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。     

认知车载网络中基于QoS保障的频谱共享新策略

构建了基于认知无线电的新型车载网络,并提出基于安全业务服务质量(QoS)保障的两步式频谱共享策略:多认知小区间的频谱分配和单认知小区内的频谱共享。仿真结果表明,提出的GNBS(generalized nash bargaining solution)分配方案综合考虑了系统的公平性和总效用,可获得明显大于最大化最小方案的系统和速率,以及明显优于最大化和速率方案的多认知小区间的公平性;GNBS方案可以根据多小区间频谱需求的差异性来动态调节资源分配的比例,有效地实现了需求非对称的多小区间频谱资源的最优化配置;此外,单小区内的协作频谱共享机制,使得协作双方均获得了优于非协作方案的系统效用,有效地提高了系统吞吐量以及认知OBU间的公平性。     

混合频谱共享方式下多用户动态频谱分配算法

为解决混合overlay/underlay频谱共享方式下多用户动态频谱分配问题,构建了混合频谱共享方式下动态频谱分配模型,提出了基于Q学习的多用户动态频谱分配算法. 该算法在不对主用户产生有害干扰的前提下,以最大化次用户总吞吐量为目标,构建了与次用户相对应的虚拟次用户作为智能体. 通过与环境交互学习,进行信道和共享方式初选;频谱分配系统根据冲突情况和各智能体的学习结果调整信道分配策略直至次用户间无冲突. 仿真结果表明,该算法在无信道检测和信道先验知识的条件下,能根据前一时隙信道状态和次用户传输速率需求,实现动态信道分配和频谱共享方式确定,避免次用户间冲突,减少主次用户间冲突,有效提升次用户总吞吐量.     

LTE FDD与GSM频谱共享方案

4G网络建设已日趋完善，伴随着大量的4G业务需求，运营商的频率资源显得弥足珍贵，而另一方面GSM网络的用户数及承载的语音量成逐年下降趋势。将宝贵的频谱资源应用到LTE这样的高制式网络来提升频谱效率，但是GSM老终端又很难完全退网，传统的Refarming方案为通过静态分配GSM、LTE频谱资源，势必会造成部分频谱浪费。采用频谱共享方案可将频谱进行动态频谱、静态频谱划分，LTE系统与GSM系统通过共享动态频谱资源的方式实现潮汐式共享，从而一方面保证了GSM网络的语音资源，另一方面也提高了LTE网络的容量，从而整体提高网络的频谱利用效率。     

基于无线电环境地图的频谱共享网络研究

现有的频谱分配模式限制了频谱高效利用,束缚了无线电技术创新发展.频谱共享被认为是有效解决频谱供需矛盾、提高频谱使用效率的技术方案之一.在综合论述欧美等国家关于频谱共享研究进展的基础上,提出了一种基于无线电环境地图和用户分级的智能频谱共享网络架构.该网络可获得完整准确、及时可靠的频谱信息,通过对用户实行分级接入,实现不同用户高效动态地共享频谱资源.重点介绍了架构中各个网络单元的组成和功能,阐述了架构中不同网络单元之间的信息交互过程,最后剖析了架构实现上待解决的关键技术问题.相关内容为我国建设频谱共享网络提供了借鉴和参考.     

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.     

授权的频谱共享技术

随着无线频谱资源需求的不断增加,如何更有效地利用稀缺的频谱资源成为了各国关注的重点问题。授权的频谱共享技术作为一种新兴的频谱资源管理方式,允许获得共享授权的用户在不影响原频谱所有者服务的情况下共享使用该频段。目前,美国和欧洲正在大力推动授权的频谱共享技术的应用,这种方式可以为我国频谱管理工作带来新的启发。     

基于次用户协作的主用户频谱洞周期稳态特征检测

实时准确地检测主用户归属的无线电系统是否存在频谱洞,即检测主用户是否在所分配的频点上处于活动状态,是机会式频谱共享法必须解决的首要问题.本文将次用户间协作检测方式和周期稳态特征检测法结合,提出了次用户协作检测主用户频谱洞的特征检测法.理论研究和和仿真分析表明,本文提出的检测法比协作能量检测法性能优越.     

