SR-DCSK Cooperative Communication System with Code Index Modulation:A New Design for 6G New Radios

This paper proposes a high-throughput short reference differential chaos shift keying cooperative communication system with the aid of code index modulation,referred to as CIM-SR-DCSK-CC system.In the proposed CIM-SR-DCSK-CC system,the source transmits information bits to both the relay and destination in the first time slot,while the relay not only forwards the source information bits but also sends new information bits to the destination in the second time slot.To be specific,the relay employs an N-order Walsh code to carry additional log_(2)N information bits,which are superimposed onto the SRDCSK signal carrying the decoded source information bits.Subsequently,the superimposed signal carrying both the source and relay information bits is transmitted to the destination.Moreover,the theoretical bit error rate(BER)expressions of the proposed CIMSR-DCSK-CC system are derived over additive white Gaussian noise(AWGN)and multipath Rayleigh fading channels.Compared with the conventional DCSKCC system and SR-DCSK-CC system,the proposed CIM-SR-DCSK-CC system can significantly improve the throughput without deteriorating any BER performance.As a consequence,the proposed system is very promising for the applications of the 6G-enabled lowpower and high-rate communication.

HiSC:A Hybrid XML Index Composing Structure-Encoded with Cluster

A new way of indexing and processing twig patterns in an XML documents is proposed in this paper. Every path in XML document can be transformed into a sequence of labels by Structure-Encoded that constructs a one-to-one correspondence between XML tree and sequence. Base on identifying characteristics of nodes in XML tree, the elements are classified and clustered. During query proceeding, the twig pattern is also transformed into its Structure-Encoded. By performing subsequence matching on the set of sequences in XML documents, all the occurrences of path in the XML documents are refined. Using the index, the numbers of elements retrieved are minimized. The search results with pertinent format provide more structure information without any false dismissals or false alarms. The index also supports keyword search Experiment results indicate the index has significantly efficiency with high precision.

Indexing the bit-code and distance for fast KNN search in high-dimensional spaces

Various index structures have recently been proposed to facilitate high-dimensional KNN queries, among which the techniques of approximate vector presentation and one-dimensional (1D) transformation can break the curse of dimensionality. Based on the two techniques above, a novel high-dimensional index is proposed, called Bit-code and Distance based index (BD). BD is based on a special partitioning strategy which is optimized for high-dimensional data. By the definitions of bit code and transformation function, a high-dimensional vector can be first approximately represented and then transformed into a 1D vector, the key managed by a B+-tree. A new KNN search algorithm is also proposed that exploits the bit code and distance to prune the search space more effectively. Results of extensive experiments using both synthetic and real data demonstrated that BD out- performs the existing index structures for KNN search in high-dimensional spaces.

基于可逆元胞自动机加密的扩展码索引调制方案

针对直接序列扩频系统伪随机(Pseudo Noise,PN)码资源有限且码索引调制系统误码率性能下降的问题,提出了一种基于可逆的初等元胞自动机加密的扩展码索引调制方案。首先,针对PN码资源有限的问题,提出使用混沌规则的初等元胞自动机对PN码进行迭代的方案,从而实现扩展PN码的目的;其次,针对码索引调制误码率性能下降的问题,提出了一种可逆元胞自动机加密的码索引调制方案,在发射端,把信息比特切割成调制比特和映射比特,并分别映射为调制符号和扩频码索引,使用对应索引的扩频码对同相分量进行扩频,同时使用可逆元胞自动机对映射比特进行加密,加密后的映射比特为调制符号的正交分量选取对应索引的扩频码进行扩频。仿真与分析结果表明,在相同频谱效率条件下,在加性高斯白噪声信道中,当误码率为10-5时,扩展码索引调制方案的误码率性能优于码索引调制和广义码索引调制方案约2~4 dB,优于非正交码移键控码索引调制方案约0.5 dB。

基于二维混合式位置编码的高精度测角

针对具有精密旋转轴系类的高端制造装备或精密测量仪器,其旋转角度采用传统圆光栅难以消除偏心误差对测量角度精度的影响,提出了一种基于二维混合式位置编码的旋转角度高精度测量方法。该测角系统由一个二维混合式位置编码盘、两个CCD相机和远心镜头组成,二维混合式位置编码盘被固定在精密旋转轴系上以获得其旋转角度。然后,建立了测角模型并从数学上证明了测角精度与安装偏心无关。利用多齿分度台对已提出测角系统精度进行检测,测量角度误差在±1″。最后,利用已提出测量方法对直驱转台的角度定位精度进行测量,角度定位误差在±5″内。与传统圆光栅测角相比,该方法不需要考虑安装偏心误差对测角精度的影响,具有稳定性好、使用简单等特点,可用于角度定位误差的检测。

时态XML索引Txmlsindex

时态XML数据操作的基本途径是相应时态索引模式,而时间信息与结构信息的整合协同是涉及索引效率的关键技术.该文研究了一种基于时态拟序和时态编码协调的时态XML快照索引Txmlsindex,实现了"一次一集合"的时态数据查询和基于Tcodes编码的结构信息重置;比较评估Txmlsindex的可行性与有效性;提出的技术框架和索引模式还可拓展到时态XML的一般查询过程当中.

