A New Approach of Overlay Method for Cognitive SW HARQ System

The aim of this paper is to obtain communication resource based on the overlay method for the secondary user (SU) in the primary communication environment operating in the Stop-and-Wait Hybrid Automatic Repeat Request (SW-HARQ) protocol. Unlike the overlay Cognitive Radio applications in the literature, in this work communication resources have been obtained for the SU in the time period in which the primary user (PU) is active in the channel. Our performance results have shown that a significant amount of sources of communication can be achieved for the SU by evaluating the waiting times in the primary SW HARQ periods, even when the PU is continuously running in the SW HARQ protocol without emptying the channel.

     

传感能力约束下的认知无线网络的多波段光谱感应优化

This paper addresses the problem of joint optimization of subchannel selection and spectrum sensing time for multiband cognitive radio networks under the sensing capability constrains. In particular, we construct a multiband spectrum sensing framework, and derive the probabilities of detection and false alarm taking the different subchannel gain into account. Furthermore, we formulate the multiband sensing as a two-parameter optimization problem under the sensing capability constrains and guaranteeing the QoS of the secondary user. Moreover, we develop a semi-analytical optimization scheme to achieve the optimal solution.     

Sparse Representation for Blind Spectrum Sensing in Cognitive Radio: A Compressed Sensing Approach

Cognitive radios enable opportunistic transmission for secondary users (SUs) without interfering the primary user (PU). Cyclo-stationary-based spectrum sensing methods are better than the energy detection methods in negative signal-to-noise (SNR) decibel (dB) regime, in which case the noise variance cannot be exactly estimated. However, blind cyclo-stationary methods require a large number of symbols (and hence measurements). This paper aims to reduce the number of measurements in a blind sensing method (using a combination of linear prediction and QR decomposition), by employing compressed sensing at the receiver front-end, so as to reduce the A/D requirements needed with a large number of measurements, along with oversampling the received signal. Till now, compressed sensing has not been investigated at very low negative SNR (dB), e.g., \(-\)12 dB, which is very crucial in spectrum sensing. The novel algorithm, in this paper, overcomes this shortcoming, and its simulation results show that the SU is able to detect the PU signal, using much less measurements, even at very low negative SNR (dB). The proposed method also investigates the effect of joint and individual measurement matrices at multiple oversampled branches.     

一种新的认知无线电频谱感知算法

频谱感知是认知无线电的关键技术之一,通过检测授权用户信号的有无来发现频谱空穴,以提高频谱利用率。基于接收信号的统计协方差理论,提出一种新的认知无线电频谱感知算法,无需信号的先验信息,且计算复杂度较低。仿真分析了该算法,结果表明其在低信噪比环境下,较传统能量检测法有更好的感知性能。     

A Novel Evolutionary-Based Cooperative Spectrum Sensing Mechanism for Cognitive Radio Networks

Cognitive radio (CR) is considered as a feasible intelligent technology for 4G wireless networks or self-organization networks and envisioned as a promising paradigm of exploiting intelligence for enhancing efficiency of underutilized spectrum bands. In CR, one of the main concerns is to reliably sense the presence of primary users, to attain protection against harmful interference caused by the potential spectrum access of secondary users (SUs). In this paper, evolutionary algorithms, namely, genetic algorithm (GA) and particle swarm optimization (PSO) are investigated. An imperialistic competitive algorithm (ICA) is proposed to minimize error detection at the common soft data fusion (SDF) center for structurally centralized cognitive radio network (CRN). By using these techniques, evolutionary operations are invoked to optimize the weighting coefficients applied on the sensing measurement components received from multiple cooperative SUs. The proposed method is compared with other evolutionary algorithms, as well as other conventional deterministic, such as maximal ratio combining- (MRC-), modified deflection coefficient- (MDC-), normal deflection coefficient- (NDC-) based SDF schemes and OR-rule HDF based. MATLAB simulations confirm the superiority of the ICA-based scheme over the PSO-, GA-based and other conventional schemes in terms of detection performance. In addition, the ICA-based scheme also shows promising convergence and time running performance as compared to other iterative-based schemes. This makes ICA an adequate solution to meet real-time requirements.     

