共查询到18条相似文献,搜索用时 125 毫秒
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认知无线电频谱切换目标信道访问机制 总被引:1,自引:0,他引:1
针对认知无线电先应式决策频谱切换,该文提出按照信道平均空闲时间递减的顺序对目标信道进行访问的机制,证明了该机制在主用户信道空闲时间服从均匀分布、Rayleigh分布以及Weibull分布下均能够保证频谱切换失败概率最小。仿真结果表明所提机制得到的频谱切换失败概率要远远小于随机访问机制的切换失败概率。另外,当能够获得数十次信道空闲时间观测样本情况下,虽然存在估计误差,但所得频谱切换失败概率与理想最优频谱切换失败概率非常接近。 相似文献
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为了尽可能地降低认知无线电频谱切换的次数,更加全面地考虑通信环境里的因素,引入模糊控制技术,提出一个可行的频谱切换策略。首先,认知用户接收方根据信噪比和主用户活动性估计信道获益,再通过信道反馈机制将结果值告知认知用户发送方;最后,认知用户发送方将业务分成两类:实时业务与非实时业务,并将信道获益与业务实时性作为两个新参数纳入频谱切换策略。仿真结果显示,与随机选择策略相比,根据信道获益选择信道可以明显降低认知用户的切换率。另外,将业务进行分类,非实时用户与实时用户相比有更低的切换可能性,这种差距可以达到32%。 相似文献
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文章利用认知频谱检测、动态频谱分配、重配置等技术,考虑短时频谱特征与业务特征的匹配程度,在通信过程中网络侧选择待切换终端发起切换命令,解决由于容量受限而导致的系统过载、无法接纳新会话等问题,并在保证用户服务质量(QoS)的前提下提高切换成功率,有效消除过载现象,从而增大系统吞吐量,允许更多的会话接入,降低阻塞率,提升通信系统性能. 相似文献
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在主动频谱切换中,预先确定目标信道存在高失效风险,从而增加切换时延的问题。该文提出一种基于混合主被动频谱切换的最优目标信道选择算法。该算法结合主动频谱切换和被动频谱切换的优点,引入最小累积切换时延评价标准,综合考虑次用户的多次中断、主用户的到达率和非理想频谱检测对次用户累积切换时延的影响,并详细分析和推导了非理想检测下次用户的累积切换时延。仿真表明,相较于主动和被动频谱切换中目标信道选择策略,在信道状态变化频繁或业务量较大等极端情况下,该算法的性能优势尤为明显。 相似文献
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认知无线网络中的频谱切换技术 总被引:1,自引:0,他引:1
针对频谱切换的研究现状,文章介绍了频谱切换的场景、分类以及对认知无线网络物理层、媒体接入控制层(MAC)的需求,总结了频谱切换技术的最新研究进展,对目前的各种方案进行了比较分析,并提出了未来面临的挑战及研究方向。 相似文献
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为满足次用户不同时延需求并提高信道利用率,该文提出一种基于次用户分级的PRP M/G/m排队论频谱切换模型。首先,根据次用户主要业务的时延需求不同,对次用户进行分级评价,将次用户分为时延敏感型和非时延敏感型用户,时延敏感型次用户具有更高的优先级来接入信道。其次,采用PRP M/G/m排队论来建立基于用户分级的频谱切换模型。同时推导和分析了该模型下不同优先级次用户扩展数据传输时间,进而提出了面向各级次用户自适应频谱切换策略。仿真结果表明,相较于已有频谱切换策略,该模型能有效降低次用户切换时延以及扩展数据传输时间,保证高优先级次用户的服务质量,提升次用户频谱切换的综合性能。 相似文献
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LEO网络中卫星切换的动态概率路由优化策略 总被引:5,自引:0,他引:5
在LEO卫星网络中,卫星切换方案需要在保证最小切换延时的同时,合理地使用网络资源,因此应该合理选择卫星切换中路由优化的触发条件。本文在综合考虑卫星切换中消耗的网络资源,包括带宽资源和信令资源的前提下,提出动态概率路由优化方案。指出在卫星切换中,为了达到对网络资源的有效使用,路由优化概率应该随LEO星座结构,呼叫带宽,业务分布等网络参数不同而动态变化。 相似文献
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《AEUE-International Journal of Electronics and Communications》2014,68(8):747-755
This paper considers a cognitive radio network where a secondary user (SU) coexists with a primary user (PU). The interference outage constraint is applied to protect the primary transmission. The power allocation problem to jointly maximize the ergodic capacity and minimize the outage probability of the SU, subject to the average transmit power constraint and the interference outage constraint, is studied. Suppose that the perfect knowledge of the instantaneous channel state information (CSI) of the interference link between the SU transmitter and the PU receiver is available at the SU, the optimal power allocation strategy is then proposed. Additionally, to manage more practical situations, we further assume only the interference link channel distribution is known and derive the corresponding optimal power allocation strategy. Extensive simulation results are given to verify the effectiveness of the proposed strategies. It is shown that the proposed strategies achieve high ergodic capacity and low outage probability simultaneously, whereas optimizing the ergodic capacity (or outage probability) only leads to much higher outage probability (or lower ergodic capacity). It is also shown that the SU performance is not degraded due to partial knowledge of the interference link CSI if tight transmit power constraint is applied. 相似文献