我国频谱共享的可行性研究与推进建议

目前,我国工业和信息化领域一系列战略稳步推进,5G、移动互联网等信息技术快速发展,无线电频谱资源的稀缺性再次凸显。频谱共享为解决频谱资源的稀缺问题提供了解决方案,并被国际主流国家积极推行。在分析国内外频谱共享研究与应用现状的基础之上,进一步讨论了我国推行频谱共享的意义和挑战,给出了频谱共享可行性评估和分析框架,并提出了频谱共享的推进建议。     

无线电频谱利用面临的问题、机遇与对策

针对日益严重的无线电频谱资源利用问题,重新审视了频谱概念和频谱稀缺性问题.分析表明,只要采用合适的频谱管理策略和高效频谱利用技术,频谱资源可以满足无线电业务高速增长的需求.结束频谱资源紧缺局面的根本途径是开发高效频谱利用技术,而多无线电系统动态频谱分配与共享技术最具潜力.同时,无线电频谱政策必须作相应的调整,使之适应技术发展和市场业务需求,充分发挥高效频谱利用技术的潜力.通过对多无线电系统动态频谱分配与共享技术的分析,结合国际频谱政策变化特点和改革实践,给出了我国频谱政策改革的几点建议.     

Efficient error detection in soft data fusion for cooperative spectrum sensing

The primary objective of cooperative spectrum sensing (CSS) is to determine whether a particular spectrum is occupied by a licensed user or not, so that unlicensed users called secondary users (SUs) can utilize that spectrum, if it is not occupied. For CSS, all SUs report their sensing information through reporting channel to the central base station called fusion center (FC). During transmission, some of the SUs are subjected to fading and shadowing, due to which the overall performance of CSS is degraded. We have proposed an algorithm which uses error detection technique on sensing measurement of all SUs. Each SU is required to re-transmit the sensing data to the FC, if error is detected on it. Our proposed algorithm combines the sensing measurement of limited number of SUs. Using Proposed algorithm, we have achieved the improved probability of detection (PD) and throughput. The simulation results compare the proposed algorithm with conventional scheme.     

一种基于非对称纳什协商的认知无线电频谱共享新算法

该文研究基于MIMO-OFDMA的认知无线电系统频谱共享的新机制。首先构造了一个基于非对称纳什协商方案的效能函数,其次通过多用户最优匹配及两两协商新算法并证明其收敛性,最终实现了基于感知贡献加权的比例公平性频谱共享。仿真结果表明提出的方案不仅实现了频谱资源的公平有效分配,而且有利于最大化频谱感知的结果。     

基于可靠次用户信息的协作频谱感知算法研究

对认知无线电系统最基本要求之一就是次用户必须有能力以高的精确率来确定主用户是否存在。而以前对认知无线电频谱感知的研究表明:在实际认知网络中次用户之间的相互协作可以提高其频谱检测性能。然而,对于协作频谱感知而言,随着协作次用户数目的增加,势必会增大用于传输本地检测结果到融合中心的专用控制信道带宽,从而增加系统开销。该文在控制信道带宽有限的约束条件下,提出一种通过考虑可靠次用户信息的协作频谱感知算法来进一步改善频谱检测的性能。该算法的基本思想:只有具有可靠的本地检测结果的次用户才发送自己的检测结果到融合中心,否则,该次用户不发送任何信息。同时,对提出的该算法在理论上进行了推导,通过仿真结果表明:在控制信道带宽受限的约束下,相比于传统的或门协作频谱感知算法,提出的算法能够大大改善对主用户的检测性能。     

先验知识未知情况下的频谱空穴检测算法

为了解决无线电频谱资源日趋匮乏的问题,对频谱空穴检测技术进行研究,设计了一种频谱空穴检测方案.首先,待检测信号通过带通滤波器,实现待检测频段的分段处理;其次,寻找到循环自相关函数的峰值,将其假定为授权信号的循环频率;最后,将该处的统计检测量与检测门限值进行比较,检测出频谱空穴,达到动态管理频谱资源,并提高频谱利用率的目的.仿真结果表明,该算法在-5 dB高斯白噪声背景下有效.     

Social-aware device-to-device communications underlaying cellular networks

This article put forward a resource allocation scheme aimming at maximizing system throughput for devide-to-device(D2D) communications underlying cellular network. Firstly, user closeness is defined and calculated through social information including friendship, interest similarity and communication strength to represent the willingness of user to share the spectrum resource with others. Then a social-aware resource allocation problem is formulated to maximize the system throughput while guaranteeing the quality of service(QoS) requirements of both the admissible D2D pairs and then the power of both CUs and D2D pairs is efficiently allocated. Finally CUs and D2D pairs are matched to reuse the spectrum resource in consideration of both user closeness and physical conditions. Simulation results certify the effectiveness of the proposed scheme which significantly enhances the system throughput compared with the existing algorithms.     

