认知无线电中基于感知门限的频谱预测研究

频谱感知为未获得频谱授权的次用户提供频谱空穴,并监测主用户以防止对其造成干扰。然而频谱感知会带来时间和能量消耗,采用准确、主动的频谱预测技术可以改善频谱感知过程。文中通过研究感知门限对平均感知时间和频谱利用率的影响,提出了基于感知门限的频谱预测-感知机制,并利用频谱预测结果按照空闲概率从大到小的顺序进行感知。仿真结果表明,文中所提出的机制能够减少感知时间并提高频谱利用率。     

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.     

一种基于对等协作的动态频谱分配算法

随着无线多媒体技术的发展,优质频谱资源越来越稀缺.针对频谱稀缺和频谱共享问题,提出了一种基于对等协作的动态频谱共享算法.运营商将自己的授权频谱资源部分或全部放入共享频谱池,并根据节点感知到的频谱的使用状况,平等分配该频谱池中的所有资源.仿真结果表明,所提的对等协作方案在运营商间没有信息交互的情况下,网络性能明显优于静态频谱分配方案,并且非常接近运营商间完全信息交互的频谱共享方案.     

动态频谱接入综述

动态频谱户在授权的频谱带宽中获得丰富频谱空隙。DSA技术可以缓解频谱短缺问题并且提高频谱利用率。文中讨论了DSA所面临的挑战,旨在揭示其未来的走向。介绍了前沿的频谱感知和频谱分享。调查了阻碍DSA成为主要的商业部署的挑战。为了应对这些挑战,建立了一个新的DSA模型,在这种模式下,授权的用户可以在DSA中相互合作,而且可以获得更加灵活的频谱共享。     

基于干扰消减的认知无线电频谱分配算法

在认知无线电网络的频谱分配过程基础上,提出了一种基于干扰消减的频谱分配算法.该算法通过将可用频谱分配给能够同时无干扰地接入同一频谱的所有认知用户来提高授权频谱的使用率.同时,该算法参考各个认知用户在初始阶段的可用频谱数量来为未分配到频谱资源的认知用户进行频谱分配,对频谱分配过程的公平性进行了优化.仿真结果表明,该算法能够在认知用户数量较多、可用频谱紧张的情况下获得较高的吞吐量.     

点对多点无线局域网中直扩序列选取

扩频序列的选择和构造是扩频通信系统设计的关键技术之一,系统的抗干扰、抗多径衰落、抗截获、保密、同步实现等均与所采用的扩频序列密切相关,扩频序列良好的相关特性和随机性对系统的性能具有决定性的作用。在点对多点通信系统中采用直接序列扩频方式,结合实际需求,通过对m序列、M序列、gold序列和kasami序列进行充分分析和仿真,得到了5种长度相关性能最优的直扩序列。     

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。     

分立双谱线的杨氏双缝干涉的计算机仿真

以分立双谱线的杨氏双缝干涉为研究对象,利用matlab软件对其实验现象进行数值仿真,研究了分立双谱线的线型和线宽对干涉条纹的可见度和强度分布的影响.发现分立双高斯形谱线比双矩形谱线更接近无限窄双谱线的干涉结果,谱线宽度越小,双高斯形或双矩形谱线的干涉图样越接近无限窄双谱线的干涉图样,即谱线宽度越小,谱线线型对干涉条纹的影响越小.     

Optimal distributed power allocation for a new spectrum sharing paradigm in cognitive radio networks

The problem of power allocation in cognitive radio networks plays an important role to improve the efficiency of spectrum utilization. However, most of previous works focus on the power allocation for secondary users in spectrum sharing overlay or spectrum sharing underlay, which needs to frequently handoff between the idle spectrum bands or considers the interference constraints in all spectrum bands respectively. In order to reduce the handoff and fully utilize the spectrum resource, we propose a new spectrum sharing paradigm which not only can just need to adjust the transmit power in spectrum bands instead of frequently handoff between idle spectrum bands, but can fully utilize the spectrum resource as we only consider the interference power constraints in active spectrum bands rather than in all spectrum bands. Then based on this new spectrum sharing paradigm and the constraint conditions, we study the distributed power allocation for secondary users and formulate the optimization problem as a non-cooperative game problem, after that the variational inequality approach is used to solve this game problem and a Nash equilibria solution is got, finally simulation results are illustrated to demonstrate the performance of the proposed scheme.     

