多进制（Q-ary）LDPC码的编译码原理

多进制(Q-ary)LDPC码是将二进制LDPC码一般化到有限域GF(q),其校验矩阵元素不再是(0,1),而是集合(0,1,…,q-1),其译码仍然采用高效的信度传递迭代译码算法.本文主要阐述了多进制LDPC码的编译码原理,并介绍了一种可简化译码的傅立叶变换译码算法.通过将多进制LDPC码的性能与二进制LDPC码和RS码的性能进行比较,可以看出多进制LDPC码在磁存储系统、下一代ADSL系统以及深空通信方面将是取代RS码的强有力的候选,有极其重要的应用价值.     

用单片机实现无线通信中数据的编解码

在利用单片机和无线数传模块进行无线数据通信时 ,通常的办法是通过单片机的串行I/O口来完成数据的串行通信。然而此方法存在许多不足之处 ,如差错检测能力差、帧格式不灵活等。针对低速通信的场合 ,提出了一种通过单片机和无线数传模块以软件方式实现对传输数据编码、解码的原理和方法。数据的编码采用了曼彻斯特编码格式 ,每帧数据包括同步头、有效数据位和冗余校验位三部分。解码包括同步头和数据位的判定及循环冗余校验。在数据位的判定中提出了用软件实现“测三取二”的判定方法。该判定方法不但可以提高采样的准确度 ,而且还具有一定的滤波功能。实验结果表明 ,与单片机的串口通信相比 ,该编解码方法具有抗干扰能力强、传输数据灵活等优点     

差分跳频码性能检验研究

差分跳频是一种新的扩展频谱通信技术．在介绍差分跳频基本原理的基础上，将差分跳频的频率跳变过程建模成齐次马尔可夫链．分析了G函数的功能，重点讨论了差分跳频码性能的检验方法，包括不可约性、频隙滞留、均匀性和随机性检验，其中频隙滞留是首次提出应用于差分跳频码性能的检验．这些检验方法对于差分跳频G函数的设计具有一定的指导意义．     

HEXTRAN–SMABRE calculation of the VVER-1000 coolant transient-1 benchmark

The VVER-1000 coolant transient benchmark is intended for validation of couplings of the thermal hydraulic codes and three-dimensional neutron kinetic core models. It concerns switching on a main coolant pump when the other three main coolant pumps are in operation. The problem is based on an experiment performed in Kozloduy NPP in Bulgaria. In addition to the real plant transient, an extreme scenario concerning a control rod ejection after switching on a main coolant pump was calculated. At VTT the three-dimensional advanced nodal code HEXTRAN is used for the core dynamics, and the system code SMABRE as a thermal hydraulic model for the primary and secondary loop. The parallelly coupled HEXTRAN–SMABRE code has been in production use since early 1990s, and it has been extensively used for analyses of VVER NPPs. The SMABRE input model is based on the standard VVER-1000 input used at VTT. The whole core calculation is performed with HEXTRAN. Also the core model is based on earlier VVER-1000 models. Nuclear data for the calculation were specified in the benchmark. The paper outlines the input models used for both codes. Calculated results are introduced both for the coupled core system with inlet and outlet boundary conditions and for the whole plant model. Parametric studies have been performed for selected parameters.     

Turbo-CRC码的设计与仿真实现

本文在分析Turbo码的迭代译码原理和算法的基础上,提出一种优化的Turbo-CRC迭代译码的设计方法,可以在不降低译码性能和不增加系统复杂度的情况下,有效地减小平均迭代次数和译码延时。计算机仿真结果表明在AWGN信道和瑞利衰落信道下,Turbo-CRC译码的平均迭代次数可以分别减小20%￣45%和10%￣15%,表明了该方法的有效性和可行性。     

多径衰落下基于多码检测的多天线CDMA信道容量

研究了基于LS码和Walsh码多天线CDMA系统在干扰方差已知和干扰方差未知两种情况下的容量，给出了理论分析。理论和仿真结果符合表明：使用LS码的系统容量远远大于基于使用Walsh码的CDMA系统；干扰方差对LS码系统没有任何影响，容量与信噪比呈线性关系；而对于传统CDMA系统，干扰方差未知要损失一定的容量，并且在信噪比大于18dB的时候有平台效应。     

高强混凝土柱的梁柱节点处理方法

高强混凝土柱的梁柱节点处 ,以前通常采用浇注少量高强混凝土的方法 ,楼层梁板则仍用普通强度混凝土。此种方法对于高流动性商品混凝土是很不适宜的。参考国外多年的试验资料 ,并根据新的抗震规范的精神 ,提出梁柱节点的设计建议 ,可供设计人员参考     

On link layer denial of service in data wireless LANs

In this paper, we investigate the resiliency to jamming of data protocols, such as IP, over WLAN. We show that, on existing WLAN, an adversary can successfully jam data packets at a very low energy cost. Such attacks allow a set of adversary nodes disseminated over an area to prevent communication, partition an ad hoc network or force packets to be routed over adversary chosen paths. The ratio of the jamming pulses duration to the transmission duration can be as low as 10⁻⁴. We investigate and analyze the performance of combining a cryptographic interleaver with various coding schemes to improve the robustness of wireless LANs for IP packets transmission 1 . A concatenated code that is simple to decode and can maintain a low frame error rate (FER) under a jamming effort ratio of 15%. We argue that LDPC codes will be very suitable to prevent this type of jamming. We investigate the theoretical limits by analyzing the performance derived from upper bounds on binary error‐control codes. We also propose an efficient anti‐jamming technique for IEEE802.11b based on Reed–Solomon codes. Copyright © 2004 John Wiley & Sons, Ltd.     

主动网络中的代码安全性研究

分析了主动代码的开发、部署、执行和撤销等问题,为保证主动网络安全性,提出了开发专用模块对新开发的代码进行评估,以实现对主动代码的安全管理;为简化协议的开发难度,提出了协议元概念,协议元是一些代码的集合,能实现基本的网络层功能,通过协议元的组合使用可快速实现新协议的开发。     

Time course of the blindness to response-compatible stimuli.

This article examines the time course of a deficit in identifying a stimulus sharing a compatible feature with a response that is executed in parallel ("blindness to response-compatible stimuli," J. Müsseler & B. Hommel, 1997a). In 5 experiments, participants performed a timed response, and the presentation point of time of a to-be-identified stimulus was varied in respect to response execution. A blindness effect was observed when the stimulus was presented between response cue offset and response execution. In contrast, the identification of a stimulus presented before the response cue or after response execution was not affected by stimulus-response compatibility—a finding that rules out a retention-based explanation. These results support an explanation that states that the perceptual processing of a stimulus feature is impaired as long as the shared perception–action feature code is integrated into the representation of a to-be-executed response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)