In this paper, the author analyzed some cryptographic properties of a class of logical functions, f(x,y)=(q(x),...,q(x))·y+h(x),over Galois rings and residue rings, presented the relationship between the characte...In this paper, the author analyzed some cryptographic properties of a class of logical functions, f(x,y)=(q(x),...,q(x))·y+h(x),over Galois rings and residue rings, presented the relationship between the character spectrum of f(x,y) and the character speetrum of q(x),h(x) and the relationship between the cryptographic properties of f(x,y) and the cryptographic properties of h(x).展开更多
In downlink cellular multiple users in multiple cells systems using beams, the should cooperate to generate beams to improve the spectrum efficiency. A mathematical model for the multi-cell multi-user downlink transm...In downlink cellular multiple users in multiple cells systems using beams, the should cooperate to generate beams to improve the spectrum efficiency. A mathematical model for the multi-cell multi-user downlink transmission is established, and the gradients of the variables including beamfonning filters, receiving filters and transmitting power are calculated. Then, a gradient-project-based cooperative beamforming scheme is proposed in which each user iteratively adjusts bearnforming variables in the direction of the gradients and projects onto feasible spaces. The information exchange protocol needed to support the scheme is also described. Simulation results show that the proposed scheme can achieve an average spectral efficiency of about 5 bit/（ s · Hz · cell）. The results show that cooperative beamforming can improve the spectrum efficiency of the cellular systems.展开更多
The Boolean functions in an affine equivalence class are of the same algebraicdegree and nonlinearity, but may satisfy different order of correlation immunity and propa-gation criterion. A method is presented in this ...The Boolean functions in an affine equivalence class are of the same algebraicdegree and nonlinearity, but may satisfy different order of correlation immunity and propa-gation criterion. A method is presented in this paper to find Boolean functions with higherorder correlation immunity or satisfying higher order propagation criterion in an affine equiv-alence class. 8 AES s-box functions are not better Boolean functions in their affine equiva-lence class.展开更多
目前常见的直接序列扩频信号均采用调相扩频形式,传统观念认为该类信号具有优良的低截获概率(Low Probability of Interception,LPI)特性,因此在现代测控与通信系统中广泛使用。针对此类信号,从电子侦察的角度对扩频码片内的相位取值随...目前常见的直接序列扩频信号均采用调相扩频形式,传统观念认为该类信号具有优良的低截获概率(Low Probability of Interception,LPI)特性,因此在现代测控与通信系统中广泛使用。针对此类信号,从电子侦察的角度对扩频码片内的相位取值随机性和码片间的相位变化平滑性这2个方面展开讨论,分析了采用非线性变换的信号侦察处理方法对此类信号的检测能力,指出了该类信号在反侦察抗截获方面所存在的缺陷。在此基础上提出采用PM模拟调相信号进行扩频来进一步增强调相扩频信号LPI特性的方法,同时阐述了这一新的扩频方式对信号扩频解扩操作所带来的新要求。通过仿真验证了上述理论分析的合理性与有效性。展开更多
文摘In this paper, the author analyzed some cryptographic properties of a class of logical functions, f(x,y)=(q(x),...,q(x))·y+h(x),over Galois rings and residue rings, presented the relationship between the character spectrum of f(x,y) and the character speetrum of q(x),h(x) and the relationship between the cryptographic properties of f(x,y) and the cryptographic properties of h(x).
基金The National Natural Science Foundation of China(No.61001103)the National Science and Technology Major Project of China (No.2008ZX03003-005)the National Basic Research Program ofChina(973 Program) (No.2007CB310603)
文摘In downlink cellular multiple users in multiple cells systems using beams, the should cooperate to generate beams to improve the spectrum efficiency. A mathematical model for the multi-cell multi-user downlink transmission is established, and the gradients of the variables including beamfonning filters, receiving filters and transmitting power are calculated. Then, a gradient-project-based cooperative beamforming scheme is proposed in which each user iteratively adjusts bearnforming variables in the direction of the gradients and projects onto feasible spaces. The information exchange protocol needed to support the scheme is also described. Simulation results show that the proposed scheme can achieve an average spectral efficiency of about 5 bit/（ s · Hz · cell）. The results show that cooperative beamforming can improve the spectrum efficiency of the cellular systems.
文摘The Boolean functions in an affine equivalence class are of the same algebraicdegree and nonlinearity, but may satisfy different order of correlation immunity and propa-gation criterion. A method is presented in this paper to find Boolean functions with higherorder correlation immunity or satisfying higher order propagation criterion in an affine equiv-alence class. 8 AES s-box functions are not better Boolean functions in their affine equiva-lence class.
文摘目前常见的直接序列扩频信号均采用调相扩频形式,传统观念认为该类信号具有优良的低截获概率(Low Probability of Interception,LPI)特性,因此在现代测控与通信系统中广泛使用。针对此类信号,从电子侦察的角度对扩频码片内的相位取值随机性和码片间的相位变化平滑性这2个方面展开讨论,分析了采用非线性变换的信号侦察处理方法对此类信号的检测能力,指出了该类信号在反侦察抗截获方面所存在的缺陷。在此基础上提出采用PM模拟调相信号进行扩频来进一步增强调相扩频信号LPI特性的方法,同时阐述了这一新的扩频方式对信号扩频解扩操作所带来的新要求。通过仿真验证了上述理论分析的合理性与有效性。
