Spectrum leasing based on Nash Bargaining Solution in cognitive radio networks

Cognitive radio is becoming an emerging technology that has the potential of dealing with the stringent requirement and scarcity of the radio spectrum resource. In this paper, we focus on the dynamic spectrum access of cognitive radio networks, in which the primary user (PU) and secondary users (SUs) coexist. In property-rights model, the PU has property of the bandwidth and may decide to lease it to secondary network for a fraction of time in exchange for appropriate remuneration. We propose a cooperative communication-aware spectrum leasing framework, in which, PU selects SUs as cooperative relays to help transmit information, while the selected SUs have the right to decide their payment made for PU in order to obtain a proportional access time to the spectrum. Then, the spectrum leasing scheme is cast into a Nash Bargaining Problem, and the Nash Bargaining Solution (NBS) can be used to fairly and efficiently address the resource allocation between PU and secondary network, enhancing both the utility of PU and secondary network. Numerical results show that spectrum leasing based on NBS is an effective method to improve performance for cognitive radio networks.     

相干光通信系统中的偏振控制技术

在相干光通信系统中,接收端的输入信号和本机振荡信号的偏振状态(SOP)必须相匹配,否则不但难以达到应有的接收灵敏度,甚至还可能劣于直接检测系统。对于目前普遍使用的单模光纤,由于其SOP转移特性是随时间和其它环境条件的影响而变化,因此必须对接收端的输入信号或本机振荡信号的SOP进行实时控制,以确保系统的性能指标。本文介绍了目前国际上常用的几种偏振控制技术,重点放在无限循环控制(Endless Control)和电光集成器件运。用Poincare球面表示法,任何一种偏振控制器的SOP转移特性都可以看作是代表SOP的点在Poincare球面上的旋转过渡。     

动态网络环境下切换成功率优化方法

GSM网络是处在一个动态发展下的移动通信网络,切换成功率的优化是GSM网络的一项重要内容,在做好日常优化的同时,我们更加需要关注在动态网络环境下的切换成功率的优化.     

WiMAX与McWiLL技术的分析与比较

本文首先介绍了WiMAX和McWiLL接入技术的发展历程,然后对两技术物理层和媒质访问层的技术特点和主要参数进行了分析与比较,最后介绍了WiMAX和McWiLL的市场发展状况。     

基于Arduino的老人环境监测系统研究

本文以居家老年人为研究对象;研究基于Arduino控制板和多传感器融合,集生活环境检测模块(温度、污染气体和湿度等)、生理参数信息采集模块(心率、体温和脉搏)与报警模块于一体的健康智能监控系统.该系统对老年人进行生活监测,对于出现异常的情况进行报警,并提醒家人或者相关人员及时救助从而保障老人的健康和安全.该系统具有价格...     

Advances in Wearable Strain Sensors Based on Electrospun Fibers

Wearable strain sensors with the ability of detecting physiological activities play an important role in personalized healthcare. Electrospun fibers have become a popular building block for wearable strain sensors due to their excellent mechanical properties, breathability, and light weight. In this review, the structure and preparation process of electrospun fibers and the conductive layer are systematically introduced. The impact of materials and structures of electrospun fibers on the wearable strain sensors with a following discussion of sensing performance optimization strategies is outlined. Furthermore, the applications of electrospun fiber-based wearable strain sensors in biomonitoring, motion detection, and human-machine interaction are presented. Finally, the challenges and promising future directions for the community of wearable strain sensors based on electrospun fibers are pointed out.     

A new composite assembly mechanism for supporting QoS in OBS networks

To provide the differential quality of service（QoS）for different classes of packets and reduce the packet loss probabil ity（PLP）,a novel priority-based composite assembly scheme for optical burst switching（OBS）networks is proposed The low and high packet classes are aggregated into a single burst simultaneously,and the highest-priority packets ar placed in the middle,while the low-priority packets are at the tail and head of the burst.The priority is lowered gradu ally from the middle to the ends.Simulation results demonstrate that the proposed assembly strategy not only guaran tees the integrity of the high-priority bursts,but also significantly reduces the average end-to-end delay of the burst and the PLP of network.So it can adapt to the flexible network with QoS requirement.     

Improved Performance of Molecular Bulk‐Heterojunction Photovoltaic Cells through Predictable Selection of Solvent Additives

Solvent additives provide an effective means to alter the morphology and thereby improve the performance of organic bulk‐heterojunction photovoltaics, although guidelines for selecting an appropriate solvent additive remain relatively unclear. Here, a family of solvent additives spanning a wide range of Hansen solubility parameters is applied to a molecular bulk‐heterojunction system consisting of an isoindigo and thiophene containing oligomer as the electron donor and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) as the electron acceptor. Hansen solubility parameters are calculated using the group contribution method and compared with the measured solubilities for use as a screening method in solvent additive selection. The additives are shown to alter the morphologies in a semipredictable manner, with the poorer solvents generally resulting in decreased domain sizes, increased hole mobilities, and improved photovoltaic performance. The additives with larger hydrogen bonding parameters, namely triethylene glycol (TEG) and N‐methyl‐2‐pyrrolidone (NMP), are demonstrated to increase the open circuit voltage by ~0.2 V. Combining a solvent additive observed to increase short circuit current, poly(dimethylsiloxane), with TEG results in an increase in power conversion efficiency from 1.4 to 3.3%.     

用窄带滤光片作为调谐元件的外腔半导体激光器

分析了窄带滤光片的调谐原理，拟合了一块实际滤光片的透射率函数，它是理论的透射率函数和一个洛仑兹函数的乘积。利用１．３μｍ的外腔式调谐激光器实现了１２７２．５ｎｍ至１２９１．７ｎｍ范围内的不连续宽带调谐。     

Detection of lead ions with AlGaAs/InGaAs pseudomorphic high electron mobility transistor

Lead poisoning is a serious environmental concern, which is a health threat. Existing technologies always have some drawbacks, which restrict their application ranges, such as real time monitoring. To solve this problem, glutathione was functionalized on the Au-coated gate area of the pseudomorphic high electron mobility transistor (pHEMT) to detect trace amounts of Pb²⁺. The positive charge of lead ions will cause a positive potential on the Au gate of the pHEMT sensor, which will increase the current between the source and the drain. The response range for Pb²⁺ detection has been determined in the concentrations from 0.1 pmol/L to 10 pmol/L. To our knowledge, this is currently the best result for detecting lead ions.