Pheromone-Based Ant Routing System for IP Networks

The pheromone-based ant routing algorithm is a distributed routing algorithm with good scalability and robustness. A 2-D cellular automata (CA) model of the computer network was presented to analyze the algorithm. The results show that the procedure of establishing a stable route is self-organized towards the attractive peculiar state, and the duration of time for the routing establishment is power-law distributed. A practical ant routing protocol over an IP network was also presented, and two simulations were done to compare the performance dynamic and the load balancing performance between this protocol and the open shortest path first (OSPF) protocol. The results show that the ant routing protocol out-performs OSPF in these aspects.     

An Anti—multipath Frequency Hopped Communication Technique in Shallow—water Acoustic Channels

This paper introduces a frequency-hopped (FH) communication system to anti-intersymbol interferences (ISI) caused by the multipath propagation in shallow-water acoustic channels, and uses high-speed digital signal processor (DSP) and serial ADC (MAX121) chip to demodulate re-ceived signal efficiently based Fast Fourier Transform (FFT) algorithm. The field experimental results show: a data rate of 1Kbit/s with the bit error rates on the order of 10^-4 is denmnstrated at 2000 m in the shallow-water acoustic channel of Xiamen harbor, and the key techniques of the system is analyzed in the paper.     

Low Complexity MMSE-SQRD Signal Detection Based on Iteration

Aiming at the problem of high computational complexity of Vertical-BLAST(V-BLAST) algorithm in Multiple-Input Multiple-Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM) system signal detection, this paper first uses Sorted QR Decomposition(SQRD) iterative operation instead of matrix inversion to reduce the computational complexity of the algorithm, and then considering that the algorithm is greatly affected by noise, Minimum Mean Square Error(MMSE) criterion is used to weaken the noise effect. At the same time, in order to reduce the noise and computational complexity, MMSE and SQRD are combined, which can not only reduce the noise and computational complexity, but also obtain the sub-optimal detection order, thus improving the detection performance of the MIMO-OFDM system. Finally, the numerical simulation of the MMSE-SQRD detection algorithm is carried out. The results show that the Eb/No of MMSE-SQRD algorithm is 2 dB greater than that of the MMSE algorithm and the computational complexity is O(N_T~3) under the conditions that N_T =N_R=2 and the BER is 10~(–2). The detection algorithm satisfies the demand of short wave and wideband wireless communication.     

An improved multiplicative exponent weighting vertical handoff algorithm for WLAN/WCDMA heterogeneous wireless networks

An improved MEW(multiplicative exponent weighting)algorithm,SLE-MEW is proposed for vertical handoff decision in heterogeneous wireless networks.It introduces the SINR(signal to interference plus noise ratio)effects,LS(least square)and information entropy method into the algorithm.An attribute matrix is constructed considering the SINR in the source network and the equivalent SINR in the target network,the required bandwidth,the traffic cost and the available bandwidth of participating access networks.Handoff decision meeting multi-attribute QoS(quality of service)requirement is made according to the traffic features.The subjective weight relation of decision elements is determined with LS method.The information entropy method is employed to derive the objective weights of the evaluation criteria,and lead to the comprehensive weight.Finally decision is made using MEW algorithm based on the attribute matrix and weight vector.Four 3GPP(the 3rd generation partnership project)defined traffic classes are considered in performance evaluation.The simulation results have shown that the proposed algorithm can provide satisfactory performance fitting to the characteristics of the traffic.     

Single-User Blind Channel Equalization Using Modified Constant Modulus Algorithm

A modified constant modulus algorithm (MCMA) for blind channel equalization is proposed by modifying the constant modulus error function. The MCMA is compared with the conventional constant modulus algorithm (CMA) for symbol-spaced equalization of 4PSK signals. The result shows that the performance of the MCMA is superior to that of the CMA in both convergence rate and intersymbol interference for frequency selective channels in noisy environments. Simulation results using 8PSK signals also demonstrate that a fractionally spaced equalizer can preserve performance over variations in symbol-timing phase, whereas a baud-rate equalizer cannot.     

Double-Talk Detection Algorithm Based on the Ι2 Norm

Echo canceller generally needs a double-talk detector which is used to keep the adaptive filter from diverging in the appearance of near-end speech. In this paper we adopt a new double-talk detection algorithm based on ι2 norm to detect the existence of near-end speech in an acoustic echo canceller. We analyze this algorithm from the point of view of functional analysis and point out that the proposed double-talk detection algorithm has the same performance as the classic one in a finite Banach space. The remarkable feature of this algorithm is its higher accuracy and better computation complexity. The fine properties of this algorithm are confirmed by computer simulation and the application in a multimedia communication system.     

