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对认知MANET的研究涉及到许多方面,其中认知MANET中的功率控制算法设计是目前的一个研究热点.为了实现认知MANET中的次用户网络和主用户网络频谱共享,从而提高频谱利用率,即次用户网络中的次用户可以机会接入授权主用户所在的频谱,且同时保证主用户和次用户的QoS需求.本文认知MANET中功率控制的目的就是在满足QoS... 相似文献
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针对工作于underlay模式的认知无线网络(CRN,Cognitive Radio Network)上行功率控制问题,本文提出一种基于多天线波束赋形,由认知基站和认知用户联合优化的分布式上行功率控制算法.联合优化的具体步骤为认知基站通过求解最大广义特征值问题完成多天线波束赋形优化;认知用户先将非线性功率优化问题转换为几何规划凸优化问题,再使用梯度法完成分布式发送功率优化;认知基站和认知用户交替优化,实现网络效用最大化.数值仿真显示,同只优化认知用户功率的上行功率控制算法相比,认知基站和认知用户联合优化的上行功率控制算法不仅能得到更大的网络效用值,而且对主用户的干扰具有鲁棒性. 相似文献
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认知无线电中基于Stackelberg博弈的分布式功率分配算法 总被引:1,自引:0,他引:1
在underlay认知无线电场景中,为了让认知用户能随机地接入主用户正在使用的授权频段,且对主用户产生的干扰不高于主用户能够容忍的干扰温度门限,该文采用Stackelberg博弈机制进行认知用户的发射功率分配。将主用户作为模型中的leader,认知用户作为follower,认知用户使用主用户的授权频段时需以干扰功率为单位支付给主用户相应的费用,而主用户则可以通过调整价格,限制认知用户产生的总干扰功率不高于其所能容忍的干扰温度门限,以便获得最大收益。同时,不同认知用户间根据主用户制定的价格,进行非协作博弈。仿真结果表明,与集中式的最优功率分配算法相比,该文可通过简单的分布式功率分配算法获得与其相近的系统性能,且主用户与认知用户间只需进行少量的信息交互,这与需进行大量信息交互的集中式最优算法相比,具有较大的优势。 相似文献
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考虑到认知用户在信息传输过程中主用户的状态可能随时变化,提出了一种新的功率分配模式——多功率分配策略。在基于频谱感知的系统模型中,以认知系统的吞吐量为目标函数,得出了主用户感知过程的多种状态,并分配三种不同的功率,最大化认知系统的容量。仿真结果表明,随着主用户活跃指数的逐渐提高,所提新模型的功率分配策略要优于传统方法。同时分析了新的功率分配下平均干扰功率与主用户接收端的信噪比对系统吞吐量和最优感知时间的影响,进一步验证了所提出新策略的有效性。
〖HT5H〗关键词:〖HT5K〗认知无线电;主用户活跃;频谱感知分配;多功率分配;吞吐量最大化 相似文献
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本文构建了一种在感知结果下具有多天线次用户的频谱共享模型,该模型由单入单出主用户对和多入单出认知用户对构成。当认知用户感知到主用户占用信道时,主用户向认知用户发送Message信息,使得认知用户发射端能够得知主用户对干扰总功率的限制要求,通过自适应地调整认知用户发射机的发射功率,以保证其对主用户不造成有害干扰;如果主用户未占用信道,认知用户立刻以最大发射功率占用信道。并分别在主用户存在和不存在两种情况下,优化认知用户发射机各天线的发射功率来最大化系统总的数据传输率。最后,通过数值仿真来验证推导出的功率分配策略,并对其进行分析和讨论。仿真结果表明:相比于机会频谱接入(Opportunistic Spectrum Access, OSA)和基于感知的频谱共享(Sensing-based spectrum sensing)模式,推导的功率分配策略在提出的模型中可以获得更高的信息传输率。 相似文献
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研究了频谱共享环境中,一种基于认知用户有限感知区域与主用户混合保护措施的功率分配方法,在考虑主用户占用子信道概率的情况下,通过建立认知系统的多区域模型,提出了适应于主用户存在与否两种不同情况下的干扰避免策略。在满足认知用户自身最大功率约束与主用户混合干扰功率约束的条件下,基于最大化认知系统传输速率的目标,提出了各子信道集合的和功率以及不同集合内功率分配的联合优化方法,且复杂度较低。仿真结果表明,本文所提方法在不同参数设置下均达到了较好的速率性能,且远远超过机会频谱接入方式所获得的最大传输速率。 相似文献
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传统的认知无线电频谱分配算法往往忽略节点的传输功率对网络干扰的影响,且存在节点间交互成本高的问题.为此,通过量化传输功率等级,以最大化弹性用户收益为目标,构建联合频谱分配与功率控制非合作博弈模型,证明了该博弈为严格潜在博弈且收敛到纳什均衡点.进一步,将随机学习理论引入博弈模型,提出了基于随机学习的策略选择算法,并给出了该算法收敛到纯策略纳什均衡点的充分条件及严格证明.仿真结果表明,所提算法在少量信息交互前提下能获得较高的传输速率,并提升用户满意度. 相似文献
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Dong Li 《Wireless Personal Communications》2012,63(3):549-559
Efficient resource allocation is a major challenge in cognitive radio networks, especially when Cognitive Users (CUs) share
the same frequency band with the Primary User. In this paper, we consider minimizing the total power consumption by combining
power control, rate control and adaptive modulation. We analyze the existence, uniqueness and Pareto optimality of Nash Equilibrium
(NE) in the power control game, and propose an iterative algorithm to find the NE followed by the adjustment of both the transmission