认知无线电在未来多媒体移动通信中的应用

未来的多媒体移动通信需要相当数量的频谱资源,认知无线电(cognitive radio)是软件无线电的特殊扩展,它使用了一类称为无线电礼仪协议(radio-etiquette protocol)的新协议,为灵活统筹无线电频谱提供了一个机制。本文介绍了无线电礼仪协议的结构并分析了认知无线电对频谱统筹可能的贡献。     

协作多点蜂窝系统中的干扰协调方案研究

在协作多点(CoMP)蜂窝系统中,为了有效利用无线频谱资源,需要设计相应的分布式干扰协调机制.首先,利用相邻小区间接口交换信息的能力,设计了一种分布式的无线资源分配冲突检测与仲裁算法.接下来,针对协作多点蜂窝系统具体场景,应用所提出冲突仲裁算法,设计了包括三个步骤的分布式干扰协调方案.仿真结果表明,设计方案能够分布式地...     

Improving vehicular safety message delivery through the implementation of a cognitive vehicular network

The Wireless Access in Vehicular Environments (WAVE) protocol stack has been recently defined to enable vehicular communication on the Dedicated Short Range Communication (DSRC) frequencies. Some recent studies have demonstrated that the WAVE technology might not provide sufficient spectrum for reliable exchange of safety information over congested urban scenarios. In this paper, we address this issue, and present a novel cognitive network architecture in order to dynamically extend the Control Channel (CCH) used by vehicles to transmit safety-related information. To this aim, we propose a cooperative spectrum sensing scheme, through which vehicles can detect available spectrum resources on the 5.8 GHz ISM band along their path, and forward the data to a fixed infrastructure known as Road Side Units (RSUs). We design a novel Fuzzy-Logic based spectrum allocation algorithm, through which the RSUs infer the actual CCH contention conditions, and dynamically extend the CCH bandwidth in network congestion scenarios, by using the vacant frequencies detected by the sensing module. The simulation results reveal the effectiveness of our architecture in providing dynamic and scalable allocation of spectrum resources, and in increasing the performance of safety-related applications.     

Group-based spectrum assignment in dynamic flex-grid optical networks

Traditional wavelength switched optical network employing wavelength-division-multiplexing (WDM) technology, allocates constant spectrum band to different kinds of services, which lacks flexibility in spectrum provisioning and thus reduces the resource utilization efficiency. Flex-grid technology, which introduces a finer spectrum granularity and allocates spectrum to different services flexibly according to their required bandwidth, is considered a promising candidate solution to improve the resource utilization efficiency of an optical network. However, since multiple contiguous spectrum granularities are usually assigned to a single service in such flex-grid optical network, the spectrum continuity and contiguity constraints should always be guaranteed, which may induce spectrum fragmentation. With the accumulation of spectrum fragmentation, available spectrum resources decrease, and this will greatly worsen the performance of the whole network, especially in networking. Therefore, spectrum fragmentation is considered a serious problem in flex-grid optical networks and many schemes have been proposed to solve it. These existing schemes, known as defragmentation, can reduce spectrum fragmentation either by rerouting the lightpath or by reallocating the spectrum for a service, which re-optimizes the spectrum resources. However, in the rerouting or reallocation procedure, existing traffic may be disrupted or extra resources, such as alternative spectrum or expensive spectrum convertors, are needed. None of these schemes can solve spectrum fragmentation with both no disrupted traffic and extra resources. It is because all these schemes utilize remedial methods to solve fragmentation problem and either disrupted traffic or extra resources are the cost when they cope with the defragmented spectrum. Different from all the above schemes, we propose a precautionary method to solve fragmentation problem in this paper. By introducing group-based spectrum assignment algorithm into flex-grid optical networks, spectrum resources are sorted into groups and each spectrum group only accommodates one specific kind of services. Since released spectrum can always be reused by the services of the same kind, spectrum fragmentation is prevented from its generation. Simulation results demonstrate that the proposed algorithm induces no spectrum fragmentations and is suitable to accommodate high-speed services.     

Adaptive resource allocation techniques in OFDMA using cross-layer architecture

This paper utilizes the cross-layer architecture to implement adaptive resource allocation in Orthogonal Frequency Division Multiple Access （OFDMA） based on the broadband wireless access system. According to the cross-layer architecture, the information in link layer is used for adaptive resource allocation in OFMDA. A new cross-layer adaptive resource allocation algorithm is developed which can guarantee the users to be in minimum average waiting time in link-layer and get the better spectrum utilization. Numerical results show that our scheme is appealing and can get about half of average waiting time less and 0.5 bps/Hz spectrum utilization more than the scheme in 1EEE802.16a.