本文選題：水下傳感器網(wǎng)絡(luò) + 時(shí)間同步　； 參考：《中國海洋大學(xué)》2014年碩士論文

【摘要】：隨著信息技術(shù)和海洋科技的飛躍發(fā)展，作為一種新興的海洋信息采集技術(shù)，水下聲學(xué)傳感器網(wǎng)絡(luò)（Underwater Acoustic Sensor Networks, UASN）越來越受到重視，被廣泛應(yīng)用于海洋環(huán)境監(jiān)測、海洋污染監(jiān)控、海洋資源勘測、水下目標(biāo)的探測、跟蹤和定位等領(lǐng)域。該網(wǎng)絡(luò)的主體由水面基站和水下傳感器節(jié)點(diǎn)組成，節(jié)點(diǎn)部署范圍大、密度低；節(jié)點(diǎn)之間采用水下聲波通信，而水聲通信的鏈路質(zhì)量受海洋環(huán)境變化的復(fù)雜因素影響，具有低傳播速度、高延遲、延遲時(shí)變、高誤碼率、低帶寬、多途效應(yīng)嚴(yán)重及高能耗等特點(diǎn)。 時(shí)間同步是傳感器網(wǎng)絡(luò)中一項(xiàng)重要的支撐技術(shù)，它為協(xié)調(diào)跨多節(jié)點(diǎn)的傳感與驅(qū)動(dòng)提供統(tǒng)一的參考時(shí)鐘，是節(jié)點(diǎn)協(xié)同工作的基礎(chǔ)，傳感器網(wǎng)絡(luò)的數(shù)據(jù)融合、時(shí)分復(fù)用調(diào)度、節(jié)點(diǎn)定位和協(xié)同休眠等關(guān)鍵技術(shù)都依賴于節(jié)點(diǎn)間的時(shí)間同步。由于水下傳感器網(wǎng)絡(luò)采用聲波通信，，傳播速度低且通信鏈路較長，并考慮到節(jié)點(diǎn)在水下隨海流移動(dòng)，導(dǎo)致了巨大的傳播延遲和時(shí)空不確定性，使得傳統(tǒng)的陸上無線傳感器網(wǎng)絡(luò)時(shí)間同步算法不能直接應(yīng)用于水下。因此，UASN時(shí)間同步中必須同時(shí)考慮延遲時(shí)變性和節(jié)點(diǎn)相對(duì)運(yùn)動(dòng)造成的影響，這為同步算法研究帶來了新的挑戰(zhàn)。 目前，國內(nèi)外對(duì)于UASN時(shí)間同步算法的研究，主要采用基于單信標(biāo)單跳的點(diǎn)到點(diǎn)同步機(jī)制，即假定整個(gè)網(wǎng)絡(luò)或網(wǎng)絡(luò)的一個(gè)分簇中，每個(gè)節(jié)點(diǎn)都存在到信標(biāo)節(jié)點(diǎn)的單跳路由，通過與信標(biāo)節(jié)點(diǎn)的多次消息交互和計(jì)算，即可完成全網(wǎng)時(shí)間同步。但是，由于海洋監(jiān)測任務(wù)涉及范圍較大，實(shí)際中水下節(jié)點(diǎn)多采用0.5km~2km的長間距部署，節(jié)點(diǎn)間通信方式一般采用基于多跳傳輸?shù)臋C(jī)會(huì)路由。所以，現(xiàn)有的點(diǎn)到點(diǎn)同步算法，難以適應(yīng)水下傳感器網(wǎng)絡(luò)的實(shí)際部署要求。 本文為解決多跳網(wǎng)絡(luò)中同步精度隨跳數(shù)降低的問題，研究和設(shè)計(jì)基于多信標(biāo)節(jié)點(diǎn)和多跳傳輸?shù)亩嘣赐较⑷诤纤惴�，充分利用多源同步消息的時(shí)間有效性，以提高整個(gè)網(wǎng)絡(luò)的同步精度。本文提出水下傳感器網(wǎng)絡(luò)多源時(shí)間同步算法MSTS（Multi-Source Time Synchronization），采用仿真實(shí)驗(yàn)探究方法評(píng)估路徑跳數(shù)對(duì)于同步消息時(shí)間有效性的影響，在多次消息交互中融合不同有效性的同步消息，運(yùn)用以消息時(shí)間置信度為權(quán)的加權(quán)線性擬合，估計(jì)節(jié)點(diǎn)時(shí)鐘頻率偏斜和相位偏差。 同時(shí)，為準(zhǔn)確評(píng)估水下同步算法的性能，本文研究和開發(fā)了水下傳感器網(wǎng)絡(luò)仿真系統(tǒng)（Underwater Sensor Network Simulator，UWSN-Sim），建立水聲通信模擬環(huán)境及節(jié)點(diǎn)運(yùn)動(dòng)模型，模擬多時(shí)間基準(zhǔn)節(jié)點(diǎn)條件下的多跳同步消息傳輸。利用UWSN-Sim仿真系統(tǒng)，設(shè)置不同的仿真場景和通信參數(shù)，通過大量仿真實(shí)驗(yàn)?zāi)M水下傳感器網(wǎng)絡(luò)不同的拓?fù)浣Y(jié)構(gòu)和部署規(guī)模，驗(yàn)證了MSTS算法在多跳拓?fù)湎戮哂休^高的同步精度；并且，在大規(guī)模部署的多跳網(wǎng)絡(luò)中，與逐跳迭代同步的MU-Sync算法相比較，MSTS算法以較低的平均消息開銷和更短的總體運(yùn)行耗時(shí)，達(dá)到了更高數(shù)量級(jí)的同步精度。
[Abstract]:With the rapid development of information technology and marine science and technology, as a new marine information acquisition technology, Underwater Acoustic Sensor Networks (UASN) has been paid more and more attention. It is widely used in marine environment monitoring, marine pollution monitoring, marine resources survey, underwater target detection, tracking and positioning. The main body of the network is composed of water surface base station and underwater sensor node, with large deployment range, low density, underwater acoustic communication between nodes, and the link quality of underwater acoustic communication is influenced by complex factors of ocean environment change, with low propagation speed, high delay, delay time change, high error rate, low bandwidth and multipath effect. The characteristics of severe and high energy consumption.