一种新型的基于神经网络的无线信道模型

本文提出了一种使用神经网络来建模和仿真无线通信信道的方法。由于神经网络优异的学习特性,文中使用神经网络对无线信道的输入输出响应进行建模,讨论了建模的方法,给出了仿真的结果,分析了遇到的问题和解决方法,并进一步阐述了在实际的无线信道环境中使用神经网络建模的优越性。     

A Novel Two-Stage Entropy-Based Robust Cooperative Spectrum Sensing Scheme with Two-Bit Decision in Cognitive Radio

Spectrum sensing is a key problem in cognitive radio. However, traditional detectors become ineffective when noise uncertainty is severe. It is shown that the entropy of Gauss white noise is constant in the frequency domain, and a robust detector based on the entropy of spectrum amplitude was proposed. In this paper a novel detector is proposed based on the entropy of spectrum power density, and its performance is better than the previous scheme with less computational complexity. Furthermore, to improve the reliability of the detection, a two-stage entropy-based cooperative spectrum sensing scheme using two-bit decision is proposed, and simulation results show its superior performance with relatively low computational complexity.     

片上螺旋带中央抽头对称电感的新解析参数提取方法

我们提出了一种针对硅基有中心抽头的片上螺旋电感的参数提取的新的解析函数方法.通过建立一系列闭合解析公式,模型参数町以通过一系列引入分块的线性特征函数方法来提取出.通过基于0.18μmCMOS工艺的测量数据的验证,同时与传统的方法进行比较,我们的方法可以在宽频带内实现电感的高精度仿真.     

A Novel Technique for Wideband Spectrum Sensing in Cognitive Radio Through Phase-Field Segmentation

The problem of wideband spectrum sensing for detecting vacant frequency subbands for opportunistic cognitive radio is investigated. This is achieved through the identification of irregularities (discontinuities) in the estimated power spectrum density. In this paper, we propose a new mathematical framework based on phase-field segmentation method, usually used in the image processing community. We show that by properly setting the parameters of the phase-field function, robustness to fluctuations of the edge threshold value (due to estimation errors for instance) used for spectrum sensing can be achieved. Our numerical results indicate that the sensing accuracy is improved, while the computational complexity is reduced, when compared to conventional methods.     

一种新的应用层对等路由机制的研究

提出了一种基于对等网的路由方案.该方案首先在网络中部署多个服务器,每个服务器维护一个连接其他服务器的时延二叉树,每个动态节点归属于某个服务器管辖.基于该树,任何两个动态节点能够以较小的代价快速建立通信所需的路由路径.仿真测试结果证明了这一方案具有较好的性能.     

基于P2P-SIP的语音组通讯机制研究

传统的SIP网络组通讯系统大多基于客户机/服务器模型,导致系统可扩展性差,并且由于中央控制服务器到与会节点时延不均衡会造成语音包接收滞后等问题,鉴于此,提出的基于会议管理节点(Conference Management Node,CMN)的组通讯机制有效地解决了上述问题,基于CMN的组通讯机制旨在为每次会议动态找到一个会议管理节点并构建一棵以会议管理节点为根节点的应用层多播树,并采用分域和保持节点闻心跳的方式来维护网络节点,准确而实时地收集中继节点信息,组通讯机制采用P2P的方式选取会议管理节点,不依赖于中央控制服务器,增强系统的可扩展性和可靠性;会议管理节点到各个与会成员时延较小(满足通话要求)且时延均衡,改善语音通话质量,防止因时延差异过大而造成的语音接收滞后现象,测试表明,通信延时大大减小,会议中转概率有明显提升.     

