基于网络编码的衰落信道频谱感知算法

针对传统认知无线电网络中频谱状态转换频繁和频谱检测时延长的问题,提出基于随机线性网络编码的累积和能量检测频谱感知算法。该算法在主用户信道中引入随机线性网络编码,利用网络编码对频谱的整形作用,使频谱状态转换稀疏,频谱结构更规律化,减小频谱检测时延,提高系统吞吐率。此外,针对传统累积和能量检测算法抗衰落性能差的问题,通过比较该算法在五种衰落信道下的检测时延和吞吐率,研究该算法的抗衰落性能。实验结果表明,在一定的虚警概率下,该算法有效降低了检测时延,提高了吞吐率及抗衰落能力,能够更好地适应复杂的衰落信道环境。     

语音转换及相关技术综述

给出了语音转换的定义,介绍了语音转换的用途,分析了表征说话人个性特征的语音参数,研究了语音转换的系统结构,对语音转换的实现主要从频谱包络和韵律两个方面的转换进行了研究讨论,分析并介绍了语音转换现在的发展水平及存在的问题。     

语音转换中系统单位冲激响应的频谱搬移方法研究

频谱包络转换是语音转换中的一项重要内容,基于双线性转换函数进行频谱搬移的方法可以有效地进行谱包络转换,而且在基于小语料库进行训练时仍能得到稳定的转换谱包络.本文基于LPC分析,提出用反傅里叶变换的方法来求解频谱搬移后的系统单位冲激响应,以此来实现频谱包络的变换,并取得了较好的效果.     

认知无线电系统中频谱分配技术的研究及应用

随着无线通信技术的快速发展,无线用户的数量急剧增加,频谱资源越来越紧张,如何提高频谱的利用率成为亟待解决的问题。认知无线电系统中的频谱分配技术,使这一问题得到了有效解决。文章简要介绍了认知无线电频谱分配的背景、研究现状,对认知无线电频谱分配的模型进行了分析,介绍了频谱分配发展过程中存在的问题,最后简要论述了频谱分配技术的一些应用。     

CLBO晶体的宽带三倍频模拟分析

为了研究高效的宽带三次谐波转换技术，采用了分步傅里叶变换和四阶Runge-Kutta法对CLBO晶体的宽带三倍频过程进行了数值模拟，分析了单倍单混和单倍双混模式下三倍频转换效率随入射基频光强度、频谱带宽的变化关系，并与KDP晶体的宽带三倍频转换特性进行了对比。在强度为3GW/cm2的40阶超高斯脉冲入射下，得到单倍双混模式下三倍频转换效率达到60%时对应的频谱宽度为650GHz，这与利用KDP晶体在相同条件下获得的频谱宽度相比，提高了近250GHz。研究结果表明，在单倍双混模式下使用CLBO晶体作为频率转换的非线性晶体可以有效地提高宽带三倍频的转换效率。     

电视空闲频谱设备的若干问题

本文介绍电视空闲频谱设备应用经常遇到的一些概念和最新的发展应用情况.无线频谱是有限的自然资源,我们必须有效使用它.模拟电视到数字电视的转换,推动了UHF频谱的有效利用,软件无线电和认知无线电技术的发展,使电视空闲频谱设备的应用得以实现.本文围绕电视空闲频谱设备的应用介绍一些概念和最新的发展情况.     

串扰感知的空分弹性光网络频谱转换器稀疏配置和资源分配方法

针对大容量多芯光纤空分复用弹性光网络(SDM-EON)中芯间串扰导致业务传输质量下降和阻塞率上升的问题,该文提出了节点稀疏配置频谱转换器降低芯间串扰的路由纤芯频谱分配方法。该方法根据网络中节点中介中心性稀疏配置频谱转换器。在业务路由阶段,设计综合考虑光路负载和节点频谱转换能力的光路选择的权重方法;为了降低串扰,在纤芯频谱分配阶段,设计纤芯分组和频谱分区分配方法;最后,针对串扰较大的业务,采用频谱转换以降低业务串扰和改善带宽阻塞率。仿真结果表明,所提算法能有效地提高频谱利用率,降低因芯间串扰导致的带宽阻塞率。     

CsLiB6O10晶体的宽带三倍频模拟分析

为了研究高效的宽带三次谐波转换技术,采用了分步傅里叶变换和四阶龙格-库塔法对CsLiB6O10(CLBO)晶体的宽带三倍频过程进行了数值模拟,分析了单倍单混和单倍双混模式下三倍频转换效率随入射基频光强度、频谱带宽的变化关系,并与KDP晶体的宽带三倍频转换特性进行了对比.在强度为3GW/cm2的0阶超高斯脉冲入射下,得到单倍双混模式下三倍频转换效率达到60%时对应的频谱宽度为650GHz,这与利用KDP晶体在相同条件下获得的频谱宽度相比,提高了近250GHz.研究结果表明,在单倍双混模式下使用CLBO晶体作为频率转换的非线性晶体可以有效地提高宽带三倍频的转换效率.     

