基于图染色思想的RFID防冲突算法研究

针对射频识别技术(RFID)存在多个阅读器同时传输数据容易产生冲突的问题,提出了一种基于图染色理论的防止冲突的算法。该算法利用图的染色算法将可能存在冲突的阅读器染成不同的颜色,使得每种不相同的颜色不能同时获得相同的时隙,降低了多个阅读器同时传输数据产生冲突的可能性。分析表明:采用该算法明显地降低了阅读器之间的冲突率,同时得到最小的时隙数,提高了信道利用率,为RFID防冲突算法提供了一种新的解决方案,同时为基于TDMA的广播调度模式也提供了一种新的时隙分配方式。     

A fast tag identification anti‐collision algorithm for RFID systems

In this work, we propose a highly efficient binary tree‐based anti‐collision algorithm for radio frequency identification (RFID) tag identification. The proposed binary splitting modified dynamic tree (BS‐MDT) algorithm employs a binary splitting tree to achieve accurate tag estimation and a modified dynamic tree algorithm for rapid tag identification. We mathematically evaluate the performance of the BS‐MDT algorithm in terms of the system efficiency and the time system efficiency based on the ISO/IEC 18000‐6 Type B standard. The derived mathematical model is validated using computer simulations. Numerical results show that the proposed BS‐MDT algorithm can provide the system efficiency of 46% and time system efficiency of 74%, outperforming all other well‐performed algorithms.     

A new anti‐collision protocol based on information of collided tags in RFID systems

Radio frequency identification (RFID) technology has recently become an integral part of a wide range of applications. One of the challenges in RFID systems is the tag anti‐collision issue, for which several anti‐collision tag identification protocols have been proposed. This paper proposes a novel slotted ALOHA‐based RFID tag anti‐collision algorithm which can be employed for tag identification. The main idea of this algorithm is to use the information available in collision slots, called collided data, to identify tags uniquely. For this purpose, the collision slots that include only two tags are selected. Then, the non‐conflict bits in these slots are used to possibly identifying the tags. Because in the proposed algorithm readers use both single slots and also the collision slots for tag identification, the performance is increased significantly compared with other protocols. Results of the study indicate that in the proposed algorithm, the optimal frame size for an individual tag number is equal to the half of tags number and the efficiency of the proposed protocol is improved to about 73%. Copyright © 2015 John Wiley & Sons, Ltd.     

一种基于图论的RFID防冲突建模与优化方法

针对RFID系统的超高频段、多读写器的静态拓扑结构,研究了读写器冲突问题,并提出了一种图论的图着色算法与遗传算法相结合的防冲突干扰方法.该静态预定义算法对读写器冲突建立图论模型,将读写器时隙分配问题转化为图论模型的K-顶点着色问题,优化遗传算法并用于求解图的K-顶点着色问题,求得最小时隙数和最优时隙分配方案.最后将算法应用于算例.实验结果表明该方法可行、实用,能够有效地防止读写器冲突干扰.     

一种基于图论的RFID防冲突建模与优化方法

针对RFID系统的超高频段、多读写器的静态拓扑结构,研究读写器冲突问题,并提出了一种图论的图着色算法与遗传算法相结合的防冲突干扰方法.该静态预定义算法对读写器冲突建立图论模型,将读写器时隙分配问题公式化为图论模型的K一顶点着色问题,优化遗传算法并用于求解图的K一顶点着色问题,以求得读写器网络所需的最小时隙数和最优的时隙分配方案.最后将该算法应用于实例.实验结果表明该方法具有可行性和实用性,并能够有效地防止读写器冲突干扰.     

用自适应图着色算法解决RFID阅读器冲突问题

建立了阅读器网络的图模型,阐述了阅读器网络拓扑结构固定和可随机改变情况下对解决阅读器冲突问题的不同要求。对于动态阅读器网络应用中的阅读器冲突问题,基于图着色方法提出了一种自适应分布式的颜色选择算法,这种算法能降低相邻阅读器冲突概率,并且使获得特定百分率的成功传输所需的总时隙数最少。     

基于碰撞检测的行人疏散算法研究

采用方位距离效应驱动行人的行走决策,并结合碰撞检测,构建一个适用于行人疏散的仿真算法。算法以经典的包围盒法为基本思路,首先经过预碰撞检测,然后再分解出交叉和同道两类精确碰撞类型,来检测行人之间是否发生碰撞。将该算法应用于计算机室内行人疏散仿真系统,有效地解决了疏散仿真过程中由于路线选择造成的行人交叠问题。     

基于可离散处理的RFID防碰撞混杂算法研究

针对一类二叉树搜索算法存在寻呼次数过高的应用局限,采用二叉树查询和离散处理相结合的方法,提出了RFID防碰撞混杂算法。理论分析表明,与以往算法不同,该算法实质上是对满足可离散处理特征的模式而非个体的标签进行二叉树搜索。算法充分考虑了阅读器寻呼次数、寻呼开销、吞吐率等重要的性能指标。仿真结果验证了该算法在寻呼次数、吞吐率等性能指标上有明显的提升。     

Array‐based reader anti‐collision scheme for highly efficient RFID network applications

Radio frequency identification (RFID) is a technology for identifying objects by radio signal. The reader collision problem is caused by the interrogation zones overlap of multiple readers, and leading to incorrect and unreliable data. This study proposes an array‐based reader anti‐collision scheme (ARCS) for solving the reader‐to‐tag interference problem. This mechanism uses array and grouping techniques to schedule the active readers to reduce the read cycle (RC) time. The ‘RC’ and ‘collision ratio (CR)’ measures serve as performance indexes in the proposed scheme. From ‘RC’ comparison, the ARCS mechanism has the maximum improvement of 55 per cent as compared with the existing mechanisms. Furthermore, take ‘CR’ index, ARCS has the maximum improvement of 42 per cent as compared to the others. Copyright © 2008 John Wiley & Sons, Ltd.     

