Resource allocation scheme for video transmissions in cognitive radio networks

Considering SUs with multiple radios, this paper discusses the cross-layer resource allocation problem for video transmissions in cognitive radio networks. Because of the coupling relationship between radio and channel, this paper proposes a new conflict graph based on the link-radio-channel, and models the resource allocation problem into an optimization problem. The constraints ensure the conflict-free and interference-free video transmissions, and provide flow routing and rate allocation for video services based on the feature of scalable video coding streams. The objective function achieves the network-level throughput maximization with fairness consideration. Simulation results show that the multi-radio transmission could gain a higher throughput. Also, the proposed scheme could provide fairness resource allocation, and use resource efficiently based on the feature of video services.     

认知MIMO干扰信道的联合干扰对齐算法

针对认知MIMO干扰信道的干扰抑制问题,前人的研究往往将其解耦为主用户和次用户的干扰抑制两个独立问题进行设计,因而需要两级处理。首先将这两类干扰的抑制进行联合处理,建立了联合干扰对齐问题模型,然后基于对交替最小化干扰对齐算法的拓展和改进,得出一种迭代的联合干扰对齐算法。理论分析和仿真结果表明,文章算法能有效抑制系统内的干扰,与现有算法相比,干扰抑制性能相当,求解过程简单,信道无需满足互易性。     

Optimization algorithm for dynamic spectrum access based on Q-learning in cognitive radio networks

Under the centralized cognitive radio network architecture, considering the network performance and users' demands. We propose an optimized dynamic spectrum access algorithm based on Q-learning. The proposed algorithm has two steps, which consist of user request according to Q-learning and the application process according to the overall system performance. Simulation results show that the proposed scheme can improve the overall system performance obviously, and that the user requirements could be satisfied at the same time.     

Multi-criteria user selection scheme for learning-based multiuser MIMO cognitive radio networks

For multiuser multiple-input-multiple-output (MIMO) cognitive radio (CR) networks a four-stage transmiision structure is proposed. In learning stage, the learning-based algorithm with low overhead and high flexibility is exploited to estimate the channel state information (CSI) between primary (PR) terminals and CR terminals. By using channel training in the second stage of CR frame, the channels between CR terminals can be achieved. In the third stage, a multi-criteria user selection scheme is proposed to choose the best user set for service. In data transmission stage, the total capacity maximization problem is solved with the interference constraint of PR terminals. Finally, simulation results show that the multi-criteria user selection scheme, which has the ability of changing the weights of criterions, is more flexible than the other three traditional schemes and achieves a tradeoff between user fairness and system performance.     

非时隙结构认知无线网络中非授权用户传输时延分析

在非时隙结构认知无线网络中,以随机侦听多址方案为基础构建了系统的数学模型,利用柯尔莫哥洛夫费勒前向方程得出系统的稳态概率,并采用拉普拉斯斯帝尔阶斯变换推导出非授权用户数据包的平均传输时延.数值分析表明,信道忙的概率和平均退避时间与传输时延呈正比关系,不同的载波侦听多址方案对传输时延影响很大,其中全侦听多址方案的传输时延最小.     

基于特征结构的频谱感知算法

为了全面认识当前的认知无线电频谱感知技术,深入研究基于特征结构的多节点合作频谱感知算法,将近年来发展的随机矩阵理论(RMT)引入到频谱感知领域,使得频谱感知性能得到提高,有可能在实际应用中实现频谱感知。通过阐述基于采样协方差矩阵及特征值类的合作频谱感知方法的基本原理,归纳其主要特点,推导出检测门限的确定方法。通过基于Matlab的仿真实验,对比和验证算法的感知性能。最后展望该方向下一步的研究趋势。     

一种适用于698~806MHz频段的认知MAC协议

针对广播系统与认知系统共存场景下的认知用户接入问题,提出一种适用于698⁸06MHz频段的认知MAC协议。该协议以分布式的方式对授权信道侦听,认知用户之间以协调的方式共享信道侦听结果,并采用基于竞争的方式接入空闲授权信道。利用蒙特卡洛仿真方法对所提出的协议进行了仿真。仿真结果表明,与传统MAC协议相比,该协议能够有效提高授权频段的频谱利用率,提升系统性能。     

场依存-场独立型认知风格对大学英语教学的影响

场依存-场独立型认知风格能够影响学生的记忆、思考、学习、沟通等,而这些因素与大学英语学习有着紧密的联系。大学英语教学,主要就包括英语听力教学、英语阅读教学等多方面内容,本文主要分为三个部分,第一部分主要是针对场独立型与场依存型学生的特征分析;第二部分主要是对场依存-场独立型认知风格学生在英语学习中采用的不同教学方法;第三部分是对本文内容进行总结。     

基于动态双门限和D-S证据理论的合作频谱感知算法

针对传统能量检测算法门限设置单一且不适应感知信道环境差异的问题,为了提高合作频谱感知结果的可靠性,减小网络开销和融合中心计算的负担,提出了将动态双门限能量检测和D-S证据理论相结合的合作频谱感知算法.在进行本地感知时,该算法可以让认知用户通过双门限能量检测方法直接得到本地判决结果,同时根据信道环境的变化自适应调整双门限值,并在双门限内使用D-S证据理论,感知双门限内未判决结果的信任度函数,将其发往融合中心,这样可以减少融合中心的计算量以及传输带来的网络开销.仿真结果表明,双门限D-S证据理论的融合结果要优于D-S证据理论和OR准则.     

How individual characteristics influence people's evaluation towards information technology in different contexts

Prior research on technology acceptance has primarily focused on understanding why individuals accept a particular technology, while very little is known about how individuals evaluate various types of technology, especially when they have different levels of experiences. In this research, we try to understand how individual characteristics influence their evaluation towards different types of technology. To test the research model empirically, a laboratory experiment was conducted, and the resulting data was used to test both measurement and structural models. Based on the statistic results, we found that people's need for cognition and originality cognitive style had different effects on technology evaluation in various contexts. This study sheds light on the rarely studied evaluation aspect of the technology acceptance. The main contribution of this study is that people employ different mechanisms to evaluate technology in different contexts, and individual characteristics play an important role in influencing technology evaluation.