rate and modulation scheme based on the convergent power. If compared with previous works, the key feature of the proposed
strategy is that each CU can prolong its battery life in energy-constrained networks to support heterogenous services with
different transmission rates and modulation schemes requirements. Simulation results are provided to confirm the effectiveness
of the proposed method in power saving, improvement of both the transmission rate and the spectral efficiency and the simplicity
of implementation. 相似文献
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针对现有的功率控制算法中存在的干扰问题和功率消耗过大问题,设计出一种新的效用函数,并根据此效用函数提出了一个基于非合作博弈的新的功率控制算法。首先,在效用函数中分别为信干噪比和功率设定了不同的代价因子,并将信道状态概念引入到代价因子里面,使其能够更加合理地控制用户,避免用户过度增加发射功率,同时减小了用户间的干扰;其次,证明了该算法纳什均衡的存在性和唯一性;最后,给出了所提算法的流程图。仿真结果表明,与Nash算法相比,在保证非授权用户服务质量( QoS)前提下,该算法功率消耗明显降低,并且具有较好的抗背景噪声性能;与K-G( Koskie-Gajic)算法相比,该算法保证了所有的用户的信干噪比满足上下限阈值要求,并且提高了系统容量。 相似文献
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Zhang J. Chong E.K.P. Kontoyiannis I. 《Selected Areas in Communications, IEEE Journal on》2001,19(7):1276-1288
In a mobile wireless system, fading effects can be classified into large-scale (long-term) effects and small-scale (short-term) effects. We use transmission power control to compensate for large-scale fading and exploit receiver antenna (space) diversity to combat small-scale fading. We show that the interferences across the antennas are jointly Gaussian in a large system, and then characterize the signal-to-interference ratio for both independent and correlated (across the antennas) small-scale fading cases. Our results show that when each user's small-scale fading effects are independent across the antennas, there is a clear separation between the gains of transmission power control and diversity combining, and the two gains are additive (in decibels). When each user's small-scale fading effects are correlated across the antennas, we observe that, in general, the gains of transmission power control and diversity combining are coupled. However, when the noise level diminishes to zero, using maximum ratio combining “decouples” the gains and achieves the same diversity gain as in the independent case. We then characterize the Pareto-optimal (minimum) transmission power allocation for the cases of perfect and noisy knowledge of the desired user's large-scale fading effects. We find that using antenna diversity leads to significant gains for the transmission power 相似文献
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Tang Zhenzhou Hu Qian Yu Guanding 《电子科学学刊(英文版)》2008,25(2):268-273
In this letter, an Opportunistic Interference Cancellation (OIC) is first introduced as a rate control strategy for secondary user in cognitive wireless networks. Based on the OIC rate control method, an optimal power control strategy for multichannel cognitive wireless networks is proposed. The algorithm aims to maximize the total transmit rate of cognitive user through appropriately controlling the transmit power of each subchannel under the constraint that the interference temperature at the primary receiver is below a certain threshold. Three suboptimal power control methods, namely Equal Power Transmission (EPT), Equal Rate Transmission (ERT) and Equal Interference Transmission (EIT), are also proposed. The performances of the proposed power control methods are compared through numerical simulations. 相似文献