一种认知无线网络中的协作感知优化方法

认知无线电技术能够显著提高频谱资源的利用率,因此越来越受到学术界的关注。频谱感知是认知无线电的基础,一方面它要求能够快速找到可用频谱,另一方面当授权用户返回时又要求能够快速释放信道避免干扰。提出了一种认知无线网络中多用户协作感知分级方法,并通过数学推导给出最优的分级策略。仿真结果表明,采用所提出的协作频谱感知方法,能够提高认知无线网络的吞吐量。     

A Novel Approach for Channel Allocation In OFDM Based Cognitive Radio Technology

Wireless Personal Communications - When the number of users in the radio environment is increasing and the rapid development in the wireless environment is examined, the efficient use of the...     

Analytical Modeling of Metal-Insulator-Semiconductor Interconnects Using the Energy Based Approach

Simple formulae for calculating circuit parameters of metal-insulator-semiconductor (MIS) interconnects are obtained using the energy based approach. The energy based approach results in a new consistent equivalent transmission line model that exhibits power equivalence to the original MIS waveguide. This new model has solid physical foundation and is valid for a wide range of frequency and impurity doping rate. At the quasi-TEM limit, this new model reduces to the existing model that was obtained using the contour integral based approach.     

A Novel Mathematical Model for Energy Detection Based Spectrum Sensing in Cognitive Radio Networks

Wireless Personal Communications - Spectrum sensing is the quintessence of cognitive radio network and is influenced by uncertain noise at low SNR. In such a scenario sensing duration imposes a...     

基于目标物理特征和压缩感知的地雷目标鉴别方法

通过压缩感知(Compressed Sensing, CS)算法可以实现对目标的稀疏成像,并获取其空间散射结构用于目标鉴别和识别。该文针对穿透地表成像的前视超宽带虚拟孔径雷达(Forward Looking Virtual Aperture Radar, FLVAR)实测数据,以CS理论为基础对地雷目标进行稀疏成像,利用地雷目标电磁散射的稀疏性实现其散射结构的提取,将目标散射特性转化为与物理结构相关的几何特征,并基于该特征进行目标的分类鉴别。新方法不仅拓展了地雷鉴别的新思路,而且也为压缩感知在目标散射结构提取和目标鉴别上的应用进行了初步有效的尝试。     

低信噪比条件下提高认知无线电的频谱感知能力的方法

为了提高认知无线电在强噪声环境下的频谱感知能力,该文提出了一种频谱感知方法。该方法利用循环谱相关函数,采用二次模式识别,可以显著提高在低信噪比条件下的信号调制方式识别准确率。试验结果表明,在AWGN 信道,信噪比不低于-10dB条件下,对常用5种数字调制信号的识别准确率高于99.9%,能够满足认知无线电中对频谱感知的性能要求。     

A Universal Overlay for Surface Impedance Calculations for Composite Conductors

Surface impedance calculations for composite conducting surfaces made of two different metals can be made amenable to a universal graphical solution. This is in the form of an overlay to be superimposed on the reflection coefficient plane and is therefore useful in conjunction with either the Smith Chart or the "Zeta-Theta" Chart. An example is given of a composite conductor consisting of a thin nickel interfacing layer underlying a thick layer of gold, such as might be found in the construction of microstrip circuit elements.     

Overlay Cognitive Radio Based on OFDM with Channel Estimation Issues

Wireless Personal Communications - Cognitive radio (CR) has been proposed as a technology to improve the spectrum efficiency by giving an opportunistic access of the licensed-user spectra to...     

Energy Detection Approach for Spectrum Sensing in Cognitive Radio Systems with the Use of Random Sampling

In radiomobile contexte, radio frequency spectrum is a ressource that needs to be used with appropriate efficiency. This can be achieved by the mean of spectrum sensing operation. This function consists to analyze the occupancy of the radio frequency spectrum in order to detect which bands are unused. This concept is largely appreciated in cognitive radio where more flexibility is required to adapt to the communication environment. Different techniques are presented in the literature. In this paper, we are interested by the application of the energy detector method for spectrum sensing. This application is performed in cognitive radio systems with the use of random sampling. The performance of this approach is evaluated in term of its receiver operating characteristic curve and compared to the uniform sampling case.