本文選題：機(jī)會(huì)性網(wǎng)絡(luò)編碼　切入點(diǎn)：無(wú)線網(wǎng)絡(luò)　出處：《電子科技大學(xué)》2014年博士論文

【摘要】：網(wǎng)絡(luò)編碼(Network Coding)被視為一種有前景的技術(shù),在無(wú)線網(wǎng)絡(luò)中可用來(lái)減少傳輸次數(shù),提高帶寬利用率,改善網(wǎng)絡(luò)吞吐率和能量效率。如何設(shè)計(jì)更好的網(wǎng)絡(luò)編碼架構(gòu)和機(jī)制來(lái)充分發(fā)揮網(wǎng)絡(luò)編碼的性能增益是目前學(xué)術(shù)界的研究熱點(diǎn)。網(wǎng)絡(luò)編碼的基本思想是允許網(wǎng)絡(luò)中間節(jié)點(diǎn)將多個(gè)數(shù)據(jù)包融合為一個(gè)編碼數(shù)據(jù)包加以發(fā)送,從而減少傳輸次數(shù),改善網(wǎng)絡(luò)吞吐率。受益于無(wú)線通信內(nèi)在的廣播特性和偵聽(tīng)能力,網(wǎng)絡(luò)編碼更加適合應(yīng)用于無(wú)線網(wǎng)絡(luò)。為使得網(wǎng)絡(luò)編碼在無(wú)線網(wǎng)絡(luò)中應(yīng)用時(shí)盡可能減少對(duì)網(wǎng)絡(luò)協(xié)議棧的改變,機(jī)會(huì)性網(wǎng)絡(luò)編碼是一個(gè)可行的選擇。根據(jù)機(jī)會(huì)性網(wǎng)絡(luò)編碼不同的應(yīng)用場(chǎng)景,需要考慮多種因素對(duì)其性能增益的影響,比如節(jié)點(diǎn)的緩存資源、處理能力等。針對(duì)不同的因素,建立相應(yīng)的數(shù)學(xué)模型,優(yōu)化其在無(wú)線網(wǎng)絡(luò)中的性能增益。因此,針對(duì)機(jī)會(huì)性網(wǎng)絡(luò)編碼在無(wú)線網(wǎng)絡(luò)中的應(yīng)用,本文指出了在不同網(wǎng)絡(luò)場(chǎng)景和情形下需要進(jìn)一步研究的問(wèn)題,并提出了相應(yīng)的優(yōu)化架構(gòu)和機(jī)制。全文的主要內(nèi)容包括:首先考慮緩存資源對(duì)機(jī)會(huì)性網(wǎng)絡(luò)編碼性能增益的影響�，F(xiàn)有機(jī)會(huì)性網(wǎng)絡(luò)編碼架構(gòu)都假定節(jié)點(diǎn)擁有無(wú)限的緩存資源和處理能力。在此前提下,網(wǎng)絡(luò)各節(jié)點(diǎn)需要解碼包池緩存所有偵聽(tīng)到的和已發(fā)送的數(shù)據(jù)包足夠長(zhǎng)時(shí)間,用以未來(lái)可能的解碼需要。同時(shí),節(jié)點(diǎn)間通過(guò)“接收?qǐng)?bào)告”相互周期性地交換各自包池中所擁有數(shù)據(jù)包信息,以確保編碼包的可解性。然而,當(dāng)節(jié)點(diǎn)緩存空間受限時(shí),機(jī)會(huì)性網(wǎng)絡(luò)編碼的性能增益將會(huì)受到影響。即使節(jié)點(diǎn)資源無(wú)限大,現(xiàn)有的機(jī)會(huì)性網(wǎng)絡(luò)編碼解碼包池緩存機(jī)制會(huì)帶來(lái)更大的網(wǎng)絡(luò)開(kāi)銷(xiāo)、從而降低網(wǎng)絡(luò)吞吐率。為了解決這一問(wèn)題,本文提出了一種機(jī)會(huì)性網(wǎng)絡(luò)編碼框架來(lái)優(yōu)化緩存資源的解碼效用。通過(guò)分析,我們將緩存資源與解碼性能之間的關(guān)系歸結(jié)為一個(gè)最優(yōu)化數(shù)學(xué)模型。通過(guò)這個(gè)優(yōu)化模型,我們推導(dǎo)出一系列的緩存規(guī)則,并提出了一種分布式的機(jī)會(huì)性網(wǎng)絡(luò)編碼緩存策略。仿真結(jié)果證實(shí)了該模型的有效性,并證明該策略可以有效改善節(jié)點(diǎn)緩存資源利用率,提高機(jī)會(huì)性網(wǎng)絡(luò)編碼性能增益。對(duì)于機(jī)會(huì)性網(wǎng)絡(luò)編碼在受干擾無(wú)線網(wǎng)絡(luò)中的應(yīng)用,現(xiàn)有機(jī)會(huì)性網(wǎng)絡(luò)編碼架構(gòu)通過(guò)偽廣播一次性將一個(gè)編碼包投遞至多個(gè)接收節(jié)點(diǎn),并依賴于捎帶在數(shù)據(jù)包包頭中的異步ACKs來(lái)確認(rèn)接收。在給定時(shí)間內(nèi)未被確認(rèn)接收的數(shù)據(jù)包將被再次插入發(fā)送隊(duì)列、編碼發(fā)送。這種機(jī)制在丟包無(wú)線網(wǎng)絡(luò)中容易由于數(shù)據(jù)包的丟失和延遲到達(dá)而招致大量冗余重傳、浪費(fèi)網(wǎng)絡(luò)帶寬。此外,為了確保編碼包的可靠投遞,現(xiàn)有網(wǎng)絡(luò)編碼架構(gòu)默認(rèn)編碼節(jié)點(diǎn)采用最低傳輸速率來(lái)加以投遞。這樣會(huì)導(dǎo)致較長(zhǎng)的傳輸時(shí)間,并增加了數(shù)據(jù)包發(fā)生碰撞的可能。針對(duì)以上問(wèn)題,我們提出了一個(gè)結(jié)合傳輸速率控制和網(wǎng)絡(luò)編碼碼字選擇的框架ORC來(lái)對(duì)網(wǎng)絡(luò)層和MAC層進(jìn)行聯(lián)合優(yōu)化。該框架將編碼包傳輸?shù)乃俾士刂茊?wèn)題歸結(jié)為一個(gè)馬爾科夫決策過(guò)程,從而獲得最優(yōu)的速率選擇策略。然后,基于以上速率選擇后的結(jié)果,從所有可能的編碼包組合中選擇最佳的編碼包組合并予以發(fā)送。對(duì)于編碼包組合問(wèn)題,我們將其歸結(jié)為一個(gè)最大加權(quán)團(tuán)問(wèn)題,并提出了一個(gè)碼的選擇算法。網(wǎng)絡(luò)仿真證實(shí),框架ORC可以有效改善網(wǎng)絡(luò)吞吐率,降低端到端的投遞延遲�，F(xiàn)有機(jī)會(huì)性網(wǎng)絡(luò)編碼架構(gòu)中存在的另一個(gè)問(wèn)題是編碼機(jī)會(huì)不足。由于無(wú)線介質(zhì)訪問(wèn)的隨機(jī)性和各條編碼數(shù)據(jù)流速率的不匹配,可能導(dǎo)致編碼機(jī)會(huì)不足,進(jìn)而降低了編碼增益。主動(dòng)性延遲數(shù)據(jù)包發(fā)送可以增加編碼機(jī)會(huì),但是會(huì)增加投遞延遲,對(duì)實(shí)時(shí)應(yīng)用尤為不利。為此,我們提出了一種結(jié)合調(diào)度和網(wǎng)絡(luò)編碼的框架SNC,在有延遲限制條件下最大化編碼機(jī)會(huì)。該框架由延遲數(shù)據(jù)包傳輸策略DTP和基于網(wǎng)絡(luò)編碼組的調(diào)度策略GSP兩部分組成。前者DTP基于延遲要求和可以取得的最大編碼度,動(dòng)態(tài)地調(diào)整可以取得的編碼度,從而最大化系統(tǒng)中的編碼機(jī)會(huì)。在此基礎(chǔ)上,對(duì)于每一個(gè)網(wǎng)絡(luò)編碼組,調(diào)度策略GSP依據(jù)權(quán)重來(lái)調(diào)度網(wǎng)絡(luò)編碼組對(duì)應(yīng)的編碼包發(fā)送,從而優(yōu)化機(jī)會(huì)性網(wǎng)絡(luò)編碼吞吐率增益。網(wǎng)絡(luò)和數(shù)值仿真證實(shí),SNC可以最大化編碼機(jī)會(huì),改善機(jī)會(huì)性網(wǎng)絡(luò)編碼在實(shí)時(shí)應(yīng)用中的吞吐率性能增益。盡管主動(dòng)性推遲數(shù)據(jù)包的發(fā)送可以增加編碼機(jī)會(huì),現(xiàn)有的工作往往局限于特定的網(wǎng)絡(luò)拓?fù)洳⒕哂休^高的計(jì)算復(fù)雜度,不易于分布式實(shí)現(xiàn)。為此,我們提出了具有編碼意識(shí)的隊(duì)列管理機(jī)制DQM,充分開(kāi)發(fā)了網(wǎng)絡(luò)編碼在存儲(chǔ)壓縮上的優(yōu)勢(shì),進(jìn)一步增加了編碼機(jī)會(huì)。仿真結(jié)果證實(shí)了DQM的有效性。本文取得的研究成果,為推進(jìn)網(wǎng)絡(luò)編碼技術(shù)在無(wú)線網(wǎng)絡(luò)中的實(shí)用化提供了有用的理論基礎(chǔ)和技術(shù)手段。