Time synchronization is an important support technology in sensor networks. It provides a unified reference clock for coordinating the sensing and driving of multiple nodes. It is the basis of the joint work of nodes. The key technologies of sensor networks, such as data fusion, time division multiplexing, node location and cooperative dormancy, depend on time synchronization between nodes. Underwater sensor networks adopt sound wave communication with low propagation speed and long communication links. Considering that nodes move with sea currents under water, it leads to huge propagation delay and time and space uncertainty, which makes the traditional time synchronization algorithm of terrestrial wireless sensor network cannot be directly used in water. Therefore, the time synchronization of UASN must be simultaneous. Considering the effect of delay time variation and node relative motion, this brings new challenges to synchronization algorithm research.
At present, at home and abroad, the research of UASN time synchronization algorithm mainly adopts the point to point synchronization mechanism based on single beacon single hop, which assumes that each node has a single hop route to the beacon node in a cluster of network or network, and can complete the whole network time synchronization through multiple message interaction and computation with the beacon node. Because the ocean monitoring task involves a large range, the actual underwater nodes are mostly deployed in long distance between 0.5km~2km, and the communication mode between nodes generally adopts the opportunity routing based on multi hop transmission. Therefore, the existing point to point synchronization algorithm is difficult to adapt to the actual deployment requirements of underwater sensor networks.
In order to solve the problem of reducing the synchronization accuracy with the number of hops in multi hop networks, this paper studies and designs a multi source synchronization message fusion algorithm based on multi beacon and multi hop transmission. It makes full use of the time validity of multi source synchronization messages to improve the synchronization accuracy of the whole network. This paper proposes a multi source time synchronization algorithm MSTS for the underwater sensor network. (Multi-Source Time Synchronization), the simulation experiment is used to evaluate the effect of path hops on synchronization message time validity. The synchronization messages with different effectiveness are fused in multiple message interaction, and the weighted linear fitting with the weight of message time confidence is used to estimate the node clock frequency skew and phase deviation.
At the same time, in order to accurately evaluate the performance of underwater synchronization algorithm, this paper studies and develops an underwater sensor network simulation system (Underwater Sensor Network Simulator, UWSN-Sim), establishes a simulation environment of underwater acoustic communication and a node motion model, and simulate multi hop synchronous message transmission under the condition of multi time datum nodes. A UWSN-Sim simulation system is used. Different simulation scenes and communication parameters are set up, and the different topology and deployment size of underwater sensor network are simulated by a large number of simulation experiments. It is verified that the MSTS algorithm has high synchronization accuracy under multi hop topology. And, in the multi hop network of large-scale deployment, the MSTS algorithm is compared with the MU-Sync algorithm which is synchronized with the hop by hop iteration. With lower average message overhead and shorter overall operation time, the synchronization accuracy is higher.
【學(xué)位授予單位】：中國海洋大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN929.3;TP212.9

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