本文選題：Ad + Hoc網路��； 參考：《沈陽航空航天大學》2017年碩士論文

【摘要】：隨著無線網絡的快速發(fā)展,網絡環(huán)境也日漸復雜,Ad Hoc網絡能夠在無基礎設施的場合或既設通信設施無法覆蓋的區(qū)域,為地理上相鄰但散布區(qū)域超過單個節(jié)點無線傳輸范圍的一組節(jié)點提供節(jié)點之間的通信服務,得到了眾多學者的重視與研究。本文對Ad Hoc網絡路徑選擇中泛洪消息沖突問題做出研究,改進了傳統(tǒng)重發(fā)策略算法,提高了廣播消息重傳效率。首先根據Ad Hoc網絡的應用環(huán)境及特點,提出了一種改進型的信道建模方法用以替代Ad Hoc網絡仿真中常用的自由空間傳播模型及兩徑模型,同時應用AODV協(xié)議及802.11 MAC協(xié)議實現路由查找及數據收發(fā)功能。通過計算機仿真,我們發(fā)現Ad Hoc網絡的性能與所使用的信道模型緊密相關,不同信道模型會導致系統(tǒng)性能產生較大差異。本文中所提出的改進型信道模型可以充分考慮信號傳播過程中的損耗、建筑物產生的陰影效應及信號傳輸過程中相位、幅度的小尺度衰減,不同信道模型將會影響Ad Hoc網絡仿真時的性能參數。其次對Ad Hoc網絡路徑選擇中泛洪消息問題做出了詳細的研究。首先分析了在Ad Hoc網絡場景下,利用概率論思想與隨機過程,建立泛洪方式下廣播包平均接收個數的閉式解,該閉式解能夠根據網絡性能得出廣播消息后能夠被接收端解調的數據包的個數,并進行真實網絡場景模擬驗證,通過仿真驗證了該閉式解的符合Ad Hoc網絡泛洪消息模型,理論值與仿真值基本相一致。最后改進了傳統(tǒng)廣播重發(fā)策略算法,該算法通過調整節(jié)點重發(fā)數據包的功率值進行重新選擇接入信道時隙發(fā)送,由于接收端是靠檢測廣播包功率值進行判決接收的,因此該算法降低了沖突數據包的丟包率。通過與原有的重發(fā)算法進行比較,改進后的算法減少了廣播重發(fā)次數,并通過仿真驗證了改進算法能夠減少廣播消息的重傳次數。因此本文所提出的無線信道模型以及改進的泛洪消息重發(fā)算法均可以應用的Ad Hoc網絡性能仿真中。
[Abstract]:With the rapid development of wireless networks, the network environment is becoming more and more complex. Many scholars have paid much attention to providing communication services for a group of nodes that are geographically adjacent but whose scattered areas exceed the wireless transmission range of a single node. In this paper, the problem of flooding message conflict in Ad Hoc network path selection is studied, the traditional retransmission strategy algorithm is improved, and the broadcast message retransmission efficiency is improved. Firstly, according to the application environment and characteristics of Ad Hoc network, an improved channel modeling method is proposed to replace the free space propagation model and two-path model commonly used in Ad Hoc network simulation. At the same time, AODV protocol and 802.11 MAC protocol are used to realize routing lookup and data transceiver. By computer simulation, we find that the performance of Ad Hoc networks is closely related to the channel models used, and different channel models will lead to great differences in system performance. The improved channel model proposed in this paper can fully take into account the loss in the signal propagation process, the shadow effect produced by the building, the phase in the signal transmission process and the small scale attenuation of the amplitude. Different channel models will affect the performance parameters of Ad Hoc network simulation. Secondly, the flooding message problem in Ad Hoc network path selection is studied in detail. Firstly, the closed-form solution of the average number of broadcast packets in flooding mode is established by using probability theory and stochastic process in Ad Hoc network scenario. According to the network performance, the closed solution can get the number of packets that can be demodulated by the receiver after broadcast message, and verify the real network scene simulation. The simulation results show that the closed solution accords with the flooding message model of Ad Hoc network. The theoretical value is basically consistent with the simulation value. Finally, the traditional broadcast retransmission strategy algorithm is improved. The algorithm reselects the time slot of access channel by adjusting the power value of the retransmission packet, because the receiver receives it by detecting the power value of the broadcast packet. Therefore, the algorithm reduces the packet loss rate of collision packets. Compared with the original retransmission algorithm, the improved algorithm reduces the number of broadcast retransmissions, and the simulation results show that the improved algorithm can reduce the number of retransmissions of broadcast messages. Therefore, the proposed wireless channel model and the improved flooding message retransmission algorithm can be used in the performance simulation of Ad Hoc networks.
【學位授予單位】：沈陽航空航天大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN929.5

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