一种新的自调整多叉树防碰撞算法

针对标签碰撞问题进行了研究,提出了一种新的自调整多叉树防碰撞算法。新算法采用曼彻斯特编码准确判断碰撞位置,根据碰撞位类型的不同自动调整树的叉数;引入异或运算优化查询请求,避免了标签识别过程中不必要空闲时隙的产生;利用二进制数替代标签EPC码,很大程度上减少了通信量。通过理论分析,准确计算出新算法的性能参数。利用Matlab平台对新算法和其他四种常见算法进行了对比仿真实验,新算法在总时隙、吞吐率以及通信复杂度等方面都表现出良好的性能。     

基于马尔科夫链的射频识别防碰撞测试

分析了自适应Q值算法的防碰撞原理以及射频识别(RFID)通信的时序,定义防碰撞过程的识别效率、识别速度和标签数目及Q值的数据状态(Q,n).在此基础上讨论并建立了多标签的状态转移过程的马尔科夫链模型.通过蒙特卡罗统计方法,对马尔科夫链模型求解,得出识别效率和识别速度.用软件无线电测试方案实现防碰撞测试,有效地实现了RFID防碰撞过程的识别效率和识别速度的量化分析.模型仿真结果和测试数据的一致证明了测试模型的有效性和测试方法的正确性. 关键词： 射频识别 防碰撞测试 马尔科夫链 时隙计数器     

基于时隙CSMA的水声无线传感器网络节能强化学习算法

针对水声无线传感器网络的节能问题,提出了一种基于时隙CSMA的强化学习算法。该算法利用强化学习协议自适应水下环境,根据数据传输的距离调整发射功率,从而减少能量消耗,再结合时隙CSMA协议,使用随机退避算法减少信道中的数据碰撞,使得重发的数据包数量减少,节省能量。为验证算法的有效性,仿真实现了本文算法,结果表明,本文算法能够有效减少能耗,并延长网络寿命。     

一种光码分多址无源接入网及其性能研究

提出了一种基于时隙分组光码分多址(OCDMA)技术的无源光接入网模型,给出了一种时隙分组OCDMA的随机接入协议,系统采用比特填充单极性m序列为地址码。推导了此种随机接入协议下的无源光网络的网络吞吐量数学模型,并对网络的吞吐量性能进行了分析研究。理论分析和仿真结果表明,分组时隙OCDMA网络具有较高的网络吞吐量,单个用户接收功率的降低或多用户干扰的增加,会降低系统网络的吞吐量。随着负载的增大,单个用户接收功率越小网络的吞吐量越低。通过减小分组长度可以提高网络的吞吐能力。     

异构网络动态配置空白子帧干扰协调算法

为了解决LTE-A系统下两层异构网络中的小区间干扰协调问题,提出了在增强小区中调度几乎空白子帧的干扰方案。为了降低干扰和进一步提高信道利用率,设计了一种动态分配几乎空白子帧的算法。该算法基于小区增强覆盖技术,指出由增强小区用户与总用户的比例来动态的调整几乎空白子帧比例。仿真结果对比了固定比例的几乎空白子帧和动态设定几乎空白子帧的算法,表明动态配置几乎空白子帧的算法,提高了系统容量,改善了信道利用率。     

结合SIFT算法的视频场景突变检测

视频场景变化检测对于视频的标注以及语义检索具有非常重要的作用。本文提出了一种结合SIFT(Scale Invariant Feature Transformation)特征点提取的场景变化检测算法。首先利用SIFT算法分别提取出视频前后帧的特征点并分别统计其数量,然后对视频前后帧进行图像匹配,统计匹配上的特征点数量,最后将该帧的匹配特征点数量与该帧前一帧的特征点数量做比值,从而通过该比值判断场景变化情况。实验结果表明,视频场景突变检测率平均可以达到95.79%。本算法可以在视频帧进行图像匹配的过程中对场景的变化情况进行判断,因此该算法不仅应用范围较广,还可以保证场景变化检测的精度,仿真结果证明了算法的有效性。     

基于动态显微成像的红细胞多角度形态学分析方法

提出一种结合显微镜和微流控芯片技术的红细胞多角度形态学分析方法,实现了红细胞的动态显微成像,用于红细胞多角度形态学的测量与分析.利用微流控芯片的缩/扩结构使红细胞在特定位置产生旋转或翻转;利用MATLAB对采集到的视频图像进行分帧处理,通过灰度调整、中值滤波、形态学处理、质心法、目标物识别、动态跟踪等算法处理后,实现对...     