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How to improve the performance of the wireless Ad Hoc network by utilizing the spectrum resources efficiently has become a
hot research topic in recent years. In this paper we propose a reactive routing algorithm that supports multiple channels
to improve the performance of the Ad Hoc network based on the minimizing of the channel handoff. Our approach allocates the
communication channel during the route discovery, and notifies the allocated channel information to the corresponding node
in the route reply packets. Each node in the route tries its best to choose the same channel with the upstream node without
interference. The simulation results show that our algorithm performs better than the K-hop distinct protocols in both average
delays and network throughputs obviously 相似文献
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围绕客户感知展开讨论,结合目前移动通信网优工作现状,阐述了基于用户感知的网优体系的建设,并对下一步工作进行了展望。 相似文献
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Cognitive Radio is an emerging technology to accommodate the growing demand for wireless technology via dynamic spectrum access to enhance spectrum efficiency. Spectrum handoff is an important component of Cognitive Radio technology for practical implementation of radio frequency access strategy and better utilization of spectrum in both primary and secondary networks. The probability of spectrum handoff and expected number of spectrum handoffs are key parameters in performance analysis and design of the cognitive radio network. This work presents an analytical model to evaluate the impact of secondary users’ mobility on intra-cell spectrum handoff considering primary users’ activity model in a cognitive radio network. A standard form of intra-cell spectrum handoff probability and expected number of intra-cell spectrum handoffs are derived for complete call duration of a non-stationary secondary user. The probability and expected number of intra-cell spectrum handoffs of a post inter-cell handoff call are also derived for generalized residual time distributions of call holding time and spectrum holes. A detailed analysis of these performance measuring metrics is presented under the impact of departure rate and cell crossing rate of secondary users. The accuracy of the derived analytical result is validated by Monte-Carlo simulation of the model. 相似文献
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针对认知无线电传感器网络(C RSN)中物理层特性高度可变带来的性能不确定性,在CRSN中定义了两种基础性能指标(带宽和时延),并分析了基于载波侦听多路访问(CSMA)的介质访问控制协议的性能.首先,在给定的主用户(PU)业务模型下利用CSMA算法估计单个次级用户(SU)的潜在带宽;然后,推导在不同业务信道同时传输多个SU的聚合带宽;最后,利用优先级队列模型M/G/C估计介质访问中的时延.性能分析表明,通过使用分布式信道协作结合CSMA的并发传输,聚合带宽可增加5倍,利用不同业务信道同时传输明显降低了分组时延. 相似文献