协作空分复用CSM系统中的信道估计算法研究

文章就当前MIMO应用过程中终端多天线受限制问题,阐述了单天线终端协作与基站组成虚拟MIMO多天线阵列——基于OFDMA的CSM协作空分复用系统结构。同时,提出对OFDMA系统中时频二维的资源进行分“块”独立进行信道估计,简化了OFDMA系统信道估计模型的复杂度。然后从应用的角度对比分析了基于OFDMA的CSM系统的信道估计算法LS和MMSE两种算法性能与优缺点。通过在PB3信道模型中仿真,得出适用于慢变信道的平滑滤波后的LS信道估计算法。     

OFDM系统基于导频的信道估计算法分析

正交频分复用（OFDM）技术是新一代宽带无线通信最具竞争力的备选方案之一,在众多的高速数据传输领域得到广泛地应用。文章对几种典型信道估计算法的复杂度和估计性能进行了理论分析,并分析了导频位置及疏密对估计性能的影响。仿真结果有力地验证了文章的理论分析。文章的分析可以为OFDM系统信道估计算法的选择及导频的放置及其疏密度的设计提供一定的参考。     

无线自组网链路状态自适应路由协议设计

文章首先指出了链路状态（LS）路由协议的不足,接着建了LSARP协议的数学模型,并详细介绍了其组成及设计过程。NS-2仿真实验表明,该协议能够提高网络数据传输速率和分组投递率,路由开销小,相比LS协议各方面性能都有明显提高,能有效缓解LS路由协议路由开销和网络拓扑结构同步之间的矛盾。     

Resolvent estimates in homogenisation of periodic problems of fractional elasticity

We provide operator-norm convergence estimates for solutions to a time-dependent equation of fractional elasticity in one spatial dimension, with rapidly oscillating coefficients that represent the material properties of a viscoelastic composite medium. Assuming periodicity in the coefficients, we prove operator-norm convergence estimates for an operator fibre decomposition obtained by applying to the original fractional elasticity problem the Fourier–Laplace transform in time and Gelfand transform in space. We obtain estimates on each fibre that are uniform in the quasimomentum of the decomposition and in the period of oscillations of the coefficients as well as quadratic with respect to the spectral variable. On the basis of these uniform estimates we derive operator-norm-type convergence estimates for the original fractional elasticity problem, for a class of sufficiently smooth densities of applied forces.     

Decay rates of solutions to a P1-approximation model arising from radiation hydrodynamics

This paper is concerned with the global existence and large time behavior of solutions to Cauchy problem for a P1-approximation radiation hydrodynamics model. The global-in-time existence result is established in the small perturbation framework around a stable radiative equilibrium states in Sobolev space $H^4({\mathbb{R}}^3)$. Moreover, when the initial perturbation is also bounded in $L^1({\mathbb{R}}^3)$, the $L^2$-decay rates of the solution and its derivatives are achieved accordingly. The proofs are based on the Littlewood–Paley decomposition techniques and elaborate energy estimates in different frequency regimes.     

Une ambition éditoriale “universelle et confraternelle” : le bulletin bibliographique de L'Enseignement mathématique (1899–1920)

In 1899 Henri Fehr and Charles Laisant founded L'Enseignement mathématique (EM) with the ambition to involve teachers in the then-growing internationalization movement of mathematics. To this purpose, their editorial project gave an important place to a bibliographical bulletin reviewing periodicals which could be of interest for the world of mathematical education. This article is dedicated to the study of this bulletin, from its creation to the 1920s, and to the initiatives and choices that Laisant and Fehr made to carry out this internationalist editorial ambition, as well as to the limits and constraints of their project. During that time, many bibliographical initiatives for periodicals developed in the mathematical press, which can be considered as a first form of interaction between journals. Our study will concern initially the year 1899 and this interaction in which EM took part, dealing at first with the bulletin of EM, then, secondly, with the confrontation between bibliographical sections of other journals. Lastly, considering the first thirty years of the 20th century, we will study the different dynamics at work in the world of mathematical periodicals which the EM serves to depict.     

数据估计精度分析

以实际工程应用为背景,介绍了一类较为简单基于多次测量的参数估计问题。详细描述了其估计的过程,并给出了部分实验数据的估计结果。在数字上对参数估计的精度进行了分析,得到了明确的表达式,实验结果与理论分析一致。     

Relations between some basic results derived from two kinds of topologies for a random locally convex module

The purpose of this paper is to exhibit the relations between some basic results derived from the two kinds of topologies (namely the (ε,λ)-topology and the stronger locally L⁰-convex topology) for a random locally convex module. First, we give an extremely simple proof of the known Hahn-Banach extension theorem for L⁰-linear functions as well as its continuous variant. Then we give the relations between the hyperplane separation theorems in [D. Filipovi?, M. Kupper, N. Vogelpoth, Separation and duality in locally L⁰-convex modules, J. Funct. Anal. 256 (2009) 3996-4029] and a basic strict separation theorem in [T.X. Guo, H.X. Xiao, X.X. Chen, A basic strict separation theorem in random locally convex modules, Nonlinear Anal. 71 (2009) 3794-3804]: in the process we also obtain a very useful fact that a random locally convex module with the countable concatenation property must have the same completeness under the two topologies. As applications of the fact, we prove that most of the previously established principal results of random conjugate spaces of random normed modules under the (ε,λ)-topology are still valid under the locally L⁰-convex topology, which considerably enriches financial applications of random normed modules.     

Variations on a theme of Boole and Stein-Weiss

We give an alternative proof of a theorem of Stein and Weiss: The distribution function of the Hilbert transform of a characteristic function of a set E only depends on the Lebesgue measure |E| of such a set. We exploit a rational change of variable of the type used by George Boole in his paper “On the comparison of transcendents, with certain applications to the theory of definite integrals” together with the observation that if two functions f and g have the same Lp norm in a range of exponents p₁<p<p₂ then their distribution functions coincide.