一种减少通信复杂度的RFID搜索树防碰撞算法

针对射频识别搜索树防碰撞算法中通信数据量大、识别时延长等问题,提出了一种减少通信复杂度的防碰撞算法.在标签中引入前缀长度寄存器和响应标志寄存器,在阅读器堆栈区存储前缀个数信息,阅读器通过发送前缀长度信息,对标签进行分类搜索,阅读器和标签不再发送对方已经识别的序列号,有效减少了通信数据量.仿真结果表明,与传统的二叉树搜索防碰撞算法相比,该算法可明显减少系统通信复杂度,提高标签的搜索速率.     

基于认知无线电网络中用户需求频谱分配算法

在认知无线电网络中,对图着色频谱分配算法进行了分析,发现只有少数已有算法考虑到用户的需求是否得到满足,导致需求低的用户分配到过多资源。为解决这个问题,根据基于用户需求的图着色论频谱分配算法,对用户的满意度设置优频谱分配优先级函数,满意度差的用户进行优先选择分配,得到一种改进算法。仿真结果表明,基于用户需求的频谱分配算法的改进算法,能够增加系统的信道效益,提高用户的需求满意程度。     

飞机碰撞检测算法的研究与设计

研究飞机碰撞检测的基本原理,通过建立三维数学模型和使用图形,深入分析解得时间值的物理意义;设计碰撞检测算法,此算法根据飞机当前的位置和速度判断是否将有碰撞产生,当检测到将有碰撞时,发出警告并计算发生碰撞的时间、位置,通过数学推导减少其计算量;使用C程序语言实现此检测算法。     

A Time‐Optimal Anti‐collision Algorithm for FSA‐Based RFID Systems

With the introduction of the new generation RFID technology, EPCglobal Class‐1 Generation‐2, there is considerable interest in improving the performance of the framed slotted Aloha (FSA)‐based tag collision arbitration protocol. We suggest a novel time‐optimal anti‐collision algorithm for the FSA protocol. Our performance evaluation demonstrates that our algorithm outperforms other tag collision arbitration schemes.     

基于碰撞概率约束的认知系统子信道分配算法

针对如何在保护主用户的同时最大化有效吞吐量的子信道分配问题,考虑由于主用户的重新到来而造成的主次用户碰撞,给出一种基于子信道碰撞概率约束的子信道分配算法。算法通过约束子信道碰撞概率来保护主用户,依据碰撞概率约束估计各子信道可容忍最大传输时长,随后认知用户根据请求业务时长选择合适的子信道接入。仿真结果表明,与不考虑子信道碰撞概率约束的算法相比,该分配算法很好地保护了主用户,且在信道条件较好时,能取得更好的有效吞吐量性能。     

双时隙动态二进制搜索RFID防碰撞算法

在二进制搜索算法的基础上引入时隙的思想,提出了一种新的防碰撞算法:双时隙动态二进制搜索防碰撞算法.该算法利用阅读器堆栈形成进一步搜索命令;响应标签分为两个子集,并分别在两个时隙发送数据信息,一次搜索最多可识别4个标签.仿真结果表明:新算法减少了搜索次数和识别时间,提高了RFID系统的性能.     

基于FM0记忆辅助特性的RFID标签碰撞检测

为实现两个射频识别(RFID)碰撞标签信息的检测和分离,提出一种利用Gen2标准中FM0标签编码固有记忆特性的检测方法。通过对FM0比特编码特点和碰撞标签信息的无记忆检测分析,得到基于单个比特持续时间的无记忆检测方法的条件错误概率和单个标签信息检测的误码率;然后利用单个FM0比特编码需要前一比特的“记忆”特性,得到对应于前一比特的一对测量值和对应于下一比特的一对测量值,进而得到碰撞标签信息的1比特记忆辅助检测时的条件错误概率和误码率性能;并对在帧Aloha媒质接入方案中采用提出的检测方法时的N个标签群的总延迟减少性能进行了分析。仿真实验结果表明,提出的1比特记忆辅助检测方法,相比于无记忆检测具有更好的误码率性能,且能减少标签群接入时的总延迟。     

RFID reader collision problem: performance analysis and medium access

The RFID reader collision problem, in which an RFID reader's interrogation is interfered by other concurrent readers' transmission, is considered an important issue to reliable operation and thus to the wide‐spread deployment of RFID networks. In this paper, we present modeling and analysis of the RFID reader collision problem. We observe asymmetry between an RFID reader's and a tag's communication capabilities and develop an RFID radio model based on the asymmetry. By the model, we characterize the spatial reuse of RFID reader networks, and derive concurrent interrogation distance beyond which readers can transmit simultaneously without causing collision and the carrier sense threshold corresponding to the distance. We also examine the dual‐channel mode where available bandwidth is divided into two channels by which reader‐to‐tag communication and tag‐to‐reader communication are separated. We analyze and evaluate the performance of the dual‐channel mode in terms of spatial reuse and interrogation completion time. Copyright © 2010 John Wiley & Sons, Ltd.     

一种采用ADS-B技术的通用航空防撞系统

为适应快速发展的通用航空对避撞的迫切需求,在基于广播式自动相关监视（Automatic Dependent Surveillance-Broadcast,ADS-B）的通用航空监视系统的基础上构建了通用航空防撞系统,该系统与无人机和运输航空一体化构建。结合ADS-B工作范围广和通用航空防撞复杂的特点,提出并构建了包括紧急避撞、一般避撞和提前避撞的三级避撞系统。分析了避撞系统中区域的划分,给出了避撞处理流程,讨论了每一级避撞需求及其关键算法。