本文選題：無線光通信　切入點：exponentiated　出處：《西安電子科技大學》2014年碩士論文　論文類型：學位論文

【摘要】：無線光通信技術是可以實現(xiàn)雙向高速傳送的一種技術。它具有帶寬高、成本低、抗干擾能力突出等優(yōu)點,受到了研究人員的廣泛關注。大氣作為無線光通信的傳輸媒介,充斥著各種物質如氣體分子、懸浮微粒等,容易造成光在傳輸過程中被吸收和散射,進而影響通信質量。針對這一技術問題,研究人員嘗試通過信道編碼、孔徑平均和分集等技術降低大氣信道對通信系統(tǒng)性能的影響,取得了較好的效果。低密度奇偶校驗碼(LDPC)作為線性分組碼的典型代表,在高速數(shù)據(jù)傳輸以及大容量存儲信道中具有逼近Shannon限的誤碼率性能,被多項國際、國內工業(yè)技術標準列為信道編碼的主要糾錯碼。論文基于exponentiated Weibull(EW)大氣衰落信道模型,研究了LDPC編碼對于FSO光通信系統(tǒng)誤碼率性能的改善作用,在此基礎上,研究了孔徑平均、分集等技術的影響。論文主要工作如下:1.基于exponentiated Weibull分布描述接收端光強的概率密度分布,建立了無線光通信LDPC編碼的系統(tǒng)模型,推導了OOK和BPSK調制下對數(shù)似然比的表達式。進而得到不同湍流、孔徑條件、不同的LDPC碼字參數(shù)和譯碼算法下誤碼率隨信噪比的變化。研究表明,exponentiated Weibull模型適應于不同強度的湍流,并且與Gamma-Gamma信道模型相比,當孔徑平均現(xiàn)象發(fā)生時,能更好地描述接收光強。校驗矩陣的碼率、最大迭代次數(shù)和譯碼算法的選取對系統(tǒng)誤碼率性能也有一定的影響。2.在上述工作的基礎上,構建了無線光通信LDPC-STBC編碼系統(tǒng)模型,利用最大似然接收準則推導了LDPC-STBC編碼系統(tǒng)的解調算法,進而得到了LDPC譯碼器的對數(shù)似然比。研究了不同大氣湍流條件下,LDPC-STBC編碼對系統(tǒng)誤碼特性的影響。仿真結果表明,隨著分集數(shù)的增加,LDPC-STBC級聯(lián)編碼可以獲得更好的編碼增益,因此信道編碼和分集技術可以很好的改善系統(tǒng)性能。本論文研究成果為無線光通信系統(tǒng)信道編碼的設計提供一定的理論參考。
[Abstract]:Wireless optical communication technology is a kind of technology that can realize two-way high-speed transmission. It has the advantages of high bandwidth, low cost, outstanding anti-jamming ability and so on. Filled with various substances such as gas molecules, suspended particles and so on, light is easily absorbed and scattered in the transmission process, thus affecting the quality of communication. In response to this technical problem, researchers try to code through channels. Aperture averaging and diversity techniques reduce the influence of atmospheric channel on the performance of communication system and obtain good results. Low density parity check code (LDPC) is a typical example of linear block codes. In high speed data transmission and large capacity storage channels, the BER performance of approaching the Shannon limit has been listed as the main error-correcting codes in channel coding by many international and domestic industrial technical standards. The effect of LDPC coding on the BER performance of FSO optical communication system is studied. Based on this, the average aperture is studied. The main work of this paper is as follows: 1. Based on the exponentiated Weibull distribution to describe the probability density distribution of light intensity at the receiving end, the system model of LDPC coding for wireless optical communication is established. The expressions of logarithmic likelihood ratio under OOK and BPSK modulation are derived. The variation of BER with signal-to-noise ratio under different turbulence, aperture conditions, different LDPC codeword parameters and decoding algorithm is obtained. It is shown that the modified Weibull model is suitable for turbulence with different intensity. Compared with the Gamma-Gamma channel model, when the average aperture phenomenon occurs, the bitrate of the received light intensity and check matrix can be better described. The maximum number of iterations and the selection of decoding algorithms also affect the BER performance of the system. 2. Based on the above work, a wireless optical communication LDPC-STBC coding system model is constructed. The demodulation algorithm of LDPC-STBC coding system is derived by using the maximum likelihood reception criterion, and the logarithmic likelihood ratio of LDPC decoder is obtained. The effects of LDPC-STBC coding on system error characteristics under different atmospheric turbulence conditions are studied. With the increase of the number of subsets, the concatenated LDPC-STBC code can obtain better coding gain. Therefore, channel coding and diversity techniques can improve the performance of the system. This paper provides a theoretical reference for the design of channel coding in wireless optical communication systems.
【學位授予單位】：西安電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN929.1;TN911.22

【參考文獻】

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1 伍艷瓊;陳名松;敖s，

本文編號：1619941