频谱池在认知无线电中的应用

认知无线电CR（Cognitive Radio）能够有效解决频率资源的稀缺性和低利用率之间的矛盾,使得频率资源得到更好的利用。在CR系统中使用频谱池可以进一步提高频谱利用率。本文首先介绍了频谱池的概念和原理,然后对频谱池实现相关问题进行了探讨,并分析了频谱池的应用前景。     

Guest Editorial - Adaptive, spectrum agile and cognitive wireless networks

The 11 papers in this special issue focus on adaptive, spectrum agile and cognitive wireless networks. Some of the topics covered include: fundamental performance aspects of spectrum sharing; spectrum sensing capabilities in cognitive radios; detection and estimation approaches to spectrum sharing; MAC design in opportunistic spectrum access; and competitive spectrum sharing and resource allocation using concepts from game theory and pricing.     

监测接收机高分辨率快速扫描设计与实现

本方案针对无线频谱监测接收机在常规监测中由于扫描速度慢,分辨率低,从而造成信号截获概率低的问题,在总结和分析不同频谱扫描方式特点的基础上,基于软件多线程协调工作的思想,在相互衔接的调谐步进点上设计了一种基于多DSP并行处理的FFT步进扫描方案,发挥其在高分辨率频谱处理上的优势,便于让用户在常规监测时尽可能地发现突发的瞬...     

频谱失配情况下TDCS性能分析及感知结果交换机制

在变换域通信系统(TDCS)中,通常假设收发两端频谱感知结果是一致的,若收发两端频谱感知结果不一致会使TDCS性能恶化。基于TDCS的基本原理,对收发两端频谱感知结果不一致(频谱失配)时的误码率性能进行了理论分析,推导并仿真验证了频谱失配情况下,理论误码率的表达式。为解决频谱失配对TDCS影响,提出了一种不需任何附加控制信道的TDCS收发两端交换频谱感知结果的机制。利用该方案,收发两端在交换各自的频谱感知结果后,利用双方频谱感知结果的交集进行通信,相当于收发两端处于同一频谱环境。最后,对该频谱感知结果交换方案进行了简单的理论分析。     

Distributed Rule-Regulated Spectrum Sharing

Dynamic spectrum access is a promising technique to use spectrum efficiently. Without being restricted to any prefixed spectrum bands, nodes choose operating spectrum on-demand. Such flexibility, however, makes efficient and fair spectrum access in large-scale networks a great challenge. Prior work in this area focused on explicit coordination where nodes communicate with peers to modify local spectrum allocation, and may heavily stress the communication resource. In this paper, we introduce a distributed spectrum management architecture where nodes share spectrum resource fairly by making independent actions following spectrum rules. We present five spectrum rules to regulate node behavior and maximize system fairness and spectrum utilization, and analyze the associated complexity and overhead. We show analytically and experimentally that the proposed rule-based approach achieves similar performance with the explicit coordination approach, while significantly reducing communication cost.     

非连续谱雷达信号设计综述

非连续谱雷达信号是一种特殊的认知雷达信号,其频谱由多个离散的频带组成,且能够随着外界干扰的变化自适应地调整离散频带的分布结构.因此,这种信号适用于干扰密布、频谱拥堵的工作场景.非连续谱信号设计主要研究两个问题:一是如何根据干扰环境选取最优的非连续频谱结构以满足雷达抗干扰和分辨性能要求;二是如何根据最优的非连续频谱求解出...     