高效Unicode/GB编码转换算法的设计和实现

为了在存储空间和运算能力严格受限的嵌入式系统中实现Unicode和GB2312编码的相互转换,设计了一种高效率的编码转换算法。该算法通过提取数据表中公共部分实现压缩存储,采用索引和二分法查找相结合的方式进行快速查找,和传统的转换算法相比约节省25%的存储空间,查找效率最高约提高3倍。该算法可在无操作系统支持的嵌入式系统中实现汉字编码之间的高效率的转换。

空间索引技术及其GIS应用综述

空间索引技术可提供高效的空间数据组织与管理方式,以支撑海量空间数据的挖掘与分析。针对当前空间索引存在的知识体系不明晰、选择难等问题,该文通过文献调查法和CiteSpace工具,依据空间划分及映射方法将空间索引划分为基于树结构、格网、空间填充曲线和地址编码的空间索引四大类,并综述其原理、空间结构、适用范围及在GIS领域的应用,最后对空间索引在数据组织、高效计算、可视化、可靠性等方面的研究进行展望。结论如下:基于树结构的空间索引最具普适性且可以处理多维度及多层次的数据,查询性能依赖于树结构的平衡性及数据的分布;基于格网的空间索引可以均匀划分空间以便于高效范围查询,却不适用于非结构化或动态数据集;基于空间填充曲线的空间索引可以在实现维度压缩的同时保持局部邻近性,但插入或删除数据可能导致整个曲线的重构难以频繁更新;基于地址编码的空间索引将语义地址信息转化为编码信息,便于高效检索,然而语义地址匹配仍存在较大误差和不确定性。研究结果可为空间数据组织和结构设计提供参考。

“双碳”背景下中国石化评估指标体系数字化创新研究

在“双碳”背景下,针对中国石油化工集团有限公司(简称中国石化)的传统评估指标体系运作反馈周期长、数据标准化程度低、体系自身缺乏可靠性和准确性数据分析,导致其使用效果无法达到预期的问题,设计了一个涵盖多视角的评估指标体系管理、运行、优化一体化平台系统,并通过国产低代码开发工具——清华数为DWF结合Python语言实现了该系统演示版和后台信效度分析模块的开发。运行试验结果证明,该系统通过对数据分析辅助指标体系的改进与优化,可以有效提升中国石化评估指标体系的运作效率,推动企业科学转型升级和高质量发展。

SCBT-index:基于谱编码的子图索引算法

随着图模型规模的扩大,单机算法难以适应大规模数据集下的子图查询.而现有的分布式算法基于无索引的简单遍历,join过程容易出现内存溢出,而且查询图分布异常时易出现负载不均衡.提出了一种基于谱编码的二叉索引树(SCBT-index),首先对数据图中的顶点谱编码,根据编码信息构建二叉索引树.然后对查询图使用最小查询计划进行分解,最后join过程使用3个剪枝策略:基于拓扑结构的预剪枝、序列化join和基于分布式下的join优化.实验结果表明,SCBT-index在图集下的综合性能优于现有主流算法,单图下的查询时间为现有算法的1/2到1/4.

一种伪码连续波体制的无线电高度表功能指标分解设计方法

文章分析了伪码测距体制无线电测高功能的基本原理和基于伪码测距体制的指标体系,重点研究无线电测高功能的各个组成部分分解各端到端的设计指标是否能满足用户需求,并通过天线仿真各种可能指标,验证指标分解方法的合理性,为后续的无线电测高功能设计提供指标分解思路,也为后续无线电高度表功能方案改进提供数据参考。

基于合并码本的码字位置序号调制SCMA方案

为满足后5G及未来6G时代对通信系统可靠性及频谱效率(spectral efficiency,SE)的严苛要求,针对上行稀疏码多址接入(sparse code multiple access,SCMA)系统,提出了一种基于合并码本的码字位置序号调制SCMA方案。该方案在时域拓展码字位置,使得码字位置全填充且由其序号携带额外信息比特,并能通过改变码字位置数和序号调制阶数灵活调整系统的谱效。此外,设计了基于消息传递算法(message passing algorithm,MPA)的联合检测算法,并给出了合并码本设计准则。系统分析及仿真结果表明,相较于其他序号调制方案,所提方案更好地兼顾了可靠性与SE,在误比特率(bit error rate,BER)性能与鲁棒性方面都有优势。

