【正文】 s, significant research has been conducted to bring out the potential of indoorand outdooroptical wireless munication systems. However, the challenges faced are due to the unpredictable atmospheric conditions.The FSO channel can be characterized by atmospheric turbulence induced scintillationand 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 literatureto provide LOS multihops for tackling distance dependent turbulence fading. The performance of serial and parallel FSO relaying systemshave 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。 (2) to analyse the performance of the system considering the effects of atmospheric turbulence induced scintillation and molecular absorption induced propagation losses。 (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, Parul Garg, 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。它是一種簡(jiǎn)化的光纖通信，可實(shí)現(xiàn)高速通信許可證免費(fèi)的帶寬?成本有效延伸。近年來(lái)，重大的研究已經(jīng)進(jìn)行了揭示室內(nèi)和戶(hù)外?無(wú)線(xiàn)光通信系統(tǒng)的潛力。然而，面臨的挑戰(zhàn)是由于不可預(yù)知的大氣條件。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。在它給出的鏈接范圍超過(guò)1km，大氣湍流引起的衰減強(qiáng)度增加，由于多次散射的影響。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。串行和并行通信中繼系統(tǒng)性能進(jìn)行了研究，從中斷和錯(cuò)誤的概率。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。這是由于一個(gè)事實(shí)，即通過(guò)單中繼的用戶(hù)終端之間的一個(gè)圓的通信需要四個(gè)時(shí)間段的完整的數(shù)據(jù)交換。因此，這樣的中繼模型導(dǎo)致頻譜損耗。它已經(jīng)在無(wú)線(xiàn)電頻率（RF）進(jìn)行通信，雙向中繼基于解碼轉(zhuǎn)發(fā)（DF）協(xié)議，采用線(xiàn)性網(wǎng)絡(luò)編碼（LNC）要求完成數(shù)據(jù)交換節(jié)點(diǎn)之間通過(guò)中繼兩時(shí)隙。LNC FSO系統(tǒng)的優(yōu)點(diǎn)已經(jīng)在描述。描述了一個(gè)多源單目標(biāo)FSO系統(tǒng)和顯示誤碼率（BER）提高網(wǎng)絡(luò)編碼的合作（netcc）比傳統(tǒng)的非合作方案。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(hù)之間。此前，在雙向，多中繼，netcc FSO系統(tǒng)描述。利用協(xié)同中繼技術(shù)提高空間分集增益的分析。然而，三個(gè)時(shí)隙用于完成數(shù)據(jù)傳輸，使系統(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?；谡`碼率分析（SER），中斷概率，和twrfso系統(tǒng)容量仍然是一個(gè)開(kāi)放的研究領(lǐng)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。我們完成一個(gè)完整的特性，所提出的系統(tǒng)通過(guò)分析系統(tǒng)的中斷，錯(cuò)誤的性能，和可達(dá)到的能力。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(hù)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。此外，進(jìn)行分析考慮獨(dú)立但不一定同分布（）通道。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)。這項(xiàng)建議背后的基本思想是設(shè)計(jì)一個(gè)FSO系統(tǒng)攔截降解的氣候條件也是頻譜效率。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。該系統(tǒng)的一個(gè)完整的特性已被中斷概率的封閉形式的表達(dá)式進(jìn)行查找，SER為二進(jìn)制和非二進(jìn)制的FSO系統(tǒng)，和網(wǎng)絡(luò)實(shí)現(xiàn)的容量區(qū)域。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?，設(shè)計(jì)一個(gè)最佳的系統(tǒng)的依賴(lài)。總之，結(jié)果是兩個(gè)節(jié)點(diǎn)之間的通信，不能建立直接的聯(lián)系因?yàn)榫嚯x較大或在障礙物的存在建立一個(gè)可行的解決方案建立twrfso。