【正文】 無線 Mesh 網(wǎng)絡 MAC 層協(xié)議優(yōu)化問題的研究 中國科學技術大學 碩士學位論文 無線 Mesh 網(wǎng)絡 MAC 層協(xié)議優(yōu)化問題研究 姓名秦桂紅 申請學位級別碩士 專業(yè)控制理論與控制工程 指導教師譚小彬 20200506 摘 要 無線 Mesh 網(wǎng)絡也稱為多跳網(wǎng)絡是一種與傳統(tǒng)無線網(wǎng)絡完全不同的新 型網(wǎng)絡技術隨著計算機網(wǎng)絡技術的不斷發(fā)展無線網(wǎng)絡越來越引起人們的重視 本文主要研究無線 Mesh 網(wǎng)絡 MAC 層協(xié)議的優(yōu)化問題 近年來針對無線 Mesh 網(wǎng)絡的研究主要分為兩大部分一部分是對 MAC 層的 DCF 機制的優(yōu)化研究另一部分是對傳輸流的優(yōu)化控制 作為一種新型的傳輸方式網(wǎng) 絡編碼可以大大提高無線網(wǎng)絡吞吐量網(wǎng)絡編 碼主要分為流內(nèi)和流間編碼兩種目前已實現(xiàn)的無線網(wǎng)絡編碼的協(xié)議主要是基于 較理想的網(wǎng)絡狀況或丟包率很低的網(wǎng)絡而實際的無線網(wǎng)絡丟包是不可避免的 而且研究表明實際無線 Mesh 網(wǎng)絡的丟包率在 30 左右或之上 本文首先針對無線 Mesh 網(wǎng)絡的退避機制提出了一種將鏈路狀況引入到退避 時間的計算上來的優(yōu)化算法然后基于無線網(wǎng)絡編碼研究提出了新型的線性編碼 和雙重解碼策略 針對 80211 MAC 層 DCF 的二進制退避算法存在的問題即不能 動態(tài)適應 網(wǎng)絡環(huán)境的變化本文采用新型的延遲退避算法將鏈路狀況引入到退避和延遲 時間的計算上來使得數(shù)據(jù)幀的傳輸能夠根據(jù)網(wǎng)絡鏈路狀況的變化而動態(tài)的調(diào) 整避免擁塞的產(chǎn)生和資源的浪費 針對前人提出的網(wǎng)絡編碼方法不能很好的適用于丟包率較高的無線網(wǎng)絡本 文提出了適合于丟包率較高的無線 Mesh 網(wǎng)絡的新型的線性網(wǎng)絡編碼和雙重解碼 方案編碼包的形成采用隨機線性編碼策略充分利用編碼包的冗余特性并且 采用線性編碼和機會轉(zhuǎn)發(fā)策略相結(jié)合創(chuàng)造更多的編碼機會在解碼過程中采 用雙重解碼策略提高解碼 成功率首先采用普通的 OVERHEARD 隊列中的普通 包進行解碼解碼失敗后再采用編碼緩存里面線性獨立的兩個編碼包解碼如果 仍然解碼失敗則放棄此編碼包處理下一個編碼包 最后通過理論分析和 NS2 實驗仿真通過比較吞吐量和解碼成功率等性能 指標驗證了我們提出的新型退避機制和新型線性編碼雙重解碼方案用于丟包 率較高的無線 Mesh 網(wǎng)絡的有效性 關鍵詞無線 Mesh 網(wǎng)絡線性網(wǎng)絡編碼丟包率 DCF I ABSTRACT Wireless Mesh works are also referred to as multihop work which is a new work technology that pletely different with the traditional wireless works With the continuous development of puter work technology people have paid more attention to the wireless work In this paper we mainly study the optimization problem of MAC layer protocol of Wireless Mesh Networks WMN The research of wireless mesh works is divided into two parts one is the optimization of DCF mechanism of the MAC layer itself and the other is the optimization of traffic control As a new transmission pattern work coding can greatly improve the throughput of wireless works it can be divided into intraflow encoding and interflow encoding pattern However the wireless work coding protocol has been realized mainly based on the ideal work conditions or the work packet loss rate is very low while in the actual wireless work packet loss is inevitable and the research shows that the actual packet loss rate is about 30 or above for wireless work In this paper we firstly propose a new backoff mechanism for WMN by introducing the link status of the work to calculate the backoff time and then propose a new type of linear encoding and dualdecoding strategy for wireless work based on the more and more popular work coding research The original DCF binary backoff algorithm of MAC layer for 80211 protocols exist some problems which can not dynamically adapt to the work environment changes So we use the new delay backoff algorithm that is to concern the link status and delay time when calculate the backoff time using this method can make the data frame transmission dynamically adjust to the work link status and avoid the congestion and waste of resources The previous proposed work coding protocols are not suitable for the WMN which has higher packet loss rate In this paper we propose a new linear coding program and dualdecoding program for WMN In the encode process we use the random linear coding strategy to take full advantages of the redundancy coding package and bine work coding and opportunity forward strategy to create more encoding opportunities and in the decoding process we adopt the III doubledecoding strategy to improve the decoding success rate Firstly the node decode the packets using the original packets in the OVERHEARD queue then it will decode using packets in the code cache when the first decode failed the node will discard this packets and handle the next one if the second decode process still failed Finally through the theoretical analysis and NS2 simulation by paring the throughput and decoding success rate performance we can prove the effectiveness of the new linear encoding and doubledecoding scheme for high packet loss rate wireless mesh work Key Words Wireless Mesh Network linear work coding packet loss rateDCF IV 中國科學技術大學學位論文原創(chuàng)性聲明 本人聲明所呈交的學位論文是本人 在導師指導下進行研究工作所取得的成 果除已特別加以標注和致謝的地方外論文中不包含任何他人已經(jīng)發(fā)表或撰寫 過的研究成果與我一同工作的同志對本研究所做的貢獻均已在論文中作了明確 的說明 作者簽名 ___________ 簽字日期_______________ 中國科學技術大學學位論文授權使用聲明 作為申請學位的條件之一學位論文著作權擁有者授權中國科學技術大學擁 有學位論文的部分使用權即學校有權按有關規(guī) 定向國家有關部門或機構(gòu)送交 論文的復印件和電子版允許論文被查閱和借閱可以將學位論文編入《中國學 位論文全文數(shù)據(jù)庫》等有關數(shù)據(jù)庫進行檢索可以采用影印縮印或掃描等復制 手段保存匯編學位論文本人提交的電子文檔的內(nèi)容和紙質(zhì)論文的內(nèi)容相一致 保密的學位論文在解密后也