Fast VLSI Implementation of Modular Inversion in Galois Field GF（p）

Modular inversion is one of the key arithmetic operations in public key cryptosystems, so low-cost,high-speed hardware implementation is absolutely necessary. This paper presents an algorithm for prime fields for hardware implementation. The algorithm involves only ordinary addition/subtraction and does not need any modular operations, multiplications or divisions. All of the arithmetic operations in the algorithm can be accomplished by only one adder, so it is very suitable for fast very large scale integration (VLSI) implementation. The VLSI implementation of the algorithm is also given with good performance and low silicon penalty.     

Some problems in the third generation wave models and a new approach to ocean wave modeling

The incompatibility, uncertainty and other difficulties involved in the computation of source terms in the third generation wave model are discussed. Among the effects of these difficulties, the lack of spectral reliability and the expected slow improvement of the model are emphasized. The newly developed model based on an adopted wind-wave directional spectrum is briefly reviewed. The justification of using a given spectrum to build up a model is discussed in full length. The new model and the third generation model are compared in terms of reliability, performance, feasibility of improvement and convenience of usage. The new model has shown its advantages in the comparison and its potential in practical applications.     

Design and implementation of instruction-driven and data-driven self-reconfigurable cell array

The reconfigurable chip, which integrates the advantages of high performance, high flexibility,high parallelism, low power consumption, and low cost, has achieved rapid development and wide application. Generally, the control part and the computing part of algorithm is accelerated based on different reconfigurable architectures, but it is difficult to obtain overall performance improvement.For improving efficiency of reconfigurable structure both for the control part and the computing part,a hyb...     

Parameter Optimization of Linear Quadratic Controller Based on Genetic Algorithm

The selection of weighting matrix in design of the linear quadratic optimal controller is an important topic in the control theory. In this paper, an approach based on genetic algorithm is presented for selecting the weighting matrix for the optimal controller. Genetic algorithm is adaptive heuristic search algorithm premised on the evolutionary ideas of natural selection and genetic. In this algorithm, the fitness function is used to evaluate individuals and reproductive success varies with fitness. In the design of the linear quadratic optimal controller, the fitness function has relation to the anticipated step response of the system. Not only can the controller designed by this approach meet the demand of the performance indexes of linear quadratic controller, but also satisfy the anticipated step response of close-loop system. The method possesses a higher calculating efficiency and provides technical support for the optimal controller in engineering application. The simulation of a three-order single-input single-output (SISO) system has demonstrated the feasibility and validity of the approach.     

基于极大似然比频谱检测的认知无线电子载波分配算法

在认知无线电多载波调制系统中,子载波分配是实现主用户与认知用户频谱共享的前提.研究了认知OFDM中基于极大似然比检测(MLD)的子载波分配算法,认知用户采用MLD模型对主用户频谱使用情况进行分布式检测,利用频谱检测信息动态分配子载波,通过认知基站对认知用户子载波频谱感知信息进行融合判决.推导了MLD模型的判决区域上下界阈值、检测概率与虚警概率,并与能量检测进行性能比较.仿真结果表明,相对于能量检测,MLD判决阈值与子载波平均接收信噪比(SNR)有关,检测性能自适应信道变化.MLD用于CR多载波调制中的子载波分配,可明显提高认知OFDM子载波频谱感知性能,从而达到高效利用频谱资源,实现"绿色通信".     

一种智能天线MC-CDMA系统中的最小二乘恒模波束成形算法

提出了智能天线多载波CDMA系统中一种最小二乘恒模波束成形算法，它是在对多载波阵列接收信号进行恒模波束成形的同时，用已估信道参数对各个子载波上的信号进行合并（采用ORC、EGC或MRC），然后对合并后的信号进行判决，用判决后的信息和期望用户的扩频码重构各个子载波上的信号，最后用此重构信号与波束成形输出信号的差去控制波束成形器的抽头系数，从而提高了系统的性能．对这种波束成形算法与传统的最小二乘恒模波束成形算法进行了仿真比较，仿真结果表明，提出的束成形算法的误码性能优于传统的算法．     

一种优化的认知无线电网络资源协同分配算法

在目前的认知无线电研究中,多用户OFDMA系统中如何实现子载波和功率的合理分配是研究的重点之一.针对认知无线电资源分配过程中出现的多认知用户资源分配不公平的问题,研究了认知无线电网络中授权用户占用子载带时,认知用户的吞吐量受限制的问题,提出了一种基于underlay频谱共享模式下的OFDMA认知无线电网络功率与子载带协同分配优化算法.该算法利用干扰门限的设置,使用原始感知信息(RSI)和信道状态信息(CSI)进行功率与子载波分配,然后分别进行功率控制和用户选择的计算,找到最优化传输功率与每个子载带最优使用用户,在保证授权用户免受有害干扰的前提下,使授权用户存在时,也可共享频谱传输,确保了系统的稳定性,提高了网络吞吐量.理论分析与仿真结果表明,相比传统的功率与子载波联合分配算法,该算法可以提高系统的平均加权吞吐量.     

