【摘要】：時間同步是無線傳感器網(wǎng)絡(luò)（Wireless Sensor Network，WSN）的一項關(guān)鍵技術(shù)，它為分布式系統(tǒng)提供了一個共同的時間基準，在數(shù)據(jù)融合、功率管理、傳輸調(diào)度、定位跟蹤等方面都具有重要意義。因此，時間同步已成為研究的熱點話題之一。 無線傳感器網(wǎng)絡(luò)部署之后，網(wǎng)絡(luò)的壽命很大程度上取決于電池的壽命。在實際無線傳感器網(wǎng)絡(luò)中，通常節(jié)點不易收回，因此能源是一種稀缺資源。能量效率是設(shè)計無線傳感器網(wǎng)絡(luò)時間同步協(xié)議時應(yīng)該優(yōu)先考慮的主要因素，因此本文深入研究了低能耗的時間同步問題。本文的主要工作如下： （1）分析了無線傳感器網(wǎng)絡(luò)時間同步技術(shù)的國內(nèi)外研究現(xiàn)狀和時間同步的基本理論，對目前經(jīng)典的時間同步算法進行了分析與比較，為后續(xù)的研究提供了理論基礎(chǔ)。 （2）運用最大似然估計原理，提出了一種時鐘頻率偏移補償方法。針對現(xiàn)有的基于發(fā)送端接收端雙向時間同步的模型（例如TPSN算法等），都未考慮時鐘頻率偏移補償問題，導致同步精度較低。本文通過將網(wǎng)絡(luò)延遲建模為指數(shù)延遲模型，并對雙向交換中第一個和最后一個的同步信標分組的時間戳進行采樣，計算出時鐘頻率偏移和時鐘偏移，提高了時間同步精度，延長了同步周期。 （3）針對時間同步中的時間間隔、節(jié)點間雙向同步時交換的同步信標數(shù)目、以及同步模式的選擇等問題，提出了一種低能耗的多跳自適應(yīng)時間同步算法（MATS：Multi-hop Adaptive Time Synchronization）。該算法設(shè)計了一套靈活的機制來調(diào)整同步模式、全網(wǎng)重同步周期以及每對節(jié)點同步時的信標數(shù)，，并給出了對應(yīng)的量化模型，同時對節(jié)點的時鐘頻率偏移和時鐘偏移進行估計，實現(xiàn)了用較小的能量損耗完成長期的、全網(wǎng)的時間同步的目標。 （4）對上述提出的MATS算法在同步精度和能耗方面的影響因素進行了分析，并給出了幾種主要節(jié)能策略。同時，對MATS算法的同步誤差和能量消耗與TPSN算法進行了實驗比較，理論與仿真結(jié)果表明：MATS算法在同步精度和同步能耗上都是優(yōu)于TPSN算法的。 對時間同步協(xié)議的設(shè)計是需要考慮實際應(yīng)用的。本文提出的時間同步算法主要是針對環(huán)境監(jiān)測的應(yīng)用，對于其他低功耗的應(yīng)用需求，本文所采用的方法和思想也具有一定的借鑒意義。
[Abstract]:Time synchronization is a key technology in wireless sensor networks (Wireless Sensor Network,WSN). It provides a common time benchmark for distributed systems, in data fusion, power management, transmission scheduling, Location and tracking are of great significance. Therefore, time synchronization has become one of the hot topics. After the deployment of wireless sensor networks, the lifetime of the network depends to a great extent on the battery life. In practical wireless sensor networks, nodes are often difficult to recover, so energy is a scarce resource. Energy efficiency is the main factor that should be considered in the design of time synchronization protocol in wireless sensor networks. Therefore, the low energy consumption time synchronization problem is studied in this paper. The main work of this paper is as follows: (1) the research status and the basic theory of time synchronization in wireless sensor networks are analyzed, and the classical time synchronization algorithms are analyzed and compared. It provides a theoretical basis for further research. (2) using the principle of maximum likelihood estimation, a clock frequency offset compensation method is proposed. For the existing bidirectional time synchronization models based on the transmitter receiver (such as TPSN algorithm), the clock frequency offset compensation is not considered, which leads to low synchronization accuracy. In this paper, the network delay is modeled as exponential delay model, and the time stamp of the first and last synchronous beacon packets in bidirectional switching is sampled, the clock frequency offset and clock offset are calculated, and the precision of time synchronization is improved. The synchronization period is extended. (3) aiming at the time interval in time synchronization, the number of synchronous beacons exchanged between nodes, and the choice of synchronization mode. A low energy consumption adaptive time synchronization algorithm (MATS:Multi-hop Adaptive Time Synchronization).) is proposed. The algorithm designs a set of flexible mechanisms to adjust the synchronization mode, the whole network resynchronization period and the number of beacons in each pair of nodes synchronization, and gives the corresponding quantization model. At the same time, the clock frequency offset and clock offset of the node are estimated. The goal of long-term, whole-network time synchronization is achieved with small energy loss. (4) the factors affecting the synchronization accuracy and energy consumption of the proposed MATS algorithm are analyzed, and several main energy-saving strategies are given. At the same time, the synchronization error and energy consumption of the MATS algorithm are compared with the TPSN algorithm. The theoretical and simulation results show that the MATS algorithm is superior to the TPSN algorithm in synchronization accuracy and energy consumption. The design of time synchronization protocol needs to consider the practical application. The time synchronization algorithm proposed in this paper is mainly aimed at the application of environmental monitoring. For other low-power applications, the methods and ideas used in this paper also have some reference significance.
【學位授予單位】：重慶理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TP212.9;TN929.5

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