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针对分布式环境下各自主域访问控制模型的异构性以及跨域访问中域自治与协作问题,提出了一种基于策略的跨自主域访问控制模型.该模型通过自主域间访问主体的不同粒度映射机制,支持域间的安全互操作;通过安全控制器并结合基于XACML的访问控制策略,实现了域间用户权限的逻辑整合.各域的相关权限信息封装在域内,既保持原有的独立性又实现了域间的协作,同时屏蔽了域间主体差异,解决了不同域系统互不认知和异构访问控制模型映射问题. 相似文献
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针对认知MIMO系统设计一种空频域机会接入策略。当存在频谱空洞时,认知业务以交叉共享方式实现传输;当无空闲频谱资源可用时,利用授权通信模式信息与系统间干扰信道信息,以重叠共享方式实现认知业务传输。该方法综合利用空间相关度与特征模式传输增益进行空域资源质量评价,实现授权频道与认知特征模式的选择分集。并且,基于授权通信模式信息的信号处理降低了认知系统天线配置要求以及认知信号的功率损失。仿真结果表明,所提策略能够在不影响授权业务的前提下显著改善认知业务性能,获得接近最佳的认知吞吐率。 相似文献
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In this paper,we study cross-layer scheduling scheme on multimedia application which considers both streaming traffic and data traffic over cognitive ad hoc networks.A cross-layer design is proposed to optimize SU's utility,which is used as an approach to balance the transmission efficiency and heterogeneous traffic in cognitive ad hoc networks.A framework is provided for utility-based optimal subcarrier assignment,power allocation strategy and corresponding modulation scheme,subject to the interference threshold to primary user(PU) and total transmit power constraint.Bayesian learning is adopted in subcarrier allocation strategy to avoid collision and alleviate the burden of information exchange on limited common control channel(CCC).In addition,the M/G/l queuing model is also introduced to analyze the expected delay of streaming traffic.Numerical results are given to demonstrate that the proposed scheme significantly reduces the blocking probability and outperforms the mentioned single-channel dynamic resource scheduling by almost 8%in term of system utility. 相似文献
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The optimal resource allocation in MIMO cognitive radio networks with heterogeneous secondary users, centralized and distributed users, is investigated in this work. The core aim of this work is to study the joint problems of transmission time and power allocation in a MIMO cognitive radio scenario. The optimization objective is to maximize the total capacity of the secondary users (SUs) with the constraint of fairness. At first, the joint problems of transmission time and power allocation for centralized SUs in uplink is optimized. Afterwards, for the heterogeneous case with both the centralized and distributed secondary users, the resource allocation problem is formulated and an iterative power water-filling scheme is proposed to achieve the optimal resource allocation for both kinds of SUs. A dynamic optimal joint transmission time and power allocation scheme for heterogeneous cognitive radio networks is proposed. The simulation results illustrate the performance of the proposed scheme and its superiority over other power control schemes. 相似文献