【摘要】：時(shí)間同步技術(shù)在無(wú)線傳感器網(wǎng)絡(luò)的數(shù)據(jù)融合、節(jié)點(diǎn)定位跟蹤、路由選擇、傳輸調(diào)度等應(yīng)用領(lǐng)域發(fā)揮著重要的作用,高精度時(shí)間同步技術(shù)的研究已成為近幾年的研究熱點(diǎn)。無(wú)線傳感器網(wǎng)絡(luò)節(jié)點(diǎn)通常被部署在惡劣的環(huán)境條件下,節(jié)點(diǎn)間的數(shù)據(jù)傳輸易受外界環(huán)境因素的干擾,因此,當(dāng)節(jié)點(diǎn)間通信數(shù)據(jù)受到干擾時(shí),如何使系統(tǒng)具有良好的容錯(cuò)性,確保數(shù)據(jù)和信息安全可靠的傳輸是本文研究的重點(diǎn)。在經(jīng)典同步協(xié)議中,泛洪時(shí)間同步協(xié)議(Flooding Time Synchronization Protocol,FTSP)兼顧了同步精度、能耗、魯棒性、可擴(kuò)展性等問(wèn)題。因此,本文是在FTSP協(xié)議的基礎(chǔ)上進(jìn)行分析與改進(jìn)的,鑒于協(xié)議在節(jié)點(diǎn)時(shí)間同步容錯(cuò)性方面考慮甚少,文章做了以下幾方面工作;(1)FTSP用線性回歸來(lái)估計(jì)時(shí)鐘漂移率,然而線性回歸估計(jì)法易受異常數(shù)據(jù)影響,估計(jì)值波動(dòng)較大。針對(duì)此問(wèn)題,本文提出了一種動(dòng)態(tài)加權(quán)平均算法,對(duì)歷史所測(cè)有限個(gè)時(shí)鐘漂移率進(jìn)行加權(quán)求解得出新的漂移值,新算法的加權(quán)系數(shù)是根據(jù)節(jié)點(diǎn)間收發(fā)時(shí)間標(biāo)動(dòng)態(tài)確定,從而減小異常數(shù)據(jù)對(duì)線性回歸的影響。(2)針對(duì)無(wú)線傳感器網(wǎng)絡(luò)節(jié)點(diǎn)的時(shí)間同步誤差隨著節(jié)點(diǎn)跳數(shù)增加而增加的問(wèn)題,本文采用多源系統(tǒng)代替?zhèn)鹘y(tǒng)的單源系統(tǒng)來(lái)降低節(jié)點(diǎn)的跳數(shù),以此來(lái)降低節(jié)點(diǎn)的同步累計(jì)誤差。在網(wǎng)絡(luò)拓?fù)浣Y(jié)構(gòu)相同的情況下,通過(guò)實(shí)驗(yàn)仿真分析,多源系統(tǒng)的節(jié)點(diǎn)平均跳步數(shù)和最大跳步數(shù)都比單源系統(tǒng)低,系統(tǒng)節(jié)點(diǎn)的累計(jì)誤差也有明顯的減小。(3)針對(duì)多源系統(tǒng)提出了一種多源抗攻擊算法,算法在FTSP原始同步信息的數(shù)據(jù)包中加入了發(fā)送節(jié)點(diǎn)ID和黑名單兩個(gè)字段,根據(jù)同一節(jié)點(diǎn)在連續(xù)兩個(gè)周期里時(shí)鐘漂移率的差值來(lái)判斷發(fā)送節(jié)點(diǎn)性質(zhì),當(dāng)差值大于預(yù)先設(shè)定的閾值時(shí),則認(rèn)為發(fā)送節(jié)點(diǎn)為惡意節(jié)點(diǎn),將節(jié)點(diǎn)的ID號(hào)加入黑名單發(fā)送出去,通知等待同步的節(jié)點(diǎn)拒絕接受惡意節(jié)點(diǎn)的同步信息,以此來(lái)提高系統(tǒng)的魯棒性和安全性。最后,通過(guò)仿真結(jié)果表明,改進(jìn)的時(shí)間同步算法在時(shí)間同步誤差、容錯(cuò)性以及安全方面都有較大的改善。
[Abstract]:Time synchronization technology plays an important role in the application fields of wireless sensor networks, such as data fusion, node location and tracking, routing, transmission scheduling and so on. The research of high precision time synchronization technology has become a hot research topic in recent years. Wireless sensor network nodes are usually deployed under harsh environmental conditions, and the data transmission between nodes is easily interfered by external environmental factors. Therefore, when the communication data between nodes is interfered, how to make the system have good fault tolerance and ensure the secure and reliable transmission of data and information is the focus of this paper. In the classical synchronization protocol, flooding time synchronization protocol (Flooding Time Synchronization Protocol,FTSP) takes into account the synchronization accuracy, energy consumption, robustness, scalability and so on. Therefore, this paper analyzes and improves on the basis of FTSP protocol, in view of the fact that the protocol has little consideration in node time synchronization fault tolerance, the following work has been done in this paper. (1) FTSP uses linear regression to estimate clock drift rate, however, linear regression estimation method is easily affected by abnormal data and the estimated value fluctuates greatly. In order to solve this problem, a dynamic weighted average algorithm is proposed to obtain a new drift value from the weighted solution of the limited clock drift rate measured in history. The weighting coefficient of the new algorithm is determined dynamically according to the inter-node transceiver time scale, so as to reduce the influence of abnormal data on linear regression. (2) aiming at the problem that the time synchronization error of wireless sensor network nodes increases with the increase of node hops, In this paper, the multi-source system is used instead of the traditional single-source system to reduce the hop number of the node, so as to reduce the synchronous cumulative error of the node. Under the condition that the network topology is the same, through the experimental simulation analysis, it is found that the average hop number and the maximum jump step number of the multi-source system are lower than those of the single-source system, and the cumulative error of the system node is also obviously reduced. (3) A multi-source anti-attack algorithm is proposed for the multi-source system. The algorithm adds two fields of sending node ID and blacklist to the packet of FTSP original synchronization information. The nature of the sending node is judged according to the difference of the clock drift rate of the same node in two consecutive cycles. When the difference is greater than the predetermined threshold, the sending node is considered to be a malicious node. The ID number of the node is added to the blacklist to notify the node waiting for synchronization to refuse to accept the synchronization information of the malicious node, so as to improve the robustness and security of the system. Finally, the simulation results show that the improved time synchronization algorithm has great improvement in time synchronization error, fault tolerance and security.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TP212.9;TN929.5

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