【摘要】：無線通信是物聯(lián)網(wǎng)系統(tǒng)和移動互聯(lián)網(wǎng)系統(tǒng)中最重要的通信方式之一。隨著社會經(jīng)濟和科學(xué)技術(shù)的發(fā)展,信息化建設(shè)的不斷推進(jìn)和深入,無線通信和無線網(wǎng)絡(luò)在各個領(lǐng)域的應(yīng)用越來越廣。多播是無線通信中最常用的數(shù)據(jù)傳輸方式之一。在無線多播通信中,由于無線信道容易受干擾及衰減、衰落等不可靠時變特性,常常導(dǎo)致較高的信道誤碼率,致使無線鏈路質(zhì)量較差且穩(wěn)定性較低,數(shù)據(jù)分組傳輸容易受損,嚴(yán)重影響了傳輸效率。為了提高無線傳輸?shù)目煽啃院蛡鬏斝?重傳技術(shù)被廣泛研究,成為無線多播通信中最主要的解決途徑之一。其中,基于網(wǎng)絡(luò)編碼的無線重傳技術(shù)因在吞吐量方面的優(yōu)勢,成為目前無線通信領(lǐng)域研究的一個熱點課題。然而,無線多播重傳中網(wǎng)絡(luò)編碼的引入帶來了許多新的問題,比如編碼方法、編碼策略和編碼時機等,迫切需要設(shè)計高效的編碼策略以提高重傳效率,并保障各種無線網(wǎng)絡(luò)環(huán)境下編碼重傳的優(yōu)越性能。在這樣的背景下,本文基于聯(lián)合優(yōu)化、中繼協(xié)作等思想,對無線多播中基于網(wǎng)絡(luò)編碼的高效重傳方法進(jìn)行了研究,其核心是在保持較低算法復(fù)雜度下,找到丟失分組的最優(yōu)網(wǎng)絡(luò)編碼組合,通過最大化每次重傳的增益來減少重傳次數(shù)或最大化系統(tǒng)平均重傳增益。本文的研究工作及貢獻(xiàn)主要包括:1.較系統(tǒng)地研究并總結(jié)了基于網(wǎng)絡(luò)編碼的無線多播重傳技術(shù)中采用的各種網(wǎng)絡(luò)編碼技術(shù),包括其提出、演進(jìn)及基本概念。從編碼優(yōu)化、解碼優(yōu)化、時延受限、鏈路質(zhì)量加權(quán)等多個方面,對基于機會網(wǎng)絡(luò)編碼的重傳技術(shù)的研究現(xiàn)狀進(jìn)行了較全面深入的研究和總結(jié)。這些內(nèi)容有助于今后的研究者快速系統(tǒng)地了解課題技術(shù)背景。2.研究了編解碼聯(lián)合優(yōu)化的無線多播重傳方法以提高編碼效率。根據(jù)編解碼聯(lián)合優(yōu)化目標(biāo),研究了丟失分組的網(wǎng)絡(luò)編碼問題,提出了基于散列鄰域關(guān)聯(lián)搜索的機會網(wǎng)絡(luò)編碼重傳方法。該方法采用“鄰域關(guān)聯(lián)搜索-多分組聯(lián)合解碼”機制。在編碼優(yōu)化方面,通過散列鄰域關(guān)聯(lián)搜索進(jìn)一步挖掘最大可解碼丟失分組組合之間的編碼機會;在解碼優(yōu)化方面,除優(yōu)先從滿秩重傳編碼分組中恢復(fù)丟失分組外,允許接收節(jié)點從多個重傳編碼分組中恢復(fù)丟失分組。在保持較低的算法復(fù)雜度下,有效地減少了重傳次數(shù),提高了傳輸性能。在此基礎(chǔ)上,為了提高重傳編碼分組的傳輸成功率,將實時無線鏈路質(zhì)量引入到丟失分組編碼組合的選擇計算當(dāng)中,提出了一種加權(quán)的丟失分組優(yōu)化組合算法,使得編碼增益最大且能讓更多接收節(jié)點恢復(fù)其丟失分組的可解丟失分組組合被優(yōu)先編碼重傳,從而進(jìn)一步提高了傳輸效率。3.研究了信道突變、連續(xù)分組丟失等無線網(wǎng)絡(luò)環(huán)境下的高效重傳方法以提高傳輸效率。當(dāng)某些接收節(jié)點因受到干擾出現(xiàn)信道突變導(dǎo)致與源節(jié)點之間的鏈路質(zhì)量變差時,由源節(jié)點進(jìn)行丟失分組重傳,重傳再丟失現(xiàn)象將非常嚴(yán)重,連續(xù)分組丟失將導(dǎo)致重傳性能急劇下降�；跓o線中繼系統(tǒng)的協(xié)作重傳思想,提出了基于網(wǎng)絡(luò)編碼的機會中繼高效重傳方法。該方法動態(tài)選擇數(shù)據(jù)分組接收情況最好且信道質(zhì)量優(yōu)于源節(jié)點的接收節(jié)點作為機會中繼,代替源節(jié)點進(jìn)行其他接收節(jié)點的丟失分組重傳,從而獲得更好的重傳性能。實時鏈路質(zhì)量通過網(wǎng)絡(luò)測量估計獲得,機會中繼選擇基于分簇及就近合并原則。這種方法同樣適用于某些接收節(jié)點處于“中繼節(jié)點”位置的較好質(zhì)量無線多播網(wǎng)絡(luò)環(huán)境。與現(xiàn)有重傳方法相比,該方法更好地利用了現(xiàn)有網(wǎng)絡(luò)資源來提高傳輸效率,理論分析和仿真測試驗證了其有效性。4.研究了連續(xù)動態(tài)網(wǎng)絡(luò)編碼重傳方法以增加最優(yōu)編碼機會。針對批(塊,代)內(nèi)編碼機制導(dǎo)致的編碼機會浪費、單次重傳效益無法最大化等問題,提出了基于機會網(wǎng)絡(luò)編碼的動態(tài)連續(xù)重傳方法。該方法通過第一緩存數(shù)據(jù)分組連續(xù)傳輸和后續(xù)逐分組傳輸來保證充分的最優(yōu)編碼機會,每次僅重傳丟失分組最優(yōu)編碼組合或滿足特定條件的最大化編碼組合,從而使得每次重傳的增益最大化,并分別給出了非實時應(yīng)用和實時應(yīng)用場景的最大化丟失分組組合的重傳條件。與現(xiàn)有重傳方法相比,該方法對節(jié)點數(shù)據(jù)緩存沒有特殊要求,容易實現(xiàn)時延控制,但連續(xù)編碼增加了節(jié)點的處理負(fù)擔(dān),為此采用高效的散列漢明搜索來支持該方法。當(dāng)接收節(jié)點數(shù)較少,發(fā)送數(shù)據(jù)緩存足夠大時,該方法在重傳效率上具有明顯的優(yōu)勢。最后通過數(shù)學(xué)分析和仿真測試驗證了該方法的有效性。