[Abstract]:Network encoding (Network Coding) is regarded as a promising technique in wireless networks can be used to reduce transmission times, improve the utilization rate of bandwidth, improve network throughput and energy efficiency. The network architecture and how to design a better encoding mechanism to give full play to the performance gain of network encoding is a hot topic in academic circles. The basic idea is to allow the network encoding network node multiple data packets into one encoding packets to be sent, so as to reduce transmission times, improve the network throughput. Benefit from wireless communication within the broadcast nature and listening ability, network encoding are more suitable for application in wireless network. In order to make the network as much as possible to reduce the encoding the network protocol stack changing applications in wireless networks, opportunistic network encoding is a feasible choice. According to different application scenarios of opportunistic network encoding, need Considering the influence of various factors on the performance gain, such as cache resource node, processing ability. According to different factors, establish the corresponding mathematical model and its optimization in wireless network performance gain. Therefore, the application of opportunistic network encoding in wireless network, this paper points out the problems that need further study in different network scene and situation, and put forward the corresponding optimization framework and mechanism. The main contents of this paper include: firstly, considering the influence on the performance of opportunistic network cache resource encoding gain. Encoding architecture of existing opportunistic network are assumed to have infinite node buffer resources and processing ability. Under this premise, the network nodes need to decode the packet buffer pool all detected and sent enough packets to decode the long time, possible future needs. At the same time, nodes through "receiving report" Periodically exchange with packet information of each packet in the pool, to ensure the solvability of the encoding package. However, when the cache space is limited, the performance gain will be affected by the opportunistic network encoding. Even if the node resource is infinite, the existing network encoding decoding opportunistic packet pool cache will bring greater network overhead, thereby reducing the throughput of the network. In order to solve this problem, this paper proposes a decoding utility framework to optimize the opportunistic network encoding cache resources. Through the analysis, we will shut down between the cache resources and decoding performance as an optimization mathematical model. Through this model, we derive a cache rule series, and proposed opportunistic network caching scheme for distributed encoding. The simulation results confirm the validity of the model, and it is proved that this method can effectively improve the node The utilization of cache resources, improve the performance of opportunistic network encoding gain. For opportunistic network encoding interference in the application of wireless networks, the existing network architecture through opportunistic encoding pseudo broadcast once a encoding packet delivery to multiple receiving