星载SAR相控阵天线展开误差的模糊性能分析

根据星载SAR天线的特点建立了天线展开误差模型，定义了展开不平直度指标，基于成对回波理论推导了存在展开误差条件下天线方向图函数的表达式，推出单频天线展开误差分量与方位模糊度之间统计关系，给出了天线展开误差影响方位模糊度指标的上界．大量的计算机仿真验证了本文分析方法的正确性．     

极低误码下的误码率估计问题

在极低误码率的情况下由于测得的误码点很少，由实测的点来直接估计误码率这一方法变得不可靠。本文提出一种方法，通过牺牲测量值的精度来换取结果的可靠性，即用误码率的上界来描述误码特性。本文还给出了误码率的上界、实际测量得到了误码点数和表示误码率上界可靠性的门限值之间的定量关系。     

慢变平坦衰落信道下空时码设计准则的改进

对用于慢变平坦瑞利衰落信道的空时码设计准则进行了研究。考察了不同长度的首事件差错概率，并基于这些概率推出误帧率的上界，进而提出一种使误帧率的上界最小化的新准则。另外，证明了空时码的几何一致性并使用该特性大大地减少了空时码搜索的复杂度。依据该准则搜索得到一些新码，并与现有好码进行性能比较。     

建立3G新业务的有效商业模式

商业模式可以从两个方面来考虑，一方面是商业活动所涉及的成员，另一方面是这些成员之间的关系。由于移动产业链是以移动运营商为中心的链条，所以这里的成员主要指的是移动运营商的合作者，而成员之间的关系主要是合作关系。所以，在分析移动新业务的商业模式类型时，从“合作伙伴数量”和“合作的紧密程度”这两个维度来进行不同业务商业模式的归类(以中国移动和NTT DoCoMo的业务为例)，如图1所示。     

星载SAR相控阵天线展开误差的模糊性能分析

根据星载SAR天线的特点建立了天线展开误差模型,定义了展开不平直度指标,基于成对回波理论推导了存在展开误差条件下天线方向图函数的表达式,推出单频天线展开误差分量与方位模糊度之间统计关系,给出了天线展开误差影响方位模糊度指标的上界.大量的计算机仿真验证了本文分析方法的正确性.     

模拟退火算法计算卷积码的自由距离

基于模拟退火算法，本文给出了计算卷积码自由距离的新算法。计算结果表明，算法能找到自由距离的真实值或给出一个比现有上界更紧的上界。     

基于信任管理系统的P2P网络安全结构SAP2P

P2P网络具有离散、动态和自治的特点．这些特点使得一些传统的安全技术并不能很好解决P2P网络认证、授权和保密通信等这些安全问题．本文设计了新的信任管理系统ExSPKI用于在P2P网络中建立信任关系，并以此为基础设计了新的安全结构SAP2P（Security Architecture of Peerto Peer Network），从而可以为P2P网络用户之间以及系统中安全功能模块之间建立有效的信任关系，为P2P网络奠定了安全基础，最后本文给出了SAP2P的参考实现．     

布尔函数全局雪崩特征的两个新指标

ZHANG Xian-Mo和ZHENG Yu-liang提出单个函数I厂的全局雪崩特征的概念,并且给出单个函数雪崩特征的平方和指标σf与绝对指标△f的上下界。周宇等将上面的概念作了推广,提出了两个函数f和g全局雪崩特征的概念。他们给出了两个函数全局雪崩特征的平方和指标f,与绝对指标σf,g进而定义两个新指标：λf（指g遍历所有凡元布尔函数时,σf,g取得的最小值）和βf（指g遍历所有n元布尔函数时,△f,g取得的最小值）。得到了λf的值,给出了λf1和βf的上界和下界。     

Hamming重量为k的布尔函数的全局特征和非线性度

该文给出了布尔函数的自相关系数和互相关系数的一些性质,得到n元布尔函数f (x)满足t 阶扩散准则时,n,t 和Hamming重量wt(f)的制约关系,给出了任意Hamming重量为k的布尔函数的平方和指标下界表达式,推出了仅由布尔函数Hamming重量所确定的非线性度的上界表达式。这些结论推广了已有结果。     

随机周期序列☆错线性复杂度的期望上界

周期序列的k错线性复杂度是衡量流密码系统的安全性能的一个重要指标。本文给出了周期序列k错线性复杂度上界的一个更强的结果,从而给出了几种不同情形下随机周期序列k错线性复杂度的期望的上界。特别地,还给出了周期N=pv,随机周期序列满足一定条件时1错线性复杂度的期望更紧的结果。     

Moment space upper and lower error bounds for digital systems with intersymbol interference