动态帧差法及其FPGA设计与实现北大核心CSCD

帧间差分法是运动目标检测的经典方法,但当运动目标速度低到一定数值时,难以检测到运动目标。针对其可检测目标速度的限制,在帧间差分法的基础上,提出了动态帧差法。结合FPGA处理的特点,进行了动态帧差算法的FPGA设计与实现,并构建了一个新的实时运动目标检测系统。系统能够根据目标运动情况自适应调整用于差分图像的帧间距,既适用于较快运动目标的检测,也适用于低速运动目标的检测,扩大了系统可检测运动目标的速度范围。对DDR3端口进行区域划分,解决了在资源有限的FPGA上对图像的多帧存储的问题。多组实验结果证实了动态帧差法及其FPGA设计模块的有效性和实时性。相比其他系统,所研究系统在检测低速运动目标方面具有明显的优势,且可处理1080p@30Hz的彩色视频流。     

基于多特征融合与ROI预测的红外目标跟踪算法

针对当前红外目标检测与跟踪算法存在场景自适应能力弱、专用性强,以及在大视场条件下,首帧图像中小目标误检率高的问题,提出一种红外序列图像目标自适应阈值分割、检测与跟踪方法.选取目标移动速度、目标轮廓的面积和周长、以及自适应分割阈值与感兴趣区域位置为动态变量,建立动态决策准则.采用首帧目标检测算法计算出序列图像的第一帧图像目标的静态变量和部分动态变量,再采用改进的局部自适应阈值分割算法分割后续帧图像,然后利用静态与动态决策准则筛选出分割后的真实目标,最后计算并更新动态决策准则.红外靶标测试结果表明:该方法对不同场景具有较好的适应性,四个场景平均跟踪准确率为95.81%,微机平台平均每帧处理时间为10.93ms,嵌入式平台为26.79ms.     

星载光电跟踪系统连续帧图像快速识别定位算法研究

为了解决星载光电跟踪系统对连续帧图像快速识别、准确定位的要求.在深入分析连续图像序列特性和星载光电跟踪系统特点的基础上,利用光电跟踪系统转台的角度变化信息,对图像序列进行帧间差值运算以获得目标残差图,并基于残差图和原始图像信息提出了一种新的目标识别定位算法,大大地减小了运算量.结合中值滤波和自适应波门跟踪算法,实现了运动目标的快速跟踪定位.通过对目标实测图像序列的实验,结果证明,该算法具有快速、稳定等优点,能满足星载光电跟踪系统实时图像跟踪的要求.     

Physical-layer distributed synchronization in wireless networks and applications

Physical-layer (pulse-coupled) techniques for distributed synchronization in wireless networks are attracting significant attention for their efficiency and scalability. In this paper, the model of pulse-coupled discrete Phase Locked Loops is reviewed and further investigated in two directions. At first, we extend the characterization of (frequency or phase) synchronous states and convergence conditions from homogeneous networks, where all the nodes have the same power constraints, to more general heterogeneous networks. Towards this goal, we build on recent results on algebraic graph theory for generally non-bidirectional graphs, and derive: (i) necessary and sufficient conditions for global synchronization of the network; (ii) closed-form expressions for the asymptotic values of frequency and phases, as a function of the network topology. In the second part of the paper, an application of pulse-coupled synchronization is considered, namely data collection in a sensor network. The energy efficiency of two medium access protocols for data collection from a set of randomly located sensors to an access point is compared: (i) basic ALOHA (which does not require time synchronization among the sensors); (ii) slotted ALOHA, where time synchronization is achieved via pulse-coupled clocks. Analysis shows that the energy spent for maintaining synchronization in slotted ALOHA pays off in terms of total energy consumption with respect to basic ALOHA provided that the number of sensors is sufficiently small. Moreover, the energy gain is proved to depend explicitly on the system load (in terms of packets /s), hardware and topology of the network.     

Low-Complexity Chase Decoding of Reed–Solomon Codes Using Channel Evaluation

A novel time-varying channel adaptive low-complexity chase (LCC) algorithm with low redundancy is proposed, where only the necessary number of test vectors (TVs) are generated and key equations are calculated according to the channel evaluation to reduce the decoding complexity. The algorithm evaluates the error symbol numbers by counting the number of unreliable bits of the received code sequence and dynamically adjusts the decoding parameters, which can reduce a large number of redundant calculations in the decoding process. We provide a simplified multiplicity assignment (MA) scheme and its architecture. Moreover, a multi-functional block that can implement polynomial selection, Chien search and the Forney algorithm (PCF) is provided. On this basis, a high-efficiency LCC decoder with adaptive error-correcting capability is proposed. Compared with the state-of-the-art LCC (TV = 16) decoding, the number of TVs of our decoder was reduced by 50.4% without loss of the frame error rate (FER) performance. The hardware implementation results show that the proposed decoder achieved 81.6% reduced average latency and 150% increased throughput compared to the state-of-the-art LCC decoder.     

