非实时业务下认知网络的频谱共享

根据某种特定业务的QoS要求制定相应的频谱共享策略,可以在这种情况下提高系统的频谱利用率,增加用户平均收益。对非实时业务下的认知网络的频谱共享策略进行了研究,考虑各非授权用户业务量和信道质量对系统频谱效率的影响,提出了一种非实时业务专用的NRT-dedicate频谱共享算法。仿真结果表明,在非实时业务情况下,该算法可以获得比通用业务的频谱共享算法的频谱利用率。     

Cooperative Communications for Cognitive Radio Networks

Cognitive radio is an exciting emerging technology that has the potential of dealing with the stringent requirement and scarcity of the radio spectrum. Such revolutionary and transforming technology represents a paradigm shift in the design of wireless systems, as it will allow the agile and efficient utilization of the radio spectrum by offering distributed terminals or radio cells the ability of radio sensing, self-adaptation, and dynamic spectrum sharing. Cooperative communications and networking is another new communication technology paradigm that allows distributed terminals in a wireless network to collaborate through some distributed transmission or signal processing so as to realize a new form of space diversity to combat the detrimental effects of fading channels. In this paper, we consider the application of these technologies to spectrum sensing and spectrum sharing. One of the most important challenges for cognitive radio systems is to identify the presence of primary (licensed) users over a wide range of spectrum at a particular time and specific geographic location. We consider the use of cooperative spectrum sensing in cognitive radio systems to enhance the reliability of detecting primary users. We shall describe spectrum sensing for cognitive radios and propose robust cooperative spectrum sensing techniques for a practical framework employing cognitive radios. We also investigate cooperative communications for spectrum sharing in a cognitive wireless relay network. To exploit the maximum spectrum opportunities, we present a cognitive space–time–frequency coding technique that can opportunistically adjust its coding structure by adapting itself to the dynamic spectrum environment.      

An overview of spectrum sharing techniques in cognitive radio communication system

As the complexities of wireless technologies increase, novel multidisciplinary approaches for the spectrum sharing/management are required with inputs from the technology, economics and regulations. Recently, the cognitive radio technology comes into action to handle the spectrum scarcity problem. To identify the available spectrum resource, decision on the optimal sensing and transmission time with proper coordination among the users for spectrum access are the important characteristics of spectrum sharing methods. In this paper, we have technically overviewed the state-of-the-art of the various spectrum sharing techniques and discussed their potential issues with emerging applications of the communication system, especially to enhance the spectral efficiency. The potential advantages, limiting factors, and characteristic features of the existing cognitive radio spectrum sharing domains are thoroughly discussed and an overview of the spectrum sharing is provided as it ensures the channel access without the interference/collision to the licensed users in the spectrum.     

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.     

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.     

认知无线电技术的国内外发展与研究现状

为了研究认知无线电技术的国内外发展现状,对从1999年至2008年的所有的IEEE中有关认知无线电技术的文章进行了统计分析,用表格形式展现了总体研究情况、系统/结构的设计、频谱感知、频谱决策、频谱共享、频谱切换等几方面的研究现状,并对文章的研究内容、目前可供研究的开放性等问题进行了总结和分析,最后统计了各国研究机构和大学在认知无线电研究领域的情况统计结果显示目前对系统/结构设计、频谱感知和频谱共享三方面的研究较多,而对其他方面研究较少;美国、欧洲和中国在认知无线电技术方面取得了一些成果     

COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS - Dynamic Spectrum Sharing: A Game Theoretical Overview

In order to fully utilize the scarce spectrum resources, with the development of cognitive radio technologies, dynamic spectrum sharing becomes a promising approach to increase the efficiency of spectrum usage. Game theoretical dynamic spectrum sharing has been extensively studied for more flexible, efficient, and fair spectrum usage through analyzing the intelligent behaviors of network users equipped with cognitive radio devices. This article provides a game theoretical overview of dynamic spectrum sharing from several aspects: analysis of network users' behaviors, efficient dynamic distributed design, and optimality analysis     