认知无线电频谱切换技术研究

认知无线电技术是为提高频谱利用率,解决目前无线频谱资源紧缺问题而提出的,准确快速的频谱切换技术是其实现的关键。论文针对认知无线电技术的频谱切换问题,总结频谱切换的关键技术及研究模型,讨论频谱切换技术面临的挑战,以及频谱切换技术的研究方向。     

动态频谱分配与频谱共享研究综述

文中针对当前无线频谱政策和无线频谱技术局限所导致的频谱整体利用率低的问题,分析了能有效提高频谱利用率的动态频谱分配和共享技术的研究现状,包括相邻和分片动态频谱分配技术,共存和覆盖式频谱共享技术,感知无线电技术,以及频谱池技术,并讨论了其未来的研究方向,尤其是感知无线电和基于OFDM的频谱池方法.     

Distributed power control algorithm for cognitive radios with primary protection via spectrum sensing under user mobility

Substantial spectrum gains have been demonstrated with the introduction of cognitive radio however; such gains are usually short lived due to the increased level of interference to licensed users of the spectrum. The interference management problem is herein tackled from the transmitter power control perspective so that transmissions by cognitive radio network does not violate the interference threshold levels at the primary users as well as maintain the QoS requirements of cognitive radio users. We model the cognitive radio network for mobile and immobile users and propose algorithms exploiting primary radio environment knowledge (spectrum use), called power control with primary protection via spectrum sensing. The algorithm is briefly introduced for time invariant systems and demonstrated that it has the ability to satisfy tight QoS constraints for cognitive radios as well as meet the interference constraints for licensed users. We, however, further show that such assumption of terminal immobility in the power control algorithm would fail in cases where user mobility is considered, resulting in increased levels of interference to the primary as well as increased outages in cognitive radio network. We model the link gain evolution process as a distance dependent shadow fading process and scale-up the target signal to interference ratio to cope with user mobility. Since mobility driven power control algorithms for cognitive radios have not been investigated before, we therefore, propose a mobility driven power control framework for cognitive radios based on spectrum sensing, which ensures that the interference limit at the primary receiver is unperturbed at all times, while concurrently maintaining the QoS within the cognitive radio network as compared to static user cases. We also corroborate our algorithms with proof of convergence.     

Spectrum management in cognitive radio ad hoc networks

The problem of spectrum scarcity and inefficiency in spectrum usage will be addressed by the newly emerging cognitive radio paradigm that allows radios to opportunistically transmit in the vacant portions of the spectrum already assigned to licensed users. For this, the ability for spectrum sensing, spectrum sharing, choosing the best spectrum among the available options, and dynamically adapting transmission parameters based on the activity of the licensed spectrum owners must be integrated within cognitive radio users. Specifically in cognitive radio ad hoc networks, distributed multihop architecture, node mobility, and spatio-temporal variance in spectrum availability are some of the key distinguishing factors. In this article the important features of CRAHNs are presented, along with the design approaches and research challenges that must be addressed. Spectrum management in CRAHNs comprises spectrum sensing, sharing, decision, and mobility. In this article each of these functions are described in detail from the viewpoint of multihop infrastructureless networks requiring cooperation among users.     

A Survey of Cooperative Games for Cognitive Radio Networks

Cooperative cognitive radio networks are new cognitive radio paradigm. Cooperative communication approaches, such as cooperative spectrum sensing and cooperative spectrum sharing, are playing key roles in the development of cognitive radio networks. To achieve the high performance, a cooperative cognitive communication framework is often used to model various cooperative spectrum sensing or sharing scenarios. However, its implementation faces numerous challenges due to the complexity of mobility and traffic models, the needs of dynamic spectrum access, the heterogeneous requirements from different users, and the distributed structure of the network. Fortunately, cooperative game theory can be used to formulate and model the interactions among licensed and unlicensed users for spectrum sensing and spectrum sharing to efficiently allocate spectrum resource in the highly dynamic and distributed radio environment. In this paper, we first present the cooperative communication technologies and describe their existing challenges, then introduce different game solutions, after that, we discuss several cooperative game strategies, and analyze the associated their applications in cognitive radio networks, at final, some open directions for future research on economic strategies in cooperative communication in cognitive radio networks are proposed.     

Comparison of Mamdani and Sugeno Inference Systems for Dynamic Spectrum Allocation in Cognitive Radio Networks

Dynamic spectrum access and cognitive radio are emerging technologies to utilize the scarce frequency spectrum in an efficient and opportunistic manner. Cognitive radio, built on software defined radio, is an intelligent radio technology that updates its operating parameters to locate the unused spectrum segments. To assign these vacant bands to unlicensed users without causing harmful interference to licensed users, a novel approach is proposed in this article based on fuzzy logic. Two different fuzzy inference system models i.e. Mamdani and Sugeno systems are developed that compute spectrum access decision based on the secondary user parameters such as signal strength, distance between the primary and secondary user, spectrum utilization efficiency and degree of mobility. 81 fuzzy rules are used to obtain the output of proposed system stating the possibilities of allotment of white spaces to secondary users.     

