本文選題：CPM　切入點：串行級聯(lián)碼　出處：《南京航空航天大學》2014年碩士論文

【摘要】：保密通信系統(tǒng)中的保密信息在傳輸過程中不僅會遭受人為竊取,還會受到噪聲干擾。本文基于以上問題對保密通信系統(tǒng)進行研究。一方面為了保證系統(tǒng)的安全性,文中采用分組加密算法對保密模塊進行設(shè)計,并用線性密碼分析驗證其安全性。另一方面為了增強系統(tǒng)的抗噪聲干擾能力,可以使用信道編碼技術(shù)。但同時信道編碼技術(shù)增加了信息的冗余位,降低了系統(tǒng)的頻譜利用率。本文提出將連續(xù)相位調(diào)制(Continuous Phase Modulation,CPM)與信道編碼級聯(lián)構(gòu)成串行級聯(lián)碼進行迭代譯碼,不僅可以提高系統(tǒng)的頻譜利用率,而且能夠達到接近Turbo碼的誤碼性能。本文的主要工作及研究成果概括如下:1、采用多輪迭代結(jié)構(gòu)的分組密碼算法進行密碼器設(shè)計。通過對加密結(jié)構(gòu)的核心部分——非線性S盒進行線性逼近,分析密碼器的安全性。針對算法中原始密鑰固定不變、長度短、抗攻擊性弱的問題,利用Logistic混沌映射進行改進,生成了動態(tài)的初始密鑰,有效擴展了密鑰空間,增強了系統(tǒng)安全性。2、研究CPM的內(nèi)在編碼特性。將CPM的傳統(tǒng)相位替換為傾斜相位,推導出Rimoldi分解模型,同時得到時不變的相位狀態(tài)轉(zhuǎn)移圖。用基于狀態(tài)網(wǎng)格圖的Viterbi算法對CPM中的MSK信號進行最大似然檢測,并針對算法中相位路徑選擇造成的延時問題進行分析改進。仿真結(jié)果驗證了Rimoldi分解模型的有效性,證明了CPM調(diào)制具有編碼增益,可等效為編碼器進行研究。3、針對保密通信系統(tǒng)中的噪聲干擾,提出將CPM應(yīng)用于串行級聯(lián)碼,構(gòu)成串行級聯(lián)CPM。推導了適用于CPM檢測器的最大后驗概率(Maximum A Posteriori,MAP)迭代譯碼算法,并通過分析修改相位分支度量,降低了運算復(fù)雜度。通過仿真,驗證了串行級聯(lián)CPM通過偽隨機交織器進行迭代譯碼能夠明顯提高系統(tǒng)的可靠性。
[Abstract]:The confidential information in the secure communication system will not only be stolen by human beings, but also be disturbed by noise during the transmission. This paper studies the secure communication system based on the above problems. On the one hand, in order to ensure the security of the system, In this paper, the block encryption algorithm is used to design the security module, and the linear cipher analysis is used to verify its security. On the other hand, in order to enhance the anti-noise ability of the system, The channel coding technique can be used, but at the same time, the channel coding technique increases the redundant bits of information and reduces the spectrum efficiency of the system. In this paper, a serial concatenated code is constructed by cascading continuous phase modulation (CPM) and channel coding to perform iterative decoding. Not only can the spectrum efficiency of the system be improved, The main work and research results of this paper are summarized as follows: 1. The block cipher algorithm with multi-round iterative structure is used to design the cipher. Linear S-box for linear approximation, This paper analyzes the security of cryptographer. Aiming at the problems of the original key fixed, short length and weak attack resistance in the algorithm, the Logistic chaotic mapping is used to improve the algorithm, and the dynamic initial key is generated, which effectively expands the key space. The system security. 2 is enhanced, and the inherent coding characteristics of CPM are studied. The traditional phase of CPM is replaced by tilted phase, and the Rimoldi decomposition model is derived. At the same time, the phase state transition diagram of time invariant is obtained. The maximum likelihood detection of MSK signal in CPM is carried out by using the Viterbi algorithm based on state grid graph. The simulation results show the validity of the Rimoldi decomposition model and the coding gain of CPM modulation. For the noise interference in the secure communication system, a serial concatenated code is constructed by applying CPM to the serial concatenated code. The maximum posterior probability Maximum A Posteriori map iterative decoding algorithm is derived for the CPM detector. By analyzing and modifying the phase branching metric, the computational complexity is reduced, and the simulation results show that the serial concatenated CPM can improve the reliability of the system obviously by using pseudorandom Interleaver to perform iterative decoding.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN918.4;TN911.3

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本文編號：1672598