大规模时空轨迹数据连接查询效率优化实践

本文提出一种低集群计算资源条件下,大规模轨迹类数据同时空关系的快速连接查询算法DPCP-CROSSJOIN.该算法通过对轨迹数据时间字段进行分段交叉编码和位置网格化等方式对连续的轨迹数据离散化,并以日期和网格区域编码进行两级分区存储.通过交叉“等值”连接查询,实现时空连接查询的三级索引、四级加速,将n·n对象间同时空关系连接查询时间复杂度从O(n^(2))降为O(nlogn).在Hadoop集群上使用Hive和TEZ等进行大规模轨迹数据连接查询时能将连接查询效率最高提升到30.66倍.该算法以时间段编码作为关联条件,巧妙绕开连接过程中复杂表达式的实时计算,以“等值”替代复杂表达式计算连接,提高MapReduce任务并行度,提升集群存储和计算资源利用率.在面对仅使用一般优化已几乎无法完成的,更大规模类似任务,仍能在数分钟内完成.实验表明,该算法具有高效和稳定等特性,尤其适用低“算力”资源条件下大规模轨迹数据的同时空关系连接查询.此方法还可作为时空轨迹伴随查找,对象间关系亲密度判定等的原子算法,可广泛应用于维护国家安全、社会治安秩序,预防和打击犯罪,辅助城乡规划统筹等领域.

BC-iDistance:an optimized high-dimensional index for KNN processing

To facilitate high-dimensional KNN queries,based on techniques of approximate vector presentation and one-dimensional transformation,an optimal index is proposed,namely Bit-Code based iDistance(BC-iDistance).To overcome the defect of much information loss for iDistance in one-dimensional transformation,the BC-iDistance adopts a novel representation of compressing a d-dimensional vector into a two-dimensional vector,and employs the concepts of bit code and one-dimensional distance to reflect the location and similarity of the data point relative to the corresponding reference point respectively.By employing the classical B+tree,this representation realizes a two-level pruning process and facilitates the use of a single index structure to further speed up the processing.Experimental evaluations using synthetic data and real data demonstrate that the BC-iDistance outperforms the iDistance and sequential scan for KNN search in high-dimensional spaces.

直接序列扩频非正交分组码索引调制技术研究

为了进一步提高传统码索引调制(Code Index Modulation, CIM)的误码率性能和降低伪随机(Pseudo Noise, PN)码索引资源的耗费量,提出非正交分组-码索引调制(Nonorthogonal Grouping-Code Index Modulation, NG-CIM)方案。NG-CIM在发送端将每一个传输时隙并行分为调制块和映射块,调制块通过比特分组后映射成为多组调制符号,映射块为各组调制符号的正交分量和同相分量索引相同的PN码进行直接序列扩频传输。仿真结果表明,在加性高斯白噪声信道中,随着频谱效率的提升,NG-CIM的误码率性能较CIM有着约2~4dB的改善,同时PN码资源的耗费量也大大减少。

THE MINIMUM SQUARED EUCLIDEAN DISTANCE OF MULTI-h PHASE CODES

The minimum squared Euclidean distance(MSED) of binary multi-h phase codes is presented. The signal segregation degree(SSD) has been put forward to determine MSED of multi-h phase codes. In order to maximize MSED, SSD should be as large as possible. The necessary and sufficient conditions of maximizing SSD are derived. Finally, SSD and the exact formulae for MSED of binary 2-h phase codes are also presented.

Performance index limits of high reinforced concrete shear wall components

The deformation performance index limits of high reinforced concrete(RC) shear wall components based on Chinese codes were discussed by the nonlinear finite element method.Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method.Then,the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0.Parametric studies were made on the influence of shear span ratio,axial compression ratio,ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined boundary members.Finally,the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results,which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.

Evolutionary algorithm based index assignment algorithm for noisy channel

A globally optimal solution to vector quantization (VQ) index assignment on noisy channel, the evolutionary algorithm based index assignment algorithm (EAIAA), is presented. The algorithm yields a significant reduction in average distortion due to channel errors, over conventional arbitrary index assignment, as confirmed by experimental results over the memoryless binary symmetric channel (BSC) for any bit error.

基于Hadoop的海洋数据存储平台设计与实现

海洋数据具有多来源、多尺度、多频度等复杂特性,传统事务型数据库无法满足海量非结构化数据在存储管理、关联查询、复杂分析等方面的需求。针对这一问题,本文采用HDFS+MapReduce+HBase的分布式数据存储架构,利用数据编码压缩存储技术,实现了数据分布式存储管理和处理,并提出了一种多级索引存储管理技术以实现数据快速关联查询;开发了基于WebService的数据查询接口、海洋环境数据信息共享接口、决策支持数据服务接口、智能分析数据服务接口等应用接口。实验表明,对比传统技术架构,该平台在非结构化海洋数据的数据存储管理、数据处理和业务应用等方面具有一定优势。