, even though WLAN can provide sufficient bandwidth for mobile applications. However, due to the limited transmission power of wireless access point (APs), its service coverage is also limited, and users are less and less able to access the Internet in the fixed AP service area. This makes the mobile terminal mobile NodeMN) need to switch frequently between different APs during the mobile process. However, the idea of "first breaking and then connecting" in IEEE 802.11 greatly limits the handoff performance of MN, and the resulting handoff delay seriously affects the quality of service of communication and the user experience of real-time applications. Therefore, how to reduce the handoff delay and improve the roaming handoff performance of MN has become a key technology in the research of IEEE 802.11 mobile handoff management. Aiming at the above problems, this paper makes the following three research points: 1) theoretically analyzes the handoff mechanism and delay of the MAC layer of traditional IEEE 802.11 wireless network, and analyzes that the scanning phase is an important factor to cause the handoff delay. In this paper, the algorithm of reducing channel number is designed, on the basis of which, the improved algorithm of selective neighbor graph cache is based on the principle of neighbor graph. The AP related information of mobile terminal MN scanning and accessing is uploaded to the server. The server optimizes the neighbor AP according to the received signal strength, user load and historical access data. Then the AP list information is cached to the local, waiting for the client mobile handover. Finally, the network protocol analysis software WireShark is used to analyze the performance of the mobile terminal MN in the MAC layer level switching between multiple APs in the shared WiFi system environment. The experimental results show that the improved handoff algorithm can effectively reduce the overall handoff delay and meet the quality of service requirements of real-time services compared with the traditional full-channel scanning algorithm.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN92

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本文編號：1854747