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Adaptive double-threshold energy detection algorithm for cognitive radio

Journal of Southeast University(English Edition) 2011年第4期27卷 351-356页

作者：苏倩宋铁成胡静沈连丰东南大学移动通信国家重点实验室南京210096

Due to the fact that the conventional spectrum sensing algorithm is susceptible to noise, an adaptive double-threshold energy detection algorithm for a cognitive radio is proposed. Based on double-threshold energy detection, the algorithm can adaptively switch between one-round sensing and two-round sensing by comparing the observations with the pre-fixed thresholds. Mathematical expressions for the probability of detection, the probability of false alarm, and the sensing time are derived. The relationships including signal to noise ratio （SNR） vs. the probability of detection and SNR vs. the sensing time are plotted using Monte Carlo simulation and the algorithm is verified in a real cognitive system based on GNU Radio and universal software radio peripheral （USRP）. Simulation and experimental results show that, compared with the existing spectrum sensing method, the proposed algorithm can achieve a higher probability of detection within a reasonable sensing time.

关键词： energy detection software radio probability of detection sensing time

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Resource allocation based on fairness and QoS provisioning for OFDMA-WLAN system

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Journal of Southeast University(English Edition) 2014年第1期30卷 1-6页

作者：鲍楠夏玮玮沈连丰东南大学移动通信国家重点实验室南京210096

To satisfy different service requirements of multiple users in the orthogo nal frequency division multiple access wireless local area network OFDMA-WLAN system downlink transmission a resource allocation algorithm based on fairness and quality of service QoS provisioning is proposed. Different QoS requirements are converted into different rate requirements to calculate the QoSs atisfaction *** optimization object is revised as a fairness-driven resource optimization function to provide fairness. The complex resource allocation problem is divided into channel allocation and power assignment sub-problems. The sub-problems are solved by the bipartite graph matching and water-filling based *** with other algorithms the proposed algorithm sacrifices less data rate for higher fairnes and QoS *** sim ulation results show that the proposed algorithm is capableo fp rovi ding QoS and fairness and performs better in a tradeoff among QoS fairness and data rate.

关键词： QoS quality of service satisfaction level fairness driven function b ipartite graph matching water-f i lling resource allocation

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Cooperative algorithm for improving network connectivity in clustered wireless sensor networks

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Journal of Southeast University(English Edition) 2011年第1期27卷 1-7页

作者：李文峰邵震洪沈连丰东南大学移动通信国家重点实验室南京210096

In order to improve network connectivity in clustered wireless sensor networks,a node cooperative algorithm based on virtual antenna arrays is *** the nodes in the network are assumed to be clustered via Poisson Voronoi tessellation（PVT）.The activation of the node cooperative algorithm is determined by the cluster heads（CHs） according to communication *** the cooperative algorithm is activated,the CH selects cooperative nodes（CNs） from its members to form a virtual antenna *** the cooperation,nodes can extend the inter-cluster communication range to directly contact with further nodes after a coverage hole is detected,or compensate for channel gains while inter-cluster transmission fails due to deep channel *** results show that the proposed algorithm achieves better network connectivity and energy *** can reduce outage probability,sustain network connectivity and maintain operations as long as possible,which prolongs network operation time.

关键词： wireless sensor network coverage cooperative communication operation time

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单轴晶体中杂化偏振矢量涡旋光场的传输特性

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东南大学学报（自然科学版） 2020年第1期50卷 33-38页

作者：练萌顾兵东南大学移动通信国家重点实验室南京210096 东南大学先进光子学中心南京210096

为了实现光场的偏振态调控,对拥有复杂偏振态分布的杂化偏振矢量涡旋光场在单轴晶体中垂直于光轴的传输特性展开研究.基于光束在各向异性单轴晶体中的傍轴矢量传输理论,推导出杂化偏振矢量涡旋光场在单轴晶体中传输的具体表达式.通过数... 详细信息