nodes, and relies on the piggyback asynchronous ACKs in the header of each packet to confirm receiving packets in. In a given period of time is not confirmed will be received again into the send queue, encoding sent. This mechanism in packet loss in wireless network easily due to packet loss and delay to incur a lot of redundant retransmission, the waste of network bandwidth. In addition, in order to ensure the reliable delivery of packet encoding, the existing network architecture with the lowest node encoding default encoding the transmission rate to be delivered. This will lead to a longer transmission time, and increase the packet collision. To solve the above problems, I have Put forward a combined transmission rate control and network encoding codeword selection framework ORC to the network layer and the MAC layer joint optimization. The framework will rate control problem encoding packet transmission is considered as a Markov decision process, so as to obtain the optimal rate selection strategy. Then, after the above rate selection based on the results. From all the possible combinations to select the best encoding packet encoding and sending packet combination. For encoding a package, we will be attributed to a maximum weighted clique problem, and propose a code selection algorithm. The network simulation confirmed that the ORC framework can effectively improve the network throughput and reduce the end to end the delivery delay. Another problem existing in the opportunistic network encoding architecture is lack of opportunities. Due to the mismatch encoding wireless medium access randomness and the encoding rate of flow of data, can Lead to the lack of opportunities and reduce the encoding, the encoding gain. Active packet delay can increase the encoding opportunity, but will increase the delivery delay, is particularly detrimental to the real-time application. Therefore, we propose a SNC framework combined with the scheduling and network encoding, the delay constraint conditions to maximize opportunities. The framework consists of encoding delay of data packet transmission strategies for DTP and GSP scheduling strategy of network encoding group is composed of two parts. Based on the former DTP based on delay requirement and can achieve the maximum degree of encoding, dynamic adjustment can be made so as to maximize the system of encoding, the encoding opportunity. On this basis, for each network encoding group, scheduling strategy GSP based on the weights of network scheduling encoding groups corresponding to the encoding packets, so as to optimize the opportunistic network encoding throughput gain. That network and numerical simulation, SNC can maximize the encoding machine Will improve the throughput performance gain of opportunistic network encoding in real-time applications. Although the initiative to postpone sending data packets can increase the encoding opportunity, existing work is often limited to specific network topology and the computational complexity is higher, not easy to realize distributed. Therefore, we propose a DQM queue management mechanism with encoding consciousness the full development of the network in the compressed storage encoding advantage, to further increase the encoding opportunity. The simulation results verify the effectiveness of DQM. The result of this research, provides the theory basis and the technical means for promoting the practical useful network encoding technology in wireless network.

【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN92
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本文編號(hào)：1672121