Joint optimization of component carrier selection and resource allocation in 5G carrier aggregation system

In this paper, we consider joint optimization of Component Carrier (CC) selection and resource allocation in 5G Carrier Aggregation (CA) system. Firstly, the upper-bound system throughput with determined number of CCs is derived and it is proved by using graph theory that the throughput optimization problem is NP hard. Then we propose a greedy based algorithm to solve this problem and prove that the proposed algorithm can achieve at least 1/2 of the optimal performance in the worst case. At last, we evaluate the throughput and computational complexity performance through a variety of simulations. Simulation results show that the proposed algorithm can obtain better performance comparing with existing schemes while keeping the computation complexity at an acceptable level.     

A novel power allocation strategy for cooperative PDMA systems

Cooperative communication technology is of great importance for increasing the user reachable rate, further improving throughput and reducing the outage probability of non-orthogonal multiple access (NOMA) systems. This paper mainly studies the power allocation optimization method based on amplify-and-forward (AF) pattern division multiple access (PDMA) to obtain the maximum achievable throughput. We formulate an optimization problem of user power allocation in a downlink PDMA system with cooperative relaying, the exact expressions of system throughput and user outage probability of the AF-PDMA system are derived, and a novel power allocation optimization method based on uniform distribution and restricted constraints is proposed. The effectiveness of the restricted constraints and optimization method is verified by theoretical analysis and simulation. The studies we have performed showed that the proposed scheme with uniform distribution and restricted constraints can be significantly improved in terms of the system throughput in comparison to the case with a genetic algorithm (GA) and fixed power allocation scheme. Concerning the proposed method, the search space is reduced to 1/3 of the original feasible region, and the runtime of the algorithm accounts for only 20% of the GA runtime.     

Mathematical modeling of a satellite communications network

A dynamic multiple-access protocol with notification of clashes is proposed for operation with a satellite communications network. Mathematical modeling is used to find some basic probabilistic and temporal characteristics of the network: the throughput, the wait time, etc. It thus becomes possible to determine the region of initial parameter values in which this protocol is more effective than the ALOHA network protocol.V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 120–127, September, 1992.     

空调蒸发器用管翅式换热器开缝翅片的数值设计

通过三维层流数值模拟,与平片计算结果对比,设计了适用于低流速和Re数(迎面风速1-3 m／s,对应Re数 901-2702)下的空调蒸发器用管翅式换热器的开缝翅片形式。研究表明:在上述迎面风速和Re数范围内,开缝翅片性能曲线和平片性能曲线不可避免地有一个交叉点,对应Re数称为转折Re数,在交叉点前的速度和Re数范围内,平片换热器的综合性能优于开缝翅片,而在高于转折Re数后,随着迎面风速的增大,开缝翅片的综合换热性能将越来越优于平片;依据“前疏后密”原则适当减少开缝翅片换热器开缝的条数,可以有效降低转折Re数,并显著改善低流速和Re数下换热器的综合性能。另外,再次验证了场协同理论-温度场和速度场的协同性与换热器换热量间的必然联系。     

基于优化YOLOv4算法的行驶车辆要素检测方法北大核心CSCD

随着车辆数量的急剧增加,带来了一系列管理问题,智能交通系统是一种有效的解决方式。由于传统的目标识别方式受天气、距离、角度、光照等因素的影响较大,且基于原YOLOv4算法的驾驶员面部、手部等信息检测的准确率不高,提出一种基于优化YOLOv4算法的检测定位方法。在给原YOLOv4网络增加一个更小的检测尺度的同时,使用模糊ISODATA动态聚类算法对先验框数目进行优化,并使用真实十字路口数据集进行实验。实验证明,优化后的网络在训练集中的类间平均准确率为98.56%,检测帧频为41.43帧/s,均高于原网络。     

基于自适应尺度的TLD目标跟踪算法

为提升TLD目标跟踪算法的每帧处理速度,以达到在更高分辨率视频中跟踪目标的实时性要求,在TLD算法框架的基础上,提出了一种基于自适应尺度检测学习的目标跟踪算法(AS-TLD)。当跟踪目标成功时,选取当前帧跟踪到的目标尺度及几个相邻的尺度作为下帧检测目标时滑动窗口尺度的选取范围;而当跟踪失败时,则选取在TLD算法初始化阶段,根据跟踪目标及视频图像大小选定的尺度来保障长时间跟踪目标,从而有效减少了平均每帧扫描的窗口数量。实验结果表明,该方法不仅有效地降低了检测模块的检测时间,显著提高了整体算法速度,而且通过动态选取尺度,在一定程度使得TLD各个模块更加协调,跟踪精确度得到提升。