认知无线网络中一种新的频谱共享方法

频谱共享是认知无线网络关键技术之一。为消除认知无线网络中频率选择性信道下授权主用户与认知用户间的相互干扰,本文提出了一种新的频谱共享方法。该方法充分利用了无线通信系统中由信道的频率选择性衰落导致的不同用户信道的不相关性,通过求解矩阵方程获得预处理矩阵的通解,并在主用户和认知用户发射端分别进行预处理。从而实现认知系统中主用户与认知用户之间的相互零干扰,并使每个用户都可有效地传输数据。理论推导及系统仿真均表明,新方法可以有效地消除授权主用户与认知用户之间的双向干扰,实现不同用户平等地共享无线频谱资源。新方法可以提高频谱的利用率,一定程度上缓解无线频谱资源在当前及未来无线通信领域日益紧缺的矛盾。而且新方法也同样适用于不同认知用户之间共享频谱。      

一种认知无线Adhoc网络跨层最优频谱共享方案

针对由认知无线电组成的Adhoc网络中的频谱共享提出了一个跨层方案。通过综合考虑认知用户之间的干扰约束和流量需求,特别考虑到用户双向连接以及信道的非均匀性,以BFP（bandwidth—footprint-product）值最小为目,建立了一个二进制整数线性规划（BILP）模型。仿真结果给出了最优的频带分配和路由选择方案。     

认知无线电网络基于F范数的频谱共享

针对多用户多输入多输出认知无线电网络的频谱共享问题,提出一种在保证授权用户服务质量要求的前提下,以认知网络容量最大化为目标的基于F范数的频谱共享方法.该方法利用信道矩阵的F范数选择认知用户以获得认知网络的多用户分集增益,并采用两次选择的方式降低算法的复杂度,通过将认知用户的发射信号投射到干扰信道的零空间来避免认知用户对...     

认知无线电中的频谱共享技术

由于认知无线电网络的一些独有的特性,比如,可用频谱资源的动态变化以及与第一类用户的共存,使得认知无线电网络中的频谱共享技术面临着许多新的挑战。当前关于频谱共享技术的研究旨在应对这些挑战,并且主要从以下四个方面着手：网络架构,频谱分配行为,频谱接入技术和共享频谱的范围。     

Spectrum sensing scheduling for group spectrum sharing in cognitive radio networks

This paper addresses the issues on spectrum sharing in a cognitive radio network consisting of a primary user and a group of cognitive users. Each cognitive user may occupy a non‐overlapped sub‐band of the primary spectrum, but it needs to perform spectrum sensing independently before accessing the sub‐band. To reduce the complexity of spectrum sensing and thus energy consumption, this paper proposes a scheduled spectrum sensing scheme. First, we consider a single spectrum sensing scenario where only one cognitive user is elected to perform spectrum sensing, and then it broadcasts its sensing results to the other cognitive users. The scheduled spectrum sensing scheme works in both network‐centric and user‐centric ways. Next, the scheduled spectrum sensing scheme is further generalized to work in a multiple spectrum sensing scenario. The results show the effectiveness of the proposed schemes compared with the traditional schemes where all cognitive users may perform spectrum sensing at the same time. Copyright © 2010 John Wiley & Sons, Ltd.     

有限用户数多认知网络部分信道共享性能分析

认知网络中动态信道共享是提高频谱资源利用率的关键.针对有限用户数下多认知网络共存场景,该文建立3维马尔科夫链部分信道共享模型,仿真分析用户有/无信道切换功能下认知网络间部分信道共享的性能.分别就阻塞概率、强迫终止概率、切换概率和系统吞吐量等,与静态频谱分配策略和分级共享策略进行比较仿真测试,结果表明,采用部分信道共享策略的系统在容忍较小的切换概率和强迫终止概率下可以获得较大的系统吞吐量.     

Performance Analysis of Wireless Network with Opportunistic Spectrum Sharing via Cognitive Radio Nodes

Cognitive radio (CR) is found to be an emerging key for efficient spectrum utilization. In this paper, spectrum sharing among service providers with the help of cognitive radio has been investigated. The technique of spectrum sharing among service providers to share the licensed spectrum of licensed service providers in a dynamic manner is considered. The performance of the wireless network with opportunistic spectrum sharing techniques is analyzed. Thus, the spectral utilization and efficiency of sensing is increased, the interference is minimized, and the call blockage is reduced.     

