End-to-end delay estimation for multi-hop wireless networks with random access policy

End-to-end delay analysis is an important element of network performance analysis in multi-hop wireless networks.In this paper,we propose an analytical model for estimating the end-to-end delay performance of wireless networks employing a random access policy for managing node’transmissions on shared channels with time-varying capacity.To obtain the closed form expression,a new concept of residual effective capacity is presented using the definitions of effective bandwidth theory and effective capacity theory.This allows us to calculate the cumulative distribution function of the queuing delay.Based on this concept,we derive a formula to calculate the average end-to-end delay for multi-hop wireless networks,with the result including the effect of a random access protocol,which has not previously been considered.Finally,we validate our analysis through simulations and provide an example application for our results.     

接收端驱动的流媒体组播拥塞控制协议

提出了一种适于流媒体业务的TCP公平的单速率组播拥塞控制协议——接收端驱动的二项式组播拥塞控制算法．该算法在各接收端独立维护拥塞窗口,采用二项式算法调整拥塞窗口,根据当前拥塞窗口值计算出期望接收速率,采用基于代表的策略实现反馈和反馈抑制．算法很好改善了丢失路径多样性问题,增强了可扩展性．仿真表明协议具有良好的TCP公平性、速率平滑性、可扩展性和较好的响应性．     

基于广义切比雪夫多项式的身份基加密体制安全性分析

Chebyshev polynomials are used as a reservoir for generating intricate classes of symmetrical and chaotic patterns, and have been used in a vast amount of applications. Using extended Chebyshev polynomial over finite field Zp , Algehawi and Samsudin presented recently an Identity Based Encryption (IBE) scheme. In this paper, we showed their proposal is not as secure as they claimed. More specifically, we presented a concrete attack on the scheme of Algehawi and Samsudin, which indicated the scheme cannot be consolidated as a real alternative of IBE schemes since one can exploit the semi group property (bilinearity) of extended Chebyshev polynomials over Zp to implement the attack without any difficulty.     

Evolving statistical rulesets for network intrusion detection

Security threats against computer networks and the Internet have emerged as a major and increasing area of concern for end-users trying to protect their valuable information and resources from intrusive attacks. Due to the amount of data to be analysed and the similarities between attack and normal traffic patterns, intrusion detection is considered a complex real world problem. In this paper, we propose a solution that uses a genetic algorithm to evolve a set of simple, interval-based rules based on statistical, continuous-valued input data. Several innovations in the genetic algorithm work to keep the ruleset small. We first tune the proposed system using a synthetic data. We then evaluate our system against more complex synthetic data with characteristics associated with network intrusions, the NSL-KDD benchmark dataset, and another dataset constructed based on MIT Lincoln Laboratory normal traffic and the low-rate DDoS attack scenario from CAIDA. This new approach provides a very compact set of simple, human-readable rules with strongly competitive detection performance in comparison to other machine learning techniques.     

应用模糊增强及均值漂移实现红外目标分割

针对复杂环境下红外图像信噪比和对比度低,边缘模糊,目标分割困难的情况,提出一种基于模糊增强和均值漂移图像滤波的红外目标分割方法。首先定义新的隶属度函数,运用模糊集理论进行红外图像增强,避免了传统模糊增强算法的弊病,有效提高目标与背景的对比度;之后利用ICI（交叉置信区）规则确定均值漂移的带宽参数,提出一种新的自适应带宽均值漂移图像滤波方法,实现图像的进一步平滑和聚类;最后利用自适应阈值实现红外目标分割。实验结果表明,算法能够正确有效地分割出复杂环境下的红外目标,并且很好地保持了目标的轮廓细节。     

低复杂度的MIMO系统粒子滤波检测

该文通过降低采样大小和信号检测搜索空间给出了两种低复杂度的多输入多输出(MIMO)系统粒子滤波(PF)检测方法：球形约束PF和多层映射PF。在球形约束PF中,首先基于迫零原则求得所需的球形约束,然后利用该球形约束减少粒子滤波过程中每一级重要性采样生成的粒子数。多层映射PF则采用多层映射将大小为4L的正交幅度调制(QAM)星座划分为L个4-QAM星座的级联以降低信号检测的搜索范围。计算机仿真结果表明,第1种方法能够在大发送天线数的情况下保持系统性能且有效地降低粒子滤波的计算复杂度;而第2种方法能够以较低的错误性能损失为代价获得计算复杂度的极大降低。     

Constellation Classification Based on Sequential Monte Carlo for Intersymbol Interference Channels

Constellation classification for phase-amplitude-modulated signals transmitted through unknown intersymbol interference channels is proposed based on the sequential Monte Carlo (SMC) framework under both stochastic and deterministic settings. The stochastic SMC-based constellation classification (SMC-CC) sampler generates constellation symbol samples based on importance sampling and resampling techniques, whereas the deterministic SMC-CC approach recursively performs exploration and selection steps in a greedy manner. Then the constellation classification is achieved according to the distribution of the drawn samples in both the stochastic SMC-CC and the deterministic SMC-CC. Moreover, both the proposed methods are achieved along with joint estimation of transmitted data symbols and channel taps. Simulations show that the proposed methods perform well on various constellations with different cardinalities, as well as constellations with symbols.     

基于分组密码的跳频序列族构造

基于迭代型分组密码的理论体系,本文从工程实现的角度提出了一种用于跳频码分多址通信系统的新型跳频序列族构造方法.该算法基于密码学的加密机制,具有好的安全性和高的计算复杂度;算法的设计遵循了密码学的"混淆"和"扩散"准则,生成序列具有各项优异的性能指标.本文从安全性、随机性、均匀性、复杂度、组网特性及跳频间隔特性等各方面对产生的跳频序列进行了全面的理论分析,证明该算法具有理想的综合系统性能指标.在此基础上,利用VHDL语言设计并开发出相应的跳频加密芯片.经测试其性能稳定、运算速度快、输入方式灵活多样,已应用于实际的高速跳频通信系统中.     

基于FPGA的LDPC码编译码器联合设计

该文通过对低密度校验(LDPC)码的编译码过程进行分析,提出了一种基于FPGA的LDPC码编译码器联合设计方法,该方法使编码器和译码器共用同一校验计算电路和复用相同的RAM存储块,有效减少了硬件资源的消耗量。该方法适合于采用校验矩阵进行编码和译码的情况,不仅适用于全并行的编译码器结构,同时也适用于目前广泛采用的部分并行结构,且能够使用和积、最小和等多种译码算法。采用该方法对两组不同的LDPC码进行部分并行结构的编译码器联合设计,在Xilinx XC4VLX80 FPGA上的实现结果表明,设计得到的编码器和译码器可并行工作,且仅占用略多于单个译码器的硬件资源,提出的设计方法能够在不降低吞吐量的同时有效减少系统对硬件资源的需求。     

竞争型无线传感器网络MAC层协议性能分析与优化

无线传感器节点对电池能量的依赖性很强,用最少的能量完成网络通信是无线传感器网络的研究重点.竞争型无线传感器网络MAC协议(如S-MAC)主要通过牺牲吞吐量和时延来节省能量.文章提出了一种全新的无线传感器MAC协议--BS-MAC.BS-MAC在S-MAC休眠/侦听制的基础上实现了数据的双向传输,提高了系统性能.理论分析和仿真结果表明,BS-MAC在维持合理的能量损耗的前提下,可以增加系统吞吐量,降低时延,性能优于S-MAC.