Impact of secondary user mobility on spectrum handoff under generalized residual time distributions in cognitive radio networks

Cognitive Radio is an emerging technology to accommodate the growing demand for wireless technology via dynamic spectrum access to enhance spectrum efficiency. Spectrum handoff is an important component of Cognitive Radio technology for practical implementation of radio frequency access strategy and better utilization of spectrum in both primary and secondary networks. The probability of spectrum handoff and expected number of spectrum handoffs are key parameters in performance analysis and design of the cognitive radio network. This work presents an analytical model to evaluate the impact of secondary users’ mobility on intra-cell spectrum handoff considering primary users’ activity model in a cognitive radio network. A standard form of intra-cell spectrum handoff probability and expected number of intra-cell spectrum handoffs are derived for complete call duration of a non-stationary secondary user. The probability and expected number of intra-cell spectrum handoffs of a post inter-cell handoff call are also derived for generalized residual time distributions of call holding time and spectrum holes. A detailed analysis of these performance measuring metrics is presented under the impact of departure rate and cell crossing rate of secondary users. The accuracy of the derived analytical result is validated by Monte-Carlo simulation of the model.     

认知无线电中的频谱共享技术

认知无线电（cognitive radio,CR）具有动态重用空闲频谱资源的能力,可以有效提高频谱利用率,是一种智能的频谱共享技术。文章给出了一种频谱共享的过程,阐述了频谱共享各个步骤包括频谱感知、频谱分配、频谱接入和频谱移动的概念、功能和研究现状,分析了频谱共享的关键技术,重点介绍了其中的频谱池策略、频谱分配算法和功率控制算法。     

A survey on spectrum management in cognitive radio networks [cognitive radio communications and networks]

Cognitive radio networks will provide high bandwidth to mobile users via heterogeneous wireless architectures and dynamic spectrum access techniques. However, CR networks impose challenges due to the fluctuating nature of the available spectrum, as well as the diverse QoS requirements of various applications. Spectrum management functions can address these challenges for the realization of this new network paradigm. To provide a better understanding of CR networks, this article presents recent developments and open research issues in spectrum management in CR networks. More specifically, the discussion is focused on the development of CR networks that require no modification of existing networks. First, a brief overview of cognitive radio and the CR network architecture is provided. Then four main challenges of spectrum management are discussed: spectrum sensing, spectrum decision, spectrum sharing, and spectrum mobility.     

战术认知无线电网络架构设计

认知无线电技术具有智能电磁频谱感知、干扰避免和动态频谱接入的能力,因此利用认知无线电技术可以提升战术网络的性能.由于战术作战的复杂性,需要建立适用于战术任务的认知无线电架构.首先分析了战术通信的特点和认知无线电技术在战术网络中的运用,以及目前国外战术认知无线网络的建设情况.结合战术通信网络移动性高、电磁对抗复杂的特点,利用对抗环境下的战术网络结构和模型,提出了分层的战术认知无线电网络结构以及面向作战任务的网络管理方法,形成拓扑结构分层次、管理运行分阶段的网络架构.该网络架构均衡考虑了网络的灵活性和稳定性,适用于动态变化的战术网络,为认知无线电在战术通信中的技术应用和网络设计提供了参考.     

Enhancing the Performance of Spectrum Mobility in Cognitive Radio Local Area Networks Using KF-ABF-SRE Estimators

Wireless Personal Communications - This paper aims at improving the performance of spectrum mobility in cognitive radio local area networks under a congested environment. Due to the atmospheric...     

认知无线电网络中的自组织优化方法（英文）

Cognitive radio(CR) is regarded as a promising technology for providing a high spectral efficiency to mobile users by using heterogeneous wireless network architectures and dynamic spectrum access techniques.However,cognitive radio networks(CRNs)may also impose some challenges due to the ever increasing complexity of network architecture,the increasing complexity with configuration and management of large-scale networks,fluctuating nature of the available spectrum,diverse Quality-of-Service(QoS)requirements of various applications,and the intensifying difficulties of centralized control,etc.Spectrum management functions with self-organization features can be used to address these challenges and realize this new network paradigm.In this paper,fundamentals of CR,including spectrum sensing,spectrum management,spectrum mobility and spectrum sharing,have been surveyed,with their paradigms of self-organization being emphasized.Variant aspects of selforganization paradigms in CRNs,including critical functionalities of Media Access Control(MAC)- and network-layer operations,are surveyed and compared.Furthermore,new directions and open problems in CRNs are also identified in this survey.