迭代KALMAN信道估计算法在MIMO-OFDM系统的性能仿真研究

讨论了MIMO-OFDM通信系统中时变信道估计的KALMAN滤波算法。为了提高传统KALMAN信道估计算法的性能,提出了一种迭代KALMAN滤波算法,将整个子载波分为2部分:一部分用于发送导频,另一部分用于发送信号。在一个OFDM符号块中,对导频子载波和信号子载波处的无线信道进行循环估计,从而提高信道估计的精度。仿真结果表明,迭代KALMAN滤波算法的性能好于传统KALMAN滤波算法。     

基于MIMO-OFDM系统的自适应调制算法研究

为了提高MIMO-OFDM系统的数据传输率和频谱利用率,提出一种新的自适应调制算法.该算法在信道传输质量满足一定系统误码率下,根据信道状态信息自适应地调整每个子载波的调制方式,使系统的发射总功率尽量最小.理论分析得出,该算法降低了MIMO-OFDM系统的运算复杂度,并使系统的整体性能得到了优化.     

采用导频子载波的OFDM系统频偏跟踪算法

为了进一步提高多径快衰落环境下,正交频分复用(orthogonal frequency-division multiplexing,OFDM)系统的载波频偏估计精度,研究了利用在OFDM符号中插入的导频子载波进行小数倍频偏跟踪的算法在多径快衰落信道下的频偏跟踪性能.通过与常规的基于循环前缀的跟踪算法进行比较,采用导频子载波的频偏跟踪算法,不仅在高斯白噪声信道下能达到很好的频偏跟踪性能,而且在多径快衰落信道下也能实现更准确的频偏估计,因此采用导频子载波的算法更适合用于多径快衰落信道下的频偏跟踪.     

正交频分多址系统中最低速率限制下的自适应载波分配

针对用户有最低传输速率要求的正交频分多址系统中,传统资源分配算法频谱利用率低的问题,提出了一种自适应载波分配算法.该算法根据用户最低传输速率的要求、信道状态和当前载波分配状况,确定子载波分配给用户的效用,进而将子载波分配给可以带来最大效用的用户.该算法综合考虑了效率和公平性,从而显著改善了系统性能.仿真结果表明,当用户数不超过系统负载时,与效率和公平分开考虑的算法相比,所提出的算法频谱效率可提高10%,系统负载在同样中断概率下可提高60%.     

不同速率的多用户MC-CDMA等效子载波分配算法研究

针对煤矿井巷通信环境,文中基于灌水原理提出能够满足不同速率需求的多用户MC-CDMA等效子载波分配算法,并建立系统模型,分析了算法的收敛性、多用户服务质量和系统的误码性能。仿真结果表明:该算法不仅能够保证每个等效子载波上用户数接近相等,对于随机特征使同道干扰达到最小,而且可以实现每个用户按照速率的大小有选择地占用一个或多个等效子载波;与随机等效子载波分配系统相比,在平均误码率为10-4时,系统大约可提供2 dB的信噪比增益。     

采用数据扩展技术的OFDM自适应调制算法

在传统的OFDM系统中,实现自适应调制需要传输大量的有关子载波调制参数信息,致使传输效率下降.文中分析了采用数据扩展技术的自适应调制OFDM系统的特征,发现最优算法就是在原始数据符号之间平均分配比特和功率,在此基础上提出了以用户需求为目标的最小化总功率的自适应调制算法.此算法的原始数据符号最多采用两种调制阶数,并且可以在原始数据符号之间按顺序分配,这样不仅降低了算法复杂度,而且大大减少了有关调制参数信息的传输.仿真结果表明该算法具有良好的性能,在复杂度相近的前提下,该算法比采用自适应功率控制的传统OFDM系统节省功率(用子载波的平均信噪比表示)约2 dB.     

基于小波分析的卫星测控信号盲识别算法

针对卫星测控通信信息侦察中测控信号识别的问题，提出一种基于小波分析的测控信号副载波识别算法。算法首先基于小波多分辨率分析去噪原理，对混合信号进行去噪处理，然后，采用零点分区法确定副载波个数，最后设计了闽值自适应判别算法来确定各个副载波的频率分界点。仿真结果表明：该测控信号副载波识别算法精度达到95％，抗噪声干扰能力强。