共查询到18条相似文献,搜索用时 218 毫秒
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在认知无线电(CR)中,频谱感知是实现动态频谱接入的关键技术之一。为适当保护主用户并最大化次级用户的性能,目前大部分相关工作均是用虚报概率和漏检概率作为感知度量来确定最佳感知参数的。但这种度量是用主次用户的碰撞概率来衡量次级用户对主用户的影响的,没有考虑干扰强度的影响,仅适合同构频谱环境;在不同位置次级用户有不同接入机会的异构频谱环境中,并不能最大化频谱利用率。为此,该文首先定义了吞吐量降,并提出在异构频谱环境下采用吞吐量降作为一种新的感知度量。吞吐量降是指由于次级用户占用授权频谱而导致主用户吞吐量下降的百分比。在衡量次级用户对主用户的影响时,它综合了主次用户的碰撞概率和干扰强度两个因素;其次,研究了以吞吐量降为约束的次级用户吞吐量优化问题。最后,数值仿真证实了该方案比目前几种传统方案的频谱利用率显著提高。 相似文献
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针对卫星认知无线网络频谱感知不确定性较大导致传统频谱接入机制效率降低的问题,该文提出一种基于动态多频谱感知的信道接入优化策略。认知LEO卫星根据频谱检测概率与授权用户干扰门限之间的关系,实时调整不同频谱感知结果下的信道接入概率。在此基础上以系统吞吐量最大化为目标,设计了一种基于频谱检测概率和虚警概率联合优化的判决门限选取策略,并推导了最佳感知频谱数量。仿真结果表明,认知用户能够在不大于授权用户最大干扰门限的前提下,根据授权信道空闲状态动态选择最佳频谱感知策略,且在检测信号信噪比较低时以更加积极的方式接入授权频谱,降低了频谱感知不确定性对信道接入效率的影响,提高了认知系统吞吐量。 相似文献
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针对非理想感知情况下感知时间与频谱分配联合优化问题,同时考虑漏检与主用户重新占用频谱两种场景所造成的主次用户碰撞,并通过量化主用户对认知用户的干扰,给出有无主用户存在时认知系统可获得的吞吐量。在总传输功率约束以及对主用户的最大干扰功率约束两个限制条件下,以最大化系统平均吞吐量为优化目标,给出感知时间与频谱分配联合优化算法。算法首先通过折半法搜索最优感知时间,在既定的感知时间下,将子信道分配给能获得最大平均吞吐量的认知用户,在此基础上,利用凸优化相关理论求得最优功率分配。仿真结果表明,本文所提算法相比于传统频谱分配算法系统平均吞吐量性能提升了10%左右。 相似文献
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如何设计最优的频谱感知与传输框架是认知无线电技术的重要环节。考虑频谱接入过程中数据传输中断对认知网络性能影响的问题,提出了一种新的基于传输中断概率的频谱感知与传输模型,联合优化频谱感知和数据传输两个阶段,将问题建模为对主用户的干扰量约束条件下的非凸优问题,以最大化认知网络吞吐量为目标联合优化感知时间、传输速率,并通过数值计算方法对其进行求解与仿真。数值分析表明,引入传输中断概率后,在满足上述约束条件的同时,在保护主用户和认知网络吞吐量、传输时延之间有了更好的权衡。 相似文献
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重复使用一定的TV频段是机会频谱接入的一个典型应用。在认知无线电机会频谱接入中,为了最大化信道的利用,授权用户与认知用户相互协作共同利用信道。文章将授权用户对信道的占用过程模拟为连续时间马尔可夫过程。认知用户在限制其对授权用户的干扰影响条件下,利用等比缩减的策略对信道进行感知,提出一个最优频谱接入策略,提高频谱的利用率。 相似文献
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在碰撞约束和非理想信道信息下,研究认知多址接入信道中多个次用户接入主用户频谱的有效吞吐量问题。在机会频谱接入方式(OSA)下,定义有效吞吐量并作为次用户的性能指标。考虑信道质量信息,在信道质量分布参数未知的情况下采用有限的信道样本对参数进行估计,并对非理想感知下次用户的性能进行分析。通过仿真实验,分别讨论了信道质量门限与碰撞概率及次用户性能之间的关系,对比了理想感知和非理想感知下次用户的性能,并与其他算法进行对比,验证了本文接入策略的有效性。 相似文献
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Performance of cognitive relay network with novel hybrid spectrum access schemes with imperfect CSI 下载免费PDF全文
Binod Prasad Abhijit Bhowmick Sanjay Dhar Roy Sumit Kundu 《International Journal of Communication Systems》2016,29(11):1761-1776
Two novel spectrum access schemes, a hybrid spectrum access scheme (HSAS) and a modified HSAS combining underlay mode and overlay mode, are proposed for a relay based cognitive radio (CR) network. The CR employs the underlay mode with imperfect channel state information of the interfering link between CR transmitter and primary user receiver if primary user is sensed to be present else it employs overlay mode. In both the schemes, transmission of CR is assisted by relay working in amplify and forward scheme by maintaining interference below an interference threshold in underlay mode and a collision constraint in overlay mode. In HSAS, CR transmits either in underlay mode or in overlay mode only during the transmission slot of a detection cycle, whereas in modified HSAS, the CR transmits for the entire frame including the sensing time. The outage probability of CR user is considered as the performance metric. Novel expressions of outage probability for both the schemes have been developed. Impact of several sensing parameters such as sensing time, correlation coefficient, and tolerable interference threshold has been investigated. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Joint cooperative spectrum sensing and channel selection optimization for satellite communication systems based on cognitive radio 下载免费PDF全文
Min Jia Xin Liu Xuemai Gu Qing Guo 《International Journal of Satellite Communications and Networking》2017,35(2):139-150
Cognitive radio has attracted considerable attention because of its ability to make full use of the available spectrum resources for wireless terrestrial communication networks. In addition, the satellite communication scenario, which requires a transparent air interface to integrated/hybrid Satellite–Terrestrial communication systems and provides a supplement for other multimedia services, will cause frequency scarcity. Satellite communication systems based on cognitive radio are available under scenarios that involve transmission with changing communications. In this paper, a cooperative spectrum‐sensing algorithm based on a time or bandwidth‐based cooperative spectrum‐sensing model of an integrated/hybrid cooperative satellite communication system is proposed. Moreover, the concept of weighted cooperative spectrum sensing is introduced. Compared with the traditional single‐user spectrum‐sensing algorithm, the cooperative spectrum sensing is able to cope with the interference to the primary user caused by a secondary user better. In addition, multiple earth stations that use some part of the bandwidth cooperatively to perform spectrum sensing throughout the whole frame can detect the presence of primary user in time. The satellite component combines the sensing results from earth stations to reach a final decision, and the optimal combination weights to maximize the detection probability of the secondary user are obtained. Numerical results that demonstrate the performance of the proposed algorithm are presented. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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认知无线电网络的MAC层关键技术 总被引:2,自引:0,他引:2
认知无线电作为一种智能的频谱共享技术,已成为无线通信领域的研究热点。为达到在不干扰授权用户的条件下有效地实现机会式频谱利用,认知无线电网络的媒体接入控制(MAC)层不仅需要提供传统的服务,还要求能支持一套全新的功能。频谱检测管理通过对检测模式的选取、检测周期及检测时长的设置、检测信道的选取和检测静默期的设置等实现检测策略和参数的选取及优化。接入控制主要采用与授权用户协调接入和透明接入两种方式避免与授权用户的接入产生碰撞。动态频谱分配针对二进制干扰模型和累积干扰模型进行不确定频谱资源的优化分配。安全机制通过增加MAC帧的认证和保密以防御MAC层的安全攻击。跨层设计结合物理层和网络层、传输层等上层信息设计和实现全局优化的MAC层技术。 相似文献
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In cognitive radio networks, the secondary users take chances to access the spectrum without causing interference to the primary users so that the spectrum access is dynamic and somewhat opportunistic. Therefore, spectrum sensing is of significant importance. In this paper, we propose a novel time-domain combining cooperative spectrum sensing framework, in which the time consumed by reporting for one secondary user is also utilized for other secondary users’ sensing. We focus on the optimal sensing settings of the proposed sensing scheme to maximize the secondary users’ throughput and minimize the average sensing error probability under the constraint that the primary users are sufficiently protected. Some simple algorithms are also derived to calculate the optimal solutions. Simulation results show that fundamental improvement of the achievable throughput and sensing performance can be obtained by optimal sensing settings. In addition, our proposed scheme outperforms the general frame structure on either achievable throughput or the performance of average sensing error probability. 相似文献
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Cognitive radio is a promising technology that deals with the scarcity of radio spectrum. In this paper, we propose a new
multi-channel transmission strategy for dynamic spectrum access in cognitive radio network. Starting with the model of spectrum
activities, we present the multi-channel transmission strategy which has primary user’s protection mechanism to improve the
spectrum efficiency and study its performance under perfect and imperfect sensing. Numerical example results reveal that the
performance of the proposed strategy has the superiority with respect to capacity performance of cognitive users and the protection
of primary users. 相似文献
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动态频谱接入策略是实现认知无线电网络高效利用频谱的关键。与传统认知无线电网络不同,认知mesh网络中不同QoS需求的多类型业务共同接入,为适应这一特点,提出服务区分的动态频谱接入策略。策略依据业务的QoS需求确立优先级,针对不同优先级业务采取不同的信道接入方案,实时业务依据最优传输延迟期望选择接入信道集合,在减小传输延迟的同时降低数据传输过程授权用户出现的概率,普通业务选择最优理想传输成功概率的信道,降低信道切换概率。理论与实验结果表明,与传统的认知网络频谱接入策略相比,提出的策略能提供不同业务的服务区分,满足实时业务的低延迟需求,降低数据传输的中断率,同时在授权信道空闲率与网络负载较大时吞吐量性能较优。 相似文献
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Spectrum sensing and access have been widely investigated in cognitive radio network for the secondary users to efficiently utilize and share the spectrum licensed by the primary user. We propose a cluster‐based adaptive multispectrum sensing and access strategy, in which the secondary users seeking to access the channel can select a set of channels to sense and access with adaptive sensing time. Specifically, the spectrum sensing and access problem is formulated into an optimization problem, which maximizes the utility of the secondary users and ensures sufficient protection of the primary users and the transmitting secondary users from unacceptable interference. Moreover, we explicitly calculate the expected number of channels that are detected to be idle, or being occupied by the primary users, or being occupied by the transmitting secondary users. Spectrum sharing with the primary and transmitting secondary users is accomplished by adapting the transmission power to keep the interference to an acceptable level. Simulation results demonstrate the effectiveness of our proposed sensing and access strategy as well as its advantage over conventional sensing and access methods in terms of improving the achieved throughput and keeping the sensing overhead low. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献