The application of Low Density Parity Check (LDPC) code in the anti-interference systems has drawn an increasing attention, due to its admiring performance which is very close to the theory limit. This paper focuses o...The application of Low Density Parity Check (LDPC) code in the anti-interference systems has drawn an increasing attention, due to its admiring performance which is very close to the theory limit. This paper focuses on a LDPC encoded slow frequency hopping (SFH) communication system with partial-band interference. Firstly, a modified soft- decision algorithm based on the utilization of interference information is proposed, and its performance is compared with some other soft-decision methods. Secondly, with numerical simulation, the influence of code rate, code length and the number of symbols per hops on the performance of the system with partial band noise interference is illustrated and examined in detail. Considering the great influence of hops per symbol on the performance, interleaver should be used and its influence on the performance is further examined by simulation. Finally, some constructive advises for the design of LDPC coded SFH system are given. Simulation results show that, with a reasonable design, the SFH system with LDPC code could achieve a desirable performance.展开更多
部分频带干扰导致宽带短波探测系统接收信噪比严重恶化,传统奇异值分解(Singular Value Decomposition)滤波方法损失了部分有用功率,影响了探测信号的完整性。本文首先推导得出干扰频带处功率成分的解析表达式,并依据干扰特性设计出一...部分频带干扰导致宽带短波探测系统接收信噪比严重恶化,传统奇异值分解(Singular Value Decomposition)滤波方法损失了部分有用功率,影响了探测信号的完整性。本文首先推导得出干扰频带处功率成分的解析表达式,并依据干扰特性设计出一种鲁棒的干扰子空间维数估计算法以得到有用功率的稳定估计,进而提出了一种低信噪比损失SVD滤波干扰抑制算法。仿真与实测数据处理结果表明,该算法在抑制干扰的同时有效减小了信号损伤,对于短波电离层信道参数的高精度提取具有特殊的重要意义。展开更多
针对双序列跳频(Binary-Sequence Frequency Hopping,BSFH)在对偶信道被干扰的情况下会导致通信瘫痪的缺点,提出了一种基于伪随机线性调频的双序列跳频通信系统。在发送端利用线性调频信号对每一跳载波进行带内扩频,接收端将解跳后的信...针对双序列跳频(Binary-Sequence Frequency Hopping,BSFH)在对偶信道被干扰的情况下会导致通信瘫痪的缺点,提出了一种基于伪随机线性调频的双序列跳频通信系统。在发送端利用线性调频信号对每一跳载波进行带内扩频,接收端将解跳后的信号作分数阶傅里叶变换,然后通过抽样判决得到发端信息。构建了相应的系统模型,推导了其在跟踪干扰和部分频带干扰下的误码率数学表达式。理论和仿真结果表明:在最坏跟踪干扰下,该系统比BSFH约有5 dB以上的性能增益;在部分频带干扰下,达到相同误码率时所需的信干比,改进方法比BSFH低约4 dB。展开更多
文摘The application of Low Density Parity Check (LDPC) code in the anti-interference systems has drawn an increasing attention, due to its admiring performance which is very close to the theory limit. This paper focuses on a LDPC encoded slow frequency hopping (SFH) communication system with partial-band interference. Firstly, a modified soft- decision algorithm based on the utilization of interference information is proposed, and its performance is compared with some other soft-decision methods. Secondly, with numerical simulation, the influence of code rate, code length and the number of symbols per hops on the performance of the system with partial band noise interference is illustrated and examined in detail. Considering the great influence of hops per symbol on the performance, interleaver should be used and its influence on the performance is further examined by simulation. Finally, some constructive advises for the design of LDPC coded SFH system are given. Simulation results show that, with a reasonable design, the SFH system with LDPC code could achieve a desirable performance.
文摘部分频带干扰导致宽带短波探测系统接收信噪比严重恶化,传统奇异值分解(Singular Value Decomposition)滤波方法损失了部分有用功率,影响了探测信号的完整性。本文首先推导得出干扰频带处功率成分的解析表达式,并依据干扰特性设计出一种鲁棒的干扰子空间维数估计算法以得到有用功率的稳定估计,进而提出了一种低信噪比损失SVD滤波干扰抑制算法。仿真与实测数据处理结果表明,该算法在抑制干扰的同时有效减小了信号损伤,对于短波电离层信道参数的高精度提取具有特殊的重要意义。
文摘针对双序列跳频(Binary-Sequence Frequency Hopping,BSFH)在对偶信道被干扰的情况下会导致通信瘫痪的缺点,提出了一种基于伪随机线性调频的双序列跳频通信系统。在发送端利用线性调频信号对每一跳载波进行带内扩频,接收端将解跳后的信号作分数阶傅里叶变换,然后通过抽样判决得到发端信息。构建了相应的系统模型,推导了其在跟踪干扰和部分频带干扰下的误码率数学表达式。理论和仿真结果表明:在最坏跟踪干扰下,该系统比BSFH约有5 dB以上的性能增益;在部分频带干扰下,达到相同误码率时所需的信干比,改进方法比BSFH低约4 dB。
