【正文】 。分析表明系統(tǒng)性能的各種參數(shù)，以及它們?nèi)绾慰梢员豢刂疲O(shè)計(jì)一個(gè)最佳的系統(tǒng)的依賴(lài)。分析已經(jīng)進(jìn)行，考慮到大氣湍流引起的衰減和分子吸收引起的傳播損耗的光信道的影響。在本文中，我們提出了一種雙向、單中繼，網(wǎng)絡(luò)編碼的通信系統(tǒng)。本文的主要貢獻(xiàn)如下：（1）模型的雙向，網(wǎng)絡(luò)編碼，兩時(shí)相、單繼電器和兩個(gè)用戶終端通信系統(tǒng)；（2）分析系統(tǒng)的考慮大氣湍流引起的閃爍和分子吸收引起的傳輸損耗性能的影響；（3）對(duì)于多進(jìn)制相移鍵控和服務(wù)中斷概率的封閉形式的表達(dá)式（MPSK），和（4）確定網(wǎng)絡(luò)實(shí)現(xiàn)的容量區(qū)域。這項(xiàng)研究的動(dòng)機(jī)是提高使用網(wǎng)絡(luò)編碼的雙向中繼通信系統(tǒng)的頻譜效率。以前的研究相關(guān)的twrfso一直局限于誤差性能僅考慮大氣湍流引起的閃爍效果沒(méi)有任何傳輸損耗。利用協(xié)同中繼技術(shù)提高空間分集增益的分析。由于FSO系統(tǒng)性能取決于距離，TWR可以有效地用于建立通信時(shí)，通信終端之間的距離兩大或當(dāng)洛杉磯通信是不可能的兩FSO用戶之間。LNC FSO系統(tǒng)的優(yōu)點(diǎn)已經(jīng)在描述。因此，這樣的中繼模型導(dǎo)致頻譜損耗。雖然多跳方案的研究到目前為止已經(jīng)減少氣候影響的嚴(yán)重程度，這些方案具有更低的數(shù)據(jù)率。因此，繼電器輔助FSO系統(tǒng)已在文學(xué)提出了解決了多跳距離相關(guān)的湍流衰落。FSO信道可由大氣湍流引起的閃爍?和傳播損耗由于霧和分子吸收。近年來(lái)，重大的研究已經(jīng)進(jìn)行了揭示室內(nèi)和戶外?無(wú)線光通信系統(tǒng)的潛力。 Mona Aggarwal自由空間光通信（FSO）是一種視距（LOS）技術(shù)，使用激光來(lái)提供光學(xué)帶寬連接。 (3) to find closed form expressions for the outage probability and SER for Mary phase shift keying (MPSK), and (4) to determine the net achievable capacity region. Additionally, the analysis is carried out considering independent but not necessarily identically distributed () channels.In this paper, we proposed a twoway, singlerelay, networkcoded FSO system. The basic idea behind this proposal is to design a FSO system that tackles the degrading climatological conditions and is also spectrally efficient. The analysis has been carried out, considering an optical channel affected by atmospheric turbulenceinduced fading and molecular absorptioninduced propagation losses. A plete characterization of the system has been carried out by finding closed form expressions for outage probability, SER for both binary and nonbinary FSO systems, and the net achievable capacity region. The analysis demonstrates the dependence of system performance on various parameters and how they can be controlled to design an optimum system. In all, the results establish the TWRFSO scheme to be a viable solution for establishing munication between two nodes that cannot establish a direct link because of larger distances or in the presence of an obstruction.譯文譯文有效利用頻譜的兩‐路繼電器輔助自由空間光學(xué)系統(tǒng)與路徑損耗大氣湍流分析Parul Puri,have been studied in terms of outage and error probabilities.Though the multihop schemes studied so far have reduced the severity of climatological effects, these schemes exhibit a lower data rate. This is due to the fact that one round munication between two user terminals via single relay requires four time slots for plete data exchange. Hence, such relay models result in spectrum loss. It has been studied in radio frequency (RF) munication, twoway relaying based on decodeandforward (DF) protocol and employing linear network coding (LNC) requires two time slots for plete data exchange between two nodes via single relay. The advantages of LNC in FSO systems have been described in. author described a multisource singledestination FSO system and showed improvement in biterrorrate (BER) of network coded cooperation (NetCC) scheme over conventional noncooperative scheme.Because the performance