改进的多载波码分多址系统多址干扰抑制算法

为了抑制多载波码分多址（MC-CDMA）系统中的多址干扰,提出了一种基于自适应并行次梯度投影的多址干扰抑制算法。它首先根据接收端信号模型建立包含最优干扰抑制滤波器系数并具有随机属性的凸集,然后运用并行次梯度投影的思想将对该凸集的投影转化为对多个闭合半平面的投影,最后将更新后的干扰抑制滤波器系数矢量投影到限定集合上。理论分析和仿真结果表明,该算法具有快速收敛性和稳定的干扰抑制性能,在不同的噪声强度下都具有较低的误码率和较高的鲁棒性。     

Quotients of Gaussian graphs and their application to perfect codes

A graph-based model of perfect two-dimensional codes is presented in this work. This model facilitates the study of the metric properties of the codes. Signal spaces are modeled by means of Cayley graphs defined over the Gaussian integers and denoted as Gaussian graphs. Codewords of perfect codes will be represented by vertices of a quotient graph of the Gaussian graph in which the signal space has been defined. It will be shown that any quotient graph of a Gaussian graph is indeed a Gaussian graph. This makes it possible to apply previously known properties of Gaussian graphs to the analysis of perfect codes. To illustrate the modeling power of this graph-based tool, perfect Lee codes will be analyzed in terms of Gaussian graphs and their quotients.     

Data dictionary systems and their application in auditing

Data dictionaries (DD) hold information about data held by an organization. The most important features of DDs to an auditor are security and reporting. DDs can be difficult to compare as there is no agreed standard for their design. One company had problems in finding a suitable DD and implementing it.     

改进粒子群算法在正交编码优化中的应用

为了避免同型号雷达发射信号之间产生的相互干扰,一般要求各雷达发射的信号是正交的,所以设计具有低自相关和互相关的正交编码信号是雷达抗干扰的关键。针对频率编码雷达信号,提出一种基于改进粒子群的正交编码信号优化算法,引入遗传算法中的交叉变异思想,从而克服基本粒子群算法(SPSO)收敛速度慢、易陷局部最优的缺点,最后对设计结果进行了分析。仿真结果表明,该方法是有效和可行的,在性能上要优于基本粒子群算法、模拟退火算法(SA)和混合遗传算法(HGA)。     

Educational recommender systems and their application in lifelong learning

The almost unlimited access to educational information plethora came with a drawback: finding meaningful material is not a straightforward task anymore. Recommender algorithms can be used to make smart decisions in complex information systems and help the users decide upon useful materials; therefore, they become a promising area in academia and industry. The current paper presents a survey on educational recommender systems (RS): a set of analysis criteria are exposed and the technological specifications and challenges of each analysed system are provided, in the context of the main trends in the development of RS. Also, an ontology-based educational recommendation mechanism is proposed and its application to lifelong learning is highlighted, proving that RS can successfully support new learning paradigms.     

Adaptive channel and power allocation of downlink multi-user MC-CDMA systems

The Multi-Carrier Code Division Multiple Access (MC-CDMA) is becoming a very attractive multiple access technique for high-rate data transmission in the future wireless communication systems. This paper is focused on the joint channel and power allocation in the downlink transmission of multi-user MC-CDMA systems and considers the throughput maximization problem as a mixed integer optimization problem. For simple analysis, the problem is divided into two less complex sub-problems: power allocation and channel allocation, which can be solved by a suboptimal Adaptive Power Allocation (APA) algorithm and an optimal Adaptive Channel Allocation (ACA) algorithm, respectively. By combining APA and ACA algorithms, an adaptive channel and power allocation scheme is proposed. The numerical results show that the proposed APA algorithm is more suitable for MC-CDMA systems than the conventional equal power allocation algorithm, and the proposed channel and power allocation scheme can significantly improve the system throughput performance.     

多变量周期系统的多模型二阶段自适应控制

对于一类参数未知的多变量周期系统,传统自适应控制方法存在参数收敛慢的问题,导致系统暂态响应差、控制效果不理想.因此,本文针对多变量周期系统设计了多模型二阶段自适应控制器.首先根据先验知识,确定不确定区域范围,并在不确定区域内建立多个自适应模型.然后根据李雅普诺夫理论得到第一阶段辨识方程;在第二阶段中,充分考虑辨识误差并...     

Lakatos queuing systems, their generalization and application

Queuing systems with cyclic waiting time are considered. The results of the Hungarian mathematician L . Lakatos are presented and generalized and possible application fields are specified.     

Performance improvement in detection and estimation of MC-CDMA systems over MIMO channels

Multiple-input Multiple-output (MIMO) multi-carrier code division multiple access (MC-CDMA) is a strong candidate for the downlink of future mobile communications to obtain high data rates. Nevertheless, during any transmission over fading channel, performance of MC-CDMA systems are highly degraded due to the presence of multiple access interference (MAI). Multi-user detection (MUD) and channel estimation play a major role in overcoming MAI and characterising the channel, respectively. In this paper, space time serial interference cancellation (STSIC) detection using random and Gold codes and turbo aided iterative channel estimation (ICE) techniques are extended for MC-CDMA system MIMO channels to overcome MAI. Simulation results show STSIC outperforms optimal MUD and linear MUD techniques in mitigating MAI and turbo aided ICE surpasses ICE in characterising the channel with reduced error rates.     