为了实现光场的偏振态调控,对拥有复杂偏振态分布的杂化偏振矢量涡旋光场在单轴晶体中垂直于光轴的传输特性展开研究.基于光束在各向异性单轴晶体中的傍轴矢量传输理论,推导出杂化偏振矢量涡旋光场在单轴晶体中传输的具体表达式.通过数值模拟,得出了不同参数下杂化偏振矢量涡旋光场在单轴晶体中传输的演变规律.结果表明,光束半径、传输距离以及单轴晶体的e光和o光折射率比值对杂化偏振矢量涡旋光场在单轴晶体中的强度分布、偏振态分布、自旋角动量分布以及涡旋相位分布有调节作用.光束半径越小,传输距离越大,单轴晶体的各向异性强度越大,则对杂化偏振矢量涡旋光场的传输特性影响越大.

关键词：杂化偏振矢量光场单轴晶体偏振旋转传输特性涡旋相位

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WPAN应用电磁环境中干扰模型的分析及仿真

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电波科学学报 2003年第1期18卷 75-81页

作者：刘彤沈连丰叶芝慧东南大学移动通信国家重点实验室江苏南京210096

文中首先介绍了无线个域网所要面对的各种干扰及它们各自的特点 ,给出干扰的拓扑结构和传播模型 ;针对干扰的特点 ,由阻塞率的模型 ,经过数学变换推导出以干扰总电平为变量的统计模型 ,以此为基础分析干扰的统计特性 ;利用统计模型分析... 详细信息

文中首先介绍了无线个域网所要面对的各种干扰及它们各自的特点 ,给出干扰的拓扑结构和传播模型 ;针对干扰的特点 ,由阻塞率的模型 ,经过数学变换推导出以干扰总电平为变量的统计模型 ,以此为基础分析干扰的统计特性 ;利用统计模型分析跳频技术在WPAN应用环境下性能的同时 ,也利用有关软件对跳频技术在这些干扰环境中的性能作了仿真 ,从两者比较结果中可以看出 ,干扰的统计模型是比较准确的 ,它对今后的实际研究工作具有一定的指导意义。

关键词： WPAN 阻塞率干扰模型仿真跳频无线个人区域网络个人通信电磁干扰

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Analysis of cumulative handoff delay for graded secondary users in cognitive radio networks

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Journal of Southeast University(English Edition) 2013年第2期29卷 111-117页

作者： Zhang Lei 张雷宋铁成吴名胡静不详东南大学移动通信国家重点实验室南京210096

According to the fact that the secondary users＇ delay requirements for data transmission are not unitary in cognitive radio networks, the secondary users are divided into two classes, denoted by SU1 and SU2, respectively. It is assumed that SU1 has a higher priority to occupy the primary users＇ unutilized channels than SU2. A preemptive resume priority M/G/1 queuing network is used to model the multiple spectrum handoffs processing. By using a state transition probability matrix and a cost matrix, the average cumulative delays of SU1 and SU2 are calculated, respectively. Numerical results show that the more the primary user＇s traffic load, the more rapidly the SU2＇s cumulative handoff delay grows. Compared with the networks where secondary users are unitary, the lower the SUI＇s arrival rate, the more obviously both SUI＇s and SU2＇s handoff delays decrease. The admission access regions limited by the maximum tolerable delay can also facilitate the design of admission control rules for graded secondary users.

关键词： cognitive radio network graded secondary users multiple spectrum handoffs cumulative handoff delay admission access region

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Hybrid spectrum access model for cognitive femtocell networks

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Journal of Southeast University(English Edition) 2013年第2期29卷 118-124页

作者： Zuo Xuzhou Shen Lianfeng 左旭舟刘继顺夏玮玮沈连丰不详东南大学移动通信国家重点实验室南京210096

In order to mitigate the interference for macrocell users caused by deploying femtocells （home base-station） in a long term evolution （LTE） system, a hybrid spectrum access model is proposed by means of applying the cognitive radio technology to the femtocell. The femtocell periodically senses the radio environment and opportunistically accesses the usable frequency band so that the frequency spectrum resource is used intelligently. The sensing process is performed in two stages, which are principal sensing in the downlink and assisted sensing in the uplink, respectively. Based on the information obtained from the sensing results, the frequency spectrum can be used flexibly in underlay or overlay modes in the femtocell. Simulation results show that by using the proposed model, the throughput of a femtocell is greatly improved with tolerable interference to macrocell users.