[Abstract]:Wireless communication is one of the most important ways of communication in an Internet of Things system and a mobile Internet system. With the development of social economy and science and technology, the continuous development and in-depth of information construction, the application of wireless communication and wireless network in various fields is becoming more and more wide. multicast is one of the most commonly used data transmission modes in wireless communication. in that wireless multicast communication, because the wireless channel is susceptible to non-reliable time-varying characteristics such as interference and attenuation, fading, and the like, the high channel error rate is often caused, so that the quality of the wireless link is poor and the stability is low, and the data packet transmission is easy to be damaged, and the transmission efficiency is seriously affected. In order to improve the reliability and transmission efficiency of the wireless transmission, the retransmission technology is widely studied and becomes one of the most important solutions in the wireless multicast communication. The wireless retransmission technology based on network coding has become a hot topic in the field of wireless communication. However, the introduction of the network coding in the wireless multicast retransmission brings many new problems, such as coding method, coding strategy and coding timing, etc., it is urgent to design efficient coding strategy to improve the retransmission efficiency and to guarantee the superiority of the coding retransmission in various wireless network environments. In this background, based on the idea of joint optimization and relay cooperation, this paper studies the method of efficient re-transmission based on network coding in the wireless multicast, the core of which is to find the optimal network coding combination of the lost packet under the complexity of keeping the lower algorithm. the number of retransmissions or the maximum system average retransmission gain is reduced by maximizing the gain of each retransmission. The research work and contribution of this paper mainly include: 1. The paper systematically studies and summarizes the various network coding techniques used in the wireless multicast retransmission technology based on network coding, including its development, evolution and basic concept. From the aspects of coding optimization, decoding optimization, time delay limited, and link quality weighting, the present situation of the retransmission technology based on opportunistic network coding is studied and summarized. these will help researchers to quickly and systematically understand the subject's technical background. The wireless multicast retransmission method with combined coding and decoding is studied to improve the coding efficiency. Based on the joint optimization goal of coding and decoding, the network coding problem of the lost packet is studied, and the method of opportunistic network coding and re-transmission based on the hash-column neighborhood association search is proposed. The method adopts a 鈥渘eighborhood association search-multi-packet combined decoding鈥，

本文編號：2344862