CS reconstruction in MIMO channel using square complex orthogonal STB codes

Microsystem Technologies - Compressed sensing (CS) is the process of signal reconstruction at a rate far below the Nyquist sampling rate. Sometimes, CS measurements need transmission over radio...     

正交空时分组码系统的一种新的盲信道估计算法

基于QR分解的信道盲估计方法是一种性能优良的新算法。将该算法推广到正交空时分组码的信道估计中,结合正交空时分组码的特性提出了一种新的信道盲估计算法。与经典的信道盲估计算法相比,新算法的计算量大为降低。同时,Monte Carlo仿真表明,当信噪比较低时,该算法比子空间法具有更好的性能。     

Conflict-avoiding codes and cyclic triple systems

The paper deals with the problem of constructing a code of the maximum possible cardinality consisting of binary vectors of length n and Hamming weight 3 and having the following property: any 3 × n matrix whose rows are cyclic shifts of three different code vectors contains a 3 × 3 permutation matrix as a submatrix. This property (in the special case w = 3) characterizes conflict-avoiding codes of length n for w active users, introduced in [1]. Using such codes in channels with asynchronous multiple access allows each of w active users to transmit a data packet successfully in one of w attempts during n time slots without collisions with other active users. An upper bound on the maximum cardinality of a conflict-avoiding code of length n with w = 3 is proved, and constructions of optimal codes achieving this bound are given. In particular, there are found conflict-avoiding codes for w = 3 which have much more vectors than codes of the same length obtained from cyclic Steiner triple systems by choosing a representative in each cyclic class.     

几类线性码的扩展码及其在密钥共享中的应用

极小线性码在构造安全高效访问结构上的密钥共享方案中应用广泛。研究了几类线性码的扩展码,并得出了其参数和重量分布。结果表明,这些扩展码都是极小码,可用于构造密钥共享方案。此外,还给出了一些最优码或几乎最优码。     

Elementary differentials,their graphs and codes

When designing high-order one-step numerical methods like Runge-Kutta, Rosenbrock, or ABC-schemes for solving ordinary differential equations, one has to take into account many tens and hundreds of elementary differentials. Graphical representation of the latter in use nowadays does not solve the problem of the computerization of the enormous amount of manual work. We have proposed a simple and intuitive way of digital coding of elementary differentials or their graphs. Algorithms for generation, analysis, and synthesis of such codes were developed and implemented in a computer program, which computes tables of codes for elementary differentials of any order together with their multiplicities and gamma-factors.     

Geoinformation systems and fields of their potential application in modern information society

This paper discusses the characteristic features of geoinformation systems (GISs) that make them different from other types of information systems. The components, functions, and application areas of GISs are considered, and GIS software solutions are described in detail. Application of GISs in different fields is demonstrated with particular examples.     

Hierarchical codes: A flexible trade-off for erasure codes in peer-to-peer storage systems

Redundancy is the basic technique to provide reliability in storage systems consisting of multiple components. A redundancy scheme defines how the redundant data are produced and maintained. The simplest redundancy scheme is replication, which however suffers from storage inefficiency. Another approach is erasure coding, which provides the same level of reliability as replication using a significantly smaller amount of storage. When redundant data are lost, they need to be replaced. While replacing replicated data consists in a simple copy, it becomes a complex operation with erasure codes: new data are produced performing a coding over some other available data. The amount of data to be read and coded is d times larger than the amount of data produced, where d, called repair degree, is larger than 1 and depends on the structure of the code. This implies that coding has a larger computational and I/O cost, which, for distributed storage systems, translates into increased network traffic. Participants of Peer-to-Peer systems often have ample storage and CPU power, but their network bandwidth may be limited. For these reasons existing coding techniques are not suitable for P2P storage. This work explores the design space between replication and the existing erasure codes. We propose and evaluate a new class of erasure codes, called Hierarchical Codes, which allows to reduce the network traffic due to maintenance without losing the benefits given by traditional erasure codes.     

一种使用未标记样本聚类信息的自训练方法*

为了有效地利用结构信息,提出了一种新的自学习算法,算法中利用聚类方法从自标记样本中选择可信度高的样本,同时用一个数据编辑方法从这些可信度高的样本中剔除被错标的可能性较高的样本。算法在UCI数据上进行了验证,效果和收敛速度比对比算法要好,说明引入聚类选择候选样本是有效的。     

Optimization planning systems and their implementation and application in vertically integrated oil companies

The approaches to planning of activities of a vertically integrated oil company by using optimization systems are considered. Development, implementation, and support of such systems are discussed. These problems fall under the APS (Advanced Planning and Scheduling) group in the modern classification. Based on the extensive experience of implementation and regular support of optimization systems in OAO LUKOIL, the general requirements necessary for effective using of such systems in vertically integrated oil companies are formulated.     

Capacity of orthogonal space-time block codes in MISO fading channels with co-channel interference and noise

Orthogonal space-time block codes(OSTBCs) are an efficient mean in order to exploit the diversity offered by the wireless multiple-input multiple-output(MIMO) channel. This paper considers capacity problems of OSTBCs over spatially correlated multiple-input single-out(MISO) Rayleigh fading channels in the presence of spatially correlated Rayleigh co-channel interference and additive Gaussian noise,and derives exact expressions of the ergodic capacity and outage probability(capacity distribution) for such OS...