【摘要】：無線Mesh網(wǎng)絡(Wireless Mesh Network,WMN)是由無線自組織網(wǎng)絡發(fā)展而來的一種新型網(wǎng)絡,是目前無線網(wǎng)絡研究的熱點。MAC層的無線信道接入技術是無線Mesh網(wǎng)絡的核心技術之一,MAC層信道接入時延和資源調度策略影響網(wǎng)絡的整體性能。文章中MAC層信道接入采用TDMA接入方式,并對時隙分配和時間同步技術進行研究。本文利用各個節(jié)點對時隙需求不同動態(tài)地進行時隙分配來提高信道利用率和降低端到端時延;通過對時鐘的漂移估計并進行補償提高時間同步精度,具體工作如下:基于TDMA動態(tài)時隙分配算法在進行時隙分配時很少考慮到節(jié)點的實際負載,一般只考慮了節(jié)點自己需要發(fā)送的信息包數(shù),沒有考慮需要此節(jié)點轉發(fā)的信息包數(shù),導致時隙分配不合理。此外,節(jié)點分配的時隙順序與節(jié)點號的順序不一致導致信息傳送中端到端延時急劇增加。因此本文提出改進算法TP-TDMA,利用預測機制來估計需要經(jīng)過本節(jié)點轉發(fā)的信息包數(shù)量,然后根據(jù)需要動態(tài)申請時隙個數(shù),同時利用鄰居節(jié)點的信息來優(yōu)化優(yōu)先級列表的權值設置,且對信息包進行優(yōu)先級劃分,降低端到端延時。仿真結果表明改進后的算法在不同跳數(shù)下、節(jié)點不同負載情況下的端到端延時都有一定的減少。本文主要研究了無線Mesh網(wǎng)絡的分布式時間同步算法,在傳統(tǒng)的同步算法中,節(jié)點只能在控制幀階段接入網(wǎng)絡,需要的時間較長,同時只是保證在同步時刻精度較高。所以本文提出了改進方法,使得節(jié)點在網(wǎng)絡中任何階段都能進行入網(wǎng)操作,大大減少了節(jié)點入網(wǎng)的時延。改進算法還在非周期同步期間對時鐘漂移進行了估計,并對時間進行調整,獲得了更高的同步精度。仿真結果顯示改進后的算法節(jié)點入網(wǎng)時延縮短很多,同步算法的收斂速度更快,可以在達到同樣的時間同步精度下可以延長同步周期,從而減少控制包的交互,降低能耗。
[Abstract]:Wireless Mesh Network (WMN) is a new type of network developed by wireless self-organizing network. MAC layer's wireless channel access technology is one of the core technologies of the wireless Mesh network, and the MAC layer channel access delay and resource scheduling policy affect the overall performance of the network. In this paper, the access mode of MAC layer in MAC layer is adopted, and the time slot allocation and time synchronization technology are studied. In this paper, the time slot allocation is used to improve the channel utilization rate and reduce the end-to-end time delay. A TDMA dynamic time slot allocation algorithm seldom takes into account the actual load of the node in the time slot allocation, and generally only considers the number of information packets that the node needs to send, and does not consider the number of packets required to be forwarded by the node, resulting in an unreasonable allocation of the time slot. In addition, the sequence of time slots allocated by the nodes does not accord with the order of the node numbers, resulting in a sharp increase in the end-to-end delay of the information transmission. therefore, the improved algorithm TP-TDMA is proposed, the number of the information packets to be forwarded by the node is estimated by the prediction mechanism, the number of the time slots is dynamically applied according to the requirement, the weight setting of the priority list is optimized by using the information of the neighbor nodes, and the information packets are prioritized, And the end-to-end delay is reduced. The simulation results show that the improved algorithm has a certain reduction in the end-to-end delay of the node under different load conditions. In this paper, the distributed time synchronization algorithm of the wireless mesh network is mainly studied. In the traditional synchronization algorithm, the nodes can only access the network in the control frame stage, and the time required is long, and the accuracy of the synchronization is only guaranteed. The improved method is proposed in this paper, so that the network access operation can be carried out at any stage in the network, and the time delay of network entry is greatly reduced. The improved algorithm also estimates the clock drift during the non-periodic synchronization and adjusts the time to obtain higher synchronization accuracy. The simulation results show that the time delay of the improved algorithm node is much shorter, the convergence rate of the synchronization algorithm is faster, and the synchronization period can be extended under the same time synchronization accuracy, thereby reducing the interaction of the control packet and reducing the energy consumption.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN929.5

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