of FSO system is distance dependent, TWR can be efficiently used for establishing munication when distance between two FSO terminals is large or when LOS munication is not possible between two FSO users. Previously, a twoway, multirelay, NetCC FSO system was described. The analysis focused on improving spatial diversity gain achieved by using cooperative relaying. However, three time slots were used for plete data transfer, which made the system spectrally inefficient. Previous studies related to TWRFSO have been limited to error performance considering only the atmospheric turbulenceinduced scintillation effects without any propagation losses. The analysis based on symbolerror rate (SER), outage probability, and capacity of TWRFSO systems is still an open area for research.The motivation for this study is to improve the spectral efficiency of FSO systems using twoway relaying with network coding. We perform a plete characterization of the proposed system by analyzing system outage, error performance, and achievable capacity. The main contributions of this paper are the following: (1) to model a bidirectional, networkcoded, twotime phase, FSO system with single relay and two user terminals。and propagation losses because of fog and molecular absorption. it is given for link ranges longer than 1km, the strength of atmospheric turbulenceinduced fading increases because of the multiple scattering effects. Hence, relay assisted FSO systems have been proposed in literatureand outdoor Parul Garg,比如：按規(guī)定應(yīng)垂直放置的儀表卻水平放置，儀器接地不良，因測(cè)試引線太長(zhǎng)而造成損耗或未考慮阻抗匹配，未按操作規(guī)程在沒(méi)有預(yù)熱，調(diào)節(jié)，校正后就迸行測(cè)量等，都會(huì)產(chǎn)生使用誤差。儀器，儀表的零位偏移，刻度不準(zhǔn)確，以及非線性等引起的誤差均屬于儀器誤差。3) 儀器，儀表誤差: 由儀器，儀表本身及其附件所引入，出于儀器的電氣或機(jī)械性能不完善所產(chǎn)生的誤差。對(duì)于某些需借助于人眼，人耳來(lái)判斷結(jié)果的測(cè)量，以及需進(jìn)行人工調(diào)節(jié)等的測(cè)量工作，均會(huì)引入人身誤差。附錄二：使用誤差分析儀時(shí)注意的誤差1)影響誤差: 又稱(chēng)為環(huán)境誤差，是指由于受到溫度，濕度，氣壓，電磁場(chǎng)，機(jī)械振動(dòng)，聲音，光，放射性等影響所造成的附加誤差?！癮”表示采用的是APD管接收?！獙儆谏鲜鲱?lèi)型，采用APD管接收。通信系的老師們，給我四年的學(xué)習(xí)、成長(zhǎng)創(chuàng)造了一個(gè)良好的環(huán)境，引導(dǎo)我充分利用學(xué)校的學(xué)習(xí)資源，去發(fā)展、充實(shí)自我，而不曾虛度光陰。四年間，無(wú)論是學(xué)習(xí)、工作生活上的問(wèn)題，恩師們都會(huì)悉心給以指導(dǎo)解答，讓我倍受感動(dòng)。 為期一個(gè)學(xué)期的畢業(yè)論文（設(shè)計(jì)）已讓我忙碌的接近尾聲了，我的四年大學(xué)生涯也即將圈上一個(gè)句號(hào)。正在撰寫(xiě)畢業(yè)論文的他們，在百忙之中抽出時(shí)間幫助我搜集文獻(xiàn)資料，幫助我理清論文寫(xiě)作思路，對(duì)我的論文提出了諸多寶貴的意見(jiàn)和建議。正是盧老師的無(wú)私幫助與熱忱鼓勵(lì)，我的畢業(yè)論文才能夠得以順利完成，謝謝盧老師。她為人隨和熱情，治學(xué)嚴(yán)謹(jǐn)細(xì)心。如今，伴隨著這篇畢業(yè)論文的最終成稿，復(fù)雜的心情煙消云散，自己甚至還有一點(diǎn)成就感。[6] 李曉彤，幾何光學(xué)和光學(xué)設(shè)計(jì)，浙江大學(xué)出版社，1997.[7] 周炳琨，高以智，激光原理，國(guó)防工業(yè)出版社，2000.[8].， .， “Fiber coupling with adaptive optics for free space optical munication”， FreeSpace Laser Communication and Laser Imaging, 2002, .[9] .,“a ray of light”,IEE review, 2001.[10], ., “Freespace optical munication through atmospheric turbulence channels”,IEEE transactions on munications,(8).[11] 信息工程學(xué)院，吉林 吉林市 132012:； ，長(zhǎng)春130021。[2]張春，侯曉霞，范忠禮，“自由空間光通信技術(shù)及其在城域光網(wǎng)絡(luò)的應(yīng)用”，電信快報(bào)，2003年第9期3941。增加自由空間光通信系統(tǒng)的傳輸距離，在不同的氣候條件下測(cè)試系統(tǒng)性能。本文需要改進(jìn)的地方：自動(dòng)跟蹤系統(tǒng)(APT)是FSO系統(tǒng)的另外一個(gè)重要組成部分。系統(tǒng)仿真表明大氣衰減和傳輸距離仍然是限制F