A method for the evaluation of upper and lower bounds to the error probability of a linear pulse-amplitude modulation (PAM) system with bounded intersymbol interference and additive Gaussian noise is obtained via an isomorphism theorem from the theory of moment spaces. These upper and lower bounds are seen to be equivalent to upper and lower envelopes of some compact convex body generated from a set of kernel functions. Depending on the selection of these kernels and their corresponding moments, different classes of bounds are obtained. In this paper, upper and lower bounds that depend on the absolute moment of the intersymbol interference random variable, the second moment, the fourth moment, and an "exponential moment" are found by analytical, graphical, or iterative approaches. We study in detail the exponential moment case and obtain a family of new upper and a family of new lower bounds. Within each family, expressions for these bounds are given explicitly as a function of an arbitrary real-valued parameter. For two channels of interest, upper and lower bounds are evaluated and compared. Results indicate these bounds to be tight and useful.     

一类广义Feistel密码的安全性评估

该文评估一类广义Feistel密码(GFC)抵抗差分和线性密码分析的能力:如果轮函数是双射且它的最大差分和线性特征的概率分别是p和q,则16轮GFC的差分和线性特征的概率的上界为p7和q7;如果轮函数采用SP结构且是双射,S盒的最大差分和线性特征的概率是ps和qs,P变换的分支数为Pd,则16轮GFC的差分和线性特征的概率的上界为(ps)3Pd+1和(qs)3Pd+1。     

New tight bounds on the pairwise error probability for unitary space-time modulations

We present two upper bounds and one lower bound on the pairwise error probability (PEP) of unitary space-time modulation (USTM) over the Rayleigh fading channel. The two new upper bounds are the tightest so far, and the new lower bound is the tightest at low signal-to-noise ratio. Some implications for USTM constellation design are also pointed out.     

序列的周期稳定性的新度量指标

本文提出了两种新的度量序列的周期稳定性的指标－定周期距离和变周期距离。文中还研究了一些序列的这两种指标的下界，并给出了衡量序列的周期稳定性的一种方法。     

New upper bounds on error exponents

We derive new upper bounds on the error exponents for the maximum-likelihood decoding and error detecting in the binary symmetric channels. This is an improvement on the best earlier known bounds by Shannon-Gallager-Berlekamp (1967) and McEliece-Omura (1977). For the probability of undetected error the new bounds are better than the bounds by Levenshtein (1978, 1989) and the bound by Abdel-Ghaffar (see ibid., vol.43, p.1489-502, 1997). Moreover, we further extend the range of rates where the undetected error exponent is known to be exact. The new bounds are based on an analysis of possible distance distributions of the codes along with some inequalities relating the distance distributions to the error probabilities     

Performance Bounds for Nonbinary Linear Block Codes Over Memoryless Symmetric Channels

The performance of nonbinary linear block codes is studied in this paper via the derivation of new upper bounds on the block error probability under maximum-likelihood (ML) decoding. The transmission of these codes is assumed to take place over a memoryless and symmetric channel. The new bounds, which are based on the Gallager bounds and their variations, are applied to the Gallager ensembles of nonbinary and regular low-density parity-check (LDPC) codes. These upper bounds are also compared with sphere-packing lower bounds. This study indicates that the new upper bounds are useful for the performance evaluation of coded communication systems which incorporate nonbinary coding techniques.      

随机周期序列k错线性复杂度的方差估计

周期序列的k错线性复杂度是衡量流密码系统的安全性能的一个重要指标.本文首次给出了随机周期序列k错线性复杂度方差的一个表达公式,同时给出了一些情形下的随机周期序列k错线性复杂度方差的上下界的估计和特定情形下的精确结果.     

New Simple and Efficient Bounds on the Probability of Error in the Presence of Interference and Gaussian Noise

The problem of determining or of bounding the probability of error in the presence of intersymbol interference and Gaussian noise is an important one in data communications. In this concise paper we describe new upper and lower bounds for the probability of error when the peak distortion is finite (in practice, when the eye is open) and the data are independent. Over a range ofS/Nof interest in data communications; these bounds compare favorably with previously published bounds of similar complexity, especially when the eye opening is small. They can be applied to multilevel AM and CPSK transmission.     

Tight exponential upper bounds on the ML decoding error probability of block codes over fully interleaved fading channels

We derive tight exponential upper bounds on the decoding error probability of block codes which are operating over fully interleaved Rician fading channels, coherently detected and maximum-likelihood decoded. It is assumed that the fading samples are statistically independent and that perfect estimates of these samples are provided to the decoder. These upper bounds on the bit and block error probabilities are based on certain variations of the Gallager bounds. These bounds do not require integration in their final version and they are reasonably tight in a certain portion of the rate region exceeding the cutoff rate of the channel. By inserting interconnections between these bounds, we show that they are generalized versions of some reported bounds for the binary-input additive white Gaussian noise channel.