The role of economic techniques in spectrum management

In recent years the management of the radio spectrum, in terms of deciding which applications and which users should have access to it, has become increasingly difficult. This is due to the dramatic growth in users and applications requiring radio spectrum and the need from the government for increasing openness and fairness in making decisions. A number of spectrum managers have investigated the use of economic tools to overcome these problems, including an analysis of the economic value of the spectrum, pricing the spectrum, allowing trading in spectrum, and using competitions to assign spectrum. This article examines the roles of these techniques and suggests that there is a strong argument for their widespread adoption within most spectrum managers     

OFDM系统的扩频性能分析

提出传统OFDM系统中隐藏着类似扩频系统的性质。通过减少系统使用的子载波数,揭示了OFDM系统的扩频特性。使用扩频系统的理论分析方法,分析了OFDM系统的扩频性能。OFDM系统具有与传统扩频系统类似的扩频性能,因此可以采用OFDM系统构建扩频系统。     

Coopetive Spectrum Trading – Creating Endogenous Spectrum Holes

Dynamic spectrum access has been proposed to address the spectrum scarcity. Based on this access mode, secondary users are allowed to opportunistically operate when primary users are absent. Secondary Users are, however, required to relinquish the spectrum upon return of the incumbent spectrum holder. Although it improves spectrum utility, opportunistic spectrum access limits secondary users’ access to exogenous spectrum holes vacated by primary users. We argue that spectrum holes should be endogenous, enabled by incentives to incumbent users to increase spectrum availability, while mitigating risk. To this end, we take a different perspective on dynamic spectrum sharing and propose a coopetive framework, whereby primary and secondary users engage in a cooperative, yet competitive, auction-driven spectrum sharing to enhance spectrum usage. In this framework, the primary users’spectrum is organized in three bands, namely exclusive usage, usage right and management right bands. Based on this structure, spectrum is traded as financial options to increase trading flexibility and capture the value primary and secondary users attach to spectrum access and usage. Spectrum trading between primary and secondary users is formalized as a utility maximization problem. Approximate solutions to this problem are derived and their performance is analyzed. The results show that spectrum trading, which combines revocable and exclusive leasing, provides higher utilities for both primary and secondary users.     

Privacy-preserving multi-attribute reverse spectrum auction scheme

Aiming the problem that the existing reverse spectrum auctions do not take the non-price attribute of spectrum into account and the security of spectrum auction,a privacy-preserving multi-attribute reverse spectrum auction was proposed.Firstly,price and non-price positive attributes of spectrum were considered as the bidding scheme of bidders and auctions was performed to judge spectrum winners.Secondly,to ensure the security of the spectrum auction,the Paillier threshold system was used to introduce a group of spectrum auction servers of auctioneers to replace the traditional single third-party agency,which could prevent the fraud collusion between spectrum auctioneers and bidders.The cryptography tools such as the anonymization technology and oblivious transfer were introduced to achieve the secure features,which could make the spectrum auction performed securely.The security analysis shows that the security protocol has strong security.The performance of the protocol is also evaluated,and experimental results show that the security scheme is superior to the multi-attribute reverse auction security scheme that can be applied in the spectrum auction scenario in terms of computational overhead.     

HC-MAC: A Hardware-Constrained Cognitive MAC for Efficient Spectrum Management

Radio spectrum resource is of fundamental importance for wireless communication. Recent reports show that most available spectrum has been allocated. While some of the spectrum bands (e.g., unlicensed band, GSM band) have seen increasingly crowded usage, most of the other spectrum resources are underutilized. This drives the emergence of open spectrum and dynamic spectrum access concepts, which allow unlicensed users equipped with cognitive radios to opportunistically access the spectrum not used by primary users. Cognitive radio has many advanced features, such as agilely sensing the existence of primary users and utilizing multiple spectrum bands simultaneously. However, in practice such capabilities are constrained by hardware cost. In this paper, we discuss how to conduct efficient spectrum management in ad hoc cognitive radio networks while taking the hardware constraints (e.g., single radio, partial spectrum sensing and spectrum aggregation limit) into consideration. A hardware-constrained cognitive MAC, HC-MAC, is proposed to conduct efficient spectrum sensing and spectrum access decision. We identify the issue of optimal spectrum sensing decision for a single secondary transmission pair, and formulate it as an optimal stopping problem. A decentralized MAC protocol is then proposed for the ad hoc cognitive radio networks. Simulation results are presented to demonstrate the effectiveness of our proposed protocol.