关键词： cognitive radio frequency spectrum sensing frequency spectrum accessing femtoceU macrocell

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Novel K-best detection algorithms for MIMO system

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Journal of Southeast University(English Edition) 2009年第1期25卷 1-5页

作者：向星宇仲文东南大学移动通信国家重点实验室南京210096

Aiming at the optimum path excluding characteristics and the full constellation searching characteristics of the K-best detection algorithm, an improved-performance K-best detection algorithm and several reduced-complexity K-best detection algorithms are proposed. The improved-performance K-best detection algorithm deploys minimum mean square error （MMSE） filtering of a channel matrix before QR decomposition. This algorithm can decrease the probability of excluding the optimum path and achieve better performance. The reducedcomplexity K-best detection algorithms utilize a sphere decoding method to reduce searching constellation points. Simulation results show that the improved performance K-best detection algorithm obtains a 1 dB performance gain compared to the K- best detection algorithm based on sorted QR decomposition （SQRD）. Performance loss occurs when K = 4 in reduced complexity K-best detection algorithms. When K = 8, the reduced complexity K-best detection algorithms require less computational effort compared with traditional K-best detection algorithms and achieve the same performance.

关键词： sorted QR decomposition K-best sphere decoding maximum-likelihood detection minimum mean square error

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EM-based detection scheme for differential unitary space-time modulation

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Journal of Southeast University(English Edition) 2007年第4期23卷 484-488页

作者：杜正锋陈杰潘文高西奇东南大学移动通信国家重点实验室南京210096

The performance loss of an approximately 3 dB signal-to-noise ratio is always paid with conventional differential detection compared to the related coherent detection. A new detection scheme consisting of two steps is proposed for the differential unitary space-time modulation （DUSTM） system. In the first step, the data sequence is estimated by conventional unitary space-time demodulation （DUSTD） and differentially encoded again to produce an initial estimate of the transmitted symbol stream. In the second step, the initial estimate of the symbol stream is utilized to initialize an expectation maximization （EM）-based iterative detector. In each iteration, the most recent detected symbol stream is employed to estimate the channel, which is then used to implement coherent sequence detection to refine the symbol stream. Simulation results show that the proposed detection scheme performs much better than the conventional DUSTD after several iterations.

关键词： unitary space-time modulation differential detection expectation maximization （EM） algorithm

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Close-formed bound on generalized distributed antenna system capacity

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Journal of Southeast University(English Edition) 2007年第4期23卷 479-483页

作者：孙欢王新宇尤肖虎东南大学移动通信国家重点实验室南京210096

The composite channel models of the generalized distributed antenna system （GDAS） such as Rayleigh-lognormal fading are studied. Then comparisons are performed between the GDAS and the traditional multiple-input multiple-output （MIMO） system to analyze the ergodic capacity of the GDAS and make conclusions that it is impossible to achieve an analytical expression for the ergodic capacity of the GDAS. Moreover, in order to evaluate the performance of the ergodic capacity of the GDAS conveniently, the analytical lower bound and upper bound of the ergodic capacity of the GDAS are derived by using the results from multivariate statistics and matrix inequalities, under the scenarios of Rayleigh-lognormal fading and equal power allocation scheme at transmitter. Finally, the analytical bounds are verified by comparisons with the numerical results.

关键词： generalized distributed antenna system ergodic capacity multiple-input multiple-output Rayleighlognormal fading

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