基于OFDM协作中继的机会主义频谱共享协议及其最优资源分配

提出了一种基于OFDM协作中继的机会主义频谱共享协议。当主用户信道不好,不能达到其要求速率时,如果认知用户能够协作帮助主用户达到其要求速率,则该认知用户就可以以协作的方式接入主用户的频谱。在该接入方式中,认知用户利用接入频谱中的一部分子载波放大转发主用户的信息,帮助主用户达到其要求速率。然后可以利用剩余的子载波发送自己的信息。对这种接入方式中的资源分配进行了分析,利用对偶算法,提出了一种以最大化认知用户速率,保证主用户速率达到要求速率为原则的最优资源分配算法。如果认知用户不能够协作帮助主用户达到要求速率,为了有效地利用频谱资源,认知用户以非协作的方式接入主用户的频谱,利用接入的全部频谱来发送自己的信息。仿真结果验证了所提频谱共享协议的有效性,同时说明了主用户和认知用户都能够从该协议中获得好处。     

Low-complexity hierarchical spectrum sharing scheme in cognitive radio networks

Fair and efficient spectrum sharing is an important problem in cognitive radios. In view of the clustering cognitive radio network with capacity-limited common channels, this letter proposes a low-complexity hierarchical spectrum sharing method, which is carried out in two steps. First, the spectrum holes are allocated to clusters in a fair and distributed way by using the list-coloring method. Then, all the channels in every spectrum hole are allocated by cluster head to minimize the outage probability by using the maximum matching method. Such a scheme not only takes a great advantage of the low signaling overhead and computation complexity, but also achieves the suboptimal outage performance which is close to that of the exhaustive search.     

基于干扰温度的多用户MIMO频谱共享系统容量分析

在无线通信认知无线电中,频谱共享系统被证实能够提供更高的频谱利用率。考虑到多用户多天线的频谱共享系统中次用户的发射功率受限于主用户的干扰温度,介绍了单天线系统和3种不同MIMO传输机制,并根据SNR分别推导出具体的容量表达式。最后通过仿真得出ST/SC方式能够获得最佳容量,而STBC方式应用于频谱共享系统没有提升容量的优势。     

填充式频谱共享中的功率分配算法分析

动态频谱共享技术允许认知用户接入未授权的频谱,可以有效地提高频谱资源的利用率。在分析了频谱共享的2种接入模式的基础上,提出了填充式频谱共享的系统模型。根据认知用户的效用函数,通过注水算法得到了用户间的功率迭代公式,进而求得了认知用户的功率和载波分配结果。仿真表明,该迭代算法在有效完成用户间功率与载波分配的同时能够在较短的时间内收敛。     

Cross‐layer design of partial spectrum sharing for two licensed networks using cognitive radios

To utilize spectrum resources more efficiently, dynamic spectrum access attempts to allocate the spectrum to users in an intelligent manner. Uncoordinated sharing with cognitive radio (CR) users is a promising approach for dynamic spectrum access. In the uncoordinated sharing model, CR is an enabling technology that allows the unlicensed or secondary users to opportunistically access the licensed spectrum bands (belonging to the so‐called primary users), without any modifications or updates for the licensed systems. However, because of the limited resources for making spectrum observations, spectrum sensing for CR is bound to have errors and will degrade the grade‐of‐service performance of both primary and secondary users. In this paper, we first propose a new partial spectrum sharing policy, which achieves efficient spectrum sharing between two licensed networks. Then, a Markov chain model is devised to analyze the proposed policy considering the effects of sensing errors. We also construct a cross‐layer design framework, in which the parameters of spectrum sharing policy at the multiple‐access control layer and the spectrum sensing parameters at the physical layer are simultaneously coordinated to maximize the overall throughput of the networks, while satisfying the grade‐of‐service constraints of the users. Numerical results show that the proposed spectrum sharing policy and the cross‐layer design strategy achieve a much higher overall throughput for the two networks. Copyright © 2013 John Wiley & Sons, Ltd.     

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.